[Federal Register Volume 71, Number 96 (Thursday, May 18, 2006)]
[Rules and Regulations]
[Pages 28924-29012]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 06-4494]



[[Page 28923]]

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Part II





Department of Labor





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Mine Safety and Health Administration



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30 CFR Part 57



Diesel Particulate Matter Exposure of Underground Metal and Nonmetal 
Miners; Final Rule

  Federal Register / Vol. 71, No. 96 / Thursday, May 18, 2006 / Rules 
and Regulations  

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DEPARTMENT OF LABOR

Mine Safety and Health Administration

30 CFR Part 57

RIN 1219-AB29


Diesel Particulate Matter Exposure of Underground Metal and 
Nonmetal Miners

AGENCY: Mine Safety and Health Administration (MSHA), Labor.

ACTION: Final rule.

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SUMMARY: This final rule revises the May 20, 2006 effective date of the 
diesel particulate matter (DPM) final concentration limit of 160 
micrograms of total carbon (TC) per cubic meter of air 
(160TC [mu]g/m3) promulgated in the 2001 final 
rule ``Diesel Particulate Matter Exposure of Underground Metal and 
Nonmetal Miners,'' and published in the Federal Register on January 19, 
2001 (66 FR 5706) and amended on September 19, 2005 (70 FR 55019).
    This final rule increases flexibility of compliance for mine 
operators by allowing staggered effective dates for implementation of 
the final DPM limit, phased-in over a two-year period, primarily based 
on feasibility issues which have surfaced since promulgation of the 
2001 final rule.
    Furthermore this final rule establishes requirements for medical 
evaluation of miners required to wear respiratory protection and 
transfer of miners who are medically unable to wear a respirator; 
deletes the existing provision that restricts newer mines from applying 
for an extension of time in which to meet the final concentration 
limit; addresses technological and economic feasibility issues, and the 
costs and benefits of this rule.

EFFECTIVE DATE: This final rule is effective on May 18, 2006 except for 
amendments to Sec.  57.5060(d), which is effective August 16, 2006.

FOR FURTHER INFORMATION CONTACT: Patricia W. Silvey, Acting Director, 
Office of Standards, Regulations, and Variances, MSHA, 1100 Wilson 
Blvd., Room 2350, Arlington, Virginia 22209-3939; 202-693-9440 
(telephone); or 202-693-9441 (facsimile).
    You may obtain copies of this final rule and the Regulatory 
Economic Analysis (REA) in alternative formats by calling 202-693-9440. 
The alternative formats are either a large print version of these 
documents or electronic files that can be sent to you either on a 
computer disk or as an attachment to an e-mail. The documents also are 
available on the Internet at http://www.msha.gov/REGSINFO.HTM.

SUPPLEMENTARY INFORMATION: 

Outline of Preamble

    This outline will assist the mining community in finding 
information in this preamble.

I. List of Common Terms
II. Background
    A. First Partial Settlement Agreement
    B. Second Partial Settlement Agreement
III. Rulemaking History
    A. Advance Notice of Proposed Rulemaking (ANPRM) on the Interim 
and Final Concentration Limits
    B. Notice of Proposed Rulemaking (NPRM) on the Interim Limit
    C. Final Rule Revising the Interim Concentration Limit
    D. September 2005 Notice of Proposed Rulemaking
IV. Risk Assessment
V. Feasibility
    A. Technological Feasibility
    B. Economic Feasibility
VI. Summary of Benefits
VII. Section 101(a)(9) of the Mine Act
VIII. Section-by-Section Analysis
    A. PEL Sec.  57.5060(b)
    B. Special Extensions Sec.  57.5060(c)(3)(i)
    C. Medical Evaluation and Transfer Sec.  57.5060(d)
    D. Diesel Particulate Records Sec.  57.5075(a)
IX. Regulatory Costs
    A. Costs of Medical Evaluation and Transfer
    B. Costs of Implementing the 160TC [mu]g/
m3 Limit
X. Regulatory Flexibility Act Certification (RFA) and Small Business 
Regulatory Enforcement Fairness Act (SBREFA)
    A. Definition of a Small Mine
    B. Factual Basis for Certification
XI. Paperwork Reduction Act
XII. Other Regulatory Considerations
    A. The Unfunded Mandates Reform Act of 1995
    B. National Environmental Policy Act
    C. The Treasury and General Government Appropriations Act of 
1999: Assessment of Federal Regulations and Policies on Families
    D. Executive Order 12630: Government Actions and Interference 
With Constitutionally Protected Property Rights
    E. Executive Order 12988: Civil Justice Reform
    F. Executive Order 13045: Protection of Children From 
Environmental Health Risks and Safety Risks
    G. Executive Order 13132: Federalism
    H. Executive Order 13175: Consultation and Coordination With 
Indian Tribal Governments
    I. Executive Order 13211: Actions Concerning Regulations That 
Significantly Affect Energy Supply, Distribution, or Use
    J. Executive Order 13272: Proper Consideration of Small Entities 
in Agency Rulemaking
XIII. Information Quality
XIV. References Cited
XV. Regulatory Text

I. List of Common Terms

    Listed below are the common terms used in the preamble.

31 Mine Study............................................................  Joint MSHA/Industry Study:
                                                                            Determinations of DPM levels in
                                                                            Underground Metal and Nonmetal
                                                                            Mines.
Commission...............................................................  Federal Mine Safety and Health Review
                                                                            Commission.
CV.......................................................................  Coefficient of Variation.
DPF......................................................................  diesel particulate filter.
DPM......................................................................  diesel particulate matter.
EC.......................................................................  elemental carbon.
ETS......................................................................  environmental tobacco smoke.
Filter Selection Guide...................................................  Diesel Particulate Filter Selection
                                                                            Guide for Diesel-powered Equipment
                                                                            in Metal and Nonmetal Mines.
First Partial Settlement Agreement.......................................  66 FR 35518 (2001) & 66 FR 35521
                                                                            (2001): basis for July 5, 2001 NPRM.
MARG.....................................................................  Methane Awareness Resource Group.
M/NM.....................................................................  metal/non-metal.
MSHA.....................................................................  Mine Safety and Health
                                                                            Administration.
NIOSH....................................................................  National Institute for Occupational
                                                                            Safety and Health.
NTP......................................................................  National Toxicology Program.
OC.......................................................................  organic carbon.
PAPR.....................................................................  powered air-purifying respirator.
PEL......................................................................  permissible exposure limit.
PPM......................................................................  parts per million.
QRA......................................................................  quantitative risk assessment.
REA......................................................................  Regulatory Economic Analysis.

[[Page 28925]]

 
Second Partial Settlement Agreement......................................  67 FR 47296 (2002): basis for August
                                                                            14, 2003 NPRM.
SD.......................................................................  standard deviation.
SKC......................................................................  SKC, Inc.
TC.......................................................................  total carbon (the sum of elemental
                                                                            and organic carbon).
USWA.....................................................................  United Steelworkers of America.
USW......................................................................  United Steelworkers.
[mu]g/cm\2\..............................................................  micrograms per square centimeter.
[mu]g/m\3\...............................................................  micrograms per cubic meter.
2001 final rule..........................................................  January 19, 2001 DPM final rule.
Amended 2001 final rule..................................................  2001 final rule amended on February
                                                                            27, 2002.
2002 final rule..........................................................  February 27, 2002 final rule.
2002 ANPRM...............................................................  Advance Notice of Proposed Rulemaking
                                                                            published on September 25, 2002.
2003 NPRM................................................................  Notice of Proposed Rulemaking
                                                                            published on August 14, 2003.
2005 final rule..........................................................  June 6, 2005 final rule.
2005 proposed rule.......................................................  Notice of Proposed Rulemaking
                                                                            published on September 7, 2005.
 

II. Background

    On January 19, 2001, MSHA published a final rule addressing the 
health hazards to underground metal and nonmetal miners from exposure 
to diesel particulate matter (DPM) (66 FR 5706). The rule established 
new health standards for these miners by requiring, among other things, 
mine operators to use engineering and work practice controls to reduce 
DPM to prescribed limits. It set an interim and final DPM concentration 
limit in the underground metal and nonmetal mining environment with 
staggered effective dates for implementation of the concentration 
limits. The interim concentration limit of 400TC [mu]g/
m3 was to become effective on July 20, 2002. The final 
concentration limit of 160TC [mu]g/m3 was 
scheduled to become effective January 20, 2006. In the 2001 final rule, 
MSHA projected that the mining industry would meet the final 
concentration limit in their mines through the use of diesel 
particulate filtration devices, ventilation changes, and the turnover 
of equipment and engines to less polluting models (66 FR 5713, 5888).
    Several mining trade associations and individual mine operators 
challenged the final rule and the United Steelworkers of America (USWA) 
intervened in the case, which is now pending in the United States Court 
of Appeals for the District of Columbia Circuit. The parties agreed to 
resolve their differences through settlement negotiations with MSHA and 
we delayed the effective date of certain provisions of the standard.

A. First Partial Settlement Agreement

    On July 5, 2001, as a result of an agreement reached in settlement 
negotiations, MSHA published two notices in the Federal Register. One 
notice (66 FR 35518) delayed the effective date of Sec.  57.5066(b) 
related to tagging requirements in the maintenance standard. The second 
notice (66 FR 35521) proposed a rule to make limited revisions to Sec.  
57.5066(b) and added a new paragraph to Sec.  57.5067(b) ``Engines'' 
regarding the definition of the term ``introduced.'' MSHA published the 
final rule on February 27, 2002 (67 FR 9180).

B. Second Partial Settlement Agreement

    Settlement negotiations continued on the remaining unresolved 
issues in the litigation, and on July 15, 2002, the parties finalized a 
written agreement (67 FR 47296, 47297). Under the agreement, the 
interim concentration limit of 400TC [mu]g/m3 
became effective on July 20, 2002, without further legal challenge. 
MSHA afforded mine operators one year to develop and implement good-
faith compliance strategies to meet the interim concentration limit, 
and MSHA agreed to provide compliance assistance during this one-year 
period. MSHA also agreed to propose rulemaking on several other 
disputed provisions of the 2001 final rule. The legal challenge to the 
rule was stayed pending completion of the additional rulemakings.
    On July 20, 2003, MSHA began full enforcement of the interim 
concentration limit of 400TC [mu]g/m3. MSHA's 
enforcement policy was also based on the terms of the second partial 
settlement agreement and includes the use of elemental carbon (EC) as 
an analyte to ensure that a citation based on the 400 TC concentration 
limit is valid and not the result of interferences (67 FR 47298). The 
policy was discussed with the DPM litigants and stakeholders on July 
17, 2003.

III. Rulemaking History

A. Advance Notice of Proposed Rulemaking (ANPRM) on the Interim and 
Final Concentration Limits

    On September 25, 2002, MSHA published an Advance Notice of Proposed 
Rulemaking (ANPRM) (67 FR 60199). MSHA noted in the ANPRM that the 
scope of the rulemaking was limited to the terms of the Second Partial 
Settlement Agreement and posed a series of questions to the mining 
community related to the 2001 final rule. MSHA also stated its intent 
to propose a rule to revise the surrogate for the interim and final 
concentration limits and to propose a DPM control scheme similar to 
that included in our longstanding hierarchy of controls scheme used in 
MSHA's air quality standards (30 CFR 56.5001 through 56.5005 and 
57.5001 through 57.5005) for M/NM mines. In addition, MSHA stated that 
it would consider technological and economic feasibility for the 
underground M/NM mining industry to comply with revised interim and 
final DPM limits. MSHA determined at that time that some mine operators 
had begun to implement control technology on their underground diesel-
powered equipment. Therefore, MSHA requested relevant information on 
current experiences with availability of control technology, 
installation of control technology, effectiveness of control technology 
to reduce DPM levels, and cost implications of compliance with the 2001 
final rule.

B. Notice of Proposed Rulemaking (NPRM) on the Interim Limit

    In response to our publication of the ANPRM, some commenters 
recommended that MSHA propose separate rulemakings for revising the 
interim and final concentration limits to give MSHA an opportunity to 
gather further information to establish a final DPM limit, particularly 
regarding feasibility. In the subsequent notice of proposed rulemaking 
(NPRM) published on August 14, 2003 (68 FR 48668), MSHA concurred with 
these commenters and notified the public in the NPRM that we would 
propose a separate rulemaking to amend the existing final concentration 
limit of 160TC [mu]g/m3. MSHA also requested 
comments on an appropriate final DPM limit and solicited additional 
information on feasibility. The proposed rule also addressed the 
interim concentration limit by proposing a

[[Page 28926]]

comparable PEL of 308 [mu]g/m3 based on the EC surrogate and 
included a number of other provisions.

C. Final Rule Revising the Interim Concentration Limit

    MSHA published the final rule revising the interim concentration 
limit on June 6, 2005 (70 FR 32868). This rule changed the interim 
concentration limit of 400 [mu]g/m3 measured by TC to a 
comparable PEL of 308 [mu]g/m3 measured by EC. The rule 
requires MSHA's longstanding hierarchy of controls that is used for 
other MSHA exposure-based health standards at M/NM mines, but retains 
the prohibition on rotation of miners for compliance. Furthermore, the 
rule, among other things, requires MSHA to consider economic as well as 
technological feasibility in determining if operators qualify for an 
extension of time in which to meet the final DPM limit, and deletes the 
requirement for a control plan.
    Currently, the following provisions of the DPM standard are 
effective: Sec.  57.5060(a), establishing the interim PEL of 308 
micrograms of EC per cubic meter of air which is comparable in effect 
to 400 micrograms of TC per cubic meter of air; Sec.  57.5060(d), 
Addressing control requirements; Sec.  57.5060(e), Prohibiting rotation 
of miners for compliance with the DPM standard; Sec.  57.5061, 
Compliance determinations; Sec.  57.5065, Fueling practices; Sec.  
57.5066, Maintenance standards; Sec.  57.5067, Engines; Sec.  57.5070, 
Miner training; Sec.  57.5071, Exposure monitoring; and, Sec.  57.5075, 
Diesel particulate records.

D. September 2005 Notice of Proposed Rulemaking

    On September 7, 2005, (70 FR 53280) MSHA proposed a rule to phase 
in the final DPM limit because MSHA was concerned that there may be 
feasibility issues for some mines to meet that limit by January 20, 
2006.
    Accordingly, the proposed rule considered staggering the effective 
date for implementation of the final DPM limit, phased in over a five-
year period, primarily based on feasibility issues which had surfaced 
since promulgation of the 2001 final rule. MSHA also proposed to delete 
existing Sec.  57.5060(c)(3)(i) that restricts new mines from applying 
for an extension of time for meeting the final concentration limit. 
MSHA sought comment and data on an appropriate conversion factor for 
the final DPM limit, technological implementation issues, and the costs 
and benefits of the final rule. In addition, MSHA requested comments on 
the appropriateness of including in a final rule a provision for 
medical evaluation of miners required to wear respiratory protection 
and transfer of miners who have been determined by a medical 
professional to be unable to wear a respirator.
    MSHA set hearing dates and a deadline for receiving comments on the 
September 7, 2005 proposed rule with the expectation that MSHA would 
complete the rulemaking to phase in the final DPM limit before January 
20, 2006.
    After publication of the September 7, 2005 proposed rule, MSHA 
received a request from the United Steel, Paper and Forestry, Rubber, 
Manufacturing, Energy, Allied Industrial and Service Workers 
International Union (USW) for more time to comment on the proposed 
rule. The USW explained that Hurricane Katrina had placed demands on 
their resources that would prevent them from participating effectively 
in the rulemaking under the current schedule for hearings and comments. 
MSHA recognized the USW's need to devote resources to respond to the 
aftermath of Hurricane Katrina and the impact that would have on their 
participation under the current timetable. MSHA also received a request 
from the National Stone, Sand and Gravel Association (NSSGA) for 
additional time to comment on the proposed rule and for an additional 
public hearing in Arlington, Virginia.
    Accordingly, due to requests from the USW and NSSGA, MSHA published 
a notice on September 19, 2005 (70 FR 55018) that changed the public 
hearing dates from September 2005 to January 2006. MSHA also extended 
the public comment period from October 14, 2005 to January 27, 2006. 
Also on September 19, 2005, MSHA issued a second notice delaying the 
applicability of the final concentration limit of 160TC [mu]g/
m3 until May 20, 2006.
    Public hearings were held on the proposed rule in Arlington, 
Virginia on January 5, 2006; Salt Lake City, Utah on January 9, 2006; 
Kansas City, Missouri on January 11, 2006; and Louisville, Kentucky on 
January 13, 2006. The comment period was scheduled to close on January 
27, 2006. However, the National Mining Association and the Methane 
Awareness Resource Group (MARG) Diesel Coalition requested that the 
comment period be extended an additional 30 days beyond January 27, 
2006 to allow for more time to prepare their comments. Additionally, 
the Agency received a request from the National Institute for 
Occupational Safety and Health (NIOSH) for a three week extension. On 
January 26, 2006, MSHA determined that a three week extension of the 
comment period was sufficient to allow additional public comment on the 
proposed rule and extended the comment period until February 17, 2006.
    What follows is a discussion of the specific revisions to the 2001 
DPM standard. The final rule addresses:
     Section 57.5060(b) addressing the final dpm concentration 
limit;
     Section 57.5060(c)(3)(i) addressing special extensions;
     Section 57.5060(d)addressing medical evaluation and 
transfer; and
     Section 57.5075 addressing recordkeeping requirements.

IV. Risk Assessment

A. Introduction

    We rely on our comprehensive January 2001 risk assessment published 
at 66 FR 5752-5855 (as corrected at 66 FR 35518-35520) to support this 
final rule. This risk assessment was updated in the 2005 final rule (70 
FR 32868) establishing the 308EC [mu]g/m3 interim 
permissible exposure limit (PEL). In the following discussion, we will 
refer to the risk assessment published in the 2001 final rule as the 
``2001 risk assessment'' and the updates published in the 2005 final 
rule as the ``updated 2001 risk assessment.''
    The discussion of the 2001 risk assessment in our 2005 final rule 
presented our evaluation of health risks associated with DPM exposure 
levels encountered in the mining industry and is based on a review of 
the scientific literature available through March 31, 2000, along with 
consideration of all material submitted during the public comment 
periods for the 2001 and 2005 rulemakings.
    The 2001 risk assessment was divided into three main sections. 
Section 1 (66 FR 5753-5764) contained a discussion of U.S. miner 
exposures based on field data collected through mid-1998. Section 2 of 
the 2001 risk assessment (66 FR 5764-5822) reviewed the extensive 
scientific literature on health effects associated with exposures to 
DPM. In section 3 of the 2001 risk assessment (66 FR 5822-5855), we 
evaluated the best available evidence to ascertain whether exposure 
levels currently existing in mines warranted regulatory action pursuant 
to the Mine Act. After careful consideration of all the submitted 
public comments, the 2001 risk assessment established three main 
conclusions:

    1. Exposure to DPM can materially impair miner health or 
functional capacity. These material impairments include acute 
sensory irritations and respiratory symptoms (including allergenic 
responses); premature death from cardiovascular, cardiopulmonary, or 
respiratory causes; and lung cancer.

[[Page 28927]]

    2. At DPM levels currently observed in underground mines, many 
miners are presently at significant risk of incurring these material 
impairments due to their occupational exposures to DPM over a 
working lifetime.
    3. By reducing DPM concentrations in underground mines, the rule 
will substantially reduce the risks of material impairment faced by 
underground miners exposed to DPM at current levels (66 FR 5854-
5855).

    Exposure to DPM can materially impair miner health or functional 
capacity. These material impairments include acute sensory irritations 
and respiratory symptoms (including allergenic responses); premature 
death from cardiovascular, cardiopulmonary, or respiratory causes; and 
lung cancer. Scientific evidence gathered after the peer-review of the 
2001 risk assessment generally supports our conclusions, and nothing in 
our reviews suggests that they should be altered.
    Some commenters presented critiques challenging the 2001 risk 
assessment and disputing scientific support for any DPM exposure limit, 
especially by means of an EC surrogate. Other commenters endorsed the 
risk assessment and stated that recent scientific publications support 
our conclusions.
    Some commenters continue to question the scientific basis for 
linking DPM exposures with an increased risk of adverse health effects. 
Many of these comments are the same as those addressed in the 2005 
final rule. We refer the reader to section VI, DPM Exposures and Risk 
Assessment, in the 2005 final rule (70 FR at 32888) for discussions 
addressing earlier commenters' positions on the underlying basis of the 
risk assessment.
    After considering the additional peer-reviewed scientific 
literature submitted in response to the proposed rule, and all of the 
comments, we did not identify any reason to reduce our concern with 
regard to adverse health risks associated with DPM exposure as 
identified in the 2001 risk assessment.
    Section IV.B, summarizes the DPM exposure data that became 
available after publication of the 2001 final rule. Section IV.C, 
Health Effects, summarizes additional scientific literature pertaining 
to adverse health effects of DPM and fine particulates submitted to the 
record since our 2005 final rule. The reader is encouraged to refer to 
the 2001 quantitative risk assessment (66 FR 5752-5855) that reviewed 
the health effects associated with exposure to DPM. This discussion 
evaluates the extent to which literature added to the record changes 
the conclusions of the 2001 risk assessment. Section IV.D, Significance 
of Risk, supplements Section 2 of the 2001 risk assessment (66 FR 5764-
5822) by addressing comments related to the risk assessment.
    We reviewed comments on the potential health effects of 
substituting EC for TC as a surrogate measure of DPM. We believe that 
the issue of an appropriate surrogate for a measure of DPM is separate 
from the issue of determining whether adverse health effects are caused 
by whole DPM or a specific component of DPM. The 2001 risk assessment 
is definitive in explaining relevant adverse health effects caused by 
exposure to DPM. The risk assessment accurately portrays adverse health 
effects ranging from sensory irritation to lung cancer caused by 
exposure to DPM. The method by which exposures are measured does not 
affect the conclusion that exposure to DPM produces serious adverse 
health effects. Comments concerning the analytical method are addressed 
in part VIII.A. Section 57.5060(b), addressing the final limits.

B. Exposures to DPM in Underground Metal and Nonmetal Mines

    The 2001 risk assessment and the update presented in 2005 used the 
best available data on exposure to DPM at underground M/NM mines to 
quantify excess lung cancer risk. ``Excess risk'' refers to the 
lifetime probability of dying from lung cancer during or after a 45-
year occupational DPM exposure. All of the exposure-response models for 
lung cancer are monotonic (i.e., increased exposure yields increased 
excess risk).
    We evaluated exposures based on 355 samples collected at 27 
underground U.S. M/NM mines prior to promulgating the 2001 rule. Mean 
DPM concentrations found in the production areas and haulageways at 
those mines ranged from about 285 [mu]g/m\3\ to about 2000 [mu]g/m\3\, 
with some individual measurements exceeding 3500 [mu]g/m\3\. The 
overall mean DPM concentration was 808 [mu]g/m\3\. All of the samples 
considered in the 2001 risk assessment were collected prior to 1999.
    Two sets of DPM exposure data, collected after promulgation of the 
2001 final rule, were compiled for underground M/NM mines: (1) data 
collected in 2001 and 2002 from 31 mines for purposes of the 31-Mine 
Study (Table IV-1) and (2) data collected between 10/30/2002 and 10/29/
2003 from 183 mines to establish a baseline for future sample 
comparisons (Table IV-2). The mean whole DPM concentration across all 
358 valid samples in the 31-Mine Study was 432DPM [mu]g/
m\3\. The mean concentration across all valid 1,194 baseline samples 
was 318DPM [mu]g/m\3\.\1\
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    \1\ The relationship DPM [ap] TC/0.8 is the same as that assumed 
in the 2001 risk assessment. The relationship TC [ap] 1.3 x EC was 
formulated under the Second Partial Settlement Agreement, based on 
TC:EC ratios observed in the joint 31-Mine Study.

Table IV-1.--DPM Concentrations ([mu]g/m\3\) by Mine Category for Samples Collected for the 31-Mine Study (2001-
                                                      2002)
                                         [DPM is estimated by TC / 0.8]
----------------------------------------------------------------------------------------------------------------
                                                                    Estimated 8-hour Full Shift Equivalent  DPM
                                                                            Concentration ([mu]g/m\3\)
                                                                 -----------------------------------------------
                                                                     Metal       Stone       Trona       Other
----------------------------------------------------------------------------------------------------------------
No. of samples..................................................         116         105          54          83
Minimum.........................................................          46          16          20          27
Maximum.........................................................       2,581       1,845         331       1,210
Median..........................................................         491         331          82         341
Mean............................................................         610         465          94         359
    Std. Error..................................................          45          36           9          27
    95% UCL.....................................................         699         537         113         412
    95% LCL.....................................................         522         394          75         306
----------------------------------------------------------------------------------------------------------------


[[Page 28928]]


 Table IV-2.--DPM Concentrations by Mine Category for Samples Collected During the Baseline Sampling Period (10/
                                               30/2002-10/29/2003)
                                     [DPM is estimated by (1.3 x EC) / 0.8.]
----------------------------------------------------------------------------------------------------------------
                                          Estimated 8-hour Full Shift Equivalent DPM Concentration ( [mu]g/m\3\)
                                         -----------------------------------------------------------------------
                                                                                                         Total
                                             Metal       Stone     Other N/M     Trona       Total     excluding
                                                                                                         Trona
----------------------------------------------------------------------------------------------------------------
No. of Samples..........................         284         689         196          25       1,194       1,169
Maximum.................................       2,532       3,724       1,200         509       3,724       3,724
Median..................................         339         186         185         102         218         223
Mean....................................         444         295         243         132         318         322
    Std. Error..........................          23          13          15          20          10          10
    95% UCL.............................         490         320         272         173         338         342
    95% LCL.............................         399         270         214          91         299         303
----------------------------------------------------------------------------------------------------------------

    Thus, despite substantial improvements attained since the 1989-1999 
sampling period addressed by the 2001 risk assessment, underground M/NM 
miners are still faced with an unacceptable risk of lung cancer due to 
their occupational exposure to DPM. The reader is referred to part D of 
this section, Significance of Risk, for further discussion of excess 
risk.
    Personal exposure samples taken after October 2003 are collected 
according to our enforcement sampling policy. These enforcement samples 
collected after the end of the Baseline Sampling period are not 
representative of the average M/NM miner's exposure to DPM because we 
collect samples to target the highest risk miner, not the average 
miner. Therefore, this exposure information is not used to characterize 
the average miner's exposure to DPM. See section V.B, Economic 
Feasibility, for a summary of enforcement sampling results. However, 
our enforcement activities from November 1, 2003 through January 31, 
2006 continue to show some miners have experienced exposures 
substantially greater than 308EC [mu]g/m\3\. During the time 
period from November 1, 2003 to January 31, 2006, 1,798 valid personal 
compliance samples from all mines covered by the regulation were 
collected. From these samples collected, 18% (324) of samples exceeded 
308EC [mu]g/m\3\, 22% (396) exceeded 350TC [mu]g/
m\3\, and 64% (1,151) exceeded 160TC [mu]g/m\3\. These 
percentages show that miners are still being exposed to high levels of 
DPM.

C. Health Effects

    A key conclusion of the 2001 risk assessment was:

    Exposure to DPM can materially impair miner health or functional 
capacity. These material impairments include acute sensory 
irritations and respiratory symptoms (including allergenic 
responses); premature death from cardiovascular, cardiopulmonary, or 
respiratory causes; and lung cancer. [66 FR 5854-5855]

    We have reviewed scientific literature pertaining to health effects 
of fine particulates in general and DPM in particular published later 
than what was considered in the 2001 risk assessment. This scientific 
evidence supports the 2001 risk assessment, and nothing in our review 
suggests that it should be altered.
    A number of commenters endorsed the 2001 risk assessment, and 
suggested that the latest evidence strengthens its conclusions. Some 
other commenters responding to our 2003 NPRM jointly stated that 
``[t]he scientific evidence for the [adverse] health effects of DPM is 
overwhelming'' and that ``evidence for the carcinogenicity and non-
cancer health effects of DPM has grown since 1998.''
    A number of commenters contended that all of the evidence to date 
is insufficient to support limitation of occupational exposure to DPM. 
We believe that these commenters did not appreciate evidence presented 
in the 2001 risk assessment and/or mischaracterized its conclusions. 
For example, a few commenters erroneously stated that promulgation of 
the 2001 rule was based on only ``two principal health concerns: (1) 
The transitory, reversible health effects of exposure to DPM; and, (2) 
the long-term impacts that may result in an excess risk of lung cancer 
for exposed workers.'' Actually, as shown in the conclusion cited 
above, the 2001 risk assessment identified three different kinds of 
material health impairment associated with DPM exposure: (1) Acute 
sensory irritations and respiratory symptoms (including allergenic 
responses); (2) premature death from cardiovascular, cardiopulmonary, 
or respiratory causes; and (3) lung cancer. Although the 
cardiovascular, cardiopulmonary, and respiratory effects were 
associated with acute exposure to DPM, commenters presented no evidence 
that any such effects were ``transitory'' or ``reversible.'' Nor did 
commenters present evidence that immunological responses associated 
with either short-term or long-term DPM exposure were ``transitory'' or 
``reversible.''
    In addition, some commenters erroneously stated that ``no 
[quantitative] dose/response relationship related to the PELs could be 
demonstrated by MSHA.'' These commenters apparently did not appreciate 
the discussion of exposure-response relationships in the 2001 risk 
assessment (66 FR 5847-54) and failed, specifically, to note the 
quantitative exposure-response relationships shown for lung cancer in 
the two tables provided (66 FR 5852-53). Relevant exposure-response 
relationships were also demonstrated in articles by Pope et al. cited 
in the 2003 NPRM, which will be discussed further below.
    Some commenters objected that the exposure-response relationships 
presented in the 2001 risk assessment did not justify adoption of the 
specific DPM exposure limits promulgated. These commenters mistakenly 
assume the limits set forth in the 2001 final rule were derived from an 
exposure-response relationship. As explained in 66 FR at 5710-14, the 
choice of exposure limits, while justified by quantifiable adverse 
health effects, was actually driven by feasibility concerns. The 
exposure-response relationships provided clear evidence of significant 
adverse human health effects (both cancer and non-cancer) at exposure 
levels far below those determined to be feasible for mining.
    The additional scientific literature cited in the 2003 NPRM, the 
2005 final rule and this 2006 final rule is meant only to update and 
supplement the evidence of health effects cited in the 2001 risk 
assessment. Although the

[[Page 28929]]

2001 risk assessment presented ample evidence to justify its 
conclusions, additional supplemental DPM health effects literature is 
reviewed in this document that became available after the 2001 risk 
assessment was published.
    The following section summarizes additional studies submitted to 
the record. Our review focuses on the implications of these study 
results for the characterization of risk presented in MSHA's 2001 
assessment. These study summaries are presented in three tables that 
correspond to the material health impairments identified in the 2001 
risk assessment: (1) Respiratory and immunological effects, including 
asthma, (2) cardiovascular and cardiopulmonary effects, and (3) cancer. 
A fourth table focuses on a recent study about potential mechanisms of 
action for DPM. These tables describe the studies that some commenters 
and the agency felt were representative of the type of new information 
available since the completion of the 2001 assessment and the updated 
2001 risk assessment, however, these tables are not to represent a 
comprehensive review of all information published about particulate 
matter.
(1) Respiratory and Immunological Effects, Including Allergenic 
Responses
    In the 2001 risk assessment, acute sensory irritations with 
respiratory symptoms, including immunological or allergenic effects 
such as asthmatic responses, were grouped together. Similar material 
health impairments likely to be caused or exacerbated by excessive 
exposures to DPM were identified. This finding was based on human 
experimental and epidemiological studies and was supported by 
experimental toxicology. (For an explanation of what type of health 
effects are considered by us to be material impairments of health, the 
reader is referred to the 2001 risk assessment (See 66 FR 5766.)
    Table IV-3 summarizes five studies dealing with respiratory and 
immunological effects of DPM and/or fine particulates in general that 
have been submitted to the record since the 2005 literature update to 
the 2001 risk assessment. The epidemiological studies by Hoppin (2004) 
and Pourazar (2004) provide additional support for the association 
between diesel exhaust exposure and development of asthma. Three of the 
studies, Gluck (2003), Stenfors (2004), and Behndig (2006), have also 
shown that exposures of human volunteers to diesel exhaust at levels 
below 160TC [mu]g/m\3\ cause inflammation of the human 
respiratory tract.

                       Table IV-3.--Studies of Human Respiratory and Immunological Effects
----------------------------------------------------------------------------------------------------------------
                Authors, year                             Description                      Key results
----------------------------------------------------------------------------------------------------------------
Behndig et al., 2006.........................  15 healthy volunteers exposed to  Exposure to diesel exhaust at
                                                diesel exhaust or air (2 hours,   this concentration is
                                                diesel concentration measured     sufficient to cause airway
                                                as PM10: 100 [mu]g/m\3\)          inflammation.
                                                Eighteen hours after exposure,
                                                the volunteers were assessed
                                                using bronchoscopy with
                                                bronchoalveolar lavage and
                                                endobronchial mucosal biopsy.
Gluck et al., 2003...........................  Comparison of nasal cytological   The exposed group was found to
                                                examinations of 136 customs       have chronic inflammatory
                                                officers involved solely in       changes of the nasal mucosa,
                                                clearance of heavy-goods          including goblet cell
                                                vehicles using diesel engines     hyperplasia, increased
                                                with examinations of 58           metaplastic and dysplastic
                                                officers working only in          epithelia, and increased
                                                offices. Examinations were        leukocytes while the unexposed
                                                performed twice a year over a     group did not.
                                                period of 5 years. Measured
                                                diesel engine emission
                                                concentrations for the exposed
                                                group varied between 31 and 60
                                                [mu]g/m\3\.
Hoppin et al., 2004..........................  An association between diesel     Driving diesel tractors was
                                                exhaust exposure and              significantly associated with
                                                development of asthma is          elevated odds of wheeze (odds
                                                explored. The study evaluated     ratio = 1.31; 95% confidence
                                                the odds of wheeze associated     interval = 1.13, 1.52). The
                                                with nonpesticide occupational    odds ratio for driving
                                                exposures in a cohort of          gasoline tractors was lower
                                                approximately 21,000 farmers in   but significant at 1.11 (95%
                                                Iowa and North Carolina.          confidence interval = 1.02,
                                                Logistic regression models        1.21). A duration-response
                                                controlling for age, state,       relationship was observed for
                                                smoking, and history of asthma    driving diesel tractors but
                                                or atopy were applied to          not for driving gasoline
                                                evaluate odds of wheeze in the    tractors.
                                                past year.
Pourazar et al., 2004........................  15 healthy volunteers were        This level of diesel exposure
                                                exposed to diesel exhaust or      caused a significant increase
                                                air for 1 hour. Diesel            in expression of the cytokine
                                                concentration was measured as     interleukin-13 in the airways
                                                PM10 at 300 [mu]g/m\3\).          of these volunteers.
                                                                                  Interleukin-13 is known to
                                                                                  play a key role in the
                                                                                  pathogenesis of asthma.
Stenfors et al., 2004........................  25 healthy volunteers and 15      Diesel exhaust exposure was
                                                mild asthmatics were exposed to   documented to cause airways
                                                diesel exhaust or air alone for   inflammation in healthy
                                                two hours (diesel concentration   volunteers. Diesel exhaust
                                                measured as PM10 at 108 [mu]g/    exposure did not significantly
                                                m\3\). At six hours after         worsen existing airways
                                                exposure, subjects underwent      inflammation in the
                                                bronchoscopy with                 asthmatics, but did
                                                bronchoalveolar lavage and        significantly increase airways
                                                mucosal biopsies.                 expression of the important
                                                                                  allergy-associated cytokine,
                                                                                  interleukin-10.
----------------------------------------------------------------------------------------------------------------

Review Article on Respiratory and Immunological Effects Considered 
after the 2005 Final Rule

    There is a progressive accumulation of evidence showing the 
inflammatory and immunologic effects of diesel exhaust particulate 
exposure plays a role in the development of allergies and asthma. The 
2001 risk assessment and the update to the risk assessment describe in 
detail review articles addressing these effects. The most recent review 
by Riedl and Diaz-Sanchez (2005), summarized in Table IV-4, provides an 
overview of observational and experimental studies that link DPM and 
asthma.

[[Page 28930]]



                      Table IV-4.--Review Articles on Respiratory and Immunological Effects
----------------------------------------------------------------------------------------------------------------
                Authors, year                             Description                      Key results
----------------------------------------------------------------------------------------------------------------
Riedl and Diaz-Sanchez, 2005.................  Review of evidence-based studies  Intact DEP and extracts of DEP
                                                of the health effects of air      induce reactive oxygen species
                                                pollutants on asthma, focusing    production. DEP and
                                                on diesel exhaust particles       particulate matter induce
                                                (DEP).                            release of Granulocyte
                                                                                  Macrophage-Colony Stimulating
                                                                                  Factor and increase
                                                                                  intracellular peroxide
                                                                                  production.
                                                                                 The ultrafine particle fraction
                                                                                  of diesel exhaust might also
                                                                                  exert biologic effects
                                                                                  independent of chemical
                                                                                  composition through
                                                                                  penetration of cellular
                                                                                  components, such as
                                                                                  mitochondria.
----------------------------------------------------------------------------------------------------------------

    In its 2002 ``Health Assessment Document for Diesel Engine 
Exhaust,'' the Environmental Protection Agency (EPA) reached the 
following conclusion with respect to immunological effects of diesel 
exhaust:

    Recent human and animal studies show that acute DE [diesel 
exhaust] exposure episodes can exacerbate immunological reactions to 
other allergens or initiate a DE-specific allergenic reaction. The 
effects seem to be associated with both the organic and carbon core 
fraction of DPM. In human subjects, intranasal administration of DPM 
has resulted in measurable increases of IgE antibody production and 
increased nasal mRNA for some proinflammatory cytokines. These types 
of responses also are markers typical of asthma, though for DE, 
evidence has not been produced in humans that DE exposure results in 
asthma. The ability of DPM to act as an adjuvant to other allergens 
also has been demonstrated in human subjects. (EPA, 2002)

    Submissions to the rulemaking record since the 2005 final rule 
support our previous position that exposure to DPM is associated with 
the development of adverse respiratory and immunological effects.
(2) Cardiovascular and Cardiopulmonary Effects
    In the 2001 risk assessment, the evidence presented for DPM's 
adverse cardiovascular and cardiopulmonary effects relied on data from 
air pollution studies in the ambient air. This evidence identifies 
premature death from cardiovascular, cardiopulmonary, or respiratory 
causes as an endpoint significantly associated with exposures to fine 
particulates. The 2001 risk assessment found that ``[t]he mortality 
effects of acute exposures appear to be primarily attributable to 
combustion-related particles in PM2.5 [i.e., fine 
Particulate Matter] (such as DPM) * * *.''
    There are difficulties involved in utilizing the evidence from such 
studies in assessing risks to miners from occupational exposure to DPM. 
As noted in the 2001 risk assessment,

    First, although DPM is a fine particulate, ambient air also 
contains fine particulates other than DPM. Therefore, health effects 
associated with exposures to fine particulate matter in air 
pollution studies are not associated specifically with exposures to 
DPM or any other one kind of fine particulate matter. Second, 
observations of adverse health effects in segments of the general 
population do not necessarily apply to the population of miners. 
Since, due to age and selection factors, the health of miners 
differs from that of the public as a whole, it is possible that fine 
particles might not affect miners, as a group, to the same degree as 
the general population (66 FR 5767).

However,

    Since DPM is a type of respirable particle, information about 
health effects associated with exposures to respirable particles, 
and especially to fine particulate matter, is certainly relevant, 
even if difficult to apply directly to DPM exposures (66 FR 5767).

    One new study on cardiovascular and cardiopulmonary effects was 
added to the record. See Toxicological Effects in this section for a 
summary of this article.
    The EPA concluded in its 2002 Health Assessment Document for Diesel 
Engine Exhaust that diesel exhaust (as measured by DPM) is ``likely to 
be a human carcinogen.'' Furthermore, the assessment concluded that 
``[s]trong evidence exists for a causal relationship between risk for 
lung cancer and occupational exposure to D[iesel]E[xhaust] in certain 
occupational workers'' (Health Assessment Document for Diesel Engine 
Exhaust, EPA, 2002, Sec. 9, p. 20). The EPA's 2004 Air Quality Criteria 
Document for particulate matter (EPA, 2004b) describes a number of 
additional studies related to the cardiopulmonary and cardiovascular 
effects of PM2.5, including work published later than that 
cited in MSHA's 2003 NPRM (68 FR 48668). One of the summary conclusions 
presented in that document is:

    Overall, there is strong epidemiological evidence linking (a) 
short-term (hours, days) exposures to PM2.5 with 
cardiovascular and respiratory mortality and morbidity, and (b) 
long-term (years, decades) PM2.5 exposure with 
cardiovascular and lung cancer mortality and respiratory morbidity. 
The associations between PM2.5 and these various health 
endpoints are positive and often statistically significant. [EPA, 
2004b, Sec. 9 p. 46]

    Submissions to the rulemaking record since the 2001 final rule 
support our previous position that exposure to DPM is associated with 
the development of adverse cardiovascular and cardiopulmonary effects.
(3) Cancer Effects
    The 2001 risk assessment concluded that DPM exposure, at 
occupational levels encountered in mining, was likely to increase the 
risk of lung cancer. The assessment also found that there was 
insufficient evidence to establish a causal relationship between DPM 
and other forms of cancer. This update contains a description of three 
human research studies and a literature review relating DPM and/or 
other fine particulate exposures to lung cancer.

Lung Cancer

    Table IV-5 presents three human studies pertaining to the 
association between lung cancer and exposures to DPM or fine 
particulates submitted to the record after the 2005 update of the 2001 
risk assessment was done.

[[Page 28931]]



                                   Table IV-5.--Studies on Lung Cancer Effects
----------------------------------------------------------------------------------------------------------------
                Authors, year                             Description                      Key results
----------------------------------------------------------------------------------------------------------------
Garshick et al., 2004........................  An evaluation of lung cancer      Railroad workers in jobs
                                                mortality in 54,793 railroad      associated with operating
                                                workers ages 40-64 with 10-20     trains had a relative risk of
                                                years of service in 1959. Based   lung cancer mortality of 1.4
                                                on evaluation of death            (95% confidence limits = 1.30-
                                                certificates, subsequent          1.51). The authors did not
                                                mortality was assessed through    think this association was due
                                                1996. Diesel-exposed workers      to uncontrolled confounding.
                                                such as engineers and             No relationship was found
                                                conductors were compared to a     between years of exposure and
                                                referent group of less exposed    lung cancer risk. The authors
                                                workers such as ticket agents,    discussed the potential for
                                                station agents, signal-           this to be due to factors such
                                                maintainers, and clerks.          as a healthy worker survivor
                                                                                  effect, lack of information on
                                                                                  historical changes in
                                                                                  exposure, and the potential
                                                                                  contribution of coal
                                                                                  combustion product before the
                                                                                  transition to diesel
                                                                                  locomotives.
Guo et al., 2004.............................  Evaluation of lung cancer         After controlling for other
                                                mortality in all working Finns    exposures such as asbestos and
                                                born between 1906 and 1945 and    quartz dust, only a slight
                                                participating in the national     excess of lung cancer was
                                                census of December 1970. Based    found in men aged 20-59
                                                on the reported occupation held   associated with diesel exhaust
                                                for longest time and a national   exposure. A parallel, but
                                                database of exposures for         weaker, association was
                                                various occupations, a variety    documented in women. The
                                                of exposures including diesel     authors concluded that risk
                                                exhaust were estimated.           associated with diesel exhaust
                                                Information about subsequent      ``was not consistently
                                                diagnosis of lung cancer during   elevated'' and speculated that
                                                the period 1971 to 1995 was       this was the result of factors
                                                obtained from the Finnish         such as low exposures or
                                                Cancer Registry.                  confounding from unmeasured
                                                                                  non occupational exposures.
Jarvholm et al., 2003........................  Mortality study of Swedish        Truck drivers had significantly
                                                construction workers.             increased risk for cancer of
                                                Information about occupation      the lung, while heavy
                                                and smoking was taken from        construction vehicle operators
                                                computerized health records       did not. In heavy construction
                                                available for the period 1971-    operators, a significant trend
                                                1992. Workers in two              of decreased risk for lung
                                                occupations exposed to diesel     cancer was associated with
                                                exhaust, 6,364 truck drivers      increasing use of vehicle
                                                and 14,364 drivers of heavy       cabins. The authors explained
                                                construction vehicles were        that there was a difference
                                                compared to a reference group     between truck and heavy
                                                of 119,984 carpenters and         equipment operators, but no
                                                electricians.                     conclusion could be reached
                                                                                  without more detailed
                                                                                  information about the duration
                                                                                  and concentration of diesel
                                                                                  exhaust exposures and smoking
                                                                                  habits.
----------------------------------------------------------------------------------------------------------------

A Cohort Mortality Study With a Nested Case-Control Study of Lung 
Cancer and Diesel Exhaust Among Nonmetal Miners [NIOSH/NCI 1997]

    A number of commenters expressed opinions on the unpublished 
document authored by Dr. Gerald Chase (2004) entitled Characterizations 
of Lung Cancer in Cohort Studies and a NIOSH Study on Health Effects of 
Diesel Exhaust in Miners. This document presents an analysis of some 
very preliminary data provided by NIOSH and the National Cancer 
Institute at a public stakeholder meeting held on Nov. 5, 2003. These 
data were taken from unpublished charts that NIOSH and NCI used to 
inform the public of the status and progress of their ongoing project, 
A Cohort Mortality Study with a Nested Case-Control Study of Lung 
Cancer and Diesel Exhaust Among Nonmetal Miners (NIOSH/NCI Study 1997). 
We previously addressed Dr. Chase's analysis in our 2005 final rule (70 
FR 32906). NIOSH and NCI researchers involved in that project have not 
yet published their analyses or conclusions based on these data. When 
the study is concluded, we will assess the results and their 
association to our updated 2001 risk assessment findings. Therefore, 
the Agency believes that the opinions expressed by commenters on Dr. 
Chase's unpublished analysis of preliminary data are inappropriate for 
identifying or assessing the relationship between occupational DPM 
exposure and excess lung cancer mortality in that data set.

Bladder Cancer and Pancreatic Cancer

    No additional information was submitted to the rulemaking record 
that would change our position that bladder cancer is associated with 
exposure to DPM. The Agency has not received additional information 
that would change our position that there is insufficient evidence to 
support a link between exposure to DPM and pancreatic cancer.
(4) Toxicological Effects of DPM Exposure
    Table IV-6 presents one new particulate matter toxicity study (Sun 
et al., 2005) obtained since the 2005 final rule. The table identifies 
the agent(s) of toxicity investigated and indicates how the results 
support the risk assessment by categorizing the toxic effects and/or 
markers of toxicity found in each study.

[[Page 28932]]



                                               Table IV-6.--Study On Toxicological Effects of DPM Exposure
--------------------------------------------------------------------------------------------------------------------------------------------------------
           Authors, year                   Description             Key results        Agent(s) of toxicity    Toxic  effect(s)*         Limitations
--------------------------------------------------------------------------------------------------------------------------------------------------------
Sun et al., 2005...................  Assessment of effects   Long-term exposure to   Concentrated PM2.5     Inflammation, Adverse  Exposure not specific
                                      of subchronic           low concentration of    from northeastern      cardiovascular         to DPM.
                                      exposure to             PM2.5 altered           regional background    effects.
                                      environmentally         vasomotor tone,         particulate.
                                      relevant particulate    induced vascular
                                      matter on               inflammation, and
                                      atherosclerosis and     potentiated
                                      vasomotor tone in a     atherosclerosis.
                                      mouse disease model.
--------------------------------------------------------------------------------------------------------------------------------------------------------

    No new review articles on various aspects of the scientific 
literature related to mechanisms of DPM toxicity were submitted to the 
record since the 2005 final rule. In summary, the peer-reviewed 
publications submitted to the rulemaking record addressing the health 
effects of exposure to diesel exhaust support our 2001 risk assessment 
(66 FR 5526; 30 CFR Part 2005) and nothing in our review suggests that 
it should be altered.

D. Significance of Risk

Adverse Health Effects
    The first principal conclusion of the 2001 risk assessment was:

    Exposure to DPM can materially impair miner health or functional 
capacity. These material impairments include acute sensory 
irritations and respiratory symptoms (including allergenic 
responses); premature death from cardiovascular, cardiopulmonary, or 
respiratory causes; and lung cancer (66 FR 5854).

    We agree with commenters who characterized the weight of evidence 
from the most recent scientific literature and the comprehensive 
scientific literature reviews carried out by other institutions and 
government agencies as supporting and potentially strengthening this 
conclusion.
    In 2002, for example, the U.S. EPA, with the concurrence of its 
Clean Air Scientific Advisory Committee (CASAC), published its Health 
Assessment Document for Diesel Engine Exhaust (EPA, 2002). With respect 
to sensory irritations, respiratory symptoms, and immunological 
effects, this document concluded that:

    At relatively high acute exposures, DE [diesel exhaust] can 
cause acute irritation to the eye and upper respiratory airways and 
symptoms of respiratory irritation which may be temporarily 
debilitating. Evidence also shows that DE has immunological toxicity 
that can induce allergic responses (some of which are also typical 
of asthma) and/or exacerbate existing respiratory allergies. [EPA, 
2002]

    In 2003, the World Health Organization (WHO) issued a review report 
on particulate matter air pollution and health. WHO concluded that 
``fine particles (commonly measured as PM2.5) are strongly 
associated with mortality and other endpoints such as hospitalization 
for cardiopulmonary disease, so that it is recommended that air quality 
guidelines for PM2.5 be further developed.'' (WHO, 2003)
    In the 10th edition of its Report on Carcinogens, the National 
Toxicology Program (NTP) of the National Institutes of Health formally 
retained its designation of diesel exhaust particulates as ``reasonably 
anticipated to be a human carcinogen.'' (U.S. Dept. of Health and Human 
Services, 2002) The report noted that:

    Diesel exhaust contains identified mutagens and carcinogens both 
in the vapor phase and associated with respirable particles. Diesel 
exhaust particles are considered likely to account for the human 
lung cancer findings because they are almost all of a size small 
enough to penetrate to the alveolar region.
    * * * Because of their high surface area, diesel exhaust 
particulates are capable of adsorbing relatively large amounts of 
organic material * * * A variety of mutagens and carcinogens such as 
PAH and nitro-PAH * * * are adsorbed by the particulates. There is 
sufficient evidence for the carcinogenicity for 15 PAHs (a number of 
these PAHs are found in diesel exhaust particulate emissions) in 
experimental animals. The nitroarenes (five listed) meet the 
established criteria for listing as ``reasonably anticipated to be a 
human carcinogen'' based on carcinogenicity experiments with 
laboratory animals. [U.S. Dept. of Health and Human Services, 2002]

    Although many commenters agreed that the adverse health effects 
associated with miners' exposure to DPM warranted an exposure limit, 
commenters from trade associations and industry continued to challenge 
the conclusions of the 2001 risk assessment. Discussions addressing 
this issue were summarized in the 2001 risk assessment and the 2005 
update. As referenced in this section, the U.S. Environmental 
Protection Agency, World Health Organization, and the National 
Toxicology Program regard DPM exposure as adversely affecting human 
health.

Statement of Excess Lung Cancer Risk

    In our 2001 risk assessment, we explained why we focused our 
quantification of health effects on lung cancer only. We estimated 
lower bounds on the significance of risks faced by miners 
occupationally exposed to DPM with respect to (1) acute sensory 
irritations and respiratory symptoms or (2) premature death from 
cardiovascular, cardiopulmonary, or respiratory causes. We expect the 
final rule to significantly and substantially reduce these two kinds of 
risk as well as (3) lung cancer. However, we were unable, based on 
available data, to quantify with confidence the reductions expected for 
the first two kinds and are still unable to do so. Therefore, MSHA's 
quantitative assessment of the rule's impact on risk is restricted to 
its expected impact on the third kind of risk--the risk of lung cancer 
(66 FR 5854).
    In the 2001 risk assessment, MSHA assumed that, in the absence of 
this rule, underground M/NM miners would be occupationally exposed to 
DPM for 45 years at a mean level of 808 [mu]g/m3, and 
estimated reductions in lifetime risk expected to result from full 
implementation of the rule, based on the various exposure-response 
relationships obtained from Saverin et al. (1999), Steenland et al. 
(1998), and Johnston et al. (1997).
    Miner's exposures to DPM levels have declined since 1989-1999. We 
expect that further improvements will continue to significantly reduce 
the health risks identified for miners. There is clear evidence of 
adverse health effects due to exposure to DPM in the rulemaking record, 
not only at pre-2001 exposure levels but also at the generally lower 
levels currently observed at many underground mines. The adverse health

[[Page 28933]]

effects associated with exposure to DPM are material health impairments 
as specified under section 101(a)(6)(A) of the Mine Act.
    Because the exposure-response relationships used in the risk 
assessment are monotonic, we expect that industry-wide implementation 
of each final limit will significantly reduce the risk of lung cancer 
and other adverse health effects among miners. The 2001 risk assessment 
used the best available data on DPM exposures at underground M/NM mines 
to quantify excess lung cancer risk. ``Excess risk'' refers to the 
lifetime probability of dying from lung cancer during or after a 45 
year occupational DPM exposure. This probability is expressed as the 
expected excess number of lung cancer deaths per thousand miners 
occupationally exposed to DPM at a specified mean DPM concentration. 
The excess is calculated relative to baseline, age-specific lung cancer 
mortality rates taken from standard mortality tables. In order to 
properly estimate this excess, it is necessary to calculate, at each 
year of life after occupational exposure begins, the expected number of 
persons surviving to that age with and without DPM exposure at the 
specified level. At each age, standard actuarial adjustments must be 
made in the number of survivors to account for the risk of dying from 
causes other than lung cancer. Occupational exposure is assumed to 
begin at age 20 and to continue, for surviving miners, until retirement 
at age 65. The accumulation of lifetime excess risk continues after 
retirement through the age of 85 years.
    Table IV-7, taken from the 2001 risk assessment, shows excess lung 
cancer estimates at mean exposures equal to the final limit equivalent 
to 200 micrograms of DPM per cubic meter of air for eight hour shift 
weighted average. The eight exposure-response models for lung cancer 
used in the 2001 risk assessment were based on studies by Saverin et 
al. (1999), Johnston et al. (1997), and Steenland et al. (1998). 
Assuming that TC is 80 percent of whole DPM, and that the mean ratio of 
TC to EC is 1.3, the DPM limit of 200 [mu]g/m3 shown in 
Table IV-7 corresponds to the 160 [mu]g/m3 TC limit adopted 
under the present rulemaking.

 Table IV-7.--Excess Lung Cancer Risk Expected at Specified DPM Exposure
                  Levels Over an Occupational Lifetime
        [Extracted from Table III-7 of the 2001 risk assessment]
------------------------------------------------------------------------
                                                          Excess lung
                                                         cancer deaths
                                                           per 1,000
                                                         occupationally
             Study and statistical model                    exposed
                                                        workers[dagger]
                                                        Final DPM Limit
                                                          200 [mu]g/m3
                                                       (160 [mu]g/m3 TC)
------------------------------------------------------------------------
Saverin et al. (1999):
    Poisson, full cohort.............................                 15
    Cox, full cohort.................................                 70
    Poisson, subcohort...............................                 93
    Cox, subcohort...................................                182
Steenland et al. (1998):
    5-year lag, log of cumulative exposure...........                 67
    5-year lag, simple cumulative exposure...........                159
Johnston et al. (1997):
    15-year lag, mine-adjusted.......................                313
    15-year lag, mine-unadjusted.....................               513
------------------------------------------------------------------------
[dagger] Assumes 45-year occupational exposure at 1,920 hours per year
  from age 20 to retirement at age 65. Lifetime risk of lung cancer
  adjusted for competing risk of death from other causes and calculated
  through age 85. Baseline lung cancer and overall mortality rates from
  NCHS (1996).

    As explained in the 2005 final rule, the exposure-response models 
shown are monotonic (i.e., increased exposure yields increased excess 
risk, though not proportionately so). Therefore, using our estimates of 
mean exposure levels, they all predict excess lung cancer risks 
somewhere above the final whole DPM limit of 200 [mu]g/m3, 
or equivalently, 160TC [mu]g/m3. Thus, despite 
substantial improvements apparently attained since the 1989-1999 
sampling period addressed by the 2001 risk assessment, underground M/NM 
miners are still faced with an unacceptable risk of lung cancer due to 
their occupational exposure to DPM.

V. Feasibility

    Section 101(a)(6)(A) of the Mine Act requires the Secretary of 
Labor, in establishing health standards, to most adequately assure, on 
the basis of the best available evidence, that no miner will suffer 
material impairment of health or functional capacity over his or her 
working life. Standards promulgated under this section must be based 
upon research, demonstrations, experiments, and such other information 
as may be appropriate. MSHA, in setting health standards, is required 
to achieve the highest degree of health and safety protection for the 
miner, and as stated in the legislative history of the Mine Act, MSHA 
must consider the latest available scientific data in the field, the 
feasibility of the standards, and experience gained under this or other 
health and safety laws.
    Though the Mine Act and its legislative history are not specific in 
defining feasibility, the Supreme Court has clarified the meaning of 
feasibility in the context of OSHA health standards in American Textile 
Manufacturers' Institute v. Donovan (OSHA Cotton Dust), 452 U.S. 490, 
508-09 (1981), as ``capable of being done, executed, or effected,'' 
both technologically and economically.
    The legislative history to the Mine Act indicates Congress' intent 
for MSHA when considering feasibility and states:

    While feasibility of the standard may be taken into 
consideration with respect to engineering controls, this factor 
should have a substantially less significant role. Thus, the

[[Page 28934]]

Secretary may appropriately consider the state of the engineering 
art in industry at the time the standard is promulgated. However, as 
the circuit courts of appeals have recognized, occupational safety 
and health statutes should be viewed as ``technology forcing'' 
legislation, and a proposed health standard should not be rejected 
as infeasible ``when the necessary technology looms on today's 
horizon''. AFL-CIO v. Brennan, 530 F.2d 109 (3d Cir. 1975); Society 
of Plastics Industry v. OSHA, 509 F.2d 1301 (2d Cir. 1975), cert. 
denied 427 U.S. 992 (1975).
    Similarly, information on the economic impact of a health 
standard, which is provided to the Secretary of Labor at a [public] 
hearing or during the public comment period, may be given weight by 
the Secretary. In adopting the language of [this section], the 
Committee wishes to emphasize that it rejects the view that cost 
benefit ratios alone may be the basis for depriving miners of the 
health protection which the law was intended to insure. The 
Committee concurs with the judicial constitution that standards may 
be economically feasible even though from the standpoint of 
employers, they are ``financially burdensome and affect profit 
margins adversely'' (I.U.D. v. Hodgson, 499 F.2d 6a47 (D.C. Cir. 
1974)). Where substantial financial outlays are needed in order to 
allow industry to reach the permissible limits necessary to protect 
miners, other regulatory strategies are available to accommodate 
economic feasibility and health considerations. These strategies 
could include delaying implementation of certain provisions or 
requirements of standards in order to allow sufficient time for 
engineering controls to be put in place or a delay in the effective 
date of the standard. S. Rep. No. 95-181, 95th Cong. 1st Sess. 21 
(1977).

    The ``arbitrary and capricious test'' is usually applied to 
judicial review of rules issued in accordance with the Administrative 
Procedure Act. The legislative history of the Mine Act further 
indicates that Congress explicitly intended the ``arbitrary and 
capricious test'' be applied to judicial review of mandatory MSHA 
standards. ``This test would require the reviewing court to scrutinize 
the Secretary's action to determine whether it was rational in light of 
the evidence before him and reasonably related to the law's purposes.'' 
S. Rep. No. 95-181, 95th Cong., 1st Sess. 21 (1977). In achieving the 
Congressional intent of feasibility under the Mine Act, MSHA may also 
consider reasonable time periods of implementation. Ibid. at 21.
    In order to establish the economic and technological feasibility of 
a new rule, an agency is required to produce a reasonable assessment of 
the likely range of costs that a new standard will have on an industry, 
and an agency must show that a reasonable probability exists that the 
typical firm in an industry will be able to develop and install 
controls that will meet the standard. United Steelworkers of America, 
AFL-CIO-CLC v. Marshall, (OSHA Lead) 647 F.2d 1189, 1273 (D.C. Cir. 
1980).
    Like, the Mine Act, the OSH Act contains the term ``technology-
forcing'' with respect to standards setting. The D.C. Circuit Court 
also determined with respect to technological feasibility under the OSH 
Act that:

    * * * ``technology-forcing'' under the OSH Act, means, at the 
very least, that OSHA can impose a standard which only the most 
technologically advanced plants in an industry have been able to 
achieve-even if only in some of their operations some of the time. 
American Iron & Steel Institute v. OSHA, supra, 577 F.2d at 832-835.
    Since ``technology-forcing'' assumes that ``an agency will make 
highly speculative projections about future technology, a standard 
is obviously not infeasible solely because OSHA has no hard evidence 
to show that the standard has been met. More to the point here, we 
cannot require OSHA to prove with any certainty that industry will 
be able to develop the necessary technology, or even to identify the 
single technological means by which it expects industry to meet the 
PEL. OSHA can force employers to invest all reasonable faith in 
their own capacity for technological innovation. Society of Plastics 
Industries, Inc. v. OSHA, supra 509 F.2d at 1309, and can thereby 
shift to industry some of the burden of choosing the best strategy 
for compliance. United Steelworkers of America, 647 F.2d at 1266.

    This same court found that proving economic feasibility presented 
different issues from that of technological feasibility, where it 
stated:

    But when the agency has proved technological feasibility by 
making reasonable predictions about experimental means of 
compliance, the court probably cannot expect hard and precise 
estimates of costs. Nevertheless, the agency must of course provide 
a reasonable assessment of the likely range of costs of its 
standard, and the likely effects of those costs on the industry. 
Ibid. at 1266.

A. Technological Feasibility

    Courts have ruled that in order for a standard to be 
technologically feasible an agency must show that modern technology has 
at least conceived some industrial strategies or devices that are 
likely to be capable of meeting the standard, and which industry is 
generally capable of adopting. Ibid. (citing American Iron and Steel 
Institute v. OSHA, (AISI-I) 577 F.2d 825 (3d Cir. 1978) at 832-35; and, 
Industrial Union Dep't., AFL-CIO v. Hodgson, 499 F.2d 467 (DC 
Cir.1974)); American Iron and Steel Institute v. OSHA, (AISI-II) 939 
F.2d 975, 980 (DC Cir. 1991). A control may be technologically feasible 
when ``if through reasonable application of existing products, devices 
or work methods with human skills and abilities, a workable engineering 
control can be applied'' to the source of the hazard. It need not be an 
``off-the-shelf'' product, but ``it must have a realistic basis in 
present technical capabilities.'' (Secretary of Labor v. Callanan 
Industries, Inc. (Noise), 5 FMSHRC 1900, 1908 (1983)). The Secretary 
may also impose a standard that requires protective equipment, such as 
respirators, if technology does not exist to lower exposures to safe 
levels. See United Steelworkers of America, 647 F.2d at 1269.
    We have established that it is technologically feasible for the 
underground M/NM mining industry to reduce miners' exposures to the DPM 
final limits as prescribed in the final rule. Unlike the 2005 NPRM, we 
are phasing in the final limit of 160 Total Carbon micrograms per cubic 
meter of air (160TC [mu]g/m\3\) over a two-year period, due 
to the updated feasibility information in the rulemaking record. This 
updated feasibility information relates primarily to the wider 
availability of alternative fuels, and in particular biodiesel, 
improved filter technology, and the impending availability of EPA 
compliant 2007 on-road diesel engines. Consequently, on May 20, 2006, 
the initial final limit will be 308 micrograms of EC per cubic meter of 
air (308EC [mu]g/m\3\), which is the same as the existing 
interim limit; on January 20, 2007, the final limit will be reduced by 
50 micrograms and will be a TC limit of 350TC [mu]g/m\3\; 
and on May 20, 2008, the final limit of 160TC [mu]g/m\3\ 
will become effective. Note that the 350TC [mu]g/m\3\ final 
limit and the 160TC [mu]g/m\3\ final limit are established 
as TC-based limits in this final rule. It is our intention to convert 
these TC limits to comparable EC limits; however, developing 
appropriate conversion factors for these limits was beyond the scope of 
the current rulemaking. These TC limits will be converted to comparable 
EC limits through a separate rulemaking.
    To meet the final DPM limits, mine operators will be able to 
continue to use existing available engineering control technology and 
various administrative control methods used in meeting the interim DPM 
limit. However, we are affording the mining industry the additional 
time from that provided under the 2001 final rule to work through their 
remaining implementation issues with DPM control technology and to gain 
access to alternative fuels and DPFs. The additional time will also 
allow mine operators, especially small mine operators, time to find 
effective approaches to utilizing available DPM

[[Page 28935]]

control technology so that they will be capable of meeting the 
standard. Altogether, the mining industry will have been afforded over 
seven years to institute control technology to reduce miners' exposures 
to the final DPM limit of 160TC [mu]g/m\3\. Our decisions in 
the final rule are based on our enforcement experience, along with 
information and data in the updated DPM rulemaking record, which 
includes the 2001 and 2005 DPM rulemaking records. The final rulemaking 
record lacks feasibility documentation to justify lowering the final 
DPM limit to 160TC [mu]g/m\3\ at this time.
    The existing requirement for methods of compliance will continue to 
be applicable to the final limits. To attain the final limits, mine 
operators are required to install, use, and maintain engineering and 
administrative controls to the extent feasible. When engineering and 
administrative controls do not reduce a miner's exposure to the DPM 
limit, the controls are infeasible, or controls do not produce 
significant reductions (defined in the 2005 rule (70 FR 32868, 32916) 
as at least 25% reduction in the affected miners' DPM exposures), 
operators must continue to use all feasible engineering and 
administrative controls and supplement them with respiratory 
protection. Though mine operators may choose to use an engineering 
control or an administrative control to reduce a miner's exposure, or a 
combination thereof, existing Sec.  57.5060(d) prohibits a mine 
operator from using respiratory protection in lieu of feasible 
controls. When respiratory protection is required under the final 
standard, mine operators must establish a respiratory protection 
program that meets the specified requirements under existing Sec.  
57.5060(d) of the DPM standard.
    MSHA emphasizes that DPM engineering and administrative controls 
may be feasible, and therefore be required by MSHA, even if controls do 
not reduce a miner's exposure to the DPM limit.
    Under this rule, MSHA intends that feasible DPM controls must be 
capable of achieving a significant reduction in DPM. We also note that 
most of the practical and effective controls that are currently 
available, such as DPM filters, enclosed cabs with filtered breathing 
air, and low-emission engines will achieve at least a 25% reduction. 
Other controls such as ventilation upgrades or alternative fuel blends 
may achieve a 25% reduction, depending on exposure circumstances and 
the specific nature of the subject control. It should also be noted 
that reductions of less than 25% could be due to normal day-to-day 
variations in mining operations as opposed to reductions due to 
implementing a control technology. Thus, for mines that are out of 
compliance with the DPM final limits, controls would be required that 
attain compliance, or that achieve at least a 25% reduction in DPM 
exposure if it is not possible to attain compliance by implementing 
feasible controls. If engineering and administrative controls are not 
capable of reducing exposure to the limits in this final rule, and 
cannot reduce DPM exposures by at least 25%, we would not require the 
implementation of those controls. In such cases, we will require miners 
to be protected using appropriate respiratory protective equipment.
    If a particular DPM control were capable of achieving at least a 
25% reduction all by itself, we would continue to evaluate the costs of 
that individual control to determine its economic feasibility. If a 
number of controls could together achieve at least a 25% reduction, but 
no individual control, if implemented by itself, could achieve a 25% 
reduction, we will evaluate the total costs of all controls added 
together to determine their economic feasibility as a group. In 
determining whether a combination of controls is economically feasible, 
we will consider whether the total cost of the combination of controls 
is wholly out of proportion to the expected results. We will not cost 
the controls individually, but will combine their expected results to 
determine if the 25% significant reduction criterion can be satisfied. 
The concept of significant reduction is not new to the M/NM mining 
industry. MSHA's 2005 Compliance Guide includes the 25% significant 
reduction for determining feasibility.
    At this time, we believe that this compliance approach coupled with 
the phased-in final limits provides mine operators with flexibility 
necessary to assure feasible compliance. This current enforcement 
approach results in feasibility of compliance for the industry as a 
whole with each of the phased-in limits contained in this final rule 
while protecting miners' health. However, we continue to acknowledge 
that compliance difficulties may be encountered at some individual 
mines, but on a much smaller scale than what we project if the final 
limit of 160TC [mu]g/m\3\ became effective in May 2006. This 
primarily will be due to implementation issues and the cost of 
purchasing and installing certain types of controls at these mines.
    Moreover, pursuant to existing Sec.  57.5060(c), mine operators can 
apply to the District Manager for a special extension for additional 
time in which to meet the final limits, including the initial final 
limit of 308EC [mu]g/m\3\. Although we anticipate that 
special extensions and our traditional hierarchy of controls in 
enforcement will address some compliance issues, we envision that some 
miners will have to wear respiratory protection under the final limit 
of 160TC [mu]g/m\3\.
    Based upon a review of enforcement data, we believe that a large 
portion of the mining industry will initially encounter implementation 
issues as they attempt to attain compliance with the final limits using 
engineering and administrative controls. However, we believe that most 
mine operators will be able to overcome these issues within the two-
year period during which the final limits will be phased-in. For 
example, the wider use of high biodiesel content fuel blends, which can 
reduce DPM emissions by up to 80% or more, will be greatly facilitated 
by the significant increases in biodiesel fuel production that will 
occur in the United States over the next two years. The National 
Biodiesel Board reports that annual biodiesel production rose from 25 
million gallons in 2004 to 75 million gallons in 2005. They also report 
that biodiesel plants that are either under construction at the present 
time or in the pre-construction phase will add another 847 million 
gallons of annual production capacity. A large portion of this added 
capacity will be on-line by 2008.
    Another example of a recent development that will help enable mine 
operators attain our final DPM limit of 160TC [mu]g/m\3\ by 
May 2008 is the impending availability of U.S. EPA 2007 on-road diesel 
engines. U.S. EPA 2007 on-road diesel engine standards have DPM 
emission limits that are about 90% lower than the current EPA limits 
allow. The DPM reduction will be attained through the use of DPFs. The 
DPFs will be part of the engine and vehicle when sold. For example, a 
new 2007 on-road pickup truck will have a DPF installed on the vehicle 
at the time of purchase. The 2007 on-road engines will be commercially 
available starting in early 2007.
    In addition to the EPA 2007 on-road DPM standards, EPA also has new 
Tier 4 off-road standards that will reduce DPM about 90%. Tier 4 will 
be phased-in beginning in 2008. Similar to the 2007 on-road engines, a 
DPF will be installed on the engine and vehicle when purchased. Even 
though the EPA implementation dates of Tier 4 is after the date of the 
final limit, the DPF technology is being developed at this

[[Page 28936]]

time by the engine and filter manufacturers in order to be ready for 
the tier 4 standards. This current work will enhance the developments 
and availability of DPF systems that can be retrofitted to mining 
vehicles.
    Although the emission limits for 2007 on-road engines were 
established some time ago, we had very little insight as to the 
strategies and technologies that the engine manufacturers would use to 
meet these limits. For competitive reasons, the engine manufacturers 
did not publicize their strategies or designs for complying with these 
EPA regulations. We were therefore uncertain as to whether any 2007 on-
road compliant engines would be compatible with typical underground M/
NM mine operational and production requirements, duty cycles, and 
maintenance practices, and thus, whether they could be readily used or 
adapted for use in underground M/NM mines.
    With the first 2007 on-road engines scheduled for release in early 
2007, however, we now have a much clearer picture of the technologies 
that will be incorporated into these engines. The predominant 
technology will be DPM filters which incorporate some form of active 
regeneration to accommodate any duty cycle, ranging from constant high-
speed over-the-road trucks to light duty delivery vehicles and pickup 
trucks and SUVs in stop-and-go traffic conditions. As noted later in 
this section of the preamble, we are confident that such filter 
technology is suitable for application in underground M/NM mines. 
Therefore, we expect appropriate 2007 on-road engines to be readily 
usable or adaptable for use in underground M/NM mining equipment. These 
engines will begin to become available in early 2007, with more and 
varied models becoming available in subsequent months and years.
    In the future, we project that the number of miners who will need 
to wear respiratory protection will decrease as mine operators learn 
more about effectively selecting, retrofitting, and maintaining DPFs, 
as they begin to use EPA compliant 2007 on-road engines with integral 
DPFs, and as mine operators in remote locations are able to gain easier 
access to alternative fuels, primarily biodiesel.
1. MSHA's 2001 Assumptions Regarding Compliance With the Final 
Concentration Limit
    We stated in the proposed rule that the assumptions that we used in 
2001 in support of our cost estimates included:
    (a) Fifty percent of the fleet will have new engines (these new 
engines do not impact cost of the rule) * * * Moreover, due to EPA 
[Environmental Protection Agency] regulations, which will limit DPM 
emissions from engines used in surface construction, surface mining, 
and over-the-road trucks (the major markets for heavy duty diesel 
engines), the market for low tech ``dirtier'' engines will dry up * * 
*; (b) one hundred percent of the production equipment and about fifty 
percent of the support equipment will be equipped with filters; (c) 
about thirty percent of all equipment will need to be equipped with 
environmentally controlled cabs; (d) twenty three percent of the mines 
would need new ventilation systems (fans and motors); (e) forty percent 
of the mines will need new motors on these fans; and (f) thirty two 
percent of the mines will need major ventilation upgrades (66 FR 5889-
90).
    Furthermore, we concluded that it would not be feasible to require 
the metal and nonmetal sector, as a whole, to lower DPM concentrations 
further, or to implement the required controls more swiftly (66 FR 
5888).
2. Reasons Why the 2001 Assumptions Were Questioned
    Over the five years since the 2001 final rule was promulgated, both 
MSHA and the mining industry have gained considerable experience with 
the implementation, use, and cost of DPM control technology. We have 
reviewed this experience, and our own enforcement data, and other 
relevant information, and conclude that effective DPM controls 
sufficient to attain compliance with the DPM limits specified in this 
final rule will be feasible and commercially available to mine 
operators by May 2008. For example, in addition to currently available 
DPM controls such as environmental cabs with filtered breathing air, a 
variety of DPF systems, low-emission engines, upgraded ventilation, and 
alternative fuels, by May 2008, we believe mine operators will benefit 
from wider availability of alternative fuels, particularly biodiesel, 
improved filter technology, and the availability of EPA compliant 2007 
on-road diesel engines and diesel powered equipment. As implementation 
issues are resolved, the most successful implementation strategies will 
be adopted by other mine operators, thereby speeding up compliance by 
the industry as a whole. For example, in 2004, we were aware of only 
one mine operator that was using a high biodiesel content fuel blend as 
a DPM compliance method. DPM levels measured in this mine were 
consistently greater than 200EC [mu]g/m3 prior to 
the change to biodiesel fuel, compared to levels less than 
100EC [mu]g/m3 after the change-over. In the most 
recent enforcement sampling at this mine, all samples were less than 
50EC [mu]g/m3. By late 2005, we were aware of at 
least four other mine operators that had learned from this experience 
and adopted this compliance strategy. Another example is the recently 
developed Diesel Particulate ReactorTM (described later in 
this section of the preamble). This new technology has been 
successfully implemented by a large nonmetal mine operator. Reactors 
are currently installed on about 80% of the mine's fleet of roughly 50 
pieces of diesel equipment with no installation, operation, or 
maintenance problems reported. These experiences demonstrate that even 
the more complex DPM control technologies can be successfully 
implemented by mine operators. As these successful experiences are 
shared throughout the mining industry, compliance by the underground M/
NM mining industry as a whole by May 2008 will be greatly facilitated. 
The extended time specified in this final rule is necessary to address 
the implementation issues that the industry as a whole must overcome. 
However, as noted above, we believe these issues can be resolved within 
the extended compliance timeframes established in the final rule.
    Several commenters quoted previous MSHA statements from the 
rulemaking record they believe support their position that the final 
DPM limit is technologically infeasible. A few quoted a passage from 
the 2005 final rule: ``MSHA acknowledges that the current DPM 
rulemaking record lacks sufficient feasibility documentation to justify 
lowering the DPM limit below 308EC [mu]g/m3 at 
this time'' (70 FR 32916). However, these commenters did not include 
the statements that followed, which explained that we believed it was 
feasible for the industry as a whole to fully comply with the interim 
limit, but that at that time--June of 2005--attaining levels lower than 
308EC [mu]g/m3 was not feasible for the entire 
industry. In our 2005 NPRM, we indicated that a DPM limit lower than 
308EC [mu]g/m3 should not become effective before 
January 2007, at the earliest, due to concerns about implementation 
difficulties. It was our intention that mine operators would use the 
period of nearly 20 months from June 2005 through January 2007 and the 
subsequent phased-in timeframes proposed in the NPRM to overcome 
implementation challenges and attain compliance with the reduced limit.

[[Page 28937]]

    Some commenters stated that any delay in the effective date for the 
final DPM limit was unjustified on either technological or economic 
grounds. A number of commenters said that our 2005 NPRM makes it clear 
that several technologies are available which, alone or in combination, 
would permit mines to meet the final limit. Doubts about whether all 
mines can do so in all operations, or doubts about whether current 
distribution networks for alternative fuels are as complete as may be 
necessary under the final rule, do not in these commenters' views 
detract from the conclusion that the final limit is feasible. According 
to these commenters, MSHA's search for certainty that all mines can 
comply at all times in all circumstances is a violation of its 
technology-forcing mandate. In response, the Mine Act does not mandate 
that MSHA standards must be technology-forcing.
    Another commenter stated that no technological reason exists for 
granting industry an additional five years, on top of the five years 
they have already had, to install existing technology to protect 
workers.
    Although technology currently exists for compliance with both the 
interim and final DPM limits, we conclude that implementation 
challenges and difficulties with this technology and the costs of 
implementing it in the M/NM mining industry affect feasibility. We have 
observed the difficult applications engineering challenges faced by a 
substantial number of mine operators in implementing these 
technologies. Consequently, these challenges have led us to determine 
that additional time is needed by the industry as a whole to feasibly 
meet the final limit.
    Another passage that several commenters in opposition to the 2005 
NPRM quoted, stated that:

    When we established the 2001 final limit, we were expecting some 
mine operators to encounter difficulties implementing control 
technology because the rule was technology forcing. We projected 
that by this time, practical and effective filter technology would 
be available that could be retrofitted onto most underground diesel 
powered equipment. However, as a result of our compliance assistance 
efforts and through our enforcement of the interim limit, we have 
become aware that this assumption may not be valid. The applications 
engineering and related technological implementation issues that we 
believed would have been easily solved by now are more complex and 
extensive than previously thought (70 FR 53283).

    Although we have evidence of successful applications of DPM 
controls in the rulemaking record and the proven effectiveness of 
various products, systems, and strategies for controlling DPM emissions 
and exposures, we believe that the implementation challenges presented 
by the industry warrant granting some additional time to attain full 
compliance with the final limit. We intend, however, for the mining 
industry to utilize this extra time to diligently move forward in 
achieving compliance with the final limits.
    Some commenters quoted the decision of Secretary of Labor v. 
Callanan Industries, Inc. (Noise), 5 FMSHRC 1900, 1908 (1983)), which 
addresses feasibility of an individual mine operator to comply with an 
MSHA exposure-based health standard. These commenters concluded that 
based on the current existence of alternative fuels and DPFs, that no 
delay in the final limit was justified. However, as noted above, based 
on present implementation issues, we have determined that additional 
time is needed by the mining industry, as a whole, to meet the final 
limits.
    Some other commenters stated that they do not believe there is a 
``realistic basis in present technical capabilities,'' [quoting 
Callanan]. These commenters believe that there is not an adequate array 
of mine worthy, technically feasible solutions that are readily 
available for implementation in underground metal and nonmetal mines. 
They believe that their conclusion is confirmed by MSHA's statement in 
the 2005 NPRM that, ``effective control technology that will reduce 
exposures to the final limit is speculative at this time'' (70 FR 
53285).
    We find these arguments made by some commenters not persuasive, 
because in the 2005 NPRM, we acknowledged that full compliance with the 
final DPM limit by the industry as a whole by the original effective 
date of January 2006 was unlikely to be feasible. Over the past five 
years, we have been working with all members of the M/NM mining 
community affected by this final rule. We believe that the industry has 
made tremendous progress and will continue to work through these 
feasibility challenges and that it will be feasible for the industry to 
comply by the dates established in this final rule.
    We continue to conclude, based on experience gained under the 
existing DPM rule, that the applications engineering required to adapt 
advanced DPM control devices and systems to new and existing mining 
equipment, to introduce alternative fuels, to train miners on their 
proper installation, operation, inspection, maintenance, and repair, 
and to integrate new methods and work practices into complex mining 
processes will take more time than we originally anticipated. However, 
we find one commenter's position that suitable DPM controls are not 
readily available to not be persuasive. The rulemaking record contains 
evidence that mine worthy control technology is available, and includes 
a number of examples of the successful implementation of such controls 
in all types of M/NM underground mines. The preamble to this final rule 
expands on those available technologies, indicating as we have 
suggested previously, that as demand for these technologies grows, 
manufacturers will respond by increasing the availability of feasible 
control systems for use at underground M/NM mines.
    We know that, when properly implemented, DPFs, environmental cabs, 
alternative diesel fuels, ventilation, and modern low emission engines 
are effective engineering controls for reducing DPM exposures in 
underground M/NM mines. They have all been successfully implemented at 
numerous mining operations to comply with the current interim limit. We 
know that when properly implemented, various administrative and work 
practice controls can also effectively reduce DPM exposures. Effective 
control technology, however, cannot be successful if mine operators are 
not diligent in resolving their unique implementation issues. 
Implementation issues vary from mine to mine, and what accounts for 
some mine operators being successful while others have had only limited 
success attaining DPM compliance primarily depends on the particular 
choices of controls selected, and the corresponding implementation 
strategies employed. Clearly, it is easier and cheaper to obtain 
compliance at some mines than at other mines, due to factors such as 
mine size, mining conditions, the amount, type, and age of diesel 
equipment in use, height and width of roadways, grades that must be 
traversed, elevation of the workings, remoteness of the mine, and so 
on.
    A commenter expressed the need for DPM controls that are, ``readily 
available for implementation in underground metal and nonmetal mines.'' 
Although we believe the rulemaking record supports the conclusion that 
the required DPM controls are commercially available, as noted above, 
the additional time offered by this final rule to meet the final limit 
is necessary for the mining community as a whole to implement these DPM 
controls.
    A commenter observed that ``The `put a filter on it' solution, 
suggested in prior MSHA analysis as the primary mode of

[[Page 28938]]

compliance, is now acknowledged to be a very goal that is not often 
achievable.'' This commenter goes on to say ``Therefore, by 
implication, the compliance model used to estimate compliance 
feasibility, and costs in the PREA and FREA is suspect.''
    Several other commenters also claimed that our technological 
feasibility determinations were based on predictions that retrofitting 
diesel equipment with exhaust filters would be the primary means of 
compliance, but that no such filters were commercially available at the 
time. We believe these commenters may not fully appreciate our position 
on technological feasibility in at least two key respects. First, we 
have never advised the industry that full compliance with either DPM 
limit would be a simple process of ``[putting] a filter on it.'' 
Rather, our feasibility determinations were based on the assumption 
that mine operators would choose the control or combination of controls 
that best suited the unique circumstances and conditions at their mine. 
In the preamble to the 2001 final rule (66 FR 5713), we said, ``the 
best actions for an individual operator to take to come into compliance 
with the interim and final concentration limits will depend upon an 
analysis of the unique conditions of the mine.'' In the same preamble 
(66 FR at 5859), we indicated that,

    The final rule contemplates that an operator of an underground 
metal or nonmetal mine have considerable discretion over the 
controls utilized to bring down dpm concentrations to the interim 
and final concentration limits. For example, an operator could 
filter the emissions from diesel-powered equipment, install cleaner-
burning engines, increase ventilation, improve fleet management, use 
traffic controls, or use a variety of other readily available 
controls. A combination of several control measures, including both 
engineering controls and work practices, may be necessary, depending 
on site specific conditions.

    We expected mine operators would have had less difficulty in 
appropriately selecting and experimenting with technology applications 
than we had observed at many mines. Also, we expected mine operators to 
be able to more effectively address their maintenance and regeneration 
issues with DPFs, and would have had better access to alternative 
fuels. Our experience revealed that many mine operators did not fully 
resolve all the complex implementation issues that were encountered. 
Some operators simply removed the controls instead of working through 
these implementation issues.
    The other aspect of our position on technological feasibility that 
these commenters may not fully appreciate is our position on current 
technological feasibility versus feasibility at a future date. They 
have assumed that because we acknowledged that it was infeasible to 
meet the final limit by May 20, 2006, that it is also infeasible to 
meet the final limit at a future date as required in the final rule. 
Again, our position is that we believe that additional time will be 
required for certain key technologies to become sufficiently diffused 
and available, and that the industry as a whole will require additional 
time under this final rule to successfully implement the necessary 
controls to attain compliance with the final phased-in limits.
    We believe it will be feasible for the industry as a whole to 
implement the required controls and attain compliance with the phased-
in DPM limits within the timeframes established in the final rule. For 
example, biodiesel production in the U.S. will increase dramatically 
over the next two years, making it increasingly easier for mine 
operators to gain access to a reliable supply of this alternative fuel. 
Also, EPA compliant 2007 on-road diesel engines will begin to become 
available in early 2007, and their availability will grow in the months 
and years to follow. We believe that the industry as a whole will be 
capable of attaining compliance with the final limits using these and 
other existing DPM control methods. We also believe that industry-wide 
compliance within the timeframes established in the final rule will not 
require the development of new technologies.
    We believe that the three-step phase-in approach for establishing 
the DPM limits and the wider use of alternative fuels, improved filter 
technology, and EPA compliant 2007 on-road engines along with other 
engineering and administrative controls, will enable the underground M/
NM mining industry as a whole to resolve lingering implementation 
challenges and difficulties relating to the 160TC [mu]g/m\3\ 
final limit.
    In our 2005 NPRM, we proposed that the final DPM limit be phased-in 
in five steps over a five-year period. The choice of five-years for the 
length of the phase-in period was based on our compliance assistance 
and enforcement experience that indicated that mine operators were 
encountering more significant implementation issues than originally 
anticipated. These issues affected a greater portion of the industry 
and presented greater challenges to resolve than we anticipated in the 
2001 final rule. The five-year phase-in period was proposed based on 
the rate at which we observed these implementation issues being 
successfully addressed at that time by the industry as a whole. We 
believed this five-year timetable for phasing-in the final limit was 
reasonable, providing for feasible compliance by the industry as a 
whole while insuring substantial annual reductions in DPM exposure of 
miners. However, we asked for comments on whether this proposed five-
year phase-in would be the appropriate timeframe for mine operators to 
attain the final DPM limit of 160TC [mu]g/m\3\. Some 
commenters provided information opposing the five-year phase-in, saying 
any delay was unjustified. Other commenters supported the five-year 
phase-in as an improvement from the original January 2006 deadline, but 
suggested that due to feasibility concerns, even more time would be 
needed to attain compliance. Other commenters have consistently 
maintained that controls sufficient to attain the final limit do not 
exist, so the timeframe for compliance is irrelevant. Other commenters 
provided information supporting a shorter phase-in of the final limit.
    We now believe that the three step phase-in of the final limit over 
two years that is incorporated into this final rule is the most 
appropriate approach and phase-in time period that both provides for 
maximum protection of miners and is also technologically and 
economically feasible for the industry to achieve. This determination 
was based on our enforcement experience, the comments in the rulemaking 
record addressing feasibility, and other relevant technical information 
we have obtained since we issued the 2005 NPRM.
    The key information that we relied on to reduce the timeframe from 
the originally proposed five-year phase-in of the final limit to the 
two-year phase-in incorporated into the final rule included wider 
availability of alternative fuels, particularly biodiesel, improved 
filter technology, and the impending availability of EPA compliant 2007 
on-road diesel engines. As previously discussed, we were also 
encouraged by the accelerating rate at which effective DPM control 
technologies were being implemented by mine operators, for example, 
high temperature disposable diesel particulate filter (HTDPF) systems. 
We believed the development of these systems would fill a critical gap 
in available filter technology, as they are particularly well suited to 
filter the exhaust from small and mid-sized equipment having low to 
medium duty cycles that were not good candidates for passive 
regeneration filter systems, and

[[Page 28939]]

on which mine operators did not wish to implement active filter 
systems. These systems demonstrated high filtration efficiency for EC, 
and did not increase NO2 emissions. However, when used in 
underground M/NM mines, these systems were subject to filter element 
damage due to occasional high temperature exhaust exposures. We are now 
confident that these systems can be used successfully in mining 
applications if a heat exchanger is placed upstream from the filter 
element in the vehicle's exhaust system. We have recently learned that 
purpose-built heat exchangers are now commercially available, either as 
separate units that can be retrofitted to an existing HTDPF system or 
as an integrated unit that combines a heat exchanger with a filter.
    Another example is the impending availability of EPA compliant 2007 
on-road diesel engines. As noted earlier in this section, these engines 
must reduce DPM emissions by about 90% compared to current models, and 
also must meet strict NOX standards. As recently as the fall of 2005, 
we could not be certain these new engines would be fully compatible 
with underground M/NM mine operational and production requirements, 
duty cycles, and maintenance practices. With the introduction of EPA 
compliant 2007 on-road engines less than 8 months away, we are now 
aware that the predominant technology that will be used by the engine 
manufacturers to comply with these requirements will be DPFs with 
provision for continuous or automatic active filter regeneration 
regardless of equipment duty cycle. As noted later in this section of 
the preamble, we are confident such DPFs can be implemented by mine 
operators. These DPFs typically have very high EC filtration efficiency 
approaching 99% or more, and the method of filter regeneration 
eliminates implementation issues relating to whether a particular 
machine's duty cycle is sufficiently severe to enable passive 
regeneration and the perceived logistical complications associated with 
active on-board or active off-board filter regeneration.
    These recent developments and technologies, along with increased 
utilization of the other engineering and administrative controls that 
we have discussed throughout the remaking record, such as environmental 
cabs with filtered breathing air, ventilation upgrades, and a host of 
administrative control options, will enable the underground M/NM mining 
industry as a whole to resolve lingering implementation challenges and 
difficulties relating to compliance with the 160TC [mu]g/
m\3\ final limit by May 2008. We are confident compliance under the 
final rule can be attained by most mines regardless of size or the 
commodity produced, because none of these technologies are mine size or 
commodity dependent.
    Regarding biodiesel, the National Biodiesel Board noted in their 
comments that the domestic annual production capacity of biodiesel fuel 
would increase by at least 100 million gallons between May 2005 and May 
2006. Based on production statistics released on November 8, 2005 by 
the National Biodiesel Board (http://www.nbb.org/ / resources / 
pressreleases / gen/20051108-- productionvolumes 05nr.pdf) we also 
learned that biodiesel production and consumption in the United States 
grew 300% in one year, from 25 million gallons per year in 2004 to an 
estimated 75 million gallons per year by the end of 2005. Biodiesel 
plants currently under construction will add 329 million gallons of 
annual production capacity (http://www.nbb.org/buyingbiodiesel/ 
producers--marketers/ProducersMap- Construction.pdf), and plants in the 
pre-construction phase will add another 518 million gallons of annual 
production capacity (http://www.nbb.org/ buyingbiodiesel / producers--
marketers / ProducersMap-Pre-Construction.pdf). Much of this added 
production capacity is expected to be on-line by 2008, and some of 
these plants are being, or will be built in areas of the country that 
are currently underserved by biodiesel production facilities, such as 
Wyoming, Montana, Washington, California, Colorado, and Texas in the 
west, and Tennessee, Kentucky, Pennsylvania, Virginia, North Carolina, 
and New York in the east. This expected increased availability of 
biodiesel fuel by 2008 supports our decision to phase-in the final DPM 
limits in three steps from 308EC [mu]g/m\3\ in May 2006 to 
350TC [mu]g/m\3\ in January 2007 to 160TC [mu]g/
m\3\ in May 2008.
    Increased use of these fuels is consistent with and in support of 
recent U.S. initiatives towards greater energy independence. On October 
22, 2004, President Bush approved a tax credit for blenders of 
biodiesel as part of H.R. 4520, also known as the American Jobs 
Creation Act of 2004 (Pub. L. 108-357). The tax credit for biodiesel 
produced from agricultural feedstocks is equal to $0.01 per gallon per 
percentage biodiesel in the blended product, essentially erasing the 
price difference between biodiesel and standard petroleum-based diesel 
fuel. In the late summer and fall of 2005 and again in the spring of 
2006, due to price swings in the market, the net cost of biodiesel, 
when the tax credit is applied, was less than the cost of standard 
2 diesel fuel in many parts of the country. As noted in more 
detail later in this section of the preamble, biodiesel consumption is 
expected to grow as more product is produced, as its availability 
increases in presently underserved parts of the country, and as the 
price gap between biodiesel and standard diesel closes, or as has 
recently occurred, when biodiesel becomes cheaper than standard diesel.
    Retrofit options for self-cleaning DPFs should increase as the 
manufacturers of these filter systems become assured of a reliable 
market both in underground mining and on diesel-powered equipment 
intended for surface applications. In addition, two manufacturers of 
synthetic high temperature disposable filters have updated their 
specification sheets (discussed further in this section) to advise mine 
operators of the exhaust gas temperature limitations when using these 
filters. In order to meet these exhaust gas temperature limits, mine 
operators can purchase commercially available heat exchanger systems 
that can lower the exhaust gas temperature before contact with the 
filter. This can allow application of this type filter to be expanded 
to a wider variety of machines, especially ones that have low to medium 
duty cycle.
    The more stringent EPA 2007 on-road exhaust emission standards 
(http://yosemite.epa. gov/opa/admpress.nsf/ 
b1ab9f485b098972852562e7004dc686/ f20d2478833ea3bd85256e 
91004d8f90?OpenDocument) that begin in 2007 for on-road diesel engines 
(http://www.epa.gov/otaq/diesel.htm) will lead to an additional 90 
percent reduction in particulate emissions when fully implemented. In 
addition, the EPA is mandating a reduction of the sulfur content of 
diesel fuel to no more than 15 ppm beginning in mid year of 2006 for on 
highway diesel engines and 2010 for nonroad diesel engines. Use of this 
fuel will enable advanced DPM control technology that would otherwise 
have been inhibited by the use of higher sulfur content fuel. Note that 
biodiesel fuel already meets this 15 ppm sulfur content requirement. 
Use of newer equipment with cleaner engines will also increase as older 
equipment is retired from service.
    We anticipate that the three-step two year phased-in approach to 
establishing the final DPM limit that is incorporated in this final 
rule will provide the needed time to resolve the logistical, 
operational, and market-based factors that make implementation of the 
final limit infeasible at this time for the

[[Page 28940]]

industry as a whole. In addition, this delay may decrease our 2001 
projection of the cost of compliance with the rule. During this phase-
in, we will continue to work with the Diesel Partnership (discussed 
below) and the mining industry to help facilitate resolution of DPF 
selection and implementation problems for the diverse metal and 
nonmetal mining environment.
3. Diversity of Underground Mines Affected by the 2001 Final DPM 
Concentration Limit
    The M/NM mining industry has approximately 168 underground mines 
that use numerous pieces of diesel powered equipment, widely 
distributed throughout each mining operation. These mines employ an 
array of mining methods to produce commodities including metals such as 
lead, zinc, platinum, gold, silver, etc. Also, there are different 
types of nonmetal mines that produce stone products such as limestone, 
dolomite, sandstone, and marble. Other underground nonmetal mines 
produce clay, potash, trona, and salt. Not only do these mines vary in 
the commodities that they produce, but they also use different mine 
designs and mining techniques such as room and pillar mining and stope 
mining. Some of these mines are large, complex multilevel mines, while 
others are small adit-type mines.
    Ventilation levels in these mines also vary widely. Many limestone 
mines have only natural ventilation with variable air movement, whereas 
trona mines have high ventilation rates to dilute and remove methane 
gas released during the mining process. There are also deep metal mines 
with multiple levels that have far less ventilation than that found in 
underground trona mines. Furthermore, many metal and nonmetal mines are 
located in remote areas of the country, at high altitudes, or are 
subject to extremely hot or cold environments.
    Considering these factors as a whole, we have found that there is 
no single control technology that would be suitable and effective for 
all M/NM mines in significantly reducing current DPM levels to or below 
the 2001 final DPM concentration limit of 160TC [mu]g/m\3\ 
by May 2006.
4. Work of the M/NM Diesel Partnership (The Partnership)
    Since promulgation of the 2005 final rule, the Partnership has been 
engaged in on-going NIOSH diesel research. One project involves a 
contract issued to Johnson Matthey Catalyst to develop a system to 
control nitrogen dioxide (NO2) emissions from diesel-powered 
underground mining vehicles equipped with Johnson Matthey's 
Continuously Regenerating Trap (CRT[reg]) system. This system promotes 
regeneration at lower temperatures and is widely used in urban bus 
applications. If the results of laboratory evaluations show that a 
system is suitable for use in underground mining, NIOSH would continue 
studying this control technology with a long-term field evaluation in 
an underground mine. The M/NM Diesel Partnership is continuing to 
investigate this and other DPF applications.
5. Remaining Technological Feasibility Issues
    In January 2001, we concluded that technology existed to accurately 
sample for DPM with a TC method and to reduce DPM levels to the 
160TC [mu]g/m\3\ limit by January 2006 (66 FR 5889). In June 
2005, we concluded that it was technologically feasible to reduce M/NM 
underground miners' exposures to the interim PEL of 308EC 
[mu]g/m\3\ by using available engineering control technology and 
various administrative control methods. However, we acknowledged that 
compliance difficulties may be encountered at some mines due to 
implementation issues and the cost of purchasing and installing certain 
types of controls. Specifically, we indicated that implementation 
issues may adversely affect the use of DPFs to reduce exposures despite 
the results reported in NIOSH's Phase I Isozone Study.
    A number of commenters expressed the view that our enforcement 
sampling experience demonstrates that both the interim DPM limit, and 
especially the final DPM limit are technologically infeasible. Some of 
these commenters stated that our sampling data published in our June 
final rule and on our web site demonstrates that 90% or more of the 
regulated industry cannot comply with the January 19, 2006 limit of 
160TC [mu]g/m\3\.
    We have carefully examined these comments, the data in the June 
final rule, and our more recent enforcement sampling data. We note 
first that the commenters were not questioning the validity of the 
sampling method or whether our sampling data are complete and 
representative. Our sampling and analytical methods have been validated 
by NIOSH, and our longstanding sampling strategy that focuses on miners 
we believe will experience the greatest exposures is fully consistent 
with good industrial hygiene practice. Second, in evaluating the 
sampling data we recognize that current DPM levels at many mines exceed 
the final limit. In the 2005 NPRM, we pointed out that, ``* * * in 2002 
and 2003, we found that over 75% of the underground mines covered by 
the 2001 final rule have levels that would exceed the final 
concentration limit of 160TC [mu]g/m\3\.'' We are 
encouraged, nevertheless, that DPM levels across the industry have been 
steadily and significantly reduced from the levels observed prior to 
the promulgation of the 2001 rule, and they are continuing to go down. 
As we stated in the 2005 NPRM (70 FR 53283), DPM exposures in affected 
mines have declined from a mean of 808 DPM [mu]g/m\3\ (646TC 
[mu]g/m\3\ equivalent) prior to the implementation of the standard, to 
a mean of 233TC [mu]g/m\3\ based on current enforcement 
sampling. During the time period from November 1, 2003 to January 31, 
2006, 1798 valid personal compliance samples from all mines covered by 
the regulation were collected. From these samples collected, 18% of 
samples exceeded the 308EC [mu]g/m\3\ interim limit, and 64% 
exceeded the 160TC [mu]g/m\3\ final limit. The fact that 64% 
of the enforcement samples collected from November 1, 2003 to January 
31, 2006 are above 160TC [mu]g/m\3\ does not establish infeasibility of 
the standard. We expect that overexposures will continue to decline as 
operators install new equipment, address implementation issues with 
DPFs, make use of biodiesel fuel, and install cleaner engines. Thus by 
May 2008, we would expect operators to achieve full compliance.
    Our experience reveals that little progress was made in reducing 
DPM levels across the industry until the interim DPM limit became 
effective. Once the interim limit became effective, mine operators 
implemented the controls they believed were necessary to attain 
compliance. Based on our experience with other health standards, we 
would not have expected the industry as a whole to have achieved 
compliance with the final limit before the compliance deadline. 
Further, as discussed throughout this section of the preamble, we 
believe sufficient technologically feasible DPM controls exist for the 
industry as a whole to comply with the final DPM limit within the 
prescribed regulatory timeframe in this final rule.
    Commenters, acknowledging that some DPM levels at some mines 
currently exceed both the interim and final DPM limits, indicated that 
the existence of such overexposures was the primary justification for 
the rule. These commenters observed that the rulemaking process is 
long, cumbersome and costly and that there ``would be little point in 
invoking it to require the

[[Page 28941]]

industry to do something it is already doing on its own.''
    These commenters continued, ``It is settled law that MSHA `can 
impose a standard which only the most technologically advanced [mines] 
have been able to achieve even if only in some of their operations some 
of the time.' '' United Steelworkers, 647 F.2d at 1264.
    We realize that some commenters will disagree with our decision not 
to presently implement the final limit. However, we have carefully 
reviewed all comments and data and believe that a number of mines have 
made good faith attempts to implement control technology but need more 
time to make such technology work. It is not our intent to have a 
majority of the mining industry apply for special extensions, or for a 
significant number of miners to be overexposed to DPM and have to wear 
respirators. We stated in the 2005 NPRM that a significant number of 
overexposures may:

    * * * lead to another problem by requiring a large number of 
miners to wear respirators until feasible controls are fully 
implemented. We have never had a standard that resulted in a 
significant percentage of the workforce being required to wear 
respiratory protection, and we are concerned about the impact on 
worker acceptance of the rule and about mine operators' ability to 
remain productive. We are interested in public comment on how many 
miners would need to wear respirators to comply with the 2001 final 
limit and proposed multi-year phase-in of the final limit, and 
whether in each case they would need to wear respirators for their 
entire work shift, whether this amount of respirator usage is 
practical, and any other comments or observations concerning this 
issue (70 FR 53285)

    The commenters that referenced the OSHA Lead decision also 
presented the results of an extensive analysis of our DPM sampling and 
enforcement actions at 11 selected mines. According to these 
commenters, these data show that we are not adequately enforcing the 
interim DPM limit because there were 56 sample results that exceeded 
the interim DPM limit, but we issued only 24 DPM citations. These 
commenters further assert that our failure to enforce the interim limit 
provides encouragement for mine operators who have delayed the 
implementation of controls that are necessary to attain both the 
interim and final DPM limit.
    These commenters did not provide information that indicated which 
mines were included in the commenter's analysis. However, assuming the 
commenters' numbers are accurate, there are three plausible reasons for 
the discrepancy between the number of samples exceeding the enforceable 
limit and the number of citations. First, the commenters indicate that 
the data for their analysis were gathered from the MSHA Data Retrieval 
System, which can be accessed from a link on the MSHA internet home 
page. The DPM sampling data contained in this database includes DPM 
samples obtained by our inspectors during the ``baseline'' sampling 
period prior to July 20, 2003. In accordance with provisions of the 
Second Partial Settlement Agreement, samples that exceeded the 
enforceable limit during the baseline sampling period were not subject 
to citation as long as the subject mine operator was exercising good 
faith efforts toward developing a DPM compliance strategy. Thus, the 
Data Retrieval System includes numerous overexposure sample results 
that were not citable because they pre-dated our full enforcement of 
the interim limit.
    Second, our enforcement policy for DPM, which is posted on our M/NM 
DPM Single Source page, identifies certain situations where a normally 
citable overexposure to DPM will not prompt a citation. In one case, a 
citation will not be issued if the mine operator can demonstrate that 
controls that would normally be effective in attaining compliance with 
the limit have been ordered, and the affected miner is wearing a 
suitable respirator in the context of a compliant respiratory 
protection program. This situation is covered in question 24 in the 
enforcement policy:

    24. If MSHA finds a miner overexposed to DPM and I have a valid 
purchase order for controls that have not been delivered to my mine 
site, will I be cited for a violation? No. If you can demonstrate to 
MSHA, through appropriate documentation such as purchase orders, 
that you are making reasonable progress toward implementing feasible 
engineering and/or administrative controls that have a reasonable 
likelihood of achieving compliance with the interim DPM limit within 
a reasonable timeframe, and you have implemented a respiratory 
protection program meeting the requirements of ANSI Z88.2-1969 that 
covers all affected miners, MSHA will not conduct compliance 
sampling of affected miners at that time. The inspector will return 
to the mine to verify that adequate progress is being made toward 
full implementation of controls and/or to conduct DPM sampling based 
on the completion timeframe established by the mine operator.

    In the other case, if the mine operator has fully implemented all 
feasible engineering and administrative controls and the affected miner 
is wearing a suitable respirator in the context of a compliant 
respiratory protection program, no citation will be issued even if an 
exposure exceeding the limit is measured. This situation is covered in 
question 29 in the enforcement policy:

    29. How will MSHA determine if a citation is warranted when 
evaluating whether I have implemented all feasible controls? Once 
you use and maintain all feasible engineering and administrative 
controls to reduce a miner's exposure, implement the required 
respiratory protection program and require the miner to use a 
respirator, you will be in compliance with Sec.  57.5060(a), even 
though a miner's DPM exposure may continue to exceed the limit and a 
citation will not be issued. Keep in mind that feasibility is an 
MSHA determination. If the agency finds that you failed to install, 
use and maintain all feasible controls, or you failed to establish 
an appropriate respiratory protection program, you will be out of 
compliance.

    Third, some samples that exceed the interim DPM limit may be 
resamples of previously cited overexposures. Our enforcement sampling 
practice requires that after an overexposure is cited, the mine 
operator is given the opportunity to implement engineering and/or 
administrative controls to reduce the subject miner's exposure to or 
below the enforceable limit. Once these steps have been taken, we 
resample the miner to confirm that controls have been successful in 
lowering the miner's exposure to or below the limit. On occasion, the 
resample is still over the limit, in which case, if the operator has 
made good faith efforts to apply normally effective controls, the 
citation will be extended so that additional controls can be 
implemented, followed by another resample.
    Thus, due either to controls being on order, to issues relating to 
feasibility, or to resample that continues to exceed the DPM limit, and 
depending on other factors, we may not issue a citation even though a 
sample result represents a DPM overexposure. We intend to continue this 
enforcement practice under this final rule and will issue necessary 
compliance guidance.
    Several commenters repeated earlier public comments regarding their 
views that previous technological and economic feasibility 
determinations are invalid because they were based partially on 
analyses conducted using a ``flawed'' computer simulation program. The 
economic feasibility issues are addressed latter in this section. The 
computer program in question, referred to as the DPM Estimator, is a 
Microsoft[reg] Excel spreadsheet program that calculates the reduction 
in DPM concentration that can be obtained within an area of a mine by 
implementing individual, or combinations of engineering controls. This 
program was the subject of a Preprint published for the 1998 Society of 
Mining Engineers Annual Meeting

[[Page 28942]]

(Preprint 98-146, March 1998), and it was fully described in a peer 
reviewed article in a professional journal (Haney and Saseen, Mining 
Engineering, April 2000). Its algorithm is accurate, and we have not 
received comments that challenged the mathematical basis for its 
calculation.
    Although this program was criticized as ``flawed'' by several 
commenters, few specific errors in the design or utilization of the 
program were offered. One commenter indicated that the

    * * * computer model was based on invalid assumptions of the 
availability of filters that would fit the entire fleet of equipment 
in use, and assumptions of perfect ventilation conditions throughout 
the industry.

This commenter continues,

    * * * no such filters were available commercially at the time of 
the MSHA prediction, nor when the 2001 rule was published, nor had 
any undergone testing.''

Regarding the issue of ventilation, this commenter stated that,

    * * * the assumption of `The Estimator' of perfect ventilation 
in mines did not exist in reality and the rule could not be declared 
feasible based on these incorrect assumptions.

This same commenter goes on to say that our technological feasibility 
determinations for all of our DPM rulemakings, from the original 2001 
final rule to this rulemaking, are invalid because they are founded on 
analytical results obtained from the Estimator.
    We have responded previously to both of these comments, and to many 
other criticisms of the Estimator. Regarding the availability of DPFs, 
we must emphasize that our DPM rules have always been performance 
oriented, and that mine operators have been given wide latitude to 
select DPM controls that were best suited to their unique circumstances 
and conditions. Neither the original 2001 rule nor this current final 
rule requires DPFs as the exclusive means of compliance with the DPM 
limit. The Estimator contains provisions for estimating the effect of 
applying DPFs, ventilation upgrades, low DPM engines, and other DPM 
controls on DPM levels in an area of a mine. At the time that we 
promulgated our 2001 final rule, however, we acknowledged our limited 
in-mine documentation on implementation of DPM control technology with 
issues such as retrofitting and regeneration of filters. Consequently, 
we committed to continue to consult with NIOSH, industry and labor 
representatives on the availability of practical mine worthy filter 
technology.
    Regarding the same commenter's concerns that ventilation issues 
were handled inappropriately in the 31 Mine Study, we believe the 
commenter used the term ``perfect ventilation,'' when they may have 
meant perfect mixing of ventilation airflows. ``Perfect ventilation'' 
is a term with which we are unfamiliar. We have never used this term in 
this or any other rulemaking, and are unfamiliar with it in the context 
of mine ventilation engineering. ``Perfect mixing,'' in the context of 
ventilation systems, is a common technical term that refers to an 
idealized process in which two or more airflows of dissimilar 
composition join, and in which the composition of the composite airflow 
is an instant and homogonous mix of the input airflows. The issue of 
perfect mixing was raised by one of the same commenters in their public 
comments on the August 14, 2003 proposed rule on the interim DPM limit, 
and we responded in detail to these comments in the preamble to the 
2005 final rule (70 FR 32920-32921).
    The commenters believe that the Estimator's computations of DPM 
concentrations are valid only if engine emissions are perfectly mixed 
with the air flow, which they suggest does not occur in an actual mine. 
As discussed in the 2005 final rule preamble, these commenters make an 
erroneous assumption with respect to our utilization of the Estimator. 
The Estimator actually incorporates two independent means of 
calculating DPM levels: one based on DPM sampling data for the subject 
mine, and one based on the absence of such sampling data. Where no 
sampling data exist, the Estimator calculates DPM levels based on a 
straightforward mathematical ratio of DPM emitted from the tailpipe (or 
DPF, in the case of filtered exhaust) per volume of ventilation air 
flow over that piece of equipment. This is referred to in the Estimator 
as the ``Column B'' option for calculating DPM concentrations. The 
commenters'' observation that the Estimator fails to account for 
imperfect mixing between DPM emissions and ventilating air flows is a 
valid criticism of the ``Column B'' option. For this and other reasons, 
the Estimator's instructions urge users to utilize the ``Column A'' 
option whenever sampling data are available.
    In the ``Column A'' option, the Estimator's calculations are 
``calibrated'' to actual sampling data. Whatever complex mixing between 
DPM emissions and ventilating air flows existed when DPM samples were 
obtained, are assumed to prevail after implementation of a DPM control. 
This is an entirely reasonable assumption, and in fact, there is no 
engineering basis to assume otherwise. Indeed, comparisons of ``Column 
A'' Estimator calculations and actual DPM measurements taken in mines 
before and after implementation of DPM controls have shown good 
agreement, indicating that Estimator calculations do adequately 
incorporate consideration for complex mixing of DPM and air flows when 
the ``Column A'' option is used.
    The Estimator was originally developed with both the Column A and 
Column B options because at the time it was developed (1997), the 
specialized equipment required for reliable and accurate in-mine DPM 
sampling, such as the submicron impactor, was not widely available. 
Consequently, few mine operators were able to obtain the in-mine DPM 
sample data required for utilizing the Column A option. Though mine 
operators may continue to use the Estimator, we rely more on our in-
mine documentation and enforcement experience on the feasibility of 
DPFs.
    This background and detailed explanation on perfect mixing was 
provided in the preamble to the 2005 final rule (70 FR 32920). However, 
the comments we received on this subject for the instant rulemaking do 
not acknowledge or respond to the background and explanation we 
provided in the earlier preamble. The commenters simply restate their 
previous assertion that the Estimator is flawed because it assumes 
perfect ventilation, which as noted above, we believe was meant to 
refer to perfect mixing.
    As we have maintained throughout this rulemaking, mine operators 
should determine the control or combination of controls that will be 
best suited to their mine-specific circumstances and conditions, and 
that controls need to be evaluated, selected, and implemented on a 
case-by-case and application-by-application basis. Nonetheless, based 
on our experience, observations, and the comments received from mine 
operators, we believe to attain the final DPM limit, many mine 
operators that are not yet using DPFs will have to start using them, 
and most mine operators that are already using DPFs to attain the 
interim limit will have to continue or increase their use to attain the 
final limit. The mining industry maintains that while some operators 
are using DPFs to control miners' exposures to the interim PEL, it is 
infeasible for them to further reduce miners' exposures through 
expanded use of DPFs. However, we maintain that feasibility 
difficulties encountered with the use of DPFs can be resolved within 
the prescribed timeframe offered in this

[[Page 28943]]

final rule, and that the greatest impediment to more widespread use of 
DPFs throughout the industry is the need to overcome implementation 
challenges and difficulties relating to specific pieces of mining 
equipment. For example, as the final limits become effective, some 
mines that were possibly using one or two DPFs on large horsepower haul 
trucks may have to install more DPF systems on other types of machines, 
such as loaders or support and utility equipment, in order to attain 
the final limit.
    As discussed extensively throughout the rulemaking record and as we 
explained in detail in the 2005 NPRM, mine operators continue to prefer 
passive DPF regeneration systems over active regeneration systems. 
Passive regeneration is the process where the temperature of the 
exhaust gas produced by the engine is sufficiently high for a 
sufficient percentage of the working shift to burn off the collected 
DPM on the DPF. In order for passive regeneration to be a viable 
option, filter regeneration has to occur frequently enough to prevent 
the DPM that accumulates in the filter from causing backpressure on the 
engine that exceeds the engine manufacturer's backpressure 
specification. Passive regeneration is normally preferred by mine 
operators because the DPF will regenerate in the normal course of 
equipment operation, with no interruption to mine production activities 
and no equipment downtime required for filter regeneration. Also, 
passive regeneration occurs without the need for intervention by the 
equipment operator, and it does not require any special external 
equipment or facilities. However, many pieces of mining equipment do 
not have engine duty cycles that will presently support consistent 
passive regeneration. This problem will take more time for individual 
mine operators to resolve.
    If a passive DPF loads up with DPM, but the exhaust temperature is 
not sufficient to ignite and burn off the accumulated DPM, the 
backpressure on the engine will increase. Prolonged engine operation in 
excess of the manufacturer's backpressure specifications can cause 
engine and DPF damage. Therefore, it is strongly recommended that when 
passive regeneration DPF systems are installed, a means for the machine 
operator to monitor the engine's exhaust backpressure should be 
included. Such a provision is important even on equipment where the 
normal duty cycle easily supports passive regeneration. For example, if 
a piece of equipment on which a filter normally passively regenerates 
is used temporarily for some other activity having a less severe duty 
cycle, the filter may not passively regenerate, and backpressure could 
build up. Likewise, if the subject equipment experiences a maintenance 
related problem that causes an increase in the level of ``engine out'' 
DPM emissions, the rate of DPM buildup in the filter could exceed the 
capacity of the filter to passively regenerate. In such cases, 
excessive engine backpressure could build up in less than a working 
shift. If the equipment is provided with a means for monitoring 
backpressure, and the equipment operator observes engine backpressure 
rising to excessive levels, corrective action can be taken before 
engine or filter damage occurs. Successful implementation of passive 
DPF systems has been reported where the mine operators have determined 
that a machine has sufficient exhaust gas temperature for passive 
regeneration and exhaust backpressure is being monitored.
    If passive regeneration is infeasible due to an insufficient duty 
cycle, active regeneration may be a feasible alternative. Active 
regeneration depends on an external heat source for burning off the DPM 
collected in a filter. Some mine operators commented that it is not 
feasible for them to utilize active regeneration due to the physical 
size of filters, machine downtime, and/or the cost associated with 
building and equipping underground regeneration stations required for 
active DPF regeneration. We disagree that these factors render active 
regenerating DPF systems infeasible. As discussed throughout the 
rulemaking record, and later in this section of the preamble, filter 
size and machine downtime issues relate to implementation challenges 
and difficulties which can impact feasibility of compliance with the 
final limits. We believe these factors can usually be effectively 
addressed through proper system selection and deployment, as described 
below, which take time to effect. We also believe the deployment of an 
active DPF system is economically feasible under the prescribed time 
frames for the final limit. Economic feasibility is discussed in detail 
later in this section in this preamble.
    Engine emissions and exhaust flows affect the size of the DPF that 
needs to be installed. These factors are important considerations for 
both passive and active regeneration. If the DPF is undersized for a 
particular application due to high DPM emissions or high exhaust flows, 
a passive or active DPF system may become overloaded, requiring the 
filter to be removed from service for regeneration. If such an 
interruption occurred mid-shift, it would typically have a greater 
negative effect on production than if it occurred at the end of a 
shift. Active regeneration DPF systems are normally sized so that the 
filter has sufficient capacity for the host vehicle to operate over its 
normal duty cycle for at least a full shift or longer. In some cases, 
especially when a machine with an older, high emission engine needs to 
be filtered, a filter having sufficient capacity to allow for a full 
shift of machine operation may be too large to fit in the available 
space on the machine. For this reason, most DPF manufacturers do not 
recommend DPF installation on older high emission engines. Some mine 
operators who have faced this dilemma have opted to compromise by 
installing a smaller filter. The result is DPM overloading. DPM 
overloading leading to excessive backpressure on the engine is the main 
problem that mine operators experience when the DPF installation is not 
correct for the application and duty cycle. Possible feasible 
corrective actions include utilizing a larger DPF or a lower DPM 
emission engine, or both. As noted later in this section of the 
preamble, installation of a new, low-emission engine, in addition to 
facilitating use of a reasonably sized DPF, can cut DPM emissions by up 
to 90% or more, and their greater operating efficiencies can reduce 
maintenance costs and lower fuel usage by 10% to 15% compared to older 
technology high emission engines.
    Regarding commenters' concern about the physical size of DPFs, if 
the DPF for a particular piece of equipment is too large to handle or 
too large to fit in the space available on the equipment, the exhaust 
could be divided into two branches fitted with smaller sized filters on 
each branch, or as noted above, the engine could be replaced by one 
with lower DPM emissions that can be effectively filtered by a 
correspondingly smaller DPF.
    Since 2001, a number of older, high DPM emitting engines have been 
replaced with new, low DPM emitting engines, either through direct 
engine replacement into existing equipment or through the acquisition 
of new equipment, but not as many as we predicted in 2001. From our 
enforcement experience, we believe this has occurred in mostly the 
larger horsepower engines, greater than 150 hp, in production 
equipment. This equipment is typically turned over more frequently 
because it has more severe duty cycles, is worked harder, and typically 
has a shorter life than smaller, lower horsepower support equipment. 
High horsepower production equipment also typically accounts for the 
greatest proportion of DPM produced in the

[[Page 28944]]

mine, so replacing these engines was the highest priority at most 
mines. Thus, the smaller engines normally found in support equipment 
often have older engines with higher DPM emissions per horsepower than 
the newer and larger production equipment.
    We estimated in the 2001 final rule that 50% of the support 
equipment would probably need DPFs for compliance with the final limit 
(66 FR 5889-90). The higher DPM emissions from these engines, however, 
can complicate the expanded use of DPFs on this equipment. It is our 
belief that the mining industry will need additional time to further 
evaluate the proper sizing of both passive and active regeneration DPF 
systems on this equipment. Consequently, we expect the implementation 
issues relating to DPFs, particularly the selection of appropriate DPFs 
for a given application, regeneration issues, filter maintenance, etc. 
may extend over a larger portion of the mining industry as operators 
work toward compliance with the final limit.
    Although we believe these implementation issues are sufficient to 
warrant the additional time offered in this final rule, we are 
nonetheless confident these issues can be effectively resolved within 
the compliance timeframes established in the final rule. For example, 
EPA compliant 2007 on-road engines will be provided with engine 
manufacturer supplied DPF systems that will regenerate continuously or 
automatically regardless of duty cycle, thereby greatly reducing 
implementation issues for the owner. Another example is the HTDPF with 
integral heat exchanger. This recently commercialized technology will 
enable filtering the exhaust from small to mid-size equipment with low 
to medium duty cycles. In addition to these and other new developments, 
competitive pressures will force the manufacturers of existing DPF 
systems to make incremental product improvements over time.
    Note that high engine exhaust temperatures are an implementation 
issue only for disposal particulate filter element type DPFs. Ceramic 
and metallic filter element type DPFs can tolerate the normal range of 
exhaust temperatures from any diesel engine. In fact, passive 
regenerating DPFs depend on high exhaust temperatures to initiate the 
regeneration process. Where high exhaust temperatures could potentially 
occur, but where the user wishes to implement a disposal particulate 
filter element system, the use of a heat exchanger upstream from the 
filter element is required to lower the exhaust gas temperature and 
prevent filter element damage. For ceramic and metallic filter element 
type DPFs, heat exchangers are neither required nor desired.
    Several commenters stated that we admitted to implementation 
problems with DPF systems in the preamble to the proposed rule. We 
agree with these commenters that we did express concerns about 
implementation issues with DPFs, and that these concerns, along with 
concerns about implementation issues with other DPM engineering 
controls led to our decision to propose delaying the effective date of 
the final limit of 160TC [mu]g/m3 until January 
2011. We continue to believe that a delay to the effective date for the 
final limit is necessary due to feasibility considerations. However, as 
we explained earlier in this section of the preamble, based on our 
enforcement experience and comments and other data in the rulemaking 
record addressing feasibility since we issued the 2005 NPRM, we have 
subsequently determined that delaying the final limit until 2011 is not 
justified. Primarily due to wider availability of alternative fuels, 
particularly biodiesel, improved filter technology, and the impending 
availability of EPA compliant 2007 on-road diesel engines, we believe 
the rulemaking record supports the three step phase-in of the final 
limit over two years, with the final limit of 160TC [mu]g/
m3 becoming effective in May 2008. This is the approach that 
is incorporated into this final rule, and we believe it provides for 
the maximum protection of miners that is technologically and 
economically feasible for the industry to achieve.
    As discussed earlier in this section of the preamble, recent 
developments in the three key areas of biodiesel, improved filters, and 
EPA compliant 2007 engines, along with the application of a variety of 
other existing DPM controls, will enable compliance by the industry as 
a whole significantly sooner than was proposed in the September 2005 
NPRM. Biodiesel, improved filters, and EPA compliant 2007 engines can 
be used by any size mine producing any M/NM commodity, and these 
technologies are not subject to many of the difficult implementation 
issues that have slowed the adoption of some DPM controls. For example, 
biodiesel can be used in any diesel engine with elastomeric fuel system 
components that are biodiesel compatible, and any non-compatible 
components can be easily replaced. No other engine or equipment 
modifications of any kind are required. Improved diesel particulate 
filters are commercially available for retrofit to any size diesel 
engine, and systems like the HTDPF and diesel particulate 
ReactorTM are particularly well suited to installation on 
small and medium sized production and support equipment that had been 
problematic for some mine operators. No implementation issues in 
regards to selection of the DPF media, sizing, or regeneration type are 
expected for EPA compliant 2007 on-road engines. As discussed 
previously in this section, the engine will have a DPF installed in the 
vehicle when purchased by the mine operator.
    DPF systems are a more effective control technology for reducing EC 
than TC. In order to comply with the final limit, we expected that most 
mine operators would need to add to the DPM controls they had 
previously implemented for compliance with the interim limit. We also 
anticipated that many mine operators that had successfully attained 
compliance with the interim limit without DPFs would need to utilize 
DPFs to obtain compliance with the final limit.
    We acknowledged in previous preambles that DPFs may not be the 
optimal solution for all machines, especially machines equipped with 
dirtier engines. But we have also advised that machines with older, 
dirtier engines should be replaced or re-powered with cleaner engines, 
and then if necessary, be equipped with DPF systems.
    We continue to emphasize to the mining industry to utilize our DPM 
Single Source Page to obtain information to assist with installation of 
DPF systems. This information stresses that DPFs require the engine to 
be maintained through a good maintenance program and to monitor the 
exhaust backpressure in order to prevent the DPF system from becoming 
overloaded with DPM. Minimizing these problems can help prevent 
premature DPF or engine failure, which affect feasibility.
    NIOSH commented that

    Although adverse health effects occur at the proposed 
concentration limits and below, NIOSH recognizes that all factors, 
including technical and economic feasibility must be considered by 
MSHA in developing an exposure standard. NIOSH is aware of the 
`implementation and operational difficulties' currently facing the 
metal and nonmetal mining industry presented in MSHA's preamble, 
Section IV. Technological Feasibility (page 53282). A phase-in 
period may provide time to resolve such issues. Requiring control 
technologies before mine operators have had sufficient time to work 
through selection and implementation problems may create hazards and 
adverse health effects, such as the elevated levels of NO2 
experienced when some PT-catalyzed

[[Page 28945]]

diesel particulate filters (DPFs) have been used in poorly or 
marginally ventilated areas.
    NIOSH also recognizes that the mines covered by this proposed 
standard have unique designs and operational differences presenting 
unique challenges in controlling and reducing diesel emissions. For 
some metal and nonmetal mines, targeted reductions in exposures of 
underground miners to DPM below the 400 [mu]g/m\3\ TC or 308 [mu]g/
m\3\ elemental carbon (EC) current limit may be achieved only 
through implementation of complex, integrated strategies and state-
of-the-art control technologies.
    The first steps to control diesel emissions are fundamental 
changes to improve mine ventilation and diesel engine maintenance 
practices, along with the introduction of cleaner engines or the use 
of alternative fuels, such as biodiesel, when practical. When these 
are insufficient to achieve compliance, more advanced diesel 
emission control technologies, such as DPF systems, may be necessary 
to achieve compliance.

    We have considered the technological and economic feasibility of 
achieving the final limits specified in this final rule as discussed 
throughout this preamble. The three step phase-in approach allows mine 
operators more time to work towards implementation of DPM control 
technologies. We agree with NIOSH that the first steps that the mine 
operators took to lower DPM levels were changes to engines, maintenance 
practices, ventilation systems, and to a lesser extent, alternative 
fuels. As we have discussed in this preamble, these efforts have 
lowered miners' exposure to DPM as our enforcement sampling has shown.
    Even though NIOSH refers to DPFs as ``more advanced diesel emission 
control technologies,'' some mines have already implemented DPFs in 
order to comply with the interim standard. These same mines will most 
likely continue using DPFs, plus add additional DPFs or other DPM 
controls such as biodiesel, to meet the final limits. However, we agree 
that the final limits will require a larger segment of the mining 
industry to implement DPFs and alternative fuels. We agree that 
underground metal and nonmetal mines present unique designs and 
operational differences which affect the application of DPM controls. 
This three step phase-in approach provides the time for mine operators 
to learn more about advanced control technologies with regards to 
implementation issues.
    NIOSH further referenced a June 25, 2003 letter to the Assistant 
Secretary from Dr. John Howard, Director, NIOSH, relating to DPFs. 
NIOSH stated that although DPFs ``* * * are commercially available, the 
successful application of these systems is predicated on solving 
technical and operational issues associated with the circumstances 
unique to each mine.'' This three step phase-in of the final limits 
will provide the necessary time for mine operators to overcome these 
technical and operational issues, since we believe that DPFs are now 
more readily available and DPF implementation issues can be resolved.
    This commenter also agreed with us that mine ventilation, 
maintenance, cleaner engines or use of alternative fuels, such as 
biodiesel were effective DPM control measures. However, the commenter 
stated that when these methods are insufficient to achieve compliance, 
more advanced control technologies would be needed, such as DPF 
systems. Gaining extensive experience with implementation and operation 
of DPF systems on production vehicles would greatly assist in resolving 
some of these issues. The commenter further stated that to ensure 
success of the phase-in period, individual mine operators or a 
consortium of mine operators or other partnerships should have 
compliance plans detailing their integrated approach to reducing DPM 
levels in terms of maintenance, ventilation, fuels, control 
technologies, retrofitting, and monitoring.
    We agree with the commenter that the final limit does require mine 
operators to continue implementing the current controls needed to meet 
the interim concentration limit, however, in order to meet the final 
limit, more controls may need to be implemented. If DPF systems are 
needed, then the mine operator will need to continue work to properly 
install and maintain DPF systems to manufacturers' specifications.
    Some commenters referred to the NIOSH Phase I and II studies, 
stating that they were successful in showing that the DPM controls, 
especially DPF systems, work in reducing DPM. However, these commenters 
believed that NIOSH did not provide reliable data to indicate that the 
selected filter technology would provide the necessary reductions of 
DPM in actual mining applications. We responded to the NIOSH Phase I 
and II studies in the 2005 final rule. We noted the successful DPM 
reductions that were achieved from the DPM controls, especially DPF, in 
the Isozone study of Phase I. We further reviewed the work done by 
NIOSH in the production area of the mine in Phase II. We maintain as we 
did in the preamble to the 2005 final rule that ``the Phase II study 
helped to confirm existing agency data that shows that it is 
technologically feasible to reduce miners' exposures to DPM to 
308 [mu]g/m\3\ interim PEL.'' (70 FR 32928) The NIOSH work 
confirmed that DPFs can reduce DPM to MSHA's DPM limits. As stated 
previously, as the final limit is reduced over the time frame specified 
in this final rule, the mine operator can implement additional DPF 
systems (or other DPM control technologies) to further reduce the DPM 
exposure. The NIOSH Phase II study and MSHA's Greens Creek study as 
discussed in the June 6 preamble (70 FR 32928--32929) showed reductions 
in EC.
    The same commenters stated that the Phase II study showed that the 
efficiencies of the DPF did not always agree with laboratory studies. 
However, the commenters failed to acknowledge that the comment was 
directed towards the DPF systems performing better than laboratory 
data, especially for EC reductions. We highlighted this finding from 
NIOSH's Phase II study in the preamble to our 2005 final rule (70 FR 
32928).
    Several commenters continued to state concerns with the use of 
catalyzed ceramic DPF systems due to increased NO2 levels. 
We discussed this issue thoroughly in the preamble to the 2005 final 
rule (70 FR 32928-32929). We concluded then, and we believe the 
evidence is still persuasive, that the NO2 issues discussed 
in the NIOSH Phase II studies were related to deficient ventilation in 
the areas where the testing occurred. The results of the Greens Creek 
study, which also evaluated heavily platinum catalyzed DPFs, showed a 
possible rise in NO2; however the small increase detected 
made it unclear as to the cause (preamble to the 2005 final rule, (70 
FR 32884 and 32921)). Even if the NO2 increases at Greens 
Creek were caused entirely by the catalyzed DPFs, the rise, which was 
about 1 ppm downstream from stopping operations involving one loader 
and two or three haulage trucks totaling over 1,000 horsepower, was 
manageable due to effective auxiliary ventilation. We continue to 
acknowledge that highly catalyzed platinum ceramic DPFs have the 
potential to generate higher levels of NO2 than the baseline 
emissions from the subject diesel engine. However, when such DPFs are 
used in conjunction with proper ventilation, NO2 has not 
increased to hazardous levels. As discussed previously in this section, 
NIOSH commented that increased NO2 levels occurred in poorly 
or marginally ventilated areas with the use of some catalyzed DPFs.
    Several commenters agree that progress has been made with the 
application of ceramic DPF systems that regenerate passively on larger

[[Page 28946]]

horsepower production machines. The DPF systems have been shown to be 
highly efficient in collecting DPM and mine operators have reported 
that they do passively regenerate on the larger horsepower, production 
machines. The production machines operate at a heavy duty cycle that 
corresponds to high exhaust gas temperatures for a sufficient portion 
of the shift. This allows the DPF to regenerate passively and burn off 
the collected DPM, thus keeping the DPF below the engine manufacturers' 
maximum allowable exhaust backpressure.
    One mine operator provided a list of their DPF systems that have 
been in operation up to 9000 hours. The DPF systems were supplied by 
two different DPF manufacturers, but were both designed for passive 
regeneration. This commenter stated that 13 of their 17 haul trucks 
were equipped with passive regeneration DPFs and they are currently 
evaluating 4 more units on their haul trucks. According to the 
information submitted by this commenter, they have plans for 
installation of DPFs on 6 of their loaders. The commenter stated that 
the process of achieving DPF reliability has been arduous, and required 
much discussion and work with the DPF manufacturer.
    Another mine operator also stated that 32 passive regeneration DPF 
systems have been installed with an average life of the DPF system from 
3000-4000 hours. The operator stated that the success has been with 
haul trucks and they are working on evaluating the installation of this 
type DPF on LHD's.
    Yet another mine reported installing four passive DPF systems on 
machines and the exhaust backpressure quickly exceeded the 
manufacturer's specification for exhaust backpressure. The commenter 
stated that the DPF would not passively regenerate, requiring the mine 
to remove them for cleaning.
    The experiences described by these three mine operators continue to 
show that DPF system selection and installation must be carefully 
evaluated. However, overall it appears that a number of mine operators 
have been successful in installing passive regeneration DPF systems on 
machines that have high duty cycles and are therefore acceptable for 
passive regeneration, particularly haulage trucks and some loaders. We 
continue to advise mine operators that DPF systems that utilize passive 
regeneration must be carefully evaluated and well-maintained for their 
successful operation. Both MSHA and NIOSH continue to post extensive 
information on DPF systems on our respective Web sites. The Filter 
Selection Guide (detailed in the preamble to the 2005 final rule (70 FR 
32922)) that was designed by NIOSH and MSHA continues to be an 
important tool for understanding the steps that must be taken to 
evaluate, select, and install a DPF system, especially one that depends 
on passive regeneration.
    The same commenters also stated that when passive DPF systems were 
not feasible for some types of machines, especially those with medium 
to low duty cycles, they began evaluating active regeneration systems. 
In contrast to passive regeneration systems that depend on the high 
temperature of the engine's exhaust for burning off the DPM collected 
in the DPF, active systems use an external heat source to initiate the 
burning process for DPM. These commenters stated they have purchased 
some active systems for evaluation. However, they question the 
feasibility of utilizing active DPF systems in their mines due to a 
variety of logistical and operational concerns. For example, they point 
out that the mining production cycle at many mines does not provide for 
sufficient machine downtime to stop the machine and take it out of 
service in order to ``plug'' the machine into a regeneration station 
for regeneration of the DPF to occur. These commenters also stated that 
if they tried to change out DPFs, then the number of DPFs they would 
need to maintain on hand to store and rotate would be both cost 
prohibitive and storage space consuming. These commenters indicated 
that machines that return to the surface at the end of the shift would 
be candidates for active regeneration.
    We agree that using active systems that require prolonged machine 
downtime for regeneration may not be feasible at all mines. However, at 
mines that only operate for a single shift or have a gap between shifts 
for blasting gases to clear, for example, regenerating active filters 
between shifts would be more feasible. For mines that operate around 
the clock, shutting down a key piece of production equipment for filter 
regeneration may present a problem. While such an implementation scheme 
would undoubtedly adversely affect mine production, the commenters did 
not provide information or data sufficient to establish the 
significance of the effect to determine the feasibility of the method.
    More importantly, however, we have continued to recommend 
alternatives to this implementation scheme for active DPFs. For 
example, the fuel burner system regenerates the filter during normal 
equipment operations, without intervention by the equipment operator, 
and regardless of equipment duty cycle. Another option is to swap out 
filters instead of regenerating them on-board the equipment. Between 
shifts, a used filter can be removed from a piece of equipment and 
swapped for a regenerated filter. The used filter can then be placed in 
a regenerating appliance so it will be ready by the beginning of the 
next shift, and the equipment can be returned to duty without further 
delay. Using this implementation method, equipment downtime to 
accommodate DPF regeneration is measured in minutes rather than hours.
    The technology for a variety of active systems continues to be 
commercially available. Implementation of active regeneration systems 
does require the mine operator to look at the logistics of time, place, 
and manpower to successfully perform the task. Those logistical 
decisions have been outlined in the NIOSH Filter Selection Guide. 
However, the mechanism for installation of a DPF system with active 
regeneration is less complex than passive regeneration because the 
location of the DPF on the machine, distance of the DPF from the 
exhaust manifold or turbocharger, and the orientation of the DPF are 
less important. On passive regeneration systems, the DPF must be as 
close as possible to the outlet of the exhaust manifold or turbocharger 
to utilize the maximum exhaust gas temperature. On active regeneration 
systems, this is not an installation requirement.
    We continue to believe that for installation of either type of 
regeneration system, engine maintenance is vital. The engine must be 
maintained in good working condition. The engine must be maintained to 
limit excess DPM being emitted from unburned fuels or oil. Intake 
filters must be maintained and the engine's intake air restrictions and 
exhaust backpressure must be maintained to the manufacturer's 
specifications.
    In addition, the exhaust gas backpressure measurement provides 
critical information on the amount of DPM loading on the DPF. Engine 
manufacturers and DPF manufacturers provide maximum limits that should 
not be exceeded to ensure proper engine and DPF operation. The exhaust 
backpressure ports and devices must be maintained. This has become a 
special concern in the underground coal sector, prompting the Coal DPM 
Partnership to form a Subcommittee to investigate the proper procedures 
to monitor backpressure and the proper type of equipment to use. MSHA 
and NIOSH

[[Page 28947]]

are working with labor and industry on this issue. Recommendations from 
this subcommittee will be shared with both coal and M/NM industry 
personnel since the information will be pertinent to both mining 
sectors involved with DPF systems. These recommendations will cover all 
types of DPF systems.
    We believe that in place of ceramic DPF systems that require 
passive or active regeneration, machines could be installed with 
disposal DPF technology. These systems are commercially available and 
include exhaust heat exchangers to limit the exhaust gas temperature at 
the DPM media. These systems are available for all horsepower ranges 
typically found in M/NM mines.
    From the comments received to the proposed rule, mine operators 
have installed synthetic high temperature disposable particulate 
filters (HTDPFs) as a means for DPM control. HTDPFs were initially used 
on permissible machines in underground coal mines to further reduce the 
chance of a filter fire that could occur more easily with paper filter 
media. Since that first introduction on permissible machines, 
manufacturers have developed systems to use HTDPFs on non-permissible 
machines in underground coal mines and on machines in underground M/NM 
mines. The HTDPFs were tested by NIOSH in the Isozone studies and shown 
to be effective in DPM EC reductions.
    One commenter stated that they estimated the DPM reduction to be 
about 60-65% with the use of HTDPFs. We would consider that reduction 
estimate to be low (assuming the data the commenter was referring to 
was EC) when compared to our laboratory test that showed up to 80-83% 
percent reduction of whole DPM and higher efficiencies for EC.
    However, several commenters stated that the synthetic HTDPF systems 
were removed from the machines that they were originally installed on 
when the DPF ``burned out'' and melted. The commenters stated that the 
backpressure would rise quickly when the DPF loading exceeded the 
specified loading capacity of the DPF media size. When this occurred, 
there was the potential for a DPF ignition.
    One of these commenters also stated that the use of HTDPF was 
discouraging because the DPFs were only lasting 4-10 hours, requiring 
filters to be discarded and replaced every two shifts or less. It is 
well known that the operating life of a disposable DPF is mainly due to 
the size of the DPF installed, the amount of DPM that the engine emits, 
and the condition of the engine. Any one of these parameters can affect 
DPF life. The size of the DPF should be evaluated and engineered into 
the machine prior to installation. The DPM output of the engine should 
also be known prior to installation, and the condition of the engine is 
an important factor that can change and can severely affect DPF life. 
However, the engine DPM output and the condition of the engine can be 
altered. If DPF life is too short due to an older engine, then an 
engine replacement with a newer, cleaner engine can usually be done. 
Engine maintenance can increase DPF life by minimizing burning oil or 
unburned fuels.
    Underground coal mine operators faced these same implementation 
issues when they began using disposable DPFs to comply with the coal 
DPM rule. They resolved these issues by replacing high DPM emitting 
engines and improving engine maintenance procedures. The same methods 
for extending DPF operating life are applicable to M/NM machines and 
are discussed in the DPF Selection Guide.
    The DPM overloading issue also led to DPF ignition events. These 
concerns were raised by the underground coal mine operators. In 
response to this, we performed an extensive investigation on the causes 
of DPF ignitions. We determined that when the DPF collected the DPM, 
oils and unburned fuels were also collected on the media. When the DPF 
was exposed to exhaust gas temperatures that were in excess of 650 
[deg]F, the DPM, oils, and unburned fuels ignited, but not the DPF 
media. However, when the burning occurred, temperatures were high 
enough to melt the DPF media. When paper filter media was involved, the 
paper filter media also caught fire.
    To help resolve this issue and to provide the mine operators with 
more awareness of the potential for an ignition of a DPF, we worked 
with DPF manufacturers that produce synthetic HTDPF systems. The DPF 
manufacturers agreed with us to update their DPF system specifications 
to specifically advise their customers that the synthetic HTDPF cannot 
be used where the exhaust gas temperature at the filter media exceeds 
650 [deg]F. We posted on the internet links to these updated 
specification sheets from the manufacturers.
    To help further resolve this issue, manufacturers have developed 
exhaust gas heat exchangers, both air to air and air to water type heat 
exchangers that can either be installed in the exhaust prior to the DPF 
media or be built in as part of the DPF canister to maintain the 
exhaust gas temperature at or below 650 [deg]F. The addition of a heat 
exchanger makes the use of the HTDPF feasible on a wider variety of 
vehicles that have duty cycles that could create exhaust gas 
temperatures at the DPF media in excess of 650 [deg]F. Instead of the 
machine manufacturer or mine operator being concerned that the engine's 
duty cycle does not exceed 650 [deg]F, a heat exchanger system can be 
built in to the exhaust system prior to the DPF to limit the exhaust 
gas temperature at the filter media to 650 [deg]F.
    Several commenters made reference to a joint NIOSH Partnership 
study at the Stillwater Mine. This study did a paper analysis of the 
equipment and based on some basic information, assigned each piece of 
equipment into a category to describe the potential for DPF 
application. The rulemaking record does not include the results of this 
study, and it is our understanding from NIOSH that this study is 
incomplete at this time. Therefore, this study was not considered by us 
in reaching our determination in this final rule.
    However, we do believe that the type of approach used by NIOSH is a 
good beginning step that each mine should take when considering the use 
of DPF control technology. Once a mine operator categorizes its 
equipment based on general assumptions, they could then begin a more 
in-depth study of each piece of equipment that may need a DPF system 
installed, and finally, determine which system or systems could be 
feasible. Again, the NIOSH Filter Selection Guide provides mine 
operators with a step by step approach to determine the best ``fit'' 
for a machine to reduce the DPM emissions.
    One commenter discussed feasibility issues with applying DPF 
systems to their mine's equipment which included Schedule 31 equipment. 
The commenter stated

    FMC's fleet falls into the category that does not support DPF's 
due to duty-cycle and manufacturers specifications. To date, FMC has 
found only one filter manufacturer that is willing to try their 
disposable filters on our fleet. Specific challenges/concerns 
include flammability of disposable filters, low engine duty cycle, 
and Schedule 31 hurdles that have yet to be addressed.

    The commenter referenced the NIOSH work conducted at the Stillwater 
Mine where NIOSH categorized equipment for DPF application as was 
discussed above.
    We believe that the issues raised by the commenter have been fully 
addressed in this preamble and in previous preambles which include 
flammability of disposable filters and the types of DPFs that can be 
used based on an engine's duty cycle.
    The commenter references his Schedule 31 equipment. Schedule 31 is

[[Page 28948]]

terminology used to refer to permissible equipment approved by us for 
use in gassy mines. Similar types of diesel powered equipment that are 
used in this mine are also used in underground coal mines in areas 
where methane gas may be present. We do not agree with the commenter 
that DPF systems are not available for permissible equipment. 
Underground coal mines have been retrofitting similar permissible 
equipment since 2001 to reduce DPM emissions from this type of 
equipment. To date, approximately 300-400 disposable type DPF systems 
have been installed on permissible equipment in coal underground. We 
believe that the equipment referred to by the commenter can be 
installed with a DPF system. We have information posted on our Web site 
on retrofitting permissible equipment. Companies such as Dry Systems 
Technologies (DST), DBT Australia Pty Limited, and EJC Mining Equipment 
have been supplying this type of DPF system to the underground coal 
permissible fleet. In addition, mine operators can contact our 
Technical Support Approval and Certification Center for information 
related to retrofitting permissible equipment.
    One manufacturer testified at the public hearings that the DPF 
systems that they supply to the underground coal permissible machines 
are available in non-permissible (non explosion proof) configurations 
for machines in M/NM mines. They stated that the technology can be 
configured for all horsepower machines and be designed for numerous 
machine configurations.
    Another area of DPF systems that we have been investigating is the 
use of on-board regeneration. On-board regeneration normally operates 
in principle between a passive system and an active system. In this 
type of DPF system, some passive regeneration occurs depending on duty 
cycle, however there is a mechanism for active regeneration when the 
duty cycles are not sufficient. The active regeneration may be in the 
form of catalyst, electrical system, or fuel burner type system. 
Several of these systems were discussed in the preamble to the 2005 
NPRM such as the ArvinMeritor. Other systems are discussed below that 
we have become aware of since the preamble to the proposed rule.
    DPF systems using this type of technology are becoming more readily 
available and feasible due to the upcoming EPA 2007 on-highway emission 
standards. We are aware the EPA emission standards are more stringent 
for reducing both DPM and NOX. Information on systems being 
designed for 2007 on-highway machines will include DPF filters and 
NOX catalysts. These systems will most likely require some 
type of active regeneration systems to account for low duty cycle on-
highway vehicles. However, at this time, most engine manufacturers have 
not released the technical details of their systems since they are 
still in on-going developments to prepare for the 2007 model year. A 
combination of passive and active regeneration will most likely be used 
to account for the various duty cycles of non-road equipment. The EPA 
DPM standards will be forcing more DPF technologies to the commercial 
market starting in 2007 which will be available to the mine operators 
during the extension of time allowed for in this final rule.
    Recently, MSHA and NIOSH have been in discussions with an 
automotive manufacturer of a commercial pickup truck and the diesel 
engine manufacturer that supplies the diesel engine for the pickup 
truck. Currently, many underground coal mines and some M/NM mines use 
commercially available automotive type pickup trucks. In 2007 model 
year, the new trucks will be sold with DPF systems in order to comply 
with the EPA on-highway standards. However, some underground coal 
operators became concerned with the new DPF systems on these pickup 
trucks. The concern relates to regeneration based on a mining duty 
cycle. The manufacturers also have not yet released all the details on 
the DPF systems. Engine and machine manufacturers are doing extensive 
testing for on-highway applications. MSHA and NIOSH have agreed with 
the manufacturers to perform laboratory and field test on the new 
pickup trucks once the trucks are available for mining. This work will 
be done during the extension of time allowed for in this final rule.
    This type of technology will become more widespread, even in the 
mining industry, as the EPA DPM emission standards become effective. In 
addition, the California Air Resources Board (CARB) continues work with 
their ``Verification Procedure, Warranty and In-Use Compliance 
Requirements for In-Use Strategies to Control Emissions from Diesel 
Engines''. This program verifies DPF systems for installation on 
machines in California. CARB maintains a Web site at: http://arb.ca.gov/diesel/verdev/home/home.htm.
    Most of the systems being developed for EPA have also been 
developed for California's program. Some commenters stated that we 
should wait till the EPA standards and technology becomes available. 
However, we believe that the delayed timeframe of the final limit will 
permit the DPF technology to become more universal in the mining 
industry. The mining industry should use its resources during this 
delay to resolve implementation issues on mining vehicles to meet the 
final limit.
    We are aware of the following DPF technologies that are either 
commercially available or being further investigated by MSHA and NIOSH. 
Many of these systems have been discussed by us in preambles for the 
2005 Final Rule (70 FR 32935) and the 2005 NPRM (70 FR 53284) and we 
are updating the discussions to include the new information that we 
have. The extension of time offered by this final rule will allow for 
more work to be done on these promising systems for implementation into 
the mining industry market.
    a. ArvinMeritor System. In the 2005 proposed rule, we noted that 
the ArvinMeritor system, which utilizes active regeneration of the DPF, 
offers great potential for underground mines in further reducing DPM 
exposures. The ArvinMeritor system utilizes an on-board fuel burner 
system to regenerate DPFs. This system actively regenerates the filter 
media during normal equipment operations by causing the fuel to ignite 
the burner and thereby increase the exhaust temperature in the filter 
system. Consequently, this system does not require the host vehicle to 
travel to a regeneration station to regenerate the DPF. The condition 
of the DPF is monitored via sensors. We also stated that while this 
product was successfully evaluated at Stillwater's Nye Mine, we 
recently learned that the manufacturer had decided to concentrate on 
working with Original Equipment Manufacturers (OEMs) where they would 
be selling 50 units or more to one customer rather than selling one or 
two units to individual customers for retrofit application. It is our 
current understanding that this system is still commercially available 
for purchase in smaller quantities from ArvinMeritor distributors and 
local dealers.
    b. Johnson Matthey's CRT System. The Johnson Matthey CRT System is 
a DPF utilizing passive regeneration. As stated above, passive 
regeneration works by using the exhaust gas generated by the engine to 
burn the DPM. Normally, DPF manufacturers utilize catalyst technology 
to lower the temperature needed for successful passive regeneration. By 
lowering the exhaust gas temperature needed for passive regeneration, a 
broader range of machines will have the necessary duty cycle to 
generate the exhaust gas temperature needed to burn the DPM. However, 
when a platinum coating is

[[Page 28949]]

used as the catalyst, it can also increase the nitrogen dioxide 
(NO2) emissions from the engine exhaust. In mines with low 
ventilation rates, the increased NO2 emissions can also 
result in increased NO2 exposures to potentially dangerous 
levels for miners. We discussed this issue in the 2005 final rule (70 
FR 32924-26).
    In 2004, the NIOSH Pittsburgh Research Laboratory issued a contract 
to Johnson Matthey to develop a system that can regenerate at lower 
exhaust gas temperatures and control NO2 emissions. The 
system is based on Johnson Matthey's CRT system and promotes 
regeneration at lower temperatures. Such DPFs are widely used in urban 
bus applications and are capable of passively regenerating DPFs at the 
temperatures commonly seen in the exhausts of underground mining 
equipment (above 250 [deg]C for at least 40% of the operation time).
    The laboratory evaluation of the systems continues under NIOSH 
contract by the Center for Diesel Research (CDR) at the University of 
Minnesota. The objective is to examine performance and suitability of 
the systems relative to heavy-duty diesel engines in underground mining 
applications, with specific focus on the effectiveness of controlling 
NO2. If the results of laboratory evaluations show that the 
system is suitable for use in underground applications, NIOSH would 
continue to study this DPM control with a field evaluation in an 
underground mine. However, at this time the laboratory data is still 
incomplete, and NIOSH continues to work with the lab and Johnson 
Matthey on this promising technology.
    c. Diesel Particulate ReactorTM. We have begun testing 
in our diesel laboratory a high performance DOC that contains a 
substrate which is a catalyst treated, woven stainless steel alloy 
fabric cartridge. This Reactor is being tested as a stand alone unit, 
in combination with a HTDPF, and with a synthetic fuel called Synpar 
200. Our preliminary laboratory data using the Reactor and the Synpar 
200 synthetic diesel fuel has shown an effective whole DPM removal 
efficiency approaching 50 percent without any adverse changes in other 
engine emissions. We are aware that several mines are planning on 
trying one or several of the combinations listed. One underground 
nonmetal mine has equipped about 80% of its fleet of about 50 pieces of 
diesel equipment with the Reactor, and reports no operational or 
maintenance problems. We will include on our DPM Single Source Page our 
efficiency numbers for DPM removal when they become available. NIOSH 
has also contracted with the Center for Diesel Research to do 
additional testing on the Reactor and the Synpar 200 synthetic diesel 
fuel at this time.
    d. Fleetguard. This company has partnered with other DPF companies 
that market such products as a Longview Lean NOX Catalyst 
DPF. The Longview Lean NOX Catalyst combines NOX 
reduction plus a DPM reduction system.
    One underground coal mine operator is planning on receiving a unit 
to investigate and install on a piece of mobile equipment. The system 
specifies a minimum exhaust gas temperature of 260[deg]C at least 25 
percent of operating time in order for regeneration to occur. We also 
understand that this device may have the ability for active 
regeneration. MSHA and NIOSH plan to work with the coal mine operator 
to monitor the device once it is installed.
    Since the system utilizes NOX reduction, we are planning 
on testing this device in our diesel laboratory to determine the amount 
of NOX reduction and to determine if there would be any 
adverse effects on engine emissions from this control scheme. NIOSH is 
also planning on testing this device at a M/NM mine, that is, if the 
work at the underground coal mine proves promising for application in 
the mining industry.
    e. Rypos. Rypos utilizes a sintered metal filter media for DPM 
filtration. The system uses electrical current for active regeneration. 
Initially, the system was used on stationary generator systems. Rypos 
has successfully tested a prototype system on a surface grader. 
Electrical power for filter regeneration was obtained from a second 
alternator on the grader that was dedicated exclusively to the DPF. At 
this time, Rypos is discussing with us and NIOSH development of a 
system for mobile mining equipment. We will update the mining community 
on our work with this device.
    f. Huss. We are aware that a M/NM mine operator has purchased a 
Huss system with a ceramic DPF using active regeneration. However, we 
have not received any information on the application of this DPF to the 
machine at the mine or its performance. If and when we do, we will 
inform the mining community through the DPM Single Source Page.
    g. Other DPF Systems. We continue to work with DPF manufacturers 
that are listed on our Web site at: http://www.msha.gov/01-995/Coal/DPM-FilterEfflist.pdf. The DPF manufacturers that have submitted data 
to us and are listed on our Web site are: CleanAir Systems, DCL 
International, Engine Control Systems, Catalytic Exhaust Products, Nett 
Technologies, Donaldson Company, and Filter Services and Testing 
Corporation. We understand that there are other DPM control 
technologies that could be available but the other manufacturers have 
not contacted us. We continue to discuss and evaluate the latest DPM 
control technologies for applicability with the mining market through 
this Technical Support Directorate.
    h. Diesel Engine Replacements. Several commenters stated that the 
mines have been replacing older, dirtier engines with newer, EPA Tier 
engines. The EPA Tier engine requirements force engine manufacturers to 
build engines that comply with more stringent emission standards for 
NOX, DPM, and CO over a time period. The Tier schedule 
normally requires the larger horsepower engines to meet more stringent 
emission standards first, then the smaller horsepower engines. At this 
time, all new engines being sold in the United States in all horsepower 
ranges are meeting a minimum of a Tier 2 EPA emission standard.
    We agree that this trend which the mine operators are following to 
replace older engines has been a feasible approach to reduce DPM 
exposure to meet the interim limit. However, in order to meet the final 
limit, mine operators must continue to evaluate their engine 
inventories to determine which engines need to be replaced as they 
become older, and new cleaner engines are available.
    In addition, if mine operators are considering adding a DPF system 
to a machine that is equipped with a high DPM emitting engine, they may 
first need to repower the machine with an engine having lower DPM 
emissions. In some cases, a Tier 1 engine may need to be replaced with 
a Tier 2 engine to allow for a successful application of the DPF. A 
lower DPM emitting engine would enable the machine to operate for a 
longer period between regenerations, or before a disposable DPF would 
need to be replaced. Interruptions to mine production activities to 
accommodate regeneration or to replace a disposable filter can be 
avoided when the engine and DPF are properly matched to each other.
    To further emphasize this point, one commenter discussed the 
application of installing disposable DPF systems on Toyota pickup 
trucks. The mine operator stated that the cost of replacing the 
disposable DPF is cost prohibitive. However, we are aware that the 
engine model used in that Toyota truck is an old model that may be out 
of production

[[Page 28950]]

at this time. The truck engine described is a 128 hp engine. Based on 
information gathered by us, we believe that this engine may have a DPM 
emissions output of between 0.8 and 0.9 g/bhp-hr. This is considered a 
dirty engine and is higher than a Tier 2 engine standard. This would 
require more frequent DPF replacements when using disposable filters, 
or more frequent active regenerations, or the use of two DPFs as was 
discussed by the commenter, thus increasing the cost. A current Tier 2 
engine in this horsepower range has a maximum DPM emission rate of 0.22 
g/bhp-hr. An engine replacement or vehicle replacement could reduce the 
DPM output from each engine by up to 90 percent.
    We believe that there are engines that could be used to repower the 
truck. As further discussed later in this section on Economic 
Feasibility, based on the cost estimates that the commenter presented, 
the cost savings of switching engines or even purchasing newer pickup 
trucks with cleaner engines could pay for the engine or truck in a 
minimal time frame.
    In addition, more stringent EPA on-highway emission standards come 
into effect with on-highway vehicle models starting in 2007. The more 
stringent standards will require engine manufacturers to install a DPF 
system on all on-highway diesel powered vehicles. The 2007 model 
pickups that will be sold in the United States will then have DPF 
systems installed at the factory.
    As discussed previously in this section, we are working with an 
engine manufacturer and a pickup manufacturer, NIOSH, and a coal mine 
operator to evaluate the technology being incorporated. We plan on 
testing the new engine/DPF system in our Diesel laboratory as soon as 
an engine/DPF system can be made available. The coal mine operator is 
concerned about the ability of the DPF system to regenerate. MSHA and 
NIOSH will be conducting in-mine studies to determine the feasibility 
of the regeneration process on the pickup trucks in both coal and M/NM 
mines. The extended period of time allowed for in this final rule 
should provide the additional time needed for this evaluation.
    i. Alternative Fuels and Ultra Low-Sulfur Fuels. In our 2005 NPRM, 
we stated that during our compliance assistance efforts, we observed 
several mines using alternative fuels, including water emulsion fuels 
and biodiesel fuels, both of which are EPA approved fuels. We 
subsequently tested these alternative fuels to determine if they could 
decrease tailpipe DPM emissions. In each application the change to an 
alternative fuel had a positive impact on reducing engine emissions and 
miners' exposures to DPM. In some cases, reductions of 50 to 80+ 
percent were measured. While we found notable benefits, the use of 
alternative fuels can also cause equipment operation issues for mine 
operators. These operational issues have included initial clogging of 
the fuel filters when biodiesel is used, reduction of horsepower with 
the use of water emulsion fuels, and management of proper fueling of 
the correct fuel into specific machines. While these operational issues 
could be overcome, we believe that the mining industry needs the 
additional time offered by this final rule to work through 
implementation issues on a case-by-case basis.
    The most common problem with alternative fuels is lack of 
geographic proximity of most mines to a fuel distributor. There are 
only three cities that are served by a water-emulsion fuel blender/
distributor: Cleveland, Ohio, Houston, Texas, and Los Angeles, 
California. Biodiesel fuel is more widely available throughout the 
country than water-emulsion fuel, but some mines, particularly in the 
intermountain west and the west coast, may be 200 miles or more from 
the nearest biodiesel producer or distributor. Thus, mine operators in 
these isolated areas could incur significantly increased fuel 
transportation costs if they utilized biodiesel fuel at their mines.
    Fuel manufacturers are building distribution centers near mining 
areas to reduce the transportation costs, but these centers will take 
some additional time to complete. Limited distribution is also a 
feasibility issue for metal and nonmetal mine operators who seek to 
obtain ultra low sulfur fuel. However, as discussed elsewhere in this 
preamble, the commercial availability of ultra low sulfur fuel (less 
than 15 ppm sulfur content) will increase during 2006 and beyond when 
on-road vehicles, and shortly after that, nonroad diesel engines in the 
United States will be required by the EPA to use only this type of 
diesel fuel. For these reasons, we believe the additional time provided 
in this final rule will allow mine operators the additional time they 
will need to comply is warranted.
    j. Water Emulsion Fuels. In the 2005 NPRM, we explained that water 
emulsion fuels, such as PuriNox[supreg], are blends of diesel fuels and 
water. The water is held in suspension with a surfactant. The water in 
the fuel reduces the engine combustion temperature resulting in reduced 
NO2 and reduced DPM emissions. However, the added water also 
reduces the engine's horsepower. While the per gallon price of the 
water emulsion fuel is the same as standard fuel, we are aware of 
increases in engine consumption of these fuels by as much as 15 
percent. However, continued increased use in mines is currently limited 
due to lack of fuel availability in most mining regions. Manufacturers 
of this fuel must install centralized blender facilities in order to 
make the fuel more available and economically feasible for use by the 
metal and nonmetal mining industry.
    We also stated that we had observed some engines using water 
emulsion fuels. One issue appears to be with the use of very efficient 
water separators used on engine fuel systems to remove water from the 
fuel lines. We advised that a very efficient water separator will 
actually remove the water from the emulsion, thus affecting the 
engine's performance. An engine manufacturer that has experienced this 
with its engines has recommended replacing the more efficient water 
separator with a less efficient one.
    Another issue identified by some mine operators is that some small 
machines cannot run, or run poorly, on this fuel. We are not aware of 
any testing that has been done to prove or disprove this. This may or 
may not be due to less complex fuel systems that cannot handle a change 
in fuel properties.
    Since water emulsion fuels have been associated with horsepower 
loss, mines will have to determine through their own in-mine testing if 
their machines can continue to operate efficiently even with the power 
loss. Some situations where the power loss could affect a machine's 
productivity occur at multilevel underground mines at high elevations. 
Also, mines that require the use of permissible engines with pre-
chamber combustion, such as the metal and nonmetal gassy mines, may 
need to determine any additional effects on these types of engines.
    Several commenters noted that PuriNox[supreg], a proprietary diesel 
fuel water emulsion product manufactured by the Lubrizol Corporation, 
will no longer be available in North America after calendar 2006. We 
regret this decision by Lubrizol, as we have documented very 
significant DPM reductions at mines that have experimented with, or 
permanently switched to PuriNox[supreg] fuel. Since most mines have 
been successful in attaining the interim limit using low DPM emission 
engines, environmental cabs, and upgraded ventilation, very few mines 
have switched to PuriNox[supreg] fuel, thus limiting demand for this 
product.

[[Page 28951]]

It's very limited geographic available in the three cities identified 
above also limited demand. It is possible that more mines might have 
switched to PuriNox[supreg] to attain the final DPM limit, if it were 
still available when the final limit becomes effective. However, as 
noted below, many of the DPM reduction benefits we have observed at 
mines using a water-emulsion fuel can also be achieved using high 
biodiesel content fuel blends.
    k. Biodiesel Fuels. As noted above, the use of high biodiesel 
content fuel blends has resulted in significant DPM reductions of up to 
80% or more at mines that have experimented with or switched entirely 
to such fuel blends. Even in blends as low as 20%, DPM reductions of 
nearly 40% have been documented. Actual DPM reductions depend on 
engines, duty cycles, etc., but reductions of at least 60% would be 
expected when fuel blends of B90 to B100 are used.
    Biodiesel fuels are more readily available than water emulsion 
fuels. As noted below, biodiesel is currently available in every state 
except Alaska. The costs and therefore the demand for biodiesel have 
been related primarily to federal excise tax credits that have been 
available since 2004 to blenders of this fuel. The tax credits are 
passed along from the fuel blender to the purchaser in the form of 
reduced fuel costs. With current tax credits, biodiesel can be an 
attractive fuel alternative for the mining industry. In the late summer 
and fall of 2005, and again in the spring of 2006, due to market 
induced price swings for standard 2 diesel fuel, the price of 
biodiesel in many parts of the country, with the tax credit applied, 
was lower than standard diesel.
    Several commenters expressed general agreement with our statements 
in the 2005 NPRM regarding the use of biodiesel fuel as an effective 
means of reducing DPM emissions (70 FR 53287). One commenter listed 
various other advantages of biodiesel, including reduced emissions of 
carbon monoxide, carbon dioxide, polycyclic aromatic hydrocarbon (PAH) 
compounds, oxides of sulfur, and total hydrocarbons, as well as better 
lubricity, higher flash point for increased fuel handling safety, and 
higher cetane number for better cold starts. However, some commenters 
asserted that biodiesel fuel is not a technologically feasible 
engineering control because it is not widely available in the eastern 
and western states, it causes unacceptable power loss, it is subject to 
gelling in cold weather, and it causes engine maintenance problems. 
These commenters also mentioned higher fuel costs as an impediment to 
increased usage of biodiesel. Technological feasibility issues relating 
to biodiesel fuel and economic feasibility issues are discussed in this 
section.
    Examples of the specific concerns expressed by commenters who doubt 
the technological feasibility of biodiesel fuel included a mining 
industry organization that stated, ``While the use of biodiesel showed 
some promise in reducing EC at some mines, biodiesel caused reduced 
horsepower problems described by mine operators and is not widely 
distributed nor accessible at a reasonable cost to many mining 
operations.'' This commenter went on to say, ``* * * there is very 
little availability of biodiesel in the Eastern or Western United 
States, where many of the mining operations are located that will be 
impacted by the proposed rule.'' A large Montana platinum mining 
company that consumes about 1,000,000 gallons of diesel fuel per year 
commented that, ``* * * cold weather concerns were evaluated to 
determine the necessary storage requirements to reduce the potential 
for the fuel to gel.'' This commenter continued by stating that 
biodiesel cold flow properties in 100% form is not good below 45 
degrees and would require some type of heating to make it flow. The 
regional supplier does not have the infrastructure to support this 
product due to the current low demand and newness of the product. This 
mine operator also evaluated the requirements for storing biodiesel on-
site at the mine, and indicated that a 10,000 gallon tank would be 
needed for diesel, a 15,000 gallon tank would be needed for biodiesel, 
and a 10,000 gallon tank would be needed for the blended product, at a 
combined cost of over $250,000.
    Another commenter stated that, ``There may be adverse effects on 
engine performance and maintenance that need careful consideration 
before selecting biodiesel as an alternative technology.'' Another 
commenter stated that, ``Cummins recommends a biodiesel fuel mix of no 
greater than 5%, but that mixture does not result in a significant DPM 
reduction.''
    We agree that these commenters have concerns based on their current 
assessments of the biodiesel fuel. The extension of time allowed for in 
this final rule for meeting the final limit will assist mine operators 
in working through these operational issues if they decide to use 
biodiesel. Many of the biodiesel issues when resolved will apply to the 
entire mining industry. One example of this would be the logistics for 
transferring biodiesel fuel during the winter. Once the logistics for 
transferring the biodiesel in winter are resolved, all mines can use 
the information. This may be as simple as locating one or more 
companies that can ship biodiesel using insulated rail cars or tankers, 
or provide a service for warming up the fuel prior to delivery at the 
mine. We can provide these vendors on our Web site for the entire 
mining community for their use.
    We are aware of several mines that are using very high biodiesel 
content blended fuels (near 100% biodiesel), and they have reported no 
operational or maintenance issues that were unanticipated or presented 
any difficulty for the respective mine. B100 has approximately 5%-7% 
less energy content than standard 2 petroleum diesel, and this 
difference is reflected in correspondingly lower horsepower output of 
an engine running on B100. Mine operators that are using high biodiesel 
fuel blends report that this horsepower loss is noticeable on some 
equipment, but manageable, and the power difference has not impacted 
production.
    Biodiesel fuel acts as a solvent, and can loosen sediment in the 
fuel tanks and fueling systems of equipment that has run previously on 
standard diesel. This sediment can clog fuel filters for a period of 
time until the fuel system is fully cleaned, which typically takes a 
few weeks. During this period, fuel filters need to be changed more 
frequently than normal to avoid loss of engine power or stalling. This 
solvent effect has a long lasting benefit, however, in that the fuel 
system and injectors run cleaner as long as biodiesel fuel is used. One 
mine operator reported that their diesel engines have never run as well 
as they are now that the mine switched to a high biodiesel content 
blended fuel. He attributed the better performance to the higher 
lubricity of biodiesel and the cleaning effect on the fuel injectors.
    The solvent properties of high biodiesel content fuel blends may 
adversely affect certain elastomeric components associated with an 
engine's fueling system, such as hoses and gaskets. Users need to 
contact the respective engine manufacturer to find out which 
components, if any, need to be replaced with their biodiesel-compatible 
counterparts. The extension of time allowed for under this final rule 
will provide the necessary time to make these contacts.
    The solvent properties of the fuel may also remove certain types of 
paint if the fuel remains in contact with a painted surface for a 
prolonged period. This property of biodiesel does not render

[[Page 28952]]

the fuel infeasible. It is simply an attribute of the fuel of which 
users need to be aware and take appropriate precautions. Likewise, 
because of its somewhat higher viscosity, a property related to its 
better lubricity, high biodiesel fuel blends may tend to more easily 
pass over the rings and dilute the engine oil. For this reason, it may 
be advisable when using high biodiesel fuel blends to shorten engine 
oil change intervals.
    Biodiesel is subject to oxidation, microbial growth, and other 
conditions during long term storage. Manufacturers typically recommend 
precautions be taken such as fuel turnover, tank mixing, and anti-
oxidant treatments if fuel is to be stored for longer than 6 months. 
Prior to use, biodiesel fuels stored for longer than 6 months should 
also be tested for acid number, sediment, and viscosity to insure it 
remains within specifications. In its publication, ``Biodiesel Handling 
and Use Guidelines, DOE-GO-102006-2288. Second Edition, March 2006,'' 
the U.S. Department of Energy indicates that, ``the least stable B100 
could be stored for up to 8 months, while the most stable could be 
stored for a year or more.'' Nonetheless, the National Biodiesel Board 
recommends biodiesel fuels be used within 6 months of purchase. 
Instituting these precautions in using biodiesel may take mine 
operators some additional time to implement thus justifying the delay 
allowed for in this final rule. For mining operations that consume 
large amounts of diesel fuel and receive fresh fuel shipments from 
reputable suppliers on a frequent basis, long term storage issues are 
not a major concern.
    We agree with the comments regarding the cold flow properties of 
biodiesel presenting storage and handling challenges. Neat soy-diesel 
(a 100% biodiesel fuel made from soybean feedstock) has a cloud point 
of 32 degrees Fahrenheit, and a pour point of 28 degrees Fahrenheit. 
The cloud point is the temperature at which crystals begin to form in 
the fuel, causing the potential for clogged fuel filters. The pour 
point is the temperature at which the fuel begins to gel and becomes 
difficult to pump. At temperatures approaching the cloud point, neat 
soy-diesel needs to be heated to prevent handling difficulties.
    Many industrial chemicals have similar cold weather handling 
properties, and practical means have been developed to enable routine 
storage and transfer of these chemicals at any temperature. The most 
common method for off-loading such materials from transportation 
vessels is to heat the tank. For example, steam can be applied at the 
railhead to rail tank cars that are specially designed to facilitate 
this process. Transportation vessels, either rail or truck, can also be 
moved into a heated building for unloading. Fixed storage tanks can be 
heated, placed inside a heated building, or in the case of underground 
mines, storage tanks can be placed underground. To prevent fuel from 
gelling during equipment operations, the equipment's fuel tanks, fuel 
lines, and fuel filters can be heated, either using recycled engine 
heat, or using an external heating source, as might be required if 
equipment is parked outside the mine overnight. Such provisions are 
common in some parts of the world for all diesel equipment.
    Although the properties of biodiesel may necessitate special 
transportation, storage, and handling procedures by mine operators, the 
precautions that would need to be taken to address these properties are 
straightforward and technologically unsophisticated, such as more 
frequent fuel filter changes during the initial change-over period, 
heating transportation and storage tanks, etc. The process of mixing 
standard diesel and biodiesel to achieve a particular biodiesel blend, 
such as B20, B35, or B50 (20%, 35%, and 50% biodiesel with the 
remainder standard diesel, respectively), though not technologically 
challenging, would normally be done by the fuel distributor.
    It is also significant that biodiesel is a ``drop in'' replacement 
for standard diesel in any diesel engine. The only engine modification 
that may be necessary in some engines is to insure that all elastomeric 
fuel system components (hoses, gaskets) are biodiesel compatible, 
however, any components that are not compatible can be easily replaced. 
For these reasons, of the many DPM controls that are available to 
underground M/NM mine operators, switching to biodiesel fuel may 
involve the fewest difficult implementation issues. The consequences of 
failing to implement the precautions listed above could be quite 
significant. But information regarding these implementation issues is 
well defined and widely distributed (MSHA will include this important 
information on its DPM Single Source Page), and fully addressing them 
would be technologically and economically feasible for most, if not all 
mine operators.
    We agree with comments that the availability of biodiesel fuel is 
more limited than standard diesel, especially in the eastern and 
western states. However, we believe that biodiesel will be more readily 
available in more areas of the country by the effective date of this 
final rule, even though its use may increase fuel transportation costs 
for some mines. Biodiesel is available from over 1,400 commercial 
petroleum distributors and over 750 retail stations across the country. 
The only state without in-state access to biodiesel is Alaska. The 
operator of a large underground metal mine in Alaska, however, reported 
that their fuel is shipped from Seattle, and their supplier has access 
to biodiesel.
    Regarding the availability of biodiesel in the eastern and western 
states, we acknowledge that most biodiesel production is concentrated 
in the Midwest, however as noted above, it is available in the 
contiguous 48 states, and Hawaii and biodiesel production and 
availability nationally is growing rapidly. Production of biodiesel in 
the U.S. grew from about 25 millions gallons in 2004 to about 75 
million gallons in 2005, and significant further production growth is 
expected in the future, including plants in currently underserved areas 
like Wyoming, Montana, Washington, California, Colorado, and Texas in 
the western part of the U.S., and Tennessee, Kentucky, Pennsylvania, 
Virginia, North Carolina, and New York in the east. This expected 
increased availability of biodiesel fuel by 2008 in currently 
underserved areas of the country supports our decision to phase-in the 
final DPM limits in three steps from 308EC [mu]g/m\3\ in May 
2006 to 350TC [mu]g/m\3\ in January 2007 to 160TC 
[mu]g/m\3\ in May 2008. Biodiesel plants currently under construction 
are rated at 329 million gallons of annual production capacity, and 
plants in the pre-construction phase will add an additional 518 million 
gallons of annual production capacity.
    The Montana platinum mining company referenced above stated that, 
``No manufacturers of biodiesel have been located in the proximity of 
the mine, making availability and delivery a significant concern.'' 
While there may be no biodiesel manufacturers in proximity to the mine 
at the present time, a 15,000,000 gallon annual capacity biodiesel 
plant is scheduled to go online in Culbertson, MT in March 2007, and 
there is currently a commercial biodiesel distributor about 140 miles 
from the mine site in Bozeman, MT. This distributor, which receives its 
supply of biodiesel via rail cars, has the capability to supply the 
mine's required 1,000,000 gallons per year, and it is equipped to use 
steam to heat the cars for off-loading during the winter months.

[[Page 28953]]

    Another commenter that expressed concern about the lack of 
biodiesel availability was a gold mine operator in the Elko, Nevada 
area. This operator said, ``B20 is available in Salt Lake City, 
approximately 300 miles away.'' While this is undoubtedly true, there 
is also a commercial biodiesel distributor at Battle Mountain, Nevada, 
about 120 miles from the mine that can supply any grade of biodiesel 
from B2 to B100. This distributor also receives its biodiesel via rail 
cars. It does not currently have the capability to apply steam to cars 
in the winter months to facilitate cold weather off-loading. However, a 
representative for the distributor indicated that such a capability 
would be provided if a customer entered into a supply contract 
providing for sufficient fuel volumes; a requirement that this mine 
should be able to satisfy within the time prescribed for the effective 
date of the final limit.
    A trona mine operator also expressed concern over the availability 
of biodiesel fuel near the mine in southwestern Wyoming. However, there 
is a commercial distributor of all grades of biodiesel fuel in Jackson, 
WY approximately 185 miles from the mine, and another commercial 
distributor in Richmond, UT approximately 180 miles from the mine. 
These fuel distributors are likely farther from the mine than the 
mine's current distributor, and shipments of fuel from these 
distributors would be subject to higher transportation costs. Although 
the mine operator would have to determine the feasibility of receiving 
biodiesel from such distance, we believe that the biodiesel industry 
will resolve these logistic problems in time for the effectiveness of 
the final limit in May 2008. The Biodiesel Board included comments to 
the 2005 NPRM stating how distribution of biodiesel fuel is expanding 
throughout the United States, which helps to make the final limit 
feasible as prescribed in the final rule.
    In response to a commenter's concerns about engine warranties, the 
engine manufacturers do not warrant their engines against fuel related 
problems, either biodiesel or standard petroleum diesel. Regarding the 
commenter's concern relating to their Cummins engines, the Cummins on-
line customer assistance fact sheet on biodiesel states that,

    Given the current understanding of bio fuels and blending with 
quality diesel fuel, it would be expected that blending up to a 5% 
volume concentration should not cause serious problems. For 
customer's intent on blending bio fuels above 5% volume 
concentration, the following concerns represent what is currently 
known in the industry.

    This on-line fact sheet goes on to identify specific areas of 
concern, including possible adverse effects on engine performance and 
fuel system integrity/durability, low temperature operability, heat 
content, oil change intervals, effects on elastomeric fuel system 
components, and a variety of issues related to long term storage, such 
as fuel stability, oxidation, corrosion, microbial growth, and fuel 
acid content. These issues are potentially significant, and if not 
appropriately addressed, could result in serious operational problems 
and engine damage. However, as noted above, we believe that solutions 
to these issues could be implemented by the extension of time offered 
by this final rule, so mine operators should not be impeded from 
utilizing high biodiesel content fuel blends.
    Regarding engine warranties, the Cummins on-line fact sheet states 
that,

    Cummins neither approves or disapproves of the use of biodiesel 
fuel. Cummins is not in a position to evaluate the many variations 
of biodiesel fuels or other additives, and their long-term effects 
on performance, durability or emissions compliance of Cummins 
products. The use of biodiesel fuel does not affect Cummins Material 
and Workmanship warranty. Failures caused by the use of biodiesel 
fuels or other fuel additives are NOT defects of workmanship and/or 
materials as supplied by Cummins Inc. and CANNOT be compensated 
under the Cummins' warranty.

    With respect to engine warranties, Cummins treats biodiesel no 
differently than it treats standard petroleum-based diesel. Most of the 
engine manufacturers have similar warranty positions.
    A trona mine operator reported that they had obtained DPM sample 
results for their mine that exceeded the 160TC [mu]g/
m3 final DPM limit despite using a B20 biodiesel fuel blend 
(20% biodiesel mixed with 80% standard petroleum diesel fuel). A stone 
mine operator reported similar results with B20 fuel. These commenters 
question whether biodiesel is a feasible control, since they were not 
able to attain compliance with the 160TC [mu]g/m3 
final DPM limit using this fuel.
    Based on extensive in-mine testing and both personal and area 
sampling at mines that have either experimented with, or switched 
permanently to biodiesel fuel blends, we believe significant DPM 
reductions would not have been expected with biodiesel blends as low as 
B20. In our evaluations, we only began to see significant DPM 
reductions at B35 or higher, with higher biodiesel content producing 
lower DPM levels. The DPM reductions of 60% to 80% that we have 
documented were achieved with fuel blends of 98% to 99% biodiesel. 
Thus, we continue to believe that biodiesel is a feasible DPM control 
that is capable of achieving significant reductions (as defined in the 
2005 rule (70 FR 32868, 32916)) in DPM exposure when this fuel is used 
in neat form (100% biodiesel) or in sufficiently high blends with 
standard petroleum diesel fuel.
    Several commenters also mentioned that they were considering, or 
had switched to ultra low sulfur (15 ppm) diesel fuel. As expected, 
these commenters did not report significant DPM reductions after the 
switch to this fuel. The primary benefit of ultralow sulfur diesel is 
to enable advanced emission reduction technologies that utilize 
catalysts that would be poisoned by higher sulfur content fuel.
    l. Installation of Environmental Cabs. Environmental cabs are a 
proven means to reduce worker exposure to DPM. While much of the 
construction-type equipment used in underground stone mines comes 
equipped with environmental cabs, the cabs on specialty mining 
equipment used in underground hard rock mining are less common, 
particularly in mines with narrow drifts or low seam heights. As mine 
operators realize the benefits of cabs, more and more pieces of 
equipment are being purchased or retrofitted with environmental cabs. 
These cabs provide protection for workers not only from diesel 
particulate but also from noise and dust.
    Only a few comments were received on the subject of environmental 
cabs. These comments typically agree that environmental cabs can be 
effective in reducing the occupant's DPM exposures, but applications 
may be limited by three factors: retrofitting cabs is not always 
possible, especially on some older machines, there may not be adequate 
clearance for cabs in certain confined areas of some mines, and cabs 
offer no protection for miners who must work outside a cab. A comment 
received from a mining industry organization was typical:

    Environmental cabs are effective. However, they can not be 
retrofitted to all mining equipment. Further, there are some jobs in 
underground mines where miners work outside of equipment and cabs 
would provide them no protection.

    Another industry organization stated,

    Simply put, fully enclosed environmental cabs provide superb 
protection to equipment operators from exposure to DPM. However, 
they provide no protection to miners working alongside such 
equipment. Furthermore, installation of fully enclosed environmental

[[Page 28954]]

cabs can only be accomplished where the resulting larger profile of 
the equipment fits properly within the heading size in the mine 
where such equipment is operated.

    We agree in general with these comments and we believe that a cab's 
feasibility needs to be evaluated on a case-by-case basis as to exactly 
which equipment is suitable for retrofit of a cab, or whether space 
limitations in certain areas at a particular mine would prevent 
utilization of equipment with cabs. In these respects, questions 
regarding the feasibility of using cabs as an engineering control to 
prevent DPM exposure are no different than questions regarding the 
feasibility of using cabs for control of dust or noise exposures.
    m. Ventilation. All underground M/NM mines rely on ventilation to 
dilute and carry away diesel particulate matter and toxic gases as well 
as to provide fresh air to the miners. Based on the comments received 
from mine operators and from our own observations during mine 
inspections and compliance assistance mine visits, it is clear that 
ventilation is a key component of nearly every mine's DPM control 
strategy.
    However, the extent to which it is feasible for ventilation system 
performance to be improved or upgraded, either to obtain compliance 
with the final DPM limit or to obtain compliance in combination with 
other controls, is disputed by some commenters. One commenter from a 
gold mine in Nevada stated that, ``Ventilation is near its capacity. 
Further increases are likely to create fugitive dust problems from 
haulage vehicles.'' Another commenter addressing conditions at a 
different multilevel metal mine indicated that increasing airflows in 
that mine's small and widely distributed working places would be 
difficult. This commenter also disputed our observation in the preamble 
to the 2005 final rule that a major multi-million dollar ventilation 
upgrade at that mine was not a DPM compliance related expense (70 FR 
32934-32936). Another commenter from a mining industry organization 
stated that a notable characteristic of underground stone mines is 
their large open spaces (room and pillar mining) that are ventilated 
naturally. To introduce forced ventilation in mines presently 
ventilated naturally would entail enormous costs in mine structures 
that would be needed to direct the ventilation inside the mine.
    These comments represent the extremes in ventilation practice in 
the underground M/NM mining industry. Deep multilevel mines, due to a 
variety of factors, typically have complex, costly, and sophisticated 
ventilation systems, often designed by a professional mine ventilation 
engineer, and usually operated and managed by engineers with specific 
mine ventilation training and experience. These systems normally 
consist of a network of main, booster and auxiliary fans, and a complex 
array of interconnected shafts, raises, and ventilation control 
structures. In contrast, room and pillar stone mines typically have 
very simple ventilation systems which may not have been designed at 
all. Such systems may rely entirely on natural ventilation alone, and 
those that do incorporate forced ventilation are often simple blowing 
or exhausting systems, or may consist of nothing more than one or a few 
free standing booster fans underground. They are normally operated or 
managed by the mine foreman or manager, and it is rare for such 
individuals to have had any professional training in mine ventilation 
engineering.
    At most multilevel metal mines, high ventilation system costs 
provide a major economic incentive to operators to optimize system 
design and performance, and therefore, there are typically few if any 
feasible upgrades to main ventilation system elements that these mines 
haven't already implemented, or would have implemented anyway, whether 
or not the DPM rule existed. Accordingly, and though it remains an 
option that might be attractive in new development, we expect very few 
mines of this type to implement major ventilation system upgrades to 
achieve compliance with this rule.
    Despite the built-in incentives to design and operate efficient 
ventilation systems, however, we have observed aspects of ventilation 
system operation at such mines that can be improved, usually relating 
to auxiliary ventilation in stopes. Auxiliary fans are sometimes sized 
inappropriately for a given application, being either too small (not 
enough air flow) or too large (causing recirculation). Auxiliary fans 
are sometimes poorly positioned, so that they draw a mixture of fresh 
and recirculated air into a stope. Auxiliary fans are sometimes 
connected to multiple branching ventilation ducts, so that the air 
volume reaching a particular stope face may be considerably less than 
the fan is capable of delivering. Perhaps most often, the ventilation 
duct is in poor repair, was installed improperly, or has been damaged 
by blasting or passing equipment to the extent that the volume of air 
reaching the face is only a tiny fraction of that supplied by the fan. 
We believe that these and similar problems exist at many mines, even if 
the main ventilation system is well designed and efficiently operated.
    Without extensive on-site study, we are unable to assess the 
validity of the commenter's assertion that the mine's ventilation is 
near its capacity, but such a condition would not be unusual, at least 
with respect to major ventilation system elements like shafts and main 
fans. Short of a major ventilation system upgrade such as a new shaft 
sinking or main fan installation or repowering, it would be more likely 
that auxiliary ventilation system performance could be improved.
    Regarding the issue of fugitive dust, which is mineral dust that is 
entrained in and carried by the ventilation air stream, if ventilation 
increases are required to reduce DPM levels, but such increased 
ventilation would be so great as to pick up dust from the mine floor or 
muck piles, it may be necessary for the mine operator to apply water 
more frequently to haul roads and working places, or use dust control 
chemicals to manage corresponding fugitive dust levels. Mine operators 
frequently face trade-offs like this, and we are confident this problem 
can be successfully handled within the prescribed time frames of this 
final rule. For example, mines that currently water their haul roads 
once a shift, may need to water their haul roads twice a shift.
    Regarding the comment relating to the difficulty of increasing 
ventilation in small and widely distributed working places, we 
conducted an extensive study of the auxiliary ventilation systems at 
this mine. The company ventilation engineer stated that the stope 
ventilation systems were designed to deliver a minimum of 12,000 cfm to 
the faces. The 12,000 cfm airflow would dilute emissions for a 100 hp 
loader (PI-5000 cfm) to 321EC [mu]g/m3. This 
value would increase by the level of DPM in the stope intake. During 
this survey, several of the stope ventilation systems failed to provide 
that level of airflow to the faces, and in fact, some systems lost over 
90% of their air volume before reaching the end of the vent duct. This 
was primarily due to long ventilation tubing lines and poor maintenance 
of the ventilation tubing. Also, it was noted during the survey that 
improper fan placement at the mouth of the stopes allowed exhaust air 
to be recirculated back to the face before being diluted by the 
footwall lateral airflow.
    This commenter also responded to our analysis of a major 
ventilation upgrade at this mine, characterizing it as ``suspect,'' but 
offering no specific comments or corrections. The mine in

[[Page 28955]]

question had instituted a major upgrade of the ventilation system 
including new aircourses, new vent raises, and new and redeployed main 
and booster ventilation fans. The $9,000,000 upgrade increased total 
mine airflow by 34% to 840,000 cfm while reducing total fan power 
requirements by 1,000 hp through more efficient deployment of booster 
fans.
    As a result of further discussions with personnel at the mine, we 
had determined that the upgrade had several objectives in addition to 
DPM control, including greater system efficiency such as eliminating an 
excessive number of booster fans (some competing with each other for 
air), the need to accommodate increased production, the need to 
ventilate a ramp used by trucks to haul ore upgrade from the levels 
below the bottom of the shaft, and the desire to increase the number of 
ventilation intakes into the mine, thereby providing more fresh air 
emergency escape routes and reducing intake aircourse air velocities 
(for reduced dust entrainment and enhanced miner comfort). We were told 
that the mine had ``overreached'' the existing ventilation system, and 
that the upgrade was overdue, even without consideration for DPM levels 
in the mine. Based on this information, and in response to comments 
from this mine operator addressing the August 14, 2003 proposed rule on 
the interim DPM limit, we had suggested that the total cost of the 
ventilation upgrade should be only partially DPM-related. We also 
pointed out that the cost of the upgrade needed to be annualized 
because the asset had an expected useful life of many years, resulting 
in a yearly cost that was a small fraction of the $9,000,000 expense. 
We disagree with the characterization of our analysis as ``suspect,'' 
because we believe it is fully supported by the facts, and because the 
commenter provided no explanations or corrections regarding our data or 
methods.
    Room and pillar stone mine ventilation is entirely different than 
multilevel metal mine ventilation. Ventilation at stone mines was 
addressed extensively in the preamble to the 2005 final rule (70 FR 
32931-32932). We agree that ventilation system upgrades may not be the 
most cost effective DPM control for many mines, and for others, 
ventilation upgrades may be entirely impractical. However, at many 
other mines, perhaps the majority of mines affected by this rule, 
ventilation improvements would be an attractive DPM control option, 
either implemented by itself or in combination with other controls. The 
additional time provided under this final rule will provide mine 
operators more time to explore these options.
    Indeed, during our DPM compliance assistance visits, we have 
observed that ventilation upgrades have been implemented at many mines 
in the stone sector for DPM control. Nearly every stone mine visited by 
us had completed, had begun, or was planning to implement ventilation 
system upgrades.
    At many high-back room-and-pillar stone mines, we observed 
ventilation systems that were characterized by (1) inadequate main fan 
capacity (or no main fan at all), (2) ventilation control structures 
(air walls, stoppings, curtains, regulators, air doors, brattices, 
etc.) that are poorly positioned, in poor condition, or altogether 
absent, (3) free standing booster fans that are too few in number, too 
small in capacity, and located inappropriately, and (4) no auxiliary 
ventilation for development ends (working faces). At some mines, the 
``piston effect'' of trucks traveling along haul roads underground, 
along with natural ventilation pressure, provide the primary or only 
driving forces to move air.
    In naturally ventilated mines, temperature-induced differences in 
air density between the surface and underground result in natural air 
flows through mine openings at different elevations. Warmer and lighter 
mine air rises up out of a mine during the colder winter months, which 
draws in cooler and heavier air at lower elevation mine openings. In 
the summer, cooler and denser mine air flows out of lower elevation 
openings, which draws warmer less dense air into higher elevation 
openings. Under the right conditions, such air flows can be 
significant, but they are usually inadequate by themselves to dilute 
and carry away DPM sufficiently to reduce miners' exposures to the 
interim limit.
    The other principal shortcoming of natural ventilation is the 
inherent lack of a method of controlling air flow quantity and 
direction. Ventilation air flows can slow or stop when temperature 
differences between the surface and underground are small (common in 
the spring and fall), and the flow direction reverses between summer 
and winter, and sometimes even between morning and afternoon.
    Mine operators normally supplement natural ventilation with booster 
fans underground. However, if overall air flow is inadequate, as is 
usually the case with naturally ventilated mines, and when mine 
elevation differences or surface and underground temperature 
differences are small, booster fans are largely ineffective.
    The all too frequent result of these deficiencies is a ventilation 
system that is plagued by insufficient dilution of airborne 
contaminants, short circuiting, recirculation, and airflow direction 
and volume that are not controllable by the mine operator. Mines 
experiencing these problems could benefit greatly from upgrading main, 
booster, and/or auxiliary fans, along with the construction and 
maintenance of effective ventilation control structures. Consequently, 
we have urged the mining industry to utilize mechanical ventilation to 
improve overall air flows and to enable better control of ventilating 
air.
    Ventilation fan upgrades for the stone mining sector are usually 
relatively inexpensive due to the low mine resistance associated with 
large openings. In many of these mines, a 250,000 cfm air flow can be 
obtained at less than 1 inch of water gage pressure. This air flow can 
be provided by a 50 horsepower motor.
    We agree with the commenter that the major cost in these 
applications is usually distribution of the air flow underground to 
insure that adequate air quantities reach the working faces rather than 
short-circuiting to a return or recirculating around free-standing 
booster fans. Good air flow distribution requires such practices as 
installing or repairing ventilation control structures (brattice line, 
air curtains, etc.) or changes in mine design to incorporate unmined 
pillars as air walls. Such ventilation control structures are not 
complex to install, and since they usually have a very long useful 
life, when the cost of such controls is annualized, the yearly cost is 
only a fraction of the initial acquisition and installation costs.
    Despite the commenter's suggestion to the contrary, a great many 
underground stone mines are currently ventilated with main and booster 
fan systems. The necessary ventilation control structures have also 
been installed in a great many such mines to facilitate the efficient 
and effective distribution of ventilation air underground. One 
commenter, a stone producer with seven underground mines, reported 
that, ``All of [their] mines have performed major ventilation 
upgrades,'' including ventilation surveys by an outside contractor, 
installation of larger main fans, installation of new and larger 
portable fans that are used at active headings, use of larger booster 
fans, and the installation of ``new ventilation stoppings and curtains 
at various locations throughout the mine at all mines.'' Clearly, based 
on this company's experiences and our

[[Page 28956]]

observations at many other mines, the technological feasibility of this 
type of DPM engineering control is well established for the stone 
sector of the underground M/NM mining industry, although it may take 
some time for mines to make the necessary changes.
    n. DPM Sampling Issues. A trona mine operator, in reporting their 
DPM sampling results in their comments, indicated that these samples 
were analyzed using the NIOSH 5040 method and calculated using the MSHA 
Sampling Method to determine exposure, which does not take into account 
significant IH factors such as shift length over 480 minutes, average 
pump flow rates using pre-sample calibration and post-sample 
calibration figures, and other environmental factors such as 
temperature and pressure. We disagree that the MSHA Sampling Method 
fails to account for these industrial hygiene (IH) factors.
    Our DPM sampling procedures are posted on the M/NM DPM Single 
Source Page, which is linked to our internet home page. Exposures are 
determined from the sampling data in accordance with the formula on 
page T-7 of the sampling procedures, as shown below:
[GRAPHIC] [TIFF OMITTED] TR18MY06.009

Where:

C is the mass of carbon, expressed in micrograms, deposited on the 
filter per square centimeter of filter surface
A is the area of the filter onto which DPM is deposited, expressed in 
square centimeters
1,000 L/m3 is a unit conversion factor to convert liters to 
cubic meters (the pump flow rate is expressed in liters per minute, 
whereas the DPM concentration is expressed in micrograms per cubic 
meter)
1.7 Lpm is the pump flow rate, expressed in liters per minute
480 min is the number of minutes in an 8-hour work shift

    We account for work shifts longer or shorter than 8 hours (480 
minutes) by shift-weighting all sample results. The shift-weighting 
process is explained in the DPM Compliance Guide, which is also posted 
on the M/NM DPM Single Source Page and is summarized below:

    ``Average full shift airborne concentration'' means that a 
miner's exposure is determined by measuring the average 
concentration of airborne DPM to which the miner is exposed over a 
full work shift, regardless of shift length. Temporary excursions 
above a limit are permitted from time to time during the shift, as 
long as the average over the entire shift is within the limit. The 
term, ``average eight hour equivalent full shift airborne 
concentration,'' refers to our longstanding practice of ``shift-
weighting'' when applying compliance limits for airborne 
contaminants to exposures that occur over a time period that is 
different from a standard 8-hour shift. Our compliance limits are 
normally based on 8 hours of workplace exposure to a contaminant and 
16 hours of recovery time in the absence of the contaminant. The 
workplace 8-hour shift weighted average (SWA) exposure is computed 
as the mass of DPM on the filter divided by the 8-hour sample 
volume, which is 0.816 cubic meter for a sample flow rate of 1.7 
liters per minute.

    Thus, our DPM sampling and analytical procedures do account for 
work shifts that are longer than 8 hours. Regarding the other 
industrial hygiene factors which the commenter claims are not 
addressed, our sampling procedures on p. T-3 requires pre-sample 
calibration of the sampling pump, and on p. T-6, requires post-sample 
calibration of the sampling pump. The pre-sample and post-sample 
calibrations are required to be performed in accordance with the 
procedures outlined in Chapter C of the M/NM Health Inspection 
Procedures Handbook. Since our pump calibration devices measure true 
volumetric flow, day to day variations in atmospheric pressure due to 
weather changes are irrelevant. However, pressure effects from 
calibrating a pump at one elevation and sampling at a significantly 
different elevation can be important. Accordingly, among the many 
requirements relating to the use of sample pumps contained in the M/NM 
Health Inspection Procedures Handbook is one specifying that pump 
calibrations must be performed within 1,000 feet of the elevation where 
sampling will be conducted, or if not, that the specified procedures 
for adjusting pump flow rate for elevation must be followed. Our 
inspectors are also required to measure and record the temperature 
where sampling occurs. Our DPM sampling field notes form has a space 
for temperature that must be filled in for every sample taken.

B. Economic Feasibility

    We have determined that phasing in the final DPM limit of 
160TC [mu]g/m\3\ as prescribed in the final rule is 
economically feasible for the M/NM mining industry. Economic 
feasibility does not guarantee the continued viability of individual 
employers, but instead, considers the industry in its entirety. In 
United Steelworkers of America v. Marshall, 647 F.2d 1189, 1265 (1980) 
regarding OSHA's statutory criteria for establishing economic 
feasibility, the Court recognized that:

    The most useful general judicial criteria for economic 
feasibility comes from Judge McGowan's opinion in Industrial Union 
Dep't, AFL-CIO v. Hodgson, supra. A standard is not infeasible 
simply because it is financially burdensome, 499 F.2d at 478, or 
even because it threatens the survival of some companies within an 
industry:
    Nor does the concept of economic feasibility necessarily 
guarantee the continued existence of individual employers. It would 
appear to be consistent with the purposes of the Act to envisage the 
economic demise of an employer who has lagged behind the rest of the 
industry in protecting the health and safety of employees and is 
consequently financially unable to comply with new standards as 
quickly as other employers. * * *

Id. (footnote omitted). A standard is feasible if it does not 
threaten ``massive dislocation'' to, AFL-CIO v. Brennan, supra, 530 
F.2d at 123, or imperil the existence of, American Iron & Steel 
Institute v. OSHA, supra, 577 F.2d at 836, the industry. No matter 
how initially frightening the projected total or annual costs of 
compliance appear, a court must examine those costs in relation to 
the financial health and profitability of the industry and the 
likely effect of such costs on unit consumer prices. Id. More 
specifically, Industrial Union Dep't, AFL-CIO v. Hodgson, supra, 
teaches us that the practical question is whether the standard 
threatens the competitive stability of an industry, 499 F.2d at 478, 
or whether any intra-industry or inter-industry discrimination in 
the standard might wreck such stability or lead to undue 
concentration. Id. at 478, 481. Granting companies reasonable time 
to comply with new PEL's might not only enhance economic feasibility 
generally, but, where the agency makes compliance deadlines uniform 
for competing segments of industry, can also prevent such injury to 
competition. Id. at 479-481. United Steelworkers of America, AFL-
CIO-CLC v. Marshall, (OSHA Lead) 647 F.2d 1189, 1265 (D.C. Cir. 
1980). To prove economic feasibility, ``OSHA must construct a 
reasonable estimate of compliance costs and demonstrate a reasonable 
likelihood that these costs will not threaten the existence or 
competitive structure of an industry, even if it does portend 
disaster for some marginal firms.'' Steelworkers, 647 F.2d at 1272. 
As with technological feasibility, OSHA is not

[[Page 28957]]

required to prove economic feasibility with certainty, but is *981 
**153 required to use the best available evidence and to support its 
conclusions with substantial evidence. See id. at 1267.

    In a separate case involving review of an OSHA standard, the D.C. 
Circuit Court stated that:

    ``Congress does not appear to have intended to protect employees 
by putting their employers out of business--either by requiring 
protective devices unavailable under existing technology or by 
making financial viability generally impossible.'' See Industrial 
Union Dep't., 499 F.2d at 467 (D.C. Circuit 1974).

    A standard would not be considered economically feasible if an 
entire industry's competitive structure were threatened. Id. at 478; 
See also, AISI-II, 939 F.2d 975, 980 (DC Cir. 1991); United 
Steelworkers, 647 F.2d at 1264-65; AISI-I, 577 F.2d 825, 835-36 (1978). 
This would be of particular concern in the case of foreign competition, 
if American companies were unable to compete with imports or substitute 
products. The cost to government and the public, adequacy of supply, 
questions of employment, and utilization of energy may all be 
considered when analyzing feasibility.
    In determining whether these factors might reasonably be 
significant in analyzing the economic feasibility of a rule, MSHA has 
relied on a 1% ``screen'' of the yearly costs industry is estimated to 
incur to comply with a rule relative to annual industry revenues. When 
yearly costs are less than 1% of annual revenues, MSHA views that the 
costs of the rule are below the threshold necessary to conclude that 
such an extensive analysis is necessary to establish the economic 
feasibility of the rule. In that case, MSHA presumptively concludes 
that the rule is economically feasible.
    This final rule will continue to require mine operators to 
establish, use and maintain all feasible engineering and administrative 
control methods to reduce a miner's exposure to the applicable final 
limit. It affords mine operators the flexibility to choose engineering 
and administrative controls, or a combination of controls to reduce a 
miner's exposure to DPM. When engineering and administrative controls 
do not reduce a miner's exposure to the DPM limit, the controls are 
infeasible, or controls do not produce significant reductions (as 
defined in the 2005 rule (70 FR 32868, 32916)) in DPM exposures, 
operators must continue to use all feasible engineering and 
administrative controls and supplement them with respiratory 
protection. Though mine operators may choose to use an engineering 
control or an administrative control to reduce a miner's exposure, or a 
combination thereof, existing Sec.  57.5060(d) prohibits a mine 
operator from using respiratory protection in lieu of feasible 
controls. Mine operators must establish a respiratory protection 
program when controls are infeasible. Section 57.5060(d), as 
promulgated under the 2005 rule, incorporates by reference MSHA's 
current respiratory protection program requirements for metal and 
nonmetal mines at Sec. Sec.  56.5005(a) and (b) and 57.5005(a) and (b). 
These provisions include requirements for selection, fit-testing, and 
maintenance of respirators. In addition, mine operators must follow the 
requirements under paragraphs (d)(1) and (d)(2) of the 2005 rule for 
appropriate filters for respirators. If we confirm that mine operators 
have met all of the abovementioned requirements for addressing a 
miner's overexposure, and the miner's exposure continues to exceed the 
final limit (not counting respirators), we will not issue a citation 
for an overexposure. Instead, we will continue to monitor the 
circumstances leading to the miner's overexposure, and as controls 
become feasible, we will require the mine operator to install and 
maintain them to reduce the miner's exposure to the final limit. We 
believe that existing controls used to reduce miners' exposures to the 
current interim limit can be used in helping mine operators achieve 
compliance with the final limits. Therefore, in determining the 
economic feasibility of engineering and administrative controls that 
the M/NM underground industry will have to use under this final rule 
and using the 2001 REA as a basis, we compared the cost of controls 
that are used to comply with the existing DPM limit of 308EC 
[mu]g/m\3\ to that of the newly promulgated final limits. These 
controls include diesel particulate filters (DPFs), ventilation 
upgrades, oxidation catalytic converters, alternative fuels, fuel 
additives, enclosures such as cabs and booths, improved maintenance 
procedures, newer engines, various work practices and administrative 
controls. Our comparison included costs of retrofitting existing 
diesel-powered equipment and regeneration of DPFs.
    On the basis of information in the rulemaking record, including our 
current enforcement experience, we have determined that the final rule 
is economically feasible for the underground M/NM mining industry as a 
whole, as was the 2005 final rule. In the 2005 final rule, we 
determined that the 308EC [mu]g/m\3\ interim limit is 
economically feasible. To determine whether this final rule is 
economically feasible, we analyze economic feasibility from two 
different perspectives. First, we analyze whether the new requirements 
of the final rule (medical evaluation and transfer) are economically 
feasible. Second, we analyze whether the additional cost of moving from 
the interim limit of 308EC [mu]g/m\3\ to the final limit of 
160TC [mu]g/m\3\ is economically feasible.
    Analyzed from the first perspective, the additional yearly costs of 
the final rule are $69,170. The derivation of the costs of medical 
evaluation and transfer provisions of the final rule are explained in 
Section IX.A of this preamble. The total yearly compliance cost of 
these new provisions for the underground M/NM mines that use diesel 
equipment is only 0.001% of the annual revenues for these mines, well 
below the 1% ``screen'' that we use as a presumptive benchmark of 
economic feasibility. Hence, we conclude that this final rule is 
economically feasible for underground M/NM mines that use diesel 
equipment. Table V-1 shows these calculations.

[[Page 28958]]

[GRAPHIC] [TIFF OMITTED] TR18MY06.000

    Analyzed from the second perspective, the additional yearly costs 
for underground M/NM mines to move from the interim limit to the final 
limit of 160TC [mu]g/m3 are $8,454,853. The 
derivation of these costs of achieving the 160TC [mu]g/
m3 final limit, given that the 308EC [mu]g/
m3 interim limit is in effect, are provided in Section IX.B 
of this preamble. The total yearly cost of meeting the final limit for 
the underground M/NM mines that use diesel equipment is only 0.175% of 
the annual revenues for these mines, well below the 1% ``screen'' that 
we use as a presumptive benchmark of economic feasibility. Hence, we 
conclude that the final limit is economically feasible for underground 
M/NM mines that use diesel equipment. Table V-2 shows these 
calculations.

[[Page 28959]]

[GRAPHIC] [TIFF OMITTED] TR18MY06.001

    In circumstances where the use of further controls may not be 
economically viable, the standard provides for a hierarchy of control 
strategy that allows specifically for the cost impact to be considered 
on a case-by-case basis. Our DPM enforcement policy, therefore, takes 
into account the financial hardship on a mine-by-mine basis, which we 
believe effectively accommodates mine operators' economic concerns, 
particularly those of small mine operators.
    Whether controls are feasible for individual mine operators is 
based in part upon legal guidance from decisions of the independent 
Federal Mine Safety and Health Review Commission (Commission) involving 
enforcement of MSHA's noise standards for M/NM mines, 30 CFR 56.5-50 
(revised and recodified at 30 CFR 62.130). According to the Commission, 
a control is feasible when it: (1) Reduces exposure; (2) is 
economically achievable; and (3) is technologically achievable. See 
Secretary of Labor v. A.H. Smith, 6 FMSHRC 199, 201-02 (1984); 
Secretary of Labor v. Callanan Industries, Inc., 5 FMSHRC 1900, 1907-09 
(1983).
    In determining the economic feasibility of an engineering control, 
the Commission has ruled that we must assess whether the costs of the 
control are disproportionate to the ``expected benefits,'' and whether 
the costs are so great that it is irrational to require implementation 
of the control to achieve those results. The Commission has expressly 
stated that cost-benefit analysis is unnecessary to determine whether a 
control is feasible.
    Consistent with Commission case law, we consider three factors in 
determining whether engineering controls are feasible at a particular 
mine: (1) The nature and extent of the overexposure; (2) the 
demonstrated effectiveness of available technology; and (3) whether the 
committed resources are wholly out of proportion to the expected 
results. A violation under the final standard will entail an agency 
determination that a miner was overexposed, that controls are feasible, 
and that the mine operator failed to install or maintain such controls. 
According to the Commission, an engineering control may be feasible 
even though it fails to reduce exposure to permissible levels contained 
in the standard, as long as there is a significant reduction in a 
miner's exposure. Todilto Exploration and Development Corporation v. 
Secretary of Labor, 5 FMSHRC 1894, 1897 (1983).
    We will consistently utilize our longstanding enforcement 
procedures that we currently use for enforcement of our interim DPM 
limit and for our other exposure-based standards at M/NM mines. As a 
result, we will consider the total cost of the control or combination 
of controls relative to the expected benefits from implementation of 
the control or combination of controls when determining whether the 
costs are wholly out of proportion to results. If controls are capable 
of achieving a 25% reduction criterion, we will evaluate the cost of 
controls and determine whether their costs would be a rational 
expenditure to achieve the expected results.
    We continue to emphasize that the concept of ``a combination of 
controls'' is not new to the mining industry. It is our consistent 
practice not to cost controls individually, but rather to combine their 
expected results to determine if the 25% significant reduction 
criterion, as discussed earlier in this section, can be satisfied. We 
heavily weigh the potential benefits to miners' health when considering 
economic feasibility and do not conclude economic infeasibility merely 
because controls are expensive. Mine operators have the responsibility 
for demonstrating to us that the costs of technologically feasible 
controls are wholly out of proportion to their expected benefits.
    In situations where we find that the mine operator has not 
installed all feasible controls, we will issue a citation

[[Page 28960]]

and establish a reasonable abatement date. Based on a mine's 
technological or economic circumstances, the standard gives us the 
flexibility to extend the period within which a violation must be 
corrected. If a particular mine operator is cited for violating the DPM 
final limit, but that operator believes that the standard is 
technologically or economically infeasible for that operation, the 
operator ultimately can challenge the citation in an enforcement 
proceeding before the Commission.
    We have found that most of the practical and effective DPM controls 
that are available, such as DPFs, ventilation upgrades, enclosed cabs 
with filtered breathing air, alternative diesel fuels, low-emission 
engines, and various work practice and administrative controls, have 
the potential to achieve a 25% reduction in DPM exposure. The actual 
percentage reduction obtained varies from application to application 
depending on the nature of the exposure and the specific choice of 
control or controls applied. For example, a DPF might reduce DPM 
tailpipe emissions from a piece of diesel-powered equipment by 95%. 
However, the equipment operator's actual exposure could be reduced by 
more than 95% if an enclosed cab with filtered breathing air is also 
provided, or the reduction could be less than 95% if other diesel-
powered equipment without filtered exhaust is operated in the same 
area.
    We have consistently advised the industry that DPM controls should 
be selected based on a thorough analysis of the circumstances and 
conditions at each mine. This final rule affords each mine operator the 
flexibility to select the DPM controls that are appropriate for their 
site-specific conditions. We have also advised that similar equipment 
may require different DPM controls due to different duty cycles or 
operating conditions. For example, a platinum-catalyzed passively-
regenerating DPF might be successfully applied on one piece of 
equipment, but it may fail on a similar piece of equipment owing to 
different duty cycles. Even if applied on similar machines with similar 
duty cycles, such a DPF might be successfully applied on one machine 
but be unsuitable for the other because it is operated in an area of 
the mine having marginal ventilation, which could result in elevated 
NO2 exposures.
    Our compliance cost estimates from the 2001 final rule (not 
adjusted for inflation) ranged from $31,373 per year for the smallest 
nonmetal mines (based on fewer than 20 miners and 2.2 pieces of diesel-
powered equipment per mine) to $659,987 for the largest precious metals 
mines (based on over 500 miners and 133 pieces of diesel-powered 
equipment per mine). Our average estimated compliance cost for the 
industry as a whole to achieve the interim and final limits was about 
$128,000 per year per mine in 1998 dollars, or about 0.68 percent of 
the mine's annual revenues, on average. Of that amount, about $90,000 
per mine, on average, was our estimated yearly compliance cost to meet 
the interim limit of 400TC [mu]g/m3. These 
estimates were reduced by a negligible amount in the 2005 final rule, 
due largely to the elimination of the provisions on DPM control plan 
and required approval from the Secretary to use respiratory protection. 
As shown in Table IX.5 of this preamble, the estimated compliance cost 
to move from the interim limit to the final limit of 160TC 
[mu]g/m3 is about $50,000 per mine in 2004 dollars.
    The 2001 final rule established DPM limits that were to be phased-
in in two steps over five years, starting with 308EC [mu]g/
m3, which is comparable to the 400TC [mu]g/
m3 that became effective July 20, 2002, 18 months after 
promulgation, followed by a final limit of 160TC [mu]g/
m3 that was to become effective three-and-one-half years 
later. Our intent with respect to the phased-in DPM limits in the 2001 
rule and in subsequent rulemaking was to provide the industry with 
adequate time to familiarize itself with DPM control technology so mine 
operators could make informed decisions regarding selection and 
implementation of controls, train miners properly on the use and 
maintenance of the controls before the limits became effective, and 
spread the cost of controls over a multi-year period. As noted above, 
our Regulatory Economic Analysis (REA) for the 2001 final rule 
determined that total annual compliance costs would average $128,000 
per mine for the industry as a whole, primarily for DPM controls. These 
costs represented about 0.68% of annual industry revenue. We believed 
that the multi-year phase-in of the DPM limits would serve to reduce 
the economic impact on affected mines by encouraging purchases of 
controls gradually over several years.
    At the time the 2001 final rule was issued, based on the 
availability of controls we understood could be implemented by mine 
operators to attain compliance with the respective limits, we believed 
the phase-in schedule of 18 months to reach the interim limit and five 
years to reach the final limit would provide sufficient time for the 
entire industry to attain compliance. However, based on the comments 
received from the mining industry, other data in the DPM rulemaking 
record, information received from NIOSH, our compliance assistance 
reports and activities, and our experience with enforcing the interim 
limit, we began to question whether it was feasible for the industry to 
attain compliance with the final limit by January 20, 2006. As we 
discussed in the preamble to the 2005 NPRM, the applications 
engineering and related technological and economic implementation 
issues that we believed would have been easily resolved by then were 
more complex and extensive than previously thought. We still believed 
the mining industry could reach compliance with the 160TC 
[mu]g/m3 final limit; however, we had determined that the 
original schedule for attaining the final limit was too ambitious for a 
significant portion of this industry.
    In the 2005 NPRM, we acknowledged the implementation issues and 
proposed modifying our phase-in schedule with the intention of 
establishing a more realistic regulatory timetable for reaching the 
final limit. Rather than requiring compliance with the 160TC 
[mu]g/m3 final limit by January 20, 2006, we proposed 
phasing-in the final limit in five steps over a five year period, and 
in 50TC [mu]g/m3 reductions for each year. The 
initial final limit would have been 308EC [mu]g/
m3 on January 20, 2006; 350TC [mu]g/m3 
on January 20, 2007; 300TC [mu]g/m3 on January 
20, 2008; 250TC [mu]g/m3 on January 20, 2009; 
200TC [mu]g/m3 on January 20, 2010; and finally 
160TC [mu]g/m3 on January 20, 2011. Our goal in 
proposing this five-year phase in was to provide the additional time we 
believed the industry needed to attain the final 160TC 
[mu]g/m3 limit, while at the same time, assuring steady 
progress would be made during that period to reduce miner exposures to 
DPM. In the NPRM, we asked for comments on this schedule for phasing in 
the final limit, and on other issues.
    After analyzing the information and data obtained from the comments 
we received on the 2005 NPRM, we have extended the amount of time we 
believe the industry will need to attain compliance with the 
160TC [mu]g/m3 final limit beyond what was 
promulgated in the 2001 final rule. Based on this new information and 
data, we now believe that requiring compliance with the final limit in 
three steps over two years, namely 308EC [mu]g/m3 
by May 20, 2006, 350TC [mu]g/m3 by January 20, 
2007, and 160TC [mu]g/m3 by May 20, 2008, is 
feasible. This timeframe for implementing the final limits will produce 
the maximum degree of miner protection from DPM exposure that is

[[Page 28961]]

both technologically and economically feasible for the M/NM underground 
mining industry, as a whole, to achieve.
    We continue to believe that establishing a final limit lower than 
160TC [mu]g/m3 is not economically feasible for 
the industry. Reducing the final limit below 160TC [mu]g/
m3 would require costly ventilation upgrades, replacement of 
most older mining equipment, and considerably increased use of DPFs on 
large numbers of, if not on all, underground diesel powered equipment.
    In our 2005 NPRM, where we proposed our five-year phase in of the 
final limit, we tentatively concluded that the 2001 160TC 
[mu]g/m3 final concentration limit presented a significant 
challenge to a large portion of the underground M/NM mining industry 
and that compliance may not be feasible by January 2006. We also stated 
that:

    Our experience since January 2001 has raised questions on 
technological feasibility for the mining industry as a whole, rather 
than for a small number of individual mines, to meet the 160 TC 
concentration limit by January 20, 2006.

We specifically requested comments on the economic feasibility of the 
final concentration limit of 160TC [mu]g/m3 and 
our proposed phase-in approach.
    We also acknowledged in the 2005 NPRM that significant compliance 
difficulties may be encountered at some mines due to implementation 
issues and the cost of purchasing and installing certain types of 
controls. We requested additional information regarding these 
technological difficulties and whether they would increase the cost to 
comply with the final concentration limit above that estimated in the 
2001 final rule.
    In addition, we proposed to eliminate Sec.  57.5060(c)(3)(i) which 
prohibits new mines from applying for special extensions and requested 
comments on the benefits (including cost savings) of doing so. Lastly, 
we requested comments on the costs to mine operators for implementing a 
rule requiring medical evaluation and transfer of miners. In response 
to these requests, we received numerous comments on the economic 
feasibility of meeting a final limit of 160TC [mu]g/m\3\ 
within the proposed phase-in timeframes, as well as on other provisions 
of the proposed rule, which we discuss in detail below.
    We believe that the reduction from 308EC [mu]g/m\3\ to 
350TC [mu]g/m\3\ in January 2007 will provide necessary 
incentive and experience for mine operators to continue to work out 
their remaining feasibility issues and not to delay implementation of 
further engineering and administrative controls until the final 
160TC [mu]g/m\3\ limit becomes effective in May 2008.
    We believe that the current rulemaking record fully supports the 
economic feasibility of the initial phase-in final limit of 
308EC [mu]g/m\3\, and the final limit of 160TC 
[mu]g/m\3\. We have no new data or information in the rulemaking record 
justifying change to our 2005 cost estimates for the interim limit of 
308EC [mu]g/m\3\. We stated in our 2005 final rule that a 
PEL of 308EC [mu]g/m\3\ was economically feasible for the M/
NM mining industry and provided considerable discussion in support of 
our position.
    Regarding the 2001 final limit of 160TC [mu]g/m\3\, we 
stated in the 2005 final rule that the evidence in the current DPM 
rulemaking record was inadequate for us to make determinations 
regarding revision of the final DPM limit at that time. We requested 
comments on the feasibility of the mining industry to comply with a 
final limit of less than 308EC [mu]g/m\3\.
    Although we did not revise the final limit in the 2005 final rule, 
we did revise the special extension requirement to provide one year, 
renewable, extensions of time for mine operators in which to comply 
with the final limit, based on either economic or technological 
constraints, but continued to prohibit newer mines from applying for 
extensions (70 FR 32966). Additionally, in this 2006 final rule, we 
have removed the prohibition on newer mines from applying for a special 
extension. Consequently, all mine operators will be able to apply for a 
one-year, renewable special extension of time to comply with each of 
the final limits, including the final limit of 308EC [mu]g/
m\3\, 350TC [mu]g/m\3\, and 160TC [mu]g/m\3\.
    The rulemaking record provides numerous examples of successful use 
of effective DPM controls. Our enforcement sampling record from 
November 2003 to January 2006 shows that 82% of the 1,798 samples we 
collected were below the 308EC [mu]g/m\3\ interim limit, 78% 
were below the January 2007 final limit of 350TC [mu]g/m\3\, 
and 46% were below the May 2008 final limit of 160TC [mu]g/
m\3\. Additionally, 46% of the mines sampled had at least one sample 
over 308EC [mu]g/m\3\, 55% over 350TC [mu]g/m\3\, 
and 82% of the mines had at least one sample over 160TC 
[mu]g/m\3\. It should be noted that we do not consider these sample 
results to necessarily represent typical or average exposures for the 
industry as a whole because we do not randomly select the miners to be 
sampled. Following good industrial hygiene practice, our sampling 
procedures dictate that when we conduct enforcement sampling, we sample 
those miners whom we believe will have the highest exposures. Thus, 
typical or average exposures for the industry as a whole would likely 
be lower than these values. We have determined that the degree of 
compliance demonstrated in our enforcement sampling and the cost of 
available control technology support our conclusion that the final 
limits are economically feasible for the industry as a whole within the 
prescribed timeframes. Our enforcement sampling results also 
demonstrate the magnitude of the compliance difficulties the M/NM 
mining industry would have experienced in meeting the 160TC 
[mu]g/m\3\ final limit by the May 2006 effective date.
    We provide for consideration of compliance difficulties on a mine-
by-mine basis in our existing use of hierarchy of controls and 
provisions on special extensions, which apply to the final limits. We 
are satisfied that the rule itself and our DPM enforcement policy take 
into account the financial difficulties on an individualized basis, 
which we believe will effectively accommodate an individual mine 
operator's economic concerns, particularly those of small mine 
operators.
    We further recognize that there currently are significant 
implementation issues, both economic and technological, that would make 
it infeasible for the industry to comply with the existing 
160TC [mu]g/m\3\ final limit by May 2006. In our 2005 NPRM, 
we proposed a five-year phase in of the final limit to address the 
remaining feasibility issues and asked for comments on the 
technological and economic feasibility of this approach. Based on our 
analysis of the comments received, the entire rulemaking record, our 
current enforcement strategy for enforcing the final limits, and our 
experience with DPM control technology and costs, we believe that 
compliance with the 160TC [mu]g/m\3\ final limit can be 
achieved in a shorter timeframe than the five years that we proposed. 
We are encouraged by the considerable progress we have seen to date in 
reducing DPM levels and in the many successful implementations of DPM 
controls addressed in the following discussion.
    As stated in our 2005 final rule, ``The trends in DPM control 
technology development, especially DPFs, indicate that manufacturers 
are creating more innovative designs. MSHA believes that more cost 
effective control methods are on the horizon.'' Another new

[[Page 28962]]

development that supports reducing the proposed five year phase-in of 
the final limit to the two year phase-in established in this rule is 
the significant DPM emission reductions achieved through the use of 
high biodiesel content fuel blends, coupled with the federal excise tax 
credit for biodiesel, and the rapidly growing availability of this 
alternative diesel fuel throughout the country. Although we acknowledge 
the high cost of some DPM controls, we do not believe they are 
significantly different from our estimated compliance costs in the 2001 
final rule, and we have identified many lower cost options.
    In the 2001 final rule, we estimated that the yearly cost of the 
rule would be about 0.68% of annual industry revenues, which was less 
than the 1% ``screen'' for costs relative to revenues that we use as a 
presumptive benchmark of economic feasibility (66 FR 5889). In the 2005 
final rule, we determined that the 308EC [mu]g/m\3\ interim 
limit was economically feasible for the M/NM mining industry. In Table 
IX.5 of this preamble, we estimate that the total yearly costs for the 
underground M/NM mines using diesel equipment to move from the current 
308EC [mu]g/m\3\ interim limit to the 350TC 
[mu]g/m\3\ and 160TC [mu]g/m\3\ final limits contained in 
this rule are $8,454,853. As previously shown in Table V-2 of this 
preamble, these yearly costs are less than 0.2% of annual industry 
revenues, well below our 1% ``screen'' that we use as a presumptive 
benchmark of economic feasibility.
    In this rulemaking to consider a phased-in approach to the final 
exposure limit of 160TC [mu]g/m\3\, we used economic 
feasibility information from the entire rulemaking record supporting 
the 2001 final rule, the 2005 final rule, comments in response to the 
2005 NPRM, and our experience gained with control technology since 
2001. We also used information obtained subsequently and entered into 
the rulemaking record, including data from the published literature, 
data developed by us through MSHA Technical Support investigations, 
public comments and testimony, and our enforcement experience relating 
to the interim PEL of 308EC [mu]g/m\3\.
    As stated above, we received numerous comments on the economic 
feasibility of the 2005 NPRM. Some commenters disagreed with our 
analytical method and the data we used to estimate compliance costs, 
and suggested that actual compliance costs will be much higher than our 
estimates. Consequently, they disputed our tentative conclusion that 
compliance with the phased-in final limits as proposed will be 
economically feasible for the industry as a whole. Other commenters 
stated that no delay is justified because there is strong evidence in 
the rulemaking record that full compliance with the 160TC 
[mu]g/m\3\ final limit is both technologically and economically 
feasible at this time for the industry as a whole. Still other 
commenters indicated that it was impossible to estimate the industry's 
compliance costs for attaining the final exposure limit at this time. 
This is because they contend that feasible technology for complying 
with this limit is not yet available and will not be available in the 
foreseeable future. Comments relating to our economic feasibility 
determinations regarding the final limit are discussed in this section. 
Comments addressing technological feasibility were discussed previously 
in this section.
    A few commenters stated that compliance with the final DPM limit 
would be cost prohibitive for their mines, and that business failure 
could result from their attempt to comply. Our technological and 
economic feasibility assessments of the final rule lead us to a 
different conclusion with respect to the possibility that business 
failures will occur as a result of implementing the final DPM limit.
    Several commenters suggested that our ``prior economic feasibility 
conclusion is based on improper sampling and analysis, inaccurate and 
incomplete data, and incorrect assumptions.'' Regarding the issue of 
sampling and analysis, our economic feasibility assessment for the 2001 
final rule was based on personal, occupational, or area sampling using 
a respirable dust sampler equipped with a submicron impactor, and 
analysis of samples for TC (EC plus OC) in accordance with NIOSH 
Analytical Method 5040. The DPM rulemaking record contains evidence 
supporting the positions of both MSHA and NIOSH regarding the 
performance of the SKC sampler. Among the conclusions drawn from the 
31-Mine Study and included in the preamble to the 2005 final rule were 
the following (70 FR 32871):

     The analytical method specified by the diesel standard 
gives an accurate measure of the TC content of a filter sample and 
the analytical method is appropriate for making compliance 
determinations of DPM exposures of underground metal and nonmetal 
miners.
     SKC satisfactorily addressed concerns over defects in 
the DPM sampling cassettes and availability of cassettes to both 
MSHA and mine operators * * *
     The submicron impactor was effective in removing the 
mineral dust, and therefore its potential interference, from DPM 
samples. Remaining interference from carbonate is removed by 
subtracting the 4th organic peak from the analysis. No reasonable 
method of sampling was found to eliminate interferences from oil 
mist or that would effectively measure DPM levels in the presence of 
environmental tobacco smoke (ETS) with TC as the surrogate * * *
    MSHA has found that the use of EC eliminates potential sampling 
interference from drill oil mist, tobacco smoke, and organic 
solvents, and that EC consistently represents DPM. In comparison to 
using TC as the DPM surrogate, using EC would impose fewer 
restrictions or caveats on sampling strategy (locations and 
durations), would produce a measurement much less subject to 
questions, and inherently would be more precise. Furthermore, NIOSH, 
the scientific literature, and the MSHA laboratory tests indicate 
that DPM, on average, is approximately 60 to 80% elemental carbon, 
firmly establishing EC as a valid surrogate for DPM.

    Some industry comments contained in Section VII of the 31-Mine 
Study final report state that, ``Fears about using Method 5040 have 
been allayed, but potential interference from ETS, oil mist, and ANFO 
are too great to permit using TC as a measure of DPM. Single samples 
and area samples are inappropriate.'' As noted below, our enforcement 
sampling procedures were subsequently changed to incorporate personal 
sampling only, and the DPM surrogate was changed to EC to eliminate 
potential non-DPM sources of OC from interfering with DPM 
determinations based on TC.
    Regarding the effectiveness of the SKC DPM sampler with integral 
submicron impactor in the presence of ore dust, the industry comments 
contained in Section III-B of the 31-Mine Study final report state 
that, ``The impactor works in most applications.'' The industry 
comments on this section also stated that, ``The industry is perplexed 
about possible continued interference in gold mines with graphitic 
ores.'' However, the 31-Mine Study final report states that, ``For 
typical samples collected in gold mines, the interference from 
elemental carbon from gold ore would be less than 1.5 [mu]g/m\3\.''
    In the 2005 final rule, we modified our compliance sampling 
strategy to utilize personal sampling only, which is the sampling 
strategy used by us for determining compliance with our other full-
shift exposure-based standards for airborne contaminants, and we 
changed the DPM surrogate from TC to EC for the interim limit. The 
change to EC as the DPM surrogate was made to eliminate the potential 
for sampling interferences from non-diesel sources of OC, such as drill 
oil mist or tobacco smoke, from causing erroneous TC analytical 
results. Our 2005 final rule on the interim DPM exposure limit 
incorporated these

[[Page 28963]]

changes, as does the current rulemaking, with the exception that we 
will undertake a separate rulemaking to convert from TC limits to EC 
limits for the 350TC [mu]g/m\3\ and 160TC [mu]g/
m\3\ final limits.
    Regarding the use of inaccurate or incomplete data for determining 
economic feasibility, some commenters suggested that the 2001 economic 
feasibility assessment should have been based on a representative 
sampling of all the underground mines affected by the rule. These 
commenters take the position that since the standard affects mines 
producing 24 different major commodities, our 2001 assessment should 
have included consideration for the impact of the standard on a 
representative sample of mines producing each commodity. The commenters 
also suggest that our practice of comparing the industry-wide cost of 
compliance to the industry's annual revenue is inappropriate. They 
indicate that this method ignores the fact that international commodity 
markets determine the viability of mines by setting market prices for 
their production, and that annual revenues of hundreds of millions, if 
not billions, of dollars have not prevented the domestic underground M/
NM mining industry from shrinking in recent years.
    We believe that the method we used to determine economic 
feasibility is valid. In the 2001 final rule, we subdivided the 
industry both by mine size class and commodity sector. The mine size 
classes were under 20 employees, 20 to 500 employees, and over 500 
employees. The commodity sectors grouped mines according to the 
commodity produced. The commodity sectors were stone, precious metals, 
other metals, evaporates, and other. The resulting matrix comprised the 
five commodity groups with three mine size classes within each 
commodity group. Compliance costs were estimated for mines within each 
size class and commodity group based on mining methods and equipment 
common for those specific types and sizes of mines. Using this 
methodology, all underground M/NM mines were included in our economic 
analysis, even though compliance costs were not necessarily determined 
on a mine by mine or individual commodity by individual commodity 
basis. Compliance cost estimates were included for each of the major 
provisions of the standard, such as DPM controls to attain the DPM 
limit (DPM filters, equipment cabs, and ventilation), newly introduced 
engines, paperwork costs associated with applying for a special 
extension, tagging and examination of equipment suspected of needed 
emissions maintenance, training, etc.
    Some commenters believe that we made incorrect assumptions in 
performing our economic feasibility assessments. The Regulatory 
Economic Analysis (REA) for the 2001 final rule was based on our 
determination that the most significant compliance cost component would 
be the cost of DPM controls to meet the respective DPM limits, 
accounting for 96% of the total cost of compliance. Our cost estimates 
for these controls were originally based on a compliance strategy that 
assumed that the interim limit would be attained primarily by replacing 
engines, installing oxidation catalytic converters, and ventilation 
improvements. We further assumed that the final limit would be attained 
primarily by adding environmental cabs with filtered breathing air and 
installing DPM filters. We recognized that mine operators had the 
flexibility to choose the engineering and administrative controls that 
best suited their mine-specific circumstances and conditions. However, 
for costing purposes, the above compliance strategies were assumed. 
Based on extensive industry comments on the Preliminary Regulatory 
Economic Analysis (PREA) for our 1998 proposed rule, we modified our 
cost estimates to favor diesel particulate filter systems and cabs for 
compliance with the interim limit, and more filters, ventilation and 
the turnover of engines for compliance with the final limit. Our 2001 
REA was based on this modified compliance strategy.
    The modified compliance strategy results in estimated industry-wide 
compliance costs that we believed were economically feasible for the 
industry as a whole. The original estimate of $19.2 million in annual 
compliance costs was revised upward to $25.1 million as a result of the 
comments received on the 1998 proposed rule. Our economic analysis for 
the 2005 final rule on the interim limit actually showed a slight 
decrease in compliance costs of $3,634 annually, primarily due to 
reduced recordkeeping requirements from elimination of the DPM control 
plan and required approval from the Secretary to use respiratory 
protection (70 FR 32944). The 2005 final rule analysis, however, did 
not address the economic impact of the final DPM limit of 
160TC [mu]g/m\3\.
    The commenters further stated that the compliance strategy used for 
developing compliance cost estimates was based on, ``incorrect 
assumptions of applicable and feasible controls.'' However, as 
discussed extensively in the technological feasibility section of this 
preamble and throughout the rulemaking record, we have established the 
feasibility of the various controls that are required to attain 
compliance with the new final limits in accordance with the phased-in 
dates.
    Through the comments received during our DPM rulemakings, 
compliance assistance visits to mines, and our enforcement experience 
with the 2001 and 2005 final rules, we have learned that the vast 
majority of mine operators have acquired at least a few EPA Tier 1 and 
Tier 2 engines, and many have fleets that are comprised of 40% to 50% 
or more of such engines. Despite disagreeing with our proposed rule, a 
stone mining operator with seven underground mines commented that all 
new equipment purchased at two of their mines were supplied with EPA 
Tier 3 engines, and they have plans to similarly upgrade the remaining 
equipment at those mines. Three other stone mining operators who also 
disagreed with our proposed rule, nonetheless, volunteered similar 
information. One reported they had recently acquired a new loader, 
drill, and scaler, all with EPA Tier 2 engines. Another reported 
acquiring two new haulage trucks in 2005 at a cost of over $600,000. 
The third operator indicated that,

    Before the initial inventory was even required, we immediately 
replaced our 1970's haul trucks with trucks built in the 1990's. 
Later we removed a 1992 loader for a 1999 loader with a Tier 2 
engine. We have recently purchased a newer roof-scaler with a Tier 2 
engine. We have retrofitted one of our drills with a Tier 2 engine, 
and are looking at buying a new drill to replace our second drill.''

Use of low emission engines has also been common in the western 
multilevel metal mines. Despite opposing our proposed rule, one mine 
operator said that replacement of old engines with new cleaner engines, 
where practicable, began in 2003. Such engine replacements have now 
become a primary focus of our efforts to control DPM. Another operator 
who opposed our proposed rule indicated they have conducted a proactive 
engine campaign to replace higher DPM emitting engines with newer EPA 
Tier 1 and Tier 2 rated engines. To date, 68% of the underground 
equipment is powered by EPA Tier 2 rated engines. A third operator who 
also disagreed with our proposed rule reported they have repowered 
eight pieces of equipment at their mine. A mining industry organization 
commented that, ``* * * as our members replace their old engines with 
new cleaner engines, that effort

[[Page 28964]]

will reduce the DPM exposures of miners.'' A comment from another mine 
operator indicated that during the last two years, they had, 
``purchased fifteen Tier 2 engines that, along with thirty Tier 1 
engines, constitute 42% of the current underground fleet and 54% of the 
total horsepower.''
    Some commenters noted they have also made improvements to their 
ventilation systems, such as upgraded auxiliary ventilation systems, 
more booster fans, and better maintenance of ventilation control 
structures. Examples include a mining company that operates several 
underground stone mines, which commented,

    All [of our] mines have performed major ventilation upgrades, 
which include installation of new larger portable fans that are used 
at active headings to help direct air flow, installation of larger 
main ventilation fans at two mines, installed larger booster fans in 
the duct tubing at three mines, installed new ventilation stoppings 
and curtains at various locations throughout the mine at all mines, 
[and] replaced less efficient ventilation fans with high volume/low 
pressure fans.

Another stone mine operator reported they had, ``installed a third 
vertical air shaft in our mine, we have added brattice cloth for over 
25 rooms and adjusted brattice cloth throughout our mine, changed 
traffic patterns, and utilized portable fans.''
    Western multilevel metal mine operators also upgraded ventilation 
systems. One operator of several underground gold mines reported 
upgrading a spray chamber, developing a new entrance drift and mine 
portal, and using large auxiliary fans to increase heading ventilation. 
A large base metal mine operator reported purchasing 17 new auxiliary 
fans that were one-third more powerful than the existing fans and also 
upgrading ventilation system maintenance.
    A few mine operators have completed major ventilation system 
upgrades, including new ventilation shafts and fan installations. 
However, it is not clear whether all operators that reported such 
upgrades did so entirely to attain compliance with the DPM interim or 
final limit. For example, despite the mine operator's claims to the 
contrary, our detailed analysis of a ventilation system improvement 
project costing over $9,000,000 at a western multilevel metal mine 
indicated that some or most of these upgrades would have been necessary 
anyway to accommodate planned production increases and other non-DPM 
related purposes. One outcome of this ventilation upgrade was a 1,000 
horsepower reduction in the ventilation system's total electrical power 
requirements, achieved through more efficient deployment of booster 
fans. Over 60% of the overall $9,000,000 project cost, when annualized, 
was offset by this electrical power cost savings.
    Through the comments submitted to the rulemaking record, the NISOH 
DPM workshops in 2003, and our compliance assistance visits to mines 
affected by the rule, we have learned that, although many of the metal 
mines have experimented with DPM filters, comparatively few are relying 
on filters as their primary means of complying with the interim limit. 
Also, environmental cabs are in widespread use throughout the industry; 
however, comparatively few such cabs have been retrofitted to existing 
equipment as a primary means of compliance with the interim limit. 
Indeed, several commenters provided information on the high cost of 
retrofitting cabs to existing equipment, indicating why cab retrofits 
were not the first option for attaining compliance. Since the final 
rule is performance-oriented and gives mine operators flexibility to 
choose the DPM engineering and administrative controls that are best 
suited to their unique circumstances and conditions, it is not 
surprising that other compliance strategies have also been employed, 
such as utilization of alternative diesel fuel (high biodiesel content 
blends and diesel-water emulsions) and implementation of a wide array 
of work practice and administrative controls. But by far the most 
common strategies employed throughout the industry to attain compliance 
with the interim limit have been low DPM emitting engines and 
ventilation improvements, which were the basis for our original 
compliance cost estimates.
    One commenter suggested that we conduct a full regulatory impact 
analysis to assess the true economic cost of our proposal. This 
commenter disagreed with the manner in which we updated the 2001 REA, 
since significant changes have occurred since then in the American 
economy, namely changes in fuel prices due to war and natural 
disasters. This commenter also believes that DPM controls are more 
costly than we projected and questioned whether these controls are 
effective. Overall, this commenter believes that we grossly 
underestimated compliance costs in our 2001 final rule. We are unaware 
of a change in the American economy presented by the commenter other 
than the price of fuel, which we agree has gone up since 2001. However, 
the commenter did not relate a rise in fuel prices with the economic 
feasibility of industry compliance with the subject rule. The recent 
rise in diesel fuel prices does not affect the 1% ``screen'' for 
compliance costs relative to industry annual revenue that we use as a 
presumptive benchmark of economic feasibility. Higher fuel prices would 
actually make the purchase of low DPM-emitting engines more attractive 
because they also have better fuel economy compared to the older 
technology high DPM emission engines. More importantly, we also note 
that the prices of the various commodities that are produced in 
underground M/NM mines have also gone up since 2001. For example, 
between 2001 and 2005, the price of gold increased 108%, zinc 53%, 
platinum 64%, crushed stone 11%, lead 40%, and rock salt 19%. The 
commenter has not established that the industry's relative financial 
position compared to 2001, if it has changed at all, has been so 
altered by a general rise in prices that compliance with the final rule 
is economically infeasible.
    In responding to the commenter's second point, the technological 
feasibility of DPM controls was discussed in detail previously in this 
section of the preamble. In the 2005 NPRM, we proposed a five year 
phase-in of the final DPM limit to allow mine operators the extra time 
they would need to overcome technological and economic implementation 
issues with DPM controls. Based on new information, primarily relating 
to DPM filters and biodiesel fuel, we have shortened the final limit 
phase-in period from five to two years. However, we believe this 
compliance schedule, coupled with provisions in the final rule relating 
to special extensions of time in which to meet the final limit, will 
enable the entire industry to attain compliance.
    Regarding the comments concerning the role of international 
commodity markets in determining the viability of mines by setting 
market prices for their production, our use of industry annual revenue 
tacitly incorporates the effects of ever-changing commodity prices. As 
prices rise, industry annual revenue rises, and as prices fall, 
industry annual revenue falls. Although commodity prices are indirectly 
incorporated into our analysis, however, for purposes of determining 
the economic feasibility of a rule, the dollar amount of the industry's 
annual revenue is not by itself determinative. Both prices and 
production determine industry annual revenue. Compliance costs that are 
only a small percentage of industry revenue help to establish economic 
feasibility.
    We have customarily used yearly compliance costs of greater than 1% 
of annual industry revenue as our

[[Page 28965]]

screening benchmark for determining whether a more detailed economic 
feasibility analysis is required. The commenters correctly point out 
that despite hundreds of millions, if not billions, of dollars of 
industry annual revenue, business failures can and do occur, and over a 
period of decades, the characteristics of an industry can change 
markedly. However, by utilizing the 1% of annual revenue screening 
benchmark, we assure that a new MSHA rule will not significantly affect 
the viability of an industry.
    While it is true that individual business failures can and do 
occur, and that over a period of many years, substantial portions of a 
domestic industry can be adversely affected by, for example, 
international competition, MSHA believes it is highly improbable that 
such events would be set into motion by a rule imposing costs equal to 
or less than 1% of industry annual revenue. Threats to an entire 
industry's competitive structure and resulting large scale dislocations 
within an industry sector are typically caused by fundamental changes 
in technology, permanent downward pressure on demand for a commodity 
due, for example, to the introduction of a superior substitute 
material, world-wide or regional business cycles, etc.
    A commenter suggested that the economic feasibility analysis in the 
31-Mine Study was flawed because our unit prices for commodities were 
significantly in error. For example, rock salt for highway de-icing 
(the primary market for the three rock salt mines included in the 
study) reportedly sold for about $20-$25 per ton when the analysis was 
made. Yet, this commenter went on to say that our estimates for 
revenues and likely annual production levels for the three salt mines 
appeared to indicate that a price of about $50-$70 per ton was used in 
our analysis.
    We are not persuaded by commenter's view that the economic 
feasibility analysis for the 31-Mine Study is invalid because we used 
erroneous commodity prices. For the 31-Mine Study, we did not have 
access to actual annual revenue data for the 31 mines in the study, so 
we indirectly estimated annual revenues using our data on the number of 
employee work hours in 2000 for each mine, the total number of employee 
work hours reported to us in 2000 by all mines producing that 
commodity, and data from the U.S. Geological Survey on the industry-
wide value of mineral production by commodity for the year 2000. We 
estimated annual revenues for a particular mine by determining the 
industry-wide production value per employee hour for the specific 
commodity each mine produced, and multiplying that amount by the number 
of annual employee work hours reported to us for that mine. This 
methodology assumes that each mine's annual revenues would be roughly 
proportional to each mine's share of the industry's total employee work 
hours. Thus, our estimates, while not necessarily exact for each mine, 
were a reasonable approximation for those mines based on industry 
averages. This methodology does not explicitly incorporate a cost per 
ton factor. However, implicit in this methodology, based on the U.S. 
Geological Survey's estimates of rock salt production in 2000 of 
45,600,000 metric tons valued at $1,000,000,000, would be a cost per 
metric ton of $21.93 (equivalent to $19.89 per short ton), which is 
actually slightly less than the commenter's estimated price of $20 to 
$25 per ton. Thus, we have no information about how the commenter came 
up with a price of $50-$70 per ton of salt purportedly used in our 
analysis. As demonstrated above we implicitly used a cost per metric 
ton of $21.93.
    Several commenters stated that our compliance cost estimates in the 
``31-Mine Study'' were unrealistically low because we didn't recommend 
major ventilation upgrades for any of the mines in the study. Other 
comments relating to the ``31-Mine Study'' were that the mines included 
in the study were not representative of the industry as a whole, that 
we voided 25% of the samples collected, that we eliminated four mines 
from the study, and that we significantly underestimated compliance 
costs for the Stillwater Mine near Nye, MT, which was one of the mines 
included in the study. In responding to the question of major 
ventilation upgrades, we noted in the preamble to the 2005 final rule 
(70 FR 32921) that we did not specify any major ventilation upgrades in 
the 31-Mine Study because, based on the study methodology, the analysis 
did not indicate the need for major ventilation upgrades in order to 
attain compliance with either the interim or final DPM limits at any of 
the 31 mines. We further went on to explain that the purpose of 
specifying controls for each mine in this study was simply to 
demonstrate that feasible controls capable of attaining compliance 
existed, and to provide a framework for costing such controls on a 
mine-by-mine basis. We explicitly stated in the final report that the 
DPM controls specified for a particular mine did not necessarily 
represent the only feasible control strategy, or the optimal control 
strategy for that mine.
    Since the completion of the 31-Mine Study, we have observed that 
mine operators in the stone industry, for example, have chosen to 
attain compliance without utilizing DPFs. These operators instead have 
opted to upgrade ventilation (usually by adding or re-positioning 
booster fans and installing or repairing ventilation control structures 
such as air curtains and brattices); install low-emission engines; 
utilize equipment that is supplied by the original equipment 
manufacturer (OEM) with cabs with filtered breathing air; initiate a 
variety of work practices that contribute to reducing personal 
exposures to DPM; and in a few cases, use alternative diesel fuels such 
as bio-diesel fuel blends and diesel/water emulsions.
    Regarding the question of the 31 mines being unrepresentative of 
the industry as a whole, we note that the mines were selected jointly 
by us and the DPM litigants, and all parties collaborated in the study 
design. Although an attempt was made to include a variety of 
commodities in the study, the selected mines were not ever intended by 
us or the collaborators to be a statistically representative sample of 
the industry.
    In a related comment, an industry organization asserted that our 
subsequent ``baseline'' sampling was ``similarly non-representative.'' 
The sampling to which this commenter refers was conducted by us in 2002 
and 2003 in accordance with a provision of the second partial 
settlement agreement. As described in the preamble to the 2005 final 
rule (70 FR 32873-32874),

    Under the second partial DPM settlement agreement, MSHA agreed 
to provide compliance assistance to the M/NM underground mining 
industry for a one-year period from July 20, 2002 through July 19, 
2003. As part of its compliance assistance activities, MSHA agreed 
to conduct baseline sampling of miners' personal exposures at every 
underground mine covered by the 2001 final rule. Our baseline 
sampling began in October 2002 and continued through October 2003. 
During this period a total of 1,194 valid baseline samples were 
collected. A total of 183 underground M/NM mines are represented by 
this analysis * * * MSHA [included] 320 additional valid samples [in 
the analysis of baseline sample data] because MSHA decided to 
continue to conduct baseline sampling after July 19, 2003 in 
response to mine operators' concerns.

    We are unclear as to why the commenter would characterize the 
baseline sampling as ``non-representative,'' as it included all 
underground M/NM mines that were in

[[Page 28966]]

operation during this period of over one year.
    Regarding voided samples, of the 464 samples obtained at the 31 
mines, 106 were voided. A key consideration in the sampling conducted 
at the 31 mines was to insure, to the extent possible, that samples 
were not contaminated by non-diesel sources of airborne carbon. Testing 
had verified that the submicron sampler would remove mineral dust 
contamination (limestone, graphite, etc.), but tobacco smoke, drill oil 
mist, and possibly vapors from ANFO loading could contaminate a sample 
filter with non-diesel organic carbon. Thus, in accordance with the 
study protocol that had been jointly developed and approved by both us 
and the litigants, any sample that was known to have been, or could 
potentially have been contaminated with such an interferant was voided. 
Of the 106 voided samples, 61 were voided due to interferences. There 
were also some samples that were voided for other reasons, such as 
laboratory error (2 samples), sample pump failure (22 samples), or 
incomplete sample or sampling the wrong location (21 samples). 
Including any of these 106 voided samples in the data analysis would 
have cast doubt on the validity of the study.
    In response to the comment that four mines were eliminated from the 
study, of the 31 mines selected to participate; only one was 
eliminated. This mine was not eliminated per se. DPM samples were 
obtained at this mine; however, none of these samples were included in 
the data analysis because they all had to be voided due to 
interferences.
    The underestimation of compliance costs for the Stillwater Mine in 
the 31-Mine Study was also discussed in the preamble to the 2005 final 
rule (70 FR 32924). We acknowledged that the DPM compliance costs for 
this mine would probably be significantly higher than we reported in 
this study because, as we explained previously, our analysts, at the 
time the 31-Mine Study was conducted, had been supplied with inaccurate 
information regarding this mine's diesel equipment inventory. Based on 
updated equipment inventory data, we subsequently revised our analysis 
and corresponding cost estimates. The revised annual estimated 
compliance cost for the Stillwater Mine of $935,000 was reported in the 
preamble to the 2005 final rule (70 FR 32943). Although, this amount is 
considerably higher than the estimate from the 31-Mine Study, it is 
significantly less than the estimated compliance cost for a precious 
metals mine of this size as detailed in our REA for the 2001 final 
rule.
    Several commenters repeated their concerns expressed in previous 
public comments that the 2001 final rule and subsequent economic 
feasibility assessment for the 31-Mine Study relied on quantitative 
analyses supported by a ``flawed'' computer simulation program. They 
believe that the Regulatory Economic Analyses for all of our DPM 
rulemakings, from the original 2001 final rule to and including the 
current rulemaking, are invalid because they incorporate analytical 
results obtained from this program.
    As discussed in the section on technological feasibility, the 
computer program in question, referred to as the DPM Estimator, is a 
Microsoft[reg] Excel spreadsheet program that calculates the reduction 
in DPM concentration that can be obtained within an area of a mine by 
implementing individual, or combinations of engineering controls. The 
two specific ``flaws'' identified by the commenters are, ``assumptions 
of the availability of filters that would fit the entire fleet of 
equipment in use, and assumptions of perfect ventilation conditions 
throughout the industry.'' We have responded previously to both of 
these comments, as well as to other criticisms of the Estimator. We 
have shown that suitable DPM filters were, and continue to be, 
available to mine operators that are capable of attaining the final DPM 
limits within the timeframes established in the final rule, and that 
the Estimator does appropriately account for complex ventilation 
effects. Our responses to the previous criticisms on the Estimator and 
to the comments on the Estimator submitted to this rulemaking are 
detailed in the technological feasibility section of this preamble.
    A number of comments related either directly or indirectly to 
activities at the Stillwater Mine near Nye, MT. The Stillwater mine is 
a large multilevel platinum mine that operates 24/7 with a workforce of 
over 900 miners. The Stillwater Mining Company currently utilizes 288 
pieces of diesel equipment in its underground mine. The company has 
been installing EPA Tier 1 and Tier 2 engines since 2001, and at 
present, approximately 16% of its engines are Tier 1, and 52% are Tier 
2. One Tier 3 engine is in operation, and three additional Tier 3 
engines were expected in late January 2006. The company has also 
upgraded its diesel engine maintenance program. Cabs have been 
installed on a few pieces of equipment which are operated in areas of 
the mine where the size of the mine openings provides sufficient 
clearance for a cab. The company has experimented with a variety of DPM 
filter systems, including platinum washcoated passively regenerating 
filters, active on-board filters, active off-board filters, a fuel 
burner type active regenerating system, and disposable filter element 
systems. The company has also evaluated a diesel-water emulsion fuel 
and various biodiesel blends, and the company has made significant 
improvements to the mine's ventilation system in recent years.
    Most of the comments relating to this mine, submitted both by the 
mine operator and various other mining companies and organizations, 
suggest that the failure to attain full and consistent compliance with 
the interim DPM limit at this mine, despite vigorous and sustained 
efforts by the company, are evidence that neither the interim DPM limit 
nor the final DPM limit are technologically feasible. They also point 
out that the funds expended by the company thus far in its effort to 
attain compliance have been excessive, and that this experience 
therefore demonstrates the economic infeasibility of the rule as well.
    We have found through our Technical Support assistance and 
enforcement experience that this mine operator, in time, could achieve 
more consistent compliance with the DPM interim limit and attain the 
final DPM limits if they would install effective engineering and 
administrative controls. Although this mine operator has experimented 
with a number of DPM control technologies, some of these trials were of 
quite limited scope and duration. Several were conducted as a part of 
collaborative studies with the NIOSH Pittsburgh Research Laboratory 
under the auspices of the NIOSH M/NM Diesel Partnership. While it is 
true that this mine operator has evaluated numerous DPM control 
technologies, only a few have been the subject of sustained and 
intensive applications engineering efforts that we believe are required 
to resolve the associated site-specific and application-specific 
implementation challenges. To mention a few examples, this operator is 
not currently utilizing fuel burner DPFs, biodiesel, or water-emulsion 
fuels. Their use of high temperature disposable diesel particulate 
filters (HTDPFs) has been hampered by the use of HTDPFs on equipment 
having very high DPM emission engines, which causes the filters to load 
up quickly and create possible fire hazards. This operator has not 
utilized heat exchangers in conjunction with HTDPFs, which would enable 
their use on a much broader range of equipment. They have expended far 
greater effort to optimize passive DPF applications compared

[[Page 28967]]

with active DPF applications, even though they indicate that the vast 
majority of their equipment is not suitable for application of passive 
DPFs. Through an extensive MSHA Technical Support study of their 
ventilation system, we had observed numerous problems with auxiliary 
ventilation systems in stopes. MSHA is continuing to work with 
Stillwater to resolve these compliance issues.
    Regarding the question of economic feasibility, although the mine 
operator has incurred substantial costs, as mentioned earlier we do not 
believe that these costs would be excessive for a mine of this type and 
size based on expected compliance costs detailed in the Regulatory 
Economic Analysis (REA) for the 2001 final rule. In the preamble to the 
2005 final rule (70 FR 32934-32936), compliance costs for this mine 
were analyzed in detail. This analysis indicated that when this 
operator's actual expenditures were annualized at a 7% annualization 
rate, the operator's yearly compliance costs for the interim limit were 
less than expected based on the estimates contained in the REA for the 
2001 final rule for a precious metals mine of this size.
    Two compliance cost issues at this mine were discussed in detail in 
the preamble to the 2005 final rule: the cost of implementing an active 
DPF program, and the cost of a major ventilation system upgrade. In 
that preamble, we presented several options for deploying active diesel 
particulate filters at this mine. These options were developed in 
response to a comment from this mine operator submitted to the 2003 
NPRM that the cost of implementing an active DPF program for this mine 
would exceed $100 million over ten years. Our deployment options were 
functionally equivalent, and the estimated costs were less than 
$400,000 per year. In the preamble to the 2005 final rule (70 FR 32935-
32936), we said,

    MSHA does not believe the particular plan developed by 
Stillwater is the optimal means of utilizing active DPM filters at 
this mine. Various alternative approaches for utilizing active 
filters exist which would be far less costly.
    Since excavating regeneration stations accounted for over 96% of 
the total cost of implementing Stillwater's active filter plan, 
alternatives that do not include such excavation costs would have a 
significant cost advantage over Stillwater's plan. It is somewhat 
curious that Stillwater developed its active DPF plan on the basis 
of this particular on-board active regeneration system, despite the 
extraordinarily high cost of excavating the regeneration stations, 
and Stillwater's prior experience with premature failure of the on-
board heating elements built into the filters.
    A lower cost alternative to Stillwater's approach utilizes an 
on-board fuel burner system to regenerate filters. The 
ArvinMeritor[supreg] system was used at this mine in 2004 with 
excellent results. It actively regenerated the filter media during 
normal equipment operations, regardless of equipment duty cycle, 
with no elevated levels of potentially harmful NO2, and 
without having to travel to a regeneration station to regenerate its 
filter.
    Another less costly alternative would be to utilize off-board 
regeneration instead of on-board regeneration. In off-board 
regeneration, a dirty filter is removed and replaced with a clean 
filter at the beginning of each shift. During shift change, the 
dirty filters are then transported by the equipment operator or a 
designated filter attendant to a central regeneration station or 
stations.
    Such stations could be a fraction of the size of the 
regeneration stations envisioned in Stillwater's plan, because they 
would only need to accommodate the filters, not the host vehicles. 
Since the host vehicles would not need to travel to the regeneration 
stations, the travel distance from normal work areas to the 
regeneration stations would be less important, greatly lessening the 
need for frequent construction of new regeneration stations as the 
workings advance. It is very likely that such stations could be co-
located in existing underground shops, unused muck bays, unused 
parking areas, or other similar areas.
    Off-board regeneration might not be practical on larger machines 
due to the size of the filters. For larger machines that are not 
suitable for passive regenerating filters, the fuel burner approach 
might be preferable. But many of the machines targeted for active 
filtration are quite small, having 40 to 80 horsepower engines. 
Active filters for these engines are correspondingly small, and 
could be easily and quickly removed and replaced using quick-
disconnect fittings. Another lower cost option would be to utilize 
disposable high-temperature synthetic fabric filters, especially on 
smaller, light duty equipment such as pickups, boss buggies, and 
skid steers. Depending on equipment utilization, such filters might 
only need to be replaced once or twice per week.

In its comments on our 2005 NPRM, the mine operator states that 
equipment identified for use with active regeneration systems has been 
limited to equipment that is parked on the surface at the end of the 
shift. This would allow the DPF to be removed and placed in a 
regeneration station. Unfortunately, not all equipment can be brought 
to the surface for regeneration due to logistical issues, according to 
this mine operator. The commenter, however, provided no rationale 
explaining why active regeneration should be limited only to equipment 
that is brought to the surface at the end of the shift, as active 
regeneration can easily be accomplished underground. Furthermore, later 
in the same section, the commenter acknowledges that underground 
regeneration is possible. The commenter states that for units that must 
be regenerated underground, additional excavations to house the 
regeneration equipment and to provide parking during regeneration would 
be required. These additional excavations are neither practical nor 
economically feasible, according to this commenter.
    These comments neither acknowledge nor refute the recommended 
options we provided in the 2005 final rule preamble and as summarized 
above.
    In another part of their comments to this rule, the mine operator 
discusses their experiences with disposable filter element type diesel 
particulate filters, and indicates that the costs of utilizing this 
system are excessive because the useful life of the filter is so short. 
The example provided by the mine operator was a particular model Toyota 
truck. The commenter operates many such Toyota trucks, which can be 
configured for a variety of service and support applications. According 
to the mine operator's analysis, the annual cost of maintaining a 
disposable element filter system on this type of vehicle is $40,000, 
which this mine operator characterized as ``cost prohibitive.'' In 
response, we note that the Toyota truck used in this example is 
equipped with a model 1HZ engine, which has very high diesel 
particulate emissions between 0.8 and 0.9 g/bhp-hr. Table 6 in this 
mine operator's comments indicated that the DPM emissions for this 
engine were 0.22 g/bhp-hr. At 0.8 g/hp-hr, the 128 hp engine on the 
subject vehicle would generate 102 g/hr of DPM. A 10 inch diameter, 26 
inch long filter with a capacity for capturing and storing 8 g of DPM 
per inch of filter length could thus store 208 g of DPM. Even with two 
such filters installed on the subject vehicle, the filters would become 
fully loaded after only (208 x 2)/102 = 4.08 hours, or about 4 hours 
and 5 minutes. The mine operator's reports of filters that, ``burnt 
out,'' may be caused by continued operation of the subject vehicle 
after the filter has been fully loaded.
    The problem with this application is the engine, not the filter 
system. If this engine were replaced with a modern low emission engine, 
filter loading would occur at a fraction of the rate experienced with 
the current high emission engine. The cost of the engine would be 
partially offset through lower fuel consumption, and the cost of 
maintaining the disposable filter system would drop by 70% to 90% 
because the truck could be operated for many more hours before the 
filter would become fully loaded and need replacement. By

[[Page 28968]]

optimizing the total system, including the engine and the filter, 
associated costs could be significantly reduced.
    Regarding the major ventilation upgrade, in its comments on the 
2003 NPRM, Stillwater provided information and costs relating to a 
major $9,000,000 ventilation upgrade they stated was a DPM-related 
compliance expense. In the preamble to the 2005 final rule (70 FR 
32934-32935), we disputed this claim. We determined that the expense 
was only partially DPM-related and that this operator was also able to 
obtain a significant electrical power cost savings as a result of more 
efficient deployment of booster fans. Over 60% of the overall 
$9,000,000 project cost, when annualized, was offset by this electrical 
power cost savings. In its comments on the current rulemaking, 
additional general information on the mine's ventilation system is 
provided, as are plans for future upgrades, but our analysis was not 
refuted. Another commenter observed that our analysis of the $9,000,000 
ventilation upgrade was, ``suspect,'' but provided no factual 
information to corroborate their position.
    Two commenters noted that our 2001 estimate of the cost of 
compliance for the industry as a whole of $25.1 million per year was 
too low. One commenter, a mining industry organization, provided no 
rationale or explanation to support this comment. The other commenter, 
a stone mining operator, presented estimated compliance costs for this 
mine and extrapolated these costs to the rest of the industry. This 
operator stated that it cannot accept our projections that this final 
rule will not have an annual effect of $100 million or more on the 
economy. A figure of $100 million divided by 200 M/NM mines would 
result in $500,000 per mine. This commenter believes that its cost 
estimates for new or newer equipment in its small mine show capital 
contribution of over three times our figure.
    This mine operator then listed the following estimated equipment 
costs:


   Drill...........................................     $350,000
   Powder truck....................................      $50,000
   Scaler..........................................     $350,000
   Loader..........................................     $250,000
   Truck 1.........................................     $225,000
   Truck 2.........................................     $225,000
   Truck 3.........................................     $225,000
   Total...........................................   $1,675,000
 


    Upon examination, we have determined that this commenter's analysis 
does not account for several important factors. First, replacement of 
equipment that is near the end of its useful life and would have been 
replaced in the near future anyway would not be considered a DPM-
related compliance cost, or at most, only partially DPM-related. It is 
extremely improbable that an entire inventory of underground equipment 
would need to be replaced all at once purely for DPM compliance. The 
oldest equipment in a mine's inventory, which would normally be the 
worst polluters, would be the first that would need to be replaced in 
the course of the normal equipment turnover process. The cost of 
replacing such worn out equipment would not be considered DPM 
compliance-related, because it would have occurred anyway, with or 
without a DPM rule. The newest equipment, typically mid to late-1990's 
model year or newer, would most likely not need to be replaced right 
away, as this equipment would have EPA Tier 1 or Tier 2 engines, and as 
a consequence, would be low, or at worst moderate polluters. Thus, new 
equipment purchased strictly for DPM compliance, if any, would 
typically be limited to only a portion of a mine's overall equipment 
inventory.
    Second, it is very unlikely that the wholesale replacement of 
equipment is the most cost effective DPM control strategy for this, or 
any mine. For example, rather than replacing all equipment, an operator 
could replace just one or two pieces of equipment (if any equipment at 
all needed to be replaced), utilize diesel particulate filters, upgrade 
ventilation, switch to a high biodiesel content fuel blend, implement 
various administrative controls, or use some combination of these 
strategies. Indeed, this same commenter earlier in their comments 
stated that buying new equipment is costly. There may be less expensive 
alternatives to improve DPM levels, such as ventilation or alternative 
fuels.
    This commenter indicates that they, ``have not tried diesel 
particulate filters due to cost and negative performance history 
reported by producers and manufacturers.'' However, as discussed 
extensively in the previous section of this preamble and throughout the 
rulemaking record, diesel particulate filters are a technologically and 
economically feasible DPM control once mine operators work through 
their implementation issues. The commenter indicated that they are 
considering the use of a B99 biodiesel fuel blend. As noted elsewhere 
in this preamble, use of high biodiesel fuel blends has been quite 
successful at other M/NM mines in significantly reducing DPM exposures.
    By overlooking lower cost DPM control alternatives, this mine 
operator's assertion of economic infeasibility of the final limit of 
160TC [mu]g/m\3\, even in 2011, is questionable. A 
fundamental concept upon which the Regulatory Economic Analysis (REA) 
for the 2001 final rule was based is that mine operators will choose 
the lowest cost method of attaining compliance with the applicable DPM 
limits. If a mine operator chooses other than the lowest cost method 
for compliance, any resulting determination of economic feasibility 
would be seriously flawed. We acknowledge that the process of 
attempting to install various alternative control technologies may be 
imprecise at best, and that testing multiple designs can be inherently 
cost-inefficient because some designs will inevitably be found to be 
unsuitable for a particular purpose. However, we continue to emphasize 
that mine operators can obtain compliance assistance from our District 
Managers, or utilize our DPM Single Source Page and access the 
internet-hosted DPF Selection Guide to help streamline this process. 
Economic feasibility is based on the assumption that optimal, lowest-
cost controls are implemented to attain compliance taking into account 
recognized implementation difficulties. In the cost estimates for this 
final rule, we have included cost related to operator evaluation of 
different technologies in an effort to determine the most effective 
method for compliance.
    Third, the equipment listed by the commenter would be expected to 
have a long useful life, possibly up to 20 years. Thus, the total first 
year acquisition cost of this equipment is an incorrect representation 
of the corresponding yearly cost to the operator. Even in the unlikely 
event that a mine operator would need to purchase all new major 
underground equipment in a single year, we would first need to 
determine that these controls are economically feasible for the 
operator. Moreover, when the $1,675,000 cost of this equipment is 
amortized over a 10-year period (to account for depreciation) at a 7% 
discount rate, the annualized cost to the operator is $238,482. This 
annualized cost is 48% of the commenter's threshold of $500,000 per 
year that, according to the commenter's calculations, would be 
required, on average, to generate industry-wide annual compliance costs 
greater than $100,000,000.
    A mining industry organization stated that even though the Mine Act 
is a ``technology forcing'' statute, the projections that we made in 
this rule ``go far beyond this into the realm of pure theory.'' They go 
on to state that,


[[Page 28969]]


    Underground stone mines cannot make purchasing decisions based 
on hypotheses as to what technologies may be available during the 
coming decade when there is scant evidence to support MSHA's 
assertions.

    We disagree with the commenter's position regarding our conclusions 
on economic feasibility. As we discussed extensively in this preamble, 
technologically and economically feasible DPM controls are available, 
however, mine operators will need to resolve these implementation 
issues to meet the final limit of 160TC [mu]g/m\3\. In the 
2005 NPRM, we stated that mine operators may need more time to comply 
with the final rule due to implementation issues, including cost 
implications. We nonetheless believe that in time, most of these 
implementation issues can be overcome, especially by May 2008. The five 
principal engineering controls discussed throughout this preamble--
DPFs, equipment for ventilation upgrades, environmental cabs, 
alternative fuels, and low emission engines--are all commercially 
available off-the-shelf from many suppliers. The final rule, however, 
provides mine operators with additional time to work through their 
individual implementation issues. These individual issues, when viewed 
as a whole, result in our need to phase-in the 160TC [mu]g/
m\3\ final limit.
    Several mine operators and an industry organization commented on 
the costs associated with DPFs. Comments included:

    Average operating life of the Englehard DPF utilized at 
Stillwater is 3000-4000 hours at a cost ranging from $7,000-$8,500 
per unit. [Note: This mine operator reported the average unit cost 
of 103 passive systems installed since 2004 plus those planned for 
installation in 2006 is $7,170.]
    For equipment not compatible with passive regeneration systems, 
active regeneration systems have been researched and tested at 
Stillwater. The cost for these systems have ranged from $4,000-
$8,000 per unit. [Note: This mine operator reported the average 
total acquisition, installation, and maintenance cost for 10 active 
off-board filter systems and 4 regeneration stations sufficient for 
filtering the DPM emissions from 5 vehicles was $95,000, resulting 
in a per vehicle cost of $19,000.]
    The passive regeneration filter systems we have purchased range 
from $6,600 to $8,700 each. These filters also have backpressure 
monitors costing roughly $700 each. Installation on equipment 
usually will cost about $1,000.
    Costs for our passive regeneration filters systems will be borne 
over the filter life, which in our experience has ranged between 
2,500 and 9,000 hours with most falling around 6,000 hours.
    The last quote we received for an on-board active regeneration 
filter was $28,000, excluding the regeneration station which would 
cost an additional $8,600 and a backpressure monitor estimated at 
$1,100, for a total cost of $37,700 excluding freight and 
installation.
    What many NSSGA members are experiencing is that they do not 
have any way of establishing the true costs of diesel particulate 
filters because, setting aside the direct costs and questionable 
results related to filter usage, the filters affect equipment in 
ways that are adverse but cannot be readily quantified.

We agree that the cost for passive regeneration diesel particulate 
filters for typical production equipment (loaders or trucks with 300 hp 
to 500 hp engines) would range from about $7,000 to about $8,500. A 
number of industry commenters agree that passive regenerating filter 
systems are feasible for equipment that operates at a sufficiently 
demanding duty cycle. Typical comments were:

    Practical experiences with equipment that have the capability to 
operate with passive regeneration systems indicate this type of 
control can reduce DPM exhaust emissions.
    At the present time, however, we are increasingly confident that 
passive regeneration filter technology can be effective in the 
mine's larger horsepower production units.
    Turquoise Ridge believes that properly sized and fitted filters 
can reduce DPM emissions, and the Turquoise Ridge Mine is now at the 
sustained level of production to begin testing.
    Both DPM filter vendors and mine operators are now gaining 
experience in the application of DPM filters underground. Some 
progress is being made. For example, the application of passive 
regeneration filter technology is becoming effective on larger 
horsepower production units. However, NMA agrees with MSHA's 
observation in the preamble of the NPR that `[r]elying on [filters] 
to be installed on older, higher DPM emitting engines may also 
introduce additional implementation issues since [filter] 
manufacturers normally do not recommend adding [filters] to older 
engines.' Furthermore, the application of DPM filters to equipment 
with medium- to low-duty cycle engines remains problematic.

    Industry objections to active filter systems center on operational 
aspects that result in higher overall costs for applying this type of 
control. These systems are very efficient in capturing and retaining 
DPM, and the hardware costs of such systems, though higher than a 
comparable passive system, are not excessive for many mine operators.
    An example of active off-board regeneration DPF system costs was 
provided by the commenter who indicated that ten filter systems and 
four off-board regeneration stations cost $95,000. This cost included 
acquisition, installation, and maintenance, and was sufficient for 
filtering the DPM emissions from five utility and support type 
vehicles. Assuming the filters would last two years and the 
regeneration stations would last five years, the per vehicle yearly 
cost, when annualized at a discount rate of 7% would be $8,963. The 
cost of an active on-board regeneration DPF system was quoted by 
another commenter at $28,000 plus an additional $1,100 for a 
backpressure monitor and $8,600 for the regeneration station, for a 
total of $37,700. The per vehicle yearly cost for this system, when 
annualized at a discount rate of 7% would be $18,192. We believe the 
difference in costs between these systems relates more to the engine 
horsepower they are intended to filter rather than the type of 
regeneration employed. The unit cost for this second active DPF system 
is about the same as we estimated in the 31-Mine Study for a similar 
system. For that study, we estimated an active system for a 400 hp to 
500 hp engine would cost $18,000 and the associated regeneration 
station would cost another $20,000 for a total of $38,000.
    Rather than the cost of the systems themselves, operators' comments 
primarily addressed the associated implementation issues, such as the 
required frequency of regeneration, travel time to a regeneration 
station, providing locations for regeneration stations, equipping 
regeneration stations with the necessary facilities and utilities, 
equipment downtime while regenerating, etc. and the perceived increased 
labor and infrastructure costs associated with applying active filter 
technology. These concerns have limited more widespread utilization of 
active systems. Comments concerning these logistical issues included:

    Active filters require that equipment be idled for a 
considerable period of time either with on-board regeneration, or 
with an off board filter change-out system * * * In addition, active 
systems require considerable space * * * The record to date has 
identified other feasibility problems with DPFs that include 
physical size of filter systems, the short life span of filter 
elements, the required downtime for regeneration of active 
regeneration systems, the need for regeneration stations with 
electric power and compressed air supply near producing zones for 
active regeneration systems * * *
    Practical experience with active regeneration systems has not 
indicated these control options are economically feasible for the 
Stillwater diesel fleet * * * Initial operating time before the unit 
is required to be removed and placed on a regeneration station is, 
at best, 10-15 hours. However, experience has shown this time can be 
as little as 4 hours before off-board regeneration is required. Due 
to the low utilization of the active DPF before the system needed to 
have active regeneration, two active DPFs were purchased to ensure 
the equipment would be

[[Page 28970]]

operational for the next shift. This option has proven to be cost 
prohibitive; it is unrealistic to logistically store spare active 
DPFs and regeneration stations for even the small fraction of 
equipment that has the capability to operate with active DPFs * * * 
For units that must be regenerated underground, additional 
excavations to house the regeneration equipment and to provide 
parking during regeneration would be required. These additional 
excavations are neither practical nor economically feasible. 
Additionally, moving equipment to the regeneration stations is time 
consuming, unproductive, and cost prohibitive.
    One active regenerative DPF system, specifically DCL Mine-X 
Black Out Soot filter, was tested on a Tamrock 1400, 8 yard\3\ scoop 
over an 8 month period. Because of filter limitations, the scoop was 
only operational for 7 to 8 hours per shift before the backpressure 
increases caused the need for filter regeneration. This rendered the 
equipment unusable for the remainder of our normal 11 hour 
production shift. The active regeneration system was determined to 
be impractical because it was not effective for an entire shift and 
could not be regenerated between shifts (regeneration typically took 
between 2 and 5 hours).
    The feasibility of equipping medium-to low-duty cycle engines 
with passive and active regeneration DPF filter systems continue to 
be evaluated by Greens Creek Mine personnel. However, the need for 
fixed locations for installation of equipment used for active filter 
regeneration poses serious logistical problems due to the spread out 
nature of the mine's layout.

    Other mine operators have not even attempted to utilize diesel 
particulate filter systems because of perceived logistical problems and 
associated costs. Typical comments from these operators who have had no 
first hand experience with diesel particulate filters included:

    * * * the current methods to achieve compliance are not 
economically feasible or present other hazards to employees, 
specifically some of the filtration technology that we've 
investigated. I would state that we have not tried those 
technologies as of yet. As I said, the current filtering technology 
is a capital cost and a long-term operating cost that's difficult to 
absorb in the operations.
    We've talked about what filters mean and what filters do and how 
they work and what they are. We've closely watched how that 
technology has moved forward. As of this point, even the employees 
don't see a benefit in doing that. Mainly because the maintenance 
that they're going to be required to do to change filters, to move 
filters around, is going to cause them to pull out the ladder and 
climb the ladder and work around the hot exhaust and move the heavy 
thing back down, you know, the ladder, put it where it needs to go. 
And they're exposed physically to something--these guys are smart. 
They understand these are real physical hazards I'm exposed to try 
and get filters on and off.
    We have not gone to diesel particulate filters. In our hierarchy 
of controls, quite honestly diesel particulate filters would be our 
last choice. First of all, just from a practical perspective, there 
is still issues with the types of filters you might use and if you 
are making the engines--if the engines are inefficient to start with 
and you have to use a--you want to use a diesel particulate filter 
as the correction method, it could very well be that because of the 
inefficiency of the engine, it makes the filters a lot more 
difficult to deal with. Because they're going to clog up, they're 
going to create problems for you and it's just going to increase the 
difficulties of implementing a program. So we looked at diesel 
particulate filters as the last resort. It certainly may be one that 
we want to take, but it's not one that we would choose to go at 
early * * * One of the things also about diesel particulate filters 
and off board regeneration is you're talking about increasing the 
labor cost.
    There's no way around it. It's going to take more people.

    We believe that active regenerating filter technology is available 
to enable compliance with the final limit. However, these commenters 
have highlighted some of the implementation issues we believe will be 
encountered by a great many mine operators that may need to utilize 
this technology to attain compliance with the final rule. The 
additional time required to resolve these issues is provided by the 
two-year phase in of the final limits incorporated in this final rule.
    We continue to advise that the ``toolbox approach'' be used for 
compliance with this rule, and that DPM controls be carefully selected 
on the basis of attaining compliance at the lowest cost. However, where 
circumstances indicate that active regenerating DPM filtration would be 
the optimum control method, we believe that the application of such a 
system would be economically feasible over time. We do intend to 
continue to assess feasibility of effective controls on a case-by-case 
basis.
    We do not dispute that implementing an active regenerating filter 
program at an underground mine will create logistical and 
implementation challenges, and that mine operators will need to incur 
costs to solve these problems. As mines begin to solve these 
implementation issues, however, most should be able to reduce miners' 
exposure to DPM in the process. We acknowledge that a certain amount of 
trial and error experimentation may be unavoidable before an optimum 
selection is made. However, we do not believe this evaluation and 
selection process is economically infeasible for mine operators to 
successfully complete over time.
    We believe that the applications engineering process followed by 
mine operators for overcoming implementation issues with passive DPF 
systems establishes a realistic model for overcoming implementation 
issues with active DPF systems. The early attempts at applying passive 
DPF systems in M/NM mines were inefficient and costly. Applications and 
duty cycles were not fully characterized, inappropriate filters were 
selected, installation methods were crude, and system maintenance 
requirements were not well understood, leading to short filter life and 
a variety of related problems. The final rule's phased-in final DPM 
limits provide the additional time required by the industry to 
successfully address these issues. With respect to the above specific 
comments, while it is true that active filter regeneration can require 
several hours, the associated piece of diesel equipment need not be 
idled for that entire period. As one mine operator indicated, two 
filter elements can be acquired for each piece of diesel equipment so 
that one element can be in use while the other element is being 
regenerated. Using quick disconnect couplings in the equipment's 
exhaust system, swapping out the active DPF elements could be 
accomplished quickly with very little physical effort. Equipment 
downtime in the context of this active filter regeneration scenario 
would be measured in minutes rather than hours.
    Nonetheless, the subject mine operator declared this strategy to be 
``cost prohibitive,'' due to the need to purchase two filters for each 
piece of equipment and the required space to store the extra filter 
elements. We disagree with this conclusion. First, the annualized 
yearly cost of providing two filters for each piece of equipment is not 
significantly greater than the annualized yearly cost of providing a 
single filter for each piece of equipment because each filter, being 
used only on every other shift, will last twice as long as it would 
have if it were used on every shift. Second, there would be no need for 
storing extra filters since filters would simply be swapped back and 
forth between the regeneration station and the piece of diesel 
equipment.
    We agree that there will be costs associated with providing 
facilities and utilities such as electrical power and compressed air 
for the regeneration stations. However, we believe these costs will be 
small or negligible in the context of implementing such a system, or at 
worst, should not be economically infeasible. As noted above, we 
believe an optimally deployed active regeneration system would utilize 
existing locations with utilities already in place as regeneration 
stations, thereby simplifying implementation and minimizing associated 
costs. Although

[[Page 28971]]

several commenters have identified this requirement as a compliance 
cost, the actual magnitude of these costs has not been presented.
    The size of active DPF filter elements has been discussed 
previously. Typically, active systems would be applied to smaller 
support and utility equipment that does not operate at a severe enough 
duty cycle to permit passive regeneration. Smaller equipment requires 
smaller DPF filter elements that can be handled without specialized 
materials handling equipment or lifting aids. Unlike passive systems 
that usually have to be installed as close as possible to the engine 
manifold so that the exhaust is hot when it reaches the filter, there 
is greater flexibility in installing active DPF systems on a piece of 
equipment, usually enabling convenient access for swapping out filters. 
In rare cases where filter elements may be too large to be conveniently 
handled by the equipment operator, accommodation could be made, such as 
providing lifting aids at the regeneration station or the exhaust could 
be divided into dual separately filtered branches with a smaller filter 
on each branch. Implementing either of these options by May 2008 would 
incur some cost, but not so great as to approach economically 
infeasible.
    In instances where filters load up with soot and require 
regeneration before the end of a shift, a possible solution is to 
utilize a larger filter that has more soot storage capacity. The mine 
operator that was able to run an actively filtered loader for only 7 to 
8 hours of an 11 hour shift could utilize a 40% larger filter to extend 
the loader's operating time to the full shift duration of 11 hours. 
Adding more filter capacity could also be accomplished by dividing the 
exhaust into dual separately filtered branches, as was done at the mine 
referenced above that used a dual element disposable filter system on 
its Toyota support and utility vehicles.
    Another option for extending the operating time of an active filter 
is to replace the diesel engine with one that produces less DPM. For 
example, replacing a 100 horsepower Tier 1 compliant engine with the 
equivalent Tier 2 engine would reduce DPM emissions by over 60%. While 
a given active filter on a Tier 1 engine may require regeneration 
before the end of the shift, the same filter on a Tier 2 engine might 
operate for the entire shift or longer. A similar situation exists at 
the Stillwater Mine in Nye, MT with respect to the disposable filter 
element systems on their Toyota trucks. As discussed earlier in this 
section, a possible solution to the problem of these filters loading up 
to quickly is to replace the engines with a model that produces 
significantly lower DPM emissions. Again, there are some costs 
associated with these approaches, but we do not believe they would 
reach the level of economic infeasibility.
    Regarding the feasibility of providing space for regeneration 
stations and parking areas, we refer to our analysis of the active 
regeneration system proposed by the Stillwater Mining Company and 
discussed in the preamble to the 2005 final rule (70 FR 32934-32936). 
The rationale supporting our suggested alternative active regeneration 
system for this mine remains our current position, and given the extra 
time afforded by the phased-in final limit included in the final rule, 
we believe a similar optimization process can be used at other mines to 
solve a number of implementation challenges.
    We do not dispute that mine operators have had less success with 
active regenerating filter systems compared to passive systems. As 
noted above, we believe this result is largely due to greater 
experimentation, trial and error, and applications engineering by mine 
operators on passive systems. During the remaining period before 
enforcement of the final limit of 160TC [mu]g/m3 
begins, mine operators will have sufficient time to meet these 
challenges and successfully apply active regeneration systems.
    Several commenters have said that they favor passive regeneration 
over active regeneration. For example, one mine operator said, 
``Research and testing of DPF regenerations systems has concluded that 
passive regeneration systems are preferred over active regenerations 
systems.'' As a result, most mine operators who have evaluated DPFs 
have concentrated their efforts on passive systems. We realize, 
however, that mine operators who have successfully implemented passive 
regeneration filter systems have had to work long and hard to overcome 
difficult implementation issues. One mine operator commented, ``The 
process of achieving filter reliability has been arduous * * *'' The 
product of these sustained efforts has been longer filter life, 
acceptance and support by operating and maintenance personnel, and the 
streamlined integration of passive filters into these mines' overall 
operating procedures, all of which we believe could contribute to 
controlling costs.
    We are confident that such efforts, applied to active systems, can 
achieve similar results. These systems are widely used in other 
industries, and they have been used successfully on a limited basis in 
M/NM mining. Their successful use on a more widespread basis in the 
mining industry is possible, but not without time and similar dedicated 
efforts by mine operators to solve the mine-specific and application-
specific logistical and implementation issues discussed above. This 
point was emphasized by NIOSH in its opinion submitted on June 25, 2003 
and repeated in its comments on the current rule that:

    With regard to the availability of filters and the interim 
standard, the experience to date has shown that while diesel 
particulate filter (DPF) systems for retrofitting most existing 
diesel-powered equipment in underground metal and nonmetal mines are 
commercially available, the successful application of these systems 
is predicated on solving technical and operational issues associated 
with the circumstances unique to each mine. Operators will need to 
make informed decisions regarding filter selection, retrofitting, 
engine and equipment deployment, operation, and maintenance, and 
specifically work through issues such as in-use efficiencies, 
secondary emissions, engine backpressure, DPF regeneration, DPF 
reliability and durability.

    When these implementation issues are resolved, we believe an 
inevitable consequence will be significantly reduced costs due to 
decreased waste, fewer damaged or failed filters, increased efficiency 
and effectiveness of filter system installations, operations, and 
maintenance, acceptance by miners, minimal adverse effects on equipment 
operations, and smoother integration of filter regeneration into the 
mining process.
    Two commenters provided information on the costs of utilizing low 
DPM emission engines. One mine operator said, ``Since 2001, Stillwater 
has performed a proactive engine campaign to replace the higher DPM 
emitting engines with the newer EPA Tier I and Tier II rated engines.'' 
This commenter also provided a table of the costs incurred in 2004 and 
2005 for engine replacements and upgrades showing that 48 new engines 
were installed at a total cost of $576,000 (average cost of $12,000 
each) and 98 engine upgrades (electronic engine governors) were 
completed at a total cost of $198,000 (average cost of $2,020 each). 
Several other commenters indicated they had replaced engines or had 
purchased new equipment with low DPM emission engines, but the only 
other commenter to provide cost data on engines said they had completed 
eight ``engine repowers'' at a total cost of $120,000, for an average 
cost of $15,000.
    As we have suggested throughout the DPM rulemakings, utilization of 
low DPM-emitting engines is an excellent

[[Page 28972]]

way of reducing DPM concentrations underground. Depending on the 
specific emissions from the original and replacement engines, DPM 
reductions of up to 90% or more are possible. However, we acknowledge 
that replacing engines can be costly, especially when the replacement 
engine requires significant adaptations to the host vehicle to 
accommodate physical size constraints, new plumbing and wiring 
harnesses, etc. Comments on the 1998 Preliminary Regulatory Economic 
Analysis (PREA) suggested such ``non-like-for-like'' retrofits could 
cost up to $60,000. Although costs may reach $60,000 in certain extreme 
or worst case situations, we believe in reality, that the costs quoted 
above of $12,000 to $15,000 are more typical. When amortized over the 
10 year life of an engine, the annualized yearly cost of a $15,000 
engine at a discount rate of 7% is $2,136.
    We also received comments to the 1998 PREA indicating that mining 
equipment at underground M/NM mines can have a useful life of up to 20 
years. However, engines typically last only half that long or less, 
meaning that engine replacement is a routine procedure that is 
necessary to maintain mine production levels. We do not view replacing 
a worn out or blown engine with a new low DPM engine as a DPM related 
compliance cost. It is not clear from the commenters' data whether the 
subject engines were replaced due to the normal engine turnover process 
or whether serviceable engines were replaced solely for DPM compliance 
purposes.
    We also note that the new low DPM emitting engines provide other 
significant benefits to mine operators. The electronic maintenance 
diagnostics reduce maintenance-related downtime, and the fuel savings 
between a non-EPA Tier rated engine and an EPA Tier 2 engine can be 
10%-15% or more. For a 400 horsepower engine that normally consumes 8 
gallons of fuel per hour (approximately 50% duty cycle), a 10% 
reduction in fuel consumption over 3,000 annual operating hours results 
in a 2,400 gallon fuel savings per year. At a diesel fuel cost of $2.00 
per gallon, the new $15,000 Tier 2 engine would almost pay for itself 
in 3 years due to lower fuel consumption. At a diesel fuel cost of 
$2.30 per gallon, if an old engine was replaced with one that consumed 
15% less fuel and was operated for 6,000 hours per year, the payback 
period for the $15,000 replacement would be less than one year. In 
fact, the current price of diesel fuel (in May 2006) has risen to 
approximately $2.90 per gallon.
    A mining company that operates two gold mines in Nevada commented 
that,

    Our estimate of the total cost of measures taken to achieve 
compliance with the current interim standard [interim DPM limit] is 
approximately $1.68 million annually ($8.4 million since 2001). Our 
experience indicates that MSHA's 2001 cost estimates dramatically 
understated the costs of compliance.

This commenter then itemized the compliance costs incurred at their two 
mines since 2001 as follows:

   Engine repowers (8 @ $15,000)...................     $120,000
   Cab installed on KMS 608........................      $43,000
   Cabs on 2 new loaders @ $43,000 each............      $86,000
   Cabs on 3 new loaders @ $48,000 each............     $144,000
   1225 South Meikle Spray Chamber.................     $139,000
   Rodeo Betze Portal Drift........................   $1,200,000
   Rodeo Betze Port Drift Vent Intake..............   $1,300,000
   Increase size of auxiliary fans.................     $750,000
   Higher power cost, $560,000/yr x 3 yrs..........   $1,680,000
   Total costs since 2001..........................   $5,462,000
 

    The sum of the items listed by the commenter, $5,462,000, is about 
65% of the $8.4 million amount the commenter claims was spent to attain 
DPM compliance. Without a thorough study of these elements, and based 
on the limited information provided by this mine operator in their 
comments, we are not able to verify that all of these costs are DPM-
related. For example, we determined at another precious metals mine 
that claimed DPM-related ventilation upgrades were actually justified 
on the basis of other needs, such as planned production increases and 
the desire to improve overall ventilation system efficiency. Of the 
approximately $5.46 million in claimed DPM compliance costs itemized 
above, over $5.07 million, or 93% are ventilation related. Likewise, 
installing cabs on mobile equipment or acquiring new equipment with OEM 
cabs can also solve dust and noise overexposure problems and improve 
operator comfort.
    However, even if all the listed costs were entirely justified 
solely on the basis of complying with the DPM rule, when the individual 
cost elements are amortized at a discount rate of 7% over their 
expected life, annualized yearly costs to the operator are about 
$980,000. The estimated yearly compliance cost for a medium sized gold 
mine was determined in the Regulatory Economic Analysis (REA) for the 
2001 final rule to be $171,778 (not adjusted for inflation) based on an 
inventory size of 24 pieces of diesel equipment. In their comments, 
this mine operator indicated they are currently operating 154 pieces of 
diesel equipment for mining and support activities. In 2002, this 
operator reported 236 pieces of diesel equipment in its diesel 
equipment inventory. Using the lower number and applying a ratio 
multiplier of 6.4 (154/24) to the $171,778 compliance cost estimate 
from the 2001 REA results in an estimated compliance cost for the 
commenter's two mines of $1,099,379. Thus, this commenter's actual 
annualized compliance cost of $980,000 is about 89% of the expected 
annualized compliance cost for gold mines of this size, as estimated 
for the 2001 final rule. Under the new final rule, the mine operator's 
compliance costs would be expected to decrease due to the phase-in of 
the final DPM limits.
    This same mine operator urged us to update our compliance cost 
estimates based on the current price of diesel fuel. They indicated 
that,

    In 2001, when the proposed limit was adopted, diesel costs were 
approximately $1.40 per gallon. Currently, diesel prices are in the 
range of $2.39 per gallon, an increase of over 70%. Available 
control technologies, particularly filters, reduce horsepower and 
increase fuel consumption and costs to accomplish the same work. The 
agency's cost estimates should acknowledge current diesel fuel 
prices.

    Since 2001, a major component of DPM compliance strategies that are 
being widely adopted throughout the industry, including by this 
operator, is the use of modern low emission engines, which in addition 
to significantly lowering DPM emissions, also reduces fuel consumption 
by 10% to 15% compared to older, high DPM emission engines. We also 
note that the fuel penalty of using a properly sized diesel particulate 
filter is very small. Even the fuel burner system, which combusts 
diesel fuel in the exhaust to raise the exhaust gas temperature 
sufficient for filter regeneration, only increases fuel consumption by 
about 1%.
    We received comments on the costs of environmental cabs from gold 
mines in Nevada. One company indicated they had retrofitted five fully 
enclosed cabs onto haulage trucks and loaders, and that as a result, 
the operators of this equipment were in compliance with the final 
limit. These cabs were installed during major re-builds on the subject 
equipment at a cost of $30,000 to $50,000 each. Another operator 
indicated they had installed environmental cabs on six loaders at a 
cost of $43,000 to $48,000 each. These unit costs are higher than we 
originally estimated for environmental cabs in the REA for the 2001 
final rule. However,

[[Page 28973]]

our original cost estimate applied to the industry in general and to 
all equipment. We expected the cost of retrofitting cabs onto purpose-
built underground mining equipment to be substantially higher than the 
cost of cabs installed at the factory on construction-type equipment by 
the OEM. The costs quoted by the commenters reflect this expected 
difference. It is also important to note that the costs of these 
retrofitted cabs are only a small part of overall compliance costs for 
these mines, and their overall compliance costs are less than expected 
based on the REA for the 2001 final rule.
    We received several comments on the cost of biodiesel fuel. These 
comments generally fell into three categories: the cost of the fuel 
itself, the biodiesel tax credit, and the cost of infrastructure for 
fuel storage and handling. Regarding the cost of the fuel itself, 
typical comments were:
    Fuel prices will have a substantial impact as Bio-Fuel cost is 
over $1.00 per gallon higher than diesel.
    [Biodiesel] * * * is not widely distributed or accessible at a 
reasonable cost to many mining operations.
    Our current diesel fuel supplier has indicated that the cost for 
bio-diesel fuel * * * would be priced at a premium of 20 to 25 cents 
per gallon for a B20 blend.

Regarding the tax credit, typical comments included:

    We are now considering a B99, with the hope that the current 
$1.00 per gallon tax credit remains to help control costs.
    The economic feasibility of alternative fuels depends upon 
uncertain government price supports that are due to expire in the 
near future.

Regarding the cost of infrastructure upgrades, typical comments 
included:

    Cost analysis concerning on-site storage was conducted with a 
regional supplier and proved cost prohibitive. The cost of the 
infrastructure to support biodiesel at the mine would include a 
10,000 gallon tank for diesel, 15,000 gallon tank for biodiesel, and 
a 10,000 gallon tank for the blended product. The cost for this 
system would be in excess of $250,000.
    [The higher cost per gallon for biodiesel] does not include 
costs for specialized transport during the winter season to keep the 
biodiesel fuel from gelling. Further, we would have to install 
separate fuel tankage to segregate biodiesel fuels from other fuels 
* * *

    We agree with the commenters who indicated that the cost of 
biodiesel is typically about $1.00 per gallon more than standard diesel 
fuel, though this has not always been the case. Prices for standard 
diesel and biodiesel are determined by the market, and when the price 
of standard diesel fuel spiked in the late summer and fall of 2005, the 
price difference between standard diesel and biodiesel was considerably 
less than $1.00 per gallon. But the $1.00 per gallon price difference 
quoted by the commenters is more typical. However, the net cost of 
biodiesel to mine operators is significantly affected by the federal 
excise tax credit for biodiesel fuels, which applies to fuel blenders 
(typically the fuel distributor), and is valued at $0.01 per gallon per 
percentage of biodiesel in a fuel blend for biodiesel made from 
agricultural feedstock (such as soy biodiesel). Because the cost of 
biodiesel is typically approximately $1.00 per gallon more than 
standard diesel, the credit of $0.01 per gallon per percent biodiesel 
has nominally eliminated the cost difference between standard diesel 
and biodiesel. For example, if standard diesel is $2.00 per gallon, and 
the cost of biodiesel before the excise tax credit is applied is $3.00 
per gallon, a 98% biodiesel fuel blend (98% biodiesel mixed with 2% 
standard diesel) with the tax credit applied would cost:

[$2.00/gal x 2%] + [$3.00/gal x 98%]-[98% x $0.01] = $2.00/gal. Thus, a 
gallon of the 98% blend of biodiesel, after the tax credit is applied, 
would cost the same as a gallon of standard diesel.
    This tax credit, which has been in effect since 2004, was scheduled 
to expire in 2006, but has been extended through 2008. It is impossible 
to predict whether the credit will be extended beyond 2008, as its 
further extension is subject to Congressional action. It is also 
impossible to predict the future price difference between standard 
diesel and biodiesel, as the prices of both commodities are determined 
by market forces. The only factor affecting the price of either fuel 
that can be predicted with any degree of certainty is the supply of 
biodiesel. Biodiesel production in the United States has grown from 0.5 
million gallons in 1999 to an estimated 75 million gallons in 2005. 
Production growth between 2004 and 2005 alone was 300%, from 25 million 
gallons to 75 million gallons. Annual production capacity that is 
currently under construction is 329 million gallons. Biodiesel 
production plants in the pre-construction phase will have an annual 
capacity of an additional 529 million gallons. To the extent that 
increased supply tends to attenuate upward pressure on price, the 
expected effect of this large increase in biodiesel supply would be to 
moderate price increases, if any, or possibly serve to lower the price. 
Another indicator of future price trends is the capacity of individual 
plants. At present, only 13 of 52 plants have an annual capacity of 10 
million gallons or more. In contrast, of the plants currently under 
construction or in the pre-construction phase, 27 have an annual 
capacity of 10 million gallons or more, including several ranging from 
30 million to 80 million gallons of annual capacity. To the extent that 
larger plants can reduce costs through economies of large scale 
production, the growth of larger plants will also attenuate upward 
price pressure. Thus, even without the tax credit, we expect the price 
difference between standard diesel and biodiesel to shrink over time. 
Our determination of whether biodiesel fuel is a feasible DPM control 
at a particular mine, however, does not depend on extension of the 
federal excise tax incentive.
    Regarding the issue of infrastructure upgrades to accommodate 
biodiesel, we agree that some upgrades may be necessary at some mines. 
For example, due to the cold weather properties of the fuel, storage 
tanks at mines that experience sub-freezing temperatures would need to 
be heated, moved to a heated indoor space, or moved underground. Some 
mines that are using high biodiesel content fuel blends have, or are 
planning such changes. There may also be costs incurred by the fuel 
distributor. Some distributors are already capable of off-loading, 
handling, and storing biodiesel in cold weather. However, those that do 
not have this capability would need to acquire the necessary 
infrastructure upgrades, and the associated costs would reasonably be 
passed along to their biodiesel customers. However, such costs, whether 
incurred by the mine operator or the fuel distributor and passed on to 
the mine operator, would largely be one-time expenses that would be 
amortized over a period of many years. For example, although we dispute 
the commenter's assertion that infrastructure upgrades to support 
biodiesel at their mine would cost $250,000, even this amount, when 
amortized over 20 years, results in an annualized yearly cost of 
$23,598. We assume a tank already exists at the mine for standard 
diesel, so it is not clear why another tank is necessary. We also 
question why a tank for blended fuel is needed, as greater DPM 
reductions are obtained when biodiesel content is maximized. While it 
is true that biodiesel needs to be blended with standard diesel to 
qualify for the federal excise tax credit, the IRS has determined that 
a 99.9% blend (nominally 10 gallons of standard diesel mixed with 
10,000 gallons of biodiesel)

[[Page 28974]]

satisfies this requirement. Such a blending process would not require a 
separate blending tank. Thus, the commenter's $250,000 cost estimate 
for infrastructure to support biodiesel appears high. However as noted 
above, even if this cost is supportable, the total cost, when amortized 
over the life of the asset, results in an annualized yearly cost of 
$23,598. It is also significant to note that this commenter's fuel 
consumption is about 80,000 gallons per month. The corresponding costs 
for infrastructure upgrades at an average or typical mine would be much 
lower.
    Depending on circumstances at a given mine, there may also be a 
need to provide vehicle fuel tank heaters, fuel line heaters, and fuel 
filter heaters. These items are commercially available at reasonable 
costs. For example, the MSRP for an Artic Fox model AF-F-203 14'' to 
29'' in-tank fuel warmer is $169.27, the MSRP for an Artic Fox model 
AF-D3085-2180 24V, 600W, 12 ft heated fuel line is $614.86, and the 
MSRP for a Diesel Therm fuel filter heater is $180.81.
    The operator of two large stone mines commented that there are 
occupations at their mines such as roof bolters that require personnel 
to work outside of a cab near the mine roof where DPM concentrations 
would be expected to be the highest. Due to the high cost of major 
ventilation upgrades, this commenter asked that consideration be given 
to allowing such miners to utilize PPE for compliance with the DPM 
limit. Another stone mine operator made a similar comment, asking:

    Is it economically sensible to expend monies to ensure 
compliance with the DPM rule for 15 employees exposed to the 
polluted air when they venture outside of the cab and can use PPE? 
MSHA also did not allow the most cost-effective method of use of PPE 
and other administrative controls to reach the final limit.

    In responding to these comments, we note first that mine operators 
have available engineering control options other than cabs and 
ventilation, and second, that under certain circumstances, PPE is 
allowed as a means of compliance. Under Sec.  57.5060(d), mine 
operators have been granted great flexibility in choosing controls to 
attain compliance, and are not limited to only cabs or ventilation. The 
operator of the two large stone mines has acknowledged having had 
success with alternative diesel fuels, and has also acquired new 
equipment with low emission engines. However, they have not utilized 
diesel particulate filters on any equipment, and it is not clear 
whether expanded use of low emission engines or the use of 
administrative controls might also be possible.
    As noted previously in the technological feasibility section, it is 
a widely accepted principle of industrial hygiene that PPE is 
inherently inferior compared to engineering and administrative controls 
for reducing exposures, so the requirement to implement all feasible 
engineering and administrative controls before PPE could be utilized as 
a means of compliance was promulgated in the 2005 final rule and is 
applicable to this final rule. We also note that, in accordance with 
our DPM sampling procedures, a miner's exposure to DPM is determined 
through full-shift personal sampling. This sampling procedure 
integrates or averages a miner's exposure throughout the shift so that 
an occasional exposure to a high concentration to DPM will not cause 
the full shift sample to exceed the DPM limit if the majority of the 
miner's exposure is sufficiently below the limit. Given adherence to 
this sampling procedure, it is highly unlikely that any of the, ``15 
employees exposed to the polluted air when they venture outside of the 
cab,'' would be overexposed to DPM on a full-shift basis if their 
excursions outside their cabs were brief, and their cabs were properly 
maintained and provided with filtered breathing air.
    The operator of the two large stone mines included cost estimates 
for a new ventilation shaft and fan for one of its mines. They 
indicated the cost of a 16-foot diameter shaft at $1,000 per vertical 
foot and 800 to 1,200 feet deep would be $800,000 to $1.2 million, and 
that when fan costs are added, the total cost approaches $1.5 million. 
We note that the upper end of the range of the commenter's estimated 
cost for a new shaft and fan of $1,500,000, would not necessarily be 
considered economically infeasible for a stone mine of this size. The 
cost of this shaft and fan, when amortized over 20 years at a discount 
rate of 7%, results in an annualized yearly cost to the operator of 
$142,000. The estimated total yearly compliance cost for a medium sized 
stone mine was determined in the Regulatory Economic Analysis (REA) for 
the 2001 final rule to be $150,738 based on an inventory size of 17 
pieces of diesel equipment. In 2002, this mine operator reported a 
total diesel equipment inventory of 60 pieces of diesel equipment at 
the subject mine. Applying a ratio multiplier of 3.5 (60/17) to the 
estimated $150,738 compliance cost from the 2001 REA results in an 
estimated yearly compliance cost for the mine of $527,583. Thus, if a 
new ventilation shaft and fan are installed to attain compliance at the 
subject mine, the annualized yearly cost of $142,000 for this major 
ventilation upgrade, though significant, is less than 30% of the 
expected total yearly compliance cost for a stone mine of this size.
    Not all commenters disagreed with the economic feasibility of the 
rule. One commenter said,

    In January 2001, MSHA estimated that compliance with the rule 
would cost approximately $25.1 million on an annual basis (66 FR 
5889). MSHA estimated that 73% of those costs would be expended to 
comply with the interim level and 27%, or just $6.6 million 
annually, to comply with the final limit. MSHA found these costs to 
be economically feasible. They represent less than one percent of 
industry revenues. Nothing in the record suggests that these 
compliance costs have increased. If anything, advances in technology 
and the availability of substitute fuels mean the likely costs of 
compliance have decreased since the 2001 estimates were completed.

Another commenter said,

    A standard is not infeasible simply because it is financially 
burdensome, or even because it threatens the survival of some 
companies within an industry. MSHA estimated that the annual cost of 
the final rule was $25.1 million or $128,000 annually for an average 
underground metal and nonmetal mine. (70 FR 53282) The NPRM does not 
contain any data suggesting that these minimal costs would be 
significantly greater than originally estimated, let alone that 
costs would be so high to threaten the economic viability of the 
industry.

    The DPM rulemaking record contains considerable comments supporting 
the need for more time to effectuate controls that are economically 
feasible for mine operators. In the cost estimates for this final rule, 
we have included cost related to operator evaluation of different 
technologies in an effort to determine the most effective method for 
compliance.
    A number of comments were received on the cost of medical 
evaluations. Under the final rule, a miner is required to wear 
respiratory protection if the miner is overexposed to DPM and all 
feasible engineering and administrative controls are installed. Prior 
to being fit tested or assigned to a task where respiratory protection 
is required, the miner must be evaluated by a physician or other 
licensed healthcare professional to determine whether the miner is 
medically capable of wearing a respirator in the mine. As shown in 
Table IX.1 later in this preamble, the estimated yearly cost to the 
underground M/NM mining industry of this medical evaluation requirement 
is about $20,000. Comments on medical evaluation included:


[[Page 28975]]


     Prior to any miner being placed into a respirator, 
steps are taken to ensure that the miners are medically fit for 
wearing a negative pressure respirator. A formal medical evaluation 
is conducted prior to being fit tested and annually thereafter. To 
date, approximately 65 miners needed additional evaluation to 
receive clearance to wear a negative pressure respirator. The 
average cost for the additional medical evaluation was $250/visit. 
Estimated annual cost for medical clearance has been $16,000.
     MSHA seeks comments on whether the final rule should 
include a provision requiring a medical evaluation to determine a 
miner's ability to use a respirator before the miner is fit tested 
or required to work in an area of the mine where respiratory 
protection must be used. Barrick already complies with this proposed 
requirement. Each of our employees undergoes a medical evaluation 
before being fitted with a respirator * * * Based on currently 
available data, we estimate that the average cost per person for 
medical evaluations for our Goldstrike operations is $660.
     Greens Creek also conducts its own pulmonary function 
tests on individuals required to wear respirators under our 
respiratory protection program. That program includes proper fit 
testing. We have on-site technicians who are certified to conduct 
these tests, however, the analysis of the pulmonary function tests 
is provided by a licensed healthcare provider. The tests cost 
roughly $17.00 per individual.
     At our mines, we provide a medical exam and 
certification of the ability to wear a respirator upon hire * * * If 
the miner's health conditions change preventing the safe use of a 
respirator, then additional tests can be provided including 
spirometry and if indicated, a medical examination. We have not had 
a case where a miner's health changed preventing the wearing of a 
respirator, that the miner was not aware of the health condition. We 
do not object to annual spirometry testing following guidelines 
developed and supervised by a medical doctor or other medical 
professional. We do object to the added expense of requiring a 
medical exam every year if there are no indicators of a medical 
necessity, either by the miner's own request or the conditions 
mentioned.

    Mine operators that provided comments on the cost of medical 
evaluations for respirator users already routinely conduct such 
evaluations. Based on the significant disparity in quoted costs from 
$17 to $660 per miner, it appears that some operators' evaluations are 
quite basic, consisting of a simple pulmonary function test and 
possibly the completion of an employee questionnaire, whereas other 
operators are apparently conducting actual medical examinations. No 
commenters provided information suggesting that the requirement for 
medical evaluations would be economically infeasible. Although we 
require a medical evaluation to determine a miner's ability to wear a 
respirator before using a respirator, we only require a re-evaluation 
when the mine operator has reason to believe that conditions have 
changed which could adversely affect the miner's ability to wear a 
respirator. We also will accept prior medical evaluations to the extent 
the mine operator has a written record and there have not been any 
changes that will adversely affect the miner's ability to wear a 
respirator. We believe that this approach will minimize the economic 
burden on the mine operator in conducting medical evaluations while 
still protecting the miner.

VI. Summary of Benefits

    In Chapter III of the Regulatory Economic Analysis in support of 
the 2001 final rule (2001 REA), we demonstrated that the DPM final rule 
for M/NM mines will reduce a significant health risk to underground 
miners. This risk included the potential for illnesses and premature 
death, as well as the attendant costs to the miners' families, the mine 
operators and society at large.
    We have incorporated into this rulemaking record the previous DPM 
rulemaking records, including the risk assessment to the 2001 final 
rule. Benefits of the 2001 final rule include continued reductions in 
lung cancers. In the long run, as the mining population turns over, we 
estimated that a minimum of 8.5 lung cancer deaths will be avoided per 
year. We noted that this estimate was a lower bound figure that could 
significantly underestimate the magnitude of the health benefits. For 
example, the mean value of all eight quantitative estimates examined in 
the 2001 final rule was 49 lung cancer deaths avoided per year.
    Other benefits noted in the 2001 REA were reductions in the risk of 
premature death from cardiovascular, cardiopulmonary, or respiratory 
causes and reductions in the risk of sensory irritation and respiratory 
symptoms. However, we did not include these health benefits in our 
estimates because we could not make reliable or precise quantitative 
estimates of them. Nevertheless, we noted that the expected reductions 
in the risk of death from cardiovascular, cardiopulmonary, or 
respiratory causes and the expected reductions in the risk of sensory 
irritation and respiratory symptoms are likely to be substantial.
    The 2001 risk assessment used the best available data on DPM 
exposures at underground M/NM mines to quantify excess lung cancer 
risk. ``Excess risk'' refers to the lifetime probability of dying from 
lung cancer during or after a 45-year occupational DPM exposure. This 
probability is expressed as the expected excess number of lung cancer 
deaths per thousand miners occupationally exposed to DPM at a specified 
mean DPM concentration. The excess is calculated relative to baseline, 
age-specific lung cancer mortality rates taken from standard mortality 
tables. In order to properly estimate this excess, it is necessary to 
calculate, at each year of life after occupational exposure begins, the 
expected number of persons surviving to that age with and without DPM 
exposure at the specified level. At each age, standard actuarial 
adjustments must be made in the number of survivors to account for the 
risk of dying from causes other than lung cancer. Occupational exposure 
is assumed to begin at age 20 and to continue, for surviving miners, 
until retirement at age 65. The accumulation of lifetime excess risk 
continues after retirement through the age of 85 years.
    Table IV-9 in Section IV of this Preamble, taken from the 2001 risk 
assessment, shows a range of excess lung cancer estimates at mean 
exposures equal to the final DPM limit. The eight exposure-response 
models employed were based on studies by S[auml]verin et al. (1999), 
Johnston et al. (1997), and Steenland et al. (1998). All of the 
exposure-response models shown are monotonic (i.e., increased exposure 
yields increased excess risk, though not proportionately so). Thus, 
despite evidence from recent sampling of substantial improvements 
attained since the 1989-1999 sampling period addressed by the 2001 risk 
assessment, underground M/NM miners are still faced with an 
unacceptable risk of lung cancer due to their occupational DPM 
exposures.
    Another principal conclusion of the 2001 risk assessment was:

    By reducing DPM concentrations in underground mines, the rule 
will substantially reduce the risks of material impairment faced by 
underground miners exposed to DPM at current levels.

    DPM levels have declined since MSHA's first sampling period (from 
1989 to 1999). MSHA expects that further improvements will continue to 
significantly reduce the health risks identified for miners. There is 
clear evidence of DPM's adverse health effects, not only at pre-2001 
levels but also at the generally lower levels currently observed at 
many underground mines. These effects are material health impairments 
as specified under section 101(a)(6)(A) of the Mine Act. During the 
time period from November 1, 2003 to January 31, 2006, 1798 valid 
personal compliance samples from all mines covered by the

[[Page 28976]]

2001 rule were collected. From these samples collected, 18% (324) of 
samples exceeded 308EC [mu]g/m\3\, 22% (396) exceeded 
350TC [mu]g/m\3\, and 64% (1151) exceeded 160TC 
[mu]g/m\3\. Because the exposure-response relationships shown are 
monotonic, MSHA expects that industry-wide implementation of the final 
limit of 160TC [mu]g/m\3\ will significantly reduce the risk 
of lung cancer and other adverse health effects among miners.
    This final rule would amend the 2001 final DPM rule by phasing in 
the final limit over a two-year period to address feasibility 
constraints that have arisen. By phasing in the final limit to address 
the feasibility issues, this final rule would contribute to the 
realization of the benefits mentioned above. In addition, the medical 
evaluation and transfer provisions of this final rule would provide 
further benefits by ensuring that miners who are required to wear a 
respirator are able to do so safely, thereby obtaining the full health 
protection available from that equipment.

VII. Section 101(a)(9) of the Mine Act

    Section 101(a)(9) of the Mine Act provides that: ``No mandatory 
health or safety standard promulgated under this title shall reduce the 
protection afforded miners by an existing mandatory health or safety 
standard.'' We interpret this provision of the Mine Act to require that 
all of the health or safety benefits resulting from a new standard be 
at least equivalent to all of the health or safety benefits resulting 
from the existing standard when the two sets of benefits are evaluated 
as a whole. The U.S. Court of Appeals for the D.C. Circuit approved 
such a ``net effects'' application of Section 101(a)(9). Int'l Union, 
UMWA v. Federal Mine Safety and Health Admin., 407 F. 3d 1250, 1256-57 
(D.C. Cir. 2005).
    We conclude that this final rule will not reduce protection 
afforded miners under the 2001 final rule. The phase-in period of the 
2001 final limit of 160TC [mu]g/m\3\ is not feasible for the 
mining industry as a whole in May 2006, but we could not justify a 
greater reduction in the final limit than 350TC [mu]g/m\3\ 
before May 2008. Feasibility issues with respect to operator compliance 
are discussed above. Moreover, we intend to convert the final limits of 
350TC [mu]g/m\3\ and 160TC [mu]g/m\3\ in a 
separate rulemaking by January 2007. As we said in the 2005 NPRM, if we 
do not complete this rulemaking by that time, we will use the EC 
equivalent as a check to validate that an overexposure to the 
350TC [mu]g/m\3\ final limit is not the result of 
interferences. This enforcement policy, which is based on the Second 
Partial Settlement Agreement and data in the rulemaking record, would 
be the same that we used to implement the 400TC [mu]g/m\3\ 
interim limit before we converted it to 308EC [mu]g/m\3\ in 
the June 2005 final rule. Whereas we have evidence that we can obtain 
an accurate sample analysis of the final limit of 350TC 
[mu]g/m\3\, there is no evidence in the rulemaking record suggesting 
that the 1.3 conversion factor is appropriate for substantially lower 
limits, such as the final limit of 160TC [mu]g/m\3\. In the 
2005 NPRM, we stated that we have an additional concern with whether an 
effective sampling strategy exists to enforce the final limit of 
160TC [mu]g/m\3\ with TC as the surrogate. Evidence after 
January 2001 suggests that without an appropriate conversion factor, 
which we do not have presently, there is no practical sampling strategy 
that would adequately remove organic carbon interferences that occur 
when TC is used as the surrogate without the ability to confirm the 
sample results with an EC analysis. Thus, we acknowledge that it is 
questionable whether the final limit with a TC surrogate of 
160TC [mu]g/m\3\ would provide more protection for miners 
than the final limits of 350TC [mu]g/m\3\ when we use the 
1.3 conversion factor to confirm an overexposure. We have the burden of 
proof in court to demonstrate that an overexposure to DPM actually 
occurred and the sample result is not due to interferences. If we were 
to enforce the final DPM limit of 160TC [mu]g/m\3\, we would 
need to validate a TC sample result, which cannot be done without an 
appropriate conversion factor for EC at that level. Discussion of the 
complexity of developing an appropriate conversion factor for the final 
limit is discussed in Variability of the Relationship Between EC and 
TC.
    We requested comments in the 2005 NPRM on whether a five-year 
phase-in period for lowering the final limit to 160TC [mu]g/
m\3\ complies with Section 101(a)(9) of the Mine Act. A number of 
commenters objected to our 2005 NPRM that would have delayed 
implementation of the final limit of 160TC [mu]g/m\3\ until 
2011. They stated that the 2005 NPRM would weaken protection provided 
by the 2001 final rule, a consequence that Section 101(a)(9) prohibits, 
since the lower level can be met in some jobs in underground metal and 
nonmetal mines, if not in all jobs. They believe that the 2005 NPRM 
violates the law since we would be raising the final limit above 
160TC [mu]g/m\3\ and extending the timeframe for its 
applicability. In response, we emphasize that we determined that it is 
presently infeasible for the mining industry to comply with 
160TC [mu]g/m\3\, and we have no data to confirm in court 
that a 160 TC sample is not the result of interferences.
    Regarding feasibility, we chose May 2008 for the effective date of 
the final limit to correspond with when we believe mine operators, 
especially small mine operators, will be able to find effective 
approaches to utilizing available DPM control technology so that they 
will be capable of meeting the standard. Over the five years since the 
2001 final rule was promulgated, both MSHA and the mining industry have 
gained considerable experience with the implementation, use, and cost 
of DPM control technology. We have reviewed this experience, and our 
own enforcement data, and conclude in the final rule that effective DPM 
controls will be feasible and commercially available to mine operators 
by 2008.
    Other commenters stated that the proposed five year phase-in 
period, a longer phase-in period, or a decision to adopt the current 
interim limit of 308EC [mu]g/m\3\ as a final standard would 
all comply with Section 101(a)(9) of the Mine Act, and that we should 
take no action to require reductions below the current interim 
standard. These commenters also noted that our inability to enforce a 
final limit of 160TC [mu]g/m\3\ is critical because Section 
101(a)(9) is predicated on the assumption that the existing standards 
are enforceable, and therefore, ensure the health of miners. They do 
not believe that the final limit of 160TC [mu]g/m\3\ would 
provide any more protection than the 308EC [mu]g/m\3\, and 
that many mines will not be able to comply with the 160TC 
[mu]g/m\3\ due to economic and technological feasibility issues. These 
commenters further stated that most miners at these sites will be 
required to wear respirators for extended periods of time.
    We disagree with these commenters. As discussed above under Section 
V.A. Technological Feasibility, and Section V.B., Economic Feasibility, 
we are confident that feasible technology exists to reduce miners' 
exposures to DPM to the final limit by May 2008. Although most mines 
can feasibly comply with the existing DPM final limit of 
308EC [mu]g/m\3\ we expect that some miners will continue to 
have to wear respiratory protection under the final limit of 
160TC [mu]g/m\3\. By phasing in the 160TC [mu]g/
m\3\ final limit over two years, we believe that many existing 
compliance difficulties can be successfully resolved as mine operators 
are able to access alternative fuels and become more adept and familiar 
with DPFs.

[[Page 28977]]

    Similarly, some commenters stated that the proposed standard is 
based on the wrong exposure matrix, is infeasible, and should be 
withdrawn. They believe that implementation of the 160TC 
[mu]g/m\3\ final limit would result in widespread experimentation with 
unproven and untested control technology that presents new and 
potentially significant risks to miners. In these commenters' views, 
such a result would violate the Mine Act and should not be permitted.
    We responded to these control technology issues in our feasibility 
discussion of this preamble at Section V. It is important to note, 
nevertheless, that we stated in the 2005 NPRM that implementation 
issues may adversely affect the feasibility of using DPFs to reduce 
exposures despite the results reported in NIOSH's Phase I Isozone 
Study. Under the prescribed timeframes of the final rule, mine 
operators should be able to resolve their unique implementation issues 
with DPFs. Moreover, proper selection of available filters will resolve 
the problem with risks to miners from increased levels of nitrogen 
dioxide. As we stated previously, we are confident that the current 
rulemaking record includes sufficient scientific data to retain the 
final limit of 160TC [mu]g/m3.
    More importantly, we have no evidence to substantiate deleting the 
final limit, especially when miners' exposures are expected to further 
decline over time, based on our enforcement sampling results. The 2001 
risk assessment and its updates confirm the serious health risks to 
miners from exposure to DPM, and we intend for the mining industry to 
continue to reduce miners' exposures to the final limit of 
160TC [mu]g/m3 by May 2008. Additionally, 
although some mines may experience implementation difficulties in 
meeting the DPM limits, the final rule allows for instances where mine 
operators may request special extensions of time in which to comply 
with the final limits in situations where controls may be 
technologically or economically infeasible. Finally, our longstanding 
enforcement policy considers an individual mine operator's ability to 
feasibly comply with the applicable limit. If we determine that the 
mine operator has installed all feasible controls and has placed 
affected miners in an appropriate respiratory protection program, we 
will not issue a citation for an overexposure.
    Another commenter stated that due to the scientific uncertainty 
that DPM poses, we should wait for the outcome of the NIOSH/NCI study 
to help identify the appropriate exposure limit. The commenter also 
stated that we are violating the requirements of Section 101(a)(6)(A) 
by proceeding with the rulemaking. We disagree. We have discussed our 
data to support our position to proceed with requiring the mining 
industry to continue to take the initiative to further reduce miners' 
exposures to DPM. Throughout this rulemaking, we expressed our intent 
to phase in the final limit of 160TC [mu]g/m3 
over time rather than in 2006. With regard to the collaborative study 
between NIOSH/NCI, if the study becomes available, we will assess it to 
determine if it provides additional information about the relationship 
between DPM exposure levels and disease outcomes. NIOSH, in its recent 
comments to our 2005 final rule, stated that, ``In summary, new peer-
reviewed publications addressing the health effects of exposure to 
diesel exhaust continue to support MSHA's 2001 risk analysis and its 
2005 updated information on health effects.'' Considering the 
foregoing, we do not believe that it is in the best interest of miners' 
health to delay beyond the implementation dates of the final rule.
    A number of other commenters believe that the five year phase-in 
period would have complied with 101(a)(9) of the Mine Act unless this 
rulemaking is not completed before May 20, 2006, the existing effective 
date of the 160TC [mu]g/m3 final limit. They 
stated that the Mine Act provision applies only upon the effective date 
of a requirement rather than the promulgation date of the standard. 
Consequently, they advise that if the Secretary were to allow the 
160TC [mu]g/m3 final limit to take effect on May 
20, 2006 then the Mine Act would prohibit any subsequent reduction or 
phase-in period. We do not agree with these commenters' interpretation 
of the Mine Act. We refer the commenters to our explanation in this 
section as to why we must phase in the final limit of 160TC 
[mu]g/m3, and why we do not believe that we have violated 
our mandate under Section 101(a)(9) not to reduce protection afforded 
by an existing standard.

VIII. Section-by-Section Analysis

A. PEL Sec.  57.5060(b)

    Section 57.5060(b) in the 2001 final rule established a final 
concentration limit of 160TC [mu]g/m3 which was 
scheduled to become effective on January 20, 2006. The final limit 
restricts total carbon (TC) concentrations in underground mines in 
areas where miners normally work or travel. Total carbon is the sum of 
elemental and organic carbon. In the 2001 final rule, we chose TC as 
the surrogate for measuring DPM concentrations. In our 2005 final rule, 
we changed the surrogate for the interim concentration limit measured 
by TC to a comparable permissible exposure limit (PEL) measured by 
elemental carbon (EC), which renders a more accurate DPM exposure 
measurement. We also committed to revising the 2001 final concentration 
limit of 160TC [mu]g/m3 in future rulemaking. 
Currently, the 160TC [mu]g/m3 final limit is to 
become applicable on May 20, 2006.
    In our 2005 NPRM, we recommended staggering the effective dates for 
implementing the final limit, to be phased-in over a five-year period, 
and decreased approximately 50 micrograms each year until the final 
limit of 160TC [mu]g/m3 would be reached in 
January 2011. This proposal was based on our position that the industry 
was encountering economic and technological implementation issues that 
could affect feasibility, while seeking to further reduce miners' 
exposures (70 FR 53283). These implementation issues surfaced following 
promulgation of the 2001 final rule. We stated in the 2005 NPRM that 
the mining industry, as a whole, may need additional time to address 
these implementation issues and find effective solutions for 
implementing additional DPM controls (70 FR 53284).
    We also proposed changing the final concentration limit to final 
permissible exposure limits (PELs), and we noted that special 
extensions of time in which to comply with the final PELs under 
existing Sec.  57.5060(c) would apply to each of the phased-in final 
limits, including the initial final limit of 308EC [mu]g/
m\3\. We explained that mine operators could apply to the District 
Manager if they were seeking additional time to come into compliance 
with each of the final limits, due to technological or economic 
constraints. We requested comments on the impact of granting extensions 
for compliance with exposure limits that are greater than the 
160TC [mu]g/m3 final limit.
    In the 2005 NPRM, we also asked the mining community to provide us 
their views on whether five years is the correct timeframe for reducing 
miners' exposures to 160TC [mu]g/m3. 
Additionally, we requested information on whether the proposed annual 
50 microgram reductions of the final DPM limit are appropriate or, in 
the alternative, should the final rule include an approach such as one 
or two reductions. We asked whether our reduction scheme for the final 
limit of 50 micrograms of TC each succeeding year, from 
400TC [mu]g/m3 (converted to a comparable limit 
of 308EC [mu]g/m3) is feasible, and whether

[[Page 28978]]

it will provide additional time for the implementation of controls, 
development of distribution centers for alternative fuels, and 
consideration of the economic impact of the proposed phased-in approach 
(70 FR 53288). Finally, we emphasized our need for information and 
views on the mining industry's current experiences with feasibility of 
compliance with a lower limit than the interim PEL of 308EC 
[mu]g/m3. In addition to our requests for comments, we 
notified the mining community that we were committed to initiating a 
separate rulemaking to determine the correct TC to EC conversion factor 
for the phased-in final limits. As discussed later in the subsection 
``Variability of the Relationship Between EC and TC'', we will address 
those comments in our future rulemaking. We further stated in the 2005 
NPRM that in the event that we did not complete this subsequent 
rulemaking to establish a conversion factor before January 20, 2007, 
the date of the first proposed reduction of the final limit, we were 
considering using the current 1.3 conversion factor that we use to 
establish the interim DPM PEL of 308EC [mu]g/m3 
to convert the phased-in final DPM TC limits to EC equivalents. As we 
did with the interim TC limit pursuant to the Second Partial Settlement 
Agreement, we would use the EC equivalents as a check to validate that 
an overexposure is not the result of interferences until this issue is 
addressed in future rulemaking.
    In development of this final rule, we also considered public 
comments related to the final limit which we received in response to 
the 2002 ANPRM to revise the DPM limits. Some commenters to the ANPRM 
recommended that we propose separate rulemakings for revising the 
interim and final DPM limits to give us an opportunity to gather 
further information to establish a final DPM limit. In the 2003 NPRM, 
we agreed with these commenters and solicited other information from 
the mining community that would lead to an appropriate final DPM 
standard. Moreover, we announced our intention to publish a separate 
rulemaking to amend the existing final concentration limit in Sec.  
57.5060(b).
    To assist us in achieving this objective, we requested comments on 
an appropriate final limit to replace the 160TC [mu]g/
m3 concentration limit, and asked for information on an 
appropriate surrogate for measuring miners' DPM exposures. We concluded 
our request for information by clarifying that revisions to the final 
DPM concentration limit would be included in a separate rulemaking. The 
public comments in response to our requests are reflected below in this 
section.
    Based on feasibility with respect to compliance and an effective 
strategy for implementing the final limits, we believe the mining 
industry as a whole can reduce DPM levels to the 2001 final limit of 
160TC [mu]g/m3 by May 20, 2008. We have 
determined that M/NM underground mines using diesel powered equipment 
are capable of reducing miners' exposures to 160TC [mu]g/
m3 by May 20, 2008, rather than on January 20, 2011. As 
proposed, the initial final limit will be the same as the current 
interim limit of 308EC [mu]g/m3 and will remain 
in effect through January 19, 2007. On January 20, 2007, the final 
limit will be reduced, as we proposed, to 350TC [mu]g/
m3, which represents a 50 microgram reduction. This limit, 
and the 160TC [mu]g/m3 final limit, will be TC 
limits rather than EC limits, since we do not have current data 
establishing a conversion factor from TC to EC. We discuss the 
complexity of developing a conversion factor later in this section 
under ``Variability of the Relationship Between EC and TC.''
    As we did with the 400TC [mu]g/m3 interim 
limit pursuant to the Second Partial Settlement Agreement, we will use 
the EC equivalent as a check to validate that an overexposure to the 
350 TC limit is not the result of interferences (67 FR 47296, 47298). 
We will implement an enforcement policy for the 350TC [mu]g/
m3 final limit that will use EC as an analyte to ensure that 
a citation based on the 350TC [mu]g/m3 limit is 
valid and not the result of interferences. Under our policy, we will 
first develop an appropriate error factor to account for variability in 
sampling and analysis from such things as pump flow rate, filters, and 
the NIOSH Analytical Method 5040. If the TC measurement is below 
350TC [mu]g/m3 plus the error factor, we will not 
issue a citation for an overexposure. If the TC measurement is above 
350TC [mu]g/m3 times the error factor, we would 
look at the EC measurement from the sample obtained through the NIOSH 
Analytical Method 5040, and multiply EC by a factor of 1.3 to produce a 
statistical valid estimate of what the TC result is without 
interferences. If the TC measurement is above this estimate, we would 
not issue a citation when the EC measurement times the multiplier is 
below the TC analysis.
    The 1.3 multiplier that we will use to estimate TC (i.e., EC x 1.3 
= estimated TC) is derived from NIOSH's determination that TC is 60-80% 
EC. We will announce our enforcement policy in our updated DPM 
Compliance Guide.
    As we stated in the 2005 proposed rule, we will continue to cite a 
violation of the DPM limit only when we have solid evidence that a 
violation actually occurred. Accordingly, we will apply the existing 
error factor to the first phased-in final limit of 308EC 
[mu]g/m3 to determine that an overexposure to the final 
limit has occurred. The error factors for the first step-down limit of 
350TC [mu]g/m3 and second step-down limit of 
160TC [mu]g/m3 will be slightly different.
    We will continue to base our compliance determinations on a single, 
personal sample, taken over the miner's full shift as specified in 
existing Sec.  57.5061, Compliance determinations. Also, under existing 
Sec.  57.5060(d), we will continue to require mine operators to install 
all feasible engineering and administrative controls to reduce miners' 
exposures to DPM. When such controls do not reduce a miner's exposure 
to the DPM limit, controls are infeasible, or controls do not produce 
significant reductions (as defined in the 2005 rule (70 FR 32868, 
32916) in DPM exposures, operators must continue to use all feasible 
engineering and administrative controls and supplement them with 
respiratory protection. When respiratory protection is required under 
the final standard, mine operators must establish a respiratory 
protection program that meets the specified requirements. See the 
discussion of respirator use in Section VIII.C. Medical Evaluation and 
Transfer.
    We have determined that these new final limits are both 
technologically and economically feasible for the M/NM mining industry 
to achieve as scheduled. Feasibility data, however, do not support 
delaying the applicability of the 160TC [mu]g/m3 
final limit until 2011, nor do they support application of the 
160TC [mu]g/m3 final limit as early as May 2006. 
Regarding feasibility, we chose May 2008 for the effective date of the 
final limit to correspond with when we believe mine operators, 
especially small mine operators, will be able to find effective 
approaches to utilizing available DPM control technology so that they 
will be capable of meeting the standard. Over the five years since the 
2001 final rule was promulgated, both MSHA and the mining industry have 
gained considerable experience with the implementation, use, and cost 
of DPM control technology. We have reviewed this experience, and our 
own enforcement data, and conclude in the final rule that effective DPM 
controls will be feasible and commercially available to mine operators 
by 2008. We

[[Page 28979]]

continue to acknowledge that our 2001 feasibility projections for the 
ability of the M/NM mining industry to comply with the final limit of 
160TC [mu]g/m3 by January 2006 were incorrect.
    In the 2005 proposed rule, we continued to project that many mine 
operators would have to use DPFs to reduce DPM levels to the final 
concentration limit. We believe that DPFs can be a very effective 
engineering control throughout the mining industry for reducing miners' 
exposures to DPM, provided mine operators address their implementation 
issues. These implementation issues include such decisions as DPF media 
selection, sizing, regeneration scheme, and installation.
    The rulemaking record includes updated data and promising 
information from the Biodiesel industry on the progress of increasing 
mine operators' access to this fuel. Accessing biodiesel fuels has been 
a feasibility issue for M/NM mine operators primarily due to the lack 
of sufficient distribution centers. The growing trend on demand and 
supply of alternative fuels; availability of special extensions; 
enforcement of our hierarchy of controls strategy; additional time for 
the mining industry to continue to resolve their existing maintenance 
and other implementation issues with control technology; ventilation 
upgrades; continued introduction of cleaner engines; and current 
enforcement data support both the economic and technological 
feasibility of the final limits as prescribed in this final rule. 
Although the risk assessment indicates that a lower DPM limit, lower 
than 160TC [mu]g/m3, would enhance miner 
protection, it is infeasible for the underground M/NM mining industry 
to reach a lower final limit.
    We acknowledge in the Technological Feasibility discussion in 
Section V of this preamble that our projections for availability of 
alternative fuels were underestimated in the 2005 proposal. We also 
considered our updated enforcement data from November 2003 to January 
2006 which show that 82% of the 1,798 samples we collected were below 
the initial final limit of 308EC [mu]g/m3, 78% 
were below the January 2007 final limit of 350TC [mu]g/
m3, and 46% were below the May 2008 final limit of 
160TC [mu]g/m3. We remain committed to assuring 
that mine operators continue the significant progress they have already 
demonstrated in reducing miners' exposures to DPM.
    We received a number of comments from the mining community on our 
proposed revisions to the final limits. Establishing a standard that 
focuses control efforts on diminishing the DPM level in air breathed by 
a miner is supported by some commenters in labor. These commenters 
stated, ``We agree that personal sampling gives a better representation 
of real exposure, and we support the change in the final rule.'' A 
number of industry commenters stated that we should rescind the 
160TC [mu]g/m3 final limit, since they believe 
that it is unjustifiable and infeasible, and urged us to adopt as the 
final limit the current interim exposure limit of 308EC 
[mu]g/m3 currently in place. We disagree, primarily because 
the 2001 risk assessment concludes that exposure to DPM could result in 
a material impairment of miners' health and functional capacity, 
including lung cancer, and that our analysis has concluded that 
controls significantly reducing DPM exposure are both technologically 
and economically feasible. Moreover, in the 2005 NPRM, when we decided 
that we should consider phasing in the final limit of 160TC 
[mu]g/m3, we acknowledged complications with feasibility and 
stated the following:

    We believe that wider use of alternative fuels and filter 
technology can make the 160TC [mu]g/m3 final 
limit feasible if a staggered phase-in approach is adopted. By 
lowering the exposure limit in intervals over five years beginning 
in January 2007, market forces should have sufficient time and 
incentive to adjust to the new standard. Specifically, a reliable 
alternative fuel distribution system should induce mine operators to 
adopt this relatively low-cost method to achieve compliance. The 
development and distribution of alternative fuels is also encouraged 
by existing tax credits. We believe that regional distribution 
networks are beginning to emerge. We seek data on alternative fuel 
distribution systems (70 FR 53283-84).

    We received comments on the availability of distribution systems 
and other means of DPM exposure controls and have discussed them in 
detail in Section V of this preamble. Our sampling data, compliance 
experience, and comments in the rulemaking record lead us to conclude 
that reductions below the 308EC [mu]g/m3 limit 
are achievable by the phase-in dates specified.
    Another industry commenter suggested that the proposed five-year 
phase-in of the final limit would drive technology development but 
would not allow sufficient time for further research and development, 
and in-field testing. This commenter did state, however, that a two-
phase approach would allow mine operators to implement changes in 
mining techniques and strategies and would provide for continued 
protection of miners. Some other commenters state that if we pursue our 
proposed course, or worse, allow the 160TC [mu]g/
m3 limit to take effect immediately, it would result in an 
infeasible rule with which the underground M/NM mining industry could 
not comply. They believe that this could potentially subject mines to 
closure orders, and require miners to wear respirators to protect 
against what many regard as undemonstrated adverse health effects. 
These commenters also urge that we retain the interim limit of 
308EC [mu]g/m3, limit pending results of NIOSH/
NCI study.
    Another mine operator noted that the proposed phase-in of the final 
limit is an improvement, but agreed with some other commenters that we 
need to stay the interim and final limits and wait for completion of 
the NIOSH/NCI Study. We have sufficient evidence in the DPM rulemaking 
record which supports the need for us to lower miners' current 
exposures to DPM beginning in January 2007. We will, however, continue 
to closely monitor the progress of the NIOSH/NCI joint study, and when 
the results of this study become available, we will carefully consider 
them.
    As discussed at length in Section V. addressing feasibility of the 
final rule, we now have more definitive information on availability of 
alternative fuels and the implementation issues that mine operators 
face to warrant the time frames under this final rule. We, therefore, 
cannot justify further delays of implementing the applicability of the 
160TC [mu]g/m3 beyond May 2008.
    We also considered that the mining industry has had since January 
2001 to work through many of their implementation issues. By now mine 
operators have implemented more effective controls to meet the interim 
limit. These controls can be used to assist in reducing miners' 
exposures even further, ultimately resulting in successful achievement 
of the final limits. We acknowledge that the mining industry as a whole 
still needs more time to meet the 160TC [mu]g/m3 
final limit and believe May 2008 will give them an appropriate amount 
of time for implementing additional controls needed to comply with the 
final limit.
    Most industry commenters, however, emphasized that compliance with 
the interim limit of 308EC [mu]g/m3 still poses 
feasibility issues for the mining industry as a whole. Some other 
industry commenters added that the proposed reductions are infeasible 
for 90% of the industry.
    We disagree with these commenters. Our data in the 2005 final rule 
demonstrate that compliance with the interim limit is both 
technologically and economically feasible (70 FR 32915,

[[Page 28980]]

32939). Moreover, our updated compliance sampling results demonstrate 
that most mines are presently capable of meeting the interim limit of 
308EC [mu]g/m3. Like in the 2005 final rule, 
compliance with this final rule also relies on our traditional 
hierarchy of controls enforcement strategy (70 FR 32915-16) discussed 
above. Thus, this regulatory scheme adequately accomplishes control of 
exposure under circumstances where an individual mine operator cannot 
reduce a miner's exposure to the final limit solely by use of 
engineering and administrative controls, including work practices.
    One commenter took the position that we should retain the current 
interim limit of 308EC [mu]g/m3 based on EPA's 
timeframe for industry to develop cleaner burning engines for diesel 
engines regulated by EPA. The commenter stated that the Tier 4 engines 
mandated by EPA are to be available in the very near future and are 
designed to reduce the DPM levels by at least 90%. Tier 4 engines that 
are greater than 130 hp are to be available in 2011; engines from 56 to 
130 hp will be available in 2012; and 19 to 56 hp will be available in 
2013. This includes the availability of very low sulfur fuel as well. 
According to the commenter, this Tier 4 technology deals with the 
source of DPM exposures; however, they believe that the final DPM limit 
should not be reduced until these engines are available and tested in 
the underground mine environment. They also remark that if MSHA 
believes that the technology will eventually catch up to its DPM final 
limit, then the phase-in schedule should coincide with the EPA mandated 
schedule for clean engines. In response, the EPA specifically exempts 
underground mining diesel powered equipment, as we addressed in the 
2001 final rule (Control of Emissions of Air Pollution From Nonroad 
Diesel Engines, 40 CFR Parts 9, 86, and 89 (1998)). However, Sec.  
57.5067, Engines, allows the mine operator to introduce EPA certified 
diesel engines into mines using either an on-highway vehicle that is a 
1994 model year or newer, a Tier 1 nonroad diesel engine, or a Tier 2 
nonroad engine dependent on the horsepower. Also in the 2001 final 
rule, we documented through our risk assessment the need for us to 
proceed presently to reduce miners' exposures. The final rule requires 
the mining industry to continue to make progress in further reducing 
DPM levels in underground M/NM mines.
    The EPA standards referred to by the commenter only include newly 
manufactured diesel engines based on EPA's implementation dates with no 
requirements on engine retrofits. As discussed in the Technological 
Feasibility section of this preamble, the EPA's emission regulations 
will significantly reduce DPM through the use of DPFs installed on 
newly manufactured engines. We agree that this technology will benefit 
the mining industry by offering mine operators the opportunity to 
purchase this technology in the form of new and used machines over 
time. However, we do not believe that it would be cost effective for 
the mining industry to purchase all new equipment when the EPA engines 
become available in order to get the DPM controls that will be mandated 
by the EPA as suggested by the commenter. We do believe however, that 
the EPA standards will make it easier for mine operators over time to 
purchase diesel engines and machines which are equipped with DPFs which 
should decrease the need to retrofit DPFs. The MSHA DPM final rule 
provides mine operators with an opportunity to purchase some on-highway 
vehicles which will include DPFs but will not be available until 
January 2007. As discussed in Section V of this preamble, this will 
initially include automotive pickup trucks and other utility trucks.
    In addition, EPA is mandating the use of ultra low sulfur diesel 
fuel, less than 15 ppm, for on-highway vehicles starting in mid 2006. 
This fuel will not be required by MSHA; however this may be the only 
economical diesel fuel to purchase over the coming years based on 
availability. Eventually by 2010, 15 ppm sulfur fuel will be required 
for all nonroad diesel powered vehicles and due to the EPA 
requirements, we anticipate that 15 ppm sulfur fuel will be the only 
available diesel fuel to purchase. Even though 15 ppm sulfur fuel does 
directly reduce DPM or EC, it will be needed for compatibility with 
specialized catalyst formulations used by engine manufacturers for DPM 
and nitrous oxide reductions.
    A number of industry commenters noted that experience of both MSHA 
and the industry under the DPM rules demonstrate an evolving learning 
process regarding controlling diesel exhaust. It is in this context 
that these commenters stated that they support the proposed staggered 
effective date schedule for implementation of the final limit, provided 
that we address their other concerns related to the final limit. They 
believe that it would be more appropriate to promulgate a two-step 
phased-in approach for the final limit ending on January 20, 2011, 
rather than an annual, 50 microgram reduction of the final limit. These 
commenters recommended that the first reduced final limit be the EC 
equivalent of 250TC [mu]g/m3 on January 20, 2009. 
The final EC equivalent of 160TC [mu]g/m3 would 
become effective on January 20, 2011. They suggest that this schedule 
would more realistically take into account the purchasing decisions by 
the mining industry to buy new equipment and engineering controls 
designed to ultimately achieve compliance with the final limit. In this 
final rule, we based our timetable on definitive information on 
availability of alternative fuels and the implementation issues that 
mine operators face in complying with the final limit of 
160TC [mu]g/m3. We discussed this at length in 
Section V, Feasibility, of this final rule.
    Organized labor commented that exposure to DPM causes cancer, and 
lawful or not, they believe that delay will cost miners' lives, since 
they are breathing these fumes at toxic levels. These commenters 
discussed what they believe to be our protracted rulemakings to revise 
the 2001 final rule. They also expressed their disagreement with us in 
changing the applicability of the 2001 final limit of 160TC 
[mu]g/m3, and not including medical evaluation and transfer 
protection for miners. They stated, among other things, that:

    On September 7, 2005, the agency proposed to postpone the final 
PEL by five more years, reducing it instead by small steps. The 
agency also suggested there might be difficulties converting the 160 
[mu]g/m3 TC limit to an appropriate EC limit, and 
proposed to leave that determination to yet another rulemaking. The 
final standard has now been delayed until May 20, but MSHA clearly 
intends to delay it far longer,\2\ ostensibly on the grounds of 
feasibility, and based primarily on unsubstantiated claims from the 
mine operators. These proposed changes would significantly weaken 
the rule by permitting the continued exposure of miners to levels of 
DPM the agency has found to be unacceptable * * *
---------------------------------------------------------------------------

    \2\ The USW did not object to the 5 month delay; it was 
necessary to allow the rulemaking process to be as complete as 
possible. However, we object strenuously to the 5 year delay.
---------------------------------------------------------------------------

    MSHA made a promise to underground M/NM miners in 2001. It told 
them that help was on the way and that they would someday be 
protected from choking levels of diesel exhaust. Relief would come 
slowly, and exposures would be reduced in steps, but by January 
2006, a protective standard would be in place. MSHA now proposes to 
break that promise.
    Instead, MSHA should withdraw the proposal to delay the 160 
[mu]g/m3 TC limit, and revise its effective date to no 
later than July 20, 2006. The USW has no objection to converting the 
standard to one based on EC at some time in the future, when the 
data exists to do so. For the time being, TC and EC measurements 
should be taken

[[Page 28981]]

simultaneously, so that MSHA or NIOSH can calculate a proper 
conversion factor when the time comes. (USW, AB29-COMM-117)

    As we stated earlier in this preamble, data continue to support our 
2001 risk assessment. That risk assessment establishes a material 
impairment of health or functional capacity to miners from exposure to 
DPM. We have incorporated into this rulemaking record the previous DPM 
rulemaking records, including the 2001 risk assessment. In the 2005 
NPRM, we discussed the decline in miners' exposures to DPM from a mean 
of 808DPM [mu]g/m3 (646TC [mu]g/
m3 equivalent) prior to the implementation of the 2001 
standard, to a mean of 233TC [mu]g/m3 based on 
enforcement sampling at that time (70 FR 53283). More recent 
enforcement data show that miners' exposures to DPM continue to 
decline. Nevertheless, we continue to believe that mine operators' 
experiences with control technology confirm that it is infeasible for 
us to implement the 160TC [mu]g/m3 final limit 
earlier than May 2008. We believe that these data dictate the need to 
afford the mining industry more time to work through their 
implementation and maintenance issues with DPFs, and to allow 
sufficient time for construction of more biodiesel fuel distribution 
centers.
    Some industry commenters strongly suggest that feasibility of the 
final DPM limits must be based on fair and effective implementation of 
existing Sec.  57.5060(c) regarding special extensions of time in which 
to comply with the final DPM limit. It is their contention that many 
mines will be unable to meet the lower DPM limit of 160TC 
[mu]g/m3, even if staggered over a five-year period as the 
agency proposed. Some other mine operators stated that the special 
extension process ``is not a feasible means of salvaging the infeasible 
160TC [mu]g/m3, or the unworkable and unsupported 
yearly `phase-in' proposal.''
    Section 57.5060(c) allows mine operators to apply to the MSHA 
District Manager for additional time to meet the final DPM limits due 
to economic or technological constraints. Mine operators must 
demonstrate infeasibility of compliance to the District Manager before 
they can qualify for a special extension. The feasibility 
considerations for the District Manager in granting special extensions 
are very similar to those for determining feasibility under our 
hierarchy of controls enforcement scheme. Given the progress the mining 
industry has shown in reducing DPM levels thus far, we do not believe 
that the industry, as a whole, will be unable to meet the lower DPM 
limit of 160TC [mu]g/m3 by May 2008. Initially, 
we expect to have greater numbers of miners overexposed to the final 
limit, than with the interim limit. However, we believe that miners in 
this category will decline over time as mine operators introduce 
improved engines and continue to resolve their implementation and 
maintenance problems with DPFs and access problems with biodiesel.
    These industry commenters also point out that we should develop, in 
their views, an accurate, scientifically supportable conversion factor 
to change the current TC-based final limit of 160TC [mu]g/
m3 to an EC-based limit. We intend to use the best available 
evidence to develop a proposed rule to appropriately and accurately 
convert the final DPM limit in the near future.
    We received comments from the mining industry on establishing an 
appropriate surrogate for the DPM final limit. In our 2005 final rule, 
we changed the surrogate for the interim limit by changing from a 
concentration limit measured by TC to a comparable PEL measured by EC, 
which renders a more accurate DPM exposure measurement, and committed 
to revising the final concentration limit in a future rulemaking. The 
final rule adopts 308EC [mu]g/m3 as the initial 
final limit, but retains TC as the surrogate for the 350TC 
[mu]g/m3 and 160TC [mu]g/m3 final 
limits. We will initiate a separate rulemaking to determine the correct 
TC to EC conversion factor for the phased-in final limit of 
160TC [mu]g/m3.
    Several commenters to the proposed rule continue to question the 
applicability of the 2001 risk assessment when using a surrogate 
measure of elemental carbon to regulate exposures to DPM. These 
commenters also question the accuracy of the NIOSH Analytical Method 
5040 and expressed disapproval for our using EC as a surrogate. In 
contrast, a number of other commenters objected to MSHA not enforcing a 
limit of 160TC [mu]g/m3 immediately. We refer the 
commenters to the preamble to the 2005 final rule (70 FR 32868) for our 
position on these issues. Commenters presented some new information, 
however, in response to the 2005 NPRM.
NIOSH Analytical Method 5040 Validation and Accuracy
    The guidelines for development and evaluation of analytical methods 
are documented in the NIOSH publications NIOSH Manual of Analytical 
Methods, Chapter E (NIOSH 2nd Supplement Publication No. 98-119) and 
Guidelines for Air Sampling and Analytical Method Development and 
Evaluation (NIOSH Publication No. 95-117). These documents are 
guidelines that are used in the process of determining that an analytic 
method accurately measures what it purports to measure. NIOSH 
validation criteria state that the NIOSH Analytical Method 5040 
provides a result that differs no more than 25% from the 
true value 95 times out of 100.
    The NIOSH Analytical Method 5040 validation is documented in 
several publications. These publications include:
    (1) Chapter Q of the NIOSH Manual of Analytical Methods (NMAM), 
DHHS (NIOSH) Publication No. 94-113,
    (2) Occupational Monitoring of Particulate Diesel Exhaust by NIOSH 
Analytical Method 5040, Birch, Applied Occupational and Environmental 
Hygiene, Vol. 17(6):400-405, 2002,
    (3) Diesel Particulate Matter (as Elemental Carbon) 5040, Issue 3: 
March 15, 2003, NIOSH Manual of Analytical Methods (NMAM), Fourth 
Edition.
    In addition to the above documented validations, there are 
additional peer-reviewed studies providing evidence that the NIOSH 
Analytical Method 5040 method is valid. In a study published by Noll, 
et al., in January 2005 evaluating sampling results of DPM cassettes, 
the authors report a 95% upper confidence limit Coefficient of 
Variation (CV) of 7% when analyzing samples for EC and 6% for TC. In 
this same study, NIOSH reported good agreement and precision between EC 
for DPM samples using SKC impactor and respirable samples in both 
laboratory and field studies. The CVs for EC measurements between SKC 
impactors and respirable samples ranged from 0.2% to 12.3% when taking 
measurements in an underground mine. The CVs for EC ranged from 3.5% to 
5.4% when samples were taken in a laboratory chamber. Two studies 
published in 2004 (Noll, et al., 2004 and Birch, et al., 2004) reported 
results from investigating sampling for EC in the presence of coal dust 
using submicron impactors. The results show good agreement between 
submicron EC and respirable samplers for collecting DPM samples.
Error Factor
    In accordance with generally accepted good industrial hygiene 
practice and MSHA policy, we develop method-specific error factors to 
assure that a personal exposure result is more than likely to represent 
an overexposure. These error factors account for normal and expected 
variability inherent in any analytic method and sampling protocol and 
provide a basis for interpretation of sampling results. When we 
interpret sampling results and make a determination of compliance, we 
apply

[[Page 28982]]

the error factor to the result to gage whether the sample indicates a 
true overexposure. We use the validated NIOSH Analytical Method 5040 
for diesel particulate matter to analyze our personal exposure samples 
collected for compliance determinations.
    The NIOSH criteria and guidelines used for method validation do not 
directly apply to the development of error factors. However, similar 
statistical procedures to develop analytical methods can also be used 
to develop error factors. The commenters fail to recognize other 
differences between validation of methods and development of error 
factors.
    Error factors are developed to compare an infinite number of 
sampling results to a specific target value of the analyte whereas the 
method validation protocol specifies a range of 0.1 to 2 times a 
specific value. Many other differences exist between the two 
procedures.
    We believe the NIOSH Analytical Method 5040 is most appropriate for 
use in a mining environment because:
    (1) The results from the additional method validation efforts by 
NIOSH using samples collected in mines, as mentioned above, show the 
method is valid, and
    (2) The data we used are generated from miners' samples and 
analyzed in our laboratory (using multiple analyzers) and other 
laboratories account for variability in the determination of the error 
factor.
    In response to commenters' concerns that ``MSHA has developed this 
Error Factor as though the NIOSH Analytical Method 5040 were perfectly 
accurate for measurements of EC,'' we refer the commenter to item (2) 
above. We have incorporated inter-laboratory variability and inter-
instrument variability into the calculation of the error factor that 
does, in fact, address accuracy. By incorporating this type of 
variability we account for some possible biases. It was stated in the 
31-Mine study that, based on the available data from all laboratories, 
the estimated coefficient of variation for analytical TC measurements 
declines from 12.7% to 8.0% at TC loadings corresponding to 8-hour 
equivalent concentrations of 160 [mu]g/m\3\ and 400 [mu]g/m\3\, 
respectively. These estimates are approximately 60 percent greater than 
those based on the MSHA and NIOSH data alone. Intra- and inter-
laboratory analytical imprecision appears to be similar to other 
airborne contaminants' monitoring methods used by us and other 
regulatory agencies.
Specific Issues Raised by Commenters on Elemental Carbon Variability of 
the Relationship Between EC and TC
    Industry commenters raised the following specific issues regarding 
the use of EC as a surrogate for DPM exposure. Commenters asserted that 
the EC content of DPM is neither stable nor predictable and thus the 
proposed conversion of TC limits to EC limits is not feasible.
    We have addressed this issue in the 2005 final rule (70 FR at 
32945-32951), and we continue to support using EC as the most suitable 
surrogate for measuring DPM. Our 2005 final rule (70 FR 32868) 
establishes the measurement of DPM using EC as a direct measure of 
total DPM. Using EC as the surrogate permits personal sampling of 
miners (such as those who smoke, operate jackleg drills, or load ANFO) 
that would otherwise be difficult or impossible using the OC components 
in the calculation of TC. Several commenters also noted that the ratio 
of EC:TC in DPM can vary widely. One commenter pointed out that EC 
appeared to make up nearly all of the TC at the mine with which he was 
affiliated. This commenter stated that replacing a 400TC 
[mu]g/m\3\ limit with a 308EC [mu]g/m\3\ limit would impose 
a much more stringent standard at that mine. Another commenter noted 
that a 308EC [mu]g/m\3\ limit would be less protective of 
miners than the 400TC [mu]g/m\3\ limit in cases where the 
ratio of EC comprised less than 78% of the TC. One industry association 
submitted comments authored by a consultant who emphasized that the 
highly variable nature of the EC to OC ratio introduces ``large and 
important uncertainties in the exposure assessments needed to sustain 
QRA [i.e., quantitative risk assessment].''
    We addressed these concerns regarding variability previously in our 
discussion of the Relationship Between EC and TC in our preamble to the 
2005 final rule (70 FR 32894-32899). In the 2005 NPRM we solicited 
comments about converting the final phased-in limits based on TC 
measurements to corresponding EC limits. In the 2005 NPRM, we also 
notified the mining community that we would initiate a separate 
rulemaking to determine what the correct TC to EC conversion factor 
would be for the phased-in TC final limits below 308EC 
[mu]g/m\3\. We requested comments on whether the record supports an EC 
PEL without regard to any conversion factor, the appropriate conversion 
factor if one is used, and any other scientific approaches for 
converting the existing TC limit to an appropriate EC limit.
    Several commenters agreed with our use of the 1.3 conversion factor 
for the interim limit and the first phased-in final limit of 
400TC [mu]g/m\3\ (308EC [mu]g/m\3\), but did not 
believe sampling evidence supported its use at a lower PEL. One 
commenter recommended we either use the EC number from the lab 
evaluation, or use a compliance strategy similar to the method used by 
the Agency in 2004 for the interim limit of 400TC [mu]g/
m\3\.
    Several commenters agreed that more work is required to develop an 
appropriate conversion factor from TC to EC for the final limits. They 
stated it was reasonable to expect sampling and analysis variability to 
increase, and accuracy and precision to decrease at lower EC levels. 
They further stated that MSHA data demonstrate that no accurate 
conversion factor exists for the highly variable ratio of TC to EC at 
levels below the interim standard and that this ratio becomes even more 
unstable once diesel equipment is modified by installation of DPM 
filtering devices.
    Other commenters also believed more research is needed to determine 
an appropriate conversion factor and noted that recent evidence 
indicated the EC to TC relationship may change depending on various 
factors such as fuel type, engine duty cycle, and the control 
technologies being used.
    A number of commenters stated that an accurate, scientifically 
supportable conversion factor was essential to their acceptance of a 
staggered effective date schedule. One of them further stipulated the 
need for peer review of the conversion factor. Other commenters believe 
that the EC content of DPM is not stable or predictable so the proposed 
conversion of TC limits to EC limits is not feasible and that the 
measurement of EC is not accurate.
    Organized labor commented that the only proper course of action for 
MSHA would be to leave the standard at 160 [mu]g/m3 TC until 
an equally protective standard based on EC can be established. They 
said that leaving the standard at 308 [mu]g/m\3\ EC, or going to an EC 
level not equivalent to 160 [mu]g/m\3\ TC would violate the ``no-less 
protection'' restriction under section 101(1)(9) of the Mine Act.
    We maintain that the 31-Mine Study data establish that a conversion 
factor of 1.3 is appropriate for both the initial and final limit of 
308EC [mu]g/m\3\. As we determined in the 2005 final rule, 
we believe that the limit of 308EC [mu]g/m\3\ is equally 
protective of miners' health and equally feasible for the mining 
industry

[[Page 28983]]

to meet. Although the EC:TC ratio can exhibit considerable variability 
in specific cases, we concluded that application of the 1.3 conversion 
factor, pursuant to the Second Partial Settlement Agreement, achieves 
the goal of equal protection and feasibility at the 308EC 
[mu]g/m\3\ final PEL.
    We are considering various alternatives for converting the 
350TC [mu]g/m\3\ and 160TC [mu]g/m\3\ final 
limits to comparable EC limits. We will consider all comments in this 
rulemaking record concerning the relationship between EC, OC and TC in 
a separate rulemaking to determine the most appropriate conversion of 
the final TC limits. Presently, we believe that the DPM rulemaking 
record is inadequate for us to make determinations regarding a more 
appropriate conversion factor other than 1.3 for the 350TC 
[mu]g/m\3\ final PEL. If a rulemaking to establish a conversion factor 
is not completed before January 20, 2007, we intend to use the 1.3 
conversion factor to convert the 350TC [mu]g/m\3\ final 
limit to an EC equivalent. We will use the EC equivalents as a check to 
validate that an overexposure is not the result of interferences as we 
did with the 400TC [mu]g/m\3\ interim limit pursuant to the 
Second Partial Settlement Agreement 67 FR 47296, 47298). We discussed 
this concept earlier in this section.
Measurement of EC
    Some commenters stated that any carcinogenic effect of DPM is due 
entirely to the organic fraction. We believe this assumption is 
speculative. This assumption contradicts findings reported by Ichinose 
et al. (1997b) and does not take into account the contribution that 
inflammation and active oxygen radicals induced by the inorganic carbon 
core of DPM may have in promoting lung cancers. Indeed, identifying the 
toxic components of DPM, and particulate matter in general, is an 
important research focus of a variety of government agencies and 
scientific organizations (see, for example: Health Effects Institute, 
2003; Environmental Protection Agency, 2004b).
    In focusing on the carcinogenic agents in OC, the commenters seem 
to have ignored non-cancer health effects documented in the 2001 risk 
assessment--e.g., immunological, inflammatory, and allergenic responses 
in healthy human volunteers exposed to 300DPM [mu]g/
m3 (i.e., [ap] 240TC [mu]g/m3) for as 
little as one hour (66 FR at 5769-70, 5816-17, 5820, 5823, 5837, 5841, 
5847). We discussed this also in our 2005 final rule (70 FR 
32898,32899).
    The implication of non-organic chemicals in a chemical pathway 
explaining the induction of lung carcinogenesis indicates that organic 
and inorganic chemical compounds, acting together, contribute to the 
toxicity of DPM. Identification of a single carcinogenic component of 
DPM (whether EC, OC, or some combination of chemicals in DPM) is not 
germane to the issue of whether DPM actually causes adverse health 
effects as established by the 2001 risk assessment and its updates. 
This rule reduces the adverse health risks associated with miners' 
exposure to DPM and not just those associated with the EC or OC 
fractions of DPM.
    The NIOSH Analytical Method 5040 characterizes compounds found in 
DPM into several classes of substances. These classifications are 
convenient categories and do not distinguish hazardous compounds from 
other compounds. As stated by NIOSH (Birch, 1996), ``[M]ethods that 
speciate EC and OC are considered operational (Cadle and Groblicki, 
1980) in the sense that the method itself defines the analyte.''
    The possible chemical pathways causing adverse health effects 
(including lung cancer) include both organic and inorganic chemical 
elements. Since we believe that both organic and inorganic chemicals 
contribute to the overall toxicity of DPM our use of EC as a surrogate 
is intended to control miners' exposure to whole DPM. As NIOSH stated:

    Elemental carbon is the superior measure of exposure to 
particulate diesel exhaust because elemental carbon constitutes a 
large portion of the particulate mass, it can be quantified at low 
levels, and its only significant source in many workplaces is the 
diesel engine. Selection of an elemental carbon marker also was 
based on previous work by Fowler (1985), who evaluated various 
analytes as indices of ``overall diesel exposure.'' (Birch, 1996)

    We have not obtained additional information, either provided in 
comments or from peer-reviewed literature, to change our position that 
the EC and OC fractions of DPM contribute to the adverse health effects 
of miners caused by exposure to DPM found in diesel exhaust and that EC 
is the superior measure of exposure to DPM.
    The 308EC [mu]g/m3 final PEL established by 
this rule is intended to be commensurate with the interim TC limit of 
400 micrograms established under the 2001 rule--i.e., to be equally 
protective and equally feasible as well as the 308 [mu]g/m3 
interim EC PEL established by the 2005 final rule. Although the EC:TC 
ratio can exhibit considerable variability in specific cases, we 
concluded that application of the 1.3 conversion factor, as suggested 
in the Second Partial Settlement Agreement, achieves equal protection 
and feasibility at the 308EC [mu]g/m3 final PEL.
    In the 2005 NPRM we solicited comments about converting the final 
phased-in limits based on TC measurements to corresponding EC limits. 
We have discussed the relationship between EC and TC and conclude the 
relationship of EC:TC is adequate to promulgate a personal exposure 
limit of 308EC [mu]g/m3 final PEL. However, we 
are considering various alternatives for converting the 
350TC [mu]g/m3 and 160TC [mu]g/
m3 final limits to commensurate EC limits. We will consider 
all comments in this rulemaking record concerning the relationship 
between EC, OC and TC in a separate rulemaking to determine the most 
appropriate conversion of the final TC limits. Presently, we believe 
that the DPM rulemaking record is inadequate for us to make 
determinations regarding a more appropriate conversion factor other 
than 1.3 for the 350TC [mu]g/m3 final PEL. If a 
rulemaking to establish a conversion factor is not completed before 
January 20, 2007, we intend to use the 1.3 conversion factor to convert 
the 350TC [mu]g/m3 final limit to an EC 
equivalent. We will use the EC equivalents as a check to validate that 
an overexposure is not the result of interferences as we did with the 
400TC [mu]g/m3 interim limit pursuant to the 
Second Partial Settlement Agreement (67 FR 47296, 47298). We discussed 
this concept earlier in this section.
    Other commenters asserted that measurement of EC is not accurate 
and the inherent inaccuracies are not accounted for by the MSHA ``error 
factor.'' NIOSH Analytical Method 5040 has been validated. The Error 
Factor accounts for uncontrollable components of measurement except for 
the variability inherent in EC:TC ratios. We have shown these ratios 
vary between mines and within mines. The commenters obtained additional 
information from us and presented a new analysis addressing the 
validity of the NIOSH Analytical Method 5040.
    Based on this new analysis, they concluded that ``* * * the MSHA 
Error Factor described in the proposed Final Rule is too small to meet 
the statistical goals (i.e., `95-percent confidence') adopted by the 
Agency.'' We disagree. We have demonstrated the mathematical fallacies 
of the commenters' position in the 2005 final rule. We show it is 
plausible to have 32 percent of sampling clusters with the experimental 
design specified by Cohen,

[[Page 28984]]

et al., 2002 with an inherent coefficient of variation (CV) of 12% and 
still be consistent with the NIOSH accuracy criterion. The Monte Carlo 
analysis we performed shows that the commenters' data are consistent 
with NIOSH validation criteria even though the commenters' collection 
procedures and analyses were substandard.
    The commenters' experimental design and results as presented to the 
2003 NPRM were critiqued in the 2005 final rule. No explanation has 
been provided by these commenters as to why the submitted data were 
restricted to 75EC [mu]g/m3 to 200EC 
[mu]g/m3 and whether additional basket data falling outside 
of this range were collected. The samples were collected without the 
submicron impactor. The sample results are, therefore, inappropriate to 
address this rulemaking. The study reference does not indicate the type 
of filter holder and cyclone attachment configuration or if the 
mineral-dust-related carbonate that occurs in the organic portion of 
the analysis was subtracted off the OC determination. When using a 
filter holder with an internal cyclone connection, the cyclone nozzle 
acts as an impactor jet and mineral dust is deposited in the center of 
the filter. This inferior sampling equipment arrangement gives a high 
level of mineral dust in the center of the filter, and a non-uniform 
deposit of material on the filter surface. A non-uniform deposit 
precludes any analysis of duplicate sample punch repeatability.
    Additionally, three of the seven mines in the referenced study 
produced either limestone or trona. Both of these minerals contain 
carbonates which are evolved in the organic portion of the analysis. 
The referenced study indicates that up to 15 mg/m3 of total 
mineral dust was present at one of the mines. Failure to remove this 
mineral dust by use of an impactor may affect the ability of the 
analytical analysis to discern between OC and EC, thus introducing an 
artificially high variability of results.
    No information is provided on sampling times or filter loadings 
([mu]g/cm2), both of which affect expected analytical 
variability. Commenters provided no information as to whether multiple 
punches were used to determine EC concentrations similar to what we do 
in our analyses. Only summary data, consisting of the EC measurement 
range, mean, standard deviation (SD), and coefficient of variation 
(CV), were provided for each group of ``four or five'' samples. No 
confidence intervals or other measures of statistical uncertainty were 
provided for their summary statistics. The commenters failed to address 
these issues.
    Some commenters presented a new analysis addressing the validity of 
the NIOSH Analytical Method 5040. The new Monte Carlo simulation study 
results are not persuasive. The commenters' statement that ``MSHA 
employed its Monte Carlo simulation to support the conclusion that 
their sampling and analytical method was adequately precise and 
therefore feasible'' misrepresents our inferences. We used a Monte 
Carlo simulation to show that, even with all the uncertainties in the 
quality of the referenced study and conjectures made by the commenter, 
it is possible for those results to have been generated by a valid 
analytical method. We generally agree with the commenters insofar as 
hypothetically generated data seem to only obscure the discussion of 
real-world data that document analytical precision.
    Industry commenters believed that our analysis of more than 600 EC 
samples (punch-repunch) show that the results are neither precise nor 
reproducible. This issue was addressed in the preamble to the 2005 
final rule. We continue to rely on our previous analysis of the 
commenters' statement. The commenters' analysis of the punch-repunch 
data used in the calculation of the error factors for the PELs is 
incorrect. We summarize our critique of the commenters' analysis here 
in response to their new analyses of their updated data set.
    1. The commenter's analysis of the punch-repunch data is now closer 
to the mathematical definition of a Coefficient of Variation (CV). 
Their calculation of a ``difference between punches, to the average of 
the two punch results'' presents artificially larger variations in the 
analytic method compared with those with properly calculated CVs. We 
point out that the commenters did not follow the guidelines specified 
in NIOSH validation guidelines. The calculation used by the commenters 
to show large variability is misleading and inconsistent with their own 
criticisms, and overstates the variation of the NIOSH Analytical Method 
5040 instrumentation.
    2. Although the commenters adjust their calculation of the 
difference between punches by the mean of the punches, they fail to 
make meaningful statistical inferences of the results. They simply 
tabulate instances in which the ``% Difference'' exceeds a specified 
CV. The CV values used for their demonstration thresholds do not 
represent an upper bound on individual deviations or differences. 
Approximately one-third of individual errors (without regard to 
direction) would normally be expected to exceed the corresponding CV.
    This is why we multiply the appropriate CVs used in calculating the 
error factor (EF) by a ``Confidence Coefficient'' when establishing a 
1-tailed confidence error factor for noncompliance determinations along 
with other sources of uncontrollable variability of the measurement 
system.
    Industry commenters also contended that there is no NIST 
``standard'' for defining EC for analysis and measurement, thus 
accurate measurement is not feasible. The National Institute of 
Standards and Technology (NIST) provides two Standard Reference 
Materials that define not only EC but also TC. These reference 
materials are well characterized to help determine the operating 
characteristics of NIOSH Analytic Method 5040 and others. NIST Standard 
Reference Material 1649a (Urban Dust) provides a Certified 
Concentration Value for TC. NIST provides an Information Concentration 
Value for the fraction of EC (EC/TC) contained in this standard 
material. Although components of the material assigned Information 
Concentration Values are not as well characterized as those with 
certified Concentration Values, they are valuable sources of 
information used by laboratories to validate and assure proper 
operation of analytic methods.
    NIST Standard Reference Material 8785 (Air Particulate Matter on 
Filter Media) has been available since July 8, 2005 and provides the 
means to compare methods and laboratories for the measurement of EC. 
This reference material has value-assignments for TC, EC, and OC 
measured according to two thermal-optical methods: the NIOSH and 
IMPROVE (Interagency Monitoring of Protected Visual Environments) 
protocols. Our laboratory utilizes these NIST Standard Reference 
Materials as part of a comprehensive quality assurance program.
Health Implications of Using EC
    Commenters also asserted that EC is not a constituent of diesel 
exhaust that is suspected of causing lung cancer, and the MSHA risk 
analysis of diesel exhaust is inapplicable to the proposed EC limits. 
The particulate component of combustion products produced by a diesel 
engine is characterized by the analytic method as primarily either EC 
or OC. The analytic decomposition of DPM defines which components are 
characterized as EC or OC without specifically determining the exact

[[Page 28985]]

chemical, physical, or carcinogenic chemicals found in DPM (NIOSH 
Analytical Method 5040, March 15, 2003). Diesel particulate matter is 
firmly characterized as a hazardous substance and we do not further 
characterize DPM into hazardous components and non-hazardous 
components. The final rule intends to limit exposures to total DPM 
rather than any single constituent of DPM. The NIOSH Analytical Method 
5040 characterizes compounds found in DPM into two classes of 
substances. These classifications are convenient categories and do not 
distinguish hazardous compounds from other compounds. As stated by 
NIOSH (Birch, 1996), ``[M]ethods that speciate EC and OC are considered 
operational (Cadle and Groblicki, 1980) in the sense that the method 
itself defines the analyte.''
    The assumption that any carcinogenic effect of DPM is due entirely 
to the organic fraction is speculative. This assumption contradicts 
findings reported by Ichinose et al. (1997b) and does not take into 
account the contribution that inflammation and active oxygen radicals 
induced by the inorganic carbon core of DPM may have in promoting lung 
cancers. Indeed, identifying the toxic components of DPM, and 
particulate matter in general, is an important research focus of a 
variety of government agencies and scientific organizations (see, for 
example: Health Effects Institute, 2003; Environmental Protection 
Agency, 2004b). The 2001 risk assessment discusses possible mechanisms 
of carcinogenesis for which both EC and OC would be relevant factors 
(66 FR at 5811-5822). Multiple routes of carcinogenesis may operate in 
human lungs--some requiring only the various organic mutagens in DPM 
and others involving induction of free radicals by the EC core, either 
alone or in combination with the organics (70 FR 32898).
    The implication of non-organic chemicals in a chemical pathway 
explaining the induction of lung carcinogenesis indicates that organic 
and inorganic chemical compounds, acting together, contribute to the 
toxicity of DPM. Identification of a single carcinogenic component of 
DPM (whether EC, OC, or some combination of chemicals in DPM) is not 
germane to the issue of whether DPM actually causes adverse health 
effects as established by the 2001 risk assessment and its updates. 
This rule reduces the adverse health risks associated with miners' 
exposure to DPM and not just those associated with the EC or OC 
fractions of DPM.
    We have not obtained additional information, either provided in 
comments or from peer-reviewed literature, to change our position that 
the EC and OC fractions of DPM contribute to the adverse health effects 
of miners caused by exposure to DPM found in diesel exhaust and that EC 
is the superior measure of exposure to DPM.

B. Special Extensions Sec.  57.5060(c)(3)(i)

    In our 2005 final rule addressing the interim limit, we revised the 
requirements at Sec.  57.5060(c) regarding special extensions of time 
in which to meet the final DPM limit. We retained the requirement in 
Sec.  57.5060(c)(3)(i), however, that the mine operator must specify in 
the application whether diesel-powered equipment was used in the mine 
prior to October 29, 1998. The purpose of the 2001 restriction was to 
limit special extensions to underground mines that operated diesel-
powered equipment prior to October 29, 1998. We chose this date because 
we released the NPRM to our 2001 final rule on that date. We reasoned 
that some mines in operation prior to that date could experience 
compliance difficulties relating to such factors as the basic mine 
design, use of older equipment with high DPM emissions, etc., and that 
as a result, some of these mines may require additional time to attain 
compliance with the 2001 final concentration limit. Also, we envisioned 
that mines opened after that date would be using cleaner engines to 
help them comply with the final limit. Furthermore, we stated in the 
2005 proposal that we had reason to believe that our 2001 assumptions 
were incorrect, and that it was unnecessary to limit extensions to 
mines operating diesel equipment prior to October 29, 1998.
    We believe the consequence of such a conclusion does not compromise 
the level of health protection afforded under the existing prohibition. 
This is because it is optional as to whether a mine operator applies 
for a special extension under current Sec.  57.5060(c). Special 
extensions involve considerable paperwork for mine operators, but they 
result in a document that a mine operator can rely on for a period of 
one year (renewable) to demonstrate to our inspectors that we have 
determined that it is infeasible for that particular mine operator to 
achieve compliance with the final limit using engineering and 
administrative controls. If affected miners are included in a 
respiratory protection program which meets the requirements of Sec.  
57.5060(d), the mine operator is in compliance and no citation will be 
issued. To qualify for a special extension, a mine operator must 
demonstrate infeasibility, which is the same test which we use for 
enforcement of Sec.  57.5060(d) at mines that don't have a special 
extension. Current Sec.  57.5060(d) requires mine operators to install, 
use, and maintain all feasible engineering and administrative controls 
to achieve compliance. If we determine that reaching the final limit is 
infeasible for technological or economic reasons, and over-exposed 
miners are in an appropriate respiratory protection program, the 
operator is deemed to be in compliance and we will not issue a 
citation. We will periodically check to determine current DPM exposures 
and the ability of the mine operator to implement new control 
technology.
    We received no comments objecting to deleting Sec.  
57.5060(c)(3)(i). Commenters supporting the deletion stated that they 
saw no reason to limit special extensions to those mine operators who 
were operating diesel equipment prior to the arbitrary date of October 
29, 1998. They also stated that there would be no reduction in the 
level of health protection from a standard that was not feasible, nor 
with which health risks were never associated. Another commenter stated 
that if this restriction is left in the DPM standard, mines that are 
just starting will not be allowed to file for a special extension. They 
claimed that in their case, if they were to develop a new mine, they 
would have essentially the same constraints as far as mine opening 
dimensions, maximum air volumes, and equipment as their existing mines 
have. Consequently, they would not necessarily have lower DPM levels in 
a new mine. For this reason, they believe that it is critical that we 
allow new mines the same opportunity to qualify for special extensions 
after taking all reasonable steps to reduce DPM emissions.
    Other commenters agreed that we should delete Sec.  
57.5060(c)(3)(i) from the existing DPM standard, but provided no 
information as to whether elimination of this requirement would result 
in a reduction in the current level of health protection afforded to 
miners.
    We also received numerous comments recommending that we make other 
changes to the special extension provisions. These commenters suggested 
that the final rule include: Comprehensive criteria for granting a 
special extension; specific language to expand the application of an 
extension to the entire mine or to portion(s) of a mine; additional 
procedures for the District Manager to consider in making a 
determination of whether to grant a special extension; requirements 
that the District Manager include reasons for any

[[Page 28986]]

denial of a special extension; and, procedures allowing appeal of the 
District Manager's determination to the Administrator, and ultimately, 
to the independent Federal Mine Safety and Health Review Commission.
    In the 2005 proposed rule, we informed the public that the scope of 
revision to Sec.  57.5060(c) was limited to the removal of paragraph 
(c)(3)(i). Accordingly, such changes would be beyond the scope of this 
rulemaking. Consequently, the final rule does not reflect consideration 
of the above stated issues. We note that we made comprehensive 
revisions to Sec.  57.5060(c) in the 2005 final rule.
    Some other commenters discussed how the special extension 
procedures enhance feasibility and that the courts have recognized that 
such procedures can resolve individual problems with feasibility. The 
commenter refers us to the United Steelworkers of America v. Marshall, 
647 F. 2d 1189, 1266 (1980). We address this comment under our 
discussions on feasibility.
    Based on the comments received supporting the deletion of Sec.  
57.5060(c)(3)(i), and our discussions above, we have deleted this 
provision from the DPM standard. For the forgoing reasons, we do not 
believe that deletion of this provision reduces miners' current level 
of health protection, and there were no comments submitted to the 
contrary.

C. Medical Evaluation and Transfer Sec.  57.5060(d)

    In the preamble to the 2005 NPRM, we requested comments from the 
mining community on whether we should include in the final rule a 
provision requiring a medical evaluation to determine a miner's ability 
to use a respirator before the miner is fit tested or required to work 
in an area of the mine where respiratory protection must be used. In 
addition, we asked for comments on whether the final rule should 
contain a requirement for transfer of a miner to an area of the mine 
where respiratory protection is not required if a medical professional 
has determined as a result of the medical evaluation that the miner is 
unable to wear a respirator for medical reasons.
    Further, we asked whether we should amend the existing respiratory 
protection requirement at Sec.  57.5060(d) by adding new paragraphs 
(d)(3) and (d)(4) to address medical evaluation and transfer rights for 
miners. We particularly wanted to know if the final rule should include 
the following language:

    (3) The mine operator must provide a medical evaluation, at no 
cost to the miner, to determine the miner's ability to use a 
respirator before the miner is fit tested or required to use the 
respirator to work at the mine.
    (4) Upon notification from the medical professional that a 
miner's medical examination shows evidence that the miner is unable 
to wear a respirator, the miner must be transferred to work in an 
existing position in an area of the same mine where respiratory 
protection is not required.
    (i) The miner must continue to receive compensation at no less 
than the regular rate of pay in the classification held by that 
miner immediately prior to the transfer.
    (ii) The miner must receive wage increases based upon the new 
work classification.

    We also requested comments in the preamble to the proposed rule on 
whether a transfer provision in the final rule should include issues of 
notification to the District Manager of the health professional's 
evaluation and the fact that a miner will be transferred; the 
appropriate time frame within which the transfer must be made; whether 
a record of the medical evaluation conducted for each miner should be 
maintained along with the correct retention period; medical 
confidentiality; and any other relevant issues such as costs to mine 
operators for implementing a rule requiring medical evaluations and 
transfer of miners. Our current DPM requirements for respiratory 
protection at Sec.  57.5060(d) do not include requirements for medical 
evaluation of miners before they are required to work in an area where 
respiratory protection must be worn, or transfer of miners who are 
medically unable to wear respirators.
    Section 101(a)(7) of the Mine Act authorizes medical evaluation and 
transfer protection for miners, and states, in pertinent part:

    Where appropriate, such mandatory standard shall also prescribe 
suitable protective equipment and control or technological 
procedures to be used in connection with such hazards and shall 
provide for monitoring or measuring miner exposure at such locations 
and intervals, and in such manner so as to assure the maximum 
protection of miners. In addition, where appropriate, any such 
mandatory standard shall prescribe the type and frequency of medical 
examinations or other tests which shall be made available, by the 
operator at his cost, to miners exposed to such hazards in order to 
most effectively determine whether the health of such miners is 
adversely affected by such exposure. Where appropriate, the 
mandatory standard shall provide that where a determination is made 
that a miner may suffer material impairment of health or functional 
capacity by reason of exposure to the hazard covered by such 
mandatory standard, that miner shall be removed from such exposure 
and reassigned. Any miner transferred as a result of such exposure 
shall continue to receive compensation for such work at no less than 
the regular rate of pay for miners in the classification such miner 
held immediately prior to his transfer. In the event of the transfer 
of a miner pursuant to the preceding sentence, increases in wages of 
the transferred miner shall be based upon the new work 
classification.

    Existing Sec.  57.5060(d) requires that mine operators comply with 
the respiratory protection requirements under Sec.  57.5005(a) and (b) 
(control of exposure to airborne contaminants) of our air quality 
standards for M/NM underground mines. Sections 57.5060(d)(1) and (d)(2) 
designate acceptable respirator filters under the standard. Section 
57.5005(a) requires that respirators be furnished and miners use the 
protective equipment in accordance with training and instruction. 
Currently, we do not require mine operators to provide miners with 
medical evaluation before they wear a respirator and transfer 
protection in the event that they cannot wear one.
    Existing Sec.  57.5005(b) for control of miners' exposures to 
airborne contaminants requires that mine operators establish a 
respiratory protection program consistent with the (ANSI Z88.2-1969) 
``American National Standard for Respiratory Protection --``ANSI Z88.2-
1969, ``American National Standards Practices for Respiratory 
Protection.'' The final rule, however, adopts our approach taken in the 
proposed preamble recommendations along with additional requirements 
which we deem necessary to protect miners. These additional 
requirements address issues related to medical confidentiality, 
evaluation of a miner's ability to wear a PAPR, reevaluation of miners, 
and recordkeeping requirements, along with other revisions to clarify 
our intent under the standard.
    We believe that there is adequate evidence in the rulemaking record 
establishing the need for medical evaluation of miners. We incorporated 
into the DPM rulemaking record the Occupational Safety and Health 
Administration's (OSHA) data from its rulemaking record supporting its 
generic respiratory protection standard at 29 CFR 1910.134 related to 
the health risk to persons from using respirators with certain medical 
conditions. Based on their data, OSHA concluded, and MSHA agrees, that 
use of a respirator may place a physiological burden on a worker while 
wearing such a device. Depending on the medical condition of the 
person, this burden could result in illness, injury, and in some 
instances, even death. OSHA also concludes that common health problems 
can cause

[[Page 28987]]

difficulty in breathing while a person is wearing a respirator. Most 
healthy persons, however, will not have physiological problems wearing 
properly chosen and fitted respirators.
    The final rule amends the existing DPM respiratory protection 
standard at Sec.  57.5060(d) by adding requirements for mine operators 
to provide, at no cost to the miner, a confidential medical evaluation 
by a physician or other licensed health care professional (PLHCP) to 
determine the miner's ability to use a respirator before the miner is 
fit tested or required to work in an area of the mine where respiratory 
protection must be used. When these conditions occur the miner must be 
reevaluated to determine the miner's ability to use the respirator.
    Also included in the final rule is the right of miners to discuss 
their medical evaluations with the PLHCP before the PLHCP submits to 
the mine operator a copy of the PLHCP's medical determination. The mine 
operator must have a written record of the most recent medical 
evaluation to confirm that the miner was evaluated. We believe that the 
final rule includes a practical approach for requiring medical 
evaluations that lessens the compliance burden on mine operators 
without compromising miners' health.
    In addition, the final rule includes requirements for transferring 
a miner to an existing job in an area of the mine where respiratory 
protection is not required if a PLHCP has determined that the miner's 
medical condition precludes the miner from safely wearing any required 
respirator, including a powered air-purifying respirator (PAPR). The 
details of this requirement are discussed below in this preamble. We 
believe that compliance with the final rule will enhance miner 
protection.
    Section 57.5060(d)(3) of the final rule requires that the mine 
operator provide a confidential medical evaluation by a PLHCP to 
determine the miner's ability to use a respirator before the miner is 
required to be fit tested or to use a respirator at the mine. The mine 
operator must provide the medical evaluation to the miner and pay the 
cost of each of the miner's medical evaluations. Mine operators must 
make certain that the PLHCP administers the testing in a manner that 
protects the confidentiality of the miner being evaluated.
    If the PLHCP determines that the miner is able to wear a negative-
pressure respirator, the mine operator must provide it and require the 
miner to wear it under our existing respiratory protection 
requirements. On the other hand, if the PLHCP concludes that the miner 
is unable to wear a negative-pressure respirator, the mine operator 
must make certain that the PLHCP also determines the miner's ability to 
wear a PAPR. If the PLHCP finds that the miner can wear a PAPR, the 
mine operator must provide the PAPR and require the miner to wear it.
    The miner must be evaluated by a PLHCP prior to the miner wearing 
the respirator for any duration or frequency of respirator use, 
including prior to fit testing of the respirator. This is because we 
intend that a miner not be assigned to tasks in the mine that require 
use of a respirator unless a PLHCP makes a written determination that 
the miner is physically able to perform the work to which the miner is 
assigned while using the respirator. For enforcement purposes, we will 
use the results of the most recent written determination of the PLHCP 
to assess compliance with this provision. Whereas we have chosen not to 
include a specific protocol for how evaluations must be conducted, we 
expect the PLHCP to conduct an evaluation based on the individual 
miner's medical information.
    As part of the PLHCP's determination, Sec.  57.5060(d)(4) requires 
that the mine operator provide the miner with an opportunity to discuss 
their evaluation results with the PLHCP before the PLHCP submits the 
written determination to the mine operator. If the miner disagrees with 
the determination of the PLHCP, the miner has up to 30 days to submit 
to the PLHCP additional evidence of their medical condition. Depending 
upon the miner's medical history, it may be critical for the miner to 
discuss any discrepancies or errors in a PLHCP's determination. The 
miner, however, may at any time provide additional medical information 
to the mine operator if the miner believes that it may impact the 
miner's ability to wear a respirator.
    Section 57.5060(d)(5) requires the mine operator to obtain a 
written determination from the PLHCP regarding the miner's ability to 
wear a respirator. The mine operator must make certain that the PLHCP 
provides a copy of the determination to the miner. Though the rule does 
not specify a timeframe in which the mine operator must have the PLHCP 
provide a copy to the miner of his or her medical determination, we 
intend for the mine operator to exercise diligence in getting this 
important information to the miner.
    Section 57.5060(d)(6) requires the mine operator to reevaluate the 
miner when the operator has reason to believe that conditions have 
changed such as when the miner is assigned to a new task requiring a 
significantly greater degree of physical exertion, or the miner is 
assigned to work at a lower level of a deep mine that is hotter and 
imposes greater physiological stress. We expect the mine operator to 
exercise sound judgment when deciding whether the miner must be 
reevaluated by a PLHCP.
    Section 57.5060(d)(7) requires that upon written notification that 
the PLHCP has determined that the miner is unable to wear a respirator 
(including a PAPR), the miner must be transferred within 30 days of the 
PLHCP's determination to work in an existing position in an area of the 
same mine where respiratory protection is not required. Congress 
specifically included in Section 101(a)(7) of the Mine Act that when 
transfer of a miner is required under this section that their 
compensation must be as we specifically stated in this final rule. As a 
result, the miner must continue to receive compensation at no less than 
the regular rate of pay in the classification held by that miner 
immediately prior to the transfer. However, wage increases of the 
transferred miner must be based on the new work classification.
    Under Sec.  57.5060(d)(8) of the final rule, the mine operator must 
maintain a record of the identity of the PLHCP and the most recent 
written determination of each miner's ability to wear a respirator for 
the duration of the miner's employment plus six months thereafter.
    In response to our 2005 NPRM, we received numerous comments on 
issues related to medical evaluation of respirator wearers and transfer 
of miners medically unable to wear respirators. We requested comments 
in the 2005 NPRM regarding whether we should amend existing Sec.  
57.5060(d) addressing respiratory protection requirements by adding 
regulatory language to provide miners medical evaluations and transfer 
rights pursuant to Section 101(a)(7) of the Mine Act. One mine operator 
commented that they still face significant challenges to compliance 
with the interim limit. They currently require miners to wear 
respirators when performing certain tasks that have been a significant 
source of DPM exposure. Based on their own samples, they believe that 
the use of respiratory protection would increase under the final limit 
and be required of all miners through the entire shift. They also 
stated their concern for the burden this would place on affected miners 
and noted that mandatory respirator usage for the entire shift would 
compromise miners' acceptance of the rule and their ability to safely 
remain productive. Further, they believe that most companies that have 
a formal respiratory protection

[[Page 28988]]

program are currently conducting medical evaluation in the program, and 
consequently, should not have to perform medical evaluation ``solely to 
comply with the rule.'' Some other mine operators commented that they 
perform medical evaluations of a miner's ability to wear a respirator 
during pre-employment examination, and annually thereafter for workers 
who must wear respirators, but did not believe it was necessary to 
require medical evaluations through regulation.
    Although some mine operators are already conducting medical 
evaluations before fit testing and requiring miners to wear 
respirators, not all underground M/NM mine operators using diesel 
powered equipment are conducting voluntary medical evaluations. We 
believe that the data establishing the need for the evaluations support 
a uniform approach for requiring reevaluations.
    We agree with the commenters who acknowledged that existing 
voluntary medical evaluations currently provided by some mine operators 
do not establish uniform protection for all miners covered under the 
DPM standard. These commenters also stated that simply because some 
mine operators have provided miners this protection does not justify 
why others should continue to be denied them. These commenters support 
the need for including medical evaluation in the final rule and stated 
that voluntary medical evaluation programs in the industry show that 
mine operators, acting in good faith, can easily implement a respirator 
program, including transfer rights, without practical or financial 
difficulty.
    One commenter recommended that we defer requiring medical 
evaluation and transfer until we are able to establish an accurate 
database on the number of miners projected to be affected. Our 2005 
NPRM preliminary estimates of the number of miners that may be affected 
resulted from the available data in the rulemaking record at the time 
of the proposal. We have since received comments from several mine 
operators who included their current costs for medical evaluations and 
the number of miners affected. We used this information in assessing 
our cost analysis for the Regulatory Economic Analysis (REA) supporting 
this final rule.
    Several other commenters voiced concern over worker acceptance of 
respirators in general, but believed that medical evaluations were a 
good idea. Organized labor stated that there is substantial evidence in 
the record of the relevant OSHA hearings to support medical 
evaluations, and requested that we incorporate that evidence into this 
record as well. We have incorporated these data into the DPM rulemaking 
record. As stated earlier, OSHA acknowledges within its current 
standards addressing respiratory protection at 29 CFR 1910.134(e) that 
use of a respirator may place a physiological burden on workers while 
using them. At a minimum, OSHA requires employers to provide medical 
evaluations before an employee is fit tested or required to use 
respiratory protection. Employers are required to have a physician or 
other licensed health care professional have the worker complete a 
questionnaire, or in the alternative, conduct an initial medical 
examination in order to make the determination. If the worker has a 
positive response to certain specified questions, the employer must 
provide a follow-up medical examination. The questionnaire is contained 
in the body of the OSHA rule. The preamble to the OSHA final rule 
states:

    Specific medical conditions can compromise an employee's ability 
to tolerate the physiological burdens imposed by respirator use, 
thereby placing the employee at increased risk of illness, injury, 
and even death (Exs. 64-363, 64-427). These medical conditions 
include cardiovascular and respiratory diseases (e.g., a history of 
high blood pressure, angina, heart attack, cardiac arrhythmias, 
stroke, asthma, chronic bronchitis, emphysema), reduced pulmonary 
function caused by other factors (e.g., smoking or prior exposure to 
respiratory hazards), neurological or musculoskeletal disorders 
(e.g., ringing in the ears, epilepsy, lower back pain), and impaired 
sensory function (e.g., a perforated ear drum, reduced olfactory 
function). Psychological conditions, such as claustrophobia, can 
also impair the effective use of respirators by employees and may 
also cause independent of physiological burdens, significant 
elevations in heart rate, blood pressure, and respiratory rate that 
can jeopardize the health of employees who are at high risk for 
cardiopulmonary disease (Ex. 22-14). One commenter (Ex. 54-429) 
emphasized the importance of evaluating claustrophobia and severe 
anxiety, noting that these conditions are often detected during 
respirator training. [See 63 FR 1152, 01/08/1998]
    Organized labor also stated:

    * * * In all of our certification programs we have included 
blood pressure and spirometry measurements. In respirator 
certification for a group of electrical workers, we identified 7.5% 
who had abnormal spirometry and were not given a respiratory 
certificate until they had received further medical evaluation and a 
repeat of the spirometry.
    This observation was [sic] supported in a study of nurses 
working in a hospital close to the World Trade Center at the time of 
the disaster. Although exhibiting no respiratory symptoms on their 
questionnaires, 10 of 110 nurses had abnormal spirograms and were 
referred to a Pulmonologist for further evaluation.
    In our evaluation of World Trade Center Rescue workers, we have 
found similar discrepancies between the questionnaire and 
spirometry.
    A report by S. Levine et al. (MMWR Sept. 10, 2004) notes that 
33% [sic] had abnormal spirometry but wheeze was [sic] only reported 
in 0.9%. (David Parkinson, MD, United Steelworkers Consultant, 
Occupational Physician)

    The final rule does not include a protocol to guide the PLHCP on 
how to conduct medical evaluations as the OSHA standard does, but 
places the responsibility on the mine operator to provide an 
appropriate medical evaluation by a PLHCP to determine the miner's 
ability to use a respirator before the miner is required to be fit 
tested or to use a respirator at the mine.
    We intend that a ``physician or other licensed health care 
professional (PLHCP)'' be a physician, physician's assistant, nurse, 
emergency medical technician or other person qualified to provide 
medical or occupational health services, as we have defined a ``health 
professional'' under our Hazard Communication standards at 30 CFR 
47.11. We will accept the license as proof of qualification to perform 
the medical evaluation. We specified that the health care worker be 
licensed to ensure an acceptable level of competency, but have not 
specified which states' licensing to accept. As we said in our preamble 
to the final rule (64 FR 49578) on Health Standards for Occupational 
Noise Exposure at 30 CFR Part 62, ``* * * although some state licensing 
requirements are more stringent than others, even the least rigorous of 
the state requirements will provide an acceptable level of competence * 
* * [for audiologists].''
    NIOSH commented that in other industries where respirators were 
used, they supported the requirements specified in the OSHA Respiratory 
Protection Standard (29 CFR 1910.134), with the exception of:

    (a) The use of irritant smoke for qualitative respirator fit 
testing, and (b) unsupervised medical evaluations conducted by 
health care professionals who are not licensed for independent 
practice to perform or supervise medical evaluations.

    We also received comments from mine operators who stated that they 
already conduct medical evaluations, or at the very least, pulmonary 
function tests, during pre-employment examinations. From the mine 
operators who commented on their frequency of these examinations, 
several commenters stated that they test annually, another tests every 
three years, while another

[[Page 28989]]

performs them bi-annually. Others noted that the tests were initially 
performed during pre-employment examinations, and thereafter, were 
conducted whenever a miner was about to be required to wear a 
respirator. One commenter that provides a medical exam upon employment 
and annually thereafter stated:

    If the miners health conditions change preventing the safe use 
of a respirator, then additional tests can be provided including 
spirometry and if indicated, a medical examination. We have not had 
a case where a miner's health changed preventing the wearing of a 
respirator, that the miner was not aware of the health condition. We 
do not object to annual spirometry testing following guidelines 
developed and supervised by a medical doctor or other medical 
professional. We do object to the added expense of requiring a 
medical exam every year if there are no indicators of a medical 
necessity, either by the miners own request or the conditions 
mentioned.

    The final rule requires that miners be reevaluated when the mine 
operator has reason to believe that conditions have changed which could 
adversely affect the miner's ability to wear the respirator. We believe 
that the final rule provision is more appropriate and cost effective 
than a restrictive schedule of frequency of reevaluation to detect or 
confirm the miner's ability to safely wear respiratory protection. We 
do not envision, in most instances, that miners will be in a 
respiratory protection program for an extended length of time. We 
recognize, however, that more miners may have to wear respirators when 
the PEL is reduced to 160TC [mu]g/m3. We received 
no comments in support of establishing the need for a specific 
frequency, but we did receive several comments opposing them. Also, a 
miner should alert the mine operator whenever the miner experiences 
changes in his or her health that could impact his or her ability to 
safely wear a respirator. Mine operators have the responsibility for 
conducting a reevaluation where a change in workplace conditions may 
result in a substantial increase in the physiological burden that 
respirator use places on the miner. For example, a change in the 
miner's work task may require greater physical exertion or a change in 
the work environment could increase the stress on the miner.
    A mine operator stated that the use of PAPRs was not practical in 
most mining applications. They believe that the need for battery 
charging stations for the PAPRs, storage facilities and maintenance 
would significantly increase the cost of a respiratory protection 
program. NIOSH commented that PAPRs have some of the same limitations 
as negative-pressure respirators in that both impede communication, 
hearing, vision, and require periodic replacement of the purifying 
elements, as well as other disadvantages. NIOSH further stated:

    * * * In addition, the battery must be recharged on a daily 
basis so that the blower will deliver enough respirable air to the 
respiratory inlet covering. Batteries have a limited useful life and 
cannot be recharged indefinitely. The blower's high speed motor can 
wear out and require replacement; if the blower fails in a loose-
fitting PAPR, the wearer will be without respiratory protection. 
Other disadvantages include the weight and bulk of the PAPR with its 
blower and battery, which can hinder movement; complex design; and 
the need for a higher level of maintenance than a negative pressure 
respirator.

    NIOSH also commented, however, that under normal use, PAPRs do not 
impose the resistance to breathing that is associated with negative-
pressure respirators and that for a miner who has a medical condition 
placing the miner at risk from using a negative-pressure respirator, 
use of a PAPR is a potential alternative to transfer of duties.
    Another commenter stated that anybody who is working underground at 
their operations is provided a pulmonary function check to make sure 
that they are capable of wearing a respirator. That commenter was not 
aware of anyone being found unable to do so. Several industry 
commenters stated that they performed medical evaluations for testing 
the ability of miners to wear a negative-pressure respirator during 
pre-employment and annually thereafter. One commenter noted that 
although they had found a few miners who were unable to wear negative-
pressure respirators initially, each of them responded to medical 
treatment and subsequently was found medically able to wear a negative-
pressure respirator.
    Another commenter specified that they have pulmonary function tests 
performed on anyone entering a respiratory protection program (about 10 
miners), and had no one who was determined to be unable to wear a 
negative-pressure respirator. While a commenter, on behalf of organized 
labor, stated that only a few miners would be unable to wear a 
negative-pressure respirator, most of these miners would be able to 
wear a PAPR. A medical testing company that provides pulmonary function 
and respiratory fits, primarily for compliance with OSHA regulations 
testified that, in their experience, ``with maybe a hundred workers, 
anywhere from three to five [workers] could not go to work because of 
their lung problems over the years.'' They also stated that they had 
not found any workers unable to wear an air-supplying respirator or 
powered air-purifying respirator, as long as they were clean-shaven. We 
agree with these commenters that few miners will be unable to wear a 
PAPR while performing their tasks in a mine.
    In the event that a miner is medically unable to wear a negative-
pressure respirator, Sec.  57.5060(d)(3) requires the mine operator to 
make certain that a PLHCP evaluates the miner's ability to use a PAPR, 
such as those that are integrated into a hard hat. Although a 
determination needs to be made that the miner is medically able to wear 
a PAPR, it is likely that most miners could wear a PAPR. We believe 
that such respirators are an effective option for persons who cannot 
wear a negative-pressure respirator and, in most instances, will negate 
the need to transfer the miner.
    One commenter suggested that mine operators be required to provide 
PAPRs to miners who are medically unable to wear a negative-pressure 
respirator, and not be required to transfer the miner to another 
position at equal pay unless the miner was unable to wear either a 
negative-or positive-pressure respirator. Most commenters favored 
leaving the choice to the mine operator. NIOSH suggested transfer be 
reserved for those who could not use either a negative-pressure 
respirator or a PAPR. Final Sec.  57.5060(d)(7) requires transfer of 
miners when the PLHCP determines that the miner cannot wear a 
respirator, including a PAPR. If the PLHCP finds that the miner cannot 
wear a negative-pressure respirator, the mine operator must make 
certain that the PLHCP tests the miner's ability to wear a PAPR. 
Pursuant to existing Sec.  57.5060(d), if the mine operator can wear a 
PAPR, the mine operator has an obligation to provide it and require the 
miner to wear it.
    One commenter stated that as the DPM standard becomes more 
stringent and respirator usage increases, the medical evaluation would 
need to be adapted to evaluate the miner's ability to wear the 
respirator for the full shift during high workload duties. The 
commenter believes this would increase the number of miners that are 
unable to successfully pass the medical evaluation, increasing the need 
for transfer or termination. Although we agree that the number of 
miners required to use respirators would increase as the DPM final 
limit is lowered, we do not believe that it would result in any 
significant increase in the

[[Page 28990]]

number of transfers, because most miners could wear a PAPR if they 
cannot wear a negative pressure respirator.
    Most commenters stated that in the event that we require medical 
transfer of a miner, they opposed creating a job for the transferred 
miner. They strongly believe that transfer rights should be limited to 
those circumstances where a position is available where respiratory 
protection is not required, and the miner is qualified for that 
position. Several of these commenters stated that not giving 
consideration to miners' skills or qualifications could result in a 
miner being transferred into a position where they are unqualified to 
perform the work. As a result, this could create a threat to the safety 
of the transferred miner as well as to other miners.
    We concluded in final Sec.  57.5060(d)(7) that the miner must be 
transferred to an existing job in an area of the same mine where 
respiratory protection is not required. We believe that the rulemaking 
record is insufficient to establish justification for requiring mine 
operators to create jobs for transferred miners. The mine operator is 
in the best position to determine if a miner is qualified to perform 
the job to which the miner is transferred based upon the tasks 
involved. We would, however, expect the mine operator to provide 
necessary task training under our existing standards at 30 CFR part 48.
    Several small mine operators were particularly concerned with the 
difficulty of moving people to different positions within their small 
workforce. One operator said they often do cross-training, but that 
their labor market was limited and it was becoming more difficult to 
find people willing to work underground. Our primary objective under 
this standard is to prevent miners from being required to use a 
respirator before the miner is determined to be medically able to wear 
the respirator. Section 101(a)(7) of the Mine Act, and the data 
confirming the potential health consequences of using a respirator with 
certain illnesses and other medical conditions, lead us to disagree 
with these commenters.
    Several mine operators commented that available positions were 
limited for transferred miners due to terms of labor contracts. One 
mine operator with several properties said it might be difficult to 
find an available job at their mine having about 25 employees, but that 
they would consider offering a position at one of their other 
properties if a position was available there. Another mine operator 
said that they might not be able to find a job underground, but that 
one on the surface might be available. The final standard does not 
prohibit mine operators from transferring a miner to an existing job on 
the surface of the same mine. Mine operators, however, must make 
certain that they comply with the compensation requirements in Sec.  
57.5060(d)(7)(i) and (ii). Moreover, they must make certain that the 
new miner is not overexposed to DPM on the new job and is not required 
to use respiratory protection, until such time that a subsequent 
medical evaluation by a PLHCP determines that the miner is able to use 
the respirator.
    One mine operator stated that most of their underground miners 
would be required to wear respirators, and as a consequence, the 
availability of alternative positions would be extremely limited. The 
commenter stated that the rate of pay should not be tied to the 
position held by the worker prior to the transfer but should be based 
on the new position because wage scales for underground workers are 
typically higher than for comparable above ground positions. Several 
other commenters also wanted the wage rate for a transferred miner to 
be based on the new position. Again, we emphasize that the final rule 
adopts our statutory mandate articulated in the Mine Act regarding 
compensation of transferred miners. Under Sec.  57.5060(d)(7)(i), 
transferred miners are to receive ``no less'' than the regular rate of 
pay that they received in the job classification that they were in 
immediately before the transfer. Under Sec.  57.5060(d)(7)(ii), mine 
operators must base increases in wages of transferred miners on the new 
work classification.
    We received several comments regarding an appropriate regulatory 
response to when a miner cannot meet the requirements of wearing a 
respirator while performing their duties, and there is no available 
work that the restricted miner is qualified to perform. Some commenters 
suggested that the miner should be considered medically unfit for duty 
and terminated subject to their company policies, collective bargaining 
agreements, and State or Federal laws. One commenter stated that they 
did not have transfer rights in their contracts, but had been assured 
that if the circumstance arose, their human resources department would 
see whether the miner could be moved to an available job. In response, 
the final rule does not require mine operators to create a job for 
miners who need to be transferred.
    Organized labor stated its strong support for medical evaluation 
and transfer. They believe that since a mine operator who assigns a 
miner to work in a respirator without a medical evaluation puts that 
worker's life at risk, we have an obligation to protect miners from 
such harm. We agree that medical evaluation and transfer requirements 
are a necessary component to the existing DPM respiratory protection 
program, and we have included this protection in the final rule for 
improving miners' health.
    In our preamble to the 2005 final rule, we stated our belief that a 
requirement for medical evaluation of respirator wearers and transfer 
of miners unable to wear respirators was inappropriate for that 
rulemaking (70 FR 32957). At that time, we believed that these 
requirements would have minimal application, particularly considering 
the extent to which mine operators were voluntarily implementing such 
provisions and the limited long term use of respirators envisioned 
under the interim rule. We are now persuaded that under the final 
limit, this is no longer the case.
    Notwithstanding the continuation of some voluntary use of these 
programs in the mining industry, we are concerned that more miners may 
be required to wear respirators for longer periods of time as the final 
limit is lowered, and therefore, medical evaluation and transfer should 
not remain an elective. If, however, we fail to include transfer rights 
for miners unable to wear respiratory protection, the effect may be 
worse than not requiring a medical evaluation at all. The mine 
operator, acting on false information given by the miner to protect his 
or her job, is then in the position of assigning a respirator to a 
miner who cannot safely wear it. The best course of action for miner's 
health is to remove the fear of reprisals to the degree necessary to 
allow the miner to truthfully and fully participate in a medical 
evaluation.
    We realize that particularly at a small mine, an alternative 
position may not exist. Under this circumstance, we believe that the 
mine operator is best suited to determine how to accommodate that miner 
based on existing employment rights pursuant to collective bargaining 
agreements, and state and federal laws, etc. The final rule, however, 
prohibits a mine operator from allowing a miner to voluntarily work in 
an area where respiratory protection is required without a respirator 
and when the miner is medically unable to wear a respirator.
    We received one comment objecting to notification to the District 
Manager of the health professional's evaluation and the fact that a 
miner will be transferred. We have not included notification 
requirements in the final rule due to our

[[Page 28991]]

objective to limit the paperwork burden on mine operators, and due to 
the fact that our inspectors have access to mine operators' records and 
can determine that miners have been transferred.
    NIOSH recommended that mine operators be required to maintain 
records of miners' medical evaluations, respirator use, and transfers 
required under this rule and that the records be kept confidential and 
in a secure location. The final rule requires mine operators to keep a 
record of the identity of the PLHCP and the most recent written 
determination of each miner's ability to wear a respirator for the 
duration of the miner's employment plus six months. It is important 
that we note that our compliance specialists have access to these 
records pursuant to Section 103(h) of the Mine Act, and operators must 
make these records available to the authorized representatives of the 
Secretary of Labor.
    NIOSH recommended that the timeframe for transfer be as rapid as 
possible if a miner is experiencing acute health effects from exposure. 
The final rule requires the mine operator to transfer the affected 
miner within 30 days of the final determination by the PLHCP that the 
miner is unable to wear a respirator. We anticipate most overexposures 
to be chronic rather than acute, and therefore, have given greater 
latitude in the time for compliance.
    A number of commenters stated that where miners' exposures cannot 
be reduced below the applicable final limit, the standard should 
provide that the mine operator may assign other miners who must wear 
respiratory protection to work in the affected area to reduce the 
amount of time that any given miner must wear respiratory protection. 
We do not agree. Allowing this practice fails to eliminate the hazard 
of DPM exposure and results in placing more miners at risk. We do 
believe that a two-year phase-in approach of the final limit of 
160TC [mu]g/m3 will resolve many of the existing 
feasibility issues as discussed in the feasibility section of this 
preamble. Although the number of miners required to wear respirators is 
likely to increase initially under the 160TC [mu]g/
m3 final limit, with the use of biodiesel and other 
available DPM controls, we project that the number of miners in 
respiratory protection should decrease over time.
    In the 2005 NPRM, we estimated that medical evaluation and transfer 
requirements would affect about 50 miners annually for evaluation, 
about 3 miners annually for transfer, and cost about $40,000 annually. 
We asked for comments on costs to mine operators for implementing a 
rule requiring medical evaluations and transfer of miners.
    One mine commented that they have a formal medical evaluation 
conducted prior to being fit tested and annually thereafter. Their 
average cost for an evaluation to be able to wear a negative-pressure 
respirator was $250 per miner. They also estimated that the cost for 
them to provide a PAPR for miners unable to wear a negative-pressure 
respirator would be approximately $700. One large gold mine commented 
that they believed approximately 70% (480) of their 686 underground 
personnel would require respiratory protection in meeting the final 160 
TC limit.
    Another commenter said they have onsite technicians who are 
certified to conduct these tests (medical evaluation), however, the 
analysis of the pulmonary function tests is provided by a licensed 
healthcare provider. Their cost for the pulmonary function tests is 
roughly $17.00 per individual. Another company estimated that the 
average cost per person for medical evaluations is $660. The range for 
costs varied widely depending on the types of tests performed and 
whether the cost of the respirator itself was included. We have 
considered these new data in our REA in support of the final rule and 
have revised our costs estimates.
    As explained in section IX.A. of this preamble, a total of 680 
miners will require a medical evaluation in the first year after the 
rule takes effect to meet the 350TC [mu]g/m3 
limit. An additional 244 miners will require a medical evaluation when 
the 160TC [mu]g/m3 takes effect. The estimated 
yearly medical evaluation and transfer costs to mine operators to meet 
the requirements of the final rule are $69,170.

D. Diesel Particulate Records Sec.  57.5075(a)

    The recordkeeping requirements of the DPM standards contained in 
Sec. Sec.  57.5060 through 57.5071 are listed in a table entitled 
``Table 57.5075(a)--Diesel Particulate Matter Recordkeeping 
Requirements.'' The table lists the records the operator must maintain 
pursuant to Sec. Sec.  57.5060 through 57.5071, and the retention 
period for these records.
    The final rule also makes a confirming change to the Table in Sec.  
57.5075(a) which includes a record of the identity of the physician or 
other licensed health care professional (PLHCP) and the most recent 
written determination of each miner's ability to wear a respirator for 
the duration of the miner's employment plus six months.
    As discussed in detail under section VIII.C. Medical Evaluation and 
Transfer, we have determined that medical evaluation and transfer 
requirements are a necessary component to the existing DPM respiratory 
protection program, and have included this requirement for improving 
miners' health in the final rule. Thus, we are amending the existing 
DPM respiratory protection standard at Sec.  57.5060(d) by adding a 
provision requiring a medical evaluation to determine a miner's ability 
to use a respirator before the miner is fit tested or required to work 
in an area of the mine where respiratory protection must be used.
    The final rule also includes requirements for transferring a miner 
to an existing job in an area of the mine where respiratory protection 
is not required if a PLHCP has determined that the miner's medical 
condition precludes the miner from safely wearing any type of 
respirator, including a PAPR.
    Under paragraph (d)(8) the mine operator must maintain a record of 
the identity of the PLHCP and the most recent written determination of 
each miner's ability to wear a respirator for the duration of the 
miner's employment plus six months. We consider this document to be a 
medical record and our retention requirements are consistent with other 
medical records that we require mine operators to maintain, such as 
those specified in our existing Hearing Conservation Program 
requirements in 30 CFR 62.171. By requiring the operator to retain a 
copy of these documents, it will help protect miner's health and assist 
with compliance with Sec.  57.5060(d). This new recordkeeping 
requirement will be incorporated into existing Table 57.5075(a)--Diesel 
Particulate Recordkeeping Requirements.

IX. Regulatory Costs

    Section IX.A discusses the costs attributable to this final rule. 
These costs arise from new provisions for medical evaluation and 
transfer. Section IX.B discusses the costs of implementing the 
160TC [mu]g/m3 final limit, given that the 
existing 308EC [mu]g/m3 interim limit is in 
effect. The move from the existing higher limit to the lower final 
limit results from a series of final rules, including both this final 
rule and two prior rules. Other than the costs for medical evaluation 
and transfer (estimated in Section IX.A and reported in Section IX.B), 
the costs presented in Section IX.B are not attributable to this final 
rule. All costs are reported in 2004 dollars.

[[Page 28992]]

A. Costs of Medical Evaluation and Transfer

    The medical evaluation and transfer provisions would require the 
mine operator to provide a medical evaluation by a physician or other 
licensed health care professional (PLHCP) to each miner required to 
wear a respirator. MSHA will accept a prior medical evaluation to the 
extent the mine operator has a written record and there have not been 
any changes that will adversely affect the miner's ability to wear a 
respirator. For those miners who do not have an existing medical 
evaluation, we expect that the mine operator would need to provide the 
PLHCP with information, including the types and weights of the 
respirator that the miner will use, the duration and frequency of 
respirator use, the expected physical work effort, additional 
protective clothing and equipment worn, and temperature and humidity 
extremes that may be encountered. The mine operator would also need to 
provide additional medical evaluations if: the miner's supervisor 
notifies the PLHCP of medical signs or symptoms related to the miner's 
ability to use a respirator; the PLHCP informs the mine operator that 
the miner needs to be reevaluated; information from the respiratory 
protection program indicates a need for miner reevaluation; or a change 
in workplace conditions occurs.
    If a respirator is needed, the mine operator would have to provide 
a negative-pressure respirator. However, if the PLHCP determines that 
the miner cannot wear a negative-pressure respirator but can wear a 
positive-pressure respirator, then the mine operator would be required 
to provide a powered air-purifying respirator (PAPR) to the miner.
    The mine operator would have to transfer the miner to an existing 
position in the same mine where respiratory protection is not required 
if the PLHCP determined that the miner was unable to wear either a 
negative-pressure respirator or a PAPR. The mine operator would be 
required to compensate the miner at no less than the regular rate of 
pay received by the miner immediately before the transfer.
    To estimate the cost of these medical evaluation and transfer 
provisions, for the 308EC [mu]g/m\3\, 350TC 
[mu]g/m\3\, and 160TC [mu]g/m\3\ limits, MSHA made the 
following assumptions:
    In each year that medical evaluations are required for a mine, it 
would take a mine health and safety specialist, earning $52.31 per 
hour, 1 hour to prepare information for the PLHCP.\3\
---------------------------------------------------------------------------

    \3\ MSHA assumes that the wage of a health and safety specialist 
is the same as the wage of a mine supervisor. The wage is reported 
in 2004 dollars.
---------------------------------------------------------------------------

    The cost of a medical evaluation is $50. This medical evaluation 
consists of a medical questionnaire or interview with the PLHCP and a 
simple pulmonary function test.
    Four miners per mine in mines with fewer than 20 employees will 
need to use respirators and therefore require a medical evaluation in 
the first year that respirators are required for mines that need 
them.\4\ Twelve miners per mine in mines with 20-500 employees will 
need to use respirators and therefore require a medical evaluation in 
the first year that respirators are required for mines that need 
them.\5\ Thirty miners per mine in mines with over 500 employees will 
need to use respirators and therefore require a medical evaluation in 
the first year that respirators are required for mines that need 
them.\6\
---------------------------------------------------------------------------

    \4\ This estimate is based on the assumption of two two-person 
crews for one shift in mines with fewer than 20 employees.
    \5\ This estimate is based on the assumption of three two-person 
crews for each of two shifts at mines with 20-500 employees.
    \6\ This estimate is based on the assumption of five two-person 
crews for each of three shifts at mines with over 500 employees.
---------------------------------------------------------------------------

    Based on these assumptions a total of 680 miners will require a 
medical evaluation in the first year after the rule takes effect to 
meet the 308EC and 350TC [mu]g/m\3\ limits. An 
additional 244 miners will require a medical evaluation at the 
beginning of the third year when the 160TC [mu]g/m\3\ limit 
takes effect.
    Because of turnover, new miners will require medical evaluations in 
years subsequent to the first year in which respirators are first used. 
In each year after the first year, approximately 0.28 additional miners 
per mine will require a medical evaluation in mines with fewer than 20 
employees. In each year after the first year, approximately 0.84 
additional miners per mine will require a medical evaluation in mines 
with 20-500 employees. In each year after the first year, approximately 
2.1 additional miners per mine will require a medical evaluation in 
mines with 20-500 employees.\7\
---------------------------------------------------------------------------

    \7\ These numbers are based on a turnover rate of 7% for the 
four miners per mine in mines with fewer than 20 employees, the 12 
miners per mine in mines with 20-500 employees , and the 30 miners 
per mine in mines with over 500: 4 x 0.07 = 0.28; 12 x 0.07 = 0.84; 
30 x 0.07 = 2.10.
---------------------------------------------------------------------------

    In ten percent of the cases, the PLHCP will determine that 
additional tests are needed for the miner's medical evaluation. These 
additional tests may include X-rays and cardio-pulmonary tests. The 
cost of the additional tests is $250.
    Five percent of the miners required to wear a respirator will need 
a PAPR. A PAPR costs approximately $1,000 and has a useful life of 
about 5 years.
    At any point in time, approximately \1/2\% of the number of miners 
using respirators will need to be transferred. The total is expected to 
be fewer than five transferred employees at any one time for the entire 
mining industry. The normal hourly wage rate in an existing position 
where respiratory protection is not required averages 20% less than the 
miner's hourly wage rate in the position where respiratory protection 
is required, taking into account the rare cases where there is no 
position in the mine to which the miner can be transferred. A miner 
works 2,000 hours per year on average. The average remaining work life 
of a miner is 20 years.
    Based on the preceding assumptions, Table IX-1 summarizes the costs 
of medical evaluation and transfer by mine size for 308EC 
[mu]g/m\3\, 350TC [mu]g/m\3\, and 160TC [mu]g/
m\3\ limits. The estimated yearly medical evaluation and transfer costs 
to mine operators to meet the requirements of the final rule are 
$69,170 in 2004 dollars.\8\ The costs shown in Table IX-1 are the only 
costs attributable to this final rule.
---------------------------------------------------------------------------

    \8\ The spreadsheets underlying the development to the cost 
estimates presented in this section, as well as in Sections V, X, 
and XI of this preamble, are posted on MSHA's Web page.
---------------------------------------------------------------------------

BILLING CODE 4510-43-P

[[Page 28993]]

[GRAPHIC] [TIFF OMITTED] TR18MY06.002

B. Costs of Implementing the 160TC [mu]g/m\3\ Limit

    This subsection discusses all the costs of reducing the existing 
308EC [mu]g/m\3\ interim limit to the 160TC 
[mu]g/m\3\ final limit. These costs arise from both this final rule and 
the existing 2001 and 2005 final DPM rules for metal/nonmetal mines. 
Most of the costs estimated in this subsection are not attributable to 
this final rule. The costs described and explained in this subsection 
are presented for purposes of completeness and clarity and to support 
the Agency's finding of feasibility for the final limit, as shown in 
Section V.
    In Chapter IV of the Regulatory Economic Analysis in support of the 
January 19, 2001 final rule (2001 REA), we estimated that underground 
M/NM mine operators would incur yearly costs to comply with the DPM 
final rule of $25,149,179 (p. 106). Of this amount, $6,612,464 was the 
discounted (from 2006 to 2001) yearly cost of compliance with the final 
limit. The yearly cost for compliance with the final limit beginning in 
2006 was estimated as $9,274,325 (p. 58). If we adjust for the change 
in the number of mines and also adjust for inflation (from 1998 
dollars, in which the costs of the 2001 rule were reported, to 2004 
dollars), this yearly cost becomes $9,259,519. These calculations are 
shown in Table IX-2.

[[Page 28994]]

[GRAPHIC] [TIFF OMITTED] TR18MY06.003

    This final rule would amend the January 19, 2001 final DPM rule by 
phasing in the 160TC [mu]g/m\3\ final limit over an 
additional two-year period, from May 20, 2006 to May 20, 2008, to 
address feasibility issues that have surfaced since the 2001 final 
rule. The discounted present value of the reduction in the cost 
estimate for this two-year phase-in period is $15,467,387. The 
annualized value of this reduced cost estimate, using an annualization 
rate of 7%, is $1,082,717 in 2004 dollars. Table IX-3 shows these 
calculations, as well as the breakdown by mine size of this reduced 
cost estimate. Because of feasibility issues associated with currently 
meeting the 160TC [mu]g/m\3\ limit, this reduction in cost 
estimate is not properly attributable as a cost saving due to this 
final rule.

[[Page 28995]]

[GRAPHIC] [TIFF OMITTED] TR18MY06.004

    The process of evaluating and implementing DPM control technologies 
has been more difficult, time consuming, and costly for some mine 
operators than we had initially anticipated in the 2001 final rule. For 
example, some mine operators that initially installed a passive 
regeneration system on a machine learned through trial and error that 
the machine did not have a consistent duty cycle that would support 
passive regeneration, so they had to alter their regeneration strategy 
to incorporate an active regeneration system. Another mine operator, 
who initially tried a high-temperature disposable particulate filter 
(HTDPF) without exhaust gas cooling prior to the filter media, needed 
to add a heat exchanger prior to the filter media to meet the 
manufacturer's exhaust gas temperature specifications. Yet another mine 
operator, who used biodiesel fuel during the summer months, needed to 
make changes to the fuel delivery system during the winter months in 
order to deal with the lower ambient temperatures.
    These evaluation and implementation costs, it should be noted, do 
not involve testing the workability of the known methods for reducing 
DPM emissions. Rather, the evaluation is for determining the 
suitability of the various existing DPM-control technologies for mine-
specific applications and integrating such technology into the mining 
and maintenance process. While the industry has provided examples of 
its experience with implementation difficulties, they provided limited 
information as to the magnitude of these

[[Page 28996]]

particular costs. Accordingly, the costs associated with evaluating 
various methods to achieve compliance are difficult to quantify.
    Evaluation costs typically will not involve all diesel equipment. 
For example, we would expect a mine operator to evaluate filters on one 
or a few pieces of diesel equipment, probably during maintenance 
shifts. We therefore expect that costs of evaluation will be only a 
fraction of MSHA's estimated costs of achieving the final limit. 
Accordingly, based on its technical expertise and experience with DPM 
controls, MSHA estimates that, for the average mine that has evaluation 
costs, annual costs of evaluating alternative methods of compliance are 
25% of the previously estimated compliance costs for mines to reduce 
the 308EC [mu]g/m3 limit to the 160TC 
[mu]g/m3 limit.
    Not all the diesel mines will incur evaluation costs, beyond the 
costs previously estimated, to comply with the rule. Many mines are 
already in compliance or can achieve compliance using technologies 
already proven to work in these mines. MSHA estimates that during the 
first two years of the rule, 50% of mines will experience evaluation 
costs. Further, MSHA estimates that during the third and fourth years 
of the rule, 10% of mines will continue to experience evaluation costs. 
These evaluation costs are being recognized in this final rule, as 
needed to achieve the final limit. However, these costs were not caused 
by, or attributable to, this final rule. These costs would exist even 
in the absence of this final rule. These cost estimates are shown in 
Table IX-4.
[GRAPHIC] [TIFF OMITTED] TR18MY06.005


[[Page 28997]]


    Table IX-5 integrates all the cost estimates and cost adjustments 
discussed in this subsection to provide an updated estimate of the cost 
for the industry to comply with the 160TC [mu]g/
m3 final limit, given that the existing 308EC 
[mu]g/m3 interim limit is already in effect. Table IX-5 also 
includes the costs of the medical evaluation and transfer provisions 
discussed in Section IX.A of this preamble and the costs of the special 
extensions for the final limit provided for in the 2005 DPM final 
rule.\9\ The yearly cost of implementing the 160TC [mu]g/
m3 final limit is $8,454,853. The economic feasibility of 
the 160TC [mu]g/m3 final limit, as reflected in 
these revised cost estimates, is discussed in Section V.B.
---------------------------------------------------------------------------

    \9\ The cost savings due to other provisions of the 2005 DPM 
final rule are not included in the estimates here because they have 
already accrued to mine operators in achieving the interim limit.
[GRAPHIC] [TIFF OMITTED] TR18MY06.006

X. Regulatory Flexibility Act Certification and Small Business 
Regulatory Enforcement Fairness Act (SBREFA)

    Pursuant to the Regulatory Flexibility Act (RFA) of 1980 as amended 
by the Small Business Regulatory Enforcement Fairness Act (SBREFA), we 
have analyzed the impact of the final rule on small businesses. 
Further, we have made a determination with respect to whether or not we 
can certify that the final rule would not have a significant economic 
impact on a substantial number of small entities that are covered by 
the final rule. Under the SBREFA amendments to the RFA, we must include 
in the rule a factual basis for this certification. If a rule would 
have a significant economic impact on a substantial number of small 
entities, we must develop a regulatory flexibility analysis.

A. Definition of a Small Mine

    Under the RFA, in analyzing the impact of a rule on small entities, 
we must use the Small Business Administration (SBA) definition for a 
small entity or, after consultation with the SBA Office of Advocacy, 
establish an alternative definition for the mining industry by 
publishing that definition in the Federal Register for notice and 
comment. We have not taken such an

[[Page 28998]]

action and hence are required to use the SBA definition. The SBA 
defines a small entity in the mining industry as an establishment with 
500 or fewer employees.
    We have also looked at the impacts of our rules on a subset of 
mines with 500 or fewer employees--those with fewer than 20 employees, 
which we and the mining community have traditionally referred to as 
``small mines.'' These small mines differ from larger mines not only in 
the number of employees, but also in economies of scale in material 
produced, in the type and amount of production equipment, and in supply 
inventory. Therefore, their costs of complying with our rules and the 
impact of our rules on them will also tend to be different. It is for 
this reason that ``small mines,'' as traditionally defined by us as 
those employing fewer than 20 workers, are of special concern to us.
    This analysis complies with the legal requirements of the RFA for 
an analysis of the impacts on ``small entities'' while continuing our 
traditional definition of ``small mines.'' We conclude that we can 
certify that the final rule would not have a significant economic 
impact on a substantial number of small entities that are covered by 
this rulemaking. We have determined that this is the case both for 
mines affected by this rulemaking with fewer than 20 employees and for 
mines affected by this rulemaking with 500 or fewer employees.

B. Factual Basis for Certification

    MSHA's analysis of impacts on ``small entities'' begins with a 
``screening'' analysis. The screening compares the estimated compliance 
costs of a rule for small entities in the sector affected by the rule 
to the estimated revenues for the affected sector. When estimated 
compliance costs are less than one percent of the estimated revenues, 
the Agency believes it is generally appropriate to conclude that there 
is no significant economic impact on a substantial number of small 
entities. When estimated compliance costs exceed one percent of 
revenues, it tends to indicate that further analysis may be warranted.
    As shown in Table X-1, using either MSHA's traditional definition 
of a small mine (those having fewer than 20 employees) or SBA's 
definition of a small mine (those having 500 or fewer employees), the 
estimated yearly costs of this final rule for small underground M/NM 
mines that use diesel-powered equipment is less than 0.01 percent of 
their estimated yearly revenues, well below the level suggesting that 
this rule might have a significant economic impact on a substantial 
number of small entities. Accordingly, we have certified that this 
final rule will not have a significant economic impact on a substantial 
number of small entities covered by the final rule.
[GRAPHIC] [TIFF OMITTED] TR18MY06.007

XI. Paperwork Reduction Act

    This final rule addresses information collection requirements under 
OMB Control Number 1219-0135 that have been submitted to the Office of 
Management and Budget (OMB) for review under 44 U.S.C. 3504(h) of the 
Paperwork Reduction Act of 1995, as amended.
    The paperwork costs presented in this section are a subset of the 
total costs presented in Table IX-1 and reflect only those costs which 
relate to burden hours that are a result of the final rule. Both 
paperwork burden hours and costs were derived from the spreadsheets 
(posted on our Web page) used to estimate the costs in Table IX-1.
    MSHA estimates that the final rule would create 3,687 burden hours 
for the first year, 299 burden hours for the second year, 1,120 burden 
hours for the third year, and 371 burden hours each year after the 
third year. This is equivalent to an annualized value of 1,261 burden 
hours per year and related annualized burden costs of $28,905 per year. 
On a per-mine basis, the annualized paperwork burden is 7.5 hours and 
$172 per year.
    The paperwork burden to the mine operator is attributable primarily 
to Sec.  57.5060(d)(3), to prepare and provide information to the PLHCP 
and to send the miner to the PLHCP for a medical evaluation to 
determine the miner's

[[Page 28999]]

ability to use a respirator. The annualized paperwork and cost burden 
to the mining industry for this provision is 1,140 hours and $26,330 
per year. The remaining paperwork burden is attributable to Sec.  
57.5060(d)(4), which allows miners to submit additional evidence of 
their medical condition to the PLHCP, and to Sec.  57.5060(d)(8), which 
requires mine operators to maintain a record of the identity and 
written determination of the PLHCP. The annualized paperwork and cost 
burden to the mining industry for these two provisions is 103 and 17 
hours per year, and $2,190 and $385 per year, respectively.
    The total paperwork hour and cost burden is summarized in Table XI-
1 by first year, second year, third year, and each year after the third 
year.
[GRAPHIC] [TIFF OMITTED] TR18MY06.008

XII. Other Regulatory Considerations

A. The Unfunded Mandates Reform Act of 1995

    This final rule does not include any Federal mandate that may 
result in increased expenditures by State, local, or tribal 
governments; nor does it increase private sector expenditures by more 
than $100 million annually; nor does it significantly or uniquely 
affect small governments. Accordingly, the Unfunded Mandates Reform Act 
of 1995 (2 U.S.C. 1501 et seq.) requires no further agency action or 
analysis.

B. National Environmental Policy Act

    We have reviewed this final rule in accordance with the 
requirements of the National Environmental Policy Act (NEPA) of 1969 
(42 U.S.C. 4321 et seq.), the regulations of the Council on 
Environmental Quality (40 U.S.C. 1500), and the Department of Labor's 
NEPA procedures (29 CFR part 11). This final rule has no significant 
impact on air, water, or soil quality; plant or animal life; the use of 
land; or other aspects on the human environment. We solicited public 
comment concerning the accuracy and completeness of this environmental 
assessment when this rule was first proposed, and received no comments 
relevant to this environmental assessment. We find, therefore, that the 
final rule has no significant impact on the human environment. 
Accordingly, we have not provided an environmental impact statement.

C. The Treasury and General Government Appropriations Act of 1999: 
Assessment of Federal Regulations and Policies on Families

    This final rule has no affect on family well-being or stability, 
marital commitment, parental rights or authority, or income or poverty 
of families and children. Accordingly, Section 654 of the Treasury and 
General Government Appropriations Act of 1999 (5 U.S.C. 601 note) 
requires no further agency action, analysis, or assessment.

D. Executive Order 12630: Government Actions and Interference With 
Constitutionally Protected Property Rights

    This final rule does not implement a policy with takings 
implications. Accordingly, Executive Order 12630, Governmental Actions 
and Interference with Constitutionally Protected Property Rights, 
requires no further agency action or analysis.

E. Executive Order 12988: Civil Justice Reform

    This final rule was written to provide a clear legal standard for 
affected conduct, and was carefully reviewed to eliminate drafting 
errors and ambiguities, so as to minimize litigation and undue burden 
on the Federal court system. Accordingly, this final rule meets the 
applicable standards provided in Section 3 of Executive Order 12988, 
Civil Justice Reform.

F. Executive Order 13045: Protection of Children From Environmental 
Health Risks and Safety Risks

    This final rule has no adverse impact on children. Accordingly, 
Executive

[[Page 29000]]

Order 13045, Protection of Children from Environmental Health Risks and 
Safety Risks, as amended by Executive Orders 13229 and 13296, requires 
no further agency action or analysis.

G. Executive Order 13132: Federalism

    This final rule does not have ``federalism implications,'' because 
it does not ``have substantial direct effects on the States, on the 
relationship between the national government and the States, or on the 
distribution of power and responsibilities among the various levels of 
government.'' Accordingly, Executive Order 13132, Federalism, requires 
no further agency action or analysis.

H. Executive Order 13175: Consultation and Coordination With Indian 
Tribal Governments

    This final rule does not have ``tribal implications,'' because it 
does not ``have substantial direct effects on one or more Indian 
tribes, on the relationship between the Federal government and Indian 
tribes, or on the distribution of power and responsibilities between 
the Federal government and Indian tribes.'' Accordingly, Executive 
Order 13175, Consultation and Coordination with Indian Tribal 
Governments, requires no further agency action or analysis.

I. Executive Order 13211: Actions Concerning Regulations That 
Significantly Affect Energy Supply, Distribution, or Use

    Regulation of the M/NM sector of the mining industry has no 
significant impact on the supply, distribution, or use of energy. This 
final rule is not a ``significant energy action,'' because it is not 
``likely to have a significant adverse effect on the supply, 
distribution or use of energy * * * (including a shortfall in supply, 
price increases, and increased use of foreign supplies).'' Accordingly, 
Executive Order 13211, Actions Concerning Regulations That 
Significantly Affect Energy Supply, Distribution, or Use, requires no 
further agency action or analysis.

J. Executive Order 13272: Proper Consideration of Small Entities in 
Agency Rulemaking

    We have thoroughly reviewed this final rule to assess and take 
appropriate account of its potential impact on small businesses, small 
governmental jurisdictions, and small organizations. As discussed in 
Chapter V of the REA, we have determined and certified that this final 
rule will not have a significant economic impact on a substantial 
number of small entities. We solicited public comment concerning the 
accuracy and completeness of this potential impact when the rule was 
first proposed. We took appropriate account of comments received 
relevant to the rule's potential impact on small entities. Accordingly, 
Executive Order 13272, Proper Consideration of Small Entities in Agency 
Rulemaking, requires no further agency action or analysis.

XIII. Information Quality

    In accordance with the Information Quality Act and the Department 
of Labor Information Quality Guidelines, we are responding to the 
substantive information quality request of the Methane Awareness 
Resource Group (MARG) as part of other information/data related 
comments received in the record to this rulemaking. Some of the 
commenters' issues are limitations of models, such as the 31-Mine Study 
and the Estimator model. No better data were offered by commenters and 
we find that that information remains the best available. We also 
conclude that some of the corrections requested were policy solutions 
rather than information corrections, thus they will not be addressed in 
our response.
    We received a number of comments from the mining industry 
suggesting that our risk assessment does not comply with the present 
requirements under the data quality guidelines to use the best 
available, peer reviewed science. In addition, industry commenters 
stated that the DPM rule does not comply with the congressional, Office 
of Management and Budget (OMB) and the Department of Labor (DOL) 
information quality guidelines because the DPM rule is not supported by 
an adequate scientific basis, and it fails to meet the reproducibility 
standard required for disseminating influential information. Moreover, 
these commenters stated that OMB requires agencies in their own data 
quality guidelines to submit for public comment data on which we rely 
or disseminate. The guidelines also establish administrative mechanisms 
that allow affected persons to seek or obtain correction of 
disseminated information if they believe such information does not 
comply with either the OMB or MSHA guidelines.
    Throughout the DPM rulemakings, we have given serious consideration 
to the issues raised by commenters. As a result, we have made some 
adjustments to our data and provided comprehensive responses in this 
preamble. For example, we conducted the 31-Mine Study, which resulted 
from a joint protocol of government, the mining industry and organized 
labor, to address and correct, where necessary, the following issues 
with regard to our 2001 data:

--The validity, precision and feasibility of the sampling and 
analysis method specified by the diesel standard (NIOSH Method 
5040);
--The magnitude of interferences that occur when conducting 
enforcement sampling for total carbon as a surrogate for diesel 
particulate matter (DPM) in mining environments; and,
--The technological and economic feasibility of the underground 
metal and nonmetal (MNM) mine operators to achieve compliance with 
the interim and final DPM concentration limits.
--The parties developed a joint MSHA/Industry study protocol to 
guide sampling and analysis of DPM levels in 31 mines. The parties 
also developed four subprotocols to guide investigations of the 
known or suspected interferences, which included mineral dust, drill 
oil mist, oil mist generated during ammonium nitrate/fuel oil (ANFO) 
loading operations, and environmental tobacco smoke (ETS). The 
parties also agreed to study other potential sampling problems, 
including any manufacturing defects of the DPM sampling cassette (70 
FR 32871). (Executive Summary, Report on the 31-Mine Study)

    MSHA requested that NIOSH peer review the draft Report on the 31-
Mine Study, and NIOSH's conclusions were placed in the rulemaking 
record and published in the 2005 final rule (70 FR 32871).
    We are confident that we have set forth the evidence and rationale 
behind our decisions to establish a rule amending the existing DPM 
standard that meets the statutory requirements for promulgating this 
health standard as required under the Federal Mine Safety and Health 
Act of 1977 (Mine Act) in Section 101(a)(6)(A). We have presented and 
discussed with commenters in Federal Register notices, in preambles and 
at public hearings, the evidence supporting our decision to revise the 
existing rule restricting miner exposure to DPM.
    With regard to the 2001 DPM risk assessment, we relied on peer-
reviewed scientific studies. Of particular note, is that the two 
quantitative meta-analyses of lung cancer studies supporting our risk 
assessment were peer reviewed and published in scientific journals. 
(Bhatia, Rajiv, et al., ``Diesel Exhaust Exposure and Lung Cancer,'' 
Journal of Epidemiology, 9:84-91, January 1998, and Lipsett M., and 
Campleman, Susan, ``Occupational Exposure to Diesel Exhaust and Lung 
Cancer: A Meta-Analysis,'' American Journal of Public Health, (89) 
1009-1017, July 1999). We informed the public as early as September 25, 
2002, in the 2002 ANPRM for the 2005 final rule at M/NM

[[Page 29001]]

mines, in the 2003 NPRM, in the 2005 final rule and again in the 2005 
proposed rule that we would incorporate the existing rulemaking record 
into the record of this rulemaking, including the 2001 risk assessment. 
In that risk assessment, we carefully laid out the evidence available 
to us, including shortcomings inherent in that evidence. Although not 
required by law to do so, we had the 2001 risk assessment independently 
peer-reviewed, published the evidence and tentative conclusions for 
public comment, and incorporated the reviewers' recommendations. We 
were open to considering any new scientific data relating to the risk 
assessment. Commenters were encouraged in the instant rulemaking to 
submit new scientific data related to the health risk from exposure to 
DPM. Some commenters did submit new evidence and we have included those 
documents in the record for consideration.
    Other commenters stated that we need to stay the interim and final 
limits and wait for completion of the NIOSH/NCI Study. They believe 
that any regulatory effort before the completion of the study is not in 
compliance with the DOL Guidelines that define influential information: 
``In rulemaking, influential information is scientific, financial, or 
statistical information that the agency believes will have a clear and 
substantial impact on the resolution of one or more key issues in an 
economically significant rulemaking, as that term is defined in section 
3(f)(1) of Executive Order 12866 (DOL Guidelines, p. 6).''
    We have a statutory obligation to consider in a rulemaking the best 
available evidence. (Section 101(a)(6)(A)). Though the NIOSH/NCI Study 
is ongoing, at this time, we are confident that the current rulemaking 
record includes credible scientific data to establish occupational 
exposure limits for DPM. The scientific basis for the health risk of 
exposure to DPM is supported by the rulemaking record in both the 2001 
and 2005 rules. We will continue to closely monitor the progress of the 
NIOSH/NCI joint study, and when the results of this study become 
available, we will carefully consider them.
    Commenters stated that our statement that TC cannot be measured 
accurately and our change to a new surrogate, EC, undermines our 2001 
justifications for our diesel rules, including the exposure limits. 
They reasoned that we regulated TC, and that we based our 2001 
determinations of risk, benefits, impacts and feasibility on TC as a 
surrogate for DPM. In response, our rules limit miners' exposures to 
DPM, not to TC. TC was chosen as the surrogate for measuring that 
exposure in the 2001 final rule. In concert with the Second Partial 
Settlement Agreement, we proposed in 2003 to ``[r]evise the existing 
diesel particulate matter (DPM) interim concentration limit measured by 
total carbon (TC) to a comparable permissible exposure limit (PEL) 
measured by elemental carbon (EC) which renders a more accurate DPM 
exposure measurement.'' (68 FR 48668). As proposed, our 2005 final rule 
(70 FR 32868) establishes the measurement of DPM using EC as a direct 
measure of total DPM. The 2001 risk assessment establishes a material 
impairment of health or functional capacity to miners from exposure to 
DPM and does not distinguish between adverse health effects specific to 
either the EC or OC fractions of DPM. The measurement of that exposure, 
whether using TC, EC or OC as a surrogate, is not related to the 
material impairment of health endpoints identified in the 2001 risk 
assessment and in subsequent literature updates. Our discussion in 
Section VIII.A. of this preamble of the variability of the EC:TC ratio 
addresses total adverse health risks of DPM. The analysis of the EC:TC 
ratio is presented in that section, and in the preamble to our 2005 
final rule (70 FR 32894-32899). The 2001 risk assessment discusses 
possible mechanisms of carcinogenesis for which both EC and OC would be 
relevant factors (66 FR at 5811-5822). Multiple routes of 
carcinogenesis may operate in human lungs, some requiring only the 
various organic mutagens in DPM and others involving induction of free 
radicals regardless of whether the source is the EC fraction, OC 
fraction, some other unidentified component, or a combination of 
components. We recognize that identifying the toxic components of DPM, 
and particulate matter in general, is an important research focus of a 
variety of government agencies and scientific organizations (see, for 
example: Health Effects Institute, 2003; Environmental Protection 
Agency, 2004b).
    We are still considering various alternatives for converting the 
350TC [mu]g/m\3\ and 160TC [mu]g/m\3\ final 
limits to commensurate EC limits. We will consider all comments in this 
rulemaking record concerning the relationship between EC, OC and TC in 
a separate rulemaking to determine the most appropriate conversion of 
the final TC limits. Presently, we believe that the DPM rulemaking 
record is inadequate for us to make determinations regarding a more 
appropriate conversion factor other than 1.3 for the 350TC 
[mu]g/m\3\ final PEL.
    Some commenters suggested that the data used in the 31-Mine Study 
and the analytical method used (NIOSH Method 5040) should be subjected 
to peer review. However, MSHA, organized labor, and the mining 
industry, through the negotiations process, jointly developed the 
protocol for conducting the 31-Mine Study. All of the parties agreed on 
the protocol following numerous discussions among industry, labor, and 
government experts, and had an opportunity to comment and make changes 
to the document. Thereafter, we conducted the study, following the 
agreed upon protocol, and published its results. Industry was given an 
opportunity to publish their separate results simultaneously with the 
government. During this rulemaking, industry submitted to us through 
the notice and comment process their conclusions on the 31-Mine Study 
in a report titled, ``Technical and Economic Feasibility of DPM 
Regulations.'' The industry report is contained in the rulemaking 
record, and we considered it in reaching determinations for the 2005 
final rule. We have been transparent about the design of the study and 
methods of analysis.
    Commenters also stated that we disseminated information that relies 
on non-representative sampling and is therefore in violation of the 
Information Quality Guidelines. The information they refer to was 
obtained in the previously discussed 31-Mine Study and also during our 
baseline sampling. Under the Second Partial DPM Settlement Agreement, 
we agreed to provide compliance assistance to the M/NM underground 
mining industry for a one-year period from July 20, 2002 through July 
19, 2003. As part of our compliance assistance activities, we agreed to 
conduct baseline sampling of miners' personal exposures at every 
underground mine covered by the 2001 final rule.
    A total of 1,194 valid baseline samples were collected. A total of 
183 underground M/NM mines are represented by this analysis. We used 
the results of this sampling in our preamble to the 2005 final rule to 
estimate current DPM exposure levels in underground M/NM mines using 
diesel equipment (70 FR 32873-32883) and in the risk assessment for 
this final rule. The sampling results also assist mine operators in 
developing compliance strategies based on actual exposure levels. Most 
commodities were well represented in this analysis with the average 
number of valid samples per mine ranging from 6.0 to 8.2 (average

[[Page 29002]]

across all mines is 6.5 samples per mine).
    MSHA compliance specialists collected baseline samples in the same 
manner they have been instructed to use for collecting samples for 
enforcement purposes. It is expected that personal exposure to DPM will 
fluctuate due to variations in day to day operations in a mine. 
Reported levels of DPM are representative of the exposures of miners 
identified as having the highest risks of overexposures to DPM during 
our compliance assistance work. In an ideal situation, and with 
unlimited resources, every potentially exposed miner would be 
individually sampled. It is not necessary or practical, however, to 
sample all miners on a mine property in order to evaluate personal 
exposures. Suspected and potential health hazards may be reasonably and 
adequately evaluated by sampling the maximum risk miner in a work area. 
Compliance specialists strive to characterize the higher exposure 
levels during typical work shifts. The baseline samples are 
representative of the conditions experienced on work shifts during the 
defined compliance assistance period. MSHA has obtained the best 
available information for characterizing recent activities at the 
relevant M/NM mines.
    Commenters questioned the accuracy and validity of the NIOSH 
Analytical Method 5040. NIOSH validation criteria state that the NIOSH 
Analytical Method 5040 provides a result that differs no more than 
25% from the true value 95 times out of 100. The NIOSH 
Analytical Method 5040 validation is documented in several 
publications. See our discussion of this in Section VIII.A. of this 
preamble for additional peer-reviewed studies providing evidence that 
the NIOSH Analytical Method 5040 method is valid. In a study published 
by Noll, et al., in January 2005 evaluating sampling results of DPM 
cassettes, the authors report a 95% upper confidence limit Coefficient 
of Variation (CV) of 7% when analyzing samples for EC and 6% for TC. In 
this same study, NIOSH reported good agreement and precision between EC 
for DPM samples using SKC impactor and respirable samples in both 
laboratory and field studies. Two studies published in 2004 (Noll, et 
al., 2004 and Birch, et al., 2004) reported results from investigating 
sampling for EC in the presence of coal dust using submicron impactors. 
The results show good agreement between submicron EC and respirable 
samplers for collecting DPM samples.
    Commenters also stated that we calculated the error factors for our 
analytical method assuming no related methodological inaccuracies. We 
develop method-specific error factors to assure that a personal 
exposure result is more than likely to represent an overexposure. These 
error factors account for normal and expected variability inherent in 
any analytic method and sampling protocol and provide a basis for 
interpretation of sampling results. When we interpret sampling results 
and make a determination of compliance, we apply the error factor to 
the result to gauge whether the sample indicates a true overexposure. 
We use the validated NIOSH Analytical Method 5040 for diesel 
particulate matter to analyze our personal exposure samples collected 
for compliance determinations.
    The NIOSH criteria and guidelines used for method validation do not 
directly apply to the development of error factors. However, similar 
statistical procedures to develop analytical methods can also be used 
to develop error factors. The commenters fail to recognize other 
differences between validation of methods and development of error 
factors. We discuss our error factor in detail in Section VIII.A. of 
this preamble.
    Commenters further questioned whether the NIOSH Method 5040 has 
been commercially tested. As in the preamble to the 2003 NPRM, we 
discussed in detail our findings regarding the NIOSH Method 5040 in the 
31-Mine Study discussion in the preamble to the 2005 final rule (70 FR 
32870-32871) and in Section VIII of this preamble. NIOSH's peer review 
of the 31-Mine Study also concludes that the analytical method 
specified by the diesel standard gives an accurate measure of the TC 
content of a filter sample and that the analytical method is 
appropriate for making compliance determinations of DPM exposures of 
underground M/NM miners. NIOSH confirmed this position by letter of 
February 8, 2002, in which NIOSH stated that,

    MSHA is following the procedures of NIOSH Method 5040, based on 
our review of MSHA P13 (MSHA's protocol for sample analysis by NIOSH 
Method 5040) and a visit to the MSHA laboratory.

    Commenters stated that MSHA's former chairman of the DPM Rulemaking 
Committee had a conflict of interest as he was also author of the ACGIH 
diesel TLV. In response, our 2001 final rule includes the basis for our 
interim limit of 400TC [mu]g/m\3\ and final limit of 
160TC [mu]g/m\3\, and states the following:

    Because of the lack of a generally accepted dose-response 
relationship, some commenters questioned the agency's rationale in 
picking a particular concentration limit: 160TC [mu]g/
m\3\ or around 200DPM [mu]g/m\3\. Capping DPM 
concentrations at this level will eliminate the worst mining 
exposures, and bring miner exposures down to a level commensurate 
with those reported for other groups of workers who use diesel-
powered equipment. The proposed rule would not bring concentrations 
down as far as the proposed ACGIH TLV\R\ of 150DPM [mu]g/
m\3\. Nor does MSHA's risk assessment suggest that the proposed rule 
would completely eliminate the significant risks to miners of DPM 
exposure.
    In setting the concentration limit at this particular value, the 
Agency is acting in accord with its statutory obligation to attain 
the highest degree of safety and health protection for miners that 
is feasible. The Agency's risk assessment supports reduction of DPM 
to the lowest level possible. But feasibility considerations 
dictated proposing a concentration limit that does not completely 
eliminate the significant risks that DPM exposure poses to miners.
    The Agency specifically explored the implications of requiring 
mines in this sector to comply with a lower concentration limit than 
that being adopted. The results, discussed in Part V of this 
preamble, indicate that although the matter is not free from 
question, it still may not be feasible at this time for the 
underground metal and nonmetal mining industry as a whole to comply 
with a significantly lower limit than that being adopted. The Agency 
notes that since this rulemaking was initiated, the efficiency of 
hot gas filters has improved significantly, the dpm emissions from 
new engines continue to decline under EPA requirements, and the 
availability of ultra-low sulfur fuel should make controls even more 
efficient than at present.
    The Agency also explored the idea of bridging the gap between 
risk and feasibility by establishing an ``action level''. In the 
case of MSHA's noise rule, for example, MSHA adopted a ``permissible 
exposure level'' of a time-weighted 8-hour average (TWA8) 
of 90 dBA (decibels, A-weighted), and an ``action level'' of half 
that amount--a TWA8 of 85 dBA. In that case, MSHA 
determined that miners are at significant risk of material harm at a 
TWA8 of 85 dBA, but technological and feasibility 
considerations preclude the industry as a whole, at this time, below 
a TWA8 of 90 dBA. Accordingly, to limit miner exposure to 
noise at or above a TWA8 of 85 dBA, MSHA requires that 
mine operators must take certain actions that are feasible (e.g., 
provide hearing protectors).
    MSHA considered the establishment of a similar ``action level'' 
for DPM-- probably at half the proposed concentration limit, or 
80TC [mu]g/m\3\. Under such an approach, mine operators 
whose DPM concentrations are above the ``action level'' would be 
required to implement a series of ``best practices''--e.g., limits 
on fuel types, idling, and engine maintenance. Only one commenter 
supported the creation of an Action Level for DPM. However, this 
commenter suggested that such an Action Level be adopted in lieu of 
a rule incorporating a concentration limit requiring mandatory 
compliance. The

[[Page 29003]]

Agency determined it is feasible for the entire underground mining 
community to implement these best practices to minimize the risks of 
DPM exposure without the need for a trigger at an Action Level (66 
FR 5710).

Consequently, MSHA did not rely on data from ACGIH in establishing its 
2001 final rule.
    Commenters leveled several other criticisms at the Estimator and 
the 31-Mine Study which they believe violate Data Quality Act 
requirements and invalidate our conclusions regarding the feasibility 
of the 2001 and 2005 final rules. The computer program in question, 
referred to as the Estimator, is a Microsoft[supreg] Excel spreadsheet 
program that calculates the reduction in DPM concentration that can be 
obtained within an area of a mine by implementing individual or 
combinations of engineering controls. This program was the subject of a 
Preprint published for the 1998 Society of Mining Engineers Annual 
Meeting (Preprint 98-146, March 1998), and it was fully described in a 
peer reviewed article in a professional journal (Haney and Saseen, 
Mining Engineering, April 2000).
    Commenters objected to the use of input data for the Estimator 
which they characterized as ``assumed ventilation air flows that do not 
reflect reality or actual MSHA measurements,'' and ``assumptions 
regarding perfect mixing of ventilation air to achieve dilution of 
exhaust particulate,'' which they further characterized as ``another 
assumption that does not reflect reality or actual measurements.'' The 
commenters stated that these failures are violations of the Data 
Quality Act's reproducibility and transparency requirements, and that 
MSHA admitted to these failures in the preamble to the 2005 final rule.
    Regarding the use of ``assumed ventilation flows that do not 
reflect reality,'' all data used in Estimator analysis for the 31-Mine 
Study were obtained by MSHA M/NM industrial hygienists or Health 
Specialists. The ventilation inputs were either measured or estimated 
by these MSHA personnel. As stated in the final report of the 31-Mine 
Study, ``Each mine was evaluated individually, based on the DPM 
concentration data obtained for that mine through sampling, coupled 
with the mine-specific equipment, operating practices, and ventilation 
observed at that mine.''
    Of the 31 mines addressed in the study, ventilation changes were 
specified for only five, and those changes were limited to auxiliary 
ventilation systems only. This fact is very important because when 
using the ``Column A'' option of the Estimator, which was the only 
option used in the 31-Mine study, if ventilation changes are not 
specified, the prevailing ventilation in a given area of the mine is 
irrelevant to Estimator analysis. The engineering rationale for this 
effect was explained thoroughly in the final report for the 31-Mine 
Study (p. 96):

    It is significant to note that when ventilation remains the same 
before and after DPM controls are specified in the Estimator (i.e. 
the DPM control chosen was not a change in ventilation), the actual 
ventilation value used is irrelevant. This characteristic of the 
Estimator applies to any mine ventilation scheme, but it is 
particularly important where ventilation velocity is low, and 
ventilation flow is difficult to accurately measure. Mine 
ventilation velocity is very low in large parts of many room and 
pillar mines with large cross-section mine openings. This situation 
suggests two possible problems with DPM measurement--difficulty 
measuring mine airflow rates, and non-homogeneous mixtures of DPM in 
mine air. DPM concentrations in the ambient air at these mines can 
be profoundly affected by near-stagnant conditions in some areas, as 
well as by localized air movement that is independent of the overall 
mine ventilation flow. Such localized air movement can result from 
pressure differences created by wind from moving vehicles, natural 
ventilation, diesel engine cooling fans, heat-induced 
stratification, etc. In these situations, perfect mixing of mine air 
with DPM emissions would not be expected, hence, the DPM 
concentration in ambient mine air could not be reasonably estimated 
by simply dividing the DPM emission rate by the ventilation flow 
rate.
    In its Column A option, the Estimator does not calculate DPM 
concentration by dividing the DPM emission rate by the ventilation 
flow rate. Thus, in MSHA's view, neither the difficulty of measuring 
airflow nor the imperfect mixing of DPM and mine air is important. 
The Estimator accounts for complex and imperfect mixing of 
ventilation air and DPM emissions by assuming that this mixing, in 
whatever manner it occurs when DPM samples are initially collected, 
would remain unchanged after DPM controls are implemented. MSHA 
considers this to be a reasonable assumption unless the DPM control 
that is specified is itself a major ventilation change. Since 
ventilation changes were not specified for any of the mines where 
complex and imperfect mixing was likely to occur, MSHA considers it 
reasonable to estimate a final DPM concentration at these mines 
based on applying a proportionality factor to the DPM concentration 
originally measured. The proportionality factor is simply the ratio 
of the DPM emission rate after controls are implemented to the DPM 
emission rate before controls are implemented, and is independent of 
the actual airflow present at that location. Although the Estimator 
makes simplifying assumptions, MSHA considers its results reasonably 
accurate. The Estimator's calculations have been compared to actual 
in-mine data, and good agreement has been achieved.

    The differences between the Estimator's user-selectable ``Column 
A'' and ``Column B'' options are addressed in Section V.A of this 
preamble and previously were thoroughly discussed in the preamble to 
the 2005 final rule (70 FR 32920):

    The Estimator actually incorporates two independent means of 
calculating DPM levels: one based on DPM sampling data for the 
subject mine, and one based on the absence of such sampling data. 
Where no sampling data exist, the Estimator calculates DPM levels 
based on a straightforward mathematical ratio of DPM emitted from 
the tailpipe (or DPF, in the case of filtered exhaust) per volume of 
ventilation air flow over that piece of equipment. This is referred 
to in the Estimator as the ``Column B'' option for calculating DPM 
concentrations. The commenters' observation that the Estimator fails 
to account for imperfect mixing between DPM emissions and 
ventilating air flows is a valid criticism of the ``Column B'' 
option. For this and other reasons, the Estimator's instructions 
urge users to utilize the ``Column A'' option whenever sampling data 
are available.''
    In the ``Column A'' option, the Estimator's calculations are 
``calibrated'' to actual sampling data. Whatever complex mixing 
between DPM emissions and ventilating air flows existed when DPM 
samples were obtained, are assumed to prevail after implementation 
of a DPM control. This is an entirely reasonable assumption, and in 
fact, there is no engineering basis to assume otherwise. Indeed, 
comparisons of ``Column A'' Estimator calculations and actual DPM 
measurements taken in mines before and after implementation of DPM 
controls have shown good agreement, indicating that Estimator 
calculations do adequately incorporate consideration for complex 
mixing of DPM and air flows when the ``Column A'' option is used. 
The Estimator was originally developed with both the Column A and 
Column B options because at the time it was developed (1997), the 
specialized equipment required for reliable and accurate in-mine DPM 
sampling, such as the submicron impactor, was not widely available. 
Consequently, few mine operators were able to obtain the in-mine DPM 
sample data required for utilizing the Column A option.

    The commenter refers to the ``Column A option'' as an alternative 
use of the Estimator. However, we have always recommended that the 
Column A option be used if sampling data are available. As noted above 
in the excerpt from the 31-Mine Study, we explained fully at the time 
the study was released in January 2003 exactly how the Estimator was 
used in that study, and we also explained its use in the preamble to 
the June 2005 final rule. The commenter states that the sample data 
used in Estimator analysis were ``non-representative of routine mining 
conditions that can vary greatly at each mine from day to day, and from 
mine

[[Page 29004]]

to mine throughout the industry.'' However, we stated in the 31-Mine 
Study final report that we followed standard MSHA enforcement sampling 
procedures to obtain the DPM samples at the 31 mines. These procedures 
are public information, and were well known by the labor and industry 
representatives that collaborated on the study protocol.
    Regarding the question of whether the data obtained in the 31-Mine 
Study were representative of the industry as a whole, the mines in the 
study were jointly selected by MSHA, labor, and industry 
representatives. A reasonable attempt was made to achieve a cross-
section of the industry in terms of commodities and mine sizes. The 
MSHA, labor, and industry personnel who collaborated on the study 
protocol were all fully aware at that time that the study was never 
intended to be statistically representative of the industry as a whole, 
and this fact was explicitly stated in the 31-Mine Study final report.
    The commenter suggests that the study is ``suspect'' because 25% of 
the samples were voided. As was explained in the 31-Mine Study final 
report, of the 464 samples obtained at the 31 mines, 106 were voided. A 
key consideration in the sampling conducted at the 31 mines was to 
ensure, to the extent possible, that samples were not contaminated by 
non-diesel sources of airborne carbon. Testing had verified that the 
submicron sampler would remove mineral dust contamination (limestone, 
graphite, etc.), but tobacco smoke, drill oil mist, and possibly vapors 
from ANFO loading could contaminate a sample filter with non-diesel 
organic carbon. Thus, in accordance with the study protocol that had 
been jointly developed and approved by both us and the litigants, any 
sample that was known to have been, or could potentially have been 
contaminated with such an interferent was voided. Of the 106 voided 
samples, 61 were voided due to interferences. There were also some 
samples that were voided for other reasons, such as laboratory error (2 
samples), sample pump failure (22 samples), or incomplete sample or 
sampling the wrong location (21 samples). Including any of these 106 
voided samples in the data analysis would have cast doubt on the 
validity of the study. The study methodology that resulted in voiding 
questionable samples was part of the mutually agreed upon study 
protocol, the rationale for voiding these samples was well known and 
supported by all parties, and it was fully explained in the study final 
report.
    For 26 of the 31 mines, ventilation flow rates did not factor into 
Estimator analysis because, as explained above, they were not relevant 
to the computations. For the remaining five mines, we continue to 
believe our estimates of ventilation flow rates were sufficiently 
accurate for the purposes of the study. Both our methods and data 
sources were explained thoroughly and we have responded previously on 
the record to these same criticisms of the Estimator.
    Some commenters questioned the quality of reports of MSHA's 
compliance assistance work at mines covered under the standard, and 
requested that they be stricken from the rulemaking record because 
these studies were conducted without an apparent protocol or 
independent peer review. Also, commenters stated that these studies 
have not been published nor submitted for publication in any scientific 
journal. In response, the compliance assistance reports in the DPM 
rulemaking record are not intended for publication in a scientific 
journal, but instead, are accounts of our experiences at mines where 
mine operators requested help from MSHA in reducing DPM exposures. 
Under the second partial DPM settlement agreement, MSHA agreed to 
provide compliance assistance at underground mining operations using 
diesel-powered equipment from July 20, 2002 through July 19, 2003.
    The Technological Feasibility section of this preamble, Section 
V.A, discusses the information and data related to feasible engineering 
and administrative controls currently available for the mining industry 
as a whole. Mines have implemented many of these DPM controls to meet 
the interim DPM limit as shown by our enforcement sampling. As further 
discussed in that section, we expect the industry as a whole will 
continue to learn more about the available control technologies and 
implement these control strategies in order to meet the final limits 
specified in this final rule. We recognized that implementation issues 
were making it difficult for some mines to use DPFs and obtain 
alternative fuels such as biodiesel. The extension of time allowed by 
this final rule was justified due to the greater availability of 
biodiesel fuels, the variety of DPF systems available, and the cleaner 
on-highway diesel engines that are becoming available.
    The data presented in the Feasibility sections of this rulemaking 
support the feasibility of the various DPM control technologies. This 
data were derived from sources such as NIOSH, MSHA, and the Biodiesel 
Board. The NIOSH work provided mine operators with data that showed 
expected DPM reductions in a diesel laboratory, an isolated zone, and 
in production areas. The expected reductions were presented to assist 
mine operators with choosing DPM controls for implementation in their 
mines. We discussed information on DPFs that can achieve EC reductions 
above 90% and informed mine operators of other products that gave very 
minimal reductions. This was done to give mine operators the ability to 
choose a single control or combination of controls that would be 
technologically and economically feasible and appropriate for their 
particular situation to implement in order to meet the interim limit 
and the final limits specified in this final rule.
    All of the data collected during the 31-Mine Study and subsequent 
studies performed by NIOSH were gathered using transparent methods, 
with protocols agreed upon by industry and union representatives. NIOSH 
performed extensive isolated zone studies that were developed and 
performed through the M/NM Diesel Partnership (the Partnership). 
NIOSH's reports were reviewed by the industry and revised based on 
comments in the record. Our compliance assistance work discussed 
previously in this section and the data obtained from those studies 
were developed with industry assistance.
    The commenters state that our feasibility determinations for 
individual mines and for the industry were based in part on the results 
of Estimator analysis that calculated compliant DPM concentrations 
after installation of DPM filters, thus demonstrating that such filters 
could be used by mine operators to attain compliance with the interim 
and final DPM limits. The commenters object to the use of the Estimator 
for this purpose because they believe such filters did not exist. They 
charge that since appropriate filters did not exist, the methodology 
for our feasibility determination failed to meet our Data Quality 
requirements.
    We disagree with the commenter's statement that our, ``assumptions 
[regarding the availability of filters] do not reflect reality.'' We 
have provided extensive discussion throughout the rulemaking record 
supporting our position that diesel particulate filters suitable for 
any size diesel engine were commercially available at the time the 2001 
final rule was issued, and that a greater variety of such filters have 
become commercially available since 2001. The commenter states that we 
were, ``forced to admit'' in the 2005 final rule that there was 
``insufficient

[[Page 29005]]

evidence of feasibility,'' thus contradicting the Estimator and 31-Mine 
Study feasibility determinations. The sentence from the preamble to the 
2005 final rule quoted by the commenter states, in full, ``MSHA 
acknowledges that the current rulemaking record lacks sufficient 
feasibility documentation to justify lowering the DPM limit below 
308EC [mu]/m\3\, at this time.'' This statement was not 
meant to imply that either the 2001 or 2005 final rule was infeasible, 
and it is irrelevant to the final DPM limit. It states that at that 
time, which was June 2005, we did not believe it was feasible for the 
industry as a whole to achieve DPM levels lower than the interim DPM 
limit, 308EC [mu]/m\3\, which was the DPM limit in effect at 
that time.
    The commenter stated that our explanation for many filter failures 
reported by Stillwater and other companies was that the user or the 
manufacturer was at fault, and that if MSHA had selected the filters, 
we would have selected or used them differently. We have extensively 
discussed in our preambles in this rulemaking record that the user of a 
DPF must evaluate and monitor each application in order to verify that 
the DPF is working properly at all times. We have continually stated 
that the majority of the DPF failures that have been reported have been 
related to DPF regeneration. We believe that better choices in 
selection and maintenance of DPFs would result in greater successes. 
However, these regeneration issues are not related to the capability of 
DPFs to effectively collect DPM. All of the data that we have presented 
on DPFs show that DPFs effectively collect DPM. Tests that were 
performed in the mining industry have consistently supported the same 
conclusions and agree with data given in the literature. Again, the 
failure of the regeneration scheme is the main cause of a clogged 
filter. The proper selection of DPFs has been discussed in the 
literature, and NIOSH's Filter Selection Guide extensively provides the 
information needed for selection.
    The commenter also discusses the NO2 issues related to 
DPFs. The data presented from studies show that catalyzed DPFs can 
increase NO2. This data have been developed with the 
Partnership. However, we continue to believe that the NO2 
problems reported have been ventilation issues and not specifically a 
DPF issue. In fact, as discussed in the Technological Feasibility 
section, NIOSH stated that NO2 elevations experienced were a 
result of poorly or marginally ventilated areas. Our data from the 
Greens Creek study that were developed and reviewed with industry 
showed no NO2 issues on production machines in well 
ventilated areas.
    Commenters raised several Data Quality issues relating to our 
determinations that the 2001 and 2005 final rules were economically 
feasible. They include whether the data used to make these 
determinations were representative of the industry, that industry 
annual revenue is an inappropriate measure of economic feasibility, 
that erroneous commodity prices were used in the 31-Mine Study to 
estimate revenue for at least one of the mines in the study, and that 
the 31-Mine Study incorrectly assumed that none of the mines in the 
study required major ventilation upgrades. They believe our economic 
feasibility conclusions were based on improper sampling, and inaccurate 
and incomplete data.
    Each of these issues is discussed in detail in the Economic 
Feasibility section of this preamble. The key information from that 
section that relates to commenters' Data Quality concerns is summarized 
here. Regarding the first issue, that the subject mines in the 31-Mine 
study were not representative of the industry, this issue has already 
been addressed above. MSHA, labor, and industry collaborated on the 
study design, and all parties were aware at the time that the study 
mines were not randomly selected. Thus, the study results would 
reasonably accurately reflect feasibility of the subject mines, but 
would not be statistically representative of the industry as a whole. 
The entire process was transparent, reproducible, and based on valid 
assumptions and sound methods.
    Regarding the second issue of whether industry annual revenue is an 
inappropriate measure of economic feasibility, commenters indicated 
that this method ignores the fact that international commodity markets 
determine the viability of mines by setting market prices for their 
production, and that annual revenues of hundreds of millions, if not 
billions, of dollars have not prevented the domestic underground M/NM 
mining industry from shrinking in recent years.
    We believe that the method we used to determine economic 
feasibility is valid. We have customarily used compliance costs of 
greater than 1% of industry annual revenue as our screening benchmark 
for determining whether a more detailed economic feasibility analysis 
is required. The commenter correctly points out that despite hundreds 
of millions, if not billions, of dollars of industry annual revenue, 
business failures can and do occur, and over a period of decades, the 
characteristics of an industry can change markedly. However, by 
utilizing the 1% of annual revenue screening benchmark, we assure that 
a complete feasibility analysis will be conducted to determine whether 
a new MSHA rule could potentially affect the viability of an industry.
    While it is true that individual business failures can and do 
occur, and that over a period of many years, substantial portions of a 
domestic industry can be adversely affected by, for example, 
international competition, it is highly improbable that such events 
would be set into motion by a rule imposing costs equal to or less than 
1% of industry annual revenue. Threats to an entire industry's 
competitive structure and resulting large scale dislocations within an 
industry sector are typically caused by fundamental changes in 
technology, permanent downward pressure on demand for a commodity due, 
for example, to the introduction of a superior substitute material, 
world-wide or regional business cycles, etc. Our practice of utilizing 
compliance costs of greater than 1% of industry annual revenue as our 
screening benchmark for determining whether a more detailed economic 
feasibility analysis is required is reproducible and transparent, and 
is based on reasonable assumptions and sound economic principles.
    The third issue raised by the commenter relating to economic 
feasibility was that erroneous commodity prices were used to estimate 
annual revenue for one of the mines in the 31-Mine Study. The commenter 
states that our revenue estimates suggest we used a price of $50 to $70 
per ton for rock salt for highway de-icing, when a more reasonable 
estimate would have been $20 to $25 per ton.
    The commenter did not explain how they inferred a $50 to $70 per 
ton price for rock salt from our analysis, so we are unable to respond 
directly to this comment. However, we did not base our economic 
feasibility determination for the subject mine on this inflated price 
for rock salt. For the 31-Mine Study, we did not have access to actual 
annual revenue data for any of the 31 individual mines in the study, so 
we indirectly estimated annual revenues using our data on the number of 
employee work hours in 2000 for each mine, the total number of employee 
work hours reported to us in 2000 by all mines producing that 
commodity, and data from the U.S. Geological Survey on the industry-
wide value of mineral

[[Page 29006]]

production by commodity for the year 2000. We estimated annual revenues 
for a particular mine by determining the industry-wide production value 
per employee hour for the specific commodity each mine produced, and 
multiplying that amount by the number of annual employee work hours 
reported to us for that mine. This methodology assumes that each mine's 
annual revenues would be roughly proportional to each mine's share of 
the industry's total employee work hours. Thus, our estimates, while 
not necessarily exact for each mine, were a reasonable approximation 
for those mines based on industry averages. Our analytical methods and 
data sources were fully explained in the final report to the 31-Mine 
Study. The process was transparent and reproducible, and the method was 
sound. This methodology does not explicitly incorporate a cost per ton 
factor. Implicit in this methodology, based on the U.S. Geological 
Survey's estimates of rock salt production in 2000 of 45,600,000 metric 
tons valued at $1,000,000,000, would be a cost per metric ton of $21.93 
(equivalent to $19.89 per short ton), which is actually slightly less 
than the commenter's estimated price of $20 to $25 per short ton.
    The final issue relating to economic feasibility raised by the 
commenter also concerns the 31-Mine Study. The commenter suggests that 
our methodology underestimated compliance costs by failing to recommend 
major ventilation upgrades for any mine in the study. They point out 
that a total of only $234,000 was recommended in the study for minor 
ventilation upgrades, whereas the operator of one of the mines in the 
study estimated at least $4.4 million in ventilation upgrades would be 
required at that mine alone to attain compliance.
    In response to a similar comment on our 2003 NPRM, we noted in the 
preamble to the 2005 final rule that we did not specify any major 
ventilation upgrades in the 31-Mine Study because, based on the study 
methodology, the analysis did not indicate the need for major 
ventilation upgrades in order to attain compliance with either the 
interim or final DPM limits at any of the 31 mines. We went on to 
explain that the purpose of specifying controls for each mine in this 
study was simply to demonstrate that feasible controls capable of 
attaining compliance existed, and to provide a framework for costing 
such controls on a mine-by-mine basis. We explicitly stated in the 31-
Mine study final report that the DPM controls specified for a 
particular mine did not necessarily represent the only feasible control 
strategy, or the optimal control strategy for that mine.
    The fact that the operator of one of the mines in the study 
estimated costs of $4.4 million for ventilation upgrades to attain 
compliance with the rule does not invalidate the methodology we used, 
or the results we obtained in the 31-Mine study. It is impossible for 
us to verify whether $4.4 million for ventilation upgrades is a 
reasonable estimate for the subject mine because we don't know which 
mine the commenter is referring to, and no additional supporting 
documentation was provided by the commenter. However, even if this 
figure is accurate, it would not necessarily invalidate our methodology 
or results. We have received numerous comments throughout the 
rulemaking process that ventilation upgrades alone would not be a cost-
effective DPM control at many mines. These comments support our 
position that mine operators need to carefully analyze all DPM control 
options in order to select the most cost-effective control or 
combination of controls to implement at a particular mine. Although a 
$4.4 million ventilation upgrade may be required to attain compliance 
at the subject mine, if ventilation alone was used to attain 
compliance, it is more likely that compliance could be achieved at this 
mine at a lower cost if an optimal combination of controls were 
implemented, including low DPM-emission engines, environmental cabs 
with filtered breathing air, DPM filters, alternative fuels such as 
biodiesel, work practices and administrative controls, as well as 
ventilation.
    With respect to ventilation upgrades for the 31 mines, the study 
methodology and the sources of all data we used in performing the 
feasibility analyses were thoroughly explained in the 31-Mine Study 
final report. The process was transparent and reproducible, and the 
study protocol was developed jointly by MSHA, labor, and industry 
representatives.

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Barrick Goldstrike Mines, Inc., Carlin, Nevada, PS&HTC-DD-03-337, 
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Black River Mine, Carmeuse Lime and Stone, Inc., Butler, Kentucky, 
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March 18 and 19, 2003, April 8 and 9, 2003, and April 29 and 30, 
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Black River Mine, Carmeuse Lime and Stone, Inc., Butler, Pendleton 
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Blue Rapids Mine, Blue Rapids, Kansas, Georgia-Pacific Gypsum 
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Burning Springs Mine, Martin Marietta Materials Inc., Wood County, 
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Carlin East Mine, Newmont Mining Corporation, Carlin, Nevada, Diesel 
Particulate Matter Compliance Assistance Visit on September 14, 
2004; dated October 19, 2004.
Clover Bottom Mine, M.A. Walker, LLC, Clover Bottom, Kentucky, July 
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Durham Mine, Martin Marietta Aggregates, Inc., Marion County, Iowa, 
PS&HTC-DD-04-423, Diesel Particulate Concentrations from Diesel 
Particulate Matter Studies, April 6 and 7, 2004 and May 25 and 26, 
2004; dated August 19, 2004.
Durham Mine, Martin Marietta Materials, Inc., Harvey, Marion County, 
Iowa, PS&HTC-DD-06-606. Diesel Particulate Matter Study on December 
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Fletcher Mine, The Doe Run Company, Viburnum, Missouri, Compliance 
Assistance Visit, July 8, 2003; dated September 4, 2003.
Georgetown Mine, Nally and Gibson, Georgetown, Kentucky, Compliance

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Assistance Visit, May 7, 2003; dated August 15, 2003.
Governeur Talc Company, Inc., No. 4 Mine, Lewis County, New York, 
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dated July 3, 2003.
Greens Creek Mine, Kennecott Minerals, Juneau, Alaska, January 22-
30, 2003; dated June 17, 2003.
Greer Limestone Mine, Greer Limestone Company, Monongalia County, 
WV, Diesel Particulate Compliance Assistance Survey, September 16, 
2003; dated December 2, 2003.
Hampton Corners Mine, American Rock Salt Company LLC, Livingston 
County, New York, Diesel Particulate Compliance Assistance Survey, 
March 23 and 24, 2004; dated May 14, 2004.
Hampton Corners Mine, Martin Marietta Materials, Inc., Livingston 
County, New York, PS&HTC-DD-04-422, Environmental Diesel Particulate 
Matter Investigation, March 23 and 24, 2004.
Hampton Corners Mine, American Rock Salt Company LLC, Livingston 
County, New York, Diesel Particulate Compliance Assistance Survey, 
September 1, 2004; dated September 23, 2004.
Independence Mine, Rocca Processing, LLC, Independence, Missouri, 
Diesel Particulate Compliance Assistance Survey, June 25, 2003; 
dated July 3, 2003.
Inland Quarries, Americold Logistics, LLC, Kansas City, Kansas, 
Diesel Particulate Compliance Assistance Survey, July 17, 2003; 
dated August 15, 2003.
Jefferson County Stone Mine, Rogers Group, Inc., Jefferson County, 
Kentucky, DPM Compliance Assistance Visit, December 12, 2002; dated 
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Jefferson County Stone Mine, Rogers Group, Inc., Jefferson County, 
Kentucky, PS&HTC-DD-03-312, Dust Compliance Assistance Visit to 
evaluate effects of Diesel Equipment Modification, January 28-30, 
2003 and June 9 and 10, 2003; dated September 4, 2003.
Kaylor No. 3 Mine, Brady's Bend Corporation, Armstrong County, 
Pennsylvania, Diesel Particulate Compliance Assistance Survey, 
September 25, 2003; dated October 20, 2003.
Kerford Limestone Mine, Kerford Limestone Company, Weeping Water, 
Nebraska, Diesel Particulate Compliance Assistance Survey, September 
10, 2003; dated October 20, 2003.
Lyons Salt Mine, Lyons Salt Company, Lyons, Kansas, Diesel 
Particulate Compliance Assistance Visit, September 9, 2003; dated 
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M&M Lime Company, Inc. Mine, Worthington, Armstrong County, 
Pennsylvania, Diesel Particulate Compliance Assistance Survey, June 
18, 2003; dated July 3, 2003.
Maysville Mine, Carmeuse North America, Inc., Maysville, Kentucky, 
PS&HTC-DD-03-308, Diesel Particulate Concentrations from Diesel 
Particulate Matter Studies, December 10-12, 2002, January 7-9, 2003, 
and February 4-6, 2003; dated August 29, 2003.
Maysville Mine, Carmeuse North America, Inc., Maysville, Kentucky, 
PS&HTC-DD-03-311, Diesel Particulate Concentrations from Diesel 
Particulate Matter Studies, February 4-6, 2003 and April 1-3, 2003; 
dated August 29, 2003.
Maysville Mine, Carmeuse North America, Inc., Maysville, Kentucky, 
PS&HTC-DD-04-416, Diesel Particulate Concentrations from Diesel 
Particulate Matter Studies, January 6-7, 2004, and February 2-3, 
2004; dated April 2, 2004.
Meikle Mine, Barrick Goldstrike Mines, Inc., Carlin, Nevada, PS&HTC-
DD-05-512, Diesel Particulate Matter Compliance Assistance Visit, 
October 28, 2004; dated November 23, 2004.
Midas Mine, Newmont Midas Operations, Midas, Nevada, PS&HTC-DD-05-
510, Diesel Particulate Matter Compliance Assistance Visit, October 
26, 2004; dated November 23, 2004.
Murray Mine, Queenstake Resources, U.S.A., Inc., Elko, Nevada, 
September 15, 2004; dated October 28, 2004.
Oldham County Stone Mine, Rogers Group, Inc., Oldham County, 
Kentucky, DPM Compliance Assistance Visit, November 20-21, 2002; 
dated February 10, 2003.
Petersburg Mine, East Fairfield Coal Company, Limestone Division, 
Petersburg, Mahoning County, Ohio, PS&HTC-DD-06-602, Diesel 
Particulate Matter Study, September 27, 2005; dated November 30, 
2005.
Randolph Mine, Hunt Midwest Mining, Inc., Diesel Particulate 
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Rock Springs Mine, Liter's Quarry, Inc., Diesel Particulate 
Compliance Assistance Survey, July 9, 2003; dated August 15, 2003.
Stamper Mine, Hunt Midwest Mining, Inc., Platte County, Missouri, 
Diesel Particulate Compliance Assistance Survey, July 15, 2003; 
dated August 15, 2003.
Stillwater Mine, Stillwater Mining Company, Nye, Montana, PS&HTC DD-
04-428, Diesel Particulate Matter Compliance Assistance, June 7-17, 
2004; dated August 6, 2004.
Stone Creek Brick Company Mine, Marsh A C JR Company, Stone Creek, 
Ohio, PS&HTC-DD-03-320, Diesel Particulate Compliance Assistance 
Visit, May 21, 2003; dated August 15, 2003.
Stone Creek Brick Company Mine, Marsh A C JR Company, Stone Creek, 
Ohio, PS&HTC-DD-03-322, Diesel Particulate Concentrations from 
Diesel Particulate Matter Studies, June 10-11, 2003-July 29-30, 
2003; dated August 29, 2003.
Sully Mine, Martin Marietta Materials, Inc., Lynnville, Jasper 
County, Iowa, PS&HTC-DD-06-607, Diesel Particulate Matter Study, 
December 14, 2005; dated February 9, 2006.
Sweetwater Mine, The Doe Run Company, Viburnum, Missouri, Diesel 
Particulate Compliance Assistance Visit, July 9, 2003; dated 
September 4, 2003.
Table Rock 1 Mine, Table Rock Asphalt Construction Company, 
Inc., Taney County, Missouri, Diesel Particulate Compliance 
Assistance Visit, November 18, 2003; dated February 18, 2004.
Table Rock 3 Mine, Table Rock Asphalt Construction Company, 
Inc., Stone County, Missouri, Diesel Particulate Compliance 
Assistance Visit, November 19, 2003; dated February 18, 2004.
Torrance Mine, Hanson Aggregates PMA, Inc., Torrance, Westmoreland 
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Turquoise Ridge Mine, Placer Turquoise Ridge, Inc., Golconda, 
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Weeping Water Mine, Martin Marietta Aggregates, Diesel Compliance 
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Winfield Lime and Stone Company, Inc., Cabot, Butler County, 
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CDC National Toxicology Program (NTP) Report on Carcinogens for 2002 
(Report on Carcinogens, Tenth Edition; December 2002).
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Disease Control (CDC), National Institute of Occupational Safety and 
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XV. Regulatory Text

List of Subjects in 30 CFR Part 57

    Diesel particulate matter, Metal and nonmetal, Mine safety and 
health, Underground miners.

    Dated: May 9, 2006.
Robert M. Friend,
Acting Deputy Assistant Secretary of Labor for Mine Safety and Health.

0
For reasons discussed in the preamble, MSHA amends 30 CFR part 57 as 
follows:

PART 57--SAFETY AND HEALTH STANDARDS--UNDERGROUND METAL AND 
NONMETAL MINES

0
1. The authority citation for part 57 continues to read as follows:

    Authority: 30 U.S.C. 811 and 813.


0
2. Section 57.5060 is amended by:
0
A. Revising paragraph (b);
0
B. Removing (c)(3)(i); and
0
C. Redesignating paragraphs (c)(3)(ii), (c)(3)(iii), and (c)(3)(iv) as 
(c)(3)(i), (c)(3)(ii), and (c)(3)(iii) respectively.

[[Page 29012]]

    The revision reads as follows:


Sec.  57.5060  Limit on exposure to diesel particulate matter.

* * * * *
    (b)(1) Effective May 20, 2006, a miner's personal exposure to 
diesel particulate matter (DPM) in an underground mine must not exceed 
an average eight-hour equivalent full shift airborne concentration of 
308 micrograms of elemental carbon per cubic meter of air 
(308EC [mu]g/m\3\).
    (2) Effective January 20, 2007, a miner's personal exposure to 
diesel particulate matter (DPM) in an underground mine must not exceed 
an average eight-hour equivalent full shift airborne concentration of 
350 micrograms of total carbon per cubic meter of air (350TC 
[mu]g/m\3\).
    (3) Effective May 20, 2008, a miner's personal exposure to diesel 
particulate matter (DPM) in an underground mine must not exceed an 
average eight-hour equivalent full shift airborne concentration of 160 
micrograms of total carbon per cubic meter of air (160TC 
[mu]g/m\3\).
* * * * *

0
3. Effective August 16, 2006, Sec.  57.5060 is amended by revising 
paragraph (d) introductory text and adding paragraphs (d)(3) through 
(d)(8).


Sec.  57.5060  Limit on exposure to diesel particulate matter.

* * * * *
    (d) The mine operator must install, use, and maintain feasible 
engineering and administrative controls to reduce a miner's exposures 
to or below the applicable DPM PEL established in this section. When 
controls do not reduce a miner's DPM exposure to the PEL, controls are 
infeasible, or controls do not produce significant reductions in DPM 
exposures, controls must be used to reduce the miner's exposure to as 
low a level as feasible and must be supplemented with respiratory 
protection in accordance with Sec.  57.5005(a), (b), and paragraphs 
(d)(1) through (d)(8) of this section.
* * * * *
    (3) The mine operator must provide a confidential medical 
evaluation by a physician or other licensed health care professional 
(PLHCP), at no cost to the miner, to determine the miner's ability to 
use a respirator before the miner is required to be fit tested or to 
use a respirator at the mine. If the PLHCP determines that the miner 
cannot wear a negative pressure respirator, the mine operator must make 
certain that the PLHCP evaluates the miner's ability to wear a powered 
air purifying respirator (PAPR).
    (4) The mine operator must provide the miner with an opportunity to 
discuss their evaluation results with the PLHCP before the PLHCP 
submits the written determination to the mine operator regarding the 
miner's ability to wear a respirator. If the miner disagrees with the 
evaluation results of the PLHCP, the miner may submit within 30 days 
additional evidence of his or her medical condition to the PLHCP.
    (5) The mine operator must obtain a written determination from the 
PLHCP regarding the miner's ability to wear a respirator, and the mine 
operator must assure that the PLHCP provides a copy of the 
determination to the miner.
    (6) The miner must be reevaluated when the mine operator has reason 
to believe that conditions have changed which could adversely affect 
the miner's ability to wear the respirator.
    (7) Upon written notification that the PLHCP has determined that 
the miner is unable to wear a respirator, including a PAPR, the miner 
must be transferred to work in an existing position in an area of the 
same mine where respiratory protection is not required. The miner must 
be transferred within 30 days of the final determination by the PLHCP.
    (i) The miner must continue to receive compensation at no less than 
the regular rate of pay in the classification held by that miner 
immediately prior to the transfer.
    (ii) Increases in wages of the transferred miner must be based upon 
the new work classification.
    (8) The mine operator must maintain a record of the identity of the 
PLHCP and the most recent written determination of each miner's ability 
to wear a respirator for the duration of the miner's employment plus 
six months.
* * * * *

0
4. Section 57.5075 is amended by revising paragraph (a) and paragraph 
(b)(3) to read as follows:


Sec.  57.5075  Diesel particulate records.

    (a) The table entitled ``Diesel Particulate Matter Recordkeeping 
Requirements'' lists the records the operator must maintain pursuant to 
Sec. Sec.  57.5060 through 57.5071, and the duration for which 
particular records need to be retained.

    Table 57.5075(a).--Diesel Particulate Recordkeeping Requirements
------------------------------------------------------------------------
                                      Section
             Record                  reference        Retention time
------------------------------------------------------------------------
1. Approved application for                 Sec.  Duration of extension.
 extension of time to comply          57.5060(c)
 with exposure limits.
2. Identity of PLHCP and most               Sec.  Duration of miner's
 recent written determination of      57.5060(d)   employment plus 6
 miner's ability to wear a                         months.
 respirator.
3. Purchase records noting                  Sec.  1 year beyond date of
 sulfur content of diesel fuel.       57.5065(a)   purchase.
4. Maintenance log..............            Sec.  1 year after date any
                                      57.5066(b)   equipment is tagged.
5. Evidence of competence to                Sec.  1 year after date
 perform maintenance.                 57.5066(c)   maintenance
                                                   performed.
6. Annual training provided to              Sec.  1 year beyond date
 potentially exposed miners.          57.5070(b)   training completed.
7. Record of corrective action..            Sec.  Until the corrective
                                      57.5071(c)   action is completed.
8. Sampling method used to                  Sec.  5 years from sample
 effectively evaluate a miner's       57.5071(d)   date.
 personal exposure, and sample
 results.
------------------------------------------------------------------------

    (b) * * *
    (3) An operator must provide access to a miner, former miner, or, 
with the miner's or former miner's written consent, a personal 
representative of a miner, to any record required to be maintained 
pursuant to Sec.  57.5071 or Sec.  57.5060(d) to the extent the 
information pertains to the miner or former miner. The operator must 
provide the first copy of a requested record at no cost, and any 
additional copies at reasonable cost.
* * * * *
[FR Doc. 06-4494 Filed 5-17-06; 8:45 am]
BILLING CODE 4510-43-P