[Federal Register Volume 59, Number 46 (Wednesday, March 9, 1994)]
[Unknown Section]
[Page 0]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 94-5423]


[[Page Unknown]]

[Federal Register: March 9, 1994]


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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Parts 52 and 81

[CO28-1-5815, CO36-1-6302; FRL-4847-4]

 

Clean Air Act Approval and Promulgation of PM-10 Implementation 
Plan for Colorado; Designation of Areas for Air Quality Planning 
Purposes

AGENCY: Environmental Protection Agency (EPA).

ACTION: Notice of proposed rulemaking.

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SUMMARY: In this document, EPA is proposing approval of the State 
implementation plan (SIP) submitted by the State of Colorado for the 
purpose of bringing about the attainment of the national ambient air 
quality standards (NAAQS) for particulate matter with an aerodynamic 
diameter less than or equal to a nominal 10 micrometers (PM-10). The 
SIP was submitted on February 24, 1993 and December 9, 1993 to satisfy 
certain federal requirements for an approvable nonattainment area PM-10 
plan for Pagosa Springs, Colorado. In addition, EPA is proposing to 
approve the PM-10 contingency measures for the Pagosa Springs 
nonattainment area, which were included in the State's December 9, 1993 
submittal.
    EPA is also proposing to amend the nonattainment area boundary for 
the Pagosa Springs nonattainment area to include some of the 
surrounding suburban area of Pagosa Springs. The revised boundary is 
based on information submitted with the SIP which provided a SIP 
equivalent demonstration showing that the revised boundary more 
accurately represents the Pagosa Springs airshed.

DATES: Comments on this proposed action must be received in writing by 
April 8, 1994.

ADDRESSES: Written comments should be addressed to:

Vicki Stamper, 8ART-AP, Environmental Protection Agency, Region VIII, 
999 18th Street, suite 500, Denver, Colorado 80202-2466.

    Copies of the State's submittal and other information are available 
for inspection during normal business hours at the following locations:

Air Programs Branch, Environmental Protection Agency, Region VIII, 999 
18th Street, suite 500, Denver, Colorado 80202-2405
Air Pollution Control Division, Colorado Department of Health, 4300 
Cherry Creek Drive South, Denver, Colorado 80222-1530.

FOR FURTHER INFORMATION CONTACT: Vicki Stamper, 8ART-AP, Environmental 
Protection Agency, Region VIII, 999 18th Street, suite 500, Denver, 
Colorado 80202-2466, (303) 293-1765.

SUPPLEMENTARY INFORMATION:

I. Background

    Pagosa Springs, Colorado was designated nonattainment for PM-10 and 
classified as moderate under sections 107(d)(4)(B) and 188(a) of the 
Act upon enactment of the Clean Air Act Amendments of 1990.\1\ (See 56 
FR 56694, November 6, 1991; 40 CFR 81.306 (specifying nonattainment 
designation for Pagosa Springs).) The air quality planning requirements 
for moderate PM-10 nonattainment areas are set out in subparts 1 and 4 
of part D of title I of the Act. The EPA has issued a ``General 
Preamble'' describing EPA's preliminary views on how EPA intends to 
review SIPs and SIP revisions submitted under title I of the Act, 
including those State submittals containing moderate PM-10 
nonattainment area SIP requirements (see generally 57 FR 13498 (April 
16, 1992) and 57 FR 18070 (April 28, 1992)). Because EPA is describing 
its interpretations here only in broad terms, the reader should refer 
to the General Preamble for a more detailed discussion of the 
interpretations of title I advanced in this proposal and the supporting 
rationale. In this notice on the Colorado moderate PM-10 SIP for the 
Pagosa Springs nonattainment area submitted on February 24, 1993 and on 
December 9, 1993, EPA is proposing to apply its interpretations taking 
into consideration the specific factual issues presented. Thus, EPA 
will consider any timely submitted comments before taking final action 
on this proposal.
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    \1\The 1990 Amendments to the Clear Air Act made significant 
changes to the Act. See Pub. L. No. 101-549, 104 Stat. 2399. 
References herein are to the Clean Air Act, as amended (``the 
Act''). The Clean Air Act is codified, as amended, in the U.S. Code 
at 42 U.S.C. 7401 et seq.
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    Those states containing initial moderate PM-10 nonattainment areas 
were required to submit, among other things, the following provisions 
by November 15, 1991:
    1. Provisions to assure that reasonably available control measures 
(RACM) (including such reductions in emissions from existing sources in 
the area as may be obtained through the adoption, at a minimum, of 
reasonably available control technology (RACT)) shall be implemented no 
later than December 10, 1993;
    2. Either a demonstration (including air quality modeling) that the 
plan will provide for attainment as expeditiously as practicable but no 
later than December 31, 1994 or a demonstration that attainment by that 
date is impracticable;
    3. Quantitative milestones which are to be achieved every 3 years 
and which demonstrate reasonable further progress (RFP) toward 
attainment by December 31, 1994; and
    4. Provisions to assure that the control requirements applicable to 
major stationary sources of PM-10 also apply to major stationary 
sources of PM-10 precursors except where the Administrator determines 
that such sources do not contribute significantly to PM-10 levels which 
exceed the NAAQS in the area. See sections 172(c), 188, and 189 of the 
Act.
    Some provisions were due at a later date. States with initial 
moderate PM-10 nonattainment areas were required to submit a permit 
program for the construction and operation of new and modified major 
stationary sources of PM-10 by June 30, 1992. (See section 189(a) of 
the Act.) Revisions to satisfy these requirements were submitted by the 
State on January 14, 1993, and EPA will be taking action on these 
requirements in a separate Federal Register notice. Such States also 
were required to submit contingency measures by November 15, 1993 which 
become effective without further action by the State or EPA, upon a 
determination by EPA that the area has failed to achieve RFP or to 
attain the PM-10 NAAQS by the applicable statutory deadline. (See 
section 172(c)(9) of the Act and 57 FR 13543-13544.) The State adopted 
contingency measures for Pagosa Springs in November of 1993, and those 
measures were included in the State's December 9, 1993 SIP submittal. 
Along with proposing action on the moderate PM-10 nonattainment area 
SIP requirements which were due to EPA on November 15, 1991, EPA is 
also proposing action on these contingency measures in this notice.

II. Proposed Action

    Section 110(k) of the Act sets out provisions governing EPA's 
review of SIP submittals (see 57 FR 13565-13566). In this action, EPA 
is proposing to grant approval of the Pagosa Springs PM-10 attainment 
plan, which was due to EPA on November 15, 1991 and submitted by the 
State on February 24, 1993 and on December 9, 1993. EPA is also 
proposing to approve the PM-10 contingency measures for Pagosa Springs, 
which were due to EPA on November 15, 1993 and submitted by the State 
on December 9, 1993. EPA believes the PM-10 attainment plan and 
contingency measures for Pagosa Springs meet all of the applicable 
requirements of the Act.
    In addition, EPA is proposing to amend the nonattainment area 
boundary for the Pagosa Springs nonattainment area to include some of 
the surrounding suburban area of Pagosa Springs. The revised boundary 
is based on information submitted with the SIP which provided a SIP 
equivalent demonstration showing that the revised boundary more 
accurately represents the Pagosa Springs airshed. (See section 
110(k)(6) of the Act.)
    Since the Pagosa Springs PM-10 attainment plan was not submitted by 
November 15, 1991 as required by section 189(a)(2)(A) of the Act, EPA 
made a finding, pursuant to section 179 of the Act, that the State 
failed to submit the SIP and notified the Governor in a letter dated 
December 16, 1991. (See 57 FR 19906 (May 8, 1992).) After the initial 
Pagosa Springs PM-10 SIP was submitted on February 24, 1993, EPA found 
the submittal to be complete pursuant to section 110(k)(1) of the Act 
and notified the Governor accordingly in a letter dated April 23, 1993. 
This completeness determination corrected the State's deficiency and, 
therefore, terminated the 18-month sanctions clock under section 179 of 
the Act.

A. Analysis of State Submittals

 1. Procedural Background
    The Act requires States to observe certain procedural requirements 
in developing implementation plans and plan revisions for submission to 
EPA. Section 110(a)(2) of the Act provides that each implementation 
plan submitted by a State must be adopted after reasonable notice and 
public hearing.\2\ Section 110(l) of the Act similarly provides that 
each revision to an implementation plan submitted by a State under the 
Act must be adopted by such State after reasonable notice and public 
hearing.
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    \2\Also section 172(c)(7) of the Act requires that plan 
provisions for nonattainment areas meet the applicable provisions of 
section 110(a)(2).
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    The EPA also must determine whether a submittal is complete and 
therefore warrants further EPA review and action (see section 110(k)(1) 
of the Act and 57 FR 13565). The EPA's completeness criteria for SIP 
submittals are set out at 40 CFR part 51, appendix V (1992). The EPA 
attempts to make completeness determinations within 60 days of 
receiving a submission. However, a submittal is deemed complete by 
operation of law if a completeness determination is not made by EPA 6 
months after receipt of the submission.
    After providing more than 30 days of prior public notice, the State 
of Colorado held a public hearing on November 19, 1992 to entertain 
public comment on the implementation plan for Pagosa Springs. The plan 
for Pagosa Springs was subsequently adopted by the State and submitted 
by the Governor by letter dated February 24, 1993 as a proposed 
revision to the SIP. EPA received the submittal on February 26, 1993.
    The SIP revision was reviewed by EPA to determine completeness 
shortly after its submittal, in accordance with the completeness the 
criteria set out at 40 CFR part 51, appendix V (1992). The submittal 
was found to be complete, and a letter dated April 23, 1993 was 
forwarded to the Governor indicating the completeness of the submittal 
and the next steps to be taken in the review process.
    On December 9, 1993, the State submitted a revision to the Pagosa 
Springs PM-10 SIP, which contained contingency measures, additional 
control measures, and a revised demonstration of attainment because the 
initial attainment demonstration in the State's February 24, 1993 
submittal did not conform to EPA modeling policy. This revision was 
submitted pursuant to a November 12, 1993 public hearing, for which the 
State again provided more than 30 days of prior public notice. After 
receiving the submittal on December 14, 1993, EPA found the December 
1993 submittal to be administratively and technically complete, and a 
letter dated February 15, 1994 was forwarded to the Governor indicating 
the completeness of the submittal.
    In this action, EPA proposes approval of the State of Colorado's 
PM-10 SIP submittals for Pagosa Springs, including the PM-10 
contingency measures submitted with the December 1993 submittal, and 
invites public comment on the action.
2. Accurate Emissions Inventory
    Section 172(c)(3) of the Act requires that nonattainment plan 
provisions include a comprehensive, accurate, current inventory of 
actual emissions from all sources of relevant pollutants in the 
nonattainment area. Because the submission of such an inventory is a 
necessary adjunct to an area's attainment demonstration (or 
demonstration that the area cannot practicably attain), the emissions 
inventory must be received with the submission (see 57 FR 13539).
    In its February 24, 1993 submittal the State of Colorado submitted 
a winter season emissions inventory for the base year of 1988. A winter 
season emissions inventory was calculated because the highest PM-10 
concentrations have occurred in the winter season in Pagosa Springs. 
The emissions inventory was generally calculated using EPA's 
``Compilation of Air Pollution Emission Factors'' (AP-42) with the 
exception of the sanding emissions, which were calculated using 
emission factors developed for the Denver PM-10 SIP at EPA's 
recommendation. EPA had previously commented that the AP-42 default 
emission factors for re-entrained road dust from paved roads likely 
underestimated the emissions from this source category for high 
elevation mountain towns, such as Pagosa Springs. The State, therefore, 
included a commitment in the Pagosa Springs SIP to conduct a silt 
loading study in Pagosa Springs during the winter of 1992-1993 and to 
use that study to improve the emissions inventory and verify the 
adequacy of the attainment and maintenance demonstration.
    The State fulfilled its commitment by submitting a revised 
emissions inventory on September 20, 1993. The results of the silt 
loading study confirmed that emissions from re-entrained road dust from 
paved roads in Pagosa Springs were much higher than the AP-42 default 
emission factors, as was suspected by EPA. The final emissions 
inventory showed that re-entrained road dust from paved roads 
contributes 78 percent to the total emissions in the area. Other 
sources of emissions include re-entrained road dust from unpaved roads 
(20 percent), residential wood burning (2 percent), and tailpipe 
emissions and coal burning stoves (0.1 percent). Only one permanent 
stationary source was identified in the area, and its emissions were 
insignificant (less than 1 ton per year).
    EPA has reviewed the revised emissions inventory and believes it 
generally appears to be accurate and comprehensive. Therefore, EPA is 
proposing to approve the emissions inventory because it provides a 
sufficient basis for determining the adequacy of the attainment 
demonstration for this area consistent with the requirements of 
sections 172(c)(3) and 110(a)(2)(K) of the Act.\3\ For further details, 
see the Technical Support Document (TSD) accompanying this notice.
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    \3\The EPA issued guidance on PM-10 emissions inventories prior 
to the enactment of the Clean Air Act Amendments in the form of the 
1987 PM-10 SIP Development Guideline. The guidance provided in this 
document appears to be consistent with the revised Act.
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3. RACM (Including RACT)
    As noted, the initial moderate PM-10 nonattainment areas must 
submit provisions to assure that RACM (including RACT) are implemented 
no later than December 10, 1993 (see sections 172(c)(1) and 
189(a)(1)(C) of the Act). The General Preamble contains a detailed 
discussion of EPA's interpretation of the RACM (including RACT) 
requirement (see 57 FR 13539-13545 and 13560-13561).
    In the State's February 24, 1993 submittal, the State identified 
re-entrained road dust from unpaved roads as the primary contributor to 
the nonattainment area problem in Pagosa Springs. The State chose to 
control this source category by requiring the paving of 6 miles of 
unpaved gravel roads, and the attainment analysis provided in the 
submittal showed that this control measure was adequate for Pagosa 
Springs to demonstrate attainment of the PM-10 NAAQS by December 31, 
1994. However, as discussed in Section II.A.2. of this notice, the 
State revised the emissions inventory for the area based on silt 
loading studies conducted during the 1992/1993 winter season, which 
showed that re-entrained road dust from paved roads was the primary 
contributor to the PM-10 emissions in the area, rather than from 
unpaved roads. Also, as more fully discussed in Section II.A.4. of this 
notice, the State did not follow EPA modeling policy in the 
demonstration of attainment provided in the February 1993 SIP 
submittal. When the State revised the analysis to conform with EPA 
policy, the results showed that the area could not demonstrate 
attainment of the PM-10 NAAQS without the adoption of additional 
control measures. Thus, on December 9, 1993, the State submitted 
additional PM-10 control measures for re-entrained road dust from paved 
roads for the Pagosa Springs nonattainment area, as well as a 
demonstration of attainment consistent with EPA modeling policy which 
showed that the control measures adopted would result in the Pagosa 
Springs area attaining the PM-10 NAAQS in 1994. (For further details, 
see the TSD accompanying this notice.)
    Thus, the State's submittals provide that the PM-10 source 
categories of re-entrained road dust from paved and unpaved roads will 
be controlled as follows: 

------------------------------------------------------------------------
                                            Benefit towards reducing PM-
       Source               Control                 10 emissions        
------------------------------------------------------------------------
Re-entrained road     Specs for 1% fines   Fines content of 1% results  
 dust from paved       content of street    in a 75% reduction in       
 roads.                sanding materials.   emissions due to fines      
                                            content of sanding          
                                            materials.                  
                      Reduction in the     Combining the 75% reduction  
                       amount of sanding    with a 10% reduction in the 
                       materials applied    amount of street sanding    
                       (by 10% in 12/93-    materials applied results in
                       11/95 and by 15%     an overall reduction of     
                       beginning in 12/     67.7% from the applicable   
                       95).                 roads in this source        
                                            category. Combining this    
                                            with a 15% reduction        
                                            beginning in 12/95 results  
                                            in an overall reduction in  
                                            69.1% from the applicable   
                                            roads in this category.     
Re-entrained road     Paving of six miles  No credit taken for this     
 dust from unpaved     of unpaved gravel    provision.                  
 roads.                roads.                                           
------------------------------------------------------------------------

    The State did not take credit for the paving of six miles of gravel 
roads due to the results of the silt loading studies conducted during 
the 1992/1993 winter and the subsequent revised emissions inventory. 
Specifically, the emission factor used for calculating re-entrained 
road dust from paved roads, based on the results of a Pagosa Springs-
specific study, was actually greater than the emission factor used for 
calculating re-entrained road dust from unpaved gravel roads. This is 
likely due to the fact that the State did not develop a Pagosa Springs-
specific emission factor for gravel roads, as was done for paved roads; 
the State simply relied upon EPA default methods for determining 
emissions from unpaved roads. Since, using these emission factors, the 
paving of gravel roads is projected to result in a slight increase in 
PM-10 emissions, the State declined to take credit for the paving of 
gravel roads towards reducing PM-10 emissions. Nevertheless, the State 
decided to retain the road paving provision because the State believes 
that it will result in an overall reduction in PM-10 emissions. See the 
TSD for further information. EPA believes it is reasonable for the 
State to retain the road paving measure in light of the potential 
uncertainty of emissions reductions in this instance due to the State's 
relying on EPA default methods for determining re-entrained road dust 
emissions from unpaved gravel roads.
    All of these requirements will be implemented through Section I. of 
the Colorado regulation entitled ``Nonattainment Areas--State 
Implementation Plan Specific Regulations for Local Elements.'' The 
requirements for street sanding material specifications and for the 
reduction in sanding material applied, found in Sections I.C. and I.D. 
of the State regulation, pertain to the major State highways through 
town and must be complied with beginning December 1, 1993. The State of 
Colorado has received verbal notification from the Colorado Department 
of Transportation that these measures have been implemented in the 
Pagosa Springs nonattainment area since December 1, 1993. Control of 
this source category is expected to result in an estimated overall 
reduction of 4997 lb/day of PM-10 emissions in the area. Section I.B. 
of the State regulation requires 3 \7/10\ miles of unpaved gravel roads 
to be paved by December 10, 1993, and an additional 2 \3/10\ miles of 
unpaved gravel roads to be paved by December 31, 1994. The Town of 
Pagosa Springs completed the paving of 3 \7/10\ miles of unpaved gravel 
roads by the end of the summer of 1992.
    In order to comply with the State's Administrative Procedures Act, 
the revisions to this regulation pertaining to the street sanding 
controls, which were adopted on November 12, 1993, did not become 
effective until December 30, 1993. However, since these provisions were 
required to be implemented by December 1, 1993, the State adopted an 
emergency rule on November 12, 1993 to make the new provisions in the 
State's nonattainment area regulation effective December 1, 1993. So, 
until the State's regulation became effective, this emergency rule 
(which is identical to the State nonattainment area regulation) applied 
beginning December 1, 1993.
    For an area that demonstrates attainment by the applicable 
attainment date, the implementation of otherwise available control 
measures is not ``reasonably'' required by RACM if such control 
measures would not expedite attainment. (see 57 FR 13543) Control of 
other PM-10 emissions in the area, such as residential wood combustion 
(which contributes 2 percent) and tailpipe emissions and coal burning 
stoves (which contribute 0.1 percent), was not required because the 
implementation of such controls would not have further advanced the 
attainment date in the area.
    Similarly, RACM (including RACT) did not require the adoption of 
otherwise available control measures for stationary sources in the 
Pagosa Springs nonattainment area because point source emissions in the 
Pagosa Springs area are de minimis (see 57 FR 13540) and control of 
such sources would not expedite attainment and maintenance of the PM-10 
NAAQS.
    There are also other Statewide control measures that already apply 
in the Pagosa Springs area, which will help curb PM-10 emissions in the 
Pagosa Springs nonattainment area. Specifically, Colorado Regulation 
No. 4 requires new wood stoves to meet the emission requirements of 
EPA's Standards of Performance for New Residential Wood Heaters in 40 
CFR 60.532(b), and Colorado Regulation No. 3 regulates the construction 
and modification of stationary sources of PM-10.\4\ These measures will 
help to reduce emissions from new stationary source growth and 
residential wood combustion. However, EPA is not proposing action on 
Regulations No. 3 and 4 because EPA has previously approved these 
regulations in separate notices. For further information, see the TSD 
accompanying this notice.
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    \4\The State is required by the amended Clean Air Act to adopt a 
revised new source review permit program for the construction and 
operation of new and modified stationary sources. See section 
189(a)(1)(A). This SIP revision, submitted by the State on January 
14, 1993, was due independent of the November 15, 1991 moderate PM-
10 nonattainment area SIP requirements addressed in this action and 
will be addressed in a separate notice. See section 189(a)(2)(A) of 
the Act.
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    A more detailed discussion of the individual source contributions, 
their associated control measures, and an explanation as to why certain 
available control measures were not implemented can be found in the 
TSD. The EPA has reviewed the State's explanation and associated 
documentation and has concluded that it adequately justifies the 
control measures to be implemented. The implementation of Pagosa 
Springs' PM-10 control strategy is projected to result in the 
attainment of the PM-10 NAAQS by December 31, 1994. Therefore, by this 
notice, EPA is proposing to approve Colorado's SIP submittals for the 
Pagosa Springs nonattainment area as meeting the RACM including RACT 
requirement. However, EPA is not proposing action on Regulations No. 3 
and 4 because EPA has previously approved these regulations in separate 
actions (see the TSD for further information).
4. Demonstration
    As noted, the initial moderate PM-10 nonattainment areas must 
submit a demonstration (including air quality modeling) showing that 
the plan will provide for attainment as expeditiously as practicable 
but no later than December 31, 1994 (see section 189(a)(1)(B) of the 
Act). Alternatively, the State must show that attainment by December 
31, 1994 is impracticable.
    EPA regulations provide that attainment be demonstrated by means of 
a proportional model or dispersion model or other procedure shown to be 
adequate and appropriate for such purposes. (see 40 CFR 51.112(a)) EPA 
policy recommends that the preferred approach for estimating the air 
quality impacts of emissions of PM-10 is to use receptor modeling in 
combination with dispersion modeling. On July 5, 1990, EPA issued 
guidance providing that, in certain situations, it may be more 
appropriate to rely on a receptor modeling demonstration alone as the 
basis for the attainment demonstration (see July 5, 1990 memo to 
Regional Air Branch Chiefs from Robert D. Bauman, Chief of SO2/
Particulate Matter Programs Branch and Joseph Tikvart, Chief of Source 
Receptor Analysis Branch). Pagosa Springs meets the criteria discussed 
in the July 5, 1990 memo to justify using receptor modeling alone.
    The State originally planned to use this approach in its initial 
SIP submittal and attainment demonstration. However, after further 
review, the State determined that the chemical mass balance (CMB) data 
available at the time which would be used in the receptor modeling was 
inadequate and decided to base the attainment and maintenance 
demonstration on simple emissions rollback modeling. Emissions rollback 
modeling involves using the ratio of the design day ambient 
concentration to the design day emissions and projecting future 
concentrations. However, EPA policy allows the use of other methods of 
demonstrating attainment, such as emissions rollback modeling, only in 
certain limited circumstances which were not met by this area. (See 
March 4, 1991 memorandum from John Calcagni, Director of EPA's Air 
Quality Management Division, and William G. Laxton, Director of EPA's 
Technical Support Division, entitled ``PM-10 SIP Attainment 
Demonstration Policy for Initial Moderate Nonattainment Areas.'')
    Because the State did not follow EPA policy in calculating the 
attainment demonstration for Pagosa Springs, the State included a 
commitment in the Pagosa Springs PM-10 SIP to conduct revised CMB 
analyses on all filters greater than 100 g/m3, as well as 
to calculate a revised emissions inventory based on a silt loading 
study in Pagosa Springs, and to use this information to assess the 
adequacy of the SIP. If the revised demonstration showed that 
additional control measures were needed, the State committed to propose 
such additional control measures to the Colorado Air Quality Control 
Commission (AQCC) for adoption by August 31, 1993.
    On July 28, 1993, the State submitted its preliminary analysis of 
the revised attainment and maintenance demonstrations using receptor 
modeling (based on the revised CMB data and emissions inventory), which 
indicated that the area could not demonstrate timely attainment and 
maintenance of the PM-10 NAAQS without the adoption of additional 
control measures. Subsequently, consistent with the State's commitment, 
the State proposed additional PM-10 control measures for the Pagosa 
Springs area to the AQCC on August 16, 1993. These measures were 
adopted on November 12, 1993 and were submitted for approval in the SIP 
on December 9, 1993. The December submittal included a revised 
attainment and maintenance demonstration which utilized receptor 
modeling coupled with emissions rollback modeling.
    The attainment and maintenance demonstrations presented in the 
December 9, 1993 submittal indicated that the NAAQS for PM-10 would be 
attained in 1994 in the Pagosa Springs area and maintained through 
December 31, 1997. The 24-hour PM-10 NAAQS is 150 g/m3, 
and the standard is attained when the expected number of days per 
calendar year with a 24-hour average concentration above 150 
g/m3 is equal to or less than one (see 40 CFR 50.6). The 
annual PM-10 NAAQS is 50 g/m3, and the standard is 
attained when the expected annual arithmetic mean concentration is less 
than or equal to 50 g/m3 (id.) The demonstration provided 
in the December 9, 1993 submittal predicted a 24-hour design 
concentration in the attainment year of 1994 of 139 g/m3. 
The demonstration also predicted a 24-hour design concentration in 1997 
of 139 g/m3. Thus, the State's attainment and maintenance 
demonstrations showed that the control measures adopted for the Pagosa 
Springs area would adequately result in attainment and maintenance of 
the 24-hour PM-10 NAAQS. Since no violations of the annual PM-10 NAAQS 
have been monitored in the Pagosa Springs area since 1987 and since the 
demonstration provided in the December 1993 SIP submittal for Pagosa 
Springs clearly shows attainment and maintenance of the 24-hour PM-10 
NAAQS, it is reasonable and adequate to assume that protection of the 
24-hour standard will be sufficient to protect the annual standard as 
well. The control strategy used to achieve these design concentrations 
is summarized in Section II.A.C. of this notice entitled ``RACM 
(including RACT).'' For a more detailed description of the attainment 
demonstration and the control strategy used, see the TSD accompanying 
this notice.
5. PM-10 Precursors
    The control requirements which are applicable to major stationary 
sources of PM-10 also apply to major stationary sources of PM-10 
precursors, unless EPA determines such sources do not contribute 
significantly to PM-10 levels in excess of the NAAQS in that area (see 
section 189(e) of the Act).
    An analysis of air quality and emissions data for the Pagosa 
Springs nonattainment area, as revised in September of 1993, indicates 
that exceedances of the NAAQS are attributable chiefly to particulate 
matter emissions from area sources, mainly re- entrained road dust from 
paved and unpaved roads. In addition, the emissions inventory for this 
area did not reveal any major stationary sources of PM-10 precursors. 
Consequently, EPA is proposing to find that major stationary sources of 
precursors of PM-10 do not contribute significantly to PM-10 levels in 
excess of the NAAQS in Pagosa Springs. The consequences of this 
proposed finding are to exclude these major stationary sources from the 
applicability of PM-10 nonattainment area control requirements. Further 
discussion of the analyses and supporting rationale for EPA's proposed 
finding are contained in the TSD accompanying this notice. Note that 
while EPA is proposing to make a general finding for this area, this 
proposed finding is based on the current character of the area 
including, for example, the existing mix of sources in the area. It is 
possible, therefore, that future growth could change the significance 
of precursors in the area. The EPA intends to issue future guidance 
addressing such potential changes in the significance of precursor 
emissions in an area.
6. Quantitative Milestones and Reasonable Further Progress
    The PM-10 nonattainment area plan revisions demonstrating 
attainment must contain quantitative milestones which are to be 
achieved every 3 years until the area is redesignated attainment and 
which demonstrate RFP, as defined in section 171(1), toward attainment 
by December 31, 1994 (see section 189(c) of the Act). RFP is defined in 
section 171(1) of the Act as such annual incremental reductions in 
emissions of the relevant air pollutant as are required by part D or 
may reasonably be required by the Administrator for the purpose of 
ensuring attainment of the applicable NAAQS by the applicable date.
    In implementing the quantitative milestone and RFP provisions for 
this initial moderate area, EPA has reviewed the attainment 
demonstration and control strategy for the area to determine whether 
annual incremental reductions different from those provided in the SIP 
submittals should be required in order to ensure attainment of the PM-
10 NAAQS by December 31, 1994 (see section 171(1) of the Act). The 
State of Colorado's PM-10 SIP submittals for Pagosa Springs indicate 
that the control measures adopted will result in an annual incremental 
reduction of 912 tons/year (4997 lb/day) of PM-10, and the State's 
December 9, 1993 submittal demonstrated that this annual incremental 
reduction will result in attainment of the PM-10 NAAQS by December 31, 
1994.\5\ Therefore, EPA believes the Pagosa Springs PM-10 SIP 
submittals satisfy the initial quantitative milestone and RFP 
requirements.
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    \5\The emissions reduction progress made prior to the attainment 
date of December 31, 1994 (only 46 days beyond the November 15, 1994 
milestone achievement date) will satisfy the first milestone 
requirement (57 FR 13539). The de minimis timing differential makes 
it administratively impracticable to require separate milestone and 
attainment demonstrations.
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7. Enforceability Issues
    All measures and other elements in the SIP must be enforceable by 
the State and EPA (see sections 172(c)(6), 110(a)(2)(A) of the Act and 
57 FR 13556). The EPA criteria addressing the enforceability of SIPs 
and SIP revisions were stated in a September 23, 1987 memorandum (with 
attachments) from J. Craig Potter, Assistant Administrator for Air and 
Radiation, et al. (see 57 FR 13541). Nonattainment area plan provisions 
must also contain a program that provides for enforcement of the 
control measures and other elements in the SIP (see section 
110(a)(2)(C) of the Act).
    The control measures contained in this SIP submittal are addressed 
above under Section II.A.3. entitled ``RACM (including RACT).'' These 
requirements, which are included in Section I. of the State regulation 
entitled ``Nonattainment Areas--State Implementation Plan Specific 
Regulations for Local Elements,'' apply to the types of activities 
identified in that discussion including re-entrained road dust from 
both paved and unpaved roads. The State regulation provides that these 
control measures apply throughout the Pagosa Springs PM-10 
nonattainment area.
    Consistent with the attainment demonstration previously described, 
the SIP and State regulation require that all affected activities for 
which the State is taking credit towards demonstrating attainment must 
be in full compliance with the applicable SIP provisions by December 1, 
1993. In addition to the applicable control measures, this includes the 
applicable recordkeeping requirements which are addressed in the 
supporting information. Compliance with certain measures, such as the 1 
percent fines limit with regard to sanding material used, must be 
determined in accordance with appropriate test methods. The regulation 
provides that compliance with the 1 percent fines limit will be 
determined in accordance with the American Society for Testing 
Materials (ASTM) ``Standard Method for Sieve Analysis of Fine and 
Coarse Aggregate.'' EPA believes this method is appropriate for 
determining compliance with this provision.
    The attached TSD contains further information on enforceability 
requirements including: a description of the rules contained in the SIP 
and the source types subject to them, test methods, and reporting and 
recordkeeping requirements. EPA has reviewed the State's nonattainment 
area regulation for enforceability and has determined that it meets all 
of the criteria included in the September 23, 1987 Potter Memorandum.
    As discussed in Section II.A.3. above, there are also Statewide 
regulations that will impact the emissions of PM-10 in the Pagosa 
Springs nonattainment area. These regulations include Colorado 
Regulation No. 4, which requires all wood stoves sold after July 1, 
1991 to meet the emission requirements of EPA's Standards of 
Performance for New Residential Wood Heaters in 40 CFR 60.532(b), and 
Colorado Regulation No. 3, which requires construction permits for new 
or modified stationary sources. EPA previously reviewed Colorado 
Regulations Nos. 3 and 4 at the time these regulations were approved by 
EPA as part of the SIP, and determined that these regulations met the 
enforceability criteria of the September 23, 1987 Potter Memorandum 
(see the TSD for information on EPA approvals of these regulations).\6\
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    \6\Note that the current version of Colorado Regulation No. 3 
approved by EPA does not meet all of the applicable requirements of 
the amended Act. As discussed in footnote number 4, the State 
submitted revisions to Regulation No. 3 in January 1993 which are 
being evaluated by EPA. EPA will act on that submittal in a separate 
notice.
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    The State of Colorado has a program that will ensure that the 
measures contained in the SIP are adequately enforced. The Colorado Air 
Pollution Control Division (APCD) has the authority to implement and 
enforce all emission limitations and control measures adopted by the 
AQCC. In addition, Colorado statute provides that the APCD shall 
enforce against any ``person'' who violates the emission control 
regulations of the AQCC, the requirements of the SIP, or the 
requirements of any permit. The definition of ``person'' includes, 
among others, any ``municipal corporation, county, city and county or 
other political subdivision of the State,'' such as the Town of Pagosa 
Springs. Civil penalties of up to $15,000 per day per violation are 
provided for in the State statute for any person in violation of these 
requirements, and criminal penalties are also provided for in the State 
statute. Thus, the APCD has adequate enforcement capabilities to ensure 
compliance with the Pagosa Springs PM-10 SIP and the State regulations. 
The TSD contains further information on the Statewide regulations, 
enforceability requirements, and a discussion of the personnel and 
funding intended to support effective implementation of the control 
measures.
8. Contingency Measures
    As provided in section 172(c)(9) of the Act, all moderate 
nonattainment area SIPs that demonstrate attainment must include 
contingency measures. See generally 57 FR 13510-13512 and 13543-13544. 
These measures were required to be submitted by November 15, 1993 for 
the initial moderate PM-10 nonattainment areas. Contingency measures 
should consist of other available measures that are not part of the 
area's core attainment control strategy. These measures must take 
effect without further action by the State or EPA, upon a determination 
by EPA that the area has failed to make RFP or attain the PM-10 NAAQS 
by the applicable statutory deadline. The State's December 9, 1993 
revision to the Pagosa Springs PM-10 SIP included the following 
contingency measure: Section I.E. of the State regulation entitled 
``Nonattainment Areas--State Implementation Plan Specific Regulations 
for Local Elements'' requires the Town of Pagosa Springs to sweep all 
traffic lanes of the major State highway through town as soon as 
practical following each sanding event using vacuum sweepers that are 
at least 34 percent effective. The Town is required to implement these 
provisions within two months of an EPA determination that the Pagosa 
Springs PM-10 nonattainment area failed to attain the PM-10 NAAQS by 
the statutory deadline of December 31, 1994 or failed to make RFP. EPA 
believes this is an adequate timeframe for implementation.
    After review of the contingency measure described above, EPA 
believes they are adequate to meet the requirements of section 
172(c)(9) of the Act. Therefore, EPA is proposing to approve the PM-10 
contingency measure for the Pagosa Springs PM-10 nonattainment area. 
For further information, see the TSD accompanying this notice.
9. Revisions to the Nonattainment Area Boundary
    The Pagosa Springs nonattainment area boundary is currently defined 
as the town limits of Pagosa Springs in 40 CFR 81.306. See 56 FR 56694 
(November 6, 1991). However, on June 20, 1991, the State adopted a more 
inclusive boundary for the Pagosa Springs PM-10 nonattainment area, 
which included the town limits and some additional areas along the San 
Juan River and along U.S. Highway 160 outside the town limits. This 
revised boundary was submitted with the February 24, 1993 Pagosa 
Springs PM-10 SIP submittal. The submittal provided a demonstration 
showing that the revised boundary represented the reasonable Pagosa 
Springs airshed by considering the local topography, meteorology, and 
land use practices.
    The information available at the time that the Pagosa Springs PM-10 
nonattainment area was promulgated did not indicate that the boundary 
should include the surrounding suburban areas. However, the subsequent 
information presented in the SIP persuasively demonstrated that the 
revised nonattainment area boundary submitted with the SIP more 
accurately represents the Pagosa Springs airshed. See, e.g., 57 FR 
56762, 56763 (November 30, 1992). Therefore, pursuant to section 
110(k)(6) of the Act, EPA is proposing to expand the Pagosa Springs PM-
10 nonattainment area boundary in 40 CFR 81.306 to include some 
additional suburban area surrounding the Town of Pagosa Springs. The 
proposed legal definition of the revised Pagosa Springs nonattainment 
area is as follows:

Township 35N & Range 2W: Sections 13, 14, 15; Section 23 NE, N\1/2\ 
SE; Section 24 all except SWSW; Section 25 N\1/2\ NE, NENW.
Township 35N & Range 1W: Section 18 W\1/2\.

    EPA is proposing to replace the boundary description currently in 
40 CFR 81.306 with this revised boundary.

III. Implications of This Action

    EPA is proposing to approve the plan revisions submitted to EPA for 
the Pagosa Springs PM-10 nonattainment area on February 24, 1993 and 
December 9, 1993. Among other things, the State of Colorado has 
adequately demonstrated that the Pagosa Springs moderate PM-10 
nonattainment area will attain the PM-10 NAAQS by December 31, 1994. 
EPA is also proposing to approve the PM-10 contingency measures for 
Pagosa Springs, which were submitted with the December 9, 1993 SIP 
revision.
    As noted, on January 14, 1993, the State submitted revisions to its 
permit program for the construction and operation of new and modified 
major stationary sources of PM-10 to comply with the amended Act. EPA 
will be taking action on these requirements in a separate Federal 
Register notice.
    Lastly, EPA is proposing to amend the nonattainment area boundary 
for the Pagosa Springs nonattainment area to include some of the area 
surrounding Pagosa Springs.

IV. Request for Public Comments

    The EPA is requesting comments on all aspects of this proposal. As 
indicated at the outset of this notice, EPA will consider any comments 
received by April 8, 1994.

V. Executive Order (EO) 12866

    This action has been classified as a Table 2 action by the Region 
Administrator under the procedures published in the Federal Register on 
January 19, 1989 (54 FR 2214-2225). On January 6, 1989, the Office of 
Management and Budget (OMB) waived Table 2 and 3 SIP revisions (54 FR 
2222) from the requirements of section 3 of Executive Order 12291 for a 
period of two years. The USEPA has submitted a request for a permanent 
waiver for Table 2 and 3 SIP revisions. The OMB has agreed to continue 
the waiver until such time as it rules on USEPA's request. This request 
continues in effect under Executive Order 12866 which superseded 
Executive Order 12291 on September 30, 1993.

VI. Regulatory Flexibility

    Under the Regulatory Flexibility Act, 5 U.S.C. 600 et seq., EPA 
must prepare a regulatory flexibility analysis assessing the impact of 
any proposed or final rule on small entities. 5 U.S.C 603 and 604. 
Alternatively, EPA may certify that the rule will not have a 
significant economic impact on a substantial number of small entities. 
Small entities include small businesses, small not-for-profit 
enterprises, and government entities with jurisdiction over populations 
of less than 50,000.
    SIP approvals under section 110 and subchapter I, part D of the Act 
do not create any new requirements, but simply approve requirements 
that the State is already imposing. Therefore, because the federal SIP-
approval does not impose any new requirements, I certify that it does 
not have a significant impact on small entities affected. Moreover, due 
to the nature of the federal-state relationship under the Act, 
preparation of a regulatory flexibility analysis would constitute 
federal inquiry into the economic reasonableness of state action. The 
Act forbids EPA to base its actions concerning SIPs on such grounds. 
Union Electric Co. v. U.S. E.P.A. , 427 U.S. 246, 256-66 (S.Ct. 1976); 
42 U.S.C. section 7410(a)(2).

VII. Applicability to Future SIP Decisions

    Nothing in this action should be construed as permitting or 
allowing or establishing a precedent for any future request for 
revision to any SIP. Each request for revision to the SIP shall be 
considered separately in light of specific technical, economic, and 
environmental factors and in relation to relevant statutory and 
regulatory requirements.

List of Subjects

40 CFR Part 52

    Environmental protection, Air pollution control, Hydrocarbons, 
Nitrogen dioxide, Particulate matter, Reporting and recordkeeping 
requirements, Sulfur dioxide, Volatile organic compounds.

40 CFR Part 81

    Air pollution control, National parks, Wilderness areas.

    Authority: 42 U.S.C. 7401-7671q.

    Dated: March 1, 1994.
William P. Yellowtail,
Regional Administrator.
[FR Doc. 94-5423 Filed 3-8-94; 8:45 am]
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