[Federal Register Volume 61, Number 182 (Wednesday, September 18, 1996)]
[Proposed Rules]
[Pages 49087-49090]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 96-23822]


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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 52

[AZ-030-0006; FRL-5611-8]


Approval and Promulgation of Implementation Plans; Arizona--
Phoenix Nonattainment Area; Carbon Monoxide Emission Inventory

AGENCY: Environmental Protection Agency (EPA).

ACTION: Proposed rule.

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SUMMARY: EPA is proposing to approve, as meeting the requirements of 
sections 172(c)(3) and 187(a)(1) of the Clean Air Act (CAA) and EPA 
guidance, the 1990 base year carbon monoxide (CO) emission inventory 
for the Phoenix CO nonattainment area. This document also discusses 
EPA's review of the 1995 projected year inventory for the Phoenix area.

DATES: Written comments on this proposal must be received by October 
18, 1996.

ADDRESSES: Written comments should be sent to: Wienke Tax, A-2-1, U.S. 
Environmental Protection Agency,

[[Page 49088]]

Region 9, 75 Hawthorne Street, San Francisco, California 94105.
    The rulemaking docket for this document, Docket No. 96-AZ-003, may 
be inspected and copied at the following location between 8 a.m. and 
4:30 p.m. on weekdays. A reasonable fee may be charged for copying 
parts of the docket. U.S. Environmental Protection Agency, Region 9, 
Air and Toxics Division, Mobile Sources Section, A-2-1, 75 Hawthorne 
Street, San Francisco, California 94105.

FOR FURTHER INFORMATION CONTACT: Wienke Tax, Mobile Sources Section, 
Air and Toxics Division, U.S. Environmental Protection Agency, Region 
9, 75 Hawthorne Street, San Francisco, California 94105, (415) 744-
1223.

SUPPLEMENTARY INFORMATION:

I. CAA Requirements and EPA Guidance for Emission Inventories

    Sections 172(c)(3) and 187(a)(1) of the CAA require that a 
comprehensive, accurate, and current base year inventory of actual 
emissions be submitted to EPA as a state implementation plan (SIP) 
revision for each area designated as nonattainment and classified 
moderate or serious for carbon monoxide.1 EPA has provided 
guidance to States for developing these CO inventories, most recently 
in Emission Inventory Requirements for Carbon Monoxide State 
Implementation Plans, (EPA-450/4-91-011) March, 1991) (``Emission 
Inventory Requirements''). While not an explicit requirement of the 
CAA, projected inventories are closely related to the base year 
inventory, and it is reasonable to review them in conjunction with the 
base year inventory.
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    \1\ At the time of the SIP submittals that are the subject of 
today's notice, Phoenix was classified as moderate and, because its 
design value is under 12.7 ppm, was considered a low moderate area. 
EPA has recently found that the Phoenix area failed to attain the CO 
NAAQS by the statutory deadline. See 61 FR 39343 (July 29, 1996) As 
a consequence of this finding, the area has been reclassified to 
``serious'' under section 186(b)(2). As a result, the area is now 
subject to the section 187(b) requirements for serious CO areas. 
These requirements include those applicable to CO areas with design 
values between 12.7 ppm and 16.4 ppm (high moderate areas) in 
section 187(a). For the purpose of today's action, however, the 
relevant CAA requirements are those that apply to low moderate CO 
nonattainment areas.
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    A technically-sound emissions inventory is important for a number 
of reasons. First, it is used to identify pollutant sources for new or 
additional controls and so provides a basis for the control strategy. 
Second, the inventory provides a means of assessing progress in 
achieving reductions from existing controls. Finally, both current and 
projected inventories are used as inputs to air quality modeling to 
demonstrate attainment of the national ambient air quality standards 
(NAAQS).
    The Clean Air Act requires that emissions inventories be 
comprehensive, accurate, and current. To be comprehensive, the 
inventory must include all stationary point and area sources, non-road 
mobile sources, and on-road mobile sources. To be accurate, the 
inventory must be based on data representative of sources within the 
nonattainment area. To be current, the inventory must represent 1990 
(the year of the CAA enactment) or later.

A. Requirements for Base Year Inventories

    The base year inventory is the primary inventory from which all 
other CO inventories are derived. The base year inventory is defined in 
the CAA as a ``current inventory'' which EPA interprets to mean 1990. 
See ``General Preamble for the Implementation of Title I of the Clean 
Air Act Amendments of 1990'' 57 FR 13498, 13530 (April 16, 1992). 
Annual emission inventory estimates are adjusted to represent the CO 
season weekday inventory (the ``planning inventory''). EPA recommends a 
three month peak CO season as the basis for the planning inventory 
estimates. See Emission Inventory Requirements, page 11.
    Stationary sources are grouped into point and area sources. Point 
sources are any stationary source emitting more than 100 tons per year 
of CO. Area sources generally include small stationary sources (e.g., 
stationary internal combustion engines) and ubiquitous emissions not 
associated with a permit (e.g., fireplaces). Mobile source estimates 
are divided into on-road and non-road categories. Emissions inventories 
for on-road mobile sources (e.g., automobiles, motorcycles, buses, and 
trucks) are generally developed using the latest version of MOBILE, 
EPA's mobile source emission factor model. The non-road mobile source 
inventory includes emissions from categories ranging from lawn mowers 
to marine vessels.
    In documenting its on-road mobile source inventory, states must 
report on how on-road vehicle emission factors and vehicle miles 
travelled (VMT) estimates were determined. The state must fully 
document how the most recent MOBILE model (MOBILE5a) was used to 
estimate emission factors for the vehicle fleet. For VMT, the state 
should describe the methodology employed to generate VMT data and the 
key assumptions and inputs to the process. Finally, the state must 
describe how the VMT data were combined with the emission factors to 
produce mobile source emissions estimates. See Emission Inventory 
Requirements, page 54.
    In its emissions inventory submittal, a state is also required to 
describe the implementation of the state's emission inventory quality 
assurance (Q/A) program and the results achieved by that program. For 
all source category types, the Q/A discussion must address the 
completeness of the inventory, reasonableness of the emissions 
estimates, and relative accuracy of the data. See Emission Inventory 
Requirements, page 55.
    A detailed discussion of EPA's emission inventory requirements can 
be found in the Technical Support Document (TSD) for this rulemaking as 
well as in the cited guidance documents. The TSD and all cited 
documents can be requested from the contact person listed at the 
beginning of this notice.

B. Guidance on Projected Emissions Inventories

    Future year inventories are needed for projecting and modeling 
attainment. Future year inventories are developed using base year 
inventory estimates adjusted using growth and control factors. EPA's 
guidance for developing projected year inventories is found in 
Procedures for Preparing Emissions Projections, (EPA-450/4-91-019) 
July, 1991.
    Inventory projections attempt to project how the combination of 
future emission controls and changes in source activity will influence 
future emission rates. Growth factors are developed using socioeconomic 
forecasts (i.e., population, housing, employment, and motor vehicle 
activity) and Standard Industrial Classification data. Growth rates for 
motor vehicles consider projected changes in vehicle miles traveled, 
trips, and vehicles in use. Control factors are used to adjust future 
year inventory estimates to account for reductions from adopted and 
scheduled measures. All growth and control factors and their derivation 
should be thoroughly documented.
    All emissions projected for future years should be based on the 
same inventory methodologies and computational principles as the base 
year emissions. For example, if a travel demand model is used for 
estimating travel in the base year, the same model should be applied to 
estimate travel demand for projected years. Using the same methodology 
ensures consistency in format and content between base year

[[Page 49089]]

and projection year emissions estimates and prevents possible spurious 
inventory differences due to changes in methodology.
    For further information on requirements for emission inventory 
projections, see the TSD.

II. The Maricopa CO Emissions Inventory Submittal

    The Arizona Department of Environmental Quality (ADEQ) initially 
submitted the 1990 base year (annual and average daily emissions) as 
well as projected 1995 and 2005 CO inventories for the entire Phoenix 
nonattainment area on November 15, 1993 as part of the Maricopa 
Association of Governments (MAG) 1993 Carbon Monoxide Plan for the 
Maricopa County Area (CO Plan). On April 4, 1994, ADEQ submitted 
updated and improved inventories as part of MAG's 1993 Carbon Monoxide 
Plan for the Maricopa County Area--Addendum (Addendum).2 These 
revised inventories reflected adjustments to growth factors and the 
impact of measures in Arizona House Bill 2001. Both submittals became 
complete by operation of law under CAA section 110(k)(1)(B) on May 15, 
1994 and October 8, 1994, respectively.
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    \2\ On August 9, 1993, EPA issued a SIP call under section 
110(k)(5) of the CAA that required Arizona to submit a plan to EPA 
that demonstrated attainment of the CO NAAQS in the Phoenix area by 
December 31, 1995. As an area with a design value under 12.7 ppm, 
the State would not otherwise have been required to submit an 
attainment plan for the Phoenix area. See section 187(a). CAA 
section 187(a)(1) requires the submittal of a comprehensive, 
accurate, current inventory of actual emission for all CO 
nonattainment areas whether or not they have a separate requirement 
to submit an attainment demonstration.
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    The Maricopa County Division of Air Pollution Control (MCAPC) 
prepared the stationary (point and area) and non-road mobile source 
portions of the inventories, while MAG Transportation and Planning 
Office prepared the transportation data and the on-road mobile sources 
emissions estimates. Quality assurance/quality control procedures were 
performed by MCAPC and ADEQ.

A. Baseline (1990) Emissions Inventory

    Because CO violations in Phoenix occur primarily from November 
through January, November and December of 1989 and January of 1990 were 
chosen as the basis for the planning inventory, as per EPA guidance. 
See Emission Inventory Requirements, page 11. The emissions data 
section of the inventories contains a summary of 1990 emissions data by 
source type (point, area and mobile), for both average daily emissions 
and annual emissions. See ``1990 Base Year Carbon Monoxide Emission 
Inventory for the Maricopa County, Arizona Nonattainment Area,'' MCAPC, 
August 1993 (located in Appendix B, Exhibit 1 of the CO Plan) (``EI 
Documentation'') at page 1-6. Inventory development procedures are 
discussed separately for point, area, non-road mobile and on-road 
mobile sources in the EI Documentation.
    MCAPC was the lead agency responsible for developing the point 
source inventory. All methods for collecting point source data and 
estimating emissions were documented, and detailed emissions 
information was provided (see Chapter 2 of the EI Documentation) and 
entered into EPA's Aerometric Information Retrieval System (AIRS). 
Point source base year emissions totalled 1299 tons CO per year (<1% of 
the inventory, without accounting for on-road mobile source emissions) 
and 8.7 tons CO per average CO season day (<1% of the inventory). See 
EI Documentation, page 1-6.
    MCAPC evaluated all area sources included in EPA's guidance 
document 3 for their significance in Maricopa County except 
residential incineration; open burning at industrial, commercial/
institutional, and residential sources; and charcoal grilling. The 
first two categories are prohibited by law; charcoal grilling was not 
addressed because suitable emission factors and activity data were not 
available and because emissions contributions from this category were 
judged to be negligible. See EI Documentation, page 3-1. A rule 
effectiveness (RE) factor of 80 percent was applied to source 
categories subject to regulation, as recommended by EPA for all 
categories except woodburning. Rule penetration was estimated per EPA 
guidance. See EI Documentation, page 3-1. While EPA recommends a 50 
percent RE factor for woodburning, woodburning is only a small fraction 
of the Maricopa CO inventory, so the assumption of a 80 percent RE 
factor is insignificant in this instance. Total CO base year emissions 
from area sources were 13,337.8 tons per year in 1990 (7.3% of 
inventory, without accounting for on-road mobile source emissions), and 
87.65 tons per average CO season day (7.7% of inventory). See EI 
Documentation, page 1-6.
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    \3\  Procedures for the Preparation of Emission Inventories for 
Precursors of Ozone, Volume I, (EPA 450/4-88-021) December 1988.
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    Non-road source categories inventoried in the CO Plan include 
aircraft, locomotives, and non-road equipment sources. EPA's Office of 
Mobile Sources prepared the emissions estimates for the non-road 
equipment source categories. See Chapter 3 of the EI Documentation. 
These categories included recreational vehicles, construction 
equipment, industrial/commercial equipment, lawn and garden equipment, 
and farm equipment. Emissions calculations were presented for aircraft 
(commercial, military, general aviation) and locomotives, per EPA 
guidance. See Procedures for Emission Inventory Preparation, Volume IV: 
Mobile Sources (EPA-450/4-81-026d Revised) 1992. (Procedures, Mobile 
Sources). Non-road CO emissions for 1990 totalled 167,303 tons (91.9% 
of inventory, without accounting for on-road mobile sources), while 
average daily CO season emissions totalled 238 tpd (20.8% of 
inventory). See EI Documentation, page 1-6.
    On-road mobile sources were inventoried per EPA guidance found in 
Procedures, Mobile Sources. MAGTPO prepared the 1990 VMT estimates, 
using the Highway Performance Monitoring System (HPMS) data for 1990 
collected by the Arizona Department of Transportation (ADOT). The HPMS 
data were supplemented by traffic count data and estimates of total 
street mileage in the CO nonattainment area from MAGTPO. The CO Plan 
contains an extensive discussion of the conversions performed on the 
HPMS data to produce inventory-compatible VMT estimates. See EI 
Documentation, Chapter 5.
    The version of the MOBILE model used to develop on-road mobile 
emission factors for the November 1993 and March 1994 submittals was 
MOBILE5. The CO Plan fully documents the inputs to the model. See EI 
Documentation, Chapter 5. On-road mobile source emission factors and 
emissions are presented by vehicle class and roadway type. Total CO 
baseline emissions from on-road mobile sources totalled 807.7 tons per 
CO season day (70.7% of inventory). See EI Documentation, Chapter 5.
    Chapter 6 of the EI Documentation contains a discussion of quality 
assurance and quality control (QA/QC) procedures used by the various 
agencies in developing the inventory. The QA/QC procedures included 
checks for accuracy, reasonableness, and completeness, including 
reviews by independent parties. More detailed procedures included 
reviewing the descriptive information contained in each section to 
assure completeness, clarity, and correctness; examining formulae, 
calculations and conversions to assure freedom from errors and 
inconsistencies; evaluating data quality to assure the worth and 
usefulness of

[[Page 49090]]

the inventory; and assessing, where possible, the significance of the 
calculated quantities to assure accuracy and justifiable precision.
    EPA has concluded that the baseyear emission inventories in the MAG 
CO Plan and Addendum conform to EPA's guidance and the CAA requirements 
for CO inventories and are therefore proposed for approval.

B. Projected Emissions Inventory

    The CO Plan contained a 1995 attainment year projected emission 
inventory. See Addendum, Exhibit 3. This inventory was prepared by MAG 
using the methodologies in EPA's guidance.4 The Addendum modified 
the projected inventory in several respects. First, in response to 
comments received during the public hearing on the Plan, MCAPC revised 
the growth factors used to project 1990 emissions to 1995. Secondly, in 
November 1993, the Arizona legislature passed H.B. 2001 which included 
additional commitments for measures designed to bring the region into 
attainment for CO. A few minor additional adjustments to modeling 
inventories were also made and the effects of the existing oxygenated 
fuels program on non-road emissions was included. Overall, these 
changes resulted in slight decreases (1-4 percent) in projected CO 
emissions for future years.
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    \4\  While the CO Plan and Addendum include a year 2005 CO 
projected emission inventory, EPA did not review that inventory. 
Neither the Clean Air Act nor EPA guidance requires states to 
demonstrate maintenance after the applicable attainment date until 
an area requests redesignation to attainment under section 175A(a).
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    EPA has concluded from its review of the 1995 projected year 
emission inventory in the MAG CO Plan and Addendum that it conformed 
EPA's guidance for CO projected inventories.

III. Summary of EPA Actions

    Because EPA has concluded that it conforms to EPA guidance for base 
year emission inventories, EPA is proposing to approve, pursuant to 
sections 172(c)(3) and 187(a)(1) of CAA, the 1990 CO base year 
inventory for the Maricopa CO nonattainment area. EPA is also finding 
that the 1995 projected year inventory conforms to EPA guidance.
    Nothing in this proposed action should be construed as permitting 
or allowing or establishing a precedent for any future request for 
revision to any SIP. Each request for a 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.

IV. Administrative Requirements

A. Executive Order 12866

    This action has been classified as a Table 3 action for signature 
by the Regional Administrator under the procedures published in the 
Federal Register on January 19, 1989 (54 FR 2214-2225), as revised by a 
July 10, 1995 memorandum from Mary Nichols, Assistant Administrator for 
Air and Radiation. The Office of Management and Budget (OMB) has 
exempted this regulatory action from E.O. 12866 review.

B. Regulatory Flexibility Act

    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 impact on a substantial number of small entities. Small 
entities include small business, small not-for-profit enterprises and 
government entities with jurisdiction over populations of less than 
50,000.
    SIP approvals under subchapter I, part D of the Clean Air Act, do 
not create any new requirements, but simply approve requirements that a 
state is already imposing. The action proposed today is simply the 
approval of technical information required to be developed under the 
CAA and imposes no state or federal requirements on any entity. 
Therefore, the Administrator certifies that it does not have a 
significant impact on any small entities affected. Moreover, due to the 
nature of the Federal-State relationship under the CAA, preparation of 
a flexibility analysis would constitute federal inquiry into the 
economic reasonableness of state action. The Clean Air 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. 7410(a)(2).

C. Unfunded Mandates

    Under section 202 of the Unfunded Mandates Reform Act of 1995 
(``Unfunded Mandates Act''), signed into law on March 22, 1995, EPA 
must prepare a budgetary impact statement to accompany any proposed or 
final rule that includes a federal mandate that may result in estimated 
costs to state, local, or tribal governments in the aggregate; or to 
the private sector, of $100 million or more. Under section 205, EPA 
must select the most cost-effective and least burdensome alternative 
that achieves that objectives of the rule and is consistent with 
statutory requirements. Section 203 requires EPA to establish a plan 
for informing and advising any small governments that may be 
significantly or uniquely impacted by this rule.
    EPA has determined that the approval action proposed does not 
include a federal mandate that may result in estimate costs of $100 
million or more to either state, local, or tribal governments in the 
aggregate, or to the private sector. This Federal action approves pre-
existing requirements under state or local law, imposes no new federal 
requirements. Accordingly, no additional costs to State, local or 
tribal governments, or to the private sector, results from this action. 
Accordingly, no costs to State, local, or tribal governments, or to the 
private sector, result from this action.

List of Subjects in 40 CFR Part 52

    Environmental protection, Air pollution control, Carbon monoxide, 
Intergovernmental relations.

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

    Dated: September 9, 1996.
Felicia Marcus,
Regional Administrator.
[FR Doc. 96-23822 Filed 9-17-96; 8:45 am]
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