[Federal Register Volume 62, Number 150 (Tuesday, August 5, 1997)]
[Proposed Rules]
[Pages 42088-42090]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 97-20582]


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ENVIRONMENTAL PROTECTTION AGENCY

40 CFR Part 52

[CO-001-0017 and CO-001-0018; FRL-5869-4]


Clean Air Act Approval and Promulgation of the Denver, Colorado 
Mobile Source Emissions Budgets for PM10 and NOX

AGENCY: Evironmental Protection Agency (EPA).

ACTION: Proposed rule.

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SUMMARY: EPA is requesting additional comments on certain aspects of 
the State Implementation Plan (SIP) revisions for the Denver 
PM10 and NOX mobile source emissions budgets that 
were submitted by the Governor of Colorado. EPA initially proposed 
approval of the SIP revisions on October 3, 1996 (61 FR 51631). During 
that rulemaking's public comment period, EPA received several comments. 
Due to the complexity of the issues, EPA is asking interested parties 
to submit additional information on two issues. This information may 
help EPA make a more informed decision on the appropriateness of 
approving both the PM10 and NOX emissions budget 
SIPs.

DATES: Comments on this request for additional information must be 
received in writing on or before September 4, 1997.

ADDRESSES: Copies of the State's original PM10 and 
NOX emissions budget SIPs, comments received during the 
public comment period, and other information are available for 
inspection during normal business hours at the Environmental Protection 
Agency, Region VIII, Air Program, 999 18th Street, 3rd Floor, South 
Terrace, Denver, Colorado 80202-2466.

FOR FURTHER INFORMATION CONTACT: Callie Videtich at (303) 312-6434.

SUPPLEMENTARY INFORMATION:

I. Background

    On July 18, 1995, and April 22, 1996, the Colorado Governor 
submitted revisions to the Denver PM10 SIP which establish 
mobile source emissions budgets for PM10 and NOX 
respectively. These budgets are used under EPA regulations for making 
transportation related conformity determinations as required by section 
176(c) of the Act. EPA's transportation conformity rule provides that 
these budgets establish a cap on motor vehicle-related emissions which 
cannot be exceeded by the predicted transportation system emissions in 
the future unless the cap is amended by the State and approved by EPA 
as a SIP revision and attainment and maintenance of the standard can be 
demonstrated.
    EPA proposed approval of both emissions budgets on October 3, 1996 
(61 FR 51631) along with the Denver PM10 SIP. Following a 60 
day public comment period, EPA finalized approval of the Denver 
PM10 SIP on April 17, 1997 (62 FR 18716). EPA did not take 
final action on the emissions budget submittals in order to more 
thoroughly consider comments received on the proposals during the 
public comment period.

II. This Action

    Based upon a thorough review, EPA has concluded that additional 
information is needed in order for EPA to make an informed decision 
about certain aspects of the SIPs based upon public comments responding 
to our proposed approval of the PM10 and NOX 
emissions budgets. EPA is seeking additional information on the two 
issues outlined below.
    1. It appears to EPA that the Colorado legislature, through Senate 
Bill 95-110 (codified at section 25-7-105(1)(a)(III), C.R.S.), changed 
the PM10 emissions budgets that the Colorado Air Quality 
Control Commission (AQCC) had adopted on February 16, 1995. EPA wishes 
to take comment on whether the PM10 budgets that were 
ultimately submitted to EPA for approval were adopted after reasonable 
notice and public hearing as required by section 110 of the Clean Air 
Act (CAA). Section 110(a)(2) of the CAA provides that ``[e]ach 
implementation plan submitted by a State under this Act shall be 
adopted by the State after reasonable notice and public hearing.'' 
Robert Yuhnke, on behalf of COPIRG, Colorado Environmental Coalition, 
Citizens for Balanced Transportation, American Lung Association of 
Colorado, Environmental Defense Fund, and Ms. Stephanie Mines, and 
Frank Johnson, on behalf of the Colorado Attorney General's Office, 
have submitted information that touches on this question. Their letters 
may be examined at the address listed above. EPA wishes to obtain 
further comment on this issue. In particular, EPA is concerned that the 
legislative action did not meet the CAA's requirements for notice and 
public hearing and that no subsequent public hearing was held before 
the AQCC. The Colorado Attorney General's Office has suggested that 
hearings held before the AQCC in September and October 1994, and in 
February 1995, were adequate to satisfy the CAA's hearing requirement, 
and that there is no requirement that a hearing be held at every step 
in the State review process. It has also indicated that the State 
legislative process is an open and public process and that the 
legislators are accountable to the electorate.
    2. Commentors were concerned that the budgets do not demonstrate 
attainment considering growth in non-mobile sources, and that the 
adopted NOX budget of 119.4 tons per day was not consistent 
with the NOX inventory of 102.7 tons per day used in the 
maintenance demonstration. (In the following discussion, EPA uses the 
terms ``mobile source'' and ``mobile source emissions'' to mean ``motor 
vehicle'' and ``motor vehicle emissions,'' consistent with the State's 
submittal. Neither the State's budget submittal nor EPA's conformity 
rule regulate emissions from non-road mobile sources.)
    The Regional Air Quality Council's(RAQC's) proposal to the AQCC to 
increase the emissions budget was based on an analysis showing that the 
Denver modeling region could tolerate mobile source PM10 
emissions of 221 tons per day in 2015 before a violation of the 
PM10 standard would occur. (This analysis was not submitted 
at the time the budgets were submitted to EPA, but was referenced in

[[Page 42089]]

proceedings before the RAQC and the AQCC in 1994 and was provided by 
the RAQC on April 23, 1997.) By contrast, the attainment and 
maintenance demonstrations are based on emissions levels of 41 and 44 
tons per day, respectively. The RAQC defined the difference between 44 
tons per day and 221 tons per day (i.e., 177 tons) as a ``safety 
margin'' in emissions and assigned 16 tons of this safety margin to 
mobile source PM10 (i.e., raised the SIP's budget to 60 tons 
per day) in order to facilitate future conformity determinations by the 
Denver Regional Council of Governments (DRCOG). The RAQC and the State 
justified the increase of the budget from 44 to 60 tons by noting that 
this increase represented only a small portion of the available safety 
margin. The RAQC's analysis assumed 2015 emissions levels of all non-
mobile sources, and assumed zero NOX emissions from mobile 
sources (i.e., that all emissions were direct PM10 
emissions).
    The RAQC's analysis is strictly a mathematical analysis of the 
maximum level of emissions that could theoretically be accommodated in 
each grid in the modeling domain; it is not an analysis of any 
particular projected growth scenario for Denver. The analysis assumes 
equal levels of emissions in each grid of the modeling domain, from 
downtown Denver to rural outlying portions of the domain. Although the 
safety margin provision in Section 93.132(b) of the conformity rule 
applies only to existing adopted SIPs which contained a built-in safety 
margin, section 93.132(a) clearly envisions cases in which a SIP 
quantifies a safety margin and explicitly assigns some or all of it to 
the mobile source budget. This general provision applies to situations 
where a state reanalyzes a SIP to quantify and assign the safety 
margin.
    As noted above, the RAQC's analysis accounts for growth in non-
mobile sources of emissions to 2015 levels but does not account for 
mobile source NOX (all mobile source emissions are treated 
as PM10 emissions). To quantify the impact of this omission, 
EPA reviewed documents related to the attainment demonstration and 
found that an increase of 10.4 tons per day of NOX would 
lead to a 1.0g/m3 increase in PM10 concentrations 
(source: July 7, 1994 and February 8, 1995 Kevin Briggs memoranda). 
Thus, the adopted budget of 119.4 tons per day of NOX would 
equate to approximately 22 tons per day of PM10. Subtracting 
this 22 tons from the RAQC's original 221 ton budget, a 199 ton 
PM10 budget along with a 119.4 ton NOX budget 
would still provide for attainment of the NAAQS. However, the State has 
only revised the SIP to establish a 60 ton PM10 budget and a 
119.4 ton NOX budget. Thus, NOX emissions of 
119.4 tons per day can be easily by accommodated within the 177 ton 
PM10 safety margin identified by the RAQC and the State.
    The fact that the 119.4 ton per day NOX budget can be 
accommodated within the safety margin identified by the RAQC is one 
reason that EPA is not concerned that this budget is inconsistent with 
the SIP's 1998 maintenance demonstration budget of 102.7 tons per day. 
The other reason is the SIP's requirement that each conformity 
determination must include a modeling analysis demonstrating attainment 
of the PM10 NAAQS (discussed below). Even though the adopted 
NOX budget is higher than the inventory used in the 
maintenance demonstration, DRCOG's transportation plans and 
transportation improvement programs (TIPs) must still pass a modeling 
analysis showing attainment of the NAAQS, incorporating the impacts of 
the 119.4 ton NOX budget, or the plans and TIPs cannot be 
found to conform.
    EPA believes that the NAAQS are protected by the SIP's requirement 
for dispersion modeling each time a conformity analysis is conducted. 
The SIP requires that DRCOG support each conformity determination with 
a dispersion modeling analysis that shows that each grid in the 
modeling domain will be in attainment, considering the emissions 
expected from implementation of the transportation plan or TIP. If the 
modeling analysis shows that emissions reductions are needed in any 
locations in order to provide for attainment of the NAAQS, it is 
incumbent upon DRCOG to identify and ensure implementation of any 
measures needed to provide those reductions. Thus, DRCOG must satisfy 
two types of tests to demonstrate conformity: compliance with the 60 
ton PM10 budget and the 119.4 ton NOX budget, and 
a dispersion modeling analysis showing no violations.
    The commentors quote the preamble to EPA's November 24, 1993 
transportation conformity regulation in objecting to the use of 
dispersion modeling in conformity determinations. EPA believes that the 
Act precludes the use of dispersion modeling as a substitute for an 
emissions budget test. However, EPA's conformity rule did not 
anticipate situations where a state would wish to require a regional 
dispersion modeling analysis in addition to an emissions budget test. 
EPA does not believe that such an application of dispersion modeling is 
precluded by either the Act or the conformity rule. One commentor 
suggested that the State adopt subregional emissions budgets in lieu of 
requiring dispersion modeling; however, as a practical matter, the 
requirement for dispersion modeling has the same effect as establishing 
subregional budgets because in either case a certain target level of 
emissions has to be met in each grid in order for each grid to show 
attainment.
    In fact, the requirement for dispersion modeling in addition to a 
budget test is arguably more protective of the NAAQS than the budget-
only process envisioned by the conformity rule. First, a supplemental 
requirement for dispersion modeling is certainly more protective than a 
region-wide budget alone. The commentors argue that subregional budgets 
for problem grids could be identified. However, establishing fixed 
subregional budgets through the SIP process would not provide the 
flexibility to consider future growth patterns. Due to changes in the 
geographic distribution of growth, NAAQS problems could emerge in areas 
of the city outside of the area for which subregional budgets had been 
established, in the geographic area covered only by the region-wide 
budget. A requirement for dispersion modeling each time a conformity 
determination is made ensures that these new ``hotspots'' are 
identified and addressed. A one-time effort to establish subregional 
budgets would not.
    EPA notes that the SIP does not require growth in non-mobile 
sources to be considered in conducting dispersion modeling for the 
purposes of conformity determinations. However, the RAQC factored in 
the future year contribution of non-mobile source emissions (estimated 
at 23.8 tons per day in 2015 in the February 8, 1995 Briggs memorandum, 
or 29 tons per day in the April 23, 1997 RAQC memorandum) in defining 
the region's 177 ton per day safety margin (and thus, in setting the 60 
ton budget). More importantly, this aspect of the conformity modeling 
methodology (that is, not considering growth in non-mobile sources each 
time a conformity determination is made) is consistent with the way 
conformity is applied in the other nonattainment areas throughout the 
country which rely solely on their SIP emission budgets. Growth in non-
mobile sources must be considered when budgets are set through the SIP 
process; however, there is no requirement for future conformity 
determinations to continually re-evaluate the adequacy of these budgets 
given growth in non-mobile sources.

[[Page 42090]]

    In summary, EPA believes that the fact that only a small portion of 
the SIP's safety margin has been allocated to the mobile source 
emissions budget, along with the requirement for dispersion modeling 
each time a conformity determination is conducted, are adequate to 
ensure that the NAAQS are protected by the emissions budgets adopted by 
the State and submitted to EPA. EPA is requesting further comment in 
support of or opposed to this rationale for approving the budget 
submittals.

III. Proposed Action

    EPA is seeking additional information from interested parties on 
two issues related to the Denver PM10 and NOX 
mobile source emissions budget SIPs. EPA initially proposed approval of 
the SIP revisions on October 3, 1996 (61 FR 51631).
    As indicated elsewhere in this document, EPA will consider any 
comments received by September 4, 1997 relating to the two issues 
described above relating to the two SIPs.

IV. Executive Order 12866

    The Office of Management and Budget (OMB) has exempted this 
regulatory action from E.O. 12866 review.

V. 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 sections 110 and subchapter I, part D of the 
CAA do not create any new requirements but simply approve requirements 
that the State is already imposing. Therefore, because this proposed 
Federal SIP approval does not impose any new requirements, I certify 
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 
CAA 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 (1976); 42 
U.S.C. 7410(a)(2).

VI. 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 the 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 the rule.
    EPA has also determined that this proposed action does not include 
a Federal mandate that may result in estimated costs of $100 million or 
more to State, local, or tribal governments in the aggregate, or to the 
private sector. This Federal action would approve pre-existing 
requirements under State or local law, and would impose no new Federal 
requirements. Accordingly, no additional costs to State, local, or 
tribal governments, or to the private sector would result form this 
action.

List of Subjects in 40 CFR Part 52

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

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

    Dated: July 14, 1997.
Jack W. McGraw,
Acting Regional Administrator.
[FR Doc. 97-20582 Filed 8-4-97; 8:45 am]
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