Clean Air Act Approval and Promulgation of the Denver, Colorado Mobile Source Emissions Budgets for PMINF10/INF and NOINFX/INF

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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