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

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

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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.

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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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