[Federal Register Volume 67, Number 100 (Thursday, May 23, 2002)]
[Proposed Rules]
[Pages 36124-36134]
From the Federal Register Online via the Government Printing Office [www.gpo.gov]
[FR Doc No: 02-12965]


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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 52

[CO-001-0067; FRL-7215-9]


Approval and Promulgation of Air Quality Implementation Plans; 
State of Colorado; Denver PM10 Redesignation to Attainment, 
Designation of Areas for Air Quality Planning Purposes

AGENCY: Environmental Protection Agency (EPA).

ACTION: Proposed rule.

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SUMMARY: On July 30, 2001, the Governor of the State of Colorado 
submitted a State Implementation Plan (SIP) revision for the purpose of 
establishing a redesignation for the Denver, Colorado area from 
nonattainment to attainment for particulate matter with an aerodynamic 
diameter less than or equal to a nominal 10 microns (PM10) 
under the 1987 standards. The Colorado Air Pollution Control Division's 
submittal, among other things, documents that the Denver area has 
attained the PM10 national ambient air quality standards 
(NAAQS), requests redesignation to attainment and includes a 
maintenance plan for the area demonstrating maintenance of the 
PM10 NAAQS for thirteen years. EPA is proposing to approve 
the redesignation

[[Page 36125]]

request and maintenance plan because the State has met the applicable 
requirements of the Clean Air Act, as amended. This action is being 
taken under sections 107, 110, and 175A of the Clean Air Act (Act).

DATES: Written comments must be received on or before June 24, 2002.

ADDRESSES: Written comments may be mailed to Richard R. Long, Director, 
Air and Radiation Program, Mailcode 8P-AR, Environmental Protection 
Agency (EPA), Region VIII, 999 18th Street, Suite 300, Denver, 
Colorado, 80202-2466. Copies of the documents relevant to this action 
are available for public inspection during normal business hours at the 
Air and Radiation Program, Environmental Protection Agency, Region 
VIII, 999 18th Street, Suite 300, Denver, Colorado, 80202-2466. Copies 
of the State documents relevant to this action are available for public 
inspection at the Colorado Department of Public Health and Environment, 
Air Pollution Control Division, 4300 Cherry Creek Drive South, Denver, 
Colorado 80246-1530.

FOR FURTHER INFORMATION CONTACT: Cindy Rosenberg, EPA, Region VIII, 
(303) 312-6436.

SUPPLEMENTARY INFORMATION: Throughout this document, wherever ``we,'' 
``us,'' or ``our'' are used, we mean the Environmental Protection 
Agency (EPA).

Table of Contents

I. EPA's Proposed Action
    A. What Action Is EPA Proposing To Take?
II. Summary of Redesignation Request and Maintenance Plan
    A. What Requirements Must be Followed for Redesignations to 
Attainment?
    B. Does the Denver Redesignation Request and Maintenance Plan 
Meet the CAA Requirements?
    C. Have the Transportation Conformity Requirements been met?
    D. Did Colorado Follow the Proper Procedures for Adopting this 
Action?
III. Background
IV. Administrative Requirements

I. EPA's Proposed Action

A. What Action Is EPA Proposing To Take?

    We are proposing to approve the Governor of Colorado's submittal of 
July 30, 2001, that requests a redesignation for the Denver 
nonattainment area to attainment for the 1987 PM10 
standards. We are using 1998-2000 ambient air quality data from the 
Denver nonattainment area as the basis for our decision. We are also 
proposing to approve the maintenance plan for the Denver 
PM10 nonattainment area, which was submitted with the 
State's July 30, 2001 redesignation request. In conjunction with the 
maintenance plan, the Governor also submitted revisions to Colorado's 
Regulation No. 1, ``Particulates, Smokes, Carbon Monoxide, & Sulfur 
Oxides,'' and Colorado's Regulation No. 16, ``Street Sanding 
Emissions.'' We are proposing to approve this request, the maintenance 
plan and its accompanying regulation revisions because the Colorado Air 
Pollution Control Division (Colorado) has adequately addressed all of 
the requirements of the Act for redesignation to attainment applicable 
to the Denver PM10 nonattainment area. Upon the effective 
date of a subsequent final action, the Denver area's designation status 
under 40 CFR part 81 will be revised to attainment. By using ``Denver'' 
or the ``Denver area,'' we mean Denver, Jefferson, and Douglas 
Counties, as well as part of Boulder, Adams and Arapahoe Counties.
    EPA is soliciting public comments on the issues discussed in this 
document or on other relevant matters. These comments will be 
considered before taking final action. Interested parties may 
participate in the Federal rulemaking procedure by submitting written 
comments to the EPA Regional office listed in the ADDRESSES section of 
this document.

II. Summary of Redesignation Request and Maintenance Plan

A. What Requirements Must Be Followed for Redesignations to Attainment?

    In order for a nonattainment area to be redesignated to attainment, 
the following conditions in section 107(d)(3)(E) of the Clean Air Act 
(CAA) must be met:
    (i) We must determine that the area has attained the NAAQS;
    (ii) The applicable implementation plan for the area must be fully 
approved under section 110(k) of the Act;
    (iii) We must determine that the improvement in air quality is due 
to permanent and enforceable reductions in emissions resulting from 
implementation of the applicable implementation plan and applicable 
Federal air pollutant control regulations and other permanent and 
enforceable reductions;
    (iv) We must fully approve a maintenance plan for the area as 
meeting the requirements of CAA section 175A; and,
    (v) The State containing such area must meet all requirements 
applicable to the area under section 110 and part D of the CAA.
    Our September 4, 1992 guidance entitled ``Procedures for Processing 
Requests to Redesignate Areas to Attainment'' (referred to in this 
action as the Calcagni Memorandum) outlines how to assess the adequacy 
of redesignation requests against the conditions listed above.
    On July 30, 2001, the Governor of Colorado submitted a revision to 
the SIP for the Denver area and a request that we redesignate the area 
to attainment for PM10. The following is a brief discussion 
of how Colorado's redesignation request and maintenance plan meets the 
requirements of the Act for redesignation of the Denver area to 
attainment for PM10.

B. Does the Denver Redesignation Request and Maintenance Plan Meet the 
CAA Requirements?

i. Attainment of the PM10 NAAQS
    Whether an area has attained the PM10 NAAQS is based 
exclusively upon measured air quality levels over the most recent and 
complete three calendar year period. See 40 CFR part 50 and 40 CFR part 
50, appendix K. A State must demonstrate that an area has attained the 
PM10 NAAQS through submittal of ambient air quality data 
from an ambient air monitoring network representing maximum 
PM10 concentrations. The data, which must be quality assured 
and recorded in the Aerometric Information Retrieval System (AIRS), 
must show that the average annual number of expected exceedances for 
the area is less than or equal to 1.0, pursuant to 40 CFR 50.6. In 
making this showing, three consecutive years of complete air quality 
data must be used.
    Between 1998 and 2000, Colorado operated thirteen PM10 
monitors, which were either State and Local Air Monitoring Stations 
(SLAMS) or National Air Monitoring Sites (NAMS), in the Denver 
PM10 nonattainment area. As part of the redesignation 
request for Denver, Colorado submitted ambient air quality data from 
the monitoring sites which demonstrates that the area has attained the 
PM10 NAAQS. This air quality data had been quality-assured 
and placed in AIRS on a quarterly basis. Only one exceedance of the 24-
hour PM10 NAAQS was measured between 1998 and 2000. In 1999, 
the Adams City monitor recorded a 24-hour value of 160 fg/m3, which is 
an exceedance. Because data collection was less than 100% at this 
monitoring site, the expected exceedance rate, as calculated according 
to 40 CFR part 50, appendix K, for 1999 at this site was 1.16. For 1998 
and 2000, it was 0.0. Thus, the three-year average was less than 1.0, 
which indicates the Denver area attained the 24-hour PM10

[[Page 36126]]

NAAQS. All other sites had expected exceedance rates of 0 for this 
three-year period. In addition, there have been no reported exceedances 
of the PM10 NAAQS so far in 2001. Review of the annual 
standard for calendar years 1998, 1999 and 2000 reveals that the Denver 
area is also in attainment with the annual PM10 NAAQS. There 
was no violation of the annual standard for the three year period from 
1998 through 2000. Further information on PM10 monitoring is 
presented in Chapter 3, section B of the redesignation request and 
maintenance plan. We have evaluated the ambient air quality data and 
believe that Colorado has adequately demonstrated that the 
PM10 NAAQS has been attained in the Denver area.
ii. State Implementation Plan Approval
    Section 107(d)(3)(E)(ii) of the CAA states that for an area to be 
redesignated to attainment, it must be determined that the 
Administrator has fully approved the applicable implementation plan for 
the area under section 110(k).
    Those States containing initial moderate PM10 
nonattainment areas were required to submit a SIP by November 15, 1991 
which demonstrated attainment of the PM10 NAAQS by December 
31, 1994. However, under section 188(d) of the CAA, moderate 
PM10 nonattainment areas are eligible for up to two one-year 
extensions of their attainment dates if they meet the requirements of 
the Act. Colorado requested an attainment date extension for Denver and 
it was granted on October 6, 1995 (60 FR 52312). The Denver 
nonattainment area subsequently attained the NAAQS by December 31, 
1995, which was the area's applicable attainment date following the 
granting of the attainment date extension. Section 107(d)(3)(E)(ii) of 
the CAA states that for an area to be redesignated to attainment, it 
must be determined that the Administrator has fully approved the 
applicable implementation plan for the area under section 110(k). We 
approved the PM10 contingency measures for the area on 
September 23, 1996 (61 FR 49682). We approved the PM10 SIP 
for Denver on April 17, 1997 (62 FR 18716) as meeting those moderate 
PM10 nonattainment plan requirements that were due to EPA on 
November 15, 1991. The transportation budgets required under the 
transportation conformity rule were approved on March 31, 1998 (63 FR 
15294).
iii. Improvement in Air Quality Due to Permanent and Enforceable 
Measures
    Section 107(d)(3)(E)(iii) of the CAA provides that for an area to 
be redesignated to attainment, the Administrator must determine that 
the improvement in air quality is due to permanent and enforceable 
reductions in emissions resulting from implementation of the applicable 
implementation plan, implementation of applicable Federal air pollutant 
control regulations, and other permanent and enforceable reductions.
    The control measures in the Denver PM10 element of the 
Colorado SIP were adopted by the AQCC on October 19, 1995, and were 
approved by the EPA on April 17, 1997 (62 FR 18716). The SIP element's 
emission control plan was based on emission reductions from stationary 
source controls, re-entrained road dust controls, woodburning 
restrictions, and mobile source emission control programs. These 
permanent and enforceable control measures are explained in more detail 
below.
    As part of the PM10 SIP, Denver has been implementing 
the requirements of Colorado Regulation No. 1 ``Particulates, Smokes, 
Carbon Monoxide, & Sulfur Oxides.'' The portion of this regulation for 
which PM10 emission reduction credits are used provides 
stationary source emission control regulations. These control measures 
include regulation limits on specific units for precursor emissions 
(NOX and SO2) at Public Service Company of 
Colorado's Cherokee, Arapahoe and Valmont Electric Generating Stations. 
There are also restrictions on the use of oil as a backup fuel for 
natural gas to control particulate emissions from the following 
stationary sources in the Denver area: Public Service Company of 
Colorado's Valmont and Zuni Electric Generating Stations, Public 
Service Company of Colorado's Delegany Steam Generating Station, 
University of Colorado Health Sciences Center (Fitzsimmons), U.S. 
Department of Energy's Rocky Flats Plant, Gates Rubber Company, and 
Trigen-Colorado Energy Corporation \1\ (this requirement only applies 
to the company's Golden, Colorado facility). This regulation requires 
that natural gas is the only fuel oil to be used from November 1 to 
March 1 of each year except under certain circumstances that are 
explained in the regulation. In addition, there are limitations on 
primary PM10 emissions from fuel burning equipment that 
apply to the boiler units at Public Service Company of Colorado's 
Arapahoe, Cherokee, and Zuni Electric Generating Stations, as well as 
Trigen-Colorado Energy Corporation. There are also particulate 
limitations on all sources with incinerators, limitations on all 
stationary sources with manufacturing processes (as defined in 
Colorado's Common Provisions Regulation), and regulations for any 
source of fugitive particulates. (See Colorado's Regulation No. 1 for 
more details on these restrictions.)
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    \1\ The federally approved version of Regulation No. 1 lists 
this source as Coors Brewing Company, Coors Brewery, Golden, CO; the 
boiler units at the brewery were sold to Trigen-Colorado Energy 
Corporation since that version of the regulation was approved. 
Colorado has subsequently made revisions to this regulation, which 
include changing the name for this facility. Colorado will submit 
these revisions to EPA in the future in order for them to be 
federally approved.
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    Denver has also been implementing the requirements of Colorado 
Regulation No. 4 ``New Wood Stoves and the use of Certain Woodburning 
Appliances During High Pollution Days.'' The primary strategy of 
Regulation No. 4 is the mandatory wood burning curtailment program that 
prohibits most wood burning activity on ``high pollution days'' between 
November 1st and March 31st of each year in the Denver metropolitan 
area. Regulation No. 4 also requires all new wood burning stoves and 
fireplace inserts sold in Colorado to meet both State and Federal 
emission control standards. In addition to this State regulation, our 
April 17, 1997 approval of the PM10 SIP incorporated 19 
local woodburning ordinances and resolutions.
    Colorado's Regulation No. 16 covers street sanding and sweeping 
requirements. Under this regulation, street sand is required to meet 
stringent specifications to reduce the amount of fines and increase the 
durability of the sanding materials. With the implementation of this 
regulation, most of the Denver area governments were required to reduce 
the amount of street sand applied to their roadways by 20 percent from 
a base sanding amount (as defined in Colorado Regulation No. 16, this 
is an average amount of street sanding material applied per lane mile 
driven by maintenance trucks during snow and ice removal operations 
according to 1989 data), with the exception of the City of Denver. 
Denver was required to reduce the amount of street sanding materials 
applied by 30 percent from the base sanding amount. Emissions in the 
Central Denver area and the Interstate 25 Corridor area were to be 
reduced by 50 percent from the base sanding amounts. The street 
sweeping requirements for the Denver nonattainment area include 
additional street sweeping in the Denver central

[[Page 36127]]

business district and the Interstate 25 Corridor area after each 
sanding event.
    The mobile source control measures implemented with the 
PM10 SIP include Colorado's Regulation No. 11, ``Motor 
Vehicle Emissions Inspection Program,'' Regulation No. 12 ``Diesel 
Inspection/Maintenance Program,'' and Regulation No. 13 ``Oxygenated 
Fuels Program.''
    Stationary source construction permits for Public Service Company 
of Colorado's Cherokee Electric Generating Station, Purina Mills, 
Electron Corporation, Trigen-Colorado Energy Corporation, Rocky 
Mountain Bottle Company (which includes earlier permits that were 
issued in 1993 under the former name of Coors Brewing Company), and 
Conoco Refinery were incorporated by reference in our April 17, 1997 
approval of the PM10 SIP. Thus, EPA also viewed these 
permits as enforceable control measures under the SIP.
    Colorado Regulation No. 3 ``Air Contaminant Emissions Notices'' and 
No. 6 ``Standards of Performance for New Stationary Sources'' also 
provide for stationary source controls. The federally approved portions 
of these regulations are part of the state-wide SIP and weren't 
approved specifically with the Denver PM10 SIP.
    We have evaluated the various State and Federal control measures, 
the original 1989 base year emission inventory and the original 1995 
attainment year emission inventory, and believe that the improvement in 
air quality in the Denver nonattainment area has resulted from emission 
reductions that are permanent and enforceable.
iv. Fully Approved Maintenance Plan Under Section 175A of the Act
    Section 107(d)(3)(E) of the Act requires that, for a nonattainment 
area to be redesignated to attainment, we must fully approve a 
maintenance plan which meets the requirements of section 175A of the 
Act. The plan must demonstrate continued attainment of the relevant 
NAAQS in the area for at least 10 years after our approval of the 
redesignation. Eight years after our approval of a redesignation, the 
State must submit a revised maintenance plan demonstrating attainment 
for the 10 years following the initial 10 year period. The maintenance 
plan must also contain a contingency plan to ensure prompt correction 
of any violation of the NAAQS. (See sections 175A(b) and (d).) Our 
September 4, 1992 guidance outlines 5 core elements that are necessary 
to ensure maintenance of the relevant NAAQS in an area seeking 
redesignation from nonattainment to attainment. Those elements, as well 
as guidelines for subsequent maintenance plan revisions, are explained 
in detail below.

a. Attainment Inventory

    EPA's interpretations of the CAA section 175A maintenance plan 
requirements are generally provided in the General Preamble (see 57 FR 
13498, April 16, 1992) and the September 4, 1992, Calcagni Memorandum 
referenced above. Under our interpretations, PM10 
maintenance plans should include an attainment emission inventory to 
identify the level of emissions in the area which is sufficient to 
maintain the NAAQS.
    An emissions inventory was developed and submitted with the 
PM10 maintenance plan for the Denver area on July 30, 2001. 
This submittal contains a 1995 attainment year inventory as well as 
interim-year projection inventories for 2002, 2003, 2005, 2010 and 
2015. The 1995 attainment inventory is an updated version of the 
attainment inventory submitted on March 30, 1995 with the 
PM10 SIP. Due to the nature of Denver's past 24-hour 
PM10 problems, these inventories reflect emission estimates 
for an average winter weekday after a snow event. The inventories 
include emissions from all sources of PM10 and 
PM10 precursor emissions (nitrogen oxides and sulfur dioxide 
(NOX and SO2)) within the modeling domain for the 
Denver area. (This modeling domain is actually smaller than the Denver 
nonattainment area due to technical modeling limitations, but does 
include all areas with the expected maximum PM10 
concentrations.) The precursor emissions are important because filter 
analyses performed in conjunction with chemical mass balance modeling, 
for the attainment SIP, indicated that a significant portion (35%) of 
the PM10 on the filters consisted of secondary ammonium 
sulfate and nitrate.
    Emission estimates for the inventories were updated based on the 
most recent demographic and vehicle miles traveled (VMT) estimates from 
the Denver Regional Council of Governments' November 2000 conformity 
analysis. This includes population, household, employment and daily VMT 
estimates. The major contributors identified in the attainment year and 
projection inventories were on-road mobile source emissions (including 
vehicle exhaust and re-entrained road dust), fugitive dust emissions 
from unpaved roads, residential heating emissions, primary 
PM10 emissions from stationary sources, and secondary 
emissions of NOX and SO2 from stationary sources 
and on-road and off-road mobile sources. More detailed descriptions of 
the 1995 attainment year inventory and the 2002, 2003, 2005, 2010 and 
2015 projected inventories are documented in the maintenance plan in 
Chapter 4, sections B and C, and in Colorado's technical support 
documentation. Colorado's submittal contains detailed emission 
inventory information that was prepared in accordance with EPA emission 
inventory guidance.\2\ Summary emission figures from the 1995 
attainment year and the interim projected years are provided in Table 
II. 1, 2 and 3 below.
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    \2\ EPA's current guidance on the preparation of PM10 
emission inventories includes, ``PM10 Emission Inventory 
Requirements,'' September 1994, ``Emission Inventory Improvement 
Program Technical Report Series, Volumes I-VII,'' July 1997 and 
September 1999, ``Revised 1999 Naitonal Emission Inventory 
Preparation Plan,'' February 2001.

                   Table II. 1.--Summary of Primary PM10 Emissions in Tons Per Day for Denver
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                                        1995         2002         2003         2005         2010         2015
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Stationary Sources................          7.7         26.1         25.2         25.5         26.1         26.7
Residential Heating*..............          5.1          4.7          4.7          4.6          4.6          4.5
Other Area Sources**..............         11.8         12.1         12.1         12.3         12.2         12.1
Non-Road Mobile Sources***........          1.2          1.1          1.1          1.0          1.2          1.2
On-Road Mobile Sources****........         41.2         42.3         43.3         44.8         48.5         51.1
    Total.........................         66.9         86.3         86.5         88.1         92.5        95.6
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* Residential Heating includes natural gas, woodstove and fireplace emissions
** Other Area Sources includes fugitive dust from construction and unpaved roads as well as charbroiler
  emissions
*** Non-Road Mobile Sources includes emissions from all airports, railroads, and industrial and construction
  equipment

[[Page 36128]]

 
**** On-Road Mobile Sources includes exhaust and re-entrained road dust


                        Table II. 2.--Summary of NOX Emissions in Tons Per Day for Denver
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                                        1995         2002         2003         2005         2010         2015
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Stationary Sources................        137.8        151.2        133.9        128.8        130.4        132.2
Mobile Exhaust....................        119.4        137.7        130.4        109.6        104.0         87.8
Non-Road Mobile Sources*..........         22.3         24.9         25.0         27.7         30.3         33.4
Residential Heating**.............         33.2         39.5         40.5         42.6         46.7         49.8
    Total.........................        312.7        353.3        329.8        308.7        311.4       303.2
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* Non-Road Mobile Sources includes airport and other non-road emissions
** Residential Heating includes natural gas and woodburning emissions


                        Table II.3.--Summary of SO2 Emissions in Tons Per Day for Denver
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                                        1995         2002         2003         2005         2010         2015
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Stationary Sources................        175.5        200.2        180.5        181.1        182.0        183.1
Mobile Exhaust....................          2.5          5.6          5.8          6.1          2.1          2.2
Non-Road Mobile Sources *.........          1.9          2.3          2.5          2.5          2.8          3.1
Residential Heating **............          0.2          0.3          0.3          0.4          0.4          0.4
                                   --------------
      Total.......................        180.1        208.4        189.1        190.1        187.3       188.8
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* Non-Road Mobile Sources includes airport and other non-road emissions
** Residential Heating includes natural gas and woodburning emissions

    We note that these tables show significant changes in some source 
categories and in most cases this is the result of changes to control 
strategies that will be implemented in future years. This is explained 
in the following section. Other minor changes in emission categories 
can be explained by demographics, as explained above. The projected 
reductions in the residential heating category are from Colorado's 
estimates for less woodburning in future years. We believe this 
projection of less woodburning is reasonable.
    There have also been several changes made to the stationary source 
emissions inventory since the development of the PM10 SIP 
for the area. One source, Brannan Sand and Gravel, was treated as a 
major source of primary particulates in the SIP and modeled at an 
allowable emission level of 180 tons per year of PM10. Since 
the development of the PM10 SIP, Brannan Sand and Gravel 
replaced its existing asphalt plant with a new, lower emitting asphalt 
plant and retained a new permit reflecting this reduction. The result 
of this reduction was that Brannan Sand and Gravel's emissions now fall 
below the major source threshold of 100 tons per year primary 
PM10, as its new allowable emissions under the permit are 
4.2 tons per year of PM10. The source is now treated as an 
area source in the maintenance plan and modeled at its actual emission 
rate with a growth factor for future years. A correction was also made 
to the emission inventory to resolve an error made in the emission 
inventory for the nonattainment SIP which underestimated emissions from 
the Conoco petroleum refinery.
    In addition to the above changes, a new major source of primary 
particulates (Robinson Brick) was added to the emissions inventory with 
the maintenance plan because its emissions of PM10 were 
found to be over 100 tons per year. Robinson Brick was then modeled 
using the sources' allowable emission rates for primary 
PM10. Following our review, we have determined that Colorado 
prepared an adequate attainment inventory for the area.
b. Maintenance Demonstration
    The September 4, 1992, Calcagni Memorandum states that where 
modeling was relied on to demonstrate maintenance, the plan is to 
contain a summary of the air quality concentrations expected to result 
from the application of the control strategies. Also, the plan is to 
identify and describe the dispersion model or other air quality model 
used to project ambient concentrations. The maintenance demonstration 
for the Denver area uses area-wide dispersion modeling for primary 
PM10 and roll-forward modeling for secondary particulate 
concentrations, which was the same level of modeling used in the 
original attainment demonstration for the moderate PM10 SIP 
for Denver. The regional air model (RAM) was used for primary 
PM10 area, mobile and minor point sources, and an industrial 
source complex model (ISC) was used for primary PM10 from 
major point sources modeled at allowable emission levels. Secondary 
particulate concentrations are projected from measured concentrations 
during high concentration periods between 1987 and 1992. The projected 
change in total NOX and SO2 emissions from the 
baseline to future years is also factored into the analysis.
    The maintenance plan delineates between the stationary sources 
considered as major under the SIP and those sources which are 
considered as minor. The same methodology was used for the Denver 
PM10 maintenance plan as was used in the nonattainment SIP. 
All sources emitting over 100 tons per year of primary PM10 
were identified as major stationary sources and modeled in the 
maintenance demonstration using either the sources' allowable emission 
limit as specified in the maintenance plan, or that sources' maximum 
emission potential (PTE). All other sources with primary 
PM10 emissions were treated as area sources in the SIP 
context and modeled using the sources' current actual emissions with a 
projected growth factor. The major stationary sources of primary 
PM10 identified in the maintenance plan are: Conoco Denver 
Refinery, Public Service Company of Colorado's Cherokee, Arapahoe and 
Zuni Electric Generating Stations, Robinson Brick, Trigen-Colorado 
Energy Corporation, and the Ultramar Diamond Shamrock refinery.
    The methodology used for the stationary sources of secondary 
emissions (NOX and SO2) is also the same as that 
used in the nonattainment SIP. Sources were modeled using actual 
emission rates of NOX and SO2 if they

[[Page 36129]]

met two criteria. The first criteria is that the difference between 
modeling the source at anticipated actual emission rates versus the 
allowable emission levels must be less than 1 fg/m3 using 
the secondary particulate roll-forward model. The second criteria was 
that the cumulative difference for all the sources modeled using actual 
emissions must be no more than 2 fg/m3. The sources modeled 
as major sources of precursor emissions in the maintenance 
demonstration are: Public Service Company of Colorado's Cherokee, 
Arapahoe and Valmont Electric Generating Stations, Trigen-Colorado 
Energy Corporation, and Rocky Mountain Bottle Company.
    Since the modeling process is based on five years of meteorological 
data, the highest 6th highest 24-hour PM10 value from all 
receptors is used to determine if the PM10 standard will be 
maintained in future years. After an analysis, Colorado concluded that 
the Adams City ambient air quality monitor (located north of Cherokee 
Electrical Generating Station in Adams County) had the highest 6th 
highest 24-hour PM10 concentration for 2002. For all other 
projection years (2003, 2005, 2010, and 2015) the Continuous Air 
Monitoring Project (CAMP) monitor, located at the intersection of 
Broadway and Champa Street in downtown Denver, was the maximum 
concentration monitor. This analysis is further detailed in Chapter 4, 
section C of the maintenance plan and in the Colorado's TSD and is 
reproduced in Table II.--4 below.

                               Table II.4.--Denver PM10 Modeling Results in g/m3:
----------------------------------------------------------------------------------------------------------------
                                                     2002
                    Sources                         (Adams        2003         2005         2010         2015
                                                    City)        (CAMP)       (CAMP)       (CAMP)       (CAMP)
----------------------------------------------------------------------------------------------------------------
Area/Mobile/Minor Point Sources (RAM)..........         80.9         81.1         75.7         80.5         84.7
Major Point Sources (ISC)......................         0.64         0.01         0.32         0.32         0.32
Secondary Roll-forward.........................         52.6         48.4         46.6         46.6         46.1
Background.....................................         14.4         15.4         17.7         17.7         17.7
                                                --------------
      Total Concentration......................        148.6        144.9        140.3        145.2        148.8
----------------------------------------------------------------------------------------------------------------

    Since Colorado's submittal of the maintenance plan, Colorado has 
made some minor technical corrections to the maintenance demonstration. 
Colorado has now factored maximum potential primary PM10 
emissions for the Conoco and Ultramar Diamond Shamrock petroleum 
refineries into the modeling analysis to show maintenance of the 
PM10 standard. In the official July 30, 2001 submittal of 
the maintenance plan, Colorado had calculated maximum potential to emit 
for the fluid catalytic cracking units (FCCUs) by using the most 
conservative AP-42 emission factor and adding an 85% control efficiency 
to that factor. After the submittal of the maintenance plan, we 
discovered that this was an inappropriate calculation because the AP-42 
emission factors for FCCUs already take into account the 85% control 
efficiency for internal cyclones that are inherent to the functioning 
of the units. On April 5, 2002, Colorado submitted a technical 
correction to the maintenance plan modeling analysis which removed 
credits for an 85% control efficiency for the FCCU at the two 
refineries. Colorado re-ran the modeling analysis and found that they 
could still demonstrate maintenance for the duration of the maintenance 
plan while modeling the sources at maximum potential to emit.
    However, because future year projections in the maintenance plan 
were below the PM10 standard of 150 fg/m3, under 
40 CFR 93.124, Colorado was allowed to allocate the difference or 
``safety margin'' (1.1 g/m3 in 2015), to the NOX 
emissions budget. This worked out to be equivalent to 13 tons per day 
of NOX. Therefore, the 101 tons/day NOX emissions 
budget includes this ``safety margin'' of 13 tons/day. (The mobile 
source budgets are explained in more detail later in this proposed 
action.)
    Colorado's correction to the maintenance demonstration for Conoco 
and Ultramar Diamond Shamrock only resulted in a 0.3 fg/m3 
impact for 2005, 2010 and 2015 \3\, and did not increase the 
maintenance demonstration to a level above 150 fg/m3. 
However, because the entire ``safety margin'' from 2015 was allocated 
to the mobile source emission budget for NOX, it appeared 
that either the resulting emission budget would need to be changed, or 
another source in the SIP would need to be reduced to offset the 0.3 
fg/m3 increase. But, a recent federal consent decree will 
require significant emission reductions at the Conoco facility before 
2015.
---------------------------------------------------------------------------

    \3\ The State determined that the entire 0.3 fg/m3 
impact results from emission inventory increases at the Conoco FCCU; 
no impacts result from re-calculation of values for Ultramar Diamond 
Shamrock.
---------------------------------------------------------------------------

    On December 20, 2001, a proposed Complaint and Consent Decree in 
United States v. Conoco Inc. was lodged with the United States District 
Court for the Southern District of Texas. (See 67 FR 107 for the notice 
of lodged consent decree.) Under the proposed consent decree, Conoco 
Denver Refinery's FCCU is required to comply with a New Source 
Performance Standard (NSPS), Subpart J, emissions limit for PM of 1 
pound per 1000 pounds of coke burned by no later than June 30, 2006. 
This restriction will limit Conoco to approximately 67 tons per year of 
primary PM10, which is far less than the 1233 tons per year 
which Colorado used to re-model Conoco's emissions and less than the 
185 tons per year Colorado used in the maintenance plan; this new limit 
will more than offset the 0.3 fg/m3 increase which would 
have affected the year 2015 ``safety margin'' allocation. Because it is 
based on an NSPS requirement, this new PM limit at Conoco will be 
permanent. We anticipate court approval of the Conoco consent decree in 
the near future. In the event court approval is not forthcoming, we may 
need to reevaluate this proposal.
i. Control Strategy
    According to the Calcagni memorandum, any assumptions concerning 
emission rates must reflect permanent, enforceable measures. A State 
can't take credit in the maintenance demonstration for reductions 
unless there are regulations in place requiring those reductions or the 
reductions are otherwise shown to be permanent. States are expected to 
maintain implemented control strategies despite redesignation to 
attainment, unless such measures are shown to be unnecessary for 
maintenance or are replaced with measures that achieve equivalent 
reductions. Emission reductions from source shutdowns can be considered 
permanent and

[[Page 36130]]

enforceable to the extent that those shutdowns have been reflected in 
the SIP and all applicable permits have been modified accordingly.
    In preparing the Denver PM10 maintenance plan, Colorado 
has chosen to make revisions to its control strategy. However, as 
demonstrated above, the Denver area is expected to maintain the 
PM10 NAAQS into the future despite these changes. The 
control strategy which is being approved with this action is explained 
here. As explained previously, Colorado Regulation No. 4, ``New Wood 
Stoves and the use of Certain Woodburning Appliances During High 
Pollution Days,'' along with local woodburning ordinances was approved 
with the PM10 SIP. There are no changes being made to this 
control program with this action. There are also no changes approved 
with this action for Regulation No. 11, the Automobile Inspection and 
Readjustment Program. Changes to this regulation were approved in a 
Federal Register action on December 14, 2001 (66 FR 64751) as part of 
the carbon monoxide maintenance plan. No further changes to this 
program were made for the PM10 maintenance plan.
    As with the PM10 attainment SIP, part of the 
PM10 control strategy in the maintenance plan relies on the 
Federal Motor Vehicle Control Program (FMVCP). In general, the FMVCP 
provisions require vehicle manufacturers to meet more stringent vehicle 
emission limitations for new vehicles in future years. These emission 
limitations are phased in (as a percentage of new vehicles 
manufactured) over a period of years. As new, lower emitting vehicles 
replace older, higher emitting vehicles (``fleet turnover''), emission 
reductions are realized for a particular area such as Denver. The 
control program that Colorado uses in the PM10 maintenance 
plan includes emission reduction credits from our Tier II motor vehicle 
emissions standards and sulfur in gasoline. The new vehicle emission 
standards lower the average emission standards to 0.07 grams per mile 
of NOX and begin in 2004 with a 3 year phase in period. The 
sulfur in gasoline standards require reductions from 300 parts per 
million to 30 parts per million of sulfur and begin in 2004 with a 3 
year phase in period for Colorado and other Western states (most areas 
around the country are under a 2 year phase in requirement). When these 
new requirements are fully implemented (this will be 2030 due to fleet 
turnover), they will reduce NOX emissions nationally by 74% 
or 2 million tons per year by 2020 and 3 million tons per year by 2030.
    The maintenance plan includes a revised version of Colorado's 
Regulation No. 16, ``Street Sanding Emissions.'' The changes to this 
regulation were adopted by the Colorado Air Quality Control Commission 
with the PM10 maintenance plan on April 19, 2001. In 
addition to the existing portions of Regulation No. 16, these revisions 
require additional emission reductions in the Denver area. These 
reductions are: 30% emission reductions region-wide, excluding the 
Foothills Area which is subject to 20% emission reductions (the 
Foothills Area is specifically defined in Colorado Regulation No. 16), 
50% emission reductions in the central Denver area (bounded by 38th 
Avenue, Federal Boulevard, Louisiana Avenue, and Downing Street), 54% 
reductions on I-25 between University and 6th Avenue; and 72% emission 
reductions in the central business district (bounded by Colfax Avenue, 
Broadway, 20th Street, Wynkoop and Speer Boulevard). The maintenance 
plan commits to implement these new requirements during the winter 
2001/2002 season. It should be noted that a portion of these additional 
reductions in street sanding, de-icing and sweeping reflect a study 
contracted by the Denver Regional Air Quality Council (RAQC) that found 
increased benefits from de-icing and sweeping beyond what has 
historically been assumed for the Denver area (previous assumptions for 
Denver were consistent with recommendations from EPA guidelines). Based 
on the recommendations of the ``Emissions Benefit Study and Analysis,'' 
the RAQC decided to increase the emission reductions from street 
sweeping using mechanical or combination equipment to 37% and the 
percent emission reductions from vacuum and regenerative air equipment 
was increased to 61%. We have reviewed this study and found it to be 
technically accurate and therefore we also approve the resulting 
emission reduction credits assumed for these activities.
    Colorado Regulation No. 1 ``Particulates, Smokes, Carbon Monoxide, 
& Sulfur Oxides,'' will remain in the PM10 maintenance plan, 
with a few important changes that will bring further emission 
reductions. The revisions to Regulation No. 1 affect Public Service 
Company of Colorado's Cherokee, Arapahoe and Valmont Electric 
Generating Stations as well as the restrictions on the use of fuel oil 
as a backup fuel. One revision requires a 0.88 pounds per million 
British Thermal Unit (lb/mmBTU) SO2 limit for the Cherokee 
boiler units 1 and 4 and Arapahoe boiler unit 4, based on a 30-day 
rolling average from November 1 to March 1 of each year. This limit is 
in addition to the existing 1.1 lb/mmBTU SO2 limit with an 
additional 20% annual tonnage reduction that applies to Arapahoe boiler 
unit 4. Another revision to Regulation No. 1 is that the January 1, 
2003 planned retirement of Arapahoe boiler units 1 and 2 is being made 
federally enforceable in order for those emission reductions to be used 
in the maintenance demonstration. In addition, a 30-day rolling average 
NOX limit of 0.60 lb/mmBTU for Cherokee boiler unit 1 will 
be effective on January 1, 2005. These emission reduction credits are 
used accordingly in the maintenance demonstration for 2005 and beyond. 
Language was added to the specific sections for Cherokee, Arapahoe and 
Valmont to specify that the sources' continuous emissions monitoring 
equipment would be certified and operated in accordance with 40 CFR 
60.13 for measuring opacity, SO2, NOX, and either 
O2 or CO2 on all the boiler units for these 
sources that are included in the regulation. Lastly, there is a 
revision to the fuel oil restrictions which ensures that these 
restrictions will continue to apply in the Denver PM10 area 
after the area is redesignated to attainment.
    We note here that any source modeled at its maximum emission 
potential (PTE) was not required to have short-term emission limits in 
the maintenance plan. These sources cannot emit more than the maximum 
PTE which was used in the maintenance plan's modeling analysis absent a 
physical modification, or a change in operational method, either of 
which would require a permit revision. Any such permitting action would 
require an analysis of potential impacts on the Denver PM10 
area. Please see Colorado's technical support documentation for more 
detailed information on each source.
    In addition to these improved control measures which are being 
added to the PM10 maintenance plan, there are also certain 
control measures which are being removed from the control strategy with 
this maintenance plan. This is acceptable under the Calcagni Memorandum 
as long as the area can still demonstrate maintenance of the 
PM10 standard. Regulation No. 12, the ``Diesel Inspection/
Maintenance Program'' will be removed from the PM10 SIP with 
the final approval of this maintenance plan. This program only achieved 
small emission reductions and therefore, Colorado demonstrated 
maintenance of the standard without taking credit for the regulation. 
Regulation No. 12 will remain as a state-

[[Page 36131]]

only requirement. Likewise, Regulation No. 13 ``Oxygenated Fuels 
Program'' will also be removed from the PM10 SIP with the 
approval of this plan due to its minor emission reductions for 
PM10. This regulation is a part of the carbon monoxide 
maintenance plan, which we approved on December 14, 2001 (66 FR 64751).
    As explained previously, the control strategy for the 
PM10 SIP included permits for seven stationary sources 
through our incorporation of these permits in the final approval of the 
SIP. These permits will be removed from the SIP with our final approval 
of this maintenance plan. We have evaluated this action and decided 
that the integrity of the control strategy will be preserved for the 
following reasons. All major emissions from Public Service Company's 
Cherokee Electric Generating Station, Trigen-Colorado Energy 
Corporation, Rocky Mountain Bottle Company and the Conoco Refinery are 
covered either by existing or new provisions in Regulation No. 1. As 
noted previously, Conoco will be subject to NSPS Subpart J limits on 
FCCU PM emissions once the federal consent decree is final. In 
addition, some of the sources, such as the Ultramar Diamond Shamrock 
refinery, were modeled at PTE, demonstrating that even at the sources' 
maximum emission rates, the Denver area would still maintain the 
PM10 standard. The permits for Purina Mills and Electron 
Corporation were included in the PM10 SIP because these 
sources had opted for synthetic minor permits during the development of 
the SIP. This was part of an agreement we made with Colorado in order 
for the Denver area to show attainment of the PM10 standard. 
Accordingly, Colorado modeled these sources at their actual emissions 
plus a growth factor for purposes of the nonattainment area SIP 
attainment demonstration. Although these sources have potentials to 
emit greater than 100 tons per year, they are no different than other 
synthetic minor sources in the Denver area that were modeled at actual 
emissions plus a growth factor in the original nonattainment area SIP, 
and there is no reason the permits for these sources need to be 
specifically incorporated by reference into the SIP. Thus, the 
maintenance plan removes the permits for Purina Mills and Electron 
Corporation from the SIP, and lists them as possible contingency 
measures should the NAAQS be violated.
    Since no violations of the annual PM10 NAAQS have ever 
occurred in Denver and since the maintenance demonstration clearly 
shows maintenance of the 24-hour PM10 NAAQS in Denver 
through the year 2015, it is reasonable to assume that protection of 
the 24-hour standard will be sufficient to protect the annual standard 
as well. Thus, EPA believes Colorado has adequately demonstrated that 
the Denver area will maintain the PM10 NAAQS for at least 
the next thirteen years.
c. Monitoring Network
    Once a nonattainment area has been redesignated to attainment, the 
State must continue to operate an appropriate air quality monitoring 
network, in accordance with 40 CFR part 58, to verify the attainment 
status of the area. The maintenance plan should contain provisions for 
continued operation of air quality monitors that will provide such 
verification. Colorado will continue to operate a core network of 
PM10 monitoring sites for the purposes of tracking 
PM10 in the Denver area. We approve these sites annually, 
and any future change would require discussion with us. In its July 30, 
2001 submittal, Colorado committed to continue to operate the 
PM10 monitoring stations in Denver, in accordance with 40 
CFR part 58.
d. Verification of Continued Attainment
    Colorado's maintenance plan submittal must indicate how the State 
will track the progress of the maintenance plan. This is necessary due 
to the fact that the emissions projections made for the maintenance 
demonstration depend on assumptions of point and area source growth. In 
Chapter 4, section E of the maintenance plan, Colorado has committed to 
the continued operation of the ambient air monitoring network and to 
conduct an annual review of the network to verify that the system 
continues to meet EPA monitoring objectives and the area continues to 
attain the PM10 NAAQS.
    In Chapter 4, section F.2, Colorado commits to track and document 
changes in new and modified stationary source permits. Also, in Chapter 
4, sections E and F.2, the State commits to track mobile source 
emissions that contribute to PM10, through the ongoing 
regional transportation planning process that is done by DRCOG. Since 
revisions to Denver's transportation improvement programs are prepared 
every two years, and must go through a transportation conformity 
finding, the State will use this process to periodically review the 
Vehicle Miles Traveled (VMT) and mobile source emissions projections 
used in the maintenance plan. This regional transportation process is 
conducted by DRCOG in coordination with the Denver Regional Air Quality 
Council (RAQC), the State's Air Pollution Control Division (APCD), the 
Air Quality Control Commission (AQCC), and EPA. If any significant 
changes appear, Colorado will perform studies to determine whether 
additional or re-sited monitors are necessary and whether the emission 
projections for future years are on target. If the future year 
projections appear to be lower than actual growth, Colorado will 
address the situation accordingly.
e. Contingency Plan
    Section 175A(d) of the Act requires that a maintenance plan also 
include contingency provisions, as necessary, to promptly correct any 
violation of the NAAQS that occurs after redesignation of the area. For 
the purposes of section 175A, a State is not required to have fully 
adopted contingency measures that will take effect without further 
action by the State in order for the maintenance plan to be approved. 
However, the contingency plan is an enforceable part of the SIP and 
should ensure that contingency measures are adopted expeditiously once 
they are triggered. The plan should discuss the measures to be adopted 
and a schedule and procedure for adoption and implementation. The 
contingency plan must require that the State will implement all 
measures contained in the Part D nonattainment plan for the area prior 
to redesignation. The State should also identify the specific 
indicators, or triggers, which will be used to determine when the 
contingency plan will be implemented.
    As stated in Chapter 4, section F of the maintenance plan, the 
contingency measures for the Denver area will be triggered by a 
violation of the PM10 NAAQS. (However, the maintenance plan 
does note that an exceedance of the PM10 NAAQS may initiate 
a voluntary, local process by the RAQC and APCD to identify and 
evaluate potential contingency measures.)
    The RAQC, in coordination with the APCD and AQCC, will initiate a 
subcommittee process to begin evaluating potential contingency measures 
no more than 60 days after being notified by the APCD that a violation 
of the PM10 NAAQS has occurred. The subcommittee will 
present recommendations to the RAQC within 120 days of notification and 
the RAQC will present recommended contingency measures to the AQCC 
within 180 days of notification. The AQCC will then hold a public 
hearing to consider the contingency measures recommended by the RAQC, 
along with any other contingency measures that the AQCC believes may be 
appropriate to

[[Page 36132]]

effectively address the violation of the PM10 NAAQS. The 
necessary contingency measures will be adopted and implemented within 
one year after the violation occurs.
    The potential contingency measures that are identified in Chapter 
4, section F of the Denver PM10 maintenance plan include the 
control measures from the Part D nonattainment plan that are being 
removed with this maintenance plan as well as additional potential 
measures. The potential contingency measures which are the result of 
relaxations to the nonattainment plan control measures are: (1) The 
repeal of certain sections of Regulation No. 11 ``Motor Vehicle 
Emissions Inspection Program,'' (2) Regulation No. 12, ``Diesel 
Inspection/Maintenance Program,'' (3) Regulation No. 13 ``Oxygenated 
Fuels Program,'and (4) the stationary source permits that were 
incorporated into the Denver PM10 nonattainment SIP. The 
contingency plan also includes other potential contingency measures 
that would bring additional reductions in particulates to the Denver 
area. These measures are: (1) Increased street sweeping requirements, 
(2) expanded, mandatory use of alternative de-icers, (3) more stringent 
street sand specifications, (4) road paving requirements, (5) further 
woodburning restrictions, (6) re-establishing nonattainment area new 
source review permitting requirements for stationary sources, (7) 
NOX RACT for stationary sources, (8) transportation control 
measures designed to reduce vehicle miles traveled, (9) an improved 
diesel inspection/maintenance program, (10) a retrofit program for 
heavy-duty diesel truck engines, and (11) other emission control 
measures appropriate for the area based on the consideration of cost-
effectiveness, PM10 emission reduction potential, economic 
and social considerations, or other factors that the State deems 
appropriate. A more complete description of the triggering mechanism 
and these contingency measures can be found in Chapter 4, section F of 
the maintenance plan.
    Based on the above, we find that the contingency measures provided 
in the Denver PM10 maintenance plan are sufficient and meet 
the requirements of section 175A(d) of the CAA.
f. Subsequent Maintenance Plan Revisions
    As mentioned above, this maintenance plan uses credits from the EPA 
Tier II standards beginning in 2004, but this is based on adjustments 
made to the MOBILE5 model and not the new MOBILE6 emissions model since 
the latter had not been officially released when the maintenance plan 
was developed. Due to the fact that the Tier II assumptions using 
MOBILE5 may not be as accurate as they would be if MOBILE6 were used, 
Colorado has committed to revise the maintenance plan within one year 
of the later of the official release of: (1) MOBILE6, (2) the MOBILE6 
particulate emissions replacement for PART5, or (3) the MOBILE6 
guidance to enable Colorado to model its vehicle inspection/maintenance 
program for the model years after 1995.
    In accordance with section 175A(b) of the Act, Colorado is required 
to submit a revision to the maintenance plan eight years after the 
redesignation of the Denver area to attainment for PM10. 
This revision is to provide for maintenance of the NAAQS for an 
additional ten years following the first ten year period. In the Denver 
redesignation request, Colorado committed to submit a revised 
maintenance plan eight years after the approval of the redesignation 
request and maintenance plan.
v. Meeting Applicable Requirements of Section 110 and Part D of the Act
    In order for an area to be redesignated to attainment, section 
107(d)(3)(E) requires that it must have met all applicable requirements 
of section 110 and part D of the Act. We interpret this to mean that, 
for a redesignation request to be approved, the State must have met all 
requirements that applied to the subject area prior to, or at the time 
of, submitting a complete redesignation request. In our evaluation of a 
redesignation request, we don't need to consider other requirements of 
the CAA that became due after the date of the submission of a complete 
redesignation request.
a. Section 110 Requirements
    Section 110(a)(2) contains general requirements for nonattainment 
plans. For purposes of redesignation, the Colorado SIP was reviewed to 
ensure that all applicable requirements under the amended Act were 
satisfied. These requirements were met with the Colorado's March 30, 
1995, November 17, 1995, and December 22, 1995 submittals for the 
Denver PM10 nonattainment area. We approved these submittals 
on September 23, 1996 (61 FR 49682) and April 17, 1997 (62 FR 18716).
b. Part D Requirements
    Before a PM10 nonattainment area may be redesignated to 
attainment, the State must have fulfilled the applicable requirements 
of part D. Subpart 1 of part D establishes the general requirements 
applicable to all nonattainment areas, while subpart 4 of part D 
establishes specific requirements applicable to PM10 
nonattainment areas. The General Preamble (see 57 FR 13530, et seq.) 
provides that the applicable requirements of CAA section 172 are 
172(c)(3) (emissions inventory), 172(c)(5)(new source review permitting 
program), 172(c)(7)(the section 110(a)(2) air quality monitoring 
requirements)), and 172(c)(9) (contingency measures). It is also worth 
noting that we interpreted the requirements of sections 172(c)(2) 
(reasonable further progress--RFP) and 172(c)(6)(other measures) as 
being irrelevant to a redesignation request because they only have 
meaning for an area that is not attaining the standard. See EPA's 
September 4, 1992, John Calcagni memorandum entitled, ``Procedures for 
Processing Requests to Redesignate Areas to Attainment'', and the 
General Preamble, 57 FR at 13564, dated April 16, 1992. Finally, the 
State has not sought to exercise the options that would trigger 
sections 172(c)(4)(identification of certain emissions increases) and 
172(c)(8)(equivalent techniques). Thus, these provisions are also not 
relevant to this redesignation request.
    The requirements of sections 172(c) and 189(a) regarding attainment 
of the PM10 NAAQS, and the requirements of section 172(c) 
regarding reasonable further progress, imposition of RACM, the adoption 
of contingency measures, and the submission of an emission inventory, 
have been satisfied through our September 23, 1996 (61 FR 49682) and 
April 17, 1997 (62 FR 18716) approvals of the Denver PM10 
SIP and the demonstration that the area is now attaining the NAAQS.
    Although EPA's regulations (see 40 CFR 51.396) require that states 
adopt transportation conformity provisions in their SIPs for areas 
designated nonattainment or subject to an EPA-approved maintenance 
plan, we have decided that a transportation conformity SIP is not an 
applicable requirement for purposes of evaluating a redesignation 
request under section 107(d) of the CAA. This decision is reflected in 
EPA's 1996 approval of the Boston carbon monoxide redesignation. (See 
61 FR 2918, January 30, 1996.)
    We approved the requirements of the part D new source review permit 
program for Colorado on August 18, 1994 (59 FR 42506). Once the Denver 
area is redesignated to attainment, the prevention of significant 
deterioration (PSD) requirements of part C of the Act will apply. We 
must ensure that the State has made any needed modifications to its PSD 
regulations so

[[Page 36133]]

that Colorado's PSD regulations will apply in the Denver area after 
redesignation. Colorado's PSD regulations, which we approved as meeting 
all applicable Federal requirements (59 FR 42500, August 18, 1994), 
apply to any area designated as unclassifiable or attainment and, thus, 
will become fully effective in the Denver area upon redesignation of 
the area to attainment.

C. Have the Transportation Conformity Requirements Been Met?

    One key provision of our conformity regulation requires a 
demonstration that emissions from the transportation plan and 
Transportation Improvement Program are consistent with the emissions 
budget(s) in the SIP (40 CFR 93.118 and 93.124). The emissions budget 
is defined as the level of mobile source emissions relied upon in the 
attainment or maintenance demonstration to maintain compliance with the 
NAAQS in the nonattainment or maintenance area. The rule's requirements 
and EPA's policy on emissions budgets are found in the preamble to the 
November 24, 1993, transportation conformity rule (58 FR 62193-62196) 
and in the sections of the rule referenced above.
    According to 40 CFR 93.118(b)(2), when a maintenance plan has been 
submitted, emissions must be less than or equal to the motor vehicle 
emissions budget(s) established for the last year of the maintenance 
plan, and for any other years for which the maintenance plan 
establishes motor vehicle emissions budgets. If the maintenance plan 
does not establish motor vehicle emissions budgets for any years other 
than the last year of the maintenance plan, the demonstration of 
consistency with the motor vehicle emissions budget(s) must be 
accompanied by a qualitative finding that there are no factors which 
would cause or contribute to a new violation or exacerbate an existing 
violation in the years before the last year of the maintenance plan. 
For years after the last year of the maintenance plan, emissions must 
be less than or equal to the maintenance plan's motor vehicle emissions 
budget(s) for the last year of the maintenance plan; and if an approved 
control strategy implementation plan has established motor vehicle 
emissions budgets for years in the timeframe of the transportation 
plan, emissions in these years must be less than or equal to the 
control strategy implementation plan's motor vehicle emissions 
budget(s) for these years.
    In the Denver PM10 nonattainment plan, Colorado had 
previously adopted a mobile source emissions budget for PM10 
for the years 1998-2005 of 54 tons/day and an emissions budget for 2006 
and beyond of 60 tons/day. A 119.4 tons/day NOX emissions 
budget was established for analysis years 1998 and beyond. In the 
Denver PM10 maintenance plan, Colorado indicated that it 
would adopt a new mobile source emissions budget of 51 tons/day for 
PM10 and a 101 tons/day NOX emissions budget for 
the years 2015 and beyond. Because future year projections in the 
maintenance plan were below the PM10 standard of 150 fg/
m\3\, under 40 CFR 93.124, Colorado was allowed to allocate the 
``safety margin'' (the difference between the 24-hour PM10 
standard and the concentration projected for the maintenance year 
2015), to the NOX emissions budget. This safety margin is 
1.1 fg/m\3\ and equates to 13 tons/day of NOX. Therefore, 
the 101 tons/day NOX emissions budget includes this ``safety 
margin'' of 13 tons/day. EPA's approval of the emissions budgets means 
that emissions projections (in a conformity analysis) for years 2015 
and beyond must be less than or equal to 51 tons/day PM10 
and 101 tons/day NOX.
    On March 2, 1999, the United States Court of Appeals for the 
District of Columbia Circuit issued a decision in Environmental Defense 
Fund vs. the Environmental Protection Agency, No. 97-1637, that we must 
make an affirmative determination that the submitted motor vehicle 
emission budgets contained in SIPs are adequate before they are used to 
determine the conformity of Transportation Improvement Programs or Long 
Range Transportation Plans. In response to the court decision, we are 
making most submitted SIP revisions containing a control strategy plan 
available for public comment and responding to these comments before 
announcing our adequacy determination. (We do not perform adequacy 
determinations for SIP revisions that only create new emission budgets 
for years in which an EPA-approved SIP already establishes a budget, 
because these new budgets cannot be used for conformity until they are 
approved by EPA.) We make SIP revisions available for comment by 
posting notification of their availability on our web site (currently, 
these notifications are posted at www.epa.gov/oms/transp/conform/
adequacy.htm). The adequacy process is discussed in greater detail in a 
May 14, 1999 memorandum from Gay MacGregor entitled ``Conformity 
Guidance on Implementation of March 2, 1999 Conformity Court 
Decision,'' also available on our web site (www.epa.gov/oms/transp/
traqconf.htm).
    EPA reviewed the Denver PM10 budgets for adequacy using 
the criteria in 40 CFR 93.118(e)(4), and determined that the budgets 
were adequate for conformity purposes. Notice of the availability of 
this SIP was posted on our adequacy web site on August 12, 2001, and a 
30-day comment period for adequacy was provided following the 
procedures described in the May 14, 1999 Gay MacGregor memorandum 
referenced above. No comments were received. EPA's adequacy 
determination was made in a letter to the Colorado APCD on September 
20, 2001, and was announced in the Federal Register on October 12, 2001 
(66 FR 52129). As a result of this adequacy finding, the emissions 
budgets took effect for conformity determinations in the Denver metro 
area on October 29, 2001. However, we are not bound by that 
determination in acting on the maintenance plan.

D. Did Colorado Follow the Proper Procedures for Adopting This Action?

    Section 110(k) of the CAA addresses our actions on submissions of 
revisions to a SIP. The Act also requires States to observe certain 
procedural requirements in developing implementation plans and plan 
revisions for submission. 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. 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.
    We also must determine whether a submittal is complete and 
therefore warrants further review and action (see section 110(k)(1) of 
the Act and 57 FR 13565, April 16, 1992). Our completeness criteria for 
SIP submittals are set out at 40 CFR part 51, appendix V. We attempt to 
make completeness determinations within 60 days of receiving a 
submission. However, a submittal is deemed complete by operation of law 
under section 110(k)(1)(B) of the Act if a completeness determination 
is not made within six months after receipt of the submission.
    Copies of the proposed changes were made available to the public 
and the AQCC held a public hearing on April 19, 2001 to entertain 
public comment on the redesignation request and maintenance plan for 
the Denver PM10 nonattainment area. Colorado did not receive 
any adverse comments and

[[Page 36134]]

therefore, the redesignation request and maintenance plan were 
subsequently adopted by the AQCC on April 19, 2001. The request was 
formally submitted to us for approval with a Governor's letter dated 
July 30, 2001. Supplementary documentation necessary for our 
completeness determination was submitted on September 5, 2001, 
September 10, 2001 and September 13, 2001. We reviewed these SIP 
materials for conformance with the completeness criteria in 40 CFR part 
51, appendix V and determined that Colorado's submittal was 
administratively and technically complete under section 110(a)(2) of 
the CAA. Thus, pursuant to section 110(k)(1)(B) of the Act, the 
submittal was deemed administratively and technically complete with a 
September 24, 2001 letter from Jack McGraw, Acting Regional 
Administrator to Governor Bill Owens. Additional documentation was also 
submitted by Colorado on November 27, 2001. This information was 
necessary in order to complete our review of the maintenance plan and 
technical support information.

III. Background

    To implement our 1987 revisions to the particulate matter NAAQS, on 
August 7, 1987 (52 FR 29383), we categorized areas of the nation into 
three groups based on the likelihood that protection of the 
PM10 NAAQS would require revisions of the existing SIP. We 
identified the Denver area as a PM10 ``Group I'' area of 
concern, i.e., an area with a strong likelihood of violating the 
PM10 NAAQS and requiring a substantial SIP revision. The 
Denver area was among several Group I PM10 areas, all of 
which were designated and classified as moderate PM10 
nonattainment areas by operation of law upon enactment of the Clean Air 
Act Amendments of 1990 (November 15, 1990). See 56 FR 56694 at 56705-
56706 (November 6, 1991).
    By November 15, 1991, States containing initial moderate 
PM10 nonattainment areas were required to submit most 
elements of their PM10 SIPs. (See sections 172(c), 188, and 
189 of the Act.) Some provisions, such as PM10 contingency 
measures required by section 172(c)(9) of the Act and nonattainment new 
source review (NSR) provisions, were due at later dates. In order for a 
nonattainment area to be redesignated to attainment, the above 
mentioned conditions in section 107(d)(3)(E) of the Act must be met. We 
approved the PM10 contingency measures for the area on 
September 23, 1996 (61 FR 49682). We approved the PM10 SIP 
for Denver on April 17, 1997 (62 FR 18716) as meeting those moderate 
PM10 nonattainment plan requirements that were due to EPA on 
November 15, 1991. The PM10 SIP's transportation budgets 
required under the transportation conformity rule were approved on 
March 31, 1998 (63 FR 15294).
    On July 30, 2001, the Governor of Colorado submitted a request to 
redesignate the Denver moderate PM10 nonattainment area to 
attainment for the 1987 PM10 NAAQS along with a maintenance 
plan for the area. On July 18, 1997, we promulgated new NAAQS for 
PM10 and PM2.5. However, on May 18, 1999, the 
United States Court of Appeals for the D.C. Circuit in American 
Trucking Associations, Inc. et al., v. United States Environmental 
Protection Agency vacated the 1997 PM10 standard. Because of 
the Court ruling, we are continuing to implement the pre-existing 
PM10 standard, and are therefore approving redesignations to 
qualified PM10 nonattainment areas.

IV. Administrative Requirements

    Under Executive Order 12866 (58 FR 51735, October 4, 1993), this 
proposed action is not a ``significant regulatory action'' and 
therefore is not subject to review by the Office of Management and 
Budget. For this reason, this action is also not subject to Executive 
Order 13211, ``Actions Concerning Regulations That Significantly Affect 
Energy Supply, Distribution, or Use'' (66 FR 28355, May 22, 2001). This 
proposed action merely proposes to approve state law as meeting Federal 
requirements and imposes no additional requirements beyond those 
imposed by state law. Accordingly, the Administrator certifies that 
this proposed rule will not have a significant economic impact on a 
substantial number of small entities under the Regulatory Flexibility 
Act (5 U.S.C. 601 et seq.). Because this rule proposes to approve pre-
existing requirements under state law and does not impose any 
additional enforceable duty beyond that required by state law, it does 
not contain any unfunded mandate or significantly or uniquely affect 
small governments, as described in the Unfunded Mandates Reform Act of 
1995 (Pub. L. 104-4).
    This proposed rule also does not have tribal implications because 
it will not have a substantial direct effect on one or more Indian 
tribes, on the relationship between the Federal Government and Indian 
tribes, or on the distribution of power and responsibilities between 
the Federal Government and Indian tribes, as specified by Executive 
Order 13175 (65 FR 67249, November 9, 2000). This action also does not 
have Federalism implications because it does not have substantial 
direct effects on the States, on the relationship between the national 
government and the States, or on the distribution of power and 
responsibilities among the various levels of government, as specified 
in Executive Order 13132 (64 FR 43255, August 10, 1999). This action 
merely proposes to approve a state rule implementing a Federal 
standard, and does not alter the relationship or the distribution of 
power and responsibilities established in the Clean Air Act. This 
proposed rule also is not subject to Executive Order 13045 ``Protection 
of Children from Environmental Health Risks and Safety Risks'' (62 FR 
19885, April 23, 1997), because it is not economically significant.
    In reviewing SIP submissions, EPA's role is to approve state 
choices, provided that they meet the criteria of the Clean Air Act. In 
this context, in the absence of a prior existing requirement for the 
State to use voluntary consensus standards (VCS), EPA has no authority 
to disapprove a SIP submission for failure to use VCS. It would thus be 
inconsistent with applicable law for EPA, when it reviews a SIP 
submission, to use VCS in place of a SIP submission that otherwise 
satisfies the provisions of the Clean Air Act. Thus, the requirements 
of section 12(d) of the National Technology Transfer and Advancement 
Act of 1995 (15 U.S.C. 272 note) do not apply. This proposed rule does 
not impose an information collection burden under the provisions of the 
Paperwork Reduction Act of 1995 (44 U.S.C. 3501 et seq.).

List of Subjects

40 CFR Part 52

    Environmental protection, Air pollution control, Intergovernmental 
relations, Particulate Matter, Reporting and recordkeeping 
requirements.

40 CFR Part 81

    Air pollution control.

    Dated: May 14, 2002.
Robert E. Roberts,
Regional Administrator, Region VIII.
[FR Doc. 02-12965 Filed 5-22-02; 8:45 am]
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