### State of Colorado Implementation Pl an to Meet the Requirements of Clean Air Act Section 110 (a)(2)(D)(i)(I) Interstate Transport Regarding th e 1997 8-Hour Ozone Standard

December 9, 2008

Colorado Department of Public Health and Environment Air Pollution Control Division 4300 Cherry Creek Drive South Denver, Colorado 80246



### Adopted by the Air Quality Control Commission December 12, 2008Colorado Department of Public Health and Environment / Air Pollution Control Division

State of Colorado Implementation Plan to Meet the Requirements of Clean Air Act Section 110 (a)(2)(D)(i)(I) - In terstate Transport Re garding 8-Hour Ozone iColorado Department of Public Health and Environment / Air Pollution Control Division

State of Colorado Implementation Plan to Meet the Requirements of Clean Air Act Section 110 (a)(2)(D)(i)(I) - In terstate Transport Re garding 8-Hour Ozone ii 

# Table of Contents

1. OZONE-SPECIFIC PROVISIONS TO MEET THE REQUIREMENTS OF CAA 110(A)(2)(D)(I)(I) – INTERSTATE TR ANSPORT ........................................................................................................... ............................1

1.1. I NTRODUCTION

............................................................................................................................... ................1 1.2. C OLORADO O ZONE M ONITORING N ETWORK ..................................................................................................2 1.3. O ZONE M ONITORING N ETWORK IN N EARBY S TATES .....................................................................................7 1.4. O ZONE T RANSPORT C ONCLUSIONS FROM THE DMA/NFR P HOTOCHEMICAL M ODELING ............................10 1.4.1. Emission Inventories and 2 006 and 2010 Base Case..............................................................................1 1 1.4.2. Discussion of 2010 Base Case CAMx Modeling Results.........................................................................15 1.5. D ENVER M ETRO A REA /N ORTH F RONT R ANGE O ZONE N ONATTAINMENT A REA C ONTRIBUTION TO D OWNWIND L OCATIONS

............................................................................................................................... ..............18 1.6. S ECTION 110( A )(2)(D)( I )(I)

– O ZONE T RANSPORT C ONCLUSIONS ...............................................................20

2. REFERENCES ..................................................................................................................... ...............................22



# List of Tables

Table 1: 2008 1-Hour Ozone Monitored Con centration (updated through Sept. 30, 2008)............. 4 Table 2: 2008 8-Hour Ozone Monitored Con centration (updated through Sept. 30, 2008)............. 5 Table 3: 8-Hour Design Value Using the 3-Year (2006-2008) Aver age of the Fourth Maximum Ozone Concentration ............................................................................................................ ..... 6 Table 4: 2005-2007 3-Year Fourth Highest Aver age Monitoring Concentrations from Kansas, Nebraska, New Mexico, Utah and Wyoming............................................................................ 7 Table 5. Base Case Inventories for 8-Hour Ozone DMA/NFR NAA Phot ochemical Modeling.... 14



# List of Figures

Figure 1. Location of Front Range Ozone Monitors ......................................................................... 2 Figure 2. Location of Stat ewide Ozone Monitors.............................................................................. 3 Figure 3: 8-Hour Ozone Nonattainment Areas.................................................................................. 9 Figure 4. Nested 12/4 km modeling domains fo r the Denver CAMx air quality and SMOKE emissions modeling............................................................................................................. ..... 10 Figure 5. Projected 2010 8-hour oz one Design Values (DVF)........................................................ 15 Figure 6. Rocky Flats North source apportionment for 29 July including boundary conditions. ... 16 Figure 7: Spatial extent of the 8-hour ozone c oncentrations that occu rred between 10am and 6pm local time on June 27, 2002 through July 1, 2002 ................................................................... 19Colorado Department of Public Health and Environment / Air Pollution Control Division

State of Colorado Implementation Plan to Meet the Requirements of Clean Air Act Section 110 (a)(2)(D)(i)(I) - In terstate Transport Re garding 8-Hour Ozone iiiColorado Department of Public Health and Environment / Air Pollution Control Division

State of Colorado Implementation Plan to Meet the Requirements of Clean Air Act Section 110 (a)(2)(D)(i)(I) - In terstate Transport Re garding 8-Hour Ozone 1 

## 1. Ozone-Specific Provisions to Meet the Requirements of CAA 110(a)(2)(D)(i)(I) – Interstate Transport

1.1. Introduction The purpose of this document is to provide a plan for the State of Colorado to meet the requirements of the Clean Air Act Section 110 (a)(2)(D)(i)(I) Interstate Transport requirements regarding the 0.08 parts per m illion (ppm) 8-Hour Ozone National Ambient Air Quality Standard (NAAQS). This a ddresses the applicable components of 110(a)(2)(D)(i)(I) demonstrating adequate provisions to prev ent emissions from Colorado from interfering with attainment or mainte nance of the federal ozone NAAQS in any other state. This analysis does not address oz one transport for the revised 0.075 ppm 8-Hour Ozone NAAQS.

This document replaces the section titled “O zone-Specific Provisions” in the document “State of Colorado Implementation Plan to Meet the Requirements of Clean Air Act Section 110 (a)(2)(D)(i)(I) - Interstate Transport Rega rding 8-Hour Ozone and PM 2.5 NAAQS.”

Currently, the Denver area is the only area in U.S. Envi ronmental Protection Agency (EPA) Region VIII that is designated as nonattainment for the 8-hour ozone NAAQS of 0.08 ppm.

In this report, relevant information from the Denver Metropolitan Area and North Front Range (DMA/NFR) 8-hour Ozone State Implemen tation Plan (SIP) process, the Denver Early Action Compact (EAC) process, ambient ozone data for Colorado, ambient ozone data for nearby states from the EPA Air Quality System (AQS) database, and other information is used to demonstrate that Colorado does not contribute significantly to nonattainment in, or interfere with maintenan ce by, any other state w ith respect to the 0.08 ppm ozone NAAQS.Colorado Department of Public Health and Environment / Air Pollution Control Division

State of Colorado Implementation Plan to Meet the Requirements of Clean Air Act Section 110 (a)(2)(D)(i)(I) - In terstate Transport Re garding 8-Hour Ozone 2 

### 1.2. Colorado Ozone Monitoring Network

The 2007/2008 ozone ambient air monitoring ne twork in the Denver area and along the northern Front Range consists of 13 stat ions operated by the Colorado Air Pollution Control Division (APCD) and one station operated by the Nati onal Park Service (NPS) in Rocky Mountain National Park. There have been other stations that have operated in the past. The geographical distribution of the Front Range monitors is presented in Figure 1.

As shown in Figure 1, the ozone monitors ar e primarily located in urbanized areas along the Front Range corridor. The monitors ar e located in areas where the highest ozone concentrations have been monitored historica lly and where elevated ozone is expected to occur. High ozone concentr ations along the Front Range oc cur near the areas with high emissions density and dense population. In ad dition, elevated ozone is observed along elevated terrain to the west of the DMA/NFR Nonattainment Area. All of these monitors are designated by the U.S. Environmental Prot ection Agency as “equivalent” analyzers and follow all quality assurance re quirements as specified in 40 CFR Part 58, Appendix A.

Figure 1. Location of Front Range Ozone MonitorsColorado Department of Public Health and Environment / Air Pollution Control Division

State of Colorado Implementation Plan to Meet the Requirements of Clean Air Act Section 110 (a)(2)(D)(i)(I) - In terstate Transport Re garding 8-Hour Ozone 3 Figure 2 shows other ozone monitoring sites that exist in Colorado for 2008. These are operated by either Colorado, the Southern Ute Tr ibe, or various Federal agencies. All of these sites use monitors that are designa ted as “equivalent” analyzers by the U.S. Environmental Protection Agency. As shown, most of the sites are in the southwest corner of Colorado, either within or near the San Juan oil and gas development area.

Figure 2. Location of Statewide Ozone Monitors

Table 1, Table 2, and Table 3 present th e monitoring data for the DMA/NFR NAA monitoring sites (including th e NPS Rocky Mountain National Park monitoring site) as well as for other sites in Colorado. In Table 3, the fourth maximum 8-hour ozone concentrations along with the 3-year average of the fourth maximum concentrations at each site are presented. As shown in both Table 1 and Table 3, the Denve r area is currently meeting the 8-hour and former 1-hour ozone NAAQS for all sites, except for the 8-Hour NAAQS at Rocky Flats North w ith a design value of 0.86 ppm.Colorado Department of Public Health and Environment / Air Pollution Control Division

State of Colorado Implementation Plan to Meet the Requirements of Clean Air Act Section 110 (a)(2)(D)(i)(I) - In terstate Transport Re garding 8-Hour Ozone 4 Table 1: 2008 1-Hour Ozone Monitored Con centration (updated through Sept. 30, 2008)

1st Max Date 2nd Max Date 3rd Max Date 4th Max Date AQS Number Site Name 1-Hour 1st Max 1-Hour 2nd Max 1-Hour 3rd Max 1-Hour 4th Max

(ppm) 1-Hour (ppm) 1-Hour ( ppm) 1-Hour (ppm) 1-Hour

08-001-3001 Welby 0.100 08/29 0.095 08/05 0.092 07/10 0.089 06/20

08-005-0002 * Highland 0.065 04/04 0.064 04/08 0.064 04/18 0.062 04/19

08-013-0011 S. Boulder Creek 0.089 07/10 0.089 07/25 0.086 07/16 0.085 05/31

08-031-0014 Carriage 0.094 08/05 0.090 08/29 0.089 07/10 0.085 06/20

08-031-0025 ** Denver - Animal Shelter 0.100 07/10 0.098 08/05 0.087 06/20 0.087 08/24

08-035-0004 Chatfield State Park 0.101 07/10 0.098 06/20 0.095 08/29 0.092 08/24

08-041-0013 Colo. Spgs. - Academy 0.085 05/24 0.083 07/10 0.082 08/06 0.080 07/18

08-041-0016 Manitou Springs 0.087 05/24 0.085 08/06 0.083 07/10 0.083 07/11

08-045-0012 ** Rifle - Health 0.081 07/09 0.080 07/10 0.075 08/19 0.074 07/11

08-059-0002 Arvada 0.093 08/05 0.093 08/29 0.092 07/10 0.088 07/25

08-059-0005 Welch 0.102 07/10 0.090 06/20 0.088 08/05 0.088 08/29

08-059-0006 Rocky Flats - N 0.088 07/10 0.088 07/18 0.088 08/29 0.087 07/02

08-059-0011 NREL 0.097 08/29 0.093 07/10 0.092 08/05 0.092 08/24

08-067-7001 *** So. Ute - Ignacio 0.076 06/04 0.075 05/31 0.073 05/03 0.072 05/3

08-067-7003 *** So. Ute - Bondad 0.080 06/04 0.078 05/31 0.077 05/27 0.071 04/21

08-067-???? USFS - Shamrock 0.081 06/04 0.079 06/10 0.077 02/29 0.077 05/30

08-069-0007 Rocky Mountain Nat'l Park 0.092 07/09 0.090 07/31 0.090 08/28 0.085 05/22

08-069-0011 Ft. Collins - West 0.093 08/19 0.092 07/09 0.092 07/18 0.088 07/24

08-069-1004 Ft. Collins - CSU 0.082 08/19 0.080 07/09 0.079 08/30 0.078 07/24

08-077-0020 ** Palisade - Water 0.081 07/09 0.079 07/10 0.075 07/08 0.074 07/05

08-083-0006 ** Cortez 0.078 07/23 0.074 07/13 0.072 08/05 0.071 07/25

08-083-0101 Mesa Verde Nat’l Park 0.075 05/01 0.075 06/04 0.074 05/31 0.072 04/30

08-123-0009 Greeley - Weld Tower 0.094 08/20 0.092 07/24 0.089 08/01 0.087 08/04

NOTES: * Highland site shut down on 4/21/08 fo r approx. 6-months. ** Denver - Animal Shelter site commenced on 4/ 22/08, Rifle - Health commenced on 6/20/08, Palisade - Water commenced on 5/30/08 and Cortez commenced on 6/17/08. *** Southern Ute sites data only thru 6/30/08.Colorado Department of Public Health and Environment / Air Pollution Control Division

State of Colorado Implementation Plan to Meet the Requirements of Clean Air Act Section 110 (a)(2)(D)(i)(I) - In terstate Transport Re garding 8-Hour Ozone 5 Table 2: 2008 8-Hour Ozone Monitored Con centration (updated through Sept. 30, 2008)

1st Max Date 2nd Max Date 3rd Max Date 4th Max Date AQS Number Site Name 8-Hour 1st Max 8-Hour 2nd Max 8-Hour 3rd Max 8-Hour 4th Max

(ppm) 8-Hour (ppm) 8-Hour ( ppm) 8-Hour (ppm) 8-Hour

08-001-3001 Welby 0.085 07/10 0.083 08/29 0.077 07/18 0.076 06/20

08-005-0002 * Highland 0.062 04/04 0.060 04/08 0.060 04/18 0.059 04/05

08-013-0011 S. Boulder Creek 0.080 07/10 0.076 05/31 0.076 07/09 0.076 07/18

08-031-0014 Carriage 0.081 07/10 0.075 08/29 0.073 06/20 0.072 07/26

08-031-0025 ** Denver - Animal Shelter 0.086 07/10 0.072 08/29 0.071 07/13 0.070 07/26

08-035-0004 Chatfield State Park 0.090 07/10 0.082 06/30 0.080 06/20 0.080 06/27

08-041-0013 Colo. Spgs. - Academy 0.078 05/24 0.077 07/10 0.073 08/06 0.070 07/18

08-041-0016 Manitou Springs 0.080 05/24 0.076 07/10 0.074 07/11 0.072 07/31

08-045-0012 ** Rifle - Health 0.076 07/09 0.076 07/10 0.069 08/19 0.066 07/13

08-059-0002 Arvada 0.081 08/29 0.080 07/10 0.077 06/20 0.074 08/05

08-059-0005 Welch 0.095 07/10 0.079 06/20 0.077 07/18 0.073 08/19

08-059-0006 Rocky Flats - N 0.083 07/10 0.080 07/18 0.079 05/31 0.079 08/29

08-059-0011 NREL 0.085 07/10 0.085 08/29 0.077 06/20 0.076 06/02

08-067-7001 *** So. Ute - Ignacio 0.069 06/04 0.067 06/10 0.066 05/10 0.066 06/13

08-067-7003 *** So. Ute - Bondad 0.073 06/04 0.067 05/27 0.067 05/31 0.067 06/05

08-067-???? USFS - Shamrock 0.074 06/04 0.073 06/10 0.071 06/13 0.069 05/30

08-069-0007 Rocky Mountain Nat'l Park 0.081 07/09 0.077 05/25 0.077 07/31 0.076 05/31

08-069-0011 Ft. Collins - West 0.081 07/18 0.079 07/09 0.078 05/25 0.076 07/24

08-069-1004 Ft. Collins - CSU 0.070 05/25 0.070 07/09 0.068 07/18 0.066 05/31

08-077-0020 ** Palisade - Water 0.077 07/09 0.075 07/10 0.070 05/31 0.070 07/29

08-083-0006 ** Cortez 0.067 08/02 0.066 07/23 0.065 08/07 0.064 08/05

08-083-0101 Mesa Verde Nat’l Park 0.071 06/04 0.070 04/30 0.069 04/21 0.069 06/10

08-123-0009 Greeley - Weld Tower 0.077 07/24 0.076 08/20 0.075 07/26 0.073 08/01

NOTES: * Highland site shut down on 4/21/08 fo r approx. 6-months. ** Denver - Animal Shelter site commenced on 4/ 22/08, Rifle - Health commenced on 6/20/08, Palisade - Water commenced on 5/30/08 and Cortez commenced on 6/17/08. *** Southern Ute sites data only thru 6/30/08.Colorado Department of Public Health and Environment / Air Pollution Control Division

State of Colorado Implementation Plan to Meet the Requirements of Clean Air Act Section 110 (a)(2)(D)(i)(I) - In terstate Transport Re garding 8-Hour Ozone 6 Table 3: 8-Hour Design Value Using the 3-Year (2006-2008) Average of the Fourth Maximum Ozone Concentration

Site Name AQS # 2006 4 th Maximum

8-Hour Average Value (ppm) 2007 4 th Maximum

8-Hour Average Value (ppm) 2008 4 th Maximum

8-Hour Average Value (ppm) Design Value (2006 – 2008) 3-Year Average 4 th Maximum Value (ppm) Welby 08-001-3001 0.069 0.070 0.076 0.071 * Highland 08-005-0002 0.081 0.075 0.059 0.071

S. Boulder Creek 08-013-0011 0.082 0.085 0.076 0.081 Carriage 08-031-0014 0.072 0.076 0.072 0.073 ** Denver - Animal Shelter 08-031-0025 --- --- 0.070 ---

Chatfield State Park 08-035-0004 0.086 0.082 0.080 0.082 USAF Academy 08-041-0013 0.072 0.072 0.070 0.071 Manitou Springs 08-041-0016 0.076 0.072 0.072 0.073

** Rifle - Health 08-045-0012 --- --- 0.066 ---

Arvada 08-059-0002 0.082 0.079 0.074 0.078

Welch 08-059-0005 0.081 0.080 0.073 0.078 Rocky Flats - North 08-059-0006 0.090 0.090 0.079 0.086

NREL 08-059-0011 0.083 0.085 0.076 0.081 *** So. Ute - Ignacio 08-067-7001 --- --- 0.066 ---

*** So. Ute - Bondad 08-067-7003 0.063 0.071 0.067 0.067

USFS - Shamrock 08-067-???? 0.074 0.069 0.069 0.070 Rocky Mountain Nat’l Park 08-069-0007 0.076 0.078 0.076 0.076

Fort Collins - West 08-069-0011 0.087 0.085 0.076 0.082

Fort Collins - CSU 08-069-1004 0.078 0.069 0.066 0.071

** Palisade - Water 08-077-0020 --- --- 0.070 ---

** Cortez 08-083-0006 --- --- 0.064 ---

Mesa Verde Nat’l Park 08-083-0101 0.074 0.070 0.069 0.071 Greeley - Weld Tower 08-123-0009 0.082 0.074 0.073 0.076

NOTES: * Highland site shut down on 4/21/08 fo r approx. 6-months. ** Denver - Animal Shelter site commenced on 4/ 22/08, Rifle - Health commenced on 6/20/08, Palisade - Water commenced on 5/30/08 and Cortez commenced on 6/17/08. *** Southern Ute sites data only thru 6/30/08. Ignacio data invalid for 01/2005 to 08/2007.Colorado Department of Public Health and Environment / Air Pollution Control Division

State of Colorado Implementation Plan to Meet the Requirements of Clean Air Act Section 110 (a)(2)(D)(i)(I) - In terstate Transport Re garding 8-Hour Ozone 7 

### 1.3. Ozone Monitoring Network in Nearby States

Table 4 present 8-hour ozone monitoring data from the surrounding states of Nebraska, Kansas, New Mexico, Wyoming, and Utah. Table 4 and s how that none of the monitors in surrounding states exceed the 8-hour ozone standard except fo r Davis County Utah. Therefore, to the extent that the network is representative of all areas, it can be concluded that the DMA/NFR sources do not significantly contribute to th e 8-hour ozone standard violations at these down wind locations or even further downwind. In addi tion, Colorado does not significan tly contribute to violations upwind including Davis County Utah. Utah’s 8- hour proposed 8-hour maintenance plan for the 1997 8-hour ozone standard does not suggest that Co lorado interferes with the maintenance of the standard in Davis County Utah.

Table 4: 2005-2007 3-Year Fourth Highest Average M onitoring Concentrations from Kansas, Nebraska, New Mexico, Utah and Wyoming

Site ID State County EPA Region 2005 8-hr Ozone 4th Max

(ppm) 2006 8-hr Ozone 4th Max

(ppm) 2007 8-hr Ozone

4th Max

(ppm) 3-yr Avg. of 4th Max

(ppm) 20-045-0004 KS Douglas 7 0.073 0.081 End 2007 N/A 20-091-0010 KS Johnson 7 0.081 0.076 0.071 0.076 20-103-0003 KS Leavenworth 7 0.077 0.074 0.080 0.077 20-107-0002 KS Linn 7 0.075 0.079 0.070 0.074 20-173-0001 KS Sedgwick 7 0.065 0.065 0.059 0.063 20-173-0010 KS Sedgwick 7 0.074 0.073 0.060 0.069 20-191-0002 KS Sumner 7 0.078 0.080 0.070 0.076 20-195-0001 KS Trego 7 0.071 0.076 0.068 0.071 20-209-0021 KS Wyandotte 7 0.079 0.081 0.073 0.077 31-055-0028 NE Douglas 7 0.069 0.072 0.066 0.069 31-055-0032 NE Douglas 7 0.067 0.066 0.056 0.063 31-055-0035 NE Douglas 7 0.070 0.067 0.061 0.066 31-109-0016 NE Lancaster 7 0.056 0.056 0.054 0.055 35-001-0019 NM Bernalillo 6 0.073 0.073 0.070 0.072 35-001-0023 NM Bernalillo 6 0.072 0.073 0.069 0.071 35-001-0024 NM Bernalillo 6 0.074 0.074 0.068 0.072 35-001-0027 NM Bernalillo 6 0.073 0.072 0.071 0.072 35-001-0029 NM Bernalillo 6 0.071 0.070 0.067 0.069 35-001-1012 NM Bernalillo 6 0.077 0.047 0.074 0.066 35-001-1013 NM Bernalillo 6 0.077 0.071 0.071 0.073 35-001-1014 NM Bernalillo 6 0.072 0.072 0.064 0.069 35-013-0008 NM Dona Ana 6 0.070 0.072 0.068 0.070 35-013-0017 NM Dona Ana 6 0.070 0.073 0.070 0.071 35-013-0020 NM Dona Ana 6 0.072 0.072 0.068 0.070 35-013-0021 NM Dona Ana 6 0.076 0.080 0.076 0.077 35-013-0022 NM Dona Ana 6 0.070 0.073 0.073 0.072 35-013-0023 NM Dona Ana 6 0.066 0.070 0.062 0.066Colorado Department of Public Health and Environment / Air Pollution Control Division

State of Colorado Implementation Plan to Meet the Requirements of Clean Air Act Section 110 (a)(2)(D)(i)(I) - In terstate Transport Re garding 8-Hour Ozone 8 Table 4 (continued) 2005-2007 3-Year Fourth Highest Average Monitoring Concentrations from Kansas, Nebraska, New Mexico, Utah and Wyoming

Site ID State County EPA Region 2005 8-hr Ozone 4th Max

(ppm) 2006 8-hr Ozone 4th Max

(ppm) 2007 8-hr Ozone

4th Max

(ppm) 3-yr Avg. of 4th Max

(ppm) 35-015-1005 NM Eddy 6 0.067 0.076 0.066 0.069 35-017-1003 NM Grant 6 0.071 0.067 0.062 0.066 35-025-0008 NM Lea 6 0.074 0.075 0.064 0.071 35-029-0003 NM Luna 6 Start 2006 0.053 0.062 N/A 35-043-1001 NM Sandoval 6 0.069 0.064 0.063 0.065 35-043-1003 NM Sandoval 6 0.075 0.074 0.071 0.073 35-043-9004 NM Sandoval 6 0.076 0.072 0.067 0.071 35-045-0009 NM San Juan 6 0.075 0.063 0.069 0.069 35-045-0018 NM San Juan 6 Start 2006 0.079 0.079 N/A 35-045-1005 NM San Juan 6 0.072 0.071 0.073 0.072 49-003-0003 UT Box Elder 8 0.079 0.078 0.077 0.078 49-003-7001 UT Box Elder 8 0.075 0.076 0.078 0.076 49-005-0004 UT Cache 8 0.069 0.073 0.074 0.072 49-011-0004 UT Davis 8 0.092 0.082 0.082 0.085 49-035-0003 UT Salt Lake 8 0.083 0.084 0.082 0.083 49-035-2004 UT Salt Lake 8 0.086 0.082 0.082 0.083 49-035-3006 UT Salt Lake 8 0.082 0.082 0.079 0.081 49-035-3007 UT Salt Lake 8 0.085 0.080 0.080 0.081 49-035-3008 UT Salt Lake 8 0.080 0.082 0.079 0.080 49-037-0101 UT San Juan 8 0.069 0.070 0.072 0.070 49-045-0003 UT Tooele 8 0.080 0.079 0.076 0.078 49-049-0002 UT Utah 8 0.078 0.074 0.075 0.075 49-049-5008 UT Utah 8 0.080 0.077 0.078 0.078 49-049-5010 UT Utah 8 0.080 0.079 0.077 0.078 49-053-0130 UT Washington 8 0.091 0.072 0.071 0.078 49-057-0007 UT Weber 8 0.081 0.083 0.080 0.081 49-057-1003 UT Weber 8 0.084 0.083 0.082 0.083 56-005-0123 WY Campbell 8 0.063 0.072 0.072 0.069 56-005-0456 WY Campbell 8 0.063 0.065 0.072 0.066 56-035-0098 WY Sublette 8 0.075 0.069 0.068 0.070 56-035-0099 WY Sublette 8 0.079 0.072 0.067 0.072 56-035-0100 WY Sublette 8 0.066 0.074 0.066 0.068 56-037-0200 WY Sweetwater 8 Start 2006 0.067 0.064 N/A 56-039-1011 WY Teton 8 0.060 0.069 0.065 0.064

Figure 3 presents a map of all the U.S. nonattainment areas fo r the 1997 8-hour ozone standard.. Since the surrounding states of Kansas, Nebraska, Wyoming, Utah, and New Mexico do not have violations the 8- hour NAAQS for ozone, it can be reasonably concluded that Colorado sources do not significantly affect the ozone nonattainment areasColorado Department of Public Health and Environment / Air Pollution Control Division

State of Colorado Implementation Plan to Meet the Requirements of Clean Air Act Section 110 (a)(2)(D)(i)(I) - In terstate Transport Re garding 8-Hour Ozone 9 even further downwind such as Dallas-Forth Worth and St. Louis nonattainment areas. In addition, it is unlikely that Co lorado would significantly affect nonattainment areas that are typically “upwind” such as Las Vegas and P hoenix. However, it is r ecognized that, under the types of synoptic scale meteorological re gimes that occur during some regional ozone episodes, simple terms like “upwind” and “downwind” may not be applicable. Thus, photochemical modeling is needed to study th e distribution of ozone under a variety of meteorological regimes.

Figure 3: 8-Hour Ozone Nonattainment AreasColorado Department of Public Health and Environment / Air Pollution Control Division

State of Colorado Implementation Plan to Meet the Requirements of Clean Air Act Section 110 (a)(2)(D)(i)(I) - In terstate Transport Re garding 8-Hour Ozone 10 

### 1.4. Ozone Transport Conc lusions from the DMA/NFR Photochemical Modeling

The DMA/NFR photochemical model domain was defined on a nested 36-kilometer (km), 12 km, and a 4 km nested-grid structure. This structure was utilized in conjunction with the Comprehensive Air-quality Model with extensions (CAMx) air quality model (ENVIRON, 2008). CAMx, SMOKE (Coats, 19 96), and CONCEPT MS (Loomis et al., 2005) air quality and emissions modeling was performed for the June-July 2006 period. Nested 36/12/4 km modeling domains were used in the Denver 8-hour ozone modeling study. The CAMx model was firs t applied to the 36 km cont inental U.S. domain using boundary conditions (BCs) from a global climat e air quality model. The CAMx 2006 and 2010 base case modeling results from the 36 km continental U.S. domain simulation were then processed to generate BCs for the CAMx 12/4 km domain (Figure 4) for the 2006 12/4 km base case and 2010 12/4 km base case and sensitivity simulations. The CAMx simulations for the 12/4 km domains were run using two-way interactiv e grid nesting (i.e., pollutants can flow back and forth between the 12 km and 4 km domains to account for recirculation). The larger 36km domain was selected to address the impact of boundary condition uncertainties for the Front Range area of Colorado, as APCD was concerned there may be transport from Southern Califor nia and Texas. The 12 km grid resolution domain essentially covers th e central Rocky Mountain States or portions thereof (i.e., Arizona, Colorado, New Mexico, Utah and Wyomi ng.) The 4 km nested-grid covers most of the state of Colorado.

Figure 4. Nested 12/4 km modeling domains for the Denver CAMx air quality and SMOKE emissions modeling.Colorado Department of Public Health and Environment / Air Pollution Control Division

State of Colorado Implementation Plan to Meet the Requirements of Clean Air Act Section 110 (a)(2)(D)(i)(I) - In terstate Transport Re garding 8-Hour Ozone 11 1.4.1. Emission Inventories and 2006 and 2010 Base Case The photochemical modeling for the “2010 base case” emissions scenario performed for the DMA/NFR Ozone SIP process demonstrat es compliance in the Front Range Region with the 8-hour 0.08 ppm ozone NAAQS. Contro l measures in place in 2006 and assumed for 2010 include:

1. Federal tailpipe standards and regulati ons, including those for small engines and non-road mobile sources. Credit is taken fo r these federal requirements but they are not part of the Colorado SIP. The cred its change from 2006 to 2010 as the United States Environmental Protection Agency (EPA) Tier II and low sulfur gasoline standards become effective.

2. Air Quality Control Commission Regulat ion No. 11--covering the Automobile Inspection and Readjustment (A.I.R.) program in place during the 2006 ozone season, which includes an enhanced Insp ection/Maintenance (I/M). For 2006, a maximum of 10% fleet cove rage is assumed, and fo r 2010, a maximum of 50% fleet coverage is assumed for the remote sensing clean screen program in the Denver metro area (DMA) based on Regulation No. 11.

3. Air Quality Control Commission Regulat ions No. 3, No. 6, No. 7, and Common Provisions--covering gasoline station and i ndustrial source control programs. The Common Provisions, Parts A and B of Regul ation No. 3, and the volatile organic compounds (VOC) control requirements of Regulation No. 7 are already included in the approved SIP. Regulation No. 6 a nd Part C of Regulation No. 3 implement the federal standards of performance for new stationary sources and the federal operating permit program. This reference to Regulation No. 6 and Part C of Regulation No. 3 shall not be construed to mean that these regul ations are included in the SIP.

4. Since 2004, gasoline sold in the Denver me tro area during the summer Reid Vapor Pressure (RVP) ozone season (June 1 to September 15) has been subject to a national RVP limit of 7.8 pounds per square in ch (psi) to reduce fu el volatility. For ethanol-blended fuels, the RVP limit is 8.8 psi due to the federal 1.0 psi RVP waiver for ethanol.

Since 1991, gasoline sold in the Larimer a nd Weld area during the summer ozone season (June 1 to September 15) has been subject to a national RVP limit of 9.0 psi to reduce fuel volatility. For ethanol-blended fuels, the RVP limit is 10.0 psi due to the federal 1.0 psi RVP waiver for ethanol.

For 2006, the RVP of gasoline for th e Denver metropolitan portion of nonattainment area was determined by survey to be at 8.2 psi, with an ethanol market share of 60%, and for the Larime r and Weld portion of the nonattainment area the RVP was determined to be 8.4 psi with the same ethanol share of 60%. For purposes of the base case 2010 mobile s ource inventory, the RVP of the baseColorado Department of Public Health and Environment / Air Pollution Control Division

State of Colorado Implementation Plan to Meet the Requirements of Clean Air Act Section 110 (a)(2)(D)(i)(I) - In terstate Transport Re garding 8-Hour Ozone 12 gasoline is assumed to be 7.8 psi for the Denver metropolitan portion of nonattainment area, with an ethanol market share of 85%, and for the Larimer and Weld portion of the nonattainment area the RVP was assumed to be 9.0 psi with an ethanol share of 25%.

5. The EPA approved the EAC Ozone Acti on Plan (OAP) on August 19, 2005. The OAP included an amendment to Regulation No. 7 requiring the reduction of flash emissions of volatile organic compounds from condensate collection, storage, processing and handling operations by Ma y 1, 2005. This initial rule required the installation of air pollution control technology to achieve a system-wide 47.5% reduction from uncontrolled emissions of vol atile organic compounds from new and existing oil and gas exploration and producti on operations located within the 8-hour ozone nonattainment area designated by EP A for operators with total emissions greater than 30 tons per year. The 2006 base case estimate was developed from actual reported emissions based on the sy stem-wide 47.5% reduction requirement.

6. In February 13, 2008, the EPA approved revi sions to Regulation No. 7 to require the system-wide reduction of condensate tank flash VOC emissions of 75% for the 2007 ozone season by May 1, 2007 and 78% reduction for the 2012 ozone season, with technology that achieves a 95% reduction in VOC emissions. The 2010 base case emissions estimate assumes the 75% system-wide reduction requirement.

7. The effect of EPA final locomotive Tier 3 standards were considered and included, where appropriate, in the 2010 area source estimates. Tier 4 locomotive standards do not go into effect until 2015 and ther efore were not included in the 2010 inventories.

All of the inventories in th is 8-hour Ozone Attainment SI P were developed using EPA approved emissions modeling methods, includ ing EPA’s MOBILE6 model and local VMT data for on-road mobile source emissions, EPA’s non-road model and local demographic information for area and off-road sources, and re ported actual emissions for point sources. Estimates for future emissions are based on the above-mentioned tools and the EPA’s Economic Growth and Analysis System (EGAS) model for estimating future point sources activity, VMT growth for on-road mobile sources, and 2010 and 2012 demographic data for off-road and area sources. The techni cal support document contains detailed information on model assumptions and parameters for each source category.

Highway mobile source emissions are from the ENVIRON Consolidated Community Emissions Processing Tool (CONCEPT) m odel inventory, which is based on DRCOG VMT data and MOBILE6 input data provided by APCD and e xpanded to the entire NAA based on VMT from the North Front Range Transportation and Air Quality Planning Council and CDOT.

Non-road source emissions are from the EPA Non-Road Model. This model includes the impact of future controls on non-road engines, which is used in equipment such as lawn and garden equipment and construction equipm ent. Oil and gas source emissions are fromColorado Department of Public Health and Environment / Air Pollution Control Division

State of Colorado Implementation Plan to Meet the Requirements of Clean Air Act Section 110 (a)(2)(D)(i)(I) - In terstate Transport Re garding 8-Hour Ozone 13 the revised Independent Petroleum Associati on of Mountain States (IPAMS) inventory, and were projected to 2010 using the me thodology in the IPAMS projection methodology document. The IPAMS inventory was sponsored by the IPAMS and is Phase III of a regional oil and gas emission inventory for the Inter-Mountain West jointly with the Western Regional Air Pa rtnership (WRAP).

Non-oil and gas area source emissions (includi ng heating, consumer solvent use, aircraft and railroads, etc.) are from the 2002 EPA Nati onal Emissions Inventory (NEI), grown to 2006 and 2010 by population growth from data fr om the State Demographer. Consumer solvent emission reductions based on 75% of the per-person reductions listed in the EPA May 30, 2007 Emission Reduction Credit Memo were applied to the projected 2010 nonoil and gas area source inventory. A check on the non-oil and gas area sources estimates comparing the recently available 2005 NEI emissions data is shown later in this document. An inventory completed in 2005 for Denver In ternational Airport (DIA) was used for aircraft and airport non-road source emissions from DIA for both 2006 and 2010.

Non-oil and gas point source emissions we re grown to 2010 by the EPA EGAS economic model, and by adding sources for which permits have been issued.

Emissions of VOC and nitrogen oxides (NOx) from biogenic sources have been generated by the Model of Emissions of Gases and Aerosols from Nature (MEGAN) Biogenic Emissions Model using land cover data base of biomass type and density and hourly meteorology data. The National Center of At mospheric Research (NCAR) has produced a global data base of land use data, the MEGAN Driving Variable Database Version 1.2, for use with MEGAN. Surface temperatures are provided by the Mesoscale Meteorological Model (MM5) modeling.

Summaries of the VOC and NOx base case i nventories for the nonattainment area for 2006 and 2010 are presented in Table 5. Emissions of NOx and VOCs are in tons per average episode day. Additional detail on the categor ies of emissions can be found in the TSD.

Wildfire emissions, though not included in ta bles, have been considered for the background ozone concentrations in the modeling effort. Wildfire emissions can vary significantly on a day-to-day basis depending on conditions.Colorado Department of Public Health and Environment / Air Pollution Control Division

State of Colorado Implementation Plan to Meet the Requirements of Clean Air Act Section 110 (a)(2)(D)(i)(I) - In terstate Transport Re garding 8-Hour Ozone 14 Table 5. Base Case Inventories for 8-Hour Ozone DMA/NFR NAA Photochemical ModelingColorado Department of Public Health and Environment / Air Pollution Control Division

State of Colorado Implementation Plan to Meet the Requirements of Clean Air Act Section 110 (a)(2)(D)(i)(I) - In terstate Transport Re garding 8-Hour Ozone 15 1.4.2. Discussion of 2010 Base Case CAMx Modeling Results Currently, Colorado’s highest emissions dens ity is along the Front Range. As shown in Figure 5 Photochemical Modeling done for the DMA/NFR SIP process shows that the highest 2010 ozone design values along the foothills west of Denver and Fort Collins. Ozone concentrations decrease rapidly to the east of Denver. The maximum projected 2010 base case 8-hour ozone Design Value of 84 ppb occurs at both the Rocky Flats North and Fort Collins West monitoring sites. As this value is 84 ppb or lower, the 2010 base case modeling results pass the EPA modeled attainment demonstration test. Although the EPA 8-hour ozone projection procedure is to trun cate the final projected DVF for comparisons with the NAAQS, the projected 2010 base case future years design value is 84.9 ppb (Morris, et al, 2008a). White (unshaded) areas in Figure 5 have future design value of less than 63.8 ppb.

Figure 5. Projected 2010 8-hour ozone Design Values (DVF)

Figure 6 presents the ozone source apporti onment results, incl uding the boundary conditions. The boundary conditions (BCs) show the contribution from sources outside theColorado Department of Public Health and Environment / Air Pollution Control Division

State of Colorado Implementation Plan to Meet the Requirements of Clean Air Act Section 110 (a)(2)(D)(i)(I) - In terstate Transport Re garding 8-Hour Ozone 1 6 12 km domain (see Figure 4) for a given high oz one day (results vary by day). On this day, of the 76.1 ppb of ozone estimated at the m onitor, approximately 48 ppb was transported into the 12 km domain and approximately 8 ppb was attributed to sources in the sevencounty Denver Metro area (Morris, et al, 2008a) while the rest was from other counties in Colorado or from other states. This suggest s that, on this day, ozone was generated primarily by global/continental scale “backgroun d” and local sources of emissions in the Denver Metro area. Transport from n earby states was relatively small.

Figure 6. Rocky Flats North source apportionment for 29 July including boundary conditions.

Conclusions from ozone source apportionment results (Morris, et al, 2008a) vary by day and by location. However, several overall trends emerged, namely:

• Regional ozone transport into the 12 km do main is the largest contributor, often accounting for more than two-thirds of the total ozone;

• At the Denver Metropolitan monitors the largest contributors are Denver Metropolitan metro area motor vehicle and non-road sources;

• At the Fort Collins and Greeley monitors , the largest contributors tend to be Larimer and Weld County motor vehicl es, non-road sources and oil and gas sources, and Denver Metropolitan sources;

• The majority of the ozone formed is attr ibutable to anthropogenic NOx emissions.Colorado Department of Public Health and Environment / Air Pollution Control Division

State of Colorado Implementation Plan to Meet the Requirements of Clean Air Act Section 110 (a)(2)(D)(i)(I) - In terstate Transport Re garding 8-Hour Ozone 1 7 In interpreting these results, it is important to keep in mind that the source apportionment results are based on the Denver SIP 2006 m odeling episode and are meteorologically dependent For instance, the source a pportionment modeling in support of the Denver Early Action Compact using a 2002 ozone epis ode (Morris, et al, 2004a) showed more impact from sources in northern Co lorado in the Denver Metropolitan area.

Other ozone transport studies also confirm that Denver is impacted by ozone from areas well outside of Colorado. A report sponsored by the Western States Air Resources Council (WESTAR) indicates that, when ozone is greater than 85 ppb in Denver, natural background accounts for 37.5% of the total c oncentration, transported anthropogenic generated ozone is 37.5%, and the local anthropogenic ozon e contribution is about 25% (MacDonald, et. al, 2006).

A common theme at all ozone monito rs is that a majority of the peak 8-hour ozone is due to ozone transport from sources outside of Co lorado and outside the 12km domain boundary. Source apportionment modeling indicates that transport into the region accounts for approximately 60-75% of the ozone formation in the DMA/NFR. This indicates that the DMA/NFR is more of a receptor of ozone and ozone precursors rather than a producer of ozone and precursors that transports ozone to areas outside of the Front Range. While the modeling suggests that the transp ort of ozone and/or ozone precu rsors is a significant issue in the west, the magnitude of ozone transport from Colorado to other states is too low to significantly contribute to nonatta inment in, or interfere w ith maintenance by, any other state with respect to the 0.08 ppm ozone NAAQS.Colorado Department of Public Health and Environment / Air Pollution Control Division

State of Colorado Implementation Plan to Meet the Requirements of Clean Air Act Section 110 (a)(2)(D)(i)(I) - In terstate Transport Re garding 8-Hour Ozone 18 

### 1.5. Denver Metro Area/North Front Range Ozone Nonattainment Area Contribution to Downwind Locations

As part of the Denver EAC, source apportionment modeling was conducted to evaluate the spatial extent of the 8-hour ozone impacts due to emissions from various source regions in Colorado. A similar analysis was not done as part of the DMA/NFR ozone SIP analysis, however, a similar conclusion would be expect ed. The conclusion is that ozone formed specifically from sources in the DMA/NFR nonattainment area decreases rapidly in concentration over the eastern plains of Co lorado. Therefore, the photochemical modeling that was done for both the DMA/NFR ozone SI P and the Denver EAC suggest that ozone and/or ozone precursors from the Front Range do not contribute sign ificantly to downwind monitors in other states.

Figure 7 displays the spatial extent of the 8-hour ozone c oncentrations that occurred between 10am and 6pm local time (the tim e when the daily maximum 8-hour ozone typically occur) on June 27, 2002 through July 1, 2002 due to all emissions (anthropogenic and biogenic) from the DMA. As shown in Figure 7, which represents a high ozone episode in Denver, the DMA can contribute approximately 10 ppb of ozone at the eastern border of Colorado. However, the concentratio n gradient falls off quickly and emissions from the DMA are not expected to be a sign ificant contributor to any ozone nonattainment area downwind of the Front Range. Weld, Elbe rt, Morgan, Larimer, El Paso and other counties contribute even less ozone to th e Colorado border states with a maximum contribution of 5-10 ppb.Colorado Department of Public Health and Environment / Air Pollution Control Division

State of Colorado Implementation Plan to Meet the Requirements of Clean Air Act Section 110 (a)(2)(D)(i)(I) - In terstate Transport Re garding 8-Hour Ozone 19 Figure 7: Spatial extent of the 8-hour ozone concentr ations that occurred between 10am and 6pm local time on June 27, 2002 through July 1, 2002Colorado Department of Public Health and Environment / Air Pollution Control Division

State of Colorado Implementation Plan to Meet the Requirements of Clean Air Act Section 110 (a)(2)(D)(i)(I) - In terstate Transport Re garding 8-Hour Ozone 20 

### 1.6. Section 110(a)(2)(D)(i)(I) – Oz one Transport Conclusions

With respect to the 0.08 ppm ozone NAAQS, em ission control programs in the Colorado SIP are expected to adequately protect dow nwind neighboring states from interstate transport of ozone, per Clean Air Ac t (CAA) Section 110(a)(2)(D)(i)(I).

Ambient monitoring data in and around Colora do support the asserti on that Colorado does not contribute signifi cantly to nonattainment in, or inte rfere with maintenance by, any other state with respect to the 1997 8-hour ozone NAAQS of 0.08 ppm. Colorado is unlikely to interfere with maintenance of the 8-hour ozone standard in downwind or potentially downwind states is supported by monitoring data collected in neighborin g states (see Table 4) and the results of photochemical modeling an alysis as discussed in Section 1.4.2 and 1.5. Specifically:

1. Ozone concentrations measured at Kansas , Nebraska, and Wyoming monitors closest to Colorado are significantly below the nonattainment threshold. In addition, the results of the photochemical an alysis discussed in the sect ions noted above show that the ozone values in the easternmost Colora do counties are sufficiently low to make it unlikely for ozone transport from Colorado to interfere with maintenance of the 1997 NAAQS in downwind state.

2. A review of recent ozone observations from the EPA AQS database shows that, with the exception of a single monitor in Je fferson County, Colorado (i.e., Rocky Flats North), all monitoring sites in Colorado and adjacent states that are likely to be impacted by Colorado demonstrated attainment of the 0.08 ppm 8-hour ozone NAAQS for the three year period of 2005-2007. Since oz one monitors in adjacent states comply with the 0.08 ppm NAAQS, it logically follows that Colorado does not cause or contribute to monitored violations or interf ere with maintenance of the 0.08 ppm ozone NAAQS in any other state.

3. For Rocky Flats North, which is the only mo nitor in Colorado that has levels above the 0.08 ppm ozone NAAQS, the preliminary three-year average (2006-2008) fourth high value is 0.086 parts per million (ppm), which is only slightly above the 0.08 ppm ozone NAAQS.

4. Observations from current networks show that the highest ozone levels in Colorado occur along the Colorado Front Range and not in other areas of Colorado.

5.Ozone monitoring data from the surroundi ng states that are most likely to be impacted by Colorado (i.e., Nebraska, Ka nsas, New Mexico, Wyoming, and Utah) show that none of the monitors exceed the 0.08 ppm 8-hour ozone standard. Since the areas represented by these monitors are in m onitored attainment, it is highly unlikely that existing 0.08 ppm ozone nonattainment areas beyond these area s are significantly affected by emissions from Colorado. The nearest 0.08 ppm ozone nonattainment areas to DMA/NFR Nonattainment Area are:

a. Phoenix, Arizona (Basic Area for 8-Hour ozone) at a distance of 586 miles;Colorado Department of Public Health and Environment / Air Pollution Control Division

State of Colorado Implementation Plan to Meet the Requirements of Clean Air Act Section 110 (a)(2)(D)(i)(I) - In terstate Transport Re garding 8-Hour Ozone 21 b. Las Vegas, Nevada (Basic Area for 8-hour ozone) at a distance of 628 miles;

c. Dallas, Texas (Moderate 8-hour ozone nona ttainment area) at a distance of 663 miles; and d. St. Louis, Missouri (Moderate 8-hou r ozone nonattainment area) at a distance of 796 miles.

Photochemical modeling and other technical analyses performed for the Denver Early Action Compact (EAC) and the Denver Metr o Area and North Front Range (DMA/NFR) 8-hour Ozone SIP support the a ssertion that Colorado does not contribute significantly to nonattainment in, or interfere with maintenan ce by, any other state w ith respect to the 0.08 ppm ozone NAAQS. Specifically:

1. The Denver 8-hour Ozone SIP photochemical modeling for 2010 and the associated weight of evidence analyses suggest th at the DMA/NFR nonattainment area and downwind areas already comply or will comply with the 0.08 ppm ozone NAAQS by 2010.

2. Photochemical modeling shows that elevated ozone concentration levels generated from local emissions decrease rapidly with distance.

3. A review of photochemical modeling perf ormed for both the DMA/NFR Ozone SIP and the Denver EAC, including boundary condition analyses, suggests that the magnitude of ozone transport from Colo rado to other states is too low to significantly contribute to nona ttainment in, or interfer e with maintenance by, any other state with respect to the 0.08 ppm ozone NAAQS.

In summary, a review of monitoring data, photochemical modeling, and weight of evidence analyses generated for the DMA/NFR SIP proce ss suggests that the tr ansport of ozone and ozone precursors from Colorado does not cause or significantly contribute to nonattainment in, or interfere with maintenance by, any other st ate with respect to the 0.08 ppm 8-hour ozone NAAQS. This analysis does not address ozone transport for the revised 0.075 ppm 8-Hour Ozone NAAQS.Colorado Department of Public Health and Environment / Air Pollution Control Division

State of Colorado Implementation Plan to Meet the Requirements of Clean Air Act Section 110 (a)(2)(D)(i)(I) - In terstate Transport Re garding 8-Hour Ozone 22 

## 2. REFERENCES

Coats, C.J. Jr. “ High-performance algorithms in the Sparse Matrix Operator Kernel Emissions (SMOKE) modeling system .” Proc. Ninth AMS Joint Conference on Applications of Air Pollution Meteorology with AWMA. Amer. Meteor. Soc., Atlanta, GA, 584-588. 1996.

ENVIRON. User’s Guide – Comprehensive Air Quality Model with Extensions – Version 4.40. ENVIRON International Corporation, Novato, CA http://www.camx.com . February 2008.

Loomis, C., J. Wilkinson, J. Haasbeek, A. Pollack and M. Jansen. 2005. “ ConCEPT – Consolidated Community Emissions Processing Tool, An Open-Source Tool for the Emissions Modeling Community. ” Presented at the 14 th International Emission Inventory Conference “Transforming Emission Inventories – Meet ing Future Challenges Today”, Las Vegas, Nevada, April 11- 14. < http://www.epa.gov/ttn/chief/conf erence/ei14/session11/loomis.pdf >

MacDonald, C., Miller, D., Raffuse, S., 2006. Regi onal and Local Contributions to Peak Local Ozone Concentrations in Six Western Citie s. Sonoma, Technology, Inc., Petaluma, CA. Prepared for WESTAR Council of Governments.. May 16

Morris R., E. Tai, Tanarit Sakulyanontvi ttaya, D. McNally and C. Loomis. 2008a. 2010 Ozone Projections for the 2010 Base Case and 2010 Sensitivity Tests and 2010 Ozone Source Apportionment Modeling for the Denver 8- Hour Ozone State Implementation Plan . ENVIRON International Corporation, Novato, California. Prepared for Denver Regional Air Quality Council (RAQC), Denver, Colorado. September 8.

Morris R., E. Tai, Tanarit Sakulyanontvi ttaya, D. McNally and C. Loomis. 2008b. 2010 Ozone Attainment Demonstration Modeling for the De nver 8-Hour Ozone St ate Implementation Plan Control Strategy. ENVIRON International Corporati on, Novato, California. Prepared for Denver Regional Air Quality Council (R AQC), Denver, Colorado. September 22.

Morris, R.E., G.E. Mansell, E. Tai, D.A. McNally and T.W. Tesche. 2004a. Air Quality Modeling Analysis for the Denver Early Action Compact: Ozone Source Apportionment Modeling for the Denver EAC . Prepared for the Colorado Department of Health and Environment and Denver Regional Air Qualit y Council, Denver, Colorado. Prepared by ENVIRON International Corpor ation, Novato, CA. May 31..

Utah Air Quality Board, 8-Hour Ozone Maintenance Prov ision for Salt Lake and Davis Counties, January 3, 2007.