California Air Resources Board 

Planning and Technical Support Division 

Air Quality Analysis Section 

California Air Resources Board’s 

2010 Monitoring Network 

Assessment Report 

Prepared for: 

U.S. EPA Region 9 

75 Hawthorne Street 

San Francisco, CA, 94105 

July 2010 

i ____________________________________________________________________ 

 California Air Resources Board’s 2010 Monitoring Network Assessment Report 

Executive Summary 

This report provides a summary assessment of the ambient air quality monitoring 

network in certain regions of California. Federal regulations require air quality 

agencies to conduct a comprehensive assessment every five years, beginning in 

2010, and forward a report summarizing the findings to the U.S. Environmental 

Protection Agency (U.S. EPA). This document comprises the first report, due 

July 1, 2010. 

The purpose of the assessment is to determine if the network achieves the 

monitoring objectives specified in federal regulations for pollutants with federal 

ambient air quality standards. These pollutants include ozone, PM10, PM2.5, 

carbon monoxide (CO), nitrogen dioxide (NO2), sulfur dioxide (SO2), and lead. 

The regulations require an assessment of whether existing monitoring sites are 

sufficient. They also require an evaluation of any needed changes to PM2.5 

population-oriented sites. In addition to the federal requirements, this report also 

provides an evaluation of key needs for implementing California ambient air 

quality standards and program requirements. 

California has the most severe air quality problem in the nation. Over time, 

California’s monitoring network has expanded to meet the increasing challenges 

of implementing air quality programs to achieve healthy air. The current 

monitoring network exceeds minimum federal requirements. Areas that violate or 

are close to violating the new ozone and PM2.5 standards now include most of 

the rural counties in northern California and in some instances, even more 

remote locations near national parks. Therefore, our fundamental conclusion is 

that as federal air quality standards for ozone and PM2.5 have become 

increasingly more stringent in recent years, monitoring at the sites covered by 

this report is critical for determining compliance with the new standards. 

Moreover, monitoring discussed in this report is also needed for State 

designation purposes and other State and local monitoring programs. 

Monitoring is a shared responsibility between local air districts and the 

Air Resources Board (ARB). The areas covered by this report are shown in 

Table 1. They include all or some of the counties in seven different air basins. 

These counties span the most rural and sparsely populated counties in northern 

California. 

Areas not included in Table 1, which include all of California’s larger districts, as 

well as many of the State’s smaller districts, are preparing their own network 

assessments. The districts expected to submit their individual network 

assessments to Region 9 include: San Francisco Bay Area, South Coast, San 

Joaquin Valley, San Luis Obispo County, Ventura County, Monterey Bay Unified, 

Santa Barbara County, Great Basin Unified, San Diego County, Sacramento 

Metropolitan, North Coast Unified, Mojave Desert, and Imperial County. 
ii ____________________________________________________________________ 

 California Air Resources Board’s 2010 Monitoring Network Assessment Report 

Air Basin County (or portions of County) Air District

Lake County Lake Lake County AQMD

Lake Tahoe El Dorado (partial) El Dorado County AQMD

Placer (partial) Placer County APCD

Mojave Desert (partial) Kern (partial) Eastern Kern APCD

Mountian Counties Amador Amador County APCD

Calaveras Calaveras County APCD

El Dorado (partial) El Dorado County AQMD

Mariposa Mariposa County APCD

Nevada Northern Sierra AQMD

Placer (partial) Placer County APCD

Plumas Northern Sierra AQMD

Sierra Northern Sierra AQMD

Tuolumne Tuolumne County APCD

North Coast Mendocino Mendocino County AQMD

Sonoma (partial) Northern Sonoma County APCD

Northeast Plateau Lassen Lassen County AQMD

Modoc Modoc County APCD

Siskiyou Siskiyou County APCD

Sacramento Valley Butte Butte County AQMD

Colusa Colusa County APCD

Glenn Glenn County APCD

Placer (partial) Placer County APCD

Shasta Shasta County AQMD

Solano (partial) Yolo-Solano AQMD

Sutter Feather River AQMD

Tehama Tehama County APCD

Yolo Yolo-Solano AQMD

Yuba Feather River AQMD

Note:

AQMD = Air Quality Management District

APCD = Air Pollution Control District

Table 1. Areas covered in this report.
iii ____________________________________________________________________ 

 California Air Resources Board’s 2010 Monitoring Network Assessment Report 

Table of Contents 

Executive Summary........................................................................ i 

Introduction.................................................................................. 1 

Network Monitoring Objectives......................................................... 2 

Approach..................................................................................... 3 

Federal Monitoring Requirements..................................................... 3 

Summary of Assessment................................................................ 4 

Lake County Air Basin.................................................................... 5 

Lake Tahoe Air Basin (portions of El Dorado and Placer Counties).......... 6 

Eastern Kern Air Pollution Control District (a portion of the Mojave 

Desert Air Basin)......................................................................... 7 

Mountain Counties Air Basin............................................................. 8 

 Nevada, Plumas, and Sierra counties..................................... 9 

 El Dorado and Placer counties................................................. 10 

 Amador and Calaveras counties............................................. 10 

 Mariposa and Tuolumne counties........................................... 11 

 

Mendocino County Air Quality Management District and Northern 

Sonoma Air Quality Management District (a portion of the North Coast Air 

Basin).......................................................................................... 12 

 Mendocino County Air Quality Management District..................... 12 

 Northern Sonoma Air Quality Management District....................... 13 

Northeast Plateau Air Basin.............................................................. 14 

Sacramento Valley Air Basin............................................................. 16

 Shasta County...................................................................... 17 

 Colusa, Glenn, and Tehama counties....................................... 17 

 Butte County........................................................................ 18 

 Sutter and Yuba counties....................................................... 18 

 Yolo County and portions of Placer and Solano counties............... 19 

Summary.......................................................................................20 

Appendix A.................................................................................... 22
1 ____________________________________________________________________ 

 California Air Resources Board’s 2010 Monitoring Network Assessment Report 

Introduction 

The United States Environmental Protection Agency (U.S. EPA) finalized 

amendments to federal monitoring regulations in 2006. These amendments 

included requirements for air quality monitoring agencies to prepare an annual 

monitoring network plan and to conduct a comprehensive assessment of its 

monitoring network every five years. Both the 2010 annual monitoring network 

plan and the five year network assessment report are due on July 1, 2010 to the 

U.S. EPA. This report summarizes the results of the network assessment. 

 

The primary requirements for the assessment report are to determine if: 

• The monitoring network (network) is meeting the monitoring objectives of 

Appendix D in 40 CFR Part 58; 

• Existing sites are no longer needed and can be terminated; 

• New sites and technologies are appropriate; and if 

• Any changes are needed to the PM2.5 population oriented sites. 

California has one of the most extensive monitoring networks in the country. 

Monitoring is routinely conducted at over 250 locations. Monitoring is a joint 

responsibility between air districts, the Air Resources Board (ARB), and other 

agencies including the National Park Service. Because of the severity of 

California’s air quality problems, the number of monitors exceeds minimum 

federal requirements but is critical to implementing programs to attain federal and 

State ambient air quality standards. 

The assessment is required to cover all pollutants for which the U.S. EPA has 

established health based air quality standards. These pollutants are ozone (O3), 

PM2.5, PM10, carbon monoxide (CO), sulfur dioxide (SO2), nitrogen dioxide 

(NO2) and lead. This report focuses on the most critical pollutants. Ozone and 

PM2.5 represent California’s most severe air quality problems and have the 

greatest public health impacts. None of the areas in this report currently monitor 

for SO2 or lead. New federal NO2, SO2 and lead monitoring requirements will 

be covered in the 2011 or 2012 annual network report. 

Separately, thirteen districts, including the largest districts in California, have 

elected to conduct their own assessment. In some districts, the network also 

includes monitors operated by ARB or the National Park Service. Districts that 

have decided to assess their own monitoring network are also responsible for 

assessing all ARB monitoring sites that are located within the district’s 

jurisdiction. The network assessment summarized in this report covers the same 

geographical area covered in the 2010 annual network plan and includes the 

following areas: Lake County Air Basin, Lake Tahoe Air Basin, the eastern Kern 
2 ____________________________________________________________________ 

 California Air Resources Board’s 2010 Monitoring Network Assessment Report 

County portion of the Mojave Desert Air Basin, Mountain Counties Air Basin, a 

portion of the North Coast Air Basin, Northeast Plateau Air Basin, and the 

Sacramento Valley Air Basin (minus the sites operated by the Sacramento 

Metropolitan Air Quality Management District). The map illustrates the areas 

covered by this assessment. 

Network Monitoring Objectives 

Federal regulations specify the monitoring objectives that should be supported 

for each pollutant by monitors that are part of the State and Local Air Monitoring 

Stations (SLAMS) network. Note that there are no SO2 or lead monitors 

operating within the geographic scope of this report. As previously noted, this 

report is limited to a number of ARB, air district and National Park operated sites 

within the smaller air districts in northern California and one in southern 

California. The ARB assessment includes a site-by-site, monitor-by-monitor 

evaluation. 

One of the most important monitoring objectives is to determine compliance with 

State and federal air quality standards. As federal standards have become more 
3 ____________________________________________________________________ 

 California Air Resources Board’s 2010 Monitoring Network Assessment Report 

stringent recently, having sufficient monitoring to meet this objective is even more 

critical. Many smaller, primarily rural counties have ozone and PM2.5 air quality 

that approaches or exceeds these new more stringent standards. Other 

monitoring objectives are also important. Below is a selected summary of typical 

monitoring objectives. 

• Establish compliance with State and federal air quality standards 

• Monitor sites with expected high concentrations 

• Understand historical trends and progress made towards standards 

• Track spatial distribution of air pollutants 

• Evaluate population exposure to air pollutants and have information to 

inform the public about air quality (AQI) 

• Characterize specific geographic locations and emissions sources 

• Provide air quality data for air quality models and emission inventory 

development 

• Provide air quality data for determining burn days for agricultural and 

prescribed burning 

• Determine relationship between sources and resulting air quality (Sourceapportionment).

• Characterize the extent of pollutant transport.

Approach 

This assessment is organized by air basin. An air basin generally has similar 

meteorological and geographical conditions throughout with similar air mass. 

California is divided into 15 air basins to better manage air pollution. We used 

this approach in the assessment because a network of monitoring sites within an 

air basin would likely serve similar monitoring objectives. It should be noted that 

several counties are located in more than one air basin and the discussion of the 

monitors is broken out by air basin. 

Within each air basin, we conducted an evaluation for each monitoring site. We 

considered a number of sources of information including applicable federal and 

State requirements, current air quality conditions and attainment status, 

population, topography and climate. The overall goal was to determine how 

effectively each site is meeting critical monitoring objectives. Throughout the 

assessment, we provide 2009 ozone and PM2.5 federal design values for many 

sites. However it should be noted that, in some instances, these design values 

may include data for potential exceptional events. 

Federal Monitoring Requirements 

U.S. EPA regulations specify the minimum number of sites at which State and 

local air agencies must deploy monitors. In practice, the State and local 

agencies find they need to deploy significantly more monitors to fulfill State and 
4 ____________________________________________________________________ 

 California Air Resources Board’s 2010 Monitoring Network Assessment Report 

local monitoring objectives, as well as federal objectives. Requirements for the 

minimum numbers of monitors appear in Appendix D of Part 58 of the CFR. For 

ozone, PM2.5, and PM10, the required minimum number is based on the 

population of an area and the severity of the air quality for the pollutant in the 

area. For CO and lead, no current monitoring is required by Appendix D unless 

an area exceeds or is close to exceeding a national ambient air quality standard, 

which is true for very few if any areas in the U.S. New federal monitoring 

requirements for NO2 and SO2 will be discussed in future annual monitoring 

network plans. For purposes of the minimum requirements, the areas are 

defined by the metropolitan statistical areas (MSA) developed by the Office of 

Management and Budget. An MSA may include one or more counties. 

However, not all counties are within an MSA. 

All areas in this report meet or exceed federal requirements. However, additional 

monitoring is often needed to implement State and local programs designed to 

attain State air quality standards as expediously as possible. A summary of the 

numbers of required and existing monitoring sites in the geographical scope of 

this report can be found in Appendix A, located at the end of this report. 

Summary of Assessment 

California’s extensive network of monitors is needed due to our severe air quality 

issues, large population and vehicle miles traveled, varied topography, large 

number of separate airsheds, and ozone and PM2.5 concentrations that are 

significantly higher than the rest of the country. As a result of this assessment, 

all existing monitors are critical and none are proposed to be discontinued or 

relocated. Under current federal regulations, no additional monitors are required 

in the geographic scope of this report. Any new federal monitoring requirements 

that take effect later in the year or in the next few years will be addressed in 

future annual monitoring network plans. Furthermore, this assessment 

demonstrates that the monitors and sites within this report meet the monitoring 

requirements of Appendix D in 40 CFR 58. At the time that this report was 

drafted no additional monitoring is under consideration. 
5 ____________________________________________________________________ 

 California Air Resources Board’s 2010 Monitoring Network Assessment Report 

Lake County Air Basin

Lake County is the only county in the Lake County Air Basin (Basin). It is a rural 

county located in northern California and borders Napa, Sonoma, Mendocino, 

Glenn and Colusa counties. It has a population of 65,000, covers 1,327 square 

miles and includes the towns of Lakeport and Clearlake. 

There is one (each) ozone, PM10, and PM2.5 

monitor at Lakeport that is part of the State 

and Local Air Monitoring Stations (SLAMS) 

network and two PM10 monitors used in the 

Geyser Air Monitoring Program (GAMP). 

Lake County has long attained State and 

federal air quality standards and has some of 

the best air quality in the State. In 2009, 

there were no violations of State or federal 

ozone, PM10, or PM2.5 standards in the 

Basin. 

However, the 2009 federal 8-hour ozone 

design value of 0.062 ppm is within the range 

proposed by U.S. EPA for the revised federal 

ozone standard (to be finalized in August 

2010). As federal standards become 

increasingly stringent over time, monitoring is critical for determining whether an 

area complies with revised federal standards. Continued ozone, PM10 and 

PM2.5 monitoring is also needed for State designations. As shown below, the 

monitoring objectives in Lake County are to measure high concentrations needed 

to make designation determinations. Because the current sites in Lake County 

are located where the highest concentrations are expected to occur and there 

are no minimum federal requirements, no additional monitoring is needed. No 

changes to the monitoring network for Lake County are being considered at this 

time. 

O3 CO NO2 PM2.5 PM10 cont. PM2.5 cont. PM10

Lakeport 

(060333001)

StateD, 

Gnrl

StateD, 

Gnrl

StateD, 

Gnrl

Middletown 

(060333010)

StateD, 

Gamp

Glenbrook 

(060333011)

StateD, 

Gamp

listed design values in this report may include data for potential exceptional events.

Monitoring Objectives:

PopEx = population exposure to pollutant

Lake County Air Basin: Lake County

Note: None of the areas discussed in this report have monitors for SO2 or lead. Moreover, 

Bkgrnd = background levels

StateD = attainment of State standards

Hconc = expected high concentration site Trans = pollutant transport

Gamp = Geyser Air Monitoring Program

Gnrl = general (i.e., public reporting, spatial 

Trends = trends analysis representation)

Rconc = representative concentration site AgBn = agriculture burning programs

Simp = local emission source
6 ____________________________________________________________________ 

 California Air Resources Board’s 2010 Monitoring Network Assessment Report 

Lake Tahoe Air Basin (portions of El Dorado and Placer counties)

The Lake Tahoe Air Basin (Basin) is the smallest air basin in California. It covers 

approximately 224 square miles and has an estimated population of 58,121 

(2010). Part of the Basin is in the State of Nevada, and part in California. The 

part that lies in California comprises the eastern part of El Dorado and Placer 

counties and includes the cities of South Lake Tahoe, Tahoe City and Tahoe 

Vista. Major U.S. Highway 50 runs through the City of South Lake Tahoe. 

There is one ozone monitor at the South 

Lake Tahoe-Airport site located in El Dorado 

County and it is a seasonal monitor that 

operates May through October. Although 

there is no current ozone monitor in the 

Placer County portion of the Basin, the South 

Lake Tahoe-Airport site is considered 

representative of the entire Basin. 

The area violates the State ozone standard 

and had one exceedance day in 2009. The 

2009 federal 8-hour design value of 0.068 

ppm is within the range proposed by U.S. 

EPA for the revised 8-hour federal ozone 

standard. The South Lake Tahoe-Airport site 

is needed for State and federal designations.

The continuous PM10 monitor at the South 

Lake Tahoe-Sandy Way site is used for 

public reporting and spatial representation as well as for State designation 

purposes. The area violates the State 24-hour PM10 standard and had one 

State exceedance day in 2009. The Basin is currently nonattainment for the 

State PM10 standard. This site is the only PM10 site in the Basin. For these 

reasons, the PM10 monitor is also needed. 

The current sites in the El Dorado County portion of the Basin are part of the 

Sacramento-Arden-Arcade-Roseville MSA and are located where the highest 

concentrations are expected to occur. No additional monitoring is required in the 

MSA and no changes to the monitoring network in the Basin are being 

considered at this time. 

O3 CO NO2 PM2.5 PM10 cont. PM2.5 cont. PM10

South Lake 

Tahoe-Airport 

(060170013)

StateD, 

Trans, 

Hconc

South Lake 

Tahoe-Sandy 

Way 

(060170011)

Grnl

Lake Tahoe Air Basin: Portions of El Dorado and Placer Counties
7 ____________________________________________________________________ 

 California Air Resources Board’s 2010 Monitoring Network Assessment Report 

Eastern Kern Air Pollution Control District (a portion of the Mojave Desert 

Air Basin)

 

This section covers the monitoring sites located in the Eastern Kern Air Pollution 

Control District (District). The District comprises the eastern portion of Kern 

County and is one of three districts located in the Mojave Desert Air Basin 

(Basin). The other two districts in the Basin will be included in a separate 

assessment prepared by the Mojave Desert Air Quality Management District. 

The District is located in the northwestern corner of the Basin and separated, to 

the south, from the South Coast Air Basin by the Antelope Valley and San 

Gabriel Mountains. The Tehachapi and the Sierra Nevada Mountains separate it 

from the San Joaquin Valley, to the west and north. Directly to the east is 

San Bernardino County. Eastern Kern’s population of 147,758 (2010) resides 

primarily in and around the major towns, including Tehachapi, Rosamond, Boron 

and Mojave. Major highways are U.S. Highways 58, 14, and 395. 

The ozone monitor at the MojavePoole site is the only ozone 

monitor in the District. In 2009, 

32 days and 61 days exceeded 

the federal and State 8-hour 

ozone standards, respectively. 

The 2009 federal 8-hour ozone 

design value of 0.084 ppm is well 

above the level proposed by U.S. 

EPA for the revised 8-hour 

federal ozone standard. This site 

is critical for both federal and 

State ozone designation 

purposes. 

The PM2.5 monitors at the 

Mojave-Poole Street and 

Ridgecrest-California Street sites 

are used for collecting data at 

expected high and representative 

concentration sites. The District 

is designated as an unclassified 

area for both State and federal PM2.5 standards. Federal 2009 PM2.5 annual 

average and 24-hour design values for the District are 6.1 ug/m3

 and 16 ug/m3, 

respectively. As federal and State PM standards become increasingly more 

stringent, monitoring becomes more critical for demonstrating whether an area 

complies with these revised standards. 

The PM10 monitors at the Mojave-Poole Street and Ridgecrest-California Street 

sites are used for collecting data at expected high and representative 
8 ____________________________________________________________________ 

 California Air Resources Board’s 2010 Monitoring Network Assessment Report 

concentration sites. The Canebrake site started on January 1, 2009 and is used 

for monitoring regional PM10 concentration levels in the area and for 

demonstrating compliance with the federal standard. This portion of eastern 

Kern County is currently a nonattainment area for PM10. For these reasons, 

continued PM10 monitoring is needed in the District. Note that the District 

recently started ozone and meteorological monitoring at Tehachapi for the 

evaluation of transport. However, there are no data reported from this site into 

the Environmental Protection Agency’s Air Quality System (AQS) at the time this 

report was drafted. 

The current sites in the District are part of the Bakersfield MSA and the majority 

of sites are located where the highest concentrations are expected to occur. No 

additional monitoring is required in the MSA and no changes to the monitoring 

network in the District are being considered at this time. 

O3 CO NO2 PM2.5 PM10 cont. PM2.5 cont. PM10

Canebrake 

(060290017) Rconc

Mojave-Poole 

(060290011)

Hconc, 

Trans Hconc Hconc

RidgecrestWest 

California 

(060290015)

Rconc Hconc

Mojave Desert Air Basin: Eastern part of Kern County

Mountain Counties Air Basin

The Mountain Counties Air Basin (Basin) 

extends from Plumas County in the north to 

Mariposa County in the south, and also 

includes all of Sierra, Nevada, Amador, 

Calaveras, Tuolumne, and Mariposa 

counties, and portions of Placer and 

El Dorado counties. The Basin covers the 

central and northern parts of the Sierra 

Nevada Mountains. The elevation ranges 

from several hundred feet in the foothills 

along the western edge of the Basin to 

more than 10,000 feet along the Sierra 

crest. Although bordering the Sacramento 

urban area to the west, the Basin is 

predominately rural, with a total population 

of 472,991 (2010). 
9 ____________________________________________________________________ 

 California Air Resources Board’s 2010 Monitoring Network Assessment Report 

Despite its rural character, the Basin includes all or part of four nonattainment 

areas for the federal 1997 ozone standard. Three nonattainment areas are 

completely contained within the Basin: Central Mountain Counties (Amador and 

Calaveras counties), Southern Mountain Counties (Tuolumne and Mariposa 

counties), and Western Nevada County (a portion of Nevada County). 

Furthermore, El Dorado and Placer counties have long been part of the 

Sacramento Metro ozone nonattainment area because they are linked to the 

Sacramento urban area through travel, employment and housing patterns. 

Most of the Basin is either attainment or unclassifiable for the federal 2006 

24-hour PM2.5 standard. A portion of El Dorado County is included in the 

Sacramento PM2.5 nonattainment area. (A portion of the Placer County is also 

included in the nonattainment area, but this portion lies in the Sacramento Valley 

rather than Mountain Counties Air Basin.) 

There are a variety of monitoring objectives in the Basin. These objectives 

include collecting data at expected high concentration sites, providing data for 

agriculture burn decisions, evaluation of ozone transport and for educating the 

public about air quality. Some sites also collect representative and background 

concentration data. All of the monitors in the Basin provide data to implement a 

variety of federal and State programs. We did not identify any new or unmet 

monitoring needs. 

The current sites in the El Dorado and Placer counties portion of the Basin are 

part of the Sacramento-Arden-Arcade-Roseville MSA. No other counties in the 

Basin are part of an MSA. No additional monitoring is required in the MSA or in 

any part of the Basin and no changes to the monitoring network in the Basin are 

being considered at this time. A summary of the monitors and their objectives 

accompanies each of the tables below. 

Nevada, Plumas, and Sierra counties 

There are more PM2.5 than ozone monitors in this northernmost part of the 

Basin. These monitors provide data for general uses, designation purposes, and 

to help assess potential wood smoke impacts and are located at potentially high 

concentration sites. In addition, the Plumas County 2009 PM2.5 design value is 

near the daily federal PM2.5 standard. The Grass Valley site is the most 

comprehensive, and includes monitors for O3, NO2, and PM2.5. Nevada County 

is nonattainment for the federal ozone standard and had a 2009 8-hour ozone 

design value of 0.087 ppm with 18 federal exceedance days in 2009. The White 

Cloud Mountain site is operated by the ARB and helps characterize air quality in 

the eastern portion of the ozone nonattainment area. Ozone concentrations at 

this site also violate the current federal and State ozone standards. Ozone 

monitoring at Truckee restarted on July 1, 2010 and the data will be submitted 

into AQS. Ozone monitoring in Penn Valley in Nevada County and PM10 

monitoring in Loyalton in Sierra County are not reporting data into AQS. These 

non-AQS monitors are used for local monitoring purposes.
10 

____________________________________________________________________ 

 California Air Resources Board’s 2010 Monitoring Network Assessment Report 

O3 CO NO2 PM2.5 PM10 cont. PM2.5 cont. PM10

Chester 

(060631007)

StateD, 

Gnrl

Grass Valley 

(060570005)

Hconc, 

Rconc, 

StateD

Rconc, 

StateD Rconc StateD, Gnrl

Portola 

(060631009) Hconc StateD, Gnrl

Quincy 

(060631006) Hconc StateD, Gnrl

Truckee 

(060571001) Hconc Hconc StateD, Gnrl

White Cloud 

Mountain 

(060570007)

StateD

Mountain Counties Air Basin: Nevada, Plumas and Sierra Counties

El Dorado and Placer counties 

El Dorado and Placer counties both split their land area among one or more air 

basins. A part of the El Dorado County is also in the Lake Tahoe Air Basin and 

Placer County is split into three air basins (Lake Tahoe, Mountain Counties, and 

Sacramento Valley). The Mountain Counties Air Basin portions of El Dorado and 

Placer counties are part of the Sacramento Metro nonattainment area for the 

federal 1997 ozone standard. Consequently, identifying areas of high ozone 

concentration is the primary monitoring objective within this part of the Basin. 

Cool has been the high ozone site during several different ozone seasons and 

had a 2009 federal 8-hour ozone design value of 0.093 ppm. Echo Summit was 

established to characterize the extent of air pollutant transport from the 

Sacramento and San Joaquin Valleys up the western slope of the Sierra Nevada. 

This area is currently nonattainment for the State 24-hour PM10 standard. For 

these reasons, continued ozone and PM10 monitoring in El Dorado and Placer 

counties is needed. 

O3 CO NO2 PM2.5 PM10 cont. PM2.5 cont. PM10

Colfax 

(060610004)

Hconc, 

StateD

Cool-Hwy 193 

(060170020)

Hconc, 

Trans, 

StateD

Echo Summit 

(060170012)

Hconc, 

Trans

PlacervilleGold Nugget 

(060170010)

Hconc, 

Trans Hconc

Mountain Counties Air Basin: Portions of El Dorado and Placer Counties

Amador and Calaveras counties 

Amador and Calaveras counties comprise the Central Mountain counties 

nonattainment area for the federal 1997 ozone standard. Two ozone monitors 

track the area’s progress toward attaining the standard. The San Andreas site is 

the 2009 federal design site for the federal 8-hour ozone nonattainment area and 
11 

____________________________________________________________________ 

 California Air Resources Board’s 2010 Monitoring Network Assessment Report 

had a 2009 federal 8-hour ozone design value of 0.082 ppm. Though neither 

county is part of a federal PM2.5 or PM10 nonattainment area, the monitors in 

San Andreas help us understand representative concentrations in that area and 

are used for State designation purposes. 

 

O3 CO NO2 PM2.5 PM10 cont. PM2.5 cont. PM10

JacksonClinton Road 

(060050002)

Hconc, 

Trans, 

StateD

San Andreas 

(060090001)

Hconc, 

Trans, 

StateD

Rconc Rconc

Mountain Counties Air Basin: Amador and Calaveras Counties

Mariposa and Tuolumne counties 

Mariposa and Tuolumne counties comprise the Southern Mountain counties 

nonattainment area for the federal 1997 ozone standard. They also violate the 

State ozone standards. The area had a 2009 federal 8-hour ozone design value 

of 0.086 ppm with more than 10 days in 2009 that exceeded the federal ozone 

standard. The ozone sites are critical in determining compliance with federal and 

State ozone standards. The ozone monitor at the Yosemite-Turtleback site is 

operated by the National Park Service. The Sonora and Yosemite-Turtleback 

sites are the 2009 federal ozone design sites in the southern portion of the Basin. 

While there were no days that exceeded the federal 24-hour PM10 standard in 

2009, three days exceeded the State 24-hour PM10 standard. A portion of 

Mariposa County is nonattainment for the State PM10 standard. This area is 

unclassifiable for both federal and State PM2.5 standards. The continuous 

PM2.5 monitor at the Yosemite Village site is used for State designation 

purposes as well as public reporting, smoke monitoring and spatial 

representation. For these reasons, continued PM2.5 and PM10 monitoring is 

needed at the Yosemite Village site, which is operated by ARB. 

O3 CO NO2 PM2.5 PM10 cont. PM2.5 cont. PM10

Jerseydale 

(060430006)

Hconc, 

Trans

Sonora 

(061090005)

Hconc, 

StateD

YosemiteTurtleback 

(060430003)

Hconc, 

Trans, 

StateD

Yosemite 

Village 

(060431001)

Hconc StateD, 

Gnrl

Mountain Counties Air Basin: Mariposa and Tuolumne Counties
12 

____________________________________________________________________ 

 California Air Resources Board’s 2010 Monitoring Network Assessment Report 

Mendocino County Air Quality Management District and Northern Sonoma 

Air Quality Management District (a portion of the North Coast Air Basin)

This section covers monitoring in the Mendocino County Air Quality Management 

District and the Northern Sonoma Air Quality Management District. These two 

districts cover the entire portion of Mendocino County and the portion of Sonoma 

County located in the North Coast Air Basin (Basin). The other three counties in 

the Basin are covered in a separate assessment report prepared by the North 

Coast Unified Air Quality Management District (Humboldt, Del Norte, and Trinity). 

Stretching along the northern 

coastline of California, the Basin 

covers 12,339 square miles and is 

home to giant coastal redwood 

trees that are found nowhere else 

in the world. The Mendocino, 

Humboldt, Trinity, Del Norte, and 

northern part of Sonoma counties 

lies within the Basin boundary, 

which borders the State of Oregon 

directly to the north, the 

Sacramento Valley and Northeast 

Plateau air basins to the west, and 

the San Francisco Air Basin to the 

south. The Basin’s population of 

333,829 (2010) resides primarily in 

and around major towns, including 

Crescent City, Eureka, Fort Bragg, 

Ukiah, Willits, and Healdsburg. 

Major highways are U.S. Highways 

101 and 1. 

While the current sites in the Mendocino County Air Quality Management District 

are not part of an MSA, the current sites in the Northern Sonoma Air Quality 

Management District are part of the Santa Rosa-Petaluma MSA. The majority of 

sites in both districts are located where the highest concentrations are expected 

to occur. No additional monitoring is required in the MSA and no changes to the 

monitoring network in the districts are being considered at this time. 

Mendocino County Air Quality Management District 

There is only one ozone monitor in Mendocino County, at Ukiah-Gobbi Street. 

Ozone monitoring at the Willits-Main Street site was suspended in 2008. Ozone 

concentrations at the Willits-Main Street site were lower than ozone 

concentrations at the Ukiah-Gobbi Street site and were below the range of the 

proposed federal ozone standard. However, the 2009 federal 8-hour design 

value of 0.062 ppm at Ukiah-Gobbi Street is within the range proposed by U.S. 
13 

____________________________________________________________________ 

 California Air Resources Board’s 2010 Monitoring Network Assessment Report 

EPA for the revised 8-hour federal ozone standard. For this reason, continued 

ozone monitoring is critical at the Ukiah-Gobbi Street site. 

PM2.5 and PM10 monitoring in Mendocino County are mainly used for collecting 

data at expected high and representative concentration sites. The District 

discontinued three filter-based PM10 monitors and one filter-based PM2.5 

monitor in 2008 and started two continuous PM2.5 FEMs and one continuous 

PM10 FEM monitor in 2009. Data from the continuous PM2.5 and PM10 

monitors are reported into AQS. Due to the recent establishment of the 

continuous FEM PM monitors in the county, continued PM monitoring is needed 

to have more completed data for regulatory purposes, including State 

designations. Mendocino County is currently nonattainment for the State 24-hour 

PM10 standard. 

Carbon monoxide monitors at the Ukiah-Gobbi Street and Willits-Main Street 

sites were discontinued in 2008, along with the nitrogen dioxide (NO2) monitor at 

Willits-Main Street in Mendocino County. Carbon monoxide concentrations in the 

District were well below both federal and State standards. Currently, there is 

only one NO2 monitor left operating in Mendocino County, which is located at the 

Ukiah-Gobbi Street site. The NO2 monitor provides useful information on ozone 

precursors and for evaluating transport. Further evaluation of NO2 monitoring 

needs will be discussed in the 2012 annual network report. 

Northern Sonoma Air Quality Management District 

One ozone monitor exists in the northern part of Sonoma County that lies within 

the North Coast Air Basin. This portion of the county comprises the Northern 

Sonoma County Air Quality Management District (District). This District attains 

State and federal ozone standards. The 2009 federal 8-hour ozone design value 

is 0.056 ppm. The ozone monitoring site is the only ozone monitor in the county 

and is needed for determining compliance with State and federal standards. The 

ozone monitor is also needed to characterize transport. For these reasons, 

continued ozone monitoring is needed at the Healdsburg-Airport site. 

Currently, there are three PM10 monitoring sites in the District. The District had 

expressed interest in discontinuing all filter-based PM10 monitoring and 

establishing continuous PM10 monitoring. The ARB is coordinating with the 

District in this effort. This area had attained the State PM10 standard and is 

listed as unclassified under federal standards; however, continued PM10 

monitoring is needed in the area to maintain State compliance. 
14 

____________________________________________________________________ 

 California Air Resources Board’s 2010 Monitoring Network Assessment Report 

O3 CO NO2 PM2.5 PM10 cont. PM2.5 cont. PM10

Cloverdale 

(060970001) Rconc

Fort Bragg 

(060450002)

Hconc, 

StateD

Guerneville 

(060973002) Rconc

HealdsburgAirport 

(060971003)

Rconc, 

StateD

HealdsburgMatheson 

(060970002)

Rconc

Ukiah-County 

Library 

(060450006)

Hconc, 

StateD

Ukiah-Gobbi 

Street 

(060450008)

Hconc, 

Trans, 

StateD

Rconc Rconc

WillitsFirehouse 

(060452001)

Hconc, 

StateD

North Coast Air Basin: Mendocino County and the northern part of Sonoma 

County

Northeast Plateau Air Basin

The Northeast Plateau Air Basin 

(Basin) is located in the remote 

northeast corner of California and 

comprises Lassen, Modoc, and 

Siskiyou counties. The northern 

part of the Basin has lofty volcanic 

peaks, such as Mount Shasta and 

Mount Lassen. To the south and 

west, forested mountains dominate 

the Basin. The Basin covers 

approximately 14,788 square miles 

and is bordered by the states of 

Oregon directly to the north and 

Nevada to the east. The Basin’s 

population of 92,112 (2010) 

predominately resides in rural 

towns, including Yreka, Mount 

Shasta, Alturas, and Susanville. 

Major highways are U.S. Highways 

5, 97, and 395. 
15 

____________________________________________________________________ 

 California Air Resources Board’s 2010 Monitoring Network Assessment Report 

While there are three monitoring sites in Siskiyou County, there are no 

monitoring sites in Lassen and Modoc counties. Lassen and Modoc counties 

have long attained the federal and State ozone standards. The City of Yreka, 

located in Siskiyou County, is the largest populated area in the Basin and 

represents an area of expected high concentrations within the Basin. For this 

reason, ARB believes that Siskiyou County adequately represents the entire 

Basin. This section describes the monitoring objectives for the ozone, PM10, 

and PM2.5 monitors in Siskiyou County. 

There is only one ozone monitor located at Yreka in Siskiyou County. Siskiyou 

County is currently designated nonattainment-transitional for the State ozone 

standard. Siskiyou County has made dramatic progress towards attainment of 

the State ozone standard. In 2009, no days exceeded either the federal or State 

8-hour ozone standard at the site. However, the 2009 federal 8-hour ozone 

design value of 0.061 ppm is within the range proposed by U.S EPA for the 

revised 8-hour federal ozone standard. This site is needed for determining 

compliance with State and federal ozone standards. For this reason, continued 

ozone monitoring at the Yreka site is needed. 

There are three PM10 monitoring sites in Siskiyou County. While the Yreka and 

Mount Shasta sites are operated by the District, the Lava Beds National 

Monument site is operated by the National Park Service. The area had attained 

the federal 24-hour PM10 standard, however, PM10 concentrations in the last 

three years exceeded the State 24-hour PM10 standard. Continued PM10 

monitoring is needed for State designation purposes. 

In 2007, the PM2.5 monitor at the Yreka site was inoperable and no data were 

reported in that year. The PM2.5 monitor was reestablished at the site in 2008 

and two years of PM2.5 data were reported into AQS. While PM2.5 

concentrations in the area are below both federal and State PM2.5 standards, 

continued monitoring of the PM2.5 monitor is needed to have more complete 

data for designation purposes. Because the majority of sites in Siskiyou County 

are located where the highest concentrations are expected to occur and there 

are no minimum federal requirements, no additional monitoring is needed and no 

changes are being proposed to the monitoring listed below. 

O3 CO NO2 PM2.5 PM10 cont. PM2.5 cont. PM10

Lave Beds 

(060930005) Hconc

Mount Shasta 

(060930004) Rconc

Yreka 

(060932001)

Hconc, 

Trans, 

StateD

Hconc Hconc

Northeast Plateau Air Basin: Siskiyou County
16 

____________________________________________________________________ 

 California Air Resources Board’s 2010 Monitoring Network Assessment Report 

Sacramento Valley Air Basin

The Sacramento Valley Air Basin (Basin) comprises the Sacramento urban area 

in the south and stretches northward for more than 150 miles. The Basin 

includes nine complete counties—Butte, Colusa, Glenn, Sacramento, Shasta, 

Sutter, Tehama, Yolo, and Yuba—and portions of two others—Solano and 

Placer. The Basin is a valley, ringed on three sides by significant mountain 

ranges—the California Coastal Range to 

the west, the Sierra Nevada Mountains to 

the east, and the Cascade Range to the 

north. 

The Basin is home to more than 2.5 million 

people, the majority of whom live in the 

Sacramento Metro ozone nonattainment 

area portion of the Basin. The rest are 

scattered among smaller cities to the north 

(Yuba City, Marysville, Chico, and Redding) 

as well as smaller towns and communities. 

There are multiple air quality concerns in 

this region. Butte, Sacramento, Yolo and 

the portions of Placer and Solano counties 

located in the Basin are currently 

designated nonattainment for federal and State ozone standards. Most of the 

other counties have federal 8-hour ozone design values within the range 

proposed for the revised 8-hour federal ozone standard and violated the State 

ozone standard. While most of the counties (excluding Butte and Sacramento) 

either had attained or are unclassifiable for the State PM2.5 standard, several 

areas in the Basin are nonattainment for the federal PM2.5 standard. All 

counties in the Basin are designated nonattainment for the State PM10 standard. 

 

The Basin includes five MSAs: Chico, Redding, Sacramento-Arden-ArcadeRoseville, Vallejo-Fairfield, and Yuba City. No other counties in the Basin are 

part of an MSA. There are a variety of monitoring objectives in the Basin. These 

objectives include collecting data at expected high concentration sites, providing 

data for agriculture burn decisions, evaluation of ozone transport and for 

educating the public about air quality. Some sites also collect representative and 

background concentration data. All of the monitors in the Basin provide data to 

implement a variety of federal and State programs. We did not identify any new 

or unmet monitoring needs. 

No additional monitoring is required in the MSA or in any part of the Basin and no 

changes to the monitoring network in the Basin are being considered at this time. 

Specific monitors and monitoring objectives are described below. The 

Sacramento Metropolitan Air Quality Management District is conducting their own 
17 

____________________________________________________________________ 

 California Air Resources Board’s 2010 Monitoring Network Assessment Report 

assessment; therefore, monitors located in Sacramento County are not 

discussed in this report. 

Shasta County 

Shasta County has a mix of ozone and PM2.5 and PM10 monitors, most of which 

are intended to measure potential high pollutant values. Shasta County is 

designated as nonattainment for the State ozone standard as well as the State 

PM10 standard. Shasta County currently is designated attainment for the State 

PM2.5 standard. However, the continuous PM2.5 monitor is needed for 

agricultural burn forecasting and general purposes.

Shasta County had a 2009 federal 8-hour ozone design value of 0.76 ppm and 

exceeded federal and State ozone standards more than five days in 2009. The 

Anderson and Redding sites are critical for determining compliance with State 

and federal ozone standards. The Lassen site is operated by the National Park 

Service and provides useful data for evaluating transport and background ozone 

concentrations. 

O3 CO NO2 PM2.5 PM10 cont. PM2.5 cont. PM10

Anderson 

(060890007)

Hconc, 

StateD Hconc StateD, Gnrl

Lassen 

Volcanic NP 

(060893003)

Rconc

Redding 

(060890004)

Hconc, 

StateD Hconc Hconc

Shasta Lake 

(060890008) Rconc

Sacramento Valley Air Basin: Shasta County

Colusa, Glenn and Tehama counties

These counties have a mix of particulate matter and ozone monitors, most are 

designed to monitor potential high concentrations. However, the Colusa and 

Willows’ continuous PM2.5 monitors help inform agricultural burning decisions, 

which are important considering that this area has a significant amount of 

agricultural land. None of these counties are currently designated nonattainment 

for the federal ozone or PM2.5 standards. The area’s 2009 federal 8-hour ozone 

design values range from 0.062 ppm to 0.082 ppm, which is within the range 

proposed by U.S. EPA for the revised 8-hour federal ozone standard. Moreover, 

this area is currently nonattainment for the State 24-hour PM10 standard. 

Continued ozone and PM monitoring is needed for determining compliance with 

State and federal standards, as well as agriculture burn forecasting. 
18 

____________________________________________________________________ 

 California Air Resources Board’s 2010 Monitoring Network Assessment Report 

Ozone CO NO2 PM2.5 PM10 cont. 

PM2.5

cont. 

PM10

Colusa 

(060111002)

Rconc, 

StateD Hconc Hconc StateD, AgBn

Red BluffMesser Drive 

(061030002)

Hconc

Red Bluff-Oak 

Street 

(061030005)

Hconc, 

StateD

Tuscan Butte 

(061030004)

Hconc, 

Trans, 

StateD

Willows 

(060210003)

Hconc, 

StateD Hconc StateD, AgBn

Sacramento Valley Air Basin: Colusa, Glenn and Tehama Counties

Butte County

Butte County is currently designated nonattainment for the federal 1997 ozone 

standard and a portion of Butte County is nonattainment for the federal 2006 

24-hour PM2.5 standard. The county had a 2009 federal 24-hour PM2.5 design 

value of 59 ug/m3. The Paradise-Airport site is the ozone design site with a 2009 

federal 8-hour design value of 0.082 ppm. With air quality challenges for both 

pollutants, multi-pollutant monitoring is needed at the Chico site. PM2.5 monitors 

at the Gridley and Paradise – Fire Station sites also help inform agricultural 

burning decisions, which is important in this region, as well as characterizing 

impacts from residential wood burning. Butte County is currently nonattainment 

for the State 24-hour PM10 standard. Continued monitoring in Butte County is 

needed. 

O3 CO NO2 PM2.5 PM10 cont. PM2.5 cont. PM10

Chico 

(060070002) Hconc Rconc Rconc Hconc Hconc StateD, Gnrl

Gridley 

(060007004)

StateD, 

AgBn

ParadiseAirport 

(060074001)

Hconc

Paradise-Fire 

Station 

(060072001)

StateD, 

AgBn

Sacramento Valley Air Basin: Butte County

Sutter and Yuba counties

Both counties are designated nonattainment for the State ozone standard. In 

addition, a portion of Sutter County is part of the Sacramento federal ozone 

nonattainment area. Sutter County had a 2009 8-hour ozone design value of 

0.079 ppm, which is above the federal 8-hour ozone standard. In addition, 

portions of Sutter and Yuba counties comprise their own nonattainment area for 

the federal 24-hour PM2.5 standard. While this area currently meets this 

standard, PM2.5 monitoring is needed to demonstrate continued attainment. 

Both ozone and particulate matter monitoring in this area is very important. 
19 

____________________________________________________________________ 

 California Air Resources Board’s 2010 Monitoring Network Assessment Report 

Yuba City, located in Sutter County, and Marysville, located in Yuba County, are 

adjacent to one another, form one combined metropolitan statistical area, and 

function more like one city than two. Consequently, although there is no monitor 

physically in Yuba County, the Yuba City site in Sutter County is considered 

representative of both Yuba City and Marysville, and therefore functions to 

represent Yuba County, as well. The Sutter Buttes site was established to 

characterize ozone transport aloft in the Sacramento Valley. This area is 

currently nonattainment for the State 24-hour PM10 standard. Continued 

monitoring at the Sutter Buttes and Yuba City sites is needed. 

Ozone CO NO2 PM2.5 PM10 cont. 

PM2.5

cont. 

PM10

Sutter Buttes 

(061010004)

Hconc, 

Trans

Yuba City 

(061010003)

Hconc, 

StateD Rconc Hconc Hconc StateD, AgBn

Sacramento Valley Air Basin: Sutter and Yuba Counties

Yolo County and portions of Placer and Solano counties 

All of these counties are nonattainment for the federal and State ozone 

standards. Solano and Yolo counties have monitors with 2009 federal 8-hour 

ozone design values exceeding 0.070 ppm. In addition, Yolo County and the 

Sacramento Valley portions of Placer and Solano counties are all part of the 

Sacramento federal ozone nonattainment area. Additionally, portions of Yolo 

and Solano counties and the Sacramento Valley portion of Placer are part of the 

Sacramento nonattainment area for the State 24-hour PM2.5 and PM10 

standards. With multiple air quality challenges, a comprehensive monitoring 

strategy is important for these areas. Consequently, four out of the seven 

monitor sites in this area monitor for two or more pollutants. As standards tighten 

and become more stringent, continued monitoring in these counties becomes 

even more important. Moreover, with agricultural lands being the predominate 

land use in and around these counties, monitoring PM2.5 for purposes of 

agricultural burning forecasts is also important. 
20 

____________________________________________________________________ 

 California Air Resources Board’s 2010 Monitoring Network Assessment Report 

O3 CO NO2 PM2.5 PM10 cont. PM2.5 cont. PM10

Auburn 

(060610002) Hconc

Davis-UCD 

Campus 

(061130004)

Hconc Rconc Rconc StateD, 

AgBn

Roseville 

(060610006) Hconc Rconc Rconc Hconc StateD, 

AgBn

West 

Sacramento 

(061132001)

Hconc

Woodland 

(061131003)

Hconc, 

StateD Hconc Hconc StateD, AgBn

VacavilleMerchant 

(060953001)

Rconc

VacavilleUlatis 

(060953003)

Hconc, 

Trans, 

StateD

StateD, 

Gnrl

Sacramento Valley Air Basin: Yolo County, part of Placer County, and 

northern and eastern parts of Solano County

Summary 

California has one of the most extensive monitoring networks in the nation. Such 

a network is needed due to our severe air quality issues, large population and 

vehicle miles traveled, varied topography and a large number of separate 

airsheds. There are more than 250 monitoring locations in California where the 

ambient air quality is routinely measured for gaseous and particulate air 

pollutants. The measured data form a backbone for air quality management 

programs, provide the public with information on the status of air quality and 

progress in improving air quality, and are used by health researchers, business 

interests, environmental groups, and others. As a result of this assessment, all 

existing monitors covered in this report are critical and none is proposed to be 

discontinued or relocated. Moreover, this assessment demonstrates that the 

monitors and sites within this report meet the monitoring objective requirements 

of Appendix D in 40 CFR 58, which is to provide air pollution data to the general 

public in a timely manner and to support compliance with ambient air quality 

standards and air pollution research studies. 
21 

____________________________________________________________________ 

 California Air Resources Board’s 2010 Monitoring Network Assessment Report 

(This page intentionally left blank) 
22 

____________________________________________________________________ 

 California Air Resources Board’s 2010 Monitoring Network Assessment Report 

This appendix provides a summary of the required and existing monitoring sites 

within the geographical scope of this report. 

APPENDIX A 

Required Existing Required Existing Required Existing Required Existing Required Existing

FRM FRM Continuous Continuous FRM FRM Continuous Continuous

67,530 0 1 0 1 0 0 0 1 0 0

58,121 0 1 0 0 0 0 0 0 0 1

2 16 3 5 2 6 4 9 0 3

147,758 0 1 0 2 0 0 0 3 0 0

2 9 2 5 1 3 2 6 0 1

472,991 0 11 0 5 0 6 0 3 0 0

2 16 3 5 2 6 4 9 0 3

333,829 0 2 0 0 0 2 0 3 0 1

1 2 0 1 0 0 0 3 0 0

92,112 0 1 0 1 0 0 0 3 0 0

2,817,815 0 16 0 6 0 11 0 13 0 0

1 2 1 1 1 3 0 1 0 0

1 3 0 1 0 0 0 3 0 0

2 16 3 5 2 6 4 9 0 3

2 4 1 1 1 2 0 2 0 0

1 2 1 1 1 1 0 1 0 0

1

 Federal minimum monitoring requirements for an area is by Metropolitan Statiscal Area (MSA). However,

for the purpose of this assessment, we are listing the number of required and existing monitoring sites

by the geographical areas that are covered in this report. Note that there are more monitoring sites in the 

geographical scope of this report than required by federal regulations. New federal monitoring requirements

for NO2 and SO2 will be discussed in future annual monitoring network plans. There are no federal 

requirements for CO and lead monitoring within the geographical scope of this report.

* Parts of these MSAs are included in the geographical scope of this report, and parts are within the 

geographical scope of the reports being completed by the districts. The numbers of sites listed are for the 

entire MSA.

Sacramento Valley Air Basin 

(minus Sacramento Metro 

AQMD)

Redding MSA

Lake County Air Basin

Sacramento-Arden-ArcadeRoseville MSA*

Bakersfield MSA*

Sacramento-Arden-ArcadeRoseville MSA*

Yuba City MSA

Lake Tahoe Air Basin 

(portions of El Dorado and 

Placer counties)

Eastern Kern Air Pollution 

Control District ( a portion of 

Mojave Desert Air Basin)

Mountain Counties Air Basin

Mendocino County and 

Northern Sonoma Air Quality 

Management Districts 

Vallejo-Fairfield MSA*

Chico MSA

Sacramento-Arden-ArcadeRoseville MSA*

Northeast Plateau Air Basin

Santa Rosa-Petaluma MSA*

Numbers of Required and Existing Sites in the Geographical Areas of this Report1

Geographical Area/MSA Pop.

Ozone PM2.5 PM10