2010 Air Monitoring Network Report

July 1, 2011

Kurt Malone

Michael Basso

Ken Crysler

and

Mark Stoelting

Technical Services Division
2

Table of Contents

Page

List of Figures........................................................................................................................... 4

List of Tables ............................................................................................................................ 4

Definition of Terms................................................................................................................... 5

Overview of Network Operation .............................................................................................. 7

Network Design .................................................................................................................. 7

Minimum Monitoring Requirements for SLAMS Sites................................................... 13

Modifications Made to Network in 2010.......................................................................... 19

Proposed Modifications to Network in 2011-2012........................................................... 21

Removing a NAAQS Compliance Monitor...................................................................... 24

Data Submission Requirement.......................................................................................... 24

Site Information Definitions................................................................................................... 25

Detailed Site Information for SLAMS Stations...................................................................... 28

Bethel Island ..................................................................................................................... 29

Concord............................................................................................................................. 31

Fairfield............................................................................................................................. 34

Fremont............................................................................................................................. 36

Gilroy................................................................................................................................ 39

Hayward............................................................................................................................ 41

Livermore.......................................................................................................................... 43

Los Gatos.......................................................................................................................... 47

Martinez ............................................................................................................................ 49

Napa .................................................................................................................................. 51

Oakland............................................................................................................................. 54

Oakland West.................................................................................................................... 56

Point Reyes....................................................................................................................... 59

Point Richmond ................................................................................................................ 61

Redwood City ................................................................................................................... 63

Richmond 7th.................................................................................................................... 66

Rodeo................................................................................................................................ 68

San Francisco.................................................................................................................... 70

San Jose............................................................................................................................. 73

San Martin......................................................................................................................... 77

San Pablo .......................................................................................................................... 79

San Rafael......................................................................................................................... 81

Santa Rosa......................................................................................................................... 83

Vallejo............................................................................................................................... 85

Detailed Site Information for SPM Stations........................................................................... 89

Berkeley............................................................................................................................ 90

Crockett............................................................................................................................. 94

Cupertino .......................................................................................................................... 96

Cupertino Monte Vista Park ............................................................................................. 98

Fort Cronkhite................................................................................................................. 102
3

Special Monitoring Programs Conducted in 2010................................................................ 104

EPA School Air Toxics Monitoring Program................................................................. 105

Meteorology Program..................................................................................................... 107

National Air Toxics Trends Station (NATTS) at San Jose............................................. 110

NCore Program............................................................................................................... 113

Photochemical Assessment Monitoring Stations (PAMS)............................................. 117

PM2.5 Speciation Sampling Programs............................................................................. 120

Toxics Program............................................................................................................... 122

West Oakland CASS Study ............................................................................................ 128

West Oakland Measurement Study................................................................................. 131
4

List of Figures

Figure Page

1. Map of Air District SLAMS and SPM Sites for 2010.......................................................12

2. Map of Stevens Creek Elementary School in Cupertino .................................................106

3. Map of Air District Meteorological Monitoring Sites for 2010 ......................................109

4. Map showing area of Neighborhood Scale at the San Jose NCore station......................114

5. Map of the three PAMS sites in the Livermore Valley ...................................................118

6. Map of Air District Toxics Monitoring Sites for 2010....................................................123

7. Map of CASS Site with Monitoring Locations and Meteorological Station ...................129

8. West Oakland Measurement Study Sampling Locations.................................................132

List of Tables

Table Page

1. SLAMS Monitoring Objectives and Appropriate Spatial Scales ........................................9

2. List of Monitoring Stations within the Air District for 2010.............................................10

3. Minimum Monitoring Requirements for Ozone SLAMS Sites.........................................13

4. Minimum Monitoring Requirements for PM2.5 SLAMS Sites..........................................14

5. Minimum Monitoring Requirements for PM10 SLAMS Sites...........................................15

6. Minimum Monitoring Requirements for SO2 SLAMS Sites in 2013................................16

7. Minimum Monitoring Requirements for NO2 SLAMS Sites in 2013 ...............................17

8. Monitor Information and EPA Air Monitoring Siting Criteria..........................................25

9. National Ambient Air Quality Standards (as of December 31, 2010)...............................27

10. List of the 15 NATTS HAPs Monitored by the Air District............................................110

11. List of 22 NATTS PAH Compounds Measured by the Air District................................112

12. NCore Monitors...............................................................................................................116

13. List of speciated hydrocarbons measured by Gas Chromatograph..................................119

14. PM2.5 Speciation Measurements at Air District Sites......................................................121

15. List of Toxic Compounds Measured by the Air District in 2010 ....................................125

16. Metals Measured at Berkeley using ICP-MS...................................................................125

17. Metals measured at Cupertino using XRF.......................................................................126

18. Elements Measured for the West Oakland CASS Study .................................................129
5

Definition of Terms

ADT ............. Average Daily Traffic

AGL ............. Above Ground Level

AQS ............. Air Quality System; the EPA national air quality database

Air District ...... Bay Area Air Quality Management District (BAAQMD)

BAM ............ Beta Attenuation Monitor, a type of continuous PM2.5 monitor

CARB ............ California Air Resources Board

CFR ............. Code of Federal Regulations

CO ............... Carbon Monoxide

CH4 ............. Methane

DL ............... (Tree) Drip Line

EPA ............. U. S. Environmental Protection Agency

FEM ............. Federal Equivalent Method

FRM ............. Federal Reference Method

GC ............. Gas Chromatograph

GIS ............... Geographic Information System

HC ............... Hydrocarbons, including CH4 and NMHC

HiVol ............ High Volume

H2S ................ Hydrogen Sulfide

ICPMS ............Inductively Coupled Plasma Mass Spectrometry

Maintenance Plan.. A Plan submitted by states to EPA that outlines how the NAAQS will be 

maintained for a particular region. 

MSA ............. Metropolitan Statistical Area

NAAQS ......... National Ambient Air Quality Standards

NATTS ........... National Air Toxics Trends Stations

NCore ............ National Core (Monitoring Program)

NMHC ........... Non-methane Hydrocarbons

NO ................. Nitric Oxide

NO2 ............... Nitrogen Dioxide

NOx ............... Oxides of Nitrogen

NOy ............... Total Reactive Nitrogen

O3 .................. Ozone

PAMS ............. Photochemical Assessment Monitoring Stations

PPB ................ Parts per billion

PM ................ Particulate Matter

PM2.5............... Particulates less than or equal to in size 

PM2.5F ............ PM2.5 measured using a filter-based monitor

PM2.5C ............ PM2.5 measured using a continuous monitor

PM10 ............... Particulates less than or equal to 10 microns in size

PM10C ............. PM10 measured using a continuous monitor

PM10-2.5 ........... PM Coarse. PM less than or equal to 10 microns and greater than 2.5 

microns in size 

SATMP ........... School Air Toxics Monitoring Program
6

Definition of Terms (continued)

SIP ................ State Implementation Plan – A Plan submitted by states to EPA that 

outlines how the NAAQS will be met for a particular region. 

SLAMS .......... State or Local Air Monitoring Station

SO2 ................. Sulfur Dioxide

SPM ............... Special Purpose Monitor

STN ............... Speciation Trends Network

TAMS............. Total Atmospheric Mercury

VOC ............... Volatile Organic Compound
7

Overview of Network Operation

Network Design

The Bay Area Air Quality Management District (Air District) is the public agency 

responsible for air quality management in the nine Bay Area counties: Alameda, Contra 

Costa, Marin, Napa, San Francisco, San Mateo, Santa Clara, southwestern Solano, and 

southern Sonoma. The Air District operates air monitoring stations in each of these nine 

counties. The Air District began measuring air quality in the San Francisco Bay Area in 

1957. In 2010 there were 29 air monitoring stations in the Air District air monitoring 

network including one station operated by the California Air Resources Board.

Twenty-four of the 29 stations are classified by EPA as State and Local Air Monitoring 

Stations (SLAMS) that are permanently sited and meet all EPA monitor siting criteria. The 

remaining five are classified as Special Purpose Monitoring (SPM) stations that do not meet 

EPA siting criteria (Crockett), measure a pollutant for which there are no siting criteria (Fort 

Cronkhite), or are short-term monitoring sites (Berkeley and Cupertino/Cupertino MV).

Short-term monitoring sites are re-locatable trailers and shelters with a comprehensive set of 

air quality instruments to characterize local air quality. Instruments at these sites are 

operated on SLAMS sampling schedules for a minimum of one year allowing data

comparison with permanent monitoring sites. Statistical data relationships between shortterm and nearby permanent sites provides long-term estimates of air quality at temporary 

monitoring sites.

The Air District also performs air monitoring as part of other programs. These include 

programs that the Air District has initiated, such as meteorological monitoring, the ambient 

toxics program, and the West Oakland studies; or programs required by EPA. EPA programs 

currently include the Cupertino School Air Toxics Monitoring Program, the National Air 

Toxics Trends Stations (NATTS) Program, the National Core (NCore) Program, the 

Photochemical Assessment Monitoring Stations (PAMS) Program, and the PM2.5 Speciation 

Trends Network (STN) Program. Summaries of these programs can be found later in this 

report.

The San Francisco Bay Area contains over 100 cities. Although resources do not allow 

placement of air pollution monitors in every city, it can be demonstrated that air pollution 

levels, in the absence of significant local sources, are similar within each geographical region 

of the Bay Area. That is, cities within each of the major valleys of the Bay Area can have 

similar air quality levels. Consequently, a few sites can characterize an area. Generally, 

locations for permanent air monitoring sites are initially based on knowledge of population 

density and local wind patterns, while the final site selection is determined after analyzing 

preliminary air quality measurements collected from field studies, temporary monitoring 

studies, and mobile monitoring data. 
8

The purpose of the Air District monitoring network is:

 To provide air pollution data to the general public in a timely manner.

 To support compliance with California and national ambient air quality standards. 

When sites do not meet the standards, attainment plans are developed to attain the 

standards.

 To support air pollution research studies.

To meet its monitoring objectives the Air District monitoring network collects ambient air 

data at locations with a variety of monitoring site types. These site types, as defined in 40 

CFR Part 58, Appendix D, Table D-1, are intended to characterize air pollution levels in 

areas of high pollution, high population, transported air pollution, and air pollution near 

specific sources. 

Ambient air monitoring at Air District stations is intended to meet one or more of the 

following monitoring objectives: 

 A determination of typical concentrations in areas of high population density.

 A determination of the highest concentrations expected to occur in the area covered 

by the network.

 A determination of impacts from significant sources.

 A determination of general background concentration levels.

 A determination of the extent of regional pollutant transport. 

UPopulation Oriented

The primary purpose of air quality standards is to protect the public health. Air monitoring 

stations are placed in areas with high population density to evaluate exposure to air pollution. 

In most cases, stations are located within the largest cities in each county. Because people 

spend more time at home than at work, air monitoring sites are generally located in 

residential areas rather than at downtown locations. To be consistent with EPA’s list of Site 

Types in Table D-1 of 40 CFR Part 58, the term “population orientated” will be used in place 

of “typical concentrations in areas of high population density”, for clarity in this monitoring 

objective.

UHighest Concentration

EPA regulations require that air quality in areas where the public has access be reduced to 

levels below the national ambient air standards. Consequently, monitoring must also be done 

at locations expected to have the highest concentrations, even if populations are sparse in that 

area. High concentrations may be found close to major sources, or further downwind if 

pollutants are emitted from tall stacks. High concentrations may also be found at distant 

downwind locations when the pollutants such as ozone or secondary particulate matter are a 

result of chemical reactions in the atmosphere.

USource Impact

There are five refineries within the Air District: Chevron, Shell, Tesoro, ConocoPhillips, and 

Valero. Because these sources have the potential to emit significant amounts of SO2 and 
9

H2S, the Air District operates SO2 and H2S monitoring stations near these sources. When the 

monitors downwind of the source show concentrations above the applicable standards or 

exceed concentrations listed in Air District Regulation 9, Rules 1 and 2, a notice of violation 

may be issued to the source. The Port of Oakland also can be a significant source of 

particulates, CO, and toxics and the Oakland West air monitoring station is located 

downwind of the Port to measure pollution impacts on West Oakland.

UGeneral Background

The Air District operates stations in areas that have no significant emissions from mobile, 

area, or industrial sources. At these sites, the measured concentrations reflect the transported 

air quality levels from upwind areas. When designing control strategies to reduce pollution 

levels, it is important to know if areas outside the boundaries of the Air District are 

contributing to high pollutant levels within the Air District. Where there are no significant 

emission sources upwind of a site, then the site is considered to be a general background site.

URegional Transport

The Air District shares a common boundary with six other air districts: Monterey Bay 

Unified APCD, San Joaquin Valley APCD, Sacramento Metropolitan AQMD, Yolo-Solano 

AQMD, Lake County AQMD, and Northern Sonoma County APCD. When upwind areas 

have significant air pollution sources, pollutants may be transported into the Bay Area Air 

District and result in overall higher air pollution levels in the Bay Area. The Air District 

operates monitoring stations near the borders of the Air District to measure the air pollution 

concentrations transported into and out of the Bay Area Air District.

 

Each monitoring objective is associated with a spatial scale for each site. For example, a 

regional transport site is meant to represent air quality levels over a large area, while a 

highest concentration site may represent a spatial scale of no more than a few blocks or so, in 

size. Spatial scales are defined in 40 CFR, Part 58, Appendix D. They are: micro scale –

having dimensions of several meters up to 100 meters; middle scale – having dimensions of 

100 meters to 0.5 km; neighborhood scale – having dimensions of 0.5 km to 4.0 km; urban 

scale – having dimensions of 4 to 50 km; and regional scale – having dimensions of up to 

hundreds of km. Table 1 lists the appropriate scales for each monitoring objective. 

Table 1. SLAMS Monitoring Objectives and Appropriate Spatial Scales.

Monitoring Objective Appropriate Spatial Scale

1. Highest Concentration Micro, middle, neighborhood

2. Population Oriented Neighborhood, urban

3. Source Impact Micro, middle, neighborhood

4. General Background Urban, regional

5. Regional Transport Urban, regional

The desired spatial scale of a monitoring site must conform to established criteria for the 

distance from roadways, based on traffic volumes. There are different distance requirements 
10

for each pollutant, which can be found in 40 CFR Part 58, Appendix E. Additionally, the 

spatial scale can also be affected if trees or obstructions are too close to the monitoring 

probe. The goal in siting monitoring stations is to match the spatial scale with the desired 

monitoring objective. Table 2 lists the stations, their monitoring objectives, and the 

pollutants measured at each site.

Table 2. List of Monitoring Stations within the Air District for 2010.

Site Station Name Type1 Monitoring Objective Pollutants Monitored1

1 Bethel Island SLAMS Regional Transport& 

Highest Concentration

O3, NOx, SO2, CO, PM10, Toxics

2 Concord SLAMS Population Oriented, 

Highest Concentration

O3, NOx, SO2, CO, HC, PM10, 

PM2.5F, Toxics

3 Fairfield SLAMS Population Oriented & 

Regional Transport

O3

4 Fremont SLAMS Population Oriented O3, NOx, CO, HC, PM2.5C, 

Toxics

5 Gilroy SLAMS Population Oriented, 

Highest Concentration, 

& Regional Transport

O3, PM2.5C

6 Hayward SLAMS Population Oriented & 

Regional Transport

O3

7 Livermore SLAMS Population Oriented & 

Highest Concentration

O3, NOx, HC, PM2.5F, PM2.5C, 

Speciated PM2.5, Toxics

8 Los Gatos SLAMS Population Oriented & 

Highest Concentration

O3

9 Martinez SLAMS Source Impact SO2, Toxics

10 Napa SLAMS Population Oriented O3, NOx, CO, PM10, PM2.5C, 

Toxics

11 Oakland SLAMS Population Oriented O3, NOx, CO,, PM2.5C, Toxics

12 Oakland West SLAMS Population Oriented &

Source Impact

O3, NOx, SO2, CO, PM2.5C,

Speciated PM2.5, Toxics

13 Point Reyes2 SLAMS General Background PM2.5C

14 Point Richmond SLAMS Source Impact H2S

15 Redwood City SLAMS Population Oriented O3, NOx, CO, PM2.5F, PM2.5C, 

Toxics

16 Richmond 7th SLAMS Source Impact SO2, H2S, Toxics

17 Rodeo SLAMS Source Impact H2S

18 San Francisco SLAMS Population Oriented O3, NOx, CO, HC, PM10, PM2.5C, 

Toxics

19 San Jose SLAMS Population Oriented & 

Highest Concentration

O3, NOx, SO2, CO, HC, PM10,

PM2.5F, PM2.5C, Speciated PM2.5, 

Toxics

20 San Martin SLAMS Highest Concentration O3

21 San Pablo SLAMS Population Oriented O3, NOx, SO2, CO, PM10, Toxics
11

Site Station Name Type1 Monitoring Objective Pollutants Monitored1

22 San Rafael SLAMS Population Oriented O3, NOx, CO, PM10, PM2.5C, 

Toxics

23 Santa Rosa SLAMS Population Oriented O3, NOx, CO, PM2.5C, Toxics

24 Vallejo SLAMS Population Oriented O3, NOx, SO2, CO, PM2.5F, 

PM2.5C, Speciated PM2.5, Toxics

25 Berkeley SPM Population Oriented 

& Source Impact

O3, NOx, SO2, CO, HC, PM10, 

PM2.5C, Toxics

26 Crockett SPM Source Impact SO2, Toxics

27 Cupertino SPM Population Oriented &

Source Impact

PM10C

28 Cupertino

Monte Vista Park

SPM Population Oriented & 

Source Impact

O3, NOx, SO2, CO, PM10, PM2.5C, 

Toxics, TAMS

29 Fort Cronkhite SPM General Background Toxics

1

 See page 5 for acronym definitions.

2

 Operated by the California Air Resources Board.

EPA suggests that the appropriate spatial scale for population oriented sites should be 

neighborhood or urban. Using the current EPA methodology to determine spatial scales, the 

air monitoring sites in Napa, Oakland, San Pablo and San Rafael would be characterized as 

middle scale. However, the Air District believes the spatial scale of the site would be better 

characterized as neighborhood scale. This is because EPA’s distance requirements from 

roads are based on 1979 vehicle emission levels. Current fleet average vehicle emission 

factors in the Bay Area are 95% lower for hydrocarbons, 95% lower for CO, 82% lower for 

NOx, and 48% lower for PM10 in 2009 compared to 1979.

Figure 1 is a map of the 2010 Air District SLAMS and SPM monitoring sites. Tables 3

through 7 lists the minimum number of monitors required within the network for each 

pollutant. The section following Table 7 describes recent changes to the monitoring network

and proposed changes to the monitoring network.

The final section provides detailed descriptions of the monitoring objectives for each air 

monitoring site and a brief explanation for choosing the type of monitor at each site.
12

Figure 1. Map of Air District SLAMS and SPM Sites for 2010.
13

Minimum Monitoring Requirements for SLAMS Sites

Minimum Monitoring Requirements for Ozone

The number of required ozone monitors for each MSA in the Bay Area is determined by its 

population and design value, as specified in Table D-2 of 40 CFR Part 58, Appendix D –

SLAMS Minimum O3 Monitoring Requirements. Ozone design values are a calculated 

concentration (see footnote a) which are used for comparison with the national standard to 

determine the attainment status of an area for that pollutant. Table 3 shows that the Air 

District monitoring network meets or exceeds the ozone minimum monitoring requirements. 

No additional monitors have been required in the State Implementation Plan (SIP) or 

Maintenance Plan for ozone.

Table 3. Minimum Monitoring Requirements for Ozone SLAMS Sites.

MSA County

Population

(2010)

8-hour 

Design 

Valuea

(ppb)

2010

Number of 

Monitors 

Required

Number of 

Monitors 

Active

Additional 

Monitors 

Needed

San 

FranciscoOaklandFremont

SF, Marin,

Alameda,

San Mateo,

Contra 

Costa

4,335,391 80 3 8

c

0

San JoseSunnyvaleSanta ClaraSanta 

Clara,

San Benito

1,836,911 75 2 5 0

Santa RosaPetaluma Sonoma 483,878 54 1 2 0

VallejoFairfield Solano 413,344 71b

2 3 0

Napa Napa 136,484 66 1 1 0

a Design values are calculated at each monitoring site by taking the 3-year mean (2008-2010) of the 4th highest 8-hour 

concentration. The design values shown for each MSA in this table are the highest design value of monitors in the MSA. 

Design values at or below the 0.075 ppm National Ambient Air Quality 8-hour Ozone Standard meet the standard. 

b The highest 8-hour design value is from Vacaville which is operated by Yolo-Solano APCD. The highest design value 

within the BAAQMD in this MSA is 69 ppb at Fairfield. 

c

 The Fremont station was closed on 10/31/10 and is not included in this total.

Minimum Monitoring Requirements for PM2.5

The number of required PM2.5 monitors for each MSA in the Bay Area is determined by its 

population and design value, as specified in Table D-5 of Appendix D to 40 CFR Part 58 –

PM2.5 Minimum Monitoring Requirements. PM2.5 design values are a calculated 

concentration (see footnotes aand b) which are used for comparison with the national 

standard to determine the attainment status of an area for that pollutant. Table 4 shows that 
14

the Air District monitoring network meets or exceeds the PM2.5 minimum monitoring 

requirements.

EPA designated the Bay Area as nonattainment of the PM2.5 standard on October 8, 2009. 

The effective date of the designation is December 14, 2009 and the Air District has three 

years to develop a State Implementation Plan (SIP) to demonstrate the Bay Area will achieve 

the revised standard by December 14, 2014. The SIP for the PM2.5 standard must be 

submitted to EPA by December 14, 2012. 

Table 4. Minimum Monitoring Requirements for PM2.5 SLAMS Sites.

MSA County

Population

(2010)

Annual 

Design

Valuea

(μg/m3)

2010

Daily 

Design

Valueb

(μg/m3)

2010

Number 

of 

Monitors 

Required

Number 

of 

Monitors 

Active

Additional 

Monitors 

Needed

San 

FranciscoOaklandFremont

SF, San 

Mateo, 

Alameda, 

Marin, 

Contra 

Costa

4,335,391 9.1 30 3 6

d

0

San JoseSunnyvaleSanta 

Clara

Santa 

Clara, 

San 

Benito

1,836,911 10.2 30 3 3 0

Santa 

RosaPetalumaSonoma 483,878 8.0 26 1 1 0

VallejoFairfield Solano 413,344 9.1 31 1 1 0

Napa Napa 136,484 N/Ac N/Ac0 0 0

a Annual design values are calculated at each monitoring site by taking the 3-year mean (2008-2010) of the annual averages 

for each site. The design values shown for each MSA in this table are the highest design value of monitors in the MSA. 

Design values at or below the national PM2.5 annual standard of 15 μg/m3indicate the area meets the standard.

b Daily design values are calculated by taking the 3-year mean (2008-2010) of the 98th percentiles for each site. The design 

values shown for each MSA in this table are the highest design value of monitors in the MSA. Design values at or below 

the national PM2.5 24-hour standard of 35 μg/m3indicate the area meets the standard. 

c There are no FRM or FEM PM2.5 monitors in Napa County.

d

 The Fremont station was closed on 10/31/10 and is not included in this total.

Minimum Monitoring Requirements for PM10

The number of required PM10 monitors for each MSA in the Bay Area is determined by its 

population and design value, as specified in Table D-4 of Appendix D to 40 CFR Part 58 –

PM10 Minimum Monitoring Requirements. PM10 design values are a calculated 

concentration (see footnote a) which are used for comparison with the national standard to 

determine the attainment status of an area for that pollutant. Table 5 shows that the Air 
15

District monitoring network meets or exceeds the PM10 minimum monitoring requirements. 

No additional monitors are required for the State Implementation Plan (SIP) or Maintenance 

Plan because the Bay Area has never been designated as non-attainment for PM10, and no SIP 

or Maintenance Plans have been prepared for PM10.

Table 5. Minimum Monitoring Requirements for PM10 SLAMS Sites.

MSA County

Population

(2010)

Design

Valuea

2010

Number 

of 

Monitors 

Required

Number 

of 

Monitors 

Active

Additional 

Monitors 

Needed

San 

FranciscoOaklandFremont

SF, San 

Mateo, 

Alameda, 

Marin, 

Contra 

Costa

4,335,391 0 2 5 0

San JoseSunnyvaleSanta 

Clara

Santa 

Clara, 

San 

Benito

1,836,911 0 2 2 0

Santa 

RosaPetalumaSonoma 483,878 0 0 1 0

VallejoFairfield Solano 413,344 0 0 1 0

Napa Napa 136,484 0 0 1 0

a

For PM10, the design value is defined as the expected number of exceedances per year, which is calculated by 

averaging the number of exceedances for the past three years (2008-2010). Since there were no exceedances in 

the past three years, the PM10 design value is zero for all MSA’s within the Bay Area Air Quality Management 

District where PM10 is measured. The 24-hour standard (150 μg/m3) is attained when the design value is less than 

or equal to one.

Minimum Monitoring Requirements for SO2

In early 2010, 40 CFR Part 58, Appendix D, Section 4.4 stated that there are no minimum 

requirements for the number of SO2 monitoring sites. No additional monitors are required 

for SIP or Maintenance Plans, because the Air District has never been designated as nonattainment for SO2, and no SIP or maintenance plans have been prepared for SO2. At the end 

of 2010 the Air District operated nine permanent SO2 monitors in its network. 

On June 22, 2010 EPA revised the monitoring requirements for SO2 to include source impact 

monitoring near major SO2 sources. These changes took effect on August 23, 2010 and are 

reflected in Table 6 below.
16

Table 6. Minimum Monitoring Requirements for SO2 SLAMS Sites in 2013.

MSA County Population

(2010)

Daily 

Designa

Value 

(ppb)

2010

Number 

of 

Monitors 

Required

Number 

of 

Monitors 

Active

Additional 

Monitors 

Needed

San 

FranciscoOaklandFremont

SF, San 

Mateo, 

Alameda, 

Marin, 

Contra 

Costa

4,335,391 19 2 6 0

San JoseSunnyvale

-Santa 

Clara

Santa 

Clara, 

San 

Benito

1,836,911 N/Ab1 1 0

Santa 

RosaPetalumaSonoma 483,878 - 0 0 0

VallejoFairfield Solano 413,344 7 0 1 0

Napa Napa 136,484 - 0 0 0

a Daily design values are calculated at each monitoring site by taking the 3-year mean (2008-2010) of the 4th highest daily 

maximum 1-hour concentration. The design values shown for each MSA in this table are the highest design value of 

monitors in the MSA. Design values at or below the national SO2 1-hour standard of 75 ppb meet the standard.

b

Insufficient data available for Design Value calculations.

Minimum Monitoring Requirements for NO2

On February 25, 2010 EPA revised the minimum monitoring requirements for NO2 in 40 

CFR Part 58, Appendix D, Section 4.3. By January 1, 2013, the Air District must operate

NO2 monitors at population-oriented sites and at sites within 50 meters of major freeways. 

Based on Bay Area population and traffic counts, the Bay Area will need to operate at least 

two monitors sited to measure the area-wide NO2 concentrations, and at three sites near 

freeways. No additional monitors were required for the SIP or Maintenance Plans because 

the Air District had not been designated as non-attainment for NO2 and no SIP or 

maintenance plans were prepared for NO2.

In 2010, the Air District operated 16 NO2 monitors in the Bay Area (14 SLAMS sites plus 

two SPM sites) because NO2 is a criteria pollutant and because NO2 and NO are important 

precursors in ozone formation. NO and NO2 are formed from vehicle, power plant and other 

industrial emissions, and contribute to the formation of fine particulate pollution and smog. 

Table 7 shows the minimum NO2 monitoring requirements.
17

Table 7. Minimum Monitoring Requirements for NO2 SLAMS Sites in 2013.

MSA County

Population

Annual

Designa

Value

Daily 

Designb

Value

Number 

of Areawide 

Monitors 

Required

Number 

of Areawide 

Monitors

Active

Additional 

Areawide 

Monitors 

Needed

(2010) (ppb)

2010

(ppb)

2010

Number 

of 

Roadside 

Monitors 

Required

Number 

of 

Roadside 

Monitors 

Active

Additional 

Roadside

Monitors 

Needed

San 

FranciscoOaklandFremont

SF, San 

Mateo, 

Alameda, 

Marin, 

Contra 

Costa

4,335,391 16 62

1 8

c

0

2 0 2

San JoseSunnyvaleSanta 

Clara

Santa 

Clara, 

San 

Benito

1,836,911 14 52

1 1 0

1 0 1

Santa 

RosaPetalumaSonoma 483,878 8 37

0 1 0

0 0 0

VallejoFairfield Solano 413,344 9 41

0 1 0

0 0 0

Napa Napa 136,484 9 37

0 1 0

0 0 0

a Annual design values are determined for each monitoring site by calculating the arithmetic average of all of the reported 

1-hour values for the most current year. The design values shown for each MSA in this table are the highest design value 

of monitors in the MSA. Design values at or below the national NO2 annual standard of 53 ppb meet the standard.

b Daily design values are calculated at each monitoring site by taking the 3-year mean (2008-2010) of the 8th highest daily 

maximum 1-hour concentration. The design values shown for each MSA in this table are the highest design value of 

monitors in the MSA. Design values at or below the national NO2 1-hour standard of 100 ppb meet the standard.

c The Fremont station was closed on 10/31/10 and is not included in this total.

Minimum Monitoring Requirements for CO

40 CFR Part 58, Appendix D, Section 4.2 states that there are no minimum requirements for 

the number of CO monitoring sites. No additional monitors are required for SIP or 

Maintenance Plans. The Air District was re-designated attainment for the 8-hour average CO 

NAAQS in 1998. The Air District CO maintenance plan is contained within the California 

Air Resource Board document “2004 Revision to the California State Implementation Plan 
18

for Carbon Monoxide.” The maintenance plan does not specify the number of CO monitors 

needed. Generally, the Air District operates one CO monitor within each of the nine Bay 

Area counties plus additional CO monitors in large cities. Also, CO monitors provide 

additional calibration system quality control information at full stations. CO monitoring 

could take on future importance because EPA is expected to review the current CO NAAQS 

and may revise the NAAQS to be more stringent. The Air District currently operates 12 CO 

monitors in its SLAMs network.
19

Modifications Made to Network in 2010

This section discusses specific changes made to instrumentation at Air District air monitoring 

stations in 2010. A more complete discussion of all instrumentation operating at the air 

monitoring stations can be found later in this document.

Concord

The collocated PM2.5 sampler was changed from a 1-in-12 day schedule to a 1-in-6 day 

schedule in April 2010. Although a 1-in-12 schedule is all that is required by regulation, the 

Air District plans to continue operating this sampler on a 1-in-6 day schedule indefinitely. 

Collocated samples are taken to obtain an estimate of the precision of the sampling 

measurement by comparing collocated samples with the samples from the primary PM2.5

sampler. 

Cupertino Monte Vista

The Air District began a one year ambient air monitoring study in Cupertino in September 

2010. The air monitoring station is located in Monte Vista Park. Although the purpose of 

the study is primarily source-oriented exposure from the cement plant and the associated 

truck traffic, the Air District is also monitoring population exposure to criteria pollutants 

including ozone, NO2, SO2, CO, PM10, PM2.5, toxics, metals, and mercury. An Air District 

meteorological system is also located in the park. The station will operate for a minimum of 

one year, after which, data will be reviewed and a determination made on how long the 

project will continue.

Cupertino Prado Vista

The Air District began operating a particulate sampler at Cupertino in October 2008 to 

determine if emissions from the nearby Lehigh Cement Plant and its associated diesel truck 

traffic could be producing elevated particulate concentrations in nearby neighborhoods. 

Monitoring ended in July 2010 when roof construction began at the site which required 

removing the particulate sampler. Because a new Cupertino site was opening at Monte Vista 

Park in September 2010, the site at Prado Vista was not reopened after the roof construction 

was completed.

Fremont

With approval from EPA, the Air District closed this station on October 31, 2010. Air 

quality levels in Fremont were similar to nearby stations and exceedances of the NAAQS 

were rare. Toxics monitoring by CARB at Fremont ended on July 19, 2010.

Hayward

The ozone monitor did not operate during 2010 due to a lengthy and major construction 

project nearby which limited site access and posed a safety hazard to staff. The monitor 

resumed operations on April 1, 2011.

Livermore

A gas chromatograph (GC) was added to the Livermore station on August 1, 2010 as part of 

the Photochemical Assessment Monitoring Station (PAMS) program. The GC measures 55
20

ozone precursor compounds on an hourly averaged basis. A list of the 55 compounds and a 

description of the PAMS program can be found in the PAMS section of this document.

Oakland West

The Air District began monitoring for ozone on December 13, 2010 to obtain additional 

pollutant data downwind of the Port of Oakland. 

Photochemical Assessment Monitoring Stations (PAMS)

EPA is funding hourly VOC speciated hydrocarbon measurements at three sites in the Bay 

Area: Livermore, Patterson Pass, and San Ramon. The Air District is supplementing these 

measurements with NOx and meteorological measurements at the three sites. The Livermore 

site was fully operational on August 1, 2010. The hydrocarbon and NOx monitoring began

at Patterson Pass on March 1, 2011 but meteorological sensors will not be installed until the 

summer of 2011. The San Ramon site is expected to be operational by late summer 2011. A 

full description of the PAMS program can be found in the PAMS section of this document.

Redwood City

The collocated PM2.5 sampler was changed from a 1-in-12 day schedule to a 1-in-6 day 

schedule in April 2010. Although a 1-in-12 schedule is all that is required by regulation, the 

Air District plans to continue operating this sampler on a 1-in-6 day schedule indefinitely. 

Collocated samples are taken to obtain an estimate of the precision of the sampling 

measurement by comparing collocated samples with measurements from the primary FEMBAM instrument.

San Francisco

The Air District discontinued monitoring ozone precursors CH4/NMHC on September 30, 

2010. Monitoring of these non-criteria pollutants was discontinued to allow better utilization 

of Air District resources as monitoring for the PAMS program was brought online.

San Pablo

The San Pablo monitoring site was closed in March 2009 due to heavy damage from a fire in 

the building. The site was completely rebuilt with new state of the art monitoring equipment 

and reopened in May 2010.

San Jose 

On December 22, 2010, the Air District changed the PM10 filter-based monitor from a highvolume to a low-volume sampler. This was necessary because of NCore program 

requirements to report PM coarse (PM10-2.5) from low-flow PM10 and PM2.5 samplers. More 

information about the NCore program can be found in the NCore section of this document.

School Air Toxics Monitoring Program

The Air District operated a sampler and meteorological system at Stevens Creek Elementary 

School in Cupertino starting in June 2009. The program and the monitoring site were closed 

in August of 2010. During the project, samplers operated on 1-in-6 day schedule and were 

analyzed for hexavalent chromium. A description of this monitoring program can be found 

in the EPA School Air Toxics Monitoring Program section of this document.
21

Proposed Modifications to Network in 2011-2012

This section discusses proposed changes to be made to the instrumentation at Air District air 

monitoring stations in the next 18 months. A more complete discussion of instrumentation 

and programs operating at the air monitoring stations can be found later in this document.

Berkeley

The Air District began a three year ambient air monitoring study in Berkeley in December 

2007. The site was closed on December 31, 2010. The purpose of the study was to 

determine the pollution impacts to local residents from vehicular traffic and industry along 

the Highway 80 corridor. Although the purpose was primarily source-oriented exposure 

from the highway and local industry emissions, the Air District also monitored for population 

exposure to criteria pollutants including ozone, NO2, SO2, CO, PM10, and PM2.5. Gaseous 

toxic compounds and metals were sampled on a 1-in-6 day schedule. 

Concord

The Air District will discontinue monitoring ozone precursors CH4 and NMHC on May 31, 

2011. Monitoring of these non-criteria pollutants is being discontinued to allow better 

utilization of Air District resources as monitoring for the PAMS program is brought online. 

A description of the PAMS program can be found in the PAMS section of this document.

Cupertino Monte Vista

On April 1, 2011, the Air District began measuring ozone precursors CH4 and NMHC at this 

site. The Air District intended to measure these compounds when the station opened in 

September 2010, but the instrumentation requires high pressure hydrogen gas cylinders 

which were not permitted by the Santa Clara County Fire Department. As an alternative to 

compressed gas cylinders, new laboratory grade equipment was procured by the Air District. 

The new equipment required modification of the monitoring trailer thus delaying the start of 

CH4/NMHC monitoring until April 2011. 

Lead Monitoring

On October 15, 2008, EPA strengthened the National Ambient Air Quality Standard 

(NAAQS) for lead by lowering the standard from 1.5 μg/m3(quarterly average) to 0.15 

μg/m3(rolling 3-month average). On December 27, 2010 EPA published a new regulation

for lead monitoring and included monitoring at NCore program sites. The new regulation

also requires lead monitoring at airports having lead emissions of one ton per year or greater. 

NCore Program Lead Monitoring

The Air District’s NCore monitoring site was brought fully online at the San Jose 

monitoring location effective January 1, 2011. Lead monitoring at San Jose has been 

on a 1-in-6 day schedule since January 2008 and will continue on this schedule 

indefinitely. A detailed description of the NCore monitoring program can be found in 

the NCore section of this document.
22

Airport Lead Monitoring

Although no airports in the Bay Area exceed the one ton per year emission threshold, 

the regulation lists an additional requirement for the Air District to participate in a1-

year EPA funded lead monitoring study at three airports: San Carlos, Palo Alto, and 

Reid-Hillview. The San Carlos airport will have a primary and a collocated sampler 

to verify the precision of the measurements. Samples will be taken on a 1-in-6 day 

schedule and on the same dates as lead samples from the San Jose NCore site.

The airports chosen for this study were selected because they are near heavily 

populated areas and service piston engine aircraft which still use leaded fuels. 

Leaded aviation gas used in piston-engine aircraft accounts for nearly 50% of the 

total lead emissions in the United States annually.

Airport lead monitoring is scheduled to begin in December 2011 and end after one 

year. However, monitoring will be extended if lead concentrations are greater than 

50% of the 0.15 g/m3 NAAQS.

Livermore

The Air District replaced the filter-based PM2.5 sampler at Livermore with a continuous 

FEM-BAM PM2.5 sampler on March 1, 2011. The new sampler will allow real-time display 

of the data on the Air District webpage, and will allow hourly analysis of the data. 

NO2 Monitoring

On April 12, 2010 EPA revised the NAAQS for NO2 by creating a one-hour standard of

100 ppb. The annual standard was left at 53 ppb. The new regulation also requires that NO2

monitoring be performed at three sites within 50 meters of major roadways in the Bay Area 

by January 1, 2013. However, the Air District plans to start this monitoring program at a 

location immediately south of the Bay Bridge toll plaza in Oakland by January 1, 2012. The 

Air District may also monitor CO and particulates to obtain additional pollutant data near 

roadways. Meteorological data from a nearby Air District operated meteorological site will 

be available to assist in the analyses of the data.

Particulate Matter (PM10) Sites

The Air District is considering replacing high-volume PM10 samplers with low-volume PM10

samplers at all stations in 2011. These samplers use less power and are more accurate than 

the current high-volume PM10 technology. This was done at San Jose in December 2010. 

Photochemical Assessment Monitoring Stations (PAMS)

EPA is funding hourly VOC speciated hydrocarbon measurements at three sites in the Bay 

Area: Livermore, Patterson Pass, and San Ramon. The Livermore site began recording the 

hydrocarbon data in 2010 and the Patterson Pass site began on March 1, 2011. The San 

Ramon site is expected to be operational by late summer 2011. A full description of the 

PAMS program can be found in this document. 
23

San Jose

The San Jose station was approved as an NCore program station by EPA in October 2009. 

The additional monitoring requirements were effective January 1, 2011. To meet NCore 

program requirements PM coarse (PM10-2.5) will be determined every 3rd day. PM10-2.5 will 

be calculated (not directly measured) as the difference between PM10 and PM2.5 

measurements. Therefore, in January 2011, PM10 sampling was changed from a 1-in-6 day 

schedule to a 1-in-3 day schedule year-round; and PM2.5 sampling was changed from 1-in-6 

day schedule to a 1-in-3 day schedule in summer and will continue to operate daily in winter. 

Also, NOy monitoring began on January 1, 2011 to meet NCore requirements. More 

information about the NCore program can be found in the NCore section of this document.

SO2 Monitoring

On June 22, 2010 EPA revised the monitoring requirements for SO2 to include source impact 

monitoring near major SO2 sources. Network changes to meet the new requirements must be 

in place by January 1, 2013. The Air District’s air monitoring network already includes three 

SLAMS SO2 monitoring sites at Richmond 7th St, San Pablo, and Martinez that meet the new 

source impact monitoring requirements, so no network modifications will be required.

South San Jose

As mentioned in the 2009 Annual Network Plan, the Air District may agree to operate a 

monitoring station near the Metcalf Energy Center power plant in South San Jose. This site 

may be established as part of an agreement between the City of San Jose and the Metcalf 

Energy Center, but no progress in the agreement has been made during the past year. The 

station would be located in a residential neighborhood one mile northwest of the power plant 

and would monitor ambient levels of pollutants emitted by the power plant. Those pollutants 

are PM10, NO/NO2, and CO. It is intended to be a long-term site. If the Air District takes 

over operation of the site, ozone may also be monitored as part of a special study for two

years.

Vallejo

The Air District replaced the filter-based PM2.5 sampler at Vallejo with a continuous FEMBAM PM2.5 sampler on March 1, 2011. The new sampler will allow real-time display of the 

data on the Air District webpage, and will allow hourly analysis of the data. 
24

Removing a NAAQS Compliance Monitor

When the Air District proposes changes to the air monitoring network, the proposed changes 

are included in the annual Monitoring Network Plan. The annual Monitoring Network Plan 

is posted on the Air District web site for 30 days to allow public comment on the proposed 

changes to the network. After the public comment period, the Air District reviews and 

considers the comments before making a final decision. The Air District then submits the 

Plan and any comments received to the EPA Region 9 Regional Administrator.

Before shutting down a SLAMS (State or Local Air Monitoring Station) monitor, 40 CFR 

Part 58.14c requires that the Air District obtain the Regional Administrator’s written 

approval. The Regional Administrator will normally approve the shutdown of a SLAMS 

monitor when any of the following situations apply:

1) Criteria pollutant monitors which have shown attainment of the national standards

during the previous five years may be removed if the probability is less than 10% that 

the monitor will exceed 80% of NAAQS during the next three years, and if the 

monitor is not required by an attainment or maintenance plan.

2) CO, PM10, SO2, or NO2 monitors may be removed if the monitor has shown 

consistently lower concentrations than another monitor for the same pollutant in the 

same county during the previous five years.

3) Criteria pollutant monitors that have not violated the national standards in the most 

recent five years may be removed if the State Implementation Plan (SIP) provides a 

method of representing the air quality in the applicable county.

4) PM2.5 monitors may be removed when EPA determines that measurements are not 

comparable to the relevant NAAQS because of siting issues.

5) Criteria pollutant monitors which are located upwind of an urban area to characterize 

transport may be removed if the monitor has not recorded violations of the relevant 

NAAQS in the previous five years, and if the monitor is being replaced by another 

monitor that characterizes transport.

6) Criteria pollutant monitors not eligible for removal under any of the above criteria 

may be moved to a nearby location with the same scale of representation if logistical 

problems beyond the agency’s control make it impossible to continue operation at its 

current site.

The closure of a SPM (Special Purpose Monitor) monitor does not require approval from 

EPA, but a change in the designation of a monitoring site from SLAMS to SPM requires 

approval of the Regional Administrator.

Data Submission Requirement

After all data review procedures are complete, the Air District submits monthly air quality 

and associated precision and accuracy reports to the EPA AQS database within 90 days of

the end of every month. Every year, the Air District submits a letter to Region 9 certifying 

that the previous calendar years’ data is complete and correct. The certification letter for 

2010 data was submitted to EPA Region 9 on April 29, 2011.
25

Site Information Definitions

The next section describes each air quality station operated within the Bay Area Air Quality 

Management District. In 2010 there were 29 stations operating in the Air District: 26 long-term 

stations (24 SLAMS stations and two SPM stations), and three temporary stations. Long-term

stations are generally operated for decades, while temporary stations are expected to operate for one

to three years. The Fremont station was closed on October 31, 2010 with approval from EPA.

The station description includes siting information about the station and the individual monitors at 

the station. Monitors must be operated following EPA requirements found in 40 CFR Part 58. 

These regulations also specify monitor siting criteria. Table 8 below lists these siting criteria where 

applicable.

Table 8. Monitor Information and EPA Air Monitoring Siting Criteria.

Monitor Information Definition of Terms

Monitoring Objective The purpose for monitoring at that location. Choices include Highest 

Concentration, Population Oriented, Source Impact, General Background, and 

Regional Transport.

Spatial scale The relative distance over which the air pollution measurements are 

representative. Choices are Micro, Middle, Neighborhood, Urban, and Regional 

scales.

Sampling method 40 CFR Part 58 Appendix C, 2.0: requires that the monitor used must be from 

EPA's current List of Designated Reference and Equivalent Methods.

PM filter analysis method Describes whether the PM filters are analyzed in-house by the local agency or at 

an outside laboratory.

Start date The date valid data collection began for that pollutant at that air monitoring 

station.

Operation schedule Describes if the monitor is operated continuously or intermittently (as for PM).

Sampling season Most monitors operate all year, but some monitors may only operate during 

months when pollution potential is highest, e.g. ozone.

Distance to road from 

gaseous probe

40 CFR Part 58 Appendix E, 6.0: requires that monitors be located far enough 

from roadways to minimize local mobile impacts on measurements. 

Recommended distances are found in Table E-1 for NOx and ozone, Table E-2 

for CO, and Figure E-1 for PM.

Ground cover 40 CFR Part 58 Appendix E, 3.0: states that particulate samplers should not be 

located in an unpaved area unless there is vegetative ground cover year round, so 

that the impact of wind blown dusts will be kept to a minimum.

Probe height (AGL) 40 CFR Part 58 Appendix E, 2.0: requires that probe height be 2-15 meters 

above ground level (AGL).

Probe height above roof 40 CFR Part 58 Appendix E, 2.0: requires the probe be at least 1 meter vertically 

or horizontally away from any supporting structure.

Distance from 

obstructions on roof

40 CFR Part 58 Appendix E, 4.0: requires that the distance from the obstacle to 

the probe or inlet must be at least twice the height that the obstacle protrudes 

above the probe or inlet. PM samplers must have a 2 meter separation from 

walls, parapets and structures. 4.0 (b)
26

Table 8 continued. Monitor Information and EPA Air Monitoring Siting Criteria.

Monitor Information Definition of Terms

Distance from 

obstructions not on roof

40 CFR Part 58 Appendix E, 4.0: requires that the distance from the obstacle to 

the probe or inlet must be at least twice the height that the obstacle protrudes 

above the probe or inlet.

Distance from tree (DL) 40 CFR Part 58 Appendix E, 5.0: requires that probe be at least 10 meters from 

the nearest tree drip line.

Distance to furnace or 

incinerator flue

40 CFR Part 58 Appendix E, 3.0: requires that scavenging be minimized by 

keeping the probe away from furnace or incineration flues or other minor sources 

of SO2 or NO. The separation distance should take into account the heights of 

the flues, type of waste or fuel burned, and the sulfur content of the fuel.

Distance between 

collocated monitors

40 CFR Part 58 appendix A, 3.2.5.6: requires that PM monitors be 2-4 meters 

apart for flow rates >200L/m and have a 1-4 meter separation for flow rates <200 

L/m.

Unrestricted airflow 40 CFR Part 58 Appendix E, 4.0: requires the probe or inlet to have unrestricted 

airflow in an arc of at least 180 degrees. This arc must include the predominant 

wind direction for the season of greatest pollutant concentration potential.

Probe material 40 CFR Part 58, Appendix E, 9.0: requires that either Pyrex glass or FEP Teflon 

be used for intake sampling lines.

Residence time 40 CFR Part 58, Appendix E, 9.0: recommends a residence time of 20 seconds or 

less for gaseous sampling.

Will there be changes 

within the next 18 mos?

Describes if any changes are expected to occur to that monitor at that station 

within the next 18 months.

Is it suitable for 

comparison against the 

annual PM2.5?

40 CFR 58.30: requires that PM2.5 data that are representative, not of area-wide, 

but rather of relatively unique population-oriented micro-scale, localized hot 

spot, or unique population-oriented middle-scale impact sites are only eligible 

for comparison to the 24-hour PM2.5 NAAQS.

Frequency of flow rate 

verification for manual 

PM samplers 

40 CFR 58, Appendix A, 3.3.2: requires that a one-point flow rate verification 

check must be performed at least once every month for low-volume PM 

samplers and quarterly for hi-volume PM samplers.

Frequency of flow rate 

verification for automated 

PM analyzers 

40 CFR 58, Appendix A 3.2.3: requires a one-point flow rate verification check 

must be performed at least once every month.

Frequency of one-point 

QC check (gaseous)

40 CFR Part 58 Appendix A, 3.2.1: requires that QC checks be performed at 

least once every two weeks.

Last Annual Performance 

Evaluation (gaseous)

40 CFR Part 58 Appendix A, 3.2.2: requires that SO2, CO, O3, and NO2 monitors 

have annual performance evaluations. Section 3.2.7 requires that performance 

evaluations of PM monitors must be performed annually through the PEP 

(Performance Evaluation Program).

Last two semi-annual 

flow rate audits for PM 

monitors

40 CFR Part 58 Appendix A, 3.2.4 (automated methods) and 3.3.3 (manual 

methods): require that PM samplers have flow rate checks every six months.
27

Included in each site description is the number of days when a criteria pollutant measurement 

exceeded the National Ambient Air Quality Standard (NAAQS). The national standards for 

hourly and daily averaging times are shown in Table 9 below. Based on the past ten years of 

air monitoring data, only ozone and PM2.5 are pollutants of interest to Bay Area residents

because the other pollutants rarely, if ever, exceed the NAAQS. The table below is 

abbreviated for clarity. A full list of national and California air quality standards can be 

found at: http://hank.baaqmd.gov/pln/air_quality/ambient_air_quality.htm

Table 9. National Ambient Air Quality Standards (as of December 31, 2010)

Pollutant Averaging Time Standard 

Ozone 8 hour 0.075 ppm

PM2.5 24 hour 35 μg/m3

PM10 24 hour 150 μg/m3

Carbon Monoxide 1 hour 35 ppm

8 hour 9 ppm

Sulfur Dioxide 1 hour 75 ppb

Nitrogen Dioxide 1 hour 100 ppb
28

Detailed Site Information for SLAMS Stations
29

Bethel Island

Site Name Bethel Island

AQS ID 06-013-1002

GIS coordinates 38.0063° N, 121.6419° W

Location Trailer in parking lot

Address 5551 Bethel Island Rd, Bethel Island CA 94511

County Contra Costa

Distance to road

from gaseous probe

Bethel Island Rd: 63 meters

Sandmound Blvd: 110 meters

Traffic count

 

Bethel Island Rd: 5,550 ADT (2009)

Sandmound Blvd: 1,537 ADT (2006)

Groundcover Gravel surrounded by grassy fields

Representative Area San Francisco-Oakland-Fremont MSA

Bethel Island was chosen for an air monitoring site to measure pollutant transport between 

the California Central Valley and the San Francisco Bay Area. The site is 26 miles east of 

the only sea-level gap (the Carquinez Strait) between the two regions. Local pollution 

emissions are low due to the rural nature of the area and the lack of any industrial sources 

within six miles of the site. The nearest town is Bethel Island, 0.6 miles to the north, with a 

population of 2,137 according to the 2010 census. The Bethel Island station was operated by 

CARB from 1981 until late 1986 and then it was transferred to the Air District. 

Ozone and NO2 are measured because the area is in the transport corridor between the San 

Francisco Bay Area and the Central Valley, both of which are major sources of ozone, ozone 

precursors, and particulates. Traffic volume near the site is low, so CO measurements tend to 

be representative of natural background levels, or regional transport. SO2 is measured 

because the area is downwind from numerous refineries, which can be large sources of SO2. 

PM10 is measured because easterly winds occasionally transport particulates from the Central 

Valley, and because the filters can be analyzed to determine sulfate and nitrate levels 

transported from the Central Valley.

Background levels of toxic compounds are also determined from canister samples taken at 

Bethel Island on a 1-in-12 day schedule and later analyzed in the Air District laboratory. 

More information about the toxics monitoring program can be found in the Toxics Program 

section of this report.

During the most recent three years, the national 8-hour ozone standard was exceeded 11 

times at this site. No exceedances of the national standards for PM10, NO2, SO2 (the new 75 

ppb 1-hour standard) or CO were measured during the last three years.
30

Bethel Island Monitor Information

Pollutant O3 CO NO/NO2 SO2 PM10

Monitoring

Objective

Regional 

Transport &

Highest Conc.

General 

Background

Regional 

Transport

Regional 

Transport

Regional 

Transport

Spatial scale Regional Regional Regional Regional Regional

Sampling method TECO 49i TECO 48i TECO 42C TECO 43C Andersen 

GUV-16HBLA

PM filter analysis method N/A N/A N/A N/A Weighed by 

Air District

Start date 01/01/87*01/01/87*

01/01/87*

01/01/87*11/05/86

Operation schedule Continuous Continuous Continuous Continuous 1-in-6

Sampling season All year All year All year All year All year

Probe height (AGL) 6.7 m 6.7 m 6.7 m 6.7 m 5.2 m

Probe height above roof 3.0 m 3.0 m 3.0 m 3.0 m 1.5 m

Distance from 

obstructions on roof

None None None None None

Distance from 

obstructions not on roof

None None None None None

Distance from tree (DL) 13.3 m 13.3 m 13.3 m 13.3 m 14.4 m

Distance to furnace or 

incinerator flue

None None None None None

Distance between 

collocated monitors

N/A N/A N/A N/A N/A

Unrestricted airflow 270° 270° 270° 270° 270°

Probe material Teflon Teflon Teflon Teflon N/A

Residence time 13 s 14 s 14 s 14 s N/A

Will there be changes 

within the next 18 mos?

No No No No No

Is it suitable for 

comparison against the 

annual PM2.5?

N/A N/A N/A N/A N/A

Frequency of flow rate 

verification for manual 

PM samplers 

N/A N/A N/A N/A Weekly

Frequency of flow rate 

verification for automated 

PM analyzers 

N/A N/A N/A N/A N/A

Frequency of one-point 

QC check (gaseous)

Every other 

day

Every other 

day

Every other 

day

Every other 

day

N/A

Last Annual Performance 

Evaluation (gaseous)

11/09/10 11/09/10 11/09/10 11/09/10 N/A

Last two semi-annual 

flow rate audits for PM 

monitors

N/A N/A N/A N/A 11/08/10

05/24/10

*

Start date of data collected by the Air District. Data was collected by CARB began on March 1, 1981.
31

Concord

Site Name Concord

AQS ID 06-013-0002

GIS coordinates 37.9360° N, 122.0262° W

Location One story commercial building

Address 2956-A Treat Blvd, Concord CA 94518

County Contra Costa

Distance to road

from gaseous probe

Treat Blvd: 181 meters

Oak Grove Rd: 244 meters

Traffic count 

 

Treat Blvd: 41,218 ADT (2005)

Oak Grove Rd: 26,742 ADT (2005)

Interstate 680 242,000 ADT (2008)

Groundcover Paved

Representative Area San Francisco-Oakland-Fremont MSA

Concord was chosen for an air monitoring site because it is the largest city in Contra Costa 

County, with a 2010 population of 122,067 according to the 2010 census; and because of the 

high pollution potential due to locally emitted and transported pollutants into the area. Since 

Concord is located in the Diablo Valley, locally emitted pollutants can become trapped when 

winds are light. Large emission sources in the valley include the two major freeways, 

Interstate 680 and California Highway 4; and two refineries at the north end of the valley. 

The air monitoring site is located in the back of a shopping center, near the intersection of 

two major streets, and surrounded by residential neighborhoods. There is no industry in the 

immediate vicinity. NO/NO2 and CH4/NMHC are measured because of local mobile 

emissions. Monitoring of CH4/NMHC was discontinued on May 31, 2011 because of the 

development of PAMS network (described elsewhere in this report), which is a more 

effective allocation of resources. The PAMS network better defines the measurement and 

sources of ozone precursors, making additional measurements of CH4/NMHC at Concord 

superfluous. 

Ozone is measured at the site because hot, inland summertime temperatures combined with 

precursor pollutants stagnating in the surrounding valley often produces high ozone levels. 

Carbon monoxide is measured because the site is near two major roads, Treat Blvd and Oak 

Grove Road. SO2 is measured because the site is six miles south of the Tesoro and the Shell 

Refineries, both potential major sources of SO2. PM10 and PM2.5 are measured because light 

winds combined with surface-based inversions during the winter months can cause elevated 

particulate levels in the valley.

The collocated PM2.5 sampler operated on a 1-in-12 day schedule in January, February, and 

March of 2010. However, to obtain additional data for comparison with the primary PM2.5

sampler, the Air District starting operating the collocated sampler on a 1-in-6 day schedule 

starting in April 2010. The Air District intends to continue operating the collocated sampler 

on a 1-in-6 day schedule indefinitely.
32

VOC toxic compounds are also sampled at Concord on a 1-in-12 day schedule and analyzed 

in the Air District laboratory. More information about the toxics monitoring program can be 

found in the Toxics Program section of this report. 

During the most recent three years, this site recorded nine exceedances of the national 8-hour 

ozone standard, and five exceedances of the national 24-hour PM2.5 standard. No 

exceedances of the national standards for PM10, NO2, SO2 (the new 75 ppb 1-hour standard) 

or CO were measured during the last three years.

Concord Monitor Information

Pollutant O3 CO NO/NO2 SO2 CH4/NMHC

Monitoring

Objective

Population 

oriented &

Highest Conc.

Population 

oriented

Population 

oriented

Population 

oriented

Population 

oriented

Spatial scale Neighborhood Neighborhood Neighborhood Urban Neighborhood

Sampling method TECO 49i TECO 48A TECO 42C TECO 43C TECO 55C

PM filter analysis method N/A N/A N/A N/A N/A

Data Start date 04/08/80 02/21/80 NO2: 01/01/80

NO: 03/01/80

02/01/80 CH4:12/31/99

NMHC:05/10/06

Operation schedule Continuous Continuous Continuous Continuous Continuous

Sampling season All year All year All year All year All year

Probe height (AGL) 9.2 m 9.2 m 9.2 m 9.2 m 9.2 m

Probe height above roof 3.1 m 3.1 m 3.1 m 3.1 m 3.1 m

Distance from 

obstructions on roof

None None None None None

Distance from 

obstructions not on roof

None None None None None

Distance from tree (DL) 24.0 m 24.0 m 24.0 m 24.0 m 24.0 m

Distance to furnace or 

incinerator flue

None None None None None

Distance between 

collocated monitors

N/A N/A N/A N/A N/A

Unrestricted airflow 360° 360° 360° 360° 360°

Probe material Teflon Teflon Teflon Teflon Teflon

Residence time 8 s 9 s 9 s 10 s 8 s

Will there be changes 

within the next 18 mos?

No No No No Yes

Is it suitable for 

comparison against the 

annual PM2.5?

N/A N/A N/A N/A N/A

Frequency of flow rate 

verification for manual 

PM samplers 

N/A N/A N/A N/A N/A

Frequency of flow rate 

verification for 

automated PM analyzers 

N/A N/A N/A N/A N/A

Frequency of one-point 

QC check (gaseous)

Every other 

day

Every other 

day

Every other 

day

Every other 

day

Every other 

day

Last Annual Performance 

Evaluation (gaseous)

08/26/10 08/26/10 08/26/10 08/26/10 08/26/10

Last two semi-annual 

flow rate audits for PM 

monitors

N/A N/A N/A N/A N/A
33

Concord Monitor Information

Pollutant PM10 FRM PM2.5 FRM PM2.5

Collocated

Monitoring Objective Population 

oriented

Population 

oriented

Population 

oriented

Spatial scale Neighborhood Neighborhood Neighborhood

Sampling method Andersen

HiVol 1200

Partisol-Plus 

2025 w/VSCC

Partisol-Plus 

2025 w/VSCC

PM filter analysis method Weighed by

Air District

Weighed by 

Air District

Weighed by 

Air District

Data Start date 11/04/86 03/19/99 03/19/99

Operation schedule 1-in-6 Apr-Sep: 1-in-3

Oct-Mar: daily

Jan-Mar: 1-in-12

Apr-Dec: 1-in-6

Sampling season All year All year All year

Probe height (AGL) 5.8 m 5.9 m 5.9 m

Probe height above roof 1.5 m 2 m 2 m

Distance from obstructions 

on roof

None None None

Distance from obstructions 

not on roof

None None None

Distance from tree (DL) 15.0 m 13.1 m 17.4 m

Distance to furnace or 

incinerator flue

None None None

Distance between 

collocated monitors

N/A 3.2 m 3.2 m

Distance between PM10

and PM2.5 monitors

7.5 m 7.5 m 3.2 m

Unrestricted airflow 360° 360° 360°

Probe material N/A N/A N/A

Residence time N/A N/A N/A

Will there be changes 

within the next 18 mos?

No No No

Is it suitable for comparison 

against the annual PM2.5?

N/A Yes Yes

Frequency of flow rate 

verification for manual PM 

samplers 

Weekly Monthly Monthly

Frequency of flow rate 

verification for automated 

PM analyzers 

N/A N/A N/A

Frequency of one-point QC 

check (gaseous)

N/A N/A N/A

Last Annual Performance 

Evaluation (gaseous)

N/A N/A N/A

Last two semi-annual flow 

rate audits for PM monitors

11/15/10

05/19/10

11/15/10

05/19/10

11/15/10

05/19/10
34

Fairfield

Site Name Fairfield

AQS ID 06-095-0005

GIS coordinates 38.2270° N, 122.0756° W

Location Small trailer in open field

Address 1010 Chadbourne Rd, Fairfield CA 94534

County Solano

Distance to road

from gaseous probe

Cordelia Rd: 194 meters

Chadbourne Rd: 705 meters

Traffic count Cordelia Rd: 3,751 ADT (2007)

Chadbourne Rd: 500 ADT (2007)

Groundcover Vegetative

Representative Area Vallejo-Fairfield MSA

Fairfield was chosen for monitoring ozone transport between the San Francisco Bay Area 

and the Sacramento Valley. Fairfield lies in the northeast part of the Air District in the 

Carquinez Strait Region, the only sea level gap between the Bay Area and the Central Valley. 

Prevailing westerly winds carry ozone and its precursors into the Sacramento Valley from the 

Bay Area. Occasionally, easterly winds transport elevated ozone levels into this region from 

the Central Valley.

Over the past decade the Fairfield/Suisun City urban area has grown considerably. 

According to the 2010 census the area has a combined population of 138,815, the largest

urban area in Solano County. As a result, Fairfield is also a population oriented ozone 

monitoring site. The monitoring site is located in a rural area, situated between the nearby 

urban area of Fairfield/Suisun City urban area, and the greater Bay Area. Prevailing winds 

are west, and the monitor normally measures ozone concentrations coming from the Bay 

Area.

Ozone concentrations measured at Fairfield exceeded the national 8-hour ozone standard on 

five days during the last three years.
35

Fairfield Monitor Information

Pollutant O3

Monitoring Objective Regional 

transport &

Population 

oriented

Spatial scale Regional

Sampling method TECO 49C

Analysis method N/A

Start date 05/29/02

Operation schedule Continuous

Sampling season Apr 1-Nov 30

Probe height (AGL) 3.7 m

Probe height above roof 1.0 m

Distance from 

obstructions on roof

None

Distance from 

obstructions not on roof

None

Distance from tree (DL) >50 m

Distance to furnace or 

incinerator flue

None

Unrestricted airflow 360°

Probe material Teflon

Residence time 5 s

Will there be changes 

within the next 18 mos?

No

Is it suitable for 

comparison against the 

annual PM2.5?

N/A

Frequency of flow rate 

verification for manual 

PM samplers 

N/A

Frequency of flow rate 

verification for 

automated PM analyzers 

N/A

Frequency of one-point 

QC check (gaseous)

Every other 

day

Last Annual Performance 

Evaluation (gaseous)

11/8/10

Last two semi-annual 

flow rate audits for PM 

monitors

N/A
36

Fremont

Site Name Fremont

AQS ID 06-001-1001

GIS coordinates 37.5358° N, 121.9618° W

Location One story commercial building

Address 40733 Chapel Way, Fremont CA 94538 

County Alameda

Distance to road

from gaseous probe

Fremont Boulevard: 120.0 meters

Chapel Way: 31.0 meters 

Traffic count Fremont Boulevard: 33,390 ADT (2008)

Chapel Way: 500 ADT (estimate)

Groundcover Paved

Representative Area San Francisco-Oakland-Fremont MSA

The Fremont air monitoring station was closed on October 31, 2010. Fremont was an 

important air monitoring location in the past. Ozone, CO, NO/NO2, CH4/NMHC and PM2.5

have been monitored at this site. In the most recent decade, air quality levels and the number 

of exceedances of the NAAQS at Fremont have shown a high correlation to nearby sites. 

This indicates that air quality levels in Fremont are adequately characterized by 

measurements at sites such as Hayward and San Jose. The Air District completed an 

assessment of the Air Monitoring Network in July 2010, and the analysis concluded that air 

quality measurements at the Fremont station had a comparatively low importance rating. The 

closure of the Fremont station allows more effective utilization of limited resources in the 

face of additional monitoring requirements mandated by EPA.

VOC toxic compounds, carbonyls, and metals were sampled at Fremont on a 1-in-12 day 

schedule and analyzed by the CARB laboratory. CARB discontinued its toxic monitoring 

program at Fremont on July 19, 2010. More information about the CARB toxics monitoring 

program can be found at http://www.arb.ca.gov/toxics/toxics.htm. Information about toxics 

monitoring by the Air District can be found in the Toxics Program section of this report.

During the most recent three years, the national 8-hour ozone standard was exceeded twice 

and the national 24-hour PM2.5 standard was exceeded once at this site. No exceedances of 

the national NO2 or CO standards were measured during the last three years.
37

Fremont Monitor Information*

Pollutant O3 CO NO/NO2 CH4/NMHC

Monitoring Objective Population 

oriented

Population 

oriented

Population 

oriented

Population 

oriented

Spatial scale Neighborhood Neighborhood Neighborhood Neighborhood

Sampling method TECO 49i TECO 48A TECO 42C TECO 55C

PM filter analysis method N/A N/A N/A N/A

Start date 07/29/76 01/01/71 NO: 07/01/76

NO2: 04/12/74

CH4: 01/01/94

NMHC: 05/25/06

Operation schedule Continuous Continuous Continuous Continuous

Sampling season All year All year All year All year

Probe height (AGL) 8.4 m 8.4 m 8.4 m 8.4 m

Probe height above roof 4.3 m 4.3 m 4.3 m 4.3 m

Distance from 

obstructions on roof

None None None None

Distance from 

obstructions not on roof

None None None None

Distance from tree (DL) 25.9 m 25.9 m 25.9 m 25.9 m

Distance to furnace or 

incinerator flue

3.7 m 3.7 m 3.7 m 3.7 m

Distance between 

collocated monitors

N/A N/A N/A N/A

Unrestricted airflow 360° 360° 360° 360°

Probe material Teflon Teflon Teflon Teflon

Residence time 13 s 14 s 12 s 13 s

Will there be changes 

within the next 18 mos?

Site closed Site closed Site closed Site closed

Is it suitable for 

comparison against the 

annual PM2.5?

N/A N/A N/A N/A

Frequency of flow rate 

verification for manual 

PM samplers 

N/A N/A N/A N/A

Frequency of flow rate 

verification for 

automated PM analyzers 

N/A N/A N/A N/A

Frequency of one-point 

QC check (gaseous)

Every other 

day

Every other 

day

Every other 

day

Every other 

day

Last Annual Performance 

Evaluation (gaseous)

10/29/10 10/29/10 10/29/10 07/23/10

Last two semi-annual 

flow rate audits for PM 

monitors

N/A N/A N/A N/A

*All Fremont monitors closed on October 31, 2010 (except CH4/NMHC closed July 31, 2010)
38

Fremont Monitor Information*

Pollutant Continuous 

PM2.5 FEM 

BAM

Monitoring Objective Population 

oriented

Spatial scale Neighborhood

Sampling method Met One 

BAM FEM 

1020

PM filter analysis method N/A

Start date 10/01/09

Operation schedule Continuous 

Sampling season All year

Probe height (AGL) 6.2 m

Probe height above roof 2.1 m

Distance from 

obstructions on roof

None

Distance from 

obstructions not on roof

None

Distance from tree (DL) 28.9 m

Distance to furnace or 

incinerator flue

4.1 m

Distance between 

collocated monitors

N/A

Unrestricted airflow 360°

Probe material N/A

Residence time N/A

Will there be changes 

within the next 18 mos?

Site closed

Is it suitable for 

comparison against the 

annual PM2.5?

Yes

Frequency of flow rate 

verification for manual 

PM samplers 

N/A

Frequency of flow rate 

verification for 

automated PM analyzers 

Every two 

weeks

Frequency of one-point 

QC check (gaseous)

N/A

Last Annual Performance 

Evaluation (gaseous)

N/A

Last two semi-annual 

flow rate audits for PM 

monitors

10/29/10

06/02/10

*All Fremont monitors closed on October 31, 2010 (except CH4/NMHC closed July 31, 2010)
39

Gilroy

Site Name Gilroy

AQS ID 06-085-0002

GIS coordinates 36.9993° N 121.5749° W

Location Air monitoring shelter next to water pump station 

Address 9P

th

P and Princevalle St, Gilroy CA 95020

County Santa Clara

Distance to road

from gaseous probe 

Princevalle St: 18.3 meters

9P

th

P St: 15.7 meters

10th St. 185.0 meters

Traffic count Princevalle St: 5,000 ADT (2008)

9P

th

P St: 1,400 ADT (estimate)

10th St. 12,700 ADT (2008)

Groundcover paved

Representative Area San Jose-Sunnyvale-Santa Clara MSA

Gilroy was originally chosen as an air monitoring site to measure ozone and particulate 

transport between the San Francisco and Monterey Bay Areas. Prevailing northwesterly 

afternoon winds carry ozone and ozone precursors from the San Jose area southward through

the Santa Clara Valley. When temperatures are hot, and solar insolation is strong, these 

precursors react and can form high concentrations of ozone in the Gilroy area. As Gilroy 

grew in population (48,821 according to the 2010 census) the site was considered not only an 

ozone transport site but also a population oriented ozone site. PM2.5 is measured because 

light winds combined with surface-based inversions during the winter months can cause 

elevated particulate levels in the valley. 

The monitoring site is located in a residential area of Gilroy on the west side of the Santa 

Clara Valley. Air quality studies have shown that the west side of the valley has higher 

ozone levels than the east side. This is due to elevated terrain on the west side that shelters 

the western part of Gilroy from the strong winds in the afternoon produced by the Monterey 

Bay sea breeze. Residents have preferred the sheltered area and built most of the town on the 

west side of the valley.

 

In the most recent three years, the national 8-hour ozone standard was exceeded seven times 

at this site. The national 24-hour PM2.5 standard was exceeded once during the last three 

years and it was due to smoke from a wildfire on August 14, 2009.
40

Gilroy Monitor Information

Pollutant O3 Continuous 

PM2.5 FEM 

BAM

Monitoring

Objective

Regional 

Transport, 

Highest 

Concentration, 

Population 

oriented 

Population 

oriented

Spatial scale Neighborhood Neighborhood

Sampling method TECO 49C Met One 

BAM 1020

PM filter analysis method N/A N/A

Data Start date 07/01/80 10/31/09

Operation schedule Continuous Continuous

Sampling season Apr 1 – Nov 30 All year

Probe height (AGL) 4.7 m 2.9 m

Probe height above roof 2.6 m N/A

Distance from 

obstructions on roof

None N/A

Distance from 

obstructions not on roof

None 1.8 m

Distance from tree (DL) 26 m 26 m

Distance to furnace or 

incinerator flue

14.3 m 14.3 m

Distance between 

collocated monitors

N/A N/A

Unrestricted airflow 360o 360°

Probe material Teflon N/A

Residence time 13 s N/A

Will there be changes 

within the next 18 mos?

No No

Is it suitable for 

comparison against the 

annual PM2.5?

N/A Yes

Frequency of flow rate 

verification for manual 

PM samplers 

N/A N/A

Frequency of flow rate 

verification for 

automated PM analyzers 

N/A Every two 

weeks

Frequency of one-point 

QC check (gaseous)

Every other 

day

N/A

Last Annual Performance 

Evaluation (gaseous)

11/09/10 N/A

Last two semi-annual 

flow rate audits for PM 

monitors

N/A 07/26/10

04/13/10
41

Hayward

Site Name Hayward

AQS ID 06-001-2001

GIS coordinates 37.6545° N, 122.0315° W 

Location Pump house near water tank

Address 3466 La Mesa Drive, Hayward CA 94542

County Alameda

Distance to road

from gaseous probe

Hayward Blvd: 26.2 meters

La Mesa Dr: 38 meters

Traffic count Hayward Blvd: 4,400 ADT (2007)

La Mesa Dr: 500 ADT (estimate)

Groundcover Paved

Representative Area San Francisco-Oakland-Fremont MSA

The Hayward air monitoring site was chosen to measure ozone at a higher elevation. 

Located on the east side of Hayward at an elevation of 951 feet, it is the highest elevation air 

monitoring site in the Air District. Studies had shown that on high ozone days, a cloud of 

ozone and precursors moves southward from Oakland on the west side of the East Bay Hills. 

Because ozone monitoring sites were already in place in the low-lying areas of the East Bay 

and South Bay, i.e. in Oakland and San Jose, this site was chosen to be between them, but at

a higher elevation. Thus, the site gives an indication of ozone levels aloft. The Hayward site 

is also important because it provides air quality forecasting information concerning residual 

ozone from the previous day. Although there is a large water tank onsite in the upwind 

direction, the instrument probe is high enough to avoid the tank being an obstacle. The scale 

of this site is considered to be regional because it is representative of ozone levels aloft. 

The Hayward site was shut down on November 6, 2009 due to the demolition and 

reconstruction of the water tank nearby the site. The construction project was completed in 

late 2010 and the site reopened at the start of the ozone sampling season on April 1, 2011.

Prior to the temporary shutdown of Hayward in 2010, during the three most recent years of 

operation of the site (2007-2009), the national 8-hour ozone standard was exceeded four 

times.
42

Hayward Monitor Information

Pollutant O3

Monitoring

Objective

Population 

oriented & 

Regional 

Transport

Spatial scale Regional

Sampling method TECO 49i

PM filter analysis method N/A

Start date 05/31/77

Operation schedule Continuous

Sampling season April 1-

November 30

Probe height (AGL) 6.7 m

Probe height above roof 3.1 m

Distance from 

obstructions on roof

None

Distance from 

obstructions not on roof

None

Distance from tree (DL) 11.4 m

Distance to furnace or 

incinerator flue

N/A

Distance between 

collocated monitors

N/A

Unrestricted airflow 360°

Probe material Teflon

Residence time 15 s

Will there be changes 

within the next 18 

months?

No

Is it suitable for 

comparison against the 

annual PM2.5?

N/A

Frequency of flow rate 

verification for manual 

PM samplers 

N/A

Frequency of flow rate 

verification for 

automated PM analyzers 

N/A

Frequency of one-point 

QC check (gaseous)

Every other 

day

Last Annual Performance 

Evaluation (gaseous)

11/03/09*

Last two semi-annual 

flow rate audits for PM 

monitors

N/A

*The Hayward site was not in operation during 2010.
43

Livermore

Site Name Livermore

AQS ID 06-001-0007

GIS coordinates 37.6875° N, 121.7842° W

Location One story commercial building

Address 793 Rincon Avenue, Livermore CA 94551

County Alameda

Distance to road

from gaseous probe

Rincon Ave: 67 meters

Pine St: 94 meters

Interstate 580: 1,400 meters

Traffic count Rincon Ave: 2,400 ADT (2005)

Pine St: 4,800 ADT (2005)

Interstate 580 at Portola Ave: 166,000 ADT (2008)

Groundcover Paved

Representative Area San Francisco-Oakland-Fremont MSA

Livermore was chosen for an air monitoring site because it is the largest city in eastern 

Alameda County, with a 2010 population of 80,968 according to the 2010 census, and 

because measurements have shown this area can have the highest ozone levels in the Bay 

Area. Livermore is located within the Livermore Valley, an east-west oriented inland valley 

between the San Francisco Bay and the Central Valley. Air flow analyses on high ozone 

days have shown ozone precursors to move into this valley from the region surrounding the 

San Francisco Bay through the Hayward and Niles Canyon Gaps to the west, and from the 

San Ramon Valley to the north. 

The air monitoring site is situated west of the city center, in a residential neighborhood. The 

station is located in a small one-story shopping center, with a little-used parking lot in front 

of the station and a city park behind it. There are no industrial sources in the immediate 

vicinity. Ozone and its precursors, CH4/NMHC and NO/NO2, are measured because the area 

is downwind of large sources of ozone precursors. PM2.5 is measured because light winds 

combined with surface-based inversions during the winter months can cause elevated 

particulate levels. 

Continuous PM2.5 (BAM) monitoring was discontinued after September 7, 2010 because the 

Air District was preparing to install and test a continuous PM2.5 FEM-BAM monitor. 

Testing was completed in late 2010 and both the new PM2.5 FEM-BAM and the existing 

PM2.5 FRM operated daily from January 1, 2011 through February 28, 2011. On March 1, 

2011 the continuous FEM-BAM monitor replaced the FRM monitor and the FRM monitor 

was removed. 

VOC toxic compounds are also sampled at Livermore on a 1-in-12 day schedule and 

analyzed in the Air District laboratory. More information about the toxics monitoring 

program can be found in the Toxics Program section of this report.
44

The Livermore site is part of a Bay Area Photochemical Assessment Monitoring Stations 

(PAMS) program. This is a program to measure hourly speciated hydrocarbons using a gas 

chromatograph analyzer at three Bay Area locations. The other two locations are San Ramon 

and Patterson Pass. A full description of the PAMS program can be found in this document.

During the most recent three years, this site recorded 15 exceedances of the national 8-hour 

ozone standard, and six exceedances of the national 24-hour PM2.5 standard. No exceedances 

of the national NO2 standard were measured during the last three years.
45

Livermore Monitor Information

Pollutant O3 NO/NO2 CH4/NMHC

Monitoring

Objective

Population 

oriented &

Highest Conc.

Population 

oriented

Population 

oriented

Spatial scale Neighborhood Neighborhood Neighborhood

Sampling method TECO 49i TECO 42C TECO 55C

PM filter analysis method N/A N/A N/A

Data Start date 01/01/00 NO2:12/31/99

NO: 01/01/00

CH4: 12/31/99

NMHC:04/20/05

Operation schedule Continuous Continuous Continuous

Sampling season All year All year All year

Probe height (AGL) 6.1 m 6.1 m 6.1 m

Probe height above roof 3.3 m 3.3 m 3.3 m

Distance from 

obstructions on roof

None None None

Distance from 

obstructions not on roof

None None None

Distance from tree (DL) 51 m 51 m 51 m

Distance to furnace or 

incinerator flue

16.5 m 16.5 m 16.5 m

Distance between 

collocated monitors

N/A N/A N/A

Unrestricted airflow 360° 360° 360°

Probe material Teflon Teflon Teflon

Residence time 11 s 12 s 10 s

Will there be changes 

within the next 18 

months?

No No No

Is it suitable for 

comparison against the 

annual PM2.5?

N/A N/A N/A

Frequency of flow rate 

verification for manual 

PM samplers 

N/A N/A N/A

Frequency of flow rate 

verification for 

automated PM analyzers 

N/A N/A N/A

Frequency of one-point 

QC check (gaseous)

Every other 

day

Every other 

day

Every other 

day

Last Annual Performance 

Evaluation (gaseous)

08/14/10 08/14/10 08/14/10

Last two semi-annual 

flow rate audits for PM 

monitors

N/A N/A N/A
46

Livermore Monitor Information

Pollutant FRM PM2.5 Continuous 

PM2.5

BAM

Speciated

PM2.5

Monitoring Objective Population 

oriented

Population 

oriented

Population 

oriented

Spatial scale Neighborhood Neighborhood Neighborhood

Sampling method Partisol-Plus 

2025 w/VSCC

Met One 

BAM 1020

Met One 

SASS

PM filter analysis 

method

Weighed by 

Air District

N/A Weighed by 

DRI

Data Start date 12/02/99 07/01/00 06/11/08

Operation schedule Apr-Sep 1-in-6 

Oct-Mar: daily

Continuous 1-in-6

Sampling season All year All year All year

Probe height (AGL) 5.4 m 5.1 m 5.1 m

Probe height above roof 2.3 m 2.0 m 2.0 m

Distance from 

obstructions on roof

None None None

Distance from 

obstructions not on roof

None None None

Distance from tree (DL) 53 m 52 m 55 m

Distance to furnace or 

incinerator flue

16 m 21 m 17 m

Distance between 

collocated monitors

N/A N/A N/A

Distance between PM10

and PM2.5 monitors

PM2.5 to SASS: 

2.7 m

PM2.5 to BAM: 

5.2 m

BAM to PM2.5: 

5.2 m

BAM to SASS: 

3.5 m

SASS to BAM: 

3.5 m

SASS to PM2.5: 

2.7 m

Unrestricted airflow 360° 360° 360°

Probe material N/A N/A N/A

Residence time N/A N/A N/A

Will there be changes 

w/in the next 18 mos?

No No No

Is it suitable for 

comparison against the 

annual PM2.5?

Yes No – not 

reference or 

equivalent 

method

No

Frequency of flow rate 

verification for manual 

PM samplers 

Monthly N/A Monthly

Frequency of flow rate 

verification for 

automated PM analyzers 

N/A Every two 

weeks

N/A 

Frequency of one-point 

QC check (gaseous)

N/A N/A N/A

Last Annual Perform. 

Evaluation (gaseous)

N/A N/A N/A

Last two semi-annual 

flow rate audits for PM 

monitors

08/03/10

04/22/10

08/03/10

04/22/10

08/03/10

04/22/10
47

Los Gatos

Site Name Los Gatos

AQS ID 06-085-1001

GIS coordinates 37.2269° N 121.9798° W

Location Top of fire station’s hose drying tower

Address 306 University Ave, Los Gatos CA 95030

County Santa Clara

Distance to road

From gaseous probe 

University Ave: 37.2 meters

Bentley Ave: 26.5 meters

State Route 17: 291 meters

Traffic count 

 

University Ave: 13,600 ADT (2005) 

Bentley Ave: 400 ADT (estimate)

State Route 17: 62,000 ADT (2008)

Groundcover Paved

Representative Area San Jose- Sunnyvale- Redwood City MSA

Los Gatos was chosen for an ozone monitoring site because prevailing northerly winds 

transport ozone and ozone precursors from the densely populated area around the south Bay 

Area to the west side of the Santa Clara Valley. Mobile sampling studies as well as longterm monitoring in the Saratoga and Los Gatos areas showed Los Gatos to have the highest 

ozone levels in the area.

High ozone levels are in part due to Los Gatos being situated at the base of the Santa Cruz 

Mountains, which act as a barrier to the movement of polluted air. The monitoring site is 

located near the downtown area at a fire station surrounded by residential neighborhoods. 

The city of Los Gatos has a 2010 population of 29,413 according to the 2010 census.

In the most recent three years, this site recorded eight exceedances of the national 8-hour 

ozone standard. 
48

Los Gatos Monitor Information

Pollutant O3

Monitoring

Objective

Population 

oriented &

Highest 

concentration

Spatial scale Neighborhood

Sampling method TECO 49i

PM filter analysis method N/A

Data Start date 04/01/72

Operation schedule Continuous

Sampling season All year

Probe height (AGL) 11.0 m

Probe height above roof 3.2 m

Distance from 

obstructions on roof

None

Distance from 

obstructions not on roof

None

Distance from tree (DL) 15.5 m

Distance to furnace or 

incinerator flue

4.3 m

Distance between 

collocated monitors

N/A

Unrestricted airflow 360o

Probe material Teflon

Residence time 11 s

Will there be changes 

within the next 18 mos?

No

Is it suitable for 

comparison against the 

annual PM2.5?

N/A

Frequency of flow rate 

verification for manual 

PM samplers 

N/A

Frequency of flow rate 

verification for 

automated PM analyzers 

N/A

Frequency of one-point 

QC check (gaseous)

Every other 

day

Last Annual Performance 

Evaluation (gaseous)

07/27/10

Last two semi-annual 

flow rate audits for PM 

monitors

N/A
49

Martinez

Site Name Martinez

AQS ID 06-013-2001

GIS coordinates 38.0128° N, 122.1345° W

Location Small sampling shelter next to fire station

Address 521 Jones St, Martinez CA 94553

County Contra Costa

Distance to road

from gaseous probe

Jones St: 22 meters

Alhambra Ave: 19 meters

Traffic count

 

Jones St: 2,000 ADT (2008)

Alhambra Ave: 9,800 ADT (2008)

Groundcover Paved

Representative Area San Francisco-Oakland-Fremont MSA

Martinez was chosen for SO2 source impact monitoring because the Shell Oil Refinery is 

located on the northern and eastern borders of the city. The Tesoro Refinery is also nearby, 

2.5 miles to the east. Although the prevailing winds in the area are from the west, east winds 

can transport SO2 emissions from the refineries over populated areas within the city. 

The monitoring site is located near downtown Martinez and 0.5 miles from the Shell 

Refinery property. According to the 2010 census, Martinez has a 2010 population of 35,824. 

There are no industrial activities or SO2 sources nearby other than the refineries. 

VOC toxic compounds are also sampled at Martinez on a 1-in-12 day schedule and analyzed 

in the Air District laboratory. More information about the toxics monitoring program can be 

found in the Toxics Program section of this report.

SO2 concentrations measured at Martinez did not exceed the national 1-hour 75-ppb standard

during the last three years. 
50

Martinez Monitor Information

Pollutant SO2

Monitoring Objective Source Impact

Spatial scale Neighborhood

Sampling method TECO 43C

Analysis method N/A

Start date 07/02/73

Operation schedule Continuous

Sampling season All year

Probe height (AGL) 7.2 m

Probe height above roof 2.7 m

Distance from 

obstructions on roof

None

Distance from 

obstructions not on roof

None

Distance from tree (DL) 11.2 m

Distance to furnace or 

incinerator flue

None

Unrestricted airflow 360°

Probe material Teflon

Residence time 13 s

Will there be changes 

within the next 18 mos?

No

Is it suitable for 

comparison against the 

annual PM2.5?

N/A

Frequency of flow rate 

verification for manual 

PM samplers 

N/A

Frequency of flow rate 

verification for 

automated PM analyzers 

N/A

Frequency of one-point 

QC check (gaseous)

Every other 

Day

Last Annual Performance 

Evaluation (gaseous)

9/15/10

Last two semi-annual 

flow rate audits for PM 

monitors

N/A
51

Napa

Site Name Napa

AQS ID 06-055-0003

GIS coordinates 38.3110° N, 122.2962° W

Location One story commercial building

Address 2552 Jefferson St, Napa CA 94558

County Napa

Distance to road

from gaseous probe

Jefferson St: 15 meters

Traffic count Jefferson St: 19,143 ADT (2007)

Groundcover Paved

Representative Area Napa MSA

Napa was chosen for an air monitoring location because it is the largest city in Napa County 

with a 2010 population of 76,915 according to the 2010 census. The city is located in the 

center of Napa Valley where agricultural burning and fireplace usage during the fall and 

winter can result in high particulate levels. In summer months, Napa can have elevated 

ozone levels when central Bay Area ozone precursors are transported northward into the 

valley.

The air monitoring site is situated about a mile north of downtown Napa in a mixed 

residential and commercial neighborhood. There are no industrial sources in the immediate 

vicinity. Ozone and NO/NO2 are measured because southerly winds carry ozone and its 

precursors into Napa. Carbon monoxide is measured because the Napa Valley is a major 

tourist attraction with resulting high traffic volumes through the city. PM10 and continuous 

PM2.5 are measured because of agricultural and household wood burning.

VOC toxic compounds are also sampled at Napa on a 1-in-12 day schedule and analyzed in 

the Air District laboratory. More information about the toxics monitoring program can be 

found in the Toxics Program section of this report.

During the most recent three years, this site recorded five exceedances of the national

8-hour ozone standard. No exceedances of the national standards for PM10, NO2 or CO were 

measured during the last three years. The continuous PM2.5 (BAM) monitor has recorded 

measurements above the national 24-hour PM2.5 standard on nine days during the most recent

three years and six of those days were during the northern California wildfire outbreak in the 

summer of 2008. This monitor is not a recognized FRM or FEM method, and the data 

cannot be used to determine violations of the national PM2.5 standards, or its attainment 

status. Only FRM or FEM based PM2.5 measurements may be used for comparison with 

national PM2.5 standards.
52

Napa Monitor Information

Pollutant O3 CO NO/NO2

Monitoring

Objective

Population 

oriented

Population 

oriented

Population 

oriented

Spatial scale Middle Middle Middle

Sampling method TECO 49i TECO 48i TECO 42C

PM filter analysis method N/A N/A N/A

Start date 07/01/76 07/01/73 07/01/73

Operation schedule Continuous Continuous Continuous

Sampling season All year All year All year

Probe height (AGL) 8.9 m 8.9 m 8.9 m

Probe height above roof 5.2 m 5.2 m 5.2 m

Distance from 

obstructions on roof

None None None

Distance from 

obstructions not on roof

None None None

Distance from tree (DL) 25 m 25 m 25 m

Distance to furnace or 

incinerator flue

5.7 m 5.7 m 5.7 m

Distance between 

collocated monitors

N/A N/A N/A

Unrestricted airflow 360° 360° 360°

Probe material Teflon Teflon Teflon

Residence time 8 s 8 s 9 s

Will there be changes 

within the next 18 mos?

No No No

Is it suitable for 

comparison against the 

annual PM2.5?

N/A N/A N/A

Frequency of flow rate 

verification for manual 

PM samplers 

N/A N/A N/A

Frequency of flow rate 

verification for 

automated PM analyzers 

N/A N/A N/A

Frequency of one-point 

QC check (gaseous)

Every other 

day

Every other 

day

Every other 

day

Last Annual Performance 

Evaluation (gaseous)

09/07/10 09/07/10 09/07/10

Last two semi-annual 

flow rate audits for PM 

monitors

N/A N/A N/A
53

Napa Monitor Information

Pollutant PM10 PM10 Co

Collocated

Continuous 

PM2.5

BAM

Monitoring

Objective

Population 

oriented

Population 

oriented

Population 

oriented

Spatial scale Middle Middle Middle

Sampling method Tisch Env. 

HiVol TE-6000

Tisch Env. 

HiVol TE-6000

Met One 

BAM 1020

PM filter analysis method Weighed by 

Air District

Weighed by 

Air District

N/A

Start date 11/04/86 06/08/04 01/04/07

Operation schedule 1-in-6 1-in-6 Continuous

Sampling season All year All year All year

Probe height (AGL) 5.5 m 5.3 m 5.5 m

Probe height above roof 1.8 m 1.8 m 1.8 m

Distance from 

obstructions on roof

None None None

Distance from 

obstructions not on roof

None None None

Distance from tree (DL) 21 m 20.7 m 26 m

Distance to furnace or 

incinerator flue

5.0 m 3.4m 8.8 m

Distance between 

collocated monitors

3.4 m 3.4m N/A

Distance between PM10

and PM2.5 monitors

6.1 m 8.8 m Prim: 6.1 m

Col: 8.8 m

Unrestricted airflow 360° 360° 360°

Probe material N/A N/A N/A

Residence time N/A N/A N/A

Will there be changes 

within the next 18 mos?

No No No

Is it suitable for 

comparison against the 

annual PM2.5?

N/A N/A No – not 

reference or 

equivalent 

method

Frequency of flow rate 

verification for manual 

PM samplers 

Weekly Weekly N/A

Frequency of flow rate 

verification for 

automated PM analyzers 

N/A N/A Every two 

weeks

Frequency of one-point 

QC check (gaseous)

N/A N/A N/A

Last Annual Performance 

Evaluation (gaseous)

N/A N/A N/A

Last two semi-annual 

flow rate audits for PM 

monitors

11/18/10

05/18/10

11/18/10

05/18/10

11/18/10

05/18/10
54

Oakland

Site Name Oakland

AQS ID 06-001-0009

GIS coordinates 37.7431 ° N, 122.1699° W

Location Two-story commercial building

Address 9925 International Blvd, Oakland CA 94603

County Alameda

Distance to road

from gaseous probe

International Blvd: 19 meters

99th St: 23 meters

98th St: 43 meters

Traffic count

 

International Blvd: 26,912 ADT (2006)

99th St: 100 ADT (estimate)

98th St: 31,340 ADT (2002)

Groundcover Paved

Representative Area San Francisco-Oakland-Fremont MSA

Oakland is an important area for air pollution monitoring because it is the largest city in 

Alameda County, with a population estimate of 390,724 according to the 2010 census. It has 

large emission sources within its boundaries, such as a major maritime port, an international 

airport, extensive areas of industry, and a number of major freeways. These sources have the 

potential to emit significant amounts of CO and ozone precursors, as well as particulates and 

organic toxic compounds.

The monitoring site is located seven miles southeast of downtown Oakland, on a commercial 

strip in a residential area. Ozone and NO2 are measured to monitor population exposure to 

these pollutants. Carbon monoxide is measured because of the high volume of traffic in the 

city, which includes several major freeways. PM2.5 is measured due to the large emission 

sources in the area, and because light winds combined with wood burning, vehicular traffic, 

and surfaced based inversions during winter can cause elevated particulate concentrations.

VOC toxic compounds are also sampled at Oakland on a 1-in-12 day schedule and analyzed 

in the Air District laboratory. More information about the toxics monitoring program can be 

found in the Toxics Program section of this report.

During the most recent three years, the national 24-hour PM2.5 standard was exceeded once at 

this site. No exceedances of the national standards for ozone, NO2 or CO were measured 

during the last three years.
55

Oakland Monitor Information

Pollutant O3 CO NO/NO2 Continuous 

PM2.5 FEM 

BAM

Monitoring

Objective

Population 

oriented

Population 

oriented

Population 

oriented

Population 

oriented

Spatial scale Middle Middle Middle Middle

Sampling method TECO 49i API 300E TECO 42i Met One FEM 

BAM 1020

Analysis method N/A N/A N/A N/A

Start date 11/01/07 11/01/07 11/01/07 10/01/2009

Operation schedule Continuous Continuous Continuous Continuous

Sampling season All year All year All year All year

Probe height (AGL) 10 m 10 m 10 m 8.0 m

Probe height above roof 4 m 4 m 4 m 2.4 m

Distance from 

obstructions on roof

None None None None

Distance from 

obstructions not on roof

None None None None

Distance from tree (DL) 21 m 21 m 21 m 21 m

Distance to furnace or 

incinerator flue

8.2 m 8.2 m 8.2 m 5.0 m 

Distance between 

collocated monitors

N/A N/A N/A N/A

Unrestricted airflow 360° 360° 360° 360°

Probe material Teflon Teflon Teflon N/A

Residence time 13 s 14 s 13 s N/A

Will there be changes 

within the next 18 mos?

No No No No

Is it suitable for 

comparison against the 

annual PM2.5?

N/A N/A N/A Yes

Frequency of flow rate 

verification for manual 

PM samplers 

N/A N/A N/A N/A

Frequency of flow rate 

verification for 

automated PM analyzers 

N/A N/A N/A Every two 

weeks

Frequency of one-point 

QC check (gaseous)

Every other 

day

Every other 

day

Every other 

day

N/A

Last Annual Performance 

Evaluation (gaseous)

11/18/10 11/18/10 11/18/10 N/A

Last two semi-annual 

flow rate audits for PM 

monitors

N/A N/A N/A 08/25/10

05/18/10
56

Oakland West

Site Name Oakland West

AQS ID 06-001-0011

GIS coordinates 37.8148 ° N, 122.2823° W

Location Trailer in parking lot

Address 1100 21st St, Oakland CA 94607

County Alameda

Distance to road

from gaseous probe

Grand Ave: 34 meters

Linden St: 33 meters

Adeline St: 168 meters

21st St: 80 meters

Traffic count

 

Grand Ave: 19,796 ADT (2002)

Linden St: 500 ADT (estimate)

Adeline St: 7,586 ADT (2002)

21st St: 500 ADT (estimate)

Groundcover Paved

Representative Area San Francisco-Oakland-Fremont MSA

The Air District opened a monitoring station one mile downwind of the Port of Oakland in 

February 2009 because the Port of Oakland is considered a major area source of diesel 

particulate matter emissions. Studies have shown that the West Oakland community is 

exposed to higher concentrations of diesel particulate matter than elsewhere in the Bay Area, 

resulting in higher potential cancer risks. 

Carbon monoxide, NO2, and continuous PM2.5 are measured to determine the impact of 

emissions from the Port of Oakland and its associated diesel-truck traffic, and vehicle traffic 

from nearby highways. SOB2 is measured to determine the impact of emissions from ship 

traffic. Ozone monitoring was added on December 13, 2010. Measurements of all these 

criteria pollutants are also used for comparisons to data obtained from non-standard sampling 

methodologies employed in West Oakland Measurement Study (WOMS) project, described 

later in this report.

Because the Port of Oakland can be a large source of VOC toxic compounds, the Air District 

has been sampling for toxics since 2001 at a site several blocks from the current Oakland 

West monitoring site. Toxics monitoring was moved to the new station when it opened in 

February 2009. VOC toxic compounds are sampled at Oakland West on a 1-in-12 day 

schedule, and analyzed in the Air District laboratory. More information about the toxics 

monitoring program can be found in the Toxics Program section of this report.

There have been no exceedances of the national standards for NO2, SO2 (the new 75 ppb 

standard) or CO since the site opened in February 2009. There have also been no 

measurements above the national 24-hour PM2.5 standard. 
57

Oakland West Monitor Information

Pollutant O3 CO NO/NO2 SO2

Monitoring

Objective

Population 

oriented

Source Impact Source Impact Source Impact

Spatial scale Neighborhood Neighborhood Neighborhood Neighborhood

Sampling method TECO 49C Teledyne 

300E

TECO 42C TECO 43C

Analysis method N/A N/A N/A N/A

Start date 12/13/10 02/25/09 02/25/09 02/25/09

Operation schedule Continuous Continuous Continuous Continuous

Sampling season All year All year All year All year

Probe height (AGL) 5.7 m 5.7 m 5.7 m 5.7 m

Probe height above roof 3.1 m 3.1 m 3.1 m 3.1 m

Distance from 

obstructions on roof

None None None None

Distance from 

obstructions not on roof

None None None None

Distance from tree (DL) 40 m 40 m 40 m 40 m

Distance to furnace or 

incinerator flue

N/A N/A N/A N/A

Distance between 

collocated monitors

N/A N/A N/A N/A

Unrestricted airflow 360° 360° 360° 360°

Probe material Teflon Teflon Teflon Teflon

Residence time 9 s 10 s 10 s 10 s

Will there be changes 

within the next 18 mos?

No No No No

Is it suitable for 

comparison against the 

annual PM2.5?

N/A N/A N/A N/A

Frequency of flow rate 

verification for manual 

PM samplers 

N/A N/A N/A N/A

Frequency of flow rate 

verification for 

automated PM analyzers 

N/A N/A N/A N/A

Frequency of one-point 

QC check (gaseous)

Every other 

day

Every other 

day

Every other 

day

Every other 

day

Last Annual Performance 

Evaluation (gaseous)

12/28/10 07/28/10 07/28/10 07/28/10

Last two semi-annual 

flow rate audits for PM 

monitors

N/A N/A N/A N/A
58

Oakland West Monitor Information

Pollutant Continuous 

PM2.5

BAM

Speciated 

PM2.5

Monitoring Objective Source Impact Source Impact

Spatial scale Neighborhood Neighborhood

Sampling method Met One 

BAM 1020

Met One 

SASS

PM filter analysis 

method

N/A Weighed by 

DRI

Data Start date 02/25/09 02/12/09

Operation schedule Continuous 1-in-6

Sampling season All year All year

Probe height (AGL) 5.2 m 4.7 m

Probe height above roof 2.6 m 2.1 m

Distance from 

obstructions on roof

None None

Dist from obstructions 

not on roof

None None

Dist from tree (DL) 40 m 39 m

Distance to furnace or 

incinerator flue

N/A N/A

Distance between 

collocated monitors

N/A N/A

Distance between PM10

and PM2.5 monitors

BAM to SASS: 

1.1 m

SASS to BAM: 

1.1 m

Unrestricted airflow 360° 360°

Probe material N/A N/A

Residence time N/A N/A

Will there be changes 

w/in the next 18 mos?

No No

Is it suitable for 

comparison against the 

annual PM2.5?

No – not 

reference or 

equivalent 

method

No

Frequency of flow rate 

verification for manual 

PM samplers 

N/A Monthly

Frequency of flow rate 

verification for 

automated PM analyzers 

Every two 

weeks

N/A 

Frequency of one-point 

QC check (gaseous)

N/A N/A

Last Annual Perform. 

Evaluation (gaseous)

N/A N/A

Last two semi-annual 

flow rate audits for PM 

monitors

11/15/10

01/25/10

11/15/10

05/17/10
59

Point Reyes

Site Name Point Reyes

AQS ID 06-041-0003

GIS coordinates 38.1228° N, 122.9083° W

Location At ground level behind a ranger residence

Address 170 Pierce Point Rd, Point Reyes CA 94956

County Marin

Distance to road

from probe

Pierce Point Rd: 95 meters

Traffic count Pierce Point Rd: 225 ADT (estimate)

Groundcover Grass

Representative Area San Francisco-Oakland-Fremont MSA

Point Reyes was chosen for an air monitoring site because it is representative of background 

PM2.5 levels. Air pollution levels at this site are usually low due to the rural nature of the 

area and because the upwind air flow is usually from the Pacific Ocean 2.5 miles to the west.

The site is located within the Point Reyes National Seashore. Within the park are scattered 

dairy farms. There are no industrial sources within 20 miles of the park. Between the ocean 

and the air monitoring site the land is relatively flat with low vegetation. The air monitoring 

site is located behind a ranger residence at the north end of the park. The closest towns are 

Marshall, three miles to the northeast with a population of a few hundred; and Inverness three 

miles to the southeast with a population of 1304 according to the 2010 census.

The continuous PM2.5 (BAM) monitor at Point Reyes recorded two days above the national 

24-hour PM2.5 standard during the most recent three years. However, this monitor is not a 

recognized FRM or FEM method, and the data cannot be used to determine violations of the 

national PM2.5 standards, or its attainment status. Only FRM or FEM based PM2.5 

measurements may be used for comparison with national PM2.5 standards. This site is 

operated by the California Air Resources Board.
60

Point Reyes Monitor Information

Pollutant Continuous 

PM2.5 BAM

Monitoring Objective General 

Background

Spatial scale Regional

Sampling method Met One 

BAM 1020

PM filter analysis method N/A

Start date 12/01/00

Operation schedule Continuous

Sampling season All year

Probe height (AGL) 2.1 m

Probe height above 

ground

2.1 m

Distance from 

obstructions on roof

None

Distance from 

obstructions not on roof

None

Distance from tree (DL) 35 m

Distance to furnace or 

incinerator flue

>50 m

Distance between 

collocated monitors

N/A

Unrestricted airflow 360°

Probe material N/A

Residence time N/A

Will there be changes 

within the next 18 mos?

No

Is it suitable for 

comparison against the 

annual PM2.5?

No – not 

reference or 

equivalent 

method

Frequency of flow rate 

verification for manual 

PM samplers 

N/A

Frequency of flow rate 

verification for automated 

PM analyzers 

2 times per 

month

Frequency of one-point 

QC check (gaseous)

N/A

Last Annual Performance 

Evaluation (gaseous)

N/A

Last two semi-annual 

flow rate audits for PM 

monitors

09/09/10

10/15/09
61

Point Richmond

Site Name Point Richmond

AQS ID 06-013-0005

GIS coordinates 37.9261° N, 122.3856° W

Location Air monitoring shelter next to fire station

Address 140 W. Richmond Ave, Richmond CA 94801

County Contra Costa 

Distance to road

From gaseous probe 

W. Richmond Ave: 10.2 meters 

Interstate 580: 266 meters

Traffic count

 

W. Richmond Ave: 1,340 ADT (2003)

Interstate 580: 70,000 ADT (2007)

Groundcover Paved

Representative Area San Francisco-Oakland-Fremont (MSA)

Point Richmond was chosen for H2S source impact monitoring because the community is at 

the immediate southern periphery of the Chevron Refinery. Although prevailing winds in the 

area are from the south-southwest, occasional northerly winds will transport H2S emissions 

from the refinery over the community. H2S gases at Chevron can be emitted from the

processing units, one mile to the north, or the Chevron Richmond Long Wharf Complex, one 

mile to the west, where crude oil and other feedstock chemicals from tankers are unloaded.

The monitoring site is located in downtown Point Richmond, 0.2 miles south of the Chevron 

Refinery boundary. Point Richmond, a neighborhood within the City of Richmond has a 

population of 3780 according to the 2010 census.
62

Point Richmond Monitor Information

Pollutant H2S

Monitoring

Objective

Source impact

Spatial scale Neighborhood

Sampling method TECO 45C

PM filter analysis method N/A

Data Start date 01/01/99

Operation schedule Continuous

Sampling season All year

Probe height (AGL) 3.4 m

Probe height above roof 0.9 m

Distance from 

obstructions on roof

None

Distance from 

obstructions not on roof

None

Distance from tree (DL) 17 m

Distance to furnace or 

incinerator flue

7.3 m

Distance between 

collocated monitors

N/A

Unrestricted airflow 360o

Probe material Teflon

Residence time 6 s

Will there be changes 

within the next 18 mos?

No

Is it suitable for 

comparison against the 

annual PM2.5?

N/A

Frequency of flow rate 

verification for manual 

PM samplers 

N/A

Frequency of flow rate 

verification for 

automated PM analyzers 

N/A

Frequency of one-point 

QC check (gaseous)

Every two 

weeks

Last Annual Performance 

Evaluation (gaseous)

11/12/10

Last two semi-annual 

flow rate audits for PM 

monitors

N/A
63

Redwood City

Site Name Redwood City

AQS ID 06-081-1001

GIS coordinates 37.4830° N 122.2036° W

Location One-story commercial building

Address 897 Barron Ave, Redwood City CA 94063 

County San Mateo

Distance to road

from gaseous probe 

Barron Ave: 13 meters

Bay Road: 24 meters

Warrington Ave: 131 meters

US Highway 101: 455 meters

Traffic count

 

Barron Ave: 1,200 ADT (2009)

Bay Road: 8350 ADT (2008)

Warrington Ave: 1140 ADT (2008)

US Highway 101: 194,000 ADT (2008) 

Groundcover Paved

Representative Area San Francisco-Oakland-Fremont MSA

Redwood City was chosen for an air monitoring site because it is one of the largest cities in 

San Mateo County, with a population of 76,815 according to the 2010 census. Being

approximately midway between San Francisco and San Jose, it is well positioned to monitor 

the progression of ozone precursors and ozone moving southward down the peninsula as they 

are channeled by the Santa Cruz Mountains. Generally, Redwood City characterizes an area 

between South San Francisco and Palo Alto, which has a low air pollution potential due to 

the frequent presence of the sea breeze. Although the sea breeze typically keeps pollution 

levels low, when winds are light high levels of ozone precursors, ozone, or particulates can 

occur due to the large number of sources in the area. 

The air monitoring site is located in a commercial/industrial zone bordered by US Highway 

101 on one side and residential areas on the other three sides. NO, NO2 and ozone are 

collected because the area is a large source of ozone precursor emissions and ozone. Carbon 

monoxide is monitored because of the high volume of traffic in the area, and US Highway 

101 is only 0.3 miles north of the site. PM2.5 is collected because light winds combined with 

surface-based inversions during the winter months can cause particulate levels to become 

elevated. 

VOC toxic compounds are also sampled at Redwood City on a 1-in-12 day schedule and 

analyzed in the Air District laboratory. More information about the toxics monitoring 

program can be found in the Toxics Program section of this report. 

An FRM PM2.5 monitor at this site acts as the collocated monitor for the FEM PM2.5

monitoring network. The collocated FRM PM2.5 monitor sampling frequency was 1-in-12

days January through March but was increased to 1-in-6 days from April through December 

in order to obtain a larger sample size to compare the FRM concentration to the FEM-BAM 
64

concentration. The Air District plans to continue operating this sampler on a 1-in-6 day 

schedule indefinitely. 

The national 24-hour PM2.5 standard was exceeded on one day during the last three years. No 

exceedances of the national standards for ozone, NO2 or CO were measured during the last 

three years.

Redwood City Monitor Information

Pollutant O3 CO NO/NO2

Monitoring

Objective

Population 

oriented

Population 

oriented

Population 

oriented

Spatial scale Neighborhood Neighborhood Neighborhood

Sampling method TECO 49i TECO 48A TECO 42C

PM filter analysis method N/A N/A N/A

Data Start date 07/01//76 03/01/67 03/01/67

Operation schedule Continuous Continuous Continuous

Sampling season All year All year All year

Probe height (AGL) 6.8 m 6.8 m 6.8 m

Probe height above roof 3.6 m 3.6 m 3.6 m

Distance from 

obstructions on roof

None None None

Distance from 

obstructions not on roof

None None None

Distance from tree (DL) 46 m 46 m 46 m

Distance to furnace or 

incinerator flue

12.7 m 12.7 m 12.7 m

Distance between 

collocated monitors

N/A N/A N/A

Unrestricted airflow 360o 360o 360o 

Probe material Teflon Teflon Teflon

Residence time 10 s 10 s 10 s

Will there be changes 

within the next 18 mos?

No No No

Is it suitable for 

comparison against the 

annual PM2.5?

N/A N/A N/A

Frequency of flow rate 

verification for manual 

PM samplers 

N/A N/A N/A

Frequency of flow rate 

verification for 

automated PM analyzers 

N/A N/A N/A

Frequency of one-point 

QC check (gaseous)

Every other 

day

Every other 

day

Every other 

day

Last Annual Performance 

Evaluation (gaseous)

08/17/10 08/17/10 08/17/10

Last two semi-annual 

flow rate audits for PM 

monitors

N/A N/A N/A
65

Redwood City Monitor Information

Pollutant Continuous 

PM2.5 FEM 

BAM

FRM PM2.5

Collocated

Monitoring Objective Population 

oriented

Population 

oriented

Spatial scale Neighborhood Neighborhood

Sampling method Met One

FEM 1020

Partisol-Plus 

2025 w/VSCC

PM filter analysis method N/A Weighed by Air 

District

Data Start date 10/01/09 10/01/09

Operation schedule Continuous Jan-Mar: 1-in-12

Apr-Dec: 1-in-6

Sampling season All year All year

Probe height (AGL) 5.5 m 5.3 m

Probe height above roof 2.2 m 2.2 m

Distance from 

obstructions on roof

None None

Dist from obstructions 

not on roof

None None

Distance from tree (DL) 47 m 44 m

Distance to furnace or 

incinerator flue

11.0 m 14.0 m

Distance between 

collocated monitors

4 m 4 m

Distance between PM2.5

samplers

BAM to PM2.5: 

4.0 m

PM2.5 to FEM 

BAM : 4.0 m

Unrestricted airflow 360o 360o 

Probe material N/A N/A

Residence time N/A N/A

Will there be changes 

within the next 18 mos?

No No

Is it suitable for 

comparison against the 

annual PM2.5?

Yes Yes

Frequency of flow rate 

verification for manual 

PM samplers 

N/A Monthly

Frequency of flow rate 

verification for 

automated PM analyzers 

Every two 

weeks

N/A 

Frequency of one-pt QC 

check (gaseous)

N/A N/A

Last Annual Perform. 

Evaluation (gaseous)

N/A N/A

Last two semi-annual 

flow rate audits for PM 

monitors

08/16/10

02/09/10

08/16/10

02/09/10
66

Richmond 7th

Site Name Richmond 7th

AQS ID 06-013-0006

GIS coordinates 37.9481° N, 122.3648° W

Location Fire station

Address 1065 7th Street, Richmond CA 94801

County Contra Costa

Distance to road

from gaseous probe

7

th St: 21.4 meters

Hensley St: 29.8 meters 

Richmond Parkway: 200 meters

Traffic count 7

th St: 3,125 ADT (2007)

Hensley St: 2,125 ADT (2007)

Richmond Parkway: 35,650 ADT (2007)

Groundcover Paved

Representative Area San Francisco-Oakland-Fremont MSA

Richmond 7th was chosen for H2S and SO2 source impact monitoring because it is near the 

eastern boundary of the Chevron Refinery. Normally, monitoring is done downwind of the 

prevailing wind direction. However, the prevailing winds are from the south, and carry 

emissions over San Pablo Bay. Since it is impractical to monitor over San Pablo Bay, a 

monitoring site was chosen downwind of the secondary wind direction, on the east side of the 

refinery. The site is located 0.5 miles east of the refinery boundary, where the monitor is 

expected to measure the highest concentrations in an area where the public has access. 

VOC toxic compounds are also sampled at Richmond 7

th on a 1-in-12 day schedule and 

analyzed in the Air District laboratory. More information about the toxics monitoring 

program can be found in the Toxics Program section of this report.

SO2 concentrations measured at Richmond 7th did not exceed the new national 1-hour 75 ppb 

standard during the last three years. 
67

Richmond 7th Monitor Information

Pollutant SO2 H2S

Monitoring

Objective

Source impact Source impact

Spatial scale Neighborhood Neighborhood

Sampling method TECO 43C TECO 43C

PM filter analysis method N/A N/A

Start date 07/01/80 01/01/99

Operation schedule Continuous Continuous

Sampling season All year All year

Probe height (AGL) 8.4 m 8.4 m

Probe height above roof 2.8 m 2.8 m

Distance from 

obstructions on roof

None None

Distance from 

obstructions not on roof

None None

Distance from tree (DL) 10 m 10 m

Distance to furnace or 

incinerator flue

12.2 m 12.2 m

Distance between 

collocated monitors

N/A N/A

Unrestricted airflow 360° 360°

Probe material Teflon Teflon

Residence time 8 s 9 s

Will there be changes 

within the next 18 mos?

No No

Is it suitable for 

comparison against the 

annual PM2.5?

N/A N/A

Frequency of flow rate 

verification for manual 

PM samplers 

N/A N/A

Frequency of flow rate 

verification for 

automated PM analyzers 

N/A N/A

Frequency of one-point 

QC check (gaseous)

Every other 

day

Every two 

weeks

Last Annual Performance 

Evaluation (gaseous)

10/21/10 10/21/10

Last two semi-annual 

flow rate audits for PM 

monitors

N/A N/A
68

Rodeo

Site Name Rodeo

AQS ID 06-013-0007

GIS coordinates 38.0343o N, 122.2704o W

Location Single story storage area at fire station

Address 326 Third Street, Rodeo CA 94572

County Contra Costa

Distance to road

from gaseous probe

Third St: 13.3 meters

Parker St: 249.0 meters

Traffic count Third St: 500 ADT (estimate)

Parker St: 7,316 ADT (2008)

Groundcover Paved

Representative Area San Francisco-Oakland-Fremont (MSA)

Rodeo was chosen for H2S source impact monitoring because the ConocoPhillips Refinery is 

on the eastern boundary of the town of Rodeo. Although the prevailing winds in the area are 

from the southwest, northeast winds can transport H2S emissions from the refinery over the 

populated area of the town. The population of Rodeo is 8,679 according to the 2010 census. 

The monitoring site is located in a residential area 0.6 miles southwest of the ConocoPhillips 

Refinery boundary.
69

Rodeo Monitor Information

Pollutant H2S

Monitoring Objective Source impact

Spatial scale Neighborhood

Sampling method TECO 45C

PM filter analysis method N/A

Start date 04/01/02

Operation schedule Continuous

Sampling season All year

Probe height (AGL) 6.7 m

Probe height above roof 2.0 m

Distance from 

obstructions on roof

None

Distance from 

obstructions not on roof

None

Distance from tree (DL) >50 m

Distance to furnace or 

incinerator flue 

10.9 m

Distance between 

collocated monitors 

N/A

Unrestricted airflow 360°

Probe material Teflon

Residence time 15 s

Will there be changes 

within the next 18 mos?

No

Is it suitable for 

comparison against the 

annual PM2.5?

N/A

Frequency of flow rate 

verification for manual 

PM samplers audit

N/A

Frequency of flow rate 

verification for 

automated PM analyzers 

N/A

Frequency of one-point 

QC check (gaseous)

Every two 

weeks

Last Annual Performance 

Evaluation (gaseous)

09/08/10

Last two semi-annual 

flow rate audits for PM 

monitors

N/A
70

San Francisco

Site Name San Francisco

AQS ID 06-075-0005

GIS coordinates 37.7659° N, 122.3990° W

Location One-story commercial building 

Address 10 Arkansas St, Suite N, San Francisco CA 94107

County San Francisco

Distance to road

from gaseous probe

16th St: 32.0 meters

Arkansas St: 17.0 meters

Interstate 280: 300 meters

U.S. Highway 101: 504 meters

Traffic count 16th St: 12,278 ADT (2006)

Arkansas St: 500 ADT (estimate)

Interstate 280: 88,000 ADT (2009)

U.S. Highway 101: 225,000 (2009)

Groundcover Paved

Representative Area San Francisco-Oakland-Fremont MSA

San Francisco was chosen for an air monitoring site because it is the second largest city in 

the San Francisco Bay Area, with a population of 805,235 according to the 2010 census. 

Although the sea breeze typically keeps pollution levels low, light wind conditions can result 

in high levels of ozone precursors or particulates due to the large number of sources in the 

city. The east side of the city was selected for a monitoring site because it is more densely 

populated (including a large number of daytime visitors and commuters), has some industry, 

and as a transportation hub, has generally higher traffic volume. The site is located near the 

fringe of the central business district, in an area of light industry that is close to a residential 

area and two major freeways. 

Ozone is measured because of the very high population density of the city. NO/NO2 and 

CH4/NMHC have been measured because this is a source area for these ozone precursors. 

Carbon monoxide is measured because of the high traffic volume. PM10 and PM2.5 are 

measured because stagnant days combined with surface based-based inversions can cause 

elevated particulate levels, and because of the contribution of heavy vehicular traffic to PM 

levels. 

Monitoring of CH4/NMHC was discontinued on September 30, 2010 because of the 

development of PAMS network (described elsewhere in this report), which is a more 

effective allocation of resources. The PAMS network better defines the measurement and 

sources of ozone precursors, making additional measurements of CH4/NMHC at San 

Francisco superfluous. 

VOC toxic compounds are sampled at San Francisco by both the Air District and CARB on a

1-in-12 day schedule and analyzed by their respective laboratories. Carbonyls and metals are 

also sampled by CARB on the same 1-in-12 day schedule. Information about the CARB 

toxics monitoring program can be found at http://www.arb.ca.gov/toxics/toxics.htm. 
71

Information about toxics monitoring by the Air District can be found in the Toxics Program 

section of this report.

During the most recent three years, the national 24-hour PM2.5 standard was exceeded on four 

days. No exceedances of the national standards for ozone, PM10, NO2, or CO were measured 

in the last three years.

San Francisco Monitor Information

Pollutant O3 CO NO/NO2 CH4/NMHC*

Monitoring

Objective

Population 

oriented

Population 

oriented

Population 

oriented

Population 

oriented

Spatial scale Neighborhood Neighborhood Neighborhood Neighborhood

Sampling method TECO 49C TECO 48 TECO 42i TECO 55C

PM Filter Analysis 

method

N/A N/A N/A N/A

Start date 01/01/86 01/01/86 NO: 12/01/85

NO2: 01/01/86

CH4: 01/01/94

NMHC: 07/12/06

Operation schedule Continuous Continuous Continuous Continuous*

Sampling season All year All year All year All year*

Probe height (AGL) 10.5 m 10.5 m 10.5 m 10.5 m

Probe height above roof 4.4 m 4.4 m 4.4 m 4.4 m

Distance from 

obstructions on roof

None None None None

Distance from 

obstructions not on roof

None None None None

Distance from tree (DL) 15.3 m 15.3 m 15.3 m 15.3 m

Distance to furnace or 

incinerator flue

5.2 m 5.2 m 5.2 m 5.2 m

Distance between 

collocated monitors

N/A N/A N/A N/A

Unrestricted airflow 360° 360° 360° 360°

Probe material Teflon Teflon Teflon Teflon

Residence time 10 s 10 s 11 s 11 s

Will there be changes 

within the next 18 mos?

No No No Monitor 

closed

Is it suitable for 

comparison against the 

annual PM2.5?

N/A N/A N/A N/A

Frequency of flow rate 

verification for manual 

PM samplers 

N/A N/A N/A N/A

Frequency of flow rate 

verification for 

automated PM analyzers 

N/A N/A N/A N/A

Frequency of one-point 

QC check (gaseous)

Every other 

day

Every other 

day

Every other 

day

Every other 

day

Last Annual Performance 

Evaluation (gaseous)

09/16/10 09/16/10 09/16/10 09/16/10

Last two semi-annual 

flow rate audits for PM 

monitors

N/A N/A N/A N/A

* CH4/NMHC analyzer removed from service on September 30, 2010.
72

San Francisco Monitor Information

Pollutant PM10 Continuous 

PM2.5 FEM 

BAM

Monitoring

Objective

Population 

oriented

Population 

oriented

Spatial scale Neighborhood Neighborhood

Sampling method Andersen 

HiVol 1200

Met One FEM 

BAM 1020

PM Filter Analysis 

method

Weighed by 

Air District

N/A

Start date 11/16/86 10/01/09

Operation schedule 1-in-6 Continuous

Sampling season All year All year

Probe height (AGL) 7.6 m 8.3 m

Probe height above roof 1.5 m 2.2 m

Distance from

obstructions on roof

None None

Distance from 

obstructions not on roof

None None

Distance from tree (DL) 17.5 m 15.9 m

Distance to furnace or 

incinerator flue

7.0 m 7.3 m 

Distance between 

collocated monitors

N/A N/A

Distance between PM10

and PM2.5 samplers

2.3 m 2.3 m

Unrestricted airflow 360° 360°

Probe material N/A N/A

Residence time N/A N/A

Will there be changes 

within the next 18 mos?

No No

Is it suitable for 

comparison against the 

annual PM2.5?

N/A Yes

Frequency of flow rate 

verification for manual 

PM samplers 

Weekly N/A

Frequency of flow rate 

verification for 

automated PM analyzers 

N/A Every two 

weeks

Frequency of one-point 

QC check (gaseous)

N/A N/A

Last Annual Performance 

Evaluation (gaseous)

N/A N/A

Last two semi-annual 

flow rate audits for PM 

monitors

12/09/10

06/08/10

12/09/10

06/08/10
73

San Jose 

Site Name San Jose

AQS ID 06-085-0005

GIS coordinates 37.3485° N, 121.8949° W

Location Top floor of two-story commercial building

Address 158 E. Jackson St, San Jose CA 95112

County Santa Clara

Distance to road

from gaseous probe

Jackson St: 15.1 meters

4

th St: 34.7 meters

Traffic count

 

Jackson St: 3,990 ADT (2007)

4

th St: 6,000 ADT (2007)

Groundcover Paved

Representative Area San Jose-Sunnyvale-Santa Clara MSA

San Jose was chosen for an air monitoring site because it is the largest city in Santa Clara 

County and the largest city in the Bay Area, with a population of 945,942 according to the 

2010 census. 

Ozone precursors emitted within the central San Francisco Bay Area are often carried into 

the San Jose area by the prevailing northwesterly winds. The northern half of the Santa Clara 

Valley is densely populated and the associated activities of the residents also add significant 

pollutant emissions into the air. 

The air monitoring site is located in the center of northern Santa Clara Valley, in a 

commercial and residential part of downtown San Jose. This area is completely encircled by 

major freeways, and has a large airport just to the west-northwest. The air quality in this 

location is representative of a large part of the valley due to the diurnal up valley and down 

valley air flow, which mixes the pollutants throughout the valley. 

NO/NO2, CH4/NMHC and ozone are monitored because of the large amount of ozone 

precursor emissions near the area as well as from upwind areas. Carbon monoxide is 

measured because of the significant traffic volume in the area. PM10 and PM2.5 are monitored 

because light winds combined with surface based inversions within the valley during winter 

months can cause elevated particulate levels. 

Gaseous VOC toxic compounds, carbonyls, and metals are sampled at San Jose on a one in 

six day schedule as part of the NATTS program. Gaseous toxic compounds and carbonyls 

are analyzed by the Air District laboratory while metals are analyzed by an outside 

laboratory. CARB also does sampling for VOC toxic compounds, carbonyls, and metals at 

San Jose but this sampling is on a 1-in-12 day schedule and the analysis is done by the 

CARB laboratory. More information about the CARB toxics monitoring program can be 

found at http://www.arb.ca.gov/toxics/toxics.htm. Information about toxics monitoring by 

the Air District can be found in the Toxics Program section of this report.
74

The San Jose station was approved by EPA as a National Core (NCore) multi-pollutant 

monitoring station on October 30, 2009 with NCore air monitoring to begin on January 1, 

2011. The NCore program requires reporting of PM coarse (PM10-2.5) every 3rd day. 

Consequently, in 2011 the PM10 sampling frequency will change from 1-in-6 days to

1-in-3 days and the PM2.5 summer frequency will change from 1-in-6 days to 1-in-3 days. 

On December 14, 2010, EPA revised the monitoring requirements for lead and required lead 

monitoring at NCore sites. The lead measurements at San Jose will come from PM10 filters 

on a 1-in-6 day schedule. Because PM10 is sampled on a 1-in-3 day schedule, only every 2nd

PM10 filter will undergo lead measurements starting in January 2011.

Monitoring of NOy began at San Jose on January 1, 2011 to meet NCore requirements. NOy 

is total reactive nitrogen and plays an important role in ozone formation. A full description 

of the NCore monitoring program can be found in the NCore section of this document.

In the most recent three years, this site recorded five exceedances of the national 8-hour 

ozone standard and eight exceedances of the national 24-hour PM2.5 standard. No 

exceedances of the national standards for PM10, NO2, SO2 (the new 75 ppb 1-hour standard) 

or CO were measured during the last three years. 
75

San Jose Monitor Information

Pollutant O3 CO* NO/NO2 CH4/NMHC SO2*

Monitoring

Objective

Population 

oriented

Population 

oriented & 

Highest 

concentration

Population 

oriented &

Highest 

concentration

Population 

oriented

Population 

oriented

Spatial scale Neighborhood Neighborhood Neighborhood Neighborhood Neighborhood

Sampling method TECO 49i TECO 48iTLE TECO 42C TECO 55C TECO 43iTLE

PM filter analysis method N/A N/A N/A N/A N/A

Data start date 11/01/02 11/01/02 11/01/02 CH4: 11/22/02

NMHC: 07/06/06

02/10/09

Operation schedule Continuous Continuous Continuous Continuous Continuous

Sampling season All year All year All year All year All year

Probe height (AGL) 11.9 m 11.9 m 11.9 m 11.9 m 11.9 m

Probe height above roof 4.3 m 4.3 m 4.3 m 4.3 m 4.3 m

Distance from 

obstructions on roof

None None None None None

Distance from 

obstructions not on roof

None None None None None

Distance from tree (DL) 13.1 m 13.1 m 13.1 m 13.1 m 13.1 m

Distance to furnace or 

incinerator flue

4.6 m 4.6 m 4.6 m 4.6 m 4.6 m

Distance between 

collocated monitors

N/A N/A N/A N/A N/A

Unrestricted airflow 360o 360o 360o 360o 360o 

Probe material Teflon Teflon Teflon Teflon Teflon

Residence time 11 s 12 s 11 s 11 s 12 s

Will there be changes 

within the next 18 mos?

No No No No No

Is it suitable for 

comparison against the 

annual PM2.5?

N/A N/A N/A N/A N/A

Frequency of flow rate 

verification for manual 

PM samplers 

N/A N/A N/A N/A N/A

Frequency of flow rate 

verification for 

automated PM analyzers 

N/A N/A N/A N/A N/A

Frequency of one-point 

QC check (gaseous)

Every other 

day

Every other 

day

Every other 

day

Every other 

day

Every other 

day

Last Annual Performance 

Evaluation (gaseous)

05/05/10 08/20/10 05/05/10 05/05/10 08/11/10

Last two semi-annual 

flow rate audits for PM 

monitors

N/A N/A N/A N/A N/A

 * High sensitivity instruments required for CO and SO2 at NCore sites.
76

San Jose Monitor Information

Pollutant PM10* FRM PM2.5 Continuous 

PM2.5 BAM

Speciated 

PM2.5

Monitoring Objective Population 

oriented

Population 

oriented

Population 

oriented

Population 

oriented

Spatial scale Neighborhood Neighborhood Neighborhood Neighborhood

Sampling method Partisol 2025*

without VSCC

Partisol-Plus 

2025 w/VSCC

Met One 

Model 1020

Met One 

SASS

PM filter analysis method Weighed by 

Air District

Weighed by 

Air District

N/A Weighed by 

RTI

Data start date 10/15/02 10/05/02 01/01/04 10/05/02

Operation schedule 1-in-6 Apr-Sep:1-in-6

Oct-Mar: daily

Continuous 1-in-3

Sampling season All year All year All year All year

Probe height 8.9 m 8.9 m 9.8m 8.9 m

Probe height above roof 2.2 m 2.2 m 2.0 m 2.1 m

Distance from 

obstructions on roof

None None None None

Dist from obstructions 

not on roof

None None None None

Distance from tree (DL) 11.0 m 14.9 m 11.9 m 16.1 m

Distance to furnace or 

incinerator flue

1.5 m 3.0 m 3.4 m 2.4 m

Distance between 

collocated monitors

N/A N/A N/A N/A

Distance between PM10

and PM2.5 samplers

PM10 to PM2.5:

3.2m

PM10 to SASS:

4.1m

PM10 to BAM:

3.5 m

PM2.5 to PM10:

3.2 m

PM2.5 to PM10: 

4.1 m

PM2.5 to BAM: 

3.9 m

BAM to PM10: 

3.5 m

BAM to PM2.5: 

3.9 m

BAM to SASS: 

7.9 m

SASS to PM10: 

4.1 m

SASS to BAM: 

7.9 m

SASS to PM2.5: 

4.1 m

Unrestricted airflow 360

o

360o 360o 360o

Probe material N/A N/A N/A N/A

Residence time N/A N/A N/A N/A

Will there be changes 

within the next 18 mos?

No No No No

Is it suitable for 

comparison against the 

annual PM2.5?

N/A Yes No – not 

reference or 

equivalent 

method

No

Frequency of flow rate 

verification for manual 

PM samplers 

Monthly Monthly N/A Monthly

Frequency of flow rate 

verification for 

automated PM analyzers 

N/A N/A Every two 

weeks

N/A

Frequency of 1-pt QC 

check (gaseous)

N/A N/A N/A N/A

Last Annual Perform. 

Evaluation (gaseous)

N/A N/A N/A N/A

Last two semi-annual 

flow rate audits for PM 

monitors

08/10/10

02/02/10

08/10/10

02/02/10

08/10/10

02/02/10

05/04/10

02/02/10

*

Partisol 2025 Low Volume replaced Anderson 1200 HiVol on 12/22/10.
77

San Martin

Site Name San Martin

AQS ID 06-085-2006

GIS coordinates 37.0794° N 121.6000° W

Location Air monitoring shelter next to maintenance shed

Address 13030 Murphy Ave, San Martin CA 95046 

County Santa Clara

Distance to road

from gaseous probe 

Murphy Ave: 57.0 meters

US Highway 101: 455 meters

Traffic count Murphy Ave: 400 ADT (2009)

US Highway 101: 107,000 ADT (2008)

Groundcover Vegetative

Representative Area San Jose- Sunnyvale- Santa Clara MSA

San Martin was chosen as an ozone air monitoring site because earlier field measurements 

showed this area to have the highest ozone concentrations in the Santa Clara Valley. 

Prevailing winds transport ozone and ozone precursors down the valley from the densely 

populated San Jose area as well as the surrounding San Francisco Bay. Because ozone is 

formed by a chemical reaction between organic and nitrogen oxide gases in the presence of 

sunlight, the highest ozone concentrations are usually observed tens of miles downwind from 

the highest concentration of emission sources (freeways, power generating facilities, etc.) 

because the reactions involving the organic gases are relatively slow.

San Martin is located in an agricultural area at the south end of the Santa Clara Valley 

approximately 24 miles southeast of downtown San Jose. The town has a small population of 

7,027 (2010 Census) and no industrial sources. The monitoring site is located at the South 

County Airport, in the center of the valley and about 0.3 miles west of US Highway 101.

In the most recent three years, this site recorded eleven exceedances of the national 8-hour 

ozone standard. 
78

San Martin Monitor Information

Pollutant O3

Monitoring

Objective

Highest 

concentration

Spatial scale Neighborhood

Sampling method TECO 49C

PM filter analysis method N/A

Data Start date 04/30/94

Operation schedule Continuous

Sampling season Apr 1 – Nov 30

Probe height (AGL) 4.8 m

Probe height above roof 2.8 m

Distance from 

obstructions on roof

None

Distance from 

obstructions not on roof

None

Distance from tree (DL) 23 m

Distance to furnace or 

incinerator flue

N/A

Distance between 

collocated monitors

N/A

Unrestricted airflow 360o

Probe material Teflon

Residence time 14 s

Will there be changes 

within the next 18 mos?

No

Is it suitable for 

comparison against the 

annual PM2.5?

N/A

Frequency of flow rate 

verification for manual 

PM samplers 

N/A

Frequency of flow rate 

verification for 

automated PM analyzers 

N/A

Frequency of one-point 

QC check (gaseous)

Every other 

day

Last Annual Performance 

Evaluation (gaseous)

07/26/10

Last two semi-annual 

flow rate audits for PM 

monitors

N/A
79

San Pablo

Site Name San Pablo

AQS ID 06-013-1004

GIS coordinates 37.96041° N, 122.35685° W

Location One story commercial building

Address 1865-D Rumrill Blvd, San Pablo CA 94806

County Contra Costa

Distance to road

from gaseous probe

Rumrill Blvd: 15.8 meters

Traffic count Rumrill Blvd: 16,800 ADT (2010)

Groundcover Paved

Representative Area San Francisco-Oakland-Fremont MSA

San Pablo was chosen for an air monitoring site because the area is in the most populated 

portion of western Contra Costa County. San Pablo, with a population of 29,139 (according 

to the 2010 census), is almost completely surrounded by the city of Richmond. Richmond 

has a population of 103,701 according to the 2010 census. This area has heavy industry, high 

traffic volume, including two major freeways, and it is very close to the Chevron Refinery. 

Ozone and NO2 are measured because the area is downwind of the central San Francisco Bay 

Area, which is a large source of ozone precursor emissions. Carbon monoxide is measured 

because the high traffic volume in the area. SO2 is measured because the site is 1.2 miles 

downwind of the Chevron refinery, which can be a significant source of SO2 emissions. 

PM10 is measured because stagnant days in the fall and winter can result in elevated 

particulate levels. 

VOC toxic compounds are also sampled at San Pablo on a 1-in-12 day schedule and analyzed 

in the Air District laboratory. More information about the toxics monitoring program can be 

found in the Toxics Program section of this report.

The station was temporarily closed from March 2009 to May 2010 due to heavy damage 

from a fire in the building.

This site recorded one exceedance of the national 8-hour ozone standard during the last three

years (as noted above, operations were suspended during a portion of this period). No 

exceedances of the national standards for NO2, SO2 (the new 75 ppb 1-hour standard), CO or 

PM10 were measured during the past three years.
80

San Pablo Monitor Information

Pollutant O3 CO NO/NO2 SO2 PM10

Monitoring

Objective

Population 

oriented

Population 

oriented

Population 

oriented

Source Impact Population 

oriented

Spatial scale Middle Middle Middle Neighborhood Middle

Sampling method TECO 49i TECO 48i TECO 42i TECO 43i Tisch Env. 

HiVol TE-6000

PM filter analysis 

method

N/A N/A N/A N/A Weighed by 

Air District

Start date 09/13/02 09/13/02 09/13/02 09/13/02 09/23/02

Operation schedule Continuous Continuous Continuous Continuous 1-in-6

Sampling season All year All year All year All year All year

Probe height (AGL) 9.0 m 9.0 m 9.0 m 9.0 m 6.4 m

Probe height above roof 5.6 m 5.6 m 5.6 m 5.6 m 2.2 m

Distance from 

obstructions on roof

None None None None None

Distance from 

obstructions not on roof

None None None None None

Distance from tree (DL) >50 m >50 m >50 m >50 m >50 m

Distance to furnace or 

incinerator flue

None None None None None

Distance between 

collocated monitors

N/A N/A N/A N/A N/A

Unrestricted airflow 360° 360° 360° 360° 360°

Probe material Teflon Teflon Teflon Teflon N/A

Residence time 8 s 9 s 8 s 8 s N/A

Will there be changes 

within the next 18 mos?

No No No No No

Is it suitable for 

comparison against the 

annual PM2.5?

N/A N/A N/A N/A N/A

Frequency of flow rate 

verification for manual 

PM samplers 

N/A N/A N/A N/A Weekly

Frequency of flow rate 

verification for 

automated PM analyzers 

N/A N/A N/A N/A N/A

Frequency of one-point 

QC check (gaseous)

Every other 

day

Every other 

day

Every other 

day

Every other 

day

N/A

Last Annual Performance 

Evaluation (gaseous)

06/02/10 06/02/10 06/02/10 06/02/10 N/A

Last two semi-annual 

flow rate audits for PM 

monitors

N/A N/A N/A N/A 11/18/10

06/02/10
81

San Rafael

Site Name San Rafael

AQS ID 06-041-0001

GIS coordinates 37.9724° N, 122.5200° W

Location Second floor of two-story commercial building

Address 534 4

th Street, San Rafael CA 94901

County Marin

Distance to road

from gaseous probe

4

th St: 18 meters

Irwin St: 48 meters

US Highway 101: 112 meters

Traffic count

 

4

th St: 4,248 ADT (2010)

Irwin St: 17,531 ADT (2007)

US Highway 101: 150,500 ADT (2009)

Groundcover Paved

Representative Area San Francisco-Oakland-Fremont MSA

San Rafael was chosen for an air monitoring site because it is the largest city in Marin 

County with a population of 57,713 according to the 2010 census. The city’s climate and air 

quality is representative of that found throughout the populous eastern side of the county. 

Afternoon sea breezes typically keep pollution levels low. However, when the sea breeze is 

absent, local sources can cause elevated pollution levels.

The monitoring site is located in a commercial building about a block east of US Highway 

101 and near major highway access ramps. It is one half mile east of the downtown San 

Rafael business district. There is no industrial activity in the immediate area. Ozone and 

NO/NO2 are measured to monitor general population exposure to these pollutants. Carbon 

monoxide and PM10 are measured because the site is close to a major transportation corridor. 

PM2.5 is measured because light winds combined with wood burning, vehicular traffic, and 

surfaced based inversions during winter can cause elevated particulate concentrations.

VOC toxic compounds are also sampled at San Rafael on a 1-in-12 day schedule and 

analyzed in the Air District laboratory. More information about the toxics monitoring 

program can be found in the Toxics Program section of this report.

In October 2009, a continuous Federal Equivalent Method (FEM) PM2.5 monitor was added 

to this site as the Air District’s PM2.5 network was expanded to have at least one monitor per 

county. The FEM PM2.5 monitor provides hourly measurements of PM2.5 concentrations.

Since PM2.5 monitoring began in October 2009, four exceedances of the national 24-hour 

PM2.5 standard have been measured. No exceedances of the national standards for ozone, 

PM10, NO2 or CO were measured during the last three years.
82

San Rafael Monitor Information

Pollutant O3 CO NO/NO2 PM10 Continuous 

PM2.5 FEM

BAM

Monitoring

Objective

Population 

oriented

Population 

oriented

Population 

oriented

Population 

oriented

Population 

oriented

Spatial scale Middle Middle Middle Middle Middle

Sampling method TECO 49i TECO 48i TECO 42C Andersen 

HiVol 1200

Met One

FEM 1020

PM filter Analysis 

method

N/A N/A N/A Weighed by 

Air District

N/A

Start date 07/01/76 10/01/67 NO: 01/01/68

NO2:10/01/67

11/04/86 10/27/09

Operation schedule Continuous Continuous Continuous 1-in-6 Continuous

Sampling season All year All year All year All year All year

Probe height (AGL) 11.9 m 11.9 m 11.9 m 7.0 m 7.1 m

Probe height above roof 5.2 m 5.2 m 5.2 m 1.9 m 2.0 m

Distance from 

obstructions on roof

None None None None None

Distance from 

obstructions not on roof

21 m 21 m 21 m 20 m 18.5 m

Distance from tree (DL) 14 m 14 m 14 m 15 m 12.5 m

Distance to furnace or 

incinerator flue

3.5 m 3.5 m 3.5 m 2.3 m 3.4 m

Distance between 

collocated monitors

N/A N/A N/A N/A N/A

Distance between

PM10 and PM2.5

samplers

N/A N/A N/A 3.2 m 3.2 m

Unrestricted airflow 360° 360° 360° 360° 360°

Probe material Teflon Teflon Teflon N/A N/A

Residence time 11 s 11 s 13 s N/A N/A

Will there be changes 

within the next 18 mos?

No No No No No

Is it suitable for 

comparison against the 

annual PM2.5?

N/A N/A N/A N/A Yes

Frequency of flow rate 

verification for manual 

PM samplers 

N/A N/A N/A Weekly Every two 

weeks

Frequency of flow rate 

verification for 

automated PM analyzers 

N/A N/A N/A N/A N/A

Frequency of one-point 

QC check (gaseous)

Every other 

day

Every other 

day

Every other 

day

N/A N/A

Last Annual Performance 

Evaluation (gaseous)

09/21/10 09/21/10 09/21/10 N/A N/A

Last two semi-annual 

flow rate audits for PM 

monitors

N/A N/A N/A 12/07/10

06/15/10

12/07/10

06/15/10
83

Santa Rosa

Site Name Santa Rosa

AQS ID 06-097-0003

GIS coordinates 38.4435° N, 122.7102° W

Location Second floor of two-story commercial building

Address 837 5th St, Santa Rosa CA 95404

County Sonoma

Distance to road

from gaseous probe

5

th St: 24 meters

E St: 79 meters

College Ave: 210 meters

Brookwood Ave: 228 meters

US Highway 101: 918 meters

Traffic count

 

5

th St: 2,347 ADT (2009)

E St: 5,876 ADT (2009)

College Ave: 13,304 ADT (2009)

Brookwood Ave: 15,604 ADT (2009)

US Highway 101: 109,000 ADT (2009)

Groundcover Paved

Representative Area Santa Rosa-Petaluma MSA

Santa Rosa was chosen for an air monitoring site because it is the largest city in Sonoma 

County with a population of 167,814 according to the 2010 census. The city’s climate is 

strongly influenced by the Pacific Ocean and the marine air flow typically keeps pollution 

levels low. However, during light winds or strong nighttime temperature inversions, local 

sources can cause elevated pollution levels. The monitoring site is located just east of the 

downtown urban core and 0.5 miles east of US Highway 101.

There are no industrial sources in the immediate area. Ozone and NO/NO2 are measured to 

monitor general population exposure to these pollutants. Carbon monoxide is measured 

because of the local urban traffic volume and proximity to the Highway 101 transportation 

artery. PM2.5 is measured because light winds combined with wood burning, vehicular 

traffic, and surface based-based inversions during the winter months can cause elevated 

particulate concentrations.

VOC toxic compounds are also sampled at Santa Rosa on a 1-in-12 day schedule and 

analyzed in the Air District laboratory. More information about the toxics monitoring 

program can be found in the Toxics Program section of this report.

Pollutant concentrations measured at Santa Rosa did not exceed the national standards for 

ozone, PM2.5, NO2 or CO during the last three years.
84

Santa Rosa Monitor Information

Pollutant O3 CO NO/NO2 Continuous 

PM2.5 FEM 

BAM

Monitoring

Objective

Population 

oriented

Population 

oriented

Population 

oriented

Population 

oriented

Spatial scale Neighborhood Neighborhood Neighborhood Neighborhood

Sampling method TECO 49i TECO 48i TECO 42i Met One

FEM 1020

Analysis method N/A N/A N/A N/A

Start date 04/17/81 04/17/81 NO: 01/01/82 

NO2:04/17/81

10/23/09

Operation schedule Continuous Continuous Continuous Continuous

Sampling season All year All year All year All year

Probe height (AGL) 10.7 m 10.7 m 10.7 m 8.1 m

Probe height above roof 5.2 m 5.2 m 5.2 m 2.0 m

Distance from 

obstructions on roof

None None None None

Distance from 

obstructions not on roof

21 m 21 m 21 m 21 m

Distance from tree (DL) 13.7 m 13.7 m 13.7 m 13.7 m

Distance to furnace or 

incinerator flue

4.7 m 4.7 m 4.7 m 5.7 m

Distance between 

collocated monitors

N/A N/A N/A N/A

Unrestricted airflow 360° 360° 360° 360°

Probe material Teflon Teflon Teflon N/A

Residence time 8 s 10 s 9 s N/A

Will there be changes 

within the next 18 mos?

No No No No

Is it suitable for 

comparison against the 

annual PM2.5?

N/A N/A N/A Yes 

Frequency of flow rate 

verification for manual 

PM samplers 

N/A N/A N/A Every two 

weeks

Frequency of flow rate 

verification for 

automated PM analyzers 

N/A N/A N/A N/A

Frequency of one-point 

QC check (gaseous)

Every other 

day

Every other 

day

Every other 

day

N/A

Last Annual Performance 

Evaluation (gaseous)

12/08/10 12/08/10 12/08/10 N/A

Last two semi-annual 

flow rate audits for PM 

monitors

N/A N/A N/A 12/07/10

06/15/10
85

Vallejo

Site Name Vallejo

AQS ID 06-095-0004

GIS coordinates 38.1025° N, 122.2380° W

Location One story commercial building 

Address 304 Tuolumne St, Vallejo CA 94590

County Solano

Dist. to road

from probe

Tuolumne St: 18 meters

Capitol St: 30 meters

Solano Ave: 33 meters

Interstate 80: 700 meters

Traffic count Tuolumne St: 5,100 ADT (2008)

Capitol St: 500 ADT (estimate)

Solano Ave: 8,600 ADT (2008)

Interstate 80: 141,000 ADT (2009)

Groundcover Paved

Representative Area Vallejo-Fairfield MSA

Vallejo was chosen for an air monitoring site because it is the largest city in Solano County 

with a population of 115,942 according to the 2010 census. Vallejo has the potential to be 

impacted by pollution from three directions: southwest winds bringing ozone and ozone 

precursors from the San Francisco Bay Area, north winds bringing particulates from the 

Napa Valley, and east winds bringing ozone and particulates from the Central Valley.

The monitoring site is located in a mixed commercial and residential neighborhood one mile 

east of downtown and 0.5 miles west of Interstate 80. Ozone and NO/NO2 are measured 

because southerly winds can transport ozone and its precursors into Vallejo from the heavily 

populated central Bay Area. Easterly winds can transport ozone from the Central Valley 

through the Carquinez Strait.

PM2.5 is measured because high concentrations typically occur during the winter when 

nighttime valley drainage winds, wood burning, and shallow temperature inversions trap 

pollutants from local sources and the Napa Valley to the north. East winds can also transport 

particulate into Vallejo through the Carquinez Strait from the Central Valley.

Carbon monoxide is measured because Interstate 80 passes through the middle of the urban 

area east of the monitoring site. SO2 is measured at Vallejo to monitor general population 

exposure and because refineries located to the south and east can be significant sources of 

SO2.

Continuous PM2.5 (BAM) monitoring was discontinued after September 13, 2010 because the 

Air District was preparing to install and test a continuous PM2.5 FEM-BAM monitor. 

Testing was completed in late 2010 and both the new PM2.5 FEM-BAM and the existing 

PM2.5 FRM operated daily from January 1, 2011 through February 28, 2011. On March 1, 
86

2011 the continuous FEM-BAM monitor replaced the FRM monitor and the FRM monitor 

was removed. 

VOC toxic compounds are also sampled at Vallejo on a 1-in-12 day schedule and analyzed in 

the Air District laboratory. More information about the toxics monitoring program can be 

found in the Toxics Program section of this report.

During the most recent three years, this site recorded one exceedance of the national 8-hour 

ozone standard and the national 24-hour PM2.5 standard was exceeded on twelve days. No 

exceedances of the national standards for NO2, SO2 (the new 75 ppb 1-hour standard) or CO

were measured during the last three years. 
87

Vallejo Monitor Information

Pollutant O3 CO NO/NO2 SO2

Monitoring

Objective

Population 

oriented

Population 

oriented

Population 

oriented

Population 

oriented

Spatial scale Neighborhood Neighborhood Neighborhood Neighborhood

Sampling method TECO 49i TECO 48i TECO 42i TECO 43i

PM Filter Analysis 

method

N/A N/A N/A N/A

Start date 07/01/76 07/01/76 07/01/76 07/01/76

Operation schedule Continuous Continuous Continuous Continuous

Sampling season All year All year All year All year

Probe height (AGL) 9.6 m 9.6 m 9.6 m 9.6 m

Probe height above roof 4.3 m 4.3 m 4.3 m 4.3 m

Distance from 

obstructions on roof

None None None None

Distance from 

obstructions not on roof

None None None None

Distance from tree (DL) N/A N/A N/A N/A

Distance to furnace or 

incinerator flue

3.7 m 3.7 m 3.7 m 3.7 m

Distance between 

collocated monitors

N/A N/A N/A N/A

Unrestricted airflow 360° 360° 360° 360°

Probe material Teflon Teflon Teflon Teflon

Residence time 10 s 12 s 12 s 12 s

Will there be changes 

within the next 18 mos?

No No No No

Is it suitable for 

comparison against the 

annual PM2.5?

N/A N/A N/A N/A

Frequency of flow rate 

verification for manual 

PM samplers 

N/A N/A N/A N/A

Frequency of flow rate 

verification for 

automated PM analyzers 

N/A N/A N/A N/A

Frequency of one-point 

QC check (gaseous)

Every other 

day

Every other 

day

Every other 

day

Every other 

day

Last Annual Performance 

Evaluation (gaseous)

11/03/10 11/03/10 11/03/10 11/03/10

Last two semi-annual 

flow rate audits for PM 

monitors

N/A N/A N/A N/A
88

Vallejo Monitor Information

Pollutant FRM PM2.5 Continuous 

PM2.5 BAM*

Speciated

PM2.5

Monitoring

Objective

Population 

oriented

Population 

oriented

Population 

oriented

Spatial scale Neighborhood Neighborhood Neighborhood

Sampling method Partisol Plus 

2025 w/VSCC

Met One BAM 

1020

Met One 

SASS

PM Filter Analysis 

method

Weighed by 

Air District

N/A Weighed by 

DRI

Start date 03/10/99 01/01/04 6/11/08

Operation schedule Apr-Sep 1-in-6 

Oct-Mar: daily

Continuous 1-in-6

Sampling season All year All year All Year

Probe height (AGL) 6.5 m 5.8 m 6.6 m

Probe height above roof 2.3 m 1.9 m 2.3 m

Distance from 

obstructions on roof

None None None

Distance from 

obstructions not on roof

None None None

Distance from tree (DL) N/A N/A N/A

Distance to furnace or 

incinerator flue

6.3m 2.5 m 5.4m

Distance between 

collocated monitors

N/A N/A N/A

Distance between SASS 

and PM2.5 samplers

PM2.5 to BAM: 

3.7 m

PM2.5 to SASS: 

3.1 m 

BAM to PM2.5: 

3.7 m

BAM to SASS: 

2.9 m

SASS to PM2.5: 

3.1 m

SASS to BAM: 

2.9 m 

Unrestricted airflow 360° 360° 360°

Probe material N/A N/A N/A

Residence time N/A N/A N/A

Will there be changes 

within the next 18 mos?

Yes Yes No

Is it suitable for 

comparison against the 

annual PM2.5?

Yes No – not 

reference or 

equivalent 

method

No

Frequency of flow rate 

verification for manual 

PM samplers 

Monthly N/A Monthly

Frequency of flow rate 

verification for 

automated PM analyzers 

N/A Every two 

weeks

N/A

Frequency of one-point 

QC check (gaseous)

N/A N/A N/A

Last Annual Performance 

Evaluation (gaseous)

N/A N/A N/A

Last two semi-annual 

flow rate audits for PM 

monitors

11/02/10

05/11/10

08/17/10

05/11/10

11/02/10

05/11/10

* Continuous PM2.5 BAM was discontinued after 9/13/10. 
89

Detailed Site Information for SPM Stations
90

Berkeley

Site Name Berkeley

AQS ID 06-001-2004

GIS coordinates 38.8778° N, 122.3013° W

Location Trailer in parking lot

Address 1398 6th St, Berkeley CA 94710

County Alameda

Distance to road

from gaseous probe

Camelia Street: 27 meters

6

th Street: 34 meters

Gilman Street: 164 meters

Interstate 80: 484 meters

Traffic count

 

Camelia Street: 500 ADT (estimate)

6

th Street: 1,500 ADT (estimate)

Gilman Street: 21,700 (2000)

Interstate 80: 266,500 (2008)

Groundcover Paved

Representative Area San Francisco-Oakland-Fremont MSA

The Air District began a three year ambient air monitoring study in Berkeley in December 

2007. The purpose of the study is to determine the pollution impacts to local residents from 

vehicular traffic and industry along the Highway 80 corridor. According to the 2010 census 

the City of Berkeley has a population of 112,580. The site closed on December 31, 2010. 

The west side of Berkeley has the highest pollutant emission density within the city. Traffic 

levels are extremely high on Highway 80, with frequent traffic slowdowns during morning 

and evening commute times, which can produce significant amounts of hydrocarbons and 

particulates. Industrial sources along the highway, particularly Pacific Steel Casting (PSC), 

have made local residents concerned about possible exposure to particulates and toxic 

compounds. These sources in the west side of Berkeley transport pollutants to the rest of the 

city due to prevailing westerly winds. 

The mobile air monitoring station is sited in western Berkeley because this area is expected 

to have the highest impacts due to close proximity to the sources. The trailer is located 0.30 

miles east of Highway 80 and 0.25 miles downwind from PSC in a residential neighborhood. 

Although the purpose of the study is primarily source-oriented exposure from the highway 

and local industry emissions, the Air District is also monitoring population exposure to 

criteria pollutants including ozone, NO2, SO2, CO, PM10, and PM2.5.

Gaseous toxic compounds and metals are sampled at Berkeley by the Air District on a 1-in-6

day schedule. In 2010, gaseous toxic compounds were analyzed at the Air District laboratory

and metals were analyzed by CARB. Information about toxics monitoring by the Air District 

can be found in the Toxics Program section of this report.
91

Pollutant concentrations measured at Berkeley did not exceed the national standards for

ozone, NO2, SO2 (the new 75 ppb 1-hour standard), CO, or PM10 since the site opened in 

December 2007. The continuous PM2.5 (BAM) monitor recorded concentrations above the 

national 24-hour PM2.5 standard on two days in 2008, one day in 2009, and no days in 2010. 

However, this monitor is not a recognized FRM or FEM method, and the data cannot be used 

to determine violations of the national PM2.5 standards, or its attainment status. Only FRM or 

FEM based PM2.5 measurements may be used for comparison with national PM2.5 standards.

Hourly gaseous concentrations are available on the Air District web site. Pollutant 

summaries for all measurements from this study will be made available to local community 

groups and the City of Berkeley. 
92

Berkeley Monitor Information

Pollutant O3 CO NO/NO2 SO2 CH4/NMHC

Monitoring

Objective

Population 

Oriented & 

Source Impact

Population 

Oriented & 

Source Impact

Population 

Oriented & 

Source Impact

Population 

Oriented & 

Source Impact

Population 

Oriented & 

Source Impact

Spatial scale Neighborhood Neighborhood Neighborhood Neighborhood Neighborhood

Sampling method TECO 49C API 300E TECO 42C TECO 43C TECO 55C

PM filter analysis method N/A N/A N/A N/A N/A

Start date 12/13/07 12/13/07 12/13/07 12/13/07 CH4: 12/13/07

NMHC: 12/13/07

Operation schedule Continuous Continuous Continuous Continuous Continuous

Sampling season All year All year All year All year All year

Probe height (AGL) 5.1 m 5.1 m 5.1 m 5.1 m 5.1 m

Probe height above roof 2.5 m 2.5 m 2.5 m 2.5 m 2.5 m

Distance from 

obstructions on roof

None None None None None

Distance from 

obstructions not on roof

None None None None None

Distance from tree (DL) 18 m 18 m 18 m 18 m 18 m

Distance to furnace or 

incinerator flue

17 m 17 m 17 m 17 m 17 m

Distance between 

collocated monitors

N/A N/A N/A N/A N/A

Unrestricted airflow 360° 360° 360° 360° 360°

Probe material Teflon Teflon Teflon Teflon Teflon

Residence time 10 s 10 s 11 s 10 s 10 s

Will there be changes 

within the next 18 mos?

Site closed Site closed Site closed Site closed Site closed

Is it suitable for 

comparison against the 

annual PM2.5?

N/A N/A N/A N/A N/A

Frequency of flow rate 

verification for manual 

PM samplers 

N/A N/A N/A N/A N/A

Frequency of flow rate 

verification for automated 

PM analyzers 

N/A N/A N/A N/A N/A

Frequency of one-point 

QC check (gaseous)

Every other 

day

Every other 

day

Every other 

day

Every other 

day

Every other 

day

Last Annual Performance 

Evaluation (gaseous)

12/29/10 12/29/10 12/29/10 12/29/10 12/29/10

Last two semi-annual 

flow rate audits for PM 

monitors

N/A N/A N/A N/A N/A
93

Berkeley Monitor Information

Pollutant PM10 Continuous 

PM2.5 BAM

Monitoring

Objective

Population 

Oriented & 

Source Impact

Population 

Oriented & 

Source Impact

Spatial scale Neighborhood Neighborhood

Sampling method Tisch Env. 

HiVol TE-6000

Met One 

BAM 1020

PM Filter Analysis 

method

Weighed by

Air District

N/A

Start date 12/14/07 12/18/07

Operation schedule 1-in-6 Continuous

Sampling season All year All year

Probe height (AGL) 4.3 m 4.8 m

Probe height above roof 1.5 m 2.2 m

Distance from 

obstructions on roof

None None

Distance from 

obstructions not on roof

None None

Distance from tree (DL) 20 m 17 m

Distance to furnace or 

incinerator flue

20 m 18 m

Distance between 

collocated monitors

N/A N/A

Distance between PM10

and PM2.5 samplers

PM10 to 

BAM: 2.7 m

BAM to 

PM10: 2.7 m

Unrestricted airflow 360° 360°

Probe material N/A N/A

Residence time N/A N/A

Will there be changes 

within the next 18 mos?

Site closed Site closed

Is it suitable for 

comparison against the 

annual PM2.5?

N/A No – not 

reference or 

equivalent 

method

Frequency of flow rate 

verification for manual 

PM samplers 

Weekly N/A

Frequency of flow rate 

verification for 

automated PM analyzers 

N/A Every two 

weeks

Frequency of one-point 

QC check (gaseous)

N/A N/A

Last Annual Performance 

Evaluation (gaseous)

N/A N/A

Last two semi-annual 

flow rate audits for PM 

monitors

04/13/10

12/29/10

04/14/10

12/29/10
94

Crockett

Site Name Crockett

AQS ID 06-013-1001

GIS Coordinates 38.0549o N, 122.2332o W

Location Pump house

Address End of Kendall Avenue, Crockett CA 94525 

County Contra Costa

Distance to road

from gaseous probe

San Pablo Ave: 68.4 meters

Traffic count San Pablo Ave: 8,763 ADT (2007)

Groundcover Vegetative 

Representative Area San Francisco-Oakland-Fremont MSA 

Crockett was chosen for SO2 source impact monitoring because it is downwind of the 

ConocoPhillips Refinery. Prevailing winds in the area are from the west, which transport 

SO2 emissions from the refinery over the town of Crockett, a predominately residential 

community with a population of 3,094 according to the 2010 census. The monitoring site is 

located on the west side of Crockett 0.9 miles northeast of the refinery boundary. The only 

other major industry near Crockett is C&H Sugar, which is not a significant source of SO2

emissions. 

VOC toxic compounds are also sampled at Crockett on a 1-in-12 day schedule and analyzed 

in the Air District laboratory. More information about the toxics monitoring program can be 

found in the Toxics Program section of this report.

Crockett is classified as an SPM site. EPA siting criteria specifies that the probe be located 

at least 10 meters from the drip line of all trees. The closest tree drip line to the probe is 1.2 

meters away, but since the tree is located outside of the required 180 degree arc of 

unrestricted airflow for source impact monitoring as determined by the predominant wind 

direction and the direction of the refinery, the close proximity of that tree is irrelevant. The 

closest tree drip line within the 180 degree arc is 4.9 meters from the probe, which does not 

meet siting criteria. The Air District has been unable to negotiate with the local 

homeowner’s association for the removal of this tree. Even though one of the siting criteria 

for a SLAMS site cannot be met, the site is still suitable for source impact monitoring as an 

SPM site. 

During the most recent three years, the national 1-hour SO2 standard of 75 ppb was exceeded 

on two days. 
95

Crockett Monitor Information

Pollutant SO2

Monitor Objective Source impact

Spatial scale Neighborhood

Sampling method TECO 43C

PM filter analysis method N/A

Start date 01/01/79

Operation schedule Continuous

Sampling season All year

Probe height (AGL) 6.2 m

Probe height above roof 2.4 m

Distance from 

obstructions on roof

None

Distance from 

obstructions not on roof

None

Distance from tree (DL) 4.9 m*

Distance to furnace or 

incinerator flue (m)

N/A

Distance between 

collocated monitors 

N/A

Unrestricted airflow 270°

Probe material Teflon

Residence time 10 s

Will there be changes 

within the next 18 mos?

No

Is it suitable for 

comparison against the 

annual PM2.5?

N/A

Frequency of flow rate 

verification for manual 

PM samplers audit

N/A

Frequency of flow rate 

verification for 

automated PM analyzers 

audit

N/A

Frequency of one-point 

QC check (gaseous)

Every other 

day

Last Annual Performance 

Evaluation (gaseous)

10/13/10

Last two semi-annual 

flow rate audits for PM 

monitors

N/A

* Closest tree within the 180 degree arc of unrestricted air flow for source impact monitoring.
96

Cupertino

Site Name Cupertino

AQS ID N/A

GIS coordinates 37.3216° N, 122.0713° W

Location One story building

Address 22638 Stevens Creek Blvd. Cupertino CA 95014

County Santa Clara

Distance to road

from monitor

Stevens Creek Blvd: 40.2 m

Prado Vista Drive: 36.6 m

Foothill Blvd: 228.6 m

Silver Oak Lane: 152.4 m

Traffic count

 

Stevens Creek Blvd: 4030 ADT (2009)

Prado Vista Drive: 200 ADT (estimate)

Foothill Blvd: 8960 ADT (2009)

Silver Oak Lane: 500 ADT (estimate)

Groundcover Gravel

Representative Area San Jose-Sunnyvale-Santa Clara MSA

In October 2008, the Air District began particulate monitoring in Cupertino to determine if 

emissions from the nearby Lehigh Cement Plant and its associated diesel truck traffic could 

be producing elevated particulate concentrations in nearby neighborhoods. According to the 

2010 census, the City of Cupertino has a population of 58,302. 

The monitoring site was in a residential area just east of Permanente Canyon where the 

Lehigh Cement Plant is located. The site was also adjacent to Stevens Creek Boulevard 

which is the main route for truck traffic using the plant. Because cement plant and diesel 

truck emissions tend to produce larger-sized particles, a PM10 monitor was used to measure 

particulate impacts. A continuous monitor was used to correlate concentrations with the 

hourly emissions from the plant and the truck traffic. 

During the period of operation, there were no measured PM10 concentrations above the 

national 24-hour PM10 standard of 150 μg/m3. The monitor measured concentrations over 

the California 24-hour standard of 50 μg/m3 on two days in 2008 and on one day in January 

2010. However, particulate concentrations at most locations in the Bay Area were high on 

those days, so the high values may be due to basin-wide sources rather than local sources. 

Hourly particulate concentrations and wind data for the Cupertino site can be viewed on the 

Air District web site. 

Monitoring ended in July 2010 when a new Cupertino monitoring site became operational at 

Monte Vista Park. Details about the Cupertino Monte Vista Park site can be found later in 

this section of the document.
97

Cupertino Monitor Information

Pollutant Continuous 

PM10 BAM

Monitoring

Objective

Population 

Oriented & 

Source Impact

Spatial scale Neighborhood

Sampling method Met One

E-BAM

PM Filter Analysis 

method

N/A

Start date 10/29/08

Operation schedule Continuous

Sampling season All year

Probe height (AGL) 5.0 m

Probe height above roof 2.2 m

Distance from 

obstructions on roof

5.1 m

Distance from 

obstructions not on roof

32.3 m

Distance from tree (DL) 24.3 m

Distance to furnace or 

incinerator flue

15.9 m

Distance between 

collocated monitors

N/A

Distance between PM10 

and PM2.5 samplers

N/A

Unrestricted airflow 360°

Probe material N/A

Residence time N/A

Will there be changes 

within the next 18 mos?

Site closed

Is it suitable for 

comparison against the 

annual PM2.5?

N/A

Frequency of flow rate 

verification for manual 

PM samplers 

N/A

Frequency of flow rate 

verification for 

automated PM analyzers 

Every two 

weeks

Frequency of one-point 

QC check (gaseous)

N/A

Last Annual Performance 

Evaluation (gaseous)

N/A

Last two semi-annual 

flow rate audits for PM 

monitors

5/28/10
98

Cupertino Monte Vista Park

Site Name Cupertino Monte Vista

AQS ID 06-085-2009

GIS coordinates 37.3184° N, 122.0697° W

Location Trailer in parking lot

Address 22601 Voss Ave, Cupertino CA 95104

County Santa Clara

Distance to road

from gaseous probe

Foothill Blvd: 91 meters

Voss Ave: 63 meters

McKlintock Lane: 118 meters

Woodbridge Ct: 70 meters

Traffic count

 

Foothill Blvd: 8,960 ADT (2009)

Voss Ave: 1,000 ADT estimate

McKlintock Lane: 200 ADT (estimate)

Woodbridge Ct: 1,000 ADT (estimate)

Groundcover Paved

Representative Area San Jose-Sunnyvale-Santa Clara MSA

The Air District began a one year ambient air monitoring study in Cupertino on September 1, 

2010. The purpose of the study is to determine the pollution impacts to local residents from

vehicle traffic and the Lehigh Cement Plant located one mile west of the site. According to 

the 2010 census, the City of Cupertino has a population of 58,302. The Air District plans to 

close this station on August 31, 2011.

The mobile air monitoring station is located in Monte Vista Park. Although the purpose of 

the study is primarily source-oriented exposure from the cement plant and the associated 

truck traffic, the Air District is also monitoring population exposure to criteria pollutants 

including ozone, NO2, SO2, CO, PM10, and PM2.5, as well as toxics, metals, and mercury. An 

Air District meteorological system is also located in the park. 

Ozone and its precursors (NO/NO2) will be measured because the area is downwind of 

precursor sources during the warmer months. Carbon monoxide will be measured because of 

car and truck traffic on residential streets and because two freeways pass through Cupertino. 

SO2 will be measured because the cement plant uses petroleum coke as fuel to heat the 

cement kiln. Continuous PM2.5 and filter based PM10 will be measured because light winds 

combined with surface-based inversions during the winter months may cause elevated 

particulate levels. Hourly data collected is posted real-time on the Air District web site.

In 2011, the Air District will also measure ozone precursors CH4/NMHC at Cupertino. These 

compounds were intended to be measured when the station opened but they require high 

pressure compressed hydrogen gas cylinders in order to operate. The gas cylinders were not 

permitted by the Santa Clara County Fire Department. As an alternate to compressed gas 

cylinders, new laboratory grade equipment was procured by the Air District. The new 
99

equipment required extensive modification of the monitoring trailer thus delaying the start of 

CH4/NMHC monitoring until April 1, 2011.

Gaseous toxic compounds and metals are sampled at Cupertino on a 1-in-6 day schedule. In 

2010, gaseous toxic compounds were analyzed at the Air District laboratory and metals were 

analyzed by CARB. Information about toxics monitoring by the Air District can be found in 

the Toxics Program section of this report. Total Atmospheric Mercury is sampled for

24-hour periods on a 1-in-6 day schedule with laboratory analysis done by Frontier 

Geosciences. Toxic monitoring results, including mercury, are posted on a monthly basis on 

the Air District’s website at:

http://www.baaqmd.gov/sitecore-s/~/media/Files/Technical%20Services/Cupertino_toxics.ashx

Since opening in September 2010, one exceedance of the national 8-hr ozone standard has 

been measured, but no exceedances of the national standards for PM10, NO2, SO2 or CO have 

been measured. The continuous PM2.5 (BAM) monitor recorded no concentrations above the 

national 24-hour PM2.5 standard. However, this monitor is not a recognized FRM or FEM 

method, and the data cannot be used to determine violations of the national PM2.5 standards, 

or its attainment status. Only FRM or FEM based PM2.5 measurements may be used for 

comparison with national 
100

Cupertino Monte Vista Monitor Information

Pollutant O3 CO NO/NO2 SO2

Monitoring

Objective

Population 

Oriented & 

Source Impact

Population 

Oriented & 

Source Impact

Population 

Oriented & 

Source Impact

Population 

Oriented & 

Source Impact

Spatial scale Neighborhood Neighborhood Neighborhood Neighborhood

Sampling method TECO 49C TECO 48I TECO 42C TECO 43C

PM filter analysis method N/A N/A N/A N/A

Start date 9/1/10 9/1/10 9/1/10 9/1/10

Operation schedule Continuous Continuous Continuous Continuous

Sampling season All year All year All year All year

Probe height (AGL) 4.6 m 4.6 m 4.6 m 4.6 m

Probe height above roof 2.0 m 2.0 m 2.0 m 2.0 m

Distance from 

obstructions on roof

None None None None

Distance from 

obstructions not on roof

None None None None

Distance from tree (DL) 5.2 m 5.2 m 5.2 m 5.2 m

Distance to furnace or 

incinerator flue

None None None None

Distance between 

collocated monitors

N/A N/A N/A N/A

Unrestricted airflow 360° 360° 360° 360°

Probe material Teflon Teflon Teflon Teflon

Residence time 13 s 14 s 15 s 15 s

Will there be changes 

within the next 18 mos?

Yes Yes Yes Yes

Is it suitable for 

comparison against the 

annual PM2.5?

N/A N/A N/A N/A

Frequency of flow rate 

verification for manual 

PM samplers 

N/A N/A N/A N/A

Frequency of flow rate 

verification for automated 

PM analyzers 

N/A N/A N/A N/A

Frequency of one-point 

QC check (gaseous)

Every other 

day

Every other 

day

Every other 

day

Every other 

day

Last Annual Performance 

Evaluation (gaseous)

9/14/10 9/14/10 9/14/10 9/14/10

Last two semi-annual 

flow rate audits for PM 

monitors

N/A N/A N/A N/A
101

Cupertino Monte Vista Monitor Information

Pollutant PM10 Continuous 

PM2.5 BAM

Monitoring

Objective

Population 

Oriented & 

Source Impact

Population 

Oriented & 

Source Impact

Spatial scale Neighborhood Neighborhood

Sampling method Tisch Env. 

HiVol TE-6000

Met One 

BAM 1020

PM Filter Analysis 

method

Weighed by

Air District

N/A

Start date 9/9/10 9/15/10

Operation schedule 1-in-6 Continuous

Sampling season All year All year

Probe height (AGL) 4.3 m 4.9 m

Probe height above roof 1.5 m 2.2 m

Distance from 

obstructions on roof

None None

Distance from 

obstructions not on roof

None None

Distance from tree (DL) 2 m 3 m

Distance to furnace or 

incinerator flue

None None

Distance between 

collocated monitors

N/A N/A

Distance between PM10

and PM2.5 samplers

PM10 to 

BAM: 2.4 m

BAM to 

PM10: 2.4 m

Unrestricted airflow 360° 360°

Probe material N/A N/A

Residence time N/A N/A

Will there be changes 

within the next 18 mos?

Yes Yes

Is it suitable for 

comparison against the 

annual PM2.5?

N/A No – not 

reference or 

equivalent 

method

Frequency of flow rate 

verification for manual 

PM samplers 

Weekly N/A

Frequency of flow rate 

verification for 

automated PM analyzers 

N/A Every two 

weeks

Frequency of one-point 

QC check (gaseous)

N/A N/A

Last Annual Performance 

Evaluation (gaseous)

N/A N/A

Last two semi-annual 

flow rate audits for PM 

monitors

12/14/10 12/14/10
102

Fort Cronkhite

Site Name Fort Cronkhite

AQS ID 06-041-0004

GIS coordinates 37.832725° N, 122.527658° W

Location At ground level behind a ranger residence

Address Building 1111, Fort Cronkhite, Sausalito CA

County Marin

Distance to road

from probe

Bunker Road: 16 meters

Traffic count Bunker Road: 948 ADT (2007)

Groundcover Vegetative

Representative Area San Francisco-Oakland-Fremont MSA

Fort Cronkhite was chosen for an air toxics monitoring site because it is representative of 

ambient levels of toxics compounds transported into the Bay Area along its western 

boundary. The site is 1⁄2 mile east of the Pacific Ocean, on the north side of the Golden Gate

gap which opens into the San Francisco Bay. The monitor is located within the Golden Gate 

National Recreation Area (GGNRA) near the visitor center at Fort Cronkhite. Because winds 

in the Bay Area are generally from the west, this site is intended to be representative of local 

background toxics concentrations originating from the Pacific Ocean. The low 

concentrations from this site provide a baseline to which other toxics measurements in the 

Bay Area can be compared.

Toxics concentrations measured at this site should not be considered to be at pristine natural 

background levels. There are toxics contributions from emissions transported across the 

Pacific Ocean from Asia, from ships headed to and from Bay Area and Central Valley ports, 

and from ships sailing up and down the coast. Additionally, there can be a small contribution 

from vehicle traffic in areas upwind of the site within the GGNRA. In spite of these 

contributions, when winds are from the west, the toxics levels at this site reflect the lowest 

levels in the Bay Area.

The closest industrial sources are in San Francisco about eight miles southeast of the site. 

The closest towns are Sausalito, three miles to the east northeast with a population of 7,061,

and Marin City, three miles to the northeast with a population of 2,666. Populations were 

based on the 2010 census. Sausalito and Marin City have little impact on the monitoring site 

because winds are typically from the west so the site is upwind of these towns, and the towns 

have no significant industrial sources. 

This site is operated as part of the Air District’s Toxics Program on a 1-in-12 day schedule. 

Samples are collected using a Xontech canister and later analyzed in the Air District 

laboratory. More information about the toxics monitoring program can be found in the 

Toxics Program section of this report. 
103

Fort Cronkhite Monitor Information

Pollutant Canister 

Toxics

Monitoring Objective General 

Background

Spatial scale Regional

Sampling method Xontech 910A

PM filter analysis method N/A

Start date 3/26/87

Operation schedule 1-in-12

Sampling season All year

Probe height (AGL) 7.3 m

Probe height above roof 0.9 m

Distance from 

obstructions on roof

None

Distance from 

obstructions not on roof

None

Distance from tree (DL) 20 m

Distance to furnace or 

incinerator flue

N/A

Distance between 

collocated monitors

N/A

Unrestricted airflow 360°

Probe material Teflon

Residence time N/A

Will there be changes 

within the next 18 mos?

No

Is it suitable for 

comparison against the 

annual PM2.5?

N/A

Frequency of flow rate 

verification for manual 

PM samplers 

N/A

Frequency of flow rate 

verification for 

automated PM analyzers 

N/A

Frequency of one-point 

QC check (gaseous)

N/A

Last Annual Performance 

Evaluation (gaseous)

N/A
104

Special Monitoring Programs Conducted in 2010
105

EPA School Air Toxics Monitoring Program

EPA established the School Air Toxics Monitoring Program (SATMP) in 2009 to understand 

whether outdoor toxic air pollution poses health concerns to schoolchildren. The program 

was planned on a national level and the field monitoring activities are being carried out by 

experienced state and local air monitoring agencies like the Air District under the supervision

of EPA Regional Offices. The program seeks to determine if an air toxics exposure problem 

exists at schools and if so, pursue risk reduction activities and consider longer-term 

monitoring efforts where more information is needed. All samples were to be collected 

between June and September 2009. The Air District elected to extend the program, at its 

cost, through August 2010. 

EPA developed a list of priority areas for an initial round of toxics monitoring. The priority 

areas were selected based on proximity to sources having a high toxicity potential. In the 

Bay Area, EPA had concerns about the impacts on nearby school children of hexavalent 

chromium emitted from the Lehigh Southwest Cement Plant in Cupertino. Studies in other 

parts of the country had shown that hexavalent chromium could be a significant air toxic 

released during cement manufacturing. 

Daytime winds in Cupertino are generally from the north or northwest, which means the 

community is frequently upwind and away from impacts from the plant. However, there is 

potential for hexavalent chromium to reach the community whenever winds are from the 

south. There is also a local down-canyon wind pattern, which can occur at night, when 

surface winds travel from the plant down the Permanente Canyon toward Cupertino. The 

Stevens Creek Elementary School was chosen as a monitoring site because it is close to the 

Lehigh cement plant (1.6 km) and the entrance to Permanente Canyon. Figure 2 is a map 

showing the location of the school and the cement plant. 

Chromium is a naturally occurring element found in rocks, animals, plants, and soil. It 

commonly exists in trivalent (chromium III) or hexavalent (chromium VI) forms. While 

trivalent chromium is an essential nutrient that helps the body use fat, sugars, and protein, 

hexavalent chromium is a highly reactive, colorless, and odorless air toxic that can damage 

the respiratory system and cause cancer when inhaled at high concentrations.

Hexavalent chromium exists in the atmosphere as tiny particles or aerosols that are measured 

by drawing ambient air through a special filter for 24 hours on a 1-in-6 day schedule. 

Exposed filters are removed from the sampler by Air District staff and sent to ERG, a 

laboratory under contract to EPA/SATMP, for analysis within 30 days of collection. All 

sampling equipment, technician training, Standard Operating Procedures (SOPs), filters, and 

laboratory analysis services and procedures are provided directly by SATMP to maintain 

measurement uniformity and quality across the entire program.
106

Figure 2. Map of Stevens Creek Elementary School in Cupertino.

The EPA sponsored SATMP Project at Stevens Creek Elementary School began in June

2009 and was completed in September 2009. As required by the project, ten primary 

samples were collected during the period. An additional three samples were also collected in 

case of possible primary sample invalidation. For the Cupertino site, all 13 samples were 

analyzed and validated, and all had concentrations that were well below levels of concern for 

cancer risk and respiratory exposure. Results and technical information for all SATMP 

monitoring locations are available at http://www.epa.gov/schoolair/schools.html. (Follow the 

navigation link to Stevens Creek Elementary School to view the most current monitoring 

data available for the school and an explanation of the results.) 

Although the EPA sponsored SATMP sampling project ended in September 2009, the Air 

District continued the project at Stevens Creek School for an additional 11 months. The 

additional samples provided a more complete picture of hexavalent chromium concentrations 

at the school for an entire year. The extended sampling program was performed by Air 

District staff, and the Air District contracted with ERG to analyze the filters. All additional 

samples were analyzed and validated, and all had concentrations that were well below levels 

of concern for cancer risk and respiratory exposure. Results of the initial sampling and the 

extended Air District sampling were submitted to the EPA AQS database (AQS site number 

06-085-5506) and may also be found at: http://www.epa.gov/cgibin/broker?_service=data&_program=dataprog.school_keydata.sas&site=060855506
107

Meteorology Program

The Air District operates a meteorological monitoring program to provide accurate 

measurements of ambient meteorological parameters to meet the requirements of many 

programs within the Air District, and to make these data available to the public. Air District 

programs which use meteorological data are: air quality forecasting, photochemical 

modeling, source modeling, and data analysis. To obtain high quality data that can be used 

for regulatory applications, the Air District follows EPA recommendations for siting, 

instrumentation, data accuracy, and quality assurance of the meteorological network. 

The placement of meteorological stations depends on the use of the data. Sites chosen for air 

quality forecasting are located in areas that show the general wind and temperature patterns 

within the Air District. Photochemical modeling sites are chosen to show boundary 

conditions, general conditions, and upper air measurements. Source modeling sites are 

chosen to be representative of the source and receptor domain to be modeled. Sites used for 

data analysis are usually located near high pollution areas to determine the trajectories 

between source areas and downwind high concentration areas, as well as the general 

atmospheric conditions occurring during the episodes. 

Because most Air District air monitoring stations are located in urban or suburban 

neighborhoods where multistory buildings and trees are nearby, it has not been possible to 

place meteorological systems at many of the Air District’s air monitoring stations and still 

meet EPA meteorological siting recommendations. EPA recommends that wind systems be 

located at a height of 10 meters or at plume height if the use is source oriented modeling. In 

addition, the distance between the wind instrument and any obstruction should be at least 10 

times the height of the obstruction. 

The current meteorological network has 23 sites. Figure 3 shows the locations of the sites in 

2010. Eight of these sites are located at or adjacent to air monitoring stations (Bethel Island, 

Cupertino Monte Vista Park, Suisun, Concord, Vallejo, Livermore, Gilroy, and San Martin). 

The other air monitoring stations have obstructions to air flow nearby, necessitating 

placement of the meteorological sites further away. Additionally, to meet forecasting or 

photochemical modeling needs, some meteorological sites have been placed on ridges or

mountain tops, such as at Chabot, Mt. Tamalpais, and Kregor Peak.

Sensors used in the Air District’s meteorological network are:

• Wind speed and direction (cup and vane).

• Temperature.

• Relative humidity (at some sites).

• Solar radiation (at some sites).

• Rainfall (at some sites).

• Ambient pressure (at one site).

Hourly-averaged data are made available to District staff and the public on the Air District’s 

web page, and are archived in the Technical Service Division’s database. An electronic 

report is generated daily that checks for out of range values, constant values, missing values, 
108

or rate of change problems. If problems are seen, a technician visits the site to investigate. 

As part of the quality assurance program, each site is visited four times per year, twice for 

calibrations and twice for audits, and reports are generated for management review. At the 

end of each quarter, the data are reviewed and edited as needed. After editing, the data are 

uploaded into the EPA AQS database, and the preliminary data on the web page are 

overwritten with final data.

Data measured at airports and reported by the National Weather Service, as well as data from

refineries as required under Air District regulations, from sewage treatment plants, from

universities, and from private companies are also included in the Technical Services Division 

database as long as they meet EPA recommended siting and maintenance specifications. If 

requested by organizations, Air District staff will advised them where to best place their 

meteorological stations and how to operate the equipment such that the data can be used for 

regulatory purposes. 
109

Figure 3. Map of Air District Meteorological Monitoring Sites for 2010.
110

National Air Toxics Trends Station (NATTS) at San Jose

EPA established the National Air Toxics Trends Stations (NATTS) network in 2003. 

NATTS was created to expand and improve national toxics monitoring with the major goal 

of identifying toxics trends in urban and rural settings throughout the United States. EPA 

and the Air District agreed to include San Jose in the NATTS network because of its history 

of high quality air toxics data back to 1991 (when canister sampling at San Jose began), and 

because San Jose is the largest city in Northern California with a 2010 population of 945,942. 

The Air District began operating a NATTS site at the San Jose air monitoring station on 

January 1, 2003. NATTS pollutants can be grouped into three categories: hazardous air 

pollutants, continuous measurements, and polycyclic aromatic hydrocarbons.

Hazardous Air Pollutants (HAPs) Measurements

The Clean Air Act Amendments of 1990 listed 188 HAPs of interest. Of these, EPA selected 

fifteen HAPs for trends analysis in the original 2003 NATTS monitoring program. These 

selections were based on toxicity, available measurement methods, cost of measurement, 

correlation with other important HAPs, and anticipated concentration levels. Table 10 lists 

the NATTS HAPs measured by the Air District along with the year NATTS measurements 

began. Hexavalent chromium is the only required NATTS airborne toxic compound that the 

Air District does not directly measure, because the current sampling methodology allows 

significant deterioration of the compound before the analysis can be performed. Chromium 

is measured instead as an estimate of hexavalent chromium concentrations. In the future, the 

Air District may sample for hexavalent chromium when better sampling techniques are 

developed.

Table 10. List of the 15 NATTS HAPs Monitored by the Air District.

Hazardous Air 

Pollutant or Species

Year NATTS

Measurements 

Began

Parameter

Type Sample Source Analyzing Lab

Analysis 

equipment

Benzene 2003 VOC SUMMA canister BAAQMD GC

1, 3 Butadiene 2003 VOC SUMMA canister BAAQMD GC

Carbon tetrachloride 2003 VOC SUMMA canister BAAQMD GC

Chloroform 2003 VOC SUMMA canister BAAQMD GC

Tetrachloroethylene 2003 VOC SUMMA canister BAAQMD GC

Trichloroethylene 2003 VOC SUMMA canister BAAQMD GC

Acrolein 2008 Carbonyl SUMMA canister BAAQMD GC/MS

Formaldehyde 2006 Carbonyl cartridge BAAQMD HPLC

Acetaldehyde 2006 Carbonyl cartridge BAAQMD HPLC

Antimony 2008 metal 1⁄4 PM10 filter1 ERG ICPMS

Arsenic 2008 metal 1⁄4 PM10 filter1 ERG ICPMS

Cadmium 2008 metal 1⁄4 PM10 filter1 ERG ICPMS

Manganese 2008 metal 1⁄4 PM10 filter1 ERG ICPMS

Nickel 2008 metal 1⁄4 PM10 filter1 ERG ICPMS

Chromium22008 metal 1⁄4 PM10 filter1 ERG ICPMS

1

PM10 Lo-Vol Teflon filter is sample source effective 12/22/10

2 Chromium is measured as an estimate of hexavalent chromium.
111

Emission sources of the NATTS HAPs in Table 10 above:

 Benzene and 1, 3 butadiene are emitted by mobile sources (cars and trucks). 

 Carbon tetrachloride, tetrachloroethylene and trichloroethylene are used for cleaning, 

but Air District regulations have significantly reduced their use. 

 Chloroform is produced in the chlorination of water. 

 Acrolein is generated by diesel and jet engines. 

 Formaldehyde and acetaldehyde are formed during combustion processes. 

Formaldehyde is also created during the manufacture of some building materials and 

household products, and continues to off gas after manufacturing. 

 Antimony comes from the soil.

 Arsenic compounds originate from soil and the smelting of metals. 

 Nickel and cadmium compounds are naturally found in some soils and can be emitted 

from fossil fuel combustion, cement manufacturing and electroplating. Also, 

cadmium comes from tire wear. 

 Manganese compounds naturally occur in some soils and can be emitted from steel 

plants, power plants and coke ovens. 

 Hexavalent chromium is emitted during chrome plating operations, and is believed to 

be a byproduct of the cement-making process. 

The Air District samples for the 14 NATTS pollutants and chromium on a 1-in-6 day 

schedule. Benzene; 1, 3 butadiene; acrolein; trichloroethylene; carbon tetrachloride;

chloroform; and trichloroethylene are collected in canisters over a 24-hour period using a 

Xontech 910a sampler. The canister contents are then analyzed in the Air District laboratory 

using a Gas Chromatograph (GC) or a Gas Chromatograph/Mass Spectrometer (GC/MS). 

Formaldehyde and acetaldehyde (carbonyls) are collected using a cartridge on one sampling 

channel of a Xontech 924 toxics sampler. In the Air District laboratory, exposed cartridges 

are analyzed for carbonyls using High Performance Liquid Chromatograph (HPLC). During 

most of 2010, metals were collected on a standard PM10 filter. A quarter section of each 

filter was sent to ERG (EPA’s designated contract laboratory) for analysis using Inductively 

Coupled Plasma Mass Spectrometry (ICPMS). With the implementation of the Lo-Vol 

collection method for PM10 in December 2010, a Teflon PM10 filter is sent to ERG for 

analysis.

Continuous Measurements

As part of the NATTS program, the Air District makes continuous measurements of CO. 

High sensitivity CO is measured as an analysis tool because of correlation to benzene and 1,

3 butadiene, two of the largest contributors to air toxic exposure. 

Polycyclic Aromatic Hydrocarbons (PAHs) Measurements

In May 2008, the Air District began sampling for a number of PAHs under the NATTS 

program. PAHs are products of incomplete combustion, and are found primarily in soil, 

sediment and oily substances, as opposed to in water or air. However, they are also a 

component of concern in particulate matter in air and have probable human carcinogenic 

(cancer), mutagenic (genetic mutation), and taratogenic (birth defects) properties. The PAH

compounds that the Air District measures are listed in Table 11. 
112

Table 11. List of 22 NATTS PAH Compounds Measured by the Air District.

9-Fluorenone Coronene

Acenaphthene Cyclopenta(cd)pyrene

Acenaphthylene Dibenz(a,h)anthracene

Anthracene Fluoranthene

Benzo(a)anthracene Fluorene

Benzo(a)pyrene Indeno(1,2,3-cd)pyrene

Benzo(b)fluoranthene Naphthalene

Benzo(e)pyrene Perylene

Benzo(g,h,i)perylene Phenanthrene

Benzo(k)fluoranthene Pyrene

Chrysene Retene

The Air District does not have the equipment to meet the specific requirements to perform 

the analysis for these compounds, so ERG (EPA’s designated contract laboratory) provides

the filter media and analysis. PAH compounds are collected on a filter for a 24-hour period 

using a standard HiVol Polyurethane Foam (PUF) sampler on the NATTS 1-in-6 day 

sampling schedule. Filters are then sent to the ERG laboratory for analysis. 

Summary NATTS data are available from the EPA’s AirData web site at 

http://www.epa.gov/oar/data/index.html. These data may also be found on the BAAQMD 

web site in the Toxic Air Contaminant Control Program Annual Report at 

http://www.baaqmd.gov/Divisions/Engineering/Air-Toxics/Toxic-Air-Contaminant-ControlProgram-Annual-Report.aspx.

In addition to the NATTS analytes discussed in this section, the Air District also samples for 

other toxics compounds at San Jose. These are discussed in the Toxics Program section of 

this report.
113

NCore Program

In October 2006 the EPA revised 40 CFR Parts 53 and 58 to enhance ambient air quality 

monitoring to improve air quality measurements. One significant revision was the 

requirement to establish National Core (NCore) multi-pollutant monitoring stations. These 

stations will provide data on several pollutants at lower detection limits and replace the 

National Air Monitoring Station (NAMS) networks that have existed for several years. 

NCore stations will also be used to monitor trends of pollutants already in attainment. EPA 

recognized that pollutants already in attainment, and likely to remain so, did not need to be 

measured at all sites in a monitoring network. NCore stations are to be located in areas 

which represent the highest pollution levels for both attainment and non-attainment 

pollutants within an agency’s boundaries. By reducing the number of monitors needed in a 

network, agencies can allocate scarce resources to other monitoring programs.

NCore stations are intended to:

• Report data to the public in a timely manner through AirNOW, air quality 

forecasting, and other public reporting mechanisms.

• Support development of emissions control strategies through air quality model 

evaluation and other observational methods.

• Track long-term trends for accountability of emissions control programs and health 

assessments that contribute to ongoing reviews and attainment of the National 

Ambient Air Quality Standards (NAAQS).

• Support scientific studies ranging across technological, health, and atmospheric 

disciplines including ecosystem assessments.

EPA designed the national NCore network to have a mixture of urban and rural sites. In 

Northern California, EPA desired a monitoring station that would represent a large urban 

area. Recommendations for locating NCore urban sites are found in 40 CFR Part 58 

Appendix D and other EPA publications:

• Urban NCore stations are to be located at neighborhood or urban scale to provide 

representative exposure levels throughout the metropolitan area population.

• Urban NCore stations should be located where significant pollution levels exist.

• Population oriented monitoring is highly recommended.

• No biasing local pollutant emission sources should be within 500 meters at urban 

stations.

• Collocation with other network programs (such as NATTS, STN, CASTNET, 

IMPROVE, NADP, PAMS) is encouraged.

• Siting of monitors at NCore sites must meet SLAMS requirements as specified in 40 

CFR Part 58.

EPA and the Air District cooperatively agreed to establish the Northern California NCore 

station in San Jose. EPA will provide funding and the Air District will operate the station. 

The station is operational as of January 1, 2011. The city of San Jose was chosen as the 

NCore site because it is the largest city in the Bay Area with over one million residents. 

Exceedances of both the ozone and 24-hour PM2.5 national standards have been measured in 
114

San Jose. Consequently, operating an NCore station in the San Jose area would meet the 

requirement of being in an urban area with significant air pollution problems.

San Jose is located in the southern part of the Bay Area, and lies within the Santa Clara 

Valley. Wind patterns in the Santa Clara Valley are influenced greatly by the terrain, 

resulting in a prevailing flow roughly parallel to the valley's northwest-southeast orientation. 

During the daytime a sea breeze commonly carries pollutants from San Francisco, San Mateo 

and Alameda counties southward into the Santa Clara Valley, while a drainage flow carrying 

pollutants toward the bay, in the opposite direction, occurs during the nighttime hours. This 

diurnal up valley and down valley air flow mixes pollutants throughout the valley, making 

San Jose representative of a large part of the Bay Area.

The monitoring objective for the current San Jose air quality monitoring station is population 

exposure. Monitoring at a population-oriented station is intended to represent air quality 

levels over a large area having a high population density. Consequently, the site cannot be 

too close to large emission sources such as industrial sources or highways, and the 

surrounding land use 

should be relatively 

uniform. EPA has 

defined neighborhood or 

urban scale as the 

appropriate area of 

representativeness for 

population oriented 

monitoring. 

Neighborhood scale has 

dimensions of 4 km 

around the monitoring 

station, and urban scale 

has a 50 km radius. 

Figure 4 shows the 

location of the current 

San Jose monitoring 

station (as a blue 

balloon), and a 4 km 

circle around the site 

representing a 

neighborhood scale area.

Figure 4. Map showing area of Neighborhood Scale at the San Jose NCore station.
115

The map shows that the current station is located in a residential/commercial area of San 

Jose. The station is located on Jackson Street, 1.6 km NW of the downtown core. The Air 

District has operated air monitoring stations at various locations near downtown San Jose 

since 1968, and current station has been in operation since 2002. The downtown area is 

encircled by freeways, but the closest freeway to the air monitoring station is 800 meters to 

the WSW, which is sufficiently distant to prevent vehicular emissions from dominating the 

general air quality at the San Jose station. The San Jose Airport is 2 to 4 km from the air 

monitoring station, distant enough that impacts from airport emissions would be relatively 

low at the monitoring station. There are no large point sources within 500 meters of the 

station. The only significant emission sources within a 4 km radius of the San Jose air 

monitoring station are:

• The Norman Y. Mineta San José International Airport, located from 2-4 km NW of 

the site, is a significant source. The airport averaged 256 commercial and 141 general 

aviation departures and landings per day in 2008.

• Reed & Graham, Inc. (an asphalt batch plant) - located 3.7 km SSW of the site.

• Central Concrete Supply Company, Inc. - located 1.9 km SSW of the site.

• San Jose State University Cogeneration Plant - located 2.6 km SSE of the site.

The San Jose air monitoring station was located to provide air quality data representative of 

neighborhood scale monitoring. The station currently monitors all criteria pollutants, toxics, 

and is part of the EPA NATTS and STN programs. This existing station meets all the site 

selection criteria for an NCore station.

NCore Monitors

Table 12 lists the NCore monitors operating at the San Jose station as well as the sampling 

methodology, sampling frequency and spatial scale for the monitors. Because ambient 

concentrations of the criteria pollutants CO and SO2 are well below the NAAQS at 

population oriented sites across the U.S., EPA requires NCore sites to use higher sensitivity 

instruments than conventional instruments for these pollutants (note the use of TLE type 

instruments for CO and sulfur dioxide, meaning Trace Level-Enhanced). PM10-2.5 is 

measured using the difference between measurements of a pair of Partisol-Plus Model 2025 

Sequential samplers, with one configured as a PM2.5 sampler and the other configured as a 

PM10 sampler. Lead is collected using the PM10 Teflon filter, which is sent to ERG (EPA’s 

designated contract laboratory) for analysis using Inductively Coupled Plasma Mass 

Spectrometry (ICPMS).
116

Table 12. NCore Monitors

Monitor Type Sampling Method Sampling

Frequency Spatial Scale

Carbon 

Monoxide (CO) TECO 48i TLE Continuously Neighborhood

Nitrogen Oxide 

(NOx)

TECO 42C Continuously Neighborhood

Ozone (O3) TECO 49i Continuously Neighborhood

Sulfur Dioxide 

(SO2)

TECO 43i TLE Continuously Neighborhood

FRM PM2.5 

Partisol-Plus 2025 

w/VSCC

Apr-Sep: 1-in-3 day

Oct-Mar: Daily Neighborhood

BAM PM2.5 Met One Model 1020 Continuously Neighborhood

PM2.5

Speciation Met One SASS 1-in-3 day Neighborhood

Total Reactive 

Nitrogen (NOy)

API 200EU Continuously Neighborhood

PM10-2.5 

Partisol-Plus 2025 

Sequential PM10-2.5 Air

Sampler Pair

1-in-3 day Neighborhood

Lead

PM10 Teflon filter 

analyzed by ERG using 

XRF

1-in-3 day Neighborhood

Meteorological

EPA approved a waiver 

to use meteorological 

data from the San Jose 

Airport as official data 

for the NCore site.

Continuously N.A.
117

Photochemical Assessment Monitoring Stations (PAMS)

The 1990 Clean Air Act Amendments required EPA to promulgate rules for the enhanced 

monitoring of ozone and its precursors (NOx and VOCs) because of continued nonattainment 

of the National Ambient Air Quality Standard (NAAQS) for ozone nationwide. Subsequent 

revisions to EPA’s Air Monitoring regulations, 40 CFR Part 58, required air pollution 

agencies to establish Photochemical Assessment Monitoring Stations (PAMS) in ozone 

nonattainment areas classified as serious, severe, or extreme. The Bay Area is not in any of 

these categories, but is in marginal nonattainment of the ozone NAAQS. Consequently, the 

Air District applied for and received funding from EPA to conduct measurements of VOC 

speciated hydrocarbons. Monitoring began in 2010 and will continue for at least three years.

The objectives of the Bay Area PAMS program are to:

 Measure air quality improvement progress

 Track emission trends

 Improve photochemical model performance

 Adjust ozone control strategies

Traditionally, summertime Bay Area ozone concentrations are highest in the Livermore and 

Santa Clara Valleys. Meteorological conditions are ideal for ozone formation in these areas 

when precursor NOx and hydrocarbons are present in upwind areas. To better understand the 

atmospheric chemistry, emissions sources, emission reductions strategies, and pollutant 

transport, three locations in the Livermore area will monitor for speciated hydrocarbons. 

Each PAMS site will also have meteorological wind and temperature sensors.

Site Parameter Start Date for PAMS Data Collection

Livermore Air Monitoring August 1, 2010

Meteorology August 1, 2010

San Ramon Air Monitoring July 2011 (approx.)

Meteorology July 2011 (approx.)

Patterson Pass Air Monitoring March 1, 2011

Meteorology Late Summer 2011 (approx.)

The Air District’s Livermore air monitoring station was selected as a PAMS site because 

Livermore usually has the most number of days per year exceeding the ozone NAAQS in the 

Bay Area. The Livermore site also has meteorological sensors measuring wind, temperature, 

and solar radiation and the site already has instruments measuring NOx and ozone. As a 

result, the cost to add speciated hydrocarbon monitoring at Livermore was minimal. 

The San Ramon and Patterson Pass sites are new, temporary sites that are being opened 

solely for the PAMS program. The San Ramon PAMS will provide information on ozone 

precursors and ozone formation in the San Ramon Valley that may contribute to ozone 

concentrations in the Livermore Valley. While the EPA provided funding for speciated 

hydrocarbon monitoring at San Ramon, the Air District is adding ozone and NOx so that data 

from this site can be compared to data collected at Livermore. This site may become a 

permanent location for ozone and NOx monitoring if these pollutants frequently exceed the 
118

NAAQS. The Patterson Pass site is located in the hills east of Livermore and will provide 

additional information on the potential transport of ozone precursor compounds eastward 

from the Bay Area to the Central Valley. EPA funded speciated hydrocarbon monitoring and 

the Air District added a NOx monitor at this site. The three PAMS locations are shown in 

Figure 5.

Figure 5. Map of the three PAMS sites in the Livermore Valley.

EPA identifies 57 organic ozone precursor compounds usually measured at PAMS locations 

because of their significance in photochemical ozone pollution. The Air District will 

measure 55 of the 57 compounds hourly using a gas chromatograph (GC) instrument. The 

GC does not analyze for two compounds EPA considers important ozone precursors: 

formaldehyde and acetone. The Air District determined that it was too costly to measure 

these compounds hourly. Table 13 below lists the 55 compounds measured by the GC.
119

Table 13. List of speciated hydrocarbons measured by Gas Chromatograph

Ethane n-decane 2-methylheptane

Ethylene Cyclopentane m/p xylene

Propane Isoprene Benzene

Propylene 2-2-dimethylbutane Toluene

Acetylene 1-hexene Ethylbenzene

n-butane 2-4-dimethylpentane o-xylene

Isobutane Cyclohexane 1-3-5-trimethylbenzene

t-2-butene 3-methylhexane 1-2-4-trimethylbenzene

c-2-butene 2-2-4-trimethylpentane n-propylbenzene

n-pentane 2-3-4-trimethylpentane Isopropylbenzene

Isopentane 3-methylheptane o-ethyltoluene

1-pentene Methylcyclohexane m-ethyltoluene

t-2-pentene Methylcyclopentane p-ethyltoluene

c-2-pentene 2-methylhexane m-diethylbenzene

3-methylpentane 1-butene p-diethylbenzene

n-hexane 2-3-dimethylbutane Styrene

n-heptane 2-methylpentane 1-2-3-trimethylbenzene

n-octane 2-3-dimethylpentane

n-nonane n-undecane

The GCs will operate year-round which is a deviation from EPA protocols that only require 

these measurements during ozone episodes. Year-round measurements are desired because 

the same hydrocarbons that lead to high ozone in summer also contribute to secondary 

formation of particulate pollution in winter. 

All ozone, NOx, and speciated hydrocarbon data are submitted to EPA’s AQS database. 

When enough data is collected to yield a better understanding of emissions and 

photochemical processes in the Livermore area, the Air District will evaluate whether 

instrumentation should be moved to the Santa Clara Valley for a similar PAMS program.
120

PM2.5 Speciation Sampling Programs 

EPA established a fine particulate (PM2.5) standard in 1997 and required States to install and 

operate new PM2.5 samplers to determine where the national ambient PM2.5 air standards are 

not being met. As part of the PM2.5 monitoring program, EPA also established a network of 

speciation monitors at sites expected to exceed the PM2.5 standard. The primary purpose of 

the speciation monitors is to provide a chemical composition of the particulate matter which 

will point to the emission sources. This network is known as the Speciation Trends Network 

(STN). 

A PM2.5 sampler was installed at the San Jose air monitoring station in January 1999 and the 

first year of data showed exceedances of the national standard. Consequently, EPA 

requested that a Met One Spiral Ambient Speciation Sampler (SASS) sampler be installed at 

San Jose in early 2000 as part of the STN network. Exceedances of the PM2.5 national 

standard have also been recorded at other Bay Area sites, and in 2008 the Air District added 

SASS samplers at Vallejo and Livermore. In 2009 the Air District added a SASS sampler at 

the new Oakland West air monitoring station. Knowing the chemical composition of 

particulates on days over the standard at four Bay Area sites will help determine which 

emission reduction strategies will most likely lead to attainment of the national standard. 

Speciation Trends Network (STN) Program

STN sites have the primary objective of defining long-term concentration trends of the 

elements, ions, and organic and elemental carbon components that make up PM2.5 particles.

San Jose was chosen as an STN station because it was already collecting PM2.5 mass, has 

recorded exceedances of the PM2.5 standard, and is the largest city in Northern California.

PM2.5 samples are collected using a SASS sampler. The sampler operates from midnight to 

midnight of the next day, and samples are on a 1-in-3 day schedule. In addition to the SASS, 

there is an FRM PM2.5 filter sampler used to measure the total mass of PM2.5 and to 

determine when exceedances of the PM2.5 standard occur. In 2010, the FRM sampling was 

on a 1-in-6 day schedule in the summer and daily in the winter. In 2011, the FRM summer 

sampling frequency will change to a 1-in-3 day schedule. SASS sampling is scheduled to 

coincide with FRM sampling days so that speciation information can be used to help identify 

sources and develop effective control strategies.

The SASS samplers draw air through size-selective nozzles that exclude particles greater 

than 2.5 microns. SASS samplers uses Teflon, nylon and quartz filters upon which to collect 

the samples, which are later weighed using a mass balance and analyzed using energydispersive X-ray fluorescence, ion chromatography, and thermal/optical analysis techniques 

to measure the components. The San Jose filter analysis is done by RTI, an EPA contract 

laboratory in North Carolina. Sixty-two chemical species listed in Table 14 are measured 

from each SASS filter sample at RTI. The San Jose data are then submitted to the EPA AQS 

database by RTI, and can be viewed on the EPA’s AirData web site at 

http://www.epa.gov/oar/data/index.html.
121

BAAQMD Supplemental Speciation Network Program

The Air District also operates SASS samplers at its stations in Vallejo, Livermore, and 

Oakland West. Vallejo and Livermore were selected for sampling because there was an 

interest in determining the source of PM2.5 particles on days that exceed the standard at those 

sites. These sites may have a different PM2.5 composition from that of San Jose because 

exceedances often occur on days when the air flow is from the Central Valley. Oakland 

West was selected because it is downwind of the Port of Oakland, a major source of diesel 

particulate matter. The samplers, sampling procedures, analysis techniques and species 

analyzed are the same as for the STN program with the following exceptions: the collection 

frequency is 1-in-6 days; DRI provides the filters, does the analysis and submits the data to 

AQS; and filters from these sites also are analyzed for palladium, thallium and uranium.

Data from the 65 chemical species listed in Table 14 can be viewed on the EPA’s AirData 

web site at http://www.epa.gov/oar/data/index.html. 

The table is color coded with green (the first 13 rows) listing elements, blue (the next two 

rows) listing anions and cations, and yellow (the next eight rows) listing organic and 

elemental carbon types.

Table 14. PM2.5 Speciation Measurements at Air District Sites.

Antimony Cesium Magnesium Sodium

Arsenic Europium Mercury Strontium

Aluminum Gallium Nickel Sulfur

Barium Gold Niobium Tantalum

Bromine Hafnium Phosphorous Terbium

Cadmium Iron Potassium Tin

Calcium Indium Rubidium Titanium

Chromium Iridium Samarium Tungsten

Cobalt Lanthanum Scandium Vanadium

Copper Lead Selenium Yttrium

Chlorine Manganese Silicon Zinc

Cerium Molybdenum Silver Zirconium

Palladium1 Thallium1 Uranium1

Ammonium Cation Chloride Anion Potassium Cation Nitrate Anion

Sodium Cation Sulfate Anion

Total Organic Carbon (sum of the OC Fractions below)

Elemental Carbon Fraction 1 (carbon released at 550oC in 10% oxygen/90% helium gas)

Elemental Carbon Fraction 2 (carbon released at 700oC in 10% oxygen/90% helium gas)

Elemental Carbon Fraction 3 (carbon released at 800oC in 10% oxygen/90% helium gas)

Organic Carbon Fraction 1 (carbon released at 120oC in helium gas)

Organic Carbon Fraction 2 (carbon released at 250oC in helium gas)

Organic Carbon Fraction 3 (carbon released at 450oC in helium gas)

Organic Carbon Fraction 4 (carbon released at 550oC in helium gas)

 1 Elements measured only at Vallejo, Livermore, and Oakland West.
122

Toxics Program

The Clean Air Act Amendments of 1990 required EPA to set emission standards for major 

sources of Hazardous Air Pollutants (HAPs). The Act also required EPA to assess the risks 

to human health from HAPs. By 2010 EPA had listed 187 compounds as HAPs. All HAPs

listed by EPA are known to cause or are suspected of causing cancer, birth defects, 

reproduction problems, and other serious illnesses. Exposure time to certain levels of some 

HAPs can cause difficulty in breathing, nausea or other illnesses and can even cause death.

Toxic pollutants (HAPs) are emitted daily by industrial and chemical manufacturing 

processes, commercial activities, refinery operations, gasoline marketing and motor vehicles 

within the Bay Area. Ambient concentrations vary by proximity to sources and current 

meteorological conditions.

The Air District established an ambient air toxics monitoring program with the objectives of:

 Establishing trends and evaluating the effectiveness of HAP reduction strategies.

 Characterizing ambient concentrations in local areas.

 Providing data to support and evaluate dispersion and deposition models.

 Providing data to the scientific community to support studies to reduce uncertainty 

about the relationships between ambient levels of HAPs, actual human exposure to air 

toxics, and health effects from such exposures.

Figure 6 is a map of the 20 toxics monitoring sites operating in 2010. Locations are at 

existing Air District SLAMS and SPM monitoring stations and were selected to obtain a 

wide geographical coverage of contaminant levels throughout the Bay Area. The sites are 

generally located in major population centers or downwind of major industrial sources such 

as refineries. There is also an ambient background site at Fort Cronkhite. The toxics data 

collected at San Jose are also reported to EPA as part of the NATTS program. Toxics 

monitoring at Fremont ended on July 19, 2010.

Air samples are collected at Air District toxics monitoring sites for a 24 hour period on a 1-

in-12 day schedule except at special study sites such as Berkeley, Cupertino, and San Jose 

where sampling is on a 1-in-6 day schedule as described later in this section. A 1-in-12 day 

schedule allows samples to be taken on a different day of the week over the course of 

months. This is the same schedule EPA and CARB use for their toxics monitoring program, 

thereby allowing Bay Area toxics concentrations to be compared to concentrations measured 

elsewhere across the country.

Gaseous (VOC) toxics are collected in 6-liter SUMMA stainless steel canisters using 

Xontech 910 samplers. The sampler continuously collects an ambient air sample for 24-

hours to ensure capturing transient and intermittent toxic releases. All canisters are analyzed 

within 30 days of sample collection using capillary gas chromatography employing 

photoionization and electron capture detectors.
123

Figure 6. Map of Air District Toxics Monitoring Sites for 2010.
124

In 1986, the toxics monitoring network used Tedlar bags to collect the ambient air samples, 

which were filled using an Air District designed and constructed sampler. This methodology 

had several problems including leaks, contamination, and the requirement to perform the

laboratory analysis within 48 hours of sample collection. Between 1991 and 1997, the Air 

District phased in an improved sampling methodology, using a 6-liter SUMMA stainless 

steel canister to replace the Tedlar bags, and replacing the Air District sampler with a 

commercially available Xontech sampler. This was the same system that CARB had been 

successfully using for a few years. This method also allowed canister contents to be 

analyzed up to 30 days after sample collection. It also provided more flexibility in 

scheduling sample days, conducting the laboratory analysis, and for transportation of the 

samples. The data collected after the switch to SUMMA canisters is considered to be of 

higher quality than data collected with Tedlar bags. 

Both the Air District and CARB have toxic monitoring programs in the Bay Area. CARB 

conducts toxic monitoring on a 1-in-12 day schedule at three sites: San Francisco, San Jose, 

and Fremont. CARB supplies the canisters and performs the laboratory analyses, while Air 

District staff operates the CARB sampler and ships the canisters to CARB. Because the Air 

District also does toxics monitoring at San Francisco and San Jose, the two sets of data allow 

calculation of the measurement precision at these sites, and by extrapolation, an estimate of 

the precision of the toxics measurement program. CARB discontinued its toxic monitoring 

program at Fremont in July 2010 because the Air District was in the processes of closing the 

Fremont station in the fall.

Once a quarter at San Francisco, an additional canister sample is taken on a scheduled sample 

day using a collocated sampler. Both samples are analyzed by the Air District laboratory, 

and the results allow an additional measure of precision.

The Air District laboratory analyzes for the 19 gaseous toxic compounds listed in Table 15. 

Compounds selected for analysis were those that had high toxicity or were known to have 

high emissions in the Bay Area, or some combination of the two. Another consideration was 

whether the current methodology could accurately detect a compound at reasonable expense, 

based on previous CARB studies. Some compounds, such as carbon tetrachloride, are 

measured because their concentration in the ambient air does not change much over time. 

This is useful because carbon tetrachloride or other similar, stable compounds can be used as 

a control for quality purposes. If the measurement of such a control is unusually high or low, 

there may be a problem in the sampling, transport, storage or analysis procedures requiring 

additional analysis of the accuracy of the affected sample.
125

Table 15. List of Toxic Compounds Measured by the Air District in 2010.

Acetone Methyl Ethyl Ketone 

Benzene Methylene Chloride

1, 3 Butadiene M/P Xylene

Carbon Tetrachloride Perchloroethylene

Chloroform 1,1,2 Trichlorotrifluoroethane

Ethylbenzene Trichloroethylene

Ethylene Dibromide Trichlorofluoromethane

Ethylene Dichloride Toluene

O-Xylene Vinyl Chloride 

Methyl Chloroform

In addition to the gaseous toxics monitoring done across the Bay Area, the Air District does 

monitoring for polycyclic aromatic hydrocarbons, metals, and aldehydes at San Jose for the 

NATTS program. See the NATTS section of this document for more information about the 

NATTS program.

Toxics Monitoring at Berkeley and Cupertino

In 2010, the Air District operated a Xontech 910 sampler to collect toxic samples in canisters 

at the SPM monitoring sites in Berkeley and Cupertino on a 1-in-6 day schedule. In addition 

to the compounds listed in Table 14, there was interest in measuring formaldehyde and 

acetaldehyde at Berkeley and Cupertino. These compounds are highly reactive and cannot be 

accurately measured using a canister sample. Instead, they are collected on a chemically 

treated cartridge using a Xontech 924 sampler, operated on the same 1-in-6 day schedule as 

the Xontech 910 used for sample collection in canisters. Samples are analyzed at the Air 

District laboratory using High Performance Liquid Chromatography. 

At Berkeley, the Xontech 924 sampler was also used to collect metals on Teflon filters on the 

same 1-in-6 day schedule used for other toxics sampling. Samples are analyzed by CARB 

using Inductively Coupled Plasma Mass Spectrometry (ICP-MS). The Berkeley site was 

closed on December 31, 2010 after the three year monitoring program concluded. The 

metals analyzed for are listed in Table 16.

Table 16. Metals measured at Berkeley using ICP-MS

Antimony Lead Sulfur

Arsenic Manganese Tin

Cadmium Molybdenum Titanium

Chromium Nickel Vanadium

Cobalt Platinum Zinc

Copper Selenium Zirconium

Iron Strontium
126

At Cupertino, the Xontech 924 sampler was used to collect metals on Teflon filters on the 

same 1-in-6 day schedule used for other toxics sampling. Samples are analyzed by CARB 

using X-Ray Fluorescence Spectrometry (XRF). The metals analyzed for are listed in Table 

17. Results are posted on the BAAQMD web site at:

http://www.baaqmd.gov/sitecore-s/~/media/Files/Technical%20Services/Cupertino_toxics.ashx

Table 17. Metals measured at Cupertino using XRF

Aluminium Chromium Molybdenum Strontium

Antimony Cobalt Nickel Sulfur

Arsenic Copper Phosphorus Tin

Barium Iron Potassium Titanium

Bromine Lead Rubidium Vanddium

Calcium Manganese Selenium Yttrium

Chlorine Mercury Silicon Zinc

In addition to CARB’s measurement of metals, the Air District laboratory began measuring

the metals listed in Table 16 in January 2011. The analysis is done using XRF on the same

samples that CARB analyzes to compare results. The measurements from both agencies 

have been comparable and, consequently, the Air District plans to discontinue the CARB

analysis starting with samples collected in April 2011. 

Additional Mercury Monitoring at Cupertino Monte Vista Park

Due to public concern about mercury emissions from the nearby Lehigh Southwest Cement 

Plant in Cupertino, the Air District began monitoring for Total Atmospheric Mercury 

(TAMS) at the Cupertino Monte Vista Park site on September 11, 2010.

Total atmospheric mercury includes both vapor and particulate forms of mercury whereas 

mercury measured on a filter using XRF methods yields solely the particulate form of 

mercury. Total atmospheric mercury is collected on a carbon trap using a Xontech 924 

sampler on the same 1-in-6 day schedule as the particulate mercury collected on Teflon 

filters. The carbon trap is analyzed by Frontier Geosciences. Results are posted on the 

BAAQMD web site at:

http://www.baaqmd.gov/sitecore-s/~/media/Files/Technical%20Services/Cupertino_toxics.ashx

Additional Gaseous Toxics Measured at San Jose

At San Jose the Air District analyzed for additional gaseous toxics compounds from the 

canisters. Acrolein is measured because San Jose is a NATTS program monitoring site and 

the NATTS program requires acrolein to be measured. The Air District uses a gas 

chromatography mass spectrometry method to measure acrolein. This method allows

detection of three other toxic compounds: acetonitrile, acrylonitrile, and ethanol. 

Acrylonitrile is measured because CARB wanted measurements to compare with other parts 

of the State. Ethanol is measured because researchers at UC Berkeley wanted to compare 

ethanol measurements taken near the Caldecott Tunnel with those taken from other areas of 
127

the Bay Area. Finally, acetonitrile is measured because it is a related compound and there 

were no other measurements of this compound in the Bay Area.

Additional Gaseous Toxics monitoring in 2011 at all sites

A modern gas chromatography mass spectrometry instrument was purchased by the Air 

District in late 2009 and installed in mid-2010. The Air District intends to measure 

Acrolein, Acetonitrile, Acroylonitrile, and Ethanol from all canister samples from the new 

instrument. However, testing found that the instrument failed to yield comparable results for 

multiple analyses done from the same canister sample. As of mid-2011, troubleshooting and 

retesting in consultation with the manufacturer continues, but a solution must be found before 

the Air District can start to measure these additional compounds from all canister samples.

Summary toxics data are available from the EPA’s AirData web site at 

http://www.epa.gov/oar/data/index.html. These data may also be found on the BAAQMD 

web site in the Toxic Air Contaminant Control Program Annual Report at

http://www.baaqmd.gov/Divisions/Engineering/Air-Toxics/Toxic-Air-Contaminant-ControlProgram-Annual-Report.aspx.
128

West Oakland CASS Study

The Air District is conducting an ambient air sampling and modeling study in the area near 

the Custom Alloy Scrap Sales (CASS) metals recycling facility in West Oakland. The 

purpose of the study is to determine if there are elevated concentrations of PM and toxic 

metals in the vicinity of the CASS facility. There is a mix of residential as well as light and 

heavy industry near CASS. In addition, two schools are located a few blocks east of the 

CASS fence line.

Initially, the Air District performed a health risk analysis of impacts from the CASS facility 

on the surrounding neighborhoods. Inputs to the modeling included stack emissions from 

CASS determined from a recent stack test, and meteorology from the nearby East Bay 

Municipal Utility District (EBMUD) meteorological station. The modeling showed that the 

highest concentrations of metals occurred east of the facility. Modeling results were then 

used to calculate cancer risk for West Oakland residents. The analysis showed that the CASS 

emissions increased cancer risk by less than one in a million (0.35 per million) and that the 

increased chronic hazard risk index was significantly less than one (0.002). Fugitive 

emissions were not included in the analysis. Following that, modeling results were compared 

with ambient concentrations.

The objectives of the sampling part of the study are to:

 Measure PM and metals concentrations near the CASS recycling facility.

 Determine whether PM or toxic metals measurements near CASS are elevated 

relative to West Oakland and Bay Area backgrounds.

 Compare measurements collected during this study with prior health risk assessment 

modeling conducted by the Air District.

 Estimate contributions from CASS.

 Use annual data to assess health risk, applying methods, unit risk factors, and 

reference exposure levels from the Office of Environmental Health Hazard 

Assessment.

 Compile a report synthesizing all available information and summarizing findings. 

Measurements began in August of 2009 at three sites near CASS and will continue for one 

year. One site is located west—predominantly upwind—of the facility, another site will be 

east—downwind—nearer to the CASS facility at the ASA Academy school, and the third site 

is further east at EXCEL High School. CASS also funded a second upwind site for the first 

three month period in 2009. Samples are collected using MiniVol sampler, operated for 24-

hours on a 1-in-6 day schedule. After collection, samples are sent to the Desert Research 

Institute (DRI) at the University of Nevada, Reno for analysis. The elements which are

analyzed are listed in Table 18. 
129

Table 18. Elements Measured for the West Oakland CASS Study.

Antimony Europium Nickel Sulfur

Arsenic Gallium Niobium Tantalum

Aluminum Gold Palladium Terbium

Barium Hafnium Phosphorous Thallium

Bromine Iron Potassium Tin

Cadmium Indium Rubidium Titanium

Calcium Iridium Samarium Tungsten

Chromium Lanthanum Scandium Uranium

Cobalt Lead Selenium Vanadium

Copper Manganese Silicon Yttrium

Chlorine Molybdenum Silver Zinc

Cerium Magnesium Sodium Zirconium

Cesium Mercury Strontium

Data from the three sites near CASS, plus the 3-month CASS site, will be compared with 

data from seven additional sites operated as part of the West Oakland Monitoring Study (see 

description of the West Oakland Monitoring Study). CASS data will also be compared with 

data from the West Oakland, Livermore, Vallejo, and San Jose monitoring sites where 

similar metals analyses are available.

Figure 7. Map of CASS Site with Monitoring Locations and Meteorological Station.
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Attributing air pollutants collected from ambient samples to specific sources can be a 

challenging task. The success of source attribution will depend on how unique emissions 

from the CASS facility are relative to surrounding sources. The Air District will examine the 

relative amounts of metals collected on filters during upwind and downwind periods, using 

wind data from the Oakland sewage treatment plant. 

If there is a statistically significant difference in the relative concentrations of toxic metals 

between upwind and downwind samples, then further analysis will be undertaken to 

determine if the downwind sample resembles the stack source samples collected from CASS 

in 2007. Other facilities, such as Central Concrete and a nearby art studio that operates 

ceramic kilns, could also be a source of metals but presumably with a distinguishable source 

mix.
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West Oakland Measurement Study

In 2009-10, the Air District and the Desert Research Institute (DRI) conducted the West 

Oakland Measurement Study (WOMS) to measure diesel emissions and other toxic air 

contaminants within the West Oakland area. The Air District invited DRI to collaborate on 

the project due to DRI’s experience in a similar study in Los Angeles. Although the 

principal focus of the study was the measurement of emissions from the Port of Oakland, 

other significant toxic sources in West Oakland were also included in this study. The study 

is part of the Air District’s Community Air Risk Evaluation (CARE) program which 

evaluates and reduces health risks associated with exposures to outdoor toxic air 

contaminants in the Bay Area.

West Oakland was selected for the study because a Health Risk Assessment (HRA)1

produced jointly by the Air District and the California Air Resources Board concluded that 

ambient concentrations of diesel particulate matter in the West Oakland area were almost 

three times higher than typical levels in the Bay Area. High diesel emissions in that area 

were also confirmed by the Air District’s emission inventory. Diesel particulate accounts for 

80% of the cancer risk from airborne toxics based on findings from the CARE Program. The 

primary diesel sources include large ships that dock at the Port of Oakland, service trucks 

that move shipping containers and other freight around at the port, passenger and freight train 

service, the Union Pacific and Joint-Intermodal rail yards, the Amtrak passenger service 

maintenance yard, and concentrated heavy duty trucks that transports goods to or from the 

port and other industries in or near West Oakland. 

Currently, there is no method to directly measure ambient concentrations of diesel 

particulate. However, black carbon (soot) and organic/elemental carbon measurements can 

be used as a surrogate to approximate diesel concentrations. Other toxics compounds 

associated with diesel combustion including criteria gases such as NO2 (and NOx) and SO2

were also measured.

To build a complete and representative ‘snapshot’ of the air toxic exposure in West Oakland,

the Air District and DRI set up a dense monitoring network which was operated over

relatively short periods of time. The three main objectives of the study were to:

 Evaluate spatial and seasonal variations of toxic air contaminants and particulate 

matter concentrations within West Oakland based on their proximity to known 

sources including the Port of Oakland, arterial roadways, and California state 

highways.

 Analyze the particulate composition and determine the source contribution of 

gasoline and diesel vehicles to ambient particulate concentrations.

 Evaluate community exposure to toxic air contaminants and identify emissions 

hotspots.

 

1

California Air Resources Board. (2008). “Diesel Particulate Matter Health Risk Assessment for the West 

Oakland Community.” Available on-line at: 

http://www.arb.ca.gov/ch/communities/ra/westoakland/documents/westoaklandreport.pdf
132

Local wind data showed that there are seasonal changes in the wind pattern. To evaluate the 

seasonal variations, four weeks of sampling were collected to characterize summer 

conditions from July to August 2009 and winter time conditions from December 2009 to 

January 2010. Figure 8 shows the West Oakland sampling locations that were used during 

both seasonal sampling periods.

WOMS 7-day Sampling

Passive BTEX, 1,2 BD

Passive aldehydes

Passive NO2, NOx, SO2 Mini-vol PM2.5 mass, 

OC, EC and metals

Red vertical line indicates 

24-hr particulate organic 

compound speciation.

Cass Sites 24-hr Sampling

Every sixth day 

PM2.5 mass and metals

WOMS 7-day Passive Only 

NOx and NO2

N

G1

G2

G3

G4

G5

G6

G7

G8

NR1

WO1

WO2

POC

EBMUD

WO3/ 

CUPW

CNDW

CFDW

POU

Gates

57-59

Gates

24-26

Figure 8. West Oakland Measurement Study Sampling Locations.

The WOMS included measurements with continuous, 24-hour, and 7-day sampling 

durations. Continuous measurements were made using a mobile monitoring van that moved 

from place to place within West Oakland, recording a set of pollutant concentrations at 

specific locations and times along a fixed route. The measurement route was preselected 

based on the preliminary pilot study and driven twice per day in the morning and afternoon 

on selected days of interest. The van measurements included O3, NO/NO2, CO, volatile 

organic carbon (VOC) estimates , black carbon, PM2.5 mass, particle size distributions and 

ultrafine particle number concentrations. The study used the data from the West Oakland

monitoring station at EBMUD as a reference for comparison to measurements collected from 

the saturation monitoring. West Oakland concentrations were also compared with data from 

the Air District’s toxic network and PM2.5 Speciation Sampling Program to determine how 

West Oakland compares with the rest of the Bay Area.
133

At three WOMS sites (one at the Air District West Oakland air monitoring station), 24-hour 

Teflon and quartz filters collected particulate samples on preselected days over the course of 

the four week study using sequential filter samplers. The filters were analyzed for daily 

concentrations of PM2.5 mass, organic and elemental carbon, and organic carbon species. 

Another set of 24-hour glass filters and resin cartridges were exposed on the same days to 

measure polycyclic aromatic hydrocarbons, alkanes, hopanes, steranes, and polar 

compounds. The Chemical Mass Balance receptor model will be applied to these speciated 

particulate data to estimate the source contributions of diesel particulate matter, gasoline 

combustion, wood smoke, and cooking emissions.

Long-term exposure (7-day composite) measurements were made at 15 WOMS locations 

plus an additional site that was part of a supplemental study being conducted at Custom 

Alloy Scrap Sales (CASS). These measurements were designed to estimate the exposure of 

local populations to the different pollutants and show the concentration gradients of these 

contaminants throughout West Oakland. Active sampling methods were used at eight 

measurement sites where ambient air flow was drawn through quartz or Teflon filters. The 

quartz filters were analyzed for total PM2.5 mass, and for organic and elemental carbon 

concentrations. The Teflon filters were analyzed for PM2.5 mass as well as metals using Xray fluorescence. The CASS study is a separate year-long metals exposure measurement 

study that was conducted at the same time in West Oakland and provides supplemental 

metals data. The CASS study is discussed previously in this report.

Passive (diffusion) samplers were employed at 16 study area sites to measure 7-day 

integrated samples of NOx, and NO2. SO2, BTEX (benzene, toluene, ethylbenzene, and 

xylenes), and carbonyl compounds (formaldehyde, acetaldehyde and acrolein) were also 

measured using passive samplers at the same eight sites where 7-day composite samples 

were collected. After each 7-day exposure period ended, passive samplers were analyzed by 

a laboratory and average pollutant concentrations estimated over the exposure period. 

Passive sampler performance was evaluated against the co-located 24-hour filter samplers 

during times both sampler methods were used.

Meteorological data for WOMS was provided by the Air District’s meteorological station

located at the EBMUD sewage treatment plant approximately one mile northeast of the study 

area near the Bay Bridge toll plaza. The station provided high quality hourly wind speed, 

wind direction, and ambient temperature data representative of the entire WOMS area.