State of California

California Environmental Protection Agency

Air Resources Board

SECOND TRIENNIAL REVIEW

OF THE ASSESSMENT OF THE IMPACTS OF TRANSPORTED POLLUTANTS

ON OZONE CONCENTRATIONS IN CALIFORNIA

(Revised)

November 1996

Staff Report: Initial Statement of Reasons

Prepared by

Technical Support Division

This report has been reviewed by the staff of the California Air Resources Board and

approved for publication. Approval does not signify that the contents necessarily reflect

the views and policies of the California Environmental Protection Agency or the Air

Resources Board, nor does mention of trade names or commercial products constitute

endorsement or recommendation for use.
ACKNOWLEDGMENTS

The 1996 transport assessment update was prepared by the staffs of the Modeling and

Meteorology Branch and the Air Quality Data Branch under the direction of Don

McNerny and Rich Bradley, respectively.

Leadership and coordination were provided by Debora Popejoy, Manager of the Air

Quality Analysis Section. Susan Lorenzen was instrumental in producing the final report.

Supervision for portions of the effort was provided by Andrew Ranzieri, Manager of

the Modeling Support Section, John DaMassa, Manager of the Control Strategy Modeling

Section, and Arndt Lorenzen, Manager of the Meteorology Section.

Special thanks go to the following ARB staff who played a major role in preparing this

assessment:

Technical Support Division

Steve Gouze Susan Lorenzen

Dennis King Bill Wilson

Cary McGregor Saffet Tanrikulu

Elliot Mulberg
TABLE OF CONTENTS

Chapters Page

Summary and Overview 1

I. Background 3

A. Introduction 3

B. Transport Assessment 3

C. Transport Impact Mitigation 4

D. Public Consultation Process 5

E. Definitions and Terminologies 5

II. Proposed Regulatory Changes 7

A. Transport Couples Identification Changes 7

B. Transport Assessment Changes 7

III. Transport Couples Assessments 9

A. Broader Sacramento Area to Mountain Counties Air Basin 9

B. San Joaquin Valley Air Basin to Mountain Counties Air Basin 13

C. San Francisco Bay Area Air Basin to Mountain Counties Air Basin 17

D. San Francisco Bay Area Air Basin to North Central Coast Air Basin 21

E. San Joaquin Valley Air Basin to North Central Coast Air Basin 27

F. San Joaquin Valley Air Basin to Great Basin Valleys Air Basin 31

G. South Coast Air Basin to Mojave Desert Air Basin 35

H. San Joaquin Valley Air Basin to Mojave Desert Air Basin 43

I. South Coast Air Basin to Salton Sea Air Basin 47

J. San Francisco Bay Area Air Basin to San Joaquin Valley Air Basin 51

K. San Francisco Bay Area Air Basin to Broader Sacramento Area 57

L. Broader Sacramento Area to Upper Sacramento Valley 61

M. South Coast Air Basin to San Diego Air Basin 67

N. South Coast Air Basin to South Central Coast Air Basin 69

IV. Impact Analysis 73

A. Public Health, Welfare, and Environmental Impacts 73

B. Economic Impacts 74

C. Alternatives 75

V. Research Needs 77

A. Transport Aloft 77

B. Specific Couples for Transport Research 78

C. Photochemical Grid Modeling 78

D. Data Analysis 78

E. Enhanced Monitoring 79

VI. References 81
TABLE OF CONTENTS

(continued)

Appendices

A. Text of Health and Safety Code Section 39610 85

B. Public Consultation Workshop Notice 89

C. Workshop Participants 93

D. Glossary 97

E. Text of Proposed Amendments to the Transport Identification and 

Mitigation Regulations 113 

F. Data Tables 123 

G. Supplemental Information 149 

H. Mojave Desert Air Pollution Transport Interim Report 161 
1

SECOND TRIENNIAL REVIEW

 OF THE ASSESSMENT AND MITIGATION OF THE IMPACTS OF

TRANSPORTED POLLUTANTS ON OZONE CONCENTRATIONS IN

CALIFORNIA

SUMMARY AND OVERVIEW

Under section 39610(b) of the Health and Safety Code, the California Clean Air Act of

1988 (the Act) requires the Air Resources Board (ARB or Board) to assess the relative

contributions of upwind emissions to downwind state ozone standard exceedances and to

update this assessment at least every three years. The first assessment was approved by

the ARB in August 1990 (see Reference 4). The first triennial update occurred in August

1993 (see Reference 6). This report, which is the second triennial update of the ozone

transport couples, reviews and updates the August 1993 assessment.

The ARB staff (the staff) recommends several changes to the ozone transport

assessments (see Table 1): 1) eliminate the inconsequential transport classification from

the Broader Sacramento Area to the Upper Sacramento Valley; 2) extend the area

impacted by overwhelming transport of ozone or ozone precursors from the Broader

Sacramento Area to include the central portion of the Mountain Counties Air Basin; and

3) identify the San Joaquin Valley Air Basin as an upwind contributor to ozone

concentrations in the North Central Coast Air Basin. 

The staff also recommends future research needs to the Board. Areas for future

research identified by the staff include transport aloft, photochemical grid modeling, data

analysis, and enhanced monitoring. The staff also identified several transport couples that

need further research.

In May 1996 (see Reference 8), the Board created two new air basins by dividing the

Southeast Desert Air Basin into the Mojave Desert Air Basin and the Salton Sea Air Basin

(the Board’s actions have not yet been approved by the Office of Administrative Law). 

These changes require the identification of four new ozone transport couples: South

Coast Air Basin to Mojave Desert Air Basin, South Coast Air Basin to Salton Sea Air

Basin, San Joaquin Valley Air Basin to Mojave Desert Air Basin, and Mexico to Salton

Sea Air Basin. These recommended transport couple updates and changes in

characterization are shown in bold in Table 1.

The ARB 1989, 1990, and 1993 transport documents on transport couple

identification, assessment, and mitigation developments are included as a part of this

report by reference. (See Chapter VI for References 3, 4, 5, and 6.)
2

Table 1

Summary of Transport Characterization by Couples*

Transport Couples Transport Characterization**

Previous Proposed

1. Broader Sacramento Area to Mountain Counties O O

2. San Joaquin Valley to Mountain Counties O O

3. San Francisco Bay Area to Mountain Counties S S

4a. Mexico to Southeast Desert O, S ---

4b. Mexico to Salton Sea --- O, S

5. Mexico to San Diego O, S, I O, S, I

6. San Joaquin Valley to South Central Coast S, I S, I

7. San Francisco Bay Area to Broader Sacramento Area O, S, I O, S, I

8. San Francisco Bay Area to San Joaquin Valley O, S, I O, S, I

9a. South Coast to Southeast Desert O, S, I ---

9b. South Coast to Mojave Desert --- O, S

10. Broader Sacramento Area to Upper Sacramento Valley O, S, I O, S

11a. San Joaquin Valley to Southeast Desert O, I ---

11b. San Joaquin Valley to Mojave Desert --- O

12. South Coast to San Diego O, S, I O, S, I

13. South Coast to South Central Coast S, I S, I

14. South Central Coast to South Coast S, I S, I

15. San Joaquin Valley to Broader Sacramento Area S, I S, I

16. San Joaquin Valley to Great Basin Valleys O O

17. Broader Sacramento Area to San Joaquin Valley S, I S, I

18. Broader Sacramento Area to San Francisco Bay Area S, I S, I

19. California Coastal Waters to South Central Coast S S

20. Bay Area to North Central Coast O, S O, S

21. San Joaquin Valley to North Central Coast --- S

22a. South Coast to Southeast Desert O, S, I ---

22b. South Coast to Salton Sea --- O, S

*Staff recommended changes shown in Bold

**O=Overwhelming, S=Significant, I=Inconsequential
3

CHAPTER I

BACKGROUND

A. Introduction

The California Clean Air Act of 1988 (the “Act,” Stats. 1988, Chapter 1568; as

amended by AB 2783, Stats. 1992, Chapter 945) requires each air pollution control and

air quality management district in which a state ambient air quality standard for ozone,

carbon monoxide, sulfur dioxide, or nitrogen dioxide is exceeded to develop a plan and an

emission control program to attain the standard(s). The Act recognizes that ozone and

ozone precursors can be carried by winds over long distances and thereby contribute to air

quality problems outside the district or air basin where they originated. To address this,

the Act requires upwind districts to mitigate the impacts on downwind areas of pollutants

emitted in the upwind districts. (See section 39610 of the Health and Safety Code) The

Act directs the Air Resources Board (ARB or Board) to assess the impacts of such

transport and to establish mitigation requirements for upwind districts. This chapter

provides background information related to the assessment of transport impacts and

describes the public consultation process.

B. Transport Assessment

The Act directs the ARB to: 1) identify downwind areas affected by transported

air pollutants and the upwind air basins or regions, which are the sources of the pollutants; 

 2) assess the relative contributions of upwind emissions to downwind ozone

concentrations as overwhelming, significant, inconsequential, or some combination

thereof, to the extent permitted by available data (Health and Safety Code section

39610(a) and (b)); and 3) update this analysis at least once every three years (Health and

safety Code section 39610(d)). The staff has and will continue to report to the Board on

significant findings between the triennial updates. (See Appendix A for the text of Health

and Safety Code section 39610.)

Transport couple assessment depends upon the exceedance values at any given

site. There are a couple of thresholds used in the assessment process that affect which

exceedances will be assessed and which will not. The first threshold is the state standard. 

All values which exceed the state standard are considered exceedances. The next

threshold is the expected peak day concentration (EPDC). This ozone concentration is

one which is not expected to occur more than one time per year. Thus, ozone

concentrations greater than the EPDC are, theoretically, expected to occur less than one

time per year on the average. The ozone concentrations which are greater than the state

standard, and less than or equal to the EPDC, are considered violations of the state

standard. The values which are greater than the EPDC are considered extreme

concentrations. Extreme concentrations are not weighed in the assessment process
4

because of the nature of their occurrence. Given that these are extreme concentrations,

the staff considers them to be beyond reasonable regulatory control and transport

assessments are not performed.

More than one assessment may apply to a transport couple. These assessments

rely on, but are not limited to, such parameters as wind speed and wind direction. As

these parameters vary from day to day, the assessments may also vary. Therefore, while

there may be a finding of inconsequential on one or more violation days, other days may

be assessed as overwhelming and/or significant. Likewise, an area that is the upwind air

basin on one day may be the downwind air basin on another day.

In December 1989 (see Reference 3), the ARB adopted a regulation identifying 14

transport couples, each consisting of an upwind area that is the source of transported

ozone or ozone precursors and a downwind receptor area impacted by those pollutants

(Title 17, California Code of Regulations, section 70500). In May 1992, the ARB

approved changes to the transport identification regulation, which redefined the

boundaries of the Upper Sacramento Valley and the Broader Sacramento Area.

In August 1990 (see Reference 4), the ARB approved a qualitative assessment of

the relative contributions of upwind emissions to downwind ozone concentrations. In that

assessment, the relative contribution was qualitatively classified as either “overwhelming,”

“significant,” or “inconsequential.”

In August 1993 (see Reference 6), the ARB approved the first required triennial

update to the 1990 assessments. In that update, new transport couples were identified and

assessed, the number of areas with mitigation responsibility was increased, and some

previous assessments were updated.

This report is the second triennial update to the 1990 assessments. Few changes

are proposed. The staff recommends modifying the assessment of one existing couple,

identifying a new couple, and enlarging the downwind area of another couple. Due to the

division of the Southeast Desert Air Basin into two new air basins, four new couples have

been identified to conform to the new air basin names. The assessment of one of these

couples has been modified. 

C. Transport Impact Mitigation

Health and Safety Code section 39610(b) directs the ARB to establish mitigation

requirements for upwind districts commensurate with their contributions to the air quality

problems in the downwind areas. This was first done with the August 1990 transport

assessment. Three parts to the mitigation requirements applicable to upwind districts were

established: (1) adopt a “no-net-increase” permitting program for all new or modified

stationary sources, (2) commit to adopt best available retrofit control technology
5

(BARCT) for some stationary sources of reactive organic gas (ROG) and oxides of

nitrogen (NOx) emissions, and (3) where overwhelming transport exists, include sufficient

measures in the air quality plans to ensure expeditious attainment of the ozone standard in

the downwind district(s).

In March 1993 (see Reference 5), the ARB approved the deletion of the “no-netincrease” requirement from the mitigation regulation (section 70600). The effects of this

deletion are that permitting requirements for all districts are those specified in the Act

based on the districts’ nonattainment classification, whether or not the district is a source

of transported pollutants. The remaining two mitigation requirements were not changed. 

The staff is not proposing to change the mitigation requirements of upwind areas at this

time. The staff only recommends amendments that redefine which areas are subject to the

mitigation requirements.

D. Public Consultation Process

Several transport working groups were formed in response to the Board’s 1993

direction that the staff work more directly with districts’ staffs to assess transport. These

groups comprised staffs from affected districts and from the ARB. In one group,

representatives of industry and affected facilities were also included. The purpose of the

working groups was to identify days for analysis and then to share data, analyses, and

recommendations pertinent to the chosen days. The working group members met every

two to four months for approximately two years.

As part of this transport assessment update, the staff conducted a public

consultation workshop on July 10, 1996, to discuss its transport assessment studies with

districts and other interested parties. A copy of the workshop notice is shown in

Appendix B, and the list of workshop participants is shown in Appendix C.

During the public workshop, an issue was raised regarding transport mitigation

requirements of upwind districts. That issue is being further investigated through

meetings with EPA, ARB, local air pollution control districts, and affected parties. This

report does not propose changes in mitigation measures.

E. Definitions and Terminologies

Below are some terms used frequently in this report. See Appendix D for a

glossary of many other commonly used terms:

Overwhelmed - ozone transport classification describing a condition when the emissions

from the upwind area independently caused a violation of the State ozone standard in the

downwind area on any single day. Significant emission sources in the downwind area
6

were not in the pathway of the air parcel that was transported from the upwind area. The

responsibility for a violation caused by overwhelming transport lies with the upwind area. 

Significant - ozone transport classification describing a condition in which the emissions

from the upwind area contributed measurably to a violation of the State ozone standard in

the downwind area on any single day, but did not overwhelm the area. A violation is

considered caused by significant transport if the emissions from sources within the

downwind area combine with the transported air parcel carrying ozone or ozone

precursors from the upwind area. A violation classified as significant is considered shared,

with responsibility lying with both the upwind and downwind areas.

Inconsequential - ozone transport classification describing a condition when upwind

emissions were not transported or did not appear to contribute significantly to a violation

of the ozone standard in the downwind area. A violation not impacted by transported

emissions is considered local and results when the wind flow patterns and atmospheric

conditions do not strongly suggest responsibility from an upwind area. The responsibility

of inconsequential transport lies with the downwind area.

Expected Peak Day Concentration - the highest concentration that is statistically

expected to occur no more frequently than once every year. 

Exceedance - any concentration that is greater than the ambient air quality standard.

Violation - an exceedance that is not excluded as a highly irregular or infrequent event,

such as an exceptional, unusual, or extreme concentration event, and is considered beyond

reasonable regulatory control.

SARMAP - stands for the SJVAQS (San Joaquin Valley Air Quality Study)/

AUSPEX(Atmospheric Utility Signatures, Predictions, and Experiments) Regional

Modeling Adaptation Program.
7

CHAPTER II

Proposed Regulatory Changes

A. Transport Couples Identification Changes

In May 1996 (see Reference 8), the ARB adopted regulations creating two new air

basins from the area that used to make up the Southeast Desert Air Basin. These new air

basins were named the Mojave Desert Air Basin and the Salton Sea Air Basin. (These

new basins have not yet been approved by the Office of Administrative Law.) Appropriate

changes are recommended to make identified transport couples conform to these two new

air basins. The staff also proposes to add a new couple, the San Joaquin Valley Air Basin

transporting to the North Central Coast Air Basin. It is recommended that these changes

be incorporated into the California Code of Regulations, Subchapter 1.5, Article 5, section

70500. 

B. Transport Assessment Changes

The staff recommends that the Board modify the characterization of overwhelming

transport impacts of pollutants from the Broader Sacramento Area on ozone

concentrations in the Mountain Counties Air Basin. Under the present characterization,

the northern portion of the Mountain Counties Air Basin, which includes Nevada, Sierra,

and Plumas Counties, is overwhelmingly impacted by transport from the Broader

Sacramento Area. The staff recommends that the Board enlarge the downwind area to

include Amador and Calaveras Counties in the central portion of the Mountain Counties

Air Basin. It is recommended that this change be incorporated into the California Code of

regulations, Subchapter 1.5, Article 6, section 70600.

The staff also proposes that the Board modify the characterization of the transport

impacts of pollutants from two transport couples which do not require changes to

regulation but may have planning implications. First, the staff proposes that the Board

modify the assessment of the impacts of transport from the South Coast Air Basin on

ozone concentrations in San Bernardino County, which was in the Southeast Desert Air

Basin but is now in the Mojave Desert Air Basin. The staff proposes that the Board

include the finding of significant transport besides the 1993 finding of overwhelming and

inconsequential transport. Second, the staff proposes to eliminate the finding of

inconsequential transport from the Broader Sacramento Area to the Upper Sacramento

Valley. 

Chapter III will discuss the staff’s analyses that support the proposed changes to

both transport couple identification and transport assessments. The details of the analyses,

including air flow charts, 850 and 500 millibar charts, ambient temperatures, profiler data,

back trajectories, and other data analyses can be reviewed at the ARB offices. Discussion
8

of a single episode in each section, gives an example of the type of transport involved. 

See Appendix E for the full text of the proposed amendments to the identification and

mitigation regulations.
9

CHAPTER III

Transport Couple Assessments

A. Broader Sacramento Area to Mountain Counties Air Basin

1. Previous Assessment

In 1993 (see Reference 6), the Air Resources Board (ARB) concluded that the

cause of all ozone violations in the northern portion of the Mountain Counties Air Basin

(MCAB) was the overwhelming impact of transported emissions from the Broader

Sacramento Area (BSA). The northern portion of the MCAB is Plumas, Sierra, and

Nevada Counties. 

2. Analysis for Northern Portion of the Mountain Counties Air Basin

During 1994-1995, 252 ozone exceedances of the state standard occurred in the

MCAB (see Table F-1 in Appendix F). Of those, 43 were in the northern portion of the

air basin (at Colfax, Grass Valley, and White Cloud Mountain). Figure 1 is a map of the

area. Since the 1993 update concluded that all violations were caused by overwhelming

transport of pollutants from the BSA, the focus of this update was to determine whether

there was evidence to contradict the previous assessment or to demonstrate that the

previous assessment is still valid. All violations were examined for possible significant or

inconsequential transport.

First, the exceedances were screened by identifying and excluding those daily

maximum ozone concentrations that exceeded the EPDCs (see Reference 9) and,

therefore, considered extreme concentrations and not considered violations. Eight

exceedances were greater than the EPDCs (see Table F-2 in Appendix F), which left 35

violations remaining for further evaluation. 

The 35 violations were examined for evidence of transport. Several criteria were

used to evaluate the violations. Some of these criteria were: the time of day of the

violations, temporal progression of exceedances, air flow patterns (surface and aloft where

available), spatial extent of the violations, and emissions from both the upwind and

downwind areas. All 35 violations had meteorological and air quality data consistent with

conditions of transport, such as elevated ozone concentrations in the Broader Sacramento

Area and winds from the south-southwest through west. 
10

Figure 1

[map of BSA to MCAB]
11

The northern MCAB precursor emission inventory trends from 1987 to 1995

remained flat. The emission inventories of precursors in the BSA continue to be much

greater than those in the northern MCAB. These emission trends suggest that local

precursor emissions in the MCAB are still not significant enough to cause a local

exceedance. Because the emissions in the northern portion of the MCAB have not

increased since the 1993 update, there still are not significant emissions in the MCAB

along the pathway of the transported air parcels which carry pollutants from the BSA to

contribute significantly to the violations.

A violation at Colfax is briefly discussed here to illustrate a typical case of

overwhelming transport from the BSA. At 1800 PST on July 11, 1994, the daily

maximum ozone concentration in Colfax was 104 parts per billion (ppb). A strong delta

breeze occurred on the day before and day of the exceedance. Exceedances of the ozone

standard occurred in the BSA on the day of the exceedance. In addition, the temporal

progression of the daily maximum ozone concentrations from the eastern Sacramento area

to Colfax is consistent with the air flow patterns of that day. These conditions indicate

that Sacramento ozone and precursor emissions overwhelmingly impacted Colfax.

3. Analysis for Central Portion of the Mountain Counties Air Basin

The ARB concluded during the 1993 transport assessment that the BSA could

overwhelmingly impact the northern portion of the MCAB. However, more recently

available data from the San Joaquin Valley Air Quality Study show that transport from the

BSA also impacts the central portion of the MCAB. Therefore, an examination of

exceedances in the central portion of the MCAB was carried out to verify whether the

BSA impacts the central portion of the MCAB. 

During 1994-1995, 252 ozone exceedances of the state ozone standard occurred in

the MCAB (see Table F-1 in Appendix F). Of those, 94 were measured in the central

portion of the air basin (at Jackson and San Andreas - see Figure 1). The 58 exceedances

at Placerville were not included, because Placerville is part of the BSA planning region. 

The 94 exceedances were screened to reduce the number of possible exceedances

for detailed analysis. First, the exceedances were screened by identifying and excluding

those daily maximum ozone concentrations that exceeded the Expected Peak Day

Concentrations (EPDCs) (see Reference 9) and, therefore, are considered extreme

concentrations, not violations. Seven exceedances were greater than the EPDCs (see

Table F-2 in Appendix F). The elimination of these 7 left 87 violations for further

evaluation.

The 87 violations were examined for evidence of transport. Several criteria were

used to evaluate the violations. Some of these criteria were: the time of day of the

violations, temporal progression of exceedances, air flow patterns (surface and aloft where
12

available), spatial extent of the violations, and emission sources of the upwind and

downwind areas. All 87 violations had meteorological and air quality data consistent with 

conditions of transport from several upwind areas. 

The emission inventory trends of the central portion of the MCAB from 1987 to

1995 remained flat. The upwind precursor emissions continue to be much greater than the

central portion of the MCAB. These emissions suggest that local precursor emissions are

still not significant enough to cause a local exceedance. There are still no significant

sources of emissions in the MCAB along the pathway of the transported air parcels which

carry pollutants from the upwind areas.

A violation at San Andreas is briefly described here to illustrate a typical case of

overwhelming transport from the BSA into Calaveras County. (Examples of transport

from the other upwind areas are discussed in Sections B and C of this report.) At 

1600 PST on June 26, 1994, the daily maximum ozone concentration in San Andreas was

101 ppb. On that violation day, northwest winds blew throughout the Sacramento Valley

to the delta area. A back trajectory analysis indicates that morning peak commute hour

traffic and other emissions from the Sacramento urban area impacted the San Andreas area

at the time of the daily maximum ozone concentration. Moreover, an increase in ozone

concentrations occurred along the transport pathway from Sacramento to San Andreas. 

This gradient suggests that the 50-mile distance gave adequate time for the conversion of

precursors to ozone. These analyses indicate that San Andreas was overwhelmingly

impacted by ozone from the BSA.

4. Conclusions and Recommendations

Based on the results of the meteorological and air quality data analyses, the ARB

staff concludes that the causes of all 35 violations in the northern portion of the MCAB

were overwhelming transport of pollutants from the BSA. Since there are no changes to

the transport findings of the 1993 report, no regulatory changes are recommended for the

BSA impact on the northern MCAB.

Based upon the results of the meteorological and air quality data analyses, the

ARB staff concludes that the causes of all 87 violations in the central portion of the

MCAB were overwhelming transport of pollutants from several possible upwind areas.

The violation on June 26, 1994, in San Andreas was shown to be caused by overwhelming

transport from the BSA. The staff recommends that the Board find that on some days the

central portion of the MCAB is impacted by overwhelming transport from the BSA. 

As a result of these assessments, the staff recommends that the downwind area

which is overwhelmed by transport from the BSA be enlarged to include all counties in the

MCAB north of the Calaveras-Tuolumne County border. 
13

B. San Joaquin Valley Air Basin to Mountain Counties Air Basin

1. Previous Assessment

In 1993 (see Reference 6), the ARB concluded that the southern portion of the

MCAB was overwhelmingly impacted by transported ozone and ozone precursors from

the San Joaquin Valley Air Basin (SJVAB) on some days and by both the SJVAB and the

San Francisco Bay Area Air Basin (SFBAAB) on others. The southern portion of the

MCAB was defined as those counties south of the Amador-El Dorado County border.

2. Analysis

The ARB concluded during the 1993 transport assessment that all violations in the

southern portion of the MCAB were overwhelmed by pollutants transported from several

upwind areas and that on some days the SJVAB emissions alone can overwhelm the

southern portion of the MCAB. Therefore, analyses of the exceedances in the southern

portion of the MCAB were carried out to determine whether if any evidence contradicts

the previous assessment.

During 1994-1995, there were 252 ozone exceedances of the state ozone standard

in the MCAB (see Table F-1 in Appendix F). Of those, 151 were measured in the

southern portion of the MCAB; 95 in Amador and Calaveras Counties and 57 in Mariposa

and Tuolumne Counties. These 57 exceedances which were measured at Sonora-Barretta,

Sonora-Old Oak Ranch, Turtleback Dome, Jerseydale, Camp Mather, and Wawona were

the focus of this assessment. These sites were chosen for analyses to minimize the impacts

of pollutants from the BSA and the SFBAAB, since these sites are further south than

those in Amador and Calaveras. See Figure 2 for a map of the area.

First, the exceedances were screened by identifying and excluding those daily

maximum ozone concentrations which exceeded the Expected Peak Day Concentrations

(EPDCs) (see Reference 9) and, therefore, are considered extreme concentrations but not

considered violations. Eight exceedances were greater than the EPDCs (see Table F-2 in

Appendix F). The elimination of these 8, left 49 violations for further evaluation.

The 49 violations were examined for evidence of transport. Several criteria were

used to evaluate the violations. Some of these criteria were: the time of day of the

violations, temporal progression of exceedances, air flow patterns (surface and aloft where

available), spatial extent of the violations, and emission sources of the upwind and

downwind areas. All 49 violations had meteorological and air quality data generally

consistent with conditions of transport such as late afternoon exceedances and winds from

the southwest. Additionally, violation days exhibited elevated ozone concentrations

upwind in the San Joaquin Valley.
14

The emission inventory trends of the southern portion of the MCAB precursor

from 1987 to 1995 remained flat. The emission inventories of precursors in the SJVAB

continue to be considerably greater than the southern portion of the MCAB. These

emission trends suggest that local precursor emissions are still not significant enough to

cause a local exceedance. There are still no significant sources of emissions in the MCAB

along the pathway of the transported air parcels which carry pollutants from the SJVAB.

A violation at Jerseydale is discussed here as an example of overwhelming

transport from the SJVAB. At 1700 PST on August 31, the daily maximum ozone

concentration in Jerseydale was 102 ppb. Light to moderate northwest winds blew

throughout the SJVAB on the day before the violation.

The late morning Fresno eddy was present on both the day before and day of the

violation. This eddy, a common phenomenon in the San Joaquin Valley, is a weak

cyclonic, or counterclockwise, circulation which occurs when the north-northwest wind

speeds are nearly equal to the drainage flow wind speeds. If the winds are too strong or

too weak, the circulation does not exist. The eddy appears to have transported morning

emissions and ozone from the greater Fresno area to the eastern side of the San Joaquin

Valley both north and east of Fresno. These precursors and ozone then travel up into the

foothills during the late morning and early afternoon to impact the higher elevations. This

scenario is evident by the daytime southwest winds at both Jerseydale and Turtleback

Dome, and further strengthened by the progression of the time of the daily maximum

ozone concentrations along the path from Fresno (1300 PST) to Jerseydale (1700 PST)

and beyond to Turtleback Dome (1800 PST).

High concentrations of ozone appear to have been confined to the central and

southern portions of the SJVAB on the day before and the day of the violation. Ozone

concentrations in the SFBAAB were below the state standard for both days. Ozone

exceedances occurred only in the north and northeastern portions of the Broader

Sacramento Area on the day of the violation. This ozone pattern suggests that the ozone

violations in the central SJVAB were mainly due to local emissions which subsequently

impacted the ozone concentrations at Jerseydale.

3. Conclusions and Recommendations

As found in the meteorological and air quality data analyses, the causes of all the

49 exceedances in the two most southern counties of the MCAB were overwhelming

transport of ozone. The violation on the August 31, 1995, in Jerseydale was shown to be

the result of overwhelming ozone transport from the SJVAB. The staff recommends that

the Board find that the southern portion of the MCAB continues to be impacted by

overwhelming transport from the SJVAB. This analysis agrees with the previous, 1993

transport assessment, and, therefore, requires no changes to the transport regulations.
15

Figure 2

[map of SJVAB to MCAB]
16
17

C. San Francisco Bay Area Air Basin to Mountain Counties Air Basin

1. Previous Assessment

In 1993 (see Reference 6), the ARB concluded that the southern portion of the

Mountain Counties Air Basin (MCAB) was significantly impacted by transported

pollutants from the San Francisco Bay Area Air Basin (SFBAAB). The conclusion was

based on an analysis of violations at Angels Camp (Calaveras County) and Pardee

Reservoir (Amador County). The Board found that emissions from the SFBAAB and the

SJVAB, collectively, impacted the southern portion of the MCAB on some days. The

staff was unable to separate out the individual air basin contributions. The staff analysis of

other days showed that the SJVAB emissions alone can overwhelm the southern portion

of the MCAB.

2. Analysis

The ARB concluded during the 1993 transport assessment that all the violations in

the southern portion of the MCAB were caused by overwhelming transport of pollutants. 

This update to the transport assessment was done to determine whether there is evidence

to contradict the previous assessment.

During 1994-1995, there were 252 ozone exceedances of the state standard in the

MCAB (see Table F-1 in Appendix F). Of those, 94 were in the central portion of the air

basin measured at Jackson (Amador County) and San Andreas (Calaveras County). This

analysis was focused on these violations because of the close proximity to the northeastern

portion of the SFBAAB, only 40 miles away. See Figure 3 for a map of the area.

The 94 exceedances were screened in order to reduce the number of possible

exceedances for detailed analysis. First, the exceedances were screened by identifying and

excluding the daily maximum ozone concentrations which exceeded the Expected Peak

Day Concentrations (EPDCs) (see Reference 9) and, therefore, were considered extreme

concentrations, not violations. Seven exceedances were greater than the EPDCs (see

Table F-2 in Appendix F). The elimination of these 7 left 87 violations for further

evaluation.

 These 87 violations were evaluated for possible impacts from the SFBAAB. 

Some of the criteria used were: time of day of the violations, air flow, spatial patterns of

the daily maximum ozone concentration for central California, and back trajectory

analyses. The analysis identified a violation day which was significantly impacted by the

SFBAAB. At 1900 PST on June 27, 1994, the daily maximum ozone concentration in

San Andreas was 111 ppb. By late morning on June 27, a strong delta breeze penetrated

into the Central Valley. With the delta breeze came precursor emissions and ozone from

the SFBAAB. On the previous day the Sacramento Valley Air Basin and delta region
18

were under the influence of northwest flow, while the SJVAB was under the influence of

the sea breeze from the SFBAAB via the Altamont and other passes to the south. 

Back trajectory analyses indicated that pollutants from the northern and

northeastern SFBAAB on June 26, along with pollutants from San Joaquin County on

June 27, impacted San Andreas at the time of the June 27 maximum daily ozone

concentration. Back trajectory analyses were conducted for the time (1600 PST) of the

maximum daily ozone concentration (91 ppb) at Jackson, which occurred three hours

prior to the San Andreas daily maximum hour concentration on June 27. These analyses

indicated that ozone in the Broader Sacramento Area on June 27 was transported to the

MCAB and impacted Jackson and San Andreas (100 ppb) at 1600 PST on June 27. 

Therefore, it appears that lingering ozone from the previous day's northwest flow could

also have contributed to the June 27 late afternoon ozone peak at San Andreas. 

It was during the sea breeze penetration on June 27 that Bethel Island, in southern

Sacramento County, and air monitoring stations in the San Joaquin County measured daily

maximum ozone concentrations greater than 100 ppb. In addition, a progression of the

daily maximum ozone concentrations from the SFBAAB to the downwind air basins is

consistent (83 ppb at 1300 PST at Concord, 113 ppb at 1400 PST at Bethel Island, 110

and 104 ppb at 1600 PST at Stockton-Hazelton and Elk Grove respectively, 119 ppb at

1700 PST at Stockton-Mariposa, and 111 ppb at 1900 PST at San Andreas) with the air

flow patterns. 

A comparison of the precursor emission inventories was conducted for those areas

that contributed to the June 27 San Andreas exceedance (based on the back trajectory

analyses). This showed that the SFBAAB, BSA, and SJVAB precursor emissions that

could possibly impact central MCAB were far greater than the central MCAB precursor

emission inventory. 

3. Conclusions and Recommendations

The above analyses establish that transport from the BSA, SFBAAB, and SJVAB

collectively impacted the central portion of the MCAB on June 27, 1994. This analysis

confirms that the SFBAAB can significantly impact the MCAB as was found in the 1993

transport assessment report.
19

Figure 3

[map of SFBAAB to MCAB]
20
21

D. San Francisco Bay Area Air Basin to North Central Coast Air Basin

1. Previous Assessment

The 1993 transport assessment (see Reference 6) classified transport from the San

Francisco Bay Area Air Basin (SFBAAB) to the North Central Coast Air Basin (NCCAB)

as overwhelming on some days and significant on other days. A reassessment of this

transport couple was performed to take advantage of the availability of new data from a

network of Radio Detection and Ranging (RADAR) wind profilers in the NCCAB and

special purpose air monitoring at Pacheco Pass and Spikes Peak.

2. Transport Working Group

 In 1993, the Board directed its staff to work more directly with the districts’ staffs

to assess transport. A result of this direction was the formation of the Bay Area to North

Central Coast Transport Working Group. This group comprised staff members from the

Bay Area Air Quality Management District, the Monterey Bay Unified Air Pollution

Control District, and the ARB.

The purpose of the working group was to identify days to be studied and then to

share data, analyses, and recommendations pertinent to those days. The working group

members met periodically for the past three years. 

3. Analysis

The Bay Area Air Quality Management District (Bay Area AQMD) is under

contract with the Monterey Bay Unified Air Pollution Control District to analyze NCCAB

ozone episodes. A detailed assessment of 1994 is included in a report by the Bay Area

AQMD (see Reference 17). A follow-on report contains a summary of the transport

assessments for 1995 NCCAB ozone exceedances (see Reference 18). 

Fourteen ozone exceedances occurred in 1994 and 1995. Table 2 identifies where

these exceedances occurred and when. Table 2 also indicates the transport assessment

assigned to each day. The working group analyzed only 12 of these 14 exceedances,

because the remaining two exceedances had daily maximum ozone concentrations that

exceeded the Expected Peak Day Concentrations (EPDCs) (see Reference 9) and are,

therefore, extreme concentrations which are not violations. Table 3 lists the EPDC values

for all the sites in the NCCAB which were used to exclude extreme concentrations. See

Figure 4 for a map of the area.

No inconsequential (local) days were identified in the previous assessment, and the

focus of this reassessment was to determine whether that pattern has continued. The

working group evaluated all 12 violations using an array of data analyses. These data
22

analyses were used to determine the origin of ozone and the contribution of transported

ozone impacting the air monitoring site when violations were measured. Each violation

episode, typically the day before and day of the violation, was evaluated using some or all

of the following analyses:

1. Spatial plots of the daily maximum ozone concentrations, and when they

occurred, were prepared to identify the transport routes.

2. Wind speed and wind direction time series plots in the form of hourly vectors

were constructed for weather monitoring stations in the SFBAAB to the

NCCAB. These plots, which contained both surface and upper air winds, were

used to determine ozone transport routes. 

3. Spatial plots of wind and temperatures were constructed for the area

encompassing the SFBAAB, northern San Joaquin Valley, and NCCAB. 

These plots were used to determine the extent of the inland penetration of air

pollutants in the marine layer.

4. Time-height cross sections of wind and temperature were constructed based on

measurements from radar wind profilers, radio acoustic sounding systems

(RASS) and sonic detection and ranging systems. These plots provided

information on transport routes. 

5. Vertical plots of temperature were constructed based on measurements taken

at Oakland by the National Weather Service. These plots were used to

determine the height of existing temperature inversion bases and the

temperature inversion intensity. 

6. Time series plots of the temperature inversion base height were constructed

based on measurements from a RASS network in the NCCAB. These plots, in

connection with Oakland upper air temperature data, were used to determine

whether surface precursor emissions could have transported over ridges or

through mountain passes. In addition, the plots were used to determine

whether aloft-transported-ozone could have fumigated to the surface.

7. Daily maximum temperature isotherm plots were constructed based on surface

measurements to determine the extent of inland penetration of precursor

emissions in the marine layer. 

8. Gridded wind plots with overlayed wind observations were constructed for

various times using an interpolation wind model. The wind plots are used to

determine ozone transport routes and source areas. 
23

9. Back trajectory plots were constructed from the violation sites in the NCCAB. 

These plots were used to determine transport routes.

 10. Mixing heights were estimated for various upper air temperature measurement

locations in the Central Valley, SFBAAB, and NCCAB. The estimates were

used to determine the depth in which surface-based-precursor emissions would

have been transported. 

 11. The synoptic weather patterns were identified by reviewing the 850 mb,

700 mb, and 500 mb constant height charts produced by the National Weather

Service and Air Resources Board. 

The working group found that NCCAB ozone violation episodes are typically

associated with an 850 mb ridge building into the northwestern part of the country

including northern California, in conjunction with a 500 mb high pressure area situated

somewhere over the southwestern states. The building of the 850 mb ridge into northern

California, resulted in northwest to northeast winds at the surface and aloft over the

Central Valley, SFBAAB, and NCCAB. These winds acted to transport ozone and ozone

precursors southward from the SFBAAB to the NCCAB; on some days southwestward

from the SJVAB to the NCCAB.

4. Conclusions and Recommendations

The working group’s analyses for 1994-95 show that overwhelming and significant

transport from the SFBAAB occurred on most violation days in the NCCAB. On the

other NCCAB violation days, the NCCAB was impacted by transport from the SFBAAB

and the SJVAB, collectively. Based on these analyses, the staff recommends no changes

to the transport mitigation regulation for the SFBAAB. However, the staff recommends

that transport from SJVAB to the NCCAB be identified as a new transport couple which

is discussed in detail in Section E of this report.
24

Table 2

State Ozone Exceedance Days 

NCCAB (1994-1995)

Max Ozone

Begin

Conc. Hour Proposed

Date Location (ppb) (PST) Assessment*

 06/09/1994 Hollister 101 1500 O - SF(1)

 06/24/1994 Pinnacles 96 1700 S-SF; S-NCC

06/28/1994 Pinnacles 95 1700 S-SF; S-NCC

07/07/1994 Pinnacles 97 1700 O-SF

08/11/1994 Pinnacles 95 1700 S-SF; S-NCC

08/12/1994 Pinnacles 95 1500 O-SF

06/23/1995 Pinnacles 95 1800 O-SF(1)

07/14/1995 Scotts Valley 97 1700 O-SF

07/15/1995 Hollister 97 1100 O-SF(1)

08/01/1995 Pinnacles 138 1700 No assessment (2)

08/02/1995 Pinnacles 110 1800 No assessment (3)

08/12/1995 Pinnacles 97 1700 O-SF(1)

08/21/1995 Pinnacles 102 1800 Inconclusive

09/18/1995 Pinnacles 96 1800 S-SF; S-NCC (1)

*I=Inconsequential; S=Significant; O=Overwhelming

(1) Unknown contribution from SJVAB

(2) Ozone concentration greater than EPDC

(3) The EPDCs used in determining the need for assessments were

based on 1992-94 data and was 10 ppm for Pinnacles. EPDCs based

on 1993-95 data were available for this report (see Table 3) but not

timely enough for performing assessment analyses. Therefore, while

the most recent EPDC for Pinnalces is 11 ppm, the decision for “no

assessment” was made on the previous, 10 ppm, EPDC.
25

Table 3

NCCAB Expected Peak Day Concentration (ppm)

1993-95

Salinas 7

Monterey 8

King City 8

Carmel Valley 10

Hollister 10

Pinnacles Nat’l Monument 11

Davenport 7

Santa Cruz 8

Watsonville 9

Scotts Valley - Scotts Valley Drive 10

Scotts Valley - Vine Hill 11
26

Figure 4

[map of SFBAAB to NCCAB]
27

E. San Joaquin Valley Air Basin to North Central Coast Air Basin

1. Previous Assessment

The transport of pollutants from the San Joaquin Valley Air Basin (SJVAB) to the

North Central Coast Air Basin (NCCAB) was not evaluated in the 1993 triennial transport

assessment. Likewise, these two air basins were not identified as a transport couple. 

However, recent analyses of the 1990-92 exceedances in the NCCAB suggested that the

SJVAB emissions impacted ozone concentrations in the NCCAB (see Reference 16).

2. Geographic Setting

 The geographic setting is included in this section because the SJVAB to the

NCCAB is proposed as a new transport couple. The NCCAB includes Monterey, San

Benito, and Santa Cruz Counties. The SFBAAB comprises Alameda, Contra Costa,

Marin, Napa, San Francisco, San Mateo, and Santa Clara Counties and parts of Solano

and Sonoma Counties. The SJVAB is composed of San Joaquin, Stanislaus, Merced,

Madera, Fresno, Kings, and Tulare Counties and parts of Kern County. See Figure 5 for a

map of the area.

The dominant topographic feature influencing air flow in the SFBAAB, SJVAB,

and NCCAB is the Coast Range. The Coast Range comprises a series of parallel

northwest to southeast oriented ridges and valleys. The ridges range in elevation from

2,000 feet near the coast to more than 3,000 feet inland. Between the ridges lie the San

Francisco Bay, the Santa Clara Valley, the San Benito Valley, and the Salinas Valley. The

Santa Clara Valley begins at the south end of the San Francisco Bay near San Jose and

extends southeastward for 35 miles from San Jose until it merges with the San Benito

Valley at the Santa Clara County line. The San Benito Valley extends southeastward from

the Santa Clara County line for approximately 35 miles to the Pinnacles National

Monument. The Santa Clara-San Benito Valley combination gently slopes upward from

an elevation of 80 feet at San Jose to an elevation of 300 feet at Hollister, 45 miles

southeast of San Jose. The two valleys without any physical barrier to the flow between

them provide the topographic setting for transport from the SFBAAB into the NCCAB. 

The Salinas Valley lies to the west of and parallel to the San Benito River Valley. 

The Salinas Valley extends approximately 75 miles southeastward from Salinas to San

Ardo. The ridge dividing the Salinas Valley and the San Benito Valley ranges in elevation

from 200 feet at the Pajaro Gap northwest of Hollister to 3,400 feet northeast of

Gonzales.

The routine influxes of marine air through the Carquinez Strait, the Altamont Pass, 

and the Pacheco Pass are the dominant features influencing air flow between the SJVAB

and the coastal areas. As a result, air flow within the SJVAB is typically northwest, along
28

the length of the valley from north to south. However, during periods of migrating high

pressure systems, surface and aloft winds can flow from the northwest through northeast

over the SFBAAB, SJVAB, and into the NCCAB. During these periods of north to

northeast winds, air pollutants from the SJVAB have the potential for transporting into the

NCCAB.

3. Analysis

 All 14 violations in the NCCAB were evaluated for transport impacts. First, the

exceedances were screened by identifying and excluding those daily maximum ozone

concentrations which exceeded the Expected Peak Day Concentrations (EPDCs) (see

Reference 9) and, therefore, are considered extreme concentrations, not violations. 

Twelve of the 14 days were determined to be violations of the ozone standard, and

warranted analyses.

The analyses performed for this assessment included studying spatial and

chronological ozone maximums, surface wind flows, profiler and mountaintop wind data,

inversion heights and strengths, surface temperatures, and air flow back trajectories. As

discussed in Section D of this report, most of the violations were determined to be caused

by either overwhelming or significant transport from the SFBAAB. Four of the 12

violations were suggestive of transport contributions from the SJVAB (see Table 2 in

Section D). 

The staff evaluated one of these four days in detail to establish the contribution of

the SJVAB on the NCCAB. Appendix G-1 describes the details of the analysis of the

violation which occurred on June 9, 1994. This analysis provides strong evidence that

ozone and its precursors in the surface layer traveled southward from the southern

SFBAAB and had an impact on Hollister. It also appears that there was flow aloft into the

NCCAB from the northern SJVAB. Ozone aloft could have mixed down to the surface as

the mixing layer deepened in the afternoon, thereby contributing to Hollister’s peak ozone. 

The transport working group concluded that the impact at Hollister is the combined

transport impact from the SFBAAB and the SJVAB. However, when there are shared

contributions from the SFBAAB and the northern SJVAB, it seems likely that the

SFBAAB would often have the greater impact since the emissions in the SFBAAB (Santa

Clara and San Mateo Counties) are far greater than the emissions from the northern

SJVAB (San Joaquin and Stanislaus Counties).

4. Conclusions and Recommendations

The staff's analysis shows that overwhelming and significant transport from the

SFBAAB caused most of the violations in the NCCAB. A few NCCAB violations days

were caused by transport from both the SFBAAB and the SJVAB. The staff also

recommends further studies for the next triennial assessment. The staff was unable to
29

quantify the separate transport impacts from the SFBAAB and the SJVAB ozone

concentrations in NCCAB. However, based on the available data, the analysis suggests

that the impact is more than inconsequential. Based on this analysis, the staff recommends

that SJVAB to NCCAB be identified as a new transport couple, causing significant

transport impacts.
30

Figure 5

[map of SJVAB to NCCAB]
31

F. San Joaquin Valley Air Basin to Great Basin Valleys Air Basin

1. Previous Assessment

The 1993 transport assessment (see Reference 6) classified transport from the San

Joaquin Valley Air Basin (SJVAB) to the Great Basin Valleys Air Basin (GBVAB) as

overwhelming on all days. The assessment was based on ozone exceedances occurring at

Mammoth Lakes in the GBVAB. A reassessment of this transport couple was performed

because of the continued occurrence of violations in Mammoth Lakes, as well as the

occurrence of exceedances at a new air monitoring site in Death Valley National

Monument.

2. Analysis

During 1994-1995 there were six ozone exceedances in the GBVAB (see Table 4). 

Two of these exceedances occurred at the new monitor site in the Death Valley National

Park. Four exceedances were reported at the Mammoth Lakes site. See Figure 6 for a

map of the area.

Ozone air monitoring began at the Death Valley National Park in December 1993. 

The data record, which is complete for 1994, shows one exceedance in May and one in

July. However, data were missing for two months in 1995. Because these two months

are during the ozone season, the data are not sufficient to calculate the Expected Peak

Day Concentration (EPDC). Without the EPDC, it is not possible to determine whether

these two exceedances are extreme concentrations or whether they are violations. 

Therefore, the staff will defer making a transport assessment for the Death Valley

National Park until there are sufficient data to determine the status of these exceedances. 

The four exceedances at the Mammoth Lakes sites were examined for potential

transport. First the exceedances were screened by identifying and excluding the daily

maximum ozone concentrations which exceeded the Expected Peak Day Concentrations

(EPDCs) (see Reference 9) and, therefore, were considered extreme concentrations, not

violations. Two exceedances were considered extreme concentrations. The remaining

two violations were examined further.

 

These violations occurred late in the day, between 1800 and 1900 PST. Based on

the time of day that the violations occurred, the characteristics of the violations, the

predominant westerly wind patterns, and the comparatively small emissions in the

GBVAB, the staff considers these violations to be the result of overwhelming transport

from the San Joaquin Valley.
32

3. Conclusions and Recommendations

The staff’s analysis shows that all violation days in Mono County in the Great

Basin Valleys Air Basin were overwhelmed by transport from the San Joaquin Valley Air

Basin. This analysis confirms the previous assessment and, therefore, the staff

recommends that no regulatory changes be made.

Table 4

State Ozone Exceedance Days 

GBVAB (1994-1995)

Max Ozone

Date Location Begin

Conc. Hour

(ppb) (PST)

05/22/1994 Death Valley National 98 1300

Monument

07/01/1994 Mammoth Lakes 120 2000

07/09/1994 Mammoth Lakes 100 1800

07/15/1994 Death Valley National 101 900

Monument

08/15/1995 Mammoth Lakes 100 1900

08/16/1995 Mammoth Lakes 110 300
33

Figure 6

[map of SJVAB to GBVAB]
34
35

G. South Coast Air Basin to Mojave Desert Air Basin

1. Previous Assessment

The 1993 transport assessment (see Reference 6) concluded that the transport

contribution from the South Coast Air Basin (SCAB) to the San Bernardino County

portion of the Southeast Desert Air Basin (SEDAB) was sometimes overwhelming and

sometimes inconsequential. In May 1996, the Board divided the SEDAB into two new air

basins, and now the San Bernardino County portion of the SEDAB is part of the Mojave

Desert Air Basin (MDAB). The previous assessment still applies, and, the SCAB’s

contribution to the ozone concentrations in the MDAB was both overwhelming and

inconsequential. A reassessment of this couple was done using information from a special

data collection effort that was conducted during the summer of 1995. 

2. Transport Working Group

In 1993, the Board directed the ARB staff to work more directly with districts’

staffs to assess transport. The Mojave Desert Transport Committee was formed, made up

of representatives from local industry, local air pollution districts, the military, and ARB. 

The committee has endeavored to:

Foster a cooperative effort among the ARB, the districts, and the regulated

community

Clarify the legal and scientific interpretations;

Identify and evaluate the available evidence for assessing upwind versus local

contributions to the SEDAB ozone exceedances; and

Obtain new evidence to better characterize transport into the SEDAB.

3. Analysis

The analysis consists of two parts. The report of the Mojave Desert Transport

Committee, following its review of all past transport studies, is the first part. The second

part consists of evaluation of data from field studies conducted by the ARB and the

Mojave Desert Transport Committee in the summer of 1995 to quantify transport impacts

to the desert. See Figure 7 for a map of the area.
36

Figure 7

[map of SCAB to MDAB]
37

Part 1 - Mojave Desert Transport Committee Findings

The Mojave Desert Transport Assessment Committee, based on its evaluation of

past studies, prepared a report on transport into the Mojave Desert. The conclusions

contained in the report “Mojave Desert Air Pollution Transport Interim Report” are the

following (see Appendix H for text of the report): 

Meteorology is the predominant factor controlling changes in the air quality

from one day to the next in the desert. On most exceedance days, a thermal

low pressure develops over the desert due to hot rising air; cooler air moves

into this low pressure area resulting in transport into the desert.

Two types of state standard exceedance days were identified. Typical

exceedance days (93% of exceedance days at Barstow) were defined as those

exceedance days which were the result of overwhelming transport. Atypical

exceedance days (7% of exceedance days at Barstow) are those occurring

under more subtle and complex meteorological conditions for which the cause

is not clearly understood. Atypical exceedance days could be caused by

overwhelming transport unrecognized as coming from one or more other

transport corridors, a combination of transport and local contribution, or only

by local contribution.

The available evidence from the six relevant studies is conflicting (see the

report “Mojave Desert Air Pollution Transport Interim Report” in Appendix H

for discussion of these studies). Shared days, where local contribution might

be significant, were not studied or identified. No single study was considered

sufficient to conclusively establish the presence or absence of transport on

atypical exceedance days.

All exceedances of the federal ozone standard in the SEDAB are the direct

result of transport.

According to Section 5 of the Roberts, et al., 1992 report, state standard

exceedance days at Barstow, with the greatest possibility of being caused by

local sources, have occurred at a rate of less than one per year over ten ozone

seasons during the 1980's.

The impact of mobile source emissions from major transportation corridors

(State Highway 58 and Interstate I-40 and I-15) on atypical exceedance days is

not quantified.

Research, such as the 1995 Mojave Desert Study preliminary data, reaffirm the

need to account for surface atmospheric conditions as well as atmospheric
38

conditions at various levels aloft. Further research is needed to quantify

transport and to evaluate the effectiveness of future control schemes aimed at

improving the SEDAB air quality.

Part 2 - 1995 Field Studies

During the summer of 1995, a special data collection effort was conducted to

evaluate transport into the Mojave Desert. The goal of this effort was to acquire data to

establish whether transport of ozone aloft contributed to violations at Barstow when

surface trajectories indicated no transport. (Table G-2 in Appendix G identifies the groups

responsible for the data collection). The data were obtained from either U. S. EPA

Aerometric Information Retrieval System (AIRS), Desert Research Institute (DRI),

National Weather Service (NWS), or California Irrigation Management Information

System (CIMIS).

Air quality in the desert was good in the summer of 1995. Normally, Barstow

experiences 30 to 40 exceedances of the state ozone standard in a year, but only 7

exceedances were observed during the study, reducing the value of the database for

analysis. 

Most of the time the Mojave Desert monitoring sites (Phelan, Hesperia,

Victorville, and Palmdale) are overwhelmed by ozone transport from the South Coast. 

However, violations of the state ozone standard at Barstow are believed to be caused

either by overwhelming transport from South Coast, emissions from within the Mojave

Desert, or a combination of transport from South Coast and contribution of emissions

from the Hesperia, Apple Valley, and Victorville urban areas. 

The seven days during which the state ozone standard was exceeded at Barstow

during the 1995 study all appeared to be impacted by transport. The staff examined the

data to see whether they could be used to identify the contribution of local sources to

ozone the exceedances. Two approaches were used. The first approach examined days

when transport from the South Coast was minimal or negligible. The days studied were

days when a weak Santa Ana condition existed over the desert. The first step in the

analysis was to screen the data to identify the Santa Ana days. This was done by plotting

all the surface wind data in the desert and neighboring air basins for the 40 days identified

in Table 5. 

The ozone concentrations for these days were plotted using the EPA’s AIRS

Voyager software. In these plots each concentration at each site is represented by a disk

of varying size depending on the concentration. Using the hourly plots, a Voyager movie

was made for each of the candidate days to show the hourly progression of the ozone

concentrations at each site. The Voyager movie files were helpful for watching transport

scenarios unfold. Using this approach, one can see how the ozone cloud propagated
39

through the critical passes into the Mojave Desert. The movie files were helpful in making

initial assessments of particular exceedance days. After reviewing the movie files, the 40

potential days were reduced to 22 (see Table 6).

Table 5

Days With Santa Ana Conditions

Over the Desert (1995)

05/03 06/03 09/13 10/16

05/15 06/09 09/18 10/17

05/16 06/10 09/29 10/19

05/23 06/21 09/30 10/20

05/25 06/22 10/01 10/22

05/26 06/23 10/02 10/23

05/27 06/24 10/04 10/24

05/28 06/25 10/05 10/25

05/29 07/16 10/12 10/26

05/30 09/12 10/13 10/29

 

Table 6

Days With Santa Ana Conditions Over the Desert

With No Apparent Transport Into the Desert

05/03 10/12

05/15 10/13

05/16 10/16

05/23 10/17

05/25 10/19

09/29 10/20

09/30 10/22

10/01 10/23

10/02 10/24

10/04 10/25

10/05 10/26

 

To minimize the effect of carry-over (residual ozone and ozone precursors from

the day prior), it is preferable to look only at periods when the Santa Ana conditions

persisted for more than one day. Although all of the 22 days were analyzed, the multi-day

episodes listed in Table 6 were the main focus. Upper air data were also examined to see

if there was transport aloft that could impact the monitors in the desert. Unfortunately,
40

the Radio Detection and Ranging (RADAR) wind profilers located at Apple Valley

Airport and Daggett-Barstow Airport did not come on line until July, and due to

equipment failure they were out of service most of August and September. Thus, upper

air data for many days in Table 5 are limited to rawinsonde soundings taken three times a

day at Edwards AFB and twice a day at Desert Rock (DRA) and Los Angeles (LAX). 

Lacking upper level data, maximum ozone concentrations from each of the Southern

Mojave Desert sites (Palmdale, Hesperia, Phelan, and Victorville) were used to determine

a range of values attributable to desert emissions.

By looking at days in the 1995 study period when no transport from the South

Coast Air Basin occurred, this analysis indicates that the maximum ozone concentration

produced in the desert is 60 ppb. Therefore, no state ozone standard violations at Barstow

during the period studied were attributed strictly to local emissions.

The second approach taken consisted of evaluations of two other significant

studies conducted during 1995 to try to identify the contribution of desert sources to

ozone exceedances in the desert and to try to determine the amount of any contribution. 

The first was Air Resources Board Contract No. 94-316 entitled Monitoring in Ozone

Transport Corridors by Technical and Business Systems Inc. (T&B), and the second was

the Barstow Halocarbon Study by the Desert Research Institute (DRI), sponsored by

members of the Mojave Desert Air Pollution Transport Committee. Neither study is

completed, but data and some preliminary results are available. 

During the study period June through October 1995 only six exceedances (of the

seven ozone exceedances for the 1995 season) of the state ozone standard were noted by

T&B at Barstow. However, several non-exceedance days with "little or no transport" into

Barstow and when the "morning and early afternoon (through 14 PST)" were "considered

to be relatively unaffected by transport” occurred.

T&B collected data for eight special sites during the June through October study

period. Six of these sites were on mountain tops or elevated areas to try to get a measure

of ozone aloft above the desert floor. Ozone concentrations from these special sites were

evaluated with other available data from the MDAB. Concentrations for days that were

not typical transport days were grouped by category as defined in Group 1 and Group 2.

Group 1 days: "Under the assumption that transport is manifested by a peak after

14 PST, days were identified when no concentration after 14 PST exceeded the value at

14 PST. The following morning and early afternoon (through 14 PST) were then

considered to have been relatively unaffected by transport into the Barstow area. There

were 24 such days in the June-October 1995 data base. 

Group 2 days: "Another group of days was identified by non-exceedances [days

that did not exceed the state standard] at each of the following locations: Lancaster,
41

Palmdale, Baldy Mesa, Hesperia and Phelan. The following morning/early afternoon

period was again considered to be relatively unaffected by transport. There were 20 such

cases in the June-October sample. 

During the period February through October 1995, DRI monitored halocarbons

just east of Barstow. In a similar manner to the T&B study, a third group of days was

identified from the halocarbon study data from DRI. Days with no or very little increase

in levels of methylchloroform or perchloroethylene near the times of ozone peaks were

considered to have been relatively unaffected by transport into the Barstow area. During

the same June-October sample period there were 38 days with very little increased

halocarbons, 19 of which occurred on a Saturday or Sunday. The maximum

morning/early afternoon ozone concentration was 69 ppb which occurred at 13 PST on

19 June 1995. 

Each of the techniques described in Part 2 demonstrates a method to identify what

ozone concentrations the MDAB area can generate in a meteorological setting where

transport was not involved. The concept here is that the MDAB can make a contribution

in the absence of transport. The MDAB makes the same emissions input to ozone

concentrations on those days when transport is involved. The emissions input may change

the time of the ozone maxima in the MDAB, and may change the location of ozone

maxima, but by their presence, the emissions make a significant contribution to ozone

classifications in the MDAB.

5. Conclusions and Recommendations

The staff’s analysis, the ARB’s contract work, the Barstow Halocarbon Study, and

the work of the Mojave Desert Transport Assessment Committee work all suggest that

there are days when a combination of local emissions and transported ozone and/or

precursors contribute to exceedances of the state ozone standard in the MDAB. Based on

the 1995 database, the staff could not find evidence of additional exceedances which were

caused solely by local emissions. The staff, therefore, recommends that the Board

characterize transport into the eastern and southern MDAB as overwhelming on some

days and significant on others, with inconsequential transport occurring less frequently

than once per year.
42
43

H. San Joaquin Valley Air Basin to Mojave Desert Air Basin

1. Previous Assessments

The 1990 and 1993 transport assessments (see References 4, 6) classified the

transport contribution from the San Joaquin Valley Air Basin (SJVAB) to the Los Angeles

County portion of the Southeast Desert Air Basin (SEDAB) as overwhelmed and to the

San Bernardino County portion of the SEDAB as inconsequential. In May 1996, the

Board divided the SEDAB into two new air basins, and now the Los Angeles County and

San Bernardino County portions of the SEDAB are part of the Mojave Desert Air Basin

(MDAB). The previous assessments now apply to the MDAB, and, therefore, the SJVAB

contribution to the MDAB was both overwhelming and inconsequential. A reassessment

of this couple was done because of the availability of data from a new monitoring site in

the town of Mojave in the Kern County portion of the MDAB and because of a special

data collection effort that was conducted during the summer of 1995.

2. Analysis

During the summer of 1995 a special data collection effort was conducted to study

transport into the Mojave Desert. (Table G-2 in Appendix G identifies the groups

responsible for the data collection). The data were obtained through either U. S. EPA

Aerometric Information Retrieval System (AIRS), Desert Research Institute (DRI),

National Weather Service (NWS), or California Irrigation Management Information

System (CIMIS).

Ozone monitoring in the town of Mojave in Kern County began in July of 1993. 

In 1995 the Mojave monitoring site experienced 24 violations of the state ozone standard. 

On August 2, the Mojave monitoring site measured its highest ozone concentration of the

year, 12 pphm. All violations were reviewed.

Transport from the San Joaquin Valley into the Mojave Desert is initially seen at

the Mojave monitoring site, located on the southeast side of the Tehachapi Pass. See

Figure 8 for a map of the area. Hourly surface wind plots generally show winds blowing

through the Tehachapi Pass from the San Joaquin Valley to the Mojave Desert on most

days. An example of the temporal progression of the maximum ozone concentration from

sites in Bakersfield to the Mojave site is shown in Table 7 for August 2, 1995.

With westerly winds throughout the day and the hourly progression of the ozone

maximum from one downwind site to another as the day progressed, there is clearly

surface transport from the San Joaquin Valley into the Mojave Desert. Other days

examined showed similar patterns. These findings are consistent with Dr. Glen Cass’
44

Figure 8

[map of SJVAB to MDAB]
45

results (see Reference 14) which found that no significant emission sources exist in eastern

Kern County to generate ozone; thus all violations are caused by overwhelming transport

from the Southern San Joaquin Valley.

Table 7

Progression of Maximum Ozone Concentration

August 2, 1995

Site Ozone Max Time of Max

Conc. (pphm) Conc. (PST)

Bakersfield-California 10 1100

Bakersfield-Golden State 11 1200

Edison 14 1300

Arvin 12 1400

Tehachapi 12 1600

Mojave 12 1700

3. Conclusions and Recommendations

Based on the staff’s analysis and the work done by Dr. Glen Cass, the staff

recommends that the transport from the SJVAB to western MDAB be classified as

overwhelming on all days. Based on the staff’s analysis of transport impacts on the San

Bernardino County in the MDAB (see Section G of this report), the staff recommends that

the 1993 classification of overwhelming transport from SJVAB to eastern and southern

MDAB remain unchanged. Staff further recommends that the inconsequential

classification be discontinued, based upon the finding that local episodes in the MDAB

occur less frequently than once per year (as discussed for the previous couple).
46
47

I. South Coast Air Basin to Salton Sea Air Basin

1. Previous Assessments

The 1993 transport assessment (see Reference 6) concluded that the transport

contribution from the South Coast Air Basin (SCAB) to Imperial County in the Southeast

Desert Air Basin (SEDAB) was significant. In May 1996, the Board divided the SEDAB

into two new air basins, and now Imperial County is part of the Salton Sea Air Basin

(SSAB). The previous assessment now applies to the SSAB, and, therefore, the SCAB

contribution to the ozone concentrations in the SSAB was significant. A reassessment of

this couple was done because of a special data collection effort that was conducted in the

summer of 1995 and because there has not been an assessment done of the impacts of the

SCAB on the Riverside County portion of the SSAB.

2. Analysis

During the summer of 1995 a special data collection effort was conducted to study

transport into the Mojave Desert. (Table G-2 in Appendix G identifies the groups

responsible for the data collected during the Summer of 1995). The data were obtained

through either U. S. EPA Aerometric Information Retrieval System (AIRS), Desert

Research Institute (DRI), National Weather Service (NWS), or California Irrigation

Management Information System (CIMIS).

A similar analysis to that done for the San Joaquin Valley was also applied to

identify transport from the South Coast to the Salton Sea Air Basin. In 1995 the Palm

Springs monitoring site measured 43 exceedances of the state ozone standard, and nine

exceedances of the federal ozone standard. See Figure 9 for a map of the area. July 23

began a period of transport that lasted ten days. On July 24, the Palm Springs monitoring

site measured its maximum ozone concentration of 16 pphm for the May through October

ozone season. Hourly plots of the surface winds in the area show that winds were

generally through the San Gorgornio Pass and into the Salton Sea Air Basin. Table 8

shows the temporal progression of the ozone maximum.

As indicated, progression of the maximum ozone concentrations starts out in the

basin early in the afternoon and follows the westerly winds toward Banning as the

afternoon progresses. Also, peak ozone increases as the plume picks up fresh emissions,

until it reaches the Salton Sea Air Basin at Palm Springs where the plume is cut off from

fresh emissions and the concentrations begin to dilute and drop. 
48

Figure 9

[map of SCAB to SSAB]
49

Table 8

Progression of Maximum Ozone Concentrations

July 24, 1995

Site Ozone Max Time of Max

Conc. (pphm) Conc. (PST)

Norco 12 1300

Rubidoux 15 1400

Perris 17 1500

Banning 18 1700

Palm Springs 16 1800

Indio 14 2000

3. Conclusions and Recommendations

Based on this analysis, the staff recommends that the transport from the SCAB to

the SSAB be classified as overwhelming on some days. Based on the previous 1993

assessment, the staff recommends maintaining the finding of significant transport on other

days.
50
51

J. San Francisco Bay Area Air Basin to San Joaquin Valley Air Basin

1. Previous Assessment

The ARB assessed ozone and ozone precursor transport to the San Joaquin Valley

Air Basin (SJVAB) in two previous reports (see Reference 4, 6). The 1990 assessment

concluded that in July and August of 1983 through 1986, 43 percent of the exceedance

days were impacted by transport, 11 percent were nontransport, and the remainder could

not be identified as either. It was concluded that the transport days were a mixture of

significant and inconsequential transport. A case study, August 7-8, 1984, was simulated

by a photochemical model. While these results of the model run were not reliable, they

provide qualitative insight. The 1990 assessment was based on two exceedance days

which were screened from routine data collected from 1986 through 1988. It was

concluded that the ozone exceedance on June 2, 1994, was not impacted by transport

(inconsequential) and that June 3, 1987, was significantly impacted by transport from the

SFBAAB.

The second report focused on a case study done during the 1990 San Joaquin

Valley Air Quality Study, specifically August 6. It was concluded from detailed surface

and upper air data that overwhelming transport occurred, with the high levels of ozone

recorded at Tracy and Crow's Landing directly related to emissions originating in the

SFBAAB. That report also reviewed data obtained from the August 3 tracer release

experiment conducted during the San Joaquin Valley Air Quality Study. It was concluded

that pollutants emitted from the tracer release sites, Pittsburg and San Jose, were

transported into the SJVAB but the degree of impact could not be quantified. The Board

identified transport to the western portion of Stanislaus County from the SFBAAB as

overwhelming.

2. Geographical Features

The California coastal mountain range separates the San Joaquin and Sacramento

Valleys from the coastal regions. A significant break in that range occurs at the Carquinez

Strait where the San Joaquin River flows into the San Francisco Bay. There exists a

30 km gap at 500 meters msl. This is important because the offshore marine layer is

typically 400 to 700 meters thick. In most cases, the coastal range acts as a barrier. See

Figure 10 for a map of the area. Another important feature is the Livermore Valley with

various passes to the east. The Livermore Valley, which is oriented east-west, is a branch

of the San Ramon Valley. The effective barrier height to the east of Livermore is

approximately 300 meters above sea level (msl) with Altamont Pass as the principal gap at

243 msl.

The Santa Clara Valley is another pathway from the San Francisco Bay Area Air

Basin (SFBAAB) to the San Joaquin Valley Air Basin (SJVAB). To the east of the head 
52

Figure 10

[map of SFBAAB to SJVAB]
53

of the Santa Clara Valley is an effective barrier of 450 - 500 msl. The principal gap is

Pacheco Pass at 410 msl.

3. General Meteorological Summer Conditions

Often during the summer a pressure difference exists between the Sacramento-San

Joaquin Valleys and the coast due to a daytime thermal low. A temperature inversion

above the offshore marine layer prevents flow from moving directly over the coastal

ranges. The Carquinez Strait and the Altamont and Pacheco Passes can, however,

experience westerly flows.

The magnitude of the gap and pass flows are dependent on the location and

strength of the Pacific surface high pressure system, Gulf of Alaska 500mb low pressure

system, the Central Valley thermal low pressure system, and to a lesser extent, the

southwest desert thermal low pressure system. The Carquinez Strait and Altamont Pass

wind flows usually split upon entering the Central Valley, with a northwesterly flow then

moving into the San Joaquin Valley. The Carquinez Strait and Altamont Pass flows have

been divided into four different San Francisco Bay Area categories; weak northwesterly,

moderate-to-strong northwesterly, southerly, and bay outflow. Both northwesterly

conditions account for 87% of all cataloged summer flows. Of that, about 69% of

summer flows were from the San Francisco Bay Area and were diverted into the San

Joaquin Valley (see Reference 1). 

4. Analysis

This assessment of transport from the SFBAAB into the SJVAB is based on

surface ozone and wind data from 1994 and 1995 for both basins. Initial review suggested

overwhelming impact on four different days. However, a more detailed analysis revealed

only two days in 1995 where SFBAAB caused overwhelming impact.

The routine data for the 1994-1995 period for the area of interest was sparse and

limited to surface observations. Consequently, no conceptual model could be created for

transport above the surface. 

The first level of screening for possible transport during the 1994-1995 period is

the selection of those days that had hourly ozone concentrations which exceeded the State

standard for stations nearest the border between the two air basins. For the SJVAB, that

is Stockton, Tracy and Crow's Landing; for the SFBAAB, that is Bethel Island, Livermore

and Gilroy. That last station unfortunately does not have a counterpart in the western area

of the SJVAB, so it will not be used. Table 9 shows the exceedance days in 1994 and

1995. 
54

The second step was the review of the ARB's objective surface flows at 1600 PST. 

Days with significant flow from the southern portion of the Sacramento Valley and/or the

Stockton area to the Crow's Landing and Tracy area were eliminated from further

consideration as possible transport impact days. The other days show surface flow either

through the Carquinez Strait or Altamont Pass and extending to the Tracy and Crow's

Landing site.

Table 9

OZONE (pphm)

Bethel Crows Tracy Livermore

Island Landing

08-17-94 10.2 10.8 N/A 8.7

09-05-94 8.3 10.1 N/A 10.8

09-16-94 10.3 8.2 10.7 10.5

 06-26-95 6.1 11.9 11.1 9.8

 07-15-95 8.4 9.7 8.8 9.8

 07-16-95 8.8 6.9 12.4 12.1

 07-27-95 12.4 11.0 9.9 15.5

 08-01-95 8.1 9.6 8.7 11.4

 08-09-95 8.5 9.9 10.9 9.5

08-14-95 10.7 8.7 10.0 13.4

08-20-95 7.3 8.9 11.5 13.0

09-07-95 12.8 9.3 10.3 7.8

09-19-95 11.4 3.7 10.0 11.8

The third step was to eliminate from further consideration those days where the

peak ozone concentration exceeded the Expected Peak Day Concentrations (EPDCs) (see

Reference 9) and were therefore considered extreme concentrations rather than violations. 

Three of the four remaining episodes had wind data from the Tracy site. In all three cases,

the wind shifted from a northerly flow to a westerly flow during the afternoon within a

span of an hour. In two of those cases, this shift fell between two ozone concentration

peaks recorded at Tracy. This suggests that before the wind shift, polluted air had come
55

through the Carquinez Strait and afterwards, polluted air had come through the Livermore

Valley.

In all four cases, the increase of ozone concentrations during the morning at both

Tracy and Crow's Landing was rapid enough to suggest two other possible sources of

ozone besides direct transport from either through the Livermore Valley or the Carquinez

Strait. One mechanism could have been the downward fumigation of ozone from aloft. 

The other could have been that ozone precursors were in the area or just upwind. As the

morning temperatures increased and there was more sunlight, more ozone was formed.

Unfortunately there are no data for wind or ozone aloft to establish ozone

fumigation and its origin. However, aircraft ozone data collected from August 3 through

6, 1990 during the San Joaquin Valley Air Quality Study (SJVAQS) does show morning

ozone concentrations between 6 and 10 pphm in the layer from 200 msl through 1500 msl. 

Morning fumigation did appear to have been important during that field study at Tracy and

Crow's Landing. 

A detailed discussion of the analysis of the four episodes can be found in

Appendix G-3.

5. Additional Study Methods

The SARMAP modeling system is used to investigate transport of ozone and its

precursors from the SFBAAB and Sacramento to San Joaquin Valleys. To investigate this

transport, emissions were set to zero first in the Bay Area and Sacramento to evaluate

their transport impact on the San Joaquin Valley. Next the San Joaquin Valley's emissions

were set to zero to evaluate its own contribution to ozone concentrations. Effects of

ozone concentrations were assessed by examining model results for geographical areas in

which the ambient ozone standard would be exceeded under these scenarios.

The SARMAP modeling system consists of the SARMAP Meteorological Model

(SMM), the Emissions Modeling System (EMS), and the SARMAP Air Quality Model

(SAQM). The modeling domain covers central California which includes the San Joaquin

Valley, the Bay Area, and the Sacramento area. The modeling system is applied to

simulate the August 3-6, 1990, ozone episode in the study domain. An extensive model

performance evaluation is performed using the rich database of the 1990 San Joaquin

Valley Air Quality Study. The modeling system met the model evaluation criteria of both

the US-EPA's and the ARB. Details of the SARMAP Modeling System can be found in

References 15, 19, and 20.

The model simulations for August 3-6, 1990, indicated that high ozone

concentrations in the SJVAB were due to varying combinations of local and transported

emissions. The greatest transport impact was seen in the northern Valley where peak
56

ozone concentrations were reduced by about one-third when Bay Area and Sacramento

emissions were zeroed. Peak ozone concentrations in the central and southern San 

Joaquin Valley were primarily attributable to emissions from within the SJVAB (see

Reference 2).

6. Conclusions and Recommendations

The August 1, 1995, and August 9, 1995, ozone exceedances at Tracy and Crow's

Landing can be attributed solely to transport from the SFBAAB. The peak ozone value at

Crow's Landing on August 1 can be attributed to emission sources near the Carquinez

Strait and the peak ozone value at Crow's Landing on August 9 can be attributed to flow

from the Livermore Valley.

Based on the defined criteria and analyses, the staff concludes that transport of

ozone and ozone precursors from the SFBAAB overwhelmingly impacted Crow's Landing

on August 1 and August 9, 1995. Since this agrees with the previous assessment, the

staff recommends no change to the transport assessment of this transport couple. 
57

K. San Francisco Bay Area to Broader Sacramento Area

1. Previous Assessments

In 1993 (see Reference 6), the ARB concluded that transport from the San

Francisco Bay Area Air Basin (SFBAAB) to the Broader Sacramento Area (BSA) be

characterized as inconsequential on some days and significant on other days. Additionally,

the Board concluded that San Francisco Bay Area Air Basin causes overwhelming

transport to the most westerly portions of the BSA. 

2. Transport Working Group

At the June 1993 Hearing, the Board directed the ARB staff to work more directly

with districts’ staffs to assess transport. A result of this direction was the formation of the

San Francisco Bay Area to Broader Sacramento Area Transport Working Group. This

group comprised staff from the Bay Area, Sacramento Metropolitan, and Yolo/Solano Air

Quality Management Districts and the ARB.

The purpose of the working group was to identify days to analyze and then to

share data, analyses, and recommendations pertinent to the chosen days. The working

group members met every two to four months for approximately two years.

3. Analysis

All 1994 and 1995 exceedance days were first screened to determine which were

violations and which were extreme concentrations using the Expected Peak Day

Concentration (EPDC) (see Reference 9). The violation days (Tables F-3 and F-4 in

Appendix F) were then screened for worst case scenarios, or those which would depict

overwhelming transport and inconsequential transport. Of these days, an in-depth analysis

was performed by the ARB and the Bay Area staffs and was reviewed by the transport

working group. Eight days were examined to represent inconsequential transport. These

days are: June 10, July 7 and 12-14, and August 5, 1994, and June 24 and July 27, 1995

(see Table 10). June 24, 1995 is a unique day because it clearly depicts inconsequential

transport at Folsom and overwhelming Bay Area transport at Vacaville. See Figure 11 for

a map of the area.

The Bay Area and the ARB staffs’ analyses were used for these assessments. The

Bay Area’s ozone concentration animation was used for June 24, 1995. The animation is

a two dimensional motion picture depicting aerial coverage of ozone concentrations. In

this animation, a model incorporated wind speeds and directions and interpolations of

ozone concentrations. The presentation was a very effective way to represent the

movement of an ozone plume. The ARB analyses included: CalTech Winds2D backward

and forward trajectories, time series showing ozone trends of significant SFBAAB and
58

BSA sites, spatial distributions of daily maximum ozone values, and spatial distributions of

the hour of maximum ozone concentration. Other considerations for each of the analyzed

days included data analyses such as the surface wind flow patterns (incorporated in the

trajectories), wind flow patterns aloft, ozone concentrations aloft (when available), the

character of the exceedance (abrupt, gradual, early, or late), and the duration of the

exceedance. Overall, the analyses combined to provide a 24-hour history along the

transport route. 

Most violation days had similar characteristics. Typically, ozone concentration

peaks rose simultaneously in the Bay Area and the Broader Sacramento Area. Also, rural

areas between the Bay Area and Sacramento metropolitan area had lower ozone

concentrations that were closer to or below the state ozone standard. In some cases, the

hour of maximum ozone was earlier in the BSA than in the SFBAAB. This is more typical

of a local episode than of a transport episode. These characteristics, combined with results

of more detailed analyses mentioned in the previous paragraph, are indicators of a locally

generated violation.

In the case of June 24, 1995, it was apparent that there were two separate wind

flow regimes affecting different parts of the BSA simultaneously. That portion located

more closely to the center of the valley underwent near stagnant atmospheric conditions

with light/variable or light/northerly wind flow. The western portion of the BSA was

undergoing stagnant conditions with light/variable or light/southwesterly wind flow. 

Atmospheric conditions in the Bay Area had also been stagnant with unusually high ozone

concentrations. As the marine air began to displace the stagnant, polluted air mass and

move it toward the east-northeast, an ozone front, effectively, passed over Vacaville and

caused ozone exceedances. This phenomenon shows up well in the Bay Area’s ozone

concentration animation.

4. Conclusions and Recommendation

The staff recommends that the previous transport classifications remain

unchanged. The analyses which were used on the 1994 and 1995 data do not conclude

different results than those already established for this couple. Therefore, SFBAAB to

BSA ozone transport should be classified as overwhelming (Solano County only),

significant, and inconsequential.
59

Table 10

Broader Sacramento Area

Ozone Violation Days

Assessed as “Inconsequential”

DATE OZONE CONC. SITE

(ppb)

06-10-94 136 Folsom

07-07-94 126 Folsom

07-12-94 142 Folsom

07-13-94 140 Folsom

07-14-94 133 Folsom

08-5-94 143 Folsom

06-24-95 100 Folsom

06-27-95 125 Folsom
60

Figure 11

[map of SFBAAB to BSA]
61

L. Broader Sacramento Area to Upper Sacramento Valley

1. Previous Assessment

In 1993 (see Reference 6), the ARB concluded that Upper Sacramento Valley

(USV) transport from the Broader Sacramento Area (BSA) was characterized as

overwhelming, significant, and inconsequential. Transport from the BSA was found to be

overwhelming to the sites in Willows (Glenn County), Yuba City (Sutter County), and

Arbuckle (Colusa County). Transport was found to be inconsequential to the sites in

Redding and Anderson in Shasta County. Significant transport occurred at Colusa

(Colusa County), Willows, Red Bluff (Tehama County), and Yuba City.

2. Transport Working Group

In 1993, the Board directed the ARB staff to work more directly with the districts’

staffs to assess transport. A result of this direction was the formation of the Bay

Area/Broader Sacramento Area to Upper Sacramento Valley Transport Working Group. 

This group comprised staff from the Bay Area, Sacramento Metropolitan, Shasta, Feather

River, and Yolo/Solano Air Quality Management Districts, the Butte, Colusa, Tehama,

and Glenn County Air Pollution Control Districts, Sacramento Valley Basinwide Control

Council, Sonora Technology, Inc. (STI - under contract with Shasta County) and ARB.

The purpose of the working group was to identify days to analyze and then to

share data, analyses, suggestions, and recommendations pertinent to the chosen days. 

The working group members met every two to four months for approximately two years. 

3. Analysis

All 1994 and 1995 exceedance days were first screened to determine which were

violations and which were extreme concentrations using the Expected Peak Day

Concentration (EPDC) (see Reference 9). The working group looked at all of these

violation days (see Table 11) with the focus on analyzing for an inconsequential transport

episode because significant and overwhelming transport episodes are already well

documented. The working group did not identify any days in which the preponderance of

data indicated inconsequential transport. The working group also reviewed data for

overwhelming and significant transport. The assessment classification of all violation days

can be found in Table 11. See Figure 12 for a map of the area.

The ARB staff and STI analyses were used for these assessments. Data collected

by STI for their contract with Shasta County filled most of the data voids normally present

due to lack of upper air data. The ARB staff analyses included: CalTech Winds2D

backward and forward trajectories, time series (ozone concentrations plotted on a graph

chronologically by hour) showing ozone trends of significant Bay Area, Broader
62

Sacramento Area, and Upper Sacramento Valley sites, spatial distributions of daily

maximum ozone values, and spatial distributions of the hour of maximum ozone

concentration. Other considerations for each of the analyzed days included data analyses

such as the surface wind flow patterns (incorporated in the trajectories), wind flow

patterns aloft, ozone concentrations aloft (when available), the nature of the exceedance

(abrupt, gradual, early, or late), the duration of the exceedance, recent agricultural burning

practices, and the emission inventory comparisons. Each analysis was a reconstruction of

the 24- to 48-hour atmospheric and pollutant history along the transport route.

 Most violation days in which surface analyses showed the slightest possibility of an

inconsequential episode were preceded, approximately 4 to 18 hours earlier, by elevated

ozone concentrations at Sutter Buttes or Tuscan Buttes. The transport mechanisms in the

USV are complex, but it is evident that there is transport taking place at the surface and

aloft. The transport aloft normally affects the northern USV sites, while surface transport

normally affects the southern USV sites closer to the metropolitan Sacramento area.

It has been determined that there is not any notable transport contribution from the

Bay Area to the USV. When air flow comes from the Bay Area, through the Carquinez

Strait, and then through the BSA, the associated pollutants are found to be diluted and

aged greatly. Additionally, they are then masked by the pollutants from the metropolitan

area of Sacramento. Therefore, the only upwind area identified as impacting ozone

concentrations in the USV is the BSA.

4. Conclusions and Recommendation

 Based on the recent analyses, the staff recommends that the USV transport

classification of inconsequential be discontinued and that the classification be changed to

overwhelming and significant only. The staff determined that ozone violations are

classified as significant transport at Redding, Willows, Yuba City, and Red Bluff on some

days; on other days, ozone violations were determined to be classified as overwhelming

transport at Yuba City, Willows, Colusa, Redding, Chico, and Red Bluff. 
63

Figure 12

[map of BSA to USV]
64

Table 11

1994-95 Ozone Violations

Upper Sacramento Valley

Max Hour

Ozone Max

Basin Site Date (ppb) Ozone Assessments*

SV Redding-Health Dept Roof 06/20/94 98 14

SV Redding-Health Dept Roof 06/21/94 101 12 S

SV Redding-Health Dept Roof 06/22/94 97 11

SV Yuba City-Almond Street 06/27/94 98 11 O

SV Willows-E Laurel Street 06/30/94 96 15 S/O

SV Yuba City-Almond Street 07/08/94 111 16

SV Colusa-Fairgrounds 07/08/94 100 16 O

SV Redding-Health Dept Roof 07/08/94 95 11

SV Yuba City-Almond Street 07/12/94 96 14

O

SV Yuba City-Almond Street 07/13/94 98 16

SV Chico-Manzanita Avenue 07/14/94 95 13

SV Yuba City-Almond Street 07/15/94 98 13

SV Yuba City-Almond Street 07/28/94 103 15

S/O

SV Red Bluff-Walnut Street 07/28/94 100 13

SV Redding-Health Dept Roof 07/29/94 101 11

SV Yuba City-Almond Street 07/29/94 98 16

SV Yuba City-Almond Street 08/17/94 107 16

SV Colusa-Fairgrounds 08/17/94 101 17 O

SV Red Bluff-Walnut Street 08/18/94 100 12

SV Colusa-Fairgrounds 08/20/94 100 15 O

SV Yuba City-Almond Street 09/17/94 99 15

SV Yuba City-Almond Street 09/18/94 106 17 S

SV Yuba City-Almond Street 09/19/94 104 16

SV Yuba City-Almond Street 09/22/94 97 14 S

SV Redding-Health Dept Roof 06/30/95 99 15 S/O
65

Table 11 (con’t)

1994-95 Ozone Violations

Upper Sacramento Valley

Max Hour

Ozone Max

Basin Site Date (ppb) Ozone Assessments*

SV Yuba City-Almond Street 07/28/95 101 12 S/O

SV Yuba City-Almond Street 08/01/95 102 15

SV Red Bluff-Walnut Street 08/02/95 100 10 O

SV Colusa-Fairgrounds 08/01/95 95 14

SV Yuba City-Almond Street 08/03/95 99 12

SV Red Bluff-Walnut Street 08/04/95 100 11

SV Red Bluff-Walnut Street 08/22/95 100 14 S

SV Tuscan Butte 09/01/95 100 14

SV Red Bluff-Walnut Street 09/09/95 100 14 S/O

SV Yuba City-Almond Street 09/08/95 95 14

SV Red Bluff-Walnut Street 09/10/95 100 15

SV Colusa-Fairgrounds 09/11/95 95 16

SV Red Bluff-Walnut Street 09/13/95 100 13

SV Colusa-Fairgrounds 09/13/95 95 15 O

SV Yuba City-Almond Street 09/13/95 96 16

SV Tuscan Butte 09/13/95 96 17

SV Yuba City-Almond Street 09/14/95 101 16

SV Red Bluff-Walnut Street 09/14/95 100 14

SV Red Bluff-Walnut Street 09/15/95 100 14

SV Yuba City-Almond Street 09/19/95 98 15

SV Colusa-Fairgrounds 09/19/95 96 13 S

SV Yuba City-Almond Street 09/20/95 109 13

*O=Overwhelming, S=Significant, I=Inconsequential
66
67

M. South Coast Air Basin to San Diego Air Basin

1. Previous Assessment

The 1993 transport assessment (see Reference 6) classified the transport impacts

from the South Coast Air Basin (SCAB) on the San Diego Air Basin (SDAB) as

overwhelming on some days, significant on others, and inconsequential on still others. 

2. Analysis

The analysis for this couple continues to be a joint ARB/District staff effort (see

References 10, 11, 12, 13). Daily, the San Diego County Air Pollution Control District

(SDCAPCD) staff reviews meteorology and air quality data to determine the contribution

of transport from the SCAB. The ARB staff reviewed the SDCAPCD staff’s procedures

and analyses on days of special interest. The studies continue to show that transport from

the SCAB to be overwhelming, significant, and inconsequential to state ozone standard

violations in the SDAB, depending on the meteorology of a specific day and location. See

Figure 13 for a map of the area. Table 12 identifies the number of days in each

classification during the last three years.

Table 12

State Ozone Exceedance Days by Transport Classification

San Diego Air Basin

1993-95

Classification 1993 1994 1995

Inconsequential 39 43 43

Significant 31 29 48

Overwhelming 20 7 5

Total Ozone Exceedance Days 90 79 96

3. Conclusions and Recommendations

The staff is not aware of any information that would change the 1993 ARB

findings. Therefore, the staff recommends the previous classifications remain unchanged. 

Transport from the SCAB to the SDAB should continue to be classified as overwhelming

on some days, significant on some other days and inconsequential on others.
68

Figure 13

[map of SCAB to SDAB]
69

N. South Coast Air Basin to South Central Coast Air Basin

1. Previous Assessment

The 1990 transport assessment (Reference 4) classifies transport from South Coast

to South Central Coast as significant on certain days, and inconsequential on other days. 

A reassessment was necessary because the previous assessment was based on

photochemical modeling simulations using the Carbon Bond II chemical mechanism which

is now outdated. In addition, there have been nine episodes with high concentrations

(exceeding the national ozone standard) between 1994 and 1996, several of which were

recorded at a new monitoring site at Las Flores Canyon. See Figure 14 for a map of the

area.

2. Analysis

Recent observations indicate nine high ozone episode days in Santa Barbara

County in the last three years, 1994-1996. The peak ozone concentrations during these

episodes ranged from 125 to 143 ppb. Table 13 identifies these high ozone episodes by

location and time of daily maximum concentration.

On these days, the vertical structure of the atmosphere was characterized by a

surface marine layer of 200-300 m and an inversion layer extending up to 1000 m. Wind

regimes in the marine layer are often different than in the inversion layer aloft. There are

at least two possible transport mechanisms, one at the surface in the marine layer and a

second aloft in the inversion layer. 

Transport within the marine layer would be indicated if, in the South Coast Air

Basin, elevated ozone concentrations are observed along the coastal regions coupled with

offshore flow in the afternoon or evening preceding the episode. On the episode day,

winds from the south or southeast would be observed in Santa Barbara County. 

Conditions indicative of transport within the marine layer were observed during the

May 1, 1996 episode. In the South Coast monitoring sites along the coast reported

elevated ozone concentrations of 100 ppb at Costa Mesa and 110 ppb at West L.A. and

Hawthorne. Late afternoon and evening winds in the South Coast were offshore on the

previous day. Meanwhile, winds at San Nicolas Island and along the Santa Barbara coast

were south to southeasterly on the episode day. 

Sometimes a widespread pattern of elevated ozone concentrations is seen with

transport within the surface marine layer. Often a Catalina Eddy is indicative of surface

transport from the South Coast to Santa Barbara. An example is the October 4, 1995

episode where the 0400 PST and 1000 PST surface winds indicated the presence of a
70

Catalina Eddy. Peak ozone concentrations were observed at El Capitan Beach with 

135 ppb and at Las Flores Canyon with 143 ppb.

Transport aloft can be determined by upper-level wind data and large scale

meteorological phenomena. Frequently the position of high and low pressure systems at

1500 m (850 mb) can be indicative of wind patterns. Winds circulate clockwise around

high pressure and counter clockwise around low pressure. If high pressure is east of the

area, winds aloft would have a southerly component that could draw ozone layers aloft

into the region. This pattern characterizes the episodes of August 13, 1994, September 6,

1995, and May 11, 1996. 

Ozone can remain aloft longer than at the surface because the ozone plume is often

trapped into a very stable inversion layer, which limits dispersion. Also, there are no

sources of nitric oxides aloft to transform ozone into other chemical species. The ozone

layer aloft acts as a reservoir that is only detrimental if there is a mechanism to bring

ozone down to the surface. One mechanism is surface heating that can induce sufficient

vertical mixing to extend into the inversion layer. Often an isolated exceedance at a

monitoring station that is at higher elevation than surrounding stations is indicative of a

situation of ozone transported aloft. 

Ozone exceedances on eight of the nine episode days occurred at Las Flores

Canyon, inland from El Capitan Beach. The Las Flores Canyon monitor is located at

160 m above sea level which typically puts it near the base of a very strong inversion. On

June 23, 1994, August 12, 1994, October 3, 1995, and May 12, 1996, exceedances were

observed at Las Flores Canyon, but not at El Capitan. Transport aloft was indicated by

southeasterly winds above the surface marine layer and sufficient surface heating on these

days, and elevated concentrations in the South Coast on the previous day. 

Due to the limitation of available data, it is difficult to quantify how much of the

observed concentrations are due to local sources and how much is due to transport. 

Certainly ozone transported into Santa Barbara county passes over sources in Ventura

County, onshore sources in Santa Barbara County, and offshore sources. All these

sources interact to produce the local component of the observed concentrations. 

However, the elevated ozone concentrations in upwind source regions suggest a

significant contribution of transport on these days.

3. Conclusions

All ozone exceedances greater than 124 ppb, from 1994-1996 inclusively, seemed

to be related to transport of ozone from outside Santa Barbara County. Some episodes

were tied to transport at the surface, while others tapped into a reservoir of ozone that

was transported within the inversion layer. A lot of inferences were made from the

Vandenberg soundings, surface wind patterns, air quality data, and temperature data. 
71

However, the preponderance of available data did indicate that all nine episode days listed

in Table 13 can be classified as shared transport days. 

Table 13

Peak Ozone Concentrations

Santa Barbara County

1994 - 1996

Date Location Max. O3 Peak Hour

(ppb) (PST)

6/23/94 Las Flores Canyon 125 1700

8/12/94 Gaviota West 127 1500

Gaviota East 133 1500

Gaviota GTC Site C 134 1500

Las Flores Canyon 142 1600

8/13/94 Goleta 127 1300

Carpenteria 129 1300

9/6/95 Gaviota GTC Site C 125 1400

Las Flores Canyon 127 1200

El Capitan Beach 130 1400

10/3/95 Las Flores Canyon 126 1300

10/4/95 El Capitan Beach 135 1400

Las Flores Canyon 143 1500

5/1/96 Carpenteria 128 1400

Goleta 128 1300

Las Flores Canyon 133 1500

5/11/96 Las Flores Canyon 125 1500

Gaviota GTC C 130 1400

5/12/96 Las Flores Canyon 134 1700
72

Figure 14

[map of SCAB to SCCAB]
73

CHAPTER IV

IMPACT ANALYSIS

A. Public Health, Welfare, And Environmental Impacts

The adoption of the proposed amendments to ozone transport identification

and mitigation is not expected to result in any adverse impacts on public health, welfare,

and environment. The proposed amendments would omit the inconsequential ozone

transport classification from the Broader Sacramento Area to Upper Sacramento Valley

couple. This amendment is not expected to cause adverse impacts because it does not

excuse either the upwind or the downwind area from mitigation of state ozone

exceedances.

Also in the proposed amendments are several transport couple redefinitions due to

the Board’s May 1996 decision to divide the Southeast Desert Air Basin into the Mojave

Desert Air Basin and the Salton Sea Air Basin (although as of the date of publication of

this report, these air basin changes have not been approved by the Office of Administrative

Law). The South Coast to Southeast Desert ozone transport couple is now South Coast

to Mojave Desert and South Coast to Salton Sea; San Joaquin Valley to Southeast Desert

is now San Joaquin Valley to Mojave Desert; and Mexico to Southeast Desert is now

Mexico to Salton Sea. Since these couple redefinitions do not change the mitigation

responsibilities, it is not expected to cause adverse impacts. 

The proposed amendments also identify a new transport couple, the San Joaquin

Valley Air Basin to the North Central Coast Air Basin. Additionally, the proposed

amendments enlarge the downwind areas of the Broader Sacramento Area to include

Amador and Calaveras counties. These amendments are not expected to cause adverse

impacts since the identification of upwind/downwind areas does not exclude exceedances

from mitigation, but rather assigns the mitigation to the responsible area or areas for

effective control strategies. The requirement on the upwind areas to provide for

attainment in downwind areas overwhelmed by transported pollutants may result in

adoption of additional controls in the affected upwind areas. The environmental impacts

of such control measures will be addressed in the formal planning and rule making process

in the upwind areas.

The staff expects that the implementation of the required measures in upwind areas

will have positive environmental impacts in the downwind and in most upwind areas. The

mitigation requirements will provide for more expeditious attainment of the ozone

standard in downwind areas by reducing emissions of ozone precursors that contribute to

the poor air quality in downwind areas. 
74

B. Economic Impacts

The Board’s Executive Officer has determined that the proposed transport

assessments and transport couple redefinitions will not create costs or savings (as defined

in Government Code section 11346.5(a)(6)) to any state agency or in federal funding to

the state, costs or mandate to any local agency or school district whether or not

reimbursable by the state pursuant to part 7 (commencing with section 17500) Division 4,

Title 2 of the government code, or result in other nondiscretionary costs or savings to

local agencies. 

The proposed transport assessments and transport couple redefinitions require the

assignment of mitigation responsibility of exceedances impacted by transported pollutants. 

The transport assessments more effectively assign mitigation responsibilities to the area

which will have the best probability of successfully reducing the ozone concentrations in

the downwind areas. The Executive Officer does not anticipate that the amendments will

result in additional controls statewide, but merely change the distribution of emission

controls from the downwind areas to the upwind areas. Ozone exceedances are already

occurring and the California Clean Air Act requires that districts adopt emission control

measures to attain the standard. If an upwind area has to do more because of the impacts

of transported pollutants to a downwind area, then the downwind area may have to do

less, perhaps much less because the downwind controls would be ineffective in some

transport situations. 

The expanded responsibility of the Broader Sacramento Area (BSA) for attainment

in the central portion of the Mountain Counties may create costs to, and impose a mandate

upon, the Broader Sacramento Area, as the upwind area, to continue to mitigate the

impact of their emissions on downwind areas. The districts in the Broader Sacramento

Area may need to adopt additional control measures in order to mitigate the impact of

their emissions on the new downwind area. However, the staff does not believe the

districts will need to adopt more measures than have already been scheduled. The

Broader Sacramento Area is already responsible for the attainment of other downwind

areas and has scheduled control measures accordingly. These control measures and

strategies which are designed to mitigate the BSA’s impacts on already identified

downwind areas (the northern portion of the Mountain Counties and the Upper

Sacramento Valley) should be sufficient to mitigate the impacts on the central portion of

the Mountain Counties. Such control measures would be proposed as part of districts’ air

quality attainment plans for ozone under the California Clean Air Act, and would be

adopted by the districts pursuant to their normal regulatory adoption procedures which

include the consideration of economic and environmental impacts resulting from the

implementation of new control measures. (See Health and Safety Code sections 40725-

40728.5)
75

The identification of the San Joaquin Valley Air Basin as an upwind contributor to

ozone exceedances in the North Central Coast Air Basin and amendments to the

mitigation regulation requires the San Joaquin Valley Air Basin to adopt best available

retrofit control technology. This is not expected to create additional costs or mandates

because the San Joaquin Valley Air Basin is already required to adopt these measures

since the air basin was previously identified as an upwind contributor.

The Executive Officer also has determined, in accordance with Government Code

section 11346.5(a)(8), that adoption of the proposed amendments will not have a

significant adverse economic impact on businesses, including the ability of California

businesses to compete with businesses in other States. Finally, the Executive Officer has

determined that there will be no potential cost impact, as defined in Government Code

section 11346.5(a)(9), on private persons or businesses directly affected as a result of

adopting the proposed amendments.

In accordance with Government Code section 11346.3, the Executive Officer has

determined that adoption of the proposed amendments will not affect the creation or

elimination of jobs within the State of California, the creation of new businesses or the

elimination of existing businesses within California, or the expansion of businesses

currently doing business within California.

Before taking final action on the proposed amendments to the regulations, the

Board must determine that no alternative considered by the agency would be more

effective in carrying out the purpose for which the action is proposed or would be as

effective or less burdensome to affected private persons than the proposed action

(Government Code section 11346.14(b)).

C. Alternatives to the Staff’s Proposed Amendments

State law explicitly requires the ARB to assess the contribution of upwind

emissions to downwind ozone concentrations based on the preponderance of evidence,

and to establish transport mitigation requirements that are commensurate with those

contributions (Health and Safety Code section 39610(b)). This mandate precludes

consideration of the “no action” alternative. The identification process leaves little room

for alternatives. Each transport couple is accompanied by discussion of the basis for the

identification. Implicit in these discussions is the consideration of possible alternative

transport assessment classifications. Various alternatives to the mitigation requirements

were considered by the staff when the regulation was revised in March 1993. This

proposal does not change the requirements; it only amends the regulation to assign

additional responsibilities to previously identified upwind areas based on new findings of

overwhelming and significant transport.
76
77

CHAPTER V

Recommendations for Further Research

Not all the questions about transport of ozone and ozone precursors have been

answered with this transport assessment. Through the process of putting this update

together, the staff has identified areas that need further research. This includes data

collection to understand and assess transport aloft, assessment of potential new couples,

photochemical modeling to quantify upwind contributions, data collection along transport

routes, analyses of existing data from field studies, and enhancing the monitoring network. 

A. Transport Aloft

Ozone formed during summer daytime hours disperses throughout the mixed layer

which can be several thousand feet deep. Most of this ozone becomes separated from the

mixed layer when nighttime inversions form. The presence of these ozone “reservoirs”

aloft has been revealed by aircraft measurements made during intensive field studies in the

South Coast, Southeast Desert, North Central Coast, San Francisco Bay Area, San

Joaquin Valley, and Sacramento Valley Air Basins. There has been some discussion

presented in this report concerning analysis of upper-level winds and air quality, but most

of the transport analyses are based on surface transport because of the lack of data aloft. 

It is likely that upper-level transport may influence the overall transport of ozone and

precursors throughout California. While there is considerable upper-level wind and air

quality data available for use in transport studies in some areas of the state for limited time

periods, the lack of upper air data is a major problem in assessing ozone transport for

most areas of the state. 

Photochemical grid models use three-dimensional wind fields and, therefore, are

able to use all available upper-level wind and air quality data for the episodes modeled. 

When models are not available, techniques for analyzing upper-level wind and air pollutant

data need to be reviewed and if needed, new techniques developed. Past studies of air

quality aloft have been done by outfitting aircraft with instrumentation or placing monitors

on towers. Siting monitors in high terrain also offers a way to measure upper-level air

quality when the site is not affected by upslope winds.

Remote sensing studies may offer several advantages over currently used methods

such as aircraft and tower monitoring and the use of high terrain sites. Remote sensing

uses equipment which may be left unattended and which has the capability to provide

continuous measurements. Aircraft can cover large upper-level volumes but the

measurements only represent a snapshot picture. Towers are ideal for longer measuring

times of the vertical picture of the atmosphere above a point. High terrain sites are also

single point measurements but can also record air quality over long time periods. Remote
78

sensing may be able to define upper-level air quality for a large volume as well as for

longer time periods. 

Specifically, and for example, data aloft measurements have been emphasized in all

phases of transport assessment from the South Coast to the Mojave Desert and from the

San Joaquin Valley to the Mojave Desert. Using the preponderance of data as suggested

in the California Clean Air Act does not always give complete understanding when there is

a void of critically necessary data. The staff recommends allotting resources to help fill

this void for better, more scientific future transport assessments statewide.

B. Specific Couples for Transport Research

The staff recommends exploring the potential for transport from the San Diego Air

Basin to the Salton Sea Air Basin. Additionally, further research is warranted for ozone

transport from the South Coast Air Basin to the Great Basin Valleys Air Basin. In the

latter couple, emphasis should be placed on the Death Valley National Park monitoring

site because ozone transport assessments have already been established for the Mammoth

monitoring site. The ARB staff also recommends more research be conducted for the San

Joaquin Valley to North Central Coast transport couple. 

C. Photochemical Grid Modeling

The staff was not able to quantify the upwind transport contribution to the

downwind areas in the 1990 or in the 1993 assessments because the modeling tools and

data sets were not available. Likewise, the staff was not able to quantify contributions in

this current assessment. However, the staff believes that quantification is ultimately

needed to equitably divide the mitigation responsibilities between the upwind and

downwind areas. 

Future studies are planned to study ozone-producing mechanisms. These studies

will include the five air basins in southern California: South Coast, Mojave Desert, Salton

Sea, San Diego, and South Central Coast. A benefit from these studies will be a wealth of

meteorological and air quality data which will be used for transport assessment.

D. Data Analysis

Innovative analytical techniques may be added to the data analysis techniques

currently used for transport assessment. The staff recommends that any new methods be

further evaluated in order to be incorporated, where appropriate, into future transport

studies.

Additionally, even though there are some trajectory models available now, they

need refining to incorporate wind flows in complex terrain, such as in the foothills of the
79

Sierra Nevada and the Mountain Counties Air Basin. These tools would meet many other

ARB needs, as well.

Data analysis techniques also need to be expanded to include more parameters than

just meteorology and ozone. Understanding the complexity of ozone production and

ozone transport requires more detailed analyses of such parameters including, but not

limited to, volatile organic compound speciation and the impact of NOx on downwind

transport receptor areas.

Researching nonstandard methods of data analysis may also be helpful. For

instance, exploring the daily minimum ozone values may provide some insight in

understanding carryover from the previous day. This phenomenon is also very complex as

the principle of NOx scavenging is taken into consideration along with emission

inventories of local areas. 

E. Enhanced Monitoring

The staff recommends increased monitoring of meteorology and ozone

concentrations to improve the data available for analyses. Increased monitoring is needed

for studying spatial variability of ozone along transport routes. The staff and research

contractors have identified transport corridors from one area to another. Some of these

corridors lack sufficient meteorological and air quality data for a complete transport

assessment. The staff recommends that more meteorology and air quality monitors be

sited in these transport corridors particularly on ridges that sometimes act as barriers to

the transport of pollutants. Monitors could be placed in areas such as, but not limited to,

Grapevine between the San Joaquin Valley and South Coast Air Basins, Santa Catalina

Island between the South Coast and San Diego Air Basins, Channel Islands between the

South Coast and South Central Coast Air Basins, and in the Fairfield/Vacaville hills

between the San Francisco Bay Area Air Basin and the Broader Sacramento Area.

In addition to increased monitoring sites, the staff recommends increasing

monitoring parameters in some locations. Specifically, staff recommends measuring

temperature, dew point, and wind at both Tracy and Crows Landing.

Staff also recommends the installation of additional wind profilers in Santa Barbara

County, perhaps at El Capitan and an inland site. These profilers provide a threedimensional cross section of winds and temperatures which is helpful for characterizing an

ozone plume.
80
81

CHAPTER VI

REFERENCES

1. Air Resources Board, 1984: California Surface Wind Climatology. ARB staff

report prepared by the Aerometric Data Division, updated by the Technical Support

Division in June 1989 and reprinted in January 1992.

2. Air Resources Board, 1995: “San Joaquin Valley Air Quality Study, Bulletin #1,"

A Report to the San Joaquin Valley Air Quality Study Policy Committee.

3. Air Resources Board, 1989: Proposed Identification of Districts Affected by

Transported Air Pollutants which contribute to violations of the State Ambient Air Quality

Standard for Ozone. ARB staff report prepared by the Technical Support Division,

Meteorology Section, October 1989, 57 pp. + 4 Appendices.

4. Air Resources Board, 1990: Assessment and Mitigation of the Impacts of

Transported Pollutants on Ozone Concentrations within California. ARB staff report

prepared by the Technical Support Division and Office of Air Quality Planning and

Liaison, June 1990.

5. Air Resources Board, 1993: Pubic Meeting to Consider the Revision of Emission

Control Requirements to Mitigate the Impact of Transported Pollutants on Ozone

Concentrations. ARB staff report, January 1993, 14 pp. + 5 Appendices.

6. Air Resources Board, 1993: Assessment and Mitigation of the Impacts of

Transported Pollutants on Ozone Concentrations in California. ARB staff report prepared

by the Technical Support Division, June 1993, 129 pp. + 5 Appendices.

7. Air Resources Board, 1996: Maps and Tables of the Area Designations for State

and National Ambient Air Quality Standards and Expected Peak Day Concentrations and

Designation Values, Attachments H and F. ARB staff report prepared by the Technical

Support Division, January 1996. 

8. Air Resources Board, 1996: Proposed Amendments to Divide the Southeast

Desert Air Basin and to Modify the Boundary of the South Coast Air Basin and Proposed

Amendments to the Related Agricultural Burning Regulations. ARB staff report prepared

by the Technical Support Division, April 1996, 54 pp. + 6 Appendices.
82

9. Air Resources Board, 1996: Proposed Amendments to the Area Designations for

State Ambient Air Quality Standards, Proposed Amendments to the Area Designations

due to Changes in Air Basin Boundaries, and Proposed maps of Area Designations for the

State and National Ambient Air Quality Standards. ARB staff report prepared by the

Technical Support Division, October 1996.

10. Bigler-Engler, V. J. and H. Brown, 1995: “Analysis of an Ozone Episode during

the San Diego Air Quality Study: The Significance of Transport Aloft,” Jour. Applied

Meteorology, 134, 1863-1876.

 11. Bigler-Engler, V. J. and H. Brown, 1995: “Episode Classification for the San

Diego Air Basin.” Proceedings, Regional Photochemical Measurement and Modeling

Studies, International Speciality Conference, Air and Waste Management Assn.

Pittsburgh, PA. 369-390.

12. Bigler-Engler, V.J., H. Brown and K.K. Wagner, 1996: “A Photochemical

Modeling Ozone Attainment Demonstration for an Area Impacted by Transport.”

Preprints, Ninth Conference on Applications of Air Pollution Meteorology, American

Meteorological Society, Boston, MA.

13. Bigler-Engler, V.J., H. Brown and K.K. Wagner, 1996: “A Hybrid Modeling

Technique to Address Coastal Meteorology and Complex Terrain in the San Diego

Photochemical Modeling Domain.” Preprints, Ninth Conference on Applications of Air

Pollution Meteorology, American Meteorological Society, Boston, MA.

14. Cass, Glen, 1996: Reclassification of the Ozone Non-Attainment Status of the

Eastern Kern County Area.

15. DaMassa, J., S. Tanrikulu, K. Magliano, A.J. Ranzieri, and L. Niccum, 1996:

Performance Evaluation of SAQM in Central California and Attainment Demonstration for

the August 3-6, 1990 Ozone Episode. California Air Resources Board, Technical Support

Division, Sacramento, CA.

16. Gouze, S.C., 1994: Ozone Transport Assessment: San Francisco Bay Area Air

Basin to the North Central Coast Air Basin 1990-1992. California Air Resources Board,

Technical Support Division, Sacramento, CA.

17. Jiang, Jih-Yih, 1995: Transport Assessment for Days in 1994 with Exceedances of

the California State Ozone Standard in the North Central Coast Air Basin (NCCAB)

Volumes I and II. Bay Area Air Quality Management District, San Francisco, CA.
83

18. Jiang, Jih-Yih, 1996: Transport Assessment for Days in 1995 with Exceedances of

the California State Ozone Standard in the North Central Coast Air Basin (NCCAB)

Volume I. Bay Area Air Quality Management District, San Francisco, CA.

19. Magliano, K.L., 1994: Summary of SARMAP Emissions Modeling. California

Air Resources Board, Technical Support Division, Sacramento, CA.

20. Seaman, N.L. and D.R. Stauffer, 1996: SARMAP Meteorological Model Final

Report. California Air Resources Board, Technical Support Division, Sacramento, CA.
84
85

APPENDIX A

TEXT OF HEALTH AND SAFETY CODE

SECTION 39610
86
87

APPENDIX A

TEXT OF HEALTH AND SAFETY CODE

SECTION 39610

Section 39610

(a) Not later than December 31, 1989, the state board shall identify each air

basin, or subregion thereof, in which transported air pollutants from upwind areas outside

the air basin, or subregion thereof, cause or contribute to a violation of the state ambient

air quality standard for ozone, and shall identify the district of origin of the transported air

pollutants based upon the preponderance of available evidence. The state board shall

identify and determine the priorities of information and studies needed to make a more

accurate determination, including, but not limited to, emission inventories, pollutant

characterization, ambient air monitoring, and air quality models. 

(b) The state board shall, in cooperation with the districts, assess the relative

contribution of upwind emissions to downwind ozone ambient air pollutant levels to the

extent permitted by available data, and shall establish mitigation requirements

commensurate with the level of contribution. In assessing the relative contribution of

upwind emissions to downwind ozone ambient air pollutant levels, the state board shall

determine if the contribution level of transported air pollutants is overwhelming,

significant, inconsequential, or some combination thereof. Any determination by the state

board shall be based upon a preponderance of available evidence.

(c) The state board shall make every reasonable effort to supply air pollutant

transport information to heavily impacted districts prior to the development of plans to

attain the state ambient air quality standards, shall consult with affected upwind and

downwind districts, and shall adopt its findings at a public hearing.

(d) The state board shall review and update its transport analysis at least once

every three years.

(e) The state board shall conduct appropriate studies to carry out its

responsibilities under this section.
88
89

APPENDIX B

PUBLIC WORKSHOP NOTICE
90
91
92
93

APPENDIX C

July 10, 1996 Transport Workshop Participants
94
95

APPENDIX C

July 10, 1996 Transport Workshop Participants

Rory MacArthur Rita Cirulis

Chevron Shasta Co. AQMD

(510) 242-4884 (916) 225-5674

Cindy Tuck S.D. Ziman

CEEB Chevron

(916) 446-3870 (510) 242-1530

Don Kindela David Schorrar

Chevron DRI

(510)242-2171 (702)677-387

Guido Franco Jan Bush

CEC BAAQMD

(916) 654-3940 (415) 749-4943

Juan Ngo Robert Nunes

CEC MBUAPCD

654-3852 (408)647-9411

Randall Woodward Scott Folwarkow

N. Sonoma County APCD WSPA

(707) 433-5911 (510) 825-9388

Lyle Chinkin Jim Sweet

Sonoma Technology, Inc. SJVUAPCD

(707) 527-9372 (209) 497-1075

Keith Golden Bill Brick

CEC SJVUAPCD

653-1643 (209) 497-1075

Jih-Yih Jiang Les Fife

BAAQMD SVABCC

(415) 749-4657 (916) 668-1559
96

Mike Murray

PE/SoCal Gas

(916) 446-5284

Todd Peterson

CEC

(916) 654-4871

Kate Zocchetti

CEC

(916) 653-4710

Cynthia Praul

CEC

(916) 654-4996

Mike Fuller

Sierra Club

9306 W. Meadow Dr.

Winton, CA 95388

ARB Attendees:

G. Osborn

Norm Marrmis

Jim Lerner

Ajith Kadurza

Steve Gouze
97

APPENDIX D

GLOSSARY
98
99

Appendix D

Transport-Meteorology Glossary

Adiabat/Adiabatic - see Lapse rate.

APOB - acronym for Airplane observation.

air basin - an area wherein there are similar meteorological and geographic conditions;

also defined by political boundaries; an area in which the air mass is homogeneous; an area

usually bounded by topographical feature.

aircraft soundings - temperature and/or pollutant measurements aloft obtained by aircraft

either at multiple levels over one location (referred to as a spiral) or one level over several

locations (referred to as a traverse).

air flow charts - the Air Resources Aboard meteorology section prepares charts which

include wind speed and wind direction for many sites. The winds are analyzed with lines

showing air flow patterns; a modified streamline chart produced by the Air Resources

Board meteorology section.

air-flow type/pattern - the Air Resources Board meteorology section first plots wind

speed and direction at various locations statewide, then they analyze the plots using a

modified streamline method, then they categorize, or type, air flow patterns in the larger,

predominant regions of the state.

aloft - above the earth’s surface, generally 50 feet elevation and higher; as opposed to the

surface is not exactly at the surface but usually anywhere from 2 to 30 feet above the

ground. 

ambient - surrounding, on all sides; in situ; for use in air pollution, ambient refers to free

moving air as opposed to, possibly, in a laboratory setting.

anti-cyclonic - clockwise; wind flow around an area of high pressure.

AUSPEX - San Joaquin Valley Air Quality Study/Atmospheric Utility Signatures,

Predictions, and Experiments (SJVAQS/AUSPEX); a field program conducted in 1990.

background - for ozone studies, background refers to an area’s normal minimum ozone

concentration, or that concentration normally experienced by an area without influence or

transport from an upwind area. For instance, clean air, such as the air mass over the Pacific

Ocean has a normal background concentration of 4 pphm. Areas in the mountains may
100

have background concentrations of 5 or 6 pphm because there is not a presence of Nox for

ozone scavenging as there is in the urban areas. Urban areas often have background ozone

concentration levels of 0 or 1 pphm.

backward trajectory - a pictorial technique which estimates the path an air parcel took

over a specified period of time. This path is estimated using wind speed and wind

direction at various sites in the domain which have been analyzed into successive hours of

wind fields. Terrain and meteorology are also considered in this analysis. In the case of

backward trajectory, the site of the ozone concentration in question is used as the start

point and then a figurative air parcel is “backed up” to determine the approximate source

area of the polluted air mass.

bimodal - an analysis in which there are two areas where a certain value, number, or

concentration occurs with high frequency.

biogenic - hydrocarbon emissions from plant species including alcohols, acetates,

aldehydes, ketones, ethers, esters, alkanes, alkenes, aromatics, and, most prevalently,

isoprene and alpha pinene (a monoterpene).

boundary conditions - for use in photochemical modeling, a boundary condition refers to

those pollutant concentrations in air entering the domain being modeled.

boundary sites - for use in transport assessments, a boundary site is a site close to the air

basin boundary line.

break (inversion) - The temperature at the top of the inversion is an indicator of when the

inversion might cease to exist, or break. This break temperature is the temperature at

which the top of the inversion would be if lowered dry adiabatically. In other words, as a

parcel of air changes altitude, it will warm if lowered or cool if raised, approximately 5F

per 1000 feet. When the surface temperature equals or exceeds that of the inversion top

temperature lowered adiabatically, vertical mixing is possible and the inversion is said to

have broken or eroded. Vertical mixing is contained only in layers of the atmosphere

where the temperature decreases with height. 

Clean Air Act - The California Clean Air Act was AB 2595, Sher (Chapter 1568, Statutes

of 1988). Referring only to transport, this Act established time frames by which districts

should improve air quality or meet attainment of the ambient air quality standard for ozone. 

This Act also established requirements for transport assessments to be made as well as

triennial updates of these assessments. The Federal Clean Air Act was passed in 1977 and

amendments were made in 1990. The state’s transport research is primarily aligned with

the California Clean Air Act.

corridor - a common path of air flow, usually unobstructed and long and usually transects

two air basins.
101

convection/convective (heating) - upward vertical motion in the atmosphere; free

convection is a result of surface heating or vertical motion caused by density differences

within the airmass; forced convection is a mechanical lifting caused by such things as

weather fronts or terrain. 

couple - a pair of geographic areas, one considered upwind and one considered downwind.

decoupled - occurs when the air mass below the inversion is distinctly different than the air

mass above the inversion.

CDEC - acronym for California Data Exchange Center.

character of exceedance - an ozone concentration trend will indicate whether the ozone

exceedance occurred abruptly or if the ozone concentrations gradually built up to exceed

the state standard. The ozone concentration trend also indicates whether the exceedance

was brief or if it spanned many hours. The ozone concentration trend for the downwind

site, compared with trends for upwind sites, will help support an assessment of transport or

no transport.

CIMIS - acronym for California Irrigation Management Information System.

contours - on constant pressure charts, ie 500 millibar chart, a contour is a line of uniform

pressure heights.

confluence - the rate at which adjacent flow is converging, or coming together, along an

axis oriented normal to the flow at the point in question; the opposite of diffluence;

referring to direction.

convergence - flowing or running together to form one mass. 

conversions -

from this to this m/sec mph knots

m/sec x1 x2.2369 x1.9425

mph x.44707 x1 x.86839

knots x.51479 x1.1516 x1
102

from this to this lbs/day tons/day F C

lbs/day x1 x.0005 -- --

tons/day x2000 x1 -- --

F -- -- x1 .5555( F-32)

C -- -- (1.8x C)+32 x1

cyclonic - counter-clockwise; wind flow around an area of low pressure.

differential heating/cooling - when the rate of heating/cooling differs spatially.

difluence - the rate at which adjacent flow is diverging, or moving apart, along an axis

oriented normal to the flow at the point in question; opposite of confluence; referring to

direction.

disperse - to break up and scatter in all directions; in transport, this term refers to the

scattering of air pollutants by wind or by convection.

diurnal - daily; especially pertaining to actions which are completed within twenty-four

hours and which recur every twenty-four hours.

divergence - flowing or moving apart from one common mass; opposite of convergence;

referring to the velocity field.

domain - a field or sphere of activity or influence; in transport, the domain is the area of

which data is input for modeling purposes.

downwind - The direction toward which the wind is blowing; with the wind.

drainage flow - general term for gravity-induced, down slope flow of relatively cold air.

duration - normally referring to the duration of the ozone exceedance at a particular site;

the number of hours of ozone exceedance can be determined by reviewing the ozone

concentration trend.

eddy - current of air moving against the main current and with a circular motion; limited

in importance or effect.

emission inventory - usually expressed in tons per day; the emission inventory is used in

photochemical modeling and in area comparisons.
103

exceedances - any ozone concentration greater than the ambient air quality standard for

ozone.

extreme concentration - a concentration that is statistically expected to occur less

frequently than once every year.

forward trajectory - a pictorial technique which estimates the path an air parcel took

over a specified period of time. This path is estimated using wind speed and wind

direction at various sites in the domain which have been analyzed into successive hours of

wind fields. Terrain and meteorology are also considered in this analysis. In the case of

forward trajectory, an upwind area or site is used at the start point and then a figurative

“air parcel” is then moved forward to determine the possible impacted area.

fumigate - this occurs as the air mass carrying a smoke plume becomes unstable and the

airmass mixes vertically causing the smoke to come in contact with the earth’s surface.

GMT - acronym for Greenwich Mean Time, the time in Greenwich, England which is

eight hours later than Pacific Standard Time; also referred to as Zulu or Z time.

gradient - usually refers to temperature or pressure change over a given distance (usually

horizontal); the ratio of change to distance. A 'tight' or 'strong' gradient refers to a high

ratio or a lot of change per given distance. A 'loose' or 'weak' gradient, therefore, is less

change over the same given distance. 

high pressure - a dominating atmospheric feature; a large area where surface pressures

are higher than the surrounding area; an area of anticyclonic circulation.

hydrocarbons - used generally and interchangeably with reactive hydrocarbons and

reactive organic gases to mean all organic compounds which may participate in the ozone

formation process.

intrusion - see Stratospheric Intrusion. 

inversion - that portion of the vertically measured atmosphere in which the temperature

increases, rather than decreases, with height.

inverted (thermal) trough - a low pressure area induced by surface heating in which the

general flow is from east to west instead of west to east; a meteorological feature

commonly found in California from the Imperial Valley northward through the

Sacramento Valley.

isopleth - a line of equal or constant value of a given quantity with respect to either space

or time.
104

isotherm - a line connecting points of equal temperature.

isobar - a line connecting points of equal pressure.

jet stream - a channel of increased wind speeds. Some low level jets are mechanically

induced such as jets near the inversion or jets funneled by terrain; upper level jet streams

(25,000 to 50,000 feet) are induced by the temperature differences between two air

masses. Jet streams are usually considered as such when they are a relatively narrow band

of greater wind speeds than the surrounding winds and are greater than 50 knots.

knot - a rate of speed equal to one nautical mile per hour (therefore, no such term as

knots per hour); equal to 1.1508 statute miles per hour or .5144 meters per second.

lapse rate - this is the rate at which a particular column of air cools. A negative lapse rate

indicates warming with height rather than cooling (see inversion). A lapse rate that equals

the standard atmospheric lapse rate is referred to as the adiabatic lapse rate. A superadiabatic lapse rate occurs as a layer of air cools with height quicker than the adiabatic

lapse.

latitude - angular distance, measured in degrees (0-90), north or south from the equator. 

lidar - a system which uses laser technology to measure atmospheric parameters.

local - a transport assessment also referred to as inconsequential; a transport assessment

given to an exceedance day in which the emission impact from an upwind district was

either non-existent or so little as to have inconsequential impact on the exceedance; a

transport assessment in which it has been determined that nearly all the emissions causing

the exceedance were locally generated.

longitude - distance east or west, measured in degrees (0-180), from the prime meridian

(or longitude) which passes through Greenwich, England.

low pressure/heights - on the surface, an area of low pressure is surrounded by an higher

pressures; aloft, an area of low heights is an area where a constant pressure is lower than

the same pressure is in surrounding areas. 

magnitude - one dimensional; a number given to a quantity for purposes of comparison

with other quantities of the same class.

marine air - air whose characteristics are developed over an extensive water surface and

which, therefore, has the basic maritime quality of high moisture content in at least its

lower levels; below the inversion, moist, thermally modified air intrudes as far inland as

100 miles or more into most of California.
105

marine layer - the layer from surface to the base of the inversion.

Marta - a system for retrieving and managing various types of meteorological data

including hourly observations and satellite imagery.

microclimate - the fine climatic structure of the air space which extends from the very

surface of the earth to a height where the effects of the immediate character of the

underlying surface no longer can be distinguished from the general local climate; generally,

four times the height of surface growth or structures defines the level where micro climatic

tones disappear.

millibar (MB) - a unit measure of atmospheric pressure. The worldwide average sea

level pressure is 1013.2 MB; 850 MB is approximately 5000 ft; 700 MB is approximately

10,000 ft; 500 MB is approximately 18,000 ft. 

mitigation - in air pollution control, mitigation refers to those measures that are taken to

prevent or reduce emissions in the atmosphere.

mixing depth - the layer of atmosphere, usually surface-based, where vertical circulation

can occur; this depth usually defined by the inversion.

model - a computer derived situation of which variables can be altered to determine an

outcome.

moderate - regarding the California Clean Air Act, an area classified as moderate for

ozone 1) is expected to reach attainment by December 31, 1997, and 2) has a once in one

year recurrence rate of 12 pphm or less.

nautical mile - 1852 meters, 6076.103 feet, or 1.1508 statute miles; the length of one

minute of arc along any great circle on the earth's surface. This distance varies slightly

with latitude and therefore the distance of a nautical mile has been reached by international

agreement. 

nephanalysis - the analysis of a synoptic chart in terms of the types and amount of clouds

and precipitation.

nitric oxides (NO) - a colorless, poisonous gas found in variable trace quantities in the

atmosphere, especially near industrial areas.

nocturnal jet - a low-level jet that exists at night due to the strength of the inversion at

that time. 

nocturnal - of, done, or happening in the night.
106

NOx - nitrogen oxides (NO and/or NO2).

NOx scavenging - method by which ozone is removed from the ambient air. When ozone

reacts with nitric oxide, the resulting concentration of ozone is lower.

ozone - a secondary ambient air pollutant generated by photochemical reaction involving

hydrocarbons and nitric oxides.

ozone concentrations - produced by the chemical reaction of nitrogen oxides and

hydrocarbons in the presence of sunlight ozone reservoir.

Pacific High - a semi-permanent synoptic condition dominating the eastern Pacific.

parcel - a theoretical 'box' of air that may be physically tracked to show movement from

an upwind area to a downwind area; a theoretical 'box' of air that contains certain masses

of atmospheric gases.

PGM - Photochemical Grid Model; mathematical representation of the three-dimensional

atmosphere to simulate the dispersion and chemical transformation of pollutant emissions

that produce ozone.

photochemical - the effect of light or other radiant energy in producing chemical action; a

chemical reaction which involves either the absorption or emission of radiation.

pibal - contraction for pilot-balloon observation; this type of observation measures winds

aloft by tracking a balloon with a theodolite.

plume - on a point-source scale, a plume is the airborne discharge from an industrial

stack, an agricultural burn location, or any other single source; on a regional scale, a

plume is considered to be the polluted air mass which may travel away from the source

region.

ppb - parts per billion; pphm x 10.

pphm - parts per hundred million; ppm x 100.

ppm - parts per million.

precursors - primary air pollutants; air pollutants which haven't undergone chemical

processes in the ambient air.
107

preponderance - term used in California Clean Air Act to describe the types and amount

of data used to make transport assessments; greater in amount, weight, power, influence,

importance; predominant.

profiler - equipment which provides continuous winds aloft measurements using the 

doppler shift principle and radar waves.

PST - Pacific Standard Time.

qualification - making a transport assessment using general, relative terms.

quantification - making a transport assessment using specific numbers.

radiosonde - a balloon-borne instrument for the simultaneous measurement and

transmission of meteorological data - specifically pressure, temperature, and humidity.

RAOB - contraction for radiosonde observation.

rawinsonde - a radiosonde observation combined with a rawin (winds-aloft) observation;

rawin is a method of winds-aloft observation; use of radiosonde to determine pressure,

temperature, dewpoint, wind speed, and wind direction aloft.

reactive hydrocarbons - used generally and interchangeably with hydrocarbons and

reactive organic gases to mean all organic compounds which may participate in the ozone

formation process.

reactive organic gases - used generally and interchangeably with hydrocarbons and

reactive hydrocarbons to mean all organic compounds which may participate in the ozone

formation process.

receptor - a downwind area; downwind from the emission source area.

ridge - as a terrain feature, a ridge is the crest line, or the line which joins the highest

peaks of a mountain range, often the air basin boundary; as a meteorological feature, a

ridge is most commonly referred to as a large area of high pressure such as the ‘ridging’

over the California coastline or a ‘ridge’ of high pressure. 

Schultz Eddy - counter-clockwise circulation found in the southwestern portion of the

Sacramento Valley. This phenomena is dependent upon wind speed and direction from

the delta area. Very strong southwest windflow will erode the eddy, very light windflow

will not support the eddy.
108

sea breeze - air flowing from the ocean to land; usually occurs in late afternoon through

mid evening and the land has become hotter causing air to rise, cooler marine air will flow

landward to replace the air which has risen; see also marine air.

serious - an area which has a once in one year recurrence rate greater than or equal to 12

pphm but less than 16 pphm.

severe - an area which has a once in one year recurrence rate greater than or equal to 16

pphm.

sloshing - a theory that polluted air flows up a mountain with the valley breeze in the

afternoon and down the mountain with drainage flow in the late night and early morning

hours leaving behind some of the polluted air near the inversion. The theory is that this

phenomena may accumulate over several days thereby causing ozone exceedances.

sounding - this term is used for any type of vertical atmospheric measurement. These

measurement methods include pibals, APOBs, lidar, rawinsonde, and profilers

source area - upwind area; the area from where emissions originate.

spatial - horizontal, geographic relationship. 

spirals - vertical aircraft patterns whereby aircraft can measure air pollutants aloft.

stable - when a warm strata of air overlies a cooler strata of air, the condition is

considered stable. Stability is determined by the lapse rate. When a lapse rate is less than

the adiabatic lapse rate (slower cooling with height), the air mass tends to be more stable. 

When a lapse rate is more than the adiabatic lapse rate (more cooling with height), or

super-adiabatic, the air mass tends to be less stable. A stable air mass will have little

vertical motion associated with it and will therefore be absent of vertically developed

clouds and weather. An unstable air mass will have greater vertical motion and may have

many vertically developed clouds, depending on the availability of moisture in the air mass.

Stability is very important in assessing air pollution transport and in real-time air pollution

matters such as agricultural burning. Even if there is not enough moisture for clouds,

vertical motion still occurs and will assist in dispersing and diluting the air pollutants into

the atmosphere. 

statute mile - the 'common' mile; 5,280 feet.

stratosphere - the atmosphere immediately above the tropopause usually beginning

somewhere between 35,000 and 65,000 feet, depending on the latitude and the season.
109

stratospheric intrusion - air which is downward vertically mixed from the stratosphere

into the troposphere. This is usually caused by a synoptic disturbance.

streamline analysis - normally, an analysis produced for areas with nearly laminar flow

such as the ocean surface and constant pressure charts (layers aloft); in this type of

analysis, wind vectors are plotted and lines drawn parallel to the vectors; airflow charts

used in transport analyses are sometimes referred to as streamline charts but are not true

streamline charts as such.

subsidence - descending air, usually associated with a high pressure area.

surface - the boundary between the earth and the atmosphere.

surface deposition - method by which ozone is removed from the ambient air. 

Deposition occurs on vegetation or other surfaces.

synoptic - presenting or involving data on weather and atmospheric conditions over a

wide area at a given time.

theodolite - a piece of survey-type equipment used for tracking weather balloons;

equipment with azimuth (direction) and elevation readings.

thermal low - an area of low atmospheric pressure due to high temperatures caused by

intensive heating at the earth's surface; non-frontal.

thermal trough - see thermal low.

time-series - a graph with hour on the x-axis, ozone concentration on the y-axis; graph

indicates ozone trend for a given period of time.

trajectory - the path an air parcel takes in movement from one area to another dependent

upon wind speed, wind direction, terrain, and meteorology; a pictorial analysis technique

which estimates the path an air parcel took over a specified period of time. This path is

estimated using wind speed and wind direction at various sites in the domain which have

been analyzed into successive hours of wind fields. Terrain and meteorology are also

considered in this analysis. See also forward and backward trajectory.

transport - horizontal movement of air pollution or air pollution precursors at the earth's

surface or aloft. Vertical movement of air pollution is referred to as mixing. 

traverses - horizontal aircraft patterns whereby aircraft can measure air pollutants

spatially.
110

tropopause - the boundary between the troposphere and the stratosphere.

troposphere - the atmosphere beginning at the earth's surface and extending to the

tropopause.

trough - an area of low pressure (surface) or low heights (aloft); wind flow around a

trough is cyclonic or counter-clockwise.

trof - same as trough.

turbulence - vertical air motion; random motion in layers of a fluid (atmosphere)

UAM - Urban Airshed Model.

upwind - in the direction from which the wind is blowing; against the wind.

UV intensity - solar radiation. 

valley breeze - wind flow up a mountain from valley during the day.

vector - wind speed and wind direction combined.

violation - an exceedance of the ambient air quality standard for ozone greater than the

ambient air quality standard for ozone but less than the once in one year expected peak

day concentration.

Winds2D - a two-dimensional air flow model used for generating parcel trajectories.

wind - Air in motion relative to surface of the earth; horizontal movement of air generated

and modified by pressure differences, earth's rotation, terrain, synoptic conditions, latitude;

measured or named as direction from which the wind is blowing such as northerly,

southeasterly, valley breeze, sea breeze.

wind run - analysis method of algebraically adding wind velocity at a given location;

unreliable analysis method due to inherent assumption of regionally uniform, unobstructed

windflow patterns.

WNI - Weather Network, Inc., a Butte County company providing weather data, historic

and real-time, to contracted users. (Company name recently changed).

Z - Zulu time.

Zulu - see GMT.
111

References

Air Resources Board, 1989: Proposed Identification of Districts Affected by

Transported Air Pollutants which Contribute to Violations of the State Ambient

Air Quality Standard for Ozone. 

Air Resources Board, 1990: Assessment and Mitigation of the Impacts of

Transported Pollutants on Ozone Concentrations within California.

Air Resources Board, 1993: Assessment and Mitigation of the Impacts of

Transported Pollutants on Ozone Concentrations within California

Huschke, Ralph E., editor, Glossary of Meteorology, 1959
112
113

APPENDIX E

PROPOSED TEXT OF REGULATION

IDENTIFYING AREAS WHICH ARE IMPACTED 

BY TRANSPORTED AIR POLLUTANTS
114
115

APPENDIX E

 PROPOSED TEXT OF REGULATION

IDENTIFYING AREAS WHICH ARE IMPACTED

BY TRANSPORTED AIR POLLUTANTS

Amend Subchapter 1.5, Article 5, Section 70500, Title 17, California Code of

Regulations to read as follows (items which have been added in previous rulemaking

procedures but subsequently omitted from the California Code of Regulations are in

italics) (proposed additions are underlined and in italics, proposed deletions are struck

out) :

1

Article 5. Transported Air Pollutants

70500 Transport Identification

(a) Purpose: This regulation identifies the areas in which transported air

pollutants from upwind areas cause or contribute to a violation of the state

ambient air quality standard for ozone and the areas of origin of the

transported pollutants. All areas identified in the table are the air basins

except as otherwise specifically described and defined.

(b) Definitions:

(1) “California Coastal Waters” includes the area between the California

coastline and a line starting at the California-Oregon border at the

Pacifica Ocean; thence to 42.0 degrees North, 125.5 degrees West;

thence to 41.0 degrees North, 125.5 degrees West; thence to 40.0

degrees North, 125.5 degrees West; thence 39.0 degrees North, 125.0

degrees West; thence to 38.0 degrees North, 124.5 degrees West;

thence to 37.0 degrees North, 123.5 degrees West; thence to 36.0

degrees North, 122.5 degrees West; thence to 35.0 degrees North,

121.5 degrees West; thence to 34.0 degrees North, 120.5 degrees

West; thence to 33.0 degrees North, 119.5 degrees West; thence to

32.5 degrees North, 118.5 degrees West; and ending at the CaliforniaMexican border at the Pacific Ocean.

(2) “Upper Sacramento Valley” includes the Colusa, Butte, Glenn,

Tehama, and Shasta County Air Pollution Control Districts, and that

area of the Feather River Air Quality Management District, which is

north of a line connecting the northern border of Yolo County to the

southwestern tip of Yuba County, and continuing along the southern

Yuba County border to Placer County.
116

(3) “Broader Sacramento Area” includes the Sacramento Metropolitan Air

Quality Management District; Yolo-Solano Air Pollution Control

District; the portions of the El Dorado County Air Pollution Control

District included in 1990 U.S. Census Tracts 306.01, 307, 308.01,

308.02, 308.03, 308.04, 309.01, 309.02, 310, 311, 312, 315.01, and

315.02; and the portions of the Placer County Air Pollution Control

District included in 1990 U.S. Census Tracts 203, 204, 205, 206.01,

206.02, 206.03, 207.01, 207.02, 207.03, 208, 209, 210.01, 210.02,

211.01, 211.02, 212, 213.01, 213.02, 214, 215.01, 215.02, 216,

218.01, and 218.02; and that area of the Feather River Air Quality

Management District which is south of a line connecting the northern

border of Yolo County to the southwestern tip of Yuba County, and

continuing along the southern Yuba County border to Placer County.

(c) Transport Identification Table

OZONE IMPACTED BY TRANSPORT: AREAS OF ORIGIN OF TRANSPORT:

1. North Central Coast San Francisco Bay Area

San Joaquin Valley

2. South Central Coast South Coast

California Coastal Waters

San Joaquin Valley

3. South Coast South Central Coast

4. San Diego South Coast

Mexico

5. Upper Sacramento Valley Broader Sacramento Area

6. Broader Sacramento Area San Francisco Bay Area

San Joaquin Valley

7. San Joaquin Valley San Francisco Bay Area

Broader Sacramento Area

8. Great Basin Valleys San Joaquin Valley

9. Southeast Mojave Desert South Coast

San Joaquin Valley

Mexico

10. San Francisco Bay Area Broader Sacramento Area

11. Mountain Counties Broader Sacramento Area

San Joaquin Valley

San Francisco Bay Area

12. Salton Sea South Coast

Mexico

Note: Authority cited: Sections 39600, 39601, 39610(a), Health and Safety Code. 

Reference: Section 39610(a), Health and Safety Code.
117

1. At the May 30, 1996 public hearing, the Air Resources Board approved amendments

to sections 60104 and 60109, and added a new Section 60114, Title 17, California Code

of Regulations which divided the Southeast Desert Air Basin into two new air basins; the

Mojave Desert Air Basin and the Salton Sea Air Basin. These amendments have not yet

been formally approved by the Office of Administrative Law. However, the transport

identification regulation above has been amended to reflect the changes in the Southeast

Desert Air Basin.
118

PROPOSED TEXT OF REGULATION

FOR MITIGATING THE UPWIND EMISSIONS 

ON DOWNWIND OZONE CONCENTRATIONS

Amend Subchapter 1.5, Article 6, Section 70600, Title 17, California Code of

Regulations, to read as follows (proposed additions are underlined and in italics, proposed

deletions are struck out) :

1

ARTICLE 6. Transport Mitigation

70600. Emission Control Requirements

Districts within the areas of origin of transported air pollutants, as identified in

section 70500(c), shall include sufficient emission control measures in their attainment

plans for ozone adopted pursuant to chapter 10 of the Health and Safety Code, Part 3,

Division 26, beginning with section 40910, to mitigate the impact of pollution sources

within their jurisdictions on ozone concentrations in downwind areas. At a minimum, the

attainment plans for districts within the air basins or areas specified below shall conform to

the following requirements:

(a) Broader Sacramento Area (as defined in section 70500(b)(3)) shall:

(1) require the adoption and implementation of best available retrofit

control technology, as defined in Health and Safety Code section

40406, on all existing stationary sources of ozone precursor emissions

as expeditiously as practicable. At a minimum, the plan shall provide

for the adoption of rules that represent best available retrofit control

technology for source categories that collectively amount to 75 percent

of the 1987 actual reactive hydrocarbon emissions inventory for

permitted stationary sources, and 75 percent of the 1987 actual

nitrogen oxides emissions inventory for permitted stationary sources,

no later than January 1, 1994.

(2) include measures sufficient to attain the state ambient air quality

standard for ozone by the earliest practicable date within the Upper

Sacramento Valley and that portion of the Mountain Counties Air

Basin north of the Amador-El Dorado Calaveras-Tuolumne County

border and south of the Sierra-Plumas County border, except as

provided in Health and Safety Code section 41503(d), during air

pollution episodes which the state board has determined meet the

following conditions:
119

(A) are likely to produce a violation of the state ozone standard in the

Upper Sacramento Valley or that portion of the Mountain

Counties Air Basin north of the Amador-El Dorado CalaverasTuolumne County border and south of the Sierra-Plumas County

border; and

(B) are dominated by overwhelming pollutant transport from the

Broader Sacramento Area; and

(C) are not measurably affected by emissions of ozone precursors

from sources located within the Upper Sacramento Valley or that

portion of the Mountain Counties Air Basin north of the AmadorEl Dorado Calaveras-Tuolumne County border and south of the

Sierra-Plumas County border.

(b) San Francisco Bay Air Basin shall:

(1) require the adoption and implementation of best available retrofit

control technology, as defined in Health and Safety Code section

40406, on all existing stationary sources of ozone precursor emissions

as expeditiously as practicable. At a minimum, the plan shall provide

for the adoption of rules that represent best available retrofit control

technology for source categories that collectively amount to 75 percent

of the 1987 actual reactive hydrocarbon emissions inventory for

permitted stationary sources, and 75 percent of the 1987 actual

nitrogen oxides emissions inventory for permitted stationary sources,

no later than January 1, 1994.

(2) include measures sufficient to attain the state ambient air quality

standard for ozone by the earliest practicable date within the North

Central Coast Air Basin, that portion of Solano County within the

Broader Sacramento Area, and that portion of Stanislaus County west

of Highway 33, except as provided in the Health and Safety Code

section 41503(d), during air pollution episodes which the state board

has determined meet the following conditions:

(A) are likely to produce a violation of the state ozone standard in the

North Central Coast Air Basin, or that portion of Solano County

within the Broader Sacramento Area, or that portion of Stanislaus

County west of Highway 33; and

(B) are dominated by overwhelming pollutant transport from the San

Francisco Bay Air Basin; and
120

(C) are not measurably affected by emissions of ozone precursors

from sources located within the North Central Coast Air Basin, or

that portion of Solano County within the Broader Sacramento

Area, or that portion of Stanislaus County west of Highway 33.

(c) San Joaquin Valley Air Basin shall:

(1) require the adoption and implementation of best available retrofit

control technology, as defined in Health and Safety Code section

40406, on all existing stationary sources of ozone precursor emissions

as expeditiously as practicable. At a minimum, the plan shall provide

for the adoption of rules that represent best available retrofit control

technology for source categories that collectively amount to 75 percent

of the 1987 actual reactive hydrocarbon emissions inventory for

permitted stationary sources, and 75 percent of the 1987 actual

nitrogen oxides emissions inventory for permitted stationary sources,

no later than January 1, 1994.

(2) include measures sufficient to attain the state ambient air quality

standard for ozone by the earliest practicable date within the Southeast

Mojave Desert Air Basin, the Great Basin Valleys Air Basin, and that

portion of the Mountain Counties Air Basin south of the Amador-El

Dorado County border, except as provided in Health and Safety Code

section 41503(d), during air pollution episodes which the state board

has determined meet the following conditions:

(A) are likely to produce a violation of the state ozone standard in the

Southeast Mojave Desert Air Basin, or the Great Basin Valleys

Air Basin, or that portion of the Mountain Counties Air Basin

south of the Amador-El Dorado County border; and

(B) are dominated by overwhelming pollutant transport from the San

Joaquin Valley Air Basin; and

(C) are not measurably affected by emissions of ozone precursors

from sources located within the Southeast Mojave Desert Air

Basin or the Great Basin Valleys Air Basin, or that portion of the

Mountain Counties Air Basin south of the Amador-El Dorado

County border.

(d) South Central Coast Air Basin south of the Santa Barbara-San Luis Obispo

County border shall, for sources located in that portion of the Basin:
121

(1) require the adoption and implementation of best available retrofit

control technology, as defined in Health and Safety Code section

40406, on all existing stationary sources of ozone precursor emissions

as expeditiously as practicable. At a minimum, the plan shall provide

for the adoption of rules that represent best available retrofit control

technology for source categories that collectively amount to 75 percent

of the 1987 actual reactive hydrocarbon emissions inventory for

permitted stationary sources, and 75 percent of the 1987 actual

nitrogen oxides emissions inventory for permitted stationary sources,

no later than January 1, 1994.

(e) South Coast Air Basin shall

(1) require the adoption and implementation of best available retrofit

control technology, as defined in Health and Safety Code section

40406, on all existing stationary sources of ozone precursor emissions

as expeditiously as practicable. At a minimum, the plan shall provide

for the adoption of rules that represent best available retrofit control

technology for source categories that collectively amount to 75 percent

of the 1987 actual reactive hydrocarbon emission inventory of

permitted stationary sources, and 75 percent of the 1987 actual

nitrogen oxides emissions inventory for permitted stationary sources,

no later than January 1, 1994.

(2) include measures sufficient to attain the state ambient air quality

standard for ozone by the earliest practicable date within the South

Central Coast Air Basin south of the Santa Barbara-San Luis Obispo

County border, the San Diego Air Basin, and the Southeast Mojave

Desert Air Basin, and the Salton Sea Air Basin, except as provided in

Health and Safety Code section 41503(d), during air pollution episodes

which the state board has determined meet the following conditions:

(A) are likely to produce a violation of the state ozone standard in the

South Central Coast Air Basin south of the Santa Barbara-San

Luis Obispo County border, or in the San Diego Air Basin, or in

the Southeast Mojave Desert Air Basin, or in the Salton Sea Air

Basin; and

(B) are dominated by overwhelming pollutant transport from the

South Coast Air Basin; and

(C) are not measurably affected by emissions of ozone precursors

from sources located within the South Central Coast Air Basin
122

south of the Santa Barbara-San Luis Obispo County border, or

the San Diego Air Basin, or the Southeast Mojave Desert Air

Basin, or the Salton Sea Air Basin,as applicable.

Note: Authority cited: Sections 39601 and 39610(b), Health and Safety Code.

Reference: Sections 39610, 40912, 40913, 40921 and 41503, Health and Safety Code.

1. At the May 30, 1996 public hearing, the Air Resources Board approved amendments

to sections 60104 and 60109, and added a new Section 60114, Title 17, California Code

of Regulations which divided the Southeast Desert Air Basin into two new air basins; the

Mojave Desert Air Basin and the Salton Sea Air Basin. These amendments have not yet

been formally approved by the Office of Administrative Law. However, the transport

mitigation regulation above has been amended to reflect the changes in the Southeast

Desert Air Basin.
123

APPENDIX F

DATA TABLES
124
125

Table F-1

MCAB State Ozone Exceedances

(1994-1995)

Max Hour of

Ozone Max Ozone

Date Location (ppb) (PST)

08/03/95 Colfax-City Hall 130 17

07/08/94 Colfax-City Hall 122 17

07/28/94 Colfax-City Hall 119 17

09/21/95 Colfax-City Hall 117 16

07/15/94 Colfax-City Hall 112 18

08/18/94 Colfax-City Hall 111 17

07/28/95 Colfax-City Hall 110 17

08/17/94 Colfax-City Hall 109 15

07/05/95 Colfax-City Hall 109 17

09/14/95 Colfax-City Hall 108 14

08/04/95 Colfax-City Hall 105 18

07/11/94 Colfax-City Hall 104 18

07/29/94 Colfax-City Hall 104 11

09/19/95 Colfax-City Hall 104 16

09/12/95 Colfax-City Hall 103 17

10/10/95 Colfax-City Hall 102 16

09/09/95 Colfax-City Hall 102 17

09/15/95 Colfax-City Hall 101 17

08/05/95 Colfax-City Hall 101 18

09/11/95 Colfax-City Hall 101 14

08/04/94 Colfax-City Hall 100 18

07/18/94 Colfax-City Hall 98 17

09/13/95 Colfax-City Hall 98 16

09/20/95 Colfax-City Hall 98 12

08/19/94 Colfax-City Hall 98 17

08/16/94 Colfax-City Hall 98 12

05/20/95 Colfax-City Hall 96 17

08/01/94 Colfax-City Hall 96 18

08/30/94 Colfax-City Hall 96 17

07/16/94 Colfax-City Hall 96 18
126

Table F-1 (con’t)

MCAB State Ozone Exceedances

(1994-1995)

Max Hour of

Ozone Max Ozone

Date Location (ppb) (PST)

05/25/94 Colfax-City Hall 95 16

07/29/94 Grass Valley-Litton Building 110 0

07/28/94 Grass Valley-Litton Building 110 18

07/08/94 Grass Valley-Litton Building 110 20

07/15/94 Grass Valley-Litton Building 100 18

07/11/94 Grass Valley-Litton Building 100 21

07/13/94 Grass Valley-Litton Building 100 21

06/20/94 Grass Valley-Litton Building 100 17

08/17/94 Grass Valley-Litton Building 100 15

08/01/95 Jackson-Clinton Road 146 16

09/20/94 Jackson-Clinton Road 123 16

08/20/95 Jackson-Clinton Road 123 17

07/17/94 Jackson-Clinton Road 119 14

08/19/95 Jackson-Clinton Road 117 18

07/26/94 Jackson-Clinton Road 115 17

08/17/94 Jackson-Clinton Road 112 18

09/13/95 Jackson-Clinton Road 111 17

07/15/94 Jackson-Clinton Road 110 16

08/15/94 Jackson-Clinton Road 109 16

05/24/94 Jackson-Clinton Road 106 17

08/02/95 Jackson-Clinton Road 106 17

06/10/94 Jackson-Clinton Road 106 16

08/15/95 Jackson-Clinton Road 105 13

07/15/95 Jackson-Clinton Road 103 17

09/18/94 Jackson-Clinton Road 103 17

09/26/94 Jackson-Clinton Road 102 14

08/16/94 Jackson-Clinton Road 101 17

09/20/95 Jackson-Clinton Road 101 13

09/12/95 Jackson-Clinton Road 99 16

08/18/94 Jackson-Clinton Road 99 17
127

Table F-1 (con’t)

MCAB State Ozone Exceedances

(1994-1995)

Max Hour of

Ozone Max Ozone

Date Location (ppb) (PST)

09/19/95 Jackson-Clinton Road 99 16

09/07/95 Jackson-Clinton Road 99 17

07/14/94 Jackson-Clinton Road 99 15

08/03/95 Jackson-Clinton Road 98 13

09/21/95 Jackson-Clinton Road 98 15

07/28/95 Jackson-Clinton Road 98 16

07/12/94 Jackson-Clinton Road 98 18

07/27/95 Jackson-Clinton Road 97 15

08/31/94 Jackson-Clinton Road 97 17

08/14/95 Jackson-Clinton Road 96 16

08/31/95 Jackson-Clinton Road 96 16

07/31/95 Jackson-Clinton Road 96 15

08/18/95 Jackson-Clinton Road 96 17

07/14/95 Jackson-Clinton Road 95 16

06/24/95 Jackson-Clinton Road 95 15

08/15/95 Jerseydale - 6440 Jerseydale 110 17

08/03/95 Jerseydale - 6440 Jerseydale 108 14

09/09/95 Jerseydale - 6440 Jerseydale 106 16

09/20/95 Jerseydale - 6440 Jerseydale 103 18

08/31/95 Jerseydale - 6440 Jerseydale 102 17

09/15/95 Jerseydale - 6440 Jerseydale 102 14

08/02/95 Jerseydale - 6440 Jerseydale 101 15

09/14/95 Jerseydale - 6440 Jerseydale 99 17

10/10/95 Jerseydale - 6440 Jerseydale 99 19

08/04/95 Jerseydale - 6440 Jerseydale 98 15

09/08/95 Jerseydale - 6440 Jerseydale 97 20

09/01/95 Jerseydale - 6440 Jerseydale 97 15

08/16/95 Jerseydale - 6440 Jerseydale 97 1

09/21/95 Jerseydale - 6440 Jerseydale 95 14

08/22/95 Jerseydale - 6440 Jerseydale 95 14
128

Table F-1 (con’t)

MCAB State Ozone Exceedances

(1994-1995)

Max Hour of

Ozone Max Ozone

Date Location (ppb) (PST)

09/03/95 Jerseydale - 6440 Jerseydale 95 5

07/12/94 Placerville-Gold Nugget Way 130 18

06/26/95 Placerville-Gold Nugget Way 126 16

06/10/94 Placerville-Gold Nugget Way 126 19

06/27/94 Placerville-Gold Nugget Way 124 17

08/16/94 Placerville-Gold Nugget Way 124 16

08/21/95 Placerville-Gold Nugget Way 121 17

09/19/95 Placerville-Gold Nugget Way 120 16

08/03/95 Placerville-Gold Nugget Way 119 17

08/14/95 Placerville-Gold Nugget Way 119 17

08/31/95 Placerville-Gold Nugget Way 117 18

08/02/95 Placerville-Gold Nugget Way 116 16

08/12/94 Placerville-Gold Nugget Way 116 16

09/12/95 Placerville-Gold Nugget Way 114 15

07/13/94 Placerville-Gold Nugget Way 113 16

07/27/95 Placerville-Gold Nugget Way 113 15

05/24/94 Placerville-Gold Nugget Way 112 17

09/13/95 Placerville-Gold Nugget Way 111 14

06/24/94 Placerville-Gold Nugget Way 111 17

09/14/95 Placerville-Gold Nugget Way 111 16

07/31/95 Placerville-Gold Nugget Way 110 17

07/14/94 Placerville-Gold Nugget Way 109 17

09/06/94 Placerville-Gold Nugget Way 109 16

07/07/94 Placerville-Gold Nugget Way 109 19

08/30/95 Placerville-Gold Nugget Way 108 17

07/06/94 Placerville-Gold Nugget Way 108 14

06/28/94 Placerville-Gold Nugget Way 107 17

07/27/94 Placerville-Gold Nugget Way 107 16

08/02/94 Placerville-Gold Nugget Way 107 18

06/23/95 Placerville-Gold Nugget Way 106 17
129

Table F-1 (con’t)

MCAB State Ozone Exceedances

(1994-1995)

Max Hour of

Ozone Max Ozone

Date Location (ppb) (PST)

09/07/95 Placerville-Gold Nugget Way 106 16

08/01/95 Placerville-Gold Nugget Way 106 10

06/01/95 Placerville-Gold Nugget Way 106 14

06/19/94 Placerville-Gold Nugget Way 106 18

08/19/95 Placerville-Gold Nugget Way 105 16

08/17/94 Placerville-Gold Nugget Way 105 19

09/01/95 Placerville-Gold Nugget Way 104 16

09/08/95 Placerville-Gold Nugget Way 103 16

07/15/94 Placerville-Gold Nugget Way 103 17

08/20/95 Placerville-Gold Nugget Way 103 14

08/05/94 Placerville-Gold Nugget Way 103 19

09/20/94 Placerville-Gold Nugget Way 103 20

06/25/95 Placerville-Gold Nugget Way 102 17

09/11/95 Placerville-Gold Nugget Way 101 16

07/28/95 Placerville-Gold Nugget Way 100 16

08/15/95 Placerville-Gold Nugget Way 99 16

07/15/95 Placerville-Gold Nugget Way 98 17

07/28/94 Placerville-Gold Nugget Way 98 18

08/20/94 Placerville-Gold Nugget Way 97 18

07/14/95 Placerville-Gold Nugget Way 97 16

09/20/95 Placerville-Gold Nugget Way 97 18

09/16/94 Placerville-Gold Nugget Way 96 15

09/10/95 Placerville-Gold Nugget Way 96 20

08/13/94 Placerville-Gold Nugget Way 96 16

09/17/94 Placerville-Gold Nugget Way 95 14

08/22/95 Placerville-Gold Nugget Way 95 11

07/18/95 Placerville-Gold Nugget Way 95 17

07/26/95 Placerville-Gold Nugget Way 95 14

08/24/94 Placerville-Gold Nugget Way 95 16

06/12/95 Quincy-N Church Street 105 15
130

Table F-1 (con’t)

MCAB State Ozone Exceedances

(1994-1995)

Max Hour of

Ozone Max Ozone

Date Location (ppb) (PST)

08/01/95 San Andreas-Gold Strike Road 146 16

08/17/94 San Andreas-Gold Strike Road 121 19

07/15/94 San Andreas-Gold Strike Road 120 17

09/18/94 San Andreas-Gold Strike Road 117 17

08/15/94 San Andreas-Gold Strike Road 114 16

07/17/94 San Andreas-Gold Strike Road 114 15

08/20/95 San Andreas-Gold Strike Road 113 17

08/31/94 San Andreas-Gold Strike Road 112 17

06/27/94 San Andreas-Gold Strike Road 111 19

09/20/94 San Andreas-Gold Strike Road 111 16

06/10/94 San Andreas-Gold Strike Road 110 17

08/16/94 San Andreas-Gold Strike Road 108 17

09/16/94 San Andreas-Gold Strike Road 107 17

09/20/95 San Andreas-Gold Strike Road 107 13

07/06/94 San Andreas-Gold Strike Road 105 15

08/15/95 San Andreas-Gold Strike Road 105 13

08/03/95 San Andreas-Gold Strike Road 105 13

08/07/94 San Andreas-Gold Strike Road 104 16

08/18/94 San Andreas-Gold Strike Road 103 17

09/19/95 San Andreas-Gold Strike Road 103 16

07/25/94 San Andreas-Gold Strike Road 103 15

07/31/95 San Andreas-Gold Strike Road 102 15

09/18/95 San Andreas-Gold Strike Road 102 17

09/15/94 San Andreas-Gold Strike Road 102 15

09/14/94 San Andreas-Gold Strike Road 101 15

08/02/95 San Andreas-Gold Strike Road 101 17

07/28/95 San Andreas-Gold Strike Road 101 16

07/27/95 San Andreas-Gold Strike Road 101 14

07/08/94 San Andreas-Gold Strike Road 101 19

06/26/94 San Andreas-Gold Strike Road 101 16
131

Table F-1 (con’t)

MCAB State Ozone Exceedances

(1994-1995)

Max Hour of

Ozone Max Ozone

Date Location (ppb) (PST)

08/31/95 San Andreas-Gold Strike Road 101 15

07/13/94 San Andreas-Gold Strike Road 100 16

07/14/94 San Andreas-Gold Strike Road 100 17

07/12/94 San Andreas-Gold Strike Road 100 18

07/14/95 San Andreas-Gold Strike Road 99 17

09/13/95 San Andreas-Gold Strike Road 99 17

06/24/95 San Andreas-Gold Strike Road 99 16

07/30/94 San Andreas-Gold Strike Road 99 17

07/15/95 San Andreas-Gold Strike Road 98 18

06/09/94 San Andreas-Gold Strike Road 97 14

09/06/94 San Andreas-Gold Strike Road 97 17

09/08/95 San Andreas-Gold Strike Road 97 14

07/28/94 San Andreas-Gold Strike Road 97 18

06/26/95 San Andreas-Gold Strike Road 96 12

09/22/94 San Andreas-Gold Strike Road 96 13

08/14/95 San Andreas-Gold Strike Road 96 16

09/26/94 San Andreas-Gold Strike Road 96 14

05/25/94 San Andreas-Gold Strike Road 96 17

05/24/94 San Andreas-Gold Strike Road 96 17

05/23/94 San Andreas-Gold Strike Road 96 17

07/11/94 San Andreas-Gold Strike Road 96 16

09/03/94 San Andreas-Gold Strike Road 96 16

09/07/95 San Andreas-Gold Strike Road 96 13

09/12/95 San Andreas-Gold Strike Road 95 17

09/21/95 San Andreas-Gold Strike Road 95 16

06/19/94 San Andreas-Gold Strike Road 95 18

07/29/94 San Andreas-Gold Strike Road 95 18

08/18/95 San Andreas-Gold Strike Road 95 17

08/01/95 Sonora-Barretta Street 135 18

07/15/94 Sonora-Barretta Street 107 18
132

Table F-1 (con’t)

MCAB State Ozone Exceedances

(1994-1995)

Max Hour of

Ozone Max Ozone

Date Location (ppb) (PST)

08/15/95 Sonora-Barretta Street 103 17

06/29/94 Sonora-Barretta Street 102 16

07/17/94 Sonora-Barretta Street 101 16

07/06/94 Sonora-Barretta Street 101 17

08/02/95 Sonora-Barretta Street 100 14

08/03/95 Sonora-Barretta Street 99 15

09/08/95 Sonora-Barretta Street 97 15

08/04/95 Sonora-Barretta Street 96 13

09/15/95 Sonora-Barretta Street 95 12

07/14/94 Sonora-Barretta Street 95 18

09/20/95 Sonora-Barretta Street 95 14

07/16/94 Sonora-Barretta Street 95 12

07/08/94 Sonora-Barretta Street 95 16

09/15/95 Sonora-Old Oak Ranch Road 103 23

09/16/95 Sonora-Old Oak Ranch Road 98 0

08/17/94 Wawona 95 16

08/09/95 White Cloud Mountain 99 20

09/07/95 White Cloud Mountain 99 18

08/15/95 White Cloud Mountain 96 14

07/15/94 Yosemite NP-Camp Mather 97 14

08/17/94 Yosemite NP-Camp Mather 95 17

08/15/95 Yosemite NP-Turtleback Dome 114 17

07/15/94 Yosemite NP-Turtleback Dome 113 15

08/17/94 Yosemite NP-Turtleback Dome 111 19

07/08/94 Yosemite NP-Turtleback Dome 109 17

09/09/95 Yosemite NP-Turtleback Dome 104 18

08/25/94 Yosemite NP-Turtleback Dome 101 17

09/07/94 Yosemite NP-Turtleback Dome 100 16

09/17/94 Yosemite NP-Turtleback Dome 100 15

07/16/95 Yosemite NP-Turtleback Dome 100 18
133

Table F-1 (con’t)

MCAB State Ozone Exceedances

(1994-1995)

Max Hour of

Ozone Max Ozone

Date Location (ppb) (PST)

08/09/95 Yosemite NP-Turtleback Dome 100 17

09/20/94 Yosemite NP-Turtleback Dome 100 17

08/03/95 Yosemite NP-Turtleback Dome 99 19

07/16/94 Yosemite NP-Turtleback Dome 98 16

08/31/95 Yosemite NP-Turtleback Dome 97 18

07/27/95 Yosemite NP-Turtleback Dome 97 18

06/10/94 Yosemite NP-Turtleback Dome 97 17

08/18/94 Yosemite NP-Turtleback Dome 96 11

09/08/95 Yosemite NP-Turtleback Dome 96 18

08/21/95 Yosemite NP-Turtleback Dome 95 18

08/04/95 Yosemite NP-Turtleback Dome 95 16

08/16/95 Yosemite NP-Turtleback Dome 95 0
134

F-2

Expected Peak Day Concentrations

for Sites in the Mountain Counties Air Basin

1993-1995

District Monitor Site Name Concentration

in ppm

Amador Jackson-Clinton Road 0.12

Calaveras San Andreas-Gold Strike Road 0.12

El Dorado Placerville-Gold Nugget Way 0.13

Mariposa Yosemite Village-Park Headquarters 0.09

Mariposa Yosemite Village-Visitor Center 0.09

Mariposa Wawona 0.11

Mariposa Jerseydale-6440 Jerseydale 0.11

Mariposa Yosemite NP-Turtleback Dome 0.12

Northern Sierra Truckee-Fire Station 0.08

Northern Sierra Nevada City-Willow Valley 0.07

Northern Sierra White Cloud Mountain 0.10

Northern Sierra Grass Valley-Litton Building 0.11

Northern Sierra Quincy-N. Church Street 0.09

Placer Colfax-City Hall 0.12

Tuolumne Yosemite NP-Camp Mather 0.10

Tuolumne Sonora-5 Mile Learning Center 0.10

Tuolumne Sonora-Barretta Street 0.11
135

Table F-3

1994 Ozone Violations

Broader Sacramento Area

Max Hour

Ozone Max

Basin Site Date (ppb) Ozone

SV Auburn-Dewitt-C Avenue 05/10/94 107 17

SV Rocklin-Rocklin Road 05/10/94 103 16

SV Folsom-City Corporation Yard 05/10/94 99 16

SV Roseville-N Sunrise Blvd 05/10/94 98 16

MC Placerville-Gold Nugget Way 05/24/94 112 17

SV Folsom-City Corporation Yard 05/24/94 110 14

SV Rocklin-Rocklin Road 05/24/94 100 14

SV Sacramento-Del Paso Manor 06/10/94 145 12

SV Folsom-City Corporation Yard 06/10/94 136 16

MC Placerville-Gold Nugget Way 06/10/94 126 19

SV Sacramento-T Street 06/10/94 108 12

SV Elk Grove-Bruceville Road 06/10/94 106 12

SV Roseville-N Sunrise Blvd 06/10/94 98 15

SV North Highlands-Blackfoot Way 06/10/94 97 13

SV Rocklin-Rocklin Road 06/10/94 95 11

SV Auburn-Dewitt-C Avenue 06/10/94 95 13

SV Folsom-City Corporation Yard 06/19/94 107 16

MC Placerville-Gold Nugget Way 06/19/94 106 18

SV Rocklin-Rocklin Road 06/19/94 98 16

SV North Highlands-Blackfoot Way 06/19/94 95 16

MC Placerville-Gold Nugget Way 06/24/94 111 17

SV Folsom-City Corporation Yard 06/24/94 108 15

MC Placerville-Gold Nugget Way 06/27/94 124 17

SV Folsom-City Corporation Yard 06/27/94 119 15

SV Auburn-Dewitt-C Avenue 06/27/94 104 14

SV Elk Grove-Bruceville Road 06/27/94 104 16

SV Sacramento-T Street 06/27/94 102 17

SV Davis-UCD Campus 06/27/94 98 15

SV Rocklin-Rocklin Road 06/27/94 96 14

SV North Highlands-Blackfoot Way 06/27/94 96 17

SV Folsom-City Corporation Yard 06/28/94 117 15

SV Rocklin-Rocklin Road 06/28/94 117 17

SV Roseville-N Sunrise Blvd 06/28/94 109 16
136

Table F-3 (con’t)

1994 Ozone Violations

Broader Sacramento Area

Max Hour

Ozone Max

Basin Site Date (ppb) Ozone

MC Placerville-Gold Nugget Way 06/28/94 107 17

SV Auburn-Dewitt-C Avenue 06/28/94 105 15

SV North Highlands-Blackfoot Way 06/28/94 98 15

SV Auburn-Dewitt-C Avenue 06/29/94 121 15

SV Folsom-City Corporation Yard 06/29/94 116 14

SV Rocklin-Rocklin Road 06/29/94 111 14

SV Roseville-N Sunrise Blvd 06/29/94 105 14

SV Auburn-Dewitt-C Avenue 07/01/94 96 16

MC Placerville-Gold Nugget Way 07/06/94 108 14

SV Folsom-City Corporation Yard 07/07/94 126 17

SV Rocklin-Rocklin Road 07/07/94 120 15

SV Auburn-Dewitt-C Avenue 07/07/94 118 16

MC Placerville-Gold Nugget Way 07/07/94 109 19

SV Roseville-N Sunrise Blvd 07/07/94 107 14

SV North Highlands-Blackfoot Way 07/07/94 98 16

SV Auburn-Dewitt-C Avenue 07/08/94 133 15

SV Rocklin-Rocklin Road 07/08/94 116 14

SV Roseville-N Sunrise Blvd 07/08/94 107 15

SV Folsom-City Corporation Yard 07/08/94 105 15

SV North Highlands-Blackfoot Way 07/08/94 102 14

SV Auburn-Dewitt-C Avenue 07/09/94 103 14

SV Rocklin-Rocklin Road 07/09/94 97 13

SV Roseville-N Sunrise Blvd 07/09/94 95 13

SV Folsom-City Corporation Yard 07/09/94 95 14

SV North Highlands-Blackfoot Way 07/11/94 118 15

SV Auburn-Dewitt-C Avenue 07/11/94 117 17

SV Roseville-N Sunrise Blvd 07/11/94 111 16

SV Rocklin-Rocklin Road 07/11/94 111 17

SV Folsom-City Corporation Yard 07/11/94 110 15

SV Sacramento-Del Paso Manor 07/11/94 99 14

SV Sacramento-T Street 07/11/94 96 13

SV Folsom-City Corporation Yard 07/12/94 142 16

MC Placerville-Gold Nugget Way 07/12/94 130 18
137

Table F-3 (con’t)

1994 Ozone Violations

Broader Sacramento Area

Max Hour

Ozone Max

Basin Site Date (ppb) Ozone

SV Rocklin-Rocklin Road 07/12/94 128 17

SV Roseville-N Sunrise Blvd 07/12/94 119 14

SV North Highlands-Blackfoot Way 07/12/94 104 14

SV Sacramento-Del Paso Manor 07/12/94 103 14

SV Auburn-Dewitt-C Avenue 07/12/94 97 12

SV Folsom-City Corporation Yard 07/13/94 140 13

SV Auburn-Dewitt-C Avenue 07/13/94 130 17

SV Rocklin-Rocklin Road 07/13/94 119 13

SV Roseville-N Sunrise Blvd 07/13/94 113 14

MC Placerville-Gold Nugget Way 07/13/94 113 16

SV North Highlands-Blackfoot Way 07/13/94 98 14

SV Sacramento-Del Paso Manor 07/13/94 95 14

SV Folsom-City Corporation Yard 07/14/94 133 14

MC Placerville-Gold Nugget Way 07/14/94 109 17

SV Roseville-N Sunrise Blvd 07/14/94 106 14

SV Rocklin-Rocklin Road 07/14/94 105 15

SV North Highlands-Blackfoot Way 07/14/94 95 14

SV Auburn-Dewitt-C Avenue 07/15/94 113 16

SV Rocklin-Rocklin Road 07/15/94 111 15

MC Placerville-Gold Nugget Way 07/15/94 103 17

SV Roseville-N Sunrise Blvd 07/15/94 102 15

SV Folsom-City Corporation Yard 07/15/94 101 15

SV Auburn-Dewitt-C Avenue 07/16/94 114 16

SV Rocklin-Rocklin Road 07/16/94 103 14

SV Roseville-N Sunrise Blvd 07/16/94 98 14

SV Folsom-City Corporation Yard 07/17/94 98 11

SV Rocklin-Rocklin Road 07/22/94 95 17

SV Davis-UCD Campus 07/26/94 95 13

SV Roseville-N Sunrise Blvd 07/27/94 124 16

SV Rocklin-Rocklin Road 07/27/94 124 16

SV Auburn-Dewitt-C Avenue 07/27/94 121 18

SV Folsom-City Corporation Yard 07/27/94 113 16

MC Placerville-Gold Nugget Way 07/27/94 107 16
138

Table F-3 (con’t)

1994 Ozone Violations

Broader Sacramento Area

Max Hour

Ozone Max

Basin Site Date (ppb) Ozone

SV North Highlands-Blackfoot Way 07/27/4 105 17

SV Auburn-Dewitt-C Avenue 07/28/94 119 16

SV Rocklin-Rocklin Road 07/28/94 106 15

SV Roseville-N Sunrise Blvd 07/28/94 100 14

MC Placerville-Gold Nugget Way 07/28/94 98 18

SV North Highlands-Blackfoot Way 07/28/94 97 14

SV Rocklin-Rocklin Road 07/29/94 103 16

SV Auburn-Dewitt-C Avenue 07/29/94 99 17

SV Auburn-Dewitt-C Avenue 08/01/94 98 16

SV Folsom-City Corporation Yard 08/02/94 115 15

MC Placerville-Gold Nugget Way 08/02/94 107 18

SV Auburn-Dewitt-C Avenue 08/02/94 97 15

SV Rocklin-Rocklin Road 08/02/94 96 15

SV Folsom-City Corporation Yard 08/03/94 98 14

SV Auburn-Dewitt-C Avenue 08/04/94 99 17

SV Folsom-City Corporation Yard 08/05/94 143 17

MC Placerville-Gold Nugget Way 08/05/94 103 19

SV Rocklin-Rocklin Road 08/05/94 100 17

SV Elk Grove-Bruceville Road 08/06/94 102 11

SV Folsom-City Corporation Yard 08/06/94 96 17

MC Placerville-Gold Nugget Way 08/12/94 116 16

SV Auburn-Dewitt-C Avenue 08/12/94 97 13

SV Folsom-City Corporation Yard 08/12/94 95 16

MC Placerville-Gold Nugget Way 08/13/94 96 16

SV Folsom-City Corporation Yard 08/14/94 103 14

SV Rocklin-Rocklin Road 08/14/94 100 17

SV Roseville-N Sunrise Blvd 08/14/94 96 17

SV Davis-UCD Campus 08/15/94 97 15

MC Placerville-Gold Nugget Way 08/16/94 124 16

SV Auburn-Dewitt-C Avenue 08/16/94 99 14

SV Folsom-City Corporation Yard 08/16/94 98 14

SV Sacramento-Del Paso Manor 08/16/94 96 14

SV Elk Grove-Bruceville Road 08/16/94 95 16
139

Table F-3 (con’t)

1994 Ozone Violations

Broader Sacramento Area

Max Hour

Ozone Max

Basin Site Date (ppb) Ozone

SV Auburn-Dewitt-C Avenue 08/17/94 131 15

SV Rocklin-Rocklin Road 08/17/94 111 14

SV Elk Grove-Bruceville Road 08/17/94 110 15

SV Sacramento-Del Paso Manor 08/17/94 107 13

SV Roseville-N Sunrise Blvd 08/17/94 105 12

MC Placerville-Gold Nugget Way 08/17/94 105 19

SV North Highlands-Blackfoot Way 08/17/94 101 14

SV Folsom-City Corporation Yard 08/17/94 101 17

SV Woodland-Sutter Street 08/17/94 100 13

SV Pleasant Grove-4 miles SW 08/17/94 97 13

SV Davis-UCD Campus 08/17/94 95 13

SV Auburn-Dewitt-C Avenue 08/18/94 130 15

SV Rocklin-Rocklin Road 08/18/94 105 14

SV Auburn-Dewitt-C Avenue 08/19/94 105 15

SV Rocklin-Rocklin Road 08/19/94 99 16

SV Folsom-City Corporation Yard 08/20/94 107 15

SV Sacramento-Del Paso Manor 08/20/94 106 13

MC Placerville-Gold Nugget Way 08/20/94 97 18

MC Placerville-Gold Nugget Way 08/24/94 95 16

SV Auburn-Dewitt-C Avenue 08/30/94 103 17

SV Auburn-Dewitt-C Avenue 08/31/94 99 16

SV Rocklin-Rocklin Road 08/31/94 95 15

SV Sacramento-Del Paso Manor 09/05/94 99 15

MC Placerville-Gold Nugget Way 09/06/94 109 16

SV Folsom-City Corporation Yard 09/06/94 106 13

SV Sacramento-Del Paso Manor 09/06/94 99 13

SV Folsom-City Corporation Yard 09/15/94 115 15

SV Sacramento-Del Paso Manor 09/15/94 105 16

SV Elk Grove-Bruceville Road 09/16/94 99 13

MC Placerville-Gold Nugget Way 09/16/94 96 15

MC Placerville-Gold Nugget Way 09/17/94 95 14

SV Sacramento-Del Paso Manor 09/18/94 108 15

SV Roseville-N Sunrise Blvd 09/18/94 105 15
140

Table F-3 (con’t)

1994 Ozone Violations

Broader Sacramento Area

Max Hour

Ozone Max

Basin Site Date (ppb) Ozone

SV Rocklin-Rocklin Road 09/18/94 102 15

SV North Highlands-Blackfoot Way 09/18/94 102 16

SV Folsom-City Corporation Yard 09/18/94 99 16

SV Sacramento-Del Paso Manor 09/19/94 101 15

SV Elk Grove-Bruceville Road 09/19/94 96 15

SV North Highlands-Blackfoot Way 09/19/94 95 16

SV Elk Grove-Bruceville Road 09/20/94 108 14

MC Placerville-Gold Nugget Way 09/20/94 103 20

SV Sacramento-Meadowview Road 09/20/94 100 16

SV Rocklin-Rocklin Road 10/02/94 114 16

SV Roseville-N Sunrise Blvd 10/02/94 107 15

SV Auburn-Dewitt-C Avenue 10/02/94 102 17

SV North Highlands-Blackfoot Way 10/02/94 99 14

SV Sacramento-Del Paso Manor 10/02/94 95 13

SV Folsom-City Corporation Yard 10/02/94 95 15
141

Table F-4

1995 Ozone Violations

Broader Sacramento Area

MAX HOUR

OZONE MAX

BASIN SITE DATE (ppb) OZONE

SV North Highlands-Blackfoot Way 04/23/95 98 15

SV Auburn-Dewitt-C Avenue 05/20/95 100 16

SV Sacramento-Del Paso Manor 05/29/95 104 13

SV Roseville-N Sunrise Blvd 05/29/95 101 15

SV North Highlands-Blackfoot Way 05/29/95 100 14

SV Rocklin-Rocklin Road 05/29/95 99 16

SV North Highlands-Blackfoot Way 05/30/95 103 15

SV Auburn-Dewitt-C Avenue 05/30/95 97 17

SV Sacramento-Del Paso Manor 05/30/95 95 15

MC Placerville-Gold Nugget Way 06/01/95 106 14

SV Folsom-City Corporation Yard 06/03/95 100 14

SV Rocklin-Rocklin Road 06/03/95 96 16

SV Folsom-City Corporation Yard 06/23/95 116 13

MC Placerville-Gold Nugget Way 06/23/95 106 17

SV Sacramento-Del Paso Manor 06/23/95 100 12

SV Rocklin-Rocklin Road 06/23/95 95 13

SV Vacaville-Allison Drive 06/24/95 106 15

SV Folsom-City Corporation Yard 06/24/95 100 14

SV Sacramento-Del Paso Manor 06/25/95 125 13

SV Folsom-City Corporation Yard 06/25/95 124 15

SV Vacaville-Allison Drive 06/25/95 115 16

SV Davis-UCD Campus 06/25/95 103 18

MC Placerville-Gold Nugget Way 06/25/95 102 17

SV Rocklin-Rocklin Road 06/25/95 99 17

SV Auburn-Dewitt-C Avenue 06/26/95 148 15

SV Rocklin-Rocklin Road 06/26/95 146 14

SV Folsom-City Corporation Yard 06/26/95 136 13

SV Roseville-N Sunrise Blvd 06/26/95 135 14

SV Sacramento-Del Paso Manor 06/26/95 132 13

MC Placerville-Gold Nugget Way 06/26/95 126 16

SV North Highlands-Blackfoot Way 06/26/95 124 13
142

Table F-4 (con’t)

1995 Ozone Violations

Broader Sacramento Area

MAX HOUR

OZONE MAX

BASIN SITE DATE (ppb) OZONE

SV Pleasant Grove-4 miles SW 06/26/95 112 14

SV Sacramento-Earhart Drive 06/26/95 104 14

SV Folsom-City Corporation Yard 06/28/95 120 15

SV Sacramento-Del Paso Manor 06/28/95 113 14

SV Sacramento-Earhart Drive 06/28/95 98 15

SV Auburn-Dewitt-C Avenue 07/05/95 96 16

SV Elk Grove-Bruceville Road 07/14/95 111 13

SV Sacramento-Del Paso Manor 07/14/95 110 12

SV Folsom-City Corporation Yard 07/14/95 106 13

MC Placerville-Gold Nugget Way 07/14/95 97 16

SV Sacramento-Del Paso Manor 07/15/95 117 12

SV Folsom-City Corporation Yard 07/15/95 114 13

SV Rocklin-Rocklin Road 07/15/95 102 12

SV Elk Grove-Bruceville Road 07/15/95 101 11

MC Placerville-Gold Nugget Way 07/15/95 98 17

SV Folsom-City Corporation Yard 07/18/95 114 14

SV Auburn-Dewitt-C Avenue 07/18/95 104 16

SV Sacramento-Del Paso Manor 07/18/95 103 12

SV Rocklin-Rocklin Road 07/18/95 100 15

SV Sacramento-Earhart Drive 07/18/95 98 15

MC Placerville-Gold Nugget Way 07/18/95 95 17

MC Placerville-Gold Nugget Way 07/26/95 95 14

SV Sacramento-Del Paso Manor 07/27/95 131 16

SV Folsom-City Corporation Yard 07/27/95 125 17

MC Placerville-Gold Nugget Way 07/27/95 113 15

SV Elk Grove-Bruceville Road 07/27/95 107 12

SV Vacaville-Allison Drive 07/27/95 105 16

SV Roseville-N Sunrise Blvd 07/27/95 104 17

SV North Highlands-Blackfoot Way 07/27/95 98 17

SV Sacramento-Earhart Drive 07/27/95 97 17

SV Auburn-Dewitt-C Avenue 07/27/95 95 15

SV Davis-UCD Campus 07/27/95 95 17

SV Sacramento-Del Paso Manor 07/28/95 133 13
143

Table F-4 (con’t)

1995 Ozone Violations

Broader Sacramento Area

MAX HOUR

OZONE MAX

BASIN SITE DATE (ppb) OZONE

SV Folsom-City Corporation Yard 07/28/95 124 14

SV Auburn-Dewitt-C Avenue 07/28/95 123 12

SV Rocklin-Rocklin Road 07/28/95 122 14

SV Roseville-N Sunrise Blvd 07/28/95 117 13

SV North Highlands-Blackfoot Way 07/28/95 115 13

MC Placerville-Gold Nugget Way 07/28/95 100 16

SV Sacramento-Earhart Drive 07/28/95 98 13

SV Sacramento-Del Paso Manor 07/31/95 154 12

SV Folsom-City Corporation Yard 07/31/95 127 15

MC Placerville-Gold Nugget Way 07/31/95 110 17

SV Roseville-N Sunrise Blvd 07/31/95 108 12

SV Auburn-Dewitt-C Avenue 07/31/95 104 13

SV Rocklin-Rocklin Road 07/31/95 103 13

SV Sacramento-T Street 07/31/95 100 12

SV North Highlands-Blackfoot Way 07/31/95 99 11

SV Sacramento-Del Paso Manor 08/01/95 125 15

SV Folsom-City Corporation Yard 08/01/95 124 11

SV Sacramento-T Street 08/01/95 114 15

SV Sacramento-Earhart Drive 08/01/95 112 16

SV Davis-UCD Campus 08/01/95 111 14

SV Elk Grove-Bruceville Road 08/01/95 109 14

SV North Highlands-Blackfoot Way 08/01/95 108 16

MC Placerville-Gold Nugget Way 08/01/95 106 10

SV Auburn-Dewitt-C Avenue 08/01/95 104 11

SV Pleasant Grove-4 miles SW 08/01/95 102 15

SV Woodland-Sutter Street 08/01/95 100 13

SV Roseville-N Sunrise Blvd 08/01/95 100 17

SV Rocklin-Rocklin Road 08/01/95 99 11

SV Folsom-City Corporation Yard 08/02/95 147 14

SV Rocklin-Rocklin Road 08/02/95 117 12

MC Placerville-Gold Nugget Way 08/02/95 116 16

SV Sacramento-Del Paso Manor 08/02/95 115 12

SV Roseville-N Sunrise Blvd 08/02/95 109 12
144

Table F-4 (con’t)

1995 Ozone Violations

Broader Sacramento Area

MAX HOUR

OZONE MAX

BASIN SITE DATE (ppb) OZONE

SV Sacramento-Earhart Drive 08/02/95 104 15

SV North Highlands-Blackfoot Way 08/02/95 99 12

SV Woodland-Sutter Street 08/02/95 97 15

SV Elk Grove-Bruceville Road 08/02/95 96 13

SV Auburn-Dewitt-C Avenue 08/03/95 145 17

SV Roseville-N Sunrise Blvd 08/03/95 134 15

SV Rocklin-Rocklin Road 08/03/95 133 16

SV Sacramento-Del Paso Manor 08/03/95 122 13

SV North Highlands-Blackfoot Way 08/03/95 121 13

MC Placerville-Gold Nugget Way 08/03/95 119 17

SV Folsom-City Corporation Yard 08/03/95 105 15

SV Pleasant Grove-4 miles SW 08/03/95 104 13

SV Sacramento-Earhart Drive 08/03/95 101 13

SV Auburn-Dewitt-C Avenue 08/04/95 99 16

SV Auburn-Dewitt-C Avenue 08/09/95 120 15

SV North Highlands-Blackfoot Way 08/09/95 102 13

SV Rocklin-Rocklin Road 08/09/95 97 14

SV Folsom-City Corporation Yard 08/09/95 96 16

MC Placerville-Gold Nugget Way 08/14/95 119 17

SV Folsom-City Corporation Yard 08/14/95 109 11

SV Sacramento-Del Paso Manor 08/14/95 102 14

SV Elk Grove-Bruceville Road 08/14/95 100 16

SV Vacaville-Allison Drive 08/14/95 98 17

SV Davis-UCD Campus 08/14/95 96 13

SV Auburn-Dewitt-C Avenue 08/15/95 110 13

MC Placerville-Gold Nugget Way 08/15/95 99 16

SV Folsom-City Corporation Yard 08/19/95 123 13

SV Sacramento-Del Paso Manor 08/19/95 120 14

MC Placerville-Gold Nugget Way 08/19/95 105 16

SV North Highlands-Blackfoot Way 08/19/95 96 12

SV Sacramento-T Street 08/19/95 95 13

SV Sacramento-Earhart Drive 08/20/95 116 15

SV Sacramento-Del Paso Manor 08/20/95 109 16
145

Table F-4 (con’t)

1995 Ozone Violations

Broader Sacramento Area

MAX HOUR

OZONE MAX

BASIN SITE DATE (ppb) OZONE

SV Elk Grove-Bruceville Road 08/20/95 104 13

SV Pleasant Grove-4 miles SW 08/20/95 104 17

MC Placerville-Gold Nugget Way 08/20/95 103 14

SV Sacramento-T Street 08/20/95 103 15

SV Folsom-City Corporation Yard 08/20/95 100 10

SV North Highlands-Blackfoot Way 08/20/95 100 17

SV Davis-UCD Campus 08/20/95 99 13

SV Woodland-Sutter Street 08/20/95 98 13

SV Vacaville-Allison Drive 08/20/95 98 13

MC Placerville-Gold Nugget Way 08/21/95 121 17

SV Auburn-Dewitt-C Avenue 08/21/95 100 14

SV Sacramento-Earhart Drive 08/21/95 95 15

SV Sacramento-Del Paso Manor 08/22/95 124 15

SV Sacramento-Earhart Drive 08/22/95 106 14

SV Folsom-City Corporation Yard 08/22/95 104 15

SV Elk Grove-Bruceville Road 08/22/95 100 16

SV Sacramento-T Street 08/22/95 97 15

MC Placerville-Gold Nugget Way 08/22/95 95 11

SV Pleasant Grove-4 miles SW 08/22/95 95 14

SV Woodland-Sutter Street 08/22/95 95 15

SV Folsom-City Corporation Yard 08/26/95 96 17

MC Placerville-Gold Nugget Way 08/30/95 108 17

SV Roseville-N Sunrise Blvd 08/31/95 120 15

SV Rocklin-Rocklin Road 08/31/95 117 15

MC Placerville-Gold Nugget Way 08/31/95 117 18

SV North Highlands-Blackfoot Way 08/31/95 115 13

SV Sacramento-Del Paso Manor 08/31/95 115 14

SV Auburn-Dewitt-C Avenue 08/31/95 110 15

SV Pleasant Grove-4 miles SW 08/31/95 96 15

SV Sacramento-Earhart Drive 08/31/95 95 15

MC Placerville-Gold Nugget Way 09/01/95 104 16

SV Rocklin-Rocklin Road 09/01/95 97 16

SV Folsom-City Corporation Yard 09/06/95 118 13
146

Table F-4 (con’t)

1995 Ozone Violations

Broader Sacramento Area

MAX HOUR

OZONE MAX

BASIN SITE DATE (ppb) OZONE

SV Elk Grove-Bruceville Road 09/07/95 114 16

SV Auburn-Dewitt-C Avenue 09/07/95 112 15

SV Folsom-City Corporation Yard 09/07/95 106 13

MC Placerville-Gold Nugget Way 09/07/95 106 16

SV Rocklin-Rocklin Road 09/07/95 102 13

SV Pleasant Grove-4 miles SW 09/07/95 96 15

SV Roseville-N Sunrise Blvd 09/07/95 95 13

SV Sacramento-Del Paso Manor 09/07/95 95 14

SV Folsom-City Corporation Yard 09/08/95 133 14

SV Sacramento-Del Paso Manor 09/08/95 111 12

SV North Highlands-Blackfoot Way 09/08/95 106 13

SV Roseville-N Sunrise Blvd 09/08/95 104 14

SV Pleasant Grove-4 miles SW 09/08/95 104 15

SV Rocklin-Rocklin Road 09/08/95 103 14

SV Auburn-Dewitt-C Avenue 09/08/95 103 14

MC Placerville-Gold Nugget Way 09/08/95 103 16

SV Sacramento-Earhart Drive 09/08/95 95 13

SV Auburn-Dewitt-C Avenue 09/09/95 102 16

SV Folsom-City Corporation Yard 09/10/95 110 16

MC Placerville-Gold Nugget Way 09/10/95 96 20

SV Roseville-N Sunrise Blvd 09/10/95 95 15

SV Auburn-Dewitt-C Avenue 09/11/95 114 17

SV Folsom-City Corporation Yard 09/11/95 108 15

SV Rocklin-Rocklin Road 09/11/95 108 15

MC Placerville-Gold Nugget Way 09/11/95 101 16

SV North Highlands-Blackfoot Way 09/11/95 98 14

SV Sacramento-Del Paso Manor 09/11/95 98 14

SV Roseville-N Sunrise Blvd 09/11/95 98 16

MC Placerville-Gold Nugget Way 09/12/95 114 15

SV Sacramento-Del Paso Manor 09/12/95 110 13

SV Auburn-Dewitt-C Avenue 09/12/95 110 15

SV Folsom-City Corporation Yard 09/12/95 110 16

SV Elk Grove-Bruceville Road 09/12/95 109 15
147

Table F-4 (con’t)

1995 Ozone Violations

Broader Sacramento Area

MAX HOUR

OZONE MAX

BASIN SITE DATE (ppb) OZONE

SV Sacramento-T Street 09/12/95 103 14

SV Pleasant Grove-4 miles SW 09/12/95 99 14

SV Sacramento-Earhart Drive 09/12/95 99 15

SV North Highlands-Blackfoot Way 09/12/95 98 16

SV Rocklin-Rocklin Road 09/12/95 97 13

SV Folsom-City Corporation Yard 09/13/95 120 15

MC Placerville-Gold Nugget Way 09/13/95 111 14

SV Sacramento-Del Paso Manor 09/13/95 105 14

SV North Highlands-Blackfoot Way 09/13/95 100 14

SV Elk Grove-Bruceville Road 09/13/95 98 13

SV Rocklin-Rocklin Road 09/13/95 98 15

SV Sacramento-Earhart Drive 09/13/95 97 15

SV Auburn-Dewitt-C Avenue 09/13/95 97 15

SV Roseville-N Sunrise Blvd 09/13/95 95 14

SV Folsom-City Corporation Yard 09/14/95 116 15

MC Placerville-Gold Nugget Way 09/14/95 111 16

SV Sacramento-Del Paso Manor 09/14/95 97 15

SV Rocklin-Rocklin Road 09/14/95 95 14

SV North Highlands-Blackfoot Way 09/14/95 95 15

SV Auburn-Dewitt-C Avenue 09/15/95 99 16

SV Sacramento-Del Paso Manor 09/18/95 116 15

SV Folsom-City Corporation Yard 09/18/95 114 17

SV Auburn-Dewitt-C Avenue 09/18/5 112 16

SV Rocklin-Rocklin Road 09/18/95 107 15

SV Roseville-N Sunrise Blvd 09/18/95 103 16

SV North Highlands-Blackfoot Way 09/18/95 99 15

SV Elk Grove-Bruceville Road 09/18/95 96 15

SV Folsom-City Corporation Yard 09/19/95 156 16

SV Sacramento-Del Paso Manor 09/19/95 154 15

SV Sacramento-T Street 09/19/95 128 14

SV North Highlands-Blackfoot Way 09/19/95 127 14

SV Elk Grove-Bruceville Road 09/19/95 120 13

SV Rocklin-Rocklin Road 09/19/95 120 14
148

Table F-4 (con’t)

1995 Ozone Violations

Broader Sacramento Area

MAX HOUR

OZONE MAX

BASIN SITE DATE (ppb) OZONE

SV Roseville-N Sunrise Blvd 09/19/95 120 15

MC Placerville-Gold Nugget Way 09/19/95 120 16

SV Sacramento-Earhart Drive 09/19/95 119 15

SV Auburn-Dewitt-C Avenue 09/19/95 114 14

SV Pleasant Grove-4 miles SW 09/19/95 112 15

SV Woodland-Sutter Street 09/19/95 108 14

SV Vacaville-Allison Drive 09/19/95 102 16

SV Davis-UCD Campus 09/19/95 101 14

SV Folsom-City Corporation Yard 09/20/95 130 16

SV Rocklin-Rocklin Road 09/20/95 129 15

SV Pleasant Grove-4 miles SW 09/20/95 126 13

SV North Highlands-Blackfoot Way 09/20/95 125 14

SV Auburn-Dewitt-C Avenue 09/20/95 124 13

SV Roseville-N Sunrise Blvd 09/20/95 122 15

SV Woodland-Sutter Street 09/20/95 114 14

SV Sacramento-Del Paso Manor 09/20/95 113 14

SV Sacramento-Earhart Drive 09/20/95 111 13

SV Davis-UCD Campus 09/20/95 108 13

SV Elk Grove-Bruceville Road 09/20/95 99 11

MC Placerville-Gold Nugget Way 09/20/95 97 18

SV Auburn-Dewitt-C Avenue 09/21/95 111 16

SV Rocklin-Rocklin Road 09/21/95 103 16

SV Roseville-N Sunrise Blvd 09/21/95 101 16

SV Elk Grove-Bruceville Road 10/06/95 97 15

SV Folsom-City Corporation Yard 10/29/95 102 14
149

APPENDIX G

SUPPLEMENTAL INFORMATION
150
151

G-1

Staff Analysis of Transport from the 

San Joaquin Valley Air Basin to the North Central Coast Air Basin

A transport working group composed of staff from the Monterey Bay Unified Air

Pollution Control District (MBUAPCD), Bay Area Air Quality Management District, and

ARB was formed to collectively analyze 1994-1995 NCCAB ozone exceedances. As

found during previous SFBAAB to NCCAB transport assessments, some days were

overwhelming and on others significant. However, on one NCCAB exceedance day (June

9, 1994) both SFBAAB and SJVAB, collectively, overwhelmed the NCCAB. On this day

at 1500 PST Hollister's daily maximum ozone concentration reached 101 ppb. The

working group's analysis is described below.

The working group reviewed the geographical distributions of the ozone maxima

and their times of occurrence for June 9, the day of the State exceedance. In the NCCAB

Scotts Valley, Carmel Valley, and the Pinnacles recorded 9 pphm. The peaks observed in

those areas occurred later than the Hollister peak. In the SFBAAB San Martin recorded a

peak ozone concentration of 11 pphm; and Gilroy, San Jose, and Fremont, 10 pphm. In

the northern SJVAB Merced had 10 pphm and Modesto and Turlock had 9 pphm. The

Broader Sacramento Area (BSA) had a maximum of only 7 pphm. The spatial ozone

pattern points to the southern SFBAAB and the northern SJVAB as possible sources of

ozone that could have had an impact on Hollister.

The group then reviewed wind data from San Jose, San Martin, Gilroy, Granite

Rock #3 and Hollister to evaluate surface flow in the Santa Clara Valley and within the

NCCAB through the Pajaro Gap. They also reviewed wind data from PG&E's Los Banos

site for evidence of possible flow from the SJVAB through the Pacheco Pass. The

persistent northwest winds at San Jose, San Martin, and Gilroy from around 0900 PST to

the evening hours suggest probable transport from the SFBAAB toward Hollister. The

wind direction at the MBUAPCD's Hollister station varied between west and northwest

from 0600 PST to 2000 PST. The winds at the Granite Rock #3 site changed from

northwest at 1300 to west at 1500 PST, suggesting possible transport within the NCCAB

through the Pajaro Gap. The north to northeast winds at Los Banos suggest possible flow

from the northern SJVAB toward the NCCAB. However, for this day there wasn’t any

available wind data from the Pacheco Pass area to verify that the flow continued on into

the NCCAB. The airflow patterns based on the surface wind data suggest that ozone and

its precursors were transported from the southern SFBAAB to Hollister. In addition,

westerly winds at Granite Rock #3 suggests that sources within the NCCAB impacted

Hollister.

Further, the group examined mountain-top wind data at several locations to

identify the possible transport directions at elevated levels. They also reviewed the radar
152

profiler data collected at Hollister, Fort Ord, and UCSC Long Marine Laboratory;

Doppler acoustic sounder data collected by PG&E at Moss Landing; and Oakland

rawinsonde data. On this day Mt. Pise (elevation 621 m) experienced continuous offshore

flow until 1300 PST. Weak onshore flow occurred between 1400 and 1900 PST,

followed by a return to offshore flow after 1900 PST. Monitors at Kregor Peak (elevation

577 m) also reported offshore flow in the morning. Moss Landing experienced offshore

flow in the lowest 500 m (the upper limit of the Doppler sounder measurements) above

mean sea level (msl) in the morning. The sea breeze started at 0900 PST at the surface

and deepened to 500 m by 1100 PST. At 1700 PST a land breeze began at the surface. 

The land-breeze layer deepened to 500 m by 2000 PST. The coastal profilers (Fort Ord

and UCSC) showed diurnal flow patterns similar to those at Moss Landing. At around

1000 m msl the winds were northeast throughout the day. The Hollister profiler showed

variable winds below 500 m in the morning. Between 500 m and 1000 m winds were

predominantly from the east to north-northwest. Above 1000 m northeast winds

prevailed. The Hollister profiler did not record winds after 1200 PST. The 0400 PST

Oakland sounding showed north-northwest winds below 150 m and north-northeast winds

above 800 m in the morning. In the afternoon Oakland recorded west-northwest winds

near the surface and northeast winds at 85 mb. The wind pattern aloft at Hollister and

Oakland suggests that transport aloft from the SFBAAB and from the northern SJVAB

could have had an impact on Hollister.

Inversion heights at Oakland, Hollister, and Fort Or were derived from the

temperature profiles. All locations observed ground-based inversions in the early morning

and late evening. The 0400 PST Oakland inversion top and strength was 500 m and 16

Celsius degrees of potential temperature, respectively, indicating that nighttime emissions

were concentrated in a shallow layer by a strong inversion cap. As a result of surface

heating, the inversion base had begun to rise by 0900 PST. The inversion base height

increased to 250 m at Fort Or and 500 m at Hollister by 1000 PST and decreased

somewhat thereafter. The maximum height of the inversion base in the afternoon was 150

m at Fort Or, and is unknown at Hollister, however, due to missing data. The inversion

base and top at 1600 PST at Oakland were 400 m and 520 m, respectively, with a strength

of 2.7 Celsius degrees. Daily maximum surface temperatures at Salinas and Sacramento

and temperature soundings at Oakland and Vandenberg were used to estimate mixing

heights at Hollister. The analysis suggests that the afternoon mixing height in the Hollister

area could have exceeded 1000 m and allowed ozone aloft to mix down to the surface. 

Hollister's maximum surface temperature of 95 degrees Fahrenheit on June 9, 1994

is similar to the maximum temperatures in the southern SFBAAB (San Martin and Gilroy)

and in the northern SJVAB. Thus, it appears that the marine layer had not penetrated as

far inland as Hollister at the time of the ozone peak.

Back trajectories were calculated for five elevations (10 m, 100 m, 300 m, 500 m,

and 1000 m above ground level (age)) using hourly gridded wind fields. The WOCSS
153

diagnostic wind model used observations to calculate interpolated winds for each grid cell. 

Then the hourly gridded winds were used to calculate backward trajectories from Hollister

at 1500 PST, the time of the ozone peak. Air parcels that arrived at Hollister in the

surface layer were traced backward to the Gilroy and San Jose area in the early morning. 

Air trajectories aloft suggest that the morning commute-time emissions near Stockton

could have traveled southwestward through the Pacheco Pass to contribute to Hollister’s

1500 PST peak ozone concentration of 101 ppb. The trajectory analyses suggest that

ozone and precursor gases from the southern SFBAAB within the lowest 100 m, and from

the northern SJVAB aloft, impacted Hollister at the time of the exceedance.

The above analyses, when taken as a whole, provide strong evidence that ozone

and its precursors in the surface layer traveled southward from the southern SFBAAB and

had an impact on Hollister. It also appears that there was flow aloft into the NCCAB

from the northern SJVAB. Ozone aloft could have mixed down to the surface as the

mixing layer deepened in the afternoon, thereby contributing to Hollister’s peak ozone. 

The transport working group concluded that the impact at Hollister is the combined

transport impact from the SFBAAB and the SJVAB. However, when there are shared

contributions from the SFBAAB and the northern SJVAB, it seems likely that the

SFBAAB would often have the greater impact since the emissions ratio between SFBAAB

(Santa Clara and San Mateo Counties) and NCCAB (San Benito County) is 25 to 1 and

the emissions ratio between the northern SJVAB (San Joaquin and Stanislaus Counties)

and NCCAB (San Benito County) is 16 to 1, respectively. To help the group estimate the

possible SJVAB transport contribution, we reviewed the SARMAP model transport

results for the August 5, 1990, ozone exceedance at Hollister. Unfortunately, the August

5, 1990, model results proved of little benefit for June 9, 1994, because local wind

patterns were dissimilar. Therefore, the group was unable to estimate the contribution of

ozone transported aloft from the SJVAB to the Hollister area. 
154
155

G-2

Data Sources

 Source Responsible Entity 

 ---------------------------------------------------------------------------------

 AIRS Arizona Department of Environmental Quality

 DRI Bureau of Land Management

AIRS California Air Resources Board

CIMIS California Irrigation Management Information System

AIRS Clark County Health Department

 AIRS Chevron Oil

 AIRS Environmental Monitoring Company

 AIRS Exxon

 AIRS Fresno County APCD

 AIRS Great Basin Unified APCD

 AIRS Imperial County APCD

 AIRS Los Angeles County APCD 

 AIRS Mariposa County Health Department

 AIRS Mojave Desert AQMD

 DRI National Parks Service

NWS National Weather Service

AIRS POPCO 

 AIRS Riverside County APCD 

 AIRS Santa Barbara APCD

 AIRS South Coast AQMD

AIRS San Diego County APCD

 AIRS Joaquin Valley Unified APCD

 AIRS San Luis Obispo County APCD

 AIRS Texaco

 DRI US Forest Service

AIRS UNOCAL

 AIRS US EPA

 AIRS Ventura County APCD

 AIRS Xontec Inc.
156
157

G-3

Staff Analysis of the Four Selected Exceedance Days

at Crow’s Landing and Tracy

1. August 17, 1994

The 1600 PST surface analysis for August 17, 1994, seems to imply a convergence

zone in the area of Tracy. There are no ozone data from Tracy for that day but Crow's

Landing to the south had a peak that day of 10.8 pphm. The surface flow path to Crow's

Landing seems to have been through Livermore; however, the peak ozone concentration

recorded at Livermore was 8.7 pphm. The peak ozone value recorded at Bethel Island of

10.2 pphm implies that higher ozone concentrations aloft had been mixed downwards just

upwind of Crow's Landing. It may have been that the flow that had passed over Bethel

Island had been forced over an underlying flow from Livermore and then eventually mixed

further south.

That same 1600 PST surface analysis does show a significant flow through the

area between the Santa Clara and Hollister Valleys and over the Pacheco Pass. In fact, an

IR satellite photograph for that same hour, strongly suggests that same flow into that part

of the San Joaquin Valley. The nearest wind data site to Crow's Landing was Turlock, 23

km (14 miles) to the west-northwest. There was northerly flow at Turlock during the

morning up to 10 am, southwesterly flow from 11 am - 2 pm, westerly flow from 3 pm - 5

pm, and southwesterly flow again during the rest of the afternoon and evening. Ozone

values at Crow's Landing above 9.5 pphm occurred between 1 and 6 pm. This suggests

polluted air from Pacheco Pass made it to Crow's Landing. At this point it is not possible

to determine the source of the original emission sources. They could have been from the

SFBAAB or the North Central Coast Air Basin.

2. September 5, 1994

The 1600 PST surface analysis for September 5, 1994, shows flows from

Livermore and the Carquinez Strait to Tracy. Flow to Crow's Landing is less certain. On

that day the peak ozone values for Livermore, Bethel Island and Crow's Landing were

10.8 pphm, 8.3 pphm and 10.1 pphm respectively. Ozone data from both Tracy and

Crow's Landing show two peaks, one in the mid-afternoon and the other in the evening. 

Ozone concentrations at Tracy and Crow's Landing began to increase early in the morning

from values below 1 pphm to 8 pphm by noon. Tracy's ozone values increased at 6 am

whereas the increase at Crow's Landing began earlier at 4 am. The light winds (< 1 m/s)

prior to noon at both sites, suggests that the early increase of ozone was due more to

fumigation from levels just above the surface. 
158

By the time ozone peaked at Tracy and Crow's Landing, the flow was northerly at

both sites. Even though this points to the Carquinez Strait, the wind speeds in the Tracy

area at the time of its ozone peak (2 - 4 m/s) and at Bethel Island prior to noon (< 3 m/s )

suggest a travel time of 6 or more hours between Tracy and the Carquinez Strait. Bethel

Island and the area near Tracy prior to 9 am experienced wind speeds 1 m/s or less. This

implies the air that passed over Tracy at 2 pm did not come through the Carquinez Strait

that day. 

On the other hand, the second ozone peak at Tracy can be attributed to transport

from Livermore based on the wind directions at Tracy. Given the wind speeds at

Livermore and Tracy (5 - 6 m/s), travel time from one to the other is about 2 hours. The

time difference between the wind direction shift at Tracy and the rapid wind speed

increase at Livermore was 3 or 4 hours. When considering the effect of the air flow

spreading horizontally after passing over Altamont Pass, the wind shift time difference and

time travel support each other.

3. August 1, 1995

The 1600 PST surface analysis for August 1, 1995, is similar to that of August 17,

1994, with an implied convergence zone in the Tracy area. The peak surface ozone

concentrations for Bethel Island, Livermore, Tracy and Crow's Landing were 8.1 pphm,

11.4 pphm, 8.7 pphm and 9.6 pphm, respectively. Ozone data from Tracy shows two

main peaks, at 1 pm and 7 pm. Ozone concentrations at Tracy began to increase early in

the morning from values below 1 pphm to 8 pphm by noon. There is no ozone data from

Crow's Landing prior to 2 pm. Because of the light winds prior to 10 am at Tracy 

(1 - 2 m/s), it is suspected that the early increase of ozone was due more to fumigation.

When ozone values peaked at Tracy, the flow was from the north-northeast. Even

though this direction points to the east of Bethel Island, the wind directions at Bethel

Island and Stockton were in alignment from the northwest, suggesting that flow from the

Bethel Island area eventually passed over Tracy. The wind speeds (3 m/s) in the Tracy

area at the time of its ozone peak and at Bethel Island prior to noon (4 - 5 m/s) suggest a

travel time of 4 - 5 hours from the Carquinez Strait to Tracy. This would indicate that the

first ozone peak recorded at Tracy is attributable to emissions from the Carquinez Strait

area.

The source of the second ozone peak at Tracy is harder to trace. The wind

direction at Tracy then was from the west-northwest. This may imply flow from the

Carquinez Strait that had passed well south of Bethel Island and followed the terrain

orientation.

The ozone peak recorded at Crow's Landing can be attributed to air having passed

near Tracy 3 hours earlier at the time the first peak was experienced at Tracy. The 3 hour
159

travel time is based on the 3 m/s wind speeds at Turlock and Tracy and the wind direction

from the north-northwest at Crow's Landing. Because the two ozone peaks are linked,

the argument can be made that the Crow's Landing peak is attributable to the emissions

from the Bay Area.

A diagnostic computer model was used to calculate the surface trajectory of a

parcel of air that passed over Crow’s Landing at the time of the maximum ozone

concentration, 4 pm, starting at midnight. These computations were based on spatial

interpolations of hourly observed data. Such analyses should be treated carefully and flow

features that are smaller than the distances between observation sites reflect the

interpolation algorithms more than actual physical processes. However, the trajectory

supports the previous subjective analysis. The trajectory path being south of Bethel Island

could explain why peak ozone at Crow’s Landing (9.6 pphm) was larger than at Bethel

Island (8.1 pphm). One could expect an increasing gradient south of Bethel Island

because of the higher peak at Livermore (11.4 pphm).

4. August 9, 1995

The 1600 PST surface analysis for August 9, 1995, shows a surface flow from

Bethel Island to Tracy and Livermore to Crow's Landing. However, hourly wind data

recorded at Tracy shows a shift from the north to the west occurring between 2 - 3 pm. 

The Tracy data was not used in the 1600 PST surface analysis which would have created a

streamline analysis linking flow from Livermore to Tracy. Prior to 1 pm and after 8 am,

data from the Mariposa site just southeast of Stockton shows wind direction between the

north and the northeast. When considering the peak surface values from Bethel Island

(8.5 pphm), Tracy (10.9 pphm), and Stockton-Mariposa (10.4 pphm), ozone levels

recorded at Tracy prior to the wind shift would then be attributable to surface air passing

over Stockton emission sources. After the wind shift, surface flow came from the

Livermore direction which had lower levels of ozone as indicated in the decline recorded

at Tracy.

The situation at Crow's Landing was different. The nearest wind data site,

Turlock, between 8 am and 5 pm had wind directions on the average from the westnorthwest. By 5 pm ozone levels increased to 9.9 pphm. Until 1 pm, surface flow at

Livermore was from the west with speeds of 4 to 5 m/s. Afterwards Livermore winds

were from the west-northwest at 9.3 m/s. Livermore recorded an ozone peak of 9.6 pphm

at noon. Assuming a flow speed of 4 m/s and the distance between Crow's Landing and

Livermore of about 65 km, a surface travel time of 4.5 hours results. This compares well

with the time difference of 5 hours between the Livermore and Crow's Landing ozone

peaks.

A surface trajectory was calculated starting at midnight and ending at the time of

the recorded ozone peak at Crow’s Landing, 5 pm. The path supports the previous
160

subjective analysis that the high ozone at Crow’s Landing was due to transport of polluted

air from the SFBAAB that had passed through the Livermore Valley. 
161

APPENDIX H

MOJAVE DESERT AIR POLLUTION TRANSPORT INTERIM REPORT