U.S. Department of the Interior

U.S. Geological Survey

Data Series 167

7FSTJPO

In cooperation with the California State Water Resources Control Board

Ground-Water Quality Data in the North San Francisco Bay 

Hydrologic Provinces, California, 2004: Results from the 

California Ground-Water Ambient Monitoring and 

Assessment (GAMA) Program

Santa Rosa
Cover Credits:

1. Photo of the Empire Building 

in Courthouse Square downtown 

Santa Rosa, California. 

Photographer: Joseph Lang, Santa Rosa, California

2. Photo of a municipal supply well. 

Sonoma County, California

Photographer: Tyler Johnson, USGS, California

3. Cover design and illustrations: 

Laurel Rogers, San Diego, California

1.

2.

3.
Ground-Water Quality Data in the North 

San Francisco Bay Hydrologic Provinces, 

California, 2004: Results from the California 

Ground-Water Ambient Monitoring and 

Assessment (GAMA) Program

By Justin T. Kulongoski, Kenneth Belitz, and Barbara J. Dawson

In cooperation with the California State Water Resources Control Board

Data Series 167

7FSTJPO

U.S. Department of the Interior

U.S. Geological Survey
U.S. Department of the Interior

P. Lynn Scarlett, Acting Secretary

U.S. Geological Survey

P. Patrick Leahy, Acting Director

U.S. Geological Survey, Reston, Virginia: 2006

Revised: 2011 

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Although this report is in the public domain, permission must be secured from the individual copyright owners to 

reproduce any copyrighted materials contained within this report.

Suggested citation:

Kulongoski, J.T., Belitz, Kenneth, and Dawson, B.J., 2006, Ground-water quality data in the North San Francisco Bay 

hydrologic provinces, California, 2004: Results from the California Ground-Water Ambient Monitoring and Assessment 

(GAMA) Program: U.S. Geological Survey Data Series Report 167, 100 p.
iii

Contents

Abstract...........................................................................................................................................................1

Introduction.....................................................................................................................................................2

Purpose and Scope ..............................................................................................................................4

Acknowledgements .............................................................................................................................4

Hydrologic Setting of the North San Francisco Bay GAMA Study Unit ...............................................4

Valley and Plains Study Area..............................................................................................................7

Volcanic Highlands Study Area..........................................................................................................7

Wilson Grove Formation Highlands Study Area ..............................................................................7

Hydrothermal Study............................................................................................................................11

Methods.........................................................................................................................................................11

Sampling Design .................................................................................................................................11

Sample Collection...............................................................................................................................13

Sample Analysis..................................................................................................................................14

Data Reporting ....................................................................................................................................15

Laboratory Reporting Conventions .........................................................................................15

Constituents on Multiple Analytical Schedules....................................................................15

Quality Control ....................................................................................................................................15

Blanks.. ........................................................................................................................................15

Replicates ...................................................................................................................................16

Matrix Spikes..............................................................................................................................16

Surrogates ..................................................................................................................................16

Results...........................................................................................................................................................17

Quality-Control Samples....................................................................................................................17

Detections in Blanks .................................................................................................................17

Equipment Blank ...............................................................................................................17

Field Blanks........................................................................................................................17

Variability in Replicate Samples..............................................................................................17

Matrix Spike Recoveries ..........................................................................................................18

Surrogate Compound Recoveries...........................................................................................18

Ground-Water Quality ........................................................................................................................20

VOCs and Gasoline Additives and (or) Oxygenates .............................................................20

Pesticides and Pesticide Degradates ....................................................................................21

Waste-Water Indicators...........................................................................................................21

Constituents of Special Interest..............................................................................................22

Nutrients and Dissolved Organic Carbon ..............................................................................22

Major and Minor Ions and Dissolved Solids .........................................................................22

Trace Elements...........................................................................................................................23

Isotopes, Radioactivity, and Dissolved Gases ......................................................................23

Microbial Constituents..............................................................................................................24

Summary........................................................................................................................................................24

References....................................................................................................................................................25

Tables.............................................................................................................................................................29
iv

Figures

Figure 1. Map showing the 10 hydrologic provinces considered for the California 

 GAMA study, with the North San Francisco Bay study unit outlined. ..............................3

Figure 2. Maps showing the North San Francisco Bay GAMA study unit, locations of

 study areas, major cities, rivers, ground-water basins and subbasins,

 target wells, and 10-square-mile randomized sampling grid cells....................................5

Figure 3. Map showing the Valley and Plains study area with the locations of 

 the randomized public-supply wells and flow-path wells sampled for the 

 North San Francisco Bay GAMA study, California...............................................................8

Figure 4. Map showing the Volcanic Highlands study area randomized 

 sampling grid cells and locations of the randomized public-supply wells 

 sampled for the North San Francisco Bay GAMA study, California. ................................9

Figure 5. Map showing the Wilson Grove Formation Highlands study area, the 

 randomized sampling grid cells, and the locations of the randomized 

 public-supply wells and flow path well sampled for the North San 

 Francisco Bay GAMA study, California................................................................................10

Figure 6. Map showing the hydrothermal study wells and spring sampled for the 

 North San Francisco Bay GAMA study, California..............................................................12

Tables

Table 1. Identification, sampling and construction information for wells sampled for the 

 North San Francisco Bay Ground-Water Ambient Monitoring and Assessment 

 (GAMA) study, California, August to November 2004.........................................................30

Table 2A. Volatile organic compounds and gasoline additives and (or) oxygenates, 

 primary use or source, Chemical Abstract Service (CAS) number, and 

 laboratory reporting level (LRL) for the U.S. Geological Survey’s National 

 Water Quality Laboratory analytic schedule 2020. ............................................................33

Table 2B. Gasoline oxygenates and (or) gasoline oxygenate degradates, primary use 

 or source, Chemical Abstract Service (CAS) number, and laboratory 

 reporting level (LRL) for the U.S. Geological Survey’s National Water Quality 

 Laboratory analytical schedule..............................................................................................35

Table 2C. Pesticides and pesticide degradates, primary use or source, Chemical 

 Abstract Service (CAS) number, and laboratory reporting level (LRL) for

 the U.S. Geological Survey’s National Water Quality Laboratory analytical 

 schedule 2003............................................................................................................................36

Table 2D. Pesticides, pesticide degradates and caffeine, primary use or source, 

 Chemical Abstract Service (CAS) number, and laboratory reporting level

 (LRL) for the U.S. Geological Survey’s National Water Quality Laboratory 

 analytical schedule 2060. ........................................................................................................38

Table 2E. Waste-water indicator constituents, primary use or source, Chemical

 Abstract Service (CAS) number, and laboratory reporting level (LRL) for

 the U.S. Geological Survey’s National Water Quality Laboratory analytical 

 schedule 1433............................................................................................................................40
v

Table 2F. Constituents of special interest: perchlorate, 1,2,3-tricholoropropane, and 

 N-nitrosodimethylamine (NDMA), Chemical Abstract Service (CAS) number, 

 and minimum reporting level (MRL) for Montgomery Watson Harza Laboratory...........42

Table 2G. Nutrients and dissolved organic carbon, Chemical Abstract Service (CAS) 

 number, and laboratory reporting level (LRL) for the U.S. Geological Survey’s 

 National Water Quality Laboratory analytical schedule 2755 and laboratory 

 code 2613. ...................................................................................................................................42

Table 2H. Major and minor ions and trace elements, Chemical Abstract Service (CAS)

 number, and laboratory reporting level (LRL) for the U.S. Geological Survey’s 

 National Water Quality Laboratory analytical schedule 1948............................................43

Table 2I. Iron, arsenic and chromium speciation, Chemical Abstract Service (CAS) 

 number, and method detection limit (MDL) for the U.S. Geological Survey’s 

 National Research Program Laboratory, Boulder, Colorado..............................................44

Table 2J. Isotopic and radioactive constituents, Chemical Abstract Service (CAS) 

 number, reporting level type, reporting level and (or) uncertainty, and reporting 

 units for the U.S. Geological Survey’s National Water Quality Laboratory, 

 Stable Isotope and Tritium Laboratory, Menlo Park, California1

, Stable Isotope 

 Laboratory, Reston, Virginia2, and the contract laboratories Eberline 

 Analytical Services3 and the University of Arizona, Accelerator Mass 

 Spectrometry Laboratory4. .......................................................................................................44

Table 2K. Tritium and dissolved gases, Chemical Abstract Service (CAS) number, 

 method uncertainty (MU) and reporting units for Lawrence Livermore 

 National Laboratory...................................................................................................................45

Table 2L. Microbial constiuents, primary use and source, and method detection limit 

 (MDL) for the U.S. Geological Survey’s Ohio Microbiology Laboratory 

 parameter codes 90901, 90900, 99335 and 99332..................................................................45

Table 3. Classes of chemical and microbial constituents and water-quality indicators 

 collected for the expanded, basic-plus, basic, and hydrothermal sampling 

 schedules for the North San Francisco Bay Ground-Water Ambient 

 Monitoring and Assessment (GAMA) study, California, August to 

 November, 2004..........................................................................................................................46

Table 4. Constituents analyzed in ground-water samples collected for the North San 

 Francisco Bay Ground-Water Ambient Monitoring and Assessment (GAMA) 

 study, that appear on multiple analytical schedules, primary constituent 

 classification, analytical schedules constituent appears on, and preferred 

 analytical schedule ...................................................................................................................47

Table 5. Quality-control summary for volatile organic compounds and gasoline additives 

 and (or) oxygenates, pesticides and (or) pesticide degradates, waste-water 

 indicators, major and minor ions, trace elements, and nutrients and dissolved 

 organic carbon, detected in equipment blanks, field blanks and ground-water 

 samples collected for the North San Francisco Bay Ground-Water Ambient 

 Monitoring and Assessment (GAMA) study, California, August to 

 November 2004...........................................................................................................................48

Table 6A. Quality-control summary of replicate volatile organic compound (VOC) and

 gasoline additives and (or) oxygenates, pesticides and (or) pesticide 

 degradates, waste-water indicators, and samples for constituents of 

 special interest with relative standard deviations greater than zero, collected 

 for the North San Francisco Bay Ground-Water Ambient Monitoring and 

 Assessment (GAMA) study, Calfiornia, August to November 2004...................................49
vi

Table 6B. Quality-control summary of replicate nutrient and dissolved organic carbon 

 samples collected for the North San Francisco Bay Ground-Water Ambient 

 Monitoring and Assessment (GAMA) study, California, August to 

 November 2004........................................................................................................................50

Table 6C. Quality-control summary of replicate major and minor ion samples collected 

 for the North San Francisco Bay Ground-Water Ambient Monitoring and 

 Assessment (GAMA) study, California, August to November 2004................................50

Table 6D. Quality-control summary of replicate trace-element samples collected for 

 the North San Francisco Bay Ground-Water Ambient Monitoring and 

 Assessment (GAMA) study, California, August to November 2004................................51

Table 6E. Quality-control summary of replicate isotope and radioactivity samples 

 collected for the North San Francisco Bay Ground-Water Ambient Monitoring 

 and Assessment (GAMA) study, California, August to November 2004. .......................52

Table 7A. Quality-control summary of volatile organic compounds (VOCs), gasoline 

 additives and oxygenates, NDMA and 1,2,3-trichloropropane matrix spike 

 recoveries in samples collected for the North San Francisco Bay Ground-

 Water Ambient Monitoring and Assessment (GAMA) study, California, 

 August to November 2004. ....................................................................................................53

Table 7B. Quality-control summary of matrix pesticide spike recoveries in samples 

 collected for the North San Francisco Bay Ground-Water Ambient Monitoring 

 and Assessment (GAMA) study, California, August to November 2004. .......................56

Table 7C. Quality-control summary of matrix waste-water indicators spike recoveries 

 in samples collected for the North San Francisco Bay Ground-Water Ambient 

 Monitoring and Assessment (GAMA) study, California, August to 

 November 2004.........................................................................................................................60

Table 8. Summary of surrogate recoveries for ground-water and quality-control analyses 

 of volatile organic compounds, gasoline additives and (or) oxygenates, pesticides 

 and (or) pesticide degradates, waste-water indicators, and constituents of special 

 interest in samples collected for the North San Francisco Ground-Water Ambient 

 Monitoring and Assessment (GAMA) study, California, August to 

 November 2004.........................................................................................................................62

Table 9. Water-quality indicators determined in the field for the North San Francisco 

 Bay Ground-Water Ambient Monitoring and Assessment (GAMA) study, 

 California, August to November 2004. .................................................................................63

Table 10A. Results of analyses for volatile organic compounds (VOCs) and gasoline 

 additives and (or) oxygenates in ground-water samples collected in the Valley 

 and Plains study area of the North San Francisco Bay Ground-Water Ambient 

 Monitoring and Assessment (GAMA) study, California, August to 

 November 2004.........................................................................................................................68

Table 10B. Results of analyses for volatile organic compounds (VOCs) and gasoline 

 additives and (or) oxygenates in ground-water samples collected in the 

 Volcanic Highlands study area of the North San Francisco Bay Ground-

 Water Ambient Monitoring and Assessment (GAMA) study, California, 

 August to November 2004 .....................................................................................................70

Table 10C. Results of analyses for volatile organic compounds (VOCs) and gasoline 

 additives and (or) oxygenates in ground-water samples collected in the 

 Wilson Grove Formation Highlands study area of the North San Francisco 

 Bay Ground-Water Ambient Monitoring and Assessment (GAMA) study, 

 California, August to November 2004 ..................................................................................71
vii

Table 11A. Pesticides and (or) pesticide degredates detected in ground-water samples 

 collected in the Valley and Plains study area of the North San Francisco Bay 

 Ground-Water Ambient Monitoring and Assessment (GAMA) study, California, 

 August to November 2004. ....................................................................................................72

Table 11B. Pesticides and (or) pesticide degredates detected in ground-water samples 

 collected in the Volcanic Highlands study area of the North San Francisco 

 Bay Ground-Water Ambient Monitoring and Assessment (GAMA) study, 

 California, August to November 2004 ..................................................................................73

Table 11C. Pesticides and (or) pesticide degradates detected in ground-water samples 

 collected in the Wilson Grove Formation Highlands study area of the North 

 San Francisco Bay Ground-Water Ambient Monitoring and Assessment 

 (GAMA) study, California, August to November 2004.......................................................73

Table 12A. Waste-water indicators measured in ground-water samples collected

 in the Valley and Plains study area of the North San Francisco Bay Ground-

 Water Ambient Monitoring and Assessment (GAMA) study, California, 

 August to November 2004. ....................................................................................................74

Table 12B Waste-water indicators measured in ground-water samples collected in the 

 Volcanic Highlands study area of the North San Francisco Bay Ground- Water 

 Ambient Monitoring and Assessment (GAMA) study, California, August to 

 November 2004........................................................................................................................75

Table 12C. Waste-water indicators measured in ground-water samples collected in the 

 Wilson Grove Formation Highlands study area of the North San Francisco Bay 

 Ground-Water Ambient Monitoring and Assessment (GAMA) study, California, 

 August to November 2004. ....................................................................................................76

Table 13. Results of analyses for the constituents of special interest: perchlorate,

 trichloropropane (1,2,3-TCP), N-nitrosodimethylamine (NDMA) in ground-

 water samples collected for the North San Francisco Bay Ground-Water 

 Ambient Monitoring and Assessment (GAMA) study, California, 

 August to November 2004. ....................................................................................................77

Table 14. Nutrients and dissolved organic carbon in ground-water samples collected 

 for the North San Francisco Bay Ground-Water Ambient Monitoring and 

 Assessment (GAMA) study, California, August to November 2004................................78

Table 15. Major and minor ions and dissolved solids in ground-water samples collected 

 for the North San Francisco Bay Ground-Water Ambient Monitoring and 

 Assessment (GAMA) study, California, August to November 2004. ..............................79

Table 16. Trace elements in ground-water samples collected for the North San Francisco 

 Bay Ground-Water Ambient Monitoring and Assessment (GAMA) study, 

 California, August to November 2004. .................................................................................81

Table 17. Inorganic arsenic and iron-speciation results measured at the U.S. Geological 

 Survey National Research Program in ground-water samples collected for 

 the North San Francisco Bay Ground-Water Ambient Monitoring and 

 Assessment (GAMA) study, California, August to November 2004................................85

Table 18. Chromium-speciation results measured by the U.S. Geological Survey 

 National Research Progam for ground-water samples collected for the 

 North San Francisco Bay Ground-Water Ambient Monitoring and 

 Assessment (GAMA) study, California, August to November 2004................................86

Table 19. Isotopes and radioactivity measured in ground-water samples collected for 

 the North San Francisco Bay Ground-Water Ambient Monitoring and 

 Assessment (GAMA) study, California, August to November 2004................................89
viii

Conversion Factors, Abbreviations, and 

Acronyms

Multiply By To obtain

Length

inch (in.) 2.54 centimeter (cm)

foot (ft) 0.3048 meter (m)

mile (mi) 1.609 kilometer (km)

Area

square mile (mi2

) 259.0 hectare (ha)

square mile (mi2

) 2.590 square kilometer (km2) 

Multiply By To obtain

Length

kilometer (km) 0.6214 mile (mi)

Area

square kilometer (km2

) 247.1 acre

square kilometer (km2

) 0.3861 square mile (mi2)

Volume

liter (L) 33.82 ounce, fluid (fl. oz)

liter (L) 0.2642 gallon (gal)

liter (L) 61.02 cubic inch (in3

) 

Pressure

millimeter (mm) of mercury at 60oF 

(in Hg)

0.1333 kilopascal (kPa) 

Radioactivity

picocurie per liter (pCi/L) 0.037 becquerel per liter (Bq/L) 

Table 20. Tritium and noble gas results, analyzed at the Lawrence Livermore National 

 Laboratory for samples collected for the North San Francisco Bay Ground-

 Water Ambient Monitoring and Assessment (GAMA) study, California, 

 August to November 2004. .......................................................................................................95

Table 21. Concentrations of the dissolved gases: carbon dioxide, nitrogen, argon, 

 oxygen, and methane analyzed at Lawrence Livermore National Laboratory 

 in samples collected for the North San Francisco Bay Ground-Water 

 Ambient Monitoring and Assessment (GAMA) study, California, August to 

 November 2004...........................................................................................................................99

Table 22. Microbial analyses of ground-water samples collected for the North San 

 Francisco Bay Ground-Water Ambient Monitoring and Assessment (GAMA) 

 study, California, August to November 2004........................................................................100
ix

Temperature in degrees Fahrenheit (°F) may be converted to degrees Celsius (°C) as follows:

°C=(°F-32)/1.8

Specific conductance is given in microsiemens per centimeter at 25 degrees Celsius (mS/cm at 

25°C).

Concentrations of chemical constituents in water are given either in milligrams per liter (mg/L) 

or micrograms per liter (mg/L)

Abbreviations and Acronyms

mL milliliter

mL microliter

mm micrometer

pCi/L picocurie per liter

AF atomic fluoresence

CAS Chemical Abstract Service

cm3 STP cubic centimeters at standard temperature and pressure (0 degrees Celsius and 1 

atmophere of pressure)

DEET deethyl atrazine

DLR detection level for the purposes of reporting

DO dissolved oxygen

DOC dissolved organic carbon

DS dissolved solids

GAMA Ground-Water Ambient Monitoring and Assessment program

GFAA graphite furnace atomic absorption

HCL hydrochloric acid

HOT hydrothermal study

ICRMS inductively coupled plasma mass spectometer

LRL laboratory reporting level

LSD land-surface datum

LT-MDL long-term method detection level

MCL maximum contaminant level

MDL method detection limit

MRL minimum reporting level

MTBE methyl tert-butyl ether

MU method uncertainty

N normal

NA not available

NAWQA National Water Quality Assessment Program

NC sample not collected

ND no data
x

NDMA N-nitrosodimethylamine

NL notification level

NRP National Research Program

NSF North San Francisco Bay

NSFHOT North San Francisco Bay Study Unit, hydrothermal study

NSFVOL North San Francisco Bay Study Unit, Volcanic Highlands study area

NSFVP North San Francisco Bay Study Unit, Valley and Plains study area

NSFVPFP North San Francisco Bay Study Unit, Valley and Plains flow-path well

NSFWG North San Francisco Bay Study Unit, Wilson Grove Formation Highlands 

study area

NSFWGFP North San Francisco Bay Study Unit, Wilson Grove Formation Highlands 

flow-path well

NWIS National Water Information System

PCE tetrachloroethylene

QC quality control

RSD relative standard deviation

SC specific conductance

SSMDC sample specific minimum detectable concentration

SMCL secondary maximum contaminant level

TCA 1,1,1,-trichloroethane

TCE trichloroethylene

TCP trichloropropane

THM trihalomethane

UCMR unregulated chemical for which monitoring is required

VP Valley and Plains study area

VOC volatile organic compound

VOL Volcanic Highlands study area

WG Wilson Grove Formation Highlands study area

Organizations

DHS California Department of Health Services

LLNL Lawrence Livermore National Laboratory

NWQL National Water Quality Laboratory

USEPA U.S. Environmental Protection Agency

USGS U.S. Geological Survey

 
Abstract

Ground-water quality in the ~1,000 square-mile (mi2) 

North San Francisco Bay study unit was investigated from 

August to November, 2004, as part of the California Groundwater Ambient Monitoring and Assessment (GAMA) program. Samples were collected from 89 public-supply wells, 

7 hydrothermal wells, and 1 hydrothermal spring in Napa, 

Sonoma and Marin Counties. Eighty-four of the public-supply 

wells sampled were selected to provide a spatially distributed, 

randomized monitoring network for statistical calculations and 

constituent detection frequency. The study was designed to 

provide a spatially-unbiased assessment of raw ground-water 

quality within the study unit, as well as a statistically-consistent basis for comparing the water quality of different study 

units. 

Ground-water samples were analyzed for major and 

minor ions, trace elements, nutrients, volatile organic compounds, pesticides and pesticide degradates, waste-water indicators, dissolved methane, nitrogen, carbon dioxide and noble 

gases (in collaboration with Lawrence Livermore National 

Laboratory). Naturally occurring isotopes (tritium, carbon-14, 

oxygen-18, deuterium and helium-4) also were measured in 

the samples to help identify the source and age of the ground 

water. Results show that no anthropogenic constituents were 

detected at concentrations higher than those levels set for 

regulatory purposes, and relatively few naturally-occurring 

constituents were detected at concentrations greater than regulatory levels.

In this study, 21 of the 88 volatile organic compounds 

(VOCs) and gasoline additives and (or) oxygenates investigated were detected in ground-water samples, however, 

detected concentrations were one-half to one-forty-thousandth 

the maximum contaminant levels (MCL). Thirty-two percent 

of the randomized wells sampled had at least a single detection of a VOC or gasoline additive and (or) oxygenate. The 

most frequently detected compounds were chloroform, found 

in 12 of the 84 randomized wells; carbon disulfide, found in 8 

of the 84 randomized wells; and toluene, found in 4 of the 84 

randomized wells. Trihalomethanes were the most frequently 

detected class of VOCs.

Nine of the 122 pesticides and (or) pesticide degradates 

investigated were detected in ground-water samples, however, 

concentrations were one-seventieth to one-eight-hundredth the 

MCLs. Seventeen percent of the randomized wells sampled 

had at least a single detection of pesticide and pesticide 

degradate. Herbicides were the most frequently detected 

class of pesticides. The most frequently detected compound 

was simazine, found in 8 of the 84 of the randomized wells. 

Chlordiamino-s-triazine and deisopropyl atrazine were both 

found in 2 of the 84 randomized wells sampled. 

Thirteen out of 63 compounds that may be indicative of 

the prescence of waste-water were detected in ground-water 

samples. Twenty-six percent of the randomized wells sampled 

for waste-water indicators had at least one detection. Isophorone was the most frequently detected in 6 of the 84 randomized wells. Bisphenol-A, caffeine, and indole each were 

detected in 3 of the 84 randomized wells.

Ground-Water Quality Data in the North San Francisco 

Bay Hydrologic Provinces, California, 2004: Results from 

the California Ground-Water Ambient Monitoring and 

Assessment (GAMA) Program

By Justin T. Kulongoski, Kenneth Belitz, and Barbara J. Dawson
Major and minor ions and dissolved solids (DS) samples 

were collected at 33 public-supply wells; 3 samples had DS 

concentrations above the secondary maximum contaminant 

level (SMCL) of 500 mg/L. Ground-water samples from 32 

public-supply wells were analyzed for trace elements. Arsenic 

concentrations above the MCL of 10 μg/L were measured at 4 

public-supply wells, boron concentrations above the detection 

level for the purpose of reporting (DLR) of 100 μg/L were 

measured at 19 wells. Iron concentrations above the SMCL 

of 300 μg/L were measured at 7 wells, a lead concentration 

above the California notification level (NL) of 15 μg/L at one 

well, and manganese concentrations above the SMCL of 50 

μg/L were measured at 17 wells. Vanadium concentrations 

above the DLR of 3 μg/L were measured at 9 public-supply 

wells; and chromium(VI) concentrations above the DLR of 1 

μg/L were measured at 48 public-supply wells.

Radon-222 was detected in all 21 ground-water samples 

collected, with activities ranging from 210 to 1,500 picocuries per liter (pCi/L). Fifteen radon samples were above the 

proposed MCL of 300 pCi/L. 

Microbial constituents were analyzed in 22 ground-water 

samples. Total coliform was detected in three wells. Counts 

ranged from 2 colonies per 100 mL to 20 colonies per 

100 mL. MCLs for microbial constituents are based on 

reoccurring detection, and will be monitored during future 

sampling.

Introduction

To assess the quality of ground water from publicsupply wells and establish a program for monitoring trends in 

ground-water quality, the U.S. Geological Survey (USGS) in 

collaboration with the State Water Board and Lawrence Livermore National Laboratory (LLNL), implemented a statewide 

ground-water-quality monitoring and assessment program 

(http://ca.water.usgs.gov/gama/). The USGS developed a comprehensive approach for this effort (Belitz and others, 2003; 

http://water.usgs.gov/pubs/wri/wri034166/). The ground-water 

ambient monitoring and assessment (GAMA) program is a 

comprehensive assessment of statewide ground-water quality designed to help better understand and identify risks to 

ground-water resources. The assessment is based on groundwater samples collected at many locations across California 

in order to characterize their constituents and identify trends 

in ground-water quality. The results of these tests provide 

information for water agencies to address a variety of issues 

ranging in scale from local water supply to statewide resource 

management.

The GAMA program was developed in response to the 

Ground-Water Quality Monitoring Act of 2001 (CAL. WATER 

§§ 10780-10782.3): a public mandate to assess and monitor 

the quality of ground water used as public supply by municipalities in California. The goal of the Ground-Water Quality 

Monitoring Act of 2001 is to improve statewide ground-water 

monitoring and facilitate the availability of information about 

ground-water quality to the public.

The three main objectives of GAMA are (1) status, 

to assess the current quality of the ground-water resource, 

(2) trends, to detect changes in ground-water quality and 

(3) understanding, to identify the natural and human factors affecting ground-water quality (Kulongoski and Belitz, 

2004). This report will assess the quality of the ground-water 

resource, objective (1), while subsequent interpretive reports 

will address the trends and understanding listed in objectives 

(2) and (3). 

The GAMA program is unique because the data collected 

during the study include analyses for chemical constituents 

that are not normally available; these data will be especially 

useful for providing an early indication of potential changes in 

water quality. Additionally, the GAMA program will analyze a 

broader suite of constituents, at detection limits that are lower 

than those currently required by the California Department 

of Health Services (DHS). An understanding of these factors 

is important for the long term management and protection of 

ground-water resources.

The range of hydrologic, geologic, and climatic conditions that exist in California must be considered in an unbiased 

assessment of ground-water quality (Belitz and others, 2003). 

To accomplish this, the state was partitioned into 10 hydrogeologic provinces that have relatively similar hydrologic, 

geologic, and climatic characteristics (fig. 1). Each of these 

hydrologic provinces contains ground-water basins, which are 

generally composed of relatively permeable, unconsolidated 

deposits of alluvial or volcanic origin (California Department 

of Water Resources, 2003). For the purpose of designing a 

state-wide ground-water assessment program, ground-water 

basins were prioritized (for sampling) based upon the number 

of public-supply wells in the basin (Belitz and others, 2003). 

Secondary consideration was given to municipal ground-water 

use, agricultural pumping, the number of leaking underground 

fuel tanks, and pesticide application within a basin. Similar 

adjacent ground-water basins were then combined and designated as GAMA study units. The North San Francisco Bay 

GAMA study unit contains 7 ground-water basins considered 

high priority based on the number of public-supply wells, 

location, agricultural use, and pesticide applications within 

each basin (Belitz and others, 2003).

2 Ground-Water Quality Data, North San Francisco Bay Hydrologic Provinces, California, 2004: GAMA Program Results
Figure 1. The 10 hydrologic provinces considered for the California GAMA study (Belitz and others, 2003), with the 

North San Francisco Bay study unit outlined.

Introduction 3

Basin and Range Central

Valley

Klamath

Mountains

Desert

Cascades and

Modoc Plateau

Transverse Ranges and

selected Peninsular Ranges

Southern Coast

Ranges

Sierra

Nevada

Northern

Coast

Ranges

NORTH

SAN FRANCISCO BAY

GAMA STUDY UNIT

(figure 2)

San Diego

Drainages

Bakersfield

San Francisco

Sacramento

OREGON

NEVADA

MEXICO

ARIZONA

Redding

Los Angeles

San Diego

Pacific Ocean

0 200 MILES

0 200 KILOMETERS

40

42 124 122 120 118 116 114

38

36

34

Base from U.S Geological Survey digital elevation data,

1999, Albers Equal Area Projection

Figure 1
Purpose and Scope

The purpose of this report is to present the results of 

analyses for organic and inorganic constituents, microbial 

constituents, and general water-quality indicators from raw 

ground-water samples collected in the North San Francisco 

Bay GAMA study unit. Discussions of the factors that influence the distribution and occurrence of the compounds and 

microbial constituents detected in ground-water samples will 

be the subject of subsequent publications. 

The concentrations of constituents detected in ground 

water sampled for this study were evaluated on the basis of 

state and federal drinking water regulatory standards, and 

constituents with concentrations greater than either primary 

(MCL), secondary maximum contaminant levels (SMCL), and 

California notification levels (NL) were identified. MCLs are 

established with regards to the protection of human health, 

whereas SMCLs are established with regards to the aesthetic 

qualities of drinking water such as taste, odor, and color. 

In addition, detections of constituents classified by DHS as 

“unregulated chemicals for which monitoring is required” 

(UCMR) were identified if concentrations in ground water 

were above the “detection level for the purposes of reporting” 

(DLR). The DLR is used for reporting constituents on the 

UCMR list because MCLs have not been established for these 

constituents. It is important to note that raw ground-water 

quality in this report does not indicate drinking-water quality 

because raw water commonly is treated or blended in order to 

improve water quality. In addition, an MCL violation is not 

determined from a single sample, but from a suite of samples 

with concentrations above the regulatory value. Also, ground 

water samples collected from hydrothermal wells and springs 

were excluded from regulatory water-quality discussions 

because these wells are not used for public drinking-water 

supply.

Detection frequencies were reported for the VOCs, 

pesticides and pesticide degradates, and waste-water indicators detected in at least one ground-water sample. Frequently 

detected constituents are useful in determining future trends 

in ground-water quality. Also presented in this report are the 

results and analysis of quality-control samples collected during the North San Francisco Bay GAMA study. 

Acknowledgements 

The authors thank the following cooperators for their 

support: California Water Boards, California Department of 

Health Services, California Department of Water Resources, 

and Lawrence Livermore National Laboratory.

We also thank the cooperating well owners and water 

purveyors for their generosity in allowing the USGS to collect 

samples from their wells. We thank Michael T. Wright for his 

assistance in organizing this report.

Hydrologic Setting of the North San 

Francisco Bay GAMA Study Unit

The North San Francisco Bay GAMA study unit 

(figs. 1,2) covers approximately 1,000 mi2 in Napa, Sonoma 

and Marin Counties across Northern California. It lies within 

two hydrologic provinces, the San Francisco Bay and North 

Coast Hydrologic Provinces, as defined by the California 

Department of Water Resources (California Department 

of Water Resources, 2003). The NSF study unit includes 7 

ground-water basins; the Napa-Sonoma Valley, Kenwood 

Valley, Alexander Valley, Santa Rosa Valley, Petaluma Valley, 

Wilson Grove Formation Highlands, Volcanic Highlands, and 

the Lower Russian River Valley (fig. 2A). 

The climate in the North San Francisco Bay study unit is 

characterized by warm, dry summers and cool, moist winters. 

At the National Climate Data Center station in Sonoma, the 

average annual temperature is 59o F, and the average annual 

precipitation is 30 inches (in.), occurring as rain during the 

winter and early spring. However, the distribution of precipitation across the study area is dependent upon the topography 

and the prevailing winds, with an increase in precipitation 

concomitant to an increase in altitude, and most of the rain 

arriving with southwesterly winds (Faye, 1973).

The study area ground-water basins are drained by several rivers and their principal tributaries including the NapaSonoma and Kenwood Valleys by the Napa River and Sonoma 

Creek, respectively; the Petaluma Valley by the Petaluma 

River; the Santa Rosa, Alexander, and Lower Russian River 

Valleys by the Laguna de Santa Rosa and Russian Rivers; 

the Wilson Grove Formation Highlands by the Americano, 

Stemple, and Salmon Creeks. The Volcanic Highlands are 

drained by tributaries of the Napa, Sonoma, and Petaluma 

Rivers (fig. 2A). 

For the purpose of this study, the 7 ground-water basins 

were grouped into three study areas based primarily on 

geology. The relatively flat lying alluvial-filled basins were 

combined into the Valley and Plains study area, the Wilson 

Grove Formation Highlands was taken as a study area, and the 

Volcanic Highlands was identified as the third study area 

(fig. 2A).

4 Ground-Water Quality Data, North San Francisco Bay Hydrologic Provinces, California, 2004: GAMA Program Results
Figure 2. (A) the North San Francisco Bay GAMA study unit, locations of study areas, major cities, rivers, ground-water basins 

and subbasins and (B) the North San Francisco Bay GAMA study unit, target wells, and 10-square-mile randomized sampling 

grid cells.

Hydrologic Setting of the North San Francisco Bay GAMA Study Unit 5

123°00' 122°30'

38°

30'

EXPLANATION

Base from U.S. Geological Survey digital elevation

data, 1999, Albers Equal-Area Conic Projection.

38°

00'

Valley and Plains

Volcanic Highlands

Wilson Grove Formation Highlands

Study Areas

Lake Berryessa

Sonoma Creek

Russian

River

Soda Creek

Napa River

Cache Creek

Petaluma River

Stemple Cr.

Salmon Cr.

Americano Cr.Americano Cr.

Laguna de Santa Rosa River

Figure 2A

San Pablo Bay

Drakes Bay

PACIFIC OCEAN

CONTRA COSTA

COUNTY

LAKE

COUNTY

YOLO

COUNTY

NAPA

SONOMA COUNTY

COUNTY

SOLANO

COUNTY

MARIN

COUNTY

MENDOCINO COUNTY

0 5

0 5 10 Kilometers

10 Miles

PETALUMA VALLEY 

SANTA ROSA VALLEY,

Santa Rosa Plain

NAPA-SONOMA

VALLEY,

Napa Valley

NAPA-SONOMA VALLEY,

Sonoma Valley

NAPA-SONOMA

VALLEY,

Napa-Sonoma

Lowlands

ALEXANDER VALLEY,

Alexander Area

SANTA ROSA VALLEY,

Healdsburg Area

LOWER RUSSIAN

RIVER VALLEY, 

ALEXANDER VALLEY,

Cloverdale Area

WILSON GROVE

FORMATION HIGHLANDS, 

SANTA ROSA

VALLEY,

Rincon Valley

KENWOOD 

VALLEY, 

NAPA-SONOMA VALLEY,

Sonoma Valley

Ground-water basin

Ground-water basin boundary

Ground-water subbasin

")

")

")

")

Santa Rosa

Napa

Sonoma

Sebastopol
Figure 2.—Continued.

6 Ground-Water Quality Data, North San Francisco Bay Hydrologic Provinces, California, 2004: GAMA Program Results

123°00' 122°30'

38°

30'

EXPLANATION

Base from U.S. Geological Survey digital elevation

data, 1999, Albers Equal-Area Conic Projection.

38°

00'

Valley and Plains

Volcanic Highlands

Wilson Grove Formation Highlands

Study Areas

Lake Berryessa

Sonoma Creek

Russian

River

Soda Creek

Napa River

Cache Creek

Petaluma River

Stemple Cr.

Salmon Cr.

Americano Cr.Americano Cr.

Laguna de Santa Rosa River

Figure 2B

San Pablo Bay

Drakes Bay

PACIFIC OCEAN

0 5

0 5 10 Kilometers

10 Miles

Target well

CONTRA COSTA

COUNTY

LAKE

COUNTY

YOLO

COUNTY

NAPA

SONOMA COUNTY

COUNTY

SOLANO

COUNTY

MARIN

COUNTY

MENDICINO COUNTY

North San Francisco Bay

 GAMA study unit boundary

 Randomized sampling grid cell

")

")

")

")

Santa Rosa

Napa

Sonoma

Sebastopol
Valley and Plains Study Area

The Valley and Plains study area (VP) extends from 

Alexander Valley in the north to the San Francisco Bay in 

the south, and includes most of the alluvial filled basins in 

the NSF Study Unit (fig. 3). These basins result from a series 

of northwest-trending structural depressions in the southern 

part of the Coast Ranges of northern California (Faye, 1973). 

Mountain ranges, from 1,000 to more than 4,000 ft in altitude, 

bound the VP study area to the north, northwest and east, and 

separate the Napa Valley, Sonoma Valley and the Santa Rosa 

Plain. The San Pablo Bay bounds the VP study area to the 

south, while the Wilson Grove Formation Highlands bounds 

the VP study area to the west.

The VP study area covers nearly 500 mi2, and includes 

the Napa, Sonoma, Santa Rosa, Kenwood, Petaluma and Alexander Valleys, as well as the Napa-Sonoma lowlands to the 

south near San Pablo Bay (fig. 3). These valleys consist of a 

relatively thin cover of Quaternary alluvium overlying a thick 

section of Pliocene Volcanics, Cretaceous sedimentary rocks, 

Franciscan Formation metamorphics, and Jurassic serpentine 

and plutonic rocks (Faye, 1973). 

In these valleys, the main water bearing unit is the alluvium that underlies and forms valley floors the thickness of 

which increases progressively from north to south and from 

the periphery of the valleys towards the rivers. In most valleys, 

the alluvium ranges in thickness from less than 10 ft to more 

than 300 ft. Except for small localized areas of semiconfinement, water in the alluvium is unconfined and moves under a 

natural hydraulic gradient that conforms in a general way to 

the surface topography (Faye, 1973). Ground-water recharge 

to the alluvial aquifers occurs by stream-channel infiltration 

beneath the major rivers and their tributaries.

Volcanic Highlands Study Area

The Volcanic Highlands (VOL) study area (fig. 4) corresponds to hilly to mountainous areas of Pliocene volcanic 

deposits, which include lava flows, agglomerates, tuffs, and 

intercalated sediments of volcanic debris. These deposits, 

identified as the Sonoma Volcanics, have been subdivided in 

ascending order into the Mark West andesite, Sonoma tuff, and 

the St. Helena rhyolite (Osmont, 1905). These rocks have been 

folded, faulted, and eroded so that they now form a series of 

elongate ridges separating narrow alluvial valleys.

The VOL study area is approximately 390 mi2 of discontinuous highlands that ring Napa Valley to the east, north, and 

northwest, and separate Santa Rosa Valley from Sonoma Valley, and Sonoma Valley from Napa Valley. For the purpose of 

this study, the VOL study area was defined as the area within 

about 2 mi of a public-supply well, completed in the volcanic 

formations.

Pumice tuff, tuff breccias, and redeposited stratified tuff 

form the most important water bearing units in the Sonoma 

Volcanics, and occur interspersed with the andesitic and 

basaltic flows that are largely impervious and act as confining 

beds, which restrict the movement of ground water (Cardwell, 

1958). The thickness of the Sonoma Volcanics is not uniform. 

On the northeast side of Kenwood valley tuff and tuff breccias 

deposits are up to 1,200 ft in thickness, overlying 800 ft of 

basalt flows.

Wilson Grove Formation Highlands Study Area

The Wilson Grove Formation Highlands (WG) study area 

is a coastal area characterized by gently rolling hills, broad 

valleys, and rounded hilltops between Santa Rosa Valley and 

the Pacific Ocean (fig. 5). The WG study area corresponds to 

the Wilson Grove Formation Highlands ground-water basin 

(California Department of Water Resources, 2003) in Marin 

and Sonoma counties of California. The WG study area covers 

approximately 140 mi2, and is bound to the north and south by 

rugged coastal mountains up to 1,000 ft in altitude; to the west 

by the Pacific Ocean; and to the east by Santa Rosa Valley. 

The Wilson Grove Formation Highlands is named for the main 

geological unit underlying the area, the Wilson Grove Formation (Fox, 1983), and was previously described as the Merced 

Formation (Johnson, 1934). The marine deposits of the Wilson 

Grove Formation contain fine grained fossiliferous sandstones 

with lenses of conglomerate and sandy shale, and are underlain by Franciscan basement rock.

The Wilson Grove Formation represents the main waterbearing unit due to its extent, high porosity, and moderate 

transmissivity (Cardwell, 1958). The Wilson Grove Formation 

shallow-marine deposits, derived from the Franciscan group, 

range between 300 to 2000 ft total thickness. 

Mean annual precipitation in the study area, at Graton, 

California, is 42 in. with a mean annual temperature of 

57o F. The WG study area is drained by the Salmon, Americano, and Stemple Creeks (fig. 5). Sources of ground-water 

recharge include percolation of precipitation, and river and 

stream runoff.

Hydrologic Setting of the North San Francisco Bay GAMA Study Unit 7
Figure 3. The Valley and Plains study area showing the locations of the randomized public-supply wells and flow-path 

wells sampled for the North San Francisco Bay GAMA study, California.

8 Ground-Water Quality Data, North San Francisco Bay Hydrologic Provinces, California, 2004: GAMA Program Results

EXPLANATION

Valley and plains

 study area

Figure 3

Randomized Valley and Plains well sampled

0 5

0 5 10 Kilometers

10 Miles

123°00' 122°30'

38°

30'

Base from U.S. Geological Survey digital elevation

data, 1999, Albers Equal-Area Conic Projection.

38°

00'

Lake Berryessa

Sonoma Creek

Russian River

Soda Creek

Napa River

Cache Creek

Petaluma River

Stemple Cr.

Salmon Cr.

Americano Cr.Americano Cr.

Laguna de Santa Rosa River

San Pablo Bay

Drakes Bay

PACIFIC OCEAN

CONTRA COSTA

COUNTY

LAKE

COUNTY

YOLO

COUNTY

NAPA

SONOMA COUNTY

COUNTY

SOLANO

COUNTY

MARIN

COUNTY

MENDICINO COUNTY

North San Francisco Bay

 GAMA study unit boundary

")

")

")

")

 Randomized sampling grid cell 

 Flow-path well sampled

NSFVP-30

NSFVP-31

NSFVP-29

NSFVP-42

NSFVP-18

NSFVP-08

NSFVP-11

NSFVP-10

NSFVP-14

NSFVP-12

NSFVP-03

NSFVP-15

NSFVP-23

NSFVP-05

NSFVP-07

NSFVP-04

NSFVP-06

NSFVP-01

NSFVP-21

NSFVP-35

NSFVP-22

NSFVP-43

NSFVP-34

NSFVP-27

NSFVP-37

NSFVP-28

NSFVP-47

NSFVP-39

NSFVP-50

NSFVP-46

NSFVP-32

NSFVP-33

NSFVP-45

NSFVP-41

NSFVP-49

NSFVP-40

NSFVP-48

NSFVP-44

NSFVP-38

NSFVP-36

NSFVP-02

NSFVP-24

NSFVP-20

NSFVP-16

NSFVP-25

NSFVP-13

NSFVP-09

NSFVP-19

NSFVP-17

NSFVP-26

Lake Berryessa

Santa

Rosa

Sebastopol

Sonoma

Napa

NSFWGFP-01

NSFVPFP-04

NSFVPFP-03

NSFVPFP-02

NSFVPFP-01
Figure 4. The Volcanic Highlands study area showing the randomized sampling grid cells and locations of the 

randomized public-supply wells sampled for the North San Francisco Bay GAMA study, California.

Hydrologic Setting of the North San Francisco Bay GAMA Study Unit 9

Figure 4

LAKE

COUNTY YOLO

COUNTY

NAPA

COUNTY

SONOMA

COUNTY

SOLANO

COUNTY

MARIN

COUNTY

 Randomized sampling grid cell

∀)

∀)

∀)

Lake Berryessa

Santa 

Rosa

Napa

Sonoma

Sonoma

Creek

Napa River

38°

30'

38°

20'

38°

10'

38°

40'

122°40' 122°30' 122°20' 122°10'

Base from U.S. Geological Survey digital elevation

data, 1999, Albers Equal-Area Conic Projection.

0 5

0 5 10 Kilometers

10 Miles

EXPLANATION

Volcanic Highlands study area

North San Francisco Bay Randomized well sampled

 GAMA study unit boundary

NSFVP-37

NSFVOL-19

NSFVOL-17

NSFVOL-16

NSFVOL-15

NSFVOL-14

NSFVOL-12 NSFVOL-13

NSFVOL-11

NSFVOL-10

NSFVOL-09

NSFVOL-08

NSFVOL-07

NSFVOL-06

NSFVOL-05

NSFVOL-04

NSFVOL-03

NSFVOL-02

NSFVOL-18

NSFVOL-20

NSFVOL-1
Figure 5. The Wilson Grove Formation Highlands study area, randomized sampling grid cells, and the locations of the 

randomized public-supply wells and flow path well sampled for the North San Francisco Bay GAMA study, California.

10 Ground-Water Quality Data, North San Francisco Bay Hydrologic Provinces, California, 2004: GAMA Program Results

SONOMA

COUNTY

MARIN

COUNTY

Americano Cr. ericano Cr.

Salmon Cr.

Stemple Cr.

 Randomized sampling grid cell

")

")

Santa Rosa

Sebastopol

PACIFIC

OCEAN

EXPLANATION

Wilson Grove Formation Highlands

 study area

Randomized well sampled

North San Francisco Bay

 GAMA study unit boundary

NSFWG-14

NSFWG-13

NSFWG-12

NSFWG-11

NSFWG-10

NSFWG-09

NSFWG-08

NSFWG-07

NSFWG-06

NSFWG-05

NSFWG-04

NSFWG-03

NSFWG-02

NSFWG-01

NSFWGFP-01

123°00'

38°

30'

38°

15'

0 5 Miles

0 5 Kilometers

Base from U.S. Geological Survey digital elevation

data, 1999, Albers Equal-Area Conic Projection.

123°15'

Figure 5

 Flow-path well sampled
Hydrothermal Study

The hydrothermal (HOT) study involved the characterization of 7 hydrothermal wells and 1 hydrothermal spring 

(fig. 6). Five hydrothermal wells were sampled in the northern 

Napa Valley near the city of Calistoga, 2 hydrothermal wells 

were sample in Sonoma Valley near Aqua Caliente, and 1 

hydrothermal spring (NSFHOT-08) was sampled east of Saint 

Helena in hills composed of Cretaceous and Jurassic Franciscan complex rocks (Cardwell, 1958).

The wells and spring sampled for the hydrothermal study 

are used for mineral baths, not for drinking water supply. 

These wells are not included in the statistical treatment of the 

data as they are not public-supply drinking-water wells.

Methods

Sampling Design

The North San Francisco Bay study was designed to 

provide a spatially-unbiased assessment of ground-water quality within the study unit, as well as a statistically-consistent 

basis for comparing water quality in different study units. The 

results of this study will provide the data to assess the status, 

or current quality of the ground-water resource.

Ground-water basins identified by the Department of 

Water Resources (California Department of Water Resources, 

2003) were used to define the study area boundaries (fig. 2), 

except in the case of the VOL study area (fig. 4). The boundary for the VOL study area was designated by the area within 

about 2 mi of a public-supply well, completed in the volcanic 

formation. For a spatially unbiased and consistent assessment 

of ground-water quality (Scott, 1990), each of the study areas 

(not including the hydrothermal study) was subdivided into 

grid cells approximating 10 mi2 (fig. 2B). 

For this assessment, the VP study area was divided into 

60 grid cells, the WG study area into 20 grid cells, and the 

VOL study area into 20 grid cells. If a grid cell contained 

more than one public-supply well, each well in that grid cell 

was randomly assigned a rank. In each grid cell with multiple 

wells, the highest ranked well was given priority for sampling. 

In this fashion, a public-supply well was selected in each cell 

to provide a spatially distributed, randomized monitoring 

network for each study area. Wells sampled as part of the gridcell network are hereafter referred to as randomized wells. An 

attempt was made to select one well per grid cell, however, 

some grid cells did not contain accessible wells. Wells from 

adjacent cells were selected to account for grid cells that had 

no active wells. Initial target wells (fig. 2B) were obtained 

from statewide databases maintained by the USGS and the 

California Department of Health Services.

Additional wells were sampled for focused studies specific to an area, including the source of high-salinity waters in 

the southern lowlands area, the contribution of hydrothermal 

water to the ground-water system in the Napa and Sonoma 

Valleys (hydrothermal study), and the source and movement of 

ground water in the Alexander, Napa, Sonoma, and Santa Rosa 

Valleys (flow paths) (figs. 3, 4, 6). Wells sampled as part of the 

focused studies were not included in the statistical characterization of water quality in the NSF study unit.

Randomized wells sampled as part of the NSF GAMA 

study unit were numbered with the following prefixes based 

on study area: The Valley and Plains study area (NSFVP), the 

Wilson Grove Formation Highlands study area (NSFWG), 

and the Volcanic Highlands study area (NSFVOL). Additional 

(non randomized) wells were sampled as part of the hydrothermal study (NSFHOT), and in the Valley and Plain and Wilson 

Grove study areas in order to ascertain ground-water quality 

along flow paths; these wells were given the designations 

NSFVPFP and NSFWGFP. 

Table 1 provides the GAMA-id (alphanumeric identification number) for each well, along with the sampling schedule, 

time and data sampled and well-construction information. 

Ground-water samples were collected from 89 public-supply 

wells, 7 hydrothermal wells, and 1 hydrothermal spring from 

August to November 2004. Of the 89 public-supply wells 

sampled, 54 were in the Valley and Plains study area, 15 in the 

Wilson Grove Formation Highlands study area, and 20 in the 

Volcanic Highlands study area. Seven hydrothermal wells and 

1 hydrothermal spring, which are used for recreational supply, 

were sampled for the hydrothermal study. 

For this study, raw (untreated) ground-water samples 

were analyzed for 88 volatile organic compounds (VOCs), 

122 pesticide and pesticide degradates, 63 waste-water 

indicators, 25 trace elements, 9 major and minor ions, 8 

isotopic constituents, 5 noble gases, 5 nutrients, 3 constituents of special interest [N-nitrosodimethylamine (NDMA), 

trichlorpropane (TCP), and perchlorate], dissolved organic 

carbon (DOC), dissolved methane, oxygen, nitrogen and 

carbon dioxide, and the microbial constituents coliform and 

coliphage (tables 2A-L). General water-quality indicators that 

were determined in the field are dissolved oxygen (DO), pH, 

specific conductance (SC), alkalinity, and temperature.

Results of analyses were tabulated as concentrations 

measured in the raw water samples. Concentrations of the constituents were compared to established maximum contaminant 

level (MCL), secondary maximum contaminant level (SMCL), 

California notification level (NL) and detection level for the 

purpose of reporting (DLR).

Methods 11
Figure 6. The hydrothermal study wells and spring sampled for the North San Francisco Bay GAMA study, California.

12 Ground-Water Quality Data, North San Francisco Bay Hydrologic Provinces, California, 2004: GAMA Program Results

")

")

Napa

!(

!( !(

!(

!(

Figure 6

Valley and Plains

Volcanic Highlands

Wilson Grove Formation Highlands

EXPLANATION

North San Francisco Bay GAMA

 study unit boundary

Hydrothermal study well 

 or spring sampled

Study Areas

Base from U.S. Geological Survey digital elevation

data, 1999, Albers Equal-Area Conic Projection.

NSFHOT-05

122°40' 122°30'

38°

30'

38°

20'

NSFHOT-07

NSFHOT-06

NSFHOT-05

NSFHOT-04

NSFHOT-01

NSFHOT-02, 03

0 5 Miles

0 5 Kilometers

NSFHOT-08

Santa

Rosa

Sonoma

Sonoma

Creek

Calistoga

Saint Helena

Agua Caliente
Sample Collection

Eighty-nine public-supply wells were sampled in the 

Valley and Plains, Wilson Grove Formation Highlands, and 

Volcanic Highlands study areas, which comprise the NSF 

study unit. During the course of this study, target wells were 

sampled on either an expanded, basic, basic-plus, or hydrothermal schedule (table 3). The expanded schedule included 

analyses of 361 constituents and 19 additional water-quality 

indicators (tables 2A-L). The basic schedule included analyses 

for 302 constituents and 2 water-quality indicators, while the 

basic plus schedule added major and minor ions, trace elements, and dissolved gases to the basic schedule. 

An attempt was made to sample wells that were located 

in areas of special interest, such as along flow paths (based on 

potentiometric surfaces), using the expanded schedule. In the 

NSF study unit, 25 percent of the ground-water wells were 

sampled on the expanded schedule, 12 percent were sampled 

on the basic-plus schedule, and 63 percent on the basic schedule. Wells along flow paths were sampled using the expanded 

or basic-plus schedules. Wells in the Napa Valley and the 

Napa-Sonoma Lowlands (fig. 3) were sampled using the basicplus schedule. Hydrothermal wells and springs were sampled 

using the hydrothermal schedule, which included dissolved 

gases, tritium, major and minor ions and chromium analyses.

Samples were collected using the USGS National Water 

Quality Assessment (NAWQA) program protocols (Koterba 

and others, 1995; U.S. Geological Survey, variously dated). 

These sampling protocols ensure that a representative sample 

of ground water was collected at each site and that the samples 

were collected and handled in a way that minimized the 

potential for airborne contamination of samples and (or) cross 

contamination between samples collected at wells. Additional 

details on sample collection may be found in the analytical 

methods references discussed in the Sample Analysis section.

Prior to sampling, each well was pumped continuously 

in order to purge at least three casing-volumes of water from 

the well. Samples were collected before filtration or chemical 

treatment, such as chlorination. If a chlorinating system was 

attached to the well, the chlorinator was shut off at least 24 hrs 

prior to purging and sampling the well. 

For ground-water sample collection, Teflon tubing was 

affixed to the hosebib or sampling port closest to the well head 

using stainless steel fittings. For the basic schedule, samples 

were collected at the well head using a 12-in. length of Teflon 

tubing.

For the expanded schedule, the samples were collected 

inside an enclosed chamber located inside a mobile laboratory 

and connected to the well head by a 10 to 50 ft length of the 

Teflon tubing. Under the expanded schedule, ground water 

was pumped through a flow-through chamber fitted with a 

multi-probe meter that simultaneously measures the following water-quality indicators: DO, temperature, pH, turbidity, 

and specific conductivity (SC). Ground-water samples were 

collected when the temperature, DO, and pH values being 

measured remained stable for 20 minutes.

Ground-water samples were filtered in the field using 

a 0.45-μm capsule or disk filter. Polyethylene bottles were 

pre-rinsed using native water three times before sample collection. Some samples were preserved with acid, to a pH of 

2 or less. Temperature sensitive samples were stored on ice 

prior to daily shipping to the various laboratories. The nontemperature sensitive samples for tritium, noble gases, stable 

isotopes, and carbon isotopes were shipped monthly, while 

radium isotopes, gross alpha/ beta, and radon-222 samples 

were shipped daily. 

 Volatile organic compounds (VOCs) and gasoline 

additives and (or) oxygenates (tables 2A, 2B, at the back of 

this report) were collected in 40-mL sample vials that were 

purged with three vial volumes of sample water before bottom 

filling to eliminate atmospheric contamination. Six normal 

(N) hydrochloric acid (HCl) was added as a preservative to 

the VOC samples, but not to the gasoline additives and (or) 

oxygenate samples. Pesticides, pesticide degradation products 

(tables 2C, 2D), waste-water indicators (table 2E), trichloropropane (1,2,3-TCP), and N-nitrosodimethylamine (NDMA) 

(table 2F) were collected in 1-L baked amber bottles; these 

samples were filtered at their respective laboratories prior to 

analysis. Perchlorate and nutrient samples each were filtered 

into 125-mL polyethylene bottles (tables 2F, 2G). DOC was 

collected at the well head after rinsing the sampling equipment 

using water from the sampling port that was filtered using 

a 50-mL syringe and 0.45-μm disk filter. The ground water 

sample then was filtered into a 125-mL baked glass bottle and 

preserved with 4.5 N sulfuric acid (table 2G). 

Ground-water samples for the analysis of major and 

minor ions, and trace elements were collected by filtering 

ground water into two 250-mL polyethylene bottles, and then 

preserving one bottle with 7.5 N nitric acid (table 2H). Arsenic and iron speciation samples were filtered into a 250-mL 

polyethylene bottle that was covered with tape to prevent light 

exposure, and preserved with 6N HCl (table 2I). 

Chromium, radon-222, tritium, and dissolved gases were 

collected from the hosebib at the well head, regardless of the 

sampling schedule (expanded, basic, or basic-plus). Chromium 

speciation samples were collected using a 10-mL syringe with 

an attached 0.45-μm disk filter. After the syringe was thoroughly rinsed and filled with ground water, 4 mL was forced 

through the disk filter, the next 2 mL of the ground water was 

slowly filtered into a small centrifuge vial for analysis of total 

chromium (table 2I). Hexavalent chromium, Cr(VI) was then 

collected by attaching a small cation exchange column to the 

syringe filter, and after conditioning the column with 2 mL of 

sample water, 2 mL was collected in a second centrifuge vial. 

Both vials were preserved with 10 μL of 7.5 N nitric acid (Ball 

and McClesky, 2003).

Methods 13
Tritium samples were collected at the well head by bottom filling two 1-L glass bottles with unfiltered ground water, 

after first rinsing the bottle with three volumes of water

(table 2J). Stable isotopes of water were collected in 60-mL 

clear glass bottles filled with unfiltered water, sealed with a 

conical cap, and secured with electrical tape to prevent leakage 

and evaporation (table 2J). Radium isotopes and gross alpha/ 

beta samples were collected and preserved in the same manner 

as major and minor ions, except 2 and 1-L aliquots of ground 

water were taken, respectively (table 2J). Mercury samples 

were collected by filtering ground water into a 250-mL glass 

bottle and preserving with 6 N HCl. Carbon isotope samples 

were filtered and bottom filled into two 500-mL baked glass 

containers that were first rinsed with three bottle volumes of 

ground water (table 2J). These samples had no headspace, and 

were sealed with a conical cap to avoid atmospheric contamination. Samples for alkalinity were collected by filtering 

ground water into a 500-mL polyethylene bottle.

For the collection of radon-222, a stainless steel and 

Teflon valve assembly was attached to the sampling port at the 

well head. The valve was partially closed to create back pressure, and a 10-mL sample was taken through a Teflon septum 

on the value assembly using a glass syringe affixed with a 

stainless steel needle. The sample was then injected into a 

25-mL vial partially filled with scintillation cocktail (mineral 

oil) and shaken. The vial was then placed in a cardboard tube 

in order to shield it from light during shipping (U.S. Geological Survey, variously dated). 

Noble gases were collected in 3/8 in. ID copper tubes 

using reinforced nylon tubing connected to the hosebib at the 

wellhead (table 2K). Ground water was flushed through the 

tubing to dislodge bubbles before flow was restricted with a 

back pressure valve. Clamps on either side of the copper tube 

were then tightened, trapping a sample of ground water for 

analyses of noble gases (Weiss, 1968). Dissolved gas (CH4, 

CO2, O2, Ar, and N2) samples were collected in 40-mL, amber 

glass vials (USEPA VOA vials with screw-top septa). The 

vials were filled to the top with no headspace, and bubbles 

(atmospheric contamination) were carefully avoided. Samples 

were taken in triplicate.

Microbial constituents also were collected at the well 

head (table 2L). Prior to the collection of samples, the sampling port was sterilized using isopropyl alcohol, and ground 

water was run through the sampling port for at least three 

minutes to remove any traces of the sterilizing agent. Two sterilized 250-mL bottles were then filled with ground water for 

coliform analyses (total and Escherichia coliform determinations), and one sterilized 3-liter carboy was filled for coliphage 

analyses (F specific and somatic coliphage determinations).

Sample Analysis

Nine laboratories performed chemical and microbial 

analyses for the NSF GAMA study. The following analytical methods were employed for the determination of organic 

and inorganic analytes by the USGS National Water-Quality 

Laboratory (NWQL): VOCs were measured by purge and trap 

capillary gas chromatography-mass spectrometry (Connor 

and others, 1998); gasoline additives and (or) oxygenates by 

heated purge and trap, gas chromatography-mass spectrometry (Rose and Sandstrom, 2003); pesticides by solid-phase 

extraction and chromatography-mass spectrometry (Furlong 

and others, 2001; Sandstrom, and others, 2001); waste-water 

indicators by polystyrene-divinylbenzene solid-phase extraction and capillary-column gas chromatography-mass spectrometry (Zaugg and others, 2002); major and minor ions, 

trace elements, and nutrients by inductively coupled plasma 

mass spectrometry (ICP-MS), graphite furnace atomic absorption (GFAA), atomic fluorescence (AF), and colorimitetry 

(Fishman and Friedman, 1989; Fishman, 1993; Garbarino, 

1999; Garbarino and Damrau, 2001; and Patton and Kryskalla, 

2003); DOC by UV-promoted persulfate oxidation and infrared spectrometry (Brenton and Arnett, 1993); radon-222 by 

liquid scintillation counting (American Society for Testing and 

Materials, 1998a,b); dissolved solids by weighing the sample 

residue on evaporation at 180°C (Fishman and Friedman, 

1989).

The following methods were used for analyses of organic 

and inorganic constituents and microbial constituents by 

laboratories other than the NWQL: Perchlorate, NDMA, and 

1,2,3-trichloropropane analysis by Montgomery Watson and 

Harza Laboratory using chromatography and mass spectrometry (U.S. Environmental Protection Agency, 1996; Hautman and others, 1999); stable isotopes of water by the USGS 

Reston Stable Isotope Laboratory using gaseous hydrogen 

and carbon dioxide-water equilibration (Coplen and others, 

1991; Coplen, 1994); chromium, iron, and arsenic analysis 

by the USGS National Research Program (NRP) laboratory 

in Boulder, Colorado, using UV-VIS spectrophotometery and 

atomic absorption spectroscopy (To and others, 1998; Ball and 

McClesky, 2003; McCleskey and others, 2003); F-specific and 

somatic coliphage analysis by the USGS Ohio Microbiology 

Laboratory (U.S. Environmental Protection Agency, 2001); 

tritium analysis at the USGS NRP Laboratory, Menlo Park, 

California, using electrolytic enrichment-liquid scintillation 

method (Thatcher and others, 1977); tritium (helium-3 ingrowth method) and noble gases using accelerator mass spectrometry at LLNL (Clarke and others, 1976; Moran and others, 

2002); dissolved gas (Ar, CH4, CO4, N2, O2) analyses, also at 

LLNL, were carried out on a Membrane Inlet Mass Spectrometer (Kana and others, 1994); radium-226, radium-228, gross 

alpha and beta radioactivity analysis by Eberline Analytical 

Services using alpha activity counting method (U.S. Environmental Protection Agency, 1980); carbon isotopes analysis by 

the University of Arizona at the Accelerated Mass Spectrometry Laboratory (Donahue and others, 1990; Jull, and others, 

2004); total and Escherichia coliform analyzed by USGS in 

the mobile lab by counting colonies (U.S. Environmental 

Protection Agency, 2002b).

14 Ground-Water Quality Data, North San Francisco Bay Hydrologic Provinces, California, 2004: GAMA Program Results
Ground-water samples for arsenic and iron were analyzed 

at two different laboratories; total concentrations were measured at the NWQL in Denver, Colorado, while speciation was 

measured at the USGS National Research Program (NRP) Lab 

in Boulder, Colorado. Cr also was analyzed in ground-water 

samples at the NRP laboratory. The NRP laboratory method 

determines chromium speciation, including analysis for 

hexavalent chromium, which is classified as an unregulated 

contaminant monitoring regulation (UCMR) compound.

Alkalinity and the concentrations of bicarbonate 

(HCO3

-

) and carbonate (CO3

2-) were measured on filtered 

samples by gran titration method (U.S. Geological Survey, 

variously dated). Turbidity, pH, SC, and temperature were 

measured in the field with calibrated instruments. Total 

coliforms and Escherichia coliform (E. coli) were counted, 

following a 22–24 hour incubation time, under an ultraviolet 

light.

Data Reporting 

Laboratory Reporting Conventions

The USGS NWQL uses the laboratory reporting level 

(LRL) as a threshold for reporting analytical results. The LRL 

is set to minimize the reporting of false negatives (not detecting a compound when it is actually present in a sample) to 

less than 1 percent (Childress and others, 1999). The LRL is 

set at two-times the long-term method detection level (LTMDL), which is the average (long term) MDL calculated from 

multiple analytical measurements (> 50). The method detection limit (MDL) is the minimum concentration of a substance 

that can be measured and reported with 99 percent confidence 

that the concentration is greater than zero (at MDL there is less 

than 1 percent chance of a false positive) (U.S. Environmental 

Protection Agency, 2002a). 

Detections below the LRL are reported as estimated 

concentrations (designated with an “E” before the value in the 

tables and text). For information-rich methods (including the 

VOC method used in this study), detections below LT-MDL 

also are reported as E-values. E-values also result from detections outside the range of calibration standards, for detections 

that did not pass laboratory quality-control analyses, and for 

samples that were diluted prior to analysis.

Some compound concentrations in this study are reported 

using minimum reporting levels (MRLs) or method uncertainties. The MRL is the smallest measurable concentration of a 

constituents the may be reliably reported using a given analytical method (Timme, 1995). The method uncertainty generally 

indicates the precision of a particular analytical measurement; 

it gives a range of values wherein the true value will be found.

Constituents on Multiple Analytical Schedules

Twenty three constituents targeted in the NSF GAMA 

study are determined by more than one analytical schedule 

(table 4). Method preference is determined by the analyzing agency (http://wwwnwql.cr.usgs.gov/USGS/Preferred_

method_selection_procedure.html). Results from certain 

analytical schedules are preferred over others because the 

methodology is more accurate and precise, and generally 

yields a greater sensitivity for a given compound. If a compound appears on multiple analytical schedules, then only the 

detections determined by the preferred analytical schedule are 

reported here.

Quality Control 

Quality-control (QC) samples collected in the NSF 

study include source-solution blanks, field blanks, equipment 

blanks, replicates, and matrix and surrogate spikes. QC samples were collected to evaluate bias and variability of the water 

chemistry data that may have resulted from sample collection, 

processing, storage, transportation, and laboratory analysis. 

Blanks

Blank samples (blanks) were collected using water 

(Nitrogen-Purged Universal blank water) certified to contain 

less than the LRL of MRL of the analytes investigated in the 

study. Three types of blanks were collected: source-solution, 

equipment, and field blanks. Source-solution blanks were collected to verify that the blank water used for equipment and 

field blanks was free of analytes. Equipment blanks were collected at the beginning of the study to determine the residual 

presence of analytes in the sampling equipment, such as if the 

fittings and tubing used to collect samples introduced contamination. The equipment blanks were collected at the beginning 

of the study at the USGS California Water Science Center in 

Sacramento, California. Field blanks were collected at 10 percent of the wells sampled to determine if procedures used in 

the field and (or) laboratory introduced contamination, and are 

analogous to equipment blanks collected in the field. Equipment and field blanks were analyzed for VOCs, pesticides, 

waste-water indicators, low-level nutrients, dissolved organic 

carbon, major and minor ions, and trace elements. 

Source-solution blanks were collected at the sampling 

site by pouring blank water directly into sample containers 

that were preserved, stored, shipped, and analyzed in the same 

manner as the ground-water samples. For equipment and field 

blanks, blank water was either pumped or poured through 

the sampling equipment (fittings and tubing) used to collect 

ground water, then processed and transported using the same 

protocols for the ground-water samples. 

Methods 15
If a constituent was detected in an equipment or field 

blank, the associated source-solution blank results were examined for similar constituent detections. If the field blank (or 

equipment blank) and the source-solution blank contained the 

constituent, then the source solution water was interpreted as 

the origin of the contamination in the blanks, and the field (or 

equipment) blank detections using the same blank water were 

disregarded. If a field blank detection could not be attributed 

to the source solution, then the ground-water samples collected prior to, and following the blank were evaluated. If the 

ground-water samples prior to or following the contaminated 

field blank had no detections, then carry-over contamination was ruled out. If an analyte was detected in a blank at a 

concentration greater than the concentration measured in a 

ground-water sample collected prior to or following the blank 

sample, then the ground-water value was censored (table 5). 

Censored values are indicated by a ‘V’ proceeding the value 

in the tables (12A–C, and 14), and are not considered in the 

summary statistics. If a compound was detected in multiple 

equipment and (or) field blanks, and the detections could not 

be attributed to the source-solution water, then any groundwater sample that had a detection of the compound in question 

was evaluated for possible contamination.

Replicates 

Sequential replicate samples assess variability that may 

result from the processing and analyses of inorganic and 

organic constituents. Relative standard deviation (RSD) of 

the measured values was used in determining the variability 

between replicate pairs for each compound (table 6A-E). The 

RSD is defined as 100 times the standard deviation divided by 

the mean concentration for each replicate pair of samples. If 

one value in a sample pair was reported as a non-detection and 

the other value was reported as an estimate below the LRL or 

MRL, the RSD was set to zero because the values are analytically identical. If one value in a sample pair was reported as 

a non-detection and the other value was greater than the LRL 

or MRL, then the non-detection value was set equal to onequarter of the LRL and the RSD was calculated (Childress and 

others, 1999). Estimated values were not used for these calculations. Values of RSD less than 20 percent are considered 

acceptable in this study (Fishman and Friedman, 1989). High 

RSD values for a compound may indicate analytical uncertainty at low concentrations, particularly for concentrations 

within an order of magnitude of LT-MDL or MDL. 

Matrix Spikes

Addition of a spike or known concentration of a constituent to a replicate environmental sample enables the analyzing 

laboratory to determine the effect of the matrix, in this case 

ground water, on the analytical technique used to measure the 

constituent. The known compounds added in matrix spikes 

are the same as those being analyzed in the method. This 

enables an analysis of matrix interferences on a compound by 

compound basis. Matrix spikes in the NSF GAMA study were 

added at the laboratory performing the analysis. Compounds 

with low recoveries (<70 percent) are of potential concern if 

environmental concentrations are close to the MCLs; a concentration below an MCL could be falsely indicated 

(table 7A-C). Conversely, compounds with high recoveries 

(>130 percent) are of potential concern if the environmental 

concentrations exceed MCLs: a high recovery could falsely 

indicate a concentration above the MCL. Recoveries between 

70 to 130 percent for matrix spikes were considered acceptable in this study (Fishman and Friedman, 1989).

Surrogates 

Surrogate compounds are added to environmental 

samples in the laboratory prior to analyses in order to evaluate the recovery of similar constituents. Surrogate compounds 

were added to all ground-water and quality-control samples 

that were analyzed for VOCs, gasoline additives and (or) 

oxygenates, pesticides, and waste-water indicators. Surrogates 

are not normally found in environmental samples and are 

used to identify potential problems associated with laboratory analyses. Potential problems include matrix interferences 

(such as high levels of dissolved organic carbon) that produce 

a positive bias, and (or) incomplete laboratory recovery (possibly due to improper maintenance and calibration of analytical equipment) that produces a negative bias. Surrogates are 

used to identify general problems that may arise during sample 

analysis that could affect the analysis results for all compounds, whereas matrix spikes are used to indicate problems 

with specific compound analysis. A 70 to 130 percent recovery of surrogates is generally considered acceptable. Values 

outside this range indicate possible problems with the processing and analysis of samples (table 8) (Fishman and Friedman, 

1989). 

16 Ground-Water Quality Data, North San Francisco Bay Hydrologic Provinces, California, 2004: GAMA Program Results
Results

Quality-Control Samples

Detections in Blanks

Equipment Blank

The equipment blank performed on August 31, 2004, 

contained the following VOC and waste-water indicators: 

ethylbenzene (E 0.06 μg/L), m-xylene plus p-xylene 

(0.29 μg/L), o-xylene (E 0.09 μg/L), toluene (0.1 μg/L), and 

phenol (0.6 μg/L). However, none of these constituents were 

observed in ground-water samples taken on the same day, 

prior to, or following the equipment blank detection, and 

therefore do not impact ground-water sample results. Also 

detected in the equipment blank taken on August 31, 2004, 

were calcium (0.01 mg/L), silica (0.04 mg/L), and arsenic 

(0.1 μg/L). However, the average concentrations of Ca, Si, 

and As observed in ground-water samples were 23 mg/L, 72 

mg/L, and 13 μg/L, respectively (table 15). The constituents 

detected in the equipment blank represent less than 1 percent 

of observed values, hence do not impact ground-water sample 

results. 

Field Blanks

In the NSF GAMA study unit, field blanks were 

collected at approximately 10 percent of the sites sampled. 

Table 5 presents a summary of compound detections in field 

blanks. The VOCs, and their maximum concentrations, 

detected in field blanks include acetone (E 2.9 μg/L), carbon 

disulfide (E 0.07 μg/L), ethylbenzene (E 0.06 μg/L), m-xylene 

plus p-xylene (0.29 μg/L), o-xylene (0.11 μg/L), and toluene 

(0.11 μg/L). Ground-water samples collected prior to, and 

following these field blanks were free from these constituents, 

hence no ground-water samples were censored as a result of 

these blank detections.

The pesticide compound atrazine, with a maximum 

estimated concentration of E 0.005 μg/L, also was detected in 

one field blank. Ground-water samples collected prior to, and 

following this blank were free from atrazine, hence none were 

censored. 

The waste-water indicators and their maximum concentrations detected in field blanks were naphthalene (E 0.04 

μg/L), phenol (E 1.1 μg/L), and triclosan (E 0.08 μg/L), 

respectively. For the constituents naphthalene and triclosan, 

ground-water samples collected prior to, and following these 

blanks were free from these constituents, hence no groundwater samples were censored. 

Eight field blank samples contained phenol with a maximum concentration of 1.1 μg/L, as did six source-solution 

blanks with a maximum concentration of 0.6 μg/L, and the 

equipment blank with a value of 0.6 μg/L. As a result of the 

high detection frequency for phenol in blank samples, and 

relatively high detection frequency for phenol in ground-water 

samples, minimum concentration detected E 0.23 μg/L, phenol 

has been removed from consideration in this study, so that further attention can be given to the analytical methodology. As 

a result, 48 ground-water sample detections for phenol were 

censored (table 5). Phenol concentrations observed in this 

study, maximum of 2.4 μg/L are far below the health advisory 

limit of 2,000 μg/L.

Two major ions and one minor ion were detected in field 

blanks, with maximum concentrations; Ca (E 0.02 mg/L), Si 

(0.06 mg/L), and I (0.001 mg/L), respectively. None of the 

ground-water samples had detections of Ca or Si lower than 

these values, hence none were censored. No ground-water 

samples prior to or following the blanks had concentrations of 

iodine lower than E 0.001 mg/L, hence no values were censored. Four trace elements were detected in field blanks, Al (E 

0.9 μg/L), Mn (E 0.1 μg/L), Ni (E 0.07 μg/L), and Zn (E 0.5 

μg/L). None of the ground-water samples had detections of Al, 

Ni, or Zn lower than these values, hence none were censored. 

Mn concentrations measured in ground-water samples ranged 

from 0.1 to 1,220 μg/L, however no detections in groundwater samples prior to or following the blanks had Mn concentrations lower than E 0.1 μg/L, hence no values were censored.

Dissolved organic carbon (DOC) was detected in 2 out of 

3 blanks, and as a result, ground-water samples with concentrations lower than 0.4 mg/L following the second blank were 

censored. Four ground-water sample DOC detections: E 0.3 

mg/L, 0.4 mg/L, 0.4 mg/L, and E 0.2 mg/L, following the 0.5 

mg/L blank detection, were censored (table 5).

Variability in Replicate Samples

The majority of replicate sample pairs collected during 

the NSF GAMA study had relative standard deviations (RSDs) 

of less than 20 percent (table 6A-E). Twenty-three replicate 

sample pairs representing 8 chemical constituents, 4 replicate 

sample pairs of radionuclides, and 9 replicate sample pairs of 

gross radioactivity in water, had RSDs greater than 20 percent; 

see tables 6A to 6E for details. However, the replicate sample 

pairs with high RSDs had very low measured concentrations, 

and at these low concentrations, small deviations in measured 

values account for large RSDs. Since the variability in measurements occurred at low concentrations, well below MCLs, 

this variability was not of QC concern, and no detections were 

censored as a result of variability in replicate sample samples.

Results 17
Matrix Spike Recoveries

Tables 7A to 7C present a summary of matrix spike 

recoveries for the NSF GAMA study. Addition of a spike or 

known concentration of a constituent to an environmental 

sample enables the analyzing laboratory to determine the 

effect of the matrix, in this case ground water, on the analytical technique used to measure the constituent. Nine environmental samples were spiked with VOCs to calculate matrix 

spike recoveries. Acceptable spike recovery values range 

between 70 and 130 percent (Friedman and Erdmann, 1982) 

(table 7A). Seventy-four of the 90 spike compounds had 

recoveries between the acceptable range of 70 and 130 percent. Fifteen spike compounds had at least one matrix spike 

recovery greater than 130 percent. Six of these 15 VOCs 

were detected in ground-water samples; 1,1,1-trichloroethane 

(TCA) was detected in 1 ground-water sample, acetone was 

detected in 1 ground-water sample, bromodichloromethane 

was detected in 1 ground-water sample, bromoform (tribromomethane) was detected in 1 ground-water sample, carbon disulfide was detected in 8 ground-water samples, and 

tetrachloromethane (carbon tetrachloride) was detected in 1 

ground-water sample. All detections in ground-water samples 

were at concentrations well below MCLs, and therefore are 

not of QC concern. Nitrosodimethylamine (NDMA) was the 

only spike compound that had a recovery below 70 percent, 

however it was not detected in ground-water samples (table 

13A). [NOTE – low recoveries may indicate that this compound was not detected in some samples if it was present at 

very low concentrations].

Five environmental samples were spiked with pesticide 

and (or) pesticide degradate compounds in order to calculate 

matrix spike recoveries. Acceptable spike recovery values 

range between 70 and 130 percent. Seventeen of the 64 spike 

compounds had recoveries between the acceptable range of 

70 and 130 percent (table 7B). Twelve spike compounds had 

recoveries greater than 130 percent. Of these 12 compounds, 

only atrazine was detected in ground-water samples. All 

detections in ground-water samples were at concentrations 

well below its MCL of 3 μg/L and, therefore, are not of QC 

concern. Thirty-eight spike compounds had recoveries below 

70 percent. Of these 38 spike compounds, 2 were detected in 

ground-water samples, deethyl atrazine (DEET) and trifluralin, at concentrations below 0.007 μg/L. Hence, if the poor 

spike recovery, even as low as 1 percent, reflects ground-water 

sample constituent recovery, reported values would still be 

below MCLs and this would not affect water-quality reporting. 

A single sample also was spiked with 63 compounds. Acceptable spike recovery values range between 70 and 130 percent. 

Fifty-one of the 63 compounds had recoveries between the 

acceptable range of 70 and 130 percent (table 7B); 2 were 

above the 130 percent limit, and 10 were below the 70 percent 

limit. None of these 12 spike compounds with poor recoveries 

were detected in ground-water samples (table 11B). [NOTE 

—low recoveries may indicate that this compound was not 

detected in some samples if it was present at very low concentrations].

Four environmental samples were spiked with wastewater indicator compounds to calculate matrix spike recoveries. Acceptable spike recovery values range between 70 and 

130 percent (Fishman and Friedman, 1989). Nine of the 63 

spike compounds had recoveries between the acceptable range 

of 70 and 130 percent (table 7C). Six spike compounds had 

at least one matrix spike recovery greater than 130 percent; of 

these 6, only phenol was detected in ground-water samples. 

Fifty-two spike compounds had at least one matrix spike 

recovery below 70 percent. Of the fifty-two compounds, 

bisphenol-A was detected in 3 ground-water samples, d-limonene was detected in 1 ground-water sample, ethoxyoctylphenol (OPEO1) was detected in 1 ground-water sample, indole 

was detected in 3 ground-water samples, menthol was detected 

in 1 ground-water sample, naphthalene was detected in 1 

ground-water sample, p-cresol was detected in 2 ground-water 

samples, phenol was detected in 47 ground-water samples, 

tetrachloroethene was detected in 3 ground-water samples, 

tribromomethane was detected in 2 ground-water samples, and 

triclosan was detected in 3 ground-water samples 

(table 12A-C). All compounds were detected at concentrations below the LT-MDL. D-limonene does not have an MCL. 

Hence, if the poor spike recovery, even as low as 1 percent, 

reflects ground-water sample constituent recovery, reported 

values would still be below MCLs and this would not affect 

water-quality reporting. [NOTE—low recoveries may indicate 

that this compound was not detected in some samples if it was 

present at very low concentrations].

Surrogate Compound Recoveries

Surrogate compounds were added to environmental 

samples in the laboratory and analyzed to evaluate the 

recovery of similar constituents. All 89 ground-water samples, 

18 replicate pairs and 13 blanks analyzed for VOCs on analytical schedule 2020 had recoveries of the surrogates 1,2-dichloroethane-d4, 1-bromo-4-fluorobenzene, and toluene-d8 that 

were between the acceptable limit of 70 and 130 percent 

(table 8). The 89 ground-water samples, 18 replicate pairs and 

13 blanks analyzed for VOCs on analytical schedule 4024 had 

recoveries of the surrogates 1,2-dichloroethane-d4, 1-bromo4-fluorobenzene, toluene-d8, and isobutyl alcohol-d6 that were 

between the acceptable limit of 70 and 130 percent (Fishman 

and Friedman, 1989). 

18 Ground-Water Quality Data, North San Francisco Bay Hydrologic Provinces, California, 2004: GAMA Program Results
All 87 ground-water samples, 19 replicate pairs and 11 

blanks analyzed for pesticide and pesticide degradates on 

analytical schedule 2003 had recoveries of the surrogate alphaHCH-d6 that were between the acceptable limit of 70 and 

130 percent (table 8). However, only 50 of the 87 groundwater samples had recoveries of the surrogate diazinon-d10 

that were between the acceptable limit of 70 and 130 percent; 

37 of the 87 ground-water samples, 8 of the 19 replicate pairs 

and 6 of the 11 blanks had recoveries of the surrogate diazinon-d10 that were below the acceptable limit of 70 percent 

recovery. None of the diazinon-d10 surrogate recoveries were 

above the acceptable limit of 130 percent in the ground-water 

samples, replicate pairs, and blanks. Eight of the 16 groundwater samples with detections of pesticides or pesticide degradates had recoveries of the surrogate diazinon-d10 that were 

below the acceptable limit of 70 percent recovery, however, 

the concentrations of the pesticide and pesticide degradate 

compounds measured in these eight ground-water samples 

were <0.2 μg/L, well below MCLs. Hence, if the poor surrogate recovery, even as low as 1 percent, reflects ground-water 

sample constituent recovery, reported values would still be 

below MCLs and this would not affect water-quality reporting.

The 22 ground-water samples, 7 of the 8 replicate pairs, 

and 4 blanks analyzed for pesticide and pesticide degradates 

on schedule 2003 had recoveries of the herbicide surrogate 

2,4,5-T (2,4,5-trichlorophenoxyacetic acid), that were between 

the acceptable limit of 70 and 130 percent (table 8); one replicate pair had a recovery of the surrogate 2,4,5-T that was 66 

percent. However, all ground-water samples with detections 

of pesticides or pesticide degradates had recoveries of the surrogate 2, 4, 5-T that were between the acceptable limit of 70 

and 130 percent. 

Twenty-one of the 22 ground-water samples, 8 replicate 

pairs, and 4 blanks analyzed for pesticide and pesticide degradates on schedule 2003 had recoveries of the surrogate Barban 

that were between the acceptable limit of 70 and 130 percent 

(table 8); one ground-water sample with a detection of pesticide or pesticide degradates had a recovery of the surrogate 

Barban that was 59 percent.

Thirteen of the 22 ground-water samples, 3 of the 8 

replicate pairs and 1 of the 4 blanks analyzed for pesticide and 

pesticide degradates on schedule 2003 had recoveries of the 

surrogate caffeine-13C that were between the acceptable limit 

of 70 and 130 percent (table 8). Nine ground-water samples, 

5 replicate pairs, and 3 blanks had recoveries of the surrogate 

caffeine-13C that were greater than 130 percent. Two groundwater samples with a detection of pesticide or pesticide degradates had recoveries of the surrogate caffeine-13C that were 

greater than 130 percent, however, no ground-water samples 

had measured pesticide and (or) pesticide degradates above 

MCL limits, and hence, amplified surrogate recovery did not 

affect water-quality reporting.

Two of the 89 ground-water samples, none of the 19 

replicate pairs, and none of the 21 blanks analyzed for wastewater indicators on schedule 1433 had recoveries of the surrogate bisphenol A-d3 that were between the acceptable limit of 

70 and 130 percent (table 8); 87 of the 89 ground-water samples, 19 replicate pairs and 21 blanks analyzed for waste-water 

indicators on schedule 1433 had recoveries of the surrogate 

bisphenol A-d3 that were less than the acceptable limit of 70 

percent. None of the bisphenol A-d3 surrogate recoveries were 

above the acceptable limit of 130 percent in the ground-water 

samples, replicate pairs, and blanks. Fifty of the 52 groundwater samples with detections of waste-water indicators had 

recoveries of the surrogate bisphenol A-d3 that were below the 

acceptable limit of 70 percent surrogate recovery, however, 

the concentrations of the waste-water indicators measured in 

these 26 ground-water samples were <1.4 μg/L, much below 

MCLs. Hence, if the poor surrogate recovery, even as low as 

1 percent, reflects ground-water sample constituent recovery, 

reported values would still be below MCLs and this would not 

affect water-quality reporting.

Seventy-six of the 89 ground-water samples, 15 of the 

19 replicate pairs and 17 of the 21 blanks analyzed for wastewater indicators on analytical schedule 1433 had recoveries of 

the surrogate caffeine-13C that were between the acceptable 

limit of 70 and 130 percent (table 8); 13 of the 89 groundwater samples, 4 of the 19 replicate pairs and 4 of the 21 

blanks analyzed for waste-water indicators had recoveries of 

the surrogate caffeine-13C that were less than the acceptable 

limit of 70 percent. None of the caffeine-13C surrogate recoveries were above the acceptable limit of 130 percent in the 

ground-water samples, replicate pairs, and blanks. Three of the 

52 ground-water samples with detections of waste-water indicators had recoveries of the surrogate caffeine-13C that were 

below the acceptable limit of 70 percent recovery, however, 

concentrations of waste-water indicator constituents measured in ground-water samples were <3.0 μg/L, well below 

MCLs. Hence, if the poor surrogate recovery, even as low as 

1 percent, reflects ground-water sample constituent recovery, 

reported values would still be below MCLs and this would not 

affect water-quality reporting.

None of the 89 ground-water samples, 19 replicate pairs 

and 21 blanks analyzed for waste-water indicators on analytical schedule 1433 had recoveries of the surrogate decafluorobiphenyl that were between the acceptable limit of 70 and 130 

percent (table 8); 89 ground-water samples, 19 replicate pairs 

and 21 blanks analyzed for waste-water indicators had recoveries of the surrogate decafluorobiphenyl that were less than 

the acceptable limit of 70 percent. None of the decafluorobiphenyl surrogate recoveries were above the acceptable limit 

of 130 percent in the ground-water samples, replicate pairs, 

and blanks. Twenty-four ground-water samples with detections of waste-water indicators had recoveries of the surrogate 

decafluorobiphenyl that were below the acceptable limit of 

70 percent recovery, however concentrations of waste-water 

indicators measured in ground-water samples were <3.0 μg/L, 

well below MCLs. Hence, if the poor surrogate recovery, even 

as low as 1 percent, reflects ground-water sample constituent 

recovery, reported values would still be below MCLs and this 

would not affect water-quality reporting.

Results 19
Eighty-five of the 89 ground-water samples, 17 of the 

19 replicate pairs and 21 blanks analyzed for waste-water 

indicators on analytical schedule 1433 had recoveries of the 

surrogate fluoranthene-d10 that were within the acceptable 

range of 70 and 130 percent (table 8); 4 of the 89 groundwater samples, 2 of the 19 replicate pairs and none of the 21 

blanks analyzed for waste-water indicators had recoveries of 

the surrogate fluoranthene-d10 that were less than the acceptable limit of 70 percent (table 8). None of the fluoranthened10 surrogate recoveries were above the acceptable limit of 

130 percent in the ground-water samples, replicate pairs, and 

blanks. Two of the 52 ground-water samples with detections 

of waste-water indicators had recoveries of the surrogate 

fluoranthene-d10 that were below the acceptable limit of 70 

percent recovery; however, concentrations of waste-water 

indicators measured in ground-water samples were <3.0 μg/L, 

well below MCLs. Hence, if the poor surrogate recovery, even 

as low as 1 percent, reflects ground-water sample constituent 

recovery, reported values would still be below MCLs and this 

would not affect water-quality reporting.

All 87 ground-water samples, 12 replicate pairs and 

4 blanks analyzed for constituents of special interest had 

recoveries of the surrogate toluene-d8 that were between the 

acceptable limit of 70 and 130 percent (table 8). Fifty-two of 

the 87 ground-water samples, 5 of the 12 replicate pairs and 

1 of the 4 blanks analyzed for constituents of special interest 

had recoveries of the surrogate fluoranthene-d10 that were 

between the acceptable limit of 70 and 130 percent; 52 of 

the 87 ground-water samples, 7 of the 12 replicate pairs and 

3 of the 4 blanks analyzed for constituents of special interest 

all had recoveries of the surrogate NDMA-d6 that were less 

than the acceptable limit of 70 percent. One of the 87 groundwater samples, 2 of the 12 replicate pairs and 1 of the 4 blanks 

analyzed for constituents of special interest had recoveries of 

the surrogate NDMA-d6 that were greater than the acceptable 

limit of 130 percent. No constituents of special interest 

(table 2F) were detected in NSF study unit ground-water 

samples.

Ground-Water Quality

Results from raw (untreated) ground-water analyses for 

the NSF GAMA study are presented in tables 9 to 22, at the 

end of this report. Table 9 includes water-quality indicators 

measured in the field, while tables 10–22 present the results 

of ground-water analyses organized by the compound types 

and classes: VOCs and gasoline additives and (or) oxygenates, 

pesticides and pesticide degradates, waste-water indicators, 

constituents of special interest, nutrients, major and minor 

ions, trace elements, arsenic and iron, chromium, isotopes and 

radioactivity, and microbial constituents. The summary tables 

present only the constituents that were detected, and only 

wells that had at least one compound detected. The tables are 

organized by study area, in which, rows list the GAMA identification number for each well. The columns list the constituents detected, the associated USGS parameter code used to 

identify the compound and store the information in a computerized database (NWIS), and method of measurement and the 

laboratory reporting level (LRL) for which the compound may 

be detected. 

The tables include the measured concentration of each 

constituent, the number of wells at which it was detected, the 

frequency at which it was detected (in relation to the total 

number of randomized wells sampled in the study area), the 

total number of constituents detected at each well, the total 

number of detections in each study area, and the detection 

frequency by compound class. Results from the flow-path 

wells and hydrothermal wells are listed in the tables, but these 

results are not included in statistical compilations because 

these wells were not part of the randomized well selection. 

Detections that have concentrations or activities above 

the maximum contaminant level (MCL) are indicated in the 

tables by bold font; detections that have concentrations or 

activities above the secondary maximum contaminant level 

(SMCL) are indicated in the tables by italicized and bold font; 

detections that have concentrations or activities above the notification level or the detection level for the purpose of reporting 

(DLR) are indicated in the tables by italicized font.

VOCs and Gasoline Additives and (or) 

Oxygenates

Analytical results of VOCs and gasoline additives and 

(or) oxygenates from schedules 2020 and 4024 were combined in tables 10A-C, which report results from the preferred 

analytical method. Ground-water samples for VOCs and 

gasoline additives and (or) oxygenates were collected at 89 

public-supply wells sampled in the NSF GAMA study unit. 

Twenty-one VOCs and gasoline additives and (or) oxygenates 

were detected in 29 wells in the NSF study unit. Thirty-three 

percent of the 89 wells sampled had at least one detection of a 

VOC and gasoline additive and (or) oxygenate. Five of the 89 

wells were flowpath wells and are not included in the following statistical calculations. 

Seventeen of the 88 VOCs analyzed were detected in 

ground-water samples from randomized wells in the NSF 

study unit. Trichloromethane (chloroform), a disinfectant 

by product, was the most frequently detected VOC; it was 

detected in 12 of the 84 randomized wells sampled. The next 

most frequently detected VOC was carbon disulfide, a compound used in organic synthesis which also occurs naturally. It 

was detected in 8 of the 84 randomized wells. The third most 

frequently detected VOC, toluene, a gasoline additive, was 

detected in 4 of the 84 randomized wells sampled. In total, 27 

wells (of the 84 total randomized wells) had 44 detections for 

a VOC detection frequency of 32 percent in the NSF study 

unit. None of the VOCs and gasoline additive and (or) oxygenate concentrations measured were greater than the concentrations established for regulatory purposes.

20 Ground-Water Quality Data, North San Francisco Bay Hydrologic Provinces, California, 2004: GAMA Program Results
In the VP study area, eleven of the 88 VOCs and gasoline 

additives and (or) oxygenates investigated were detected in 

17 ground-water samples from 50 randomized wells (table 

10A). Trihalomethanes were the most frequently detected 

class of constituents in the VP study area; found in 9 of the 50 

ground-water samples. Chloroform was the most frequently 

detected VOC; it was detected in 8 of the 50 randomized VP 

wells sampled. The next most frequently detected class of 

constituents was organic synthesis constituents, found in 8 of 

the wells. Carbon disulfide, a compound used in organic synthesis which also occurs naturally, was detected in 6 of the 50 

randomized VP wells. The third most frequently detected class 

of constituents, gasoline additives and (or) oxygenates, were 

found in 4 of the 50 wells sampled. 

In the VOL study area, eight of the 88 VOCs and gasoline 

additives and (or) oxygenates investigated were detected in 6 

of the 20 ground-water samples from randomized wells 

(table 10B). Organic synthesis constituents were the most frequently detected class of constituents in the VOL study area; 

found in 3 of the 20 wells. Carbon disulfide was detected in 2 

of the 20 randomized VOL wells sampled. The next most frequently detected class of constituents, gasoline additives and 

(or) oxygenates, were found in 2 of the 20 VOL wells; toluene 

and m-xylene plus p-xylene were each detected in 2 of the 20 

randomized VOL wells sampled. The third most frequently 

detected class of constituents, trihalomethanes, were also 

found in 2 of the 20 VOL randomized wells sampled; chloroform was found in 2 of the 20 VOL samples. 

In the WG study area, seven of the 88 VOCs or gasoline 

additives and (or) oxygenates investigated were detected in 4 

of the 14 ground-water samples from randomized wells 

(table 10C). Trihalomethanes and solvents were the most frequently detected classes of constituents in the WG study area, 

each found in 2 of the 14 ground-water samples; chloroform 

was detected in 2 of the 14 randomized WG wells sampled. 

The next most frequently detected class of constituents, 

gasoline additives and (or) oxygenates, were found in 1 of the 

14 WG wells. Ground-water samples for VOCs and gasoline 

additives and (or) oxygenates were not collected for the hydrothermal study.

Pesticides and Pesticide Degradates

Ground-water samples for pesticides and pesticide 

degradates, using analytical schedules 2003 and 2060, were 

collected at 89 wells in the NSF GAMA study unit. Nine pesticides and pesticide degradates were detected in 16 wells in 

the total NSF study unit. Sixteen of the 89 wells sampled had 

at least a single detection of a pesticide or pesticide degradate. Five of these 89 wells were flowpath wells and are not 

included in the following statistical calculations. 

Nine of the 122 pesticides and pesticide degradates investigated were detected in ground-water samples from randomized wells in the NSF study unit. Simazine, an herbicide, was 

the most frequently detected. It was detected in 8 of the 84 

ground-water samples from randomized wells. The pesticide 

degradates deethylatrazine and deisopropyl atrazine both were 

detected in 2 of the 84 randomized wells sampled. In total, 18 

detections in 14 randomized wells, of the 84 were observed 

in the NSF study unit. None of the pesticide concentrations 

measured were greater than concentrations established for 

regulatory purposes.

In the VP study area, 4 herbicides and 3 pesticide degradates were detected in 12 of the 50 ground-water samples 

from randomized wells (table 11A). Herbicides were the most 

frequently detected among the pesticides and (or) pesticide 

degradates in the VP study area, found in 11 of the 50 groundwater samples. Simazine was the most frequently detected 

herbicide; it was detected in 8 of the 50 randomized VP wells 

sampled. The next most frequently detected class of constituents was pesticides and (or) pesticide degradates, found in 4 

of the 50 wells; deethylatrazine and deisopropyl atrazine were 

each detected in 2 of the 50 randomized VP wells sampled. 

In the VOL study area, one herbicide was detected in one 

of the 20 ground-water samples from randomized wells 

(table 11B). Diphenamid, an herbicide, was found in one of the 

ground-water samples. In the WG study area, one herbicide, 

diazinon, was detected in one of the 14 ground-water samples 

from randomized wells (table 11C). Ground-water samples for 

pesticides and pesticide degradates were not collected for the 

hydrothermal study. 

Waste-Water Indicators

Ground-water samples for waste-water indicators, determined by analytical schedule 1433, were collected at 89 wells 

in the NSF GAMA study unit. Although compounds analyzed 

by schedule 1433 are referred to as waste-water indicators, 

these compounds may originate from sources other than waste 

water. Thirteen waste-water indicators were detected in 24 of 

the wells in the NSF study unit. Twenty-four of the 89 wells 

sampled had at least a single detection of a waste-water indicator. Forty-seven phenol detections were censored (concentration preceded by a V in tables 12A-C) as a result of contamination of the equipment and field blanks, reflecting problems 

with the analytical procedures, see Quality-control section. 

These results were censored from summary statistical calculations. Five of the 89 wells were flowpath wells, and also were 

not included in the following statistical calculations. 

Thirteen of the 63 waste-water indicators analyzed were 

detected in at least one ground-water sample from the randomized wells. Isophorone, a solvent, was the most frequently 

detected constituent; it was detected in 6 of the 84 randomized 

wells sampled. Caffeine and bisphenol-A were both detected 

in 3 of the 84 randomized wells sampled. In total, 30 detections in 22 randomized wells of the 84 were observed in the 

NSF study unit. None of the waste-water indicators detected in 

this study have regulatory standards.

Results 21
In the VP study area, 5 of the 63 waste-water indicators investigated were detected in 12 of the 50 ground-water 

samples from randomized wells (table 12A). Caffeine was 

the most frequently detected compound in the VP study area; 

it was detected in 4 of the 50 randomized VP wells sampled. 

Isophorone, a solvent, was detected in 3 of the 50 randomized 

wells. Triclosan, tetrachlorethene, and bromoform (tribromoethane) were all detected in 2 of the 50 randomized VP wells 

sampled. 

In the VOL study area, eight waste-water indicators were 

detected in 6 of the 20 ground-water samples from the randomized wells (table 12B). Bisphenol-A, a flame retardant, 

and isophorone both were found in 2 of the 20 randomized 

VOL wells. 

In the WG study area, five waste-water indicators were 

detected in 4 of the 14 ground-water samples from randomized 

wells (table 12C). Indole, a pesticide ingredient, and p-cresol, 

a wood preservative, were found in 2 of the 14 WG groundwater samples. Ground-water samples for waste-water indicators were not collected for the hydrothermal study.

Constituents of Special Interest

Ground-water samples for the constituents of special 

interest: perchlorate, 1,2,3-trichloropropane (TCP) and 

N-nitrosodimethylamine (NDMA), were collected at 89 wells 

(table 13), however, these constituents were not detected in 

any of the wells sampled.

Nutrients and Dissolved Organic Carbon

Nutrients and dissolved organic carbon (DOC) samples 

were collected at 22 wells (table 14) sampled under the 

expanded schedule in the NSF study unit. Ammonia was 

detected in 9 of the 22 wells, at concentrations ranging from an 

estimated value (E) of 0.03 to 3.11 mg/L. Nitrate plus nitrite 

was detected in 16 of the 22 ground-water samples, whereas 

nitrite was detected in only 6 of the 22 samples. Concentrations of nitrate plus nitrite were less than the MCL of 

10 mg/L for nitrate alone; values ranged from an estimated 

value of 0.03 mg/L to a concentration of 3.22 mg/L. Nitrite 

was detected in 6 wells at concentrations that ranged from 

an estimated value of 0.004 mg/L to a concentration of 0.03 

mg/L; much below the nitrite MCL of 1 mg/L. Dissolved 

phosphorus was measured in all 22 wells at concentrations that 

ranged from 0.008 to 0.559 mg/L. Total nitrogen, dissolved 

(nitrate plus nitrite plus ammonia plus organic-N) was measured in all 22 wells at concentrations that ranged from 

0.04 to 3.42 mg/L. DOC was measured in all 22 wells at 

concentrations that ranged from E 0.2 mg/L to 1.2 mg/L. Four 

samples had DOC detections in the preceding blanks greater 

than the sample values, and hence were censored and these 

data were not used for summary statistical calculations. Censored values are preceded by a V in table 14. 

Major and Minor Ions and Dissolved Solids

Major and minor ions and dissolved solids (DS) samples 

were collected at 33 public-supply wells, 7 hydrothermal 

wells, and 1 hydrothermal spring (table 15). Three of the 

public-supply wells sampled in NSF study unit had DS 

concentrations above the recommended SMCL of 500 mg/L, 

with values of 503, 685, and 1,000 mg/L respectively, and a 

mean value of 320 mg/L. Calcium concentrations in publicsupply wells ranged from 0.9 to 53.6 mg/L, with a mean value 

of 25.6 mg/L. Magnesium concentrations in public-supply 

wells ranged from 0.1 to 50.8 mg/L, with a mean value of 

15.4 mg/L. Potassium concentrations in public-supply wells 

ranged from 0.5 to 19.7 mg/L, with a mean value of 4.0 mg/L. 

Sodium concentrations in public-supply wells ranged from 

8.4 to 270 mg/L, with a mean value of 53.5 mg/L. Bromide 

concentrations in public-supply wells ranged from 0.03 mg/L 

to 1.4 mg/L, with a mean value of 0.2 mg/L. Chloride concentrations in public-supply wells ranged from 4.6 to 249 mg/L; 

just below the SMCL of 250 mg/L, with a mean value of 32.8 

mg/L. Fluoride concentrations in public-supply wells ranged 

from 0.1 to 0.7 mg/L, with a mean value of 0.3 mg/L; well 

below the MCL of 2 mg/L. Iodide concentrations in publicsupply wells ranged from an estimated value of (E) 0.001 

mg/L to 1.1 mg/L, with a mean value of 0.07 mg/L. Silica 

concentrations in public-supply wells ranged from 15.9 to 134 

mg/L, with a mean value of 61.4 mg/L. Sulfate concentrations 

in public-supply wells ranged from 1.4 to 239 mg/L; below the 

SMCL of 250 mg/L. 

22 Ground-Water Quality Data, North San Francisco Bay Hydrologic Provinces, California, 2004: GAMA Program Results
Trace Elements

Ground-water samples for trace elements were collected 

at 32 public-supply wells, 7 hydrothermal wells, and 

1 hydrothermal spring (table 16) in the NSF study unit. Aluminum was detected in 18 ground-water samples with concentrations ranging from an estimated value of 1 to a value of 

7 μg/L. Antimony was detected in 4 ground-water samples 

with concentrations ranging from an estimated value of (E) 

0.11 to a value of 0.28 μg/L. Arsenic was detected in 29 

ground-water samples with concentrations ranging from an 

estimated value of (E) 0.1 to a concentration of 32.8 μg/L. The 

MCL for As will be 10 μg/L in 2006. In four public-supply 

wells, As concentrations were measured above 10 μg/L, with 

concentrations of 13.0, 17.2, 24.6 and 32.8 μg/L respectively. 

Barium was detected in 32 ground-water samples with concentrations ranging from 1 to 492 μg/L. Beryllium was not 

detected in ground-water samples from public-supply wells. 

Boron was detected in 32 ground-water samples with concentrations ranging from 16 to 3,830 μg/L; with 19 wells having 

concentrations of boron above the DLR of 100 μg/L with 

concentrations of between 120 and 3,830 μg/L. Cadmium was 

detected in 5 ground-water samples with concentrations ranging from an estimated concentration of E 0.03 to a concentration of 0.05 μg/L, all below the MCL of 5 μg/L. Chromium 

was detected in 6 ground-water samples with concentrations 

ranging from an estimated value of (E) 0.4 to a concentration of 4.4 μg/L; all below the MCL of 50 μg/L. Cobalt was 

detected in 31 ground-water samples with concentrations 

ranging from 0.019 to 0.509 μg/L. Copper was detected in 

29 ground-water samples with concentrations ranging from 

an estimated value of (E) 0.2 to a concentration of 14.8 μg/L; 

below the MCL of 1,000 μg/L.

Iron was detected in 32 ground-water samples with 

concentrations ranging from an estimated value of (E) 4 to a 

value of 1,090 μg/L. Seven public-supply wells had Fe concentrations above the SMCL of 300 μg/L with concentrations 

between 308 to 1,090 μg/L. Lead was detected in 28 groundwater samples with concentrations ranging from an estimated value of (E) 0.05 to a concentration of 15.3 μg/L. One 

public-supply well had a lead concentration of 15.3, above 

the California notification level (NL) of 15 μg/L. Lithium was 

detected in 28 ground-water samples with concentrations ranging from 3 to 81 μg/L. Manganese was detected in 28 groundwater samples with concentrations ranging from an estimated 

value of (E) 0.1 to a concentration of 1,220 μg/L. Seventeen 

of the public-supply wells had concentrations above the Mn 

SMCL of 50 μg/L. Mercury was not detected (<0.001) in any 

of the public-supply wells. 

Molybdenum was detected in 32 ground-water samples 

with concentrations ranging from an estimated value of (E) 

0.2 to a concentration of 20.3 μg/L. Nickel was detected in 

31 ground-water samples with concentrations ranging from an 

estimated value of (E) 0.05 to a concentration of 5.58 μg/L. 

Selenium was detected in 12 ground-water samples with 

concentrations ranging from an estimated value of (E) 0.2 to 

a concentration of 2 μg/L. Silver was detected in 2 groundwater samples with concentrations ranging from 0.26 to 0.52 

μg/L. Strontium was detected in 32 ground-water samples 

with concentrations ranging from 29.8 to 440 μg/L. Thallium 

was detected in 4 ground-water samples with concentrations 

ranging from an estimated value of (E) 0.03 μg/L to a concentration of 0.22 μg/L; below the MCL of 2 μg/L. Tungsten 

was detected in 6 ground-water samples with concentrations 

ranging from 0.6 to 2.3 μg/L. Vanadium was detected in 30 

ground-water samples with concentrations ranging from 0.2 to 

19.6 μg/L. Nine wells had Vanadium concentrations above 3 

μg/L, the detection level for the purposes of reporting (DLR). 

Zinc was detected in 31 ground-water samples with concentrations ranging from an estimated value of (E) 0.6 to a concentration of 63.8 μg/L. Uranium was detected in 26 ground-water 

samples with concentrations ranging from 0.04 to 3.53 μg/L. 

When converted from mass units to activities using the standard conversion factor of 0.67 pCi/ μg, all uranium activities 

were below the DHS MCL of 20 pCi/L.

Table 17 presents the results from the USGS NRP 

Boulder lab for total dissolved inorganic As and Fe, as well as 

the individual species As (III) and Fe (II) for samples collected in the NSF study unit; 4 samples from public supply 

wells had total As concentrations above the MCL of 10 μg/L, 

with concentrations of 12.0, 16.2, 22.0 and 29.8, respectively. 

Three samples from public supply wells had concentrations of 

total iron above the SMCL of 300 μg/L, with values of 301, 

313 and 900 μg/L, respectively. These results agree well with 

samples from the same wells identified in table 16, which 

were analyzed at the USGS NWQL in Denver. 

Table 18 presents Cr speciation analyses from the USGS 

NRP Boulder lab; total dissolved Cr and hexavalent Cr (VI). 

Values ranged from 0.1 to 15.6 μg/L. None of the total Cr concentrations were above regulatory levels, however, 47 wells 

had Cr (VI) values above 1 μg/L, the detection level for the 

purposes of reporting (DLR).

Isotopes, Radioactivity, and Dissolved Gases

Isotope activities, stable isotopes, and gross alpha/

beta radioactivity were determined in ground-water samples 

collected for the NSF GAMA study unit (table 19). Stable 

isotopes of water were collected at all 93 wells. Radium-226, 

radium-228, radon-222, alpha radioactivity (72-hour and 

30-day count), beta radioactivity (72-hour and 30-day count), 

and carbon isotopes were collected at 21 wells. Ground-water 

samples for tritium, analyzed at the USGS laboratory, were 

collected at 89 public-supply wells. 

Results 23
Alpha radioactivity in 21 samples (table 19) ranged from 

below quantification limits (<0.001 pCi/L) to 2.2 pCi/L for 

72-hour counts, and from below quantification limits (<0.001 

pCi/L) to 3.9 pCi/L for 30 day counts; neither are above 

the alpha radioactivity MCL of 15 pCi/L. Beta radioactivity in 21 samples ranged from below quantification limits 

(<0.001 pCi/L) to 20.2 pCi/L for 72-hour counts, and from 

below quantification limits (<0.001 pCi/L) to 21.6 pCi/L in 

30-day counts. The MCL for beta radioactivity is 50 pCi/L. 

Tritium was detected in 76 out of 89 samples with activities 

that ranged from below 1 to 9.9 pCi/L; the MCL for tritium is 

20,000 pCi/L. Carbon-14, as percent modern carbon (pmc), 

was measured at 22 wells, and had values that ranged from 

0.01 to 1.05 pmc. Radon-222 was detected in all 21 samples 

collected, and had activities ranging from 210 to 1,500 pCi/L. 

Seventy-one percent (15 samples) of the radon-222 activities 

were above the proposed MCL of 300 pCi/L. Radium-226 was 

detected in all 21 samples collected, however concentrations 

did not exceed 0.17 pCi/L. Radium-228 was detected in 13 out 

of 21 samples, with a maximum concentration of 0.63 pCi/L. 

No wells had activities above the combined radium-226 and 

radium-228 MCL of 5 pCi/L. 

Tritium and noble gas samples (analyzed at LLNL) were 

collected at 95 wells (table 20). Tritium, measured by the 

helium ingrowth method, was detected in 93 samples. Activities ranged from below 1 to 11.0 pCi/L; the MCL for tritium 

is 20,000 pCi/L. Noble gas concentrations and the helium 

isotope ratios (helium-3/helium-4) measured in each sample 

are presented in table 20. 

The dissolved gases carbon dioxide, nitrogen, argon, 

oxygen, and methane were measured in ground-water samples 

from 4 production wells in the Valley and Plains study area, 

and 7 hydrothermal wells as part of the hydrothermal study 

(table 21). Dissolved gas concentrations in production-well 

ground water are low, do not adversely affect ground-water 

quality, and are not regulated for water-quality purposes.

Microbial Constituents

Microbial constituents were analyzed in 22 ground-water 

samples collected for the North San Francisco Bay GAMA 

study (table 22). The following microbial constituents were 

determined: total coliform and Escherichia coliform, and the 

viruses F-specific coliphage and somatic coliphage. Total coliform was detected in three wells, two in the Valley and Plains 

study area, and one in the Wilson Grove Formation Highlands 

study area. Counts ranged from an estimated 2 colonies/100 

mL to 20 colonies/100 mL. MCLs for microbial constituents 

are based on reoccurring detection, and will be monitored during future sampling.

Summary

The NSF GAMA study assessed the ground-water quality 

of 89 public-supply wells across the ~1,000 mi2 study unit. 

Results from 84 randomized wells, statistically representative of the study unit, show that no anthropogenic constituents 

were detected at concentrations higher than those levels set for 

regulatory purposes. Naturally occurring constituents represent the only concentrations above regulatory thresholds for 

drinking-water supply, with concentrations of arsenic, manganese, radon-222, and microbiological contaminants in a small 

percentage of public-supply wells greater than recommended 

MCLs, and dissolved solids, iron and manganese above recommended SMCLs, boron and vanadium above the DLR, and 

lead above the NL.

Ground-water samples were analyzed for major and 

minor ions, trace elements, nutrients, volatile organic compounds (VOCs), pesticides, waste-water indicators, dissolved 

methane, nitrogen, carbon dioxide, and noble gases (in 

collaboration with Lawrence Livermore National Laboratory). Naturally occurring isotopes (tritium, carbon-14, and 

helium-4) also were measured in these samples to help interpret the source and age of the sampled ground water. 

In this study, twenty-one of the 88 VOCs and gasoline 

additives and (or) oxygenates investigated were detected in 

ground-water samples, however, no concentrations observed 

were above established maximum contaminant levels (MCLs). 

Thirty-two percent of the randomized wells sampled during the North San Francisco Bay GAMA study had at least 

a single detection of VOCs or gasoline additives and (or) 

oxygenates. The most frequently detected compounds were 

chloroform found in 12 of 84 randomized wells sampled 

(14 percent), carbon disulfide in 8 of 84 randomized wells 

sampled (10 percent), and toluene in 4 of 84 randomized wells 

sampled (5 percent). Trihalomethanes were the most frequently detected class of VOCs.

Nine of the 122 pesticides and pesticide degradates 

investigated were detected in ground-water samples, however, 

none were above MCLs. Seventeen percent of the 84 randomized wells sampled during the NSF GAMA study had at 

least a single detection of pesticides and pesticide degradates. 

Herbicides were the most frequently detected class of pesticides. The most frequently detected compound was simazine, 

detected in water from 8 of the 84 (10 percent) of the randomized wells. Chlordiamino-s-triazine and deisopropyl atrazine 

were both found in 2 of the 84 (2 percent) randomized wells 

sampled. 

24 Ground-Water Quality Data, North San Francisco Bay Hydrologic Provinces, California, 2004: GAMA Program Results
Thirteen waste-water indicators were detected in groundwater samples in the NSF study unit. Twenty-six percent of 

the wells sampled for waste-water indicators had at least a 

single detection. Isophorone, a solvent and the most frequently 

detected waste-water indicator compound, was detected in 6 

out of 84 randomized wells (7 percent of the wells). Bisphenol-A (plastic resins; flame retardant), caffeine (beverages), 

and indole (pesticide, fragrance in coffee) were each detected 

in 3 out of 84 randomized wells (4 percent of the wells).

Major and minor ion and dissolved solids (DS) samples 

were collected at 33 public-supply wells, concentrations of 

DS were above the secondary maximum contaminant level 

(SMCL) in three samples. Ground-water samples from 32 

public-supply wells were analyzed for trace elements. Arsenic 

concentrations in 4 public-supply wells were above the MCL 

of 10 μg/L, boron concentrations were above the DLR of 100 

μg/L in 19 samples, iron concentrations were above the SMCL 

of 300 μg/L in seven samples, lead concentration was above 

the California notification level (NL) of 15 μg/L in one pubicsupply well sample, manganese concentrations were above 

the SMCL of 50 μg/L in 17 wells, vanadium concentrations 

were above the DLR of 3 μg/L in 9 wells, and chromium (VI) 

concentrations were above the DLR of 1 μg/L in 47 wells.

 Radon-222 was detected in all 21 ground-water samples 

collected, with activities ranging from 210 to 1,500 pico 

Curies per liter (pCi/L). Fifteen samples were above the proposed MCL of 300 pCi/L. 

Microbial constituents were analyzed in 22 ground-water 

samples. Total coliform was detected in three wells, two in the 

Valley and Plains study area, and one in the Wilson Grove Formation Highlands study area. Counts ranged from 2 colonies 

per 100 mL to 20 colonies per 100 mL. MCLs for microbial 

constituents are based on reoccurring detection, and will be 

monitored during future sampling.

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Paper, v. 1239, p. 33.

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water and fluvial sediments: U.S. Geological Survey 

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chap. A6, 181 p.

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P., Coffey, L. J. and Burkhardt, M. R., 2001, Methods of 

analysis by the U.S. Geological Survey National Water 

Quality Laboratory-determination of pesticides in water by 

graphitized carbon-based solid-phase extraction and highperformance liquid chromatography/mass spectrometry: 

U.S. Geological Survey Water-Resources Investigations 

Report 01-4134, 73 p.

Garbarino, J. R., 1999, Methods of analysis by the U.S. 

Geological Survey National Water Quality Laboratory —

Determination of dissolved arsenic, boron, lithium, selenium, strontium, thallium, and vanadium using inductively 

coupled plasma-mass spectrometry: U.S. Geological Survey 

Open-File Report 99-093, 31 p.

Garbarino, J. R. and Damrau, D. L., 2001, Methods of analysis 

by the U.S. Geological Survey National Water Quality 

Laboratory—Determination of organic plus inorganic 

mercury in filtered and unfiltered natural water with cold 

vapor—atomic fluorescence spectrometry: U.S. Geological 

Survey Water-Resources Investigations Report 01-4132, 

16 p.

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26 Ground-Water Quality Data, North San Francisco Bay Hydrologic Provinces, California, 2004: GAMA Program Results
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References 27
28 Ground-Water Quality Data, North San Francisco Bay Hydrologic Provinces, California, 2004: GAMA Program Results
Tables

Tables 29
Sampling information

GAMA

 identification 

No.

Date Time Sampling

schedule

Well depth

(ft below LSD)

Top of highest 

perforation

 (ft below LSD)

Bottom lowest 

perforation

(ft below LSD)

Valley and Plains wells

NSFVP-01 08/31/2004 0910 Basic 864 441 862

NSFVP-02 08/31/2004 1300 Basic 350 65 341

NSFVP-03 08/31/2004 1620 Basic 120 ND ND

NSFVP-04 09/01/2004 0900 Basic 397 ND ND

NSFVP-05 09/01/2004 1150 Basic 502 130 450

NSFVP-06 09/01/2004 1400 Basic 700 170 680

NSFVP-07 09/02/2004 0830 Basic 685 295 670

NSFVP-08 09/02/2004 1200 Basic 102 70 88

NSFVP-09 09/02/2004 1350 Basic 400 260 400

NSFVP-10 09/13/2004 1210 Expanded 99 75 95

NSFVP-11 09/13/2004 1330 Basic 80 60 70

NSFVP-12 09/13/2004 1630 Basic 808 650 800

NSFVP-13 09/14/2004 0840 Basic ND ND ND

NSFVP-14 09/14/2004 1240 Basic 550 507 547

NSFVP-15 09/14/2004 1450 Basic 60 40 60

NSFVP-16 09/15/2004 0930 Basic 206 50 190

NSFVP-17 09/15/2004 1430 Basic ND ND ND

NSFVP-18 09/16/2004 0940 Basic 63 48 58

NSFVP-19 09/16/2004 1040 Expanded 100 20 60

NSFVP-20 09/16/2004 1600 Basic 110 70 110

NSFVP-21 09/20/2004 1000 Basic 314 80 310

NSFVP-22 09/20/2004 1320 Basic 502 60 502

NSFVP-23 09/20/2004 1600 Basic 530 369 530

NSFVP-24 09/22/2004 1300 Basic 85 65 85

NSFVP-25 09/23/2004 1240 Basic 265 160 265

NSFVP-26 09/27/2004 1030 Expanded 600 125 600

NSFVP-27 09/28/2004 0830 Basic 372 50 372

NSFVP-28 09/28/2004 1110 Basic 216 116 216

NSFVP-29 09/28/2004 1200 Expanded 120 62 120

NSFVP-30 09/29/2004 1210 Expanded ND ND ND

NSFVP-31 09/30/2004 0840 Basic 315 20 315

NSFVP-32 10/07/2004 0940 Basic-plus 400 ND ND

NSFVP-33 10/07/2004 1320 Basic-plus ND ND ND

NSFVP-34 10/18/2004 1120 Expanded 258 41 258

NSFVP-35 10/18/2004 1300 Basic-plus 300 85 300

NSFVP-36 10/19/2004 0900 Basic-plus 306 145 300

NSFVP-37 10/19/2004 1000 Expanded 360 60 350

Table 1. Identification, sampling and construction information for wells sampled for the North San Francisco Bay Ground-Water Ambient 

Monitoring and Assessment (GAMA) study, California, August to November 2004.

[ft, foot; LSD, land surface datum; NA, not available; ND, no data; NSFVP, Valley and Plains study area; NSFVPFP, Valley and Plains flow-path well; 

NSFVOL, Volcanic Highlands study area; NSFWG, Wilson Grove Formation Highlands study area; NSFWGFP, Wilson Grove Formation Highlands flow-path 

well; NSFHOT, hydrothermal study]

30 Ground-Water Quality Data, North San Francisco Bay Hydrologic Provinces, California, 2004: GAMA Program Results
Sampling information

GAMA

 identification 

No.

Date Time Sampling

schedule

Well depth

(ft below LSD)

Top of highest 

perforation

 (ft below LSD)

Bottom lowest 

perforation

(ft below LSD)

NSFVP-38 10/20/2004 1040 Expanded 770 210 770

NSFVP-39 10/21/2004 0940 Basic-plus 460 56 460

NSFVP-40 10/21/2004 1130 Expanded ND ND ND

NSFVP-41 10/21/2004 1250 Basic-plus 235 60 235

NSFVP-42 10/25/2004 1410 Basic 209 52 209

NSFVP-43 10/26/2004 1110 Basic-plus 790 690 790

NSFVP-44 10/26/2004 1520 Basic-plus 318 140 302

NSFVP-45 11/02/2004 1230 Expanded ND ND ND

NSFVP-46 11/03/2004 1040 Expanded 180 40 180

NSFVP-47 11/03/2004 1230 Basic-plus 79 ND ND

NSFVP-48 11/04/2004 1420 Basic-plus 200 60 200

NSFVP-49 11/17/2004 1400 Expanded 460 140 220

NSFVP-50 11/18/2004 1120 Expanded 199 ND ND

NSFVPFP-01 09/14/2004 1020 Expanded 1,040 410 1,020

NSFVPFP-02 09/30/2004 1100 Expanded 231 61 231

NSFVPFP-03 10/20/2004 0920 Basic-plus 25 13 25

NSFVPFP-04 09/13/2004 0940 Basic 99 75 95

Volcanic Highlands wells

NSFVOL-01 09/15/2004 1020 Expanded 323 ND ND

NSFVOL-02 09/15/2004 1710 Basic 380 ND ND

NSFVOL-03 09/27/2004 0840 Basic ND ND ND

NSFVOL-04 09/27/2004 1120 Basic 542 ND ND

NSFVOL-05 09/27/2004 1450 Basic 510 330 510

NSFVOL-06 09/28/2004 1440 Basic 280 200 280

NSFVOL-07 09/29/2004 0830 Basic 395 215 395

NSFVOL-08 09/29/2004 1130 Basic ND ND ND

NSFVOL-09 09/29/2004 1440 Basic ND ND ND

NSFVOL-10 10/05/2004 0940 Basic 136 76 136

NSFVOL-11 10/06/2004 0830 Basic 555 398 555

NSFVOL-12 10/06/2004 1140 Basic 368 148 368

NSFVOL-13 10/06/2004 1440 Basic 510 30 510

NSFVOL-14 10/07/2004 1140 Expanded 417 57 417

NSFVOL-15 10/07/2004 1620 Basic 115 65 113

NSFVOL-16 10/19/2004 1400 Basic 420 75 419

NSFVOL-17 10/20/2004 1230 Basic 265 ND ND

NSFVOL-18 10/20/2004 1420 Basic 670 135 660

NSFVOL-19 11/02/2004 1100 Expanded 705 285 705

NSFVOL-20 11/04/2004 1130 Expanded 250 170 250

Table 1. Identification, sampling and construction information for wells sampled for the North San Francisco Bay Ground-Water Ambient 

Monitoring and Assessment (GAMA) study, California, August to November 2004—Continued.

[ft, foot; LSD, land surface datum; NA, not available; ND, no data; NSFVP, Valley and Plains study area; NSFVPFP, Valley and Plains flow-path well; 

NSFVOL, Volcanic Highlands study area; NSFWG, Wilson Grove Formation Highlands study area; NSFWGFP, Wilson Grove Formation Highlands flow-path 

well; NSFHOT, hydrothermal study]

Tables 31
Sampling information

GAMA

 identification 

No.

Date Time Sampling

schedule

Well depth

(ft below LSD)

Top of highest 

perforation

 (ft below LSD)

Bottom lowest 

perforation

(ft below LSD)

Wilson Grove Formation Highlands wells

NSFWG-01 09/16/2004 1240 Basic 350 90 350

NSFWG-02 09/21/2004 1030 Basic 240 ND ND

NSFWG-03 09/21/2004 1520 Basic 552 270 552

NSFWG-04 09/22/2004 0840 Basic 452 432 452

NSFWG-05 09/22/2004 1110 Basic 215 135 215

NSFWG-06 09/23/2004 0830 Basic 161 ND ND

NSFWG-07 09/30/2004 1520 Basic 550 140 540

NSFWG-08 10/04/2004 1400 Expanded 600 332 600

NSFWG-09 10/04/2004 1600 Basic ND ND ND

NSFWG-10 10/06/2004 1100 Expanded ND ND ND

NSFWG-11 10/27/2004 1030 Basic ND ND ND

NSFWG-12 10/27/2004 1250 Basic ND ND ND

NSFWG-13 10/28/2004 1300 Basic ND ND ND

NSFWG-14 11/04/2004 1130 Basic 295 155 295

NSFWGFP-01 10/05/2004 1120 Expanded 528 138 528

Hydrothermal study

NSFHOT-01 10/19/2004 1410 Hydrothermal 200 ND ND

NSFHOT-02 10/21/2004 1030 Hydrothermal 200 ND ND

NSFHOT-03 10/21/2004 1100 Hydrothermal 45 ND ND

NSFHOT-04 10/19/2004 1210 Hydrothermal ND ND ND

NSFHOT-05 10/19/2004 1010 Hydrothermal ND ND ND

NSFHOT-06 10/20/2004 1530 Hydrothermal ND ND ND

NSFHOT-07 10/20/2004 1730 Hydrothermal 1,000 ND ND

NSFHOT-081 10/20/2004 1020 Hydrothermal NA NA NA

1

Hydrothermal spring.

Table 1. Identification, sampling and construction information for wells sampled for the North San Francisco Bay Ground-Water 

Ambient Monitoring and Assessment (GAMA) study, California, August to November 2004—Continued.

[ft, foot; LSD, land surface datum; NA, not available; ND, no data; NSFVP, Valley and Plains study area; NSFVPFP, Valley and Plains flow-path well; 

NSFVOL, Volcanic Highlands study area; NSFWG, Wilson Grove Formation Highlands study area; NSFWGFP, Wilson Grove Formation Highlands flow-path 

well; NSFHOT, hydrothermal study]

32 Ground-Water Quality Data, North San Francisco Bay Hydrologic Provinces, California, 2004: GAMA Program Results
Constituent Primary use/source CAS number LRL

(μg/L)

1,1,1,2-Tetrachloroethane Solvent 630-20-6 0.03

1,1,1-Trichloroethane (TCA) Solvent 71-55-6 0.032

1,1,2,2-Tetrachloroethane Solvent 79-34-5 0.08

1,1,2-Trichloroethane Solvent 79-00-5 0.04

1,1,2-Trichlorotrifluoroethane (CFC-113) Refrigerant 76-13-1 0.038

1,1-Dichloroethane Solvent 75-34-3 0.035

1,1-Dichloroethylene (DCE) Organic synthesis 75-35-4 0.024

1,1-Dichloropropene Organic synthesis 563-58-6 0.026

1,2,3,4-Tetramethylbenzene Hydrocarbon 488-23-3 0.14

1,2,3,5-Tetramethylbenzene (isodurene) Hydrocarbon 527-53-7 0.14

1,2,3-Trichlorobenzene Organic synthesis 87-61-6 0.18

1,2,3-Trichloropropane Solvent 96-18-4 0.18

1,2,3-Trimethylbenzene Gasoline 526-73-8 0.06

1,2,4-Trichlorobenzene Solvent 120-82-1 0.12

1,2,4-Trimethylbenzene Organic synthesis 95-63-6 0.056

1,2-Dibromo-3-chloropropane (DBCP) Fumigant 96-12-8 0.51

1,2-Dibromoethane Solvent 106-93-4 0.036

1,2-Dichlorobenzene Solvent 95-50-1 0.048

1,2-Dichloroethane Solvent 107-06-2 0.13

1,2-Dichloropropane Solvent 78-87-5 0.029

1,3,5-Trimethylbenzene Gasoline 108-67-8 0.044

1,3-Dichlorobenzene Solvent 541-73-1 0.03

1,3-Dichloropropane Organic synthesis 142-28-9 0.06

1,4-Dichlorobenzene Fumigant 106-46-7 0.034

2,2-Dichloropropane Organic synthesis 594-20-7 0.05

2-Butanone (ethyl methyl ketone) Solvent 78-93-3 2

2-Chlorotoluene Solvent 95-49-8 0.04

2-Hexanone Solvent 591-78-6 0.4

3-Chloropropene Organic synthesis 107-05-1 0.5

4-Chlorotoluene Solvent 106-43-4 0.05

4-Isopropyl-1-methylbenzene Organic synthesis 99-87-6 0.08

4-Methyl-2-pentanone Solvent 108-10-1 0.37

Acetone Solvent 67-64-1 6

Acrylonitrile Organic synthesis 107-13-1 0.8

Benzene Gasoline 71-43-2 0.021

Bromobenzene Solvent 108-86-1 0.028

Bromochloromethane Organic synthesis 74-97-5 0.12

Bromodichloromethane Disinfection by-product 75-27-4 0.028

Bromoethene Fire retardant 593-60-2 0.1

Bromoform (tribromomethane) Disinfection by-product 75-25-2 0.1

Bromomethane Fumigant 74-83-9 0.26

Table 2A. Volatile organic compounds and gasoline additives and (or) oxygenates, primary use or source, Chemical Abstract Service 

(CAS) number, and laboratory reporting level (LRL) for the U.S. Geological Survey’s National Water Quality Laboratory analytical 

schedule 2020. 

[μg/L, micrograms per liter]

Tables 33
Constituent Primary use/source CAS number LRL

(μg/L)

Butylbenzene Organic synthesis 104-51-8 0.12

Carbon disulfide Organic synthesis 75-15-0 0.038

Chlorobenzene Solvent 108-90-7 0.028

Chloroethane Solvent 75-00-3 0.12

Chloroform (trichloromethane) Disinfection by-product 67-66-3 0.024

Chloromethane Refrigerant 74-87-3 0.17

cis-1,2-Dichloroethylene Solvent 156-59-2 0.024

cis-1,3-Dichloropropene Fumigant 10061-01-5 0.05

Dibromochloromethane Disinfection by-product 124-48-1 0.1

Dibromomethane Solvent 74-95-3 0.05

Dichlorodifluoromethane (CFC-12) Refrigerant 75-71-8 0.18

Dichloromethane (methylene chloride) Solvent 75-09-2 0.06

Diethyl ether Solvent 60-29-7 0.08

Diisopropyl ether Gasoline 108-20-3 0.1

Ethyl methacrylate Organic synthesis 97-63-2 0.18

Ethyl tert-butyl ether (ETBE) Gasoline 637-92-3 0.03

Ethylbenzene Gasoline 100-41-4 0.03

Hexachlorobutadiene Organic synthesis 87-68-3 0.14

Hexachloroethane Solvent 67-72-1 0.14

Isopropylbenzene Organic synthesis 98-82-8 0.038

m- plus p-Xylene Gasoline 108-38-3/106-42-3 0.06

Methyl acrylate Organic synthesis 96-33-3 1

Methyl acrylonitrile Organic synthesis 126-98-7 0.4

Methyl iodide Organic synthesis 74-88-4 0.5

Methyl methacrylate Organic synthesis 80-62-6 0.2

Methyl tert-Butyl ether (MTBE) Gasoline 1634-04-4 0.1

Naphthalene Organic synthesis 91-20-3 0.52

n-Propylbenzene Solvent 103-65-1 0.042

o-Ethyl toluene Hydrocarbon 611-14-3 0.06

o-Xylene Gasoline 95-47-6 0.038

sec-Butylbenzene Organic synthesis 135-98-8 0.06

Styrene Organic synthesis 100-42-5 0.042

tert-Amyl methyl ether Gasoline 994-05-8 0.04

tert-Butylbenzene Organic synthesis 98-06-6 0.06

Tetrachloroethylene (PCE) Solvent 127-18-4 0.03

Tetrachloromethane (carbon tetrachloride) Solvent 56-23-5 0.06

Tetrahydrofuran Solvent 109-99-9 1

Table 2A. Volatile organic compounds and gasoline additives and (or) oxygenates, primary use or source, Chemical Abstract Service 

(CAS) number, and laboratory reporting level (LRL) for the U.S. Geological Survey’s National Water Quality Laboratory analytical 

schedule 2020—Continued. 

[μg/L, micrograms per liter]

34 Ground-Water Quality Data, North San Francisco Bay Hydrologic Provinces, California, 2004: GAMA Program Results
Constituent Primary use/source CAS number LRL

(μg/L)

Toluene Gasoline 108-88-3 0.02

trans-1,2-Dichloroethylene Solvent 156-60-5 0.032

trans-1,3-Dichloropropene Fumigant 10061-02-6 0.09

trans-1,4-Dichloro-2-butene Organic synthesis 110-57-6 0.7

Trichloroethylene (TCE) Solvent 79-01-6 0.038

Trichlorofluoromethane (CFC-11) Refrigerant 75-69-4 0.08

Vinyl chloride Organic synthesis 75-01-4 0.08

Table 2A. Volatile organic compounds and gasoline additives and (or) oxygenates, primary use or source, Chemical Abstract Service 

(CAS) number, and laboratory reporting level (LRL) for the U.S. Geological Survey’s National Water Quality Laboratory analytical 

schedule 2020—Continued. 

[μg/L, micrograms per liter]

Constituent Primary use/source CAS number LRL 

(μg/L)

Acetone Degradate 67-64-1 1.2

Diisopropyl ether Gasoline oxygenate 108-20-3 0.08

Ethyl tert-butyl ether (ETBE) Gasoline oxygenate 637-92-3 0.1

Methyl acetate Degradate 79-20-9 0.4

tert-Amyl alcohol Degradate 75-85-4 0.43

tert-Butyl alcohol Degradate 75-65-0 1

tert-Butyl methyl ether (MTBE) Gasoline oxygenate 1634-04-4 0.08

tert-Amyl methyl ether Gasoline oxygenate 994-05-8 0.07

Table 2B. Gasoline oxygenates and (or) gasoline oxygenate degradates, primary use or source, Chemical Abstract Service (CAS) 

number, and laboratory reporting level (LRL) for the U.S. Geological Survey’s National Water Quality Laboratory analytical schedule 4024.

[μg/L, micrograms per liter]

Tables 35
Constituent Primary use/source CAS number LRL 

(μg/L)

1-Naphthol Degradate 90-15-3 0.088

2,6-Diethylaniline Degradate 579-66-8 0.006

2-Chloro-2,6-diethylacetanilide Degradate 6967-29-9 0.005

2-Ethyl-6-methylaniline Degradate 24549-06-2 0.004

3,4-Dichloroaniline Degradate 95-76-1 0.004

4-Chloro-2-methylphenol Degradate 1570-64-5 0.005

Acetochlor Herbicide 34256-82-1 0.006

Alachlor Herbicide 15972-60-8 0.005

Atrazine Herbicide 1912-24-9 0.007

Azinphos-methyl oxygen analog Degradate 90-15-4 0.016

Azinphos-methyl Degradate 90-15-4 0.05

Benfluralin Degradate 579-66-9 0.01

Carbaryl Insecticide 63-25-2 0.041

Chlorpyrifos Insecticide 2921-88-2 0.005

Chlorpyrofos, oxygen analog Degradate 5598-15-2 0.056

cis-Permethrin Insecticide 54774-45-7 0.006

Cyfluthrin Insecticide 68359-37-5 0.008

Cypermethrin Insecticide 52315-07-8 0.008

Dacthal (DCPA) Herbicide 1861-32-1 0.003

Deethylatrazine Degradate 6190-65-4 0.006

Desulfinylfipronil Degradate NA 0.012

Desulfinylfipronil amide Degradate NA 0.029

Diazinon Insecticide 333-41-5 0.005

Diazinon, oxygen analog Insecticide 962-58-3 0.01

Dichlorvos Fumigant 62-73-7 0.011

Dicrotophos Insecticide 141-66-2 0.084

Dieldrin Insecticide 60-57-1 0.009

Dimethoate Insecticide 60-51-5 0.006

Ethion Insecticide 563-12-2 0.004

Ethion monoxon Degradate 17356-42-2 0.033

Fenamiphos Insecticide 22224-92-6 0.029

Fenamiphos sulfone Degradate 31972-44-8 0.007

Fenamiphos sulfoxide Degradate 31972-43-7 0.031

Fipronil Insecticide 120068-37-3 0.016

Fipronil sulfide Degradate 120067-83-6 0.013

Fipronil sulfone Degradate 120068-36-2 0.024

Fonofos Insecticide 944-22-9 0.003

Fonofos, oxygen analog Degradate 944-21-8 0.002

Hexazinone Herbicide 51235-04-2 0.012

Iprodione Fungicide 36734-19-7 1.422

Isofenphos Insecticide 25311-71-1 0.003

Table 2C. Pesticides and pesticide degradates, primary use or source, Chemical Abstract Service (CAS) number, and laboratory 

reporting level (LRL) for the U.S. Geological Survey’s National Water Quality Laboratory analytical schedule 2003.

[NA, not available; μg/L, micrograms per liter]

36 Ground-Water Quality Data, North San Francisco Bay Hydrologic Provinces, California, 2004: GAMA Program Results
Constituent Primary use/source CAS number LRL 

(μg/L)

Malaoxon Degradate 1634-78-2 0.008

Malathion Insecticide 121-75-5 0.027

Metalaxyl Fungicide 57837-19-1 0.005

Methidathion Insecticide 950-37-8 0.005

Metolachlor Herbicide 51218-45-2 0.013

Metribuzin Herbicide 21087-64-9 0.006

Myclobutanil Fungicide 88671-89-0 0.008

Paraoxon-methyl Degradate 950-35-6 0.029

Parathion-methyl Insecticide 298-00-0 0.015

Pendimethalin Herbicide 40487-42-1 0.022

Phorate Insecticide 298-02-2 0.011

Phorate oxygen analog Degradate 2600-69-3 0.097

Phosmet Insecticide 732-11-6 0.007

Phosmet oxon Degradate 3735-33-9 0.055

Prometon Herbicide 1610-18-0 0.005

Prometryn Herbicide 7287-19-6 0.005

Propyzamide Herbicide 23950-58-5 0.004

Simazine Herbicide 122-34-9 0.005

Tebuthiuron Herbicide 34014-18-1 0.016

Terbufos Insecticide 13071-79-9 0.017

Terbufos oxygen analog sulfone Degradate 56070-15-6 0.067

Terbuthylazine Herbicide 5915-41-3 0.010

Trifluralin Herbicide 1582-09-8 0.009

Table 2C. Pesticides and pesticide degradates, primary use or source, Chemical Abstract Service (CAS) number, and laboratory 

reporting level (LRL) for the U.S. Geological Survey’s National Water Quality Laboratory analytical schedule 2003—Continued.

[NA, not available; μg/L, micrograms per liter]

Tables 37
Constituent Primary

 use/source

CAS 

number

 LRL 

(μg/L)

2,4-D (2,4-Dichlorophenoxyacetic acid) Herbicide 94-75-7 0.021

2,4-D methyl ester Herbicide 1928-38-7 0.008

2,4-DB (4-(2,4-dichlorophenoxy)butanoic acid) Herbicide 94-82-6 0.016

2,4,5-T (2,4,5-trichlorophenoxyacetic acid) Negative ion surrogate 93-76-5 0.1

2-Chloro-4-isopropylamino-6-amino-s-triazine (deethylatrazine) Degradate 6190-65-4 0.028

2-Chloro-6-ethylamino-4-amino-s-triazine (deisopropylatrazine) Degradate 1007-28-9 0.01

2-Hydroxy-4-isopropylamino-6-ethylamino-s-triazine (hydroxyatrazine) Degradate 2163-68-0 0.008

3(4-Chlorophenyl)-1-methyl urea Degradate 5352-88-5 0.024

3-Hydroxycarbofuran Degradate 16655-82-6 0.005

3-Ketocarbofuran Degradate 16709-30-1 0.014

Acifluorfen Herbicide 50594-66-6 0.006

Aldicarb Insecticide 116-06-3 0.04

Aldicarb sulfone Degradate 1646-88-4 0.02

Aldicarb sulfoxide Degradate 1646-87-3 0.008

Atrazine Herbicide 1912-24-9 0.009

Bendiocarb Insecticide 22781-23-3 0.025

Benomyl Fungicide 17804-35-2 0.003

Bensulfuron-methyl Herbicide 83055-99-6 0.015

Bentazon Herbicide 25057-89-0 0.011

Bromacil Herbicide 314-40-9 0.033

Bromoxynil Herbicide 1689-84-5 0.017

Caffeine Beverages 58-08-2 0.009

Carbaryl Insecticide 63-25-2 0.028

Carbofuran Herbicide 1563-66-2 0.005

Chloramben, methyl ester Herbicide 7286-84-2 0.018

Chlordiamino-s-triazine (Deethyldeisopropyl atrazine) Degradate 3397-62-4 0.04

Chlorimuron-ethyl Herbicide 90982-32-4 0.009

Chlorothalonil Herbicide 1897-45-6 0.035

Clopyralid Herbicide 1702-17-6 0.013

Cycloate Herbicide 1134-23-2 0.013

Dacthal monoacid Degradate 887-54-7 0.011

Dicamba Herbicide 1918-00-9 0.012

Dichlorprop Herbicide 120-36-5 0.013

Dinoseb Herbicide 88-85-7 0.012

Diphenamid Herbicide 957-51-7 0.026

Diuron Herbicide 330-54-1 0.015

Fenuron Herbicide 101-42-8 0.031

Flumetsulam Herbicide 98967-40-9 0.011

Fluometuron Herbicide 2164-17-2 0.031

Imazaquin Herbicide 81335-37-7 0.016

Table 2D. Pesticides, pesticide degradates and caffiene, primary use or source, Chemical Abstract Service (CAS) number, and 

laboratory reporting level (LRL) for the U.S. Geological Survey’s National Water Quality Laboratory analytical schedule 2060.

[μg/L, micrograms per liter]

38 Ground-Water Quality Data, North San Francisco Bay Hydrologic Provinces, California, 2004: GAMA Program Results
Constituent Primary

 use/source

CAS 

number

 LRL 

(μg/L)

Imazethapyr Herbicide 81335-77-5 0.017

Imidacloprid Insecticide 138261-41-3 0.006

Linuron Herbicide 330-55-2 0.014

MCPA (2-methyl-4-chlorophenoxyacetic acid) Herbicide 94-74-6 0.016

MCPB (2-methyl-4-chlorophenoxy butyric acid) Herbicide 94-81-5 0.015

Metalaxyl Fungicide 57837-19-1 0.02

Methiocarb Insecticide 2032-65-7 0.008

Methomyl Insecticide 16752-77-5 0.004

Metsulfuron methyl Herbicide 74223-64-6 0.025

Neburon Herbicide 555-37-3 0.012

Nicosulfuron Herbicide 111991-09-4 0.013

Norflurazon Herbicide 27314-13-2 0.016

Oryzalin Herbicide 19044-88-3 0.017

Oxamyl Insecticide 23135-22-0 0.012

Picloram Herbicide 6607 0.019

Propham Herbicide 122-42-9 0.009

Propiconazole Fungicide 60207-90-1 0.021

Propoxur Insecticide 114-26-1 0.008

Siduron Herbicide 1982-49-6 0.016

Sulfometuron-methyl Herbicide 74222-97-2 0.008

Tebuthiuron Herbicide 34014-18-1 0.006

Terbacil Herbicide 5902-51-2 0.009

Tribenuron-methyl Herbicide 101200-48-0 0.008

Triclopyr Herbicide 55335-06-3 0.022

Table 2D. Pesticides, pesticide degradates, and caffiene, primary use or source, Chemical Abstract Service (CAS) number, and 

laboratory reporting limits (LRLs) for the U.S. Geological Survey’s National Water Quality Laboratory analytical schedule 2060

—Continued.

[μg/L, micrograms per liter]

Tables 39
Constituent Primary use/source CAS number LRL

(μg/L)

1,4-Dichlorobenzene Moth repellant, fumigant, deodorant 106-46-7 0.5

1-Methylnaphthalene Gasoline, diesel fuel, or crude oil 90-12-0 0.5

2,6-Dimethylnaphthalene Diesel/kerosene (trace in gasoline) 581-42-0 0.5

2-Methylnaphthalene Gasoline, diesel fuel, or crude oil 91-57-6 0.5

3-beta-Coprostanol Carnivore fecal indicator 360-68-9 2

3-Methyl-1(H)-indole (Skatole) Fragrance, stench in feces and coal tar 83-34-1 1

3-tert-Butyl-4-hydroxy anisole (BHA) Antioxidant, general preservative 25013-16-5 5

4-Cumylphenol Nonionic detergent metabolite 599-64-4 1

4-n-Octylphenol Nonionic detergent metabolite 1806-26-4 1

4-tert-Octylphenol Nonionic detergent metabolite 140-66-9 1

5-Methyl-1H-benzotriazole Antioxidant in antifreeze and deicers 136-85-6 2

Acetophenone Fragrance in detergent and tobacco, flavor in 

beverages 

98-86-2 0.5

Acetyl hexamethyl tetrahydronaphthalene 

(AHTN) 

Musk fragrance 21145-77-7 0.5

Anthracene Wood preservative, tar, diesel, crude oil, 

combustion product 

120-12-7 0.5

Anthraquinone Manufacturing dye/textiles, seed treatment, bird 

repellant

84-65-1 0.5

Benzo[a]pyrene Cancer research, combustion product 50-32-8 0.5

Benzophenone Fixative for perfumes and soaps 119-61-9 0.5

beta-Sitosterol Plant sterol 83-46-5 2

beta-Stigmastanol Plant sterol 19466-47-8 2

Bisphenol A Manufacturing polycarbonate resins, antioxidant, 

flame retardant

80-05-7 1

Bromacil Herbicide, >80% noncrop usage on grass/brush 314-40-9 0.5

Bromoform (tribromomethane) Byproduct waste water treatment, military/

explosives 

75-25-2 0.5

Caffeine Beverages 58-08-2 0.5

Camphor Flavor, odorant, ointments 76-22-2 0.5

Carbaryl Insecticide , crop and garden uses 63-25-2 1

Carbazole Insecticide, manuf. dyes, explosives, and 

lubricants 

86-74-8 0.5

Chlorpyrifos Insecticide, domestic pest and termite control 2921-88-2 0.5

Cholesterol Fecal indicator, plant sterol 57-88-5 2

Cotinine Primary nicotine metabolite 486-56-6 1

Diazinon Insecticide, > 40 percent nonagricultural usage, 

ants, flies 

333-41-5 0.5

Dichlorvos Insecticide degradate of naled or trichlofon 62-73-7 1

d-Limonene Fungicide, antimicrobial, antiviral, fragrance in 

aerosols 

5989-27-5 0.5

Fluoranthene Component of coal tar and asphalt 206-44-0 0.5

Hexadydrohexamethylcyclopentabenzopyran 

(HHCB) 

Musk fragrance 1222-05-5 0.5

Table 2E. Waste-water indicator constituents, primary use or source, Chemical Abstract Service (CAS) number, and laboratory reporting 

level (LRL) for the U.S. Geological Survey’s National Water Quality Laboratory analytical schedule 1433.

[NA, not available; μg/L, micrograms per liter; >, greater than]

40 Ground-Water Quality Data, North San Francisco Bay Hydrologic Provinces, California, 2004: GAMA Program Results
Constituent Primary use/source CAS number LRL

(μg/L)

Indole Pesticide ingredient, fragrance in coffee 120-72-9 0.5

Isoborneol Fragrance in perfumery, in disinfectants 124-76-5 0.5

Isophorone Solvent for lacquer, plastic, oil, silicon, resin 78-59-1 0.5

Isopropylbenzene Manufacturing phenol/acetone, fuels and paint 

thinner 

98-82-8 0.5

Isoquinoline Flavors and fragrances 119-65-3 0.5

Menthol Cigarettes, cough drops, liniment, mouthwash 89-78-1 0.5

Metalaxyl Herbicide, fungicide, mildew, blight, pathogens, 

golf/turf 

57837-19-1 0.5

Methyl salicylate Liniment, food, beverage, UV-absorbing lotion 119-36-8 0.5

Metolachlor Herbicide, indicator of agricultural drainage 51218-45-2 0.5

N,N-diethyl-meta-toluamide (DEET) Insecticide, urban uses, mosquito repellent 134-62-3 0.5

Naphthalene Fumigant, moth repellent, major component of 

gasoline 

91-20-3 0.5

4-Nonylphenol, diethoxylates Nonionic detergent metabolite NA 5

4-Octylphenol, diethoxylates Nonionic detergent metabolite NA 1

Octylphenol, monoethoxylates Nonionic detergent metabolite NA 1

para-Nonylphenol (total) Nonionic detergent metabolite 84852-15-3 5

p-Cresol Wood preservative 106-44-5 1

Pentachlorophenol Herbicide, fumigant, wood preservative, termite 

control 

87-86-5 2

Phenanthrene Manufacturing explosives, tar, diesel, crude oil, 

combustion product 

85-01-8 0.5

Phenol Disinfectant, product manufacturing, leachate 108-95-2 0.5

Prometon Herbicide (non-crop only) applied prior to 

blacktop 

1610-18-0 0.5

Pyrene Component of coal tar and asphalt 129-00-0 0.5

Tetrachloroethylene Solvent, degreaser, veterinary anthelmintic 127-18-4 0.5

Tri(2-butoxyethyl)phosphate Flame retardant 78-51-3 0.5

Tri(2-chloroethyl)phosphate Plasticizer, flame retardant 115-96-8 0.5

Tributyl phosphate Antifoaming agent, flame retardant 126-73-8 0.5

Triclosan Disinfectant, antimicrobial 3380-34-5 1

Triethyl citrate (ethyl citrate) Cosmetics, pharmaceuticals 77-93-0 0.5

Triphenyl phosphate Plasticizer, resin, wax, finish, roofing paper, 

flame retardant

115-86-6 0.5

Tris(dichlorisopropyl)phosphate Flame retardant 13674-87-8 0.5

Table 2E. Waste-water indicator constituents, primary use or source, Chemical Abstract Service (CAS) number, and laboratory reporting 

level (LRL) for the U.S. Geological Survey’s National Water Quality Laboratory analytical schedule 1433—Continued.

[NA, not available; μg/L, micrograms per liter; >, greater than]

Tables 41
Constituent Primary use/source CAS number MRL 

(μg/L)

Perchlorate Rocket fuel, fireworks, flares 14797-73-0 0.5

1,2,3-Trichloropropane Solvent 25735-29-9 0.005

N-Nitrosodimethylamine Rocket fuel manuf., plasticizer 62-75-9 0.002

Table 2F. Constituents of special interest: perchlorate, 1,2,3-tricholoropropane, and N-nitrosodimethylamine (NDMA), Chemical Abstract 

Service (CAS) number, and minimum reporting level (MRL) for Montgomery Watson Harza Laboratory.

[μg/L, micrograms per liter]

Constituent CAS number LRL 

μg/L)

Ammonia 7664-41-7 0.04

Nitrite 14797-65-0 0.008

Nitrate plus nitrite NA 0.06

Total nitrogen (ammonia, nitrite, nitrate, organic nitrogen) 17778-88-0 0.03

Phosphorus, phosphate, ortho 14265-44-2 0.006

Dissolved organic carbon NA 0.3

Table 2G. Nutrients and dissolved organic carbon, Chemical Abstract Service (CAS) number, and laboratory reporting level (LRL) for the 

U.S. Geological Survey’s National Water Quality Laboratory analytical schedule 2755 and laboratory code 2613.

[NA, not available; μg/L, micrograms per liter]

42 Ground-Water Quality Data, North San Francisco Bay Hydrologic Provinces, California, 2004: GAMA Program Results
Constituent CAS number LRL

Major and Minor Ions (μg/L)

Bromide 24959-67-9 0.02

Calcium 7440-70-2 0.02

Chloride 16887-00-6 0.2

Fluoride 16984-48-8 0.1

Iodide 20461-54-5 0.002

Magnesium 7439-95-4 0.008

Potassium 2023695 0.16

Silica 7631-86-9 0.04

Sodium 7440-23-5 0.2

Sulfate 14808-79-8 0.18

Dissolved solids (residue on evaporation) NA 10

Trace Elements (μg/L)

Aluminum 7429-90-5 1.6

Antimony 7440-36-0 0.2

Arsenic 7440-38-2 0.2

Barium 7440-39-3 0.2

Beryllium 7440-41-7 0.06

Boron 7440-42-8 8

Cadmium 7440-43-9 0.04

Chromium 7440-47-3 0.8

Cobalt 7440-48-4 0.014

Copper 7440-50-8 0.4

Iron 7439-89-6 6

Lead 7439-92-1 0.08

Lithium 7439-93-2 0.6

Manganese 7439-96-5 0.2

Mercury 7439-97-6 0.01

Molybdenum 7439-98-7 0.4

Nickel 7440-02-0 0.06

Selenium 7782-49-2 0.4

Silver 7440-22-4 0.2

Strontium 7440-24-6 0.4

Thallium 7440-28-0 0.04

Tungsten 7440-33-7 0.5

Uranium 7440-61-1 0.04

Vanadium 7440-62-2 0.14

Zinc 7440-66-6 0.6

Table 2H. Major and minor ions and trace elements, Chemical Abstract Service (CAS) number, and laboratory reporting level (LRL) for 

the U.S. Geological Survey’s National Water Quality Laboratory analytical schedule 1948.

[NA, not available; mg/L, milligrams per liter; μg/L, micrograms per liter]

Tables 43
Constituent CAS number MDL

(μg/L)

Iron 7439-89-6 1

Iron (II) 7439-89-6 1

Arsenic 7440-38-2 0.5

Arsenic (III) 1327-53-3 1

Chromium 7440-47-3 0.1

Hexavalent chromium (VI) 11104-59-9 0.1

Table 2I. Iron, arsenic and chromium speciation, Chemical Abstract Service (CAS) number, and method detection limit (MDL) for the U.S. 

Geological Survey’s National Research Program Laboratory, Boulder, Colorado.

[μg/L, micrograms per liter]

Constituent CAS number Reporting 

level type

Reporting level/

uncertainty Reporting units

Radon-222 14859-67-7 SSMDC 26 pCi/L

Tritium1 10028-17-8 SSMDC 1 pCi/L

Deuterium/protium2 7782-39-0/1333-74-0 MU 2 Per mil

Oxygen-18/oxygen-162 NA/7782-44-7 MU 0.2 Per mil

Gross-alpha radioactivity, 72-hour count3 12587-46-1 SSMDC 3 pCi/L

Gross-alpha radioactivity, 30-day count3 12587-46-1 SSMDC 3 pCi/L

Gross-beta radioactivity, 72-hour count3 12587-47-2 SSMDC 4 pCi/L

Gross-beta radioactivity, 30-day count3 12587-47-2 SSMDC 4 pCi/L

Radium-2263 13982-63-3 SSMDC 0.04 pCi/L

Radium-2283 15262-20-1 SSMDC 1 pCi/L

Carbon-13/Carbon-124 NA/7440-44-0 1 sigma 0.05 Per mil

Carbon-144 14762-75-5 1 sigma 0.0015 Percent modern

Table 2J. Isotopic and radioactive constituents, Chemical Abstract Service (CAS) number, reporting level type, reporting level and 

(or) uncertainty, and reporting units for the U.S. Geological Survey’s National Water Quality Laboratory, Stable Isotope and Tritium 

Laboratory, Menlo Park, California1, Stable Isotope Laboratory, Reston, Virginia2, and the contract laboratories Eberline Analytical 

Services3 and the University of Arizona, Accelerator Mass Spectrometry Laboratory4.

[MU, method uncertainty; NA, not available; pCi/L, picocuries per liter; SSMDC, sample specific minimum detectable concentration]

44 Ground-Water Quality Data, North San Francisco Bay Hydrologic Provinces, California, 2004: GAMA Program Results
Constituent CAS number MU 

(percent) Unit

Tritium 10028-17-8 NA pCi/L

Helium-3/Helium-4 NA/7440-59-7 0.75 NA

Helium-4 7440-59-7 2 cm3 STP/g

Argon 7440-37-1 2 cm3 STP/g

Krypton 7439-90-9 2 cm3 STP/g

Neon 7440-01-09 2 cm3 STP/g

Xenon 7440-63-3 2 cm3 STP/g

Methane 74-82-8 4 cm3 STP/g

Nitrogen 7727-37-9 2 cm3 STP/g

Oxygen 7782-44-7 2 cm3 STP/g

Carbon dioxide 124-38-9 4 cm3 STP/g

Table 2K. Tritium and dissolved gases, Chemical Abstract Service (CAS) number, method uncertainty (MU) and reporting units for 

Lawrence Livermore National Laboratory.

[NA, not available; cm3 STP/g, cubic centimeter of gas at standard temperature and pressure per gram of water; pCi/L, picocuries per liter] 

Microbial constiuent Primary use/source MDL

Total coliforms Water quality indicator/Soil, water and intestinal tracts of animals 1 colony/100ml

Escherichia coliform Sewage and animal waste indicator/ Intestinal tracts of humans and animals 1 colony/100ml

F-specific coliphage Viral indicator/Intestinal tracts of warm-blooded animals NA

Somatic coliphage Viral indicator/Fecal contaminated waters NA

Table 2L. Microbial constiuents, primary use and source, and method detection limit (MDL) for the U.S. Geological Survey’s Ohio 

Microbiology Laboratory parameter codes 90901, 90900, 99335 and 99332.

[NA, not available; ml, milliliters]

Tables 45
Expanded schedule Basic-plus schedule

Water-quality indicators (pH, SC, DO, temperature, alkalinity) Water-quality indicators (SC and temperature)

Volatile organic compounds Volatile organic compounds

Gasoline additives and oxygenates Gasoline additives and oxygenates

Pesticides Pesticides

Polar pesticides and degradates Polar pesticides and degradates

Waste-water indicator constituents Waste-water indicator constituents

Compounds of special interest (perchlorate, NDMA, 

trichloropropane)

Compounds of special interest (perchlorate, NDMA, 

trichloropropane)

Nutrients and dissolved organic carbon Major and minor ions and trace elements

Major and minor ions and trace elements Chromium abundance and speciation 

Chromium abundance and speciation Arsenic and iron speciation

Arsenic and iron speciation Stable isotopes of hydrogen and oxygen

Stable isotopes of hydrogen and oxygen Tritium1

Carbon isotopes Tritium and noble gases2

Radium isotopes

Radon-222

Tritium1

Tritium and noble gases2

Gross alpha/beta radiation

Microbial constituents

Basic schedule Hydrothermal schedule

Water-quality indicators (SC and temperature) Water-quality indicators (pH, SC, DO, temperature, alkalinity)

Volatile organic compounds Major and minor ions and trace elements

Gasoline additives and oxygenates Chromium abundance and speciation 

Pesticides Arsenic and iron speciation

Polar pesticides and degradates Stable isotopes of hydrogen and oxygen

Waste-water indicator constituents Tritium1

Compounds of special interest (perchlorate, NDMA, trichloropropane) Tritium and noble gases2

Chromium abundance and speciation Dissolved gases2 (nitrogen, carbon dioxide, argon, oxygen, and 

methane)

Stable isotopes of hydrogen and oxygen

Tritium1

Tritium and noble gases2

1

Analyzed at the U.S. Geological Survey stable isotope and tritium lab, Menlo Park, California. 

2

Analyzed at Lawrence Livermore National Laboratory, Livermore, California.

Table 3. Classes of chemical and microbial constituents and water-quality indicators collected for the expanded, basic-plus, basic, and 

hydrothermal sampling schedules for the North San Francisco Bay Ground-Water Ambient Monitoring and Assessment (GAMA) study, 

California, August to November 2004.

[DO, dissolved oxygen; NDMA, N-nitrosodimethylamine; SC, specific conductance]

46 Ground-Water Quality Data, North San Francisco Bay Hydrologic Provinces, California, 2004: GAMA Program Results
Constituent Primary classification Analytical schedules Preferred1

 analytical schedule

Acetone VOC 2020, 4204 2020

Diisopropyl ether VOC 2020, 4204 2020

Methyl tert-butyl ether (MTBE) VOC 2020, 4204 2020

Methyl tert-amyl ether VOC 2020, 4204 2020

tert-Butyl ethyl ether VOC 2020, 4204 2020

1,4-Dichlorobenzene VOC 1433, 2020 2020

Isopropylbenzene VOC 1433, 2020 2020

Naphthalene VOC 1433, 2020 2020

Tetrachloroethene VOC 1433, 2020 2020

Tribromomethane (bromoform) VOC 1433, 2020 2020

Caffeine Waste-water indicator 1433, 2060, 9003 2060

Cotinine Waste-water indicator 1433, 9003 1433

Atrazine Pesticide 2003, 2060 2003

Bromacil Pesticide 1433, 2060 2060

Carbaryl Pesticide 1433, 2003, 2060 2003

Chlorpyrifos Pesticide 1433, 2003 2003

Deethyl atrazine Pesticide degradate 2003, 2060 2003

Diazinon Pesticide 1433, 2003 2003

Dichlorvos Pesticide 1433, 2003 2003

Metalaxyl Pesticide 1433, 2003, 2060 2060

Metolachlor Pesticide 1433, 2003 2003

Prometon Pesticide 1433, 2003 2003

1

Preferred analytical schedules are the most accurate and precise methods of analysis for the constituent shown.

Table 4. Constituents analyzed in ground-water samples collected for the North San Francisco Bay Ground-Water Ambient Monitoring 

and Assessment (GAMA) study, that appear on multiple analytical schedules, primary constituent classification, analytical schedules 

constituent appears on, and preferred analytical schedule.

[VOC, volatile organic compound]

Tables 47
Constituent 

Maximum

 concentration 

detected in 

equipment 

blank samples

(μg/L)

Number of

 field blank

 detections/

analyses

Maximum 

concentration

 detected in field

blank samples

(μg/L) 

Minimum

 concentration 

detected in groundwater samples 

(μg/L)

Number of 

ground-water 

samples 

censored

Volatile Organic Compounds and Gasoline Additives and (or) Oxygenates

Acetone — 1/131 E2.9 E3 0

Carbon disulfide — 1/131 E0.07 E0.078 0

Ethyl benzene E0.06 4/13 E0.06 — 0

m-Xylene plus p-xylene 0.29 4/131 0.29 E0.04 0

o-Xylene E0.09 4/13 0.11 E0.065 0

Toluene 0.1 4/131 0.11 E0.08 0

Trimethylbenzene — 0/131 — E0.06 0

Pesticides and (or) Pesticide Degradates

Atrazine — 1/132 E0.005 E0.006 0

Waste-Water Indicators

Naphthalene — 1/21 E0.04 E0.41 0

Phenol 0.6 8/211 1.1 E0.23 483

Triclosan — 1/21 E0.08 E0.07 0

Major and Minor Ions

Calcium4 0.01 5/5 0.014 0.86 0

Chloride4 — 1/5 E0.1 4.6 0

Iodide — 1/2 E0.001 E0.001 0

Silica4 0.04 5/5 0.06 15.3 0

Trace Elements

Aluminum — 1/5 E0.9 E0.8 0

Arsenic 0.1 1/5 E0.1 E0.1 0

Manganese — 2/5 E0.1 E0.1 0

Nickel — 1/5 0.07 E0.05 0

Zinc — 2/5 E0.5 0.6 0

Nutrients and Dissolved Organic Carbon

DOC — 2/3 0.5 0.2 4

1

Constituents also detected in associated source solution blanks.

2

Waste-water indicators detected in one of two associated source solution blanks.

3

Due to ongoing problems with the analytical procedures used to determine phenol, all ground-water samples with phenol were censored.

4

Concentration in milligrams per liter.

Table 5. Quality-control summary for volatile organic compounds and gasoline additives and (or) oxygenates, pesticides and (or) 

pesticide degradates, waste-water indicators, major and minor ions, trace elements, and nutrients and dissolved organic carbon, 

detected in equipment blanks, field blanks and ground-water samples collected for the North San Francisco Bay Ground-Water 

Ambient Monitoring and Assessment (GAMA) study, California, August to November 2004.

[Censored data are reported but not used in summary statistics; E, estimated value; μg/L, micrograms per liter; —, not detected]

48 Ground-Water Quality Data, North San Francisco Bay Hydrologic Provinces, California, 2004: GAMA Program Results
Constituent1

Number of relative standard 

deviations greater than 

20 percent/replicate pairs

Maximum relative standard 

deviation

(percent)

Median of relative standard 

deviations greater than zero 

(percent)

Volatile Organic Compounds and Gasoline Oxygenates and (or) Additives (Schedules 2020 and 4204)

All additional VOCs from 

Schedule 2020 and 4204

0/8 0 NA

Pesticides and (or) Pesticide Degradates (Schedules 2003 and 2060)

Simazine 0/8 8.3 0

All additional pesticides from 

Schedule 2003

0/9 0 NA

All additional pesticides from 

Schedule 2060

0/4 0 NA

Waste-Water Indicators (Schedule 1433)

Phenol 2/6 54 11

All additional waste-water compounds from Schedule 14330/8 0 NA

Constituents of Special Interest 

Perchlorate2 0/6 0 NA

1,2,3 - Trichloropropane2 0/6 0 NA

N-Nitrosodimethylamine2 0/6 0 NA

1

Due to the large number of constituents, only constituents with relative standard deviations above zero are shown.

2

Samples analyzed at Montgomery Watson Laboratories, California.

Table 6A. Quality-control summary of replicate volatile organic compound (VOC) and gasoline additives and (or) oxygenates, pesticides 

and (or) pesticide degradates, waste-water indicators, and samples for constituents of special interest with relative standard deviations 

greater than zero, collected for the North San Francisco Bay Ground-Water Ambient Monitoring and Assessment (GAMA) study, 

California, August to November 2004.

[NA, not available]

Tables 49
Table 6B. Quality-control summary of replicate nutrient and dissolved organic carbon samples collected for the North San Francisco 

Bay Ground-Water Ambient Monitoring and Assessment (GAMA) study, California, August to November 2004.

[NA, not available]

Constituent 

Number of relative standard 

deviations greater than

 20 percent/replicate pairs

Maximum relative standard 

deviation 

(percent)

Median of relative standard 

deviations greater than zero 

(percent)

Dissolved organic carbon 0/3 0 NA

Phosphorus 0/3 0.4 0

Total nitrogen 0/3 1.2 0

Nitrate plus nitrite 0/3 1.1 0

Ammonia 0/3 0 NA

Nitrite 0/3 0 NA

Constituent 

Number of relative standard 

deviations greater than 

20 percent/replicate pairs

Maximum relative standard 

deviation

 (percent)

Median of relative standard 

deviations greater than zero 

(percent)

Bromide 1/4 84.9 25.3

Calcium 0/4 4.0 1.6

Chloride 0/4 1.6 0.4

Fluorine 0/4 8.8 4.0

Iodide 0/3 0.0 NA

Magnesium 0/4 3.0 1.5

Potassium 0/4 3.2 2.2

Silica 0/4 4.4 1.9

Sodium 0/4 2.1 1.0

Sulfate 0/4 16.2 4.1

Table 6C. Quality-control summary of replicate major and minor ion samples collected for the North San Francisco Bay Ground-Water 

Ambient Monitoring and Assessment (GAMA) study, California, August to November 2004.

[NA, not available]

50 Ground-Water Quality Data, North San Francisco Bay Hydrologic Provinces, California, 2004: GAMA Program Results
Constituent

Number of relative standard 

deviations greater than 

20 percent/replicate pairs

Maximum relative 

standard deviation

 (percent)

Median of relative standard 

deviations greater than zero 

(percent)

Aluminum 0/3 0 NA

Antimony 0/3 0 NA

Arsenic1 0/3 8.4 4.2

Arsenic2 0/4 7.7 1.9

Arsenic (III)2 0/4 6.7 1.9

Barium 0/3 0.9 0.6

Beryllium 0/3 0 NA

Boron 0/3 5.2 1.1

Cadmium 0/3 0 NA

Chromium1 0/3 7.4 0

Chromium2 5/11 53 27

Chromium (VI)2 6/13 96 31

Cobalt 0/3 4.3 3.8

Copper 0/3 20 19

Iron1 0/4 6.6 3.1

Iron2 1/4 57 15

Iron (II)2 1/4 61 17

Lead 0/3 18 4.2

Lithium 0/3 2.2 1.2

Manganese 0/3 1.7 0.6

Mercury 0/3 0 NA

Molybdenum 0/3 13 0

Nickel 0/3 4.2 3.6

Selenium 0/3 0 NA

Silver 0/3 0 NA

Strontium 0/3 0.7 0.6

Thallium 0/0 0 NA

Tungsten 0/4 0 NA

Uranium 0/3 13 0

Vanadium 1/3 46 2.4

Zinc 0/3 17 1.4

1

Samples analyzed at U.S. Geological Survey national water-quality laboratory, Denver, Colorado.

2

Samples analyzed at U.S. Geological Survey national research program laboratory, Boulder, Colorado.

Table 6D. Quality-control summary of replicate trace-element samples collected for the North San Francisco Bay Ground-Water 

Ambient Monitoring and Assessment (GAMA) study, California, August to November 2004.

[NA, not available]

Tables 51
Constituent 

Number of relative standard 

deviations greater than 

20 percent/replicate pairs

Maximum relative 

standard deviation 

(percent)

Median of relative standard 

deviations greater than zero 

(percent)

Alpha radioactivity, 30 day count 3/3 138 57

Alpha radioactivity, 72 hour count 3/3 36 31

Beta radioactivity, 30 day count 2/3 39 33

Beta radioactivity, 72 hour count 1/3 25 13

Radon-222 0/3 2.1 1.0

Radium-226 1/3 48 20

Radium-228 3/3 110 54

Deuterium/Protium 0/10 3.2 0.6

Tritium1 4/11 137 31

Tritium2 0/9 19 10

Carbon-13/Carbon-12 NA NA NA

Carbon-14 percent modern 1/6 33 0.3

Oxygen-18/Oxygen-16 0/10 1.4 0.5

He1 0/10 6.6 0.5 

Ne1 0/10 5.9 1.7 

Ar1 0/10 11 0.4 

Kr1 0/10 3.6 1.6

Xe1 0/10 2.2 0.6

 1Analysis done at Lawrence Livermore National Laboratory, Livermore, California. 

2

Analysis done at U.S. Geological Survey, Menlo Park, California.

Table 6E. Quality-control summary of replicate isotope and radioactivity samples collected for the North San Francisco Bay GroundWater Ambient Monitoring and Assessment (GAMA) study, California, August to November 2004.

[NA, not available]

52 Ground-Water Quality Data, North San Francisco Bay Hydrologic Provinces, California, 2004: GAMA Program Results
Constituent

Number of 

spike 

samples

Minimum 

recovey

 (percent)

Maximum 

recovey 

(percent)

Median 

recovey

 (percent)

1,1,1,2-Tetrachloroethane 9 94 120 111

1,1,1-Trichloroethane (TCA)1 9 104 135 128

1,1,2,2-Tetrachloroethane 9 98 123 110

1,1,2-Trichloroethane 9 106 136 114

1,1,2-Trichlorotrifluoroethane (CFC-113) 9 96 129 112

1,1-Dichloroethane1 9 104 127 118

1,1-Dichloroethylene (DCE) 9 102 130 111

1,1-Dichloropropene 9 109 132 118

1,2,3,4-Tetramethylbenzene 9 87 115 104

1,2,3,5-Tetramethylbenzene (isodurene) 9 92 128 117

1,2,3-Trichlorobenzene1 9 86 113 102

1,2,3-Trichloropropane 9 97 127 111

1,2,3-Trimethylbenzene1 9 87 113 103

1,2,4-Trichlorobenzene 9 82 112 96

1,2,4-Trimethylbenzene 9 93 117 108

1,2-Dibromo-3-chloropropane (DBCP) 9 95 111 106

1,2-Dibromoethane 9 95 123 110

1,2-Dichlorobenzene 9 95 111 105

1,2-Dichloroethane 9 107 137 126

1,2-Dichloropropane 9 93 120 105

1,3,5-Trimethylbenzene 9 82 112 101

1,3-Dichlorobenzene 9 90 109 101

1,3-Dichloropropane 9 97 118 107

1,4-Dichlorobenzene 9 90 107 99

1,2,3-Tricholorpropane (TCP)2 10 93 101 95

2,2-Dichloropropane 9 104 126 117

2-Chlorotoluene 9 91 113 103

2-Hexanone 9 101 127 115

3-Chloropropene 9 102 125 114

4-Chlorotoluene 9 89 113 101

4-Isopropyl-1-methylbenzene 9 89 110 101

4-Methyl-2-pentanone 9 94 118 110

Acetone1,3 9 111 149 126

Acrylonitrile 9 100 122 113

Benzene 9 100 120 111

Bromobenzene 9 90 108 101

Bromochloromethane1 9 99 119 109

Bromodichloromethane 9 111 136 121

Bromoethene 9 102 131 113

Bromoform (tribromomethane)1 9 101 132 115

Table 7A. Quality-control summary of volatile organic compounds (VOCs), gasoline additives and oxygenates, NDMA and 1,2,3-

trichloropropane matrix spike recoveries in samples collected for the North San Francisco Bay Ground-Water Ambient Monitoring 

and Assessment (GAMA) study, California, August to November 2004.

[Bold values indicate recovery values outside acceptable range, 70 to 130 percent]

Tables 53
Constituent

Number of 

spike 

samples

Minimum 

recovey

 (percent)

Maximum 

recovey 

(percent)

Median 

recovey

 (percent)

Bromomethane 9 88 148 123

Butylbenzene 9 76 103 91

Carbon disulfide1 9 80 153 96

Chlorobenzene 9 94 114 106

Chloroethane 9 96 122 113

Chloroform (trichloromethane)1 9 102 119 113

Chloromethane 9 91 128 105

cis-1,2-Dichloroethylene1 9 95 119 108

cis-1,3-Dichloropropene 9 89 109 98

Dibromochloromethane1 9 101 125 115

Dibromomethane 9 104 124 111

Dichlorodifluoromethane (CFC-12) 9 81 124 104

Dichloromethane (methylene chloride) 9 95 116 109

Diethyl ether 9 94 128 113

Diisopropyl ether1 9 98 115 111

Ethyl methacrylate 9 95 114 102

Ethyl tert-butyl ether (ETBE)1 9 111 135 123

Ethylbenzene 9 96 115 106

Hexachlorobutadiene 9 92 116 98

Hexachloroethane 9 98 117 112

Isopropylbenzene 9 100 119 108

m- and p-Xylene1 9 96 114 102

Methyl acetate 9 98 112 104

Methyl acrylate 9 100 128 112

Methyl acrylonitrile 9 97 122 112

Methyl iodide 9 80 126 99

Methyl methacrylate 9 91 111 100

Methyl tert-butyl ether(MTBE)1,3 9 97 127 113

Naphthalene 9 75 106 98

Nitrosodimethylamine2 (NDMA) 10 56 90 73

n-Propylbenzene 9 87 113 102

o-Ethyl toluene 9 91 109 100

o-Xylene1 9 94 114 104

sec-Butylbenzene 9 98 114 104

Styrene 9 87 111 107

tert-Amyl methyl ether1 9 96 123 111

tert-Amyl alcohol 9 93 111 101

tert-Butyl alcohol 9 93 117 105

tert-Butyl ethyl ether1 9 104 128 116

tert-Butylbenzene 9 104 127 115

Table 7A. Quality-control summary of volatile organic compounds (VOCs), gasoline additives and oxygenates, NDMA and 1,2,3-

trichloropropane matrix spike recoveries in samples collected for the North San Francisco Bay Ground-Water Ambient Monitoring 

and Assessment (GAMA) study, California, August to November 2004—Continued.

[Bold values indicate recovery values outside acceptable range, 70 to 130 percent]

54 Ground-Water Quality Data, North San Francisco Bay Hydrologic Provinces, California, 2004: GAMA Program Results
Constituent

Number of 

spike 

samples

Minimum 

recovey

 (percent)

Maximum 

recovey 

(percent)

Median 

recovey

 (percent)

Tetrachloroethylene (PCE)1 9 97 121 106

Tetrachloromethane (carbon tetrachloride)1 9 100 138 134

Tetrahydrofuran1 9 96 125 118

Toluene1 9 96 115 106

trans-1,2-Dichloroethylene 9 96 118 107

trans-1,3-Dichloropropene 9 94 116 111

trans-1,4-Dichloro-2-butene 9 114 155 141

Trichloroethylene (TCE)1 9 99 121 112

Trichlorofluoromethane (CFC-11) 9 107 148 134

Vinyl chloride 9 110 145 121

 1Constituent detected in ground-water samples.

2

Constituent analyzed by Montgomery Watson on the constituents of special interest schedule.

3

Constituent on schedules 2020 and 4024; only 2020 values are reported because it is the preferred analytical schedule.

Table 7A. Quality-control summary of volatile organic compounds (VOCs), gasoline additives and oxygenates, NDMA and 1,2,3-

trichloropropane matrix spike recoveries in samples collected for the North San Francisco Bay Ground-Water Ambient Monitoring 

and Assessment (GAMA) study, California, August to November 2004—Continued.

[Bold values indicate recovery values outside acceptable range, 70 to 130 percent]

Tables 55
Constituent

Number 

of spike 

samples

Minimum 

recovery 

(percent)

Maximum 

recovery 

(percent)

Median 

recovery 

(percent)

Single 

value 

(percent)

1-Naphthol 5 8 24 16 NA

2,6-Diethylaniline 5 80 115 98 NA

2-Chloro-2’,6’-diethylacetanilide 5 80 130 91 NA

2-Chloro-4-isopropylamino-6-amino-s-triazine (deethyl atrazine)1 5 36 70 43 NA

2-Ethyl-6-methylaniline 5 71 104 95 NA

3,4-Dichloroaniline 5 43 92 81 NA

4-Chloro-2-methylphenol 5 53 100 69 NA

Acetochlor 5 70 125 91 NA

Alachlor 5 77 127 97 NA

Atrazine1 5 91 134 106 NA

Azinphos-methyl 5 50 134 62 NA

Azinphos-methyl oxygen analog 5 31 111 42 NA

Benfluralin, water 5 54 68 57 NA

Carbaryl 5 77 112 98 NA

Chlorpyrifos 5 76 122 86 NA

Chlorpyrifos oxygen analog 5 15 52 50 NA

cis-Permethrin 5 33 80 46 NA

Cyfluthrin 5 29 116 42 NA

Cypermethrin 5 27 93 35 NA

dacthal (DCPA) 5 97 143 118 NA

Desulfinyl fipronil 5 79 129 94 NA

Desulfinylfipronil amide 5 57 127 66 NA

Diazinon1 5 82 119 86 NA

Diazinon oxygen analog 5 58 86 63 NA

Dichlorvos 5 19 68 46 NA

Dicrotophos 5 12 32 26 NA

Dieldrin 5 86 270 108 NA

Dimethoate 5 17 27 27 NA

Ethion 5 44 107 62 NA

Ethion monoxon 5 72 139 77 NA

Fenamiphos 5 31 131 63 NA

Fenamiphos sulfone 5 40 148 62 NA

Fenamiphos sulfoxide 5 19 94 56 NA

Fipronil 5 67 82 81 NA

Fipronil sulfide 5 69 111 85 NA

Fipronil sulfone 5 52 118 77 NA

Fonofos 5 72 105 97 NA

Fonofos oxygen analog 5 57 83 58 NA

Hexazinone 5 44 111 61 NA

Iprodione 5 52 100 83 NA

Table 7B. Quality-control summary of matrix pesticide spike recoveries in samples collected for the North San Francisco Bay GroundWater Ambient Monitoring and Assessment (GAMA) study, California, August to November 2004. 

[Bold values indicate spike recoveries outside the acceptable range, 70 to 130 percent; NA, not available]

56 Ground-Water Quality Data, North San Francisco Bay Hydrologic Provinces, California, 2004: GAMA Program Results
Constituent

Number 

of spike 

samples

Minimum 

recovery 

(percent)

Maximum 

recovery 

(percent)

Median 

recovery 

(percent)

Single 

value 

(percent)

Isofenphos 5 65 101 80 NA

Malaoxon 5 61 78 69 NA

Malathion 5 103 142 107 NA

Metalaxyl 5 73 110 85 NA

Methidathion 5 75 149 82 NA

Methyl paraoxon 5 53 68 59 NA

Methyl parathion 5 62 86 76 NA

Metolachlor 5 109 143 113 NA

Metribuzin 5 60 90 66 NA

Myclobutanil 5 67 128 76 NA

Pendimethalin 5 78 88 84 NA

Phorate 5 15 70 30 NA

Phorate oxygen analog 5 34 70 48 NA

Phosmet 5 13 63 31 NA

Phosmet oxygen analog 5 10 52 21 NA

Prometon 5 74 115 85 NA

Prometryn 5 72 108 81 NA

Pronamide 5 74 118 91 NA

Simazine1 5 85 123 95 NA

Tebuthiuron 5 82 163 100 NA

Terbufos 5 39 71 59 NA

Terbufos oxygen analog sulfone 5 75 85 78 NA

Terbuthylazine 5 89 136 107 NA

Trifluralin1 5 55 77 68 NA

2,4-D (2,4-Dichlorophenoxyacetic acid) 1 NA NA NA 108

2,4-D methyl ester 1 NA NA NA 96

2,4-DB (4-(2,4-dichlorophenoxy)butanoic acid) 1 NA NA NA 91

2-Chloro-4-isopropylamino-6-amino-s-triazine (deethyl atrazine)1 1 NA NA NA 86

2-Chloro-6-ethylamino-4-amino-s-triazine (deisopropyl atrazine)1 1 NA NA NA 83

2-Hydroxy-4-isopropylamino-6-ethylamino-s-triazine (hydroyatrazine) 1 NA NA NA 126

3-Hydroxy carbofuran 1 NA NA NA 93

3-Ketocarbofuran 1 NA NA NA 14

Acifluorfen 1 NA NA NA 112

Aldicarb 1 NA NA NA 62

Aldicarb sulfone 1 NA NA NA 69

Aldicarb sulfoxide 1 NA NA NA 67

Atrazine1 1 NA NA NA 97

Bendiocarb 1 NA NA NA 101

Benomyl 1 NA NA NA 63

Bensulfuron 1 NA NA NA 128

Table 7B. Quality-control summary of matrix pesticide spike recoveries in samples collected for the North San Francisco Bay GroundWater Ambient Monitoring and Assessment (GAMA) study, California, August to November 2004—Continued. 

[Bold values indicate spike recoveries outside the acceptable range, 70 to 130 percent; NA, not available]

Tables 57
Constituent

Number 

of spike 

samples

Minimum 

recovery 

(percent)

Maximum 

recovery 

(percent)

Median 

recovery 

(percent)

Single 

value 

(percent)

Bentazon 1 NA NA NA 70

Bromacil 1 NA NA NA 87

Bromoxynil 1 NA NA NA 71

Caffeine 1 NA NA NA 84

Carbaryl 1 NA NA NA 96

Carbofuran 1 NA NA NA 95

Chloramben methyl ester 1 NA NA NA 83

Chlorimuron 1 NA NA NA 160

Chlorodiamino-s-triazine 1 NA NA NA 121

Chlorothalonil 1 NA NA NA 13

Clopyralid 1 NA NA NA 50

Cycloate 1 NA NA NA 85

Dacthal monoacid 1 NA NA NA 102

Dicamba 1 NA NA NA 87

Dichlorprop 1 NA NA NA 95

Dinoseb 1 NA NA NA 107

Diphenamid1 1 NA NA NA 96

Diuron 1 NA NA NA 101

Fenuron 1 NA NA NA 93

Flumetsulam 1 NA NA NA 137

Fluometuron 1 NA NA NA 97

Imazaquin 1 NA NA NA 110

Imazethapyr 1 NA NA NA 108

Imidacloprid 1 NA NA NA 116

Linuron 1 NA NA NA 94

MCPA 1 NA NA NA 95

MCPB 1 NA NA NA 102

Metalaxyl 1 NA NA NA 95

Methiocarb 1 NA NA NA 98

Methomyl 1 NA NA NA 58

Metsulfuron 1 NA NA NA 94

N-(4-Chlorophenyl)-N’-methylurea 1 NA NA NA 66

Neburon 1 NA NA NA 97

Nicosulfuron 1 NA NA NA 101

Norflurazon 1 NA NA NA 99

Oryzalin 1 NA NA NA 79

Oxamyl 1 NA NA NA 92

Picloram 1 NA NA NA 79

Propham 1 NA NA NA 99

Table 7B. Quality-control summary of matrix pesticide spike recoveries in samples collected for the North San Francisco Bay GroundWater Ambient Monitoring and Assessment (GAMA) study, California, August to November 2004—Continued. 

[Bold values indicate spike recoveries outside the acceptable range, 70 to 130 percent; NA, not available]

58 Ground-Water Quality Data, North San Francisco Bay Hydrologic Provinces, California, 2004: GAMA Program Results
Constituent

Number 

of spike 

samples

Minimum 

recovery 

(percent)

Maximum 

recovery 

(percent)

Median 

recovery 

(percent)

Single 

value 

(percent)

Propiconazole 1 NA NA NA 86

Propoxur 1 NA NA NA 93

Siduron 1 NA NA NA 105

Sulfometuron1 1 NA NA NA 120

Tebuthiuron 1 NA NA NA 103

Terbacil 1 NA NA NA 91

Tribenuron methyl 1 NA NA NA 0

Triclopyr 1 NA NA NA 103

 1Constituent detected in ground-water samples.

Table 7B. Quality-control summary of matrix pesticide spike recoveries in samples collected for the North San Francisco Bay GroundWater Ambient Monitoring and Assessment (GAMA) study, California, August to November 2004—Continued. 

[Bold values indicate spike recoveries outside the acceptable range, 70 to 130 percent; NA, not available]

Tables 59
Constituent

Number of 

spike

 samples

Minimum

 recovery 

(percent)

Maximum 

recovery 

(percent)

Median

 recovey

 (percent)

1,4-Dichlorobenzene 4 43 70 57

1-Methylnaphthalene 4 61 90 80

2,6-Dimethylnaphthalene 4 57 93 85

2-Methylnaphthalene 4 57 98 84

3-beta-Coprostanol 4 23 92 56

3-Methyl-1H-indole (skatol) 4 54 120 96

3-tert-Butyl-4-hydroxyanisole (BHA) 4 11 33 21

4-Cumylphenol, water 4 48 98 85

4-Nonylphenol 4 41 101 58

4-Octylphenol 4 41 89 69

4-tert-Octylphenol 4 46 98 85

5-Methyl-1H-benzotriazole 4 22 85 54

9,10-Anthraquinone 4 38 97 79

Acetophenone 4 63 112 110

Acetyl hexamethyl tetrahydro naphthalene (tonalide) 4 61 122 96

Anthracene, water 4 70 111 98

Benzo[a]pyrene 4 52 91 72

Benzophenone 4 57 120 104

beta-Sitosterol 4 0 73 49

beta-Stigmastanol 4 0 65 51

Bisphenol A1 4 32 102 77

Bromacil 4 77 108 106

Caffeine1 4 73 120 102

Camphor 4 73 99 92

Carbaryl 4 30 87 69

Carbazole 4 70 120 100

Chlorpyrifos 4 61 112 90

Cholesterol 4 42 78 59

Cotinine 4 55 108 83

DEET 4 59 120 103

Diazinon1 4 70 133 103

Dichlorvos 3 0 3 2

Diethoxynonylphenol NPEO2 total) 4 38 114 107

Diethoxyoctylphenol (OPEO2) 4 32 174 44

d-Limonene1 4 16 55 36

Ethoxyoctylphenol (OPEO1)1 4 27 106 40

Fluoranthene 4 77 120 102

Hexahydrohexamethyl cyclopentabenzopyran (galaxolide) 4 55 122 81

Indole, water1 4 57 92 79

Isoborneol, water 4 64 102 92

Isophorone1 4 70 107 101

Table 7C. Quality-control summary of matrix waste-water indicators spike recoveries in samples collected for the North San Francisco 

Bay Ground-Water Ambient Monitoring and Assessment (GAMA) study, California, August to November 2004.

[Bold values indicate spike recoveries outside the acceptable range, 70 to 130 percent]

60 Ground-Water Quality Data, North San Francisco Bay Hydrologic Provinces, California, 2004: GAMA Program Results
Constituent

Number of 

spike

 samples

Minimum

 recovery 

(percent)

Maximum 

recovery 

(percent)

Median

 recovey

 (percent)

Isopropylbenzene (Cumene) 4 25 56 38

Isoquinoline 4 46 97 86

Menthol1 4 50 104 79

Metalaxyl 4 68 133 111

Methyl salicylate 4 57 102 98

Metolachlor 4 64 122 103

Naphthalene1 4 55 90 76

p-Cresol1 4 50 111 95

Pentachlorophenol 4 31 86 72

Phenanthrene 4 68 107 95

Phenol1 4 67 189 155

Prometon 4 54 122 98

Pyrene 4 66 99 94

Tetrachloroethene1 4 16 36 24

Tribromomethane1 4 50 78 65

Tributyl phosphate 4 48 143 105

Triclosan1 4 52 100 95

Triethyl citrate 4 54 120 109

Triphenyl phosphate1 4 73 112 104

Tris(2-butoxyethyl) phosphate 4 75 152 122

Tris(2-chloroethyl) phosphate 4 64 120 107

Tris(dichloroisopropyl) phosphate 4 73 112 101

 1Constituent detected in ground-water samples.

Table 7C. Quality-control summary of matrix waste-water indicators spike recoveries in samples collected for the North San Francisco 

Bay Ground-Water Ambient Monitoring and Assessment (GAMA) study, California, August to November 2004—Continued.

[Bold values indicate spike recoveries outside the acceptable range, 70 to 130 percent]

Tables 61
Surrogate Analytical 

schedule

Constituent

 class

Number of 

analyses

(environmental, blank, 

replicate)

Number of 

surrogate 

recoveries 

below 70 percent (environmental, blank, 

replicate)

Number of 

surrogate 

recoveries 

between 

70 and 130 

percent 

(environmental, blank, 

replicate)

Number of 

surrogate 

recoveries 

above 130 

percent 

(environmental, blank, 

replicate)

1,2-Dichloroethane-d4 2020 Volatile organic compound 89, 13, 18 0, 0, 0 89, 13, 18 0, 0, 0

1-Bromo-4-fluorobenzene 2020 Volatile organic compound 89, 13, 18 0, 0, 0 89, 13, 18 0, 0, 0

Toluene-d8 2020 Volatile organic compound 89, 13, 18 0, 0, 0 89, 13, 18 0, 0, 0

1,2-Dichloroethane-d4 4024 Gasoline additive/oxygenate 89, 13, 18 0, 0, 0 89, 13, 18 0, 0, 0

1-Bromo-4-fluorobenzene 4024 Gasoline additive/oxygenate 89, 13, 18 0, 0, 0 89, 13, 18 0, 0, 0

Toluene-d8 4024 Gasoline additive/oxygenate 89, 13, 18 0, 0, 0 89, 13, 18 0, 0, 0

Isobutyl alcohol-d6 4024 Gasoline additive/oxygenate 89, 12, 17 0, 0, 0 89, 12, 17 0, 0, 0

alpha-HCH-d6 2003 Pesticides and/or degradate 87, 11, 19 0, 0, 0 87, 11, 19 0, 0, 0

Diazinon-d10 2003 Pesticides and/or degradate 87, 11, 19 37, 6, 8 50, 5, 11 0, 0, 0

2,4,5-T(2,4,5-trichlorophenoxyacetic acid)2060 Pesticides and/or degradate 22, 4, 8 0, 0, 1 22, 4, 7 0, 0, 0

Barban 2060 Pesticides and/or degradate 22, 4, 8 1, 0, 0 21, 4, 8 0, 0, 0

Caffeine-13C 2060 Pesticides and/or degradate 22, 4, 8 0, 0, 0 13, 1, 3 9, 3, 5

Bisphenol A-d3 1433 Waste-water indicator 89, 21, 19 87, 21, 19 2, 0, 0 0, 0, 0

Caffeine-13C 1433 Waste-water indicator 89, 21, 19 13, 4, 4 76, 17, 15 0, 0, 0

Decafluorobiphenyl 1433 Waste-water indicator 89, 21, 19 89, 21, 19 0, 0, 0 0, 0, 0

Fluoranthene-d10 1433 Waste-water indicator 89, 21, 19 4, 0, 2 85, 21, 17 0, 0, 0

Toluene-d8 MWL1 Constituent of special interest 87, 4, 12 0, 0, 0 87, 4, 12 0, 0, 0

NDMA-D6 MWL1 Constituent of special interest 87, 4, 12 52, 3, 7 34, 0, 3 1, 1, 2

1

Constituent analyzed at Montgomery Watson Harza Laboratory.

Table 8. Summary of surrogate recoveries for ground-water and quality-control analyses of volatile organic compounds, gasoline 

additives and (or) oxygenates, pesticides and (or) pesticide degradates, waste-water indicators, and constituents of special interest in 

samples collected for the North San Francisco Ground-Water Ambient Monitoring and Assessment (GAMA) study, California, August to 

November 2004.

62 Ground-Water Quality Data, North San Francisco Bay Hydrologic Provinces, California, 2004: GAMA Program Results
GAMA

 identification 

No.

Turbidity

(NTRU)

(63676)

Barometric 

pressure

 (mm of

 mercury)

(00025)

Dissolved 

oxygen 

(mg/L)

(00300)

pH, field

(standard

 units)

(00400)

Specific 

conductance, 

field

(μScm@25oC)

(00095)

Water 

temperature 

(oC) 

(00010)

Total

hardness 

(mg/L as 

CaCO3)

(00900) 

Alkalinity, 

dissolved

 (mg/L as 

CaCO3) 

(29802)

Bicarbonate, 

dissolved 

(mg/L as HCO3) 

(63786)

Carbonate, 

dissolved 

(mg/L as CO3) 

(63788)

Valley and Plains wells

NSFVP-01 NC NC NC NC 617 23.0 NC NC NC NCNSFVP-02 NC NC NC NC 380 19.8 NC NC NC NCNSFVP-03 NC NC NC NC 570 NC NC NC NC NCNSFVP-04 NC NC NC NC 180 20.0 NC NC NC NCNSFVP-05 NC NC NC NC 451 19.6 NC NC NC NCNSFVP-06 NC NC NC NC 361 18.5 NC NC NC NCNSFVP-07 NC NC NC NC 483 24.7 NC NC NC NCNSFVP-08 NC NC NC NC 256 17.6 NC NC NC NCNSFVP-09 NC NC NC NC 334 24.4 NC NC NC NCNSFVP-10 0.2 759 0.1 6.5 337 16.5 170 163 198 MNSFVP-11 NC NC NC NC 244 20.9 NC NC NC NCNSFVP-12 NC NC NC NC 278 25.4 NC NC NC NCNSFVP-13 NC NC NC NC 304 23.6 NC NC NC NCNSFVP-14 NC NC NC NC 348 28.3 NC NC NC NCNSFVP-15 NC NC NC NC 563 19.2 NC NC NC NCNSFVP-16 NC NC NC NC 506 27.3 NC NC NC NCNSFVP-17 NC NC NC NC 310 17.8 NC NC NC NCNSFVP-18 NC NC NC NC 164 15.5 NC NC NC NCNSFVP-19 0.1 756 0.4 6.7 269 22.9 130 125 152 MNSFVP-20 NC NC NC NC 612 17.2 NC NC NC NCNSFVP-21 NC NC NC NC 753 17.5 NC NC NC NCNSFVP-22 NC NC NC NC 614 18.5 NC NC NC NCNSFVP-23 NC NC NC NC 713 21.0 NC NC NC NCNSFVP-24 NC NC NC NC 817 19.0 NC NC NC NC

Table 9. Water-quality indicators determined in the field for the North San Francisco Bay Ground-Water Ambient Monitoring and Assessment (GAMA) study, California, August to November 2004.[The five-digit number below the constituent name is the U.S. Geological Survey parameter code used to uniquely identify a specific constituent or property; NTRU, nephelometric turbidity unit; NSFVP, Valley and Plains study area; NSFVPFP, Valley and Plains flow-path well; NSFVOL, Volcanic Highlands study area; NSFWG, Wilson Grove Formation Highlands study area; NSFWGFP, Wilson Grove Formation Highlands flow-path well; NSFHOT, hydrothermal study; μS/cm, microsiemens per centimeter; oC, degrees celsius; mg/L, milligrams per liter; mm, millimeter; NC, sample not collected; M, presence verified not quantified; —, not detected]

Tables 63
GAMA

 identification 

No.

Turbidity

(NTRU)

(63676)

Barometric 

pressure

 (mm of

 mercury)

(00025)

Dissolved 

oxygen 

(mg/L)

(00300)

pH, field

(standard

 units)

(00400)

Specific 

conductance, 

field

(μScm@25oC)

(00095)

Water 

temperature 

(

oC) 

(00010)

Total

hardness 

(mg/L as 

CaCO3

)

(00900) 

Alkalinity, 

dissolved

 (mg/L as 

CaCO3) 

(29802)

Bicarbonate, 

dissolved 

(mg/L as HCO3) 

(63786)

Carbonate, 

dissolved 

(mg/L as CO3) 

(63788)

NSFVP-25 NC NC NC NC 366 22.0 NC NC NC NCNSFVP-26 1.0 756 0.1 7.4 640 22.0 170 298 361 1NSFVP-27 NC NC NC NC 408 17.3 NC NC NC NCNSFVP-28 NC NC NC NC 869 20.1 NC NC NC NCNSFVP-29

— 756 5.7 6.8 362 16.7 190 167 203

M

NSFVP-30

— 753 0.6 7.2 440 18.0 200 189 229

M

NSFVP-31 NC NC NC NC 488 19.6 NC NC NC NCNSFVP-32 NC NC NC NC 441 35.4 130 NC NC NCNSFVP-33 NC NC NC NC 318 21.2 130 NC NC NCNSFVP-34 2.0 750 0.2 7.3 211 19.4 50 90.5 110

M

NSFVP-35 NC NC NC NC 499 19.3 120 NC NC NCNSFVP-36 NC NC NC NC 1,250 18.6 340 NC NC NCNSFVP-37 3.0 748 3.5 6.8 345 19.3 120 124 152

M

NSFVP-38 0.2 753 0.1 8.2 734 25.7 20 381 454 5NSFVP-39 NC NC NC NC 332 20.0 70 NC NC NCNSFVP-40 0.1 760

M 7.6 621 33.0 170 158 191 1

NSFVP-41 NC NC NC NC 510 20.4 170 NC NC NCNSFVP-42 NC NC NC NC 240 20.0 NC NC NC NCNSFVP-43 NC NC NC NC 383 27.6 100 NC NC NCNSFVP-44 NC NC NC NC 1,680 21.0 180 NC NC NCNSFVP-45

— 767 0.3 7.5 460 28.0 60 230 279 1

NSFVP-46 0.3 762 1.1 6.5 406 18.1 170 144 176

—

NSFVP-47 NC NC NC 6.4 299 18.1 90 NC 48

—

NSFVP-48 NC 762 NC 7.7 758 19.8 110 NC 19

—

NSFVP-49

— 769 0.1 7.4 605 19.6 100 280 340 1

Table 9. Water-quality indicators determined in the field for the North San Francisco Bay Ground-Water Ambient Monitoring and Assessment (GAMA) study, California, August to November 2004—Continued.[The five-digit number below the constituent name is the U.S. Geological Survey parameter code used to uniquely identify a specific constituent or property; NTRU, nephelometric turbidity unit; NSFVP, Valley and Plains study area; NSFVPFP, Valley and Plains flow-path well; NSFVOL, Volcanic Highlands study area; NSFWG, Wilson Grove Formation Highlands study area; NSFWGFP, Wilson Grove Formation Highlands flow-path well; NSFHOT, hydrothermal study; μS/cm, microsiemens per centimeter; oC, degrees celsius; mg/L, milligrams per liter; mm, millimeter; NC, sample not collected; M, presence verified not quantified; —, not detected]

64 Ground-Water Quality Data, North San Francisco Bay Hydrologic Provinces, California, 2004: GAMA Program Results
GAMA

 identification 

No.

Turbidity

(NTRU)

(63676)

Barometric 

pressure

 (mm of

 mercury)

(00025)

Dissolved 

oxygen 

(mg/L)

(00300)

pH, field

(standard

 units)

(00400)

Specific 

conductance, 

field

(μScm@25oC)

(00095)

Water 

temperature 

(oC) 

(00010)

Total

hardness 

(mg/L as 

CaCO3)

(00900) 

Alkalinity, 

dissolved

 (mg/L as 

CaCO3) 

(29802)

Bicarbonate, 

dissolved 

(mg/L as HCO3) 

(63786)

Carbonate, 

dissolved 

(mg/L as CO3) 

(63788)

NSFVP-50 — 764 0.7 7.2 394 18.6 140 197 240 MNSFVPFP-01 0.1 758 0.1 8.0 259 28.0 60 105 126 1NSFVPFP-02 2.0 757 0.3 7.4 619 18.0 230 225 273 1NSFVPFP-03 NC NC NC NC 567 18.2 240 NC NC NCNSFVPFP-04 NC NC NC NC 325 15.7 NC NC NC NC

Volcanic Highlands wells

NSFVOL-01 2.8 750 3.2 6.6 210 23.5 90 107 130 —NSFVOL-02 NC NC NC NC 724 23.2 NC NC NC NCNSFVOL-03 NC NC NC NC 190 26.8 NC NC NC NCNSFVOL-04 NC NC NC NC 274 NC NC NC NC NCNSFVOL-05 NC NC NC NC 138 20.0 NC NC NC NCNSFVOL-06 NC NC NC NC 544 24.2 NC NC NC NCNSFVOL-07 NC NC NC NC 215 22.5 NC NC NC NCNSFVOL-08 NC NC NC NC 296 22.0 NC NC NC NCNSFVOL-09 NC NC NC NC 317 26.0 NC NC NC NCNSFVOL-10 NC NC NC NC 227 14.3 NC NC NC NCNSFVOL-11 NC NC NC NC 103 17.0 NC NC NC NCNSFVOL-12 NC NC NC NC 251 24.6 NC NC NC NCNSFVOL-13 NC NC NC NC 158 17.8 NC NC NC NCNSFVOL-14 — 760 4.3 6.5 191 21.5 60 66 80 —NSFVOL-15 NC NC NC NC 177 17.7 NC NC NC NCNSFVOL-16 NC NC NC NC 710 25.8 NC NC NC NCNSFVOL-17 NC NC NC NC 424 24.6 NC NC NC NCNSFVOL-18 NC NC NC NC 397 26.7 NC NC NC NCNSFVOL-19 1.7 750 1.9 6.4 156 24.8 50 152 93 —

Table 9. Water-quality indicators determined in the field for the North San Francisco Bay Ground-Water Ambient Monitoring and Assessment (GAMA) study, California, August to November 2004—Continued.[The five-digit number below the constituent name is the U.S. Geological Survey parameter code used to uniquely identify a specific constituent or property; NTRU, nephelometric turbidity unit; NSFVP, Valley and Plains study area; NSFVPFP, Valley and Plains flow-path well; NSFVOL, Volcanic Highlands study area; NSFWG, Wilson Grove Formation Highlands study area; NSFWGFP, Wilson Grove Formation Highlands flow-path well; NSFHOT, hydrothermal study; μS/cm, microsiemens per centimeter; oC, degrees celsius; mg/L, milligrams per liter; mm, millimeter; NC, sample not collected; M, presence verified not quantified; —, not detected]

Tables 65
GAMA

 identification 

No.

Turbidity

(NTRU)

(63676)

Barometric 

pressure

 (mm of

 mercury)

(00025)

Dissolved 

oxygen 

(mg/L)

(00300)

pH, field

(standard

 units)

(00400)

Specific 

conductance, 

field

(μScm@25oC)

(00095)

Water 

temperature 

(

oC) 

(00010)

Total

hardness 

(mg/L as 

CaCO3

)

(00900) 

Alkalinity, 

dissolved

 (mg/L as 

CaCO3) 

(29802)

Bicarbonate, 

dissolved 

(mg/L as HCO3) 

(63786)

Carbonate, 

dissolved 

(mg/L as CO3) 

(63788)

NSFVOL-20

— 755 2.9 7.4 222 25.2 40 102 124

M

Wilson Grove Formation Highlands wells

NSFWG-01 NC NC NC NC 265 18.6 NC NC NC NCNSFWG-02 NC NC NC NC 606 18.0 NC NC NC NCNSFWG-03 NC NC NC NC 260 16.5 NC NC NC NCNSFWG-04 NC NC NC NC 216 21.5 NC NC NC NCNSFWG-05 NC NC NC NC 676 18.0 NC NC NC NCNSFWG-06 NC NC NC NC 383 15.7 NC NC NC NCNSFWG-07 NC NC NC NC 518 20.5 NC NC NC NCNSFWG-08

— 761 0.8 7.4 391 19.0 160 162 197

M

NSFWG-09 NC NC NC NC 267 18.1 NC NC NC NCNSFWG-10

— 760 0.1 9.4 447 23.0 0 193 177 28

NSFWG-11 NC NC NC NC 426 20.5 NC NC NC NCNSFWG-12 NC NC NC NC 277 19.5 NC NC NC NCNSFWG-13 NC NC NC NC 727 19.5 NC NC NC NCNSFWG-14 NC 761 NC NC 722 18.7 NC NC NC NCNSFWGFP-01

— 761 0.2 7.5 363 19.5 140 143 174

M

Hydrothermal study

NSFHOT-01 NC NC NC 7.8 1,090 81.0 20 NC NC NCNSFHOT-02 NC NC NC 7.5 942 60.0 10 NC NC NCNSFHOT-03 NC NC NC 6.9 774 29.5 110 NC NC NCNSFHOT-04 NC NC NC 7.3 970 63.0 20 NC NC NC

Table 9. Water-quality indicators determined in the field for the North San Francisco Bay Ground-Water Ambient Monitoring and Assessment (GAMA) study, California, August to November 2004—Continued.[The five-digit number below the constituent name is the U.S. Geological Survey parameter code used to uniquely identify a specific constituent or property; NTRU, nephelometric turbidity unit; NSFVP, Valley and Plains study area; NSFVPFP, Valley and Plains flow-path well; NSFVOL, Volcanic Highlands study area; NSFWG, Wilson Grove Formation Highlands study area; NSFWGFP, Wilson Grove Formation Highlands flow-path well; NSFHOT, hydrothermal study; μS/cm, microsiemens per centimeter; oC, degrees celsius; mg/L, milligrams per liter; mm, millimeter; NC, sample not collected; M, presence verified not quantified; —, not detected]

66 Ground-Water Quality Data, North San Francisco Bay Hydrologic Provinces, California, 2004: GAMA Program Results
GAMA

 identification 

No.

Turbidity

(NTRU)

(63676)

Barometric 

pressure

 (mm of

 mercury)

(00025)

Dissolved 

oxygen 

(mg/L)

(00300)

pH, field

(standard

 units)

(00400)

Specific 

conductance, 

field

(μScm@25oC)

(00095)

Water 

temperature 

(oC) 

(00010)

Total

hardness 

(mg/L as 

CaCO3)

(00900) 

Alkalinity, 

dissolved

 (mg/L as 

CaCO3) 

(29802)

Bicarbonate, 

dissolved 

(mg/L as HCO3) 

(63786)

Carbonate, 

dissolved 

(mg/L as CO3) 

(63788)

NSFHOT-05 NC NC NC 8.0 985 97.5 20 NC NC NCNSFHOT-06 NC NC NC 7.5 1,290 34.3 130 NC NC NCNSFHOT-07 NC NC NC 8.3 2,020 41.5 20 NC NC NCNSFHOT-08 NC NC NC 8.7 1,170 35.5 20 NC NC NC

Table 9. Water-quality indicators determined in the field for the North San Francisco Bay Ground-Water Ambient Monitoring and Assessment (GAMA) study, California, August to November 2004—Continued.[The five-digit number below the constituent name is the U.S. Geological Survey parameter code used to uniquely identify a specific constituent or property; NTRU, nephelometric turbidity unit; NSFVP, Valley and Plains study area; NSFVPFP, Valley and Plains flow-path well; NSFVOL, Volcanic Highlands study area; NSFWG, Wilson Grove Formation Highlands study area; NSFWGFP, Wilson Grove Formation Highlands flow-path well; NSFHOT, hydrothermal study; μS/cm, microsiemens per centimeter; oC, degrees celsius; mg/L, milligrams per liter; mm, millimeter; NC, sample not collected; M, presence verified not quantified; —, not detected]

Tables 67
Class: Trihalomethanes 

(18 percent of wells)

Organic synthesis 

(16 percent of wells)

Gasoline 

additives

(6 percent of 

wells)

GAMA 

identification

No.

Chloroform 

(Trichloromethane)

(μg/L) 

(32106)

1,1,1-Trichloroethane

 (TCA) 

(μg/L)

(34506) 

1,1,2-Trichlorotrifluoroethane (CFC-113)

(μg/L) 

(77652)

Carbon

 disulfide

(μg/L) 

(77041)

1,2,4-Trimethylbenzene 

(μg/L)

(77222)

Toluene

(μg/L)

(34010)

[LRL] [0.02] [0.03] [0.04] [0.04] [0.06] [0.05 (0.02)]

Valley and Plains wells (50 randomized wells sampled)

NSFVP-08 — — — E0.06 — —

NSFVP-15 — — — — — —

NSFVP-18 E0.02 — — — — —

NSFVP-23 E0.02 — 0.19 — — —

NSFVP-27 E0.02 — — — — —

NSFVP-31 0.11 — — — E0.03 —

NSFVP-36 — — — 0.33 — —

NSFVP-37 E0.06 — — — — —

NSFVP-39 — — — 0.13 — —

NSFVP-40 — — — — E0.06 E0.01

NSFVP-41 E0.02 — — — — —

NSFVP-45 — — — E0.08 — —

NSFVP-46 — E0.02 — — — —

NSFVP-47 E0.03 — — — — —

NSFVP-48 — — — E0.08 — —

NSFVP-49 — — — E0.03 — —

NSFVP-50 E0.08 — — — — —

Number of wells with 

detections

8 1 1 6 2 1

Detection frequency 

(percent)

16 2 2 12 4 2

Valley and Plains flow-path well

NSFVPFP-031 — — — — — E0.01

S

See footnote at end of table.

Table 10A. Results of analyses for volatile organic compounds (VOCs) and gasoline additives and (or) oxygenates in ground-water 

samples collected in the Valley and Plains study area of the North San Francisco Bay Ground-Water Ambient Monitoring and 

Assessment (GAMA) study, California, August to November 2004. 

[The five-digit number in parentheses below the constituent name is the U.S. Geological Survey parameter code used to uniquely identify a specific constituent 

or property; LRL, laboratory reporting level; NSFVP, Valley and Plains study area; NSFVPFP, Valley and Plains flow-path well; μg/L, microgram per liter; 

E, estimated value; —, not detected; percentage values are detection frequencies]

68 Ground-Water Quality Data, North San Francisco Bay Hydrologic Provinces, California, 2004: GAMA Program Results
Class:

Gasoline additives 

and oxygenates

(6 percent of wells)

Solvents

(4 percent of wells)

Detections 

per 

well

GAMA 

identification

No.

m-Xylene plus 

p-xylene

(μg/L)

(85795)

tert-Butyl 

methyl ether 

(MTBE) 

(μg/L) 

(78032) 

1,1-Dichloroethane

 (μg/L)

(34496) 

2-Butanone

(ethyl methyl 

ketone) 

(μg/L)

(81595)

Tetrachloromethane 

(Carbon 

tetrachloride)

 (μg/L) 

(32102)

Tetrahydrofuran

(μg/L)

(81607)

[LRL] [0.06] [0.2 (0.1)] [0.04] [4 (2)] [0.06] [2.2 (1)]

Valley and Plains wells (50 randomized wells sampled)

NSFVP-08 — — — — — — 1

NSFVP-15 — E0.1 — — — — 1

NSFVP-18 — — — — — — 1

NSFVP-23 — — — — — — 2

NSFVP-27 — — — — — — 1

NSFVP-31 — — — — — — 2

NSFVP-36 — — — — — — 1

NSFVP-37 — — — — E0.03 — 2

NSFVP-39 — — — — — — 1

NSFVP-40 — — — — — — 2

NSFVP-41 — — — — — — 1

NSFVP-45 E0.04 — — — — — 2

NSFVP-46 — — — — — — 1

NSFVP-47 — — — — — — 1

NSFVP-48 — — — 2.3 — 7 3

NSFVP-49 — — — — — — 1

NSFVP-50 — — — — — — 1

Number of wells 

with detections

1 1 0 1 1 1 24 Total 

 detections

Detection frequency (percent)2 2 0 2 2 2 17 Total

 wells

Valley and Plains flow-path well

NSFVPFP-031 — — E0.03 — — — 2

1

Flowpath wells were not included in statistical calculations.

Table 10A. Results of analyses for volatile organic compounds (VOCs) and gasoline additives and (or) oxygenates in ground-water 

samples collected in the Valley and Plains study area of the North San Francisco Bay Ground-Water Ambient Monitoring and 

Assessment (GAMA) study, California, August to November 2004—Continued. 

[The five-digit number in parentheses below the constituent name is the U.S. Geological Survey parameter code used to uniquely identify a specific constituent 

or property; LRL, laboratory reporting level; NSFVP, Valley and Plains study area; NSFVPFP, Valley and Plains flow-path well; μg/L, microgram per liter; 

E, estimated value; —, not detected; percentage values are detection frequencies]

Tables 69
Class: Organic synthesis (15 percent of wells) Gasoline additives and oxygenates (10 percent of wells)

Trihalomethanes 

(10 percent

of wells)

Solvents 

(5 percent 

of wells)

Detections 

per well GAMA

 identification 

No.

Carbon 

disulfide

 (μg/L) 

(77041)

1,2,4-Trimethylbenzene

 (μg/L)

(77222)

m-Xylene 

plus 

p-xylene

(μg/L)

(85795)

Toluene

 (μg/L)

(34010)

Benzene

 (μg/L) 

(34030)

o-Xylene

(μg/L)

(77135)

Chloroform 

(Trichloromethane) 

(μg/L) 

(32106)

2-Butanone

(ethyl methyl 

ketone )

(μg/L)

(81595)

[LRL] [0.04] [0.06] [0.06] [0.05 (0.02)] [0.02] [0.04] [0.02] [4 (2)]

Volcanic Highlands wells (20 randomized wells sampled)

NSFVOL-02

—

— E0.06 E0.08 0.60 E0.06

— E1.1 5

NSFVOL-03

—

—

—

—

—

— 0.50

— 1

NSFVOL-09 E0.05

—

—

—

—

—

—

— 1

NSFVOL-11

—

—

—

—

—

— E0.06

— 1

NSFVOL-17 0.37

—

—

—

—

—

—

— 1

NSFVOL-20

— E0.02 E0.05 E0.02

—

—

—

— 3

Number of wells 

with detections

2 1 2 2 1 1 2 1 12 Total detections

Detection frequency 

(percent)

10 5 10 10 5 5 10 5 6 Total wells

Table 10B. Results of analyses for volatile organic compounds (VOCs) and gasoline additives and (or) oxygenates in ground-water samples collected in the Volcanic Highlands study area of the North San Francisco Bay Ground-Water Ambient Monitoring and Assessment (GAMA) study, California, August to November 2004. [The five-digit number in parentheses below the constituent name is the U.S. Geological Survey parameter code used to uniquely identify a specific constituent or property; LRL, laboratory reporting level; NSFVOL, Volcanic Highlands study area; mg/L, microgram per liter; E, estimated value; —, not detected; percentage values are detection frequencies]

70 Ground-Water Quality Data, North San Francisco Bay Hydrologic Provinces, California, 2004: GAMA Program Results
Class Trihalomethanes (14 percent of wells) Solvents (14 percent of wells)

Gasoline 

additives 

and 

oxygenates 

(7 percent of 

wells)

GAMA 

identification 

No.

Chloroform 

(Trichloromethane) 

(μg/L)

(32106)

Bromodichloromethane

 (μg/L)

(32101)

Dibromochloromethane 

(μg/L)

(32105)

Bromoform 

(Tribromomethane) 

(μg/L) 

(32104)

Acetone

(μg/L)

(81552)

cis-1,2-

Dichloroethylene 

(μg/L)

(77093)

Tetrachloroethylene 

(PCE)

(μg/L)

(34475)

Tetrahydrofuran

(μg/L)

(81607)

Trichloroethylene 

(TCE) 

(μg/L) 

(39180)

Toluene 

(μg/L)

(34010)

Detections 

per well

[LRL] [0.024] [0.03] [0.1] [0.1] [6] [0.02] [0.06 (0.03)] [2.2 (1)] [0.04] [0.05 (0.02)]

 Wilson Grove Formation Highlands wells (14 randomized wells sampled)

NSFWG-05 — — — — E3 — — — — — 1NSFWG-06 0.44 0.28 0.4 0.34 — — — — — — 4NSFWG-08 E0.02 — — — — — — — — — 1NSFWG-14 — — — — — — — 2.0 — E0.02 2Number of wells 

with detections

2 1 1 1 1 0 0 1 0 1 8 Total detections

Detection frequency 

(percent)

14 7 7 7 7 0 0 7 0 7 4 Total wells

Wilson Grove Formation Highlands flow-path well

NSFWGFP-011 — — — — — 0.15 2.67 — 0.4 — 3

 Hydrothermal study not sampled

1Flowpath wells were not included in statistical calculations.

Table 10C. Results of analyses for volatile organic compounds (VOCs) and gasoline additives and (or) oxygenates in ground-water samples collected in the Wilson Grove Formation Highlands study area of the North San Francisco Bay Ground-Water Ambient Monitoring and Assessment (GAMA) study, California, August to November 2004.[The five-digit number in parentheses below the constituent name is the U.S. Geological Survey parameter code used to uniquely identify a specific constituent or property. LRL, laboratory reporting level; NSFWG, Wilson Grove Formation Highlands study area; NSFWGFP, Wilson Grove Formation Highlands flow-path well; μg/L, microgram per liter; E, estimated value; —, not detected; percentage values are detection frequencies]

Tables 71
Class: Herbicides (22 percent of wells) Pesticide degradates (8 percent of wells)

GAMA 

identification 

No.

Simazine

(μg/L)

(04035)

Atrazine

(μg/L)

(39632)

Trifluralin 

(μg/L)

(82661)

Sulfometuron-methyl1

(μg/L)

(50337)

Deethylatrazine 

(μg/L)

(04040)

Deisopropyl 

atrazine1

(μg/L)

(04038) 

Chlordiaminos-triazine1

(μg/L)

(04039)

Detections 

per well

[LRL] [0.005] [0.007] [0.009] [0.009(0.04)] [0.006] [0.01 (0.08)] [0.04]

Valley and Plains wells (50 randomized wells sampled)

NSFVP-06

—

— E0.006

—

—

—

— 1

NSFVP-08 0.01

—

—

—

—

—

— 1

NSFVP-10 0.006

—

—

—

—

—

— 1

NSFVP-11 0.052

—

—

—

—

—

— 1

NSFVP-17 E0.003

—

—

—

—

—

— 1

NSFVP-18 0.018

—

—

—

—

—

— 1

NSFVP-19 0.016

—

—

—

— E0.01

— 2

NSFVP-21

— E0.007

—

— E0.006

—

— 2

NSFVP-22

—

—

—

— E0.005

—

— 1

NSFVP-29 0.009

—

—

—

—

M E0.01 3

NSFVP-47 0.011

—

—

—

—

—

— 1

NSFVP-38

—

—

— 0.052

—

—

— 1

Number of wells with detections 8 1 1 0 2 2 1 15 Total detectionsDetection frequency (percent) 16 2 2 0 4 4 2 12 Total wells

Valley and Plains flow-path well

NSFVPFP-032 E0.004

—

—

—

—

—

— 1 1Constituent analyzed under pesticide schedule 2060.

2Flowpath wells were not included in statistical calculations.

Table 11A. Pesticides and (or) pesticide degredates detected in ground-water samples collected in the Valley and Plains study area of the North San Francisco Bay GroundWater Ambient Monitoring and Assessment (GAMA) study, California, August to November 2004.[The five-digit number in parentheses below the constituent name is the U.S. Geological Survey parameter code used to uniquely identify a specific constituent or property; LRL, laboratory reporting level; NSFVP, Valley and Plains study area; NSFVPFP, Valley and Plains flow-path well; μg/L, microgram per liter; E, estimated value; —, not detected; M, presence verified, not quantified; percentage values are detection frequencies]

72 Ground-Water Quality Data, North San Francisco Bay Hydrologic Provinces, California, 2004: GAMA Program Results
Class Herbicide (5 percent of wells)

Detections

 per well

GAMA 

identification 

No.

Diphenamid1

(μg/L)

(04033)

[LRL] [0.01]

Volcanic Highlands wells (20 wells sampled)

NSFVOL-01 M 1

Number of wells with detections 1 1 Total detections

Detection frequency (percent) 5 1 Total wells

 1Constituent analyzed by pesticide schedule 2060.

Table 11B. Pesticides and (or) pesticide degredates detected in ground-water samples collected in the Volcanic Highlands study area of 

the North San Francisco Bay Ground-Water Ambient Monitoring and Assessment (GAMA) study, California, August to November 2004.

[The five-digit number in parentheses below the constituent name is the U.S. Geological Survey parameter code used to uniquely identify a specific constituent 

or property; LRL, laboratory reporting level; NSFVOL, Volcanic Highlands study area; μg/L, microgram per liter; M, presence verified, not quantified; 

percentage values are detection frequencies]

Class Herbicides (7 percent of wells)

Detections 

per well

GAMA 

identification 

No.

Diazinon 

(μg/L)

(39572)

Atrazine

(μg/L)

(39632)

[LRL] [0.005] [0.007]

Wilson Grove Formation Highlands wells (14 randomized wells sampled)

NSFWG-07 0.108 — 1

Number of wells with detections1 0 1 Total detections

Detection frequency (percent) 7 0 1 Total wells

 Wilson Grove Formation Highlands flow-path well

NSFWGFP-011 — E0.006 1

Hydrothermal study (not sampled) 

1

Flowpath wells were not included in statistical calculations.

Table 11C. Pesticides and (or) pesticide degradates detected in ground-water samples collected in the Wilson Grove Formation 

Highlands study area of the North San Francisco Bay Ground-Water Ambient Monitoring and Assessment (GAMA) study, California, 

August to November 2004.

[The five-digit number in parentheses below the constituent name is the U.S. Geological Survey parameter code used to uniquely identify a specific constituent 

or property; LRL, laboratory reporting level; NSFWG, Wilson Grove Formation Highlands study area; NSFWGFP, Wilson Grove Formation Highlands 

flow-path well; μg/L, microgram per liter; E, estimated value; —, not Formation detected; percentage values are detection frequencies]

Tables 73
GAMA

 identification 

No.

Phenol1

(μg/L) 

(34466)

Caffeine2

(μg/L)

(50305)

Isophorone 

(μg/L)

(34409)

Triclosan 

(μg/L) 

(62090)

Tetrachloroethylene

(μg/L) 

(34476)

Bromoform 

(μg/L)

(34288) 

Detections 

per well

[LRL] [0.5] [0.010 (0.5)] [0.5] [1] [0.5] [0.5]

Valley and Plains wells (50 randomized wells sampled)

NSFVP-12 VE0.4 — — — — — 0

NSFVP-13 V0.5 M — — — — 1

NSFVP-14 V0.8 — — M — — 1

NSFVP-15 V1.1 M — — — — 1

NSFVP-18 V0.9 — — — — — 0

NSFVP-20 V0.8 — — — — — 0

NSFVP-21 VE0.4 — — — M — 1

NSFVP-22 V1.5 — — — — — 0

NSFVP-24 V0.6 — — — — — 0

NSFVP-26 VE0.3 — — — — — 0

NSFVP-27 V0.6 — — — — — 0

NSFVP-29 V1.3 — — M M — 2

NSFVP-31 VE0.3 — — — — M 1

NSFVP-32 V1.6 — — — — — 0

NSFVP-34 VE0.3 — — — — — 0

NSFVP-35 V1.0 — — — — — 0

NSFVP-36 V0.5 — — — — — 0

NSFVP-37 — — — — — E0.5 1

NSFVP-38 V2.0 0.067 — — — — 1

NSFVP-39 V0.7 — M — — — 1

NSFVP-40 VE0.4 — M — — — 1

NSFVP-41 VE0.4 — M — — — 1

NSFVP-44 VE1.1 — — — — — 0

NSFVP-46 V0.8 — — — — — 0

NSFVP-47 V1.0 — — — — — 0

NSFVP-49 — 0.029 — — — — 1

Number of wells 

with detections3

01 4 3 2 2 2 13 Total detections

Detection frequency 

(percent)3

01 8 6 4 4 4 12 Total wells

Valley and Plains flow-path well

NSFVPFP-013 VE0.4 — — M — — 1

NSFVPFP-023 — 0.017 — — — — 1

NSFVPFP-033 V1.0 — M — — — 1

NSFVPFP-043 V0.7 — — — — — 0

1

Due to high phenol contents in the blank samples, phenol detecions have been censored.

2

Caffeine concentraion determined by the preferred analysis method, pesticide analytical schedule 2060.

3

Flowpath wells were not included in statistical calculations.

Table 12A. Waste-water indicators measured in ground-water samples collected in the Valley and Plains study area of the North San 

Francisco Bay Ground-Water Ambient Monitoring and Assessment (GAMA) study, California, August to November 2004.

[The five-digit number in parentheses below the compound name is the U.S. Geological Survey parameter code used to uniquely identify a specific constituent 

or property; LRL, laboratory reporting level; NSFVP, Valley and Plains study area; NSFVPFP, Valley and Plains flow-path well; μg/L, microgram per liter; E, 

estimated value; —, not detected; V, value censored due to contamination and not included in ground-water quality analyses; M, presence verified but not 

quantified]

74 Ground-Water Quality Data, North San Francisco Bay Hydrologic Provinces, California, 2004: GAMA Program Results
GAMA

 identification

 No.

Phenol1

(μg/L)

(34466) 

Bisphenol 

A 

(μg/L) 

(62069)

Isophorone 

(μg/L)

(34409)

Caffeine2

(μg/L)

(50305)

d-Limonene

 (μg/L)

(62073) 

Octylphenol,

monoethoxy-

(OPEO1)

(μg/L) 

(61706)

Indole 

(μg/L)

(62076)

Napthalene

(μg/L) 

(34443)

Triphenyl 

phosphate 

(μg/L) 

(62092)

Detections 

per well

[LRL] [0.5] [1] [0.5] [0.010(0.5)] [0.5] [1] [0.5] [0.5] [0.5]

Volcanic Highlands wells (20 wells sampled)

NSFVOL-01 V0.5 — — E0.0076 — — — — — 1NSFVOL-02 V0.9 M — — — M — E0.4 — 3NSFVOL-04 V2.4 — — — — — — — — 0NSFVOL-06 V0.5 — — — — — — — — 0NSFVOL-07 V1.0 — — — — — — — — 0NSFVOL-09 V2.4 — — — — — — — — 0NSFVOL-10 V0.8 — — — — — — — — 0NSFVOL-15 V0.9 — — — — — — — — 0NSFVOL-16 VE0.3 — — — — — E0.1 — — 1NSFVOL-17 VE0.2 M M — — — — — E0.1 3NSFVOL-18 VE0.4 — M — — — — — — 1NSFVOL-19 — — — — E0.1 — — — — 1Number of wells with 

detections

01 2 2 1 1 1 1 1 1 10 Total detections

Detection frequency

(percent)

01 10 10 5 5 5 5 5 5 6 Total wells

1Due to high phenol contents in the blank samples, phenol detecions have been censored.

2Caffeine concentraion determined by the preferred analysis method, pesticide analytical schedule 2060.

Table 12B. Waste-water indicators measured in ground-water samples collected in the Volcanic Highlands study area of the North San Francisco Bay Ground- Water Ambient Monitoring and Assessment (GAMA) study, California, August to November 2004. [The five-digit number in parentheses below the constituent name is the U.S. Geological Survey parameter code used to uniquely identify a specific constituent or property; LRL, laboratory reporting level; NSFVOL, Volcanic Highlands study area; μg/L, microgram per liter; E, estimated value; v, value censored due to contamination and not included in ground-water quality analyses;—, not detected; M, presence verified but not quantified]

Tables 75
GAMA 

identification 

No.

Phenol1

(μg/L)

(34466) 

Indole 

(μg/L)

(62076)

p-Cresol 

(μg/L)

(62084)

Bisphenol A 

(μg/L) 

(62069)

Isophorone 

(μg/L)

(34409)

Menthol 

(μg/L)

(62080)

Tetrachloroethylene 

(μg/L)

(34476)

Detections 

per well

[LRL] [0.5] [0.5] [1] [1] [0.5] [0.5] [0.5]

 Wilson Grove Formation Highlands wells (14 randomized wells sampled)

NSFWG-02 V1.4

—

—

—

—

—

— 0

NSFWG-03 VE0.3

—

M

—

—

—

— 1

NSFWG-04 V0.7

—

—

—

— E0.2

— 1

NSFWG-05 V0.7 E0.1

—

—

—

—

— 1

NSFWG-07 V0.8

—

—

—

—

—

— 0

NSFWG-08 VE0.2

—

—

—

—

—

— 0

NSFWG-09 VE0.7

—

—

—

—

—

— 0

NSFWG-10 V1.1

—

—

—

—

—

— 0

NSFWG-13 VE1.1 1.4

M

M

M

—

— 4

Number of wells with 

detections

01 2 2 1 1 1 0 7 Total detections

Detection frequency 

(percent)

01 14 14 7 7 7 0 4 Total wells

Wilson Grove Formation Highlands flow-path well

NSFWGFP-012 VE1.0

—

—

—

—

— E1.3 1

 Hydrothermal study (not sampled)

1Due to high phenol contents in the blank samples, phenol detecions have been censored.2Flowpath wells were not included in statistical calculations.

Table 12C. Waste-water indicators measured in ground-water samples collected in the Wilson Grove Formation Highlands study area of the North San Francisco Bay GroundWater Ambient Monitoring and Assessment (GAMA) study, California, August to November 2004. [The five-digit number in parentheses below the compound name is the U.S. Geological Survey parameter code used to uniquely identify a specific constituent or property; LRL, laboratory reporting level; NSFWG, Wilson Grove Formation Highlands study area; NSFWGFP, Wilson Grove Formation Highlands flow-path well; μg/L, microgram per liter; E, estimated value; V, value censored due to contamination and not included in ground-water quality analyses; —, not detected; M, presence verified but not quantified]

76 Ground-Water Quality Data, North San Francisco Bay Hydrologic Provinces, California, 2004: GAMA Program Results
GAMA

 identification 

No.

Perchlorate

(μg/L)

1,2,3-Trichlorpropane

(μg/L)

N-nitrosodimethylamine 

(NDMA)

(μg/L)

[MRL] [0.5] [0.005] [0.002]

Valley and Plains wells Not detected Not detected Not detected

Volcanic Highlands wells Not detected Not detected Not detected

Wilson Grove Formation Highlands wells Not detected Not detected Not detected

Hydrothermal study Not sampled Not sampled Not sampled

Table 13. Results of analyses for the constituents of special interest: perchlorate, trichloropropane (1,2,3-TCP), N-nitrosodimethylamine 

(NDMA) in ground-water samples collected for the North San Francisco Bay Ground-Water Ambient Monitoring and Assessment 

(GAMA) study, California, August to November 2004.

[MRL, minimum reporting level; μg/L, micrograms per liter]

Tables 77
GAMA 

identification 

No.

Ammonia, 

dissolved

 (mg/L as N) 

(00608)

Nitrate plus 

nitrite, 

dissolved

(mg/L as N)

(00631)

 Nitrite, 

dissolved 

(mg/L as N) 

(00613)

 Phosphorus, 

dissolved 

(mg/L as P)

(00671) 

Total nitrogen 

(nitrate + nitrite 

+ ammonia + 

organic-N), 

dissolved

(62854)

Dissolved 

organic 

carbon

(mg/L) 

(00681)

[LRL] [0.04] [0.06] [0.008] [0.006] [0.03] [0.3]

 Valley and Plains wells (15 wells sampled)

NSFVP-10 — 0.31 — 0.019 0.32 0.6

NSFVP-19 — 0.09 — 0.021 0.12 0.6

NSFVP-26 0.16 E0.04 — 0.090 0.21 E0.2

NSFVP-291 — 1.89 — 0.010 1.78 E0.3

NSFVP-301 — 0.62 — 0.034 0.61 E0.2

NSFVP-341 0.07 — — 0.318 E0.06 E0.3

NSFVP-37 — 3.22 — 0.112 3.42 0.4

NSFVP-38 0.22 E0.06 — 0.146 0.28 1.1

NSFVP-40 0.27 — — 0.024 0.27 0.4

NSFVP-45 2.50 — E0.004 0.023 2.84 V0.42

NSFVP-461 — 2.48 — 0.012 2.44 V0.42

NSFVP-49 3.11 — E0.004 0.559 3.14 1.2

NSFVP-50 0.10 E0.05 E0.007 0.329 0.16 0.4

NSFVPFP-01 E0.03 — — 0.094 0.04 0.4

NSFVPFP-02 — 1.55 0.030 0.099 1.56 0.4

 Volcanic Highlands wells (4 wells sampled)

NSFVOL-01 — E0.05 — 0.191 0.07 E0.2

NSFVOL-141 — 0.79 — 0.180 0.76 0.9

NSFVOL-19 — E0.03 E0.004 0.059 E0.06 VE0.32

NSFVOL-201 — 0.10 — 0.061 0.09 VE0.22

Wilson Grove Formation Highlands wells (3 wells sampled)

NSFWG-081 — 1.21 0.008 0.053 1.20 0.4

NSFWG-10 0.14 — — 0.027 0.16 0.5

NSFWGFP-01 — 0.06 — 0.008 0.09 E0.3

1

Total nitrogen in these samples is less than the sum of the filtered nitrogen analytes but falls within the U.S. Geological Survey National Water Quality 

Laboratory acceptance criteria of a 10-percent relative percent difference.

2

Detection in blank, value censored.

Table 14. Nutrients and dissolved organic carbon in ground-water samples collected for the North San Francisco Bay Ground-Water 

Ambient Monitoring and Assessment (GAMA) study, California, August to November 2004.

[The five-digit number in parentheses below the constituent name is the U.S. Geological Survey parameter code used to uniquely identify a specific constituent 

or property; LRL, laboratory reporting level; mg/L, milligram per liter; NSFVP, Valley and Plains study area; NSFVPFP, Valley and Plains flow-path well; 

NSFVOL, Volcanic Highlands study area; NSFWG, Wilson Grove Formation Highlands study area; NSFWGFP, Wilson Grove Formation Highlands flow-path 

well; E, estimated value; V, value censored due to contamination and not included in ground-water quality analyses; —, not detected]

78 Ground-Water Quality Data, North San Francisco Bay Hydrologic Provinces, California, 2004: GAMA Program Results
GAMA

 identification 

No.

Dissolved 

solids 

(residue on 

evaporation) 

(mg/L)

(70300)

Calcium, 

dissolved

(mg/L)

(00915)

Magnesium, 

dissolved 

(mg/L)

(00925) 

Potassium, 

dissolved 

(mg/L)

(00935) 

Sodium,

 dissolved 

(mg/L) 

(00930)

Bromide, 

dissolved 

(mg/L) 

(71870)

Chloride, 

dissolved

(mg/L) 

(00940)

Fluoride, 

dissolved 

(mg/L)

(00950) 

Iodide, 

dissolved 

(mg/L) 

(71865)

Silica, 

dissolved 

(mg/L)

(00955) 

Sulfate, 

dissolved 

(mg/L)

(00945) 

[LRL] [10] [0.01] [0.008] [0.16] [0.1] [0.02] [0.2] [0.2] [0.002] [0.04] [0.2]

Valley and Plains wells

NSFVP-10 213 23.2 26.3 0.94 10.9 0.06 6.73 NC 0.005 29.6 11.3NSFVP-19 162 22.8 18.7 1.20 8.39 0.03 5.19 NC 0.004 22.5 9.6NSFVP-26 381 34.5 19.2 1.30 76.7 0.11 13.2 0.3 0.069 38.1 21.7NSFVP-29 231 35.7 24.8 0.90 9.06 0.17 5.94 — E0.001 24.9 26.2NSFVP-30 254 38.4 24.5 0.99 13.3 0.07 9.82 — 0.007 24.8 19.1NSFVP-32 375 29.6 14.7 9.93 40.2 0.10 9.34 0.3 0.012 134 32.1NSFVP-33 270 26.0 15.6 3.48 19.6 0.14 8.52 0.2 0.011 94.4 19.3NSFVP-34 185 9.14 6.26 4.70 23.4 0.07 10.6 0.3 0.020 85.3 2.6NSFVP-35 318 25.1 12.6 2.20 58.8 0.07 30.8 0.2 0.003 74.6 21.2NSFVP-36 685 51.6 50.8 7.14 148 1.44 249 0.2 0.260 46.8 12.4NSFVP-37 255 25.1 14.7 1.32 28.5 0.12 23.0 0.2 0.002 67.8 14.8NSFVP-38 503 6.26 1.51 2.29 177 0.10 25.5 0.4 0.140 52.9 1.7NSFVP-39 267 13.9 7.88 6.79 42.3 0.09 7.00 0.4 0.077 105 5.5NSFVP-40 428 34.5 21.0 5.68 57.8 0.37 99.1 0.4 0.047 110 3.2NSFVP-41 313 33.0 20.9 2.09 39.2 0.19 42.4 0.2 0.015 50.2 23.6NSFVP-43 269 27.6 7.07 3.52 49.0 0.16 7.70 0.2 0.010 54.7 12.0NSFVP-44 1,000 36.5 21.6 3.03 270 0.99 191 0.1 1.100 27.9 239NSFVP-45 399 15.5 5.95 19.7 77.9 0.06 6.83 0.7 0.009 126 19.9NSFVP-46 249 32.7 22.4 0.59 21.5 0.71 9.88 0.1 0.003 29.7 43.7NSFVP-47 194 22.9 7.47 0.55 25.4 0.14 21.3 0.6 0.005 33.1 37.9NSFVP-48 464 18.6 16.2 13.2 113 0.11 62.9 0.2 0.180 47.6 14.9NSFVP-49 417 20.0 11.0 9.02 104 0.16 42.5 0.2 0.077 64.3 7.1NSFVP-50 261 18.9 22.7 8.19 27.1 0.07 5.10 0.3 0.038 69.5 3.8

Table 15. Major and minor ions and dissolved solids in ground-water samples collected for the North San Francisco Bay Ground-Water Ambient Monitoring and Assessment (GAMA) study, California, August to November 2004. [The five-digit number in parentheses below the constituent name is the U.S. Geological Survey parameter code used to uniquely identify a specific constituent or property; LRL, laboratory reporting level; NSFVP, Valley and Plains study area; NSFVPFP, Valley and Plains flow-path well; NSFVOL, Volcanic Highlands study area; NSFWG, Wilson Grove Formation Highlands study area; NSFWGFP, Wilson Grove Formation Highlands flow-path well; NSFHOT, hydrothermal study; mg/L, milligram per liter; NC, sample not collected; E, estimated value; —, not detected; values in bold indicate concentrations above maximum contaminant level (MCL); values in bold and italics indicate concentrations above the recommended secondary maximum contaminant level (SMCL)]

Tables 79
GAMA

 identification 

No.

Dissolved 

solids 

(residue on 

evaporation) 

(mg/L)

(70300)

Calcium, 

dissolved

(mg/L)

(00915)

Magnesium, 

dissolved 

(mg/L)

(00925) 

Potassium, 

dissolved 

(mg/L)

(00935) 

Sodium,

 dissolved 

(mg/L) 

(00930)

Bromide, 

dissolved 

(mg/L) 

(71870)

Chloride, 

dissolved

(mg/L) 

(00940)

Fluoride, 

dissolved 

(mg/L)

(00950) 

Iodide, 

dissolved 

(mg/L) 

(71865)

Silica, 

dissolved 

(mg/L)

(00955) 

Sulfate, 

dissolved 

(mg/L)

(00945) 

[LRL] [10] [0.01] [0.008] [0.16] [0.1] [0.02] [0.2] [0.2] [0.002] [0.04] [0.2]

NSFVPFP-01 179 17.5 3.6 1.50 30.2 0.05 13.2 NC 0.006 54.4 4.7NSFVPFP-02 364 44.2 29.4 1.90 40.0 0.13 47.2

— 0.024 38.0 15.4

NSFVPFP-03 346 28.4 40.1 2.67 31.0 0.25 41.7 0.3 0.011 52.9 32.7

Volcanic Highlands wells

NSFVOL-01 214 19.2 10.8 1.70 12.9 0.03 5.55 NC E0.001 98.5 1.4NSFVOL-14 185 12.8 7.57 2.18 13.4 0.03 7.79 0.2 0.004 87.0 7.4NSFVOL-19 184 7.34 8.10 4.41 15.9 0.04 5.34 0.3 0.002 97.9 5.9NSFVOL-20 197 8.96 4.09 4.34 31.3 0.03 4.62 0.3 E0.001 87.0 4.6

Wilson Grove Formation Highlands wells

NSFWG-08 263 53.6 6.38 1.24 18.2 0.06 13.2 E0.1 0.004 42.2 20.3NSFWG-10 291 0.86 0.056 0.46 111 0.09 34.2 0.1 0.006 15.9 5.9NSFWGFP-01 242 50.0 3.77 1.33 22.0 0.08 15.4 E0.1 0.007 37.9 15.9

Hydrothermal study1

NSFHOT-01 646 7.63 0.134 7.54 186 0.80 183 10.2 0.2999 108 30.8NSFHOT-02 685 5.04 0.274 8.37 185 0.73 190 9.6 0.334 165 1.0NSFHOT-03 539 22.3 12.9 8.93 138 0.16 51 1.9 0.010 84 58.3NSFHOT-04 670 4.31 0.883 7.90 174 0.90 194 10.6 0.351 164 27.4NSFHOT-05 648 6.32 0.015 7.91 173 0.75 187 11.3 0.226 151 10.8NSFHOT-06 673 39.7 6.33 17.5 208 0.37 255 2.0 0.190 85.6 14.0NSFHOT-07 1,230 9.01 0.078 20.2 381 2.44 578 8.5 1.61 100 40.5NSFHOT-08 750 5.50 0.901 3.30 224 0.90 207 6.0 0.522 49.5 114

1Not considered for drinking water-quality standards.

Table 15. Major and minor ions and dissolved solids in ground-water samples collected for the North San Francisco Bay Ground-Water Ambient Monitoring and Assessment (GAMA) study, California, August to November 2004—Continued. [The five-digit number in parentheses below the constituent name is the U.S. Geological Survey parameter code used to uniquely identify a specific constituent or property; LRL, laboratory reporting level; NSFVP, Valley and Plains study area; NSFVPFP, Valley and Plains flow-path well; NSFVOL, Volcanic Highlands study area; NSFWG, Wilson Grove Formation Highlands study area; NSFWGFP, Wilson Grove Formation Highlands flow-path well; NSFHOT, hydrothermal study; mg/L, milligram per liter; NC, sample not collected; E, estimated value; —, not detected; values in bold indicate concentrations above maximum contaminant level (MCL); values in bold and italics indicate concentrations above the recommended secondary maximum contaminant level (SMCL)]

80 Ground-Water Quality Data, North San Francisco Bay Hydrologic Provinces, California, 2004: GAMA Program Results
GAMA 

identification 

No.

Aluminum, 

dissolved 

(μg/L)

(01106)

Antimony, 

dissolved 

(μg/L) 

(01095)

Arsenic, 

dissolved 

(μg/L) 

(01000)

Barium, 

dissolved 

(μg/L) 

(01005)

Beryllium, 

dissolved 

(μg/L) 

(01010)

Boron, 

dissolved 

(μg/L) 

(01020)

Cadmium, 

dissolved 

(μg/L) 

(01025)

Chromium, 

dissolved 

(μg/L) 

(01030)

Cobalt, 

dissolved 

(μg/L) 

(01035)

Copper, 

dissolved 

(μg/L) 

(01040)

Iron, 

dissolved 

(μg/L)

(01046) 

Lead, 

dissolved 

(μg/L) 

(01049)

[LRL] [2] [0.2] [0.2] [0.2] [4] [8] [0.04] [0.8] [0.014] [0.4] [6] [0.08]

Valley and Plains wells

NSFVP-10 — — 0.3 100 — 323 — — 0.141 E0.4 117 E0.05NSFVP-19 — — 0.4 100 — 331 — — 0.072 1.8 9.8 2.07NSFVP-26 — — 1.5 247 — 124 — — 0.113 1.0 20.6 0.09NSFVP-29 — — E0.1 172 — 258 — 0.9 0.127 2.3 — 1.02NSFVP-30 E1 — 0.5 203 — 1,350 — — 0.155 0.6 13.1 0.32NSFVP-32 M — 8.8 69 — 283 — — 0.258 4.5 E5 4.12NSFVP-33 — — 3.8 31 — 29 — — 0.139 — 1,090 7.97NSFVP-34 — — 7.1 35 — 120 — — 0.072 E0.4 999 —NSFVP-35 E1 0.28 8 35 — 171 — — 0.067 0.7 17 0.38NSFVP-36 — — 5.7 492 — 136 — — 0.141 E0.3 671 1.07NSFVP-37 — — 3.4 64 — 73 — 1.4 0.056 3.4 E6 0.37NSFVP-38 E1 — 17.2 69 — 3,830 E0.04 — 0.031 3.3 12 0.73NSFVP-39 M — 6 27 — 293 — — 0.096 E0.3 43 2.68NSFVP-40 E1 — — 13 — 474 — — 0.067 — 331 —NSFVP-41 — — 2.6 148 — 52 — — 0.331 13.1 — 1.77NSFVP-44 E1 — 3.3 121 — 819 0.04 — 0.092 1.4 310 —NSFVP-45 — 0.27 32.8 56 — 496 — — 0.033 E0.2 135 0.77NSFVP-46 M — — 106 — 70 — — 0.079 0.5 22 0.35NSFVP-47 4 — E0.2 19 — 627 — — 0.052 14.8 — 15.30NSFVP-48 M — 4.9 194 — 380 — — 0.061 E0.3 714 0.08NSFVP-49 2 — 24.6 115 — 316 0.05 — 0.216 E0.3 362 0.24NSFVP-50 — E0.15 7.7 71 — 109 — — 0.205 — 57 E0.07NSFVPFP-01 E1 — 1.0 9 — 53 — 4.4 0.080 0.4 36.5 0.58NSFVPFP-02 — — 2.2 223 — 93 — — 0.138 0.5 — 0.27NSFVPFP-03 — — 1.3 70 — 825 E 0.03 — 0.509 2.5 E4 0.29

Table 16. Trace elements in ground-water samples collected for the North San Francisco Bay Ground-Water Ambient Monitoring and Assessment (GAMA) study, California, August to November 2004.[The five-digit number in parentheses below the constituent name is the U.S. Geological Survey parameter code used to uniquely identify a specific constituent or property; LRL, laboratory reporting level; NSFVP, Valley and Plains study area; NSFVPFP, Valley and Plains flow-path well; NSFVOL, Volcanic Highlands study area; NSFWG, Wilson Grove Formation Highlands study area; NSFWGFP, Wilson Grove Formation Highlands flow-path well; NSFHOT, hydrothermal study; values in bold indicate concentrations that exceed the maximum contaminant level (MCL); values in bold and italics indicate concentrations that are above the secondary maximum contaminant level (SMCL), or for iron, the California notification level (NL); values in italics indicate concentrations above the detection levels for the purpose of reporting (DLR); μg/L, microgram per liter; E, estimated value; M, presence of compound verified but not quanitifed; NC, sample not collected; —, not detected]

Tables 81
GAMA 

identification 

No.

Aluminum, 

dissolved 

(μg/L)

(01106)

Antimony, 

dissolved 

(μg/L) 

(01095)

Arsenic, 

dissolved 

(μg/L) 

(01000)

Barium, 

dissolved 

(μg/L) 

(01005)

Beryllium, 

dissolved 

(μg/L) 

(01010)

Boron, 

dissolved 

(μg/L) 

(01020)

Cadmium, 

dissolved 

(μg/L) 

(01025)

Chromium, 

dissolved 

(μg/L) 

(01030)

Cobalt, 

dissolved 

(μg/L) 

(01035)

Copper, 

dissolved 

(μg/L) 

(01040)

Iron, 

dissolved 

(μg/L)

(01046) 

Lead, 

dissolved 

(μg/L) 

(01049)

[LRL] [2] [0.2] [0.2] [0.2] [4] [8] [0.04] [0.8] [0.014] [0.4] [6] [0.08]

 Volcanic Highlands wells

NSFVOL-01

—

— 1.4 8 — 28

— 1 0.048 2.8 79.6 0.73

NSFVOL-14

M

— 7.1 6 — 18

— E0.4 0.132 3.5

— 2.79

NSFVOL-19

M E0.11 1.3 49

— 42

—

— 0.436 0.6 235 0.35

NSFVOL-20

—

— 5.6 9 — 71 0.04

— 0.019 0.4 E4 0.63

 Wilson Grove Formation Highlands wells

NSFWG-08 E1

— 13.0 1 — 16

— 1.6 0.17 0.9 40 0.11

NSFWG-10 7 —

— 18

— 42

—

—

— E0.3

—

—

NSFWGFP-01

—

— 4.8 4 — 22

—

— 0.14 E0.4 29 0.59

Hydrothermal study1

NSFHOT-01 17 387 70.5

M 0.31 9,590

—

— 0.017 0.6 45 E0.06

NSFHOT-02 6 201 50.2

M 0.08 11,000

—

— E0.012 0.5 28

—

NSFHOT-03 E1 0.24 30.9 25

— 2,530 0.13

— 0.144 1.3 E4

—

NSFHOT-04 6 6.93 64.6

M 0.15 11,200

—

— 0.018 1.0 272 E0.04

NSFHOT-05 126 95.6 128 1 0.15 11,100 E0.02

— 0.016 0.6 14 0.11

NSFHOT-06 2 1.67 12.4 14

— 3,570

—

— 0.094 1.2 302 E0.04

NSFHOT-07 5 E0.19 3.0 20

— 15,700 E0.03

— 0.023 E0.3 41 0.19

NSFHOT-08 30

—

— 7 — 28,500

—

— 0.031 1.0 10

—

SSee footnote at end of table.

Table 16. Trace elements in ground-water samples collected for the North San Francisco Bay Ground-Water Ambient Monitoring and Assessment (GAMA) study, California, August to November 2004—Continued.[The five-digit number in parentheses below the constituent name is the U.S. Geological Survey parameter code used to uniquely identify a specific constituent or property; LRL, laboratory reporting level; NSFVP, Valley and Plains study area; NSFVPFP, Valley and Plains flow-path well; NSFVOL, Volcanic Highlands study area; NSFWG, Wilson Grove Formation Highlands study area; NSFWGFP, Wilson Grove Formation Highlands flow-path well; NSFHOT, hydrothermal study; values in bold indicate concentrations that exceed the maximum contaminant level (MCL); values in bold and italics indicate concentrations that are above the secondary maximum contaminant level (SMCL), or for iron, the California notification level (NL); values in italics indicate concentrations above the detection levels for the purpose of reporting (DLR); μg/L, microgram per liter; E, estimated value; M, presence of compound verified but not quanitifed; NC, sample not collected; —, not detected]

82 Ground-Water Quality Data, North San Francisco Bay Hydrologic Provinces, California, 2004: GAMA Program Results
GAMA

 identification 

No.

Lithium, 

dissolved 

(μg/L)

(01130)

Manganese, 

dissolved 

(μg/L) 

(01056)

Mercury, 

dissolved 

(μg/L)

(71890)

Molybdenum, 

dissolved

 (μg/L)

(01060) 

Nickel, 

dissolved 

(μg/L)

(01065)

Selenium, 

dissolved 

(μg/L)

(01145)

Silver, 

dissolved 

(μg/L) 

(01075)

Strontium, 

dissolved 

(μg/L) 

(01080)

Thallium, 

dissolved 

(μg/L) 

(01057)

Tungsten, 

dissolved 

(μg/L) 

(01155)

Vanadium, 

dissolved 

(μg/L)

(01085) 

Zinc,

 dissolved 

(μg/L) 

(01090)

Uranium, 

dissolved 

(μg/L) 

(22703)

[LRL} [0.6] [0.2] [2] [0.4] [0.06] [0.4] [0.2] [0.4] [0.04] [0.5] [0.7] [0.6] [0.04]

Valley and Plains wells

NSFVP-10 3.5 203 — 0.5 3.02 — — 195 — — 0.9 2.5 0.05NSFVP-19 3.4 42.2 — 0.6 1.76 — — 214 — — 1.2 9.2 0.14NSFVP-26 14.6 241 — 4.5 0.39 — — 264 E0.03 — 2.7 5 0.51NSFVP-29 6.5 E0.1 — E0.2 2.48 — — 352 — — 1.4 49.7 0.09NSFVP-30 18.8 36.8 — 0.7 2.23 0.7 — 379 — — 1.9 6.3 0.19NSFVP-32 52.5 129 NC 1.5 0.24 E0.2 — 124 — 0.9 1.5 4.2 0.1NSFVP-33 14.1 139 NC 0.5 1.03 — — 127 — — — 19 —NSFVP-34 4.7 434 — 1.8 0.26 — — 30.9 — — 1.3 20.1 —NSFVP-35 27.5 3.6 NC 5.1 0.69 1.6 — 384 — — 7.4 10.1 3.53NSFVP-36 33.8 1,220 NC 1 0.65 2 0.26 440 — — 0.4 49.8 0.07NSFVP-37 25.6 6.4 — 0.6 1.49 0.7 0.52 134 — — 11.2 5.6 0.25NSFVP-38 61.3 14.5 — 13.7 0.25 0.5 — 83.9 — — 1.0 5.9 0.11NSFVP-39 68.9 78.1 — 1.8 0.34 — — 39.8 0.22 0.9 3.7 9.4 1NSFVP-40 80.9 40.1 — 1.8 1.23 — — 127 — 0.7 0.6 15.6 0.04NSFVP-41 33.5 928 NC 1.6 0.62 — — 262 — — 3.1 5.8 0.25NSFVP-44 68.3 137 NC 20 0.63 E0.3 — 384 — — 0.4 29.6 0.26NSFVP-45 72 50.1 — 8.4 0.68 — — 84.6 — 2.3 2.0 13.2 —NSFVP-46 6.2 1.6 — 0.6 2 1 — 278 — — 1.5 18.8 0.06NSFVP-47 12.3 0.4 — E0.4 0.4 — — 98.9 — — 0.6 34.3 —NSFVP-48 17.2 151 — 0.7 5.21 0.7 — 213 — 0.8 0.7 0.7 —NSFVP-49 72.9 435 — 20.3 0.66 — — 142 — — 0.9 4.3 0.92NSFVP-50 2.9 687 — 5.7 0.62 — — 131 — — 6.4 8.9 1.57

Table 16. Trace elements in ground-water samples collected for the North San Francisco Bay Ground-Water Ambient Monitoring and Assessment (GAMA) study, California, August to November 2004—Continued.[The five-digit number in parentheses below the constituent name is the U.S. Geological Survey parameter code used to uniquely identify a specific constituent or property; LRL, laboratory reporting level; NSFVP, Valley and Plains study area; NSFVPFP, Valley and Plains flow-path well; NSFVOL, Volcanic Highlands study area; NSFWG, Wilson Grove Formation Highlands study area; NSFWGFP, Wilson Grove Formation Highlands flow-path well; NSFHOT, hydrothermal study; values in bold indicate concentrations that exceed the maximum contaminant level (MCL); values in bold and italics indicate concentrations that are above the secondary maximum contaminant level (SMCL), or for iron, the California notification level (NL); values in italics indicate concentrations above the detection levels for the purpose of reporting (DLR); μg/L, microgram per liter; E, estimated value; M, presence of compound verified but not quanitifed; NC, sample not collected; —, not detected]

Tables 83
GAMA

 identification 

No.

Lithium, 

dissolved 

(μg/L)

(01130)

Manganese, 

dissolved 

(μg/L) 

(01056)

Mercury, 

dissolved 

(μg/L)

(71890)

Molybdenum, 

dissolved

 (μg/L)

(01060) 

Nickel, 

dissolved 

(μg/L)

(01065)

Selenium, 

dissolved 

(μg/L)

(01145)

Silver, 

dissolved 

(μg/L) 

(01075)

Strontium, 

dissolved 

(μg/L) 

(01080)

Thallium, 

dissolved 

(μg/L) 

(01057)

Tungsten, 

dissolved 

(μg/L) 

(01155)

Vanadium, 

dissolved 

(μg/L)

(01085) 

Zinc,

 dissolved 

(μg/L) 

(01090)

Uranium, 

dissolved 

(μg/L) 

(22703)

[LRL} [0.6] [0.2] [2] [0.4] [0.06] [0.4] [0.2] [0.4] [0.04] [0.5] [0.7] [0.6] [0.04]

NSFVPFP-01 20.5 66.4

— 1.1 E0.05

—

— 86.2 0.04

—

— E0.6 0.06

NSFVPFP-02 10.8 355

— 1.1 0.3

—

— 276

—

— 10.0 1.9 0.95

NSFVPFP-03 4.8 938 NC 1.3 5.58 1.7

— 167

—

— 1.4 2.2 0.32

 Volcanic Highlands wells

NSFVOL-01 10.3 4.8

— E0.2 0.46

—

— 61.9

—

— 19.6 3.5 0.09

NSFVOL-14 11.2 10.7

— 1.5 0.76

—

— 38

—

— 15.4 8.2 0.13

NSFVOL-19 23.2 123

— 0.6 3.72

—

— 33.5 E0.03

— 1.5 63.8 0.06

NSFVOL-20 42.3 0.3

— 1.9 0.25

—

— 29.8

— 0.6 11.6 15 0.07

 Wilson Grove Formation Highlands wells

NSFWG-08 12.4 12.9

— 1.2 1.08 E0.3

— 198

—

— 1.1 1.7 0.08

NSFWG-10 26.3 0.5

— 0.7

— 0.5

— 36

—

— 0.2

—

—

NSFWGFP-01 10.6 16

— 0.7 0.43

—

— 188

—

— 1.7 4.2 0.14

Hydrothermal study1

NSFHOT-01 1,920 12.4 0.125 6.5 0.27 0.8

— 110 0.04 112 0.6 0.6

—

NSFHOT-02 1,450 17.2 0.017 6.2 0.17

—

— 39.6

— 138

—

—

—

NSFHOT-03 224 559

— 3.4 1.21 0.7

— 102

— 2.0 9.3 1.4 0.85

NSFHOT-04 1,440 88.8 0.099 3.4 0.57 0.7

— 34.5

— 234 E0.1 26.8

—

NSFHOT-05 1,720 2.8 0.402 10.3 0.2

— NC 54.9

— 152 0.7 15.7

—

NSFHOT-06 703 373 E0.006 2.8 0.5 0.4

— 161

— 7.6 0.2 8.8 0.04

NSFHOT-07 1,650 11.9

— 13.2 0.21 1.4

— 21.8

— 54.0

—

—

—

NSFHOT-08 322 6.1 0.402 <0.4 0.26 0.7 NC 225

— 25.0 0.3 0.9

—

1Not considered for drinking water-quality standards.

Table 16. Trace elements in ground-water samples collected for the North San Francisco Bay Ground-Water Ambient Monitoring and Assessment (GAMA) study, California, August to November 2004—Continued.[The five-digit number in parentheses below the constituent name is the U.S. Geological Survey parameter code used to uniquely identify a specific constituent or property; LRL, laboratory reporting level; NSFVP, Valley and Plains study area; NSFVPFP, Valley and Plains flow-path well; NSFVOL, Volcanic Highlands study area; NSFWG, Wilson Grove Formation Highlands study area; NSFWGFP, Wilson Grove Formation Highlands flow-path well; NSFHOT, hydrothermal study; values in bold indicate concentrations that exceed the maximum contaminant level (MCL); values in bold and italics indicate concentrations that are above the secondary maximum contaminant level (SMCL), or for iron, the California notification level (NL); values in italics indicate concentrations above the detection levels for the purpose of reporting (DLR); μg/L, microgram per liter; E, estimated value; M, presence of compound verified but not quanitifed; NC, sample not collected; —, not detected]

84 Ground-Water Quality Data, North San Francisco Bay Hydrologic Provinces, California, 2004: GAMA Program Results
GAMA

identification 

No.

Arsenic,

 dissolved

(μg/L) 

Arsenic (III), 

dissolved 

(μg/L) 

Iron, 

dissolved

(μg/L) 

Iron (II), 

dissolved 

(μg/L) 

[MDL] [0.5] [1] [1] [1]

Valley and Plains wells

NSFVP-10 — — — —

NSFVP-19 — — 10 8

NSFVP-29 — — — —

NSFVP-30 — — 11 8

NSFVP-34 7.7 6.7 900 860

NSFVP-37 3.1 — 2 —

NSFVP-38 16.2 2.8 9 7

NSFVP-40 — — 301 277

NSFVP-45 29.8 25.1 122 91

NSFVP-46 — — 19 15

NSFVP-49 22.0 22.0 313 313

NSFVP-50 7.2 — 50 34

NSFVPFP-01 1.2 — 36 30

NSFVPFP-02 2.1 — 2 —

 Volcanic Highlands wells

NSFVOL-01 1.5 — 68 58

NSFVOL-05 1.6 — 12 5

NSFVOL-14 7.0 — 2 2

NSFVOL-19 1.2 1.1 180 179

NSFVOL-20 5.7 — 2 —

Wilson Grove Formation Highlands wells

NSFWG-08 12.0 3.4 37 7

NSFWG-10 — — 19 —

NSFWGFP-01 4.5 — 28 26

 Hydrothermal study1

NSFHOT-01 35.7 36.0 41 41

NSFHOT-02 45.0 45.0 23 23

NSFHOT-03 28.1 2.5 4 2

NSFHOT-04 53.0 53.0 247 210

NSFHOT-05 81.0 78.0 10 10

NSFHOT-06 10.0 5.6 315 174

NSFHOT-07 4.3 3.6 31 27

1

Not considered for drinking water-quality standards.

Table 17. Inorganic arsenic and iron-speciation results measured at the U.S. Geological Survey National Research Program in groundwater samples collected for the North San Francisco Bay Ground-Water Ambient Monitoring and Assessment (GAMA) study, California, 

August to November 2004.

[MDL, method detection limit; NSFVP, Valley and Plains study area; NSFVPFP, Valley and Plains flow-path well; NSFVOL, Volcanic Highlands study area; 

NSFWG, Wilson Grove Formation Highlands study area; NSFWG, Wilson Grove Formation Highlands flow-path well; NSFHOT, hydrothermal study; values in 

bold indicate concentrations that exceed the maximum oontaminant level (MCL); values in bold and italics indicate concentrations that are above the secondary 

maximum contaminant level (SMCL), or for iron, the California notification level (NL); μg/L, microgram per liter; —, not detected]

Tables 85
GAMA

 identification 

No.

Chromium,

 dissolved

 (μg/L) 

Chromium (VI) 

(hexavalent),

dissolved 

(μg/L) 

[MDL] [0.1] [0.1]

Valley and Plains wells

NSFVP-01 0.8 0.2

NSFVP-02 0.9 0.5

NSFVP-03 0.4 0.6

NSFVP-04 0.5 —

NSFVP-05 1.1 0.4

NSFVP-06 5.0 3.4

NSFVP-07 — —

NSFVP-08 0.7 0.5

NSFVP-09 0.2 0.2

NSFVP-10 0.2 0.4

NSFVP-11 — —

NSFVP-12 0.1 0.3

NSFVP-13 0.2 0.2

NSFVP-14 0.1 0.1

NSFVP-15 0.3 0.2

NSFVP-16 0.2 —

NSFVP-17 — 0.5

NSFVP-18 2.2 2.5

NSFVP-19 0.2 0.2

NSFVP-20 2.1 2.5

NSFVP-21 6.4 6.6

NSFVP-22 10.0 11.6

NSFVP-23 5.9 7.8

NSFVP-24 5.1 4.4

NSFVP-25 5.5 4.3

NSFVP-26 — 0.4

NSFVP-27 11.5 9.3

NSFVP-28 4.5 4.0

NSFVP-29 3.1 7.9

NSFVP-30 0.4 0.5

NSFVP-31 5.8 6.3

NSFVP-32 14.8 13.2

NSFVP-33 13.7 14.7

NSFVP-34 3.5 3.1

NSFVP-35 1.1 0.6

NSFVP-36 0.8 0.4

NSFVP-37 4.9 3.9

Table 18. Chromium-speciation results measured by the U.S. Geological Survey National Research Progam for ground-water samples 

collected for the North San Francisco Bay Ground-Water Ambient Monitoring and Assessment (GAMA) study, California, August to 

November, 2004.

[MDL, method detection limit; NSFVP, Valley and Plains study area; NSFVPFP, Valley and Plains flow-path well; NSFVOL, Volcanic Highlands study area; 

NSFWG, Wilson Grove Formation Highlands study area; NSFWGFP, Wilson Grove Formation Highlands flow-path well; NSFHOT, hydrothermal study; 

values in italics indicate concentrations above the detection levels for the purpose of reporting (DLR); μg/L, microgram per liter; —, not detected]

86 Ground-Water Quality Data, North San Francisco Bay Hydrologic Provinces, California, 2004: GAMA Program Results
GAMA

 identification 

No.

Chromium,

 dissolved

 (μg/L) 

Chromium (VI) 

(hexavalent),

dissolved 

(μg/L) 

[MDL] [0.1] [0.1]

NSFVP-38 3.9 3.0

NSFVP-39 0.2 —

NSFVP-40 3.5 2.8

NSFVP-41 0.4 —

NSFVP-42 — —

NSFVP-43 0.6 0.3

NSFVP-44 3.1 —

NSFVP-45 0.9 0.2

NSFVP-46 3.4 3.2

NSFVP-47 0.6 0.7

NSFVP-48 4.9 3.5

NSFVP-49 3.9 3.3

NSFVP-50 3.3 5.6

NSFVPFP-01 0.7 0.1

NSFVPFP-02 0.3 0.3

NSFVPFP-03 0.3 0.3

NSFVPFP-04 — 0.4

Volcanic Highlands wells

NSFVOL-01 1.2 0.8

NSFVOL-02 0.3 —

NSFVOL-03 5.0 4.7

NSFVOL-04 4.8 5.3

NSFVOL-05 4.9 6.6

NSFVOL-06 6.0 5.1

NSFVOL-07 6.1 5.5

NSFVOL-08 5.0 4.5

NSFVOL-09 5.3 5.8

NSFVOL-10 13.0 10.2

NSFVOL-11 12.2 10.4

NSFVOL-12 12.6 10.2

NSFVOL-13 12.9 11.3

NSFVOL-14 1.4 3.4

NSFVOL-15 17.1 15.6

NSFVOL-16 0.6 0.2

NSFVOL-17 0.3 —

NSFVOL-18 1.0 —

NSFVOL-19 3.4 3.1

NSFVOL-20 0.5 0.7

Table 18. Chromium speciation results measured by the U.S. Geological Survey National Research Progam for ground-water samples 

collected for the North San Francisco Bay Ground-Water Ambient Monitoring and Assessment (GAMA) study, California, August to 

November, 2004—Continued.

[MDL, method detection limit; NSFVP, Valley and Plains study area; NSFVPFP, Valley and Plains flow-path well; NSFVOL, Volcanic Highlands study area; 

NSFWG, Wilson Grove Formation Highlands study area; NSFWGFP, Wilson Grove Formation Highlands flow-path well; NSFHOT, hydrothermal study; values 

in italics indicate concentrations above the detection levels for the purpose of reporting (DLR); μg/L, microgram per liter; —, not detected]

Tables 87
GAMA

 identification 

No.

Chromium,

 dissolved

 (μg/L) 

Chromium (VI) 

(hexavalent),

dissolved 

(μg/L) 

[MDL] [0.1] [0.1]

 Wilson Grove Formation Highlands wells

NSFWG-01 1.7 1.8

NSFWG-02 5.9 4.4

NSFWG-03 6.1 6.9

NSFWG-04 4.3 3.4

NSFWG-05 4.4 4.6

NSFWG-06 7.4 4.4

NSFWG-07 6.4 6.3

NSFWG-08 2.3 1.6

NSFWG-09 13.4 8.9

NSFWG-10 2.7 2.5

NSFWG-11 0.7 —

NSFWG-12 1.9 0.4

NSFWG-13 0.2 0.2

NSFWG-14 4.0 3.0

NSFWGFP-01 2.9 1.5

Hydrothermal study1

NSFHOT-01 0.7 —

NSFHOT-02 0.2 0.1

NSFHOT-03 — —

NSFHOT-04 0.4 —

NSFHOT-05 5.6 0.4

NSFHOT-06 — —

NSFHOT-07 0.2 —

NSFHOT-08 — —

1

Not considered for drinking water-quality standards.

Table 18. Chromium speciation results measured by the U.S. Geological Survey National Research Progam for ground-water samples 

collected for the North San Francisco Bay Ground-Water Ambient Monitoring and Assessment (GAMA) study, California, August to 

November, 2004—Continued.

[MDL, method detection limit; NSFVP, Valley and Plains study area; NSFVPFP, Valley and Plains flow-path well; NSFVOL, Volcanic Highlands study area; 

NSFWG, Wilson Grove Formation Highlands study area; NSFWGFP, Wilson Grove Formation Highlands flow-path well; NSFHOT, hydrothermal study; values 

in italics indicate concentrations above the detection levels for the purpose of reporting (DLR); μg/L, microgram per liter; —, not detected]

88 Ground-Water Quality Data, North San Francisco Bay Hydrologic Provinces, California, 2004: GAMA Program Results
GAMA

 identification 

No.

Alpha 

radioactivity, 

72-hour 

count 

(pCi/L) 

(62636)

Alpha 

radioactivity, 

30-day 

count

(pCi/L) 

(62369)

Beta 

radioactivity, 

72-hour count 

(pCi/L) 

(62642)

Beta

radioactivity, 

30-day 

count 

(pCi/L) 

(62645)

Tritium 

(pCi/L)

(07000)

Tritium 

2-sigma 

combined 

uncertainty 

(pCi/L) 

(75985)

Carbon-14 

(percent 

modern)

(49933)

Valley and Plains wells

NSFVP-01 NC NC NC NC 1.6 0.6 NC

NSFVP-02 NC NC NC NC 2.2 0.6 NC

NSFVP-03 NC NC NC NC 1.9 0.6 NC

NSFVP-04 NC NC NC NC <1.0 0.6 NC

NSFVP-05 NC NC NC NC <1.0 0.6 NC

NSFVP-06 NC NC NC NC 1.6 0.6 NC

NSFVP-07 NC NC NC NC 1.0 1.0 NC

NSFVP-08 NC NC NC NC 7.4 0.6 NC

NSFVP-09 NC NC NC NC <1.0 0.6 NC

NSFVP-10 <3 <3 <4 — 7.4 1.0 1.04

NSFVP-11 NC NC NC NC 6.4 1.0 NC

NSFVP-12 NC NC NC NC — 0.6 NC

NSFVP-13 NC NC NC NC <1.0 0.6 NC

NSFVP-14 NC NC NC NC <1.0 0.8 NC

NSFVP-15 NC NC NC NC 5.1 1.0 NC

NSFVP-16 NC NC NC NC — 0.6 NC

NSFVP-17 NC NC NC NC 6.7 1.0 NC

NSFVP-18 NC NC NC NC 6.4 1.0 NC

NSFVP-19 — — <4 <4 6.7 1.0 0.97

NSFVP-20 NC NC NC NC 6.7 1.0 NC

NSFVP-21 NC NC NC NC 8.0 1.6 NC

NSFVP-22 NC NC NC NC 6.4 1.0 NC

NSFVP-23 NC NC NC NC 1.9 0.6 NC

NSFVP-24 NC NC NC NC <1.0 0.6 NC

NSFVP-25 NC NC NC NC <1.0 0.8 NC

NSFVP-26 <3 <3 <4 <4 — 0.6 0.13

NSFVP-27 NC NC NC NC 4.8 0.6 NC

NSFVP-28 NC NC NC NC 5.4 1.0 NC

NSFVP-29 <3 <3 <4 <4 7.4 1.0 1.05

NSFVP-30 — <3 <4 <4 8.3 1.0 0.70

NSFVP-31 NC NC NC NC 4.5 0.6 NC

NSFVP-32 NC NC NC NC 1.3 1.0 NC

NSFVP-33 NC NC NC NC 2.6 1.0 NC

Table 19. Isotopes and radioactivity measured in ground-water samples collected for the North San Francisco Bay Ground-Water 

Ambient Monitoring and Assessment (GAMA) study, California, August to November 2004.

[The five-digit number in parentheses below the constituent name is the U.S. Geological Survey parameter code used to uniquely identify a specific constituent 

or property; LRL, laboratory reporting level; NSFVP, Valley and Plains study area; NSFVPFP, Valley and Plains flow-path well; NSFVOL, Volcanic Highlands 

study area; NSFWG, Wilson Grove Formation Highlands study area; NSFWGFP, Wilson Grove Formation Highlands flow-path well; NSFHOT, 

hydrothermal study; values in bold indicate concentrations that exceed the proposed maximum contaminant level (MCL); pCi/L, picocuries per liter; NC, sample 

not collected; <, less than; —, not detected]

Tables 89
GAMA

 identification 

No.

Alpha 

radioactivity, 

72-hour 

count 

(pCi/L) 

(62636)

Alpha 

radioactivity, 

30-day 

count

(pCi/L) 

(62369)

Beta 

radioactivity, 

72-hour count 

(pCi/L) 

(62642)

Beta

radioactivity, 

30-day 

count 

(pCi/L) 

(62645)

Tritium 

(pCi/L)

(07000)

Tritium 

2-sigma 

combined 

uncertainty 

(pCi/L) 

(75985)

Carbon-14 

(percent 

modern)

(49933)

NSFVP-34 <3 <3 5 4 — 0.6 0.20

NSFVP-35 NC NC NC NC 2.9 0.6 NC

NSFVP-36 NC NC NC NC <1.0 0.6 NC

NSFVP-37 <3 <3 <4 <4 5.8 1.0 0.97

NSFVP-38 <3 <3 <4 4 — 0.6 0.01

NSFVP-39 NC NC NC NC 1.9 1.0 NC

NSFVP-40 <3 4 7 8 — 0.6 0.13

NSFVP-41 NC NC NC NC 7.0 1.0 NC

NSFVP-42 NC NC NC NC <1.0 0.6 NC

NSFVP-43 NC NC NC NC <1.0 0.6 NC

NSFVP-44 NC NC NC NC — 0.6 NC

NSFVP-45 — — 20 22 1.0 0.6 0.07

NSFVP-46 <3 — — — 7.4 1.0 NC

NSFVP-47 NC NC NC NC 7.7 0.6 NC

NSFVP-48 NC NC NC NC <1.0 0.6 NC

NSFVP-49 <3 <3 10 11 — 0.6 0.02

NSFVP-50 <3 <3 9 9 <1.0 0.6 0.19

NSFVPFP-01 <3 — <4 <4 <1.0 0.6 0.24

NSFVPFP-02 <3 <3 <4 <4 1.6 0.6 0.85

NSFVPFP-03 NC NC NC NC 7.7 1.0 NC

NSFVPFP-04 NC NC NC NC 8.0 1.0 NC

Volcanic Highlands wells

NSFVOL-01 <3 — <4 <4 <1.0 0.6 0.69

NSFVOL-02 NC NC NC NC 1.6 0.6 NC

NSFVOL-03 NC NC NC NC <1.0 0.6 NC

NSFVOL-04 NC NC NC NC <1.0 0.6 NC

NSFVOL-05 NC NC NC NC 2.2 0.8 NC

NSFVOL-06 NC NC NC NC <1.0 0.6 NC

NSFVOL-07 NC NC NC NC 1.0 0.6 NC

NSFVOL-08 NC NC NC NC — 1.0 NC

NSFVOL-09 NC NC NC NC <1.0 0.6 NC

NSFVOL-10 NC NC NC NC 7.7 1.0 NC

NSFVOL-11 NC NC NC NC 2.9 0.6 NC

NSFVOL-12 NC NC NC NC — 0.6 NC

Table 19. Isotope and radioactivity measured in ground-water samples collected for the North San Francisco Bay Ground-Water 

Ambient Monitoring and Assessment (GAMA) study, California, August to November 2004—Continued.

[The five-digit number in parentheses below the constituent name is the U.S. Geological Survey parameter code used to uniquely identify a specific constituent 

or property; LRL, laboratory reporting level; NSFVP, Valley and Plains study area; NSFVPFP, Valley and Plains flow-path well; NSFVOL, Volcanic Highlands 

study area; NSFWG, Wilson Grove Formation Highlands study area; NSFWGFP, Wilson Grove Formation Highlands flow-path well; NSFHOT, 

hydrothermal study; values in bold indicate concentrations that exceed the proposed maximum contaminant level (MCL); pCi/L, picocuries per liter; NC,

 sample not collected; <, less than; —, not detected]

90 Ground-Water Quality Data, North San Francisco Bay Hydrologic Provinces, California, 2004: GAMA Program Results
GAMA

 identification 

No.

Alpha 

radioactivity, 

72-hour 

count 

(pCi/L) 

(62636)

Alpha 

radioactivity, 

30-day 

count

(pCi/L) 

(62369)

Beta 

radioactivity, 

72-hour count 

(pCi/L) 

(62642)

Beta

radioactivity, 

30-day 

count 

(pCi/L) 

(62645)

Tritium 

(pCi/L)

(07000)

Tritium 

2-sigma 

combined 

uncertainty 

(pCi/L) 

(75985)

Carbon-14 

(percent 

modern)

(49933)

NSFVOL-13 NC NC NC NC 9.9 1.0 NC

NSFVOL-14 <3 — <4 <4 4.2 0.6 0.93

NSFVOL-15 NC NC NC NC <1.0 1.0 NC

NSFVOL-16 NC NC NC NC <1.0 1.0 NC

NSFVOL-17 NC NC NC NC 1.6 0.6 NC

NSFVOL-18 NC NC NC NC 1.0 1.0 NC

NSFVOL-19 — <3 5 5 <1.0 0.6 0.52

NSFVOL-20 <3 <3 6 6 1.0 0.6 0.48

Wilson Grove Formation Highlands wells

NSFWG-01 NC NC NC NC 2.9 0.8 NC

NSFWG-02 NC NC NC NC 1.9 0.8 NC

NSFWG-03 NC NC NC NC — 0.8 NC

NSFWG-04 NC NC NC NC <1.0 0.8 NC

NSFWG-05 NC NC NC NC <1.0 0.8 NC

NSFWG-06 NC NC NC NC 6.1 1.0 NC

NSFWG-07 NC NC NC NC <1.0 0.6 NC

NSFWG-08 — — <4 <4 2.6 0.6 0.57

NSFWG-09 NC NC NC NC 1.3 0.6 0.88

NSFWG-10 — — — <4 — 0.6 0.23

NSFWG-11 NC NC NC NC — 1.0 NC

NSFWG-12 NC NC NC NC — 0.6 NC

NSFWG-13 NC NC NC NC <1.0 0.6 NC

NSFWG-14 <3 NC NC NC 1.0 NC

NSFWGFP-01 NC NC NC NC 2.2 0.6 0.45

Hydrothermal study

NSFHOT-01 NC NC NC NC NC NC NC

NSFHOT-02 NC NC NC NC NC NC NC

NSFHOT-03 NC NC NC NC NC NC NC

NSFHOT-04 NC NC NC NC NC NC NC

NSFHOT-05 NC NC NC NC NC NC NC

NSFHOT-06 NC NC NC NC NC NC NC

NSFHOT-07 NC NC NC NC NC NC NC

NSFHOT-08 NC NC NC NC NC NC NC

Table 19. Isotope and radioactivity measured in ground-water samples collected for the North San Francisco Bay Ground-Water 

Ambient Monitoring and Assessment (GAMA) study, California, August to November 2004—Continued.

[The five-digit number in parentheses below the constituent name is the U.S. Geological Survey parameter code used to uniquely identify a specific constituent 

or property; LRL, laboratory reporting level; NSFVP, Valley and Plains study area; NSFVPFP, Valley and Plains flow-path well; NSFVOL, Volcanic Highlands 

study area; NSFWG, Wilson Grove Formation Highlands study area; NSFWGFP, Wilson Grove Formation Highlands flow-path well; NSFHOT, 

hydrothermal study; values in bold indicate concentrations that exceed the proposed maximum contaminant level (MCL); pCi/L, picocuries per liter; NC,

 sample not collected; <, less than; —, not detected]

Tables 91
GAMA

 identification 

No.

Radon-222 

(pCi/L) 

(82303)

Radon-222 

2-sigma 

combined 

uncertainty 

(pCi/L) 

(76002)

Radium-226 

(pCi/L)

(09511)

Radium-228 

(pCi/L) 

(81366)

Deuterium/

protium 

(per mil)

(82082)

Carbon-13/

carbon-12 

(per mil)

(82081)

Oxygen-18/

oxygen-16

(per mil) 

(82085)

Valley and Plains wells

NSFVP-01 NC NC NC NC –41 NC –6.2

NSFVP-02 NC NC NC NC –36 NC –5.7

NSFVP-03 NC NC NC NC –38 NC –5.9

NSFVP-04 NC NC NC NC –39 NC –6.0

NSFVP-05 NC NC NC NC –41 NC –6.3

NSFVP-06 NC NC NC NC –40 NC –6.0

NSFVP-07 NC NC NC NC –42 NC –6.3

NSFVP-08 NC NC NC NC –41 NC –6.2

NSFVP-09 NC NC NC NC –41 NC –6.4

NSFVP-10 280 22 0.16 <1 –40 –19.44 –6.3

NSFVP-11 NC NC NC NC –45 NC –6.7

NSFVP-12 NC NC NC NC –36 NC –5.7

NSFVP-13 NC NC NC NC –39 NC –6.3

NSFVP-14 NC NC NC NC –43 NC –6.5

NSFVP-15 NC NC NC NC –36 NC –5.8

NSFVP-16 NC NC NC NC –43 NC –6.6

NSFVP-17 NC NC NC NC –47 NC –7.2

NSFVP-18 NC NC NC NC –37 NC –5.9

NSFVP-19 240 22 0.05 — –51 –15.68 –7.4

NSFVP-20 NC NC NC NC –38 NC –6.0

NSFVP-21 NC NC NC NC –39 NC –6.0

NSFVP-22 NC NC NC NC –39 NC –5.9

NSFVP-23 NC NC NC NC –41 NC –6.3

NSFVP-24 NC NC NC NC –39 NC –6.2

NSFVP-25 NC NC NC NC –41 NC –6.5

NSFVP-26 570 27 0.08 <1 –44 –17.64 –6.9

NSFVP-27 NC NC NC NC –42 NC –6.7

NSFVP-28 NC NC NC NC –40 NC –6.3

NSFVP-29 330 24 0.07 <1 –44 –17.85 –7.0

NSFVP-30 380 24 0.08 — –46 –13.97 –7.0

NSFVP-31 NC NC NC NC –41 NC –6.4

NSFVP-32 NC NC NC NC –44 NC –6.8

NSFVP-33 NC NC NC NC –40 NC –6.4

Table 19. Isotope and radioactivity measured in ground-water samples collected for the North San Francisco Bay Ground-Water 

Ambient Monitoring and Assessment (GAMA) study, California, August to November 2004—Continued.

[The five-digit number in parentheses below the constituent name is the U.S. Geological Survey parameter code used to uniquely identify a specific constituent 

or property; LRL, laboratory reporting level; NSFVP, Valley and Plains study area; NSFVPFP, Valley and Plains flow-path well; NSFVOL, Volcanic Highlands 

study area; NSFWG, Wilson Grove Formation Highlands study area; NSFWGFP, Wilson Grove Formation Highlands flow-path well; NSFHOT, 

hydrothermal study; values in bold indicate concentrations that exceed the proposed maximum contaminant level (MCL); pCi/L, picocuries per liter; NC,

 sample not collected; <, less than; —, not detected]

92 Ground-Water Quality Data, North San Francisco Bay Hydrologic Provinces, California, 2004: GAMA Program Results
GAMA

 identification 

No.

Radon-222 

(pCi/L) 

(82303)

Radon-222 

2-sigma 

combined 

uncertainty 

(pCi/L) 

(76002)

Radium-226 

(pCi/L)

(09511)

Radium-228 

(pCi/L) 

(81366)

Deuterium/

protium 

(per mil)

(82082)

Carbon-13/

carbon-12 

(per mil)

(82081)

Oxygen-18/

oxygen-16

(per mil) 

(82085)

NSFVP-34 1,200 36 0.07 <1 –47 –17.58 –7.1

NSFVP-35 NC NC NC NC –40 NC –5.9

NSFVP-36 NC NC NC NC –53 NC –7.7

NSFVP-37 770 30 0.05 — –39 –19.98 –6.0

NSFVP-38 680 29 0.06 <1 –50 –14.62 –7.8

NSFVP-39 NC NC NC NC –47 NC –7.1

NSFVP-40 250 21 0.08 <1 –47 –15.57 –7.0

NSFVP-41 NC NC NC NC –40 NC –6.0

NSFVP-42 NC NC NC NC –40 NC –6.5

NSFVP-43 NC NC NC NC –40 NC –6.3

NSFVP-44 NC NC NC NC –48 NC –7.2

NSFVP-45 1,100 35 0.17 <1 –52 –13.63 –7.8

NSFVP-46 1,000 32 0.09 — –43 NC –6.4

NSFVP-47 NC NC NC NC –40 NC –6.1

NSFVP-48 NC NC NC NC –41 NC –6.4

NSFVP-49 990 32 0.09 <1 –51 –17.1 –7.5

NSFVP-50 940 34 0.07 <1 –49 –19.31 –7.2

NSFVPFP-01 260 22 0.09 — –39 –19.53 –6.3

NSFVPFP-02 670 28 0.09 — –39 –18.12 –5.9

NSFVPFP-03 NC NC NC NC –41 NC –6.3

NSFVPFP-04 NC NC NC NC –39 NC –6.1

Volcanic Highlands wells

NSFVOL-01 670 28 0.08 — –41 –19.88 –6.5

NSFVOL-02 NC NC NC NC NC NC NC

NSFVOL-03 NC NC NC NC NC NC NC

NSFVOL-04 NC NC NC NC NC NC NC

NSFVOL-05 NC NC NC NC –43 NC –6.7

NSFVOL-06 NC NC NC NC –45 NC –6.9

NSFVOL-07 NC NC NC NC –42 NC –6.6

NSFVOL-08 NC NC NC NC –42 NC –6.8

NSFVOL-09 NC NC NC NC –41 NC –6.6

NSFVOL-10 NC NC NC NC –42 NC –6.8

NSFVOL-11 NC NC NC NC –46 NC –7.3

NSFVOL-12 NC NC NC NC –50 NC –7.7

Table 19. Isotope and radioactivity measured in ground-water samples collected for the North San Francisco Bay Ground-Water 

Ambient Monitoring and Assessment (GAMA) study, California, August to November 2004—Continued.

[The five-digit number in parentheses below the constituent name is the U.S. Geological Survey parameter code used to uniquely identify a specific constituent 

or property; LRL, laboratory reporting level; NSFVP, Valley and Plains study area; NSFVPFP, Valley and Plains flow-path well; NSFVOL, Volcanic Highlands 

study area; NSFWG, Wilson Grove Formation Highlands study area; NSFWGFP, Wilson Grove Formation Highlands flow-path well; NSFHOT, 

hydrothermal study; values in bold indicate concentrations that exceed the proposed maximum contaminant level (MCL); pCi/L, picocuries per liter; NC,

 sample not collected; <, less than; —, not detected]

Tables 93
GAMA

 identification 

No.

Radon-222 

(pCi/L) 

(82303)

Radon-222 

2-sigma 

combined 

uncertainty 

(pCi/L) 

(76002)

Radium-226 

(pCi/L)

(09511)

Radium-228 

(pCi/L) 

(81366)

Deuterium/

protium 

(per mil)

(82082)

Carbon-13/

carbon-12 

(per mil)

(82081)

Oxygen-18/

oxygen-16

(per mil) 

(82085)

NSFVOL-13 NC NC NC NC –34 NC –4.5

NSFVOL-14 400 23 0.07 <1 –40 –17.6 –6.1

NSFVOL-15 NC NC NC NC –45 NC –7.2

NSFVOL-16 NC NC NC NC –47 NC –7.1

NSFVOL-17 NC NC NC NC –46 NC –7.1

NSFVOL-18 NC NC NC NC –48 NC –7.2

NSFVOL-19 670 29 0.14 <1 –47 –13.12 –7.4

NSFVOL-20 1,500 39 0.10 <1 –45 –19.11 –7.0

Wilson Grove Formation Highlands wells

NSFWG-01 NC NC NC NC –37 NC –6.2

NSFWG-02 NC NC NC NC –37 NC –5.9

NSFWG-03 NC NC NC NC –37 NC –6.2

NSFWG-04 NC NC NC NC NC NC NC

NSFWG-05 NC NC NC NC –41 NC –6.7

NSFWG-06 NC NC NC NC –32 NC –5.4

NSFWG-07 NC NC NC NC –44 NC –6.6

NSFWG-08 210 21 0.10 <1 –38 –17.99 –6.1

NSFWG-09 NC NC NC NC –38 –20.46 –6.1

NSFWG-10 210 22 0.05 — –36 –18.11 –5.8

NSFWG-11 NC NC NC NC –37 NC –5.9

NSFWG-12 NC NC NC NC –38 NC –5.9

NSFWG-13 NC NC NC NC –35 NC –5.6

NSFWG-14 NC NC NC NC –35 NC –5.5

NSFWGFP-01 NC NC NC NC –38 –15.48 –6.1

Hydrothermal study

NSFHOT-01 NC NC NC NC –51 NC –7.8

NSFHOT-02 NC NC NC NC –53 NC –8.3

NSFHOT-03 NC NC NC NC –41 NC –6.2

NSFHOT-04 NC NC NC NC –54 NC –8.2

NSFHOT-05 NC NC NC NC –53 NC –8.3

NSFHOT-06 NC NC NC NC –42 NC –6.1

NSFHOT-07 NC NC NC NC –52 NC –7.6

NSFHOT-08 NC NC NC NC –51 NC –7.5

Table 19. Isotope and radioactivity measured in ground-water samples collected for the North San Francisco Bay Ground-Water 

Ambient Monitoring and Assessment (GAMA) study, California, August to November 2004—Continued.

[The five-digit number in parentheses below the constituent name is the U.S. Geological Survey parameter code used to uniquely identify a specific constituent 

or property; LRL, laboratory reporting level; NSFVP, Valley and Plains study area; NSFVPFP, Valley and Plains flow-path well; NSFVOL, Volcanic Highlands 

study area; NSFWG, Wilson Grove Formation Highlands study area; NSFWGFP, Wilson Grove Formation Highlands flow-path well; NSFHOT, 

hydrothermal study; values in bold indicate concentrations that exceed the proposed maximum contaminant level (MCL); pCi/L, picocuries per liter; NC,

 sample not collected; <, less than; —, not detected]

94 Ground-Water Quality Data, North San Francisco Bay Hydrologic Provinces, California, 2004: GAMA Program Results
GAMA

 identification 

No.

Collection 

date

Tritium

(pCi/L)

Tritium, 

measurement 

uncertainty (+/-)

(pCi/L)

Dissolved 

gas

 analysis 

date

Helium-3/

Helium-4 

(atom ratio)

Helium-4 Neon Argon Krypton Xenon

(cm3 STP g-1H O) 2

x 10-6 x 10-7 x 10-7 x 10-4 x 10-8 x 10-8

Valley and Plains wells

NSFVP-01 08/31/2004 1.82 0.2 12/15/2004 2.47 2.45 2.06 3.65 8.90 1.24NSFVP-02 08/31/2004 2.06 0.2 12/15/2004 1.40 0.53 2.14 3.66 8.56 1.14NSFVP-03 08/31/2004 1.91 0.2 12/15/2004 1.29 0.79 2.32 3.84 8.74 1.17NSFVP-04 09/01/2004 <1.0 0.1 12/15/2004 1.19 0.57 2.07 3.50 8.18 1.11NSFVP-05 09/01/2004 <1.0 0.2 12/15/2004 1.44 3.08 2.50 4.11 9.19 1.27NSFVP-06 09/01/2004 1.21 0.2 12/15/2004 1.44 0.89 2.96 4.32 9.58 1.25NSFVP-07 09/02/2004 <1.0 0.1 12/16/2004 0.94 0.98 2.57 4.04 8.99 1.21NSFVP-08 09/02/2004 7.71 0.4 12/16/2004 1.46 0.52 2.05 3.50 7.91 1.09NSFVP-09 09/02/2004 <1.0 0.9 12/16/2004 1.05 0.78 2.53 4.03 8.88 1.23NSFVP-10 09/13/2004 8.34 0.4 12/17/2004 1.16 0.79 2.51 4.00 8.91 1.19NSFVP-11 09/13/2004 7.96 0.4 12/16/2004 1.36 0.44 1.88 3.07 6.84 0.94NSFVP-12 09/13/2004 <1.0 0.2 03/04/2005 1.38 0.44 1.91 3.14 6.98 0.92NSFVP-13 09/14/2004 3.18 1.0 12/16/2004 1.23 0.60 2.35 3.75 8.22 1.13NSFVP-14 09/14/2004 — 0.2 12/16/2004 1.02 2.55 2.47 4.15 9.61 1.31NSFVP-15 09/14/2004 5.59 0.4 12/17/2004 1.45 1.61 5.99 6.47 12.14 1.44NSFVP-16 09/15/2004 1.50 0.2 03/04/2005 3.57 2.60 2.92 9.00 7.96 1.17NSFVP-17 09/15/2004 7.65 0.4 12/17/2004 1.33 0.53 2.08 3.44 7.82 1.07NSFVP-18 09/16/2004 8.35 0.4 12/17/2004 1.35 0.45 2.04 3.47 7.98 1.15NSFVP-19 09/16/2004 9.03 0.5 12/18/2004 1.34 0.54 2.06 3.13 6.91 0.92NSFVP-20 09/16/2004 7.56 0.4 12/18/2004 1.42 0.77 2.67 4.13 9.03 1.23NSFVP-21 09/20/2004 7.06 0.4 12/21/2004 1.54 0.81 3.20 4.42 9.22 1.24NSFVP-22 09/20/2004 5.54 0.3 12/21/2004 1.45 0.85 2.70 4.01 8.54 1.15NSFVP-23 09/20/2004 2.57 0.2 12/21/2004 0.72 2.62 2.49 4.68 8.71 1.25NSFVP-24 09/22/2004 <1.0 0.2 12/22/2004 1.50 1.20 2.41 3.83 8.50 1.15NSFVP-25 09/23/2004 <1.0 0.2 12/22/2004 1.18 0.80 2.49 3.71 8.47 1.09

Table 20. Tritium and noble gas results, analyzed at the Lawrence Livermore National Laboratory for samples collected for the North San Francisco Bay Ground-Water Ambient Monitoring and Assessment (GAMA) study, California, August to November 2004.[NSFVP, Valley and Plains study area; NSFVPFP, Valley and Plains flow-path well; NSFVOL, Volcanic Highlands study area; NSFWG, Wilson Grove Formation Highlands study area; NSFWGFP, Wilson Grove Formation Highlands flow-path well; NSFHOT, hydrothermal study; cm3 STP g-1H O, cubic centimeters at standard temperature and pressure, per gram of water; pCi/L, picocuries per liter; NC, sample 2not collected; <, less than; —, not detected]

Tables 95
GAMA

 identification 

No.

Collection 

date

Tritium

(pCi/L)

Tritium, 

measurement 

uncertainty (+/-)

(pCi/L)

Dissolved 

gas

 analysis 

date

Helium-3/

Helium-4 

(atom ratio)

Helium-4 Neon Argon Krypton Xenon

(cm3 STP g-1H O)

2

x 10-6 x 10-7 x 10-7 x 10-4 x 10-8 x 10-8

NSFVP-26 09/27/2004 <1.0 0.2 12/22/2004 0.81 1.91 2.64 4.07 8.70 1.19NSFVP-27 09/28/2004 2.24 0.3 12/22/2004 1.20 0.86 2.53 3.97 8.78 1.18NSFVP-28 09/28/2004 2.72 0.3 12/23/2004 1.15 1.28 3.04 4.26 8.95 1.15NSFVP-29 09/28/2004 7.90 0.4 12/23/2004 1.43 0.47 2.00 3.46 7.83 1.07NSFVP-30 09/29/2004 7.78 0.5 12/29/2004 1.13 0.90 2.18 3.61 8.32 1.11NSFVP-31 09/30/2004 4.50 0.3 12/29/2004 1.56 0.89 2.82 4.23 8.97 1.16NSFVP-32 10/07/2004 1.30 0.2 12/30/2004 2.19 1.70 2.70 4.13 9.07 1.19NSFVP-33 10/07/2004 2.62 0.2 01/03/2005 1.26 0.85 2.95 4.10 8.84 1.16NSFVP-34 10/18/2004

— 0.1 03/04/2005 3.98 6.80 2.03 3.11 7.17 0.95

NSFVP-35 10/18/2004 3.71 0.2 01/03/2005 1.47 0.68 2.69 4.05 8.91 1.19NSFVP-36 10/19/2004 <1.0 0.1 01/03/2005 0.45 2.22 2.33 4.04 9.32 1.29NSFVP-37 10/19/2004 6.28 0.3 11/04/2004 1.88 0.70 2.45 3.98 8.65 1.14NSFVP-38 10/20/2004 <1.0 0.2 11/05/2004 1.61 12.77 2.22 3.69 8.33 1.17NSFVP-39 10/21/2004 2.03 0.2 03/05/2005 1.64 1.11 2.33 3.65 8.28 1.10NSFVP-40 10/21/2004 <1.0 0.1 11/05/2004 5.01 7.06 2.14 3.57 7.97 1.15NSFVP-41 10/21/2004 7.81 0.4 03/05/205 1.38 1.96 2.69 3.94 8.63 1.13NSFVP-42 10/25/2004 <1.0 0.1 03/05/2005 1.37 0.64 2.72 4.09 9.15 1.18NSFVP-43 10/26/2004 <1.0 0.1 03/03/2005 1.12 0.73 2.42 3.81 8.73 1.15NSFVP-44 10/26/2004 <1.0 0.1 NC NC NC NC NC NC NCNSFVP-45 11/02/2004 <1.0 0.1 03/04/2005 0.29 3.56 2.93 4.34 9.71 1.25NSFVP-46 11/03/2004 6.86 0.5 03/02/2005 4.13 1.82 2.50 3.83 8.48 1.10NSFVP-47 11/03/2004 7.15 0.3 03/02/2005 1.71 0.49 1.85 3.18 7.19 0.98NSFVP-48 11/04/2004 <1.0 0.1 03/04/2005 0.55 3.26 2.26 5.97 7.86 1.15NSFVP-49 11/17/2004 NC NC 03/03/2005 6.47 18.42 2.38 8.88 7.99 1.30NSFVP-50 11/18/2004 NC NC 03/03/2005 0.89 1.19 2.65 4.11 9.30 1.22

Table 20. Tritium and noble gas results, analyzed at the Lawrence Livermore National Laboratory for samples collected for the North San Francisco Bay Ground-Water Ambient Monitoring and Assessment (GAMA) study, California, August to November 2004—Continued.[NSFVP, Valley and Plains study area; NSFVPFP, Valley and Plains flow-path well; NSFVOL, Volcanic Highlands study area; NSFWG, Wilson Grove Formation Highlands study area; NSFWGFP, Wilson Grove Formation Highlands flow-path well; NSFHOT, hydrothermal study; cm3 STP g-1H O, cubic centimeters at standard temperature and pressure, per gram of water; pCi/L, picocuries per liter; NC, sample 

2

not collected; <, less than; —, not detected]

96 Ground-Water Quality Data, North San Francisco Bay Hydrologic Provinces, California, 2004: GAMA Program Results
GAMA

 identification 

No.

Collection 

date

Tritium

(pCi/L)

Tritium, 

measurement 

uncertainty (+/-)

(pCi/L)

Dissolved 

gas

 analysis 

date

Helium-3/

Helium-4 

(atom ratio)

Helium-4 Neon Argon Krypton Xenon

(cm3 STP g-1H O) 2

x 10-6 x 10-7 x 10-7 x 10-4 x 10-8 x 10-8

NSFVPFP-01 09/14/2004 <1.0 0.2 12/17/2004 0.85 1.43 2.63 4.12 9.08 1.25NSFVPFP-02 09/30/2004 3.29 0.2 12/28/2004 1.35 0.76 2.80 4.26 9.33 1.23NSFVPFP-03 10/20/2004 8.73 0.4 01/04/2005 0.53 12.29 2.09 3.68 8.32 1.11NSFVPFP-04 09/13/2004 8.23 0.4 12/16/2004 1.30 0.65 2.32 3.81 8.78 1.21

Volcanic Highlands wells

NSFVOL-01 09/15/2004 <1.0 0.2 12/17/2004 1.28 0.63 2.49 3.62 8.07 1.10NSFVOL-02 09/15/2004 3.14 0.2 NC NC NC NC NC NC NCNSFVOL-03 09/27/2004 <1.0 0.2 12/22/2004 0.75 1.72 2.18 3.37 7.36 0.98NSFVOL-04 09/27/2004 <1.0 0.2 12/22/2004 1.36 0.72 2.58 4.08 8.92 1.23NSFVOL-05 09/27/2004 1.14 0.2 12/22/2004 1.40 0.56 2.32 3.73 8.37 1.13NSFVOL-06 09/29/2004 <1.0 0.2 12/23/2004 0.83 2.56 2.74 4.07 8.69 1.15NSFVOL-07 09/29/2004 <1.0 0.1 12/28/2004 1.22 0.67 2.45 3.71 8.20 1.06NSFVOL-08 09/29/2004 <1.0 0.2 12/29/2004 1.27 0.68 2.62 3.76 8.17 1.08NSFVOL-09 09/29/2004 <1.0 0.4 12/29/2004 1.13 0.73 2.50 3.73 8.45 1.12NSFVOL-10 10/05/2004 8.01 0.4 12/30/2004 1.36 0.57 2.43 3.78 8.52 1.18NSFVOL-11 10/06/2004 2.91 0.2 12/30/2004 1.32 0.59 2.37 3.78 8.44 1.13NSFVOL-12 10/06/2004 <1.0 0.1 12/30/2004 1.21 0.81 2.28 3.58 8.17 1.09NSFVOL-13 10/06/2004 10.98 0.5 12/30/2004 1.61 0.76 3.04 4.13 8.69 1.18NSFVOL-14 10/07/2004 5.20 0.3 01/03/2005 1.44 0.58 2.50 3.83 8.35 1.14NSFVOL-15 10/07/2004 1.09 0.2 01/03/2005 1.35 0.70 2.56 3.91 8.53 1.17NSFVOL-16 10/19/2004 <1.0 0.1 01/03/2005 3.43 4.30 2.38 4.42 6.67 0.96NSFVOL-17 10/20/2004 1.70 0.2 01/04/2005 1.16 0.78 2.72 4.05 8.98 1.19NSFVOL-18 10/20/2004 <1.0 0.4 01/04/2005 1.83 1.87 2.23 3.57 8.22 1.11NSFVOL-19 11/02/2004 1.67 0.2 03/04/2005 1.26 0.75 2.83 3.78 8.24 1.08NSFVOL-20 11/04/2004 1.11 0.1 03/03/2005 1.21 0.57 2.25 4.03 9.47 1.28

Table 20. Tritium and noble gas results, analyzed at the Lawrence Livermore National Laboratory for samples collected for the North San Francisco Bay Ground-Water Ambient Monitoring and Assessment (GAMA) study, California, August to November 2004—Continued.[NSFVP, Valley and Plains study area; NSFVPFP, Valley and Plains flow-path well; NSFVOL, Volcanic Highlands study area; NSFWG, Wilson Grove Formation Highlands study area; NSFWGFP, Wilson Grove Formation Highlands flow-path well; NSFHOT, hydrothermal study; cm3 STP g-1H O, cubic centimeters at standard temperature and pressure, per gram of water; pCi/L, picocuries per liter; NC, sample 2not collected; <, less than; —, not detected]

Tables 97
GAMA

 identification 

No.

Collection 

date

Tritium

(pCi/L)

Tritium, 

measurement 

uncertainty (+/-)

(pCi/L)

Dissolved 

gas

 analysis 

date

Helium-3/

Helium-4 

(atom ratio)

Helium-4 Neon Argon Krypton Xenon

(cm3 STP g-1H O)

2

x 10-6 x 10-7 x 10-7 x 10-4 x 10-8 x 10-8

Wilson Grove Formation Highlands wells

NSFWG-01 09/16/2004 2.79 0.3 12/18/2004 1.50 0.60 2.61 3.94 8.85 1.19NSFWG-02 09/21/2004 1.76 0.2 12/21/2004 1.38 0.44 1.84 3.33 7.67 1.08NSFWG-03 09/21/2004 <1.0 0.1 12/21/2004 1.35 0.65 2.74 4.05 8.83 1.17NSFWG-04 09/22/2004

—

— 12/21/2004 1.31 0.83 3.29 4.54 9.50 1.22

NSFWG-05 09/22/2004 <1.0 0.1 NC NC NC NC NC NC NCNSFWG-06 09/23/2004 5.95 0.4 NC NC NC NC NC NC NCNSFWG-07 09/30/2004 <1.0 0.1 12/28/2004 0.82 1.57 2.31 3.88 9.00 1.21NSFWG-08 10/04/2004 2.77 0.2 12/28/2004 1.42 0.79 3.05 4.31 9.02 1.19NSFWG-09 10/04/2004 1.50 0.2 12/30/2004 1.39 0.57 2.50 3.86 8.57 1.14NSFWG-10 10/06/2004 <1.0 0.1 NC NC NC NC NC NC NCNSFWG-11 10/27/2004 <1.0 0.1 12/30/2004 1.15 0.73 2.34 3.79 8.39 1.13NSFWG-12 10/27/2004 <1.0 0.1 01/04/2005 1.14 0.64 2.25 3.74 8.44 1.15NSFWG-13 10/28/2004 <1.0 0.1 NC NC NC NC NC NC NCNSFWG-14 11/04/2004 <1.0 0.1 03/02/2005 0.71 0.95 2.04 3.40 8.06 1.10NSFWGFP-01 10/05/2004 2.61 0.2 12/30/2004 1.38 0.69 2.65 4.04 8.91 1.19

Hydrothermal study

NSFHOT-01 10/19/2004 1.61 0.2 11/05/2004 6.90 15.38 1.22 1.87 5.14 0.61NSFHOT-02 10/21/2004 <1.0 0.1 11/05/2004 6.94 20.52 1.46 2.00 6.22 0.63NSFHOT-03 10/21/2004 9.05 0.4 03/02/2005 2.35 0.85 2.79 3.66 7.62 0.96NSFHOT-04 10/19/2004 <1.0 0.2 11/04/2004 6.86 18.88 1.10 1.69 4.06 0.56NSFHOT-05 10/19/2004 <1.0 0.2 03/04/2005 7.01 0.90 0.07 1.35 0.79 0.07NSFHOT-06 10/20/2004 3.77 0.3 11/05/2004 3.77 38.90 2.14 3.51 7.50 1.09NSFHOT-07 10/20/2004

—

— NC NC NC NC NC NC NC

NSFHOT-08 NC NC NC NC NC NC NC NC NC NC

Table 20. Tritium and noble gas results, analyzed at the Lawrence Livermore National Laboratory for samples collected for the North San Francisco Bay Ground-Water Ambient Monitoring and Assessment (GAMA) study, California, August to November 2004—Continued.[NSFVP, Valley and Plains study area; NSFVPFP, Valley and Plains flow-path well; NSFVOL, Volcanic Highlands study area; NSFWG, Wilson Grove Formation Highlands study area; NSFWGFP, Wilson Grove Formation Highlands flow-path well; NSFHOT, hydrothermal study; cm3 STP g-1H O, cubic centimeters at standard temperature and pressure, per gram of water; pCi/L, picocuries per liter; NC, sample 

2

not collected; <, less than; —, not detected]

98 Ground-Water Quality Data, North San Francisco Bay Hydrologic Provinces, California, 2004: GAMA Program Results
GAMA

 identification 

No.

Carbon dioxide Nitrogen Argon Oxygen Methane

(cm3 STP g-1 H20)

x 10-2 x 10-2 x 10-2 x 10-2 x 10-4

Valley and Plains wells

NSFVP-34 35.5 4.71 4.31 1.16 0.41

NSFVP-37 117 6.05 5.08 2.31 0.32

NSFVP-38 16.7 4.48 4.20 0.72 4.87

NSFVP-40 29.6 4.54 4.17 0.43 8.03

Hydrothermal study

NSFHOT-01 14.2 1.05 1.10 0.56 44.0

NSFHOT-02 22.7 1.97 1.49 0.41 97.3

NSFHOT-03 283 4.75 3.86 1.42 0.66

NSFHOT-04 50.8 2.18 2.01 1.21 103

NSFHOT-05 4.58 0.36 0.44 0.45 3.35

NSFHOT-06 22.1 4.35 3.76 0.60 98.4

NSFHOT-07 4.94 3.41 1.89 0.71 313

Table 21. Concentrations of the dissolved gases: carbon dioxide, nitrogen, argon, oxygen, and methane analyzed at Lawrence Livermore 

National Laboratory in samples collected for the North San Francisco Bay Ground-Water Ambient Monitoring and Assessment (GAMA) 

study, California, August to November 2004.

[cm3 STP g-1 H20, centimeters cubed at standard temperature and pressure, per gram of water; NSFVP, Valley and Plains study area; NSFHOT, hydrothermal 

study]

Tables 99
GAMA 

identification No.

Coliphage 

F-specific

(99335)

Coliphage 

somatic

(99332)

E. coli

(colonies/

100ml)

(90901)

Total coliforms

 (colonies/100ml)

(90900)

Valley and Plains wells

NSFVP-10 — — — —

NSFVP-19 — — — —

NSFVP-26 — — — —

NSFVP-29 — — — —

NSFVP-30 — — — —

NSFVP-34 — — — —

NSFVP-37 — — — —

NSFVP-38 — — NR E2

NSFVP-40 — — — —

NSFVP-45 — — — —

NSFVP-46 — — — 9

NSFVP-49 — — — —

NSFVP-50 — — — —

NSFVPFP-01 — — — —

NSFVPFP-02 — — — —

Volcanic Highlands wells

NSFVOL-01 — — — —

NSFVOL-14 — — — —

NSFVOL-19 — — — —

NSFVOL-20 — — — —

Wilson Grove Highlands Formation wells

NSFWG-08 — — — —

NSFWG-10 — — — 20

NSFWGFP-01 — — — —

Hydrothermal study (not collected)

Table 22. Microbial analyses of ground-water samples collected for the North San Francisco Bay Ground-Water Ambient Monitoring 

and Assessment (GAMA) study, California, August to November 2004.

[The five-digit number below the compound name is the U.S. Geological Survey parameter code used to uniquely identify a specific constituent or property. 

NSFVP, Valley and Plains study area; NSFVPFP, Valley and Plains flow-path well; NSFVOL, Volcanic Highlands study area; NSFWG, Wilson Grove Formation Highlands study area; NSFWGFP, Wilson Grove Formation Highlands flow-path well; ml, milliliter; NR, not reported; —, not detected]

100 Ground-Water Quality Data, North San Francisco Bay Hydrologic Provinces, California, 2004: GAMA Program Results