Data Series 196

California GAMA Program: Ground-Water Quality Data in the 

Northern San Joaquin Basin Study Unit, 2005

In cooperation with the

California State Water Resources Control Board

Ground-Water Ambient Monitoring and Assessment (GAMA) Program

U.S. Department of the Interior

U.S. Geological Survey

STOCKTON

LODI

TRACY

California GAMA Program: Ground-Water 

Quality Data in the Northern San Joaquin 

Basin Study Unit, 2005

By George L. Bennett V, Kenneth Belitz, and Barbara J. Milby Dawson

A product of the California Ground-Water Ambient Monitoring and 

Assessment (GAMA) Program 

Data Series 196

U.S. Department of the Interior

U.S. Geological Survey

In cooperation with the California State Water Resources Control Board
U.S. Department of the Interior

Dirk Kempthorne, Secretary

U.S. Geological Survey

Mark D. Myers, Director

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

For product and ordering information:

World Wide Web: http://www.usgs.gov/pubprod

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U.S. Government.

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 :

Bennett, G.L., V, Belitz, Kenneth,Milby Dawson, B.J., 2006, California GAMA Program—Ground-water quality data in 

the northern San Joaquin basin study unit, 2005: U.S. Geological Survey Data Series 196, 122 p.
iii

Contents

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

Introduction.....................................................................................................................................................3

Purpose and Scope...............................................................................................................................5

Acknowledgments.................................................................................................................................6

Hydrogeologic Setting of the Northern San Joaquin Basin Study Unit........................................6

Eastern San Joaquin Basin Study Area....................................................................................6

Tracy Basin Study Area...............................................................................................................8

Cosumnes Basin Study Area......................................................................................................8

Uplands Basin Study Area..........................................................................................................8

Methods of Study............................................................................................................................................8

Study and Sampling Design.................................................................................................................9

Field Methods.........................................................................................................................................9

Laboratory Methods............................................................................................................................12

Data Reporting and Constituents on Multiple Analytical Schedules..........................................12

Quality-Control Procedures and Results.........................................................................................13

Blanks ..........................................................................................................................................13

Source-Solution Results............................................................................................................14

Depth-Dependent Equipment Blank Results.................................................................14

Portable Pump Equipment Blank Results......................................................................15

Field Blank Results............................................................................................................16

Replicates and Results..............................................................................................................17

Laboratory Surrogates and Results.........................................................................................18

Laboratory Matrix Spikes and Results....................................................................................19

Ground-Water-Quality Results....................................................................................................................19

VOCs, Gasoline Oxygenates, and Tentatively Identified Compounds.........................................20

Pesticides and Pesticide Degradates..............................................................................................20

Wastewater-Indicator Constituents.................................................................................................21

Perchlorate, N-Nitrosodimethylamine, and 1,2,3-Trichloropropane...........................................21

Nutrients and Dissolved Organic Carbon........................................................................................21

Major and Minor Ions and Total Dissolved Solids..........................................................................23

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

Isotopes, Radioactivity, and Noble Gases.......................................................................................27

Microbial Constituents........................................................................................................................27

Summary........................................................................................................................................................27

References.....................................................................................................................................................31

Tables ............................................................................................................................................................35
iv

Figures

1. Map showing hydrogeologic provinces of California and the location of the 

Northern San Joaquin Basin study unit (black area) .............................................................4

2. Map showing northern San Joaquin Basin Ground-Water Ambient Monitoring and 

Assessment (GAMA) study unit and locations of the four study areas...............................7

3. Map showing northern San Joaquin Basin Ground-Water Ambient Monitoring and 

Assessment (GAMA) study unit showing study areas, distribution of study area grid 

cells, and location of sampled grid cell wells........................................................................10

4. Map showing northern San Joaquin Basin Ground-Water Ambient Monitoring and 

Assessment (GAMA) study unit, study areas, and distribution of additional wells 

sampled ........................................................................................................................................11

5. Bar graph that compares concentrations of constituents suspected to be the 

result of contamination detected in the portable pump equipment blank and 

subsequent ground-water samples collected using the same equipment.......................16

6. Map showing northern San Joaquin Basin Ground-Water Ambient Monitoring and 

Assessment (GAMA) study unit showing study areas, and locations of wells sampled 

for DBCP 

and EDB with detections referenced to the Maximum Contaminant Level (MCL)..........22

7. Map showing northern San Joaquin Basin Ground-Water Ambient Monitoring and 

Assessment (GAMA) study unit showing study areas, and locations of wells sampled 

with 

detections referenced to the Secondary Maximum Contaminant Level (SMCL) ............24

8. Map showing northern San Joaquin Basin Ground-Water Ambient Monitoring and 

Assessment (GAMA) study unit showing study areas, and locations of wells................25

9. Map showing northern San Joaquin Basin Ground-Water Ambient Monitoring and 

Assessment (GAMA) study unit showing study areas, and locations of wells 

sampled for radon-222 with detections referenced to the proposed Maximum 

Contaminant Level (MCL) of 300 pCi/L.....................................................................................28

10. Map showing northern San Joaquin Basin Ground-Water Ambient Monitoring and 

Assessment (GAMA) study unit showing study areas, and locations of wells sampled 

for coliform with detections referenced to colonies detected in one 100-mL sample of 

ground water ..............................................................................................................................29
v

Tables

1. Classes of chemical, radioactive, and microbial constituents and water-quality 

indicators collected for the slow, intermediate, fast, and depth-dependent analyte 

lists in the Northern San Joaquin Basin Ground-Water Ambient Monitoring and 

Assessmenf (GAMA) study, California, December 2004 to February 2005.............................. 36

2A. Volatile organic compounds, primary use or source, U.S. Geological Survey (USGS) 

parameter code, Chemical Abstracts Service (CAS) number, USGS laboratory 

reporting levels (LRLs) for the USGS’s National Water Quality Laboratory 

analytical Schedule....................................................................................................................37

2B. Gasoline oxygenates and gasoline oxygenate degradates, primary use or source, 

U.S. Geological Survey (USGS) parameter code, Chemical Abstracts Service (CAS) 

number, USGS laboratory reporting level (LRL) for the USGS’s National Water 

Quality Laboratory analytical Schedule 4024, type of comparison threshold for groundwater detections, and the threshold concentration..................................................................41

2C. Pesticides and pesticide degradates, primary use or source, U.S. Geological Survey 

(USGS) parameter code, Chemical Abstracts Service (CAS) number, USGS 

laboratory reporting levels (LRLs) for the USGS’s National Water Quality 

Laboratory (NWQL) analytical Schedule 2003, type of comparison threshold for 

ground-water detections, and the corresponding threshold level ....................................42

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

Geological Survey (USGS) parameter code, Chemical Abstracts Service (CAS) 

number, USGS laboratory reporting level (LRL) for the USGS’s National Water 

Quality Laboratory analytical Schedule 2060, type of comparison threshold for 

ground-water detections, and the corresponding threshold level ....................................45

2E. Low-detection limit 1,2-dibromo-3-chloropropane (DBCP) and 1,2-dibromoethane 

(EDB), primary use or source, U.S. Geological Survey (USGS) parameter code, 

Chemical Abstracts Service (CAS) number, USGS minimum reporting levels (MRLs) 

for the USGS’s National Water Quality Laboratory analytical Schedule 1306, type of 

comparison threshold for ground-water detections, and the corresponding 

threshold level ..............................................................................................................................48

2F. Wastewater-indicator constituents, primary uses or sources, U.S. Geological Survey 

(USGS) parameter code, Chemical Abstracts Service (CAS) number, USGS 

laboratory reporting levels (LRLs) for the USGS National Water Quality Laboratory 

nalytical Schedule 1433, type of comparison threshold for ground-water detections, 

and the corresponding threshold level ...................................................................................49

2G. Constituents of special interest, primary use or source, Chemical Abstracts 

Service (CAS) number, Montgomery Watson Harza Laboratory method detection 

limits (MDLs), type of comparison threshold for ground-water detections, and the 

corresponding threshold level ....................................................................................................52

2H. Nutrients and dissolved organic carbon, U.S. Geological Survey (USGS) parameter 

code, Chemical Abstracts Service (CAS) number, USGS laboratory reporting levels 

(LRLs) for the USGS’s National Water Quality Laboratory analytical Schedule 2755 

and laboratory code 2613, type of comparison threshold for ground-water 

detections, and the corresponding threshold level ..............................................................52

2I. Major ions and trace elements, U.S. Geological Survey (USGS) parameter code, 

Chemical Abstracts Service (CAS) number, USGS laboratory reporting levels (LRLs) 

for the USGS’s National Water Quality Laboratory analytical Schedule 1948, type 

of comparison threshold for ground-water detections, and the corresponding 

threshold level.............................................................................................................................53
vi

2J. Iron, arsenic, and chromium speciation, U.S. Geological Survey (USGS) parameter 

code, Chemical Abstracts Service (CAS) number, USGS method detection limit 

(MDL) for the USGS’s Trace Metal Laboratory, Boulder, Colorado, type of comparison

threshold for ground-water detections, and the corresponding threshold level ............54

2K. Stable isotopes and radioactive constituents, U.S. Geological Survey (USGS) parameter 

code, Chemical Abstracts Service (CAS) number, reporting level type, reporting units 

and reporting level/uncertainty, type of comparison threshold for ground-water detections, and the corresponding threshold level ............................................................................55

2L. Tritium and noble gas compounds, U.S. Geological Survey (USGS) parameter code, 

Chemical Abstracts Service (CAS) number, method uncertainty (MU), reporting 

units from the Lawrence Livermore National Laboratory, type of comparison 

threshold, and threshold level....................................................................................................56

2M. Microbial constituents, U.S. Geological Survey (USGS) parameter code, primary 

uses and sources, method detection limit (MDL) for the USGS’s Ohio Water 

Microbiology Laboratory parameter codes 90901, 90900, 99335 and 99332, type of 

comparison threshold, and threshold level................................................................................56

3. Identification, sampling, altitude, and construction information for sampled wells 

in the Northern San Joaquin Basin Ground-Water Ambient Monitoring and 

Assessment (GAMA) study, California, December 2004 to February 2005........................57

4. Analytical methods used for the determination of organic, inorganic, and microbial

constituents by the U.S. Geological Survey’s (USGS) National Water Quality 

Laboratory (NWQL) and laboratories other than NWQL......................................................60

5. Constituents analyzed in ground-water samples collected for the Northern San 

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

California, December 2004 to February 2005 which appears on multiple analytical

schedules, primary constituent classification, analytical schedules the constituent

appears on, and the preferred analytical schedule..............................................................62

6. Quality-control summary for volatile organic compounds, gasoline oxygenates, 

tentatively identified compounds (TICs), major and minor ions, trace elements, and

 nutrients detected in the depth-dependent sampling equipment blank and groundwater samples collected in the Northern San Joaquin Basin Ground-Water 

Ambient Monitoring and Assessment (GAMA) study, California, December 2004 to

February 2005 ..............................................................................................................................63

7. Quality-control summary for volatile organic compounds, gasoline oxygenates, 

wastewater-indicator constituents, major and minor ions, and trace elements 

detected in the portable pump equipment blank and ground-water samples 

collected in the Northern San Joaquin Basin Ground-Water Ambient Monitoring 

and Assessment (GAMA) study, California, December 2004 to February 2005.......................64

8. Quality-control summary for volatile organic compounds, gasoline oxygenates, 

wastewater-indicator constituents, major and minor ions, trace elements, 

nutrients, and dissolved organic carbon, detected in field blanks and groundwater samples collected in the Northern San Joaquin Basin Ground-Water 

Ambient Monitoring and Assessment (GAMA) study, California, December 2004 

to February 2005..........................................................................................................................65

9A. Quality-control summary of replicate volatile organic compound and gasoline 

oxygenates, and pesticide and pesticide degradates, with relative standard 

deviations greater than zero, collected for the Northern San Joaquin Basin 

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

December 2004 to February 2005 ................................................................................................66
vii

9B. Quality-control summary of replicate nutrient and dissolved organic carbon samples 

collected for the Northern San Joaquin Basin Ground-Water Ambient Monitoring 

and Assessment (GAMA) study, California, December 2004 to February 2005................66

9C. Quality-control summary of replicate major- and minor-ion samples collected for the

Northern San Joaquin Basin Ground-Water Ambient Monitoring and Assessment 

(GAMA) study, California, December 2004 to February 2005...............................................67

9D. Quality-control summary of replicate trace element samples collected for the 

Northern San Joaquin Basin Ground-Water Ambient Monitoring and Assessment 

(GAMA) study, California, December 2004 to February 2005...............................................68

9E. Quality-control summary of replicate stable isotope and radioactive constituent 

samples collected for the Northern San Joaquin Basin Ground-Water Ambient 

Monitoring and Assessment (GAMA) study, California, December 2004 to 

February 2005 ..............................................................................................................................69

10. Summary of surrogate-constituent recoveries for ground water and quality-control 

analyses of volatile organic compounds, gasoline oxygenates, pesticides and 

pesticide degradates, wastewater-indicator constituents, and constituents of 

special interest collected for the Northern San Joaquin Basin Ground-Water 

Ambient Monitoring and Assessment (GAMA) study, California, December 2004 

to February 2005..........................................................................................................................70

11A. Quality-control summary of volatile organic compounds, gasoline oxygenates, 

N-nitrosodimethylamine, and 1,2,3-trichloropropane matrix-spike recoveries for 

samples collected for the Northern San Joaquin Basin Ground-Water Ambient 

Monitoring and Assessment (GAMA) study, California, December 2004 to 

February 2005................................................................................................................................71

11B. Quality-control summary of pesticide matrix-spike recoveries for samples collected 

for the Northern San Joaquin Basin Ground-Water Ambient Monitoring and 

Assessment (GAMA) study, California, December 2004 to February 2005........................74

11C. Quality-control summary of wastewater-indicator constituent matrix-spike recoveries 

for samples collected for the Northern San Joaquin Basin Ground-Water Ambient 

Monitoring and Assessment (GAMA) study, California, December 2004 to February 

2005 ...............................................................................................................................................77

12. General water-quality indicators determined in the field and at the U.S. Geological 

Survey’s (USGS) National Water Quality Laboratory for the Northern San Joaquin 

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

Dece..............................................................................................................................................79

13A. Summary of volatile organic compounds and gasoline oxygenates in ground-water 

samples collected for the Northern San Joaquin Basin Ground-Water Ambient 

Monitoring and Assessment (GAMA) study, California, December 2004 to 

February 2005 ..............................................................................................................................83

13B. Summary of tentatively identified compounds (TICs) detected in ground-water 

samples collected for the Northern San Joaquin Basin Ground-Water Ambient 

Monitoring and Assessment (GAMA) study, California, December 2004 to 

February 2005 ..............................................................................................................................92

14. Summary of pesticides and pesticide degradates in ground-water samples collected 

for the Northern San Joaquin Basin Ground-Water Ambient Monitoring and 

Assessment (GAMA) study, California, December 2004 to February 2005........................94

15. Summary of wastewater-indicator constituents in ground-water samples collected 

for the Northern San Joaquin Basin Ground-Water Ambient Monitoring and 

Assessment (GAMA) study unit, California, December 2004 to February 2005. ..............98
viii

16. Summary of constituents of special interest for the ground-water samples 

collected in the Northern San Joaquin Basin Ground-Water Ambient Monitoring 

and Assessment (GAMA) study, California, December 2004 to February 2005................99

17. Summary of nutrient and dissolved organic carbon data collected from groundwater samples in the Northern San Joaquin Basin Ground-Water Ambient 

Monitoring and Assessment (GAMA) study, California, December 2004 to 

February 2005 ............................................................................................................................100

18. Summary of major and minor ions and total dissolved solids in ground-water 

samples collected for the Northern San Joaquin Basin Ground-Water Ambient 

Monitoring and Assessment (GAMA) study, California, December 2004 to 

February 2005 ............................................................................................................................101

19. Summary of trace elements detected in ground-water samples collected for the 

Northern San Joaquin Basin Ground-Water Ambient Monitoring and Assessment 

(GAMA) study, California, December 2004 to February 2005.............................................104

20. Summary of chromium, arsenic, and iron speciation data from the U.S. Geological 

Survey’s (USGS) Trace Metal Laboratory, Boulder, Colorado, for ground-water 

samples collected in the Northern San Joaquin Basin Ground-Water Ambient 

Monitoring and Assessment (GAMA) study, California, December 2004 to 

February 2005..............................................................................................................................113

21. Summary of stable isotopes and radioactive constituents in ground-water samples collected for the Northern San Joaquin Basin Ground-Water Ambient Monitoring 

and Assessment (GAMA) study, California, December 2004 to February 2005..............115

22. Summary of tritium and noble gas analysis performed at Lawrence Livermore 

National Laboratory for ground-water samples collected for the Northern San 

Joaquin Basin Ground-Water Ambient Monitoring and Assessment (GAMA) 

study, California, December 2004 to February 2005 ..............................................................120

23. Summary of microbial indicators detected in ground-water samples collected for 

the Northern San Joaquin Basin Ground-Water Ambient Monitoring and 

Assessment (GAMA) study, California, December 2004 to February 2005......................122
i

Abbreviations, Acronyms, and Initialisms

(Clarification or additional information given in parentheses)

Abbreviation: A shortened form of a word, such as “m” for meter, “L” for liter, “St.” for street, 

and “Calif.” or “CA” for California.

Acronym: A shortened form of a group of words, usually taking the first letters of each word. An 

acronym can be pronounced, such as NASA, NAWQA, and FEMA.

Initialism: A shortened form of a group of words, usually taking the first letters of each word. An 

initialism is pronounced by each letter in the initialism, such as AMCL, CWSC, and GIS.

AMCL Alternate Maximum Contaminant Level (USEPA)

CAS Chemical Abstracts Service (American Chemical Society)

COS Cosumnes Basin

CFC-12 dichlorodifluoromethane

CSU combined standard uncertainty

CWSC California Water Science Center (USGS)

DBCP 1,2-dibromo-3-chloropropane

DLR detection level for the purpose of reporting

DO dissolved oxygen

DOC dissolved organic carbon

EDB 1,2-dibromoethane

ESJ Eastern San Joaquin Basin

ESJDD Eastern San Joaquin Basin depth dependent

ESJFP Eastern San Joaquin Basin flowpath

ESJMW Eastern San Joaquin Basin monitoring well

Freon21 dichlorofluoromethane

GAMA Ground-Water Ambient Monitoring and Assessment (State Water Board)

GC/MS gas chromatography/mass spectrometry

HA-L lifetime health advisory (USEPA)

HCFC-22 chlorodifluromethane

IRL interim reporting level

LRL laboratory reporting level

LSD land-surface datum

LT-MDL long-term method detection level

MCL Maximum Contaminant Level (CADHS and USEPA)

MDL method detection limit

MRL Minimum Reporting Level

NAWQA National Water Quality Assessment (USGS)

NDMA N-Nitrosodimethylamine

NIST National Institute for Standards and Technology

NL notification level (CADHS)
x

NRP National Research Program (USGS)

NWIS National Water Information System (USGS)

PCE tetrachloroethylene

QC quality control

QPC Uplands Basin (Quaternary Pleistocene semiconsolidated deposits)

RSD relative standard deviation

RSD5 risk-specific dose at a cancer risk level of 1 in 100,000 or 10E–5 (USEPA)

SC specific conductance

SMCL Secondary Maximum Contaminant Level (CADHS and USEPA)

SSMDC sample-specific minimum detectable concentration

TCE trichloroethylene

1,2,3-TCP 1,2,3-trichloropropane

TDS total dissolved solids

THM trihalomethane

TIC tentatively identified compound

TRCY Tracy Basin

TRCYFP Tracy Basin flowpath

UV-VIS ultraviolet-visible

VOC volatile organic compound

Organizations

CADHS California Department of Health Services

CADWR California Department of Water Resources

CWSC California Water Science Center (USGS)

LLNL Lawrence Livermore National Laboratory

MWH Montgomery Watson Harza Laboratory

NWQL National Water Quality Laboratory (USGS)

RSIL Reston Stable Isotope Laboratory (USGS)

USEPA U.S. Environmental Protection Agency

USGS U.S. Geological Survey

Note: In this report, the California State Water Resources Control Board is referred to in its 

abbreviated form as the “State Water Board.” The initialism “SWB” is not used in the text.
xi

Units of measurement

ft foot (feet)

in inch

kg kilogram (103 grams)

km2 square kilometer

L liter

mg milligram (10–3 gram)

mg/L milligram per liter (10–3 gram per liter)

mi2 square mile

mL milliliter (10–3 liter)

μg/L microgram per liter (10–6 gram per liter)

μL microliter (10–6 liter)

μm micrometer (10–6 meter)

pCi/L picocurie per liter

pCi/μg picocurie per microgram

Notes

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

 °F = (1.8 × °C) + 32

Vertical coordinate information is referenced to the North American Vertical Datum of 1988 

(NAVD 88).

Horizontal coordinate information is referenced to the North American Datum of 1983 (NAD 83).

Altitude, as used in this report, refers to distance above the vertical datum.

Specific conductance is given in microsiemens per centimeter at 25 degrees Celsius

(μS/cm at 25 °C).

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

or micrograms per liter (μg/L). One thousand micrograms per liter is equivalent to 1 milligram 

per liter. Milligrams per liter is equivalent to parts per million (ppm) and micrograms per liter is 

equivalent to parts per billion (ppb).

In this report, the USEPA designation for “lifetime health advisory” is “HA-L,” to avoid possible 

confusion with USEPA’s Health Advisory Level (HAL), which is a nonregulatory health-based 

reference level of chemical traces (usually in ppm) in drinking water at which there are no 

adverse health risks when ingested over various periods of time. It is an estimate of acceptable 

drinking-water concentrations and provides guidance to water-supply managers. HA-L 

represents the concentration of a chemical in drinking water that is not expected to cause any 

adverse noncarcinogenic effects for a lifetime of exposure. The HA-L assumes consumption of 

2 liters of water per day over a 70-year lifetime by a 70-kilogram (154 pound) adult and that

20 percent of exposure comes from drinking water. Only the HA-L is used in this report.

California GAMA Program: Ground-Water Quality Data 

in the Northern San Joaquin Basin Study Unit, 2005

By George L. Bennett V, Kenneth Belitz, and Barbara J. Milby Dawson

Abstract

Growing concern over the closure of public-supply wells 

because of ground-water contamination has led the State 

Water Board to establish the Ground-Water Ambient Monitoring and Assessment (GAMA) Program. With the aid of the 

U.S. Geological Survey (USGS) and Lawrence Livermore 

National Laboratory, the program goals are to enhance understanding and provide a current assessment of ground-water 

quality in areas where ground water is an important source of 

drinking water. The Northern San Joaquin Basin GAMA study 

unit covers an area of approximately 2,079 square miles (mi2) 

across four hydrologic study areas in the San Joaquin Valley. 

The four study areas are the California Department of Water 

Resources (CADWR) defined Tracy subbasin, the CADWRdefined Eastern San Joaquin subbasin, the CADWR-defined 

Cosumnes subbasin, and the sedimentologically distinct 

USGS-defined Uplands study area, which includes portions of 

both the Cosumnes and Eastern San Joaquin subbasins.

Seventy ground-water samples were collected from 64 

public-supply, irrigation, domestic, and monitoring wells 

within the Northern San Joaquin Basin GAMA study unit. 

Thirty-two of these samples were collected in the Eastern San 

Joaquin Basin study area, 17 in the Tracy Basin study area, 

10 in the Cosumnes Basin study area, and 11 in the Uplands 

Basin study area. Of the 32 samples collected in the Eastern 

San Joaquin Basin, 6 were collected using a depth-dependent 

sampling pump. This pump allows for the collection of samples from discrete depths within the pumping well. Two wells 

were chosen for depth-dependent sampling and three samples 

were collected at varying depths within each well. Over 350 

water-quality field parameters, chemical constituents, and 

microbial constituents were analyzed and are reported as 

concentrations and as detection frequencies, by compound 

classification as well as for individual constituents, for the 

Northern San Joaquin Basin study unit as a whole and for each 

individual study area. Results are presented in a descending 

order based on detection frequencies (most frequently detected 

compound listed first), or alphabetically when a detection 

frequency could not be calculated. Only certain wells were 

measured for all constituents and water-quality parameters. 

The results of all of the analyses were compared with 

U.S. Environmental Protection Agency (USEPA) and California Department of Health Services (CADHS) Maximum 

Contaminant Levels (MCLs), Secondary Maximum Contaminant Levels (SMCLs), USEPA lifetime health advisories 

(HA-Ls), the risk-specific dose at a cancer risk level equal to 1 

in 100,000 or 10E-5 (RSD5), and CADHS notification levels 

(NLs). When USEPA and CADHS MCLs are the same, detection levels were compared with the USEPA standard; however, 

in some cases, the CADHS MCL may be lower. In those cases, 

the data were compared with the CADHS MCL. 

Constituents listed by CADHS as “unregulated chemicals 

for which monitoring is required” were compared with the 

CADHS “detection level for the purposes of reporting” (DLR). 

DLRs unlike MCLs are not health based standards. Instead, 

they are levels at which current laboratory detection capabilities allow eighty percent of qualified laboratories to achieve 

measurements within thirty percent of the true concentration.

Twenty-three volatile organic compounds (VOCs) and 

seven gasoline oxygenates were detected in ground-water 

samples collected in the Northern San Joaquin Basin GAMA 

study unit. Additionally, 13 tentatively identified compounds 

were detected. VOCs were most frequently detected in the 

Eastern San Joaquin Basin study area and least frequently 

detected in samples collected in the Cosumnes Basin study 

area. Dichlorodifluoromethane (CFC-12), a CADHS “unregulated chemical for which monitoring is required,” was detected 

in two wells at concentrations greater than the DLR. Trihalomethanes were the most frequently detected class of VOC 

constituents. Chloroform (trichloromethane) was the most 

frequently detected VOC. None of the 88 VOCs analyzed were 

detected at concentrations above an MCL, SMCL, NL, HA-L, 

or RSD5. 
Fifteen pesticides and pesticide degradates were detected 

in ground-water samples within the Northern San Joaquin 

Basin GAMA study unit. Pesticide and pesticide degradates 

were detected in 27 of the 70 samples collected for pesticide 

analysis. Pesticides were most frequently detected in groundwater samples from the Eastern San Joaquin Basin study area 

and least frequently detected in the Cosumnes Basin study 

area. Herbicides were the most frequently detected class of 

pesticide; simazine, a herbicide, was the most frequently 

detected pesticide. Two herbicides, 1,2-dibromo-3-chloropropane and 1,2-dibromoethane, were detected at concentrations 

above their USEPA MCLs. None of the other 120 pesticide or 

pesticide degradates analyzed were detected at concentrations 

above an MCL, SMCL, NL, HA-L, or RSD5.

Five wastewater-indicator constituents were identified in ground-water samples collected in the Northern San 

Joaquin Basin GAMA study unit. Thirteen of the 16 samples 

analyzed for wastewater-indicator constituents had at least a 

single detection. Isophorone was the most frequently detected 

wastewater-indicator constituent. None of the 63 wastewaterindicator constituents analyzed were detected at concentrations 

above an MCL, SMCL, NL, HA-L, or RSD5.

Twenty-four pharmaceutical constituents were analyzed 

for in ground-water samples collected at all wells in the Northern San Joaquin Basin GAMA study unit. However, as of the 

writing of this report, the analytical methods employed in the 

detection and quantification of the selected pharmaceutical 

constituents were still in development, and additional qualitycontrol data were needed to verify the results. The results of 

the pharmaceutical analysis within the Northern San Joaquin 

Basin GAMA study unit are planned for publication in a future 

report.

Thirty-four ground-water samples were analyzed for 

the following constituents of special interest: perchlorate, 

N-nitrosodimethylamine (NDMA), and 1,2,3-trichloropropane (1,2,3-TCP). Perchlorate, an “unregulated chemical for 

which monitoring is required,” was detected in two groundwater samples in the Eastern San Joaquin Basin study area at 

concentrations below the CADHS DLR and NL. NDMA and 

1,2,3-TCP were not detected in any ground-water samples.

Eighteen ground-water samples were collected for nutrient analysis, and 10 samples were collected for dissolved 

organic carbon analysis. Nitrite plus nitrate was detected in 

11 of 13 samples (excluding the depth-dependent analyses), 

whereas nitrite was detected in only two samples; concentrations of nitrite were not above the USEPA MCL of 1 milligram per liter (mg/L) (as nitrogen). Concentrations of nitrite 

plus nitrate were not above the USEPA MCL of 10 mg/L (as 

nitrogen). Dissolved organic carbon was detected in 5 of the 

10 samples in which it was analyzed.

Thirty-nine ground-water samples were analyzed for 10 

major and minor ions, as well as total dissolved solids (TDS). 

Eight samples had TDS concentrations above the USEPA 

recommended SMCL of 500 mg/L. All eight samples with 

TDS concentrations above the USEPA SMCL were from wells 

located within the Tracy Basin study area. Three ground-water 

samples had detections of sulfate above the USEPA SMCL of 

250 mg/L, which like TDS, were all located in the Tracy Basin 

study area.

Thirty-nine ground-water samples were collected and 

analyzed for 25 different trace elements. Arsenic was detected 

in all 39 samples; however, it was detected in only three 

samples above the USEPA MCL of 10 μg/L. Hexavalent chromium, a CADHS “unregulated chemical for which monitoring 

is required,” was detected in 16 of 39 ground-water samples 

in which it was analyzed, all of which were at concentrations 

above the CADHS DLR of 1 μg/L. Iron, detected in 26 of 

39 samples, was detected in three samples at concentrations 

above the USEPA SMCL of 300 μg/L. Manganese, detected 

in 36 of 39 samples, was detected in eight samples at concentrations above the USEPA SMCL of 50 μg/L. In addition, 

three samples contained manganese at concentrations above 

the CADHS NL of 500 μg/L. Boron, a CADHS “unregulated 

chemical for which monitoring is required,” was detected in all 

39 ground-water samples in which it was analyzed. Of those 

39 detections, 11 were at concentrations above the CADHS 

DLR of 100 μg/L, and 5 were at concentrations above the 

CADHS NL of 1,000 μg/L. Concentrations of boron above the 

CADHS NL were found only in the Tracy Basin study area. 

Boron concentrations above the DLR were most frequently 

found in ground-water samples in the Tracy Basin study area, 

followed by the Eastern San Joaquin Basin study area, and 

lastly in the Uplands Basin study area. Vanadium, a CADHS 

“unregulated chemical for which monitoring is required,” was 

detected in 38 of 39 ground-water samples, and of those, 33 

were above the CADHS DLR of 3 μg/L. However, none of the 

vanadium detections in ground water were at concentrations 

above the CADHS NL of 50 μg/L.

2 California GAMA Program: Ground-Water Quality Data in the Northern San Joaquin Basin Study Unit, 2005
USGS laboratories analyzed 70 ground-water samples 

for stable isotopes of water and tritium. Stable isotopes of 

water (deuterium and oxygen-18) are used in the assessment 

of ground-water recharge sources, whereas tritium is often 

used as an environmental tracer. In addition to the analyses 

performed by the USGS laboratories, 27 samples were also 

analyzed for tritium, and 16 were analyzed for noble gases 

at the Lawrence Livermore National Laboratory. Finally, 13 

wells were sampled for radium-226, radium-228, radon-222, 

gross-alpha radioactivity (72-hour and 30-day count), grossbeta radioactivity (72-hour and 30-day count), and stable 

carbon isotopes. Tritium was detected in 61 of 70 samples of 

which all detections showed activities well below the CADHS 

MCL of 20,000 picocuries per liter (pCi/L). Radium-226 was 

detected in all ground-water samples in which it was analyzed, 

whereas radon-228 was detected in only three samples. None 

of the ground-water samples collected were above the USEPA 

combined radium-226 and radium-228 MCL of 5 pCi/L. 

Gross-alpha and gross-beta radioactivity in ground-water 

samples were in all cases below their USEPA MCLs. Radon222 was detected in all ground-water samples in which it was 

analyzed. The proposed USEPA MCL for radon-222 is 300 

pCi/L, whereas the proposed Alternate Maximum Concentration Level (AMCL) is 4,000 pCi/L (U.S. Environmental Protection Agency, 2006). Of the 13 samples in which radon-222 

was analyzed and detected, only one was below the proposed 

USEPA MCL, whereas all were below the AMCL. Stable 

isotope values, reported as ratios of hydrogen and oxygen 

isotopes, ranged from –81.1 per mill to –43.0 per mill for the 

hydrogen isotopes and from –11.2 per mill to –5.6 per mill for 

the oxygen isotopes.

Microbial constituents, including total coliform and 

Escherichia spp. coliform (E. coli), as well as the viruses 

F-specific coliphage and somatic coliphage, were analyzed 

in eight ground-water samples. F-specific coliphage, somatic 

coliphage, and Escherichia spp. coliform were not detected in 

any ground-water samples, whereas an estimated three total 

coliform colonies per 100 milliliters of water were detected in 

a sample collected in the Uplands Basin study area.

Introduction

The U.S. Geological Survey (USGS) is collaborating 

with the State Water Board, the California Department of 

Health Services (CADHS), and Lawrence Livermore National 

Laboratory (LLNL) on implementing the Ground-Water 

Ambient Monitoring and Assessment (GAMA) Program. The 

GAMA Program was developed in response to the California Ground-Water Quality Monitoring Act of 2001 (Sections 10780–10782.3 of the California Water Code) and is 

designed to address a growing concern about ground-water 

quality throughout the State of California. The program has 

three main objectives (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 

(Belitz and others, 2003; Kulongoski and Belitz, 2004).

To achieve the program goals, the USGS developed a 

systematic approach to sampling (Belitz and others, 2003) 

that will provide a comprehensive and statistically unbiased 

assessment of statewide ground-water quality. This approach 

was achieved through the design of a randomized well-selection routine within a grid cell framework designed within 

distinct study areas. Samples collected by the GAMA Program are intended to represent the wide range of geologic, 

hydrologic, and climatic conditions found within the State 

of California (Belitz and others, 2003). Therefore, the state 

has been separated into 10 hydrogeologic provinces (fig. 1), 

each with its own unique physical, geologic, hydrologic, and 

geographic characteristics. Each province contains groundwater basins composed of primarily unconsolidated deposits 

of alluvial or volcanic origin (California Department of Water 

Resources, 2003). Eighty percent of public supply wells in 

California are located within ground-water basins, whereas the 

other twenty percent are located in relatively low-permeability 

hard rock areas. By targeting both areas, the GAMA Program 

will provide a full assessment of the quality of ground water 

used for drinking-water supply within the state. Analysis of 

a broad suite of chemical constituents, analyzed at detection 

levels lower than those currently required by the CADHS, 

will provide a database of information that may aid in the 

early identification and understanding of contamination issues 

throughout the state.

Introduction 3
Figure 1. Hydrogeologic provinces of California and the location of the Northern San Joaquin Basin study unit (black 

area).

 California GAMA Program: Ground-Water Quality Data in the Northern San Joaquin Basin Study Unit, 2005

Basin and Range

Klamath

Mountains

Desert

Cascades and

Modoc Plateau

Transverse

Ranges and

Selected Peninsular

Ranges

Southern

Coast

Ranges

Central

Valley

Sierra

Nevada

Northern

San Joaquin

Basin Study Unit

Northern

Coast

Ranges

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 Conic Projection

Provinces from Belitz and others, 2004
Purpose and Scope

The purpose of this report is to present the analytical results for general water-quality parameters, inorganic 

constituents, organic constituents, and microbial constituents 

obtained for ground-water samples collected for the Northern 

San Joaquin Basin GAMA study unit. Constituent detections 

are presented within classes (for example, “organic solvents”) 

in a descending order that is based on the constituent’s frequency of detection. Seventy samples were collected from 

a variety of well types, including public supply, domestic, 

irrigation, and monitoring wells. Wells located in Amador, 

Calaveras, Contra Costa, Sacramento, San Joaquin, and 

Stanislaus counties were randomly selected for sampling, and 

ground-water samples were collected between December 2004 

and February 2005. The constituents that were targeted for 

analysis included 88 volatile organic compounds (VOCs), 122 

pesticides and pesticide degradates, 63 wastewater-indicator 

constituents, 24 pharmaceutical constituents, 3 constituents

of special interest (perchlorate, N-nitrosodimethylamine 

[NDMA], and 1,2,3-trichloropropane [1,2,3-TCP]), 5 nutrients, dissolved organic carbon (DOC), 10 major and minor 

ions, total dissolved solids (TDS), 25 trace elements, eight 

isotopic constituents, five noble gases, and the microbial constituents coliform and coliphage. General water-quality indicators were measured and included dissolved oxygen (DO), pH, 

specific conductance (SC), alkalinity, and water temperature.

Detected concentrations in ground-water samples of 

constituents that are regularly monitored by the CADHS were 

compared with CADHS and U.S. Environmental Protection 

Agency (USEPA) drinking-water regulations (California 

Department of Health Services, 2005a, 2005b, and 2005c; 

U.S. Environmental Protection Agency, 2005). Concentrations 

above USEPA or CADHS primary Maximum Contaminant 

Levels (MCLs), whichever is lower, and Secondary Maximum 

Contaminant Levels (SMCLs) will be highlighted. Constituents detected in ground-water samples that lack MCLs were 

compared with CADHS notification levels (NLs). For those 

constituents that lack an MCL or NL, concentrations are 

compared with the USEPA lifetime health advisory (HA-L). 

Lastly, for those constituents that lack an MCL, NL, or HA-L, 

concentrations were compared with the risk-specific dose at 

a cancer risk level equal of 1 in 100,000 or 10E-5 (RSD5). 

Comparisons of raw ground water to MCLs, SMCLs, NLs, 

HA-Ls, and RSD5s are for illustrative purposes only and do 

not indicate a drinking-water violation or noncompliance with 

drinking-water regulations. Explanations of the levels used in 

this report are provided as follows:

MCLs—Legally enforceable standards that apply to 

public-water systems and are designed to protect public health 

by limiting the levels of contaminants in drinking water (U.S. 

Environmental Protection Agency, 1974).

SMCLs—Nonenforceable contaminant concentration 

levels that affect the aesthetic qualities of drinking water, such 

as the taste, odor, and color (U.S. Environmental Protection 

Agency, 1974).

NLs—Health-based advisory levels established by the 

CADHS for chemicals in drinking water that lack MCLs. If a 

chemical is detected above its NL, State law requires timely 

notification of the local governing bodies and recommends 

consumer notification (California Department of Health Services, 2005d).

HA-Ls—The concentration of a chemical in drinking 

water that is not expected to cause any adverse noncarcinogenic effects for a lifetime of exposure. The USEPA lifetime 

health advisory, assumes consumption of 2 liters (L) of water 

per day over a 70-year lifetime by a 70-kilogram (70-kg or 

154-pound) adult, and that 20 percent of exposure comes 

from drinking water (U.S. Environmental Protection Agency, 

2004b).

RSD5—The concentration of a chemical in drinking 

water corresponding to an excess estimated lifetime cancer 

risk of 1 in 100,000, hereinafter referred to as the risk specific 

dose at 10–5 (U.S. Environmental Protection Agency, 2004b).

In addition to the above listed comparison thresholds, 

constituents classified by CADHS as “unregulated chemicals 

for which monitoring is required” will be compared with the 

“detection level for the purpose of reporting” (DLR) set by 

CADHS (California Department of Health Services, 2005b). 

DLRs are the minimum concentration at or above which any 

analytical finding of a contaminant in drinking water as a 

result of monitoring required by Title 22 of the California 

Code of Regulations must be reported to the CADHS. DLRs 

are analytical detection limits that are based on the level of 

confidence in the quantification of a contaminant’s presence in 

drinking water and are set on the basis of interlaboratory measurement precision of 20 percent or better, where at least 80 

percent of qualified laboratories could achieve results within 

±30 percent of the true concentration (California Department 

of Health Services, 2005e).

Detection frequencies will be reported for each anthropogenic (man-made) compound that is detected in at least one 

ground-water sample. Anthropogenic constituents include 

VOCs, pesticides, pesticide degradates, wastewater-indicator constituents, and contaminants of special interest. Any 

regulated anthropogenic or CADHS “unregulated chemical 

for which monitoring is required” classified compound that 

is detected at a frequency greater than, or equal to, 10 percent 

will be highlighted. Constituents with a detection frequency 

of 10 percent or greater may be indicative of degradation of 

ground-water quality.

Also presented in this report are the results and interpretation of the quality-control (QC) samples collected during the 

Northern San Joaquin GAMA study unit. Results for pharmaceutical analyses of ground-water and QC samples will not 

be presented here, but are planned for publication in a future 

report. As of the writing of this report, the pharmaceutical 

analytical method was still in development, and additional QC 

data were needed to verify results. Discussion of factors that 

may influence the occurrence and distribution of chemical and 

microbial constituents detected in ground-water samples is 

beyond the scope of this report.

Introduction 5
Acknowledgments

This study was funded and supported by the State Water 

Board. The authors also thank the following agencies for their 

support: 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. 

Hydrogeologic Setting of the Northern San 

Joaquin Basin Study Unit

The Northern San Joaquin Basin GAMA study unit lies 

within the Central Valley Hydrogeologic Province described 

by Belitz and others (2003) and includes three California 

Department of Water Resources (CADWR) San Joaquin 

Valley ground-water subbasins: Tracy subbasin, Eastern San 

Joaquin subbasin, and Cosumnes subbasin. Combined, they 

define the outline of the Northern San Joaquin Basin GAMA 

study unit. The three subbasins together cover an area of 

approximately 2,079 square miles (mi2) that includes most 

of San Joaquin County and portions of Alameda, Amador, 

Calaveras, Contra Costa, and Stanislaus Counties. The study 

unit is bounded by the Southern Coast Ranges to the west, the 

Sierra Nevada to the east, the San Joaquin Delta and Sacramento Valley to the north, and the central San Joaquin Valley 

to the south.

The Northern San Joaquin Basin GAMA study unit has a 

Mediterranean climate, with hot and dry summers, and winters 

that are cool and moist. Average rainfall across the study unit 

ranges from 11 inches (in.) in the southern to southwesterly 

portions of the study unit to upwards of 25 in. in the eastern 

to northeastern portions study unit (California Department of 

Water Resources, 2005a, 2005b, 2005c). Several creeks and 

rivers drain the Northern San Joaquin Basin GAMA study 

unit. The Calaveras, Cosumnes, Mokelumne, and Stanislaus 

Rivers, as well as their tributaries, drain the eastern portions of the study unit. Each of these rivers ultimately drains 

directly into either the San Joaquin River, which flows north 

and empties into the Sacramento and San Joaquin Delta, or 

directly into the Delta, which discharges its waters into the 

San Francisco Bay. The west side of the study unit is drained 

by Middle and Old Rivers as well as other smaller tributaries, 

which also drain into the San Joaquin River or the Sacramento 

and San Joaquin Delta. For the purposes of this report, the 

Northern San Joaquin Basin GAMA study unit is divided into 

four separate study areas: the Eastern San Joaquin Basin study 

area, the Tracy Basin study area, the Cosumnes Basin study 

area, and the Uplands Basin study area (fig. 2).

Eastern San Joaquin Basin Study Area

The GAMA-defined boundaries of the Eastern San Joaquin Basin study area (fig. 2) closely match those defined by 

the CADWR for the “eastern San Joaquin subbasin,” which are 

described as the aerial extent of unconsolidated to semiconsolidated sedimentary deposits south of the Mokelumne River, 

east of the San Joaquin River, north of the Stanislaus River, 

and west of the consolidated bedrock of the Sierra Nevada 

(California Department of Water Resources, 2005a). For the 

purposes of this report, the Eastern San Joaquin Basin GAMA 

study area is defined as the aerial extent of the unconsolidated 

Quaternary age deposits west of the older exposed Pliocene 

and Pleistocene age semiconsolidated deposits that border the 

consolidated bedrock of the Sierra Nevada. The study area 

covers approximately 757 mi2 and is located in San Joaquin 

County with small portions in Stanislaus and Calaveras counties. Average annual precipitation within the Eastern San 

Joaquin Basin study area ranges from 11 in. in the southwest 

to upwards of 20 in. in the northeast (California Department 

of Water Resources, 2005a). The study area is drained by the 

San Joaquin River and its major tributaries, which include 

the Stanislaus, Calaveras, and Mokelumne Rivers. The main 

aquifers within the Eastern San Joaquin Basin study area 

include the older alluvial deposits of the Modesto and Riverbank Formations, flood basin deposits, and the deeper Laguna, 

Mehrten, and Valley Springs Formations (California Department of Water Resources, 2005a). The Mehrten Formation 

is a Miocene−Pliocene age volcanic deposit considered to be 

the oldest fresh water-bearing deposit on the east side of the 

basin because the older underlying Valley Springs Formation 

produces only minor amounts of water (California Department 

of Water Resources, 1967).

6 California GAMA Program: Ground-Water Quality Data in the Northern San Joaquin Basin Study Unit, 2005
Figure 2. Northern San Joaquin Basin Ground-Water Ambient Monitoring and Assessment (GAMA) study 

unit and locations of the four study areas.

Introduction 7

12130 121

37

40

0 5 10 20 MILES

0 5 10 20 KILOMETERS

LODI

TRACY

STOCKTON

Study areas

Cosumnes Basin (COS)

Eastern San Joaquin Basin (ESJ)

Tracy Basin (TRCY)

Uplands Basin (QPC)

EXPLANATION

Base from U.S. Geological Survey digital elevation data,

1999, Albers Equal Area Conic Projection

Cosumnes River

Dry Creek

Middle River

Mokelumne River

Stanislaus River

JOAQUIN

RIVER

Calaveras River

Dry Creek

Camanche

Reservoir

Woodward

Reservoir

Farmington

Flood Control

Basin

Old

River

SAN SIERRA

NEVADA

ALAMEDA COUNTY

CALAVERAS COUNTY

CALAVERAS COUNTY

AMADOR COUNTY

SOLANO COUNTY

SACRAMENTO COUNTY

YOLO COUNTY

AMADOR COUNTY

STANISLAUS COUNTY

SAN JOAQUIN COUNTY

STANISLAUS COUNTY

SAN JOAQUINCOUNTY

CONTRA COSTA COUNTY

Los Angeles

San Diego

San

Francisco

California

38

20

38
Tracy Basin Study Area

The boundaries of the GAMA-defined Tracy Basin 

study area (fig. 2) match those defined by the CADWR for 

the “Tracy subbasin” and are described as the aerial extent of 

unconsolidated to semiconsolidated sedimentary deposits that 

are bounded by the Diablo Mountain range to the west, the 

Mokelumne and San Joaquin Rivers to the north, the Eastern 

San Joaquin subbasin to the east, and the Delta–Mendota subbasin to the south (California Department of Water Resources, 

2005b). The study area covers approximately 539 mi2 and lies 

within portions of San Joaquin, Contra Costa, and Alameda 

counties. Annual precipitation within the Tracy Basin study 

area is reported to range from 11 in. in the south to 16 in. in 

the north, (California Department of Water Resources, 2005b). 

Precipitation is drained from the study area by the San Joaquin, Middle, and Old Rivers, in addition to smaller creeks and 

sloughs that all eventually flow into and become part of the 

Sacramento and San Joaquin Delta (California Department of 

Water Resources, 2005b). The main aquifers within the Tracy 

Basin study area are the Late Tertiary to Quaternary Tulare 

Formation, Older Alluvium, flood basin deposits, and Younger 

Alluvium, which when combined, range from a few hundred 

feet thick near the Coast Ranges to more than 3,000-feet (ft) 

thick near the eastern edge of the Tracy Basin study area 

(Davis and others, 1964; Hotchkiss and Balding, 1971; and 

Bertoldi and others, 1991).

Cosumnes Basin Study Area

The boundaries of the GAMA-defined Cosumnes Basin 

study area (fig. 2) closely match those defined by the CADWR 

for the “Cosumnes subbasin,” which is described as the aerial 

extent of the unconsolidated and semiconsolidated deposits that are bounded to the north and west by the Cosumnes 

River, to the south by the Mokelumne River, and to the east 

by the consolidated bedrock of the Sierra Nevada (California 

Department of Water Resources, 2005c). For this report, the 

Cosumnes Basin study area has been limited to the exposed 

unconsolidated Quaternary age deposits west of the older 

exposed Pliocene and Pleistocene age semiconsolidated deposits that border the consolidated bedrock of the Sierra Nevada. 

The Cosumnes Basin study area covers approximately 194 

mi2. Annual precipitation within the Cosumnes Basin study 

area ranges from 15 in. in the west to 22 in. in the east (California Department of Water Resources, 2005c). The Cosumnes 

Basin study area is drained by three main rivers, namely the 

Cosumnes, Dry Creek, and the Mokelumne, which all flow 

westward towards the Sacramento and San Joaquin Delta. The 

main aquifers within the Cosumnes Basin study area are the 

Younger Alluvium, the Older Alluvium, and the Mehrten Formation. The Younger Alluvium consists of recent stream channel deposits and dredge tailings (Olmstead and Davis, 1961). 

The Older Alluvium consists of Quaternary, Pliocene, and 

Pleistocene age alluvial deposits that have been assigned many 

different formation names including the Modesto, Riverbank, 

Victor, and Laguna (Olmstead and Davis, 1961; California 

Department of Water Resources, 1974; and Helley and Harwood, 1985). The Mehrten Formation is a Miocene−Pliocene 

age volcanic deposit, which is composed of “black sands,” 

gravels, silts, and clay interbedded with layers of dense tuff 

breccia (Olmstead and Davis, 1961; California Department of 

Water Resources, 2005c).

Uplands Basin Study Area

The Uplands study area (fig. 2) is defined as those portions of the CADWR defined as the eastern San Joaquin and 

Cosumnes subbasins that represent the exposed aerial extent 

of the Pliocene and Pleistocene age semiconsolidated deposits west of the consolidated bedrock of the Sierra Nevada, 

also referred to in this report as the “Quaternary Pleistocene 

age semiconsolidated deposits,” or “QPC” (Jennings, 1977). 

Annual precipitation within the Uplands study area averages 

about 22 in. in the northern area (California Department of 

Water Resources, 2005c) and upwards of 20 in. in the central 

to southern area (California Department of Water Resources, 

2005a). Precipitation in the Uplands Basin study area is 

drained by several rivers including the Calaveras, Cosumnes, 

Dry Creek, Mokelumne, and Stanislaus Rivers. Within the 

Uplands Basin study area the Mokelumne River is constrained 

by the Camanche Dam, creating the Camanche Reservoir. 

Two other reservoirs are located in the Uplands Basin study 

area: the Farmington Flood Control Basin and the Woodward 

Reservoir, both of which are located at the southern end of the 

study area and are fed by several small creeks and canals. The 

geologic formations identified within this study area include 

the Modesto, Riverbank, Victor, Laguna, Mehrten, and Valley 

Springs (Piper and others 1939; Olmstead and Davis, 1961; 

California Department of Water Resources, 1974; and Helley and Harwood, 1985). The Arroyo Seco and South Fork 

Gravels have also been identified in the Cosumnes portion 

of the Uplands study area (Piper and others 1939; Shlemon, 

1972; California Department of Water Resources, 1974). The 

Uplands study area covers approximately 588 mi2.

Methods of Study

The following sections introduce study and sampling 

design, field methods, laboratory methods, data-reporting 

conventions, and QC procedures and results.

8 California GAMA Program: Ground-Water Quality Data in the Northern San Joaquin Basin Study Unit, 2005
Study and Sampling Design

The primary objectives in the selection of wells for 

study-area assessments within the Central Valley hydrogeologic province are (1) to attain a sampling density of at least 

one well per 100 square kilometers (km2), (2) randomly select 

at least 10 wells per study area wherever possible, and (3) 

minimize variability in well type (Gilliom and others, 1995). 

These objectives assure an adequate and statistically unbiased 

assessment of the quality of ground-water resources used for 

public supply. In the Northern San Joaquin Basin GAMA 

study unit, public-supply wells were the preferred choice, but 

in cases where public-supply wells were not available because 

of sparse population density or inadequate well characteristics, 

domestic or irrigation wells were substituted in the selection 

process. Wells that had available construction information 

(well depth, depth of perforations, date constructed) were 

selected when possible for sampling; however, construction 

information was not available for some of the sampled wells.

Well selection within each study area was developed 

using a grid-based program that produces random, equal-area 

cells within each study area (fig. 3; Scott, 1990). The program 

was used to generate 20 cells in the Eastern San Joaquin Basin 

study area and 15 cells each in the Tracy, Cosumnes, and 

Upland Basin study areas. For grid cells with multiple wells, 

each well was randomly assigned a rank. The lowest randomly 

ranked well that met as many sampling criteria as possible (for 

example, sampling point prior to treatment, capability to pump 

over extended periods of time, and available well construction 

information) were chosen for sampling. Using this method, 

one randomly ranked well was selected for each grid cell 

throughout the entire study unit; the selected wells are subsequently referred to as “grid wells” (fig. 3). Analytical results 

from an individual study area’s set of grid wells are presumed 

to be representative of ground-water quality in that study 

area. To enhance the understanding of ground-water quality 

throughout the study area, additional wells were selected for 

sampling within the study unit; specifically, additional wells 

were sampled along two flowpaths, whereas others were 

aerially distributed to provide a better sampling coverage in 

specific areas (fig. 4). These additional wells are referred to as 

“nongrid cell wells.”

Wells were sampled for a “slow,” “intermediate,” “fast,” 

and (or) “depth-dependent” list of analytes (table 1), depending on the well type. The fast analyte list was collected at all 

wells sampled in this study and provides an initial assessment of ground-water quality in the area. Slow-list wells were 

selected along ground-water flowpaths and were sampled 

for all analytes, including those on the fast list. Grid wells 

that were near or along the selected ground-water flowpaths 

or in areas of interest had additional analytes added to their 

fast list (becoming intermediate-list wells). Depth-dependent 

samples were collected in two public supply-wells along the 

flowpaths (fig. 4: ESJFP-19 and ESJFP-10) and were sampled 

for a subset of the slow list of analytes. Monitoring wells 

along the flowpaths were sampled for the slow list analytes, 

with the exception of the microbial constituents. Wells that 

were sampled off the randomized grid (nongrid wells) were 

located along flowpaths or in select locations within the basin 

off of the flowpaths to enhance study-unit coverage and were 

sampled for slow, intermediate, and depth-dependent lists of 

analytes.

Samples collected in the four study areas of the Northern 

San Joaquin Basin GAMA study unit were assigned a GAMA 

identification number based on study area designation and 

sequence number in the order of sample collection (figs. 3

and 4). Study areas were designated as follows: TRCY (Tracy 

Basin), COS (Cosumnes Basin), ESJ (Eastern San Joaquin 

Basin) and QPC (Uplands Basin), which includes portions of 

both the Eastern San Joaquin and Cosumnes Basins. QPC is an 

initialism for “Quaternary Pleistocene age semiconsolidated 

deposits.” Additional samples were collected in the Tracy 

Basin and Eastern San Joaquin Basin study areas to ascertain 

how ground-water-quality changes as it moves along two flowpaths; these samples were given the designations TRCYFP or 

ESJFP. Depth-dependent samples collected at two wells in the 

Eastern San Joaquin Basin study area are identified as ESJDD. 

Samples collected at a multilevel monitoring well located 

close to a public-supply well chosen for depth-dependent 

sample collection were identified as ESJMW.

Field Methods

Tables 2A–M list the names of all the chemical and 

microbial constituents analyzed for in ground-water samples 

collected as part of the Northern San Joaquin Basin GAMA 

study unit. In addition, the tables provide regulatory information, including MCLs, SMCLs, and NLs for those constituents 

being monitored, as well as laboratory reporting levels. 

Table 3 provides the GAMA identification number, the date 

and time each sample in the Northern San Joaquin Basin 

GAMA study unit was collected, the constituent list that 

was sampled at each site, and well-construction information, 

including date of construction and opening information when 

available. A total of 70 ground-water samples were collected 

from a combination of 46 public supply, 10 domestic, five 

irrigation, and three monitoring wells between mid-December 

2004 and mid-February 2005, with six additional depth-dependent samples collected from two of the 46 public-supply wells 

sampled. Of the 64 wells sampled, 26 are in the Eastern San 

Joaquin Basin study area, 17 are in the Tracy Basin study area, 

10 are in the Cosumnes Basin study area, and 11 are in the 

Uplands Basin study area.

Methods of Study 9
Figure 3. Northern San Joaquin Basin Ground-Water Ambient Monitoring and Assessment (GAMA) 

study unit showing study areas, distribution of study area grid cells, and location of sampled grid cell 

wells.

10 California GAMA Program: Ground-Water Quality Data in the Northern San Joaquin Basin Study Unit, 2005

37

40

38

20

38

121 30 121

0 5 10 20 MILES

0 5 10 20 KILOMETERS

Study areas and well number

Cosumnes Basin (COS)

Eastern San Joaquin Basin (ESJ)

Tracy Basin (TRCY)

Uplands Basin (QPC)

EXPLANATION

03

01

01

04

07

08

10 02

02

03

09

17

18

01

11

16

19

15

06

04

04

06

05

05

07

07

01

01

11

06

08

08

03 03

02

10

10

14

11

12 13

07

09

09

09

10 06

05

05

04

02

08

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!

!

Base from U.S. Geological Survey digital elevation data,

1999, Albers Equal Area Conic Projection
Figure 4. Northern San Joaquin Basin Ground-Water Ambient Monitoring and Assessment 

(GAMA) study unit showing study areas and distribution of additional wells sampled.

Methods of Study 11

38

20

38

37

40

! ! !

!

!

!

!

!

!

! !

!

!

!!

!

! !

!

!

!

!

Study areas

Cosumnes Basin (COS)

Eastern San Joaquin Basin (ESJ)

Tracy Basin (TRCY)

Uplands Basin (QPC)

Additional wells

Flowpath lines (FP)

Depth dependent (DD)

Monitoring well (MW)

Nonflowpath nongrid cell well

Flowpath nongrid cell well

Flowpath grid cell well

EXPLANATION

01 !

01 !

01 !

19

DD-04

DD-05

DD-06

!!

Base from U.S. Geological Survey digital elevation data,

1999, Albers Equal Area Conic Projection

0 5 10 20 MILES

0 5 10 20 KILOMETERS

FP-04 03

FP-05

FP-06

FP-03

FP-01

FP-07

12

07

FP-02

FP-09

FP-08

16

15

01

07

13

12130 121

FP-10: !

DD-01

DD-02

DD-03

MW-01

MW-02 

! MW-03 

! !
Ground-water samples were collected from the selected 

wells using standard and modified USGS protocols (U.S. 

Geological Survey, 1999; Koterba and others, 1995) and 

protocols described by Weiss, 1968; Shelton and others, 2001; 

Ball and McClesky, 2003a,b; and Wright and others, 2005, 

which helps ensure that a representative sample was collected 

from the aquifer. Public-supply, domestic, and irrigation wells 

were sampled using Teflon tubing with brass and stainlesssteel fittings attached to a sampling point on the well discharge 

pipe as close to the well as possible. If a site was sampled 

using the fast or intermediate analyte list, a modified USGS 

protocol was used and samples were collected at the sampling 

point using a foot-long section of Teflon tubing after a total 

of three casing volumes were extracted from the well. If a site 

was sampled using the slow analyte list, including monitoring 

wells, USGS ground-water sampling protocols were followed and samples were collected inside an enclosed chamber 

located in a mobile water-quality laboratory once field parameters (pH, DO, and SC) measured in a flow-thru chamber 

fitted with a multiprobe meter became stable. Field parameters 

were considered stable once their measurements, taken every 

five minutes, were consistent for at least 20 minutes. Monitoring wells were sampled using a portable, stainless-steel 

submersible pump attached to Teflon tubing with stainlesssteel fittings.

For depth-dependent samples, ground water was pumped 

to the surface using a gas-displacement small-diameter pump 

to collect samples at discrete depths within the well bore 

(Izbicki, 2004). The sampling equipment consisted of two 1/8-

in.-diameter Teflon tubes bundled together to form a single 

strand mounted on a motorized reel. Once lowered to the 

desired depth, compressed ultra-high purity (grade 5) nitrogen 

gas was used to displace water from one line into the other 

while one-way flow valves prevented the displaced water from 

flowing back toward the pump at the lower end of the hose 

(Izbicki, 2004). Repeated pressurization and depressurization 

of the lines was used to slowly bring the water at depth to the 

surface where it could be collected following the protocols 

described for the fast and intermediate analyte lists.

When possible, samples were collected before any type 

of filtration or chemical treatment, such as chlorination. 

Chlorination of the water, however, could not be avoided at 

one public-supply well (ESJ-19). At this well, 25 milligrams 

(mg) of powdered ascorbic acid was added to all of the organic 

samples as a preservative to prevent organic compound degradation as a result of exposure chlorine. At the site where 

chlorination took place in the well bore, the chlorinator was 

shut off at least 24 hours prior to sampling to minimize the 

degree of chlorination of the sample water.

Laboratory Methods

Ten laboratories performed chemical and microbial 

analyses for the Northern San Joaquin Basin GAMA study 

unit ground-water samples. Table 4 lists the analyte, analytical 

method, laboratory at which each analysis was conducted, and 

method citation.

Data Reporting and Constituents on Multiple 

Analytical Schedules

As summarized in the San Diego GAMA study unit data 

report by Wright and others, (2005) the USGS’s National 

Water Quality Laboratory (NWQL) uses laboratory reporting 

levels (LRLs), long-term method detection limits (LT-MDLs), 

interim reporting levels (IRLs), method detection limits 

(MDLs), and Minimum Reporting Levels (MRLs) to communicate the level at which method performance is sufficient 

to allow for quantitative measurement of an analyte. These 

reporting levels each serve to minimize the reporting of falsenegative and false-positive readings. Some concentrations in 

the Northern San Joaquin Basin unit study are reported using 

method uncertainties. The method uncertainty generally indicates the precision of a particular analytical measurement, and 

therefore, indicates the range of values wherein the true value 

will be found.

MDLs—“Minimum concentration of a substance that 

can be measured and reported with 99-percent confidence that 

the analyte concentration is greater than zero. It is determined 

from the analysis of a sample in a given matrix containing the 

analyte (U.S. Environmental Protection Agency, 2002a). At 

the MDL concentration, the risk of a false positive is predicted 

to be less than or equal to 1 percent” (Childress and others, 

1999).

LT-MDLs—“A detection level derived by determining 

the standard deviation of a minimum of 24 MDL spike sample 

measurements over an extended period of time. LT-MDL data 

are collected continually to assess year-to-year variations in 

the LT-MDL. The LT-MDL controls false-positive error. The 

chance of falsely reporting a concentration at or greater than 

the LT–MDL for a sample that did not contain the analyte is 

predicted to be less than or equal to 1 percent” (Childress and 

others, 1999).

LRLs—“Generally equal to twice the yearly determined 

LT-MDL. The LRL controls false-negative error. The probability of falsely reporting a nondetection for a sample that 

contained an analyte at a concentration equal to or greater 

than the LRL is predicted to be less than or equal to 1 percent. 

These values are re-evaluated annually using the most current 

QC data and may, therefore, change” (Childress and others, 

1999).

12 California GAMA Program: Ground-Water Quality Data in the Northern San Joaquin Basin Study Unit, 2005
IRLs—“A temporary reporting level used for new or custom schedules when LT-MDL data are unavailable and a LRL 

has not been established” (U.S. Geological Survey, 2005).

MRLs—“Smallest measured concentration of a constituent that may be reliably reported by using a given analytical 

method” (Timme, 1995).

The reporting levels for selected radioactive constituents 

(gross-alpha­ radioactivity, gross-beta radioactivity, radium226, and radium-228) are based on a sample-specific minimum detectable concentration (SSMDC), a critical value 

(also sample specific), and the combined standard uncertainty 

(CSU) (U.S. Environmental Protection Agency and others, 

2004). In this report, a result above the critical value represents 

a greater-than-95-percent certainty that the result is greater 

than zero (significantly different from the instruments background response to a blank sample), whereas a result above 

the SSMDC represents a greater-than-95-percent certainty 

that the result is greater than the critical value (U.S. Environmental Protection Agency and others, 2004). Using these 

reporting level elements, three unique cases were possible 

when screening the raw analytical data. First, if the analytical result is less than the critical value (case 1), the analyte is 

considered not detected, and a value is presented in the table 

as less than the SSMDC. If the analytical result is greater than 

the critical value, the ratio of the CSU to the analytical result 

(relative CSU) was calculated as a percent. For those samples 

with results that have a relative CSU less than 20 percent, the 

analytical result is reported unqualified (case 2). For those 

samples with results that have a relative CSU greater than 

20 percent, the analytical results were qualified as estimated 

values and are preceded in the table with an “E” (case 3). For 

table clarity, only the screened results are reported here. The 

unnamed table provided below gives an example of the screening process for each of the three cases described above.

Twenty-four constituents targeted in the Northern San 

Joaquin Basin GAMA study unit are analyzed on more than 

one analytical schedule (table 5). Some analytical schedules 

are preferred over others because the methodology is more 

accurate and precise, and generally yields a greater sensitivity for a specific constituent. When a constituent appears on 

multiple analytical schedules, only the detections determined 

by the preferred analytical schedule are reported.

Quality-Control Procedures and Results

QC samples were collected concurrently with approximately 10 percent of the samples in Northern San Joaquin 

Basin GAMA study unit. QC samples are collected to assess 

the bias and variability of ground-water data potentially introduced during sample collection, processing, storage, transportation, and laboratory analysis, as well as intrinsic variability 

within the ground water itself. Four types of QC samples were 

analyzed: blanks, sequential field replicates, laboratory surrogate compounds, and laboratory matrix spikes.

Blanks

Three types of blanks were collected for the Northern San 

Joaquin Basin GAMA study unit: source-solution, equipment, 

and field. All blanks were collected using nitrogen-purged 

blank water that was certified to be free of VOCs, pesticides, 

wastewater-indicator constituents, low-level nutrients, dissolved organic carbon, major ions, and trace elements above 

their reporting levels. Associated blanks and ground-water 

samples in this study are defined as samples that were collected at the same site.

Scenario

Critical 

value 

(pCi/L)

SSMDC 

(pCi/L)

Combined 

standard 

uncertainty 

(pCi/L)

Relative 

CSU 

(percent)

Raw 

result 

(pCi/L)

Reported 

result

 (pCi/L)

Case 1—Result less than critical value 1.4 3.2 ±1.2 133 0.9 <3.2

Case 2—Relative combined standard uncertainty less than 20 percent 0.4 1.1 ±0.5 14 3.2 3.2

Case 3—Relative combined standard uncertainty greater than 20 percent 0.5 1.4 ±0.6 32 2.0 1

E2.0

1

Estimated.

Methods of Study 13
Source-solution blanks—Source-solution blanks were 

collected to verify that the blank water (source solution) used 

for the associated equipment and field blanks had no detectable concentrations of VOCs, pesticides, pesticide degradates, 

or wastewater-indicator constituents. Source-solution blanks 

were analyzed for VOCs, pesticides, and wastewater-indicator constituents because some of these chemicals are volatile 

and ubiquitous, and could contaminate the blank water used 

for QC purposes. Source-solution blanks were collected at 

the sampling site by pouring blank water directly into sample 

containers that were then stored, shipped, and analyzed in the 

same manner as the other blanks and ground-water samples.

Equipment blanks—Equipment blanks were analyzed to 

evaluate the sampling pumps used to collect depth-dependent 

and monitoring-well samples to determine if the equipment 

could introduce contaminants to the samples. The equipment blank for the depth-dependent sampler was collected at 

the USGS’s California Water Science Center (CWSC) San 

Diego Projects Office. The equipment blank for the portable 

submersible pump used to sample the monitoring wells was 

collected at the USGS’s CWSC Sacramento Field Office.

Field blanks—Field blanks were collected at selected 

sampling sites and were used to evaluate potential bias 

introduced by sampling equipment, processing, shipping, and 

analysis. Depending on the list of analytes (depth dependent, 

slow, intermediate, or fast) collected at a particular sampling 

site, blank water was either pumped or poured through the 

same sampling equipment (fittings and tubing) used to collect 

the ground-water samples, then processed and transported 

using the same protocols that were used for the ground-water 

samples.

A constituent was of potential QC concern if the following criteria were met: (1) a constituent was detected in one or 

more equipment or field blanks and in ground-water samples, 

(2) the concentration detected in the equipment or field blank 

was greater than the concentration in the associated sourcesolution blank, and (3) the minimum concentration detected in 

ground-water samples was less than the maximum concentration detected in field blanks plus one half of that constituent’s 

reporting level. If the results for a constituent met the above 

criteria, the pattern of detections in blanks and ground-water 

samples was evaluated. If a constituent was detected in the 

field blanks, but not in the associated ground-water sample, 

then the ground-water data were not censored. If a constituent 

was detected in at least one associated blank and ground-water 

sample at similar concentrations, then all detections in groundwater samples were censored.

Detections in ground-water samples that were determined 

to be of QC concern were censored and counted as nondetections; however, the measured values are reported here and 

flagged within the appropriate tables with a “V” remark code. 

The threshold for censoring data was determined by summing 

the highest blank concentration with the LT-MDL or MDL 

for the constituent in question. For example, if the highest 

concentration of toluene in a field blank was 0.02 micrograms 

per liter (μg/L), and the LT-MDL for toluene is 0.02 μg/L, then 

the concentration of toluene in the associated ground-water 

sample would have to be greater than, or equal to, 0.04 μg/L to 

be considered a numerical value. This method of censoring is 

based on the assumption that the amount of contamination in 

the field blank and the associated ground-water sample(s) are 

comparable. Therefore, detections in ground-water samples 

that are not censored will have at least a concentration equal 

to, or greater than the LT-MDL or MDL.

Source-Solution Results

Detections of constituents within the source-solution 

water may help explain detection within the equipment and 

field blanks conducted as part of this study. If any such detection within the blank water aids in the explanation of a blank 

detection, it will be evaluated in the equipment and field blank 

results sections.

Depth-Dependent Equipment Blank Results

Table 6 summarizes the depth-dependent equipment 

blanks collected on January 4, 2005, by the CWSC San Diego 

Projects Office using the depth-dependent sampling pump. 

Wastewater-indicator constituents, constituents of special 

interest, and pesticide and pesticide degradate constituents 

were not detected in the depth-dependent equipment blank. 

Constituents detected in the depth-dependent equipment blank, 

but interpreted to be of no concern, included the major ions 

calcium, magnesium, and silica as well as the trace elements 

barium, strontium, and zinc. These analytes were detected in 

the blank samples; however, their concentrations were all well 

below the concentrations observed in ground-water samples 

collected using the depth-dependent equipment.

Toluene was detected in the depth-dependent equipment 

blank as well as the associated source-solution blank. The 

depth-dependent equipment was used to collect six groundwater samples in the Northern San Joaquin Basin GAMA 

study unit, and toluene was detected in all of those samples 

within the range of concentrations observed in the equipment 

blank. Given the numerous occurrences of toluene in ground 

water and blank samples collected throughout the Northern 

San Joaquin GAMA study unit, regardless of equipment type, 

all occurrences of toluene in ground water at or below the censor limit (0.31 μg/L) were censored.

14 California GAMA Program: Ground-Water Quality Data in the Northern San Joaquin Basin Study Unit, 2005
Tentatively identified compounds (TICs), detected in the 

depth-dependent equipment blank included hexofluoropropene (Chemical Abstracts Service [CAS] number 116-15-4), 

pentafluoropropene (CAS number 690-27-7), and an unknown 

compound. These constituents were not identified in the associated source-solution blank. TICs are identified by comparison with the National Institute for Standards and Technology 

library spectra and examination by a gas chromatography/mass 

spectrometry (GC/MS) analyst. Reported concentrations of 

TICs are approximate (Connor and others, 1998). These TICs 

were also identified in ground-water samples collected using 

the depth-dependent equipment. The minimum concentration 

of hexofluoropropene in ground water was below the level 

detected in the equipment blank, suggesting contamination. 

Pentafluoropropene and the unknown constituent were each 

detected in two ground-water samples. In all three cases, the 

concentrations in ground-water samples were at the same level 

or below the equipment-blank concentrations, suggesting the 

detections were the result of equipment contamination; therefore, these constituent concentrations were censored.

Manganese was detected in the depth-dependent equipment blank at a concentration greater than the minimum 

detection in ground water, suggesting contamination. Therefore, values less than 0.7 μg/L (maximum concentration in the 

equipment blank plus the LT-MDL) were censored.

The concentration of total nitrogen (nitrate, nitrite, 

ammonia, and organic nitrogen) in the depth-dependent equipment blank was 0.2 milligrams per liter (mg/L), whereas the 

minimum concentration in ground-water samples collected 

using the same equipment was 0.04 mg/L. Because the equipment blank concentration was greater than the minimum concentration in ground water, values of total nitrogen less than or 

equal to 0.23 mg/L were censored.

Portable Pump Equipment Blank Results

Table 7 summarizes the results from the portable pump 

equipment blank collected on January 27, 2005, at the CWSC 

Sacramento Field Office. TICs, constituents of special interest, pesticide and pesticide degradate constituents, as well as 

nutrients and dissolved organic carbon were not detected in the 

portable pump equipment blank used to sample three monitoring wells in the Northern San Joaquin Basin GAMA study 

unit. Detections in the portable pump equipment blank of the 

major ion silica and the trace element vanadium had concentrations well below those observed in ground water and are, 

therefore, interpreted to have a minimal effect on the measured 

concentrations of these constituents in ground water. The VOC 

benzene was also detected in the portable equipment blank; 

however, it was not detected in any ground-water samples 

collected using this equipment; therefore potential contamination can be ruled out. It should be noted that samples collected 

using this equipment also pass through sample lines used in 

the GAMA mobile laboratory camper vehicle. Therefore, 

constituent detections may not be directly attributed to the 

portable pump.

In addition to benzene, five VOCs—1,2,4-trichlorobenzene, ethylbenzene, m-and p-xylene, o-xylene, and toluene—were detected in the portable pump equipment blank. 

Three ground-water samples were collected using this equipment. Within the second of those three ground-water samples, 

ethylbenzene, m-and p-xylene, o-xylene, and 1,2,4-trichlorobenzene were detected. The concentrations at which they 

were detected were within the same range of concentrations 

observed in the equipment blank for the same constituents. 

One sample a day for three consecutive days was collected 

using this equipment. The first ground-water sample collected 

(sample 1) using this equipment following the collection of the 

equipment blank yielded no detections of the previously listed 

constituents; however, the sample collected the following day 

(sample 2) did. The last sample (sample 3) collected using 

this equipment contained none of the previously mentioned 

constituents. Although these constituents were not detected in 

the sample immediately following the equipment blank, the 

similarity in the detection concentrations suggests a relation 

between the blank and the ground-water detections. This similarity is demonstrated in figure 5, which graphically compares 

the concentrations of the constituents detected in the equipment blank with those concentrations detected in the second 

ground-water sample. On the basis of this comparison, these 

VOCs are assumed to be the result of sample contamination. 

Potential sources of contamination include the cleaning procedures, vehicle exhaust, and ambient air quality. Detections 

of these constituents within ground-water samples collected 

using this equipment have, therefore, been treated as nondetects. Toluene was detected in the portable pump equipment 

blank and was also detected in the associated source-solution 

blank, but the concentration of toluene in the source-solution 

blank does not explain the equipment blank detection. Toluene 

was also detected in all of the ground-water samples collected 

using this equipment. Given the persistent presence of toluene 

in field blanks, equipment blanks, associated source-solution 

blanks, at concentrations similar to those observed in groundwater samples collected in the Northern San Joaquin Basin 

GAMA study unit, toluene detections have been censored.

Phenol was the only wastewater-indicator constituent 

detected in the portable pump equipment blank. Phenol was 

also detected in the associated source-solution blank at a concentration greater than the equipment blank, therefore providing a source for the detection in the field blank. However, as 

described earlier, phenol has been a persistent contaminant in 

blanks across the nation (Wright and others, 2005). Therefore, 

all phenol detections less than or equal to 0.9 μg/L, which is 

the maximum blank detection (0.4 μg/L) plus the LT-MDL for 

phenol (0.5 μg/L) have been censored.

Methods of Study 15
Zinc was detected in the portable pump equipment blank 

at a concentration equal to the minimum concentration of zinc 

in ground-water samples collected using this equipment. Given 

that zinc contamination was present in field and equipment 

blanks in the Northern San Joaquin Basin GAMA study unit, 

any ground-water detection of zinc, regardless of equipment 

used, at concentrations less than 2.3 μg/L have been censored 

and will not be included in analyses of ground-water-quality 

data.

Field Blank Results

A summary of compound detections in field blanks 

collected for the Northern San Joaquin Basin GAMA study 

unit is provided in table 8. Six VOCs (acetone, ethyl methyl 

ketone, ethylbenzene, m- and p-xylene, o-xylene, and toluene), 

one wastewater-indicator constituent (phenol), three major 

ions (calcium, iodide, and silica), five trace elements (barium, 

copper, manganese, nickel, and zinc), and DOC were detected 

in one or more field blanks. Constituents of special interest, 

TICs, and pesticides were not detected in any of the field 

blanks. Of the six VOCs detected in field blanks, acetone, ethylbenzene, m- and p-xylene, o-xylene, and ethyl methyl ketone 

were interpreted not to be of concern after implementing the 

blank contamination QC criteria outlined above. Additional 

constituents that were detected in field blanks, but were interpreted to be of no concern, included the major ions calcium 

and silica, and the trace elements barium and nickel.

The VOC toluene was detected in three field blanks as 

well as the associated source-solution blanks. Toluene was 

also detected in 16 ground-water samples collected using 

the same equipment tested by the field blanks. Associated 

source-solution blank concentrations only explain one of the 

field-blank detections. Therefore, toluene may be a potential 

laboratory or field contaminant, and ground-water samples 

that have reported detections of toluene may not be representative of actual toluene occurrence in the ground water. To avoid 

misrepresenting the occurrence of toluene in ground-water 

samples collected as part of the Northern San Joaquin Basin 

GAMA study unit, toluene detections have been censored. The 

censor limit is based on the maximum concentration detected 

in the field blanks (0.3 μg/L) plus the LT-MDL (0.01 μg/L). 

Therefore, any detections of toluene below the censor threshold of 0.31 μg/L was reported as not detected.

As initially reported in Wright and others (2005), phenol, a wastewater indicator, has a known history of being a 

persistent contaminant in field blanks collected across the 

nation. QC data presented by the National Water Quality 

Assessment’s (NAWQA) Source Water Quality Assessment 

shows phenol present in 66 percent of field blanks collected 

nationwide (Wright and others, 2005). Phenol was the only 

wastewater-indicator constituent detected in the Northern San 

Joaquin GAMA study unit. Therefore, all phenol detections in 

this study unit were censored. The maximum concentration of 

phenol detected in field blanks was 0.4 μg/L (estimated value), 

whereas the LT-MDL for phenol at the time of reporting was 

0.5 μg/L, thus the censor level was established at 0.9 μg/L. 

No detections of phenol in the Northern San Joaquin GAMA 

study unit were equal to or greater than the censor threshold.

0

0.02

0.04

0.06

0.08

0.1

0.12

0.14

PORTABLE PUMP

EQUIPMENT BLANK

SAMPLE 1 SAMPLE 2 SAMPLE 3

CONCENTRATION, IN MICROGRAMS PER LITER

Ethylbenzene

m-Xylene plus p-xylene

o-Xylene

1,2,4-Trimethylbenzene

No DetectionsNo Detections

Figure 5. Bar graph that compares concentrations of constituents suspected to be the result of 

contamination detected in the portable pump equipment blank and subsequent ground-water samples 

collected using the same equipment.

16 California GAMA Program: Ground-Water Quality Data in the Northern San Joaquin Basin Study Unit, 2005
Iodide was detected at a concentration of 0.001 mg/L 

(estimated value) in two field blanks collected in the Northern San Joaquin Basin GAMA study unit. Concentrations of 

iodide in ground-water samples ranged from 0.001 mg/L (estimated value) to 1.8 mg/L. Iodide was not detected in the associated source-solution blanks. The maximum iodide concentration in any field blank was 0.001 mg/L (estimated value), 

whereas the LT-MDL for iodide was 0.001 mg/L. Therefore, 

detections in ground water that were less than or equal to the 

maximum field blank concentration plus the LT-MDL (0.002 

mg/L) will be censored.

The minimum concentration of copper observed in 

ground water was less than the maximum field-blank detection; therefore, copper detections in ground-water samples 

were censored using the sum of the maximum concentration 

observed in the field blanks (0.5 μg/L) and the LT-MDL (0.2 

μg/L), which establishes a censor level of 0.7 μg/L. Manganese was detected in one field blank within the range of 

manganese detections in ground water. Therefore, manganese 

concentrations in ground water below 0.2 μg/L have been censored. Zinc was detected in all four trace element field blanks, 

yet it was not detected in any of the associated source-solution 

blanks. The minimum concentration of zinc detected in ground 

water was less than the maximum field-blank concentration. 

Therefore, zinc detections in ground-water samples that were 

below 2.3 μg/L have been censored.

Thirty-nine ground-water samples collected in the 

Northern San Joaquin Basin GAMA study unit were analyzed 

for the oxidation species of arsenic, chromium, and iron at 

the USGS’s Trace Metal Laboratory in Boulder, Colorado. In 

addition to the 39 environmental samples, four field blanks 

were also analyzed. Total arsenic, which is the sum of all dissolved arsenic species in a sample, and arsenic(V), which is 

measured independently, were not detected in any of the four 

field blanks analyzed by the Trace Metal Laboratory.

Total chromium, which is the sum of all dissolved chromium species in a sample, was detected in two field blanks 

analyzed at the Trace Metal Laboratory. The concentration of 

total chromium in those field blanks was 1 μg/L and 6 μg/L. 

The minimum concentration in ground-water samples of total 

chromium was 1 μg/L. Because the maximum field blank 

concentration was greater then the minimum ground-water 

concentration, ground-water samples with concentrations less 

than the sum of the maximum field blank concentration (6 

μg/L) and the MDL (1 μg/L) were censored. This procedure 

established a censor threshold of 7 μg/L for total chromium 

samples analyzed at the Trace Metal Laboratory and resulted 

in the censoring of 21 detections of total chromium (table 8).

Hexavalent chromium (chromium(VI)), which is measured independently of total chromium, was detected in three 

field blanks analyzed at the Trace Metal Laboratory. Within 

the three field blank samples, hexavalent chromium was 

detected at concentrations of 1 μg/L, 1 μg/L, and 5 μg/L. The 

minimum concentration of hexavalent chromium in groundwater samples was 1 μg/L. Because the maximum field blank 

concentration is greater then the minimum ground-water 

concentration, ground-water samples less than the sum of the 

maximum field blank concentration (5 μg/L) and the MDL 

(1 μg/L) were censored. This procedure established a censor 

threshold of 6 μg/L for hexavalent chromium samples analyzed at the Trace Metal Laboratory and resulted in the censoring of 16 detections of hexavalent chromium (chromium(VI); 

table 8).

Total iron, which is the sum of all dissolved iron species in a sample, was detected in one of the four field blanks 

analyzed at the Trace Metal Laboratory, whereas iron(II), 

measured independently of total iron, was not detected in any. 

Within the field blank sample, total iron was detected at a 

concentration of 3 μg/L. The minimum concentration of total 

iron as measured by the Trace Metal Laboratory in groundwater samples was 2 μg/L. Because the maximum field blank 

concentration was greater then the minimum ground-water 

concentration, ground-water samples less than the sum of the 

maximum field blank concentration (3 μg/L) and the MDL 

(2 μg/L) were censored. This procedure established a censor threshold of 5 μg/L for total iron samples analyzed at the 

Trace Metal Laboratory and resulted in the censoring of 20 of 

39 ground-water samples (table 8).

DOC was detected in two field blanks at concentrations 

of 0.2 mg/L (estimated value), which is below the LRL of 

0.3 mg/L, yet DOC was not detected in the associated sourcesolution blanks. The minimum concentration detected in 

ground water was 0.2 mg/L (estimated value). Because the 

concentrations observed in the field blanks were within the 

range detected in ground-water samples, values of DOC below 

0.3 mg/L were censored.

Replicates and Results

Sequential replicate samples were collected to assess 

the variability in concentrations of inorganic and organic 

constituents. Because ground water moves relatively slowly, 

there should be little intrinsic variability between sequential 

replicates. Sample handling and laboratory processing can be 

additional sources of variability. Variability between replicates was expressed as the relative standard deviation (RSD), 

which is defined as the standard deviation divided by the mean 

concentration for each replicate pair sample, multiplied by 

100 percent. If one value in a sample pair was reported as not 

detected, and the other value was reported as below the reporting level, the RSD was set to zero because the values are analytically identical. If one value in a sample pair was reported 

as not detected, and the other value was greater than the LRL 

or MRL, then the nondetection value was set equal to onequarter of the LRL, which is also one half of the LT-MDL, and 

the RSD was calculated (Childress and others, 1999). Values 

of RSD less than 20 percent are considered acceptable in this 

study (Hamlin and others, 2002). RSD values above 

20 percent for a compound may be due to analytical uncertainty at low concentrations, particularly for concentrations 

below the reporting level.

Methods of Study 17
Tables 9A–E summarize replicate sample pairs with 

RSD greater than zero for samples collected in the Northern 

San Joaquin Basin GAMA study unit. For those RSD values 

greater than zero, the maximum RSD value and the median of 

all RSDs greater than zero are given. Median RSD values for 

replicate analyses that were greater than 20 percent include 

hexavalent chromium, radium-228, and gross-alpha radioactivity (both 72-hour and 30-day counts). All other median RSD 

values were below the acceptable threshold of 20 percent.

Of the nearly 1,500 replicate analyses, 23 were above 

the acceptable RSD set for this study of 20 percent, whereas 

most replicate analyses (1,345) had RSDs less than 10 percent. 

Replicate analyses with RSDs above 20 percent represent one 

VOC compound, one measure of DOC, six trace element constituents, and five isotope or radioactive constituents. RSDs for 

pesticides and pesticide degradates, nutrients, and major ions 

were all less than 7 percent. Nine trace elements had replicate 

pairs with RSDs above 10 percent (table 9D).

Two measures of gross alpha and beta radioactivity in 

water and three radioisotopes had replicate analyses RSDs that 

were higher than the acceptable level of 20 percent (table 9E). 

Two replicate pairs for 72-hour count gross-alpha radioactivity 

had high RSDs, whereas one replicate analysis of the 30-day 

count gross-alpha radioactivity had a high RSD. The radioisotope radium-226 had one replicate analysis slightly higher 

than the acceptable limit at 29 percent, whereas radium-228 

had a replicate analysis with an RSD of 44 percent. Two of 

six replicate pairs of tritium measured by the USGS’s Stable 

Isotope and Tritium Laboratory in Menlo Park, California, had 

RSDs above the acceptable limit, with one slightly higher at 

22 percent and the other much higher at 141 percent.

Laboratory Surrogates and Results

Surrogates are compounds that are not normally found 

in the environment, but are similar in physical and chemical 

properties to the target analytes. Prior to analysis at a lab, each 

sample analyzed for VOCs, gasoline oxygenates, NDMA, 

1,2,3-TCP, pesticides, and wastewater-indicator constituents 

was spiked with one or more surrogate compounds. Surrogate 

recovery data are used to evaluate the capability of the analysis 

methods to detect the target analytes in each sample and to 

assess bias and variability attributed to matrix effects and gross 

sample-processing errors. Surrogate data in blank samples are 

used to identify general problems that may arise during sample 

analysis: surrogate data in ground-water, replicate, and spike 

samples are used to evaluate matrix interferences. For most of 

the analytical schedules, a 70- to 130-percent recovery of surrogates is generally considered acceptable (Hamlin and others, 

2002). However, the NWQL analytical schedule for wastewater-indicator constituents (1433) has higher control limits; 

therefore, recoveries of 100 percent may not be expected under 

ideal conditions. In the case of the Schedule 1433 analytes, a 

70- to 130-percent recovery may be inappropriate. In samples 

with low surrogate recoveries (less than 70 percent), target 

analytes may not have been detected when they were present 

at low concentrations. Samples with high surrogate recoveries 

(greater than 130 percent) indicate that the target analytes will 

be detected if present; however, the concentrations measured 

in these samples may be greater than the actual concentration. 

When all surrogates for a sample are outside of the acceptable 

range, there could have been an issue with the analytical methods. When one or more surrogates for a sample are outside of 

the acceptable range, then the sample chemistry may be interfering with the capability of the analytical methods to detect 

and quantify the target analytes (matrix interference).

Table 10 summarizes the surrogate recoveries for groundwater and QC samples. Median surrogate recoveries for 

nonblank samples were acceptable, except for the wastewaterindicator surrogates decafluorobiphenyl and bisphenol A-d3, 

which had low median surrogate recoveries. Median surrogate 

recoveries for the blank samples were acceptable, with the 

exception of caffeine-13C, which was above the 130-percent 

threshold, and bisphenol A-d3, which was below the 70-percent threshold.

Surrogate compounds added to samples analyzed for 

VOCs and gasoline oxygenates include isobutyl alcohol-d6, 

1,2-dichloroethane-d4, 1-bromo-4-fluorobenzene, and toluened8. Recoveries for the surrogate compound isobutyl alcohol-d6 

were below the acceptable limit of 70 percent in two groundwater samples and one replicate sample. The recovery for the 

surrogate compound 1,2-dichloroethane-d4 was above the 

acceptable limit of 130 percent in one ground-water sample. 

Recoveries for the surrogates 1-bromo-4-fluorobenzene and 

toluene-d8 were all within the acceptable range of 70 to 130 

percent.

Surrogate compounds added to samples for pesticide 

analysis included a-HCH-d6, barban, caffeine-13c, diazinond10, and 2,4,5-T. Recoveries for the surrogate compound 

diazinon-d10 were below the 70-percent threshold in 26 

samples (20 ground-water samples, four blank samples, and 

two replicate pairs). Recoveries for the surrogate compound 

a-HCH-d6 were above the 130-percent threshold in two 

ground-water samples. Seven of the 20 ground-water samples 

with diazinon-d10 surrogate recoveries below 70 percent had 

pesticide detections, whereas the two ground-water samples 

with recoveries of a-HCH-d6 above 130 percent had no 

detections of pesticides. Sixteen ground-water samples, three 

blanks, two spiked samples, and two replicate pairs were 

analyzed for recoveries of 2,4,5-T, barban, and caffeine-13C. 

The surrogate compound 2,4,5-T was recovered below the 

70-percent threshold in four ground-water samples, two spiked 

samples, and two replicate pairs. Caffeine-13C was detected 

above the 130-percent threshold in six ground-water samples, 

two blank samples, and one replicate pair.

18 California GAMA Program: Ground-Water Quality Data in the Northern San Joaquin Basin Study Unit, 2005
Surrogate compounds added to samples for wastewater-indicator analysis include bisphenol A-d3, caffeine-13C, 

decafluorobiphenyl, and floranthene-d10. Of those four 

compounds, only fluoranthene-d10 was recovered within the 

acceptable range (between 70 and 130 percent) of recoveries 

in all analyses. Conversely, 25 analyses of the surrogate compound bisphenol A-d3 were below the 70-percent threshold, 

11 of 26 analyses of caffeine-13C were below the 70-percent 

threshold, and the surrogate compound decafluorobiphenyl 

was detected below the 70-percent threshold in 18 of 26 analyses. On the basis of the high number of surrogate recoveries 

within the wastewater-indicator samples below the 70-percent 

threshold analyses of constituents within this schedule, the 

results may be biased, which may be the result of sample processing or analytical method problems, or both.

For the constituents of special interest, which were analyzed at the Montgomery Watson Harza Laboratory, the surrogate constituents toluene-d8 and NDMA-d6 were added to 34 

ground-water samples, 12 blanks (NDMA-d6 was only added 

to ten blanks), five spiked samples, and four replicate pairs. 

Toluene-d8 was recovered within the acceptable range of 70 

to 130 percent in all cases, whereas NDMA-d6 was recovered 

below the 70-percent threshold in one of the replicate pairs.

Laboratory Matrix Spikes and Results

Laboratory matrix spikes are QC samples used to evaluate the bias and variability of analytical results attributed to 

potential interferences from the chemistry of the ground water 

sampled (matrix interferences). Laboratory matrix spikes are 

prepared by adding solutions containing known concentrations 

of target analytes to replicate ground-water samples before 

sample preparation and analysis at the lab. The constituents 

added in matrix spikes are the same as those being analyzed. 

Constituents with low recoveries, generally less than 70 percent, are of potential concern because the constituent may not 

have been detected if present in ground water at low concentrations. Low recoveries are also a concern if environmental 

concentrations are close to an MCL, because low spike recoveries indicate that the true concentration of the target analyte 

could be greater than the reported concentration. Conversely, 

constituents with high recoveries, generally greater than 130 

percent, are of potential concern if the environmental concentrations are above MCLs, because a high spike recovery could 

indicate that the true concentration of the target analyte is 

lower than the reported concentration. Recoveries between 70 

to 130 percent for matrix spikes were considered acceptable in 

this study (Hamlin and others, 2002). Matrix-spike recoveries 

were background-corrected by subtracting the concentrations 

of any spike analytes detected in the nonspiked samples.

A summary of matrix-spike recoveries for the Northern 

San Joaquin Basin GAMA study unit is provided in 

tables 11A–C. Four VOCs had matrix-spike recoveries greater 

than the acceptable limit of 130 percent (table 11A). Of 

those four, only two were detected in ground-water samples: 

bromodichloromethane was detected in five ground-water 

samples and bromomethane was detected in one ground-water 

sample. The concentration of the single detection of bromomethane in ground water was too low to be quantified. Neither 

bromomethane nor bromodichloromethane have an MCL. 

Seven VOCs had matrix-spike recoveries below the 70-percent 

threshold. Of those seven, three were detected in ground-water 

samples. The first two, carbon disulfide and dichlorodifluoromethane (CFC-12), are both unregulated constituents; however, two detections of CFC-12 in ground water were above 

the CADHS DLR of 0.5 μg/L. The herbicide 1,2-dibromo3-chloropropane (DBCP) was detected in four ground-water 

samples, twice at levels above the USEPA MCL of 0.2 μg/L.

Twenty-one pesticides had at least one matrix-spike 

recovery greater than 130 percent (table 11B). Of those 21 

pesticides, only imazaquin was detected in ground water; 

however, the concentration could not be quantified by the 

laboratory. No Federal or State MCL has been established for 

imazaquin. Sixty-four pesticides had matrix-spike recoveries below 70 percent (table 11B). Of these 64 pesticides, five 

were detected in ground water: 3,4-dichloroaniline, trifluralin, hexazinone, phorate, and deisopropyl-atrazine. None of 

the pesticides with a low matrix-spike recovery are regulated 

constituents.

Only one wastewater-indicator constituent, 4-Nonylphenoldiethoxylate, had a matrix-spike recovery greater than 

130 percent (table 11C). This compound was not detected in 

any ground-water samples and has no MCL. Nine wastewater-indicator constituents had matrix-spike recoveries below 

70 percent. These nine constituents were not detected in any 

ground-water samples, and only two of the nine constituents 

are regulated: tetrachloroethylene and 1,4-dichlorobenzene.

Ground-Water-Quality Results

The Northern San Joaquin Basin GAMA study unit 

ground-water-quality data presented in this report are archived 

in the USGS’s National Water Information System database (NWIS), except for the following constituents: tritium 

and noble gases analyzed at the LLNL; chromium, arsenic, 

and iron speciation analyzed at the Trace Metal Laboratory; 

stable isotopes analyzed at the USGS’s Reston Stable Isotope 

Laboratory (RSIL); and perchlorate, NDMA, and 1,2,3-TCP 

analyzed at Montgomery Watson Harza Laboratory. Data not 

available from NWIS are maintained by the CWSC in Sacramento, California, and are available upon request.

Ground-Water-Quality Results 19
Table 12 shows the general water-quality indicators determined in the field; tables 13–23 show the results of analysis 

of ground-water samples organized by constituent class and 

are presented as follows: VOCs; gasoline oxygenates; TICs; 

pesticide constituents; wastewater-indicator constituents; 

constituents of special interest; nutrients and DOC; major 

inorganic ions and total dissolved solids; trace elements; 

chromium, arsenic and iron speciation; stable isotopes and 

radioactive constituents; tritium and noble gases; and microbial indicators. These tables are limited in presentation only to 

those constituents that were detected and only to those wells 

with one or more constituent detections. Each table shows the 

number of times a particular constituent was detected, the frequency at which that constituent was detected, and the number 

of constituent detections per well (or sample in the case of 

depth-dependent samples). Additionally, VOCs and gasoline 

oxygenates have been combined into one table. Constituent 

concentrations and radioisotope activities that are above an 

MCL, SMCL, NL, HA-L, RSD5, or DLR in the case of the 

“unregulated chemical for which monitoring is required,” 

are highlighted in the tables in bold font. Additionally, the 

locations of wells with constituent detections above an MCL, 

SMCL, NL, HA-L, RSD5, or DLR (for those constituents 

which CADHS requires monitoring) have also been highlighted in figures 6–10.

Study areas containing nongrid cell wells in addition to 

the randomly selected grid cell wells have had their constituent detections divided into two categories: grid cell wells or 

nongrid cell wells. Nongrid cell wells were excluded from 

comparisons made between the four study areas because they 

could introduce a spatial bias as a result of increased sampling 

density in a particular area within the study unit. Additionally, 

nongrid cell wells were not used in the calculation of detection 

frequencies.

The chemical and microbial data presented in this report 

are meant to characterize the quality of the untreated groundwater resources within the Northern San Joaquin Basin 

GAMA study unit and are in no way intended to represent 

the treated drinking water delivered to consumers by water 

purveyors. The chemical and microbial composition of treated 

drinking water may differ from untreated ground water in that 

treated drinking water may be subjected to disinfection, filtration, mixing with other waters, and exposure to the atmosphere 

prior to its delivery to consumers.

VOCs, Gasoline Oxygenates, and Tentatively 

Identified Compounds

Table 13A provides a summary of VOC and gasoline 

oxygenate constituents detected in ground-water samples 

collected in the Northern San Joaquin Basin GAMA study 

unit, and table 13B provides a summary of the TICs detected 

in ground-water samples. VOCs and gasoline oxygenates 

constituents were collected at all wells (grid cell and nongrid 

cell) sampled with the exception of three gasoline oxygenate 

constituents (methyl acetate, tert-amyl alcohol, and tert-butyl 

alcohol), which were only sampled at thirteen slow analyte list 

wells. Thirty-seven of those 70 samples had at least a single 

detection of a VOC, gasoline oxygenate, or TIC (tables 13A

and 13B).

Thirty of the 88 VOC and gasoline oxygenate constituents analyzed were detected in ground-water samples of 

either the grid cell or nongrid cell wells (table 13A). Solvents 

were the most frequently detected compound class and were 

detected in 11 of 51 samples from the grid cell wells 

(22 percent). Trihalomethanes were detected in 10 of 51 

samples from the grid cell wells (20 percent). Organic synthesis constituents were detected in 6 of 51 samples from 

the grid cell wells (12 percent). Gasoline class constituents 

were detected in 5 of 51 samples from the grid cell wells (10 

percent). Refrigerants, the least frequently detected constituent class, were detected in 4 of 51 samples from the grid cell 

wells (8 percent). Chloroform, a trihalomethane, was the most 

frequently detected VOC and was detected in 18 percent of 

samples collected from the grid cell wells followed by tetrachloroethylene (PCE), which was detected in 14 percent of 

samples from the grid cell wells. No other VOC was detected 

at greater than 10 percent of the samples from the grid cell 

wells. No VOC analyzed was detected in ground-water 

samples at concentrations above an MCL, SMCL, NL, HA-L, 

or RSD5; however, dichlorodifluoromethane (CFC-12) a DHS 

“unregulated chemicals for which monitoring is required” was 

detected in ground-water samples from two wells (ESJ-09 and 

ESJFP-09) at concentrations above the CADHS DLR

(table 13A).

In addition to the 88 VOCs targeted for analysis, 6 TICs 

(cyclopentane, chlorodifluoromethane (HCFC-22), dichlorofluoromethane (Freon 21), 1-pentene (C5-alkene), cyclopropane-C2, and sulfur dioxide) were detected in grid cell wells 

(table 13B). In any of the grid cell wells, only one TIC was 

detected more than once; cyclopentane was detected in five 

samples (table 13B). HCFC-22, Freon 21, C5-alkene, cyclopropane-C2, and sulfur dioxide were each detected in one 

sample.

Pesticides and Pesticide Degradates

Table 14 provides the summary of pesticide and pesticide 

degradate constituents detected in ground-water samples collected in the Northern San Joaquin Basin GAMA study unit. A 

primary list of pesticide and pesticide degradate samples were 

collected at 63 grid and nongrid cell wells sampled 

(table 2C). In addition, a secondary list of pesticide and 

pesticide degradate samples were collected at 16 grid and 

nongrid cell wells sampled within the study unit (table 2D). 

The secondary pesticide constituent list sample was not uniformly sampled throughout the entire Northern San Joaquin 

Basin GAMA study unit; therefore, its constituents were not 

included in the calculation of detection frequencies within the 

individual study areas.

20 California GAMA Program: Ground-Water Quality Data in the Northern San Joaquin Basin Study Unit, 2005
Fifteen of the 122 pesticide and pesticide degradate 

constituents analyzed were detected in ground-water samples. 

Herbicides were the most frequently detected class of pesticide: these were detected in 14 of 51 samples from grid 

cell wells (27 percent). Pesticide degradates, as a class, were 

detected in 11 of 51 samples from grid cell wells (22 percent). 

Simazine, an herbicide that is regulated by the USEPA, and 2-

chloro-4-isopropylamino-6-amino-s-triazine (deethylatrazine), 

a pesticide degradate of atrazine, were the most frequently 

detected pesticide constituents and were each detected in eight 

samples (16 percent) collected from grid cell wells. Atrazine 

and DBCP, both regulated by the USEPA, were the second 

most frequently detected pesticide constituents and were each 

detected in four samples (8 percent) collected from grid cell 

wells. No other pesticide or pesticide degradate was detected 

in greater than 5 percent of ground-water samples from grid 

cell wells. The herbicide DBCP was detected in samples from 

two wells (COS-05 and ESJ-07) at concentrations above the 

USEPA MCL of 0.2 μg/L (table 14, fig. 6). The herbicide 

EDB was detected in a nongrid cell well (ESJFP-09) at a concentration above the USEPA MCL of 0.05 μg/L (table 14, 

fig. 6). No other pesticide or pesticide degradates were 

detected in ground-water samples at concentrations above an 

MCL, SMCL, NL, HA-L, or RSD5.

Wastewater-Indicator Constituents

Table 15 provides a summary of wastewater-indicator 

constituents detected in ground-water samples collected in 

the Northern San Joaquin Basin GAMA study unit. Sixteen 

samples were analyzed for wastewater-indicator constituents 

collected from thirteen wells, and three additional depthdependent samples were collected at ESJ-19. Wastewater-indicator constituents were not uniformly collected throughout the 

study unit; therefore, constituent detections will not be used 

when calculating detection frequencies throughout the entire 

Northern San Joaquin Basin GAMA study unit. Additionally, 

the following summary of wastewater-indicator constituent 

detections is presented without separating grid cell and nongrid cell wells because wastewater-indicator constituents were 

collected exclusively at “slow” analyte list wells, which were 

typically nongrid cell wells.

Six different wastewater-indicator constituents were 

identified in ground water. Thirteen of the 16 samples had at 

least a single detection of a wastewater-indicator constituent. 

The most frequently detected wastewater-indicator constituent was isophorone, which was detected in 7 of 16 groundwater samples in which it was analyzed (44 percent). Two 

compounds, 4-nonylphenol and benzophenone, were detected 

in the same four wells and were the second and third most 

frequently detected wastewater-indicator constituents. Caffeine 

was detected in 3 of 16 samples. The least frequently detected 

wastewater-indicator constituents were bisphenol A and tris 

(dichloroisopropyl) phosphate, each detected in only one of 

the 16 samples collected. None of the wastewater-indicator 

constituents detected in ground-water samples collected for 

this study were detected above an MCL, SMCL, NL, HA-L, or 

RSD5.

Perchlorate, N-Nitrosodimethylamine, and 

1,2,3-Trichloropropane

Table 16 provides a summary of detections of perchlorate, NDMA, and 1,2,3-TCP in ground-water samples that 

were collected at 34 grid and nongrid cell wells throughout 

the Northern San Joaquin Basin GAMA study unit. These 

constituents of special interest were not uniformly collected at 

all wells in the Northern San Joaquin Basin GAMA study unit, 

and therefore, these constituents will not be used for calculating detection frequencies throughout the study unit.

Perchlorate, a CADHS “unregulated chemical for which 

monitoring is required,” was detected at a concentration of 

0.7 μg/L in a depth-dependent sample (ESJDD-03) collected 

at a depth of 500 ft within the ESJFP-10 well (table 16). Concentrations of constituents detected using the depth-dependent 

sampler were not corrected for potential dilution as a result 

of mixing with water from above or below the point at which 

the samples were collected. Perchlorate was also detected 

at a concentration of 1 μg/L in ground-water samples from 

ESJ-16 (table 16). The DLR for perchlorate is 4 μg/L and 

the CADHS NL is 6 μg/L, both of which are greater than the 

detected concentrations observed in the Northern San Joaquin 

Basin GAMA study unit. Drinking-water standards have not 

been established for NDMA or 1,2,3-TCP; however, both 

have CADHS NLs, and 1,2,3-TCP is on the CADHS list of 

“unregulated chemicals for which monitoring is required.” 

NDMA and 1,2,3-TCP were not detected in any ground-water 

samples collected as part of this investigation of the Northern 

San Joaquin Basin GAMA study unit.

Nutrients and Dissolved Organic Carbon

Table 17 provides a summary of nutrient and DOC detections in ground-water samples collected from the Northern 

San Joaquin GAMA study unit. Eighteen ground-water 

samples were collected for nutrients (13 wells and 5 depthdependent samples), whereas only 10 ground-water samples 

were collected for DOC. Nitrite plus nitrate was detected in 

11 ground-water samples (excluding the depth-dependent 

analyses), whereas nitrite was detected in only two groundwater samples. Concentrations of nitrite plus nitrate were not 

above the USEPA MCL of 10 mg/L (as nitrogen). Similarly, 

the concentrations of nitrite in ground-water samples were 

below the USEPA MCL of 1 mg/L (as nitrogen). DOC was 

detected in 5 of the 10 ground-water samples in which it was 

analyzed, with values ranging from 0.3 to 9.6 mg/L.

Ground-Water-Quality Results 21
Figure 6. Northern San Joaquin Basin Ground-Water Ambient Monitoring and Assessment 

(GAMA) study unit showing study areas and locations of wells sampled for DBCP and EDB with 

detections referenced to the Maximum Contaminant Level (MCL).

22 California GAMA Program: Ground-Water Quality Data in the Northern San Joaquin Basin Study Unit, 2005

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Study areas

Cosumnes Basin (COS)

Eastern San Joaquin Basin (ESJ)

Tracy Basin (TRCY)

Uplands Basin (QPC)

Well detections

No DBCP and EDB

DBCP MCL

DBCP MCL

EDB MCL

EXPLANATION

!!

0 5 10 20 MILES

0 5 10 20 KILOMETERS

MW-01

MW-02

MW-03 

04

04

05

06 10

18

17

10

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15

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07

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16 19

DD-04

DD-05

DD-06

FP-04

01

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13 12

11

FP-05

FP-02

10

FP-06

FP-03

FP-08

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09

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FP-07

FP-10:

DD-01

DD-02

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37

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38

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12130 121

Base from U.S. Geological Survey digital elevation data,

1999, Albers Equal Area Conic Projection
Major and Minor Ions and Total Dissolved 

Solids

Table 18 provides a summary of major ions and TDS 

detections and concentrations obtained in the Northern San 

Joaquin GAMA study unit. Thirty-nine ground-water samples 

(33 wells and 6 depth-dependent samples) were analyzed 

for 10 major and minor ions as well as TDS. Ground-water 

samples from TRCYFP-01 and TRCY-07 had chloride concentrations above the CADHS chloride SMCL of 250 mg/L 

(fig. 7A). Ground-water samples from TRCYFP-02, TRCYFP04, and TRCY-07 had sulfate concentrations above the USEPA 

recommended SMCL of 250 mg/L (fig. 7B). Eight groundwater samples had TDS concentrations above the USEPA 

recommended SMCL of 500 mg/L (table 18, fig. 7C). All 

eight ground-water samples with TDS concentrations above 

the USEPA SMCL were from wells located within the Tracy 

Basin study area. Of all the ground-water samples collected 

outside of the Tracy Basin study area at which TDS was measured, the maximum concentration was 355 mg/L.

Trace Elements

Table 19 provides a summary of trace element detections 

in ground water analyzed by the NWQL. Thirty-nine samples 

(33 wells and 6 depth-dependent samples) were analyzed for 

25 trace elements (table 2I). Additionally, table 20 provides a 

summary of arsenic, chromium, and iron speciation analyses 

conducted at the Trace Metal Laboratory. The Trace Metal 

Laboratory is used in this study because this laboratory is able 

to provide analyses of hexavalent chromium (chromium(VI)), 

identified by the CADHS as an “unregulated chemical for 

which monitoring is required.” Of the 22 trace elements analyzed by NWQL, the dissolved total arsenic, total chromium, 

and total iron analyzed by both NWQL and the Trace Metal 

Laboratory and the arsenic(III), chromium(VI), and iron(II) 

species analyzed at the Trace Metal Laboratory, 14 have 

MCLs, 5 have HA-Ls, and 3 have NLs (table 2I). Additionally, boron, manganese, and vanadium are listed as CADHS 

“unregulated chemicals for which monitoring is required” 

and, therefore, can be compared with their CADHS DLRs 

(table 2I). Trace element detections in ground-water samples 

that were above their respective MCLs, HA-Ls, NLs or DLRs 

include arsenic, boron, hexavalent chromium, iron, manganese, and vanadium (table 19). Only those trace elements 

with detections greater then an MCL, HA-L, NL, or DLR are 

discussed.

Total dissolved arsenic, analyzed by both NWQL and 

the Trace Metal Laboratory, was detected in all 39 samples in 

which it was analyzed. Arsenic was detected in three samples 

above the USEPA MCL of 10 μg/L (tables 19, 20, and fig. 8A).

Boron, a CADHS “unregulated chemical for which 

monitoring is required,” was analyzed by NWQL and was 

also detected in all 39 ground-water samples. Five samples 

(13 percent) analyzed for boron had concentrations above the 

CADHS NL of 1,000 μg/L (table 19 and fig. 8B), whereas 

11 samples (28 percent) had boron concentrations above the 

CADHS DLR of 100 μg/L (table 19).

 Hexavalent chromium (chromium(VI)) was analyzed by 

the Trace Metal Laboratory and was detected in all 39 groundwater samples. However, an anomalously high concentration 

of hexavalent chromium in a field blank sample (5.4 μg/L) 

resulted in the application of a relatively high censoring 

threshold. Detections below the censoring threshold are considered nondetects, are preceded by a “V” in table 20, and will 

not be used in any additional ground-water analysis; however, 

the reported concentrations are still listed for comparative 

purposes. After applying the censoring threshold of 5.5 μg/L, 

23 out of the 39 samples were censored, leaving 16 hexavalent 

chromium detections with concentrations above the CADHS 

DLR of 1 μg/L (table 20). Given the application of a censor 

threshold and the uncertainty of contamination in samples with 

concentrations of total dissolved chromium and hexavalent 

chromium above the censor limit, all detections in table 20

above the censor threshold are preceded by an “E,” indicating 

that their concentrations are potentially biased high.

Total dissolved iron, measured by both NWQL and 

the Trace Metal Laboratory, was detected in three samples 

(TRCY-07, TRCY-09, and TRCYFP-01) at concentrations 

above its USEPA SMCL of 300 μg/L (tables 19, 20, and 

fig. 8C). One of four field blank samples analyzed at the Trace 

Metal Laboratory contained iron at a concentration of 3 μg/L, 

which was greater than the minimum detected ground-water 

concentration. This resulted in the establishment of a censor 

threshold of 5 μg/L and the censoring of 14 total dissolved 

iron detections from the Trace Metal Laboratory.

Manganese, analyzed by the NWQL, was detected in 

three ground-water samples at concentrations above the 

CADHS NL of 500 μg/L (table 19 and figure 8D). Additionally, manganese was detected in 8 of 39 ground-water samples 

above its USEPA SMCL of 50 μg/L (table 19).

Lastly, vanadium, an “unregulated chemical for which 

monitoring is required,” was analyzed by NWQL and detected 

in 38 ground-water samples, of which 33 (85 percent) were 

above the CADHS DLR of 3 μg/L. However, none of the 

vanadium detections in ground-water samples were above the 

CADHS NL of 50 μg/L (table 19).

Ground-Water-Quality Results 23
Figure 7. Northern San Joaquin Basin Ground-Water Ambient Monitoring and Assessment (GAMA) study unit showing study 

areas and locations of wells sampled with detections referenced to the Secondary Maximum Contaminant Level (SMCL). A, 

wells sampled for chloride. B, wells sampled for sulfate. C, wells sampled for total dissolved solids.

24 California GAMA Program: Ground-Water Quality Data in the Northern San Joaquin Basin Study Unit, 2005

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FP-10:

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1999, Albers Equal Area Conic Projection

Base from U.S. Geological Survey digital elevation data,

1999, Albers Equal Area Conic Projection

Base from U.S. Geological Survey digital elevation data,

1999, Albers Equal Area Conic Projection

19

DD-04

DD-05

DD-06

04

07

07

06

01

08

14

06

FP-07

FP-08

10 FP-09

15

19

DD-04

DD-05

DD-06

FP-04

03

11

FP-05

FP-03

FP-02

07

09

FP-01

17

08

10

18

16

12 13

0 5 10 20KILOMETERS

0 5 10 20KILOMETERS

0 5 10 20KILOMETERS

EXPLANATION

04 04

06 06

10 10

12 12

16 16

15 15

03 03

07 07 17 17

09 09

11 FP-03 11 FP-03 FP-05 FP-05

FP-01 FP-01

FP-02

18 18

FP-08 FP-08

FP-04

FP-09

FP-07 FP-07

FP-09

06 06

08 08

08 08

13 13

01 01

10 10

07

14 14

19

DD-04

DD-05

DD-06

FP-04

FP-02

Sampled wells

concentrations  SMCL

concentrations  SMCL

!

12130

37

40

38

12130 121

38

20

38

37

40

121 12130 121

38

20

38

37

40

!

0 5 10 20MILES

0 5 10 20MILES

0 5 10 20MILES

!

!

!

!!

!

!

!

!

!

! ! !

!

!

!

!!

!

!

!

!

!

!

!

Study areas

Cosumnes Basin (COS)

Eastern San Joaquin Area (ESJ)

Tracy Basin (TRCY)

Uplands Basin (QPC)

Depth dependent (DD)

Monitoring well (MW)

Flowpath (FP)

38

20

!

!

!

!!

!

!

!

!

!

! ! !

!

!

!

!!

!

!

!

!

!

!

!

! ! !

!

!

!

!

! ! ! !

!

!

!

!!

!

!

!

!

!

! ! !

!

!

!

!!

!

!

!

!

!

!

!

!

!

! !

!

!!
Figure 8. Northern San Joaquin Basin Ground-Water Ambient Monitoring and Assessment (GAMA) study unit showing 

study areas and locations of wells. A, wells sampled for arsenic with detections referenced to the Maximum Contaminant 

Level (MCL). B, wells sampled for boron with detections referenced to the notification level (NL). C, wells sampled for iron 

with detections referenced to the Secondary Maximum Contaminant Level (SMCL). D, wells sampled for manganese with 

detections referenced to the notification level (NL).

Ground-Water-Quality Results 25

Depth dependent (DD)

Monitoring well (MW)

Flowpath (FP)

Base from U.S. Geological Survey digital elevation data,

1999, Albers Equal Area Conic Projection

Base from U.S. Geological Survey digital elevation data,

1999, Albers Equal Area Conic Projection

37

40

Study areas Sampled wells

EXPLANATION

concentrations  MCL

concentrations  MCL

01

!01

!

concentrations  NL

concentrations  NL

01

!01

!

Cosumnes Basin (COS)

Eastern San Joaquin Area (ESJ)

Tracy Basin (TRCY)

Uplands Basin (QPC)

!

!

!

!!

!

!

!

!

!

! !

! !

!

!

!

!

!

!

!

!

!

!!

!

!

!

!!

!

!

!

!

!

! !

!

!

!

!!

!

!

!

!

!

!

!

!

!

!

!!

!

!

! 04

17

18

08

03

01

10

07

FP-08

12

16

FP-07

06

08

13

06

10 FP-09

14

07

09

11

FP-04

FP-03 FP-05 0 5 10 20MILES

5 10 20KILOMETERS

0 5 10 20MILES

5 10 20KILOMETERS

A

A Arsenic detections

B Boron detections

B

12 13

!

! ! !

!

!

14

15

17

04

07

01

06

06

16

08

08

18

10

10

FP-08

FP-07

FP-09

19

DD-04

DD-05

DD-06

09

FP-01

07

03

FP-03 11

FP-05

FP-02

FP-04

15

FP-01 19

DD-04

DD-05

DD-06

!

!

FP-02

12130 121

38

20

38

!

!

0

!!

MW-01

MW-02

MW-03 FP-10:

DD-01

DD-02

DD-03

0

!

!

MW-01

MW-02

MW-03 FP-10:

DD-01

DD-02

DD-03

!

37

40

38

20

38

12130 121
CA-3153_fig08cd

Base from U.S Geological Survey digital elevation data,

1999, Albers Equal Area Conic Projection Base from U.S Geological Survey digital elevation data,

1999, Albers Equal Area Conic Projection

EXPLANATION

01

01

!

!

01

no detections

concentrations  NL

concentrations  NL

01

01

!

!

01

Study areas

Cosumnes Basin (COS)

Eastern San Joaquin Area (ESJ)

Tracy Basin (TRCY)

Uplands Basin (QPC)

Sampled wells

no detections

concentrations  SMCL

concentrations  SMCL

C Iron detections

Depth dependent (DD)

Monitoring well (MW)

Flowpath (FP)

C

D Manganese detections

!

!!

!

! !!

!

!

!

!

!

!

!

!

!

!

!

!

!

!

! !

!

!

03

FP-03 11

FP-05

FP-02

FP-04

MW-01

MW-02

MW-03 04

07

01

06

08

12 13

17

08

18

10

07

09

FP-01

FP-08

19 16

DD-04

DD-05

DD-06

15

10

14

06

FP-07

FP-09

!

!

!!

!

!

!

!

!

! ! !

!

!

!

!!

!

!

!

!

!

!

!

!

!

!

!

!

!

!!

03

FP-04

11

FP-03 FP-05

FP-02

07

09

FP-01

06

08 06

14

04

17

18

08 10

01

07

12 13

FP-08

16

10

15

19

DD-04

DD-05

DD-06

FP-07

FP-09

D

0 5 10 20MILES

0 5 10 20KILOMETERS

0 5 10 20MILES

0 5 10 20KILOMETERS

!

!

!

!

!

FP-10:

DD-01

DD-02

DD-03

12130 121 12130 121

38

20 38

20

38 38

37

40 37

40

Base from U.S. Geological Survey digital elevation data,

1999, Albers Equal Area Conic Projection

Base from U.S. Geological Survey digital elevation data,

1999, Albers Equal Area Conic Projection

! FP-10:

DD-01

DD-02

DD-03

MW-01

MW-02

MW-03 

Figure 8.—Continued.

26 California GAMA Program: Ground-Water Quality Data in the Northern San Joaquin Basin Study Unit, 2005
Isotopes, Radioactivity, and Noble Gases

Tables 21 and 22 provide summaries of isotope activities, 

stable isotopes, and gross alpha–beta radioactivity determined 

in ground-water samples collected for the Northern San Joaquin Basin GAMA study unit. Seventy samples (64 wells and 

6 depth-dependent samples) were analyzed for stable isotopes 

of water (analyzed at the USGS’s Reston Stable Isotope Laboratory) and tritium (analyzed at the USGS’s Menlo Park Stable 

Isotope and Tritium Laboratory (table 21). Twenty-seven 

samples (23 wells and 4 depth-dependent samples) were also 

analyzed for tritium at LLNL (table 22). Additionally, LLNL 

also analyzed 16 samples (13 wells and 3 depth-dependent 

samples) for the noble gases helium-4, neon, argon, krypton, 

and xenon (table 22). Tritium and noble gas analyses can be 

used to help determine the chronology and source of groundwater recharge. Thirteen wells were sampled for the following 

radioactive constituents: radium-226, radium-228, radon-222, 

gross-alpha radioactivity (72-hour and 30-day count), and 

gross-beta radioactivity 

(72-hour and 30-day count). Lastly, sixteen ground-water 

samples were analyzed for stable carbon isotopes.

Tritium was detected in 45 of 70 ground-water samples 

analyzed at the Stable Isotope and Tritium Laboratory 

(table 21). The highest activity detected in any ground-water 

sample was 37 picocuries per liter (pCi/L), whereas the 

USEPA MCL for tritium is 20,000 pCi/L. Radium-226 was 

detected in all 13 ground-water samples for which it was analyzed, at concentrations below the USEPA MCL of 3 pCi/L. 

Radium-228 was detected in 3 of the 13 samples, all of which 

were below the USEPA MCL of 2 pCi/L. No ground-water 

sample was above the combined radium-226 and radium228 USEPA MCL of 5 pCi/L. Gross-alpha radioactivity in 

ground-water samples was not found above the USEPA MCL 

of 15 pCi/L. Similarly, gross-beta radioactivity was below 

the USEPA MCL of 50 pCi/L. Radon-222 was detected in all 

ground-water samples in which it was analyzed (table 21). The 

USEPA proposed MCL for radon-222 is 300 pCi/L, whereas 

the proposed Alternate Maximum Contaminant Level (AMCL) 

is 4,000 pCi/L (U.S. Environmental Protection Agency, 2006). 

Of the 13 ground-water samples for which radon-222 was 

analyzed, all except one were greater than the proposed MCL; 

however, all were below the AMCL (fig. 9).

Stable isotopes of water were collected at all sampled 

wells and are reported in table 21 as the ratio of deuterium 

to protium and the ratio of oxygen-18 to oxygen-16. These 

values are used to aid in the interpretation of ground-water 

recharge sources. The values of the ratio of deuterium to protium ranged from –81.1 per mill to –43.0 per mill. The values 

of the ratio of oxygen-18 to oxygen-16 ranged from –11.2 per 

mill to –5.6 per mill.

Microbial Constituents

Microbial constituents, including total coliform and 

Escherichia spp. coliform (E. coli), as well as the viruses 

F-specific coliphage and somatic coliphage, were analyzed 

in eight ground-water samples collected from the Northern 

San Joaquin Basin GAMA study unit (table 23). F-specific 

coliphage, somatic coliphage, and E. coli were not detected in 

any ground-water samples. An estimated three total coliform 

colonies were detected in one 100-mL sample of ground water 

collected at QPC-01 (fig. 10).

Summary

The Ground-Water Ambient Monitoring and Assessment (GAMA) Program is intended to provide a comprehensive statewide assessment of ground-water quality in areas 

of California where ground water is a significant source of 

drinking water. The Northern San Joaquin Basin GAMA 

study unit is the third region in which the GAMA Program 

has implemented its program objectives. The Northern San 

Joaquin Basin GAMA study unit lies within the Central Valley 

Hydrologic Province and consists of four hydrogeologic study 

areas: the Tracy Basin study area, the Eastern San Joaquin 

Basin study area, the Cosumnes Basin study area, and the 

Uplands Basin study area. A total of 70 ground-water samples 

(grid cell and nongrid cell) were collected from a combination 

of public-supply, irrigation, domestic, and monitoring wells 

within the study unit. Thirty-two of these samples were collected in the Eastern San Joaquin Basin study area, 17 samples 

were collected in the Tracy Basin study area, 11 samples were 

collected in the Uplands Basin study area, and 10 samples 

were collected in the Cosumnes Basin study area.

This report presents the results of ground-water sample 

collection and analyses for over 350 water-quality field parameters, chemical, and microbial constituents, measured in the 70 

samples obtained between December 2004 and February 2005. 

The chemical and microbial data presented in this report are 

compared to health-based regulatory values set by CADHS or 

the USEPA (maximum contaminant level or MCL), healthbased advisory levels set by CADHS (notification level NL) 

or USEPA (lifetime health advisory level or HA-L), nonenforceble levels set for aesthetic qualities (secondary maximum 

contaminant level or SMCL), and levels set by CADHS for the 

purposes of tracking “unregulated chemicals for which monitoring is required” (detection limit for the purposes of reporting or DLR). The data presented in this report are intended to 

characterize the quality of untreated ground-water resources 

within the study unit, not the treated drinking water delivered 

to consumers by water purveyors. The composition of treated 

drinking water may differ considerably from untreated ground 

water as a result of treatment processes, such as disinfection, filtration, mixing with other waters, and exposure to the 

atmosphere.

Summary 27
Figure 9. Northern San Joaquin Basin Ground-Water Ambient Monitoring and Assessment (GAMA) 

study unit showing study areas and locations of wells sampled for radon-222 with detections referenced 

to the proposed Maximum Contaminant Level (MCL) of 300 pCi/L. 

28 California GAMA Program: Ground-Water Quality Data in the Northern San Joaquin Basin Study Unit, 2005

!

!

!

!

!

!

!

!

!

!

!!

37

40

38

20

38

121 30 121

MW-01

MW-02

MW-03 

FP-10

DD-03

0 5 10 20 MILES

0 5 10 20 KILOMETERS

!

!

Sampled wells with radon-222 detections

Activities proposed MCL (300 pCi/L)

Activities proposed MCL (300 pCi/L)

EXPLANATION

01

01

01

12

FP-07

FP-02

FP-04

07

FP-01

FP-23

Study areas

Cosumnes Basin (COS)

Eastern San Joaquin Area (ESJ)

Tracy Basin (TRCY)

Uplands Basin (QPC)

Base from U.S. Geological Survey digital elevation data,

1999, Albers Equal Area Conic Projection

Depth dependent (DD)

Monitoring well (MW)

Flowpath (FP)
Figure 10. Northern San Joaquin Basin Ground-Water Ambient Monitoring and Assessment 

(GAMA) study unit showing study areas and locations of wells sampled for coliform with detections 

referenced to colonies detected in one 100-mL sample of ground water. 

Summary 29

! !

!

!

!

!

!

! 37

40

38

20

38

121 30 121

01

01

01

12

03

07

FP-07

FP-01

FP-02

FP-04

!

!

Sampled wells 

No coliform detections

Coliform detections

EXPLANATION

Study areas

Cosumnes Basin (COS)

Eastern San Joaquin Area (ESJ)

Tracy Basin (TRCY)

Uplands Basin (QPC)

Base from U.S. Geological Survey digital elevation data,

1999, Albers Equal Area Conic Projection

0 5 10 20 MILES

0 5 10 20 KILOMETERS

Flowpath (FP)
Thirty of the 88 VOCs and gasoline oxygenates analyzed 

were detected in ground-water samples and 13 TICs were also 

detected. VOCs and gasoline oxygenates were detected in 43 

ground-water samples (25 grid cell samples and 18 nongrid cell samples). These constituents were most frequently 

detected in the Eastern San Joaquin Basin study area (24 of 

32 samples) and least detected in the Cosumnes Basin 

study area (2 of 10 samples). Trihalomethanes, which are a 

byproduct of water treatment using chlorination, were the 

most frequently detected class of VOC constituents (21 of 70 

samples). Within the trihalomethane class, chloroform was the 

most frequently detected constituent (20 of 70 samples). None 

of the VOCs analyzed were detected at concentrations above a 

USEPA MCL or CADHS NL; however, dichlorodifluoromethane (CFC-12), an “unregulated chemical for which monitoring is required,” was detected in two wells at concentrations 

greater than the California Department of Health Services 

DLR.

Fifteen of the 122 pesticides and pesticide degradate constituents analyzed for in ground-water samples were detected 

in this study (table 14). Pesticide and pesticide degradates 

were detected in 27 of 70 (grid cell and nongrid cell wells) 

samples collected. These constituents were most frequently 

detected in the Eastern San Joaquin Basin study area (17 of 32 

samples) and least frequently detected in the Cosumnes Basin 

study area (4 of 10 samples). Herbicides were the most frequently detected class of constituents throughout the Northern 

San Joaquin Basin GAMA study unit (21 of 70 samples), and 

simazine, an herbicide, was the most frequently detected compound (27 of 70 samples). Two herbicides, DBCP and EDB, 

were detected at concentrations above established USEPA 

MCLs.

Six wastewater-indicator constituents were identified in 

samples collected in the Northern San Joaquin Basin GAMA 

study unit (table 15). Thirteen of the 16 samples analyzed for 

wastewater-indicator constituents had at least a single detection. Isophorone was the most frequently detected wastewaterindicator compound (7 of 16 samples), yet it was only detected 

at concentrations high enough to be quantified twice. None 

of wastewater-indicator constituents were detected above an 

MCL, SMCL, NL, HA-L, or RSD5.

Thirty-four ground-water samples of perchlorate, NDMA, 

and 1,2,3-TCP (constituents of special interest) were collected 

throughout the Northern San Joaquin Basin GAMA study unit. 

Perchlorate was detected in two samples located in the Eastern 

San Joaquin Basin study area (table 16). Neither concentration 

of perchlorate was above the CADHS NL or CADHS DLR. 

The constituents NDMA and 1,2,3-trichloropropane were not 

detected in any ground-water samples.

Eighteen ground-water samples were collected for nutrient constituents (13 wells and 5 depth-dependent samples), 

whereas only 10 samples were collected for DOC (table 17). 

Nitrite plus nitrate was detected in 11 samples (excluding the 

depth-dependent analyses), whereas nitrite was detected in 

only two samples. Concentrations of nitrite plus nitrate were 

below the USEPA MCL of 10 mg/L (as nitrogen). Similarly, 

nitrite concentrations were below the USEPA MCL of 1 mg/L 

(as nitrogen). Dissolved organic carbon was detected in 5 of 

the 10 samples in which it was analyzed.

Thirty-nine ground-water samples (33 wells and 6 depthdependent samples) were collected for 10 major and minor 

ions as well as TDS. Eight ground-water samples had TDS 

concentrations above the USEPA recommended SMCL of 

500 mg/L. Two samples had chloride concentrations above 

the CADHS SMCL of 250 mg/L, whereas three samples had 

sulfate concentrations above the USEPA SMCL of 250 mg/L.

Thirty-nine ground-water samples (33 wells and 6 depthdependent samples) were collected for trace element analyses. 

A total of 25 trace elements and three oxidation species were 

analyzed. Trace elements detected in ground-water samples 

that were above their respective MCL, NL, HA-L, or DLR, 

(for CADHS “unregulated chemical for which monitoring 

is required”) included arsenic, boron, hexavalent chromium 

(chromium(VI)), iron, manganese, and vanadium. Arsenic 

was detected in three samples above the USEPA MCL of 

10 μg/L. Boron, an “unregulated chemical for which monitoring is required,” was detected in five samples at concentrations 

above the CADHS NL of 1,000 μg/L and in 11 samples above 

the CADHS DLR of 100 μg/L. Hexavalent chromium, also 

an “unregulated chemical for which monitoring is required,” 

was detected in all 39 samples in which it was analyzed at 

the USGS’s Trace Metal Laboratory in Boulder, Colorado. 

Sixteen of the 39 hexavalent chromium ground-water samples 

had concentrations above the CADHS DLR of 1 μg/L. Iron 

was detected in three samples at concentrations above its 

USEPA SMCL of 300 μg/L. Manganese was detected in 8 

of 39 samples above its USEPA SMCL of 30 μg/L. Of those 

eight samples with concentrations of Manganese greater than 

the SMCL, three were detected at concentrations above the 

CADHS NL of 500 μg/L. Lastly, vanadium, an “unregulated 

chemical for which monitoring is required,” was detected in 

38 of 39 samples, of which 33 were above the CADHS DLR 

of 3 μg/L. Of the 33 samples detected at concentrations above 

the DLR, none were detected at concentrations above the 

CADHS NL of 50 μg/L.

30 California GAMA Program: Ground-Water Quality Data in the Northern San Joaquin Basin Study Unit, 2005
Seventy ground-water samples (64 wells and 6 depthdependent samples) were analyzed for stable isotopes of 

water and tritium. Samples from 13 wells were analyzed for 

radium-226, radium-228, radon-222, gross-alpha radioactivity (72-hour and 30-day count), and gross-beta radioactivity 

(72-hour and 30-day count), and sixteen ground-water samples 

were analyzed for stable carbon isotopes. None of the groundwater samples had measured activities above the combined 

radium-226 and radium-228 USEPA MCL of 5 pCi/L. Grossalpha and gross-beta radioactivity in ground-water samples 

were not found to be above the USEPA MCLs of 15 and 50 

pCi/L, respectively. Radon-222 was detected in all samples in 

which it was analyzed; however, the proposed USEPA MCL 

for radon-222 is 300 pCi/L, whereas the proposed AMCL is 

4,000 pCi/L (U.S. Environmental Protection Agency, 2006). 

Of the 13 ground-water samples in which radon-222 was analyzed, 12 were above the proposed USEPA MCL; however, all 

samples were below the AMCL. Stable isotopes of water are 

reported as the ratio of deuterium to protium and the ratio of 

oxygen-18 to oxygen-16, and values of the ratio of deuterium 

to protium (hydrogen isotopes) ranged from –81.1 per mill to 

–43.0 per mill, whereas the values of the ratio of oxygen-18 to 

oxygen-16 ranged from –11.2 per mill to –5.6 per mill.

Microbial constituents, including total coliform and 

Escherichia spp. coliform, as well as the viruses F-specific 

coliphage and somatic coliphage, were analyzed for in eight 

ground-water samples collected for the Northern San Joaquin 

Basin GAMA study unit (table 23). F-specific coliphage, 

somatic coliphage, and Escherichia spp. coliform were not 

detected in any ground-water samples, whereas an estimated 

three total coliform colonies were detected in 100 mL of 

ground water from one a sample collected at QPC-01.

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book of ASTM standards—water and environmental technology: Philadelphia, Pennsylvania, American Society for 

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Ball, J.W., and McCleskey, R.B., 2003a, A new cationexchange method for accurate field speciation of hexavalent 

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Ball, J.W., and McCleskey, R.B., 2003b, A new cationexchange method for accurate field speciation of hexavalent 

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Belitz, Kenneth; Dubrovsky, N.M.; Burow, K.R.; Jurgens, 

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desc/5-22.15.pdf

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California Department of Water Resources, 2005c, California 

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Childress, C.J.O., Foreman, W.T., Connor, B.F., and Maloney, T.J., 1999, New reporting procedures based on longterm method detection levels and some considerations for 

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Geological Survey Open-File Report 99-193, 19 p.

Connor, B.F., Rose, D.L., Noriega, M.C., Murtagh, L.K., and 

Abney, S.R., 1998, Methods of analysis by the U.S. Geological Survey National Water Quality Laboratory—determination of 86 volatile organic compounds in water by gas 

chromatography/mass spectrometry, including detections 

less than reporting limits: U.S. Geological Survey OpenFile Report 97-829, 78 p.

Coplen, T.B.; Wildman, J.D.; and Chen, Julie; 1991, Improvements in the gaseous hydrogen-water equilibrium technique 

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Davis, G.H., Lofgren, B.E., and Mack, S., 1964, Use of 

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Donahue, D.J., Linick, T.W., and Jull, A.J.T., 1990, Ratio and 

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Series, no. 868, p. 235–245.

Epstein, Samuel; and Mayeda, T.K.; 1953, Variation of O-18 

content of water from natural sources: Geochimica et Cosmochimica Acta, v. 4, p. 213–224.

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34 California GAMA Program: Ground-Water Quality Data in the Northern San Joaquin Basin Study Unit, 2005
Tables

Tables 35
36 California GAMA Program: Ground-Water Quality Data in the Northern San Joaquin Basin Study Unit, 2005 Slow analyte list Intermediate analyte list Fast analyte list Depth-dependent analyte list Water-quality indicators (alkalinity, DO, pH, SC, temperature, turbidity) Water-quality indicators (SC and temperature) Water-quality indicators (SC and temperature) Water-quality indicators (alkalinity, DO, pH, SC, temperature) Volatile organic compounds Volatile organic compounds Volatile organic compounds Volatile organic compounds Gasoline oxygenates Gasoline oxygenates nc Gasoline oxygenates Pesticides, including low-detection limit DBCP and EDB Pesticides, including low-detection limit DBCP and EDB Pesticides, including low-detection limit DBCP and EDB Pesticides, including low-detection limit DBCP and EDB Polar pesticides and degradates nc nc nc Wastewater-indicator constituents nc nc Wastewater-indicator constituents Pharmaceuticals Pharmaceuticals Pharmaceuticals nc Constituents of Special Interest (perchlorate, NDMA, 1,2,3-trichloropropane)1 Constituents of Special Interest (perchlorate, NDMA, 1,2,3-trichloropropane)1 nc Constituents of Special Interest (perchlorate, NDMA, 1,2,3-trichloropropane)1 Nutrients and dissolved organic carbon nc nc Nutrients and dissolved organic carbon Major ions and trace elements Major ions and trace elements nc Major ions and trace elements Chromium speciation Chromium speciation nc Chromium speciation Arsenic and iron speciation Arsenic and iron speciation nc Arsenic and iron speciation Stable isotopes of water Stable isotopes of water Stable isotopes of water Stable isotopes of water Carbon isotopes nc nc Carbon isotopes Radium isotopes nc nc nc Gross alpha and beta radioactivity nc nc nc Radon-222 nc nc nc Tritium2 Tritium2 Tritium2 Tritium2 Tritium and noble gases3 nc nc Tritium and noble gases3 Microbial constituents nc nc nc

1Analyzed at Montgomery Watson Harza Laboratory, Monrovia, California.2Analyzed at the U.S. Geological Survey’s Stable Isotope and Tritium Laboratory, Menlo Park, California.3Analyzed at Lawrence Livermore National Laboratory, Livermore, California.

Table 1. Classes of chemical, radioactive, and microbial constituents and water-quality indicators collected for the slow, intermediate, fast, and depth-dependent analyte lists in the Northern San Joaquin Basin Ground-Water Ambient Monitoring and Assessment (GAMA) study, California, December 2004 to February 2005.[DBCP, 1,2-dibromo-3-chloropropane; DO, dissolved oxygen; EDB, 1,2-dibromoethane; nc, not collected; NDMA, 

N-nitrosodimethylamine; SC, specific conductance]

36 California GAMA Program: Ground-Water Quality Data in the Northern San Joaquin Basin Study Unit, 2005
Tables 37

Constituent Primary use/source USGS parameter code CAS number LRL (μg/L) Type of comparison threshold Threshold level (μg/L)

Acetone Solvent 81552 67-64-1 6 n/a n/aAcrylonitrile Organic synthesis 34215 107-13-1 0.8 RSD5 0.6Benzene Gasoline 34030 71-43-2 0.021 MCL-CA 1Bromobenzene Solvent 81555 108-86-1 0.028 n/a n/aBromochloromethane Organic synthesis 77297 74-97-5 0.12 HA-L 9Bromodichloromethane (THM) Disinfection by-product 32101 75-27-4 0.028 MCL-US 80Bromoethene Fire retardant 50002 593-60-2 0.1 n/a n/aBromoform (tribromomethane) (THM) Disinfection by-product 32104 75-25-2 0.1 MCL-US 80Bromomethane Fumigant 34413 74-83-9 0.26 HA-L 102-Butanone (ethyl methyl ketone) Solvent 81595 78-93-3 2 HA-L 4,000n-Butylbenzene Organic synthesis 77342 104-51-8 0.12 NL 260sec-Butylbenzene Organic synthesis 77350 135-98-8 0.06 NL 260tert-Butylbenzene Organic synthesis 77353 98-06-6 0.06 NL 260Carbon disulfide Organic synthesis 77041 75-15-0 0.038 NL 160Chlorobenzene Solvent 34301 108-90-7 0.028 MCL-CA 70Chloroethane Solvent 34311 75-00-3 0.12 n/a n/aChloroform (trichloromethane) (THM) Disinfection by-product 32106 67-66-3 0.024 MCL-US 80Chloromethane Refrigerant 34418 74-87-3 0.17 HA-L 303-Chloropropene Organic synthesis 78109 107-05-1 0.5 n/a n/a2-Chlorotoluene Solvent 77275 95-49-8 0.04 NL 1404-Chlorotoluene Solvent 77277 106-43-4 0.05 NL 140Dibromochloromethane (THM) Disinfection by-product 32105 124-48-1 0.1 MCL-US 801,2-Dibromo-3-chloropropane (DBCP) Fumigant 82625 96-12-8 0.51 MCL-US 0.21,2-Dibromoethane (EDB) Solvent/Fumigant 77651 106-93-4 0.036 MCL-US 0.05

Table 2A. Volatile organic compounds, primary use or source, U.S. Geological Survey (USGS) parameter code, Chemical Abstracts Service (CAS) number, USGS laboratory reporting levels (LRLs) for the USGS’s National Water Quality Laboratory analytical Schedule 2020, type of comparison threshold for ground-water detections, and the corresponding threshold level.[The five digit number below the USGS parameter code is used to uniquely identify a specific constituent or property. HA-L, lifetime health advisory (U.S. Environmental Protection Agency, 2004b); MCL-CA, California Department of Health Services Maximum Contaminant Level (California Department of Health Services, 2005a); MCL-US, U.S. Environmental Protection Agency Maximum Contaminant Level (U.S. Environmental Protection Agency, 2004b); n/a, not applicable; NL, notification level (California Department of Health Services, 2005d); RSD5, risk-specific dose at 10E-5 (Note: RSD5 = RSD4 (risk level = 10E-4)/10) (U.S. Environmental Protection Agency, 2004b); μg/L, microgram per liter]

See footnote at end of table.

Tables 37
Constituent Primary use/source USGS parameter code CAS number LRL (μg/L) Type of comparison threshold Threshold level (μg/L)

Dibromomethane Solvent 30217 74-95-3 0.05 n/a n/a1,2-Dichlorobenzene Solvent 34536 95-50-1 0.048 MCL-US 6001,3-Dichlorobenzene Solvent 34566 541-73-1 0.03 HA-L 6001,4-Dichlorobenzene Fumigant 34571 106-46-7 0.034 MCL-CA 5trans-1,4-Dichloro-2-butene Organic synthesis 73547 110-57-6 0.700 n/a n/aDichlorodifluoromethane (CFC-12) Refrigerant 34668 75-71-8 0.18 NL 1,0001,1-Dichloroethane Solvent 34496 75-34-3 0.035 MCL-US 51,2-Dichloroethane Solvent 32103 107-06-2 0.13 MCL-CA 0.51,1-Dichloroethylene Organic synthesis 34501 75-35-4 0.024 MCL-CA 6cis-1,2-Dichloroethylene Solvent 77093 156-59-2 0.024 MCL-CA 6trans-1,2-Dichloroethylene Solvent 34546 156-60-5 0.032 MCL-CA 10Dichloromethane (methylene chloride) Solvent 34423 75-09-2 0.06 MCL-US 51,2-Dichloropropane Solvent 34541 78-87-5 0.029 MCL-US 51,3-Dichloropropane Organic synthesis 77173 142-28-9 0.06 MCL-US 52,2-Dichloropropane Organic synthesis 77170 594-20-7 0.05 n/a n/a1,1-Dichloropropene Organic synthesis 77168 563-58-6 0.026 n/a n/acis-1,3-Dichloropropene Fumigant 34704 10061-01-5 0.05 RSD5 1

4

trans-1,3-Dichloropropene Fumigant 34699 10061-02-6 0.09 RSD5 1

4

Diethyl ether Solvent 81576 60-29-7 0.08 n/a n/aDiisopropyl ether Gasoline oxygenate 81577 108-20-3 0.1 n/a n/aEthylbenzene Gasoline 34371 100-41-4 0.03 MCL-CA 300Ethyl tert-butyl ether (ETBE) Gasoline oxygenate 50004 637-92-3 0.03 n/a n/aEthyl methacrylate Organic synthesis 73570 97-63-2 0.18 n/a n/ao-Ethyl toluene Hydrocarbon 77220 611-14-3 0.06 n/a n/a

Table 2A. Volatile organic compounds, primary use or source, U.S. Geological Survey (USGS) parameter code, Chemical Abstracts Service (CAS) number, USGS laboratory reporting levels (LRLs) for the USGS’s National Water Quality Laboratory analytical Schedule 2020, type of comparison threshold for ground-water detections, and the corresponding threshold level—Continued.[The five digit number below the USGS parameter code is used to uniquely identify a specific constituent or property. HA-L, lifetime health advisory (U.S. Environmental Protection Agency, 2004b); MCL-CA, California Department of Health Services Maximum Contaminant Level (California Department of Health Services, 2005a); MCL-US, U.S. Environmental Protection Agency Maximum Contaminant Level (U.S. Environmental Protection Agency, 2004b); n/a, not applicable; NL, notification level (California Department of Health Services, 2005d); RSD5, risk-specific dose at 10E-5 (Note: RSD5 = RSD4 (risk level = 10E-4)/10) (U.S. Environmental Protection Agency, 2004b); μg/L, microgram per liter]

See footnote at end of table.

38 California GAMA Program: Ground-Water Quality Data in the Northern San Joaquin Basin Study Unit, 2005
Constituent Primary use/source USGS parameter code CAS number LRL (μg/L) Type of comparison threshold Threshold level (μg/L)

Hexachlorobutadiene Organic synthesis 39702 87-68-3 0.14 HA-L 1Hexachloroethane Solvent 34396 67-72-1 0.14 HA-L 12-Hexanone Solvent 77103 591-78-6 0.4 n/a n/aIsopropylbezene Organic synthesis 77223 98-82-8 0.038 NL 7704-Isopropyl-1-methylbenzene Organic synthesis 77356 99-87-6 0.08 n/a n/am- and p-Xylene Gasoline 85795 108-38-3/106-

42-3

0.06 MCL-CA 1,750

Methyl acrylate Organic synthesis 49991 96-33-3 1 n/a n/aMethyl acrylonitrile Organic synthesis 81593 126-98-7 0.4 n/a n/aMethyl tert-butyl ether (MTBE) Gasoline oxygenate 78032 1634-04-4 0.1 MCL-US 13Methyl iodide Organic synthesis 77424 74-88-4 0.5 n/a n/aMethyl methacrylate Organic synthesis 81597 80-62-6 0.2 n/a n/a4-Methyl-2-pentanone (MIBK) Solvent 78133 108-10-1 0.37 NL 120Methyl tert-pentyl ether Gasoline oxygenate 50005 994-05-8 0.04 n/a n/aNaphthalene Organic synthesis 34696 91-20-3 0.52 NL 17n-Propylbenzene Solvent 77224 103-65-1 0.042 NL 260Styrene Organic synthesis 77128 100-42-5 0.042 MCL-US 1001,1,1,2-Tetrachloroethane Solvent 77562 630-20-6 0.03 HA-L 701,1,2,2-Tetrachloroethane Solvent 34516 79-34-5 0.08 MCL-CA 1Tetrachloroethylene (PCE) Solvent 34475 127-18-4 0.03 MCL-US 5Tetrahydrofuran Solvent 81607 109-99-9 1.0 n/a n/aTetrachloromethane (carbon tetrachloride) Solvent 32102 56-23-5 0.06 MCL-CA 0.51,2,3,4-Tetramethylbenzene Hydrocarbon 49999 488-23-3 0.14 n/a n/a1,2,3,5-Tetramethylbenzene (isodurene) Hydrocarbon 50000 527-53-7 0.14 n/a n/a

Table 2A. Volatile organic compounds, primary use or source, U.S. Geological Survey (USGS) parameter code, Chemical Abstracts Service (CAS) number, USGS laboratory reporting levels (LRLs) for the USGS’s National Water Quality Laboratory analytical Schedule 2020, type of comparison threshold for ground-water detections, and the corresponding threshold level—Continued.[The five digit number below the USGS parameter code is used to uniquely identify a specific constituent or property. HA-L, lifetime health advisory (U.S. Environmental Protection Agency, 2004b); MCL-CA, California Department of Health Services Maximum Contaminant Level (California Department of Health Services, 2005a); MCL-US, U.S. Environmental Protection Agency Maximum Contaminant Level (U.S. Environmental Protection Agency, 2004b); n/a, not applicable; NL, notification level (California Department of Health Services, 2005d); RSD5, risk-specific dose at 10E-5 (Note: RSD5 = RSD4 (risk level = 10E-4)/10) (U.S. Environmental Protection Agency, 2004b); μg/L, microgram per liter]

See footnote at end of table.

Tables 39
Constituent Primary use/source USGS parameter code CAS number LRL (μg/L) Type of comparison threshold Threshold level (μg/L)

Toluene Gasoline 34010 108-88-3 0.02 MCL-CA 1501,2,3-Trichlorobenzene Organic synthesis 77613 87-61-6 0.18 n/a n/a1,2,4-Trichlorobenzene Solvent 34551 120-82-1 0.12 MCL-CA 51,1,1-Trichloroethane (TCA) Solvent 34506 71-55-6 0.032 MCL-US 2001,1,2-Trichloroethane Solvent 34511 79-00-5 0.04 MCL-US 5Trichloroethylene (TCE) Solvent 39180 79-01-6 0.038 MCL-US 5Trichlorofluoromethane (CFC-11) Refrigerant 34488 75-69-4 0.08 MCL-CA 1501,2,3-Trichloropropane (1,2,3-TCP) Solvent 77443 96-18-4 0.18 NL 0.0051,1,2-Trichlorotrifluoroethane (CFC-113) Refrigerant 77652 76-13-1 0.038 MCL-US 1,2001,2,3-Trimethylbenzene Gasoline 77221 526-73-8 0.06 n/a n/a1,2,4-Trimethylbenzene Organic synthesis 77222 95-63-6 0.056 NL 3301,3,5-Trimethylbenzene Gasoline 77226 108-67-8 0.044 NL 330o-Xylene Gasoline 77135 95-47-6 0.038 MCL-CA 1,750Vinyl chloride Organic synthesis 39175 75-01-4 0.08 MCL-CA 0.5

1The RSD5 threshold for 1,3-dichloropropene is the sum of its isomers (cis and trans).

Table 2A. Volatile organic compounds, primary use or source, U.S. Geological Survey (USGS) parameter code, Chemical Abstracts Service (CAS) number, USGS laboratory reporting levels (LRLs) for the USGS’s National Water Quality Laboratory analytical Schedule 2020, type of comparison threshold for ground-water detections, and the corresponding threshold level—Continued.[The five digit number below the USGS parameter code is used to uniquely identify a specific constituent or property. HA-L, lifetime health advisory (U.S. Environmental Protection Agency, 2004b); MCL-CA, California Department of Health Services Maximum Contaminant Level (California Department of Health Services, 2005a); MCL-US, U.S. Environmental Protection Agency Maximum Contaminant Level (U.S. Environmental Protection Agency, 2004b); n/a, not applicable; NL, notification level (California Department of Health Services, 2005d); RSD5, risk-specific dose at 10E-5 (Note: RSD5 = RSD4 (risk level = 10E-4)/10) (U.S. Environmental Protection Agency, 2004b); μg/L, microgram per liter]

40 California GAMA Program: Ground-Water Quality Data in the Northern San Joaquin Basin Study Unit, 2005
Constituent Primary use/source USGS parameter code CAS number LRL (μg/L) Type of comparison threshold Threshold level (μg/L)

Acetone Degradate/solvent 81552 67-64-1 1.2 n/a n/aDiisopropyl ether Gasoline oxygenate 81577 108-20-3 0.04 n/a n/aEthyl tert-butyl ether (ETBE) Gasoline oxygenate 50004 637-92-3 0.04 DLR 3Methyl acetate Degradate 77032 79-20-9 0.43 n/a n/atert-Amyl alcohol Degradate 77073 75-85-4 1 n/a n/atert-Butyl alcohol (TBA) Degradate 77035 75-65-0 1 NL 12Methyl tert-butyl ether (MTBE) Gasoline oxygenate 78032 1634-04-4 0.04 MCL-US 13Methyl tert-pentyl ether Gasoline oxygenate 50005 994-05-8 0.04 DLR 3

Table 2B. Gasoline oxygenates and gasoline oxygenate degradates, primary use or source, U.S. Geological Survey (USGS) parameter code, Chemical Abstracts Service (CAS) number, USGS laboratory reporting level (LRL) for the USGS’s National Water Quality Laboratory analytical Schedule 4024, type of comparison threshold for ground-water detections, and the threshold concentration.[The five digit number below the USGS parameter code is used to uniquely identify a specific constituent or property. DLR, detection level for the purpose of reporting (California Department of Health Services, 2005a); MCL-US, U.S. Environmental Protection Agency Maximum Contaminant Level (U.S. Environmental Protection Agency, 2004b); n/a, not applicable; NL, notification level (California Department of Health Services, 2005d); μg/L, microgram per liter]

Tables 41
Constituent Primary use/source USGS parameter code CAS number LRL (μg/L) Type of comparison threshold Threshold level (μg/L)

Acetochlor Herbicide 49260 34256-82-1 0.006 n/a n/aAlachlor Herbicide 46342 15972-60-8 0.005 MCL-US 2Atrazine Herbicide 39632 1912-24-9 0.007 MCL-CA 1Azinphos-methyl Insecticide 82686 86-50-0 0.05 n/a n/aAzinphos-methyl-oxon Degradate 61635 961-22-8 0.07 n/a n/aBenfluralin Herbicide 82673 1861-40-1 0.01 n/a n/aCarbaryl Insecticide 82680 63-25-2 0.041 HA-L 7002-Chloro-2,6-diethylacetanilide Degradate 61618 6967-29-9 0.005 n/a n/a2-Chloro-4-isopropylamino-6-amino-s-triazine 

(deethylatrazine)

Degradate 04040 6190-65-4 0.006 n/a n/a

4-Chloro-2-methylphenol Degradate 61633 1570-64-5 0.005 n/a n/aChlorpyrifos Insecticide 38933 2921-88-2 0.005 HA-L 20Chlorpyrofos, oxygen analog Degradate 61636 5598-15-2 0.056 n/a n/acis-Permethrin Insecticide 82687 54774-45-7 0.006 n/a n/aCyfluthrin Insecticide 61585 68359-37-5 0.008 n/a n/aCypermethrin Insecticide 61586 52315-07-8 0.008 n/a n/aDacthal (DCPA) Herbicide 82682 1861-32-1 0.003 HA-L 70Desulfinylfipronil Degradate 62170 n/a 0.012 n/a n/aDesulfinylfipronil amide Degradate 62169 n/a 0.029 n/a n/aDiazinon Insecticide 39572 333-41-5 0.005 HA-L 0.6Diazinon, oxon Insecticide 61638 962-58-3 0.01 n/a n/a3,4-Dichloroaniline Degradate 61625 95-76-1 0.004 n/a n/aDichlorvos Fumigant 38775 62-73-7 0.012 n/a n/aDicrotophos Insecticide 38454 141-66-2 0.084 n/a n/aDieldrin Insecticide 39381 60-57-1 0.009 RSD5 0.02

Table 2C. Pesticides and pesticide degradates, primary use or source, U.S. Geological Survey (USGS) parameter code, Chemical Abstracts Service (CAS) number, USGS laboratory reporting levels (LRLs) for the USGS’s National Water Quality Laboratory (NWQL) analytical Schedule 2003, type of comparison threshold for ground-water detections, and the corresponding threshold level.[The five digit number below the USGS parameter code is used to uniquely identify a specific constituent or property. HA-L, lifetime health advisory (U.S. Environmental Protection Agency, 2004b); MCL-CA, California Department of Health Services Maximum Contaminant Level (California Department of Health Services, 2005a); MCL-US, U.S. Environmental Protection Agency Maximum Contaminant Level (U.S. Environmental Protection Agency, 2004b); n/a, not applicable; RSD5, risk-specific dose at 10E-5 (Note: RSD5 = RSD4 (risk level = 10E-4)/10) (U.S. Environmental Protection Agency, 2004b); μg/L, microgram per liter]

42 California GAMA Program: Ground-Water Quality Data in the Northern San Joaquin Basin Study Unit, 2005
Constituent Primary use/source USGS parameter code CAS number LRL (μg/L) Type of comparison threshold Threshold level (μg/L)

2,6-Diethylaniline Degradate 82660 579-66-8 0.006 n/a n/aDimethoate Insecticide 82662 60-51-5 0.006 n/a n/aEthion Insecticide 82346 563-12-2 0.004 n/a n/aEthion monoxon Degradate 61644 17356-42-2 0.002 n/a n/a2-Ethyl-6-methylaniline Degradate 61620 24549-06-2 0.004 n/a n/aFenamiphos Insecticide 61591 22224-92-6 0.029 HA-L 2Fenamiphos sulfone Degradate 61645 31972-44-8 0.049 n/a n/aFenamiphos sulfoxide Degradate 61646 31972-43-7 0.039 n/a n/aFipronil Insecticide 62166 120068-37-3 0.016 n/a n/aFipronil sulfide Degradate 62167 120067-83-6 0.013 n/a n/aFipronil sulfone Degradate 62168 120068-36-2 0.024 n/a n/aFonofos Insecticide 04095 944-22-9 0.003 HA-L 10Hexazinone Herbicide 04025 51235-04-2 0.013 HA-L 400Iprodione Fungicide 61593 36734-19-7 0.387 n/a n/aIsofenphos Insecticide 61594 25311-71-1 0.003 n/a n/aMalaoxon Degradate 61652 1634-78-2 0.03 n/a n/aMalathion Insecticide 39532 121-75-5 0.027 HA-L 100Metalaxyl Fungicide 61596 57837-19-1 0.005 n/a n/aMethidathion Insecticide 61598 950-37-8 0.006 n/a n/aMetolachlor Herbicide 39415 51218-45-2 0.006 HA-L 100Metribuzin Herbicide 82630 21087-64-9 0.006 HA-L 200Myclobutanil Fungicide 61599 88671-89-0 0.008 n/a n/aParaoxon-methyl Insecticide 61664 950-35-6 0.03 n/a n/aParathion-methyl Insecticide 82667 298-00-0 0.015 n/a n/a1-Naphthol Degradate 49295 90-15-3 0.088 n/a n/a

Table 2C. Pesticides and pesticide degradates, primary use or source, U.S. Geological Survey (USGS) parameter code, Chemical Abstracts Service (CAS) number, USGS laboratory reporting levels (LRLs) for the USGS’s National Water Quality Laboratory (NWQL) analytical Schedule 2003, type of comparison threshold for ground-water detections, and the corresponding threshold level—Continued.[The five digit number below the USGS parameter code is used to uniquely identify a specific constituent or property. HA-L, lifetime health advisory (U.S. Environmental Protection Agency, 2004b); MCL-CA, California Department of Health Services Maximum Contaminant Level (California Department of Health Services, 2005a); MCL-US, U.S. Environmental Protection Agency Maximum Contaminant Level (U.S. Environmental Protection Agency, 2004b); n/a, not applicable; RSD5, risk-specific dose at 10E-5 (Note: RSD5 = RSD4 (risk level = 10E-4)/10) (U.S. Environmental Protection Agency, 2004b); μg/L, microgram per liter]

Tables 43
Constituent Primary use/source USGS parameter code CAS number LRL (μg/L) Type of comparison threshold Threshold level (μg/L)

Pendimethalin Herbicide 82683 40487-42-1 0.022 n/a n/aPhorate Insecticide 82664 298-02-2 0.011 n/a n/aPhorate oxon Degradate 61666 2600-69-3 0.105 n/a n/aPhosmet Insecticide 61601 732-11-6 0.008 n/a n/aPhosmet oxon Degradate 61668 3735-33-9 0.051 n/a n/aPrometon Herbicide 04037 1610-18-0 0.01 HA-L 100Prometryn Herbicide 04036 7287-19-6 0.005 n/a n/aPropyzamide Herbicide 82676 23950-58-5 0.004 n/a n/aSimazine Herbicide 04035 122-34-9 0.005 MCL-US 4Tebuthiuron Herbicide 82670 34014-18-1 0.016 HA-L 500Terbufos Insecticide 82675 13071-79-9 0.017 HA-L 0.9Terbufos oxon sulfone Degradate 61674 56070-15-6 0.068 n/a n/aTerbuthylazine Herbicide 04022 5915-41-3 0.01 n/a n/aTrifluralin Herbicide 82661 1582-09-8 0.009 HA-L 5

Table 2C. Pesticides and pesticide degradates, primary use or source, U.S. Geological Survey (USGS) parameter code, Chemical Abstracts Service (CAS) number, USGS laboratory reporting levels (LRLs) for the USGS’s National Water Quality Laboratory (NWQL) analytical Schedule 2003, type of comparison threshold for ground-water detections, and the corresponding threshold level—Continued.[The five digit number below the USGS parameter code is used to uniquely identify a specific constituent or property. HA-L, lifetime health advisory (U.S. Environmental Protection Agency, 2004b); MCL-CA, California Department of Health Services Maximum Contaminant Level (California Department of Health Services, 2005a); MCL-US, U.S. Environmental Protection Agency Maximum Contaminant Level (U.S. Environmental Protection Agency, 2004b); n/a, not applicable; RSD5, risk-specific dose at 10E-5 (Note: RSD5 = RSD4 (risk level = 10E-4)/10) (U.S. Environmental Protection Agency, 2004b); μg/L, microgram per liter]

44 California GAMA Program: Ground-Water Quality Data in the Northern San Joaquin Basin Study Unit, 2005
Constituent Primary use/source USGS parameter code CAS number LRL (μg/L) Type of comparison threshold Threshold level (μg/L)

Acifluorfen Herbicide 49315 50594-66-6 0.028 n/a n/a

Aldicarb1 Insecticide 49312 116-06-3 0.04 MCL-US 3Aldicarb sulfone Insecticide/degradate 49313 1646-88-4 0.018 MCL-US 3Aldicarb sulfoxide Degradate 49314 1646-87-3 0.022 MCL-US 4Atrazine Herbicide 39632 1912-24-9 0.008 MCL-CA 1Bendiocarb Insecticide 50299 22781-23-3 0.02 n/a n/aBenomyl Fungicide 50300 17804-35-2 0.022 n/a n/aBensulfuron-methyl Herbicide 61693 83055-99-6 0.018 n/a n/aBentazon Herbicide 38711 25057-89-0 0.012 MCL-CA 18Bromacil Herbicide 04029 314-40-9 0.018 HA-L 90Bromoxynil Herbicide 49311 1689-84-5 0.028 n/a n/aCaffeine Beverages 50305 58-08-2 0.018 n/a n/aCarbaryl Herbicide 49310 63-25-2 0.018 HA-L 700Carbofuran Herbicide 49309 1563-66-2 0.016 MCL-CA 18Chloramben, methyl ester Herbicide 61188 7286-84-2 0.024 n/a n/aChlordiamino-s-triazine Degradate 04039 3397-62-4 0.04 n/a n/aChlorimuron-ethyl Herbicide 50306 90982-32-4 0.032 n/a n/a2-Chloro-6-ethylamino-4-amino-s-triazine

(deisopropylatrazine)

Degradate 04038 1007-28-9 0.08 n/a n/a

2-Chloro-4-isopropylamino-6-amino-s-triazine 

(deethylatrazine)

Degradate 04040 6190-65-4 0.028 n/a n/a

Chlorothalonil Herbicide 49306 1897-45-6 0.035 RSD5 15Clopyralid Herbicide 49305 1702-17-6 0.024 n/a n/aCycloate Herbicide 04031 1134-23-2 0.014 n/a n/a

Table 2D. Pesticides, pesticide degradates and caffeine, primary use or source, U.S. Geological Survey (USGS) parameter code, Chemical Abstracts Service (CAS) number, USGS laboratory reporting level (LRL) for the USGS’s National Water Quality Laboratory analytical Schedule 2060, type of comparison threshold for ground-water detections, and the corresponding threshold level.[The five digit number below the USGS parameter code is used to uniquely identify a specific constituent or property. HA-L, lifetime health advisory (U.S. Environmental Protection Agency, 2004b); MCL-CA, California Department of Health Services Maximum Contaminant Level (California Department of Health Services, 2005a); MCL-US, U.S. Environmental Protection Agency Maximum Contaminant Level (U.S. Environmental Protection Agency, 2004b); n/a, not applicable; RSD5, risk-specific dose at 10E-5 (Note: RSD5 = RSD4 (risk level = 10E-4)/10) (U.S. Environmental Protection Agency, 2004b); μg/L, microgram per liter]

See footnote at end of table.

Tables 45
Constituent Primary use/source USGS parameter code CAS number LRL (μg/L) Type of comparison threshold Threshold level (μg/L)

Dacthal monoacid Degradate 49304 887-54-7 0.028 n/a n/a

Dicamba Herbicide 38442 1918-00-9 0.036 HA-L 2002,4-Dichlorophenoxyacetic acid (2,4-D) Herbicide 39732 94-75-7 0.038 MCL-US 702,4-Dichlorophenoxyacetic acid (2,4-D) methyl ester Herbicide 50470 1928-38-7 0.016 n/a n/a4-(2,4-Dichlorophenoxy)butyric acid (2,4-DB) Herbicide 38746 94-82-6 0.020 n/a n/aDichlorprop Herbicide 49302 120-36-5 0.028 n/a n/aDinoseb Herbicide 49301 88-85-7 0.038 MCL-CA 7Diphenamid Herbicide 04033 957-51-7 0.01 HA-L 200Diuron Herbicide 49300 330-54-1 0.014 HA-L 10Fenuron Herbicide 49297 101-42-8 0.018 n/a n/aFlumetsulam Herbicide 61694 98967-40-9 0.04 n/a n/aFluometuron Herbicide 38811 2164-17-2 0.016 HA-L 903-Hydroxycarbofuran Degradate 49308 16655-82-6 0.008 n/a n/a2-Hydroxy-4-isopropylamino-6-ethylamino-s-triazine Degradate 50355 2163-68-0 0.032 n/a n/aImazaquin Herbicide 50356 81335-37-7 0.036 n/a n/aImazethapyr Herbicide 50407 81335-77-5 0.038 n/a n/aImidacloprid Insecticide 61695 138261-41-3 0.02 n/a n/a3-Ketocarbofuran Degradate 50295 16709-30-1 0.02 n/a n/aLinuron Herbicide 38478 330-55-2 0.014 n/a n/a2-Methyl-4-chlorophenoxyacetic acid (MCPA) Herbicide 38482 94-74-6 0.03 HA-L 44-(2-Methyl-4-chlorophenoxy) butyric acid (MCPB) Herbicide 38487 94-81-5 0.01 n/a n/aMetalaxyl Fungicide 50359 57837-19-1 0.012 n/a n/aMethiocarb Insecticide 38501 2032-65-7 0.01 n/a n/a

Table 2D. Pesticides, pesticide degradates and caffeine, primary use or source, U.S. Geological Survey (USGS) parameter code, Chemical Abstracts Service (CAS) number, USGS laboratory reporting level (LRL) for the USGS’s National Water Quality Laboratory analytical Schedule 2060, type of comparison threshold for ground-water detections, and the corresponding threshold level—Continued.[The five digit number below the USGS parameter code is used to uniquely identify a specific constituent or property. HA-L, lifetime health advisory (U.S. Environmental Protection Agency, 2004b); MCL-CA, California Department of Health Services Maximum Contaminant Level (California Department of Health Services, 2005a); MCL-US, U.S. Environmental Protection Agency Maximum Contaminant Level (U.S. Environmental Protection Agency, 2004b); n/a, not applicable; RSD5, risk-specific dose at 10E-5 (Note: RSD5 = RSD4 (risk level = 10E-4)/10) (U.S. Environmental Protection Agency, 2004b); μg/L, microgram per liter]

See footnote at end of table.

46 California GAMA Program: Ground-Water Quality Data in the Northern San Joaquin Basin Study Unit, 2005
Constituent Primary use/source USGS parameter code CAS number LRL (μg/L) Type of comparison threshold Threshold level (μg/L)

Methomyl Insecticide 49296 16752-77-5 0.02 HA-L 200

3-(4-Chlorophenyl)-1-methyl urea Degradate 61692 5352-88-5 0.036 n/a n/aMetsulfuron methyl1 Herbicide 61697 74223-64-6 0.025 n/a n/aNeburon Herbicide 49294 555-37-3 0.012 n/a n/aNicosulfuron Herbicide 50364 111991-09-4 0.04 n/a n/aNorflurazon Herbicide 49293 27314-13-2 0.02 n/a n/aOryzalin Herbicide 49292 19044-88-3 0.012 n/a n/aOxamyl Insecticide 38866 23135-22-0 0.03 MCL-CA 50Picloram Herbicide 49291 1918-02-01 0.032 MCL-US 500Propham Herbicide 49236 122-42-9 0.03 HA-L 100Propiconazole Fungicide 50471 60207-90-1 0.01 n/a n/aPropoxur Insecticide 38538 114-26-1 0.008 n/a n/aSiduron Herbicide 38548 1982-49-6 0.02 n/a n/aSulfometuron-methyl Herbicide 50337 74222-97-2 0.038 n/a n/aTebuthiuron Herbicide 82670 34014-18-1 0.026 HA-L 500Terbacil Herbicide 04032 5902-51-2 0.016 HA-L 90Triclopyr Herbicide 49235 55335-06-3 0.026 n/a n/a

1Although listed as an LRL, these constituents are reported using method reporting levels (MRLs)

Table 2D. Pesticides, pesticide degradates and caffeine, primary use or source, U.S. Geological Survey (USGS) parameter code, Chemical Abstracts Service (CAS) number, USGS laboratory reporting level (LRL) for the USGS’s National Water Quality Laboratory analytical Schedule 2060, type of comparison threshold for ground-water detections, and the corresponding threshold level—Continued.The five digit number below the USGS parameter code is used to uniquely identify a specific constituent or property. HA-L, lifetime health advisory (U.S. Environmental Protection Agency, 2004b); MCL-CA, California Department of Health Services Maximum Contaminant Level (California Department of Health Services, 2005a); MCL-US, U.S. Environmental Protection Agency Maximum Contaminant Level (U.S. Environmental Protection Agency, 2004b); n/a, not applicable; RSD5, risk-specific dose at 10E-5 (Note: RSD5 = RSD4 (risk level = 10E-4)/10) (U.S. Environmental Protection Agency, 2004b); μg/L, microgram per liter]

Tables 47
Constituent Primary use/source USGS parameter code CAS number MRL (μg/L) Type of comparison threshold Threshold level (μg/L)

1,2-Dibromo-3-chloropropane (DBCP) Fumigant 82625 96-12-8 0.03 MCL-US 0.21,2-Dibromoethane (EDB) Fumigant/solvent 77651 106-93-4 0.036 MCL-US 0.05

Table 2E. Low-detection limit 1,2-dibromo-3-chloropropane (DBCP) and 1,2-dibromoethane (EDB), primary use or source, U.S. Geological Survey (USGS) parameter code, Chemical Abstracts Service (CAS) number, USGS minimum reporting levels (MRLs) for the USGS’s National Water Quality Laboratory analytical Schedule 1306, type of comparison threshold for ground-water detections, and the corresponding threshold level.[The five digit number below the USGS parameter code is used to uniquely identify a specific constituent or property. MCL-US, U.S. Environmental Protection Agency Maximum Contaminant Level (U.S. Environmental Protection Agency, 2004b); μg/L, microgram per liter]

48 California GAMA Program: Ground-Water Quality Data in the Northern San Joaquin Basin Study Unit, 2005
Constituent Primary uses/sources USGS parameter code CAS number LRL (μg/L) Type of comparison threshold Threshold level (μg/L)

Acetophenone Fragrance in detergent and tobacco, flavor in beverages 62064 98-86-2 0.5 n/a n/aAcetyl hexamethyl tetrahydronaphthalene (AHTN) Musk fragrance 62065 21145-77-7 0.5 n/a n/aAnthracene Wood preservative, tar, diesel, crude oil, combustion 

product 

34221 120-12-7 0.5 n/a n/a

Anthraquinone Manufactured dye/textiles, seed treatment, bird 

repellant

62066 84-65-1 0.5 n/a n/a

Benzo[a]pyrene Cancer research, combustion product 34248 50-32-8 0.5 MCL-US 0.2Benzophenone Fixative for perfumes and soaps 62067 119-61-9 0.5 n/a n/aß-Sitosterol Plant sterol 62068 83-46-5 2 n/a n/aß-Stigmastanol Plant sterol 62086 19466-47-8 2 n/a n/aBisphenol A Manufactured polycarbonate resins, antioxidant, 

flame retardant

62069 80-05-7 1 n/a n/a

3-tert-Butyl-4-hydroxy anisole (BHA) Antioxidant, general preservative 62059 25013-16-5 5 n/a n/aBromacil Herbicide, greater than 80 percent noncrop usage 

on grass/brush 

04029 314-40-9 0.5 n/a n/a

Bromoform (tribromomethane) Byproduct wastewater treatment, military/explosives 34288 75-25-2 0.5 MCL-US 100Caffeine Beverages 50305 58-08-2 0.5 n/a n/aCamphor Flavor, odorant, ointments 62070 76-22-2 0.5 n/a n/aCarbaryl Insecticide, crop and garden uses 82680 63-25-2 1 HA-L 700Carbazole Insecticide, manuf. dyes, explosives, and lubricants 62071 86-74-8 0.5 n/a n/aChlorpyrifos Insecticide, domestic pest and termite control 38933 2921-88-2 0.5 HA-L 20Cholesterol Fecal indicator, plant sterol 62072 57-88-5 2 n/a n/a3ß-Coprostanol Carnivore fecal indicator 62057 360-68-9 2 n/a n/aCotinine Primary nicotine metabolite 62005 486-56-6 1 n/a n/a4-Cumylphenol Nonionic detergent metabolite 62060 599-64-4 1 n/a n/a

Table 2F. Wastewater-indicator constituents, primary uses or sources, U.S. Geological Survey (USGS) parameter code, Chemical Abstracts Service (CAS) number, USGS laboratory reporting levels (LRLs) for the USGS National Water Quality Laboratory analytical Schedule 1433, type of comparison threshold for ground-water detections, and the corresponding threshold level.[The five digit number below the USGS parameter code is used to uniquely identify a specific constituent or property. HA-L, lifetime health advisory (U.S. Environmental Protection Agency, 2004b); MCLCA, California Department of Health Services Maximum Contaminant Level (California Department of Health Services, 2005a); MCL-US, U.S. Environmental Protection Agency Maximum Contaminant Level (U.S. Environmental Protection Agency, 2004b); n/a, not applicable; UV, ultraviolet; μg/L, microgram per liter]

Tables 49
Constituent Primary uses/sources USGS parameter code CAS number LRL (μg/L) Type of comparison threshold Threshold level (μg/L)

Diazinon Insecticide, greater than 40 percent nonagricultural usage, ants, flies 39572 333-41-5 0.5 HA-L 0.61,4-Dichlorobenzene Moth repellant, fumigant, deodorant 34572 106-46-7 0.5 MCL-CA 5Dichlorvos Insecticide degradate of naled or trichlofon 38775 62-73-7 1 n/a n/a2,6-Dimethylnaphthalene Diesel/kerosene (trace in gasoline) 62055 581-42-0 0.5 n/a n/ad-Limonene Fungicide, antimicrobial, antiviral, fragrance in aerosols 62073 5989-27-5 0.5 n/a n/aFluoranthene Component of coal tar and asphalt 34377 206-44-0 0.5 n/a n/aHexahydrohexamethylcyclopentabenzopyran (HHCB) Musk fragrance 62075 1222-05-5 0.5 n/a n/aIndole Pesticide ingredient, fragrance in coffee 62076 120-72-9 0.5 n/a n/aIsoborneol Fragrance in perfumery, in disinfectants 62077 124-76-5 0.5 n/a n/aIsophorone Solvent for lacquer, plastic, oil, silicon, resin 34409 78-59-1 0.5 HA-L 100Isopropylbenzene Manufactured phenol/acetone, fuels and paint thinner 62078 98-82-8 0.5 n/a n/aIsoquinoline Flavors and fragrances 62079 119-65-3 0.5 n/a n/aMenthol Cigarettes, cough drops, liniment, mouthwash 62080 89-78-1 0.5 n/a n/aMetalaxyl Herbicide, fungicide, mildew, blight, pathogens, golf/

turf 

50359 57837-19-1 0.5 n/a n/a

5-Methyl-1H-benzotriazole Antioxidant in antifreeze and deicers 62063 136-85-6 2 n/a n/a3-Methyl-1(H)-indole (Skatole) Fragrance, stench in feces and coal tar 62058 83-34-1 1 n/a n/a1-Methylnaphthalene Gasoline, diesel fuel, or crude oil 62054 90-12-0 0.5 n/a n/a2-Methylnaphthalene Gasoline, diesel fuel, or crude oil 62056 91-57-6 0.5 n/a n/aMethyl salicylate Liniment, food, beverage, UV-absorbing lotion 62081 119-36-8 0.5 n/a n/aMetolachlor Herbicide, indicator of agricultural drainage 39415 51218-45-2 0.5 HA-L 100N,N-diethyl-meta-toluamide (DEET) Insecticide, urban uses, mosquito repellent 62082 134-62-3 0.5 n/a n/aNaphthalene Fumigant, moth repellent, major component of gasoline 34443 91-20-3 0.5 HA-L 1004-Nonylphenol diethoxylates Nonionic detergent metabolite 62083 n/a 5 n/a n/a

Table 2F. Wastewater-indicator constituents, primary uses or sources, U.S. Geological Survey (USGS) parameter code, Chemical Abstracts Service (CAS) number, USGS laboratory reporting levels (LRLs) for the USGS National Water Quality Laboratory analytical Schedule 1433, type of comparison threshold for ground-water detections, and the corresponding threshold level—Continued.[The five digit number below the USGS parameter code is used to uniquely identify a specific constituent or property. HA-L, lifetime health advisory (U.S. Environmental Protection Agency, 2004b); MCL-CA, California Department of Health Services Maximum Contaminant Level (California Department of Health Services, 2005a); MCL-US, U.S. Environmental Protection Agency Maximum Contaminant Level (U.S. Environmental Protection Agency, 2004b); n/a, not applicable; UV, ultraviolet; μg/L, microgram per liter]

50 California GAMA Program: Ground-Water Quality Data in the Northern San Joaquin Basin Study Unit, 2005
Constituent Primary uses/sources USGS parameter code CAS number LRL (μg/L) Type of comparison threshold Threshold level (μg/L)

4-Octylphenol diethoxylates Nonionic detergent metabolite 61705 n/a 1 n/a n/a4-Octylphenol monoethoxylates Nonionic detergent metabolite 61706 n/a 1 n/a n/a4-n-Octylphenol Nonionic detergent metabolite 62061 1806-26-4 1 n/a n/a4-tert-Octylphenol Nonionic detergent metabolite 62062 140-66-9 1 n/a n/apara-Nonylphenol (total) Nonionic detergent metabolite 62085 84852-15-3 5 n/a n/apara-Cresol Wood preservative 62084 106-44-5 1 n/a n/aPentachlorophenol Herbicide, fumigant, wood preservative, termite control 34459 87-86-5 2 MCL-US 1Phenanthrene Manufactured explosives, tar, diesel, crude oil, 

combustion product 

34462 85-01-8 0.5 n/a n/a

Phenol Disinfectant, product manufacturing, leachate 34466 108-95-2 0.5 HA-L 2,000Prometon Herbicide (noncrop only) applied prior to blacktop 04037 1610-18-0 0.5 HA-L 100Pyrene Component of coal tar and asphalt 34470 129-00-0 0.5 n/a n/aTetrachloroethylene (PCE) Solvent, degreaser, veterinary anthelmintic 34476 127-18-4 0.5 MCL-US 5Tri(2-butoxyethyl)phosphate Flame retardant 62093 78-51-3 0.5 n/a n/aTri(2-chloroethyl)phosphate Plasticizer, flame retardant 62087 115-96-8 0.5 n/a n/aTributyl phosphate Antifoaming agent, flame retardant 62089 126-73-8 0.5 n/a n/aTriclosan Disinfectant, antimicrobial 62090 3380-34-5 1 n/a n/aTriethyl citrate (ethyl citrate) Cosmetics, pharmaceuticals 62091 77-93-0 0.5 n/a n/aTriphenyl phosphate Plasticizer, resin, wax, finish, roofing paper, 

flame retardant

62092 115-86-6 0.5 n/a n/a

Tri(dichlorisopropyl)phosphate Flame retardant 62088 13674-87-8 0.5 n/a n/a

Table 2F. Wastewater-indicator constituents, primary uses or sources, U.S. Geological Survey (USGS) parameter code, Chemical Abstracts Service (CAS) number, USGS laboratory reporting levels (LRLs) for the USGS National Water Quality Laboratory analytical Schedule 1433, type of comparison threshold for ground-water detections, and the corresponding threshold level—Continued.[The five digit number below the USGS parameter code is used to uniquely identify a specific constituent or property. HA-L, lifetime health advisory (U.S. Environmental Protection Agency, 2004b); MCL-CA, California Department of Health Services Maximum Contaminant Level (California Department of Health Services, 2005a); MCL-US, U.S. Environmental Protection Agency Maximum Contaminant Level (U.S. Environmental Protection Agency, 2004b); n/a, not applicable; UV, ultraviolet; μg/L, microgram per liter]

Tables 51
Constituent Primary use/source CAS number MDL (μg/L) Type of comparison threshold Threshold level (μg/L)

Perchlorate Rocket fuel, fireworks, flares 14797-73-0 0.5 NL 61,2,3-Trichloropropane (1,2,3-TCP) Industrial solvent, organic synthesis 96-18-4 0.005 NL 0.005N-Nitrosodimethylamine (NDMA) Rocket fuel, plasticizer 62-75-9 0.002 NL 0.010

Table 2G. Constituents of special interest, primary use or source, Chemical Abstracts Service (CAS) number, Montgomery Watson Harza Laboratory method detection limits (MDLs), type of comparison threshold for ground-water detections, and the corresponding threshold level.[NL, notification level (California Department of Health Services, 2005d); μg/L, microgram per liter]

Constituent

USGS

 parameter 

code

CAS

number

 LRL 

(mg/L)

Type of

 comparison

 threshold

Threshold level 

(mg/L)

Ammonia 00608 7664-41-7 0.04 HA-L 30Nitrite 00613 14797-65-0 0.008 MCL-US 1 (as N)Nitrate plus nitrite 00631 n/a 0.06 MCL-US 10 (as N)Total nitrogen (ammonia, nitrite, nitrate, organic nitrogen) 62854 17778-88-0 0.06 n/a n/aPhosphorus, phosphate, orthophosphate 00671 14265-44-2 0.006 n/a n/aDissolved organic carbon (DOC) 00681 n/a 0.3 n/a n/a

Table 2H. Nutrients and dissolved organic carbon, U.S. Geological Survey (USGS) parameter code, Chemical Abstracts Service (CAS) number, USGS laboratory reporting levels (LRLs) for the USGS’s National Water Quality Laboratory analytical Schedule 2755 and laboratory code 2613, type of comparison threshold for ground-water detections, and the corresponding threshold level.[The five digit number below the USGS parameter code is used to uniquely identify a specific constituent or property. HA-L, lifetime health advisory (U.S. Environmental Protection Agency, 2004b); MCL-US, U.S. Environmental Protection Agency Maximum Contaminant Level (U.S. Environmental Protection Agency, 2004b); mg/L, milligram per liter; N, nitrogen; n/a, not applicable]

52 California GAMA Program: Ground-Water Quality Data in the Northern San Joaquin Basin Study Unit, 2005
Constituent USGS

 parameter code

CAS 

number

 LRL 

(mg/L)

Type of 

comparison 

threshold

Threshold 

level 

(mg/L)

 Major ions

Bromide 71870 24959-67-9 0.02 n/a n/a

Calcium 00915 7440-70-2 0.02 n/a n/a

Chloride 00940 16887-00-6 0.20 SMCL-US 250

Fluoride 00950 16984-48-8 0.1 MCL 2

Iodide 71865 7553-56-2 0.002 n/a n/a

Magnesium 00925 7439-95-4 0.008 n/a n/a

Potassium 00935 7440-09-7 0.16 n/a n/a

Silica 00955 7631-86-9 0.04 n/a n/a

Sodium 00930 7440-23-5 0.2 n/a n/a

Sulfate 00945 14808-79-8 0.18 SMCL-US 250

Residue on evaporation 70300 n/a 10 SMCL-US 500

Constituent USGS

 parameter code

CAS 

number

 LRL 

(μg/L)

Type of 

comparison 

threshold

Threshold 

level 

(μg/L)

 Trace elements

Aluminum 01106 7429-90-5 1.6 MCL-US 1,000

Antimony 01095 7440-36-0 0.2 MCL-US 6

Arsenic 01000 7440-38-2 0.2 MCL-US 10

Barium 01005 7440-39-3 0.2 MCL-CA 1,000

Beryllium 01010 7440-41-7 0.06 MCL-US 4

Boron 01020 7440-42-8 8 NL 1,000

Cadmium 01025 7440-43-9 0.04 MCL-US 5

Chromium 01030 7440-47-3 0.8 MCL-CA 50

Cobalt 01035 7440-48-4 0.014 n/a n/a

Copper 01040 7440-50-8 0.4 MCL-US 11,300

Iron 01046 7439-89-6 6 HA-L 300

Lead 01049 7439-92-1 0.08 MCL-US 115

Lithium 01130 7439-93-2 0.6 n/a n/a

Manganese 01056 7439-96-5 0.2 NL 500

Mercury 71890 7439-97-6 0.01 MCL-US 2

Molybdenum 01060 7439-98-7 0.4 HA-L 40

Table 2I. Major ions and trace elements, U.S. Geological Survey (USGS) parameter code, Chemical Abstracts Service (CAS) number, 

USGS laboratory reporting levels (LRLs) for the USGS’s National Water Quality Laboratory analytical Schedule 1948, type of comparison 

threshold for ground-water detections, and the corresponding threshold level.

[The five digit number below the USGS parameter code is used to uniquely identify a specific constituent or property. Standard conversion from mass units to 

activity is 0.67 pCi/μg for uranium (U.S. Environmental Protection Agency, 2004a). HA-L, lifetime health advisory (U.S. Environmental Protection Agency, 

2004b); MCL-CA, California Department of Health Services Maximum Contaminant Level (California Department of Health Services, 2005a); MCL-US, U.S. 

Environmental Protection Agency Maximum Contaminant Level (U.S. Environmental Protection Agency, 2004b); n/a, not applicable; NL, notification level 

(California Department of Health Services, 2005d); RSD5, risk-specific dose at 10E-5 (Note: RSD5 = RSD4 (risk level = 10E-4)/10) (U.S. Environmental Protection Agency, 2004b); SMCL-US, U.S. Environmental Protection Agency Secondary Maximum Contaminant Level (U.S. Environmental Protection Agency, 

2004b); mg/L, milligram per liter; pCi/μg, picocurie per microgram; μg/L, microgram per liter]

See footnote at end of table.

Tables 53
Constituent USGS

 parameter code

CAS 

number

 LRL 

(mg/L)

Type of 

comparison 

threshold

Threshold 

level 

(mg/L)

Nickel 01065 7440-02-0 0.06 MCL-CA 100

Selenium 01145 7782-49-2 0.4 MCL-US 50

Silver 01075 7440-22-4 0.2 HA-L 100

Strontium 01080 7440-24-6 0.4 HA-L 4,000

Thallium 01057 7440-28-0 0.04 MCL-US 2

Tungsten 01155 7440-33-7 0.5 n/a n/a

Uranium 22703 7440-61-1 0.04 MCL-US 30

Vanadium 01085 7440-62-2 0.14 NL 50

Zinc 01090 7440-66-6 0.6 HA-L 2,000

1

Values refered to as MCLs for lead and copper are “notification levels” under the lead and copper rule (California Department of Health Services, 2005a).

Table 2I. Major ions and trace elements, U.S. Geological Survey (USGS) parameter code, Chemical Abstracts Service (CAS) number, 

USGS laboratory reporting levels (LRLs) for the USGS’s National Water Quality Laboratory analytical Schedule 1948, type of comparison 

threshold for ground-water detections, and the corresponding threshold level—Continued.

[The five digit number below the USGS parameter code is used to uniquely identify a specific constituent or property. Standard conversion from mass units to 

activity is 0.67 pCi/μg for uranium (U.S. Environmental Protection Agency, 2004a). HA-L, lifetime health advisory (U.S. Environmental Protection Agency, 

2004b); MCL-CA, California Department of Health Services Maximum Contaminant Level (California Department of Health Services, 2005a); MCL-US, U.S. 

Environmental Protection Agency Maximum Contaminant Level (U.S. Environmental Protection Agency, 2004b); n/a, not applicable; NL, notification level 

(California Department of Health Services, 2005d); RSD5, risk-specific dose at 10E-5 (Note: RSD5 = RSD4 (risk level = 10E-4)/10) (U.S. Environmental Protection Agency, 2004b); SMCL-US, U.S. Environmental Protection Agency Secondary Maximum Contaminant Level (U.S. Environmental Protection Agency, 

2004b); mg/L, milligram per liter; pCi/μg, picocurie per microgram; μg/L, microgram per liter]

Constituent

USGS

parameter 

code

CAS 

number

MDL

(μg/L)

Type of 

comparison

 threshold

Threshold 

level 

(μg/L)

Iron 01046 7439-89-6 1 HA-L 300

Iron(II) 01047 7439-89-6 1 n/a n/a

Arsenic 99033 7440-38-2 0.5 MCL-US 10

Arsenic(III) 99034 1327-53-3 1 n/a n/a

Chromium 01030 7440-47-3 0.1 MCL-CA 50

Chromium(VI), hexavalent 01032 18540-29-9 0.1 DLR 1

Table 2J. Iron, arsenic, and chromium speciation, U.S. Geological Survey (USGS) parameter code, Chemical Abstracts Service (CAS) 

number, USGS method detection limit (MDL) for the USGS’s Trace Metal Laboratory, Boulder, Colorado, type of comparison threshold for 

ground-water detections, and the corresponding threshold level.

[The five digit number below the USGS parameter code is used to uniquely identify a specific constituent or property. DLR, detection level for the purpose 

of reporting (California Department of Health Services, 2005a); HA-L, lifetime health advisory (U.S. Environmental Protection Agency, 2004b); MCL-CA, 

California Department of Health Services Maximum Contaminant Level (California Department of Health Services, 2005a); MCL-US, U.S. Environmental 

Protection Agency Maximum Contaminant Level (U.S. Environmental Protection Agency, 2004b); n/a, not applicable; μg/L, microgram per liter]

54 California GAMA Program: Ground-Water Quality Data in the Northern San Joaquin Basin Study Unit, 2005

Constituent USGS

 parameter code

CAS 

number

 LRL 

(μg/L)

Type of 

comparison 

threshold

Threshold 

level 

(μg/L)
Constituent

USGS 

parameter 

code

CAS

number

Reporting

 level 

type

Reporting 

units

Reporting 

level/

uncertainty

Type of 

comparison 

threshold

Threshold 

level

Radon-222 82303 14859-67-7 SSMDC pCi/L see Table 21 Proposed MCL-US 3001Tritium 07000 10028-17-8 MRL pCi/L 1 MCL-CA 20,0002Deuterium/protium 82082 7782-39-0 / 

1333-74-0

MU per mil 2 n/a n/a

2Oxygen-18/oxygen-16 82085 n/a / 7782-44-7 MU per mil 0.20 n/a n/a3Gross-alpha radioactivity, 72 hr count 62636 12587-46-1 SSMDC pCi/L see Table 21 MCL-US 153Gross-alpha radioactivity, 30 day count 62639 12587-46-1 SSMDC pCi/L see Table 21 MCL-US 153Gross-beta radioactivity, 72 hr count 62642 12587-47-2 SSMDC pCi/L see Table 21 MCL-CA 503Gross-beta radioactivity, 30 day count 62645 12587-47-2 SSMDC pCi/L see Table 21 MCL-CA 503Radium-226 09511 13982-63-3 SSMDC pCi/L see Table 21 MCL-US 53Radium-228 81366 15262-20-1 SSMDC pCi/L see Table 21 MCL-US 54Carbon-13/carbon-12 82081 n/a / 7440-44-0 1σ per mill n/a n/a n/a4Carbon-14 49933 14762-75-5 1σ percent 

modern

n/a n/a n/a

1U.S. Geological Survey’s National Water Quality Laboratory, Stable Isotope and Tritium Laboratory, Menlo Park, California.2U.S. Geological Survey’s Stable Isotope Laboratory, Reston, Virginia.3Eberline Analytical Services4University of Waterloo’s Environmental Isotope Laboratory and the University of Arizona’s Accelerator Mass Spectrometry Laboratory.

Table 2K. Stable isotopes and radioactive constituents, U.S. Geological Survey (USGS) parameter code, Chemical Abstracts Service (CAS) number, reporting level type, reporting units and reporting level/uncertainty, type of comparison threshold for ground-water detections, and the corresponding threshold level.[The reporting level type, reporting units, and reporting level/uncertainty are from USGS’s National Water Quality Laboratory, USGS’s Stable Isotope and Tritium Laboratory, Menlo Park, California, USGS’s Stable Isotope Laboratory, Reston, Virginia (RSIL), and the contract laboratories Eberline Analytical Services, the University of Waterloo’s Environmental Isotope Laboratory, and the University of Arizona’s Accelerator Mass Spectrometry Laboratory. The five digit number below the USGS parameter code is used to uniquely identify a specific constituent or property. Dual entries for CAS number correspond to dual entries for constituent. MCL-CA, California Department of Health Services Maximum Contaminant Level (California Department of Health Services, 2005a); MCL-US, U.S. Environmental Protection Agency Maximum Contaminant Level (U.S. Environmental Protection Agency, 2004b); MRL, Minimum Reporting Level; MU, method uncertainty; n/a, not applicable; SSMDC, sample-specific minimum detectable concentration; pCi/L, picocurie per liter]

Tables 55
Constituent USGS parameter code CAS number MU (percent) Reporting units Type of comparison threshold Threshold level

Argon 85563 7440-37-1 2 cm3 STP/g n/a n/a

Helium-3/helium-4 61040 n/a / 7440-59-7 0.75 n/a n/a n/aHelium-4 85561 7440-59-7 2 cm3 STP/g n/a n/aKrypton 85565 7439-90-9 2 cm3 STP/g n/a n/aNeon 61046 7440-01-09 2 cm3 STP/g n/a n/aTritium 07000 10028-17-8 n/a pCi/L MCL-CA 20,000Xenon 85567 7440-63-3 2 cm3 STP/g n/a n/a

Table 2L. Tritium and noble gas compounds, U.S. Geological Survey (USGS) parameter code, Chemical Abstracts Service (CAS) number, method uncertainty (MU), reporting units from the Lawrence Livermore National Laboratory, type of comparison threshold, and threshold level.[The five digit number below the USGS parameter code is used to uniquely identify a specific constituent or property. Dual entry for CAS number corresponds to dual entry for constituent. MCL-CA, California Department of Health Services Maximum Contaminant Level (California Department of Health Services, 2005a); n/a, not applicable; cm3 STP/g, cubic centimeter of gas at standard temperature and pressure per gram of water; pCi/L, picocurie per liter]

Microbial 

constiuent

USGS

 parameter code

Primary 

use/source MDL

Type of

 comparison 

threshold

Threshold 

level

Escherichia coliform—(E. coli) 90901 Sewage and animal waste indicator/Intestinal tracts of humans and animals 1 colony/100 mL TT No fecal coliforms are allowed.Total coliform (including fecal 

coliform and E. coli)

90900 Water-quality indicator/Soil, water, and 

intestinal tracts of animals

1 colony/100 mL MCL-US No more then 5.0% samples total 

coliform-positives in a month. Every sample that has total coloforms must be analyzed for fecal coliforms; no fecal coliforms are allowed.

F-specific coliphage 99335 Viral indicator/Intestinal tracts of warmblooded animals n/a TT 99.99% killed /inactivatedSomatic coliphage 99332 Viral indicator/Fecal contaminated waters n/a TT 99.99% killed /inactivated

Table 2M. Microbial constituents, U.S. Geological Survey (USGS) parameter code, primary uses and sources, method detection limit (MDL) for the USGS’s Ohio Water Microbiology Laboratory parameter codes 90901, 90900, 99335 and 99332, type of comparison threshold, and threshold level.[The five digit number below the USGS parameter code is used to uniquely identify a specific constituent or property. Abbreviations and symbols: MCL-US, U.S. Environmental Protection Agency Maximum Contaminant Level (U.S. Environmental Protection Agency, 2004b); mL, milliliter; n/a, not applicable; TT, treatment technique—a required process intended to reduce the level of a contaminant in drinking water (U.S. Environmental Protection Agency, 2004b)]

56 California GAMA Program: Ground-Water Quality Data in the Northern San Joaquin Basin Study Unit, 2005
GAMA well 

identification 

number

Sampling information Construction information

Date 

(mm/dd/yy)

Time 

(hhmm)

Sampling 

schedule

Well head 

altitude

(ft above LSD)

Year of

construction

Well depth

 (ft below 

LSD)

Top 

perforation

 (ft below LSD)

Bottom 

perforation 

(ft below LSD)

Total open 

length

(ft)

Number of 

openings 

 Cosumnes Basin wells

COS-01 12/13/04 1340 Fast 84 1978 360 300 360 60 1COS-02 12/14/04 0950 Fast 53 1995 930 750 910 160 2COS-03 12/14/04 1010 Fast 45 1988 470 250 460 210 4COS-04 12/14/04 1150 Fast 51 1985 660 180 650 470 10COS-05 12/15/04 0920 Fast 90 1972 256 nd nd nd ndCOS-06 12/15/04 1630 Fast 38 1969 117 117 nd nd ndCOS-07 01/03/05 1410 Fast 62 1978 160 nd nd nd ndCOS-08 01/03/05 1600 Fast 42 1999 575 178 570 392 11COS-09 01/10/05 0950 Fast 12 nd nd nd nd nd ndCOS-10 01/25/05 1330 Fast 79 nd nd nd nd nd nd

 Eastern San Joaquin Basin wells

ESJ-01 01/04/05 0910 Fast 28 1985 270 180 265 85 2ESJ-02 01/04/05 1110 Fast 39 1998 340 138 340 202 4ESJ-03 01/04/05 1230 Fast 42 1995 360 50 360 310 3ESJ-04 01/04/05 1550 Fast 42 nd nd nd nd nd ndESJ-05 01/10/05 1120 Fast 102 1979 535 224 455 231 2ESJ-06 01/10/05 1330 Intermediate 40 1980 403 200 395 195 1ESJ-07 01/11/05 0840 Fast 75 nd nd nd nd nd ndESJ-08 01/11/05 1010 Intermediate 126 1997 610 280 600 320 1ESJ-09 01/12/05 1210 Fast 39 1986 365 130 345 215 2ESJ-10 01/12/05 1350 Intermediate 14 2000 364 156 354 198 ndESJ-11 01/13/05 0930 Fast 12 1978 245 135 nd nd 1ESJ-12 01/13/05 1030 Slow 82 1961 270 190 270 80 1ESJ-13 01/13/05 1350 Intermediate 89 1955 619 619 nd nd nd

Table 3. Identification, sampling, altitude, and construction information for sampled wells in the Northern San Joaquin Basin Ground-Water Ambient Monitoring and Assessment (GAMA) study, California, December 2004 to February 2005.[COS, Cosumnes Basin; ESJ, Eastern San Joaquin Basin; ESJDD, Eastern San Joaquin Basin depth dependent; ESJFP, Eastern San Joaquin Basin flowpath; ESJMW, Eastern San Joaquin Basin monitoring well; ft, feet; LSD, land surface datum; mm/dd/yy, month/day/year; nd, no data; QPC, Uplands Basin; TRCY, Tracy Basin; TRCYFP, Tracy Basin flowpath]

Tables 57
GAMA well 

identification 

number

Sampling information Construction information

Date 

(mm/dd/yy)

Time 

(hhmm)

Sampling 

schedule

Well head 

altitude

(ft above LSD)

Year of

construction

Well depth

 (ft below 

LSD)

Top 

perforation

 (ft below LSD)

Bottom 

perforation 

(ft below LSD)

Total open 

length

(ft)

Number of 

openings 

ESJ-14 01/13/05 1430 Intermediate 20 2001 212 nd nd nd ndESJ-15 01/25/05 0910 Intermediate 11 1954 268 170 236 66 1ESJ-16 02/08/05 0910 Intermediate 34 1954 427 196 419 223 1ESJ-17 02/14/05 1120 Intermediate 92 1985 390 290 390 100 1ESJ-18 02/15/05 0810 Intermediate 100 nd nd nd nd nd ndESJ-19 02/18/05 1000 Slow 17 1957 519 195 495 300 3

 Tracy Basin wells

TRCY-01 01/05/05 1350 Fast 16 1953 502 384 480 96 1TRCY-02 01/05/05 1540 Fast 62 1994 200 50 200 150 2TRCY-03 01/06/05 1030 Slow 207 1989 900 420 890 470 1TRCY-04 01/06/05 1110 Fast 52 1993 325 nd 325 325 2TRCY-05 01/06/05 1300 Fast 54 1980 380 nd nd nd ndTRCY-06 01/06/05 1510 Fast 7 nd nd nd nd nd ndTRCY-07 02/08/05 1120 Slow 2 1984 83 23 73 50 2TRCY-08 02/08/05 1200 Fast 105 1997 340 320 340 20 1TRCY-09 02/09/05 1030 Intermediate –3 nd nd nd nd nd ndTRCY-10 02/17/05 1030 Fast –10 1978 185 175 185 10 1TRCY-11 02/17/05 1430 Intermediate 26 1985 400 310 400 90 2

 Upland Basin wells

QPC-01 01/11/05 1050 Slow 172 1942 nd nd nd nd ndQPC-02 01/11/05 1330 Fast 151 1975 nd 130 175 45 1QPC-03 01/24/05 1020 Fast 302 nd nd nd nd nd ndQPC-04 01/24/05 1300 Intermediate 260 1971 520 235 512 277 5QPC-05 01/24/05 1630 Fast 297 1990 200 160 200 40 1QPC-06 01/25/05 1650 Intermediate 192 1966 208 nd nd nd ndQPC-07 01/27/05 0950 Intermediate 722 1994 310 100 310 210 2

Table 3. Identification, sampling, altitude, and construction information for sampled wells in the Northern San Joaquin Basin Ground-Water Ambient Monitoring and Assessment (GAMA) study, California, December 2004 to February 2005—Continued.[COS, Cosumnes Basin; ESJ, Eastern San Joaquin Basin; ESJDD, Eastern San Joaquin Basin depth dependent; ESJFP, Eastern San Joaquin Basin flowpath; ESJMW, Eastern San Joaquin Basin monitoring well; ft, feet; LSD, land surface datum; mm/dd/yy, month/day/year; nd, no data; QPC, Uplands Basin; TRCY, Tracy Basin; TRCYFP, Tracy Basin flowpath]

58 California GAMA Program: Ground-Water Quality Data in the Northern San Joaquin Basin Study Unit, 2005
GAMA well 

identification 

number

Sampling information Construction information

Date 

(mm/dd/yy)

Time 

(hhmm)

Sampling 

schedule

Well head 

altitude

(ft above LSD)

Year of

construction

Well depth

 (ft below 

LSD)

Top 

perforation

 (ft below LSD)

Bottom 

perforation 

(ft below LSD)

Total open 

length

(ft)

Number of 

openings 

QPC-08 02/09/05 1330 Intermediate 90 1966 164 nd nd nd ndQPC-09 02/10/05 0910 Fast 262 1977 366 150 350 200 3QPC-10 02/14/05 1440 Intermediate 197 1972 nd nd nd nd ndQPC-11 02/15/05 1240 Fast 147 nd nd nd nd nd nd

 Nongrid cell wells

TRCYFP-01 01/03/05 1130 Slow –5 1995 130 90 130 40 1TRCYFP-02 01/04/05 1300 Slow 29 1961 1,148 337 561 224 5TRCYFP-03 01/05/05 1040 Intermediate 22 nd 400 nd nd nd ndTRCYFP-04 01/05/05 1230 Slow 199 1988 870 420 850 430 1TRCYFP-05 01/05/05 1340 Intermediate 45 1989 990 490 980 490 1TRCYFP-06 01/06/05 0840 Fast 12 1974 148 128 148 20 1ESJFP-07 01/10/05 1400 Slow 105 1957 368 335 350 15 ndESJFP-08 01/12/05 0930 Intermediate 23 1978 425 199 415 216 ndESJFP-09 01/12/05 1330 Intermediate 38 nd nd nd nd nd ndESJFP-10 01/28/05 0830 Slow 27 1997 540 200 520 320 7

 Monitoring wells

ESJMW-01 02/01/05 1230 Slow 27 nd 530 500 520 20 1ESJMW-02 02/02/05 1100 Slow 27 nd 460 400 410 10 3ESJMW-03 02/03/05 1130 Slow 27 nd 232 195 215 20 1

 Depth-dependent samples

ESJDD-01 01/26/05 1250 Depth dependent 27 1997 540 200 520 320 7ESJDD-02 01/27/05 0900 Depth dependent 27 1997 540 200 520 320 7ESJDD-03 01/27/05 1300 Depth dependent 27 1997 540 200 520 320 7ESJDD-04 02/16/05 1500 Depth dependent 17 1957 519 195 495 300 3ESJDD-05 02/17/05 1130 Depth dependent 17 1957 519 195 495 300 3ESJDD-06 02/17/05 1900 Depth dependent 17 1957 519 195 495 300 3

Table 3. Identification, sampling, altitude, and construction information for sampled wells in the Northern San Joaquin Basin Ground-Water Ambient Monitoring and Assessment (GAMA) study, California, December 2004 to February 2005—Continued.[COS, Cosumnes Basin; ESJ, Eastern San Joaquin Basin; ESJDD, Eastern San Joaquin Basin depth dependent; ESJFP, Eastern San Joaquin Basin flowpath; ESJMW, Eastern San Joaquin Basin monitoring well; ft, feet; LSD, land surface datum; mm/dd/yy, month/day/year; nd, no data; QPC, Uplands Basin; TRCY, Tracy Basin; TRCYFP, Tracy Basin flowpath]

Tables 59
Analyte Method Laboratory Citation(s)

VOCs Purge and trap capillary gas chromatography/mass spectrometry NWQL Connor and others, 1998Gasoline oxygenates Heated purge and trap/gas chromatography/

mass spectrometry 

NWQL Rose and Sandstrom, 2003

Pesticides Solid-phase extraction and chromatography/

mass spectrometry

NWQL Furlong and others, 2001; Sandstrom and others, 2001

Wastewater-indicator constituents Polystyrene-divinylbenzene solid-phase 

extraction and capillary-column gas chromatography/mass spectrometry 

NWQL Zaugg and others, 2002

Major and minor ions, trace elements and nutrients Several methods NWQL Fishman and Friedman, 1989; Fishman, 1993; Faires, 1993; McLain, 1993; Garbarino, 1999; Garbarino and Damrau, 

2001; Patton and Kryskalla, 2003 

Dissolved organic carbon UV-promoted persulfate oxidation and infrared spectrometry NWQL Brenton and Arnett, 1993Radon-222 Liquid scintillation counting NWQL American Society for Testing and Materials, 1998Stable isotopes of water Gaseous hydrogen and carbon dioxidewater equilibration USGS Stable Isotope Laboratory, Reston, Virginia Epstein and Mayeda, 1953; Coplen and others, 1991 Chromium, arsenic, and iron speciation Various techniques of ultraviolet visible (UV-VIS) spectrophotometery and atomic 

absorbance spectroscopy

USGS Trace Metal Laboratory, 

Boulder, Colorado

Stookey, 1970; To and others, 1998; Ball and McCleskey, 

2003a and 2003b; McCleskey and others, 2003

F-specific and somatic coliphage Single-agar layer (SAL) and two-step 

enrichment methods

USGS Ohio Water Microbiology 

Laboratory

U.S. Environmental Protection Agency, 2000

Tritium Electrolytic enrichment-liquid scintillation USGS Stable Isotope and Tritium 

Laboratory, Menlo Park, California

Thatcher and others, 1977

Perchlorate and 

N-nitrosodimethylamine (NDMA) Chromatography and mass spectrometry Montgomery Watson Harza Laboratory U.S. Environmental Protection Agency, 1996; Hautman and others, 1999; U.S. Environmental Protection Agency, 

1999

1,2,3-Trichloropropane Gas chromatography/electron capture 

detector

Montgomery Watson Harza 

Laboratory

U.S. Environmental Protection Agency, 1995

Table 4. Analytical methods used for the determination of organic, inorganic, and microbial constituents by the U.S. Geological Survey’s (USGS) National Water Quality Laboratory (NWQL) and laboratories other than NWQL.[MI agar, supplemented nutrient agar that cause coliforms (total and escherichia) to produce distinctly different fluorescence under ultraviolet lighting, thus aiding in their detection and enumeration; UV, ultraviolet; VIS, visible; VOCs, volatile organic compounds]

60 California GAMA Program: Ground-Water Quality Data in the Northern San Joaquin Basin Study Unit, 2005
Analyte Method Laboratory Citation(s)

Tritium and noble gases Helium in-growth and accelerator mass 

spectometry

Lawrence Livermore National 

Laboratory

Eaton and others, 2004

Radium 226/228, gross alpha and 

beta radioactivity

Several methods Eberline Services U.S. Environmental Protection Agency, 1980

Carbon isotopes Accelerator mass spectometry University of Waterloo, Environmental Isotope Laboratory; 

University of Arizona Isotope Geochemistry Laboratory

Donahue and others, 1990; Jull and others, 2004

Total and escherichia coliform Membrane filter technique with “MI agar” USGS field personel U.S. Environmental Protection Agency, 2002b

Table 4. Analytical methods used for the determination of organic, inorganic, and microbial constituents by the U.S. Geological Survey’s (USGS) National Water Quality Laboratory (NWQL) and laboratories other than NWQL—Continued.[MI agar, supplemented nutrient agar that cause coliforms (total and Escherichia) to produce distinctly different fluorescence under ultraviolet lighting, thus aiding in their detection and enumeration; UV, ultraviolet; VIS, visible; VOCs, volatile organic compounds]

Tables 61
Constituent Primary constituent classification Analytical schedules Preferred analytical schedule

Acetone VOC 2020, 4024 2020Bromoform (tribromomethane) VOC 1433, 2020 20201,4-Dichlorobenzene VOC 1433, 2020 2020Diisopropyl ether VOC 2020, 4024 2020Ethyl tert-Butyl ether (ETBE) VOC 2020, 4024 2020Isopropylbenzene VOC 1433, 2020 2020Methyl tert-butyl ether (MTBE) VOC 2020, 4024 2020Methyl tert-pentyl ether VOC 2020, 4024 2020Naphthalene VOC 1433, 2020 2020Tetrachloroethylene VOC 1433, 2020 20201,2,3-Trichloropropane (1,2,3-TCP) VOC 2020, MHW MWHCaffeine Wastewater-indicator constituent 1433, 2060, 9003 2060Cotinine Wastewater-indicator constituent 1433, 9003 1433Atrazine Pesticide 2003, 2060 2003Bromacil Pesticide 1433, 2060 2060Carbaryl Pesticide 1433, 2003, 2060 20032-Chloro-4-isopropylamino-6-amino-s-triazine (deethylatrazine) Pesticide degradate 2003, 2060 2003Chlorpyrifos Pesticide 1433, 2003 2003Diazinon Pesticide 1433, 2003 20031,2-Dibromo-3-chloropropane (DBCP) Pesticide 1306, 2020 13061,2-Dibromoethane (EDB) Pesticide 1306, 2020 1306Dichlorvos Pesticide 1433, 2003 2003Metalaxyl Pesticide 1433, 2003, 2060 2060Metolachlor Pesticide 1433, 2003 2003Prometon Pesticide 1433, 2003 2003

Table 5. Constituents analyzed in ground-water samples collected for the Northern San Joaquin Basin Ground-Water Ambient Monitoring and Assessment (GAMA) study, California, December 2004 to February 2005 which appears on multiple analytical schedules, primary constituent classification, analytical schedules the constituent appears on, and the preferred analytical schedule.[Preferred analytical schedules are the methods of analysis with the greatest accuracy and precision out of the ones used for the compound in question. MWH, Montgomery Watson Harza Laboratory; VOC, volatile organic compound]

62 California GAMA Program: Ground-Water Quality Data in the Northern San Joaquin Basin Study Unit, 2005
Constituent 

Maximum concentration 

detected in 

equipment 

blank sample 

(μg/L) 

Minimum concentration 

detected in

ground-water samples 

using this equipment

 (μg/L)

Number of 

ground-water 

samples censored

 Volatile organic compounds and gasoline oxygenates

Toluene 1E0.03 E0.02 6

 Tentatively identified compounds2

Hexafluoropropene (116-15-4) 7.3 0.8 4

Pentafluoropropene (690-27-7) 0.8 0.1 2

Unknown 0.2 0.1 2

 Major and minor ions3

Calcium 0.12 21.1 0

Magnesium E0.004 12.6 0

Silica 0.05 51 0

 Trace elements

Barium E0.2 56.8 0

Manganese 0.6 E0.1 3

Strontium 0.5 257 0

Zinc 1 2.8 0

 Nutrients3

Total nitrogen4 0.2 E0.04 0

1

Compound also detected in associated source-solution blank.

2

TICs are based on comparison with the National Institute for Standards and Technology library spectra and examination by a GC/MS analyst; 

 reported concentrations are approximate.

3

Concentration in mg/L.

4

Total nitrogen (nitrate + nitrite + ammonia + organic nitrogen), analytically determined.

Table 6. Quality-control summary for volatile organic compounds, gasoline oxygenates, tentatively identified compounds (TICs), major 

and minor ions, trace elements, and nutrients detected in the depth-dependent sampling equipment blank and ground-water samples

collected in the Northern San Joaquin Basin Ground-Water Ambient Monitoring and Assessment (GAMA) study, California, December 

2004 to February 2005.

[Numbers in parentheses are the Chemical Abstracts Service (CAS) registry numbers. E, estimated value; GC/MS, gas chromatography/mass spectrometry; 

mg/L, milligram per liter; μg/L, microgram per liter]

Tables 63
Constituent

Maximum concentration 

detected in equipment 

blank sample

 (μg/L) 

Minimum concentration 

detected in ground-water 

samples using this equipment

 (μg/L)

Number of ground-water 

samples censored

 Volatile organic compounds and gasoline oxygenates

Benzene E0.013 — 0

Ethylbenzene E0.018 E0.023 3

Toluene 10.11 E0.02 3

1,2,4-Trichlorobenzene E0.026 E0.039 3

m- and p-Xylene E0.13 E0.12 3

o-Xylene E0.038 E0.048 3

 Wastewater-indicator constituents

Phenol 1E0.4 E0.17 2

 Major and minor ions2

Silica 0.04 60.5 0

 Trace elements

Vanadium 0.17 20.7 0

Zinc 0.8 0.8 3

1

Compound also detected in associated source-solution blank.

2

Concentration in mg/L.

Table 7. Quality-control summary for volatile organic compounds, gasoline oxygenates, wastewater-indicator constituents, major and 

minor ions, and trace elements detected in the portable pump equipment blank and ground-water samples collected in the Northern 

San Joaquin Basin Ground-Water Ambient Monitoring and Assessment (GAMA) study, California, December 2004 to February 2005.

[E, estimated value; mg/L, milligram per liter; μg/L, microgram per liter; —, not detected]

64 California GAMA Program: Ground-Water Quality Data in the Northern San Joaquin Basin Study Unit, 2005
Constituent 

Maximum concentration 

detected in 

field blanks

 (μg/L) 

Minimum concentration 

detected in 

ground-water samples 

(μg/L)

Number of 

ground-water 

samples 

censored

Volatile organic compounds and gasoline oxygenates

Acetone E4 — 0

2-Butanone (methyl ethyl keytone) E0.6 — 0

Ethylbenzene 0.12 E0.01 0

m- and p-Xylene 0.52 E0.05 0

o-Xylene 0.23 E0.06 0

Toluene 10.30 E0.01 24

Wastewater-indicator compounds

Phenol E0.4 E0.2 6

Major and minor ions2

Calcium E0.02 4.6 0

Iodide E0.001 E0.001 17

Silica 21.6 20.1 0

Trace elements

Barium 0.3 25.1 0

Chromium(Total)3 6 1 21

Chromium(VI)3 5 1 16

Copper 0.5 E0.3 3

Iron3 3 2 20

Manganese E0.1 0.2 4

Nickel E0.05 0.13 0

Zinc 2.0 0.9 5

Nutrients and dissolved organic carbon2

Dissolved organic carbon E0.2 E0.2 4

1

Compound also detected in associated source solution blank.

2

Constituent concentrations are reported in mg/L.

3

Constituent analyzed at the U.S. Geological Survey’s Trace Metal Laboratory, Boulder, Colorado.

Table 8. Quality-control summary for volatile organic compounds, gasoline oxygenates, wastewater-indicator constituents, major and 

minor ions, trace elements, nutrients, and dissolved organic carbon, detected in field blanks and ground-water samples collected in the 

Northern San Joaquin Basin Ground-Water Ambient Monitoring and Assessment (GAMA) study, California, December 2004 to February 

2005.

[E, estimated value; mg/L, milligram per liter; μg/L, microgram per liter; —, not detected].

Tables 65
Constituent

Number of relative standard 

deviations greater than 

zero/replicate pairs

Maximum relative standard 

deviation

 (percent)

Median of relative standard 

deviations greater than zero 

(percent)

Volatile organic compounds and gasoline oxygenates

1,2-Dichloropropane 1/6 3 n/a

1,2,4-Trimethylbenzene 1/6 88 n/a

Pesticides and pesticide degradates

Diphenamid 1/2 4 n/a

Table 9A. Quality-control summary of replicate volatile organic compound and gasoline oxygenates, and pesticide and pesticide 

degradates, with relative standard deviations greater than zero, collected for the Northern San Joaquin Basin Ground-Water Ambient 

Monitoring and Assessment (GAMA) study, California, December 2004 to February 2005.

[Because of the large number of compounds, only compounds with relative standard deviations above zero are shown. No replicate pairs for wastewater-indicator constituents, constituents of special interest, or coliphage had a relative standard deviation greater than zero. n/a, not applicable (because median values 

require more than one value)]

Constituent

Number of relative standard 

deviations greater than

 zero/replicate pairs

Maximum relative 

standard deviation 

(percent)

Median of relative standard 

deviations greater than zero 

(percent)

Ammonia 0/1 0 n/a

Nitrite 0/1 0 n/a

Nitrate plus nitrite 0/1 0 n/a

Total nitrogen 2/2 3 2

Phosphorus 1/1 2 n/a

Dissolved organic carbon 1/1 27 n/a

Table 9B. Quality-control summary of replicate nutrient and dissolved organic carbon samples collected for the Northern San Joaquin 

Basin Ground-Water Ambient Monitoring and Assessment (GAMA) study, California, December 2004 to February 2005.

[n/a, not applicable (because median values require more than one value)]

66 California GAMA Program: Ground-Water Quality Data in the Northern San Joaquin Basin Study Unit, 2005
Constituent

Number of relative standard 

deviations greater than 

zero/replicate pairs

Maximum relative 

standard deviation 

(percent)

Median of relative standard 

deviations greater than zero 

(percent)

Bromide 1/2 4 n/a

Calcium 2/3 1 1

Chloride 2/3 1 <1

Fluoride 2/3 7 4

Iodide 0/2 0 n/a

Magnesium 2/3 2 <1

Potassium 3/3 2 1

Silica 2/3 1 1

Sodium 2/3 1 <1

Sulfate 2/3 0 <1

Residue on evaporation 3/3 1 1

Table 9C. Quality-control summary of replicate major- and minor-ion samples collected for the Northern San Joaquin Basin GroundWater Ambient Monitoring and Assessment (GAMA) study, California, December 2004 to February 2005.

[n/a, not applicable (because median values require more than one value); <, less than]

Tables 67
Constituent

Number of relative standard 

deviations greater than

 zero/replicate pairs

Maximum relative 

standard deviation 

(percent)

Median of relative standard 

deviations greater than zero 

(percent)

Aluminum 1/3 7 n/a

Antimony 0/3 0 n/a

Arsenic 3/3 4 1

Arsenic1 4/4 10 3

Arsenic(III)1 1/4 0 n/a

Barium 3/3 3 3

Beryllium 0/3 0 n/a

Boron 2/3 19 6

Cadmium 2/3 20 5

Chromium 0/3 0 n/a

Chromium1 4/4 29 14

Chromium(VI)1 4/4 39 25

Cobalt 3/3 2 1

Copper 1/3 2 n/a

Iron 1/3 1 n/a

Iron1 2/4 28 <1

Iron(II)1 1/4 0 n/a

Lead 2/3 37 3

Lithium 3/3 15 7

Manganese 2/3 2 1

Mercury 0/2 0 n/a

Molybdenum 1/3 2 n/a

Nickel 3/3 3 1

Selenium 2/3 22 12

Silver 0/3 0 n/a

Strontium 3/3 3 3

Thallium 0/3 0 n/a

Tungsten 0/3 0 n/a

Uranium 3/3 6 3

Vanadium 3/3 8 4

Zinc 2/3 5 1

1

Samples analyzed at U.S. Geological Survey’s Trace Metal Laboratory, Boulder, Colorado. All other samples were analyzed at the U.S. Geological 

 Survey’s National Water Quality Laboratory, Denver, Colorado.

Table 9D. Quality-control summary of replicate trace element samples collected for the Northern San Joaquin Basin Ground-Water 

Ambient Monitoring and Assessment (GAMA) study, California, December 2004 to February 2005.

[n/a, not applicable (because median values require more than one value); <, less than]

68 California GAMA Program: Ground-Water Quality Data in the Northern San Joaquin Basin Study Unit, 2005
Isotopes and

 radioactive constituents

Number of relative standard 

deviations greater than

zero/replicate pairs

Maximum relative 

standard deviation

(percent)

Median of relative standard 

deviations greater than zero 

(percent)

Deuterium/protium 4/4 1 <1

Oxygen-18/oxygen-16 3/4 1 <1

Tritium1 1/1 2 n/a

Tritium2 6/6 141 15

Gross-alpha radioactivity, 72 hour count 2/2 625 340

Gross-alpha radioactivity, 30 day count 2/2 106 54

Gross-beta radioactivity, 72 hour count 2/2 11 8

Gross-beta radioactivity, 30 day count 2/2 9 5

Radon-222 1/2 7 n/a

Radium-226 2/2 29 15

Radium-228 2/2 44 29

1

Analyses done at Lawrence Livermore National Laboratory. 

2

Analyses done at the U.S. Geological Survey’s Stable Isotope and Tritium Laboratory, Menlo Park, California.

Table 9E. Quality-control summary of replicate stable isotope and radioactive constituent samples collected for the Northern San 

Joaquin Basin Ground-Water Ambient Monitoring and Assessment (GAMA) study, California, December 2004 to February 2005.

[n/a, not applicable (because median values require more than one value); <, less than]

Tables 69
Surrogate 

constituent

Analytical 

schedule

Constituent

class

Number 

of blank 

sample 

analyses

Number of 

nonblank 

sample 

analyses

Median 

recovery 

of blank 

samples 

(percent)

Median 

recovery of 

nonblank 

samples 

(percent)

Total 

number 

of sample 

analyses

Number of 

surrogate 

recoveries 

below 70 

percent

Number of 

surrogate 

recoveries 

between 

70 and 130 

percent

Number of 

surrogate 

recoveries 

above 130 

percent

α-HCH-d6 2003 Pesticides and degradates 9 82 94 96 91 0 89 2Barban 2060 Pesticides and degradates 3 20 91 106 23 0 23 0Bisphenol A-d3 1433 Wastewater indicators 6 20 36 27 26 25 1 01-Bromo-4-fluorobenzene 2020, 4024 VOC/Gasoline oxygenate 15 85 108 102 100 0 100 0Caffeine-13C 2060 Pesticides and degradates 3 20 152 122 23 0 14 9Caffeine-13C 1433 Wastewater-indicator 

constituent

6 20 71 77 26 11 15 0

Decafluorobiphenyl 1433 Wastewater-indicator 

constituent

6 20 85 57 26 18 8 0

Diazinon-d10 2003 Pesticides and degradates 9 82 70 82 91 26 65 01,2-Dichloroethane-d4 2020, 4024 VOC/Gasoline oxygenate 15 85 107 112 100 0 99 1Fluoranthene-d10 1433 Wastewater indicators 6 20 83 93 26 0 26 0Isobutyl alcohol-d6 2020, 4024 VOC/Gasoline oxygenate 5 17 88 85 22 3 19 01NDMA-d6 MWH Constituent of special 

interest

10 43 101 84 53 1 52 0

2,4,5-T 2060 Pesticides and degradates 3 20 92 91 23 8 15 0Toluene-d8 2020, 4024 VOC/Gasoline oxygenate 15 85 98 98 100 0 100 01Toluene-d8 MWH Constituent of special 

interest

12 43 99 99 55 0 55 0

1Compound analyzed at Montgomery Watson Harza Laboratory.

Table 10. Summary of surrogate-constituent recoveries for ground water and quality-control analyses of volatile organic compounds, gasoline oxygenates, pesticides and pesticide degradates, wastewater-indicator constituents, and constituents of special interest collected for the Northern San Joaquin Basin Ground-Water Ambient Monitoring and Assessment (GAMA) study, California, December 2004 to February 2005.[ MWH, Montgomery Watson Harza Laboratory; VOC, volatile organic compound]

70 California GAMA Program: Ground-Water Quality Data in the Northern San Joaquin Basin Study Unit, 2005
Constituent Number of spike 

samples

Minimum recovery 

(percent)

Maximum recovery 

(percent)

Median recovery 

(percent)

1

Acetone 7 100 117 106

Acrylonitrile 7 100 112 110

tert-Amyl alcohol 2 93 97 95

Benzene 7 99 113 106

Bromobenzene 7 84 100 92

Bromochloromethane 7 94 109 99

Bromodichloromethane 7 96 136 107

Bromoethene 7 91 110 104

Bromoform (tribromomethane) 7 87 123 96

Bromomethane 7 71 142 94

2-Butanone (ethyl methyl ketone) 7 103 116 111

tert-Butyl alcohol 2 100 105 103

n-Butylbenzene 7 62 97 80

sec-Butylbenzene 7 75 100 87

tert-Butylbenzene 7 82 106 97

Carbon disulfide 7 69 101 88

Chlorobenzene 7 85 102 90

Chloroethane 7 88 116 104

Chloroform (trichloromethane) 7 98 119 104

Chloromethane 7 98 125 104

3-Chloropropene 7 93 116 106

2-Chlorotoluene 7 81 100 92

4-Chlorotoluene 7 79 98 86

2

1,2-Dibromo-3-chloropropane (DBCP) 7 66 111 89

Dibromochloromethane 7 89 119 95

2

1,2-Dibromoethane (EDB) 7 70 107 93

Dibromomethane 7 98 108 102

1,2-Dichlorobenzene 7 96 103 100

1,3-Dichlorobenzene 7 80 98 92

1,4-Dichlorobenzene 7 76 96 90

trans-1,4-Dichloro-2-butene 7 99 124 117

Dichlorodifluoromethane (CFC-12) 7 60 87 69

1,1-Dichloroethane 7 97 111 106

1,2-Dichloroethane 7 101 115 107

1,1-Dichloroethylene 7 89 103 94

cis-1,2-Dichloroethylene 7 96 113 99

trans-1,2-Dichloroethylene 7 89 104 98

Dichloromethane (methylene chloride) 7 95 107 101

1,2-Dichloropropane 7 92 135 99

Table 11A. Quality-control summary of volatile organic compounds, gasoline oxygenates, N-nitrosodimethylamine, and 1,2,3-

trichloropropane matrix-spike recoveries for samples collected for the Northern San Joaquin Basin Ground-Water Ambient Monitoring 

and Assessment (GAMA) study, California, December 2004 to February 2005.

Tables 71

See footnotes at end of table.
Constituent Number of spike 

samples

Minimum recovery 

(percent)

Maximum recovery 

(percent)

Median recovery 

(percent)

2,2-Dichloropropane 7 81 108 96

1,3-Dichloropropane 7 98 107 98

1,1-Dichloropropene 7 90 113 99

cis-1,3-Dichloropropene 7 80 94 83

trans-1,3-Dichloropropene 7 88 102 96

Diethyl ether 7 100 106 100

1

Diisopropyl ether 7 88 109 97

Ethylbenzene 7 86 107 90

1

Ethyl tert-butyl ether (ETBE) 7 88 114 107

Ethyl methacrylate 7 89 108 92

o-Ethyl toluene 7 81 100 86

Hexachlorobutadiene 7 61 92 84

Hexachloroethane 7 78 101 95

2-Hexanone 7 91 107 100

Isopropylbenzene 7 80 103 88

4-Isopropyl-1-methylbenzene 7 73 99 84

Methyl acetate 2 41 44 43

Methyl acrylate 7 96 122 106

Methyl acrylonitrile 7 99 112 104

1

Methyl tert-butyl ether (MTBE) 7 89 110 100

Methyl iodide 7 66 136 87

Methyl methacrylate 7 81 99 90

4-Methyl-2-pentanone 7 92 103 96

1

Methyl tert-pentyl ether 7 87 107 100

Naphthalene 7 85 128 98

4

N-Nitrosodimethylamine (NDMA) 4 85 87 87

n-Propylbenzene 7 73 94 84

Styrene 7 84 93 86

1,1,1,2-Tetrachloroethane 7 86 103 99

1,1,2,2-Tetrachloroethane 7 92 112 100

Tetrachloroethylene (PCE) 7 75 104 83

Tetrachloromethane (carbon tetrachloride) 7 80 103 97

Tetrahydrofuran 7 105 119 108

1,2,3,4-Tetramethylbenzene 7 97 111 101

1,2,3,5-Tetramethylbenzene (isodurene) 7 93 115 106

Toluene 7 90 105 99

1,2,3-Trichlorobenzene 7 87 106 94

1,2,4-Trichlorobenzene 7 80 97 89

Table 11A. Quality-control summary of volatile organic compounds, gasoline oxygenates, N-nitrosodimethylamine, and 1,2,3-

trichloropropane matrix-spike recoveries for samples collected for the Northern San Joaquin Basin Ground-Water Ambient Monitoring 

and Assessment (GAMA) study, California, December 2004 to February 2005—Continued.

72 California GAMA Program: Ground-Water Quality Data in the Northern San Joaquin Basin Study Unit, 2005

See footnotes at end of table.
Constituent Number of spike 

samples

Minimum recovery 

(percent)

Maximum recovery 

(percent)

Median recovery 

(percent)

1,1,1-Trichloroethane (TCA) 7 91 106 102

1,1,2-Trichloroethane 7 96 111 105

Trichloroethylene (TCE) 7 84 99 95

Trichlorofluoromethane (CFC-11) 7 87 112 102

1,1,2-Trichloro-1,2,2-trifluoroethane (CFC-113) 7 87 100 91

3

1,2,3-Trichloropropane (1,2,3 TCP) 7 86 106 96

4

1,2,3-Trichloropropane (1,2,3 TCP) 4 88 100 95

1,2,3-Trimethylbenzene 7 79 106 97

1,2,4-Trimethylbenzene 7 83 106 94

1,3,5-Trimethylbenzene 7 81 100 89

Vinyl chloride 7 97 116 106

m- and p-Xylene 7 83 103 87

o-Xylene 7 86 104 90

1

Compounds on Schedules 2020 and 4024; only 2020 values are reported in this table.

2

Compounds on Schedules 1306 and 2020; only 1306 values are reported in this table. 

3

Compound analyzed at the U.S. Geological Survey’s National Water Quality Laboratory.

4

Compound analyzed at the Montgomery Watson Harza Laboratory.

Table 11A. Quality-control summary of volatile organic compounds, gasoline oxygenates, N-nitrosodimethylamine, and 1,2,3-

trichloropropane matrix-spike recoveries for samples collected for the Northern San Joaquin Basin Ground-Water Ambient Monitoring 

and Assessment (GAMA) study, California, December 2004 to February 2005—Continued.

Tables 73
Constituent Number of 

spike samples

Minimum recovery 

(percent)

Maximum recovery 

(percent)

Median recovery 

(percent)

Acetochlor 7 73 106 87

Acifluorfen 2 105 125 115

Alachlor 7 75 104 96

Aldicarb sulfone 2 21 87 54

Aldicarb sulfoxide 2 8 22 15

1

Atrazine 7 85 108 95

Azinphos-methyl 7 44 75 54

Azinphos-methyl oxon 7 36 58 47

Bendiocarb 2 98 101 99

Benfluralin 7 46 66 55

Benomyl 2 64 97 80

Bensulfuron 2 91 210 150

Bentazon 2 60 66 63

Bromacil 2 39 91 65

Bromoxynil 2 63 91 77

1

Carbaryl 7 81 108 91

Carbofuran 2 102 117 110

Chloramben, methyl ester 2 95 97 96

Chlorimuron 2 65 120 93

Chlorodiamino-s-triazine 2 117 136 126

2-Chloro-2,6-diethylacetanilide 7 81 104 101

2-Chloro-6-ethylamino-4-amino-s-triazine 2 41 90 66

1

2-Chloro-4-isopropylamino-6-amino-s-triazine 

(deethylatrazine)

7 38 54 45

4-Chloro-2-methylphenol 7 53 73 65

Chlorothalonil 2 13 90 51

Chlorpyrifos 7 69 91 79

Chlorpyrifos oxon 7 26 58 35

Clopyralid 2 61 72 67

Cycloate 2 102 130 116

Cyfluthrin 7 24 53 39

Cypermethrin 7 28 40 33

Dacthal (DCPA) 7 88 106 98

Dacthal monoacid 2 104 107 105

Desulfinyl fipronil 7 79 90 85

Desulfinylfipronil amide 7 47 104 70

Diazinon 7 77 95 91

Diazinon oxon 7 52 99 77

Dicamba 2 70 102 86

3,4-Dichloroaniline 7 59 81 74

Table 11B. Quality-control summary of pesticide matrix-spike recoveries for samples collected for the Northern San Joaquin Basin 

Ground-Water Ambient Monitoring and Assessment (GAMA) study, California, December 2004 to February 2005.

74 California GAMA Program: Ground-Water Quality Data in the Northern San Joaquin Basin Study Unit, 2005

See footnote at end of table.
Constituent Number of 

spike samples

Minimum recovery 

(percent)

Maximum recovery 

(percent)

Median recovery 

(percent)

2,4-Dichlorophenoxyacetic acid (2,4-D) methyl ester 2 104 139 121

4-(2,4-Dichlorophenoxy)butyric acid (2,4-DB) 2 71 71 71

Dichlorprop 2 97 111 104

Dichlorvos 7 18 58 38

Dicrotophos 7 17 48 19

Dieldrin 7 78 102 92

2,6-Diethylaniline 7 82 91 90

Dimethoate 7 19 44 29

Dinoseb 2 91 120 105

Diphenamid 2 106 145 126

Diuron 2 104 131 118

2,4-D methyl ester 2 92 132 112

Ethion 7 43 60 46

Ethion monoxon 7 45 87 57

2-Ethyl-6-methylaniline 7 82 103 98

Fenamiphos 7 43 58 45

Fenamiphos sulfone 7 40 78 48

Fenamiphos sulfoxide 7 26 39 36

Fenuron 2 89 104 96

Fipronil 7 46 67 54

Fipronil sulfide 7 64 82 72

Fipronil sulfone 7 46 67 54

Flumetsulam 2 142 167 155

Fluometuron 2 104 129 116

Fonofos 7 69 94 78

Hexazinone 7 41 101 49

Hydroxyatrazine 2 117 144 131

3-Hydroxy carbofuran 2 55 82 68

Imazaquin 2 125 134 129

Imazethapyr 2 112 127 120

Imidacloprid 2 125 147 136

Iprodione 7 42 87 57

Isofenphos 7 54 90 72

3-Ketocarbofuran 2 83 90 86

Linuron 2 98 134 116

Malaoxon 7 56 101 70

Malathion 7 59 126 87

Metalaxyl 2 100 140 120

Metalaxyl 7 74 99 96

Methidathion 7 55 88 66

Table 11B. Quality-control summary of pesticide matrix-spike recoveries for samples collected for the Northern San Joaquin Basin 

Ground-Water Ambient Monitoring and Assessment (GAMA) study, California, December 2004 to February 2005—Continued.

Tables 75

See footnote at end of table.
Constituent Number of 

spike samples

Minimum recovery 

(percent)

Maximum recovery 

(percent)

Median recovery 

(percent)

Methiocarb 2 102 144 123

Methomyl 2 1 3 2

2-Methyl-4-chlorophenoxyacetic acid (MCPA) 2 69 79 74

4-(2-Methyl-4-chlorophenoxy) butyric acid (MCPB) 2 56 79 67

Methyl paraoxon 7 38 68 52

Methyl parathion 7 51 71 66

Metolachlor 7 83 119 93

Metribuzin 7 51 80 63

Metsulfuron 2 65 129 97

Myclobutanil 7 40 78 59

1-Naphthol 7 9 29 10

3-(4-Chlorophenyl)-1-methyl urea 2 60 100 80

Neburon 2 100 139 120

Nicosulfuron 2 109 158 133

Norflurazon 2 105 147 126

Oryzalin 2 99 141 120

Oxamyl 2 87 99 93

Pendimethalin 7 49 71 58

Phorate 7 20 77 34

Phorate oxon 7 45 97 57

Phosmet 7 15 42 25

Phosmet oxon 7 9 39 17

Picloram 2 87 97 92

Prometon 7 60 99 82

Prometryn 7 69 97 83

Propham 2 64 86 75

Propiconazole 2 95 130 113

Propoxur 2 57 72 65

Propyzamide 7 68 87 82

Siduron 2 112 162 137

Simazine 7 79 98 89

Sulfometuron 2 83 146 115

1

Tebuthiuron 7 73 126 90

Terbacil 2 47 103 75

Terbufos 7 34 77 57

Terbufos oxon sulfone 7 61 116 75

Terbuthylazine 7 86 108 100

Triclopyr 2 84 100 92

Trifluralin 7 50 65 63

1

Compounds on Schedules 2003 and 2060; only 2003 values are reported in this table.

Table 11B. Quality-control summary of pesticide matrix-spike recoveries for samples collected for the Northern San Joaquin Basin 

Ground-Water Ambient Monitoring and Assessment (GAMA) study, California, December 2004 to February 2005—Continued.

76 California GAMA Program: Ground-Water Quality Data in the Northern San Joaquin Basin Study Unit, 2005
Constituent

Number 

of spike 

samples

Minimum recovery 

(percent)

Maximun recovery 

(percent)

Median recovery 

(percent)

Acetophenone 1 115 115 n/a

Acetyl hexamethyl tetrahydronaphthalene (AHTN) 1 95 95 n/a

Anthracene 1 82 82 n/a

Anthraquinone 1 92 92 n/a

Benzo[a]pyrene 1 82 82 n/a

Benzophenone 1 101 101 n/a

Bisphenol A 1 81 81 n/a

3-tert-Butyl-4-hydroxy anisole (BHA) 1 69 69 n/a

1

Caffeine 2 92 104 98

Camphor 1 95 95 n/a

Carbaryl 1 104 104 n/a

Carbazole 1 91 91 n/a

Cholesterol 1 81 81 n/a

3-ß-Coprostanol 1 86 86 n/a

Cotinine 1 84 84 n/a

4-Cumylphenol 1 92 92 n/a

p-Cresol 1 92 92 n/a

N,N-Diethyl-meta-toluamide (DEET) 1 104 104 n/a

2,6-Dimethylnaphthalene 1 88 88 n/a

Fluoranthene 1 93 93 n/a

Hexahydrohexamethylcyclopentabenzopyran 

(HHCB) 

1 104 104 n/a

Indole 1 82 82 n/a

Isoborneol 1 97 97 n/a

Isophorone 1 97 97 n/a

Isoquinoline 1 83 83 n/a

D-Limonene 1 33 33 n/a

Menthol 1 98 98 n/a

Metalaxyl 1 115 115 n/a

5-Methyl-1H-benzotriazole 1 69 69 n/a

3-Methyl-1(H)-indole (Skatole) 1 92 92 n/a

1-Methylnaphthalene 1 88 88 n/a

2-Methylnaphthalene 1 85 85 n/a

Methyl salicylate 1 96 96 n/a

4-Nonylphenol 1 79 79 n/a

4-Nonylphenol diethoxylates 1 173 173 n/a

4-n-Octylphenol 1 81 81 n/a

4-tert-Octylphenol 1 92 92 n/a

Table 11C. Quality-control summary of wastewater-indicator constituent matrix-spike recoveries for samples collected for the Northern 

San Joaquin Basin Ground-Water Ambient Monitoring and Assessment (GAMA) study, California, December 2004 to February 2005.

 [n/a, not applicable (because median values require more than one value)]

Tables 77

See footnote at end of table.
Constituent

Number 

of spike 

samples

Minimum recovery 

(percent)

Maximun recovery 

(percent)

Median recovery 

(percent)

4-Octylphenol diethoxylates 1 98 98 n/a

4-Octylphenol monoethoxylates 1 86 86 n/a

Pentachlorophenol 1 86 86 n/a

Phenanthrene 1 92 92 n/a

Phenol 1 109 109 n/a

Pyrene 1 93 93 n/a

ß-Sitosterol 1 63 63 n/a

ß-Stigmastanol 1 66 66 n/a

Tri(2-butoxyethyl)phosphate 1 104 104 n/a

Tri(2-chloroethyl)phosphate 1 104 104 n/a

Tri(dichlorisopropyl)phosphate 1 104 104 n/a

Tributyl phosphate 1 103 103 n/a

Triclosan 1 104 104 n/a

Triethyl citrate 1 99 99 n/a

Triphenyl phosphate 1 105 105 n/a

1

Analyzed on pesticide Schedule 2060. 

Table 11C. Quality-control summary of wastewater-indicator constituent matrix-spike recoveries for samples collected for the Northern 

San Joaquin Basin Ground-Water Ambient Monitoring and Assessment (GAMA) study, California, December 2004 to February 2005—

Continued.

[n/a, not applicable (because median values require more than one value)]

78 California GAMA Program: Ground-Water Quality Data in the Northern San Joaquin Basin Study Unit, 2005
GAMA well 

identification 

number

Turbidity 

(NTU, field) 

(61028)

Barometric 

pressure 

(mm of 

mercury, 

field)

 (00025)

Water temperature

(°C, field) 

(00010)

Dissolved 

oxygen 

(mg/L, field) 

(00300)

pH

(standard 

units, 

field)

 (00400) 

pH 

(standard 

units, 

laboratory) 

(00403)

Specific 

conductance 

(μS/cm at 

25°C, field) 

(00095)

Total 

hardness, 

as CaCO3

(mg/L, 

laboratory) 

(00900)

Alkalinity, 

dissolved,

 as CaCO3

 (mg/L, field) 

(29802)

Bicarbonate, 

dissolved, 

as HCO3

(mg/L, field) 

(63786)

Carbonate, 

dissolved, 

as CO3

 (mg/L, field) 

(63788)

Cosumnes Basin samples

COS-01 nc nc nc nc nc nc 239 nc nc nc ncCOS-02 nc nc 24 nc nc nc 208 nc nc nc ncCOS-03 nc nc 20.4 nc nc nc 260 nc nc nc ncCOS-04 nc nc 16.7 nc nc nc 257 nc nc nc ncCOS-05 nc nc 18 nc nc nc 360 nc nc nc ncCOS-06 nc nc 16.5 nc nc nc 193 nc nc nc ncCOS-07 nc nc 16.5 nc nc nc 412 nc nc nc ncCOS-08 nc nc 20 nc nc nc 216 nc nc nc ncCOS-09 nc nc nc nc nc nc 280 nc nc nc ncCOS-10 nc nc nc nc nc nc 410 nc nc nc nc

 Eastern San Joaquin Basin samples

ESJ-01 nc nc 19 nc nc nc 663 nc nc nc ncESJ-02 nc nc 21 nc nc nc 323 nc nc nc ncESJ-03 nc nc 19.5 nc nc nc 444 nc nc nc ncESJ-04 nc nc 16 nc nc nc 352 nc nc nc ncESJ-05 nc nc nc nc nc nc 214 nc nc nc ncESJ-06 nc nc nc nc nc 7.4 340 120 nc nc ncESJ-07 nc nc nc nc nc nc 335 nc nc nc ncESJ-08 nc nc nc nc nc 7.3 203 64 nc nc ncESJ-09 nc nc nc nc nc nc 637 nc nc nc ncESJ-10 nc nc 20.1 nc nc 7.6 252 91 nc nc ncESJ-11 nc nc nc nc nc nc 463 nc nc nc nc

Table 12. General water-quality indicators determined in the field and at the U.S. Geological Survey’s (USGS) National Water Quality Laboratory for the Northern San Joaquin Basin Ground-Water Ambient Monitoring and Assessment (GAMA) study, California, December 2004 to February 2005.[The five digit number below the constituent name is the USGS parameter code used to uniquely identify a specific constituent or property. A, averaged value; °C, degrees Celsius; COS, Cosumnes Basin; E, estimated value; ESJ, Eastern San Joaquin Basin; ESJFP, Eastern San Joaquin Basin flowpath; LRL, laboratory reporting level; mg/L, milligram per liter; mm, millimeter; nc, sample not collected, not analyzed; NTU, nephelometric turbidity units; QPC, Uplands Basin; TRCY, Tracy Basin; TRCYFP, Tracy Basin flowpath; μS/cm, microsiemens per centimeter]

Tables 79
GAMA well 

identification 

number

Turbidity 

(NTU, field) 

(61028)

Barometric 

pressure 

(mm of 

mercury, 

field)

 (00025)

Water temperature

(°C, field) 

(00010)

Dissolved 

oxygen 

(mg/L, field) 

(00300)

pH

(standard 

units, 

field)

 (00400) 

pH 

(standard 

units, 

laboratory) 

(00403)

Specific 

conductance 

(μS/cm at 

25°C, field) 

(00095)

Total 

hardness, 

as CaCO3

(mg/L, 

laboratory) 

(00900)

Alkalinity, 

dissolved,

 as CaCO3

 (mg/L, field) 

(29802)

Bicarbonate, 

dissolved, 

as HCO3

(mg/L, field) 

(63786)

Carbonate, 

dissolved, 

as CO3

 (mg/L, field) 

(63788)

ESJ-12 0.6 768 17.2 5.8 7.5 E6.9 768 110 A121 A147 <1ESJ-13 nc nc nc nc nc 7.2 198 80 nc nc ncESJ-14 nc nc nc nc nc 7.8 298 98 nc nc ncESJ-15 nc nc 19 nc nc 7.7 607 250 nc nc ncESJ-16 nc nc 18.4 nc nc 7.5 290 120 nc nc ncESJ-17 nc nc 22.5 nc nc 7.6 208 67 nc nc ncESJ-18 nc nc 21.3 nc nc 7.6 211 71 nc nc ncESJ-19 1.1 757 17.8 3.4 7.7 7.6 468 160 A179 A217 <1

 Upland Basin samples

QPC-01 0.2 754 15 5.6 6.8 6.8 369 160 A130 A158 <1QPC-02 nc nc nc nc nc nc 487 nc nc nc ncQPC-03 nc nc 19 nc nc nc 170 nc nc nc ncQPC-04 nc nc 22 nc nc 6.8 140 22 nc nc ncQPC-05 nc nc 19 nc nc nc 164 nc nc nc ncQPC-06 nc nc 19 nc nc 7.3 195 59 nc nc ncQPC-07 nc nc 20.5 nc nc 7.2 389 150 nc nc ncQPC-08 nc nc 21.5 nc nc 7.4 219 75 nc nc ncQPC-09 nc nc 21.4 nc nc nc 333 nc nc nc ncQPC-10 nc nc 19.7 nc nc 7.6 204 72 nc nc ncQPC-11 nc nc 21 nc nc nc 129 nc nc nc nc

 Tracy Basin samples

TRCY-01 nc nc nc nc nc nc 1,880 nc nc nc ncTRCY-02 nc nc 20 nc nc nc 29,000 nc nc nc ncTRCY-03 0.2 762 22.2 6.2 7.5 E6.6 1,000 310 A194 A235 <1

Table 12. General water-quality indicators determined in the field and at the U.S. Geological Survey’s (USGS) National Water Quality Laboratory for the Northern San Joaquin Basin Ground-Water Ambient Monitoring and Assessment (GAMA) study, California, December 2004 to February 2005—Continued.[The five digit number below the constituent name is the USGS parameter code used to uniquely identify a specific constituent or property. A, averaged value; °C, degrees Celsius; COS, Cosumnes Basin; E, estimated value; ESJ, Eastern San Joaquin Basin; ESJFP, Eastern San Joaquin Basin flowpath; LRL, laboratory reporting level; mg/L, milligram per liter; mm, millimeter; nc, sample not collected, not analyzed; NTU, nephelometric turbidity units; QPC, Uplands Basin; TRCY, Tracy Basin; TRCYFP, Tracy Basin flowpath; μS/cm, microsiemens per centimeter]

80 California GAMA Program: Ground-Water Quality Data in the Northern San Joaquin Basin Study Unit, 2005
GAMA well 

identification 

number

Turbidity 

(NTU, field) 

(61028)

Barometric 

pressure 

(mm of 

mercury, 

field)

 (00025)

Water temperature

(°C, field) 

(00010)

Dissolved 

oxygen 

(mg/L, field) 

(00300)

pH

(standard 

units, 

field)

 (00400) 

pH 

(standard 

units, 

laboratory) 

(00403)

Specific 

conductance 

(μS/cm at 

25°C, field) 

(00095)

Total 

hardness, 

as CaCO3

(mg/L, 

laboratory) 

(00900)

Alkalinity, 

dissolved,

 as CaCO3

 (mg/L, field) 

(29802)

Bicarbonate, 

dissolved, 

as HCO3

(mg/L, field) 

(63786)

Carbonate, 

dissolved, 

as CO3

 (mg/L, field) 

(63788)

TRCY-04 nc nc 20 nc nc nc 1,260 nc nc nc ncTRCY-05 nc nc 19.2 nc nc nc 1,550 nc nc nc ncTRCY-06 nc nc 18.5 nc nc nc 969 nc nc nc ncTRCY-07 0.2 766 17.8 0.1 6.4 6.3 4,180 1,900 A139 A169 <1TRCY-08 nc nc 21.7 nc nc nc 699 nc nc nc ncTRCY-09 nc nc 18.6 nc nc 7.3 711 170 nc nc ncTRCY-10 nc nc 16.9 nc nc nc 957 nc nc nc ncTRCY-11 nc nc 21.2 nc nc 7.9 938 160 nc nc nc

 Nongrid cell samples

TRCYFP-01 0.2 762 16.3 0.1 7.4 7.5 5,990 1,200 A110 A133 <1TRCYFP-02 0.1 760 22.9 1.8 7.7 E7.2 999 290 A122 A149 <1TRCYFP-03 nc nc 22.5 nc nc 7.5 1,060 210 nc nc ncTRCYFP-04 0.2 765 21.4 4.4 7.5 7.3 1,250 370 A184 A224 <1TRCYFP-05 nc nc 24 nc nc 7.5 1,290 250 nc nc ncTRCYFP-06 nc nc 14.5 nc nc nc 1,150 nc nc nc ncESJFP-07 0.4 758 19.2 6.6 7.8 7.6 240 98 A114 A138 <1ESJFP-08 nc nc nc nc nc 7.5 541 170 nc nc ncESJFP-09 nc nc nc nc nc 7.6 483 230 nc nc ncESJFP-10 0.1 763 18 3.9 7.6 7.7 352 150 A151 A183 <1

 Depth-dependent samples

ESJDD-01 nc nc nc nc nc 7.7 393 150 nc nc ncESJDD-02 nc nc nc nc nc 7.8 260 100 nc nc ncESJDD-03 nc nc nc nc nc E7.6 298 130 nc nc ncESJDD-04 nc 765 16.6 0.0 7.9 7.6 488 180 195 237 <1

Table 12. General water-quality indicators determined in the field and at the U.S. Geological Survey’s (USGS) National Water Quality Laboratory for the Northern San Joaquin Basin Ground-Water Ambient Monitoring and Assessment (GAMA) study, California, December 2004 to February 2005—Continued.[The five digit number below the constituent name is the USGS parameter code used to uniquely identify a specific constituent or property. A, averaged value; °C, degrees Celsius; COS, Cosumnes Basin; E, estimated value; ESJ, Eastern San Joaquin Basin; ESJFP, Eastern San Joaquin Basin flowpath; LRL, laboratory reporting level; mg/L, milligram per liter; mm, millimeter; nc, sample not collected, not analyzed; NTU, nephelometric turbidity units; QPC, Uplands Basin; TRCY, Tracy Basin; TRCYFP, Tracy Basin flowpath; μS/cm, microsiemens per centimeter]

Tables 81
GAMA well 

identification 

number

Turbidity 

(NTU, field) 

(61028)

Barometric 

pressure 

(mm of 

mercury, 

field)

 (00025)

Water temperature

(°C, field) 

(00010)

Dissolved 

oxygen 

(mg/L, field) 

(00300)

pH

(standard 

units, 

field)

 (00400) 

pH 

(standard 

units, 

laboratory) 

(00403)

Specific 

conductance 

(μS/cm at 

25°C, field) 

(00095)

Total 

hardness, 

as CaCO3

(mg/L, 

laboratory) 

(00900)

Alkalinity, 

dissolved,

 as CaCO3

 (mg/L, field) 

(29802)

Bicarbonate, 

dissolved, 

as HCO3

(mg/L, field) 

(63786)

Carbonate, 

dissolved, 

as CO3

 (mg/L, field) 

(63788)

ESJDD-05 nc 762 14.6 0.0 7.9 7.8 467 180 A180 A218 <1ESJDD-06 nc 762 15.3 0.0 8.1 7.7 451 160 178 215 <1

Monitoring well samples

ESJMW-01 36 770 20.7 3.4 8.0 7.8 252 99 A118 A143 <1ESJMW-02 1.5 770 20.5 5.9 7.7 7.9 262 100 A116 A141 <1ESJMW-03 0.4 769 21.1 1.4 7.6 7.6 313 130 A129 A157 <1

Table 12. General water-quality indicators determined in the field and at the U.S. Geological Survey’s (USGS) National Water Quality Laboratory for the Northern San Joaquin Basin Ground-Water Ambient Monitoring and Assessment (GAMA) study, California, December 2004 to February 2005—Continued.[The five digit number below the constituent name is the USGS parameter code used to uniquely identify a specific constituent or property. A, averaged value; °C, degrees Celsius; COS, Cosumnes Basin; E, estimated value; ESJ, Eastern San Joaquin Basin; ESJFP, Eastern San Joaquin Basin flowpath; LRL, laboratory reporting level; mg/L, milligram per liter; mm, millimeter; nc, sample not collected, not analyzed; NTU, nephelometric turbidity units; QPC, Uplands Basin; TRCY, Tracy Basin; TRCYFP, Tracy Basin flowpath; μS/cm, microsiemens per centimeter]

82 California GAMA Program: Ground-Water Quality Data in the Northern San Joaquin Basin Study Unit, 2005
GAMA well

 identification 

number

Trihalomethanes Solvents

Chloroform 

(Trichloromethane)

 (μg/L)

 (32106) 

Bromoform 

(Tribromomethane) 

(μg/L)

 (32104) 

Bromodichloromethane

 (μg/L)

 (32101)

Dibromochloromethane 

(μg/L) 

(32105)

Tetrachloroethylene 

(PCE) 

(μg/L) 

(34475) 

1,2-Dichloropropane 

(μg/L) 

(34541)

Trichloroethylene 

(TCE)

 (μg/L) 

(39180) 

1,1-

Dichloroethene

(μg/L) 

(34501) 

cis-1,2-

Dichloroethene 

(μg/L) 

(77093)

Tetrahydrofuran 

(μg/L) 

(81607)

 Threshold type MCL-US MCL-US MCL-US MCL-US MCL-US MCL-US MCL-US MCL-CA MCL-CA n/a Threshold level (μg/L) 80 80 80 80 5 5 5 6 6 n/a LRL 0.02 0.1 0.03 0.1 0.03 0.03 0.04 0.02 0.02 1

 Grid cell samples

COS-02 — — — — — — — — — —COS-06 — — — — — — — — — —ESJ-01 E0.01 — — — — — — — — —ESJ-02 — — — — — E0.02 — — — —ESJ-03 — E0.1 — — — — — — — —ESJ-04 — — — — — — — — — —ESJ-06 E0.04 — — — — — — — — —ESJ-07 — — — — E0.1 — E0.02 — — —ESJ-09 0.11 — — — 0.95 E0.05 0.19 E0.05 E0.02 —

ESJ-13 0.11 — — — E0.02 — — — — —ESJ-15 0.19 — — — E0.01 — — — — —ESJ-16 E0.05 — — — E0.02 — — — — —ESJ-19 E0.01 E0.1 E0.04 E0.1 — — — — — —QPC-01 — — — — E0.02 — — — — —QPC-02 E0.05 — — — 0.24 — E0.07 E0.03 E0.07 —

QPC-04 — — — — — — — — — —

Table 13A. Summary of volatile organic compounds and gasoline oxygenates in ground-water samples collected for the Northern San Joaquin Basin Ground-Water Ambient Monitoring and Assessment (GAMA) study, California, December 2004 to February 2005.[Concentrations preceded by a “V” indicate detections potentially biased by contamination. Percentage values are detection frequencies. The five digit number below the constituent name is the USGS parameter code used to uniquely identify a specific constituent or property. The threshold type identifies the source of the comparison threshold. The threshold level is the level with which ground-water detections are compared. COS, Cosumnes Basin; E, estimated value; ESJ, Eastern San Joaquin Basin; ESJDD, Eastern San Joaquin Basin depth dependent; ESJFP, Eastern San Joaquin Basin flowpath; ESJMW, Eastern San Joaquin Basin monitoring well; HA-L, lifetime health advisory (U.S. Environmental Protection Agency, 2004b); LRL, laboratory reporting level; MCL-CA, California Department of Health Services Maximum Contaminant Level (California Department of Health Services, 2005a); MCL-US, U.S. Environmental Protection Agency Maximum Contaminant Level (U.S. Environmental Protection Agency, 2005); n/a, not applicable; NL, notification level (California Department of Health Services, 2005d); QPC, Upland Basin; TRCY, Tracy Basin; TRCYFP, Tracy Basin flowpath; USGS, U.S. Geological Survey; μg/L, microgram per liter; —, analyzed but not detected]

See footnotes at end of table.

Tables 83
GAMA well

 identification 

number

Trihalomethanes Solvents

Chloroform 

(Trichloromethane)

 (μg/L)

 (32106) 

Bromoform 

(Tribromomethane) 

(μg/L)

 (32104) 

Bromodichloromethane

 (μg/L)

 (32101)

Dibromochloromethane 

(μg/L) 

(32105)

Tetrachloroethylene 

(PCE) 

(μg/L) 

(34475) 

1,2-Dichloropropane 

(μg/L) 

(34541)

Trichloroethylene 

(TCE)

 (μg/L) 

(39180) 

1,1-

Dichloroethene

(μg/L) 

(34501) 

cis-1,2-

Dichloroethene 

(μg/L) 

(77093)

Tetrahydrofuran 

(μg/L) 

(81607)

QPC-05

—

—

—

—

—

—

—

—

— E0.4

TRCY-02

—

—

—

—

—

—

—

—

— 10

TRCY-03 E0.02

—

—

—

—

—

—

—

—

—

TRCY-04

—

—

—

—

—

—

—

—

—

—

TRCY-05

—

—

—

—

—

—

—

—

—

—

TRCY-07

—

—

—

—

— 0.20

—

—

—

—

TRCY-09

—

—

—

—

—

—

—

—

—

—

 Nongrid cell samples1

TRCYFP-01 

—

—

—

—

—

—

—

—

—

—

TRCYFP-02 1.82 1.2 3.06 2.9

—

—

—

—

—

—

TRCYFP-03 2.39 3.8 5.91 6.8

—

—

—

—

—

—

TRCYFP-04 E0.02

— E0.03

—

—

—

—

—

—

—

TRCYFP-05 E0.03

—

—

—

—

—

—

—

—

—

ESJFP-07 

—

—

—

—

—

—

—

—

—

—

ESJFP-08 E0.07 0.4 0.12 0.3

—

— 0.20

—

—

—

ESJFP-09 0.13 0.3

—

— 2.45

— 0.42

— 0.34

—

ESJFP-10 E0.01

—

—

—

—

—

—

—

—

—

ESJDD-01 0.19

—

—

—

—

—

—

—

—

—

ESJDD-02 E0.02

—

—

—

—

—

—

—

—

—

ESJDD-03 E0.01

—

—

—

—

—

—

—

—

—

Table 13A. Summary of volatile organic compounds and gasoline oxygenates in ground-water samples collected for the Northern San Joaquin Basin Ground-Water Ambient Monitoring and Assessment (GAMA) study, California, December 2004 to February 2005—Continued.[Concentrations preceded by a “V” indicate detections potentially biased by contamination. Percentage values are detection frequencies. The five digit number below the constituent name is the USGS parameter code used to uniquely identify a specific constituent or property. The threshold type identifies the source of the comparison threshold. The threshold level is the level with which ground-water detections are compared. COS, Cosumnes Basin; E, estimated value; ESJ, Eastern San Joaquin Basin; ESJDD, Eastern San Joaquin Basin depth dependent; ESJFP, Eastern San Joaquin Basin flowpath; ESJMW, Eastern San Joaquin Basin monitoring well; HA-L, lifetime health advisory (U.S. Environmental Protection Agency, 2004b); LRL, laboratory reporting level; MCL-CA, California Department of Health Services Maximum Contaminant Level (California Department of Health Services, 2005a); MCL-US, U.S. Environmental Protection Agency Maximum Contaminant Level (U.S. Environmental Protection Agency, 2005); n/a, not applicable; NL, notification level (California Department of Health Services, 2005d); QPC, Upland Basin; TRCY, Tracy Basin; TRCYFP, Tracy Basin flowpath; USGS, U.S. Geological Survey; μg/L, microgram per liter; —, analyzed but not detected]

See footnotes at end of table.

84 California GAMA Program: Ground-Water Quality Data in the Northern San Joaquin Basin Study Unit, 2005
GAMA well

 identification 

number

Trihalomethanes Solvents

Chloroform 

(Trichloromethane)

 (μg/L)

 (32106) 

Bromoform 

(Tribromomethane) 

(μg/L)

 (32104) 

Bromodichloromethane

 (μg/L)

 (32101)

Dibromochloromethane 

(μg/L) 

(32105)

Tetrachloroethylene 

(PCE) 

(μg/L) 

(34475) 

1,2-Dichloropropane 

(μg/L) 

(34541)

Trichloroethylene 

(TCE)

 (μg/L) 

(39180) 

1,1-

Dichloroethene

(μg/L) 

(34501) 

cis-1,2-

Dichloroethene 

(μg/L) 

(77093)

Tetrahydrofuran 

(μg/L) 

(81607)

ESJDD-04 — — — — — — — — — —ESJDD-05 — — — — — — — — — —ESJDD-06 — — — — — — — — — —ESJMW-01 E0.04 — — — — — — — — —ESJMW-02 — — — — — — — — — —ESJMW-03 — — — — — — — — — —Grid cell wells with 

VOC detections

9 2 1 1 7 3 3 2 2 2

Detection frequency 

in grid cell wells (percent)

18 4 2 2 14 6 6 4 4 4

Table 13A. Summary of volatile organic compounds and gasoline oxygenates in ground-water samples collected for the Northern San Joaquin Basin Ground-Water Ambient Monitoring and Assessment (GAMA) study, California, December 2004 to February 2005—Continued.[Concentrations preceded by a “V” indicate detections potentially biased by contamination. Percentage values are detection frequencies. The five digit number below the constituent name is the USGS parameter code used to uniquely identify a specific constituent or property. The threshold type identifies the source of the comparison threshold. The threshold level is the level with which ground-water detections are compared. COS, Cosumnes Basin; E, estimated value; ESJ, Eastern San Joaquin Basin; ESJDD, Eastern San Joaquin Basin depth dependent; ESJFP, Eastern San Joaquin Basin flowpath; ESJMW, Eastern San Joaquin Basin monitoring well; HA-L, lifetime health advisory (U.S. Environmental Protection Agency, 2004b); LRL, laboratory reporting level; MCL-CA, California Department of Health Services Maximum Contaminant Level (California Department of Health Services, 2005a); MCL-US, U.S. Environmental Protection Agency Maximum Contaminant Level (U.S. Environmental Protection Agency, 2005); n/a, not applicable; NL, notification level (California Department of Health Services, 2005d); QPC, Upland Basin; TRCY, Tracy Basin; TRCYFP, Tracy Basin flowpath; USGS, U.S. Geological Survey; μg/L, microgram per liter; —, analyzed but not detected]

See footnotes at end of table.

Tables 85
GAMA well

 identification 

number

Solvents Gasoline

Dichloromethane 

(μg/L) 

(34423)

Dibromomethane 

(μg/L) 

(30217)

trans-1,2-Dichloroethene 

(μg/L) 

(34546)

Tetrachloromethane 

(Carbon tetrachloride) 

(μg/L)

 (32102) 

Ethylbenzene 

(μg/L) 

(34371)

Methyl tertbutyl ether 

(MTBE)

 (μg/L) 

(78032)

Benzene 

(μg/L) 

(34030) 

Methyl tertpentyl ether 

(μg/L) 

(50005)

Toluene 

(μg/L) 

(34010)

m-and 

pXylene

(μg/L)

 (85795)

 Threshold type MCL-US n/a MCL-CA MCL-CA MCL-CA MCL-US MCL-CA n/a MCL-CA MCL-CA Threshold level (μg/L) 5 n/a 10 0.5 300 13 1 n/a 150 1,750 LRL 0.06 0.05 0.03 0.06 0.03 0.1 0.02 0.04 0.02 0.06

 Grid cell samples

COS-02

—

—

—

—

—

— E0.02

— V0.01

—

COS-06

—

—

—

—

— 0.3

—

—

—

—

ESJ-01

—

—

—

—

—

—

—

—

—

—

ESJ-02

—

—

—

—

—

—

—

—

—

—

ESJ-03

—

—

—

—

—

—

—

—

—

—

ESJ-04

—

—

—

—

—

—

—

— V0.01

—

ESJ-06

—

—

—

—

—

—

—

—

—

—

ESJ-07

—

—

—

—

—

—

—

—

—

—

ESJ-09

—

—

—

—

—

—

—

—

—

—

ESJ-13

—

—

—

—

—

—

—

— V0.02

—

ESJ-15 E0.04

—

—

—

—

—

—

—

—

—

ESJ-16

—

—

—

—

—

—

—

—

—

—

ESJ-19

—

—

—

— E0.03

—

—

— V0.04 E0.16

QPC-01

—

—

—

—

—

—

—

— V0.01

—

QPC-02

—

—

—

—

—

—

—

—

—

—

QPC-04

—

—

—

—

—

—

—

— V0.01

—

Table 13A. Summary of volatile organic compounds and gasoline oxygenates in ground-water samples collected for the Northern San Joaquin Basin Ground-Water Ambient Monitoring and Assessment (GAMA) study, California, December 2004 to February 2005—Continued.[Concentrations preceded by a “V” indicate detections potentially biased by contamination. Percentage values are detection frequencies. The five digit number below the constituent name is the USGS parameter code used to uniquely identify a specific constituent or property. The threshold type identifies the source of the comparison threshold. The threshold level is the level with which ground-water detections are compared. COS, Cosumnes Basin; E, estimated value; ESJ, Eastern San Joaquin Basin; ESJDD, Eastern San Joaquin Basin depth dependent; ESJFP, Eastern San Joaquin Basin flowpath; ESJMW, Eastern San Joaquin Basin monitoring well; HA-L, lifetime health advisory (U.S. Environmental Protection Agency, 2004b); LRL, laboratory reporting level; MCL-CA, California Department of Health Services Maximum Contaminant Level (California Department of Health Services, 2005a); MCL-US, U.S. Environmental Protection Agency Maximum Contaminant Level (U.S. Environmental Protection Agency, 2005); n/a, not applicable; NL, notification level (California Department of Health Services, 2005d); QPC, Upland Basin; TRCY, Tracy Basin; TRCYFP, Tracy Basin flowpath; USGS, U.S. Geological Survey; μg/L, microgram per liter; —, analyzed but not detected]

See footnotes at end of table.

86 California GAMA Program: Ground-Water Quality Data in the Northern San Joaquin Basin Study Unit, 2005
GAMA well

 identification 

number

Solvents Gasoline

Dichloromethane 

(μg/L) 

(34423)

Dibromomethane 

(μg/L) 

(30217)

trans-1,2-Dichloroethene 

(μg/L) 

(34546)

Tetrachloromethane 

(Carbon tetrachloride) 

(μg/L)

 (32102) 

Ethylbenzene 

(μg/L) 

(34371)

Methyl tertbutyl ether 

(MTBE)

 (μg/L) 

(78032)

Benzene 

(μg/L) 

(34030) 

Methyl tertpentyl ether 

(μg/L) 

(50005)

Toluene 

(μg/L) 

(34010)

m-and pXylene

(μg/L)

 (85795)

QPC-05 — — — — — — — — 0.460 —TRCY-02 — — — — E0.05 — — — V0.02 —TRCY-03 — — — — — — — — — —TRCY-04 — — — — — — — — V0.01 —TRCY-05 — — — — — — — — V0.01 —TRCY-07 — — — — — — — — V0.01 —TRCY-09 — — — — — 2.0 — E0.03 — —

 Nongrid cell samples1

TRCYFP-01 — — — — — — — — V0.02 E0.05TRCYFP-02 — 0.14 — E0.02 — — — — — —TRCYFP-03 E0.03 0.38 — — — — — — V0.01 —TRCYFP-04 — — — — — — — — — —TRCYFP-05 — — — — — — — — V0.01 —ESJFP-07 — — — — — — — — V0.02 —ESJFP-08 — — — — — — — — — —ESJFP-09 — — E0.05 — — — — — — —ESJFP-10 — — — — — — — — V0.01 —ESJDD-01 — — — — — — — — V0.05 E0.05ESJDD-02 — — — — — — — — V0.02 —ESJDD-03 — — — — — — — — V0.02 E0.03

Table 13A. Summary of volatile organic compounds and gasoline oxygenates in ground-water samples collected for the Northern San Joaquin Basin Ground-Water Ambient Monitoring and Assessment (GAMA) study, California, December 2004 to February 2005—Continued.[Concentrations preceded by a “V” indicate detections potentially biased by contamination. Percentage values are detection frequencies. The five digit number below the constituent name is the USGS parameter code used to uniquely identify a specific constituent or property. The threshold type identifies the source of the comparison threshold. The threshold level is the level with which ground-water detections are compared. COS, Cosumnes Basin; E, estimated value; ESJ, Eastern San Joaquin Basin; ESJDD, Eastern San Joaquin Basin depth dependent; ESJFP, Eastern San Joaquin Basin flowpath; ESJMW, Eastern San Joaquin Basin monitoring well; HA-L, lifetime health advisory (U.S. Environmental Protection Agency, 2004b); LRL, laboratory reporting level; MCL-CA, California Department of Health Services Maximum Contaminant Level (California Department of Health Services, 2005a); MCL-US, U.S. Environmental Protection Agency Maximum Contaminant Level (U.S. Environmental Protection Agency, 2005); n/a, not applicable; NL, notification level (California Department of Health Services, 2005d); QPC, Upland Basin; TRCY, Tracy Basin; TRCYFP, Tracy Basin flowpath; USGS, U.S. Geological Survey; μg/L, microgram per liter; —, analyzed but not detected]

See footnotes at end of table.

Tables 87
GAMA well

 identification 

number

Solvents Gasoline

Dichloromethane 

(μg/L) 

(34423)

Dibromomethane 

(μg/L) 

(30217)

trans-1,2-Dichloroethene 

(μg/L) 

(34546)

Tetrachloromethane 

(Carbon tetrachloride) 

(μg/L)

 (32102) 

Ethylbenzene 

(μg/L) 

(34371)

Methyl tertbutyl ether 

(MTBE)

 (μg/L) 

(78032)

Benzene 

(μg/L) 

(34030) 

Methyl tertpentyl ether 

(μg/L) 

(50005)

Toluene 

(μg/L) 

(34010)

m-and 

pXylene

(μg/L)

 (85795)

ESJDD-04 

—

—

—

—

—

—

—

— V0.04 E0.03

ESJDD-05 

—

—

—

— E0.01

—

—

— V0.05 E0.05

ESJDD-06 

—

—

—

— E0.02

—

—

— V0.05 E0.07

ESJMW-01 

—

—

—

—

—

—

—

— V0.02

—

ESJMW-02 

—

—

—

— E0.02

—

—

— V0.12 E0.12

ESJMW-03 

—

—

—

—

—

—

—

— V0.02

—

Grid cell wells with 

VOC detections

1 0 0 0 2 2 1 1 1 1

Detection frequency 

in grid cell wells (percent)

2 0 0 0 4 4 2 2 2 2

Table 13A. Summary of volatile organic compounds and gasoline oxygenates in ground-water samples collected for the Northern San Joaquin Basin Ground-Water Ambient Monitoring and Assessment (GAMA) study, California, December 2004 to February 2005—Continued.[Concentrations preceded by a “V” indicate detections potentially biased by contamination. Percentage values are detection frequencies. The five digit number below the constituent name is the USGS parameter code used to uniquely identify a specific constituent or property. The threshold type identifies the source of the comparison threshold. The threshold level is the level with which ground-water detections are compared. COS, Cosumnes Basin; E, estimated value; ESJ, Eastern San Joaquin Basin; ESJDD, Eastern San Joaquin Basin depth dependent; ESJFP, Eastern San Joaquin Basin flowpath; ESJMW, Eastern San Joaquin Basin monitoring well; HA-L, lifetime health advisory (U.S. Environmental Protection Agency, 2004b); LRL, laboratory reporting level; MCL-CA, California Department of Health Services Maximum Contaminant Level (California Department of Health Services, 2005a); MCL-US, U.S. Environmental Protection Agency Maximum Contaminant Level (U.S. Environmental Protection Agency, 2005); n/a, not applicable; NL, notification level (California Department of Health Services, 2005d); QPC, Upland Basin; TRCY, Tracy Basin; TRCYFP, Tracy Basin flowpath; USGS, U.S. Geological Survey; μg/L, microgram per liter; —, analyzed but not detected]

See footnotes at end of table.

88 California GAMA Program: Ground-Water Quality Data in the Northern San Joaquin Basin Study Unit, 2005
GAMA well

 identification 

number

Gasoline Organic synthesis Refrigerants

Detections 

per well

o-Xylene 

(μg/L) 

(77135)

1,1-Dichloroethane 

(μg/L)

 (34496) 

1,2,4-Trimethylbenzene

(μg/L) 

(77222)

Carbon 

disulfide 

(μg/L) 

(77041) 

Styrene

(μg/L) 

(77128) 

Bromochloromethane 

(μg/L) 

(77297)

Trichlorofluoromethane 

(CFC-11) 

(μg/L) 

(34488) 

Dichlorodifluoromethane

(CFC-12)

 (μg/L)

 (34668) 

Chloromethane

 (μg/L) 

(34418) 

 Threshold type MCL-CA MCL-US NL NL MCL-US HA-L MCL-CA NL HA-L

 Threshold level (μg/L) 1,750 5 330 160 100 9 100 1,000 30 LRL 0.04 0.04 0.06 0.04 0.04 0.12 0.08 0.18 0.17

 Grid cell samples

COS-02 — — — — — — — — — 1COS-06 — — — — — — — — — 1ESJ-01 — — — — — — — — — 1ESJ-02 — — — — — — — — — 1ESJ-03 — — — — — — — — — 1ESJ-04 — — — — — — — — — 0ESJ-06 — — — — — — — — — 1ESJ-07 — E0.06 — — — — E0.03 — — 4ESJ-09 — E0.10 — — — — E0.16 E0.78 — 9ESJ-13 — — — — — — — — — 2ESJ-15 — — — — — — E0.07 — — 4ESJ-16 — — — — — — — — — 2ESJ-19 E0.06 — — — — — — — — 7QPC-01 — — 0.15 — — — — — — 2QPC-02 — E0.04 — — — — — — — 6QPC-04 — — — — — — — — — 0

Table 13A. Summary of volatile organic compounds and gasoline oxygenates in ground-water samples collected for the Northern San Joaquin Basin Ground-Water Ambient Monitoring and Assessment (GAMA) study, California, December 2004 to February 2005—Continued.[Concentrations preceded by a “V” indicate detections potentially biased by contamination. Percentage values are detection frequencies. The five digit number below the constituent name is the USGS parameter code used to uniquely identify a specific constituent or property. The threshold type identifies the source of the comparison threshold. The threshold level is the level with which ground-water detections are compared. COS, Cosumnes Basin; E, estimated value; ESJ, Eastern San Joaquin Basin; ESJDD, Eastern San Joaquin Basin depth dependent; ESJFP, Eastern San Joaquin Basin flowpath; ESJMW, Eastern San Joaquin Basin monitoring well; HA-L, lifetime health advisory (U.S. Environmental Protection Agency, 2004b); LRL, laboratory reporting level; MCL-CA, California Department of Health Services Maximum Contaminant Level (California Department of Health Services, 2005a); MCL-US, U.S. Environmental Protection Agency Maximum Contaminant Level (U.S. Environmental Protection Agency, 2005); n/a, not applicable; NL, notification level (California Department of Health Services, 2005d); QPC, Upland Basin; TRCY, Tracy Basin; TRCYFP, Tracy Basin flowpath; USGS, U.S. Geological Survey; μg/L, microgram per liter; —, analyzed but not detected]

See footnotes at end of table.

Tables 89
GAMA well

 identification 

number

Gasoline Organic synthesis Refrigerants

Detections 

per well o-Xylene (μg/L) 

(77135)

1,1-Dichloroethane 

(μg/L)

 (34496) 

1,2,4-Trimethylbenzene

(μg/L) 

(77222)

Carbon 

disulfide 

(μg/L) 

(77041) 

Styrene

(μg/L) 

(77128) 

Bromochloromethane 

(μg/L) 

(77297)

Trichlorofluoromethane 

(CFC-11) 

(μg/L) 

(34488) 

Dichlorodifluoromethane

(CFC-12)

 (μg/L)

 (34668) 

Chloromethane

 (μg/L) 

(34418) 

QPC-05

—

—

—

—

—

—

—

—

— 2

TRCY-02

—

—

— 0.40 E0.02

—

—

—

— 4

TRCY-03

—

— E0.08

—

—

—

—

—

— 2

TRCY-04

—

—

—

—

—

—

—

—

— 0

TRCY-05

—

—

—

—

—

—

—

—

— 0

TRCY-07

—

— E0.06

—

—

—

—

—

— 2

TRCY-09

—

—

—

—

—

—

—

—

— 2

Nongrid cell samples1

TRCYFP-01 

—

— E0.07

—

—

—

—

—

— 2

TRCYFP-02 

—

—

—

—

—

—

—

—

— 6

TRCYFP-03 

—

—

—

—

— 0.24

—

—

— 7

TRCYFP-04

—

— E0.09

—

—

—

—

—

— 3

TRCYFP-05 

—

—

—

—

—

—

—

—

— 1

ESJFP-07 

—

—

—

—

—

—

—

—

— 0

ESJFP-08 

—

—

—

—

—

—

—

— E0.10 6

ESJFP-09 

— E0.07

—

—

—

—

— E30.0

— 9

ESJFP-10 

—

—

—

—

—

—

—

—

— 1

ESJDD-01 

—

— 0.76

—

—

—

—

—

— 3

ESJDD-02 

—

—

—

—

—

—

—

—

— 1

Table 13A. Summary of volatile organic compounds and gasoline oxygenates in ground-water samples collected for the Northern San Joaquin Basin Ground-Water Ambient Monitoring and Assessment (GAMA) study, California, December 2004 to February 2005—Continued.[Concentrations preceded by a “V” indicate detections potentially biased by contamination. Percentage values are detection frequencies. The five digit number below the constituent name is the USGS parameter code used to uniquely identify a specific constituent or property. The threshold type identifies the source of the comparison threshold. The threshold level is the level with which ground-water detections are compared. COS, Cosumnes Basin; E, estimated value; ESJ, Eastern San Joaquin Basin; ESJDD, Eastern San Joaquin Basin depth dependent; ESJFP, Eastern San Joaquin Basin flowpath; ESJMW, Eastern San Joaquin Basin monitoring well; HA-L, lifetime health advisory (U.S. Environmental Protection Agency, 2004b); LRL, laboratory reporting level; MCL-CA, California Department of Health Services Maximum Contaminant Level (California Department of Health Services, 2005a); MCL-US, U.S. Environmental Protection Agency Maximum Contaminant Level (U.S. Environmental Protection Agency, 2005); n/a, not applicable; NL, notification level (California Department of Health Services, 2005d); QPC, Upland Basin; TRCY, Tracy Basin; TRCYFP, Tracy Basin flowpath; USGS, U.S. Geological Survey; μg/L, microgram per liter; —, analyzed but not detected]

See footnotes at end of table.

90 California GAMA Program: Ground-Water Quality Data in the Northern San Joaquin Basin Study Unit, 2005
GAMA well

 identification 

number

Gasoline Organic synthesis Refrigerants

Detections 

per well

o-Xylene 

(μg/L) 

(77135)

1,1-Dichloroethane 

(μg/L)

 (34496) 

1,2,4-Trimethylbenzene

(μg/L) 

(77222)

Carbon 

disulfide 

(μg/L) 

(77041) 

Styrene

(μg/L) 

(77128) 

Bromochloromethane 

(μg/L) 

(77297)

Trichlorofluoromethane 

(CFC-11) 

(μg/L) 

(34488) 

Dichlorodifluoromethane

(CFC-12)

 (μg/L)

 (34668) 

Chloromethane

 (μg/L) 

(34418) 

ESJDD-03 — — — — — — — — — 2ESJDD-04 — — — — — — — — — 1ESJDD-05 E0.02 — — — — — — — — 3ESJDD-06 E0.03 — — — — — — — — 3ESJMW-01 — — — E0.01 — — — — — 2ESJMW-02 E0.05 — E0.04 — — — — — — 4ESJMW-03 — — — — — — — — — 0Grid cell wells with 

VOC detections

1 3 3 1 1 0 3 1 0 2108

Detection frequency 

in grid cell wells (percent)

2 6 6 2 2 0 6 2 0 341

1These samples have been identified as nongrid samples and are not used in the calculation of a detection frequency.2Total number of detections.3Total number of samples with at least a single detection.

Table 13A. Summary of volatile organic compounds and gasoline oxygenates in ground-water samples collected for the Northern San Joaquin Basin Ground-Water Ambient Monitoring and Assessment (GAMA) study, California, December 2004 to February 2005—Continued.[Concentrations preceded by a “V” indicate detections potentially biased by contamination. Percentage values are detection frequencies. The five digit number below the constituent name is the USGS parameter code used to uniquely identify a specific constituent or property. The threshold type identifies the source of the comparison threshold. The threshold level is the level with which ground-water detections are compared. COS, Cosumnes Basin; E, estimated value; ESJ, Eastern San Joaquin Basin; ESJDD, Eastern San Joaquin Basin depth dependent; ESJFP, Eastern San Joaquin Basin flowpath; ESJMW, Eastern San Joaquin Basin monitoring well; HA-L, lifetime health advisory (U.S. Environmental Protection Agency, 2004b); LRL, laboratory reporting level; MCL-CA, California Department of Health Services Maximum Contaminant Level (California Department of Health Services, 2005a); MCL-US, U.S. Environmental Protection Agency Maximum Contaminant Level (U.S. Environmental Protection Agency, 2005); n/a, not applicable; NL, notification level (California Department of Health Services, 2005d); QPC, Upland Basin; TRCY, Tracy Basin; TRCYFP, Tracy Basin flowpath; USGS, U.S. Geological Survey; μg/L, microgram per liter; —, analyzed but not detected]

Tables 91
GAMA well

 identification

 number

Tentatively identified compounds with CAS numbers1

Cyclopentane 

(μg/L)

 (287-92-3) 

Methane chlorodifluoro

(μg/L)

 (75-45-6)

Methane 

dichlorofluoro 

(μg/L)

 (75-43-4)

C5-Alkene 

(μg/L)

 (109-67-1)

C2-cyclopropane 

(μg/L)

 (1191-96-4)

Sulfur 

dioxide

 (μg/L)

 (7446-09-5)

Hexafluoropropene 

(μg/L) 

(116-15-40)

LRL 0.1 0.1 0.1 0.1 0.1 0.1 0.1

Grid cell wells

ESJ-01 0.1

—

—

—

—

—

—

ESJ-02

—

—

— 0.1

—

—

—

ESJ-09

— 0.1 0.8

—

—

—

—

ESJ-13 0.2

—

—

—

—

—

—

ESJ-16

—

—

—

— 0.1

—

—

QPC-07 0.1

—

—

—

—

—

—

QPC-09

—

—

—

—

— 14.6

—

QPC-01 0.1

—

—

—

—

—

—

TRCY-03 0.1

—

—

—

—

—

—

Nongrid cell wells2

ESJFP-09 

— 1.3

—

—

—

—

—

ESJDD-01 

—

—

—

—

—

—

—

ESJDD-02 

—

—

—

—

—

— V5.7

ESJDD-03 

—

—

—

—

—

—

—

ESJDD-04 

—

—

—

—

—

— V1.5

ESJDD-05 

—

—

—

—

—

— V1.6

ESJDD-06 

—

—

—

—

—

— V0.8

Grid cell wells with TIC detections 5 1 1 1 1 1 0Detection frequency in grid cell wells (percent) 10 2 2 2 2 2 0

Table 13B. Summary of tentatively identified compounds (TICs) detected in ground-water samples collected for the Northern San Joaquin Basin Ground-Water Ambient Monitoring and Assessment (GAMA) study, California, December 2004 to February 2005.[Concentrations preceded by a “V” indicate detections potentially biased by contamination. Percentage values are detection frequencies. CAS, Chemical Abstracts Service; E, estimated value; ESJ, Eastern San Joaquin Basin; ESJDD, Eastern San Joaquin Basin depth dependent; ESJFP, Eastern San Joaquin Basin flowpath; GC/MS, gas chromatography/mass spectrometry; LRL, laboratory reporting level; QPC, Upland Basin; TRCY, Tracy Basin; μg/L, microgram per liter; —, analyzed but not detected]

See footnotes at end of table.

92 California GAMA Program: Ground-Water Quality Data in the Northern San Joaquin Basin Study Unit, 2005
GAMA well

 identification

 number

Tentatively identified compounds with CAS numbers1

Detections

 per well

Pentafluoropropene 

(μg/L) 

(690-27-7)

Hexafluoropropene

 and CO2

 (μg/L)

Pentafluoropropene and CO2

 (μg/L)

Unknown (a) 

(μg/L)

C1-Cyclobutane 

(μg/L)

 (598-61-8) 

Unknown (b)

 (μg/L) 

LRL 0.1 0.1 0.1 0.1 0.1 0.1

 Grid cell wells

ESJ-01 — — — — — — 1ESJ-02 — — — — — — 1ESJ-09 — — — — — — 2ESJ-13 — — — — — — 1ESJ-16 — — — — — — 1QPC-07 — — — — — — 1QPC-09 — — — — — — 1QPC-01 — — — — — — 1TRCY-03 — — — — — — 1

 Nongrid cell wells2

ESJFP-09 — — — — — — 1ESJDD-01 — V2.3 V0.3 — — — 2ESJDD-02 V0.8 — — V0.1 — — 3ESJDD-03 — V3.3 V0.7 V0.2 0.1 0.2 5ESJDD-04 — — — — — — 1ESJDD-05 V0.1 — — — — — 2ESJDD-06 — — — — — — 1Grid cell wells with TIC detections 0 0 0 0 0 0 325Detection frequency in grid cell wells (percent) 0 0 0 0 0 0 416

1TICs are based on comparison with the National Institute for Standards and Technology library spectra and examination by a GC/MS analyst; reported concentrations are approximate. 2These samples have been identified as nongrid wells and are not used in the calculation of a detection frequency.3Total number of detections.4Total number of samples with at least a single detection.

Table 13B. Summary of tentatively identified compounds (TICs) detected in ground-water samples collected for the Northern San Joaquin Basin Ground-Water Ambient Monitoring and Assessment (GAMA) study, California, December 2004 to February 2005—Continued.[Concentrations preceded by a “V” indicate detections potentially biased by contamination. Percentage values are detection frequencies. CAS, Chemical Abstracts Service; E, estimated value; ESJ, Eastern San Joaquin Basin; ESJDD, Eastern San Joaquin Basin depth dependent; ESJFP, Eastern San Joaquin Basin flowpath; GC/MS, gas chromatography/mass spectrometry; LRL, laboratory reporting level; QPC, Upland Basin; TRCY, Tracy Basin; μg/L, microgram per liter; —, analyzed but not detected]

Tables 93
GAMA well 

identification

number

Herbicides

Simazine 

(μg/L) 

(04035)

Atrazine

(μg/L)

 (39632)

11,2-Dibromo-3-

chloropropane 

(DBCP) 

(μg/L) 

(82625) 

2Diphenamid 

(μg/L)

 (04033)

Hexazinone 

(μg/L)

 (04025)

Metolachlor 

(μg/L)

(39415)

Tebuthiuron 

(μg/L) 

(82670)

Trifluralin

(μg/L)

 (82661)

 Threshold type MCL-US MCL-CA MCL-US HA-L HA-L HA-L HA-L HA-L Threshold level (μg/L) 4 1 0.2 200 400 100 500 5 LRL 0.005 0.007 30.03 0.01 0.013 0.006 0.02 0.009

 Grid cell wells

COS-04 0.009

—

—

—

—

—

—

—

COS-05

—

— 1.43

—

—

—

—

—

COS-06 0.053

— E0.02

—

—

—

—

—

COS-07

—

—

—

—

—

—

—

—

ESJ-01 0.008 0.011

—

—

—

—

—

—

ESJ-03 0.006

—

—

—

—

—

—

—

ESJ-06

—

— 0.10

—

—

—

—

—

ESJ-07

—

— 0.22

—

—

—

—

—

ESJ-09 0.009 0.009

—

—

— 0.012

—

—

ESJ-15 0.006

—

—

—

—

—

— E0.005

ESJ-16 0.058 0.081

—

—

—

—

—

—

ESJ-19 0.011

—

—

—

—

—

—

—

QPC-01

—

—

—

—

—

—

—

—

QPC-02

— 0.008

—

—

—

—

—

—

TRCY-02

—

—

—

—

—

—

—

—

TRCY-07

—

—

— 0.02

—

—

—

—

TRCY-09

—

—

—

— 0.066

— 0.03

—

Table 14. Summary of pesticides and pesticide degradates in ground-water samples collected for the Northern San Joaquin Basin Ground-Water Ambient Monitoring and Assessment (GAMA) study, California, December 2004 to February 2005.[Bold numbers indicate values above the comparison threshold level. Percentage values are detection frequencies. The five digit number below the constituent name is the USGS parameter code used to uniquely identify a specific constituent or property. The threshold type identifies the source of the comparison threshold. The threshold level is the level with which ground-water detections are compared. COS, Cosumnes Basin; E, estimated value; ESJ, Eastern San Joaquin Basin; ESJDD, Eastern San Joaquin Basin depth dependent; ESJFP, Eastern San Joaquin Basin flowpath; ESJMW, Eastern San Joaquin Basin monitoring well; HA-L, lifetime health advisory (U.S. Environmental Protection Agency, 2004b); LRL, laboratory reporting level; MCL-CA, California Department of Health Services Maximum Contaminant Level (California Department of Health Services, 2005a); MCL-US, U.S. Environmental Protection Agency Maximum Contaminant Level (U.S. Environmental Protection Agency, 2005); MRL, minimum reporting level; n/a, not applicable; nq, compound identified but not quantified; QPC, Upland Basin; TRCY, Tracy Basin; TRCYFP, Tracy Basin flowpath; USGS, U.S. Geological Survey; μg/L, microgram per liter; —, analyzed but not detected]

See footnotes at end of table.

94 California GAMA Program: Ground-Water Quality Data in the Northern San Joaquin Basin Study Unit, 2005
GAMA well 

identification

number

Herbicides

Simazine 

(μg/L) 

(04035)

Atrazine

(μg/L)

 (39632)

11,2-Dibromo-3-

chloropropane 

(DBCP) 

(μg/L) 

(82625) 

2Diphenamid 

(μg/L)

 (04033)

Hexazinone 

(μg/L)

 (04025)

Metolachlor 

(μg/L)

(39415)

Tebuthiuron 

(μg/L) 

(82670)

Trifluralin

(μg/L)

 (82661)

 Nongrid cell wells4

ESJFP-08 — 0.008 — — — — — —ESJFP-09 — — — — — — — —ESJFP-10 — — — — — — — —TRCYFP-02 — — — — E0.008 0.006 — —ESJMW-01 — — — — — — — —ESJDD-01 0.007 — — — — — — —ESJDD-02 0.006 — — — — — — —ESJDD-04 0.018 — — — — — — —ESJDD-05 0.023 — — — — — — —ESJDD-06 0.018 — — — — — — —Detections per compound in grid cell 

wells

8 4 4 1 1 1 1 1

Detection frequency in grid cell wells 

(percent)

16 8 8 2 2 2 2 2

Table 14. Summary of pesticides and pesticide degradates in ground-water samples collected for the Northern San Joaquin Basin Ground-Water Ambient Monitoring and Assessment (GAMA) study, California, December 2004 to February 2005—Continued.[Bold numbers indicate values above the comparison threshold level. Percentage values are detection frequencies. The five digit number below the constituent name is the USGS parameter code used to uniquely identify a specific constituent or property. The threshold type identifies the source of the comparison threshold. The threshold level is the level with which ground-water detections are compared. COS, Cosumnes Basin; E, estimated value; ESJ, Eastern San Joaquin Basin; ESJDD, Eastern San Joaquin Basin depth dependent; ESJFP, Eastern San Joaquin Basin flowpath; ESJMW, Eastern San Joaquin Basin monitoring well; HA-L, lifetime health advisory (U.S. Environmental Protection Agency, 2004b); LRL, laboratory reporting level; MCL-CA, California Department of Health Services Maximum Contaminant Level (California Department of Health Services, 2005a); MCL-US, U.S. Environmental Protection Agency Maximum Contaminant Level (U.S. Environmental Protection Agency, 2005); MRL, minimum reporting level; n/a, not applicable; nq, compound identified but not quantified; QPC, Upland Basin; TRCY, Tracy Basin; TRCYFP, Tracy Basin flowpath; USGS, U.S. Geological Survey; μg/L, microgram per liter; —, analyzed but not detected]

See footnotes at end of table.

Tables 95
GAMA well 

identification

number

Herbicides Pesticide degradates

11,2-Dibromoethane

 (EDB) (μg/L) 

(77651)

2Imazaquin 

(μg/L)

 (50356)

Phorate

 (μg/L)

 (82664)

2-Chloro-4-isopropylamino-6-aminos-triazine (deethylatrazine) (μg/L)

 (04040)

22-Chloro-6-ethylamino-4-amino-striazine (deisopropylatrazine)

(μg/L)

 (04038)

2,6-Diethylaniline 

(μg/L)

 (82660)

3,4-Dichloroaniline 

(μg/L)

 (61625)

Detections 

per well

 Threshold type MCL-US n/a n/a n/a n/a n/a n/a Threshold level (μg/L) 0.05 n/a n/a n/a n/a n/a n/a LRL 30.04 0.036 0.011 0.006 0.01 0.006 0.004

Grid cell wells

COS-04

—

—

—

—

—

—

— 1

COS-05

—

—

—

—

—

—

— 1

COS-06

—

—

—

—

—

—

— 2

COS-07

—

—

— E0.046

—

—

— 1

ESJ-01

—

—

— E0.007

—

—

— 3

ESJ-03

—

—

—

—

—

—

— 1

ESJ-06

—

—

—

—

—

—

— 1

ESJ-07

—

—

— E0.009

—

—

— 1

ESJ-09

—

—

— E0.007

—

—

— 4

ESJ-15

—

—

—

—

—

—

— 2

ESJ-16

—

—

— E0.035

—

—

— 3

ESJ-19

—

—

— E0.008 E0.04

—

— 3

QPC-01

—

—

— E0.006 E0.02

—

— 2

QPC-02

—

—

— E0.008

—

—

— 2

TRCY-02

—

—

—

—

—

— 0.045 1

TRCY-07

—

—

—

—

— E0.004

— 2

TRCY-09

—

—

—

—

— E0.004

— 3

Table 14. Summary of pesticides and pesticide degradates in ground-water samples collected for the Northern San Joaquin Basin Ground-Water Ambient Monitoring and Assessment (GAMA) study, California, December 2004 to February 2005—Continued.[Bold numbers indicate values above the comparison threshold level. Percentage values are detection frequencies. The five digit number below the constituent name is the USGS parameter code used to uniquely identify a specific constituent or property. The threshold type identifies the source of the comparison threshold. The threshold level is the level with which ground-water detections are compared. COS, Cosumnes Basin; E, estimated value; ESJ, Eastern San Joaquin Basin; ESJDD, Eastern San Joaquin Basin depth dependent; ESJFP, Eastern San Joaquin Basin flowpath; ESJMW, Eastern San Joaquin Basin monitoring well; HA-L, lifetime health advisory (U.S. Environmental Protection Agency, 2004b); LRL, laboratory reporting level; MCL-CA, California Department of Health Services Maximum Contaminant Level (California Department of Health Services, 2005a); MCL-US, U.S. Environmental Protection Agency Maximum Contaminant Level (U.S. Environmental Protection Agency, 2005); MRL, minimum reporting level; n/a, not applicable; nq, compound identified but not quantified; QPC, Upland Basin; TRCY, Tracy Basin; TRCYFP, Tracy Basin flowpath; USGS, U.S. Geological Survey; μg/L, microgram per liter; —, analyzed but not detected]

See footnotes at end of table.

96 California GAMA Program: Ground-Water Quality Data in the Northern San Joaquin Basin Study Unit, 2005
GAMA well 

identification

number

Herbicides Pesticide degradates

11,2-Dibromoethane

 (EDB) (μg/L) 

(77651)

2Imazaquin 

(μg/L)

 (50356)

Phorate

 (μg/L)

 (82664)

2-Chloro-4-isopropylamino-6-aminos-triazine (deethylatrazine) (μg/L)

 (04040)

22-Chloro-6-ethylamino-4-amino-striazine (deisopropylatrazine)

(μg/L)

 (04038)

2,6-Diethylaniline 

(μg/L)

 (82660)

3,4-Dichloroaniline 

(μg/L)

 (61625)

Detections 

per well

Nongrid cell wells4

ESJFP-08 — — — E0.008 — — — 2ESJFP-09 0.14 — — — — — — 1ESJFP-10 — — — — E0.02 — — 1TRCYFP-02 — — — — — — — 2ESJMW-01 — nq — — — — — 1ESJDD-01 — — — — — — — 1ESJDD-02 — — — — — — — 1ESJDD-04 — — — E0.009 E0.08 — — 3ESJDD-05 — — — E0.006 E0.06 — — 3ESJDD-06 — — E0.004 E0.005 E0.04 — — 4Detections per compound in grid cell 

wells

0 0 0 8 2 2 1 552

Detection frequency in grid cell 

wells (percent)

0 0 0 16 4 4 2 627

11,2-Dibromo-3-chloropropane (DBCP) and 1,2-Dibromoethane (EDB) concentrations reported from the preferred analysis method, pesticide analytical Schedule 1306.2Concentrations of these compounds are reported from the preferred analytical Schedule 2060.3Although listed as LRLs, DBCP and EDB are reported to the Minimum Reporting Level or MRL.4These samples have been identified as nongrid wells and are not used in the calculation of a detection frequency.5Total number of detections.6Total number of samples with at least a single detection.

Table 14. Summary of pesticides and pesticide degradates in ground-water samples collected for the Northern San Joaquin Basin Ground-Water Ambient Monitoring and Assessment (GAMA) study, California, December 2004 to February 2005—Continued.[[Bold numbers indicate values above the comparison threshold level. Percentage values are detection frequencies. The five digit number below the constituent name is the USGS parameter code used to uniquely identify a specific constituent or property. The threshold type identifies the source of the comparison threshold. The threshold level is the level with which ground-water detections are compared. COS, Cosumnes Basin; E, estimated value; ESJ, Eastern San Joaquin Basin; ESJDD, Eastern San Joaquin Basin depth dependent; ESJFP, Eastern San Joaquin Basin flowpath; ESJMW, Eastern San Joaquin Basin monitoring well; HA-L, lifetime health advisory (U.S. Environmental Protection Agency, 2004b); LRL, laboratory reporting level; MCL-CA, California Department of Health Services Maximum Contaminant Level (California Department of Health Services, 2005a); MCL-US, U.S. Environmental Protection Agency Maximum Contaminant Level (U.S. Environmental Protection Agency, 2005); MRL, minimum reporting level; n/a, not applicable; nq, compound identified but not quantified; QPC, Upland Basin; TRCY, Tracy Basin; TRCYFP, Tracy Basin flowpath; USGS, U.S. Geological Survey; μg/L, microgram per liter; —, analyzed but not detected]

Tables 97
GAMA well 

identification 

number

Isophorone 

(μg/L) 

(34409) 

Benzophenone 

(μg/L)

 (62067)

4-Nonylphenol 

(μg/L)

 (62085)

1Caffeine

 (μg/L)

 (50305)

Bisphenol A 

(μg/L) 

(62069) 

Tris

(dichloroisopropyl) 

phosphate 

(μg/L)

 (62088)

2Phenol 

(μg/L)

 (34466) Detections

 per well

 Threshold type HA-L n/a n/a n/a n/a n/a HA-L Threshold level (μg/L) 100 n/a n/a n/a n/a n/a 2,000 IRL 0.5 0.5 5.0 0.018 1.0 0.5 0.5ESJ-12 nq

—

—

—

—

— VE0.5 1

ESJ-19

— nq nq

—

—

— VE0.2 2

QPC-01 nq

—

— 0.078

—

— VE0.5 2

TRCY-07 nq

—

— E0.005

—

—

— 2

TRCY-03 E0.1

—

—

—

—

— V0.7 1

ESJFP-07

—

—

—

—

—

— VE0.3 0

ESJFP-10

—

—

—

—

—

— V0.9 0

TRCYFP-01 nq

—

—

—

—

—

— 1

TRCYFP-02 nq

—

—

—

— nq

— 2

TRCYFP-04 nq

—

—

—

—

—

— 1

ESJDD-04

— nq nq

—

—

— VE0.3 2

ESJDD-05

— nq nq

—

—

— VE0.5 2

ESJDD-06

— E0.1 E2

—

—

— VE0.3 2

ESJMW-01

—

—

— E0.005

—

—

— 1

ESJMW-02

—

—

—

—

—

— V0.9 0

ESJMW-03

—

—

—

— nq

— VE0.2 1

Detections per compound3 7 4 4 3 1 1 0 420Detection frequency 

(percent)3

44 25 25 19 6 6 0 513

1Caffeine concentration reported is from the preferred analysis method, pesticide analytical Schedule 2060.2Because of the high phenol contents in the blank samples, phenol detections have been censored.3Wastewater-indicator constituents were not collected at all sites; therefore, the detection frequency does not represent the detection frequency throughout the entire study unit.

Table 15. Summary of wastewater-indicator constituents in ground-water samples collected for the Northern San Joaquin Basin Ground-Water Ambient Monitoring and Assessment (GAMA) study unit, California, December 2004 to February 2005. [Concentrations preceded by a “V” indicate detections potentially biased by contamination and are not included in ground-water quality analysis. Percentage values are detection frequencies. Wastewaterindicator constituents were not collected at all sites; therefore, the detection frequency does not represent the detection frequency throughout the entire study unit. The five digit number below the constituent name is the USGS parameter code used to uniquely identify a specific constituent or property. The threshold type identifies the source of the comparison threshold. The threshold level is the level with which ground-water detections are compared. E, estimated value; ESJ, Eastern San Joaquin Basin; ESJDD, Eastern San Joaquin Basin depth dependent; ESJFP, Eastern San Joaquin Basin flowpath; ESJMW, Eastern San Joaquin Basin monitoring well; HA-L, lifetime health advisory (U.S. Environmental Protection Agency, 2004b); IRL, interim reporting limit; n/a, not applicable; nq, compound identified but not quantified; QPC, Uplands Basin; TRCY, Tracy Basin; TRCYFP, Tracy Basin flowpath; USGS, U.S. Geological Survey; μg/L, microgram per liter; —, not detected]

4Total number of detections.5Total number of samples with at least a single detection.

98 California GAMA Program: Ground-Water Quality Data in the Northern San Joaquin Basin Study Unit, 2005
GAMA well

 identification number

Perchlorate

(μg/L)

(61209)

N-Nitrosodimethylamine

(NDMA)

(μg/L) 

(64176)

1,2,3-Trichloropropane 

(1,2,3-TCP)

(μg/L) 

(77443)

Detections 

per well

 Threshold type NL NL NL

 Threshold level (μg/L) 6 0.01 0.005

 MRL 0.5 0.002 0.005

ESJ-16 1.0 — — 1

ESJDD-01 0.7 — — 1

Detections per compound 2 0 0 12

Detection frequency (percent) 6 0 0 22

1

Total number of detections.

2

Total number of samples with at least a single detection.

Table 16. Summary of constituents of special interest for the ground-water samples collected in the Northern San Joaquin Basin 

Ground-Water Ambient Monitoring and Assessment (GAMA) study, California, December 2004 to February 2005.

[The constituents of special interest were not collected at all sites; therefore, the detection frequencies presented in this table do not represent detection frequencies throughout the entire study unit. Percentage values are detection frequencies. The five digit number below the constituent name is the USGS parameter 

code used to uniquely identify a specific constituent or property. The threshold type identifies the source of the comparison threshold. The threshold level is the 

level with which ground-water detections are compared. ESJ, Eastern San Joaquin Basin; ESJDD, Eastern San Joaquin Basin depth dependent; MRL, Minimum 

Reporting Level; NL, notification level (California Department of Health Services, 2005d); USGS, U.S. Geological Survey; μg/L, microgram per liter; —, 

analyzed but not detected]

Tables 99
GAMA well

 identification 

number

Ammonia, 

dissolved 

as nitrogen 

(mg/L)

(00608)

 Nitrite, 

dissolved 

as nitrogen 

(mg/L)

 (00613)

Nitrite plus nitrate, 

dissolved 

as nitrogen 

(mg/L)

 (00631)

Total nitrogen (nitrate 

+ nitrite + ammonia 

+ organic-nitrogen) 

dissolved as nitrogen 

(mg/L) 

(62854)

Orthophosphate,

 dissolved as 

phosphorous 

(mg/L) 

(00671)

Dissolved 

organic carbon

(mg/L) 

(00681)

 Threshold type HA-L MCL-US MCL-US n/a n/a n/a Threshold level (mg/L) 30 1 10 n/a n/a n/a LRL 0.04 0.008 0.06 0.06 0.006 0.3

 Grid cell samples

ESJ-12

—

— 0.91 0.95 0.046 VE0.2

ESJ-19

—

— E0.05 0.06 0.054 0.4

QPC-01

—

— 3.31 3.5 0.044 0.4

TRCY-03

—

— 2.30 2.44 0.016 VE0.2

TRCY-07 0.63 0.026

— 0.81 0.227 9.6

 Flowpath samples

TRCYFP-01 0.71

—

— 0.75 0.148 8.5

TRCYFP-02 E0.03

— 1.69 1.79 0.02 0.3

TRCYFP-04

—

— 1.86 2.01 0.02 VE0.2

ESJFP-07

—

— 0.54 0.57 0.025 VE0.2

ESJFP-10

—

— 1.37 1.44 0.033

—

 Monitoring well samples

ESJMW-01

— 0.016 0.77 0.78 0.022 nc

ESJMW-02

—

— 0.70 0.7 0.03 nc

ESJMW-03

—

— 1.06 1.1 0.031 nc

 Depth-dependent samples

ESJDD-02

—

— 0.69 0.78 0.034 nc

ESJDD-03

—

— 0.95 0.99 0.034 nc

ESJDD-04

—

— E0.04 V0.12 0.034 nc

ESJDD-05

—

—

— VE0.04 0.044 nc

ESJDD-06

—

—

—

— 0.05 nc

Table 17. Summary of nutrient and dissolved organic carbon data collected from ground-water samples in the Northern San Joaquin Basin Ground-Water Ambient Monitoring and Assessment (GAMA) study, California, December 2004 to February 2005.[Concentrations preceded by a “V” indicate detections potentially biased by contamination and are not included in ground-water quality analysis. The five digit number below the constituent name is the USGS parameter code used to uniquely identify a specific constituent or property. The threshold type identifies the source of the comparison threshold. The threshold level is the level with which ground-water detections are compared. E, estimated value; ESJ, Eastern San Joaquin Basin; ESJDD, Eastern San Joaquin Basin depth dependent; ESJFP, Eastern San Joaquin Basin flowpath; ESJMW, Eastern San Joaquin Basin monitoring well; HA-L, lifetime health advisory (U.S. Environmental Protection Agency, 2004b); LRL, laboratory reporting level; MCL-US, U.S. Environmental Protection Agency Maximum Contaminant Level (U.S. Environmental Protection Agency, 2005); mg/L, milligram per liter; n/a, not applicable; nc, not collected; QPC, Uplands Basin; TRCY, Tracy Basin; TRCYFP, Tracy Basin flowpath; USGS, U.S. Geological Survey; —, analyzed but not detected]

100 California GAMA Program: Ground-Water Quality Data in the Northern San Joaquin Basin Study Unit, 2005
GAMA 

well identification 

number

Bromide,

 dissolved 

(mg/L)

(71870) 

Calcium, 

dissolved 

(mg/L) 

(00915) 

Chloride, 

dissolved 

(mg/L) 

(00940) 

Fluoride, 

dissolved 

(mg/L)

(00950) 

Iodide,

dissolved

(mg/L)

(71865)

Magnesium, 

dissolved 

(mg/L)

 (00925) 

Potassium,

 dissolved 

(mg/L)

 (00935) 

Silica, 

dissolved 

(mg/L)

 (00955) 

Sodium,

 dissolved 

(mg/L)

(00930) 

Sulfate,

 dissolved

 (mg/L) 

(00945) 

Total dissolved solids

 (residue on 

evaporation) 

(mg/L)

 (70300)

 Threshold type n/a n/a SMCL-US MCL-US n/a n/a n/a n/a n/a SMCL-US SMCL-USThreshold level (mg/L) n/a n/a 250 2 n/a n/a n/a n/a n/a 250 500 LRL 0.02 0.02 0.2 0.1 0.002 0.008 0.16 0.04 0.2 0.18 10

 Eastern San Joaquin Basin wells

ESJ-06 0.08 28.1 13.5 0.1 0.004 13.2 7.42 67.2 19.2 13.6 243ESJ-08 0.03 13.1 7.6 0.3 V0.002 7.57 3.25 82.5 16.2 2.93 190ESJ-10 0.10 23.4 15.5 0.1 0.037 7.7 4.34 56 19.8 4.16 189ESJ-12 0.06 24.8 4.1 0.2 VE0.001 11.8 3.52 68 12 3.63 200ESJ-13 0.04 19.1 3.7 0.1 VE0.001 7.86 4.41 70.3 10.5 3.61 177ESJ-14 0.08 23.6 13.1 0.1 0.025 9.27 2.06 51 27.6 6.34 204ESJ-15 0.20 63.9 48.6 0.1 0.048 22 3.76 48.3 25.8 30.9 355ESJ-16 0.06 26.3 6.2 0.1 V0.002 12.5 5.71 66.2 15.3 12.1 224ESJ-17 0.06 13.7 10.2 0.2 V0.002 7.89 3.13 80.7 16.1 11.2 194ESJ-18 0.06 14.8 9.3 0.2 VE0.001 8.22 3.57 78.5 12.7 7.91 188ESJ-19 0.10 37.6 25.7 E0.1 0.003 16.8 4.77 49.6 33.2 24.7 294

 Upland Basin wells

QPC-01 0.10 37.6 9.5 0.1 VE0.002 15.9 2.42 53.3 12 27.9 257QPC-04 0.04 4.59 3.9 0.2 0.004 2.58 4.1 93.3 22.8 2.33 165QPC-06 0.07 12.8 10.8 0.3 0.012 6.55 6.66 88.4 15.1 1.4 181QPC-07 0.10 22.3 18 0.2 0.012 22.4 2.62 59.2 27.2 10.8 259QPC-08 0.10 15.2 5.6 0.2 — 8.87 3.21 84.2 16.8 5.72 198

Table 18. Summary of major and minor ions and total dissolved solids in ground-water samples collected for the Northern San Joaquin Basin Ground-Water Ambient Monitoring and Assessment (GAMA) study, California, December 2004 to February 2005.[Bold numbers indicate ground-water detections above the threshold level. Values preceded by a “V” indicate detections potentially biased by contamination. The five digit number below the constituent name is the USGS parameter code used to uniquely identify a specific constituent or property. The threshold type identifies the source of the comparison threshold. The threshold level is the level with which groundwater detections are compared. Although listed as an LRL, total dissolved solids are reported as the MRL (Timme, 1995). E, estimated value; ESJ, Eastern San Joaquin Basin; ESJDD, Eastern San Joaquin Basin depth dependent; ESJFP, Eastern San Joaquin Basin flowpath; ESJMW, Eastern San Joaquin Basin monitoring well; LRL, laboratory reporting level; MCL-US, U.S. Environmental Protection Agency Maximum Contaminant Level (U.S. Environmental Protection Agency, 2005); mg/L, milligram per liter; MRL, Minimum Reporting Level (Timme, 1995); n/a, not applicable; QPC, Uplands Basin; SMCL-US, U.S. Environmental Protection Agency Secondary Maximum Contaminant Level (U.S. Environmental Protection Agency, 2005); TRCY, Tracy Basin; TRCYFP, Tracy Basin flowpath; USGS, U.S. Geological Survey; —, analyzed but not detected]

Tables 101
GAMA 

well identification 

number

Bromide,

 dissolved 

(mg/L)

(71870) 

Calcium, 

dissolved 

(mg/L) 

(00915) 

Chloride, 

dissolved 

(mg/L) 

(00940) 

Fluoride, 

dissolved 

(mg/L)

(00950) 

Iodide,

dissolved

(mg/L)

(71865)

Magnesium, 

dissolved 

(mg/L)

 (00925) 

Potassium,

 dissolved 

(mg/L)

 (00935) 

Silica, 

dissolved 

(mg/L)

 (00955) 

Sodium,

 dissolved 

(mg/L)

(00930) 

Sulfate,

 dissolved

 (mg/L) 

(00945) 

Total dissolved solids

 (residue on 

evaporation) 

(mg/L)

 (70300)

QPC-10 0.06 14.3 8.4 0.3 VE0.002 8.76 2.64 76 15.3 5.07 185

 Tracy Basin wells

TRCY-03 0.39 80.9 102 0.2 0.015 26.8 3.17 23.4 138 248 751TRCY-09 0.46 38.7 108 0.2 0.068 18.3 2.82 29.4 77.5 34 414TRCY-11 0.51 38.5 82.1 E0.1 0.12 16.2 3.39 34.3 134 191 604TRCY-07 3.07 397 1,020 0.2 0.15 213 4.2 45.7 240 750 2,740

 Flowpath wells

TRCYFP-01 8.77 254 2,400

— 1.8 141 5.85 35.1 1,090 62.9 4,350

TRCYFP-02 0.44 66.5 114 0.2 0.017 30.6 4 21.3 120 252 721TRCYFP-03 0.46 49.0 126 0.1 0.044 21.9 3.67 24 145 223 675TRCYFP-04 0.50 94 124 0.2 0.016 33.2 3.41 24.8 156 309 889TRCYFP-05 0.71 57.9 168 0.1 0.032 24.7 4.49 20.1 170 244 778ESJFP-07 0.03 20.4 4.3 0.1 V0.002 11.3 5.28 70.9 12.2 6.05 192ESJFP-08 0.11 41.4 58.5 0.1 0.006 15 2.76 53.9 53.2 18.8 339ESJFP-09 0.10 47.7 12.8 0.1 VE0.002 26.1 4.92 67 17.5 18.7 323ESJFP-10 0.07 31.3 6.9 E0.1 VE0.001 18.1 6.03 64.1 14.3 16.1 243

Monitoring wells

ESJMW-01 0.06 19.2 5.0 E0.1 0.004 12.2 5.25 60.5 16.4 7.7 186ESJMW-02 0.06 20.4 4.8 0.1 VE0.002 12.2 5.11 66.7 13.4 9.45 194ESJMW-03 0.08 27.4 5.7 0.1 VE0.002 15.7 4.72 68.8 15.3 20.1 235

Table 18. Summary of major and minor ions and total dissolved solids in ground-water samples collected for the Northern San Joaquin Basin Ground-Water Ambient Monitoring and Assessment (GAMA) study, California, December 2004 to February 2005—Continued.[Bold numbers indicate ground-water detections above the threshold level. Values preceded by a “V” indicate detections potentially biased by contamination. The five digit number below the constituent name is the USGS parameter code used to uniquely identify a specific constituent or property. The threshold type identifies the source of the comparison threshold. The threshold level is the level with which groundwater detections are compared. Although listed as an LRL, total dissolved solids are reported as the MRL (Timme, 1995). E, estimated value; ESJ, Eastern San Joaquin Basin; ESJDD, Eastern San Joaquin Basin depth dependent; ESJFP, Eastern San Joaquin Basin flowpath; ESJMW, Eastern San Joaquin Basin monitoring well; LRL, laboratory reporting level; MCL-US, U.S. Environmental Protection Agency Maximum Contaminant Level (U.S. Environmental Protection Agency, 2005); mg/L, milligram per liter; MRL, Minimum Reporting Level (Timme, 1995); n/a, not applicable; QPC, Uplands Basin; SMCL-US, U.S. Environmental Protection Agency Secondary Maximum Contaminant Level (U.S. Environmental Protection Agency, 2005); TRCY, Tracy Basin; TRCYFP, Tracy Basin flowpath; USGS, U.S. Geological Survey; —, analyzed but not detected]

102 California GAMA Program: Ground-Water Quality Data in the Northern San Joaquin Basin Study Unit, 2005
GAMA 

well identification 

number

Bromide,

 dissolved 

(mg/L)

(71870) 

Calcium, 

dissolved 

(mg/L) 

(00915) 

Chloride, 

dissolved 

(mg/L) 

(00940) 

Fluoride, 

dissolved 

(mg/L)

(00950) 

Iodide,

dissolved

(mg/L)

(71865)

Magnesium, 

dissolved 

(mg/L)

 (00925) 

Potassium,

 dissolved 

(mg/L)

 (00935) 

Silica, 

dissolved 

(mg/L)

 (00955) 

Sodium,

 dissolved 

(mg/L)

(00930) 

Sulfate,

 dissolved

 (mg/L) 

(00945) 

Total dissolved solids

 (residue on 

evaporation) 

(mg/L)

 (70300)

 Depth-dependent samples

ESJDD-01 0.07 31.5 7.0 E0.1 V0.002 18.3 6.06 63.1 16 17.3 253ESJDD-02 0.04 21.1 5.1 0.1 VE0.001 12.6 5.4 62.4 12.1 8 193ESJDD-03 0.07 26.1 5.8 E0.1 VE0.001 15.2 5.81 62.2 12.6 11 223ESJDD-04 0.22 42 20.4 0.1 0.033 18.7 4.09 51.7 28.3 23.8 313ESJDD-05 0.22 41 20.6 0.1 0.032 17.9 4.24 52.4 28.8 22.4 294ESJDD-06 0.11 37.3 21.4 0.2 0.031 16.6 4.35 51 33 19.1 271

Table 18. Summary of major and minor ions and total dissolved solids in ground-water samples collected for the Northern San Joaquin Basin Ground-Water Ambient Monitoring and Assessment (GAMA) study, California, December 2004 to February 2005—Continued.[Bold numbers indicate ground-water detections above the threshold level. Values preceded by a “V” indicate detections potentially biased by contamination. The five digit number below the constituent name is the USGS parameter code used to uniquely identify a specific constituent or property. The threshold type identifies the source of the comparison threshold. The threshold level is the level with which groundwater detections are compared. Although listed as an LRL, total dissolved solids are reported as the MRL (Timme, 1995). E, estimated value; ESJ, Eastern San Joaquin Basin; ESJDD, Eastern San Joaquin Basin depth dependent; ESJFP, Eastern San Joaquin Basin flowpath; ESJMW, Eastern San Joaquin Basin monitoring well; LRL, laboratory reporting level; MCL-US, U.S. Environmental Protection Agency Maximum Contaminant Level (U.S. Environmental Protection Agency, 2005); mg/L, milligram per liter; MRL, Minimum Reporting Level (Timme, 1995); n/a, not applicable; QPC, Uplands Basin; SMCL-US, U.S. Environmental Protection Agency Secondary Maximum Contaminant Level (U.S. Environmental Protection Agency, 2005); TRCY, Tracy Basin; TRCYFP, Tracy Basin flowpath; USGS, U.S. Geological Survey; —, analyzed but not detected]

Tables 103
GAMA well

identification

number

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) 

 Threshold type MCL-US MCL-US MCL-US MCL-CA MCL-US NL MCL-US MCL-CA Threshold level (μg/L) 1,000 6 10 1,000 4 1,000 5 50 LRL 1.6 0.2 0.2 0.2 0.06 8 0.04 0.8

Eastern San Joaquin Basin wells

ESJ-06 nq

— 4.5 97

— 34

— 4.6

ESJ-08 E1

— 3.3 68

— 65

— 4.3

ESJ-10 nq E0.1 7 174

— 36

—

—

ESJ-12 E1

— 1.2 85

— 21

— 4.9

ESJ-13 nq

— 1.2 83

— 22

— 2.9

ESJ-14 E1

— 24.9 175

— 41

—

—

ESJ-15 nq

— 4.8 282

— 35

—

—

ESJ-16 E1

— 6.5 116

— 37

— 1.0

ESJ-17 E1

— 2.1 64

— 122 E0.02 4.3

ESJ-18 E1

— 2 78

— 48

— 2.3

ESJ-19 E1 E0.2 8 195

— 68

—

—

 Upland Basin wells

QPC-01 —

— 0.7 101

— 37

— 1.1

QPC-04 nq

— 2.3 30

— 32

— 1.2

QPC-06 nq E0.2 3.3 53

— 18

—

—

QPC-07 —

— 1.7 98

— 222

—

—

Table 19. Summary of trace elements detected in ground-water samples collected for the Northern San Joaquin Basin Ground-Water Ambient Monitoring and Assessment (GAMA) study, California, December 2004 to February 2005.[Bold numbers indicate ground-water detections above the threshold level. Concentrations preceded by a “V” indicate detections potentially biased by contamination. The five digit number below the constituent name is the USGS parameter code used to uniquely identify a specific constituent or property. The threshold type identifies the source of the comparison threshold. The threshold level is the level with which ground-water detections are compared. Although listed as an LRL, tungsten is reported as the MRL (Timme, 1995). E, estimated value; ESJ, Eastern San Joaquin Basin; ESJDD, Eastern San Joaquin Basin depth dependent; ESJFP, Eastern San Joaquin Basin flowpath; ESJMW, Eastern San Joaquin Basin monitoring well; HA-L, lifetime health advisory (U.S. Environmental Protection Agency, 2004b); LRL, laboratory reporting level; MCL-CA, California Department of Health Services Maximum Contaminant Level (California Department of Health Services, 2005a); MCL-US, U.S. Environmental Protection Agency Maximum Contaminant Level (U.S. Environmental Protection Agency, 2005); MRL, Minimum Reporting Level (Timme, 1995); n/a, not applicable; nc, not collected; NL, notification level (California Department of Health Services, 2005d; nq, constituent detected but not quantified; QPC, Uplands Basin; SMCL-US, U.S. Environmental Protection Agency Secondary Maximum Contaminant Level (U.S. Environmental Protection Agency, 2005); TRCY, Tracy Basin; TRCYFP, Tracy Basin flowpath; USGS, U.S. Geological Survey; μg/L, microgram per liter; —, analyzed but not detected]

See footnote at end of table.

104 California GAMA Program: Ground-Water Quality Data in the Northern San Joaquin Basin Study Unit, 2005
GAMA well

identification

number

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) 

QPC-08 nq — 1.9 45.1 — 18 — 2.7QPC-10 E1 — 2.8 83 — 50 — 1.4

 Tracy Basin wells

TRCY-03 — — 0.8 25 — 2,190 — 7.2TRCY-07 — — 23.6 59 — 77 0.16 —TRCY-09 E1 — 4.7 102 — 194 — —TRCY-11 3 — 7.2 44 — 916 — —

Flowpath wells

TRCYFP-01 — — 7.2 158 — 738 — —TRCYFP-02 — — 1.3 30 — 1,340 — 6.7TRCYFP-03 E3 — 2.5 28 — 1,180 — 1.2TRCYFP-04 E1 — 0.8 26 — 2,310 — 7.1TRCYFP-05 — — 1.7 26 — 1,180 — 1.9ESJFP-07 2 — 1.9 69 — 24 — 3.9ESJFP-08 E1 — 13.9 210 — 201 — E0.4ESJFP-09 E1 — 2.5 141 — 22 — 5.6ESJFP-10 nq — 3.3 86 — 26 — 6.3

 Monitoring wells

ESJMW-01 nq — 3.9 49 — 35 0.1 2.7ESJMW-02 — — 4.2 61 — 26 E0.03 7.7ESJMW-03 nq — 3.3 83 — 22 E0.03 2.1

Table 19. Summary of trace elements detected in ground-water samples collected for the Northern San Joaquin Basin Ground-Water Ambient Monitoring and Assessment (GAMA) study, California, December 2004 to February 2005—Continued.[Bold numbers indicate ground-water detections above the threshold level. Concentrations preceded by a “V” indicate detections potentially biased by contamination. The five digit number below the constituent name is the USGS parameter code used to uniquely identify a specific constituent or property. The threshold type identifies the source of the comparison threshold. The threshold level is the level with which ground-water detections are compared. Although listed as an LRL, tungsten is reported as the MRL (Timme, 1995). E, estimated value; ESJ, Eastern San Joaquin Basin; ESJDD, Eastern San Joaquin Basin depth dependent; ESJFP, Eastern San Joaquin Basin flowpath; ESJMW, Eastern San Joaquin Basin monitoring well; HA-L, lifetime health advisory (U.S. Environmental Protection Agency, 2004b); LRL, laboratory reporting level; MCL-CA, California Department of Health Services Maximum Contaminant Level (California Department of Health Services, 2005a); MCL-US, U.S. Environmental Protection Agency Maximum Contaminant Level (U.S. Environmental Protection Agency, 2005); MRL, Minimum Reporting Level (Timme, 1995); n/a, not applicable; nc, not collected; NL, notification level (California Department of Health Services, 2005d; nq, constituent detected but not quantified; QPC, Uplands Basin; SMCL-US, U.S. Environmental Protection Agency Secondary Maximum Contaminant Level (U.S. Environmental Protection Agency, 2005); TRCY, Tracy Basin; TRCYFP, Tracy Basin flowpath; USGS, U.S. Geological Survey; μg/L, microgram per liter; —, analyzed but not detected]

See footnote at end of table.

Tables 105
GAMA well

identification

number

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) 

 Depth-dependent samples

ESJDD-01 2 — 3.9 88

— 31

— 6.4

ESJDD-02 3 — 3.9 57

— 28

— 8.3

ESJDD-03 E2

— 3.6 71

— 27

— 7.4

ESJDD-04 9 E0.1 8.2 193 E0.04 65

—

—

ESJDD-05 E1 E0.1 8.9 192

— 70

—

—

ESJDD-06 nq E0.2 8.5 181

— 74

—

—

Table 19. Summary of trace elements detected in ground-water samples collected for the Northern San Joaquin Basin Ground-Water Ambient Monitoring and Assessment (GAMA) study, California, December 2004 to February 2005—Continued.[Bold numbers indicate ground-water detections above the threshold level. Concentrations preceded by a “V” indicate detections potentially biased by contamination. The five digit number below the constituent name is the USGS parameter code used to uniquely identify a specific constituent or property. The threshold type identifies the source of the comparison threshold. The threshold level is the level with which ground-water detections are compared. Although listed as an LRL, tungsten is reported as the MRL (Timme, 1995). E, estimated value; ESJ, Eastern San Joaquin Basin; ESJDD, Eastern San Joaquin Basin depth dependent; ESJFP, Eastern San Joaquin Basin flowpath; ESJMW, Eastern San Joaquin Basin monitoring well; HA-L, lifetime health advisory (U.S. Environmental Protection Agency, 2004b); LRL, laboratory reporting level; MCL-CA, California Department of Health Services Maximum Contaminant Level (California Department of Health Services, 2005a); MCL-US, U.S. Environmental Protection Agency Maximum Contaminant Level (U.S. Environmental Protection Agency, 2005); MRL, Minimum Reporting Level (Timme, 1995); n/a, not applicable; nc, not collected; NL, notification level (California Department of Health Services, 2005d; nq, constituent detected but not quantified; QPC, Uplands Basin; SMCL-US, U.S. Environmental Protection Agency Secondary Maximum Contaminant Level (U.S. Environmental Protection Agency, 2005); TRCY, Tracy Basin; TRCYFP, Tracy Basin flowpath; USGS, U.S. Geological Survey; μg/L, microgram per liter; —, analyzed but not detected]

See footnote at end of table.

106 California GAMA Program: Ground-Water Quality Data in the Northern San Joaquin Basin Study Unit, 2005
GAMA well 

identification

 number

Cobalt, 

dissolved 

(μg/L)

 (01035) 

Copper, 

dissolved

 (μg/L)

 (01040) 

Iron, 

dissolved 

(μg/L) 

(01046) 

Lead, 

dissolved 

(μg/L) 

(01049) 

Lithium,

dissolved 

(μg/L) 

(01130) 

Manganese, 

dissolved 

(μg/L) 

(01056) 

Mercury, 

dissolved 

(μg/L) 

(71890) 

Molybdenum, 

dissolved 

(μg/L) 

(01060) 

 Threshold type n/a MCL-US SMCL-US MCL-US n/a NL MCL-US HA-L Threshold level (μg/L) n/a 11,300 300 115 n/a 500 2 40 LRL 0.014 0.4 6 0.08 0.6 0.2 0.01 0.4

 Eastern San Joaquin Basin wells

ESJ-06 0.073 VE0.4 — E0.07 0.8 — nc 0.9ESJ-08 0.033 1.7 — 1.75 1.2 0.4 nc 0.9ESJ-10 0.072 2.4 17 1.08 1.5 66.2 nc 1.4ESJ-12 0.067 2.8 6 1.37 1.6 0.4 — 0.6ESJ-13 0.048 1.5 14 0.23 2.6 1.2 nc 0.8ESJ-14 0.062 — 65 — 0.7 187 nc 4.4ESJ-15 0.145 1.4 — 0.65 1.8 19 nc 1ESJ-16 0.056 4.2 13 6.48 1.3 6.5 nc 0.7ESJ-17 0.053 VE0.4 — 0.27 2.6 2.2 nc 0.7ESJ-18 0.032 1.1 — 0.22 5.1 V0.2 nc 0.6ESJ-19 0.118 2.3 E4 0.91 2.1 0.9 — 1

 Upland Basin wells

QPC-01 0.103 3.2 — 2.30 E0.6 V0.2 — E0.3QPC-04 0.025 — 150 0.12 3.7 54.8 nc 0.8

QPC-06 0.017 — E3 0.13 13.6 2.6 nc 0.5QPC-07 0.041 1.7 E5 1.14 49.8 0.4 nc 0.7QPC-08 0.029 2.4 E3 0.37 1.1 — nc 0.5

Table 19. Summary of trace elements detected in ground-water samples collected for the Northern San Joaquin Basin Ground-Water Ambient Monitoring and Assessment (GAMA) study, California, December 2004 to February 2005—Continued.[Bold numbers indicate ground-water detections above the threshold level. Concentrations preceded by a “V” indicate detections potentially biased by contamination. The five digit number below the constituent name is the USGS parameter code used to uniquely identify a specific constituent or property. The threshold type identifies the source of the comparison threshold. The threshold level is the level with which ground-water detections are compared. Although listed as an LRL, tungsten is reported as the MRL (Timme, 1995). E, estimated value; ESJ, Eastern San Joaquin Basin; ESJDD, Eastern San Joaquin Basin depth dependent; ESJFP, Eastern San Joaquin Basin flowpath; ESJMW, Eastern San Joaquin Basin monitoring well; HA-L, lifetime health advisory (U.S. Environmental Protection Agency, 2004b); LRL, laboratory reporting level; MCL-CA, California Department of Health Services Maximum Contaminant Level (California Department of Health Services, 2005a); MCL-US, U.S. Environmental Protection Agency Maximum Contaminant Level (U.S. Environmental Protection Agency, 2005); MRL, Minimum Reporting Level (Timme, 1995); n/a, not applicable; nc, not collected; NL, notification level (California Department of Health Services, 2005d; nq, constituent detected but not quantified; QPC, Uplands Basin; SMCL-US, U.S. Environmental Protection Agency Secondary Maximum Contaminant Level (U.S. Environmental Protection Agency, 2005); TRCY, Tracy Basin; TRCYFP, Tracy Basin flowpath; USGS, U.S. Geological Survey; μg/L, microgram per liter; —, analyzed but not detected]

See footnote at end of table.

Tables 107
GAMA well 

identification

 number

Cobalt, 

dissolved 

(μg/L)

 (01035) 

Copper, 

dissolved

 (μg/L)

 (01040) 

Iron, 

dissolved 

(μg/L) 

(01046) 

Lead, 

dissolved 

(μg/L) 

(01049) 

Lithium,

dissolved 

(μg/L) 

(01130) 

Manganese, 

dissolved 

(μg/L) 

(01056) 

Mercury, 

dissolved 

(μg/L) 

(71890) 

Molybdenum, 

dissolved 

(μg/L) 

(01060) 

QPC-10 0.022 0.7 E4 0.39 4.1 0.3 nc 0.4

 Tracy Basin wells

TRCY-03 0.247 3.0 E4 0.89 32.3 VE0.2

— 1.9

TRCY-07 3.64 3.6 24,500 0.24 17.7 17,100

— 3

TRCY-09 0.131 VE0.3 4,180

— 5 519 nc 3

TRCY-11 0.107 1.1 8 0.27 5.4 194 nc 4.5

Flowpath wells

TRCYFP-01 0.85 3.4 1,240

— 10.2 2,480

— 5.1

TRCYFP-02 0.211 3.0 E3 1.15 20.8

— E0.01 1.5

TRCYFP-03 0.142 1.2 9 0.44 16.6 1.9 nc 2.3TRCYFP-04 0.29 3.8 15 1 35.3 1.5

— 1.8

TRCYFP-05 0.163 1.1

— 0.65 18.8 2.1 nc 1.5

ESJFP-07 0.052 4.6 E4 2.25 E0.4 0.8

— 0.4

ESJFP-08 0.111 9.1 13 1.16 2.6 87.9 nc 1.1ESJFP-09 0.128 4.4 E5 0.5 1.4 0.4 nc 0.5ESJFP-10 0.046 2.7

— 0.88 0.8 V0.2

— 0.5

 Monitoring wells

ESJMW-01 0.072

— 38

— E0.3 9 — 1.5

ESJMW-02 0.065 VE0.2

—

— E0.6 VE0.1

— 0.9

ESJMW-03 0.07 VE0.3

—

— 1.3 0.2

— 0.8

Table 19. Summary of trace elements detected in ground-water samples collected for the Northern San Joaquin Basin Ground-Water Ambient Monitoring and Assessment (GAMA) study, California, December 2004 to February 2005—Continued.[Bold numbers indicate ground-water detections above the threshold level. Concentrations preceded by a “V” indicate detections potentially biased by contamination. The five digit number below the constituent name is the USGS parameter code used to uniquely identify a specific constituent or property. The threshold type identifies the source of the comparison threshold. The threshold level is the level with which ground-water detections are compared. Although listed as an LRL, tungsten is reported as the MRL (Timme, 1995). E, estimated value; ESJ, Eastern San Joaquin Basin; ESJDD, Eastern San Joaquin Basin depth dependent; ESJFP, Eastern San Joaquin Basin flowpath; ESJMW, Eastern San Joaquin Basin monitoring well; HA-L, lifetime health advisory (U.S. Environmental Protection Agency, 2004b); LRL, laboratory reporting level; MCL-CA, California Department of Health Services Maximum Contaminant Level (California Department of Health Services, 2005a); MCL-US, U.S. Environmental Protection Agency Maximum Contaminant Level (U.S. Environmental Protection Agency, 2005); MRL, Minimum Reporting Level (Timme, 1995); n/a, not applicable; nc, not collected; NL, notification level (California Department of Health Services, 2005d; nq, constituent detected but not quantified; QPC, Uplands Basin; SMCL-US, U.S. Environmental Protection Agency Secondary Maximum Contaminant Level (U.S. Environmental Protection Agency, 2005); TRCY, Tracy Basin; TRCYFP, Tracy Basin flowpath; USGS, U.S. Geological Survey; μg/L, microgram per liter; —, analyzed but not detected]

See footnote at end of table.

108 California GAMA Program: Ground-Water Quality Data in the Northern San Joaquin Basin Study Unit, 2005
GAMA well 

identification

 number

Cobalt, 

dissolved 

(μg/L)

 (01035) 

Copper, 

dissolved

 (μg/L)

 (01040) 

Iron, 

dissolved 

(μg/L) 

(01046) 

Lead, 

dissolved 

(μg/L) 

(01049) 

Lithium,

dissolved 

(μg/L) 

(01130) 

Manganese, 

dissolved 

(μg/L) 

(01056) 

Mercury, 

dissolved 

(μg/L) 

(71890) 

Molybdenum, 

dissolved 

(μg/L) 

(01060) 

 Depth-dependent samples

ESJDD-01 0.055 V0.5 — — 0.7 V0.4 nc 0.8ESJDD-02 0.036 V0.4 — E0.06 0.6 VE0.1 — 0.7ESJDD-03 0.047 V0.5 — — 0.6 V0.2 — 0.6ESJDD-04 0.103 2.3 11 E0.06 1.2 1.2 — 1.1ESJDD-05 0.13 V0.3 6 — 1.8 1.2 — 1ESJDD-06 0.12 V0.3 7 — 1.9 1.1 — 1

Table 19. Summary of trace elements detected in ground-water samples collected for the Northern San Joaquin Basin Ground-Water Ambient Monitoring and Assessment (GAMA) study, California, December 2004 to February 2005—Continued.[Bold numbers indicate ground-water detections above the threshold level. Concentrations preceded by a “V” indicate detections potentially biased by contamination. The five digit number below the constituent name is the USGS parameter code used to uniquely identify a specific constituent or property. The threshold type identifies the source of the comparison threshold. The threshold level is the level with which ground-water detections are compared. Although listed as an LRL, tungsten is reported as the MRL (Timme, 1995). E, estimated value; ESJ, Eastern San Joaquin Basin; ESJDD, Eastern San Joaquin Basin depth dependent; ESJFP, Eastern San Joaquin Basin flowpath; ESJMW, Eastern San Joaquin Basin monitoring well; HA-L, lifetime health advisory (U.S. Environmental Protection Agency, 2004b); LRL, laboratory reporting level; MCL-CA, California Department of Health Services Maximum Contaminant Level (California Department of Health Services, 2005a); MCL-US, U.S. Environmental Protection Agency Maximum Contaminant Level (U.S. Environmental Protection Agency, 2005); MRL, Minimum Reporting Level (Timme, 1995); n/a, not applicable; nc, not collected; NL, notification level (California Department of Health Services, 2005d; nq, constituent detected but not quantified; QPC, Uplands Basin; SMCL-US, U.S. Environmental Protection Agency Secondary Maximum Contaminant Level (U.S. Environmental Protection Agency, 2005); TRCY, Tracy Basin; TRCYFP, Tracy Basin flowpath; USGS, U.S. Geological Survey; μg/L, microgram per liter; —, analyzed but not detected]

See footnote at end of table.

Tables 109
GAMA well 

identification 

number

Nickel,

 dissolved 

(μg/L)

 (01065) 

Selenium,

dissolved 

(μg/L) 

(01145) 

Strontium, 

dissolved 

(μg/L)

 (01080)

Thallium,

dissolved

(μg/L)

 (01057) 

Tungsten,

 dissolved 

(μg/L)

 (01155)

Uranium, 

dissolved 

(μg/L)

 (22703)

Vanadium,

 dissolved 

(μg/L) 

(01085) 

Zinc, 

dissolved 

(μg/L) 

(01090)

 Threshold type MCL-CA MCL-US HA-L MCL-US n/a MCL-US NL HA-L Threshold level (μg/L) 100 50 4,000 2 n/a 30 50 2,000 LRL 0.06 0.4 0.4 0.04 0.5 0.04 0.14 0.6

 Eastern San Joaquin Basin wells

ESJ-06 0.8 0.5 340

—

— 3.81 33.4 V0.9

ESJ-08 0.42 E0.2 169

—

— 0.13 30.4 2.9

ESJ-10 0.73

— 304

—

— 1.73 13.2 5.0

ESJ-12 0.95 0.5 240

—

— 0.73 11.5 12.8

ESJ-13 0.6 E0.4 179

—

— 0.42 9.4 4.7

ESJ-14 0.61

— 265

—

— 0.42 E0.1 V1.8

ESJ-15 1.25 1.3 799

—

— 7.53 8.8 12.8

ESJ-16 0.58

— 267

—

— 0.91 25.1 7.0

ESJ-17 0.2 E0.3 163

—

— 0.06 22.7 25.7

ESJ-18 0.39 E0.3 169

—

— 0.07 21.9 6.3

ESJ-19 1.56 E0.3 449

—

— 2.56 11.2 4.7

Upland Basin wells

QPC-01 0.76 1.3 331

—

— 0.98 3 21.9

QPC-04 0.18

— 48

—

— 0.07 9.1 V0.9

QPC-06 0.13 E0.3 153

—

— 0.15 14.7 7.9

QPC-07 0.58 0.7 434

—

— 0.47 6.8 V2.1

QPC-08 0.25 E0.3 193

—

— 0.08 20.7 11.2

Table 19. Summary of trace elements detected in ground-water samples collected for the Northern San Joaquin Basin Ground-Water Ambient Monitoring and Assessment (GAMA) study, California, December 2004 to February 2005—Continued.[Bold numbers indicate ground-water detections above the threshold level. Concentrations preceded by a “V” indicate detections potentially biased by contamination. The five digit number below the constituent name is the USGS parameter code used to uniquely identify a specific constituent or property. The threshold type identifies the source of the comparison threshold. The threshold level is the level with which ground-water detections are compared. Although listed as an LRL, tungsten is reported as the MRL (Timme, 1995). E, estimated value; ESJ, Eastern San Joaquin Basin; ESJDD, Eastern San Joaquin Basin depth dependent; ESJFP, Eastern San Joaquin Basin flowpath; ESJMW, Eastern San Joaquin Basin monitoring well; HA-L, lifetime health advisory (U.S. Environmental Protection Agency, 2004b); LRL, laboratory reporting level; MCL-CA, California Department of Health Services Maximum Contaminant Level (California Department of Health Services, 2005a); MCL-US, U.S. Environmental Protection Agency Maximum Contaminant Level (U.S. Environmental Protection Agency, 2005); MRL, Minimum Reporting Level (Timme, 1995); n/a, not applicable; nc, not collected; NL, notification level (California Department of Health Services, 2005d; nq, constituent detected but not quantified; QPC, Uplands Basin; SMCL-US, U.S. Environmental Protection Agency Secondary Maximum Contaminant Level (U.S. Environmental Protection Agency, 2005); TRCY, Tracy Basin; TRCYFP, Tracy Basin flowpath; USGS, U.S. Geological Survey; μg/L, microgram per liter; —, analyzed but not detected]

See footnote at end of table.

110 California GAMA Program: Ground-Water Quality Data in the Northern San Joaquin Basin Study Unit, 2005
GAMA well 

identification 

number

Nickel,

 dissolved 

(μg/L)

 (01065) 

Selenium,

dissolved 

(μg/L) 

(01145) 

Strontium, 

dissolved 

(μg/L)

 (01080)

Thallium,

dissolved

(μg/L)

 (01057) 

Tungsten,

 dissolved 

(μg/L)

 (01155)

Uranium, 

dissolved 

(μg/L)

 (22703)

Vanadium,

 dissolved 

(μg/L) 

(01085) 

Zinc, 

dissolved 

(μg/L) 

(01090)

QPC-10 0.23 — 183 — — 0.31 25.7 9.5

 Tracy Basin wells

TRCY-03 0.77 1.2 1,060 — — 3.37 2.7 VE2.0TRCY-07 5 1.9 2,320 — — 1.21 1.2 4.2TRCY-09 0.62 E0.2 342 — 2.3 — 0.7 3.8TRCY-11 1.11 0.7 664 — 0.6 0.21 0.3 10.3

Flowpath wells

TRCYFP-01 3.9 — 2,740 — — E0.07 3.7TRCYFP-02 0.8 1.3 1,630 — — 1.69 4.6 12.4TRCYFP-03 1.7 1.7 1,190 — — 1.05 8.3 17.2TRCYFP-04 1.05 1.6 1,310 — — 3.68 3.1 2.8TRCYFP-05 1.44 3.2 1,590 — — 0.97 6.3 3.1ESJFP-07 0.8 0.4 252 — — 0.6 16.3 23.1ESJFP-08 1.23 0.6 401 — — 2.14 3.8 7.6ESJFP-09 1.66 0.9 589 — — 9.43 27.4 9.8ESJFP-10 0.3 0.8 352 — — 2.64 26.1 4.7

 Monitoring wells

ESJMW-01 1.19 0.5 226 0.04 — 0.66 20.7 V0.8ESJMW-02 0.49 0.5 241 — — 0.86 29.9 V1.1ESJMW-03 0.79 1.1 321 — — 1.61 30.2 V1.0

Table 19. Summary of trace elements detected in ground-water samples collected for the Northern San Joaquin Basin Ground-Water Ambient Monitoring and Assessment (GAMA) study, California, December 2004 to February 2005—Continued.[Bold numbers indicate ground-water detections above the threshold level. Concentrations preceded by a “V” indicate detections potentially biased by contamination. The five digit number below the constituent name is the USGS parameter code used to uniquely identify a specific constituent or property. The threshold type identifies the source of the comparison threshold. The threshold level is the level with which ground-water detections are compared. Although listed as an LRL, tungsten is reported as the MRL (Timme, 1995). E, estimated value; ESJ, Eastern San Joaquin Basin; ESJDD, Eastern San Joaquin Basin depth dependent; ESJFP, Eastern San Joaquin Basin flowpath; ESJMW, Eastern San Joaquin Basin monitoring well; HA-L, lifetime health advisory (U.S. Environmental Protection Agency, 2004b); LRL, laboratory reporting level; MCL-CA, California Department of Health Services Maximum Contaminant Level (California Department of Health Services, 2005a); MCL-US, U.S. Environmental Protection Agency Maximum Contaminant Level (U.S. Environmental Protection Agency, 2005); MRL, Minimum Reporting Level (Timme, 1995); n/a, not applicable; nc, not collected; NL, notification level (California Department of Health Services, 2005d; nq, constituent detected but not quantified; QPC, Uplands Basin; SMCL-US, U.S. Environmental Protection Agency Secondary Maximum Contaminant Level (U.S. Environmental Protection Agency, 2005); TRCY, Tracy Basin; TRCYFP, Tracy Basin flowpath; USGS, U.S. Geological Survey; μg/L, microgram per liter; —, analyzed but not detected]

See footnote at end of table.

Tables 111
GAMA well 

identification 

number

Nickel,

 dissolved 

(μg/L)

 (01065) 

Selenium,

dissolved 

(μg/L) 

(01145) 

Strontium, 

dissolved 

(μg/L)

 (01080)

Thallium,

dissolved

(μg/L)

 (01057) 

Tungsten,

 dissolved 

(μg/L)

 (01155)

Uranium, 

dissolved 

(μg/L)

 (22703)

Vanadium,

 dissolved 

(μg/L) 

(01085) 

Zinc, 

dissolved 

(μg/L) 

(01090)

 Depth-dependent samples

ESJDD-01 0.68 0.7 360

—

— 2.66 24.9 50.6

ESJDD-02 0.65 0.5 257

—

— 0.98 30.6 50.6

ESJDD-03 0.7 0.7 312

—

— 1.61 28.1 7.0

ESJDD-04 3.09 E0.3 441

—

— 2.82 13.7 17.6

ESJDD-05 3.67 E0.3 449

—

— 3.89 16.3 2.8

ESJDD-06 4.77 E0.3 416

—

— 2.96 15.3 4.4

1Values referred to as MCLs for lead and copper are “notification levels” under the lead and copper rule (California Department of Health Services, 2005a). 

Table 19. Summary of trace elements detected in ground-water samples collected for the Northern San Joaquin Basin Ground-Water Ambient Monitoring and Assessment (GAMA) study, California, December 2004 to February 2005—Continued.[Bold numbers indicate ground-water detections above the threshold level. Concentrations preceded by a “V” indicate detections potentially biased by contamination. The five digit number below the constituent name is the USGS parameter code used to uniquely identify a specific constituent or property. The threshold type identifies the source of the comparison threshold. The threshold level is the level with which ground-water detections are compared. Although listed as an LRL, tungsten is reported as the MRL (Timme, 1995). E, estimated value; ESJ, Eastern San Joaquin Basin; ESJDD, Eastern San Joaquin Basin depth dependent; ESJFP, Eastern San Joaquin Basin flowpath; ESJMW, Eastern San Joaquin Basin monitoring well; HA-L, lifetime health advisory (U.S. Environmental Protection Agency, 2004b); LRL, laboratory reporting level; MCL-CA, California Department of Health Services Maximum Contaminant Level (California Department of Health Services, 2005a); MCL-US, U.S. Environmental Protection Agency Maximum Contaminant Level (U.S. Environmental Protection Agency, 2005); MRL, Minimum Reporting Level (Timme, 1995); n/a, not applicable; nc, not collected; NL, notification level (California Department of Health Services, 2005d; nq, constituent detected but not quantified; QPC, Uplands Basin; SMCL-US, U.S. Environmental Protection Agency Secondary Maximum Contaminant Level (U.S. Environmental Protection Agency, 2005); TRCY, Tracy Basin; TRCYFP, Tracy Basin flowpath; USGS, U.S. Geological Survey; μg/L, microgram per liter; —, analyzed but not detected]

112 California GAMA Program: Ground-Water Quality Data in the Northern San Joaquin Basin Study Unit, 2005
GAMA well

 identification number

Inorganic 

arsenic,

 dissolved

 (μg/L) 

(99033) 

Inorganic

 arsenic(III),

 dissolved 

(μg/L)

 (99034) 

Chromium,

dissolved

 (μg/L) 

(01030) 

Hexavalent 

chromium

(chromium(VI)) 

dissolved

 (μg/L)

 (01032) 

Iron, 

dissolved 

(μg/L)

 (01046) 

Iron(II), 

dissolved

 (μg/L)

 (01047) 

 Threshold type MCL-US n/a MCL-CA DLR HA-L n/a

Threshold level (μg/L) 10 n/a 50 1 300 n/a

 MDL 0.5 1 1 1 2 2

Eastern San Joaquin Basin wells

ESJ-06 5.7 — V5 E6 — —

ESJ-08 4.2 — V5 V5 — —

ESJ-10 8.4 1 — — 8 —

ESJ-12 1.9 — V6 V5 5 4

ESJ-13 1.5 — V4 V3 6 —

ESJ-14 28.0 22 — — 57 38

ESJ-15 3.9 — — — V3 —

ESJ-16 6.7 — V2 V1 V3 2

ESJ-17 1.8 — V6 E6 V3 —

ESJ-18 2.1 — V5 V4 — —

ESJ-19 7 — E9 E9 — —

 Upland Basin wells

QPC-01 0.7 — V2 V2 5 —

QPC-04 1.9 — V2 V1 57 34

QPC-06 2.8 — — — V4 —

QPC-07 1.2 — — — 5 —

QPC-08 1.7 — V4 V4 V3 —

QPC-10 2.3 — V3 V3 V3 —

Tracy Basin wells

TRCY-03 1.1 — E15 E13 V4 —

TRCY-07 18.7 19 V5 V2 22,650 22,650

TRCY-09 4.5 3 V3 V1 3,876 3,744

TRCY-11 6.4 4 V3 V4 V4 —

Flowpath wells

TRCYFP-01 9.9 9 V6 V5 1,133 1,067

TRCYFP-02 1.5 — E13 E12 V3 —

Table 20. Summary of chromium, arsenic, and iron speciation data from the U.S. Geological Survey’s (USGS) Trace Metal Laboratory, 

Boulder, Colorado, for ground-water samples collected in the Northern San Joaquin Basin Ground-Water Ambient Monitoring and 

Assessment (GAMA) study, California, December 2004 to February 2005.

[Bold numbers indicate ground-water detections above the threshold level. Values preceded by a “V” indicate detections potentially biased by contamination. 

The five digit number below the constituent name is the USGS parameter code used to uniquely identify a specific constituent or property. The threshold type 

identifies the source of the comparison threshold. The threshold level is the level with which ground-water detections are compared. DLR, detection level for 

the purpose of reporting (California Department of Health Services, 2005a); E, estimated value; ESJ, Eastern San Joaquin Basin; ESJDD, Eastern San Joaquin 

Basin depth dependent; ESJFP, Eastern San Joaquin Basin flowpath; ESJMW, Eastern San Joaquin Basin monitoring well; HA-L, lifetime health advisory 

(U.S. Environmental Protection Agency, 2004b); MCL-CA, California Department of Health Services Maximum Contaminant Level (California Department of 

Health Services, 2005a); MCL-US, U.S. Environmental Protection Agency Maximum Contaminant Level (U.S. Environmental Protection Agency, 2005); MDL, 

method detection level; n/a, not applicable; QPC, Uplands Basin; TRCY, Tracy Basin; TRCYFP, Tracy Basin flowpath; μg/L, microgram per liter; —, analyzed 

but not detected]

Tables 113
GAMA well

 identification number

Inorganic 

arsenic,

 dissolved

 (μg/L) 

(99033) 

Inorganic

 arsenic(III),

 dissolved 

(μg/L)

 (99034) 

Chromium,

dissolved

 (μg/L) 

(01030) 

Hexavalent 

chromium

(chromium(VI)) 

dissolved

 (μg/L)

 (01032) 

Iron, 

dissolved 

(μg/L)

 (01046) 

Iron(II), 

dissolved

 (μg/L)

 (01047) 

TRCYFP-03 3.2 — V1 — 9 6

TRCYFP-04 1 — E14 E12 14 4

TRCYFP-05 1.8 — V2 V2 V4 3

ESJFP-07 2.8 — V5 V4 V4 3

ESJFP-08 16.4 — V1 — 10 —

ESJFP-09 3 — V6 E6 V3 2

ESJFP-10 3.4 — E7 E7 V3 —

Monitoring wells

ESJMW-01 4 — E11 E10 18 —

ESJMW-02 3.9 — E15 E14 V2 —

ESJMW-03 3 — E10 E10 5 —

Depth-dependent samples

ESJDD-01 3.3 — V5 E9 V3 —

ESJDD-02 3.4 — E9 E9 V3 —

ESJDD-03 3.4 — E8 V5 V2 2

ESJDD-04 7.4 — E9 E9 V4 3

ESJDD-05 8.3 — E10 E9 V3 3

ESJDD-06 8.1 — E10 E9 V3 3

Table 20. Summary of chromium, arsenic, and iron speciation data from the U.S. Geological Survey’s (USGS) Trace Metal Laboratory, 

Boulder, Colorado, for ground-water samples collected in the Northern San Joaquin Basin Ground-Water Ambient Monitoring and 

Assessment (GAMA) study, California, December 2004 to February 2005.

[[Bold numbers indicate ground-water detections above the threshold level. Values preceded by a “V” indicate detections potentially biased by contamination. 

The five digit number below the constituent name is the USGS parameter code used to uniquely identify a specific constituent or property. The threshold type 

identifies the source of the comparison threshold. The threshold level is the level with which ground-water detections are compared. DLR, detection level for 

the purpose of reporting (California Department of Health Services, 2005a); E, estimated value; ESJ, Eastern San Joaquin Basin; ESJDD, Eastern San Joaquin 

Basin depth dependent; ESJFP, Eastern San Joaquin Basin flowpath; ESJMW, Eastern San Joaquin Basin monitoring well; HA-L, lifetime health advisory 

(U.S. Environmental Protection Agency, 2004b); MCL-CA, California Department of Health Services Maximum Contaminant Level (California Department of 

Health Services, 2005a); MCL-US, U.S. Environmental Protection Agency Maximum Contaminant Level (U.S. Environmental Protection Agency, 2005); MDL, 

method detection level; n/a, not applicable; QPC, Uplands Basin; TRCY, Tracy Basin; TRCYFP, Tracy Basin flowpath; μg/L, microgram per liter; —, analyzed 

but not detected]

114 California GAMA Program: Ground-Water Quality Data in the Northern San Joaquin Basin Study Unit, 2005
GAMA well 

identification

number

Alpha 

radioactivity, 72-hour 

count 

(pCi/L) 

(62636)

Alpha

radioactivity, 30-day 

count 

(pCi/L) 

(62639) 

Beta radioactivity, 72-

hour count 

(pCi/L) 

(62642) 

Beta radioactivity, 30-

day count 

(pCi/L) 

(62645) 

Carbon 

isotopes

Radium226 

(pCi/L) 

(09511) 

Radium228 

(pCi/L) 

(81366) 

Radon-222 

(pCi/L) 

(82303)

Stable isotopes

of water

Tritium 

(pCi/L) 

(07000)

Result Result Result Result

Carbon-13/

carbon-12 

ratio

 (per mill)

 (82081)

Carbon-14 

(percent 

modern) 

(49933) 

Result Result Result

Deuterium/ 

protium 

ratio 

(per mill) 

(82082) 

Oxygen-18/

oxygen-16 

ratio 

(per mill) 

(82085) 

Result

Threshold type MCL-US MCL-US MCL-CA MCL-CA n/a n/a MCL-US MCL-US Proposed

 MCL-US1

n/a n/a MCL-CA

Threshold level 15 15 50 50 n/a n/a 3 2.00 300 n/a n/a 20,000

Cosumnes Basin wells

COS-01 nc nc nc nc nc nc nc nc nc –60.8 –8.57 —COS-02 nc nc nc nc nc nc nc nc nc –60.6 –8.26 —COS-03 nc nc nc nc nc nc nc nc nc –55.2 –7.61 1COS-04 nc nc nc nc nc nc nc nc nc –56.6 –7.94 3COS-05 nc nc nc nc nc nc nc nc nc –78 –10.86 28COS-06 nc nc nc nc nc nc nc nc nc –79.1 –10.62 13COS-07 nc nc nc nc nc nc nc nc nc –43.0 –5.6 3COS-08 nc nc nc nc nc nc nc nc nc –53.7 –7.33 —COS-09 nc nc nc nc nc nc nc nc nc –49.5 –6.8 1COS-10 nc nc nc nc nc nc nc nc nc –52.9 –7.54 2

Eastern San Joaquin Basin wells

ESJ-01 nc nc nc nc nc nc nc nc nc –67.6 –9.31 20ESJ-02 nc nc nc nc nc nc nc nc nc –53.6 –7.13 1ESJ-03 nc nc nc nc nc nc nc nc nc –60.3 –8.15 12

Table 21. Summary of stable isotopes and radioactive constituents in ground-water samples collected for the Northern San Joaquin Basin Ground-Water Ambient Monitoring and Assessment (GAMA) study, California, December 2004 to February 2005.[Bold numbers indicate ground-water detections above the threshold level. The five digit number below the constituent name is the USGS parameter code used to uniquely identify a specific constituent or property. The threshold type identifies the source of the comparison threshold. The threshold level is the level with which ground-water detections are compared. COS, Cosumnes Basin; E, estimated value; ESJ, Eastern San Joaquin Basin; ESJDD, Eastern San Joaquin Basin depth dependent; ESJFP, Eastern San Joaquin Basin flowpath; ESJMW, Eastern San Joaquin Basin monitoring well; MCL-CA, California Department of Health Services Maximum Contaminant Level (California Department of Health Services, 2005a); MCL-US, U.S. Environmental Protection Agency Maximum Contaminant Level (U.S. Environmental Protection Agency, 2005); n/a, not applicable; nc, sample not collected; pCi/L, picocurie per liter; QPC, Uplands Basin; SSMDC, sample-specific minimum detectable concentration; TRCY, Tracy Basin; TRCYFP, Tracy Basin flowpath; USGS, U.S. Geological Survey; —, analyzed but not detected]

Tables 115See footnotes at end of table.
GAMA well 

identification

number

Alpha 

radioactivity, 72-hour 

count 

(pCi/L) 

(62636)

Alpha

radioactivity, 30-day 

count 

(pCi/L) 

(62639) 

Beta radioactivity, 72-

hour count 

(pCi/L) 

(62642) 

Beta radioactivity, 30-

day count 

(pCi/L) 

(62645) 

Carbon 

isotopes

Radium226 

(pCi/L) 

(09511) 

Radium228 

(pCi/L) 

(81366) 

Radon-222 

(pCi/L) 

(82303)

Stable isotopes

of water

Tritium 

(pCi/L) 

(07000)

Result Result Result Result

Carbon-13/

carbon-12 

ratio

 (per mill)

 (82081)

Carbon-14 

(percent 

modern) 

(49933) 

Result Result Result

Deuterium/ 

protium 

ratio 

(per mill) 

(82082) 

Oxygen-18/

oxygen-16 

ratio 

(per mill) 

(82085) 

Result

ESJ-04 nc nc nc nc nc nc nc nc nc –81.1 –11.21 14ESJ-05 nc nc nc nc nc nc nc nc nc –52.3 –7.1

—

ESJ-06 nc nc nc nc nc nc nc nc nc –63.5 –8.86 7ESJ-07 nc nc nc nc nc nc nc nc nc –71.4 –9.85 27ESJ-08 nc nc nc nc nc nc nc nc nc –52.7 –7.4 1ESJ-09 nc nc nc nc nc nc nc nc nc –49.5 –6.7 4ESJ-10 nc nc nc nc nc nc nc nc nc –59.9 –8.46 3ESJ-11 nc nc nc nc nc nc nc nc nc –74.6 –10.13 2ESJ-12 E0.6 <1.1 E3.9 4.2 –17.51 92.06 0.06 <0.48 640 –60.5 –8.58

—

ESJ-13 nc nc nc nc nc nc nc nc nc –59.2 –8.44

—

ESJ-14 nc nc nc nc nc nc nc nc nc –69.6 –9.36 1ESJ-15 nc nc nc nc nc nc nc nc nc –58.8 –8.08 4ESJ-16 nc nc nc nc nc nc nc nc nc –56.4 –7.59 16ESJ-17 nc nc nc nc nc nc nc nc nc –49.9 –6.63

—

ESJ-18 nc nc nc nc nc nc nc nc nc –48.8 –6.43

—

ESJ-19 2.5 E1.0 E4.8 5.9 –15.7 85.03 0.09 <0.47 nc –59.5 –8.1 15

Table 21. Summary of stable isotopes and radioactive constituents in ground-water samples collected for the Northern San Joaquin Basin Ground-Water Ambient Monitoring and Assessment (GAMA) study, California, December 2004 to February 2005—Continued.[Bold numbers indicate ground-water detections above the threshold level. The five digit number below the constituent name is the USGS parameter code used to uniquely identify a specific constituent or property. The threshold type identifies the source of the comparison threshold. The threshold level is the level with which ground-water detections are compared. COS, Cosumnes Basin; E, estimated value; ESJ, Eastern San Joaquin Basin; ESJDD, Eastern San Joaquin Basin depth dependent; ESJFP, Eastern San Joaquin Basin flowpath; ESJMW, Eastern San Joaquin Basin monitoring well; MCL-CA, California Department of Health Services Maximum Contaminant Level (California Department of Health Services, 2005a); MCL-US, U.S. Environmental Protection Agency Maximum Contaminant Level (U.S. Environmental Protection Agency, 2005); n/a, not applicable; nc, sample not collected; pCi/L, picocurie per liter; QPC, Uplands Basin; SSMDC, sample-specific minimum detectable concentration; TRCY, Tracy Basin; TRCYFP, Tracy Basin flowpath; USGS, U.S. Geological Survey; —, analyzed but not detected]

116 California GAMA Program: Ground-Water Quality Data in the Northern San Joaquin Basin Study Unit, 2005

See footnotes at end of table.
GAMA well 

identification

number

Alpha 

radioactivity, 72-hour 

count 

(pCi/L) 

(62636)

Alpha

radioactivity, 30-day 

count 

(pCi/L) 

(62639) 

Beta radioactivity, 72-

hour count 

(pCi/L) 

(62642) 

Beta radioactivity, 30-

day count 

(pCi/L) 

(62645) 

Carbon 

isotopes

Radium226 

(pCi/L) 

(09511) 

Radium228 

(pCi/L) 

(81366) 

Radon-222 

(pCi/L) 

(82303)

Stable isotopes

of water

Tritium 

(pCi/L) 

(07000)

Result Result Result Result

Carbon-13/

carbon-12 

ratio

 (per mill)

 (82081)

Carbon-14 

(percent 

modern) 

(49933) 

Result Result Result

Deuterium/ 

protium 

ratio 

(per mill) 

(82082) 

Oxygen-18/

oxygen-16 

ratio 

(per mill) 

(82085) 

Result

 Uplands Basin wells

QPC-01 E1.3 <1.9 E2.8 E2.8 –15.73 117.1 E0.04 <0.50 390 –54.4 –7.55 14QPC-02 nc nc nc nc nc nc nc nc nc –77.5 –10.6 37QPC-03 nc nc nc nc nc nc nc nc nc –51.7 –6.84 —QPC-04 nc nc nc nc nc nc nc nc nc –55.4 –7.12 5QPC-05 nc nc nc nc nc nc nc nc nc –57.4 –8.13 —QPC-06 nc nc nc nc nc nc nc nc nc –51.2 –6.93 —QPC-07 nc nc nc nc nc nc nc nc nc –55.5 –7.58 3QPC-08 nc nc nc nc nc nc nc nc nc –57.8 –8.05 —QPC-09 nc nc nc nc nc nc nc nc nc –59.1 –7.91 —QPC-10 nc nc nc nc nc nc nc nc nc –65.6 –8.9 3QPC-11 nc nc nc nc nc nc nc nc nc –52.4 –7.0 —

Tracy Basin wells

TRCY-01 nc nc nc nc nc nc nc nc nc –64.5 –8.76 —TRCY-02 nc nc nc nc nc nc nc nc nc –49.2 –5.78 2TRCY-03 E1.4 <2.3 <5.4 E3.0 –12.76 69.03 0.06 <0.43 790 –55.9 –7.5 —TRCY-04 nc nc nc nc nc nc nc nc nc –48.4 –6.95 —TRCY-05 nc nc nc nc nc nc nc nc nc –68.3 –9.26 —

Table 21. Summary of stable isotopes and radioactive constituents in ground-water samples collected for the Northern San Joaquin Basin Ground-Water Ambient Monitoring and Assessment (GAMA) study, California, December 2004 to February 2005—Continued.[Bold numbers indicate ground-water detections above the threshold level. The five digit number below the constituent name is the USGS parameter code used to uniquely identify a specific constituent or property. The threshold type identifies the source of the comparison threshold. The threshold level is the level with which ground-water detections are compared. COS, Cosumnes Basin; E, estimated value; ESJ, Eastern San Joaquin Basin; ESJDD, Eastern San Joaquin Basin depth dependent; ESJFP, Eastern San Joaquin Basin flowpath; ESJMW, Eastern San Joaquin Basin monitoring well; MCL-CA, California Department of Health Services Maximum Contaminant Level (California Department of Health Services, 2005a); MCL-US, U.S. Environmental Protection Agency Maximum Contaminant Level (U.S. Environmental Protection Agency, 2005); n/a, not applicable; nc, sample not collected; pCi/L, picocurie per liter; QPC, Uplands Basin; SSMDC, sample-specific minimum detectable concentration; TRCY, Tracy Basin; TRCYFP, Tracy Basin flowpath; USGS, U.S. Geological Survey; —, analyzed but not detected]

Tables 117See footnotes at end of table.
GAMA well 

identification

number

Alpha 

radioactivity, 72-hour 

count 

(pCi/L) 

(62636)

Alpha

radioactivity, 30-day 

count 

(pCi/L) 

(62639) 

Beta radioactivity, 72-

hour count 

(pCi/L) 

(62642) 

Beta radioactivity, 30-

day count 

(pCi/L) 

(62645) 

Carbon 

isotopes

Radium226 

(pCi/L) 

(09511) 

Radium228 

(pCi/L) 

(81366) 

Radon-222 

(pCi/L) 

(82303)

Stable isotopes

of water

Tritium 

(pCi/L) 

(07000)

Result Result Result Result

Carbon-13/

carbon-12 

ratio

 (per mill)

 (82081)

Carbon-14 

(percent 

modern) 

(49933) 

Result Result Result

Deuterium/ 

protium 

ratio 

(per mill) 

(82082) 

Oxygen-18/

oxygen-16 

ratio 

(per mill) 

(82085) 

Result

TRCY-06 nc nc nc nc nc nc nc nc nc –45.9 –6.78

—

TRCY-07 2E6.7 2E3.1 2E6.0 24.8 –16.6 90.01 0.46 E1.29 290 –72.0 –9.25 9TRCY-08 nc nc nc nc nc nc nc nc nc –59.7 –7.65

—

TRCY-09 nc nc nc nc nc nc nc nc nc –67.7 –8.84 12TRCY-10 nc nc nc nc nc nc nc nc nc –49.4 –6.88

—

TRCY-11 nc nc nc nc nc nc nc nc nc –67.1 –8.94

—

 Flowpath wells

TRCYFP-01 <7.9 <9.8 13.4 E6.8 –18.58 7.84 1.13 1.24 760 –70.0 –9.27

—

TRCYFP-02 <1.1 <2.4 <2.3 E3.6 –12.56 35.95 0.05 <0.44 560 –60.1 –8.08 2TRCYFP-03 nc nc nc nc nc nc nc nc nc –63.1 –8.36 2TRCYFP-04 <3.2 <3.3 E4.1 E3.1 –13.02 62.1 0.08 <0.51 740 –56.0 –7.4 1TRCYFP-05 nc nc nc nc nc nc nc nc nc –65.2 –8.61 1TRCYFP-06 nc nc nc nc nc nc nc nc nc –75.9 –10.07

—

ESJFP-07 <1.9 <1.7 5.3 4.6 –16.49 71.76 E0.04 <0.50 380 –60.6 –8.7

—

ESJFP-08 nc nc nc nc nc nc nc nc nc –62.7 –8.49 10ESJFP-09 nc nc nc nc nc nc nc nc nc –68.8 –9.51 34

Table 21. Summary of stable isotopes and radioactive constituents in ground-water samples collected for the Northern San Joaquin Basin Ground-Water Ambient Monitoring and Assessment (GAMA) study, California, December 2004 to February 2005—Continued.[Bold numbers indicate ground-water detections above the threshold level. The five digit number below the constituent name is the USGS parameter code used to uniquely identify a specific constituent or property. The threshold type identifies the source of the comparison threshold. The threshold level is the level with which ground-water detections are compared. COS, Cosumnes Basin; E, estimated value; ESJ, Eastern San Joaquin Basin; ESJDD, Eastern San Joaquin Basin depth dependent; ESJFP, Eastern San Joaquin Basin flowpath; ESJMW, Eastern San Joaquin Basin monitoring well; MCL-CA, California Department of Health Services Maximum Contaminant Level (California Department of Health Services, 2005a); MCL-US, U.S. Environmental Protection Agency Maximum Contaminant Level (U.S. Environmental Protection Agency, 2005); n/a, not applicable; nc, sample not collected; pCi/L, picocurie per liter; QPC, Uplands Basin; SSMDC, sample-specific minimum detectable concentration; TRCY, Tracy Basin; TRCYFP, Tracy Basin flowpath; USGS, U.S. Geological Survey; —, analyzed but not detected]

118 California GAMA Program: Ground-Water Quality Data in the Northern San Joaquin Basin Study Unit, 2005

See footnotes at end of table.
GAMA well 

identification

number

Alpha 

radioactivity, 72-hour 

count 

(pCi/L) 

(62636)

Alpha

radioactivity, 30-day 

count 

(pCi/L) 

(62639) 

Beta radioactivity, 72-

hour count 

(pCi/L) 

(62642) 

Beta radioactivity, 30-

day count 

(pCi/L) 

(62645) 

Carbon 

isotopes

Radium226 

(pCi/L) 

(09511) 

Radium228 

(pCi/L) 

(81366) 

Radon-222 

(pCi/L) 

(82303)

Stable isotopes

of water

Tritium 

(pCi/L) 

(07000)

Result Result Result Result

Carbon-13/

carbon-12 

ratio

 (per mill)

 (82081)

Carbon-14 

(percent 

modern) 

(49933) 

Result Result Result

Deuterium/ 

protium 

ratio 

(per mill) 

(82082) 

Oxygen-18/

oxygen-16 

ratio 

(per mill) 

(82085) 

Result

ESJFP-10 E2.0 2 5.1 6.3 –15.97 88.42 0.09 <0.40 980 –61.8 –8.61 9

Monitoring wells

ESJMW-01 <2.6 E1.0 5.4 6.1 –16.04 66.66 E0.04 E0.22 680 –60.5 –8.46 3ESJMW-02 E0.5 <0.8 4.9 6.4 –16.24 79.43 0.06 <0.46 1,600 –60.6 –8.49 6ESJMW-03 <1.9 E0.8 4.8 5.1 –15.66 110.5 0.12 <0.54 880 –59.3 –8.17 33

 Depth-dependent samples

ESJDD-01 nc nc nc nc nc nc nc nc nc –62.2 –8.73 12ESJDD-02 nc nc nc nc nc nc nc nc nc –61.2 –8.68 2ESJDD-03 nc nc nc nc nc nc nc nc 900 –61.1 –8.61 3ESJDD-04 nc nc nc nc –16.5 79.5 nc nc nc –58.8 –8.01 13ESJDD-05 nc nc nc nc –16.1 86.4 nc nc nc –56.8 –7.81 11ESJDD-06 nc nc nc nc –16.0 84.01 nc nc nc –56.4 –7.59 10

1U.S. Environmental Protection Agency, 2006.2Sample affected by high solid concentration.

Table 21. Summary of stable isotopes and radioactive constituents in ground-water samples collected for the Northern San Joaquin Basin Ground-Water Ambient Monitoring and Assessment (GAMA) study, California, December 2004 to February 2005—Continued.[Bold numbers indicate ground-water detections above the threshold level. The five digit number below the constituent name is the USGS parameter code used to uniquely identify a specific constituent or property. The threshold type identifies the source of the comparison threshold. The threshold level is the level with which ground-water detections are compared. COS, Cosumnes Basin; E, estimated value; ESJ, Eastern San Joaquin Basin; ESJDD, Eastern San Joaquin Basin depth dependent; ESJFP, Eastern San Joaquin Basin flowpath; ESJMW, Eastern San Joaquin Basin monitoring well; MCL-CA, California Department of Health Services Maximum Contaminant Level (California Department of Health Services, 2005a); MCL-US, U.S. Environmental Protection Agency Maximum Contaminant Level (U.S. Environmental Protection Agency, 2005); n/a, not applicable; nc, sample not collected; pCi/L, picocurie per liter; QPC, Uplands Basin; SSMDC, sample-specific minimum detectable concentration; TRCY, Tracy Basin; TRCYFP, Tracy Basin flowpath; USGS, U.S. Geological Survey; —, analyzed but not detected]

Tables 119
GAMA well

identification 

number

Collection 

date 

(mm/dd/yy)

Tritium, 

pCi/L

 (07000)

Tritium 

measurment 

uncertaintity 

(pCi/L) 

(07001)

Dissolved gas 

analysis date 

(mm/dd/yy)

Helium-3/

helium-4 

(atom ratio)

 (61040)

Helium-4 

(cm3 STP/g) 

(85561)

Neon 

(cm3 STP/g) 

(61046)

Argon

 (cm3 STP/g) 

(85563)

Krypton 

(cm3 STP/g) 

(85565)

Xenon 

(cm3 STP/g) 

(85567)

× 10–6 × 10–8 × 10–7 × 10–4 × 10–8 × 10–8

 Threshold type n/a MCL-CA n/a n/a n/a n/a n/a n/a n/a n/a

 Threshold level n/a 20,000 n/a n/a n/a n/a n/a n/a n/a n/a

 Eastern San Joaquin Basin wells

ESJ-06 01/10/05 6.9 0.3 n/a n/a nc nc nc nc ncESJ-08 01/11/05 <1.0 0.1 n/a n/a nc nc nc nc ncESJ-10 01/12/05 3.05 0.2 n/a n/a nc nc nc nc ncESJ-12 01/13/05 <1.0 0.1 04/27/05 1.39 6.51 2.68 4.10 9.04 1.12ESJ-13 01/13/05 <1.0 0.1 n/a n/a nc nc nc nc ncESJ-14 01/13/05 1.88 0.2 n/a n/a nc nc nc nc ncESJ-19 02/18/05 14.45 0.6 04/26/05 2.58 7.77 2.84 4.15 9.08 1.20

 Upland Basin wells

QPC-01 01/11/05 14.26 0.6 03/22/05 1.20 12.65 2.23 3.71 8.33 1.13QPC-04 01/24/05 5.37 0.3 n/a n/a nc nc nc nc nc

Tracy Basin wells

TRCY-03 01/06/05 1.18 0.2 04/25/05 1.34 7.66 3.08 4.13 8.65 1.11TRCY-07 02/08/05 9.90 0.4 04/26/05 0.77 20.68 1.92 3.44 7.88 1.08

 Flowpath wells

TRCYFP-01 01/03/05 <1.0 0.1 03/22/05 0.46 665.02 2.95 4.25 9.29 1.31TRCYFP-02 01/04/05 1.44 0.1 03/21/05 1.08 9.93 3.17 4.29 9.06 1.21TRCYFP-03 01/05/05 2.64 0.2 n/a n/a nc nc nc nc ncTRCYFP-04 01/05/05 1.28 0.1 03/21/05 1.21 9.13 3.25 4.26 9.03 1.12

Table 22. Summary of tritium and noble gas analysis performed at Lawrence Livermore National Laboratory for ground-water samples collected for the Northern San Joaquin Basin Ground-Water Ambient Monitoring and Assessment (GAMA) study, California, December 2004 to February 2005.[The five digit number below the constituent name is the USGS parameter code used to uniquely identify a specific constituent or property. The threshold type identifies the source of the comparison threshold. The threshold level is the level with which ground-water detections are compared. cm3 STP/g, cubic centimeters of gas at standard temperature and pressure per gram of water; ESJ, Eastern San Joaquin Basin; ESJDD, Eastern San Joaquin Basin depth dependent; ESJFP, Eastern San Joaquin Basin flowpath; ESJMW, Eastern San Joaquin Basin monitoring well; MCL-CA, California Department of Health Services Maximum Contaminant Level (California Department of Health Services, 2005a); mm/dd/yy, month/day/year; n/a, not applicable; nc, sample not collected; pCi/L, picocurie per liter; QPC, Uplands Basin; TRCY, Tracy Basin; TRCYFP, Tracy Basin flowpath; USGS, U.S. Geological Survey; —, analyzed but not detected]

120 California GAMA Program: Ground-Water Quality Data in the Northern San Joaquin Basin Study Unit, 2005
GAMA well

identification 

number

Collection 

date 

(mm/dd/yy)

Tritium, 

pCi/L

 (07000)

Tritium 

measurment 

uncertaintity 

(pCi/L) 

(07001)

Dissolved gas 

analysis date 

(mm/dd/yy)

Helium-3/

helium-4 

(atom ratio)

 (61040)

Helium-4 

(cm3 STP/g) 

(85561)

Neon 

(cm3 STP/g) 

(61046)

Argon

 (cm3 STP/g) 

(85563)

Krypton 

(cm3 STP/g) 

(85565)

Xenon 

(cm3 STP/g) 

(85567)

TRCYFP-05 01/05/05 1.67 0.2 n/a n/a nc nc nc nc ncESJFP-07 01/10/05 — 0.7 03/22/05 1.32 6.85 2.72 4.19 9.19 1.24ESJFP-08 01/12/05 10.23 0.4 n/a n/a nc nc nc nc ncESJFP-09 01/12/05 31.81 1.2 n/a n/a nc nc nc nc ncESJFP-10 01/28/05 8.96 0.4 04/27/05 2.00 6.75 2.69 4.10 8.86 1.19

 Monitoring wells

ESJMW-01 02/01/05 2.62 0.2 04/26/05 1.53 7.27 2.70 4.12 9.14 1.18ESJMW-02 02/02/05 5.78 0.3 04/26/05 2.61 6.70 2.79 4.07 8.80 1.10ESJMW-03 02/03/05 31.06 1.2 04/26/05 3.25 6.28 2.72 3.97 8.50 1.08

 Depth-dependent samples

ESJDD-03 01/26/05 12.64 0.5 n/a n/a nc nc nc nc ncESJDD-04 02/17/05 9.81 0.4 04/26/05 1.46 3.70 1.78 3.98 8.97 1.27ESJDD-05 02/17/05 11.07 0.5 04/26/05 1.53 1.24 0.88 3.06 7.25 1.06ESJDD-06 02/16/05 11.63 0.6 04/26/05 1.62 1.44 0.96 3.26 7.52 1.07

Table 22. Summary of tritium and noble gas analysis performed at Lawrence Livermore National Laboratory for ground-water samples collected for the Northern San Joaquin Basin Ground-Water Ambient Monitoring and Assessment (GAMA) study, California, December 2004 to February 2005—Continued.[The five digit number below the constituent name is the USGS parameter code used to uniquely identify a specific constituent or property. The threshold type identifies the source of the comparison threshold. The threshold level is the level with which ground-water detections are compared. cm3 STP/g, cubic centimeters of gas at standard temperature and pressure per gram of water; ESJ, Eastern San Joaquin Basin; ESJDD, Eastern San Joaquin Basin depth dependent; ESJFP, Eastern San Joaquin Basin flowpath; ESJMW, Eastern San Joaquin Basin monitoring well; MCL-CA, California Department of Health Services Maximum Contaminant Level (California Department of Health Services, 2005a); mm/dd/yy, month/day/year; n/a, not applicable; nc, sample not collected; pCi/L, picocurie per liter; QPC, Uplands Basin; TRCY, Tracy Basin; TRCYFP, Tracy Basin flowpath; USGS, U.S. Geological Survey; —, analyzed but not detected]

Tables 121
GAMA well 

identification

 number

Coliphage

 F-specific 

(99335)

Coliphage 

somatic

(99332)

E. coli

colonies/100 mL 

(90901)

Total coliforms 

colonies/100 mL

 (90900)

 Threshold type TT TT TT MCL-US

 Threshold level 99.9%

killed/inactive

99.9%

killed/inactive

No fecal 

coliforms are allowed

 5%

ESJ-12 — — — —

ESJ-19 nc nc nc nc

QPC-01 — — — E3

TRCY-03 — — — —

TRCY-07 — — — —

TRCYFP-01 — — — —

TRCYFP-02 — — — —

TRCYFP-04 — — — —

ESJFP-07 — — — —

ESJFP-10 nc nc nc nc

Table 23. Summary of microbial indicators detected in ground-water samples collected for the Northern San Joaquin Basin GroundWater Ambient Monitoring and Assessment (GAMA) study, California, December 2004 to February 2005.

[The five digit number below the constituent name is the USGS parameter code used to uniquely identify a specific constituent or property. The threshold type 

identifies the source of the comparison threshold. The threshold level is the level with which ground-water detections are compared. E, estimated value; ESJ, 

Eastern San Joaquin Basin; ESJFP, Eastern San Joaquin Basin flowpath; MCL-US, U.S. Environmental Protection Agency Maximum Contaminant Level (U.S. 

Environmental Protection Agency, 2005); mL, milliliter; nc, sample not collected; QPC, Uplands Basin; TRCY, Tracy Basin; TRCYFP, Tracy Basin flowpath; 

TT, treatment technique—a required process intended to reduce the level of a contaminant in drinking water (U.S. Environmental Protection Agency, 2005); 

USGS, U.S. Geological Survey; —, analyzed but not detected]

122 California GAMA Program: Ground-Water Quality Data in the Northern San Joaquin Basin Study Unit, 2005

Bennett and others—California GAMA Program: Ground-Water Quality Data in the Northern San Joaquin Basin Study Unit, 2005—Data Series 196

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