Pacific

Ocean

County Los Angeles

Ventura

County

Ojai

Ventura

Newhall

Camarillo

Simi Valley

Port Hueneme Santa Monica Mountains

Topatopa Mountains

San Gabriel Mountains

South Mtn

Oak Ridge

Sulphur Mtn

Santa Susana Mountains

San Ynez Mts

Pacific Ocean

Santa

Clara

River

Port Hueneme

Ground-Water Quality Data in the Santa Clara River Valley Study Unit, 2007:

Results from the California GAMA Program

Prepared in cooperation with the California State Water Resources Control Board

U.S. Geological Survey

U.S. Department of the Interior

Data Series 408
Cover: Top photograph: Looking west over Santa Clara River. Photograph taken by Jill Densmore, 

U.S. Geological Survey. Bottom: Pumping well used for sampling. Photograph taken by Cathy Munday, 

U.S. Geological Survey.
Ground-Water Quality Data in the Santa 

Clara River Valley Study Unit, 2007:

Results from the California GAMA Program 

By Joseph Montrella and Kenneth Belitz

Prepared in cooperation with the California State Water Resources Control Board

Data Series 408

U.S. Department of the Interior

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

KEN SALAZAR, Secretary

U.S. Geological Survey

Suzette M. Kimball, Acting Director

U.S. Geological Survey, Reston, Virginia: 2009

For more information on the USGS—the Federal source for science about the Earth, its natural and living resources, 

natural hazards, and the environment, visit http://www.usgs.gov or call 1-888-ASK-USGS

For an overview of USGS information products, including maps, imagery, and publications, 

visit http://www.usgs.gov/pubprod

To order this and other USGS information products, visit http://store.usgs.gov

Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the 

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:

Montrella, Joseph, and Belitz, Kenneth, 2009, Ground-water quality data in the Santa Clara River Valley study unit, 

2007: Results from the California GAMA Program: U.S. Geological Survey Data Series 408, 84 p. 

Available at http://pubs.usgs.gov/ds/408
iii

Contents

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

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

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

Hydrogeologic Setting ..................................................................................................................................4

Methods ..........................................................................................................................................................4

Study Design..........................................................................................................................................4

Sample Collection and Analysis.........................................................................................................8

Data Reporting.......................................................................................................................................9

Quality Assurance.................................................................................................................................9

Water-Quality Results ..................................................................................................................................9

Quality-Control Sample Results..........................................................................................................9

Comparison Thresholds.....................................................................................................................10

Ground-Water-Quality Data ..............................................................................................................11

Field Parameters........................................................................................................................11

Organic Constituents.................................................................................................................11

Constituent of Special Interest................................................................................................11

Inorganic Constituents..............................................................................................................11

Inorganic Tracer Constituents .................................................................................................12

Radioactive Constituents..........................................................................................................13

Microbial Indicators..................................................................................................................13

Future Work .........................................................................................................................................13

Summary .......................................................................................................................................................13

Acknowledgments.......................................................................................................................................14

References Cited..........................................................................................................................................14

Appendix .......................................................................................................................................................60
iv

Figures

Figure 1. Map showing the hydrogeologic provinces of California and the Santa Clara 

River Valley Groundwater Ambient Monitoring and Assessment (GAMA) 

study unit .................................................................................... 3

Figure 2 Map of the Santa Clara River Valley Groundwater Ambient Monitoring and 

Assessment (GAMA) study unit showing the ground-water basins defined 

by the California Department of Water Resources and major hydrologic 

features ....................................................................................... 5

Figure 3. Map of the Santa Clara River Valley Groundwater Ambient Monitoring and 

Assessment (GAMA) study unit showing the distribution of study area grid 

cells and the locations of sampled grid wells .......................................... 6

Figure 4. Map of the Santa Clara River Valley Groundwater Ambient Monitoring and 

Assessment (GAMA) study unit showing the distribution of study area grid 

cells and the locations of sampled grid wells and understanding wells ............ 7

Tables

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

Santa Clara River Valley Groundwater Ambient Monitoring and Assessment 

(GAMA) study, California, April to June 2007............................................. 20

Table 2. Classes of chemical and microbial constituents and water-quality indicators 

collected for the slow, intermediate, fast, and depth-dependent well sampling 

schedules for the Santa Clara River Valley Groundwater Ambient Monitoring 

and Assessment (GAMA) study, California, April to June 2007......................... 22

Table 3A. Volatile organic compounds, primary uses or sources, comparative thresholds, 

and reporting information for the U.S. Geological Survey National Water Quality 

Laboratory Schedule 2020 .................................................................. 23

Table 3B. Gasoline oxygenates and degradates, primary uses or sources, comparative 

thresholds, and reporting information for the U.S. Geological Survey National 

Water Quality Laboratory Schedule 4024 ................................................ 25

Table 3C. Pesticides and pesticide degradates, primary uses or sources, comparative 

thresholds, and reporting information for the U.S. Geological Survey National 

Water Quality Laboratory Schedule 2003 ................................................ 26

Table 3D. Potential wastewater-indicator compounds, primary uses or sources, 

comparative thresholds, and reporting information for the U.S. Geological 

Survey National Water Quality Laboratory Schedule 4433 ........................... 28

Table 3E. Pharmaceutical compounds, primary uses or sources, comparative 

thresholds, and reporting information for the U.S. Geological Survey National 

Water Quality Laboratory Code 9003 ...................................................... 31

Table 3F. Polar pesticides and pesticide degradates, primary uses or sources, 

comparative thresholds, and reporting information for the USGS National 

Water Quality Laboratory Schedule 2060 ................................................ 32

Table 3G. Nutrients and dissolved organic carbon, comparative thresholds, and 

reporting information for the U.S. Geological Survey National Water 

Quality Laboratory Schedule 2755, laboratory code 2612, and perchlorate 

(constituent of special interest) analyzed at the Montgomery 

Watson-Harza Laboratory .................................................................. 34
v

Table 3H. Major and minor ions and trace elements, comparative thresholds, and 

reporting information for the U.S. Geological Survey National Water Quality 

Laboratory Schedule 1948 .................................................................. 35

Table 3I. Arsenic, chromium, and iron species, comparative thresholds, and reporting 

information for the U.S. Geological Survey Trace Metal Laboratory, Boulder, 

Colorado .................................................................................... 36

Table 3J. Isotopic and radioactive constituents, comparative thresholds, and reporting 

information for laboratories ............................................................... 37

Table 3K. Noble gases and tritium, comparison thresholds, and reporting information 

for the Lawrence Livermore National Laboratory ....................................... 38

Table 3L. Microbial constituents, comparison thresholds, and reporting information for 

the U.S. Geological Survey Ohio Microbiology Laboratory parameter codes 

90901, 90900, 99335, and 99332 ............................................................ 38

Table 4. Water-quality indicators in samples collected for the Santa Clara River Valley 

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

April to June 2007 ........................................................................... 39

Table 5. Volatile organic compounds (VOC), including gasoline oxygenates and 

degradates, detected in samples collected for the Santa Clara River Valley 

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

April to June 2007 ........................................................................... 41

Table 6. Pesticides and pesticide degradates detected in samples collected for the 

Santa Clara River Valley Groundwater Ambient Monitoring and Assessment 

(GAMA) study, California, April to June 2007............................................. 43

Table 7. Potential wastewater-indicator compounds detected in samples collected 

for the Santa Clara River Valley Groundwater Ambient Monitoring and 

Assessment (GAMA) study, California, April to June 2007 ........................... 44

Table 8. Constituent of special interest (perchlorate) detected in samples collected 

for the Santa Clara River Valley Groundwater Ambient Monitoring and 

Assessment (GAMA) study, California, April to June 2007 ........................... 45

Table 9. Nutrients and dissolved organic carbon detected in samples collected for the 

Santa Clara River Valley Groundwater Ambient Monitoring and Assessment 

(GAMA) study, California, April to June 2007............................................. 46

Table 10. Major and minor ions and dissolved solids detected in samples collected for 

the Santa Clara River Valley Groundwater Ambient Monitoring and Assessment 

(GAMA) study, California, April to June 2007............................................. 47

Table 11. Trace elements detected in samples collected for the Santa Clara River Valley 

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

April to June 2007 ........................................................................... 49

Table 12. Species of inorganic arsenic, iron, and chromium in samples collected for the 

Santa Clara River Valley Groundwater Ambient Monitoring and Assessment 

(GAMA) study, California, April to June 2007............................................. 53

Table 13. Results for analyses of stable isotope ratios and tritium and carbon-14 activities 

in samples collected for the Santa Clara River Valley Groundwater Ambient 

Monitoring and Assessment (GAMA) study, California, April to June 2007 ......... 54

Table 14. Results for analyses of noble gases in and helium isotope ratios derived for 

samples collected for the Santa Clara River Valley Groundwater Ambient 

Monitoring and Assessment (GAMA) study, California, April to June 2007 ......... 56

Tables—Continued
vi

Table 15. Radioactive constituents detected in samples collected for the Santa Clara 

River Valley Groundwater Ambient Monitoring and Assessment (GAMA) study, 

California, April to June 2007............................................................... 58

Table 16. Microbial indicator results for samples collected for the Santa Clara River 

Valley Groundwater Ambient Monitoring and Assessment (GAMA) study, 

California, April to June 2007............................................................... 59

Table A1. Analytical methods used by the U.S. Geological Survey (USGS) National 

Water Quality Laboratory (NWQL) and additional contract laboratories to 

determine organic, inorganic, and microbial constituents ........................... 69

Table A2. Preferred analytical schedules for constituents appearing on multiple schedules 

for samples collected for the Santa Clara River Valley Groundwater Ambient 

Monitoring and Assessment (GAMA) study, California, April to June 2007 ......... 71

Table A3. Quality-control summary for constituents detected in blank samples collected 

for the Santa Clara River Valley Groundwater Ambient Monitoring and 

Assessment (GAMA) study, California, April to June 2007 ........................... 72

Table A4A. Quality-control summary for replicate analyses of organic constituents 

detected in samples collected for the Santa Clara River Valley Groundwater 

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

June 2007 .................................................................................... 73

Table A4B. Quality-control summary for replicate analyses of major and minor ions, 

nutrients, and a constituent of special interest [perchlorate] detected in samples 

collected for the Santa Clara River Valley Groundwater Ambient Monitoring and 

Assessment (GAMA) study, California, April to June 2007 ........................... 74

Table A4C. Quality-control summary for replicate analyses of trace elements detected in 

samples collected for the Santa Clara River Valley Groundwater Ambient 

Monitoring and Assessment (GAMA) study, California, April to June 2007 ......... 75

Table A4D. Quality-control summary of replicate analyses of radioactive constituents and 

stable isotopes detected in samples collected for the Santa Clara River Valley 

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

April to June 2007 ........................................................................... 76

Table A5A. Quality-control summary for matrix-spike recoveries of volatile organic 

compounds (NWQL schedule 2020) including gasoline oxygenates and 

degradates (NWQL schedule 4024) in samples collected for the Santa Clara 

River Valley Groundwater Ambient Monitoring and Assessment (GAMA) study, 

California, April to June 2007............................................................... 77

Table A5B. Quality-control summary for matrix-spike recoveries of pesticides and pesticide 

degradates (NWQL schedule 2003) in samples collected for the Santa Clara 

River Valley Groundwater Ambient Monitoring and Assessment (GAMA) study, 

California, April to June 2007............................................................... 79

Table A5C. Quality-control summary for matrix-spike recoveries of potential wastewaterindicator compounds in samples collected for the Santa Clara River Valley 

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

April to June 2007 ........................................................................... 81

Tables—Continued

Appendix Tables
vii

Table A5D. Quality-control summary for matrix-spike recoveries of pesticides and pesticide 

degradates (NWQL schedule 2060) in samples collected for the Santa Clara 

River Valley Groundwater Ambient Monitoring and Assessment (GAMA) study, 

California, April to June 2007............................................................... 83

Table A6. Quality-control summary for surrogate recoveries of volatile organic 

compounds, including gasoline oxygenates and degradates, pesticides and 

pesticide degradates, potential wastewater-indicator compounds, and 

pharmaceutical compounds in samples collected for the Santa Clara River 

Valley Groundwater Ambient Monitoring and Assessment (GAMA) study,

California, April to June 2007............................................................... 84

Abbreviations and Acronyms

AB Assembly Bill (through the California State Assembly)

AL-US action level (USEPA)

CAS Chemical Abstracts Service (American Chemical Society)

CSU combined standard uncertainty

E estimated or having a higher degree of uncertainty

GAMA Groundwater Ambient Monitoring and Assessment program

GPS Global Positioning System

HAL-US Lifetime Health Advisory Level (USEPA)

HPLC high-performance liquid chromatography

LRL laboratory reporting level

LSD land-surface datum

LT-MDL long-term method detection level

MCL-CA maximum contaminant level (CDPH)

MCL-US maximum contaminant level (USEPA)

MDL method detection limit

MRL minimum reporting level

MU method uncertainty

N Normal (1-gram-equivalent per liter of solution)

na not available

nc sample not collected

NL notification level

NL-CA California notification level (CDPH)

NWIS National Water Information System (USGS)

PCFF personal computer field forms program

QC quality control

RPD relative percent difference

RSD relative standard deviation

RSD5 risk-specific dose at 10–5 (USEPA)

SCRV Santa Clara River Valley study unit

Appendix Tables—Continued
viii

SMCL-CA secondary maximum contaminant level (CDPH)

SSMDC sample-specific minimum detectable concentration

TT-US Treatment Technique (USEPA)

US United States

V value censored due to possible blank contamination and was not included in 

ground-water quality analyses

VPDB Vienna Peedee Belemite

VSMOW Vienna Standard Mean Ocean Water

Abbreviations and Acronyms—Continued

Organizations

CDPH California Department of Public Health

LLNL Lawrence Livermore National Laboratory

MWH Montgomery Watson Harza 

NAWQA National Water Quality Assessment (USGS)

NWQL National Water Quality Laboratory (USGS)

SWRCB State Water Resources Control Board (California)

TML National Research Program Trace Metal Laboratory (USGS)

USEPA U.S. Environmental Protection Agency

USGS U. S. Geological Survey

UWCD United Water Conservation District

Selected Chemical Names

CaCO3 calcium carbonate

CFC chlorofluorocarbon

CO3

–2 carbonate

Cr chromium

DOC dissolved organic carbon

Fe iron

HCl hydrochloric acid

HCO3

– bicarbonate

PCE perchloroethene

TDS total dissolved solids

THM trihalomethane

VOC volatile organic compound
ix

Abbreviations and Acronyms—Continued

Units of Measurement

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

and 1 atmosphere of pressure per gram of water) 

cm centimeter

oC degrees Celsius

oF degrees Fahrenheit

ft foot (feet)

in. inch

km2 square kilometers

L liter

mg milligram

mg/L milligrams per liter (parts per million)

mi mile

mL milliliter

μg/L micrograms per liter (parts per billion)

μL microliter

μm micrometer

pCi/L picocurie per liter

δi

E delta notation, the ratio of a heavier isotope of an element (i

E) to the more 

common lighter isotope of that element, relative to a standard reference, 

expressed as per mil (per thousand)

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).

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

micrograms per liter is equivalent to parts per billion (ppb).
x

This page intentionally left blank.
Ground-Water Quality Data in the Santa Clara River 

Valley Study Unit, 2007: Results from the California 

GAMA Program

By Joseph Montrella and Kenneth Belitz

Abstract 

Ground-water quality in the approximately 460-squaremile Santa Clara River Valley study unit (SCRV) was 

investigated from April to June 2007 as part of the statewide 

Priority Basin project of the Ground-Water Ambient 

Monitoring and Assessment (GAMA) Program. The 

GAMA Priority Basin project was developed in response 

to the Groundwater Quality Monitoring Act of 2001 and is 

being conducted by the U.S. Geological Survey (USGS) in 

cooperation with the California State Water Resources Control 

Board (SWRCB).

The study was designed to provide a spatially unbiased 

assessment of the quality of raw ground water used for public 

water supplies within SCRV, and to facilitate a statistically 

consistent basis for comparing water quality throughout 

California. Fifty-seven ground-water samples were collected 

from 53 wells in Ventura and Los Angeles Counties. Forty-two 

wells were selected using a randomized grid-based method to 

provide statistical representation of the study area (grid wells). 

Eleven wells (understanding wells) were selected to further 

evaluate water chemistry in particular parts of the study 

area, and four depth-dependent ground-water samples were 

collected from one of the eleven understanding wells to help 

understand the relation between water chemistry and depth.

The ground-water samples were analyzed for a large 

number of synthetic organic constituents (volatile organic 

compounds [VOC], pesticides and pesticide degradates, 

potential wastewater-indicator compounds, and pharmaceutical 

compounds), a constituent of special interest (perchlorate), 

naturally occurring inorganic constituents (nutrients, major 

and minor ions, and trace elements), radioactive constituents, 

and microbial constituents. Naturally occurring isotopes 

(tritium, carbon-13, carbon-14 [abundance], stable isotopes of 

hydrogen and oxygen in water, stable isotopes of nitrogen and 

oxygen in nitrate, chlorine-37, and bromine-81), and dissolved 

noble gases also were measured to help identify the source and 

age of the sampled ground water. 

Quality-control samples (blanks or replicates, or samples 

for matrix spikes) were collected from approximately 

26 percent of the wells, and the analyses of these samples were 

used to evaluate the quality of the data for the ground-water 

samples. Assessment of the quality-control results showed that 

the quality of the environmental data was good, with low bias 

and low variability, and as a result, less than 0.1 percent of the 

analytes detected in ground-water samples were censored. 

This study did not attempt to evaluate the quality of water 

delivered to consumers; after withdrawal from the ground, 

water typically is treated, disinfected, and (or) blended with 

other waters to maintain acceptable water quality. Regulatory 

thresholds apply to treated water that is delivered (or, 

supplied) to the consumer, not to raw ground water. However, 

to provide some context for the results, concentrations of 

constituents measured in the raw ground water were compared 

with regulatory and non-regulatory thresholds established 

by the U.S. Environmental Protection Agency (USEPA) and 

the California Department of Public Health (CDPH) and 

thresholds established for aesthetic concerns (secondary 

maximum contaminant levels, SMCL-CA) by CDPH.

Most constituents that were detected in groundwater samples were reported at concentrations below their 

established health-based thresholds. VOCs, pesticides and 

pesticide degradates, and potential wastewater-indicator 

compounds were detected in about 33 percent or less of the 

42 SCRV grid wells. Concentrations of all detected organic 

constituents were below established health-based thresholds. 

Perchlorate was detected in approximately 12 percent of the 

SCRV grid wells; all concentrations reported were below the 

NL-CA threshold. 

Additional constituents, including major ions, trace 

elements, and nutrients were collected at 26 wells (16 grid 

wells and 10 understanding wells) of the 53 wells sampled for 

the SCRV study. The concentration of total dissolved solids 

(TDS) was reported above the upper SMCL-CA threshold in 

18 of the 26 SCRV wells sampled for TDS. The concentration 

of sulfate was reported above the upper SMCL-CA threshold 

in 10 of 26 SCRV wells sampled for sulfate. Chloride was 

reported above the upper SMCL-CA threshold in 4 of 26 

wells sampled for chloride; none of these 4 wells were used 

for public supply. The concentration of nitrite plus nitrate was 

reported above the health-based threshold in 5 of 26 SCRV 

wells sampled for nitrite plus nitrate. Iron and manganese 
2 Ground-Water Quality Data in the Santa Clara River Valley Study Unit, 2007: Results from the California GAMA Program

were above their respective SMCL-US thresholds in 7 and 

14 SCRV wells, respectively. The gross alpha radioactivity 

(72-hour count) for one SCRV grid well was slightly above 

the established health-based threshold, and the gross alpha 

radioactivity (30-day count) in one SCRV understanding well 

was slightly above the established health-based threshold. 

Activities of radon-222 in samples from six wells were above 

the proposed MCL-US, 300 pCi/L, but below the alternative 

MCL-US, 4,000 pCi/L. 

Introduction 

Ground water comprises nearly half of the water 

used for public supply in California (Hutson and others, 

2004). To assess the quality of ground water in aquifers 

used for drinking-water supply and to establish a program 

for monitoring trends in ground-water quality, the State 

Water Resources Control Board (SWRCB), in collaboration 

with the U.S. Geological Survey (USGS) and Lawrence 

Livermore National Laboratory (LLNL), implemented the 

Groundwater Ambient Monitoring and Assessment (GAMA) 

Program (http://www.waterboards.ca.gov/gama). The GAMA 

program consists of three projects: Priority Basin Assessment, 

conducted by the USGS (http://ca.water.usgs.gov/gama/); 

Voluntary Domestic Well Assessment, conducted by the 

SWRCB; and Special Studies, conducted by LLNL. 

The SWRCB initiated the GAMA Priority Basin project 

in response to the Ground-Water Quality Monitoring Act of 

2001 (Sections 10780-10782.3 of the California Water Code, 

Assembly Bill 599). AB 599 is a public mandate to assess and 

monitor the quality of ground water used as public supply for 

municipalities in California. The project is a comprehensive 

assessment of statewide ground-water quality designed to help 

better understand and identify risks to ground-water resources, 

and to increase the availability of information about groundwater quality to the public. As part of the AB 599 process, 

the USGS, in collaboration with the SWRCB, developed the 

monitoring plan for the project (Belitz and others, 2003; State 

Water Resources Control Board, 2003). Key aspects of the 

project are inter-agency collaboration, and cooperation with 

local water agencies and well owners. Local participation in 

the project is entirely voluntary.

The GAMA Priority Basin project is unique in California 

because the data collected during the study include analyses 

for an extensive number of chemical constituents at very 

low concentrations, analyses that are not normally available. 

A broader understanding of ground-water composition 

will be especially useful for providing an early indication 

of changes in water quality, and for identifying the natural 

and human factors affecting water quality. Additionally, the 

GAMA Priority Basin project will analyze a broader suite of 

constituents than required by the California Department of 

Public Health (CDPH; formerly California Department of 

Health Services – replaced on July 1, 2007). An understanding 

of the occurrence and distribution of these constituents is 

important for the long-term management and protection of 

ground-water resources.

 The range of hydrologic, geologic, and climatic 

conditions that exists in California must be considered in an 

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

partitioned the state conceptually into 10 hydrogeologic 

provinces, each with distinctive hydrologic, geologic, and 

climatic characteristics (fig. 1), and representative regions in 

all 10 provinces were included in the project design. Eighty 

percent of California’s approximately 16,000 public-supply 

wells are in ground-water basins within these hydrologic 

provinces. Most of these ground-water basins, defined by 

the California Department of Water Resources, consist of 

relatively permeable, unconsolidated deposits of alluvial or 

volcanic origin (California Department of Water Resources, 

2003). Ground-water basins were prioritized for sampling on 

the basis of the number of public-supply wells in the basin, 

with secondary consideration given to municipal ground-water 

use, agricultural pumping, the number of leaking underground 

fuel tanks, and pesticide applications within the basins 

(Belitz, and others, 2003). In addition, some ground-water 

basins or groups of adjacent similar basins with relatively few 

public-supply wells were assigned high priority so that all 

hydrogeologic provinces would be represented in the subset 

of basins sampled. The 116 priority basins were grouped into 

35 study units. Some areas not in the defined ground-water 

basins were included in several of the study units to represent 

the 20 percent of public-supply wells outside the groundwater basins. The SCRV was the seventeenth study unit in the 

GAMA program. 

Three types of water-quality assessments are being 

conducted using the data collected in each study unit: 

(1) Status: assessment of the current quality of the groundwater resource, (2) Trends: detection of changes in groundwater quality and (3) Understanding: identification of the 

natural and human factors affecting ground-water quality 

(Kulongoski and Belitz, 2004). This report is one of a series 

of reports presenting the status of current water quality 

conditions in each study unit (Wright and others, 2005; 

Kulongoski and others, 2006; Bennett and others, 2006; 

Dawson and others, 2007; Fram and Belitz, 2007; Kulongoski 

and Belitz, 2007). Subsequent reports will address the trends 

and understanding aspects of the water-quality assessments.

The Santa Clara River Valley GAMA study unit, 

hereinafter referred to as SCRV, contains eight ground-water 

basins. The SCRV study unit was considered high priority for 

sampling to adequately represent the Transverse Ranges and 

Selected Peninsular Ranges hydrogeologic province (Belitz, 

and others, 2003). 
Introduction 3

Figure 1. The hydrogeologic provinces of California and the Santa Clara River Valley Groundwater Ambient 

Monitoring and Assessment (GAMA) study unit.

Basin and Range

Klamath

Mountains

Desert

Cascades and

Modoc Plateau

Southern 

Coast

 Ranges

Sierra

Nevada

Central

Valley

Northern

Coast

Ranges

San Diego

Drainages

Transverse Ranges and Selected Peninsular Ranges

Bakersfield

San Francisco

OREGON

NEVADA

MEXICO

ARIZONA

Redding

Los Angeles

San Diego

Pacific Ocean

0 200 MILES

0 200 KILOMETERS

40

42 124 122 120 118 116 114

38

36

34

Base from U.S. Geological Survey digital elevation

data, 1999, Albers Equal Area Projection

Provinces from Belitz and others, 2003

Sacramento

Santa Clara River Valley 

GAMA Study Unit
4 Ground-Water Quality Data in the Santa Clara River Valley Study Unit, 2007: Results from the California GAMA Program

Purpose and Scope

The purposes of this report are: (1) to describe the 

study design and study methods; (2) to present the results of 

quality-control tests, and (3) to present the analytical results 

for ground-water samples collected in SCRV. Ground-water 

samples were analyzed for organic, inorganic, microbial 

constituents, field parameters, and chemical tracers. The 

chemical and microbial data presented in this report were 

evaluated by comparing them to state and federal drinking 

water regulatory and non-regulatory standards that are applied 

to treated drinking water. Regulatory and non-regulatory 

thresholds considered for this report are those established by 

the United States Environmental Protection Agency (USEPA) 

and the California Department of Public Health (CDPH) (U.S. 

Environmental Protection Agency, 2006, 2007a,b; California 

Department of Public Health, 2007a,b). The data presented in 

this report are to characterize the quality of untreated groundwater resources within the study unit, not the treated drinking 

water delivered to consumers by water purveyors. Discussions 

of the factors that influence the distribution and occurrence of 

the constituents detected in ground-water samples will be the 

subject of subsequent publications.

Hydrogeologic Setting 

Knowledge of the hydrologeologic setting is important 

in the design of a ground-water quality investigation. The 

Santa Clara River Valley (SCRV) GAMA study unit covers 

approximately 460 square miles (1,191 km2) in Los Angeles 

and Ventura Counties, California (fig. 2). The study unit is 

located in the Transverse Ranges and Selected Peninsular 

Ranges hydrogeologic province (fig. 1) and includes eight 

ground-water basins (fig. 2); two of the basins, Santa Clara 

River Valley and Ventura River Valley ground-water basins, 

are divided into additional ground-water subbasins (California 

Department of Water Resources, 2003). The study unit is 

bounded on the south by the Santa Monica Mountains and on 

the north by the Topatopa and Santa Ynez Mountains. The San 

Gabriel Mountains form the eastern boundary, and the Pacific 

Ocean lies to the west of the study area. 

The wells sampled in Ventura County, or western part 

of SCRV study unit, are in or near the Ojai Valley, Upper 

Ojai Valley, Ventura River Valley, Santa Clara River Valley, 

Pleasant Valley, Arroyo Santa Rosa Valley, Las Posas Valley, 

and Simi Valley ground-water basins (fig. 2). The wells 

sampled in Los Angeles County are in the eastern part of 

the Santa Clara River Valley ground-water basin (California 

Department of Water Resources, 2004a–n). 

The topographic relief of the SCRV study unit rises 

from sea level to an elevation of 5,800 feet (1,768 meters) 

in the surrounding Topatopa Mountains of the Transverse 

Ranges. The climate in the SCRV study unit is characterized 

as Mediterranean, having cool, moist winters and dry, warm 

summers. The average annual precipitation range in SCRV 

is 12 to 28 inches (30 to 71 centimeters) per year, with the 

majority of the rain falling in the winter months and at higher 

elevations (California Department of Water Resources 2004c, 

e, i, m). The average annual air temperature in SCRV ranges 

from 44°F to 77°F (7°C to 25°C) (Oregon State University 

PRISM Group, 1971-2000). 

Natural and artificial ground-water recharge exists in 

the SCRV (Hansen and others, 2003). Most natural recharge 

consists of streamflow and direct-precipitation infiltration. 

The Ventura River, Santa Clara River, and Calleguas Creek are 

three main river systems that drain the study area, eventually 

emptying into the Pacific Ocean (fig. 2). Sources of water 

for streams are natural precipitation, reservoir discharge, 

imported-northern California water, dewatering wells, and 

treated wastewater effluent. In the Oxnard subbasin, the 

United Water Conservation District’s (UWCD) artificial 

recharge facilities located in the Oxnard forebay play an 

important role in recharging the aquifers underlying the 

Oxnard plain (United Water Conservation District, 2004). 

Percolation of irrigation return water also contributes to 

ground-water recharge, but varies across the study area.

Methods 

Methods used for the GAMA program were selected 

to achieve the following objectives: (1) design a sampling 

plan suitable for statistical analysis, (2) collect samples in 

a consistent manner, (3) analyze samples using proven and 

reliable laboratory methods, (4) assure the quality of the 

ground-water data, and (5) maintain data securely and with 

relevant documentation. The Appendix to this report contains 

detailed descriptions of the sample collection protocols and 

analytical methods, and the quality-assurance methods.

Study Design

The wells selected for sampling in this study reflect the 

combination of two well selection strategies. Forty-two wells, 

referred to as grid wells (fig. 3), were selected to provide 

a statistically unbiased, spatially distributed assessment 

of the quality of ground-water resources used for public 

drinking-water supply, and 11 additional wells, referred to as 

understanding wells (fig. 4), were selected to provide greater 

sampling density in several areas to increase an understanding 

of specific ground-water quality issues in these areas. In 

addition to selecting 11 additional wells, four depth-dependent 

samples were collected from one of these eleven wells to 

address specific ground-water quality issues.
Methods 5

Figure 2 The Santa Clara River Valley Groundwater Ambient Monitoring and Assessment (GAMA) study unit showing the groundwater basins defined by the California Department of Water Resources and major hydrologic features.

Pacific Ocean

Water bodies

Stream or river

Aqueduct

34 00’

34 30’

119 00’ 118 30’

0 5 10 MILES

0 5 10 KILOMETERS

Shaded relief derived from U.S. Geological Survey 

National Elevation Dataset, 2006, 

Albers Equal Area Conic Projection

County

Los Angeles

Santa Monica Mountains

Topatopa Mountains

San Gabriel Mountains

South Mtn

Oak Ridge

Sulphur Mtn

River

River

Santa

Clara

Ventura

Calleguas

Creek

Santa Susana Mountains

Ventura

County

Ojai

Ventura

Santa Clara River Valley

Santa

Clara

River

Valley

Las Posas Valley

Newhall

Camarillo

Simi Valley

Simi Valley

Pleasant Valley

Port Hueneme

San Ynez Mts Ojai

Valley Upper

Ojai

Valley

Ventura

River

Valley

Study unit boundary

Ground-water basins within the 

study unit (from California Department

of Water Resources)

EXPLANATION

Arroyo Santa

Rosa Valley

Arroyo Santa

Rosa Valley
6 Ground-Water Quality Data in the Santa Clara River Valley Study Unit, 2007: Results from the California GAMA Program

Pacific Ocean

.

.

.

.

.

.

.

.

.

.

.

.

. .

. . .

.

.

.

..

.

.

.

.

.

.

.

.

.

.

.

.

.

.

.

.

.

.

.

. 42

41

40

39

38

37

36

35

34

33

32

31 30

29

28

27

26

25

24

23

22 21

20

19

18

17 16

15

14 13

12

11

10

09

08

07

06

05

04

03

02

01

Water bodies

Stream or river

Aqueduct

.37

Grid well and well number

 (prefix “SCRV” is not shown)

 SCRV-11 was selected to

 represent grid cell number 29

29

21

21

7 8

6 6

7

40

23

8

8

19

19

23 32

32

40

42

42

42

39 39

48

35

35

48

5

5

34 00’

34 30’

119 00’ 118 30’

0 5 10 MILES

0 5 10 KILOMETERS

Shaded relief derived from U.S. Geological Survey 

National Elevation Dataset, 2006, 

Albers Equal Area Conic Projection

County

Los Angeles

San Gabriel Mountains

South Mtn

Oak Ridge

River

Santa

Clara

Calleguas

Creek

Santa Susana Mountains

Ventura

County

Santa Monica Mountains

Topatopa Mountains

Sulphur Mtn

San Ynez Mts

River

Ventura

Santa Clara study

 unit boundary

EXPLANATION

Randomized sampling

 grid cell-Selected grid

 cell number indicates cell

 is continued across an area

 not included in the study unit

32

Figure 3. The Santa Clara River Valley Groundwater Ambient Monitoring and Assessment (GAMA) study unit showing the distribution 

of study area grid cells and the locations of sampled grid wells.
Methods 7

Figure 4. The Santa Clara River Valley Groundwater Ambient Monitoring and Assessment (GAMA) study unit showing the distribution 

of study area grid cells and the locations of sampled grid wells and understanding wells.

Pacific Ocean

11

10

10

08, 09

07

06

05

04

03

02 01

Understanding well and

 well number (prefix “SCRVU”

 is not shown)

.

.

.

.

.

.

.

.

.

.

.

.

. .

. . .

.

.

.

..

.

.

.

.

.

.

.

.

.

.

.

.

.

.

.

.

.

.

.

. 42

41

40

39

38

37

36

35

34

33

32

31 30

29

28

27

26

25

24

23

22 21

20

19

18

17 16

15

14 13

12

11

10

09

08

07

06

05

04

03

02

01

.

.

.

.

.

.. .

.

.

.

34 00’

34 30’

119 00’ 118 30’

0 5 10 MILES

0 5 10 KILOMETERS

Shaded relief derived from U.S. Geological Survey 

National Elevation Dataset, 2006, 

Albers Equal Area Conic Projection

County

Los Angeles

San Gabriel Mountains

South Mtn

Oak Ridge

River

Santa

Clara

Calleguas

Creek

Santa Susana Mountains

Ventura

County

Santa Monica Mountains

Topatopa Mountains

Sulphur Mtn

San Ynez Mts

River

Ventura

EXPLANATION

Santa Clara study

 unit boundary

Randomized sampling

 grid cell-Selected grid

 cell number indicates cell

 is continued across an area

 not included in the study unit

32

.37

Grid well and well number

 (prefix “SCRV” is not shown)

 SCRV-11 was selected to

 represent grid cell number 29

Water bodies

Stream or river

Aqueduct

29

21

21

7 8

6 6

7

40

23

8

8

19

19

23 32

32

40

42

42

42

39 39

48

35

35

48

5

5
8 Ground-Water Quality Data in the Santa Clara River Valley Study Unit, 2007: Results from the California GAMA Program

The spatially distributed wells were selected using a 

randomized grid-based method (Scott, 1990). The study area 

was subdivided into forty-eight grid cells each approximating 

10 mi2 (25 km2) (fig. 3). Locations of wells listed in statewide 

databases maintained by the CDPH and USGS were plotted. 

If a grid cell contained more than one public-supply well, 

each well was randomly assigned a rank. The lowest ranked 

well that met basic sampling criteria (for example, sample 

collection point before water treatment, capability to pump for 

several hours, and available well-construction information) 

and for which permission to sample could be obtained was 

then sampled. If a grid cell contained no accessible publicsupply wells, domestic and irrigation wells were considered. 

An attempt was made to select domestic and irrigation wells 

having depths and screened intervals similar to those in 

public-supply wells in the area. In this fashion, a well was 

selected for a cell that had any wells to provide a spatially 

distributed, randomized monitoring network for each study 

area. Samples were collected from 42 of the 48 grid cells; the 

other 6 grid cells did not contain accessible wells. Grid wells 

in SCRV were numbered in the order of sample collection, 

and the prefix “SCRV” was appended to each number. One 

grid well (SCRV-11) outside but near the randomized grid cell 

network was included in the study because the nearby grid cell 

had no accessible wells.

Many of the understanding wells sampled in the study 

unit were near the coastal area in the southwestern portion 

of the study area (fig. 4). Understanding wells were sampled 

to assess movement and source of salinity in ground-water 

in these areas. Understanding wells sampled as part of these 

studies for better understanding were not included in the 

statistical characterization of water quality in SCRV because 

they were not selected using the randomized grid-based 

method. These additional wells were numbered in the order of 

sample collection, and the prefix “SCRVU” (“U” indicating 

“understanding”) was appended to each number. Four depthdependent ground-water samples were collected from one 

“understanding” well (SCRVU-04). These samples were 

numbered in the order of sample collection and assigned the 

prefix “DD” (“DD” indicating depth-dependent sample).

Table 1 provides the GAMA-ID (alphanumeric 

identification number) for each well, along with the date 

sampled, sampling schedule, elevation, and well-construction 

information. Ground-water samples were collected from 28 

public-supply wells, 15 irrigation wells, five monitoring wells, 

two dewatering wells, two standby wells, and one domestic 

well from April to June 2007. 

Well locations and identifications were verified using 

Global Positioning System (GPS), 1:24,000 scale USGS 

topographic maps, comparison with existing well information 

in USGS and CDPH databases, and information provided 

by well owners. Driller’s logs for wells were obtained when 

available. Well information was recorded by hand on field 

sheets and electronically using specialized software on field 

laptop computers. All information was verified and then 

uploaded into the USGS National Water Information System 

(NWIS). 

The wells in SCRV were sampled using a tiered 

analytical approach. All wells were sampled for a standard set 

of constituents, including pH, dissolved oxygen, temperature, 

and specific conductance, VOCs, pesticides and pesticide 

degradates (NWQL Schedule 2003), potential wastewaterindicator compounds, perchlorate, stable isotopes of hydrogen 

and oxygen in water, dissolved noble gases, and tritium. 

The sampling schedule for a standard set of constituents 

was termed the “fast” schedule (table 2). Wells on the 

“intermediate” schedule were sampled for all the constituents 

on the fast schedule plus nutrients and dissolved organic 

carbon; major and minor ions and trace elements; stable 

isotopes of nitrogen and oxygen in nitrate; stable isotopes 

of chlorine and bromine; arsenic and iron abundance and 

speciation, and chromium abundance and speciation. Wells 

on the “slow” schedule were sampled for all the constituents 

on the intermediate schedule plus gasoline oxygenates and 

degradates, polar pesticides and pesticide degradates (NWQL 

Schedule 2060), pharmaceutical compounds, carbon isotopes, 

radioactive constituents, and microbial constituents. Fast, 

intermediate, and slow refer to the time required to sample the 

well for all the analytes on the schedule. Generally, one slow, 

or two intermediate, or three fast wells could be sampled in 

one day. The four depth-dependent samples were collected 

from one understanding well (SCRVU-04) and were analyzed 

for major and minor ions and trace elements, and stable 

isotopes of hydrogen and oxygen in water. The deepest depthdependent sample was also analyzed for stable isotopes of 

chlorine and bromine (table 2). In SCRV, 27 of the 57 groundwater samples were collected on the fast schedule, 17 groundwater samples were collected on the intermediate schedule, 9 

ground-water samples were collected on the slow schedule, 

and 4 depth-dependent samples were collected from SCRVU04 (table 1).

Sample Collection and Analysis

Samples were collected in accordance with the protocols 

established by the USGS National Water Quality Assessment 

(NAWQA) program (Koterba and others, 1995) and the USGS 

National Field Manual (U.S. Geological Survey, variously 

dated). These sampling protocols ensure that a representative 

sample of ground water is collected at each site and that the 

samples are collected and handled in a way that minimizes 

contamination. The methods used to collect samples are 

described in the Appendix section “Sample Collection and 

Analysis”.

Tables 3A–L list the compounds analyzed in each 

constituent class. Ground-water samples were analyzed for: 

85 VOCs (table 3A), 8 gasoline oxygenates and degradates 

(table 3B); 63 pesticides and pesticide degradates (NWQL 

Schedule 2003) (table 3C); 69 potential wastewater-indicator 

compounds (table 3D); 14 pharmaceutical compounds 

(table 3E); and 59 polar pesticides and pesticide degradates 

(NWQL Schedule 2060) (table 3F); 1 constituent of special 
Water-Quality Results 9

interest (perchlorate) (table 3G); 5 nutrients and dissolved 

organic carbon (table 3G); 10 major and minor ions, and total 

dissolved solids, and 24 trace elements (table 3H); arsenic, 

iron, and chromium species (table 3I); stable isotopes of 

hydrogen and oxygen in water stable isotopes of nitrogen and 

oxygen in nitrate, stable isotopes of chlorine and bromine, 

9 radioactive constituents, including tritium and carbon-14 

(table 3J); 5 dissolved noble gases, helium stable isotope 

ratios (table 3K); and four microbial constituents (table 3L). 

The methods used for sample analysis are described in the 

Appendix section “Sample Collection and Analysis”.

Data Reporting

The methods and conventions used for reporting the 

data are described in the Appendix. Twenty-two constituents 

analyzed in this study were measured by more than one 

method at the NWQL, but only the results from the 

preferred method are reported. Arsenic, iron, and chromium 

concentrations, and tritium activities, were measured by more 

than one laboratory, and both sets of results are reported. 

Quality Assurance

The quality assurance methods used for this study follow 

the protocols used by USGS NAWQA program (Koterba 

and others, 1995) and are described in the USGS National 

Field Manual (U.S. Geological Survey, variously dated). The 

NWQL quality assurance plan followed by the NWQL, the 

primary laboratory used to analyze samples for this study, is 

described by Maloney (2005) and Pirkey and Glodt (1998). 

Quality-control (QC) samples collected in the SCRV study 

include source-solution blanks, field blanks, an equipment 

blank, field replicates, matrix spikes, and surrogate spikes. 

QC samples were collected to evaluate contamination of the 

samples and bias and variability of the water chemistry data 

that may have resulted from collecting, processing, storing, 

transporting, and analyzing the samples in the laboratory. The 

quality assurance methods and quality-control sample results 

are described in the Appendix.

Water-Quality Results 

Results from analyses of raw (untreated) ground-water 

samples from SCRV are given in tables 4 through 16. Groundwater samples collected in SCRV were analyzed for up to 

350 constituents, and 240 of those constituents were not 

detected in any of the samples (tables 3A–L). The result tables 

(tables 4–16) give only the constituents that were detected, 

and list only wells in which at least one constituent was 

detected. For constituent classes that were analyzed for all of 

the grid wells, the tables include the number of wells at which 

each analyte was detected, the frequency at which it was 

detected (in relation to the number of grid wells), and the total 

number of constituents detected at each well. Results from the 

understanding wells are given in the tables, but these results 

were excluded from the detection frequency calculations 

to avoid statistically over-representing the areas near the 

understanding wells.

Table 4 includes water-quality indicators measured in 

the field and at the NWQL, while tables 5 through 16 give 

the results of ground-water analyses organized by compound 

classes: 

•	 Organic constituents

•	 VOCs and gasoline oxygenates and degradates 

(table 5)

•	 Pesticides and pesticide degradates (table 6)

•	 Potential wastewater-indicator compounds (table 7)

•	 Constituent of special interest – perchlorate (table 8)

•	 Inorganic constituents

•	 Nutrients and dissolved organic carbon (table 9)

•	 Major and minor ions (table 10)

•	 Trace elements (table 11)

•	 Arsenic, iron, and chromium species (table 12)

•	 Inorganic tracer constituents

•	 Stable isotope ratios, and tritium and carbon-14 

activities (table 13)

•	 Nitrogen and oxygen isotopes of nitrate (table 13)

•	 Noble gases and helium isotopes (table 14)

•	 Radioactive constituents (table 15)

•	 Microbial indicators (table 16) 

Results for pharmaceutical compounds are not presented 

in this report; they will be included in subsequent publications. 

The results of analyses of quality-control and ground-water 

samples are briefly described in the sections below. Healthbased thresholds used to compare concentrations in groundwater samples also are described. 

Quality-Control Sample Results

Results of quality-control analyses (blanks, replicates, 

matrix spikes, and surrogates) were used to evaluate the 

quality of the data for the ground-water samples (see 

Appendix). Assessing the blanks resulted in qualifying of less 

than 0.1 percent of the data for the ground-water samples. 

Matrix spike recoveries for a number of organic constituents 

were lower than the acceptable limits, which may indicate that 

these constituents might not have been detected in samples 

if they were present at very low concentrations. The qualitycontrol results are described in the Appendix section “QualityControl Sample Results”.
10 Ground-Water Quality Data in the Santa Clara River Valley Study Unit, 2007: Results from the California GAMA Program

Comparison Thresholds

Concentrations of constituents in ground-water samples 

were compared with CDPH and USEPA drinking-water 

health-based thresholds and thresholds established for 

aesthetic purposes (U.S. Environmental Protection Agency, 

2006, 2007a; California Department of Public Health, 2007a). 

CDPH replaced California Department of Health Services 

(CDHS) on July 1, 2007. The chemical and microbial 

data presented in this report characterize the quality of the 

untreated ground-water resources within SCRV and are not 

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 because treated drinking water may be 

disinfected, filtered, mixed with other waters, and exposed to 

the atmosphere before being delivered to consumers. 

The following thresholds were used for comparisons:

•	 MCL– Maximum Contaminant Level. 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. MCLs established by the USEPA are the 

minimum standards with which states are required to 

comply, and individual states may choose to set more 

stringent standards. CDPH has established MCLs for 

constituents not regulated by the USEPA, as well as 

lowered the threshold concentration for a number of 

constituents with MCLs established by the USEPA. In 

this report, a threshold set by the USEPA and adopted 

by CDPH is labeled “MCL-US,” and one set by CDPH 

that is more stringent than the MCL-US is labeled 

“MCL-CA.” CDPH is notified when constituents are 

detected at concentrations exceeding MCL-US or 

MCL-CA thresholds in public supply well samples 

collected for the GAMA Statewide Basin Assessment 

project.

•	 AL – Action Level. Legally enforceable standards 

that apply to public water systems and are designed to 

protect public health by limiting the levels of copper 

and lead in drinking water. Concentrations of copper 

or lead above the action-level thresholds trigger 

requirements for mandatory water treatment to reduce 

the corrosiveness of water to water pipes. The action 

levels established by the USEPA and CDPH are the 

same, thus the thresholds are labeled “AL-US” in this 

report.

•	 TT – Treatment Technique. Legally enforceable 

standards that apply to public-water systems and 

are designed to protect public health by limiting the 

levels of microbial constituents in drinking water. 

Concentrations of microbial constituents above the 

treatment-technique thresholds trigger requirements 

for additional mandatory disinfection during water 

treatment. The action levels established by the USEPA 

and CDPH are the same; thus the thresholds are 

labeled “TT-US” in this report.

•	 SMCL – Secondary Maximum Contaminant Level. 

Non-enforceable standards applied to constituents that 

affect the aesthetic qualities of drinking water, such as 

taste, odor, and color, or technical qualities of drinking 

water, such as scaling and staining. Both the USEPA 

and CDPH define SMCLs, but unlike MCLs, SMCLs 

established by CDPH are not required to be at least 

as stringent as those established by USEPA. SMCLs 

established by CDPH (SMCL-CA) are used in this 

report for all constituents that have SMCL-CA values. 

The SMCL-US is used for pH because no SMCL-CA 

for pH has been defined.

•	 NL – Notification Level. Health-based notification 

levels established by CDPH for some of the 

constituents in drinking water that lack MCLs (NLCA). If a constituent is detected above its NL-CA, 

California state law requires timely notification of 

local governing bodies and recommends consumer 

notification.

•	 HAL – Lifetime Health Advisory Level. The 

maximum concentration of a constituent at which its 

presence in drinking water is not expected to cause any 

adverse carcinogenic effects for a lifetime of exposure. 

HALs are established by the USEPA (HAL-US) and 

are calculated assuming 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 a person’s 

exposure comes from drinking water.

•	 RSD5 – Risk-Specific Dose. The concentration of 

a constituent in drinking water corresponding to an 

excess estimated lifetime cancer risk of 1 in 100,000. 

RSD5 is an acronym for risk-specific dose at 10-5. 

RSD5s are calculated by dividing the 10-4 cancer 

risk concentration established by the USEPA by ten 

(RSD5-US).

For constituents having MCLs, concentrations in groundwater samples were compared to the MCL-US or MCL-CA. 

If a constituent had an SMCL, its concentration was compared 

to the SMCL-CA. For chloride, sulfate, specific conductance, 

and total dissolved solids, CDPH defines a “recommended” 

and an “upper” SMCL-CA; concentrations of these 

constituents in ground-water samples were compared with 

both levels. The SMCL-US for these constituents corresponds 

to the recommended SMCL-CA. Detected concentrations 

of constituents that lack an MCL or SMCL were compared 

to the NL-CA. For constituents that lack an MCL, SMCL, 

or NL-CA, detected concentrations were compared to the 
Water-Quality Results 11

HAL-US. For constituents that lack an MCL, SMCL, NL-CA, 

or HAL-US, detected concentrations were compared to the 

RSD5-US. Note that the result of using this hierarchy to select 

comparison thresholds for constituents that have multiple 

types of established thresholds may not be the threshold that 

has the lowest concentration. The comparison thresholds used 

in this report are listed in tables 3A–L for all constituents 

and in tables 4-16 for constituents detected in ground-water 

samples from SCRV. Not all constituents analyzed for this 

study have established thresholds available. Detections 

of constituents at concentrations greater than the selected 

comparison threshold are marked with asterisks in tables 4-16. 

Ground-Water-Quality Data

Field Parameters

Field and laboratory measurements of dissolved 

oxygen, pH, specific conductance, alkalinity, and associated 

parameters (turbidity and water temperature) are presented in 

table 4. Dissolved oxygen and alkalinity are used as indicators 

of natural processes that control water chemistry. Specific 

conductance is the electrical conductivity unit for water and 

is proportional to amount of total dissolved solids (TDS) in 

the water. The pH value indicates the acidity or basicity of the 

water. Twenty-nine of 41 grid wells had specific conductance 

field values above the recommended SMCL-CA, and of these 

29 grid wells, 8 were above the upper SMCL-CA. The specific 

conductance was not measured at one grid well because of 

a malfunctioning field meter. The specific conductance of 

samples was measured in the laboratory and in the field, but 

the field measurement is preferred. No wells had pH values 

outside of the SMCL-US range for pH. 

Organic Constituents

Volatile organic compounds (VOC) are in paints, 

solvents, fuels, fuel additives, refrigerants, fumigants, and 

disinfected water, and are characterized by their tendency to 

evaporate. VOCs generally persist longer in ground water than 

in surface water because ground water is isolated from the 

atmosphere. Of the 85 VOCs analyzed, 18 were detected in 

ground-water samples; all concentrations were below healthbased thresholds, and most were several orders of magnitude 

below the thresholds (table 5). One or more VOCs were 

detected in 13 of the 42 grid wells. The only VOC detected 

in more than 10 percent of grid wells was chloroform, a 

byproduct of disinfecting drinking-water.

Pesticides include herbicides, insecticides, and fungicides 

and are used to control weeds, insects, fungi, and other pests in 

agricultural, urban, and suburban settings. Of the 122 pesticide 

or pesticide degradates analyzed, 13 were detected. Five of the 

13 pesticides detected had established health-based thresholds, 

and all detections were below their established health-based 

thresholds (table 6). One or more pesticide compounds were 

detected in 13 of the 42 grid wells sampled. Three pesticides 

compounds were detected in more than 10 percent of samples 

from grid wells: the herbicides atrazine and simazine, and 

a degradate of atrazine. These three compounds are among 

the most commonly detected pesticide compounds in ground 

water nationally (Gilliom and others, 2006). 

The potential wastewater-indicator compounds were 

collected at all 42 grid wells. Potential wastewater-indicator 

compounds include a wide variety of constituents. Compounds 

analyzed include cotinine (primary nicotine metabolite), 

p-cresol (wood preservative), and menthol (cigarettes, cough 

drops, liniment, mouthwash) (table 3D). Although these 

compounds may indicate the presence of wastewater, they 

have other sources also. Of the 69 potential wastewaterindicator compounds analyzed, 10 were detected. One or more 

potential wastewater-indicator compounds were detected in 10 

of the 42 grid wells sampled (table 7). Of the ten compounds 

detected, phenol was the only compound having an 

established health-based threshold. Phenol was detected in one 

understanding well at a concentration four orders of magnitude 

below the health based-threshold. Each of the detected 

potential wastewater-indicator compounds was detected in less 

than 10 percent of the 42 grid wells (table 7). 

Constituent of Special Interest

Perchlorate is a constituent of special interest in 

California because it may adversely affect water-quality 

and recently has been found in water supplies (California 

Department of Health Services, 2007b). Perchlorate 

was detected in 5 of the 42 grid wells sampled, and all 

concentrations measured in SCRV wells were below the 

MCL-CA threshold of 6 μg/L (table 8). Perchlorate was not 

detected in any of the understanding wells.

Inorganic Constituents

Unlike the organic constituents, most of the inorganic 

constituents are naturally present in ground water, although 

their concentrations may be influenced by human activities. 

Samples to be analyzed for inorganic constituent were 

collected at all 17 intermediate and 9 slow wells, of which 16 

were grid wells and 10 were understanding wells. Although 

dissolved organic carbon is an organic constituent it is 

included in this section. Depth-dependent samples are not 

included in the discussion of results. 

Nutrients (nitrogen and phosphorus) and dissolved 

organic carbon in ground water can affect biological activity in 

aquifers and in surface-water bodies that receive ground-water 

discharge. Nitrogen may be present in the form of ammonia, 

nitrite, or nitrate, depending on the oxidation-reduction 

state of the ground water. High concentrations of nitrate can 

adversely affect human health, particularly the health of 
12 Ground-Water Quality Data in the Santa Clara River Valley Study Unit, 2007: Results from the California GAMA Program

infants. Nutrients, nitrogen and phosphorus, and the dissolved 

organic carbon were measured in 16 grid wells (table 9). The 

concentrations of nitrite plus nitrate were detected above 

the health-based threshold in five SCRV grid wells. The 

concentration of ammonia measured in samples from SCRV 

wells were below health-based thresholds. 

 The major-ion composition, total dissolved solids (TDS) 

content, and levels of certain trace elements in ground water 

affect the aesthetic properties of water, such as taste, color, and 

odor, and the technical properties, such as scaling and staining. 

Although there are no adverse health effects associated with 

these properties, they may reduce consumer satisfaction 

with the water or may have economic impacts. CDPH has 

established non-enforceable thresholds (SMCL-CAs) that are 

based on aesthetic or technical properties rather than healthbased concerns for sulfate, chloride, TDS, and several trace 

elements.

 Sulfate concentrations were measured in samples 

from 17 intermediate and 9 slow SCRV wells, of which 16 

were grid wells and 10 were understanding wells. Sulfate 

concentrations were measured above the recommended 

SMCL-CA threshold of 250 mg/L from samples in 19 

wells; of these, 10 had sulfate concentrations above 

the upper SMCL-CA threshold of 500 mg/L (table 10). 

Chloride concentrations were measured in samples from 

17 intermediate and 9 slow SCRV wells, of which 16 were 

grid wells and 10 were understanding wells. Chloride 

concentrations were measured above the recommended 

SMCL-CA threshold of 250 mg/L from samples in 7 wells; 

of these, 4 wells had chloride concentrations above the 

upper SMCL-CA threshold of 500 mg/L. Samples collected 

from all 26 SCRV wells had total dissolved solids (TDS) 

concentrations above the recommended SMCL-CA threshold 

of 500 mg/L; of these, 18 wells contained TDS concentrations 

above the upper SMCL-CA threshold of 1,000 mg/L. 

Eighteen of the 24 trace elements analyzed in samples 

from SCRV wells have health-based thresholds. Of the 

possible 24 trace elements, 22 were detected (table 11). Five 

trace elements were reported above their respective thresholds: 

barium, boron, iron, manganese, and strontium. Iron and 

manganese were reported above their respective SMCL-US 

thresholds in 7 and 14 SCRV wells, respectively. Iron and 

manganese are trace elements whose concentrations are 

affected by the oxidation-reduction state of the ground water. 

Precipitation of minerals containing iron or manganese may 

stain surfaces orange, brown, or black. 

Arsenic, iron, and chromium exist as different species, 

depending on the oxidation-reduction state of the ground 

water. The oxidized and reduced species have different 

solubility in ground water, and may have different effects on 

human health. The relative proportions of the oxidized and the 

reduced species of each element can be used to help interpret 

the oxidation–reduction state of the aquifer. Concentrations 

of total arsenic, iron, and chromium, and the concentrations 

of either the reduced or the oxidized species of each element 

were analyzed at the USGS Trace Metal Laboratory (TML) 

and are given in table 12. The concentration of the other 

species can be calculated by the difference from the total. 

The concentrations of arsenic, iron, and chromium given in 

table 12 may be different than those given in table 11 because 

different analytical methods were used (see Appendix, 

table A1). On the basis of the analytical method used, the 

concentrations of arsenic, iron, and chromium, reported on 

table 11 are considered to be more accurate. In general, the 

iron in the SCRV ground-water samples in which the iron 

concentrations were elevated (table 12) existed in the reduced 

(Fe-II) state (table 13)

Inorganic Tracer Constituents

Stable-isotope ratios, tritium and carbon-14 activities, 

stable isotopes of nitrate, and noble gas concentrations can 

be used as tracers of natural processes affecting ground-water 

composition. Hydrogen and oxygen stable isotope ratios of 

water (table 13) can be used to help interpret ground-water 

recharge sources. The stable isotope ratios of water depend on 

the altitude, latitude, and temperature of precipitation and on 

the extent of evaporation of surface water or soil water. Stableisotope ratios of nitrogen and oxygen of dissolved nitrate can 

be used to help interpret sources and processes affecting these 

solutes in aquifers. Noble-gas concentrations (table 14) can be 

used to help interpret ground-water recharge sources because 

the concentrations of the different noble gases depend on 

water temperature.

Tritium activities (tables 13), carbon-14 activities 

(table 13), and helium isotope ratios (table 14) can provide 

information about the age of the ground-water. Tritium is a 

radioactive isotope of hydrogen that is continuously produced, 

albeit at low levels (or background levels), by the interaction 

of cosmic radiation with the Earth’s atmosphere where it 

becomes part of the water molecule. However, a large amount 

of tritium was produced by atmospheric testing of nuclear 

weapons between 1952 and 1963. Thus, concentrations of 

tritium in water above background levels generally indicate 

that the water was recharged since the early 1950s. Helium 

isotope ratios can be used with tritium concentrations to 

estimate ages for young ground water. 

Carbon-14 is a radioactive isotope of carbon that is 

incorporated into dissolved carbonate species in water. 

Low levels of carbon-14 are continuously produced by 

interaction of cosmic radiation with the Earth’s atmosphere, 

and incorporated into atmospheric carbon dioxide. The 

carbon dioxide dissolves in precipitation, surface water, and 

ground water exposed to the atmosphere, thereby entering the 

hydrologic cycle. Because carbon-14 decays with a half-life 

of approximately 5,700 years, low activities (or low percent 

modern [table 13]) of carbon-14 generally indicate presence of 

ground water that is at least several thousand years old. 
Summary 13

A total of 17 samples were collected to be analyzed for 

the stable isotopes chlorine-37 and bromine-81 (table 13). 

Analyzing for these two isotopes in conjunction may improve 

the understanding of the origin and movement of saline 

ground-water.

Of the inorganic tracer constituents analyzed for this 

study, the only one that has a health-based threshold is tritium. 

All measured tritium activities in samples from SCRV wells 

were well below the established MCL-CA (table 13).

Radioactive Constituents

Radioactivity is the release of energy or energetic 

particles during changes in the structure of the nucleus of an 

atom. Most of the radioactivity in ground water comes from 

decay of naturally-occurring isotopes of uranium and thorium 

in minerals in the sediments or fractured rocks of the aquifer. 

Uranium and thorium decay in a series of steps, eventually 

forming stable isotopes of lead. Radium-226, radium-228, and 

radon-222 are radioactive isotopes formed during the uranium 

or thorium decay series. In each step in the decay series, one 

radioactive element turns into a different radioactive element 

by emitting an alpha particle (two protons and two neutrons) 

or a beta particle (electron or positron) from its nucleus. For 

example, radium-226 emits an alpha particle and therefore 

turns into radon-222. Radium-228 emits a beta particle to form 

actinium-228. The alpha and beta particles emitted during 

radioactive decay are hazardous to human health because these 

energetic particles may damage cells. Radiation damage to cell 

DNA increases the risk of getting cancer.

Activity is often used instead of concentration for 

reporting the presence of radioactive constituents. Activity 

of radioactive constituents in ground water is measured in 

units of picocuries per liter (pCi/L), and one picocurie equals 

approximately two atoms decaying per minute. The number 

of atoms decaying is equal to the number of alpha or beta 

particles emitted. 

 Groundwater samples from 9 slow wells (5 grid wells 

and 4 understanding wells) were analyzed for the 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 counts) (table 15). The 

SCRV wells that were analyzed for radioactive constituents 

had activities of radium-226, radium-228, and gross beta 

radioactivity less than established health-based standards. 

The gross alpha radioactivity (72-hour count) in one SCRV 

grid well was slightly above the established health-based 

threshold of 15 pCi/L; the gross alpha radioactivity (30-day 

count) in one SCRV understanding well was slightly above 

the established health-based threshold of 15 pCi/L. Activities 

of radon-222 in samples from six SCRV wells were above the 

proposed MCL-US of 300 pCi/L; however, no sample had an 

activity that was above the proposed alternative MCL-US of 

4,000 pCi/L. 

Microbial Indicators

Water is disinfected during drinking-water treatment to 

prevent diseases that may be spread by water-borne microbial 

constituents derived from human or animal wastes. Most of 

the specific viruses and bacteria responsible for diseases were 

not measured because routine analytical methods are not 

available. Measurements are made of microbial constituents 

that are more easily analyzed and serve as indicators of human 

or animal waste in water. Drinking water purveyors respond 

to detections of microbial indicators by applying additional 

disinfection techniques to the water.

Ground-water samples from 9 slow wells were analyzed 

for microbial indicators (table 16). No samples from the 9 

slow wells contained the viral indicators F-specific coliphage 

and somatic coliphage, or the bacterial indicator Escherichia 

coli (E. coli). Low levels of the bacterial indicator total 

coliforms were detected in two understanding wells. The 

threshold for total coliforms in pubic-supply wells is based 

on recurring detections; the wells in which they were detected 

were non-public-supply wells. 

Future Work

Subsequent reports will be focused on assessment of 

the data shown presented in this report using a variety of 

statistical, qualitative, and quantitative approaches to evaluate 

the natural and human factors affecting ground-water quality. 

Water-quality data contained in the CDPH and USGS NWIS 

databases, and water-quality data available from other State 

and local water agencies will be compiled, evaluated, and 

used in combination with the data presented in this report; the 

results of these efforts will be presented in future publications.

Summary 

Ground-water quality in the approximately 460-squaremile Santa Clara River Valley study unit (SCRV) was 

investigated from April to June 2007 as part of the Priority 

Basin project of Ground-Water Ambient Monitoring and 

Assessment (GAMA) Program. The California State Water 

Resources Control Board (SWRCB), in collaboration with 

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

Livermore National Laboratory, is implementing the GAMA 

Program (http://www.waterboards.ca.gov/gama/). The Priority 

Basin project was designed by the SWRCB and the USGS 

in response to the Ground-Water Quality Monitoring Act of 

2001 (Belitz and others, 2003; State Water Resources Control 

Board, 2003). The project is a comprehensive assessment 

of statewide ground-water quality designed to identify and 

characterize risks to ground-water resources, and to increase 

the availability of information about ground-water quality to 

the public. SCRV was the seventeenth study unit sampled as 

part of the project. 
14 Ground-Water Quality Data in the Santa Clara River Valley Study Unit, 2007: Results from the California GAMA Program

SCRV is located in the northwest part of the Transverse 

Ranges and Selected Peninsular Ranges hydrogeologic 

province and includes eight ground-water basins as defined 

by the California Department of Water Resources (California 

Department of Water Resources, 2003). Forty-two wells were 

selected using a randomized grid-based method to provide 

statistical representation of the study area (grid wells). Eleven 

wells (understanding wells) were selected to further evaluate 

water chemistry in particular parts of the study area, and four 

depth-dependent ground-water samples were collected from 

one of the eleven understanding wells to help understand the 

relation between water chemistry and depth.

Ground-water samples were analyzed for VOCs, 

pesticides and pesticide degradates, potential wastewaterindicator compounds, pharmaceutical compounds, nutrients, 

major and minor ions, trace elements, radioactivity, and 

microbial indicators. Naturally occurring isotopes (stable 

isotopes of hydrogen, oxygen, nitrogen, and carbon, chlorine, 

bromine, and activities of tritium and carbon-14) and dissolved 

gases also were measured to help interpret the source and 

age of the sampled ground water. This report describes the 

hydrogeologic setting of the SCRV region, the sampling, 

analytical, and quality-assurance methods used in the study, 

and the results of the chemical and microbial analyses of the 

ground-water samples collected from April to June 2007.

Quality-control samples (blanks or replicates, or samples 

for matrix spikes) were collected at approximately 26 percent 

of the wells, and the results for these samples were used to 

evaluate the quality of the data for the ground-water samples. 

Assessment of the data derived from the blank samples 

resulted in censoring less than 0.1 percent of the ground-water 

quality data.

This study did not attempt to evaluate the quality of 

water delivered to consumers; after withdrawal from the 

ground, water typically is treated, disinfected, and blended 

with other waters to maintain acceptable water quality. 

Regulatory thresholds apply to treated water that is served to 

the consumer, not to raw ground water. However, to provide 

some context for the results, concentrations of constituents 

measured in the raw ground water were compared with 

regulatory and non-regulatory thresholds established by 

the U.S. Environmental Protection Agency (USEPA) and 

California Department of Public Health (CDPH). 

VOCs, pesticides and pesticide degradates, and 

potential wastewater-indicator compounds were detected 

in about 33 percent or less of the 42 SCRV grid wells. 

All concentrations of organic constituents were below 

established health-based thresholds. Perchlorate was detected 

in approximately 12 percent of the SCRV grid wells; all 

concentrations were below the NL-CA threshold. The 

concentration of total dissolved solids (TDS) was above 

the upper SMCL-CA threshold in 18 of the 26 SCRV wells 

sampled for TDS. The concentration of sulfate was above 

the upper SMCL-CA threshold in 10 of the 26 SCRV wells 

sampled for sulfate. The concentration of nitrite plus nitrate 

was above the health-based threshold in 5 of the 26 SCRV 

wells sampled for nitrite plus nitrate. Chloride was above 

the upper SMCL-CA threshold in 5 of 26 wells sampled for 

chloride. Iron and manganese were above their respective 

SMCL-US thresholds in 7 and 14 SCRV wells, respectively. 

The gross alpha radioactivity (72-hour count) for one SCRV 

grid well was slightly above the established health-based 

threshold; the gross alpha radioactivity (30-day count) for one 

SCRV understanding well was slightly above the established 

health-based threshold. Activities of radon-222 in samples 

from 6 wells were above the proposed MCL-US of 300 pCi/L, 

but below the alternative MCL-US of 4,000 pCi/L. 

Subsequent reports will present analyses of the data 

in this report using a variety of statistical, qualitative, and 

quantitative approaches to assess the natural and human 

factors affecting ground-water quality.

Acknowledgments

The authors thank the following cooperators for their 

support: the State Water Resources Control Board (SWRCB), 

California Department of Health Services, California 

Department of Water Resources, and Lawrence Livermore 

National Laboratory. We especially thank the cooperating well 

owners and water purveyors for their generosity in allowing 

the USGS to collect samples from their wells. Two reviewers, 

Jan Stepek (SWRCB) and Jennifer Shelton (USGS), provided 

comments to improve this work. Funding for this work was 

provided by State bonds authorized by Proposition 50 and 

administered by the SWRCB.

References Cited

American Public Health Association, 1998, Standard 

methods for the examination of water and wastewater 

(20th ed.): Washington, D.C., American Public Health 

Association, American Water Works Association, and Water 

Environment Federation, p. 3-37–3-43.

American Society for Testing and Materials, 1998, Annual 

book of ASTM standards - water and environmental 

technology: Philadelphia, Pennsylvania, American Society 

for Testing and Materials, v. 11.02 (Water II), p. 664–666.

Ball, J.W., and McCleskey, R.B., 2003, A new cationexchange method for accurate field speciation of hexavalent 

chromium: Talanta, v. 61, p. 305–313.
References Cited 15

Belitz, Kenneth, Dubrovsky, N.M., Burow, K.R., Jurgens, 

B.C., and Johnson, T., 2003, Framework for a ground-water 

quality monitoring and assessment program for California: 

U.S. Geological Survey Water-Resources Investigations 

Report 03-4166, 78 p.

Bennett, G.L., V, Belitz, K., and 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.

Brenton, R.W., and Arnett, T.L., 1993, Methods of analysis 

by the U.S. Geological Survey National Water-Quality 

Laboratory - determination of dissolved organic carbon 

by UV-promoted persulfate oxidation and infrared 

spectrometry: U.S. Geological Survey Open-File 

Report 92-480, 12 p.

Bushon, R.N., 2003, Fecal indicator viruses: U.S. Geological 

Survey Techniques of Water-Resources Investigations, 

book 9, chap. A7.2. Accessed June 28, 2007, at http://pubs.

water.usgs.gov/twri9A7.2/

California Department of Public Health, 2007a, California 

drinking water-related laws: Drinking water-related 

regulations (Title 22) (pdf document). Accessed October 27, 

2007, at http://www.cdph.ca.gov/certlic/drinkingwater/

Pages/Lawbook.aspx

California Department of Public Health, 2007b, Chemical 

contaminants in drinking water. Accessed October 27, 2007, 

at http://www.dhs.ca.gov/ps/ddwem/chemicals/default.htm

California Department of Water Resources, 2003, California’s 

groundwater: California Department of Water Resources 

Bulletin 118, 246 p. Accessed October 27, 2007, at http://

www.dpla2.water.ca.gov/publications/groundwater/

bulletin118/Bulletin118_Entire.pdf

California Department of Water Resources, 2004a, Arroyo 

Santa Rosa Valley groundwater basin: California’s

Groundwater Bulletin 118. Accessed August 22, 2007, at 

http://www.dpla2.water.ca.gov/publications/groundwater/

bulletin118/basins/pdfs_desc/4-7.pdf

 California Department of Water Resources, 2004b, Santa 

Clara River Valley Basin, Fillmore subbasin, California’s 

Groundwater Bulletin 118. Accessed August 22, 2007, at 

http://www.dpla2.water.ca.gov/publications/groundwater/

bulletin118/basins/pdfs_desc/4-4.05.pdf

California Department of Water Resources, 2004c, Las Posas 

Valley groundwater basin, California’s Groundwater 

Bulletin 118. Accessed August 22, 2007, at http://www.

dpla2.water.ca.gov/publications/groundwater/bulletin118/

basins/pdfs_desc/4-8.pdf

California Department of Water Resource, 2004d, Ventura 

River Valley groundwater basin, Lower Ventura River 

subbasin, California’s Groundwater Bulletin 118. Accessed 

August 22, 2007, at http://www.dpla2.water.ca.gov/

publications/groundwater/bulletin118/basins/pdfs_desc/4-

3.02.pdf

California Department of Water Resources, 2004e, Santa 

Clara River Valley basin,Mound subbasin, California’s 

Groundwater Bulletin 118. Accessed August 22, 2007, at 

http://www.dpla2.water.ca.gov/publications/groundwater/

bulletin118/basins/pdfs_desc/4-4.03.pdf

California Department of Water Resources, 2004f, Ojai Valley 

groundwater basin, California’s Groundwater Bulletin 118. 

Accessed August 22, 2007, at http://www.dpla2.water.

ca.gov/publications/groundwater/bulletin118/basins/pdfs_

desc/4-2.pdf

California Department of Water Resources, 2004g, Santa 

Clara River Valley groundwater basin, Oxnard subbasin, 

California’s Groundwater Bulletin 118, Accessed August 

22, 2007, at http://www.dpla2.water.ca.gov/publications/

groundwater/bulletin118/basins/pdfs_desc/4-4.02.pdf

California Department of Water Resources, 2004h, Santa 

Clara River River Valley Basin, Piru subbasin, California’s 

Groundwater Bulletin 118. Accessed August 22, 2007, at 

http://www.dpla2.water.ca.gov/publications/groundwater/

bulletin118/basins/pdfs_desc/4-4.06.pdf

California Department of Water Resources, 2004i, Pleasant 

Valley groundwater basin, California‘s Groundwater 

Bulletin 118. Accessed August 22, 2007, at http://www.

dpla2.water.ca.gov/publications/groundwater/bulletin118/

basins/pdfs_desc/4-6.pdf

California Department of Water Resources, 2004j, Santa Clara 

River Valley Basin, Santa Paula subbasin, California’s 

Groundwater Bulletin 118. Accessed August 22, 2007, at 

http://www.dpla2.water.ca.gov/publications/groundwater/

bulletin118/basins/pdfs_desc/4-4.04.pdf

California Department of Water Resources, 2004k, Santa 

Clara River Valley East groundwater subbasin, California’s 

Groundwater Bulletin 118. Accessed August 22, 2007, at 

http://www.dpla2.water.ca.gov/publications/groundwater/

bulletin118/basins/pdfs_desc/4-4.07.pdf

California Department of Water Resources, 2004l, Simi Valley 

groundwater basin, California’s Groundwater Bulletin 118. 

Accessed August 22, 2007, at http://www.dpla2.water.

ca.gov/publications/groundwater/bulletin118/basins/pdfs_

desc/4-9.pdf
16 Ground-Water Quality Data in the Santa Clara River Valley Study Unit, 2007: Results from the California GAMA Program

California Department of Water Resources, 2004m, Upper 

Ojai Valley groundwater basin, California’s Groundwater 

Bulletin 118. Accessed August 22, 2007, at http://www.

dpla2.water.ca.gov/publications/groundwater/bulletin118/

basins/pdfs_desc/4-1.pdf

California Department of Water Resources, 2004n, Ventura 

River Valley groundwater basin, Upper Ventura River 

subbasin, California’s Groundwater Bulletin 118. Accessed 

August 22, 2007, at http://www.dpla2.water.ca.gov/

publications/groundwater/bulletin118/basins/pdfs_desc/4-

3.01.pdf

Casciotti, K.L., Sigman, D.M., Hastings, M.G., Böhlke, J.K., 

and Hilkert, A., 2002, Measurement of the oxygen isotopic 

composition of nitrate in seawater and freshwater using the 

denitrifier method: Analytical Chemistry, v. 74, p. 4905–

4912.

Childress, C.J.O., Foreman, W.T., Connor, B.F., and Maloney, 

T.J., 1999, New reporting procedures based on long-term 

method detection levels and some considerations for 

interpretations of water-quality data provided by the U.S. 

Geological Survey National Water Quality Laboratory: U.S. 

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 Open-File Report 97-829, 78 p.

Coplen, T.B., 1994, Reporting of stable hydrogen, carbon, and 

oxygen isotopic abundances: Pure and Applied Chemistry, 

v. 66, p. 273–276.

Coplen, T.B., Hopple, J.A., Böhlke, J.K., Peiser, H.S., Rieder, 

S.E., Krouse, H.R., Rosman, K.J.R., Ding, T., Vocke, R.D., 

Jr., Revesz, K.M., Lamberty, A., Taylor, P., and DeBierve, 

P., 2002, Compilation of minimum and maximum isotope 

ratios of selected elements in naturally occurring terrestrial 

materials and reagents: U.S. Geological Survey WaterResources Investigations Report 01-4222, 98 p.

Coplen, T.B., Wildman, J.D., and Chen, J., 1991, 

Improvements in the gaseous hydrogen-water equilibrium 

technique for hydrogen isotope analysis: Analytical 

Chemistry, v. 63, p. 910–912.

Dawson, B.J., Bennett, G.L., V, and Belitz, K., 2008, Groundwater quality data in the Southern Sacramento Valley study 

unit, California, 2005—Results from the California GAMA 

Program: U.S. Geological Survey Data Series 285, 93 p..

Donahue, D.J., Linick, T.W., and Jull, A.J.T., 1990, Ratio and 

background corrections for accelerator mass spectrometry 

radiocarbon measurements: Radiocarbon, v. 32, p. 135–142.

Eaton, G.F., Hudson, G.B., and Moran, J.E., 2004, Tritiumhelium-3 age-dating of groundwater in the Livermore Valley 

of California: American Chemical Society ACS Symposium 

Series, v. 868, p. 235–245.

Epstein, S., and Mayeda, T.K., 1953, Variation of O-18 

content of water from natural sources: Geochimica et 

Cosmochimica Acta, v. 4, p. 213–224.

Faires, L.M., 1993, Methods of analysis by the U.S. 

Geological Survey National Water Quality Laboratory - 

determination of metals in water by inductively coupled 

plasma-mass spectrometry: U.S. Geological Survey 

Open-File Report 92-634, 28 p.

Fishman, M.J., 1993, Methods of analysis by the U.S. 

Geological Survey National Water Quality Laboratory - 

determination of inorganic and organic constituents in water 

and fluvial sediments: U.S. Geological Survey Open-File 

Report 93-125, 217 p.

Fishman, M.J., and Friedman, L.C., 1989, Methods for 

determination of inorganic substances in water and fluvial 

sediments: U.S. Geological Survey Techniques of WaterResources Investigations, book 5, chap. A1, 545 p.

Firestone, R.B., Shirley, V.S., Baglin, C.M., Chu, S.Y.F., and 

Zipkin, J., 1996, Table of Isotopes, 8th ed.: New York, John 

Wiley & Sons, 3168 p. Also available at http://ie.lbl.gov/

toipdf/toi20.pdf.

Fram, M.S. and Belitz, Kenneth, 2007. Ground-Water Quality 

Data in the Southern Sierra Study Unit, 2006 - Results from 

the California GAMA Program: U.S. Geological Survey 

Data Series 301, 78 p.

Furlong, Edward T; Anderson, Bruce D; Werner, Stephen 

L; Soliven, Paul P; Coffey, Laura J; Burkhardt, Mark R., 

2001, Methods of analysis by the U. S. Geological Survey 

National Water Quality Laboratory; determination of 

pesticides in water by graphitized carbon-based solid-phase 

extraction and high-performance liquid chromatography/

mass spectrometry: U. S. Geological Survey, Report: 

WRI 01-4134, 73 p.

Garbarino, J.R., 1999, Methods of analysis by the U.S. 

Geological Survey National Water Quality Laboratory 

- determination of dissolved arsenic, boron, lithium, 

selenium, strontium, thallium, and vanadium using 

inductively coupled plasma-mass spectrometry: U.S. 

Geological Survey Open-File Report 99-093, 31 p.

Garbarino, J.R., and Damrau, D.L., 2001, Methods of analysis 

by the U.S. Geological Survey National Water Quality 

Laboratory - determination of organic plus inorganic 

mercury in filtered and unfiltered natural water with cold 

vapor - atomic fluorescence spectrometry: U.S. Geological 

Survey Water-Resources Investigations Report 01-4132, 

16 p.
References Cited 17

Garbarino, J.R., Kanagy, J.R., and Cree, M.E., 2006, 

Determination of elements in natural-water, biota, sediment, 

and soil samples using collision/reaction cell inductively 

coupled plasma-mass spectrometry: U.S. Geological Survey 

Techniques and Methods, book 5, chap. B1, 88 p.

Gilliom, R.J., Barbash, J.E., Crawford, C.G., Hamilton, P.A., 

Martin, J.D., Nakagaki, N., Nowell, L.H., Scott, J.C., 

Stackelberg, P.E., Thelin, G.P., and Wolock, D.M., 2006, 

The quality of our nation’s waters: Pesticides in the nation’s 

streams and ground water, 1992–2001: U.S. Geological 

Survey Circular 1291, 172 p.

Gran, G., 1952, Determination of the equivalence point 

in potentiometric titrations - Part II, The Analyst, v. 77, 

p. 661–671.

Grob, R.L, ed., 1995, Modern practice of gas chromatography 

(3rd ed.): New York, John Wiley & Sons, 888 p.

Hamlin, S.N., Belitz, K., Kraja, S., and Dawson, B.J., 

2002, Ground-water quality in the Santa Ana watershed, 

California: Overview and data summary: U.S. Geological 

Survey Water-Resources Investigations Report 02-4243, 

137 p.

Hautman, D.P., Munch, D.J., Eaton, A.D., and Haghani, 

A.W., 1999, Method 314.0 Determination of perchlorate in 

drinking water using ion chromatography, revision 1.0, U.S. 

Environmental Protection Agency, accessed June 22, 2004.

Hutson, S.S., Barber, N.L., Kenny, J.F., Linsey, K.S., Lumia, 

D.S., and Maupin, M.A., 2004, Estimated use of water in 

the United States in 2000: U.S. Geological Survey Circular 

1268, 46 p.

Izbicki, J.A., 2004, A small-diameter sample pump for sample 

collection of depth-dependent samples from production 

wells under pumping conditions: U.S. Geological Survey, 

Fact Sheet 2004-3096, 2 p.

Jull, A.J.T., Burr, G.S., McHargue, L.R., Lange, T.E., Lifton, 

N.A., Beck, J.W., Donahue, D.J., and Lal, D., 2004, 

New frontiers in dating of geological, paleoclimatic, 

and anthropological applications using accelerator mass 

spectrometric measurements of 14C and 10Be in diverse 

samples: Global and Planetary Change, v. 41, p. 309–323.

Kolpin, D.W., Furlong, E.T., Meyer, M.T., Thurman, E.M., 

Zaugg, S.D., Barber, L.B., and Buxton, H.T., 2002, 

Pharmaceuticals, hormones and other organic wastewater 

contaminants in U.S. streams, 1999-2000: Environmental 

Science & Technology, v. 36, no. 6, p. 1202–1211. 

Koterba, M.T., Wilde, F.D., and Lapham, W.W., 1995, 

Ground-water data-collection protocols and procedures for 

the National Water-Quality Assessment Program - collection 

and documentation of water-quality samples and related 

data: U.S. Geological Survey Open-File Report 95-399, 

113 p.

Kulongoski, J., and Belitz, K., 2004, Ground-water ambient 

monitoring and assessment program: U.S. Geological 

Survey Fact Sheet 2004-3088, 2 p.

Kulongoski, J.T., and Belitz, K., 2007, Ground-water quality 

data in the Monterey Bay and Salinas Valley Basins, 

California, 2005 – Results from the California GAMA 

Program: U.S. Geological Survey Data Series DS-258, 84 p.

Kulongoski, J.T., Belitz, K., and Dawson, B.J., 2006, 

Ground-water quality data in the North San Francisco Bay 

Hydrogeologic provinces, California, 2004: Results form 

the California Ground-Water Ambient Monitoring and 

Assessment (GAMA) Program: U.S. Geological Survey 

Data Series 167, 100 p.

Lane, S.L., Flanagan, S., and Wilde, F.D., 2003, Selection of 

equipment for water sampling (ver. 2.0): U.S. Geological 

Survey Techniques of Water-Resources Investigations, book 

9, chap. A2. Accessed June 28, 2007, at http://pubs.water.

usgs.gov/twri9A2/

Lewis, M.E., 2006, Dissolved Oxygen (ver. 2.1): U.S. 

Geological Survey Techniques of Water-Resources 

Investigations, book 9, chap. A6.2. Accessed June 28, 2007 

at http://pubs.water.usgs.gov/twri9A6.2/

Lindley, C.E., Stewart, J.T., and Sandstrom, M.W., 1996, 

Determination of low concentrations of acetochlor in 

water by automated solid-phase extraction and gas 

chromatography with mass selective detection: Journal of 

AOAC International, v. 79, no. 4, p. 962–966.

Madsen, J.E., Sandstrom, M.W., and Zaugg, S.D., 2003, 

Methods of analysis by the U.S. Geological Survey 

National Water Quality Laboratory - A method supplement 

for the determination of fipronil and degradates in water by 

gas chromatography/mass spectrometry: U.S. Geological 

Survey Open-File Report 02-462, 11 p.

Maloney, T.J., ed., 2005, Quality management system, U.S. 

Geological Survey National Water Quality Laboratory: 

U.S. Geological Survey Open-File Report 2005-1263. 

Also available at http://pubs.usgs.gov/of/2005/1263/pdf/

OFR2005-1263.pdf
18 Ground-Water Quality Data in the Santa Clara River Valley Study Unit, 2007: Results from the California GAMA Program

McCleskey, R.B., Nordstrom, D.K., and Ball, J.W., 2003, 

Metal interferences and their removal prior to the 

determination of As(T) and As(III) in acid mine waters 

by hydride generation atomic absorption spectrometry: 

U.S. Geological Survey Water-Resources Investigations 

Report 03-4117, 85 p.

McLain, B., 1993, Methods of analysis by the U.S. Geological 

Survey National Water Quality Laboratory - determination 

of chromium in water by graphite furnace atomic absorption 

spectrophotometry: U.S. Geological Survey Open-File 

Report 93-449, 16 p.

Moran, J.E., Hudson, G.B., Eaton, G.F., and Leif, R., 

2002, A contamination vulnerability assessment for the 

Livermore-Amador and Niles Cone Groundwater Basins 

UCRL-AR-148831, 25 p.

Myers, D.N., 2004, Fecal indicator bacteria (ver. 1.2): 

U.S. Geological Survey Techniques of Water-Resources 

Investigations, book 9, chap. A7.1. Accessed January 2, 

2008, at http://pubs.water.usgs.gov/twri9A7.1/

Patton, C.J., and Kryskalla, J.R., 2003, Methods of analysis 

by the U.S. Geological Survey National Water Quality 

Laboratory - evaluation of alkaline persulfate digestion 

as an alternative to Kjeldahl digestion for determination 

of total and dissolved nitrogen and phosphorous in water: 

U.S. Geological Survey Water-Resources Investigations 

Report 03-4174, 33 p.

Pirkey, K.D., and Glodt, S.R., 1998, Quality control at the 

U.S. Geological Survey National Water Quality Laboratory: 

U.S. Geological Survey Fact-Sheet FS-026-98, 4 p. Also 

available at http://pubs.er.usgs.gov/usgspubs/fs/fs02698

Radtke, D.B., Davis, J.V., and Wilde, F.D., 2005, Specific 

electrical conductance (ver. 1.2): U.S. Geological Survey 

Techniques of Water-Resources Investigations, book 9, 

chap. A6.3. Accessed June 28, 2007 at http://pubs.water.

usgs.gov/twri9A6.3/

Rose, D.L., and Sandstrom, M.W., 2003, Methods of analysis 

by the U.S. Geological Survey National Water Quality 

Laboratory - determination of gasoline oxygenates, selected 

degradates, and BTEX in water by heated purge and trap/

gas chromatography/mass spectrometry: U.S. Geological 

Survey Water-Resources Investigations Report 03-4079, 

31 p.

Sandstrom, M.W., Stroppel, M.E., Foreman, W.T., and 

Schroeder, M.P., 2001, Methods of analysis by the U.S. 

Geological Survey National Water Quality Laboratory 

- determination of moderate-use pesticides and selected 

degradates in water by C-18 solid-phase extraction and 

gas chromatography/mass spectrometry: U.S. Geological 

Survey Water-Resources Investigations Report 01-4098, 

70 p.

Scott, J.C., 1990, Computerized stratified random site 

selection approaches for design of a ground-water quality 

sampling network: U.S. Geological Survey Water-Resources 

Investigations Report 90-4101, 109 p.

Shelton, J.L., Burow, K.R., Belitz, K., Dubrovsky, N.M., 

Land, M.T., and Gronberg, J.M., 2001, Low-level volatile 

organic compounds in active public supply wells as groundwater tracers in the Los Angeles physiographic basin, 

California, 2000: U.S. Geological Survey Water-Resources 

Investigations Report 01-4188. 29 p.

Shouakar-Stash, O., Drimmie, R.J., and Frape, S.K., 2005a, 

Determination of inorganic chlorine stable isotopes by 

Continuous Flow Isotope Ratio Mass spectrometry: Rapid 

Communication in Mass Spectrometry, v. 19, p.121–127.

Shouakar-Stash, O., Frape, S.K., and Drimmie, R.J., 2005b, 

Determination of bromine stable isotopes using ContinuousFlow Isotope Ratio Mass Spectrometry: Analytical 

Chemistry, v. 77, no. 13, p.4027–4033.

State Water Resources Control Board, 2003, A comprehensive 

groundwater quality monitoring program for California: 

Assembly Bill 599 Report to the Governor and Legislature, 

March 2003, 100 p. Available at http://www.waterboards.

ca.gov/gama/docs/final_ab_599_rpt_to_legis_7_31_03.pdf

Stookey, L.L., 1970, FerroZine - a new spectrophotometric 

reagent for iron: Analytical Chemistry, v. 42, p. 779–781.

Stumm, W. and Morgan, J.J., 1996, Aquatic chemistry: 

Chemical equilibria and rates in natural waters, 3rd ed.: New 

York, John Wiley & Sons, 1022 p.

Thatcher, L.L., Janzer, V.J., and Edwards, K.W., 1977, 

Methods for the determination of radioactive substances 

in water: U.S. Geological Survey Techniques of WaterResources Investigations, book 5, chap. A5, 95 p.

Timme, P.J., 1995, National Water Quality Laboratory 1995 

services catalog: U.S. Geological Survey Open-File 

Report 95-352, 120 p.

To, T.B., Nordstrom, D.K., Cunningham, K.M., Ball, J.W., 

and McCleskey, R.B., 1998, New method for the direct 

determination of dissolved Fe(III) concentration in acid 

mine waters: Environmental Science and Technology, v. 33, 

p. 807–813.

U.S. Environmental Protection Agency, 1980, Prescribed 

procedures for measurement of radioactivity in drinking 

water: U.S. Environmental Protection Agency EPA-600-4-

80-032.
References Cited 19

U.S. Environmental Protection Agency, 2001, Method 1601 

- Male-specific (F+) and somatic Coliphage in water by 

two-step enrichment procedure - April 2000 Draft: U.S. 

Environmental Protection Agency EPA 821-R-00-009.

U.S. Environmental Protection Agency, 2002, Method 1604 - 

total coliforms and Escherichia coli in water by membrane 

filtration using a simultaneous detection technique (MI 

medium): U.S. Environmental Protection Agency EPA 821-

R-02-024.

U.S. Environmental Protection Agency, 2004, National 

primary drinking water regulations - analytical method for 

uranium: U.S. Code of Federal Regulations, Title 40, part 

141, revised as of June 2004, p. 31008–31013.

U.S. Environmental Protection Agency, 2006, 2006 Edition 

of the Drinking Water Standards and Health Advisories, 

6: U.S. Environmental Protection Agency, Office of Water 

EPA 822-R-06-013. Available at http://www.epa.gov/

waterscience/criteria/drinking/dwstandards.pdf

U.S. Environmental Protection Agency, 2007a, Drinking water 

contaminants. Accessed October, 27 2008, at URL http://

www.epa.gov/safewater/contaminants/index.html

U.S. Environmental Protection Agency, 2007b, Proposed 

radon in drinking water rule. Accessed October 27, 2007, at 

URL http://www.epa.gov/safewater/radon/proposal.html

U.S. Geological Survey, variously dates, National field manual 

for the collection of water-quality data: U.S. Geological 

Survey Techniques of Water-Resources Investigations, book 

9, chap. A1-A9. Available at http://water.usgs.gov/owq/

FieldManual/

United Water Conservation District, 2004, 2003 Coastal Saline 

Intrusion Report, Oxnard Plain, Ventura County, California, 

24 p. 

Weiss, R.F., 1968, Piggyback sampler for dissolved gas 

studies on sealed water samples: Deep Sea Research, v. 15, 

p. 721–735.

Wilde, F.D., ed., 2004, Cleaning of equipment for water 

sampling (ver. 2.0): U.S. Geological Survey Techniques of 

Water-Resources Investigations, book 9, chap. A3. Accessed 

January 2, 2008 at http://pubs.water.usgs.gov/twri9A3/

Wilde, F.D., 2006, Temperature (ver. 2): U.S. Geological 

Survey Techniques of Water-Resources Investigations, book 

9, chap. A6.1. Accessed January 2, 2007 at http://pubs.

water.usgs.gov/twri9A6.1/

Wilde, F.D., Busenberg, E., and Radtke, D.B., 2006a, pH 

(ver. 1.3): U.S. Geological Survey Techniques of WaterResources Investigations, book 9, chap. A6.4. Accessed 

January 2, 2008 at http://pubs.water.usgs.gov/twri9A6.4/

Wilde, F.D., Radtke, D.B., Gibs, J., and Iwatsubo, R.T., 1999, 

Collection of water samples: U.S. Geological Survey 

Techniques of Water Resources Investigations, book 

9, chap. A4, chapters and appendixes variously paged. 

Available at http://pubs.water.usgs.gov/twri9A4/

Wilde, F.D., and Radtke, D.B., 2005, General information and 

guidelines (ver. 1.2): U.S. Geological Survey Techniques 

of Water-Resources Investigations, book 9, chap. A6.0. 

Accessed January 2, 2008 at http://pubs.water.usgs.gov/

twri9A6.0/

Wilde, F.D., Radtke, D.B., Gibs, J., and Iwatsubo, R.T., 2004, 

Processing of water samples: U.S. Geological Survey 

Techniques of Water-Resources Investigations, book 9, 

chap. A5. Accessed January 2, 2008 at http://pubs.water.

usgs.gov/twri9A5/

Wilde, F.D., Radtke, D.B., Gibs, J., and Iwatsubo, R.T., 2006b, 

Collection of water samples (ver 2.0): U.S. Geological 

Survey Techniques of Water-Resources Investigations, book 

9, chap. A4. Accessed January 2, 2008 at http://pubs.water.

usgs.gov/twri9A4/

Wright, M.T., Belitz, K., and Burton, C.A., 2005, California 

GAMA program - ground-water quality in the San Diego 

drainages hydrologic province, California, 2004: U.S. 

Geological Survey Data Series 129, 91 p.

Zaugg, S.D., Sandstrom, M.W., Smith, S.G., and Fehlberg, 

K.M., 1995, Methods of Analysis by the U.S. Geological 

Survey National Water Quality Laboratory - Determination 

of pesticides in water by C-18 solid-phase extraction and 

capillary-column gas chromatography/mass spectrometry: 

U.S. Geological Survey Open-File Report 95-181, 60 p.

Zaugg, S.D., Smith, S.G., and Schroeder, M.P., 2006, Methods 

of analysis by the U.S. Geological Survey National 

Water Quality Laboratory – Determination of wastewater 

compounds in whole water by continuous liquid-liquid 

extraction and capillary-column gas chromatography/mass 

spectrometry: U.S. Geological Survey Techniques and 

Methods, book 5, chap. B4, 30 p.
20 Ground-Water Quality Data in the Santa Clara River Valley Study Unit, 2007: Results from the California GAMA Program

GAMA

identification no.

Sampling information

Well type

Construction information

Date 

(mm/dd/yy)

Sampling

schedule

Elevation of LSD 

(ft above 

NAVD 88)

Well depth 

(ft below 

LSD)

Top perforation

(ft below 

LSD)

Bottom 

perforation 

(ft below 

LSD)

Grid wells

SCRV-01 4/2/07 Fast 35 Production 1,300 590 1,280

SCRV-02 4/2/07 Fast 46 Production 1,310 750 1,290

SCRV-03 4/2/07 Slow 24 Production 1,023 443 1,003

SCRV-04 4/3/07 Intermediate 1,036 Production na na na

SCRV-05 4/3/07 Fast 447 Production 300 50 280

SCRV-06 4/4/07 Intermediate 57 Production 220 120 220

SCRV-07 4/4/07 Slow 590 Production 242 92 232

SCRV-08 4/4/07 Fast 95 Production 910 700 890

SCRV-09 4/5/07 Intermediate 191 Production 863 703 863

SCRV-10 4/5/07 Slow 7 Production 766 610 738

SCRV-11 4/9/07 Fast 587 Production 636 316 636

SCRV-12 4/9/07 Slow 20 Production 1,200 720 1,180

SCRV-13 4/9/07 Fast 233 Production 399 204 375

SCRV-14 4/9/07 Fast 252 Production 830 512 740

SCRV-15 4/10/07 Fast 254 Production 670 452 653

SCRV-16 4/10/07 Intermediate 283 Production 700 260 700

SCRV-17 4/11/07 Fast 253 Production 60 15 60

SCRV-18 4/11/07 Fast 162 Production 420 300 400

SCRV-19 4/11/07 Intermediate 473 Production 100 na na

SCRV-20 4/12/07 Fast 377 Production 1,440 800 1,440

SCRV-21 4/12/07 Fast 613 Production 980 650 na

SCRV-22 4/12/07 Fast 588 Production 980 670 980

SCRV-23 4/16/07 Fast 1,142 Production na na na

SCRV-24 4/16/07 Fast 222 Production 1,042 642 1,042

SCRV-25 4/16/07 Fast 1,135 Production 203 60 165

SCRV-26 4/16/07 Fast 1,033 Production 142 na na

SCRV-27 4/16/07 Intermediate 61 Production 873 403 853

SCRV-28 4/17/07 Intermediate 446 Production 334 105 240

SCRV-29 4/17/07 Fast 81 Production 252 107 na

SCRV-30 4/17/07 Fast 1,121 Production 208 na na

SCRV-31 4/18/07 Fast 1,353 Production 150 56 150

SCRV-32 4/18/07 Fast 725 Production 300 50 230

SCRV-33 4/18/07 Intermediate 122 Production 504 224 504

SCRV-34 4/19/07 Fast 615 Production 920 500 920

SCRV-35 4/19/07 Slow 767 Production 300 70 290

SCRV-36 4/19/07 Fast 690 Production 300 na na

SCRV-37 5/8/07 Intermediate 9 Production 541 421 521

SCRV-38 5/14/07 Fast 802 Production 644 281 644

SCRV-39 5/14/07 Intermediate 247 Production 1,190 580 1,080

SCRV-40 5/15/07 Fast 1,400 Production na na na

SCRV-41 5/16/07 Fast 35 Production 300 na na

SCRV-42 6/6/07 Intermediate 641 Production 275 110 275

Table 1. Identification, sampling, and construction information for wells sampled for the Santa Clara River Valley Groundwater 

Ambient Monitoring and Assessment (GAMA) study, California, April to June 2007.

[Sampling schedules are described in table 2. GAMA identification No.: SCRV, Santa Clara River Valley study unit grid well; SCRVU, Santa Clara River 

Valley study unit understanding well; DD, depth-dependent sample. Land-surface datum (LSD) is a datum plane that is approximately at land surface at 

each well. The elevation of the LSD is described in feet above the North American Vertical Datum 1988 (NAVD 88). Abbreviations: ft, foot; na, data not 

available]
Table 1 21

GAMA

identification no.

Sampling information

Well type

Construction information

Date 

(mm/dd/yy)

Sampling

schedule

Elevation of LSD 

(ft above 

NAVD 88)

Well depth 

(ft below 

LSD)

Top perforation

(ft below 

LSD)

Bottom 

perforation 

(ft below 

LSD)

Understanding wells

SCRVU-01 4/3/07 Slow 76 Production 820 400 820

SCRVU-02 4/10/07 Slow 210 Production 759 459 759

SCRVU-03 4/11/07 Slow 144 Production 330 100 320

SCRVU-04 4/12/07 Slow 92 Production 1,483 403 1,463

 DD-01 6/7/07 Depth-dependent 92 Production 1

790 na na

 DD-02 6/7/07 Depth-dependent 92 Production 1

830 na na

 DD-03 6/7/07 Depth-dependent 92 Production 1

970 na na

 DD-04 6/7/07 Depth-dependent 92 Production 1

1,130 na na

SCRVU-05 4/18/07 Fast 1,443 Production na na na

SCRVU-06 5/7/07 Intermediate 14 Monitoring 740 na na

SCRVU-07 5/8/07 Intermediate 13 Monitoring 720 680 720

SCRVU-08 5/9/07 Intermediate 14 Monitoring 640 600 640

SCRVU-09 5/9/07 Intermediate 14 Monitoring 970 930 970

SCRVU-10 5/10/07 Intermediate 12 Monitoring 220 200 220

SCRVU-11 5/16/07 Intermediate 14 Production 810 400 810

1

 Depth below land surface where depth-dependent sample was collected.

Table 1. Identification, sampling, and construction information for wells sampled for the Santa Clara River Valley Groundwater 

Ambient Monitoring and Assessment (GAMA) study, California, April to June 2007.—Continued

[Sampling schedules are described in table 2. GAMA identification No.: SCRV, Santa Clara River Valley study unit grid well; SCRVU, Santa Clara River 

Valley study unit understanding well; DD, depth-dependent sample. Land-surface datum (LSD) is a datum plane that is approximately at land surface at 

each well. The elevation of the LSD is described in feet above the North American Vertical Datum 1988 (NAVD 88). Abbreviations: ft, foot; na, data not 

available]
22 Ground-Water Quality Data in the Santa Clara River Valley Study Unit, 2007: Results from the California GAMA Program

Analyte classes

Sampling schedule Table

Slow Intermediate Fast

Depthdependent 

schedule

Analyte 

list Results

Water-quality indicators

pH, dissolved oxygen, temperature, specific conductance X X X X1 4

Alkalinity and turbidity X 4

Organic constituents

Volatile organic compounds X X X 3A 5

Gasoline oxygenates and degradates X 3B 5

Pesticides and pesticide degradates (NWQL 

schedule 2003)

X X X 3C 6

Potential wastewater-indicator compounds X X X 3D 7

Polar pesticides and pesticide degradates (NWQL 

schedule 2060)

X 3F 6

Dissolved organic carbon X X 3G 9

Constituent of special interest

Perchlorate X X X 3G 8

Inorganic constituents

Nutrients X X 3G 9

Major and minor ions X X X 3H 10

Trace elements X X X 3H 11

Chromium abundance and speciation X X 3I 12

Arsenic and iron abundances and speciation X X 3I 12

Stable isotopes

Stable isotopes of hydrogen and oxygen in water X X X X 3J 13

Stable isotopes of nitrogen and oxygen in nitrate X X 3J 13

Stable isotopes of carbon and carbon-14 abundance X 3J 13

Stable isotopes of chlorine and bromine X X2 X3 3J 13

Radioactivity and gases

Tritium X X X 3J 13

Tritium and noble gases X X X 3K 14

Radium isotopes X 3J 15

Radon-222 X 3J 15

Gross alpha and gross beta radiation X 3J 15

Microbial constituents

F-specific coliphage X 3L 16

Somatic coliphage X 3L 16

Escherichia coli X 3L 16

Total coliform X 3L 16

Additional analytes collected, but not included in this report

Pharmaceutical compounds X 3E

1

 Dissolved oxygen not collected. 

2

 Collected at 7 of the 15 intermediate wells.

3

 Only collected for the deepest sample (DD-04).

Table 2. Classes of chemical and microbial constituents and water-quality indicators collected for the slow, intermediate, fast, and 

depth-dependent well sampling schedules for the Santa Clara River Valley Groundwater Ambient Monitoring and Assessment (GAMA) 

study, California, April to June 2007.

[Abbreviations: NWQL, National Water-Quality Laboratory]
Table 3A 23

Constituent Primary use 

or source

USGS 

parameter 

code

CAS 

number

 LRL 

(μg/L)

Threshold 

type

Threshold 

value 

(μg/L)

Detection

Acetone Solvent 81552 67-64-1 6 na na –

Acrylonitrile Organic synthesis 34215 107-13-1 0.4 RSD5-US 0.6 –

tert-Amyl methyl ether (TAME) Gasoline oxygenate 50005 994-05-8 0.04 na na –

Benzene Gasoline hydrocarbon 34030 71-43-2 0.016 MCL-CA 1 D

Bromobenzene Solvent 81555 108-86-1 0.02 na na –

Bromochloromethane Fire retardant 77297 74-97-5 0.06 HAL-US 90 D

Bromodichloromethane Disinfection by-product 

(THM)

32101 75-27-4 0.04 MCL-US 1

80 D

Bromoform (Tribromomethane) Disinfection by-product 

(THM)

32104 75-25-2 0.08 MCL-US 1

80 D

Bromomethane (Methyl bromide) Fumigant 34413 74-83-9 0.4 HAL-US 10 –

n-Butylbenzene Gasoline hydrocarbon 77342 104-51-8 0.14 NL-CA 260 –

sec-Butylbenzene Gasoline hydrocarbon 77350 135-98-8 0.04 NL-CA 260 –

tert-Butylbenzene Gasoline hydrocarbon 77353 98-06-6 0.08 NL-CA 260 –

Carbon disulfide Organic synthesis 77041 75-15-0 0.06 NL-CA 160 D

Carbon tetrachloride 

(Tetrachloromethane)

Solvent 32102 56-23-5 0.08 MCL-CA 0.5 D

Chlorobenzene Solvent 34301 108-90-7 0.02 MCL-CA 70 –

Chloroethane Solvent 34311 75-00-3 0.1 na na –

Chloroform (Trichloromethane) Disinfection by-product 

(THM)

32106 67-66-3 0.04 MCL-US 1

80 D

Chloromethane Refrigerant/organic synthesis 34418 74-87-3 0.1 HAL-US 30 –

3-Chloropropene Organic synthesis 78109 107-05-1 0.08 na na –

2-Chlorotoluene Solvent 77275 95-49-8 0.04 NL-CA 140 –

4-Chlorotoluene Solvent 77277 106-43-4 0.04 NL-CA 140 –

Dibromochloromethane Disinfection by-product 

(THM)

32105 124-48-1 0.12 MCL-US 1

80 D

1,2-Dibromo-3-chloropropane (DBCP)Fumigant 82625 96-12-8 0.5 MCL-US 0.2 –

1,2-Dibromoethane (EDB) Fumigant 77651 106-93-4 0.04 MCL-US 0.05 –

Dibromomethane Solvent 30217 74-95-3 0.04 na na D

1,2-Dichlorobenzene Solvent 34536 95-50-1 0.04 MCL-CA 600 –

1,3-Dichlorobenzene Solvent 34566 541-73-1 0.04 HAL-US 600 –

1,4-Dichlorobenzene Fumigant 34571 106-46-7 0.04 MCL-CA 5 –

trans-1,4-Dichloro-2-butene Organic synthesis 73547 110-57-6 0.6 na na –

Dichlorodifluoromethane (CFC-12) Refrigerant 34668 75-71-8 0.14 NL-CA 1,000 –

1,1-Dichloroethane (1,1-DCA) Solvent 34496 75-34-3 0.06 MCL-CA 5 –

1,2-Dichloroethane (1,2-DCA) Solvent 32103 107-06-2 0.1 MCL-CA 0.5 –

1,1-Dichloroethene (1,1-DCE) Organic synthesis 34501 75-35-4 0.02 MCL-CA 6 –

cis-1,2-Dichloroethene (cis-1,2-DCE) Solvent 77093 156-59-2 0.02 MCL-CA 6 –

trans-1,2-Dichloroethene (trans-1,2-

DCE)

Solvent 34546 156-60-5 0.018 MCL-CA 10 D

1,2-Dichloropropane Fumigant 34541 78-87-5 0.02 MCL-US 5 –

1,3-Dichloropropane Fumigant 77173 142-28-9 0.06 na na –

2,2-Dichloropropane Fumigant 77170 594-20-7 0.06 na na –

1,1-Dichloropropene Organic synthesis 77168 563-58-6 0.04 na na –

cis-1,3-Dichloropropene Fumigant 34704 10061-01-5 0.06 RSD5-US 2

4 –

trans-1,3-Dichloropropene Fumigant 34699 10061-02-6 0.1 RSD5-US 2

4 –

Diethyl ether Solvent 81576 60-29-7 0.08 na na –

Diisopropyl ether (DIPE) Gasoline oxygenate 81577 108-20-3 0.06 na na –

Table 3A. Volatile organic compounds, primary uses or sources, comparative thresholds, and reporting information for the U.S. 

Geological Survey National Water Quality Laboratory Schedule 2020.

[The five-digit U.S. Geological Survey (USGS) parameter code is used to uniquely identify a specific constituent or property. CAS number: This report 

contains CAS Registry Numbers®, which is a Registered Trademark of the American Chemical Society. CAS recommends the verification of the CASRNs 

through CAS Client ServicesSM. Thresholds and threshold values as of October 29, 2007. Threshold type: Maximum contaminant level thresholds are listed 

as MCL-US when the MCL-US and MCL-CA are identical, and as MCL-CA when the MCL-CA is lower than the MCL-US or no MCL-US exists. HAL-US, 

U.S. Environmental Protection Agency Lifetime Health Advisory; MCL-CA, California Department of Public Health maximum contaminant level; MCL-US, 

U.S. Environmental Protection Agency maximum contaminant level; NL-CA, California Department of Public Health notification level; RSD5-US, U.S. 

Environmental Protection Agency risk specific dose at a risk factor of 10-5. Abbreviations: CAS, Chemical Abstract Service; LRL, laboratory reporting level. 

THM, trihalomethane; D, detected in ground-water sample (table 5); na, not available; μg/L, microgram per liter; –, not detected]
24 Ground-Water Quality Data in the Santa Clara River Valley Study Unit, 2007: Results from the California GAMA Program

Constituent Primary use 

or source

USGS 

parameter 

code

CAS 

number

 LRL 

(μg/L)

Threshold 

type

Threshold 

value 

(μg/L)

Detection

Ethylbenzene Gasoline hydrocarbon 34371 100-41-4 0.02 MCL-CA 300 –

Ethyl tert-butyl ether (ETBE) Gasoline oxygenate 50004 637-92-3 0.04 na na –

Ethyl methacrylate Organic synthesis 73570 97-63-2 0.14 na na –

o-Ethyl toluene (1-Ethyl-2-

methylbenzene)

Gasoline hydrocarbon 77220 611-14-3 0.04 na na –

Hexachlorobutadiene Organic synthesis 39702 87-68-3 0.1 RSD5-US 9 –

Hexachloroethane Solvent 34396 67-72-1 0.14 HAL-US 1 –

2-Hexanone (n-Butyl methyl ketone) Solvent 77103 591-78-6 0.4 na na –

Iodomethane (Methyl iodide) Organic synthesis 77424 74-88-4 0.4 na na –

Isopropylbenzene Gasoline hydrocarbon 77223 98-82-8 0.04 NL-CA 770 –

4-Isopropyl-1-methylbenzene Gasoline hydrocarbon 77356 99-87-6 0.08 na na –

Methyl acrylate Organic synthesis 49991 96-33-3 0.4 na na –

Methyl acrylonitrile Organic synthesis 81593 126-98-7 0.4 na na –

Methyl tert-butyl ether (MTBE) Gasoline oxygenate 78032 1634-04-4 0.1 MCL-CA 13 –

Methyl isobutyl ketone (MIBK) Solvent 78133 108-10-1 0.2 NL-CA 120 –

Methylene chloride (Dichloromethane)Solvent 34423 75-09-2 0.04 MCL-US 5 –

Methyl ethyl ketone (2-Butanone, 

MEK)

Solvent 81595 78-93-3 1.6 HAL-US 4,000 –

Methyl methacrylate Organic synthesis 81597 80-62-6 0.2 na na –

Naphthalene Gasoline hydrocarbon 34696 91-20-3 0.4 NL-CA 17 –

Perchloroethene (Tetrachloroethene, 

PCE)

Solvent 34475 127-18-4 0.04 MCL-US 5 D

n-Propylbenzene Solvent 77224 103-65-1 0.04 NL-CA 260 –

Styrene Gasoline hydrocarbon 77128 100-42-5 0.04 MCL-US 100 –

1,1,1,2-Tetrachloroethane Solvent 77562 630-20-6 0.04 HAL-US 70 –

1,1,2,2-Tetrachloroethane Solvent 34516 79-34-5 0.1 MCL-CA 1 –

Tetrahydrofuran Solvent 81607 109-99-9 1 na na D

1,2,3,4-Tetramethylbenzene Gasoline hydrocarbon 49999 488-23-3 0.14 na na –

1,2,3,5-Tetramethylbenzene Gasoline hydrocarbon 50000 527-53-7 0.12 na na –

Toluene Gasoline hydrocarbon 34010 108-88-3 0.018 MCL-CA 150 D

1,2,3-Trichlorobenzene Organic synthesis 77613 87-61-6 0.12 na na –

1,2,4-Trichlorobenzene Solvent 34551 120-82-1 0.12 MCL-CA 5 –

1,1,1-Trichloroethane Solvent 34506 71-55-6 0.04 MCL-CA 200 D

1,1,2-Trichloroethane Solvent 34511 79-00-5 0.04 MCL-CA 5 –

Trichloroethene (TCE) Solvent 39180 79-01-6 0.02 MCL-US 5 D

Trichlorofluoromethane (CFC-11) Refrigerant 34488 75-69-4 0.08 MCL-CA 150 D

1,2,3-Trichloropropane (1,2,3-TCP) Solvent/organic synthesis 77443 96-18-4 0.12 HAL-US 40 –

Trichlorotrifluoroethane (CFC-113) Refrigerant 77652 76-13-1 0.04 MCL-CA 1,200 D

1,2,3-Trimethylbenzene Gasoline hydrocarbon 77221 526-73-8 0.08 na na –

1,2,4-Trimethylbenzene Gasoline hydrocarbon 77222 95-63-6 0.04 NL-CA 330 –

1,3,5-Trimethylbenzene Organic synthesis 77226 108-67-8 0.04 NL-CA 330 –

Vinyl bromide (Bromoethene) Fire retardant 50002 593-60-2 0.12 na na –

Vinyl chloride (Chloroethene) Organic synthesis 39175 75-01-4 0.08 MCL-CA 0.5 –

m- and p-Xylene Gasoline hydrocarbon 85795 108-38-3 / 106-42-3 0.08 MCL-CA 3

1,750 –

o-Xylene Gasoline hydrocarbon 77135 95-47-6 0.04 MCL-CA 3

1,750 –

1The MCL-US, and MCL-CA thresholds for trihalomethanes are the sum of chloroform, bromoform, bromodichloromethane, and dibromochloromethane.

2The RSD5 threshold for 1,3-dichloropropene is the sum of its isomers (cis and trans). 3The MCL-CA thresholds for m- and p-Xylene and o-Xylene is the sum of all three xylene compounds.

Table 3A. Volatile organic compounds, primary uses or sources, comparative thresholds, and reporting information for the U.S. 

Geological Survey National Water Quality Laboratory Schedule 2020.—Continued

[The five-digit U.S. Geological Survey (USGS) parameter code is used to uniquely identify a specific constituent or property. CAS number: This report 

contains CAS Registry Numbers®, which is a Registered Trademark of the American Chemical Society. CAS recommends the verification of the CASRNs 

through CAS Client ServicesSM. Thresholds and threshold values as of October 29, 2007. Threshold type: Maximum contaminant level thresholds are listed 

as MCL-US when the MCL-US and MCL-CA are identical, and as MCL-CA when the MCL-CA is lower than the MCL-US or no MCL-US exists. HAL-US, 

U.S. Environmental Protection Agency Lifetime Health Advisory; MCL-CA, California Department of Public Health maximum contaminant level; MCL-US, 

U.S. Environmental Protection Agency maximum contaminant level; NL-CA, California Department of Public Health notification level; RSD5-US, U.S. 

Environmental Protection Agency risk specific dose at a risk factor of 10-5. Abbreviations: CAS, Chemical Abstract Service; LRL, laboratory reporting level. 

THM, trihalomethane; D, detected in ground-water sample (table 5); na, not available; μg/L, microgram per liter; –, not detected]
Table 3B 25

Constituent

(common name)

Primary use 

or source

USGS 

parameter 

code

CAS 

number

 LRL

 (μg/L)

Threshold 

type

Threshold 

value 

(μg/L)

Detection

Acetone Solvent 81552 67-64-1 1.2 na na –

tert-Amyl alcohol Gasoline oxygenate 77073 75-85-4 0.6 na na –

tert-Amyl methyl ether (TAME) Gasoline oxygenate 50005 994-05-8 0.04 na na –

tert-Butyl alcohol (TBA) Oxygenate/degradate 77035 75-65-0 2 NL-CA 12 –

Diisopropyl ether (DIPE) Gasoline oxygenate 81577 108-20-3 0.06 na na –

Ethyl tert-butyl ether (ETBE) Gasoline oxygenate 50004 637-92-3 0.06 na na –

Methyl acetate Solvent 77032 79-20-9 0.4 na na –

Methyl tert-butyl ether (MTBE) Gasoline oxygenate 78032 1634-04-4 0.05 MCL-US 13 –

Table 3B. Gasoline oxygenates and degradates, primary uses or sources, comparative thresholds, and reporting information for the 

U.S. Geological Survey National Water Quality Laboratory Schedule 4024.

[The five-digit U.S. Geological Survey (USGS) parameter code is used to uniquely identify a specific constituent or property. Thresholds and threshold values as 

of October 29, 2007. Threshold type: MCL-US, U.S. Environmental Protection Agency maximum contaminant level; NL-CA, California Department of Public 

Health notification level; Abbreviations: CAS, Chemical Abstract Service; LRL, laboratory reporting level; na, not available; μg/L, microgram per liter; –, not 

detected]
26 Ground-Water Quality Data in the Santa Clara River Valley Study Unit, 2007: Results from the California GAMA Program

Constituent

(common name)

Primary use 

or source

USGS 

parameter 

code

CAS 

number

 LRL 

(μg/L)

Threshold 

type

Threshold

value 

(μg/L)

Detection

Acetochlor Herbicide 49260 34256-82-1 0.006 na na –

Alachlor Herbicide 46342 15972-60-8 0.005 MCL-US 2 –

Atrazine Herbicide 39632 1912-24-9 0.007 MCL-CA 1 D

Azinphos-methyl Insecticide 82686 86-50-0 0.08 na na 1

–

Azinphos-methyl-oxon Insecticide 

degradate

61635 961-22-8 0.042 na na –

Benfluralin Herbicide 82673 1861-40-1 0.01 na na –

Carbaryl Insecticide 82680 63-25-2 0.06 RSD5-US 400 –

2-Chloro-2,6-diethylacetanilide Herbicide 

degradate

61618 6967-29-9 0.0065 na na –

4-Chloro-2-methylphenol Herbicide 

degradate

61633 1570-64-5 0.005 na na 1

–

Chlorpyrifos Insecticide 38933 2921-88-2 0.005 HAL-US 2 –

Chlorpyrifos, oxon Insecticide 

degradate

61636 5598-15-2 0.0562 na na 1

–

Cyfluthrin Insecticide 61585 68359-37-5 0.053 na na 1

–

Cypermethrin Insecticide 61586 52315-07-8 0.046 na na 1

–

Dacthal (DCPA) Herbicide 82682 1861-32-1 0.003 HAL-US 70 –

Deethylatrazine (2-Chloro-4-

isopropylamino-6-amino-striazine)

Herbicide 

degradate

04040 6190-65-4 0.014 na na 1

D

Desulfinylfipronil Insecticide 

degradate

62170 na 0.012 na na D

Desulfinylfipronil amide Insecticide 

degradate

62169 na 0.029 na na –

Diazinon Insecticide 39572 333-41-5 0.005 HAL-US 1 –

3,4-Dichloroaniline Herbicide 

degradate

61625 95-76-1 0.0045 na na D

Dichlorvos Insecticide 38775 62-73-7 0.013 na na 1

–

Dicrotophos Insecticide 38454 141-66-2 0.0843 na na 1

–

Dieldrin Insecticide 39381 60-57-1 0.009 RSD5-US 0.02 –

2,6-Diethylaniline Herbicide 

degradate

82660 579-66-8 0.006 na na –

Dimethoate Insecticide 82662 60-51-5 0.0061 na na 1

–

Ethion Insecticide 82346 563-12-2 0.016 na na –

Ethion monoxon Insecticide 

degradate

61644 17356-42-2 0.021 na na –

2-Ethyl-6-methylaniline Herbicide 

degradate

61620 24549-06-2 0.01 na na –

Fenamiphos Insecticide 61591 22224-92-6 0.029 HAL-US 0.7 –

Fenamiphos sulfone Insecticide 

degradate

61645 31972-44-8 0.053 na na 1

–

Fenamiphos sulfoxide Insecticide 

degradate

61646 31972-43-7 0.040 na na 1

–

Fipronil Insecticide 62166 120068-37-3 0.016 na na D

Fipronil sulfide Insecticide 

degradate

62167 120067-83-6 0.013 na na D

Table 3C. Pesticides and pesticide degradates, primary uses or sources, comparative thresholds, and reporting information for the 

U.S. Geological Survey National Water Quality Laboratory Schedule 2003.

[The five-digit U.S. Geological Survey (USGS) parameter code is used to uniquely identify a specific constituent or property. Thresholds and threshold values 

as of October 29, 2007. Threshold type: Maximum contaminant level thresholds are listed as MCL-US when the MCL-US and MCL-CA are identical, and as 

MCL-CA when the MCL-CA is lower than the MCL-US or no MCL-US exists. HAL-US, U.S. Environmental Protection Agency Lifetime Health Advisory; 

MCL-CA, California Department of Public Health maximum contaminant level; MCL-US, U.S. Environmental Protection Agency maximum contaminant level; 

RSD5-US, U.S. Environmental Protection Agency risk specific dose at a risk factor of 10-5 Abbreviations: CAS, Chemical Abstract Service; LRL, laboratory 

reporting level; D, detected in ground-water sample (table 6); na, not available; μg/L, microgram per liter;–, not detected]
Table 3C 27

Constituent

(common name)

Primary use 

or source

USGS 

parameter 

code

CAS 

number

 LRL 

(μg/L)

Threshold 

type

Threshold

value 

(μg/L)

Detection

Fipronil sulfone Insecticide 

degradate

62168 120068-36-2 0.024 na na D

Fonofos Insecticide 04095 944-22-9 0.006 HAL-US 10 –

Hexazinone Herbicide 04025 51235-04-2 0.026 HAL-US 400 D

Iprodione Fungicide 61593 36734-19-7 0.026 na na –

Isofenphos Insecticide 61594 25311-71-1 0.011 na na –

Malaoxon Insecticide 

degradate

61652 1634-78-2 0.039 na na –

Malathion Insecticide 39532 121-75-5 0.016 HAL-US 100 –

Metalaxyl Fungicide 61596 57837-19-1 0.0069 na na D

Methidathion Insecticide 61598 950-37-8 0.0087 na na –

Metolachlor Herbicide 39415 51218-45-2 0.01 HAL-US 700 D

Metribuzin Herbicide 82630 21087-64-9 0.012 HAL-US 70 –

Myclobutanil Fungicide 61599 88671-89-0 0.033 na na –

1-Naphthol Insecticide 

degradate

49295 90-15-3 0.0882 na na 1

–

Paraoxon-methyl Insecticide 

degradate

61664 950-35-6 0.019 na na 1–

Parathion-methyl Insecticide 82667 298-00-0 0.008 HAL-US 1 –

Pendimethalin Herbicide 82683 40487-42-1 0.02 na na –

cis-Permethrin Insecticide 82687 54774-45-7 0.01 na na 1

–

Phorate Insecticide 82664 298-02-2 0.02 na na –

Phorate oxon Insecticide 

degradate

61666 2600-69-3 0.027 na na –

Phosmet Insecticide 61601 732-11-6 0.0079 na na 1

–

Phosmet oxon Insecticide 

degradate

61668 3735-33-9 0.0511 na na 1

–

Prometon Herbicide 04037 1610-18-0 0.01 HAL-US 100 –

Prometryn Herbicide 04036 7287-19-6 0.0059 na na D

Pronamide (Propyzamide) Herbicide 82676 23950-58-5 0.004 RSD5-US 20 –

Simazine Herbicide 04035 122-34-9 0.006 MCL-US 4 D

Tebuthiuron Herbicide 82670 34014-18-1 0.016 HAL-US 500 D

Terbufos Insecticide 82675 13071-79-9 0.012 HAL-US 0.4 –

Terbufos oxon sulfone Insecticide 

degradate

61674 56070-15-6 0.045 na na –

Terbuthylazine Herbicide 04022 5915-41-3 0.0083 na na –

Tribufos Herbicide 61610 78-48-8 0.035 na na –

Trifluralin Herbicide 82661 1582-09-8 0.009 HAL-US 10 –

 1 The median matrix-spike recovery was less than 70 percent. Low recoveries may indicate that the compound might not have been detected in some samples if 

it was present at very low concentrations.

Table 3C. Pesticides and pesticide degradates, primary uses or sources, comparative thresholds, and reporting information for the 

U.S. Geological Survey National Water Quality Laboratory Schedule 2003.—Continued

[The five-digit U.S. Geological Survey (USGS) parameter code is used to uniquely identify a specific constituent or property. Thresholds and threshold values 

as of October 29, 2007. Threshold type: Maximum contaminant level thresholds are listed as MCL-US when the MCL-US and MCL-CA are identical, and as 

MCL-CA when the MCL-CA is lower than the MCL-US or no MCL-US exists. HAL-US, U.S. Environmental Protection Agency Lifetime Health Advisory; 

MCL-CA, California Department of Public Health maximum contaminant level; MCL-US, U.S. Environmental Protection Agency maximum contaminant level; 

RSD5-US, U.S. Environmental Protection Agency risk specific dose at a risk factor of 10-5 Abbreviations: CAS, Chemical Abstract Service; LRL, laboratory 

reporting level; D, detected in ground-water sample (table 6); na, not available; μg/L, microgram per liter;–, not detected]
28 Ground-Water Quality Data in the Santa Clara River Valley Study Unit, 2007: Results from the California GAMA Program

Constituent

(common name)

Primary use 

or source

USGS 

parameter 

code

CAS 

number

 LRL 

(μg/L)

Threshold

type

Threshold

value 

(μg/L)

Detection

Acetophenone Fragrance, flavor 

additive

62811 98-86-2 0.2 na na –

Acetyl hexamethyl tetrahydro 

naphthalene (AHTN)

Musk fragrance 62812 21145-77-7 0.2 na na –

Anthracene Wood preservative, 

combustion product 

34220 120-12-7 0.2 na na –

9,10-Anthraquinone Dye/textiles, seed 

treatment

62813 84-65-1 0.2 na na –

Atrazine Herbicide 39630 1912-24-9 0.2 MCL-CA 1 –

Benzo[a]pyrene Combustion product 34247 50-32-8 0.2 MCL-US 0.2 –

Benzophenone Fixative for perfumes 

and soaps 

62814 119-61-9 0.2 na na –

Bis(2-ethylhexyl)phthalate Plasticizer, softener 39100 117-81-7 2 na na D

Bisphenol A Polycarbonate resins, 

flame retardant

62816 80-05-7 0.4 na na D

Bromacil Herbicide 30234 314-40-9 0.2 HAL-US 70 –

Bromoform (Tribromomethane) Disinfection byproduct32104 75-25-2 0.08 MCL-US 80 D

3-tert-Butyl-4-hydroxy anisole (BHA) Antioxidant, general 

preservative 

61702 25013-16-5 0.2 na na –

Caffeine Beverages 81436 58-08-2 0.2 na na –

Camphor Flavor, odorant, 

ointments 

62817 76-22-2 0.2 na na –

Carbaryl Insecticide 39750 63-25-2 0.2 RSD5-US 400 –

Carbazole Insecticide 77571 86-74-8 0.2 na na –

Chlorpyrifos Insecticide 38932 2921-88-2 0.2 HAL-US 2 –

Cholesterol Fecal indicator, plant 

sterol 

62818 57-88-5 0.8 na na D

3-β-Coprostanol Carnivore fecal 

indicator 

62806 360-68-9 0.8 na na –

Cotinine Primary nicotine 

metabolite 

61945 486-56-6 0.8 na na –

p-Cresol Wood preservative 77146 106-44-5 0.2 na na –

4-Cumylphenol Nonionic detergent 

metabolite 

62808 599-64-4 0.2 na na –

Diazinon Insecticide 39570 333-41-5 0.2 HAL-US 1 –

Dichlorvos Insecticide 30218 62-73-7 0.2 na na –

DEET (N,N-diethyl-m-toluamide) Insecticide 61947 134-62-3 0.2 na na –

1,4-Dichlorobenzene Moth repellant, 

fumigant, deodorant 

34571 106-46-7 0.04 MCL-CA 5 –

3,4-Dichlorophenyl isocyanate Intermediate for the 

synthesis of organic 

compounds

63145 102-36-3 2 na na –

Diethyl phthalate Wood stains and 

varnishes, 

plasticizer, softener

34336 84-66-2 0.2 na na –

2,6-Dimethylnaphthalene Diesel/kerosene 62085 581-42-0 0.2 na na –

Table 3D. Potential wastewater-indicator compounds, primary uses or sources, comparative thresholds, and reporting information for 

the U.S. Geological Survey National Water Quality Laboratory Schedule 4433.

[The five-digit U.S. Geological Survey (USGS) parameter code is used to uniquely identify a specific constituent or property. Thresholds and threshold values 

as of October 29, 2007. Threshold type: Maximum contaminant level thresholds are listed as MCL-US when the MCL-US and MCL-CA are identical, and as 

MCL-CA when the MCL-CA is lower than the MCL-US or no MCL-US exists. HAL-US, U.S. Environmental Protection Agency Lifetime Health Advisory; 

MCL-CA, California Department of Public Health maximum contaminant level; MCL-US, U.S. Environmental Protection Agency maximum contaminant 

level; NL-CA, California Department of Public Health notification level; RSD5-US, U.S. Environmental Protection Agency risk specific dose at a risk factor of 

10-5. Abbreviations: CAS, Chemical Abstract Service; LRL, laboratory reporting level; D, detected in ground-water sample (table 7); na, not available; μg/L, 

microgram per liter; –, not detected]
Table 3D 29

Constituent

(common name)

Primary use 

or source

USGS 

parameter 

code

CAS 

number

 LRL 

(μg/L)

Threshold

type

Threshold

value 

(μg/L)

Detection

4-Nonylphenol monoethoxylates Nonionic detergent 

metabolite

61704 na 2 na na –

4-Nonylphenol diethoxylates Nonionic detergent 

metabolite 

61703 na 3.2 na na –

4-Octylphenol diethoxylates Nonionic detergent 

metabolite 

61705 na 0.32 na na D

4-Octylphenol monoethoxylates Nonionic detergent 

metabolite 

61706 na 1 na na D

Fluoranthene Component of coal tar 

and asphalt 

34376 206-44-0 0.2 na na –

Hexahydrohexamethycyclopentabenzopyran (HHCB)Musk fragrance 62823 1222-05-5 0.2 na na –

Indole Pesticide ingredient 62824 120-72-9 0.2 na na –

Isoborneol Fragrance in 

perfumery

62825 124-76-5 0.2 na na –

Isophorone Solvent 34409 78-59-1 0.2 HAL-US 100 –

Isopropylbenzene Fuels, paint thinner 77223 98-82-8 0.04 NL-CA 770 –

Isoquinoline Flavors and fragrances 62826 119-65-3 0.2 na na –

d-Limonene Fungicide 62819 5989-27-5 0.2 na na –

Menthol Cigarettes, cough 

drops, liniment

62827 89-78-1 0.2 na na –

Metalaxyl Herbicide, fungicide 04254 57837-19-1 0.2 na na –

3-Methyl-1H-indole (Skatole) Fragrance, stench in 

feces

62807 83-34-1 0.2 na na –

5-Methyl-1H-benzotriazole Antioxidant in 

antifreeze and 

deicers 

61944 136-85-6 1.6 na na –

1-Methylnaphthalene Gasoline, diesel fuel, 

or crude oil 

81696 90-12-0 0.2 na na –

2-Methylnaphthalene Gasoline, diesel fuel, 

or crude oil 

30194 91-57-6 0.2 na na D

Methyl salicylate Liniment, UVabsorbing lotion 62828 119-36-8 0.2 na na –

Metolachlor Herbicide 82612 51218-45-2 0.2 HAL-US 700 –

Naphthalene Fumigant, moth 

repellent, gasoline 

34696 91-20-3 0.4 NL-CA 17 –

4-Nonylphenol (total) Nonionic detergent 

metabolite 

62829 84852-15-3 1.6 na na –

4-n-Octylphenol Nonionic detergent 

metabolite 

62809 1806-26-4 0.2 na na –

4-tert-Octylphenol Nonionic detergent 

metabolite 

62810 140-66-9 0.2 na na D

Pentachlorophenol Herbicide, wood 

preservative

39032 87-86-5 0.8, 2 MCL-US 1 –

Perchloroethene (Tetrachloroethene, 

PCE)

Solvent, degreaser 34475 127-18-4 0.04 MCL-US 5 D

Table 3D. Potential wastewater-indicator compounds, primary uses or sources, comparative thresholds, and reporting information for 

the U.S. Geological Survey National Water Quality Laboratory Schedule 4433.—Continued

[The five-digit U.S. Geological (USGS) parameter code is used to uniquely identify a specific constituent or property. Thresholds and threshold values as 

of October 29, 2007. Threshold type: Maximum contaminant level thresholds are listed as MCL-US when the MCL-US and MCL-CA are identical, and as 

MCL-CA when the MCL-CA is lower than the MCL-US or no MCL-US exists. HAL-US, U.S. Environmental Protection Agency Lifetime Health Advisory; 

MCL-CA, California Department of Public Health maximum contaminant level; MCL-US, U.S. Environmental Protection Agency maximum contaminant 

level; NL-CA, California Department of Public Health notification level; RSD5-US, U.S. Environmental Protection Agency risk specific dose at a risk factor of 

10-5. Abbreviations: CAS, Chemical Abstract Service; LRL, laboratory reporting level; D, detected in ground-water sample (table 7); na, not available; μg/L, 

microgram per liter; –, not detected]
30 Ground-Water Quality Data in the Santa Clara River Valley Study Unit, 2007: Results from the California GAMA Program

Constituent

(common name)

Primary use 

or source

USGS 

parameter 

code

CAS 

number

 LRL 

(μg/L)

Threshold

type

Threshold

value 

(μg/L)

Detection

Phenanthrene Explosives, oil, 

combustion product 

34461 85-01-8 0.2 na na –

Phenol Disinfectant, organic 

synthesis

34694 108-95-2 0.2 HAL-US 2,000 D

Prometon Herbicide 39056 1610-18-0 0.2 HAL-US 100 –

Pyrene Component of coal tar 

and asphalt 

34469 129-00-0 0.2 na na –

β-Sitosterol Plant sterol 62815 83-46-5 0.8 na na –

β-Stigmastanol Plant sterol 61948 19466-47-8 0.8 na na –

2,2',4,4'-Tetrabromodiphenyl ether Brominated flame 

retardant

63147 5436-43-1 0.2 na na –

Tributyl phosphate Antifoaming agent, 

flame retardant 

62832 126-73-8 0.2 na na –

Triclosan Disinfectant, 

antimicrobial 

61708 3380-34-5 0.2 na na –

Triethyl citrate Cosmetics, 

pharmaceuticals 

62833 77-93-0 0.2 na na –

Triphenyl phosphate Plasticizer, resin, flame 

retardant

62834 115-86-6 0.2 na na –

Tris(2-butoxyethyl) phosphate Flame retardant 62830 78-51-3 0.2 na na –

Tris(2-chloroethyl) phosphate Plasticizer, flame 

retardant 

62831 115-96-8 0.2 na na –

Tris(dichloroisopropyl) phosphate Flame retardant 61707 13674-87-8 0.2 na na –

Table 3D. Potential wastewater-indicator compounds, primary uses or sources, comparative thresholds, and reporting information for 

the U.S. Geological Survey National Water Quality Laboratory Schedule 4433.—Continued

[The five-digit U.S. Geological Survey (USGS) parameter code is used to uniquely identify a specific constituent or property. Thresholds and threshold values 

as of October 29, 2007. Threshold type: Maximum contaminant level thresholds are listed as MCL-US when the MCL-US and MCL-CA are identical, and as 

MCL-CA when the MCL-CA is lower than the MCL-US or no MCL-US exists. HAL-US, U.S. Environmental Protection Agency Lifetime Health Advisory; 

MCL-CA, California Department of Public Health maximum contaminant level; MCL-US, U.S. Environmental Protection Agency maximum contaminant 

level; NL-CA, California Department of Public Health notification level; RSD5-US, U.S. Environmental Protection Agency risk specific dose at a risk factor of 

10-5. Abbreviations: CAS, Chemical Abstract Service; LRL, laboratory reporting level; D, detected in ground-water sample (table 7); na, not available; μg/L, 

microgram per liter; –, not detected]
Table 3E 31

Table 3E. Pharmaceutical compounds, primary uses or sources, comparative thresholds, and reporting information for the U.S. 

Geological Survey National Water Quality Laboratory Code 9003.

[The five-digit U.S. Geological Survey (USGS) parameter code is used to uniquely identify a specific constituent or property. The California Groundwater 

Ambient Monitoring and Assessment (GAMA) program uses more conservative reporting limits for the pharmaceutical compounds than recommended by the 

USGS National Water Quality Laboratory. For albuterol, carbamazepine, codeine, dehydronifedipine, diltiazem, sulfamethoxazole, thiabendazole, trimethoprim, 

and warfarin, the MDL corresponds to the long-term method detection limit determined by the USGS Branch of Quality Systems in October 2007 (BQS 

LT-MDL). For acetaminophen, caffeine, cotinine, diphenhydramine, and paraxanthine, the MDL corresponds to the effective method detection limit determined 

from assessment of quality-control data associated with GAMA samples collected from May 2004 through September 2007 (GAMA E-MDL). The GAMA 

E-MDL are higher than the BQS LT-MDL for those compounds. Detections reported by the USGS National Water Quality Laboratory with concentrations lower 

than the BQS LT-MDL or GAMA E-MDL are reported as non-detections by the GAMA program. Abbreviations: CAS, Chemical Abstract Service; na, not 

available; μg/L, microgram per liter]

Constituent

(common name)

Primary use 

or source

USGS 

parameter

code

CAS 

number

MDL

(μg/L)

Threshold 

type

Threshold 

value

(μg/L)

Acetaminophen Analgesic 62000 103-90-2 0.04 na na

Albuterol Anti-inflammatory; bronchodilator 62020 18559-94-9 0.02 na na

Caffeine Stimulant 50305 58-08-2 0.03 na na

Carbamazapine Anticonvulsant; analgesic; mood 

stabilizer

62793 298-46-4 0.02 na na

Codeine Opioid narcotic 62003 76-57-3 0.02 na na

Cotinine Nicotine metabolite 62005 486-56-6 0.015 na na

Dehydronifedipine Antianginal metabolite 62004 67035-22-7 0.03 na na

Diltiazem Antianginal; antihypertensive 62008 42399-41-7 0.02 na na

Diphenhydramine Antihistamine 62796 58-73-1 0.025 na na

Paraxanthine Caffeine metabolite 62030 611-59-6 0.05 na na

Sulfamethoxazole Antibacterial, antiprotozoal 62021 723-46-6 0.05 na na

Thiabendazole Anthelmintic 62801 148-79-8 0.05 na na

Trimethoprim Antibacterial 62023 738-70-5 0.02 na na

Warfarin Anticoagulant 62024 81-81-2 0.03 na na
32 Ground-Water Quality Data in the Santa Clara River Valley Study Unit, 2007: Results from the California GAMA Program

Table 3F. Polar pesticides and pesticide degradates, primary uses or sources, comparative thresholds, and reporting information for 

the U.S. Geological Survey National Water Quality Laboratory Schedule 2060.

[The five-digit U.S. Geological Survey (USGS) parameter code is used to uniquely identify a specific constituent or property. Thresholds and threshold values 

as of October 29, 2007. Threshold type: Maximum contaminant level thresholds are listed as MCL-US when the MCL-US and MCL-CA are identical, and as 

MCL-CA when the MCL-CA is lower than the MCL-US or no MCL-US exists. HAL-US, U.S. Environmental Protection Agency Lifetime Health Advisory; 

MCL-CA, California Department of Public Health maximum contaminant level; MCL-US, U.S. Environmental Protection Agency maximum contaminant level; 

RSD5-US, U.S. Environmental Protection Agency risk specific dose at a risk factor of 10-5. Abbreviations: CAS, Chemical Abstract Service; LRL, laboratory 

reporting level; D, detected in ground-water sample (table 6); na, not available; μg/L, microgram per liter; –, not detected]

Constituent

(common name)

Primary use 

or source

USGS 

parameter 

code

CAS 

number

 LRL

(μg/L)

Threshold 

type

Threshold 

(μg/L) Detection

Acifluorfen Herbicide 49315 50594-66-6 0.028 na na –

Aldicarb1 Insecticide 49312 116-06-3 0.04 MCL-US 3 –

Aldicarb sulfone Insecticide/degradate 49313 1646-88-4 0.018 MCL-US 3 2

–

Aldicarb sulfoxide Degradate 49314 1646-87-3 0.022 MCL-US 4 –

Atrazine Herbicide 39632 1912-24-9 0.008 MCL-CA 1 D

Bendiocarb Insecticide 50299 22781-23-3 0.020 na na –

Benomyl Fungicide 50300 17804-35-2 0.022 na na –

Bensulfuron-methyl Herbicide 61693 83055-99-6 0.018 na na –

Bentazon Herbicide 38711 25057-89-0 0.012 MCL-CA 18 2

–

Bromacil Herbicide 04029 314-40-9 0.018 HAL-US 70 –

Bromoxynil Herbicide 49311 1689-84-5 0.028 na na 2

–

Caffeine Wastewater indicator 50305 58-08-2 0.018 na na –

Carbaryl Herbicide 49310 63-25-2 0.018 RSD5-US 400 –

Carbofuran Herbicide 49309 1563-66-2 0.016 MCL-CA 18 –

Chloramben, methyl ester Herbicide 61188 7286-84-2 0.024 na na –

Chlorimuron-ethyl Herbicide 50306 90982-32-4 0.032 na na 2

–

3-(4-Chlorophenyl)-1-methyl urea Degradate 61692 5352-88-5 0.036 na na –

Clopyralid Herbicide 49305 1702-17-6 0.024 na na 2

–

Cycloate Herbicide 04031 1134-23-2 0.014 na na –

2,4-D plus 2,4-D methyl ester Herbicides 66496 na 0.020 MCL-US 70 –

2,4-D methyl ester 

(2,4-Dichlorophenoxyacetic 

acid methyl ester)

Herbicide 50470 1928-38-7 0.016 na na –

2,4-DB (4-(2,4-Dichlorophenoxy)

butyric acid)

Herbicide 38746 94-82-6 0.020 na na 2

–

DCPA (Dacthal) monoacid Degradate 49304 887-54-7 0.028 na na –

Deethylatrazine (2-Chloro-4-

isopropylamino-6-amino-striazine)

Degradate 04040 6190-65-4 0.028 na na 2

D

Deisopropyl atrazine (2-chloro-6-

ethylamino-4-amino-s-triazine)

Degradate 04038 1007-28-9 0.08 na na –

Dicamba Herbicide 38442 1918-00-9 0.036 HAL-US 4,000 2

–

Dichlorprop Herbicide 49302 120-36-5 0.028 na na –

Dinoseb (Dinitrobutyl phenol) Herbicide 49301 88-85-7 0.038 MCL-CA 7 2

–

Diphenamid Herbicide 04033 957-51-7 0.010 HAL-US 200 –

Diuron Herbicide 49300 330-54-1 0.015 HAL-US 10 –

Fenuron Herbicide 49297 101-42-8 0.019 na na –

Flumetsulam Herbicide 61694 98967-40-9 0.040 na na 2

–

Fluometuron Herbicide 38811 2164-17-2 0.016 HAL-US 90 –

Hydroxyatrazine (2-Hydroxy-4-

isopropylamino-6-ethylaminos-triazine)

Degradate 50355 2163-68-0 0.032 na na –

3-Hydroxycarbofuran Degradate 49308 16655-82-6 0.008 na na –

Imazaquin Herbicide 50356 81335-37-7 0.036 na na –

Imazethapyr Herbicide 50407 81335-77-5 0.038 na na –

Imidacloprid Insecticide 61695 138261-41-3 0.020 na na 2

–

Linuron Herbicide 38478 330-55-2 0.014 na na –
Table 3F 33

Constituent

(common name)

Primary use 

or source

USGS 

parameter 

code

CAS 

number

 LRL

(μg/L)

Threshold 

type

Threshold 

(μg/L) Detection

MCPA (2-Methyl-4-

chlorophenoxyacetic acid) 

Herbicide 38482 94-74-6 0.030 HAL-US 30 –

MCPB (4-(2-Methyl-4-

chlorophenoxy) butyric acid)

Herbicide 38487 94-81-5 0.010 na na 2

–

Metalaxyl Fungicide 50359 57837-19-1 0.012 na na D

Methiocarb Insecticide 38501 2032-65-7 0.010 na na –

Methomyl Insecticide 49296 16752-77-5 0.020 HAL-US 200 –

Metsulfuron methyl1 Herbicide 61697 74223-64-6 0.025 na na 2

–

Neburon Herbicide 49294 555-37-3 0.012 na na –

Nicosulfuron Herbicide 50364 111991-09-4 0.04 na na –

Norflurazon Herbicide 49293 27314-13-2 0.020 na na –

Oryzalin Herbicide 49292 19044-88-3 0.012 na na –

Oxamyl Insecticide 38866 23135-22-0 0.030 MCL-CA 50 –

Picloram Herbicide 49291 1918-02-01 0.032 MCL-US 500 2

–

Propham Herbicide 49236 122-42-9 0.030 HAL-US 100 –

Propiconazole Fungicide 50471 60207-90-1 0.010 na 70 –

Propoxur Insecticide 38538 114-26-1 0.008 na na –

Siduron Herbicide 38548 1982-49-6 0.020 na na –

Sulfometuron-methyl Herbicide 50337 74222-97-2 0.038 na na –

Tebuthiuron Herbicide 82670 34014-18-1 0.026 HAL-US 500 D

Terbacil Herbicide 04032 5902-51-2 0.016 HAL-US 90 –

Triclopyr Herbicide 49235 55335-06-3 0.026 na na 2

–

1

Although listed as an LRL, these constitiuents are reported using method reporting levels (MRL).

2The median matrix-spike recovery was less than 70 percent. Low recoveries may indicate that the compound might not have been detected in some samples 

if it was present at very low concentrations.

Table 3F. Polar pesticides and pesticide degradates, primary uses or sources, comparative thresholds, and reporting information for 

the U.S. Geological Survey National Water Quality Laboratory Schedule 2060.—Continued

[The five-digit U.S. Geological Survey (USGS) parameter code is used to uniquely identify a specific constituent or property. Thresholds and threshold values 

as of October 29, 2007. Threshold type: Maximum contaminant level thresholds are listed as MCL-US when the MCL-US and MCL-CA are identical, and as 

MCL-CA when the MCL-CA is lower than the MCL-US or no MCL-US exists. HAL-US, U.S. Environmental Protection Agency Lifetime Health Advisory; 

MCL-CA, California Department of Public Health maximum contaminant level; MCL-US, U.S. Environmental Protection Agency maximum contaminant level; 

RSD5-US, U.S. Environmental Protection Agency risk specific dose at a risk factor of 10-5. Abbreviations: CAS, Chemical Abstract Service; LRL, laboratory 

reporting level; D, detected in ground-water sample (table 6); na, not available; μg/L, microgram per liter; –, not detected]
34 Ground-Water Quality Data in the Santa Clara River Valley Study Unit, 2007: Results from the California GAMA Program

Table 3G. Nutrients and dissolved organic carbon, comparative thresholds, and reporting information for the U.S. Geological Survey 

National Water Quality Laboratory Schedule 2755, laboratory code 2612, and perchlorate (constituent of special interest) analyzed at the 

Montgomery Watson-Harza Laboratory.

[The five-digit U.S. Geological Survey (USGS) parameter code is used to uniquely identify a specific constituent or property. Thresholds and threshold values 

as of October 29, 2007. Threshold type: Maximum contaminant level thresholds are listed as MCL-US when the MCL-US and MCL-CA are identical, and as 

MCL-CA when the MCL-CA is lower than the MCL-US or no MCL-US exists. HAL-US, U.S. Environmental Protection Agency Lifetime Health Advisory; 

MCL-CA, California Department of Public Health maximum contaminant level; MCL-US, U.S. Environmental Protection Agency maximum contaminant 

level. Abbreviations: CAS, Chemical Abstract Service; LRL, laboratory reporting level; D, detected in ground-water sample (table 9); na, not available; mg/L, 

milligram per liter; –, not detected]

Constituent

(common name)

USGS 

parameter 

code

CAS 

number

 LRL 

(mg/L)

Threshold 

type

Threshold 

value 

(mg/L)

Detection

Nutrients and dissolved organic carbon

Ammonia 00608 7664-41-7 0.010 HAL-US 1

25 D

Nitrite (as nitrogen) 00613 14797-65-0 0.002 MCL-US 1 D

Nitrate plus nitrite (as nitrogen) 00631 na 0.060 MCL-US 10 D

Total nitrogen (ammonia, nitrite, nitrate, organic nitrogen) 62854 17778-88-0 0.06 na na D

Phosphorus, phosphate, orthophosphate (as phosphorus) 00671 14265-44-2 0.006 na na D

Dissolved organic carbon (DOC) 00681 na 0.33 na na D

Constituent of special interst

Perchlorate 61209 14797-73-0 0.5 MCL-CA 6 D

1 In earlier reports in this series, the HAL-US of 30 mg/L was used as the comparison threshold; however, ammonia “as NH3” was used for that comparison.
Table 3H 35

Table 3H. Major and minor ions and trace elements, comparative thresholds, and reporting information for the U.S. Geological Survey 

National Water Quality Laboratory Schedule 1948.

[The five-digit U.S. Geological Survey (USGS) parameter code is used to uniquely identify a specific constituent or property. Thresholds and threshold values 

as of October 29, 2007. Threshold type: SMCL-CA, California Department of Public Health secondary maximum contaminant level; Maximum contaminant 

level thresholds are listed as MCL-US when the MCL-US and MCL-CA are identical, and as MCL-CA when the MCL-CA is lower than the MCL-US or no 

MCL-US exists. HAL-US, U.S. Environmental Protection Agency Lifetime Health Advisory; MCL-CA, California Department of Public Health maximum 

contaminant level; MCL-US, U.S. Environmental Protection Agency maximum contaminant level; AL-US, U.S. Environmental Protection Agency action level. 

Abbreviations: CAS, Chemical Abstract Service; LRL, laboratory reporting level; D, detected in ground-water sample (tables 10 and 11); na, not available; 

mg/L, milligram per liter; μg/L, microgram per liter; –, not detected] 

Constituent

USGS 

parameter 

code

CAS 

number LRL Threshold type

Threshold 

value Detection

Major and minor ions (mg/L)

Bromide 71870 24959-67-9 0.02 na na D

Calcium 00915 7440-70-2 0.02 na na D

Chloride 00940 16887-00-6 0.2 SMCL-CA 1

250 (500) D

Fluoride 00950 16984-48-8 0.10 MCL-CA 2 D

Iodide 78165 7553-56-2 0.002 na na D

Magnesium 00925 7439-95-4 0.008 na na D

Potassium 00935 7440-09-7 0.16 na na D

Silica 00955 7631-86-9 0.04 na na D

Sodium 00930 7440-23-5 0.20 na na D

Sulfate 00945 14808-79-8 0.18 SMCL-CA 1

250 (500) D

Residue on evaporation (total dissolved solids, 

TDS)

70300 na 10 SMCL-US 1

500 (1,000) D

Trace elements (μg/L)

Aluminum 01106 7429-90-5 1.6 MCL-CA 1,000 D

Antimony 01095 7440-36-0 0.2 MCL-US 6 D

Arsenic 01000 7440-38-2 0.12 MCL-US 10 D

Barium 01005 7440-39-3 0.2 MCL-CA 1,000 D

Beryllium 01010 7440-41-7 0.06 MCL-US 4 –

Boron 01020 7440-42-8 8 NL-CA 1,000 D

Cadmium 01025 7440-43-9 0.04 MCL-US 5 D

Chromium 01030 7440-47-3 0.04 MCL-CA 50 D

Cobalt 01035 7440-48-4 0.04 na na D

Copper 01040 7440-50-8 0.4 AL-US 1,300 D

Iron 01046 7439-89-6 6 SMCL-CA 300 D

Lead 01049 7439-92-1 0.08 AL-US 15 D

Lithium 01130 7439-93-2 0.6 na na D

Manganese 01056 7439-96-5 0.2 SMCL-CA 50 D

Molybdenum 01060 7439-98-7 0.4 HAL-US 40 D

Nickel 01065 7440-02-0 0.06 MCL-CA 100 D

Selenium 01145 7782-49-2 0.08 MCL-US 50 D

Silver 01075 7440-22-4 0.20 SMCL-CA 100 D

Strontium 01080 7440-24-6 0.4 HAL-US 4,000 D

Thallium 01057 7440-28-0 0.04 MCL-US 2 D

Tungsten 01155 7440-33-7 0.06 na na D

Uranium 22703 7440-61-1 0.04 MCL-US 30 D

Vanadium 01085 7440-62-2 0.10 NL-CA 50 D

Zinc 01090 7440-66-6 0.6 HAL-US 2,000 D

1The recommended SMCL-CA thresholds for chloride, sulfate, and TDS are listed with the upper SMCL-CA thresholds in parentheses.
36 Ground-Water Quality Data in the Santa Clara River Valley Study Unit, 2007: Results from the California GAMA Program

Table 3I. Arsenic, chromium, and iron species, comparative thresholds, and reporting information for the U.S. Geological Survey Trace 

Metal Laboratory, Boulder, Colorado.

[The five-digit U.S. Geological Survey (USGS) parameter code is used to uniquely identify a specific constituent or property. Thresholds and threshold values 

as of October 29, 2007. Threshold type: Maximum contaminant level thresholds are listed as MCL-US when the MCL-US and MCL-CA are identical, and 

as MCL-CA when the MCL-CA is lower than the MCL-US or no MCL-US exists. MCL-CA, California Department of Public Health maximum contaminant 

level; MCL-US, U.S. Environmental Protection Agency maximum contaminant level; SMCL-CA, California Department of Public Health secondary maximum 

contaminant level. Abbreviations: CAS, Chemical Abstract Service; MDL, Method detection limit; na, not available; μg/L, micrograms per liter; D, detected in 

ground-water sample (table 12); –, not detected]

Constituent

USGS 

parameter 

code

CAS 

number

MDL 

(μg/L)

Threshold 

type

Threshold 

level 

(μg/L)

Detection

Arsenic(III) 99034 22569-72-8 1 na na –

Arsenic (total) 01000 7440-38-2 0.5 MCL-US 10 D

Chromium(VI) 01032 18540-29-9 1 na na D

Chromium (total) 01030 7440-47-3 1 MCL-CA 50 D

Iron(II) 01047 7439-89-6 2 na na D

Iron (total) 01046 7439-89-6 2 SMCL-CA 300 D
Table 3J 37

Table 3J. Isotopic and radioactive constituents, comparative thresholds, and reporting information for laboratories.

[The five-digit U.S. Geological Survey (USGS) parameter code is used to uniquely identify a specific constituent or property. Thresholds and threshold values 

as of October 29, 2007. Stable isotope ratios are reported in the standard delta notation (δ), the ratio of a heavier isotope to more common lighter isotope of

that element, relative to a standard reference material. Threshold type: Maximum contaminant level thresholds are listed as MCL-US when the MCL-US and 

MCL-CA are identical, and as MCL-CA when the MCL-CA is lower than the MCL-US or no MCL-US exists. MCL-CA, California Department of Public 

Health maximum contaminant level; MCL-US, U.S. Environmental Protection Agency maximum contaminant level. Abbreviations: CAS, Chemical Abstract 

Service; MRL, minimum reporting level; MU, method uncertainty; CSU, combined standard uncertainty; CV, critical value; SD, standard deviation; na, not 

available; pCi/L, picocurie per liter; SSMDC, sample specific minimum detectable concentration; D, detected in ground-water sample (tables 13 and 15); na, not 

available]

Constituent

USGS 

parameter 

code

CAS 

number

Reporting 

level 

type

Reporting 

level or 

uncertainty

Threshold 

type1

Threshold 

value Detection

Stable isotope ratios (per mil)

δ2

H of water1 82082 na MU 2 na na D

δ18O of water1 82085 na MU 0.20 na na D

δ15N of nitrate1 82690 na MU 0.30 na na D

δ18O of nitrate1 63041 na MU 0.50 na na D

δ13C of dissolved carbonates2 82081 na 1 sigma 0.05 na na D

δ37Cl in water2 na na MU SD na na D

δ81Br in water2 na na MU SD na na D

Radioactive constituents (percent modern)

Carbon-143 49933 14762-75-5 1 sigma 0.0015 na na D

Radioactive constituents (pCi/L)

Radon-2224 82303 14859-67-7 SSMDC CSU and CV Proposed 

MCL-US

5

 300 (4,000) D

Tritium6,7 07000 10028-17-8 MRL 1 MCL-CA 20,000 D

Gross-alpha radioactivity, 72 hr count8 99920 12587-46-1 SSMDC CSU and CV MCL-US 15 D

Gross-alpha radioactivity, 30 day 

count8

99921 12587-46-1 SSMDC CSU and CV MCL-US 15 D

Gross-beta radioactivity, 72 hour count8 99922 12587-47-2 SSMDC CSU and CV MCL-CA 50 D

Gross-beta radioactivity, 30 day count8 99923 12587-47-2 SSMDC CSU and CV MCL-CA 50 D

Radium-2268 99915 13982-63-3 SSMDC CSU and CV MCL-US 9 5 D

Radium-2288 99916 15262-20-1 SSMDC CSU and CV MCL-US 9 5 D

 1 USGS Stable Isotope Laboratory, Reston, Virginia.

2University of Waterloo (contract laboratory).

3University of Arizona, Accelerator Mass Spectrometry Laboratory (contract laboratory).

4USGS National Water Quality Laboratory.

5Two MCLs have been proposed for radon-222. The proposed alternative MCL is given in parentheses.

6USGS Stable Isotope and Tritium Laboratory, Menlo Park, California.

7Lawrence Livermore National Laboratory.

8Eberline Analytical Services (contract laboratory).

9The MCL-US threshold for radium is the sum of radium-226 and radium-228 thresholds.
38 Ground-Water Quality Data in the Santa Clara River Valley Study Unit, 2007: Results from the California GAMA Program

Table 3K. Noble gases and tritium, comparison thresholds, and reporting information for the Lawrence Livermore National Laboratory.

[The five-digit U.S. Geological Survey (USGS) parameter code is used to uniquely identify a specific constituent or property. Thresholds and threshold values 

as of October 29, 2007. Threshold type: Maximum contaminant level thresholds are listed as MCL-US when the MCL-US and MCL-CA are identical, and as 

MCL-CA when the MCL-CA is lower than the MCL-US or no MCL-US exists. MCL-CA, California Department of Public Health maximum contaminant level; 

MCL-US, U.S. Environmental Protection Agency maximum contaminant level. Abbreviations: CAS, Chemical Abstract Service; MU, method uncertainty; na, 

not available; cm3 STP/g, cubic centimeters of gas at standard temperature and pressure per gram of water; pCi/L, picocurie per liter; D, detected in groundwater sample (table 14)]

Constituent

USGS 

parameter 

code

CAS 

number

MU 

(percent)

Reporting 

units

Threshold 

type

Threshold 

value 

(pCi/L)

Detection

Helium-3 / Helium-4 ratio 61036 na / 7440-59-7 0.75 atom ratio na na D

Argon 85563 7440-37-1 2 cm3

STP/g na na D

Helium-4 85561 7440-59-7 2 cm3

STP/g na na D

Krypton 85565 7439-90-9 2 cm3

STP/g na na D

Neon 61046 7440-01-09 2 cm3

STP/g na na D

Xenon 85567 7440-63-3 2 cm3

STP/g na na D

Tritium 07000 10028-17-8 1 pCi/L MCL-CA 20,000 D

Table 3L. Microbial constituents, comparison thresholds, and reporting information for the U.S. Geological Survey Ohio Microbiology 

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

[The five-digit U.S. Geological Survey (USGS) parameter code is used to uniquely identify a specific constituent or property. Thresholds and threshold values 

as of October 29, 2007. Threshold type: Maximum contaminant level thresholds are listed as MCL-US when the MCL-US and MCL-CA are identical, and as 

MCL-CA when the MCL-CA is lower than the MCL-US or no MCL-US exists. MCL-CA, California Department of Public Health maximum contaminant level; 

MCL-US, U.S. Environmental Protection Agency maximum contaminant level; TT-US, U.S. Environmental Protection Agency treatment technique - a required 

process intended to reduce the level of contamination in drinking water. Abbreviations: MDL, Method detection limit; mL, milliliter; D, detected in groundwater sample (table 16); na, not available; –, not detected]

Constituent

USGS 

parameter 

code

Primary source MDL

Threshold

Detection

Type Value

Escherichia coli 1 90901 Sewage and animal 

waste indicator

1 colony/100 mL TT-US Zero –

Total coliform - including 

fecal coliform and 

E. coli) 1

90900 Sewage and animal 

waste indicator

1 colony/100 mL MCL-US 5 percent of samples 

positive per month

D

F-specific coliphage 99335 Sewage and animal 

waste indicator

na TT-US 99.99 percent killed / 

inactivated

–

Somatic coliphage 99332 Sewage and animal 

waste indicator

na TT-US 99.99 percent killed / 

inactivated

–

1Analyzed in the field.
Table 4 39

GAMA 

identification no.

Turbidity 

(NTU) 

(63676)

Dissolved 

oxygen 

(mg/L) 

(00300) 

Water 

temperature 

(oC) 

(00010)

pH, lab 

(standard 

units) 

(00403)

pH, field 

(standard 

units) 

(00400)

Specific 

conductance, 

lab 

(μS/cm at 

25oC) 

(90095)

Specific 

conductance, 

field 

(μS/cm at 

25oC) 

(00095)

Alkalinity, 

lab 

(mg/L as 

CaCO3

)

(29801)

Alkalinity,

dissloved, 

field 

(mg/L as 

CaCO3

) 

(29802)

Threshold type TT-US na na SMCL-US SMCL-US SMCL-CA1 SMCL-CA1 na na

Threshold level 1 na na 6.5–8.5 6.5–8.5 900 (1,600) 900 (1,600) na na

Grid wells

SCRV-01 nc < 0.2 22.0 nc 7.7 nc *1,180 nc nc

SCRV-02 nc < 0.2 23.5 nc 7.6 nc 834 nc nc

SCRV-03 0.1 0.4 23.5 7.8 7.7 *924 895 258 250

SCRV-04 nc 5.0 18.5 7.2 7.0 *967 820 240 nc

SCRV-05 nc 4.1 18.0 nc 7.0 nc *1,010 nc nc

SCRV-06 nc 0.3 18.0 7.4 7.2 ** 1,890 **1,710 259 nc

SCRV-07 0.1 5.9 17.5 7.4 6.8 856 835 196 186

SCRV-08 nc < 0.2 25.5 nc 7.5 nc *1,030 nc nc

SCRV-09 nc < 0.2 19.0 7.3 7.1 ** 2,090 **2,040 287 nc

SCRV-10 0.1 < 0.2 20.0 7.7 7.6 * 1,120 *1,130 202 197

SCRV-11 nc 0.2 21.5 nc 7.5 nc * 919 nc nc

SCRV-12 0.2 0.3 21.0 7.8 7.6 * 1,180 *1,180 203 197

SCRV-13 nc 2.7 20.0 nc 7.4 nc *1,540 nc nc

SCRV-14 nc 1.8 23.0 nc 7.4 nc *1,150 nc nc

SCRV-15 nc 0.4 18.0 nc 7.3 nc *1,370 nc nc

SCRV-16 nc < 0.2 17.0 7.4 7.5 * 1,370 *1,290 229 nc

SCRV-17 nc 2.6 17.0 nc 7.1 nc *1,010 nc nc

SCRV-18 nc 0.7 19.5 nc 7.2 nc *1,430 nc nc

SCRV-19 nc 7.3 17.0 7.5 7.3 * 1,260 *1,190 202 nc

SCRV-20 nc 0.8 29.0 nc 7.8 nc 576 nc nc

SCRV-21 nc 0.5 24.5 nc 7.6 nc 607 nc nc

SCRV-22 nc 0.5 24.0 nc 7.5 nc 704 nc nc

SCRV-23 nc < 0.2 16.0 nc 7.6 nc 684 nc nc

SCRV-24 nc 1.1 22.0 nc 7.4 nc *1,530 nc nc

SCRV-25 nc 7.2 18.0 nc 7.7 nc 498 nc nc

SCRV-26 nc 2.2 20.0 nc 7.5 nc *1,100 nc nc

SCRV-27 nc 0.3 20.0 7.5 7.4 ** 1,660 **1,620 239 nc

SCRV-28 nc 3.2 20.0 7.3 7.1 * 1,590 *1,540 263 nc

SCRV-29 nc E 3.4 17.5 nc 7.3 nc *1,230 nc nc

SCRV-30 nc 3.0 18.0 nc 7.4 nc 890 nc nc

SCRV-31 nc 6.1 18.0 nc 7.4 nc * 996 nc nc

SCRV-32 nc < 0.2 22.0 nc 7.0 nc **2,020 nc nc

SCRV-33 nc 2.6 20.5 7.3 7.0 ** 2,930 **2,770 308 nc

SCRV-34 nc 0.7 21.0 nc 7.3 nc 722 nc nc

SCRV-35 0.2 7.7 21.5 7.2 7.0 ** 2,500 **2,390 262 251

SCRV-36 nc 3.0 19.0 nc 7.4 nc *1,040 nc nc

SCRV-37 nc < 0.2 22.0 7.6 7.5 ** 1,910 **1,880 278 nc

SCRV-38 nc 0.2 23.0 nc 7.2 nc 866 nc nc

SCRV-39 nc < 0.2 20.5 7.3 nc ** 2,060 **2,040 307 nc

SCRV-40 nc nc nc nc nc nc nc nc nc

SCRV-41 nc 4.0 17.0 nc nc nc *1,360 nc nc

SCRV-42 nc 4.6 16.5 nc 7.6 * 1,160 *1,090 194 nc

Table 4. Water-quality indicators in samples collected for the Santa Clara River Valley Groundwater Ambient Monitoring and 

Assessment (GAMA) study, California, April to June 2007.

[The five digit number below the constituent name is the U.S. Geological Survey parameter code used to uniquely identify a specific constituent or property. 

Thresholds and threshold values as of October 29, 2007. Threshold type: SMCL-US, U.S. Environmental Protection Agency secondary maximum contaminant 

level; TT-US, U.S. Environmental Protection Agency treatment technique - a required process intended to reduce the level of contamination in drinking water. 

GAMA identification No.: SCRV, Santa Clara River Valley study unit grid well; SCRVU, Santa Clara River Valley study unit understanding well; DD, depth 

dependent sample. Abbreviations: °C, degree Celsius; mg/L, milligram per liter; nc, constituent not collected; na, not available; NTU, nephelometric turbidity 

unit; μS/cm, microsiemens per centimeter; CaCO3, calcium carbonate; <, less than]
40 Ground-Water Quality Data in the Santa Clara River Valley Study Unit, 2007: Results from the California GAMA Program

GAMA 

identification no.

Turbidity 

(NTU) 

(63676)

Dissolved 

oxygen 

(mg/L) 

(00300) 

Water 

temperature 

(oC) 

(00010)

pH, lab 

(standard 

units) 

(00403)

pH, field 

(standard 

units) 

(00400)

Specific 

conductance, 

lab 

(μS/cm at 

25oC) 

(90095)

Specific 

conductance, 

field 

(μS/cm at 

25oC) 

(00095)

Alkalinity, 

lab 

(mg/L as 

CaCO3

)

(29801)

Alkalinity,

dissolved, 

field 

(mg/L as 

CaCO3

) 

(29802)

Threshold type TT-US na na SMCL-US SMCL-US SMCL-CA1 SMCL-CA1 na na

Threshold level 1 na na 6.5–8.5 6.5–8.5 900 (1,600) 900 (1,600) na na

Understanding wells

SCRVU-01 0.4 1.1 18.5 7.5 7.0 *1,370 *1,260 213 207

SCRVU-02 0.6 < 0.2 23.0 7.3 7.2 **1,920 **1,870 237 222

SCRVU-03 0.4 7.9 15.5 7.7 7.6 *1,540 *1,510 222 220

SCRVU-04 0.2 < 0.2 24.5 7.7 7.6 **1,780 **1,760 316 315

 DD-01 nc nc 24.0 7.8 7.6 **1,890 **1,860 333 nc

 DD-02 nc nc 26.5 7.8 7.7 **1,980 **1,980 353 nc

 DD-03 nc nc 26.0 8.0 7.8 **2,680 **2,660 532 nc

 DD-04 nc nc 24.5 8.0 8.4 **2,910 **2,880 578 nc

SCRVU-05 nc 5.1 17.5 nc 7.4 nc 888 nc nc

SCRVU-06 nc < 0.2 23.0 7.7 7.4 *1,150 *1,120 238 nc

SCRVU-07 nc < 0.2 21.0 6.9 7.1 **16,600 **16,900 146 nc

SCRVU-08 nc < 0.2 23.0 7.1 6.9 **14,200 **14,300 199 nc

SCRVU-09 nc 0.2 23.0 7.5 7.3 **12,600 **13,100 284 nc

SCRVU-10 nc 0.4 19.0 7.0 7.2 **44,000 **44,800 165 nc

SCRVU-11 nc nc 26.0 7.3 nc **1,730 **1,840 276 nc

1The SMCL-CA for specific conductance has recommended and upper threshold values. The upper value is shown in parentheses.

*Value exceeds recommended threshold.

**Value exceeds upper threshold.

Table 4. Water-quality indicators in samples collected for the Santa Clara River Valley Groundwater Ambient Monitoring and 

Assessment (GAMA) study, California, April to June 2007.—Continued

[The five digit number below the constituent name is the U.S. Geological Survey parameter code used to uniquely identify a specific constituent or property. 

Thresholds and threshold values as of October 29, 2007. Threshold type: SMCL-US, U.S. Environmental Protection Agency secondary maximum contaminant 

level; TT-US, U.S. Environmental Protection Agency treatment technique - a required process intended to reduce the level of contamination in drinking water. 

GAMA identification No.: SCRV, Santa Clara River Valley study unit grid well; SCRVU, Santa Clara River Valley study unit understanding well; DD, depth 

dependent sample. Abbreviations: °C, degree Celsius; mg/L, milligram per liter; nc, constituent not collected; na, not available; NTU, nephelometric turbidity 

unit; μS/cm, microsiemens per centimeter; CaCO3, calcium carbonate; <, less than]
Table 5 41

GAMA 

identification 

no.

Trihalomethane Solvent

Chloroform

(trichloromethane) 

(μg/L) 

(32106)

Bromodichlomethane 

(μg/L) 

(32101)

Dibromochloromethane 

(μg/L) 

(32105)

Bromoform

(Tribromomethane 

(μg/L) 

(32104)

Perchloroethene

(PCE)

 (μg/L) 

(34475)

1,1,1-

Trichloroethane 

(TCA) 

(μg/L) 

(34506)

Carbon

tetrachloride

(Tetrachloromethane) 

(μg/L) 

(32102)

Dibromomethane 

(μg/L) 

(30217)

trans-1,2-

Dichloroethene

(trans-1,2-

DCE)

(μg/L)

 (34546)

LRL [0.04] [0.04] [0.12] [0.08] [0.04] [0.04] [0.08] [0.04] [0.018]

Threshold type MCL-US MCL-US MCL-US MCL-US MCL-US MCL-US MCL-CA na MCL-CA

Threshold level 1

80 180 180 180 5 200 0.5 na 10

Grid wells

SCRV-03 – – – – – – – – –

SCRV-06 E 0.02 – – – – – – – –

SCRV-10 – – – – E 0.02 – – – –

SCRV-12 – 0.07 0.2 0.31 – – – – –

SCRV-13 0.26 – – – E 0.09 – E 0.07 – 0.12

SCRV-15 E 0.05 – – – – – – – –

SCRV-17 E 0.04 – – – – E 0.06 – – –

SCRV-19 – – – – – – – – –

SCRV-20 – – – – – – – – –

SCRV-25 1.87 3.98 7.3 4.74 – – – 0.22 –

SCRV-33 3.88 – – – – – – – –

SCRV-35 – – – – 0.15 – – – –

SCRV-37 – – – – – – – – –

SCRV-42 E 0.06 – – – – – – – –

Number of detections 7 2 2 2 3 1 1 1 1

Detection frequency 

(percent) for grid wells

17 4.8 4.8 4.8 7.1 2.4 2.4 2.4 2.4

Understanding wells

SCRVU-05 E 0.03 0.12 0.3 0.6 – – – – –

SCRVU-06 E 0.01 – – – – – – – –

SCRVU-07 – – – – – – – – –

SCRVU-08 – – – – – – – – –

SCRVU-09 – – – – – – – – –

SCRVU-10 – – – – – – – – –

Table 5. Volatile organic compounds (VOC), including gasoline oxygenates and degradates, detected in samples collected for the 

Santa Clara River Valley Groundwater Ambient Monitoring and Assessment (GAMA) study, California, April to June 2007.

[The five-digit number in parentheses below the constituent name is the U.S. Geological Survey parameter code used to uniquely identify a specific constituent 

or property. Thresholds and threshold values as of October 29, 2007. Samples from all grid and understanding wells were analyzed, but only samples with 

detections are listed. Analytes are listed in order of decreasing detection frequency in the 14 grid wells. Threshold type: Maximum contaminant level thresholds 

are listed as MCL-US when the MCL-US and MCL-CA are identical, and as MCL-CA when the MCL-CA is lower than the MCL-US or no MCL-US exists. 

HAL-US, U.S. Environmental Protection Agency Lifetime Health Advisory; MCL-CA, California Department of Public Health maximum contaminant level; 

MCL-US, U.S. Environmental Protection Agency maximum contaminant level; NL-CA, California Department of Public Health notification level. GAMA 

identification No.: SCRV, Santa Clara River Valley study unit grid well; SCRVU, Santa Clara River Valley study unit understanding well. Abbreviations: LRL, 

laboratory reporting level; E, estimated value; V, analyte detected in sample and an associated blank; thus, result is not considered a detection in ground-water 

quality assessment; μg/L, microgram per liter; –, not detected]
42 Ground-Water Quality Data in the Santa Clara River Valley Study Unit, 2007: Results from the California GAMA Program

GAMA

identification 

no.

Solvent Gasoline oxygenate Refrigerant Organic synthesis

VOC 

detections 

per well

Trichloroethene 

(TCE) 

(μg/L) 

(39180)

Tetrahydrofuran 

(μg/L) 

(81607)

Toluene 

(μg/L) 

(34010)

Benzene 

(μg/L) 

(34030)

m-Xylene 

plus pxylene 

(μg/L) 

(85795)

Trichlorofluoromethane 

(CFC-11) 

(μg/L) 

(34488)

Trichlorotrifluoroethane 

(CFC-113) 

(μg/L) 

(77652)

Carbon 

disulfide 

(μg/L) 

(77041)

Bromochloromethane

(μg/L)

 (77297)

LRL [0.02] [1] [0.018] [0.016] [0.08] [0.08] [0.04] [0.06] [0.06]

Threshold type1 MCL-US na MCL-CA MCL-CA MCL-CA MCL-CA MCL-CA NL-CA HAL-US

Threshold level 5 na 150 1 1,750 150 1,200 160 90

Grid wells

SCRV-03 – – – – – – – 0.31 – 1

SCRV-06 – – – – – – – – – 1

SCRV-10 – – 1.02 E 0.02 – – – 0.15 – 4

SCRV-12 – – – – – – – – – 3

SCRV-13 0.99 – – – – 12.9 31.3 – – 7

SCRV-15 – – – – – – – – – 1

SCRV-17 – – – – – – – – – 2

SCRV-19 – – – – – – E 0.05 – – 1

SCRV-20 – – – E 0.02 – – – – – 1

SCRV-25 – – – – E 0.03 – – – 0.18 7

SCRV-33 – – – – – – – – – 1

SCRV-35 – – – – – – – – – 1

SCRV-37 – – V 0.03 – – – – – – 0

SCRV-42 – – – – – – – – – 1

Number of detections 1 1 2 1 1 2 2 1

Detection frequency 

(percent) for grid wells

2.4 2.4 4.8 2.4 2.4 4.8 4.8 2.4 233

Understanding wells

SCRVU-05 – – – – – – – – –

SCRVU-06 – – V 0.02 – – – – – –

SCRVU-07 – 2 V 0.02 – – – – – –

SCRVU-08 – – V 0.02 – – – – – –

SCRVU-09 – – V 0.02 – – – – – –

SCRVU-10 – – V 0.03 – – – – – –

1The MCL-US threshold for trihalomethanes is the sum of the chloroform, bromoform, bromodichloromethane, and dibromochloromethane thresholds.

2Frequency of detection of at least one VOC in the grid wells. Detections with V remark codes are not included.

Table 5. Volatile organic compounds (VOC), including gasoline oxygenates and degradates, detected in samples collected for the 

Santa Clara River Valley Groundwater Ambient Monitoring and Assessment (GAMA) study, California, April to June 2007.—Continued

[The five-digit number in parentheses below the constituent name is the U.S. Geological Survey parameter code used to uniquely identify a specific constituent 

or property. Thresholds and threshold values as of October 29, 2007. Samples from all grid and understanding wells were analyzed, but only samples with 

detections are listed. Analytes are listed in order of decreasing detection frequency in the 14 grid wells. Threshold type: Maximum contaminant level thresholds 

are listed as MCL-US when the MCL-US and MCL-CA are identical, and as MCL-CA when the MCL-CA is lower than the MCL-US or no MCL-US exists. 

HAL-US, U.S. Environmental Protection Agency Lifetime Health Advisory; MCL-CA, California Department of Public Health maximum contaminant level; 

MCL-US, U.S. Environmental Protection Agency maximum contaminant level; NL-CA, California Department of Public Health notification level. GAMA 

identification No.: SCRV, Santa Clara River Valley study unit grid well; SCRVU, Santa Clara River Valley study unit understanding well. Abbreviations: LRL, 

laboratory reporting level; E, estimated value; V, analyte detected in sample and an associated blank; thus, result is not considered a detection in ground-water 

quality assessment; μg/L, microgram per liter; –, not detected]
Table 6 43

Table 6. Pesticides and pesticide degradates detected in samples collected for the Santa Clara River Valley Groundwater Ambient Monitoring and Assessment (GAMA) study, California, April to June 2007.[The five digit number in parentheses below the constituent name is the U.S. Geological Survey parameter code used to uniquely identify a specific constituent or property. Thresholds and threshold values as of October 29, 2007. Samples from the 42 grid wells and 11 understanding wells were analyzed. Threshold type: Maximum contaminant level thresholds are listed as MCL-US when the MCL-US and MCL-CA are identical, and as MCL-CA when the MCL-CA is lower than the MCL-US or no MCL-US exists. HAL-US, U.S. Environmental Protection Agency Lifetime Health Advisory; MCL-CA, California Department of Public Health maximum contaminant level; MCL-US, U.S. Environmental Protection Agency maximum contaminant level. GAMA identification No.: SCRV, Santa Clara River Valley study 

unit grid well; SCRVU, Santa Clara River Valley study unit understanding well. Abbreviations: E, estimated value; LRL, laboratory reporting level; mg/L, milligram per liter; na, not available; –, not detected]

GAMA identification no.

Simazine 

(μg/L) 

(04035)

Deethylatrazine 

(2-Chloro-4-

isopropylamino-6-

aminos-triazine) 

(μg/L) 

(04040)

Atrazine 

(μg/L) 

(39632)

Hexazinone 

(μg/L) 

(04025)

3,4-

Dichloroaniline 

(μg/L) 

(61625)

Desulfinylfipronil 

(μg/L) 

(62170)

Fipronil 

sulfide 

(μg/L) 

(62167)

Fipronil 

sulfone 

(μg/L) 

(62168)

Fipronil 

(μg/L) 

(62166)

Metolachlor

 (μg/L)

(39415)

Prometryn 

(μg/L) 

(04036)

Tebuthiuron 

(μg/L) 

(82670)

Metalaxyl 

(μg/L) 

(61596)

Pesticide 

detections 

per well

[LRL] [0.006] [0.014] [0.007] [0.026] [0.0045] [0.012] [0.013] [0.024] [0.016] [0.01] [0.0059] [0.016] [0.0069]Threshold type MCL-US na MCL-CA HAL-US na na na na na HAL-US na HAL-US na

Threshold level 4 na 1 400 na na na na na 700 na 500 na

Grid wells

SCRV-07 E 0.006 E 0.007 E 0.004 – – – – – – – – – – 3

SCRV-13 E 0.005 E 0.013 0.010 – – – – – – – – – – 3

SCRV-14 0.015 E 0.008 0.010 – – – – – – – – – – 3

SCRV-17 E 0.006 E 0.007 – – – – – – – – – – – 2

SCRV-23 E 0.007 – E 0.005 E 0.012 – – – – – – – – – 3

SCRV-25 0.010 E 0.006 E 0.005 E 0.009 E 0.006 E 0.006 E 0.008 E 0.005 E 0.005 E 0.007 – – – 10

SCRV-26 E 0.005 – – – – – – – – – – – – 1

SCRV-29 E 0.005 – – – – – – – – – – – – 1

SCRV-31 E 0.005 – – – – – – – – – – – – 1

SCRV-32 – E 0.006 – – – – – – – – – – – 1

SCRV-33 0.016 E 0.031 E 0.006 – – – – – – – – – – 3

SCRV-35 – E 0.018 – – – – – – – – – – – 1

SCRV-42 0.027 E 0.005 E 0.006 – – – – – – – E 0.005 E 0.02 – 5

Number of detections 11 9 7 2 1 1 1 1 1 1 1 1

Detection frequency (percent) 26 21 17 4.8 2.4 2.4 2.4 2.4 2.4 2.4 2.4 2.4 131

Understanding wells

SCRVU-02 E 0.005 – – – – – – – – – – – 0.010

SCRVU-03 0.008 – – – – – – – – – – – –

1Frequency of detecting at least one pesticide or pesticide degradate in grid wells.
44 Ground-Water Quality Data in the Santa Clara River Valley Study Unit, 2007: Results from the California GAMA Program Table 7. Potential wastewater-indicator compounds detected in samples collected for the Santa Clara River Valley Groundwater Ambient Monitoring and Assessment (GAMA) study, California, April to June 2007. [The five digit number in parentheses below the constituent name is the U.S. Geological Survey parameter code used to uniquely identify a specific constituent or property. Thresholds and threshold values as of October 29, 2007. Samples from the 42 grid wells and 11 understanding wells were analyzed. Threshold type: HAL-US, U.S. Environmental Protection Agency Lifetime Health Advisory. GAMA identification No.: SCRV, Santa Clara River Valley study unit grid well; SCRVU, Santa Clara River Valley study unit understanding well. Abbreviations: E, estimated value; LRL, laboratory reporting level; μg/L, micrograms per liter; na, not available; –, not detected] GAMA identification no. Cholesterol (μg/L) (62818) Bis(2- ethylhexyl) phthalate (μg/L) (39100) 4-Octylphenol diethoxylates (μg/L) (61705) Bisphenol A (μg/L) (62816) Indole (μg/L) (62824)) 2-Methyl- naph- thalene (μg/L) (30194) 4-tert- Octylphenol (μg/L) (62810) 4-Octyl- phenol monoetho- xylates (μg/L) (61706) Phenol (μg/L) (34694)

p-Cresol 

(μg/L) 

(77146)

Detections 

per well

LRL [0.8] [2] [0.32] [0.4] [0.2] [0.2] [0.2] [1] [0.2] [0.2]

Threshold type na na na na na na na na HAL-US na

Threshold level na na na na na na na na 2,000 na

Grid wells

SCRV-02 – 3 – – – – – – – – 1

SCRV-10 – – – 1.5 E 0.02 – – – – – 2SCRV-12 – – E 2 – – – E 0.3 E 0.5 – – 3

SCRV-16 – E 0.8 – – – – – – – – 1SCRV-22 E 0.7 – – – – – – – – – 1

SCRV-23 E 0.7 – – – – – – – – – 1

SCRV-26 E 0.8 – – E 0.2 – – – – – – 2SCRV-33 – E 1 – – – – – – – – 1SCRV-34 – – E 0.2 – – – – – – – 1SCRV-36 – – – – – E 0.03 – – – – 1

Number of detections 3 3 2 2 1 1 1 1

Detection frequency (percent) 7.1 7.1 4.8 4.8 2.4 2.4 2.4 2.4 124

Understanding wells

SCRVU-03 – 18 – – – – – – – – 1SCRVU-07 – – – E 0.08 – – – – E 0.2 E 0.04 3

1Frequency of detecting at least one potential wastewater-indicator compound in grid wells.
Table 8 45

Table 8. Constituent of special interest (perchlorate) detected in samples collected for the 

Santa Clara River Valley Groundwater Ambient Monitoring and Assessment (GAMA) study, 

California, April to June 2007.

[The five-digit number in parentheses below the constituent name is the U.S. Geological Survey parameter code 

used to uniquely identify a specific constituent or property. Thresholds and threshold values as of October 29, 

2007. Samples analyzed by the Montgomery Watson Harza laboratory (laboratory entity code CA-MWHL). 

Samples from all 53 wells were analyzed for perchlorate; only wells with a detection are listed. SCRV, Santa 

Clara River Valley study unit grid well; MRL, method reporting level; MCL-CA, California Department of Public 

Health maximum contaminant level; μg/L, microgram per liter]

GAMA

identification no.

Perchlorate 

(μg/L)

(61209)

Threshold type MCL-CA

Threshold level 6

MRL 0.5

Grid wells

SCRV-04 0.84

SCRV-13 3.0

SCRV-28 1.7

SCRV-35 4.2

SCRV-38 1.9

Number of wells with detections 5

Detection frequency (percent) 12
46 Ground-Water Quality Data in the Santa Clara River Valley Study Unit, 2007: Results from the California GAMA Program

GAMA

identification no.

Total nitrogen 

(ammonia + 

nitrite + nitrate 

+ organicnitrogen) 

as nitrogen 

(mg/L) 

(62854)

Phosphorus, 

phosphate, 

orthophosphate 

(as phosphorus) 

(mg/L)

 (00671)

Nitrite plus nitrate, 

as nitrogen 

(mg/L) 

(00631)

Ammonia, 

as nitrogen 

(mg/L) 

(00608)

Nitrite, 

as nitrogen 

(mg/L) 

(00613)

Dissolved 

organic carbon 

(DOC) 

(mg/L) 

(00681)

LRL [0.06] [0.006] [0.06] [0.02] [0.002] [0.4]

Threshold type na na MCL-US HAL-US MCL-US na

Threshold level na na 10 1

24.7 1 na

Grid wells

SCRV-03 0.25 0.047 – 0.214 – 0.7

SCRV-04 11.8 0.013 * 11.2 – – V 0.4

SCRV-06 13.5 0.048 * 12.9 – 0.006 1.2

SCRV-07 0.98 0.010 0.94 – – V 0.3

SCRV-09 0.12 0.046 – 0.070 – 1.5

SCRV-10 0.24 0.031 – 0.186 – 0.6

SCRV-12 0.69 0.034 E 0.04 0.610 – 0.8

SCRV-16 1.93 0.102 1.86 – 0.007 V 0.5

SCRV-19 2.80 0.052 2.71 – – 1.1

SCRV-27 3.13 0.035 3.09 E 0.012 0.074 1.0

SCRV-28 22.3 0.023 * 22.2 – – V 0.5

SCRV-33 15.9 0.044 * 15.2 – – 1.2

SCRV-35 12.7 0.027 * 12.4 – – 1.5

SCRV-37 1.55 0.040 – 1.33 E 0.001 1.5

SCRV-39 0.62 0.067 0.38 0.188 0.002 1.2

SCRV-42 2.24 0.071 2.10 – – 1.1

Understanding wells

SCRVU-01 2.16 0.031 2.07 – 0.006 0.9

SCRVU-02 0.40 0.037 – 0.308 – 1.6

SCRVU-03 2.38 0.071 2.34 – 0.005 1.4

SCRVU-04 1.14 0.040 – 1.01 – 1.4

SCRVU-06 0.99 0.033 – 0.855 0.004 0.8

SCRVU-07 6.21 0.058 – 5.88 0.003 4.8

SCRVU-08 3.48 0.061 – 3.73 – –

SCRVU-09 3.89 0.198 – 3.80 – –

SCRVU-10 2.99 0.066 – 3.31 0.002 –

SCRVU-11 1.16 0.027 – 0.991 – 1.5

1The HAL-US is 30 mg/L “as ammonia.” To facilitate comparison to the analytical results, we have converted and reported this HAL-US as 24.7 mg/L “as 

nitrogen.”

* Indicates value above or equal to the threshold level.

Table 9. Nutrients and dissolved organic carbon detected in samples collected for the Santa Clara River Valley Groundwater Ambient 

Monitoring and Assessment (GAMA) study, California, April to June 2007.

[The five digit number in parentheses below the constituent name is the U.S. Geological Survey parameter code used to uniquely identify a specific constituent 

or property. Thresholds and threshold values as of October 29, 2007. Samples from 17 intermediate wells and nine slow wells were analyzed, of which 16 were 

grid wells and 10 were understanding wells. Threshold type: Maximum contaminant level thresholds are listed as MCL-US when the MCL-US and MCL-CA 

are identical, and as MCL-CA when the MCL-CA is lower than the MCL-US or no MCL-US exists. HAL-US, U.S. Environmental Protection Agency Lifetime 

Health Advisory; MCL-CA, California Department of Public Health maximum contaminant level; MCL-US, U.S. Environmental Protection Agency maximum 

contaminant level. GAMA identification No.: SCRV, Santa Clara River Valley study unit grid well; SCRVU, Santa Clara River Valley study unit understanding 

well. Abbreviation: E, estimated value; V, analyte detected in sample and an associated blank; thus, result is not considered a detection in ground-water quality 

assessment; mg/L, milligram per liter; na, not available; –, not detected]
Table 10 47

Table 10. Major and minor ions and dissolved solids detected in samples collected for the Santa Clara River Valley Groundwater Ambient Monitoring and Assessment (GAMA) study, California, April to June 2007.[The five digit number in parenthesis below the constituent name is the U.S. Geological Survey parameter code used to uniquely identify a specific constituent or property. Thresholds and threshold values as of October 29, 2007. Samples from 17 intermediate wells and 9 slow wells were sampled, of which 16 were grid wells and 10 were understanding wells. The 4 depth dependent samples were analyzed. SMCL-CA, California Department of Public Health secondary maximum contaminant level; Maximum contaminant level thresholds are listed as MCL-US when the MCL-US and MCL-CA are identical, and as MCL-CA when the MCL-CA is lower than the MCL-US or no MCL-US exists. MCL-CA, California Department of Public Health maximum contaminant level; MCL-US, U.S. Environmental Protection Agency maximum contaminant level. GAMA identification No.: SCRV, Santa Clara River Valley study unit grid well; SCRVU, Santa Clara River Valley study unit understanding well; DD, depth dependent sample. Abbreviations: LRL, laboratory reporting level; mg/L, milligram per liter; E, estimated value; na, not available; –, not detected. Bicarbonate and carbonate concentrations were calculated from the alkalinity and pH values (table 4) using the advanced speciation method (http://or.water.usgs.gov/alk/methods.html) with pK1 = 6.35, pK2 = 10.33, and pKW = 14. pK1, equals -log10(K1), where K1 is the first acid 

dissociation constant of carbonic acid; pK2, equals -log10(K2), where K2 is the second acid dissociation constant of carbonic acid; pKw, equals -log(Kw), where Kw is the acid dissociation constant of water]

GAMA 

identification no.

Calcium 

(mg/L) 

(00915

Magnesium 

(mg/L) 

(00925) 

Potassium 

(mg/L) 

(00935)

Sodium 

(mg/L) 

(00930) 

Bicarbonate 

(mg/L)

Carbonate 

(mg/L)

Bromide 

(mg/L) 

(71870)

Chloride 

(mg/L) 

(00940) 

Fluoride 

(mg/L) 

(00950)

Iodide 

(mg/L) 

(71865)

Silica 

(mg/L) 

(00955)

Sulfate 

(mg/L) 

(00945)

Total 

dissolved 

solids (TDS) 

(mg/L) 

(70300)

[LRL] [0.02] [0.014] [0.04] [0.2] na na [0.02] [0.12] [0.1] [0.002] [0.018] [0.18] [10]

Threshold type1 na na na na na na na SMCL-CA1 MCL-CA na na SMCL-CA1 SMCL-CA1

Threshold level na na na na 1 1 na 250 (500) 2 na na 250 (500) 500 (1000)

Grid wells

SCRV-03 56.9 29.1 2.85 101 304 1 0.33 61.2 0.25 0.114 44.2 137 * 604

SCRV-04 136 31.4 1.13 31.8 292 – 0.06 13.9 0.35 – 22.9 225 * 681

SCRV-06 210 72.3 5.53 115 316 – 2.67 65.3 0.67 0.013 30.4 ** 673 ** 1,490

SCRV-07 108 26.6 1.94 39.7 227 – 0.07 23.7 0.57 – 15.8 227 * 596

SCRV-09 292 71.4 4.53 105 350 – 1.02 84.4 0.46 0.187 36.4 ** 811 ** 1,700

SCRV-10 118 33.6 4.61 81.8 239 – 0.25 37.2 0.67 0.04 34.8 * 343 * 818

SCRV-12 128 31.3 4.72 87.2 240 – 0.27 42.2 0.32 0.041 33.2 * 367 * 871

SCRV-16 138 45.1 4.14 96.4 279 – 0.2 39.3 0.69 0.027 30.6 * 448 ** 1,030

SCRV-19 128 44.4 4.48 81.6 247 – 0.23 50.1 0.85 0.003 25.8 * 387 * 924

SCRV-27 164 52.6 4.96 136 291 – 0.52 64.4 0.61 0.029 31.6 ** 572 ** 1,280

SCRV-28 206 55.7 1.95 67.8 321 – 0.28 51.2 0.6 0.002 22.4 * 483 ** 1,190

SCRV-33 261 85.8 5.25 271 375 – 1.15 240 0.31 0.018 39 ** 905 ** 2,250

SCRV-35 271 81.9 4.27 170 306 – 0.9 152 0.55 0.01 42.9 ** 893 ** 2,010

SCRV-37 118 40.8 8.17 205 339 – 2.61 * 433 0.31 0.715 39.6 39.5 ** 1,080

SCRV-39 198 64.8 6.03 187 373 – 0.94 88 0.6 0.125 33.7 ** 719 ** 1,580

SCRV-42 91.1 35.2 4.57 98.4 236 – 0.25 85.8 0.61 0.007 19.4 * 268 * 774
48 Ground-Water Quality Data in the Santa Clara River Valley Study Unit, 2007: Results from the California GAMA Program Table 10. Major and minor ions and dissolved solids detected in samples collected for the Santa Clara River Valley Groundwater Ambient Monitoring and Assessment (GAMA) study, California, April to June 2007.—Continued [The five digit number in parenthesis below the constituent name is the U.S. Geological Survey parameter code used to uniquely identify a specific constituent or property. Thresholds and threshold values as of October 29, 2007. Samples from 17 intermediate wells and 9 slow wells were sampled, of which 16 were grid wells and 10 were understanding wells. The 4 depth dependent samples were analyzed. SMCL-CA, California Department of Public Health secondary maximum contaminant level; Maximum contaminant level thresholds are listed as MCL-US when the MCL-US and MCL-CA are identical, and as MCL-CA when the MCL-CA is lower than the MCL-US or no MCL-US exists. MCL-CA, California Department of Public Health maximum contaminant level; MCL-US, U.S. Environmental Protection Agency maximum contaminant level. GAMA identification No.: SCRV, Santa Clara River Valley study unit grid well; SCRVU, Santa Clara River Valley study unit understanding well; DD, depth dependent sample. Abbreviations: LRL, laboratory reporting level; mg/L, milligram per liter; E, estimated value; na, not available; –, not detected. Bicarbonate and carbonate concentrations were calculated from the alkalinity and pH values (table 4) using the advanced speciation method (http://or.water.usgs.gov/alk/methods.html) with pK1 = 6.35, pK2 = 10.33, and pKW = 14. pK1, equals -log10(K1), where K1 is the first acid dissociation constant of carbonic acid; pK2, equals -log10(K2), where K2 is the second acid dissociation constant of carbonic acid; pKw, equals -log(Kw), where Kw is the acid dissociation constant of water] GAMA identification no. Calcium (mg/L) (00915) Magnesium (mg/L) (00925) Potassium (mg/L) (00935) Sodium (mg/L) (00930) Bicarbonate (mg/L) Carbonate (mg/L) Bromide (mg/L) (71870) Chloride (mg/L) (00940) Fluoride (mg/L) (00950) Iodide (mg/L) (71865) Silica (mg/L) (00955) Sulfate (mg/L) (00945) Total dissolved solids (TDS) (mg/L) (70300) [LRL] [0.02] [0.014] [0.04] [0.2] na na [0.02] [0.12] [0.1] [0.002] [0.018] [0.18] [10] Threshold type1 na na na na na na na SMCL-CA1 MCL-CA na na SMCL-CA1 SMCL-CA1 Threshold level na na na na 1 1 na 250 (500) 2 na na 250 (500) 500 (1000) Understanding wells SCRVU-01 140 48.2 4.50 101 253 – 0.43 45.5 0.76 0.012 30.1 * 461 ** 1,050 SCRVU-02 214 52.1 5.33 139 270 – 0.7 148 0.22 0.05 33.8 ** 586 ** 1,400 SCRVU-03 153 57.4 4.55 103 267 – 0.32 66.3 0.64 0.008 18.7 ** 518 ** 1,140 SCRVU-04 92.5 32.3 6.80 246 383 1 1.12 188 0.42 0.235 42.2 * 316 ** 1,150 DD-01 93.8 33.4 6.84 259 405 1 1.22 203 0.44 0.348 41.5 * 333 ** 1,220 DD-02 93.2 34.4 7.32 284 429 1 1.35 223 0.43 0.360 41.6 * 336 ** 1,270 DD-03 35.8 22.2 10.3 484 645 2 2.72 * 412 0.52 0.859 47.8 201 ** 1,570 DD-04 28.2 22.4 13.0 571 689 8 3.03 * 463 0.5 0.857 51.6 184 ** 1,700 SCRVU-06 76.7 31.3 6.88 117 290 – 0.54 94.7 0.37 0.105 36.7 214 * 713 SCRVU-07 1,700 707 28.8 539 179 – 43.7 ** 6,130 0.12 12.6 41.4 < 4.50 ** 11,200 SCRVU-08 799 425 25.8 1,660 242 – 16.9 ** 4,730 0.16 0.245 50.1 ** 635 ** 8,740 SCRVU-09 321 215 38.2 2,110 345 – 15.1 ** 4,060 0.43 0.647 23.4 * 330 ** 7,640 SCRVU-10 662 1,110 240 8,140 201 – 57.4 ** 16,100 0.18 0.213 34.3 ** 2,060 ** 30,000 SCRVU-11 70.7 40.0 7.98 220 337 – 1.32 232 0.34 0.335 51.2 247 ** 1,080

* Indicates value is above or equal to recommended threshold level.** Indicates value is above or equal to upper threshold level.1The SMCL-CA for chloride, sulfate, and total dissolved solids have recommended and upper threshold values. The upper value is shown in parentheses.
Table 11 49

Table 11. Trace elements detected in samples collected for the Santa Clara River Valley Groundwater Ambient Monitoring and Assessment (GAMA) study, California, April to June 2007.[The five digit number in parentheses below the constituent name is the U.S. Geological Survey parameter code used to uniquely identify a specific constituent or property. Thresholds and threshold values as of October 29, 2007. Samples from 17 intermediate wells and 9 slow wells were analyzed, of which 16 were grid wells and 10 were understanding wells. Threshold type: SMCL-CA, California Department of Public Health secondary maximum contaminant level; Maximum contaminant level thresholds are listed as MCL-US when the MCL-US and MCL-CA are identical, and as MCL-CA when the MCL-CA is lower than the MCL-US or no MCL-US exists. HAL-US, U.S. Environmental Protection Agency Lifetime Health Advisory; MCL-CA, California Department of Public Health maximum contaminant level; MCL-US, U.S. Environmental Protection Agency maximum contaminant level; AL-US, U.S. Environmental Protection Agency action level. GAMA identification No.: SCRV, Santa Clara River Valley study 

unit grid well; SCRVU, Santa Clara River Valley study unit understanding well; DD, depth dependent sample. Abbreviations: E, estimated value; LRL, laboratory reporting level; na, not available; μg/L, microgram per liter; –, not detected]

GAMA 

identification no.

Aluminum 

(μg/L) 

(01106) 

Antimony 

(μg/L) 

(01095) 

Arsenic 

(μg/L) 

(01000)

Barium 

(μg/L) 

(01005)

Boron 

(μg/L) 

(01020)

Cadmium 

(μg/L) 

(01025)

Chromium 

(μg/L) 

(01030)

Cobalt 

(μg/L) 

(01035) 

Copper 

(μg/L) 

(01040)

Iron 

(μg/L) 

(01046)

Lead 

(μg/L) 

(01049)

Lithium 

(μg/L) 

(01130

LRL [1.6] [0.06] [0.12] [0.08] [8] [0.04] [0.12] [0.04] [0.4] [6] [0.12] [0.6]

Threshold type MCL-CA MCL-US MCL-US MCL-CA NL-CA MCL-US MCL-CA na AL-US SMCL-CA AL-US na

Threshold level 1000 6 10 1,000 1,000 5 50 na 1,300 300 15 na

Grid wells

SCRV-03 – – 0.69 46 327 0.04 – – – 76 E 0.09 22.4

SCRV-04 – – E 0.07 54 29 E 0.02 0.12 – 0.93 9 1.13 18.7

SCRV-06 1.6 0.14 0.87 52 759 0.29 0.15 E 0.03 3.1 14 0.64 57.0

SCRV-07 – E 0.04 E 0.10 23 398 – 0.14 – 1.1 – 0.28 40.4

SCRV-09 – E 0.03 1.5 30 469 – – 0.06 – * 1,420 0.4 57.6

SCRV-10 2.6 – – 26 570 E 0.03 – – – * 906 – 33.0

SCRV-12 E 1.2 – 0.53 42 556 0.04 – E 0.03 – * 319 E 0.11 40.5

SCRV-16 E 0.9 0.06 0.55 21 616 0.31 – 0.18 0.53 E 3 0.35 35.5

SCRV-19 – 0.14 0.72 21 511 0.19 0.29 – E 1.1 E 3 E 0.1 28.9

SCRV-27 – – 0.71 21 478 0.20 – 0.08 2.3 44 1.28 48.8

SCRV-28 – E 0.03 E 0.10 45 159 0.04 0.17 0.04 0.75 30 E 0.11 39.1

SCRV-33 E 3.1 0.16 1.6 20 867 0.14 2.6 E 0.06 2.3 – 3.24 76.4

SCRV-35 – 0.11 0.79 16 978 0.09 2.3 E 0.03 2.1 – 0.52 64.6

SCRV-37 – E 0.03 0.18 131 690 – – E 0.03 E 0.26 * 330 – 57.0

SCRV-39 E 0.9 0.09 3.0 26 659 0.05 – 0.06 0.42 * 934 0.43 109

SCRV-42 – 0.10 0.66 25 506 0.05 0.25 0.26 1.6 8 – 29.0
50 Ground-Water Quality Data in the Santa Clara River Valley Study Unit, 2007: Results from the California GAMA Program Table 11. Trace elements detected in samples collected for the Santa Clara River Valley Groundwater Ambient Monitoring and Assessment (GAMA) study, California, April to June 2007.—Continued [The five digit number in parentheses below the constituent name is the U.S. Geological Survey parameter code used to uniquely identify a specific constituent or property. Thresholds and threshold values as of October 29, 2007. Samples from 17 intermediate wells and 9 slow wells were analyzed, of which 16 were grid wells and 10 were understanding wells. Threshold type: SMCL-CA, California Department of Public Health secondary maximum contaminant level; Maximum contaminant level thresholds are listed as MCL-US when the MCL-US and MCL-CA are identical, and as MCL-CA when the MCL-CA is lower than the MCL-US or no MCL-US exists. HAL-US, U.S. Environmental Protection Agency Lifetime Health Advisory; MCL-CA, California Department of Public Health maximum contaminant level; MCL-US, U.S. Environmental Protection Agency maximum contaminant level; AL-US, U.S. Environmental Protection Agency action level. GAMA identification No.: SCRV, Santa Clara River Valley study unit grid well; SCRVU, Santa Clara River Valley study unit understanding well; DD, depth dependent sample. Abbreviations: E, estimated value; LRL, laboratory reporting level; na, not available; μg/L, microgram per liter; –, not detected] GAMA identification no. Aluminum (μg/L) (01106) Antimony (μg/L) (01095) Arsenic (μg/L) (01000) Barium (μg/L) (01005) Boron (μg/L) (01020) Cadmium (μg/L) (01025) Chromium (μg/L) (01030) Cobalt (μg/L) (01035) Copper (μg/L) (01040) Iron (μg/L) (01046) Lead (μg/L) (01049) Lithium (μg/L) (01130) LRL [1.6] [0.06] [0.12] [0.08] [8] [0.04] [0.12] [0.04] [0.4] [6] [0.12] [0.6] Threshold type MCL-CA MCL-US MCL-US MCL-CA NL-CA MCL-US MCL-CA na AL-US SMCL-CA AL-US na Threshold level 1000 6 10 1,000 1,000 5 50 na 1,300 300 15 na Understanding wells SCRVU-01 – 0.26 0.96 22 610 0.24 E 0.11 0.06 1.3 7 0.31 44.0 SCRVU-02 E 0.9 E 0.03 0.92 63 459 0.04 – 0.04 – 137 E 0.06 45.1 SCRVU-03 – 0.23 1.2 26 744 0.21 E 0.1 0.06 2.7 13 0.55 41.5 SCRVU-04 3.1 – E 0.11 36 757 E 0.02 E 0.07 – – 128 – 48.3 DD-01 – – E 0.10 39 798 – E 0.07 E 0.03 – 106 – 53.3 DD-02 E 1.2 – E 0.07 40 859 – E 0.09 E 0.02 – 75 – 56.2 DD-03 – – E 0.16 71 * 1,470 – E 0.18 E 0.04 – 18 – 71.4 DD-04 – – 0.24 102 * 1,620 – E 0.22 E 0.04 – E 14 – 82.7 SCRVU-06 2.8 – 0.86 65 220 0.07 – 0.07 E 0.32 62 – 47.0 SCRVU-07 – – 1.2 * 2,730 565 E 0.2 – E 0.19 – * 7,960 – 208 SCRVU-08 – – – 156 689 – 1.8 – – – – 176 SCRVU-09 – – – 145 * 2,330 – – – – – – 150 SCRVU-10 – E 0.63 – 108 * 2,620 – E 2.4 – – * 10,200 – 198 SCRVU-11 E 1.2 – – 81 655 – – – – 17 – 59.0
Table 11 51

Table 11. Trace elements detected in samples collected for the Santa Clara River Valley Groundwater Ambient Monitoring and Assessment (GAMA) study, California, April to June 2007.—Continued[The five digit number in parentheses below the constituent name is the U.S. Geological Survey parameter code used to uniquely identify a specific constituent or property. Thresholds and threshold values as of October 29, 2007. Samples from 17 intermediate wells and 9 slow wells were analyzed, of which 16 were grid wells and 10 were understanding wells. Threshold type: SMCL-CA, California Department of Public Health secondary maximum contaminant level; Maximum contaminant level thresholds are listed as MCL-US when the MCL-US and MCL-CA are identical, and as MCL-CA when the MCL-CA is lower than the MCL-US or no MCL-US exists. HAL-US, U.S. Environmental Protection Agency Lifetime Health Advisory; MCL-CA, California Department of Public Health maximum contaminant level; MCL-US, U.S. Environmental Protection Agency maximum contaminant level; AL-US, U.S. Environmental Protection Agency action level. GAMA identification No.: SCRV, Santa Clara River Valley study 

unit grid well; SCRVU, Santa Clara River Valley study unit understanding well; DD, depth dependent sample. Abbreviations: E, estimated value; LRL, laboratory reporting level; na, not available; μg/L, microgram per liter; –, not detected]

GAMA 

identification no.

Manganese 

(μg/L) 

(01056) 

Molybdenum 

(μg/L) 

(01060) 

Nickel 

(μg/L) 

(01065) 

Selenium 

(μg/L) 

(01145)

Silver 

(μg/L) 

(01075) 

Strontium 

(μg/L) 

(01080)

Thallium 

(μg/L) 

(01057) 

Tungsten 

(μg/L) 

(01155)

Uranium 

(μg/L) 

(22703)

Vanadium 

(μg/L) 

(01085)

Zinc

(μg/L) 

(01090)

[LRL] [0.2] [0.12] [0.06] [0.08] [0.1] [0.4] [0.04] [0.06] [0.04] [0.04] [0.6]

Threshold type SMCL-CA HAL-US MCL-CA MCL-US SMCL-CA HAL-US MCL-US na MCL-US NL-CA SMCL-CA

Threshold level 50 40 100 50 100 4,000 2 na 30 50 5,000

Grid wells

SCRV-03 * 66.5 16.6 0.17 – – 510 – 0.06 0.06 0.08 –

SCRV-04 0.4 0.6 0.15 0.79 – 945 – – 1.19 0.36 21.4

SCRV-06 17.5 10.9 4.7 20.5 – 1,980 – E 0.05 17.3 3.2 9.9

SCRV-07 – 0.9 0.18 0.84 – 1,260 – E 0.05 0.86 0.45 11.0

SCRV-09 * 230 8.3 0.43 E 0.05 – 1,880 – E 0.04 6.06 0.07 3.5

SCRV-10 * 174 18.9 0.25 – – 926 – E 0.05 0.16 0.04 12.8

SCRV-12 * 188 15.5 0.16 – – 1,140 – 0.10 0.33 0.78 5.0

SCRV-16 *396 12.8 1.1 5.2 – 1,060 – E 0.04 6.78 2.8 3.6

SCRV-19 E 0.1 20.9 0.54 4.8 – 1,190 – – 7.49 3.0 4.3

SCRV-27 * 243 16.0 0.26 25.1 – 1,430 – E 0.04 5.61 2.0 3.7

SCRV-28 1.9 1.7 0.28 6.1 – 787 – – 6.76 0.53 15.1

SCRV-33 11.7 20.2 0.76 23.3 – 2,670 – – 26.8 7.2 8.5

SCRV-35 – 28.2 0.79 49.5 – 2,420 – – 23 7.8 13.7

SCRV-37 * 176 0.8 0.21 – – 1,280 – – 0.4 0.14 8.6

SCRV-39 * 253 26.2 0.39 2.1 – 1,420 – E 0.03 19.5 0.3 8.9

SCRV-42 0.5 10.5 2.9 1.9 – 726 – – 4.55 0.81 2.6
52 Ground-Water Quality Data in the Santa Clara River Valley Study Unit, 2007: Results from the California GAMA Program Table 11. Trace elements detected in samples collected for the Santa Clara River Valley Groundwater Ambient Monitoring and Assessment (GAMA) study, California, April to June 2007.—Continued [The five digit number in parentheses below the constituent name is the U.S. Geological Survey parameter code used to uniquely identify a specific constituent or property. Thresholds and threshold values as of October 29, 2007. Samples from 17 intermediate wells and 9 slow wells were analyzed, of which 16 were grid wells and 10 were understanding wells. Threshold type: SMCL-CA, California Department of Public Health secondary maximum contaminant level; Maximum contaminant level thresholds are listed as MCL-US when the MCL-US and MCL-CA are identical, and as MCL-CA when the MCL-CA is lower than the MCL-US or no MCL-US exists. HAL-US, U.S. Environmental Protection Agency Lifetime Health Advisory; MCL-CA, California Department of Public Health maximum contaminant level; MCL-US, U.S. Environmental Protection Agency maximum contaminant level; AL-US, U.S. Environmental Protection Agency action level. GAMA identification No.: SCRV, Santa Clara River Valley study unit grid well; SCRVU, Santa Clara River Valley study unit understanding well; DD, depth dependent sample. Abbreviations: E, estimated value; LRL, laboratory reporting level; na, not available; μg/L, microgram per liter; –, not detected] GAMA identification no. Manganese (μg/L) (01056) Molyb- denum (μg/L) (01060) Nickel (μg/L) (01065) Selenium (μg/L) (01145) Silver (μg/L) (01075) Strontium (μg/L) (01080 Thallium (μg/L) (01057) Tungsten (μg/L) (01155) Uranium (μg/L) (22703) Vanadium (μg/L) (01085) Zinc (μg/L) (01090) [LRL] [0.2] [0.12] [0.06] [0.08] [0.1] [0.4] [0.04] [0.06] [0.04] [0.04] [0.6] Threshold type SMCL-CA HAL-US MCL-CA MCL-US SMCL-CA HAL-US MCL-US na MCL-US NL-CA SMCL-CA Threshold level 50 40 100 50 100 4,000 2 na 30 50 5,000 Understanding wells SCRVU-01 5.5 17.0 0.42 10.3 – 1,330 – – 9.15 10 4.5 SCRVU-02 * 149 15.0 3.4 E 0.05 – 1,460 – – 3.99 0.25 2.2 SCRVU-03 0.6 20.4 0.77 4.1 – 1,470 – 0.07 11.8 1.6 3.0 SCRVU-04 27.6 8.4 0.07 – – 829 – 0.09 0.97 0.19 – DD-01 26.7 6.3 0.36 – – 840 E 0.03 0.10 0.78 0.14 – DD-02 23.9 5.6 0.4 – – 832 – 0.11 0.64 0.13 0.83 DD-03 3.8 E 0.2 0.2 – – 523 – 0.44 0.2 0.32 – DD-04 2.8 – E 0.1 – – 516 – 0.4 E 0.06 0.52 – SCRVU-06 * 155 7.6 0.41 – – 894 – 1.2 0.36 0.3 2.1 SCRVU-07 * 2,370 0.8 1.1 – 1.4 * 22,000 – E 0.35 – 0.51 6.4 SCRVU-08 * 186 – 0.60 1.9 na * 11,900 – – – 0.39 E 1.9 SCRVU-09 * 221 – 0.44 2.3 na * 5,490 – E 0.29 – 0.35 – SCRVU-10 * 784 10.0 E 0.91 – na * 10,700 – – – 1.4 – SCRVU-11 8.9 0.2 – E 0.05 – 1,110 – 0.06 0.04 0.05 –

*Indicates value is above or equal to threshold level.
Table 12 53

GAMA

identification no.

Iron

(μg/L) 

(01046)

Iron(II) 

(μg/L) 

(01047)

Arsenic 

(μg/L) 

(99033)

Arsenic(III) 

(μg/L) 

(99034)

Chromium 

(μg/L) 

(01030)

Chromium(VI) 

(μg/L) 

(01032)

Threshold type1 SMCL-CA na MCL-US na MCL-CA na

Threshold level 300 na 10 na 50 na

[MDL] [2] [2] [0.5] [1] [1] [1]

Grid wells

SCRV-03 74 74 <0.5 <1 <1 <1

SCRV-04 8 3 <0.5 <1 <1 <1

SCRV-06 17 5 <0.5 <1 <1 <1

SCRV-07 5 <2 <0.5 <1 <1 <1

SCRV-09 *1,590 1,270 <0.5 <1 <1 <1

SCRV-10 * 855 659 <0.5 <1 <1 <1

SCRV-12 * 321 321 <0.5 <1 <1 <1

SCRV-16 V 4 3 <0.5 <1 <1 <1

SCRV-19 V 2 2 <0.5 <1 <1 <1

SCRV-27 42 4 <0.5 <1 <1 <1

SCRV-28 31 22 0.61 <1 <1 <1

SCRV-33 V 3 <2 <0.5 <1 1 1

SCRV-35 V 2 2 <0.5 <1 2 2

SCRV-37 * 320 322 <0.5 <1 <1 <1

SCRV-39 * 914 836 1.3 <1 <1 <1

SCRV-42 6 3 <0.5 <1 <1 <1

Understanding wells

SCRVU-01 7 4 <0.5 <1 <1 <1

SCRVU-02 134 118 0.99 <1 <1 <1

SCRVU-03 13 4 <0.5 <1 <1 <1

SCRVU-04 140 140 <0.5 <1 <1 <1

SCRVU-06 56 26 <0.5 <1 <1 <1

SCRVU-07 * 8,160 7,590 0.75 <1 <1 <1

SCRVU-08 3 3 6 <1 <1 <1

SCRVU-09 14 14 5.5 <1 <1 <1

SCRVU-10 * 9,630 9,500 <0.5 <1 2 <1

SCRVU-11 17 17 3.6 <1 <1 <1

* Indicates value is above or equal to threshold level.

Table 12. Species of inorganic arsenic, iron, and chromium in samples collected for the Santa Clara River Valley Groundwater Ambient 

Monitoring and Assessment (GAMA) study, California, April to June 2007.

[The five-digit number in parentheses below the constituent name is the U.S. Geological Survey parameter code used to uniquely identify a specific constituent 

or property. Thresholds and threshold values as of October 29, 2007. Analyses made by the U.S. Geological Survey Trace Metals Laboratory (laboratory entity 

code USGSTMCO). Samples from 26 intermediate and slow wells were analyzed for iron, arsenic, and chromium. Threshold type: Maximum contaminant 

level thresholds are listed as MCL-US when the MCL-US and MCL-CA are identical, and as MCL-CA when the MCL-CA is lower than the MCL-US or no 

MCL-US exists. MCL-CA, California Department of Public Health maximum contaminant level; MCL-US, U.S. Environmental Protection Agency maximum 

contaminant level; SMCL-CA, California Department of Public Health secondary maximum contaminant level. GAMA identification No.: SCRV, Santa Clara 

River Valley study unit grid well; SCRVU, Santa Clara River Valley study unit understanding well. Abbreviations: MDL, method detection level; V, analyte 

detected in sample and an associated blank, thus data are not included in ground-water quality assessment; na, not available; μg/L, microgram per liter; <, less 

than]
54 Ground-Water Quality Data in the Santa Clara River Valley Study Unit, 2007: Results from the California GAMA Program

GAMA

identification no.

δ18O of H2

O 

(per mil) 

(82082)1

δ18O of H2O 

(per mil) 

(82085)1

Tritium

(pCi/L) 

(07000)2

δ15N of

Nitrate 

(per mil) 

(82690)2

δ18O of

Nitrate 

(per mil) 

(63041)2

δ13C

(per mil) 

(82081)3

Carbon-14 

(percent 

modern) 

(49933)4

δ37Cl

(per mil) 

(82725)3

δ81Br

(per mil) 

(82726)3

Threshold type na na MCL-CA na na na na na na

Threshold level na na 20,000 na na na na na na

Grid wells

SCRV-01 -50.4 -7.45 – nc nc nc nc nc nc

SCRV-02 -46.4 -6.95 0.6 nc nc nc nc nc nc

SCRV-03 -44.5 -6.71 – – – -14.18 13.65 0.03 0.72

SCRV-04 -41.0 -6.16 6.7 3.43 5.67 nc nc nc nc

SCRV-05 -51.6 -7.74 5.8 nc nc nc nc nc nc

SCRV-06 -48.2 -7.16 6.7 10.26 10.74 nc nc nc nc

SCRV-07 -46.1 -7.23 5.1 5.58 4.28 -11.41 88.92 0.45 1.16

SCRV-08 -42.4 -6.46 – nc nc nc nc nc nc

SCRV-09 -43.8 -6.78 0.3 – – nc nc nc nc

SCRV-10 -51.3 -7.65 0.3 – – -9.91 62.22 0.37 0.72

SCRV-11 -38.7 -5.51 1.6 nc nc nc nc nc nc

SCRV-12 -49.6 -7.43 1.0 8.15 2.99 -10.84 39.32 -0.01 0.56

SCRV-13 -39.1 -5.48 8.3 nc nc nc nc nc nc

SCRV-14 -36.8 -5.46 – nc nc nc nc nc nc

SCRV-15 -47.1 -7.30 3.2 nc nc nc nc nc nc

SCRV-16 -52.1 -7.61 5.1 11.24 10.61 nc nc nc nc

SCRV-17 -45.1 -6.73 6.7 nc nc nc nc nc nc

SCRV-18 -45.8 -7.11 0.3 nc nc nc nc nc nc

SCRV-19 -54.0 -7.34 8.0 7.16 4.95 nc nc nc nc

SCRV-20 -41.6 -6.65 – nc nc nc nc nc nc

SCRV-21 -46.0 -6.78 0.6 nc nc nc nc nc nc

SCRV-22 -42.9 -6.72 0.3 nc nc nc nc nc nc

SCRV-23 -62.0 -7.63 9.0 nc nc nc nc nc nc

SCRV-24 -49.7 -6.99 6.7 nc nc nc nc nc nc

SCRV-25 -68.0 -9.01 7.7 nc nc nc nc nc nc

SCRV-26 -56.4 -7.22 9.9 nc nc nc nc nc nc

SCRV-27 -50.1 -7.26 3.2 16.74 11.85 nc nc nc nc

SCRV-28 -43.6 -6.60 3.5 6.03 5.77 nc nc nc nc

SCRV-29 -51.6 -7.26 11.5 nc nc nc nc nc nc

SCRV-30 -60.7 -8.71 9.0 nc nc nc nc nc nc

SCRV-31 -69.7 -9.42 10.2 nc nc nc nc nc nc

SCRV-32 -44.1 -6.46 3.2 nc nc nc nc nc nc

SCRV-33 -38.8 -5.92 4.5 5.68 4.86 nc nc nc nc

SCRV-34 -46.9 -7.36 – nc nc nc nc nc nc

SCRV-35 -45.0 -6.78 9.0 6.74 3.34 -11.58 66.04 0.09 0.56

SCRV-36 -55.8 -7.69 8.3 nc nc nc nc nc nc

SCRV-37 -48.5 -7.27 0.6 – – nc nc -0.12 0.17

SCRV-38 -46.5 -7.16 1.9 nc nc nc nc nc nc

Table 13. Results for analyses of stable isotope ratios and tritium and carbon-14 activities in samples collected for the Santa Clara 

River Valley Groundwater Ambient Monitoring and Assessment (GAMA) study, California, April to June 2007.

[The five digit number in parentheses below the constituent name is the U.S. Geological Survey parameter code used to uniquely identify a specific constituent 

or property. Thresholds and threshold values as of October 29, 2007. Laboratory entity codes are listed in the footnotes. Samples from all 53 wells and four 

depth dependent were analyzed for stable isotopes of water and tritium; samples from fourteen of the intermediate and slow wells were analyzed for nitrogen 

(N) and oxygen (O) isotopic ratios of nitrate; samples from the nine slow wells were analyzed for carbon isotopes. Eleven samples from slow and intermediate 

wells and one depth-dependent sample were analyzed for stable isotopes of chloride (Cl) and bromide (Br). Stable isotope ratios are reported in the standard 

delta notation (δ), the ratio of a heavier isotope to more common lighter isotope of that element, relative to a standard reference material. Threshold type:

Maximum contaminant level thresholds are listed as MCL-US when the MCL-US and MCL-CA are identical, and as MCL-CA when the MCL-CA is lower than 

the MCL-US or no MCL-US exists. MCL-CA, California Department of Public Health maximum contaminant level; MCL-US, U.S. Environmental Protection 

Agency maximum contaminant level. GAMA identification No.: SCRV, Santa Clara River Valley study unit grid well; SCRVU, Santa Clara River Valley study 

unit understanding well; DD, depth dependent sample. Abbreviations: na, not available; nc, not collected; –, not detected; pCi/L, picocurie per liter; <, less than]
Table 13 55

GAMA

identification no.

δ18O of H2

O 

(per mil) 

(82082)1

δ18O of H2O 

(per mil) 

(82085)1

Tritium

(pCi/L) 

(07000)2

δ15N of

Nitrate 

(per mil) 

(82690)2

δ18O of

Nitrate 

(per mil) 

(63041)2

δ13C

(per mil) 

(82081)3

Carbon-14 

(percent 

modern) 

(49933)4

δ37Cl

(per mil) 

(82725)3

δ81Br

(per mil) 

(82726)3

Threshold type na na MCL-CA na na na na na na

Threshold level na na 20,000 na na na na na na

Grid wells–Continued

SCRV-39 -44.4 -6.80 – 36.21 26.05 nc nc nc nc

SCRV-40 -66.4 -9.34 5.1 nc nc nc nc nc nc

SCRV-41 -50.5 -7.22 7.4 nc nc nc nc nc nc

SCRV-42 -56.1 -7.65 11.5 13.12 3.89 nc nc nc nc

Understanding wells

SCRVU-01 -50.3 -7.41 6.4 9.36 6.36 -10.49 84.14 0.24 1.22

SCRVU-02 -49.3 -6.69 8.6 – – -13.41 67.83 0.43 1.16

SCRVU-03 -49.1 -6.96 6.3 13.44 5.49 -9.79 87.76 -0.06 0.97

SCRVU-04 -44.1 -6.66 0.6 – – -16.18 25.22 0.21 0.91

 DD-01 -43.0 -6.69 nc nc nc nc nc nc nc

 DD-02 -43.0 -6.69 nc nc nc nc nc nc nc

 DD-03 -44.6 -6.98 nc nc nc nc nc nc nc

 DD-04 -46.4 -7.06 nc nc nc nc nc -0.04 0.96

SCRVU-05 -68.8 -9.37 9.6 nc nc nc nc nc nc

SCRVU-06 -42.2 -6.59 – – – nc nc 0.16 0.64

SCRVU-07 -39.0 -6.06 – – – nc nc 0.11 0.13

SCRVU-08 -36.1 -5.66 0.3 – – nc nc 0.14 0.11

SCRVU-09 -41.2 -6.18 – – – nc nc 0.33 0.23

SCRVU-10 -9.2 -1.46 1.3 – – nc nc -0.11 -0.15

SCRVU-11 -44.1 -6.76 – – – nc nc -0.08 0.64

1USGS Stable Isotope Laboratory, Reston, Virginia (USGSSIVA).

2USGS Stable Isotope and Tritium Laboratory, Menlo Park, California (USGSH3CA).

3University of Waterloo (contract laboratory) (CAN-UWIL).

4University of Arizona, Accelerator Mass Spectrometry Laboratory (contract laboratory) (AZ-UAMSL).

Table 13. Results for analyses of stable isotope ratios and tritium and carbon-14 activities in samples collected for the Santa Clara 

River Valley Groundwater Ambient Monitoring and Assessment (GAMA) study, California, April to June 2007.—Continued

[The five digit number in parentheses below the constituent name is the U.S. Geological Survey parameter code used to uniquely identify a specific constituent 

or property. Thresholds and threshold values as of October 29, 2007. Laboratory entity codes are listed in the footnotes. Samples from all 53 wells and four 

depth dependent were analyzed for stable isotopes of water and tritium; samples from fourteen of the intermediate and slow wells were analyzed for nitrogen 

(N) and oxygen (O) isotopic ratios of nitrate; samples from the nine slow wells were analyzed for carbon isotopes. Eleven samples from slow and intermediate 

wells and one depth-dependent sample were analyzed for stable isotopes of chloride (Cl) and bromide (Br). Stable isotope ratios are reported in the standard 

delta notation (δ), the ratio of a heavier isotope to more common lighter isotope of that element, relative to a standard reference material. Threshold type:

Maximum contaminant level thresholds are listed as MCL-US when the MCL-US and MCL-CA are identical, and as MCL-CA when the MCL-CA is lower than 

the MCL-US or no MCL-US exists. MCL-CA, California Department of Public Health maximum contaminant level; MCL-US, U.S. Environmental Protection 

Agency maximum contaminant level. GAMA identification No.: SCRV, Santa Clara River Valley study unit grid well; SCRVU, Santa Clara River Valley study 

unit understanding well; DD, depth dependent sample. Abbreviations: na, not available; nc, not collected; –, not detected; pCi/L, picocurie per liter; <, less than]
56 Ground-Water Quality Data in the Santa Clara River Valley Study Unit, 2007: Results from the California GAMA Program

GAMA

identification no.

Helium-3/

Helium-4 

(atom ratio)

(61040)

Helium-4 

(85561)

Neon 

(61046)

Argon 

(85563)

Krypton 

(85565)

Xenon 

(85567)

(cm3

 STP/g-1 H2O)

Threshold type na na na na na na

Threshold level na na na na na na

Grid wells

SCRV-01 9.81E-07 7.13E-08 2.18E-07 3.37E-04 7.58E-08 1.05E-08

SCRV-02 7.66E-07 1.90E-07 2.27E-07 5.30E-04 7.39E-08 1.02E-08

SCRV-03 9.68E-07 2.43E-07 2.43E-07 3.45E-04 7.31E-08 1.01E-08

SCRV-04 1.41E-06 1.11E-07 4.82E-07 4.58E-04 8.83E-08 1.09E-08

SCRV-05 1.39E-06 7.99E-08 3.39E-07 4.08E-04 8.11E-08 1.07E-08

SCRV-06 1.42E-06 1.29E-07 5.10E-07 5.29E-04 9.98E-08 1.24E-08

SCRV-07 1.31E-06 5.32E-08 2.16E-07 3.37E-04 7.40E-08 9.89E-09

SCRV-08 8.94E-07 1.24E-07 2.31E-07 3.36E-04 7.34E-08 9.94E-09

SCRV-09 1.33E-06 6.14E-08 2.64E-07 3.53E-04 7.60E-08 9.99E-09

SCRV-10 1.31E-06 4.94E-08 2.06E-07 3.20E-04 7.40E-08 9.80E-09

SCRV-11 1.32E-06 9.60E-08 3.55E-07 4.05E-04 8.08E-08 1.01E-08

SCRV-12 1.14E-06 5.83E-08 2.08E-07 3.24E-04 7.32E-08 1.00E-08

SCRV-13 1.32E-06 8.77E-08 2.96E-07 3.82E-04 7.93E-08 1.01E-08

SCRV-14 1.00E-06 2.17E-07 4.26E-07 4.20E-04 8.06E-08 1.01E-08

SCRV-15 1.44E-06 7.12E-08 2.87E-07 3.72E-04 7.82E-08 1.02E-08

SCRV-16 1.40E-06 9.16E-08 3.43E-07 4.10E-04 8.24E-08 1.09E-08

SCRV-17 1.36E-06 4.60E-08 1.99E-07 3.18E-04 6.96E-08 9.58E-09

SCRV-18 1.29E-06 8.77E-08 3.15E-07 3.87E-04 7.79E-08 1.03E-08

SCRV-19 1.42E-06 9.59E-08 3.85E-07 4.32E-04 8.45E-08 1.10E-08

SCRV-20 1.26E-06 6.44E-08 2.57E-07 3.70E-04 7.73E-08 1.02E-08

SCRV-21 1.16E-06 6.45E-08 2.28E-07 3.32E-04 7.13E-08 9.38E-09

SCRV-22 1.09E-06 6.89E-08 2.30E-07 3.20E-04 6.90E-08 9.01E-09

SCRV-23 1.42E-06 4.47E-08 1.84E-07 3.08E-04 6.98E-08 9.24E-09

SCRV-24 1.40E-06 1.15E-07 4.53E-07 5.01E-04 9.42E-08 1.11E-08

SCRV-25 1.33E-06 1.37E-07 4.95E-07 4.69E-04 9.15E-08 1.19E-08

SCRV-26 1.06E-06 1.05E-07 3.22E-07 3.76E-04 7.53E-08 9.71E-09

SCRV-27 1.44E-06 1.02E-07 3.94E-07 4.66E-04 8.96E-08 1.13E-08

SCRV-28 1.43E-06 7.96E-08 3.79E-07 3.71E-04 7.52E-08 9.91E-09

SCRV-29 1.40E-06 1.13E-07 4.46E-07 4.83E-04 9.16E-08 1.19E-08

SCRV-30 1.24E-06 9.10E-08 3.17E-07 4.04E-04 8.24E-08 1.09E-08

SCRV-31 1.03E-06 8.98E-08 2.65E-07 3.86E-04 8.03E-08 1.08E-08

SCRV-32 9.61E-07 1.67E-07 4.17E-07 4.85E-04 9.12E-08 1.15E-08

SCRV-33 1.37E-06 8.35E-08 3.09E-07 4.16E-04 8.62E-08 1.14E-08

SCRV-34 1.36E-06 9.62E-08 3.78E-07 4.29E-04 8.45E-08 1.09E-08

SCRV-35 1.29E-06 5.65E-08 2.19E-07 3.47E-04 7.60E-08 1.01E-08

Table 14. Results for analyses of noble gases in and helium isotope ratios derived for samples collected for the Santa Clara River 

Valley Groundwater Ambient Monitoring and Assessment (GAMA) study, California, April to June 2007.

[The five-digit number in parentheses below the constituent name is the U.S. Geological Survey parameter code used to uniquely identify a specific constituent 

or property. Thresholds and threshold values as of October 29, 2007. Analyses made by the Lawrence Livermore National Laboratory (laboratory entity code 

CA-LLNL). Samples from all 53 wells were analyzed. Threshold type: Maximum contaminant level thresholds are listed as MCL-US when the MCL-US 

and MCL-CA are identical, and as MCL-CA when the MCL-CA is lower than the MCL-US or no MCL-US exists. MCL-CA, California Department of Public 

Health maximum contaminant level; MCL-US, U.S. Environmental Protection Agency maximum contaminant level. GAMA identification No.: SCRV, Santa 

Clara River Valley study unit grid well; SCRVU, Santa Clara River Valley study unit understanding well. Abbreviations: cm3 STP/g-1 H20, cubic centimeters at 

standard temperature and pressure per gram of water; na, not available; nc, sample not collected; pCi/L, picocurie per liter]
Table 14 57

GAMA

identification no.

Helium-3/

Helium-4 

(atom ratio)

(61040)

Helium-4 

(85561)

Neon 

(61046)

Argon 

(85563)

Krypton 

(85565)

Xenon 

(85567)

(cm3

 STP/g-1 H2O)

Threshold type na na na na na na

Threshold level na na na na na na

Grid wells–Continued

SCRV-36 1.37E-06 1.01E-07 4.00E-07 3.95E-04 8.06E-08 9.96E-09

SCRV-37 nc nc nc nc nc nc

SCRV-38 1.06E-06 1.99E-07 7.28E-07 4.78E-04 9.16E-08 1.09E-08

SCRV-39 1.22E-06 7.32E-08 2.75E-07 3.64E-04 7.59E-08 1.02E-08

SCRV-41 1.45E-06 1.17E-07 4.49E-07 4.81E-04 9.42E-08 1.13E-08

SCRV-42 1.39E-06 1.18E-07 4.17E-07 4.12E-04 7.95E-08 1.04E-08

Understanding wells

SCRVU-01 1.48E-06 1.51E-07 5.71E-07 4.96E-04 9.17E-08 1.13E-08

SCRVU-02 8.93E-07 6.79E-07 8.17E-07 7.10E-04 1.24E-07 1.37E-08

SCRVU-03 1.38E-06 5.99E-08 2.50E-07 3.43E-04 7.35E-08 9.99E-09

SCRVU-04 7.12E-07 4.33E-07 2.35E-07 3.82E-04 7.54E-08 1.02E-08

SCRVU-05 1.12E-06 8.66E-08 2.80E-07 3.55E-04 7.27E-08 9.95E-09

SCRVU-06 8.22E-07 2.41E-07 2.39E-07 3.36E-04 7.28E-08 1.00E-08

SCRVU-07 nc nc nc nc nc nc

SCRVU-08 nc nc nc nc nc nc

SCRVU-09 nc nc nc nc nc nc

SCRVU-10 1.18E-06 1.78E-07 2.45E-07 3.16E-04 6.43E-08 8.59E-09

SCRVU-11 9.00E-07 9.36E-07 2.34E-07 4.20E-04 7.42E-08 1.00E-08

Table 14. Results for analyses of noble gases in and helium isotope ratios derived for samples collected for the Santa Clara River 

Valley Groundwater Ambient Monitoring and Assessment (GAMA) study, California, April to June 2007.—Continued

[The five-digit number in parentheses below the constituent name is the U.S. Geological Survey parameter code used to uniquely identify a specific constituent 

or property. Thresholds and threshold values as of October 29, 2007. Analyses made by the Lawrence Livermore National Laboratory (laboratory entity code 

CA-LLNL). Samples from all 53 wells were analyzed. Threshold type: Maximum contaminant level thresholds are listed as MCL-US when the MCL-US 

and MCL-CA are identical, and as MCL-CA when the MCL-CA is lower than the MCL-US or no MCL-US exists. MCL-CA, California Department of Public 

Health maximum contaminant level; MCL-US, U.S. Environmental Protection Agency maximum contaminant level. GAMA identification No.: SCRV, Santa 

Clara River Valley study unit grid well; SCRVU, Santa Clara River Valley study unit understanding well. Abbreviations: cm3 STP/g-1 H20, cubic centimeters at 

standard temperature and pressure per gram of water; na, not available; nc, sample not collected; pCi/L, picocurie per liter; nc, not collected]
58 Ground-Water Quality Data in the Santa Clara River Valley Study Unit, 2007: Results from the California GAMA Program

Table 15. Radioactive constituents detected in samples collected for the Santa Clara River Valley Groundwater Ambient Monitoring 

and Assessment (GAMA) study, California, April to June 2007.

[The five digit number in parentheses below the constituent name is the U.S. Geological Survey parameter code used to uniquely identify a specific constituent 

or property. Thresholds and threshold values as of October 29, 2007. Analyses made by Eberline Services (laboratory entity code CA-EBRL). A total of nine 

samples from slow wells were analyzed. Five of the wells sampled were grid wells and four wells were understanding wells. Threshold type: Maximum 

contaminant level thresholds are listed as MCL-US when the MCL-US and MCL-CA are identical, and as MCL-CA when the MCL-CA is lower than the 

MCL-US or no MCL-US exists. MCL-CA, California Department of Public Health maximum contaminant level; MCL-US, U.S. Environmental Protection 

Agency maximum contaminant level; GAMA idenification No.: SCRV, Santa Clara River Valley study unit grid well; SCRVU, Santa Clara River Valley study 

unit understanding well. Abbreviations: E, estimated value; pCi/L, picocurie per liter; <, less than]

GAMA

identification no.

Radium-226

(pCi/L) 

(99915)

Radium-228

(pCi/L) 

(99916)

Radon-222

(pCi/L) 

(82303)

Gross alpha

radioactivity,

72-hour count

(pCi/L) 

(99920)

Gross alpha

radioactivity,

30-day count

(pCi/L) 

(99921)

Gross beta

radioactivity,

72-hour count 

(pCi/L) 

(99922)

Gross beta

radioactivity,

30-day count

(pCi/L) 

(99923)

Threshold type MCL-US MCL-US Proposed 

MCLs-US MCL-US MCL-US MCL-US MCL-US

Threshold value 1

5 15 2300 (4,000) 15 15 50 50

Grid wells

SCRV-03 0.12 0.55 220 < 3.3 < 2.9 E 3.5 2.8

SCRV-07 E 0.03 < 0.42 * 910 < 3.6 < 2.9 2.0 3.0

SCRV-10 0.17 E 0.39 200 < 5.5 < 4.1 4.5 5.0

SCRV-12 0.21 0.46 140 < 3.7 < 4.0 5.6 5.4

SCRV-35 0.10 0.10 * 960 * E 15.4 < 11 E 5.2 9.9

Understanding wells

SCRVU-01 0.29 0.71 * 560 E 6.2 E 4.3 5.0 6.4

SCRVU-02 0.27 0.71 * 570 E 8.9 * E 15.3 7.6 9.9

SCRVU-03 0.15 < 0.44 * 600 E 5.1 E 5.5 E 4.4 6.8

SCRVU-04 0.31 0.68 * 350 E 3.8 < 6.9 6.3 5.4

*Value exceeds lower threshold.

1The MCL-US threshold for radium is the sum of the radium-226 and radium-228 thresholds.

2Two MCLs have been proposed for Radon-222. The proposed alternative MCL is in parentheses.
Tabale 16 59

Table 16. Microbial indicator results for samples collected for the Santa Clara River Valley 

Groundwater Ambient Monitoring and Assessment (GAMA) study, California, April to June 2007.

[The five digit number in parentheses below the constituent name is the U.S. Geological Survey parameter code used to 

uniquely identify a specific constituent or property. Thresholds and threshold values as of October 29, 2007. A total of 

nine samples from slow wells were analyzed. Five of the wells sampled were grid wells and four wells were understanding 

wells. Threshold type: Maximum contaminant level thresholds are listed as MCL-US when the MCL-US and MCL-CA 

are identical, and as MCL-CA when the MCL-CA is lower than the MCL-US or no MCL-US exists. MCL-CA, California 

Department of Public Health maximum contaminant level; MCL-US, U.S. Environmental Protection Agency maximum 

contaminant level; TT-US, U.S. Environmental Protection Agency treatment technique - a required process intended to 

reduce the level of contamination in drinking water. GAMA identification No.: SCRV, Santa Clara River Valley study unit 

grid well; SCRVU, Santa Clara River Valley study unit understanding well. Abbreviations: mL, milliliter; E, estimated 

value]

GAMA 

identification no.

F-specific 

coliphage 

(units) 

(99335)

Somatic 

coliphage 

(99332)

Escherichia coli

colonies/ 100mL 

(90901)

Total coliform 

colonies/ 100mL 

(90900)

Threshold type TT-US TT-US TT-US MCL-US

Threshold level 99.9% 

Killed/Inactive

99.9% 

Killed/Inactive

No fecal coliforms 

are allowed

5% of samples 

per month

Grid wells

SCRV-03 – – – –

SCRV-07 – – – –

SCRV-10 – – – –

SCRV-12 – – – –

SCRV-35 – – – –

Understanding wells

SCRVU-01 – – – –

SCRVU-02 – – – –

SCRVU-03 – – – 1

E 1

SCRVU-04 – – – 2

E 12

1Analyte detected in the sample and the associated procedure blank.

2Analyte detected in the environmental sample but not in the associated replicate sample.
60 Ground-Water Quality Data in the Santa Clara River Valley Study Unit, 2007: Results from the California GAMA Program

Appendix 

This appendix includes discussions of the methods used 

to collect and analyze ground-water samples and report the 

resulting water-quality data. These methods were selected to 

obtain representative samples of the ground water from each 

well and to minimize the potential for contamination of the 

samples or bias in the data. Procedures used to collect and 

assess quality-control data collected as part of SCRV sampling 

also are discussed.

Sample Collection and Analysis

Sample Collection

Ground-water samples were collected using standard and 

modified USGS protocols (Koterba and others, 1995; U.S. 

Geological Survey, variously dated), and protocols described 

by Weiss (1968), Shelton and others (2001), and Ball and 

McClesky (2003). Before sampling, each well was pumped 

continuously in order to purge at least three casing-volumes of 

water from the well (Wilde and others, 2006). Samples were 

collected using Teflon tubing with brass and stainless-steel 

fittings attached to a collecting point on the well discharge 

pipe as close to the well as possible. The collecting point was 

always located upstream of any well-head treatment system or 

water storage tank. If a chlorinating system was attached to the 

well, the chlorinator was shut off before the well was purged 

and sampled in order to clear all chlorine out of the system. 

Samples of constituents on the fast (fewest constituents) and 

intermediate (more constituents) schedules were collected 

at the wellhead using a foot-long length of Teflon tubing. 

Samples of constituents on the slow schedule were collected 

inside an enclosed chamber located inside a mobile laboratory 

and connected to the wellhead by a 10- to 50-foot length of the 

Teflon tubing (Lane and others, 2003). All fittings and lengths 

of tubing were cleaned between samples (Wilde, 2004).

For the field measurements, ground water was pumped 

through a flow-through chamber fitted with a multi-probe 

meter that simultaneously measures the water-quality 

indicators: dissolved oxygen, temperature, pH, turbidity, 

and specific conductance. Field measurements were made in 

accordance with protocols in the USGS National Field Manual 

(Radtke and others, 2005; Wilde and Radtke, 2005; Lewis, 

2006; Wilde, 2006; Wilde and others, 2006a). All sensors 

on the multi-probe meter were calibrated daily. Measured 

temperature, dissolved oxygen, pH, and specific conductance 

values were recorded at 5-minute intervals for at least 30 

minutes. After these values remained stable for 20 minutes, 

samples to be analyzed in the laboratory were collected. Field 

measurements and instrument calibrations were recorded 

by hand on field record sheets and electronically in PCFF, a 

software package designed by the USGS with support from 

the GAMA program. Analytical service requests and chain 

of custody documentation were also managed by PCFF. 

Information from PCFF was uploaded directly into NWIS at 

the end of each week during which samples were collected.

 For analyses requiring filtered water, ground-water 

was diverted through a 0.45-μm pore size vented capsule

filter, a disk filter, or a baked glass-fiber filter, depending 

on the protocol for the analysis (Wilde and others, 2006b; 

Wilde and others, 2004). Before samples were collected, 

polyethylene sample bottles were pre-rinsed three times using 

deionized water and then once with sample water. Samples 

requiring acidification were acidified to a pH of 2 or less with 

the appropriate acids using ampoules of certified, traceable 

concentrated acids obtained from the USGS National Water 

Quality Laboratory (NWQL).

Samples were collected from monitoring wells using a 

portable, stainless-steel submersible pump attached to Teflon 

tubing with stainless-steel fittings. Once monitoring wells 

were sufficiently purged following USGS ground-water 

sampling protocols, samples were collected at the surface 

following the procedure described for the intermediate 

sampling schedule (Wilde and others, 2006b). For depthdependent 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-inch diameter 

polyethylene 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 oneway flow valves prevented the displaced water from flowing 

back toward the pump at the lower end of the hose. Repeated 

pressurizing and depressurizing the lines slowly brought the 

water at depth to the surface where it could be collected. 

Temperature-sensitive samples (VOCs, pesticides, 

potential wastewater-indicator compounds, pharmaceuticals, 

perchlorate, DOC, major and minor ions and trace elements, 

and nutrients) were stored on ice before being shipped daily 

to the various laboratories. The non-temperature sensitive 

samples collected to be analyzed for tritium, noble gases, 

chromium speciation and stable isotopes of hydrogen and 

oxygen in water were shipped monthly, while the radium 

isotopes, gross alpha and beta radioactivity, and radon222 samples were shipped daily from the field. Additional 

temperature-sensitive samples collected to be analyzed for 

stable isotopes of nitrogen and oxygen in nitrate, stable 

isotopes of carbon and carbon-14 abundance, arsenic and iron 

abundances and speciation were stored on ice before being 

shipped monthly to appropriate laboratories.

Detailed sampling protocols for individual analyses and 

groups of analytes are described by Koterba and others (1995) 

and in the USGS National Field Manual (Wilde and others, 
Appendix 61

1999; Wilde and others, 2004) and the references for analytical 

methods listed in table 4; only brief descriptions are given 

here. Volatile organic compounds (VOC) including gasoline 

oxygenates and degradates in samples were collected in 

40-mL sample vials that were purged with three vial volumes 

of sample water before bottom filling to eliminate atmospheric 

contamination. Six normal (6 N) hydrochloric acid (HCl) was 

added as a preservative to the VOC samples, but not to the 

gasoline oxygenate and degradate samples. The perchlorate 

sample was collected in a 125-mL polyethylene bottle. Tritium 

samples were collected by bottom filling two 1-L polyethylene 

bottles with unfiltered ground water after first overfilling 

the bottle with three volumes of water. Stable isotopes of 

water were collected in 60-mL clear glass bottles filled with 

unfiltered water, sealed with a conical cap, and secured with 

electrical tape to prevent leakage and evaporation.

Samples analyzed for pesticides and pesticide degradation 

products, potential wastewater-indicator constituents, and 

pharmaceutical compounds were collected in 1-L baked amber 

bottles. Pesticide and pharmaceutical samples were filtered 

through a glass fiber filter during collection. 

Ground-water samples for major and minor ions, trace 

elements, alkalinity, and total dissolved solids analyses 

required filling one 250-mL polyethylene bottle with raw 

ground water, and one 500-mL and one 250-mL polyethylene 

bottle with filtered ground water (Wilde and others, 2004). 

The filter used was a Whatman capsule filter. The 250-mL 

filtered sample was then preserved with 7.5 N nitric acid. 

The arsenic and iron speciation samples were filtered into 

a 250-mL polyethylene bottle that was covered with tape to 

prevent light exposure and preserved with 6 N hydrochloric 

acid. The nutrient sample was filtered into a 125-mL 

brown polyethylene bottle. Samples for stable nitrogen and 

oxygen isotopes of nitrate were filtered into 125-mL brown 

polyethylene bottle. Samples to be analyzed for radium 

isotopes and gross alpha and gross beta radioactivity were 

filtered into 1-L polyethylene bottles and acidified with nitric 

acid. Carbon isotope samples were filtered and bottom filled 

into two 500-mL glass bottles that were first overfilled with 

three bottle volumes of ground water; these samples had no 

headspace and were sealed and with a septa cap to avoid 

atmospheric contamination. Field alkalinity titration samples 

were collected by filtering ground water into a 500-mL 

polyethylene bottle. Chlorine-37 and bromine-81 isotope 

analysis sample was collected by filtering ground-water into 

a 5-gallon polyethylene container, then securing the cap with 

electrical tape to prevent leakage and evaporation.

DOC, chromium speciation, radon-222, dissolved gases, 

and microbial constituents were collected from the hose bib 

at the wellhead, regardless of the sampling schedule (fast, 

intermediate or slow). DOC was collected after rinsing the 

sampling equipment with blank water (Wilde and others, 

2004). The ground water sample was filtered through a 50-mL 

syringe and a 0.45-μm disk filter into a 125-mL baked glass

bottle and preserved with 4.5 N sulfuric acid. Chromium 

speciation samples were collected using a 10-mL syringe 

with an attached 0.45-μm disk filter. Before collecting the

chromium speciation sample, the syringe was thoroughly 

rinsed and filled with ground water, then 4 mL of the ground 

water was forced through the disk filter; and the next 2 mL of 

the ground water was slowly filtered into a small centrifuge 

vial to be analyzed for total chromium. The hexavalent 

chromium (Cr-VI) sample was then collected by attaching 

a small exchange column to the syringe filter, and after 

conditioning the column with 2 mL of sample water, 2 mL 

was collected in a second centrifuge vial. Both vials were 

preserved with 10 μL of 7.5 N nitric acid (Ball and McClesky,

2003a,b).

To collect radon-222, a stainless steel and Teflon valve 

assembly was attached to the sampling port at the well head 

(Wilde and others, 2004). The valve was partially closed 

to create back pressure, and a 10-mL sample was collected 

through a Teflon septum on the value assembly using a glass 

syringe affixed with a stainless steel needle. The sample 

was then injected into a 25-mL vial partially filled with a 

scintillation mixture (mineral oil) and shaken. The vial was 

then placed in a cardboard tube in order to shield it from light 

during shipping. 

Noble gas samples were collected in 3/8-inch copper 

tubes using reinforced nylon tubing connected to the hose bib 

at the wellhead. Ground water was flushed through the tubing 

to dislodge bubbles before flow was restricted with a back 

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

then tightened, trapping a sample of ground water (Weiss, 

1968). 

Microbial constituent samples were collected at the 

wellhead also (Bushon, 2003, Myers, 2004). Before the 

samples were collected, the sampling port was sterilized using 

isopropyl alcohol and flushed with ground water for at least 

three minutes to remove any traces of the sterilizing agent. 

Two sterilized 250-mL bottles were then filled with ground 

water to be analyzed for coliform (total and Escherichia 

coliform determinations), and one sterilized 3-liter carboy 

was filled with ground water to be analyzed for coliphage 

(F-specific coliphage and somatic coliphage determinations).

Sample Analysis

Ten laboratories analyzed chemical and microbial 

samples for this study (table A1), although most of the samples 

were analyzed at the NWQL or by labs contracted by the 

NWQL. The NWQL maintains a rigorous quality assurance 

program (Pirkey and Glodt, 1998; Maloney, 2005). Laboratory 

quality control samples, including method blanks, continuingcalibration verification standards, standard reference samples, 

reagent spikes, external certified reference materials, and 

external blind proficiency samples, are analyzed regularly. 
62 Ground-Water Quality Data in the Santa Clara River Valley Study Unit, 2007: Results from the California GAMA Program

Method detection limits are continuously tested and laboratory 

reporting levels updated accordingly. NWQL maintains the 

National Environmental Laboratory Accreditation Program 

(NELAP) and other certifications (http://nwql.usgs.gov/lab_

cert.shtml). In addition, the Branch of Quality Systems within 

the USGS Office of Water Quality independently oversees 

quality assurance at the NWQL and laboratories contracted 

by the NWQL. The Branch of Quality Systems also runs a 

national field quality assurance program that annually tests the 

proficiency of all USGS field personnel who measure waterquality in the field (http://bqs.usgs.gov/nfqa/). Results of 

analyses made at the NWQL or laboratories contracted by the 

NWQL are uploaded directly into NWIS by the NWQL. 

Turbidity, alkalinity, and total coliforms and Escherichia 

coliform (E. coli) were measured in the mobile laboratory 

at the well site. Turbidity was measured in the field with a 

calibrated turbidity meter. Total coliforms and Escherichia 

coli (E. coli) plates were prepared using sterilized equipment 

and reagents (Myers, 2004). Plates were counted under an 

ultraviolet light, following a 22-24 hour incubation time. 

Alkalinity and the concentrations of bicarbonate (HCO3

-

) 

and carbonate (CO3

2-) were measured on filtered samples by 

Gran’s titration method (Gran, 1952; Stumm and Morgan, 

1996; Rounds, 2006). 

Concentrations of HCO3

-

 and CO3

2- were also calculated 

from the laboratory alkalinity and pH measurements. 

Calculations were made using the advanced speciation method 

(http://or.water.usgs.gov/alk/methods.html) with pK1 = 6.35, 

pK2 = 10.33, and pKW = 14. 

Data Reporting

The following section details the laboratory reporting 

conventions and the constituents that are determined by 

multiple methods or by multiple laboratories.

Reporting Limits

The USGS NWQL uses the laboratory reporting level 

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

is set to minimize false negatives (not detecting a compound 

when it is actually present in a sample) to less than 1 percent 

(Childress and others, 1999). The LRL is usually set at 

two-times the long-term method detection level (LT-MDL). 

The LT-MDL is derived from the standard deviation of at 

least 24 method detection limit (MDL) determinations made 

over an extended period of time. The MDL is the minimum 

concentration of a substance that can be measured and 

reported with 99 percent confidence that the concentration is 

greater than zero (at MDL, there is less than 1 percent chance 

of a false positive) (U.S. Environmental Protection Agency, 

2002). The USGS NWQL monitors and updates LT-MDL and 

LRL values regularly, and the values listed in this report were 

in effect during the period when ground-water samples from 

the SCRV study were analyzed (April through June, 2007).

Concentrations between the LRL and the LT-MDL 

are reported as estimated concentrations . For informationrich methods, concentrations below the LRL have a high 

certainty of detection, but the precise concentration is 

uncertain. Information-rich methods are those that utilize gas 

chromatography or high-performance liquid chromatography 

(HPLC) with mass spectrometry to detect VOCs, gasoline 

oxygenates and degradates, pesticides, pharmaceuticals, 

potential wastewater indicators). Compounds are identified by 

characteristic fragmentation patterns in their mass spectra in 

addition to being quantified by measurements of peak areas 

at their associated chromatographic retention times. E-coded 

values also may result from concentrations outside the range 

of calibration standards, for concentrations that did not meet 

all laboratory quality-control criteria, and for samples that 

were diluted before analysis (Childress and others, 1999). The 

potential for sample contamination was assessed using results 

from field, source-solution, and laboratory blanks.

Some constituents in this study are reported using 

minimum reporting levels (MRL) or method uncertainties. The 

MRL is the smallest measurable concentration of a constituent 

that may be reliably reported using a given analytical method 

(Timme, 1995). The method uncertainty (MU) usually 

indicates the precision of a particular analytical measurement; 

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

The reporting levels for radiochemical constituents 

(gross-alpha radioactivity, gross-beta radioactivity, 

radium-226, and radium-228) are based on a sample-specific 

minimum detectable concentration (SSMDC), a samplespecific critical value, and the combined standard uncertainty 

(CSU) (U.S. Environmental Protection Agency, 2004; Bennett 

and others, 2006). A result above the critical value represents a 

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

zero (significantly different from the instrument’s background 

response to a blank sample), and a result above the SSMDC 

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

is greater than the critical value. Using these reporting level 

elements, three unique cases were possible when the raw 

analytical data was screened. If the analytical result is less 

than the critical value (case 1), the analyte is considered not 

detected and the concentration is reported as less than the 

SSMDC. If the analytical result is greater than the critical 

value, the ratio of the CSU to the analytical result is calculated 

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

having percent relative CSU greater than 20 percent (case 2), 

concentrations are reported as estimated values. For those 

samples having percent relative CSU less than 20 percent 

(case 3), concentrations are reported as unqualified.

Stable isotopic compositions of oxygen, hydrogen, 

carbon, nitrogen, chlorine, and bromine are reported as 

relative isotope ratios in units of per mil using the standard 

delta notation (Coplen and others, 2002):
Appendix 63

sample

reference

1 1,000,

where

is the atomic mass of the heavier isotope of

the element,

is the element (O for oxygen, C for carbon, 

or H for hydrogen, N for nitrogen, Cl for

chlorine, or Br 

i R

E

R

i

E

  d = −    



sample

18 13 2 15

37 81

16 12 1 14 35 79

for abromine),

is the ratio of the abundance of the heavier

 isotope of the element ( O, C, H, N,

Cl, or Br) to the lighter isotope of the 

element ( O, C, H, N, Cl, or Br), in 

th

R

reference

e sample and,

is the ratio of the abundance of the heavier

isotope of the element to the lighter isotope 

of the element in the reference material 

hydrogen.

R

(1)

The reference material for oxygen and hydrogen is 

Vienna Standard Mean Ocean Water (VSMOW), which is 

assigned δ18O and δ2H values of 0 per mil (note that δ2H is 

also written as δD because the common name of the heavier

isotope of hydrogen, hydrogen-2, is deuterium). The reference 

material for carbon is Vienna Peedee Belemnite (VPDB), 

which is assigned a δ13C value of 0 per mil. The reference 

material for nitrogen is atmospheric nitrogen gas, which is 

assigned a d15N value of 0 per mil. The reference material for 

chloride is Standard Mean Ocean Chloride (SMOC), which 

is assigned a d37Cl value of 0 per mil (Shouakar-Stash and 

others, 2005a). The reference material for bromide is Standard 

Mean Ocean Bromide (SMOB), and the isotopic composition 

is defined according to the standard definition (ShouakarStash and others, 2005b). Positive values indicate enrichment 

of the heavier isotope and negative values indicate depletion 

of the heavier isotope, relative to the ratios observed from the 

standard reference material.

Constituents on Multiple Analytical Schedules

Twenty-nine constituents targeted in this study are 

measured by more than one analytical schedule or more than 

one laboratory (table A2). The procedure recommended by 

the NWQL (http://wwwnwql.cr.usgs.gov/USGS/Preferred_

method_selection_procedure.html) was used to select the 

preferred methods for these constituents. Methods having full 

approval are preferred over those having provisional approval 

and approved methods are favored over research methods. 

The most accurate and precise method and lower LRL for 

the overlapping constituents is preferred. A method may be 

selected as the preferred method to provide consistency with 

historical data analyzed by the same method.

Twenty-two constituents appear on at least two of the 

following NWQL analytical schedules: VOCs (Schedule 

2020), gasoline oxygenates and degradates (Schedule 4024), 

pesticides (Schedule 2003), polar pesticides (Schedule 

2060), pharmaceutical compounds (lab code 9003), and 

potential wastewater-indicator compounds (Schedule 4433) 

(table A2). For constituents on Schedules 2020 and 4024, the 

preferred method was Schedule 2020 to provide consistency. 

For constituents on Schedules 2020 and 4433, the preferred 

method was Schedule 2020 because it is more accurate 

and precise, and the VOCs listed have lower LRLs. For 

constituents on Schedules 2003, 2060, and 4433, the preferred 

method was Schedule 2003 because it has greater accuracy 

and precision and lower LRLs for pesticide constituents. 

For constituents that appear on multiple NWQL analytical 

schedules, only the results from the preferred method are 

reported.

The water-quality indicators pH, specific conductance, 

and alkalinity were measured in the field and at the NWQL 

(table A2). The field measurements are the preferred method 

for all three constituents; however, laboratory alkalinity results 

are presented in this report when a field alkalinity sample was 

not collected. 

For arsenic, chromium, and iron concentrations, standard 

methods used by the NWQL are preferred over the research 

methods used by the USGS Trace Metal Laboratory. The 

concentrations measured by the Trace Metal Laboratory are 

used only to calculated ratios of redox species for each

element, As(V)

As(III) for arsenic, Cr(VI)Cr(III) for chromium, and

Fe(III)

Fe(II) for iron. For example:

Fe(III)

Fe(II)

Fe(T) - Fe(II)

Fe(II) ,

where

Fe(T) is the total 

=

iron concentration (measured),

Fe(II) is the concentration of ferrous iron (measured), 

and

Fe(III) is the concentration of ferric iron (calculated).

(2)

Quality-Assurance

The purpose of quality-assurance is to identify which 

data best represent environmental conditions and which may 

have been affected by contamination or bias during sample 

collection, processing, storage, transportation, or laboratory 

analysis. Four types of quality-control (QC) tests were used 

in this study: (1) blank samples were collected to assess the 

potential for inadvertent sample contamination, (2) replicate 

samples were collected to assess variability, (3) matrix spike 

tests were done to assess the potential for matrix effects, and 

(4) surrogate compounds were added to samples analyzed 
64 Ground-Water Quality Data in the Santa Clara River Valley Study Unit, 2007: Results from the California GAMA Program

for organic constituents to identify general problems that 

may arise during sample analysis that could affect the results 

for all compounds in that sample. In this report, detections 

of analytes in ground-water that may have resulted from 

contamination were not included in water-quality assessments.

The quality-assurance used for this study followed the 

protocols used by the USGS NAWQA program (Koterba 

and others, 1995) and described in the USGS National Field 

Manual (U.S. Geological Survey, variously dated). The 

quality assurance plan followed by the NWQL, the primary 

laboratory used to analyze samples for this study, is described 

by Maloney (2005) and Pirkey and Glodt (1998). 

Blanks

Blank samples (blanks) were collected using blank water 

certified by the NWQL to contain less than the LRL or MRL 

of the analytes investigated in the study. Nitrogen-purged, 

organic-free blank water was used for field blanks of organic 

constituents, and inorganic-free blank water was used for 

field blanks of other constituents. Three types of blanks were 

collected: source-solution, field, and equipment. Sourcesolution blanks were collected to verify that blank water used 

for the field blank samples was free of analytes of interest. 

Field blanks were collected to assess potential contamination 

of samples during collection, processing, transport, and 

analysis. The equipment blank was collected at the USGS 

San Diego Project office before the scheduled field sample 

was collected in order to assure the sampling equipment was 

free of analytes of interest. Source-solution and field blanks 

were collected at 9 percent of the wells sampled to determine 

if equipment or procedures used in the field or laboratory 

introduced contamination. Blank samples were analyzed 

for VOCs, gasoline oxygenates and degradates, pesticides 

and pesticide degradates, potential wastewater-indicator 

compounds, pharmaceuticals, perchlorate, nutrients, dissolved 

organic carbon, major and minor ions, trace elements, iron, 

arsenic, and chromium species, and radioactive constituents. 

Source-solution blanks were collected at the field 

sampling site by pouring blank water directly into sample 

containers that were preserved, stored, shipped, and analyzed 

in the same manner as the environmental samples. Field 

blanks were collected after the source-solution blanks at the 

field sampling site. For field blank samples and the equipment 

blank sample, blank water was either pumped or poured 

through the sampling equipment (fittings and tubing) used to 

collect ground water, then processed and transported using the 

same protocols as those used for the environmental samples. 

The equipment used to collect samples on the slow 

schedule was different than the equipment used to collect 

samples on the fast and intermediate schedules. Therefore, 

detections of constituents in field blanks collected at slow 

wells were compared with detections of constituents in ground 

water samples from slow wells, and detections in field blanks 

collected at fast and intermediate wells were compared with 

detections in ground water samples from fast and intermediate 

wells. In addition, two different submersible pumps were 

used to collect ground-water samples from several monitoring 

wells. An equipment blank was collected using one of the 

submersible pumps (KeckTM pump), and a field blank was 

collected using the other submersible pump (Bennett Pump) 

used for sampling monitor wells. Detections of constituents 

in blank samples collected from the submersible pumps were 

compared with detections of constituents in ground water 

samples collected at the corresponding monitor wells. 

Contamination in field blanks may originate from several 

different types of sources, including the source-solution water, 

carry-over from the previous sample, known sources specific 

to a field site, and (or) systematic or random contamination 

from field or laboratory equipment or processes. These 

different sources of contamination require different strategies 

for censoring (excluding) detections in ground-water samples 

on the basis of detections in field blanks.

Detections in source-solution blanks were used to 

evaluate potential contamination of the source-solution 

water. If a constituent was detected in a field blank, the 

associated source-solution blank results were examined 

for similar constituent detection. If the field blank and the 

source-solution blank contained a similar concentration 

of the same constituent, the source-solution water was 

interpreted as the origin of the contamination in the blanks, 

and the field blank detections collected using the same blank 

water were disregarded as indicating any contamination bias 

in the ground-water samples. If the ground-water sample 

collected just before the contaminated field blank had high 

concentration of the constituent in question, carry-over was 

considered to be the cause of the contamination.

If a constituent in a field blank could not be accounted for 

by contamination of the source-solution, carry-over, or another 

identifiable source of contamination, that field blank was used 

to censor detections in ground-water samples collected using 

the same equipment. The censoring level was defined as the 

concentration of the constituent in the field blank plus onehalf the LRL for that constituent. Detections in ground-water 

samples below the censoring level were censored. Censored 

values are counted as non-detections for the summary 

statistics.

Replicates

Sequential replicate samples were collected to assess 

variability that may have resulted from the processing and 

analyses of inorganic and organic constituents. Relative 

standard deviation (RSD) of the measured values was used in 

determining the variability between replicate pairs for each 

compound. The RSD is defined as 100 times the standard 
Appendix 65

deviation divided by the mean concentration for each replicate 

pair of samples, multiplied by 100 percent. If a constituent 

was not detected in one replicate and its concentration was 

estimated to be below the LRL or MRL in the other replicate, 

the RSD was set to zero because the values are analytically 

identical. If one value for a sample pair was reported as a 

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

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

and others, 2002). Values of RSD less than 20 percent 

were considered acceptable in this study. An RSD value 

of 20 percent corresponds to a relative percent difference 

(RPD) value of 29 percent. High RSD values for a compound 

measured at low concentrations may indicate analytical 

uncertainty, particularly for concentrations within an order of 

magnitude of LT-MDL or MDL. 

Matrix Spikes

Adding a known concentration of a constituent (‘spike’) 

to a replicate environmental sample enables the analyzing 

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

groundwater, on the analytical technique used to measure the 

constituent. The known compounds added as matrix spikes 

are the same as those being analyzed using the method. 

Therefore, matrix interferences caused by each compound can 

be analyzed. Matrix spikes were added at the laboratory doing 

the analysis. Compounds with low recoveries are of concern 

if ground-water concentrations are close to the MCLs because 

a concentration below a MCL could be falsely indicated. 

Conversely, compounds with high recoveries are of concern 

if the ground-water concentration exceeds a MCL because a 

high recovery could falsely indicate a concentration above the 

MCL. 

Acceptable ranges for matrix-spike recoveries are 

based on the acceptable ranges established for laboratory 

“set” spike recoveries. Laboratory set spikes are aliquots of 

laboratory blank water to which the same spike solution as 

that used for the matrix spikes has been added. One set spike 

is analyzed with each set of samples. Acceptable ranges for set 

spike recoveries are 70 to 130 percent for NWQL Schedules 

2020, 4024, and 4433 (Connor and others, 1998; Rose and 

Sandstrom, 2003; Zaugg and others, 2006), 60 to 120 percent 

for NWQL Schedule 2003 (Sandstrom and others, 2001), 

and 60 to 130 percent for Schedule 2080 (Kolpin and others, 

2002). On the basis of these ranges, 70 to 130 percent was 

defined as the acceptable range for matrix-spike recoveries for 

organic compounds in the SCRV study unit. 

Constituents used as matrix spikes in ground-water 

samples include VOCs, gasoline oxygenate and degradate 

compounds, pesticide compounds, and potential wastewaterindicator compounds because the analytical methods for 

these constituents are chromatographic methods which may 

be susceptible to matrix interferences. Replicate samples for 

matrix spike additions were collected at 15 percent of the 

wells sampled, although not all analyte classes were tested at 

every well (tables A5A–D). 

Surrogates

Surrogate compounds are added to environmental 

samples in the laboratory before analysis in order to compare 

the recovery of similar constituents. Surrogate compounds 

were added to all environmental and quality-control samples 

that were analyzed for VOCs, gasoline oxygenate and 

degradate compounds, pesticide compounds, pharmaceutical 

compounds, and potential wastewater-indicator compounds 

(table A6). Most of the surrogate compounds are deuterated 

analogs of compounds being analyzed. For example, the 

surrogate toluene-d8 added to the VOC analytical method 

has the same chemical structure as toluene, but the eight 

hydrogen-1 atoms on the molecule have been replaced by 

deuterium (hydrogen-2). Toluene-d8 and toluene behave 

very similarly during the analytical procedure, but the small 

mass difference between the two results in slightly different 

chromatographic retention times. The use of a toluene-d8 

surrogate does not interfere with the analysis of toluene (Grob, 

1995). Only 0.015 percent of hydrogen atoms are deuterium 

(Firestone and others, 1996). Thus deuterated compounds 

like toluene-d8 do not occur naturally and are not found in 

environmental samples. Surrogates are used to identify general 

problems that may arise during sample analysis that could 

affect the analysis results for all compounds in that sample. 

Potential problems include matrix interferences or incomplete 

laboratory recovery that produces a bias. A range of 70 to 

130 percent recovery of surrogates was considered acceptable 

for the SCRV study unit; values outside this range indicate 

possible problems with processing and analyzing the samples 

(Connor and others, 1998; Sandstrom and others, 2001).

Quality-Control Sample Results

Detections of Constituents in Field Blanks, 

Source-Solution Blanks, and an Equipment Blank

Field and source-solution blanks were collected at 5 of 

the 53 sites sampled in SCRV. In addition, one equipment 

blank was collected from a submersible sampling pump 

used to collect ground-water samples from two monitoring 

wells during this study. One source-solution blank sample 

was not analyzed for organic constituents because no 

organic constituents were detected in the associated field 

blank sample. Table A3 gives a summary of detections of 

constituents in field blanks, source-solution blanks, and the 

equipment blank. Two VOCs detected in blank samples 

were methyl ethyl ketone (2-butanone, MEK) and toluene. 
66 Ground-Water Quality Data in the Santa Clara River Valley Study Unit, 2007: Results from the California GAMA Program

Methyl ethyl ketone was detected in 1 of 10 blank samples 

analyzed at a maximum concentration of E 0.9 μg/L. Methyl 

ethyl ketone was not detected in an environmental sample; 

therefore, no samples were censored. Toluene was detected 

in 3 of the 10 blank samples, ranging in concentration from 

an estimated (E) 0.02 μg/L to E0.06 μg/L. Toluene was 

detected in 7 environmental samples; concentrations in 6 

of the 7 environmental samples ranged from E0.02 μg/L 

to E0.03 μg/L. Toluene was detected in the seventh 

environmental sample (SCRV-10) at a concentration of 

1.02 μg/L. Toluene was detected in the 3 blank samples and 

the 6 environmental samples with the same sample collection 

equipment being used. In addition, the concentration of 

toluene in blank samples was equal to or greater than the 

maximum concentration detected in the six environmental 

samples (table A3). Therefore, toluene was censored in these 

six environmental samples. The concentration of toluene in the 

seventh environmental sample (SCRV-10) was not censored 

because this concentration was higher (or more elevated) 

than that detected in the blank samples and different sample 

collection equipment was used. Toluene was detected in 

source-solution and field blanks from earlier GAMA study 

units (Wright and others, 2005; Kulongoski and others, 

2006; Bennett and others, 2007; Dawson and others, 2007; 

Kulongoski and Belitz, 2007).

One equipment blank and 3 (of 5) field blanks collected 

for SCRV were analyzed for major ions, minor ions, and 

trace elements. Major ions, minor ions, and trace elements 

were not collected for source-solution blanks. Calcium was 

detected in 2 blank samples, 1 field blank and 1 equipment 

blank, at a concentration of 0.02 mg/L and 0.03 mg/L, 

respectively. The field blank was collected a submersible 

piston-pump, and the equipment blank was collected from a 

submersible rotary-pump, both of which were used to collect 

environmental samples from several monitoring wells. The 

lowest concentration of calcium detected in environmental 

samples was 35.6 mg/L; therefore, the calcium results were 

not censored. Silica was detected in the equipment blank at 

a concentration of 0.018 mg/L. The lowest concentration 

of silica detected in environmental samples was 15.8 

mg/L; therefore, the silica results were not censored. Total 

nitrogen was detected in one field blank at a concentration 

of E0.03 mg/L. The lowest concentration of total nitrogen 

detected in environmental samples was reported at 0.12 mg/l; 

therefore, the total nitrogen data were not censored.

The concentration of chromium detected in the 

equipment blank was of 0.38 μg/L; it was collected from 

the submersible pump (KeckTM pump). The concentrations 

of chromium in the two environmental samples collected 

utilizing this submersible pump were 1.8 μg/L and E2.4 μg/L; 

thus no chromium data were censored on the basis of the 

detection in the equipment blank. Zinc was detected in 3 of 

4 blank samples at concentrations ranging from E0.3 μg/L 

to 1.6 μg/L. One field blank containing 1.6 μg/L of zinc was 

collected using the “slow” schedule sampling equipment; 

thus, data for other wells sampled using the “slow” schedule 

equipment were evaluated for contamination. No detections 

of zinc in environmental samples having concentrations 

less than 1.9 μg/L (1.6 μg/L plus one-half the LRL of 

0.6 μg/L) were reported for “slow” schedule environmental 

samples; therefore, no data were censored (tables 12, A3). 

In addition, 1 field blank and 1 equipment blank containing 

zinc concentrations 0.86 μg/L and 0.34 μg/L, respectively, 

were collected from the two submersible pumps used to 

collect environmental samples. Both of the detected zinc 

concentrations in the environmental samples were greater 

than 1.16 μg/L (0.86 μg/L plus one-half the LRL of 0.6 μg/L); 

therefore, the environmental samples were not censored. 

Barium was detected in the equipment blank and two of the 

field blanks at a maximum concentration of E0.07 μg/L. The 

minimum concentration of barium detected in environmental 

samples was 16 μg/L; therefore, no environmental samples 

were censored. An estimated 0.2 μg/L of copper was 

detected in a field blank using the equipment for a “slow” 

sampling schedule. The minimum concentration detected 

in a “slow” environmental sample was 1.1 μg/L; therefore, 

no environmental samples were censored. Molybdenum 

was detected in the equipment blank at a concentration of 

E 0.1 μg/L and at a minimum concentration of 10.0 μg/L in 

environmental samples collected using the same equipment. 

The ground-water data for molybdenum was not censored. 

Nickel was detected in the equipment blank and a field 

blank (0.08 μg/L and E 0.04 μg/L, respectively) that were 

collected using the submersible sampling pumps. The 

minimum concentrations of nickel detected in the associated 

environmental samples (0.60 μg/L and 0.44 μg/L) utilizing 

the same equipment indicated that no ground-water samples 

should be censored. 

Chromium species in 3 field blanks and arsenic and 

iron species in 2 field blanks were analyzed at the USGS 

Trace Metal Laboratory (TML). No source-solution blanks or 

equipment blanks were collected to be analyzed for arsenic, 

chromium, and iron species. Two field blanks contained 

3 μg/L of iron. Because of iron detected in two field blanks, 

four detections of iron in ground-water analyzed by the TML 

at concentrations of 4 μg/L or less were censored (table 13). 

Note that iron was not detected in the field blanks collected at 

the same time to be analyzed by the NWQL (NWQL Schedule 

1948). Arsenic and chromium were reported as not being 

detected in all field blanks analyzed by TML. 

DOC was detected in 1 of the 3 field blanks at an 

estimated concentration of 0.3 mg/L, and low concentrations 

of DOC were detected in field blanks collected previously 

in other GAMA study units (Bennett and others, 2006; 

Kulongoski and Belitz, 2007). Also, the censoring level is 

defined as the concentration of the constituent in the field 
Appendix 67

blank plus one-half the LRL for that constituent; thus, the data 

for concentrations ranging from 0.3 mg/L to 0.5 mg/L in four 

environmental samples were censored (table 10).

Variability in Replicate Samples

Tables A4A–D summarizes the results of replicate 

analyses of constituents detected in ground-water samples 

collected in the SCRV study unit. Replicate sample pairs 

were collected at 3 of the 53 sites sampled in SCRV. All the 

constituents that were detected in ground-water samples are 

included in tables A4A–D. Constituents that were not detected 

in replicate samples are not included in tables A4A–D. 

Concentrations or activities in the environmental and their 

respective replicate samples are reported for all replicate 

analyses yielding RSD values greater than zero. Most replicate 

analyses yielded RSD values less than 5 percent and only one 

RSD value was greater than the acceptable limit of 20 percent. 

The replicate analyses of arsenic (total) analyzed at USGS 

TML yielded a RSD value of 110 percent (table A4C). The 

preferred analytical method for arsenic is the NWQL Schedule 

1948 and not the USGS TML analytical method. For this 

particular replicate/environmental sample, arsenic was not 

detected in the replicate sample but was detected above the 

LRL in the environmental sample. In order to calculate the 

RSD value, the value of the LRL (0.5 μg/L) for the replicate 

sample was changed to one-fourth of the LRL. At these low 

concentrations, small deviations in measured values result in 

large RSDs. No data were flagged as a result of variability in 

replicate analyses.

Matrix-Spike Recoveries

Tables A5A–E summarizes matrix-spike recoveries for 

the SCRV study. Adding a spike or known concentration of a 

constituent to an environmental sample enables the analyzing 

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

ground water, on the analytical technique used to measure 

the constituent. Five environmental samples were spiked 

with VOCs to calculate matrix-spike recoveries (table A5A). 

Eighty of the 89 VOCs had spike recoveries within the 

acceptable range of 70 and 130 percent. Seven VOCs had 

at least 1 matrix-spike recovery greater than 130 percent, 

and 2 of these compounds (perchloroethene [PCE] and 

trichlorofluoromethane [CFC-11]) were detected in groundwater samples. The greatest matrix-spike recovery of PCE 

was 161 percent, and the greatest reported concentration in 

environmental samples was 0.15 μg/L. The greatest matrixspike recovery of trichlorofluoromethane (CFC-11) was 

131 percent, and the only detection of trichlorofluoromethane 

was reported at 12.9 μg/L. The median percent recoveries of 

all 89 VOC compounds were within the acceptable range of 70 

to 130 percent. Styrene and trans-1,4-dichloro-2-butene had 

minimum matrix-spike recoveries below 70 percent; however, 

these compounds were not detected in environmental samples 

(table 5). [NOTE – low recoveries may indicate that the 

compound might not have been detected in some samples if it 

was present at very low concentrations].

Five ground-water samples were spiked with the 

pesticide and pesticide degradate compounds (NWQL 

Schedule 2003) in order to calculate matrix-spike recoveries 

(table A5B). Twenty-three of the 63 compounds had matrixspike recoveries within the acceptable range of 70 and 

130 percent for all five matrix-spike samples (table A5B). Six 

of the 11 compounds detected in ground-water samples had 

spike recoveries within the acceptable range. Two compounds 

(fipronil and fipronil sulfide) that were detected at low 

concentrations (E 0.005 μg/L and E 0.008 μg/L, respectively) 

in the same ground-water sample had at least one matrix-spike 

recovery greater than 130 percent. Three of the compounds 

(deethylatrazine, fipronil sulfone, and hexazinone) detected in 

ground-water samples had at least one matrix-spike recovery 

less than 70 percent. A total of 25 spike compounds had at 

least one matrix-spike recovery below 70 percent, and the 

median recovery was below 70 percent for 16 compounds. 

[NOTE – low matrix-spike recovery may indicate that the 

compound might not have been detected in some samples if it 

was present at very low concentrations].

 Five ground-water samples were spiked with potential 

wastewater-indicator compounds (NWQL Schedule 4433). 

Sixty of the 69 compounds had recoveries less than 70 percent 

and 6 compounds had recoveries greater than 130 percent 

(table A5C). Three potential wastewater-indicator compounds 

(bisphenol A, cholesterol, and 4-octylphenol monoethoxylates) 

detected in environmental samples had at least one matrixspike recovery below 70 percent. Two potential wastewaterindicator compounds (bis(2-ethylhexyl) phthalate and 

4-octylphenol diethoxylates) detected in an environmental 

sample had one matrix-spike recovery greater than 

130 percent. One of the compounds detected in environmental 

samples, perchloroethene (PCE), had a recovery of only 

24 percent, but the potential wastewater-indicator analytical 

method (NWQL Schedule 4433) is not the preferred analytical 

method for perchloroethene (table A2). 

One ground-water sample was spiked with pesticide and 

pesticide degradates (NWQL Schedule 2060). Forty-five of 

the 59 compounds had recoveries within the acceptable range 

of 70 to 130 percent; 15 of the compounds had recoveries less 

than 70 percent (table A5D). No compound had a matrix-spike 

recovery greater than 130 percent. Deethylatrazine (2-chloro4-isopropylamino-6-amino-s-triazine) was the only compound 

detected in an environmental sample that had a matrix-spike 

recovery less than 70 percent on the NWQL Schedule 2060. 
68 Ground-Water Quality Data in the Santa Clara River Valley Study Unit, 2007: Results from the California GAMA Program

The NWQL Schedule 2060 was not the preferred analytical 

method for the three compounds (atrazine, deethylatrazine, 

and metalaxyl) detected in environmental samples (table A2). 

Results for pharmaceutical compounds are not presented in 

this report; they will be included in subsequent publications.

Surrogate Compound Recoveries

Surrogates are used to identify general problems that 

may arise during sample analysis that could affect the analysis 

results for all compounds in that sample. Table A6 lists the 

surrogate, the analytical schedule on which it was applied, 

the number of analyses of blanks and ground-water samples, 

the number of surrogate recoveries below 70 percent, and 

the number of surrogate recoveries above 130 percent for 

the blank samples and ground-water samples. Blank and 

ground-water samples were considered separately to assess 

whether the matrices in non-blank samples affect surrogate 

recoveries. No systematic differences between surrogate 

recoveries from blank and non-blank samples were measured. 

Seventy-nine percent of surrogate recoveries for VOC and 

gasoline oxygenate and degradate analyses were within the 

acceptable range of 70 to 130 percent. Pesticides and pesticide 

degradates (NWQL Schedule 2003) analyses had 95 percent 

of the surrogate recoveries within the acceptable range of 70 

to 130 percent. Potential wastewater-indicator analyses had 

68 percent of the surrogate recoveries within the acceptable 

range of 70 to 130 percent. Pesticide and pesticide degradates 

(NWQL Schedule 2060) analyses had 83 percent of the 

surrogate recoveries within the acceptable range of 70 to 

130 percent. 
Table A1 69

Analyte Analytical method Laboratory and 

analytical schedule Citation(s)

Water-quality indicators

Field parameters Calibrated field meters and test kits USGS field measurement U.S. Geological Survey, 

variously dated

Organic constituents

VOCs Purge and trap capillary gas 

chromatography/mass spectrometry

NWQL, schedule 2020 Connor and others, 1998

Gasoline oxygenates Heated purge and trap/gas 

chromatography/mass spectrometry 

NWQL, schedule 4024 Rose and Sandstrom, 2003

Pesticides and degradates Solid-phase extraction and gas 

chromatography/mass spectrometry

NWQL, schedule 2003 Zaugg and others, 1995; Lindley 

and others, 1996; Madsen and 

others, 2003; Sandstrom and 

others, 2001

Polar pesticides and degradates High-performance liquid 

chromatography/mass spectrometry

NWQL, schedule 2060 Furlong and others, 2001

Pharmaceuticals Solid-phase extraction and HPLC/mass 

spectrometry

NWQL, laboratory 

code 9003

Kolpin and others, 2002

Potential wastewater-indicators Solid-phase extraction and gas 

chromatography/mass spectrometry

NWQL, schedule 4433 Zaugg and others, 2006

Constituents of special interest

Perchlorate Chromatography and mass spectrometry Montgomery Watson-Harza 

Laboratory

Hautman and others, 1999

Inorganic constituents

Nutrients Alkaline persulfate digestion, Kjedahl 

digestion

NWQL, schedule 2755 Fishman, 1993; Patton and 

Kryskalla, 2003

Dissolved organic carbon UV-promoted persulfate oxidation and 

infrared spectrometry

NWQL, schedule 2613 Brenton and Arnett, 1993

Major and minor ions, trace 

elements and nutrients

Atomic absorption spectrometry, 

colorimetry, ion-exchange 

chromatography, inductively-coupled 

plasma atomic emission spectrometry 

and mass spectrometry

NWQL, schedule 1948 Fishman and Friedman, 1989; 

Fishman, 1993; Faires, 1993; 

McLain, 1993; Garbarino, 

1999; Garbarino and Damrau, 

2001; American Public Health 

Association, 1998; Garbarino 

and others, 2006

Chromium, arsenic and iron 

speciation

Various techniques of ultraviolet visible 

(UV-VIS) spectrophotometry and 

atomic absorbance spectroscopy

USGS Trace Metal 

Laboratory, Boulder, 

Colorado

Stookey, 1970; Stumm and 

Morgan, 1996; To and others, 

1998; Ball and McCleskey, 

2003a and 2003b; McCleskey 

and others, 2003

Table A1. Analytical methods used by the U.S. Geological Survey (USGS) National Water Quality Laboratory (NWQL) and additional 

contract laboratories to determine organic, inorganic, and microbial constituents.

[Analytical method: MI agar, supplemented nutrient agar in which coliforms (total and Escherichia) produce distinctly different fluorescence under ultraviolet 

lighting, thus aiding in their detection and enumeration. Abbreviations: NWQL, National Water-Quality Laboratory; HPLC, high-performance liquid 

chromatography; UV, ultraviolet; VOC, volatile organic compound; USEPA, U.S. Environmental Protection Agency; VIS, visible; δ, stable isotope ratios are

reported in the standard delta notation (δ), the ratio of a heavier isotope to more common lighter isotope of that element, relative to a standard reference material]
70 Ground-Water Quality Data in the Santa Clara River Valley Study Unit, 2007: Results from the California GAMA Program

Analyte Analytical method Laboratory and 

analytical schedule Citation(s)

Stable isotopes

Stable isotopes of water: δ2

H and 

δ18O

Gaseous hydrogen and carbon dioxidewater equilibration and stable-isotope 

mass spectrometry

USGS Stable Isotope 

Laboratory, Reston, 

Virginia

Epstein and Mayeda, 1953; 

Coplen and others, 1991; 

Coplen, 1994

Nitrogen and oxygen isotopes

 of nitrate: δ15N-NO3

 and 

δ18O-NO3

Denitrifier method and mass 

spectrometry

USGS Stable Isotope 

Laboratory, Reston, 

Virginia, lab code 2900

Casciotti and others, 2002

Carbon isotopes: δ13C of 

dissolved inorganic carbon

Accelerator mass spectrometry University of Waterloo, 

Environmental Isotope 

Lab; University of 

Arizona Accelerator Mass 

Spectrometry Lab

Donahue and others, 1990; Jull 

and others, 2004

Chlorine and bromine isotopes: 

δ37Cl and δ81Br

Isotope ratio mass spectrometry University of Waterloo, 

Environmental Isotope Lab

Shouakar-Stash and others, 

2005a; Shouakar-Stash and 

others, 2005b

Radioactivity and gases

Tritium Electrolytic enrichment-liquid 

scintillation

USGS Stable Isotope and 

Tritium Laboratory, 

Menlo Park, California

Thatcher and others, 1977

Tritium and noble gases Helium-3 in-growth and mass 

spectrometry

Lawrence Livermore 

National Laboratory

Moran and others, 2002; Eaton 

and others, 2004

Radon-222 Liquid scintillation counting NWQL, schedule 1369 American Society for Testing 

and Materials, 1998

Radium -226/228 Alpha activity counting Eberline Analytical Services, 

NWQL method 1262

U.S. Environmental Protection 

Agency, 1980 (USEPA 

methods 903 and 904)

Gross alpha and beta radioactivity Alpha and beta activity counting Eberline Analytical Services, 

NWQL method 1792

U.S. Environmental Protection 

Agency, 1980 (USEPA method 

900.0)

Microbial constituents

F-specific and somatic coliphage Single-agar layer (SAL) and two-step 

enrichment methods

USGS Ohio Water 

Microbiology Laboratory

U.S. Environmental Protection 

Agency, 2001

Total and Escherichia coliform Membrane filter technique with 

"MI agar"

USGS field measurement U.S. Environmental Protection 

Agency, 2002

Table A1. Analytical methods used by the U.S. Geological Survey (USGS) National Water Quality Laboratory (NWQL) and additional 

contract laboratories to determine organic, inorganic, and microbial constituents.—Continued

[Analytical method: MI agar, supplemented nutrient agar in which coliforms (total and Escherichia) produce distinctly different fluorescence under ultraviolet 

lighting, thus aiding in their detection and enumeration. Abbreviations: NWQL, National Water-Quality Laboratory; HPLC, high-performance liquid 

chromatography; UV, ultraviolet; VOC, volatile organic compounds; USEPA, U.S. Environmental Protection Agency; VIS, visible; δ, stable isotope ratios are

reported in the standard delta notation (δ), the ratio of a heavier isotope to more common lighter isotope of that element, relative to a standard reference material]
Table A2 71

Table A2. Preferred analytical schedules for constituents appearing on multiple schedules for samples collected for the Santa Clara 

River Valley Groundwater Ambient Monitoring and Assessment (GAMA) study, California, April to June 2007.

[Laboratory: LLNL, Lawrence Livermore National Laboratory; MWH, Montgomery Watson Harza Laboratory; SITL, U.S. Geological Survey Stable Isotope 

and Tritium Laboratory; TML, U.S. Geological Survey Trace Metal Laboratory. Abbreviation: VOC, volatile organic compound]

Constituent Primary constituent 

classification

Analytical 

schedules

Preferred 

analytical 

schedule

Results from preferred method reported

Acetone Solvent 2020, 4024 2020

Atrazine Pesticide 2003, 2060, 4433 2003

Bromoform (Tribromomethane) VOC 2020, 4433 2020

Caffeine Wastewater indicator 4433, 2060, 2080 2060

Carbaryl Pesticide 2003, 2060, 4433 2003

Chlorpyrifos Pesticide 2003, 4433 2003

Cotinine Wastewater indicator 2080, 4433 2080

Deethylatrazine (2-Chloro-4-

isopropylamino-6-amino-striazine)

Pesticide degradate 2003, 2060 2003

Diazinon Pesticide 2003, 4433 2003

1,4-Dichlorobenzene VOC, pesticide 2020, 4433 2020

Dichlorvos Pesticide 2003, 4433 2003

Diisopropyl ether (DIPE) VOC, gasoline oxygenate 2020, 4024 2020

Ethyl tert-Butyl ether (ETBE) VOC, gasoline oxygenate 2020, 4024 2020

Isopropylbenzene VOC 2020, 4433 2020

Metalaxyl Pesticide 2003, 2060, 4433 2003

Methyl tert-butyl ether (MTBE) VOC, gasoline oxygenate 2020, 4024 2020

Methyl tert-pentyl ether VOC, gasoline oxygenate 2020, 4024 2020

Metolachlor Pesticide 2003, 4433 2003

Naphthalene VOC 2020, 4433 2020

Perchloroethene (PCE) VOC 2020, 4433 2020

Prometon Pesticide 2003, 4433 2003

Tebuthiuron Herbicide 2003, 2060 2003

Results from both methods reported (different USGS parameter codes)

Alkalinity Water-quality indicator field, 1948 field

Arsenic, total Trace element 1948, TML 1948

Chromium, total Trace element 1948, TML 1948

Iron, total Trace element 1948, TML 1948

pH Water-quality indicator field, 1948 field

Specific conductance Water-quality indicator field, 1948 field

Tritium Radioactive LLNL, SITL both
72 Ground-Water Quality Data in the Santa Clara River Valley Study Unit, 2007: Results from the California GAMA Program

Constituent

Number of source 

solution blank 

detections/analyses

Number of 

field blank 

detections/analyses

Number of 

equipment blank 

detections/analyses

Number of 

ground-water 

samples censored

 Organic constituents (μg/L)

Methyl ethyl ketone (2-Butanone, MEK) 0/4 1/5 0/1 0

Toluene 1/4 1/5 1/1 6

Dissolved organic carbon 0/0 1/3 0/1 4

 Inorganic constituents (mg/L)

Calcium 0/0 1/3 1/1 0

Silica 0/0 0/3 1/1 0

Total nitrogen 0/0 1/3 0/1 0

 Trace elements (μg/L)

Barium 0/0 2/3 1/1 0

Chromium 0/0 0/3 1/1 0

Copper 0/0 1/3 0/1 0

Iron (TML)1 0/0 2/2 0/0 4

Molybdenum 0/0 0/3 1/1 0

Nickel 0/0 1/3 1/1 0

Zinc 0/0 2/3 1/1 0

1 Iron analyzed by U.S. Geological Survey Trace Metal Laboratory (TML). Note that NWQL Schedule 1948 is preferred method for iron. Iron was not 

detected in field blanks analyzed by NWQL Schedule 1948.

Table A3. Quality-control summary for constituents detected in blank samples collected for the Santa Clara River Valley 

Groundwater Ambient Monitoring and Assessment (GAMA) study, California, April to June 2007.

[Abbreviations: mg/L, milligram per liter; μg/L, microgram per liter; TML, U.S. Geological Survey Trace Metal Laboratory]
Table A4A 73

Constituent

Number of 

RSDs greater than 

zero/number of 

replicates

RSD (percent) Measured values for replicates 

with RSD greater than zero 

(environmental, replicate)

(μg/L)

Maximum Median

Volatile organic compounds and gasoline oxygenates (Schedules 2020 and 4024)

Benzene 0/3 0 0

Bromochloromethane 0/3 0 0

Bromodichloromethane 0/3 0 0

Bromoform (Tribromomethane) 0/3 0 0

Carbon disulfide 0/3 0 0

Carbon tetrachloride (Tetrachloromethane) 0/3 0 0

Chloroform (Trichloromethane) 0/3 0 0

Dibromochloromethane 0/3 0 0

Dibromomethane 0/3 0 0

trans-1,2-Dichloroethene 0/3 0 0

m- and p-Xylene 0/3 0 0

Perchloroethene (PCE) 0/3 0 0

1,1,1-Trichloroethane (TCA) 0/3 0 0

Trichlorotrifluoroethane (CFC-113) 0/3 0 0

Tetrahydrofuran 0/3 0 0

Toluene 0/3 0 0

Trichloroethene (TCE) 0/3 0 0

Trichlorofluoromethane (CFC-11) 0/3 0 0

Pesticides and pesticide degradates (Schedule 2003)

Atrazine 0/3 0 0

Deethylatrazine (2-Chloro-4-isopropylamino-6-

amino-s-triazine)

0/3 0 0

Desulfinyl fipronil 0/3 0 0

3,4-Dichloroaniline 0/3 0 0

Fipronil sulfide 0/3 0 0

Fipronil sulfone 0/3 0 0

Fipronil 0/3 0 0

Hexazinone 0/3 0 0

Metalaxyl 1/3 7 7 (0.010, 0.009)

Metolachlor 0/3 0 0

Prometryn 0/3 0 0

Simazine 0/3 0 0

Tebuthiuron 0/3 0 0

Potential wastewater-indicator compounds (Schedule 4433)

Bis(2-ethylhexyl) phthalate 0/3 0 0

Bisphenol A 0/3 0 0

Cholesterol 0/3 0 0

p-Cresol 0/3 0 0

3,4-Dichlorophenyl isocyanate 0/3 0 0

Indole 0/3 0 0

2-Methylnaphthalene 0/3 0 0

4-Octylphenol diethoxylates 0/3 0 0

4-Octylphenol monoethoxylates 0/3 0 0

4-tert-Octylphenol 0/3 0 0

Phenol 0/3 0 0

Pharmaceuticals (Schedule 2080)

Sulfamethoxazole 0/1 0 0

Diphenhydramine 0/1 0 0

Carbamazepine 1/1 4 4 (0.017, 0.018)

Table A4A. Quality-control summary for replicate analyses of organic constituents detected in samples collected for the Santa Clara 

River Valley Groundwater Ambient Monitoring and Assessment (GAMA) study, California, April to June 2007. 

[Abbreviations: RSD, relative standard deviation in percent; μg/L, microgram per liter; >, greater than]
74 Ground-Water Quality Data in the Santa Clara River Valley Study Unit, 2007: Results from the California GAMA Program

Constituent

Number of 

RSDs greater than 

zero/number of 

replicates

RSD (percent) Concentrations for replicates with 

RSD greater than zero 

(environmental/replicate)

(mg/L)

Maximum Median

Major and minor ions

Calcium 2/3 1 0.7 (210, 212), (138, 140)

Magnesium 3/3 0.5 0.3 (72.3, 72.6), (45.1, 45.4), (52.1, 52.2)

Potassium 1/3 1 0.0 (4.14, 4.20)

Sodium 2/3 1 0.4 (115, 117), (96.4, 97.0)

Bromide 2/3 3 2 (2.68, 2.60), (0.20, 0.21)

Chloride 3/3 1 0.2 (65.3, 65.4), (39.3, 39.4), (148, 145)

Fluoride 2/3 2 1 (0.67, 0.68), (0.69, 0.67)

Iodide 3/3 5 3 (0.014, 0.013), (0.027, 0.026), (0.050, 0.048)

Sulfate 2/3 1 0.1 (673, 672), (586, 575)

Silica 3/3 0.9 0.7 (30.4, 30.1), (30.6, 30.2), (33.8, 33.5)

Total dissolved solids 2/3 0.5 0.2 (950, 953), (1,320, 1,310)

Residue on evaporation 1/3 1 0.0 (1,400, 1,380)

Nutrients and dissolved organic carbon

Dissolved organic 

carbon

1/3 5 0.0 (1.6, 1.5)

Orthophosphate as 

phosphorous

3/3 13 5 (0.048, 0.049), (0.102, 0.085), (0.037, 0.040)

Total nitrogen 2/3 2 0.5 (13.5, 13.4), (0.40, 0.39)

Nitrate plus nitrite 1/3 0.5 0.0 (12.9, 13.0)

Ammonia 1/3 0.9 0.0 (0.308, 0.312)

Nitrite 1/3 9 0.0 (0.007, 0.008)

Constituent of special interest

Perchlorate 0/3 0 0

Table A4B. Quality-control summary for replicate analyses of major and minor ions, nutrients, and a constituent of special interest 

(perchlorate) detected in samples collected for the Santa Clara River Valley Groundwater Ambient Monitoring and Assessment (GAMA) 

study, California, April to June 2007. 

[Abbreviations: RSD, relative standard deviation in percent; mg/L, milligram per liter]
Table A4C 75

Constituent

Number of 

RSDs greater than 

zero/number of 

replicates

RSD (percent) Concentrations for replicates with 

RSD greater than zero 

(environmental/replicate)

(μg/L)

Maximum Median

USGS National Water Quality Laboratory (Schedule 1948)

Aluminum 1/3 8 0.0 (1.6, 1.8)

Antimony 1/3 11 0.0 (0.06, 0.07)

Arsenic 2/3 2 2 (0.87, 0.90), (0.92, 0.94)

Barium 1/3 3 0.0 (21, 22)

Boron 3/3 17 8 (759, 845), (616, 631), (459, 586)

Cadmium 2/3 20 5 (0.29, 0.27), (0.04, E 0.03)

Chromium 1/3 5 0.0 (0.15, 0.14)

Cobalt 0/3 0.0 0.0

Copper 2/3 4 1 (3.1, 3.3), (0.53, 0.54)

Iron 2/3 5 2 (14, 13), (137, 140)

Lead 2/3 4 2 (0.64, 0.68), (0.35, 0.34)

Lithium 3/3 2 2 (57.0, 55.7), (35.5, 35.4), (45.1, 46.3)

Manganese 3/3 3 1 (17.5, 16.8), (396, 388), (149, 150)

Molybdenum 1/3 1 0.0 (12.8, 12.9)

Nickel 2/3 5 0.4 (4.72, 4.40), (3.40, 3.38)

Selenium 2/3 16 1 (20.5, 20.1), (E 0.05, E 0.04)

Silver 0/3 0.0 0.0

Strontium 2/3 1 1 (1980, 1940), (1460, 1480)

Thallium 0/3 0.0 0.0

Tungsten 0/3 0.0 0.0

Uranium 3/3 0.7 0.5 (17.3, 17.4), (6.78, 6.85), (3.99, 4.02)

Vanadium 2/3 3 2 (3.2, 3.1), (0.25, 0.26)

Zinc 3/3 14 9 (9.9, 8.7), (3.6, 3.3), (2.2, 1.8)

USGS Trace Metals Laboratory

Iron 2/3 16 3 (4, 5), (134, 140)

Iron(II) 2/3 20 4 (3, 4), (118, 125)

Arsenic 2/3 110 110 (<0.5, 1), (0.99, <0.5)

Arsenic(III) 0/3 0.0 0.0

Chromium 0/3 0.0 0.0

Chromium(VI) 0/3 0.0 0.0

Table A4C. Quality-control summary for replicate analyses of trace elements detected in samples collected for the Santa Clara River 

Valley Groundwater Ambient Monitoring and Assessment (GAMA) study, California, April to June 2007. 

[Abbreviations: RSD, relative standard deviation in percent; nd, not detected; μg/L, microgram per liter; <, less than]
76 Ground-Water Quality Data in the Santa Clara River Valley Study Unit, 2007: Results from the California GAMA Program

Constituent

Number of 

RSDs greater than 

zero/number of 

replicates

RSD (percent) Concentrations for replicates with 

RSD greater than zero 

(environmental/replicate)

(μg/L)

Maximum Median

Radioactive constituents (pCi/L)

Radon-222 1/1 14 14 (573, 696)

Tritium 2/3 5 3 (6.7, 6.4) (8.6, 8.0)

Stable isotope ratios (per mil)

Hydrogen-2/Hydrogen-1 in water 3/3 2 1 (-48.2, -47.8) (-52.1, -51.1) (-49.3, -47.9)

Oxygen-18/Oxygen-16 in water 2/3 2 0.2 (-7.16, -7.01) (-7.61, -7.59)

Nitrogen-15/Nitrogen-14 in nitrate 2/2 1 1 (10.26, 10.11) (11.24, 11.05)

Oxygen-18/Oxygen-16 in nitrate 2/2 0.6 0.4 (10.74, 10.71) (10.61, 10.52)

Chlorine-37/Chlorine-35 in water 1/1 65 65 (0.43, 0.16)

Bromine-81/Bromine-79 in water 1/1 14 14 (1.16, 0.95)

Table A4D. Quality-control summary of replicate analyses of radioactive constituents and stable isotopes detected in samples 

collected for the Santa Clara River Valley Ground-Water Ambient Monitoring and Assessment (GAMA) study, California, April to 

June 2007. 

[Abbreviations: RSD, relative standard deviation in percent; μg/L, microgram per liter; pCi/L, picocuries per liter]
Table A5A 77

Constituent Number of 

spike samples

Recovery (percent)

Minimum Maximum Median 

Acetone1 5 91 114 112

Acrylonitrile 5 94 114 107

tert-Amyl methyl ether (TAME) 5 95 103 100

tert-Amyl alcohol 1 101 101 101

Benzene2 5 105 107 107

Bromobenzene 5 101 107 103

Bromochloromethane2 5 104 114 108

Bromodichloromethane (THM)2 5 102 110 105

Bromoform (Tribromomethane, THM)2 5 99 108 103

Bromomethane (Methyl bromide) 5 93 124 108

tert-Butyl alcohol (TBA) 1 97 97 97

n-Butylbenzene 5 84 113 93

sec-Butylbenzene 5 104 117 112

tert-Butylbenzene 5 105 119 118

Carbon disulfide1 5 84 102 85

Carbon tetrachloride (Tetrachloromethane)2 5 98 122 108

Chlorobenzene 5 102 108 106

Chloroethane 5 72 227 112

Chloroform (Trichloromethane, THM)2 5 102 116 114

Chloromethane 5 102 137 109

3-Chloro-1-propene 5 112 124 122

2-Chlorotoluene 5 104 113 112

4-Chlorotoluene 5 103 113 107

Dibromochloromethane (THM)2 5 96 105 97

1,2-Dibromo-3-chloropropane (DBCP) 5 93 102 100

1,2-Dibromoethane (EDB) 5 101 109 103

Dibromomethane1 5 97 116 108

1,2-Dichlorobenzene 5 103 114 105

1,3-Dichlorobenzene 5 103 115 106

1,4-Dichlorobenzene 5 104 116 105

trans-1,4-Dichloro-2-butene 5 47 101 100

Dichlorodifluoromethane (CFC-12) 5 79 114 100

1,1-Dichloroethane (1,1-DCA) 5 110 102 111

1,2-Dichloroethane (1,2-DCA) 5 101 110 104

1,1-Dichloroethene (1,1-DCE) 5 103 115 108

cis-1,2-Dichloroethene (cis-1,2-DCE) 5 102 116 111

trans-1,2-Dichloroethene (trans-1,2-DCE)2 5 112 122 114

1,1-Dichloropropene 5 100 111 105

1,2-Dichloropropane 5 95 105 101

1,3-Dichloropropane 5 103 115 106

2,2-Dichloropropane 5 81 94 91

1,1-Dichloropropene 5 100 111 105

cis-1,3-Dichloropropene 5 90 95 91

trans-1,3-Dichloropropene 5 87 99 97

Diethyl ether 5 96 109 107

Diisopropyl ether (DIPE)1 5 93 106 103

Ethylbenzene 5 108 115 109

Ethyl tert-butyl ether (ETBE)1 5 91 98 97

Ethyl methacrylate 5 86 100 93

o-Ethyl toluene (1-Ethyl-2-methylbenzene) 5 100 109 104

Hexachlorobutadiene 5 76 93 84

Hexachloroethane 5 79 108 104

Table A5A. Quality-control summary for matrix-spike recoveries of volatile organic compounds (NWQL schedule 2020) including 

gasoline oxygenates and degradates (NWQL schedule 4024) in samples collected for the Santa Clara River Valley Groundwater 

Ambient Monitoring and Assessment (GAMA) study, California, April to June 2007.

[Acceptable recovery range is between 70 and 130 percent; values in bold fall outside this range. Abbreviation: THM, trihalomethane]
78 Ground-Water Quality Data in the Santa Clara River Valley Study Unit, 2007: Results from the California GAMA Program

Constituent Number of 

spike samples

Recovery (percent)

Minimum Maximum Median 

2-Hexanone (n-Butyl methyl ketone) 5 94 114 109

Iodomethane (Methyl iodide) 5 90 132 116

Isopropylbenzene 5 104 112 108

4-Isopropyl-1-methylbenzene 5 99 116 109

Methyl acetate 1 108 108 108

Methyl acrylate 5 94 108 103

Methyl acrylonitrile 5 104 133 113

Methyl tert-butyl ether (MTBE)1 5 92 101 98

Methyl methacrylate 5 86 94 91

Methyl isobutyl ketone (MIBK) 5 90 109 101

Methylene chloride (Dichloromethane)2 5 98 113 111

Methyl ethyl ketone (2-Butanone, MEK) 5 90 108 103

Naphthalene 5 76 113 94

Perchloroethene (Tetrachloroethene, PCE)2 5 104 161 115

n-Propylbenzene 5 102 115 109

Styrene 5 57 112 104

1,1,1,2-Tetrachloroethane 5 102 110 105

1,1,2,2-Tetrachloroethane 5 97 111 101

Tetrahydrofuran1 5 98 120 110

1,2,3,4-Tetramethylbenzene 5 80 113 91

1,2,3,5-Tetramethylbenzene 5 97 130 109

Toluene1 5 99 105 103

1,2,3-Trichlorobenzene 5 93 120 103

1,2,4-Trichlorobenzene 5 88 112 91

1,1,1-Trichloroethane (TCA)2 5 105 115 110

1,1,2-Trichloroethane 5 102 113 102

Trichloroethene (TCE)2 5 95 104 101

Trichlorofluoromethane (CFC-11)2 5 111 131 113

1,2,3-Trichloropropane (1,2,3-TCP) 5 97 110 101

Trichlorotrifluoroethane (CFC-113)2 5 85 106 97

1,2,3-Trimethylbenzene 5 104 119 111

1,2,4-Trimethylbenzene 5 107 122 113

1,3,5-Trimethylbenzene 5 104 114 109

Vinyl bromide (Bromoethene) 5 111 127 118

Vinyl chloride (Chloroethene) 5 112 135 119

m- and p-Xylene 5 109 122 116

o-Xylene 5 103 109 107

1

Constituents on schedules 2020 and 4024; only values from schedule 2020 are reported because it is the preferred analytical schedule. 

2

Constituents detected in ground-water samples.

Table A5A. Quality-control summary for matrix-spike recoveries of volatile organic compounds (NWQL schedule 2020) including 

gasoline oxygenates and degradates (NWQL schedule 4024) in samples collected for the Santa Clara River Valley Groundwater 

Ambient Monitoring and Assessment (GAMA) study, California, April to June 2007.—Continued

[Acceptable recovery range is between 70 and 130 percent; values in bold fall outside this range. Abbreviation: THM, trihalomethane]
Table A5B 79

Constituent Number of 

spike samples

Recovery (percent)

Minimum Maximum Median 

Acetochlor 5 99 120 108

Alachlor 5 101 120 105

Atrazine1 5 95 116 100

Azinphos-methyl 5 80 149 92

Azinphos-methyl-oxon 5 26 109 42

Benfluralin 5 59 91 75

Carbaryl 5 106 131 121

2-Chloro-2,6-diethylacetanilide 5 93 113 100

4-Chloro-2-methylphenol 5 49 69 56

Chlorpyrifos 5 95 117 100

Chlorpyrofos, oxygen analog 5 14 78 28

Cyfluthrin 5 48 97 68

Cypermethrin 5 48 96 62

Dacthal (DCPA) 5 97 134 100

Deethylatrazine (2-Chloro-4-isopropylamino6-amino-s-triazine)1

5 40 54 44

Desulfinyl fipronil1 5 79 120 92

Desulfinyl fipronil amide 5 67 166 90

Diazinon 5 94 108 97

3,4-Dichloroaniline1 5 73 96 75

Dichlorvos 5 15 61 29

Dicrotophos 5 24 49 39

Dieldrin 5 87 128 103

2,6-Diethylaniline 5 90 115 94

Dimethoate 5 27 42 31

Ethion 5 71 134 95

Ethion monoxon 5 73 147 102

2-Ethyl-6-methylaniline 5 88 102 93

Fenamiphos 5 77 194 115

Fenamiphos sulfone 5 50 159 60

Fenamiphos sulfoxide 5 19 68 44

Fipronil1 5 86 182 99

Fipronil sulfide1 5 71 137 100

Fipronil sulfone1 5 53 121 76

Fonofos 5 85 104 92

Hexazinone1 5 64 98 71

Iprodione 5 63 109 75

Isofenphos 5 105 159 113

Malaoxon 5 82 122 109

Malathion 5 96 118 113

Metalaxyl1 5 92 120 100

Methidathion 5 82 137 97

Metolachlor1 5 104 120 108

Metribuzin 5 75 100 85

Myclobutanil 5 80 146 98

1-Naphthol 5 28 83 40

Paraoxon-methyl 5 41 86 60

Parathion-methyl 5 77 119 87

Pendimethalin 5 89 168 100

cis-Permethrin 5 53 101 68

Phorate 5 53 98 84

Phorate oxon 5 78 163 119

Table A5B. Quality-control summary for matrix-spike recoveries of pesticides and pesticide degradates (NWQL schedule 2003) in 

samples collected for the Santa Clara River Valley Groundwater Ambient Monitoring and Assessment (GAMA) study, California, April 

to June 2007.

[Acceptable recover range is between 70 and 130 percent; values in bold fall outside this range]
80 Ground-Water Quality Data in the Santa Clara River Valley Study Unit, 2007: Results from the California GAMA Program

Constituent Number of 

spike samples

Recovery (percent)

Minimum Maximum Median 

Phosmet 5 11 30 16

Phosmet oxon 4 7 25 9

Prometon 5 89 114 99

Prometryn1 5 99 120 106

Pronamide (Propyzamide) 5 89 119 102

Simazine1 5 98 121 100

Tebuthiuron1 5 87 144 107

Terbufos 5 80 108 102

Terbufos oxon sulfone 5 63 115 91

Terbuthylazine 5 99 118 102

Tribufos 5 56 112 80

Trifluralin 5 66 100 83

1Constituents detected in ground-water samples.

Table A5B. Quality-control summary for matrix-spike recoveries of pesticides and pesticide degradates (NWQL schedule 2003) in 

samples collected for the Santa Clara River Valley Groundwater Ambient Monitoring and Assessment (GAMA) study, California, April 

to June 2007.—Continued

[Acceptable recover range is between 70 and 130 percent; values in bold fall outside this range]
Table A5C 81

Constituent Number of 

spike samples

Recovery (percent)

Minimum Maximum Median 

Acetophenone 4 71 112 96

Acetyl hexamethyl tetrahydronaphthalene 

(AHTN)

5 68 101 98

Anthracene 5 57 95 85

9,10-Anthraquinone 5 57 114 95

Atrazine 5 49 94 87

Benzo[a]pyrene 5 53 129 72

Benzophenone 5 70 107 97

Bisphenol A1 5 60 117 113

Bromacil 5 50 96 93

Bromoform (tribromomethane) 4 55 83 79

3-tert-Butyl-4-hydroxy anisole (BHA) 5 49 78 75

Caffeine 5 45 113 82

Camphor 5 57 91 88

Carbaryl 5 61 107 100

Carbazole 5 61 100 90

Chlorpyrifos 5 60 89 84

Cholesterol1 5 49 103 68

3-β-Coprostanol 5 48 115 70

Cotinine 5 25 67 54

p-Cresol 4 56 98 93

4-Cumylphenol 5 60 96 92

Diazinon 5 43 89 82

Dichlorvos 5 50 114 91

N,N-diethyl-meta-toluamide (DEET) 5 72 121 98

1,4-Dichlorobenzene 4 46 89 79

3,4-Dichlorophenyl isocyanate 5 0 83 56

Diethyl phthalate 5 72 117 101

2,6-Dimethylnaphthalene 5 58 96 83

bis(2-Ethylhexyl) phthalate1 5 96 607 259

Nonylphenol, monoethoxy- (total) 5 59 109 103

4-Nonylphenol diethoxylates 5 52 105 93

4-Octylphenol diethoxylates1 5 74 131 108

4-Octylphenol monoethoxylates1 5 68 114 99

Fluoranthene 5 64 207 93

Hexahydrohexamethylcyclopentabenzopyran 

(HHCB) 

5 66 105 97

Indole 5 55 102 93

Isoborneol 5 60 111 88

Isophorone 5 54 104 85

Isopropylbenzene 4 34 78 65

Isoquinoline 5 44 115 93

d-Limonene 4 29 65 52

Menthol 5 60 113 83

Metalaxyl 5 63 97 92

3-Methyl-1(H)-indole (Skatole) 5 58 102 91

5-Methyl-1H-benzotriazole 5 72 110 93

1-Methylnaphthalene 5 60 95 84

2-Methylnaphthalene 5 59 93 83

Methyl salicylate 5 65 115 107

Metolachlor 5 59 92 88

Naphthalene 5 61 97 86

para-Nonylphenol (total) 5 67 112 94

Table A5C. Quality-control summary for matrix-spike recoveries of potential wastewater-indicator compounds in samples collected 

for the Santa Clara River Valley Groundwater Ambient Monitoring and Assessment (GAMA) study, California, April to June 2007.

[Acceptable recovery range is between 70 and 130 percent; values in bold fall outside this range]
82 Ground-Water Quality Data in the Santa Clara River Valley Study Unit, 2007: Results from the California GAMA Program

Constituent Number of 

spike samples

Recovery (percent)

Minimum Maximum Median 

4-n-Octylphenol 5 60 98 88

4-tert-Octylphenol1 5 76 113 103

Pentachlorophenol 5 26 100 87

Phenanthrene 5 58 145 83

Phenol1 4 80 96 89

Prometon 5 58 145 83

Pyrene 5 61 167 88

β-Sitosterol 5 48 86 58

β-Stigmastanol 5 58 73 63

2,2',4,4'-Tetrabromodiphenyl ether 1 11 11 11

Perchloroethene (Tetrachloroethene, PCE) 4 24 59 44

Tributyl phosphate 5 68 115 102

Triclosan 5 57 117 102

Triethyl citrate (ethyl citrate) 5 57 107 93

Triphenyl phosphate 5 60 91 89

Tri(2-butoxyethyl)phosphate 5 44 102 91

Tri(2-chloroethyl)phosphate 5 57 93 84

Tri(dichlorisopropyl)phosphate 5 58 94 91

1Constituents detected in ground-water samples.

Table A5C. Quality-control summary for matrix-spike recoveries of potential wastewater-indicator compounds in samples collected 

for the Santa Clara River Valley Groundwater Ambient Monitoring and Assessment (GAMA) study, California, April to June 2007.—

Continued

[Acceptable recovery range is between 70 and 130 percent; values in bold fall outside this range]
Table A5D 83

Constituent

Number of 

spike 

samples

Recovery 

(percent)

Acifluorfen 1 70

Aldicarb 1 123

Aldicarb sulfone 1 59

Aldicarb sulfoxide 1 101

Atrazine1 1 88

Bendiocarb 1 82

Benomyl 1 81

Bensulfuron-methyl 1 85

Bentazon 1 67

Bromacil 1 91

Bromoxynil 1 49

Caffeine 1 75

Carbaryl 1 86

Carbofuran 1 87

Chloramben, methyl ester 1 85

Chlorimuron-ethyl 1 67

3-(4-Chlorophenyl)-1-methyl urea 1 98

Clopyralid 1 58

Cycloate 1 80

2,4-D (2,4-Dichlorophenoxyacetic acid) 1 80

2,4-D methyl ester 

(2,4-Dichlorophenoxyacetic acid methyl 

ester)

1 85

2,4-DB (4-(2,4-Dichlorophenoxy)butyric 

acid)

1 62

DCPA (Dacthal) monoacid 1 79

Deethylatrazine (2-Chloro-4-

isopropylamino-6-amino-s-triazine)1

1 64

Deisopropyl atrazine (2-chloro-6-

ethylamino-4-amino-s-triazine)

1 76

Dicamba 1 58

Dichlorprop 1 77

Dinoseb 1 62

Diphenamid 1 92

Table A5D. Quality-control summary for matrix-spike recoveries of pesticides and pesticide degradates (NWQL schedule 2060) in 

samples collected for the Santa Clara River Valley Groundwater Ambient Monitoring and Assessment (GAMA) study, California, April to 

June 2007.

[Acceptable recover range is between 70 and 130 percent; values in bold fall outside this range]

Constituent

Number of 

spike 

samples

Recovery 

(percent)

Diuron 1 92

Fenuron 1 81

Flumetsulam 1 65

Fluometuron 1 93

Hydroxyatrazine (2-Hydroxy-4-

isopropylamino-6-ethylamino-s-triazine)

1 88

3-Hydroxycarbofuran 1 79

Imazaquin 1 85

Imazethapyr 1 82

Imidacloprid 1 63

Linuron 1 92

MCPA (2-Methyl-4-chlorophenoxyacetic 

acid) 

1 75

MCPB (4-(2-Methyl-4-chlorophenoxy) 

butyric acid)

1 63

Metalaxyl1 1 92

Methiocarb 1 87

Methomyl 1 120

Metsulfuron methyl 1 69

Neburon 1 92

Nicosulfuron 1 121

Norflurazon 1 89

Oryzalin 1 83

Oxamyl 1 106

Picloram 1 57

Propham 1 95

Propiconazole 1 89

Propoxur 1 96

Siduron 1 94

Sulfometuron-methyl 1 82

Tebuthiuron 1 89

Terbacil 1 88

Triclopyr 1 69

1

Constituents detected in ground-water samples.
84 Ground-Water Quality Data in the Santa Clara River Valley Study Unit, 2007: Results from the California GAMA Program Table A6. Quality-control summary for surrogate recoveries of volatile organic compounds, including gasoline oxygenates and degradates, pesticides and pesticide degradates, potential wastewater-indicator compounds, and pharmaceutical compounds in samples collected for the Santa Clara River Valley Groundwater Ambient Monitoring and Assessment (GAMA) study, California, April to June 2007. [Acceptable recovery range is between 70 and 130 percent. Abbreviations: MWH, Montgomery Watson Harza Laboratory; VOC, volatile organic compound] Surrogate Analytical schedule Constitutent or constituent class analyzed Blank samples Ground-water samples Number of blank analyses Median recovery in blanks (percent) Number of surrogate recoveries Number of ground-water sample analyses Median recovery in ground-water samples (percent) Number of surrogate recoveries Below 70 percent in blanks Aove 130 percent in blanks Below 70 percent in ground-water samples Above 130 percent in ground-water samples 1-Bromo-4- fluorobenzene 2020, 4024 VOC, gas oxygenate 10 71 5 0 53 72 24 0 1,2-Dichloroethane-d4 2020, 4024 VOC, gas oxygenate 10 122 0 0 53 122 0 12 Isobutyl alcohol-d6 4024 Gas oxygenate 1 104 0 0 9 106 0 0 Toluene-d8 2020, 4024 VOC, gas oxygenate 10 97 0 0 53 97 0 0 Diazinon-d10 2003 Pesticide 6 117 0 0 52 114 0 5 α-HCH-d6 2003 Pesticide 6 98 0 0 52 92 0 1 Barban 2060 Pesticide 1 93 0 0 9 88 0 0 Caffeine-13C 2060 Potential wastewater-indicator 1 107 0 0 9 73 3 0 2,4,5-T 2060 Pesticide 1 84 0 0 9 73 2 0 Caffeine-13C 4433 Potential wastewater-indicator 11 81 5 2 50 80 12 1 Decafluorobiphenyl 4433 Potential wastewater-indicator 11 74 5 0 50 71 23 0 Fluoranthene-d10 4433 Potential wastewater-indicator 11 92 1 2 50 94 3 1 Bisphenol A-d3 4433 Potential wastewater-indicator 11 62 7 0 48 70 24 0

Montrella and Belitz–Ground-Water Quality Data in the Santa Clara River Valley Study Unit, 2007: Results from the California GAMA Program–Data Series 408

Printed on recycled paper