U.S. Department of the Interior

U.S. Geological Survey

Data Series 795

Prepared in cooperation with the California State Water Resources Control Board

A product of the California Groundwater Ambient Monitoring and Assessment (GAMA) Program

Groundwater-Quality Data in Seven GAMA Study Units: 

Results from Initial Sampling, 2004–2005, and Resampling, 

2007–2008, of Wells: California GAMA Program Priority 

Basin Project
Cover. 1. Cotton fields near Fresno, California. (Photograph taken by Justin Kulongoski, U.S. Geological Survey.)

2. Almond orchard near near Fresno, California. (Photograph taken by Cathy Munday, U.S. Geological Survey.)

3. Tower Bridge over the Sacramento River, Sacramento, California. (Photograph taken by Cathy Munday, U.S. Geological Survey.)

4. Salinas Valley agriculture in Monterey County, California. (Photograph taken by Andrea Altmann, U.S. Geological Survey.)

5. Lake Henshaw in San Diego County, California. (Photograph taken by Barbara Dawson, U.S. Geological Survey.)

6. Vineyards in the North San Francisco Bay area, California. (Photograph taken by George Bennett, V, U.S. Geological Survey.)

7. Looking northeast from Griffith Park. Downtown Glendale is in the middle ground, and the San Gabriel Mountains are in the 

 background. (Photograph taken July 12, 2006, by Will Bebeck.) 

Cover photographs

1 2

3

4

5

6

7
Groundwater-Quality Data in Seven GAMA Study 

Units: Results from Initial Sampling, 2004–2005, 

and Resampling, 2007–2008, of Wells: California 

GAMA Program Priority Basin Project 

By Robert Kent, Kenneth Belitz, and Miranda S. Fram

A product of the California Groundwater Ambient Monitoring and Assessment (GAMA) Program

Prepared in cooperation with the California State Water Resources Control Board 

Data Series 795

U.S. Department of the Interior

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

SALLY JEWELL, Secretary

U.S. Geological Survey

Suzette M. Kimball, Acting Director

U.S. Geological Survey, Reston, Virginia: 2014

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Suggested citation:

Kent, Robert, Belitz, Kenneth, and Fram, M.S., 2014, Groundwater-quality data in seven GAMA study units: Results 

from initial sampling, 2004–2005, and resampling, 2007–2008, of wells: California GAMA Program Priority Basin 

Project: U.S. Geological Survey Data Series 795, 170 p., http://dx.doi.org/10.3133/ds795.

ISSN 2327-638X (online)
iii

Contents

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

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

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

Study Units......................................................................................................................................................4

San Diego Drainages Study Unit........................................................................................................5

North San Francisco Bay Study Unit.................................................................................................5

Northern San Joaquin Basin Study Unit...........................................................................................5

Southern Sacramento Valley Study Unit...........................................................................................5

San Fernando–San Gabriel Study Unit............................................................................................10

Monterey Bay and Salinas Valley Basins Study Unit ...................................................................10

Southeast San Joaquin Valley Study Unit .....................................................................................10

Methods ........................................................................................................................................................14

Sample Collection and Analysis.......................................................................................................15

Duplicate Analyses for Selected Constituents ....................................................................16

Quality-Assurance Procedures........................................................................................................16

Quality-Control Samples....................................................................................................................16

Comparison Benchmarks ..................................................................................................................16

Water-Quality Results .................................................................................................................................18

Water-Quality Indicators ..................................................................................................................18

Organic Constituents..........................................................................................................................19

Volatile Organic Compounds....................................................................................................19

Pesticide Compounds ...............................................................................................................20

Constituents of Special Interest.......................................................................................................20

Inorganic Constituents.......................................................................................................................20

Nutrients......................................................................................................................................21

Major and Minor Ions, TDS, and Trace Elements.................................................................21

Isotopic Tracers ..................................................................................................................................23

Future Work .................................................................................................................................................23

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

Acknowledgments ......................................................................................................................................25

References Cited..........................................................................................................................................25

Tables ...........................................................................................................................................................32

Appendix......................................................................................................................................................144
iv

Figures

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

GAMA study units featured in this report.................................................................................3

2. Map showing the San Diego Drainages GAMA study unit with locations of study 

areas, status wells, and trend wells..........................................................................................6

3. Map showing the North San Francisco Bay GAMA study unit with locations of 

study areas, status wells, and trend wells ...............................................................................7

4. Map showing the Northern San Joaquin Basin GAMA study unit with locations of 

study areas, status wells, and trend wells ...............................................................................8

5. Map showing the Southern Sacramento Valley GAMA study unit with locations of 

study areas, status wells, and trend wells ...............................................................................9

6. Map showing the San Fernando–San Gabriel GAMA study unit with locations of 

study areas, status wells, and trend wells .............................................................................11

7. Map showing the Monterey Bay and Salinas Valley Basins GAMA study unit 

with locations of study areas, status wells, and trend wells ..............................................12

8. Map showing the Southeast San Joaquin Valley GAMA study unit with locations 

of study areas, status wells, and trend wells.........................................................................13

Tables

1. Identification, sampling, and construction information for trend wells sampled 

for seven GAMA study units .....................................................................................................32

2. Number of water-quality indicators and chemical constituents measured in 

samples collected at trend wells for the GAMA study units featured in this 

report ............................................................................................................................................34

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

and reporting information for the USGS National Water Quality Laboratory 

Schedule 2020 .............................................................................................................................41

3B. 1,2-Dibromo-3-chloropropane (DBCP) and 1,2-dibromoethane (EDB), primary uses 

or sources, comparative benchmarks, and reporting information for the USGS 

National Water Quality Laboratory Schedule 1306...............................................................45

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

benchmarks, and reporting information for the USGS National Water Quality 

Laboratory Schedule 2003, and the expanded versions Schedule 2032 and 

Schedule 2033 .............................................................................................................................46

3D. Polar pesticides, pesticide degradates, and caffeine, primary uses or sources, 

comparative benchmarks, and reporting information for the USGS National 

Water Quality Laboratory Schedule 2060 ...............................................................................50

3E. Nutrients, comparative benchmarks, and reporting information for the USGS 

National Water Quality Laboratory Schedule 2755...............................................................53

3F. Major and minor ions, total dissolved solids, trace elements, comparative 

benchmarks, and reporting information for the USGS National Water Quality 

Laboratory Schedule 1948.........................................................................................................54

3G. Arsenic and iron species, comparative benchmarks, and reporting information 

for the USGS Trace Metal Laboratory, Boulder, Colorado...................................................56
v

3H. Constituents of special interest, primary uses or sources, comparative 

benchmarks, and reporting information for the Montgomery Watson Harza 

Laboratory and Weck Laboratories, Inc. ................................................................................57

3I. Isotopic and radioactive constituents, comparative benchmarks, and reporting 

information for laboratories ......................................................................................................58

4. Water-quality indicators in samples collected from trend wells for seven GAMA 

study units....................................................................................................................................59

5. Volatile organic compounds (VOCs) in samples collected from trend wells for 

seven GAMA study units ...........................................................................................................66

6A. Pesticides and pesticide degradates (Schedules, 2003, 2032, and 2033) in 

samples collected from trend wells for seven GAMA study units .....................................89

6B. Polar pesticides (Schedule 2060) in samples collected from trend wells for 

seven GAMA study units .........................................................................................................104

7. Constituents of special interest in samples collected from trend wells sampled 

for seven GAMA study units ...................................................................................................109

8. Nutrients in samples collected from trend wells for seven GAMA study units.............114

9. Major and minor ions and dissolved solids in samples collected from trend 

wells for seven GAMA study units.........................................................................................119

10. Trace elements in groundwater samples collected from trend wells for seven 

GAMA study units.....................................................................................................................125

11. Arsenic and iron oxidation-reduction species in samples collected from trend 

wells for seven GAMA study units.........................................................................................137

12. Isotopic tracers in samples collected from trend wells for seven GAMA 

study units..................................................................................................................................139

Tables—Continued
vi

Conversion Factors, Datums, and Abbreviations and 

Acronyms

Conversion Factors

Inch/foot/mile to SI

Multiply By To obtain

Length

inch (in.) 2.54 centimeter (cm)

inch (in.) 25.4 millimeter (mm)

foot (ft) 0.3048 meter (m)

mile (mi) 1.609 kilometer (km)

Area

square foot (ft2) 0.09290 square meter (m2)

square mile (mi2) 2.590 square kilometer (km2)

Radioactivity

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

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

°F=(1.8×°C)+32.

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

°C=(°F−32)/1.8.

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

25 °C).

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

or micrograms per liter (μg/L). One milligram per liter is equivalent to 1 part per million (ppm); 

1 microgram per liter is equivalent to 1 part per billion (ppb); 1 nanogram per liter (ng/L) is 

equivalent to 1 part per trillion (ppt). Isotopic constituents are given in delta notation (diE) as the 

ratio of a heavier isotope of an element (iE) relative to the more common lighter isotope of that 

element, relative to a standard reference material, expressed as per mil; 1 per mil is equivalent 

to 1 part per thousand.

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

(NAVD 88).

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

Abbreviations and Acronyms

AL-US U.S. Environmental Protection Agency action level 

APE Alternate Place Entry program (USGS)

CAS Chemical Abstract Service (American Chemical Society Registry Number®)

CSU combined standard uncertainties

E estimated or having a high degree of uncertainty

GAMA Groundwater Ambient Monitoring and Assessment Program

GPS global positioning system

HAL-US U.S. Environmental Protection Agency lifetime health advisory level 

LRL laboratory reporting level

LSD land-surface datum

LT-MDL long-term method detection level

MCL-CA California Department of Public Health maximum contaminant level 

MCL-US U.S. Environmental Protection Agency maximum contaminant level 

MDL method detection limit

MRL minimum reporting level

na not available

NAVD 88 North American Vertical Datum of 1988

nc not collected 

NFM National Field Manual (USGS)

NL-CA California Department of Public Health notification level 

nv no value in category

NWIS National Water Information System (USGS)

PBP Priority Basin Project

PCFF Personal Computer Field Form program designed for USGS sampling

QA quality assurance

QC quality control

RL reporting level

RSD relative standard deviation

RSD5-US U.S. Environmental Protection Agency risk-specific dose at a risk factor of 10–5

SMCL-CA California Department of Public Health secondary maximum contaminant level 

SMCL-US U.S. Environmental Protection Agency secondary maximum contaminant level 

SRL study reporting level

ssLC sample-specific critical level
viii

Well Identifier Prefixes

COS Prefix for well in the Cosumnes Basin study area of the Northern San Joaquin 

Basin study unit

ESJ Prefix for well in the Eastern San Joaquin Basin study area of the Northern San 

Joaquin Basin study unit

KING Prefix for well in the Kings study area of the Southeast San Joaquin Valley 

study unit

KWH Prefix for well in the Kaweah study area of the Southeast San Joaquin Valley 

study unit

MSMB Prefix for well in the Monterey Bay study area of the Monterey Bay and Salinas 

Valley study unit

MSPR Prefix for well in the Paso Robles study area of the Monterey Bay and Salinas 

Valley study unit

MSSC Prefix for well in the Santa Cruz study area of the Monterey Bay and Salinas Valley 

study unit

MSSV Prefix for well in the Salinas Valley study area of the Monterey Bay and Salinas 

Valley study unit

NAM Prefix for well in the North American study area of the Southern Sacramento Valley 

study unit

NSFVOL Prefix for well in the Volcanic Highlands study area of the North San Francisco Bay 

study unit

NSFVP Prefix for well in the Valley and Plains study area of the North San Francisco Bay 

study unit

NSFWG Prefix for well in the Wilson Grove Formation Highlands study area of the North 

San Francisco Bay study unit

NSFWGFP Prefix for well on a flow path in the Wilson Grove Formation Highlands study area 

of the North San Francisco Bay study unit

NSJ-QPC Prefix for well in the Uplands Basin study area of the Northern San Joaquin Basin 

study unit

SAM Prefix for well in the South American study area of the Southern Sacramento Valley 

study unit

SDALLV Prefix for well in the Alluvial Basins study area of the San Diego Drainages 

study unit

SDHDRK Prefix for well in the Hard Rock study area of the San Diego Drainages study unit

SDTEM Prefix for well in the Temecula Valley study area of the San Diego Drainages 

study unit

SDTEMFP Prefix for well on a flow path in the Temecula Valley study area of the San Diego 

Drainages study unit

SDWARN Prefix for well in the Warner Valley study area of the San Diego Drainages 

study unit
ix

SOL Prefix for well in the Solano study area of the Southern Sacramento Valley 

study unit

SSV-QPC Prefix for well in the Uplands study area of the Southern Sacramento Valley 

study unit

SUI Prefix for well in the Suisun-Fairfield study area of the Southern Sacramento Valley 

study unit

TLR Prefix for well in the Tulare Lake study area of the Southeast San Joaquin Valley 

study unit

TRCY Prefix for well in the Tracy Basin study area of the Northern San Joaquin Basin 

study unit

TULE Prefix for well in the Tule study area of the Southeast San Joaquin Valley study unit

ULASF Prefix for well in the San Fernando study area of the San Fernando–San Gabriel 

study unit

ULASG Prefix for well in the San Gabriel study area of the San Fernando–San Gabriel 

study unit

YOL Prefix for well in the Yolo study area of the Southern Sacramento Valley study unit

Organizations

BQS Branch of Quality Systems (USGS)

CDPH California Department of Public Health 

CDPR California Department of Pesticide Regulation

CDWR California Department of Water Resources

LLNL Lawrence Livermore National Laboratory, Livermore, California

MWH Montgomery Watson Harza Laboratory 

NAWQA National Water-Quality Assessment Program (USGS)

NELAP National Environmental Laboratory Accreditation Program

NFQA National Field Quality Assurance Program (USGS)

NRP National Research Program (USGS)

NWQL National Water Quality Laboratory, Denver, Colorado (USGS)

SWRCB State Water Resources Control Board (California)

TML Trace Metal Laboratory, Boulder, Colorado (USGS)

USEPA U.S. Environmental Protection Agency

USGS U.S. Geological Survey

Weck Weck Laboratories, Inc., City of Industry, California

Well Identifier Prefixes—Continued
x

Selected chemical names

CaCO3 calcium carbonate

CO3

2– carbonate

DBCP 1,2-dibromo-3-chloropropane

EDB 1,2-dibromoethane

HCl hydrochloric acid

HCO3

– bicarbonate

MTBE methyl tert-butyl ether

NDMA N-nitrosodimethylamine

PCE perchloroethene, tetrachloroethene

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

TCE trichloroethene

TDS total dissolved solids

THM trihalomethane

VOC volatile organic compound

Units of Measure

L liter

mg milligram

mg/L milligrams per liter

mi mile

mL milliliter

μg/L micrograms per liter

pCi/L picocuries per liter

pmc percent modern carbon

diE delta notation, the ratio of a heavier isotope of an element (iE) to the more common 

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

expressed as per mil

> greater than

< less than

≤ less than or equal to 

% percent

* concentration greater than benchmark level

** concentration greater than upper benchmark level
Abstract

The Priority Basin Project (PBP) of the Groundwater 

Ambient Monitoring and Assessment (GAMA) Program 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 GAMA-PBP began 

sampling, primarily public supply wells in May 2004. By the 

end of February 2006, seven (of what would eventually be 35) 

study units had been sampled over a wide area of the State. 

Selected wells in these first seven study units were resampled 

for water quality from August 2007 to November 2008 as part 

of an assessment of temporal trends in water quality by the 

GAMA-PBP. 

The initial sampling was designed to provide a spatially 

unbiased assessment of the quality of raw groundwater 

used for public water supplies within the seven study units. 

In the 7 study units, 462 wells were selected by using a 

spatially distributed, randomized grid-based method to 

provide statistical representation of the study area. Wells 

selected this way are referred to as grid wells or status wells. 

Approximately 3 years after the initial sampling, 55 of these 

previously sampled status wells (approximately 10 percent in 

each study unit) were randomly selected for resampling. The 

seven resampled study units, the total number of status wells 

sampled for each study unit, and the number of these wells 

resampled for trends are as follows, in chronological order 

of sampling: San Diego Drainages (53 status wells, 7 trend 

wells), North San Francisco Bay (84, 10), Northern San 

Joaquin Basin (51, 5), Southern Sacramento Valley (67, 7), 

San Fernando–San Gabriel (35, 6), Monterey Bay and Salinas 

Valley Basins (91, 11), and Southeast San Joaquin Valley 

(83, 9). 

The groundwater samples were analyzed for a 

large number of synthetic organic constituents (volatile 

organic compounds [VOCs], pesticides, and pesticide 

degradates), constituents of special interest (perchlorate, 

N-nitrosodimethylamine [NDMA], and 1,2,3-trichloropropane 

[1,2,3-TCP]), and naturally-occurring inorganic constituents 

(nutrients, major and minor ions, and trace elements). 

Naturally-occurring isotopes (tritium, carbon-14, and 

stable isotopes of hydrogen and oxygen in water) also were 

measured to help identify processes affecting groundwater 

quality and the sources and ages of the sampled groundwater. 

Nearly 300 constituents and water-quality indicators were 

investigated.

Quality-control samples (blanks, replicates, and 

samples for matrix spikes) were collected at 24 percent of 

the 55 status wells resampled for trends, and the results for 

these samples were used to evaluate the quality of the data 

for the groundwater samples. Field blanks rarely contained 

detectable concentrations of any constituent, suggesting 

that contamination was not a noticeable source of bias in 

the data for the groundwater samples. Differences between 

replicate samples were mostly within acceptable ranges, 

indicating acceptably low variability in analytical results. 

Matrix-spike recoveries were within the acceptable range (70 

to 130 percent) for 75 percent of the compounds for which 

matrix spikes were collected.

This study did not attempt to evaluate the quality of 

water delivered to consumers. After withdrawal, groundwater 

typically is treated, disinfected, and blended with other 

waters to maintain acceptable water quality. The benchmarks 

used in this report apply to treated water that is served to the 

consumer, not to untreated groundwater. To provide some 

context for the results, however, concentrations of constituents 

measured in these groundwater samples were compared with 

benchmarks established by the U.S. Environmental Protection 

Agency (USEPA) and California Department of Public 

Health (CDPH). Comparisons between data collected for this 

study and benchmarks for drinking water are for illustrative 

purposes only and are not indicative of compliance or noncompliance with those benchmarks.

Groundwater-Quality Data in Seven GAMA Study Units: 

Results from Initial Sampling, 2004–2005, and Resampling, 

2007–2008, of Wells: California GAMA Program Priority 

Basin Project 

By Robert Kent, Kenneth Belitz, and Miranda S. Fram
2 Groundwater-Quality Data in Seven GAMA Study Units: Results from Initial Sampling and Resampling of Wells

Most constituents that were detected in groundwater 

samples from the trend wells were found at concentrations 

less than drinking-water benchmarks. Four VOCs—

trichloroethene, tetrachloroethene, 1,2-dibromo-3-

chloropropane, and methyl tert-butyl ether—were detected 

in one or more wells at concentrations greater than their 

health-based benchmarks, and six VOCs were detected in 

at least 10 percent of the samples during initial sampling 

or resampling of the trend wells. No pesticides were 

detected at concentrations near or greater than their healthbased benchmarks. Three pesticide constituents—atrazine, 

deethylatrazine, and simazine—were detected in more than 

10 percent of the trend-well samples during both sampling 

periods. Perchlorate, a constituent of special interest, was 

detected more frequently, and at greater concentrations during 

resampling than during initial sampling, but this may be 

due to a change in analytical method between the sampling 

periods, rather than to a change in groundwater quality. 

Another constituent of special interest, 1,2,3-TCP, was also 

detected more frequently during resampling than during initial 

sampling, but this pattern also may not reflect a change in 

groundwater quality. Samples from several of the wells where 

1,2,3-TCP was detected by low-concentration-level analysis 

during resampling were not analyzed for 1,2,3-TCP using a 

low-level method during initial sampling. Most detections 

of nutrients and trace elements in samples from trend wells 

were less than health-based benchmarks during both sampling 

periods. Exceptions include nitrate, arsenic, boron, and 

vanadium, all detected at concentrations greater than their 

health-based benchmarks in at least one well during both 

sampling periods, and molybdenum, detected at concentrations 

greater than its health-based benchmark during resampling 

only. The isotopic ratios of oxygen and hydrogen in water 

and tritium and carbon-14 activities generally changed little 

between sampling periods, suggesting that the predominant 

sources and ages of groundwater in most trend wells were 

consistent between the sampling periods.

Introduction 

About one-half of the water used for public and 

domestic drinking-water supply in California is groundwater 

(Kenny and others, 2009). To assess the quality of ambient 

groundwater in aquifers used for public drinking-water supply 

and to establish a baseline groundwater-quality monitoring 

program, the California State Water Resources Control Board 

(SWRCB) in cooperation with the U.S. Geological Survey 

(USGS) and Lawrence Livermore National Laboratory 

(LLNL) implemented the Groundwater Ambient Monitoring 

and Assessment (GAMA) Program in 2000 (California State 

Water Resources Control Board, 2012, website at http://

www.waterboards.ca.gov/gama/). The main goals of the 

GAMA Program are to improve groundwater monitoring 

and to increase the availability of groundwater-quality data 

to the public. The GAMA Program currently consists of 

four projects: (1) the GAMA Priority Basin Project (PBP), 

conducted by the USGS (U.S. Geological Survey, 2011, 

California Water Science Center website at http://ca.water.

usgs.gov/gama/); (2) the GAMA Domestic Well Project, 

conducted by the SWRCB; (3) GAMA Special Studies 

Project, conducted by LLNL; and (4) GeoTracker GAMA, 

conducted by the SWRCB. The GAMA-PBP primarily 

focuses on the deep part of the groundwater resource, which 

is typically used for public drinking-water supply. The GAMA 

Domestic Well Project generally focuses on the shallow 

aquifer systems, which may be particularly at risk as a result 

of surficial contamination. The GAMA Special Studies Project 

focuses on using research methods to help explain the source, 

fate, transport, and occurrence of chemicals that can affect 

groundwater quality. GeoTracker GAMA is an online interface 

serving data from the GAMA Program and other efforts to the 

public (http://geotracker.waterboards.ca.gov/).

The GAMA Program was initiated by the SWRCB 

in 2000 and later expanded by the Groundwater Quality 

Monitoring Act of 2001 (State of California, 2001a, b; 

Sections 10780–10782.3 of the California Water Code, 

Assembly Bill 599). The GAMA-PBP assesses groundwater 

quality in key groundwater basins that account for more 

than 90 percent of all groundwater used for public supply in 

the State. For the GAMA-PBP, the USGS, in collaboration 

with the SWRCB, developed the monitoring plan to assess 

groundwater basins through direct and other statistically 

reliable sampling approaches (Belitz and others, 2003; 

California State Water Resources Control Board, 2003). 

Additional partners in the GAMA-PBP include the California 

Department of Public Health (CDPH), California Department 

of Water Resources (CDWR), California Department of 

Pesticide Regulation (CDPR), local water agencies, and well 

owners (Kulongoski and Belitz, 2004). Participation in the 

GAMA-PBP is entirely voluntary.

The GAMA-PBP is unique in California because it 

includes many chemical analyses that are not otherwise 

available in the statewide water-quality monitoring datasets. 

Groundwater samples collected for the GAMA-PBP 

are typically analyzed for approximately 300 chemical 

constituents using analytical methods with lower detection 

limits than required by the CDPH for regulatory monitoring 

of water from drinking-water wells. These analyses will 

be useful for providing an early indication of changes in 

groundwater quality. In addition, the GAMA-PBP analyzes 

samples for a suite of constituents more extensive than 

required by CDPH and for a suite of chemical and isotopic 

tracers for understanding hydrologic and geochemical 

processes. This understanding of groundwater composition is 

useful for identifying the natural and human factors affecting 

water quality. Understanding the occurrence and distribution 

of chemical constituents of significance to water quality is 

important for the long-term management and protection of 

groundwater resources.
Introduction 3

The range of hydrologic, geologic, and climatic 

conditions in California were considered in this statewide 

assessment of groundwater quality. Belitz and others (2003) 

partitioned the State into 10 hydrogeologic provinces, 

each with distinctive hydrologic, geologic, and climatic 

characteristics: Cascades and Modoc Plateau, Klamath 

Mountains, Northern Coast Ranges, Central Valley, Sierra 

Nevada, Basin and Range, Southern Coast Ranges, Transverse 

Ranges and selected Peninsular Ranges, Desert, and San 

Diego Drainages (fig. 1). These 10 hydrogeologic provinces 

include groundwater basins and subbasins designated by 

the CDWR (California Department of Water Resources, 

2003). Groundwater basins and subbasins generally consist 

of relatively permeable, unconsolidated deposits of alluvial 

origin. Eighty percent of California’s approximately 

16,000 active and standby drinking-water wells listed in the 

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

Shaded relief derived from U.S. Geological Survey 

National Elevation Dataset, 2006, 

Albers Equal Area Conic Projection

Provinces from Belitz and others, 2003

Sacramento

Southeast San Joaquin 

Valley study unit

San Fernando–San Gabriel

study unit

Northern San Joaquin 

Basin study unit

Southern Sacramento 

Valley study unit

North San

Francisco Bay 

study unit

Monterey Bay

and Salinas

Valley Basins

study unit

San Diego

Drainages

study unit

Figure 1. Hydrogeologic provinces of California and the locations of the Groundwater Ambient Monitoring and Assessment (GAMA)

study units featured in this report.
4 Groundwater-Quality Data in Seven GAMA Study Units: Results from Initial Sampling and Resampling of Wells

statewide database maintained by the CDPH (hereinafter 

referred to as CDPH wells) are located in groundwater 

basins and subbasins within the 10 hydrogeologic provinces. 

Groundwater basins and subbasins were prioritized for 

sampling on the basis of the number of CDPH wells in the 

basin, with secondary consideration given to municipal 

groundwater use, agricultural pumping, the number of 

formerly leaking underground fuel tanks, and the number of 

square-mile sections with registered pesticide applications 

(Belitz and others, 2003). Of the 472 basins and subbasins 

designated by the CDWR, 116 basins and subbasins, defined 

as the priority basins, contained 90 percent of the CDPH 

wells in basins. The remaining 356 basins and subbasins 

were defined as low-use basins. The 116 priority basins and 

subbasins, selected low-use basins, and selected areas outside 

of the defined groundwater basins were selected and grouped 

into 35 GAMA study units, representing approximately 

95 percent of the CDPH wells in California. 

The data collected in each study unit is used for three 

types of water-quality assessments: (1) status—assessment 

of the current quality of the groundwater resource; 

(2) understanding—identification of the natural and human 

factors affecting groundwater quality; and (3) trends—

detection of changes in groundwater quality over time 

(Kulongoski and Belitz, 2004). The assessments are intended 

to characterize the quality of groundwater in the primary 

aquifer systems of the study units, not the treated drinking 

water delivered to consumers by water purveyors. The primary 

aquifer systems are defined as parts of aquifers corresponding 

to the depths of the perforation intervals of wells listed in 

the CDPH databases for the study units. The CDPH database 

lists wells used for public drinking-water supplies and 

includes wells from systems classified as community (such 

as cities, towns, and mobile-home parks), non-transient, 

non-community (such as those in schools, workplaces, 

and restaurants), and transient, non-community (such as 

campgrounds, parks, and highway rest areas). Collectively, 

the CDPH refers to these wells as “public-supply” wells. 

Groundwater quality in shallow or very deep parts of the 

aquifer systems may differ from that in the primary aquifer 

systems. In particular, shallow groundwater may be more 

vulnerable to surface contamination. As a result, samples 

from shallow wells (such as many private domestic wells 

and environmental monitoring wells) can have greater 

concentrations of constituents (such as volatile organic 

compounds [VOCs] and nitrate) from anthropogenic sources 

than samples from wells screened in the underlying primary 

aquifer systems (for example, Landon and others, 2010).

All published and quality-assurance/quality-control 

(QA/QC) approved analytical data collected for the GAMA 

Program are stored in the web-based Geotracker Database 

(California State Water Resources Control Board, 2009, 

website at https://geotracker.waterboards.ca.gov/gama/). The 

Geotracker Database also stores groundwater-quality data and 

related reports collected by other State agencies, such as the 

CDPH, CDWR, and CDPR, and data collected by the SWRCB 

and Regional Boards from environmental monitoring wells at 

contaminated and (or) remediated sites.

This report presents water-quality data collected in 

seven GAMA-PBP study units that were initially sampled 

from July 2004 to December 2005 and then were resampled 

from August 2007 to November 2008 to evaluate temporal 

trends. Data are presented from initial sampling, as well 

as from resampling for trends in the San Diego Drainages, 

North San Francisco Bay, Northern San Joaquin Basin, 

Southern Sacramento Valley, San Fernando–San Gabriel, 

Monterey Bay and Salinas Valley Basins, and Southeast San 

Joaquin Valley study units. Data for additional parameters, 

evaluation of the QC data, and detailed descriptions of these 

seven GAMA study units can be found in published USGS 

Data-Series Reports for each study unit (Wright and others, 

2005; Kulongoski and others, 2006; Bennett and others, 2006; 

Dawson and others, 2008; Land and Belitz, 2008; Kulongoski 

and Belitz, 2007; and Burton and Belitz, 2008, respectively). 

Purpose and Scope

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

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

measurements, and (3) present the results of resampling 

for an assessment of trends in the first seven GAMA study 

units. Groundwater samples were analyzed for organic 

and inorganic constituents, field parameters, and chemical 

tracers for groundwater source and age. The chemical data 

presented in this report were evaluated by comparison to 

State and Federal drinking-water standards. The health-based 

and non-health-based benchmarks considered for this report 

are those established by the U.S. Environmental Protection 

Agency (USEPA) and (or) the CDPH. The data presented in 

this report are intended to characterize the quality of untreated 

groundwater resources within the study units and to provide 

a means to evaluate whether or not the groundwater quality 

is changing over time. Discussion of the occurrence of the 

constituents detected in groundwater samples and factors 

influencing the distribution can be found in published USGS 

Scientific Investigation Reports for these GAMA-PBP study 

units (Wright and Belitz, 2011; Kulongoski and others, 2010; 

Bennett and others, 2010; Bennett and others, 2011; Land and 

others, 2012; Kulongoski and Belitz; 2011; and Burton and 

others, 2012, respectively).

Study Units

Detailed information on the hydrogeologic settings of the 

seven GAMA-PBP study units discussed in this report, along 

with descriptions of data collection and analytical results from 

the first round of sampling of these study units can be found in 

published USGS Data-Series Reports referenced throughout 

this report. Only brief descriptions of the study units are 

presented here. 
Study Units 5

San Diego Drainages Study Unit

The San Diego Drainages study unit (figs. 1, 2) covers 

approximately 3,900 square miles (mi2) in San Diego, Orange, 

and Riverside Counties and is located in the San Diego 

Drainages hydrogeologic province (Belitz and others, 2003). 

The San Diego Drainages study unit consists of four study 

areas (fig. 2). The Temecula Valley study area lies within 

the boundaries of the Temecula Valley Groundwater Basin 

as defined by the CDWR (California Department of Water 

Resources, 2004a). The Warner Valley study area lies within 

the boundaries of the Warner Valley Groundwater Basin 

as defined by the CDWR (California Department of Water 

Resources, 2004b). The Alluvial Basins study area consists of 

the 12 CDWR-defined alluvial basins within the San Diego 

Drainages study unit that have at least one public supply well 

(California Department of Water Resources, 2003; 2004c, d). 

The Hard Rock study area consists of areas within the San 

Diego Drainages hydrogeologic province that are outside 

of CDWR-defined groundwater basins and within a radius 

of 3 kilometers (km) of a CDPH well. Descriptions of the 

hydrogeologic settings of the San Diego Drainages study unit, 

its groundwater basins, and its individual study areas are given 

by Wright and others (2005).

North San Francisco Bay Study Unit

The North San Francisco Bay study unit (figs. 1, 3) 

covers approximately 1,000 mi2, mostly in Napa, Sonoma, and 

Marin Counties, and lies within the Northern Coast Ranges 

hydrogeologic province (Belitz and others, 2003). For the 

purpose of this study, the seven CDWR-defined groundwater 

basins that lie within the North San Francisco Bay study unit 

were grouped into three study areas (fig. 3). The Valley and 

Plains study area includes most of the alluvial-filled basins in 

the study unit. The Volcanic Highlands study area includes the 

hilly to mountainous areas of Pliocene volcanic deposits. The 

Wilson Grove Formation Highlands study area is characterized 

by gently rolling hills, broad valleys, and rounded hilltops 

and lies closer to the coast than the other two study areas. The 

hydrogeologic settings of the North San Francisco Bay study 

unit, its groundwater basins, and its individual study areas are 

described by Kulongoski and others (2006).

Northern San Joaquin Basin Study Unit

The Northern San Joaquin Basin study unit (figs. 1, 4) 

covers approximately 2,079 mi2 in San Joaquin, Alameda, 

Amador, Calaveras, Contra Costa, Sacramento, and Stanislaus 

Counties, and lies within the Central Valley hydrogeologic 

province (Belitz and others, 2003). The study unit consists of 

three CDWR-defined groundwater subbasins located within 

the San Joaquin Valley Groundwater Basin: the Eastern San 

Joaquin subbasin (California Department of Water Resources, 

2006a), the Tracy subbasin (California Department of Water 

Resources, 2006b), and the Cosumnes subbasin (California 

Department of Water Resources, 2006c). For the purpose of 

this study, the Northern San Joaquin Basin study unit was 

divided into four study areas (fig. 4). The Tracy Basin study 

area lies within the boundaries of the Tracy subbasin. The 

Cosumnes Basin study area covers about half of the area 

within the boundaries of the Cosumnes subbasin. The Eastern 

San Joaquin Basin study area covers about two-thirds of the 

Eastern San Joaquin subbasin. The Uplands Basin study area 

is defined as those portions of the Eastern San Joaquin and 

Cosumnes subbasins that represent the exposed areal extent 

of semiconsolidated deposits of Pliocene and Pleistocene 

age west of the consolidated bedrock of the Sierra Nevada 

Mountains. The hydrogeologic settings of the Northern San 

Joaquin Basin study unit, its groundwater basin and subbasins, 

and its individual study areas are described by Bennett and 

others (2006). 

Southern Sacramento Valley Study Unit

The Southern Sacramento Valley study unit (figs. 1, 

5) covers approximately 2,100 mi2 in Placer, Sacramento, 

Solano, Sutter, and Yolo Counties. It lies mostly within the 

Central Valley hydrogeologic province, and partly within the 

Northern Coast Ranges hydrogeologic province (Belitz and 

others, 2003). The study unit consists of the CDWR-defined 

Suisun-Fairfield Groundwater Basin (California Department of 

Water Resources, 2003) and four CDWR-defined groundwater 

subbasins located within the Sacramento Valley Groundwater 

Basin: the North American subbasin (California Department 

of Water Resources, 2006d), the South American subbasin 

(California Department of Water Resources, 2004e), the 

Solano subbasin (California Department of Water Resources, 

2004f), and the Yolo subbasin (California Department of 

Water Resources, 2004g). For the purpose of this study, the 

Southern Sacramento Valley study unit was divided into six 

study areas (fig. 5). The North American study area covers 

about two-thirds of the North American subbasin. The South 

American study area covers about three-quarters of the South 

American subbasin. The Solano study area lies within the 

boundaries of the Solano subbasin. The Suisun-Fairfield 

study area lies within the boundaries of the Suisun-Fairfield 

Groundwater Basin. The Yolo study area lies within the 

boundaries of the Yolo subbasin. The Uplands Basin study 

area is defined as those portions of the North American 

and South American subbasins that represent the exposed 

areal extent of semiconsolidated deposits of Pliocene and 

Pleistocene age west of the consolidated bedrock of the 

Sierra Nevada Mountains. The hydrogeologic settings of the 

Southern Sacramento Valley study unit, its groundwater basins 

and subbasins, and its individual study areas are described by 

Dawson and others (2008).
6 Groundwater-Quality Data in Seven GAMA Study Units: Results from Initial Sampling and Resampling of Wells

117 30' 117 00' 116 30'

SAN DIEGO COUNTY

RIVERSIDE COUNTY

Desert province

Transverse Ranges and selected

Peninsular Ranges hydrogeologic province

33

30'

33

00'

UNITED STATES

MEXICO

ORANGE

COUNTY

Dana Point

San Diego

Temecula

0 10 20 MILES

0 10 20 KILOMETERS

Shaded relief derived from U.S. Geological Survey

National Elevation Dataset, 2006,

Albers Equal Area Conic Projection

PENINSULAR 

RANGES

Temecula Valley 

Warner Valley

Alluvial Basins Trend well

Hard Rock Status well

Study unit boundary

EXPLANATION

Oceanside

PACIFIC OCEAN

SDWARN-01

SDALLV-11

SDALLV-07

SDHDRK-01

SDHDRK-09

SDTEMFP-01 SDTEM-04

Temecula

Valley

Warner

Valley

Study

area

San Diego Drainages study unit

Figure 2. San Diego Drainages Groundwater Ambient Monitoring and Assessment (GAMA) study unit with locations of study areas, 

status wells, and trend wells. 
Study Units 7

Figure 3. North San Francisco Bay Groundwater Ambient Monitoring and Assessment (GAMA) study unit with locations of study areas, 

status wells, and trend wells.

Pacific Ocean

San Pablo Bay

Sonoma Creek

Russian

River

Napa River

Petaluma River

Laguna de Santa Rosa River

CONTRA COSTA

COUNTY

LAKE

COUNTY

YOLO

COUNTY

NAPA

COUNTY

SONOMA

COUNTY

SOLANO

COUNTY

MARIN

COUNTY

MENDOCINO COUNTY

Santa Rosa

Petaluma

Napa

Sonoma

Valleys and Plains

Volcanic Highlands

Wilson Grove Formation Highlands

EXPLANATION

Lake Berryessa

0 5

0 5 10 Kilometers

10 Miles Shaded relief derived from U.S. Geological Survey

National Elevation Dataset, 2006. 

Albers Equal Area Conic Projection

N o r t h C o a s t R a n g e s

Sonoma Mts

M a y a c m a s M t s

H o w e l l M t s

Lake

Sonoma

Trend well

Status well

Study unit boundary

IP-032958_Kent_Figure 3 North SFBay wells

Study

area

North San Francisco Bay study unit

NSFVP-41

NSFVP-36

NSFVP-38

NSFVP-34

NSFVP-39

NSFVP-29

NSFVOL-14

NSFVOL-18

NSFWGFP-01

NSFWG-03
8 Groundwater-Quality Data in Seven GAMA Study Units: Results from Initial Sampling and Resampling of Wells

Figure 4. Northern San Joaquin Basin Groundwater Ambient Monitoring and Assessment (GAMA) study unit with locations of study 

areas, status wells, and trend wells.

37

40

38

20

38

121 30 121

0 5 10 20 MILES

0 5 10 20 KILOMETERS

SOLANO

COUNTY

YOLO

COUNTY SACRAMENTO

COUNTY

AMADOR

COUNTY

CALAVERAS

COUNTY

SAN JOAQUIN

COUNTY 

CONTRA COSTA

COUNTY 

ALAMEDA

COUNTY STANISLAUS

COUNTY

ESJ-01

TRCY-03

EJS-06

COS-08

NSJ-QPC-04

EXPLANATION

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

1999, Albers Equal Area Conic Projection

Cosumnes Basin

Eastern San Joaquin Basin

Tracy Basin

Uplands Basin

Trend well

Status well

Lodi

Stockton

Tracy

Joaquin

River 

San

Stanislaus River

Calaveras River

Mokelumne River

Cosumnes River

Dry Creek

IP-032958_Kent_Figure 4 NSJ wells

Tracy

Basin Eastern

San Joaquin

Basin

Uplands

Basin

Cosumnes

Basin

Study

area

Northern San Joaquin Basin study unit

Study unit boundary
Study Units 9

Figure 5. Southern Sacramento Valley Groundwater Ambient Monitoring and Assessment (GAMA) study unit with locations of study 

areas, status wells, and trend wells.

Putah Creek

Cache Creek

Sacramento–San Joaquin Delta

Sacramento River

Feather River

American River

Bear River

San Joaquin River

YOLO

COUNTY

COLUSA

COUNTY SUTTER

COUNTY

YUBA

COUNTY

NEVADA

COUNTY

PLACER

COUNTY

EL DORADO

COUNTY

NAPA

COUNTY

SOLANO

COUNTY

CONTRA COSTA

COUNTY

SAN JOAQUIN

COUNTY

SACRAMENTO

COUNTY

AMADOR COUNTY

IP-032958_Kent_Figure 5 SSAC wells

0

0 4 8 16 KILOMETERS

4 8 16 MILES

North American

Solano

South American

Suisun-Fairfield

Uplands

Yolo

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

1999, Albers Equal Area Conic Projection

Consumnes River

Davis

Fairfield

Rio vista

Sacramento

122 121 30 121

39

38

30

38

COAST RANGES

Trend well

Status well

Study unit boundary

Solano

Basin

Yolo

Basin

South

American

Basin

North

American

Basin

Uplands

Basin

Suisun-Fairfield

Basin

Southern Sacramento Valley study unit

Study

area

SOL-08

YOL-08

YOL-14

SAM-10

NAM-03

SSV-QPC-07

SUI-03
10 Groundwater-Quality Data in Seven GAMA Study Units: Results from Initial Sampling and Resampling of Wells

San Fernando–San Gabriel Study Unit

The San Fernando–San Gabriel study unit (figs. 1, 6) 

covers approximately 500 mi2 in Los Angeles County and lies 

within the Transverse Range and selected Peninsular Ranges 

hydrogeologic province (Belitz and others, 2003). The study 

unit consists of three CDWR-defined groundwater basins: 

the San Fernando Valley Groundwater Basin (California 

Department of Water Resources, 2004h), the San Gabriel 

Valley Groundwater Basin (California Department of Water 

Resources, 2004i), and the Raymond Groundwater Basin 

(California Department of Water Resources, 2004j). For 

the purpose of this study, the San Fernando–San Gabriel 

study unit was divided into two study areas (fig. 6). The San 

Fernando study area lies within the boundaries of the San 

Fernando Valley Groundwater Basin, and the San Gabriel 

study area combines the boundaries of the San Gabriel Valley 

and Raymond Groundwater Basins. The hydrogeologic 

settings of the San Fernando–San Gabriel study unit, its 

groundwater basins, and its individual study areas are 

described by Land and Belitz (2008).

Monterey Bay and Salinas Valley Basins 

Study Unit

The Monterey Bay and Salinas Valley Basins study 

unit (figs. 1, 7) covers approximately 1,000 mi2 in Monterey, 

Santa Cruz, and San Luis Obispo Counties and lies within 

the Southern Coast Ranges hydrogeologic province (Belitz 

and others, 2003). The study unit consists of eight CDWRdefined groundwater basins. For the purpose of this study, 

the Monterey Bay and Salinas Valley Basins study unit was 

divided into four study areas (fig. 7). 

The Santa Cruz study area combines five CDWR-defined 

groundwater basins: the Felton Area Groundwater Basin 

(California Department of Water Resources, 2004k), the 

Scotts Valley Groundwater Basin (California Department of 

Water Resources, 2006e), the Santa Cruz Purisima Formation 

Highlands Groundwater Basin (California Department 

of Water Resources, 2004l), the West Santa Cruz Terrace 

Groundwater Basin (California Department of Water 

Resources, 2004m), and the Soquel Valley Groundwater Basin 

(California Department of Water Resources, 2004n). 

The Monterey Bay study area consists of the Carmel 

Valley Groundwater Basin (California Department of Water 

Resources, 2004o), the Pajaro Valley Groundwater Basin 

(California Department of Water Resources, 2006f), and five 

subbasins of the Salinas Valley Groundwater Basin: the Corral 

de Tierra Area subbasin (California Department of Water 

Resources, 2004p), the Langley Area subbasin (California 

Department of Water Resources, 2004q), the Seaside Area 

subbasin (California Department of Water Resources, 2004r), 

the Eastside Aquifer subbasin (California Department of Water 

Resources, 2004s), and the 180/400-Foot Aquifer subbasin 

(California Department of Water Resources, 2004t). 

The Salinas Valley study area consists of two more 

subbasins of the Salinas Valley Groundwater Basin: the 

Upper Valley Aquifer subbasin (California Department of 

Water Resources, 2004u) and the Forebay Aquifer subbasin 

(California Department of Water Resources, 2004v). 

Finally, the Paso Robles study area consists of the 

low-lying alluvium-fill portions of the Paso Robles Subbasin 

(California Department of Water Resources, 2004w) of the 

Salinas Valley Groundwater Basin. The hydrogeologic settings 

of the Monterey Bay and Salinas Valley Basins study unit, its 

groundwater basins and subbasins, and its individual study 

areas are described by Kulongoski and Belitz (2007). 

Southeast San Joaquin Valley Study Unit 

The Southeast San Joaquin Valley study unit (figs. 1, 8) 

covers approximately 3,780 mi2 in Fresno, Kings, and Tulare 

Counties and lies within the Central Valley hydrogeologic 

province (Belitz and others, 2003). The study unit consists 

of four CDWR-defined subbasins of the CDWR-defined San 

Joaquin Valley Groundwater Basin: the Kings subbasin, the 

Kaweah subbasin, the Tule subbasin, and the Tulare Lake 

subbasin (California Department of Water Resources, 2006g, 

h, i, and j, respectively). For the purpose of this study, the 

Southeast San Joaquin Valley study unit was divided into four 

study areas corresponding with the names and boundaries of 

the four subbasins (fig. 8). The hydrogeologic settings of the 

Southeast San Joaquin study unit, its groundwater subbasins, 

and corresponding study areas are described by Burton and 

Belitz (2008).
Study Units 11

Figure 6. San Fernando–San Gabriel Groundwater Ambient Monitoring and Assessment (GAMA) study unit with locations of study 

areas, status wells, and trend wells.

Cali fornia Aqueduct

Los Angeles River

Los Angeles Aqueduct

Los Angeles River

San

Gabriel River

Santa Ana River

Rio Hondo

Pacific Ocean

San Pedro Bay

San Gabriel Mountains

Santa Monica Mountains

Santa Susana

Mountains

LOS ANGELES

COUNTY

ORANGE

COUNTY

SAN

BERNARDINO

COUNTY

Azusa

Burbank

Northridge

Pasadena

San

Fernando

West Covina

Alhambra

0 5 10 Miles

0 5 10 Kilometers

EXPLANATION

San Fernando Study unit

 boundary San Gabriel

Santiago

Dam

Raymond

Basin

San Gabriel

Valley

Basin

San Fernando

Valley

Basin

Shaded relief derived from U.S. Geological Survey 

National Elevation Dataset, 2006, 

Albers Equal Area Conic Projection

North American Datum of 1983 (NAD 83)

Trend well

Status well

IP-032958_Kent_Figure 6 ULAB wells

Study

area

ULASG-17

ULASG-15

ULASG-08

ULASF-09

ULASF-10

ULASG-01

San Fernando–San Gabriel study unit
12 Groundwater-Quality Data in Seven GAMA Study Units: Results from Initial Sampling and Resampling of Wells

Figure 7. Monterey Bay and Salinas Valley Basins Groundwater Ambient Monitoring and Assessment (GAMA) study unit with 

locations of study areas, status wells, and trend wells.

MADERA

CO

FRESNO

CO

KINGS

CO

KERN

CO

SAN LUIS OBISPO

CO

MONTEREY

CO

SAN BENITO

CO

SANTA CLARA

CO

SANTA CRUZ

CO MERCED

CO

Salinas

Monterey

King City

Santa Cruz Watsonville

Paso

Robles

0 10 20 Miles

0 10 20 Kilometers

Shaded relief derived from U.S. Geological Survey 

National Elevation Dataset, 2006, 

Albers Equal Area Conic Projection EXPLANATION

Study unit

 boundary

Santa Cruz

Monterey Bay

Salinas Valley

Paso Robles

Paso Robles

Basin PA C I F I C O C E A N

S a n t a L u c i a R a n g e

Lake

San Antonio

Lake

Nacimiento

Trend well

Status well

IP-032958_Kent_Figure 7 MS wells

Salinas Valley

Basin

Monterey Bay

Basin

Santa Cruz

Basin

Study

area

MSPR-09

MSPR-03

MSSV-06

MSSV-15

MSMB-28

MSMB-31

MSMB-03

MSMB-04

MSSC-11

MSSC-06

MSMB-16

Monterey Bay and Salinas Valley Basins study unit
Study Units 13

Figure 8. Southeast San Joaquin Valley Groundwater Ambient Monitoring and Assessment (GAMA) study unit with locations of study 

areas, status wells, and trend wells.

Fresno

Tulare

Visalia

Shaded relief derived from U.S. Geological Survey 

National Elevation Dataset, 2006, 

Albers Equal Area Conic Projection EXPLANATION

Tulare lakebed

0 10 20 Miles

0 10 20 Kilometers

S i e r r a N e v a d a

Kaweah

Kaweah

Basin

Tule

Basin

Tulare Lake

Basin

Kings

Basin

Study

area

Southeast San Joaquin Valley study unit

Kings

Tulare Lake

Tule

IP-032958_Kent_Figure 8 SSJV wells

MADERA

CO

FRESNO

CO

MONTEREY

CO

TULARE

KINGS CO

CO

KERN

CO

SAN LUIS

OBISPO

CO

120° 119°

36°

36°

30’ 

Trend well

Study unit Status well

 boundary

KING-24

KING-17

KING-13

KING-11

TLR-03

KWH-12

KWH-10

TULE-10

TULE-05
14 Groundwater-Quality Data in Seven GAMA Study Units: Results from Initial Sampling and Resampling of Wells

Methods 

Methods used for the GAMA-PBP were selected to 

achieve the following objectives: (1) collect groundwater 

samples that are statistically representative of the primary 

aquifer system in each study unit; (2) collect samples in a 

consistent manner; (3) analyze samples by using proven and 

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

groundwater data; and (5) maintain data securely and with 

relevant documentation. 

The initial sampling was designed to provide a spatially 

unbiased assessment of the quality of raw groundwater used 

for public water supplies within the seven study units. Each 

study area was divided into equal-area grid cells. A total of 

570 grid cells were defined in the 27 study areas making up 

the 7 study units, and the number of grid cells per study area 

ranged from 10 cells to 60 cells. The CDPH wells within each 

cell were assigned random ranks, and the highest ranked well 

that met basic sampling criteria and for which permission to 

be sampled could be obtained was sampled. For some cells 

having no available CDPH wells, an irrigation or a domestic 

well having a perforation interval similar to that of CDPH 

wells in the area was sampled. One well was sampled in each 

of 462 grid cells; the remaining cells contained no wells that 

were appropriate for sampling and accessible. Wells selected 

to be sampled in this manner are referred to as grid wells, or 

status wells, because they are sampled to evaluate the status of 

groundwater quality in the study unit. In this report, they are 

referred to as status wells.

Fifty-five status wells were selected for resampling as 

part of trends analysis. These wells are referred to as trend 

wells and are a subset of status wells. The basic method for 

selecting trend wells was to randomly rank the grid wells in 

each study area and then sample the highest ranked wells. At 

least 10 percent of the status wells in each study area were 

resampled (trend wells). Methods for the selection of trend 

wells evolved during trend sampling of the first seven GAMAPBP study units. After the first few study units, information 

on well depth and well construction was required in order for 

a well to be selected as a trend well, and additional criteria 

were used to ensure an approximately even spatial distribution 

among the trend wells. Table 1 lists the 55 trend wells by study 

unit and provides the GAMA alphanumeric identification 

number, along with the paired sampling dates, land-surface 

altitude, and construction information (when available) for 

each well. The wells are identified by the GAMA identification 

numbers assigned when they were first sampled by the 

GAMA-PBP. 

Fifty-eight wells were sampled in the San Diego 

Drainages study unit from May through July 2004 (Wright 

and others, 2005). Fifty-three of these wells were status wells. 

The other five wells were sampled as part of a flow-path study 

in the Temecula Valley study area (SDTEMFP-01 through 

SDTEMFP-05) and are considered to be “understanding 

wells.” After the publication of Wright and others (2005), 

six additional grid wells were re-classified as “understanding 

wells” (Wright and Belitz, 2011), including SDHDRK-01 

(presently known as SDHRKU-01) which had been selected 

and sampled as a trend well. Resampling of the San Diego 

Drainages study unit occurred in September 2007. Seven trend 

wells were sampled from the four study areas in this study 

unit (table 1): two each from the Alluvial Basins, Hard Rock, 

and Temecula Valley study areas, and one from the Warner 

Valley study area (fig. 2). One of the trend wells selected from 

the Temecula Valley study area (SDTEMFP-01) was one of 

a series of wells that were sampled to evaluate changes in 

groundwater quality along a flow path (understanding wells). 

Ninety-seven wells were sampled in the North 

San Francisco Bay study unit from August through 

November 2004 (Kulongoski and others, 2006). Eighty-four 

of these wells were status wells (the remaining 13 wells were 

understanding wells). Resampling of the North San Francisco 

Bay study unit took place during August and November 2007. 

Ten trend wells were sampled from the three study areas in 

this study unit (table 1): six trend wells from the Valley and 

Plains study area, two from the Volcanic Highlands study area, 

and two from the Wilson Grove Formation Highlands study 

area (fig. 3). One of the trend wells selected from the Wilson 

Grove Formation Highlands study area (NSFWGFP-01) was 

one of a series of wells along a flow path that was sampled to 

evaluate spatial changes in groundwater quality.

Sixty-four wells were sampled in the Northern San 

Joaquin Basin study unit from December 2004 through 

February 2005 (Bennett and others, 2006). Fifty-one of these 

wells were status wells. Resampling of the Northern San 

Joaquin Basin study unit took place from March 31 through 

April 3, 2008. Five trend wells were sampled from the four 

study areas in the study unit (table 1): one trend well each 

from the Cosumnes Basin, Tracy Basin, and Uplands Basin 

study areas, and two trend wells from the Eastern San Joaquin 

Basin study area (fig. 4). 

Eighty-three wells were sampled in the Southern 

Sacramento Valley study unit from March through June 2005 

(Dawson and others, 2008). Sixty-seven of these wells were 

status wells. Resampling of the Southern Sacramento Valley 

study unit occurred during April 2008. Seven trend wells 

were sampled from the six study areas in the study unit 

(table 1): one trend well each from the North American, South 

American, Solano, Suisun, and Uplands Basin study areas, and 

two trends wells from the Yolo study area (fig. 5). 

Fifty-two wells were sampled in the San Fernando–San 

Gabriel study unit from May through July 2005 (Land and 

Belitz, 2008). Thirty-five of these wells were status wells. 

Resampling of the San Fernando–San Gabriel study unit 

occurred during June 2008. Six trend wells were sampled from 

the two study areas in the study unit (table 1): two trend wells 

from the San Fernando study area and four trend wells from 

the San Gabriel study area (fig. 6). 

Ninety-seven wells were sampled in the Monterey 

Bay and Salinas Valley Basins study unit from July through 

September 2005 (Kulongoski and Belitz, 2007). Ninety-one 

of these wells were status wells. Resampling of the Monterey 
Methods 15

Bay and Salinas Valley Basins study unit took place in two 

distinct periods during August and November 2008. Eleven 

trend wells were sampled from the four study areas in the 

study unit (table 1): five trend wells from the Monterey Bay 

study area and two trend wells each from the Santa Cruz, Paso 

Robles, and Salinas Valley study areas (fig. 7). 

Ninety-nine wells were sampled in the Southeast 

San Joaquin Valley study unit from October through 

December 2005 (Burton and Belitz, 2008). Eighty-three of 

these wells were status wells. Resampling of the Southeast 

San Joaquin Valley study unit took place in November 2008. 

Nine trend wells were sampled from the four study areas in 

the study unit (table 1): four trend wells from the Kings study 

area, one trend well from the Tulare Lake study area, and 

two trend wells each from the Kaweah and Tule study areas 

(fig. 8). 

Well locations were verified by using a global positioning 

system (GPS), 1:24,000-scale USGS topographic maps, well 

information in USGS and CDPH databases, and information 

provided by well owners, drillers’ logs, and (or) other sources 

of construction information. Well location and information 

were recorded in the field by hand on field sheets and 

electronically on field laptop computers using the Alternate 

Place Entry (APE) program designed by the USGS. All 

information was verified and then uploaded into the USGS 

National Water Information System (NWIS) database. Well 

owner, well use, and well location are not published.

Sample Collection and Analysis

Samples were collected by following modified USGS 

National Field Manual (NFM) (U.S. Geological Survey, 

variously dated) and modified USGS National Water-Quality 

Assessment (NAWQA) Program (Koterba and others, 1995) 

sampling protocols. These sampling protocols were followed 

so that samples representative of groundwater in the aquifer 

were collected at each site and so that the samples were 

collected and handled in ways that minimized the potential 

for contamination. Following these protocols also allows for 

comparison of data collected by GAMA-PBP throughout 

California with other USGS projects in California and the 

Nation. The methods used for sample collection and analysis 

are described in the appendix section titled “Sample Collection 

and Analysis.”

Various strategies were used to select constituents for 

resampling for trends in these seven study units. Trend wells 

were sampled for between 135 and 262 distinct constituents 

during the 2007–2008 resampling (table 2). Tables 3A–I list 

the constituents in each constituent class by name and other 

identifiers, their primary use or source (when relevant), and 

their reporting and benchmark levels. Tables 3A–D and H

also indicate whether or not each constituent was detected 

during sampling or resampling of these study units and, if so, 

in which of the study units they were detected. Trend samples 

were analyzed for 85 VOCs (table 3A), between 63 and 

81 pesticides and pesticide degradates (table 3C), perchlorate 

(table 3H), stable isotopes of hydrogen and oxygen in water 

(table 3I), and dissolved tritium. Two trend samples collected 

from wells in the San Diego Drainages study unit (SDTEM-04 

and SDWARN-01) were not resampled for pesticides.

Additional analyses were added to this basic set of 

analyses for selected trend wells in each study unit. Only 

the additional constituents that were sampled during the 

2004–2005 initial sampling and also during the 2007–2008 

resampling are reported here. 

The additional analyses for selected wells in all seven 

study units included nutrients (table 3E) and major ions 

and trace elements (table 3F). Other analyses were added 

in only one study unit or a few study units. All study 

units except for the San Diego Drainages and North San 

Francisco Bay study units added low-level analysis of 

1,2,3-trichloropropane (1,2,3-TCP) performed by Weck 

Laboratories, Inc. (hereinafter referred to as Weck) (table 3H). 

Samples for the San Fernando–San Gabriel and the Monterey 

Bay and Salinas Valley Basins study units were analyzed for 

N-nitrosodimethylamine (NDMA) by Weck (table 3H). The 

Northern San Joaquin Basin and Southeast San Joaquin Valley 

study units were sampled for 1,2-dibromo-3-chloropropane 

(DBCP) and 1,2-dibromoethane (EDB) (table 3B). The North 

San Francisco Bay, Southern Sacramento Valley, and San 

Fernando–San Gabriel study units were sampled for polar 

pesticide compounds (table 3D) in addition to the pesticide 

compounds that were part of the basic set of analyses 

(table 3C). The North San Francisco Bay and San Fernando–

San Gabriel study units also were sampled for oxidized 

and reduced species of arsenic and iron (table 3G). The 

San Fernando–San Gabriel study unit also was sampled for 

14 pharmaceutical compounds, but these results are discussed 

only briefly and are not included in the tables. Finally, all 

study units except the San Fernando–San Gabriel and the 

Southeast San Joaquin Valley study units were sampled for 

carbon isotopes in selected wells (table 3I). 

Two methods were used to analyze for pesticides and 

pesticide degradates in this study. The first method included a 

basic set of 63 constituents (Schedule 2003) or an expanded 

number of compounds (70 for Schedule 2032 or 81 for 

Schedule 2033), depending on the specific laboratory schedule 

requested when the sample was submitted to the NWQL 

(table 3C). NWQL Schedules 2003, 2032, and 2033 all use the 

same analytical method (Zaugg and others, 1995; Sandstrom 

and others, 2001). The second analytical method for pesticide 

compounds (NWQL Schedule 2060) included 59 polar 

pesticide compounds (table 3D) and caffeine. Five of the 

pesticide compounds on Schedule 2060 were in common with 

all of the schedules (2003, 2032, or 2033) of the first method. 

A sixth compound included on Schedule 2060, carbofuran, 

was also on the two expanded schedules of the first method 

(Schedules 2032 and 2033), but was not on Schedule 2003. 
16 Groundwater-Quality Data in Seven GAMA Study Units: Results from Initial Sampling and Resampling of Wells

The samples from all but two of the study units included in 

this study were analyzed by using basic Schedule 2003. The 

samples from the Southern Sacramento Valley study unit were 

analyzed by using Schedule 2032, and the samples from the 

Southeast San Joaquin Valley study unit were analyzed by 

using Schedule 2033. All samples discussed in this report were 

analyzed using one of the schedules employing this method 

except for one sample from the Southern Sacramento Valley 

study unit during initial sampling in 2005 (SUI-03) and one 

sample from the San Diego Drainages study unit (SDTEM-04) 

during resampling in 2007, which were not analyzed for 

pesticide compounds. Schedule 2060 was used for 19 samples 

during initial sampling in 2004–2005 and for 23 samples 

during resampling in 2007–2008; the use of this analytical 

method varied widely by study unit (tables 2, 6A–B). For 

all four schedules, the NWQL reports concentrations below 

LT-MDLs; these concentrations are reported in tables 6A–B, 

but are not considered detections for the purpose of calculating 

detection frequencies.

Duplicate Analyses for Selected Constituents 

Fourteen constituents were measured two different ways 

for some samples for this study. Eight of these constituents 

were measured by duplicate methods for at least some 

samples at the USGS National Water Quality Laboratory 

(NWQL). Atrazine, deethylatrazine, carbaryl, carbofuran, 

metalaxyl, and tebuthiuron were analyzed by Laboratory 

Schedules 2003/2032/2033 and 2060; and DBCP and EDB 

were analyzed by Laboratory Schedules 2020 and 1306. In 

addition, for some samples, 1,2,3-trichloropropane, arsenic, 

and iron concentrations were measured by the NWQL, as 

well as by a laboratory other than the NWQL. Perchlorate 

was measured by two different outside laboratories—

Montgomery Watson Harza Laboratory (hereinafter referred 

to as MWH) and Weck—for a few samples collected in the 

San Diego Drainages and North San Francisco Bay study 

units. The MWH analyses were performed on unfiltered 

samples, while the Weck analyses were performed on filtered 

samples. Finally, water-quality indicator measurements of pH 

and specific conductance were performed onsite by USGS 

field personnel. The NWQL also measured pH and specific 

conductance, as part of all samples analyzed for Laboratory 

Schedule 1948. During initial sampling, a few samples were 

measured for the additional water-quality indicator alkalinity 

both in the field and by NWQL. However during resampling, 

alkalinity was only measured by the NWQL as part of 

Laboratory Schedule 1948, and therefore is not counted here 

among constituents receiving duplicate analysis.

Quality-Assurance Procedures

QA procedures used for this study followed the protocols 

described in the NFM (U.S. Geological Survey, variously 

dated) and used by the NAWQA Program (Koterba and others, 

1995). The QA plan followed by the NWQL, the primary 

laboratory used to analyze samples for this study, is described 

in Pirkey and Glodt (1998) and in Maloney (2005). 

Quality-Control Samples

QC samples collected during resampling of the first seven 

GAMA study units included blanks, replicates, and matrix 

spikes. QC samples were collected at more than 20 percent 

of the trend wells (13 of the 55 trend wells). During the trend 

resampling of some study units, additional wells were sampled 

within the seven study units for reasons other than trend 

evaluation (wells not included in table 1). Nine additional 

QC samples were collected from these additional wells. The 

results from these additional QC samples were used, along 

with the results from analysis of QC samples collected at the 

trend wells, to evaluate potential contamination as well as bias 

and variability of the data that may have resulted from sample 

collection, processing, storage, transportation, and laboratory 

analysis. Surrogate spikes were an additional type of QC, and 

these were added to all of the groundwater samples collected 

for analyses of organic compounds. QC results are described 

in the appendix section titled “Quality-Control Results” and 

are summarized in appendix tables A3–A6. 

On the basis of detections in laboratory and field blanks 

collected during the seven GAMA-PBP study units covered in 

this report and subsequent study units, the laboratory reporting 

levels (LRLs) for 6 VOCs (tables 3A, 5) and 11 inorganic 

constituents (tables 3F, 10) were adjusted in this report using 

methods described by Fram and others (2012) and Olsen 

and others (2010) and are greater than those provided by 

the NWQL. The GAMA Program refers to these adjusted 

reporting levels as “study reporting levels” (SRLs). 

Comparison Benchmarks

Concentrations of constituents detected in groundwater 

samples were compared with USEPA and CDPH regulatory 

and non-regulatory drinking-water health-based benchmarks 

and benchmarks established for aesthetic purposes (California 

Department of Public Health, 2008a, b; U.S. Environmental 

Protection Agency, 2006, 2009). The chemical data presented 

in this report are meant to characterize the quality of the 

untreated groundwater in the trend wells and are not intended 

to represent the treated drinking water delivered to consumers 

by water purveyors. The chemical composition of treated 

drinking water may differ from untreated groundwater because 

treated drinking water may be subjected to disinfection, 

filtration, mixing with other waters, and (or) exposure to the 

atmosphere prior to its delivery to consumers. Comparisons 

of untreated groundwater to benchmarks are for illustrative 

purposes only and are not indicative of compliance or noncompliance with drinking-water regulations. The following 

benchmarks were used for comparisons:
Methods 17

• 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 additional 

constituents not regulated by the USEPA, as well as 

lowered the benchmark concentration for a number of 

constituents with MCLs established by the USEPA. 

In this report, a benchmark set by the USEPA and 

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

set by CDPH that is more stringent than the MCL-US 

is labeled “MCL-CA.” Well owners are notified when 

constituents are detected at concentrations greater than 

an MCL-US or an MCL-CA benchmark in samples 

collected for the GAMA-PBP, but these detections do 

not constitute violations of CDPH regulations.

• 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. Detections of copper or 

lead greater than the action-level benchmarks 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 benchmarks are labeled “AL-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 the technical qualities of 

drinking water, such as scaling and staining. Both the 

USEPA and CDPH define SMCLs, but unlike MCLs, 

SMCLs established by the CDPH are not required 

to be at least as stringent as those established by the 

USEPA. SMCLs established by the CDPH are used in 

this report (SMCL-CA) for all constituents that have 

SMCL-CA values. The SMCL-US is used for pH 

because no SMCL-CA has been defined.

• NL—Notification Level. Health-based notification 

levels established by CDPH (NL-CA) for some of 

the constituents in drinking water that lack MCLs. 

If a constituent is detected at concentrations greater 

than 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 (L) 

(2.1 quarts) 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 10 

(RSD5-US).

For constituents with regulatory benchmarks (MCLs 

or ALs), detections in groundwater samples were compared 

to the MCL-US, MCL-CA, or AL-US. Constituents with 

SMCLs were compared with the SMCL-CA. For chloride, 

sulfate, specific conductance, and TDS, the CDPH defines 

a “recommended” and an “upper” SMCL-CA; detections of 

these constituents in groundwater samples were compared 

with both levels. The SMCL-USs for these constituents 

correspond to the recommended SMCL-CAs. Detected 

concentrations of constituents without an MCL or SMCL were 

compared to the NL-CA. For constituents without an MCL, 

SMCL, or NL-CA, detected concentrations were compared 

with the HAL-US. For constituents without an MCL, SMCL, 

NL-CA, or HAL-US, detected concentrations were compared 

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

the comparison benchmark for a constituent with more than 

one type of established benchmark will not necessarily result 

in selection of the benchmark with the lowest concentration. 

For example, for zinc the SMCL-CA is 5,000 micrograms 

per liter (μg/L) and the HAL-US is 2,000 μg/L, but the 

comparison benchmark selected by this hierarchy is the 

SMCL-CA. The comparison benchmarks used in this report 

are listed in tables 3A–I for all constituents and in tables 4–12

for constituents detected in groundwater samples collected 

for this trends study. Not all constituents analyzed have 

established benchmarks available. Detections of constituents 

at concentrations greater than the selected comparison 

benchmark are marked with asterisk (*) in tables 4, 5, 

and 7–11. 
18 Groundwater-Quality Data in Seven GAMA Study Units: Results from Initial Sampling and Resampling of Wells

Water-Quality Results

Results from analyses of groundwater samples from this 

study are presented in tables 4–12. During resampling of trend 

wells, 288 water-quality parameters were measured, including 

water-quality indicators measured onsite and at the NWQL. 

However, as noted earlier in “Duplicate Analyses for Selected 

Constituents,” 14 of the constituents were analyzed for some 

samples by using two different methods. Therefore, although 

up to 288 water-quality measurements could have been made 

on each sample collected during resampling for trends, 274 of 

these measurements are unique water-quality constituents. 

Samples collected during the initial sampling of the trend 

wells were analyzed for additional constituents. The results for 

constituents not analyzed during resampling are not presented 

in this report, with one exception. Alkalinity measurements 

during resampling were made only by the NWQL and not in 

the field. In contrast, most samples collected during initial 

sampling were not submitted for determination of alkalinity 

by the NWQL. Therefore, field-measured alkalinity results 

from initial sampling are presented for comparison with 

laboratory alkalinity results from resampling. Indirect 

estimates of carbonate and bicarbonate concentrations were 

calculated from the laboratory alkalinity and pH values using 

the advanced speciation method (http://or.water.usgs.gov/alk/

methods.html) with pK1 = 6.35, pK2 = 10.33, and pKW = 14.

Groundwater samples collected from the 55 trend 

wells during initial sampling in 2004–2005 were analyzed 

for between 90 and 279 of the total parameters possible 

(median 172) (table 2). Groundwater samples collected from 

these wells during resampling in 2007–2008 were analyzed for 

between 135 and 262 of the parameters (median 219) (table 2). 

One-hundred and seventy-eight of the constituents were 

undetected in all samples collected from trend wells during 

both sampling periods (tables 3A−I). Tables 4−12 present 

paired results of the samples collected from the 55 trend 

wells during the two sampling periods for constituents that 

were detected in at least one sample. Constituents listed in 

tables 3A−I that were not detected in any samples are not 

included in tables 4−12, with one exception. NDMA was 

not detected in any of the samples, but is included in table 7

because the decision to analyze for NDMA in samples from 

selected wells was often made independently from the other 

constituents of special interest, and its inclusion in table 7

allows the reader to easily determine which samples were 

analyzed for NDMA.

Table 4 lists water-quality indicators measured in the 

field and at the NWQL, and tables 5−12 present the results of 

groundwater analyses organized by compound classes: 

• Organic constituents

• Volatile organic compounds and gasoline 

components (table 5)

• Pesticides and pesticide degradates (tables 6A, B)

• Constituents of special interest (table 7)

• Inorganic constituents

• Nutrients (table 8)

• Major and minor ions, silica, and total dissolved 

solids (table 9)

• Trace elements (table 10)

• Arsenic and iron species (table 11)

• Isotopic tracers (table 12)

Water-Quality Indicators 

Measurements of dissolved oxygen, pH, specific 

conductance, alkalinity, and associated parameters (water 

temperature and bicarbonate and carbonate concentrations) are 

presented in table 4. Dissolved oxygen, alkalinity, bicarbonate, 

and carbonate concentrations are used as indicators of natural 

processes that affect water chemistry. The pH value indicates 

the acidity of the water. Specific conductance is the measure of 

electrical conductivity of the water and is proportional to the 

amount of dissolved solids in the water. 

The specific conductance of all samples was measured 

in the field. Specific conductance was also measured 

for more than half of the samples by the NWQL as part 

of Schedule 1948 (table 4). In all cases where specific 

conductance was measured both in the field and by the 

laboratory, the field and laboratory measurements were 

comparable. 

During resampling in 2007–2008, 12 wells had specific 

conductance values greater than the recommended SMCL-CA 

of 900 microsiemens per centimeter at 25 degrees Celsius 

(μS/cm at 25 °C), and all study units except the Southeast 

San Joaquin study unit had at least one well with specific 

conductance greater than this benchmark (table 4). In addition, 

two wells in the San Diego Drainages study unit and one well 

in the Southern Sacramento Valley study unit had specific 

conductance values greater than the upper SMCL-CA of 

1,600 μS/cm at 25 °C. All wells that had specific conductance 

above the recommended SMCL-CA in 2007–2008 also 

had specific conductance greater than this recommended 

benchmark during initial sampling in 2004–2005. However, 

specific conductance in a well in the Southeast San Joaquin 

Valley study unit (TULE-05) that had been greater than the 

recommended SMCL-CA in 2005 was measured at less 

than this lower benchmark in 2008. Both wells in the San 

Diego Drainages study unit that had specific conductance 

values greater than the upper SMCL-CA in 2007 also had 

values greater than this upper benchmark in 2004. Specific 

conductance in the well in the Southern Sacramento Valley 

study unit that was greater than the upper SMCL-CA in 2008 

(YOL-14) was between the lower and upper benchmarks 

in 2005. 
Water-Quality Results 19

The pH of all samples collected during 2007–2008 

was measured in the field. The pH of most of these samples 

was also measured by the NWQL as part of Schedule 1948 

(table 4). In contrast, pH was measured in the field and (or) 

laboratory for only 24 trend wells during the initial sampling 

in 2004–2005. With few exceptions, pH values were within 

the SMCL-US acceptable range (>6.5 and <8.5) during both 

sampling periods (table 4). In most cases where pH was 

measured in the field and by the laboratory, the field and 

laboratory measurements were comparable; however, field and 

laboratory measurements of pH differed substantially for three 

samples collected during the initial sampling in 2004–2005. 

For samples collected from a well in the Northern San Joaquin 

Basin study unit (TRCY-03) and from a well in the San 

Fernando–San Gabriel study unit (ULASG-08), it appears that 

the laboratory measurements of pH for the samples collected 

in 2005 from these wells are unusually low, based on other 

measurements of pH in samples from these wells. On the other 

hand, the field measurement of pH for a sample collected in 

2005 from a well in the Southern Sacramento Valley study 

unit (YOL-14) seems suspiciously low when compared to the 

laboratory measurement of this sample and pH measurements 

for the sample collected from this well in 2008. In addition, 

the difference between the values for specific conductance 

measured in the field and in the laboratory was greater for 

this 2005 sample than for any other sample represented in this 

report. Therefore, field measurements may have been recorded 

for this sample before the well was sufficiently purged. 

Organic Constituents

Organic constituents typically are chemicals that enter 

water through human activities. The two broad categories 

of organic constituents discussed in this report are volatile 

organic compounds and pesticides (including pesticide 

degradates). VOCs are present in paints, solvents, fuels, fuel 

additives, refrigerants, fumigants, and disinfected water, 

and are characterized by their tendency to evaporate. VOCs 

generally persist longer in groundwater than in surface 

water because groundwater is isolated from the atmosphere. 

Pesticides are chemicals used to control weeds, insects, 

fungi, and other pests in agricultural, urban, and suburban 

settings, and include herbicides, insecticides, and fungicides. 

Pesticide degradates are the product of the environmental 

transformations of the parent pesticide, and they can have 

similar properties to the parent pesticide (Andreu and Pico, 

2004).

Volatile Organic Compounds

Of the 85 VOCs analyzed by NWQL Schedule 2020, 

25 were detected in at least 1 groundwater sample from 

the trend wells during initial sampling or resampling. Two 

of these 25 detected VOCs—DBCP and 1,2,3-TCP—were 

analyzed, but not detected using Schedule 2020. They were 

only detected by alternative methods that had lower detection 

limits than did Schedule 2020 for these compounds (tables 3B, 

3H, 5, 7). NWQL Schedule 1306 was used to analyze for 

low levels of DBCP in the Northern San Joaquin Basin and 

Southeast San Joaquin Valley study units during resampling 

in 2008. Low-level analyses for 1,2,3-TCP were performed on 

samples from all study units by MWH during initial sampling 

in 2004–2005 and by Weck during resampling in 2007–2008. 

Nearly all VOC detections were less than health-based 

benchmarks, and most were less than one-tenth of the 

benchmarks. However, the solvents tetrachloroethene (PCE) 

and trichloroethene (TCE) were detected at concentrations 

greater than their respective MCLs in samples from two wells, 

and the fumigant DBCP and the gasoline oxygenate methyl 

tert-butyl ether (MTBE) were detected in samples from one 

well each at concentrations greater than their respective MCLs 

(table 5). Concentrations of PCE and TCE that were greater 

than the MCLs in the sample collected from a trend well in 

the San Diego Drainages study unit (SDHDRK-01) in 2007 

were similar to the concentrations in the sample collected from 

this well in 2004. In contrast, the concentrations of PCE and 

TCE that were greater than the MCLs in a sample collected 

from a trend well in the San Fernando–San Gabriel study unit 

(ULASG-17) in 2008 were substantially greater than they 

had been in the sample collected from this well in 2004. The 

concentration of DBCP greater than the MCL-US in a trend 

well in the Southeast San Joaquin study unit (KING-24) in 

2008 was similar to the concentration detected in this well 

in 2005. In contrast, the MTBE concentration greater than 

the MCL-CA in a trend well in the San Diego Drainages 

study unit (SDALLV-11) in 2004 was more than 10 times the 

concentration detected in this well in 2007.

Five VOCs were detected in more than 10 percent of 

the trend wells during both sampling periods. These were the 

trihalomethanes (byproducts of drinking-water disinfection) 

chloroform and bromodichlormethane, and the solvents PCE, 

TCE, and cis-1,2-dichloroethene. These five compounds are 

among the most commonly detected VOCs in groundwater 

nationally (Zogorski and others, 2006). Carbon tetrachloride, 

another VOC commonly detected in groundwater nationally 

(Zogorski and others, 2006), was detected in more than 

10 percent of the trend wells during initial sampling in 2004–

2005, but was detected in fewer than 10 percent of the trend 

wells during resampling in 2007–2008. The other 21 VOCs 

detected in trend well samples were detected in fewer than 

10 percent of the wells during both sampling periods (table 5). 

In addition to the 25 VOCs considered detected 

for the purposes of statistical summaries, 6 other 

VOCs (ethylbenzene, toluene, 1,2,3-trimethylbenzene, 

1,2,4-trimethylbenzene, m + p-xylene, and o-xylene) were 

observed in at least 1 trend well at concentrations less than 

their long-term method detection limits (LT-MDLs) or SRLs 

(table 5) (see appendix section on Data Reporting). Such 

concentrations are not considered detections for the purposes 

of statistical summaries in this report because of the reduced 

confidence at such low levels. However, these concentrations 

less than the LT-MDLs or SRLs are reported in table 5 for 

completeness. 
20 Groundwater-Quality Data in Seven GAMA Study Units: Results from Initial Sampling and Resampling of Wells

Pesticide Compounds

Of the 132 unique pesticides and pesticide degradates 

analyzed, 16 were detected in groundwater samples; all 

detections were at concentrations less than one-tenth of 

the health-based benchmarks (tables 6A–B). Half (8) 

of the pesticide compounds that were detected in trend 

wells were only detected in a single sample during either 

the initial sampling in 2004–2005 or the resampling in 

2007–2008. Thirteen pesticide compounds were detected 

using Schedule 2003 (or one of its expanded versions—

Schedules 2032 or 2033): atrazine, deethylatrazine, dacthal 

(DCPA), 3,4-dichloroaniline, 3,5-dichloroaniline, S-Ethyl 

depropylthio-carbamate (EPTC), fipronil, desulfinyl fipronil, 

fipronil sulfide, hexazinone, prometon, simazine, and 

tebuthiuron. Six pesticide compounds were detected using 

Schedule 2060: atrazine, deethylatrazine, deisopropylatrazine, 

diuron, sulfometuron methyl, and tebuthiuron. Three 

compounds analyzed in common by the two methods were 

detected by both: atrazine, deethylatrazine, and tebuthiuron 

(tables 6A–B). Although not a pesticide, caffeine was analyzed 

by Schedule 2060. Caffeine was detected in samples collected 

from three trend wells during initial sampling, but was 

not detected in any of the wells that were resampled using 

Schedule 2060.

The herbicides atrazine, simazine, and deethylatrazine (a 

degradate of atrazine) were detected in more than 10 percent 

of the trend-well samples during both sampling periods, 

although all three were detected more frequently during 

initial sampling in 2004–2005. These three compounds are 

among the most commonly detected pesticide compounds 

in groundwater nationally (Gilliom and others, 2006). 

Concentrations of the detected pesticide compounds were 

similar between the two sampling periods (no obvious trend) 

and, for compounds analyzed by both methods, the detected 

concentrations between the two methods were generally 

similar (tables 6A–B).

Constituents of Special Interest

Perchlorate, NDMA, and 1,2,3-TCP were defined 

as constituents of special interest at the beginning of the 

GAMA-PBP in 2004 because they began to be detected in 

groundwater in the late 1990s after advances in analytical 

methods resulted in lower detection limits and because they 

were considered to have the potential to adversely affect 

drinking-water quality in California (California Department 

of Public Health, 2008b). An MCL-CA benchmark was 

established for perchlorate in 2007. Analyses for these 

constituents were performed by MWH laboratory during 

initial sampling in 2004–2005 and by Weck and MWH during 

resampling in 2007–2008. 

Perchlorate was analyzed for 36 trend wells during 

initial sampling in 2004–2005 and at all 55 trend wells 

during resampling in 2007–2008 (tables 3H, 7). Perchlorate 

analyses during initial sampling in 2004–2005 were performed 

by MWH on unfiltered samples, with a reporting level of 

0.5 μg/L. Perchlorate analyses during resampling in 2007–

2008 were performed by Weck on filtered samples, with a 

lower reporting level of 0.1 μg/L. Perchlorate was detected 

at concentrations greater than the MCL-CA of 6 μg/L in two 

trend wells, both in the San Fernando–San Gabriel study unit 

(ULASG-01 and ULASG-17) during resampling in 2008 

(table 7). Samples from these two wells were not analyzed for 

perchlorate in 2005, and perchlorate was not detected in any 

other trend wells at concentrations greater than the MCL-CA 

during initial sampling in 2004–2005.

Samples collected from the San Fernando–San Gabriel 

and Monterey Bay and Salinas study units were analyzed 

for NDMA during resampling in 2007–2008. NDMA was 

analyzed for in selected wells during initial sampling in 2004–

2005 in all seven study units included in this report. NDMA 

was not detected in any of the samples during either sampling 

period. NDMA data, which were collected from selected wells 

in different study units according to study unit design criteria, 

are included in table 7 to allow the reader to easily determine 

the wells with samples analyzed for NDMA.

Samples from both sampling periods were analyzed for 

1,2,3-TCP as part of NWQL Schedule 2020 with a reporting 

limit ranging from 0.12 to 0.18 μg/L (table 3A), and it was 

not detected above the LT-MDL in any sample analyzed by 

this method (table 5). Because it is a constituent of special 

interest, a low-level analysis for 1,2,3-TCP, with a reporting 

level of 0.005 μg/L, was performed for selected samples 

of all study units included in this report except for the San 

Diego Drainages study unit (tables 2, 7). A total of 25 trend 

wells during the initial sampling, and 38 trend wells during 

resampling, were analyzed for low-level concentrations of 

1,2,3-TCP. During initial sampling in 2004–2005, 1,2,3-TCP 

was detected in one well (KWH-12) in the Southeast San 

Joaquin Valley study unit (table 7). During resampling in 

2007–2008, 1,2,3-TCP was detected in five wells in the 

Southern Sacramento Valley study unit and in two wells 

in the Southeast San Joaquin Valley study unit. One of the 

two Southeast San Joaquin Valley study unit wells in which 

1,2,3-TCP was detected during resampling was KWH-12, 

the same well that had a detection of 1,2,3-TCP during initial 

sampling.

Inorganic Constituents

Unlike the organic constituents and the constituents 

of special interest, most of the inorganic constituents are 

naturally present in groundwater, although their concentrations 

may be influenced by human activities. 
Water-Quality Results 21

Nutrients

Nutrients (nitrogen and phosphorus) present in 

groundwater can affect biological activity in aquifers and 

in surface-water bodies that receive groundwater discharge. 

Inorganic nitrogen may be present in the form of ammonia, 

nitrite, or nitrate, depending on the oxidation-reduction state 

of the groundwater. Analyses for nutrients in GAMA-PBP 

samples include the determination of these forms of nitrogen, 

as well as total nitrogen (dissolved) and orthophosphate 

(the most biologically available form of phosphorus). Less 

than half (19 out of 55) of the trend wells were sampled for 

nutrients during initial sampling in 2004–2005 (table 8). 

During resampling in 2007–2008, 50 trend wells were 

sampled for nutrients. Samples from five trend wells (all from 

the San Diego Drainages study unit) were not analyzed for 

nutrients during resampling.

All concentrations of ammonia and nitrite measured 

in the trend wells were less than health-based benchmarks 

during both sampling periods (table 8). Results for these 

two nitrogen species were similar between the two sampling 

periods for the 18 trend wells sampled for both periods; 

most trend-well results for both periods were non-detections 

for ammonia and nitrite. In contrast, orthophosphate was at 

greater concentrations for most (16 of the 18) of these wells 

during resampling than during initial sampling. No Federal 

or State drinking-water standard, such as an MCL, exists for 

phosphorus and phosphorus compounds. 

In most cases, sample concentrations of nitrite plus nitrate 

(as nitrogen) consist nearly entirely of nitrate, so this analysis 

will hereafter be referred to as nitrate. During resampling in 

2007–2008, concentrations of nitrate greater than the MCL-US 

of 10 milligrams per liter (mg/L) were detected in four trend 

wells sampled in the San Fernando–San Gabriel study unit and 

in one trend well sampled in the Southeast San Joaquin Valley 

study unit (table 8). Two of the San Fernando–San Gabriel 

study unit wells (ULASF-09 and ULASG-08) with nitrate (as 

nitrogen) greater than 10 mg/L had been sampled for nutrients 

during initial sampling in 2005. Both wells had similar, but 

lower nitrate concentrations in 2005 than in 2008. Samples 

from the other three trend wells with nitrate (as nitrogen) 

concentrations greater than the MCL-US of 10 mg/L in 2008 

were not analyzed for nutrients in 2005 (table 8).

Major and Minor Ions, TDS, and Trace Elements

Benchmarks for major and minor ions, total dissolved 

solids (TDS), and trace elements in water used for public 

supply are based on human-health concerns, aesthetic 

properties (such as taste, color, and odor), or technical 

properties (such as scaling and staining). The CDPH 

has established non-health-based secondary benchmarks 

(SMCL-CAs) based on aesthetic and technical properties for 

iron, manganese, silver, zinc, chloride, sulfate, and TDS. A 

health-based MCL-CA has been established for fluoride (a 

minor ion), and 17 of the 24 trace elements analyzed in this 

study have health-based benchmarks (MCL-US, MCL-CA, 

NL-US, AL-US, and HAL-US). Samples from 24 trend 

wells were analyzed for major and minor ions, silica, TDS, 

and trace elements during the initial sampling period in 

2004–2005; samples from 45 trend wells were analyzed for 

these constituents during resampling in 2007–2008. The 

concentrations of the major and minor ions, silica, and TDS 

are given in table 9. The concentrations of the trace elements 

are given in table 10.

Chloride concentrations greater than the recommended 

SMCL-CA benchmark of 250 mg/L were detected in two trend 

wells during resampling in 2007–2008; one well each from the 

Southern Sacramento Valley (YOL-14) and the Monterey Bay 

and Salinas Valley Basins (MSMB-04) study units (table 9). 

Chloride in the Southern Sacramento Valley trend well was at 

a concentration similar to what it was during initial sampling 

in 2005. The chloride concentration in the Monterey Bay and 

Salinas Valley trend well was greater than the SMCL-CA 

in 2008, and less than the SMCL-CA in 2005. The chloride 

concentration in another trend well (NSFVP-36) from the 

North San Francisco Bay study unit was slightly greater than 

the benchmark in 2005 (rounded to 250 mg/L in table 9), but 

the sample from this well in 2007 was not analyzed for major 

ions. 

Sulfate concentrations greater than the recommended 

SMCL-CA benchmark of 250 mg/L were detected in only 

one trend well in the Northern San Joaquin Basin study unit 

(TRCY-03) during resampling in 2008 (table 9). The sulfate 

concentration in this well during initial sampling in 2005 was 

just under the recommended SMCL-CA. 

Fluoride is the only minor ion with an MCL-CA, and 

no trend wells had concentrations greater than the MCL-CA 

during either sampling period.

TDS concentrations greater than the recommended 

SMCL-CA benchmark of 500 mg/L were detected in samples 

from 10 trend wells during resampling in 2007–2008; one of 

these wells (MSPR-09 in the Monterey Bay and Salinas Valley 

Basins study unit) had a TDS concentration greater than the 

upper SMCL-CA benchmark of 1,000 mg/L (table 9). In 4 of 

these 10 trend wells with TDS concentrations greater than 

the recommended SMCL-CA benchmark during 2007–2008, 

TDS concentrations were also greater than 500 mg/L during 

initial sampling. Samples from the other six trend wells were 

not analyzed for TDS during the initial sampling. In addition 

to the four trend wells with TDS concentrations greater than 

the benchmark during both sampling periods, two wells 

sampled only during the initial sampling period for TDS had 

concentrations greater than that benchmark. 

Seventeen of the 24 trace elements analyzed in this study 

have health-based benchmarks (MCL-US, MCL-CA, NL-US, 

AL-US, and HAL-US). Concentrations of 13 of the 17 trace 

elements that have health-based benchmarks were less than 

these health-based benchmarks in samples collected during 

both sampling periods (table 10). Arsenic, boron, vanadium, 

and molybdenum were detected in some trend wells at 

concentrations greater than their health-based benchmarks. 
22 Groundwater-Quality Data in Seven GAMA Study Units: Results from Initial Sampling and Resampling of Wells

Arsenic was detected in five trend wells at concentrations 

greater than its MCL-US of 10 μg/L during resampling in 

2008 (table 10). Two of these wells were in the Northern 

San Joaquin Basin study unit, and the other three were in the 

Southern Sacramento Valley, the Monterey Bay and Salinas 

Valley Basins, and the Southeast San Joaquin Valley study 

units. None of these wells were sampled for trace elements 

during initial sampling in 2005. Arsenic was detected in 

one trend well in the North San Francisco Bay study unit 

(NSFVP-38) at a concentration greater than the MCL-US 

during initial sampling in 2004; this well was not sampled for 

trace elements in 2007.

Boron was detected in samples from five trend wells at 

concentrations greater than its NL-CA of 1,000 μg/L during 

resampling in 2008 (table 10). Three of these wells were in 

the Southern Sacramento Valley study unit. The other two 

wells were in the Northern San Joaquin Basin and Monterey 

Bay and Salinas Valley Basins study units. Two of the wells 

in the Southern Sacramento Valley study unit and the well 

in the Northern San Joaquin Basin study unit with boron 

concentrations greater than the benchmark in 2008 were also 

sampled for trace elements in 2005. Boron concentrations in 

one of the Southern Sacramento Valley trend wells and in the 

Northern San Joaquin Basin trend well were also greater than 

the benchmark in 2005. However, the boron concentration in 

the other Southern Sacramento Valley trend well (YOL-14) in 

2005 was substantially lower than its concentration in 2008 

and was less than the benchmark. The boron concentration 

detected in a trend well in the North San Francisco Bay study 

unit during initial sampling in 2004 (NSFVP-38) was nearly 

four times the NL-CA; this well was not sampled for trace 

elements in 2007 (table 10). 

Vanadium was detected in two trend wells at 

concentrations greater than its NL-CA of 50 μg/L during 

resampling in 2007–2008. One of the wells was in the San 

Diego Drainages study unit, and the other well was in the 

Southeast San Joaquin Valley study unit (table 10). Both of 

these wells were also sampled for trace elements during initial 

sampling in 2004–2005. The vanadium concentration in the 

San Diego Drainages trend well in 2004 was nearly identical 

to its concentration in that well in 2007 and also was greater 

than the benchmark. The vanadium concentration in the 

Southeast San Joaquin Valley trend well in 2005 was slightly 

lower than its concentration in 2008 and just less than the 

NL-CA.

Molybdenum was detected above its HAL-US in two 

wells in the Monterey Bay and Salinas Valley Basins study 

unit during resampling in 2008 (table 10). These two wells 

were not sampled for trace elements in 2005. Molybdenum 

was not detected at concentrations above the health-based 

benchmark in any trend wells that were sampled for trace 

elements during initial sampling in 2004–2005.

Four trace elements analyzed in this study—iron, 

manganese, silver, and zinc—have benchmarks that are nonhealth-based SMCLs established for aesthetic concerns (taste 

and odor). Samples from six wells had iron concentrations 

above the SMCL, and samples from ten trend wells had 

manganese concentrations above the SMCL, during one or 

both sampling periods (table 10). Iron and manganese are trace 

elements whose concentrations are affected by the oxidationreduction state of the groundwater. Precipitation of minerals 

containing iron or manganese may cause orange, brown, or 

black staining of surfaces. Relatively high concentrations 

of manganese often co-occurred with relatively high 

concentrations of iron. In every case in which the samples 

from a well had concentrations of iron or manganese above 

the SMCL and were analyzed for trace elements during both 

sampling periods, the concentrations of these constituents 

were above the SMCL for both periods. Silver was not 

detected in the trend wells during either sampling period, and 

all detections of zinc were below the SMCL for both sampling 

periods. 

Arsenic and iron can occur as different species depending 

on the oxidation-reduction state of the groundwater. The 

oxidized and reduced species have different solubilities in 

groundwater, and the relative proportions of the oxidized 

and reduced species of each element can be used in the 

interpretation of the oxidation-reduction conditions of the 

aquifer. Concentrations of total dissolved arsenic and iron 

and the concentrations of the reduced species of each element 

were analyzed by the USGS National Research Program 

(NRP) Trace Metal Laboratory (TML), Boulder, Colorado, 

for samples from 21 trend wells during the initial sampling 

in 2004–2005 and samples from 14 trend wells during the 

resampling in 2007–2008 (table 11). The concentrations of the 

oxidized species can be calculated by difference. 

The proportions of reduced to oxidized species between 

the sampling periods changed little for six of the nine trend 

wells that were resampled. However, dissolved arsenic in three 

wells in the North San Francisco Bay study unit (NSFVOL-14, 

NSFVP-38, NSFWGFP-01) went from being predominantly 

in the oxidized form, As(V), in 2004 to mostly in the reduced 

form, As(III), in 2007. 
Future Work 23

Isotopic Tracers

The isotopic ratios of oxygen and hydrogen in water 

and tritium and carbon-14 activities may be used as tracers 

of hydrologic processes. The isotopic ratios of hydrogen and 

oxygen in water (δ2H and δ18O) aid in interpretation of the 

sources of groundwater recharge. These stable isotopic ratios 

reflect the altitude, latitude, and temperature of precipitation 

and also the extent of evaporation of the water in surfacewater bodies or soils prior to infiltration into the aquifer. 

The isotopic ratios of hydrogen and oxygen in water were 

measured for all trend wells during both sampling periods 

(table 12). These ratios appeared to change little between the 

sampling periods with one exception; a San Diego Drainages 

study unit well (SDTEM-04) had a substantially more negative 

isotopic ratio in 2007 than in 2004. 

Tritium and carbon-14 activities also provide information 

about the age (time since recharge) of the groundwater. 

Tritium is a short-lived radioactive isotope of hydrogen that 

is incorporated into the water molecule. Low levels of tritium 

are continuously produced by interaction of cosmic radiation 

with the Earth’s atmosphere, and a large amount of tritium 

was produced as a result of atmospheric testing of nuclear 

weapons between 1952 and 1963. Thus, concentrations of 

tritium above background generally indicate the presence 

of water recharged since the early 1950s. All samples from 

trend wells were analyzed for tritium except for five samples 

from the Southeast San Joaquin Valley study unit during 

initial sampling in 2005 (tables 2, 12). Tritium analyses 

were performed by the USGS Stable Isotope and Tritium 

Laboratory, Menlo Park, California. The method of reporting 

uncertainties in tritium activities by this laboratory changed 

between the initial sampling in 2004–2005 and the resampling 

in 2007−2008. Therefore, most resampling results for tritium 

in table 12 are reported as the measured value in picocuries 

per liter plus or minus (±) the combined standard uncertainty. 

Results for initial sampling, as well as the earlier resampling 

results, do not include the combined standard uncertainty. 

Of the isotopic tracers analyzed for this study, tritium is 

the only one with a health-based benchmark—an MCL-CA 

of 20,000 picocuries per liter (pCi/L). All tritium activities in 

samples from trend wells during both sampling periods were 

less than one one-thousandth of this benchmark (table 12). The 

differences in tritium activities between sampling periods were 

small for the trend wells.

Carbon-14 is a radioactive isotope of carbon. Low 

levels of carbon-14 are continuously produced by interaction 

of cosmic radiation with the Earth’s atmosphere and are 

incorporated into atmospheric carbon dioxide. The carbon 

dioxide dissolves in precipitation, surface water, and 

groundwater exposed to the atmosphere, thereby entering the 

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

approximately 5,700 years, low activities of carbon-14 relative 

to modern values generally indicate presence of groundwater 

that is several thousand years old. Seventeen trend wells were 

sampled for carbon-14 during initial sampling in 2004−2005. 

Twenty-nine trend wells were sampled for carbon-14 during 

resampling in 2007−2008 (tables 2, 12). In most cases, if a 

well was sampled for carbon-14 during initial sampling, it was 

not resampled for carbon-14. Nine trend wells were sampled 

for carbon-14 during both sampling periods. In eight of these 

nine wells, the percentages of modern carbon (pmc) were 

similar for the two sampling periods. However, groundwater 

from one well in the Monterey Bay and Salinas Valley Basins 

study unit (MSMB-04) had results of 5.7 pmc in 2005 and 

83 pmc in 2008. 

Future Work 

Reports similar to this one are planned to present data 

from initial sampling and resampling for trend evaluations 

of the remaining 28 GAMA-PBP study units not included 

here. Reports subsequent to these trends data reports will be 

focused on assessment of the data presented in this report and 

the other trend data reports by using a variety of statistical, 

qualitative, and quantitative approaches to evaluate the natural 

and human factors affecting temporal changes in groundwater 

quality. Water-quality data contained in the CDPH and USGS 

databases, and water-quality data available from other State 

and local water agencies will be compiled, evaluated, and used 

in combination with the data that is presented in the trends 

data reports. The results of these future efforts will appear in 

one or more subsequent reports.
24 Groundwater-Quality Data in Seven GAMA Study Units: Results from Initial Sampling and Resampling of Wells

Summary 

Data from 55 wells sampled during two sampling 

periods (2004–2005 and 2007–2008) in seven study units 

are presented in this report as part of an assessment of 

temporal trends in groundwater quality being conducted 

by the California State Water Resources Control Board 

(SWRCB) Groundwater Ambient Monitoring and Assessment 

(GAMA) Program’s Priority Basin Project (PBP). The GAMA 

Program was created to provide a comprehensive baseline of 

groundwater quality in the State, and to evaluate changes over 

time (trends) in this groundwater quality. The GAMA-PBP 

was created as a result of the Groundwater Quality Monitoring 

Act of 2001 (Sections 10780–10782.3 of the California Water 

Code, Assembly Bill 599) to assess and monitor the quality 

of groundwater. The GAMA-PBP is being conducted by 

the USGS in cooperation with the SWRCB and Lawrence 

Livermore National Laboratory (LLNL). 

The GAMA-PBP was designed to provide a spatially 

unbiased assessment of untreated-groundwater quality within 

the primary aquifer systems and to facilitate statistically 

consistent comparisons of untreated-groundwater quality 

throughout California. The primary aquifer systems are 

defined as parts of aquifers corresponding to the perforation 

intervals of wells listed in the California Department of 

Public Health (CDPH) database for each study unit. The 

quality of groundwater in shallow or deep water-bearing 

zones may differ from that in the primary aquifer systems; 

shallow groundwater may be more vulnerable to surficial 

contamination.

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. The benchmarks 

used in this report apply to treated water that is served to the 

consumer, not to untreated groundwater. However, to provide 

some context for the results, concentrations of constituents 

measured in these groundwater samples were compared to 

benchmarks established by the U.S. Environmental Protection 

Agency (USEPA) and CDPH.

During the initial sampling period (2004−2005) for the 

7 study units discussed in this report, 462 wells were selected 

using a randomized grid approach to achieve a statistically 

unbiased representation of groundwater used for public 

drinking-water supplies (grid wells). Fifty-five of these grid 

wells (approximately 10 percent in each of the 7 study units) 

were resampled for trends during 2007−2008. The study 

units, the number of grid wells during initial sampling, and 

the number of these wells that were resampled for trends in 

each study unit were as follows: the San Diego Drainages 

(51 grid wells, 7 trend wells), North San Francisco Bay (84, 

10), Northern San Joaquin Basin (51, 5), Southern Sacramento 

Valley (67, 7), San Fernando–San Gabriel (35, 6), Monterey 

Bay and Salinas Valley Basins (91, 11), and Southeast San 

Joaquin Valley (83, 9). 

Groundwater samples were analyzed for water-quality 

indicators, organic constituents, special-interest constituents, 

inorganic constituents, and isotopic tracers. Seventeen of the 

constituents were analyzed by using two different methods of 

analysis, resulting in up to 288 measurements that could have 

been made on each sample. This report describes the sampling, 

analytical, and quality-assurance methods used in the study 

and presents the results of the chemical analyses of the 288 

measurements from initial sampling and resampling for trends 

in the primary aquifer systems. 

Quality-control samples (blanks, replicates, and matrix 

spikes) were collected at more than 20 percent of the wells 

during resampling for trends, and the results for these 

samples were used to evaluate the quality of the data for the 

groundwater samples. Blanks rarely contained detectable 

concentrations of any constituent. Replicate samples generally 

were within the acceptable limits of variability, and matrixspike recoveries were largely within the acceptable range.

Twenty-five volatile organic compounds (VOCs) and 

16 pesticide compounds were detected in trend wells. All 

pesticide detections and nearly all VOC detections were 

at concentrations less than health-based benchmarks. The 

VOCs detected at concentrations greater than health-based 

benchmarks were 1,2-dibromo-3-chloropropane (DBCP), 

methyl tert-butyl ether (MTBE), tetrachloroethene (PCE), 

and trichloroethene (TCE). The VOCs detected in more 

than 10 percent of the trend wells during both sampling 

periods were chloroform, bromodichloromethane, cis1,2-dichloroethene, PCE, and TCE. In addition, carbon 

tetrachloride was detected in more than 10 percent of the 

trend wells during the initial sampling period. The pesticide 

compounds that were detected in more than 10 percent of 

the trend wells during both sampling periods were atrazine, 

deethylatrazine, and simazine. 

Perchlorate, N-nitrosodimethylamine (NDMA), and 

1,2,3-trichloropropane (1,2,3-TCP) are constituents of 

special interest in California. Perchlorate was detected at 

concentrations greater than health-based benchmarks in two 

trend wells in the San Fernando–San Gabriel study unit during 

the resampling period in 2008. NDMA was not detected 

during either sampling period. 1,2,3-TCP was detected 

more frequently during resampling; however, more samples 

were submitted for low-level analysis of 1,2,3-TCP during 

resampling than during initial sampling.

Most inorganic constituents are naturally present in 

groundwater but at concentrations less than water-quality 

benchmarks. Nitrate concentrations were greater than the 

health-based benchmark in samples from a few trend wells 

in the San Fernando–San Gabriel and Southeast San Joaquin 

Valley study units, and these concentrations generally were 

similar between sampling periods for wells that were sampled 

for nutrients both times. Arsenic, boron, and vanadium were 

detected in some trend wells at concentrations greater than 

their health-based benchmarks during both sampling periods. 

Similarly, total dissolved solids, iron, and manganese were 

detected at concentrations greater than secondary maximum 
References Cited 25

contaminant levels (SMCL-CAs) (non-health-based 

benchmarks set for aesthetic concerns) in samples from a few 

wells during both sampling periods. Subsequent reports will 

present analyses of the data presented in this report using a 

variety of statistical, qualitative, and quantitative approaches 

to assess the natural and human factors affecting changes in 

groundwater quality.

Acknowledgments 

The authors thank the following cooperators for their 

support: the California State Water Resources Control 

Board, California Department of Public Health, California 

Department of Water Resources, and Lawrence Livermore 

National Laboratory. In addition, we especially thank the well 

owners and water purveyors for allowing the U.S. Geological 

Survey to collect samples from their wells. Funding for this 

work was provided by State of California bonds authorized by 

Proposition 50 and administered by the California State Water 

Resources Control Board.

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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 June 28, 2007, at http://pubs.water.usgs.

gov/twri9A5/.

Wright, M.T., and Belitz, K., 2011, Status and understanding 

of groundwater quality in the San Diego Drainages 

hydrogeologic province, 2004—California GAMA 

Priority Basin Project: U.S. Geological Survey Scientific 

Investigations Report 2011-5154, 100 p. (Also available at 

http://pubs.usgs.gov/sir/2011/5154/.)

Wright, M.T., Belitz, Kenneth, and Burton, C.A., 2005, 

California GAMA Program—Ground-water quality in the 

San Diego Drainages hydrogeologic province, California, 

2004: U.S. Geological Survey Data Series 129, 91 p. (Also 

available at http://pubs.usgs.gov/ds/2005/129/.)

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.

Zogorski, J.S., Carter, J.M., Ivahnenko, T., Lapham, W.W., 

Moran, M.J., Rowe, B.L., Squillace, P.J., and Toccalino, 

P.L., 2006, Volatile organic compounds in the Nation’s 

ground water and drinking-water supply wells: U.S. 

Geological Survey Circular 1292, 101 p. (Also available at 

http://pubs.usgs.gov/circ/circ1292/.)
32 Groundwater-Quality Data in Seven GAMA Study Units: Results from Initial Sampling and Resampling of Wells

Table 1. Identification, sampling, and construction information for trend wells sampled for seven Groundwater Ambient Monitoring 

and Assessment (GAMA) study units.

[GAMA well identification number acronyms: San Diego Drainages study unit: SDALLV, Alluvial Basins study area; SDHDRK, Hard Rock study area; 

SDTEM, Temecula Valley study area; SDTEMFP, Temecula Valley study area flow-path well; SDWARN, Warner Valley study area. North San Francisco 

Bay study unit: NSFVOL, Volcanic Highlands study area; NSFVP, Valley and Plains study area; NSFWG, Wilson Grove Formation Highlands study 

area; NSFWGFP, Wilson Grove Formation Highlands study area flow-path well. Northern San Joaquin Basin study unit: COS, Cosumnes Basin study 

area; ESJ, Eastern San Joaquin Basin study area; NSJ-QPC, Uplands Basin study area; TRCY, Tracy Basin study area. Southern Sacramento Valley study 

unit: NAM, North American study area; SAM, South American study area; SOL, Solano study area; SSV-QPC, Uplands study area; SUI, Suisun-Fairfield study 

area; YOL, Yolo study area. San Fernando–San Gabriel study unit: ULASF, San Fernando study area; ULASG, San Gabriel study area. Monterey Bay and 

Salinas Valley Basins study unit: MSMB, Monterey Bay study area; MSPR, Paso Robles study area; MSSC, Santa Cruz study area; MSSV, Salinas Valley study 

area. Southeast San Joaquin Valley study unit: KING, Kings study area; KWH, Kaweah study area; TLR, Tulare Lake study area; TULE, Tule study area. 

Other abbreviations: ft, foot; LSD, land-surface datum; na, not available; NAVD 88, North American Vertical Datum of 1988]

GAMA well 

identification 

number

Sample 

date

Previous 

sample date

Elevation of LSD 

(ft above 

NAVD 88)1

Well depth 

(ft below LSD)

Top of highest 

perforation 

(ft below LSD)

Bottom of lowest 

perforation 

(ft below LSD)

San Diego Drainages study unit

SDALLV-07 9/12/2007 7/14/2004 44 200 39 na

SDALLV-11 9/13/2007 7/15/2004 381 148 50 148

SDHDRK-01 9/13/2007 7/12/2004 421 906 110 906

SDHDRK-09 9/11/2007 7/27/2004 2,402 400 75 400

SDTEM-04 9/18/2007 5/24/2004 1,186 252 95 245

SDTEMFP-01 9/19/2007 5/19/2004 1,057 2,500 234 2,147

SDWARN-01 9/11/2007 6/17/2004 2,780 473 113 473

North San Francisco Bay study unit

NSFVOL-14 8/21/2007 10/7/2004 140 417 57 417

NSFVOL-18 8/28/2007 10/20/2004 203 670 135 660

NSFVP-29 8/27/2007 9/28/2004 210 120 62 120

NSFVP-34 8/22/2007 10/18/2004 323 258 41 258

NSFVP-36 8/20/2007 10/19/2004 8 306 145 300

NSFVP-38 8/22/2007 10/20/2004 33 770 210 770

NSFVP-39 11/16/2007 10/21/2004 248 460 56 460

NSFVP-41 8/20/2007 10/21/2004 49 235 60 235

NSFWG-03 8/29/2007 9/21/2004 275 552 270 552

NSFWGFP-01 8/29/2007 10/5/2004 83 528 138 528

Northern San Joaquin Basin study unit 

COS-08 4/3/2008 1/3/2005 42 575 178 570

ESJ-01 4/2/2008 1/24/2005 28 270 180 265

ESJ-06 4/2/2008 1/10/2005 40 403 200 395

NSJ-QPC-04 4/1/2008 1/24/2005 260 520 235 512

TRCY-03 3/31/2008 1/6/2005 207 900 420 890

Southern Sacramento Valley study unit

NAM-03 4/10/2008 3/29/2005 87 660 185 655

SAM-10 4/8/2008 4/21/2005 29 278 156 162

SOL-08 4/8/2008 5/10/2005 108 1,780 1,100 1,760

SSV-QPC-07 4/10/2008 4/4/2005 158 303 175 303

SUI-03 4/9/2008 5/12/2005 88 225 60 220

YOL-01 4/7/2008 4/11/2005 59 470 210 460

YOL-14 4/9/2008 5/25/2005 13 1,350 530 797

Tables
Tables 33

GAMA well 

identification 

number

Sample 

date

Previous 

sample date

Elevation of LSD 

(ft above 

NAVD 88)1

Well depth 

(ft below LSD)

Top of highest 

perforation 

(ft below LSD)

Bottom of lowest 

perforation 

(ft below LSD)

San Fernando–San Gabriel study unit 

ULASF-09 6/16/2008 6/7/2005 1,016 184 50 170

ULASF-10 6/16/2008 6/8/2005 662 930 268 894

ULASG-01 6/16/2008 6/7/2005 462 810 670 790

ULASG-08 6/17/2008 6/15/2005 718 399 110 299

ULASG-15 6/17/2008 6/23/2005 683 na 115 340

ULASG-17 6/17/2008 7/11/2005 720 186 na na

Monterey Bay and Salinas Valley Basins study unit

MSMB-03 8/20/2008 8/31/2005 23 1,364 1,301 1,361

MSMB-04 8/20/2008 8/17/2005 10 800 200 800

MSMB-16 8/19/2008 8/17/2005 158 552 315 535

MSMB-28 8/21/2008 8/3/2005 61 490 413 465

MSMB-31 8/21/2008 8/11/2005 148 619 198 607

MSPR-03 11/14/2008 7/28/2005 753 680 260 660

MSPR-09 11/14/2008 7/18/2005 581 502 72 495

MSSC-06 8/18/2008 8/24/2005 43 230 110 200

MSSC-11 8/19/2008 9/13/2005 353 320 255 320

MSSV-06 11/13/2008 8/2/2005 303 220 160 220

MSSV-15 11/13/2008 8/12/2005 190 200 60 180

Southeast San Joaquin Valley study unit

KING-11 11/5/2008 10/20/2005 340 540 280 520

KING-13 11/5/2008 10/20/2005 315 420 260 400

KING-17 11/4/2008 10/26/2005 280 650 320 640

KING-24 11/3/2008 11/5/2005 325 236 140 236

KWH-10 11/5/2008 11/17/2005 410 323 na na

KWH-12 11/6/2008 11/28/2005 291 404 205 381

TLR-03 11/4/2008 11/29/2005 246 1,420 1,067 1,395

TULE-05 11/3/2008 12/5/2005 577 1,368 930 1,348

TULE-10 11/3/2008 12/7/2005 403 965 201 965

1

 LSD is a datum plane that is approximately at land surface at each well. The altitude of the LSD is described in feet above the North American Vertical 

Datum of 1988.

Table 1. Identification, sampling, and construction information for trend wells sampled for seven Groundwater Ambient Monitoring 

and Assessment (GAMA) study units.—Continued

[GAMA well identification number acronyms: San Diego Drainages study unit: SDALLV, Alluvial Basins study area; SDHDRK, Hard Rock study area; 

SDTEM, Temecula Valley study area; SDTEMFP, Temecula Valley study area flow-path well; SDWARN, Warner Valley study area. North San Francisco 

Bay study unit: NSFVOL, Volcanic Highlands study area; NSFVP, Valley and Plains study area; NSFWG, Wilson Grove Formation Highlands study 

area; NSFWGFP, Wilson Grove Formation Highlands study area flow-path well. Northern San Joaquin Basin study unit: COS, Cosumnes Basin study 

area; ESJ, Eastern San Joaquin Basin study area; NSJ-QPC, Uplands Basin study area; TRCY, Tracy Basin study area. Southern Sacramento Valley study 

unit: NAM, North American study area; SAM, South American study area; SOL, Solano study area; SSV-QPC, Uplands study area; SUI, Suisun-Fairfield study 

area; YOL, Yolo study area. San Fernando–San Gabriel study unit: ULASF, San Fernando study area; ULASG, San Gabriel study area. Monterey Bay and 

Salinas Valley Basins study unit: MSMB, Monterey Bay study area; MSPR, Paso Robles study area; MSSC, Santa Cruz study area; MSSV, Salinas Valley study 

area. Southeast San Joaquin Valley study unit: KING, Kings study area; KWH, Kaweah study area; TLR, Tulare Lake study area; TULE, Tule study area. 

Other abbreviations: ft, foot; LSD, land-surface datum; na, not available; NAVD 88, North American Vertical Datum of 1988]
34 Groundwater-Quality Data in Seven GAMA Study Units: Results from Initial Sampling and Resampling of Wells Table 2. Number of water-quality indicators and chemical constituents measured in samples collected at trend wells for the Groundwater Ambient Monitoring and Assessment 

(GAMA) study units featured in this report. [GAMA well identification number acronyms: San Diego Drainages study unit: SDALLV, Alluvial Basins study area; SDHDRK, Hard Rock study area; SDTEM, Temecula Valley study area; SDTEMFP, Temecula Valley study area flow-path well; SDWARN, Warner Valley study area. North San Francisco Bay study unit: NSFVOL, Volcanic Highlands study area; NSFVP, Valley and Plains study area; NSFWG, Wilson Grove Formation Highlands study area; NSFWGFP, Wilson Grove Formation Highlands study area flow-path well. Northern San Joaquin Basin study unit: COS, Cosumnes Basin study area; ESJ, Eastern San Joaquin Basin study area; NSJ-QPC, Uplands Basin study area; TRCY, Tracy Basin study area. Southern Sacramento Valley study unit: NAM, North American study area; SAM, South American study area; SOL, Solano study area; SSV-QPC, Uplands study area; SUI, Suisun-Fairfield study area; YOL, Yolo study area. San Fernando–San Gabriel study unit: ULASF, San Fernando study area; ULASG, San Gabriel study area. Monterey Bay and Salinas Valley Basins study unit: MSMB, Monterey Bay study area; MSPR, Paso Robles study area; MSSC, Santa Cruz study area; MSSV, Salinas Valley study area. Southeast San Joaquin Valley study unit: KING, Kings study area; KWH, Kaweah study area; TLR, Tulare Lake study area; TULE, Tule study area. Other abbreviations: NWQL, National Water Quality Laboratory; VOCs, volatile organic compounds; DBCP, 1,2-dibromo-3-chloropropane; EDB, 1,2-dibromoethane; 1,2,3-TCP, 1,2,3-trichloropropane; NDMA, 

N-nitrosodimethylamine. Analytical 

methods are reported in table A1]

GAMA well 

identification 

number

Sample 

dates

Water-quality indicators Organic constituents Special-interest constituents Inorganic constituents Geochemical and age-dating tracers

Total 

number 

of distinct 

constituents 

measured 

per well4

Measured 

onsite

Measured 

by NWQL VOCs1

DBCP 

and 

EDB1

Pesticides and 

degradates2

Polar 

pesticides2 1,2,3- TCP1 NDMA Per- chlorate3 Nutri- ents Major ions and trace elements Arsenic and iron species

Stable 

isotopes of 

hydrogen 

and oxygen 

in water

Tritium Carbon isotopes

Laboratory Schedule 2020 1306 2003, 2032, or 2033 2060 non-USGS laboratory 2755 1948 non-USGS laboratory 1142 laboratory code 1565 2255San Diego Drainages study unitSDALLV-07 7/14/2004 1 0 85 0 0 0 0 1 1 0 0 0 2 1 0 91SDALLV-07 9/12/2007 4 3 85 0 63 0 0 0 2 0 0 0 2 1 0 160SDALLV-11 7/15/2004 2 0 85 0 63 0 0 1 1 0 0 0 2 1 0 155SDALLV-11 9/13/2007 4 3 85 0 63 0 0 0 2 0 0 0 2 1 0 160SDHDRK-01 7/12/2004 1 0 85 0 63 0 0 1 1 0 0 0 2 1 0 154SDHDRK-01 9/13/2007 4 3 85 0 63 0 0 0 2 0 0 0 2 1 0 160SDHDRK-09 7/27/2004 1 0 85 0 63 0 0 1 1 0 0 0 2 1 0 154SDHDRK-09 9/11/2007 4 5 85 0 63 0 0 0 2 5 34 0 2 1 0 201SDTEM-04 5/24/2004 2 0 85 0 63 0 0 0 0 0 0 0 2 1 0 153SDTEM-04 9/18/2007 4 5 85 0 0 0 0 0 2 0 34 0 2 1 2 135SDTEMFP-01 5/19/2004 7 2 85 0 63 58 0 1 1 5 34 4 2 1 2 258SDTEMFP-01 9/19/2007 4 5 85 0 63 0 0 0 2 0 34 0 2 1 2 198SDWARN-01 6/17/2004 2 0 85 0 63 0 0 1 1 0 0 0 2 1 0 155SDWARN-01 9/11/2007 4 5 85 0 0 0 0 0 2 5 34 0 2 1 0 138North San Francisco Bay study unitNSFVOL-14 10/7/2004 7 2 85 0 63 58 1 1 1 5 35 4 2 1 2 259NSFVOL-14 8/21/2007 4 3 85 0 63 58 0 0 2 5 0 4 2 1 2 224NSFVOL-18 10/20/2004 2 0 85 0 63 0 1 1 1 0 0 0 2 1 0 155NSFVOL-18 8/28/2007 4 5 85 0 63 58 0 0 1 5 35 4 2 1 2 258
Tables 35

GAMA well 

identification 

number

Sample 

dates

Water-quality indicators Organic constituents Special-interest constituents Inorganic constituents Geochemical and age-dating tracers

Total 

number 

of distinct 

constituents 

measured 

per well4

Measured 

onsite

Measured 

by NWQL VOCs1

DBCP 

and 

EDB1

Pesticides and 

degradates2

Polar 

pesticides2 1,2,3- TCP1 NDMA Per- chlorate3 Nutri- ents Major ions and trace elements Arsenic and iron species

Stable 

isotopes of 

hydrogen 

and oxygen 

in water

Tritium Carbon isotopes

Laboratory Schedule 2020 1306 2003, 2032, or 2033 2060 non-USGS laboratory 2755 1948 non-USGS laboratory 1142 laboratory code 1565 2255North San Francisco Bay study unit—ContinuedNSFVP-29 9/28/2004 7 2 85 0 63 58 1 1 1 5 35 4 2 1 2 259NSFVP-29 8/27/2007 4 3 85 0 63 58 0 0 1 5 0 4 2 1 2 223NSFVP-34 10/18/2004 7 2 85 0 63 58 1 1 1 5 35 4 2 1 2 259NSFVP-34 8/22/2007 4 3 85 0 63 58 0 0 1 5 0 4 2 1 2 223NSFVP-36 10/19/2004 2 2 85 0 63 0 1 1 1 0 35 0 2 1 0 192NSFVP-36 8/20/2007 4 0 85 0 63 58 0 0 2 5 0 0 2 1 2 217NSFVP-38 10/20/2004 7 2 85 0 63 58 1 1 1 5 35 4 2 1 2 259NSFVP-38 8/22/2007 4 3 85 0 63 58 0 0 1 5 0 4 2 1 2 223NSFVP-39 10/21/2004 2 2 85 0 63 0 1 1 1 0 35 0 2 1 0 192NSFVP-39 11/16/2007 4 5 85 0 63 58 0 0 1 5 35 4 2 1 2 258NSFVP-41 10/21/2004 2 2 85 0 63 0 1 1 1 0 35 0 2 1 0 192NSFVP-41 8/20/2007 4 3 85 0 63 58 0 0 2 5 0 0 2 1 2 220NSFWG-03 9/21/2004 2 0 85 0 63 0 1 1 1 0 0 0 2 1 0 155NSFWG-03 8/29/2007 4 5 85 0 63 58 0 0 1 5 35 4 2 1 2 258NSFWGFP-01 10/5/2004 7 2 85 0 63 58 1 1 1 5 35 4 2 1 2 259NSFWGFP-01 8/29/2007 4 3 85 0 63 58 0 0 1 5 0 4 2 1 2 223Northern San Joaquin Basin study unitCOS-08 1/3/2005 2 0 85 0 63 0 0 0 0 0 0 0 2 1 0 153COS-08 4/3/2008 4 5 85 2 63 0 1 0 1 5 35 0 2 1 2 203

Table 2. Number of water-quality indicators and chemical constituents measured in samples collected at trend wells for the Groundwater Ambient Monitoring and Assessment (GAMA) study units featured in this report.—Continued[GAMA well identification number acronyms: San Diego Drainages study unit: SDALLV, Alluvial Basins study area; SDHDRK, Hard Rock study area; SDTEM, Temecula Valley study area; SDTEMFP, Temecula Valley study area flow-path well; SDWARN, Warner Valley study area. North San Francisco Bay study unit: NSFVOL, Volcanic Highlands study area; NSFVP, Valley and Plains study area; NSFWG, Wilson Grove Formation Highlands study area; NSFWGFP, Wilson Grove Formation Highlands study area flow-path well. Northern San Joaquin Basin study unit: COS, Cosumnes Basin study area; ESJ, Eastern San Joaquin Basin study area; NSJ-QPC, Uplands Basin study area; TRCY, Tracy Basin study area. Southern Sacramento Valley study unit: NAM, North American study area; SAM, South American study area; SOL, Solano study area; SSV-QPC, Uplands study area; SUI, Suisun-Fairfield study area; YOL, Yolo study area. San Fernando–San Gabriel study unit: ULASF, San Fernando study area; ULASG, San Gabriel study area. Monterey Bay and Salinas Valley Basins study unit: MSMB, Monterey Bay study area; MSPR, Paso Robles study area; MSSC, Santa Cruz study area; MSSV, Salinas Valley study area. Southeast San Joaquin Valley study unit: KING, Kings study area; KWH, Kaweah study area; TLR, Tulare Lake study area; TULE, Tule study area. Other abbreviations: NWQL, National Water Quality Laboratory; VOCs, volatile organic compounds; DBCP, 1,2-dibromo-3-chloropropane; EDB, 1,2-dibromoethane; 1,2,3-TCP, 1,2,3-trichloropropane; NDMA, N-nitrosodimethylamine. Analytical methods are reported in table A1]
36 Groundwater-Quality Data in Seven GAMA Study Units: Results from Initial Sampling and Resampling of Wells GAMA well identification number Sample dates Water-quality indicators Organic constituents Special-interest constituents Inorganic constituents Geochemical and age-dating tracers Total number of distinct constituents measured per well4 Measured onsite Measured by NWQL VOCs1 DBCP and EDB1 Pesti- cides and degrad- ates2 Polar pesti- cides2 1,2,3- TCP1 NDMA Per- chlorate3 Nutri- ents Major ions and trace elements Arsenic and iron species Stable isotopes of hydrogen and oxygen in water Tritium Carbon isotopes Laboratory Schedule 2020 1306 2003, 2032, or 2033 2060 non-USGS laboratory 2755 1948 non-USGS laboratory 1142 laboratory code 1565 2255 Northern San Joaquin Basin study unit—Continued ESJ-01 1/24/2005 2 0 85 0 63 0 0 0 0 0 0 0 2 1 0 153 ESJ-01 4/2/2008 4 5 85 2 63 0 1 0 1 5 35 0 2 1 2 203 ESJ-06 1/10/2005 2 5 85 0 63 0 1 1 1 0 35 4 2 1 0 197 ESJ-06 4/2/2008 4 5 85 2 63 0 1 0 1 5 35 0 2 1 2 203 NSJ-QPC-04 1/24/2005 3 5 85 0 63 0 1 1 1 0 35 4 2 1 0 198 NSJ-QPC-04 4/1/2008 4 5 85 2 63 0 1 0 1 5 35 0 2 1 2 203 TRCY-03 1/6/2005 7 5 85 0 63 58 1 1 1 5 35 4 2 1 2 262 TRCY-03 3/31/2008 4 5 85 2 63 0 1 0 1 5 35 0 2 1 2 203 Southern Sacramento Valley study unit NAM-03 3/29/2005 2 0 85 0 70 0 0 0 0 0 0 0 2 1 0 160 NAM-03 4/10/2008 4 5 85 0 70 58 1 0 1 5 35 0 2 1 2 262 SAM-10 4/21/2005 2 0 85 0 70 0 0 0 0 0 0 0 2 1 0 160 SAM-10 4/8/2008 4 5 85 0 70 58 1 0 1 5 35 0 2 1 2 262 SOL-08 5/10/2005 2 0 85 0 70 0 0 0 0 0 0 0 2 1 0 160 SOL-08 4/8/2008 4 5 85 0 70 58 1 0 1 5 35 0 2 1 2 262 SSV-QPC-07 4/4/2005 7 5 85 0 70 58 1 1 1 5 35 4 2 1 2 268

SSV-QPC-07 4/10/2008 4 5 85 0 70 58 1 0 1 5 35 0 2 1 0 260SUI-03 5/12/2005 2 0 85 0 0 0 0 0 0 0 0 0 2 1 0 90SUI-03 4/9/2008 4 5 85 0 70 58 1 0 1 5 35 0 2 1 2 262

Table 2. Number of water-quality indicators and chemical constituents measured in samples collected at trend wells for the Groundwater Ambient Monitoring and Assessment (GAMA) study units featured in this report.—Continued[GAMA well identification number acronyms: San Diego Drainages study unit: SDALLV, Alluvial Basins study area; SDHDRK, Hard Rock study area; SDTEM, Temecula Valley study area; SDTEMFP, Temecula Valley study area flow-path well; SDWARN, Warner Valley study area. North San Francisco Bay study unit: NSFVOL, Volcanic Highlands study area; NSFVP, Valley and Plains study area; NSFWG, Wilson Grove Formation Highlands study area; NSFWGFP, Wilson Grove Formation Highlands study area flow-path well. Northern San Joaquin Basin study unit: COS, Cosumnes Basin study area; ESJ, Eastern San Joaquin Basin study area; NSJ-QPC, Uplands Basin study area; TRCY, Tracy Basin study area. Southern Sacramento Valley study unit: NAM, North American study area; SAM, South American study area; SOL, Solano study area; SSV-QPC, Uplands study area; SUI, Suisun-Fairfield study area; YOL, Yolo study area. San Fernando–San Gabriel study unit: ULASF, San Fernando study area; ULASG, San Gabriel study area. Monterey Bay and Salinas Valley Basins study unit: MSMB, Monterey Bay study area; MSPR, Paso Robles study area; MSSC, Santa Cruz study area; MSSV, Salinas Valley study area. Southeast San Joaquin Valley study unit: KING, Kings study area; KWH, Kaweah study area; TLR, Tulare Lake study area; TULE, Tule study area. Other abbreviations: NWQL, National Water Quality Laboratory; VOCs, volatile organic compounds; DBCP, 1,2-dibromo-3-chloropropane; EDB, 1,2-dibromoethane; 1,2,3-TCP, 1,2,3-trichloropropane; NDMA, 

N-nitrosodimethylamine. Analytical 

methods are reported in table A1]
Tables 37

GAMA well 

identification 

number

Sample 

dates

Water-quality indicators Organic constituents Special-interest constituents Inorganic constituents Geochemical and age-dating tracers

Total 

number 

of distinct 

constituents 

measured 

per well4

Measured 

onsite

Measured 

by NWQL VOCs1

DBCP 

and 

EDB1

Pesticides and 

degradates2

Polar 

pesticides2 1,2,3- TCP1 NDMA Per- chlorate3 Nutri- ents Major ions and trace elements Arsenic and iron species

Stable 

isotopes of 

hydrogen 

and oxygen 

in water

Tritium Carbon isotopes

Laboratory Schedule 2020 1306 2003, 2032, or 2033 2060 non-USGS laboratory 2755 1948 non-USGS laboratory 1142 laboratory code 1565 2255Southern Sacramento Valley study unit—ContinuedYOL-01 4/11/2005 2 0 85 0 70 0 0 0 0 0 0 0 2 1 0 160YOL-01 4/7/2008 4 5 85 0 70 58 1 0 1 5 35 0 2 1 2 262YOL-14 5/25/2005 7 5 85 0 70 58 1 1 1 5 35 4 2 1 2 268YOL-14 4/9/2008 4 5 85 0 70 58 1 0 1 5 35 0 2 1 0 260San Fernando–San Gabriel study unit ULASF-09 6/27/2005 7 5 85 0 63 58 1 1 1 5 35 4 2 1 2 262ULASF-09 6/16/2008 4 5 85 0 63 58 1 1 1 5 35 4 2 1 0 257ULASF-10 6/8/2005 7 5 85 0 63 58 1 1 1 5 35 4 2 1 2 262ULASF-10 6/16/2008 4 5 85 0 63 58 1 1 1 5 35 4 2 1 0 257ULASG-01 6/7/2005 3 0 85 0 63 0 0 0 0 0 0 0 2 1 0 154ULASG-01 6/16/2008 4 5 85 0 63 58 1 1 1 5 35 4 2 1 0 257ULASG-08 6/15/2005 7 5 85 0 63 58 1 1 1 5 35 4 2 1 2 262ULASG-08 6/17/2008 4 5 85 0 63 58 1 1 1 5 35 4 2 1 0 257ULASG-15 6/23/2005 7 5 85 0 63 58 1 1 1 5 35 4 2 1 2 262ULASG-15 6/17/2008 4 5 85 0 63 58 1 1 1 5 35 4 2 1 0 257ULASG-17 7/11/2005 3 0 85 0 63 0 0 0 0 0 0 0 2 1 0 154ULASG-17 6/17/2008 4 5 85 0 63 58 1 1 1 5 35 4 2 1 0 257

Table 2. Number of water-quality indicators and chemical constituents measured in samples collected at trend wells for the Groundwater Ambient Monitoring and Assessment (GAMA) study units featured in this report.—Continued[GAMA well identification number acronyms: San Diego Drainages study unit: SDALLV, Alluvial Basins study area; SDHDRK, Hard Rock study area; SDTEM, Temecula Valley study area; SDTEMFP, Temecula Valley study area flow-path well; SDWARN, Warner Valley study area. North San Francisco Bay study unit: NSFVOL, Volcanic Highlands study area; NSFVP, Valley and Plains study area; NSFWG, Wilson Grove Formation Highlands study area; NSFWGFP, Wilson Grove Formation Highlands study area flow-path well. Northern San Joaquin Basin study unit: COS, Cosumnes Basin study area; ESJ, Eastern San Joaquin Basin study area; NSJ-QPC, Uplands Basin study area; TRCY, Tracy Basin study area. Southern Sacramento Valley study unit: NAM, North American study area; SAM, South American study area; SOL, Solano study area; SSV-QPC, Uplands study area; SUI, Suisun-Fairfield study area; YOL, Yolo study area. San Fernando–San Gabriel study unit: ULASF, San Fernando study area; ULASG, San Gabriel study area. Monterey Bay and Salinas Valley Basins study unit: MSMB, Monterey Bay study area; MSPR, Paso Robles study area; MSSC, Santa Cruz study area; MSSV, Salinas Valley study area. Southeast San Joaquin Valley study unit: KING, Kings study area; KWH, Kaweah study area; TLR, Tulare Lake study area; TULE, Tule study area. Other abbreviations: NWQL, National Water Quality Laboratory; VOCs, volatile organic compounds; DBCP, 1,2-dibromo-3-chloropropane; EDB, 1,2-dibromoethane; 1,2,3-TCP, 1,2,3-trichloropropane; NDMA, N-nitrosodimethylamine. Analytical methods are reported in table A1]
38 Groundwater-Quality Data in Seven GAMA Study Units: Results from Initial Sampling and Resampling of Wells GAMA well identification number Sample dates Water-quality indicators Organic constituents Special-interest constituents Inorganic constituents Geochemical and age-dating tracers Total number of distinct constituents measured per well4 Measured onsite Measured by NWQL VOCs1 DBCP and EDB1 Pesti- cides and degrad- ates2 Polar pesti- cides2 1,2,3- TCP1 NDMA Per- chlorate3 Nutri- ents Major ions and trace elements Arsenic and iron species Stable isotopes of hydrogen and oxygen in water Tritium Carbon isotopes Laboratory Schedule 2020 1306 2003, 2032, or 2033 2060 non-USGS laboratory 2755 1948 non-USGS laboratory 1142 laboratory code 1565 2255 Monterey Bay and Salinas Valley Basins study unit MSMB-03 8/31/2005 3 0 85 0 63 0 0 0 0 0 0 0 2 1 0 154 MSMB-03 8/20/2008 4 5 85 0 63 0 1 1 1 5 35 0 2 1 2 204 MSMB-04 8/17/2005 7 5 85 0 63 58 1 1 1 5 35 4 2 1 2 262 MSMB-04 8/20/2008 4 5 85 0 63 0 1 1 1 5 35 0 2 1 2 204 MSMB-16 8/17/2005 3 0 85 0 63 0 0 0 0 0 0 0 2 1 0 154 MSMB-16 8/19/2008 4 5 85 0 63 0 1 1 1 5 35 0 2 1 2 204 MSMB-28 8/3/2005 2 0 85 0 63 0 0 0 0 0 0 0 2 1 0 153 MSMB-28 8/21/2008 4 5 85 0 63 0 1 1 1 5 35 0 2 1 2 204 MSMB-31 8/11/2005 3 0 85 0 63 0 0 0 0 0 0 0 2 1 0 154 MSMB-31 8/21/2008 4 5 85 0 63 0 1 1 1 5 35 0 2 1 2 204 MSPR-03 7/28/2005 3 0 85 0 63 0 0 0 0 0 0 0 2 1 0 154 MSPR-03 11/14/2008 4 5 85 0 63 0 1 1 1 5 35 0 2 1 0 202 MSPR-09 7/18/2005 2 0 85 0 63 0 0 0 0 0 0 0 2 1 0 153 MSPR-09 11/14/2008 4 5 85 0 63 0 1 1 1 5 35 0 2 1 0 202 MSSC-06 8/24/2005 7 5 85 0 63 58 1 1 1 5 35 4 2 1 2 262 MSSC-06 8/18/2008 4 5 85 0 63 0 1 1 1 5 35 0 2 1 2 204

MSSC-11 9/13/2005 3 0 85 0 63 0 0 0 0 0 0 0 2 1 0 154MSSC-11 8/19/2008 4 5 85 0 63 0 1 1 1 5 35 0 2 1 2 204MSSV-06 8/2/2005 2 0 85 0 63 0 0 0 0 0 0 0 2 1 0 153

Table 2. Number of water-quality indicators and chemical constituents measured in samples collected at trend wells for the Groundwater Ambient Monitoring and Assessment (GAMA) study units featured in this report.—Continued[GAMA well identification number acronyms: San Diego Drainages study unit: SDALLV, Alluvial Basins study area; SDHDRK, Hard Rock study area; SDTEM, Temecula Valley study area; SDTEMFP, Temecula Valley study area flow-path well; SDWARN, Warner Valley study area. North San Francisco Bay study unit: NSFVOL, Volcanic Highlands study area; NSFVP, Valley and Plains study area; NSFWG, Wilson Grove Formation Highlands study area; NSFWGFP, Wilson Grove Formation Highlands study area flow-path well. Northern San Joaquin Basin study unit: COS, Cosumnes Basin study area; ESJ, Eastern San Joaquin Basin study area; NSJ-QPC, Uplands Basin study area; TRCY, Tracy Basin study area. Southern Sacramento Valley study unit: NAM, North American study area; SAM, South American study area; SOL, Solano study area; SSV-QPC, Uplands study area; SUI, Suisun-Fairfield study area; YOL, Yolo study area. San Fernando–San Gabriel study unit: ULASF, San Fernando study area; ULASG, San Gabriel study area. Monterey Bay and Salinas Valley Basins study unit: MSMB, Monterey Bay study area; MSPR, Paso Robles study area; MSSC, Santa Cruz study area; MSSV, Salinas Valley study area. Southeast San Joaquin Valley study unit: KING, Kings study area; KWH, Kaweah study area; TLR, Tulare Lake study area; TULE, Tule study area. Other abbreviations: NWQL, National Water Quality Laboratory; VOCs, volatile organic compounds; DBCP, 1,2-dibromo-3-chloropropane; EDB, 1,2-dibromoethane; 1,2,3-TCP, 1,2,3-trichloropropane; NDMA, 

N-nitrosodimethylamine. Analytical 

methods are reported in table A1]
Tables 39

GAMA well 

identification 

number

Sample 

dates

Water-quality indicators Organic constituents Special-interest constituents Inorganic constituents Geochemical and age-dating tracers

Total 

number 

of distinct 

constituents 

measured 

per well4

Measured 

onsite

Measured 

by NWQL VOCs1

DBCP 

and 

EDB1

Pesticides and 

degradates2

Polar 

pesticides2 1,2,3- TCP1 NDMA Per- chlorate3 Nutri- ents Major ions and trace elements Arsenic and iron species

Stable 

isotopes of 

hydrogen 

and oxygen 

in water

Tritium Carbon isotopes

Laboratory Schedule 2020 1306 2003, 2032, or 2033 2060 non-USGS laboratory 2755 1948 non-USGS laboratory 1142 laboratory code 1565 2255Monterey Bay and Salinas Valley Basins study unit—ContinuedMSSV-06 11/13/2008 4 5 85 0 63 0 1 1 1 5 35 0 2 1 0 202MSSV-15 8/12/2005 2 0 85 0 63 0 0 0 0 0 0 0 2 1 0 153MSSV-15 11/13/2008 4 5 85 0 63 0 1 1 1 5 35 0 2 1 0 202Southeast San Joaquin Valley study unitKING-11 10/20/2005 3 5 85 0 81 58 1 1 1 5 35 4 2 1 0 273KING-11 11/5/2008 4 5 85 2 81 0 1 0 1 5 35 0 2 1 0 219KING-13 10/20/2005 3 5 85 0 81 58 1 1 1 5 35 4 2 1 0 273KING-13 11/5/2008 4 5 85 2 81 0 1 0 1 5 35 0 2 1 0 219KING-17 10/26/2005 7 5 85 0 81 58 1 1 1 5 35 4 2 1 2 279KING-17 11/4/2008 4 5 85 2 81 0 1 0 1 5 35 0 2 1 0 219KING-24 11/5/2005 3 0 85 0 81 0 0 0 1 0 0 0 2 0 0 172KING-24 11/3/2008 4 5 85 2 81 0 1 0 1 5 35 0 2 1 0 219KWH-10 11/17/2005 3 0 85 0 81 0 0 0 1 0 0 0 2 0 0 172KWH-10 11/5/2008 4 5 85 2 81 0 1 0 1 5 35 0 2 1 0 219KWH-12 11/28/2005 7 5 85 0 81 58 1 1 1 5 35 4 2 1 2 279KWH-12 11/6/2008 4 5 85 2 81 0 1 0 1 5 35 0 2 1 0 219TLR-03 11/29/2005 3 0 85 0 81 0 0 0 1 0 0 0 2 0 0 172TLR-03 11/4/2008 4 5 85 2 81 0 1 0 1 5 35 0 2 1 0 219TULE-05 12/5/2005 3 0 85 0 81 0 0 0 1 0 0 0 2 0 0 172

Table 2. Number of water-quality indicators and chemical constituents measured in samples collected at trend wells for the Groundwater Ambient Monitoring and Assessment (GAMA) study units featured in this report.—Continued[GAMA well identification number acronyms: San Diego Drainages study unit: SDALLV, Alluvial Basins study area; SDHDRK, Hard Rock study area; SDTEM, Temecula Valley study area; SDTEMFP, Temecula Valley study area flow-path well; SDWARN, Warner Valley study area. North San Francisco Bay study unit: NSFVOL, Volcanic Highlands study area; NSFVP, Valley and Plains study area; NSFWG, Wilson Grove Formation Highlands study area; NSFWGFP, Wilson Grove Formation Highlands study area flow-path well. Northern San Joaquin Basin study unit: COS, Cosumnes Basin study area; ESJ, Eastern San Joaquin Basin study area; NSJ-QPC, Uplands Basin study area; TRCY, Tracy Basin study area. Southern Sacramento Valley study unit: NAM, North American study area; SAM, South American study area; SOL, Solano study area; SSV-QPC, Uplands study area; SUI, Suisun-Fairfield study area; YOL, Yolo study area. San Fernando–San Gabriel study unit: ULASF, San Fernando study area; ULASG, San Gabriel study area. Monterey Bay and Salinas Valley Basins study unit: MSMB, Monterey Bay study area; MSPR, Paso Robles study area; MSSC, Santa Cruz study area; MSSV, Salinas Valley study area. Southeast San Joaquin Valley study unit: KING, Kings study area; KWH, Kaweah study area; TLR, Tulare Lake study area; TULE, Tule study area. Other abbreviations: NWQL, National Water Quality Laboratory; VOCs, volatile organic compounds; DBCP, 1,2-dibromo-3-chloropropane; EDB, 1,2-dibromoethane; 1,2,3-TCP, 1,2,3-trichloropropane; NDMA, N-nitrosodimethylamine. Analytical methods are reported in table A1]
40 Groundwater-Quality Data in Seven GAMA Study Units: Results from Initial Sampling and Resampling of Wells Table 2. Number of water-quality indicators and chemical constituents measured in samples collected at trend wells for the Groundwater Ambient Monitoring and Assessment (GAMA) study units featured in this report.—Continued

[GAMA well identification number acronyms: San Diego Drainages study unit: SDALLV, Alluvial Basins study area; SDHDRK, Hard Rock study area; SDTEM, Temecula Valley study area; SDTEMFP, Temecula Valley study area flow-path well; SDWARN, Warner Valley study area. North San Francisco Bay study unit: NSFVOL, Volcanic Highlands study area; NSFVP, Valley and Plains study area; NSFWG, Wilson Grove Formation Highlands study area; NSFWGFP, Wilson Grove Formation Highlands study area flow-path well. Northern San Joaquin Basin study unit: COS, Cosumnes Basin study area; ESJ, Eastern San Joaquin Basin study area; NSJ-QPC, Uplands Basin study area; TRCY, Tracy Basin study area. Southern Sacramento Valley study unit: NAM, North American study area; SAM, South American study area; SOL, Solano study area; SSV-QPC, Uplands study area; SUI, Suisun-Fairfield study area; YOL, Yolo study area. San Fernando–San Gabriel study unit: ULASF, San Fernando study area; ULASG, San Gabriel study area. Monterey Bay and Salinas Valley Basins study unit: MSMB, Monterey Bay study area; MSPR, Paso Robles study area; MSSC, Santa Cruz study area; MSSV, Salinas Valley study area. Southeast San Joaquin Valley study unit: KING, Kings study area; KWH, Kaweah study area; TLR, Tulare Lake study area; TULE, Tule study area. Other abbreviations: NWQL, National Water Quality Laboratory; VOCs, volatile organic compounds; DBCP, 1,2-dibromo-3-chloropropane; EDB, 1,2-dibromoethane; 1,2,3-TCP, 1,2,3-trichloropropane; NDMA, 

N-nitrosodimethylamine. Analytical 

methods are reported in table A1]

GAMA well 

identification 

number

Sample 

dates

Water-quality indicators Organic constituents Special-interest constituents Inorganic constituents Geochemical and age-dating tracers

Total 

number 

of distinct 

constituents 

measured 

per well4

Measured 

onsite

Measured 

by NWQL VOCs1

DBCP 

and 

EDB1

Pesticides and 

degradates2

Polar 

pesticides2 1,2,3- TCP1 NDMA Per- chlorate3 Nutri- ents Major ions and trace elements Arsenic and iron species

Stable 

isotopes of 

hydrogen 

and oxygen 

in water

Tritium Carbon isotopes

Laboratory Schedule 2020 1306 2003, 2032, or 2033 2060 non-USGS laboratory 2755 1948 non-USGS laboratory 1142 laboratory code 1565 2255Southeast San Joaquin Valley study unit—ContinuedTULE-05 11/3/2008 4 5 85 2 81 0 1 0 1 5 35 0 2 1 0 219TULE-10 12/7/2005 3 0 85 0 81 0 0 0 1 0 0 0 2 0 0 172TULE-10 11/3/2008 4 5 85 2 81 0 1 0 1 5 35 0 2 1 0 219

1 For a subset of samples, DBCP, EDB, and 1,2,3-TCP also were analyzed using methods having lower-level detection limits than the method used for analysis of VOCs as a class (table A1). The results from 

the method having the lower detection limit are reported (table A2).

2 Pesticides and degradates were analyzed using the same analytical method in all samples (table A1). Three analytical schedules having 64, 71, or 83 compounds were used, and the base set of 64 compounds 

is included in all three schedules. Polar pesticides were analyzed using a different analytical method (table A1), and for compounds analyzed using both methods, the results from the pesticides and degradates method are reported (table A2).

3 Perchlorate was analyzed in unfiltered samples with a reporting limit of 0.25, 0.5, or 1 μg/L prior to October 1, 2007, and was analyzed in filtered samples with a reporting limit of 0.1 μg/L after August 15, 

2007. Some samples collected between those dates were analyzed using both methods.

4 Constituents analyzed by more than one method (table A2) are only counted once in the total number of constituents analyzed.
Tables 41

Table 3A. Volatile organic compounds, primary uses or sources, comparative benchmarks, and reporting information for the USGS National Water Quality Laboratory Schedule 2020.[The five-digit USGS parameter code is used to uniquely identify a specific constituent or property. Benchmarks and benchmark values as of April 1, 2010. Benchmark type: HAL-US, USEPA Lifetime Health Advisory level; MCL-CA, CDPH maximum contaminant level; MCL-US, USEPA maximum contaminant level; NL-CA, CDPH notification level; RSD5-US,USEPA risk specific dose at a risk factor of 10–5; 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. Other abbreviations: CAS, Chemical Abstract Service; CDPH, California Department of Public Health; USEPA, U.S. Environmental Protection Agency; LRL, laboratory reporting level; SRL, study reporting level; THM, trihalomethane; D, detected in groundwater samples (table 5); na, not available; nv, no value in category; μg/L, micrograms per liter; —, not detected]

Constituent 

(synonym or abbreviation)

Primary use 

or source

USGS 

parameter 

code

CAS 

registry 

number

Minimum LRL 

2004–2008 

(μg/L)

Maximum LRL 

2004–2008 

(μg/L)

SRL1

(μg/L)

Benchmark 

type2

Benchmark 

value 

(μg/L)

Trend-well 

detection 

(2004–2005)

Trend-well 

detection 

(2007–2008)

Acetone Solvent 81552 67-64-1 4 6 nv3 na na — —Acrylonitrile Organic synthesis 34215 107-13-1 0.4 1.2 nv RSD5-US 0.6 — —tert-Amyl methyl ether (TAME) Gasoline oxygenate 50005 994-05-8 0.04 0.08 nv na na — —Benzene Gasoline hydrocarbon 34030 71-43-2 0.016 0.021 nv MCL-CA 1 — —Bromobenzene Solvent 81555 108-86-1 0.02 0.028 nv na na — —Bromochloromethane Fire retardant 77297 74-97-5 0.06 0.12 nv HAL-US 90 D g —Bromodichloromethane Disinfection byproduct (THM) 32101 75-27-4 0.028 0.04 nv MCL-US 4 80 D e,g D a,e,gBromoform (Tribromomethane) Disinfection byproduct (THM) 32104 75-25-2 0.08 0.1 nv MCL-US 4 80 D g —Bromomethane (Methyl bromide) Fumigant 34413 74-83-9 0.26 0.4 nv HAL-US 10 — —n-Butylbenzene Gasoline hydrocarbon 77342 104-51-8 0.08 0.14 nv NL-CA 260 — —sec-Butylbenzene Gasoline hydrocarbon 77350 135-98-8 0.02 0.06 nv NL-CA 260 — —tert-Butylbenzene Gasoline hydrocarbon 77353 98-06-6 0.06 0.08 nv NL-CA 260 — —Carbon disulfide Organic synthesis 77041 75-15-0 0.04 0.06 0.03 NL-CA 160 D b,e,g D fCarbon tetrachloride (Tetrachloromethane) Solvent 32102 56-23-5 0.06 0.08 nv MCL-CA 0.5 D d,e,f D a,d,e,fChlorobenzene Solvent 34301 108-90-7 0.02 0.028 nv MCL-CA 70 — —Chloroethane Solvent 34311 75-00-3 0.1 0.12 nv na na — —Chloroform (Trichloromethane) Disinfection byproduct (THM) 32106 67-66-3 0.02 0.04 nv MCL-US 4 80 D a,b,c,d,e,g D a,b,c,d,e,f,gChloromethane Solvent 34418 74-87-3 0.1 0.17 nv HAL-US 30 — —3-Chloropropene Organic synthesis 78109 107-05-1 0.08 0.5 nv na na — —2-Chlorotoluene Solvent 77275 95-49-8 0.02 0.04 nv NL-CA 140 — —4-Chlorotoluene Solvent 77277 106-43-4 0.02 0.05 nv NL-CA 140 — —Dibromochloromethane Disinfection byproduct (THM) 32105 124-48-1 0.1 0.12 nv MCL-US 4 80 D e,g D e1,2-Dibromo-3-chloropropane 

(DBCP)

Fumigant 82625 96-12-8 0.03 1 nv MCL-US 0.2 —(5) —(5)

1,2-Dibromoethane (EDB) Fumigant 77651 106-93-4 0.02 0.04 nv MCL-US 0.05 — —Dibromomethane Solvent 30217 74-95-3 0.04 0.05 nv na na D g —1,2-Dichlorobenzene Solvent 34536 95-50-1 0.02 0.048 nv MCL-US 600 — D e1,3-Dichlorobenzene Solvent 34566 541-73-1 0.02 0.04 nv HAL-US 600 — —
42 Groundwater-Quality Data in Seven GAMA Study Units: Results from Initial Sampling and Resampling of Wells Constituent (synonym or abbreviation) Primary use or source USGS parameter code CAS registry number Minimum LRL 2004–2008 (μg/L) Maximum LRL 2004–2008 (μg/L) SRL1 (μg/L) Benchmark type2 Benchmark value (μg/L) Trend-well detection (2004–2005) Trend-well detection (2007–2008) 1,4-Dichlorobenzene Fumigant 34571 106-46-7 0.02 0.04 nv MCL-CA 5 —

—

trans-1,4-Dichloro-2-butene Organic synthesis 73547 110-57-6 0.4 0.7 nv na na

—

—

Dichlorodifluoromethane (CFC-12) Refrigerant 34668 75-71-8 0.1 0.18 nv NL-CA 1,000 D e D e,g1,1-Dichloroethane (1,1-DCA) Solvent 34496 75-34-3 0.035 0.06 nv MCL-CA 5 D e D e1,2-Dichloroethane (1,2-DCA) Solvent 32103 107-06-2 0.06 0.13 nv MCL-CA 0.5 D a D a,e1,1-Dichloroethene (1,1-DCE) Organic synthesis 34501 75-35-4 0.02 0.024 nv MCL-CA 6 D a,e D a,ecis-1,2-Dichloroethene 

(cis-1,2-DCE)

Solvent 77093 156-59-2 0.02 0.024 nv MCL-CA 6 D a,b,e,f D a,b,d,e,f

trans-1,2-Dichloroethene 

(trans-1,2-DCE)

Solvent 34546 156-60-5 0.018 0.032 nv MCL-CA 10

— D a

1,2-Dichloropropane Fumigant 34541 78-87-5 0.02 0.029 nv MCL-US 5 —

—

1,3-Dichloropropane Fumigant 77173 142-28-9 0.06 0.06 nv na na

—

—

2,2-Dichloropropane Fumigant 77170 594-20-7 0.05 0.06 nv na na

—

—

1,1-Dichloropropene Organic synthesis 77168 563-58-6 0.026 0.04 nv na na

—

—

cis-1,3-Dichloropropene Fumigant 34704 10061-01-5 0.05 0.1 nv RSD5-US 6 4

—

—

trans-1,3-Dichloropropene Fumigant 34699 10061-02-6 0.09 0.1 nv RSD5-US 6 4

—

—

Diethyl ether Solvent 81576 60-29-7 0.08 0.12 nv na na

—

—

Diisopropyl ether (DIPE) Gasoline oxygenate 81577 108-20-3 0.06 0.1 nv na na D a D aEthylbenzene Gasoline hydrocarbon 34371 100-41-4 0.02 0.04 0.06 MCL-CA 300

—

—

Ethyl tert-butyl ether (ETBE) Gasoline oxygenate 50004 637-92-3 0.03 0.05 nv na na

—

—

Ethyl methacrylate Organic synthesis 73570 97-63-2 0.14 0.18 nv na na

—

—

Ethyl methyl ketone (2-butanone) Solvent 81595 78-93-3 1.6 4 nv3 HAL-US 4,000

—

—

o-Ethyl toluene 

(1-Ethyl-2-methyl benzene)

Gasoline hydrocarbon 77220 611-14-3 0.02 0.06 nv na na

—

—

Hexachlorobutadiene Organic synthesis 39702 87-68-3 0.06 0.14 nv RSD5-US 9 —

—

Hexachloroethane Solvent 34396 67-72-1 0.14 0.14 nv HAL-US 1 —

—

2-Hexanone 

(n-Butyl methyl ketone)

Solvent 77103 591-78-6 0.4 0.7 nv na na

—

—

Iodomethane (Methyl iodide) Fumigant, natural 77424 74-88-4 0.4 0.8 nv na na

—

—

Table 3A. Volatile organic compounds, primary uses or sources, comparative benchmarks, and reporting information for the USGS National Water Quality Laboratory Schedule 2020.—Continued[The five-digit USGS parameter code is used to uniquely identify a specific constituent or property. Benchmarks and benchmark values as of April 1, 2010. Benchmark type: HAL-US, USEPA Lifetime Health Advisory level; MCL-CA, CDPH maximum contaminant level; MCL-US, USEPA maximum contaminant level; NL-CA, CDPH notification level; RSD5-US,USEPA risk specific dose at a risk factor of 10–5; 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. Other abbreviations: CAS, Chemical Abstract Service; CDPH, California Department of Public Health; USEPA, U.S. Environmental Protection Agency; LRL, laboratory reporting level; SRL, study reporting level; THM, trihalomethane; D, detected in groundwater samples (table 5); na, not available; nv, no value in category; μg/L, micrograms per liter; —, not detected]
Tables 43

Constituent 

(synonym or abbreviation)

Primary use 

or source

USGS 

parameter 

code

CAS 

registry 

number

Minimum LRL 

2004–2008 

(μg/L)

Maximum LRL 

2004–2008 

(μg/L)

SRL1

(μg/L)

Benchmark 

type2

Benchmark 

value 

(μg/L)

Trend-well 

detection 

(2004–2005)

Trend-well 

detection 

(2007–2008)

Isopropylbenzene Gasoline hydrocarbon 77223 98-82-8 0.038 0.04 nv NL-CA 770 — —4-Isopropyl-1-methyl benzene Gasoline hydrocarbon 77356 99-87-6 0.06 0.08 nv na na — —Methyl acrylate Organic synthesis 49991 96-33-3 0.4 2 nv na na — —Methyl acrylonitrile Organic synthesis 81593 126-98-7 0.2 0.76 nv na na — —Methyl tert-butyl ether (MTBE) Gasoline oxygenate 78032 1634-04-4 0.1 0.17 nv MCL-CA 13 D a,e D a,eMethyl iso-butyl ketone (MIBK) Solvent 78133 108-10-1 0.2 0.4 nv NL-CA 120 — —Methylene chloride (Dichloromethane) Solvent 34423 75-09-2 0.04 0.06 nv MCL-US 5 D e,g D a,e,gMethyl methacrylate Organic synthesis 81597 80-62-6 0.2 0.35 nv na na — —Naphthalene Gasoline hydrocarbon 34696 91-20-3 0.2 0.52 nv NL-CA 17 — —n-Propylbenzene Solvent 77224 103-65-1 0.04 0.042 nv NL-CA 260 — —Styrene Gasoline hydrocarbon 77128 100-42-5 0.04 0.042 nv MCL-US 100 — —1,1,1,2-Tetrachloroethane Solvent 77562 630-20-6 0.03 0.04 nv HAL-US 70 — —1,1,2,2-Tetrachloroethane Solvent 34516 79-34-5 0.08 0.16 nv MCL-CA 1 — —Tetrachloroethene (PCE) Solvent 34475 127-18-4 0.03 0.06 nv MCL-US 5 D a,b,d,e D a,b,d,eTetrahydrofuran Solvent 81607 109-99-9 1 2.2 nv 3 na na — —1,2,3,4-Tetramethylbenzene Gasoline hydrocarbon 49999 488-23-3 0.08 0.14 nv na na — —1,2,3,5-Tetramethylbenzene Gasoline hydrocarbon 50000 527-53-7 0.08 0.14 nv na na — —Toluene Gasoline hydrocarbon 34010 108-88-3 0.018 0.05 0.69 MCL-CA 150 — —1,2,3-Trichlorobenzene Organic synthesis 77613 87-61-6 0.06 0.27 nv na na — —1,2,4-Trichlorobenzene Solvent 34551 120-82-1 0.04 0.12 nv MCL-CA 5 — —1,1,1-Trichloroethane (TCA) Solvent 34506 71-55-6 0.02 0.04 nv MCL-US 200 D e —1,1,2-Trichloroethane Solvent 34511 79-00-5 0.04 0.064 nv MCL-CA 5 — —Trichloroethene (TCE) Solvent 39180 79-01-6 0.02 0.038 nv MCL-US 5 D a,b,d,e,f D a,b,d,e,fTrichlorofluoromethane (CFC-11) Refrigerant 34488 75-69-4 0.08 0.16 nv MCL-CA 150 D e D b,e1,2,3-Trichloropropane (1,2,3-TCP) Fumigant/solvent 77443 96-18-4 0.12 0.18 nv HAL-US 7 40 —(5) —(5)Trichlorotrifluoroethane (CFC-113) Refrigerant 77652 76-13-1 0.038 0.04 nv MCL-CA 1,200 D e,g D e,g1,2,3-Trimethylbenzene Gasoline hydrocarbon 77221 526-73-8 0.06 0.08 nv na na — —1,2,4-Trimethylbenzene Gasoline hydrocarbon 77222 95-63-6 0.04 0.12 0.56 NL-CA 330 — —

Table 3A. Volatile organic compounds, primary uses or sources, comparative benchmarks, and reporting information for the USGS National Water Quality Laboratory Schedule 2020.—Continued[The five-digit USGS parameter code is used to uniquely identify a specific constituent or property. Benchmarks and benchmark values as of April 1, 2010. Benchmark type: HAL-US, USEPA Lifetime Health Advisory level; MCL-CA, CDPH maximum contaminant level; MCL-US, USEPA maximum contaminant level; NL-CA, CDPH notification level; RSD5-US,USEPA risk specific dose at a risk factor of 10–5; 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. Other abbreviations: CAS, Chemical Abstract Service; CDPH, California Department of Public Health; USEPA, U.S. Environmental Protection Agency; LRL, laboratory reporting level; SRL, study reporting level; THM, trihalomethane; D, detected in groundwater samples (table 5); na, not available; nv, no value in category; μg/L, micrograms per liter; —, not detected]
44 Groundwater-Quality Data in Seven GAMA Study Units: Results from Initial Sampling and Resampling of Wells Constituent (synonym or abbreviation) Primary use or source USGS parameter code CAS registry number Minimum LRL 2004–2008 (μg/L) Maximum LRL 2004–2008 (μg/L) SRL1 (μg/L) Benchmark type2 Benchmark value (μg/L) Trend-well detection (2004–2005) Trend-well detection (2007–2008) 1,3,5-Trimethylbenzene Organic synthesis 77226 108-67-8 0.04 0.044 nv NL-CA 330

—

—

Vinyl bromide (Bromoethene) Fire retardant 50002 593-60-2 0.1 0.12 nv na na

—

—

Vinyl chloride (Chloroethene) Organic synthesis 39175 75-01-4 0.06 0.08 nv MCL-CA 0.5

—

—

m- and 

p-Xylene Gasoline hydrocarbon 85795 108-38-3, 

106-42-3

0.06 0.08 0.33 MCL-CA 8 1,750

—

—

o-Xylene Gasoline hydrocarbon 77135 95-47-6 0.038 0.04 0.12 MCL-CA 8 1,750

—

—

1 Study reporting levels for VOCs are based on Fram and others (2012).2 Maximum contaminant level benchmarks 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.3 GAMA project policy for acetone, ethyl methyl ketone, and tetrahydrofuran is to report all detections as “not analyzed” (Fram and others, 2012).4 The MCL-US benchmark for trihalomethanes is the sum of chloroform, bromoform, bromodichloromethane, and dibromochloromethane.5 DBCP and 1,2,3-TCP were detected in a few samples that were analyzed using their respective preferred method with lower detection limits. See tables 3B and 3H respectively for DBCP and 1,2,3-TCP.6 The RSD5 benchmark for 1,3-dichloropropene is the sum of its isomers (cis and trans).7 In earlier reports in this series, the NL-CA (0.005 μg/L) was used as the comparison benchmark for 1,2,3-TCP.8 The MCL-CA benchmarks for 

m- plus 

p-Xylene and o-Xylene is the sum of all three xylene compounds.

a Detected in the San Diego Drainages study unit.b Detected in the North San Francisco Bay study unit.c Detected in the Northern San Joaquin Basin study unit.d Detected in the Southern Sacramento Valley study unit.e Detected in the San Fernando–San Gabriel study unit.f Detected in the Monterey Bay and Salinas Valley Basins study unit.g Detected in the Southeast San Joaquin Valley study unit.

Table 3A. Volatile organic compounds, primary uses or sources, comparative benchmarks, and reporting information for the USGS National Water Quality Laboratory Schedule 2020.—Continued[The five-digit USGS parameter code is used to uniquely identify a specific constituent or property. Benchmarks and benchmark values as of April 1, 2010. Benchmark type: HAL-US, USEPA Lifetime Health Advisory level; MCL-CA, CDPH maximum contaminant level; MCL-US, USEPA maximum contaminant level; NL-CA, CDPH notification level; RSD5-US,USEPA risk specific dose at a risk factor of 10–5; 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. Other abbreviations: CAS, Chemical Abstract Service; CDPH, California Department of Public Health; USEPA, U.S. Environmental Protection Agency; LRL, laboratory reporting level; SRL, study reporting level; THM, trihalomethane; D, detected in groundwater samples (table 5); na, not available; nv, no value in category; μg/L, micrograms per liter; —, not detected]
Tables 45

Table 3B. 1,2-Dibromo-3-chloropropane (DBCP) and 1,2-Dibromoethane (EDB), primary uses or sources, comparative benchmarks, and reporting information for the USGS National Water Quality Laboratory Schedule 1306.[The five-digit USGS parameter code is used to uniquely identify a specific constituent or property. This analytical schedule is the preferred method for these two constituents, but was used only for analyses of samples from the Northern San Joaquin Basin and the Southeast San Joaquin Valley study units. Benchmarks and benchmark values as of April 1, 2010. Benchmark type: MCL-US, U.S. Environmental Protection Agency maximum contaminant level. 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. Other abbreviations: CAS, Chemical Abstract Service; LRL, laboratory reporting level; D, detected in groundwater samples (table 5); μg/L, micrograms per liter; —, not detected]

Constituent 

(synonym or abbreviation)

Primary use 

or source

USGS 

parameter 

code

CAS 

registry 

number

Minimum LRL 

2004–2008 

(μg/L)

Maximum LRL 

2004–2008 

(μg/L)

Benchmark 

type1

Benchmark 

value 

(μg/L)

Trend-well 

detection 

(2004–2005)

Trend-well 

detection 

(2007–2008)

1,2-Dibromo-3-chloropropane (DBCP) Fumigant 82625 96-12-8 0.030 0.030 MCL-US 0.2 D c,g D c,g1,2-Dibromoethane (EDB) Fumigant 77651 106-93-4 0.02 0.040 MCL-US 0.05 — —

1 Maximum contaminant level benchmarks 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.c Detected in the Northern San Joaquin Basin study unit.g Detected in the Southeast San Joaquin Valley study unit.
46 Groundwater-Quality Data in Seven GAMA Study Units: Results from Initial Sampling and Resampling of Wells Table 3C. Pesticides and pesticide degradates, primary uses or sources, comparative benchmarks, and reporting information for the USGS National Water Quality Laboratory Schedule 2003, and the expanded versions Schedule 2032 and Schedule 2033. [The five-digit USGS parameter code is used to uniquely identify a specific constituent or property. Benchmarks and benchmark values as of April 1, 2010. Benchmark type: HAL-US, USEPA Lifetime Health Advisory level; MCL-CA, CDPH maximum contaminant level; MCL-US, USEPA maximum contaminant level; RSD5-US, USEPA risk-specific dose at a risk factor of 10–5; 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. Other abbreviations: CAS, Chemical Abstract Service; CDPH, California Department of Public Health; USEPA, U.S. Environmental Protection Agency; LRL, laboratory reporting level; D, detected in groundwater samples (table 6A); na, not available; μg/L, micrograms per liter; —, not detected] Constituent (synonym or abbreviation) Primary use or source USGS parameter code CAS registry number Minimum LRL 2004–2008 (μg/L) Maximum LRL 2004–2008 (μg/L) Benchmark type1 Benchmark value (μg/L) Trend-well detection (2004–2005) Trend-well detection (2007–2008) Acetochlor Herbicide 49260 34256-82-1 0.006 0.010 na na

—(3)

—(3)

Alachlor Herbicide 46342 15972-60-8 0.005 0.008 MCL-US 2 —

—

Atrazine 2 Herbicide 39632 1912-24-9 0.007 0.007 MCL-CA 1 D a,b,c,e,f,g D a,c,d,e,f,gAzinphos-methyl Insecticide 82686 86-50-0 0.050 0.120 na na

—(3)

—(3)

Azinphos-methyl oxon Insecticide degradate 61635 961-22-8 0.016 0.070 na na

—(3)

—(3)

Benfluralin Herbicide 82673 1861-40-1 0.010 0.014 na na

—(3)

—(3)

Carbaryl 2 Insecticide 82680 63-25-2 0.041 0.200 RSD5-US 400

—

—

Carbofuran 2,4 Insecticide 82674 1563-66-2 0.020 0.060 MCL-CA 18

—

—

2-Chloro-2,6-diethylacetanilide Herbicide degradate 61618 6967-29-9 0.005 0.010 na na

—

—

4-Chloro-2-methylphenol Herbicide degradate 61633 1570-64-5 0.005 0.006 na na

—(3)

—(3)

Chlorpyrifos Insecticide 38933 2921-88-2 0.005 0.010 HAL-US 2 —(3)

—(3)

ChlorpyrIfos oxon Insecticide degradate 61636 5598-15-2 0.050 0.056 na na

—(3)

—(3)

Cyanazine 5 Herbicide 04041 21725-46-2 0.018 0.040 HAL-US 1 —

—

Cyfluthrin Insecticide 61585 68359-37-5 0.008 0.053 na na

—(3)

—(3)

λ-Cyhalothrin 4 Insecticide 61595 91465-08-6 0.004 0.010 na na

—(3)

—(3)

Cypermethrin Insecticide 61586 52315-07-8 0.009 0.046 na na

—(3)

—(3)

DCPA (Dacthal) Herbicide 82682 1861-32-1 0.003 0.006 HAL-US 70 D f —Deethylatrazine 

(2-Chloro-4-isopropylamino-6-amino-s-triazine) 2

Herbicide degradate 04040 6190-65-4 0.006 0.014 na na D a,c,e,f,g,3 D a,c,e,f,g,3

Desulfinylfipronil Insecticide degradate 62170 na 0.012 0.012 na na

— D g

Desulfinylfipronil amide Insecticide degradate 62169 na 0.029 0.029 na na

—

—

Diazinon Insecticide 39572 333-41-5 0.005 0.005 HAL-US 1 —

—

3,4-Dichloroaniline Herbicide degradate 61625 95-76-1 0.004 0.006 na na D e,g D e,g3,5-Dichloroaniline 5 Herbicide degradate 61627 626-43-7 0.004 0.004 na na

— D g

Dichlorvos Insecticide 38775 62-73-7 0.012 0.020 na na

—(3)

—(3)

Dicrotophos Insecticide 38454 141-66-2 0.080 0.084 na na

—(3)

—(3)

Dieldrin Insecticide 39381 60-57-1 0.009 0.009 RSD5-US 0.02

—

—

2,6-Diethylaniline Herbicide degradate 82660 579-66-8 0.006 0.006 na na

—

—
Tables 47

Constituent 

(synonym or abbreviation)

Primary use 

or source

USGS 

parameter 

code

CAS 

registry 

number

Minimum LRL 

2004–2008 

(μg/L)

Maximum LRL 

2004–2008 

(μg/L)

Benchmark 

type1

Benchmark 

value 

(μg/L)

Trend-well 

detection 

(2004–2005)

Trend-well 

detection 

(2007–2008)

Dimethoate Insecticide 82662 60-51-5 0.006 0.006 na na —(3) —(3)Disulfoton 5 Insecticide 82677 298-04-4 0.021 0.040 HAL-US 0.7 — —Disulfoton sulfone 5 Insecticide degradate 61640 2497-06-5 0.006 0.014 na na — —α-Endosulfan 5 Insecticide 34362 959-98-8 0.005 0.006 na na — —Endosulfan sulfate 5 Insecticide degradate 61590 1031-07-8 0.014 0.022 na na — —Ethion Insecticide 82346 563-12-2 0.004 0.016 na na —(3) —(3)Ethion monoxon Insecticide degradate 61644 17356-42-2 0.002 0.034 na na —(3) —(3)Ethoprophos 5 Herbicide 82672 13194-48-4 0.005 0.016 na na — —S-Ethyl-dipropylthiocarbamate (EPTC) 5 Herbicide 82668 759-94-4 0.002 0.004 na na D g D g2-Ethyl-6-methylaniline Herbicide degradate 61620 24549-06-2 0.004 0.010 na na — —Fenamiphos Insecticide 61591 22224-92-6 0.029 0.029 HAL-US 0.7 —(3) —(3)Fenamiphos sulfone Insecticide degradate 61645 31972-44-8 0.008 0.053 na na —(3) —(3)Fenamiphos sulfoxide Insecticide degradate 61646 31972-43-7 0.031 0.200 na na —(3) —(3)Fipronil Insecticide 62166 120068-37-3 0.016 0.040 na na —(3) D g,3Fipronil sulfide Insecticide degradate 62167 120067-83-6 0.013 0.013 na na —(3) D g,3Fipronil sulfone Insecticide degradate 62168 120068-36-2 0.024 0.024 na na —(3) —(3)Fonofos Insecticide 04095 944-22-9 0.003 0.010 HAL-US 10 — —Hexazinone Herbicide 04025 51235-04-2 0.008 0.026 HAL-US 400 D e,g,3 D e,g,3Iprodione Fungicide 61593 36734-19-7 0.010 1.422 na na —(3) —(3)Isofenphos Insecticide 61594 25311-71-1 0.003 0.011 na na —(3) —(3)Malaoxon Insecticide degradate 61652 1634-78-2 0.008 0.080 na na —(3) —(3)Malathion Insecticide 39532 121-75-5 0.016 0.027 HAL-US 100 —(3) —(3)Metalaxyl 2 Fungicide 61596 57837-19-1 0.005 0.007 na na — —Methidathion Insecticide 61598 950-37-8 0.004 0.009 na na — —Metolachlor Herbicide 39415 51218-45-2 0.006 0.014 HAL-US 700 — —Metribuzin Herbicide 82630 21087-64-9 0.006 0.016 HAL-US 70 —(3) —(3)

Table 3C. Pesticides and pesticide degradates, primary uses or sources, comparative benchmarks, and reporting information for the USGS National Water Quality Laboratory Schedule 2003, and the expanded versions Schedule 2032 and Schedule 2033.—Continued[The five-digit USGS parameter code is used to uniquely identify a specific constituent or property. Benchmarks and benchmark values as of April 1, 2010. Benchmark type: HAL-US, USEPA Lifetime Health Advisory level; MCL-CA, CDPH maximum contaminant level; MCL-US, USEPA maximum contaminant level; RSD5-US, USEPA risk-specific dose at a risk factor of 10–5; 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. Other abbreviations: CAS, Chemical Abstract Service; CDPH, California Department of Public Health; USEPA, U.S. Environmental Protection Agency; LRL, laboratory reporting level; D, detected in groundwater samples (table 6A); na, not available; μg/L, micrograms per liter; —, not detected]
48 Groundwater-Quality Data in Seven GAMA Study Units: Results from Initial Sampling and Resampling of Wells Constituent (synonym or abbreviation) Primary use or source USGS parameter code CAS registry number Minimum LRL 2004–2008 (μg/L) Maximum LRL 2004–2008 (μg/L) Benchmark type1 Benchmark value (μg/L) Trend-well detection (2004–2005) Trend-well detection (2007–2008) Molinate 4 Herbicide 82671 2212-67-1 0.002 0.003 MCL-CA 20

—

—

Myclobutanil Fungicide 61599 88671-89-0 0.008 0.033 na na

—(3)

—(3)

1-Naphthol Insecticide degradate 49295 90-15-3 0.040 0.088 na na

—(3)

—(3)

Oxyfluorfen 5 Herbicide 61600 42874-03-3 0.006 0.007 na na

—(3)

—(3)

Paraoxon-methyl Insecticide degradate 61664 950-35-6 0.010 0.030 na na

—(3)

—(3)

Parathion-methyl Insecticide 82667 298-00-0 0.008 0.015 HAL-US 1 —(3)

—(3)

Pendimethalin Herbicide 82683 40487-42-1 0.012 0.022 na na

—(3)

—(3)

cis-Permethrin Insecticide 82687 54774-45-7 0.006 0.014 na na

—(3)

—(3)

Phorate Insecticide 82664 298-02-2 0.011 0.040 na na

—(3)

—(3)

Phorate oxon Insecticide degradate 61666 2600-69-3 0.030 0.100 na na

—(3)

—(3)

Phosmet Insecticide 61601 732-11-6 0.008 0.200 na na

—(3)

—(3)

Phosmet oxon Insecticide degradate 61668 3735-33-9 0.051 0.060 na na

—(3)

—(3)

Prometon Herbicide 04037 1610-18-0 0.005 0.012 HAL-US 100 D a,g,3 D a,e,g,3Prometryn Herbicide 04036 7287-19-6 0.005 0.006 na na

—

—

Pronamide (Propyzamide) Herbicide 82676 23950-58-5 0.004 0.004 RSD5-US 20

—

—

Propanil 4 Herbicide 82679 709-98-8 0.006 0.014 na na

—

—

Propargite 5 Insecticide 82685 2312-35-8 0.020 0.023 na na

—

—

cis-Propiconazole 4 Fungicide 79846 60207-90-1 0.006 0.008 na na

—(3)

—(3)

trans-Propiconazole 4 Fungicide 79847 60207-90-1 0.013 0.020 na na

—

—

Simazine Herbicide 04035 122-34-9 0.005 0.010 MCL-US 4 D a,b,c,e,f,g D a,b,c,e,gTebuthiuron 2 Herbicide 82670 34014-18-1 0.016 0.020 HAL-US 500 D a,e D a,eTefluthrin 5 Insecticide 61606 79538-32-2 0.008 0.010 na na

—(3)

—(3)

Terbufos Insecticide 82675 13071-79-9 0.012 0.018 HAL-US 0.4

—

—

Terbufos oxon sulfone Insecticide degradate 61674 56070-15-6 0.045 0.068 na na

—(3)

—(3)

Terbuthylazine Herbicide 04022 5915-41-3 0.006 0.010 na na

—

—

Thiobencarb Herbicide 82681 28249-77-6 0.010 0.016 MCL-CA 70

—

—

Table 3C. Pesticides and pesticide degradates, primary uses or sources, comparative benchmarks, and reporting information for the USGS National Water Quality Laboratory Schedule 2003, and the expanded versions Schedule 2032 and Schedule 2033.—Continued[The five-digit USGS parameter code is used to uniquely identify a specific constituent or property. Benchmarks and benchmark values as of April 1, 2010. Benchmark type: HAL-US, USEPA Lifetime Health Advisory level; MCL-CA, CDPH maximum contaminant level; MCL-US, USEPA maximum contaminant level; RSD5-US, USEPA risk-specific dose at a risk factor of 10–5; 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. Other abbreviations: CAS, Chemical Abstract Service; CDPH, California Department of Public Health; USEPA, U.S. Environmental Protection Agency; LRL, laboratory reporting level; D, detected in groundwater samples (table 6A); na, not available; μg/L, micrograms per liter; —, not detected]
Tables 49

Constituent 

(synonym or abbreviation)

Primary use 

or source

USGS 

parameter 

code

CAS 

registry 

number

Minimum LRL 

2004–2008 

(μg/L)

Maximum LRL 

2004–2008 

(μg/L)

Benchmark 

type1

Benchmark 

value 

(μg/L)

Trend-well 

detection 

(2004–2005)

Trend-well 

detection 

(2007–2008)

Tribufos Defoliant 61610 78-48-8 0.004 0.035 na na —(3) —(3)Trifluralin Herbicide 82661 1582-09-8 0.009 0.012 HAL-US 10 —(3) —(3)

1 Maximum contaminant level benchmarks 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.2 Compound also analyzed for selected samples by the additional Laboratory Schedule 2060 (table 3D).3 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 even if it was present.4 Compound analyzed by Schedule 2032, used only for the Southern Sacramento Valley study unit, and by Schedule 2033, used only for the Southeast San Joaquin Valley study unit.5 Compound analyzed by Schedule 2033, used only for the Southeast San Joaquin Valley study unit.a Detected in the San Diego Drainages study unit.b Detected in the North San Francisco Bay study unit.c Detected in the Northern San Joaquin Basin study unit.d Detected in the Southern Sacramento Valley study unit.e Detected in the San Fernando–San Gabriel study unit.f Detected in the Monterey Bay and Salinas Valley Basins study unit.g Detected in the Southeast San Joaquin Valley study unit.

Table 3C. Pesticides and pesticide degradates, primary uses or sources, comparative benchmarks, and reporting information for the USGS National Water Quality Laboratory Schedule 2003, and the expanded versions Schedule 2032 and Schedule 2033.—Continued[The five-digit USGS parameter code is used to uniquely identify a specific constituent or property. Benchmarks and benchmark values as of April 1, 2010. Benchmark type: HAL-US, USEPA Lifetime Health Advisory level; MCL-CA, CDPH maximum contaminant level; MCL-US, USEPA maximum contaminant level; RSD5-US, USEPA risk-specific dose at a risk factor of 10–5; 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. Other abbreviations: CAS, Chemical Abstract Service; CDPH, California Department of Public Health; USEPA, U.S. Environmental Protection Agency; LRL, laboratory reporting level; D, detected in groundwater samples (table 6A); na, not available; μg/L, micrograms per liter; —, not detected]
50 Groundwater-Quality Data in Seven GAMA Study Units: Results from Initial Sampling and Resampling of Wells Table 3D. Polar pesticides, pesticide degradates, and caffeine, primary uses or sources, comparative benchmarks, and reporting information for the USGS National Water Quality Laboratory Schedule 2060. [The five-digit USGS parameter code is used to uniquely identify a specific constituent or property. Benchmarks and benchmark values as of April 1, 2010. Benchmark type: HAL-US, USEPA Lifetime Health Advisory level; MCL-CA, CDPH maximum contaminant level; MCL-US, USEPA maximum contaminant level; RSD5-US, USEPA risk specific dose at a risk factor of 10–5; 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. Other abbreviations: CAS, Chemical Abstract Service; CDPH, California Department of Public Health; USEPA, U.S. Environmental Protection Agency; LRL, laboratory reporting level; D, detected in groundwater samples (table 6B); na, not available; μg/L, micrograms per liter; —, not detected] Constituent (synonym or abbreviation) Primary use or source USGS parameter code CAS registry number Minimum LRL 2004–2008 (μg/L) Maximum LRL 2004–2008 (μg/L) Benchmark type1 Benchmark value (μg/L) Trend-well detection2 (2004–2005) Trend-well detection2 (2007–2008) Acifluorfen Herbicide 49315 50594-66-6 3 0.007 0.060 na na

—(4)

—(4)

Aldicarb Insecticide 49312 116-06-3 3 0.040 0.120 MCL-US 3 —

—

Aldicarb sulfone Degradate 49313 1646-88-4 0.018 0.080 MCL-US 3 —(4)

—(4)

Aldicarb sulfoxide Degradate 49314 1646-87-3 3 0.008 0.060 MCL-US 4 —

—

Atrazine 5 Herbicide 39632 1912-24-9 0.008 0.040 MCL-CA 1 D e,g D gBendiocarb Insecticide 50299 22781-23-3 0.020 0.040 na na

—

—

Benomyl Fungicide 50300 17804-35-2 3 0.004 0.040 na na

—

—

Bensulfuron-methyl Herbicide 61693 83055-99-6 3 0.016 0.060 na na

—

—

Bentazon Herbicide 38711 25057-89-0 3 0.011 0.040 MCL-CA 18

—

—

Bromacil Herbicide 04029 314-40-9 0.018 0.040 HAL-US 70

—

—

Bromoxynil Herbicide 49311 1689-84-5 3 0.017 0.120 na na

—

—

Caffeine Beverages 50305 58-08-2 3 0.010 0.060 na na D d,e,g

—

Carbaryl 5 Herbicide 49310 63-25-2 0.018 0.040 RSD5-US 400

—

—

Carbofuran 5 Herbicide 49309 1563-66-2 3 0.006 0.060 MCL-CA 18

—

—

Chloramben, methyl ester Herbicide 61188 7286-84-2 3 0.018 0.100 na na

—

—

Chlorimuron-ethyl Herbicide 50306 90982-32-4 3 0.010 0.080 na na

—

—

3-(4-Chlorophenyl)-1-methyl urea Degradate 61692 5352-88-5 3 0.024 0.120 na na

—(4)

—(4)

Clopyralid Herbicide 49305 1702-17-6 3 0.014 0.060 na na

—

—

Cycloate Herbicide 04031 1134-23-2 3 0.013 0.060 na na

—

—

2,4-D 6 Herbicide 39732 94-75-7 3 0.022 0.060 HAL-US 70

—

—

2,4-D methyl ester 6 Herbicide 50470 1928-38-7 3 0.009 0.200 na na

—

—

2,4-D plus 2,4-D methyl ester 6 Herbicides 66496 na 3 0.020 3 0.020 na na

—

—

2,4-DB (4-(2,4-Dichlorophenoxy)butyric acid) Herbicide 38746 94-82-6 3 0.016 0.020 na na

—

—

DCPA (Dacthal) monoacid Degradate 49304 887-54-7 3 0.012 0.028 na na

—

—

Deethylatrazine (2-Chloro-4-isopropylamino-6-amino-s-triazine) 5 Degradate 04040 6190-65-4 0.020 0.060 na na D e D eDeisopropyl atrazine (2-Chloro-6-ethylamino-4-amino-s-triazine) Degradate 04038 1007-28-9 3 0.044 0.080 na na

— D e

Dicamba Herbicide 38442 1918-00-9 3 0.013 0.080 HAL-US 4,000

—(4)

—(4)

Dichlorprop Herbicide 49302 120-36-5 3 0.014 0.040 na na

—

—
Tables 51

Constituent 

(synonym or abbreviation)

Primary use 

or source

USGS 

parameter 

code

CAS 

registry 

number

Minimum LRL 

2004–2008 

(μg/L)

Maximum LRL 

2004–2008 

(μg/L)

Benchmark 

type1

Benchmark 

value 

(μg/L)

Trend-well 

detection2

(2004–2005)

Trend-well 

detection2

(2007–2008)

Dinoseb (Dinitrobutyl phenol) Herbicide 49301 88-85-7 0.038 0.040 MCL-CA 7 — —Diphenamid Herbicide 04033 957-51-7 0.010 0.040 HAL-US 200 — —Diuron Herbicide 49300 330-54-1 0.015 0.040 HAL-US 10 D e —Fenuron Herbicide 49297 101-42-8 0.018 0.040 na na — —Flumetsulam Herbicide 61694 98967-40-9 3 0.011 0.060 na na — —Fluometuron Herbicide 38811 2164-17-2 0.016 0.040 HAL-US 90 — —Hydroxyatrazine 

(2-Hydroxy-4-isopropylamino-6-ethylamino-s-triazine)

Degradate 50355 2163-68-0 3 0.008 0.080 na na — —

3-Hydroxycarbofuran Degradate 49308 16655-82-6 3 0.006 0.020 na na — —Imazaquin Herbicide 50356 81335-37-7 3 0.016 0.040 na na — —Imazethapyr Herbicide 50407 81335-77-5 3 0.017 0.040 na na — —Imidacloprid Insecticide 61695 138261-41-3 3 0.007 0.060 na na — —Linuron Herbicide 38478 330-55-2 0.014 0.040 na na — —MCPA (2-Methyl-4-chlorophenoxyacetic acid) Herbicide 38482 94-74-6 3 0.016 0.060 HAL-US 30 — —MCPB (4-(2-Methyl-4-chlorophenoxy)butyric acid) Herbicide 38487 94-81-5 0.010 0.200 na na — —Metalaxyl 5 Fungicide 50359 57837-19-1 0.012 0.040 na na — —Methiocarb Insecticide 38501 2032-65-7 3 0.008 0.040 na na — —Methomyl Insecticide 49296 16752-77-5 3 0.004 0.120 HAL-US 200 — —Metsulfuron methyl Herbicide 61697 74223-64-6 3 0.025 3 0.14 na na — —Neburon Herbicide 49294 555-37-3 0.012 0.020 na na — —Nicosulfuron Herbicide 50364 111991-09-4 3 0.013 0.100 na na — —Norflurazon Herbicide 49293 27314-13-2 3 0.016 0.040 na na — —Oryzalin Herbicide 49292 19044-88-3 0.012 0.040 na na — —Oxamyl Insecticide 38866 23135-22-0 0.012 0.120 MCL-CA 50 — —Picloram Herbicide 49291 1918-02-01 3 0.020 0.120 MCL-US 500 — —Propham Herbicide 49236 122-42-9 3 0.010 0.060 HAL-US 100 — —Propiconazole Fungicide 50471 60207-90-1 0.010 0.060 na na — —Propoxur Insecticide 38538 114-26-1 0.008 0.040 na na — —Siduron Herbicide 38548 1982-49-6 3 0.017 0.040 na na — —

Table 3D. Polar pesticides, pesticide degradates, and caffeine, primary uses or sources, comparative benchmarks, and reporting information for the USGS National Water Quality Laboratory Schedule 2060.—Continued[The five-digit USGS parameter code is used to uniquely identify a specific constituent or property. Benchmarks and benchmark values as of April 1, 2010. Benchmark type: HAL-US, USEPA Lifetime Health Advisory level; MCL-CA, CDPH maximum contaminant level; MCL-US, USEPA maximum contaminant level; RSD5-US, USEPA risk specific dose at a risk factor of 10–5; 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. Other abbreviations: CAS, Chemical Abstract Service; CDPH, California Department of Public Health; USEPA, U.S. Environmental Protection Agency; LRL, laboratory reporting level; D, detected in groundwater samples (table 6B); na, not available; μg/L, micrograms per liter; —, not detected]
52 Groundwater-Quality Data in Seven GAMA Study Units: Results from Initial Sampling and Resampling of Wells Constituent (synonym or abbreviation) Primary use or source USGS parameter code CAS registry number Minimum LRL 2004–2008 (μg/L) Maximum LRL 2004–2008 (μg/L) Benchmark type1 Benchmark value (μg/L) Trend-well detection2 (2004–2005) Trend-well detection2 (2007–2008) Sulfometuron-methyl Herbicide 50337 74222-97-2 3 0.009 0.091 na na D b,7

—(7)

Tebuthiuron 5 Herbicide 82670 34014-18-1 0.026 0.060 HAL-US 500

— D e

Terbacil Herbicide 04032 5902-51-2 3 0.010 0.040 HAL-US 90

—

—

Triclopyr Herbicide 49235 55335-06-3 3 0.022 0.080 na na

—

—

1 Maximum contaminant level benchmarks 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.2 Analysis by this laboratory schedule was performed for fewer than half of the samples during each time period.3 Value is an interim reporting level or a method reporting level rather than a laboratory reporting level.4 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 even if it was present.5 The preferred analytical method for this constituent is Laboratory Schedule 2003/2032/2033 (table 3C).6 Because 2,4-D and 2,4-D methyl ester can convert interchangeably during analysis, they are considered one constituent (parameter code 66496) in this report.7 The median laboratory matrix-spike recovery during 2007–2008 sampling was greater than 130 percent. High recoveries may indicate that reported values could be higher than what is in the samples.b Detected in the North San Francisco Bay study unit.d Detected in the Southern Sacramento Valley study unit.e Detected in the San Fernando–San Gabriel study unit.g Detected in the Southeast San Joaquin Valley study unit.

Table 3D. Polar pesticides, pesticide degradates, and caffeine, primary uses or sources, comparative benchmarks, and reporting information for the USGS National Water Quality Laboratory Schedule 2060.—Continued[The five-digit USGS parameter code is used to uniquely identify a specific constituent or property. Benchmarks and benchmark values as of April 1, 2010. Benchmark type: HAL-US, USEPA Lifetime Health Advisory level; MCL-CA, CDPH maximum contaminant level; MCL-US, USEPA maximum contaminant level; RSD5-US, USEPA risk specific dose at a risk factor of 10–5; 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. Other abbreviations: CAS, Chemical Abstract Service; CDPH, California Department of Public Health; USEPA, U.S. Environmental Protection Agency; LRL, laboratory reporting level; D, detected in groundwater samples (table 6B); na, not available; μg/L, micrograms per liter; —, not detected]
Tables 53

Table 3E. Nutrients, comparative benchmarks, and reporting information for the USGS National Water Quality Laboratory Schedule 2755.[The five-digit USGS parameter code is used to uniquely identify a specific constituent or property. Benchmarks and benchmark values as of February 10, 2007. Benchmark type: HAL-US, U.S. Environmental Protection Agency lifetime health advisory level; MCL-US, U.S. Environmental Protection Agency maximum contaminant level. 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. Other abbreviations: CAS, Chemical Abstract Service; LRL, laboratory reporting level; na, not available; mg/L, milligrams per liter]

Constituent

USGS 

parameter 

code

CAS 

registry 

number

Minimum LRL or MRL 

2004–2008 

(mg/L)

Maximum LRL or MRL, 

or SRL1

2004–2008 

(mg/L)

Benchmark 

type1

Benchmark 

value 

(mg/L)

Ammonia (as nitrogen) 00608 7664-41-7 0.010 0.04 HAL-US 2 24.7Nitrite (as nitrogen) 00613 14797-65-0 0.002 0.008 MCL-US 1Nitrate plus nitrite (as nitrogen) 00631 na 0.04 0.06 MCL-US 10Total nitrogen (ammonia, nitrite, nitrate, organic nitrogen) 62854 17778-88-0 0.03 0.1 na naOrthophosphate (as phosphorus) 00671 14265-44-2 0.006 0.006 na na

1 Maximum contaminant level benchmarks 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.2 The HAL-US is 30 mg/L “as ammonia.” To facilitate comparson to the analytical results, we have converted and reported this HAL-US as 24.7 mg/L “as nitrogen.”
54 Groundwater-Quality Data in Seven GAMA Study Units: Results from Initial Sampling and Resampling of Wells Table 3F. Major and minor ions, total dissolved solids, trace elements, comparative benchmarks, and reporting information for the USGS National Water Quality Laboratory Schedule 1948. [The five-digit USGS parameter code is used to uniquely identify a specific constituent or property. Benchmarks and benchmark values as of June 1, 2008. Benchmark type: AL-US, U.S. Environmental Protection Agency action level; 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; SMCL-CA, California Department of Public Health secondary maximum contaminant level. 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. Other abbreviations: CAS, Chemical Abstract Service; LRL, laboratory reporting level; MRL, minimum reporting level; nv, no value in category; SRL, study reporting level; na, not available; mg/L, milligrams per liter; μg/L, micrograms per liter] Constituent USGS parameter code CAS registry number Minimum LRL or MRL 2004–2008 Maximum LRL or MRL 2004–2008 SRL1 Benchmark type2 Benchmark value Major and minor ions (mg/L) Bromide 71870 24959-67-9 0.02 0.02 nv na na Calcium 00915 7440-70-2 0.02 0.04 nv na na Chloride 00940 16887-00-6 0.12 0.20 nv SMCL-CA 3 250 (500) Fluoride 00950 16984-48-8 0.08 0.12 nv MCL-CA 2 Iodide 4 71865 7553-56-2 0.002 0.002 nv na na Magnesium 00925 7439-95-4 0.008 0.02 nv na na Potassium 00935 7440-09-7 0.02 0.16 nv na na Silica 00955 7631-86-9 0.02 0.04 nv na na Sodium 00930 7440-23-5 0.10 0.20 nv na na Sulfate 00945 14808-79-8 0.18 0.18 nv SMCL-CA 3 250 (500) Residue on evaporation (total dissolved solids, TDS) 70300 na 10 10 nv SMCL-CA 3 500 (1,000) Trace elements (μg/L) Aluminum 01106 7429-90-5 1.6 4 1.6 MCL-CA 1,000 Antimony 01095 7440-36-0 0.04 0.2 nv MCL-US 6 Arsenic 01000 7440-38-2 0.06 0.12 nv MCL-US 10 Barium 01005 7440-39-3 0.08 1 0.36 MCL-CA 1,000 Beryllium 01010 7440-41-7 0.008 0.06 nv MCL-US 4 Boron 01020 7440-42-8 4 8 nv NL-CA 1,000 Cadmium 01025 7440-43-9 0.02 0.04 nv MCL-US 5 Chromium 01030 7440-47-3 0.04 0.8 0.42 MCL-CA 50 Cobalt 01035 7440-48-4 0.014 0.04 nv na na Copper 01040 7440-50-8 0.4 1 1.7 AL-US 1,300 Iron 01046 7439-89-6 4 8 6 SMCL-CA 300 Lead 01049 7439-92-1 0.06 0.12 0.65 AL-US 15

Lithium 01130 7439-93-2 0.6 1 nv na naManganese 01056 7439-96-5 0.2 0.2 0.2 SMCL-CA 50
Tables 55

Constituent

USGS 

parameter 

code

CAS 

registry 

number

Minimum 

LRL or MRL 

2004–2008 

Maximum 

LRL or MRL 

2004–2008 

 SRL1 Benchmark 

type2

Benchmark 

value

Trace elements (μg/L)—ContinuedMolybdenum 01060 7439-98-7 0.02 0.4 nv HAL-US 40Nickel 01065 7440-02-0 0.06 0.2 0.36 MCL-CA 100Selenium 01145 7782-49-2 0.04 0.4 nv MCL-US 50Silver 01075 7440-22-4 0.008 0.2 nv SMCL-CA 100Strontium 01080 7440-24-6 0.4 0.8 nv HAL-US 4,000Thallium 01057 7440-28-0 0.04 0.04 nv MCL-US 2Tungsten 5 01155 7440-33-7 0.02 0.06 0.11 na naUranium 22703 7440-61-1 0.006 0.04 nv MCL-US 30Vanadium 01085 7440-62-2 0.04 0.16 0.11 NL-CA 50Zinc 01090 7440-66-6 0.6 2 4.8 SMCL-CA 6 5,000

1 Study reporting levels (SRLs) for trace elements were defined on the basis of the examination of field blanks collected in GAMA study units from May 2004 through January 2008 (Olsen and others, 2010).2 Maximum contaminant level benchmarks 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.3 The recommended SMCL-CA benchmarks for chloride, sulfate, and TDS are listed with the upper SMCL-CA benchmarks in parentheses.4 Samples collected for the San Diego Drainages study unit were not analyzed for iodide during either period.5 Samples collected for the San Diego Drainages, Northern San Joaquin Basin, and Southern Sacramento Valley study units were not analyzed for tungsten during either period.6 The secondary maximum contaminant level (SMCL-CA) for zinc is listed as SMCL-CA because SMCLs established by CDPH are used in this report for all constituents that have SMCL-CA values.

Table 3F. Major and minor ions, total dissolved solids, trace elements, comparative benchmarks, and reporting information for the USGS National Water Quality Laboratory Schedule 1948.—Continued[The five-digit USGS parameter code is used to uniquely identify a specific constituent or property. Benchmarks and benchmark values as of June 1, 2008. Benchmark type: AL-US, U.S. Environmental Protection Agency action level; 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; SMCL-CA, California Department of Public Health secondary maximum contaminant level. 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. Other abbreviations: CAS, Chemical Abstract Service; LRL, laboratory reporting level; MRL, minimum reporting level; nv, no value in category; SRL, study reporting level; na, not available; mg/L, milligrams per liter; μg/L, micrograms per liter]
56 Groundwater-Quality Data in Seven GAMA Study Units: Results from Initial Sampling and Resampling of Wells

Table 3G. Arsenic and iron species, comparative benchmarks, and reporting information for the USGS Trace Metal Laboratory, 

Boulder, Colorado.

[The five-digit USGS parameter code is used to uniquely identify a specific constituent or property. Benchmarks and benchmark values as of April 1, 2010. 

Benchmark type: 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. 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. 

Other abbreviations: CAS, Chemical Abstract Service; MDL, method detection limit; NWQL, USGS National Water Quality Laboratory; na, not available; 

μg/L, micrograms per liter]

Constituent 

(valence state)

USGS 

parameter code

CAS 

registry number

MDL 

(μg/L)

Benchmark 

type1

Benchmark level 

(μg/L)

Arsenic (III) 99034 22569-72-8 1 na na

Arsenic (total) 2 99033 7440-38-2 0.5 MCL-US 10

Iron (II) 01047 7439-89-6 2 na na

Iron (total) 2 01046 7439-89-6 2 SMCL-CA 300

1

 Maximum contaminant level benchmarks 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.

2

 The preferred analytical method for this constituent is NWQL Schedule 1948 (table 3F).
Tables 57

Table 3H. Constituents of special interest, primary uses or sources, comparative benchmarks, and reporting information for the Montgomery Watson Harza Laboratory and Weck Laboratories, Inc.[The five-digit USGS parameter code is used to uniquely identify a specific constituent or property. Benchmarks and benchmark values as of April 1, 2010. Benchmark type: HAL-US, U.S. Environmental Protection Agency lifetime health advisory; MCL-CA, California Department of Public Health maximum contaminant level; NL-CA, California Department of Public Health notification level; MCL-US, U.S. Environmental Protection Agency maximum contaminant level. 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. Other abbreviations: CAS, Chemical Abstract Service; MRL, minimum reporting level; LRL, laboratory reporting level; D, detected in groundwater samples (table 7); μg/L, micrograms per liter; nc, not collected; —, not detected]

Constituent

Primary use 

or 

source

USGS 

parameter 

code

CAS 

registry 

number

MRL 

or LRL

(μg/L)

Benchmark 

type1

Benchmark 

value 

(μg/L)

Trend-well 

detection 

(2004–2005)

Trend-well 

detection 

(2007–2008)

Perchlorate (unfiltered) 2 Rocket fuel, fireworks, flares, natural 61209 14797-73-0 0.5 MCL-CA 6 D a,d,e,g D aPerchlorate (filtered) 3 Rocket fuel, fireworks, flares, natural 63790 14797-73-0 0.1 MCL-CA 6 nc D a,b,c,d,e,f,gN-Nitrosodimethylamine (NDMA) 4 Disinfection byproduct 34438 62-75-9 0.002 NL-CA 0.010 — —1,2,3-Trichloropropane (1,2,3-TCP) 4 Fumigant, solvent 77443 96-18-4 0.005 HAL-US 5 40 D g D d,g

1 Maximum contaminant level benchmarks 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.2 Perchlorate analyses from unfiltered samples (all samples during 2004–05, and San Diego Drainages and North San Francisco Bay study units only during 2007–08) were performed by Montgomery Watson 

Harza Laboratory. The nominal MRLs were 0.25 or 0.5 μg/L; some higher salinity samples were diluted for analysis and had an MRL of 1 μg/L.

3 Perchlorate analyses from filtered samples performed by Weck Laboratories, Inc., during 2007–08.4 NDMA and 1,2,3-TCP analyses were performed by Montgomery Watson Harza Laboratory for initial sampling and by Weck Laboratories, Inc., for resampling. All samples were additionally analyzed for 

1,2,3-TCP by the USGS National Water Quality Laboratory Schedule 2020, which had an LRL ranging from 0.12 to 0.18.

5 In some earlier reports in this series, the NL-CA (0.005 μg/L) was used as the comparison benchmark for 1,2,3-TCP.a Detected in the San Diego Drainages study unit.b Detected in the North San Francisco Bay study unit.c Detected in the Northern San Joaquin Basin study unit.d Detected in the Southern Sacramento Valley study unit.e Detected in the San Fernando–San Gabriel study unit.f Detected in the Monterey Bay and Salinas Valley Basins study unit.g Detected in the Southeast San Joaquin Valley study unit.
58 Groundwater-Quality Data in Seven GAMA Study Units: Results from Initial Sampling and Resampling of Wells

Table 3I. Isotopic and radioactive constituents, comparative benchmarks, and reporting information for laboratories.

[The five-digit USGS parameter code is used to uniquely identify a specific constituent or property. 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. Benchmark type and 

value for tritium were in effect during both sampling periods and continue to be in effect (July 2012). Benchmark type: MCL-CA, California Department 

of Public Health maximum contaminant level; MCL-US, U.S. Environmental Protection Agency maximum contaminant level. 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. Other abbreviations: CAS, Chemical Abstract Service; MRL, minimum reporting level; MU, method uncertainty; na, not available; 

pCi/L, picocuries per liter]

Constituent

USGS 

parameter 

code

CAS 

registry 

number

Reporting 

level 

type

Reporting level 

or uncertainty 

(range)

Benchmark 

type1

Benchmark 

value

Stable isotope ratios (per mil)

δ2H of water 2 82082 4 na MU 2 na na

δ18O of water 2 82085 4 na MU 0.20 na na

δ13C of dissolved carbonates 3 82081 4 na 1 sigma 0.05 na na

Radioactive constituents (percent modern)

Carbon-14 5 49933 14762-75-5 1 sigma (0.0015–0.002) na na

Radioactive constituents (pCi/L)

Tritium 6 07000 10028-17-8 MRL (0.3–1) MCL-CA 20,000

1

 Maximum contaminant level benchmarks 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.

2

 USGS Stable Isotope Laboratory, Reston, Virginia.

3

 University of Waterloo (contract laboratory).

4

 Parameters 82081, 82082, and 82085 are isotopes that are inherent constituents of the substance being measured. Parameter 82081 was not detected in 

Southeast San Joaquin Valley study unit wells during resampling in 2008 because those samples were not analyzed for it.

5

 University of Arizona, Accelerator Mass Spectrometry Laboratory (contract laboratory).

6

 USGS Stable Isotope and Tritium Laboratory, Menlo Park, California.
Tables 59

Table 4. Water-quality indicators in samples collected from trend wells for seven Groundwater Ambient Monitoring and Assessment (GAMA) study units.[The five-digit USGS parameter code below the constituent name is used to uniquely identify a specific constituent or property. GAMA well identification number acronyms: San Diego Drainages study unit: SDALLV, Alluvial Basins study area; SDHDRK, Hard Rock study area; SDTEM, Temecula Valley study area; SDTEMFP, Temecula Valley study area flow-path well; SDWARN, Warner Valley study area. North San Francisco Bay study unit: NSFVOL, Volcanic Highlands study area; NSFVP, Valley and Plains study area; NSFWG, Wilson Grove Formation Highlands study area; NSFWGFP, Wilson Grove Formation Highlands study area flow-path well. Northern San Joaquin Basin study unit: COS, Cosumnes Basin study area; ESJ, Eastern San Joaquin Basin study area; NSJ-QPC, Uplands Basin study area; TRCY, Tracy Basin study area. Southern Sacramento Valley study unit: NAM, North American study area; SAM, South American study area; SOL, Solano study area; SSV-QPC, Uplands study area; SUI, Suisun-Fairfield study area; YOL, Yolo study area. San Fernando–San Gabriel study unit: ULASF, San Fernando study area; ULASG, San Gabriel study area. Monterey Bay and Salinas Valley Basins study unit: MSMB, Monterey Bay study area; MSPR, Paso Robles study area; MSSC, Santa Cruz study area; MSSV, Salinas Valley study area. Southeast San Joaquin Valley study unit: KING, Kings study area; KWH, Kaweah study area; TLR, Tulare Lake study area; TULE, Tule study area. Benchmark type: SMCL-US, U.S. Environmental Protection Agency secondary maximum contaminant level; SMCL-CA, California Department of Public Health secondary maximum contaminant level. Benchmark type, benchmark level, and RL as of April 1, 2010. Other abbreviations: USGS, U.S. Geological Survey; °C, degrees Celsius; mg/L, milligrams per liter; nc, not collected; na, not available; RL, reporting level or range; μS/cm, microsiemens per centimeter; <, less than; >, greater than; CaCO3, calcium carbonate; *, concentration is greater than the benchmark level; **, concentration is greater than the upper benchmark level; —, not detected; E, estimated or having a higher degree of uncertainty]

GAMA well 

identification 

number

Sample 

dates

Dissolved 

oxygen, 

field 

(mg/L) 

(00300) 

Water 

temperature, 

field 

(°C) 

(00010)

pH, 

laboratory 

(standard 

units) 

(00403)1

pH, 

field 

(standard 

units) 

(00400)

Specific 

conductance, 

laboratory 

(μS/cm at 25 °C) 

(90095)1

Specific 

conductance, 

field 

(μS/cm at 25 °C) 

(00095)

Alkalinity, 

laboratory 

(mg/L as 

CaCO3) 

(29801)1

Alkalinity, 

field 

(mg/L as 

CaCO3) 

(29802)

Bicarbonate, 

laboratory 3

(mg/L)

Bicarbonate, 

field 

(mg/L) 

(63786)

Carbonate, 

laboratory 3

(mg/L)

Carbonate, 

field 

(mg/L) 

(63788)

Benchmark type na na SMCL-US SMCL-US SMCL-CA SMCL-CA na na na na na naBenchmark level na na <6.5 or >8.5 <6.5 or >8.5 2 900 (1,600) 2 900 (1,600) na na na na na na[RL] [0.2] [0.0–38.5] [0–14] [0–14] [5] [5] [1] [1] [1] [1] [1] [1]San Diego Drainages study unitSDALLV-07 7/14/2004 nc nc nc nc nc 806 nc nc nc nc nc ncSDALLV-07 9/12/2007 3.0 19.5 nc 6.8 nc 772 153 nc 186 nc 0.1 ncSDALLV-11 7/15/2004 nc 20.5 nc nc nc **2,070 nc nc nc nc nc ncSDALLV-11 9/13/2007 1.9 21.0 nc 6.8 nc **1,750 243 nc 296 nc 0.1 ncSDHDRK-01 7/12/2004 nc nc nc nc nc **2,280 nc nc nc nc nc ncSDHDRK-01 9/13/2007 0.3 25.0 nc 7.3 nc **2,270 220 nc 268 nc 0.2 ncSDHDRK-09 7/27/2004 nc nc nc nc nc 568 nc nc nc nc nc ncSDHDRK-09 9/11/2007 2.5 20.0 7.2 6.7 673 627 206 nc 251 nc 0.2 ncSDTEM-04 5/24/2004 nc 19.5 nc nc nc *1,020 nc nc nc nc nc ncSDTEM-04 9/18/2007 5.8 19.0 7.6 7.4 *956 *947 167 nc 203 nc 0.4 ncSDTEMFP-01 5/19/2004 4.6 24.0 8.2 8.1 632 704 nc 116 nc 142 nc 2SDTEMFP-01 9/19/2007 3.0 23.5 8.2 8.2 722 716 135 nc 162 nc 1.1 ncSDWARN-01 6/17/2004 nc 20.0 nc nc nc 773 nc nc nc nc nc ncSDWARN-01 9/11/2007 3.1 20.0 7.2 7.3 806 751 221 nc 269 nc 0.2 ncNorth San Francisco Bay study unitNSFVOL-14 10/7/2004 4.3 21.5 E7.2 6.5 186 191 nc 66 nc 80 nc —NSFVOL-14 8/21/2007 4.6 19.0 nc *6.3 nc 201 80 nc 98 nc — ncNSFVOL-18 10/20/2004 nc 26.5 nc nc nc 397 nc nc nc nc nc ncNSFVOL-18 8/28/2007 0.2 28.5 7.2 6.9 398 398 189 nc 230 nc 0.2 nc
60 Groundwater-Quality Data in Seven GAMA Study Units: Results from Initial Sampling and Resampling of Wells GAMA well identification number Sample dates Dissolved oxygen, field (mg/L) (00300) Water temperature, field (°C) (00010) pH, laboratory (standard units) (00403)1 pH, field (standard units) (00400) Specific conductance, laboratory (μS/cm at 25 °C) (90095)1 Specific conductance, field (μS/cm at 25 °C) (00095) Alkalinity, laboratory (mg/L as CaCO3) (29801)1 Alkalinity, field (mg/L as CaCO3) (29802) Bicarbonate, laboratory 3 (mg/L) Bicarbonate, field (mg/L) (63786) Carbonate, laboratory 3 (mg/L) Carbonate, field (mg/L) (63788) Benchmark type na na SMCL-US SMCL-US SMCL-CA SMCL-CA na na na na na na Benchmark level na na <6.5 or >8.5 <6.5 or >8.5 2 900 (1,600) 2 900 (1,600) na na na na na na [RL] [0.2] [0.0–38.5] [0–14] [0–14] [5] [5] [1] [1] [1] [1] [1] [1] North San Francisco Bay study unit—Continued NSFVP-29 9/28/2004 5.7 16.5 7.5 6.8 409 362 nc 167 nc 203 nc 0.2 NSFVP-29 8/27/2007 6.2 16.5 nc 6.9 nc 379 164 nc 200 nc 0.1 nc NSFVP-34 10/18/2004 0.2 19.5 7.7 7.3 199 211 nc 91 nc 110 nc 0.2 NSFVP-34 8/22/2007 <0.2 20.0 nc 7.0 nc 221 94 nc 115 nc 0.1 nc NSFVP-36 10/19/2004 nc 18.5 7.6 nc *1,360 *1,250 nc nc nc nc nc nc NSFVP-36 8/20/2007 0.7 19.0 nc 7.3 nc *1,410 nc nc nc nc nc nc NSFVP-38 10/20/2004 <0.2 25.5 8.2 8.2 693 734 nc 381 nc 454 nc 4.8 NSFVP-38 8/22/2007 <0.2 28.5 nc 6.7 nc 765 389 nc 474 nc 0.1 nc NSFVP-39 10/21/2004 nc 20.0 7.6 nc 310 332 nc nc nc nc nc nc NSFVP-39 11/16/2007 0.8 23.0 7.2 7.3 318 318 157 nc 191 nc 0.1 nc NSFVP-41 10/21/2004 nc 20.5 7.3 nc 477 510 nc nc nc nc nc nc NSFVP-41 8/20/2007 1.2 18.5 nc 6.7 nc 428 161 nc 196 nc

— nc

NSFWG-03 9/21/2004 nc 16.5 nc nc nc 260 nc nc nc nc nc ncNSFWG-03 8/29/2007 <0.2 17.0 6.5 *6.1 251 256 38 nc 46 nc

— nc

NSFWGFP-01 10/5/2004 0.2 19.5 7.8 7.5 347 363 nc 143 nc 174 nc 0.4NSFWGFP-01 8/29/2007 <0.2 20.0 nc 7.4 nc 356 149 nc 181 nc 0.2 ncNorthern San Joaquin Basin study unit COS-08 1/3/2005 nc 20.0 nc nc nc 216 nc nc nc nc nc ncCOS-08 4/3/2008 1.3 20.0 7.8 7.6 217 214 99 nc 120 nc 0.3 nc

Table 4. Water-quality indicators in samples collected from trend wells for seven Groundwater Ambient Monitoring and Assessment (GAMA) study units.—Continued[The five-digit USGS parameter code below the constituent name is used to uniquely identify a specific constituent or property. GAMA well identification number acronyms: San Diego Drainages study unit: SDALLV, Alluvial Basins study area; SDHDRK, Hard Rock study area; SDTEM, Temecula Valley study area; SDTEMFP, Temecula Valley study area flow-path well; SDWARN, Warner Valley study area. North San Francisco Bay study unit: NSFVOL, Volcanic Highlands study area; NSFVP, Valley and Plains study area; NSFWG, Wilson Grove Formation Highlands study area; NSFWGFP, Wilson Grove Formation Highlands study area flow-path well. Northern San Joaquin Basin study unit: COS, Cosumnes Basin study area; ESJ, Eastern San Joaquin Basin study area; NSJ-QPC, Uplands Basin study area; TRCY, Tracy Basin study area. Southern Sacramento Valley study unit: NAM, North American study area; SAM, South American study area; SOL, Solano study area; SSV-QPC, Uplands study area; SUI, Suisun-Fairfield study area; YOL, Yolo study area. San Fernando–San Gabriel study unit: ULASF, San Fernando study area; ULASG, San Gabriel study area. Monterey Bay and Salinas Valley Basins study unit: MSMB, Monterey Bay study area; MSPR, Paso Robles study area; MSSC, Santa Cruz study area; MSSV, Salinas Valley study area. Southeast San Joaquin Valley study unit: KING, Kings study area; KWH, Kaweah study area; TLR, Tulare Lake study area; TULE, Tule study area. Benchmark type: SMCL-US, U.S. Environmental Protection Agency secondary maximum contaminant level; SMCL-CA, California Department of Public Health secondary maximum contaminant level. Benchmark type, benchmark level, and RL as of April 1, 2010. Other abbreviations: USGS, U.S. Geological Survey; °C, degrees Celsius; mg/L, milligrams per liter; nc, not collected; na, not available; RL, reporting level or range; μS/cm, microsiemens per centimeter; <, less than; >, greater than; CaCO3, calcium carbonate; *, concentration is greater than the benchmark level; **, concentration is greater than the upper benchmark level; —, not detected; E, estimated or having a higher degree of uncertainty]
Tables 61

GAMA well 

identification 

number

Sample 

dates

Dissolved 

oxygen, 

field 

(mg/L) 

(00300) 

Water 

temperature, 

field 

(°C) 

(00010)

pH, 

laboratory 

(standard 

units) 

(00403)1

pH, 

field 

(standard 

units) 

(00400)

Specific 

conductance, 

laboratory 

(μS/cm at 25 °C) 

(90095)1

Specific 

conductance, 

field 

(μS/cm at 25 °C) 

(00095)

Alkalinity, 

laboratory 

(mg/L as 

CaCO3) 

(29801)1

Alkalinity, 

field 

(mg/L as 

CaCO3) 

(29802)

Bicarbonate, 

laboratory 3

(mg/L)

Bicarbonate, 

field 

(mg/L) 

(63786)

Carbonate, 

laboratory 3

(mg/L)

Carbonate, 

field 

(mg/L) 

(63788)

Benchmark type na na SMCL-US SMCL-US SMCL-CA SMCL-CA na na na na na naBenchmark level na na <6.5 or >8.5 <6.5 or >8.5 2 900 (1,600) 2 900 (1,600) na na na na na na[RL] [0.2] [0.0–38.5] [0–14] [0–14] [5] [5] [1] [1] [1] [1] [1] [1]Northern San Joaquin Basin study unit—ContinuedESJ-01 1/24/2005 nc 19.0 nc nc nc 663 nc nc nc nc nc ncESJ-01 4/2/2008 0.4 19.5 7.9 7.7 619 603 182 nc 221 nc 0.8 ncESJ-06 1/10/2005 nc nc 7.4 7.4 319 340 130 nc 158 nc — ncESJ-06 4/2/2008 5.9 20.5 7.7 7.5 354 348 134 nc 163 nc 0.4 ncNSJ-QPC-04 1/24/2005 nc 22.0 6.8 6.8 143 140 61 nc 74 nc — ncNSJ-QPC-04 4/1/2008 4.8 22.5 7.4 7.1 150 151 63 nc 76 nc — ncTRCY-03 1/6/2005 6.2 22.0 E6.6 7.5 *1,140 *1,110 202 194 246 235 — 1TRCY-03 3/31/2008 4.8 22.5 7.5 7.6 *1,210 *1,170 201 nc 245 nc 0.4 ncSouthern Sacramento Valley study unitNAM-03 3/29/2005 nc 21.0 nc nc nc 382 nc nc nc nc nc ncNAM-03 4/10/2008 6.2 22.5 7.3 7.2 390 390 119 nc 145 nc 0.1 ncSAM-10 4/21/2005 nc 18.5 nc nc nc 590 nc nc nc nc nc ncSAM-10 4/8/2008 5.1 19.5 7.6 7.4 660 648 242 nc 295 nc 0.5 ncSOL-08 5/10/2005 nc 26.0 nc nc nc 443 nc nc nc nc nc ncSOL-08 4/8/2008 4.7 26.0 7.8 7.8 458 443 226 nc 274 nc 0.9 ncSSV-QPC-07 4/4/2005 4.7 20.0 7.0 7.0 570 604 138 136 168 165 0.1 0.1SSV-QPC-07 4/10/2008 5.8 20.5 7.4 7.0 603 602 140 nc 170 nc 0.2 ncSUI-03 5/12/2005 nc 20.0 nc nc nc 712 nc nc nc nc nc ncSUI-03 4/9/2008 7.8 20.0 7.6 7.5 776 764 193 nc 234 nc 0.4 nc

Table 4. Water-quality indicators in samples collected from trend wells for seven Groundwater Ambient Monitoring and Assessment (GAMA) study units.—Continued[The five-digit USGS parameter code below the constituent name is used to uniquely identify a specific constituent or property. GAMA well identification number acronyms: San Diego Drainages study unit: SDALLV, Alluvial Basins study area; SDHDRK, Hard Rock study area; SDTEM, Temecula Valley study area; SDTEMFP, Temecula Valley study area flow-path well; SDWARN, Warner Valley study area. North San Francisco Bay study unit: NSFVOL, Volcanic Highlands study area; NSFVP, Valley and Plains study area; NSFWG, Wilson Grove Formation Highlands study area; NSFWGFP, Wilson Grove Formation Highlands study area flow-path well. Northern San Joaquin Basin study unit: COS, Cosumnes Basin study area; ESJ, Eastern San Joaquin Basin study area; NSJ-QPC, Uplands Basin study area; TRCY, Tracy Basin study area. Southern Sacramento Valley study unit: NAM, North American study area; SAM, South American study area; SOL, Solano study area; SSV-QPC, Uplands study area; SUI, Suisun-Fairfield study area; YOL, Yolo study area. San Fernando–San Gabriel study unit: ULASF, San Fernando study area; ULASG, San Gabriel study area. Monterey Bay and Salinas Valley Basins study unit: MSMB, Monterey Bay study area; MSPR, Paso Robles study area; MSSC, Santa Cruz study area; MSSV, Salinas Valley study area. Southeast San Joaquin Valley study unit: KING, Kings study area; KWH, Kaweah study area; TLR, Tulare Lake study area; TULE, Tule study area. Benchmark type: SMCL-US, U.S. Environmental Protection Agency secondary maximum contaminant level; SMCL-CA, California Department of Public Health secondary maximum contaminant level. Benchmark type, benchmark level, and RL as of April 1, 2010. Other abbreviations: USGS, U.S. Geological Survey; °C, degrees Celsius; mg/L, milligrams per liter; nc, not collected; na, not available; RL, reporting level or range; μS/cm, microsiemens per centimeter; <, less than; >, greater than; CaCO3, calcium carbonate; *, concentration is greater than the benchmark level; **, concentration is greater than the upper benchmark level; —, not detected; E, estimated or having a higher degree of uncertainty]
62 Groundwater-Quality Data in Seven GAMA Study Units: Results from Initial Sampling and Resampling of Wells GAMA well identification number Sample dates Dissolved oxygen, field (mg/L) (00300) Water temperature, field (°C) (00010) pH, laboratory (standard units) (00403)1 pH, field (standard units) (00400) Specific conductance, laboratory (μS/cm at 25 °C) (90095)1 Specific conductance, field (μS/cm at 25 °C) (00095) Alkalinity, laboratory (mg/L as CaCO3) (29801)1 Alkalinity, field (mg/L as CaCO3) (29802) Bicarbonate, laboratory 3 (mg/L) Bicarbonate, field (mg/L) (63786) Carbonate, laboratory 3 (mg/L) Carbonate, field (mg/L) (63788) Benchmark type na na SMCL-US SMCL-US SMCL-CA SMCL-CA na na na na na na Benchmark level na na <6.5 or >8.5 <6.5 or >8.5 2 900 (1,600) 2 900 (1,600) na na na na na na [RL] [0.2] [0.0–38.5] [0–14] [0–14] [5] [5] [1] [1] [1] [1] [1] [1] Southern Sacramento Valley study unit—Continued YOL-01 4/11/2005 nc 20.0 nc nc nc 883 nc nc nc nc nc nc YOL-01 4/7/2008 8.1 19.0 7.7 7.7 *927 895 328 nc 398 nc 1.0 nc YOL-14 5/25/2005 <0.2 19.0 7.6 *6.3 *1,400 *1,240 171 169 207 E204 0.4 E0.7 YOL-14 4/9/2008 <0.2 17.5 7.6 7.6 **1,760 **1,650 275 nc 334 nc 0.7 nc San Fernando–San Gabriel study unit ULASF-09 6/27/2005 5.8 20.0 6.8 6.6 *1,030 *1,080 178 167 217 204 0.1 0.1 ULASF-09 6/16/2008 4.5 20.5 6.8 6.8 *922 *927 152 nc 186 nc 0.1 nc ULASF-10 6/8/2005 4.2 22.5 7.7 7.7 701 740 179 174 217 211 0.5 0.5 ULASF-10 6/16/2008 2.6 23.5 7.9 7.8 770 779 153 nc 186 nc 0.7 nc ULASG-01 6/7/2005 3.4 21.0 nc nc nc *1,140 nc nc nc nc nc nc ULASG-01 6/16/2008 4.0 21.5 7.2 *6.2 *1,190 *1,200 271 nc 331 nc 0.3 nc ULASG-08 6/15/2005 7.6 22.0 6.9 7.5 556 636 161 155 196 188 0.1 0.6 ULASG-08 6/17/2008 4.9 22.5 7.9 7.7 671 675 161 nc 195 nc 0.7 nc ULASG-15 6/23/2005 5.2 16.5 7.6 7.4 315 313 155 151 188 183 0.4 0.5 ULASG-15 6/17/2008 8.1 17.5 7.7 7.6 395 394 151 nc 183 nc 0.4 nc ULASG-17 7/11/2005 2.6 21.5 nc nc nc *1,100 nc nc nc nc nc nc

ULASG-17 6/17/2008 4.2 21.5 7.3 7.0 *1,140 *1,150 327 nc 398 nc 0.3 nc

Table 4. Water-quality indicators in samples collected from trend wells for seven Groundwater Ambient Monitoring and Assessment (GAMA) study units.—Continued[The five-digit USGS parameter code below the constituent name is used to uniquely identify a specific constituent or property. GAMA well identification number acronyms: San Diego Drainages study unit: SDALLV, Alluvial Basins study area; SDHDRK, Hard Rock study area; SDTEM, Temecula Valley study area; SDTEMFP, Temecula Valley study area flow-path well; SDWARN, Warner Valley study area. North San Francisco Bay study unit: NSFVOL, Volcanic Highlands study area; NSFVP, Valley and Plains study area; NSFWG, Wilson Grove Formation Highlands study area; NSFWGFP, Wilson Grove Formation Highlands study area flow-path well. Northern San Joaquin Basin study unit: COS, Cosumnes Basin study area; ESJ, Eastern San Joaquin Basin study area; NSJ-QPC, Uplands Basin study area; TRCY, Tracy Basin study area. Southern Sacramento Valley study unit: NAM, North American study area; SAM, South American study area; SOL, Solano study area; SSV-QPC, Uplands study area; SUI, Suisun-Fairfield study area; YOL, Yolo study area. San Fernando–San Gabriel study unit: ULASF, San Fernando study area; ULASG, San Gabriel study area. Monterey Bay and Salinas Valley Basins study unit: MSMB, Monterey Bay study area; MSPR, Paso Robles study area; MSSC, Santa Cruz study area; MSSV, Salinas Valley study area. Southeast San Joaquin Valley study unit: KING, Kings study area; KWH, Kaweah study area; TLR, Tulare Lake study area; TULE, Tule study area. Benchmark type: SMCL-US, U.S. Environmental Protection Agency secondary maximum contaminant level; SMCL-CA, California Department of Public Health secondary maximum contaminant level. Benchmark type, benchmark level, and RL as of April 1, 2010. Other abbreviations: USGS, U.S. Geological Survey; °C, degrees Celsius; mg/L, milligrams per liter; nc, not collected; na, not available; RL, reporting level or range; μS/cm, microsiemens per centimeter; <, less than; >, greater than; CaCO3, calcium carbonate; *, concentration is greater than the benchmark level; **, concentration is greater than the upper benchmark level; —, not detected; E, estimated or having a higher degree of uncertainty]
Tables 63

GAMA well 

identification 

number

Sample 

dates

Dissolved 

oxygen, 

field 

(mg/L) 

(00300) 

Water 

temperature, 

field 

(°C) 

(00010)

pH, 

laboratory 

(standard 

units) 

(00403)1

pH, 

field 

(standard 

units) 

(00400)

Specific 

conductance, 

laboratory 

(μS/cm at 25 °C) 

(90095)1

Specific 

conductance, 

field 

(μS/cm at 25 °C) 

(00095)

Alkalinity, 

laboratory 

(mg/L as 

CaCO3) 

(29801)1

Alkalinity, 

field 

(mg/L as 

CaCO3) 

(29802)

Bicarbonate, 

laboratory 3

(mg/L)

Bicarbonate, 

field 

(mg/L) 

(63786)

Carbonate, 

laboratory 3

(mg/L)

Carbonate, 

field 

(mg/L) 

(63788)

Benchmark type na na SMCL-US SMCL-US SMCL-CA SMCL-CA na na na na na naBenchmark level na na <6.5 or >8.5 <6.5 or >8.5 2 900 (1,600) 2 900 (1,600) na na na na na na[RL] [0.2] [0.0–38.5] [0–14] [0–14] [5] [5] [1] [1] [1] [1] [1] [1]Monterey Bay and Salinas Valley Basins study unitMSMB-03 8/31/2005 1.9 33.0 nc nc nc 338 nc nc nc nc nc ncMSMB-03 8/20/2008 <0.2 32.0 *8.8 *8.7 507 537 169 nc 195 nc 5.2 ncMSMB-04 8/17/2005 <0.2 23.0 8.0 8.1 *1,170 *1,210 164 163 198 199 0.8 1.6MSMB-04 8/20/2008 <0.2 23.5 7.8 8.0 *1,540 *1,590 149 nc 181 nc 0.6 ncMSMB-16 8/17/2005 4.1 19.5 nc nc nc 651 nc nc nc nc nc ncMSMB-16 8/19/2008 6.2 19.5 7.6 7.3 671 647 101 nc 122 nc 0.2 ncMSMB-28 8/3/2005 nc 20.0 nc nc nc 719 nc nc nc nc nc ncMSMB-28 8/21/2008 6.7 20.0 7.2 7.0 761 736 192 nc 234 nc 0.2 ncMSMB-31 8/11/2005 5.2 16.5 nc nc nc 594 nc nc nc nc nc ncMSMB-31 8/21/2008 6.9 16.5 7.3 7.1 613 585 210 nc 256 nc 0.2 ncMSPR-03 7/28/2005 1.7 33.0 nc nc nc 815 nc nc nc nc nc ncMSPR-03 11/14/2008 0.7 26.5 7.9 7.8 875 884 290 nc 352 nc 1.2 ncMSPR-09 7/18/2005 nc 23.5 nc nc nc *1,590 nc nc nc nc nc ncMSPR-09 11/14/2008 0.4 24.0 7.9 7.8 *1,590 *1,600 328 nc 397 nc 1.6 ncMSSC-06 8/24/2005 <0.2 18.5 7.6 7.5 665 694 136 128 165 156 0.3 0.2MSSC-06 8/18/2008 <0.2 18.5 7.6 7.4 699 688 141 nc 171 nc 0.3 ncMSSC-11 9/13/2005 <0.2 17.5 nc nc nc 414 nc nc nc nc nc ncMSSC-11 8/19/2008 <0.2 17.0 8.0 7.8 438 413 209 nc 253 nc 1.0 ncMSSV-06 8/2/2005 nc 19.0 nc nc nc 538 nc nc nc nc nc nc

Table 4. Water-quality indicators in samples collected from trend wells for seven Groundwater Ambient Monitoring and Assessment (GAMA) study units.—Continued[The five-digit USGS parameter code below the constituent name is used to uniquely identify a specific constituent or property. GAMA well identification number acronyms: San Diego Drainages study unit: SDALLV, Alluvial Basins study area; SDHDRK, Hard Rock study area; SDTEM, Temecula Valley study area; SDTEMFP, Temecula Valley study area flow-path well; SDWARN, Warner Valley study area. North San Francisco Bay study unit: NSFVOL, Volcanic Highlands study area; NSFVP, Valley and Plains study area; NSFWG, Wilson Grove Formation Highlands study area; NSFWGFP, Wilson Grove Formation Highlands study area flow-path well. Northern San Joaquin Basin study unit: COS, Cosumnes Basin study area; ESJ, Eastern San Joaquin Basin study area; NSJ-QPC, Uplands Basin study area; TRCY, Tracy Basin study area. Southern Sacramento Valley study unit: NAM, North American study area; SAM, South American study area; SOL, Solano study area; SSV-QPC, Uplands study area; SUI, Suisun-Fairfield study area; YOL, Yolo study area. San Fernando–San Gabriel study unit: ULASF, San Fernando study area; ULASG, San Gabriel study area. Monterey Bay and Salinas Valley Basins study unit: MSMB, Monterey Bay study area; MSPR, Paso Robles study area; MSSC, Santa Cruz study area; MSSV, Salinas Valley study area. Southeast San Joaquin Valley study unit: KING, Kings study area; KWH, Kaweah study area; TLR, Tulare Lake study area; TULE, Tule study area. Benchmark type: SMCL-US, U.S. Environmental Protection Agency secondary maximum contaminant level; SMCL-CA, California Department of Public Health secondary maximum contaminant level. Benchmark type, benchmark level, and RL as of April 1, 2010. Other abbreviations: USGS, U.S. Geological Survey; °C, degrees Celsius; mg/L, milligrams per liter; nc, not collected; na, not available; RL, reporting level or range; μS/cm, microsiemens per centimeter; <, less than; >, greater than; CaCO3, calcium carbonate; *, concentration is greater than the benchmark level; **, concentration is greater than the upper benchmark level; —, not detected; E, estimated or having a higher degree of uncertainty]
64 Groundwater-Quality Data in Seven GAMA Study Units: Results from Initial Sampling and Resampling of Wells GAMA well identification number Sample dates Dissolved oxygen, field (mg/L) (00300) Water temperature, field (°C) (00010) pH, laboratory (standard units) (00403)1 pH, field (standard units) (00400) Specific conductance, laboratory (μS/cm at 25 °C) (90095)1 Specific conductance, field (μS/cm at 25 °C) (00095) Alkalinity, laboratory (mg/L as CaCO3) (29801)1 Alkalinity, field (mg/L as CaCO3) (29802) Bicarbonate, laboratory 3 (mg/L) Bicarbonate, field (mg/L) (63786) Carbonate, laboratory 3 (mg/L) Carbonate, field (mg/L) (63788) Benchmark type na na SMCL-US SMCL-US SMCL-CA SMCL-CA na na na na na na Benchmark level na na <6.5 or >8.5 <6.5 or >8.5 2 900 (1,600) 2 900 (1,600) na na na na na na [RL] [0.2] [0.0–38.5] [0–14] [0–14] [5] [5] [1] [1] [1] [1] [1] [1] Monterey Bay and Salinas Valley Basins study unit—Continued MSSV-06 11/13/2008 0.3 18.0 7.5 7.2 529 531 149 nc 181 nc 0.3 nc MSSV-15 8/12/2005 nc 18.0 nc nc nc 606 nc nc nc nc nc nc MSSV-15 11/13/2008 0.4 17.0 7.5 7.5 605 593 161 nc 195 nc 0.3 nc Southeast San Joaquin Valley study unit KING-11 10/20/2005 5.7 22.5 8.0 nc 423 409 149 nc 181 nc 0.8 nc KING-11 11/5/2008 4.7 23.0 8.0 7.9 538 528 143 nc 173 nc 0.7 nc KING-13 10/20/2005 6.9 23.0 7.7 nc 316 318 132 nc 160 nc 0.3 nc KING-13 11/5/2008 5.7 22.5 7.8 7.6 315 312 129 nc 157 nc 0.4 nc KING-17 10/26/2005 4.7 23.5 7.8 7.9 308 322 129 131 156 159 0.5 0.6 KING-17 11/4/2008 4.5 23.5 8.0 7.9 320 320 128 nc 155 nc 0.6 nc KING-24 11/5/2005 5.9 21.0 nc nc nc 480 nc nc nc nc nc nc KING-24 11/3/2008 5.4 21.0 7.6 7.4 521 517 212 nc 258 nc 0.4 nc KWH-10 11/17/2005 11.0 21.0 nc nc nc 650 nc nc nc nc nc nc KWH-10 11/5/2008 6.6 22.0 7.8 7.8 630 621 183 nc 221 nc 0.6 nc KWH-12 11/28/2005 5.8 19.5 8.0 8.5 213 218 66 65 79 78 0.3 0.8 KWH-12 11/6/2008 7.1 20.0 7.7 8.2 240 235 72 nc 87 nc 0.2 nc

TLR-03 11/29/2005 <0.2 24.0 nc nc nc 425 nc nc nc nc nc ncTLR-03 11/4/2008 <0.2 26.5 *9.1 *9.2 488 491 124 nc 134 nc 7.9 ncTULE-05 12/5/2005 0.4 27.5 nc nc nc *1,120 nc nc nc nc nc nc

Table 4. Water-quality indicators in samples collected from trend wells for seven Groundwater Ambient Monitoring and Assessment (GAMA) study units.—Continued[The five-digit USGS parameter code below the constituent name is used to uniquely identify a specific constituent or property. GAMA well identification number acronyms: San Diego Drainages study unit: SDALLV, Alluvial Basins study area; SDHDRK, Hard Rock study area; SDTEM, Temecula Valley study area; SDTEMFP, Temecula Valley study area flow-path well; SDWARN, Warner Valley study area. North San Francisco Bay study unit: NSFVOL, Volcanic Highlands study area; NSFVP, Valley and Plains study area; NSFWG, Wilson Grove Formation Highlands study area; NSFWGFP, Wilson Grove Formation Highlands study area flow-path well. Northern San Joaquin Basin study unit: COS, Cosumnes Basin study area; ESJ, Eastern San Joaquin Basin study area; NSJ-QPC, Uplands Basin study area; TRCY, Tracy Basin study area. Southern Sacramento Valley study unit: NAM, North American study area; SAM, South American study area; SOL, Solano study area; SSV-QPC, Uplands study area; SUI, Suisun-Fairfield study area; YOL, Yolo study area. San Fernando–San Gabriel study unit: ULASF, San Fernando study area; ULASG, San Gabriel study area. Monterey Bay and Salinas Valley Basins study unit: MSMB, Monterey Bay study area; MSPR, Paso Robles study area; MSSC, Santa Cruz study area; MSSV, Salinas Valley study area. Southeast San Joaquin Valley study unit: KING, Kings study area; KWH, Kaweah study area; TLR, Tulare Lake study area; TULE, Tule study area. Benchmark type: SMCL-US, U.S. Environmental Protection Agency secondary maximum contaminant level; SMCL-CA, California Department of Public Health secondary maximum contaminant level. Benchmark type, benchmark level, and RL as of April 1, 2010. Other abbreviations: USGS, U.S. Geological Survey; °C, degrees Celsius; mg/L, milligrams per liter; nc, not collected; na, not available; RL, reporting level or range; μS/cm, microsiemens per centimeter; <, less than; >, greater than; CaCO3, calcium carbonate; *, concentration is greater than the benchmark level; **, concentration is greater than the upper benchmark level; —, not detected; E, estimated or having a higher degree of uncertainty]
Tables 65

GAMA well 

identification 

number

Sample 

dates

Dissolved 

oxygen, 

field 

(mg/L) 

(00300) 

Water 

temperature, 

field 

(°C) 

(00010)

pH, 

laboratory 

(standard 

units) 

(00403)1

pH, 

field 

(standard 

units) 

(00400)

Specific 

conductance, 

laboratory 

(μS/cm at 25 °C) 

(90095)1

Specific 

conductance, 

field 

(μS/cm at 25 °C) 

(00095)

Alkalinity, 

laboratory 

(mg/L as 

CaCO3) 

(29801)1

Alkalinity, 

field 

(mg/L as 

CaCO3) 

(29802)

Bicarbonate, 

laboratory 3

(mg/L)

Bicarbonate, 

field 

(mg/L) 

(63786)

Carbonate, 

laboratory 3

(mg/L)

Carbonate, 

field 

(mg/L) 

(63788)

Benchmark type na na SMCL-US SMCL-US SMCL-CA SMCL-CA na na na na na naBenchmark level na na <6.5 or >8.5 <6.5 or >8.5 2 900 (1,600) 2 900 (1,600) na na na na na na[RL] [0.2] [0.0–38.5] [0–14] [0–14] [5] [5] [1] [1] [1] [1] [1] [1]Southeast San Joaquin Valley study unit—ContinuedTULE-05 11/3/2008 0.5 28.0 8.4 8.3 721 624 122 nc 146 nc 1.5 ncTULE-10 12/7/2005 7.6 21.0 nc nc nc 580 nc nc nc nc nc ncTULE-10 11/3/2008 5.7 21.0 7.4 7.4 657 650 201 nc 245 nc 0.3 nc

1 Field measurement is the preferred method of determination.2 The SMCL-CA for specific conductance has recommended and upper benchmark values. The upper value is shown in parentheses.3 Bicarbonate and carbonate concentrations were calculated from the laboratory alkalinity and pH values using the advanced speciation method (http://or.water.usgs.gov/alk/methods.html) with pK1 = 6.35, 

pK2 = 10.33, and pKW = 14.Table 4. Water-quality indicators in samples collected from trend wells for seven Groundwater Ambient Monitoring and Assessment (GAMA) study units.—Continued[The five-digit USGS parameter code below the constituent name is used to uniquely identify a specific constituent or property. GAMA well identification number acronyms: San Diego Drainages study unit: SDALLV, Alluvial Basins study area; SDHDRK, Hard Rock study area; SDTEM, Temecula Valley study area; SDTEMFP, Temecula Valley study area flow-path well; SDWARN, Warner Valley study area. North San Francisco Bay study unit: NSFVOL, Volcanic Highlands study area; NSFVP, Valley and Plains study area; NSFWG, Wilson Grove Formation Highlands study area; NSFWGFP, Wilson Grove Formation Highlands study area flow-path well. Northern San Joaquin Basin study unit: COS, Cosumnes Basin study area; ESJ, Eastern San Joaquin Basin study area; NSJ-QPC, Uplands Basin study area; TRCY, Tracy Basin study area. Southern Sacramento Valley study unit: NAM, North American study area; SAM, South American study area; SOL, Solano study area; SSV-QPC, Uplands study area; SUI, Suisun-Fairfield study area; YOL, Yolo study area. San Fernando–San Gabriel study unit: ULASF, San Fernando study area; ULASG, San Gabriel study area. Monterey Bay and Salinas Valley Basins study unit: MSMB, Monterey Bay study area; MSPR, Paso Robles study area; MSSC, Santa Cruz study area; MSSV, Salinas Valley study area. Southeast San Joaquin Valley study unit: KING, Kings study area; KWH, Kaweah study area; TLR, Tulare Lake study area; TULE, Tule study area. Benchmark type: SMCL-US, U.S. Environmental Protection Agency secondary maximum contaminant level; SMCL-CA, California Department of Public Health secondary maximum contaminant level. Benchmark type, benchmark level, and RL as of April 1, 2010. Other abbreviations: USGS, U.S. Geological Survey; °C, degrees Celsius; mg/L, milligrams per liter; nc, not collected; na, not available; RL, reporting level or range; μS/cm, microsiemens per centimeter; <, less than; >, greater than; CaCO3, calcium carbonate; *, concentration is greater than the benchmark level; **, concentration is greater than the upper benchmark level; —, not detected; E, estimated or having a higher degree of uncertainty]
66 Groundwater-Quality Data in Seven GAMA Study Units: Results from Initial Sampling and Resampling of Wells Table 5. Volatile organic compounds (VOCs) in samples collected from trend wells for seven Groundwater Ambient Monitoring and Assessment (GAMA) study units. [The five-digit USGS parameter code below the constituent name is used to uniquely identify a specific constituent or property. VOCs were analyzed in samples from 55 trend wells during 2004–05 and 2007–08. Information about analytes given in table 3A. GAMA well identification number acronyms: San Diego Drainages study unit: SDALLV, Alluvial Basins study area; SDHDRK, Hard Rock study area; SDTEM, Temecula Valley study area; SDTEMFP, Temecula Valley study area flow-path well; SDWARN, Warner Valley study area. North San Francisco Bay study unit: NSFVOL, Volcanic Highlands study area; NSFVP, Valley and Plains study area; NSFWG, Wilson Grove Formation Highlands study area; NSFWGFP, Wilson Grove Formation Highlands study area flow-path well. Northern San Joaquin Basin study unit: COS, Cosumnes Basin study area; ESJ, Eastern San Joaquin Basin study area; NSJ-QPC, Uplands study area; TRCY, Tracy Basin study area. Southern Sacramento Valley study unit: NAM, North American study area; SAM, South American study area; SOL, Solano study area; SSV-QPC, Uplands study area; SUI, Suisun-Fairfield study area; YOL, Yolo study area. San Fernando–San Gabriel study unit: ULASF, San Fernando study area; ULASG, San Gabriel study area. Monterey Bay and Salinas Valley Basins study unit: MSMB, Monterey Bay study area; MSPR, Paso Robles study area; MSSC, Santa Cruz study area; MSSV, Salinas Valley study area. Southeast San Joaquin Valley study unit: KING, Kings study area; KWH, Kaweah study area; TLR, Tulare Lake study area; TULE, Tule study area. Benchmark type: MCL-US, USEPA maximum contaminant level; MCL-CA, CDPH maximum contaminant level; HAL-US, USEPA lifetime health advisory level; NL-CA, CDPH notification level. Benchmark type and benchmark level as of April 1, 2010. Other abbreviations: USGS, U.S. Geological Survey; USEPA, U.S. Environmental Protection Agency; CDPH, California Department of Public Health; μg/L, micrograms per liter; LRL, laboratory reporting level; SRL, study reporting level; *, value greater than benchmark level; E, estimated or having a higher degree of uncertainty; ≤, less than or equal to; —, not detected] GAMA well identification number Sample dates Trihalomethane Solvent Chloroform (Trichloro- methane) (μg/L) (32106) Bromo- dichloro- methane (μg/L) (32101) Dibromo- chloro- methane (μg/L) (32105) Bromoform (Tribromo- methane) (μg/L) (32104) Perchloro- ethene (PCE, Tetra- chloroethene) (μg/L) (34475) Trichloro- ethene (TCE) (μg/L) (39180) cis-1,2- Dichloro- ethene (μg/L) (77093) Carbon tetra- chloride (Tetrachloro- methane) (μg/L) (32102) 1,1-Dichloro- ethene (1,1-DCE) (μg/L) (34501) 1,1-Dichloro- ethane (1,1-DCA) (μg/L) (34496) Methylene chloride (Dichloro- methane) (μg/L) (34423) Benchmark type1 MCL-US MCL-US MCL-US MCL-US MCL-US MCL-US MCL-CA MCL-CA MCL-CA MCL-CA MCL-US Benchmark level 3 80 3 80 3 80 3 80 5 5 6 0.5 6 5 5 [LRL or SRL]2 [0.02, 0.04] [0.028, 0.04] [0.1, 0.12] [0.08, 0.1] [0.03, 0.06] [0.02, 0.038] [0.02, 0.024] [0.06, 0.08] [0.02, 0.024] [0.035, 0.06] [0.04, 0.06] Number of wells with detec- tions 2004−05 21 7 2 1 11 9 6 6 5 4 2 Detection frequency (percent) 2004–05 38.2 12.7 3.6 1.8 20.0 16.4 10.9 10.9 9.1 7.3 3.6 Number of wells with detec- tions 2007–08 21 8 1 0 9 9 6 5 4 3 4 Detection frequency (percent) 2007–08 38.2 14.5 1.8 0.0 16.4 16.4 10.9 9.1 7.3 5.5 7.3 San Diego Drainages study unit SDALLV-07 7/14/2004 E0.02

—

—

—

—

—

—

—

—

—

—

SDALLV-07 9/12/2007

—

—

—

—

—

—

—

—

—

—

—

SDALLV-11 7/15/2004 0.20

—

—

— 0.37 E0.03

— E0.02 4 E0.03

—

—

SDALLV-11 9/13/2007 0.80

—

—

— 0.90

—

— 0.10 E0.03

— E0.03

SDHDRK-01 7/12/2004 0.27

—

—

— *9.75 *7.27 1.08

— E0.08

—

—

SDHDRK-01 9/13/2007 0.24

—

—

— *7.85 *6.19 0.80

— E0.10

—

—

SDHDRK-09 7/27/2004

—

—

—

—

—

—

—

—

—

—

—

SDHDRK-09 9/11/2007

—

—

—

—

—

—

—

—

—

—

—

SDTEM-04 5/24/2004

—

—

—

—

—

—

—

—

—

—

—
Tables 67

GAMA well 

identification 

number

Sample 

dates

Trihalomethane Solvent

Chloroform 

(Trichloromethane) 

(μg/L) 

(32106)

Bromodichloromethane 

(μg/L) 

(32101) 

Dibromochloromethane 

(μg/L) 

(32105)

Bromoform 

(Tribromomethane) 

(μg/L) 

(32104)

Perchloroethene 

(PCE, Tetrachloroethene) 

(μg/L) 

(34475)

Trichloroethene 

(TCE) 

(μg/L) 

(39180)

cis-1,2-

Dichloroethene 

(μg/L) 

(77093)

Carbon tetrachloride 

(Tetrachloromethane) 

(μg/L) 

(32102)

1,1-Dichloroethene 

(1,1-DCE) 

(μg/L) 

(34501)

1,1-Dichloroethane 

(1,1-DCA) 

(μg/L) 

(34496)

Methylene 

chloride 

(Dichloromethane) 

(μg/L) 

(34423)

Benchmark type1 MCL-US MCL-US MCL-US MCL-US MCL-US MCL-US MCL-CA MCL-CA MCL-CA MCL-CA MCL-USBenchmark level 3 80 3 80 3 80 3 80 5 5 6 0.5 6 5 5[LRL or SRL]2 [0.02, 0.04] [0.028, 0.04] [0.1, 0.12] [0.08, 0.1] [0.03, 0.06] [0.02, 0.038] [0.02, 0.024] [0.06, 0.08] [0.02, 0.024] [0.035, 0.06] [0.04, 0.06]San Diego Drainages study unit—ContinuedSDTEM-04 9/18/2007 E0.07 — — — — — — — — — —SDTEMFP-01 5/19/2004 — — — — E0.01 4 — — — — — —SDTEMFP-01 9/19/2007 E0.04 E0.03 — — — — — — — — —SDWARN-01 6/17/2004 — — — — — — — — — — —SDWARN-01 9/11/2007 — — — — — — — — — — —North San Francisco Bay study unitNSFVOL-14 10/7/2004 — — — — — — — — — — —NSFVOL-14 8/21/2007 — — — — — — — — — — —NSFVOL-18 10/20/2004 — — — — — — — — — — —NSFVOL-18 8/28/2007 — — — — — — — — — — —NSFVP-29 9/28/2004 — — — — — — — — — — —NSFVP-29 8/27/2007 — — — — — — — — — — —NSFVP-34 10/18/2004 — — — — — — — — — — —NSFVP-34 8/22/2007 — — — — — — — — — — —NSFVP-36 10/19/2004 — — — — — — — — — — —NSFVP-36 8/20/2007 — — — — — — — — — — —

Table 5. Volatile organic compounds (VOCs) in samples collected from trend wells for seven Groundwater Ambient Monitoring and Assessment (GAMA) study units.—Continued[The five-digit USGS parameter code below the constituent name is used to uniquely identify a specific constituent or property. VOCs were analyzed in samples from 55 trend wells during 2004–05 and 2007–08. Information about analytes given in table 3A. GAMA well identification number acronyms: San Diego Drainages study unit: SDALLV, Alluvial Basins study area; SDHDRK, Hard Rock study area; SDTEM, Temecula Valley study area; SDTEMFP, Temecula Valley study area flow-path well; SDWARN, Warner Valley study area. North San Francisco Bay study unit: NSFVOL, Volcanic Highlands study area; NSFVP, Valley and Plains study area; NSFWG, Wilson Grove Formation Highlands study area; NSFWGFP, Wilson Grove Formation Highlands study area flow-path well. Northern San Joaquin Basin study unit: COS, Cosumnes Basin study area; ESJ, Eastern San Joaquin Basin study area; NSJ-QPC, Uplands study area; TRCY, Tracy Basin study area. Southern Sacramento Valley study unit: NAM, North American study area; SAM, South American study area; SOL, Solano study area; SSV-QPC, Uplands study area; SUI, Suisun-Fairfield study area; YOL, Yolo study area. San Fernando–San Gabriel study unit: ULASF, San Fernando study area; ULASG, San Gabriel study area. Monterey Bay and Salinas Valley Basins study unit: MSMB, Monterey Bay study area; MSPR, Paso Robles study area; MSSC, Santa Cruz study area; MSSV, Salinas Valley study area. Southeast San Joaquin Valley study unit: KING, Kings study area; KWH, Kaweah study area; TLR, Tulare Lake study area; TULE, Tule study area. Benchmark type: MCL-US, USEPA maximum contaminant level; MCL-CA, CDPH maximum contaminant level; HAL-US, USEPA lifetime health advisory level; NL-CA, CDPH notification level. Benchmark type and benchmark level as of April 1, 2010. Other abbreviations: USGS, U.S. Geological Survey; USEPA, U.S. Environmental Protection Agency; CDPH, California Department of Public Health; μg/L, micrograms per liter; LRL, laboratory reporting level; SRL, study reporting level; *, value greater than benchmark level; E, estimated or having a higher degree of uncertainty; ≤, less than or equal to; —, not detected]
68 Groundwater-Quality Data in Seven GAMA Study Units: Results from Initial Sampling and Resampling of Wells GAMA well identification number Sample dates Trihalomethane Solvent Chloroform (Trichloro- methane) (μg/L) (32106) Bromo- dichloro- methane (μg/L) (32101) Dibromo- chloro- methane (μg/L) (32105) Bromoform (Tribromo- methane) (μg/L) (32104) Perchloro- ethene (PCE, Tetra- chloroethene) (μg/L) (34475) Trichloro- ethene (TCE) (μg/L) (39180) cis-1,2- Dichloro- ethene (μg/L) (77093) Carbon tetra- chloride (Tetrachloro- methane) (μg/L) (32102) 1,1-Dichloro- ethene (1,1-DCE) (μg/L) (34501) 1,1-Dichloro- ethane (1,1-DCA) (μg/L) (34496) Methylene chloride (Dichloro- methane) (μg/L) (34423) Benchmark type1 MCL-US MCL-US MCL-US MCL-US MCL-US MCL-US MCL-CA MCL-CA MCL-CA MCL-CA MCL-US Benchmark level 3 80 3 80 3 80 3 80 5 5 6 0.5 6 5 5 [LRL or SRL]2 [0.02, 0.04] [0.028, 0.04] [0.1, 0.12] [0.08, 0.1] [0.03, 0.06] [0.02, 0.038] [0.02, 0.024] [0.06, 0.08] [0.02, 0.024] [0.035, 0.06] [0.04, 0.06] North San Francisco Bay study unit—Continued NSFVP-38 10/20/2004

—

—

—

—

—

—

—

—

—

—

—

NSFVP-38 8/22/2007 E0.02

—

—

—

—

—

—

—

—

—

—

NSFVP-39 10/21/2004

—

—

—

—

—

—

—

—

—

—

—

NSFVP-39 11/16/2007

—

—

—

—

—

—

—

—

—

—

—

NSFVP-41 10/21/2004 E0.02

—

—

—

—

—

—

—

—

—

—

NSFVP-41 8/20/2007 E0.02

—

—

—

—

—

—

—

—

—

—

NSFWG-03 9/21/2004

—

—

—

—

—

—

—

—

—

—

—

NSFWG-03 8/29/2007

—

—

—

—

—

—

—

—

—

—

—

NSFWGFP-01 10/5/2004

—

—

—

— 2.67 0.40 0.15

—

—

—

—

NSFWGFP-01 8/29/2007

—

—

—

— 1.04 0.16 E0.04

—

—

—

—

Northern San Joaquin Basin study unit COS-08 1/3/2005

—

—

—

—

—

—

—

—

—

—

—

COS-08 4/3/2008

—

—

—

—

—

—

—

—

—

—

—

ESJ-01 1/24/2005 E0.01 4 —

—

—

—

—

—

—

—

—

—

ESJ-01 4/2/2008

—

—

—

—

—

—

—

—

—

—

—

ESJ-06 1/10/2005 E0.04

—

—

—

—

—

—

—

—

—

—

Table 5. Volatile organic compounds (VOCs) in samples collected from trend wells for seven Groundwater Ambient Monitoring and Assessment (GAMA) study units.—Continued[The five-digit USGS parameter code below the constituent name is used to uniquely identify a specific constituent or property. VOCs were analyzed in samples from 55 trend wells during 2004–05 and 2007–08. Information about analytes given in table 3A. GAMA well identification number acronyms: San Diego Drainages study unit: SDALLV, Alluvial Basins study area; SDHDRK, Hard Rock study area; SDTEM, Temecula Valley study area; SDTEMFP, Temecula Valley study area flow-path well; SDWARN, Warner Valley study area. North San Francisco Bay study unit: NSFVOL, Volcanic Highlands study area; NSFVP, Valley and Plains study area; NSFWG, Wilson Grove Formation Highlands study area; NSFWGFP, Wilson Grove Formation Highlands study area flow-path well. Northern San Joaquin Basin study unit: COS, Cosumnes Basin study area; ESJ, Eastern San Joaquin Basin study area; NSJ-QPC, Uplands study area; TRCY, Tracy Basin study area. Southern Sacramento Valley study unit: NAM, North American study area; SAM, South American study area; SOL, Solano study area; SSV-QPC, Uplands study area; SUI, Suisun-Fairfield study area; YOL, Yolo study area. San Fernando–San Gabriel study unit: ULASF, San Fernando study area; ULASG, San Gabriel study area. Monterey Bay and Salinas Valley Basins study unit: MSMB, Monterey Bay study area; MSPR, Paso Robles study area; MSSC, Santa Cruz study area; MSSV, Salinas Valley study area. Southeast San Joaquin Valley study unit: KING, Kings study area; KWH, Kaweah study area; TLR, Tulare Lake study area; TULE, Tule study area. Benchmark type: MCL-US, USEPA maximum contaminant level; MCL-CA, CDPH maximum contaminant level; HAL-US, USEPA lifetime health advisory level; NL-CA, CDPH notification level. Benchmark type and benchmark level as of April 1, 2010. Other abbreviations: USGS, U.S. Geological Survey; USEPA, U.S. Environmental Protection Agency; CDPH, California Department of Public Health; μg/L, micrograms per liter; LRL, laboratory reporting level; SRL, study reporting level; *, value greater than benchmark level; E, estimated or having a higher degree of uncertainty; ≤, less than or equal to; —, not detected]
Tables 69

GAMA well 

identification 

number

Sample 

dates

Trihalomethane Solvent

Chloroform 

(Trichloromethane) 

(μg/L) 

(32106)

Bromodichloromethane 

(μg/L) 

(32101) 

Dibromochloromethane 

(μg/L) 

(32105)

Bromoform 

(Tribromomethane) 

(μg/L) 

(32104)

Perchloroethene 

(PCE, Tetrachloroethene) 

(μg/L) 

(34475)

Trichloroethene 

(TCE) 

(μg/L) 

(39180)

cis-1,2-

Dichloroethene 

(μg/L) 

(77093)

Carbon tetrachloride 

(Tetrachloromethane) 

(μg/L) 

(32102)

1,1-Dichloroethene 

(1,1-DCE) 

(μg/L) 

(34501)

1,1-Dichloroethane 

(1,1-DCA) 

(μg/L) 

(34496)

Methylene 

chloride 

(Dichloromethane) 

(μg/L) 

(34423)

Benchmark type1 MCL-US MCL-US MCL-US MCL-US MCL-US MCL-US MCL-CA MCL-CA MCL-CA MCL-CA MCL-USBenchmark level 3 80 3 80 3 80 3 80 5 5 6 0.5 6 5 5[LRL or SRL]2 [0.02, 0.04] [0.028, 0.04] [0.1, 0.12] [0.08, 0.1] [0.03, 0.06] [0.02, 0.038] [0.02, 0.024] [0.06, 0.08] [0.02, 0.024] [0.035, 0.06] [0.04, 0.06]Northern San Joaquin Basin study unit—ContinuedESJ-06 4/2/2008 E0.06 — — — — — — — — — —NSJ-QPC-04 1/24/2005 — — — — — — — — — — —NSJ-QPC-04 4/1/2008 — — — — — — — — — — —TRCY-03 1/6/2005 E0.02 — — — — — — — — — —TRCY-03 3/31/2008 E0.02 — — — — — — — — — —Southern Sacramento Valley study unitNAM-03 3/29/2005 — — — — E0.02 — — — — — —NAM-03 4/10/2008 — — — — 0.14 E0.05 E0.09 — — — —SAM-10 4/21/2005 0.27 — — — — E0.02 — E0.04 — — —SAM-10 4/8/2008 0.44 — — — — E0.04 — E0.06 — — —SOL-08 5/10/2005 — — — — — — — — — — —SOL-08 4/8/2008 — — — — — — — — — — —SSV-QPC-07 4/4/2005 E0.02 — — — — — — — — — —SSV-QPC-07 4/10/2008 E0.05 — — — — — — — — — —SUI-03 5/12/2005 — — — — — — — — — — —SUI-03 4/9/2008 — — — — — — — — — — —

Table 5. Volatile organic compounds (VOCs) in samples collected from trend wells for seven Groundwater Ambient Monitoring and Assessment (GAMA) study units.—Continued[The five-digit USGS parameter code below the constituent name is used to uniquely identify a specific constituent or property. VOCs were analyzed in samples from 55 trend wells during 2004–05 and 2007–08. Information about analytes given in table 3A. GAMA well identification number acronyms: San Diego Drainages study unit: SDALLV, Alluvial Basins study area; SDHDRK, Hard Rock study area; SDTEM, Temecula Valley study area; SDTEMFP, Temecula Valley study area flow-path well; SDWARN, Warner Valley study area. North San Francisco Bay study unit: NSFVOL, Volcanic Highlands study area; NSFVP, Valley and Plains study area; NSFWG, Wilson Grove Formation Highlands study area; NSFWGFP, Wilson Grove Formation Highlands study area flow-path well. Northern San Joaquin Basin study unit: COS, Cosumnes Basin study area; ESJ, Eastern San Joaquin Basin study area; NSJ-QPC, Uplands study area; TRCY, Tracy Basin study area. Southern Sacramento Valley study unit: NAM, North American study area; SAM, South American study area; SOL, Solano study area; SSV-QPC, Uplands study area; SUI, Suisun-Fairfield study area; YOL, Yolo study area. San Fernando–San Gabriel study unit: ULASF, San Fernando study area; ULASG, San Gabriel study area. Monterey Bay and Salinas Valley Basins study unit: MSMB, Monterey Bay study area; MSPR, Paso Robles study area; MSSC, Santa Cruz study area; MSSV, Salinas Valley study area. Southeast San Joaquin Valley study unit: KING, Kings study area; KWH, Kaweah study area; TLR, Tulare Lake study area; TULE, Tule study area. Benchmark type: MCL-US, USEPA maximum contaminant level; MCL-CA, CDPH maximum contaminant level; HAL-US, USEPA lifetime health advisory level; NL-CA, CDPH notification level. Benchmark type and benchmark level as of April 1, 2010. Other abbreviations: USGS, U.S. Geological Survey; USEPA, U.S. Environmental Protection Agency; CDPH, California Department of Public Health; μg/L, micrograms per liter; LRL, laboratory reporting level; SRL, study reporting level; *, value greater than benchmark level; E, estimated or having a higher degree of uncertainty; ≤, less than or equal to; —, not detected]
70 Groundwater-Quality Data in Seven GAMA Study Units: Results from Initial Sampling and Resampling of Wells GAMA well identification number Sample dates Trihalomethane Solvent Chloroform (Trichloro- methane) (μg/L) (32106) Bromo- dichloro- methane (μg/L) (32101) Dibromo- chloro- methane (μg/L) (32105) Bromoform (Tribromo- methane) (μg/L) (32104) Perchloro- ethene (PCE, Tetra- chloroethene) (μg/L) (34475) Trichloro- ethene (TCE) (μg/L) (39180) cis-1,2- Dichloro- ethene (μg/L) (77093) Carbon tetra- chloride (Tetrachloro- methane) (μg/L) (32102) 1,1-Dichloro- ethene (1,1-DCE) (μg/L) (34501) 1,1-Dichloro- ethane (1,1-DCA) (μg/L) (34496) Methylene chloride (Dichloro- methane) (μg/L) (34423) Benchmark type1 MCL-US MCL-US MCL-US MCL-US MCL-US MCL-US MCL-CA MCL-CA MCL-CA MCL-CA MCL-US Benchmark level 3 80 3 80 3 80 3 80 5 5 6 0.5 6 5 5 [LRL or SRL]2 [0.02, 0.04] [0.028, 0.04] [0.1, 0.12] [0.08, 0.1] [0.03, 0.06] [0.02, 0.038] [0.02, 0.024] [0.06, 0.08] [0.02, 0.024] [0.035, 0.06] [0.04, 0.06] Southern Sacramento Valley study unit—Continued YOL-01 4/11/2005 E0.02

—

—

—

—

—

—

—

—

—

—

YOL-01 4/7/2008 E0.02

—

—

—

—

—

— E0.03 4 —

—

—

YOL-14 5/25/2005

—

—

—

—

—

—

—

—

—

—

—

YOL-14 4/9/2008

—

—

—

—

—

—

—

—

—

—

—

San Fernando–San Gabriel study unit ULASF-09 6/27/2005 0.44 0.14

—

— 1.89 0.11 E0.02 E0.03

— E0.06

—

ULASF-09 6/16/2008 0.80 0.28

—

— 1.30 E0.09 E0.03

—

— E0.04 E0.03

ULASF-10 6/8/2005 0.17

—

—

— 1.18 3.65 0.15 E0.06 E0.02 E0.04

—

ULASF-10 6/16/2008

—

—

—

—

— E0.05

—

—

—

—

—

ULASG-01 6/7/2005 0.29 E0.08

—

— 0.18

—

—

—

—

—

—

ULASG-01 6/16/2008 0.39 E0.10

—

— 0.30

—

—

—

—

—

—

ULASG-08 6/15/2005 0.82 0.27 E0.1

— 0.23 1.44 0.39 E0.04 E0.04 0.18 E0.04

ULASG-08 6/17/2008 2.93 2.19 0.6

— 0.52 1.8 0.44 E0.05 E0.10 0.44 0.14

ULASG-15 6/23/2005

—

—

—

—

—

—

—

—

—

—

—

ULASG-15 6/17/2008

—

—

—

—

—

—

—

—

—

—

—

ULASG-17 7/11/2005 3.23 0.12

—

— 1.80 E0.06

— E0.04 E0.07 E0.03

—

ULASG-17 6/17/2008 5.28 E0.09

—

— *10.89 *5.52

— E0.08 0.49 E0.05

—

Table 5. Volatile organic compounds (VOCs) in samples collected from trend wells for seven Groundwater Ambient Monitoring and Assessment (GAMA) study units.—Continued[The five-digit USGS parameter code below the constituent name is used to uniquely identify a specific constituent or property. VOCs were analyzed in samples from 55 trend wells during 2004–05 and 2007–08. Information about analytes given in table 3A. GAMA well identification number acronyms: San Diego Drainages study unit: SDALLV, Alluvial Basins study area; SDHDRK, Hard Rock study area; SDTEM, Temecula Valley study area; SDTEMFP, Temecula Valley study area flow-path well; SDWARN, Warner Valley study area. North San Francisco Bay study unit: NSFVOL, Volcanic Highlands study area; NSFVP, Valley and Plains study area; NSFWG, Wilson Grove Formation Highlands study area; NSFWGFP, Wilson Grove Formation Highlands study area flow-path well. Northern San Joaquin Basin study unit: COS, Cosumnes Basin study area; ESJ, Eastern San Joaquin Basin study area; NSJ-QPC, Uplands study area; TRCY, Tracy Basin study area. Southern Sacramento Valley study unit: NAM, North American study area; SAM, South American study area; SOL, Solano study area; SSV-QPC, Uplands study area; SUI, Suisun-Fairfield study area; YOL, Yolo study area. San Fernando–San Gabriel study unit: ULASF, San Fernando study area; ULASG, San Gabriel study area. Monterey Bay and Salinas Valley Basins study unit: MSMB, Monterey Bay study area; MSPR, Paso Robles study area; MSSC, Santa Cruz study area; MSSV, Salinas Valley study area. Southeast San Joaquin Valley study unit: KING, Kings study area; KWH, Kaweah study area; TLR, Tulare Lake study area; TULE, Tule study area. Benchmark type: MCL-US, USEPA maximum contaminant level; MCL-CA, CDPH maximum contaminant level; HAL-US, USEPA lifetime health advisory level; NL-CA, CDPH notification level. Benchmark type and benchmark level as of April 1, 2010. Other abbreviations: USGS, U.S. Geological Survey; USEPA, U.S. Environmental Protection Agency; CDPH, California Department of Public Health; μg/L, micrograms per liter; LRL, laboratory reporting level; SRL, study reporting level; *, value greater than benchmark level; E, estimated or having a higher degree of uncertainty; ≤, less than or equal to; —, not detected]
Tables 71

GAMA well 

identification 

number

Sample 

dates

Trihalomethane Solvent

Chloroform 

(Trichloromethane) 

(μg/L) 

(32106)

Bromodichloromethane 

(μg/L) 

(32101) 

Dibromochloromethane 

(μg/L) 

(32105)

Bromoform 

(Tribromomethane) 

(μg/L) 

(32104)

Perchloroethene 

(PCE, Tetrachloroethene) 

(μg/L) 

(34475)

Trichloroethene 

(TCE) 

(μg/L) 

(39180)

cis-1,2-

Dichloroethene 

(μg/L) 

(77093)

Carbon tetrachloride 

(Tetrachloromethane) 

(μg/L) 

(32102)

1,1-Dichloroethene 

(1,1-DCE) 

(μg/L) 

(34501)

1,1-Dichloroethane 

(1,1-DCA) 

(μg/L) 

(34496)

Methylene 

chloride 

(Dichloromethane) 

(μg/L) 

(34423)

Benchmark type1 MCL-US MCL-US MCL-US MCL-US MCL-US MCL-US MCL-CA MCL-CA MCL-CA MCL-CA MCL-USBenchmark level 3 80 3 80 3 80 3 80 5 5 6 0.5 6 5 5[LRL or SRL]2 [0.02, 0.04] [0.028, 0.04] [0.1, 0.12] [0.08, 0.1] [0.03, 0.06] [0.02, 0.038] [0.02, 0.024] [0.06, 0.08] [0.02, 0.024] [0.035, 0.06] [0.04, 0.06]Monterey Bay and Salinas Valley Basins study unitMSMB-03 8/31/2005 — — — — — — — — — — —MSMB-03 8/20/2008 — — — — — — — — — — —MSMB-04 8/17/2005 — — — — — — — — — — —MSMB-04 8/20/2008 — — — — — — — — — — —MSMB-16 8/17/2005 E0.04 — — — E0.04 0.41 E0.04 E0.06 — — —MSMB-16 8/19/2008 E0.05 — — — — 0.72 E0.05 0.10 — — —MSMB-28 8/3/2005 — — — — — — — — — — —MSMB-28 8/21/2008 — — — — — — — — — — —MSMB-31 8/11/2005 E0.02 — — — — — — — — — —MSMB-31 8/21/2008 — — — — — — — — — — —MSPR-03 7/28/2005 — — — — — — — — — — —MSPR-03 11/14/2008 — — — — — — — — — — —MSPR-09 7/18/2005 — — — — — — — — — — —MSPR-09 11/14/2008 — — — — — — — — — — —MSSC-06 8/24/2005 — — — — — — — — — — —MSSC-06 8/18/2008 — — — — — — — — — — —

Table 5. Volatile organic compounds (VOCs) in samples collected from trend wells for seven Groundwater Ambient Monitoring and Assessment (GAMA) study units.—Continued[The five-digit USGS parameter code below the constituent name is used to uniquely identify a specific constituent or property. VOCs were analyzed in samples from 55 trend wells during 2004–05 and 2007–08. Information about analytes given in table 3A. GAMA well identification number acronyms: San Diego Drainages study unit: SDALLV, Alluvial Basins study area; SDHDRK, Hard Rock study area; SDTEM, Temecula Valley study area; SDTEMFP, Temecula Valley study area flow-path well; SDWARN, Warner Valley study area. North San Francisco Bay study unit: NSFVOL, Volcanic Highlands study area; NSFVP, Valley and Plains study area; NSFWG, Wilson Grove Formation Highlands study area; NSFWGFP, Wilson Grove Formation Highlands study area flow-path well. Northern San Joaquin Basin study unit: COS, Cosumnes Basin study area; ESJ, Eastern San Joaquin Basin study area; NSJ-QPC, Uplands study area; TRCY, Tracy Basin study area. Southern Sacramento Valley study unit: NAM, North American study area; SAM, South American study area; SOL, Solano study area; SSV-QPC, Uplands study area; SUI, Suisun-Fairfield study area; YOL, Yolo study area. San Fernando–San Gabriel study unit: ULASF, San Fernando study area; ULASG, San Gabriel study area. Monterey Bay and Salinas Valley Basins study unit: MSMB, Monterey Bay study area; MSPR, Paso Robles study area; MSSC, Santa Cruz study area; MSSV, Salinas Valley study area. Southeast San Joaquin Valley study unit: KING, Kings study area; KWH, Kaweah study area; TLR, Tulare Lake study area; TULE, Tule study area. Benchmark type: MCL-US, USEPA maximum contaminant level; MCL-CA, CDPH maximum contaminant level; HAL-US, USEPA lifetime health advisory level; NL-CA, CDPH notification level. Benchmark type and benchmark level as of April 1, 2010. Other abbreviations: USGS, U.S. Geological Survey; USEPA, U.S. Environmental Protection Agency; CDPH, California Department of Public Health; μg/L, micrograms per liter; LRL, laboratory reporting level; SRL, study reporting level; *, value greater than benchmark level; E, estimated or having a higher degree of uncertainty; ≤, less than or equal to; —, not detected]
72 Groundwater-Quality Data in Seven GAMA Study Units: Results from Initial Sampling and Resampling of Wells GAMA well identification number Sample dates Trihalomethane Solvent Chloroform (Trichloro- methane) (μg/L) (32106) Bromo- dichloro- methane (μg/L) (32101) Dibromo- chloro- methane (μg/L) (32105) Bromoform (Tribromo- methane) (μg/L) (32104) Perchloro- ethene (PCE, Tetra- chloroethene) (μg/L) (34475) Trichloro- ethene (TCE) (μg/L) (39180) cis-1,2- Dichloro- ethene (μg/L) (77093) Carbon tetra- chloride (Tetrachloro- methane) (μg/L) (32102) 1,1-Dichloro- ethene (1,1-DCE) (μg/L) (34501) 1,1-Dichloro- ethane (1,1-DCA) (μg/L) (34496) Methylene chloride (Dichloro- methane) (μg/L) (34423) Benchmark type1 MCL-US MCL-US MCL-US MCL-US MCL-US MCL-US MCL-CA MCL-CA MCL-CA MCL-CA MCL-US Benchmark level 3 80 3 80 3 80 3 80 5 5 6 0.5 6 5 5 [LRL or SRL]2 [0.02, 0.04] [0.028, 0.04] [0.1, 0.12] [0.08, 0.1] [0.03, 0.06] [0.02, 0.038] [0.02, 0.024] [0.06, 0.08] [0.02, 0.024] [0.035, 0.06] [0.04, 0.06] Monterey Bay and Salinas Valley Basins study unit—Continued MSSC-11 9/13/2005

—

—

—

—

—

—

—

—

—

—

—

MSSC-11 8/19/2008

—

—

—

—

—

—

—

—

—

—

—

MSSV-06 8/2/2005

—

—

—

—

—

—

—

—

—

—

—

MSSV-06 11/13/2008

—

—

—

—

—

—

—

—

—

—

—

MSSV-15 8/12/2005

—

—

—

—

—

—

—

—

—

—

—

MSSV-15 11/13/2008

—

—

—

—

—

—

—

—

—

—

—

Southeast San Joaquin Valley study unitKING-11 10/20/2005

—

—

—

—

—

—

—

—

—

—

—

KING-11 11/5/2008

—

—

—

—

—

—

—

—

—

—

—

KING-13 10/20/2005

—

—

—

—

—

—

—

—

—

—

—

KING-13 11/5/2008

—

—

—

—

—

—

—

—

—

—

—

KING-17 10/26/2005

—

—

—

—

—

—

—

—

—

—

—

KING-17 11/4/2008

—

—

—

—

—

—

—

—

—

—

—

KING-24 11/5/2005 E0.07

—

—

—

—

—

—

—

—

—

—

KING-24 11/3/2008 E0.07

—

—

—

—

—

—

—

—

—

—

KWH-10 11/17/2005 1.35 E0.04

—

—

—

—

—

—

—

—

—

Table 5. Volatile organic compounds (VOCs) in samples collected from trend wells for seven Groundwater Ambient Monitoring and Assessment (GAMA) study units.—Continued[The five-digit USGS parameter code below the constituent name is used to uniquely identify a specific constituent or property. VOCs were analyzed in samples from 55 trend wells during 2004–05 and 2007–08. Information about analytes given in table 3A. GAMA well identification number acronyms: San Diego Drainages study unit: SDALLV, Alluvial Basins study area; SDHDRK, Hard Rock study area; SDTEM, Temecula Valley study area; SDTEMFP, Temecula Valley study area flow-path well; SDWARN, Warner Valley study area. North San Francisco Bay study unit: NSFVOL, Volcanic Highlands study area; NSFVP, Valley and Plains study area; NSFWG, Wilson Grove Formation Highlands study area; NSFWGFP, Wilson Grove Formation Highlands study area flow-path well. Northern San Joaquin Basin study unit: COS, Cosumnes Basin study area; ESJ, Eastern San Joaquin Basin study area; NSJ-QPC, Uplands study area; TRCY, Tracy Basin study area. Southern Sacramento Valley study unit: NAM, North American study area; SAM, South American study area; SOL, Solano study area; SSV-QPC, Uplands study area; SUI, Suisun-Fairfield study area; YOL, Yolo study area. San Fernando–San Gabriel study unit: ULASF, San Fernando study area; ULASG, San Gabriel study area. Monterey Bay and Salinas Valley Basins study unit: MSMB, Monterey Bay study area; MSPR, Paso Robles study area; MSSC, Santa Cruz study area; MSSV, Salinas Valley study area. Southeast San Joaquin Valley study unit: KING, Kings study area; KWH, Kaweah study area; TLR, Tulare Lake study area; TULE, Tule study area. Benchmark type: MCL-US, USEPA maximum contaminant level; MCL-CA, CDPH maximum contaminant level; HAL-US, USEPA lifetime health advisory level; NL-CA, CDPH notification level. Benchmark type and benchmark level as of April 1, 2010. Other abbreviations: USGS, U.S. Geological Survey; USEPA, U.S. Environmental Protection Agency; CDPH, California Department of Public Health; μg/L, micrograms per liter; LRL, laboratory reporting level; SRL, study reporting level; *, value greater than benchmark level; E, estimated or having a higher degree of uncertainty; ≤, less than or equal to; —, not detected]
Tables 73

GAMA well 

identification 

number

Sample 

dates

Trihalomethane Solvent

Chloroform 

(Trichloromethane) 

(μg/L) 

(32106)

Bromodichloromethane 

(μg/L) 

(32101) 

Dibromochloromethane 

(μg/L) 

(32105)

Bromoform 

(Tribromomethane) 

(μg/L) 

(32104)

Perchloroethene 

(PCE, Tetrachloroethene) 

(μg/L) 

(34475)

Trichloroethene 

(TCE) 

(μg/L) 

(39180)

cis-1,2-

Dichloroethene 

(μg/L) 

(77093)

Carbon tetrachloride 

(Tetrachloromethane) 

(μg/L) 

(32102)

1,1-Dichloroethene 

(1,1-DCE) 

(μg/L) 

(34501)

1,1-Dichloroethane 

(1,1-DCA) 

(μg/L) 

(34496)

Methylene 

chloride 

(Dichloromethane) 

(μg/L) 

(34423)

Benchmark type1 MCL-US MCL-US MCL-US MCL-US MCL-US MCL-US MCL-CA MCL-CA MCL-CA MCL-CA MCL-USBenchmark level 3 80 3 80 3 80 3 80 5 5 6 0.5 6 5 5[LRL or SRL]2 [0.02, 0.04] [0.028, 0.04] [0.1, 0.12] [0.08, 0.1] [0.03, 0.06] [0.02, 0.038] [0.02, 0.024] [0.06, 0.08] [0.02, 0.024] [0.035, 0.06] [0.04, 0.06]Southeast San Joaquin Valley study unit—ContinuedKWH-10 11/5/2008 1.95 E0.09 — — E0.01 4 — — — — E0.01 4 —KWH-12 11/28/2005 E0.04 — — — 0.24 — — — — — —KWH-12 11/6/2008 E0.06 — — — 0.32 — — E0.03 4 — — —TLR-03 11/29/2005 — — — — — — — — — — —TLR-03 11/4/2008 — — — — — — — — — — —TULE-05 12/5/2005 1.83 2.16 4.1 3.08 — — — — — — 1.38TULE-05 11/3/2008 0.64 E0.08 — — E0.01 4 E0.01 4 — — — — 0.16TULE-10 12/7/2005 0.31 E0.05 — — — — — — — — —TULE-10 11/3/2008 0.51 E0.08 — — — — — — — — —

Table 5. Volatile organic compounds (VOCs) in samples collected from trend wells for seven Groundwater Ambient Monitoring and Assessment (GAMA) study units.—Continued[The five-digit USGS parameter code below the constituent name is used to uniquely identify a specific constituent or property. VOCs were analyzed in samples from 55 trend wells during 2004–05 and 2007–08. Information about analytes given in table 3A. GAMA well identification number acronyms: San Diego Drainages study unit: SDALLV, Alluvial Basins study area; SDHDRK, Hard Rock study area; SDTEM, Temecula Valley study area; SDTEMFP, Temecula Valley study area flow-path well; SDWARN, Warner Valley study area. North San Francisco Bay study unit: NSFVOL, Volcanic Highlands study area; NSFVP, Valley and Plains study area; NSFWG, Wilson Grove Formation Highlands study area; NSFWGFP, Wilson Grove Formation Highlands study area flow-path well. Northern San Joaquin Basin study unit: COS, Cosumnes Basin study area; ESJ, Eastern San Joaquin Basin study area; NSJ-QPC, Uplands study area; TRCY, Tracy Basin study area. Southern Sacramento Valley study unit: NAM, North American study area; SAM, South American study area; SOL, Solano study area; SSV-QPC, Uplands study area; SUI, Suisun-Fairfield study area; YOL, Yolo study area. San Fernando–San Gabriel study unit: ULASF, San Fernando study area; ULASG, San Gabriel study area. Monterey Bay and Salinas Valley Basins study unit: MSMB, Monterey Bay study area; MSPR, Paso Robles study area; MSSC, Santa Cruz study area; MSSV, Salinas Valley study area. Southeast San Joaquin Valley study unit: KING, Kings study area; KWH, Kaweah study area; TLR, Tulare Lake study area; TULE, Tule study area. Benchmark type: MCL-US, USEPA maximum contaminant level; MCL-CA, CDPH maximum contaminant level; HAL-US, USEPA lifetime health advisory level; NL-CA, CDPH notification level. Benchmark type and benchmark level as of April 1, 2010. Other abbreviations: USGS, U.S. Geological Survey; USEPA, U.S. Environmental Protection Agency; CDPH, California Department of Public Health; μg/L, micrograms per liter; LRL, laboratory reporting level; SRL, study reporting level; *, value greater than benchmark level; E, estimated or having a higher degree of uncertainty; ≤, less than or equal to; —, not detected]
74 Groundwater-Quality Data in Seven GAMA Study Units: Results from Initial Sampling and Resampling of Wells GAMA well identification number Sample dates Solvent Fumigant Gasoline oxygenate Natural Fire retardant 1,2-Dichloro- ethane (μg/L) (32103) 1,1,1-Trichloro- ethane (1,1,1-TCA) (μg/L) (34506) Dibromo- methane (μg/L) (30217) 1,2-Dichloro- benzene (μg/L) (34536) trans-1,2-Di- chloroethene (μg/L) (34546) 1,2-Dibromo- 3-chloropro- pane (DBCP) (82625) Methyl tert- butyl ether (MTBE) (μg/L) (78032) Diisopropyl ether (DIPE) (μg/L) (81577) Carbon disulfide (μg/L) (77041) Bromochloro- methane (μg/L) (77297) Benchmark type1 MCL-CA MCL-US na MCL-US MCL-CA MCL-US MCL-CA na NL-CA HAL-US Benchmark level 0.5 200 na 600 10 0.2 13 na 160 90 [LRL or SRL]2 [0.06, 0.13] [0.02, 0.04] [0.04, 0.05] [0.02, 0.048] [0.018, 0.032] [0.03, 1]6 [0.1, 0.17] [0.06, 0.1] [0.03] [0.06, 0.12] Number of wells with detections 2004−05 1 1 1 0 0 4 4 1 6 1 Detection frequency (percent) 2004–05 1.8 1.8 1.8 0.0 0.0 7.3 7.3 1.8 10.9 1.8 Number of wells with detections 2007–08 2 0 0 1 1 4 4 1 1 0 Detection frequency (percent) 2007–08 3.6 0.0 0.0 1.8 1.8 7.3 7.3 1.8 1.8 0.0 San Diego Drainages study unit SDALLV-07 7/14/2004

—

—

—

—

—

—

—

—

—

—

SDALLV-07 9/12/2007

—

—

—

—

—

—

—

—

—

—

SDALLV-11 7/15/2004

—

—

—

—

—

— *28.3

—

—

—

SDALLV-11 9/13/2007

—

—

—

—

—

— 2.2

—

—

—

SDHDRK-01 7/12/2004 0.31

—

—

—

—

— 0.8 0.11

—

—

SDHDRK-01 9/13/2007 0.27

—

—

— E0.02

— 0.7 0.13

—

—

SDHDRK-09 7/27/2004

—

—

—

—

—

—

—

—

—

—

SDHDRK-09 9/11/2007

—

—

—

—

—

—

—

— ≤0.02 5 —

SDTEM-04 5/24/2004

—

—

—

—

—

—

—

—

—

—

SDTEM-04 9/18/2007

—

—

—

—

—

—

—

—

—

—

SDTEMFP-01 5/19/2004

—

—

—

—

—

—

—

—

—

—

SDTEMFP-01 9/19/2007

—

—

—

—

—

—

—

—

—

—

SDWARN-01 6/17/2004

—

—

—

—

—

—

—

—

—

—

SDWARN-01 9/11/2007

—

—

—

—

—

—

—

—

—

—

Table 5. Volatile organic compounds (VOCs) in samples collected from trend wells for seven Groundwater Ambient Monitoring and Assessment (GAMA) study units.—Continued[The five-digit USGS parameter code below the constituent name is used to uniquely identify a specific constituent or property. VOCs were analyzed in samples from 55 trend wells during 2004–05 and 2007–08. Information about analytes given in table 3A. GAMA well identification number acronyms: San Diego Drainages study unit: SDALLV, Alluvial Basins study area; SDHDRK, Hard Rock study area; SDTEM, Temecula Valley study area; SDTEMFP, Temecula Valley study area flow-path well; SDWARN, Warner Valley study area. North San Francisco Bay study unit: NSFVOL, Volcanic Highlands study area; NSFVP, Valley and Plains study area; NSFWG, Wilson Grove Formation Highlands study area; NSFWGFP, Wilson Grove Formation Highlands study area flow-path well. Northern San Joaquin Basin study unit: COS, Cosumnes Basin study area; ESJ, Eastern San Joaquin Basin study area; NSJ-QPC, Uplands study area; TRCY, Tracy Basin study area. Southern Sacramento Valley study unit: NAM, North American study area; SAM, South American study area; SOL, Solano study area; SSV-QPC, Uplands study area; SUI, Suisun-Fairfield study area; YOL, Yolo study area. San Fernando–San Gabriel study unit: ULASF, San Fernando study area; ULASG, San Gabriel study area. Monterey Bay and Salinas Valley Basins study unit: MSMB, Monterey Bay study area; MSPR, Paso Robles study area; MSSC, Santa Cruz study area; MSSV, Salinas Valley study area. Southeast San Joaquin Valley study unit: KING, Kings study area; KWH, Kaweah study area; TLR, Tulare Lake study area; TULE, Tule study area. Benchmark type: MCL-US, USEPA maximum contaminant level; MCL-CA, CDPH maximum contaminant level; HAL-US, USEPA lifetime health advisory level; NL-CA, CDPH notification level. Benchmark type and benchmark level as of April 1, 2010. Other abbreviations: USGS, U.S. Geological Survey; USEPA, U.S. Environmental Protection Agency; CDPH, California Department of Public Health; μg/L, micrograms per liter; LRL, laboratory reporting level; SRL, study reporting level; *, value greater than benchmark level; E, estimated or having a higher degree of uncertainty; ≤, less than or equal to; —, not detected]
Tables 75

GAMA 

well 

identification 

number

Sample 

dates

Solvent Fumigant Gasoline oxygenate Natural Fire retardant

1,2-Dichloroethane 

(μg/L) 

(32103)

1,1,1-Trichloroethane 

(1,1,1-TCA) 

(μg/L) 

(34506)

Dibromomethane 

(μg/L) 

(30217)

1,2-Dichlorobenzene 

(μg/L) 

(34536)

trans-1,2-Dichloroethene 

(μg/L) 

(34546)

 1,2-Dibromo3-chloropropane 

(DBCP) 

(82625)

Methyl tertbutyl ether 

(MTBE) 

(μg/L) 

(78032)

Diisopropyl 

ether 

(DIPE) 

(μg/L) 

(81577)

Carbon 

disulfide 

(μg/L) 

(77041)

Bromochloromethane 

(μg/L) 

(77297)

Benchmark type1 MCL-CA MCL-US na MCL-US MCL-CA MCL-US MCL-CA na NL-CA HAL-USBenchmark level 0.5 200 na 600 10 0.2 13 na 160 90[LRL or SRL]2 [0.06, 0.13] [0.02, 0.04] [0.04, 0.05] [0.02, 0.048] [0.018, 0.032] [0.03, 1]6 [0.1, 0.17] [0.06, 0.1] [0.03] [0.06, 0.12] North San Francisco Bay study unitNSFVOL-14 10/7/2004 — — — — — — — — — —NSFVOL-14 8/21/2007 — — — — — — — — — —NSFVOL-18 10/20/2004 — — — — — — — — — —NSFVOL-18 8/28/2007 — — — — — — — — — —NSFVP-29 9/28/2004 — — — — — — — — — —NSFVP-29 8/27/2007 — — — — — — — — — —NSFVP-34 10/18/2004 — — — — — — — — — —NSFVP-34 8/22/2007 — — — — — — — — — —NSFVP-36 10/19/2004 — — — — — — — — 0.33 —NSFVP-36 8/20/2007 — — — — — — — — — —NSFVP-38 10/20/2004 — — — — — — — — — —NSFVP-38 8/22/2007 — — — — — — — — — —NSFVP-39 10/21/2004 — — — — — — — — 0.13 —NSFVP-39 11/16/2007 — — — — — — — — — —NSFVP-41 10/21/2004 — — — — — — — — — —NSFVP-41 8/20/2007 — — — — — — — — — —NSFWG-03 9/21/2004 — — — — — — — — — —

Table 5. Volatile organic compounds (VOCs) in samples collected from trend wells for seven Groundwater Ambient Monitoring and Assessment (GAMA) study units.—Continued[The five-digit USGS parameter code below the constituent name is used to uniquely identify a specific constituent or property. VOCs were analyzed in samples from 55 trend wells during 2004–05 and 2007–08. Information about analytes given in table 3A. GAMA well identification number acronyms: San Diego Drainages study unit: SDALLV, Alluvial Basins study area; SDHDRK, Hard Rock study area; SDTEM, Temecula Valley study area; SDTEMFP, Temecula Valley study area flow-path well; SDWARN, Warner Valley study area. North San Francisco Bay study unit: NSFVOL, Volcanic Highlands study area; NSFVP, Valley and Plains study area; NSFWG, Wilson Grove Formation Highlands study area; NSFWGFP, Wilson Grove Formation Highlands study area flow-path well. Northern San Joaquin Basin study unit: COS, Cosumnes Basin study area; ESJ, Eastern San Joaquin Basin study area; NSJ-QPC, Uplands study area; TRCY, Tracy Basin study area. Southern Sacramento Valley study unit: NAM, North American study area; SAM, South American study area; SOL, Solano study area; SSV-QPC, Uplands study area; SUI, Suisun-Fairfield study area; YOL, Yolo study area. San Fernando–San Gabriel study unit: ULASF, San Fernando study area; ULASG, San Gabriel study area. Monterey Bay and Salinas Valley Basins study unit: MSMB, Monterey Bay study area; MSPR, Paso Robles study area; MSSC, Santa Cruz study area; MSSV, Salinas Valley study area. Southeast San Joaquin Valley study unit: KING, Kings study area; KWH, Kaweah study area; TLR, Tulare Lake study area; TULE, Tule study area. Benchmark type: MCL-US, USEPA maximum contaminant level; MCL-CA, CDPH maximum contaminant level; HAL-US, USEPA lifetime health advisory level; NL-CA, CDPH notification level. Benchmark type and benchmark level as of April 1, 2010. Other abbreviations: USGS, U.S. Geological Survey; USEPA, U.S. Environmental Protection Agency; CDPH, California Department of Public Health; μg/L, micrograms per liter; LRL, laboratory reporting level; SRL, study reporting level; *, value greater than benchmark level; E, estimated or having a higher degree of uncertainty; ≤, less than or equal to; —, not detected]
76 Groundwater-Quality Data in Seven GAMA Study Units: Results from Initial Sampling and Resampling of Wells GAMA well identification number Sample dates Solvent Fumigant Gasoline oxygenate Natural Fire retardant 1,2-Dichloro- ethane (μg/L) (32103) 1,1,1-Trichloro- ethane (1,1,1-TCA) (μg/L) (34506) Dibromo- methane (μg/L) (30217) 1,2-Dichloro- benzene (μg/L) (34536) trans-1,2-Di- chloroethene (μg/L) (34546) 1,2-Dibromo- 3-chloropro- pane (DBCP) (82625) Methyl tert- butyl ether (MTBE) (μg/L) (78032) Diisopropyl ether (DIPE) (μg/L) (81577) Carbon disulfide (μg/L) (77041) Bromochloro- methane (μg/L) (77297) Benchmark type1 MCL-CA MCL-US na MCL-US MCL-CA MCL-US MCL-CA na NL-CA HAL-US Benchmark level 0.5 200 na 600 10 0.2 13 na 160 90 [LRL or SRL]2 [0.06, 0.13] [0.02, 0.04] [0.04, 0.05] [0.02, 0.048] [0.018, 0.032] [0.03, 1]6 [0.1, 0.17] [0.06, 0.1] [0.03] [0.06, 0.12] North San Francisco Bay study unit—Continued NSFWG-03 8/29/2007

—

—

—

—

—

—

—

—

—

—

NSFWGFP-01 10/5/2004

—

—

—

—

—

—

—

—

—

—

NSFWGFP-01 8/29/2007

—

—

—

—

—

—

—

—

—

—

Northern San Joaquin Basin study unit COS-08 1/3/2005

—

—

—

—

—

—

—

—

—

—

COS-08 4/3/2008

—

—

—

—

—

—

—

—

—

—

ESJ-01 1/24/2005

—

—

—

—

—

—

—

—

—

—

ESJ-01 4/2/2008

—

—

—

—

—

—

—

—

—

—

ESJ-06 1/10/2005

—

—

—

—

— 0.10

—

—

—

—

ESJ-06 4/2/2008

—

—

—

—

— 0.06

—

—

—

—

NSJ-QPC-04 1/24/2005

—

—

—

—

—

—

—

—

—

—

NSJ-QPC-04 4/1/2008

—

—

—

—

—

—

—

—

—

—

TRCY-03 1/6/2005

—

—

—

—

—

—

—

—

—

—

TRCY-03 3/31/2008

—

—

—

—

—

—

—

—

—

—

 Southern Sacramento Valley study unitNAM-03 3/29/2005

—

—

—

—

—

—

—

—

—

—

NAM-03 4/10/2008

—

—

—

—

—

—

—

—

—

—

Table 5. Volatile organic compounds (VOCs) in samples collected from trend wells for seven Groundwater Ambient Monitoring and Assessment (GAMA) study units.—Continued[The five-digit USGS parameter code below the constituent name is used to uniquely identify a specific constituent or property. VOCs were analyzed in samples from 55 trend wells during 2004–05 and 2007–08. Information about analytes given in table 3A. GAMA well identification number acronyms: San Diego Drainages study unit: SDALLV, Alluvial Basins study area; SDHDRK, Hard Rock study area; SDTEM, Temecula Valley study area; SDTEMFP, Temecula Valley study area flow-path well; SDWARN, Warner Valley study area. North San Francisco Bay study unit: NSFVOL, Volcanic Highlands study area; NSFVP, Valley and Plains study area; NSFWG, Wilson Grove Formation Highlands study area; NSFWGFP, Wilson Grove Formation Highlands study area flow-path well. Northern San Joaquin Basin study unit: COS, Cosumnes Basin study area; ESJ, Eastern San Joaquin Basin study area; NSJ-QPC, Uplands study area; TRCY, Tracy Basin study area. Southern Sacramento Valley study unit: NAM, North American study area; SAM, South American study area; SOL, Solano study area; SSV-QPC, Uplands study area; SUI, Suisun-Fairfield study area; YOL, Yolo study area. San Fernando–San Gabriel study unit: ULASF, San Fernando study area; ULASG, San Gabriel study area. Monterey Bay and Salinas Valley Basins study unit: MSMB, Monterey Bay study area; MSPR, Paso Robles study area; MSSC, Santa Cruz study area; MSSV, Salinas Valley study area. Southeast San Joaquin Valley study unit: KING, Kings study area; KWH, Kaweah study area; TLR, Tulare Lake study area; TULE, Tule study area. Benchmark type: MCL-US, USEPA maximum contaminant level; MCL-CA, CDPH maximum contaminant level; HAL-US, USEPA lifetime health advisory level; NL-CA, CDPH notification level. Benchmark type and benchmark level as of April 1, 2010. Other abbreviations: USGS, U.S. Geological Survey; USEPA, U.S. Environmental Protection Agency; CDPH, California Department of Public Health; μg/L, micrograms per liter; LRL, laboratory reporting level; SRL, study reporting level; *, value greater than benchmark level; E, estimated or having a higher degree of uncertainty; ≤, less than or equal to; —, not detected]
Tables 77

GAMA 

well 

identification 

number

Sample 

dates

Solvent Fumigant Gasoline oxygenate Natural Fire retardant

1,2-Dichloroethane 

(μg/L) 

(32103)

1,1,1-Trichloroethane 

(1,1,1-TCA) 

(μg/L) 

(34506)

Dibromomethane 

(μg/L) 

(30217)

1,2-Dichlorobenzene 

(μg/L) 

(34536)

trans-1,2-Dichloroethene 

(μg/L) 

(34546)

 1,2-Dibromo3-chloropropane 

(DBCP) 

(82625)

Methyl tertbutyl ether 

(MTBE) 

(μg/L) 

(78032)

Diisopropyl 

ether 

(DIPE) 

(μg/L) 

(81577)

Carbon 

disulfide 

(μg/L) 

(77041)

Bromochloromethane 

(μg/L) 

(77297)

Benchmark type1 MCL-CA MCL-US na MCL-US MCL-CA MCL-US MCL-CA na NL-CA HAL-USBenchmark level 0.5 200 na 600 10 0.2 13 na 160 90[LRL or SRL]2 [0.06, 0.13] [0.02, 0.04] [0.04, 0.05] [0.02, 0.048] [0.018, 0.032] [0.03, 1]6 [0.1, 0.17] [0.06, 0.1] [0.03] [0.06, 0.12] Southern Sacramento Valley study unit—ContinuedSAM-10 4/21/2005 — — — — — — — — — —SAM-10 4/8/2008 — — — — — — — — — —SOL-08 5/10/2005 — — — — — — — — — —SOL-08 4/8/2008 — — — — — — — — — —SSV-QPC-07 4/4/2005 — — — — — — — — — —SSV-QPC-07 4/10/2008 — — — — — — — — — —SUI-03 5/12/2005 — — — — — — — — — —SUI-03 4/9/2008 — — — — — — — — — —YOL-01 4/11/2005 — — — — — — — — — —YOL-01 4/7/2008 — — — — — — — — — —YOL-14 5/25/2005 — — — — — — — — — —YOL-14 4/9/2008 — — — — — — — — — — San Fernando–San Gabriel study unit ULASF-09 6/27/2005 — — — — — — 0.2 — — —ULASF-09 6/16/2008 — — — — — — 0.6 — — —ULASF-10 6/8/2005 — — — — — — — — — —ULASF-10 6/16/2008 — — — — — — — — — —

Table 5. Volatile organic compounds (VOCs) in samples collected from trend wells for seven Groundwater Ambient Monitoring and Assessment (GAMA) study units.—Continued[The five-digit USGS parameter code below the constituent name is used to uniquely identify a specific constituent or property. VOCs were analyzed in samples from 55 trend wells during 2004–05 and 2007–08. Information about analytes given in table 3A. GAMA well identification number acronyms: San Diego Drainages study unit: SDALLV, Alluvial Basins study area; SDHDRK, Hard Rock study area; SDTEM, Temecula Valley study area; SDTEMFP, Temecula Valley study area flow-path well; SDWARN, Warner Valley study area. North San Francisco Bay study unit: NSFVOL, Volcanic Highlands study area; NSFVP, Valley and Plains study area; NSFWG, Wilson Grove Formation Highlands study area; NSFWGFP, Wilson Grove Formation Highlands study area flow-path well. Northern San Joaquin Basin study unit: COS, Cosumnes Basin study area; ESJ, Eastern San Joaquin Basin study area; NSJ-QPC, Uplands study area; TRCY, Tracy Basin study area. Southern Sacramento Valley study unit: NAM, North American study area; SAM, South American study area; SOL, Solano study area; SSV-QPC, Uplands study area; SUI, Suisun-Fairfield study area; YOL, Yolo study area. San Fernando–San Gabriel study unit: ULASF, San Fernando study area; ULASG, San Gabriel study area. Monterey Bay and Salinas Valley Basins study unit: MSMB, Monterey Bay study area; MSPR, Paso Robles study area; MSSC, Santa Cruz study area; MSSV, Salinas Valley study area. Southeast San Joaquin Valley study unit: KING, Kings study area; KWH, Kaweah study area; TLR, Tulare Lake study area; TULE, Tule study area. Benchmark type: MCL-US, USEPA maximum contaminant level; MCL-CA, CDPH maximum contaminant level; HAL-US, USEPA lifetime health advisory level; NL-CA, CDPH notification level. Benchmark type and benchmark level as of April 1, 2010. Other abbreviations: USGS, U.S. Geological Survey; USEPA, U.S. Environmental Protection Agency; CDPH, California Department of Public Health; μg/L, micrograms per liter; LRL, laboratory reporting level; SRL, study reporting level; *, value greater than benchmark level; E, estimated or having a higher degree of uncertainty; ≤, less than or equal to; —, not detected]
78 Groundwater-Quality Data in Seven GAMA Study Units: Results from Initial Sampling and Resampling of Wells GAMA well identification number Sample dates Solvent Fumigant Gasoline oxygenate Natural Fire retardant 1,2-Dichloro- ethane (μg/L) (32103) 1,1,1-Trichloro- ethane (1,1,1-TCA) (μg/L) (34506) Dibromo- methane (μg/L) (30217) 1,2-Dichloro- benzene (μg/L) (34536) trans-1,2-Di- chloroethene (μg/L) (34546) 1,2-Dibromo- 3-chloropro- pane (DBCP) (82625) Methyl tert- butyl ether (MTBE) (μg/L) (78032) Diisopropyl ether (DIPE) (μg/L) (81577) Carbon disulfide (μg/L) (77041) Bromochloro- methane (μg/L) (77297) Benchmark type1 MCL-CA MCL-US na MCL-US MCL-CA MCL-US MCL-CA na NL-CA HAL-US Benchmark level 0.5 200 na 600 10 0.2 13 na 160 90 [LRL or SRL]2 [0.06, 0.13] [0.02, 0.04] [0.04, 0.05] [0.02, 0.048] [0.018, 0.032] [0.03, 1]6 [0.1, 0.17] [0.06, 0.1] [0.03] [0.06, 0.12] San Fernando–San Gabriel study unit—Continued ULASG-01 6/7/2005

—

—

—

—

—

—

—

—

—

—

ULASG-01 6/16/2008

—

—

—

—

—

— E0.04 4 —

—

—

ULASG-08 6/15/2005

—

—

—

—

—

—

—

—

—

—

ULASG-08 6/17/2008 E0.06

—

— E0.04

—

—

—

—

—

—

ULASG-15 6/23/2005

—

—

—

—

—

—

—

—

—

—

ULASG-15 6/17/2008

—

—

—

—

—

—

—

—

—

—

ULASG-17 7/11/2005

— E0.02

—

—

—

— E0.1

— E0.03

—

ULASG-17 6/17/2008

—

—

—

—

—

— 0.1

—

—

—

 Monterey Bay and Salinas Valley Basins study unitMSMB-03 8/31/2005

—

—

—

—

—

—

—

—

—

—

MSMB-03 8/20/2008

—

—

—

—

—

—

—

—

—

—

MSMB-04 8/17/2005

—

—

—

—

—

—

—

—

—

—

MSMB-04 8/20/2008

—

—

—

—

—

—

—

—

—

—

MSMB-16 8/17/2005

—

—

—

—

—

—

—

—

—

—

MSMB-16 8/19/2008

—

—

—

—

—

—

—

—

—

—

MSMB-28 8/3/2005

—

—

—

—

—

—

—

—

—

—

MSMB-28 8/21/2008

—

—

—

—

—

—

—

—

—

—

Table 5. Volatile organic compounds (VOCs) in samples collected from trend wells for seven Groundwater Ambient Monitoring and Assessment (GAMA) study units.—Continued[The five-digit USGS parameter code below the constituent name is used to uniquely identify a specific constituent or property. VOCs were analyzed in samples from 55 trend wells during 2004–05 and 2007–08. Information about analytes given in table 3A. GAMA well identification number acronyms: San Diego Drainages study unit: SDALLV, Alluvial Basins study area; SDHDRK, Hard Rock study area; SDTEM, Temecula Valley study area; SDTEMFP, Temecula Valley study area flow-path well; SDWARN, Warner Valley study area. North San Francisco Bay study unit: NSFVOL, Volcanic Highlands study area; NSFVP, Valley and Plains study area; NSFWG, Wilson Grove Formation Highlands study area; NSFWGFP, Wilson Grove Formation Highlands study area flow-path well. Northern San Joaquin Basin study unit: COS, Cosumnes Basin study area; ESJ, Eastern San Joaquin Basin study area; NSJ-QPC, Uplands study area; TRCY, Tracy Basin study area. Southern Sacramento Valley study unit: NAM, North American study area; SAM, South American study area; SOL, Solano study area; SSV-QPC, Uplands study area; SUI, Suisun-Fairfield study area; YOL, Yolo study area. San Fernando–San Gabriel study unit: ULASF, San Fernando study area; ULASG, San Gabriel study area. Monterey Bay and Salinas Valley Basins study unit: MSMB, Monterey Bay study area; MSPR, Paso Robles study area; MSSC, Santa Cruz study area; MSSV, Salinas Valley study area. Southeast San Joaquin Valley study unit: KING, Kings study area; KWH, Kaweah study area; TLR, Tulare Lake study area; TULE, Tule study area. Benchmark type: MCL-US, USEPA maximum contaminant level; MCL-CA, CDPH maximum contaminant level; HAL-US, USEPA lifetime health advisory level; NL-CA, CDPH notification level. Benchmark type and benchmark level as of April 1, 2010. Other abbreviations: USGS, U.S. Geological Survey; USEPA, U.S. Environmental Protection Agency; CDPH, California Department of Public Health; μg/L, micrograms per liter; LRL, laboratory reporting level; SRL, study reporting level; *, value greater than benchmark level; E, estimated or having a higher degree of uncertainty; ≤, less than or equal to; —, not detected]
Tables 79

GAMA 

well 

identification 

number

Sample 

dates

Solvent Fumigant Gasoline oxygenate Natural Fire retardant

1,2-Dichloroethane 

(μg/L) 

(32103)

1,1,1-Trichloroethane 

(1,1,1-TCA) 

(μg/L) 

(34506)

Dibromomethane 

(μg/L) 

(30217)

1,2-Dichlorobenzene 

(μg/L) 

(34536)

trans-1,2-Dichloroethene 

(μg/L) 

(34546)

 1,2-Dibromo3-chloropropane 

(DBCP) 

(82625)

Methyl tertbutyl ether 

(MTBE) 

(μg/L) 

(78032)

Diisopropyl 

ether 

(DIPE) 

(μg/L) 

(81577)

Carbon 

disulfide 

(μg/L) 

(77041)

Bromochloromethane 

(μg/L) 

(77297)

Benchmark type1 MCL-CA MCL-US na MCL-US MCL-CA MCL-US MCL-CA na NL-CA HAL-USBenchmark level 0.5 200 na 600 10 0.2 13 na 160 90[LRL or SRL]2 [0.06, 0.13] [0.02, 0.04] [0.04, 0.05] [0.02, 0.048] [0.018, 0.032] [0.03, 1]6 [0.1, 0.17] [0.06, 0.1] [0.03] [0.06, 0.12] Monterey Bay and Salinas Valley Basins study unit—ContinuedMSMB-31 8/11/2005 — — — — — — — — — —MSMB-31 8/21/2008 — — — — — — — — — —MSPR-03 7/28/2005 — — — — — — — — — —MSPR-03 11/14/2008 — — — — — — — — — —MSPR-09 7/18/2005 — — — — — — — — — —MSPR-09 11/14/2008 — — — — — — — — — —MSSC-06 8/24/2005 — — — — — — — — 0.17 —MSSC-06 8/18/2008 — — — — — — — — 0.35 —MSSC-11 9/13/2005 — — — — — — — — — —MSSC-11 8/19/2008 — — — — — — — — — —MSSV-06 8/2/2005 — — — — — — — — — —MSSV-06 11/13/2008 — — — — — — — — — —MSSV-15 8/12/2005 — — — — — — — — — —MSSV-15 11/13/2008 — — — — — — — — — — Southeast San Joaquin Valley study unitKING-11 10/20/2005 — — — — — E0.05 — — — —KING-11 11/5/2008 — — — — — E0.03 — — — —KING-13 10/20/2005 — — — — — — — — — —

Table 5. Volatile organic compounds (VOCs) in samples collected from trend wells for seven Groundwater Ambient Monitoring and Assessment (GAMA) study units.—Continued[The five-digit USGS parameter code below the constituent name is used to uniquely identify a specific constituent or property. VOCs were analyzed in samples from 55 trend wells during 2004–05 and 2007–08. Information about analytes given in table 3A. GAMA well identification number acronyms: San Diego Drainages study unit: SDALLV, Alluvial Basins study area; SDHDRK, Hard Rock study area; SDTEM, Temecula Valley study area; SDTEMFP, Temecula Valley study area flow-path well; SDWARN, Warner Valley study area. North San Francisco Bay study unit: NSFVOL, Volcanic Highlands study area; NSFVP, Valley and Plains study area; NSFWG, Wilson Grove Formation Highlands study area; NSFWGFP, Wilson Grove Formation Highlands study area flow-path well. Northern San Joaquin Basin study unit: COS, Cosumnes Basin study area; ESJ, Eastern San Joaquin Basin study area; NSJ-QPC, Uplands study area; TRCY, Tracy Basin study area. Southern Sacramento Valley study unit: NAM, North American study area; SAM, South American study area; SOL, Solano study area; SSV-QPC, Uplands study area; SUI, Suisun-Fairfield study area; YOL, Yolo study area. San Fernando–San Gabriel study unit: ULASF, San Fernando study area; ULASG, San Gabriel study area. Monterey Bay and Salinas Valley Basins study unit: MSMB, Monterey Bay study area; MSPR, Paso Robles study area; MSSC, Santa Cruz study area; MSSV, Salinas Valley study area. Southeast San Joaquin Valley study unit: KING, Kings study area; KWH, Kaweah study area; TLR, Tulare Lake study area; TULE, Tule study area. Benchmark type: MCL-US, USEPA maximum contaminant level; MCL-CA, CDPH maximum contaminant level; HAL-US, USEPA lifetime health advisory level; NL-CA, CDPH notification level. Benchmark type and benchmark level as of April 1, 2010. Other abbreviations: USGS, U.S. Geological Survey; USEPA, U.S. Environmental Protection Agency; CDPH, California Department of Public Health; μg/L, micrograms per liter; LRL, laboratory reporting level; SRL, study reporting level; *, value greater than benchmark level; E, estimated or having a higher degree of uncertainty; ≤, less than or equal to; —, not detected]
80 Groundwater-Quality Data in Seven GAMA Study Units: Results from Initial Sampling and Resampling of Wells GAMA well identification number Sample dates Solvent Fumigant Gasoline oxygenate Natural Fire retardant 1,2-Dichloro- ethane (μg/L) (32103) 1,1,1-Trichloro- ethane (1,1,1-TCA) (μg/L) (34506) Dibromo- methane (μg/L) (30217) 1,2-Dichloro- benzene (μg/L) (34536) trans-1,2-Di- chloroethene (μg/L) (34546) 1,2-Dibromo- 3-chloropro- pane (DBCP) (82625) Methyl tert- butyl ether (MTBE) (μg/L) (78032) Diisopropyl ether (DIPE) (μg/L) (81577) Carbon disulfide (μg/L) (77041) Bromochloro- methane (μg/L) (77297) Benchmark type1 MCL-CA MCL-US na MCL-US MCL-CA MCL-US MCL-CA na NL-CA HAL-US Benchmark level 0.5 200 na 600 10 0.2 13 na 160 90 [LRL or SRL]2 [0.06, 0.13] [0.02, 0.04] [0.04, 0.05] [0.02, 0.048] [0.018, 0.032] [0.03, 1]6 [0.1, 0.17] [0.06, 0.1] [0.03] [0.06, 0.12] Southeast San Joaquin Valley study unit—Continued KING-13 11/5/2008

—

—

—

—

—

—

—

—

—

—

KING-17 10/26/2005

—

—

—

—

—

—

—

—

—

—

KING-17 11/4/2008

—

—

—

—

—

—

—

—

—

—

KING-24 11/5/2005

—

—

—

—

— *0.35

—

— 0.10

—

KING-24 11/3/2008

—

—

—

—

— *0.22

—

—

—

—

KWH-10 11/17/2005

—

—

—

—

—

—

—

—

—

—

KWH-10 11/5/2008

—

—

—

—

—

—

—

—

—

—

KWH-12 11/28/2005

—

—

—

—

—

—

—

—

—

—

KWH-12 11/6/2008

—

—

—

—

—

—

—

—

—

—

TLR-03 11/29/2005

—

—

—

—

—

—

—

—

—

—

TLR-03 11/4/2008

—

—

—

—

—

—

—

—

—

—

TULE-05 12/5/2005

—

— 1.54

—

—

—

—

— E0.05 2.03

TULE-05 11/3/2008

—

—

—

—

—

—

—

—

—

—

TULE-10 12/7/2005

—

—

—

—

— 0.18

—

—

—

—

TULE-10 11/3/2008

—

—

—

—

— 0.08 E0.05 4 —

—

—

Table 5. Volatile organic compounds (VOCs) in samples collected from trend wells for seven Groundwater Ambient Monitoring and Assessment (GAMA) study units.—Continued[The five-digit USGS parameter code below the constituent name is used to uniquely identify a specific constituent or property. VOCs were analyzed in samples from 55 trend wells during 2004–05 and 2007–08. Information about analytes given in table 3A. GAMA well identification number acronyms: San Diego Drainages study unit: SDALLV, Alluvial Basins study area; SDHDRK, Hard Rock study area; SDTEM, Temecula Valley study area; SDTEMFP, Temecula Valley study area flow-path well; SDWARN, Warner Valley study area. North San Francisco Bay study unit: NSFVOL, Volcanic Highlands study area; NSFVP, Valley and Plains study area; NSFWG, Wilson Grove Formation Highlands study area; NSFWGFP, Wilson Grove Formation Highlands study area flow-path well. Northern San Joaquin Basin study unit: COS, Cosumnes Basin study area; ESJ, Eastern San Joaquin Basin study area; NSJ-QPC, Uplands study area; TRCY, Tracy Basin study area. Southern Sacramento Valley study unit: NAM, North American study area; SAM, South American study area; SOL, Solano study area; SSV-QPC, Uplands study area; SUI, Suisun-Fairfield study area; YOL, Yolo study area. San Fernando–San Gabriel study unit: ULASF, San Fernando study area; ULASG, San Gabriel study area. Monterey Bay and Salinas Valley Basins study unit: MSMB, Monterey Bay study area; MSPR, Paso Robles study area; MSSC, Santa Cruz study area; MSSV, Salinas Valley study area. Southeast San Joaquin Valley study unit: KING, Kings study area; KWH, Kaweah study area; TLR, Tulare Lake study area; TULE, Tule study area. Benchmark type: MCL-US, USEPA maximum contaminant level; MCL-CA, CDPH maximum contaminant level; HAL-US, USEPA lifetime health advisory level; NL-CA, CDPH notification level. Benchmark type and benchmark level as of April 1, 2010. Other abbreviations: USGS, U.S. Geological Survey; USEPA, U.S. Environmental Protection Agency; CDPH, California Department of Public Health; μg/L, micrograms per liter; LRL, laboratory reporting level; SRL, study reporting level; *, value greater than benchmark level; E, estimated or having a higher degree of uncertainty; ≤, less than or equal to; —, not detected]
Tables 81

GAMA well 

identification 

number

Sample 

dates

Gasoline hydrocarbon Refrigerant

Detections 

per sample

VOC 

detection 

summary

m-Xylene plus 

p-Xylene 

(μg/L) 

(85795)

o-Xylene 

(μg/L) 

(77135)

Ethylbenzene 

(μg/L) 

(34371)

Toluene 

(μg/L) 

(34010)

1,2,3-Trimethylbenzene 

(μg/L) 

(77221)

1,2,4-Trimethylbenzene 

(μg/L) 

(77222)

Dichlorodifluoromethane 

(CFC-12) 

(μg/L) (34668)

 1,1,2-Trichloro1,2,2-trifluoroethane 

(CFC-113) 

(μg/L) 

(77652)

Trichlorofluoromethane 

(CFC-11) 

(μg/L) 

(34488)

Benchmark type1 MCL-CA MCL-CA MCL-CA MCL-CA na NL-CA NL-CA MCL-CA MCL-CABenchmark level 7 1,750 7 1,750 300 10 na 330 1,000 1,200 150[LRL or SRL]2 [0.33] [0.12] [0.06] [0.69] [0.06, 0.08] [0.56] [0.1, 0.18] [0.038, 0.04] [0.08, 0.16]Number of wells with detections 2004−05 0 0 0 0 0 0 2 2 1 27Detection frequency (percent) 

2004–05

0.0 0.0 0.0 0.0 0.0 0.0 3.6 3.6 1.8 49.1

Number of wells with detections 2007–08 0 0 0 0 0 0 3 2 2 26Detection frequency (percent) 

2007–08

0.0 0.0 0.0 0.0 0.0 0.0 5.5 3.6 3.6 47.3

 San Diego Drainages study unitSDALLV-07 7/14/2004 — — — — — — — — — 1SDALLV-07 9/12/2007 — — — — — — — — — 0SDALLV-11 7/15/2004 — — — — — — — — — 5SDALLV-11 9/13/2007 — — — — — — — — — 6SDHDRK-01 7/12/2004 — — — — — — — — — 8SDHDRK-01 9/13/2007 — — — — — — — — — 9SDHDRK-09 7/27/2004 — — — — — — — — — 0SDHDRK-09 9/11/2007 — — — — — — — — — 0SDTEM-04 5/24/2004 — — — — — — — — — 0SDTEM-04 9/18/2007 — — — — — — — — — 1

Table 5. Volatile organic compounds (VOCs) in samples collected from trend wells for seven Groundwater Ambient Monitoring and Assessment (GAMA) study units.—Continued[The five-digit USGS parameter code below the constituent name is used to uniquely identify a specific constituent or property. VOCs were analyzed in samples from 55 trend wells during 2004–05 and 2007–08. Information about analytes given in table 3A. GAMA well identification number acronyms: San Diego Drainages study unit: SDALLV, Alluvial Basins study area; SDHDRK, Hard Rock study area; SDTEM, Temecula Valley study area; SDTEMFP, Temecula Valley study area flow-path well; SDWARN, Warner Valley study area. North San Francisco Bay study unit: NSFVOL, Volcanic Highlands study area; NSFVP, Valley and Plains study area; NSFWG, Wilson Grove Formation Highlands study area; NSFWGFP, Wilson Grove Formation Highlands study area flow-path well. Northern San Joaquin Basin study unit: COS, Cosumnes Basin study area; ESJ, Eastern San Joaquin Basin study area; NSJ-QPC, Uplands study area; TRCY, Tracy Basin study area. Southern Sacramento Valley study unit: NAM, North American study area; SAM, South American study area; SOL, Solano study area; SSV-QPC, Uplands study area; SUI, Suisun-Fairfield study area; YOL, Yolo study area. San Fernando–San Gabriel study unit: ULASF, San Fernando study area; ULASG, San Gabriel study area. Monterey Bay and Salinas Valley Basins study unit: MSMB, Monterey Bay study area; MSPR, Paso Robles study area; MSSC, Santa Cruz study area; MSSV, Salinas Valley study area. Southeast San Joaquin Valley study unit: KING, Kings study area; KWH, Kaweah study area; TLR, Tulare Lake study area; TULE, Tule study area. Benchmark type: MCL-US, USEPA maximum contaminant level; MCL-CA, CDPH maximum contaminant level; HAL-US, USEPA lifetime health advisory level; NL-CA, CDPH notification level. Benchmark type and benchmark level as of April 1, 2010. Other abbreviations: USGS, U.S. Geological Survey; USEPA, U.S. Environmental Protection Agency; CDPH, California Department of Public Health; μg/L, micrograms per liter; LRL, laboratory reporting level; SRL, study reporting level; *, value greater than benchmark level; E, estimated or having a higher degree of uncertainty; ≤, less than or equal to; —, not detected]
82 Groundwater-Quality Data in Seven GAMA Study Units: Results from Initial Sampling and Resampling of Wells GAMA well identification number Sample dates Gasoline hydrocarbon Refrigerant Detections per sample VOC detection summary

m-Xylene plus 

p-Xylene 

(μg/L) 

(85795)

o-Xylene 

(μg/L) 

(77135)

Ethylbenzene 

(μg/L) 

(34371)

Toluene 

(μg/L) 

(34010)

1,2,3-Trimethylbenzene 

(μg/L) 

(77221)

1,2,4-Trimethylbenzene 

(μg/L) 

(77222)

Dichlorodifluoromethane 

(CFC-12) 

(μg/L) (34668)

 1,1,2-Trichloro1,2,2-trifluoroethane 

(CFC-113) 

(μg/L) 

(77652)

Trichlorofluoromethane 

(CFC-11) 

(μg/L) 

(34488)

Benchmark type1 MCL-CA MCL-CA MCL-CA MCL-CA na NL-CA NL-CA MCL-CA MCL-CABenchmark level 7 1,750 7 1,750 300 10 na 330 1,000 1,200 150[LRL or SRL]2 [0.33] [0.12] [0.06] [0.69] [0.06, 0.08] [0.56] [0.1, 0.18] [0.038, 0.04] [0.08, 0.16] San Diego Drainages study unit—ContinuedSDTEMFP-01 5/19/2004

—

—

— ≤0.01 5 —

—

—

—

— 0

SDTEMFP-01 9/19/2007

—

—

—

—

— ≤0.02 5 —

—

— 2

SDWARN-01 6/17/2004

—

—

—

—

—

—

—

—

— 0

SDWARN-01 9/11/2007

—

—

—

—

—

—

—

—

— 0

 North San Francisco Bay study unitNSFVOL-14 10/7/2004

—

—

—

—

—

—

—

—

— 0

NSFVOL-14 8/21/2007

—

—

—

—

— ≤0.08 5 —

—

— 0

NSFVOL-18 10/20/2004

—

—

—

—

—

—

—

—

— 0

NSFVOL-18 8/28/2007

—

—

—

—

— ≤0.06 5 —

—

— 0

NSFVP-29 9/28/2004

—

—

—

—

—

—

—

—

— 0

NSFVP-29 8/27/2007 ≤0.06 5 ≤0.02 5 ≤0.01 5 ≤0.01 5 —

—

—

—

— 0

NSFVP-34 10/18/2004

—

—

—

—

—

—

—

—

— 0

NSFVP-34 8/22/2007

—

—

—

—

— ≤0.04 5 —

—

— 0

NSFVP-36 10/19/2004

—

—

—

—

—

—

—

—

— 1

NSFVP-36 8/20/2007

—

—

—

—

— ≤0.05 5 —

—

— 0

NSFVP-38 10/20/2004

—

—

—

—

—

—

—

—

— 0

Table 5. Volatile organic compounds (VOCs) in samples collected from trend wells for seven Groundwater Ambient Monitoring and Assessment (GAMA) study units.—Continued[The five-digit USGS parameter code below the constituent name is used to uniquely identify a specific constituent or property. VOCs were analyzed in samples from 55 trend wells during 2004–05 and 2007–08. Information about analytes given in table 3A. GAMA well identification number acronyms: San Diego Drainages study unit: SDALLV, Alluvial Basins study area; SDHDRK, Hard Rock study area; SDTEM, Temecula Valley study area; SDTEMFP, Temecula Valley study area flow-path well; SDWARN, Warner Valley study area. North San Francisco Bay study unit: NSFVOL, Volcanic Highlands study area; NSFVP, Valley and Plains study area; NSFWG, Wilson Grove Formation Highlands study area; NSFWGFP, Wilson Grove Formation Highlands study area flow-path well. Northern San Joaquin Basin study unit: COS, Cosumnes Basin study area; ESJ, Eastern San Joaquin Basin study area; NSJ-QPC, Uplands study area; TRCY, Tracy Basin study area. Southern Sacramento Valley study unit: NAM, North American study area; SAM, South American study area; SOL, Solano study area; SSV-QPC, Uplands study area; SUI, Suisun-Fairfield study area; YOL, Yolo study area. San Fernando–San Gabriel study unit: ULASF, San Fernando study area; ULASG, San Gabriel study area. Monterey Bay and Salinas Valley Basins study unit: MSMB, Monterey Bay study area; MSPR, Paso Robles study area; MSSC, Santa Cruz study area; MSSV, Salinas Valley study area. Southeast San Joaquin Valley study unit: KING, Kings study area; KWH, Kaweah study area; TLR, Tulare Lake study area; TULE, Tule study area. Benchmark type: MCL-US, USEPA maximum contaminant level; MCL-CA, CDPH maximum contaminant level; HAL-US, USEPA lifetime health advisory level; NL-CA, CDPH notification level. Benchmark type and benchmark level as of April 1, 2010. Other abbreviations: USGS, U.S. Geological Survey; USEPA, U.S. Environmental Protection Agency; CDPH, California Department of Public Health; μg/L, micrograms per liter; LRL, laboratory reporting level; SRL, study reporting level; *, value greater than benchmark level; E, estimated or having a higher degree of uncertainty; ≤, less than or equal to; —, not detected]
Tables 83

GAMA well 

identification 

number

Sample 

dates

Gasoline hydrocarbon Refrigerant

Detections 

per sample

VOC 

detection 

summary

m-Xylene plus 

p-Xylene 

(μg/L) 

(85795)

o-Xylene 

(μg/L) 

(77135)

Ethylbenzene 

(μg/L) 

(34371)

Toluene 

(μg/L) 

(34010)

1,2,3-Trimethylbenzene 

(μg/L) 

(77221)

1,2,4-Trimethylbenzene 

(μg/L) 

(77222)

Dichlorodifluoromethane 

(CFC-12) 

(μg/L) (34668)

 1,1,2-Trichloro1,2,2-trifluoroethane 

(CFC-113) 

(μg/L) 

(77652)

Trichlorofluoromethane 

(CFC-11) 

(μg/L) 

(34488)

Benchmark type1 MCL-CA MCL-CA MCL-CA MCL-CA na NL-CA NL-CA MCL-CA MCL-CABenchmark level 7 1,750 7 1,750 300 10 na 330 1,000 1,200 150[LRL or SRL]2 [0.33] [0.12] [0.06] [0.69] [0.06, 0.08] [0.56] [0.1, 0.18] [0.038, 0.04] [0.08, 0.16] North San Francisco Bay study unit—ContinuedNSFVP-38 8/22/2007 — — — — — ≤0.06 5 — — — 1NSFVP-39 10/21/2004 — — — — — — — — — 1NSFVP-39 11/16/2007 — — — — — — — — — 0NSFVP-41 10/21/2004 — — — — — — — — — 1NSFVP-41 8/20/2007 — — — — — — — — E0.06 2NSFWG-03 9/21/2004 — — — — — — — — — 0NSFWG-03 8/29/2007 — — — — — ≤0.03 5 — — — 0NSFWGFP-01 10/5/2004 — — — — — — — — — 3NSFWGFP-01 8/29/2007 — — — — — ≤0.04 5 — — — 3 Northern San Joaquin Basin study unit COS-08 1/3/2005 — — — — — — — — — 0COS-08 4/3/2008 — — — — — — — — — 0ESJ-01 1/24/2005 — — — — — — — — — 0ESJ-01 4/2/2008 — — — ≤0.01 5 — — — — — 0ESJ-06 1/10/2005 — — — — — — — — — 2ESJ-06 4/2/2008 — — — — — — — — — 2

Table 5. Volatile organic compounds (VOCs) in samples collected from trend wells for seven Groundwater Ambient Monitoring and Assessment (GAMA) study units.—Continued[The five-digit USGS parameter code below the constituent name is used to uniquely identify a specific constituent or property. VOCs were analyzed in samples from 55 trend wells during 2004–05 and 2007–08. Information about analytes given in table 3A. GAMA well identification number acronyms: San Diego Drainages study unit: SDALLV, Alluvial Basins study area; SDHDRK, Hard Rock study area; SDTEM, Temecula Valley study area; SDTEMFP, Temecula Valley study area flow-path well; SDWARN, Warner Valley study area. North San Francisco Bay study unit: NSFVOL, Volcanic Highlands study area; NSFVP, Valley and Plains study area; NSFWG, Wilson Grove Formation Highlands study area; NSFWGFP, Wilson Grove Formation Highlands study area flow-path well. Northern San Joaquin Basin study unit: COS, Cosumnes Basin study area; ESJ, Eastern San Joaquin Basin study area; NSJ-QPC, Uplands study area; TRCY, Tracy Basin study area. Southern Sacramento Valley study unit: NAM, North American study area; SAM, South American study area; SOL, Solano study area; SSV-QPC, Uplands study area; SUI, Suisun-Fairfield study area; YOL, Yolo study area. San Fernando–San Gabriel study unit: ULASF, San Fernando study area; ULASG, San Gabriel study area. Monterey Bay and Salinas Valley Basins study unit: MSMB, Monterey Bay study area; MSPR, Paso Robles study area; MSSC, Santa Cruz study area; MSSV, Salinas Valley study area. Southeast San Joaquin Valley study unit: KING, Kings study area; KWH, Kaweah study area; TLR, Tulare Lake study area; TULE, Tule study area. Benchmark type: MCL-US, USEPA maximum contaminant level; MCL-CA, CDPH maximum contaminant level; HAL-US, USEPA lifetime health advisory level; NL-CA, CDPH notification level. Benchmark type and benchmark level as of April 1, 2010. Other abbreviations: USGS, U.S. Geological Survey; USEPA, U.S. Environmental Protection Agency; CDPH, California Department of Public Health; μg/L, micrograms per liter; LRL, laboratory reporting level; SRL, study reporting level; *, value greater than benchmark level; E, estimated or having a higher degree of uncertainty; ≤, less than or equal to; —, not detected]
84 Groundwater-Quality Data in Seven GAMA Study Units: Results from Initial Sampling and Resampling of Wells GAMA well identification number Sample dates Gasoline hydrocarbon Refrigerant Detections per sample VOC detection summary

m-Xylene plus 

p-Xylene 

(μg/L) 

(85795)

o-Xylene 

(μg/L) 

(77135)

Ethylbenzene 

(μg/L) 

(34371)

Toluene 

(μg/L) 

(34010)

1,2,3-Trimethylbenzene 

(μg/L) 

(77221)

1,2,4-Trimethylbenzene 

(μg/L) 

(77222)

Dichlorodifluoromethane 

(CFC-12) 

(μg/L) (34668)

 1,1,2-Trichloro1,2,2-trifluoroethane 

(CFC-113) 

(μg/L) 

(77652)

Trichlorofluoromethane 

(CFC-11) 

(μg/L) 

(34488)

Benchmark type1 MCL-CA MCL-CA MCL-CA MCL-CA na NL-CA NL-CA MCL-CA MCL-CABenchmark level 7 1,750 7 1,750 300 10 na 330 1,000 1,200 150[LRL or SRL]2 [0.33] [0.12] [0.06] [0.69] [0.06, 0.08] [0.56] [0.1, 0.18] [0.038, 0.04] [0.08, 0.16] Northern San Joaquin Basin study unit—ContinuedNSJ-QPC-04 1/24/2005

—

—

— ≤0.01 5 —

—

—

—

— 0

NSJ-QPC-04 4/1/2008

—

—

—

—

—

—

—

—

— 0

TRCY-03 1/6/2005

—

—

—

—

— ≤0.08 5 —

—

— 1

TRCY-03 3/31/2008

—

—

—

—

—

—

—

—

— 1

 Southern Sacramento Valley study unitNAM-03 3/29/2005

—

—

—

—

—

—

—

—

— 1

NAM-03 4/10/2008

—

—

—

—

—

—

—

—

— 3

SAM-10 4/21/2005

—

—

—

—

—

—

—

—

— 3

SAM-10 4/8/2008

—

—

—

—

—

—

—

—

— 3

SOL-08 5/10/2005

—

—

—

—

—

—

—

—

— 0

SOL-08 4/8/2008

—

—

—

—

—

—

—

—

— 0

SSV-QPC-07 4/4/2005

—

—

—

—

—

—

—

—

— 1

SSV-QPC-07 4/10/2008

—

—

—

—

—

—

—

—

— 1

SUI-03 5/12/2005

—

—

—

—

—

—

—

—

— 0

SUI-03 4/9/2008

—

—

— ≤0.43 5 —

—

—

—

— 0

YOL-01 4/11/2005

—

—

—

—

—

—

—

—

— 1

Table 5. Volatile organic compounds (VOCs) in samples collected from trend wells for seven Groundwater Ambient Monitoring and Assessment (GAMA) study units.—Continued[The five-digit USGS parameter code below the constituent name is used to uniquely identify a specific constituent or property. VOCs were analyzed in samples from 55 trend wells during 2004–05 and 2007–08. Information about analytes given in table 3A. GAMA well identification number acronyms: San Diego Drainages study unit: SDALLV, Alluvial Basins study area; SDHDRK, Hard Rock study area; SDTEM, Temecula Valley study area; SDTEMFP, Temecula Valley study area flow-path well; SDWARN, Warner Valley study area. North San Francisco Bay study unit: NSFVOL, Volcanic Highlands study area; NSFVP, Valley and Plains study area; NSFWG, Wilson Grove Formation Highlands study area; NSFWGFP, Wilson Grove Formation Highlands study area flow-path well. Northern San Joaquin Basin study unit: COS, Cosumnes Basin study area; ESJ, Eastern San Joaquin Basin study area; NSJ-QPC, Uplands study area; TRCY, Tracy Basin study area. Southern Sacramento Valley study unit: NAM, North American study area; SAM, South American study area; SOL, Solano study area; SSV-QPC, Uplands study area; SUI, Suisun-Fairfield study area; YOL, Yolo study area. San Fernando–San Gabriel study unit: ULASF, San Fernando study area; ULASG, San Gabriel study area. Monterey Bay and Salinas Valley Basins study unit: MSMB, Monterey Bay study area; MSPR, Paso Robles study area; MSSC, Santa Cruz study area; MSSV, Salinas Valley study area. Southeast San Joaquin Valley study unit: KING, Kings study area; KWH, Kaweah study area; TLR, Tulare Lake study area; TULE, Tule study area. Benchmark type: MCL-US, USEPA maximum contaminant level; MCL-CA, CDPH maximum contaminant level; HAL-US, USEPA lifetime health advisory level; NL-CA, CDPH notification level. Benchmark type and benchmark level as of April 1, 2010. Other abbreviations: USGS, U.S. Geological Survey; USEPA, U.S. Environmental Protection Agency; CDPH, California Department of Public Health; μg/L, micrograms per liter; LRL, laboratory reporting level; SRL, study reporting level; *, value greater than benchmark level; E, estimated or having a higher degree of uncertainty; ≤, less than or equal to; —, not detected]
Tables 85

GAMA well 

identification 

number

Sample 

dates

Gasoline hydrocarbon Refrigerant

Detections 

per sample

VOC 

detection 

summary

m-Xylene plus 

p-Xylene 

(μg/L) 

(85795)

o-Xylene 

(μg/L) 

(77135)

Ethylbenzene 

(μg/L) 

(34371)

Toluene 

(μg/L) 

(34010)

1,2,3-Trimethylbenzene 

(μg/L) 

(77221)

1,2,4-Trimethylbenzene 

(μg/L) 

(77222)

Dichlorodifluoromethane 

(CFC-12) 

(μg/L) (34668)

 1,1,2-Trichloro1,2,2-trifluoroethane 

(CFC-113) 

(μg/L) 

(77652)

Trichlorofluoromethane 

(CFC-11) 

(μg/L) 

(34488)

Benchmark type1 MCL-CA MCL-CA MCL-CA MCL-CA na NL-CA NL-CA MCL-CA MCL-CABenchmark level 7 1,750 7 1,750 300 10 na 330 1,000 1,200 150[LRL or SRL]2 [0.33] [0.12] [0.06] [0.69] [0.06, 0.08] [0.56] [0.1, 0.18] [0.038, 0.04] [0.08, 0.16] Southern Sacramento Valley study unit—ContinuedYOL-01 4/7/2008 — — — — — — — — — 1YOL-14 5/25/2005 — — — — — — — — — 0YOL-14 4/9/2008 — — — ≤0.02 5 — — — — — 0 San Fernando–San Gabriel study unit ULASF-09 6/27/2005 — — — — — — E0.13 — — 9ULASF-09 6/16/2008 — — — — — — E0.11 — — 9ULASF-10 6/8/2005 — — — — — — E0.32 — — 8ULASF-10 6/16/2008 — — — — — — — — — 1ULASG-01 6/7/2005 — — — — — — — — — 3ULASG-01 6/16/2008 — — — — — — — — — 3ULASG-08 6/15/2005 — — — — — — — — — 10ULASG-08 6/17/2008 — — — — — — — — — 12ULASG-15 6/23/2005 — — — — — — — — — 0ULASG-15 6/17/2008 — — — — — ≤0.06 5 — — — 0ULASG-17 7/11/2005 — — — — — — — 1.26 E0.09 12ULASG-17 6/17/2008 — — — — — — — 1.94 0.13 10

Table 5. Volatile organic compounds (VOCs) in samples collected from trend wells for seven Groundwater Ambient Monitoring and Assessment (GAMA) study units.—Continued[The five-digit USGS parameter code below the constituent name is used to uniquely identify a specific constituent or property. VOCs were analyzed in samples from 55 trend wells during 2004–05 and 2007–08. Information about analytes given in table 3A. GAMA well identification number acronyms: San Diego Drainages study unit: SDALLV, Alluvial Basins study area; SDHDRK, Hard Rock study area; SDTEM, Temecula Valley study area; SDTEMFP, Temecula Valley study area flow-path well; SDWARN, Warner Valley study area. North San Francisco Bay study unit: NSFVOL, Volcanic Highlands study area; NSFVP, Valley and Plains study area; NSFWG, Wilson Grove Formation Highlands study area; NSFWGFP, Wilson Grove Formation Highlands study area flow-path well. Northern San Joaquin Basin study unit: COS, Cosumnes Basin study area; ESJ, Eastern San Joaquin Basin study area; NSJ-QPC, Uplands study area; TRCY, Tracy Basin study area. Southern Sacramento Valley study unit: NAM, North American study area; SAM, South American study area; SOL, Solano study area; SSV-QPC, Uplands study area; SUI, Suisun-Fairfield study area; YOL, Yolo study area. San Fernando–San Gabriel study unit: ULASF, San Fernando study area; ULASG, San Gabriel study area. Monterey Bay and Salinas Valley Basins study unit: MSMB, Monterey Bay study area; MSPR, Paso Robles study area; MSSC, Santa Cruz study area; MSSV, Salinas Valley study area. Southeast San Joaquin Valley study unit: KING, Kings study area; KWH, Kaweah study area; TLR, Tulare Lake study area; TULE, Tule study area. Benchmark type: MCL-US, USEPA maximum contaminant level; MCL-CA, CDPH maximum contaminant level; HAL-US, USEPA lifetime health advisory level; NL-CA, CDPH notification level. Benchmark type and benchmark level as of April 1, 2010. Other abbreviations: USGS, U.S. Geological Survey; USEPA, U.S. Environmental Protection Agency; CDPH, California Department of Public Health; μg/L, micrograms per liter; LRL, laboratory reporting level; SRL, study reporting level; *, value greater than benchmark level; E, estimated or having a higher degree of uncertainty; ≤, less than or equal to; —, not detected]
86 Groundwater-Quality Data in Seven GAMA Study Units: Results from Initial Sampling and Resampling of Wells GAMA well identification number Sample dates Gasoline hydrocarbon Refrigerant Detections per sample VOC detection summary

m-Xylene plus 

p-Xylene 

(μg/L) 

(85795)

o-Xylene 

(μg/L) 

(77135)

Ethylbenzene 

(μg/L) 

(34371)

Toluene 

(μg/L) 

(34010)

1,2,3-Trimethylbenzene 

(μg/L) 

(77221)

1,2,4-Trimethylbenzene 

(μg/L) 

(77222)

Dichlorodifluoromethane 

(CFC-12) 

(μg/L) (34668)

 1,1,2-Trichloro1,2,2-trifluoroethane 

(CFC-113) 

(μg/L) 

(77652)

Trichlorofluoromethane 

(CFC-11) 

(μg/L) 

(34488)

Benchmark type1 MCL-CA MCL-CA MCL-CA MCL-CA na NL-CA NL-CA MCL-CA MCL-CABenchmark level 7 1,750 7 1,750 300 10 na 330 1,000 1,200 150[LRL or SRL]2 [0.33] [0.12] [0.06] [0.69] [0.06, 0.08] [0.56] [0.1, 0.18] [0.038, 0.04] [0.08, 0.16] Monterey Bay and Salinas Valley Basins study unitMSMB-03 8/31/2005

—

—

—

—

—

—

—

—

— 0

MSMB-03 8/20/2008

—

—

—

—

—

—

—

—

— 0

MSMB-04 8/17/2005

—

—

—

—

—

—

—

—

— 0

MSMB-04 8/20/2008

—

—

—

—

—

—

—

—

— 0

MSMB-16 8/17/2005

—

—

—

—

—

—

—

—

— 5

MSMB-16 8/19/2008

—

—

—

—

—

—

—

—

— 4

MSMB-28 8/3/2005

—

—

—

—

—

—

—

—

— 0

MSMB-28 8/21/2008

—

—

—

—

—

—

—

—

— 0

MSMB-31 8/11/2005

—

—

—

—

—

—

—

—

— 1

MSMB-31 8/21/2008

—

—

—

—

—

—

—

—

— 0

MSPR-03 7/28/2005

—

—

—

—

—

—

—

—

— 0

MSPR-03 11/14/2008

—

—

—

—

—

—

—

—

— 0

MSPR-09 7/18/2005

—

—

—

—

—

—

—

—

— 0

MSPR-09 11/14/2008

—

—

—

—

—

—

—

—

— 0

MSSC-06 8/24/2005

—

—

—

—

—

—

—

—

— 1

MSSC-06 8/18/2008

—

—

—

—

—

—

—

—

— 1

MSSC-11 9/13/2005

—

—

—

—

—

—

—

—

— 0

Table 5. Volatile organic compounds (VOCs) in samples collected from trend wells for seven Groundwater Ambient Monitoring and Assessment (GAMA) study units.—Continued[The five-digit USGS parameter code below the constituent name is used to uniquely identify a specific constituent or property. VOCs were analyzed in samples from 55 trend wells during 2004–05 and 2007–08. Information about analytes given in table 3A. GAMA well identification number acronyms: San Diego Drainages study unit: SDALLV, Alluvial Basins study area; SDHDRK, Hard Rock study area; SDTEM, Temecula Valley study area; SDTEMFP, Temecula Valley study area flow-path well; SDWARN, Warner Valley study area. North San Francisco Bay study unit: NSFVOL, Volcanic Highlands study area; NSFVP, Valley and Plains study area; NSFWG, Wilson Grove Formation Highlands study area; NSFWGFP, Wilson Grove Formation Highlands study area flow-path well. Northern San Joaquin Basin study unit: COS, Cosumnes Basin study area; ESJ, Eastern San Joaquin Basin study area; NSJ-QPC, Uplands study area; TRCY, Tracy Basin study area. Southern Sacramento Valley study unit: NAM, North American study area; SAM, South American study area; SOL, Solano study area; SSV-QPC, Uplands study area; SUI, Suisun-Fairfield study area; YOL, Yolo study area. San Fernando–San Gabriel study unit: ULASF, San Fernando study area; ULASG, San Gabriel study area. Monterey Bay and Salinas Valley Basins study unit: MSMB, Monterey Bay study area; MSPR, Paso Robles study area; MSSC, Santa Cruz study area; MSSV, Salinas Valley study area. Southeast San Joaquin Valley study unit: KING, Kings study area; KWH, Kaweah study area; TLR, Tulare Lake study area; TULE, Tule study area. Benchmark type: MCL-US, USEPA maximum contaminant level; MCL-CA, CDPH maximum contaminant level; HAL-US, USEPA lifetime health advisory level; NL-CA, CDPH notification level. Benchmark type and benchmark level as of April 1, 2010. Other abbreviations: USGS, U.S. Geological Survey; USEPA, U.S. Environmental Protection Agency; CDPH, California Department of Public Health; μg/L, micrograms per liter; LRL, laboratory reporting level; SRL, study reporting level; *, value greater than benchmark level; E, estimated or having a higher degree of uncertainty; ≤, less than or equal to; —, not detected]
Tables 87

GAMA well 

identification 

number

Sample 

dates

Gasoline hydrocarbon Refrigerant

Detections 

per sample

VOC 

detection 

summary

m-Xylene plus 

p-Xylene 

(μg/L) 

(85795)

o-Xylene 

(μg/L) 

(77135)

Ethylbenzene 

(μg/L) 

(34371)

Toluene 

(μg/L) 

(34010)

1,2,3-Trimethylbenzene 

(μg/L) 

(77221)

1,2,4-Trimethylbenzene 

(μg/L) 

(77222)

Dichlorodifluoromethane 

(CFC-12) 

(μg/L) (34668)

 1,1,2-Trichloro1,2,2-trifluoroethane 

(CFC-113) 

(μg/L) 

(77652)

Trichlorofluoromethane 

(CFC-11) 

(μg/L) 

(34488)

Benchmark type1 MCL-CA MCL-CA MCL-CA MCL-CA na NL-CA NL-CA MCL-CA MCL-CABenchmark level 7 1,750 7 1,750 300 10 na 330 1,000 1,200 150[LRL or SRL]2 [0.33] [0.12] [0.06] [0.69] [0.06, 0.08] [0.56] [0.1, 0.18] [0.038, 0.04] [0.08, 0.16] Monterey Bay and Salinas Valley Basins study unit—ContinuedMSSC-11 8/19/2008 — — — — — — — — — 0MSSV-06 8/2/2005 — — — — — — — — — 0MSSV-06 11/13/2008 — — — — — — — — — 0MSSV-15 8/12/2005 — — — — — — — — — 0MSSV-15 11/13/2008 — — — — — — — — — 0 Southeast San Joaquin Valley study unitKING-11 10/20/2005 ≤0.04 5 — — — — — — — — 1KING-11 11/5/2008 — — — — — — E0.15 — — 2KING-13 10/20/2005 ≤0.04 5 — — — — — — — — 0KING-13 11/5/2008 — — — — — — — — — 0KING-17 10/26/2005 — — — — — — — — — 0KING-17 11/4/2008 — — — — — — — — — 0KING-24 11/5/2005 — — — — — — — — — 3KING-24 11/3/2008 — — — — — — — — — 2KWH-10 11/17/2005 — — — — — — — — — 2KWH-10 11/5/2008 — — — — — — — — — 2

Table 5. Volatile organic compounds (VOCs) in samples collected from trend wells for seven Groundwater Ambient Monitoring and Assessment (GAMA) study units.—Continued[The five-digit USGS parameter code below the constituent name is used to uniquely identify a specific constituent or property. VOCs were analyzed in samples from 55 trend wells during 2004–05 and 2007–08. Information about analytes given in table 3A. GAMA well identification number acronyms: San Diego Drainages study unit: SDALLV, Alluvial Basins study area; SDHDRK, Hard Rock study area; SDTEM, Temecula Valley study area; SDTEMFP, Temecula Valley study area flow-path well; SDWARN, Warner Valley study area. North San Francisco Bay study unit: NSFVOL, Volcanic Highlands study area; NSFVP, Valley and Plains study area; NSFWG, Wilson Grove Formation Highlands study area; NSFWGFP, Wilson Grove Formation Highlands study area flow-path well. Northern San Joaquin Basin study unit: COS, Cosumnes Basin study area; ESJ, Eastern San Joaquin Basin study area; NSJ-QPC, Uplands study area; TRCY, Tracy Basin study area. Southern Sacramento Valley study unit: NAM, North American study area; SAM, South American study area; SOL, Solano study area; SSV-QPC, Uplands study area; SUI, Suisun-Fairfield study area; YOL, Yolo study area. San Fernando–San Gabriel study unit: ULASF, San Fernando study area; ULASG, San Gabriel study area. Monterey Bay and Salinas Valley Basins study unit: MSMB, Monterey Bay study area; MSPR, Paso Robles study area; MSSC, Santa Cruz study area; MSSV, Salinas Valley study area. Southeast San Joaquin Valley study unit: KING, Kings study area; KWH, Kaweah study area; TLR, Tulare Lake study area; TULE, Tule study area. Benchmark type: MCL-US, USEPA maximum contaminant level; MCL-CA, CDPH maximum contaminant level; HAL-US, USEPA lifetime health advisory level; NL-CA, CDPH notification level. Benchmark type and benchmark level as of April 1, 2010. Other abbreviations: USGS, U.S. Geological Survey; USEPA, U.S. Environmental Protection Agency; CDPH, California Department of Public Health; μg/L, micrograms per liter; LRL, laboratory reporting level; SRL, study reporting level; *, value greater than benchmark level; E, estimated or having a higher degree of uncertainty; ≤, less than or equal to; —, not detected]
88 Groundwater-Quality Data in Seven GAMA Study Units: Results from Initial Sampling and Resampling of Wells GAMA well identification number Sample dates Gasoline hydrocarbon Refrigerant Detections per sample VOC detection summary

m-Xylene plus 

p-Xylene 

(μg/L) 

(85795)

o-Xylene 

(μg/L) 

(77135)

Ethylbenzene 

(μg/L) 

(34371)

Toluene 

(μg/L) 

(34010)

1,2,3-Trimethylbenzene 

(μg/L) 

(77221)

1,2,4-Trimethylbenzene 

(μg/L) 

(77222)

Dichlorodifluoromethane 

(CFC-12) 

(μg/L) (34668)

 1,1,2-Trichloro1,2,2-trifluoroethane 

(CFC-113) 

(μg/L) 

(77652)

Trichlorofluoromethane 

(CFC-11) 

(μg/L) 

(34488)

Benchmark type1 MCL-CA MCL-CA MCL-CA MCL-CA na NL-CA NL-CA MCL-CA MCL-CABenchmark level 7 1,750 7 1,750 300 10 na 330 1,000 1,200 150[LRL or SRL]2 [0.33] [0.12] [0.06] [0.69] [0.06, 0.08] [0.56] [0.1, 0.18] [0.038, 0.04] [0.08, 0.16] Southeast San Joaquin Valley study unit—ContinuedKWH-12 11/28/2005

—

—

—

—

—

—

—

—

— 2

KWH-12 11/6/2008

—

—

—

—

—

—

—

—

— 2

TLR-03 11/29/2005

—

—

—

—

—

—

—

—

— 0

TLR-03 11/4/2008

—

—

—

—

—

—

—

—

— 0

TULE-05 12/5/2005 ≤0.12 5 ≤0.06 5 ≤0.04 5 ≤0.09 5 E0.03 4 ≤0.02 5 — 0.31

— 9

TULE-05 11/3/2008

—

—

— ≤0.01 5 —

—

— 1.35

— 4

TULE-10 12/7/2005

—

—

—

—

—

—

—

—

— 3

TULE-10 11/3/2008

—

—

—

—

—

— E0.01 4 —

— 3

1 Maximum contaminant level benchmarks are listed as MCL-US when the MCL-US and the MCL-CA are identical and as MCL-CA when the MCL-CA is lower than the MCL-US or no MCL-US exists.2 For constituents with SRLs defined by Fram and others (2012), the SRL is given. For all other constituents, the minimum and maximum LRLs used during the study period are given.3 The MCL-US benchmark for trihalomethanes is for the sum of chloroform, bromoform, bromodichloromethane, and dibromochloromethane.4 The detected concentration was less than the LT-MDL for this constituent. These results are counted as non-detections for the purpose of calculating detection frequencies.5 The detected concentrations were less than the SRLs defined by Fram and others (2012). These results are counted as non-detections for the purpose of calculating detection frequencies.6 Detections of DBCP occurred only in samples from the Northern San Joaquin Basin and the Southeast San Joaquin Valley study units, for which samples were analyzed by Laboratory Schedule 1306 

(table 3B) in addition to Schedule 2020 (table 3A). Schedule 1306 is the preferred method and has a lower LRL at 0.030 μg/L than does Schedule 2020 at between 0.5 and 1 μg/L. Therefore, results for this compound are by Schedule 1306 for these two study units. The detections in 2008 for the wells KING-24 and TULE-10 were confirmed by Schedule 2020 analysis, with detections at concentrations similar to those determined by Schedule 1306 analysis. The other six occurrences of DBCP detected by Laboratory Schedule 1306 were not detected by Laboratory Schedule 2020. 

7 The MCL-CA benchmark for 

m- plus 

p-xylene and o-xylene is for the sum of all three xylene compounds.

Table 5. Volatile organic compounds (VOCs) in samples collected from trend wells for seven Groundwater Ambient Monitoring and Assessment (GAMA) study units.—Continued[The five-digit USGS parameter code below the constituent name is used to uniquely identify a specific constituent or property. VOCs were analyzed in samples from 55 trend wells during 2004–05 and 2007–08. Information about analytes given in table 3A. GAMA well identification number acronyms: San Diego Drainages study unit: SDALLV, Alluvial Basins study area; SDHDRK, Hard Rock study area; SDTEM, Temecula Valley study area; SDTEMFP, Temecula Valley study area flow-path well; SDWARN, Warner Valley study area. North San Francisco Bay study unit: NSFVOL, Volcanic Highlands study area; NSFVP, Valley and Plains study area; NSFWG, Wilson Grove Formation Highlands study area; NSFWGFP, Wilson Grove Formation Highlands study area flow-path well. Northern San Joaquin Basin study unit: COS, Cosumnes Basin study area; ESJ, Eastern San Joaquin Basin study area; NSJ-QPC, Uplands study area; TRCY, Tracy Basin study area. Southern Sacramento Valley study unit: NAM, North American study area; SAM, South American study area; SOL, Solano study area; SSV-QPC, Uplands study area; SUI, Suisun-Fairfield study area; YOL, Yolo study area. San Fernando–San Gabriel study unit: ULASF, San Fernando study area; ULASG, San Gabriel study area. Monterey Bay and Salinas Valley Basins study unit: MSMB, Monterey Bay study area; MSPR, Paso Robles study area; MSSC, Santa Cruz study area; MSSV, Salinas Valley study area. Southeast San Joaquin Valley study unit: KING, Kings study area; KWH, Kaweah study area; TLR, Tulare Lake study area; TULE, Tule study area. Benchmark type: MCL-US, USEPA maximum contaminant level; MCL-CA, CDPH maximum contaminant level; HAL-US, USEPA lifetime health advisory level; NL-CA, CDPH notification level. Benchmark type and benchmark level as of April 1, 2010. Other abbreviations: USGS, U.S. Geological Survey; USEPA, U.S. Environmental Protection Agency; CDPH, California Department of Public Health; μg/L, micrograms per liter; LRL, laboratory reporting level; SRL, study reporting level; *, value greater than benchmark level; E, estimated or having a higher degree of uncertainty; ≤, less than or equal to; —, not detected]
Tables 89

Table 6A. Pesticides and pesticide degradates (Schedules 2003, 2032, and 2033) in samples collected from trend wells for seven Groundwater Ambient Monitoring and Assessment (GAMA) study units.[The five-digit USGS parameter code below the constituent name is used to uniquely identify a specific constituent or property. Pesticides and degradates were analyzed in samples from 54 trend wells in 2004–05 and 54 trend wells in 2007–08; samples from 53 trend wells were analyzed during both time periods. Information about analytes given in table 3C. GAMA well identification number acronyms: San Diego Drainages study unit: SDALLV, Alluvial Basins study area; SDHDRK, Hard Rock study area; SDTEM, Temecula Valley study area; SDTEMFP, Temecula Valley study area flow-path well; SDWARN, Warner Valley study area. North San Francisco Bay study unit: NSFVOL, Volcanic Highlands study area; NSFVP, Valley and Plains study area; NSFWG, Wilson Grove Formation Highlands study area; NSFWGFP, Wilson Grove Formation Highlands study area flow-path well. Northern San Joaquin Basin study unit: COS, Cosumnes Basin study area; ESJ, Eastern San Joaquin Basin study area; NSJ-QPC, Uplands study area; TRCY, Tracy Basin study area. Southern Sacramento Valley study unit: NAM, North American study area; SAM, South American study area; SOL, Solano study area; SSV-QPC, Uplands study area; SUI, Suisun-Fairfield study area; YOL, Yolo study area. San Fernando–San Gabriel study unit: ULASF, San Fernando study area; ULASG, San Gabriel study area. Monterey Bay and Salinas Valley Basins study unit: MSMB, Monterey Bay study area; MSPR, Paso Robles study area; MSSC, Santa Cruz study area; MSSV, Salinas Valley study area. Southeast San Joaquin Valley study unit: KING, Kings study area; KWH, Kaweah study area; TLR, Tulare Lake study area; TULE, Tule study area. Benchmark type: MCL-US, USEPA maximum contaminant level; MCL-CA, California Department of Public Health maximum contaminant level; HAL-US, USEPA lifetime health advisory level; RSD5-US, USEPA risk-specific dose at a factor of 10–5. Benchmark type and benchmark level as of April 1, 2010. Other abbreviations: USGS, U.S. Geological Survey; USEPA, U.S. Environmental Protection Agency; μg/L, micrograms per liter; na, not available; nc, not collected; —, not detected; E, estimated or having a higher degree of uncertainty]

GAMA 

well 

identification 

number

Sample dates

Herbicide Herbicide degradate

Simazine 

(μg/L) 

(04035)

Atrazine 

(μg/L) 

(39632)

Tebuthiuron 

(μg/L) 

(82670)

Prometon 

(μg/L) 

(04037)

Hexazinone 

(μg/L) 

(04025)

EPTC 

(S-Ethyl depropylthio-carbamate) 

(μg/L) 

(82668)

DCPA 

(Dacthal)

(μg/L) 

(82682)

Trifluralin 

(μg/L) 

(82661)

Deethylatrazine 

(2-Chloro-4-isopropylamino6-amino-s-triazine) 

(μg/L) 

(04040)

Benchmark type MCL-US MCL-CA HAL-US HAL-US HAL-US na HAL-US HAL-US naBenchmark level 4 1 500 100 400 na 70 10 na[LRL]1 [0.005, 0.010] [0.007] [0.016, 0.020] [0.005, 0.012] [0.008, 0.026] [0.002, 0.004] [0.003, 0.006] [0.009, 0.012] [0.006, 0.014]Number of trend wells with detections 

2004–05

20 15 5 3 2 1 1 0 15

Detection frequency (percent) 2004–05 37 28 9 6 4 na2 2 0 28Number of trend wells with detections 

2007–08

17 14 5 5 2 1 0 0 12

Detection frequency (percent) 2007–08 31 26 9 9 4 na2 0 0 22San Diego Drainages study unitSDALLV-07 7/14/2004 0.008 — — — — nc — — E0.006SDALLV-07 9/12/2007 E0.007 — — — — nc — — —SDALLV-11 7/15/2004 0.026 E0.007 E0.088 0.015 — nc — — E0.006SDALLV-11 9/13/2007 0.010 — E0.145 0.027 — nc — — E0.005 3SDHDRK-01 7/12/2004 0.027 0.085 E0.025 0.007 — nc — — E0.013SDHDRK-01 9/13/2007 0.020 0.050 E0.018 E0.007 — nc — — E0.014SDHDRK-09 7/27/2004 0.006 — — — — nc — — E0.006SDHDRK-09 9/11/2007 E0.006 — — — — nc — — E0.004 3SDTEM-04 5/24/2004 — — — — — nc — — —SDTEM-04 9/18/2007 nc nc nc nc nc nc nc nc ncSDTEMFP-01 5/19/2004 0.006 — — — — nc — — —
90 Groundwater-Quality Data in Seven GAMA Study Units: Results from Initial Sampling and Resampling of Wells GAMA well identification number Sample dates Herbicide Herbicide degradate Simazine (μg/L) (04035) Atrazine (μg/L) (39632) Tebuthiuron (μg/L) (82670) Prometon (μg/L) (04037) Hexazinone (μg/L) (04025) EPTC 

(S-Ethyl depropylthio-carbamate) 

(μg/L) 

(82668)

DCPA 

(Dacthal) 

(μg/L) 

(82682)

Trifluralin 

(μg/L) 

(82661)

Deethylatrazine 

(2-Chloro-4-isopropylamino6-amino-s-triazine) 

(μg/L) 

(04040)

Benchmark type MCL-US MCL-CA HAL-US HAL-US HAL-US na HAL-US HAL-US naBenchmark level 4 1 500 100 400 na 70 10 na[LRL]1 [0.005, 0.010] [0.007] [0.016, 0.020] [0.005, 0.012] [0.008, 0.026] [0.002, 0.004] [0.003, 0.006] [0.009, 0.012] [0.006, 0.014]San Diego Drainages study unit—ContinuedSDTEMFP-01 9/19/2007 E0.005

—

—

—

— nc

—

—

—

SDWARN-01 6/17/2004

—

—

—

—

— nc

—

—

—

SDWARN-01 9/11/2007

—

—

—

—

— nc

—

—

—

North San Francisco Bay study unitNSFVOL-14 10/7/2004

—

—

—

—

— nc

—

—

—

NSFVOL-14 8/21/2007

—

—

—

—

— nc

—

—

—

NSFVOL-18 10/20/2004

—

—

—

—

— nc

—

—

—

NSFVOL-18 8/28/2007

—

—

—

—

— nc

—

—

—

NSFVP-29 9/28/2004 0.009

—

—

—

— nc

—

—

—

NSFVP-29 8/27/2007 0.010

—

—

—

— nc

—

—

—

NSFVP-34 10/18/2004

—

—

—

—

— nc

—

—

—

NSFVP-34 8/22/2007

—

—

—

—

— nc

—

—

—

NSFVP-36 10/19/2004

—

—

—

—

— nc

—

—

—

NSFVP-36 8/20/2007

—

—

—

—

— nc

—

—

—

NSFVP-38 10/20/2004

—

—

—

—

— nc

—

—

—

NSFVP-38 8/22/2007

—

—

—

—

— nc

—

—

—

Table 6A. Pesticides and pesticide degradates (Schedules 2003, 2032, and 2033) in samples collected from trend wells for seven Groundwater Ambient Monitoring and Assessment (GAMA) study units.—Continued[The five-digit USGS parameter code below the constituent name is used to uniquely identify a specific constituent or property. Pesticides and degradates were analyzed in samples from 54 trend wells in 2004–05 and 54 trend wells in 2007–08; samples from 53 trend wells were analyzed during both time periods. Information about analytes given in table 3C. GAMA well identification number acronyms: San Diego Drainages study unit: SDALLV, Alluvial Basins study area; SDHDRK, Hard Rock study area; SDTEM, Temecula Valley study area; SDTEMFP, Temecula Valley study area flow-path well; SDWARN, Warner Valley study area. North San Francisco Bay study unit: NSFVOL, Volcanic Highlands study area; NSFVP, Valley and Plains study area; NSFWG, Wilson Grove Formation Highlands study area; NSFWGFP, Wilson Grove Formation Highlands study area flow-path well. Northern San Joaquin Basin study unit: COS, Cosumnes Basin study area; ESJ, Eastern San Joaquin Basin study area; NSJ-QPC, Uplands study area; TRCY, Tracy Basin study area. Southern Sacramento Valley study unit: NAM, North American study area; SAM, South American study area; SOL, Solano study area; SSV-QPC, Uplands study area; SUI, Suisun-Fairfield study area; YOL, Yolo study area. San Fernando–San Gabriel study unit: ULASF, San Fernando study area; ULASG, San Gabriel study area. Monterey Bay and Salinas Valley Basins study unit: MSMB, Monterey Bay study area; MSPR, Paso Robles study area; MSSC, Santa Cruz study area; MSSV, Salinas Valley study area. Southeast San Joaquin Valley study unit: KING, Kings study area; KWH, Kaweah study area; TLR, Tulare Lake study area; TULE, Tule study area. Benchmark type: MCL-US, USEPA maximum contaminant level; MCL-CA, California Department of Public Health maximum contaminant level; HAL-US, USEPA lifetime health advisory level; RSD5-US, USEPA risk-specific dose at a factor of 10–5. Benchmark type and benchmark level as of April 1, 2010. Other abbreviations: USGS, U.S. Geological Survey; USEPA, U.S. Environmental Protection Agency; μg/L, micrograms per liter; na, not available; nc, not collected; —, not detected; E, estimated or having a higher degree of uncertainty]
Tables 91

GAMA 

well 

identification 

number

Sample dates

Herbicide Herbicide degradate

Simazine 

(μg/L) 

(04035)

Atrazine 

(μg/L) 

(39632)

Tebuthiuron 

(μg/L) 

(82670)

Prometon 

(μg/L) 

(04037)

Hexazinone 

(μg/L) 

(04025)

EPTC 

(S-Ethyl depropylthio-carbamate) 

(μg/L) 

(82668)

DCPA 

(Dacthal) 

(μg/L) 

(82682)

Trifluralin 

(μg/L) 

(82661)

Deethylatrazine 

(2-Chloro-4-isopropylamino6-amino-s-triazine) 

(μg/L) 

(04040)

Benchmark type MCL-US MCL-CA HAL-US HAL-US HAL-US na HAL-US HAL-US naBenchmark level 4 1 500 100 400 na 70 10 na[LRL]1 [0.005, 0.010] [0.007] [0.016, 0.020] [0.005, 0.012] [0.008, 0.026] [0.002, 0.004] [0.003, 0.006] [0.009, 0.012] [0.006, 0.014]North San Francisco Bay study unit—ContinuedNSFVP-39 10/21/2004 — — — — — nc — — —NSFVP-39 11/16/2007 — — — — — nc — — —NSFVP-41 10/21/2004 — — — — — nc — — —NSFVP-41 8/20/2007 — — — — — nc — — —NSFWG-03 9/21/2004 — — — — — nc — — —NSFWG-03 8/29/2007 — — — — — nc — — —NSFWGFP-01 10/5/2004 — E0.006 — — — nc — — —NSFWGFP-01 8/29/2007 — — — — — nc — — —Northern San Joaquin Basin study unitCOS-08 1/3/2005 — — — — — nc — — —COS-08 4/3/2008 — — — — — nc — — —ESJ-01 1/24/2005 0.008 0.011 — — — nc — — E0.007ESJ-01 4/2/2008 E0.006 E0.007 — — — nc — — E0.008ESJ-06 1/10/2005 — — — — — nc — — —ESJ-06 4/2/2008 — — — — — nc — — —NSJ-QPC-04 1/24/2005 — — — — — nc — — —

Table 6A. Pesticides and pesticide degradates (Schedules 2003, 2032, and 2033) in samples collected from trend wells for seven Groundwater Ambient Monitoring and Assessment (GAMA) study units.—Continued[The five-digit USGS parameter code below the constituent name is used to uniquely identify a specific constituent or property. Pesticides and degradates were analyzed in samples from 54 trend wells in 2004–05 and 54 trend wells in 2007–08; samples from 53 trend wells were analyzed during both time periods. Information about analytes given in table 3C. GAMA well identification number acronyms: San Diego Drainages study unit: SDALLV, Alluvial Basins study area; SDHDRK, Hard Rock study area; SDTEM, Temecula Valley study area; SDTEMFP, Temecula Valley study area flow-path well; SDWARN, Warner Valley study area. North San Francisco Bay study unit: NSFVOL, Volcanic Highlands study area; NSFVP, Valley and Plains study area; NSFWG, Wilson Grove Formation Highlands study area; NSFWGFP, Wilson Grove Formation Highlands study area flow-path well. Northern San Joaquin Basin study unit: COS, Cosumnes Basin study area; ESJ, Eastern San Joaquin Basin study area; NSJ-QPC, Uplands study area; TRCY, Tracy Basin study area. Southern Sacramento Valley study unit: NAM, North American study area; SAM, South American study area; SOL, Solano study area; SSV-QPC, Uplands study area; SUI, Suisun-Fairfield study area; YOL, Yolo study area. San Fernando–San Gabriel study unit: ULASF, San Fernando study area; ULASG, San Gabriel study area. Monterey Bay and Salinas Valley Basins study unit: MSMB, Monterey Bay study area; MSPR, Paso Robles study area; MSSC, Santa Cruz study area; MSSV, Salinas Valley study area. Southeast San Joaquin Valley study unit: KING, Kings study area; KWH, Kaweah study area; TLR, Tulare Lake study area; TULE, Tule study area. Benchmark type: MCL-US, USEPA maximum contaminant level; MCL-CA, California Department of Public Health maximum contaminant level; HAL-US, USEPA lifetime health advisory level; RSD5-US, USEPA risk-specific dose at a factor of 10–5. Benchmark type and benchmark level as of April 1, 2010. Other abbreviations: USGS, U.S. Geological Survey; USEPA, U.S. Environmental Protection Agency; μg/L, micrograms per liter; na, not available; nc, not collected; —, not detected; E, estimated or having a higher degree of uncertainty]
92 Groundwater-Quality Data in Seven GAMA Study Units: Results from Initial Sampling and Resampling of Wells GAMA well identification number Sample dates Herbicide Herbicide degradate Simazine (μg/L) (04035) Atrazine (μg/L) (39632) Tebuthiuron (μg/L) (82670) Prometon (μg/L) (04037) Hexazinone (μg/L) (04025) EPTC 

(S-Ethyl depropylthio-carbamate) 

(μg/L) 

(82668)

DCPA 

(Dacthal) 

(μg/L) 

(82682)

Trifluralin 

(μg/L) 

(82661)

Deethylatrazine 

(2-Chloro-4-isopropylamino6-amino-s-triazine) 

(μg/L) 

(04040)

Benchmark type MCL-US MCL-CA HAL-US HAL-US HAL-US na HAL-US HAL-US naBenchmark level 4 1 500 100 400 na 70 10 na[LRL]1 [0.005, 0.010] [0.007] [0.016, 0.020] [0.005, 0.012] [0.008, 0.026] [0.002, 0.004] [0.003, 0.006] [0.009, 0.012] [0.006, 0.014]Northern San Joaquin Basin study unit—ContinuedNSJ-QPC-04 4/1/2008

—

—

—

—

— nc

—

— E0.008

TRCY-03 1/6/2005

—

—

—

—

— nc

—

—

—

TRCY-03 3/31/2008

—

—

—

—

— nc

—

—

—

Southern Sacramento Valley study unit NAM-03 3/29/2005

—

—

—

—

— nc

—

—

—

NAM-03 4/10/2008

—

—

—

—

— nc

—

—

—

SAM-10 4/21/2005

—

—

—

—

— nc

—

—

—

SAM-10 4/8/2008

—

—

—

—

— nc

—

—

—

SOL-08 5/10/2005

—

—

—

—

— nc

—

—

—

SOL-08 4/8/2008

—

—

—

—

— nc

—

—

—

SSV-QPC-07 4/4/2005

—

—

—

—

— nc

—

—

—

SSV-QPC-07 4/10/2008

—

—

—

—

— nc

—

— E0.005 3

SUI-03 5/12/2005 nc nc nc nc nc nc nc nc ncSUI-03 4/9/2008

— E0.006

—

—

— nc

—

—

—

YOL-01 4/11/2005

—

—

—

—

— nc

—

—

—

YOL-01 4/7/2008

—

—

—

—

— nc

—

—

—

Table 6A. Pesticides and pesticide degradates (Schedules 2003, 2032, and 2033) in samples collected from trend wells for seven Groundwater Ambient Monitoring and Assessment (GAMA) study units.—Continued[The five-digit USGS parameter code below the constituent name is used to uniquely identify a specific constituent or property. Pesticides and degradates were analyzed in samples from 54 trend wells in 2004–05 and 54 trend wells in 2007–08; samples from 53 trend wells were analyzed during both time periods. Information about analytes given in table 3C. GAMA well identification number acronyms: San Diego Drainages study unit: SDALLV, Alluvial Basins study area; SDHDRK, Hard Rock study area; SDTEM, Temecula Valley study area; SDTEMFP, Temecula Valley study area flow-path well; SDWARN, Warner Valley study area. North San Francisco Bay study unit: NSFVOL, Volcanic Highlands study area; NSFVP, Valley and Plains study area; NSFWG, Wilson Grove Formation Highlands study area; NSFWGFP, Wilson Grove Formation Highlands study area flow-path well. Northern San Joaquin Basin study unit: COS, Cosumnes Basin study area; ESJ, Eastern San Joaquin Basin study area; NSJ-QPC, Uplands study area; TRCY, Tracy Basin study area. Southern Sacramento Valley study unit: NAM, North American study area; SAM, South American study area; SOL, Solano study area; SSV-QPC, Uplands study area; SUI, Suisun-Fairfield study area; YOL, Yolo study area. San Fernando–San Gabriel study unit: ULASF, San Fernando study area; ULASG, San Gabriel study area. Monterey Bay and Salinas Valley Basins study unit: MSMB, Monterey Bay study area; MSPR, Paso Robles study area; MSSC, Santa Cruz study area; MSSV, Salinas Valley study area. Southeast San Joaquin Valley study unit: KING, Kings study area; KWH, Kaweah study area; TLR, Tulare Lake study area; TULE, Tule study area. Benchmark type: MCL-US, USEPA maximum contaminant level; MCL-CA, California Department of Public Health maximum contaminant level; HAL-US, USEPA lifetime health advisory level; RSD5-US, USEPA risk-specific dose at a factor of 10–5. Benchmark type and benchmark level as of April 1, 2010. Other abbreviations: USGS, U.S. Geological Survey; USEPA, U.S. Environmental Protection Agency; μg/L, micrograms per liter; na, not available; nc, not collected; —, not detected; E, estimated or having a higher degree of uncertainty]
Tables 93

GAMA 

well 

identification 

number

Sample dates

Herbicide Herbicide degradate

Simazine 

(μg/L) 

(04035)

Atrazine 

(μg/L) 

(39632)

Tebuthiuron 

(μg/L) 

(82670)

Prometon 

(μg/L) 

(04037)

Hexazinone 

(μg/L) 

(04025)

EPTC 

(S-Ethyl depropylthio-carbamate) 

(μg/L) 

(82668)

DCPA 

(Dacthal) 

(μg/L) 

(82682)

Trifluralin 

(μg/L) 

(82661)

Deethylatrazine 

(2-Chloro-4-isopropylamino6-amino-s-triazine) 

(μg/L) 

(04040)

Benchmark type MCL-US MCL-CA HAL-US HAL-US HAL-US na HAL-US HAL-US naBenchmark level 4 1 500 100 400 na 70 10 na[LRL]1 [0.005, 0.010] [0.007] [0.016, 0.020] [0.005, 0.012] [0.008, 0.026] [0.002, 0.004] [0.003, 0.006] [0.009, 0.012] [0.006, 0.014]Southern Sacramento Valley study unit—ContinuedYOL-14 5/25/2005 — — — — — nc — — —YOL-14 4/9/2008 — — — — — nc — — —San Fernando–San Gabriel study unit ULASF-09 6/27/2005 0.044 0.026 E0.016 — — nc — — E0.014ULASF-09 6/16/2008 0.022 0.014 E0.009 — — nc — — E0.013ULASF-10 6/8/2005 0.005 0.009 — — — nc — — E0.007ULASF-10 6/16/2008 — — — — — nc — — —ULASG-01 6/7/2005 0.072 0.020 0.025 — — nc — — E0.018ULASG-01 6/16/2008 0.065 0.020 0.022 — — nc — — E0.029ULASG-08 6/15/2005 0.010 0.029 — — — nc — — E0.021ULASG-08 6/17/2008 0.010 0.008 — E0.006 — nc — — E0.008ULASG-15 6/23/2005 0.008 — — — — nc — — —ULASG-15 6/17/2008 0.008 — — — — nc — — —ULASG-17 7/11/2005 0.012 0.047 0.143 — 0.058 nc — — E0.037ULASG-17 6/17/2008 0.011 0.034 0.081 — 0.038 nc — — E0.031

Table 6A. Pesticides and pesticide degradates (Schedules 2003, 2032, and 2033) in samples collected from trend wells for seven Groundwater Ambient Monitoring and Assessment (GAMA) study units.—Continued[The five-digit USGS parameter code below the constituent name is used to uniquely identify a specific constituent or property. Pesticides and degradates were analyzed in samples from 54 trend wells in 2004–05 and 54 trend wells in 2007–08; samples from 53 trend wells were analyzed during both time periods. Information about analytes given in table 3C. GAMA well identification number acronyms: San Diego Drainages study unit: SDALLV, Alluvial Basins study area; SDHDRK, Hard Rock study area; SDTEM, Temecula Valley study area; SDTEMFP, Temecula Valley study area flow-path well; SDWARN, Warner Valley study area. North San Francisco Bay study unit: NSFVOL, Volcanic Highlands study area; NSFVP, Valley and Plains study area; NSFWG, Wilson Grove Formation Highlands study area; NSFWGFP, Wilson Grove Formation Highlands study area flow-path well. Northern San Joaquin Basin study unit: COS, Cosumnes Basin study area; ESJ, Eastern San Joaquin Basin study area; NSJ-QPC, Uplands study area; TRCY, Tracy Basin study area. Southern Sacramento Valley study unit: NAM, North American study area; SAM, South American study area; SOL, Solano study area; SSV-QPC, Uplands study area; SUI, Suisun-Fairfield study area; YOL, Yolo study area. San Fernando–San Gabriel study unit: ULASF, San Fernando study area; ULASG, San Gabriel study area. Monterey Bay and Salinas Valley Basins study unit: MSMB, Monterey Bay study area; MSPR, Paso Robles study area; MSSC, Santa Cruz study area; MSSV, Salinas Valley study area. Southeast San Joaquin Valley study unit: KING, Kings study area; KWH, Kaweah study area; TLR, Tulare Lake study area; TULE, Tule study area. Benchmark type: MCL-US, USEPA maximum contaminant level; MCL-CA, California Department of Public Health maximum contaminant level; HAL-US, USEPA lifetime health advisory level; RSD5-US, USEPA risk-specific dose at a factor of 10–5. Benchmark type and benchmark level as of April 1, 2010. Other abbreviations: USGS, U.S. Geological Survey; USEPA, U.S. Environmental Protection Agency; μg/L, micrograms per liter; na, not available; nc, not collected; —, not detected; E, estimated or having a higher degree of uncertainty]
94 Groundwater-Quality Data in Seven GAMA Study Units: Results from Initial Sampling and Resampling of Wells GAMA well identification number Sample dates Herbicide Herbicide degradate Simazine (μg/L) (04035) Atrazine (μg/L) (39632) Tebuthiuron (μg/L) (82670) Prometon (μg/L) (04037) Hexazinone (μg/L) (04025) EPTC 

(S-Ethyl depropylthio-carbamate) 

(μg/L) 

(82668)

DCPA 

(Dacthal) 

(μg/L) 

(82682)

Trifluralin 

(μg/L) 

(82661)

Deethylatrazine 

(2-Chloro-4-isopropylamino6-amino-s-triazine) 

(μg/L) 

(04040)

Benchmark type MCL-US MCL-CA HAL-US HAL-US HAL-US na HAL-US HAL-US naBenchmark level 4 1 500 100 400 na 70 10 na[LRL]1 [0.005, 0.010] [0.007] [0.016, 0.020] [0.005, 0.012] [0.008, 0.026] [0.002, 0.004] [0.003, 0.006] [0.009, 0.012] [0.006, 0.014]Monterey Bay and Salinas Valley Basins study unitMSMB-03 8/31/2005

—

—

—

—

— nc

—

—

—

MSMB-03 8/20/2008

—

—

—

—

— nc

—

—

—

MSMB-04 8/17/2005

—

—

—

—

— nc

—

—

—

MSMB-04 8/20/2008

— E0.007

—

—

— nc

—

—

—

MSMB-16 8/17/2005

—

—

—

—

— nc

—

—

—

MSMB-16 8/19/2008

—

—

—

—

— nc

—

—

—

MSMB-28 8/3/2005

—

—

—

—

— nc

—

—

—

MSMB-28 8/21/2008

—

—

—

—

— nc

—

—

—

MSMB-31 8/11/2005

—

—

—

—

— nc

—

—

—

MSMB-31 8/21/2008

—

—

—

—

— nc

—

— E0.005 3

MSPR-03 7/28/2005

—

—

—

—

— nc

—

—

—

MSPR-03 11/14/2008

—

—

—

—

— nc

—

—

—

MSPR-09 7/18/2005

— E0.006

—

—

— nc

—

— E0.005

MSPR-09 11/14/2008

— 0.008

—

—

— nc

—

— E0.007

MSSC-06 8/24/2005

—

—

—

—

— nc

—

—

—

MSSC-06 8/18/2008

—

—

—

—

— nc

—

—

—

MSSC-11 9/13/2005

—

—

—

—

— nc

—

—

—

Table 6A. Pesticides and pesticide degradates (Schedules 2003, 2032, and 2033) in samples collected from trend wells for seven Groundwater Ambient Monitoring and Assessment (GAMA) study units.—Continued[The five-digit USGS parameter code below the constituent name is used to uniquely identify a specific constituent or property. Pesticides and degradates were analyzed in samples from 54 trend wells in 2004–05 and 54 trend wells in 2007–08; samples from 53 trend wells were analyzed during both time periods. Information about analytes given in table 3C. GAMA well identification number acronyms: San Diego Drainages study unit: SDALLV, Alluvial Basins study area; SDHDRK, Hard Rock study area; SDTEM, Temecula Valley study area; SDTEMFP, Temecula Valley study area flow-path well; SDWARN, Warner Valley study area. North San Francisco Bay study unit: NSFVOL, Volcanic Highlands study area; NSFVP, Valley and Plains study area; NSFWG, Wilson Grove Formation Highlands study area; NSFWGFP, Wilson Grove Formation Highlands study area flow-path well. Northern San Joaquin Basin study unit: COS, Cosumnes Basin study area; ESJ, Eastern San Joaquin Basin study area; NSJ-QPC, Uplands study area; TRCY, Tracy Basin study area. Southern Sacramento Valley study unit: NAM, North American study area; SAM, South American study area; SOL, Solano study area; SSV-QPC, Uplands study area; SUI, Suisun-Fairfield study area; YOL, Yolo study area. San Fernando–San Gabriel study unit: ULASF, San Fernando study area; ULASG, San Gabriel study area. Monterey Bay and Salinas Valley Basins study unit: MSMB, Monterey Bay study area; MSPR, Paso Robles study area; MSSC, Santa Cruz study area; MSSV, Salinas Valley study area. Southeast San Joaquin Valley study unit: KING, Kings study area; KWH, Kaweah study area; TLR, Tulare Lake study area; TULE, Tule study area. Benchmark type: MCL-US, USEPA maximum contaminant level; MCL-CA, California Department of Public Health maximum contaminant level; HAL-US, USEPA lifetime health advisory level; RSD5-US, USEPA risk-specific dose at a factor of 10–5. Benchmark type and benchmark level as of April 1, 2010. Other abbreviations: USGS, U.S. Geological Survey; USEPA, U.S. Environmental Protection Agency; μg/L, micrograms per liter; na, not available; nc, not collected; —, not detected; E, estimated or having a higher degree of uncertainty]
Tables 95

GAMA 

well 

identification 

number

Sample dates

Herbicide Herbicide degradate

Simazine 

(μg/L) 

(04035)

Atrazine 

(μg/L) 

(39632)

Tebuthiuron 

(μg/L) 

(82670)

Prometon 

(μg/L) 

(04037)

Hexazinone 

(μg/L) 

(04025)

EPTC 

(S-Ethyl depropylthio-carbamate) 

(μg/L) 

(82668)

DCPA 

(Dacthal) 

(μg/L) 

(82682)

Trifluralin 

(μg/L) 

(82661)

Deethylatrazine 

(2-Chloro-4-isopropylamino6-amino-s-triazine) 

(μg/L) 

(04040)

Benchmark type MCL-US MCL-CA HAL-US HAL-US HAL-US na HAL-US HAL-US naBenchmark level 4 1 500 100 400 na 70 10 na[LRL]1 [0.005, 0.010] [0.007] [0.016, 0.020] [0.005, 0.012] [0.008, 0.026] [0.002, 0.004] [0.003, 0.006] [0.009, 0.012] [0.006, 0.014]Monterey Bay and Salinas Valley Basins study unit—ContinuedMSSC-11 8/19/2008 — — — — — nc — — —MSSV-06 8/2/2005 E0.005 — — — — nc — — —MSSV-06 11/13/2008 — — — — — nc — — —MSSV-15 8/12/2005 E0.006 — — — — nc E0.002 — —MSSV-15 11/13/2008 — — — — — nc — — —Southeast San Joaquin Valley study unitKING-11 10/20/2005 — — — — — — — — —KING-11 11/5/2008 — — — — — — — — —KING-13 10/20/2005 — — — — — — — — —KING-13 11/5/2008 — — — — — — — — —KING-17 10/26/2005 — — — — — — — — —KING-17 11/4/2008 — — — — — — — — —KING-24 11/5/2005 0.012 0.015 — — — — — — —KING-24 11/3/2008 0.088 0.019 — E0.005 — — — — —KWH-10 11/17/2005 0.024 0.009 — — — — — — E0.007KWH-10 11/5/2008 0.031 E0.006 — — — — — — E0.012

Table 6A. Pesticides and pesticide degradates (Schedules 2003, 2032, and 2033) in samples collected from trend wells for seven Groundwater Ambient Monitoring and Assessment (GAMA) study units.—Continued[The five-digit USGS parameter code below the constituent name is used to uniquely identify a specific constituent or property. Pesticides and degradates were analyzed in samples from 54 trend wells in 2004–05 and 54 trend wells in 2007–08; samples from 53 trend wells were analyzed during both time periods. Information about analytes given in table 3C. GAMA well identification number acronyms: San Diego Drainages study unit: SDALLV, Alluvial Basins study area; SDHDRK, Hard Rock study area; SDTEM, Temecula Valley study area; SDTEMFP, Temecula Valley study area flow-path well; SDWARN, Warner Valley study area. North San Francisco Bay study unit: NSFVOL, Volcanic Highlands study area; NSFVP, Valley and Plains study area; NSFWG, Wilson Grove Formation Highlands study area; NSFWGFP, Wilson Grove Formation Highlands study area flow-path well. Northern San Joaquin Basin study unit: COS, Cosumnes Basin study area; ESJ, Eastern San Joaquin Basin study area; NSJ-QPC, Uplands study area; TRCY, Tracy Basin study area. Southern Sacramento Valley study unit: NAM, North American study area; SAM, South American study area; SOL, Solano study area; SSV-QPC, Uplands study area; SUI, Suisun-Fairfield study area; YOL, Yolo study area. San Fernando–San Gabriel study unit: ULASF, San Fernando study area; ULASG, San Gabriel study area. Monterey Bay and Salinas Valley Basins study unit: MSMB, Monterey Bay study area; MSPR, Paso Robles study area; MSSC, Santa Cruz study area; MSSV, Salinas Valley study area. Southeast San Joaquin Valley study unit: KING, Kings study area; KWH, Kaweah study area; TLR, Tulare Lake study area; TULE, Tule study area. Benchmark type: MCL-US, USEPA maximum contaminant level; MCL-CA, California Department of Public Health maximum contaminant level; HAL-US, USEPA lifetime health advisory level; RSD5-US, USEPA risk-specific dose at a factor of 10–5. Benchmark type and benchmark level as of April 1, 2010. Other abbreviations: USGS, U.S. Geological Survey; USEPA, U.S. Environmental Protection Agency; μg/L, micrograms per liter; na, not available; nc, not collected; —, not detected; E, estimated or having a higher degree of uncertainty]
96 Groundwater-Quality Data in Seven GAMA Study Units: Results from Initial Sampling and Resampling of Wells GAMA well identification number Sample dates Herbicide Herbicide degradate Simazine (μg/L) (04035) Atrazine (μg/L) (39632) Tebuthiuron (μg/L) (82670) Prometon (μg/L) (04037) Hexazinone (μg/L) (04025) EPTC 

(S-Ethyl depropylthio-carbamate) 

(μg/L) 

(82668)

DCPA 

(Dacthal) 

(μg/L) 

(82682)

Trifluralin 

(μg/L) 

(82661)

Deethylatrazine 

(2-Chloro-4-isopropylamino6-amino-s-triazine) 

(μg/L) 

(04040)

Benchmark type MCL-US MCL-CA HAL-US HAL-US HAL-US na HAL-US HAL-US naBenchmark level 4 1 500 100 400 na 70 10 na[LRL]1 [0.005, 0.010] [0.007] [0.016, 0.020] [0.005, 0.012] [0.008, 0.026] [0.002, 0.004] [0.003, 0.006] [0.009, 0.012] [0.006, 0.014]Southeast San Joaquin Valley study unit—ContinuedKWH-12 11/28/2005 0.026 0.021

— E0.005

—

—

—

— E0.006

KWH-12 11/6/2008 0.021 0.018

— E0.005

—

—

—

— E0.007

TLR-03 11/29/2005

—

—

—

—

—

—

—

—

—

TLR-03 11/4/2008

—

—

—

—

—

—

—

—

—

TULE-05 12/5/2005 0.008 0.009

—

—

—

—

—

— E0.005

TULE-05 11/3/2008 E0.006 0.009

—

—

—

—

—

— E0.010

TULE-10 12/7/2005 0.019 0.009

—

— E0.010 0.039

—

— E0.007

TULE-10 11/3/2008 0.022 0.009

—

— 0.028 0.026

— E0.003 3 E0.008

Table 6A. Pesticides and pesticide degradates (Schedules 2003, 2032, and 2033) in samples collected from trend wells for seven Groundwater Ambient Monitoring and Assessment (GAMA) study units.—Continued[The five-digit USGS parameter code below the constituent name is used to uniquely identify a specific constituent or property. Pesticides and degradates were analyzed in samples from 54 trend wells in 2004–05 and 54 trend wells in 2007–08; samples from 53 trend wells were analyzed during both time periods. Information about analytes given in table 3C. GAMA well identification number acronyms: San Diego Drainages study unit: SDALLV, Alluvial Basins study area; SDHDRK, Hard Rock study area; SDTEM, Temecula Valley study area; SDTEMFP, Temecula Valley study area flow-path well; SDWARN, Warner Valley study area. North San Francisco Bay study unit: NSFVOL, Volcanic Highlands study area; NSFVP, Valley and Plains study area; NSFWG, Wilson Grove Formation Highlands study area; NSFWGFP, Wilson Grove Formation Highlands study area flow-path well. Northern San Joaquin Basin study unit: COS, Cosumnes Basin study area; ESJ, Eastern San Joaquin Basin study area; NSJ-QPC, Uplands study area; TRCY, Tracy Basin study area. Southern Sacramento Valley study unit: NAM, North American study area; SAM, South American study area; SOL, Solano study area; SSV-QPC, Uplands study area; SUI, Suisun-Fairfield study area; YOL, Yolo study area. San Fernando–San Gabriel study unit: ULASF, San Fernando study area; ULASG, San Gabriel study area. Monterey Bay and Salinas Valley Basins study unit: MSMB, Monterey Bay study area; MSPR, Paso Robles study area; MSSC, Santa Cruz study area; MSSV, Salinas Valley study area. Southeast San Joaquin Valley study unit: KING, Kings study area; KWH, Kaweah study area; TLR, Tulare Lake study area; TULE, Tule study area. Benchmark type: MCL-US, USEPA maximum contaminant level; MCL-CA, California Department of Public Health maximum contaminant level; HAL-US, USEPA lifetime health advisory level; RSD5-US, USEPA risk-specific dose at a factor of 10–5. Benchmark type and benchmark level as of April 1, 2010. Other abbreviations: USGS, U.S. Geological Survey; USEPA, U.S. Environmental Protection Agency; μg/L, micrograms per liter; na, not available; nc, not collected; —, not detected; E, estimated or having a higher degree of uncertainty]
Tables 97

GAMA 

well 

identification 

number

Sample 

dates

Herbicide degradate Insecticide Insecticide degradate

Detections 

per 

sample

Detection 

summary

3,4-Dichloroaniline 

(μg/L) 

(61625)

3,5-Dichloroaniline 

(μg/L) 

(61627)

Dieldrin 

(μg/L) 

(39381)

Fipronil 

(μg/L) 

(62166)

Desulfinyl 

fipronil 

(μg/L) 

(62170)

Fipronil 

sulfide 

(μg/L) 

(62167)

Desulfinylfipronil 

amide 

(μg/L) 

(62169)

Benchmark type na na RSD5-US na na na naBenchmark level na na 0.02 na na na na[LRL]1 [0.004, 0.006] [0.004] [0.009] [0.016, 0.040] [0.012] [0.013] [0.029]Number of trend wells with detections 2004–05 2 0 0 0 0 0 0 22Detection frequency (percent) 2004–05 4 na2 0 0 0 0 0 41Number of trend wells with detections 2007–08 5 1 0 1 1 1 0 21Detection frequency (percent) 2007–08 9 na2 0 2 2 2 0 39San Diego Drainages study unitSDALLV-07 7/14/2004 — nc — — — — — 2SDALLV-07 9/12/2007 — nc — — — — — 1SDALLV-11 7/15/2004 — nc — — — — — 5SDALLV-11 9/13/2007 — nc — — — — — 3SDHDRK-01 7/12/2004 — nc — — — — — 5SDHDRK-01 9/13/2007 — nc — — — — — 5SDHDRK-09 7/27/2004 — nc — — — — — 2SDHDRK-09 9/11/2007 — nc — — — — — 1SDTEM-04 5/24/2004 — nc — — — — — 0SDTEM-04 9/18/2007 nc nc nc nc nc nc nc ncSDTEMFP-01 5/19/2004 — nc — — — — — 1SDTEMFP-01 9/19/2007 — nc — — — — — 1SDWARN-01 6/17/2004 — nc — — — — — 0SDWARN-01 9/11/2007 — nc — — — — — 0

Table 6A. Pesticides and pesticide degradates (Schedules 2003, 2032, and 2033) in samples collected from trend wells for seven Groundwater Ambient Monitoring and Assessment (GAMA) study units.—Continued[The five-digit USGS parameter code below the constituent name is used to uniquely identify a specific constituent or property. Pesticides and degradates were analyzed in samples from 54 trend wells in 2004–05 and 54 trend wells in 2007–08; samples from 53 trend wells were analyzed during both time periods. Information about analytes given in table 3C. GAMA well identification number acronyms: San Diego Drainages study unit: SDALLV, Alluvial Basins study area; SDHDRK, Hard Rock study area; SDTEM, Temecula Valley study area; SDTEMFP, Temecula Valley study area flow-path well; SDWARN, Warner Valley study area. North San Francisco Bay study unit: NSFVOL, Volcanic Highlands study area; NSFVP, Valley and Plains study area; NSFWG, Wilson Grove Formation Highlands study area; NSFWGFP, Wilson Grove Formation Highlands study area flow-path well. Northern San Joaquin Basin study unit: COS, Cosumnes Basin study area; ESJ, Eastern San Joaquin Basin study area; NSJ-QPC, Uplands study area; TRCY, Tracy Basin study area. Southern Sacramento Valley study unit: NAM, North American study area; SAM, South American study area; SOL, Solano study area; SSV-QPC, Uplands study area; SUI, Suisun-Fairfield study area; YOL, Yolo study area. San Fernando–San Gabriel study unit: ULASF, San Fernando study area; ULASG, San Gabriel study area. Monterey Bay and Salinas Valley Basins study unit: MSMB, Monterey Bay study area; MSPR, Paso Robles study area; MSSC, Santa Cruz study area; MSSV, Salinas Valley study area. Southeast San Joaquin Valley study unit: KING, Kings study area; KWH, Kaweah study area; TLR, Tulare Lake study area; TULE, Tule study area. Benchmark type: MCL-US, USEPA maximum contaminant level; MCL-CA, California Department of Public Health maximum contaminant level; HAL-US, USEPA lifetime health advisory level; RSD5-US, USEPA risk-specific dose at a factor of 10–5. Benchmark type and benchmark level as of April 1, 2010. Other abbreviations: USGS, U.S. Geological Survey; USEPA, U.S. Environmental Protection Agency; μg/L, micrograms per liter; na, not available; nc, not collected; —, not detected; E, estimated or having a higher degree of uncertainty]
98 Groundwater-Quality Data in Seven GAMA Study Units: Results from Initial Sampling and Resampling of Wells GAMA well identification number Sample dates Herbicide degradate Insecticide Insecticide degradate Detections per sample Detection summary 3,4-Dichloroaniline (μg/L) (61625) 3,5-Dichloroaniline (μg/L) (61627) Dieldrin (μg/L) (39381) Fipronil (μg/L) (62166) Desulfinyl fipronil (μg/L) (62170) Fipronil sulfide (μg/L) (62167) Desulfinylfipronil amide (μg/L) (62169) Benchmark type na na RSD5-US na na na na Benchmark level na na 0.02 na na na na [LRL]1 [0.004, 0.006] [0.004] [0.009] [0.016, 0.040] [0.012] [0.013] [0.029] North San Francisco Bay study unit NSFVOL-14 10/7/2004

— nc

—

—

—

—

— 0

NSFVOL-14 8/21/2007

— nc

—

—

—

—

— 0

NSFVOL-18 10/20/2004

— nc

—

—

—

—

— 0

NSFVOL-18 8/28/2007

— nc

—

—

—

—

— 0

NSFVP-29 9/28/2004

— nc

—

—

—

—

— 1

NSFVP-29 8/27/2007

— nc

—

—

—

—

— 1

NSFVP-34 10/18/2004

— nc

—

—

—

—

— 0

NSFVP-34 8/22/2007

— nc

—

—

—

—

— 0

NSFVP-36 10/19/2004

— nc

—

—

—

—

— 0

NSFVP-36 8/20/2007

— nc

—

—

—

—

— 0

NSFVP-38 10/20/2004

— nc

—

—

—

—

— 0

NSFVP-38 8/22/2007

— nc

—

—

—

—

— 0

NSFVP-39 10/21/2004

— nc

—

—

—

—

— 0

NSFVP-39 11/16/2007

— nc

—

—

—

—

— 0

NSFVP-41 10/21/2004

— nc

—

—

—

—

— 0

NSFVP-41 8/20/2007

— nc

—

—

—

—

— 0

NSFWG-03 9/21/2004

— nc

—

—

—

—

— 0

Table 6A. Pesticides and pesticide degradates (Schedules 2003, 2032, and 2033) in samples collected from trend wells for seven Groundwater Ambient Monitoring and Assessment (GAMA) study units.—Continued[The five-digit USGS parameter code below the constituent name is used to uniquely identify a specific constituent or property. Pesticides and degradates were analyzed in samples from 54 trend wells in 2004–05 and 54 trend wells in 2007–08; samples from 53 trend wells were analyzed during both time periods. Information about analytes given in table 3C. GAMA well identification number acronyms: San Diego Drainages study unit: SDALLV, Alluvial Basins study area; SDHDRK, Hard Rock study area; SDTEM, Temecula Valley study area; SDTEMFP, Temecula Valley study area flow-path well; SDWARN, Warner Valley study area. North San Francisco Bay study unit: NSFVOL, Volcanic Highlands study area; NSFVP, Valley and Plains study area; NSFWG, Wilson Grove Formation Highlands study area; NSFWGFP, Wilson Grove Formation Highlands study area flow-path well. Northern San Joaquin Basin study unit: COS, Cosumnes Basin study area; ESJ, Eastern San Joaquin Basin study area; NSJ-QPC, Uplands study area; TRCY, Tracy Basin study area. Southern Sacramento Valley study unit: NAM, North American study area; SAM, South American study area; SOL, Solano study area; SSV-QPC, Uplands study area; SUI, Suisun-Fairfield study area; YOL, Yolo study area. San Fernando–San Gabriel study unit: ULASF, San Fernando study area; ULASG, San Gabriel study area. Monterey Bay and Salinas Valley Basins study unit: MSMB, Monterey Bay study area; MSPR, Paso Robles study area; MSSC, Santa Cruz study area; MSSV, Salinas Valley study area. Southeast San Joaquin Valley study unit: KING, Kings study area; KWH, Kaweah study area; TLR, Tulare Lake study area; TULE, Tule study area. Benchmark type: MCL-US, USEPA maximum contaminant level; MCL-CA, California Department of Public Health maximum contaminant level; HAL-US, USEPA lifetime health advisory level; RSD5-US, USEPA risk-specific dose at a factor of 10–5. Benchmark type and benchmark level as of April 1, 2010. Other abbreviations: USGS, U.S. Geological Survey; USEPA, U.S. Environmental Protection Agency; μg/L, micrograms per liter; na, not available; nc, not collected; —, not detected; E, estimated or having a higher degree of uncertainty]
Tables 99

GAMA 

well 

identification 

number

Sample 

dates

Herbicide degradate Insecticide Insecticide degradate

Detections 

per 

sample

Detection 

summary

3,4-Dichloroaniline 

(μg/L) 

(61625)

3,5-Dichloroaniline 

(μg/L) 

(61627)

Dieldrin 

(μg/L) 

(39381)

Fipronil 

(μg/L) 

(62166)

Desulfinyl 

fipronil 

(μg/L) 

(62170)

Fipronil 

sulfide 

(μg/L) 

(62167)

Desulfinylfipronil 

amide 

(μg/L) 

(62169)

Benchmark type na na RSD5-US na na na naBenchmark level na na 0.02 na na na na[LRL]1 [0.004, 0.006] [0.004] [0.009] [0.016, 0.040] [0.012] [0.013] [0.029]North San Francisco Bay study unit—ContinuedNSFWG-03 8/29/2007 — nc — — — — — 0NSFWGFP-01 10/5/2004 — nc — — — — — 1NSFWGFP-01 8/29/2007 — nc — — — — — 0Northern San Joaquin Basin study unitCOS-08 1/3/2005 — nc — — — — — 0COS-08 4/3/2008 — nc — — — — — 0ESJ-01 1/24/2005 — nc — — — — — 3ESJ-01 4/2/2008 — nc — — — — — 3ESJ-06 1/10/2005 — nc — — — — — 0ESJ-06 4/2/2008 — nc — — — — — 0NSJ-QPC-04 1/24/2005 — nc — — — — — 0NSJ-QPC-04 4/1/2008 — nc — — — — — 1TRCY-03 1/6/2005 — nc — — — — — 0TRCY-03 3/31/2008 — nc — — — — — 0Southern Sacramento Valley study unit NAM-03 3/29/2005 — nc — — — — — 0NAM-03 4/10/2008 — nc — — — — — 0SAM-10 4/21/2005 — nc — — — — — 0

Table 6A. Pesticides and pesticide degradates (Schedules 2003, 2032, and 2033) in samples collected from trend wells for seven Groundwater Ambient Monitoring and Assessment (GAMA) study units.—Continued[The five-digit USGS parameter code below the constituent name is used to uniquely identify a specific constituent or property. Pesticides and degradates were analyzed in samples from 54 trend wells in 2004–05 and 54 trend wells in 2007–08; samples from 53 trend wells were analyzed during both time periods. Information about analytes given in table 3C. GAMA well identification number acronyms: San Diego Drainages study unit: SDALLV, Alluvial Basins study area; SDHDRK, Hard Rock study area; SDTEM, Temecula Valley study area; SDTEMFP, Temecula Valley study area flow-path well; SDWARN, Warner Valley study area. North San Francisco Bay study unit: NSFVOL, Volcanic Highlands study area; NSFVP, Valley and Plains study area; NSFWG, Wilson Grove Formation Highlands study area; NSFWGFP, Wilson Grove Formation Highlands study area flow-path well. Northern San Joaquin Basin study unit: COS, Cosumnes Basin study area; ESJ, Eastern San Joaquin Basin study area; NSJ-QPC, Uplands study area; TRCY, Tracy Basin study area. Southern Sacramento Valley study unit: NAM, North American study area; SAM, South American study area; SOL, Solano study area; SSV-QPC, Uplands study area; SUI, Suisun-Fairfield study area; YOL, Yolo study area. San Fernando–San Gabriel study unit: ULASF, San Fernando study area; ULASG, San Gabriel study area. Monterey Bay and Salinas Valley Basins study unit: MSMB, Monterey Bay study area; MSPR, Paso Robles study area; MSSC, Santa Cruz study area; MSSV, Salinas Valley study area. Southeast San Joaquin Valley study unit: KING, Kings study area; KWH, Kaweah study area; TLR, Tulare Lake study area; TULE, Tule study area. Benchmark type: MCL-US, USEPA maximum contaminant level; MCL-CA, California Department of Public Health maximum contaminant level; HAL-US, USEPA lifetime health advisory level; RSD5-US, USEPA risk-specific dose at a factor of 10–5. Benchmark type and benchmark level as of April 1, 2010. Other abbreviations: USGS, U.S. Geological Survey; USEPA, U.S. Environmental Protection Agency; μg/L, micrograms per liter; na, not available; nc, not collected; —, not detected; E, estimated or having a higher degree of uncertainty]
100 Groundwater-Quality Data in Seven GAMA Study Units: Results from Initial Sampling and Resampling of Wells GAMA well identification number Sample dates Herbicide degradate Insecticide Insecticide degradate Detections per sample Detection summary 3,4-Dichloroaniline (μg/L) (61625) 3,5-Dichloroaniline (μg/L) (61627) Dieldrin (μg/L) (39381) Fipronil (μg/L) (62166) Desulfinyl fipronil (μg/L) (62170) Fipronil sulfide (μg/L) (62167) Desulfinylfipronil amide (μg/L) (62169) Benchmark type na na RSD5-US na na na na Benchmark level na na 0.02 na na na na [LRL]1 [0.004, 0.006] [0.004] [0.009] [0.016, 0.040] [0.012] [0.013] [0.029] Southern Sacramento Valley study unit—Continued SAM-10 4/8/2008

— nc

—

—

—

—

— 0

SOL-08 5/10/2005 nc

—

—

—

—

— 0

SOL-08 4/8/2008

— nc

—

—

—

—

— 0

SSV-QPC-07 4/4/2005

— nc

—

—

—

—

— 0

SSV-QPC-07 4/10/2008

— nc

—

—

—

—

— 0

SUI-03 5/12/2005 nc nc nc nc nc nc nc ncSUI-03 4/9/2008

— nc

—

—

—

—

— 1

YOL-01 4/11/2005

— nc

—

—

—

—

— 0

YOL-01 4/7/2008

— nc

—

—

—

—

— 0

YOL-14 5/25/2005

— nc

—

—

—

—

— 0

YOL-14 4/9/2008

— nc

—

—

—

—

— 0

San Fernando–San Gabriel study unit ULASF-09 6/27/2005

— nc E0.0002 3 —

—

—

— 4

ULASF-09 6/16/2008

— nc

—

—

—

—

— 4

ULASF-10 6/8/2005

— nc

—

—

—

—

— 3

ULASF-10 6/16/2008

— nc

—

—

—

—

— 0

ULASG-01 6/7/2005

— nc

—

—

—

—

— 4

Table 6A. Pesticides and pesticide degradates (Schedules 2003, 2032, and 2033) in samples collected from trend wells for seven Groundwater Ambient Monitoring and Assessment (GAMA) study units.—Continued[The five-digit USGS parameter code below the constituent name is used to uniquely identify a specific constituent or property. Pesticides and degradates were analyzed in samples from 54 trend wells in 2004–05 and 54 trend wells in 2007–08; samples from 53 trend wells were analyzed during both time periods. Information about analytes given in table 3C. GAMA well identification number acronyms: San Diego Drainages study unit: SDALLV, Alluvial Basins study area; SDHDRK, Hard Rock study area; SDTEM, Temecula Valley study area; SDTEMFP, Temecula Valley study area flow-path well; SDWARN, Warner Valley study area. North San Francisco Bay study unit: NSFVOL, Volcanic Highlands study area; NSFVP, Valley and Plains study area; NSFWG, Wilson Grove Formation Highlands study area; NSFWGFP, Wilson Grove Formation Highlands study area flow-path well. Northern San Joaquin Basin study unit: COS, Cosumnes Basin study area; ESJ, Eastern San Joaquin Basin study area; NSJ-QPC, Uplands study area; TRCY, Tracy Basin study area. Southern Sacramento Valley study unit: NAM, North American study area; SAM, South American study area; SOL, Solano study area; SSV-QPC, Uplands study area; SUI, Suisun-Fairfield study area; YOL, Yolo study area. San Fernando–San Gabriel study unit: ULASF, San Fernando study area; ULASG, San Gabriel study area. Monterey Bay and Salinas Valley Basins study unit: MSMB, Monterey Bay study area; MSPR, Paso Robles study area; MSSC, Santa Cruz study area; MSSV, Salinas Valley study area. Southeast San Joaquin Valley study unit: KING, Kings study area; KWH, Kaweah study area; TLR, Tulare Lake study area; TULE, Tule study area. Benchmark type: MCL-US, USEPA maximum contaminant level; MCL-CA, California Department of Public Health maximum contaminant level; HAL-US, USEPA lifetime health advisory level; RSD5-US, USEPA risk-specific dose at a factor of 10–5. Benchmark type and benchmark level as of April 1, 2010. Other abbreviations: USGS, U.S. Geological Survey; USEPA, U.S. Environmental Protection Agency; μg/L, micrograms per liter; na, not available; nc, not collected; —, not detected; E, estimated or having a higher degree of uncertainty]
Tables 101

GAMA 

well 

identification 

number

Sample 

dates

Herbicide degradate Insecticide Insecticide degradate

Detections 

per 

sample

Detection 

summary

3,4-Dichloroaniline 

(μg/L) 

(61625)

3,5-Dichloroaniline 

(μg/L) 

(61627)

Dieldrin 

(μg/L) 

(39381)

Fipronil 

(μg/L) 

(62166)

Desulfinyl 

fipronil 

(μg/L) 

(62170)

Fipronil 

sulfide 

(μg/L) 

(62167)

Desulfinylfipronil 

amide 

(μg/L) 

(62169)

Benchmark type na na RSD5-US na na na naBenchmark level na na 0.02 na na na na[LRL]1 [0.004, 0.006] [0.004] [0.009] [0.016, 0.040] [0.012] [0.013] [0.029]San Fernando–San Gabriel study unit—ContinuedULASG-01 6/16/2008 E0.004 nc — — — — — 5ULASG-08 6/15/2005 — nc — — — — — 3ULASG-08 6/17/2008 E0.004 nc — — — — — 4ULASG-15 6/23/2005 E0.003 nc — — — — — 2ULASG-15 6/17/2008 E0.004 nc — — — — — 2ULASG-17 7/11/2005 — nc — — — — — 5ULASG-17 6/17/2008 — nc — — — — — 5Monterey Bay and Salinas Valley Basins study unitMSMB-03 8/31/2005 — nc — — — — — 0MSMB-03 8/20/2008 — nc — — — — — 0MSMB-04 8/17/2005 — nc — — — — — 0MSMB-04 8/20/2008 — nc — — — — — 1MSMB-16 8/17/2005 — nc — — — — — 0MSMB-16 8/19/2008 — nc — — — — — 0MSMB-28 8/3/2005 — nc — — — — — 0MSMB-28 8/21/2008 — nc — — — — — 0MSMB-31 8/11/2005 — nc — — — — — 0

Table 6A. Pesticides and pesticide degradates (Schedules 2003, 2032, and 2033) in samples collected from trend wells for seven Groundwater Ambient Monitoring and Assessment (GAMA) study units.—Continued[The five-digit USGS parameter code below the constituent name is used to uniquely identify a specific constituent or property. Pesticides and degradates were analyzed in samples from 54 trend wells in 2004–05 and 54 trend wells in 2007–08; samples from 53 trend wells were analyzed during both time periods. Information about analytes given in table 3C. GAMA well identification number acronyms: San Diego Drainages study unit: SDALLV, Alluvial Basins study area; SDHDRK, Hard Rock study area; SDTEM, Temecula Valley study area; SDTEMFP, Temecula Valley study area flow-path well; SDWARN, Warner Valley study area. North San Francisco Bay study unit: NSFVOL, Volcanic Highlands study area; NSFVP, Valley and Plains study area; NSFWG, Wilson Grove Formation Highlands study area; NSFWGFP, Wilson Grove Formation Highlands study area flow-path well. Northern San Joaquin Basin study unit: COS, Cosumnes Basin study area; ESJ, Eastern San Joaquin Basin study area; NSJ-QPC, Uplands study area; TRCY, Tracy Basin study area. Southern Sacramento Valley study unit: NAM, North American study area; SAM, South American study area; SOL, Solano study area; SSV-QPC, Uplands study area; SUI, Suisun-Fairfield study area; YOL, Yolo study area. San Fernando–San Gabriel study unit: ULASF, San Fernando study area; ULASG, San Gabriel study area. Monterey Bay and Salinas Valley Basins study unit: MSMB, Monterey Bay study area; MSPR, Paso Robles study area; MSSC, Santa Cruz study area; MSSV, Salinas Valley study area. Southeast San Joaquin Valley study unit: KING, Kings study area; KWH, Kaweah study area; TLR, Tulare Lake study area; TULE, Tule study area. Benchmark type: MCL-US, USEPA maximum contaminant level; MCL-CA, California Department of Public Health maximum contaminant level; HAL-US, USEPA lifetime health advisory level; RSD5-US, USEPA risk-specific dose at a factor of 10–5. Benchmark type and benchmark level as of April 1, 2010. Other abbreviations: USGS, U.S. Geological Survey; USEPA, U.S. Environmental Protection Agency; μg/L, micrograms per liter; na, not available; nc, not collected; —, not detected; E, estimated or having a higher degree of uncertainty]
102 Groundwater-Quality Data in Seven GAMA Study Units: Results from Initial Sampling and Resampling of Wells GAMA well identification number Sample dates Herbicide degradate Insecticide Insecticide degradate Detections per sample Detection summary 3,4-Dichloroaniline (μg/L) (61625) 3,5-Dichloroaniline (μg/L) (61627) Dieldrin (μg/L) (39381) Fipronil (μg/L) (62166) Desulfinyl fipronil (μg/L) (62170) Fipronil sulfide (μg/L) (62167) Desulfinylfipronil amide (μg/L) (62169) Benchmark type na na RSD5-US na na na na Benchmark level na na 0.02 na na na na [LRL]1 [0.004, 0.006] [0.004] [0.009] [0.016, 0.040] [0.012] [0.013] [0.029] Monterey Bay and Salinas Valley Basins study unit—Continued MSMB-31 8/21/2008

— nc

—

—

—

—

— 0

MSPR-03 7/28/2005

— nc

—

—

—

—

— 0

MSPR-03 11/14/2008

— nc

—

—

—

—

— 0

MSPR-09 7/18/2005

— nc

—

—

—

—

— 2

MSPR-09 11/14/2008

— nc

—

—

—

—

— 2

MSSC-06 8/24/2005

— nc

—

—

—

—

— 0

MSSC-06 8/18/2008

— nc

—

—

—

—

— 0

MSSC-11 9/13/2005

— nc

—

—

—

—

— 0

MSSC-11 8/19/2008

— nc

—

—

—

—

— 0

MSSV-06 8/2/2005

— nc

—

—

—

—

— 1

MSSV-06 11/13/2008

— nc

—

—

—

—

— 0

MSSV-15 8/12/2005

— nc

—

—

—

—

— 2

MSSV-15 11/13/2008

— nc

—

—

—

—

— 0

Southeast San Joaquin Valley study unitKING-11 10/20/2005

—

—

—

—

—

—

— 0

KING-11 11/5/2008

—

—

—

—

—

—

— 0

KING-13 10/20/2005

—

—

—

—

—

—

— 0

Table 6A. Pesticides and pesticide degradates (Schedules 2003, 2032, and 2033) in samples collected from trend wells for seven Groundwater Ambient Monitoring and Assessment (GAMA) study units.—Continued[The five-digit USGS parameter code below the constituent name is used to uniquely identify a specific constituent or property. Pesticides and degradates were analyzed in samples from 54 trend wells in 2004–05 and 54 trend wells in 2007–08; samples from 53 trend wells were analyzed during both time periods. Information about analytes given in table 3C. GAMA well identification number acronyms: San Diego Drainages study unit: SDALLV, Alluvial Basins study area; SDHDRK, Hard Rock study area; SDTEM, Temecula Valley study area; SDTEMFP, Temecula Valley study area flow-path well; SDWARN, Warner Valley study area. North San Francisco Bay study unit: NSFVOL, Volcanic Highlands study area; NSFVP, Valley and Plains study area; NSFWG, Wilson Grove Formation Highlands study area; NSFWGFP, Wilson Grove Formation Highlands study area flow-path well. Northern San Joaquin Basin study unit: COS, Cosumnes Basin study area; ESJ, Eastern San Joaquin Basin study area; NSJ-QPC, Uplands study area; TRCY, Tracy Basin study area. Southern Sacramento Valley study unit: NAM, North American study area; SAM, South American study area; SOL, Solano study area; SSV-QPC, Uplands study area; SUI, Suisun-Fairfield study area; YOL, Yolo study area. San Fernando–San Gabriel study unit: ULASF, San Fernando study area; ULASG, San Gabriel study area. Monterey Bay and Salinas Valley Basins study unit: MSMB, Monterey Bay study area; MSPR, Paso Robles study area; MSSC, Santa Cruz study area; MSSV, Salinas Valley study area. Southeast San Joaquin Valley study unit: KING, Kings study area; KWH, Kaweah study area; TLR, Tulare Lake study area; TULE, Tule study area. Benchmark type: MCL-US, USEPA maximum contaminant level; MCL-CA, California Department of Public Health maximum contaminant level; HAL-US, USEPA lifetime health advisory level; RSD5-US, USEPA risk-specific dose at a factor of 10–5. Benchmark type and benchmark level as of April 1, 2010. Other abbreviations: USGS, U.S. Geological Survey; USEPA, U.S. Environmental Protection Agency; μg/L, micrograms per liter; na, not available; nc, not collected; —, not detected; E, estimated or having a higher degree of uncertainty]
Tables 103

GAMA 

well 

identification 

number

Sample 

dates

Herbicide degradate Insecticide Insecticide degradate

Detections 

per 

sample

Detection 

summary

3,4-Dichloroaniline 

(μg/L) 

(61625)

3,5-Dichloroaniline 

(μg/L) 

(61627)

Dieldrin 

(μg/L) 

(39381)

Fipronil 

(μg/L) 

(62166)

Desulfinyl 

fipronil 

(μg/L) 

(62170)

Fipronil 

sulfide 

(μg/L) 

(62167)

Desulfinylfipronil 

amide 

(μg/L) 

(62169)

Benchmark type na na RSD5-US na na na naBenchmark level na na 0.02 na na na na[LRL]1 [0.004, 0.006] [0.004] [0.009] [0.016, 0.040] [0.012] [0.013] [0.029]Southeast San Joaquin Valley study unit—ContinuedKING-13 11/5/2008 — — — — — — — 0KING-17 10/26/2005 — — — — — — — 0KING-17 11/4/2008 — — — — — — — 0KING-24 11/5/2005 — — — — — — — 2KING-24 11/3/2008 E0.006 — — E0.021 E0.006 E0.009 E0.006 3 7KWH-10 11/17/2005 — — — — — — — 3KWH-10 11/5/2008 — — — — — — — 3KWH-12 11/28/2005 — — — — — — — 4KWH-12 11/6/2008 — — — — — — — 4TLR-03 11/29/2005 — — — — — — — 0TLR-03 11/4/2008 — — — — — — — 0TULE-05 12/5/2005 — — — — — — — 3TULE-05 11/3/2008 — — — — — — — 3TULE-10 12/7/2005 E0.006 — — — — — — 6TULE-10 11/3/2008 E0.010 E0.004 — — — — — 7

1 Minimum and maximum LRL, or only LRL used during study period.2 Detection frequencies for EPTC and 3,5-dichloroaniline were not calculated because only 9 of 54 samples were analyzed for these compounds. 3 The detected concentration was less than the LT-MDL for this compound. These results are counted as non-detections for the purpose of calculating detection frequencies.

Table 6A. Pesticides and pesticide degradates (Schedules 2003, 2032, and 2033) in samples collected from trend wells for seven Groundwater Ambient Monitoring and Assessment (GAMA) study units.—Continued[The five-digit USGS parameter code below the constituent name is used to uniquely identify a specific constituent or property. Pesticides and degradates were analyzed in samples from 54 trend wells in 2004–05 and 54 trend wells in 2007–08; samples from 53 trend wells were analyzed during both time periods. Information about analytes given in table 3C. GAMA well identification number acronyms: San Diego Drainages study unit: SDALLV, Alluvial Basins study area; SDHDRK, Hard Rock study area; SDTEM, Temecula Valley study area; SDTEMFP, Temecula Valley study area flow-path well; SDWARN, Warner Valley study area. North San Francisco Bay study unit: NSFVOL, Volcanic Highlands study area; NSFVP, Valley and Plains study area; NSFWG, Wilson Grove Formation Highlands study area; NSFWGFP, Wilson Grove Formation Highlands study area flow-path well. Northern San Joaquin Basin study unit: COS, Cosumnes Basin study area; ESJ, Eastern San Joaquin Basin study area; NSJ-QPC, Uplands study area; TRCY, Tracy Basin study area. Southern Sacramento Valley study unit: NAM, North American study area; SAM, South American study area; SOL, Solano study area; SSV-QPC, Uplands study area; SUI, Suisun-Fairfield study area; YOL, Yolo study area. San Fernando–San Gabriel study unit: ULASF, San Fernando study area; ULASG, San Gabriel study area. Monterey Bay and Salinas Valley Basins study unit: MSMB, Monterey Bay study area; MSPR, Paso Robles study area; MSSC, Santa Cruz study area; MSSV, Salinas Valley study area. Southeast San Joaquin Valley study unit: KING, Kings study area; KWH, Kaweah study area; TLR, Tulare Lake study area; TULE, Tule study area. Benchmark type: MCL-US, USEPA maximum contaminant level; MCL-CA, California Department of Public Health maximum contaminant level; HAL-US, USEPA lifetime health advisory level; RSD5-US, USEPA risk-specific dose at a factor of 10–5. Benchmark type and benchmark level as of April 1, 2010. Other abbreviations: USGS, U.S. Geological Survey; USEPA, U.S. Environmental Protection Agency; μg/L, micrograms per liter; na, not available; nc, not collected; —, not detected; E, estimated or having a higher degree of uncertainty]
104 Groundwater-Quality Data in Seven GAMA Study Units: Results from Initial Sampling and Resampling of Wells Table 6B. Polar pesticides (Schedule 2060) in samples collected from trend wells for seven Groundwater Ambient Monitoring and Assessment (GAMA) study units. [The five-digit USGS parameter code below the constituent name is used to uniquely identify a specific constituent or property. Polar pesticides were analyzed in samples from 19 trend wells in 2004–05 and 23 trend wells in 2007–08; samples from 10 trend wells were analyzed during both time periods. Only wells analyzed during at least one of the periods are listed. Information about analytes given in table 3D. GAMA well identification number acronyms: San Diego Drainages study unit: SDALLV, Alluvial Basins study area; SDHDRK, Hard Rock study area; SDTEM, Temecula Valley study area; SDTEMFP, Temecula Valley study area flow-path well; SDWARN, Warner Valley study area. North San Francisco Bay study unit: NSFVOL, Volcanic Highlands study area; NSFVP, Valley and Plains study area; NSFWG, Wilson Grove Formation Highlands study area; NSFWGFP, Wilson Grove Formation Highlands study area flow-path well. Northern San Joaquin Basin study unit: COS, Cosumnes Basin study area; ESJ, Eastern San Joaquin Basin study area; NSJ-QPC, Uplands study area; TRCY, Tracy Basin study area. Southern Sacramento Valley study unit: NAM, North American study area; SAM, South American study area; SOL, Solano study area; SSV-QPC, Uplands study area; SUI, Suisun-Fairfield study area; YOL, Yolo study area. San Fernando–San Gabriel study unit: ULASF, San Fernando study area; ULASG, San Gabriel study area. Monterey Bay and Salinas Valley Basins study unit: MSMB, Monterey Bay study area; MSPR, Paso Robles study area; MSSC, Santa Cruz study area; MSSV, Salinas Valley study area. Southeast San Joaquin Valley study unit: KING, Kings study area; KWH, Kaweah study area; TLR, Tulare Lake study area; TULE, Tule study area. Benchmark type: MCL-CA, California Department of Public Health maximum contaminant level; HAL-US, U.S. Environmental Protection Agency lifetime health advisory level. Benchmark type and benchmark level as of April 1, 2010. Other abbreviations: USGS, U.S. Geological Survey; μg/L, micrograms per liter; na, not available; nc, not collected; —, not detected; E, estimated or having a higher degree of uncertainty] GAMA well identification number Sample dates Herbicide Herbicide degradate Beverage Detections per sample Detection summary Atrazine2 (μg/L) (39632) Tebuthiuron2 (μg/L) (82670) Diuron (μg/L) (49300) Metsulfuron- methyl (μg/L) (61697) Sulfome- turon- methyl (μg/L) (50337) Bromacil (μg/L) (04029) Dinoseb (μg/L) (49301) Diphenamid (μg/L) (04033) Deethyl- atrazine (2-Chloro-4-iso- propylamino-6- amino-s- triazine)2 (μg/L) (04040) Deisopropyl atrazine (2-Chloro-6- ethylamino- 4-amino-s- triazine) (μg/L) (04038) Caffeine (μg/L) (50305) Benchmark type MCL-CA HAL-US HAL-US na na na MCL-CA na na na na Benchmark level 1 500 10 na na na 7 na na na na [LRL]1 [0.008, 0.040] [0.026, 0.040] [0.015, 0.040] [0.025, 0.140] [0.009, 0.091] [0.018, 0.040] [0.003, 0.040] [0.010, 0.040] [0.020, 0.060] [0.044, 0.080] [0.010, 0.060] Number of trend wells with detections 2004–05

4 0 1 1 1 0 0 0 2 0 3 7

Detection frequency (percent) 2004–05 21 0 5 5 5 0 0 0 11 0 16 37Number of trend wells with 

detections 2007–08

2 2 0 0 0 0 0 0 2 1 0 2

Detection frequency (percent) 2007–08

9 9 0 0 0 0 0 0 9 4 0 9

San Diego Drainages study unitSDTEMFP-01 5/19/2004

—

—

—

—

—

—

—

—

—

—

— 0

SDTEMFP-01 9/19/2007 nc nc nc nc nc nc nc nc nc nc nc ncNorth San Francisco Bay study unitNSFVOL-14 10/7/2004

—

—

—

—

—

—

—

—

—

—

— 0

NSFVOL-14 8/21/2007

—

—

—

—

—

—

—

—

—

—

— 0

NSFVOL-18 10/20/2004 nc nc nc nc nc nc nc nc nc nc nc ncNSFVOL-18 8/28/2007

—

—

—

—

—

—

—

—

—

—

— 0

NSFVP-29 9/28/2004

—

—

—

—

—

—

—

—

— E0.004 3 — 0
Tables 105

GAMA well 

identification 

number

Sample 

dates

Herbicide Herbicide degradate Beverage

Detections 

per 

sample

Detection 

summary

Atrazine2

(μg/L) 

(39632)

Tebuthiuron2

(μg/L) 

(82670)

Diuron 

(μg/L) 

(49300)

Metsulfuronmethyl 

(μg/L) 

(61697)

Sulfometuronmethyl 

(μg/L) 

(50337)

Bromacil 

(μg/L) 

(04029)

Dinoseb 

(μg/L) 

(49301)

Diphenamid 

(μg/L) 

(04033)

Deethylatrazine 

(2-Chloro-4-isopropylamino-6-

amino-striazine)2

(μg/L) 

(04040)

Deisopropyl 

atrazine 

(2-Chloro-6-

ethylamino4-amino-striazine) 

(μg/L) 

(04038)

Caffeine 

(μg/L) 

(50305)

Benchmark type MCL-CA HAL-US HAL-US na na na MCL-CA na na na naBenchmark level 1 500 10 na na na 7 na na na na[LRL]1 [0.008, 0.040] [0.026, 0.040] [0.015, 0.040] [0.025, 0.140] [0.009, 0.091] [0.018, 0.040] [0.003, 0.040] [0.010, 0.040] [0.020, 0.060] [0.044, 0.080] [0.010, 0.060]North San Francisco Bay study unit—ContinuedNSFVP-29 8/27/2007 — — — — — — — — — — — 0NSFVP-34 10/18/2004 — — — — — — — — — — — 0NSFVP-34 8/22/2007 — — — — — — — — — — — 0NSFVP-36 10/19/2004 nc nc nc nc nc nc nc nc nc nc nc ncNSFVP-36 8/20/2007 — — — — — — — — — — — 0NSFVP-38 10/20/2004 — — — — 0.052 — — — — — — 1NSFVP-38 8/22/2007 — — — — — — — — — — — 0NSFVP-39 10/21/2004 nc nc nc nc nc nc nc nc nc nc nc ncNSFVP-39 11/16/2007 — — — — — — — — — — — 0NSFVP-41 10/21/2004 nc nc nc nc nc nc nc nc nc nc nc ncNSFVP-41 8/20/2007 — — — — — — — — — — — 0NSFWG-03 9/21/2004 nc nc nc nc nc nc nc nc nc nc nc ncNSFWG-03 8/29/2007 — — — — — — — — — — — 0NSFWGFP-01 10/5/2004 — — — — — — — — — — — 0NSFWGFP-01 8/29/2007 E0.001 3 — — — — — — — — — — 0

Table 6B. Polar pesticides (Schedule 2060) in samples collected from trend wells for seven Groundwater Ambient Monitoring and Assessment (GAMA) study units.—Continued[The five-digit USGS parameter code below the constituent name is used to uniquely identify a specific constituent or property. Polar pesticides were analyzed in samples from 19 trend wells in 2004–05 and 23 trend wells in 2007–08; samples from 10 trend wells were analyzed during both time periods. Only wells analyzed during at least one of the periods are listed. Information about analytes given in table 3D. GAMA well identification number acronyms: San Diego Drainages study unit: SDALLV, Alluvial Basins study area; SDHDRK, Hard Rock study area; SDTEM, Temecula Valley study area; SDTEMFP, Temecula Valley study area flow-path well; SDWARN, Warner Valley study area. North San Francisco Bay study unit: NSFVOL, Volcanic Highlands study area; NSFVP, Valley and Plains study area; NSFWG, Wilson Grove Formation Highlands study area; NSFWGFP, Wilson Grove Formation Highlands study area flow-path well. Northern San Joaquin Basin study unit: COS, Cosumnes Basin study area; ESJ, Eastern San Joaquin Basin study area; NSJ-QPC, Uplands study area; TRCY, Tracy Basin study area. Southern Sacramento Valley study unit: NAM, North American study area; SAM, South American study area; SOL, Solano study area; SSV-QPC, Uplands study area; SUI, Suisun-Fairfield study area; YOL, Yolo study area. San Fernando–San Gabriel study unit: ULASF, San Fernando study area; ULASG, San Gabriel study area. Monterey Bay and Salinas Valley Basins study unit: MSMB, Monterey Bay study area; MSPR, Paso Robles study area; MSSC, Santa Cruz study area; MSSV, Salinas Valley study area. Southeast San Joaquin Valley study unit: KING, Kings study area; KWH, Kaweah study area; TLR, Tulare Lake study area; TULE, Tule study area. Benchmark type: MCL-CA, California Department of Public Health maximum contaminant level; HAL-US, U.S. Environmental Protection Agency lifetime health advisory level. Benchmark type and benchmark level as of April 1, 2010. Other abbreviations: USGS, U.S. Geological Survey; μg/L, micrograms per liter; na, not available; nc, not collected; —, not detected; E, estimated or having a higher degree of uncertainty]
106 Groundwater-Quality Data in Seven GAMA Study Units: Results from Initial Sampling and Resampling of Wells GAMA well identification number Sample dates Herbicide Herbicide degradate Beverage Detections per sample Detection summary Atrazine2 (μg/L) (39632) Tebuthiuron2 (μg/L) (82670) Diuron (μg/L) (49300) Metsulfuron- methyl (μg/L) (61697) Sulfome- turon- methyl (μg/L) (50337) Bromacil (μg/L) (04029) Dinoseb (μg/L) (49301) Diphenamid (μg/L) (04033) Deethyl- atrazine (2-Chloro-4-iso- propylamino-6- amino-s- triazine)2 (μg/L) (04040) Deisopropyl atrazine (2-Chloro-6- ethylamino- 4-amino-s- triazine) (μg/L) (04038) Caffeine (μg/L) (50305) Benchmark type MCL-CA HAL-US HAL-US na na na MCL-CA na na na na Benchmark level 1 500 10 na na na 7 na na na na [LRL]1 [0.008, 0.040] [0.026, 0.040] [0.015, 0.040] [0.025, 0.140] [0.009, 0.091] [0.018, 0.040] [0.003, 0.040] [0.010, 0.040] [0.020, 0.060] [0.044, 0.080] [0.010, 0.060] Northern San Joaquin Basin study unit TRCY-03 1/6/2005

—

—

—

—

—

—

—

—

—

—

— 0

TRCY-03 3/31/2008 nc nc nc nc nc nc nc nc nc nc nc ncSouthern Sacramento Valley study unit NAM-03 3/29/2005 nc nc nc nc nc nc nc nc nc nc nc ncNAM-03 4/10/2008

—

—

—

—

—

—

—

—

—

—

— 0

SAM-10 4/21/2005 nc nc nc nc nc nc nc nc nc nc nc ncSAM-10 4/8/2008

—

—

—

—

—

—

—

—

—

—

— 0

SOL-08 5/10/2005 nc nc nc nc nc nc nc nc nc nc nc ncSOL-08 4/8/2008

—

—

—

—

—

—

—

—

—

—

— 0

SSV-QPC-07 4/4/2005

—

—

—

—

—

—

—

—

—

— E0.011 1

SSV-QPC-07 4/10/2008

—

—

—

—

—

—

—

—

—

—

— 0

SUI-03 5/12/2005 nc nc nc nc nc nc nc nc nc nc nc ncSUI-03 4/9/2008

—

—

—

—

—

—

—

—

—

—

— 0

YOL-01 4/11/2005 nc nc nc nc nc nc nc nc nc nc nc ncYOL-01 4/7/2008

—

—

—

—

—

—

—

—

—

—

— 0

Table 6B. Polar pesticides (Schedule 2060) in samples collected from trend wells for seven Groundwater Ambient Monitoring and Assessment (GAMA) study units.—Continued[The five-digit USGS parameter code below the constituent name is used to uniquely identify a specific constituent or property. Polar pesticides were analyzed in samples from 19 trend wells in 2004–05 and 23 trend wells in 2007–08; samples from 10 trend wells were analyzed during both time periods. Only wells analyzed during at least one of the periods are listed. Information about analytes given in table 3D. GAMA well identification number acronyms: San Diego Drainages study unit: SDALLV, Alluvial Basins study area; SDHDRK, Hard Rock study area; SDTEM, Temecula Valley study area; SDTEMFP, Temecula Valley study area flow-path well; SDWARN, Warner Valley study area. North San Francisco Bay study unit: NSFVOL, Volcanic Highlands study area; NSFVP, Valley and Plains study area; NSFWG, Wilson Grove Formation Highlands study area; NSFWGFP, Wilson Grove Formation Highlands study area flow-path well. Northern San Joaquin Basin study unit: COS, Cosumnes Basin study area; ESJ, Eastern San Joaquin Basin study area; NSJ-QPC, Uplands study area; TRCY, Tracy Basin study area. Southern Sacramento Valley study unit: NAM, North American study area; SAM, South American study area; SOL, Solano study area; SSV-QPC, Uplands study area; SUI, Suisun-Fairfield study area; YOL, Yolo study area. San Fernando–San Gabriel study unit: ULASF, San Fernando study area; ULASG, San Gabriel study area. Monterey Bay and Salinas Valley Basins study unit: MSMB, Monterey Bay study area; MSPR, Paso Robles study area; MSSC, Santa Cruz study area; MSSV, Salinas Valley study area. Southeast San Joaquin Valley study unit: KING, Kings study area; KWH, Kaweah study area; TLR, Tulare Lake study area; TULE, Tule study area. Benchmark type: MCL-CA, California Department of Public Health maximum contaminant level; HAL-US, U.S. Environmental Protection Agency lifetime health advisory level. Benchmark type and benchmark level as of April 1, 2010. Other abbreviations: USGS, U.S. Geological Survey; μg/L, micrograms per liter; na, not available; nc, not collected; —, not detected; E, estimated or having a higher degree of uncertainty]
Tables 107

GAMA well 

identification 

number

Sample 

dates

Herbicide Herbicide degradate Beverage

Detections 

per 

sample

Detection 

summary

Atrazine2

(μg/L) 

(39632)

Tebuthiuron2

(μg/L) 

(82670)

Diuron 

(μg/L) 

(49300)

Metsulfuronmethyl 

(μg/L) 

(61697)

Sulfometuronmethyl 

(μg/L) 

(50337)

Bromacil 

(μg/L) 

(04029)

Dinoseb 

(μg/L) 

(49301)

Diphenamid 

(μg/L) 

(04033)

Deethylatrazine 

(2-Chloro-4-isopropylamino-6-

amino-striazine)2

(μg/L) 

(04040)

Deisopropyl 

atrazine 

(2-Chloro-6-

ethylamino4-amino-striazine) 

(μg/L) 

(04038)

Caffeine 

(μg/L) 

(50305)

Benchmark type MCL-CA HAL-US HAL-US na na na MCL-CA na na na naBenchmark level 1 500 10 na na na 7 na na na na[LRL]1 [0.008, 0.040] [0.026, 0.040] [0.015, 0.040] [0.025, 0.140] [0.009, 0.091] [0.018, 0.040] [0.003, 0.040] [0.010, 0.040] [0.020, 0.060] [0.044, 0.080] [0.010, 0.060]Southern Sacramento Valley study unit—ContinuedYOL-14 5/25/2005 — — — — — — — — — — — 0YOL-14 4/9/2008 — — — — — — — — — — — 0San Fernando–San Gabriel study unit ULASF-09 6/27/2005 E0.029 — — — — E0.008 3 — — E0.017 E0.019 3 E0.012 3ULASF-09 6/16/2008 E0.018 3 — — — — — — — E0.008 3 E0.015 3 — 0ULASF-10 6/8/2005 E0.007 — — — — — — — E0.011 3 E0.005 3 — 1ULASF-10 6/16/2008 — — — — — — — — — — — 0ULASG-01 6/7/2005 nc nc nc nc nc nc nc nc nc nc nc ncULASG-01 6/16/2008 E0.024 E0.016 — — — — — — E0.029 E0.054 — 4ULASG-08 6/15/2005 E0.025 — 0.019 — — — — E0.006 3 E0.028 — — 3ULASG-08 6/17/2008 E0.005 3 — E0.005 3 — — — — E0.017 3 E0.003 3 — — 0ULASG-15 6/23/2005 — — — — — — — — — — — 0ULASG-15 6/17/2008 — — — — — — — — — — — 0ULASG-17 7/11/2005 nc nc nc nc nc nc nc nc nc nc nc ncULASG-17 6/17/2008 0.046 0.079 — — — — — — E0.053 — — 3

Table 6B. Polar pesticides (Schedule 2060) in samples collected from trend wells for seven Groundwater Ambient Monitoring and Assessment (GAMA) study units.—Continued[The five-digit USGS parameter code below the constituent name is used to uniquely identify a specific constituent or property. Polar pesticides were analyzed in samples from 19 trend wells in 2004–05 and 23 trend wells in 2007–08; samples from 10 trend wells were analyzed during both time periods. Only wells analyzed during at least one of the periods are listed. Information about analytes given in table 3D. GAMA well identification number acronyms: San Diego Drainages study unit: SDALLV, Alluvial Basins study area; SDHDRK, Hard Rock study area; SDTEM, Temecula Valley study area; SDTEMFP, Temecula Valley study area flow-path well; SDWARN, Warner Valley study area. North San Francisco Bay study unit: NSFVOL, Volcanic Highlands study area; NSFVP, Valley and Plains study area; NSFWG, Wilson Grove Formation Highlands study area; NSFWGFP, Wilson Grove Formation Highlands study area flow-path well. Northern San Joaquin Basin study unit: COS, Cosumnes Basin study area; ESJ, Eastern San Joaquin Basin study area; NSJ-QPC, Uplands study area; TRCY, Tracy Basin study area. Southern Sacramento Valley study unit: NAM, North American study area; SAM, South American study area; SOL, Solano study area; SSV-QPC, Uplands study area; SUI, Suisun-Fairfield study area; YOL, Yolo study area. San Fernando–San Gabriel study unit: ULASF, San Fernando study area; ULASG, San Gabriel study area. Monterey Bay and Salinas Valley Basins study unit: MSMB, Monterey Bay study area; MSPR, Paso Robles study area; MSSC, Santa Cruz study area; MSSV, Salinas Valley study area. Southeast San Joaquin Valley study unit: KING, Kings study area; KWH, Kaweah study area; TLR, Tulare Lake study area; TULE, Tule study area. Benchmark type: MCL-CA, California Department of Public Health maximum contaminant level; HAL-US, U.S. Environmental Protection Agency lifetime health advisory level. Benchmark type and benchmark level as of April 1, 2010. Other abbreviations: USGS, U.S. Geological Survey; μg/L, micrograms per liter; na, not available; nc, not collected; —, not detected; E, estimated or having a higher degree of uncertainty]
108 Groundwater-Quality Data in Seven GAMA Study Units: Results from Initial Sampling and Resampling of Wells GAMA well identification number Sample dates Herbicide Herbicide degradate Beverage Detections per sample Detection summary Atrazine2 (μg/L) (39632) Tebuthiuron2 (μg/L) (82670) Diuron (μg/L) (49300) Metsulfuron- methyl (μg/L) (61697) Sulfome- turon- methyl (μg/L) (50337) Bromacil (μg/L) (04029) Dinoseb (μg/L) (49301) Diphenamid (μg/L) (04033) Deethyl- atrazine (2-Chloro-4-iso- propylamino-6- amino-s- triazine)2 (μg/L) (04040) Deisopropyl atrazine (2-Chloro-6- ethylamino- 4-amino-s- triazine) (μg/L) (04038) Caffeine (μg/L) (50305) Benchmark type MCL-CA HAL-US HAL-US na na na MCL-CA na na na na Benchmark level 1 500 10 na na na 7 na na na na [LRL]1 [0.008, 0.040] [0.026, 0.040] [0.015, 0.040] [0.025, 0.140] [0.009, 0.091] [0.018, 0.040] [0.003, 0.040] [0.010, 0.040] [0.020, 0.060] [0.044, 0.080] [0.010, 0.060] Monterey Bay and Salinas Valley Basins study unit MSMB-04 8/17/2005

—

—

—

—

—

—

—

—

—

—

— 0

MSMB-04 8/20/2008 nc nc nc nc nc nc nc nc nc nc nc ncMSSC-06 8/24/2005

—

—

—

—

—

—

—

—

—

—

— 0

MSSC-06 8/18/2008 nc nc nc nc nc nc nc nc nc nc nc ncSoutheast San Joaquin Valley study unitKING-11 10/20/2005

—

—

—

—

—

—

—

—

—

—

— 0

KING-11 11/5/2008 nc nc nc nc nc nc nc nc nc nc nc ncKING-13 10/20/2005

—

—

—

—

—

—

—

—

—

— 0.020 1

KING-13 11/5/2008 nc nc nc nc nc nc nc nc nc nc nc ncKING-17 10/26/2005

—

—

—

—

—

—

—

—

—

—

— 0

KING-17 11/4/2008 nc nc nc nc nc nc nc nc nc nc nc ncKWH-12 11/28/2005 0.030

—

— E0.067 

— E0.008 3 E0.003 3 — E0.007 3 E0.034 3 — 2

KWH-12 11/6/2008 nc nc nc nc nc nc nc nc nc nc nc nc

1 Minimum and maximum LRL used during study period, or only LRL used during study period.2 Schedule 2003/2032/2033 is the preferred method for atrazine, tebuthiuron, and deethylatrazine (table 6A). Results from Schedule 2060 are reported here for comparison purposes only.3 The detected concentration was less than the LT-MDL for this compound. These results are counted as non-detections for the purpose of calculating detection frequencies.

Table 6B. Polar pesticides (Schedule 2060) in samples collected from trend wells for seven Groundwater Ambient Monitoring and Assessment (GAMA) study units.—Continued[The five-digit USGS parameter code below the constituent name is used to uniquely identify a specific constituent or property. Polar pesticides were analyzed in samples from 19 trend wells in 2004–05 and 23 trend wells in 2007–08; samples from 10 trend wells were analyzed during both time periods. Only wells analyzed during at least one of the periods are listed. Information about analytes given in table 3D. GAMA well identification number acronyms: San Diego Drainages study unit: SDALLV, Alluvial Basins study area; SDHDRK, Hard Rock study area; SDTEM, Temecula Valley study area; SDTEMFP, Temecula Valley study area flow-path well; SDWARN, Warner Valley study area. North San Francisco Bay study unit: NSFVOL, Volcanic Highlands study area; NSFVP, Valley and Plains study area; NSFWG, Wilson Grove Formation Highlands study area; NSFWGFP, Wilson Grove Formation Highlands study area flow-path well. Northern San Joaquin Basin study unit: COS, Cosumnes Basin study area; ESJ, Eastern San Joaquin Basin study area; NSJ-QPC, Uplands study area; TRCY, Tracy Basin study area. Southern Sacramento Valley study unit: NAM, North American study area; SAM, South American study area; SOL, Solano study area; SSV-QPC, Uplands study area; SUI, Suisun-Fairfield study area; YOL, Yolo study area. San Fernando–San Gabriel study unit: ULASF, San Fernando study area; ULASG, San Gabriel study area. Monterey Bay and Salinas Valley Basins study unit: MSMB, Monterey Bay study area; MSPR, Paso Robles study area; MSSC, Santa Cruz study area; MSSV, Salinas Valley study area. Southeast San Joaquin Valley study unit: KING, Kings study area; KWH, Kaweah study area; TLR, Tulare Lake study area; TULE, Tule study area. Benchmark type: MCL-CA, California Department of Public Health maximum contaminant level; HAL-US, U.S. Environmental Protection Agency lifetime health advisory level. Benchmark type and benchmark level as of April 1, 2010. Other abbreviations: USGS, U.S. Geological Survey; μg/L, micrograms per liter; na, not available; nc, not collected; —, not detected; E, estimated or having a higher degree of uncertainty]
Tables 109

Table 7. Constituents of special interest in samples collected from trend wells sampled for seven Groundwater Ambient Monitoring 

and Assessment (GAMA) study units.

[The five-digit USGS parameter code below the constituent name is used to uniquely identify a specific constituent or property. Perchlorate was analyzed 

in samples from 36 trend wells during 2004–05 and 55 trend wells in 2007–08. NDMA was analyzed in 31 wells during 2004–05 and 17 wells in 2007–08; 

6 wells were analyzed during both periods. 1,2,3-Trichloropropane was analyzed in 25 wells during 2004–05 and 38 wells during 2007–08; 15 wells were 

analyzed during both periods. Information about analytes given in table 3H. GAMA well identification number acronyms: San Diego Drainages study 

unit: SDALLV, Alluvial Basins study area; SDHDRK, Hard Rock study area; SDTEM, Temecula Valley study area; SDTEMFP, Temecula Valley study area 

flow-path well; SDWARN, Warner Valley study area. North San Francisco Bay study unit: NSFVOL, Volcanic Highlands study area; NSFVP, Valley and Plains 

study area; NSFWG, Wilson Grove Formation Highlands study area; NSFWGFP, Wilson Grove Formation Highlands study area flow-path well. Northern 

San Joaquin Basin study unit: COS, Cosumnes Basin study area; ESJ, Eastern San Joaquin Basin study area; NSJ-QPC, Uplands study area; TRCY, Tracy 

Basin study area. Southern Sacramento Valley study unit: NAM, North American study area; SAM, South American study area; SOL, Solano study area; 

SSV-QPC, Uplands study area; SUI, Suisun-Fairfield study area; YOL, Yolo study area. San Fernando–San Gabriel study unit: ULASF, San Fernando study 

area; ULASG, San Gabriel study area. Monterey Bay and Salinas Valley Basins study unit: MSMB, Monterey Bay study area; MSPR, Paso Robles study 

area; MSSC, Santa Cruz study area; MSSV, Salinas Valley study area. Southeast San Joaquin Valley study unit: KING, Kings study area; KWH, Kaweah 

study area; TLR, Tulare Lake study area; TULE, Tule study area. Benchmark type: HAL-US, U.S. Environmental Protection Agency lifetime health advisory 

level; NL-CA, CDPH notification level; MCL-CA, CDPH maximum contaminant level. Benchmark type and benchmark level as of April 1, 2010. Other 

abbreviations: USGS, U.S. Geological Survey; CDPH, California Department of Public Health; μg/L, micrograms per liter; LRL, laboratory reporting level; 

MRL, minimum reporting level; *, value greater than benchmark level; — not detected; <, less than; nc, not collected]

GAMA 

well 

identification 

number

Sample 

dates

Perchlorate 2

(μg/L) 

(61209)

Perchlorate 3

(μg/L) 

(63790)

N-Nitrosodimethylamine 

(NDMA) 4

(μg/L) 

(64176, 34438)

1,2,3-Trichloropropane 5

(μg/L) 

(77443)

Benchmark type1 MCL-CA MCL-CA NL-CA HAL-US6

Benchmark level 6 6 0.002 40

[MRL(s)] [0.25 0.5, 1] [0.1] [0.002] [0.005]

San Diego Drainages study unit

SDALLV-07 7/14/2004 <1 nc — nc

SDALLV-07 9/12/2007 <1 1.01 nc nc

SDALLV-11 7/15/2004 2.5 nc — nc

SDALLV-11 9/13/2007 3.6 4.89 nc nc

SDHDRK-01 7/12/2004 1.2 nc — nc

SDHDRK-01 9/13/2007 1.0 1.93 nc nc

SDHDRK-09 7/27/2004 <0.5 nc — nc

SDHDRK-09 9/11/2007 nc — nc nc

SDTEM-04 5/24/2004 nc nc nc nc

SDTEM-04 9/18/2007 1.6 2.14 nc nc

SDTEMFP-01 5/19/2004 1.4 nc — nc

SDTEMFP-01 9/19/2007 1.1 1.18 nc nc

SDWARN-01 6/17/2004 <0.25 nc — nc

SDWARN-01 9/11/2007 <0.5 0.28 nc nc

North San Francisco Bay study unit

NSFVOL-14 10/7/2004 <0.5 nc — —

NSFVOL-14 8/21/2007 <0.5 0.33 nc nc

NSFVOL-18 10/20/2004 <0.5 nc — —

NSFVOL-18 8/28/2007 <0.5 nc nc nc

NSFVP-29 9/28/2004 <0.5 nc — —

NSFVP-29 8/27/2007 <0.5 nc nc nc

NSFVP-34 10/18/2004 <0.5 nc — —

NSFVP-34 8/22/2007 <0.5 nc nc nc

NSFVP-36 10/19/2004 <0.5 nc — —

NSFVP-36 8/20/2007 <1 — nc nc

NSFVP-38 10/20/2004 <0.5 nc — —

NSFVP-38 8/22/2007 <1 nc nc nc
110 Groundwater-Quality Data in Seven GAMA Study Units: Results from Initial Sampling and Resampling of Wells

GAMA 

well 

identification 

number

Sample 

dates

Perchlorate 2

(μg/L) 

(61209)

Perchlorate 3

(μg/L) 

(63790)

N-Nitrosodimethylamine 

(NDMA) 4

(μg/L) 

(64176, 34438)

1,2,3-Trichloropropane 5

(μg/L) 

(77443)

Benchmark type1 MCL-CA MCL-CA NL-CA HAL-US6

Benchmark level 6 6 0.002 40

[MRL(s)] [0.25 0.5, 1] [0.1] [0.002] [0.005]

North San Francisco Bay study unit—Continued

NSFVP-39 10/21/2004 <0.5 nc — —

NSFVP-39 11/16/2007 <0.5 nc nc nc

NSFVP-41 10/21/2004 <0.5 nc — —

NSFVP-41 8/20/2007 <0.5 — nc nc

NSFWG-03 9/21/2004 <0.5 nc — —

NSFWG-03 8/29/2007 <0.5 nc nc nc

NSFWGFP-01 10/5/2004 <0.5 nc — —

NSFWGFP-01 8/29/2007 <0.5 nc nc nc

Northern San Joaquin Basin study unit 

COS-08 1/3/2005 nc nc nc nc

COS-08 4/3/2008 nc — nc —

ESJ-01 1/24/2005 nc nc nc nc

ESJ-01 4/2/2008 nc — nc —

ESJ-06 1/10/2005 <0.5 nc — —

ESJ-06 4/2/2008 nc 0.45 nc —

NSJ-QPC-04 1/24/2005 <0.5 nc — —

NSJ-QPC-04 4/1/2008 nc — nc —

TRCY-03 1/6/2005 <0.5 nc — —

TRCY-03 3/31/2008 nc 0.47 nc —

Southern Sacramento Valley study unit

NAM-03 3/29/2005 nc nc nc nc

NAM-03 4/10/2008 nc 0.27 nc —

SAM-10 4/21/2005 nc nc nc nc

SAM-10 4/8/2008 nc 1.95 nc 0.006

SOL-08 5/10/2005 nc nc nc nc

SOL-08 4/8/2008 nc 0.47 nc 0.006

SSV-QPC-07 4/4/2005 0.89 nc — —

Table 7. Constituents of special interest in samples collected from trend wells sampled for seven Groundwater Ambient Monitoring 

and Assessment (GAMA) study units.—Continued

[The five-digit USGS parameter code below the constituent name is used to uniquely identify a specific constituent or property. Perchlorate was analyzed 

in samples from 36 trend wells during 2004–05 and 55 trend wells in 2007–08. NDMA was analyzed in 31 wells during 2004–05 and 17 wells in 2007–08; 

6 wells were analyzed during both periods. 1,2,3-Trichloropropane was analyzed in 25 wells during 2004–05 and 38 wells during 2007–08; 15 wells were 

analyzed during both periods. Information about analytes given in table 3H. GAMA well identification number acronyms: San Diego Drainages study 

unit: SDALLV, Alluvial Basins study area; SDHDRK, Hard Rock study area; SDTEM, Temecula Valley study area; SDTEMFP, Temecula Valley study area 

flow-path well; SDWARN, Warner Valley study area. North San Francisco Bay study unit: NSFVOL, Volcanic Highlands study area; NSFVP, Valley and Plains 

study area; NSFWG, Wilson Grove Formation Highlands study area; NSFWGFP, Wilson Grove Formation Highlands study area flow-path well. Northern 

San Joaquin Basin study unit: COS, Cosumnes Basin study area; ESJ, Eastern San Joaquin Basin study area; NSJ-QPC, Uplands study area; TRCY, Tracy 

Basin study area. Southern Sacramento Valley study unit: NAM, North American study area; SAM, South American study area; SOL, Solano study area; 

SSV-QPC, Uplands study area; SUI, Suisun-Fairfield study area; YOL, Yolo study area. San Fernando–San Gabriel study unit: ULASF, San Fernando study 

area; ULASG, San Gabriel study area. Monterey Bay and Salinas Valley Basins study unit: MSMB, Monterey Bay study area; MSPR, Paso Robles study 

area; MSSC, Santa Cruz study area; MSSV, Salinas Valley study area. Southeast San Joaquin Valley study unit: KING, Kings study area; KWH, Kaweah 

study area; TLR, Tulare Lake study area; TULE, Tule study area. Benchmark type: HAL-US, U.S. Environmental Protection Agency lifetime health advisory 

level; NL-CA, CDPH notification level; MCL-CA, CDPH maximum contaminant level. Benchmark type and benchmark level as of April 1, 2010. Other 

abbreviations: USGS, U.S. Geological Survey; CDPH, California Department of Public Health; μg/L, micrograms per liter; LRL, laboratory reporting level; 

MRL, minimum reporting level; *, value greater than benchmark level; — not detected; <, less than; nc, not collected]
Tables 111

GAMA 

well 

identification 

number

Sample 

dates

Perchlorate 2

(μg/L) 

(61209)

Perchlorate 3

(μg/L) 

(63790)

N-Nitrosodimethylamine 

(NDMA) 4

(μg/L) 

(64176, 34438)

1,2,3-Trichloropropane 5

(μg/L) 

(77443)

Benchmark type1 MCL-CA MCL-CA NL-CA HAL-US6

Benchmark level 6 6 0.002 40

[MRL(s)] [0.25 0.5, 1] [0.1] [0.002] [0.005]

Southern Sacramento Valley study unit—Continued

SSV-QPC-07 4/10/2008 nc 0.67 nc 0.005

SUI-03 5/12/2005 nc nc nc nc

SUI-03 4/9/2008 nc 0.9 nc —

YOL-01 4/11/2005 nc nc nc nc

YOL-01 4/7/2008 nc 0.56 nc 0.006

YOL-14 5/25/2005 <1 nc — —

YOL-14 4/9/2008 nc — nc 0.005

San Fernando–San Gabriel study unit 

ULASF-09 6/27/2005 <0.5 nc — —

ULASF-09 6/16/2008 nc 2.24 — —

ULASF-10 6/8/2005 <0.5 nc — —

ULASF-10 6/16/2008 nc — — —

ULASG-01 6/7/2005 nc nc nc nc

ULASG-01 6/16/2008 nc *7.77 — —

ULASG-08 6/15/2005 3.8 nc — —

ULASG-08 6/17/2008 nc 3.98 — —

ULASG-15 6/23/2005 <0.5 nc — —

ULASG-15 6/17/2008 nc 0.19 — —

ULASG-17 7/11/2005 nc nc nc nc

ULASG-17 6/17/2008 nc *7.60 — —

Monterey Bay and Salinas Valley Basins study unit

MSMB-03 8/31/2005 nc nc nc nc

MSMB-03 8/20/2008 nc 0.10 — —

MSMB-04 8/17/2005 <1 nc — —

MSMB-04 8/20/2008 nc — — —

MSMB-16 8/17/2005 nc nc nc nc

MSMB-16 8/19/2008 nc 0.50 — —

Table 7. Constituents of special interest in samples collected from trend wells sampled for seven Groundwater Ambient Monitoring 

and Assessment (GAMA) study units.—Continued

[The five-digit USGS parameter code below the constituent name is used to uniquely identify a specific constituent or property. Perchlorate was analyzed 

in samples from 36 trend wells during 2004–05 and 55 trend wells in 2007–08. NDMA was analyzed in 31 wells during 2004–05 and 17 wells in 2007–08; 

6 wells were analyzed during both periods. 1,2,3-Trichloropropane was analyzed in 25 wells during 2004–05 and 38 wells during 2007–08; 15 wells were 

analyzed during both periods. Information about analytes given in table 3H. GAMA well identification number acronyms: San Diego Drainages study 

unit: SDALLV, Alluvial Basins study area; SDHDRK, Hard Rock study area; SDTEM, Temecula Valley study area; SDTEMFP, Temecula Valley study area 

flow-path well; SDWARN, Warner Valley study area. North San Francisco Bay study unit: NSFVOL, Volcanic Highlands study area; NSFVP, Valley and Plains 

study area; NSFWG, Wilson Grove Formation Highlands study area; NSFWGFP, Wilson Grove Formation Highlands study area flow-path well. Northern 

San Joaquin Basin study unit: COS, Cosumnes Basin study area; ESJ, Eastern San Joaquin Basin study area; NSJ-QPC, Uplands study area; TRCY, Tracy 

Basin study area. Southern Sacramento Valley study unit: NAM, North American study area; SAM, South American study area; SOL, Solano study area; 

SSV-QPC, Uplands study area; SUI, Suisun-Fairfield study area; YOL, Yolo study area. San Fernando–San Gabriel study unit: ULASF, San Fernando study 

area; ULASG, San Gabriel study area. Monterey Bay and Salinas Valley Basins study unit: MSMB, Monterey Bay study area; MSPR, Paso Robles study 

area; MSSC, Santa Cruz study area; MSSV, Salinas Valley study area. Southeast San Joaquin Valley study unit: KING, Kings study area; KWH, Kaweah 

study area; TLR, Tulare Lake study area; TULE, Tule study area. Benchmark type: HAL-US, U.S. Environmental Protection Agency lifetime health advisory 

level; NL-CA, CDPH notification level; MCL-CA, CDPH maximum contaminant level. Benchmark type and benchmark level as of April 1, 2010. Other 

abbreviations: USGS, U.S. Geological Survey; CDPH, California Department of Public Health; μg/L, micrograms per liter; LRL, laboratory reporting level; 

MRL, minimum reporting level; *, value greater than benchmark level; — not detected; <, less than; nc, not collected]
112 Groundwater-Quality Data in Seven GAMA Study Units: Results from Initial Sampling and Resampling of Wells

GAMA 

well 

identification 

number

Sample 

dates

Perchlorate 2

(μg/L) 

(61209)

Perchlorate 3

(μg/L) 

(63790)

N-Nitrosodimethylamine 

(NDMA) 4

(μg/L) 

(64176, 34438)

1,2,3-Trichloropropane 5

(μg/L) 

(77443)

Benchmark type1 MCL-CA MCL-CA NL-CA HAL-US6

Benchmark level 6 6 0.002 40

[MRL(s)] [0.25 0.5, 1] [0.1] [0.002] [0.005]

Monterey Bay and Salinas Valley Basins study unit—Continued

MSMB-28 8/3/2005 nc nc nc nc

MSMB-28 8/21/2008 nc 0.79 — —

MSMB-31 8/11/2005 nc nc nc nc

MSMB-31 8/21/2008 nc 0.65 — —

MSPR-03 7/28/2005 nc nc nc nc

MSPR-03 11/14/2008 nc — — —

MSPR-09 7/18/2005 nc nc nc nc

MSPR-09 11/14/2008 nc 0.12 — —

MSSC-06 8/24/2005 <0.5 nc — —

MSSC-06 8/18/2008 nc — — —

MSSC-11 9/13/2005 nc nc nc nc

MSSC-11 8/19/2008 nc — — —

MSSV-06 8/2/2005 nc nc nc nc

MSSV-06 11/13/2008 nc — — —

MSSV-15 8/12/2005 nc nc nc nc

MSSV-15 11/13/2008 nc — — —

Southeast San Joaquin Valley study unit

KING-11 10/20/2005 0.94 nc — —

KING-11 11/5/2008 nc 0.73 nc —

KING-13 10/20/2005 0.62 nc — —

KING-13 11/5/2008 nc 0.68 nc —

KING-17 10/26/2005 <0.5 nc — —

KING-17 11/4/2008 nc 0.86 nc —

KING-24 11/5/2005 <0.5 nc nc nc

KING-24 11/3/2008 nc 0.61 nc —

KWH-10 11/17/2005 2.7 nc nc nc

KWH-10 11/5/2008 nc 3.92 nc —

Table 7. Constituents of special interest in samples collected from trend wells sampled for seven Groundwater Ambient Monitoring 

and Assessment (GAMA) study units.—Continued

[The five-digit USGS parameter code below the constituent name is used to uniquely identify a specific constituent or property. Perchlorate was analyzed 

in samples from 36 trend wells during 2004–05 and 55 trend wells in 2007–08. NDMA was analyzed in 31 wells during 2004–05 and 17 wells in 2007–08; 

6 wells were analyzed during both periods. 1,2,3-Trichloropropane was analyzed in 25 wells during 2004–05 and 38 wells during 2007–08; 15 wells were 

analyzed during both periods. Information about analytes given in table 3H. GAMA well identification number acronyms: San Diego Drainages study 

unit: SDALLV, Alluvial Basins study area; SDHDRK, Hard Rock study area; SDTEM, Temecula Valley study area; SDTEMFP, Temecula Valley study area 

flow-path well; SDWARN, Warner Valley study area. North San Francisco Bay study unit: NSFVOL, Volcanic Highlands study area; NSFVP, Valley and Plains 

study area; NSFWG, Wilson Grove Formation Highlands study area; NSFWGFP, Wilson Grove Formation Highlands study area flow-path well. Northern 

San Joaquin Basin study unit: COS, Cosumnes Basin study area; ESJ, Eastern San Joaquin Basin study area; NSJ-QPC, Uplands study area; TRCY, Tracy 

Basin study area. Southern Sacramento Valley study unit: NAM, North American study area; SAM, South American study area; SOL, Solano study area; 

SSV-QPC, Uplands study area; SUI, Suisun-Fairfield study area; YOL, Yolo study area. San Fernando–San Gabriel study unit: ULASF, San Fernando study 

area; ULASG, San Gabriel study area. Monterey Bay and Salinas Valley Basins study unit: MSMB, Monterey Bay study area; MSPR, Paso Robles study 

area; MSSC, Santa Cruz study area; MSSV, Salinas Valley study area. Southeast San Joaquin Valley study unit: KING, Kings study area; KWH, Kaweah 

study area; TLR, Tulare Lake study area; TULE, Tule study area. Benchmark type: HAL-US, U.S. Environmental Protection Agency lifetime health advisory 

level; NL-CA, CDPH notification level; MCL-CA, CDPH maximum contaminant level. Benchmark type and benchmark level as of April 1, 2010. Other 

abbreviations: USGS, U.S. Geological Survey; CDPH, California Department of Public Health; μg/L, micrograms per liter; LRL, laboratory reporting level; 

MRL, minimum reporting level; *, value greater than benchmark level; — not detected; <, less than; nc, not collected]
Tables 113

GAMA 

well 

identification 

number

Sample 

dates

Perchlorate 2

(μg/L) 

(61209)

Perchlorate 3

(μg/L) 

(63790)

N-Nitrosodimethylamine 

(NDMA) 4

(μg/L) 

(64176, 34438)

1,2,3-Trichloropropane 5

(μg/L) 

(77443)

Benchmark type1 MCL-CA MCL-CA NL-CA HAL-US6

Benchmark level 6 6 0.002 40

[MRL(s)] [0.25 0.5, 1] [0.1] [0.002] [0.005]

Southeast San Joaquin Valley study unit—Continued

KWH-12 11/28/2005 <0.5 nc — 0.008

KWH-12 11/6/2008 nc 0.93 nc 0.009

TLR-03 11/29/2005 <0.5 nc nc nc

TLR-03 11/4/2008 nc — nc —

TULE-05 12/5/2005 <1 nc nc nc

TULE-05 11/3/2008 nc 0.82 nc —

TULE-10 12/7/2005 0.64 nc nc nc

TULE-10 11/3/2008 nc 0.75 nc 0.006

1

 Maximum contaminant level benchmarks are listed as MCL-US when the MCL-US and the MCL-CA are identical and as MCL-CA when the MCL-CA is 

lower than the MCL-US or no MCL-US exists.

2

 Prior to October 1, 2007, perchlorate analyses were performed on unfiltered samples by Mongomery Watson Harza (MWH) Laboratories (table A1). The 

nominal MRLs were 0.25 or 0.5 μg/L; some higher salinity samples were diluted for analysis and had an MRL of 1 μg/L.

3

 After August 15, 2007, perchlorate analyses were performed on filtered samples by Weck Laboratories, Inc. (table A1).

4

 NDMA analyses performed prior to October 1, 2007, by MWH were reported using parameter code 64176 and expressed in nanograms per liter, converted 

to micrograms per liter here. NDMA analyses performed after October 1, 2007, by Weck were reported using paramenter code 34438.

5

 1,2,3-Trichloropropane (1,2,3-TCP) analyses were performed by MWH prior to October 1, 2007, and by Weck after that date. All samples were additionally 

analyzed for 1,2,3-TCP by the USGS NWQL Schedule 2020 with no detections by that analytical method, which had an LRL ranging from 0.12 to 0.18 μg/L. 

6

 In some earlier reports in this series, the NL-CA (0.005 μg/L) was used as the comparison benchmark for 1,2,3-TCP.

Table 7. Constituents of special interest in samples collected from trend wells sampled for seven Groundwater Ambient Monitoring 

and Assessment (GAMA) study units.—Continued

[The five-digit USGS parameter code below the constituent name is used to uniquely identify a specific constituent or property. Perchlorate was analyzed 

in samples from 36 trend wells during 2004–05 and 55 trend wells in 2007–08. NDMA was analyzed in 31 wells during 2004–05 and 17 wells in 2007–08; 

6 wells were analyzed during both periods. 1,2,3-Trichloropropane was analyzed in 25 wells during 2004–05 and 38 wells during 2007–08; 15 wells were 

analyzed during both periods. Information about analytes given in table 3H. GAMA well identification number acronyms: San Diego Drainages study 

unit: SDALLV, Alluvial Basins study area; SDHDRK, Hard Rock study area; SDTEM, Temecula Valley study area; SDTEMFP, Temecula Valley study area 

flow-path well; SDWARN, Warner Valley study area. North San Francisco Bay study unit: NSFVOL, Volcanic Highlands study area; NSFVP, Valley and Plains 

study area; NSFWG, Wilson Grove Formation Highlands study area; NSFWGFP, Wilson Grove Formation Highlands study area flow-path well. Northern 

San Joaquin Basin study unit: COS, Cosumnes Basin study area; ESJ, Eastern San Joaquin Basin study area; NSJ-QPC, Uplands study area; TRCY, Tracy 

Basin study area. Southern Sacramento Valley study unit: NAM, North American study area; SAM, South American study area; SOL, Solano study area; 

SSV-QPC, Uplands study area; SUI, Suisun-Fairfield study area; YOL, Yolo study area. San Fernando–San Gabriel study unit: ULASF, San Fernando study 

area; ULASG, San Gabriel study area. Monterey Bay and Salinas Valley Basins study unit: MSMB, Monterey Bay study area; MSPR, Paso Robles study 

area; MSSC, Santa Cruz study area; MSSV, Salinas Valley study area. Southeast San Joaquin Valley study unit: KING, Kings study area; KWH, Kaweah 

study area; TLR, Tulare Lake study area; TULE, Tule study area. Benchmark type: HAL-US, U.S. Environmental Protection Agency lifetime health advisory 

level; NL-CA, CDPH notification level; MCL-CA, CDPH maximum contaminant level. Benchmark type and benchmark level as of April 1, 2010. Other 

abbreviations: USGS, U.S. Geological Survey; CDPH, California Department of Public Health; μg/L, micrograms per liter; LRL, laboratory reporting level; 

MRL, minimum reporting level; *, value greater than benchmark level; — not detected; <, less than; nc, not collected]
114 Groundwater-Quality Data in Seven GAMA Study Units: Results from Initial Sampling and Resampling of Wells

Table 8. Nutrients in samples collected from trend wells for seven Groundwater Ambient Monitoring and Assessment (GAMA) study 

units.

[The five-digit USGS parameter code below the constituent name is used to uniquely identify a specific constituent or property. Nutrients were analyzed 

in samples from 19 trend wells during 2004–05 and 50 trend wells in 2007–08; 18 wells were analyzed during both periods. Information about analytes 

given in table 3E. GAMA well identification number acronyms: San Diego Drainages study unit: SDALLV, Alluvial Basins study area; SDHDRK, Hard 

Rock study area; SDTEM, Temecula Valley study area; SDTEMFP, Temecula Valley study area flow path well; SDWARN, Warner Valley study area. North 

San Francisco Bay study unit: NSFVOL, Volcanic Highlands study area; NSFVP, Valley and Plains study area; NSFWG, Wilson Grove Formation Highlands 

study area; NSFWGFP, Wilson Grove Formation Highlands study area flow-path well. Northern San Joaquin Basin study unit: COS, Cosumnes Basin 

study area; ESJ, Eastern San Joaquin Basin study area; NSJ-QPC, Uplands study area; TRCY, Tracy Basin study area. Southern Sacramento Valley study 

unit: NAM, North American study area; SAM, South American study area; SOL, Solano study area; SSV-QPC, Uplands study area; SUI, Suisun-Fairfield 

study area; YOL, Yolo study area. San Fernando–San Gabriel study unit: ULASF, San Fernando study area; ULASG, San Gabriel study area. Monterey 

Bay and Salinas Valley Basins study unit: MSMB, Monterey Bay study area; MSPR, Paso Robles study area; MSSC, Santa Cruz study area; MSSV, 

Salinas Valley study area. Southeast San Joaquin Valley study unit: KING, Kings study area; KWH, Kaweah study area; TLR, Tulare Lake study area; 

TULE, Tule study area. Benchmark type: HAL-US, USEPA lifetime health advisory level; MCL-US, USEPA maximum contaminant level; MCL-CA, CDPH 

maximum contaminant level; CDPH, California Department of Public Health. Benchmark type, benchmark level, and RL as of April 1, 2010. Other 

abbreviations: USGS, U.S. Geological Survey; USEPA, U.S. Environmental Protection Agency; mg/L, milligrams per liter; LRL, laboratory reporting level; 

E, estimated or having a higher degree of uncertainty; nc, not collected; na, not available; *, value greater than benchmark level; —, not detected]

GAMA 

well 

identification 

number

Sample 

dates

Ammonia 

(as nitrogen) 

(mg/L) 

(00608)

 Nitrite 

(as nitrogen) 

(mg/L) 

(00613)

Nitrite plus 

nitrate 

(as nitrogen) 

(mg/L) 

(00631)

Total nitrogen 

(ammonia + nitrate + 

nitrite + organic nitrogen) 

(mg/L) 

(62854)

Orthophosphate 

(as phosphorus) 

(mg/L) 

(00671)

Benchmark type1 HAL-US MCL-US MCL-US na na

Benchmark level 2 24.7 1 10 na na

[LRL]3 [0.010, 0.04] [0.002, 0.008] [0.04, 0.06] [0.03, 0.10] [0.006]

 San Diego Drainages study unit

SDHDRK-09 7/27/2004 nc nc nc nc nc

SDHDRK-09 9/11/2007 — — 0.56 0.6 0.056

SDTEMFP-01 5/19/2004 — 0.028 3.84 3.67 0.015

SDTEMFP-01 9/19/2007 nc nc nc nc nc

SDWARN-01 6/17/2004 nc nc nc nc nc

SDWARN-01 9/11/2007 — 0.006 2.14 2.23 0.341

 North San Francisco Bay study unit

NSFVOL-14 10/7/2004 — — 0.79 0.76 0.181

NSFVOL-14 8/21/2007 0.026 E0.001 0.69 0.76 0.164

NSFVOL-18 10/20/2004 nc nc nc nc nc

NSFVOL-18 8/28/2007 0.151 — — 0.2 0.207

NSFVP-29 9/28/2004 — — 1.89 1.78 0.010

NSFVP-29 8/27/2007 — — 1.4 1.47 0.019

NSFVP-34 10/18/2004 0.070 — — E0.06 0.318

NSFVP-34 8/22/2007 0.072 E0.001 — 0.09 0.338

NSFVP-36 10/19/2004 nc nc nc nc nc

NSFVP-36 8/20/2007 1.45 E0.001 — 1.66 0.586

NSFVP-38 10/20/2004 0.220 — E0.06 0.28 0.146

NSFVP-38 8/22/2007 0.252 E0.002 — 0.31 0.158

NSFVP-39 10/21/2004 nc nc nc nc nc

NSFVP-39 11/16/2007 E0.019 — — — 0.135

NSFVP-41 10/21/2004 nc nc nc nc nc

NSFVP-41 8/20/2007 0.027 0.055 0.82 0.86 0.221

NSFWG-03 9/21/2004 nc nc nc nc nc

NSFWG-03 8/29/2007 — — — — 0.147

NSFWGFP-01 10/5/2004 — — 0.06 0.09 0.008

NSFWGFP-01 8/29/2007 — — 0.09 0.06 0.019
Tables 115

GAMA 

well 

identification 

number

Sample 

dates

Ammonia 

(as nitrogen) 

(mg/L) 

(00608)

 Nitrite 

(as nitrogen) 

(mg/L) 

(00613)

Nitrite plus 

nitrate 

(as nitrogen) 

(mg/L) 

(00631)

Total nitrogen 

(ammonia + nitrate + 

nitrite + organic nitrogen) 

(mg/L) 

(62854)

Orthophosphate 

(as phosphorus) 

(mg/L) 

(00671)

Benchmark type1 HAL-US MCL-US MCL-US na na

Benchmark level 2 24.7 1 10 na na

[LRL]3 [0.010, 0.04] [0.002, 0.008] [0.04, 0.06] [0.03, 0.10] [0.006]

 Northern San Joaquin Basin study unit

COS-08 1/3/2005 nc nc nc nc nc

COS-08 4/3/2008 0.035 — 0.18 0.20 0.162

ESJ-01 1/24/2005 nc nc nc nc nc

ESJ-01 4/2/2008 — — 3.52 3.71 0.034

ESJ-06 1/10/2005 nc nc nc nc nc

ESJ-06 4/2/2008 — — 2.77 2.9 0.039

NSJ-QPC-04 1/24/2005 nc nc nc nc nc

NSJ-QPC-04 4/1/2008 — — 1.09 1.15 0.286

TRCY-03 1/6/2005 — — 2.30 2.44 0.016

TRCY-03 3/31/2008 — — 2.48 2.61 0.021

 Southern Sacramento Valley study unit 

NAM-03 3/29/2005 nc nc nc nc nc

NAM-03 4/10/2008 — — 0.85 0.90 0.107

SAM-10 4/21/2005 nc nc nc nc nc

SAM-10 4/8/2008 — — 7.27 7.65 0.040

SOL-08 5/10/2005 nc nc nc nc nc

SOL-08 4/8/2008 — — 0.75 0.77 0.025

SSV-QPC-07 4/4/2005 — — 1.80 1.79 0.084

SSV-QPC-07 4/10/2008 — — 1.84 1.90 0.101

SUI-03 5/12/2005 nc nc nc nc nc

SUI-03 4/9/2008 — — 5.79 6.08 0.041

YOL-01 4/11/2005 nc nc nc nc nc

YOL-01 4/7/2008 E0.010 — 5.17 5.52 0.040

YOL-14 5/25/2005 0.080 — — 0.09 0.027

YOL-14 4/9/2008 0.082 — E0.02 0.09 0.121

Table 8. Nutrients in samples collected from trend wells for seven Groundwater Ambient Monitoring and Assessment (GAMA) study 

units.—Continued

[The five-digit USGS parameter code below the constituent name is used to uniquely identify a specific constituent or property. Nutrients were analyzed 

in samples from 19 trend wells during 2004–05 and 50 trend wells in 2007–08; 18 wells were analyzed during both periods. Information about analytes 

given in table 3E. GAMA well identification number acronyms: San Diego Drainages study unit: SDALLV, Alluvial Basins study area; SDHDRK, Hard 

Rock study area; SDTEM, Temecula Valley study area; SDTEMFP, Temecula Valley study area flow path well; SDWARN, Warner Valley study area. North 

San Francisco Bay study unit: NSFVOL, Volcanic Highlands study area; NSFVP, Valley and Plains study area; NSFWG, Wilson Grove Formation Highlands 

study area; NSFWGFP, Wilson Grove Formation Highlands study area flow-path well. Northern San Joaquin Basin study unit: COS, Cosumnes Basin 

study area; ESJ, Eastern San Joaquin Basin study area; NSJ-QPC, Uplands study area; TRCY, Tracy Basin study area. Southern Sacramento Valley study 

unit: NAM, North American study area; SAM, South American study area; SOL, Solano study area; SSV-QPC, Uplands study area; SUI, Suisun-Fairfield 

study area; YOL, Yolo study area. San Fernando–San Gabriel study unit: ULASF, San Fernando study area; ULASG, San Gabriel study area. Monterey 

Bay and Salinas Valley Basins study unit: MSMB, Monterey Bay study area; MSPR, Paso Robles study area; MSSC, Santa Cruz study area; MSSV, 

Salinas Valley study area. Southeast San Joaquin Valley study unit: KING, Kings study area; KWH, Kaweah study area; TLR, Tulare Lake study area; 

TULE, Tule study area. Benchmark type: HAL-US, USEPA lifetime health advisory level; MCL-US, USEPA maximum contaminant level; MCL-CA, CDPH 

maximum contaminant level; CDPH, California Department of Public Health. Benchmark type, benchmark level, and RL as of April 1, 2010. Other 

abbreviations: USGS, U.S. Geological Survey; USEPA, U.S. Environmental Protection Agency; mg/L, milligrams per liter; LRL, laboratory reporting level; 

E, estimated or having a higher degree of uncertainty; nc, not collected; na, not available; *, value greater than benchmark level; —, not detected]
116 Groundwater-Quality Data in Seven GAMA Study Units: Results from Initial Sampling and Resampling of Wells

GAMA 

well 

identification 

number

Sample 

dates

Ammonia 

(as nitrogen) 

(mg/L) 

(00608)

 Nitrite 

(as nitrogen) 

(mg/L) 

(00613)

Nitrite plus 

nitrate 

(as nitrogen) 

(mg/L) 

(00631)

Total nitrogen 

(ammonia + nitrate + 

nitrite + organic nitrogen) 

(mg/L) 

(62854)

Orthophosphate 

(as phosphorus) 

(mg/L) 

(00671)

Benchmark type1 HAL-US MCL-US MCL-US na na

Benchmark level 2 24.7 1 10 na na

[LRL]3 [0.010, 0.04] [0.002, 0.008] [0.04, 0.06] [0.03, 0.10] [0.006]

 San Fernando–San Gabriel study unit 

ULASF-09 6/27/2005 — — 9.74 9.61 0.024

ULASF-09 6/16/2008 — — *10.9 11.2 0.036

ULASF-10 6/8/2005 — — 1.90 1.83 0.022

ULASF-10 6/16/2008 — — 0.56 0.54 0.021

ULASG-01 6/7/2005 nc nc nc nc nc

ULASG-01 6/16/2008 — — *10.4 10.8 0.066

ULASG-08 6/15/2005 — — *10.3 10.5 0.018

ULASG-08 6/17/2008 — — *11.6 12 0.028

ULASG-15 6/23/2005 — — 0.79 0.85 E0.003

ULASG-15 6/17/2008 — — 1.05 1.08 0.009

ULASG-17 7/11/2005 nc nc nc nc nc

ULASG-17 6/17/2008 — — *11.9 12.4 0.028

 Monterey Bay and Salinas Valley Basins study unit

MSMB-03 8/31/2005 nc nc nc nc nc

MSMB-03 8/20/2008 0.192 — — 0.20 0.161

MSMB-04 8/17/2005 — — — — 0.011

MSMB-04 8/20/2008 — — — — 0.019

MSMB-16 8/17/2005 nc nc nc nc nc

MSMB-16 8/19/2008 — — 4.64 4.79 0.036

MSMB-28 8/3/2005 nc nc nc nc nc

MSMB-28 8/21/2008 — — 1.9 1.94 0.039

MSMB-31 8/11/2005 nc nc nc nc nc

MSMB-31 8/21/2008 — — 7.06 7.75 0.048

MSPR-03 7/28/2005 nc nc nc nc nc

MSPR-03 11/14/2008 0.314 — 0.06 0.38 0.019

Table 8. Nutrients in samples collected from trend wells for seven Groundwater Ambient Monitoring and Assessment (GAMA) study 

units.—Continued

[The five-digit USGS parameter code below the constituent name is used to uniquely identify a specific constituent or property. Nutrients were analyzed 

in samples from 19 trend wells during 2004–05 and 50 trend wells in 2007–08; 18 wells were analyzed during both periods. Information about analytes 

given in table 3E. GAMA well identification number acronyms: San Diego Drainages study unit: SDALLV, Alluvial Basins study area; SDHDRK, Hard 

Rock study area; SDTEM, Temecula Valley study area; SDTEMFP, Temecula Valley study area flow path well; SDWARN, Warner Valley study area. North 

San Francisco Bay study unit: NSFVOL, Volcanic Highlands study area; NSFVP, Valley and Plains study area; NSFWG, Wilson Grove Formation Highlands 

study area; NSFWGFP, Wilson Grove Formation Highlands study area flow-path well. Northern San Joaquin Basin study unit: COS, Cosumnes Basin 

study area; ESJ, Eastern San Joaquin Basin study area; NSJ-QPC, Uplands study area; TRCY, Tracy Basin study area. Southern Sacramento Valley study 

unit: NAM, North American study area; SAM, South American study area; SOL, Solano study area; SSV-QPC, Uplands study area; SUI, Suisun-Fairfield 

study area; YOL, Yolo study area. San Fernando–San Gabriel study unit: ULASF, San Fernando study area; ULASG, San Gabriel study area. Monterey 

Bay and Salinas Valley Basins study unit: MSMB, Monterey Bay study area; MSPR, Paso Robles study area; MSSC, Santa Cruz study area; MSSV, 

Salinas Valley study area. Southeast San Joaquin Valley study unit: KING, Kings study area; KWH, Kaweah study area; TLR, Tulare Lake study area; 

TULE, Tule study area. Benchmark type: HAL-US, USEPA lifetime health advisory level; MCL-US, USEPA maximum contaminant level; MCL-CA, CDPH 

maximum contaminant level; CDPH, California Department of Public Health. Benchmark type, benchmark level, and RL as of April 1, 2010. Other 

abbreviations: USGS, U.S. Geological Survey; USEPA, U.S. Environmental Protection Agency; mg/L, milligrams per liter; LRL, laboratory reporting level; 

E, estimated or having a higher degree of uncertainty; nc, not collected; na, not available; *, value greater than benchmark level; —, not detected]
Tables 117

GAMA 

well 

identification 

number

Sample 

dates

Ammonia 

(as nitrogen) 

(mg/L) 

(00608)

 Nitrite 

(as nitrogen) 

(mg/L) 

(00613)

Nitrite plus 

nitrate 

(as nitrogen) 

(mg/L) 

(00631)

Total nitrogen 

(ammonia + nitrate + 

nitrite + organic nitrogen) 

(mg/L) 

(62854)

Orthophosphate 

(as phosphorus) 

(mg/L) 

(00671)

Benchmark type1 HAL-US MCL-US MCL-US na na

Benchmark level 2 24.7 1 10 na na

[LRL]3 [0.010, 0.04] [0.002, 0.008] [0.04, 0.06] [0.03, 0.10] [0.006]

 Monterey Bay and Salinas Valley Basins study unit—Continued

MSPR-09 7/18/2005 nc nc nc nc nc

MSPR-09 11/14/2008 0.258 0.008 0.43 0.68 0.021

MSSC-06 8/24/2005 0.070 — — 0.09 0.103

MSSC-06 8/18/2008 0.070 — — 0.08 0.131

MSSC-11 9/13/2005 nc nc nc nc nc

MSSC-11 8/19/2008 0.046 — — — 0.039

MSSV-06 8/2/2005 nc nc nc nc nc

MSSV-06 11/13/2008 — — 0.95 0.9 0.066

MSSV-15 8/12/2005 nc nc nc nc nc

MSSV-15 11/13/2008 — — 1.05 1.06 0.084

 Southeast San Joaquin Valley study unit

KING-11 10/20/2005 — — 4.09 3.94 0.014

KING-11 11/5/2008 — — 4.10 3.82 0.026

KING-13 10/20/2005 — — 3.21 3.29 0.020

KING-13 11/5/2008 — — 3.05 2.93 0.035

KING-17 10/26/2005 — — 4.80 4.76 0.014

KING-17 11/4/2008 — — 4.65 4.40 0.030

KING-24 11/5/2005 nc nc nc nc nc

KING-24 11/3/2008 — — 6.74 6.43 0.041

KWH-10 11/17/2005 nc nc nc nc nc

KWH-10 11/5/2008 — — *14.7 14.2 0.021

KWH-12 11/28/2005 — — 3.26 3.37 —

KWH-12 11/6/2008 — — 3.70 3.85 E0.007

TLR-03 11/29/2005 nc nc nc nc nc

TLR-03 11/4/2008 0.022 — — — 0.048

TULE-05 12/5/2005 nc nc nc nc nc

TULE-05 11/3/2008 0.102 0.148 6.42 6.61 0.017

Table 8. Nutrients in samples collected from trend wells for seven Groundwater Ambient Monitoring and Assessment (GAMA) study 

units.—Continued

[The five-digit USGS parameter code below the constituent name is used to uniquely identify a specific constituent or property. Nutrients were analyzed 

in samples from 19 trend wells during 2004–05 and 50 trend wells in 2007–08; 18 wells were analyzed during both periods. Information about analytes 

given in table 3E. GAMA well identification number acronyms: San Diego Drainages study unit: SDALLV, Alluvial Basins study area; SDHDRK, Hard 

Rock study area; SDTEM, Temecula Valley study area; SDTEMFP, Temecula Valley study area flow path well; SDWARN, Warner Valley study area. North 

San Francisco Bay study unit: NSFVOL, Volcanic Highlands study area; NSFVP, Valley and Plains study area; NSFWG, Wilson Grove Formation Highlands 

study area; NSFWGFP, Wilson Grove Formation Highlands study area flow-path well. Northern San Joaquin Basin study unit: COS, Cosumnes Basin 

study area; ESJ, Eastern San Joaquin Basin study area; NSJ-QPC, Uplands study area; TRCY, Tracy Basin study area. Southern Sacramento Valley study 

unit: NAM, North American study area; SAM, South American study area; SOL, Solano study area; SSV-QPC, Uplands study area; SUI, Suisun-Fairfield 

study area; YOL, Yolo study area. San Fernando–San Gabriel study unit: ULASF, San Fernando study area; ULASG, San Gabriel study area. Monterey 

Bay and Salinas Valley Basins study unit: MSMB, Monterey Bay study area; MSPR, Paso Robles study area; MSSC, Santa Cruz study area; MSSV, 

Salinas Valley study area. Southeast San Joaquin Valley study unit: KING, Kings study area; KWH, Kaweah study area; TLR, Tulare Lake study area; 

TULE, Tule study area. Benchmark type: HAL-US, USEPA lifetime health advisory level; MCL-US, USEPA maximum contaminant level; MCL-CA, CDPH 

maximum contaminant level; CDPH, California Department of Public Health. Benchmark type, benchmark level, and RL as of April 1, 2010. Other 

abbreviations: USGS, U.S. Geological Survey; USEPA, U.S. Environmental Protection Agency; mg/L, milligrams per liter; LRL, laboratory reporting level; 

E, estimated or having a higher degree of uncertainty; nc, not collected; na, not available; *, value greater than benchmark level; —, not detected]
118 Groundwater-Quality Data in Seven GAMA Study Units: Results from Initial Sampling and Resampling of Wells

GAMA 

well 

identification 

number

Sample 

dates

Ammonia 

(as nitrogen) 

(mg/L) 

(00608)

 Nitrite 

(as nitrogen) 

(mg/L) 

(00613)

Nitrite plus 

nitrate 

(as nitrogen) 

(mg/L) 

(00631)

Total nitrogen 

(ammonia + nitrate + 

nitrite + organic nitrogen) 

(mg/L) 

(62854)

Orthophosphate 

(as phosphorus) 

(mg/L) 

(00671)

Benchmark type1 HAL-US MCL-US MCL-US na na

Benchmark level 2 24.7 1 10 na na

[LRL]3 [0.010, 0.04] [0.002, 0.008] [0.04, 0.06] [0.03, 0.10] [0.006]

 Southeast San Joaquin Valley study unit—Continued

TULE-10 12/7/2005 nc nc nc nc nc

TULE-10 11/3/2008 — — 9.25 9.17 0.020

1

 Maximum contaminant level benchmarks 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.

2

 The 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.”

3

 Minimum and maximum LRL used during study period, or only LRL used during study period.

Table 8. Nutrients in samples collected from trend wells for seven Groundwater Ambient Monitoring and Assessment (GAMA) study 

units.—Continued

[The five-digit USGS parameter code below the constituent name is used to uniquely identify a specific constituent or property. Nutrients were analyzed 

in samples from 19 trend wells during 2004–05 and 50 trend wells in 2007–08; 18 wells were analyzed during both periods. Information about analytes 

given in table 3E. GAMA well identification number acronyms: San Diego Drainages study unit: SDALLV, Alluvial Basins study area; SDHDRK, Hard 

Rock study area; SDTEM, Temecula Valley study area; SDTEMFP, Temecula Valley study area flow path well; SDWARN, Warner Valley study area. North 

San Francisco Bay study unit: NSFVOL, Volcanic Highlands study area; NSFVP, Valley and Plains study area; NSFWG, Wilson Grove Formation Highlands 

study area; NSFWGFP, Wilson Grove Formation Highlands study area flow-path well. Northern San Joaquin Basin study unit: COS, Cosumnes Basin 

study area; ESJ, Eastern San Joaquin Basin study area; NSJ-QPC, Uplands study area; TRCY, Tracy Basin study area. Southern Sacramento Valley study 

unit: NAM, North American study area; SAM, South American study area; SOL, Solano study area; SSV-QPC, Uplands study area; SUI, Suisun-Fairfield 

study area; YOL, Yolo study area. San Fernando–San Gabriel study unit: ULASF, San Fernando study area; ULASG, San Gabriel study area. Monterey 

Bay and Salinas Valley Basins study unit: MSMB, Monterey Bay study area; MSPR, Paso Robles study area; MSSC, Santa Cruz study area; MSSV, 

Salinas Valley study area. Southeast San Joaquin Valley study unit: KING, Kings study area; KWH, Kaweah study area; TLR, Tulare Lake study area; 

TULE, Tule study area. Benchmark type: HAL-US, USEPA lifetime health advisory level; MCL-US, USEPA maximum contaminant level; MCL-CA, CDPH 

maximum contaminant level; CDPH, California Department of Public Health. Benchmark type, benchmark level, and RL as of April 1, 2010. Other 

abbreviations: USGS, U.S. Geological Survey; USEPA, U.S. Environmental Protection Agency; mg/L, milligrams per liter; LRL, laboratory reporting level; 

E, estimated or having a higher degree of uncertainty; nc, not collected; na, not available; *, value greater than benchmark level; —, not detected]
Tables 119

Table 9. Major and minor ions and dissolved solids in samples collected from trend wells for seven Groundwater Ambient Monitoring and Assessment (GAMA) study units.[The five-digit USGS parameter code below the constituent name is used to uniquely identify a specific constituent or property. Major ions were analyzed in samples from 24 trend wells during 2004–05 and 45 trend wells in 2007–08; 17 wells were analyzed during both periods. Information about analytes given in table 3F. GAMA well identification number acronyms: San Diego Drainages study unit: SDALLV, Alluvial Basins study area; SDHDRK, Hard Rock study area; SDTEM, Temecula Valley study area; SDTEMFP, Temecula Valley study area flow-path well; SDWARN, Warner Valley study area. North San Francisco Bay study unit: NSFVOL, Volcanic Highlands study area; NSFVP, Valley and Plains study area; NSFWG, Wilson Grove Formation Highlands study area; NSFWGFP, Wilson Grove Formation Highlands study area flow-path well. Northern San Joaquin Basin study unit: COS, Cosumnes Basin study area; ESJ, Eastern San Joaquin Basin study area; NSJ-QPC, Uplands study area; TRCY, Tracy Basin study area. Southern Sacramento Valley study unit: NAM, North American study area; SAM, South American study area; SOL, Solano study area; SSV-QPC, Uplands study area; SUI, Suisun-Fairfield study area; YOL, Yolo study area. San Fernando–San Gabriel study unit: ULASF, San Fernando study area; ULASG, San Gabriel study area. Monterey Bay and Salinas Valley Basins study unit: MSMB, Monterey Bay study area; MSPR, Paso Robles study area; MSSC, Santa Cruz study area; MSSV, Salinas Valley study area. Southeast San Joaquin Valley study unit: KING, Kings study area; KWH, Kaweah study area; TLR, Tulare Lake study area; TULE, Tule study area. Benchmark type: MCL-CA, CDPH maximum contaminant level; SMCL-CA, CDPH secondary maximum contaminant level; MCL-US, USEPA maximum contaminant level; USEPA, U.S. Environmental Protection Agency. Benchmark type and benchmark level as of April 1, 2010. Other abbreviations: USGS, U.S. Geological Survey; CDPH, California Department of Public Health; mg/L, milligrams per liter; LRL, laboratory reporting level; E, estimated or having a higher degree of uncertainty; nc, not collected; na, not available; *, value greater than benchmark level; **, concentration greater than upper benchmark level; —, not detected]

GAMA 

well 

identification 

number

Sample 

dates

Calcium 

(mg/L) 

(00915)

Magnesium 

(mg/L) 

(00925)

Potassium 

(mg/L) 

(00935)

Sodium 

(mg/L) 

(00930)

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)

Benchmark type1 na na na na na SMCL-CA3 MCL-CA na na SMCL-CA3 SMCL-CA3Benchmark level na na na na na 250 (500) 2 na na 250 (500) 500 (1,000)[LRL]2 [0.02, 0.04] [0.008, 0.02] [0.02, 0.16] [0.10, 0.20] [0.02] [0.12, 0.20] [0.08, 0.12] [0.002] [0.02, 0.04] [0.18] [10]San Diego Drainages study unitSDHDRK-09 7/27/2004 nc nc nc nc nc nc nc nc nc nc ncSDHDRK-09 9/11/2007 48.1 16.5 3.39 62.4 0.32 70.3 0.34 nc 56.8 27.1 414SDTEM-04 5/24/2004 nc nc nc nc nc nc nc nc nc nc ncSDTEM-04 9/18/2007 66.3 16.6 4.18 101 0.29 89.1 0.50 nc 26.2 162 *597SDTEMFP-01 5/19/2004 25.6 3.00 1.77 116 0.32 86.8 0.82 nc 18.2 61.1 423SDTEMFP-01 9/19/2007 26.7 3.70 1.77 117 0.31 84.4 0.68 nc 16.8 67.1 428SDWARN-01 6/17/2004 nc nc nc nc nc nc nc nc nc nc ncSDWARN-01 9/11/2007 52.5 8.19 1.28 105 0.35 79.6 0.31 nc 31.4 57.7 480North San Francisco Bay study unitNSFVOL-14 10/7/2004 12.8 7.57 2.18 13.4 0.03 7.79 0.15 0.004 87.0 7.40 185NSFVOL-14 8/21/2007 nc nc nc nc nc nc nc nc nc nc ncNSFVOL-18 10/20/2004 nc nc nc nc nc nc nc nc nc nc ncNSFVOL-18 8/28/2007 14.5 17.9 6.48 42.6 0.06 12.6 0.35 0.024 119.6 3.76 321NSFVP-29 9/28/2004 35.7 24.8 0.90 9.06 0.17 5.94 — E0.001 24.9 26.2 231NSFVP-29 8/27/2007 nc nc nc nc nc nc nc nc nc nc ncNSFVP-34 10/18/2004 9.14 6.26 4.70 23.5 0.07 10.6 0.34 0.020 85.3 2.6 185NSFVP-34 8/22/2007 nc nc nc nc nc nc nc nc nc nc ncNSFVP-36 10/19/2004 51.6 50.8 7.14 148 1.44 *250 0.16 0.261 46.8 12.4 *685NSFVP-36 8/20/2007 nc nc nc nc nc nc nc nc nc nc ncNSFVP-38 10/20/2004 6.26 1.51 2.29 177 0.10 25.5 0.42 0.138 52.9 1.72 *503
120 Groundwater-Quality Data in Seven GAMA Study Units: Results from Initial Sampling and Resampling of Wells GAMA well identification number Sample dates Calcium (mg/L) (00915) Magnesium (mg/L) (00925) Potassium (mg/L) (00935) Sodium (mg/L) (00930) 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) Benchmark type1 na na na na na SMCL-CA3 MCL-CA na na SMCL-CA3 SMCL-CA3 Benchmark level na na na na na 250 (500) 2 na na 250 (500) 500 (1,000) [LRL]2 [0.02, 0.04] [0.008, 0.02] [0.02, 0.16] [0.10, 0.20] [0.02] [0.12, 0.20] [0.08, 0.12] [0.002] [0.02, 0.04] [0.18] [10] North San Francisco Bay study unit—Continued NSFVP-38 8/22/2007 nc nc nc nc nc nc nc nc nc nc nc NSFVP-39 10/21/2004 13.9 7.88 6.79 42.3 0.09 7.00 0.37 0.077 104.6 5.46 267 NSFVP-39 11/16/2007 13.8 8.36 6.33 41.7 0.07 6.95 0.35 0.084 98.0 5.25 270 NSFVP-41 10/21/2004 33.0 20.9 2.09 39.2 0.19 42.4 0.24 0.015 50.2 23.6 313 NSFVP-41 8/20/2007 nc nc nc nc nc nc nc nc nc nc nc NSFWG-03 9/21/2004 nc nc nc nc nc nc nc nc nc nc nc NSFWG-03 8/29/2007 13.5 6.11 1.65 22.5 0.11 27.2 E0.08 0.009 62.3 32.9 202 NSFWGFP-01 10/5/2004 50.0 3.77 1.33 22.0 0.08 15.4 E0.10 0.007 37.9 15.9 243 NSFWGFP-01 8/29/2007 nc nc nc nc nc nc nc nc nc nc nc Northern San Joaquin Basin study unit COS-08 1/3/2005 nc nc nc nc nc nc nc nc nc nc nc COS-08 4/3/2008 9.43 6.15 1.35 30.2 0.03 7.42 E0.09 0.017 63.6 3.08 174 ESJ-01 1/24/2005 nc nc nc nc nc nc nc nc nc nc nc ESJ-01 4/2/2008 60.3 14.0 4.08 45.7 0.20 63.5 0.14 0.032 48.2 20.6 391 ESJ-06 1/10/2005 28.1 13.2 7.42 19.2 0.08 13.5 0.13 0.004 67.2 13.6 243 ESJ-06 4/2/2008 30.1 13.0 7.43 19.3 0.06 14.3 0.14 E0.002 61.2 14.4 250

NSJ-QPC-04 1/24/2005 4.59 2.58 4.10 22.8 0.04 3.94 0.20 0.004 93.4 2.33 165NSJ-QPC-04 4/1/2008 4.54 2.53 4.06 21.7 E0.02 4.98 0.21 0.005 85.8 2.36 167

Table 9. Major and minor ions and dissolved solids in samples collected from trend wells for seven Groundwater Ambient Monitoring and Assessment (GAMA) study units.—Continued[The five-digit USGS parameter code below the constituent name is used to uniquely identify a specific constituent or property. Major ions were analyzed in samples from 24 trend wells during 2004–05 and 45 trend wells in 2007–08; 17 wells were analyzed during both periods. Information about analytes given in table 3F. GAMA well identification number acronyms: San Diego Drainages study unit: SDALLV, Alluvial Basins study area; SDHDRK, Hard Rock study area; SDTEM, Temecula Valley study area; SDTEMFP, Temecula Valley study area flow-path well; SDWARN, Warner Valley study area. North San Francisco Bay study unit: NSFVOL, Volcanic Highlands study area; NSFVP, Valley and Plains study area; NSFWG, Wilson Grove Formation Highlands study area; NSFWGFP, Wilson Grove Formation Highlands study area flow-path well. Northern San Joaquin Basin study unit: COS, Cosumnes Basin study area; ESJ, Eastern San Joaquin Basin study area; NSJ-QPC, Uplands study area; TRCY, Tracy Basin study area. Southern Sacramento Valley study unit: NAM, North American study area; SAM, South American study area; SOL, Solano study area; SSV-QPC, Uplands study area; SUI, Suisun-Fairfield study area; YOL, Yolo study area. San Fernando–San Gabriel study unit: ULASF, San Fernando study area; ULASG, San Gabriel study area. Monterey Bay and Salinas Valley Basins study unit: MSMB, Monterey Bay study area; MSPR, Paso Robles study area; MSSC, Santa Cruz study area; MSSV, Salinas Valley study area. Southeast San Joaquin Valley study unit: KING, Kings study area; KWH, Kaweah study area; TLR, Tulare Lake study area; TULE, Tule study area. Benchmark type: MCL-CA, CDPH maximum contaminant level; SMCL-CA, CDPH secondary maximum contaminant level; MCL-US, USEPA maximum contaminant level; USEPA, U.S. Environmental Protection Agency. Benchmark type and benchmark level as of April 1, 2010. Other abbreviations: USGS, U.S. Geological Survey; CDPH, California Department of Public Health; mg/L, milligrams per liter; LRL, laboratory reporting level; E, estimated or having a higher degree of uncertainty; nc, not collected; na, not available; *, value greater than benchmark level; **, concentration greater than upper benchmark level; —, not detected]
Tables 121

GAMA 

well 

identification 

number

Sample 

dates

Calcium 

(mg/L) 

(00915)

Magnesium 

(mg/L) 

(00925)

Potassium 

(mg/L) 

(00935)

Sodium 

(mg/L) 

(00930)

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)

Benchmark type1 na na na na na SMCL-CA3 MCL-CA na na SMCL-CA3 SMCL-CA3Benchmark level na na na na na 250 (500) 2 na na 250 (500) 500 (1,000)[LRL]2 [0.02, 0.04] [0.008, 0.02] [0.02, 0.16] [0.10, 0.20] [0.02] [0.12, 0.20] [0.08, 0.12] [0.002] [0.02, 0.04] [0.18] [10]Northern San Joaquin Basin study unit —ContinuedTRCY-03 1/6/2005 80.9 26.8 3.17 138 0.39 102 0.23 0.015 23.4 249 *751TRCY-03 3/31/2008 82.4 26.3 3.12 135 0.37 108 0.25 0.003 20.5 *259 *782Southern Sacramento Valley study unit NAM-03 3/29/2005 nc nc nc nc nc nc nc nc nc nc ncNAM-03 4/10/2008 18.2 10.7 1.97 43.5 0.14 41.5 0.29 0.006 84.2 9.67 281SAM-10 4/21/2005 nc nc nc nc nc nc nc nc nc nc ncSAM-10 4/8/2008 65.1 29.7 3.84 21.4 0.12 32.7 E0.09 E0.002 59.2 27.0 413SOL-08 5/10/2005 nc nc nc nc nc nc nc nc nc nc ncSOL-08 4/8/2008 25.8 25.5 3.29 30.5 E0.02 6.37 0.22 — 54.2 13.4 282SSV-QPC-07 4/4/2005 39.4 13.6 1.80 64.4 0.23 82.5 0.24 0.014 86.5 27.0 408SSV-QPC-07 4/10/2008 35.9 12.3 1.65 60.2 0.26 80.3 0.23 0.018 80.3 29.0 411SUI-03 5/12/2005 nc nc nc nc nc nc nc nc nc nc ncSUI-03 4/9/2008 46.7 36.5 5.00 41.6 0.32 110 0.71 0.008 70.9 8.90 450YOL-01 4/11/2005 nc nc nc nc nc nc nc nc nc nc ncYOL-01 4/7/2008 62.2 45.4 2.63 60.1 0.24 74.6 0.15 0.004 24.4 34.8 *535YOL-14 5/25/2005 83.3 25.9 8.14 163 1.12 *342 E0.07 0.807 57.2 E0.12 *888YOL-14 4/9/2008 86.1 59.6 6.70 157 0.98 *352 E0.12 0.690 47.1 71.9 *970

Table 9. Major and minor ions and dissolved solids in samples collected from trend wells for seven Groundwater Ambient Monitoring and Assessment (GAMA) study units.—Continued[The five-digit USGS parameter code below the constituent name is used to uniquely identify a specific constituent or property. Major ions were analyzed in samples from 24 trend wells during 2004–05 and 45 trend wells in 2007–08; 17 wells were analyzed during both periods. Information about analytes given in table 3F. GAMA well identification number acronyms: San Diego Drainages study unit: SDALLV, Alluvial Basins study area; SDHDRK, Hard Rock study area; SDTEM, Temecula Valley study area; SDTEMFP, Temecula Valley study area flow-path well; SDWARN, Warner Valley study area. North San Francisco Bay study unit: NSFVOL, Volcanic Highlands study area; NSFVP, Valley and Plains study area; NSFWG, Wilson Grove Formation Highlands study area; NSFWGFP, Wilson Grove Formation Highlands study area flow-path well. Northern San Joaquin Basin study unit: COS, Cosumnes Basin study area; ESJ, Eastern San Joaquin Basin study area; NSJ-QPC, Uplands study area; TRCY, Tracy Basin study area. Southern Sacramento Valley study unit: NAM, North American study area; SAM, South American study area; SOL, Solano study area; SSV-QPC, Uplands study area; SUI, Suisun-Fairfield study area; YOL, Yolo study area. San Fernando–San Gabriel study unit: ULASF, San Fernando study area; ULASG, San Gabriel study area. Monterey Bay and Salinas Valley Basins study unit: MSMB, Monterey Bay study area; MSPR, Paso Robles study area; MSSC, Santa Cruz study area; MSSV, Salinas Valley study area. Southeast San Joaquin Valley study unit: KING, Kings study area; KWH, Kaweah study area; TLR, Tulare Lake study area; TULE, Tule study area. Benchmark type: MCL-CA, CDPH maximum contaminant level; SMCL-CA, CDPH secondary maximum contaminant level; MCL-US, USEPA maximum contaminant level; USEPA, U.S. Environmental Protection Agency. Benchmark type and benchmark level as of April 1, 2010. Other abbreviations: USGS, U.S. Geological Survey; CDPH, California Department of Public Health; mg/L, milligrams per liter; LRL, laboratory reporting level; E, estimated or having a higher degree of uncertainty; nc, not collected; na, not available; *, value greater than benchmark level; **, concentration greater than upper benchmark level; —, not detected]
122 Groundwater-Quality Data in Seven GAMA Study Units: Results from Initial Sampling and Resampling of Wells GAMA well identification number Sample dates Calcium (mg/L) (00915) Magnesium (mg/L) (00925) Potassium (mg/L) (00935) Sodium (mg/L) (00930) 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) Benchmark type1 na na na na na SMCL-CA3 MCL-CA na na SMCL-CA3 SMCL-CA3 Benchmark level na na na na na 250 (500) 2 na na 250 (500) 500 (1,000) [LRL]2 [0.02, 0.04] [0.008, 0.02] [0.02, 0.16] [0.10, 0.20] [0.02] [0.12, 0.20] [0.08, 0.12] [0.002] [0.02, 0.04] [0.18] [10] San Fernando–San Gabriel study unit ULASF-09 6/27/2005 113 41.9 3.44 44.2 0.23 111 0.23 0.005 45.6 166 *702 ULASF-09 6/16/2008 91.8 32.3 3.18 41.1 0.18 88.8 0.23 0.003 38.3 146 *608 ULASF-10 6/8/2005 63.3 14.3 3.88 68.8 0.31 58.5 0.36 0.055 24.3 101 454 ULASF-10 6/16/2008 53.8 10.9 3.61 91.4 0.40 70.7 0.38 0.038 19.2 121 482 ULASG-01 6/7/2005 nc nc nc nc nc nc nc nc nc nc nc ULASG-01 6/16/2008 127 41.7 2.28 62.4 0.24 86.9 0.48 0.005 37.7 207 *813 ULASG-08 6/15/2005 65.2 20.2 2.26 35.6 0.11 40.4 0.67 E0.001 26.1 65.0 400 ULASG-08 6/17/2008 60.0 17.2 2.44 47.4 0.12 42.0 0.78 E0.001 20.6 67.9 419 ULASG-15 6/23/2005 38.6 11.2 3.07 21.7 0.02 6.40 0.30 E0.001 14.3 17.0 199 ULASG-15 6/17/2008 40.3 11.0 3.42 21.4 0.07 17.3 0.29

— 13.1 25.5 225

ULASG-17 7/11/2005 nc nc nc nc nc nc nc nc nc nc ncULASG-17 6/17/2008 163.0 34.3 2.77 35.5 0.60 49.8 0.33 E0.002 28.1 196 *607Monterey Bay and Salinas Valley Basins study unitMSMB-03 8/31/2005 nc nc nc nc nc nc nc nc nc nc ncMSMB-03 8/20/2008 1.6 0.5 3.20 109 0.15 42.6 0.47 0.015 62.3 24.2 361MSMB-04 8/17/2005 40.2 52.4 16.9 112 1.01 241 E0.07 E0.015 31.2 61.9 *658MSMB-04 8/20/2008 49.3 62.2 19.5 134 1.34 *358 E0.10 0.028 26.9 69.7 *847MSMB-16 8/17/2005 nc nc nc nc nc nc nc nc nc nc ncMSMB-16 8/19/2008 60.9 17.2 2.91 37.0 0.35 99.9 0.29 E0.002 39.2 54.9 430

Table 9. Major and minor ions and dissolved solids in samples collected from trend wells for seven Groundwater Ambient Monitoring and Assessment (GAMA) study units.—Continued[The five-digit USGS parameter code below the constituent name is used to uniquely identify a specific constituent or property. Major ions were analyzed in samples from 24 trend wells during 2004–05 and 45 trend wells in 2007–08; 17 wells were analyzed during both periods. Information about analytes given in table 3F. GAMA well identification number acronyms: San Diego Drainages study unit: SDALLV, Alluvial Basins study area; SDHDRK, Hard Rock study area; SDTEM, Temecula Valley study area; SDTEMFP, Temecula Valley study area flow-path well; SDWARN, Warner Valley study area. North San Francisco Bay study unit: NSFVOL, Volcanic Highlands study area; NSFVP, Valley and Plains study area; NSFWG, Wilson Grove Formation Highlands study area; NSFWGFP, Wilson Grove Formation Highlands study area flow-path well. Northern San Joaquin Basin study unit: COS, Cosumnes Basin study area; ESJ, Eastern San Joaquin Basin study area; NSJ-QPC, Uplands study area; TRCY, Tracy Basin study area. Southern Sacramento Valley study unit: NAM, North American study area; SAM, South American study area; SOL, Solano study area; SSV-QPC, Uplands study area; SUI, Suisun-Fairfield study area; YOL, Yolo study area. San Fernando–San Gabriel study unit: ULASF, San Fernando study area; ULASG, San Gabriel study area. Monterey Bay and Salinas Valley Basins study unit: MSMB, Monterey Bay study area; MSPR, Paso Robles study area; MSSC, Santa Cruz study area; MSSV, Salinas Valley study area. Southeast San Joaquin Valley study unit: KING, Kings study area; KWH, Kaweah study area; TLR, Tulare Lake study area; TULE, Tule study area. Benchmark type: MCL-CA, CDPH maximum contaminant level; SMCL-CA, CDPH secondary maximum contaminant level; MCL-US, USEPA maximum contaminant level; USEPA, U.S. Environmental Protection Agency. Benchmark type and benchmark level as of April 1, 2010. Other abbreviations: USGS, U.S. Geological Survey; CDPH, California Department of Public Health; mg/L, milligrams per liter; LRL, laboratory reporting level; E, estimated or having a higher degree of uncertainty; nc, not collected; na, not available; *, value greater than benchmark level; **, concentration greater than upper benchmark level; —, not detected]
Tables 123

GAMA 

well 

identification 

number

Sample 

dates

Calcium 

(mg/L) 

(00915)

Magnesium 

(mg/L) 

(00925)

Potassium 

(mg/L) 

(00935)

Sodium 

(mg/L) 

(00930)

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)

Benchmark type1 na na na na na SMCL-CA3 MCL-CA na na SMCL-CA3 SMCL-CA3Benchmark level na na na na na 250 (500) 2 na na 250 (500) 500 (1,000)[LRL]2 [0.02, 0.04] [0.008, 0.02] [0.02, 0.16] [0.10, 0.20] [0.02] [0.12, 0.20] [0.08, 0.12] [0.002] [0.02, 0.04] [0.18] [10]Monterey Bay and Salinas Valley Basins study unit—ContinuedMSMB-28 8/3/2005 nc nc nc nc nc nc nc nc nc nc ncMSMB-28 8/21/2008 73.0 22.0 3.68 52.0 0.28 81.5 0.39 E0.002 39.1 65.0 468MSMB-31 8/11/2005 nc nc nc nc nc nc nc nc nc nc ncMSMB-31 8/21/2008 70.0 15.8 1.80 32.5 0.61 37.1 0.34 E0.001 26.3 25.8 367MSPR-03 7/28/2005 nc nc nc nc nc nc nc nc nc nc ncMSPR-03 11/14/2008 19.5 9.2 3.11 165 0.18 36.3 0.35 0.092 46.2 110 *570MSPR-09 7/18/2005 nc nc nc nc nc nc nc nc nc nc ncMSPR-09 11/14/2008 21.9 10.7 2.20 317 0.57 157 0.49 0.093 41.2 242 **1,010MSSC-06 8/24/2005 70.4 16.8 6.95 43.0 0.36 70.0 0.14 0.004 67.8 102 455MSSC-06 8/18/2008 66.2 15.5 7.31 45.0 0.25 68.1 0.17 0.005 61.7 103 480MSSC-11 9/13/2005 nc nc nc nc nc nc nc nc nc nc ncMSSC-11 8/19/2008 37.0 26.0 2.41 14.3 0.02 9.9 0.16 0.002 26.1 20.0 242MSSV-06 8/2/2005 nc nc nc nc nc nc nc nc nc nc ncMSSV-06 11/13/2008 48.6 20.0 1.48 31.5 0.10 26.1 0.26 0.003 33.6 78.7 345MSSV-15 8/12/2005 nc nc nc nc nc nc nc nc nc nc ncMSSV-15 11/13/2008 43.6 26.3 1.54 45.7 0.12 27.5 0.31 0.007 32.2 108 387Southeast San Joaquin Valley study unitKING-11 10/20/2005 33.9 15.4 2.10 31.4 0.10 32.4 0.14 0.002 36.6 7.55 263KING-11 11/5/2008 30.5 18.8 2.38 53.5 0.23 68.8 0.13 0.009 31.8 8.88 300

Table 9. Major and minor ions and dissolved solids in samples collected from trend wells for seven Groundwater Ambient Monitoring and Assessment (GAMA) study units.—Continued[The five-digit USGS parameter code below the constituent name is used to uniquely identify a specific constituent or property. Major ions were analyzed in samples from 24 trend wells during 2004–05 and 45 trend wells in 2007–08; 17 wells were analyzed during both periods. Information about analytes given in table 3F. GAMA well identification number acronyms: San Diego Drainages study unit: SDALLV, Alluvial Basins study area; SDHDRK, Hard Rock study area; SDTEM, Temecula Valley study area; SDTEMFP, Temecula Valley study area flow-path well; SDWARN, Warner Valley study area. North San Francisco Bay study unit: NSFVOL, Volcanic Highlands study area; NSFVP, Valley and Plains study area; NSFWG, Wilson Grove Formation Highlands study area; NSFWGFP, Wilson Grove Formation Highlands study area flow-path well. Northern San Joaquin Basin study unit: COS, Cosumnes Basin study area; ESJ, Eastern San Joaquin Basin study area; NSJ-QPC, Uplands study area; TRCY, Tracy Basin study area. Southern Sacramento Valley study unit: NAM, North American study area; SAM, South American study area; SOL, Solano study area; SSV-QPC, Uplands study area; SUI, Suisun-Fairfield study area; YOL, Yolo study area. San Fernando–San Gabriel study unit: ULASF, San Fernando study area; ULASG, San Gabriel study area. Monterey Bay and Salinas Valley Basins study unit: MSMB, Monterey Bay study area; MSPR, Paso Robles study area; MSSC, Santa Cruz study area; MSSV, Salinas Valley study area. Southeast San Joaquin Valley study unit: KING, Kings study area; KWH, Kaweah study area; TLR, Tulare Lake study area; TULE, Tule study area. Benchmark type: MCL-CA, CDPH maximum contaminant level; SMCL-CA, CDPH secondary maximum contaminant level; MCL-US, USEPA maximum contaminant level; USEPA, U.S. Environmental Protection Agency. Benchmark type and benchmark level as of April 1, 2010. Other abbreviations: USGS, U.S. Geological Survey; CDPH, California Department of Public Health; mg/L, milligrams per liter; LRL, laboratory reporting level; E, estimated or having a higher degree of uncertainty; nc, not collected; na, not available; *, value greater than benchmark level; **, concentration greater than upper benchmark level; —, not detected]
124 Groundwater-Quality Data in Seven GAMA Study Units: Results from Initial Sampling and Resampling of Wells GAMA well identification number Sample dates Calcium (mg/L) (00915) Magnesium (mg/L) (00925) Potassium (mg/L) (00935) Sodium (mg/L) (00930) 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) Benchmark type1 na na na na na SMCL-CA3 MCL-CA na na SMCL-CA3 SMCL-CA3 Benchmark level na na na na na 250 (500) 2 na na 250 (500) 500 (1,000) [LRL]2 [0.02, 0.04] [0.008, 0.02] [0.02, 0.16] [0.10, 0.20] [0.02] [0.12, 0.20] [0.08, 0.12] [0.002] [0.02, 0.04] [0.18] [10] Southeast San Joaquin Valley study unit—Continued KING-13 10/20/2005 28.6 10.7 2.32 24.3 0.06 13.5 0.15 E0.002 47.0 5.30 224 KING-13 11/5/2008 26.8 9.6 2.35 26.6 0.06 13.6 0.16

— 49.5 5.59 214

KING-17 10/26/2005 23.3 12.3 3.51 26.0 0.05 10.9 0.16 E0.001 39.7 4.30 200KING-17 11/4/2008 22.6 11.3 3.41 26.7 0.06 12.4 0.12

— 36.5 4.26 211

KING-24 11/5/2005 nc nc nc nc nc nc nc nc nc nc ncKING-24 11/3/2008 43.4 28.5 3.10 23.8 0.13 8.6 0.14 E0.001 50.4 30.2 334KWH-10 11/17/2005 nc nc nc nc nc nc nc nc nc nc ncKWH-10 11/5/2008 40.5 19.2 3.80 62.3 0.12 35.1 0.19 0.004 23.9 34.6 393KWH-12 11/28/2005 17.4 0.5 1.36 27.8 0.04 8.6 E0.10

— 15.0 12.9 144

KWH-12 11/6/2008 20.3 0.6 1.48 27.7 0.05 11.9 0.10

— 15.3 16.6 154

TLR-03 11/29/2005 nc nc nc nc nc nc nc nc nc nc ncTLR-03 11/4/2008 2.2 0.1 0.47 108 0.22 72.8 1.25 0.197 16.5 0.74 274TULE-05 12/5/2005 nc nc nc nc nc nc nc nc nc nc ncTULE-05 11/3/2008 15.9 1.7 2.22 144 0.38 107 0.81 0.187 27.2 42.3 438TULE-10 12/7/2005 nc nc nc nc nc nc nc nc nc nc ncTULE-10 11/3/2008 64.2 16.7 2.67 41.6 0.10 48.9 E0.09 0.003 25.8 24.4 378

1 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.2 Minimum and maximum LRL used during study period, or only LRL used during study period.3 The SMCL-CAs for chloride, sulfate, and total dissolved solids have recommended and upper threshold values. The upper value is shown in parentheses.

Table 9. Major and minor ions and dissolved solids in samples collected from trend wells for seven Groundwater Ambient Monitoring and Assessment (GAMA) study units.—Continued[The five-digit USGS parameter code below the constituent name is used to uniquely identify a specific constituent or property. Major ions were analyzed in samples from 24 trend wells during 2004–05 and 45 trend wells in 2007–08; 17 wells were analyzed during both periods. Information about analytes given in table 3F. GAMA well identification number acronyms: San Diego Drainages study unit: SDALLV, Alluvial Basins study area; SDHDRK, Hard Rock study area; SDTEM, Temecula Valley study area; SDTEMFP, Temecula Valley study area flow-path well; SDWARN, Warner Valley study area. North San Francisco Bay study unit: NSFVOL, Volcanic Highlands study area; NSFVP, Valley and Plains study area; NSFWG, Wilson Grove Formation Highlands study area; NSFWGFP, Wilson Grove Formation Highlands study area flow-path well. Northern San Joaquin Basin study unit: COS, Cosumnes Basin study area; ESJ, Eastern San Joaquin Basin study area; NSJ-QPC, Uplands study area; TRCY, Tracy Basin study area. Southern Sacramento Valley study unit: NAM, North American study area; SAM, South American study area; SOL, Solano study area; SSV-QPC, Uplands study area; SUI, Suisun-Fairfield study area; YOL, Yolo study area. San Fernando–San Gabriel study unit: ULASF, San Fernando study area; ULASG, San Gabriel study area. Monterey Bay and Salinas Valley Basins study unit: MSMB, Monterey Bay study area; MSPR, Paso Robles study area; MSSC, Santa Cruz study area; MSSV, Salinas Valley study area. Southeast San Joaquin Valley study unit: KING, Kings study area; KWH, Kaweah study area; TLR, Tulare Lake study area; TULE, Tule study area. Benchmark type: MCL-CA, CDPH maximum contaminant level; SMCL-CA, CDPH secondary maximum contaminant level; MCL-US, USEPA maximum contaminant level; USEPA, U.S. Environmental Protection Agency. Benchmark type and benchmark level as of April 1, 2010. Other abbreviations: USGS, U.S. Geological Survey; CDPH, California Department of Public Health; mg/L, milligrams per liter; LRL, laboratory reporting level; E, estimated or having a higher degree of uncertainty; nc, not collected; na, not available; *, value greater than benchmark level; **, concentration greater than upper benchmark level; —, not detected]
Tables 125

Table 10. Trace elements in groundwater samples collected from trend wells for seven Groundwater Ambient Monitoring and Assessment (GAMA) study units.[The five-digit USGS parameter code below the constituent name is used to uniquely identify a specific constituent or property. Trace elements were analyzed in samples from 24 trend wells during 2004–05 and 45 trend wells in 2007–08; 17 wells were analyzed during both periods. Information about analytes given in table 3F. GAMA well identification number acronyms: San Diego Drainages study unit: SDALLV, Alluvial Basins study area; SDHDRK, Hard Rock study area; SDTEM, Temecula Valley study area; SDTEMFP, Temecula Valley study area flow-path well; SDWARN, Warner Valley study area. North San Francisco Bay study unit: NSFVOL, Volcanic Highlands study area; NSFVP, Valley and Plains study area; NSFWG, Wilson Grove Formation Highlands study area; NSFWGFP, Wilson Grove Formation Highlands study area flow-path well. Northern San Joaquin Basin study unit: COS, Cosumnes Basin study area; ESJ, Eastern San Joaquin Basin study area; NSJ-QPC, Uplands study area; TRCY, Tracy Basin study area. Southern Sacramento Valley study unit: NAM, North American study area; SAM, South American study area; SOL, Solano study area; SSV-QPC, Uplands study area; SUI, Suisun-Fairfield study area; YOL, Yolo study area. San Fernando–San Gabriel study unit: ULASF, San Fernando study area; ULASG, San Gabriel study area. Monterey Bay and Salinas Valley Basins study unit: MSMB, Monterey Bay study area; MSPR, Paso Robles study area; MSSC, Santa Cruz study area; MSSV, Salinas Valley study area. Southeast San Joaquin Valley study unit: KING, Kings study area; KWH, Kaweah study area; TLR, Tulare Lake study area; TULE, Tule study area. Benchmark type: HAL-US, USEPA lifetime health advisory level; MCL-US, USEPA maximum contaminant level; AL-US, USEPA action level; MCL-CA, CDPH maximum contaminant level; NL-CA, CDPH notification level; SMCL, CDPH secondary maximum contaminant level. Benchmark type and benchmark level as of April 1, 2010. Other abbreviations: USGS, U.S. Geological Survey; USEPA, U.S. Environmental Protection Agency; CDPH, California Department of Public Health; μg/L, micrograms per liter; LRL, laboratory reporting level; E, estimated or having a higher degree of uncertainty; nc, not collected; na, not available; *, value greater than benchmark level; —, not detected; ≤, less than or equal to]

GAMA well 

identification 

number

Sample 

dates

Aluminum 

(μg/L) 

(01106)

Antimony 

(μg/L) 

(01095)

Arsenic 

(μg/L) 

(01000)

Barium 

(μg/L) 

(01005)

Beryllium 

(μg/L) 

(01010)

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)

Benchmark type3 MCL-CA MCL-US MCL-US MCL-CA MCL-US NL-CA MCL-US MCL-CA na AL-US SMCL-CA AL-USBenchmark level 1,000 6 10 1,000 4 1,000 5 50 na 1,300 300 15[LRL or SRL]1 [1.6]2 [0.06, 0.2] [0.06, 0.12] [0.36]2 [0.008, 0.06] [4, 8] [0.02, 0.04] [0.42]2 [0.014, 0.04] [1.7]2 [6]2 [0.65]2San Diego Drainages study unitSDHDRK-09 7/27/2004 nc nc nc nc nc nc nc nc nc nc nc ncSDHDRK-09 9/11/2007 — — 1.8 73 — 62 — ≤0.10 E0.04 2.0 12 0.98SDTEM-04 5/24/2004 nc nc nc nc nc nc nc nc nc nc nc ncSDTEM-04 9/18/2007 ≤1.0 E0.03 1.6 56 — 166 E0.03 0.97 E0.03 ≤1.6 ≤4 ≤0.15SDTEMFP-01 5/19/2004 4.8 — 7.8 63 — 299 — 1.6 0.07 ≤0.9 ≤6 ≤0.11SDTEMFP-01 9/19/2007 4.3 — 6.1 63 — 289 — 1.9 E0.02 ≤0.7 16 —SDWARN-01 6/17/2004 nc nc nc nc nc nc nc nc nc nc nc ncSDWARN-01 9/11/2007 ≤1.0 — 1.2 126 — 90 — 0.63 E0.02 ≤1.4 32 ≤0.26North San Francisco Bay study unitNSFVOL-14 10/7/2004 ≤0.9 — 7.1 6 — 18 — ≤0.40 0.13 3.5 — 2.79NSFVOL-14 8/21/2007 nc nc nc nc nc nc nc nc nc nc nc ncNSFVOL-18 10/20/2004 nc nc nc nc nc nc nc nc nc nc nc ncNSFVOL-18 8/28/2007 ≤1.0 — 0.88 112 — 463 — — 0.05 — *332 —NSFVP-29 9/28/2004 — — E0.10 172 — 258 — 0.90 0.13 2.3 — 1.02NSFVP-29 8/27/2007 nc nc nc nc nc nc nc nc nc nc nc ncNSFVP-34 10/18/2004 — — 7.1 35 — 120 — — 0.07 ≤0.4 *999 —NSFVP-34 8/22/2007 nc nc nc nc nc nc nc nc nc nc nc ncNSFVP-36 10/19/2004 — — 5.7 492 — 136 — — 0.14 ≤0.3 *671 1.07NSFVP-36 8/20/2007 nc nc nc nc nc nc nc nc nc nc nc ncNSFVP-38 10/20/2004 ≤1.2 — *17.2 69 — *3,830 E0.04 — 0.03 3.3 12 0.73
126 Groundwater-Quality Data in Seven GAMA Study Units: Results from Initial Sampling and Resampling of Wells GAMA well identification number Sample dates Aluminum (μg/L) (01106) Antimony (μg/L) (01095) Arsenic (μg/L) (01000) Barium (μg/L) (01005) Beryllium (μg/L) (01010) 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) Benchmark type3 MCL-CA MCL-US MCL-US MCL-CA MCL-US NL-CA MCL-US MCL-CA na AL-US SMCL-CA AL-US Benchmark level 1,000 6 10 1,000 4 1,000 5 50 na 1,300 300 15 [LRL or SRL]1 [1.6]2 [0.06, 0.2] [0.06, 0.12] [0.36]2 [0.008, 0.06] [4, 8] [0.02, 0.04] [0.42]2 [0.014, 0.04] [1.7]2 [6]2 [0.65]2 North San Francisco Bay study unit—Continued NSFVP-38 8/22/2007 nc nc nc nc nc nc nc nc nc nc nc nc NSFVP-39 10/21/2004 ≤0.8

— 6.0 27

— 293

—

— 0.10 ≤0.3 44 2.68

NSFVP-39 11/16/2007 24.6

— 5.5 21 0.011 247

—

— 0.06

— 30 ≤0.45

NSFVP-41 10/21/2004

—

— 2.6 148

— 52

—

— 0.33 13.1

— 1.77

NSFVP-41 8/20/2007 nc nc nc nc nc nc nc nc nc nc nc ncNSFWG-03 9/21/2004 nc nc nc nc nc nc nc nc nc nc nc ncNSFWG-03 8/29/2007 2.2

— 1.6 3 — E7

—

— 0.45

— *2,420 ≤0.23

NSFWGFP-01 10/5/2004

—

— 4.8 4 — 22

—

— 0.14 ≤0.4 29 ≤0.59

NSFWGFP-01 8/29/2007 nc nc nc nc nc nc nc nc nc nc nc ncNorthern San Joaquin Basin study unitCOS-08 1/3/2005 nc nc nc nc nc nc nc nc nc nc nc ncCOS-08 4/3/2008 ≤1.3

— *21.5 136

— 141 4 — ≤0.12 E0.01

— 81

—

ESJ-01 1/24/2005 nc nc nc nc nc nc nc nc nc nc nc ncESJ-01 4/2/2008

—

— *17.8 294

— 152 4 — 3.0 0.04 ≤0.7

— ≤0.46

ESJ-06 1/10/2005 ≤1.0

— 4.5 97

— 34

— 4.6 0.07 ≤0.4

— ≤0.07

ESJ-06 4/2/2008

—

— 4.3 96

— 32 4 — 5.4 E0.02 ≤0.7

— ≤0.20

NSJ-QPC-04 1/24/2005 ≤0.9

— 2.3 31

— 32

— 1.2 0.03

— 150 ≤0.12

NSJ-QPC-04 4/1/2008

— E0.08 2.2 32

— 30 4 — 1.5 E0.02

— 93 ≤0.06

TRCY-03 1/6/2005 8.0

— 0.80 25

— *2,190

— 7.2 0.25 3.0 ≤4 0.89

TRCY-03 3/31/2008 ≤1.3

— 0.79 25

— *2,120 4 — 6.9 0.03 2.1 ≤6 1.19

Table 10. Trace elements in groundwater samples collected from trend wells for seven Groundwater Ambient Monitoring and Assessment (GAMA) study units.—Continued[The five-digit USGS parameter code below the constituent name is used to uniquely identify a specific constituent or property. Trace elements were analyzed in samples from 24 trend wells during 2004–05 and 45 trend wells in 2007–08; 17 wells were analyzed during both periods. Information about analytes given in table 3F. GAMA well identification number acronyms: San Diego Drainages study unit: SDALLV, Alluvial Basins study area; SDHDRK, Hard Rock study area; SDTEM, Temecula Valley study area; SDTEMFP, Temecula Valley study area flow-path well; SDWARN, Warner Valley study area. North San Francisco Bay study unit: NSFVOL, Volcanic Highlands study area; NSFVP, Valley and Plains study area; NSFWG, Wilson Grove Formation Highlands study area; NSFWGFP, Wilson Grove Formation Highlands study area flow-path well. Northern San Joaquin Basin study unit: COS, Cosumnes Basin study area; ESJ, Eastern San Joaquin Basin study area; NSJ-QPC, Uplands study area; TRCY, Tracy Basin study area. Southern Sacramento Valley study unit: NAM, North American study area; SAM, South American study area; SOL, Solano study area; SSV-QPC, Uplands study area; SUI, Suisun-Fairfield study area; YOL, Yolo study area. San Fernando–San Gabriel study unit: ULASF, San Fernando study area; ULASG, San Gabriel study area. Monterey Bay and Salinas Valley Basins study unit: MSMB, Monterey Bay study area; MSPR, Paso Robles study area; MSSC, Santa Cruz study area; MSSV, Salinas Valley study area. Southeast San Joaquin Valley study unit: KING, Kings study area; KWH, Kaweah study area; TLR, Tulare Lake study area; TULE, Tule study area. Benchmark type: HAL-US, USEPA lifetime health advisory level; MCL-US, USEPA maximum contaminant level; AL-US, USEPA action level; MCL-CA, CDPH maximum contaminant level; NL-CA, CDPH notification level; SMCL, CDPH secondary maximum contaminant level. Benchmark type and benchmark level as of April 1, 2010. Other abbreviations: USGS, U.S. Geological Survey; USEPA, U.S. Environmental Protection Agency; CDPH, California Department of Public Health; μg/L, micrograms per liter; LRL, laboratory reporting level; E, estimated or having a higher degree of uncertainty; nc, not collected; na, not available; *, value greater than benchmark level; —, not detected; ≤, less than or equal to]
Tables 127

GAMA well 

identification 

number

Sample 

dates

Aluminum 

(μg/L) 

(01106)

Antimony 

(μg/L) 

(01095)

Arsenic 

(μg/L) 

(01000)

Barium 

(μg/L) 

(01005)

Beryllium 

(μg/L) 

(01010)

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)

Benchmark type3 MCL-CA MCL-US MCL-US MCL-CA MCL-US NL-CA MCL-US MCL-CA na AL-US SMCL-CA AL-USBenchmark level 1,000 6 10 1,000 4 1,000 5 50 na 1,300 300 15[LRL or SRL]1 [1.6]2 [0.06, 0.2] [0.06, 0.12] [0.36]2 [0.008, 0.06] [4, 8] [0.02, 0.04] [0.42]2 [0.014, 0.04] [1.7]2 [6]2 [0.65]2Southern Sacramento Valley study unit NAM-03 3/29/2005 nc nc nc nc nc nc nc nc nc nc nc ncNAM-03 4/10/2008 — — 2.2 62 — 394 4 — 2.9 0.03 ≤0.5 E7 ≤0.23SAM-10 4/21/2005 nc nc nc nc nc nc nc nc nc nc nc ncSAM-10 4/8/2008 — — 3.1 157 — 14 4 — 7.3 0.03 ≤1.4 — ≤0.64SOL-08 5/10/2005 nc nc nc nc nc nc nc nc nc nc nc ncSOL-08 4/8/2008 ≤0.90 — 2.6 205 — 76 — 26 — 2.3 — 1.45SSV-QPC-07 4/4/2005 ≤1.3 — 1.6 47 — *1,490 — 3.5 0.09 2.3 21 ≤0.65SSV-QPC-07 4/10/2008 — — 1.9 44 — *1,250 4 — 3.2 E0.02 1.8 15 ≤0.46SUI-03 5/12/2005 nc nc nc nc nc nc nc nc nc nc nc ncSUI-03 4/9/2008 — — *12.8 120 — 314 4 — 6.3 0.03 — 9 2.31YOL-01 4/11/2005 nc nc nc nc nc nc nc nc nc nc nc ncYOL-01 4/7/2008 — — 1.2 247 — *1,920 4 — 14.9 0.02 ≤0.8 — ≤0.22YOL-14 5/25/2005 ≤1.0 — 5.7 731 — 941 — — 0.16 ≤1.4 *413 ≤0.09YOL-14 4/9/2008 ≤1.1 — 6.7 492 E0.005 *1,310 4 — — 0.09 — *579 —San Fernando–San Gabriel study unit ULASF-09 6/27/2005 — — 0.50 121 — 123 E0.02 E0.50 0.37 4.0 ≤4 ≤0.43ULASF-09 6/16/2008 — E0.11 0.49 89 — 100 — ≤0.41 0.11 13.2 — 7.99ULASF-10 6/8/2005 ≤1.1 — 0.60 69 — 295 E0.03 2.4 0.10 ≤1.2 — ≤0.09ULASF-10 6/16/2008 ≤1.0 — 0.76 53 E0.007 408 0.04 18 0.16 1.8 136 ≤0.09ULASG-01 6/7/2005 nc nc nc nc nc nc nc nc nc nc nc nc

Table 10. Trace elements in groundwater samples collected from trend wells for seven Groundwater Ambient Monitoring and Assessment (GAMA) study units.—Continued[The five-digit USGS parameter code below the constituent name is used to uniquely identify a specific constituent or property. Trace elements were analyzed in samples from 24 trend wells during 2004–05 and 45 trend wells in 2007–08; 17 wells were analyzed during both periods. Information about analytes given in table 3F. GAMA well identification number acronyms: San Diego Drainages study unit: SDALLV, Alluvial Basins study area; SDHDRK, Hard Rock study area; SDTEM, Temecula Valley study area; SDTEMFP, Temecula Valley study area flow-path well; SDWARN, Warner Valley study area. North San Francisco Bay study unit: NSFVOL, Volcanic Highlands study area; NSFVP, Valley and Plains study area; NSFWG, Wilson Grove Formation Highlands study area; NSFWGFP, Wilson Grove Formation Highlands study area flow-path well. Northern San Joaquin Basin study unit: COS, Cosumnes Basin study area; ESJ, Eastern San Joaquin Basin study area; NSJ-QPC, Uplands study area; TRCY, Tracy Basin study area. Southern Sacramento Valley study unit: NAM, North American study area; SAM, South American study area; SOL, Solano study area; SSV-QPC, Uplands study area; SUI, Suisun-Fairfield study area; YOL, Yolo study area. San Fernando–San Gabriel study unit: ULASF, San Fernando study area; ULASG, San Gabriel study area. Monterey Bay and Salinas Valley Basins study unit: MSMB, Monterey Bay study area; MSPR, Paso Robles study area; MSSC, Santa Cruz study area; MSSV, Salinas Valley study area. Southeast San Joaquin Valley study unit: KING, Kings study area; KWH, Kaweah study area; TLR, Tulare Lake study area; TULE, Tule study area. Benchmark type: HAL-US, USEPA lifetime health advisory level; MCL-US, USEPA maximum contaminant level; AL-US, USEPA action level; MCL-CA, CDPH maximum contaminant level; NL-CA, CDPH notification level; SMCL, CDPH secondary maximum contaminant level. Benchmark type and benchmark level as of April 1, 2010. Other abbreviations: USGS, U.S. Geological Survey; USEPA, U.S. Environmental Protection Agency; CDPH, California Department of Public Health; μg/L, micrograms per liter; LRL, laboratory reporting level; E, estimated or having a higher degree of uncertainty; nc, not collected; na, not available; *, value greater than benchmark level; —, not detected; ≤, less than or equal to]
128 Groundwater-Quality Data in Seven GAMA Study Units: Results from Initial Sampling and Resampling of Wells GAMA well identification number Sample dates Aluminum (μg/L) (01106) Antimony (μg/L) (01095) Arsenic (μg/L) (01000) Barium (μg/L) (01005) Beryllium (μg/L) (01010) 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) Benchmark type3 MCL-CA MCL-US MCL-US MCL-CA MCL-US NL-CA MCL-US MCL-CA na AL-US SMCL-CA AL-US Benchmark level 1,000 6 10 1,000 4 1,000 5 50 na 1,300 300 15 [LRL or SRL]1 [1.6]2 [0.06, 0.2] [0.06, 0.12] [0.36]2 [0.008, 0.06] [4, 8] [0.02, 0.04] [0.42]2 [0.014, 0.04] [1.7]2 [6]2 [0.65]2 San Fernando–San Gabriel study unit—Continued ULASG-01 6/16/2008

—

— 0.72 84

— 80 0.13 2.6 0.10 ≤1.0

— 3.38

ULASG-08 6/15/2005 ≤1.4 E0.14 0.70 41

— 128

— 5.1 0.13 3.6

— ≤0.55

ULASG-08 6/17/2008 3.0 0.14 0.86 43

— 137

— 6.2 0.05 ≤0.6 ≤4 1.07

ULASG-15 6/23/2005 ≤1.5 0.46 2.5 84

— 78

—

— 0.08 ≤1.5

— ≤0.10

ULASG-15 6/17/2008 ≤1.3 0.46 2.8 96

— 79

— ≤0.15 0.03 4.7

— 1.16

ULASG-17 7/11/2005 nc nc nc nc nc nc nc nc nc nc nc ncULASG-17 6/17/2008

—

— 0.41 103

— 71

— 1.7 0.12 3.1

— ≤0.48

Monterey Bay and Salinas Valley Basins study unitMSMB-03 8/31/2005 nc nc nc nc nc nc nc nc nc nc nc ncMSMB-03 8/20/2008 17.5

— 3.5 2 — 227

—

— E0.01

— 14 4 ≤0.06

MSMB-04 8/17/2005 ≤1.0

—

— 4 — 88

—

— 0.07 4.4 48 ≤0.55

MSMB-04 8/20/2008 ≤1.0

— 0.34 5 — 75

— ≤0.40 0.05

— 96 0.84

MSMB-16 8/17/2005 nc nc nc nc nc nc nc nc nc nc nc ncMSMB-16 8/19/2008

—

— 1.5 43

— 86 0.10 4.1 0.04 ≤1.4 — 4 ≤0.37

MSMB-28 8/3/2005 nc nc nc nc nc nc nc nc nc nc nc ncMSMB-28 8/21/2008

—

— 0.77 57

— 46 0.04 1.4 0.04 2.5 — 4 0.74

MSMB-31 8/11/2005 nc nc nc nc nc nc nc nc nc nc nc ncMSMB-31 8/21/2008

— E0.07 0.69 74

— 19 E0.03 0.77 0.05 ≤1.3 — 4 ≤0.24

MSPR-03 7/28/2005 nc nc nc nc nc nc nc nc nc nc nc ncMSPR-03 11/14/2008

— 0.13 *17.7 38

— 764 0.22

— 0.03

— 49 4 ≤0.32

Table 10. Trace elements in groundwater samples collected from trend wells for seven Groundwater Ambient Monitoring and Assessment (GAMA) study units.—Continued[The five-digit USGS parameter code below the constituent name is used to uniquely identify a specific constituent or property. Trace elements were analyzed in samples from 24 trend wells during 2004–05 and 45 trend wells in 2007–08; 17 wells were analyzed during both periods. Information about analytes given in table 3F. GAMA well identification number acronyms: San Diego Drainages study unit: SDALLV, Alluvial Basins study area; SDHDRK, Hard Rock study area; SDTEM, Temecula Valley study area; SDTEMFP, Temecula Valley study area flow-path well; SDWARN, Warner Valley study area. North San Francisco Bay study unit: NSFVOL, Volcanic Highlands study area; NSFVP, Valley and Plains study area; NSFWG, Wilson Grove Formation Highlands study area; NSFWGFP, Wilson Grove Formation Highlands study area flow-path well. Northern San Joaquin Basin study unit: COS, Cosumnes Basin study area; ESJ, Eastern San Joaquin Basin study area; NSJ-QPC, Uplands study area; TRCY, Tracy Basin study area. Southern Sacramento Valley study unit: NAM, North American study area; SAM, South American study area; SOL, Solano study area; SSV-QPC, Uplands study area; SUI, Suisun-Fairfield study area; YOL, Yolo study area. San Fernando–San Gabriel study unit: ULASF, San Fernando study area; ULASG, San Gabriel study area. Monterey Bay and Salinas Valley Basins study unit: MSMB, Monterey Bay study area; MSPR, Paso Robles study area; MSSC, Santa Cruz study area; MSSV, Salinas Valley study area. Southeast San Joaquin Valley study unit: KING, Kings study area; KWH, Kaweah study area; TLR, Tulare Lake study area; TULE, Tule study area. Benchmark type: HAL-US, USEPA lifetime health advisory level; MCL-US, USEPA maximum contaminant level; AL-US, USEPA action level; MCL-CA, CDPH maximum contaminant level; NL-CA, CDPH notification level; SMCL, CDPH secondary maximum contaminant level. Benchmark type and benchmark level as of April 1, 2010. Other abbreviations: USGS, U.S. Geological Survey; USEPA, U.S. Environmental Protection Agency; CDPH, California Department of Public Health; μg/L, micrograms per liter; LRL, laboratory reporting level; E, estimated or having a higher degree of uncertainty; nc, not collected; na, not available; *, value greater than benchmark level; —, not detected; ≤, less than or equal to]
Tables 129

GAMA well 

identification 

number

Sample 

dates

Aluminum 

(μg/L) 

(01106)

Antimony 

(μg/L) 

(01095)

Arsenic 

(μg/L) 

(01000)

Barium 

(μg/L) 

(01005)

Beryllium 

(μg/L) 

(01010)

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)

Benchmark type3 MCL-CA MCL-US MCL-US MCL-CA MCL-US NL-CA MCL-US MCL-CA na AL-US SMCL-CA AL-USBenchmark level 1,000 6 10 1,000 4 1,000 5 50 na 1,300 300 15[LRL or SRL]1 [1.6]2 [0.06, 0.2] [0.06, 0.12] [0.36]2 [0.008, 0.06] [4, 8] [0.02, 0.04] [0.42]2 [0.014, 0.04] [1.7]2 [6]2 [0.65]2Monterey Bay and Salinas Valley Basins study unit—ContinuedMSPR-09 7/18/2005 nc nc nc nc nc nc nc nc nc nc nc ncMSPR-09 11/14/2008 — 0.11 5.8 25 E0.010 *2,210 0.16 1.3 E0.02 — 30 ≤0.28MSSC-06 8/24/2005 — — 0.20 22 — 47 — — 0.18 ≤0.7 *657 ≤0.09MSSC-06 8/18/2008 ≤1.3 — 0.11 23 — 41 — — 0.05 — *787 4 ≤0.23MSSC-11 9/13/2005 nc nc nc nc nc nc nc nc nc nc nc ncMSSC-11 8/19/2008 ≤1.4 — 3.9 2 — 17 — — 0.03 — 152 4 —MSSV-06 8/2/2005 nc nc nc nc nc nc nc nc nc nc nc ncMSSV-06 11/13/2008 — 0.13 2.1 40 — 134 0.23 0.60 0.03 ≤1.0 — 4 ≤0.16MSSV-15 8/12/2005 nc nc nc nc nc nc nc nc nc nc nc ncMSSV-15 11/13/2008 E2.1 0.16 2.7 15 — 153 0.24 0.70 0.04 ≤0.8 9 4 ≤0.17Southeast San Joaquin Valley study unitKING-11 10/20/2005 — — 1.8 58 — 27 E0.03 1.3 — ≤0.7 7 ≤0.07KING-11 11/5/2008 — 0.04 2.0 76 — 45 4 E0.01 2.2 E0.02 — — 4 ≤0.18KING-13 10/20/2005 — — 2.6 55 — 32 — 2.0 — 3.0 — 0.89KING-13 11/5/2008 — 0.05 2.9 58 — 35 4 — 2.0 E0.02 ≤0.6 — 4 ≤0.32KING-17 10/26/2005 — — 2.5 46 — 23 0.04 6.6 — 1.9 — 0.91KING-17 11/4/2008 — 0.07 2.7 49 — 20 4 — 6.8 E0.01 — — 4 ≤0.04KING-24 11/5/2005 nc nc nc nc nc nc nc nc nc nc nc ncKING-24 11/3/2008 — 0.06 1.1 100 — 19 4 — 1.7 0.05 1.8 — ≤0.50KWH-10 11/17/2005 nc nc nc nc nc nc nc nc nc nc nc nc

Table 10. Trace elements in groundwater samples collected from trend wells for seven Groundwater Ambient Monitoring and Assessment (GAMA) study units.—Continued[The five-digit USGS parameter code below the constituent name is used to uniquely identify a specific constituent or property. Trace elements were analyzed in samples from 24 trend wells during 2004–05 and 45 trend wells in 2007–08; 17 wells were analyzed during both periods. Information about analytes given in table 3F. GAMA well identification number acronyms: San Diego Drainages study unit: SDALLV, Alluvial Basins study area; SDHDRK, Hard Rock study area; SDTEM, Temecula Valley study area; SDTEMFP, Temecula Valley study area flow-path well; SDWARN, Warner Valley study area. North San Francisco Bay study unit: NSFVOL, Volcanic Highlands study area; NSFVP, Valley and Plains study area; NSFWG, Wilson Grove Formation Highlands study area; NSFWGFP, Wilson Grove Formation Highlands study area flow-path well. Northern San Joaquin Basin study unit: COS, Cosumnes Basin study area; ESJ, Eastern San Joaquin Basin study area; NSJ-QPC, Uplands study area; TRCY, Tracy Basin study area. Southern Sacramento Valley study unit: NAM, North American study area; SAM, South American study area; SOL, Solano study area; SSV-QPC, Uplands study area; SUI, Suisun-Fairfield study area; YOL, Yolo study area. San Fernando–San Gabriel study unit: ULASF, San Fernando study area; ULASG, San Gabriel study area. Monterey Bay and Salinas Valley Basins study unit: MSMB, Monterey Bay study area; MSPR, Paso Robles study area; MSSC, Santa Cruz study area; MSSV, Salinas Valley study area. Southeast San Joaquin Valley study unit: KING, Kings study area; KWH, Kaweah study area; TLR, Tulare Lake study area; TULE, Tule study area. Benchmark type: HAL-US, USEPA lifetime health advisory level; MCL-US, USEPA maximum contaminant level; AL-US, USEPA action level; MCL-CA, CDPH maximum contaminant level; NL-CA, CDPH notification level; SMCL, CDPH secondary maximum contaminant level. Benchmark type and benchmark level as of April 1, 2010. Other abbreviations: USGS, U.S. Geological Survey; USEPA, U.S. Environmental Protection Agency; CDPH, California Department of Public Health; μg/L, micrograms per liter; LRL, laboratory reporting level; E, estimated or having a higher degree of uncertainty; nc, not collected; na, not available; *, value greater than benchmark level; —, not detected; ≤, less than or equal to]
130 Groundwater-Quality Data in Seven GAMA Study Units: Results from Initial Sampling and Resampling of Wells GAMA well identification number Sample dates Aluminum (μg/L) (01106) Antimony (μg/L) (01095) Arsenic (μg/L) (01000) Barium (μg/L) (01005) Beryllium (μg/L) (01010) 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) Benchmark type3 MCL-CA MCL-US MCL-US MCL-CA MCL-US NL-CA MCL-US MCL-CA na AL-US SMCL-CA AL-US Benchmark level 1,000 6 10 1,000 4 1,000 5 50 na 1,300 300 15 [LRL or SRL]1 [1.6]2 [0.06, 0.2] [0.06, 0.12] [0.36]2 [0.008, 0.06] [4, 8] [0.02, 0.04] [0.42]2 [0.014, 0.04] [1.7]2 [6]2 [0.65]2 Southeast San Joaquin Valley study unit—Continued KWH-10 11/5/2008

— 0.05 2.2 130

— 94 4 E0.02 2.2 0.04

— — 4 ≤0.06

KWH-12 11/28/2005 2.3

— 0.66 25

— 19

— 1.8 E0.02 ≤1.6 9 1.68

KWH-12 11/6/2008 9.9 0.09 0.62 34

— 17 4 — 1.9 E0.02 2.3 9 4 ≤0.25

TLR-03 11/29/2005 nc nc nc nc nc nc nc nc nc nc nc ncTLR-03 11/4/2008 257 0.04 *27.7 14

— 460 4 0.03 ≤0.06

—

— 8 ≤0.04

TULE-05 12/5/2005 nc nc nc nc nc nc nc nc nc nc nc ncTULE-05 11/3/2008 E3.0 0.17 3.9 29

— 495 4 0.04 ≤0.28 0.03

— 15 4 ≤0.04

TULE-10 12/7/2005 nc nc nc nc nc nc nc nc nc nc nc ncTULE-10 11/3/2008

— 0.06 1.0 129

— 79 4 — 0.60 0.07

— — 4 ≤0.18

Table 10. Trace elements in groundwater samples collected from trend wells for seven Groundwater Ambient Monitoring and Assessment (GAMA) study units.—Continued[The five-digit USGS parameter code below the constituent name is used to uniquely identify a specific constituent or property. Trace elements were analyzed in samples from 24 trend wells during 2004–05 and 45 trend wells in 2007–08; 17 wells were analyzed during both periods. Information about analytes given in table 3F. GAMA well identification number acronyms: San Diego Drainages study unit: SDALLV, Alluvial Basins study area; SDHDRK, Hard Rock study area; SDTEM, Temecula Valley study area; SDTEMFP, Temecula Valley study area flow-path well; SDWARN, Warner Valley study area. North San Francisco Bay study unit: NSFVOL, Volcanic Highlands study area; NSFVP, Valley and Plains study area; NSFWG, Wilson Grove Formation Highlands study area; NSFWGFP, Wilson Grove Formation Highlands study area flow-path well. Northern San Joaquin Basin study unit: COS, Cosumnes Basin study area; ESJ, Eastern San Joaquin Basin study area; NSJ-QPC, Uplands study area; TRCY, Tracy Basin study area. Southern Sacramento Valley study unit: NAM, North American study area; SAM, South American study area; SOL, Solano study area; SSV-QPC, Uplands study area; SUI, Suisun-Fairfield study area; YOL, Yolo study area. San Fernando–San Gabriel study unit: ULASF, San Fernando study area; ULASG, San Gabriel study area. Monterey Bay and Salinas Valley Basins study unit: MSMB, Monterey Bay study area; MSPR, Paso Robles study area; MSSC, Santa Cruz study area; MSSV, Salinas Valley study area. Southeast San Joaquin Valley study unit: KING, Kings study area; KWH, Kaweah study area; TLR, Tulare Lake study area; TULE, Tule study area. Benchmark type: HAL-US, USEPA lifetime health advisory level; MCL-US, USEPA maximum contaminant level; AL-US, USEPA action level; MCL-CA, CDPH maximum contaminant level; NL-CA, CDPH notification level; SMCL, CDPH secondary maximum contaminant level. Benchmark type and benchmark level as of April 1, 2010. Other abbreviations: USGS, U.S. Geological Survey; USEPA, U.S. Environmental Protection Agency; CDPH, California Department of Public Health; μg/L, micrograms per liter; LRL, laboratory reporting level; E, estimated or having a higher degree of uncertainty; nc, not collected; na, not available; *, value greater than benchmark level; —, not detected; ≤, less than or equal to]
Tables 131

GAMA well 

identification 

number

Sample 

dates

Lithium 

(μg/L) 

(01130)

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)

Benchmark type3 na SMCL-CA HAL-US MCL-CA MCL-US SMCL-CA HAL-US MCL-US na MCL-US NL-CA SMCL-CABenchmark level na 50 40 100 50 100 4,000 2 na 30 50 5,000[LRL or SRL]1 [0.6, 1] [0.2]2 [0.02, 0.4] [0.36]2 [0.04, 0.4] [0.008, 0.2] [0.4, 0.8] [0.04] [0.11]2 [0.006, 0.04] [0.11]2 [4.8]2San Diego Drainages study unitSDHDRK-09 7/27/2004 nc nc nc nc nc nc nc nc nc nc nc ncSDHDRK-09 9/11/2007 8.6 0.5 6.4 ≤0.36 0.90 — 182 — nc 9.97 28.2 52.9 5SDTEM-04 5/24/2004 nc nc nc nc nc nc nc nc nc nc nc ncSDTEM-04 9/18/2007 3.0 — 11.0 0.48 1.9 — 361 — nc 2.35 14.6 ≤4.0 5SDTEMFP-01 5/19/2004 4.2 — 2.0 0.55 1.8 — 277 — 13.7 2.55 *69.0 ≤0.6SDTEMFP-01 9/19/2007 5.3 0.3 1.8 ≤0.18 1.9 — 279 — nc 2.84 *69.4 ≤0.9 5SDWARN-01 6/17/2004 nc nc nc nc nc nc nc nc nc nc nc ncSDWARN-01 9/11/2007 6.2 1.6 3.3 ≤0.16 1.8 — 484 — nc 8.81 6.4 ≤4.3 5North San Francisco Bay study unitNSFVOL-14 10/7/2004 11.2 10.7 1.5 0.76 — — 38 — nc 0.128 15.4 8.2NSFVOL-14 8/21/2007 nc nc nc nc nc nc nc nc nc nc nc ncNSFVOL-18 10/20/2004 nc nc nc nc nc nc nc nc nc nc nc ncNSFVOL-18 8/28/2007 48.5 *54.4 1.8 ≤0.16 — — 97.2 — 0.66 — 1.0 ≤2.0 5NSFVP-29 9/28/2004 6.5 ≤0.1 E0.21 2.5 — — 352 — nc 0.088 1.4 49.7NSFVP-29 8/27/2007 nc nc nc nc nc nc nc nc nc nc nc ncNSFVP-34 10/18/2004 4.7 *434 1.9 ≤0.26 — — 30.9 — nc — 1.3 20.1NSFVP-34 8/22/2007 nc nc nc nc nc nc nc nc nc nc nc ncNSFVP-36 10/19/2004 33.8 *1,220 1.0 0.65 2 0.26 440 — nc 0.065 0.40 49.8NSFVP-36 8/20/2007 nc nc nc nc nc nc nc nc nc nc nc ncNSFVP-38 10/20/2004 61.3 14.5 13.7 ≤0.25 0.50 — 83.9 — nc 0.109 1.0 5.9

Table 10. Trace elements in groundwater samples collected from trend wells for seven Groundwater Ambient Monitoring and Assessment (GAMA) study units.—Continued[The five-digit USGS parameter code below the constituent name is used to uniquely identify a specific constituent or property. Trace elements were analyzed in samples from 24 trend wells during 2004–05 and 45 trend wells in 2007–08; 17 wells were analyzed during both periods. Information about analytes given in table 3F. GAMA well identification number acronyms: San Diego Drainages study unit: SDALLV, Alluvial Basins study area; SDHDRK, Hard Rock study area; SDTEM, Temecula Valley study area; SDTEMFP, Temecula Valley study area flow-path well; SDWARN, Warner Valley study area. North San Francisco Bay study unit: NSFVOL, Volcanic Highlands study area; NSFVP, Valley and Plains study area; NSFWG, Wilson Grove Formation Highlands study area; NSFWGFP, Wilson Grove Formation Highlands study area flow-path well. Northern San Joaquin Basin study unit: COS, Cosumnes Basin study area; ESJ, Eastern San Joaquin Basin study area; NSJ-QPC, Uplands study area; TRCY, Tracy Basin study area. Southern Sacramento Valley study unit: NAM, North American study area; SAM, South American study area; SOL, Solano study area; SSV-QPC, Uplands study area; SUI, Suisun-Fairfield study area; YOL, Yolo study area. San Fernando–San Gabriel study unit: ULASF, San Fernando study area; ULASG, San Gabriel study area. Monterey Bay and Salinas Valley Basins study unit: MSMB, Monterey Bay study area; MSPR, Paso Robles study area; MSSC, Santa Cruz study area; MSSV, Salinas Valley study area. Southeast San Joaquin Valley study unit: KING, Kings study area; KWH, Kaweah study area; TLR, Tulare Lake study area; TULE, Tule study area. Benchmark type: HAL-US, USEPA lifetime health advisory level; MCL-US, USEPA maximum contaminant level; AL-US, USEPA action level; MCL-CA, CDPH maximum contaminant level; NL-CA, CDPH notification level; SMCL, CDPH secondary maximum contaminant level. Benchmark type and benchmark level as of April 1, 2010. Other abbreviations: USGS, U.S. Geological Survey; USEPA, U.S. Environmental Protection Agency; CDPH, California Department of Public Health; μg/L, micrograms per liter; LRL, laboratory reporting level; E, estimated or having a higher degree of uncertainty; nc, not collected; na, not available; *, value greater than benchmark level; —, not detected; ≤, less than or equal to]
132 Groundwater-Quality Data in Seven GAMA Study Units: Results from Initial Sampling and Resampling of Wells GAMA well identification number Sample dates Lithium (μg/L) (01130) 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) Benchmark type3 na SMCL-CA HAL-US MCL-CA MCL-US SMCL-CA HAL-US MCL-US na MCL-US NL-CA SMCL-CA Benchmark level na 50 40 100 50 100 4,000 2 na 30 50 5,000 [LRL or SRL]1 [0.6, 1] [0.2]2 [0.02, 0.4] [0.36]2 [0.04, 0.4] [0.008, 0.2] [0.4, 0.8] [0.04] [0.11]2 [0.006, 0.04] [0.11]2 [4.8]2 North San Francisco Bay study unit—Continued NSFVP-38 8/22/2007 nc nc nc nc nc nc nc nc nc nc nc nc NSFVP-39 10/21/2004 68.9 *78.1 1.8 ≤0.34

—

— 39.8 0.22 nc 1.00 3.7 9.4

NSFVP-39 11/16/2007 60.8 *70.7 1.6 ≤0.34

—

— 45.4 0.23 1.1 0.974 2.5 ≤3.1 5

NSFVP-41 10/21/2004 33.5 *928 1.6 0.62

—

— 262

— nc 0.250 3.1 5.8

NSFVP-41 8/20/2007 nc nc nc nc nc nc nc nc nc nc nc ncNSFWG-03 9/21/2004 nc nc nc nc nc nc nc nc nc nc nc ncNSFWG-03 8/29/2007 8.5 *76.0 0.60 8.8

—

— 176

—

—

— ≤0.06 ≤3.9 5

NSFWGFP-01 10/5/2004 10.6 16.0 0.70 0.43

—

— 188

— nc 0.143 1.7 ≤4.2

NSFWGFP-01 8/29/2007 nc nc nc nc nc nc nc nc nc nc nc ncNorthern San Joaquin Basin study unitCOS-08 1/3/2005 nc nc nc nc nc nc nc nc nc nc nc ncCOS-08 4/3/2008 E0.7 *132 2.2

— 0.07

— 104

— nc 0.157 1.5 ≤1.5 5

ESJ-01 1/24/2005 nc nc nc nc nc nc nc nc nc nc nc ncESJ-01 4/2/2008 3.6 0.3 1.1 0.41 0.66

— 553

— nc 6.10 17.3 ≤2.7 5

ESJ-06 1/10/2005 0.8

— 0.87 0.80 0.50

— 340

— nc 3.81 33.4 ≤0.9

ESJ-06 4/2/2008 E0.8

— 0.78 ≤0.23 0.34

— 329

— nc 3.30 32.4 ≤1.6 5

NSJ-QPC-04 1/24/2005 3.7 *54.8 0.76 ≤0.18

—

— 48.4

— nc 0.075 9.1 ≤0.9

NSJ-QPC-04 4/1/2008 3.3 *64.9 0.71

— 0.07

— 54.6

— nc 0.071 8.1 ≤2.4 5

TRCY-03 1/6/2005 32.3 ≤0.2 1.9 0.77 1.2

— 1,060

— nc 3.37 2.7 ≤2.0

TRCY-03 3/31/2008 33.6 0.3 1.7 ≤0.32 1.1

— 1,060

— nc 2.87 2.6 ≤4.6 5

Table 10. Trace elements in groundwater samples collected from trend wells for seven Groundwater Ambient Monitoring and Assessment (GAMA) study units.—Continued[The five-digit USGS parameter code below the constituent name is used to uniquely identify a specific constituent or property. Trace elements were analyzed in samples from 24 trend wells during 2004–05 and 45 trend wells in 2007–08; 17 wells were analyzed during both periods. Information about analytes given in table 3F. GAMA well identification number acronyms: San Diego Drainages study unit: SDALLV, Alluvial Basins study area; SDHDRK, Hard Rock study area; SDTEM, Temecula Valley study area; SDTEMFP, Temecula Valley study area flow-path well; SDWARN, Warner Valley study area. North San Francisco Bay study unit: NSFVOL, Volcanic Highlands study area; NSFVP, Valley and Plains study area; NSFWG, Wilson Grove Formation Highlands study area; NSFWGFP, Wilson Grove Formation Highlands study area flow-path well. Northern San Joaquin Basin study unit: COS, Cosumnes Basin study area; ESJ, Eastern San Joaquin Basin study area; NSJ-QPC, Uplands study area; TRCY, Tracy Basin study area. Southern Sacramento Valley study unit: NAM, North American study area; SAM, South American study area; SOL, Solano study area; SSV-QPC, Uplands study area; SUI, Suisun-Fairfield study area; YOL, Yolo study area. San Fernando–San Gabriel study unit: ULASF, San Fernando study area; ULASG, San Gabriel study area. Monterey Bay and Salinas Valley Basins study unit: MSMB, Monterey Bay study area; MSPR, Paso Robles study area; MSSC, Santa Cruz study area; MSSV, Salinas Valley study area. Southeast San Joaquin Valley study unit: KING, Kings study area; KWH, Kaweah study area; TLR, Tulare Lake study area; TULE, Tule study area. Benchmark type: HAL-US, USEPA lifetime health advisory level; MCL-US, USEPA maximum contaminant level; AL-US, USEPA action level; MCL-CA, CDPH maximum contaminant level; NL-CA, CDPH notification level; SMCL, CDPH secondary maximum contaminant level. Benchmark type and benchmark level as of April 1, 2010. Other abbreviations: USGS, U.S. Geological Survey; USEPA, U.S. Environmental Protection Agency; CDPH, California Department of Public Health; μg/L, micrograms per liter; LRL, laboratory reporting level; E, estimated or having a higher degree of uncertainty; nc, not collected; na, not available; *, value greater than benchmark level; —, not detected; ≤, less than or equal to]
Tables 133

GAMA well 

identification 

number

Sample 

dates

Lithium 

(μg/L) 

(01130)

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)

Benchmark type3 na SMCL-CA HAL-US MCL-CA MCL-US SMCL-CA HAL-US MCL-US na MCL-US NL-CA SMCL-CABenchmark level na 50 40 100 50 100 4,000 2 na 30 50 5,000[LRL or SRL]1 [0.6, 1] [0.2]2 [0.02, 0.4] [0.36]2 [0.04, 0.4] [0.008, 0.2] [0.4, 0.8] [0.04] [0.11]2 [0.006, 0.04] [0.11]2 [4.8]2Southern Sacramento Valley study unit NAM-03 3/29/2005 nc nc nc nc nc nc nc nc nc nc nc ncNAM-03 4/10/2008 24.9 0.5 0.59 0.46 0.21 — 200 — nc 0.230 16.8 ≤2.5 5SAM-10 4/21/2005 nc nc nc nc nc nc nc nc nc nc nc ncSAM-10 4/8/2008 E0.5 — 0.42 ≤0.27 0.20 — 556 — nc 8.58 16.1 ≤3.7 5SOL-08 5/10/2005 nc nc nc nc nc nc nc nc nc nc nc ncSOL-08 4/8/2008 21.9 ≤0.1 0.70 ≤0.21 0.43 — 575 — nc 1.53 14.6 ≤3.7 5SSV-QPC-07 4/4/2005 45.7 1.6 0.51 8.4 — — 415 — nc 0.814 13.6 7.5SSV-QPC-07 4/10/2008 54.7 1.2 0.48 ≤0.27 0.20 — 351 — nc 0.781 13.6 8.1 5SUI-03 5/12/2005 nc nc nc nc nc nc nc nc nc nc nc ncSUI-03 4/9/2008 29.4 — 2.3 ≤0.31 0.45 — 665 — nc 2.68 25.0 12.1 5YOL-01 4/11/2005 nc nc nc nc nc nc nc nc nc nc nc ncYOL-01 4/7/2008 48.0 — 0.52 0.38 2.8 — 766 — nc 1.15 4.8 ≤1.3 5YOL-14 5/25/2005 1.4 *501 3.8 1.1 — — 1,070 — nc — — ≤4.0YOL-14 4/9/2008 2.6 *811 2.7 0.50 0.06 — 910 — nc 0.120 0.54 ≤3.5 5San Fernando–San Gabriel study unit ULASF-09 6/27/2005 3.4 ≤0.1 4.2 5.7 0.80 — 925 — nc 9.25 4.2 ≤3.7ULASF-09 6/16/2008 2.2 ≤0.2 4.2 1.0 0.34 — 767 — — 6.68 3.9 25 5ULASF-10 6/8/2005 3.5 1.1 13.9 1.7 0.70 — 559 — nc 3.12 7.5 ≤0.4ULASF-10 6/16/2008 4.4 8.6 17.2 12.4 0.71 — 556 — ≤0.09 1.62 8.9 ≤3.1 5ULASG-01 6/7/2005 nc nc nc nc nc nc nc nc nc nc nc nc

Table 10. Trace elements in groundwater samples collected from trend wells for seven Groundwater Ambient Monitoring and Assessment (GAMA) study units.—Continued[The five-digit USGS parameter code below the constituent name is used to uniquely identify a specific constituent or property. Trace elements were analyzed in samples from 24 trend wells during 2004–05 and 45 trend wells in 2007–08; 17 wells were analyzed during both periods. Information about analytes given in table 3F. GAMA well identification number acronyms: San Diego Drainages study unit: SDALLV, Alluvial Basins study area; SDHDRK, Hard Rock study area; SDTEM, Temecula Valley study area; SDTEMFP, Temecula Valley study area flow-path well; SDWARN, Warner Valley study area. North San Francisco Bay study unit: NSFVOL, Volcanic Highlands study area; NSFVP, Valley and Plains study area; NSFWG, Wilson Grove Formation Highlands study area; NSFWGFP, Wilson Grove Formation Highlands study area flow-path well. Northern San Joaquin Basin study unit: COS, Cosumnes Basin study area; ESJ, Eastern San Joaquin Basin study area; NSJ-QPC, Uplands study area; TRCY, Tracy Basin study area. Southern Sacramento Valley study unit: NAM, North American study area; SAM, South American study area; SOL, Solano study area; SSV-QPC, Uplands study area; SUI, Suisun-Fairfield study area; YOL, Yolo study area. San Fernando–San Gabriel study unit: ULASF, San Fernando study area; ULASG, San Gabriel study area. Monterey Bay and Salinas Valley Basins study unit: MSMB, Monterey Bay study area; MSPR, Paso Robles study area; MSSC, Santa Cruz study area; MSSV, Salinas Valley study area. Southeast San Joaquin Valley study unit: KING, Kings study area; KWH, Kaweah study area; TLR, Tulare Lake study area; TULE, Tule study area. Benchmark type: HAL-US, USEPA lifetime health advisory level; MCL-US, USEPA maximum contaminant level; AL-US, USEPA action level; MCL-CA, CDPH maximum contaminant level; NL-CA, CDPH notification level; SMCL, CDPH secondary maximum contaminant level. Benchmark type and benchmark level as of April 1, 2010. Other abbreviations: USGS, U.S. Geological Survey; USEPA, U.S. Environmental Protection Agency; CDPH, California Department of Public Health; μg/L, micrograms per liter; LRL, laboratory reporting level; E, estimated or having a higher degree of uncertainty; nc, not collected; na, not available; *, value greater than benchmark level; —, not detected; ≤, less than or equal to]
134 Groundwater-Quality Data in Seven GAMA Study Units: Results from Initial Sampling and Resampling of Wells GAMA well identification number Sample dates Lithium (μg/L) (01130) 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) Benchmark type3 na SMCL-CA HAL-US MCL-CA MCL-US SMCL-CA HAL-US MCL-US na MCL-US NL-CA SMCL-CA Benchmark level na 50 40 100 50 100 4,000 2 na 30 50 5,000 [LRL or SRL]1 [0.6, 1] [0.2]2 [0.02, 0.4] [0.36]2 [0.04, 0.4] [0.008, 0.2] [0.4, 0.8] [0.04] [0.11]2 [0.006, 0.04] [0.11]2 [4.8]2 San Fernando–San Gabriel study unit—Continued ULASG-01 6/16/2008 10.0 0.4 30.3 0.93 3.1

— 643

—

— 15.7 8.5 ≤4.7 5

ULASG-08 6/15/2005 3.7 0.8 7.2 2.6 0.50

— 474

— nc 13.0 6.7 ≤3.3

ULASG-08 6/17/2008 5.3 0.7 8.0 0.39 0.40

— 479

— 0.12 13.6 7.1 ≤2.2 5

ULASG-15 6/23/2005 2.4

— 2.2 1.8 E0.3

— 336

— nc 1.48 1.6 ≤2.6

ULASG-15 6/17/2008 2.2

— 2.1 ≤0.34 0.20

— 392

— 0.30 1.71 1.3 9.1 5

ULASG-17 7/11/2005 nc nc nc nc nc nc nc nc nc nc nc ncULASG-17 6/17/2008 1.3 0.3 2.4 1.0 2.2

— 819

— ≤0.04 12.5 3.1 ≤2.1 5

Monterey Bay and Salinas Valley Basins study unitMSMB-03 8/31/2005 nc nc nc nc nc nc nc nc nc nc nc ncMSMB-03 8/20/2008 13.7 3.4 11.0 ≤0.12

—

— 9.49

— 1.9

— 0.28

—

MSMB-04 8/17/2005 10.9 13.3 2.1 1.2

—

— 276

— nc 0.738 0.30 ≤3.0

MSMB-04 8/20/2008 13.1 26.1 2.0 0.59 0.04

— 348

—

— 0.740 0.98 ≤1.0 5

MSMB-16 8/17/2005 nc nc nc nc nc nc nc nc nc nc nc ncMSMB-16 8/19/2008 17.5

— 6.5 0.57 0.51

— 353

—

— 1.39 7.4 7.0 5

MSMB-28 8/3/2005 nc nc nc nc nc nc nc nc nc nc nc ncMSMB-28 8/21/2008 13.8

— 6.2 1.2 1.2

— 431

—

— 3.55 5.7 13.8 5

MSMB-31 8/11/2005 nc nc nc nc nc nc nc nc nc nc nc ncMSMB-31 8/21/2008 7.1 0.4 2.0 0.70 0.40

— 321

—

— 7.54 3.3 7.2 5

MSPR-03 7/28/2005 nc nc nc nc nc nc nc nc nc nc nc ncMSPR-03 11/14/2008 58.1 46.3 *71.8 0.42 0.14

— 297 E0.03 0.23 6.22 15.8 ≤2.0 5

Table 10. Trace elements in groundwater samples collected from trend wells for seven Groundwater Ambient Monitoring and Assessment (GAMA) study units.—Continued[The five-digit USGS parameter code below the constituent name is used to uniquely identify a specific constituent or property. Trace elements were analyzed in samples from 24 trend wells during 2004–05 and 45 trend wells in 2007–08; 17 wells were analyzed during both periods. Information about analytes given in table 3F. GAMA well identification number acronyms: San Diego Drainages study unit: SDALLV, Alluvial Basins study area; SDHDRK, Hard Rock study area; SDTEM, Temecula Valley study area; SDTEMFP, Temecula Valley study area flow-path well; SDWARN, Warner Valley study area. North San Francisco Bay study unit: NSFVOL, Volcanic Highlands study area; NSFVP, Valley and Plains study area; NSFWG, Wilson Grove Formation Highlands study area; NSFWGFP, Wilson Grove Formation Highlands study area flow-path well. Northern San Joaquin Basin study unit: COS, Cosumnes Basin study area; ESJ, Eastern San Joaquin Basin study area; NSJ-QPC, Uplands study area; TRCY, Tracy Basin study area. Southern Sacramento Valley study unit: NAM, North American study area; SAM, South American study area; SOL, Solano study area; SSV-QPC, Uplands study area; SUI, Suisun-Fairfield study area; YOL, Yolo study area. San Fernando–San Gabriel study unit: ULASF, San Fernando study area; ULASG, San Gabriel study area. Monterey Bay and Salinas Valley Basins study unit: MSMB, Monterey Bay study area; MSPR, Paso Robles study area; MSSC, Santa Cruz study area; MSSV, Salinas Valley study area. Southeast San Joaquin Valley study unit: KING, Kings study area; KWH, Kaweah study area; TLR, Tulare Lake study area; TULE, Tule study area. Benchmark type: HAL-US, USEPA lifetime health advisory level; MCL-US, USEPA maximum contaminant level; AL-US, USEPA action level; MCL-CA, CDPH maximum contaminant level; NL-CA, CDPH notification level; SMCL, CDPH secondary maximum contaminant level. Benchmark type and benchmark level as of April 1, 2010. Other abbreviations: USGS, U.S. Geological Survey; USEPA, U.S. Environmental Protection Agency; CDPH, California Department of Public Health; μg/L, micrograms per liter; LRL, laboratory reporting level; E, estimated or having a higher degree of uncertainty; nc, not collected; na, not available; *, value greater than benchmark level; —, not detected; ≤, less than or equal to]
Tables 135

GAMA well 

identification 

number

Sample 

dates

Lithium 

(μg/L) 

(01130)

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)

Benchmark type3 na SMCL-CA HAL-US MCL-CA MCL-US SMCL-CA HAL-US MCL-US na MCL-US NL-CA SMCL-CABenchmark level na 50 40 100 50 100 4,000 2 na 30 50 5,000[LRL or SRL]1 [0.6, 1] [0.2]2 [0.02, 0.4] [0.36]2 [0.04, 0.4] [0.008, 0.2] [0.4, 0.8] [0.04] [0.11]2 [0.006, 0.04] [0.11]2 [4.8]2Monterey Bay and Salinas Valley Basins study unit—ContinuedMSPR-09 7/18/2005 nc nc nc nc nc nc nc nc nc nc nc ncMSPR-09 11/14/2008 60.1 3.5 *48.2 ≤0.29 2.1 — 304 — 0.25 5.50 30.3 ≤2.2 5MSSC-06 8/24/2005 19.1 *197 2.8 3.4 0.70 — 226 — nc E0.026 — 10.0MSSC-06 8/18/2008 20.1 *192 2.8 0.54 E0.03 — 223 — ≤0.04 — 0.18 ≤4.0 5MSSC-11 9/13/2005 nc nc nc nc nc nc nc nc nc nc nc ncMSSC-11 8/19/2008 11.2 21.3 0.80 ≤0.28 — — 161 — ≤0.03 — ≤0.02 ≤1.2 5MSSV-06 8/2/2005 nc nc nc nc nc nc nc nc nc nc nc ncMSSV-06 11/13/2008 11.9 — 5.2 0.83 1.3 — 319 — — 1.10 4.2 ≤2.9 5MSSV-15 8/12/2005 nc nc nc nc nc nc nc nc nc nc nc ncMSSV-15 11/13/2008 19.3 3.1 10.2 1.1 3.2 — 322 — — 1.62 5.5 ≤4.0 5Southeast San Joaquin Valley study unitKING-11 10/20/2005 E0.4 1.5 3.5 — 0.22 — 262 — ≤0.04 0.690 46.6 ≤1.4KING-11 11/5/2008 E0.7 ≤0.1 3.7 ≤0.32 0.30 — 268 — nc 0.726 *53.1 ≤1.4KING-13 10/20/2005 1.2 ≤0.1 2.0 ≤0.03 0.27 — 172 — ≤0.11 0.530 44.4 ≤1.7KING-13 11/5/2008 1.6 ≤0.2 2.0 ≤0.17 0.35 — 156 — nc 0.590 48.9 ≤2.0KING-17 10/26/2005 1.4 ≤0.1 1.6 — 0.26 — 173 — 0.39 1.56 37.1 ≤3.1KING-17 11/4/2008 1.3 — 1.6 ≤0.16 0.31 — 178 — nc 1.78 38.7 ≤1.4KING-24 11/5/2005 nc nc nc nc nc nc nc nc nc nc nc ncKING-24 11/3/2008 E0.6 0.5 0.89 1.1 E0.04 — 267 — nc 3.65 23.8 6.1KWH-10 11/17/2005 nc nc nc nc nc nc nc nc nc nc nc nc

Table 10. Trace elements in groundwater samples collected from trend wells for seven Groundwater Ambient Monitoring and Assessment (GAMA) study units.—Continued[The five-digit USGS parameter code below the constituent name is used to uniquely identify a specific constituent or property. Trace elements were analyzed in samples from 24 trend wells during 2004–05 and 45 trend wells in 2007–08; 17 wells were analyzed during both periods. Information about analytes given in table 3F. GAMA well identification number acronyms: San Diego Drainages study unit: SDALLV, Alluvial Basins study area; SDHDRK, Hard Rock study area; SDTEM, Temecula Valley study area; SDTEMFP, Temecula Valley study area flow-path well; SDWARN, Warner Valley study area. North San Francisco Bay study unit: NSFVOL, Volcanic Highlands study area; NSFVP, Valley and Plains study area; NSFWG, Wilson Grove Formation Highlands study area; NSFWGFP, Wilson Grove Formation Highlands study area flow-path well. Northern San Joaquin Basin study unit: COS, Cosumnes Basin study area; ESJ, Eastern San Joaquin Basin study area; NSJ-QPC, Uplands study area; TRCY, Tracy Basin study area. Southern Sacramento Valley study unit: NAM, North American study area; SAM, South American study area; SOL, Solano study area; SSV-QPC, Uplands study area; SUI, Suisun-Fairfield study area; YOL, Yolo study area. San Fernando–San Gabriel study unit: ULASF, San Fernando study area; ULASG, San Gabriel study area. Monterey Bay and Salinas Valley Basins study unit: MSMB, Monterey Bay study area; MSPR, Paso Robles study area; MSSC, Santa Cruz study area; MSSV, Salinas Valley study area. Southeast San Joaquin Valley study unit: KING, Kings study area; KWH, Kaweah study area; TLR, Tulare Lake study area; TULE, Tule study area. Benchmark type: HAL-US, USEPA lifetime health advisory level; MCL-US, USEPA maximum contaminant level; AL-US, USEPA action level; MCL-CA, CDPH maximum contaminant level; NL-CA, CDPH notification level; SMCL, CDPH secondary maximum contaminant level. Benchmark type and benchmark level as of April 1, 2010. Other abbreviations: USGS, U.S. Geological Survey; USEPA, U.S. Environmental Protection Agency; CDPH, California Department of Public Health; μg/L, micrograms per liter; LRL, laboratory reporting level; E, estimated or having a higher degree of uncertainty; nc, not collected; na, not available; *, value greater than benchmark level; —, not detected; ≤, less than or equal to]
136 Groundwater-Quality Data in Seven GAMA Study Units: Results from Initial Sampling and Resampling of Wells GAMA well identification number Sample dates Lithium (μg/L) (01130) 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) Benchmark type3 na SMCL-CA HAL-US MCL-CA MCL-US SMCL-CA HAL-US MCL-US na MCL-US NL-CA SMCL-CA Benchmark level na 50 40 100 50 100 4,000 2 na 30 50 5,000 [LRL or SRL]1 [0.6, 1] [0.2]2 [0.02, 0.4] [0.36]2 [0.04, 0.4] [0.008, 0.2] [0.4, 0.8] [0.04] [0.11]2 [0.006, 0.04] [0.11]2 [4.8]2 Southeast San Joaquin Valley study unit—Continued KWH-10 11/5/2008 6.5 ≤0.1 6.5 ≤0.19 0.46

— 317

— nc 3.33 34.8 ≤1.1

KWH-12 11/28/2005 0.9 0.4 1.4 ≤0.27 0.30

— 275

— ≤0.10 3.53 7.5 ≤3.2

KWH-12 11/6/2008 E0.9 0.3 1.2 ≤0.26 0.34

— 315

— nc 4.37 6.8 ≤2.0

TLR-03 11/29/2005 nc nc nc nc nc nc nc nc nc nc nc ncTLR-03 11/4/2008 1.1 6.1 8.9 ≤0.26

—

— 35.9

— nc 0.014 0.46

—

TULE-05 12/5/2005 nc nc nc nc nc nc nc nc nc nc nc ncTULE-05 11/3/2008 20.8 3.0 12.5 ≤0.28 6.1

— 121

— nc 3.94 15.8 ≤2.1

TULE-10 12/7/2005 nc nc nc nc nc nc nc nc nc nc nc ncTULE-10 11/3/2008 4.5 0.4 1.1 0.62 0.24

— 483

— nc 16.8 12.4 ≤1.1

1 Minimum and maximum LRL used during study period, or only LRL used during study period, or SRL. Study reporting levels (SRLs) were defined on the basis of the examination of field blanks collected 

for GAMA-PBP study units between May 2004 and January 2008 (Olsen and others, 2010).

2 Values equal to or less than the SRL are reported as less than or equal to the value reported by the laboratory. Values reported with a ≤ symbol in this table have the following field comment included in the 

USGS NWIS database: Result is < or = reported value, based on QC data (including but not limited to field blanks, source-solution blanks, trip blanks, NWQL set blanks, NWQL blank water certificates, and BQS Blind Blank Program data).

3 Maximum contaminant level benchmarks 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.4 The USGS Branch of Quality Systems determined that results for this constituent from the USGS National Water Quality Laboratory had a negative analytical bias greater than 10 percent at the time of this 

measurement.

5 The USGS Branch of Quality Systems determined that results for this constituent from the USGS National Water Quality Laboratory had a positive analytical bias greater than 10 percent at the time of this 

Table 10.measurement.

Trace elements in groundwater samples collected from trend wells for seven Groundwater Ambient Monitoring and Assessment (GAMA) study units.—Continued

[The five-digit USGS parameter code below the constituent name is used to uniquely identify a specific constituent or property. Trace elements were analyzed in samples from 24 trend wells during 2004–05 and 45 trend wells in 2007–08; 17 wells were analyzed during both periods. Information about analytes given in table 3F. GAMA well identification number acronyms: San Diego Drainages study unit: SDALLV, Alluvial Basins study area; SDHDRK, Hard Rock study area; SDTEM, Temecula Valley study area; SDTEMFP, Temecula Valley study area flow-path well; SDWARN, Warner Valley study area. North San Francisco Bay study unit: NSFVOL, Volcanic Highlands study area; NSFVP, Valley and Plains study area; NSFWG, Wilson Grove Formation Highlands study area; NSFWGFP, Wilson Grove Formation Highlands study area flow-path well. Northern San Joaquin Basin study unit: COS, Cosumnes Basin study area; ESJ, Eastern San Joaquin Basin study area; NSJ-QPC, Uplands study area; TRCY, Tracy Basin study area. Southern Sacramento Valley study unit: NAM, North American study area; SAM, South American study area; SOL, Solano study area; SSV-QPC, Uplands study area; SUI, Suisun-Fairfield study area; YOL, Yolo study area. San Fernando–San Gabriel study unit: ULASF, San Fernando study area; ULASG, San Gabriel study area. Monterey Bay and Salinas Valley Basins study unit: MSMB, Monterey Bay study area; MSPR, Paso Robles study area; MSSC, Santa Cruz study area; MSSV, Salinas Valley study area. Southeast San Joaquin Valley study unit: KING, Kings study area; KWH, Kaweah study area; TLR, Tulare Lake study area; TULE, Tule study area. Benchmark type: HAL-US, USEPA lifetime health advisory level; MCL-US, USEPA maximum contaminant level; AL-US, USEPA action level; MCL-CA, CDPH maximum contaminant level; NL-CA, CDPH notification level; SMCL, CDPH secondary maximum contaminant level. Benchmark type and benchmark level as of April 1, 2010. Other abbreviations: USGS, U.S. Geological Survey; USEPA, U.S. Environmental Protection Agency; CDPH, California Department of Public Health; μg/L, micrograms per liter; LRL, laboratory reporting level; E, estimated or having a higher degree of uncertainty; nc, not collected; na, not available; *, value greater than benchmark level; —, not detected; ≤, less than or equal to]
Tables 137

GAMA 

well 

identification 

number

Sample 

dates

Arsenic 

(total, 

filtered) 

(99033)1

(μg/L) 

Arsenic-III 

(filtered) 

(99034) 

(μg/L) 

Iron 

(total, 

filtered) 

(01046)1

(μg/L) 

Iron-II 

(filtered) 

(01047) 

(μg/L) 

Benchmark 

type

MCL-US na SMCL-CA na

Benchmark 

level 10 na 300 na

[MDL] [0.5] [1] [2] [2]

San Diego Drainages study unit

SDTEMFP-01 5/19/2004 7.4 — — —

SDTEMFP-01 9/19/2007 nc nc nc nc

North San Francisco Bay study unit

NSFVOL-14 10/7/2004 7.0 — 2 2

NSFVOL-14 8/21/2007 3.7 2.0 38 28

NSFVOL-18 10/20/2004 nc nc nc nc

NSFVOL-18 8/28/2007 0.7 — 280 243

NSFVP-29 9/28/2004 — — — —

NSFVP-29 8/27/2007 — — — —

NSFVP-34 10/18/2004 7.7 6.7 *900 860

NSFVP-34 8/22/2007 6.4 4.9 *1,030 863

NSFVP-38 10/20/2004 *16.2 2.8 9 7

NSFVP-38 8/22/2007 *14.0 10.0 9 9

NSFVP-39 10/21/2004 nc nc nc nc

NSFVP-39 11/16/2007 2.0 1.3 22 17

NSFWG-03 9/21/2004 nc nc nc nc

NSFWG-03 8/29/2007 1.9 — *2,030 2,000

NSFWGFP-0110/5/2004 4.5 — 28 26

NSFWGFP-018/29/2007 3.6 2.0 30 26

Northern San Joaquin Basin study unit 

ESJ-06 1/10/2005 5.7 — — —

ESJ-06 4/2/2008 nc nc nc nc

NSJ-QPC-04 1/24/2005 1.9 — 57 34

NSJ-QPC-04 4/1/2008 nc nc nc nc

Table 11. Arsenic and iron oxidation-reduction species in samples collected from trend wells for seven Groundwater Ambient 

Monitoring and Assessment (GAMA) study units. 

[The five-digit USGS parameter code below the constituent name is used to uniquely identify a specific constituent or property. Arsenic and iron oxidationreduction species were analyzed in samples from 21 trend wells during 2004–05 and 14 trend wells in 2007–08; 9 wells were analyzed during both periods. 

Only wells sampled in at least one period are listed. Information about analytes given in table 3G. GAMA well identification number acronyms: San Diego 

Drainages study unit: SDALLV, Alluvial Basins study area; SDHDRK, Hard Rock study area; SDTEM, Temecula Valley study area; SDTEMFP, Temecula 

Valley study area flow-path well; SDWARN, Warner Valley study area. North San Francisco Bay study unit: NSFVOL, Volcanic Highlands study area; 

NSFVP, Valley and Plains study area; NSFWG, Wilson Grove Formation Highlands study area; NSFWGFP, Wilson Grove Formation Highlands study area 

flow-path well. Northern San Joaquin Basin study unit: COS, Cosumnes Basin study area; ESJ, Eastern San Joaquin Basin study area; NSJ-QPC, Uplands 

study area; TRCY, Tracy Basin study area. Southern Sacramento Valley study unit: NAM, North American study area; SAM, South American study area; 

SOL, Solano study area; SSV-QPC, Uplands study area; SUI, Suisun-Fairfield study area; YOL, Yolo study area. San Fernando–San Gabriel study unit: 

ULASF, San Fernando study area; ULASG, San Gabriel study area. Monterey Bay and Salinas Valley Basins study unit: MSMB, Monterey Bay study area; 

MSPR, Paso Robles study area; MSSC, Santa Cruz study area; MSSV, Salinas Valley study area. Southeast San Joaquin Valley study unit: KING, Kings study 

area; KWH, Kaweah study area; TLR, Tulare Lake study area; TULE, Tule study area. Benchmark type: MCL-US, USEPA maximum contaminant level; 

SMCL-CA, California Department of Public Health secondary maximum contaminant level. Benchmark type and benchmark level as of April 1, 2010. Other 

abbreviations: USGS, U.S. Geological Survey; USEPA, U.S. Environmental Protection Agency; μg/L, micrograms per liter; MDL, method detection level; 

nc, not collected; na, not available; *, value greater than benchmark level; —, not detected]

GAMA 

well 

identification 

number

Sample 

dates

Arsenic 

(total, 

filtered) 

(99033)1

(μg/L) 

Arsenic-III 

(filtered) 

(99034) 

(μg/L) 

Iron 

(total, 

filtered) 

(01046)1

(μg/L) 

Iron-II 

(filtered) 

(01047) 

(μg/L) 

Benchmark 

type

MCL-US na SMCL-CA na

Benchmark 

level 10 na 300 na

[MDL] [0.5] [1] [2] [2]

Northern San Joaquin Basin study unit—Continued

TRCY-03 1/6/2005 1.1 — 4 —

TRCY-03 3/31/2008 nc nc nc nc

Southern Sacramento Valley study unit

SSV-QPC-07 4/4/2005 1.4 — 18 9

SSV-QPC-07 4/10/2008 nc nc nc nc

YOL-14 5/25/2005 5.2 4.9 *384 374

YOL-14 4/9/2008 nc nc nc nc

San Fernando–San Gabriel study unit 

ULASF-09 6/27/2005 — — — —

ULASF-09 6/16/2008 — — — —

ULASF-10 6/8/2005 — — — —

ULASF-10 6/16/2008 — — 30 —

ULASG-01 6/7/2005 nc nc nc nc

ULASG-01 6/16/2008 — — — —

ULASG-08 6/15/2005 0.9 — 3 —

ULASG-08 6/17/2008 — — 3 —

ULASG-15 6/23/2005 2.1 — — —

ULASG-15 6/17/2008 — — — —

ULASG-17 7/11/2005 nc nc nc nc

ULASG-17 6/17/2008 — — — —

Monterey Bay and Salinas Valley Basins study unit

MSMB-04 8/17/2005 — — 45 9

MSMB-04 8/20/2008 nc nc nc nc

MSSC-06 8/24/2005 — — *607 588

MSSC-06 8/18/2008 nc nc nc nc
138 Groundwater-Quality Data in Seven GAMA Study Units: Results from Initial Sampling and Resampling of Wells

GAMA 

well 

identification 

number

Sample 

dates

Arsenic 

(total, 

filtered) 

(99033)1

(μg/L) 

Arsenic-III 

(filtered) 

(99034) 

(μg/L) 

Iron 

(total, 

filtered) 

(01046)1

(μg/L) 

Iron-II 

(filtered) 

(01047) 

(μg/L) 

Benchmark 

type

MCL-US na SMCL-CA na

Benchmark 

level 10 na 300 na

[MDL] [0.5] [1] [2] [2]

Southeast San Joaquin Valley study unit

KING-11 10/20/2005 1.1 — 6 —

KING-11 11/5/2008 nc nc nc nc

KING-13 10/20/2005 1.5 — — —

KING-13 11/5/2008 nc nc nc nc

KING-17 10/26/2005 1.5 — — —

KING-17 11/4/2008 nc nc nc nc

KWH-12 11/28/2005 — — — —

KWH-12 11/6/2008 nc nc nc nc

1

The preferred analytical method for this constituent is Laboratory Schedule 

1948 (table 10).

Table 11. Arsenic and iron oxidation-reduction species in 

samples collected from trend wells for seven Groundwater 

Ambient Monitoring and Assessment (GAMA) study units.

—Continued

[The five-digit USGS parameter code below the constituent name is used 

to uniquely identify a specific constituent or property. Arsenic and iron 

oxidation-reduction species were analyzed in samples from 21 trend wells 

during 2004–05 and 14 trend wells in 2007–08; 9 wells were analyzed during 

both periods. Only wells sampled in at least one period are listed. Information 

about analytes given in table 3G. GAMA well identification number 

acronyms: San Diego Drainages study unit: SDALLV, Alluvial Basins study 

area; SDHDRK, Hard Rock study area; SDTEM, Temecula Valley study area; 

SDTEMFP, Temecula Valley study area flow-path well; SDWARN, Warner 

Valley study area. North San Francisco Bay study unit: NSFVOL, Volcanic 

Highlands study area; NSFVP, Valley and Plains study area; NSFWG, 

Wilson Grove Formation Highlands study area; NSFWGFP, Wilson Grove 

Formation Highlands study area flow-path well. Northern San Joaquin 

Basin study unit: COS, Cosumnes Basin study area; ESJ, Eastern San 

Joaquin Basin study area; NSJ-QPC, Uplands study area; TRCY, Tracy Basin 

study area. Southern Sacramento Valley study unit: NAM, North American 

study area; SAM, South American study area; SOL, Solano study area; 

SSV‐QPC, Uplands study area; SUI, Suisun-Fairfield study area; YOL, Yolo 

study area. San Fernando–San Gabriel study unit: ULASF, San Fernando 

study area; ULASG, San Gabriel study area. Monterey Bay and Salinas 

Valley Basins study unit: MSMB, Monterey Bay study area; MSPR, Paso 

Robles study area; MSSC, Santa Cruz study area; MSSV, Salinas Valley study 

area. Southeast San Joaquin Valley study unit: KING, Kings study area; 

KWH, Kaweah study area; TLR, Tulare Lake study area; TULE, Tule study 

area. Benchmark type: MCL-US, USEPA maximum contaminant level; 

SMCL-CA, California Department of Public Health secondary maximum 

contaminant level. Benchmark type and benchmark level as of April 1, 

2010. Other abbreviations: USGS, U.S. Geological Survey; USEPA, U.S. 

Environmental Protection Agency; μg/L, micrograms per liter; MDL, method 

detection level; nc, not collected; na, not available; *, value greater than 

benchmark level; —, not detected]
Tables 139

Table 12. Isotopic tracers in samples collected from trend wells for seven Groundwater Ambient Monitoring and Assessment (GAMA)

study units.

[The five-digit USGS parameter code below the constituent name is used to uniquely identify a specific constituent or property. Stable isotope ratios of 

hydrogen, oxygen, and carbon are reported in delta notation (δ), the ratio of a heavier isotope to more common lighter isotope of that element, relative to a 

standard reference material. Tritium values less than the reporting level1 (MRL or ssLc) are reported as non-detections (—). Stable isotopes of water were 

measured in 55 trend-well samples during both time periods. Tritium was analyzed in samples from 50 trend wells during 2004–05 and 55 trend wells in 2007–

08. Carbon isotopes were analyzed in samples from 17 trend wells during 2004–05 and 29 trend wells in 2007–08; 9 wells were analyzed during both periods. 

Information about analytes given in table 3I. GAMA well identification number acronyms: San Diego Drainages study unit: SDALLV, Alluvial Basins 

study area; SDHDRK, Hard Rock study area; SDTEM, Temecula Valley study area; SDTEMFP, Temecula Valley study area flow-path well; SDWARN, Warner 

Valley study area. North San Francisco Bay study unit: NSFVOL, Volcanic Highlands study area; NSFVP, Valley and Plains study area; NSFWG, Wilson 

Grove Formation Highlands study area; NSFWGFP, Wilson Grove Formation Highlands study area flow-path well. Northern San Joaquin Basin study 

unit: COS, Cosumnes Basin study area; ESJ, Eastern San Joaquin Basin study area; NSJ-QPC, Uplands study area; TRCY, Tracy Basin study area. Southern 

Sacramento Valley study unit: NAM, North American study area; SAM, South American study area; SOL, Solano study area; SSV-QPC, Uplands study area; 

SUI, Suisun-Fairfield study area; YOL, Yolo study area. San Fernando–San Gabriel study unit: ULASF, San Fernando study area; ULASG, San Gabriel study 

area. Monterey Bay and Salinas Valley Basins study unit: MSMB, Monterey Bay study area; MSPR, Paso Robles study area; MSSC, Santa Cruz study area; 

MSSV, Salinas Valley study area. Southeast San Joaquin Valley study unit: KING, Kings study area; KWH, Kaweah study area; TLR, Tulare Lake study area; 

TULE, Tule study area. Benchmark type: MCL-CA, California Department of Public Health maximum contaminant level. Benchmark type and benchmark 

level as of April 1, 2010. Other abbreviations: USGS, U.S. Geological Survey; H, hydrogen; O, oxygen; C, carbon; CSU, 1-sigma combined standard 

uncertainty; pCi/L, picocuries per liter; MRL, minimum reporting level; ssLc,sample-specific critical level; ±, plus or minus; nc, not collected; na, not available]

GAMA 

identification 

number

Sample 

dates

δ2H of water 

(per mil) 

(82082)

δ18O of water 

(per mil) 

(82085)

Tritium 

(pCi/L) 

(07000)

δ13C 

(per mil) 

(82081)

Carbon-14 

(percent modern) 

(49933)

Benchmark type na na MCL-CA na na

Benchmark level na na 20,000 na na

Result ± 

CSU 

Reporting 

level

Reporting 

level type1

San Diego Drainages study unit

SDALLV-07 7/14/2004 –37.1 –5.77 13.8 ± 1 1 MRL nc nc

SDALLV-07 9/12/2007 –36.1 –5.90 10.2 ± 1 1 MRL nc nc

SDALLV-11 7/15/2004 –46.9 -6.54 22.1 ± 1.3 1 MRL nc nc

SDALLV-11 9/13/2007 –47.6 –6.94 14.1 ± 1.3 1 MRL nc nc

SDHDRK-01 7/12/2004 –39.5 –5.70 8.3 ± 1 1 MRL nc nc

SDHDRK-01 9/13/2007 –39.1 –5.78 6.7 ± 1 1 MRL nc nc

SDHDRK-09 7/27/2004 –43.3 –6.93 7.1 ± 1 1 MRL nc nc

SDHDRK-09 9/11/2007 –42.2 –6.68 7.7 ± 1 1 MRL nc nc

SDTEM-04 5/24/2004 –46.0 –5.90 10.6 ± 1 1 MRL nc nc

SDTEM-04 9/18/2007 –66.6 –8.43 12.4 ± 1.3 1 MRL –10.92 100

SDTEMFP-01 5/19/2004 –48.1 –7.02 — 1 MRL –16.50 74

SDTEMFP-01 9/19/2007 –47.4 –7.05 — 1 MRL –14.69 77

SDWARN-01 6/17/2004 –51.4 –7.57 — 1 MRL nc nc

SDWARN-01 9/11/2007 –50.4 –7.44 — 1 MRL nc nc

North San Francisco Bay study unit

NSFVOL-14 10/7/2004 –39.9 –6.12 4.2 ± 0.6 1 MRL –17.60 93

NSFVOL-14 8/21/2007 –38.4 –5.66 6.1 ± 1 1 MRL –16.32 104

NSFVOL-18 10/20/2004 –48.2 –7.24 — 1 MRL nc nc

NSFVOL-18 8/28/2007 –48.6 –7.22 — 0.6 MRL –13.03 26

NSFVP-29 9/28/2004 –43.7 –6.98 7.4 ± 1 1 MRL –17.85 105

NSFVP-29 8/27/2007 –44.7 –6.91 5.8 ± 1 1 MRL –17.34 104

NSFVP-34 10/18/2004 –46.5 –7.12 — 1 MRL –17.58 20

NSFVP-34 8/22/2007 –46.1 –7.07 — 1 ssLC –16.79 19

NSFVP-36 10/19/2004 –52.9 –7.72 — 1 MRL nc nc

NSFVP-36 8/20/2007 –52.7 –7.72 — 1 MRL –20.23 10

NSFVP-38 10/20/2004 –50.4 –7.75 — 1 MRL –14.62 0.56
140 Groundwater-Quality Data in Seven GAMA Study Units: Results from Initial Sampling and Resampling of Wells

GAMA 

identification 

number

Sample 

dates

δ2H of water 

(per mil) 

(82082)

δ18O of water 

(per mil) 

(82085)

Tritium 

(pCi/L) 

(07000)

δ13C 

(per mil) 

(82081)

Carbon-14 

(percent modern) 

(49933)

Benchmark type na na MCL-CA na na

Benchmark level na na 20,000 na na

Result ± 

CSU 

Reporting 

level

Reporting 

level type1

North San Francisco Bay study unit—Continued

NSFVP-38 8/22/2007 –49.7 –7.69 — 0.6 MRL –13.75 0.26

NSFVP-39 10/21/2004 –46.8 –7.11 1.9 ± 1 1 MRL nc nc

NSFVP-39 11/16/2007 –48.2 –7.01 1.9 ± 0.8 0.8 MRL –17.96 56

NSFVP-41 10/21/2004 –40.3 –5.99 7.0 ± 1 1 MRL nc nc

NSFVP-41 8/20/2007 –39.7 –6.03 3.5 ± 0.6 1 MRL –20.95 89

NSFWG-03 9/21/2004 –36.8 –6.17 — 1 MRL nc nc

NSFWG-03 8/29/2007 –37.2 –6.06 — 0.6 MRL –20.08 87

NSFWGFP-01 10/5/2004 –37.7 –6.14 2.2 ± 0.6 1 MRL –15.48 45

NSFWGFP-01 8/29/2007 –37.6 –6.10 1.6 ± 0.6 0.6 MRL –15.36 41

Northern San Joaquin Basin study unit

COS-08 1/3/2005 –53.7 –7.33 — 1 MRL nc nc

COS-08 4/3/2008 –53.7 –7.27 na2 na2 na2 –15.72 31

ESJ-01 1/24/2005 –67.6 –9.31 20.5 ± 1.3 1 MRL nc nc

ESJ-01 4/2/2008 –63.2 –8.42 na2 na2 na2 –15.67 75

ESJ-06 1/10/2005 –63.5 –8.86 7.4 ± 1 1 MRL nc nc

ESJ-06 4/2/2008 –65.8 –8.94 4.5 ± 0.35 0.32 ssLC –15.20 80

NSJ-QPC-04 1/24/2005 –55.4 –7.12 5.4 ± 0.6 1 MRL nc nc

NSJ-QPC-04 4/1/2008 –50.9 –7.13 2.1 ± 0.32 0.32 ssLC –17.00 81

TRCY-03 1/6/2005 –55.9 –7.50 — 1 MRL –12.76 69

TRCY-03 3/31/2008 –57.3 –7.54 1.6 + 0.35 0.35 ssLC –12.30 69

Southern Sacramento Valley study unit 

NAM-03 3/29/2005 –53.0 –7.32 — 1 MRL nc nc

NAM-03 4/10/2008 –50.8 –7.40 0.6 + 0.35 0.35 ssLC –17.14 68

SAM-10 4/21/2005 –50.1 –6.94 4.5 ± 1 1 MRL nc nc

SAM-10 4/8/2008 –50.4 –7.08 4.4 + 0.32 0.32 ssLC –18.07 99

SOL-08 5/10/2005 –48.4 –7.19 — 1 MRL nc nc

Table 12. Isotopic tracers in samples collected from trend wells for seven Groundwater Ambient Monitoring and Assessment (GAMA) 

study units.—Continued

[The five-digit USGS parameter code below the constituent name is used to uniquely identify a specific constituent or property. Stable isotope ratios of 

hydrogen, oxygen, and carbon are reported in delta notation (δ), the ratio of a heavier isotope to more common lighter isotope of that element, relative to a 

standard reference material. Tritium values less than the reporting level1 (MRL or ssLc) are reported as non-detections (—). Stable isotopes of water were 

measured in 55 trend-well samples during both time periods. Tritium was analyzed in samples from 50 trend wells during 2004–05 and 55 trend wells in 2007–

08. Carbon isotopes were analyzed in samples from 17 trend wells during 2004–05 and 29 trend wells in 2007–08; 9 wells were analyzed during both periods. 

Information about analytes given in table 3I. GAMA well identification number acronyms: San Diego Drainages study unit: SDALLV, Alluvial Basins 

study area; SDHDRK, Hard Rock study area; SDTEM, Temecula Valley study area; SDTEMFP, Temecula Valley study area flow-path well; SDWARN, Warner 

Valley study area. North San Francisco Bay study unit: NSFVOL, Volcanic Highlands study area; NSFVP, Valley and Plains study area; NSFWG, Wilson 

Grove Formation Highlands study area; NSFWGFP, Wilson Grove Formation Highlands study area flow-path well. Northern San Joaquin Basin study 

unit: COS, Cosumnes Basin study area; ESJ, Eastern San Joaquin Basin study area; NSJ-QPC, Uplands study area; TRCY, Tracy Basin study area. Southern 

Sacramento Valley study unit: NAM, North American study area; SAM, South American study area; SOL, Solano study area; SSV-QPC, Uplands study area; 

SUI, Suisun-Fairfield study area; YOL, Yolo study area. San Fernando–San Gabriel study unit: ULASF, San Fernando study area; ULASG, San Gabriel study 

area. Monterey Bay and Salinas Valley Basins study unit: MSMB, Monterey Bay study area; MSPR, Paso Robles study area; MSSC, Santa Cruz study area; 

MSSV, Salinas Valley study area. Southeast San Joaquin Valley study unit: KING, Kings study area; KWH, Kaweah study area; TLR, Tulare Lake study area; 

TULE, Tule study area. Benchmark type: MCL-CA, California Department of Public Health maximum contaminant level. Benchmark type and benchmark 

level as of April 1, 2010. Other abbreviations: USGS, U.S. Geological Survey; H, hydrogen; O, oxygen; C, carbon; CSU, 1-sigma combined standard 

uncertainty; pCi/L, picocuries per liter; MRL, minimum reporting level; ssLc,sample-specific critical level; ±, plus or minus; nc, not collected; na, not available]
Tables 141

GAMA 

identification 

number

Sample 

dates

δ2H of water 

(per mil) 

(82082)

δ18O of water 

(per mil) 

(82085)

Tritium 

(pCi/L) 

(07000)

δ13C 

(per mil) 

(82081)

Carbon-14 

(percent modern) 

(49933)

Benchmark type na na MCL-CA na na

Benchmark level na na 20,000 na na

Result ± 

CSU 

Reporting 

level

Reporting 

level type1

Southern Sacramento Valley study unit—Continued

SOL-08 4/8/2008 –50.6 –7.08 — 0.32 ssLC –14.65 48

SSV-QPC-07 4/4/2005 –52.7 –7.40 1.3 ± 1 1 MRL –17.00 77

SSV-QPC-07 4/10/2008 –55.5 –7.46 1.7 ± 0.38 0.35 ssLC nc nc

SUI-03 5/12/2005 –45.2 –6.46 — 1 MRL nc nc

SUI-03 4/9/2008 –6.40 0.6 ± 0.35 0.35 ssLC –13.15 62

YOL-01 4/11/2005 –41.4 –5.29 7.7 ± 1 1 MRL nc nc

YOL-01 4/7/2008 –41.9 –5.34 6.0 ± 0.35 0.32 ssLC –13.32 86

YOL-14 5/25/2005 –66.4 –9.08 — 1 MRL –2.13 7.4

YOL-14 4/9/2008 –63.9 –8.40 2.2 ± 0.32 0.32 ssLC nc nc

San Fernando–San Gabriel study unit 

ULASF-09 6/27/2005 –54.5 –7.61 20.5 ± 1.6 1 MRL –16.00 100

ULASF-09 6/16/2008 –53.8 –7.79 16.9 ± 0.67 0.38 ssLC nc nc

ULASF-10 6/8/2005 –51.6 –7.66 3.8 ± 0.6 1 MRL –14.90 79

ULASF-10 6/16/2008 –47.2 –7.25 0.6 ± 0.45 0.45 ssLC nc nc

ULASG-01 6/7/2005 –45.4 –6.45 8.0 ± 0.6 1 MRL nc nc

ULASG-01 6/16/2008 –44.7 –6.57 8.9 ± 0.48 0.35 ssLC nc nc

ULASG-08 6/15/2005 –47.6 –7.20 6.1 ± 0.6 1 MRL –14.90 93

ULASG-08 6/17/2008 –48.5 –7.31 4.5 ± 0.32 0.32 ssLC nc nc

ULASG-15 6/23/2005 –60.5 –9.22 14.7 ± 1.3 1 MRL –11.40 96

ULASG-15 6/17/2008 –55.3 –7.93 17.6 ± 0.64 0.32 ssLC nc nc

ULASG-17 7/11/2005 –50.8 –7.68 9.0 ± 1 1 MRL nc nc

ULASG-17 6/17/2008 –51.1 –7.67 7.6 ± 0.38 0.32 ssLC nc nc

Monterey Bay and Salinas Valley Basins study unit

MSMB-03 8/31/2005 –50.7 –7.38 — 1 MRL nc nc

MSMB-03 8/20/2008 –50.7 –7.42 — 0.32 ssLC –15.68 5.4

MSMB-04 8/17/2005 –45.9 –7.32 2.2 ± 1 1 MRL –15.50 5.7

Table 12. Isotopic tracers in samples collected from trend wells for seven Groundwater Ambient Monitoring and Assessment (GAMA) 

study units.—Continued

[The five-digit USGS parameter code below the constituent name is used to uniquely identify a specific constituent or property. Stable isotope ratios of 

hydrogen, oxygen, and carbon are reported in delta notation (δ), the ratio of a heavier isotope to more common lighter isotope of that element, relative to a 

standard reference material. Tritium values less than the reporting level1 (MRL or ssLc) are reported as non-detections (—). Stable isotopes of water were 

measured in 55 trend-well samples during both time periods. Tritium was analyzed in samples from 50 trend wells during 2004–05 and 55 trend wells in 2007–

08. Carbon isotopes were analyzed in samples from 17 trend wells during 2004–05 and 29 trend wells in 2007–08; 9 wells were analyzed during both periods. 

Information about analytes given in table 3I. GAMA well identification number acronyms: San Diego Drainages study unit: SDALLV, Alluvial Basins 

study area; SDHDRK, Hard Rock study area; SDTEM, Temecula Valley study area; SDTEMFP, Temecula Valley study area flow-path well; SDWARN, Warner 

Valley study area. North San Francisco Bay study unit: NSFVOL, Volcanic Highlands study area; NSFVP, Valley and Plains study area; NSFWG, Wilson 

Grove Formation Highlands study area; NSFWGFP, Wilson Grove Formation Highlands study area flow-path well. Northern San Joaquin Basin study 

unit: COS, Cosumnes Basin study area; ESJ, Eastern San Joaquin Basin study area; NSJ-QPC, Uplands study area; TRCY, Tracy Basin study area. Southern 

Sacramento Valley study unit: NAM, North American study area; SAM, South American study area; SOL, Solano study area; SSV-QPC, Uplands study area; 

SUI, Suisun-Fairfield study area; YOL, Yolo study area. San Fernando–San Gabriel study unit: ULASF, San Fernando study area; ULASG, San Gabriel study 

area. Monterey Bay and Salinas Valley Basins study unit: MSMB, Monterey Bay study area; MSPR, Paso Robles study area; MSSC, Santa Cruz study area; 

MSSV, Salinas Valley study area. Southeast San Joaquin Valley study unit: KING, Kings study area; KWH, Kaweah study area; TLR, Tulare Lake study area; 

TULE, Tule study area. Benchmark type: MCL-CA, California Department of Public Health maximum contaminant level. Benchmark type and benchmark 

level as of April 1, 2010. Other abbreviations: USGS, U.S. Geological Survey; H, hydrogen; O, oxygen; C, carbon; CSU, 1-sigma combined standard 

uncertainty; pCi/L, picocuries per liter; MRL, minimum reporting level; ssLc,sample-specific critical level; ±, plus or minus; nc, not collected; na, not available]
142 Groundwater-Quality Data in Seven GAMA Study Units: Results from Initial Sampling and Resampling of Wells

GAMA 

identification 

number

Sample 

dates

δ2H of water 

(per mil) 

(82082)

δ18O of water 

(per mil) 

(82085)

Tritium 

(pCi/L) 

(07000)

δ13C 

(per mil) 

(82081)

Carbon-14 

(percent modern) 

(49933)

Benchmark type na na MCL-CA na na

Benchmark level na na 20,000 na na

Result ± 

CSU 

Reporting 

level

Reporting 

level type1

Monterey Bay and Salinas Valley Basins study unit—Continued

MSMB-04 8/20/2008 –47.8 –7.28 — 0.32 ssLC –13.97 83

MSMB-16 8/17/2005 –45.6 –6.72 1.0 ± 0.6 1 MRL nc nc

MSMB-16 8/19/2008 –45.3 –6.71 5.1 ± 0.35 0.32 ssLC –16.85 60

MSMB-28 8/3/2005 –46.5 –6.66 1.6 ± 0.6 1 MRL nc nc

MSMB-28 8/21/2008 –44.8 –6.58 2.0 ± 0.32 0.32 ssLC –14.44 99

MSMB-31 8/11/2005 –41.7 –6.30 6.7 ± 1 1 MRL nc nc

MSMB-31 8/21/2008 –42.1 –6.26 1.6 ± 0.38 0.38 ssLC –12.20 65

MSPR-03 7/28/2005 –58.4 –8.30 — 1 MRL nc nc

MSPR-03 11/14/2008 –58.2 –8.18 — 0.32 ssLC nc nc

MSPR-09 7/18/2005 –55.2 –7.93 — 1 MRL nc nc

MSPR-09 11/14/2008 –56.0 –7.81 — 0.32 ssLC nc nc

MSSC-06 8/24/2005 –32.9 –5.45 4.5 ± 1 1 MRL –20.40 72

MSSC-06 8/18/2008 –32.4 –5.37 3.6 ± 0.32 0.32 ssLC –20.62 74

MSSC-11 9/13/2005 –38.1 –6.28 — 1 MRL nc nc

MSSC-11 8/19/2008 –38.3 –6.32 — 0.32 ssLC –9.08 1.6

MSSV-06 8/2/2005 –34.9 –4.87 6.7 ± 1 1 MRL nc nc

MSSV-06 11/13/2008 –32.7 –4.46 5.6 ± 0.35 0.32 ssLC nc nc

MSSV-15 8/12/2005 –27.0 –3.58 7 ± 1 1 MRL nc nc

MSSV-15 11/13/2008 –30.2 –4.24 5.1 ± 0.41 0.35 ssLC nc nc

Southeast San Joaquin Valley study unit

KING-11 10/20/2005 –61.3 –8.14 — 1 MRL nc nc

KING-11 11/5/2008 –62.7 –8.28 — 0.48 ssLC nc nc

KING-13 10/20/2005 –61.7 –8.10 — 1 MRL nc nc

KING-13 11/5/2008 –62.5 –8.42 1.1 ± 0.35 0.35 ssLC nc nc

KING-17 10/26/2005 –61.2 –7.71 — 1 MRL –14.10 67

KING-17 11/4/2008 –61.4 –7.80 — 0.45 ssLC nc nc

Table 12. Isotopic tracers in samples collected from trend wells for seven Groundwater Ambient Monitoring and Assessment (GAMA) 

study units.—Continued

[The five-digit USGS parameter code below the constituent name is used to uniquely identify a specific constituent or property. Stable isotope ratios of 

hydrogen, oxygen, and carbon are reported in delta notation (δ), the ratio of a heavier isotope to more common lighter isotope of that element, relative to a 

standard reference material. Tritium values less than the reporting level1 (MRL or ssLc) are reported as non-detections (—). Stable isotopes of water were 

measured in 55 trend-well samples during both time periods. Tritium was analyzed in samples from 50 trend wells during 2004–05 and 55 trend wells in 2007–

08. Carbon isotopes were analyzed in samples from 17 trend wells during 2004–05 and 29 trend wells in 2007–08; 9 wells were analyzed during both periods. 

Information about analytes given in table 3I. GAMA well identification number acronyms: San Diego Drainages study unit: SDALLV, Alluvial Basins 

study area; SDHDRK, Hard Rock study area; SDTEM, Temecula Valley study area; SDTEMFP, Temecula Valley study area flow-path well; SDWARN, Warner 

Valley study area. North San Francisco Bay study unit: NSFVOL, Volcanic Highlands study area; NSFVP, Valley and Plains study area; NSFWG, Wilson 

Grove Formation Highlands study area; NSFWGFP, Wilson Grove Formation Highlands study area flow-path well. Northern San Joaquin Basin study 

unit: COS, Cosumnes Basin study area; ESJ, Eastern San Joaquin Basin study area; NSJ-QPC, Uplands study area; TRCY, Tracy Basin study area. Southern 

Sacramento Valley study unit: NAM, North American study area; SAM, South American study area; SOL, Solano study area; SSV-QPC, Uplands study area; 

SUI, Suisun-Fairfield study area; YOL, Yolo study area. San Fernando–San Gabriel study unit: ULASF, San Fernando study area; ULASG, San Gabriel study 

area. Monterey Bay and Salinas Valley Basins study unit: MSMB, Monterey Bay study area; MSPR, Paso Robles study area; MSSC, Santa Cruz study area; 

MSSV, Salinas Valley study area. Southeast San Joaquin Valley study unit: KING, Kings study area; KWH, Kaweah study area; TLR, Tulare Lake study area; 

TULE, Tule study area. Benchmark type: MCL-CA, California Department of Public Health maximum contaminant level. Benchmark type and benchmark 

level as of April 1, 2010. Other abbreviations: USGS, U.S. Geological Survey; H, hydrogen; O, oxygen; C, carbon; CSU, 1-sigma combined standard 

uncertainty; pCi/L, picocuries per liter; MRL, minimum reporting level; ssLc,sample-specific critical level; ±, plus or minus; nc, not collected; na, not available]
Tables 143

GAMA 

identification 

number

Sample 

dates

δ2H of water 

(per mil) 

(82082)

δ18O of water 

(per mil) 

(82085)

Tritium 

(pCi/L) 

(07000)

δ13C 

(per mil) 

(82081)

Carbon-14 

(percent modern) 

(49933)

Benchmark type na na MCL-CA na na

Benchmark level na na 20,000 na na

Result ± 

CSU 

Reporting 

level

Reporting 

level type1

Southeast San Joaquin Valley study unit—Continued

KING-24 11/5/2005 –85.2 –11.50 nc nc nc nc nc

KING-24 11/3/2008 –86.5 –11.68 17.3 ± 0.70 0.35 ssLC nc nc

KWH-10 11/17/2005 –64.0 –7.84 nc nc nc nc nc

KWH-10 11/5/2008 –64.8 –8.01 10.0 ± 0.51 0.35 ssLC nc nc

KWH-12 11/28/2005 –87.2 –12.21 16 ± 1.6 1 MRL –15.30 86

KWH-12 11/6/2008 –86.1 –12.12 12.5 ± 0.61 0.38 ssLC nc nc

TLR-03 11/29/2005 –80.5 –11.06 nc nc nc nc nc

TLR-03 11/4/2008 –81.2 –11.01 0.4 ± 0.38 0.38 ssLC nc nc

TULE-05 12/5/2005 –68.4 –8.66 nc nc nc nc nc

TULE-05 11/3/2008 –64.3 –7.90 0.9 ± 0.32 0.32 ssLC nc nc

TULE-10 12/7/2005 –72.9 –10.30 nc nc nc nc nc

TULE-10 11/3/2008 –71.4 –10.10 4.5 ± 0.32 0.32 ssLC nc nc

1

 Tritium reporting levels were expressed as MRL before August 2008 and as ssLc after August 2008 (both reporting level types were used during 

August 2008).

2

 Result was rejected after quality-assurance review.

Table 12. Isotopic tracers in samples collected from trend wells for seven Groundwater Ambient Monitoring and Assessment (GAMA) 

study units.—Continued

[The five-digit USGS parameter code below the constituent name is used to uniquely identify a specific constituent or property. Stable isotope ratios of 

hydrogen, oxygen, and carbon are reported in delta notation (δ), the ratio of a heavier isotope to more common lighter isotope of that element, relative to a 

standard reference material. Tritium values less than the reporting level1 (MRL or ssLc) are reported as non-detections (—). Stable isotopes of water were 

measured in 55 trend-well samples during both time periods. Tritium was analyzed in samples from 50 trend wells during 2004–05 and 55 trend wells in 2007–

08. Carbon isotopes were analyzed in samples from 17 trend wells during 2004–05 and 29 trend wells in 2007–08; 9 wells were analyzed during both periods. 

Information about analytes given in table 3I. GAMA well identification number acronyms: San Diego Drainages study unit: SDALLV, Alluvial Basins 

study area; SDHDRK, Hard Rock study area; SDTEM, Temecula Valley study area; SDTEMFP, Temecula Valley study area flow-path well; SDWARN, Warner 

Valley study area. North San Francisco Bay study unit: NSFVOL, Volcanic Highlands study area; NSFVP, Valley and Plains study area; NSFWG, Wilson 

Grove Formation Highlands study area; NSFWGFP, Wilson Grove Formation Highlands study area flow-path well. Northern San Joaquin Basin study 

unit: COS, Cosumnes Basin study area; ESJ, Eastern San Joaquin Basin study area; NSJ-QPC, Uplands study area; TRCY, Tracy Basin study area. Southern 

Sacramento Valley study unit: NAM, North American study area; SAM, South American study area; SOL, Solano study area; SSV-QPC, Uplands study area; 

SUI, Suisun-Fairfield study area; YOL, Yolo study area. San Fernando–San Gabriel study unit: ULASF, San Fernando study area; ULASG, San Gabriel study 

area. Monterey Bay and Salinas Valley Basins study unit: MSMB, Monterey Bay study area; MSPR, Paso Robles study area; MSSC, Santa Cruz study area; 

MSSV, Salinas Valley study area. Southeast San Joaquin Valley study unit: KING, Kings study area; KWH, Kaweah study area; TLR, Tulare Lake study area; 

TULE, Tule study area. Benchmark type: MCL-CA, California Department of Public Health maximum contaminant level. Benchmark type and benchmark 

level as of April 1, 2010. Other abbreviations: USGS, U.S. Geological Survey; H, hydrogen; O, oxygen; C, carbon; CSU, 1-sigma combined standard 

uncertainty; pCi/L, picocuries per liter; MRL, minimum reporting level; ssLc,sample-specific critical level; ±, plus or minus; nc, not collected; na, not available]
144 Groundwater-Quality Data in Seven GAMA Study Units: Results from Initial Sampling and Resampling of Wells

Appendix

This appendix includes discussions of the methods used 

to collect and analyze groundwater samples and report the 

resulting water-quality data. Methods used during initial 

sampling are described in published GAMA Data Series 

Reports for each study unit (Wright and others, 2005; 

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

Dawson and others, 2008; Land and Belitz, 2008; Kulongoski 

and Belitz, 2007; and Burton and Belitz, 2008). In each case, 

the methods were selected to obtain representative samples 

of the groundwater from each well and to minimize the 

potential for contamination of the samples or bias in the data. 

Procedures used to collect and assess QC data and the results 

of the QC assessments for the resampled trend wells also are 

discussed.

Groundwater samples were collected and QA procedures 

were implemented using standard and modified USGS 

protocols from the NFM (U.S. Geological Survey, variously 

dated; Wilde and others, 1999, 2004) and the NAWQA 

Program (Koterba and others, 1995). The QA plan followed 

by the NWQL, the primary laboratory used to analyze samples 

for this study, is described in Maloney (2005) and Pirkey and 

Glodt (1998).

Sample Collection and Analysis

Prior to sampling, wells were pumped continuously 

until field measurements of water temperature, dissolved 

oxygen, pH, and specific conductance were stable (Wilde and 

others, 1999). Wells were sampled using Teflon® tubing with 

brass and stainless-steel fittings attached to a sampling point 

(usually a hose-bib fitting) on the well-discharge pipe as close 

to the well head as possible. The sampling point was located 

upstream from water-storage tanks and from the well-head 

treatment system (if a system existed). If a chlorinating system 

was attached to the well, the chlorinator was shut off, when 

possible, before the well was purged and sampled in order 

to clear all chlorine out of the system. The absence of free 

chlorine was verified using a Hach® field test kit. All samples 

were collected outdoors by connecting a 1- to 3-foot length 

of Teflon® tubing to the sampling point (Lane and others, 

2003). All fittings and lengths of tubing were cleaned between 

samples (Wilde, 2004). 

For the field measurements, groundwater was pumped 

through a flow-through chamber (that was attached to 

the sampling point) fitted with a multi-probe meter that 

simultaneously measured the field water-quality indicators—

dissolved oxygen, temperature, pH, and specific conductance. 

Field measurements were made in accordance with protocols 

in the NFM (Radtke and others, 2005; Wilde and Radtke, 

2005; Lewis, 2006; Wilde, 2006; Wilde and others, 2006). 

All sensors on the multi-probe meter were calibrated daily. 

Measured dissolved oxygen, temperature, pH, and specific 

conductance values were recorded at approximately 5-minute 

(min) intervals, and when these values remained stable for 

a minimum of 30 min, samples for laboratory analyses then 

were collected. 

Field measurements and instrument calibrations were 

recorded by hand on field record sheets and electronically 

in the Personal Computer Field Form (PCFF) program. 

Analytical service requests for the NWQL also were managed 

by PCFF, whereas analytical service requests for other 

laboratories were entered into laboratory-specific spreadsheets. 

Information from PCFF was uploaded directly into NWIS at 

the end of every week of sample collection. 

Detailed sampling protocols for individual analyses 

and groups of analytes are described in Koterba and others 

(1995), in the NFM (Wilde and others, 1999, 2004), and in 

the references for analytical methods listed in table A1; only 

brief descriptions are given here. VOC samples were collected 

in three 40-millilter (mL) sample vials that were purged with 

three vial volumes of unfiltered groundwater before bottomfilling to eliminate atmospheric contamination. One to one 

(1:1) hydrochloric acid to water (HCl/H2O) solution was 

added as a preservative to the VOC samples. Perchlorate 

samples were collected in 125-mL polystyrene bottles and 

then filtered in two or three 20-mL aliquots of groundwater 

through a 0.20-micrometer (μm) pore-size Corning® syringetip disk filter into sterilized 125-mL bottles. Tritium samples 

were collected by bottom-filling one 1-L polyethylene bottle 

with unfiltered groundwater, after first overfilling the bottles 

with three volumes of unfiltered groundwater. Samples for 

analysis of stable isotopes of hydrogen and oxygen in water 

were each collected in a 60-mL clear glass bottle filled with 

unfiltered groundwater, sealed with a conical cap, and secured 

with electrical tape to prevent leakage and evaporation.

Samples for analysis of pesticides (including polar 

pesticides) and pesticide degradates were collected in 1-L 

baked amber glass bottles. These samples were each filtered 

through a 0.7-μm nominal pore-size glass fiber filter during 

collection. NDMA samples were collected in 500-mL baked 

amber bottles treated with 0.05 gram (g) of sodium thiosulfate 

(Na2S2O3) as a preservative and were filtered at Weck prior to 

analysis.

Groundwater samples for trace elements, major and 

minor ions, silica, laboratory alkalinity, and TDS analyses 

required filling one 250-mL polyethylene bottle with 

unfiltered groundwater and one 500-mL and one 250-mL 

polyethylene bottle with filtered groundwater (Wilde and 

others, 2004). Filtration was done using a 0.45-μm pore-size 

PALL® unvented capsule filter that was pre-rinsed with 2 L 

of deionized water, then rinsed with 1 L of groundwater prior 

to sampling. The 250-mL filtered sample to be analyzed for 

trace elements was preserved with 7.5-Normal (N) nitric acid. 

Nutrient samples were collected by filtering groundwater 

into 125-mL brown polyethylene bottles. Arsenic and iron 
Appendix 145

species samples were filtered into 250-mL polyethylene 

bottles that were covered with tape to prevent light exposure 

and preserved with 6-N hydrochloric acid. Stable isotopes 

of carbon in dissolved inorganic carbon and carbon-14 

abundance samples were filtered and bottom-filled into 

500-mL glass bottles that first were overfilled with three 

bottle volumes of filtered groundwater. These samples had 

no headspace and were sealed with conical caps to avoid 

atmospheric contamination. Bicarbonate and carbonate 

concentrations were calculated from the laboratory alkalinity 

and pH values using the advanced speciation method (http://

or.water.usgs.gov/alk/methods.html) with pK1 = 6.35, pK2 = 

10.33, and pKW = 14. 

Temperature-sensitive samples were stored on ice 

prior to and during shipping to the various laboratories. The 

non-temperature-sensitive samples for tritium and stable 

isotopes of hydrogen and oxygen in water were shipped 

monthly. Temperature-sensitive or time-sensitive samples for 

VOCs, pesticides (including polar pesticides) and pesticide 

degradates, perchlorate, NDMA, trace elements, nutrients, 

major and minor ions, silica, TDS, and laboratory alkalinity 

were shipped daily whenever possible. Samples to be analyzed 

for arsenic and iron species were shipped weekly. The 

temperature-sensitive samples for stable isotopes of carbon 

in dissolved inorganic carbon and carbon-14 abundance were 

stored on ice, archived in a laboratory refrigerator, and shipped 

after all of the laboratory alkalinity measurements were 

received. 

Seven laboratories performed chemical analyses on 

samples collected during resampling for trends (table A1), 

although most of the analyses were performed at the NWQL. 

The NWQL maintains a rigorous QA program (Pirkey and 

Glodt, 1998; Maloney, 2005). Laboratory QC samples, 

including method blanks, continuing calibration verification 

standards, standard reference samples, reagent spikes of target 

analytes and surrogates, external certified reference materials, 

and external blind proficiency samples are analyzed regularly. 

Method detection limits are tested continuously and laboratory 

reporting levels updated accordingly. NWQL maintains 

National Environmental Laboratory Accreditation Program 

(NELAP) and other certifications (http://www.nelac-institute.

org/accred-labs.php). The USGS Branch of Quality Systems 

(BQS) maintains independent oversight of QA at the NWQL. 

The BQS also runs the National Field Quality Assurance 

Program (NFQA) that includes annual testing of all USGS 

field personnel for proficiency in making field water-quality 

measurements (http://qadata.cr.usgs.gov/nfqa/). Results for 

analyses made at the NWQL or by laboratories contracted 

by the NWQL are uploaded directly into the USGS NWIS 

database. Results of analyses made at other laboratories are 

compiled in a project database and uploaded from there into 

the USGS NWIS database. 

Data Reporting

The following section gives details for the laboratory 

reporting conventions and the constituents sampled for trends 

that are determined by multiple methods or by multiple 

laboratories.

Reporting Limits

The USGS NWQL uses different conventions for 

reporting results for organic and inorganic constituents. 

For organic constituents, LRLs and LT-MDLs are used as 

thresholds for reporting analytical results. The LRL is set to 

minimize the reporting of false negatives (not detecting a 

compound when it actually is present in a sample) to less than 

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

set at two times the 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 the MDL, there 

is less than a 1 percent chance of a false positive) (Childress 

and others, 1999; U.S. Environmental Protection Agency, 

2002). Inorganic detections at concentrations less than the 

LT-MDL are reported as non-detections with a dash (–) in the 

data tables. The USGS NWQL updates LRL and LT-MDL 

values regularly, and the values or ranges of values listed in 

this report were in effect during the initial sampling period 

(May 2004 to February 2006) and the resampling period 

(September 2007 to November 2008) for trend wells from the 

first seven GAMA-PBP study units. 

For organic constituents, concentrations between the 

LRL and the LT-MDL are reported as having a higher degree 

of uncertainty (coded by the letter “E” preceding the values in 

the tables and text). For information-rich methods, detections 

less than the LT-MDL have a high certainty of presence, 

but the precise concentration is uncertain. Detections of 

organic compounds at concentrations less than the LT-MDL 

are reported in the data tables, but are qualified with E-code 

remarks and footnotes, and are not considered detections 

in the calculations of detection statistics. Information-rich 

methods are those that use gas chromatography or highperformance liquid chromatography (HPLC) with mass 

spectrometry detection, such as those methods used to analyze 

VOCs and pesticides. Compounds are identified by presence 

of characteristic fragmentation patterns in their mass spectra 

in addition to being quantified by measurement of peak areas 

at their associated chromatographic retention times. E-coded 

values also may result from detections outside the range of 

calibration standards, from detections that did not meet all 

laboratory QC criteria, and from samples that were diluted 

prior to analysis (Childress and others, 1999).
146 Groundwater-Quality Data in Seven GAMA Study Units: Results from Initial Sampling and Resampling of Wells

Total dissolved solids, perchlorate, and NDMA are 

reported by using minimum reporting levels (MRLs). The 

MRL is the smallest measurable concentration of a constituent 

that may be reliably reported using a given analytical method 

(Timme, 1995). 

The reporting limits for radiochemical constituents 

(carbon-14 and tritium) are based on sample-specific critical 

levels (ssLC) (McCurdy and others, 2008). The critical level 

is analogous to the LT-MDL used for reporting analytical 

results for organic and non-radioactive inorganic constituents. 

Here, the critical level is defined as the minimum measured 

activity that indicates a positive detection of the radionuclide 

in the sample with less than a 5 percent probability of a false 

positive detection. Sample-specific critical levels are used 

for radiochemical measurements because the critical level is 

sensitive to sample size and sample yield during analytical 

processing and is dependent on instrument background, on 

counting times for the sample and background, and on the 

characteristics of the instrument being used and the nuclide 

being measured. An ssLC is calculated for each sample, and 

the measured activity in the sample is compared to the ssLC

associated with that sample. Measured activities less than the 

ssLC are reported as non-detections with a dash (–) in the data 

tables. 

The analytical uncertainties associated with measurement 

of activities also are sensitive to sample-specific parameters, 

including sample size, sample yield during analytical 

processing, and time elapsed between sample collection and 

various steps in the analytical procedure, as well as parameters 

associated with the instrumentation. Therefore, tritium 

activities are reported as plus or minus (±) sample-specific 

combined standard uncertainties (CSU) (table 12). The CSU is 

reported at the 68 percent confidence level (1-sigma). Tritium 

reporting levels were expressed as MRLs before August 2007, 

and as ssLCs after August 2007. Both reporting level types 

were used during August 2007.

Results for some organic and inorganic constituents are 

presented using SRLs derived from assessment of data from 

QC samples associated with groundwater samples collected 

as part of the GAMA-PBP (Olsen and others, 2010; Fram and 

others, 2012). SRLs are equal to or greater than the reporting 

levels used by the laboratory. Detections reported by the 

laboratory with concentrations less than SRLs may have 

significant contamination bias. Such detections are expressed 

in the results tables as equal to or less than (≤) the reported 

concentration.

Notation 

Stable isotopic compositions of hydrogen, oxygen, and 

carbon are reported as relative isotope ratios in units of per mil 

using the standard delta notation (Coplen and others, 2002):

δi sample

reference

E

R

R = −

















1 × 1,000 per mil (A1)

where i is the atomic mass of the heavier isotope of 

the element,

E is the element (H for hydrogen, O for oxygen, 

C for carbon),

Rsample is the ratio of the abundance of the heavier 

isotope of the element (2H, 18O, 13C) to the 

lighter isotope of the element (1H, 16O, 12C) 

in the sample, and

Rreference is the ratio of the abundance of the heavier 

isotope of the element to the lighter isotope 

of the element in the reference material.

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 sometimes written as δD because the common name of 

the heavier isotope of hydrogen, hydrogen-2, is deuterium) 

(Coplen and others, 2002). The reference material for carbon 

is Vienna Pee Dee Belemnite (VPDB), which is assigned a 

δ13C value of 0 per mil (Coplen and others, 2002). Positive 

values indicate enrichment of the heavier isotope, and negative 

values indicate depletion of the heavier isotope, compared to 

the ratios observed in the standard reference material.

Constituents on Multiple Analytical Schedules

Fourteen constituents targeted in this study were 

measured by more than one analytical method or by more 

than one laboratory (table A2). Preferred analytical methods 

are indicated in the constituent tables (tables 3A, 3B, 3D, 

3E, 3G, 3H) and the results tables (tables 4, 5, 6, 7, 10, 11). 

The preferred methods were generally selected on the basis 

of better performance or sensitivity for the constituent but, 

in all cases, results are given for both methods in the results 

tables. Six pesticide compounds—atrazine, deethylatrazine, 

carbaryl, carbofuran, metalaxyl, and tebuthiuron—as well as 

two VOCs—DBCP and EDB—were analyzed by two different 

NWQL analytical methods (table A2). An additional VOC—

1,2,3-TCP—was analyzed by the NWQL, as well as by an 

outside laboratory (MWH during initial sampling, and Weck 

during resampling). 

Similarly, total dissolved arsenic and iron concentrations 

were measured by the NWQL, as well as by the USGS 

NRP-TML as part of the determination of the oxidationreduction species of these metals. The process, using iron as 

an example, is as follows:
Appendix 147

Fe III

Fe II

Fe T Fe II

Fe II

( )

( )

( ) ( )

( ) = − (A2)

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). 

For arsenic, the measured oxidationreduction species is arsenite [As(III)], and 

the calculated species is arsenate [As(V)].

The field water-quality indicators—pH and specific 

conductance—were measured in the field and at the NWQL 

during the resampling period and for some samples collected 

from trend wells during initial sampling. During initial 

sampling, field measurements of alkalinity were often 

performed on samples for which alkalinity was also measured 

by the NWQL. The field measurements are the preferred 

method for these three water-quality indicators. However, field 

and laboratory measurements are reported in table 4. Field 

values are preferred because field conditions are considered 

more representative of groundwater conditions (Hem, 1985).

Additionally, perchlorate was measured by two 

laboratories (MWH and Weck) for nine samples collected 

from trend wells in the San Diego Drainages and North San 

Francisco Bay study units (table 7). Prior to August 2007, 

perchlorate analysis for GAMA-PBP was performed 

on unfiltered samples by MWH. After December 2007, 

perchlorate analysis was performed on filtered samples by 

Weck. From August to December 2007, perchlorate analyses 

were performed by both laboratories on selected samples in an 

effort to determine the comparability of results from the two 

laboratories. 

Quality-Control Methods and Results

The purpose of QC samples 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, and (or) 

laboratory analysis. Four types of QC measurements were 

evaluated in this study: (1) blank samples were collected to 

assess positive bias as a result of contamination during sample 

handling or analysis, (2) replicate samples were collected 

to assess variability, (3) matrix-spike tests were done for 

organic constituents to assess positive or negative bias, and 

(4) surrogate compounds were added to samples analyzed for 

organic constituents to assess potential matrix effects from the 

chemical composition of each groundwater sample, as well as 

to assess potential bias of laboratory analytical methods.

Blank Samples

The primary purposes of collecting blanks are to evaluate 

the magnitude of potential contamination of samples with 

compounds of interest during sample handling or analysis and 

to identify and mitigate the sources of sample contamination. 

Blank Collection and Analysis

Blanks were collected using blank water certified by the 

NWQL to contain less than the reporting levels for selected 

constituents investigated in the study (National Water Quality 

Laboratory, written commun., 2012). Nitrogen-purged, 

organic-free blank water was used for blanks of organic 

constituents, and inorganic-free blank water was used for 

blanks of inorganic constituents. Two types of blanks (field 

and source-solution) were collected during resampling in 

2007–2008 (table A3).

Field blanks were collected to assess potential 

contamination of samples during collection, processing, 

transport, and analysis. To collect field blanks at the sampling 

sites, blank water was either pumped or poured through the 

sampling equipment (fittings and tubing) used to collect 

groundwater samples, then processed and transported using 

the same protocols used for the groundwater samples. Field 

blanks were analyzed for VOCs (11 field blanks), pesticides 

and pesticide degradates (10), perchlorate (9), 1,2,3-TCP (7), 

NDMA (2), trace elements (11), nutrients (11), major and 

minor ions (11), silica (11), TDS (11), total arsenic and iron 

(1), and arsenic and iron species (1). 

Source-solution blanks are collected at the beginning 

of a study, or when using a new lot of blank water, to assess 

potential contamination of samples during transport and 

analysis and potential contamination of the certified blank 

water obtained from the NWQL. Source-solution blanks were 

collected in the field inside the mobile laboratory by pouring 

blank water directly into sample containers. These samples 

were then preserved, stored, shipped, and analyzed in the 

same manner as the groundwater samples. Source-solution 

blanks were analyzed for VOCs (4 source solution blanks), 

perchlorate (5), 1,2,3-TCP (2), trace elements (2), nutrients 

(1), major and minor ions (2), silica (2), and TDS (2). 

Blanks were not collected for isotopic ratios. Isotopic 

ratios of hydrogen, oxygen, and carbon are an intrinsic 

property of any of these elements; therefore, the concept of a 

blank does not apply to these ratios. In addition, blanks were 

not collected for tritium. Tritium is in the atmosphere and 

would dissolve into any solution used in collecting a blank, 

making it impractical to collect a blank for tritium.
148 Groundwater-Quality Data in Seven GAMA Study Units: Results from Initial Sampling and Resampling of Wells

Blank Sample Results 

Blanks were analyzed for 272 constituents. Field blanks 

were not analyzed for the four field water-quality indicators 

(dissolved oxygen, water temperature, pH, and specific 

conductance), the five laboratory water-quality indicators 

(specific conductance, pH, alkalinity, bicarbonate, and 

carbonate), the four species of arsenic and iron, or the five 

isotopic tracers (two stable isotopes of water, tritium, and 

two isotopes of carbon). Of the 272 constituents for which 

blanks were performed, 12 constituents were detected in at 

least 1 field blank (table A3). For three trace elements (copper, 

lead, and nickel), a nutrient (nitrite), a major ion (calcium), 

and silica, the detected concentrations in blanks were less 

than the applicable reporting limits (LRL, LT-MDL, MDL, 

MRL, or SRL); thus, no change in reporting limits was applied 

to results for these constituents due to detections in blanks. 

An additional trace element, chromium, had a measured 

concentration in a blank of 0.89 μg/L, which is greater than 

the SRL of 0.42 μg/L established by Olsen and others (2010). 

The detection was considered isolated, however, because the 

chromium concentration in the associated groundwater sample 

was less than 0.42 μg/L. Therefore, the SRL of 0.42 μg/L for 

chromium was used for this study. 

Similar to chromium, isolated low-level detections of 

acetone and chloroform in blanks were not accompanied by 

detections in their associated groundwater samples; therefore, 

acetone and chloroform results are reported here in accordance 

with the LRLs in effect for acetone and chloroform at the time 

of analysis (table A3). For the single field blank detection of 

1,2,3-TCP, the source-solution blank and the groundwater 

sample associated with the field blank also had detections 

at concentrations similar to the detection in the field blank. 

Therefore, the detection of 1,2,3-TCP in the Southern 

Sacramento Valley study unit well YOL-01 during resampling 

may be attributed to inadvertent sample contamination 

affecting all three samples. Similar to copper, lead, and 

nickel, the detected concentrations in blanks for two VOCs—

1,2,4-trimethylbenzene and toluene—were all less than the 

SRLs established by Fram and others (2012); thus, these SRLs 

were applied to results for these constituents. Detections of 

constituents at concentrations less than SRLs were coded as 

less than or equal to (≤) their measured concentrations in the 

samples and are counted as non-detections for the purpose of 

calculating detection frequencies for this report.

All but 2 of the 12 constituents detected in field blanks 

collected during resampling of trend wells in 2007–2008 

(nitrite and 1,2,3-TCP) were also detected in at least one field 

blank collected during initial sampling of the 7 resampled 

study units. An additional 45 constituents were detected in 

at least one field blank collected during the initial sampling 

of these study units, which occurred during 2004–2005, 

and decisions to qualify results from these sampling efforts 

were made during preparation of the pertinent data series 

reports (Wright and others, 2005; Bennett and others, 2006; 

Kulongoski and others, 2006; Kulongoski and Belitz, 2007; 

Burton and Belitz, 2008; Dawson and others, 2008; Land and 

Belitz, 2008). In some cases, blank sample data qualification 

done after initial sampling has been superceded by GAMA 

policy in effect since the application of study reporting levels 

(Olsen and others, 2010; Fram and others, 2012). 

Replicate Samples

Sequential replicate samples were collected to assess 

the precision of the water-quality data. Estimates of 

data precision are needed to assess whether differences 

between concentrations in samples are due to differences in 

groundwater quality (for example, spatial or temporal trends) 

or to variability that may result from collecting, processing, 

and analyzing the samples. 

Replicate Collection and Analysis

The acceptable limits for differences in measured 

concentrations between replicate paired samples were 

determined using one of two criteria. The criterion selection 

depended on the magnitude of the measured concentration of 

a constituent relative to its reporting level. If the concentration 

of a constituent was less than 5 times its reporting level, 

a standard deviation (SD) for the sample pair of less than 

half the reporting level was considered acceptable. If the 

concentration of a constituent was greater than or equal to 

5 times its reporting level, a relative standard deviation (RSD) 

of less than 10 percent was considered acceptable. The RSD 

is defined as the SD divided by the mean concentration for 

each replicate pair of samples expressed as a percentage. An 

RSD of less than 10 percent was also used for isotopes, with 

the exception of tritium. For tritium, the activity in the paired 

samples could differ by no more than the combined standard 

uncertainty reported for the samples in order to be acceptable. 

When one or both values of a replicate pair were reported 

as non-detections, variability was evaluated in the following 

manner. If both values were reported as non-detections, the 

variability was considered acceptable because the results 

are perfectly consistent. If one value was reported as a 

non-detection (<RL) and the other value was reported as a 

detection less than the RL, the variability was considered 

acceptable because these two values, while not perfectly 

consistent, are in agreement as being less than the RL. If one 

value was reported as a non-detection and the other value was 

reported as a detection greater than or equal to the RL, the 

variability for the pair was considered unacceptable.

Replicate Results 

Tables A4A–A4B summarize the results of replicate 

analyses for constituents in groundwater samples collected 

during resampling for trends and that were detected in at least 

one of the samples of a replicate pair. One or 2 replicates for 

10 constituents indicated unacceptable variability, including 

2 of 5 replicates for perchlorate (method performed on filtered 
Appendix 149

samples); 2 of 6 replicates for aluminum, nickel, and zinc; 1 of 

6 replicates for chromium, copper, and iron; 1 of 5 replicates 

for 1,2,3-TCP and pmc; and 1 of 3 replicates for arsenite 

[As(III)]. Environmental detections were not modified on the 

basis of the replicate analyses.

Matrix-Spike Samples

Addition of 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 

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

environmental samples. This enables an analysis of matrix 

interferences on a compound-by-compound basis. For this 

study, matrix spikes were added by the laboratories performing 

the analysis rather than in the field. Low matrix-spike recovery 

may indicate that the compound might not have been detected 

in some samples if it were present at very low concentrations. 

Low and high matrix-spike recoveries may be a potential 

concern if the concentration of a compound in a groundwater 

sample is close to the health-based benchmark; a low recovery 

could result in a falsely measured concentration less than the 

health-based benchmark, whereas a high recovery could result 

in a falsely measured concentration greater than the healthbased benchmark.

The GAMA-PBP defined the data-quality objective 

range for acceptable median matrix-spike recoveries as 

70–130 percent. Only constituents with median matrixspike recoveries outside of this range were flagged as 

having unacceptable recoveries. For some constituents, an 

acceptable range of 70–130 percent for median matrix-spike 

recovery was more restrictive than the acceptable control 

limits for laboratory set-spike recoveries. Laboratory set 

spikes are aliquots of laboratory blank water to which the 

same spike solution used for the matrix spikes has been 

added. One set spike is analyzed with each set of samples. 

Acceptable control limits for set spikes are defined relative 

to the long-term variability in recovery. For example, for 

many NWQL analyses, acceptable set-spike recovery is 

within ± 3 F-pseudosigma of the median recovery for at least 

30 set spikes (Conner and others, 1998). The F-psuedosigma 

is calculated by dividing the fourth-spread (analogous to 

interquartile range) by 1.349; therefore, the smaller the 

F-pseudosigma, the more precise the determinations (Hoaglin, 

1983). Laboratory matrix spikes were performed for 231 out 

of the 232 organic constituents sampled in this study, 

including VOCs, pesticides (including polar pesticides), and 

pesticide degradates because the analytical methods for these 

constituents may be susceptible to matrix interference. NDMA 

was sampled for in only two of the study units, and no matrix 

spikes were performed for NDMA. 

Matrix-Spike Recoveries 

Tables A5A–A5E present a summary of matrix-spike 

recoveries of organic constituents analyzed in trend samples. 

Median matrix-spike recoveries were within acceptable limits 

for all VOCs (tables A5A, A5B, A5E). However, median 

matrix-spike recoveries for 50 of the 143 pesticide compounds 

were lower than the acceptable limits (tables A5C, A5D), 

which may indicate that these constituents might not have 

been detected in some samples even if they were present in 

the samples. In addition, median recoveries for seven pesticide 

compounds were higher than acceptable limits, but despite 

this indication of positive analytical bias, only one of these 

seven compounds (tebuthiuron) was detected in unspiked 

groundwater samples during this study. 

Surrogate Compounds

Surrogate compounds are added to groundwater samples 

in the laboratory prior to analysis to evaluate the recovery 

of similar constituents. Surrogate compounds were added in 

the laboratory to all groundwater and QC samples that were 

analyzed by the NWQL for VOCs and pesticides and pesticide 

degradates. Surrogates are used to identify general problems 

that may arise during laboratory sample analysis that could 

affect the analysis results for all compounds in that sample. 

Potential problems include matrix interferences (such as high 

levels of dissolved organic carbon) that can produce a positive 

or negative bias or incomplete laboratory recovery (possibly 

because of improper maintenance and calibration of analytical 

equipment) that produces a negative bias. A 70 to 130 percent 

recovery of surrogates, in general, is considered acceptable; 

values outside this range indicate possible problems with 

the processing and analysis of samples (Connor and others, 

1998; Sandstrom and others, 2001) or groundwater matrix 

interference. 

Surrogate recoveries

Median recoveries were within the acceptable range for 

all surrogates added to samples for the analyses of VOCs and 

pesticide compounds (table A6). However, all of the surrogates 

had recoveries that fell outside the acceptable ranges for 

samples from individual wells on a few occasions. Only 

rarely did this occur in samples from the same well for both 

sampling periods. Therefore, it is unlikely that groundwater 

matrix interferences caused the recoveries to be outside of the 

acceptable ranges in most cases.
150 Groundwater-Quality Data in Seven GAMA Study Units: Results from Initial Sampling and Resampling of Wells Table A1. Analytical methods used for the determination of organic and inorganic constituents by the U.S. Geological Survey (USGS) National Water Quality Laboratory (NWQL) and contract laboratories. [Laboratory entity codes in the USGS National Water Information System (NWIS) for laboratories other than the USGS NWQL are given in parentheses after the laboratory names. UV, ultraviolet; VOC, volatile organic compound; δ, 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 material, expressed 

as per mil]

Constituent 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 U.S. Environmental Protection Agency, 1995; 

Connor and others, 1998

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 Solid-phase extraction and high-performance liquid chromatography (HPLC)/mass spectrometry with 

selective-ion monitoring

NWQL, Schedule 2060 Furlong and others, 2001

Constituents of special interest

Perchlorate (on unfiltered samples) Chromatography and mass spectrometry Montgomery Watson Harza Laboratory Hautman and others, 1999Perchlorate (on filtered samples) Liquid chromatography with mass spectrometry/mass spectrometry (USEPA Method 331.0) Weck Laboratories, Inc., Industry, California, stan- dard operating procedure ORG099.R01 U.S. Environmental Protection Agency, 2005N-Nitrosodimethylamine (NDMA) Isotopic dilution with gas chromatography and chemicalionization mass spectrometry (USEPA Method 1625 

modified)

Weck Laboratories, Inc., Industry, California, standard operating procedure ORG065.R10 U.S. Environmental Protection Agency, 1989; Plomley and others, 1994

1,2,3-Trichloropropane Purge and trap gas chromatography/mass spectrometry Weck Laboratories, Inc., Industry, California, 

SRL 524M-TCP

Okamato and others, 2002

Inorganic constituents

Nutrients Alkaline persulfate digestion, Kjedahl digestion NWQL, Schedule 2755 Fishman, 1993; Patton and Kryskalla, 2003Major and minor ions, trace elements Atomic absorption spectrometry, colorimetry, ion-exchange 

chromatography, inductively-coupled plasma atomicemission spectrometry and mass spectrometry

NWQL, Schedule 1948 Fishman and Friedman, 1989; Fishman, 1993; 

Faires, 1993; McLain, 1993; Garbarino, 1999; American Public Health Association, 1998; Garbarino and others, 2006

Arsenic and iron species Various techniques of ultraviolet visible (UV-VIS) spectrophotometry and atomic-absorbance spectroscopy USGS Trace Metal Laboratory, Boulder, Colorado (USGSTMCO) Stookey, 1970; To and others, 1998; McCles- key and others, 2003
Appendix 151

Constituent Analytical method Laboratory and analytical schedule Citation(s)

Isotopes

Stable isotopes of hydrogen (δ2H) 

and oxygen (δ18O) of water

Gaseous hydrogen and carbon dioxide–water equilibration and 

stable-isotope mass spectrometry

USGS Stable Isotope Laboratory, Reston, Virginia 

(USGSSIVA), NWQL Schedule 1142

Epstein and Mayeda, 1953; Coplen and others, 1991; Coplen, 1994

δ13C of dissolved inorganic carbon 

and carbon-14 abundance

Accelerator mass spectrometry Woods Hole Oceanographic Institution, National 

Ocean Sciences Accelerator Mass Spectrometry Facility (NOSAMS), Woods Hole, Massachusetts (MA-WHAMS), NWQL Schedule 2255

Vogel and others, 1987; Donahue and others, 

1990; McNichol and others, 1992; Gagnon and Jones, 1993; McNichol and others, 1994; Schneider and others, 1994

Tritium Electrolytic enrichment-liquid scintillation USGS Stable Isotope and Tritium Laboratory, 

Menlo Park, California (USGSH3CA)

Thatcher and others, 1977

Table A1. Analytical methods used for the determination of organic and inorganic constituents by the U.S. Geological Survey (USGS) National Water Quality Laboratory (NWQL) and contract laboratories.—Continued[Laboratory entity codes in the USGS National Water Information System (NWIS) for laboratories other than the USGS NWQL are given in parentheses after the laboratory names. UV, ultraviolet; VOC, volatile organic compound; δ, delta notation, the ratio of a heavier isotope of an element (iE) to the more common lighter isotope of that element, relative to a standard reference material, expressed as per mil]
152 Groundwater-Quality Data in Seven GAMA Study Units: Results from Initial Sampling and Resampling of Wells

Table A2. Preferred analytical methods or laboratories for selected constituents collected during resampling for trends in the 

Groundwater Ambient Monitoring and Assessment (GAMA) Priority Basin Project, California, September 2007 to November 2008.

[Preferred analytical schedules are generally the methods of analysis with the greatest accuracy and precision out of the ones used for the constituent in question. 

USGS National Water Quality Laboratory (NWQL) schedules are referred to by number; Weck, Weck Laboratories, Inc.; MWH, Montgomery Watson Harza 

Laboratories; TML, USGS Trace Metal Laboratory, Boulder, Colorado; VOC, volatile organic compound; field, analysis performed by field crew upon sample 

collection]

Constituent Primary constituent 

classification

Preferred 

analytical method 1

Secondary 

analytical method

Duplicate analyses performed by two different analytical schedules at the NWQL

Atrazine Pesticide 2003 a,b,d,e,f or 2032 c or 2033 g 2060 b,d,e

Deethylatrazine (2-Chloro-4-isopropylamino-6-amino-s-triazine) Pesticide degradate 2003 a,b,d,e,f or 2032 c

 or 2033 g 2060 b,d,e

Carbaryl Pesticide 2003 a,b,d,e,f or 2032 c or 2033 g 2060 b,d,e

Carbofuran Pesticide 2032 c or 2033 g 2060 b,d,e

Tebuthiuron Pesticide 2003 a,b,d,e,f or 2032 c or 2033 g 2060 b,d,e

Metalaxyl Pesticide 2003 a,b,d,e,f or 2032 c or 2033 g 2060 b,d,e

1,2-Dibromo-3-chloropropane (DBCP) VOC, fumigant 1306 c,g 2020 a,b,c,d,e,f,g

1,2-Dibromoethane (EDB) VOC, fumigant 1306 c,g 2020 a,b,c,d,e,f,g

Duplicate analyses performed by two different laboratories (or by USGS field personnel and NWQL)

pH Water-quality indicator 2 field a,b,c,d,e,f,g 1948 a,b,c,d,e,f,g

Specific conductance Water-quality indicator 2 field a,b,c,d,e,f,g 1948 a,b,c,d,e,f,g

1,2,3-Trichloropropane (1,2,3-TCP) Constituent of special interest Weck c,d,e,f,g 2020 a,b,c,d,e,f,g

Perchlorate Constituent of special interest Weck a,b,c,d,e,f,g MWH a,b

Arsenic (total) Trace element 1948 a,b,c,d,e,f,g TML b,e

Iron (total) Trace element 1948 a,b,c,d,e,f,g TML b,e

1

 NWQL SC 2032 and 2033 use the same analytical method as NWQL SC 2003, but analyze for additional compounds.

2

 An additional water-quality indicator, alkalinity, was measured both in the field and by NWQL during initial sampling, but was only measured by NWQL 

during resampling.

a

 Analysis used in the San Diego Drainages study unit during resampling for trends.

b

 Analysis used in the North San Francisco Bay study unit during resampling for trends.

c

 Analysis used in the Northern San Joaquin Basin study unit during resampling for trends.

d

 Analysis used in the Southern Sacramento Valley study unit during resampling for trends.

e

 Analysis used in the San Fernando–San Gabriel study unit during resampling for trends.

f

 Analysis used in the Monterey Bay and Salinas Valley Basins study unit during resampling for trends.

g

 Analysis used in the Southeast San Joaquin Valley study unit during resampling for trends.
Appendix 153

Table A3. Constituents detected in blanks collected during resampling of the first seven Groundwater Ambient Monitoring and 

Assessment (GAMA) Priority Basin Project study units and constituents for which study reporting levels were established by the GAMA 

Program.

[E, estimated or having a high degree of uncertainty; LRL, laboratory reporting level; mg/L, milligrams per liter; μg/L, micrograms per liter; nv, no value in 

category; SRL, study reporting level; <, less than or equal to; —, not detected]

Constituent Field 

blanks

Sourcesolution 

blanks

LRL 1

Concentrations or range of 

concentrations detected in 

blanks druing 2007–08

SRL 2

Number of trend-well samples 

<-coded/total number of 

detections during 2007–08

Volatile organic compounds (μg/L)

Acetone 1/11 1/4 4, 6 E1.4 3 all 4 0/0

Carbon disulfide 0/11 0/4 0.04, 0.06 — 0.03 1/2

Chloroform 1/11 0/4 0.02, 0.04 E0.02 nv 0/21

Ethylbenzene 0/11 0/4 0.02, 0.04 — 0.06 1/1

Ethyl methyl ketone 0/11 0/4 1.6, 4 — all 4 1/1

1,2,4-Trimethylbenzene 4/11 0/4 0.04, 0.12 E0.03–0.11 0.56 9/9 

Toluene 2/11 1/4 0.018, 0.05 E0.02, E0.02 0.69 5/5

m-Xylene plus p-xylene 0/11 0/4 0.06, 0.08 — 0.33 1/1

o-Xylene 0/11 0/4 0.038, 0.04 — 0.12 1/1

Constituent of special interest (μg/L)

1,2,3-Trichloropropane 5 1/7 1/2 0.005 0.0054, 0.0056 nv 0/7

Nutrients and major and minor ions (mg/L)

Nitrite, as nitrogen 1/11 0/1 0.002, 0.008 E0.001 nv 0/50

Calcium 2/11 0/2 0.02, 0.04 E0.011, 0.021 nv 0/45

Silica 3/11 0/2 0.02, 0.04 E0.01–0.17 nv 0/45

Trace elements (μg/L)

Aluminum 0/11 0/2 1.6, 4 — 1.6 12/21

Barium 0/11 0/2 0.08, 1 — 0.36 0/45

Chromium 1/11 0/2 0.12, 0.8 0.89 0.42 7/37

Copper 1/11 0/2 0.4, 1 E0.23 1.7 15/26

Iron 0/11 0/2 4, 8 — 6 3/26

Lead 1/11 1/2 0.06, 0.12 0.11 0.65 30/40

Manganese 0/11 0/2 0.2, 0.2 — 0.2 5/35

Nickel 2/11 1/2 0.06, 0.2 0.12, 0.24 0.36 22/43

Tungsten 0/5 0/2 0.02, 0.06 — 0.11 4/11

Vanadium 0/11 0/2 0.04, 0.16 — 0.11 2/45

Zinc 0/11 0/2 0.6, 2 — 4.8 34/43

1

 Minimum and maximum LRLs used during study period, or only LRL used during study period.

2

 SRLs for trace elements from Olsen and others (2010) and SRLs for volatile organic compounds from Fram and others (2012).

3

 The detected concentration was less than the LT-MDL for this constituent. This result in a groundwater sample would have counted as a non-detection.

4

 Based on findings by Fram and others (2012), all detections of this compound are reported as “not analyzed.”

5

 Field blanks performed for low-level analyses of 1,2,3-trichloropropane were analyzed by Weck Laboratories, Inc.
154 Groundwater-Quality Data in Seven GAMA Study Units: Results from Initial Sampling and Resampling of Wells Table A4A. Quality-control summary for replicate analyses of organic constituents and constituents of special interest in samples collected for trends in seven Groundwater Ambient Monitoring and Assessment (GAMA) Priority Basin Project study units. [Constituents for which all replicate pairs were non-detections are not listed. Abbreviations: RL, reporting level; ≥, greater than or equal to; <, less than; nv, no value in category] Constituent Number of replicates performed Result categories considered to be within acceptable agreement Result categories not considered to be within acceptable agreement Number of replicate pairs for which both samples were non-detections1 Number of replicate pairs for which both samples were detections and their concentrations were within acceptable agreement4 Number of replicate pairs for which one sample was a non- detection and the other sample a detection at a concentration <RL2 Number of replicate pairs for which one sample was a non- detection and the other sample a detection at a concentration ≥RL3 Number of replicate pairs for which both samples were detections and their concentrations were not within acceptable agreement5 Paired concentrations of replicates not within acceptable agreement3,4 Volatile organic compounds (VOCs) 1,1-Dichloroethene 8 7 0 1 0 0 nv 1,2-Dichloroethane 8 7 0 1 0 0 nv Bromodichloromethane 8 7 0 1 0 0 nv cis-1,2-Dichloroethene 8 6 0 2 0 0 nv Diisopropyl ether (DIPE) 8 7 0 1 0 0 nv Methyl tert-butyl ether (MTBE) 8 6 0 2 0 0 nv Tetrachloroethene (PCE) 8 4 0 4 0 0 nv Carbon tetrachloride (Tetrachloro- methane)

8 6 0 2 0 0 nv

trans-1,2-Dichloroethene 8 7 0 1 0 0 nvTrichloroethene 8 4 0 4 0 0 nvChloroform (Trichloromethane) 8 1 0 6 0 0 nvPesticides, pesticide degradates, and caffeineSimazine 7 4 0 3 0 0 nvDeethylatrazine (2-Chloro-4-isopropylamino-6-amino-s-triazine)

7 2 0 5 0 0 nv

Atrazine 7 3 0 4 0 0 nvPrometon 7 6 0 1 0 0 nvTebuthiuron 7 5 0 2 0 0 nv3,4-Dichloroaniline 7 6 0 1 0 0 nvDeisopropyl atrazine (2-Chloro-6-

ethylamino-4-amino-s-triazine)

4 3 0 1 0 0 nv
Appendix 155

Constituent

Number 

of 

replicates 

performed

Result categories 

considered to be 

within acceptable agreement

Result categories 

not considered to be 

within acceptable agreement

Number of 

replicate pairs 

for which 

both samples 

were 

non-detections1

Number of replicate pairs 

for which both samples 

were detections and 

their concentrations 

were within acceptable 

agreement4

Number of replicate 

pairs for which one 

sample was a nondetection and the other 

sample a detection at a 

concentration <RL2

Number of replicate 

pairs for which one 

sample was a nondetection and the other 

sample a detection at a 

concentration ≥RL3

Number of replicate pairs 

for which both samples 

were detections and their 

concentrations were 

not within acceptable 

agreement5

Paired 

concentrations 

of replicates 

not within 

acceptable 

agreement3,4

Constituents of special interestPerchlorate (unfiltered) 5 3 0 2 0 0 nvPerchlorate (filtered) 5 1 2 0 1 1 (0.259, <0.1) 

(1.95, 1.56)

1,2,3-Trichloropropane 5 4 0 0 1 0 (0.0055, <0.005)

1 When the constituent is not detected in either sample of the replicate, agreement is considered acceptable.2 When the constituent is not detected in one of the two samples making up the replicate and is detected at a concentration less than the RL in the other sample, agreement is considered acceptable.3 When the constituent is not detected in one of the two samples making up the replicate and is detected at a concentration greater than or equal to the RL in the other sample, agreement is considered 

unacceptable.

4 In order for two detected concentrations of the samples making up a replicate to be considered within acceptable agreement, one of the following two criteria must be met: 1. For sample concentrations less 

Table A4A.than 5 times the RL for the constituent in question, the standard deviation for the two sample concentrations must be less than 1/2 the RL. 2. For sample concentrations greater than or equal to 5 times the RL, the relative standard deviation must be less than 10 percent.

Quality-control summary for replicate analyses of organic constituents and constituents of special interest in samples collected for trends in seven Groundwater 

Ambient Monitoring and Assessment (GAMA) Priority Basin Project study units.—Continued[Constituents for which all replicate pairs were non-detections are not listed. Abbreviations: RL, reporting level; ≥, greater than or equal to; <, less than; nv, no value in category]
156 Groundwater-Quality Data in Seven GAMA Study Units: Results from Initial Sampling and Resampling of Wells Table A4B. Quality-control summary for replicate analyses of inorganic constituents in samples collected for trends in seven Groundwater Ambient Monitoring and Assessment (GAMA) Priority Basin Project study units. [Constituents for which all replicate pairs were non-detections are not listed. Abbreviations: RL, reporting level; ≥, greater than or equal to; <, less than; E, estimated or having a higher degree of uncertainty; nv, no value in category; %, percent] Constituent Number of replicate analyses performed Result categories considered to be within acceptable agreement Result categories not considered to be within acceptable agreement Number of replicate pairs for which both samples were non-detections1 Number of replicate pairs for which both samples were detections and their concentrations were within acceptable agreement4 Number of replicate pairs for which one sample was a non-detection and the other sample a detection at a concentration <RL2 Number of replicate pairs for which one sample was a non-detection and the other sample a detection at a concentration ≥RL3 Number of replicate pairs for which both samples were detections and their concentrations were not within acceptable agreement4 Paired concentrations of replicates not within acceptable agreement3,4 Trace Elements Aluminum 6 3 1 0 1 1 (<1.6, 8.1) (5.3, 1.8) Antimony 6 2 4 0 0 0 nv Arsenic 6 0 6 0 0 0 nv Barium 6 0 6 0 0 0 nv Boron 6 0 6 0 0 0 nv Cadmium 6 4 2 0 0 0 nv Chromium 6 0 5 0 0 1 (0.20, 0.26) Cobalt 6 0 5 1 0 0 nv Copper 6 1 4 0 0 1 (E0.50, E0.72) Iron 6 2 2 1 0 1 (4.6, 3.6) Lead 6 0 6 0 0 0 nv Lithium 6 0 6 0 0 0 nv Manganese 6 0 5 1 0 0 nv Molybdenum 6 0 6 0 0 0 nv Nickel 6 1 3 0 0 2 (0.13, 0.15) (0.38, 0.64) Selenium 6 0 6 0 0 0 nv Strontium 6 0 6 0 0 0 nv Uranium 6 0 6 0 0 0 nv Vanadium 6 0 6 0 0 0 nv Zinc 6 0 4 0 0 2 (0.7, E0.3) 

(3.7, 4,7)
Appendix 157

Constituent

Number 

of 

replicate 

analyses 

performed

Result categories 

considered to be 

within acceptable agreement

Result categories 

not considered to be 

within acceptable agreement

Number of 

replicate pairs 

for which 

both samples 

were 

non-detections1

Number of replicate pairs 

for which both samples 

were detections and their 

concentrations were within 

acceptable agreement4

Number of replicate pairs 

for which one sample was 

a non-detection and the 

other sample a detection at 

a concentration <RL2

Number of replicate pairs 

for which one sample was 

a non-detection and the 

other sample a detection at 

a concentration ≥RL3

Number of replicate pairs 

for which both samples 

were detections and their 

concentrations were 

not within acceptable 

agreement4

Paired 

concentrations 

of replicates 

not within 

acceptable 

agreement3,4

Nutrients Ammonia (as nitrogen) 7 6 1 0 0 0 nvNitrate plus nitrite (as nitrogen) 5 7 1 6 0 0 0 nvNitrite (as nitrogen) 7 6 1 0 0 0 nvTotal nitrogen (ammonia + nitrite 

+ nitrate + organic nitrogen)

7 0 7 0 0 0 nv

Phosphate, orthophosphate (as 

phosphorus)

7 0 7 0 0 0 nv

Major and minor ions, silica, and total dissolved solids (TDS) Bromide 6 0 6 0 0 0 nvCalcium 6 0 6 0 0 0 nvChloride 6 0 6 0 0 0 nvFluoride 6 1 5 0 0 0 nvIodide 5 1 4 0 0 0 nvMagnesium 6 0 6 0 0 0 nvPotassium 6 0 6 0 0 0 nvSodium 6 0 6 0 0 0 nvSulfate 6 0 6 0 0 0 nvSilica (as SiO2) 6 0 6 0 0 0 nvTDS 6 0 6 0 0 0 nvArsenic speciesArsenic (total) 3 1 2 0 0 0 nvArsenic-III 3 2 0 0 1 0 (1, <1)

Table A4B. Quality-control summary for replicate analyses of inorganic constituents in samples collected for trends in seven Groundwater Ambient Monitoring and Assessment (GAMA) Priority Basin Project study units.—Continued[Constituents for which all replicate pairs were non-detections are not listed. Abbreviations: RL, reporting level; ≥, greater than or equal to; <, less than; E, estimated or having a higher degree of uncertainty; nv, no value in category; %, percent]
158 Groundwater-Quality Data in Seven GAMA Study Units: Results from Initial Sampling and Resampling of Wells Constituent Number of replicate analyses performed Result categories considered to be within acceptable agreement Result categories not considered to be within acceptable agreement Number of replicate pairs for which both samples were non-detections1 Number of replicate pairs for which both samples were detections and their concentrations were within acceptable agreement4 Number of replicate pairs for which one sample was a non-detection and the other sample a detection at a concentration <RL2 Number of replicate pairs for which one sample was a non-detection and the other sample a detection at a concentration ≥RL3 Number of replicate pairs for which both samples were detections and their concentrations were not within acceptable agreement4 Paired concentrations of replicates not within acceptable agreement3,4 Isotopic Tracers

δ2H of water 8 nv 8 nv nv nv nvδ18O of water 8 nv 8 nv nv nv nvTritium 7 nv 7 nv nv nv nvδ13C of dissolved carbonates 5 nv 5 nv nv nv nvCarbon-14 (percent modern 

carbon)

5 nv 4 nv nv 1 (17.52%, 31.70%)

1 When the constituent is not detected in either sample of the replicate, agreement is considered acceptable.2 When the constituent is not detected in one of the two samples of the replicate pair and is detected at a concentration less than the RL in the other sample, agreement is considered acceptable.3 When the constituent is not detected in one of the two samples of the replicate pair and is detected at a concentration greater than or equal to the RL in the other sample, agreement is considered 

unacceptable.

4 In order for two detected concentrations of the samples of a replicate pair to be considered within acceptable agreement, one of the following two criteria must be met: 1. For sample concentrations less 

than 5 times the RL for the constituent, the standard deviation for the two sample concentrations must be less than 1/2 the RL. 2. For sample concentrations greater than or equal to 5 times the RL, the relative standard deviation must be less than 10 percent.

5 Nitrite plus nitrate (as nitrogen) is refered to as nitrate in the text for brevity.

Table A4B. Quality-control summary for replicate analyses of inorganic constituents in samples collected for trends in seven Groundwater Ambient Monitoring and Assessment (GAMA) Priority Basin Project study units.—Continued[Constituents for which all replicate pairs were non-detections are not listed. Abbreviations: RL, reporting level; ≥, greater than or equal to; <, less than; E, estimated or having a higher degree of uncertainty; nv, no value in category; %, percent]
Appendix 159

Table A5A. Quality-control summary for matrix-spike recoveries of volatile organic compounds (VOCs) in spiked samples collected for 

trends in seven Groundwater Ambient Monitoring and Assessment (GAMA) Priority Basin Project study units.

[Acceptable recovery range is between 70 and 130 percent]

Constituent Number of 

spike samples

Minimum recovery 

(percent)

Maximum recovery 

(percent)

Median recovery 

(percent)

Acetone 7 97 133 107

Acrylonitrile 7 97 115 110

tert-Amyl methyl ether (TAME) 7 94 121 106

Benzene 7 96 112 103

Bromobenzene 7 94 128 101

Bromochloromethane 1 7 90 118 105

Bromodichloromethane 1 7 98 118 103

Bromoform (Tribromomethane) 1 7 95 123 103

Bromomethane (Methyl bromide) 7 89 145 111

n-Butylbenzene 7 80 108 90

sec-Butylbenzene 7 92 122 99

tert-Butylbenzene 7 95 123 108

Carbon disulfide 1 7 65 123 82

Carbon tetrachloride (Tetrachloromethane) 1 7 96 117 107

Chlorobenzene 7 95 117 101

Chloroethane 7 70 127 109

Chloroform (Trichloromethane) 1 7 84 124 113

Chloromethane 7 82 114 95

3-Chloropropene 7 90 119 110

2-Chlorotoluene 7 95 128 110

4-Chlorotoluene 7 96 119 104

Dibromochloromethane 1 7 98 109 100

1,2-Dibromo-3-chloropropane (DBCP) 1 7 87 113 101

1,2-Dibromoethane (EDB) 7 96 114 100

Dibromomethane 1 7 90 115 104

1,2-Dichlorobenzene 1 7 93 125 103

1,3-Dichlorobenzene 7 94 120 104

1,4-Dichlorobenzene 7 94 119 101

trans-1,4-Dichloro-2-butene 7 94 118 103

Dichlorodifluoromethane (CFC-12) 1 7 61 112 81

1,1-Dichloroethane (1,1-DCA) 1 7 93 119 108

1,2-Dichloroethane (1,2-DCA) 1 7 96 122 106

1,1-Dichloroethene (1,1-DCE) 1 7 92 114 99

cis-1,2-Dichloroethene (cis-1,2-DCE) 1 7 90 118 107

trans-1,2-Dichloroethene (trans-1,2-DCE) 1 7 92 114 109

1,2-Dichloropropane 7 91 114 103

1,3-Dichloropropane 7 92 118 107

2,2-Dichloropropane 7 74 104 100

1,1-Dichloropropene 7 92 105 101

cis-1,3-Dichloropropene 7 87 103 98

trans-1,3-Dichloropropene 7 89 102 97

Diethyl ether 7 88 121 116

Diisopropyl ether (DIPE) 1 7 90 120 112
160 Groundwater-Quality Data in Seven GAMA Study Units: Results from Initial Sampling and Resampling of Wells

Constituent Number of 

spike samples

Minimum recovery 

(percent)

Maximum recovery 

(percent)

Median recovery 

(percent)

Ethylbenzene 1 7 98 117 103

Ethyl tert-butyl ether (ETBE) 7 94 120 105

Ethyl methacrylate 7 94 113 100

Ethyl methyl ketone (2-butanone) 1 7 93 123 111

o-Ethyl toluene (2-ethyl toluene) 7 95 115 101

Hexachlorobutadiene 7 69 112 84

Hexachloroethane 7 90 110 97

2-Hexanone (n-Butyl methyl ketone) 7 93 124 113

Iodomethane (Methyl iodide) 7 67 121 112

Isopropylbenzene 7 93 120 103

4-Isopropyl-1-methyl benzene (p-isopropyltoluene) 7 88 113 100

Methyl acrylate 7 93 116 106

Methyl acrylonitrile 7 90 121 110

Methyl tert-butyl ether (MTBE) 1 7 90 122 108

Methyl iso-butyl ketone (MIBK) 7 100 121 104

Methylene chloride (Dichloromethane) 1 7 93 114 100

Methyl methacrylate 7 89 112 102

Naphthalene 7 91 113 101

n-Propylbenzene 7 90 114 101

Styrene 7 75 114 102

1,1,1,2-Tetrachloroethane 7 89 116 108

1,1,2,2-Tetrachloroethane 7 94 128 106

Tetrachloroethene (PCE, Perchloroethene) 1 7 91 110 101

Tetrahydrofuran 7 94 123 113

1,2,3,4-Tetramethylbenzene 7 89 107 100

1,2,3,5-Tetramethylbenzene 7 94 116 104

Toluene 7 97 110 102

1,2,3-Trichlorobenzene 7 94 114 104

1,2,4-Trichlorobenzene 7 81 103 99

1,1,1-Trichloroethane (1,1,1-TCA) 1 7 93 121 108

1,1,2-Trichloroethane (1,1,2-TCA) 7 92 116 106

Trichloroethene (TCE) 1 7 90 110 97

Trichlorofluoromethane (CFC-11) 1 7 94 116 108

1,2,3-Trichloropropane (1,2,3-TCP) 7 95 128 100

Trichlorotrifluoroethane (CFC-113) 1 7 81 104 95

1,2,3-Trimethylbenzene 7 93 127 109

1,2,4-Trimethylbenzene 7 93 173 104

1,3,5-Trimethylbenzene 7 97 118 103

Vinyl bromide (Bromoethene) 7 85 116 101

Vinyl chloride (Chloroethene) 7 88 117 103

m- plus p-Xylene 1 7 100 118 107

o-Xylene 1 7 94 120 104

1

 Constituent detected in groundwater samples.

Table A5A. Quality-control summary for matrix-spike recoveries of volatile organic compounds (VOCs) in spiked samples collected for 

trends in seven Groundwater Ambient Monitoring and Assessment (GAMA) Priority Basin Project study units.—Continued

[Acceptable recovery range is between 70 and 130 percent]
Appendix 161

Table A5B. Quality-control summary for matrix-spike recoveries of low-level fumigants in spiked samples collected for trends in seven 

Groundwater Ambient Monitoring and Assessment (GAMA) Priority Basin Project study units.

[Acceptable recovery range is between 70 and 130 percent]

Constituent Number of 

spike samples

Minimum recovery 

(percent)

Maximum recovery 

(percent)

Median recovery 

(percent)

1,2-Dibromo-3-chloropropane (DBCP) 1 2 96 129 112

1,2-Dibromoethane (EDB) 2 90 123 106

1

 Constituent detected in groundwater samples.
162 Groundwater-Quality Data in Seven GAMA Study Units: Results from Initial Sampling and Resampling of Wells

Table A5C. Quality-control summary for matrix-spike recoveries of pesticides and pesticide degradates (Laboratory 

Schedules 2003/2032/2033) in spiked samples collected for trends in seven Groundwater Ambient Monitoring and Assessment (GAMA) 

Priority Basin Project study units.

[Acceptable recovery range is between 70 and 130 percent]

Constituent Number of 

spike samples

Minimum recovery 

(percent)

Maximum recovery 

(percent)

Median recovery 

(percent)

Acetochlor 5 59 96 67

Alachlor 5 64 100 74

Atrazine 1 5 66 100 83

Azinphos-methyl 5 38 72 64

Azinphos-methyl oxon 5 16 58 41

Benfluralin 5 43 63 46

Carbaryl 5 48 92 80

Carbofuran 1 70 70 70

2-Chloro-2,6-diethylacetanilide 5 58 88 73

4-Chloro-2-methylphenol 5 43 83 59

Chlorpyrifos 5 50 84 63

Chlorpyrifos oxon 5 0 55 15

Cyanazine 1 85 85 85

Cyfluthrin 5 35 51 46

λ-Cyhalothrin 1 48 48 48

Cypermethrin 5 36 49 44

DCPA (Dacthal) 1 5 71 99 88

Deethylatrazine (2-Chloro-4-isopropylamino-6-amino-s-triazine) 15 32 55 43

Desulfinylfipronil 1 5 46 91 81

Desulfinylfipronil amide 5 46 90 78

Diazinon 5 66 85 76

3,4-Dichloroaniline 1 5 52 87 73

3,5-Dichloroaniline 1 1 91 91 91

Dichlorvos 5 5 26 8

Dicrotophos 5 13 47 28

Dieldrin 5 75 104 87

2,6-Diethylaniline 5 71 92 82

Dimethoate 5 25 36 36

Disulfoton 1 78 78 78

Disulfoton sulfone 1 83 83 83

α-Endosulfan 1 79 79 79

Endosulfan sulfate 1 82 82 82

Ethion 5 47 97 64

Ethion monoxon 5 49 75 68

Ethoprophos 1 79 79 79

S-Ethyl-dipropylthiocarbamate (EPTC) 1 1 88 88 88

2-Ethyl-6-methylaniline 1 5 72 94 85

Fenamiphos 5 45 90 66

Fenamiphos sulfone 5 41 76 64

Fenamiphos sulfoxide 5 10 79 35

Fipronil 1 5 45 75 59

Fipronil sulfide 1 5 36 94 66
Appendix 163

Constituent Number of 

spike samples

Minimum recovery 

(percent)

Maximum recovery 

(percent)

Median recovery 

(percent)

Fipronil sulfone 5 33 77 54

Fonofos 5 66 85 71

Hexazinone 1 5 36 61 55

Iprodione 5 36 61 53

Isofenphos 5 53 83 69

Malaoxon 5 41 97 54

Malathion 5 52 85 66

Metalaxyl 5 59 85 80

Methidathion 5 56 99 73

Metolachlor 5 60 91 76

Metribuzin 5 53 72 60

Molinate 1 90 90 90

Myclobutanil 5 62 93 69

1-Naphthol 5 15 41 28

Oxyfluorfen 1 69 69 69

Paraoxon-methyl 5 25 50 35

Parathion-methyl 5 52 64 62

Pendimethalin 5 57 80 64

cis-Permethrin 5 34 81 39

Phorate 5 38 69 51

Phorate oxon 5 49 71 67

Phosmet 5 10 30 26

Phosmet oxon 5 0 31 9

Prometon 1 5 58 87 68

Prometryn 5 58 103 75

Pronamide 5 57 96 71

Propanil 1 82 82 82

Propargite 1 61 61 61

cis-Propiconazole 1 89 89 89

trans-Propiconazole 1 85 85 85

Simazine 1 5 57 101 74

Tebuconazole 1 52 52 52

Tebuthiuron 1 5 89 210 138

Tefluthrin 1 46 46 46

Terbufos 5 49 210 75

Terbufos oxon sulfone 5 44 75 51

Terbuthylazine 5 68 94 82

Thiobencarb 1 98 98 98

Tribufos 5 29 65 51

Trifluralin 5 49 68 52

1

 Constituent detected in groundwater samples.

Table A5C. Quality-control summary for matrix-spike recoveries of pesticides and pesticide degradates (Laboratory 

Schedules 2003/2032/2033) in spiked samples collected for trends in seven Groundwater Ambient Monitoring and Assessment (GAMA) 

Priority Basin Project study units.—Continued

[Acceptable recovery range is between 70 and 130 percent]
164 Groundwater-Quality Data in Seven GAMA Study Units: Results from Initial Sampling and Resampling of Wells

Table A5D. Quality-control summary for matrix-spike recoveries of polar pesticides, pesticide degradates, and caffeine (Laboratory 

Schedule 2060) in spiked samples collected for trends in seven Groundwater Ambient Monitoring and Assessment (GAMA) Priority 

Basin Project study units.

[Acceptable recovery range is between 70 and 130 percent]

Constituent Number of 

spike samples

Minimum recovery 

(percent)

Maximum recovery 

(percent)

Median recovery 

(percent)

Acifluorfen 2 64 73 69

Aldicarb 2 70 76 73

Aldicarb sulfone 2 59 77 68

Aldicarb sulfoxide 2 96 100 98

Atrazine 1 2 99 109 104

Bendiocarb 2 77 88 83

Benomyl 2 73 77 75

Bensulfuron-methyl 2 118 139 129

Bentazon 2 79 82 81

Bromacil 2 72 89 81

Bromoxynil 2 77 85 81

Caffeine 1 2 78 83 81

Carbaryl 2 88 91 90

Carbofuran 2 100 102 101

Chloramben, methyl ester 2 84 85 85

Chlorimuron-ethyl 2 133 157 145

3-(4-Chlorophenyl)-1-methyl urea 2 45 82 64

Clopyralid 2 68 77 73

Cycloate 2 61 84 73

2,4-D plus 2,4-D methyl ester 2 82 89 86

2,4-DB (4-(2,4-Dichlorophenoxy)butyric acid) 2 78 81 80

DCPA (Dacthal) monoacid 2 85 87 86

Deethylatrazine (2-Chloro-4-isopropylamino6-amino-s-triazine) 12 78 89 84

Deisopropyl atrazine (2-Chloro-6-ethylamino4-amino-s-triazine) 12 82 104 93

Dicamba 2 66 71 69

Dichlorprop 2 96 98 97

Dinoseb (Dinitrobutyl phenol) 2 85 88 87

Diphenamid 2 104 111 108

Diuron 1 2 93 103 98

Fenuron 2 99 104 102

Flumetsulam 2 133 161 147

Fluometuron 2 95 95 95

Hydroxyatrazine (2-Hydroxy-4-isopropylamino-6-ethylamino-s-triazine)2 86 121 104

3-Hydroxycarbofuran 2 86 86 86

Imazaquin 2 128 141 135

Imazethapyr 2 111 121 116

Imidacloprid 2 108 109 109

Linuron 2 86 98 92

MCPA (2-Methyl-4-chlorophenoxyacetic acid) 2 92 94 93
Appendix 165

Constituent Number of 

spike samples

Minimum recovery 

(percent)

Maximum recovery 

(percent)

Median recovery 

(percent)

MCPB (4-(2-Methyl-4-chlorophenoxy)butyric 

acid)

2 69 74 72

Metalaxyl 2 101 103 102

Methiocarb 2 83 105 94

Methomyl 2 98 105 102

Metsulfuron methyl 2 108 181 145

Neburon 2 93 94 94

Nicosulfuron 2 287 346 317

Norflurazon 2 104 110 107

Oryzalin 2 83 84 84

Oxamyl 2 92 94 93

Picloram 2 72 76 74

Propham 2 61 91 76

Propiconazole 2 84 87 86

Propoxur 2 102 102 102

Siduron 2 105 123 114

Sulfometuron-methyl 1 2 126 145 136

Tebuthiuron 1 2 110 122 116

Terbacil 2 78 87 83

Triclopyr 2 84 92 88

1

 Constituent detected in groundwater samples.

Table A5D. Quality-control summary for matrix-spike recoveries of polar pesticides, pesticide degradates, and caffeine (Laboratory 

Schedule 2060) in spiked samples collected for trends in seven Groundwater Ambient Monitoring and Assessment (GAMA) Priority 

Basin Project study units.—Continued

[Acceptable recovery range is between 70 and 130 percent]

Table A5E. Quality-control summary for matrix-spike recoveries of the constiuent of special interest1, 1,2,3-trichloropropane, in spiked 

samples collected for trends in seven Groundwater Ambient Monitoring and Assessment (GAMA) Priority Basin Project study units.

[Acceptable recovery range is between 70 and 130 percent]

Constituent Number of 

spike samples

Minimum recovery 

(percent)

Maximum recovery 

(percent)

Median recovery 

(percent)

1,2,3-Trichloropropane (1,2,3-TCP) 2 3 88 147 118

1

 Matrix spikes were not collected for perchlorate or N-nitrosodimethylamine during re-sampling for trends.

2

 Constituent detected in groundwater samples.
166 Groundwater-Quality Data in Seven GAMA Study Units: Results from Initial Sampling and Resampling of Wells Table A6. Quality-control summary for surrogate recoveries of volatile organic compounds (VOCs), pesticides and pesticide degradates, and polar pesticides and degradates in samples collected for trends in seven Groundwater Ambient Monitoring and Assessment (GAMA) study units. [Values underlined and in bold font represent recoveries greater than 130 percent; values underlined and in italic font represent recoveries less than 70 percent. GAMA well identification number acronyms: San Diego Drainages study unit: SDALLV, Alluvial Basins study area; SDHDRK, Hard Rock study area; SDTEM, Temecula Valley study area; SDTEMFP, Temecula Valley study area flow-path well; SDWARN, Warner Valley study area. North San Francisco Bay study unit: NSFVOL, Volcanic Highlands study area; NSFVP, Valley and Plains study area; NSFWG, Wilson Grove Formation Highlands study area; NSFWGFP, Wilson Grove Formation Highlands study area flow-path well. Northern San Joaquin Basin study unit: COS, Cosumnes Basin study area; ESJ, Eastern San Joaquin Basin study area; NSJ-QPC, Uplands study area; TRCY, Tracy Basin study area. Southern Sacramento Valley study unit: NAM, North American study area; SAM, South American study area; SOL, Solano study area; SSV-QPC, Uplands study area; SUI, Suisun-Fairfield study area; YOL, Yolo study area. San Fernando–San Gabriel study unit: ULASF, San Fernando study area; ULASG, San Gabriel study area. Monterey Bay and Salinas Valley Basins study unit: MSSC, Santa Cruz study area; MSMB, Monterey Bay study area; MSPR, Paso Robles study area; MSSC, Santa Cruz study area; MSSV, Salinas Valley study area. Southeast San Joaquin Valley study unit: KING, Kings study area; KWH, Kaweah study area; TLR, Tulare Lake study area; TULE, Tule study area. Abbreviations: NWQL SC, National Water Quality Laboratory schedule; E, estimated or having a high degree of uncertainty; >, greater than; <, less than] GAMA well identification number Surrogates Volatile organic compounds NWQL SC 2020 Pesticides and degradates NWQL SC 2003/2032/2033 Polar pesticides NWQL SC 2060 1,2-Dichloroethane-d4 Toluene-d8 1-Bromo-4- fluorobenzene alpha-HCH-d6 Diazinon-d10 2,4,5-T Barban Caffeine-13C 2004–05 2007–08 2004–05 2007–08 2004–05 2007–08 2004–05 2007–08 2004–05 2007–08 2004–05 2007–08 2004–05 2007–08 2004–05 2007–08 San Diego Drainages study unit SDALLV-07 120 116 101 76 103 95 71 88 71 93 nc nc nc nc nc nc SDALLV-11 132 111 102 88 106 99 82 90 76 101 nc nc nc nc nc nc SDHDRK-01 122 109 99 92 98 100 92 86 94 95 nc nc nc nc nc nc SDHDRK-09 110 112 99 79 97 95 78 90 72 98 nc nc nc nc nc nc SDTEM-04 109 125 99 75 92 95 84 nc 63 nc nc nc nc nc nc nc SDTEMFP-01 121 126 99 74 84 96 93 88 110 96 95 nc 124 nc 132 nc SDWARN-01 95 114 102 79 104 94 77 83 72 87 nc nc nc nc nc nc North San Francisco Bay study unit NSFVOL-14 117 144 100 71 96 94 95 93 86 96 87 70 84 79 96 60 NSFVOL-18 112 115 97 92 93 100 89 88 83 78 86 nc 82 nc 71 nc NSFVP-29 115 107 101 105 97 100 90 69 72 91 97 83 89 66 124 E70 NSFVP-34 111 138 98 71 98 91 87 94 75 101 77 71 80 84 E135 98 NSFVP-36 117 136 97 68 94 91 95 89 79 94 72 nc 79 nc 69 nc NSFVP-38 119 147 96 71 91 94 101 108 85 119 74 70 71 75 101 59 NSFVP-39 115 93 94 77 94 99 107 86 91 93 72 nc 63 nc 61 nc NSFVP-41 116 135 96 69 92 94 104 90 90 94 76 nc 80 nc 71 nc NSFWG-03 110 120 100 93 79 100 74 68 54 67 79 nc 82 nc 67 nc NSFWGFP-01 119 100 107 87 106 98 84 85 70 91 92 89 112 76 129 E50
Appendix 167

GAMA 

well 

identification 

number

Surrogates

Volatile organic compounds

NWQL SC 2020

Pesticides and degradates

NWQL SC 2003/2032/2033

Polar pesticides

NWQL SC 2060

1,2-Dichloroethane-d4 Toluene-d8 1-Bromo-4- fluorobenzene alpha-HCH-d6 Diazinon-d10 2,4,5-T Barban Caffeine-13C

2004–05 2007–08 2004–05 2007–08 2004–05 2007–08 2004–05 2007–08 2004–05 2007–08 2004–05 2007–08 2004–05 2007–08 2004–05 2007–08

Northern San Joaquin Basin study unitCOS-08 108 120 97 89 102 97 77 79 56 80 nc nc nc nc nc ncESJ-01 110 121 94 88 101 97 82 78 76 79 nc nc nc nc nc ncESJ-06 111 120 95 91 105 98 88 84 60 86 nc nc nc nc nc ncNSJ-QPC-04 111 132 104 94 120 100 102 81 79 89 nc nc nc nc nc ncTRCY-03 112 133 93 91 103 101 124 76 105 68 E123 nc 117 nc 110 ncSouthern Sacramento Valley study unitNAM-03 96 103 92 86 79 97 97 90 67 70 89 nc 81 nc 83 ncSAM-10 102 139 99 88 94 99 102 90 98 75 85 nc 88 nc 83 ncSOL-08 100 136 99 82 96 97 119 83 97 73 87 nc 79 nc 70 ncSSV-QPC-07 103 134 97 102 96 106 101 94 107 69 102 85 91 83 E143 72SUI-03 143 128 103 100 80 104 nc 94 nc 95 86 nc 81 nc 71 ncYOL-01 125 126 104 89 83 97 94 92 85 91 83 nc 82 nc 62 ncYOL-14 105 131 100 100 93 104 89 89 93 101 84 76 106 75 115 74San Fernando–San Gabriel study unitULASF-09 114 108 98 90 94 94 99 78 99 65 67 70 86 50 118 66ULASF-10 119 109 99 88 84 96 99 91 90 100 73 75 91 70 127 75ULASG-01 124 131 96 95 62 101 92 85 85 78 E55 nc 86 nc 82 ncULASG-08 104 125 99 91 100 99 102 92 97 79 80 E100 78 84 106 90ULASG-15 93 126 96 95 88 100 88 95 83 97 89 E97 92 83 E121 95ULASG-17 99 129 104 98 92 102 100 99 102 94 E101 nc 86 nc 96 nc

Table A6. Quality-control summary for surrogate recoveries of volatile organic compounds (VOCs), pesticides and pesticide degradates, and polar pesticides and degradates in samples collected for trends in seven Groundwater Ambient Monitoring and Assessment (GAMA) study units.—Continued[Values underlined and in bold font represent recoveries greater than 130 percent; values underlined and in italic font represent recoveries less than 70 percent. GAMA well identification number acronyms: San Diego Drainages study unit: SDALLV, Alluvial Basins study area; SDHDRK, Hard Rock study area; SDTEM, Temecula Valley study area; SDTEMFP, Temecula Valley study area flow-path well; SDWARN, Warner Valley study area. North San Francisco Bay study unit: NSFVOL, Volcanic Highlands study area; NSFVP, Valley and Plains study area; NSFWG, Wilson Grove Formation Highlands study area; NSFWGFP, Wilson Grove Formation Highlands study area flow-path well. Northern San Joaquin Basin study unit: COS, Cosumnes Basin study area; ESJ, Eastern San Joaquin Basin study area; NSJ-QPC, Uplands study area; TRCY, Tracy Basin study area. Southern Sacramento Valley study unit: NAM, North American study area; SAM, South American study area; SOL, Solano study area; SSV-QPC, Uplands study area; SUI, Suisun-Fairfield study area; YOL, Yolo study area. San Fernando–San Gabriel study unit: ULASF, San Fernando study area; ULASG, San Gabriel study area. Monterey Bay and Salinas Valley Basins study unit: MSSC, Santa Cruz study area; MSMB, Monterey Bay study area; MSPR, Paso Robles study area; MSSC, Santa Cruz study area; MSSV, Salinas Valley study area. Southeast San Joaquin Valley study unit: KING, Kings study area; KWH, Kaweah study area; TLR, Tulare Lake study area; TULE, Tule study area. Abbreviations: NWQL SC, National Water Quality Laboratory schedule; E, estimated or having a high degree of uncertainty; >, greater than; <, less than]
168 Groundwater-Quality Data in Seven GAMA Study Units: Results from Initial Sampling and Resampling of Wells GAMA well identification number Surrogates Volatile organic compounds NWQL SC 2020 Pesticides and degradates NWQL SC 2003/2032/2033 Polar pesticides NWQL SC 2060 1,2-Dichloroethane-d4 Toluene-d8 1-Bromo-4- fluorobenzene alpha-HCH-d6 Diazinon-d10 2,4,5-T Barban Caffeine-13C 2004–05 2007–08 2004–05 2007–08 2004–05 2007–08 2004–05 2007–08 2004–05 2007–08 2004–05 2007–08 2004–05 2007–08 2004–05 2007–08 Monterey Bay and Salinas Valley Basins study unit MSMB-03 93 103 101 81 104 100 89 89 88 85 nc nc nc nc nc nc MSMB-04 103 100 94 78 84 100 91 92 100 91 E125 nc 101 nc 148 nc MSMB-16 109 134 95 72 83 94 83 80 89 66 nc nc nc nc nc nc MSMB-28 144 138 105 79 70 95 69 83 68 71 nc nc nc nc nc nc MSMB-31 109 137 100 82 96 95 85 82 75 76 nc nc nc nc nc nc MSPR-03 105 104 102 92 113 98 93 90 98 91 nc nc nc nc nc nc MSPR-09 127 106 101 94 61 100 100 88 86 98 nc nc nc nc nc nc MSSC-06 104 135 99 73 95 93 100 78 107 69 E128 nc 110 nc E126 nc MSSC-11 87 139 93 75 95 94 82 89 86 90 nc nc nc nc nc nc MSSV-06 140 102 104 92 70 99 69 80 55 63 nc nc nc nc nc nc MSSV-15 125 103 100 92 69 100 82 75 78 63 nc nc nc nc nc nc Southeast San Joaquin Valley study unit KING-11 116 126 93 87 84 98 71 77 57 65 E138 nc 111 nc 137 nc KING-13 112 124 93 86 81 99 85 84 66 72 162 nc 116 nc 140 nc KING-17 158 126 92 87 69 99 76 86 55 72 171 nc 102 nc 132 nc KING-24 95 118 100 88 98 98 83 78 82 106 nc nc nc nc nc nc KWH-10 95 127 100 86 95 98 82 89 77 92 nc nc nc nc nc nc KWH-12 97 108 105 97 118 99 77 78 78 67 130 nc 94 nc 127 nc TLR-03 97 122 98 91 96 97 79 77 81 78 nc nc nc nc nc nc

TULE-05 103 121 99 89 100 99 82 80 98 81 nc nc nc nc nc ncTULE-10 105 123 97 90 98 99 74 82 67 67 nc nc nc nc nc nc

Table A6. Quality-control summary for surrogate recoveries of volatile organic compounds (VOCs), pesticides and pesticide degradates, and polar pesticides and degradates in samples collected for trends in seven Groundwater Ambient Monitoring and Assessment (GAMA) study units.—Continued[Values underlined and in bold font represent recoveries greater than 130 percent; values underlined and in italic font represent recoveries less than 70 percent. GAMA well identification number acronyms: San Diego Drainages study unit: SDALLV, Alluvial Basins study area; SDHDRK, Hard Rock study area; SDTEM, Temecula Valley study area; SDTEMFP, Temecula Valley study area flow-path well; SDWARN, Warner Valley study area. North San Francisco Bay study unit: NSFVOL, Volcanic Highlands study area; NSFVP, Valley and Plains study area; NSFWG, Wilson Grove Formation Highlands study area; NSFWGFP, Wilson Grove Formation Highlands study area flow-path well. Northern San Joaquin Basin study unit: COS, Cosumnes Basin study area; ESJ, Eastern San Joaquin Basin study area; NSJ-QPC, Uplands study area; TRCY, Tracy Basin study area. Southern Sacramento Valley study unit: NAM, North American study area; SAM, South American study area; SOL, Solano study area; SSV-QPC, Uplands study area; SUI, Suisun-Fairfield study area; YOL, Yolo study area. San Fernando–San Gabriel study unit: ULASF, San Fernando study area; ULASG, San Gabriel study area. Monterey Bay and Salinas Valley Basins study unit: MSSC, Santa Cruz study area; MSMB, Monterey Bay study area; MSPR, Paso Robles study area; MSSC, Santa Cruz study area; MSSV, Salinas Valley study area. Southeast San Joaquin Valley study unit: KING, Kings study area; KWH, Kaweah study area; TLR, Tulare Lake study area; TULE, Tule study area. Abbreviations: NWQL SC, National Water Quality Laboratory schedule; E, estimated or having a high degree of uncertainty; >, greater than; <, less than]
Appendix 169

Surrogates

Volatile organic compounds

NWQL SC 2020

Pesticides and degradates

NWQL SC 2003/2032/2033

Polar pesticides

NWQL SC 2060

1,2-Dichloroethane-d4 Toluene-d8 1-Bromo-4- fluorobenzene alpha-HCH-d6 Diazinon-d10 2,4,5-T Barban Caffeine-13C

2004–05 2007–08 2004–05 2007–08 2004–05 2007–08 2004–05 2007–08 2004–05 2007–08 2004–05 2007–08 2004–05 2007–08 2004–05 2007–08

Summary:Median recovery 

(percent)

111 124 99 88 95 98 88 86 83 86 87 76 86 76 110 72

Number of recoveries 

<70 percent

0 0 0 2 4 0 2 2 12 11 2 0 1 2 4 4

Number of recoveries 

>130 percent

5 17 0 0 0 0 0 0 0 0 4 0 0 0 7 0

Table A6. Quality-control summary for surrogate recoveries of volatile organic compounds (VOCs), pesticides and pesticide degradates, and polar pesticides and degradates in samples collected for trends in seven Groundwater Ambient Monitoring and Assessment (GAMA) study units.—Continued[Values underlined and in bold font represent recoveries greater than 130 percent; values underlined and in italic font represent recoveries less than 70 percent. GAMA well identification number acronyms: San Diego Drainages study unit: SDALLV, Alluvial Basins study area; SDHDRK, Hard Rock study area; SDTEM, Temecula Valley study area; SDTEMFP, Temecula Valley study area flow-path well; SDWARN, Warner Valley study area. North San Francisco Bay study unit: NSFVOL, Volcanic Highlands study area; NSFVP, Valley and Plains study area; NSFWG, Wilson Grove Formation Highlands study area; NSFWGFP, Wilson Grove Formation Highlands study area flow-path well. Northern San Joaquin Basin study unit: COS, Cosumnes Basin study area; ESJ, Eastern San Joaquin Basin study area; NSJ-QPC, Uplands study area; TRCY, Tracy Basin study area. Southern Sacramento Valley study unit: NAM, North American study area; SAM, South American study area; SOL, Solano study area; SSV-QPC, Uplands study area; SUI, Suisun-Fairfield study area; YOL, Yolo study area. San Fernando–San Gabriel study unit: ULASF, San Fernando study area; ULASG, San Gabriel study area. Monterey Bay and Salinas Valley Basins study unit: MSSC, Santa Cruz study area; MSMB, Monterey Bay study area; MSPR, Paso Robles study area; MSSC, Santa Cruz study area; MSSV, Salinas Valley study area. Southeast San Joaquin Valley study unit: KING, Kings study area; KWH, Kaweah study area; TLR, Tulare Lake study area; TULE, Tule study area. Abbreviations: NWQL SC, National Water Quality Laboratory schedule; E, estimated or having a high degree of uncertainty; >, greater than; <, less than]
170 Groundwater-Quality Data in Seven GAMA Study Units: Results from Initial Sampling and Resampling of Wells

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Kent and otherrs—Groundwater-Quality Data in Seven GAMA Study Units: Results from Initial Sampling, 2004–2005, and Resampling, 2007–2008, 

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