Long Beach

Los Angeles

Anaheim

Beverly Hills

Santa

Monica

Central Basin

Hollywood Basin

Santa Monica

Basin

Orange County 

Coastal Plain

West Coast Basin

Data Series 387

Version 1.1, March 2009

Ground-Water Quality Data in the Coastal Los Angeles Basin

Study Unit, 2006: Results from the California GAMA Program

In cooperation with the California State Water Resources Control Board

U.S. Geological Survey

U.S. Department of the Interior
Cover: Top photograph: Refinery in Long Beach, California. 

Bottom: Beverly Hills, California. Photographs taken by Dara Goldrath, U.S. Geological Survey.
Ground-Water Quality Data in the Coastal 

Los Angeles Basin Study Unit, 2006: 

Results from the California GAMA Program

By Timothy M. Mathany, Michael Land, and Kenneth Belitz

Prepared in cooperation with the California State Water Resources Control Board

Data Series 387

Version 1.1, March 2009

U.S. Department of the Interior

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

DIRK KEMPTHORNE, Secretary

U.S. Geological Survey

Mark D. Myers, Director

U.S. Geological Survey, Reston, Virginia: 2008

For product and ordering information:

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natural hazards, and the environment:

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U.S. Government.

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

reproduce any copyrighted materials contained within this report.

Suggested reference:

Mathany, T.M., Land, Michael, and Belitz, Kenneth, 2008, Ground-water quality data in the coastal Los Angeles Basin 

Study Unit, 2006: Results from the California GAMA Program: U.S. Geological Survey Data Series 387, 98 p. Available 

at http://pubs.usgs.gov/ds/387/
iii

Contents

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

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

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

Acknowledgments ...............................................................................................................................4

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

Methods...........................................................................................................................................................6

Study Design..........................................................................................................................................6

Sample Collection and Analysis.......................................................................................................10

Data Reporting.....................................................................................................................................10

Quality-Assurance..............................................................................................................................10

Quality-Control Sample Results........................................................................................................11

Comparison Thresholds.....................................................................................................................11

Ground-Water-Quality Data .......................................................................................................................12

Field Parameters.................................................................................................................................12

Organic Constituents..........................................................................................................................12

Constituents of Special Interest.......................................................................................................13

Inorganic Constituents.......................................................................................................................13

Inorganic Tracer Constituents ..........................................................................................................14

Radioactive Constituents...................................................................................................................14

Microbial Indicators...........................................................................................................................15

Future Work ..................................................................................................................................................15

Summary........................................................................................................................................................15

References Cited..........................................................................................................................................16

Appendix .......................................................................................................................................................77
iv

Figures

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

Groundwater Ambient Monitoring and Assessment (GAMA) study with the 

Coastal Los Angeles Basin study unit outlined .......................................... 3

Figure 2. Map showing the Coastal Los Angeles Basin GAMA study unit, locations 

of study areas, major cities, rivers, reservoirs, salt-water barrier projects, 

CDPH and USGS public-supply wells, topographic features, and 

ground-water basins ........................................................................ 5

Figure 3. Map showing the Orange County Coastal Plain study area, the distribution of the 

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

wells in the Coastal Los Angeles Basin GAMA study unit, California ............... 7

Figure 4. Map showing the West Coast Basin and Central Basin study areas, the 

distribution of study area grid cells, and the locations of sampled grid wells 

and understanding wells in the Coastal Los Angeles Basin GAMA study unit, 

California .................................................................................... 8

Figure 5. Map showing the Santa Monica Basin and Hollywood Basin study areas, and 

the locations of direct assessment wells sampled in the Coastal Los Angeles 

Basin GAMA study unit, California ...................................................... 9

Tables

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

Coastal Los Angeles Basin Groundwater Ambient Monitoring and Assessment 

(GAMA) study, California, June to November 2006 .................................... 22

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

collected for the slow, intermediate, and fast well sampling schedules in the 

Coastal Los Angeles Basin Groundwater Ambient Monitoring and Assessment 

(GAMA) study, California, June to November 2006 .................................... 24

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

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

Laboratory Schedule 2020 .................................................................. 25

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

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

Water Quality Laboratory Schedule 4024 ................................................ 27

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

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

Water Quality Laboratory Schedule 2003 ................................................ 28

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

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

Water Quality Laboratory Schedule 2060 ................................................ 30

Table 3E. Potential wastewater indicators, primary uses or sources, comparative 

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

Water Quality Laboratory Schedule 4433 ................................................ 32

Table 3F. Pharmaceutical compounds, primary uses or sources, comparative thresholds, 

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

Laboratory Schedule 2080 .................................................................. 35

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

thresholds, and reporting information for compounds analyzed at the 

Montgomery Watson-Harza Laboratory ................................................ 36
v

Tables—Continued

Table 3H. Nutrients and dissolved organic carbon, comparative thresholds, and reporting 

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

Schedule 2755 and parameter code 2612. ................................................ 36

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

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

Schedule 1948. .............................................................................. 37

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

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

Colorado. .................................................................................... 38

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

information for laboratories. ............................................................... 39

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

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

90901, 90900, 99335 and 99332. ............................................................ 40

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

the Lawrence Livermore National Laboratory. .......................................... 40

Table 4. Water-quality indicators in samples collected for the Coastal Los Angeles 

Basin Groundwater Ambient Monitoring and Assessment (GAMA) study unit, 

California, June to November 2006. ...................................................... 41

Table 5. Volatile organic compounds (VOCs), and gasoline oxygenates and degradates 

detected in samples collected for the Coastal Los Angeles Basin Groundwater 

Ambient Monitoring and Assessment (GAMA) study unit, California, June to 

November 2006............................................................................... 43

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

Coastal Los Angeles Basin Groundwater Ambient Monitoring and Assessment 

(GAMA) study unit, California, June to November 2006. .............................. 53

Table 7. Polar pesticides and pesticide degradates detected in samples collected for the 

Coastal Los Angeles Basin Groundwater Ambient Monitoring and Assessment 

(GAMA) study unit, California, June to November 2006. .............................. 57

Table 8. Potential wastewater indicators detected in samples collected for the Coastal 

Los Angeles Basin Groundwater Ambient Monitoring and Assessment (GAMA) 

study unit, California, June to November 2006. .......................................... 58

Table 9. Results of analyses for the constituents of special interest: perchlorate, 

N-nitrosodimethylamine (NDMA), and 1,4-dioxane detected in the samples 

collected in the Coastal Los Angeles Basin Ground-Water Ambient Monitoring 

and Assessment (GAMA) study unit, California, June to November 2006............. 65

Table 10. Nutrients and dissolved organic carbon detected in samples collected for the 

Coastal Los Angeles Basin Groundwater Ambient Monitoring and Assessment 

(GAMA) study unit, California, June to November 2006. .............................. 66

Table 11. Major and minor ions and dissolved solids detected in samples collected for the 

Coastal Los Angeles Basin Groundwater Ambient Monitoring and Assessment 

(GAMA) study unit, California, June to November 2006. .............................. 67

Table 12. Trace elements detected in samples collected for the Coastal Los Angeles 

Basin Groundwater Ambient Monitoring and Assessment (GAMA) study unit, 

California, June to November. ............................................................ 68

Table 13. Species of inorganic arsenic, iron, and chromium detected in samples collected 

for the Coastal Los Angeles Basin Groundwater Ambient Monitoring and 

Assessment (GAMA) study unit, California, June to November 2006. ............... 70
vi

Tables—Continued

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

tritium in samples collected for the Coastal Los Angeles Basin Groundwater 

Ambient Monitoring and Assessment (GAMA) study unit, California, June to 

November 2006............................................................................... 73

Table 15. Radioactive constituents detected in samples collected for the Coastal Los 

Angeles Basin Groundwater Ambient Monitoring and Assessment (GAMA) 

study unit, California, June to November 2006. .......................................... 74

Table 16. Microbial indicators detected in samples collected for the Coastal Los Angeles 

Basin Groundwater Ambient Monitoring and Assessment (GAMA) study unit, 

California, June to November 2006. ...................................................... 75

Table A1. Analytical methods used for the determination of organic, inorganic, and 

microbial constituents by the U.S. Geological Survey (USGS) National Water 

Quality Laboratory (NWQL) and additional contract laboratories ..................... 86

Table A2. Preferred analytical schedules for constituents appearing on multiple 

schedules for samples collected for the Coastal Los Angeles Basin Groundwater 

Ambient Monitoring and Assessment (GAMA) study unit, California, June to 

November 2006 .............................................................................. 88

Table A3. Constituents detected in field blanks collected for the Coastal Los Angeles Basin 

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

June to November 2006..................................................................... 89

Table A4. Quality-control summary of replicate analyses collected for the Coastal Los 

Angeles Basin Groundwater Ambient Monitoring and Assessment (GAMA) study 

unit, California, June to November 2006 ................................................ 90

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

compounds (VOCs) and gasoline oxygenates and degradates in samples 

collected for the Coastal Los Angeles Basin Groundwater Ambient Monitoring 

and Assessment (GAMA) study, California, June to November 2006 ............... 92

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

degradates in samples collected for the Coastal Los Angeles Basin Groundwater 

Ambient Monitoring and Assessment (GAMA) study unit, California, June to 

November 2006 .............................................................................. 94

Table A5C. Quality-control summary of matrix-spike recoveries for polar pesticides and 

pesticide degradates in samples collected for the Coastal Los Angeles Basin 

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

June to November 2006..................................................................... 95

Table A5D. Quality-control summary of matrix-spike recoveries for potential waste-water 

indicators in samples collected for the Coastal Los Angeles Basin Groundwater 

Ambient Monitoring and Assessment (GAMA) study unit, California, June to 

November 2006 .............................................................................. 96

Table A5E. Quality-control summary of matrix-spike recoveries for constituents of special 

interest in samples collected for the Coastal Los Angeles Basin Groundwater 

Ambient Monitoring and Assessment (GAMA) study unit, California, June to 

November 2006 .............................................................................. 97

Appendix Tables
vii

Appendix Tables—Continued

Abbreviations and Acronyms

AB Assembly Bill (through the California Assembly)

AL-US Action level (USEPA)

CAS Chemical Abstract Service (American Chemical Society)

CSU combined standard uncertainty

E estimated or having a higher degree of uncertainty

GAMA Groundwater Ambient Monitoring and Assessment program

GPS Global Positioning System

IRL interim reporting level

HAL-US Lifetime Health Advisory level (USEPA)

HPLC high-performance liquid chromatography

LRL laboratory reporting level

LSD land-surface datum

LT-MDL long-term method detection level

MCL-US maximum contaminant level (USEPA)

MCL-CA maximum contaminant level (CDPH)

MDL method detection limit

MRL minimum reporting level

MU method uncertainty

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

na not available

nc sample not collected

NL-CA California notification level (CDPH)

NWIS National Water Information System (USGS)

PCFF personal computer field forms

QC quality control

RPD relative percent difference

RSD relative standard deviation

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

SMCL-CA secondary maximum contaminant level (CDPH)

SMCL-US secondary maximum contaminant level (USEPA)

CLAB Coastal Los Angeles Basin study unit

CB Central Basin study area

DA Direct assessment wells

OC Orange County Coastal Plain study area

U Understanding wells

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

compounds, gasoline oxygenates and degradates, pesticides and pesticide 

degradates, potential waste-water indicators, and constituents of special 

interest, collected for the Coastal Los Angeles Basin Groundwater Ambient 

Monitoring and Assessment (GAMA) study unit, California, June to 

November 2006 .............................................................................. 98
viii

Abbreviations and Acronyms—Continued

WB West Coast Basin study area

SSMDC sample-specific minimum detectable concentration

TT-US Treatment Technique (USEPA)

US United States

V analyte detected in sample and an associated blank thus data are not included in 

ground-water-quality assessment

Organizations

CDPH California Department of Public Health 

USEPA U.S. Environmental Protection Agency

LLNL Lawrence Livermore National Laboratory

MWH Montgomery Watson-Harza

NAWQA National Water Quality Assessment (USGS)

NWQL National Water Quality Laboratory (USGS)

SWRCB State Water Resources Control Board (California)

USGS U.S. Geological Survey

Selected Chemical Names

CaCO3 calcium carbonate

CFC chlorofluorocarbon

CO3

-2 carbonate

DOC dissolved organic carbon

HCl hydrochloric acid

HCO3- bicarbonate

MTBE methyl tert-butyl ether

NDMA N-nitrosodimethylamine

PCE perchloroethene

TCP trichloropropane

TDS total dissolved solids

THM trihalomethane

VOC volatile organic compound
ix

Abbreviations and Acronyms—Continued

Units of Measure

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

Celsius and 1 atmosphere of pressure)

ft foot (feet)

in inch

L liter

mg milligram

mg/L milligrams per liter (parts per million)

mi mile

mL milliliter

μg/L micrograms per liter (parts per billion)

μL microliter

μm micrometer

pCi/L picocurie per liter

δiE 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 in per mil

Notes

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

°F = (1.8 × °C) + 32

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

(NAVD 88).

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

25°C).

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

or micrograms per liter (μg/L). Milligrams per liter is equivalent to parts per million (ppm) and 

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

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Ground-Water Quality Data in the Coastal Los Angeles 

Basin Study Unit, 2006: Results from the California GAMA 

Program

By Timothy M. Mathany, Michael Land, and Kenneth Belitz

Abstract

Ground-water quality in the approximately 860 squaremile Coastal Los Angeles Basin study unit (CLAB) was 

investigated from June to November of 2006 as part of the 

Statewide Basin Assessment Project of the Ground-Water 

Ambient Monitoring and Assessment (GAMA) Program. 

The GAMA Statewide Basin Assessment was developed in 

response to the Ground-Water 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 Coastal Los Angeles Basin study was designed to 

provide a spatially unbiased assessment of raw ground-water 

quality within CLAB, as well as a statistically consistent 

basis for comparing water quality throughout California. 

Samples were collected from 69 wells in Los Angeles and 

Orange Counties. Fifty-five of the wells were selected using a 

spatially distributed, randomized grid-based method to provide 

statistical representation of the study area (“grid wells”). 

Fourteen additional wells were selected to evaluate changes 

in ground-water chemistry or to gain a greater understanding 

of the ground-water quality within a specific portion of the 

Coastal Los Angeles Basin study unit (“understanding wells”). 

Ground-water samples were analyzed for: a large number 

of synthetic organic constituents [volatile organic compounds 

(VOCs), gasoline oxygenates and their degradates, pesticides, 

polar pesticides, and pesticide degradates, pharmaceutical 

compounds, and potential wastewater-indicators]; constituents 

of special interest [perchlorate, N-nitrosodimethylamine 

(NDMA), 1,4-dioxane, and 1,2,3-trichloropropane (1,2,3-

TCP)]; inorganic constituents that can occur naturally 

[nutrients, major and minor ions, and trace elements]; 

radioactive constituents [gross-alpha and gross-beta radiation, 

radium isotopes, and radon-222]; and microbial indicators. 

Naturally occurring isotopes [stable isotopic ratios of 

hydrogen and oxygen, and activities of tritium and carbon-14] 

and dissolved noble gases also were measured to help identify 

the sources and ages of the sampled ground water. 

Quality-control samples (blanks, replicates, and samples 

for matrix spikes) were collected at approximately one-fourth 

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

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

Field blanks rarely contained detectable concentrations of 

any constituent, suggesting that contamination was not a 

significant source of bias. Differences between replicate 

samples were within acceptable ranges, indicating acceptably 

low variability. Matrix spike recoveries were within acceptable 

ranges for most compounds. Assessment of the quality-control 

information resulted in applying “V” codes to approximately 

0.1 percent of the data collected for ground-water samples 

(meaning a constituent was detected in blanks as well as the 

corresponding environmental data). 

This study did not attempt to evaluate the quality of 

drinking water delivered to consumers; after withdrawal 

from the ground, water typically is treated, disinfected, 

and (or) blended with other waters to maintain acceptable 

drinking-water quality. Regulatory thresholds are applied 

to the treated drinking water that is served to the consumer, 

not to raw ground water. However, to provide some context 

for the results, concentrations of constituents measured in 

the raw ground water were compared with regulatory and 

non-regulatory health-based thresholds established by the 

U.S. Environmental Protection Agency (USEPA), California 

Department of Public Health (CDPH, formerly California 

Department of Health Services [CADHS]) and thresholds 

established for aesthetic concerns (secondary maximum 

contaminant levels, SMCL-CA) by CDPH. Comparisons 

between data collected for this study and drinking-water 

thresholds are for illustrative purposes only, and are not 

indicative of compliance or non-compliance with those 

thresholds.

VOCs were detected in almost three-quarters of the 

grid wells, and pesticides and pesticide degradates were 

detected in 42 percent of the grid wells. Potential wastewater 

indicators were detected in 44 percent of the grid wells. All of 

the detections of these organic compounds in samples from 

CLAB grid wells were below health-based thresholds, with 
2 Ground-Water Quality Data in the Coastal Los Angeles Basin Study Unit, 2006: Results from the California GAMA Program

the exception of tetrachloromethane (carbon tetrachloride), 

a VOC, which was detected above the MCL-CA. In 

CLAB understanding wells, there were two detections of 

trichloroethene (TCE) and one detection of perchloroethene 

(PCE) above the MCL-US.

Nutrient and trace-element concentrations in the CLAB 

grid wells were below health-based thresholds. There were 

two detections of boron above the NL-CA of 1,000 μg/L 

in the CLAB understanding wells. Activities of radioactive 

constituents in water samples collected in CLAB grid wells 

were below health-based thresholds, with the exception of 

two detections of radon-222 that were above the proposed 

MCL-US of 300 pCi/L; however, none of the samples had 

an activity above the proposed alternative MCL-US of 

4,000 pCi/L. Total coliforms were detected at one of CLAB’s 

understanding wells. Most of the samples from CLAB 

grid wells had concentrations of major elements and total 

dissolved solids below the non-enforceable thresholds set 

for aesthetic concerns. Four grid wells had total dissolved 

solids concentrations above the SMCL-CA recommended 

threshold (SMCL-CA threshold for total dissolved solids 

has a recommended value of 500 mg/L, and an upper value 

of 1,000 mg/L). There were two detections of manganese, 

and four detections of iron in CLAB grid wells above their 

respective SMCL-CAs, and a single detection of arsenic above 

the MCL-US. Two understanding wells had concentrations of 

chloride and sulfate above the recommended SMCL-CA (both 

have a recommended threshold value of 250 mg/L, an upper 

value of 500 mgL).

Introduction

Ground water comprises nearly half of the water used 

for public-supply in California (Hutson and others, 2004). To 

assess the quality of ground water from public-supply wells 

and establish a program for monitoring trends in ground-water 

quality, the State Water Resources Control Board (SWRCB), 

in collaboration with the U.S. Geological Survey (USGS) 

and Lawrence Livermore National Laboratory (LLNL), 

implemented a statewide ground-water-quality monitoring and 

assessment program (http://www.waterboards.ca.gov/gama. 

The GAMA program consists of three projects: Priority Basin 

project, conducted by the USGS (http://ca.water.usgs.gov/

gama/); Voluntary Domestic Well Assessment, conducted by 

the SWRCB; and Special Studies, conducted by LLNL. 

The SWRCB initiated the GAMA Priority Basin project 

in response to the Groundwater Quality Monitoring Act of 

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

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

monitor the quality of ground water used as public supply for 

municipalities in California. The project is a comprehensive 

assessment of statewide ground-water quality designed to help 

better understand and identify risks to ground-water resources, 

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

the USGS, in collaboration with the SWRCB, developed the 

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

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

project are inter-agency collaboration, and cooperation with 

local water agencies and well owners. Local participation in 

the project is entirely voluntary.

The GAMA Priority Basin project is unique in California 

because the data collected during the study include analyses 

for an extensive number of chemical constituents at very 

low concentrations, analyses that are not normally available. 

A broader understanding of ground-water composition 

will be especially useful for providing an early indication 

of changes in water quality, and for identifying the natural 

and human factors affecting water quality. Additionally, the 

GAMA Priority Basin project will analyze a broader suite of 

constituents than required by the California Department of 

Public Health (CDPH). An understanding of the occurrence 

and distribution of these constituents is important for the longterm management and protection of ground-water resources.

The range of hydrologic, geologic, and climatic 

conditions that exist in California must be considered in 

an assessment of ground-water quality. Belitz and others 

(2003) partitioned the State into ten hydrogeologic provinces, 

each with distinctive hydrologic, geologic, and climatic 

characteristics (fig. 1), and representative regions in all ten 

provinces were included in the project design. Eighty percent 

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

are located in ground-water basins within these hydrologic 

provinces. These ground-water basins, defined by the 

California Department of Water Resources, generally consist 

of relatively permeable, unconsolidated deposits of alluvial or 

volcanic origin (California Department of Water Resources, 

2003). Ground-water basins were prioritized for sampling 

based upon the number of public-supply wells in the basin, 

with secondary consideration given to municipal ground-water 

use, agricultural pumping, the number of leaking underground 

fuel tanks, and pesticide applications within the basins (Belitz 

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

or groups of adjacent similar basins with relatively few 

public-supply wells were assigned high priority so that all 

hydrogeologic provinces would be represented in the subset 

of basins sampled. The 116 priority basins were grouped into 

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

basins were included in several of the study units to achieve 

representation of the 20 percent of public-supply wells not 

located in the ground-water basins. 
Introduction 3

Basin and Range

Klamath

Mountains

Desert

Cascades and

Modoc Plateau

Southern 

Coast

 Ranges

Sierra

Nevada

Central

Valley

Northern

Coast

Ranges

San Diego

Drainages

Transverse Ranges and selected Peninsular Ranges

Bakersfield

San Francisco

OREGON

NEVADA

MEXICO

ARIZONA

Redding

Los Angeles

San Diego

Pacific Ocean

0 200 MILES

0 200 KILOMETERS

40

42 124 122 120 118 116 114

38

36

34

Base from U.S. Geological Survey digital elevation

data, 1999, Albers Equal Area Projection

Provinces from Belitz and others, 2004

Sacramento

Coastal Los Angeles Basin 

GAMA Study Unit

Figure 1. The 10 hydrogeologic provinces considered for the California Groundwater Ambient Monitoring and 

Assessment (GAMA) study with the Coastal Los Angeles Basin study unit outlined (Belitz and others, 2003).
4 Ground-Water Quality Data in the Coastal Los Angeles Basin Study Unit, 2006: Results from the California GAMA Program

Three types of water-quality assessments are 

being conducted with the data collected in each study 

unit: (1) Status: assessment of the current quality of the 

groundwater resource, (2) Trends: detection of changes in 

ground-water quality, and (3) Understanding: identification 

of the natural and human factors affecting ground-water 

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

a series of reports presenting water-quality data collected in 

each study unit (Wright and others, 2005; Kulongoski and 

others, 2006; Bennett and others, 2006; Fram and Belitz, 

2007; Kulongoski and Belitz, 2007; Dawson and others, 2008; 

Landon and Belitz, 2008; Ferrari and others (2008); Shelton 

and others, 2008; Burton and Belitz, 2008; Land and Belitz, 

2008). Subsequent reports will address the status, trends, and 

understanding aspects of the water-quality assessments of each 

study unit. 

The Coastal Los Angeles Basin GAMA study unit, 

hereafter referred to as CLAB, contains five ground-water 

basins (fig. 2). CLAB was considered high priority for 

sampling on the basis of the large number of public-supply 

wells and to provide adequate representation of the Southern 

Coastal Plain area of the Transverse Ranges and Selected 

Peninsular Ranges hydrogeologic province (Belitz and others, 

2003). 

Purpose and Scope

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

design, including the hydrogeologic setting of CLAB and the 

study methods; (2) to present the results of quality-control 

tests, and (3) to present the analytical results for ground-water 

samples collected in CLAB. Ground-water samples were 

analyzed for organic, inorganic, and microbial constituents, 

field parameters, and chemical tracers. The chemical and 

microbial data presented in this report were evaluated by 

comparison to State and Federal drinking-water regulatory 

and non-regulatory thresholds and other health-based 

standards that are applied to treated drinking water. Regulatory 

thresholds considered for this report were established by the 

United States Environmental Protection Agency (USEPA) 

and the California Department of Public Health (CDPH). The 

data presented in this report are intended to characterize the 

quality of untreated ground-water resources within the study 

unit, not the treated drinking water delivered to consumers 

by water purveyors. Discussions of the factors that influence 

the distribution and occurrence of the constituents detected 

in ground-water samples will be the subject of subsequent 

publications. 

Acknowledgments 

The authors thank the following cooperators for their 

support: the California State Water Resources Control Board 

(SWRCB), California Department of Public Health (CDPH), 

California Department of Water Resources (DWR), and the 

Lawrence Livermore National Laboratory (LLNL). We also 

thank the cooperating well owners and water purveyors for 

their generosity in allowing the USGS to collect samples from 

their wells. Two reviewers, Jan Stepek (SWRCB) and George 

Bennett (USGS) provided comments to improve this work. 

Funding for this work was provided by State bonds authorized 

by Proposition 50 and administered by the SWRCB.

Hydrogeologic Setting

The Coastal Los Angeles Basin study unit (CLAB) lies 

at the southwest end of the Transverse Ranges and Selected 

Peninsular Ranges Hydrogeologic Province described by 

Belitz and others (2003), and includes a total of five groundwater basins: Orange County Coastal Plain, Central, West 

Coast, Santa Monica, and Hollywood (California Department 

of Water Resources, 2003). The five study areas of CLAB 

were selected to correspond with the boundaries of the five 

DWR-defined ground-water basins, and cover an area of 

approximately 860 square-miles (mi2), in Los Angeles and 

Orange Counties, California (fig. 2).

 The topography of the CLAB study unit is relatively flat. 

The study unit is bounded on the north by the Santa Monica 

Mountains, and the Elysian, Repetto, Merced, Puente, and 

Chino Hills; on the east by the Santa Ana Mountains; on the 

south by the San Joaquin Hills and the Pacific Ocean (San 

Pedro Bay); and, on the west by the Palos Verdes Hills and 

Pacific Ocean (Santa Monica Bay). The major drainages of 

CLAB are the Los Angeles, the San Gabriel, and the Santa 

Ana Rivers, all of which have headwaters outside of the study 

unit (Department of Water Resources, 2003). 

The main water-bearing formations within the CLAB 

study unit occur in unconsolidated and semi-consolidated 

marine and alluvial sediments of Holocene, Pleistocene, and 

Pliocene age. Periodic encroachment of the sea, and alluvium 

derived from weathering and erosion of the rocks in the 

surrounding mountains, has filled the Coastal Los Angeles 

basin with deposits of various thicknesses, consisting of 

sand, gravel, and conglomerate with some silt and clay beds 

(Department of Water Resources, 2003). 
Hydrogeologic Setting 5

0 5 10 MILES

0 5 10 KILOMETERS

33 40’

33 50’

34 00’

118 30’ 118 20’ 118 10’ 118 00’ 117 50’ 117 40’

Riverside County

Orange County

Los Angeles County

San Bernardino County

Pacific Ocean

San Pedro Bay

Santa Monica Bay

Long Beach

Santa Monica Mountains

Santa Ana Mountains

Repetto Hills

Elysian

Hills

Merced Hills

Puente Hills

Chino Hills

San Joaquin Hills

San

Valley Gabriel

Los Angeles

Huntington

Beach

Dominguez

Hills

Anaheim

Palos Verdes Hills

Santa

Monica

Hollywood

Carson

Beverly Hills

Terminal Island

Public-supply well-With record in California

 Department of Public Health or U.S. Geological

 Survey National Water Information System

 (NWIS) Database

Water bodies

Stream or River

Central Basin

West Coast Basin

Santa Monica

Basin

Hollywood Basin

West Coast Basin

Barrier Project

Alamitos Gap

Barrier Project

Talbert

Barrier Project

Dominguez Gap

Barrier Project

Orange County Coastal Plain

Unconsolidated deposits

Ground-water basin 

 boundary

Uplifted (or) older deposits

Area outside study unit

EXPLANATION

Newport-Inglewood Fault

 Zone

Base from U.S. Geological Survey National Elevation

Dataset, 2006, Albers Equal-Area Conic Projection

Figure 2. The Coastal Los Angeles Basin GAMA study unit, locations of study areas, major cities, rivers, reservoirs, saltwater barrier projects, CDPH and USGS public-supply wells, topographic features, and ground-water basins.
6 Ground-Water Quality Data in the Coastal Los Angeles Basin Study Unit, 2006: Results from the California GAMA Program

The climate in the CLAB study unit area is classified 

as Mediterranean, characterized by warm summers, cool 

winters, and markedly seasonal rainfall. Daytime highs in the 

winter average about 70oF and summer highs average between 

80–85oF. Nearly all rain falls from late autumn to early 

spring; virtually no precipitation falls during the summer. The 

average rainfall in the Coastal Los Angeles Basin area is about 

15 inches (National Oceanic Atmospheric Administration, 

2007). Potential evapotranspiration in the coastal plain 

exceeds precipitation on an annual basis, and under natural 

conditions, the lower reaches of rivers that drain the basin are 

dry in the summer (Department of Water Resources, 2003). 

Ground-water flow is largely controlled by engineered 

recharge along the San Gabriel, the Rio Hondo, and the Santa 

Ana Rivers, and by ground-water pumping from the many 

hundreds of wells distributed across the area. The direction 

of ground-water flow is primarily lateral and radial from the 

recharge facilities towards the coast. Along the coast near the 

saltwater-intrusion barriers, the direction of ground-water 

flow is in the inland direction, affected by water injection in 

the intrusion barrier and by ground-water pumping to the east 

(Shelton and others, 2000). 

Methods

Methods used for the GAMA program were selected 

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

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

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

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

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

relevant documentation. The Appendix to this report contains 

detailed descriptions of the sample-collection protocols and 

analytical methods, the quality-assurance plan, and the results 

of analyses of quality-control samples.

Study Design

The wells selected for sampling in this study reflect the 

combination of two selection strategies. Fifty-five wells were 

selected to provide a statistically unbiased, spatially distributed 

assessment of the quality of ground-water resources used for 

public drinking-water supply, and fourteen additional wells 

were targeted to provide greater sampling density in several 

specific areas to gain a greater understanding of ground-water 

quality within the CLAB study unit. 

The spatially-distributed wells were selected using a 

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

for the CLAB study unit within the GAMA Transverse Ranges 

and Selected Peninsular Ranges Hydrogeologic Province was 

to create a sampling density network of at least one well per 

10 mi2

 while having at least 10 grid cells per study area. A 

large number of public-supply wells were listed in statewide 

databases maintained by the CDPH and USGS. These wells 

are fairly evenly distributed, and are shown in figure 2. 

To ensure that the grid network included only those areas 

in which wells were commonly available for public supply, 

adjustments to the grid were made in three of the CLAB study 

areas. For the assessment of the Orange County Coastal Plain 

and Central Basin study areas, those areas mapped as uplifted 

(or) older deposits near the coast or the surrounding hills 

were excluded from the grid portion. The resulting area was 

divided into 27 and 21 grid cells (respectively), each having 

an approximate area of 10 mi2

 (figs. 3, 4). For the assessment 

of the West Coast basin, Terminal Island and an area bounded 

by the Newport–Inglewood Fault Zone, San Pedro Bay, and 

the Los Angeles River were excluded from the grid portion. 

The resulting area was divided into thirteen 10-mi2 grid cells 

(fig. 4). 

The objective was to then randomly select one publicsupply well per grid cell. If a grid cell contained more than one 

public-supply well, each well was randomly assigned a rank. 

The highest ranked well that met basic sampling criteria (for 

example; sampling point prior to treatment, capability to pump 

for several hours, available well-construction information) and 

for which permission to sample could be obtained was then 

sampled. If a grid cell contained no accessible public-supply 

wells, then irrigation or industrial wells were considered 

for sampling. An attempt was made to select irrigation or 

industrial wells with depths and screened intervals similar to 

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

was selected in each cell to provide a spatially distributed, 

randomized monitoring network for each study area. Wells 

sampled as part of the grid-cell network are hereafter referred 

to as “grid wells”. Grid wells in the CLAB study unit were 

named for their respective CADWR ground-water basins then 

numbered in the order of sample collection with the following 

prefixes based on study area: “OC” (indicating “Orange 

County coastal plain”), “CB” (indicating “Central Basin”), and 

“WB” (indicating “West Coast basin”).

 Fifty-five of the 61 grid cells in CLAB had wells that 

could be sampled; the other six grid cells did not contain 

active or accessible wells. In the Orange County Coastal Plain, 

there were no actively pumping wells in three grid cells. In 

the Central Basin study area there was complete coverage, 

with every grid cell represented by a well sampled. In the West 

Coast Basin, there were no actively pumping wells in one cell, 

and in two cells there were no wells available for sampling 

during the timeframe of the CLAB study. 

Fourteen additional “understanding” wells were sampled 

within the GAMA CLAB study unit. Eight of the fourteen 

wells were selected along a regional ground-water flow path, 

and within specific portions of the Central Basin and Orange 

County Coastal Plain study areas; they were numbered in the 

order of sample collection and given the prefix “U” (indicating 

“understanding”) (figs. 3 and 4).
Methods 7

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..

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.

.

.

.

.

.

.

.

.

.

.

.

.

.

.

.

. .

.

.

.

OC-23

OC-24

OC-21

OC-20

OC-17

OC-16

OC-15

OC-13

OC-12

OC-12

OC-11

OC-10

OC-09

OC-08

OC-07

OC-06

OC-05

OC-04

OC-03

OC-02

OC-01

U-04

U-01

U-01

OC-22

OC-19

OC-18

OC-14

U-08

EXPLANATION

Orange County Coastal

Plain study area

Ground-water basin boundary

(from California Department of

Water Resources) Understanding well

Water bodies

Stream or river

Grid well

Randomized sampling

 grid cell

Orange County

Riverside County

Los Angeles County

San Bernardino County

33 40’

33 50’

118 00’ 117 50’ 117 40’

Pacific Ocean

Santa Ana

River

0 5 10 MILES

0 5 10 KILOMETERS

Talbert

Barrier Project

Alamitos Gap

Barrier Project

Uplifted (or) older deposits

(Within the study basins)

Area outside of study area

(Not included in Study)

Newport-Inglewood Fault Zone

Base from U.S. Geological Survey National Elevation

Dataset, 2006, Albers Equal-Area Conic Projection

San Joaquin Hills

Santa Ana Mountains

Chino Hills

Other Study Areas

of CLAB

Anaheim

Figure 3. The Orange County Coastal Plain study area, the distribution of the study area grid cells, and the locations of 

sampled grid wells and understanding wells in the Coastal Los Angeles Basin GAMA study unit, California.
8 Ground-Water Quality Data in the Coastal Los Angeles Basin Study Unit, 2006: Results from the California GAMA Program

.

.

.

.

.

.

.

.

.

.

.

.

.

.

.

.

.

.

..

.

.

.

.

.

.

.

.

.

.

.

.

.

.

.

.

.

CB-20

CB-19

WB-05

WB-04

WB-03

WB-02 CB-14

CB-09

CB-08

CB-01

CB-21

CB-18

CB-17

CB-16

CB-15

CB-13

CB-12

CB-11

CB-10

CB-07

CB-03

CB-02

U-07

U-05

U-03

U-02

WB-10

WB-09

WB-08

WB-07

WB-06

WB-01 CB-06

CB-05

CB-05

CB-04

U-06

EXPLANATION

West Coast basin 

 study area

Ground-water basin boundary

(from California Department of

Water Resources)

Understanding well Cental basin study area

Water bodies

Stream or river

Randomized sampling Grid well

 grid cell

Los Angeles

River

Rio Hondo

San Gabriel River

Elysian Hills

Merced Hills

Puente Hills

Pacific Ocean

Santa

Monica

Bay

San Pedro Bay

Alamitos Gap

Barrier Project

West Coast Basin

Barrier Project

Dominguez Gap

Barrier Project

Terminal Island

Uplifted (or) older deposits

(Within the study basins)

Base from U.S. Geological Survey National Elevation

Dataset, 2006, Albers Equal-Area Conic Projection

Area outside of study area

(Not included in Study)

Newport-Inglewood Fault Zone

33 50’

34 00’

118 20’ 118 10’ 118 00’

0 5 10 MILES

0 5 10 KILOMETERS

Repetto Hills

Palos Verdes Hills

Other Study Areas

of CLAB

Other Study Areas

of CLAB

Long Beach

Los Angeles

Carson

Figure 4. The West Coast Basin and Central Basin study areas, the distribution of study area grid cells, and the locations of 

sampled grid wells and understanding wells in the Coastal Los Angeles Basin GAMA study unit, California.
Methods 9

The six remaining understanding wells were located in 

the Santa Monica and Hollywood basins, which are small in 

area, and the distribution of DPH wells prevented the grid-cell 

network exercise; therefore, a “direct assessment”, instead of 

randomized grid-based method, was taken. Four wells were 

sampled in the Santa Monica basin and two in the Hollywood 

basin. These six wells were numbered in the order of sample 

collection, and were given the prefix “DA” (indicating “direct 

assessment”) (fig. 5). 

.

.

.

.

.

DA-06 .

DA-06

DA-05

DA-04

DA-03

DA-02

DA-01

Other Study Areas

of CLAB

Other Study Areas

of CLAB

0 5 MILES

0 5 KILOMETERS

34 05’

34 00’

118 30’ 118 25’ 118 20’

Santa Monica Bay

Santa Monica Mountains

Santa

Monica

Hollywood

Beverly Hills

EXPLANATION

Santa Monica basin study area Direct assessment well .

Hollywood basin study area Water bodies

Stream or river

Newport-Inglewood Fault Zone

Ground-water basin boundary

(from California Department of

Water Resources)

Base from U.S. Geological Survey National Elevation

Dataset, 2006, Albers Equal-Area Conic Projection

Figure 5. The Santa Monica Basin and Hollywood Basin study areas, and the locations of direct assessment wells sampled 

in the Coastal Los Angeles Basin GAMA study unit, California.
10 Ground-Water Quality Data in the Coastal Los Angeles Basin Study Unit, 2006: Results from the California GAMA Program

The fourteen non-randomized wells (“understanding” 

and “direct assessment”) are not considered in the statistical 

calculations of the sampling results from the grid wells, and 

are classified together in this report as “understanding wells”. 

Table 1 provides the GAMA-id (alphanumeric 

identification number) for each well, along with the date 

sampled, sampling schedule type, elevation, and wellconstruction information. Sixty-nine production wells were 

sampled in CLAB from June to November 2006. 

Well locations and identifications were verified using 

GPS, 1:24,000 scale USGS topographic maps, comparison 

with existing well information in USGS and CDPH databases, 

and information provided by well owners. Driller’s logs 

for wells were obtained when available. Well information 

was recorded by hand on field sheets and electronically 

using specialized software on field laptop computers. All 

information was verified and then uploaded into the USGS 

National Water Information System (NWIS). 

The wells in CLAB were sampled using a tiered 

analytical approach. All wells were sampled for a standard 

set of water-quality constituents and environmental tracers, 

including VOCs, pesticides and pesticide degradates, 

pharmaceutical compounds, potential wastewater indicators, 

perchlorate, hexavalent chromium, arsenic and iron speciation, 

tritium, stable isotopes of water, and dissolved noble gases. 

The standard sampling also included the field parameters: 

temperature, specific conductance, and dissolved oxygen. 

This standard set of constituents was termed the “fast” 

schedule (table 2). Wells on the “intermediate” schedule were 

sampled for all the constituents on the fast schedule, plus: 

polar pesticides and pesticide degradates; NDMA; 1,2,3-

TCP; 1,4-dioxane; nutrients; dissolved organic carbon; major 

and minor ions; trace elements; stable isotopes of carbon, 

carbon-14 abundance; and pH. Wells on the “slow” schedule 

were sampled for all the constituents on the intermediate 

schedule, plus gross-alpha and gross-beta radiation, radium 

isotopes, radon-222, and microbial constituents, alkalinity, 

and turbidity (table 2). Fast, intermediate, and slow refer to 

the time required to sample the well for all the analytes on the 

collection schedule. Generally, one slow, two intermediate, 

or four fast wells could be sampled in one day. In CLAB, 50 

of the ground-water wells were sampled on the fast schedule, 

nine were sampled on the intermediate schedule, and 10 on the 

slow schedule (table 1).

Sample Collection and Analysis

Samples were collected in accordance with the protocols 

established by the USGS National Water Quality Assessment 

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

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

variously dated). These sampling protocols ensure that a 

representative sample of ground water is collected at each 

site, and that the samples are collected and handled in a way 

that minimizes the potential for contamination of samples and 

(or) cross contamination between samples collected at wells. 

The methods used for sample collection are described in the 

Appendix section “Sample Collection and Analysis”.

Tables 3A–L list the compounds analyzed in each 

constituent class. Ground-water samples were analyzed for 85 

VOCs (table 3A); eight gasoline oxygenates and degradates 

(table 3B); 122 pesticides, polar pesticides, and pesticide 

degradates (tables 3C, D); 69 potential wastewater indicators 

(table 3E); 14 pharmaceutical compounds (table 3F); four 

constituents of special interest (table 3G); five nutrients and 

dissolved organic carbon (table 3H); 10 major and minor 

ions and total dissolved solids (table 3I); 25 trace elements 

(table 3I); arsenic, iron, and chromium species (table 3J); 

stable isotopes of water, nine radioactive constituents, 

including tritium and carbon-14 (table 3K); four microbial 

constituents (table 3L); and six dissolved noble gases and 

tritium/helium age dates (table 3M). The methods used 

for sample analysis are described in the Appendix section 

“Sample Collection and Analysis”.

Results for pharmaceutical compounds are not presented 

in this CLAB report; they will be included in a subsequent 

publication. In addition, as of the publishing date of this data 

report, the samples collected in CLAB for noble gases, tritium 

and helium isotope ratios had not been analyzed by LLNL, 

therefore, results are not presented at this time.

Data Reporting

The methods and conventions used for reporting the 

data are described in the Appendix. Twenty-two constituents 

analyzed in this study were measured by more than one 

method at the USGS National Water Quality Laboratory 

(NWQL). For these constituents, only the results from the 

preferred method are reported. Five constituents collected 

at each well—arsenic, iron, and chromium concentrations, 

tritium activities, and concentrations of 1,2,3-TCP—were 

measured at more than one laboratory; both sets of results are 

reported for these constituents. 

Quality-Assurance

The quality-assurance methods used for this study follow 

the protocols of the U.S. Geological Survey National Field 

Manual (U.S. Geological Survey, variously dated) and the 

USGS NAWQA program (Koterba and others, 1995). Standard 

quality-control procedures were followed at the USGS NWQL 

(Pirkey and Glodt, 1998; Maloney, 2005). Quality-control 

(QC) samples collected in the CLAB study include sourcesolution blanks, field blanks, replicates, and matrix and 

surrogate spikes. QC samples were collected to evaluate bias 

and variability of the water-quality data that may have resulted 

from sample collection, processing, storage, transportation, 

and laboratory analysis. Quality-control procedures and 

quality-control sample results are described in the Appendix

section “Quality-Assurance Methods”.
Methods 11

Quality-Control Sample Results

Results of quality-control analyses (blanks, replicates, 

matrix spikes, and surrogates) were used to evaluate the 

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

Appendix). Assessment of the quality-control information 

from blanks resulted in qualifying of less than 0.1 percent of 

the data for the ground-water samples. Data from replicates 

indicated that variability between measurements was 

acceptably low, confirming that the procedures used to collect 

the samples were consistent. Average matrix spike recoveries 

for a number of organic constituents analyzed were lower 

than the acceptable limits, which may indicate that these 

constituents might not have been detected in some samples if 

they were present at very low concentrations. Some surrogate 

recoveries were not within acceptable limits for the analyses 

that use surrogates, which may indicate possible problems 

with the processing and analysis of some samples. 

The quality-control results are described in the Appendix

section “Quality-Control Sample Results”.

Comparison Thresholds

Concentrations of constituents detected in ground-water 

samples were compared with CDPH and USEPA drinkingwater health-based thresholds and thresholds established for 

aesthetic purposes (California Department of Public Health, 

2008a, 2008b; U.S. Environmental Protection Agency, 2008a, 

2008b, 2008c). The chemical data presented in this report are 

meant to characterize the quality of the untreated ground-water 

resources within CLAB, 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 ground water because treated 

drinking water may be subjected to disinfection, filtration, 

mixing with other waters, and exposure to the atmosphere 

prior to its delivery to consumers. Comparisons of raw 

(untreated) ground water to thresholds are for illustrative 

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

The following thresholds were used for comparisons:

MCL– Maximum Contaminant Level. Legally 

enforceable standards that apply to public-water systems 

and are designed to protect public health by limiting the 

levels of contaminants in drinking water. National MCLs are 

established by the USEPA, 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 threshold concentrations for a number of 

constituents with USEPA MCLs. In this report, a threshold set 

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

that is different from the MCL-US is labeled “MCL-CA”. 

CDPH is notified when constituents are detected at 

concentrations exceeding MCL-US or MCL-CA thresholds in 

samples collected for the GAMA Statewide Basin Assessment 

project.

AL – Action Level. Legally enforceable standards that 

apply to public water systems and are designed to protect 

public health by limiting the levels of copper and lead in 

drinking water. Detections of copper or lead above the actionlevel thresholds trigger requirements for mandatory water 

treatment to reduce the corrosiveness of water to water pipes. 

The action levels established by the USEPA and CDPH are the 

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

TT – Treatment Technique. Legally enforceable 

standards that apply to public-water systems and are designed 

to protect public health by limiting the levels of copper, lead, 

and microbial constituents in drinking water. TT requirements 

are applied when water delivered to consumers exceeds 

specified action levels. Detections of microbial constituents 

above thresholds trigger requirements for mandatory 

additional disinfection during water treatment. The action 

levels established by the USEPA and CDPH are the same, thus 

these thresholds are labeled “TT-US” in this report.

SMCL – Secondary Maximum Contaminant Level.

Non-enforceable standards applied to constituents that affect 

the aesthetic qualities of drinking water, such as taste, odor, 

and color, or technical qualities of drinking water, such as 

scaling and staining. Both the USEPA and CDPH define 

SMCLs, but unlike MCLs, SMCLs established by CDPH are 

not required to be at least as stringent as those established by 

USEPA. SMCLs established by CDPH 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 for some of the constituents in 

drinking water that lack MCLs (NL-CA). If a constituent 

is detected above its NL-CA, California state law requires 

timely notification of local governing bodies and recommends 

consumer notification.

HAL-US – Lifetime Health Advisory Level. The 

concentration of a constituent in drinking water at which, 

or below, its presence 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 (2.1 quarts) of water per day 

over a 70-year lifetime by a 70-kilogram (154-pound) adult 

and that 20 percent of that 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).
12 Ground-Water Quality Data in the Coastal Los Angeles Basin Study Unit, 2006: Results from the California GAMA Program

For constituents with MCLs, detections in groundwater samples were compared to the MCL-US or MCL-CA, 

whichever is lower. Constituents with SMCLs were 

compared with the SMCL-CA. For chloride, sulfate, specific 

conductance, and total dissolved solids, CDPH defines a 

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

these constituents in ground-water samples were compared 

with both levels. Detected concentrations of constituents 

that lack MCLs and SMCLs were compared to NL-CAs. 

For constituents that lack an MCL, SMCL, or NL-CA, 

detected concentrations were compared with the HAL-US. 

For constituents that lack an MCL, SMCL, NL-CA, or 

HAL-US, detected concentrations were compared with 

the RSD5-US. Note that this hierarchy of selection of 

comparison thresholds means that for constituents that 

have multiple types of established thresholds, the threshold 

used for comparison purposes may not be the one with the 

lowest concentration. The comparison thresholds used in this 

report are listed in table 3A–M for all constituents, and in 

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

from CLAB. Not all constituents analyzed for this study have 

established thresholds available. Detections of constituents at 

concentrations greater than the selected comparison threshold 

are marked with asterisk in tables 4–16. 

Ground-Water-Quality Data

Results from analyses of raw (untreated) ground-water 

samples from CLAB are presented in tables 4–16. Groundwater samples collected in CLAB were analyzed for over 340 

constituents, and 204 of those constituents were not detected 

in any of the samples (tables 3A–M). For organic constituents, 

the summary tables present only the constituents that were 

detected, and list only samples that had at least one compound 

detected. For constituent classes that were analyzed at all of 

the grid wells, the tables include, the summary statistics for 

the 55 CLAB grid wells, and for each study area, the number 

of wells at which each analyte was detected, the frequency 

at which it was detected (in relation to the number of grid 

wells), and the total number of constituents detected at each 

well. For inorganic, radioactive, and microbial constituents, 

the summary tables include all wells, constituents, and 

samples analyzed. Results from the understanding wells are 

presented in the tables, but these results were excluded from 

the detection frequency calculations to avoid statistical overrepresentation of grid cells that included understanding wells 

in addition to their grid wells.

Table 4 includes water-quality indicators measured in 

the field and at the NWQL, and tables 5 through 16 present 

the results of ground-water analyses organized by compound 

classes: 

• Organic constituents

• VOCs and gasoline oxygenates (table 5)

• Pesticides and pesticide degradates (table 6)

• Polar pesticides and degradates (table 7)

• Potential wastewater indicators (table 8)

• Constituents of special interest (table 9)

• Inorganic constituents

• Nutrients and dissolved organic carbon (table 10)

• Major and minor ions (table 11)

• Trace elements (table 12)

• Arsenic, iron, and chromium speciation (table 13)

• Inorganic tracer constituents

• Stable isotopes and carbon-14 activities (table 14)

• Radioactive constituents (table 15)

• Microbial indicators (table 16)

Field Parameters

Field measurements of turbidity, water temperature, 

dissolved oxygen, pH, specific conductance, temperature, and 

alkalinity are presented in table 4. Laboratory measurements 

of pH, specific conductance, and alkalinity also were 

performed for some samples by the USGS NWQL (table 4). 

Dissolved oxygen and alkalinity are used as indicators of 

natural processes that control water chemistry. Specific 

conductance is a measure of the unit electrical conductivity of 

the water and is proportional to the amount of dissolved salts 

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

of the water. Thirty-six percent of CLAB’s grid wells had 

field specific conductance values above the recommended 

SMCL-CA, although only one grid well, a saltwater 

desalination well (WB-01), was above the upper threshold 

of 1,600 μS/cm. One understanding well had a field specific 

conductance value above the SMCL-CA upper threshold of 

1,600 μS/cm. Two of CLAB’s grid wells had field pH values 

outside of the SMCL-US range for pH. 

Organic Constituents

Volatile organic compounds (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 ground water 

than in surface water because ground water is isolated from 
Ground-Water-Quality Data 13

the atmosphere. Twenty-eight of the 88 VOCs analyzed were 

detected in CLAB. All detections of VOCs in samples from 

the CLAB grid wells were below health-based thresholds, 

with the exception of one detection of carbon tetrachloride 

above the MCL-CA. Approximately three-quarters of the 

grid wells sampled had at least one detection of a VOC or 

gasoline oxygenate or degradate (table 5). Seven of the 88 

VOCs sampled were detected in more than 10 percent of the 

grid wells: chloroform (trichloromethane); trichloroethene 

(TCE); perchloroethene (PCE); bromodichloromethane, cis1,2-dichloroethene, 1,1-dichloroethene (1,1-DCE); and methyl 

tert-butyl ether (MTBE). For the understanding wells sampled 

in CLAB, there were two detections of trichloroethene 

(TCE) and one detection of perchloroethene (PCE) above 

health-based standards. VOCs were detected in 10 of the 14 

understanding wells. 

Pesticides include herbicides, insecticides, and 

fungicides, and are used to control weeds, insects, fungi, 

and other pests in agricultural, urban, and suburban settings. 

Sixty-three pesticides and pesticide degradates were 

analyzed in the CLAB study. All detections of pesticides and 

pesticide degradates were below health-based thresholds. 

Approximately 42 percent of the grid wells sampled had 

at least one detection of a pesticide or pesticide degradate 

(table 6). Six pesticides were detected in more than 10 percent 

of the grid wells: deethylatrazine (a degradate of atrazine), 

atrazine, simazine, 3,4-dichloroaniline, prometon, and 

tebuthiuron. The first three pesticides listed are among the 

most commonly detected pesticide compounds in ground 

water nationally (Gilliom and others, 2006). Pesticides 

and pesticide degradates were detected in five of the 14 

understanding wells. 

In addition, ground-water samples for 60 polar pesticides 

and pesticide degradates, were collected at the intermediate 

and slow wells. Of the 60 polar pesticides and pesticide 

degradates analyzed, five were detected (table 7). These 

detections occurred in two grid and three understanding wells. 

All detections of polar pesticides and pesticide degradates 

were below health-based thresholds.

Potential wastewater indicators include; detergents, 

fragrances, flame retardants, and other man-made compounds, 

and may originate from sources other than treated wastewater. 

Approximately 44 percent of the grid wells sampled had at 

least one detection of a potential wastewater indicator, and 

all of the detections were below health-based thresholds for 

the constituents that have health-based thresholds (table 8). 

One potential wastewater indicator (camphor) was detected in 

more than 10 percent of the grid wells. Potential wastewater 

indicators were detected in five of the 14 understanding well 

Results for pharmaceutical compounds are not presented 

in the CLAB report; they will be included in a subsequent 

publication.

Constituents of Special Interest

Perchlorate, 1,2,3-TCP, 1,4-dioxane, and NDMA are 

constituents of special interest in California because they 

recently have been found to be widely distributed in or are 

considered to have the potential to reach, water supplies 

(California Department of Public Health, 2007b). Perchlorate 

was sampled for at all 69 wells and was detected in samples 

at 40 percent of the grid wells; however, all concentrations 

measured were below the MCL-CA of 6 μg/L (table 9). 1,2,3-

TCP, 1,4-dioxane, and NDMA were analyzed for at 17 of the 

19 intermediate and slow wells in CLAB. 1,2,3-TCP was not 

detected in any of the 17 wells for which it was analyzed in the 

CLAB study unit. One grid well and two understanding wells 

had detections of 1,4-dioxane. In one of these understanding 

wells (DA-2), the detection was at a concentration greater 

than the NL-CA of 3 μg/L. NDMA was detected in one 

understanding well, at a level below the NL-CA. 

Inorganic Constituents

Unlike the organic constituents and the constituents of 

special interest, most of the inorganic constituents are naturally 

present in ground water, although their concentrations may 

be influenced by human activities. Inorganic constituents 

were sampled for at only the intermediate and slow wells in 

CLAB (19 of 69 wells). However, arsenic, iron, and chromium 

speciation samples were collected at all 69 wells. 

Nutrients (nitrogen and phosphorus) and dissolved 

organic carbon present in ground water can affect biological 

activity in aquifers and in surface-water bodies that receive 

ground-water discharge. Nitrogen may be present in the form 

of ammonia, nitrite, or nitrate, depending on the oxidationreduction state of the ground water. High concentrations of 

nitrate adversely can affect human health, particularly the 

health of infants. All concentrations of nitrate, nitrite, and 

ammonia measured in samples from CLAB wells were below 

health-based thresholds (table 10). 

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

content, and levels of certain trace elements in ground water 

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

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

Although there are no adverse health effects associated with 

these properties, they may reduce consumer satisfaction 

with the water or may have economic impacts. CDPH has 

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

based on aesthetic or technical properties rather than healthbased concerns for the major ions chloride and sulfate, TDS, 

and several trace elements.
14 Ground-Water Quality Data in the Coastal Los Angeles Basin Study Unit, 2006: Results from the California GAMA Program

 The concentrations of chloride and sulfate measured in 

samples from the CLAB wells were below the recommended 

SMCL-CAs (table 11), with the exception of two 

understanding wells. Fourteen out of the 19 CLAB wells (four 

grid and 10 understanding), had TDS concentrations above 

the recommended SMCL-CA, but only one of these samples 

(an understanding well) was above the upper SMCL-CA of 

1,000 mg/L.

Eighteen of the 25 trace elements analyzed in this study 

have health-based thresholds. Trace element concentrations 

in samples from CLAB wells were below health-based 

thresholds, with the exception of two understanding wells that 

had boron detections at concentrations above the NL-CA of 

1,000 μg/L (table 12).

Iron and manganese are trace elements of which 

concentrations are affected by the oxidation-reduction state 

of the ground water. Precipitation of minerals containing iron 

or manganese may cause orange or black staining of surfaces. 

Five of 19 wells, including two grid wells, had concentrations 

of manganese above the SMCL-CA of 50 μg/L (table 12). 

Concentrations of iron typically were below 6 μg/L, however 

two wells (one grid and one understanding) had concentrations 

above the SMCL-CA of 300 μg/L. The results were slightly 

different for iron measured by the speciation method (see 

below). 

Arsenic, iron, and chromium occur in different species, 

depending on the oxidation-reduction state of the ground 

water. The oxidized and reduced species have different 

solubilities in ground water and may have different effects 

on human health. The relative proportions of the oxidized 

and reduced species of each element can be used to aid in 

interpretation of the oxidation-reduction state of the aquifer. 

Arsenic, iron, and chromium speciation samples for analysis 

at the USGS Trace Metal Laboratory were collected from 

all 69 wells in the CLAB study unit. Concentrations of total 

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

oxidized or the reduced species of each element are reported 

on table 13. The concentrations of the other species can be 

calculated by difference. Four of CLAB’s 55 grid wells and 

two of 14 understanding wells had concentrations of total 

iron above the SMCL-CA of 300 μg/L. In addition, one grid 

and one understanding well had total arsenic concentrations 

above the health-based threshold, the MCL-US of 300 μg/L. 

None of the 69 wells had chromium detections at levels above 

the MCL-CA of 50 μg/L. Concentrations of total arsenic, 

iron, and chromium analyzed at the USGS Trace Metal 

Laboratory (table 13) generally were similar to those from the 

USGS NWQL (table 12); minor differences could be due to 

the different analytical methods (Appendix); concentrations 

reported on table 12 are considered to be more accurate.

Inorganic Tracer Constituents

Stable isotope ratios, tritium and carbon-14 activities, 

and noble-gas concentrations can be used as tracers of natural 

and human processes affecting ground-water composition. 

Hydrogen and oxygen stable-isotope ratios of water (table 14) 

can be used to aid in interpretation of ground-water recharge 

sources. The stable-isotope ratios of water depend on the 

altitude, latitude, and temperature of precipitation and on the 

extent of evaporation of surface water or soil water. Noble-gas 

concentrations can be used to aid in interpretation of groundwater recharge sources because the concentrations of the 

different noble gases depend on water temperature. Noble-gas 

concentrations also are used as an aid in interpreting the age of 

ground water.

As of the publishing date of this data report, the samples 

collected in CLAB for noble gases, tritium and helium isotope 

ratios had not been analyzed by LLNL, therefore results are 

not presented at this time.

Tritium activities, carbon-14 activities (table 14), and 

helium isotope ratios provide information about the age 

of the ground water. Tritium is a radioactive isotope of 

hydrogen that is incorporated into the water molecule. Low 

levels of tritium are continuously produced by cosmic ray 

bombardment of water in the atmosphere, and a large amount 

of tritium was produced by atmospheric testing of nuclear 

weapons between 1952 and 1963. Thus, concentrations of 

tritium above background generally indicate the presence of 

water that has been recharged since the early 1950’s (Izbicki, 

1996). Helium isotope ratios can be used in conjunction with 

tritium concentrations to estimate more exact ages for young 

ground water. Carbon-14 (table 14) is a radioactive isotope of 

carbon that is incorporated into dissolved carbonate species 

in water. Low levels of carbon-14 are produced continuously 

by cosmic ray bombardment of nitrogen in the atmosphere. 

Because carbon-14 decays with a half-life of approximately 

5,700 years, low activities of carbon-14, relative to modern 

values, generally indicate the presence of ground water that is 

several thousand years old (Kalin, 2000). 

Of the aforementioned tracers, the only one with a 

health-based threshold is tritium. A single tritium sample in 

CLAB was collected for analysis at the USGS Stable Isotope 

and Tritium Laboratory, in Menlo Park, California, and the 

measured tritium activity in this sample was well below the 

MCL-CA (table 14).

Radioactive Constituents

Radioactivity is the release of energy or energetic 

particles during changes in the structure of the nucleus of an 

atom. Most of the radioactivity in ground water comes from 
Summary 15

decay of naturally occurring isotopes of uranium and thorium 

that are present in minerals in the sediments or fractured rocks 

of an aquifer. Both uranium and thorium decay in a series of 

steps, eventually forming stable isotopes of lead. Radium-226, 

radium-228, and radon-222 are radioactive isotopes formed 

during the uranium and thorium decay series. In each step in 

the decay series, one radioactive element turns into a different 

radioactive element by emitting an alpha or a beta particle 

from its nucleus. For example, radium-226 emits an alpha 

particle and, therefore, turns into radon-222. Radium-228 

decays to form actinium-228 by emission of a beta particle. 

The alpha and beta particles emitted during radioactive 

decay are hazardous to human health because these energetic 

particles may damage cells. Radiation damage to cell DNA 

may increase the risk of getting cancer.

Activity often is used instead of concentration for 

reporting the relative presence of radioactive constituents. 

Activity of radioactive constituents in ground water is 

measured in units of picocuries per liter (pCi/L), and one 

picocurie is approximately equal to two atoms decaying per 

minute. The number of atoms decaying is equal to the number 

of alpha or beta particles emitted.

 Ten CLAB samples on the slow schedule were analyzed 

for radioactive constituents and had activities of radium, 

gross-alpha radioactivity (72-hour and 30-day counts), and 

gross-beta radioactivity (72-hour and 30-day counts) that were 

much less than established health-based standards (table 15). 

Samples for activities of radon-222 were collected at nine 

of the slow wells and six of those were above the proposed 

MCL-US of 300 pCi/L; however, none of the samples had 

an activity above the proposed alternative MCL-US of 

4,000 pCi/L. The alternative MCL-US will apply if the State 

or local water agency has an approved multimedia mitigation 

program to address radon in indoor air (U.S. Environmental 

Protection Agency, 1999). 

Microbial Indicators

Water is disinfected during drinking-water treatment to 

prevent diseases that may be spread by water-borne microbial 

constituents derived from human or animal wastes. The 

specific viruses and bacteria responsible for diseases generally 

are not measured because routine analytical methods are not 

available. Measurements are made of more easily analyzed 

microbial constituents that serve as indicators of the presence 

of human or animal waste in water. Drinking-water purveyors 

respond to detections of microbial indicators by applying 

additional disinfection techniques to the water.

Samples from ten CLAB slow wells were analyzed 

for microbial indicators. None of the samples contained 

the viral indicators F-specific and somatic coliphage, and 

none contained the bacterial indicator Escherichia coli

(E. coli); however, there was one low-level detection of 

a bacterial indicator (total coliforms) in an understanding 

well (table 16). The threshold for total coliforms is based 

on recurring detections in treated drinking water; thus, the 

detection reported here does not constitute an exceedance of 

the MCL-US. Total coliforms will be monitored during future 

sampling.

Future Work

Subsequent reports will be focused on assessment of 

the data presented in this report using a variety of statistical, 

qualitative, and quantitative approaches to evaluate the 

natural and human factors affecting ground-water quality. 

Water-quality data contained in the CDPH and USGS NWIS 

databases, and water-quality data available from other State 

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

in combination with the data that is presented in this report; 

the results of these future efforts will appear in one or more 

subsequent reports.

Summary

Ground-water quality in the approximately 860 squaremile Coastal Los Angeles Basin study unit (CLAB) was 

investigated from June to November of 2006 as part of the 

Priority Basin project of Ground-Water Ambient Monitoring 

and Assessment (GAMA) Program. The California State 

Water Resources Control Board (SWRCB), in collaboration 

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

Livermore National Laboratory, is implementing the GAMA 

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

Basin project was designed by the SWRCB and the USGS 

in response to the Ground-Water Quality Monitoring Act of 

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

Board, 2003). The project is a comprehensive assessment 

of statewide ground-water quality designed to identify and 

characterize risks to ground-water resources, and to increase 

the availability of information about ground-water quality to 

the public. CLAB was the thirteenth study unit sampled as part 

of the project. 

CLAB is in the Southern Coastal Plain area of the 

Transverse Ranges and Selected Peninsular Ranges 

hydrogeologic province and includes within it five groundwater basins, as defined by the California Department of 

Water Resources (California Department of Water Resources, 

2003). A total of 69 wells were sampled in Los Angeles 
16 Ground-Water Quality Data in the Coastal Los Angeles Basin Study Unit, 2006: Results from the California GAMA Program

and Orange Counties. Fifty-five of the wells were selected 

using a randomized grid approach to achieve a statistically 

unbiased representation of ground-water used for public 

drinking-water supplies. Fourteen of the wells were selected 

to provide additional sampling density to aid in understanding 

processes affecting ground-water quality. Ground-water 

samples were analyzed for VOCs, pesticides, polar pesticides, 

and pesticide degradates, potential wastewater-indicators, 

pharmaceutical compounds, compounds of special interest 

[perchlorate, N-nitrosodimethylamine (NDMA), 1,4-dioxane, 

and 1,2,3-trichloropropane (1,2,3-TCP)], nutrients, major and 

minor ions, trace elements, radioactive constituents [grossalpha and gross-beta radiation, radium isotopes, and radon222], and microbial indicators. Naturally occurring isotopes 

[stable isotopic ratios of hydrogen and oxygen, and activities 

of tritium and carbon-14] and dissolved noble gases also were 

measured to provide data that will be used to help interpret 

the sources and ages of the sampled ground water. This report 

describes the hydrogeologic setting of the CLAB region, the 

sampling, analytical, and quality-assurance methods used 

in the study, and the results of the chemical and microbial 

analyses of the ground-water samples collected June through 

November of 2006.

Quality-control samples (blanks, replicates, and samples 

for matrix spikes) were collected at over 20 percent of 

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

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

Field blanks rarely contained detectable concentrations of 

any constituent, suggesting that contamination was not a 

significant source of bias. Differences between replicate 

samples were within acceptable ranges, indicating acceptably 

low variability. Matrix spike recoveries were within acceptable 

ranges for most compounds. Assessment of the quality-control 

information resulted in applying “V” codes to approximately 

0.1 percent of the data collected for ground-water samples 

(meaning a constituent was detected in blanks as well as the 

corresponding environmental data). 

This study did not attempt to evaluate the quality of water 

delivered to consumers; after withdrawal from the ground, 

water typically is treated, disinfected, and blended with other 

waters to maintain acceptable water quality. Regulatory 

thresholds do not apply to raw ground water, but do apply 

to treated water that is served to the consumer. However, 

to provide some context for the results, concentrations of 

constituents measured in the raw ground water were compared 

with regulatory and non-regulatory health-based thresholds 

established by the U.S. Environmental Protection Agency 

(USEPA) and California Department of Public Health (CDPH, 

formerly the California Department of Health Services).

In this study, only six constituents were detected at 

concentrations higher than health-based thresholds [arsenic, 

boron, trichloroethene (TCE), perchloroethene (PCE), 

tetrachloromethane (carbon tetrachloride), and radon-222 

(detected above the proposed MCL-US threshold, but not the 

proposed alternative MCL-US threshold)]. Seven additional 

constituents (pH, specific conductance, chloride, sulfate, 

total dissolved solids, manganese, and iron) were detected at 

concentrations above thresholds set for aesthetic concerns.

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 ground-water quality.

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22 Ground-Water Quality Data in the Coastal Los Angeles Basin Study Unit, 2006: Results from the California GAMA Program

Table 1. Identification, sampling and construction information for wells sampled for the Coastal Los Angeles Basin Groundwater 

Ambient Monitoring and Assessment (GAMA) study, California, June to November 2006.

[CLAB; Coastal Los Angeles Basin; CLAB Grid Wells; CLAB Understanding Wells; All wells in CLAB are public supply wells, with the exception of one 

desalination well denoted below with an asterisk. Abbreviations: ft, foot; LSD, land surface datum; na, not available]

Sampling information Construction information

GAMA 

identification No.

Date 

(mm/dd/yyyy)

Sampling 

schedule

Elevation of LSD 

(ft above NAVD88)

Well depth 

(ft below LSD)

Top perforation 

(ft below LSD)

Bottom perforation 

(ft below LSD)

CLAB Grid Wells

Central Basin Wells

CB-01 08/09/2006 Fast 128 456 200 456

CB-02 08/15/2006 Intermediate 65 674 602 644

CB-03 08/16/2006 Slow 157 520 242 446

CB-04 08/17/2006 Slow 19 838 507 838

CB-05 08/21/2006 Fast 40 910 300 898

CB-06 08/21/2006 Fast 22 1,680 605 1,640

CB-07 08/21/2006 Fast 152 900 200 900

CB-08 08/22/2006 Fast 138 1,096 420 1,076

CB-09 08/22/2006 Fast 119 1,428 408 1,400

CB-10 08/22/2006 Fast 142 1,500 500 1,500

CB-11 08/22/2006 Fast 126 1,504 500 1,504

CB-12 08/29/2006 Fast 157 1,182 475 1,094

CB-13 08/29/2006 Fast 108 746 610 746

CB-14 08/29/2006 Fast 71 501 451 501

CB-15 08/30/2006 Fast 87 688 626 688

CB-16 08/30/2006 Fast 88 736 684 718

CB-17 09/14/2006 Intermediate 140 627 277 584

CB-18 11/15/2006 Fast 221 400 na na

CB-19 11/15/2006 Fast 198 1,010 617 973

CB-20 11/15/2006 Fast 108 502 331 338

CB-21 11/16/2006 Fast 59 660 640 660

Orange County Coastal Plain Wells

OC-01 06/05/2006 Intermediate 202 1,300 399 1,270

OC-02 06/07/2006 Slow 180 1,550 599 1,530

OC-03 08/23/2006 Fast 147 450 309 425

OC-04 08/23/2006 Fast 112 1,420 482 1,375

OC-05 08/23/2006 Fast 99 1,240 505 1,220

OC-06 08/23/2006 Fast 67 1,300 540 1,280

OC-07 08/24/2006 Fast 68 972 390 940

OC-08 08/24/2006 Fast 125 1,310 570 1,290

OC-09 08/24/2006 Fast 80 1,152 330 1,140

OC-10 08/24/2006 Fast 144 1,180 560 1,160

OC-11 08/28/2006 Fast 34 600 305 580

OC-12 08/28/2006 Fast 32 1,060 310 1,025

OC-13 08/28/2006 Fast 252 420 90 406

OC-14 08/31/2006 Fast 24 880 374 860

OC-15 08/31/2006 Fast 42 1,135 345 1,125

OC-16 08/31/2006 Fast 30 366 201 356

OC-17 08/31/2006 Fast 236 1,230 530 1,210

OC-18 09/11/2006 Fast 6 486 342 486

OC-19 09/11/2006 Fast 27 306 265 291

OC-20 09/13/2006 Intermediate 383 98 60 84

OC-21 09/14/2006 Fast 92 998 397 995

OC-22 11/13/2006 Fast 34 260 na na

OC-23 11/13/2006 Fast 242 970 460 950

OC-24 11/16/2006 Fast 316 604 256 584
Table 1 23

Sampling information Construction information

GAMA 

identification No.

Date 

(mm/dd/yyyy)

Sampling 

schedule

Elevation of LSD 

(ft above NAVD88)

Well depth 

(ft below LSD)

Top perforation 

(ft below LSD)

Bottom perforation 

(ft below LSD)

West Coast Basin Wells

WB-01* 08/29/2006 Fast 111 445 310 425

WB-02 08/30/2006 Fast 78 490 210 420

WB-03 08/30/2006 Fast 91 445 215 425

WB-04 09/12/2006 Intermediate 76 620 200 600

WB-05 09/12/2006 Fast 53 800 340 730

WB-06 11/13/2006 Fast 35 930 480 910

WB-07 11/14/2006 Fast 83 822 630 800

WB-08 11/14/2006 Fast 26 780 450 750

WB-09 11/14/2006 Fast 63 810 200 786

WB-10 11/16/2006 Fast 174 600 300 600

CLAB Understanding Wells

Direct Assessment Wells

DA-011 08/07/2006 & 

08/10/2006

Slow 243 250 120 220

DA-02 08/08/2006 Slow 157 550 210 530

DA-03 08/09/2006 Slow 268 665 360 630

DA-04 08/10/2006 Slow 313 282 151 250

DA-05 11/14/2006 Slow 235 740 398 730

DA-06 11/15/2006 Slow 234 440 260 430

Understanding Wells

U-01 06/06/2006 Intermediate 58 844 312 844

U-02 08/14/2006 Slow 92 572 546 572

U-03 09/13/2006 Intermediate 202 414 183 386

U-04 11/13/2006 Fast 60 540 497 540

U-05 11/15/2006 Fast 67 222 212 220

U-06 11/16/2006 Intermediate 494 300 62 300

U-07 11/16/2006 Intermediate 91 na na na

U-08 11/16/2006 Fast 55 120 na na

1

 Well sampled twice because of SC4433 (potential wastewater indicators) sample bottle breakage.

Table 1. Identification, sampling and construction information for wells sampled for the Coastal Los Angeles Basin Groundwater 

Ambient Monitoring and Assessment (GAMA) study, California, June to November 2006.—Continued

[CLAB; Coastal Los Angeles Basin; CLAB Grid Wells; CLAB Understanding Wells; All wells in CLAB are public supply wells, with the exception of one 

desalination well denoted below with an asterisk. Abbreviations: ft, foot; LSD, land surface datum; na, not available]
24 Ground-Water Quality Data in the Coastal Los Angeles Basin Study Unit, 2006: Results from the California GAMA Program

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

intermediate, and fast well sampling schedules in the Coastal Los Angeles Basin Groundwater Ambient Monitoring and 

Assessment (GAMA) study, California, June to November 2006.

Analyte classes Analyte 

list table

Schedule

Slow Intermediate Fast 

Water-quality indicators 

Dissolved oxygen, temperature, specific conductance X X X

pH X X

Turbidity, alkalinity X

Organic constituents

Volatile organic compounds 3A X X X

Gasoline additives and oxygenates 3B X X

Pesticides and pesticide degradates 3C X X X

Polar pesticides and pesticide degradates 3D X X

Pharmaceutical compounds1 3E X X X

Potential wastewater indicator compounds 3F X X X

Constituents of special interest

Perchlorate 3G X X X

1,4-Dioxane 3G X X

N-Nitrosodimethylamine (NDMA) 3G X X

1,2,3-Trichloropropane 3G X X

Inorganic constituents

Nutrients and dissolved organic carbon 3H X X

Major and minor ions and trace elements 3I X X

Chromium abundance and speciation 3J X X X

Arsenic and iron abundances and speciation 3J X X X

Stable isotopes

Stable isotopes of hydrogen and oxygen in water 3K X X X

Stable isotopes of carbon and carbon-14 abundance 3K X X

Radioactivity and noble gases

Gross alpha and beta radioactivity 3K X

Radium isotopes 3K X

Radon-222 3K X

Tritium and noble gases2 – X X X

Microbial constituents

Microbial constituents 3L X

1 Results for pharmaceutical compounds are not presented in the CLAB report; they will be included in a subsequent 

publication.

2

 As of the publishing date of this report, the samples collected in CLAB for noble gases, tritium, and helium isotope ratios 

had not been analyzed by LLNL, therefore results are not presented at this time.
Table 3A 25

Table 3A. Volatile organic compounds, primary uses or sources, comparative thresholds, and reporting information for the U.S. 

Geological Survey National Water Quality Laboratory Schedule 2020.

[The five-digit U.S. Geological Survey (USGS) parameter code is used to uniquely identify a specific constituent or property. Thresholds, threshold values, 

and LRLs as of November 16, 2006. CAS, Chemical Abstract Service. 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 Threshold: Maximum contaminant 

level thresholds are listed as MCL-US when the MCL-US and MCL-CA are identical, and as MCL-CA when the MCL-CA is lower than the MCL-US or no 

MCL-US exists. HAL-US, U.S. Environmental Protection Agency Lifetime Health Advisory; MCL-CA, California Department of Public Health maximum 

contaminant level; MCL-US, U.S. Environmental Protection Agency maximum contaminant level; NL-CA, California Department of Public Health notification 

level; RSD5-US, U.S. Environmental Protection Agency risk specific dose at a risk factor of 10-5. Detection: D, detected in ground-water samples (table 5). 

Abbreviations: LRL, laboratory reporting level; THM, trihalomethane; μg/L, micrograms per liter; na, not available; –, analyzed but not detected]

Constituent Primary use 

or source

USGS

parameter 

code

CAS 

number

 LRL

 (μg/L)

Threshold

Detection

Type Value

(μg/L)

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

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

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

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

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

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

Bromodichloromethane Disinfection by-product 

(THM)

32101 75-27-4 0.04 MCL-US 1

 80 D

Bromoform (Tribromomethane) Disinfection by-product 

(THM)

32104 75-25-2 0.08 MCL-US 1

 80 D

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

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

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

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

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

Carbon tetrachloride 

(Tetrachloromethane)

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

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

Chloroethane Solvent 34311 75-00-3 0.10 na na –

Chloroform (Trichloromethane) Disinfection by-product 

(THM)

32106 67-66-3 0.04 MCL-US 1

 80 D

Chloromethane Solvent 34418 74-87-3 0.10 HAL-US 30 –

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

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

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

Dibromochloromethane Disinfection by-product 

(THM)

32105 124-48-1 0.12 MCL-US 1

 80 –

1,2-Dibromo-3-chloropropane 

(DBCP)

Fumigant 82625 96-12-8 0.5 MCL-US 0.2 –

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

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

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

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

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

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

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

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

1,2-Dichloroethane (1,2-DCA) Solvent 32103 107-06-2 0.10 MCL-CA 5 D

1,1-Dichloroethene (1,1-DCE) Organic synthesis 34501 75-35-4 0.04 MCL-CA 7 D

cis-1,2-Dichloroethene (cis-1,2-

DCE)

Solvent 77093 156-59-2 0.02 MCL-CA 6 D

trans-1,2-Dichloroethene (trans-1,2-

DCE)

Solvent 34546 156-60-5 0.018 MCL-CA 10 D

1,2-Dichloropropane Fumigant 34541 78-87-5 0.02 MCL-US 5 –
26 Ground-Water Quality Data in the Coastal Los Angeles Basin Study Unit, 2006: Results from the California GAMA Program

Constituent Primary use 

or source

USGS

parameter 

code

CAS 

number

 LRL

 (μg/L)

Threshold

Detection

Type Value

(μg/L)

1,3-Dichloropropane Fumigant 77173 142-28-9 0.06 na na –

2,2-Dichloropropane Fumigant 77170 594-20-7 0.06 na na –

1,1-Dichloropropene Organic synthesis 77168 563-58-6 0.04 na na –

cis-1,3-Dichloropropene Fumigant 34704 10061-01-5 0.06 RSD5-US 2

 4 –

trans-1,3-Dichloropropene Fumigant 34699 10061-02-6 0.10 RSD5-US 2

 4 –

Diethyl ether Solvent 81576 60-29-7 0.08 na na –

Diisopropyl ether (DIPE) Gasoline oxygenate 81577 108-20-3 0.06 na na D

Ethylbenzene Gasoline hydrocarbon 34371 100-41-4 0.02 MCL-CA 300 D

Ethyl tert-butyl ether (ETBE) Gasoline oxygenate 50004 637-92-3 0.04 na na –

Ethyl methacrylate Organic synthesis 73570 97-63-2 0.14 na na –

o-Ethyl toluene (1-Ethyl-2-methyl 

benzene)

Gasoline hydrocarbon 77220 611-14-3 0.04 na na –

Hexachlorobutadiene Organic synthesis 39702 87-68-3 0.10 RSD5-US 9 –

Hexachloroethane Solvent 34396 67-72-1 0.14 HAL-US 1 –

2-Hexanone (n-Butyl methyl ketone) Solvent 77103 591-78-6 0.4 na na –

Iodomethane (Methyl iodide) Organic synthesis 77424 74-88-4 0.4 na na –

Isopropylbenzene Gasoline hydrocarbon 77223 98-82-8 0.04 NL-CA 770 –

4-Isopropyl-1-methyl benzene Gasoline hydrocarbon 77356 99-87-6 0.08 na na –

Methyl acrylate Organic synthesis 49991 96-33-3 0.4 na na –

Methyl acrylonitrile Organic synthesis 81593 126-98-7 0.40 na na –

Methyl tert-butyl ether (MTBE) Gasoline oxygenate 78032 1634-04-4 0.10 MCL-CA 13 D

Methyl iso-butyl ketone (MIBK) Solvent 78133 108-10-1 0.2 NL-CA 120 –

Methylene chloride 

(Dichloromethane)

Solvent 34423 75-09-2 0.04 MCL-US 5 –

Methyl ethyl ketone (2-butanone, 

MEK)

Solvent 81595 78-93-3 1.6 HAL-US 4,000 –

Methyl methacrylate Organic synthesis 81597 80-62-6 0.20 na na –

Naphthalene Gasoline hydrocarbon 34696 91-20-3 0.4 HAL-US 100 D

n-Propylbenzene Solvent 77224 103-65-1 0.04 NL-CA 260 –

Styrene Gasoline hydrocarbon 77128 100-42-5 0.04 MCL-US 100 –

1,1,1,2-Tetrachloroethane Solvent 77562 630-20-6 0.04 na na –

1,1,2,2-Tetrachloroethane Solvent 34516 79-34-5 0.10 na na –

Tetrachloroethene (PCE) Solvent 34475 127-18-4 0.04 MCL-US 5 D

Tetrahydrofuran Solvent 81607 109-99-9 1.0 na na –

1,2,3,4-Tetramethylbenzene Gasoline hydrocarbon 49999 488-23-3 0.14 na na –

1,2,3,5-Tetramethylbenzene Gasoline hydrocarbon 50000 527-53-7 0.12 na na –

Toluene Gasoline hydrocarbon 34010 108-88-3 0.018 MCL-CA 150 D

1,2,3-Trichlorobenzene Organic synthesis 77613 87-61-6 0.12 na na –

1,2,4-Trichlorobenzene Solvent 34551 120-82-1 0.12 MCL-CA 5 –

1,1,1-Trichloroethane (1,1,1-TCA) Solvent 34506 71-55-6 0.04 MCL-CA 200 D

1,1,2-Trichloroethane (1,1,2-TCA) Solvent 34511 79-00-5 0.04 MCL-CA 5 –

Table 3A. Volatile organic compounds, primary uses or sources, comparative thresholds, and reporting information for the U.S. 

Geological Survey National Water Quality Laboratory Schedule 2020.—Continued

[The five-digit U.S. Geological Survey (USGS) parameter code is used to uniquely identify a specific constituent or property. Thresholds, threshold values, 

and LRLs as of November 16, 2006. CAS, Chemical Abstract Service. 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 Threshold: Maximum contaminant 

level thresholds are listed as MCL-US when the MCL-US and MCL-CA are identical, and as MCL-CA when the MCL-CA is lower than the MCL-US or no 

MCL-US exists. HAL-US, U.S. Environmental Protection Agency Lifetime Health Advisory; MCL-CA, California Department of Public Health maximum 

contaminant level; MCL-US, U.S. Environmental Protection Agency maximum contaminant level; NL-CA, California Department of Public Health notification 

level; RSD5-US, U.S. Environmental Protection Agency risk specific dose at a risk factor of 10-5. Detection: D, detected in ground-water samples (table 5). 

Abbreviations: LRL, laboratory reporting level; THM, trihalomethane; μg/L, micrograms per liter; na, not available; –, analyzed but not detected]
Table 3B 27

Constituent Primary use 

or source

USGS

parameter 

code

CAS 

number

 LRL

 (μg/L)

Threshold

Detection

Type Value

(μg/L)

Trichloroethene (TCE) Solvent 39180 79-01-6 0.02 MCL-US 5 D

Trichlorofluoromethane (CFC-11) Refrigerant 34488 75-69-4 0.08 MCL-CA 150 D

1,2,3-Trichloropropane (1,2,3-TCP) Solvent/organic 

synthesis

77443 96-18-4 0.12 NL-CA3 0.005 –

Trichlorotrifluoroethane (CFC-113) Refrigerant 77652 76-13-1 0.04 MCL-CA 1,200 D

1,2,3-Trimethylbenzene Gasoline hydrocarbon 77221 526-73-8 0.08 na na –

1,2,4-Trimethylbenzene Gasoline hydrocarbon 77222 95-63-6 0.04 NL-CA 330 D

1,3,5-Trimethylbenzene Organic synthesis 77226 108-67-8 0.04 NL-CA 330 –

Vinyl bromide (Bromoethene) Fire retardant 50002 593-60-2 0.12 na na –

Vinyl chloride (Chloroethene) Organic synthesis 39175 75-01-4 0.08 MCL-US 2 D

m- and p-Xylene Gasoline hydrocarbon 85795 108-38-3/ 

106-42-3

0.08 MCL-CA 4

1,750 D

o-Xylene Gasoline hydrocarbon 77135 95-47-6 0.04 MCL-CA 4

1,750 –

1

 The MCL-US threshold for trihalomethanes is for the sum of chloroform, bromoform, bromodichloromethane, and dibromochloromethane.

2

 The RSD5 threshold for 1,3-dichloropropene is the sum of its isomers (cis and trans). 3

 In earlier reports in this series, the NL-CA (0.005 μg/L) was used as the comparison threshold for 1,2,3-TCP.

4

 The MCL-CA threshold for Xylenes is the sum of m- and p-Xylene and o-Xylene.

Table 3A. Volatile organic compounds, primary uses or sources, comparative thresholds, and reporting information for the U.S. 

Geological Survey National Water Quality Laboratory Schedule 2020.—Continued

[The five-digit U.S. Geological Survey (USGS) parameter code is used to uniquely identify a specific constituent or property. Thresholds, threshold values, 

and LRLs as of November 16, 2006. CAS, Chemical Abstract Service. 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 Threshold: Maximum contaminant 

level thresholds are listed as MCL-US when the MCL-US and MCL-CA are identical, and as MCL-CA when the MCL-CA is lower than the MCL-US or no 

MCL-US exists. HAL-US, U.S. Environmental Protection Agency Lifetime Health Advisory; MCL-CA, California Department of Public Health maximum 

contaminant level; MCL-US, U.S. Environmental Protection Agency maximum contaminant level; NL-CA, California Department of Public Health notification 

level; RSD5-US, U.S. Environmental Protection Agency risk specific dose at a risk factor of 10-5. Detection: D, detected in ground-water samples (table 5). 

Abbreviations: LRL, laboratory reporting level; THM, trihalomethane; μg/L, micrograms per liter; na, not available; –, analyzed but not detected]

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

information for the U.S. Geological Survey National Water Quality Laboratory Schedule 4024.

[The five-digit U.S. Geological Survey (USGS) parameter code is used to uniquely identify a specific constituent or property. Thresholds, 

threshold values, and LRLs as of November 16, 2006. CAS, Chemical Abstract Service. 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

Threshold: Maximum contaminant level thresholds are listed as MCL-US when the MCL-US and MCL-CA are identical, and as MCL-CA when 

the MCL-CA is lower than the MCL-US or no MCL-US exists. MCL-CA, California Department of Public Health maximum contaminant level; 

NL-CA, California Department of Public Health notification level; Detection: D, detected in ground-water samples (table 5). Abbreviations:

LRL, laboratory reporting level; μg/L, micrograms per liter; na, not available; –, analyzed but not detected]

Constituent Primary use 

or source

USGS 

parameter 

code

CAS 

number

 LRL

(μg/L)

Threshold

Detection

Type Value 

(μg/L)

Acetone Degradate 81552 67-64-1 1.8 na na –

tert-Amyl alcohol Oxygenate 77073 75-85-4 0.6 na na D

tert-Amyl methyl ether 

(TAME)

Oxygenate 50005 994-05-8 0.05 na na –

tert-Butyl alcohol (TBA) Degradate 77035 75-65-0 1 NL-CA 12 D

Diisopropyl ether (DIPE) Oxygenate 81577 108-20-3 0.2 na na D

Ethyl tert-butyl ether 

(ETBE)

Oxygenate 50004 637-92-3 0.06 na na –

Methyl acetate Degradate 77032 79-20-9 0.4 na na –

Methyl tert-butyl ether 

(MTBE)

Oxygenate 78032 1634-04-4 0.04 MCL-CA 13 –
28 Ground-Water Quality Data in the Coastal Los Angeles Basin Study Unit, 2006: Results from the California GAMA Program

Table 3C. Pesticides and pesticide degradates, primary uses or sources, comparative thresholds, and reporting information for the 

U.S. Geological Survey National Water Quality Laboratory Schedule 2003.

[The five-digit U.S. Geological Survey (USGS) parameter code is used to uniquely identify a specific constituent or property. Thresholds, threshold values, 

and LRLs as of November 16, 2006. CAS, Chemical Abstract Service. 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 Threshold type: Maximum contaminant level 

thresholds are listed as MCL-US when the MCL-US and MCL-CA are identical, and as MCL-CA when the MCL-CA is lower than the MCL-US or no MCL-US 

exists. HAL-US, U.S. Environmental Protection Agency Lifetime Health Advisory; MCL-CA, California Department of Public Health maximum contaminant 

level; MCL-US, U.S. Environmental Protection Agency maximum contaminant level; RSD5-US, U.S. Environmental Protection Agency risk specific dose at a 

risk factor of 10-5. Detection: D, detected in ground-water samples (table 6). Abbreviations: LRL, laboratory reporting level; μg/L, micrograms per liter; na, not 

available; –, analyzed but not detected]

Constituent

(common name)

Primary use

or source

USGS

parameter 

code

CAS 

number

 LRL

 (μg/L)

Threshold

Detection

Type Value

(μg/L)

Acetochlor Herbicide 49260 34256-82-1 0.006 na na –

Alachlor Herbicide 46342 15972-60-8 0.005 MCL-US 2 –

Atrazine Herbicide 39632 1912-24-9 0.007 MCL-CA 1 D

Azinphos-methyl Insecticide 82686 86-50-0 0.08 na na –1

Azinphos-methyl oxon Insecticide degradate 61635 961-22-8 0.042 na na –1

Benfluralin Herbicide 82673 1861-40-1 0.01 na na –1

Carbaryl Insecticide 82680 63-25-2 0.06 RSD5-US 400 –

2-Chloro-2,6-diethylacetanilide Herbicide degradate 61618 6967-29-9 0.0065 na na –

4-Chloro-2-methylphenol Herbicide degradate 61633 1570-64-5 0.0050 na na –1

Chlorpyrifos Insecticide 38933 2921-88-2 0.005 HAL-US 2 –

Chlorpyrifos oxon Insecticide degradate 61636 5598-15-2 0.0562 na na –1

Cyfluthrin Insecticide 61585 68359-37-5 0.053 na na –1

Cypermethrin Insecticide 61586 52315-07-8 0.046 na na –1

Dacthal (DCPA) Herbicide 82682 1861-32-1 0.003 HAL-US 70 –

Deethylatrazine (2-Chloro-4-

isopropylamino6-amino-s-triazine)

Herbicide degradate 04040 6190-65-4 0.014 na na D

Desulfinylfipronil Insecticide degradate 62170 na 0.012 na na D

Desulfinylfipronil amide Insecticide degradate 62169 na 0.029 na na –

Diazinon Insecticide 39572 333-41-5 0.005 HAL-US 1 –

Diazinon oxon Insecticide degradate 61638 962-58-3 0.006 na na –

3,4-Dichloroaniline Herbicide degradate 61625 95-76-1 0.0045 na na D

Dichlorvos Insecticide 38775 62-73-7 0.013 na na D

Dicrotophos Insecticide 38454 141-66-2 0.0843 na na –1

Dieldrin Insecticide 39381 60-57-1 0.009 RSD5-US 0.02 –

2,6-Diethylaniline Herbicide degradate 82660 579-66-8 0.006 na na –

Dimethoate Insecticide 82662 60-51-5 0.0061 na na –1

Ethion Insecticide 82346 563-12-2 0.016 na na –

Ethion monoxon Insecticide degradate 61644 17356-42-2 0.021 na na –

2-Ethyl-6-methylaniline Herbicide degradate 61620 24549-06-2 0.010 na na –

Fenamiphos Insecticide 61591 22224-92-6 0.029 HAL-US 0.7 –

Fenamiphos sulfone Insecticide degradate 61645 31972-44-8 0.053 na na –1

Fenamiphos sulfoxide Insecticide degradate 61646 31972-43-7 0.040 na na –1

Fipronil Insecticide 62166 120068-37-3 0.016 na na D

Fipronil sulfide Insecticide degradate 62167 120067-83-6 0.013 na na D

Fipronil sulfone Insecticide degradate 62168 120068-36-2 0.024 na na D

Fonofos Insecticide 04095 944-22-9 0.006 HAL-US 10 –

Hexazinone Herbicide 04025 51235-04-2 0.026 HAL-US 400 D

Iprodione Fungicide 61593 36734-19-7 0.026 na na –1

Isofenphos Insecticide 61594 25311-71-1 0.011 na na –

Malaoxon Insecticide degradate 61652 1634-78-2 0.039 na na –

Malathion Insecticide 39532 121-75-5 0.016 HAL-US 100 –

Metalaxyl Fungicide 61596 57837-19-1 0.0069 na na D
Table 3C 29

Constituent

(common name)

Primary use

or source

USGS

parameter 

code

CAS 

number

 LRL

 (μg/L)

Threshold

Detection

Type Value

(μg/L)

Methidathion Insecticide 61598 950-37-8 0.0087 na na –

Metolachlor Herbicide 39415 51218-45-2 0.0010 HAL-US 100 D

Metribuzin Herbicide 82630 21087-64-9 0.012 HAL-US 70 –

Myclobutanil Fungicide 61599 88671-89-0 0.033 na na –

1-Naphthol Insecticide degradate 49295 90-15-3 0.0882 na na –1

Paraoxon-methyl Insecticide degradate 61664 950-35-6 0.019 na na –1

Parathion-methyl Insecticide 82667 298-00-0 0.008 HAL-US 1 –

Pendimethalin Herbicide 82683 40487-42-1 0.02 na na –

cis-Permethrin Insecticide 82687 54774-45-7 0.01 na na –1

Phorate Insecticide 82664 298-02-2 0.02 na na –

Phorate oxon Insecticide degradate 61666 2600-69-3 0.027 na na –

Phosmet Insecticide 61601 732-11-6 0.0079 na na –1

Phosmet oxon Insecticide degradate 61668 3735-33-9 0.0511 na na –1

Prometon Herbicide 04037 1610-18-0 0.01 HAL-US 100 D

Prometryn Herbicide 04036 7287-19-6 0.0059 na na –

Pronamide (Propyzamide) Herbicide 82676 23950-58-5 0.004 RSD5-US 20 –

Simazine Herbicide 04035 122-34-9 0.006 MCL-US 4 D

Tebuthiuron Herbicide 82670 34014-18-1 0.016 HAL-US 500 D

Terbufos Insecticide 82675 13071-79-9 0.012 HAL-US 0.4 –

Terbufos oxon sulfone Insecticide degradate 61674 56070-15-6 0.045 na na –

Terbuthylazine Herbicide 04022 5915-41-3 0.0083 na na –

Trifluralin Herbicide 82661 1582-09-8 0.009 HAL-US 5 –

1

 The median matrix-spike recovery was less than 70 percent. Low recoveries may indicate that the compound might not have been detected in some samples if it 

was present at very low concentrations.

Table 3C. Pesticides and pesticide degradates, primary uses or sources, comparative thresholds, and reporting information for the 

U.S. Geological Survey National Water Quality Laboratory Schedule 2003.—Continued

[The five-digit U.S. Geological Survey (USGS) parameter code is used to uniquely identify a specific constituent or property. Thresholds, threshold values, 

and LRLs as of November 16, 2006. CAS, Chemical Abstract Service. 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 Threshold type: Maximum contaminant level 

thresholds are listed as MCL-US when the MCL-US and MCL-CA are identical, and as MCL-CA when the MCL-CA is lower than the MCL-US or no MCL-US 

exists. HAL-US, U.S. Environmental Protection Agency Lifetime Health Advisory; MCL-CA, California Department of Public Health maximum contaminant 

level; MCL-US, U.S. Environmental Protection Agency maximum contaminant level; RSD5-US, U.S. Environmental Protection Agency risk specific dose at a 

risk factor of 10-5. Detection: D, detected in ground-water samples (table 6). Abbreviations: LRL, laboratory reporting level; μg/L, micrograms per liter; na, not 

available; –, analyzed but not detected]
30 Ground-Water Quality Data in the Coastal Los Angeles Basin Study Unit, 2006: Results from the California GAMA Program

Table 3D. Polar pesticides and pesticide degradates, primary uses or sources, comparative thresholds, and reporting information for 

the U.S. Geological Survey National Water Quality Laboratory Schedule 2060.

[The five-digit U.S. Geological Survey (USGS) parameter code is used to uniquely identify a specific constituent or property. Thresholds, threshold values, 

and LRLs as of November 16, 2006. CAS, Chemical Abstract Service. 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 Threshold: Maximum contaminant level 

thresholds are listed as MCL-US when the MCL-US and MCL-CA are identical, and as MCL-CA when the MCL-CA is lower than the MCL-US or no MCL-US 

exists. HAL-US, U.S. Environmental Protection Agency Lifetime Health Advisory; MCL-CA, California Department of Public Health maximum contaminant 

level; MCL-US, U.S. Environmental Protection Agency maximum contaminant level. RSD5-US, U.S. Environmental Protection Agency risk specific dose at a 

risk factor of 10-5 Detection: D, detected in ground-water samples (table 7). Abbreviations: LRL, laboratory reporting level; μg/L, micrograms per liter; na, not 

available; –, analyzed but not detected]

Constituent

(common name)

Primary use 

or source

USGS

parameter 

code

CAS 

number

 LRL

 (μg/L)

Threshold

Detection

Type Value

(μg/L)

Acifluorfen Herbicide 49315 50594-66-6 0.060 na na –

Aldicarb Insecticide 49312 116-06-3 1 0.04 MCL-US 3 –

Aldicarb sulfone Insecticide/degradate 49313 1646-88-4 0.08 MCL-US 3 –2

Aldicarb sulfoxide Degradate 49314 1646-87-3 0.04 MCL-US 4 –

Atrazine Herbicide 39632 1912-24-9 0.04 MCL-CA 3 –

Bendiocarb Insecticide 50299 22781-23-3 0.04 na na –

Benomyl Fungicide 50300 17804-35-2 0.02 na na –

Bensulfuron-methyl Herbicide 61693 83055-99-6 0.06 na na –

Bentazon Herbicide 38711 25057-89-0 0.02 MCL-CA 200 –2

Bromacil Herbicide 04029 314-40-9 0.04 HAL-US 90 –

Bromoxynil Herbicide 49311 1689-84-5 0.12 na na –

Caffeine Wastewater indicator 50305 58-08-2 0.04 na na –

Carbaryl Herbicide 49310 63-25-2 0.02 RSD5-US 700 –

Carbofuran Herbicide 49309 1563-66-2 0.06 MCL-CA 40 –

Chloramben, methyl ester Herbicide 61188 7286-84-2 0.10 HAL-US 100 –

Chlorimuron-ethyl Herbicide 50306 90982-32-4 0.08 na na –

3-(4-Chlorophenyl)-1-methyl 

urea 

Degradate 61692 5352-88-5 0.06 na na D

Clopyralid Herbicide 49305 1702-17-6 0.06 na na –

Cycloate Herbicide 04031 1134-23-2 0.06 na na –

2,4-D 

(2,4-Dichlorophenoxyacetic 

acid); 2,4-D methyl ester 

(2,4-Dichlorophenoxyacetic 

acid methyl ester)

Herbicides 39732; 

50470

94-75-7; 

1928-38-7

0.04 MCL-US 70 –

2,4-DB 

(4-(2,4-Dichlorophenoxy)

butyric acid)

Herbicide 38746 94-82-6 0.020 na na –2

DCPA (Dacthal) monoacid Degradate 49304 887-54-7 0.02 na na –2

Deethylatrazine (2-Chloro-4-

isopropylamino6-amino-s-triazine)

Degradate 04040 6190-65-4 0.02 na na –2

Deisopropyl atrazine 

(2-chloro-6-ethylamino4-amino-s-triazine)

Degradate 04038 1007-28-9 0.08 na na D

Dicamba Herbicide 38442 1918-00-9 0.08 HAL-US 200 –2

Dichlorprop Herbicide 49302 120-36-5 0.04 na na –

Dinoseb Herbicide 49301 88-85-7 0.04 MCL-CA 7 –2

Diphenamid Herbicide 04033 957-51-7 0.04 HAL 200 D

Diuron Herbicide 49300 330-54-1 0.04 HAL 10 D

Fenuron Herbicide 49297 101-42-8 0.04 na na –

Flumetsulam Herbicide 61694 98967-40-9 0.06 na na –

Fluometuron Herbicide 38811 2164-17-2 0.04 HAL-US 90 –

Hydroxyatrazine (2-Hydroxy4-isopropylamino6-ethylamino-s-triazine)Degradate 50355 2163-68-0 0.080 na na –
Table 3D 31

Constituent

(common name)

Primary use 

or source

USGS

parameter 

code

CAS 

number

 LRL

 (μg/L)

Threshold

Detection

Type Value

(μg/L)

3-Hydroxycarbofuran Degradate 49308 16655-82-6 0.02 na na –

Imazaquin Herbicide 50356 81335-37-7 0.04 na na –

Imazethapyr Herbicide 50407 81335-77-5 0.04 na na –

Imidacloprid Insecticide 61695 138261-41-3 0.06 na na –

Linuron Herbicide 38478 330-55-2 0.04 na na –

MCPA (2-Methyl-4-

chlorophenoxyacetic acid) 

Herbicide 38482 94-74-6 0.06 HAL-US 4 –

MCPB (4-(2-Methyl-4-

chlorophenoxy) butyric 

acid)

Herbicide 38487 94-81-5 0.2 na na –2

Metalaxyl Fungicide 50359 57837-19-1 0.04 na na –

Methiocarb Insecticide 38501 2032-65-7 0.04 na na –

Methomyl Insecticide 49296 16752-77-5 0.06 HAL-US 200 –

Metsulfuron methyl Herbicide 61697 74223-64-6 1 0.14 na na –

Neburon Herbicide 49294 555-37-3 0.02 na na –

Nicosulfuron Herbicide 50364 111991-09-4 0.10 na na –

Norflurazon Herbicide 49293 27314-13-2 0.04 na na D

Oryzalin Herbicide 49292 19044-88-3 0.04 na na –

Oxamyl Insecticide 38866 23135-22-0 0.04 MCL-CA 200 –

Picloram Herbicide 49291 1918-02-01 0.12 MCL-US 500 –2

Propham Herbicide 49236 122-42-9 0.06 HAL-US 100 –

Propiconazole Fungicide 50471 60207-90-1 0.06 na na –

Propoxur Insecticide 38538 114-26-1 0.04 HAL-US 3 –

Siduron Herbicide 38548 1982-49-6 0.04 na na –

Sulfometuron-methyl Herbicide 50337 74222-97-2 0.06 na na –

Tebuthiuron Herbicide 82670 34014-18-1 0.04 HAL-US 500 –

Terbacil Herbicide 04032 5902-51-2 0.04 HAL-US 90 –

Triclopyr Herbicide 49235 55335-06-3 0.04 na na –2

1

 Value is an MRL rather than an LRL.

2

 The median matrix-spike recovery was less than 70 percent. Low recoveries may indicate that the compound might not have been detected in some samples 

if it was present at very low concentrations.

Table 3D. Polar pesticides and pesticide degradates, primary uses or sources, comparative thresholds, and reporting information for 

the U.S. Geological Survey National Water Quality Laboratory Schedule 2060.—Continued

[The five-digit U.S. Geological Survey (USGS) parameter code is used to uniquely identify a specific constituent or property. Thresholds, threshold values, 

and LRLs as of November 16, 2006. CAS, Chemical Abstract Service. 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 Threshold: Maximum contaminant level 

thresholds are listed as MCL-US when the MCL-US and MCL-CA are identical, and as MCL-CA when the MCL-CA is lower than the MCL-US or no MCL-US 

exists. HAL-US, U.S. Environmental Protection Agency Lifetime Health Advisory; MCL-CA, California Department of Public Health maximum contaminant 

level; MCL-US, U.S. Environmental Protection Agency maximum contaminant level. RSD5-US, U.S. Environmental Protection Agency risk specific dose at a 

risk factor of 10-5 Detection: D, detected in ground-water samples (table 7). Abbreviations: LRL, laboratory reporting level; μg/L, micrograms per liter; na, not 

available; –, analyzed but not detected]
32 Ground-Water Quality Data in the Coastal Los Angeles Basin Study Unit, 2006: Results from the California GAMA Program

Table 3E. Potential wastewater indicators, primary uses or sources, comparative thresholds, and reporting information for the U.S. 

Geological Survey National Water Quality Laboratory Schedule 4433.

[The five-digit U.S. Geological Survey (USGS) parameter code is used to uniquely identify a specific constituent or property. Thresholds, threshold values, 

and LRLs as of November 16, 2006. CAS, Chemical Abstract Service. 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. Threshold type: Maximum contaminant 

level thresholds are listed as MCL-US when the MCL-US and MCL-CA are identical, and as MCL-CA when the MCL-CA is lower than the MCL-US or no 

MCL-US exists. HAL-US, U.S. Environmental Protection Agency Lifetime Health Advisory; MCL-CA, California Department of Public Health maximum 

contaminant level; MCL-US, U.S. Environmental Protection Agency maximum contaminant level; NL-CA, California Department of Public Health notification 

level; RSD5-US, U.S. Environmental Protection Agency risk specific dose at a risk factor of 10-5. Detection: D, detected in ground-water samples (table 8). 

Abbreviations: LRL, laboratory reporting level; na, not available; –, not detected: μg/L, micrograms per liter]

Constituent

(common name)

Primary use 

or source

USGS

parameter 

code

CAS 

number

 LRL

 (μg/L)

Threshold

Detection

Type Value

(μg/L)

Acetophenone Fragrance, flavor additive 62811 98-86-2 0.2 na na –

Acetyl hexamethyl tetrahydro 

naphthalene 

(AHTN)

Musk fragrance 62812 21145-77-7 0.2 na na D

Anthracene Wood preservative, 

combustion product 

34220 120-12-7 0.2 na na –

9,10-Anthraquinone Dye/textiles, seed treatment 62813 84-65-1 0.2 na na –

Atrazine Herbicide 39630 1912-24-9 0.2 MCL-CA 1 –

Benzo[a]pyrene Combustion product 34247 50-32-8 0.2 MCL-US 0.2 –(1)

Benzophenone Fixative for perfumes and 

soaps 

62814 119-61-9 0.2 na na D

Bisphenol A Polycarbonate resins, flame 

retardant

62816 80-05-7 0.4 na na D

Bromacil Herbicide 30234 314-40-9 0.2 HAL-US 70 –

Bromoform (tribromomethane) Disinfection by-product 32104 75-25-2 0.2 MCL-US 80 –

3-tert-Butyl-4-hydroxy anisole 

(BHA) 

Antioxidant, general 

preservative 

61702 25013-16-5 0.2 na na –(1)

Caffeine Beverages 81436 58-08-2 0.2 na na –

Camphor Flavor, odorant, ointments 62817 76-22-2 0.2 na na D

Carbaryl Insecticide 39750 63-25-2 0.2 RSD5-US 400 –

Carbazole Insecticide 77571 86-74-8 0.2 na na –

Chlorpyrifos Insecticide 38932 2921-88-2 0.2 HAL-US 2 –

Cholesterol Fecal indicator, plant sterol 62818 57-88-5 0.8 na na D

3-β-Coprostanol Carnivore fecal indicator 62806 360-68-9 0.8 na na D

Cotinine Primary nicotine metabolite 61945 486-56-6 0.8 na na –

p-Cresol Wood preservative 77146 106-44-5 0.2 na na D

4-Cumylphenol Nonionic detergent 

metabolite 

62808 599-64-4 0.2 na na D

Diazinon Insecticide 39570 333-41-5 0.2 HAL-US 1 –

Dichlorvos Insecticide 30218 62-73-7 0.2 na na

N,N-Diethyl-meta-toluamide 

(DEET) 

Insecticide 61947 134-62-3 0.2 na na D

1,4-Dichlorobenzene Moth repellant, fumigant, 

deodorant 

34571 106-46-7 0.2 MCL-CA 5 –(1)

3,4-Dichlorophenyl isocyanate Intermediate for the 

synthesis of organic 

compounds

63145 102-36-3 2 na na D

Diethyl phthalate Wood stains and varnishes, 

plasticizer, softener

34336 84-66-2 0.2 na na D

2,6-Dimethylnaphthalene Diesel/kerosene 62085 581-42-0 0.2 na na D

Bis(2-ethylhexyl) phthalate Plasticizer, softener 39100 117-81-7 2 MCL-CA na D

Nonylphenol monoethoxylates 

(total)

Nonionic detergent 

metabolite

61704 na 2 na na D

4-Nonylphenol diethoxylates Nonionic detergent 

metabolite 

61703 na 3.2 na na D
Table 3E 33

Constituent

(common name)

Primary use 

or source

USGS

parameter 

code

CAS 

number

 LRL

 (μg/L)

Threshold

Detection

Type Value

(μg/L)

4-Octylphenol diethoxylates Nonionic detergent 

metabolite 

61705 na 0.32 na na D

4-Octylphenol monoethoxylates Nonionic detergent 

metabolite 

61706 na 1 na na –

Fluoranthene Component of coal tar and 

asphalt 

34376 206-44-0 0.2 na na D

Hexahydrohexamethylcyclopentabenzopyran (HHCB) Musk fragrance 62823 1222-05-5 0.2 na na D

Indole Pesticide ingredient 62824 120-72-9 0.2 na na D

Isoborneol Fragrance in perfumery 62825 124-76-5 0.2 na na –

Isophorone Solvent 34409 78-59-1 0.2 HAL-US 100 –

Isopropylbenzene Fuels, paint thinner 77223 98-82-8 0.2 NL-CA 770 –(1)

Isoquinoline Flavors and fragrances 62826 119-65-3 0.2 na na –

d-Limonene Fungicide 62819 5989-27-5 0.2 na na D

Menthol Cigarettes, cough drops, 

liniment

62827 89-78-1 0.2 na na –

Metalaxyl Herbicide, fungicide 04254 57837-19-1 0.2 na na –

3-Methyl-1(H)-indole (Skatole) Fragrance, stench in feces 62807 83-34-1 0.2 na na –

5-Methyl-1H-benzotriazole Antioxidant in antifreeze 

and deicers 

61944 136-85-6 1.6 na na D

1-Methylnaphthalene Gasoline, diesel fuel, or 

crude oil 

81696 90-12-0 0.2 na na D

2-Methylnaphthalene Gasoline, diesel fuel, or 

crude oil 

30194 91-57-6 0.2 na na D

Methyl salicylate Liniment, UV-absorbing 

lotion 

62828 119-36-8 0.2 na na D

Metolachlor Herbicide 82612 51218-45-2 0.2 HAL-US 700 –

Naphthalene Fumigant, moth repellent, 

gasoline 

34696 91-20-3 0.4 NL-CA 17 –

4-Nonylphenol (total) Nonionic detergent 

metabolite 

62829 84852-15-3 1.6 na na D

4-n-Octylphenol Nonionic detergent 

metabolite 

62809 1806-26-4 0.2 na na –(1)

4-tert-Octylphenol Nonionic detergent 

metabolite 

62810 140-66-9 0.2 na na –

Pentachlorophenol Fumigant, moth repellent, 

gasoline 

39032 87-86-5 0.8 MCL-US 1 –(1)

Phenanthrene Manufactured explosives 34461 85-01-8 0.2 na na –

Phenol Disinfectant, organic 

synthesis

34694 108-95-2 0.2 HAL-US 2,000 D

Prometon Herbicide 39056 1610-18-0 0.2 HAL-US 100 D

Pyrene Component of coal tar and 

asphalt 

34469 129-00-0 0.2 na na D

β-Sitosterol Plant sterol 62815 83-46-5 0.8 na na –(1)

β-Stigmastanol Plant sterol 61948 19466-47-8 0.8 na na –(1)

Table 3E. Potential wastewater indicators, primary uses or sources, comparative thresholds, and reporting information for the U.S. 

Geological Survey National Water Quality Laboratory Schedule 4433.—Continued

[The five-digit U.S. Geological Survey (USGS) parameter code is used to uniquely identify a specific constituent or property. Thresholds, threshold values, 

and LRLs as of November 16, 2006. CAS, Chemical Abstract Service. 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. Threshold type: Maximum contaminant 

level thresholds are listed as MCL-US when the MCL-US and MCL-CA are identical, and as MCL-CA when the MCL-CA is lower than the MCL-US or no 

MCL-US exists. HAL-US, U.S. Environmental Protection Agency Lifetime Health Advisory; MCL-CA, California Department of Public Health maximum 

contaminant level; MCL-US, U.S. Environmental Protection Agency maximum contaminant level; NL-CA, California Department of Public Health notification 

level; RSD5-US, U.S. Environmental Protection Agency risk specific dose at a risk factor of 10-5. Detection: D, detected in ground-water samples (table 8). 

Abbreviations: LRL, laboratory reporting level; na, not available; –, not detected: μg/L, micrograms per liter]
34 Ground-Water Quality Data in the Coastal Los Angeles Basin Study Unit, 2006: Results from the California GAMA Program

Constituent

(common name)

Primary use 

or source

USGS

parameter 

code

CAS 

number

 LRL

 (μg/L)

Threshold

Detection

Type Value

(μg/L)

2,2',4,4'-Tetrabromodiphenyl etherBrominated flame retardant 63147 5436-43-1 0.2 na na –(1)

Tetrachloroethene (PCE) Solvent, degreaser 34475 127-18-4 0.4 MCL-US 5 –

Tributyl phosphate Antifoaming agent, flame 

retardant 

62832 126-73-8 0.2 na na D

Triclosan Disinfectant, antimicrobial 61708 3380-34-5 0.2 na na D

Triethyl citrate (ethyl citrate) Cosmetics, pharmaceuticals 62833 77-93-0 0.2 na na –

Triphenyl phosphate Plasticizer 62834 115-86-6 0.2 na na D

Tris(2-butoxyethyl)phosphate Flame retardant 62830 78-51-3 0.2 na na D

Tris(2-chloroethyl)phosphate Plasticizer, flame retardant 62831 115-96-8 0.2 na na D

Tris(dichlorisopropyl)phosphate Flame retardant 61707 13674-87-8 0.2 na na D

1The median matrix-spike recovery was less than 70 percent. Low recoveries may indicate that the compound might not have been detected in some samples if it 

was present at very low concentrations.

Table 3E. Potential wastewater indicators, primary uses or sources, comparative thresholds, and reporting information for the U.S. 

Geological Survey National Water Quality Laboratory Schedule 4433.—Continued

[The five-digit U.S. Geological Survey (USGS) parameter code is used to uniquely identify a specific constituent or property. Thresholds, threshold values, 

and LRLs as of November 16, 2006. CAS, Chemical Abstract Service. 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. Threshold type: Maximum contaminant 

level thresholds are listed as MCL-US when the MCL-US and MCL-CA are identical, and as MCL-CA when the MCL-CA is lower than the MCL-US or no 

MCL-US exists. HAL-US, U.S. Environmental Protection Agency Lifetime Health Advisory; MCL-CA, California Department of Public Health maximum 

contaminant level; MCL-US, U.S. Environmental Protection Agency maximum contaminant level; NL-CA, California Department of Public Health notification 

level; RSD5-US, U.S. Environmental Protection Agency risk specific dose at a risk factor of 10-5. Detection: D, detected in ground-water samples (table 8). 

Abbreviations: LRL, laboratory reporting level; na, not available; –, not detected: μg/L, micrograms per liter]
Table 3F 35

Table 3F. Pharmaceutical compounds, primary uses or sources, comparative thresholds, and reporting information for the U.S. 

Geological Survey National Water Quality Laboratory Schedule 2080.

[The five-digit USGS parameter code is used to uniquely identify a specific constituent or property. Thresholds, threshold values, and LRLs as of November 16, 

2006. CAS, Chemical Abstract Service. 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. MDL: The California Groundwater Ambient Monitoring and Assessment 

(GAMA) program uses more conservative reporting limits for the pharmaceutical compounds than recommended by the USGS National Water Quality 

Laboratory. For albuterol, carbamazepine, codeine, dehydronifedipine, diltiazem, sulfamethoxazole, thiabendazole, trimethoprim, and warfarin, the MDL 

corresponds to the long-term method detection limit determined by the USGS Branch of Quality Systems in October 2007 (BQS LT-MDL). For acetaminophen, 

caffeine, cotinine, diphenhydramine, and paraxanthine, the MDL corresponds to the effective method detection limit determine from assessment of qualitycontrol data associated with GAMA samples collected from May 2004 through September 2007 (GAMA E-MDL). The GAMA E-MDL are higher than the 

BQS LT-MDL for those compounds. Detections reported by the USGS National Water Quality Laboratory with concentrations lower than the BQS LT-MDL or 

GAMA E-MDL are reported as non-detections by the GAMA program. Abbreviations: MDL, method detection limit; na, not available; μg/L, micrograms per 

liter]

Constituent

(common name)

Primary use 

or source

USGS

parameter 

code

CAS 

number

 MDL

 (μg/L)

Threshold

Detection

Type Value

(μg/L)

Acetaminophen Analgesic 62000 103-90-2 0.0239 na na na

Caffeine Stimulant 50305 58-08-2 0.0149 na na na

Carbamazapine Anticonvulsant; analgesic; 

mood stabilizer

62793 298-46-4 0.0179 na na na

Codeine Opiod narcotic 62003 76-57-3 0.0223 na na na

Cotinine Nicotine metabolite 62005 486-56-6 0.0284 na na na

Dehydronifedipine Antianginal metabolite 62004 67035-22-7 0.022 na na na

Diltiazem Antianginal; 

antihypertensive

62008 42399-41-7 0.0178 na na na

1,7-Dimethylxanthine Caffeine metabolite 62030 611-59-6 0.0208 na na na

Diphenhydramine Antihistamine 62796 58-73-1 0.0229 na na na

Salbutamol (albuterol) Anti-inflammatory; 

bronchodilator

62020 18559-94-9 0.0139 na na na

Sulfamethoxazole Antibacterial, antiprotozoal 62021 723-46-6 0.0237 na na na

Thiabendazole Anthelmintic 62801 148-79-8 0.025 na na na

Trimethoprim Antibacterial 62023 738-70-5 0.0203 na na na

Warfarin Anticoagulant 62024 81-81-2 0.0188 na na na
36 Ground-Water Quality Data in the Coastal Los Angeles Basin Study Unit, 2006: Results from the California GAMA Program

Constituent 

(common name)

Primary use 

or source

USGS 

parameter code

CAS 

number

 MRL 

(μg/L)

Threshold

Detection

Type Value 

(μg/L)

Perchlorate Rocket fuel, 

fireworks, flares

61209 14797-73-0 0.5 MCL-CA 6 D

1,2,3-Trichloropropane 

(TCP)

Industrial solvent, 

organic synthesis

77443 96-18-4 0.005 HAL-US 40 –

1,4-Dioxane Industrial solvent, 

synthetic synthesis

81582 123-91-1 2 NL-CA 3 D

N-Nitrosodimethylamine 

(NDMA)

Disinfection byproduct64176 62-75-9 2 NL-CA 0.01 D

Table 3G. Constituents of special interest, primary uses or sources, comparative thresholds, and reporting information for compounds 

analyzed at the Montgomery Watson-Harza Laboratory.

[The five-digit U.S. Geological Survey (USGS) parameter code is used to uniquely identify a specific constituent or property. Thresholds, threshold values, 

and LRLs as of November 16, 2006. CAS, Chemical Abstract Service. 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. Threshold type, Maximum contaminant level 

thresholds are listed as MCL-US when the MCL-US and MCL-CA are identical, and as MCL-CA when the MCL-CA is lower than the MCL-US or no MCL-US 

exists. HAL-US, U.S. Environmental Protection Agency lifetime health advisory; MCL-CA, California Department of Public Health maximum contaminant 

level; NL-CA, California Department of Public Health notification level. Abbreviations: MRL, minimum reporting level; D, detected in ground-water samples 

(table 9); μg/L, micrograms per liter; –, analyzed but not detected]

Constituent 

(common name)

USGS 

parameter 

code

CAS 

number

 LRL 

(mg/L)

Threshold

Detection

Type Value 

(mg/L)

Ammonia (as nitrogen) 00608 7664-41-7 0.010 HAL-US 1

30 D

Nitrite (as nitrogen) 00613 14797-65-0 0.002 MCL-US 1 D

Nitrate plus nitrite (as nitrogen) 00631 na 0.060 MCL-US 10 D

Total nitrogen (ammonia, nitrite, nitrate, 

organic nitrogen)

62854 17778-88-0 0.06 na na D

Phosphorus, phosphate, orthophosphate (as 

phosphorus)

00671 14265-44-2 0.006 na na D

Dissolved organic carbon (DOC) 00681 na 0.33 na na D

1

 Threshold value is “as ammonia.”

Table 3H. Nutrients and dissolved organic carbon, comparative thresholds, and reporting information for the U.S. Geological Survey 

National Water Quality Laboratory Schedule 2755 and parameter code 2612.

[The five-digit U.S. Geological Survey (USGS) parameter code is used to uniquely identify a specific constituent or property. Thresholds, threshold values, 

and LRLs as of November 16, 2006. CAS, Chemical Abstract Service. 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.Threshold type: Maximum contaminant level 

thresholds are listed as MCL-US when the MCL-US and MCL-CA are identical, and as MCL-CA when the MCL-CA is lower than the MCL-US or no MCL-US 

exists. HAL-US, U.S. Environmental Protection Agency lifetime health advisory level; MCL-US, U.S. Environmental Protection Agency maximum contaminant 

level. Abbreviations: LRL, laboratory reporting level; D, detected in groundwater samples (table 10); na, not available; mg/L, milligrams per liter]
Table 3I 37

Constituent

USGS 

parameter 

code

CAS 

number LRL

Threshold

Detection

Type Value

Major and minor ions (mg/L)

Bromide 71870 24959-67-9 0.02 na na D

Calcium 00915 7440-70-2 0.02 na na D

Chloride 00940 16887-00-6 0.2 SMCL-CA 1

250 (500) D

Fluoride 00950 16984-48-8 0.10 MCL-CA 2 D

Iodide 78165 7553-56-2 0.002 na na D

Magnesium 00925 7439-95-4 0.008 na na D

Potassium 00935 7440-09-7 0.16 na na D

Silica 00955 7631-86-9 0.04 na na D

Sodium 00930 7440-23-5 0.20 na na D

Sulfate 00945 14808-79-8 0.18 SMCL-CA 1

250 (500) D

Residue on evaporation 

(total dissolved solids, TDS)

70300 na 10 SMCL-US 1500 (1,000) D

Trace elements (μg/L)

Aluminum 01106 7429-90-5 1.6 MCL-CA 1,000 D

Antimony 01095 7440-36-0 0.2 MCL-US 6 D

Arsenic 01000 7440-38-2 0.12 MCL-US 10 D

Barium 01005 7440-39-3 0.2 MCL-CA 1,000 D

Beryllium 01010 7440-41-7 0.06 MCL-US 4 –

Boron 01020 7440-42-8 8 NL-CA 1,000 D

Cadmium 01025 7440-43-9 0.04 MCL-US 5 D

Chromium 01030 7440-47-3 0.04 MCL-CA 50 D

Cobalt 01035 7440-48-4 0.04 na na D

Copper 01040 7440-50-8 0.4 AL-US 1,300 D

Iron 01046 7439-89-6 6 SMCL-CA 300 D

Lead 01049 7439-92-1 0.08 AL-US 15 D

Lithium 01130 7439-93-2 0.6 na na D

Manganese 01056 7439-96-5 0.2 SMCL-CA 50 D

Mercury 71890 7439-97-6 0.010 MCL-US 2 D

Molybdenum 01060 7439-98-7 0.4 HAL-US 40 D

Nickel 01065 7440-02-0 0.06 MCL-CA 100 D

Selenium 01145 7782-49-2 0.08 MCL-US 50 D

Silver 01075 7440-22-4 0.2 SMCL-CA 100 –

Strontium 01080 7440-24-6 0.4 HAL-US 4,000 D

Thallium 01057 7440-28-0 0.04 MCL-US 2 D

Tungsten 01155 7440-33-7 0.06 na na D

Uranium 22703 7440-61-1 0.04 MCL-US 30 D

Vanadium 01085 7440-62-2 0.10 NL-CA 50 D

Zinc 01090 7440-66-6 0.6 HAL-US 2,000 D

1

 The recommended SMCL-CA thresholds for chloride, sulfate, and TDS are listed with the upper SMCL-CA thresholds in parentheses.

Table 3I. Major and minor ions and trace elements, comparative thresholds, and reporting information for the U.S. Geological Survey 

National Water Quality Laboratory Schedule 1948.

[The five-digit U.S. Geological Survey (USGS) parameter code is used to uniquely identify a specific constituent or property. Thresholds, threshold values, 

and LRLs as of November 16, 2006. CAS, Chemical Abstract Service. 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. Threshold type: Maximum contaminant level 

thresholds are listed as MCL-US when the MCL-US and MCL-CA are identical, and as MCL-CA when the MCL-CA is lower than the MCL-US or no MCL-US 

exists. HAL-US, U.S. Environmental Protection Agency Lifetime Health Advisory; MCL-CA, California Department of Public Health maximum contaminant 

level; MCL-US, U.S. Environmental Protection Agency maximum contaminant level; NL-CA, California Department of Public Health notification level; 

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

maximum contaminant level; AL-US, U.S. Environmental Protection Agency action level. Abbreviations: LRL, laboratory reporting level; D, detected in 

ground-water samples (tables 11 and 12); na, not available; mg/L, milligrams per liter; μg/L, micrograms per liter; –, analyzed but not detected]
38 Ground-Water Quality Data in the Coastal Los Angeles Basin Study Unit, 2006: Results from the California GAMA Program

Constituent 

(valence state)

USGS 

parameter 

code

CAS 

number

MDL 

(μg/L)

Threshold

Detection

Type Level

(μg/L)

Arsenic (III) 99034 22569-72-8 1 na na D

Arsenic (total) 01000 7440-38-2 0.5 MCL-US 10 D

Chromium (VI) 01032 18540-29-9 1 na na D

Chromium (total) 01030 7440-47-3 1 MCL-CA 50 D

Iron (II) 01047 7439-89-6 2 na na D

Iron (total) 01046 7439-89-6 2 HAL-US 300 D

Table 3J. Arsenic, chromium, and iron species, comparative thresholds, and reporting information for the U.S. Geological Survey Trace 

Metal Laboratory, Boulder, Colorado.

[The five-digit U.S. Geological Survey (USGS) parameter code is used to uniquely identify a specific constituents or property. Thresholds, threshold values, 

and LRLs as of November 16, 2006. CAS, Chemical Abstract Service. 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.Threshold type: Maximum contaminant level 

thresholds are listed as MCL-US when the MCL-US and MCL-CA are identical, and as MCL-CA when the MCL-CA is lower than the MCL-US or no MCL-US 

exists. HAL-US, U.S. Environmental Protection Agency lifetime health advisory; MCL-CA, California Department of Public Health maximum contaminant 

level; MCL-US, U.S. Environmental Protection Agency maximum contaminant level. Abbreviations: MDL, method detection limit; na, not available; μg/L, 

micrograms per liter; D, detected in ground-water samples (table 13)]
Table 3K 39

Constituent

USGS 

parameter 

code

CAS 

number

Reporting 

level 

type

Reporting 

level or 

uncertainty

Threshold

Detection

Type Value

Stable isotope ratios (per mil)

δ2

H of water1 82082 na MU 2 na na D

δ18O of water1 82085 na MU 0.20 na na D

δ13C of dissolved carbonates2 82081 na 1 sigma 0.05 na na D

Radioactive constituents (percent modern)

3

Carbon-14 49933 14762-75-5 1 sigma 0.002 na na D

Radioactive constituents (pCi/L)

4 Radon-222 82303 14859-67-7 SSMDC 17 – 41 Prop. MCL-US 5

300 (4,000) D

Tritium6, 7 07000 10028-17-8 MRL 1 MCL-CA 20,000 D

Gross-alpha radioactivity, 72-hour counts8 99920 12587-46-1 SSMDC 0.59 – 11.0 MCL-US 15 D

Gross-alpha radioactivity, 30-day counts8 99921 12587-46-1 SSMDC 0.69 – 7.0 MCL-US 15 D

Gross-beta radioactivity, 72-hour counts8 99922 12587-47-2 SSMDC 0.49 – 3.5 MCL-CA 50 D

Gross-beta radioactivity, 30-day counts8 99923 12587-47-2 SSMDC 0.48 – 3.2 MCL-CA 50 D 8 Radium-226 99915 13982-63-3 SSMDC 0.011 – 0.016 MCL-US 9

5 D 8 Radium-228 99916 15262-20-1 SSMDC 0.19 – 0.24 MCL-US 9

5 D

1

 USGS Stable Isotope Laboratory, Reston, Virginia.

2

 University of Waterloo (contract laboratory).

3

 University of Arizona, Accelerator Mass Spectrometry Laboratory (contract laboratory).

4

 USGS National Water Quality Laboratory.

5

 Two MCLs have been proposed for Radon-222. The proposed Alternative MCL is in parentheses.

6

 USGS Stable Isotope and Tritium Laboratory, Menlo Park, California.

7

 Lawrence Livermore National Laboratory.

8

 Eberline Analytical Services (contract laboratory).

9 The MCL-US threshold for radium is the sum of radium-226 and radium-228.

Table 3K. Isotopic and radioactive constituents, comparative thresholds, and reporting information for laboratories.

[The five-digit USGS parameter code is used to uniquely identify a specific constituent or property. Thresholds, threshold values, and LRLs as of November 

16, 2006. 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. CAS, Chemical Abstract Service. 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. Threshold type: Maximum contaminant 

level thresholds are listed as MCL-US when the MCL-US and MCL-CA are identical, and as MCL-CA when the MCL-CA is lower than the MCL-US or no 

MCL-US exists. MCL-CA, California Department of Public Health maximum contaminant level; MCL-US, U.S. Environmental Protection Agency maximum 

contaminant level. Abbreviations: MU, method uncertainty; SSMDC, sample specific minimum detectable concentration; MRL, minimum reporting level; na, 

not available; pCi/L, picocuries per liter; D, detected in ground-water samples (tables 14 and 15)]
40 Ground-Water Quality Data in the Coastal Los Angeles Basin Study Unit, 2006: Results from the California GAMA Program

Constituent

USGS 

parameter 

code

Primary source MDL

Threshold

Detection

Type Value

Escherichia coli1 90901 Sewage and animal 

waste indicator

1 colony/

100 mL

TT-US Zero –

Total coliform - including 

fecal coliform and E. coli)1

90900 Sewage and animal 

waste indicator

1 colony/

100 mL

MCL-US 5 percent of samples 

positive per month

D

F-specific coliphage 99335 Sewage and animal 

waste indicator

na TT-US 99.99 percent killed/

inactivated

–

Somatic coliphage 99332 Sewage and animal 

waste indicator

na TT-US 99.99 percent killed/

inactivated

–

1

 Analyzed in the field.

Table 3L. Microbial constituents, comparison thresholds, and reporting information for the U.S. Geological Survey Ohio Microbiology 

Laboratory parameter codes 90901, 90900, 99335 and 99332.

[The five-digit U.S. Geological Survey (USGS) parameter code is used to uniquely identify a specific constituent or property. Thresholds and threshold values 

as of November 16, 2006. Threshold type: Maximum contaminant level thresholds are listed as MCL-US when the MCL-US and MCL-CA are identical, and 

as MCL-CA when the MCL-CA is lower than the MCL-US or no MCL-US exists. MCL-US, U.S. Environmental Protection Agency maximum contaminant 

level; TT-US, U.S. Environmental Protection Agency treatment technique—a required process intended to reduce the level of contamination in drinking water. 

Abbreviations: MDL, method detection limit; mL, milliliters; D, detected in ground-water samples (table 16); –, analyzed but not detected]

Constituent

USGS 

parameter 

code

CAS 

number

MU 

(percent)

Reporting 

units

Threshold

Detection

Type Value (pCi/L)

Argon na 7440-37-1 2 cm3

STP/g na na na

Helium-3 / Helium-4 ratio na na / 7440-59-7 0.75 atom ratio na na na

Helium-4 na 7440-59-7 2 cm3

STP/g na na na

Krypton na 7439-90-9 2 cm3

STP/g na na na

Neon na 7440-01-09 2 cm3

STP/g na na na

Tritium 07000 10028-17-8 1 pCi/L MCL-CA 20,000 na

Xenon na 7440-63-3 2 cm3

STP/g na na na

Table 3M. Noble gases and tritium, comparison thresholds and reporting information for the Lawrence Livermore National Laboratory.

[The five-digit U.S. Geological Survey (USGS) parameter code is used to uniquely identify a specific constituent or property. Thresholds, threshold values, 

and LRLs as of November 16, 2006. CAS, Chemical Abstract Service. 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. Threshold type: Maximum contaminant level 

thresholds are listed as MCL-US when the MCL-US and MCL-CA are identical, and as MCL-CA when the MCL-CA is lower than the MCL-US or no MCL-US 

exists. MCL-CA, California Department of Public Health maximum contaminant level. Abbreviations: MU, method uncertainty; na, not available; cm3 STP/g, 

cubic centimeters of gas at standard temperature and pressure per gram of water; pCi/L, picocuries per liter]
Table 4 41

GAMA 

identification 

No.

Turbidity 

(NTRU) 

(63676)

Dissolved 

oxygen 

(mg/L) (00300) 

Water 

temperature 

(°C) 

(00010)

pH, 

lab 

(standard units) 

(00403)

pH, 

field 

(standard 

units) (00400)

Specific 

conductance, 

lab 

(μS/cm at 25°C) 

(90095)

Specific 

conductance, 

field 

(μS/cm at 25°C) 

(00095)

Alkalinity, 

lab 

(mg/L as

 CaCO3) 

(29801)

Alkalinity, 

field 

(mg/L as 

CaCO3) 

(29802)

Threshold type TT-US na na SMCL-US SMCL-US SMCL-CA SMCL-CA na na

Threshold level 5 na na 6.5–8.5 6.5–8.5 900 (1,600) 900 (1,600) na na

[RL] [0.1] [0.2] [0.0–38.5] [0–14] [0–14] [5] [5] [1] [1]

CLAB Grid wells

CB-01 nc 0.6 21.0 nc 7.1 nc 746 nc nc

CB-02 nc 0.2 19.5 7.5 7.3 613 611 198 nc

CB-03 0.2 0.8 19.5 7.4 7.1 775 752 144 142

CB-04 0.2 <0.2 29.0 * 8.8 * 8.7 337 350 128 126

CB-05 nc <0.2 28.0 nc nc nc 311 nc nc

CB-06 nc 1.2 22.0 nc nc nc 395 nc nc

CB-07 nc E 1.7 21.0 nc nc nc * 914 nc nc

CB-08 nc E 1.0 19.0 nc nc nc 661 nc nc

CB-09 nc <0.2 22.5 nc nc nc 523 nc nc

CB-10 nc <0.2 21.0 nc nc nc 553 nc nc

CB-11 nc E 0.4 21.0 nc nc nc 657 nc nc

CB-12 nc <0.2 24.0 nc nc nc 697 nc nc

CB-13 nc 1.2 19.0 nc nc nc 688 nc nc

CB-14 nc 0.2 23.5 nc nc nc 534 nc nc

CB-15 nc 1.1 18.5 nc nc nc 855 nc nc

CB-16 nc 3.8 20.0 nc nc nc 850 nc nc

CB-17 nc 3.0 19.0 7.7 7.3 814 808 224 nc

CB-18 nc 0.2 25.0 nc 7.7 nc * 1,100 nc nc

CB-19 nc 3.6 18.5 nc 7.2 nc 896 nc nc

CB-20 nc <0.2 23.5 nc 7.5 nc * 1,560 nc nc

CB-21 nc <0.2 24.0 nc 7.8 nc 501 nc nc

OC-01 0.1 1.5 21.5 7.7 7.4 741 753 nc 158

OC-02 0.1 1.1 17.5 7.8 7.5 * 965 * 952 210 208

OC-03 nc E 5.4 20.0 nc nc nc * 990 nc nc

OC-04 nc E 3.2 19.0 nc nc nc 738 nc nc

OC-05 nc E 3.5 18.5 nc nc nc * 967 nc nc

OC-06 nc E 4.0 19.0 nc nc nc 858 nc nc

OC-07 nc E 4.5 18.5 nc nc nc 490 nc nc

OC-08 nc E 4.6 19.0 nc nc nc 806 nc nc

OC-09 nc E 2.9 23.0 nc nc nc 743 nc nc

OC-10 nc E 2.6 26.5 nc nc nc 654 nc nc

OC-11 nc 0.5 25.0 nc nc nc 476 nc nc

OC-12 nc 0.5 30.0 nc nc nc 613 nc nc

OC-13 nc 0.3 19.0 nc nc nc 794 nc nc

OC-14 nc 0.3 20.0 nc nc nc 414 nc nc

OC-15 nc 3.9 18.0 nc nc nc 507 nc nc

OC-16 nc 0.6 20.5 nc nc nc * 961 nc nc

OC-17 nc 2.5 20.0 nc nc nc * 997 nc nc

Table 4. Water-quality indicators in samples collected for the Coastal Los Angeles Basin Groundwater Ambient Monitoring and 

Assessment (GAMA) study unit, California, June to November 2006.

[The five-digit U.S. Geological Survey (USGS) parameter code below the constituent name is used to uniquely identify a specific constituent or property. 

Thresholds, threshold values, and LRLs as of November 16, 2006. Threshold type: Maximum contaminant level thresholds are listed as MCL-US when the 

MCL-US and MCL-CA are identical, and as MCL-CA when the MCL-CA is lower than the MCL-US or no MCL-US exists. SMCL-US, U.S. Environmental 

Protection Agency secondary maximum contaminant level; TT-US, U.S. Environmental Protection Agency treatment technique—a required process intended to 

reduce the level of contamination in drinking water; SMCL-CA, California Department of Public Health secondary maximum contaminant level. The SMCL-CA

for specific conductance has recommended and upper threshold values. The upper value is shown in parentheses. Abbreviations: CLAB; Coastal Los Angeles 

Basin; CLAB Grid Wells; CLAB Understanding Wells; RL, reporting limit or range; °C, degrees celsius; CaCO3, calcium carbonate; E, estimated or having 

a higher degree of uncertainty; >, greater than; <, less than; mg/L, milligrams per liter; nc, not collected; NTRU, nephelometric turbidity ratio units; μS/cm, 

microsiemens per centimeter]
42 Ground-Water Quality Data in the Coastal Los Angeles Basin Study Unit, 2006: Results from the California GAMA Program

GAMA 

identification 

No.

Turbidity 

(NTRU) 

(63676)

Dissolved 

oxygen 

(mg/L) (00300) 

Water 

temperature 

(°C) 

(00010)

pH, 

lab 

(standard units) 

(00403)

pH, 

field 

(standard 

units) (00400)

Specific 

conductance, 

lab 

(μS/cm at 25°C) 

(90095)

Specific 

conductance, 

field 

(μS/cm at 25°C) 

(00095)

Alkalinity, 

lab 

(mg/L as

 CaCO3) 

(29801)

Alkalinity, 

field 

(mg/L as 

CaCO3) 

(29802)

Threshold type TT-US na na SMCL-US SMCL-US SMCL-CA SMCL-CA na na

Threshold level 5 na na 6.5–8.5 6.5–8.5 900 (1,600) 900 (1,600) na na

[RL] [0.1] [0.2] [0.0–38.5] [0–14] [0–14] [5] [5] [1] [1]

CLAB Grid wells—Continued

OC-18 nc <0.2 24.5 nc * 8.8 nc 412 nc nc

OC-19 nc 0.2 19.0 nc 7.5 nc 632 nc nc

OC-20 nc <0.2 20.0 7.6 7.2 * 1,030 *1,030 218 nc

OC-21 nc 3.4 23.5 nc 7.4 nc * 975 nc nc

OC-221 nc E 7.0 E 17.0 nc E 7.9 nc E 450 nc nc

OC-23 nc 0.3 28.5 nc 7.7 nc * 1,340 nc nc

OC-24 nc 2.5 18.5 nc 7.2 nc * 1,020 nc nc

WB-01 nc <0.2 22.5 nc nc nc >** 10,000 nc nc

WB-02 nc 2.1 22.5 nc nc nc * 1,360 nc nc

WB-03 nc 0.3 23.5 nc nc nc * 1,130 nc nc

WB-04 nc 0.2 24.0 7.8 7.6 * 1,220 * 1,210 456 nc

WB-05 nc <0.2 24.0 nc 8.0 nc 640 nc nc

WB-06 nc 0.2 29.5 nc 8.2 nc * 1,060 nc nc

WB-07 nc <0.2 25.5 nc 8.0 nc * 1,350 nc nc

WB-08 nc 3.6 25.0 nc 8.2 nc 425 nc nc

WB-09 nc 0.2 21.0 nc 6.5 nc * 1,270 nc nc

WB-10 nc 0.2 20.0 nc 7.4 nc * 1,300 nc nc

CLAB Understanding wells

DA-01 0.6 1.8 21.0 6.8 6.5 * 1,170 * 1,190 272 258

DA-02 .2 2.5 20.5 7.1 6.7 * 1,290 * 1,290 314 314

DA-03 .2 <0.2 24.5 7.7 7.4 890 * 913 308 296

DA-04 .3 2.9 20.0 7.0 6.5 * 1,310 * 1,310 335 319

DA-05 .2 <0.2 26.0 8.0 7.8 * 1,460 * 1,470 410 392

DA-06 .3 0.2 23.0 7.4 7.2 ** 3,660 ** 3,680 485 479

U-01 .1 2.8 19.5 7.6 7.3 509 507 nc 167

U-02 .1 <0.2 19.5 7.5 7.2 854 859 219 215

U-03 nc 0.8 19.0 7.7 7.3 865 865 178 nc

U-04 nc 3.7 18.0 nc 7.5 nc 778 nc nc

U-05 nc 0.3 19.0 nc 7.5 nc 782 nc nc

U-06 nc 2.1 21.0 7.3 6.9 * 1,250 * 1,290 290 nc

U-07 nc 0.2 20.0 7.3 7.2 * 1,430 * 1,440 336 nc

U-08 nc 1.3 18.5 nc 7.4 nc 543 nc nc

*

 Value exceeds threshold.

**

 Value exceeds recommended upper threshold.

1

 E-codes for OC-22 values were as a result of an abbreviated well purge time.

Table 4. Water-quality indicators in samples collected for the Coastal Los Angeles Basin Groundwater Ambient Monitoring and 

Assessment (GAMA) study unit, California, June to November 2006.—Continued

[The five-digit U.S. Geological Survey (USGS) parameter code below the constituent name is used to uniquely identify a specific constituent or property. 

Thresholds, threshold values, and LRLs as of November 16, 2006. Threshold type: Maximum contaminant level thresholds are listed as MCL-US when the 

MCL-US and MCL-CA are identical, and as MCL-CA when the MCL-CA is lower than the MCL-US or no MCL-US exists. SMCL-US, U.S. Environmental 

Protection Agency secondary maximum contaminant level; TT-US, U.S. Environmental Protection Agency treatment technique—a required process intended to 

reduce the level of contamination in drinking water; SMCL-CA, California Department of Public Health secondary maximum contaminant level. The SMCL-CA

for specific conductance has recommended and upper threshold values. The upper value is shown in parentheses. Abbreviations: CLAB; Coastal Los Angeles 

Basin; CLAB Grid Wells; CLAB Understanding Wells; RL, reporting limit or range; °C, degrees celsius; CaCO3, calcium carbonate; E, estimated or having 

a higher degree of uncertainty; >, greater than; <, less than; mg/L, milligrams per liter; nc, not collected; NTRU, nephelometric turbidity ratio units; μS/cm, 

microsiemens per centimeter]
Table 5 43

Table 5. Volatile organic compounds (VOCs), and gasoline oxygenates and degradates detected in samples collected for the Coastal 

Los Angeles Basin Groundwater Ambient Monitoring and Assessment (GAMA) study unit, California, June to November 2006.

[The five-digit U.S. Geological Survey (USGS) parameter code below the constituent name is used to uniquely identify a specific constituent or property. 

Thresholds, threshold values, and LRLs as of November 16, 2006. Samples from all 69 wells were analyzed, but only samples with detections are listed. 

Analytes are listed in order of decreasing detection frequency in the 55 grid wells. All analytes are listed in tables 3A and 3B. Threshold: Maximum 

contaminant level thresholds are listed as MCL-US when the MCL-US and MCL-CA are identical, and as MCL-CA when the MCL-CA is lower than the 

MCL-US or no MCL-US exists. HAL-US, Lifetime Health Advisory Level; MCL-US, U.S. Environmental Protection Agency maximum contaminant 

level; MCL-CA; California Department of Public Health maximum contaminant level; NL-CA, California notification level. The MCL-US threshold for 

trihalomethanes is for the sum of chloroform, bromoform, bromodichloromethane, and dibromochloromethane. The MCL-CA thresholds for Xylenes is for 

the sum of m- and p-Xylene and o-Xylene. Abbreviations: CLAB; Coastal Los Angeles Basin; CLAB Grid Wells; CLAB Understanding Wells; E, estimated 

or having a higher degree of uncertainty; LRL, laboratory reporting level; na, not available; –, not detected; μg/L, microgram per liter; percentage values are 

detection frequencies]

 GAMA 

identification 

No.

Trihalomethane Solvent Gasoline Solvent Organic 

synthesis

Trihalomethane

Chloroform 

(Trichloromethane) 

(μg/L) (32106)

Trichloroethene 

(TCE)

(μg/L) (39180)

Tetrachloroethene 

(PCE)

(μg/L) 

(34475)

Methyl tert-butyl 

ether (MTBE) 

(μg/L) 

(78032)

cis-1,2-

Dichloroethene 

(μg/L) 

(77093)

1,1-Dichloroethene 

(1,1-DCE) 

(μg/L) 

(34501)

Bromodichloromethane 

(μg/L) 

(32101)

[LRL] [0.04] [0.02] [0.04] [0.10] [0.02] [0.04] [0.04]

Threshold type MCL-US MCL-US MCL-US MCL-CA MCL-CA MCL-CA MCL-US

Threshold (μg/L) 80 5 5 13 6 7 80

CLAB Study Unit (55 grid wells sampled)

Number of wells 

with detections

25 16 14 11 9 8 6

Detection frequency 

(percent)

45 29 25 20 16 15 11

Total Detections

CLAB Central Basin Study Area (21 grid wells sampled)

CB-02 E 0.06 – E0.04 – – – –

CB-03 E 0.06 – – 0.3 – – –

CB-07 E 0.07 1.72 0.35 – – E 0.04 –

CB-08 – 0.22 E 0.04 – – – –

CB-10 E 0.07 – – – – – –

CB-11 E 0.10 0.79 0.33 – – – –

CB-12 E 0.03 0.13 E 0.02 – E 0.02 – –

CB-13 E 0.14 2.22 1.72 0.1 E 0.06 0.26 –

CB-15 E 0.13 0.12 0.34 0.2 – 0.42 –

CB-16 E 0.31 1.04 0.93 – E 0.05 2.47 E 0.03

CB-17 E 0.06 0.62 4.14 E .1 – – –

CB-18 E 0.01 – – – – – –

CB-19 0.28 1.15 0.14 – – – –

Number of wells with 

detections

12 9 10 4 3 4 1

Detection frequency 

(percent)

57 43 48 19 14 19 5

Total Detections
44 Ground-Water Quality Data in the Coastal Los Angeles Basin Study Unit, 2006: Results from the California GAMA Program

 GAMA 

identification 

No.

Solvent Refrigerant Solvent Organic 

synthesis Solvent Gasoline

1,1-Dichloroethane 

(1,1-DCA) 

(μg/L) 

(34496)

Trichlorotrifluoroethane 

(CFC-113) 

(μg/L) (77652)

1,1,1-Trichloroethane 

(1,1,1-TCA) 

(μg/L) 

(34506)

Carbon 

disulfide 

(μg/L) 

(77041)

Dichloromethane

(μg/L) 

(34423)

Diisopropyl 

ether 

(DIPE) 

(μg/L) 

(81577)

Toluene 

(μg/L) 

(34010)

[LRL] [0.06] [0.04] [0.04] [0.06] [0.04] [0.06] [0.018]

Threshold type MCL-CA MCL-CA MCL-US NL-CA MCL-US na MCL-CA

Threshold (μg/L) 5 1,200 200 160 5 na 150

CLAB Study Unit (55 grid wells sampled)—Continued

Number of wells with 

detections

5 5 4 4 2 2 2

Detection frequency 

(percent)

9 9 7 7 4 4 4

Total Detections 

CLAB Central Basin Study Area (21 grid wells sampled)—Continued

CB-02 – – – – – – –

CB-03 – – – – – – –

CB-07 E 0.09 E 0.03 – – – – –

CB-08 – – – – – – –

CB-10 – – – – – – –

CB-11 – – – – – – –

CB-12 – – – – – – –

CB-13 E 0.05 – E 0.03 – – – –

CB-15 E 0.05 – E 0.05 – – – –

CB-16 0.10 – E 0.08 – – – –

CB-17 E 0.07 – – – – – –

CB-18 – – – E0.02 – – –

CB-19 – – – – – – –

Number of wells with 

detections

5 1 3 1 0 0 0

Detection frequency 

(percent)

24 5 14 5 0 0 0

Total Detections 

Table 5. Volatile organic compounds (VOCs), and gasoline oxygenates and degradates detected in samples collected for the Coastal 

Los Angeles Basin Groundwater Ambient Monitoring and Assessment (GAMA) study unit, California, June to November 2006.—

Continued

[The five-digit U.S. Geological Survey (USGS) parameter code below the constituent name is used to uniquely identify a specific constituent or property. 

Thresholds, threshold values, and LRLs as of November 16, 2006. Samples from all 69 wells were analyzed, but only samples with detections are listed. 

Analytes are listed in order of decreasing detection frequency in the 55 grid wells. All analytes are listed in tables 3A and 3B. Threshold: Maximum 

contaminant level thresholds are listed as MCL-US when the MCL-US and MCL-CA are identical, and as MCL-CA when the MCL-CA is lower than the 

MCL-US or no MCL-US exists. HAL-US, Lifetime Health Advisory Level; MCL-US, U.S. Environmental Protection Agency maximum contaminant 

level; MCL-CA; California Department of Public Health maximum contaminant level; NL-CA, California notification level. The MCL-US threshold for 

trihalomethanes is for the sum of chloroform, bromoform, bromodichloromethane, and dibromochloromethane. The MCL-CA thresholds for Xylenes is for 

the sum of m- and p-Xylene and o-Xylene. Abbreviations: CLAB; Coastal Los Angeles Basin; CLAB Grid Wells; CLAB Understanding Wells; E, estimated 

or having a higher degree of uncertainty; LRL, laboratory reporting level; na, not available; –, not detected; μg/L, microgram per liter; percentage values are 

detection frequencies]
Table 5 45

 GAMA 

identification 

No.

Gasoline Trihalomethane Solvent Refrigerant Gasoline Refrigerant

Benzene 

(μg/L) 

(34030)

Bromoform

 (Tribromomethane) 

(μg/L) 

(32104)

Carbon 

tetrachloride 

(Tetrachloromethane) 

(μg/L) 

(32102)

Dichlorodifluormethane 

(CFC-12) 

(μg/L) 

(34668)

Naphthalene, 

(μg/L) 

(34696)

1,2,4-Trimethylbenzene 

(μg/L) 

(77222)

Trichlorofluoromethane 

(CFC-11) 

(μg/L) 

(34488)

[LRL] [0.016] [0.08] [0.08] [0.14] [0.4] [0.04] [0.08]

Threshold type MCL-CA MCL-US MCL-CA HAL-US HAL-US NL-CA MCL-CA

Threshold (μg/L) 1 80 0.5 1,000 100 330 150

CLAB Study Unit (55 grid wells sampled)—Continued

Number of wells with 

detections

1 1 1 1 1 1 1

Detection frequency 

(percent)

2 2 2 2 2 2 2

Total Detections

CLAB Central Basin Study Area (21 grid wells sampled)—Continued

CB-02 – E 0.17 – – – – –

CB-03 – – – – – E 0.07 –

CB-07 – – – – – – –

CB-08 – – – – – – –

CB-10 – – – – – – –

CB-11 – – – – – – –

CB-12 – – – – – – –

CB-13 – – – – – – –

CB-15 – – – – – – –

CB-16 – – – – – – –

CB-17 – – – – – – –

CB-18 – – – – – – –

CB-19 – – *1.29 – – – –

Number of wells with 

detections

0 1 1 0 0 1 0

Detection frequency 

(percent)

0 5 5 0 0 5 0

Total Detections

Table 5. Volatile organic compounds (VOCs), and gasoline oxygenates and degradates detected in samples collected for the Coastal 

Los Angeles Basin Groundwater Ambient Monitoring and Assessment (GAMA) study unit, California, June to November 2006.—

Continued

[The five-digit U.S. Geological Survey (USGS) parameter code below the constituent name is used to uniquely identify a specific constituent or property. 

Thresholds, threshold values, and LRLs as of November 16, 2006. Samples from all 69 wells were analyzed, but only samples with detections are listed. 

Analytes are listed in order of decreasing detection frequency in the 55 grid wells. All analytes are listed in tables 3A and 3B. Threshold: Maximum 

contaminant level thresholds are listed as MCL-US when the MCL-US and MCL-CA are identical, and as MCL-CA when the MCL-CA is lower than the 

MCL-US or no MCL-US exists. HAL-US, Lifetime Health Advisory Level; MCL-US, U.S. Environmental Protection Agency maximum contaminant 

level; MCL-CA; California Department of Public Health maximum contaminant level; NL-CA, California notification level. The MCL-US threshold for 

trihalomethanes is for the sum of chloroform, bromoform, bromodichloromethane, and dibromochloromethane. The MCL-CA thresholds for Xylenes is for 

the sum of m- and p-Xylene and o-Xylene. Abbreviations: CLAB; Coastal Los Angeles Basin; CLAB Grid Wells; CLAB Understanding Wells; E, estimated 

or having a higher degree of uncertainty; LRL, laboratory reporting level; na, not available; –, not detected; μg/L, microgram per liter; percentage values are 

detection frequencies]
46 Ground-Water Quality Data in the Coastal Los Angeles Basin Study Unit, 2006: Results from the California GAMA Program

GAMA 

identification 

No.

Solvent Gasoline Organic 

synthesis

Detections 

per well Any 

VOC

1,2-Dichloroethane 

(1,2-DCA) 

(μg/L) (32103)

trans-1,2-

Dichloroethene 

(trans-1,2-DCE) 

(μg/L) 

(34546)

Ethylbenzene 

(μg/L) 

(34371)

m-Xylene 

plus p-xylene 

(μg/L)

 (85795)

tert-Amyl 

alcohol 

(μg/L) 

(77073)

tert-Butyl 

alcohol 

(μg/L) 

(77035)

Vinyl 

chloride 

(μg/L) 

(39175)

[LRL] [0.10] [0.018] [0.02] [0.08] [0.6] [1] [0.08]

Threshold type MCL-US MCL-CA MCL-CA MCL-CA na NL-CA MCL-US

Threshold (μg/L) 5 10 300 1,750 na 12 2

CLAB Study Unit (55 grid wells sampled)—Continued

Number of wells with 

detections

0 0 0 0 0 0 0 41

Detection frequency 

(percent)

0 0 0 0 0 0 0 75

Total Detections 118

CLAB Central Basin Study Area (21 grid wells sampled)—Continued

CB-02 – – – – – – – 3

CB-03 – – – – – – – 3

CB-07 – – – – – – – 6

CB-08 – – – – – – – 2

CB-10 – – – – – – – 1

CB-11 – – – – – – – 3

CB-12 – – – – – – – 4

CB-13 – – – – – – – 8

CB-15 – – – – – – – 7

CB-16 – – – – – – – 8

CB-17 – – – – – – – 5

CB-18 – – – – – – – 2

CB-19 – – – – – – – 4

Number of wells with 

detections

0 0 0 0 0 0 0 13

Detection frequency 

(percent)

0 0 0 0 0 0 0 62

Total Detections 56

Table 5. Volatile organic compounds (VOCs), and gasoline oxygenates and degradates detected in samples collected for the Coastal 

Los Angeles Basin Groundwater Ambient Monitoring and Assessment (GAMA) study unit, California, June to November 2006.—

Continued

[The five-digit U.S. Geological Survey (USGS) parameter code below the constituent name is used to uniquely identify a specific constituent or property. 

Thresholds, threshold values, and LRLs as of November 16, 2006. Samples from all 69 wells were analyzed, but only samples with detections are listed. 

Analytes are listed in order of decreasing detection frequency in the 55 grid wells. All analytes are listed in tables 3A and 3B. Threshold: Maximum 

contaminant level thresholds are listed as MCL-US when the MCL-US and MCL-CA are identical, and as MCL-CA when the MCL-CA is lower than the 

MCL-US or no MCL-US exists. HAL-US, Lifetime Health Advisory Level; MCL-US, U.S. Environmental Protection Agency maximum contaminant 

level; MCL-CA; California Department of Public Health maximum contaminant level; NL-CA, California notification level. The MCL-US threshold for 

trihalomethanes is for the sum of chloroform, bromoform, bromodichloromethane, and dibromochloromethane. The MCL-CA thresholds for Xylenes is for 

the sum of m- and p-Xylene and o-Xylene. Abbreviations: CLAB; Coastal Los Angeles Basin; CLAB Grid Wells; CLAB Understanding Wells; E, estimated 

or having a higher degree of uncertainty; LRL, laboratory reporting level; na, not available; –, not detected; μg/L, microgram per liter; percentage values are 

detection frequencies]
Table 5 47

GAMA 

identification 

No.

Trihalomethane Solvent Gasoline Solvent Organic 

synthesis

Trihalomethane

Chloroform 

(Trichloromethane) 

(μg/L) 

(32106)

Trichloroethene 

(TCE)

(μg/L) 

(39180)

Tetrachloroethene 

(PCE)

(μg/L) 

(34475)

Methyl 

tert-butyl 

ether (MTBE) 

(μg/L) 

(78032)

cis-1,2-

Dichloroethene 

(μg/L) 

(77093)

1,1-Dichloroethene 

(1,1-DCE) 

(μg/L) 

(34501)

Bromodichloromethane 

(μg/L) 

(32101)

[LRL] [0.04] [0.02] [0.04] [0.10] [0.02] [0.04] [0.04]

Threshold type MCL-US MCL-US MCL-US MCL-CA MCL-CA MCL-CA MCL-US

Threshold (μg/L) 80 5 5 13 6 7 80

CLAB Orange County Coastal Plain Study Area (24 grid wells sampled)

OC-01 E 0.06 – – E 0.1 – – –

OC-02 E 0.05 – – 0.1 – – –

OC-03 0.49 1.45 0.28 0.1 – 0.23 E 0.04

OC-04 0.49 E 0.03 – – E 0.02 0.28 E 0.08

OC-05 0.89 E 0.09 – – – – 0.10

OC-06 0.35 – – – – E 0.05 E 0.07

OC-08 – – – E 0.1 – E 0.03 –

OC-10 – – – – – – –

OC-12 – – – – – – –

OC-13 E 0.02 – E 0.04 E 0.1 – – –

OC-16 – E 0.05 E 0.07 0.2 E 0.03 – –

OC-17 E 0.05 – 0.14 0.1 – – –

OC-18 – – – – – – –

OC-20 E 0.01 – – – – – –

OC-21 E 0.02 – – – – – –

OC-22 E 0.14 – – – – – E 0.07

OC-23 – – – – – – –

OC-24 E 0.08 E 0.05 – – – – –

Number of wells with 

detections

12 5 4 7 2 4 5

Detection frequency 

(percent)

50 21 17 29 8 17 21

Total Detections

CLAB West Coast Basin Study Area (10 grid wells sampled)

WB-01 – E 0.04 – – E 0.03 – –

WB-02 – – – – E 0.05 – –

WB-03 – E 0.02 – – E 0.03 – –

WB-04 – – – – – – –

WB-05 – – – – – – –

WB-06 – – – – – – –

WB-07 E 0.02 – – – – – –

WB-08 – – – – – – –

WB-09 – – – – – – –

WB-10 – – – – E 0.02 – –

Number of wells with 

detections

1 2 0 0 4 0 0

Detection frequency 

(percent)

10 20 0 0 40 0 0

Total Detections 

Table 5. Volatile organic compounds (VOCs), and gasoline oxygenates and degradates detected in samples collected for the Coastal 

Los Angeles Basin Groundwater Ambient Monitoring and Assessment (GAMA) study unit, California, June to November 2006.—

Continued

[The five-digit U.S. Geological Survey (USGS) parameter code below the constituent name is used to uniquely identify a specific constituent or property. 

Thresholds, threshold values, and LRLs as of November 16, 2006. Samples from all 69 wells were analyzed, but only samples with detections are listed. 

Analytes are listed in order of decreasing detection frequency in the 55 grid wells. All analytes are listed in tables 3A and 3B. Threshold: Maximum 

contaminant level thresholds are listed as MCL-US when the MCL-US and MCL-CA are identical, and as MCL-CA when the MCL-CA is lower than the 

MCL-US or no MCL-US exists. HAL-US, Lifetime Health Advisory Level; MCL-US, U.S. Environmental Protection Agency maximum contaminant 

level; MCL-CA; California Department of Public Health maximum contaminant level; NL-CA, California notification level. The MCL-US threshold for 

trihalomethanes is for the sum of chloroform, bromoform, bromodichloromethane, and dibromochloromethane. The MCL-CA thresholds for Xylenes is for 

the sum of m- and p-Xylene and o-Xylene. Abbreviations: CLAB; Coastal Los Angeles Basin; CLAB Grid Wells; CLAB Understanding Wells; E, estimated 

or having a higher degree of uncertainty; LRL, laboratory reporting level; na, not available; –, not detected; μg/L, microgram per liter; percentage values are 

detection frequencies]
48 Ground-Water Quality Data in the Coastal Los Angeles Basin Study Unit, 2006: Results from the California GAMA Program

 GAMA 

identification 

No.

Solvent Refrigerant Solvent Organic 

synthesis Solvent Gasoline

1,1-Dichloroethane 

(1,1-DCA) 

(μg/L) (34496)

Trichlorotrifluoroethane 

(CFC-113) 

(μg/L) (77652)

1,1,1-Trichloroethane 

(1,1,1-TCA) 

(μg/L) 

(34506)

Carbon 

disulfide 

(μg/L) 

(77041)

Dichloromethane

(μg/L) 

(34423)

Diisopropyl 

ether 

(DIPE) 

(μg/L) 

(81577)

Toluene 

(μg/L) 

(34010)

[LRL] [0.06] [0.04] [0.04] [0.06] [0.04] [0.06] [0.018]

Threshold type MCL-CA MCL-CA MCL-US NL-CA MCL-US na MCL-CA

Threshold (μg/L) 5 1,200 200 160 5 na 150

CLAB Orange County Coastal Plain Study Area (24 grid wells sampled)—Continued

OC-01 – – – – – – –

OC-02 – E 0.09 – – – – –

OC-03 – 0.12 E 0.03 – – – –

OC-04 – – – – – – –

OC-05 – 0.27 – – – – –

OC-06 – E 0.05 – – – – –

OC-08 – – – – – – –

OC-10 – – – – – – E 0.01

OC-12 – – – E 0.03 – – –

OC-13 – – – – – – –

OC-16 – – – – – – –

OC-17 – – – – – – –

OC-18 – – – E 0.04 – – –

OC-20 – – – – – – –

OC-21 – – – – – – –

OC-22 – – – – – – –

OC-23 – – – 0.12 – – –

OC-24 – – – – – – –

Number of wells 

with detections

0 4 1 3 0 0 1

Detection frequency 

(percent)

0 17 4 13 0 0 4

Total Detections 

CLAB West Coast Basin Study Area (10 grid wells sampled)—Continued

WB-01 – – – – – 0.15 –

WB-02 – – – – E 0.03 – –

WB-03 – – – – – – –

WB-04 – – – 0.17 – – –

WB-05 – – – – E 0.02 – –

WB-06 – – – – – – –

WB-07 – – – – – – –

WB-08 – – – – – 0.13 –

WB-09 – – – – – – 6.98

WB-10 – – – – – – –

Number of wells 

with detections

0 0 0 1 2 2 1

Detection frequency 

(percent)

0 0 0 10 20 20 10

Total Detections

Table 5. Volatile organic compounds (VOCs), and gasoline oxygenates and degradates detected in samples collected for the Coastal 

Los Angeles Basin Groundwater Ambient Monitoring and Assessment (GAMA) study unit, California, June to November 2006.—

Continued

[The five-digit U.S. Geological Survey (USGS) parameter code below the constituent name is used to uniquely identify a specific constituent or property. 

Thresholds, threshold values, and LRLs as of November 16, 2006. Samples from all 69 wells were analyzed, but only samples with detections are listed. 

Analytes are listed in order of decreasing detection frequency in the 55 grid wells. All analytes are listed in tables 3A and 3B. Threshold: Maximum 

contaminant level thresholds are listed as MCL-US when the MCL-US and MCL-CA are identical, and as MCL-CA when the MCL-CA is lower than the 

MCL-US or no MCL-US exists. HAL-US, Lifetime Health Advisory Level; MCL-US, U.S. Environmental Protection Agency maximum contaminant 

level; MCL-CA; California Department of Public Health maximum contaminant level; NL-CA, California notification level. The MCL-US threshold for 

trihalomethanes is for the sum of chloroform, bromoform, bromodichloromethane, and dibromochloromethane. The MCL-CA thresholds for Xylenes is for 

the sum of m- and p-Xylene and o-Xylene. Abbreviations: CLAB; Coastal Los Angeles Basin; CLAB Grid Wells; CLAB Understanding Wells; E, estimated 

or having a higher degree of uncertainty; LRL, laboratory reporting level; na, not available; –, not detected; μg/L, microgram per liter; percentage values are 

detection frequencies]
Table 5 49

 GAMA 

identification 

No.

Gasoline Trihalomethane Solvent Refrigerant Gasoline Gasoline Refrigerant

Benzene 

(μg/L) 

(34030)

Bromoform 

(Tribromomethane) 

(μg/L) 

(32104)

Carbon 

tetrachloride 

(Tetrachloromethane) 

(μg/L) 

(32102)

Dichlorodifluoromethane 

(CFC-12) 

(μg/L) 

(34668)

Naphthalene, 

(μg/L) 

(34696)

1,2,4-Trimethylbenzene 

(μg/L) 

(77222)

Trichlorofluoromethane 

(CFC-11) 

(μg/L) 

(34488)

[LRL] [0.016] [0.08] [0.08] [0.14] [0.4] [0.04] [0.08]

Threshold type MCL-CA MCL-US MCL-CA HAL-US HAL-US NL-CA MCL-CA

Threshold (μg/L) 1 80 0.5 1000 100 330 150

CLAB Orange County Coastal Plain Study Area (24 grid wells sampled)—Continued

OC-01 – – – – – – –

OC-02 – – – – – – –

OC-03 – – – – – – –

OC-04 – – – – – – –

OC-05 – – – – – – –

OC-06 – – – – – – –

OC-08 – – – – – – 0.15

OC-10 – – – – – – –

OC-12 – – – – – – –

OC-13 – – – – – – –

OC-16 – – – – – – –

OC-17 – – – E 0.04 – – –

OC-18 – – – – – – –

OC-20 – – – – – – –

OC-21 – – – – – – –

OC-22 – – – – – – –

OC-23 – – – – – – –

OC-24 – – – – – – –

Number of wells with 

detections

0 0 0 1 0 0 1

Detection frequency 

(percent)

0 0 0 4 0 0 4

Total Detections 

CLAB West Coast Basin Study Area (10 grid wells sampled)—Continued

WB-01 – – – – – – –

WB-02 – – – – – – –

WB-03 – – – – – – –

WB-04 – – – – – – –

WB-05 – – – – – – –

WB-06 E 0.02 – – – – – –

WB-07 – – – – E 0.4 – –

WB-08 – – – – – – –

WB-09 – – – – – – – 

WB-10 – – – – – – – 

Number of wells with 

detections

1 0 0 0 1 0 0

Detection frequency 

(percent)

10 0 0 0 10 0 0

Total Detections

Table 5. Volatile organic compounds (VOCs), and gasoline oxygenates and degradates detected in samples collected for the Coastal 

Los Angeles Basin Groundwater Ambient Monitoring and Assessment (GAMA) study unit, California, June to November 2006.—

Continued

[The five-digit U.S. Geological Survey (USGS) parameter code below the constituent name is used to uniquely identify a specific constituent or property. 

Thresholds, threshold values, and LRLs as of November 16, 2006. Samples from all 69 wells were analyzed, but only samples with detections are listed. 

Analytes are listed in order of decreasing detection frequency in the 55 grid wells. All analytes are listed in tables 3A and 3B. Threshold: Maximum 

contaminant level thresholds are listed as MCL-US when the MCL-US and MCL-CA are identical, and as MCL-CA when the MCL-CA is lower than the 

MCL-US or no MCL-US exists. HAL-US, Lifetime Health Advisory Level; MCL-US, U.S. Environmental Protection Agency maximum contaminant 

level; MCL-CA; California Department of Public Health maximum contaminant level; NL-CA, California notification level. The MCL-US threshold for 

trihalomethanes is for the sum of chloroform, bromoform, bromodichloromethane, and dibromochloromethane. The MCL-CA thresholds for Xylenes is for 

the sum of m- and p-Xylene and o-Xylene. Abbreviations: CLAB; Coastal Los Angeles Basin; CLAB Grid Wells; CLAB Understanding Wells; E, estimated 

or having a higher degree of uncertainty; LRL, laboratory reporting level; na, not available; –, not detected; μg/L, microgram per liter; percentage values are 

detection frequencies]
50 Ground-Water Quality Data in the Coastal Los Angeles Basin Study Unit, 2006: Results from the California GAMA Program

 GAMA 

identification 

No.

Solvent Gasoline Organic 

synthesis

Detections 

per well

Any 

VOC

1,2-Dichloroethane 

(1,2-DCA) 

(μg/L) (32103)

trans-1,2-

Dichloroethene 

(trans-1,2-DCE) 

(μg/L) (34546)

Ethylbenzene 

(μg/L) 

(34371)

m-Xylene plus 

p-xylene 

(μg/L) 

(85795)

tert-Amyl 

alcohol 

(μg/L) 

(77073)

tert-Butyl 

alcohol 

(μg/L) 

(77035)

Vinyl 

chloride 

(μg/L) 

(39175)

[LRL] [0.10] [0.018] [0.02] [0.08] [0.6] [1] [0.08]

Threshold type MCL-US MCL-CA MCL-CA MCL-CA na NL-CA MCL-US

Threshold (μg/L) 5 10 300 1,750 na 12 2

CLAB Orange County Coastal Plain Study Area (24 grid wells sampled)—Continued

OC-01 – – – – – – – 2

OC-02 – – – – – – – 3

OC-03 – – – – – – – 8

OC-04 – – – – – – – 5

OC-05 – – – – – – – 4

OC-06 – – – – – – – 4

OC-08 – – – – – – – 3

OC-10 – – – – – – – 1

OC-12 – – – – – – – 1

OC-13 – – – – – – – 3

OC-16 – – – – – – – 4

OC-17 – – – – – – – 4

OC-18 – – – – – – – 1

OC-20 – – – – – – – 1

OC-21 – – – – – – – 1

OC-22 – – – – – – – 2

OC-23 – – – – – – – 1

OC-24 – – – – – – – 2

Number of wells with 

detections

0 0 0 0 0 0 0 18

Detection frequency 

(percent)

0 0 0 0 0 0 0 75

Total Detections 50

CLAB West Coast Basin Study Area (10 grid wells sampled)—Continued

WB-01 – – – – – – – 3

WB-02 – – – – – – – 2 

WB-03 – – – – – – – 2 

WB-04 – – – – – – – 1

WB-05 – – – – – – – 1

WB-06 – – – – – – – 1

WB-07 – – – – – – – 2

WB-08 – – – – – – – 1

WB-09 – – – – – – – 1

WB-10 – – – – – – – 1

Number of wells with 

detections

0 0 0 0 0 0 0 10

Detection frequency 

(percent)

0 0 0 0 0 0 0 100

Total Detections 15

Table 5. Volatile organic compounds (VOCs), and gasoline oxygenates and degradates detected in samples collected for the Coastal 

Los Angeles Basin Groundwater Ambient Monitoring and Assessment (GAMA) study unit, California, June to November 2006.—

Continued

[The five-digit U.S. Geological Survey (USGS) parameter code below the constituent name is used to uniquely identify a specific constituent or property. 

Thresholds, threshold values, and LRLs as of November 16, 2006. Samples from all 69 wells were analyzed, but only samples with detections are listed. 

Analytes are listed in order of decreasing detection frequency in the 55 grid wells. All analytes are listed in tables 3A and 3B. Threshold: Maximum 

contaminant level thresholds are listed as MCL-US when the MCL-US and MCL-CA are identical, and as MCL-CA when the MCL-CA is lower than the 

MCL-US or no MCL-US exists. HAL-US, Lifetime Health Advisory Level; MCL-US, U.S. Environmental Protection Agency maximum contaminant 

level; MCL-CA; California Department of Public Health maximum contaminant level; NL-CA, California notification level. The MCL-US threshold for 

trihalomethanes is for the sum of chloroform, bromoform, bromodichloromethane, and dibromochloromethane. The MCL-CA thresholds for Xylenes is for 

the sum of m- and p-Xylene and o-Xylene. Abbreviations: CLAB; Coastal Los Angeles Basin; CLAB Grid Wells; CLAB Understanding Wells; E, estimated 

or having a higher degree of uncertainty; LRL, laboratory reporting level; na, not available; –, not detected; μg/L, microgram per liter; percentage values are 

detection frequencies]
Table 5 51

 GAMA 

identification 

No.

Trihalomethane Solvent Solvent Gasoline Solvent Organic 

synthesis

Trihalomethane

Chloroform 

(Trichloromethane) 

(μg/L) 

(32106)

Trichloroethene 

(TCE) 

(μg/L) 

(39180)

Tetrachloroethene 

(PCE)

(μg/L) 

(34475)

Methyl

tert-butyl 

ether (MTBE) 

(μg/L) 

(78032)

cis-1,2-

Dichloroethene 

(μg/L) 

(77093)

1,1-Dichloroethene 

(1,1-DCE) 

(μg/L) 

(34501)

Bromodichloromethane 

(μg/L) 

(32101)

[LRL] [0.04] [0.02] [0.04] [0.10] [0.02] [0.04] [0.04]

Threshold type MCL-US MCL-US MCL-US MCL-CA MCL-CA MCL-CA MCL-US

Threshold (μg/L) 80 5 5 13 6 7 80

CLAB Understanding wells1

 (14 wells sampled)

DA-01 0.49 – – – – E 0.03 –

DA-02 12.2 *24.8 *13.2 E 0.1 0.57 2.17 0.1

DA-04 0.78 – – – – – E 0.07

DA-05 – – – – 0.12 – –

DA-06 – – – – – – –

U-02 – E 0.05 E 0.02 E 0.1 – – –

U-03 0.12 1.21 2.24 0.1 E 0.07 E 0.07 –

U-04 E 0.02 – – – – – –

U-06 0.39 – 0.48 E 0.1 – – E 0.03

U-07 – *13.2 0.17 – 3.12 0.11 –

 GAMA 

identification 

No.

Solvent Refrigerant Solvent Organic 

synthesis Solvent Gasoline

1,1-Dichloroethane 

(1,1-DCA) 

(μg/L) 

(34496)

Trichlorotrifluoroethane 

(CFC-113) 

(μg/L) 

(77652)

1,1,1-Trichloroethane (1,1,1-

TCA) 

(μg/L) 

(34506)

Carbon 

disulfide 

(μg/L) 

(77041)

Dichloromethane

(μg/L) 

(34423)

Diisopropyl 

ether 

(DIPE) 

(μg/L) 

(81577)

Toluene 

(μg/L) 

(34010)

[LRL] [0.06] [0.04] [0.04] [0.06] [0.04] [0.06] [0.018]

Threshold type MCL-CA MCL-CA MCL-US NL-CA MCL-US na MCL-CA

Threshold (μg/L) 5 1,200 200 160 5 na 150

CLAB Understanding wells1

 (14 wells sampled)—Continued

DA-01 E 0.09 – E 0.04 – – – E 0.01

DA-02 0.28 0.34 – – – – –

DA-04 – – E 0.02 – – – –

DA-05 – – – – – – E 0.04

DA-06 – – – – – – –

U-02 E 0.05 – – – – – –

U-03 E 0.05 – – – – – –

U-04 – 0.23 – – – – –

U-06 – – – – – – –

U-07 E 0.08 – – – – 0.24 –

Table 5. Volatile organic compounds (VOCs), and gasoline oxygenates and degradates detected in samples collected for the Coastal 

Los Angeles Basin Groundwater Ambient Monitoring and Assessment (GAMA) study unit, California, June to November 2006.—

Continued

[The five-digit U.S. Geological Survey (USGS) parameter code below the constituent name is used to uniquely identify a specific constituent or property. 

Thresholds, threshold values, and LRLs as of November 16, 2006. Samples from all 69 wells were analyzed, but only samples with detections are listed. 

Analytes are listed in order of decreasing detection frequency in the 55 grid wells. All analytes are listed in tables 3A and 3B. Threshold: Maximum 

contaminant level thresholds are listed as MCL-US when the MCL-US and MCL-CA are identical, and as MCL-CA when the MCL-CA is lower than the 

MCL-US or no MCL-US exists. HAL-US, Lifetime Health Advisory Level; MCL-US, U.S. Environmental Protection Agency maximum contaminant 

level; MCL-CA; California Department of Public Health maximum contaminant level; NL-CA, California notification level. The MCL-US threshold for 

trihalomethanes is for the sum of chloroform, bromoform, bromodichloromethane, and dibromochloromethane. The MCL-CA thresholds for Xylenes is for 

the sum of m- and p-Xylene and o-Xylene. Abbreviations: CLAB; Coastal Los Angeles Basin; CLAB Grid Wells; CLAB Understanding Wells; E, estimated 

or having a higher degree of uncertainty; LRL, laboratory reporting level; na, not available; –, not detected; μg/L, microgram per liter; percentage values are 

detection frequencies]
52 Ground-Water Quality Data in the Coastal Los Angeles Basin Study Unit, 2006: Results from the California GAMA Program

GAMA 

identification 

No.

Gasoline Trihalomethane Solvent Refrigerant Gasoline Refrigerant

Benzene 

(μg/L) 

(34030)

Bromoform 

(Tribromomethane) 

(μg/L) 

(32104)

Carbon tetrachloride

 (Tetrachloromethane) 

(μg/L) 

(32102)

Dichlorodifluoromethane 

(CFC-12) 

(μg/L) 

(34668)

Naphthalene, 

(μg/L) 

(34696)

1,2,4-Trimethylbenzene 

(μg/L) 

(77222)

Trichlorofluoromethane 

(CFC-11) 

(μg/L) (34488)

[LRL] [0.016] [0.08] [0.08] [0.14] [0.4] [0.04] [0.08]

Threshold type MCL-CA MCL-US MCL-CA HAL-US HAL-US NL-CA MCL-CA

Threshold (μg/L) 1 80 0.5 1,000 100 330 150

CLAB Understanding wells1

 (14 wells sampled)—Continued

DA-01 – – 0.14 – – – –

DA-02 – – 0.32 E 0.28 – – 0.1

DA-04 – – 0.18 – – – –

DA-05 – – – – – E 0.06 –

DA-06 – – – – – – –

U-02 – – – – – – –

U-03 – – – – – – –

U-04 – – – – – – –

U-06 – – E 0.03 E .05 – – –

U-07 – – – – – – –

 GAMA 

identification 

No.

Solvent Gasoline Organic 

synthesis

Detections 

per well

Any 

VOC

1,2-Dichloroethane 

(1,2-DCA) 

(μg/L) 

(32103)

trans-1,2-

Dichloroethene 

(trans-1,2-DCE) 

(μg/L) 

(34546)

Ethylbenzene 

(μg/L) 

(34371)

m-Xylene plus 

p-xylene 

(μg/L) 

(85795)

tert-Amyl 

alcohol 

(μg/L) 

(77073)

tert-Butyl 

alcohol 

(μg/L) 

(77035)

Vinyl 

chloride 

(μg/L) 

(39175)

[LRL] [0.10] [0.018] [0.02] [0.08] [0.6] [1] [0.08]

Threshold type MCL-US MCL-CA MCL-CA MCL-CA na NL-CA MCL-US

Threshold (μg/L) 5 10 300 1,750 na 12 2

CLAB Understanding wells1

 (14 wells sampled)—Continued

DA-01 – – – – – – 6

DA-02 – E 0.03 – – – – – 13

DA-04 – – – – – – – 4

DA-05 – – E 0.04 E 0.13 – – – 5

DA-06 – – – – E 0.2 E 1.15 – 2

U-02 – – – – – – – 4

U-03 – – – – – – – 7

U-04 – – – – – – – 2

U-06 – – – – – – – 6

U-07 0.3 E 0.09 – – – – E 0.1 9

*

 Value exceeds threshold.

1

 Understanding wells were not included in statistical calculations.

Table 5. Volatile organic compounds (VOCs), and gasoline oxygenates and degradates detected in samples collected for the Coastal 

Los Angeles Basin Groundwater Ambient Monitoring and Assessment (GAMA) study unit, California, June to November 2006.—

Continued

[The five-digit U.S. Geological Survey (USGS) parameter code below the constituent name is used to uniquely identify a specific constituent or property. 

Thresholds, threshold values, and LRLs as of November 16, 2006. Samples from all 69 wells were analyzed, but only samples with detections are listed. 

Analytes are listed in order of decreasing detection frequency in the 55 grid wells. All analytes are listed in tables 3A and 3B. Threshold: Maximum 

contaminant level thresholds are listed as MCL-US when the MCL-US and MCL-CA are identical, and as MCL-CA when the MCL-CA is lower than the 

MCL-US or no MCL-US exists. HAL-US, Lifetime Health Advisory Level; MCL-US, U.S. Environmental Protection Agency maximum contaminant 

level; MCL-CA; California Department of Public Health maximum contaminant level; NL-CA, California notification level. The MCL-US threshold for 

trihalomethanes is for the sum of chloroform, bromoform, bromodichloromethane, and dibromochloromethane. The MCL-CA thresholds for Xylenes is for 

the sum of m- and p-Xylene and o-Xylene. Abbreviations: CLAB; Coastal Los Angeles Basin; CLAB Grid Wells; CLAB Understanding Wells; E, estimated 

or having a higher degree of uncertainty; LRL, laboratory reporting level; na, not available; –, not detected; μg/L, microgram per liter; percentage values are 

detection frequencies]
Table 6 53

GAMA 

identification 

No.

Deethylatrazine 

(μg/L) (04040)

Atrazine 

(μg/L) 

(39632)

Simazine 

(μg/L) 

(04035)

3,4-Dichloroaniline

(μg/L) (61625)

Prometon 

(μg/L) 

(04037)

Tebuthiuron 

(μg/L) 

(82670)

Metalaxyl 

(μg/L) 

(61596)

Hexazinone 

(μg/L) (04025)

[LRL] [0.014] [0.007] [0.006] [0.0045] [0.01] [0.016] [0.0069] [0.026]

Threshold type1 na MCL-CA MCL-US na HAL-US HAL-US na HAL-US

Threshold (μg/L) na 1 4 na 100 500 na 400

CLAB Study Unit (55 grid wells sampled)

Number of wells with 

detections

19 19 15 8 7 6 4 3

Detection frequency 

(percent)

35 35 27 15 13 11 7 5

Total Detections

CLAB Central Basin Study Area (21 grid wells sampled)

CB-02 E 0.013 0.013 – – – – – –

CB-03 E 0.008 0.019 0.076 E 0.021 0.02 0.03 0.010 –

CB-07 E 0.017 0.049 E 0.006 – – – – –

CB-08 E 0.007 E 0.004 – – – – – –

CB-10 E 0.006 E 0.004 – – – – – –

CB-11 E 0.042 0.164 0.026 – – – – –

CB-12 E 0.008 0.009 E 0.004 E 0.006 – – – –

CB-13 E 0.027 0.183 0.117 E 0.005 – – E 0.006 –

CB-15 E 0.038 0.247 0.261 E 0.005 – 0.02 E 0.006 –

CB-16 E 0.025 0.018 – – – – – –

CB-17 E 0.051 0.045 0.021 E 0.005 – – – –

Number of wells with 

detections

11 11 7 5 1 2 3 0

Detection frequency 

(percent)

52 52 33 24 5 10 14 0

Total Detections 44

CLAB Orange County Coastal Plain Study Area (24 grid wells sampled)

OC-02 E 0.015 0.046 0.063 – – E 0.02 – E 0.013 

OC-03 E 0.019 0.041 0.08 – E 0.01 0.02 – –

OC-04 E 0.006 E 0.004 – – – – – –

OC-05 E 0.007 E 0.004 – – – – – –

OC-08 – – – – – – – –

OC-13 E 0.011 0.059 0.268 E 0.024 0.01 E 0.01 – E 0.016

OC-17 E 0.01 0.019 0.191 E 0.017 0.01 0.02 – E 0.009 

OC-20 E 0.006 E 0.005 0.158 E 0.01 0.01 – – –

OC-24 E 0.008 0.008 E 0.006 – – – – –

Number of wells with 

detections

8 8 6 3 4 4 0 3

Detection frequency 

(percent)

33 33 25 12 17 17 0 12

Total Detections

Table 6. Pesticides and pesticide degradates detected in samples collected for the Coastal Los Angeles Basin Groundwater Ambient 

Monitoring and Assessment (GAMA) study unit, California, June to November 2006.

[The five-digit U.S. Geological Survey (USGS) parameter code below the constituent name is used to uniquely identify a specific constituent or property. 

Thresholds, threshold values, and LRLs values as of November 16, 2006. Samples from all 69 wells were analyzed, but only samples with detections are listed. 

Analytes are listed in order of decreasing detection frequency in the 55 grid wells. All analytes are listed in table 3C. Threshold type: Maximum contaminant 

level thresholds are listed as MCL-US when the MCL-US and MCL-CA are identical, and as MCL-CA when the MCL-CA is lower than the MCL-US or no 

MCL-US exists. HAL-US, U.S. Environmental Protection Agency Lifetime Health Advisory; MCL-US, U.S. Environmental Protection Agency maximum 

contaminant level; MCL-CA; California Department of Public Health maximum contaminant level. Abbreviations: CLAB; Coastal Los Angeles Basin; CLAB 

Grid Wells; CLAB Understanding Wells; E, estimated or having a higher degree of uncertainty; LRL, laboratory reporting level; μg/L, microgram per liter; na, 

not available; –, not detected; Analytes are ordered by frequency of detection]
54 Ground-Water Quality Data in the Coastal Los Angeles Basin Study Unit, 2006: Results from the California GAMA Program

Table 6. Pesticides and pesticide degradates detected in samples collected for the Coastal Los Angeles Basin Groundwater Ambient 

Monitoring and Assessment (GAMA) study unit, California, June to November 2006.—Continued

[The five-digit U.S. Geological Survey (USGS) parameter code below the constituent name is used to uniquely identify a specific constituent or property. 

Thresholds, threshold values, and LRLs values as of November 16, 2006. Samples from all 69 wells were analyzed, but only samples with detections are listed. 

Analytes are listed in order of decreasing detection frequency in the 55 grid wells. All analytes are listed in table 3C. Threshold type: Maximum contaminant 

level thresholds are listed as MCL-US when the MCL-US and MCL-CA are identical, and as MCL-CA when the MCL-CA is lower than the MCL-US or no 

MCL-US exists. HAL-US, U.S. Environmental Protection Agency Lifetime Health Advisory; MCL-US, U.S. Environmental Protection Agency maximum 

contaminant level; MCL-CA; California Department of Public Health maximum contaminant level. Abbreviations: CLAB; Coastal Los Angeles Basin; CLAB 

Grid Wells; CLAB Understanding Wells; E, estimated or having a higher degree of uncertainty; LRL, laboratory reporting level; μg/L, microgram per liter; na, 

not available; –, not detected; Analytes are ordered by frequency of detection]

GAMA 

identification 

No.

Deethylatrazine 

(μg/L) (04040)

Atrazine 

(μg/L) 

(39632)

Simazine 

(μg/L) 

(04035)

3,4-Dichloroaniline

(μg/L) (61625)

Prometon 

(μg/L) 

(04037)

Tebuthiuron 

(μg/L) 

(82670)

Metalaxyl 

(μg/L) 

(61596)

Hexazinone 

(μg/L) (04025)

[LRL] [0.014] [0.007] [0.006] [0.0045] [0.01] [0.016] [0.0069] [0.026]

Threshold type1 na MCL-CA MCL-US na HAL-US HAL-US na HAL-US

Threshold (μg/L) na 1 4 na 100 500 na 400

CLAB West Coast Basin Study Area (10 grid wells sampled)

WB-01 – – 0.013 – E 0.01 – – –

WB-04 – – E 0.007 – – – – –

WB-10 – – – – 0.01 – E 0.007 –

Number of wells with 

detections

0 0 2 0 2 0 1 0

Detection frequency 

(percent)

0 0 20 0 20 0 10 0

Total Detections

CLAB Understanding wells1

 (14 wells sampled)

U-01 – – – – – – – –

U-02 E 0.019 0.104 0.045 – – – 0.008 –

U-03 E 0.018 0.020 0.060 E 0.012 0.01 – – E 0.010

U-06 E 0.007 – E 0.008 – – – – –

U-07 – E 0.008 – – – – – –
Table 6 55

GAMA 

identification 

No.

Desulfinyl 

fipronil 

(μg/L) (62170)

Fipronil 

(μg/L) 

(62166)

Dichlorvos 

(μg/L) 

(38775)

Fipronil

 sulfone 

(μg/L) (62168)

Metolachlor 

(μg/L)

 (39415)

Fipronil 

sulfide

 (μg/L) (62167) Detections 

per well

Any 

[LRL] [0.012] [0.016] [0.013] [0.024] [0.010] [0.013] pesticide

Threshold type1 na na na na HAL-US na

Threshold (μg/L) na na na na 100 na

CLAB Study Unit (55 grid wells sampled)

Number of wells 

with detections

2 2 1 1 1 0 23

Detection frequency 

(percent)

4 4 2 2 2 0 42

Total Detections 88

CLAB Central Basin Study Area (21 grid wells sampled)

CB-02 – – – – – – 2

CB-03 E 0.005 E 0.007 – E 0.007 E 0.006 – 11

CB-07 – – – – – – 3

CB-08 – – – – – – 2

CB-10 – – – – – – 2

CB-11 – – – – – – 3

CB-12 – – – – – – 4

CB-13 – – – – – – 5

CB-15 – – – – – – 6

CB-16 – – – – – – 2

CB-17 – – – – – – 4

Number of wells 

with detections

1 1 0 1 1 0 11

Detection frequency 

(percent)

5 5 0 5 5 0 52

Total Detections 44

CLAB Orange County Coastal Plain Study Area (24 grid wells sampled)

OC-02 – – – – – – 5

OC-03 – – – – – – 5

OC-04 – – – – – – 2

OC-05 – – – – – – 2

OC-08 – – E 0.01 – – – 1

OC-13 – – – – – – 7

OC-17 – – – – – – 7

OC-20 E 0.006 E 0.007 – – – – 7

OC-24 – – – – – – 3

Number of wells 

with detections

1 1 1 0 0 0 9

Detection frequency 

(percent)

4 4 4 0 0 0 38

Total Detections 39

Table 6. Pesticides and pesticide degradates detected in samples collected for the Coastal Los Angeles Basin Groundwater Ambient 

Monitoring and Assessment (GAMA) study unit, California, June to November 2006.—Continued

[The five-digit U.S. Geological Survey (USGS) parameter code below the constituent name is used to uniquely identify a specific constituent or property. 

Thresholds, threshold values, and LRLs values as of November 16, 2006. Samples from all 69 wells were analyzed, but only samples with detections are listed. 

Analytes are listed in order of decreasing detection frequency in the 55 grid wells. All analytes are listed in table 3C. Threshold type: Maximum contaminant 

level thresholds are listed as MCL-US when the MCL-US and MCL-CA are identical, and as MCL-CA when the MCL-CA is lower than the MCL-US or no 

MCL-US exists. HAL-US, U.S. Environmental Protection Agency Lifetime Health Advisory; MCL-US, U.S. Environmental Protection Agency maximum 

contaminant level; MCL-CA; California Department of Public Health maximum contaminant level. Abbreviations: CLAB; Coastal Los Angeles Basin; CLAB 

Grid Wells; CLAB Understanding Wells; E, estimated or having a higher degree of uncertainty; LRL, laboratory reporting level; μg/L, microgram per liter; na, 

not available; –, not detected; Analytes are ordered by frequency of detection]
56 Ground-Water Quality Data in the Coastal Los Angeles Basin Study Unit, 2006: Results from the California GAMA Program

Table 6. Pesticides and pesticide degradates detected in samples collected for the Coastal Los Angeles Basin Groundwater Ambient 

Monitoring and Assessment (GAMA) study unit, California, June to November 2006.—Continued

[The five-digit U.S. Geological Survey (USGS) parameter code below the constituent name is used to uniquely identify a specific constituent or property. 

Thresholds, threshold values, and LRLs values as of November 16, 2006. Samples from all 69 wells were analyzed, but only samples with detections are listed. 

Analytes are listed in order of decreasing detection frequency in the 55 grid wells. All analytes are listed in table 3C. Threshold type: Maximum contaminant 

level thresholds are listed as MCL-US when the MCL-US and MCL-CA are identical, and as MCL-CA when the MCL-CA is lower than the MCL-US or no 

MCL-US exists. HAL-US, U.S. Environmental Protection Agency Lifetime Health Advisory; MCL-US, U.S. Environmental Protection Agency maximum 

contaminant level; MCL-CA; California Department of Public Health maximum contaminant level. Abbreviations: CLAB; Coastal Los Angeles Basin; CLAB 

Grid Wells; CLAB Understanding Wells; E, estimated or having a higher degree of uncertainty; LRL, laboratory reporting level; μg/L, microgram per liter; na, 

not available; –, not detected; Analytes are ordered by frequency of detection]

GAMA 

identification 

No.

Desulfinyl 

fipronil 

(μg/L) (62170)

Fipronil 

(μg/L) 

(62166)

Dichlorvos 

(μg/L) 

(38775)

Fipronil

 sulfone 

(μg/L) (62168)

Metolachlor 

(μg/L)

 (39415)

Fipronil 

sulfide

 (μg/L) (62167) Detections 

per well

Any 

[LRL] [0.012] [0.016] [0.013] [0.024] [0.010] [0.013] pesticide

Threshold type1 na na na na HAL-US na

Threshold (μg/L) na na na na 100 na

CLAB West Coast Basin Study Area (10 grid wells sampled)

WB-01 – – – – – – 2

WB-04 – – – – – – 1

WB-10 – – – – – – 2

Number of wells 

with detections

0 0 0 0 0 0 3

Detection frequency 

(percent)

0 0 0 0 0 0 30

Total Detections 5

CLAB Understanding wells1

 (14 wells sampled)

U-01 – – – – E 0.004 – 1

U-02 – – – – – – 5

U-03 E 0.006 E 0.007 – – – E 0.009 12

U-06 – – – – – – 2

U-07 – – – – – – 2

1

Understanding wells were not included in statistical calculations.
Table 7 57

GAMA 

identification 

No.

Diuron 

(μg/L) 

(49300)

Norflurazon 

(μg/L) 

(49293)

3-(4-Chlorophenyl)-

1-methyl urea 

(μg/L) 

(61692)

Deisopropyl 

atrazine (2-chloro6-ethylamino-4-

amino-s-triazine) 

(μg/L) 

(04038)

Diphenamid 

(μg/L) 

(04033)

[LRL] [0.04] [0.04] [0.06] [0.08] [0.04]

Threshold type HAL-US na na na HAL-US

Threshold (μg/L) 10 na na na 200

CLAB Grid Wells (7 wells sampled)

CB-03 0.19 0.07 E 0.02 – –

OC-20 0.15 0.02 – E 0.01 –

CLAB Understanding wells (10 wells sampled)

U-02 – – – – E 0.01

U-03 E 0.16 E 0.02 – – –

U-07 – – – – E 0.01

Table 7. Polar pesticides and pesticide degradates detected in samples collected for the Coastal Los Angeles Basin 

Groundwater Ambient Monitoring and Assessment (GAMA) study unit, California, June to November 2006.

[The five-digit U.S. Geological (USGS) parameter code below the constituent name is used to uniquely identify a specific constituent or property. 

Thresholds, threshold values, and LRLs as of November 16, 2006. Samples from 17 slow and intermediate wells were analyzed, but only samples 

with detections are listed. All analytes are listed in table 3D. Threshold type: Maximum contaminant level thresholds are listed as MCL-US 

when the MCL-US and MCL-CA are identical, and as MCL-CA when the MCL-CA is lower than the MCL-US or no MCL-US exists. HAL-US, 

U.S. Environmental Protection Agency Lifetime Health Advisory. Abbreviations: CLAB; Coastal Los Angeles Basin; CLAB Grid Wells; CLAB 

Understanding Wells; E, estimated or having a higher degree of uncertainty; LRL, laboratory reporting level; μg/L, microgram per liter; na, not 

available; –, not detected]
58 Ground-Water Quality Data in the Coastal Los Angeles Basin Study Unit, 2006: Results from the California GAMA Program

Table 8. Potential wastewater indicators detected in samples collected for the Coastal Los Angeles Basin Groundwater Ambient 

Monitoring and Assessment (GAMA) study unit, California, June to November 2006.

[The five-digit U.S. Geological Survey (USGS) parameter code below the constituent name is used to uniquely identify a specific constituent or property. 

Thresholds, threshold values, and IRLs as of November 16, 2006. Samples from all 69 wells were analyzed, but only samples with detections are listed. Analytes 

are listed in order of decreasing detection frequency in the 55 grid wells. All analytes are listed in table 3E. Threshold: Maximum contaminant level thresholds 

are listed as MCL-US when the MCL-US and MCL-CA are identical, and as MCL-CA when the MCL-CA is lower than the MCL-US or no MCL-US exists. 

HAL-US, U.S. Environmental Protection Agency Lifetime Health Advisory. Abbreviations: CLAB; Coastal Los Angeles Basin; CLAB Grid Wells; CLAB 

Understanding Wells; E, estimated or having a higher degree of uncertainty; IRL, interim reporting limit; μg/L, microgram per liter; na, not available; –, not 

detected]

GAMA 

identification 

No.

Camphor

(μg/L) (62817)

Bis(2-ethylhexyl) 

phthalate

(μg/L) 

(39100)

5-Methyl-1Hbenzotriazole 

(μg/L) 

(61944)

Tris(2-

butoxyethyl) 

phosphate

(μg/L) (62830)

3,4-Dichlorophenyl 

isocyanate

(μg/L) 

(63145)

1-Methylnaphthalene 

(μg/L) 

(81696)

2-Methylnaphthalene 

(μg/L) 

(30194)

[IRL] [0.2] [2] [1.6] [0.2] [2] [0.2] [0.2]

Threshold type na na na na na na na

Threshold (μg/L) na na na na na na na

CLAB Study Unit (55 grid wells sampled)

Number of wells with detections 6 5 4 4 2 2 2

Detection frequency (percent) 11 9 7 7 4 4 4

Total Detections

CLAB Central Basin Study Area (21 grid wells sampled)

CB-03 – – – 0.4 E 1.9 – –

CB-05 – – – 0.4 – – –

CB-07 – – – – – – –

CB-08 E 0.009 – – – – – –

CB-11 – – – – – – –

CB-19 – E 0.8 – – – – –

Number of wells with detections 1 1 0 2 1 0 0

Detection frequency (percent) 5 5 0 10 5 0 0

Total Detections

CLAB Orange County Coastal Plain Study Area (24 grid wells sampled)

OC-03 na – – – – – na

OC-04 E 0.007 – – – – – –

OC-05 E 0.008 – – – – – –

OC-06 E 0.012 – – – – – –

OC-07 E 0.007 – – – – – –

OC-08 E 0.009 – – – – – –

OC-10 – – – – – – –

OC-19 – – 8 – na – –

OC-20 – – – E 0.04 E 0.50 – –

OC-21 – E 2 – – – – –

OC-23 – E 0.3 – – – – –

Number of wells with detections 5 2 1 1 1 0 0

Detection frequency (percent) 21 8 4 4 4 0 0

Total Detections

CLAB West Coast Basin Study Area (10 grid wells sampled)

WB-03 – 3 4 – na – –

WB-04 – – – – – – –

WB-05 – – E 0.4 – – – –

WB-06 – – – – – E 0.02 E 0.02

WB-07 – – – – – E 1.8 E 2.4

WB-08 – 5 – E 0.9 – – –

WB-09 – – E 1 – – – –

Number of wells with detections 0 2 3 1 0 2 2

Detection frequency (percent) 0 20 30 10 0 20 20

Total Detections
Table 8 59

GAMA 

identification 

No.

3-β-Coprostanol, 

(μg/L) 

(62806)

4-Cumylphenol, 

(μg/L) 

(62808)

4-Nonylphenol, 

(μg/L) 

(62829)

Acetyl hexamethyl 

tetrahydro 

naphthalene

 (AHTN)

(μg/L) 

(62812)

Cholesterol, 

(μg/L) (62818)

DEET, (μg/L) 

(61947)

Fluoranthene, 

(μg/L) 

(34376)

[IRL] [0.8] [0.2] [1.6] [0.2] [0.8] [0.2] [0.2]

Threshold type na na na na na na na

Threshold (μg/L) na na na na na na na

CLAB Study Unit (55 grid wells sampled)—Continued

Number of wells with detections 2 2 2 2 2 2 2

Detection frequency (percent) 4 4 4 4 4 4 4

Total Detections

CLAB Central Basin Study Area (21 grid wells sampled)—Continued

CB-03 – – – E 0.1 – – –

CB-05 – – – – – – –

CB-07 – E 0.01 – – – – –

CB-08 – – – – – – –

CB-11 – – – – – – –

CB-19 – – – – – – –

Number of wells with detections 0 1 0 1 0 0 0

Detection frequency (percent) 0 5 0 5 0 0 0

Total Detections

CLAB Orange County Coastal Plain Study Area (24 grid wells sampled)—Continued

OC-03 – E 0.01 – – – – –

OC-04 – – – – – – –

OC-05 – – – – – – –

OC-06 – – – – – – –

OC-07 – – – – – – –

OC-08 – – – – – – –

OC-10 – – E 0.1 – – – E 0.003

OC-19 – – – – – – –

OC-20 – – – E 0.03 – – –

OC-21 – – – – – – –

OC-23 – – – – – – –

Number of wells with detections 0 1 1 1 0 0 1

Detection frequency (percent) 0 4 4 4 0 0 4

Total Detections

CLAB West Coast Basin Study Area (10 grid wells sampled)—Continued

WB-03 – – – – – – –

WB-04 E 0.4 – – – E 0.4 E 0.01 –

WB-05 – – – – – – –

WB-06 – – – – – – –

WB-07 E 1 – E 0.8 – E 1 E 0.04 E 0.02

WB-08 – – – – – – –

WB-09 – – – – – – –

Number of wells with detections 2 0 1 1 2 2 1

Detection frequency (percent) 20 0 10 10 20 20 10

Total Detections

Table 8. Potential wastewater indicators detected in samples collected for the Coastal Los Angeles Basin Groundwater Ambient 

Monitoring and Assessment (GAMA) study unit, California, June to November 2006.—Continued

[The five-digit U.S. Geological Survey (USGS) parameter code below the constituent name is used to uniquely identify a specific constituent or property. 

Thresholds, threshold values, and IRLs as of November 16, 2006. Samples from all 69 wells were analyzed, but only samples with detections are listed. Analytes 

are listed in order of decreasing detection frequency in the 55 grid wells. All analytes are listed in table 3E. Threshold: Maximum contaminant level thresholds 

are listed as MCL-US when the MCL-US and MCL-CA are identical, and as MCL-CA when the MCL-CA is lower than the MCL-US or no MCL-US exists. 

HAL-US, U.S. Environmental Protection Agency Lifetime Health Advisory. Abbreviations: CLAB; Coastal Los Angeles Basin; CLAB Grid Wells; CLAB 

Understanding Wells; E, estimated or having a higher degree of uncertainty; IRL, interim reporting limit; μg/L, microgram per liter; na, not available; –, not 

detected]
60 Ground-Water Quality Data in the Coastal Los Angeles Basin Study Unit, 2006: Results from the California GAMA Program

GAMA 

identification 

No.

Hexahydrohexamethylcyclopentabenzopyran 

(HHCB), (μg/L) (62823)

Metolachlor, 

(μg/L) (82612)

Tris (dichloroisopropyl) 

phosphate, 

(μg/L) (61707)

4-Octylphenol 

diethoxylates, 

(μg/L) 

(61705)

d-Limonene, 

(μg/L) 

(62819)

2,6-Dimethylnaphthalene, 

(μg/L) 

(62805)

Benzophenone, 

(μg/L) 

(62814)

[IRL] [0.2] [0.2] [0.2] [0.32] [0.2] [0.2] [0.2]

Threshold type na HAL-US na na na na na

Threshold (μg/L) na 700 na na na na na

CLAB Study Unit (55 grid wells sampled)—Continued

Number of wells with detections 2 2 2 1 1 1 1

Detection frequency (percent) 4 4 4 2 2 2 2

Total Detections

CLAB Central Basin Study Area (21 grid wells sampled)—Continued

CB-03 – – – – – – –

CB-05 – E 0.02 E 0.04 – – – –

CB-07 – – – – – – –

CB-08 – – – – – – –

CB-11 – – – – E 0.01 – –

CB-19 – – – – – – –

Number of wells with detections 0 1 1 0 1 0 0

Detection frequency (percent) 0 5 5 0 5 0 0

Total Detections

CLAB Orange County Coastal Plain Study Area (24 grid wells sampled)—Continued

OC-03 – – – – na – –

OC-04 – – – – – – –

OC-05 – – – – – – –

OC-06 – – – – – – –

OC-07 – – – – – – –

OC-08 – – – – – – –

OC-10 – E 0.02 – – – – –

OC-19 – – – – – – –

OC-20 E 0.03 – E 0.1 – – – –

OC-21 – – – – – – –

OC-23 – – – – – – –

Number of wells with detections 1 1 1 0 0 0 0

Detection frequency (percent) 4 4 4 0 0 0 0

Total Detections

CLAB West Coast Basin Study Area (10 grid wells sampled)—Continued

WB-03 – – – – – – –

WB-04 – – – – – – E 0.03

WB-05 – – – – – – –

WB-06 – – – – – – –

WB-07 E 0.03 – – E 0.4 – E 0.5 –

WB-08 – – – – – – –

WB-09 – – – – – – –

Number of wells with 

detections

0 0 0 1 0 1 1

Detection frequency (percent) 0 0 0 10 0 10 10

Total Detections

Table 8. Potential wastewater indicators detected in samples collected for the Coastal Los Angeles Basin Groundwater Ambient 

Monitoring and Assessment (GAMA) study unit, California, June to November 2006.—Continued

[The five-digit U.S. Geological Survey (USGS) parameter code below the constituent name is used to uniquely identify a specific constituent or property. 

Thresholds, threshold values, and IRLs as of November 16, 2006. Samples from all 69 wells were analyzed, but only samples with detections are listed. Analytes 

are listed in order of decreasing detection frequency in the 55 grid wells. All analytes are listed in table 3E. Threshold: Maximum contaminant level thresholds 

are listed as MCL-US when the MCL-US and MCL-CA are identical, and as MCL-CA when the MCL-CA is lower than the MCL-US or no MCL-US exists. 

HAL-US, U.S. Environmental Protection Agency Lifetime Health Advisory. Abbreviations: CLAB; Coastal Los Angeles Basin; CLAB Grid Wells; CLAB 

Understanding Wells; E, estimated or having a higher degree of uncertainty; IRL, interim reporting limit; μg/L, microgram per liter; na, not available; –, not 

detected]
Table 8 61

GAMA 

identification 

No.

Bisphenol A, 

(μg/L) 

(62816)

4-Nonylphenol 

diethoxylates, 

(μg/L) 

(61703)

Diethyl 

phthalate, 

(μg/L) 

(34336)

Nonylphenol 

monoethoxylates, 

(μg/L) 

(61704)

Indole, 

(μg/L) 

(62824)

Methyl 

salicylate, 

(μg/L)

 (62828)

p-Cresol, 

(μg/L) 

(77146)

Phenol, 

(μg/L) 

(34694)

Prometon, 

(μg/L) 

(39056)

[IRL] [0.4] [3.2] [0.2] [2] [0.2] [0.2] [0.2] [0.2] [0.2]

Threshold type na na na na na na na HAL-US HAL-US

Threshold (μg/L) na na na na na na na 2000 100

CLAB Study Unit (55 grid wells sampled)—Continued

Number of wells with detections 1 1 1 1 1 1 1 1 1

Detection frequency (percent) 2 2 2 2 2 2 2 2 2

Total Detections

CLAB Central Basin Study Area (21 grid wells sampled)—Continued

CB-03 – – – – – – – – –

CB-05 – – – – – – – – –

CB-07 – – – – – – – – –

CB-08 – – – – – – – – –

CB-11 – – – – – – – – –

CB-19 – – – – – – – – –

Number of wells with detections 0 0 0 0 0 0 0 0 0

Detection frequency (percent) 0 0 0 0 0 0 0 0 0

Total Detections

CLAB Orange County Coastal Plain Study Area (24 grid wells sampled)—Continued

OC-03 – – – – na na na na –

OC-04 – – – – – – – – –

OC-05 – – – – – – – – –

OC-06 – – – – – – – – –

OC-07 – – – – – – – – –

OC-08 – – – – – – – – –

OC-10 – – – – – – – – –

OC-19 – – – – – – – – –

OC-20 – – – – – – – – E 0.04

OC-21 – – – – – – – – –

OC-23 – – – – – – – – –

Number of wells with detections 0 0 0 0 0 0 0 0 1

Detection frequency (percent) 0 0 0 0 0 0 0 0 4

Total Detections

CLAB West Coast Basin Study Area (10 grid wells sampled)—Continued

WB-03 E 0.1 – – – – – – – –

WB-04 – E 1 – E 0.1 – – – – –

WB-05 – – – – – E 0.04 – – –

WB-06 – – – – – – – – –

WB-07 – – – – – – – – –

WB-08 – – – – E 0.04 – E 0.1 – –

WB-09 – – E 0.1 – – – – E 0.1 –

Number of wells with detections 1 1 1 1 1 1 1 1 0

Detection frequency (percent) 10 10 10 10 10 10 10 10 0

Total Detections

Table 8. Potential wastewater indicators detected in samples collected for the Coastal Los Angeles Basin Groundwater Ambient 

Monitoring and Assessment (GAMA) study unit, California, June to November 2006.—Continued

[The five-digit U.S. Geological Survey (USGS) parameter code below the constituent name is used to uniquely identify a specific constituent or property. 

Thresholds, threshold values, and IRLs as of November 16, 2006. Samples from all 69 wells were analyzed, but only samples with detections are listed. Analytes 

are listed in order of decreasing detection frequency in the 55 grid wells. All analytes are listed in table 3E. Threshold: Maximum contaminant level thresholds 

are listed as MCL-US when the MCL-US and MCL-CA are identical, and as MCL-CA when the MCL-CA is lower than the MCL-US or no MCL-US exists. 

HAL-US, U.S. Environmental Protection Agency Lifetime Health Advisory. Abbreviations: CLAB; Coastal Los Angeles Basin; CLAB Grid Wells; CLAB 

Understanding Wells; E, estimated or having a higher degree of uncertainty; IRL, interim reporting limit; μg/L, microgram per liter; na, not available; –, not 

detected]
62 Ground-Water Quality Data in the Coastal Los Angeles Basin Study Unit, 2006: Results from the California GAMA Program

GAMA 

identification

No.

Pyrene, (μg/L) 

(34469)

Tributyl 

phosphate, (μg/L) 

(62832)

Triclosan, (μg/L) 

(61708)

Triphenyl 

phosphate, 

(μg/L) 

(62834)

Tris(2-

chloroethyl) 

phosphate, 

(μg/L) (62831) Detections 

per 

well

Any 

potenital 

waste-water 

indicator [IRL] [0.2] [0.2] [0.2] [0.2] [0.2]

Threshold type na na na na na

Threshold (μg/L) na na na na na

CLAB Study Unit (55 grid wells sampled)—Continued

Number of wells with detections 1 1 1 1 0 24

Detection frequency (percent) 2 2 2 2 0 44

Total Detections 62

CLAB Central Basin Study Area (21 grid wells sampled)—Continued

CB-03 – – – – – 3

CB-05 – – – E 0.03 – 4

CB-07 – – – – – 1

CB-08 – – – – – 1

CB-11 – – – – – 1

CB-19 – – – – – 1

Number of wells with detections 0 0 0 1 0 6

Detection frequency (percent) 0 0 0 5 0 29

Total Detections 11

CLAB Orange County Coastal Plain Study Area (24 grid wells sampled)—Continued

OC-03 – – – – – 1

OC-04 – – – – – 1

OC-05 – – – – – 1

OC-06 – – – – – 1

OC-07 – – – – – 1

OC-08 – – – – – 1

OC-10 E 0.003 – – – – 4

OC-19 – – – – – 1

OC-20 – E 0.1 – – – 7

OC-21 – – – – – 1

OC-23 – – – – – 1

Number of wells with detections 1 1 0 0 0 11

Detection frequency (percent) 4 4 0 0 0 46

Total Detections 20

CLAB West Coast Basin Study Area (10 grid wells sampled)—Continued

WB-03 – – – – – 3

WB-04 – – – – – 6

WB-05 – – – – – 2

WB-06 – – – – – 2

WB-07 – – E 0.1 – – 11

WB-08 – – – – – 4

WB-09 – – – – – 3

Number of wells with detections 0 0 1 0 0 7

Detection frequency (percent) 0 0 10 0 0 70

Total Detections 31

Table 8. Potential wastewater indicators detected in samples collected for the Coastal Los Angeles Basin Groundwater Ambient 

Monitoring and Assessment (GAMA) study unit, California, June to November 2006.—Continued

[The five-digit U.S. Geological Survey (USGS) parameter code below the constituent name is used to uniquely identify a specific constituent or property. 

Thresholds, threshold values, and IRLs as of November 16, 2006. Samples from all 69 wells were analyzed, but only samples with detections are listed. Analytes 

are listed in order of decreasing detection frequency in the 55 grid wells. All analytes are listed in table 3E. Threshold: Maximum contaminant level thresholds 

are listed as MCL-US when the MCL-US and MCL-CA are identical, and as MCL-CA when the MCL-CA is lower than the MCL-US or no MCL-US exists. 

HAL-US, U.S. Environmental Protection Agency Lifetime Health Advisory. Abbreviations: CLAB; Coastal Los Angeles Basin; CLAB Grid Wells; CLAB 

Understanding Wells; E, estimated or having a higher degree of uncertainty; IRL, interim reporting limit; μg/L, microgram per liter; na, not available; –, not 

detected]
Table 8 63

GAMA 

identification 

No.

Camphor, 

(μg/L) 

(62817)

Bis(2-ethylhexyl) 

phthalate

(μg/L) 

(39100)

5-Methyl-1Hbenzotriazole 

(μg/L) 

(61944)

Tris(2-butoxyethyl) 

phosphate 

(μg/L) 

(62830)

3,4-Dichlorophenyl 

isocyanate

(μg/L) 

(63145)

1-Methylnaphthalene 

(μg/L) 

(81696)

2-Methylnaphthalene 

(μg/L) 

(30194)

[IRL] [0.2] [2] [1.6] [0.2] [2] [0.2] [0.2]

Threshold type na na na na na na na

Threshold (μg/L) na na na na na na na

CLAB Understanding wells1

 (14 wells sampled)

DA-05 – – – – – – –

U-03 – – E 1 E 0.1 E 0.28 – –

U-06 – – – – – – –

U-07 – 4 – – – – –

U-08 – – 2 – – – –

GAMA 

identification 

No.

3-β-Coprostanol, 

(μg/L) 

(62806)

4-Cumylphenol, 

(μg/L) 

(62808)

4-Nonylphenol, 

(μg/L) 

(62829)

Acetyl hexamethyl 

tetrahydro 

naphthalene (AHTN) 

(μg/L) (62812)

Cholesterol 

(μg/L) 

(62818)

DEET

(μg/L) 

(61947)

Fluoranthene 

(μg/L) 

(34376)

[IRL] [0.8] [0.2] [1.6] [0.2] [0.8] [0.2] [0.2]

Threshold type na na na na na na na

Threshold (μg/L) na na na na na na na

CLAB Understanding wells1 (14 wells sampled)—Continued

DA-05 – – – – – – –

U-03 – – – E 0.03 – E 0.01 –

U-06 – – – – – – –

U-07 – – – – – – –

U-08 – – – – – – –

GAMA 

identification 

No.

Hexahydrohexamethylcyclopentabenzopyran 

(HHCB)

(μg/L) 

(62823)

Metolachlor (μg/L)

 (82612)

Tris (dichloroisopropyl) 

phosphate 

(μg/L) (61707)

4-Octylphenol 

diethoxylates 

(μg/L) 

(61705)

d-Limonene

(μg/L) 

(62819)

2,6-Dimethylnaphthalene (μg/L) 

(62805)

Benzophenone 

(μg/L) 

(62814)

[IRL] [0.2] [0.2] [0.2] [0.32] [0.2] [0.2] [0.2]

Threshold type na HAL-US na na na na na

Threshold (μg/L) na 700 na na na na na

CLAB Understanding wells1 (14 wells sampled)—Continued

DA-05 – – – – – – –

U-03 E 0.04 – E 0.1 – – – E 0.03

U-06 – – – – – – –

U-07 – – – – – – –

U-08 – – – – – – –

Table 8. Potential wastewater indicators detected in samples collected for the Coastal Los Angeles Basin Groundwater Ambient 

Monitoring and Assessment (GAMA) study unit, California, June to November 2006.—Continued

[The five-digit U.S. Geological Survey (USGS) parameter code below the constituent name is used to uniquely identify a specific constituent or property. 

Thresholds, threshold values, and IRLs as of November 16, 2006. Samples from all 69 wells were analyzed, but only samples with detections are listed. Analytes 

are listed in order of decreasing detection frequency in the 55 grid wells. All analytes are listed in table 3E. Threshold: Maximum contaminant level thresholds 

are listed as MCL-US when the MCL-US and MCL-CA are identical, and as MCL-CA when the MCL-CA is lower than the MCL-US or no MCL-US exists. 

HAL-US, U.S. Environmental Protection Agency Lifetime Health Advisory. Abbreviations: CLAB; Coastal Los Angeles Basin; CLAB Grid Wells; CLAB 

Understanding Wells; E, estimated or having a higher degree of uncertainty; IRL, interim reporting limit; μg/L, microgram per liter; na, not available; –, not 

detected]
64 Ground-Water Quality Data in the Coastal Los Angeles Basin Study Unit, 2006: Results from the California GAMA Program

GAMA 

identification 

No.

Bisphenol A, 

(μg/L) 

(62816)

4-Nonylphenol 

diethoxylates 

(μg/L) 

(61703)

Diethyl 

phthalate, (μg/L) 

(34336)

Nonylphenol 

monoethoxylates, 

(μg/L) (61704)

Indole

(μg/L) 

(62824)

Methyl 

salicylate, 

(μg/L) 

(62828)

p-Cresol, 

(μg/L) 

(77146)

Phenol

(μg/L) 

(34694)

Prometon, 

(μg/L) 

(39056)

[IRL] [0.4] [3.2] [0.2] [2] [0.2] [0.2] [0.2] [0.2] [0.2]

Threshold type na na na na na na na HAL-US HAL-US

Threshold (μg/L) na na na na na na na 2000 100

CLAB Understanding wells1

 (14 wells sampled)—Continued

DA-05 – – – – – – – E 0.1 –

U-03 – – – – – E 0.03 – – E 0.04

U-06 – – – – – – – E 0.1 –

U-07 – – – – – – – – –

U-08 E 0.1 – – – – – – – –

GAMA

 identification 

No.

Pyrene, 

(μg/L) 

(34469)

Tributyl 

phosphate, 

(μg/L) 

(62832)

Triclosan, 

(μg/L) 

(61708)

Triphenyl 

phosphate, 

(μg/L) 

(62834)

Tris

(2-chloroethyl) 

phosphate, 

(μg/L) 

(62831)

Detections per 

well

Any potenital 

waste-water 

indicator 

[IRL] [0.2] [0.2] [0.2] [0.2] [0.2]

Threshold type na na na na na

Threshold (μg/L) na na na na na

CLAB Understanding wells1

 (14 wells sampled)—Continued

DA-05 – – – – – 1

U-03 – E 0.1 – – E 0.05 14

U-06 – – – – – 1

U-07 – – – – – 1

U-08 – – – – – 2

1

 Understanding wells were not included in statistical calculations.

*

 Values exceed regulatory threshold.

Table 8. Potential wastewater indicators detected in samples collected for the Coastal Los Angeles Basin Groundwater Ambient 

Monitoring and Assessment (GAMA) study unit, California, June to November 2006.—Continued

[The five-digit U.S. Geological Survey (USGS) parameter code below the constituent name is used to uniquely identify a specific constituent or property. 

Thresholds, threshold values, and IRLs as of November 16, 2006. Samples from all 69 wells were analyzed, but only samples with detections are listed. Analytes 

are listed in order of decreasing detection frequency in the 55 grid wells. All analytes are listed in table 3E. Threshold: Maximum contaminant level thresholds 

are listed as MCL-US when the MCL-US and MCL-CA are identical, and as MCL-CA when the MCL-CA is lower than the MCL-US or no MCL-US exists. 

HAL-US, U.S. Environmental Protection Agency Lifetime Health Advisory. Abbreviations: CLAB; Coastal Los Angeles Basin; CLAB Grid Wells; CLAB 

Understanding Wells; E, estimated or having a higher degree of uncertainty; IRL, interim reporting limit; μg/L, microgram per liter; na, not available; –, not 

detected]
Table 9 65

GAMA 

identification 

No.

Perchlorate 

(μg/L) 

(61209)

N-Nitrosodimethylamine 

(μg/L) 

(64176)

1,4-Dioxane 

(μg/L)

(81582)

Threshold type MCL-CA NL-CA NL-CA

Threshold (μg/L) 6 0.01 3

[MRL] [0.5] [0.002] [2]

CLAB Grid wells

CB-02 0.6 – –

CB-07 2.0 nc nc

CB-11 1.0 nc nc

CB-12 0.6 nc nc

CB-13 1.1 nc nc

CB-15 1.5 nc nc

CB-16 5.1 nc nc

CB-17 1.8 – 3.0

CB-19 3.4 nc nc

OC-03 3.3 nc nc

OC-04 3.5 nc nc

OC-05 4.4 nc nc

OC-06 5.0 nc nc

OC-07 0.8 nc nc

OC-08 3.8 nc nc

Table 9. Results of analyses for the constituents of special interest: perchlorate, N-nitrosodimethylamine (NDMA), and 1,4-dioxane 

detected in the samples collected in the Coastal Los Angeles Basin Ground-Water Ambient Monitoring and Assessment (GAMA) study 

unit, California, June to November 2006.

[The five-digit USGS parameter code below the constituent name is used to uniquely identify a specific constituent or property. Thresholds, threshold 

values, and LRLs as of November 16, 2006. All analytes are listed in table 3G. Samples from all 69 wells were analyzed for perchlorate, 17 wells 

for N-Nitrosodimethylamine and 1,4-Dioxane, but only wells with detections are listed. Perchlorate: Perchlorate was sampled at all 69 wells. NNitrosodimethylamine: N-Nitrosodimethylamine and 1,4-dioxane were sampled at 17 slow and intermediate wells. Abbreviations: CLAB; Coastal Los 

Angeles Basin; CLAB Grid Wells; CLAB Understanding Wells; MRL, method reporting level; NL-CA, California notification level; MCL-CA; California 

Department of Public Health maximum contaminant level; μg/L, microgram per liter; nc, not collected; –, not detected. Note: 1,2,3,TCP was sampled at 17 slow 

and intermediate wells and not detected]

GAMA 

identification 

No.

Perchlorate 

(μg/L) 

(61209)

N-Nitrosodimethylamine 

(μg/L) 

(64176)

1,4-Dioxane 

(μg/L)

(81582)

Threshold type MCL-CA NL-CA NL-CA

Threshold (μg/L) 6 0.01 3

[MRL] [0.5] [0.002] [2]

CLAB Grid wells—Continued

OC-09 1.2 nc nc

OC-10 2.1 nc nc

OC-15 0.6 nc nc

OC-16 1.5 nc nc

OC-19 0.6 nc nc

OC-21 3.9 nc nc

WB-07 1.7 nc nc

CLAB Understanding wells

DA-02 1.9 – 17.0

DA-04 1.3 – –

U-02 – – 2.7

U-03 0.6 0.003 –

U-04 4.0 nc nc

U-06 4.2 – –

*

Value above regulatory threshold.
66 Ground-Water Quality Data in the Coastal Los Angeles Basin Study Unit, 2006: Results from the California GAMA Program

GAMA 

identification 

No.

Ammonia, 

 as nitrogen 

(mg/L) 

(00608)

Nitrite plus nitrate,

 as nitrogen 

(mg/L) 

(00631)

 Nitrite, 

 as nitrogen 

(mg/L) 

(00613)

Total nitrogen 

(nitrate + nitrite 

+ ammonia 

+ organic-nitrogen) 

as nitrogen 

(mg/L) 

(62854)

Orthophosphate, 

as phosphorus 

(mg/L) 

00671)

Dissolved organic 

carbon (DOC) 

(mg/L) 

(00681)

Threshold type HAL-US MCL-US MCL-US na na na

Threshold (mg/L) 30 10 1 na na na

[LRL] [0.01] [0.06] [0.002] [0.06] [0.006] [0.33]

CLAB Grid Wells (8 wells sampled)

CB-02 V 0.012 0.58 – 0.62 0.067 E 0.3

CB-03 V 0.010 3.29 – 3.44 0.027 0.9

CB-04 0.233 – – 0.33 0.022 1.2

CB-17 – 2.78 – 1

2.69 0.025 0.3

OC-01 – 1.67 0.029 1.72 0.023 nc

OC-02 – 4.14 – 1

4.00 0.030 0.5

OC-20 V 0.01 2.22 0.253 1

2.17 0.351 1.6

WB-04 2.93 – – 3.19 0.160 4.1

CLAB Understanding wells2

 (11 wells sampled)

DA-01 0.04 2.94 – 1

2.85 0.076 0.4

DA-02 V 0.01 6.51 – 6.84 0.110 0.3

DA-03 0.29 – – 1

0.28 0.038 0.5

DA-04 V 0.01 4.19 – 4.23 0.125 0.3

DA-05 1.10 – – 1.09 0.054 1.2

DA-06 2.07 – – 2.13 0.135 3.4

U-01 V 0.01 1.29 – 1

1.29 0.04 nc

U-02 V 0.01 1.17 – 1.21 0.025 0.6

U-03 – 2.45 – 1

2.39 0.015 0.8

U-06 – 7.07 – 5.94 0.138 0.8

U-07 – – – E 0.04 0.026 1.1

1

Total nitrogen in these samples is less than the sum of the filtered nitrogen analytes, but falls within the U.S. Geological Survey National Water Quality 

Laboratory acceptance criteria of a 10 percent relative percent difference.

Table 10. Nutrients and dissolved organic carbon detected in samples collected for the Coastal Los Angeles Basin Groundwater 

Ambient Monitoring and Assessment (GAMA) study unit, California, June to November 2006.

[The five-digit U.S. Geological Survey (USGS) parameter code below the constituent name is used to uniquely identify a specific constituent or property. 

Thresholds, threshold values, and LRLs as of November 16, 2006. Samples from the 19 slow and intermediate wells were analyzed. All analytes are listed in 

table 3H. Ammonia: Threshold value is “as ammonia.” Threshold type: Maximum contaminant level thresholds are listed as MCL-US when the MCL-US 

and MCL-CA are identical, and as MCL-CA when the MCL-CA is lower than the MCL-US or no MCL-US exists. HAL-US, Lifetime Health Advisory; 

MCL-US, U.S. Environmental Protection Agency maximum contaminant level. Abbreviations: CLAB; Coastal Los Angeles Basin; CLAB Grid Wells; CLAB 

Understanding Wells; E, estimated or having a higher degree of uncertainty; V, analyte detected in sample and an associated blank thus data are not included in 

ground-water-quality assessment; LRL, laboratory reporting level; mg/L, milligram per liter; na, not available; nc, not collected; –, not detected]
Table 11 67

GAMA 

Identification 

No.

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)

Threshold type na na na na na SMCL-CA MCL-US na na SMCL-CA SMCL-CA

Threshold (mg/L) na na na na na 250 (500) 2 na na 250 (500) 500 (1,000)

[LRL] [0.02] [0.014] [0.04] [0.2] [0.02] [0.12] [0.1] [0.002] [0.018] [0.18] [10]

CLAB Grid Wells (8 wells sampled)

CB-02 81.2 14.4 3.33 27.7 0.07 30.9 0.48 0.002 22.6 73.2 376

CB-03 58.4 13.8 3.81 70.8 0.17 83.3 0.35 0.012 20.1 99.6 472

CB-04 9.10 0.377 0.74 62.7 0.05 12.0 0.62 0.010 16.1 27.2 219

CB-17 101 20.5 3.47 31.2 0.16 53.2 0.31 E 0.002 21.7 118 *511

OC-01 70 13.8 1.93 58.2 0.14 63.6 0.30 nc 20.6 106 438

OC-02 96.9 17.3 4.23 67.5 0.23 91.4 0.49 0.010 21.4 133 *512

OC-20 93.4 21.6 6.10 86.0 0.18 96.1 0.50 0.022 21.0 166 *658

WB-04 62.4 28.4 13.4 160 0.76 106 0.36 0.196 37.2 54.2 *729

CLAB Understanding wells (11 wells sampled)

DA-01 115 53.2 3.04 72.9 0.30 111 0.34 0.018 35.0 188 *775

DA-02 128 56.4 2.16 74.3 0.39 85.6 0.37 0.005 31.8 235 *873

DA-03 59.5 32.3 4.68 85.6 0.12 36.9 0.53 0.037 40.0 121 *579

DA-04 112 55.0 3.08 88.6 0.24 102 0.36 0.002 27.5 215 *857

DA-05 23.8 21.5 6.03 254 1.19 220 1.50 0.226 37.6 7.05 *818

DA-06 252 110 14.8 438 6.14 **640 0.26 1.12 39.2 **561 **2,430

U-01 53.3 10.8 1.67 34 0.06 23.6 0.47 nc 21.7 50.1 303

U-02 106 20.6 4.45 47.0 0.15 64.2 0.42 0.009 20.6 133 *551

U-03 88.2 15.2 4.48 56.7 0.19 81.1 0.26 0.013 19.6 135 *544

U-06 136 61.4 1.62 59.4 0.29 105 0.57 0.005 37.6 233 *851

U-07 180 33.6 5.36 95.8 0.39 116 0.34 0.013 24.9 *279 *971

*

 Value exceeds recommended threshold.

**

 Value exceeds upper threshold.

Table 11. Major and minor ions and dissolved solids detected in samples collected for the Coastal Los Angeles Basin Groundwater 

Ambient Monitoring and Assessment (GAMA) study unit, California, June to November 2006.

[The five-digit USGS parameter code below the constituent name is used to uniquely identify a specific constituent or property. Thresholds, threshold values, 

and LRLs as of November 16, 2006. Samples from the 19 slow and intermediate wells were analyzed. All analytes are listed in table 3I. Threshold type:

Maximum contaminant level thresholds are listed as MCL-US when the MCL-US and MCL-CA are identical, and as MCL-CA when the MCL-CA is lower 

than the MCL-US or no MCL-US exists. MCL-US, U.S. Environmental Protection Agency maximum contaminant level; SMCL-CA, California Department of 

Public Health secondary maximum contaminant level. The SMCL-CA for chloride, sulfate, and total dissolved solids have recommended and upper threshold 

values. The upper value is shown in parentheses. Abbreviations: CLAB; Coastal Los Angeles Basin; CLAB Grid Wells; CLAB Understanding Wells; LRL, 

laboratory reporting level; mg/L, milligrams per liter; na, not available; nc, not collected; E, estimated or having a higher degree of uncertainty]
68 Ground-Water Quality Data in the Coastal Los Angeles Basin Study Unit, 2006: Results from the California GAMA Program

Table 12. Trace elements detected in samples collected for the Coastal Los Angeles Basin Groundwater Ambient Monitoring and 

Assessment (GAMA) study unit, California, June to November.

[The five-digit U.S. Geological Survey (USGS) parameter code below the constituent name is used to uniquely identify a specific constituent or property. 

Thresholds, threshold values, and LRLs as of November 16, 2006. Samples from the 19 slow and intermediate wells were analyzed. All analytes are listed in 

table 3I. Threshold: 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. AL-US, U.S. Environmental Protection Agency action level; HAL-US (USEPA), 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-US, U.S. Environmental Protection Agency secondary maximum 

contaminant level. Abbreviations: CLAB; Coastal Los Angeles Basin; CLAB Grid Wells; CLAB Understanding Wells; V, analyte detected in sample and an 

associated blank thus data are not included in ground-water-quality assessment; E, estimated or having a higher degree of uncertainty; LRL, laboratory reporting 

level; na, not available; nc, not collected; –, not detected: μg/L, microgram per liter]

GAMA 

identification 

No. 

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

Lithium 

(μg/L) 

(01130) 

Threshold type MCL-US MCL-US MCL-US MCL-CA MCL-CA NL-CA MCL-US MCL-CA na AL-US SMCL-US NL-CA na

Threshold 1,000 6 10 1,000 4 1,000 5 50 na 1,300 300 15 na

[LRL] [1.6] [0.20] [0.12] [0.20] [0.06] [8] [0.04] [0.04] [0.04] [0.40] [6] [0.08] [0.6]

CLAB Grid Wells (8 wells sampled)

CB-02 1.9 – 3.6 163 – 75 E 0.02 0.26 E 0.03 1.1 E 4 0.91 1.6

CB-03 E1.0 E 0.15 1.8 67 – 228 0.04 0.17 3.9 2.9 E 3 0.50 1.2

CB-04 17.0 – 0.12 0.73 – 70 – V 0.04 – – E 3 0.12 4.6

CB-17 E 0.9 – 1.8 96 – 73 – 1.1 0.05 2.3 – 0.95 1.6

OC-01 2.5 – 0.83 92 – 106 E 0.03 0.25 0.164 2.2 – 1.11 7.8

OC-02 – – 1.5 96 – 184 E 0.02 0.29 0.245 1.2 – 0.25 5.8

OC-20 E 1.5 0.21 6.8 54 – 261 0.15 V 0.06 1.6 4.1 E 6 0.38 12.6

WB-04 E 1.5 – – 60 – 492 – 0.22 0.04 – *500 0.44 16.1

CLAB Understanding wells (11 wells sampled)

DA-01 – – 0.37 46 – 127 – 0.84 0.14 E 0.37 68 – 20.3

DA-02 – E 0.04 0.73 48 – 95 0.06 2.4 E 0.03 9.7 12 1.14 16.3

DA-03 2.3 – 0.93 54 – 239 – 0.14 0.08 0.42 47 0.15 28.0

DA-04 – – 0.81 53 – 149 0.05 1.2 – 2.3 14 1.78 23.0

DA-05 – – 3.8 102 – *1,190 – V 0.07 – – 47 – 25.0

DA-06 V 2.5 – – 99 – *1,260 – – E 0.04 – *793 – 30.6

U-01 – – 0.92 49 – 68 E 0.03 2.5 0.11 1.2 – 0.26 4.9

U-02 E 1.3 – 1.6 166 – 155 – 0.58 0.10 1.2 – 1.32 1.7

U-03 E 1.3 E 0.15 1.6 67 – 87 – 0.65 1.3 1.9 – 0.72 1.9

U-06 – E 0.04 0.44 158 – 71 E 0.02 1.2 E 0.02 1.3 – 0.65 9.5

U-07 – 0.10 1.5 48 – 232 E 0.02 E 0.11 0.37 0.51 48 0.56 2.3
Table 12 69

GAMA 

identification 

No. 

Manganese 

(μg/L) 

(01056) 

Mercury 

(μg/L) 

(71890) 

Molyb 

denum 

(μg/L) 

(01060) 

Nickel 

(μg/L) 

(01065) 

Selenium 

(μg/L) 

(01145) 

Silver 

(μg/L) 

(01075)

Strontium 

(μg/L) 

(01080)

Thallium 

(μg/L) 

(01057)

Tungsten 

(μg/L) 

(01155)

Uranium 

(μg/L) 

(22703)

Vanadium 

(μg/L) 

(01085) 

Zinc

(μg/L) 

(01090)

Threshold type SMCL MCL-US HAL-US MCL-CA MCL-US MCL-US HAL-US MCL-US na MCL-US NL-CA SMCL-CA

Threshold 50 2 40 100 50 100 4,000 2 na 30 50 5,000

[LRL] [0.2] [0.010] [0.4] [0.06] [0.08] [0.2] [0.4] [0.04] [0.06] [0.04] [0.10] [0.60]

CLAB Grid Wells (8 wells sampled)—Continued

CB-02 19.1 – 3.0 V 0.15 0.54 – 595 – 0.42 3.08 2.0 2.5

CB-03 6.7 – 4.5 3.6 0.21 – 451 – E 0.14 1.09 2.8 3.5

CB-04 1.3 – 6.9 0.30 – – 28.5 – 8.1 – 0.51 1.1

CB-17 0.8 – 2.0 0.50 1.3 – 769 – 0.11 8.70 4.0 4.0

OC-01 0.4 nc 7.5 2.50 0.3 – 540 – nc 2.49 2.4 2.6

OC-02 – – 3.8 3.44 0.54 – 669 – 0.19 14.7 4.4 1.2

OC-20 *709 0.012 9.9 2.6 0.28 – 648 – 3.7 8.03 5.2 1.5

WB-04 *154 – 3.9 V 0.19 – – 482 – 0.25 0.05 0.52 2.8

CLAB Understanding wells (11 wells sampled)—Continued

DA-01 *52.7 – 5.4 1.6 2.6 – 514 – – 3.46 2.1 5.1

DA-02 5.3 nc 8.6 0.57 3.8 – 595 – – 9.29 4.9 4.7

DA-03 30.6 – 2.0 V 0.11 E 0.06 – 432 – 0.13 0.55 0.13 0.63

DA-04 3.3 – 2.4 0.61 2.9 – 557 E 0.02 – 1.37 2.0 9.0

DA-05 12.3 – 1.2 V 0.03 – – 284 – 7.8 – 0.15 E 0.39

DA-06 *177 – 0.8 0.54 E 0.12 – 1,950 – – 0.08 0.28 –

U-01 E 0.2 nc 5.5 1.76 1.10 393 – nc 2.64 3.2 1.3

U-02 E0.3 E 0.008 2.1 0.96 0.15 – 745 – 0.12 4.69 2.5 5.8

U-03 1.8 – 1.0 1.6 0.19 – 587 – 0.28 3.28 3.4 2.2

U-06 – nc 2.4 V 0.23 1.0 – 708 – – 2.67 8.3 6.7

U-07 *173 – 2.5 1.1 E 0.05 – 856 – 0.15 5.99 1.9 3.3

*

Value exceeds threshold.

Table 12. Trace elements detected in samples collected for the Coastal Los Angeles Basin Groundwater Ambient Monitoring and 

Assessment (GAMA) study unit, California, June to November.—Continued

[The five-digit U.S. Geological Survey (USGS) parameter code below the constituent name is used to uniquely identify a specific constituent or property. 

Thresholds, threshold values, and LRLs as of November 16, 2006. Samples from the 19 slow and intermediate wells were analyzed. All analytes are listed in 

table 3I. Threshold: 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. AL-US, U.S. Environmental Protection Agency action level; HAL-US (USEPA), 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-US, U.S. Environmental Protection Agency secondary maximum 

contaminant level. Abbreviations: CLAB; Coastal Los Angeles Basin; CLAB Grid Wells; CLAB Understanding Wells; V, analyte detected in sample and an 

associated blank thus data are not included in ground-water-quality assessment; E, estimated or having a higher degree of uncertainty; LRL, laboratory reporting 

level; na, not available; nc, not collected; –, not detected: μg/L, microgram per liter]
70 Ground-Water Quality Data in the Coastal Los Angeles Basin Study Unit, 2006: Results from the California GAMA Program

GAMA 

identification 

No.

Iron 

(μg/L) 

Iron (II) 

(μg/L) 

Arsenic 

(μg/L) 

Arsenic (III) 

(μg/L) 

Chromium 

(μg/L) 

Chromium (VI) 

(μg/L) 

Detections 

per well

Any 

Detection Threshold type SMCL-CA na MCL-US na MCL-CA na

Threshold (μg/L) 300 na 10 na 50 na

[MDL] [2] [2] [0.5] [1] [1] [1]

CLAB Study Unit (55 grid wells sampled)

Number of wells with detections 37 33 29 2 11 7 51

Detection frequency (percent) 67 60 53 4 20 13 93

Total Detections 124

CLAB Central Basin Study Area (21 grid wells sampled)

CB-01 5 5 – – – – 2

CB-02 – – 2.8 – – – 1

CB-03 – – 2.7 – – – 1

CB-04 2 2 – – – – 2

CB-05 6 6 0.6 – – – 3

CB-06 21 18 *19 19 – – 4

CB-07 9 2 0.8 – 2 1 5

CB-08 8 4 0.8 – 2 1 5

CB-09 25 16 – – – – 2

CB-10 52 24 1.4 – – – 3

CB-11 9 4 3.2 – – – 3

CB-12 32 4 1.3 – – – 3

CB-13 – – 3.2 – 2 – 2

CB-14 31 28 – – – – 2

CB-15 2 – 2.2 – – – 2

CB-16 19 6 – – 1 – 3

CB-17 – – 1.0 – – – 1

CB-18 180 180 – – – – 2

CB-19 4 3 – – 1 1 4

CB-20 188 174 – – – – 2

CB-21 103 4 2 – – – 3

Number of wells with detections 17 16 13 1 5 3 21

Detection frequency (percent) 81 76 62 5 24 14 100

Total Detections 55

Table 13. Species of inorganic arsenic, iron, and chromium detected in samples collected for the Coastal Los Angeles Basin 

Groundwater Ambient Monitoring and Assessment (GAMA) study unit, California, June to November 2006.

[Samples analyzed by U.S. Geological Survey Trace Metals Labratory using research methods. Values on table 12 are considered more accurate therefore 

values on this table are not stored in the USGS NWIS database. Thresholds, threshold values, and LRLs as of November 16, 2006. Samples from all 69 wells 

were analyzed for arsenic, iron, and chromium speciation. All analytes are listed in table 3J. Threshold: Maximum contaminant level thresholds are listed as 

MCL-US when the MCL-US and MCL-CA are identical, and as MCL-CA when the MCL-CA is lower than the MCL-US or no MCL-US exists. MCL-US, U.S. 

Environmental Protection Agency maximum contaminant level; MCL-CA, California Department of Public Health maximum contaminant level; SMCL-CA, 

California Department of Public Health secondary maximum contaminant level. Abbreviations: CLAB; Coastal Los Angeles Basin; CLAB Grid Wells; CLAB 

Understanding Wells; MDL, method detection level; na, not available; nc, not collected; –, not detected; μg/L, micrograms per liter]
Table 13 71

GAMA 

identification 

No.

Iron 

(μg/L) 

Iron (II) 

(μg/L) 

Arsenic 

(μg/L) 

Arsenic (III) 

(μg/L) 

Chromium 

(μg/L) 

Chromium (VI) 

(μg/L) 

Detections 

per well

Any 

Detection Threshold type SMCL-CA na MCL-US na MCL-CA na

Threshold (μg/L) 300 na 10 na 50 na

[MDL] [2] [2] [0.5] [1] [1] [1]

CLAB Orange County Coastal Plain Study Area (24 grid wells sampled)

OC-01 nc nc nc nc – – 0

OC-02 nc nc nc nc 3 2 2

OC-03 – – 0.8 – – – 1

OC-04 2 – 2.1 – 1 1 4

OC-05 – – 1.2 – 1 – 2

OC-06 – – 0.6 – 2 2 3

OC-07 – – 1.6 – 1 1 3

OC-08 6 – 2.5 – – – 2

OC-09 4 – 1.5 – – – 2

OC-10 – – 0.8 – – – 1

OC-11 – – 1.2 – – – 1

OC-12 – – – – – – 0

OC-13 2 2 2.8 – – – 3

OC-14 11 8 1.6 – – – 3

OC-15 4 3 1.0 – – – 3

OC-16 – – – – – – 0

OC-17 3 2 1.1 – – – 3

OC-18 – – – – – – 0

OC-19 – – 1.1 – – – 1

OC-20 – – 5.1 – – – 1

OC-21 17 3 1.2 – – – 3

OC-22 64 45 2.0 1.8 – – 4

OC-23 133 133 – – – – 2

OC-24 11 8 2.4 – – – 3

Number of wells with detections 11 8 18 1 5 4 20

Detection frequency (percent) 46 33 75 4 21 17 83

Total Detections 47

CLAB West Coast Basin Study Area (10 grid wells sampled)

WB-01 12 10 – – 2 – 3

WB-02 80 64 – – – – 2

WB-03 74 74 – – – – 2

WB-04 *488 477 – – – – 2

WB-05 *331 302 – – – – 2

WB-06 30 31 – – – – 2

WB-07 130 130 – – – – 2

WB-08 13 13.0 – – – – 2

WB-09 *2,820 2,830 – – – – 2

WB-10 *990 940 0.6 – – – 3

Number of wells with detections 10 10 1 0 1 0 10

Detection frequency (percent) 100 100 10 0 10 0 100

Total Detections 22

Table 13. Species of inorganic arsenic, iron, and chromium detected in samples collected for the Coastal Los Angeles Basin 

Groundwater Ambient Monitoring and Assessment (GAMA) study unit, California, June to November 2006.—Continued

[Samples analyzed by U.S. Geological Survey Trace Metals Labratory using research methods. Values on table 12 are considered more accurate therefore 

values on this table are not stored in the USGS NWIS database. Thresholds, threshold values, and LRLs as of November 16, 2006. Samples from all 69 wells 

were analyzed for arsenic, iron, and chromium speciation. All analytes are listed in table 3J. Threshold: Maximum contaminant level thresholds are listed as 

MCL-US when the MCL-US and MCL-CA are identical, and as MCL-CA when the MCL-CA is lower than the MCL-US or no MCL-US exists. MCL-US, U.S. 

Environmental Protection Agency maximum contaminant level; MCL-CA, California Department of Public Health maximum contaminant level; SMCL-CA, 

California Department of Public Health secondary maximum contaminant level. Abbreviations: CLAB; Coastal Los Angeles Basin; CLAB Grid Wells; CLAB 

Understanding Wells; MDL, method detection level; na, not available; nc, not collected; –, not detected; μg/L, micrograms per liter]
72 Ground-Water Quality Data in the Coastal Los Angeles Basin Study Unit, 2006: Results from the California GAMA Program

GAMA 

identification 

No.

Iron 

(μg/L) 

Iron (II) 

(μg/L) 

Arsenic 

(μg/L) 

Arsenic (III) 

(μg/L) 

Chromium 

(μg/L) 

Chromium (VI) 

(μg/L) 

Detections 

per well

Any 

Detection Threshold type SMCL-CA na MCL-US na MCL-CA na

Threshold (μg/L) 300 na 10 na 50 na

[MDL] [2] [2] [0.5] [1] [1] [1]

CLAB Understanding wells1

 (14 wells sampled)

DA-01 69 60 – – – – 2

DA-02 12 6 0.9 – 2 2 5

DA-03 46 46 1.2 1.2 – – 4

DA-04 13 6 – – – – 2

DA-05 47 47 3.1 3.4 – – 4

DA-06 *728 722 – – – – 2

U-01 nc nc nc nc 3 2 2

U-02 2 – 2.2 – – – 2

U-03 – – 2.5 – – – 1

U-04 9 7 1.0 – – – 3

U-05 *316 263 *14 – – – 3

U-06 – – – – – – 0

U-07 39 22 0.9 – – – 3

U-08 28 4 1.0 – – – 3

*

 Value exceeds threshold.

1

 Understanding wells were not included in statistical calculations.

Table 13. Species of inorganic arsenic, iron, and chromium detected in samples collected for the Coastal Los Angeles Basin 

Groundwater Ambient Monitoring and Assessment (GAMA) study unit, California, June to November 2006.—Continued

[Samples analyzed by U.S. Geological Survey Trace Metals Labratory using research methods. Values on table 12 are considered more accurate therefore 

values on this table are not stored in the USGS NWIS database. Thresholds, threshold values, and LRLs as of November 16, 2006. Samples from all 69 wells 

were analyzed for arsenic, iron, and chromium speciation. All analytes are listed in table 3J. Threshold: Maximum contaminant level thresholds are listed as 

MCL-US when the MCL-US and MCL-CA are identical, and as MCL-CA when the MCL-CA is lower than the MCL-US or no MCL-US exists. MCL-US, U.S. 

Environmental Protection Agency maximum contaminant level; MCL-CA, California Department of Public Health maximum contaminant level; SMCL-CA, 

California Department of Public Health secondary maximum contaminant level. Abbreviations: CLAB; Coastal Los Angeles Basin; CLAB Grid Wells; CLAB 

Understanding Wells; MDL, method detection level; na, not available; nc, not collected; –, not detected; μg/L, micrograms per liter]
Table 14 73

GAMA well 

identification 

No.

δ2H 

(per mil) 

(82082)

δ18O 

(per mil) 

(82085)

δ13C 

(per mil) 

(82081)

Carbon-14 

(percent 

modern) 

(49933)

Tritium 

(pCi/L) 

(07000)

Threshold type na na na na MCL-CA

Threshold level na na na na 20,000

CLAB Grid Wells

CB-01 -46.40 -7.17 nc nc nc

CB-02 -57.00 -8.34 -12.34 93.37 nc

CB-03 -57.00 -8.08 -12.91 95.61 nc

CB-04 -56.60 -8.39 -13.64 28.11 nc

CB-05 -58.50 -8.60 nc nc nc

CB-06 -53.80 -8.08 nc nc nc

CB-07 -57.30 -8.28 nc nc nc

CB-08 -46.70 -7.26 nc nc nc

CB-09 -48.10 -7.29 nc nc nc

CB-10 -48.80 -7.45 nc nc nc

CB-11 -57.30 -8.27 nc nc nc

CB-12 -54.40 -7.92 nc nc nc

CB-13 -55.10 -7.86 nc nc nc

CB-14 -48.50 -7.27 nc nc nc

CB-15 -59.20 -8.16 nc nc nc

CB-16 -62.60 -8.67 nc nc nc

CB-17 -60.70 -8.42 nc nc nc

CB-18 -43.20 -6.68 nc nc nc

CB-19 -44.80 -6.92 nc nc nc

CB-20 -48.20 -7.40 -11.96 59.03 nc

CB-21 -49.20 -7.54 nc nc nc

 

OC-01 -53.30 -7.54 nc nc nc

OC-02 -56.30 -7.85 -12.31 105.0 13.8

OC-03 -67.20 -8.81 nc nc nc

OC-04 -61.70 -8.73 nc nc nc

OC-05 -64.30 -8.80 nc nc nc

OC-06 -58.70 -8.39 nc nc nc

OC-07 -57.20 -8.38 nc nc nc

OC-08 -58.70 -8.30 nc nc nc

OC-09 -51.60 -7.59 nc nc nc

OC-10 -53.90 -7.81 nc nc nc

OC-11 -57.00 -8.32 nc nc nc

OC-12 -58.00 -8.57 nc nc nc

OC-13 -55.40 -7.71 nc nc nc

OC-14 -58.20 -8.49 nc nc nc

OC-15 -57.10 -8.23 nc nc nc

OC-16 -55.60 -7.94 nc nc nc

Table 14. Results for analyses of stable-isotope ratios, carbon-14 activities, and tritium in samples collected for the Coastal Los 

Angeles Basin Groundwater Ambient Monitoring and Assessment (GAMA) study unit, California, June to November 2006.

[The five-digit U.S. Geological Survey (USGS) parameter code below the constituent name is used to uniquely identify a specific constituent or property. 

Samples from all 69 wells were analyzed for stable isotopes of water; samples from 14 wells were analyzed for carbon; one sample was analyzed for tritium. 

Information about analytes given in table 3K. Stable isotope ratios are reported in the standard delta notation (δ), the ratio of a heavier isotope to more common 

lighter isotope of that element, relative to a standard reference material. Threshold: Maximum contaminant level thresholds are listed as MCL-US when the 

MCL-US and MCL-CA are identical, and as MCL-CA when the MCL-CA is lower than the MCL-US or no MCL-US exists. MCL-CA, California Department 

of Public Health maximum contaminant level. Abbreviations: CLAB; Coastal Los Angeles Basin; CLAB Grid Wells; CLAB Understanding Wells; pCi/L, 

picocuries per liter; na, not available; nc, not collected]

GAMA well 

identification 

No.

δ2H 

(per mil) 

(82082)

δ18O 

(per mil) 

(82085)

δ13C 

(per mil) 

(82081)

Carbon-14 

(percent 

modern) 

(49933)

Tritium 

(pCi/L) 

(07000)

Threshold type na na na na MCL-CA

Threshold level na na na na 20,000

CLAB Grid Wells—Continued

OC-17 -56.60 -7.76 nc nc nc

OC-18 -58.40 -8.57 nc nc nc

OC-19 -57.20 -8.20 nc nc nc

OC-20 -54.20 -7.50 -14.27 98.82 nc

OC-21 -50.00 -7.18 nc nc nc

OC-22 -55.50 -8.20 nc nc nc

OC-23 -41.70 -6.41 nc nc nc

OC-24 -50.00 -6.95 nc nc nc

 

WB-01 -79.10 -10.08 nc nc nc

WB-02 -56.10 -7.81 nc nc nc

WB-03 -56.00 -7.91 nc nc nc

WB-04 -42.20 -6.54 -13.50 35.71 nc

WB-05 -46.70 -7.08 nc nc nc

WB-06 -54.00 -8.05 nc nc nc

WB-07 -49.10 -7.46 nc nc nc

WB-08 -47.10 -7.34 nc nc nc

WB-09 -44.10 -6.80 nc nc nc

WB-10 -39.10 -6.09 nc nc nc

CLAB Understanding and wells

DA-01 -54.50 -7.80 -15.65 88.99 nc

DA-02 -47.30 -7.12 nc nc nc

DA-03 -36.80 -5.96 -15.45 41.17 nc

DA-04 -57.00 -8.03 -16.12 93.93 nc

DA-05 -39.40 -6.31 -10.00 20.94 nc

DA-06 -45.60 -6.63 nc nc nc

 

U-01 -56.60 -8.33 nc nc nc

U-02 -57.30 -8.27 nc nc nc

U-03 -57.60 -7.97 -13.80 92.70 nc

U-04 -61.20 -8.72 nc nc nc

U-05 -51.20 -7.78 nc nc nc

U-06 -54.50 -7.72 -16.41 88.70 nc

U-07 -55.60 -7.89 -13.91 106.4 nc

U-08 -55.40 -8.23 nc nc nc
74 Ground-Water Quality Data in the Coastal Los Angeles Basin Study Unit, 2006: Results from the California GAMA Program

GAMA well 

identification 

No.

Radium-226 

(pCi/L) 

(99915)

Radium-228 

(pCi/L) 

(99916)

Radon-222 

(pCi/L) 

(82303)

Alpha

radioactivity

(pCi/L)

Beta

radioactivity

(pCi/L)

72-hour 

count 

(99920)

30-day 

count 

(99921)

72-hour 

count 

(99922)

30-day 

count 

(99923)

Threshold type MCL-US MCL-US Proposed 

MCL-US MCL-US MCL-US MCL-CA MCL-CA

Threshold value 5 5 300 (4,000) 15 15 50 50

CLAB Grid wells

CB-03 E 0.056 < 0.520 *370 <2.6 <1.9 E 2.17 4.47

CB-04 < 0.032 < 0.480 80 <1.3 <3.0 <1.1 E 1.11

OC-02 0.086 E 0.37 *390 E 7.4 7 4.4 8.1

CLAB Understanding wells 

DA-01 1.042 E 0.327 *3,180 <5.7 <3.5 7.4 3.95

DA-02 E 0.045 E 0.27 *360 <3.9 E 2.25 E 2.01 E 2.84

DA-03 0.464 E 0.47 *1,560 E 1.14 E 2.37 E 3.49 E 3.5

DA-04 E 0.046 < 0.410 nc <4.7 <4 E 3.17 E 1.05

DA-05 0.141 E 0.378 *590 <7.5 <6.4 5.5 E 4.6

DA-06 0.404 1.02 160 <24.0 <16.0 14.4 12.3

U-02 0.126 E 0.277 300 E 1.7 <3.1 4.36 5.62

*

Value exceeds threshold.

Table 15. Radioactive constituents detected in samples collected for the Coastal Los Angeles Basin Groundwater 

Ambient Monitoring and Assessment (GAMA) study unit, California, June to November 2006.

[The five-digit U.S. Geological Survey (USGS) parameter code below the constituent name is used to uniquely identify a specific constituent 

or property. Thresholds, threshold values, and LRLs as of November 16, 2006. Samples from 10 slow wells were analyzed. All analytes are 

listed in table 3K. Threshold: Maximum contaminant level thresholds are listed as MCL-US when the MCL-US and MCL-CA are identical, 

and as MCL-CA when the MCL-CA is lower than the MCL-US or no MCL-US exists. MCL-CA, California Department of Public Health 

maximum contaminant level; MCL-US, U.S. Environmental Protection Agency maximum contaminant level. The MCL-US threshold for radium 

is the sum of radium-226 and radium-228. Two MCLs have been proposed for Radon-222. The proposed alternative MCL is in parentheses. 

Abbreviations: CLAB; Coastal Los Angeles Basin; CLAB Grid Wells; CLAB Understanding Wells; E, estimated or having a higher degree of 

uncertainty; nc, not collected; pCi/L, picocuries per liter; <, less than]
Table 16 75

GAMA 

Identification 

No.

Total coliforms 

colonies/ 100 mL 

(90900)

Threshold type MCL-US

Threshold 5 percent of 

 samples per month

DA-02 1

Table 16. Microbial indicators detected in samples collected for 

the Coastal Los Angeles Basin Groundwater Ambient Monitoring 

and Assessment (GAMA) study unit, California, June to November 

2006.

[The five-digit U.S.Geological Survey (USGS) parameter code below 

the constituent name is used to uniquely identify a specific constituent or 

property. All analytes are listed in table 3L. Threshold: Thresholds and 

threshold values as of November 16, 2006. Samples from 10 slow wells 

were analyzed, but only the sample with a detection is listed. Maximum 

contaminant level thresholds are listed as MCL-US when the MCL-US and 

MCL-CA are identical, and as MCL-CA when the MCL-CA is lower than the 

MCL-US or no MCL-US exists. MCL-US, U.S. Environmental Protection 

Agency maximum contaminant level. Abbreviations: mL, milliliter]
76 Ground-Water Quality Data in the Coastal Los Angeles Basin Study Unit, 2006: Results from the California GAMA Program

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Appendix 77

Appendix 

This appendix includes discussions of the methods used 

to collect and analyze ground-water samples and report the 

resulting water-quality data. These methods were selected 

to obtain representative samples of the ground water from 

each well and to minimize the potential for contamination 

of the samples or bias in the data. Procedures used to collect 

and assess quality-control data, and the results of the qualitycontrol assessments are also discussed. 

Sample Collection and Analysis

Field Methods

Ground-water samples were collected using standard and 

modified USGS National Field Manual protocols (Koterba 

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

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

2001; Ball and McClesky, 2003a,b; and Wright and others, 

2005. These sampling protocols ensure that a representative 

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

samples were collected and handled in a way that minimized 

the potential for airborne contamination of samples or cross 

contamination between samples collected at wells.

Prior to sampling, each well was pumped continuously 

to purge at least three casing-volumes of water from the well 

(Wilde and others, 1999). Wells were sampled using Teflon 

tubing with brass and stainless-steel fittings attached to a 

sampling point on the well discharge pipe as close as possible 

to the well. The sampling point always was located upstream 

of any well-head treatment system or water storage tank. 

Samples were collected before filtration or chemical treatment, 

such as chlorination. If well chlorination could not be avoided, 

when possible, the chlorinator was shut off at least 24 hours 

prior to purging and sampling the well to clear all chlorine 

out of the system. For the fast and intermediate schedules, 

samples were collected at the well head using a foot-long 

length of Teflon tubing. For the slow schedule, the samples 

were collected inside an enclosed chamber that was located 

inside a mobile laboratory and connected to the well head by 

an insulated 10- to 50-ft length of the Teflon tubing (Lane and 

others, 2003). All fittings and lengths of tubing were cleaned 

between samples (Wilde, 2004).

For the field measurements, ground water was pumped 

through a flow-through chamber fitted with a multi-probe 

meter that simultaneously measures the water-quality 

indicators (temperature, dissolved oxygen, pH, and specific 

conductance). Turbidity was measured in the field with a 

calibrated turbidity meter. Field measurements were made in 

accordance with protocols in the USGS National Field Manual 

(Radtke and others, 2005; Wilde and Radtke, 2005; Lewis, 

2006; Wilde, 2006; and Wilde and others, 2006). All sensors 

on the multi-probe meter were calibrated daily. Measured 

temperature, dissolved oxygen, pH, specific conductance, and 

turbidity values were recorded at 5-minute intervals for at 

least 30 minutes, and when these values remained stable for 

20 minutes, samples for laboratory analyses were collected. 

Field measurements and instrument calibrations were 

recorded by hand on field record sheets and electronically in 

PCFF-GAMA, a software package designed by the USGS 

with support from the GAMA program. Analytical service 

requests and chain-of-custody documentation also were 

managed by PCFF-GAMA. Information from PCFF-GAMA 

was uploaded directly into NWIS at the end of every week of 

sample collection. 

For analyses requiring filtered water, ground water was 

diverted through a 0.45-μm pore-size vented capsule filter, 

a disk filter, or a baked glass-fiber filter, depending on the 

protocol for the analysis (Wilde and others, 1999; 2004). Prior 

to sample collection, polyethylene sample bottles were prerinsed using native water three times before sample collection. 

Samples requiring acidification were acidified to a pH of 2 or 

less with the appropriate acids using ampoules of certified, 

traceable concentrated acids obtained from the USGS National 

Water Quality Laboratory (NWQL).

Temperature-sensitive samples were stored on ice 

prior to daily shipping to the various laboratories. The 

non-temperature-sensitive samples for tritium, noble gases, 

chromium speciation, and stable isotopes were shipped 

monthly, while samples for volatile organic compounds, 

pesticides, potential wastewater indicators, pharmaceutical 

compounds, compounds of special interest, dissolved organic 

carbon, nutrients, major and minor and trace elements, radium 

isotopes, gross alpha and beta radioactivity, and radon-222 

were shipped daily. 

Detailed sampling protocols for individual analyses and 

groups of analytes are described in Koterba and others (1995) 

and the USGS National Field Manual (Wilde and others, 1999; 

Wilde and others, 2004) and in the references for analytical 

methods listed in table A1; only brief descriptions are given 

here. Volatile organic compounds (VOCs) and gasoline 

oxygenates and degradates and 1,2,3-trichloropropane (1,2,3-

TCP) samples were collected in 40-mL baked amber glass 

sample vials that were purged with three vial volumes of 

sample water before bottom-filling to eliminate atmospheric 

contamination. Six normal (6 N) hydrochloric acid (HCl) 

was added as a preservative to the VOC samples, but not to 

the gasoline additives samples or to the 1,2,3-TCP samples. 

Perchlorate samples were collected in a 125-mL polyethylene 

bottles. Tritium samples were collected by bottom-filling two 

1-L polyethylene bottles with unfiltered ground water, after 

first overfilling the bottle with three volumes of water. Stable 

isotopes of hydrogen and oxygen in water were collected in 

60-mL clear glass bottles filled with unfiltered water, sealed 

with a conical cap, and secured with electrical tape to prevent 

leakage and evaporation.
78 Ground-Water Quality Data in the Coastal Los Angeles Basin Study Unit, 2006: Results from the California GAMA Program

Pesticides, polar pesticides and pesticide 

degradation products, potential wastewater-indicator 

compounds, pharmaceutical compounds, 1,4-dioxane, and 

N-nitrosodimethylamine (NDMA) samples were collected in 

1-L baked amber glass bottles. Pesticide, polar pesticide, and 

pharmaceutical samples were filtered with a glass fiber filter, 

whereas the 1,4-dioxane and NDMA samples were filtered 

at the Montgomery Watson-Harza (MWH) laboratory prior 

to analysis. Potential wastewater indicators were collected 

unfiltered in 1-L baked amber glass bottles.

Ground-water samples for major and minor ions, trace 

elements, field alkalinity, and total dissolved solids analyses 

required filling one 250-mL polyethylene bottle with raw 

ground water, and one 500-mL and one 250-mL polyethylene 

bottles with filtered ground water (Wilde and others, 2004). 

Filtration was done using a Whatman capsule filter. The 

250-mL filtered sample then was preserved with 7.5 N nitric 

acid. Mercury samples were collected by filtering ground 

water into 250-mL glass bottles and preserving with 6 N 

hydrochloric acid. Arsenic and iron speciation samples were 

filtered into 250-mL polyethylene bottles that were covered 

with tape to prevent light exposure, and preserved with 6 N 

hydrochloric acid. Nutrient samples were filtered into 125-mL 

brown polyethylene bottles. Radium isotopes and gross alpha 

and beta radiation samples were filtered into 1-L polyethylene 

bottles and acidified with nitric acid. Carbon isotope samples 

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

that were first overfilled with three bottle volumes of ground 

water. These samples had no headspace and were sealed with 

a conical cap to avoid atmospheric contamination. Samples 

for field alkalinity titrations were collected by filtering ground 

water into a 500-mL polyethylene bottles. 

DOC, chromium, radon-222, dissolved gases, and 

microbial constituents were collected from the hose bib at 

the well head, regardless of the sampling schedule (fast, 

intermediate, or slow). DOC was collected after rinsing the 

sampling equipment with VOC free blank water (Wilde and 

others, 2004). Using a 50-mL syringe and 0.45-μm disk filter, 

each ground-water sample was filtered into a 125-mL baked 

glass bottle and preserved with 4.5-N sulfuric acid. Chromium 

speciation samples were collected using a 10-mL syringe with 

an attached 0.45-μm disk filter. After the syringe was rinsed 

thoroughly and filled with ground water, 4 mLs were forced 

through the disk filter; the next 2 mLs of the ground water 

were filtered slowly into a small centrifuge vial for analysis 

of total chromium. Hexavalent chromium, Cr (VI), then was 

collected by attaching a small cation-exchange column to the 

syringe filter, and after conditioning the column with 2 mLs 

of sample water, 2 mLs were collected in a second centrifuge 

vial. Both vials were preserved with 10 μL of 7.5-N nitric acid 

(Ball and McClesky, 2003a,b).

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

Teflon valve assembly was attached to the sampling port at 

the well head (Wilde and others, 2004). The valve was closed 

partially to create back pressure, and a 10-mL sample was 

taken through a Teflon septum on the valve assembly using 

a glass syringe affixed with a stainless-steel needle. The 

sample then was injected into a 25-mL vial partially filled 

with scintillation mixture (mineral oil) and shaken. The vial 

then was placed in a cardboard tube to be shielded from light 

during shipping.

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

using reinforced nylon tubing connected to the hose bib at 

the wellhead. Ground water was flushed through the tubing 

to dislodge bubbles before flow was restricted with a back 

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

were tightened, trapping a sample of ground water for analyses 

of noble gases (Weiss, 1968). 

Samples for analysis of microbial constituents also were 

collected at the well head following protocols described in 

Myers (2004) and Bushon (2003). Prior to the collection of 

samples, the sampling port was sterilized using isopropyl 

alcohol, and ground water was run through the sampling port 

for at least 3 minutes to remove any traces of the sterilizing 

agent. Two sterilized 250-mL bottles then were filled with 

ground water for coliform analyses (total and Escherichia 

coliform determinations), and one sterilized 3-L carboy was 

filled for coliphage analyses (F-specific and somatic coliphage 

determinations).

Alkalinity, total coliforms, and Escherichia coliform

(E. coli) were measured in the mobile laboratory at the well 

site. Alkalinity and the concentrations of bicarbonate (HCO3

-

) 

and carbonate (CO3

2-) were measured on filtered samples by 

Gran’s titration method (Gran, 1952; Stumm and Morgan, 

1996). Titration data were entered directly into PCFF-GAMA 

and the concentrations of bicarbonate (HCO3

-

) and carbonate 

(CO3

2-) automatically were calculated from the titration data 

using the advanced speciation method. Total coliforms and 

Escherichia coliform (E. coli) plates were prepared using 

sterilized equipment and reagents (Myers, 2004). Plates were 

counted under an ultraviolet light, following a 22- to 24-hour 

incubation time.

Laboratory Methods

Nine laboratories performed chemical and microbial 

analyses for this study (table A1). Most of the analyses were 

performed at the NWQL or by laboratories contracted by the 

NWQL. The NWQL maintains a rigorous quality-assurance 

program (Maloney, 2005). Laboratory quality-control samples, 

including method blanks, continuing calibration verification 

standards, standard reference samples, reagent spikes, external 
Appendix 79

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://nwql.usgs.gov/lab_cert.shtml). In 

addition, the Branch of Quality Systems within the USGS 

Office of Water Quality maintains independent oversight of 

quality assurance at the NWQL and laboratories contracted 

by the NWQL. The Branch of Quality Systems also runs 

a National Field Quality Assurance program that includes 

annual testing of all USGS field personnel for proficiency in 

making field water-quality measurements (http://bqs.usgs.

gov/nfqa/). Results for analyses made at the NWQL or by 

laboratories contracted by the NWQL are uploaded directly 

into NWIS by the NWQL. Laboratory quality-control data 

also are stored in NWIS.

Data Reporting

Laboratory Reporting Conventions

The USGS NWQL uses the laboratory reporting level 

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

LRL is set to minimize the reporting of false negatives (not 

detecting a compound when it is actually present in a sample) 

to less than one percent (Childress and others, 1999). The LRL 

usually is set at two-times the long-term method detection 

level (LT-MDL). The LT-MDL is derived from the standard 

deviation of at least 24 MDL determinations made over an 

extended period of time. The method detection limit (MDL) 

is the minimum concentration of a substance that can be 

measured and reported with a 99-percent confidence level 

that the concentration is greater than zero (at MDL there 

is less than a one percent chance of a false positive) (U.S. 

Environmental Protection Agency, 2002a). The USGS NWQL 

monitors and updates LT-MDL and LRL values regularly, and 

the values listed in this report were in effect during the period 

that analyses were made for ground-water samples from the 

CLAB study.

Some concentrations in this study are reported using 

minimum reporting levels (MRLs) or method uncertainties 

(MU). The MRL is the smallest measurable concentration 

of a constituent that may be reliably reported using a given 

analytical method (Timme, 1995). The MU generally indicates 

the precision of a particular analytical measurement; it gives a 

range of values wherein the true value will be found. 

Detections between the LRL and the LT-MDL are 

reported as estimated concentrations (designated with 

an “E” before the values in the tables and text). For 

information-rich methods, detections below the LRL have 

high certainty of detection, but the precise concentration is 

uncertain. Information-rich methods are those that utilize gas 

chromatography or high-performance liquid chromatography 

(HPLC) with mass spectrometry detection (VOCs, gasoline 

oxygenates, pesticides, polar pesticides, and pesticides 

degradates, potential wastewater indicators, pharmaceutical 

compounds). For these methods, 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, for detections that did not meet 

all laboratory quality-control criteria, and for samples that 

were diluted prior to analysis (Childress and others, 1999).

Detections that could have resulted from unintended 

sample contamination are reported with a “V” before the 

values in the tables. The potential for sample contamination 

was assessed using results from field, source-solution, and 

laboratory blanks.

The reporting levels for radiochemical constituents 

(gross-alpha radioactivity, gross-beta radioactivity, 

radium-226, and radium-228) are based on a sample-specific 

critical value, a combined standard uncertainty (CSU), and a 

sample-specific minimum detectable concentration (SSMDC) 

(Bennett and others, 2006). A result above the critical value 

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

greater than zero (significantly different from the instrument’s 

background response to a blank sample), and a result above 

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

that the result is greater than the critical value. Using these 

reporting level elements, three unique cases were possible 

when screening the raw analytical data. If the raw analytical 

result was less than the critical value (case 1), the analyte was 

considered “not detected”, and the concentration was reported 

on table 15 as less than the SSMDC. If the analytical result 

was greater than the critical value, the ratio of the CSU to the 

analytical result is calculated as a percent (percent-relative 

CSU). For those samples with percent-relative CSU greater 

than 20 percent (case 2), concentrations were reported as 

“estimated” values (designated by an “E” preceding the value 

on table 15). For those samples that have a relative CSU less 

than 20 percent, concentrations were reported on table 15 with 

no qualifiers (case 3).
80 Ground-Water Quality Data in the Coastal Los Angeles Basin Study Unit, 2006: Results from the California GAMA Program

Stable isotopic compositions of oxygen, hydrogen, and 

carbon are reported as relative isotope ratios in units of per mil 

using the standard delta notation (Coplen and others, 2002):

i sample

reference

i

sample

R

E 1 1,000, R

where

i is the atomic mass of the heavier isotope of

the element,

E is the element (O for oxygen, C for carbon, 

or H for hydrogen),

R is the ratio of the abundance 

  δ = −    



18 13

2

16 12 1

reference

of the heavier

 isotope of the element ( O, C, or

or H) to the lighter isotope of the element

( O, C, or H), in the sample and,

R is the ratio of the abundance of the heavier

isotope of the element to the lighter isotope 

of the element in the reference material 

hydrogen.

(1)

The reference material for oxygen and hydrogen is 

Vienna Standard Mean Ocean Water (VSMOW), which is 

assigned δ18O and δ2H values of 0 per mil (note than δ2H also 

is written as δD because the common name of the heavier 

isotope of hydrogen, hydrogen-2, is deuterium). The reference 

material for carbon is Vienna Peedee Belemnite (VPDB), 

which is assigned a δ13C value of 0 per mil. 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

Twenty-seven constituents targeted in this study were 

measured by more than one analytical schedule or by more 

than one laboratory (table A2). The preferred methods for 

these constituents were selected based on the procedure 

recommended by the NWQL (http://wwwnwql.cr.usgs.gov/

USGS/Preferred_method_selection_procedure.html). Methods 

with full approval are preferred over those with provisional 

approval and approved methods are favored over research 

methods. The method with greater accuracy and precision and 

lower LRLs for the overlapping constituents often is preferred; 

however, a method also may be selected as the preferred 

method to provide consistency with historical data analyzed 

by the same method.

Twenty-two of the 27 constituents targeted for analyses 

appear on schedules at the NWQL. Analytical schedules, 

which have overlapping constituents, include the VOCs 

(Schedule 2020; table 3A), gasoline oxygenates and 

degradates (Schedule 4024; table 3B), pesticides and pesticide 

degradates (Schedule 2003; table 3C), polar pesticides and 

pesticide degradates (Schedule 2060; table 3D), potential 

wastewater-indicators (Schedule 4433; table 3E [table A2], 

pharmaceutical compounds [SC2080; table 3F]). For 

constituents on Schedules 2020 and 4024, the preferred 

method was Schedule 2020 to provide consistency (all 

samples collected for the GAMA Priority Basin project are 

analyzed using Schedule 2020). For constituents on Schedules 

2020 and 4433, the preferred method was Schedule 2020 

because it has greater precision and accuracy, and lower 

LRLs for VOCs. For constituents on Schedules 2003 and 

4433, the preferred method was Schedule 2003 because 

it has greater accuracy and precision and lower LRLs for 

pesticide constituents, and for consistency (all samples 

collected for the GAMA Priority Basin project are analyzed 

using Schedule 2003 or an equivalent). For constituents on 

Schedules 2060 and 4433, the preferred method was Schedule 

2060 because it has greater precision and accuracy, and lower 

LRLs for polar pesticides. For constituents on SC2080 and 

Schedule 4433, the preferred method at the time of the CLAB 

study was SC2080 because it had a lower LRL for the two 

overlapping constituents. However, as of 2007, the NWQL 

considered Schedule 4433 the preferred method because 

SC2080 had provisional approval, whereas, Schedule 4433 

had full approval. For constituents that appear on two NWQL 

analytical schedules, only the results from the preferred 

method are reported.

The water-quality indicators—pH, specific conductance, 

and alkalinity—were measured in the field and at the NWQL. 

The field measurements are the preferred method for all three 

constituents; however, both are reported because laboratory 

pH and alkalinity measurements were made on a greater 

number of samples. 

Scenario

Critical 

value 

(pCi/L)

SSMDC 

(pCi/L)

Combined 

standard 

uncertainty 

(pCi/L)

Relative CSU 

(percent)

Raw result 

(pCi/L)

Reported 

result 

(pCi/L)

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

Case 2 – Relative combined standard 

uncertainty greater than 20 percent

0.5 1.4 ±0.6 32 2.0 E2.0

Case 3 – Relative combined standard 

uncertainty less than 20 percent

0.4 1.1 ±0.5 14 3.2 3.2
Appendix 81

For arsenic, chromium, and iron concentrations, the 

approved method, Schedule 1948, used by the NWQL is 

preferred over the research methods used by the USGS 

Trace Metal Laboratory, although both are reported. The 

concentrations measured by the Trace Metal Laboratory are 

used only to calculated ratios of redox species for each

element, As(V)

As(III) for arsenic, Cr(VI)Cr(III) for chromium, and

Fe(III)

Fe(II) for iron. For example:

Fe(III) Fe(T) - Fe(II) , Fe(II) Fe(II)

where

Fe(T) is the total iron concentration (measured),

Fe(II) is the concentration of ferrous iron (measured), 

and

Fe(III)is the concentration of ferric iron (calculated

=

).

(2)

Tritium results from both the USGS Stable Isotope 

and Tritium Laboratory and LLNL will be reported (as they 

become available) even though the LLNL method is preferred.

Quality-Assurance Methods

The quality-assurance methods used for this study follow 

protocols described in the USGS National Field Manual 

(U.S. Geological Survey, variously dated), protocols used 

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

and the NWQL quality-assurance plan (Maloney, 2005). 

Quality-control (QC) samples were collected concurrently 

with approximately 22 percent of samples in the CLAB study. 

This was done to assess the bias and variability of waterquality data potentially introduced during sample collection, 

processing, storage, transportation, and laboratory analysis, as 

well as intrinsic variability within the ground water itself. Four 

types of QC samples were collected and analyzed: blanks, 

field replicates, laboratory matrix spikes, and laboratory 

surrogates.

Blanks

Blank samples (blanks) were collected using water (VOpurged organic-free blank water and inorganic-free blank 

water) certified by the NWQL to contain less than the LRL 

or MRL of the analytes investigated in the study. Two types 

of blanks were collected: source-solution and field blanks. 

Source-solution blanks were collected to verify that the blank 

water used for the field blanks was free of analytes of interest. 

Field blanks and source-solution blanks for organic constituent 

analyses were collected at approximately nine percent of 

the wells sampled. Field blanks for inorganic analysis were 

collected at four percent of the wells sampled. These blank 

analysis were used to determine if equipment or procedures 

used in the field and (or) laboratory introduced contamination. 

Field blanks were analyzed for VOCs; gasoline oxygenates; 

pesticides, polar pesticides, and pesticide degradates; 

pharmaceuticals; potential wastewater indicator; perchlorate; 

NDMA; 1,2,3-TCP; 1,4-dioxane; nutrients; dissolved organic 

carbon; major and minor ions; trace elements; iron, arsenic, 

and chromium speciation; and radioactive constituents. 

Source-solution blanks were collected at the sampling 

site by pouring blank water directly into sample containers 

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

manner as the ground-water samples. For field blanks, blank 

water either was pumped or poured through the sampling 

equipment (fittings and tubing) used to collect ground water, 

then processed and transported using the same protocols for 

the ground-water samples. 

If a constituent was detected in a field blank, the 

associated source-solution blank results were examined 

for similar constituent detections. If the field blank and the 

source-solution blank contained the same constituent(s), then 

the source-solution water was interpreted as the origin of the 

contamination in the blanks, and any field-blank detections 

originating from the same blank water were disregarded 

as having any affect on the environmental samples. If a 

field blank detection could not be attributed to the source 

solution, then the ground-water samples collected prior to, 

and following the blank were evaluated. If the ground-water 

samples prior to, or following the contaminated field blank 

had no detections, then carry-over contamination was ruled 

out. If a compound was detected in multiple field blanks and 

the detections could not be attributed to the source-solution 

water, then any ground-water sample that had a detection of 

the compound in question was evaluated for possible bias due 

to contamination.

This report uses a preliminary strategy for qualifying 

ground-water data due to random contamination. If the 

concentration of an analyte detected in a field blank was 

greater than the concentration measured in a ground-water 

sample collected prior to or following the blank sample, then 

the ground-water value was qualified. In addition, another 

screening level was defined as the highest concentration of the 

constituent detected in a field blank plus one-half of the LRL 

for that constituent. Detections of the constituent in groundwater samples at concentrations less than this screening 

level were qualified. Qualified values are indicated by a ‘V’ 

preceding the value in the data tables, noted in table A3, and 

these values also are excluded from the assessment of groundwater quality.

However, results from the small number of field blanks 

collected during a single study unit may not be representative 

of the results for a large number of field blanks collected over 

many study units. A subsequent report will present a more 

robust strategy for qualifying that is based on a statistical 

assessment of results for over 100 field blanks collected 

during 20 study units. The preliminary strategy used in this 

report may over- or underestimate the qualifying levels 

derived from the statistical assessment. 
82 Ground-Water Quality Data in the Coastal Los Angeles Basin Study Unit, 2006: Results from the California GAMA Program

Field blanks were not collected for noble gases, 

carbon-14, stable isotopes, and tritium, as described below. 

Noble gases, carbon-14 (in atmospheric carbon dioxide), and 

tritium are present in the atmosphere and would dissolve into 

any solution used in collecting a blank, making it impractical 

to collect a field blank for these analytes. An indirect indicator 

of the quality of sampling data is that for tritium, activities 

are expected to be less than three pCi/L in water recharged 

prior to the 1950s. The presence of tritium below the MRL of 

one pCi/L in the sample collected implies that the sampling 

methods did not bias the sampling result for tritium. Stableisotopic ratios of oxygen, hydrogen, and carbon are an 

intrinsic property of any of these elements and the concept of a 

blank does not apply to these ratios, which always have values 

as long as the element is present and cannot be measured if the 

element is absent.

Replicates

Sequential replicate samples were collected to assess 

variability that may result from the processing and analyses 

of inorganic and organic constituents. Relative standard 

deviation (RSD) of the measured values was used to express 

the variability between replicate pairs for each compound 

(table A4). The RSD is defined as the standard deviation 

divided by the mean concentration for each replicate pair of 

samples, multiplied by 100 percent. If one value in a sample 

pair was reported as a non-detection and the other value was 

reported as an estimate below the LRL or MRL, the RSD 

was set to zero because the values are analytically identical. 

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

and the other value was greater than the LRL or MRL, then 

the non-detection value was set equal to one-quarter of the 

LRL and the RSD was calculated (Hamlin and others, 2002). 

Values of RSD less than 20 percent are considered acceptable 

in this study. An RSD value of 20 percent corresponds to a 

relative percent difference (RPD) value of 29 percent. High 

RSD values for a compound at low concentrations may be the 

result of analytical uncertainty, particularly for concentrations 

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

replicate samples were collected at up to seven percent of the 

wells sampled, although not all analyte classes were tested at 

every well.

Matrix Spikes

Addition of a known concentration of a constituent 

(‘spike’) to a replicate environmental sample enables the 

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

ground water—on the analytical technique used to measure 

the constituent. The known compounds added in matrix spikes 

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

enables an analysis of matrix interferences on a compound-bycompound basis. Matrix spikes were added at the laboratory 

performing the analysis. Compounds with low recoveries 

are of particular concern if environmental concentrations are 

close to the MCLs; a low recovery could falsely indicate a 

concentration below the MCL. Conversely, compounds with 

high recoveries are of potential concern if the environmental 

concentrations exceed MCLs: a high recovery could falsely 

indicate a concentration above the MCL. 

Acceptable ranges for matrix-spike recoveries are based 

on the acceptable ranges established for laboratory “set” spike 

recoveries. Laboratory set spikes are aliquots of laboratory 

blank water to which the same spike solution used for the 

matrix spikes has been added. One set spike is analyzed with 

each set of samples. Acceptable ranges for set spike recoveries 

are 70 to 130 percent for NWQL schedules 2020, 4024, and 

4433 (Connor and others, 1998; Zaugg and others, 2002; and 

Rose and Sandstrom, 2003), 60 to 120 percent for NWQL 

schedules 2003 and 2060 (pesticides; Furlong and others, 

2001; Sandstrom and others, 2001), and 60 to 130 percent 

for schedule 2080 (Kolpin and others, 2002). Based on these 

ranges, we defined 70 to 130 percent as the acceptable range 

for matrix-spike recoveries for organic compounds in this 

study. 

Matrix spikes were done for VOCs, gasoline oxygenates 

and their degradates, pesticide, polar pesticide, and pesticide 

degradate compounds, pharmaceutical compounds, potential 

wastewater indicators, NDMA, 1,4-dioxane, and 1,2,3-TCP 

because the analytical methods for these constituents are 

chromatographic methods which may be susceptible to matrix 

interferences. Replicate samples for matrix spike additions 

were collected at four percent of the wells sampled, although 

not all analyte classes were tested at every well (table A5A-E).

Surrogates

Surrogate compounds are added to environmental 

samples in the laboratory prior to analysis to monitor the 

method performance for each sample. Surrogate compounds 

were added to all of the ground-water and quality-control 

samples that were analyzed for VOCs, gasoline oxygenates 

and their degradates, pesticides and their degradates, potential 

wastewater indicators, 1,4-dioxane, NDMA, and 1,2,3-TCP 

(table A5E). Most of the surrogate compounds are deuterated 

analogs of compounds being analyzed. For example, the 

surrogate toluene-d8 used for the VOC analytical method 

has the same chemical structure as toluene, except that the 

eight hydrogen-1 atoms on the molecule have been replaced 

by deuterium (hydrogen-2). Toluene-d8 and toluene behave 

very similarly in the analytical procedure, but the small 

mass difference between the two results in slightly different 

chromatographic retention times, thus the use of a toluene-d8 

surrogate does not interfere with the analysis of toluene (Grob, 

1995). Only 0.015 percent of hydrogen atoms are deuterium 

(Firestone and others, 1996), thus, deuterated compounds 

like toluene-d8 do not occur naturally and are not found in 
Appendix 83

environmental samples. Surrogates are used to identify general 

problems that may arise during sample analysis that could 

affect the analysis results for all compounds in that sample. 

Potential problems include matrix interferences (such as high 

levels of dissolved organic carbon) that produce a positive 

bias, or incomplete laboratory recovery (possibly due to 

improper maintenance and calibration of analytical equipment) 

that produces a negative bias. A 70- to 130-percent recovery of 

surrogates generally is considered acceptable, values outside 

this range indicate possible problems with the processing 

and analysis of samples (table A6) (Connor and others, 1998; 

Sandstrom and others, 2001).

Quality-Control Sample Results

Detections in Field and Source-Solution Blanks

Table A3 presents a summary of detections in field 

blanks. In the CLAB study unit, field and source-solution 

blanks were collected at approximately nine percent of the 

sites sampled. 

VOCs observed in field blanks, with their maximum 

detected concentration in parentheses, include acetone (E 

3 μg/L), bromodichloromethane (0.11 μg/L), carbon disulfide 

(E 0.03 μg/L), chloroform (trichloromethane) (0.19 μg/L), 

dichloromethane (E 0.05 μg/L), and toluene (0.06 μg/L). All 

of the environmental samples collected prior to, during, and 

following these field blanks were free from these constituents, 

as were the source-solution blanks collected with these 

samples; hence no ground-water sample detections were 

qualified as a result of these blank detections. There was one 

situation where toluene was detected in the source-solution 

blank (E 0.01 μg/L) and in the associated environmental 

sample (E 0.01 μg/L); however, it was not detected in the 

associated field blank, or in any other environmental samples 

collected during this field sampling phase and, therefore, not 

of potential QC concern.

Field blanks were collected at three of the 17 sites 

sampled for analysis of nutrients. Ammonia was detected in 

two of the three field blanks at 0.007 mg/L and 0.008 mg/L, 

respectively. The later detection was used to establish 

a qualifying threshold at 0.018 mg/L (maximum field 

blank detection plus one-half the LRL). As a result, seven 

ground-water samples were coded with a “V” in table 10. 

Orthophosphate was detected in one of the three field blanks 

at 0.005 mg/L. This blank detection resulted in a qualifying 

concentration set at 0.008 mg/L (field blank detection plus onehalf the LRL). None of the 19 ground-water samples collected 

had orthophosphate levels below the qualifying threshold; 

therefore, the field blank detection was not of QC concern. 

Field blanks were collected at three (and source-solution 

blanks at one) of the 17 sites sampled for analysis of trace 

elements. Chromium was detected in one field blank and 

one source-solution blank at concentrations of 0.07 and 

E 0.03 mg/L, respectively. The concentration of chromium in 

the field blank (0.07 mg/L) added to half the LRL (0.02 mg/L) 

were used to establish a qualifying threshold at 0.09 mg. The 

source-solution detection was accompanied with a field blank 

sample free of chromium, so the source-solution detection 

was not of QC concern. Three ground-water samples had 

concentrations of chromium below the established qualifying 

threshold; therefore, they were qualified with a “V” in 

table 12. Calcium was detected in one source-solution blank 

and one of three field blanks samples at concentrations of 

0.04 and 0.05 mg/L, respectively. The field blank associated 

with the source-solution blank was free of calcium, therefore, 

the source solution blank detection was not of potential QC 

concern. The concentration of calcium in the field blank was 

less than one percent of the lowest concentration in any of 

the environmental detections of calcium in CLAB (9.1 mg/L), 

therefore, none of the environmental samples were qualified. 

Vanadium was detected in one of three field blanks at 

0.05 mg/L, the corresponding source solution blank was free 

of vanadium, and all environmental samples were above the 

qualifying threshold (maximum field blank detection plus onehalf the LRL), therefore no environmental data were qualified, 

as a result. Copper, lead, and zinc each were detected in one 

of three field blanks at concentrations of 1.71, 0.92, and 

6.6 mg/L, respectively. The corresponding environmental 

samples collected successively were free of these trace 

elements, therefore, the blank detections were not of potential 

QC concern, and no environmental samples were qualified as 

a result. 

Barium and strontium each were detected once in one 

of three field blanks at 0.5 and E 0.3 mg/L, correspondingly. 

These concentrations were much lower than the associated 

environmental samples of 99 and 1,950 mg/L. All 

environmental samples were above the qualifying threshold 

(maximum field blank detection plus one-half the LRL), 

therefore, no environmental data were qualified as a result. 

Silicon was detected in one of the three field blanks; this 

detection was paired with a source solution blank detection, 

both detections were 0.03 mg/L. These detections were 

about one-thousandth the level of any of the environmental 

detections; therefore, these blank detections did not result 

in the qualifying of any environmental samples. Nickel was 

detected in two of the three field blanks at concentrations 

of E 0.04 mg/L and 0.22 mg/L, respectively. The later blank 

detection set a qualifying threshold at 0.25 mg/L (maximum 

field blank detection plus one-half the LRL). As a result, five 

environmental ground-water samples were coded with a “V” 

in table 12. Aluminum was detected in the final of the three 

field blanks at a concentration of 1.8 mg/L. This detection 

was determined to be exclusive to the final week of CLAB 

sampling (11/13/06 to 11/16/06, [table 1]) since the two 

previous field blanks collected had no detections of aluminum. 

The only detection of aluminum in ground-water samples for 

this sampling week was the one paired with the field blank; 

therefore, it was coded with a “V” in table 12. 
84 Ground-Water Quality Data in the Coastal Los Angeles Basin Study Unit, 2006: Results from the California GAMA Program

Field blanks were collected at six of the 69 sites sampled 

for chromium, arsenic, and iron speciation analysis at the 

USGS Trace Metal Laboratory (TML). One field blank out of 

the six collected contained 0.7 mg/L of arsenic (total), 4 mg/L 

of iron (total), and 2 mg/L of iron (II). These blank detections 

were hypothesized to be from sporadic contamination at the 

TML, which could have affected other samples, but which is 

not systematic enough to support any pattern of “V-coding”. 

However, it is important to note that measurements of iron 

(total) and arsenic (total) from the NWQL were preferred 

over measurements at the TML (table A2), so not qualifying 

the ground-water samples with potential contamination 

concerns did not affect the interpretations of environmental 

concentrations. There were no detections of arsenic (III), 

chromium (III) chromium (VI), or chromium (total) in the six 

field blanks analyzed at the TML. 

Radium 226 and Radium 228 were the only radioactive 

constituents collected for field blank analysis; they were 

detected at (0.0108 pCi/L and 0.02 pCi/L [respectively]). 

Analysis of the corresponding environmental samples showed 

that these concentrations were of limited concern due to the 

relatively low blank concentrations and no environmental 

values were qualified as a result of the blank detections.

No compounds were detected in field blanks for the 

following analyte groups: pesticides and pesticide degradates 

(six field blanks), polar pesticides and pesticide degradates 

(one field blank), potential wastewater indicators (four field 

blanks), perchlorate (three field blanks); NDMA, 1,4-dioxane, 

and 1,2,3-TCP (one field blank [respectively]); microbial 

indicators, F-specific or somatic coliphage (one field blank), 

and no detections in ground-water samples.

Variability in Replicate Samples

Table A4 summarizes the results of replicate sample pairs 

for analytes in ground-water samples collected in the CLAB 

study. Over 1,300 (1,388) replicate pairs (by constituent) 

were considered in the replicate QC analysis. Almost 1,300 

(1,297) replicate pairs had non-detections and are not reported 

in table A4. Additionally, concentrations or activities in the 

environmental and replicate samples are reported only for all 

replicate sample pairs with analyte detections and RSD values 

greater than 20 percent (table A4). Most replicate analyses 

had RSD values less than five percent and only 28 had 

RSD values greater than the acceptable limit of 20 percent. 

Of the replicate pairs, for which both concentrations 

were detections, constituents with one or more replicate 

analyses with RSD values greater than 20 percent include: 

1,2,4-trimethylbenzene, 2-chloro-6-ethylamino-4-amino-striazine, diuron, norflurazon, 3,4-dichlorophenyl isocyanate, 

diethyl phthalate, phenol, zinc, iron, chromium, aluminum, 

and arsenic (total) analyzed by the USGS Trace Metal 

Laboratory. Most replicate pairs with RSD values greater than 

20 percent had concentrations within a factor of five of the 

LRLs for the respective analytes. At these low concentrations, 

small deviations in measured values result in large RSDs. 

Thirteen pairs of replicate analyses included one detection and 

one non-detection (3-methyl-1[H]-indole [skatole], 5-methyl1H-benzotriazole, bis[2-ethylhexyl] phthalate, bisphenol 

A, caffeine, methyl salicylate, p-cresol, phenol, aluminum, 

chromium, iron, nickel, arsenic [total] analyzed by the USGS 

Trace Metal Laboratory). All of the detected concentrations 

were less than twice the LRLs, therefore, none of the data 

were censored as a result of variability in replicate analyses.

Matrix-Spike Recoveries

Tables A5A-E presents a summary of matrix-spike 

recoveries for the CLAB study. Addition of a spike or known 

concentration of a constituent to an environmental sample 

enables the laboratory to determine the effect of the matrix, 

in this case ground water, on the analytical technique used 

to measure the constituent. Three environmental samples 

on schedule 2020 and one on schedule 4024 were spiked 

with VOCs to calculate matrix-spike recoveries (table A5A). 

In total, 87 of the 88 VOC spike compounds had median 

recoveries within the acceptable range of 70 and 130 percent. 

Only one matrix-spike sample, (carbon disulfide) had a 

median recovery below 70 percent (69 percent), thus, no VOC 

detections in the ground-water were qualified. 

Three ground-water samples were spiked with pesticide 

and pesticide degradate compounds to calculate matrix-spike 

recoveries. Forty-three of the 63 spike compounds had median 

recoveries within the acceptable range of 70 and 130 percent 

(table A5B). Twelve of the 14 compounds detected in 

ground-water samples had spike median recoveries within 

the acceptable range. Five spike compounds had at least one 

recovery greater than 130 percent. Of the 63 spike compounds, 

42 had at least one recovery below 70 percent. [NOTE – low 

recoveries may indicate that the compound might not have 

been detected in some samples if it was present at very low 

concentrations].

One ground-water sample was spiked with polar pesticide 

and pesticide degradate compounds to calculate matrixspike recoveries. Forty-two of the 59 spike compounds had 

recoveries within the acceptable range of 70 and 130 percent 

(table A5C). Four of the five compounds detected in groundwater samples had spike recoveries within the acceptable 

range. Six spike compounds in the ground-water samples had 

a recovery greater than 130 percent, while 12 compounds had 

a recovery below 70 percent. [NOTE – low recoveries may 

indicate that the compound might not have been detected in 

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

Two ground-water samples were spiked with potential 

wastewater indicators with two exceptions; on one occasion 

14 compounds were omitted from the spike mixture and 

only spiked once, while one compound, bis (2-ethylhexyl) 

phthalate, was not included in any of the spike mixtures. 
Appendix 85

Twenty-three of the 69 compounds had median spike 

recoveries less than 70 percent and none had recoveries 

greater than 130 percent (table A5D). Twenty-two of the 34 

compounds detected in ground-water samples had median 

recoveries within the acceptable range of 70 and 130 percent. 

[NOTE – low recoveries may indicate that the compound 

might not have been detected in some samples if it was present 

at very low concentrations].

Results for pharmaceutical compounds are not presented 

in the CLAB report; they will be included in a subsequent 

publication.

One ground-water sample was spiked with NDMA, 1,2,3-

TCP, and 1,4-dioxane. All spike recoveries were within the 

acceptable range of 70 to 130 percent (table A5E).

Surrogate Compound Recoveries

Surrogate compounds were added to environmental 

samples in the laboratory and analyzed to evaluate the 

recovery of similar constituents. Table A6 lists in columns 

the surrogate, analytical schedule on which it was applied, 

the number of analyses for blank and non-blank samples, 

the number of surrogate recoveries below 70 percent, and 

the number of surrogate recoveries above 130 percent for 

the blank and non-blank samples. Blank and non-blank 

samples were considered separately to assess whether the 

matrices present in non-blank samples affect surrogate 

recoveries. No systematic differences between surrogate 

recoveries in blank and non-blank samples were observed. 

Eighty-nine of surrogate recoveries in analyses of VOC 

and gasoline oxygenate and degradate analyses were in the 

acceptable range of 70 to 130 percent, as were 92 percent 

of the surrogate recoveries for pesticide, polar pesticide and 

pesticide degradates. Sixty percent of the surrogate recoveries 

for potential wastewater indicators, and 72 percent of NDMA, 

1,2,3-TCP, and 1,4-dioxane surrogate recoveries were in the 

acceptable the range of 70 to 130 percent. 

Eleven environmental samples with detections of VOCs 

had recoveries of the surrogate 1,2-dichloroethane-d4 greater 

than 130 percent (table A6). A number of VOCs detected in 

these seven samples elute near 1,2-dichloroethane-d4 in the 

chromatographic sequence. A high recovery for a surrogate 

suggests that the measured concentrations of analytes 

eluting near the surrogate may be biased toward higher 

concentrations, and that their true concentrations could be 

lower than reported. 
86 Ground-Water Quality Data in the Coastal Los Angeles Basin Study Unit, 2006: Results from the California GAMA Program

Analyte Analytical 

method

Laboratory and analytical 

schedule/lab code Citation(s)

Water-quality indicators

Field parameters USGS field measurement U.S. Geological Survey, variously dated

Organic constituents

VOCs Purge and trap capillary gas 

chromatography/mass spectrometry

NWQL, Schedule 2020 Connor and others, 1998

Gasoline oxygenates and 

degradates

Heated purge and trap/gas 

chromatography/mass spectrometry 

NWQL, Schedule 4024 Rose and Sandstrom, 2003

Pesticides and degradates Solid-phase extraction and gas 

chromatography/mass spectrometry

NWQL, Schedule 2003 Zaugg and others, 1995; Lindley and 

others, 1996; Madsen and others, 2003; 

Sandstrom and others, 2001

Polar pesticides and 

degradates

Solid-phase extraction and highperformance liquid chromatography/

mass spectrometry

NWQL, Schedule 2060 Furlong and others, 2001

Pharmaceuticals Solid-phase extraction and HPLC/mass 

spectrometry

NWQL, Schedule 2080 Kolpin and others, 2002; Furlong and 

others, 2008

Wastewater-indicators Solid-phase extraction and gas 

chromatography/mass spectrometry

NWQL, Schedule 4433 Zaugg and others, 2002

Constituents of special interest

Perchlorate Ion chromatography and mass 

spectrometry 

Montgomery Watson-Harza 

Laboratory (CA-MHWL)

Hautman and others, 1999

N-Nitrosodimethylamine 

(NDMA)

Gas chromatography and mass 

spectrometry 

Montgomery Watson-Harza 

Laboratory (CA-MHWL)

U.S. Environmental Protection Agency, 

1996; U.S. Environmental Protection 

Agency, 1999

1,4-Dioxane Chromatography / mass spectrometry Montgomery Watson-Harza 

Laboratory (CA-MHWL)

U.S. Environmental Protection Agency, 

1996

1,2,3-Trichloropropane Gas chromatography/electron capture 

detector

Montgomery Watson-Harza 

Laboratory (CA-MHWL)

U.S. Environmental Protection Agency, 

1995

Inorganic constituents

Nutrients Alkaline persulfate digestion, Kjedahl 

digestion

NWQL, Schedule 2755 Fishman, 1993; Patton and Kryskalla, 2003

Dissolved organic carbon UV-promoted persulfate oxidation and 

infrared spectrometry

NWQL, Lab Code 2612 Brenton and Arnett, 1993

Major and minor ions, 

trace elements and 

nutrients

Atomic absorption spectrometry, 

colorimetry, ion-exchange 

chromatography, inductively-coupled 

plasma atomic emission spectrometry 

and mass spectrometry

NWQL, Schedule 1948 Fishman and Friedman, 1989; Fishman, 

1993; Faires, 1993; McLain, 1993; 

Garbarino, 1999; Garbarino and 

Damrau, 2001; American Public Health 

Association, 1998; Garbarino and 

others, 2006

Chromium, arsenic and 

iron speciation

Various techniques of ultraviolet visible 

(UV-VIS) spectrophotometry and 

atomic absorbance spectroscopy

USGS Trace Metal 

Laboratory, Boulder, 

Colorado (USGSTMCO)

Stookey, 1970; To and others, 1998; Ball 

and McCleskey, 2003a and 2003b; 

McCleskey and others, 2003

Table A1. Analytical methods used for the determination of organic, inorganic, and microbial constituents by the U.S. Geological 

Survey (USGS) National Water Quality Laboratory (NWQL) and additional contract laboratories.

[Laboratory entity codes in the U.S. Geological Survey (USGS) National Water Information System (NWIS) for laboratories other than the USGS National 

Water Quality Laboratory (NWQL) are given in parentheses after the laboratory names. Abbreviations: MI agar, supplemented nutrient agar in which coliforms 

(total and Escherichia) produce distinctly different fluorescence under ultraviolet lighting; UV, ultraviolet; VOCs, volatile organic compounds]
Table A1 87

Analyte Analytical 

method

Laboratory and analytical 

schedule/lab code Citation(s)

Stable isotopes

Stable isotopes of water Gaseous hydrogen and carbon dioxidewater 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

Carbon isotopes Accelerator mass spectrometry University of Waterloo, 

Environmental Isotope Lab 

(CAN-UWIL); University 

of Arizona Accelerator 

Mass Spectrometry Lab 

(AZ-UAMSL), NWQL 

Schedule 2015

Donahue and others, 1990; Jull and others, 

2004

Radioactivity and gases

Tritium Electrolytic enrichment-liquid 

scintillation

USGS Stable Isotope and 

Tritium Laboratory, 

Menlo Park, California 

(USGSH3CA)

Thatcher and others, 1977

Tritium and noble gases Helium-3 in-growth and mass 

spectrometry

Lawrence Livermore National 

Laboratory (CA-LLNL)

Moran and others, 2002; Eaton and others, 

2004

Dissolved gases: nitrogen, 

argon, and methane

Membrane inlet mass spectrometry Lawrence Livermore National 

Laboratory (CA-LLNL)

Singleton and Hudson, 2005; Singleton 

and others, 2007

Radon-222 Liquid scintillation counting NWQL, Schedule 1369 American Society for Testing and 

Materials, 1998

Radium isotopes Alpha activity counting Eberline Analytical Services 

(CA-EBERL), NWQL 

Schedule 1262 

Kreiger and Whittaker, 1980 (USEPA 

methods 903 and 904)

Gross alpha and beta 

radioactivity

Alpha and beta activity counting Eberline Analytical Services, 

NWQL Schedule 1792

Kreiger and Whittaker, 1980 (USEPA 

method 900.0)

Microbial constituents

F-specific and somatic 

coliphage

Single-agar layer (SAL) and two-step 

enrichment methods

USGS Ohio Water 

Microbiology Laboratory 

(USGSOHML)

U.S. Environmental Protection Agency, 

2001

Total and Escherichia 

coliform

Membrane filter technique with “MI 

agar”

USGS field measurement U.S. Environmental Protection Agency, 

2002; U.S. Geological Survey, variously 

dated

Table A1. Analytical methods used for the determination of organic, inorganic, and microbial constituents by the U.S. Geological 

Survey (USGS) National Water Quality Laboratory (NWQL) and additional contract laboratories.—Continued

[Laboratory entity codes in the U.S. Geological Survey (USGS) National Water Information System (NWIS) for laboratories other than the USGS National 

Water Quality Laboratory (NWQL) are given in parentheses after the laboratory names. Abbreviations: MI agar, supplemented nutrient agar in which coliforms 

(total and Escherichia) produce distinctly different fluorescence under ultraviolet lighting; UV, ultraviolet; VOCs, volatile organic compounds]
88 Ground-Water Quality Data in the Coastal Los Angeles Basin Study Unit, 2006: Results from the California GAMA Program

Constituent Primary constituent 

classification

Analytical 

schedules

Preferred 

analytical schedule

Results from preferred method reported

Acetone VOC 2020, 4024 2020

Atrazine Pesticide 2003, 2060, 4433 2003

Bromacil Pesticide 2060, 4433 2060

Bromoform VOC 2020, 4433 2020

Caffeine Potential waste-water indicator 2060, 2080, 4433 2080

Carbaryl Pesticide 2003, 2060, 4433 2003

Deethylatrazine (2-Chloro-4-

isopropylamino-6-amino-s-triazine)

Pesticide degradate 2003, 2060 2003

Chlorpyrifos Pesticide 2003, 4433 2003

Cotitine Potential waste-water indicator 4433, 2080 2080

Diazinon Pesticide 2003, 4433 2003

1,4-Dichlorobenzene VOC, pesticide 2020, 4433 2020

Dichlorvos Pesticide 2003, 4433 2003

Diisopropyl ether VOC 2020, 4024 2020

Ethyl tert-Butyl ether (ETBE) VOC 2020, 4024 2020

Isopropylbenzene VOC 2020, 4433 2020

Metalaxyl Pesticide 2003, 2060, 4433 2003

Methyl tert-butyl ether (MTBE) VOC 2020, 4024 2020

Methyl tert-pentyl ether VOC 2020, 4024 2020

Metolachlor Pesticide 2003, 4433 2003

Naphthalene VOC 2020, 4433 2020

Tetrachloroethene (PCE) VOC 2020, 4433 2020

Tebuthiuron Pesticide 2003, 2060 2003

Results from both methods reported

Arsenic, total Trace element 1948, TML 1948

Chromium, total Trace element 1948, TML 1948

Iron, total Trace element 1948, TML 1948

1,2,3-Trichloropropane (TCP) VOC 2020, MWH MWH

Tritium Radioactive LLNL, SITL LLNL

Table A2. Preferred analytical schedules for constituents appearing on multiple schedules for samples collected for the Coastal Los 

Angeles Basin Groundwater Ambient Monitoring and Assessment (GAMA) study unit, California, June to November 2006.

[Preferred analytical schedules are methods of analysis preferred for the compound in question on the basis of the greatest accuracy, precision, or historical 

consistency of the results. Abbreviations: LLNL, Lawrence Livermore National Laboratory; MWH, Montgomery Watson-Harza Laboratory; SITL, U.S. 

Geological Survey Stable Isotope and Tritium Laboratory; TML, U.S. Geological Survey Trace Metal Laboratory; VOC, volatile organic compound]
Table A3 89

Constituent

Number of 

field blank 

detections/analyses

Maximum 

concentration 

detected in

 field blanks 

Minimum 

concentration 

detected in 

environmental 

samples

Number of 

environmental 

samples qualified 

with a V-code

Organic constituents (μg/L)

Acetone 1/7 E 3.0 – 0

Bromodichloromethane 1/7 0.11 E 0.03 0

Carbon disulfide 1/7 E 0.03 E 0.02 0

Chloroform (trichloromethane) 1/7 0.19 E 0.01 0

Dichloromethane 1/7 E 0.05 E 0.02 0

Toluene 1,24/7 E 0.06 E 0.01 0

Inorganic constituents (μg/L)

Orthophosphate (as phosphorus) 1/3 E 0.005 0.015 0

Ammonia (as nitrogen) 2/3 0.005 E 0.005 7

Calcium 2

2/3 0.05 9.1 0

Aluminum 1/3 1.8 E 0.9 1

Barium 1/3 0.5 0.73 0

Chromium 2

2/3 E 0.03 0.04 3

Copper 1/3 1.71 E 0.37 0

Lead 3

1/3 0.92 0.25 0

Nickel 2/3 0.22 E 0.03 5

Silica 1/3 0.03 16.08 0

Strontium 1/3 E 0.3 28.5 0

Vanadium 2

1/3 E 0.05 0.15 0

Zinc 3

1/3 6.6 E 0.39 0

Arsenic (TML)4 1/6 0.7 0.6 0

Iron (TML)4 1/6 4.0 2.0 0

Radioactive constituents (pCi/L)

Radium-226 1/1 0.011 E 0.045 0

Radium-228 1/1 0.02 E 0.27 0

1

 Constituents also detected in associated source-solution blanks.

2

 Constituents detected in source-solution blank and environmental sample, but not in associated field blank so it was not of potential QC concern.

3

 Constituents detected in field blank, but not in associated environmental sample so it was not of potential QC concern.

4

 Iron and and arsenic analyses performed by the U.S. Geological Survey Trace Metal Laboratory.

Table A3. Constituents detected in field blanks collected for the Coastal Los Angeles Basin Groundwater Ambient Monitoring and 

Assessment (GAMA) study unit, California, June to November 2006.

[Data qualified due to associated blank contamination are reported but not used in summary statistics. Number of environmental samples qualified with 

a V-code: Environmental samples were not censored as a result of detections in the corresponding blank samples if the environmental samples taken prior 

to, and following the blank sample detections were free from the constituent observed in the blank sample. Abbreviations: E, estimated or having a higher 

degree of uncertainty; μg/L, micrograms per liter; pCi/L, picocuries per liter; –, not detected]
90 Ground-Water Quality Data in the Coastal Los Angeles Basin Study Unit, 2006: Results from the California GAMA Program

Constitutent

Number of 

relative standard deviations 

greater than 20 percent/ 

number of replicate pairs

Maximum 

relative standard 

deviation 

(percent)

Measured values 

for pairs with RSD 

greater than 20 

(environmental/replicate) 

Volatile organic compounds, gasoline oxygenates and degradates from schedules 2020 and 4024

1,2,4-Trimethylbenzene 1/5 74 (E 0.6; 0.19)

All other VOCs from schedule 2020 and 4024 0/5 < 20 nv

Pesticides, polar pesticides and pesticide degradates from schedules 2003 and 2060

All pesticides and pesticide degradates from schedule 2003 0/5 < 20 nv

Deethylatrazine (2-Chloro-4-isopropylamino-6-amino-striazine) (μg/L)

1/1 47 (E 0.01; E 0.02)

Diuron (μg/L) 1/1 20 (0.15; 0.20)

Norflurazon (μg/L) 1/1 28 (0.02; 0.03)

All other polar pesticides and pesticide degradates from 

schedule 2060

0/1 < 20 nv

Potential waste-water indicators from schedule 4433 

3-Methyl-1(H)-indole (Skatole) (μg/L) 1/5 98 (– ; E 0.04)

3,4- Dichlorophenyl isocyanate (mg/L) 1/5 21 (E 1.94; E 2.63)

5-Methyl-1H-benzotriazole (μg/L) 1/5 64 (4.28; –)

Bis(2-ethylhexyl) phthalate (μg/L) 1/5 28 (2.97; –)

Bisphenol A (μg/L) 1/5 72 (E 0.13; –)

Caffeine (μg/L) 1/5 58 (– ; E 0.08)

Diethyl phthalate (μg/L) 1/5 32 (E 0.14; E 0.09)

Methyl salicylate (μg/L) 1/5 102 (– ; E 0.03)

p-Cresol (μg/L) 1/5 87 (– ; 0.85)

Phenol (μg/L) 2/5 97 (E 0.13; 0.73)(E 0.07; –)

All other potential waste-water indicator compounds from 

schedule 4433

0/5 < 20 nv

Constituents of special interest1

Perchlorate 0/5 < 20 nv

1,2,3-Trichloropropane, 1,4-dioxane and Nnitrosodimethylamine (NDMA)

0/3 < 20 nv

Major ions, minor ions, trace elements, nutrients, and arsenic, chromium, and iron speciation 

Aluminum (mg/L) 2/3 34 (E 2.0; E 1.2) (– ; E 1.03)

Chromium (μg/L) 2/3 37 (0.17; 0.23) (E 0.07; –)

Iron (μg/L) 2/3 47 (E 3.00; –) (E 6.00; E4.37)

Nickel (μg/L) 1/3 47 (E 0.03; –)

Zinc (μg/L) 2/3 30 (1.50; 1.02) (E 0.39; 0.60)

Arsenic (total) (μg/L)2 2/5 94 (2.7; 1.6) (– ; 2.5)

Iron (total), iron(III), chromium (total), chromium(VI), 

arsenic(III) (μg/L)2

0/5 < 20 nv

All additional major ions, minor ions, trace elements 

from schedule 1948, nutrients from schedule 2755, and 

dissolved organic carbon from lab code 2612

0/3 < 20 nv

Table A4. Quality-control summary of replicate analyses collected for the Coastal Los Angeles Basin Groundwater Ambient Monitoring 

and Assessment (GAMA) study unit, California, June to November 2006.

[Abbreviations: E, estimated or having a higher degree of uncertainty; <, less than; mg/L, milligram per liter; μg/L, microgram per liter; –, not detected; RSD, 

relative standard deviation in percent; nv, no measured values with RSD greater than 20 percent]
Table A4 91

Constitutent

Number of 

relative standard deviations 

greater than 20 percent/ 

number of replicate pairs

Maximum 

relative standard 

deviation 

(percent)

Measured values 

for pairs with RSD 

greater than 20 

(environmental/replicate) 

Isotopes and radioactivity

Oxygen and hydrogen isotopes 0/5 < 20 nv

Carbon-14 0/2 < 20 nv

Radon-222 0/2 < 20 nv

Microbial indicators

F-specific and somatic coliphage 0/1 < 20 nv

E. coli and total coliforms 0/10 < 20 nv

1

 Analyses performed at Montgomery Watson-Harza Laboratories, Monrovia, California.

2

 Analyses performed at U.S. Geological Survey Trace Metal Laboratory, Boulder, Colorado.

Table A4. Quality-control summary of replicate analyses collected for the Coastal Los Angeles Basin Groundwater Ambient Monitoring 

and Assessment (GAMA) study unit, California, June to November 2006.—Continued

[Abbreviations: E, estimated or having a higher degree of uncertainty; <, less than; mg/L, milligram per liter; μg/L, microgram per liter; –, not detected; RSD, 

relative standard deviation in percent; nv, no measured values with RSD greater than 20 percent]
92 Ground-Water Quality Data in the Coastal Los Angeles Basin Study Unit, 2006: Results from the California GAMA Program

Constituent

Number 

of spike 

samples

Recovery

(percent)

MinimumMaximum

Median

Acetone1 3 94 103 97

Acrylonitrile 3 93 102 102

tert-Amyl alcohol 1 103 103 103

Benzene2 3 96 100 98

Bromobenzene 3 96 100 98

Bromochloromethane 3 102 108 104

Bromodichloromethane 

(THM)2

3 98 113 102

Bromoethene 3 101 117 112

Bromoform 

(tribromomethane)2

3 92 100 97

Bromomethane 3 89 111 94

2-Butanone (ethyl methyl 

ketone)

3 94 102 96

tert-Butyl alcohol (TBA) 1 100 100 100

Butylbenzene 

(n-Butylbenzene)

3 70 91 75

sec-Butylbenzene 3 81 96 87

tert-Butylbenzene 3 93 100 97

Carbon disulfide2 3 56 77 69

Chlorobenzene 3 96 98 96

Chloroethane 3 96 106 96

Chloroform 

(trichloromethane) 

3 96 111 106

Chloromethane 3 92 113 99

3-Chloropropene 3 109 115 109

2-Chlorotoluene 3 91 98 91

4-Chlorotoluene 3 89 100 89

Dibromochloromethane 3 90 101 95

1,2-Dibromo-3-

chloropropane (DBCP)

3 94 99 94

1,2-Dibromoethane (EDB) 3 100 106 100

Dibromomethane 3 104 115 104

1,2-Dichlorobenzene 3 94 98 98

1,3-Dichlorobenzene 3 91 102 96

1,4-Dichlorobenzene 3 87 98 94

trans-1,4-Dichloro-2-butene 3 94 98 94

Dichlorodifluoromethane 

(CFC-12)2

3 70 89 80

1,1-Dichloroethane2 3 105 110 106

1,1-Dichloroethene (DCE)2 3 89 96 89

1,2-Dichloroethane2 3 97 111 111

cis-1,2-Dichloroethene2 3 98 109 102

trans-1,2-Dichloroethene2 3 96 102 100

Dichloromethane 

(methylene chloride)

3 106 106 106

Table A5A. Quality-control summary of matrix-spike recoveries for volatile organic compounds (VOCs) and gasoline oxygenates and 

degradates in samples collected for the Coastal Los Angeles Basin Groundwater Ambient Monitoring and Assessment (GAMA) study, 

California, June to November 2006.

[Acceptable recovery range is between 70 and 130 percent]

Constituent

Number 

of spike 

samples

Recovery

(percent)

MinimumMaximum

Median

1,1-Dichloropropene 3 84 90 90

1,2-Dichloropropane 3 98 102 100

1,3-Dichloropropane 3 99 106 99

cis-1,3-Dichloropropene 3 84 88 85

trans-1,3-Dichloropropene 3 79 95 86

2,2-Dichloropropane 3 86 90 89

Diethyl ether 3 96 102 96

Diisopropyl ether1,2 3 94 102 95

Ethylbenzene2 3 89 98 91

Ethyl tert-butyl ether 

(ETBE, tert-butyl ethyl 

ether)1

3 83 96 88

Ethyl methacrylate 3 86 93 89

o-Ethyl toluene 

(2-Ethyltoluene)

3 83 89 85

Hexachlorobutadiene 3 63 85 70

Hexachloroethane 3 91 102 96

2-Hexanone (n-Butyl 

methyl ketone)

3 89 102 95

Iodomethane (Methyl 

iodide)

3 98 109 99

Isopropylbenzene (cumene) 3 94 98 94

4-Isopropyl-1-

methylbenzene

3 77 98 83

Methyl acetate 1 107 107 107

Methyl acrylate 3 94 103 96

Methyl acrylonitrile 3 96 113 100

Methyl tert-butyl ether 

(MTBE)1,2

3 91 96 96

Methyl methacrylate 3 88 97 91

4-Methyl-2-pentanone 

(MIBK, isobutyl methyl 

ketone)

3 89 93 93

Methyl tert-pentyl ether1 3 90 95 95

Naphthalene2 3 77 107 91

n-Propylbenzene 3 79 94 87

Styrene 3 85 96 88

1,1,1,2-Tetrachloroethane 3 96 104 96
Table A5A 93

Constituent

Number 

of spike 

samples

Recovery

(percent)

MinimumMaximum

Median

1,1,2,2-Tetrachloroethane 3 98 104 98

Tetrachloroethene (PCE)2 3 87 98 96

Tetrachloromethane (carbon 

tetrachloride)2

3 94 136 99

Tetrahydrofuran 3 96 112 101

1,2,3,4-Tetramethylbenzene 3 70 105 84

1,2,3,5-Tetramethylbenzene 3 78 113 85

Toluene2 3 96 98 96

1,2,3-Trichlorobenzene 3 85 106 85

1,2,4-Trichlorobenzene 3 77 92 77

1,1,1-Trichloroethane 

(1,1,1-TCA)2

3 98 106 100

1,1,2-Trichloroethane 

(1,1,2-TCA)

3 98 102 100

Trichloroethene (TCE)2 3 45 98 89

Table A5A. Quality-control summary of matrix-spike recoveries for volatile organic compounds (VOCs) and gasoline oxygenates and 

degradates in samples collected for the Coastal Los Angeles Basin Groundwater Ambient Monitoring and Assessment (GAMA) study, 

California, June to November 2006.—Continued

[Acceptable recovery range is between 70 and 130 percent]

Constituent

Number 

of spike 

samples

Recovery

(percent)

MinimumMaximum

Median

Trichlorofluoromethane 

(CFC-11)2

3 99 112 100

1,2,3-Trichloropropane 

(1,2,3-TCP)2

3 96 104 104

1,1,2-Trichlorotrifluoroethane (CFC-113)2

3 70 87 74

1,2,3-Trimethylbenzene 3 95 105 95

1,2,4-Trimethylbenzene2 3 83 106 88

1,3,5-Trimethylbenzene 3 83 100 88

Vinyl chloride2 3 96 117 106

m- and p-Xylene2 3 88 101 93

o-Xylene 3 89 91 89

1

 Constituents on schedules 2020 and 4024; only values from schedule 2020 are reported because it is the preferred analytical schedule.

2

 Constituents detected in ground-water samples.
94 Ground-Water Quality Data in the Coastal Los Angeles Basin Study Unit, 2006: Results from the California GAMA Program

Constituent

Number 

of spike 

samples

Recovery

(percent)

MinimumMaximum

Median

Acetochlor 3 72 115 103

Alachlor 3 76 107 103

Atrazine1 3 85 119 111

Azinphos-methyl 3 37 119 67

Azinphos-methyl-oxon 3 27 108 27

Benfluralin, water 3 41 72 63

Carbaryl 3 58 111 99

2-Chloro-2,6-

diethylacetanilide 

3 68 107 98

4-Chloro-2-methylphenol 3 59 76 67

Chlorpyrifos 3 82 101 99

Chlorpyrifos oxon 3 33 35 34

Cyfluthrin 3 32 77 62

Cypermethrin 3 30 68 58

Dacthal (DCPA) 3 97 118 98

Deethylatrazine (2-Chloro4-isopropylamino-6-

amino-s-triazine)1

3 90 107 94

Desulfinylfipronil1 3 67 123 87

Desulfinylfipronil amide 3 41 121 98

Diazinon 3 76 95 94

Diazinon oxon 3 47 101 98

3,4-Dichloroaniline1 3 77 98 88

Dichlorvos1 3 27 38 37

Dicrotophos 3 22 35 31

Dieldrin 3 74 93 89

2,6-Diethylaniline 3 87 108 98

Dimethoate 3 20 36 31

Ethion 3 58 97 88

Ethion monoxon 3 58 97 88

2-Ethyl-6-methylaniline 3 90 107 94

Fenamiphos 3 57 143 87

Fenamiphos sulfone 3 34 214 51

Fenamiphos sulfoxide 3 16 62 19

Fipronil1 3 50 123 113

Table A5B. Quality-control summary of matrix-spike recoveries for pesticides and pesticide degradates in samples collected for the 

Coastal Los Angeles Basin Groundwater Ambient Monitoring and Assessment (GAMA) study unit, California, June to November 2006.

[Acceptable recovery range is between 70 and 130 percent]

Constituent

Number 

of spike 

samples

Recovery

(percent)

MinimumMaximum

Median

Fipronil sulfide1 3 53 100 90

Fipronil sulfone1 3 50 131 94

Fonofos 3 76 106 94

Hexazinone1 3 42 124 64

Iprodione 3 32 80 58

Isofenphos 3 70 124 119

Malaoxon 3 58 113 91

Malathion 3 70 114 103

Metalaxyl1 3 72 100 97

Methidathion 3 79 120 94

Metolachlor1 3 89 112 108

Metribuzin 3 44 80 78

Myclobutanil 3 56 111 100

1-Naphthol 3 20 39 35

Paraoxon-methyl 3 36 56 50

Parathion-methyl 3 46 91 87

Pendimethalin 3 56 105 92

cis-Permethrin 3 40 68 57

Phorate 3 64 80 73

Phorate oxon 3 57 116 115

Phosmet 1 34 34 34

Phosmet oxon 1 18 18 18

Prometon1 3 62 101 101

Prometryn 3 76 117 111

Pronamide (Propyzamide) 3 63 99 95

Simazine1 3 72 113 110

Tebuthiuron1 3 29 186 127

Terbufos 3 112 142 118

Terbufos oxon sulfone 3 46 119 76

Terbuthylazine 3 83 107 104

Trifluralin 3 46 80 71

1

 Constituents detected in ground-water samples.
Table A5C 95

Constituent

Number 

of spike 

samples

Recovery

(percent)

Acifluorfen 1 77

Aldicarb 1 77

Aldicarb sulfone 1 57

Aldicarb sulfoxide 1 90

Atrazine 1 108

Bendiocarb 1 80

Benomyl 1 76

Bensulfuron-methyl 1 169

Bentazon 1 57

Bromacil 1 96

Bromoxynil 1 46

Caffeine 1 87

Carbaryl 1 96

Carbofuran 1 97

Chloramben, methyl ester 1 103

Chlorimuron-ethyl 1 195

3-(4-Chlorophenyl)-1-methyl urea1 1 65

Clopyralid 1 88

Cycloate 1 77

2,4-D (2,4-Dichlorophenoxyacetic acid) 1 77

2,4-D methyl ester 

(2,4-Dichlorophenoxyacetic acid methyl 

ester)

1 91

2,4-DB (4-(2,4-Dichlorophenoxy)butyric 

acid)

1 61

DCPA (Dacthal) monoacid 1 69

Deethylatrazine (2-Chloro-4-

isopropylamino-6-amino-s-triazine)

1 69

Deisopropyl atrazine (2-chloro-6-

ethylamino-4-amino-s-triazine)1

1 88

Dicamba 1 54

Dichlorprop 1 73

Dinoseb 1 61

Diphenamid1 1 96

Diuron1 1 103

Fenuron 1 84

Table A5C. Quality-control summary of matrix-spike recoveries for polar pesticides and pesticide degradates in samples collected 

for the Coastal Los Angeles Basin Groundwater Ambient Monitoring and Assessment (GAMA) study unit, California, June to November

2006.

[Acceptable recovery range is between 70 and 130 percent]

Constituent

Number 

of spike 

samples

Recovery

(percent)

Flumetsulam 1 176

Fluometuron 1 96

Hydroxyatrazine (2-Hydroxy-4-

isopropylamino-6-ethylamino-s-triazine)

1 96

3-Hydroxycarbofuran 1 84

Imazaquin 1 126

Imazethapyr 1 107

Imidacloprid 1 108

Linuron 1 96

MCPA (2-Methyl-4-chlorophenoxyacetic 

acid) 

1 73

MCPB (4-(2-Methyl-4-chlorophenoxy) 

butyric acid)

1 61

Metalaxyl 1 103

Methiocarb 1 97

Methomyl 1 92

Metsulfuron methyl 1 161

Neburon 1 107

Nicosulfuron 1 180

Norflurazon1 1 107

Oryzalin 1 77

Oxamyl 1 80

Picloram 1 46

Propham 1 91

Propiconazole 1 123

Propoxur 1 96

Siduron 1 107

Sulfometuron-methyl 1 164

Tebuthiuron 1 115

Terbacil 1 94

Triclopyr 1 61

1

 Constituents detected in ground-water samples.
96 Ground-Water Quality Data in the Coastal Los Angeles Basin Study Unit, 2006: Results from the California GAMA Program

Constituent

Number 

of spike 

samples

Recovery

(percent)

MinimumMaximum

Mean

Acetophenone 1 76 76 76

Acetyl hexamethyl 

tetrahydronaphthalene1

2 69 73 71

Anthracene, water 2 72 75 73

9,10-Anthraquinone 2 69 78 74

Atrazine 2 83 93 88

Benzo[a]pyrene 2 64 68 66

Benzophenone1 2 78 82 80

Bis(2-ethylhexyl) phthalate1 0 – – –

Bisphenol A1 2 73 81 77

Bromacil 2 77 83 80

Bromoform 

(tribromomethane)

2 61 64 62

3-tert-Butyl-4-

hydroxyanisole

2 44 57 50

Caffeine 2 72 78 75

Camphor1 1 77 77 77

Carbaryl 2 68 71 70

Carbazole 2 81 83 82

Chlorpyrifos 2 65 79 72

Cholesterol1 2 64 67 66

3-β-Coprostanol1 2 68 68 68

Cotinine 2 41 61 51

p-Cresol1 1 72 72 72

4-Cumylphenol1 2 81 83 82

N,N-diethyl-meta-toluamide 

(DEET)1

2 82 90 86

Diazinon 2 73 76 75

1,4-Dichlorobenzene 2 26 61 44

3,4-Dichlorophenyl 

isocyanate

2 69 102 86

Dichlorvos 1 74 74 74

Diethyl phthalate1 2 83 94 88

2,6-Dimethylnaphthalene1 2 54 69 62

Fluoranthene1 2 67 76 72

Hexahydrohexamethyl 

cyclopentabenzopyran1

2 67 72 69

Indole1 1 78 78 78

Isoborneol 1 71 71 71

Isophorone 1 78 78 78

Isopropylbenzene 2 12 49 31

Isoquinoline 1 75 75 75

d-Limonene1 1 42 42 42

Menthol 1 83 83 83

Metalaxyl 2 80 89 85

Table A5D. Quality-control summary of matrix-spike recoveries for potential waste-water indicators in samples collected for the 

Coastal Los Angeles Basin Groundwater Ambient Monitoring and Assessment (GAMA) study unit, California, June to November 2006.

[Acceptable recovery range is between 70 and 130 percent. Symbols: –, not included in spike mixture]

Constituent

Number 

of spike 

samples

Recovery

(percent)

MinimumMaximum

Mean

1-Methylnaphthalene1 2 63 73 68

2-Methylnaphthalene1 1 72 72 72

3-Methyl-1H-indole 2 76 86 81

5-Methyl-1H-benzotriazole1 2 69 70 69

Methyl salicylate1 1 71 71 71

Metolachlor 2 82 90 86

Naphthalene 2 58 75 67

Nonylphenol, monoethoxy- 

(total)

2 71 73 72

4-Nonylphenol 

diethoxylates1

2 64 64 64

4-Octylphenol1 2 67 76 71

4-Octylphenol 

diethoxylates1

2 52 96 74

4-Octylphenol 

monoethoxylates

2 65 74 69

4-tert-Octylphenol 2 77 78 78

4-Nonylphenol1 2 74 79 76

Pentachlorophenol 2 52 82 67

Phenanthrene 2 74 77 76

Phenol1 1 74 74 74

Prometon1 2 74 84 79

Pyrene1 2 67 76 72

β-Sitosterol 2 58 72 65

β-Stigmastanol 2 51 82 67

2,2',4,4'-Tetrabromodiphenyl ether2 40 51 45

Tetrachloroethylene1 1 – 27 27

Tributyl phosphate1 2 74 84 79

Triclosan1 2 69 69 69

Triethyl citrate 2 70 109 90

Triphenyl phosphate1 2 66 69 67

Tris(2-butoxyethyl) 

phosphate1

2 79 82 80

Tris(2-chloroethyl) 

phosphate1

2 73 82 80

Tris(dichloroisopropyl) 

phosphate1

2 69 74 71

1

 Constituents detected in ground-water samples.
Table A5E 97

Constituent

Number 

of spike 

samples

Recovery

(percent)

1,2,3-Trichloropropane (TCP) 1 95

1,4-Dioxane1 1 90

N-Nitrosodimethylamine (NDMA)1 1 94

1

Constituents detected in ground-water samples.

Table A5E. Quality-control summary of matrix-spike recoveries 

for constituents of special interest in samples collected for the 

Coastal Los Angeles Basin Groundwater Ambient Monitoring 

and Assessment (GAMA) study unit, California, June to 

November 2006.

[Acceptable recovery range is between 70 and 130 percent]
98 Ground-Water Quality Data in the Coastal Los Angeles Basin Study Unit, 2006: Results from the California GAMA Program

Table A6. Quality-control summary of surrogate recoveries for volatile organic compounds, gasoline oxygenates and degradates, 

pesticides and pesticide degradates, potential waste-water indicators, and constituents of special interest, collected for the Coastal Los 

Angeles Basin Groundwater Ambient Monitoring and Assessment (GAMA) study unit, California, June to November 2006.

[Abbreviations: MWH, Montgomery Watson-Harza Laboratory; VOC, volatile organic compound]

Surrogate Analytical 

schedule

Constituent or 

constituent

class

analyzed

Number of 

blank 

sample 

analyses

Median 

recovery 

in blanks 

(percent)

Number of surrogate 

recoveries in blanks

Number of 

environmental 

sample 

analyses

Median 

recovery in 

environmental 

samples 

(percent)

Number of surrogate 

recoveries in 

environmental samples

Below 

70 percent

Above 

130 percent

Below 

70 percent

Above 

130 percent

1,2-Dichloroethane-d42020, 4024 VOC, gasoline 

oxygenate

12 113 0 3 69 116 0 11

1-Bromo-4-

fluorobenzene

2020, 4024 VOC, gasoline 

oxygenate

12 96 0 0 69 92 14 0

Toluene-d8 2020, 4024 VOC, gasoline 

oxygenate

12 82 0 0 69 98 0 0

Isobutyl alcohol-d6 4024 Gasoline 

oxygenate

2 91 0 0 17 92 0 0

alpha-HCH-d6 2003 Pesticide 6 96 0 0 68 95 1 0

Diazinon-d10 2003 Pesticide 6 108 0 0 68 100 1 0

2,4,5-T (2,4,5-trichlorophenoxyacetic acid)2060 Pesticide 

degradate

1 70 1 0 17 71 7 0

Barban 2060 Pesticide 

degradate

1 86 0 0 17 88 1 0

Caffeine-13C 2060 Pesticide 

degradate

1 90 0 0 17 77 5 0

Bisphenol A-d3 4433 Potential 

waste-water 

indicator 

8 64 6 0 69 73 28 0

Caffeine-C13 4433 Potential 

waste-water 

indicator

8 80 0 0 69 75 25 0

Decafluorobiphenyl 4433 Potential 

waste-water 

indicator 

8 67 5 0 69 64 53 0

Fluoranthene-d10 4433 Potential 

waste-water 

indicator 

8 89 0 0 69 85 7 0

Toluene-d8 MWH 1,2,3-TCP1 2 97 0 0 15 99 0 0

NDMA-d6 MWH NDMA1 2 71 1 0 14 101 2 0

Nitrobenzene-d5 MWH 1,4 Dioxane1 2 82 0 0 14 74 5 0

Terphenyl-d14 MWH 1,4 Dioxane1 2 81 0 0 14 51 11 0

2-Flurobiphenyl MWH 1,4 Dioxane1 2 92 0 0 14 81 4 0

1

Constituent analyzed at Montgomery Watson-Harza Laboratory (MWH), Monrovia, California.
Mathany, Land, and Belitz–Ground-Water Quality Data in the Coastal Los Angeles Basin Study Unit, 2006: Results from the California GAMA Program–DS 387, Version 1.1

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Mathany, Land, and Belitz–Ground-Water Quality Data in the Coastal Los Angeles Basin Study Unit, 2006: Results from the California GAMA Program–DS 387, Version 1.1

Printed on recycled paper