Prepared in cooperation with the California State Water Resources Control Board 

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

Groundwater Quality Data in the Mojave Study Unit, 2008: 

Results from the California GAMA Program 

Barstow

Victorville

Data Series 440 

U.S. Department of the Interior 

U.S. Geological Survey 
Cover Photographs:
 

Top: Mojave River at Helendale, California. (Photograph taken by Michael Wright, U.S. Geological Survey.)
 

Bottom: Production well, Apple Valley, California. (Photograph taken by Peter Bennett, U.S. Geological Survey.)
 
 

 

 

 

 

 

 

Groundwater Quality Data in the 

Mojave Study Unit, 2008: Results from the 

California GAMA Program 

By Timothy M. Mathany and Kenneth Belitz 

In cooperation with the California State Water Resources Control Board 

Data Series 440 

U.S. Department of the Interior 

U.S. Geological Survey 
 

U.S. Department of the Interior 

KEN SALAZAR, Secretary 

U.S. Geological Survey 

Suzette M. Kimball, Acting Director 

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

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


owners to reproduce any copyrighted materials contained within this report.
 

Suggested citation:
 

Mathany, T.M., and Belitz, Kenneth, 2009, Groundwater quality data in the Mojave study unit, 2008: Results 


from the California GAMA Program: U.S. Geological Survey Data Series 440, 80 p. Available at http://pubs.
 

usgs.gov/ds/440/
 
 

iii 

Contents 

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

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

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

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

Methods ..........................................................................................................................................................7
 

Study Design..........................................................................................................................................7
 

Sample Collection and Analysis.........................................................................................................9
 

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

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

Water-Quality Results ................................................................................................................................10
 

Quality-Control Results ......................................................................................................................10
 

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

Groundwater-Quality Data ................................................................................................................11
 

Water-Quality Indicators (Field Parameters) ........................................................................11
 

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

Constituents of Special Interest..............................................................................................12
 

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

Isotopic Tracers and Noble Gases..........................................................................................13
 

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

Future Work ..................................................................................................................................................14
 

Summary .......................................................................................................................................................14
 

Acknowledgments.......................................................................................................................................15
 

References Cited..........................................................................................................................................15
 

Tables ...........................................................................................................................................................21
 

Appendix .......................................................................................................................................................60
 

Appendix Tables...........................................................................................................................................70
 
 

 

 

 

 

 

iv 

Figures 

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

Mojave Groundwater Ambient Monitoring and Assessment (GAMA) study unit .........3 

Figure 2.	 Map of the Mojave Groundwater Ambient Monitoring and Assessment (GAMA) 

study unit showing the California Department of Water Resources groundwater 

basins within the study unit, location of public supply wells, major cities, roads, 

topographic features, and hydrologic features ..................................................................5 

Figure 3.	 Map of the Mojave Groundwater Ambient Monitoring and Assessment (GAMA) 

study unit showing the 3-kilometer buffer zones around all public-supply wells, 

the distribution of study-area grid cells, the aerial extent of the floodplain aquifer, 

and the location of sampled grid wells. Alphanumeric identification numbers for 

grid wells have the prefix “MOJO”, but only the numeric portions are shown on 

the map .....................................................................................................................................6 

Figure 4.	 Map of the Mojave Groundwater Ambient Monitoring and Assessment (GAMA) 

study unit showing the 3-kilometer buffer zones around all public-supply wells, 

the distribution of study-area grid cells, the floodplain aquifer, and the location 

of sampled understanding wells. Alphanumeric identification numbers for understanding wells have the prefix “MOJOU”, but only the letter “U” and numeric 

portions are shown on the map .............................................................................................8 

Tables 

Table 1. Well identification, sampling, and construction information for wells sampled 

for the Mojave Groundwater Ambient Monitoring and Assessment (GAMA) 

study, California, February to April 2008 .............................................................................22 

Table 2. Classes of chemical constituents and water-quality indicators (field parameters) 

collected for the slow and fast well sampling schedules in the Mojave 

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

February to April 2008............................................................................................................24 

Table 3A. Volatile organic compounds (VOCs), primary uses or sources, comparative 

thresholds, and reporting information for the U.S. Geological Survey (USGS) 

National Water Quality Laboratory Schedule 2020 ..........................................................25 

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

thresholds, and reporting information for the U.S. Geological Survey (USGS) 

National Water Quality Laboratory Schedule 2003 ..........................................................29 

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

and reporting information for the U.S. Geological Survey (USGS) National Water 

Quality Laboratory schedule 2080 .......................................................................................32 

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

thresholds, and reporting information for Weck Laboratories, Inc. analyses .............33 

Table 3E. Nutrients and dissolved organic carbon (DOC), comparative thresholds, and 

reporting information for the U.S. Geological Survey (USGS) National Water 

Quality Laboratory Schedule 2755 and laboratory code 2612.........................................33 

Table 3F. Major and minor ions, silica, total dissolved solids (TDS), and trace elements, 

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

(USGS) National Water Quality Laboratory Schedule 1948 ............................................34 
 

 

 

 

 

 

v 

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

information for the U.S. Geological Survey (USGS) Trace Metal Laboratory, 

Boulder, Colorado, analyses.................................................................................................35 

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

information for laboratory analyses....................................................................................36 

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

the Lawrence Livermore National Laboratory analyses .................................................37 

Table 4. Water-quality indicators (field parameters) in samples collected for the 

Mojave Groundwater Ambient Monitoring and Assessment (GAMA) study, 

California, February to April 2008.........................................................................................38 

Table 5. Volatile organic compounds (VOC) detected in samples collected for the Mojave 

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

February to April 2008............................................................................................................42 

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

Mojave Groundwater Ambient Monitoring and Assessment (GAMA) study, 

California, February to April 2008.........................................................................................46 

Table 7. Constituents of special interest (perchlorate and N-nitrosodimethylamine 

[NDMA]) detected in samples collected in the Mojave Groundwater Ambient 

Monitoring and Assessment (GAMA) study, California, February to April 2008..........48 

Table 8. Nutrients and dissolved organic carbon (DOC) detected in samples collected 

for the Mojave Groundwater Ambient Monitoring and Assessment (GAMA) 

study, California, February to April 2008 .............................................................................49 

Table 9. Major and minor ions, silica, and total dissolved solids (TDS) detected in 

samples collected for the Mojave Groundwater Ambient Monitoring and 

Assessment (GAMA) study, California, February to April 2008.......................................50 

Table 10. Trace elements collected for the Mojave Groundwater Ambient Monitoring 

and Assessment (GAMA) study, California, February to April 2008 ..............................52 

Table 11. Species of inorganic arsenic, chromium, and iron detected in samples 

collected for the Mojave Groundwater Ambient Monitoring and Assessment 

 (GAMA) study, California, February to April 2008...............................................................54 

Table 12. Results for analyses of stable isotope ratios and tritium and carbon-14 activities 

detected in samples collected for the Mojave Groundwater Ambient Monitoring 

 and Assessment (GAMA) study, California, February to April 2008................................55 

Table 13A. Radium isotope activity levels detected in samples collected for the Mojave 

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

February to April 2008............................................................................................................57 

Table 13B. Gross alpha and gross beta radioactivity detected in samples collected for 

the Mojave Groundwater Ambient Monitoring and Assessment (GAMA) study, 

California, February to April 2008.........................................................................................58 

Table 13C. Radon-222 detected in samples collected for the Mojave Groundwater Ambient 

Monitoring and Assessment (GAMA) study, California, February to April 2008..........59 
 

vi 

Appendix Tables 

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

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

Laboratory (NWQL) and additional contract laboratories...............................................71 

Table A2.	 Preferred analytical schedules for constituents appearing on multiple 

schedules for samples collected for the Mojave Groundwater Ambient Monitoring 

and Assessment (GAMA) study, California, February to April 2008...............................73 

Table A3.	 Constituents detected in field blanks collected for the Mojave Groundwater 

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

April 2008 .................................................................................................................................74 

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

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

February to April 2008............................................................................................................75 

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

compounds (VOC) in samples collected for the Mojave Groundwater Ambient 

Monitoring and Assessment (GAMA) study, California, February to April 2008..........76 

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

pesticide degradates in samples collected for the Mojave Groundwater Ambient 

Monitoring and Assessment (GAMA) study, California, February to April 2008..........78 

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

N-nitrosodimethylamine (NDMA) in groundwater samples collected for the 

Mojave Groundwater Ambient Monitoring and Assessment (GAMA) study, 

California, February to April 2008.........................................................................................79 

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

compounds (VOCs), pesticides and pesticide degradates in samples collected 

for the Mojave Groundwater Ambient Monitoring and Assessment (GAMA) 

study, California, February to April 2008 .............................................................................80 
 

vii 

Abbreviations and Acronyms
 

AB Assembly Bill (through the California State Assembly) 

AL-US action level (USEPA) 

CAS Chemical Abstract Service (American Chemical Society) 

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

CSU combined standard uncertainty 

D detected 

E estimated or having a higher degree of uncertainty 

GAMA Groundwater Ambient Monitoring and Assessment program 

GPS Global Positioning System 

HAL-US lifetime health advisory level (USEPA) 

HPLC high-performance liquid chromatography 

LRL laboratory reporting level 

LSD land-surface datum 

LT-MDL long-term method detection level 

MCL-US maximum contaminant level (USEPA) 

MCL-CA maximum contaminant level (CDPH) 

MDL method detection limit 

MOJO Mojave study unit 

MOJOU Mojave study unit understanding (well) 

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 notification level (CDPH) 

nv no measured values with RSD greater than 20 percent 

np no preference 

NWIS National Water Information System (USGS) 

PCFF portable computer field forms program designed for USGS sampling 

QC quality control 

RL reporting level 

RSD relative standard deviation 

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

SMCL-CA secondary maximum contaminant level (CDPH) 

SRL study reporting limit (concentration cutoff for applying the ≤ symbol) 

ssLC sample-specific critical level 

U.S. United States 

UV ultraviolet 

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

groundwater quality assessment 

VPDB Vienna Pee Dee Belemnite (the international reference standard for carbon isotopes) 

VSMOW Vienna Standard Mean Ocean Water (an isotopic water standard defined in 1968 by the 

International Atomic Energy Agency) 
viii 

Symbols 

= equal to 

> greater than 

< less than 

≤ less than or equal to 

— not detected 

± plus or minus 

* value above threshold level or outside threshold range 

** value is above upper threshold level 

Organizations 

CDPH California Department of Public Health 

CDWR California Department of Water Resources 

LLNL Lawrence Livermore National Laboratory 

NAWQA National Water Quality Assessment (USGS) 

NELAP National Environmental Laboratory Accreditation Program 

NWQL National Water Quality Laboratory (USGS) 

NRP National Research Program (USGS) 

SWRCB State Water Resources Control Board 

TML Trace Metal Laboratory (USGS) 

USEPA U.S. Environmental Protection Agency 

USGS U.S. Geological Survey 

Selected chemical names 

CaCO3 calcium carbonate 

CO3

–2 carbonate 

CFC chlorofluorocarbon 

DOC dissolved organic carbon 

HCl hydrochloric acid 

– HCO3 bicarbonate 

MTBE methyl tert-butyl ether 

Na2

S2O3 sodium thiosulfate 

NDMA N-nitrosodimethylamine 

NO2

+NO3 nitrite plus nitrate, as nitrogen 

PCE perchloroethene (tetrachloroethene) 

SiO2 silicon dioxide 

TCE trichloroethene 

TCP trichloropropane 

TDS total dissolved solids 

THM trihalomethane 

VOC volatile organic compound 

Units of measurement 

C Celsius 

cm3

 STP/g cubic centimeters of gas at standard temperature and pressure (0 degrees Celsius and 1 

atmosphere of pressure) per gram of water 

ft foot (feet) 

km kilometer 
ix 

km2 square kilometer
 

L liter
 

mg/L milligrams per liter (parts per million)
 

mi mile
 

mi2 square mile
 

mL milliliter
 

μg/L micrograms per liter (parts per billion)
 

μm micrometer
 

NTU nephelometric turbidity unit
 

NAD North American Datum of 1983
 

NAVD North American Vertical Datum of 1988
 

pCi/L picocuries per liter
 

pH measure of the acidity or basicity of water
 

pK1,2 acid dissociation constant of carbonic acid
 

pKw acid dissociation constant of water
 

ppb parts per billion
 

ppm parts per million
 

δi

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


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

per mil 

Notes 

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

°F = (1.8×°C) + 32 

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

(NAVD 88). 

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

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

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

25°C). 

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

or micrograms per liter (μg/L). 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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Groundwater Quality Data in the Mojave Study Unit, 2008: 

Results from the California GAMA Program 

By Timothy M. Mathany and Kenneth Belitz 

Abstract 

Groundwater quality in the approximately 1,500 squaremile Mojave (MOJO) study unit was investigated from February to April 2008, as part of the Priority Basin Project of the 

Groundwater Ambient Monitoring and Assessment (GAMA) 

Program. The GAMA Priority Basin Project was developed in 

response to the Groundwater Quality Monitoring Act of 2001 

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

in cooperation with the California State Water Resources Control Board (SWRCB). MOJO was the 23rd of 37 study units to 

be sampled as part of the GAMA Priority Basin Project. 

The MOJO study was designed to provide a spatially 

unbiased assessment of the quality of untreated groundwater 

used for public water supplies within MOJO, and to facilitate 

statistically consistent comparisons of groundwater quality 

throughout California. Samples were collected from 59 wells 

in San Bernardino and Los Angeles Counties. Fifty-two of 

the wells were selected using a spatially distributed, randomized grid-based method to provide statistical representation 

of the study area (grid wells), and seven were selected to aid 

in evaluation of specific water-quality issues (understanding 

wells). 

The groundwater samples were analyzed for a large 

number of organic constituents (volatile organic compounds 

[VOCs], pesticides and pesticide degradates, and pharmaceutical compounds), constituents of special interest (perchlorate 

and N-nitrosodimethylamine [NDMA]) naturally occurring 

inorganic constituents (nutrients, dissolved organic carbon 

[DOC], major and minor ions, silica, total dissolved solids 

[TDS], and trace elements), and radioactive constituents 

(gross alpha and gross beta radioactivity, radium isotopes, and 

radon-222). Naturally occurring isotopes (stable isotopes of 

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

oxygen in nitrate, and activities of tritium and carbon-14), 

and dissolved noble gases also were measured to help identify 

the sources and ages of the sampled groundwater. In total, over 

230 constituents and water-quality indicators (field parameters) were investigated. 

Three types of quality-control samples (blanks, replicates, and matrix spikes) each were collected at approximately 

5–8 percent of the wells, and the results for these samples 

were used to evaluate the quality of the data for the groundwater samples. Field blanks rarely contained detectable concentrations of any constituent, suggesting that contamination was 

not a significant source of bias in the data for the groundwater 

samples. Differences between replicate samples generally 

were within acceptable ranges, indicating acceptable 

analytical reproducibility. Matrix spike recoveries were within 

acceptable ranges for most compounds. 

This study did not attempt to evaluate the quality of water 

delivered to consumers; after withdrawal from the ground, 

untreated groundwater typically is treated, disinfected, or 

blended with other waters to maintain water quality. Regulatory thresholds apply to water that is served to the consumer, 

not to untreated groundwater. However, to provide some context for the results, concentrations of constituents measured in 

the untreated groundwater 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) and thresholds established for aesthetic and technical concerns by CDPH. Comparisons between data collected for this study and thresholds 

for drinking-water are for illustrative purposes only, and are 

not indicative of compliance or non-compliance with those 

thresholds. 

Most constituents that were detected in groundwater 

samples in the 59 wells in MOJO were found at concentrations 

below drinking-water thresholds. In MOJO’s 52 grid wells, 

volatile organic compounds (VOCs) were detected in 

40 percent of the wells, and pesticides and pesticide degradates were detected in 23 percent of the grid wells. Results for 

health-based thresholds in MOJO grid wells showed that all of 

the detections of organic compounds in samples from MOJO 

grid wells were below health-based thresholds, with the 

exception of a single detection of NDMA above the California 

Department of Public Health notification level (NL-CA). 
2 Groundwater Quality Data in the Mojave Study Unit, 2008: Results from the California GAMA Program 

Trace elements and radioactive constituents were 

sampled for at 19 MOJO grid wells and most detections were 

below health-based thresholds. Exceptions include: six detections of arsenic above the USEPA maximum contaminant 

level (MCL-US), two detections of boron and one detection of 

vanadium above the NL-CA, one detection each of molybdenum and strontium that were above the USEPA lifetime health 

advisory level (HAL-US), and one detection of fluoride just 

above the MCL-CA of 2 μg/L. Most detections of radioactive 

constituents in the MOJO grid wells were below health-based 

thresholds, with the exception of one detection of gross alpha 

radioactivity (72-hour count and 30-day count) above the 

MCL-CA, and 17 grid wells (of 19 sampled) that had activities of radon-222 above the proposed MCL-US of 300 pCi/L, 

but all were below the proposed alternative MCL-US of 

4,000 pCi/L. 

All of the samples collected from the 19 MOJO grid 

wells for trace elements, and most of the samples for major 

ions and total dissolved solids (TDS), had measured concentrations below the non-enforceable thresholds set for aesthetic 

concerns. Four grid wells had TDS concentrations above the 

California Department of Public Health secondary maximum 

contaminant level (SMCL-CA) recommended threshold 

of 500 mg/L, and three of these wells were also above the 

SMCL-CA upper threshold of 1,000 mg/L. Four grid wells (of 

19 sampled) had sulfate measured at concentrations above the 

recommended SMCL-CA threshold of 250 mg/L, and one of 

these detections was also above the upper SMCL-CA threshold of 500 mg/L. One grid well had chloride levels at a concentration above the upper SMCL-CA threshold of 500 mg/L. 

Eleven grid wells (of 52 sampled) had pH values outside of 

the SMCL-US range for pH. 

Introduction 

Groundwater comprises nearly half of the water used 

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

assess the quality of ambient groundwater in aquifers used for 

public supply and to establish a baseline groundwater quality monitoring program, the State Water Resources Control 

Board (SWRCB), in cooperation with the U.S. Geological 

Survey (USGS) and Lawrence Livermore National Laboratory 

(LLNL), implemented the Groundwater Ambient Monitoring 

and Assessment (GAMA) Program (http://www.waterboards.

ca.gov/gama). The GAMA program currently consists of 

three projects: GAMA Priority Basin Project, conducted by 

the USGS (http://ca.water.usgs.gov/gama/); GAMA Domestic 

Well Project, conducted by the SWRCB; and GAMA Special 

Studies, conducted by LLNL. 

The SWRCB initiated the GAMA Priority Basin project 

in response to Legislative mandates (Supplemental Report of 

the 1999 Budget Act 1999-00 Fiscal Year; and, the Groundwater Quality Monitoring Act of 2001 {Sections 10780-10782.3 

of the California Water Code, Assembly Bill 599}) to assess 

and monitor the quality of groundwater used as public supply 

for municipalities in California. The GAMA Priority Basin 

Project is a comprehensive assessment of statewide groundwater quality designed to help better understand and identify 

risks to groundwater resources, and to increase the availability 

of information about groundwater quality to the public. For 

the Priority Basin Project, the USGS, in collaboration with the 

SWRCB, developed the monitoring plan to assess groundwater basins through direct and other statistically reliable sample 

approaches (Belitz and others, 2003; State Water Resources 

Control Board, 2003). Key aspects of the project are interagency 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 it includes many chemical analyses that are not otherwise available in statewide water-quality monitoring datasets. 

Groundwater samples collected for the project are analyzed 

for an large number of chemical constituents using analytical 

methods with much lower detection limits than required by the 

California Department of Public Health (CDPH). These analyses will be especially useful for providing an early indication 

of changes in groundwater quality. In addition, the GAMA Priority Basin Project analyzes samples for a suite of constituents 

more extensive than that required by CDPH, and for a suite of 

chemical and isotopic tracers of hydrologic and geochemical 

processes. A broader understanding of groundwater composition will be useful for identifying the natural and human factors affecting water quality. Understanding the occurrence 

and distribution of chemical constituents of significance to 

water quality is important for the long-term management and 

protection of groundwater resources. 

The range of hydrologic, geologic, and climatic conditions that exist in California must be considered in an assessment of groundwater quality. Belitz and others (2003) partitioned the State into 10 hydrogeologic provinces, each with 

distinctive hydrologic, geologic, and climatic characteristics 

(fig. 1), and representative regions in all 10 provinces were 

included in the project design. Eighty percent of California’s 

approximately 16,000 public-supply wells are located in 

groundwater basins within these hydrologic provinces. These 

groundwater basins, defined by the California Department 

of Water Resources (CDWR), generally consist of relatively 

permeable, unconsolidated deposits of alluvial or volcanic 

origin (California Department of Water Resources, 2003). 

Groundwater basins were prioritized for sampling based upon 

the number of public-supply wells in the basin, with secondary 

consideration given to municipal groundwater use, agricultural pumping, the number of formerly leaking underground 

fuel tanks, and pesticide applications within the basins (Belitz 

and others, 2003). In addition, some groundwater basins or 

groups of adjacent similar basins with relatively few publicsupply 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 37 study 

units. Some areas not in the defined groundwater basins were 
Basin and Range

Central 

Valley 

Klamath 

Mountains 

Desert 

Cascades and 

Modoc Plateau 

Transverse Ranges and 

selected Peninsular Ranges 

Southern Coast 

Ranges 

Sierra 

Nevada 

Northern 

Coast 

Ranges 

San Diego 

Drainages 

Mojave Study Unit 

(figure 2) 

Bakersfield 

San 

Francisco 

Sacramento 

OREGON 

NEVADA 

MEXICO 

ARIZONA 

Redding 

Los Angeles 

San Diego 

PA C I F I C O C E A N 

0 200 MILES

0 200 KILOMETERS

Introduction 3 

Shaded relief derived from U.S. Geological Survey Provinces from Belitz and others, 2003.
 

National Elevation Dataset, 2006. 


Albers Equal Area Conic Projection
 

Figure 1. The hydrogeologic provinces of California and the location of the Mojave Groundwater Ambient Monitoring and 

Assessment (GAMA) study unit. 
 

 

4 Groundwater Quality Data in the Mojave Study Unit, 2008: Results from the California GAMA Program 

included in the nearest respective study unit to achieve representation of the 20 percent of public-supply wells not located 

in the groundwater basins. 

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 groundwater quality, and 

(3) Understanding: identification of the natural and human 

factors affecting groundwater quality (Kulongoski and Belitz, 

2004). This status report is one of a series of reports presenting water-quality data collected in each study unit (Wright 

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

others, 2006; Fram and Belitz, 2007; Kulongoski and Belitz, 

2007; Burton and Belitz, 2008; Dawson and others, 2008; Ferrari and others, 2008; Land and Belitz, 2008; Landon 

and Belitz, 2008; Mathany and others, 2008; Schmitt and 

others, 2008; Shelton and others, 2008; Montrella and Belitz, 

2009; and, Ray and others, 2009). Subsequent reports will 

address the status, trends, and understanding aspects of the 

water-quality assessments of each study unit. 

The Mojave GAMA study unit, hereafter referred to as 

MOJO, contains four groundwater basins. MOJO was considered high priority for sampling, to provide adequate representation of the Desert Hydrologic Province; Mojave River Basin 

(Belitz and others, 2003). 

Purpose and Scope 

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

design, including the hydrogeologic setting of MOJO and the 

study methods; (2) the results of quality-control tests; and 

(3) the analytical results for groundwater samples collected in 

MOJO. Groundwater samples were analyzed for water-quality 

indicators (field parameters), organic and inorganic constituents, radioactive constituents, naturally occurring isotopes, 

and dissolved noble gases. The chemical data presented in 

this report were evaluated by comparison to State and Federal 

drinking water regulatory and other non-regulatory healthbased standards that are applied to treated drinking water. 

Regulatory and non-regulatory thresholds considered for this 

report are those established by the United States Environmental Protection Agency (USEPA) and the California Department 

of Public Health (CDPH). The data presented in this report are 

intended to characterize the quality of untreated groundwater 

resources within the study unit, not the treated drinking water 

delivered to consumers by water purveyors. Discussion of 

the factors that influence the distribution and occurrence of 

the constituents detected in groundwater samples will be the 

subject of subsequent publications. 

Hydrogeologic Setting 

The Mojave study unit (MOJO) lies within the 

Desert Hydrogeologic Province described by Belitz and others (2003), and includes four California Department of Water 

Resources (CDWR) South Lahontan Hydrologic Regional 

groundwater basins: Upper, Middle, and Lower Mojave River 

Basins (hereafter referred to as the Mojave River Valley 

Basin system), and the El Mirage Valley Basin (California 

Department of Water Resources, 2004a,b,c,d). Combined, 

these basins define the extent of MOJO, and cover an area of 

approximately 1,500 square miles (mi2

), in San Bernardino, 

Kern, and Los Angeles Counties, California (fig. 2). 

The MOJO study unit is located in the western part of the 

Mojave Desert, and has an altitude ranging from 1,700 ft to 

6,400 ft above sea level. The topography of the study area is 

characterized as a alluvial plain, incised by the Mojave River, 

and is bounded on the west by the Los Angeles County Line, 

the Shadow Mountains, and the Kramer Hills. It is bordered 

to the north by Iron Mountain, the Camp Rock–Harper Lake 

Fault Zone, and the Calico Mountains. The eastern boundaries 

of the study unit include; Afton Canyon, the Cady, Rodman, 

Newberry, Ord, and Granite Mountains, and the Helendale 

Fault Zone. The southernmost border of MOJO is formed by 

the San Gabriel and San Bernardino Mountains. The major 

drainage of the MOJO study unit is the Mojave River, which 

has its headwaters in the San Bernardino Mountains and is dry 

for most of the year. 

The climate throughout the MOJO study unit is classified as arid desert, characterized by hot, dry summers and cold 

winters. Most precipitation falls during the winter rainy season 

(November through March), and in most of the study unit the 

average annual precipitation is less than 6 inches (Izbicki and 

others, 2004). 

There are two distinct and separate water-bearing formations within the Mojave River Valley basin system—the 

regional aquifer and the floodplain aquifer. The regional aquifer underlies the basin system, and consists of regional Pliocene deposits and younger alluvial fan deposits. The regional 

aquifer is less permeable than the floodplain aquifer, except 

where highly-permeable deposits from the ancestral Mojave 

River are present (Izbicki and Michel, 2003). The floodplain 

aquifer, the aerial extent of which is outlined in figure 3, consists of overlying Pleistocene and younger river channel floodplain deposits (California Department of Water Resources, 

2004a,b, c). This unconsolidated alluvial aquifer is highly permeable, and is composed of sand and gravel weathered from 

granitic rocks in the San Gabriel and San Bernardino Mountains. The floodplain aquifer is surrounded and underlain by 

the regional aquifer (Stamos and Predmore, 1995; Izbicki and 

Michel, 2003). Other potential, but not regionally significant, 

water-bearing units include older alluvium, old fan deposits, 

old lake and lakeshore deposits, and dune sand deposits (California Department of Water Resources, 2004a,b,c). The waterbearing formations of El Mirage Valley consist of Quaternary 

alluvium and include unconsolidated younger alluvial deposits 

and underlying unconsolidated to semi-consolidated older 

alluvial deposits (California Department of Water Resources, 

2004d). 
Mirage Valley Fault 

Helendale Fault Zone 

Camp Rock-Harper Lake Fault Zone 

San Bernardino Mts 

San Gabriel Mts 

Granite Mts 

Shadow Mts 

Ord Mts 

Kramer

Hills 

Newberry Mts 

Cady Mts 

Calico Mts 

Iron Mt 

Rodman Mt 

Mojave 

Sheep Ck 

River 

Kern County Los Angeles County 

San Bernardino County 

Afton
 

Canyon
 

15

58 Barstow

C
 

Newberry

Springs

40

395 B Helendale

El Mirage
 

Lake (Dry)
 

D Victorville

Lucerne 

Lake 

(Dry) Apple

Valley 15 Hesperia

N

0 10 20 Miles 138

138 A
 

215

0 10 20 Kilometers 

Shaded relief derived from U.S. Geological Survey Faults from Cal Div of Mines and Geology 

National Elevation Dataset, 2006. 

Albers Equal Area Conic Projection 

EXPLANATION

California Department of Water Resources Public-supply well—With record in California Department

D defined groundwater basin of Public Health database 

and identifier 

A Upper Mojave River 

B Middle Mojave River 

C Lower Mojave River 

D El MIrage Valley 

Introduction 5 

Figure 2. The Mojave Groundwater Ambient Monitoring and Assessment (GAMA) study unit showing the California Department of 

Water Resources groundwater basins within the study unit, location of public supply wells, major cities, roads, topographic features, 

and hydrologic features. 
 

Barstow

Victorville

52 

51 50 

49 

48 

47 

46 

45 

44 

43 

42 

41 40 

39 38 

37 36 

35 

34 

33 

32 

31 

30 

29 

28 

27 

17 

26 

25 

24 

23 

22 

21 

20 

19 

16 

18 

04 

15 

14 

13 

12 

11 

10 

09 

08 

07 

06 

05 

03 

02 

01 

0 10 20 Miles 

0 10 20 Kilometers 

Shaded relief derived from U.S. Geological Survey 

National Elevation Dataset, 2006. 

Albers Equal Area Conic Projection 

EXPLANATION

N

California Department of Aerial outline of MOJO grid cell Water Resources defined flood-plain aquifer
 

groundwater basin
 

27 

MOJO grid well

 "MOJO" identifier has been

 omitted from figure due to

 spatial concerns 

6 Groundwater Quality Data in the Mojave Study Unit, 2008: Results from the California GAMA Program 

Figure 3. The Mojave Groundwater Ambient Monitoring and Assessment (GAMA) study unit showing the 3-kilometer buffer zones 

around all public-supply wells, the distribution of study-area grid cells, the aerial extent of the floodplain aquifer, and the location of 

sampled grid wells. Alphanumeric identification numbers for grid wells have the prefix “MOJO”, but only the numeric portions are 

shown on the map. 
 7 

The aquifers of the Mojave River Basin receive recharge 

from natural and engineered sources. Natural recharge is 

infrequent; as in most of the arid southwestern United States, 

recharge from the direct infiltration of precipitation does not 

typically occur in the study area (Izbicki and Michel, 2003). 

Under present-day climatic conditions, any natural recharge of 

the regional aquifer is small compared to the recharge of the 

floodplain aquifer. The recharge that does occur in the regional 

aquifer results primarily as infiltration from small streams near 

the flanks of the San Gabriel and San Bernardino Mountains 

that flow as a result of winter stormflows and snowmelt runoff 

(Izbicki and Michel, 2003). The floodplain aquifer is recharged 

readily by surface-water infiltration along the Mojave River, 

the principal source of which is runoff from snowmelt and 

precipitation in the San Bernardino Mountains (Densmore 

and others, 2005). Engineered recharge in the Mojave River 

Basin system occurs from septic tank effluent, treated wastewater effluent, effluent from two fish hatchery operations, and 

irrigation that reaches the saturated zone, and irrigation runoff, 

which are allowed to percolate into the ground and recharge 

the groundwater system (California Department of Water 

Resources, 2004a,b,c). 

The general groundwater-flow direction is toward the 

active channel of the Mojave River and then beneath the 

course of the river in the downstream direction. Groundwater 

flow northeast of Apple Valley is also affected by the Helendale Fault Zone, which forms a barrier directing groundwater 

flow northwestward under a surface drainage divide into the 

Mojave River drainage instead of northeastward into Lucerne 

Lake (dry) in the Lucerne Valley basin (fig.2) (Stamos and 

Predmore, 1995; Lines, 1996). 

The El Mirage Valley basin is recharged chiefly from 

snowmelt and rainfall runoff in the San Gabriel Mountains, 

percolating through alluvial deposits at the mouth of Sheep 

Creek. Groundwater moves northwards, as does the surface 

flow, towards El Mirage Lake (dry). Groundwater flow also 

is affected by the Mirage Valley fault, located in the northern 

part of the basin (fig.2), which may impede the movement 

of groundwater (California Department of Water Resources, 

2004d). 

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

documentation. The Appendix to this report contains detailed 

Methods 

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 well selection strategies. Fifty-two 

“grid” wells were selected to provide a statistically unbiased, 

spatially distributed assessment of the quality of groundwater 

resources used for public drinking-water supply, and seven 

additional “understanding” wells were selected to provide 

greater sampling density in several areas to aid in understanding of specific groundwater quality issues in the study unit.

The spatially distributed wells were selected using a 

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

grid-based method generates equal area grid cells; however, 

geographic features of the study unit may force the same grid 

cell to be divided into multiple pieces in order to obtain the 

designated coverage area for each cell. For instance, a portion of a grid-cell may be located on either side of a mountain 

range, but the grid-cell is still considered one grid-cell. MOJO 

had relatively few public-supply wells, and these wells were 

not distributed evenly (fig.2). To minimize the number of grid 

cells without any wells, only the portion of MOJO in close 

proximity to a public-supply well was included in the grid 

area. Location of public-supply wells listed in the statewide 

database maintained by the CDPH were plotted and 1.86-mi-

(3-km) radius circles were drawn around each well. The area 

encompassed by the circles then was divided into sixty-five 

25- km2

 grid cells (fig. 3). The objective was to select one 

public-supply well per grid cell. Fifty-two of the 65 grid cells 

were sampled in MOJO; the other 13 grid cells did not contain 

active or accessible wells. If a grid cell contained more than 

one public-supply well, each well randomly was assigned a 

rank. The highest ranking well that met basic sampling criteria 

(for example, sampling point located prior to treatment, 

capability to pump for several hours, and available wellconstruction information), and for which permission to sample 

could be obtained, then was sampled. If a grid cell contained 

no accessible public-supply wells, other types of wells, such 

as domestic or irrigation, were considered for sampling. An 

attempt was made to select “alternative” wells that had depths 

and screened intervals similar to those in public-supply wells 

in the area. In this fashion, one well was selected in each 

cell to provide a spatially distributed, randomized monitoring network for the study area. Wells sampled as part of the 

spatially distributed, randomized grid-cell network, hereafter, 

are referred to as “grid wells.” Grid wells in MOJO were numbered in the order of sample collection and by using the prefix 

“MOJO” (fig. 3). 
 

California Department of Aerial outline of floodplain MOJO grid cell Water Resources defined aquifer
 

groundwater basin
 U-02 MOJO understanding well

 and identifier 

Barstow

Victorville

MOJOU-02 

MOJOU-05 

MOJOU-04 

MOJOU-07 

MOJOU-03 

MOJOU-06 

MOJOU-01 

0 10 20 Miles 

0 10 20 Kilometers 

Shaded relief derived from U.S. Geological Survey 

National Elevation Dataset, 2006. 

Albers Equal Area Conic Projection 

EXPLANATION

N

8 Groundwater Quality Data in the Mojave Study Unit, 2008: Results from the California GAMA Program 

Additional wells were sampled to evaluate changes in numbered in the order of sample collection and by using the 

water chemistry along selected groundwater flow paths or prefix “MOJOU” (“U” indicating “understanding”) (fig. 4). 

between shallow and deep portions of the aquifers. Wells The GAMA alphanumeric identification number for each 

sampled as part of these studies were not included in the well, along with the date sampled, sampling schedule, well 

statistical characterization of water quality in MOJO because elevation, well type, and well-construction information is 

inclusion of these wells would have caused overrepresentation shown in table 1. Groundwater samples were collected from 

of certain cells. These additional, non-randomized wells were 39 public-supply wells, 9 domestic wells, 4 irrigation wells, 

selected along the slope of the San Gabriel Mountains, within 4 monitoring (observation) wells, 2 standby wells, and 1 well 

the central portion of the Upper Mojave River Valley basin, used for mining activities, from February to April 2008. 

and along the Mojave River floodplain aquifer, and were 

Figure 4. The Mojave Groundwater Ambient Monitoring and Assessment (GAMA) study unit showing the 3-kilometer buffer zones 

around all public-supply wells, the distribution of study-area grid cells, the floodplain aquifer, and the location of sampled understanding 

wells. Alphanumeric identification numbers for understanding wells have the prefix “MOJOU”. 
 

 

Methods 9 

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 on field 

laptop computers using the portable computer field forms 

(PCFF) program, designed for USGS sampling. All information was verified and then uploaded into the USGS National 

Water Information System (NWIS). Well owner information is 

confidential. Well location information and all chemical data 

currently are inaccessible from NWIS’s public website. 

The wells in MOJO were sampled using a tiered analytical approach. All wells were sampled for a standard set of 

constituents, including VOCs, pesticides and pesticide degradates, perchlorate, stable isotopes of hydrogen and oxygen in 

water, dissolved noble gases, tritium, and helium isotopes. The 

standard set of constituents was termed the “fast” schedule 

(table 2). Wells on the “slow” schedule were sampled for all 

the constituents on the fast schedule, plus pharmaceuticals, 

NDMA, nutrients, major and minor ions, silica, total dissolved 

solids (TDS), trace elements, arsenic, chromium, and iron 

speciation, tritium, gross alpha and gross beta radioactivity, 

radium isotopes, radon-222, stable isotopes of carbon, carbon-14 abundance, and stable isotopes of nitrogen and oxygen 

in nitrate (table 2). There also were wells on both the fast and 

slow schedules for which dissolved organic carbon (DOC) was 

added to the sampling schedule; this addition coincided with 

the well’s locality along the Mojave River floodplain aquifer. 

Fast and slow refer to the time required to sample the well 

for all the analytes on the schedule. Generally, three fast or 

two slow wells could be sampled in 1 day. In MOJO, 26 wells 

were sampled on the fast schedule (25 grid and 1 understanding), 9 wells were sampled on the fast plus DOC schedule (8 

grid and 1 understanding), 17 wells were sampled on the slow 

schedule (12 grid and 5 understanding), and 7 grid wells were 

sampled on the slow plus DOC schedule. 

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 representative 

samples of groundwater are collected at each site and that the 

samples are collected and handled in ways that minimizes the 

potential for contamination. 

Tables 3A-I list the compounds analyzed in each constituent class. Groundwater samples were analyzed for 85 VOCs 

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

14 pharmaceutical compounds (table 3C); 2 constituents of 

special interest (table 3D); 5 nutrients and dissolved organic 

carbon (DOC) (table 3E); 9 major and minor ions, silica, total 

dissolved solids (TDS), and 24 trace elements (table 3F); 

arsenic, chromium, and iron species (table 3G); stable isotopes 

of hydrogen and oxygen, as well as the radioactive constituent of carbon in water; stable isotopes of nitrogen and oxygen 

in nitrate; and 7 radioactive constituents, including carbon-14 

(table 3H); 5 dissolved noble gases, tritium, and helium 

stable isotope ratios (table 3I). The methods used for sample 

collection and analysis are described in the Appendix section 

“Sample Collection and Analysis.” 

Data Reporting 

The methods and conventions used for reporting the data 

are described in the Appendix. Seven constituents analyzed in 

this study were measured by more than one analytical schedule or more than one laboratory, and all results are reported for 

these constituents. 

Quality-Assurance 

The quality-assurance and quality-control procedures 

used for this study followed the protocols used by the USGS 

NAWQA program (Koterba and others, 1995) and described 

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

variously dated). The quality-assurance plan followed by 

the USGS National Water Quality Laboratory (NWQL), the 

primary laboratory used to analyze samples for this study, is 

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

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

include: source-solution blanks, field blanks, replicates, and 

matrix and surrogate spikes. QC samples were collected to 

evaluate potential contamination as well as bias and variability of the data that may have resulted from sample collection, 

processing, storage, transportation, and laboratory analysis. 

Quality-control procedures and quality-control results are 

described in the Appendix section “Quality Assurance.” 
10 Groundwater Quality Data in the Mojave Study Unit, 2008: Results from the California GAMA Program 

Water-Quality Results 

Quality-Control Results 

Results of quality-control analyses (blanks, replicates, 

matrix spikes, and surrogates) were used to evaluate the 

quality of the data for the groundwater samples. On the basis 

of detections in field blanks collected for this and previous 

GAMA study units, detections reported by the laboratory for 

one organic compound (DOC) was considered suspect and 

therefore was removed from the set of groundwater quality 

data presented in this report (see table A3 and additional discussion in Appendix). Results from the replicates confirm that 

the procedures used to collect and analyze the samples were 

consistent. Ninety-nine percent of the replicate pairs for constituents detected in samples had variability within acceptable 

limits; additional discussion can be found in the Appendix. 

Median matrix-spike recoveries for 31 of the 150 organic 

constituents analyzed were lower than the acceptable limits 

(table 3B), which may indicate that these constituents might 

not have been detected in some samples if they were 

present in the samples at concentrations near the LRLs. 

The quality-control results are described in the Appendix

section “Quality-Control Results.” 

Comparison Thresholds 

Concentrations of constituents detected in groundwater 

samples were compared with CDPH and USEPA regulatory 

and non regulatory drinking-water health-based thresholds 

and thresholds established for aesthetic purposes (California 

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

Protection Agency, 2008a,b,c). The chemical data presented 

in this report are meant to characterize the quality of the 

untreated groundwater resources within MOJO, and are not 

intended to represent the treated drinking water delivered to 

consumers by water purveyors. The chemical composition of 

treated drinking water may differ from untreated groundwater 

because treated drinking water may be subjected to disinfection, filtration, mixing with other waters, and exposure to the 

atmosphere prior to its delivery to consumers. Comparisons 

of untreated groundwater 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. 

MCLs established by the USEPA are the minimum 

standards with which states are required to comply, 

and individual states may choose to set more stringent 

standards. CDPH has established MCLs for additional 

constituents not regulated by the USEPA, as well as 

lowered the threshold concentration for a number of 

constituents with MCLs established by the USEPA. In 

this report, a threshold set by the USEPA and adopted 

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

that is more stringent than the MCL-US is labeled 

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

detected at concentrations greater than an MCL-US 

or MCL-CA thresholds in samples collected for the 

GAMA Priority Basin Project, but these detections do 

not constitute violations of CDPH regulations. 

•	 AL—Action Level. Legally enforceable standards that 

apply to public water systems and are designed to protect public health by limiting the levels of copper and 

lead in drinking water. Detections of copper or lead 

above the action-level thresholds trigger requirements 

for mandatory water treatment to reduce the corrosiveness of water to water pipes. The action levels established by the USEPA and CDPH are the same, thus, the 

thresholds are labeled “AL-US” in this report. 

•	 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 (SMCLCA) 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—Lifetime Health Advisory Level. The maximum 

concentration of a constituent at which its presence 

in drinking water is not expected to cause any adverse 

carcinogenic effects for a lifetime of exposure. 

HALs are established by the USEPA (HAL-US) 

and are calculated assuming consumption of 2 liters 

(2.1 quarts) of water per day over a 70-year lifetime by 

a 70-kilogram (154-pound) adult and that 20 percent of 

a person’s exposure comes from drinking water. 

• RSD5—Risk-Specific Dose. The concentration of 

a constituent in drinking water corresponding to an 

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

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

RSD5s are calculated by dividing the 10-4 cancer risk 

concentration established by the USEPA by 10 

(RSD5-US). 
 

 

Water-Quality Results 11 

For constituents with MCLs, detections in groundwater 

samples were compared to the MCL-US or MCL-CA. 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 groundwater 

samples were compared with both levels. The SMCL-US for 

these constituents corresponds to the recommended SMCLCA. Detected concentrations of constituents that lack an MCL 

or SMCL were compared to the NL-CA. For constituents that 

lack an MCL, SMCL, or NL-CA, detected concentrations were 

compared 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 if a constituent 

has more than one type of established threshold, using this 

hierarchy to select the comparison threshold will not necessarily result in selection of the threshold with the lowest concentration. For example, zinc has an SMCL-CA of 5,000 μg/L 

and a HAL-US of 2,000 μg/L, and the comparison threshold 

selected by this hierarchy is the SMCL-CA. The comparison 

thresholds used in this report are listed in tables 3A–I for all 

constituents and in tables 4–13 for constituents detected in 

groundwater samples from MOJO. Not all constituents analyzed for this study have established thresholds 

available. Detections of constituents at concentrations greater 

than the selected comparison threshold are marked with 

asterisks in tables 4–13. 

Groundwater-Quality Data 

Results from analyses of untreated groundwater samples 

from MOJO are presented in tables 4–13. Groundwater 

samples collected in MOJO were analyzed for up to 234 

constituents, and 144 of those constituents were not detected 

in any of the samples (tables 3A–I). The results tables present 

only the constituents that were detected (with the exception of 

table 10); all results tables list only the wells that had at least 

one constituent detected. For constituent classes that were 

analyzed at all of the grid wells, the tables include the number 

of wells at which each analyte was detected, the frequency 

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

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

well. Results from the understanding wells are presented in 

the tables, but these results were excluded from the detection 

frequency calculations to avoid statistically over-representing 

the areas in the vicinity of the understanding wells. 

Table 4 includes water-quality indicators (field parameters) measured in the field and at the NWQL. Tables 5–13 

present the results of groundwater analyses organized by 

compound classes: 

•	 Organic constituents 

• Volatile organic compounds (VOCs) (table 5) 

• Pesticides and pesticide degradates (table 6) 

•	 Constituents of special interest (table 7) 

•	 Inorganic constituents 

•	 Nutrients and dissolved organic carbon (DOC) 

(table 8) 

•	 Major and minor ions, silica, and total dissolved 

solids (TDS) (table 9) 

•	 Trace elements (table 10) 

•	 Arsenic, chromium, and iron speciation (table 11) 

•	 Isotopic tracers (table 12) 

•	 Radioactive constituents (tables 13A,B,C) 

•	 Results for pharmaceutical compounds are not presented in the MOJO data report; they will be included 

in a subsequent publication. In addition, as of the publishing date of this data report, the samples collected in 

MOJO for noble gases and tritium and helium isotope 

ratios were not available from LLNL; therefore, these 

results are not included at this time. 

Water-Quality Indicators (Field Parameters) 

Field and laboratory measurements of dissolved oxygen, 

pH, specific conductance, alkalinity, and associated parameters 

(turbidity, water temperature, bicarbonate, and carbonate) are 

presented in table 4. Alkalinity, dissolved oxygen, bicarbonate, 

and carbonate are used as indicators of natural processes that 

affect water chemistry. Specific conductance is the measure 

of electrical conductivity of the water, and is proportional 

to the amount of total dissolved solids (TDS) in the water. 

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

Nineteen percent of MOJO’s grid wells (10 of 52 wells) had 

field specific conductance values above the recommended 

SMCL-CA of 900 μS/cm; five of these grid wells also were 

above the upper threshold of 1,600 μS/cm. Two understanding 

wells (of seven sampled) had field specific conductance values 

above the SMCL-CA upper threshold of 1,600 μS/cm. Eleven 

grid wells (of 52 sampled) and 2 understanding wells (of 7 

sampled) had pH values outside of the SMCL-US range for 

pH (table 4). (Laboratory pH values may be dissimilar to field 

pH values because the pH of groundwater may change upon 

exposure to the atmosphere [see Appendix]). 

Organic Constituents 

Volatile organic compounds (VOCs) can be present in 

paints, solvents, fuels, fuel additives, refrigerants, fumigants, 

and disinfected water, and are characterized by their tendency 

to evaporate. VOCs generally persist longer in groundwater 

than in surface water because groundwater is isolated from the 

atmosphere. 
 

 

12 Groundwater Quality Data in the Mojave Study Unit, 2008: Results from the California GAMA Program 

Of the 85 VOCs analyzed in MOJO, 20 were detected in 

groundwater samples; all detections were below health-based 

thresholds (table 5). Chloroform, a byproduct of drinkingwater disinfection, and 1,2,4-trimethylbenzene, a gasoline 

hydrocarbon, were detected in more than 10 percent of the 

grid well samples. One or more VOCs were detected in 21 out 

of the 52 grid wells and in 5 of the 7 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. Of the 

63 pesticides and pesticide degradates analyzed in the MOJO 

study, 10 pesticides were detected in groundwater samples; all 

detections were well below health-based thresholds (table 6). 

The herbicides simazine, and deethylatrazine (a degradate of 

atrazine), were detected in more than or 10 percent of the grid 

well samples. These two compounds are among the nation’s 

most commonly detected pesticide compounds in groundwater 

(Gilliom and others, 2006). One or more pesticide compounds 

were detected in 12 out of the 52 grid wells and in 3 of the 7 

understanding wells. 

Constituents of Special Interest 

Perchlorate and NDMA are constituents of special interest in California because they may adversely affect water quality and recently have been found in water supplies (California 

Department of Public Health, 2008b). Perchlorate was analyzed for at all 59 wells in MOJO and was detected in approximately 63 percent of the grid wells (33 of 52 wells); however 

all of these detections were below the MCL–CA (table 7). 

NDMA was analyzed for at the 24 slow wells (19 grid and 

5 understanding) in MOJO, and was detected in one slow grid 

well (MOJO-42), at a level above the NL–CA threshold of 

0.010 μg/L. 

Inorganic Constituents 

Unlike the organic constituents and the constituents of 

special interest, most of the inorganic constituents are naturally present in groundwater, although their concentrations 

may be influenced by human activities. Inorganic constituents, 

including arsenic, chromium, and iron species were sampled 

on the slow sampling schedule in MOJO (24 of 59 wells). Dissolved organic carbon was sampled only on the fast plus DOC 

and the slow plus DOC sampling schedules (16 of 59 wells). 

Twenty-one of 24 trace elements analyzed in this study 

have regulatory or non-regulatory health-based thresholds. Of 

the 17 trace elements with health-based thresholds, 1 trace element (thallium) was not detected, and most detections of the 

other 16 trace elements were below health-based thresholds 

(table 10). In MOJO, samples from 6 grid wells (of 19 sampled) and 3 understanding wells (of 5 sampled) had arsenic 

and 1 understanding well was found to have uranium at concentrations above their respective MCL-US thresholds. Two 

out of the 19 grid wells sampled had concentrations of boron 

above the NL-CA. Additionally, 1 grid well (of 19 sampled) 

and 1 understanding well (of 5 sampled) were found to have 

concentrations of vanadium above the NL-CA. A single grid 

well (of 19 sampled) had molybdenum and strontium above 

their respective HAL-US thresholds (table 10). 

Nutrients (nitrogen and phosphorus) and dissolved 

organic carbon (DOC) present in groundwater can affect 

biological activity in aquifers and in surface-water bodies 

that receive groundwater discharge. Inorganic nitrogen may 

be present in the form of ammonia, nitrite, or nitrate depending on the oxidation-reduction state of the groundwater. High 

concentrations of nitrate can adversely affect human health, 

particularly the health of infants. All concentrations of nitrate, 

nitrite, ammonia, and DOC measured in samples from MOJO 

wells were below health-based thresholds (table 8). It should 

be noted that the nutrients sample for MOJO-49 exceeded 

maximum allowable temperature at the NWQL before sample 

analysis; footnotes have been added in NWIS and table 8 to 

reflect.

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

content, and levels of certain trace elements in groundwater 

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 directly 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.

 Concentrations of chloride measured in samples from 

the MOJO wells were below the recommended SMCL-CA 

(table 9), with the exception of one grid well. Four grid wells 

(of 19 sampled) and 1 understanding well (of 5 sampled) had 

sulfate concentration above the recommended SMCL-CA, but 

only one of these samples (a grid well), was above the upper 

SMCL-CA of 500 mg/L. Four grid wells (of 19 sampled) and 

3 understanding wells (of 5 sampled) had TDS values above 

the recommended SMCL-CA, and 3 of the grid and 1 understanding well also were above the upper SMCL-CA. Fluoride 

is the only major ion with a MCL-CA threshold (2 μg/L); it 

was detected at concentrations above this threshold in 1 of the 

19 grid and 2 of the 5 understanding samples. 

Iron and manganese are trace elements whose concentrations are affected by the oxidation-reduction state of the 

groundwater. Precipitation of minerals containing iron or 

manganese may cause orange, brown, or black staining of 

surfaces. Iron was detected in 7 of the 19 grid and 2 of the 5 

understanding well samples, and none of these concentrations 

were above the SMCL-CA. Concentration of manganese in 

MOJO wells also were low, with only a single understanding 

well (of 5 sampled) having a concentration above the 

SMCL-CA of 50 μg/L (table 10). 
 

 

13 

Arsenic, chromium, and iron occur in different species 

depending on the oxidation-reduction state of the groundwater. 

The oxidized and reduced species have different solubilities in groundwater 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. Concentrations 

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

either the reduced or the oxidized species of each element are 

reported in table 11. The concentration of the other species 

can be calculated by difference. The concentrations of arsenic, 

chromium, and iron reported in table 11 may be different than 

those reported in table 10 because different analytical methods 

were used (see Appendix). The concentrations reported in table 

10 are considered to be more accurate and precise. 

Isotopic Tracers and Noble Gases 

The isotopic ratios of oxygen and hydrogen in water, 

the tritium and carbon-14 activities, and the concentrations 

of dissolved noble gases may be used as tracers of hydrologic processes. The isotopic ratios of hydrogen and oxygen 

in water (table 12) aid in the interpretation of the sources of 

groundwater recharge. These stable isotopic ratios reflect the 

altitude, latitude, and temperature of precipitation and also 

the extent of evaporation of the water in surface water bodies 

or soils prior to infiltration into the aquifer. Concentrations 

of dissolved noble gases are used to estimate the conditions 

of groundwater recharge, particularly the temperature of the 

recharge water. Noble gas analyses were not completed in 

time for inclusion in this report; results will be presented in a 

subsequent publication. 

Additional stable-isotope ratios of nitrogen and oxygen 

of dissolved nitrate (table 12) can be used to aid in interpretation of sources and processes affecting this solute in aquifers. 

Tritium activities (table 12) and carbon-14 activities 

(table 12), and helium isotope ratios also provide information 

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

is a short-lived radioactive isotope of hydrogen that is incorporated into the water molecule. Low levels of tritium are 

produced continuously by interaction of cosmic radiation with 

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

produced as a result atmospheric testing of nuclear weapons 

between 1952 and 1963. Thus, concentrations of tritium above 

background generally indicate the presence of water recharged 

since the early 1950s. Helium isotope ratios are used in 

conjunction with tritium concentrations to estimate ages for 

young groundwater. Helium isotope ratio analyses were not 

completed in time for inclusion in this report; results will be 

presented in a subsequent publication. 

Carbon-14 (table 12) is a radioactive isotope of carbon. 

Low levels of carbon-14 are produced continuously by interaction of cosmic radiation with the Earth’s atmosphere, and 

incorporated into atmospheric carbon dioxide. Carbon dioxide 

Water-Quality Results 

dissolves in precipitation, surface water, and groundwater 

exposed to the atmosphere, thereby entering the hydrologic 

cycle. Because carbon-14 decays with a half-life of approximately 5,700 years, low activities of carbon-14, relative to 

modern values, generally indicate a presence of groundwater 

that is several thousand years old. 

Of the isotopic tracer constituents analyzed for this study, 

tritium is the only one with a health-based threshold. All 

measured tritium activities in samples from MOJO wells were 

about one one-thousandth of the MCL-CA (table 12). 

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 groundwater comes from 

decay of naturally occurring isotopes of uranium and thorium 

that are present in minerals in the sediments or fractured rocks 

of the 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 or 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 presence of radioactive constituents. Activity of 

radioactive constituents in groundwater 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. 

The 24 MOJO slow samples were analyzed for radioactive constituents and all had activities of radium-226, 

radium-228 and of gross beta radioactivity less than established health-based thresholds (tables 13A,B). Gross alpha 

radioactivity (30-day count and 72-hour count) exceeded the 

MCL-US of 15 pCi/L in 1 grid well (of 19 sampled) and 1 

understanding well (of 5 sampled) (table 13B). Activities of 

radon-222 in samples from 17 grid wells (of 19 sampled) and 

3 understanding wells (of 5 sampled) were above the proposed 

MCL-US of 300 pCi/L, although no samples had activities that 

were above the proposed alternative MCL-US of 4,000 pCi/L 

(table 13C). The proposed alternative MCL-US will apply if 

the state or local water agency has an approved multimedia 

mitigation program to address radon levels in indoor air (U.S. 

Environmental Protection Agency, 1999). 
14 Groundwater Quality Data in the Mojave Study Unit, 2008: Results from the California GAMA Program 

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 groundwater quality. Water-quality data contained in the CDPH databases will be compiled, 

evaluated, and used in combination with the data that are 

presented in this report; the results of these future efforts will 

appear in one or more subsequent reports. 

Summary 

Groundwater quality in the approximately 1,500 squaremile (mi2

) Mojave study unit (MOJO) was investigated from 

February to April 2008 as part of the Priority Basin Project 

of the Groundwater 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 USGS and the SWRCB in response to 

the Groundwater Quality Monitoring Act of 2001 (Belitz and 

others, 2003; State Water Resources Control Board, 2003). 

The project is a comprehensive assessment of statewide 

groundwater quality designed to identify and characterize risks 

to groundwater resources, and to increase the availability of 

information about groundwater quality to the public. MOJO 

was the 23rd of 37 study units to be sampled as part of the 

GAMA Priority Basin Project. 

MOJO is located in the Desert hydrogeologic province 

and includes four groundwater basins defined by the California Department of Water Resources (California Department 

of Water Resources, 2004a,b,c,d). The MOJO study included 

assessment of the groundwater quality from 59 wells in San 

Bernardino and Los Angeles Counties. Fifty-two of the wells 

were selected using a randomized grid approach to achieve 

statistically unbiased representation of groundwater used 

for public drinking-water supplies. Seven of the wells were 

selected to provide additional sampling density to aid in 

understanding processes affecting groundwater quality. 

Groundwater samples were analyzed for volatile organic 

compounds (VOCs), pesticides and pesticide degradates, 

pharmaceutical compounds, perchlorate, NDMA, nutrients, 

dissolved organic carbon (DOC), major and minor ions, silica, 

total dissolved solids (TDS), trace elements, and radioactivity (gross alpha and gross beta radiation, radium isotopes, and 

radon-222). Naturally occurring isotopes (stable isotopes of 

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

oxygen in nitrate, and activities of tritium and carbon-14) and 

dissolved noble gases also were measured to provide a data 

set that will be used to help interpret the sources and ages of 

the sampled groundwater. In total, over 230 constituents and 

water-quality indicators (field parameters) were investigated 

for this study. This report describes the sampling, analytical, 

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

the results of the chemical analyses made of the groundwater 

samples collected from February to April 2008. 

Three types of quality-control samples (blanks, replicates, 

and matrix spikes) each were collected at approximately 5–8 

percent of the wells, and the results for these samples were 

used to evaluate the quality of the data for the groundwater 

samples. Field blanks rarely contained detectable concentrations of any constituent, suggesting that contamination was 

not a significant source of bias in the data for the groundwater 

samples. Differences between replicate samples generally 

were within acceptable ranges, indicating acceptable analytical 

reproducibility. Matrix spike recoveries were within acceptable ranges for most compounds. 

This study did not attempt to evaluate the quality of water 

delivered to consumers; after withdrawal from the ground, 

water typically is treated, disinfected, and blended with 

other waters to maintain acceptable water quality. Regulatory thresholds apply to treated water that is served to the 

consumer, not to untreated groundwater. However, to provide 

some context for the results, concentrations of constituents 

measured in the untreated groundwater 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) and nonregulatory thresholds established for aesthetic and technical 

concerns by CDPH. 

All detections of VOCs and pesticides in samples from 

all 59 MOJO grid and understanding wells were below 

health-based thresholds and all of the detections of organic 

compounds (constituents of special interest) from MOJO wells 

were below health-based thresholds, with the exception of a 

single grid well detection of NDMA above the NL-CA. 

Trace elements and radioactive constituents were 

sampled for at 19 MOJO grid wells and most detections were 

below health-based thresholds. Exceptions include; six detections of arsenic above the USEPA maximum contaminant 

level (MCL-US), two detections of boron and one detection 

of vanadium above the NL-CA, one detection each of molybdenum and strontium that were above the USEPA lifetime 

health advisory level (HAL-US), and one detection of fluoride just above the MCL-CA of 2 μg/L. Most detections of 

radioactive constituents in the MOJO grid wells were below 

health-based thresholds, with the exception of one detection 

of gross alpha radioactivity (72-hour count and 30-day count) 

above the MCL-CA, and 17 grid wells (of 19 sampled) having 

activities of radon-222 above the proposed lower MCL-US of 

300 pCi/L, but all were below the proposed alternative 

MCL-US of 4,000 pCi/L. 
 15 

All of the samples collected from the 19 MOJO grid 

wells for trace elements and most of the samples for major 

ions and total dissolved solids (TDS) had concentrations measured below the non-enforceable thresholds set for aesthetic 

concerns. Four grid wells had TDS concentrations above 

the SMCL-CA recommended lower threshold and three of 

these wells also had concentrations above the upper threshold (SMCL-CA threshold for total dissolved solids (TDS) 

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

1,000 mg/L). Sulfate was measured at concentrations above 

the recommended SMCL-CA threshold in 3 grid wells (of 

19 sampled). One grid well had sulfate and one grid well had 

chloride detected at concentrations above the upper threshold 

(both sulfate and chloride have a SMCL-CA recommended 

threshold value of 250 mg/L, an upper value of 500 mg/L). 

Eleven grid wells (of 52 sampled) had pH values outside of 

the SMCL-US range for pH. 

Results from MOJO’s seven understanding wells showed 

three detections of arsenic and one detection of uranium that 

were above the USEPA maximum contaminant levels (MCLUS). Two understanding wells (of seven sampled) had fluoride 

concentrations above the MCL-CA, and one had vanadium 

above the NL-CA. A single understanding well had a detection of manganese above the SMCL-CA of 50 μg/L. One 

understanding well had gross alpha radioactivity (72-hour 

count and 30-day count) above the MCL-CA of 15 pCi/L and 

three understanding wells (of seven sampled) had activities of 

radon-222 above the proposed lower MCL-US, but all were 

below the alternative MCL-US of 4,000 pCi/L. Two understanding wells (of seven sampled) had pH values outside of 

the SMCL-US range for pH. 

Acknowledgments 

The authors thank the following cooperators for their 

support: the State Water Resources Control Board, California 

Department of Public Health, California Department of Water 

Resources, and Lawrence Livermore National Laboratory. We 

especially thank the well owners and water purveyors for their 

generosity in allowing the USGS to collect samples from their 

wells. Two reviewers, Jan Stepek (SWRCB) and Joe Montrella 

(USGS) provided comments to improve this work. Funding for this work was provided by State bonds authorized by 

Proposition 50 and administered by the SWRCB. 

References Cited 

American Public Health Association, 1998, Standard methods 

for the examination of water and wastewater (20th ed.): 

Washington, D.C., American Public Health Association, 

American Water Works Association, and Water Environment Federation, p. 3-37–3-43. 

References Cited 

American Society for Testing and Materials, 1998, Annual 

book of ASTM standards—water and environmental technology: Philadelphia, Pennsylvania, American Society for 

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

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

chromium: U.S. Geological Survey Water-Resources Investigations Report 03-4018, 17 p. 

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

chromium: Talanta, v. 61, p. 305–313. 

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

Bryant, and Johnson, Tyler, 2003, Framework for a groundwater quality monitoring and assessment program for California: U.S. Geological Survey Water-Resources Investigations Report 03-4166, 78 p. 

Bennett, G.L., V, Belitz, Kenneth, and Milby Dawson, B.J., 

2006, California GAMA Program—Groundwater quality 

data in the northern San Joaquin basin study unit, 2005: 

U.S. Geological Survey Data-Series 196, 122 p. 

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

the U.S. Geological Survey National Water-Quality Laboratory—Determination of dissolved organic carbon by UVpromoted persulfate oxidation and infrared spectrometry: 

U.S. Geological Survey Open-File Report 92-480, 12 p. 

Burton, C.A., and Belitz, Kenneth, 2008, Groundwater quality 

data in the southeast San Joaquin Valley, 2005–2006— 

Results from the California GAMA Program: U.S. Geological Survey Data-Series 351, 103 p. 

California Department of Public Health, 2008a, California 

drinking water-related laws: Drinking water-related regulations (Title 22) (pdf document), accessed April 17, 2008, at 

URL http://www.cdph.ca.gov/certlic/drinkingwater/Pages/

Lawbook.aspx

California Department of Public Health, 2008b, Drinking 

water notification levels: Notification levels (pdf document), 

accessed April 17, 2008, at URL http://www.cdph.ca.gov/

certlic/drinkingwater/Pages/NotificationLevels.aspx 

California Department of Water Resources, 2003, California’s 

groundwater: California Department of Water Resources 

Bulletin 118, 246 p., accessed June 16, 2008, at http://www.

groundwater.water.ca.gov/bulletin118 

California Department of Water Resources, 2004a, California’s 

groundwater: Individual basin descriptions, Lower Mojave 

River Valley: California Department of Water Resources 

Bulletin 118, accessed June 16, 2008, at http://www.dpla2. 

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

pdfs_desc/6-40.pdf 
16 Groundwater Quality Data in the Mojave Study Unit, 2008: Results from the California GAMA Program 

California Department of Water Resources, 2004b, California’s groundwater: Individual basin descriptions, Middle 

Mojave River Valley: California Department of Water 

Resources Bulletin 118, accessed June 16, 2008, at http://

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

bulletin118/basins/pdfs_desc/6-41.pdf 

California Department of Water Resources, 2004c, California’s 

groundwater: Individual basin descriptions, Upper Mojave 

River Valley: California Department of Water Resources 

Bulletin 118, accessed June 16, 2008, at http://www.dpla2. 

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

pdfs_desc/6-42.pdf 

California Department of Water Resources, 2004d, California’s groundwater: Individual basin descriptions, El Mirage 

River Valley: California Department of Water Resources 

Bulletin 118, accessed June 16, 2008, at http://www.dpla2. 

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

pdfs_desc/6-43.pdf 

Childress, C.J.O., Foreman, W.T., Connor, B.F., and Maloney, T.J., 1999, New reporting procedures based on longterm method-detection levels and some considerations for 

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

Geological Survey National Water Quality Laboratory: U.S. 

Geological Survey Open-File Report 99-193, 19 p. 

Connor, B.F., Rose, D.L., Noriega, M.C., Murtagh, L.K., and 

Abney, S.R., 1998, Methods of analysis by the U.S. Geological Survey National Water Quality Laboratory—Determination of 86 volatile organic compounds in water by gas 

chromatography/mass spectrometry, including detections 

less than reporting limits: U.S. Geological Survey OpenFile Report 97-829, 78 p. 

Coplen, T.B., Wildman, J.D., and Chen, J., 1991, Improvements in the gaseous hydrogen-water equilibrium technique 

for hydrogen isotope analysis: Analytical Chemistry, v. 63, 

p. 910–912. 

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

oxygen isotopic abundances: Pure and Applied Chemistry, 

v. 66, p. 273–276. 

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

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

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

P., 2002, Compilation of minimum and maximum isotope 

ratios of selected elements in naturally occurring terrestrial 

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

Dawson, B.J., Bennett, G.L., V, and Belitz, Kenneth, 2008, 

California GAMA Program: Groundwater quality data in 

the Southern Sacramento Valley study unit, California, 

2005: U.S. Geological Survey Data-Series DS 285, 93 p. 

Densmore, J.N., Belitz, K., Wright, M.T., Dawson, B.J., 

Johnson, T., and Hudson, G.B., 2005, Evaluation of Volatile 

Organic Compounds in Two Mojave Desert Basins-Mojave 

River and Antelope Valley-in San Bernardino, Los Angeles, 

and Kern Counties, California, June-October 2002 : U.S. 

Geological Survey Scientific Investigations Report 2004–

5248, 40 p. 

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

background corrections for accelerator mass spectrometry 

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

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

of California: American Chemical Society ACS Symposium 

Series, v. 868, p. 235–245. 

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

of water from natural sources: Geochimica et Cosmochimica Acta, v. 4, p. 213–224. 

Faires, L.M., 1993, Methods of analysis by the U.S. Geological Survey National Water Quality Laboratory—determination of metals in water by inductively coupled plasma-mass 

spectrometry: U.S. Geological Survey Open-File Report 

92–634, 28 p. 

Ferrari, M.J., Fram, M.S., and Belitz, Kenneth, 2008, Groundwater quality in the central Sierra study unit, California, 

2006: Results from the California GAMA program: U.S. 

Geological Survey Data-Series 335, 60 p. 

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

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

Wiley & Sons, 3168 p., accessed on June 3, 2008, at http://

ie.lbl.gov/toipdf/toi20.pdf 

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

determination of inorganic substances in water and fluvial 

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

Fishman, M.J., 1993, Methods of analysis by the U.S. Geological Survey National Water Quality Laboratory—determination of inorganic and organic constituents in water and 

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

93-125, 217 p. 

Fram, M.S. and Belitz, Kenneth, 2007, Groundwater quality 

data in the Southern Sierra Study Unit, 2006: Results from 

the California GAMA Program: U.S. Geological Survey 

Data-Series 258, 78 p. 
 17 

Furlong, E.T., Werner, S.L., Anderson, B.D., and Cahill, J.D., 

2008, Methods of analysis by the U.S. Geological Survey 

National Water Quality Laboratory—Determination of 

human-health pharmaceuticals in filtered water by chemically modified styrene-divinylbenzene resin-based soldphase extraction and high-performance liquid chromatography/mass spectrometry: U.S. Geological Survey Techniques 

and Methods, book 5, chap. A9, 56 p. 

Garbarino, J.R., 1999, Methods of analysis by the U.S. Geological Survey National Water Quality Laboratory—Determination of dissolved arsenic, boron, lithium, selenium, 

strontium, thalium, and vanadium using inductively coupled 

plasma-mass spectrometry: U.S. Geological Survey OpenFile Report 99–093, 31 p. 

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

by the U.S. Geological Survey National Water Quality Laboratory—Determination of organic plus inorganic mercury 

in filtered and unfiltered natural water with cold vapor—

atomic fluorescence spectrometry: U.S. Geological Survey 

Water-Resources Investigations Report 01–4132, 16 p. 

Garbarino, J.R., Kanagy, J.R., and Cree, M.E., 2006, Determination of elements in natural-water, biota, sediment, and soil 

samples using collision/reaction cell inductively coupled 

plasma-mass spectrometry: U.S. Geological Survey Techniques and Methods, Book 5, Chap. B1, 88 p. 

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

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

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

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

streams and groundwater, 1992–2001: U.S. Geological 

Survey Circular 1291, 172 p. 

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

potentiometric titration. Part II. Analyst, v. 77, 661 p. 

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

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

Hahn, G.J. and Meeker W.Q., 1991, Statistical intervals: a 

guide for practitioners: New York, John Wiley & Sons, 

392 p. 

Hamlin, S.N., Belitz, Kenneth, Kraja, Sarah, and Dawson, 

B.J., 2002, Groundwater quality in the Santa Ana watershed, California: Overview and data summary: U.S. 

Geological Survey Water-Resources Investigations Report 

02–4243, 137 p. 

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

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

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

1268, 46 p. 

References Cited 

Izbicki, J.A. and Michel, R.L., 2003, Movement and age of 

groundwater in the western part of the Mojave Desert, 

Southern California, USA: U.S. Geological Survey WaterResources Investigations Report 03-4314, 17 p. 

Izbicki, J.A., Stamos, C.L., Nishikawa, Tracy, and Martin, 

Peter, 2004, Comparison of groundwater flow model 

particle-tracking results and isotopic data in the Mojave 

River groundwater basin, southern California, USA: Journal 

of Hydrology, v. 292, p. 30-47. 

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

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

frontiers in dating of geological, paleoclimatic, and anthropological applications using accelerator mass spectrometric 

measurements of 14C and 10Be in diverse samples: Global 

and Planetary Change, v. 41, p. 309–323. 

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

Zaugg, S.D., Barber, L.B., and Buxton, H.T., 2002, Pharmaceuticals, hormones and other organic wastewater contaminants in U.S. streams, 1999–2000: Environmental Science 

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

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

Groundwater data-collection protocols and procedures for 

the National Water-Quality Assessment Program—Collection and documentation of water-quality samples and related 

data: U.S. Geological Survey Open-File Report 95–399, 113 

p. 

Kreiger, H.L. and Whittaker, E.L., 1980, Prescribed procedures for measurement of radioactivity in drinking water: 

U.S. Environmental Protection Agency EPA-600-4-80-032, 

142 p. Available from the National Technical Information 

Service (http://www.ntis.gov) as PB80-224744. 

Kulongoski, J.T. and Belitz, Kenneth, 2004, Groundwater 

ambient monitoring and assessment program: U.S. Geological Survey Fact Sheet 2004–3088, 2 p. 

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

Groundwater quality data in the North San Francisco Bay 

Hydrogeologic provinces, California, 2004: Results from 

the California Groundwater Ambient Monitoring and 

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

Data-Series 167, 100 p. 

Kulongoski, J.T., and Belitz, Kenneth, 2007, Groundwater 

quality data in the Monterey Bay and Salinas Valley Basins, 

California, 2005—Results from the California GAMA Program: U.S. Geological Survey Data-Series 258, 84 p. 

Land, M.K. and Belitz, Kenneth, 2008, Groundwater quality 

data in the San Fernando–San Gabriel study unit, 2005— 

Results from the California GAMA Program: U.S. Geological Survey Data-Series 356, 84 p. 
18 Groundwater Quality Data in the Mojave Study Unit, 2008: Results from the California GAMA Program 

Landon, M.K. and Belitz, Kenneth, 2008, Groundwater quality data in the Central Eastside San Joaquin Basin 2006: 

Results from the California GAMA Program: U.S. Geological Survey Data-Series 325, 88 p. 

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

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

Survey Techniques of Water-Resources Investigations, book 

9, chap. A2, accessed June 4, 2008, at http://pubs.water.

usgs.gov/twri9A2/ 

Lewis, M.E., 2006, Dissolved oxygen (ver. 2.1): U.S. Geological Survey Techniques of Water-Resources Investigations, 

book 9, chap. A6.2, accessed June 4, 2008, at http://pubs.

water.usgs.gov/twri9A6.2/ 

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

Determination of low concentrations of acetochlor in water 

by automated solid-phase extraction and gas chromatography with mass selective detection: Journal of AOAC 

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

Lines, G.C., 1996, Groundwater and surface-water relations 

along the Mojave River, Southern California: U.S. Geological Survey Water-Resources Investigations Report 95-4189, 

43 p. 

Madsen, J.E., Sandstrom, M.W., and Zaugg, S.D., 2003, Methods of analysis by the U.S. Geological Survey National 

Water Quality Laboratory—A method supplement for the 

determination of fipronil and degradates in water by gas 

chromatography/mass spectrometry: U.S. Geological Survey Open-File Report 02–462, 11 p. 

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

Geological Survey National Water Quality Laboratory: U.S. 

Geological Survey Open-File Report 2005–1263, accessed 

June 4, 2008, at http://pubs.usgs.gov/of/2005/1263/pdf/ 

OFR2005-1263.pdf 

Mathany, T.M., Land, Michael, and Belitz, Kenneth, 2008, 

Groundwater 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. 

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

Metal interferences and their removal prior to the determination of As(T) and As(III) in acid mine waters by hydride 

generation atomic absorption spectrometry: U.S. Geological 

Survey Water-Resources Investigations Report 03-4117, 

14 p. 

McCurdy, D.E., Garbarino, J.R., and Mullin, A.H., 2008, 

Interpreting and reporting radiological water-quality data: 

U.S. Geological Survey Techniques and Methods, book 5, 

chap. B6, 33 p. 

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

Survey National Water Quality Laboratory—Determination 

of chromium in water by graphite furnace atomic absorption spectrophotometry: U.S. Geological Survey Open-File 

Report 93–449, 16 p. 

Montrella, Joseph, and Belitz, Kenneth, 2009, Groundwater 

quality data in the Santa Clara River Valley study unit, 

2007—Results from the California GAMA Program: U.S. 

Geological Survey Data-Series 408, 84 p. 

Moran, J.E., Hudson, G.B., Eaton, G.F., and Leif, R., 2002, A 

contamination vulnerability assessment for the Livermore– 

Amador and Niles Cone Groundwater Basins: UCRLAR-148831, 25 p. 

Olsen, L.D., Fram, M.S., and Belitz, Kenneth, in review, 

Review of trace element field blank data collected for the 

California Groundwater Ambient Monitoring and Assessment (GAMA) Program, May 2004—January 2008: U.S. 

Geological Survey Scientific Investigations Report XXXXXX

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

by the U.S. Geological Survey National Water Quality 

Laboratory—Evaluation of alkaline persulfate digestion 

as an alternative to Kjeldahl digestion for determination of 

total and dissolved nitrogen and phosphorous in water: U.S. 

Geological Survey Water-Resources Investigations Report 

03-4174, 33 p. 

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

Geological Survey National Water Quality Laboratory: U.S. 

Geological Survey Fact-Sheet 026–98, 4 p., http://pubs.

er.usgs.gov/usgspubs/fs/fs02698 

Plomley, J.B. , Koester, C.J., and March, R.E., 1994, Determination of NDMA in complex environmental matrices by 

quadrupole ion storage tandem mass spectrometry enhanced 

by unidirectional ion ejection: Analytical Chemistry, v. 66, 

no. 24, p. 4,437-4,443. 

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

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

Techniques of Water-Resources Investigations, book 9, 

chap. A6.3, accessed May 28, 2008, at http://pubs.water.

usgs.gov/twri9A6.3/ 

Ray, M.C., Kulongoski, J.T., and Belitz, Kenneth, 2009, 

Groundwater quality data in the San Francisco Bay study 

unit, 2007—Results from the California GAMA program: 

U.S. Geological Survey Data-Series 396, 92 p. 

Révész, K., and Casciotti, K., 2007, Determination of the 

δ(15N/14N) and δ(18O/16O) of Nitrate in Water: RSIL Lab 

Code 2900, chap. C17 of Révész, Kinga, and Coplen, Tyler 

B., eds., Methods of the Reston Stable Isotope Laboratory: 

Reston, Virginia, U.S. Geological Survey, Techniques and 

Methods, book 10, sec. C, chap. 17, 24 p. 
 19 

Sandstrom, M.W., Stroppel, M.E., Foreman, W.T., and Schroeder, M.P., 2001, Methods of analysis by the U.S. Geological Survey National Water Quality Laboratory—Determination of moderate-use pesticides and selected degradates in 

water by C-18 solid-phase extraction and gas chromatography/mass spectrometry: U.S. Geological Survey WaterResources Investigations Report 01-4098, 70 p. 

Schmitt, S.J., Fram, M.S., Milby Dawson, B.J., Belitz, K., 

2008, Groundwater quality data in the middle Sacramento 

Valley study unit, 2006—results from the California GAMA 

program: U.S. Geological Survey Data Series 385, 100 p. 

Scott, J.C., 1990, Computerized stratified random site selection approaches for design of a groundwater quality sampling network: U.S. Geological Survey Water-Resources 

Investigations Report 90-4101, 109 p. 

Shelton, J.L., Burow, K.R., Belitz, Kenneth, Dubrovsky, 

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

volatile organic compounds in active public supply wells as 

groundwater tracers in the Los Angeles physiographic basin, 

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

Investigations Report 01-4188, 29 p. 

Shelton, J.L., Pimentel, I., Fram, M.S., Belitz, Kenneth, 2008, 

Groundwater quality in the Kern County Subbasin Study 

Unit, 2006—Results from the California GAMA Program: 

U.S. Geological Survey Data-Series 337, 75 p. 

Stamos, C.L. and Predmore, S.K., 1995, Data and water-table 

map of the Mojave River Groundwater Basin, San Bernardino County, California, November 1992: U.S. Geological Survey Water-Resources Investigations Report 95-4148, 

1 sheet. 

State Water Resources Control Board, 2003, Report to the 

Governor and Legislature, A comprehensive groundwater 

quality monitoring program for California: Assembly Bill 

599 March 2003, 100 p. http://www.waterboards.ca.gov/

gama/docs/final_ab_599_rpt_to_legis_7_31_03.pdf 

Stookey, L.L., 1970, FerroZine—A new spectrophotometric 

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

Thatcher, L.L., Janzer, V.J., and Edwards, K.W., 1977, Methods for the determination of radioactive substances in water: 

U.S. Geological Survey Techniques of Water-Resources 

Investigations, book 5, chap. A5, 95 p. 

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

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

95–352, 120 p. 

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

McCleskey, R.B., 1998, New method for the direct determination of dissolved Fe(III) concentration in acid mine 

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

807–813. 

References Cited 

U.S. Environmental Protection Agency, 1989, Semivolatile 

organic compounds by isotope dilution GSMS (July 1989): 

U.S. Environmental Protection Agency, Washington, D.C., 

68 p. 

U.S. Environmental Protection Agency, 1999, National 

primary drinking water regulations, Radon-222: Federal 

Register, v. 64, no. 211, p. 59,245–59,294. 

U.S. Environmental Protection Agency, 2002, Guidelines for 

establishing procedures for the analysis of pollutants: U.S. 

Code of Federal Regulations, Title 40, 136 p. 

U.S. Environmental Protection Agency, 2005, Method 331.0— 

Determination of perchlorate in drinking water by liquid 

chromatography electrospray ionization mass spectrometry 

(Revision 1.0, January 2005): Office of Groundwater and 

Drinking Water, EPA Document # 815-R-05-007, 34 p., 

accessed August 8, 2008, at http://www.epa.gov/safewater/

methods/pdfs/methods/met331_0.pdf 

U.S. Environmental Protection Agency, 2008a, Drinking water 

contaminants, accessed April 2, 2008, at URL http://www.

epa.gov/safewater/contaminants/index.html

U.S. Environmental Protection Agency, 2008b, Drinking water 

health advisories: 2006 Drinking water standards and health 

advisory tables (pdf document), accessed April 2, 2008, at 

URL http://www.epa.gov/waterscience/criteria/drinking/

U.S. Environmental Protection Agency, 2008c, Proposed 

radon in drinking water rule, accessed May 15, 2008, at 

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

U.S. Geological Survey Branch of Quality Systems, 2008, 

Inorganic blind sample project, accessed August 9, 2008, at 

URL http://bqs.usgs.gov/bsp/

U.S. Geological Survey, variously dated, National field manual for the collection of water-quality data: U.S. Geological 

Survey Techniques of Water-Resources Investigations, book 

9, chap. A1–A9, accessed May 28, 2008, at http://water.

usgs.gov/owq/FieldManual/ 

Weiss, R.F., 1968, Piggyback sampler for dissolved gas studies on sealed water samples: Deep Sea Research, v. 15, p. 

721–735. 

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

Survey Techniques of Water-Resources Investigations, book 

9, chap. A6.1, accessed May 28, 2008, at http://pubs.water.

usgs.gov/twri9A6.1/ 

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

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

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

May 28, 2008, at http://pubs.water.usgs.gov/twri9A3/ 
20 Groundwater Quality Data in the Mojave Study Unit, 2008: Results from the California GAMA Program 

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

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

28, 2008, at http://pubs.water.usgs.gov/twri9A6.4/ 

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

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

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

accessed May 28, 2008, at http://pubs.water.usgs.gov/

twri9A6.0/ 

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

Collection of water samples: U.S. Geological Survey Techniques of Water-Resources Investigations, book 9, chap. 

A4, accessed May 28, 2008, at http://pubs.water.usgs.gov/

twri9A4/ 

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

Processing of water samples: U.S. Geological Survey Techniques of Water-Resources Investigations, book 9, chap. 

A5, accessed May 28, 2008, at http://pubs.water.usgs.gov/

twri9A5/ 

Wright, M.T., Belitz, Kenneth, and Burton, C.A., 2005, California GAMA program—Groundwater quality in the San 

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

Geological Survey Data-Series 129, 91 p. 

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

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

Survey National Water Quality Laboratory—Determination 

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

capillary-column gas chromatography/mass spectrometry: 

U.S. Geological Survey Open-File Report 95–181, 60 p. 
Tables 21
 

Tables 

22 Groundwater Quality Data in the Mojave Study Unit, 2008: Results from the California GAMA Program

Table 1. Well identification, sampling, and construction information for wells sampled for the Mojave Groundwater Ambient 

Monitoring and Assessment (GAMA) study, California, February to April 2008.—Continued

[Sampling schedules are described in table 2. Land-surface datum (LSD) is a datum plane that is approximately at land surface at each well. The elevation of 

the LSD is described in feet above the North American Vertical Datum 1988. GAMA well identification No.: MOJO, Mojave study unit grid well; MOJOU, 

Mojave study unit understanding well. Other abbreviations: DOC, dissolved organic carbon; ft, feet; LSD, land surface datum; NAVD 88, North American 

Vertical Datum 1988; na, not available]

GAMA well 

identification 

No.

Sampling information Elevation of LSD 

(ft above 

NAVD 88)

Construction information

Date sampled Sampling 

(mm/dd/yyyy) schedule Well type Well depth Top perforation (ft below LSD) (ft below LSD)

Bottom 

perforation 

(ft below LSD)

Grid wells

MOJO-01

MOJO-02

MOJO-03

MOJO-04

MOJO-05

MOJO-06

MOJO-07

MOJO-08

MOJO-09

MOJO-10

MOJO-11

MOJO-12

MOJO-13

MOJO-14

MOJO-15

MOJO-16

MOJO-17

MOJO-18

MOJO-19

MOJO-20

MOJO-21

MOJO-22

MOJO-23

MOJO-24

MOJO-25

MOJO-26

MOJO-27

MOJO-28

MOJO-29

MOJO-30

MOJO-31

MOJO-32

MOJO-33

MOJO-34

MOJO-35

MOJO-36

MOJO-37

MOJO-38

MOJO-39

MOJO-40

02/04/2008

02/04/2008

02/04/2008

02/05/2008

02/05/2008

02/06/2008

02/06/2008

02/06/2008

02/07/2008

02/07/2008

02/07/2008

02/11/2008

02/11/2008

02/12/2008

02/12/2008

02/13/2008

02/13/2008

02/14/2008

02/14/2008

02/25/2008

02/25/2008

02/26/2008

02/26/2008

02/26/2008

02/27/2008

02/27/2008

02/28/2008

03/03/2008

03/03/2008

03/04/2008

03/05/2008

03/06/2008

03/17/2008

03/17/2008

03/18/2008

03/19/2008

03/19/2008

03/19/2008

03/20/2008

03/24/2008

Fast plus DOC

Fast

Fast

Fast

Fast plus DOC

Fast plus DOC

Fast

Fast

Fast plus DOC

Fast

Fast

Slow plus DOC

Slow

Slow

Slow

Slow

Slow plus DOC

Slow plus DOC

Slow plus DOC

Fast

Fast

Fast

Fast

Fast

Slow plus DOC

Fast plus DOC

Slow

Fast

Slow

Slow plus DOC

Slow

Fast

Fast

Fast plus DOC

Slow

Slow

Fast

Fast

Slow

Fast plus DOC

2,790

2,922

3,017

3,173

3,204

2,822

3,530

3,348

2,431

3,238

3,055

2,465

2,867

2,945

3,055

3,255

3,098

2,858

2,783

2,914

2,943

3,963

3,483

3,161

2,623

2,713

3,368

6,404

3,013

2,901

3,683

3,571

2,873

3,070

1,957

1,797

1,830

1,835

2,300

2,197

Production

Production

Production

Production

Production

Production

Production

Production

Production

Production

Production

Production

Production

Production

Production

Production

Production

Production

Production

Production

Production

Production

Production

Production

Production

Production

Production

Production

Production

Production

Production

Production

Production

Production

Production

Production

Production

Production

Production

Production

393

330

310

877

700

na

na

660

425

1,010

630

360

na

530

720

1,000

810

460

420

na

na

na

na

300

na

390

1,110

230

480

650

1,130

800

140

na

400

140

na

na

na

350

168

133

221

445

420

164

na

na

150

600

310

110

na

365

495

515

410

200

160

na

na

na

na

120

na

180

850

50

na

430

660

na

105

na

160

na

na

na

na

190

373

330

310

865

700

334

na

na

415

na

610

360

na

505

700

1,000

810

450

400

na

na

na

na

300

na

390

1,110

165

na

630

1,120

na

140

na

400

na

na

na

na

350
Tables 23 

Table 1. Well identification, sampling, and construction information for wells sampled for the Mojave Groundwater Ambient 

Monitoring and Assessment (GAMA) study, California, February to April 2008.—Continued 

[Sampling schedules are described in table 2. Land-surface datum (LSD) is a datum plane that is approximately at land surface at each well. The elevation of 

the LSD is described in feet above the North American Vertical Datum 1988. GAMA well identification No.: MOJO, Mojave study unit grid well; MOJOU, 

Mojave study unit understanding well. Other abbreviations: DOC, dissolved organic carbon; ft, feet; LSD, land surface datum; NAVD 88, North American 

Vertical Datum 1988; na, not available] 

GAMA well 

identification 

No. 

Sampling information 

Date sampled 

(mm/dd/yyyy) 

Sampling 

schedule 

Elevation of LSD 

(ft above 

NAVD 88) Well type 

Construction information 

Well depth 

(ft below LSD) 

Top perforation 

(ft below LSD) 

Bottom 

perforation 

(ft below LSD) 

MOJO-41 03/25/2008 Slow plus DOC 1,822 Production na na na 

MOJO-42 03/26/2008 Slow 1,920 Production 388 242 na 

MOJO-43 03/26/2008 Fast 3,378 Production na na na 

MOJO-44 03/27/2008 Fast 2,410 Production 700 na na 

MOJO-45 03/27/2008 Fast 2,104 Production 200 na na 

MOJO-46 03/31/2008 Fast 3,068 Production 606 258 565 

MOJO-47 03/31/2008 Fast 2,971 Production na na na 

MOJO-48 04/01/2008 Fast 2,978 Production 540 200 520 

MOJO-49 04/01/2008 Slow 2,007 Production 400 200 390 

MOJO-50 04/01/2008 Fast 2,084 Production 150 na na 

MOJO-51 04/02/2008 Fast plus DOC 1,822 Production 300 na na 

MOJO-52 04/02/2008 Fast 1,829 Production na na na 

Understanding wells 

MOJOU-01 03/05/2008 Slow 4,873 Production 451 251 451 

MOJOU-02 03/10/2008 Slow 2,986 Monitoring 790 770 790 

MOJOU-03 03/11/2008 Slow 2,036 Monitoring 610 590 610 

MOJOU-04 03/12/2008 Slow 2,593 Monitoring 583 534 574 

MOJOU-05 03/13/2008 Slow 3,263 Monitoring 750 730 750 

MOJOU-06 03/18/2008 Fast 1,960 Production na na na 

MOJOU-07 03/24/2008 Fast plus DOC 2,353 Production 150 90 150 
24 Groundwater Quality Data in the Mojave Study Unit, 2008 :Results from the California GAMA Program 

Table 2. Classes of chemical constituents and water-quality indicators (field parameters) collected for the slow and fast well 

sampling schedules in the Mojave Groundwater Ambient Monitoring and Assessment (GAMA) study, California, February to April 2008. 

Analyte classes Slow schedule Fast schedule Analyte list table Results table 

Water-quality indicators 

Dissolved oxygen, pH, temperature, specific conductance X X 4
 

4 

Turbidity X

Alkalinity, bicarbonate, and carbonate X
 

4 

Organic constituents 

Volatile organic compounds (VOCs) X X 3A 5
 

Pesticides and pesticide degradates X X 3B 6
 

Pharmaceutical compounds X 3C none1
 

Constituents of special interest 

Perchlorate X X 3D 7
 

N-nitrosodimethylamine (NDMA) X 3D 7
 

Inorganic constituents 

Nutrients X 3E
 

Dissolved organic carbon (DOC)2 X2 X2 3E 8
 

Major and minor ions and trace elements X 3F 9,10
 

Arsenic, chromium, and iron speciation X 3G 11
 

Stable isotopes 

Stable isotopes of hydrogen and oxygen in water X X 3H 12
 

Stable isotopes of nitrogen and oxygen in nitrate X 3H 12
 

Stable isotopes of carbon and carbon-14 abundance X 3H 12
 

Radioactivity and noble gases 

Tritium X X 3I 13
 

Tritium and noble gases X X 3I none1
 

Radium isotopes X 3I 13
 

Radon-222 X 3I 13
 

Gross alpha and gross beta radiation X 3I 13
 

1

 Results for pharmaceutical compounds are not presented in the MOJO data report; they will be included in a subsequent publication. In addition, as of the 

publishing date of this data report, the samples collected in MOJO for noble gases and tritium and helium isotope ratios were not available from LLNL; therefore, these results are not included at this time. 

2

 Dissolved organic carbon was sampled for at eight slow and eight fast wells. 
Tables 25

Table 3A. Volatile organic compounds (VOCs), primary uses or sources, comparative thresholds, and reporting information for the 

U.S. Geological Survey (USGS) National Water Quality Laboratory Schedule 2020.—Continued

[The five-digit USGS parameter code is used to uniquely identify a specific constituent or property. This report contains CAS Registry Numbers®, which is 

a Registered Trademark of the American Chemical Society. CAS recommends the verification of the CAS registry numbers through CAS Client ServicesSM. 

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. Threshold type and threshold level as of April 2, 2008. Threshold type: HAL-US, U.S. Environmental Protection 

Agency lifetime health advisory level; 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. Other abbreviations: CAS, Chemical Abstract Service; LRL, laboratory reporting level; THM, trihalomethane; D, detected in groundwater samples (table 5); na, not available; μg/L, micrograms per liter; —, not detected]

Constituent (synonym or abbreviation)Primary use or 

source

USGS parameter codeCAS 

number

 LRL 

(μg/L)

Threshold 

type

Threshold 

level 

(μg/L)

Detection

Acetone

Acrylonitrile

tert-Amyl methyl ether (TAME)

Benzene

Bromobenzene

Bromochloromethane

Bromodichloromethane

Bromoform (Tribromomethane)

Bromomethane (Methyl bromide)

n-Butylbenzene

sec-Butylbenzene

tert-Butylbenzene

Carbon disulfide

Carbon tetrachloride (Tetrachloromethane)

Chlorobenzene

Chloroethane

Chloroform (Trichloromethane)

Chloromethane

3-Chloropropene

2-Chlorotoluene

4-Chlorotoluene

Dibromochloromethane

Solvent

Organic synthesis

Gasoline oxygenate

Gasoline hydrocarbon

Solvent

Fire retardant

Disinfection 

by-product 

(THM)

Disinfection 

by-product 

(THM)

Fumigant

Gasoline hydrocarbon

Gasoline hydrocarbon

Gasoline hydrocarbon

Organic synthesis

Solvent

Solvent

Solvent

Disinfection 

by-product 

(THM)

Solvent

Organic synthesis

Solvent

Solvent

Disinfection 

by-product 

81552

34215

50005

34030

81555

77297

32101

32104

34413

77342

77350

77353

77041

32102

34301

34311

32106

34418

78109

77275

77277

32105

67-64-1

107-13-1

994-05-8

71-43-2

108-86-1

74-97-5

75-27-4

75-25-2

74-83-9

104-51-8

135-98-8

98-06-6

75-15-0

56-23-5

108-90-7

75-00-3

67-66-3

74-87-3

107-05-1

95-49-8

106-43-4

124-48-1

4

0.4

0.06

0.016

0.02

0.06

0.04

0.08

0.4

0.14

0.04

0.06

0.06

0.08

0.02

0.10

0.02

0.10

0.08

0.04

0.04

0.12

na

RSD5-US

na

MCL-CA

na

HAL-US

MCL-US

MCL-US

HAL-US

NL-CA

NL-CA

NL-CA

NL-CA

MCL-CA

MCL-CA

na

MCL-US

HAL-US

na

NL-CA

NL-CA

MCL-US

na

0.6

na

1

na

90

1

 80

1

 80

10

260

260

260

160

0.5

70

na

1

 80

30

na

140

140

1

 80

—

—

—

—

—

—

D

D

—

—

—

—

—

D

D

—

D

—

—

—

—

D

(THM)
26 Groundwater Quality Data in the Mojave Study Unit, 2008: Results from the California GAMA Program 

Table 3A. Volatile organic compounds (VOCs), primary uses or sources, comparative thresholds, and reporting information for the 

U.S. Geological Survey (USGS) National Water Quality Laboratory Schedule 2020.—Continued 

[The five-digit USGS parameter code is used to uniquely identify a specific constituent or property. This report contains CAS Registry Numbers®, which is 

a Registered Trademark of the American Chemical Society. CAS recommends the verification of the CAS registry numbers through CAS Client ServicesSM . 

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. Threshold type and threshold level as of April 2, 2008. Threshold type: HAL-US, U.S. Environmental Protection 

Agency lifetime health advisory level; 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. Other abbreviations: CAS, Chemical Abstract Service; LRL, laboratory reporting level; THM, trihalomethane; D, detected in groundwater samples (table 5); na, not available; μg/L, micrograms per liter; —, not detected] 

Constituent (synonym or abbreviation) Primary use or 

source 

USGS parameter code CAS 

number

 LRL 

(μg/L) 

Threshold 

type 

Threshold 

level 

(μg/L) 

Detection 

1,2-Dibromo-3-chloropropane Fumigant 82625 96-12-8 0.5 MCL-US 0.2 — 

(DBCP) 

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 0.02 MCL-CA 600 — 

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

1,4-Dichlorobenzene Fumigant 34571 106-46-7 0.02 MCL-CA 5 — 

trans-1,4-Dichloro-2-butene Organic syn­ 73547 110-57-6 0.6 na na — 

thesis 

Dichlorodifluoromethane Refrigerant 34668 75-71-8 0.14 NL-CA 1,000 — 

(CFC-12) 

1,1-Dichloroethane (1,1-DCA) Solvent 34496 75-34-3 0.04 MCL-CA 5 D 

1,2-Dichloroethane (1,2-DCA) Solvent 32103 107-06-2 0.06 MCL-CA 0.5 D 

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

thesis 

cis-1,2-Dichloroethene Solvent 77093 156-59-2 0.02 MCL-CA 6 D 

(cis-1,2-DCE) 

trans-1,2-Dichloroethene Solvent 34546 156-60-5 0.018 MCL-CA 10 D 

(trans-1,2-DCE) 

1,2-Dichloropropane Fumigant 34541 78-87-5 0.02 MCL-US 5 — 

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

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

1,1-Dichloropropene Organic syn­ 77168 563-58-6 0.04 na na — 

thesis 

cis-1,3-Dichloropropene Fumigant 34704 10061-01-5 0.1 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 0.12 na na — 

Diisopropyl ether (DIPE) Gasoline oxy­ 81577 108-20-3 0.06 na na — 

genate 

Ethylbenzene Gasoline hy­ 34371 100-41-4 0.04 MCL-CA 300 — 

drocarbon 

Ethyl tert-butyl ether (ETBE) Gasoline oxy­ 50004 637-92-3 0.04 na na — 

genate 

Ethyl methacrylate Organic syn­ 73570 97-63-2 0.14 na na — 

thesis 

o-Ethyl toluene (1-Ethyl-2-meth- Gasoline hy­ 77220 611-14-3 0.04 na na — 

yl benzene) drocarbon 

Hexachlorobutadiene Organic syn­ 39702 87-68-3 0.06 RSD5-US 9 — 

thesis 
Tables 27 

Table 3A. Volatile organic compounds (VOCs), primary uses or sources, comparative thresholds, and reporting information for the 

U.S. Geological Survey (USGS) National Water Quality Laboratory Schedule 2020.—Continued 

[The five-digit USGS parameter code is used to uniquely identify a specific constituent or property. This report contains CAS Registry Numbers®, which is 

a Registered Trademark of the American Chemical Society. CAS recommends the verification of the CAS registry numbers through CAS Client ServicesSM . 

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. Threshold type and threshold level as of April 2, 2008. Threshold type: HAL-US, U.S. Environmental Protection 

Agency lifetime health advisory level; 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. Other abbreviations: CAS, Chemical Abstract Service; LRL, laboratory reporting level; THM, trihalomethane; D, detected in groundwater samples (table 5); na, not available; μg/L, micrograms per liter; —, not detected] 

Constituent (synonym or abbreviation) Primary use or 

source 

USGS parameter code CAS 

number

 LRL 

(μg/L) 

Threshold 

type 

Threshold 

level 

(μg/L) 

Detection 

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

2-Hexanone (n-Butyl methyl 

ketone) 

Solvent 77103 591-78-6 0.6 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 0.6 na na — 

Methyl acrylonitrile Organic synthesis 81593 126-98-7 0.2 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 0.4 NL-CA 120 — 

Methylene chloride (Dichloromethane) Solvent 34423 75-09-2 0.04 MCL-US 5 D 

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 0.2 NL-CA 17 — 

Perchloroethene (PCE, tetrachloroethene) Solvent 34475 127-18-4 0.04 MCL-US 5 D 

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

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

1,1,1,2-Tetrachloroethane Solvent 77562 630-20-6 0.04 HAL-US 70 — 

1,1,2,2-Tetrachloroethane Solvent 34516 79-34-5 0.10 MCL-CA 1 — 

Tetrahydrofuran Solvent 81607 109-99-9 1.4 na na D 

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

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

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

1,2,3-Trichlorobenzene Organic synthesis 77613 87-61-6 0.08 na na — 
28 Groundwater Quality Data in the Mojave Study Unit, 2008: Results from the California GAMA Program 

Table 3A. Volatile organic compounds (VOCs), primary uses or sources, comparative thresholds, and reporting information for the 

U.S. Geological Survey (USGS) National Water Quality Laboratory Schedule 2020.—Continued 

[The five-digit USGS parameter code is used to uniquely identify a specific constituent or property. This report contains CAS Registry Numbers®, which is 

a Registered Trademark of the American Chemical Society. CAS recommends the verification of the CAS registry numbers through CAS Client ServicesSM . 

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. Threshold type and threshold level as of April 2, 2008. Threshold type: HAL-US, U.S. Environmental Protection 

Agency lifetime health advisory level; 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. Other abbreviations: CAS, Chemical Abstract Service; LRL, laboratory reporting level; THM, trihalomethane; D, detected in groundwater samples (table 5); na, not available; μg/L, micrograms per liter; —, not detected] 

Constituent (synonym or abbreviation) Primary use or 

source 

USGS parameter code CAS 

number

 LRL 

(μg/L) 

Threshold 

type 

Threshold 

level 

(μg/L) 

Detection 

1,2,4-Trichlorobenzene Solvent 34551 120-82-1 0.08 MCL-CA 5 — 

1,1,1-Trichloroethane 

(1,1,1-TCA) 

Solvent 34506 71-55-6 0.02 MCL-CA 200 — 

1,1,2-Trichloroethane 

(1,1,2-TCA) 

Solvent 34511 79-00-5 0.06 MCL-CA 5 — 

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

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

1,2,3-Trichloropropane 

(1,2,3-TCP) 

Solvent/organic synthesis 77443 96-18-4 0.12 HAL-US 3 40 — 

Trichlorotrifluoroethane 

(CFC-113) 

Refrigerant 77652 76-13-1 0.04 MCL-CA 1,200 — 

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-CA 0.5 — 

m- and p-Xylene Gasoline hydrocarbon 

85795 108-38-3 / 106­

42-3 

0.08 MCL-CA 4

 1,750 — 

o-Xylene Gasoline hydrocarbon 

77135 95-47-6 0.04 MCL-CA 4

 1,750 — 

1

The MCL-US thresholds for trihalomethanes is 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 thresholds for m - and p-Xylene and o-Xylene is the sum all three xylene compounds.
 
Tables 29

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

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

[The five-digit USGS parameter code is used to uniquely identify a specific constituent or property. Threshold type and threshold level as of April 2, 2008. 

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. Threshold type: HAL-US, U.S. Environmental Protection Agency lifetime health advisory level; 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. Other abbreviations: CAS, Chemical Abstract Service; LRL, 

laboratory reporting level; D, detected in groundwater samples (table 6); na, not available; μg/L, micrograms per liter; —, not detected]

Constituent Primary use 

or source

USGS parameter code CAS number LRL 

(μg/L)

Threshold 

type

Threshold 

level 

(μg/L)

Detection

Acetochlor 

Alachlor 

Atrazine 

Azinphos-methyl 

Azinphos-methyl oxon 

Benfluralin 

Carbaryl 

2-Chloro-2,6-diethylacetanilide 

4-Chloro-2-methylphenol 

Chlorpyrifos 

Chlorpyrifos oxon

Cyfluthrin 

Cypermethrin 

Dacthal (DCPA)

Deethylatrazine (2-Chloro-4-

isopropylamino-6-amino-striazine)

Desulfinylfipronil 

Desulfinylfipronil amide 

Diazinon 

3,4-Dichloroaniline 

Dichlorvos 

Dicrotophos 

Dieldrin 

2,6-Diethylaniline 

Dimethoate 

Ethion 

Ethion monoxon 

2-Ethyl-6-methylaniline 

Herbicide

Herbicide

Herbicide

Insecticide

Insecticide 

degradate

Herbicide

Insecticide

Herbicide 

degradate

Herbicide 

degradate

Insecticide

Insecticide 

degradate

Insecticide

Insecticide

Herbicide

Herbicide 

degradate

Insecticide 

degradate

Insecticide 

degradate

Insecticide

Herbicide 

degradate

Insecticide

Insecticide

Insecticide

Herbicide 

degradate

Insecticide

Insecticide

Insecticide 

degradate

Herbicide 

49260

46342

39632

82686

61635

82673

82680

61618

61633

38933

61636

61585

61586

82682

04040

62170

62169

39572

61625

38775

38454

39381

82660

82662

82346

61644

61620

34256-82-1

15972-60-8

1912-24-9

86-50-0

961-22-8

1861-40-1

63-25-2

6967-29-9

1570-64-5

2921-88-2

5598-15-2

68359-37-5

52315-07-8

1861-32-1

6190-65-4

na

na

333-41-5

95-76-1

62-73-7

141-66-2

60-57-1

579-66-8

60-51-5

563-12-2

17356-42-2

24549-06-2

0.006

0.006

0.007

0.12

0.042

0.01

0.06

0.01

0.0050

0.005

0.0562

0.016

0.014

0.003

0.014

0.012

0.029

0.005

0.006

0.013

0.0843

0.009

0.006

0.006

0.006

0.021

0.0049

na

MCL-US

MCL-CA

na

na

na

RSD5-US

na

na

HAL-US

na

na

na

HAL-US

na

na

na

HAL-US

na

na

na

RSD5-US

na

na

na

na

na

na

2

1

na

na

na

400

na

na

2

na

na

na

70

na

na

na

1

na

na

na

0.02

na

na

na

na

na

—

—

D

—(1)

—(1)

—(1)

—

—

—(1)

—(1)

—(1)

—(1)

—(1)

—

D(1)

D

—

—

D

—(1)

—(1)

D

—

—(1)

—

—(1)

—(1)

degradate
30 Groundwater Quality Data in the Mojave Study Unit, 2008: Results from the California GAMA Program 

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

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

[The five-digit USGS parameter code is used to uniquely identify a specific constituent or property. Threshold type and threshold level as of April 2, 2008. 

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. Threshold type: HAL-US, U.S. Environmental Protection Agency lifetime health advisory level; 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. Other abbreviations: CAS, Chemical Abstract Service; LRL, 

laboratory reporting level; D, detected in groundwater samples (table 6); na, not available; μg/L, micrograms per liter; —, not detected] 

Constituent Primary use 

or source 

USGS parameter code CAS number LRL 

(μg/L) 

Threshold 

type 

Threshold 

level 

(μg/L) 

Detection 

Fenamiphos 

Fenamiphos sulfone 

Fenamiphos sulfoxide 

Fipronil 

Fipronil sulfide 

Fipronil sulfone 

Fonofos 

Insecticide 

Insecticide 

degradate 

Insecticide 

degradate 

Insecticide 

Insecticide 

degradate 

Insecticide 

degradate 

Insecticide 

61591 

61645 

61646 

62166 

62167 

62168 

04095 

22224-92-6 

31972-44-8 

31972-43-7 

120068-37-3 

120067-83-6 

120068-36-2 

944-22-9 

0.029 

0.053 

0.2 

0.02 

0.013 

0.024 

0.01 

HAL-US 

na 

na 

na 

na 

na 

HAL-US 

0.7 

na 

na 

na 

na 

na 

10 

— 

— 

—(1) 

D(1) 

D(1) 

—(1) 

— 

Hexazinone Herbicide 04025 51235-04-2 0.008 HAL-US 400 —(1) 

Iprodione 

Isofenphos 

Malaoxon 

Malathion 

Fungicide 

Insecticide 

Insecticide 

degradate 

Insecticide 

61593 

61594 

61652 

39532 

36734-19-7 

25311-71-1 

1634-78-2 

121-75-5 

0.01 

0.006 

0.02 

0.016 

na 

na 

na 

HAL-US 

na 

na 

na 

100 

—(1) 

— 

—(1) 

— 

Metalaxyl 

Methidathion 

Fungicide 

Insecticide 

61596 

61598 

57837-19-1 

950-37-8 

0.0069 

0.004 

na 

na 

na 

na 

— 

— 

Metolachlor Herbicide 39415 51218-45-2 0.010 HAL-US 700 D 

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

Myclobutanil 

1-Naphthol 

Paraoxon-methyl 

Parathion-methyl 

Pendimethalin 

Fungicide 

Insecticide 

degradate 

Insecticide 

degradate 

Insecticide 

Herbicide 

61599 

49295 

61664 

82667 

82683 

88671-89-0 

90-15-3 

950-35-6 

298-00-0 

40487-42-1 

0.01 

0.04 

0.01 

0.008 

0.012 

na 

na 

na 

HAL-US 

na 

na 

na 

na 

1 

na 

— 

—(1) 

—(1) 

—(1) 

— 

cis-Permethrin Insecticide 82687 54774-45-7 0.01 na na —(1) 

Phorate Insecticide 82664 298-02-2 0.04 na na —(1) 

Phorate oxon 

Phosmet 

Insecticide 

degradate 

Insecticide 

61666 

61601 

2600-69-3 

732-11-6 

0.027 

0.0079 

na 

na 

na 

na 

— 

—(1) 

Phosmet oxon 

Prometon 

Insecticide 

degradate 

Herbicide 

61668 

04037 

3735-33-9 

1610-18-0 

0.0511 

0.01 

na 

HAL-US 

na 

100 

—(1) 

D 

Prometryn 

Pronamide (Propyzamide) 

Herbicide 

Herbicide 

04036 

82676 

7287-19-6 

23950-58-5 

0.0059 

0.004 

na 

RSD5-US 

na 

20 

— 

— 
Tables 31 

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

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

[The five-digit USGS parameter code is used to uniquely identify a specific constituent or property. Threshold type and threshold level as of April 2, 2008. 

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. Threshold type: HAL-US, U.S. Environmental Protection Agency lifetime health advisory level; 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. Other abbreviations: CAS, Chemical Abstract Service; LRL, 

laboratory reporting level; D, detected in groundwater samples (table 6); na, not available; μg/L, micrograms per liter; —, not detected] 

Constituent Primary use 

or source 

USGS parameter code CAS number LRL 

(μg/L) 

Threshold 

type 

Threshold 

level 

(μg/L) 

Detection 

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

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

Terbufos Insecticide 82675 13071-79-9 0.018 HAL-US 0.4 — 

Terbufos oxon sulfone Insecticide 61674 56070-15-6 0.045 na na —(1) 

degradate 

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

Tribufos Defoliant 61610 78-48-8 0.035 na na — 

Trifluralin Herbicide 82661 1582-09-8 0.009 HAL-US 10 —(1) 

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. 
32 Groundwater Quality Data in the Mojave Study Unit, 2008: Results from the California GAMA Program 

Table 3C. Pharmaceutical compounds, primary uses or sources, comparative thresholds, and reporting information for the U.S. 

Geological Survey (USGS) National Water Quality Laboratory schedule 2080. 

[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 xanthine, the MDL corresponds to the study 

reporting levels determined from assessment of quality-control data associated with GAMA samples collected from May 2004 through September 2007 (GAMA 

SRL). The GAMA SRLs 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 SRL are reported as non-detections by the GAMA program. The five-digit USGS parameter code is used 

to uniquely identify a specific constituent or property. Abbreviations: CAS, Chemical Abstract Service; MDL, method detection limit; na, not available; μg/L, 

micrograms per liter] 

Constituent Primary use 

or source 

USGS 

parameter 

code 

CAS number MDL 

(μg/L) 

Threshold 

type 

Threshold 

level 

(μg/L) 

1,7-Dimethylxanthine Caffeine metabolite 62030 611-59-6 0.10 na na 

Acetaminophen Analgesic 62000 103-90-2 0.60 na na 

Albuterol Anti-inflammatory; bronchodilator 62020 18559-94-9 0.03 na na 

Caffeine Stimulant 50305 58-08-2 0.40 na na 

Carbamazapine Anticonvulsant; analgesic; mood 62793 298-46-4 0.02 na na 

stabilizer 

Codeine Opiod narcotic 62003 76-57-3 0.02 na na 

Cotinine Nicotine metabolite 62005 486-56-6 0.03 na na 

Dehydronifedipine Antianginal metabolite 62004 67035-22-7 0.03 na na 

Diltiazem Antianginal; antihypertensive 62008 42399-41-7 0.02 na na 

Diphenhydramine Antihistamine 62796 58-73-1 0.03 na na 

Sulfamethoxazole Antibacterial, antiprotozoal 62021 723-46-6 0.05 na na 

Thiabendazole Anthelmintic 62801 148-79-8 0.02 na na 

Trimethoprim Antibacterial 62023 738-70-5 0.01 na na 

Warfarin Anticoagulant 62024 81-81-2 0.03 na na 
 

 

Tables 33 

Table 3D. Constituents of special interest, primary uses or sources, comparative thresholds, and reporting information for Weck 

Laboratories, Inc. analyses. 

[The five-digit U.S. Geological Survey (USGS) parameter code is used to uniquely identify a specific constituent or property. Threshold type and threshold level 

as of April 2, 2008. 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. Threshold type: MCL-CA, California Department of Public Health maximum contaminant level; 

NL-CA, California Department of Public Health notification level. Other abbreviations: CAS, Chemical Abstract Service; MRL, minimum reporting level; D, 

detected in groundwater samples (table 7); μg/L, micrograms per liter] 

Constituent Primary use 

or source 

USGS 

parameter 

code 

CAS number MRL 

(μg/L) 

Threshold 

type 

Threshold 

level 

(μg/L) 

Detection 

Perchlorate Rocket fuel, fireworks, flares 63790 14797-73-0 0.10 MCL-CA 6 D 

N-nitrosodimethylamine Disinfection by-product 34438 62-75-9 0.0020 NL-CA 0.010 D 

(NDMA) 

Table 3E. Nutrients and dissolved organic carbon (DOC), comparative thresholds, and reporting information for the U.S. Geological 

Survey (USGS) National Water Quality Laboratory Schedule 2755 and laboratory code 2612. 

[The five-digit USGS parameter code is used to uniquely identify a specific constituent or property. Threshold type and threshold level as of April 2, 2008. 

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. Threshold type: HAL-US, U.S. Environmental Protection Agency lifetime health advisory level; MCL-US, U.S. Environmental Protection Agency maximum contaminant level. Other abbreviations: CAS, Chemical Abstract Service; LRL, laboratory reporting level; D, detected in 

groundwater samples (table 8); na, not available; mg/L, milligrams per liter] 

Constituent 

USGS 

parameter 

code 

CAS number LRL 

(mg/L) 

Threshold 

type 

Threshold 

level 

(mg/L) 

Detection 

Ammonia (as nitrogen) 00608 7664-41-7 0.02 HAL-US 1 24.7 D 

Nitrite (as nitrogen) 00613 14797-65-0 0.002 MCL-US 1 D 

Nitrate plus nitrite (as nitrogen) 00631 na 0.04 MCL-US 10 D 

Total nitrogen (ammonia, nitrite, nitrate, organic nitrogen) 62854 17778-88-0 0.06 na na D 

Phosphate, orthophosphate (as phosphorus) 00671 14265-44-2 0.006 na na D 

Dissolved organic carbon (DOC) 00681 na 0.4 na na D

 1The HAL-US is 30 mg/L "as ammonia." To facilitate comparison to the analytical results, we have converted and reported this HAL-US as 24.7 mg/L "as 

nitrogen." 
34 Groundwater Quality Data in the Mojave Study Unit, 2008: Results from the California GAMA Program 

Table 3F. Major and minor ions, silica, total dissolved solids (TDS), and trace elements, comparative thresholds, and reporting 

information for the U.S. Geological Survey (USGS) National Water Quality Laboratory Schedule 1948. 

[The five-digit USGS parameter code is used to uniquely identify a specific constituent or property. Threshold type and threshold level as of April 2, 2008. 

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. The recommended SMCL-CA thresholds for chloride, sulfate, and TDS are listed with the upper SMCL-CA thresholds in 

parentheses. Threshold type: AL-US, U.S. Environmental Protection Agency action level; HAL-US, U.S. Environmental Protection Agency lifetime health 

advisory level; MCL-CA, California Department of Public Health (CDPH) 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. Other abbreviations: CAS, Chemical Abstract Service; LRL, laboratory reporting level; SRL, study reporting limit; D, detected 

in groundwater samples (tables 9 and 10); na, not available; mg/L, milligrams per liter; μg/L, micrograms per liter; —, not detected] 

Constituent 

USGS 

parameter 

code 

CAS number LRL/SRL Threshold 

type 

Threshold 

level Detection 

Major and minor ions, silica, and total dissolved solids (TDS) (mg/L) 

Bromide 71870 24959-67-9 0.02 na na D 

Calcium 00915 7440-70-2 0.04 na na D 

Chloride 00940 16887-00-6 0.12 SMCL-CA 250 (500) D 

Fluoride 00950 16984-48-8 0.12 MCL-CA 2 D 

Iodide 71865 7553-56-2 0.002 na na D 

Magnesium 00925 7439-95-4 0.02 na na D 

Potassium 00935 7440-09-7 0.02 na na D 

Silica (as SiO2

) 00955 7631-86-9 0.018 na na D 

Sodium 00930 7440-23-5 0.12 na na D 

Sulfate 00945 14808-79-8 0.18 SMCL-CA 250 (500) D 

Residue on evaporation (total dissolved solids, TDS) 70300 na 10 SMCL-CA 500 (1,000) D 

Trace elements (μg/L) 

Aluminum 01106 7429-90-5 1.6 MCL-CA 1,000 D 

Antimony 01095 7440-36-0 0.14 MCL-US 6 D 

Arsenic 01000 7440-38-2 0.06 MCL-US 10 D 

Barium 01005 7440-39-3 0.4 MCL-CA 1,000 D 

Beryllium 01010 7440-41-7 0.008 MCL-US 4 D 

Boron 01020 7440-42-8 6 NL-CA 1,000 D 

Cadmium 01025 7440-43-9 0.04 MCL-US 5 D 

Chromium 01030 7440-47-3 0.12 MCL-CA 50 D 

Cobalt 01035 7440-48-4 0.02 na na D 

Copper 01040 7440-50-8 1 AL-US 1,300 D 

Iron 01046 7439-89-6 8 SMCL-CA 300 D 

Lead 01049 7439-92-1 0.08 AL-US 15 D 

Lithium 01130 7439-93-2 1 na na D 

Manganese 01056 7439-96-5 0.2 SMCL-CA 50 D 

Molybdenum 01060 7439-98-7 0.2 HAL-US 40 D 

Nickel 01065 7440-02-0 0.2 MCL-CA 100 D 

Selenium 01145 7782-49-2 0.04 MCL-US 50 D 

Silver 01075 7440-22-4 0.1 SMCL-CA 100 — 

Strontium 01080 7440-24-6 0.8 HAL-US 4,000 D 

Thallium 01057 7440-28-0 0.04 MCL-US 2 — 

Tungsten 01155 7440-33-7 0.06 na na D 

Uranium 22703 7440-61-1 0.02 MCL-US 30 D 

Vanadium 01085 7440-62-2 0.04 NL-CA 50 D 

Zinc 01090 7440-66-6 1.8 SMCL-CA1 5,000 D 1

The secondary maximum contaminant level for zinc is listed as SMCL-CA since SMCLs established by CDPH are used in this report for all constituents that 

have SMCL-CA values. 
Tables 35 

Table 3G. Arsenic, chromium, and iron species, comparative thresholds, and reporting information for the U.S. Geological Survey 

(USGS) Trace Metal Laboratory, Boulder, Colorado, analyses. 

[The five-digit USGS parameter code is used to uniquely identify specific constituents or property. Threshold type and threshold level as of April 2, 2008. 

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

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

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

Other abbreviations: CAS, Chemical Abstract Service; MDL, method detection limit; na, not available; μg/L, micrograms per liter; D, detected in groundwater 

samples (table 11)] 

Constituent USGS parameter 

code CAS number MDL (μg/L) Threshold type 

Threshold 

level 

(μg/L) 

Detection 

Arsenic (III) 99034 22569-72-8 1 na na D 

Arsenic (total) 99033 7440-38-2 0.5 MCL-US 10 D 

Chromium (VI) 01032 18540-29-9 1 na na D 

Chromium (total) 01030 7440-47-3 1 MCL-CA 50 D 

Iron (II) 01047 7439-89-6 2 na na D 

Iron (total) 01046 7439-89-6 2 SMCL-US 300 D 
 

 

36 Groundwater Quality Data in the Mojave Study Unit, 2008: Results from the California GAMA Program 

Table 3H. Isotopic and radioactive constituents, comparative thresholds, and reporting information for laboratory analyses. 

[The five-digit U.S. Geological Survey (USGS) parameter code is used to uniquely identify a specific constituent or property. Stable isotope ratios are reported 

in the standard delta notation (δ), the ratio of a heavier isotope to more common lighter isotope of that element, relative to a standard reference material. Threshold type and threshold level as of April 2, 2008. 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. Threshold type: MCL-CA, California Department of Public Health 

maximum contaminant level; MCL-US, U.S. Environmental Protection Agency maximum contaminant level. Other abbreviations: CAS, Chemical Abstract 

Service; CSU, combined standard uncertainty; ssLC, sample-specific critical level; MRL, minimum reporting level; MU, method uncertainty; na, not available; 

pCi/L, picocuries per liter; 2SCU, 2-sigma combined uncertainty; D, detected in groundwater samples (tables 12 and 13)] 

Constituent 

USGS parameter 

code 

CAS number Reporting 

level type 

Reporting level 

or uncertainty 

Threshold 

type 

Threshold 

level Detection 

Stable isotope ratios (per mil) 

δ2H of water1 82082 na MU 2 na na D 

δ18O of water1 82085 na MU 0.20 na na D 

δ15N of nitrate1 82690 na MU 0.50 na na D 

δ18O of nitrate1 63041 na MU 1.00 na na D 

δ18C of dissolved carbonates2 82081 na 1 sigma 0.05 na na D 

Radioactive constituents (percent modern) 

Carbon-143 49933 14762-75-5 1 sigma 0.0015 na na D 

Radioactive constituents (pCi/L) 

Radon-2224 82303 14859-67-7 na 2SCU Prop. MCL-US 5

300 D 

(4,000) 

Tritium6 07000 10028-17-8 MRL 1 MCL-CA 20,000 D 

Gross alpha radioactivity, 72-hour 99920, 12587-46-1 ssLC CSU MCL-US 15 D 

and 30-day counts7 99921 

Gross beta radioactivity, 72-hour 99922, 12587-47-2 ssLC CSU MCL-CA 50 D 

and 30-day counts7 99923 

Radium-2267 99915 13982-63-3 ssLC CSU MCL-US 8

5 D 

Radium-2287 99916 15262-20-1 ssLC CSU MCL-US 8

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

Eberline Analytical Services (contract laboratory). 

8

The MCL-US threshold for radium is the sum of radium-226 and radium-228. 
Tables 37 

Table 3I. Noble gases and tritium, comparison thresholds and reporting information for the Lawrence Livermore National Laboratory 

analyses. 

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

values as of April 2, 2008. 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. Other abbreviations: CAS, Chemical Abstract Service; MU, method uncertainty; na, not available; cm3 STP/g, cubic centimeters of gas at standard 

temperature and pressure per gram of water; pCi/L, picocuries per liter; D, detected in groundwater samples] 

Constituent 

USGS parameter 

code 

CAS number MU 

(percent) 

Reporting 

units 

Threshold 

type 

Threshold 

level 

(pCi/L) 

Detection 

Helium-3/Helium-4 61040 na/7440-59-7 0.75 atom ratio na na D 

Argon 85563 7440-37-1 2 cm3

 STP/g na na D 

Helium-4 85561 7440-59-7 2 cm3

 STP/g na na D 

Krypton 85565 7439-90-9 2 cm3

 STP/g na na D 

Neon 61046 7440-01-09 2 cm3

 STP/g na na D 

Xenon 85567 7440-63-3 2 cm3

 STP/g na na D 

Tritium 07000 10028-17-8 1 pCi/L MCL-CA 20,000 D 
Table 4. Water-quality indicators (field parameters) in samples collected for the Mojave Groundwater Ambient Monitoring and Assessment (GAMA) study, California, 

February to April 2008.—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. GAMA well identification No.: MOJO, Mojave 

study unit grid well; MOJOU, Mojave study unit understanding well. Threshold type and threshold level as of April 2, 2008. The SMCL-CA for specific conductance has recommended and upper threshold values. The upper value is shown in parentheses. Threshold type: SMCL-US, U.S. Environmental Protection Agency secondary maximum contaminant level; SMCL-CA, California Department of Public Health secondary maximum contaminant level. Other abbreviations: C, celsius; mg/L, milligrams per liter; nc, sample not collected; na, not available; NTU, nephelometric turbidity unit; RL, reporting limit 

or range; μS/cm, microsiemens per centimeter; <, less than; >, greater than; CaCO3 , calcium carbonate; *, value above threshold level or outside threshold range; **, value above upper threshold level]

38 Table 4. Water-quality indicators (field parameters) in samples collected for the Mojave Groundwater Ambient Monitoring and Assessment (GAMA) study, California, February to April 2008. [The five-digit U.S. Geological Survey (USGS) parameter code below the constituent name is used to uniquely identify a specific constituent or property. GAMA well identification No.: MOJO, Mojave study unit grid well; MOJOU, Mojave study unit understanding well. Threshold type and threshold level as of April 2, 2008. The SMCL-CA for specific conductance has recommended and upper threshold values. The upper value is shown in parentheses. Threshold type: SMCL-US, U.S. Environmental Protection Agency secondary maximum contaminant level; SMCL-CA, California Department of Public Health secondary maximum contaminant level. Other abbreviations: C, celsius; mg/L, milligrams per liter; nc, sample not collected; na, not available; NTU, nephelometric turbidity unit; RL, reporting limit or range; μS/cm, microsiemens per centimeter; <, less than; >, greater than; CaCO3, calcium carbonate; *, value above threshold level or outside threshold range; **, value above upper threshold level] Specific Specific Water conduct- Dissolved pH, pH, conduct- Alkalinity, Alkalinity, GAMA Turbidity, temper-ature, ance, Bicarbonate, Carbonate, oxygen, lab field ance, lab field well identifi - field field lab field field field (standard (standard field (mg/L as (mg/L as cation (NTU) (degrees (μS/cm (mg/L) (mg/L) (mg/L) units) units) (μS/cm CaCO ) CaCO ) No. (63676) C) at 25 3 3 (63786) (63788) (00300) 00403) (00400) at 25C) (29801) (29802) (00010) degrees C) (00095) (90095) Threshold na na na SMCL-US SMCL-US SMCL-CA SMCL-CA na na na na type Threshold na na na <6.5–8.5> <6.5–8.5> 900 (1,600) 900 (1,600) na na na na level [RL] [0.1] [0.2] [0.0–38.5] [0–14] [0–14] [5] [5] [1] [1] [1] [1] Grid wells (52 wells sampled) MOJO-01 nc 5.4 17.0 nc *8.8 nc 173 nc nc nc nc MOJO-02 nc 1.4 21.0 nc 8.0 nc 882 nc nc nc nc MOJO-03 nc 4.2 23.0 nc 7.8 nc 714 nc nc nc nc MOJO-04 nc 7.2 22.0 nc 8.5 nc 187 nc nc nc nc MOJO-05 nc 4.3 17.0 nc 7.6 nc 273 nc nc nc nc MOJO-06 nc 5.5 15.0 nc 7.8 nc 185 nc nc nc nc MOJO-07 nc 1.5 27.0 nc *8.9 nc 206 nc nc nc nc MOJO-08 nc 2.1 27.0 nc 8.1 nc 494 nc nc nc nc 

MOJO-09 nc <0.2 20.0 nc 8.1 nc *981 nc nc nc nc 

MOJO-10 nc <0.2 31.5 nc *9.3 nc 289 nc nc nc nc MOJO-11 nc 0.3 27.5 nc *8.6 nc 422 nc nc nc nc 

MOJO-12 nc 0.6 18.0 7.5 7.3 613 606 172 163 199 <1.0 

MOJO-13 nc 0.3 20.5 8.1 8.3 *905 *910 52 48.3 58 <1.0 

MOJO-14 nc 5.0 23.0 *9.4 *9.3 230 228 102 100 98 11.7 MOJO-15 nc 4.1 27.5 *9.6 *9.6 216 221 97 91.5 78 15.6 

Groundwater Quality Data in the Mojave Study Unit, 2008: Results from the California GAMA Program 
 

Table 4. Water-quality indicators (field parameters) in samples collected for the Mojave Groundwater Ambient Monitoring and Assessment (GAMA) study, California, February to April 2008.—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. GAMA well identification No.: MOJO, Mojave

study unit grid well; MOJOU, Mojave study unit understanding well. Threshold type and threshold level as of April 2, 2008. The SMCL-CA for specific conductance has recommended and upper threshold values. The upper value is shown in parentheses. Threshold type: SMCL-US, U.S. Environmental Protection Agency secondary maximum contaminant level; SMCL-CA, California Department of Public Health secondary maximum contaminant level. Other abbreviations: C, celsius; mg/L, milligrams per liter; nc, sample not collected; na, not available; NTU, nephelometric turbidity unit; RL, reporting limit

or range; μS/cm, microsiemens per centimeter; <, less than; >, greater than; CaCO3, calcium carbonate; *, value above threshold level or outside threshold range; **, value above upper threshold level]

Specific Specific Water conduct- Dissolved pH, pH, conduct- Alkalinity, Alkalinity, GAMA Turbidity, temper-ature, ance, Bicarbonate, Carbonate, oxygen, lab field ance, lab field well identifi - field field lab field field field (standard (standard field (mg/L as (mg/L as cation (NTU) (degrees (μS/cm (mg/L) (mg/L) (mg/L) units) units) (μS/cm CaCO ) CaCO ) No. (63676) C) at 25 3 3 (63786) (63788) (00300) 00403) (00400) at 25C) (29801) (29802) (00010) degrees C) (00095) (90095) 

Threshold 

na na na SMCL-US SMCL-US SMCL-CA SMCL-CA na na na na type

Threshold 

na na na <6.5–8.5> <6.5–8.5> 900 (1,600) 900 (1,600) na na na na level

[RL] [0.1] [0.2] [0.0–38.5] [0–14] [0–14] [5] [5] [1] [1] [1] [1] MOJO-16 nc 5.6 22.5 8.5 *8.6 178 177 81 73.3 89 <1.0 

MOJO-17 nc 10.0 14.5 7.3 7.0 417 405 109 100 122 <1.0 

MOJO-18 nc 9.6 12.5 7.6 7.3 213 199 65 nc nc nc 

MOJO-19 nc 5.3 19.5 8.5 *8.6 453 371 67 nc nc nc 

MOJO-20 nc 1.5 14.5 nc 8.3 nc 502 nc nc nc nc 

MOJO-21 nc 7.2 22.0 nc 7.8 nc *1,420 nc nc nc nc 

MOJO-22 nc 5.1 26.5 nc 8.1 nc 809 nc nc nc nc 

MOJO-23 nc 6.6 26.0 nc 8.0 nc 425 nc nc nc nc 

MOJO-24 nc 6.7 25.0 nc 7.3 nc 443 nc nc nc nc MOJO-25 0.1 0.3 20.5 7.4 7.5 656 668 144 138 167 <1.0 

MOJO-26 nc 0.7 19.0 nc 7.8 nc 525 nc nc nc nc MOJO-27 0.1 1.6 28.0 *9.0 *9.0 202 209 74 nc nc nc MOJO-28 nc 7.9 10.5 nc 6.9 nc 529 nc nc nc nc 

MOJO-29 0.1 2.5 23.0 7.7 7.6 **2,750 **2,750 94 90.0 109 <1.0 MOJO-30 0.3 2.9 22.0 8.4 8.4 559 547 77 73.2 87 1.0 

Tables 39
 
40 Table 4. Water-quality indicators (field parameters) in samples collected for the Mojave Groundwater Ambient Monitoring and Assessment (GAMA) study, California, February to April 2008.—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. GAMA well identification No.: MOJO, Mojave study unit grid well; MOJOU, Mojave study unit understanding well. Threshold type and threshold level as of April 2, 2008. The SMCL-CA for specific conductance has recommended and upper threshold values. The upper value is shown in parentheses. Threshold type: SMCL-US, U.S. Environmental Protection Agency secondary maximum contaminant level; SMCL-CA, California Department of Public Health secondary maximum contaminant level. Other abbreviations: C, celsius; mg/L, milligrams per liter; nc, sample not collected; na, not available; NTU, nephelometric turbidity unit; RL, reporting limit or range; μS/cm, microsiemens per centimeter; <, less than; >, greater than; CaCO3, calcium carbonate; *, value above threshold level or outside threshold range; **, value above upper threshold level] Specific Specific Water conduct- Dissolved pH, pH, conduct- Alkalinity, Alkalinity, GAMA Turbidity, temper-ature, ance, Bicarbonate, Carbonate, oxygen, lab field ance, lab field well identifi - field field lab field field field (standard (standard field (mg/L as (mg/L as cation (NTU) (degrees (μS/cm (mg/L) (mg/L) (mg/L) units) units) (μS/cm CaCO ) CaCO ) No. (63676) C) at 25 3 3 (63786) (63788) (00300) 00403) (00400) at 25C) (29801) (29802) (00010) degrees C) (00095) (90095) Threshold na na na SMCL-US SMCL-US SMCL-CA SMCL-CA na na na na type Threshold na na na <6.5–8.5> <6.5–8.5> 900 (1,600) 900 (1,600) na na na na level [RL] [0.1] [0.2] [0.0–38.5] [0–14] [0–14] [5] [5] [1] [1] [1] [1] MOJO-31 3.3 0.4 27.0 8.4 8.3 482 485 90 85.5 102 1.0 MOJO-32 nc 5.4 25.5 nc *8.7 nc 195 nc nc nc nc MOJO-33 nc 9.5 22.5 nc 7.7 nc 418 nc nc nc nc MOJO-34 nc 8.7 15.5 nc 6.8 nc 231 nc nc nc nc MOJO-35 0.5 5.1 21.5 7.5 7.7 610 600 148 142 173 <1.0 MOJO-36 nc 0.2 23.0 8.0 8.0 540 537 152 nc nc nc MOJO-37 nc 2.2 25.5 nc 8.0 nc 411 nc nc nc nc MOJO-38 nc 4.4 23.5 nc 7.8 nc 486 nc nc nc nc MOJO-39 13.0 8.6 22.0 7.8 8.2 **1,630 *1,570 156 nc nc nc MOJO-40 nc 3.9 22.5 nc 7.7 nc **3,210 nc nc nc nc 

MOJO-41 0.2 5.3 22.5 7.7 7.6 722 728 191 180 219 1.0 

MOJO-42 0.4 4.5 22.5 8.0 7.9 451 450 151 140 170 1.0 

MOJO-43 nc 4.7 24.5 nc 7.4 nc 710 nc nc nc nc MOJO-44 nc 5.5 23.5 nc 7.9 nc **2,350 nc nc nc nc 

MOJO-45 nc 5.4 20.0 nc 7.2 nc 868 nc nc nc nc 

Groundwater Quality Data in the Mojave Study Unit, 2008: Results from the California GAMA Program 
 

Table 4. Water-quality indicators (field parameters) in samples collected for the Mojave Groundwater Ambient Monitoring and Assessment (GAMA) study, California, February to April 2008.—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. GAMA well identification No.: MOJO, Mojave

study unit grid well; MOJOU, Mojave study unit understanding well. Threshold type and threshold level as of April 2, 2008. The SMCL-CA for specific conductance has recommended and upper threshold values. The upper value is shown in parentheses. Threshold type: SMCL-US, U.S. Environmental Protection Agency secondary maximum contaminant level; SMCL-CA, California Department of Public Health secondary maximum contaminant level. Other abbreviations: C, celsius; mg/L, milligrams per liter; nc, sample not collected; na, not available; NTU, nephelometric turbidity unit; RL, reporting limit

or range; μS/cm, microsiemens per centimeter; <, less than; >, greater than; CaCO3, calcium carbonate; *, value above threshold level or outside threshold range; **, value above upper threshold level]

Specific Specific Water conduct- Dissolved pH, pH, conduct- Alkalinity, Alkalinity, GAMA Turbidity, temper-ature, ance, Bicarbonate, Carbonate, oxygen, lab field ance, lab field well identifi - field field lab field field field (standard (standard field (mg/L as (mg/L as cation (NTU) (degrees (μS/cm (mg/L) (mg/L) (mg/L) units) units) (μS/cm CaCO ) CaCO ) No. (63676) C) at 25 3 3 (63786) (63788) (00300) 00403) (00400) at 25C) (29801) (29802) (00010) degrees C) (00095) (90095) 

Threshold 

na na na SMCL-US SMCL-US SMCL-CA SMCL-CA na na na na type

Threshold 

na na na <6.5–8.5> <6.5–8.5> 900 (1,600) 900 (1,600) na na na na level

[RL] [0.1] [0.2] [0.0–38.5] [0–14] [0–14] [5] [5] [1] [1] [1] [1] MOJO-46 nc 7.0 15.5 nc 7.5 nc 176 nc nc nc ncMOJO-47 nc 5.4 18.5 nc 8.1 nc **1820 nc nc nc nc

MOJO-48 nc 0.3 27.0 nc *9.8 nc 462 nc nc nc nc

MOJO-49 0.2 3.3 26.0 7.7 7.9 **3,020 **2,990 122 117 141 <1.0MOJO-50 nc 7.6 18.9 nc 7.5 nc *957 nc nc nc nc

MOJO-51 nc 2.5 22.0 nc 7.8 nc 520 nc nc nc nc

MOJO-52 nc 1.8 24.5 nc 8.0 nc 384 nc nc nc nc

Understanding wells (7 wells sampled)

MOJOU-01 0.3 6.1 15.0 7.3 7.2 *953 *939 307 299 364 <1.0

MOJOU-02 nc 0.3 20.5 *9.6 *9.4 301 298 146 141 125 21.9MOJOU-03 nc 1.1 21.0 7.5 7.4 **1,660 **1,610 228 212 258 <1.0MOJOU-04 2.3 0.8 24.0 8.3 8.4 *956 *952 143 133 158 1.6

MOJOU-05 45 0.3 25.5 *9.7 *9.7 332 338 137 127 109 21.4MOJOU-06 nc 8.0 22.0 nc 7.9 nc 608 nc nc nc nc

MOJOU-07 nc 5.6 20.0 nc 7.1 nc **3,080 nc nc nc nc

Tables 41
 
42 Groundwater Quality Data in the Mojave Study Unit, 2008: Results from the California GAMA Program Table 5. Volatile organic compounds (VOC) detected in samples collected for the Mojave Groundwater Ambient Monitoring and Assessment (GAMA) study, California, February to April 2008.—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. Samples from all fifty-nine wells were analyzed, but only samples with detections are listed. Analytes are listed in order of decreasing detection frequency in the fifty-two grid wells. All analytes are listed in table 3A. 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. GAMA well identification No.: MOJO, Mojave study unit grid well; MOJOU, Mojave study unit understanding well. Threshold type and threshold level as of April 2, 2008. Threshold type: MCL-US, U.S. Environmental Protection Agency maximum contaminant level; MCL-CA; California Department of Public Health maximum contaminant level. Other abbreviations: E, estimated or having a higher degree of uncertainty; LRL, laboratory reporting level; V, analyte detected in sample and an associated blank, thus data are not included in groundwater quality assessment; μg/L, microgram per liter; na, not available; —, not detected] Trihalomethane Gasoline Trihalomethane Solvent Trihalomethane Trihalomethane Solvent Solvent Solvent Solvent Perchloro- Chloroform Dibromo- Bromoform 1,1-Dichloro- 1,2-Dichloro- 1,2,4-Trimethyl- Bromodi- ethene (PCE, 1,3-Dichloro- Chloro- GAMA well identi- (Trichloro- chloro- (Tribromo ethane ethane benzene chloromethane Tetrachloro- benzene benzene fication No. methane) methane methane) (1,1-DCA) (1,2-DCA) (μg/L) (μg/L) ethene) (μg/L) (μg/L) (μg/L) (μg/L) (μg/L) (μg/L) (μg/L) (77222) (32101) (μg/L) (34566) (34301) (32106) (32105) (32104) (34496) (32103) (34475) Threshold type MCL-US NL-CA MCL-US MCL-US MCL-US MCL-US MCL-CA MCL-CA HAL-US MCL-CA Threshold level 1 80 330 1 80 5 1 80 1 80 5 0.5 600 70 [LRL] [0.02] [0.04] [0.04] [0.04] [0.12] [0.08] [0.04] [0.06] [0.04] [0.02] Grid wells (52 wells sampled) MOJO-03 0.14

—

—

—

—

—

—

—

—

—

MOJO-09 E0.02

—

—

—

—

—

—

—

—

—

MOJO-14 — E0.06

—

—

—

—

—

—

—

—

MOJO-15 — E0.02

—

—

—

—

—

—

—

—

MOJO-17 0.28 E0.09

—

—

—

—

—

—

—

—

MOJO-19 E0.03

—

— 0.11

—

—

— — E0.01

—

MOJO-22 E0.05

— E0.04

—

—

—

—

—

—

—

MOJO-25 0.47

— E0.04

—

—

—

—

— — E0.01

MOJO-26 1.31

— 0.72

— 0.7 0.47

—

—

—

—

MOJO-27

— 0.12

—

—

—

—

—

—

—

—

MOJO-30 0.18

— E0.05

—

—

—

—

—

—

—

MOJO-32 — E0.01

—

—

— — E0.04

—

—

—

MOJO-35 E0.04

—

—

—

—

—

—

—

—

—

MOJO-39 E0.06 E0.02 — E0.06

—

—

—

—

—

—

MOJO-40 0.12

—

—

—

—

—

—

—

—

—

MOJO-41 E0.05

—

—

—

—

—

—

—

—

—
 

Table 5. Volatile organic compounds (VOC) detected in samples collected for the Mojave Groundwater Ambient Monitoring and Assessment (GAMA) study, California, February to April 2008.—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. Samples from all fifty-nine wells were analyzed, but only samples with detections are listed. Analytes are listed in order of decreasing detection frequency in the fifty-two grid wells. All analytes are listed in table 3A. 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. GAMA well identification No.: MOJO, Mojavestudy unit grid well; MOJOU, Mojave study unit understanding well. Threshold type and threshold level as of April 2, 2008. Threshold type: MCL-US, U.S. Environmental Protection Agency maximum contaminant level; MCL-CA; California Department of Public Health maximum contaminant level. Other abbreviations: E, estimated or having a higher degree of uncertainty; LRL, laboratory reportinglevel; V, analyte detected in sample and an associated blank, thus data are not included in groundwater quality assessment; μg/L, microgram per liter; na, not available; —, not detected]

Trihalomethane Gasoline Trihalomethane Solvent Trihalomethane Trihalomethane Solvent Solvent Solvent Solvent 

Perchloro- Chloroform Dibromo- Bromoform 1,1-Dichloro- 1,2-Dichloro­ 1,2,4-Trimethyl- Bromodi- ethene (PCE, 1,3-Dichloro- Chloro- GAMA well identi- (Trichloro- chloro- (Tribromo ethane ethane benzene chloromethane Tetrachloro- benzene benzene fication No. methane) methane methane) (1,1-DCA) (1,2-DCA) (μg/L) (μg/L) ethene) (μg/L) (μg/L) (μg/L) (μg/L) (μg/L) (μg/L) (μg/L) (77222) (32101) (μg/L) (34566) (34301) (32106) (32105) (32104) (34496) (32103) (34475) 

Threshold type MCL-US NL-CA MCL-US MCL-US MCL-US MCL-US MCL-CA MCL-CA HAL-US MCL-CA Threshold level 1 80 330 1 80 5 1 80 1 80 5 0.5 600 70 

[LRL] [0.02] [0.04] [0.04] [0.04] [0.12] [0.08] [0.04] [0.06] [0.04] [0.02] 

MOJO-44 E0.04 — — — — — — — — — MOJO-45 — — — E0.06 — — — — — — 

MOJO-49 — — — — — — — — — — MOJO-50 0.35 — — 0.93 — — 0.42 E0.1 — — MOJO-52 4.36 — 0.71 — 1 1.72 — — — — Number of wells 15 6 5 4 2 2 2 1 1 1 

with detections

Detection 28.8 11.5 9.6 7.7 3.8 3.8 3.8 1.9 1.9 1.9 

frequency(percent)

Total Detections 

Understanding wells2 (7 wells sampled)

MOJOU-01 E0.04 — — E0.03 — — — — — — 

MOJOU-03 — — — — — — — — — — MOJOU-05 — — — — — — — — — — MOJOU-06 E0.04 — — — — — — — — — 

MOJOU-07 — E0.04 — — — — — — — — 

Tables 43
 
44 Table 5. Volatile organic compounds (VOCs) detected in samples collected for the Mojave Groundwater Ambient Monitoring and Assessment (GAMA) study, California, February to April 2008.—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. Samples from all fifty-nine wells were analyzed, but only samples with detections are listed. Analytes are listed in order of decreasing detection frequency in the fifty-two grid wells. All analytes are listed in table 3A. 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. GAMA well Identification number: MOJO, Mojave study unit grid well; MOJOU, Mojave study unit understanding well. Threshold type and threshold level as of April 2, 2008. Threshold type: MCL-US, U.S. Environmental Protection Agency maximum contaminant level; MCL-CA; California Department of Public Health maximum contaminant level. Other abbreviations: E, estimated or having a higher degree of uncertainty; LRL, laboratory reporting level; V, analyte detected in sample and an associated blank, thus data are not included in groundwater quality assessment; μg/L, microgram per liter; na, not available; —, not detected] Organic syn- Solvent Solvent Solvent Solvent Solvent Solvent Refrigerant Gasoline Fumigant thesis trans-1,2­ Methylene Carbon Trichloro- Methyl Detec­ cis-1,2- Tetra- Dichloro- Trichloro- 1,1-Dichloro- GAMA identifica- chloride tetrachloride fluoro- tert-butyl tions Any Dichloro- hydro- ethene ethene ethene Toluene tion no. (dichloro- (tetrachloro- methane ether per VOC ethene furan (trans- (TCE) (1,1-DCE) (μg/L) methane) methane) (CFC-11) (MTBE) well (cis-1,2-DCE) (μg/L) 1,2-DCE) (μg/L) (μg/L) (34010) (μg/L) (μg/L) (μg/L) (μg/L) (μg/L) (77093) (81607) (μg/L) (39180) (34501) (34423) (32102) (34488) (78032) (34546) Threshold type MCL-CA MCL-US MCL-CA na MCL-CA MCL-US MCL-CA MCL-CA MCL-CA MCL-CA Threshold level 6 5 0.5 na 10 5 150 6 150 13 [LRL] [0.02] [0.04] [0.08] [1.4] [0.018] [0.02] [0.08] [0.02] [0.018] [0.10] Grid wells (52 wells sampled) MOJO-03 — — — — — — — — — — 1 MOJO-09 — — — — — — — — — — 1 MOJO-14 — — — — — — — — — — 1 MOJO-15 — — — — — — — — — — 1 MOJO-17 — — — — — — — — — — 2 MOJO-19 — — — — — — — — — — 3 MOJO-22 — — — — — — — — — — 2 MOJO-25 — 0.1 — — — — — — — — 4 MOJO-26 — — — — — — — — — — 4 MOJO-27 — — — — — — — — — — 1 MOJO-30 — — — — — — — — — — 2 

MOJO-32 — — — — — — — — — — 2 MOJO-35 — — — — — — — — — — 1 MOJO-39 — — — — — — — — — — 3 MOJO-40 — — — — — — — — — — 1 

Groundwater Quality Data in the Mojave Study Unit, 2008: Results from the California GAMA Program 
 

Table 5. Volatile organic compounds (VOCs) detected in samples collected for the Mojave Groundwater Ambient Monitoring and Assessment (GAMA) study, California, February to April 2008.—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. Samples from all fifty-nine wells were analyzed, but only samples with detections are listed. Analytes are listed in order of decreasing detection frequency in the fifty-two grid wells. All analytes are listed in table 3A. 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. GAMA well Identification number: MOJO, Mojavestudy unit grid well; MOJOU, Mojave study unit understanding well. Threshold type and threshold level as of April 2, 2008. Threshold type: MCL-US, U.S. Environmental Protection Agency maximum contaminant level; MCL-CA; California Department of Public Health maximum contaminant level. Other abbreviations: E, estimated or having a higher degree of uncertainty; LRL, laboratory reportinglevel; V, analyte detected in sample and an associated blank, thus data are not included in groundwater quality assessment; μg/L, microgram per liter; na, not available; —, not detected]

Organic syn- Solvent Solvent Solvent Solvent Solvent Solvent Refrigerant Gasoline Fumigant thesis 

trans-1,2­ Methylene Carbon Trichloro- Methyl Detec­ cis-1,2- Tetra- Dichloro- Trichloro- 1,1-Dichloro- GAMA identifica- chloride tetrachloride fluoro- tert-butyl tions Any Dichloro- hydro- ethene ethene ethene Toluene tion no. (dichloro- (tetrachloro- methane ether per VOC ethene furan (trans- (TCE) (1,1-DCE) (μg/L) methane) methane) (CFC-11) (MTBE) well (cis-1,2-DCE) (μg/L) 1,2-DCE) (μg/L) (μg/L) (34010) (μg/L) (μg/L) (μg/L) (μg/L) (μg/L) (77093) (81607) (μg/L) (39180) (34501) (34423) (32102) (34488) (78032) (34546) 

Threshold type MCL-CA MCL-US MCL-CA na MCL-CA MCL-US MCL-CA MCL-CA MCL-CA MCL-CA 

Threshold level 6 5 0.5 na 10 5 150 6 150 13 

[LRL] [0.02] [0.04] [0.08] [1.4] [0.018] [0.02] [0.08] [0.02] [0.018] [0.10] 

MOJO-41 — — — — — — — — — — 1 MOJO-44 — — — — — — — — — — 1 MOJO-45 — — — — — — E0.06 — — — 2 MOJO-49 — — — — — — — — E0.02 — 1 MOJO-50 0.12 — — — E0.06 0.43 — 0.43 — — 8 MOJO-52 — — E0.09 4 — — — — — — 6 Number of wells 1 1 1 1 1 1 1 1 1 0 21 

with detections

Detection 1.9 1.9 1.9 1.9 1.9 1.9 1.9 1.9 1.9 0 40 

frequency(percent)

Total Detections 48 

Understanding wells2 (7 wells sampled)

MOJOU-01 — — — — — — — — — 0.2 3 MOJOU-03 — — — 3 — — — — V0.04 E0.1 3 

MOJOU-05 — — — — — — — — 1.06 — 1 MOJOU-06 — — — — — 0.11 — E0.03 — — 3 MOJOU-07 — — — — — — — — — — 1 

Tables 45
 1 The MCL-US threshold for trihalomethanes is for the sum of chloroform, bromoform, bromodichloromethane, and dibromochloromethane. 2 Understanding wells were not included in statistical calculations. 
Table 6. Pesticides and pesticide degradates detected in samples collected for the Mojave Groundwater Ambient Monitoring and Assessment (GAMA) study, California, 

February to April 2008—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. Samples from all fifty-nine wells were analyzed, but only samples with detections are listed. Analytes are listed in order of decreasing detection frequency in the fifty-two grid wells. All analytes are listed in table 3B. 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. Understanding wells were not included 

in statistical calculations. GAMA well identification No.: MOJO, Mojave study unit grid well; MOJOU, Mojave study unit understanding well. Threshold type and threshold level as of April 2, 2008. 

Threshold type: HAL-US, U.S. Environmental Protection Agency lifetime health advisory level; MCL-US, U.S. Environmental Protection Agency maximum contaminant level; MCL-CA; California Department of Public Health maximum contaminant level; RSD5-US, U.S. Environmental Protection Agency risk specific dose at a risk factor of 10–5 . Other abbreviations: E, estimated or having a higher 

degree of uncertainty; LRL, laboratory reporting level; μg/L, microgram per liter; na, not available; —, not detected]

46 Table 6. Pesticides and pesticide degradates detected in samples collected for the Mojave Groundwater Ambient Monitoring and Assessment (GAMA) study, California, February to April 2008. [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 fifty-nine wells were analyzed, but only samples with detections are listed. Analytes are listed in order of decreasing detection frequency in the fifty-two grid wells. All analytes are listed in table 3B. 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. Understanding wells were not included in statistical calculations. GAMA well identification No.: MOJO, Mojave study unit grid well; MOJOU, Mojave study unit understanding well. Threshold type and threshold level as of April 2, 2008. Threshold type: HAL-US, U.S. Environmental Protection Agency lifetime health advisory level; MCL-US, U.S. Environmental Protection Agency maximum contaminant level; MCL-CA; California Department of Public Health maximum contaminant level; RSD5-US, U.S. Environmental Protection Agency risk specific dose at a risk factor of 10–5. Other abbreviations: E, estimated or having a higher degree of uncertainty; LRL, laboratory reporting level; μg/L, microgram per liter; na, not available; —, not detected] Deethyl­ atrazine
 (2-Chloro-4­ 3,4-Dichloro- Desulfinyl- Fipronil GAMA well Simazine isopropyl- Atrazine Prometon Dieldrin Fipronil Pesticide aniline fipronil sulfide Any pesti­ identification (μg/L) amino-6- (μg/L) (μg/L) (μg/L) (μg/L) detections (μg/L) (μg/L) (μg/L) cide No. (04035) amino-s- (39632) (04037) (39381) (62166) per well (61625) (62170) (62167) triazine)
 (μg/L)
 (04040)
 Threshold MCL-US na MCL-CA na HAL-US na RSD5-US na na type Threshold 4 na 1 na 100 na 0.02 na na level [LRL] [0.006] [0.014] [0.007] [0.006] [0.01] [0.012] [0.009] [0.02] [0.013] Grid wells (52 wells sampled) MOJO-05 — E0.005 — — — — — — — 1 MOJO-06 0.008 E0.005 — — — — — — — 2 MOJO-09 0.008 — — — — — — — — 1 MOJO-12 0.008 — — — — — — — — 1 MOJO-17 — E0.007 — E0.004 — — — — — 2 MOJO-18 E0.006 E0.007 E0.007 — — — — — — 3 MOJO-19 E0.007 E0.009 E0.008 E0.006 — — — — — 4 

MOJO-25 0.016 — — E0.057 E0.01 E0.004 — E0.006 E0.005 6 MOJO-30 E0.006 — — — E0.01 — E0.006 — — 3 MOJO-44 — E0.007 — — — — — — — 1 

MOJO-45 E0.008 E0.007 0.008 — — — — — — 3 

Groundwater Quality Data in the Mojave Study Unit, 2008: Results from the California GAMA Program 
 

Table 6. Pesticides and pesticide degradates detected in samples collected for the Mojave Groundwater Ambient Monitoring and Assessment (GAMA) study, California, February to April 2008—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. Samples from all fifty-nine wells were analyzed, but only samples with detections are listed. Analytes are listed in order of decreasing detection frequency in the fifty-two grid wells. All analytes are listed in table 3B. 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. Understanding wells were not included 

in statistical calculations. GAMA well identification No.: MOJO, Mojave study unit grid well; MOJOU, Mojave study unit understanding well. Threshold type and threshold level as of April 2, 2008. 

Threshold type: HAL-US, U.S. Environmental Protection Agency lifetime health advisory level; MCL-US, U.S. Environmental Protection Agency maximum contaminant level; MCL-CA; California Department of Public Health maximum contaminant level; RSD5-US, U.S. Environmental Protection Agency risk specific dose at a risk factor of 10–5. Other abbreviations: E, estimated or having a higher

degree of uncertainty; LRL, laboratory reporting level; μg/L, microgram per liter; na, not available; —, not detected]

Deethylatrazine


(2-Chloro-4­ 3,4-Dichloro- Desulfinyl- Fipronil GAMA well Simazine isopropyl- Atrazine Prometon Dieldrin Fipronil Pesticide aniline fipronil sulfide Any pesti­ identification (μg/L) amino-6- (μg/L) (μg/L) (μg/L) (μg/L) detections (μg/L) (μg/L) (μg/L) cide No. (04035) amino-s- (39632) (04037) (39381) (62166) per well (61625) (62170) (62167) triazine)


(μg/L)


(04040)
 

Threshold MCL-US na MCL-CA na HAL-US na RSD5-US na na type

Threshold 4 na 1 na 100 na 0.02 na na level

[LRL] [0.006] [0.014] [0.007] [0.006] [0.01] [0.012] [0.009] [0.02] [0.013] 

MOJO-50 0.010 E0.034 0.014 — E0.01 — — — — 4 

Number of 9 8 4 3 3 1 1 1 1 12 

wells withdetections

Detection 17.3 15.4 9.6 5.8 5.8 1.9 1.9 1.9 1.9 23 

frequency(percent)

Total Detec- 31 

tions 

Understanding wells (7 wells sampled)

MOJOU-01 — E0.007 — — — — — — — 1 

MOJOU-03 — E0.028 0.053 — 0.010 — — — — 3 

MOJOU-06 E0.006 — — — — — — — — 1 Tables 47
 
48 Groundwater Quality Data in the Mojave Study Unit, 2008: Results from the California GAMA Program 

Table 7. Constituents of special interest (perchlorate and N-nitrosodimethylamine [NDMA]) detected in samples collected in the 

Mojave Groundwater Ambient Monitoring and Assessment (GAMA) study, California, February to April 2008. 

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

Information about the analytes given in table 3D. Samples from all fifty-nine wells were analyzed for perchlorate; samples from the twenty-four slow wells 

were sampled for NDMA; only wells with at least one detection are listed; detection frequency presented for perchlorate only. GAMA well identification No.: 

MOJO, Mojave study unit grid well; MOJOU, Mojave study unit understanding well. Threshold type and threshold level as of April 2, 2008. 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; NL-CA, California Department of Public 

Health notification level. Other abbreviations: MRL, method reporting level; μg/L, microgram per liter; nc, not collected; —, not detected; *, value above 

threshold level] 

GAMA 

well 

identification 

No. 

Perchlorate 

(μg/L) 

(63790) 

N-nitrosodimethylamine1 

(NDMA) 

(μg/L) 

(34438) 

GAMA 

well 

identification 

No. 

Perchlorate 

(μg/L) 

(63790) 

N-nitrosodimethylamine1 

(NDMA) 

(μg/L) 

(34438) 

Threshold type MCL-CA NL-CA Threshold type MCL-CA NL-CA 

Threshold level 6 0.010 Threshold level 6 0.010 

[MRL] [0.10] [0.0020] [MRL] [0.10] [0.0020] 

Grid wells (52 wells sampled) Grid wells (52 wells sampled)—Continued 

MOJO-02 0.35 nc MOJO-31 0.15 — 

MOJO-03 1.0 nc MOJO-32 0.70 nc 

MOJO-04 0.23 nc MOJO-33 0.82 nc 

MOJO-05 0.35 nc MOJO-38 0.10 nc 

MOJO-06 0.18 nc MOJO-39 0.40 — 

MOJO-07 0.78 nc MOJO-40 0.35 nc 

MOJO-08 0.38 nc MOJO-42 — *0.0540 

MOJO-11 0.11 nc MOJO-43 0.27 nc 

MOJO-13 0.25 — MOJO-44 2.8 nc 

MOJO-16 0.12 — MOJO-45 0.21 nc 

MOJO-17 0.35 — MOJO-46 0.41 nc 

MOJO-18 0.70 — MOJO-49 1.7 — 

MOJO-19 0.33 — MOJO-50 1.6 nc 

MOJO-21 0.35 nc Number of wells 33 

MOJO-22 0.16 nc with detections 

MOJO-23 1.2 nc Detection frequency 63 

MOJO-24 0.31 nc (percent) 

MOJO-25 0.17 — Understanding wells1

 (7 wells sampled) 

MOJO-27 0.67 — MOJOU-02 0.31 — 

MOJO-29 0.41 — MOJOU-04 0.40 — 

MOJO-30 0.34 — MOJOU-07 0.38 nc 

1

 Understanding wells were not included in statistical calculations. 
Tables 49 

Table 8. Nutrients and dissolved organic carbon (DOC) detected in samples collected for the Mojave Groundwater Ambient Monitoring 

and Assessment (GAMA) study, California, February to April 2008. 

[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 the twenty-four slow wells were analyzed for nutrients. Samples from eight fast wells and eight slow wells were analyzed for dissolved organic 

carbon (DOC). All analytes are listed in table 3E. GAMA well identification No.: MOJO, Mojave study unit grid well; MOJOU, Mojave study unit understanding well. Threshold type and threshold level as of April 2, 2008. The HAL-US is 30 mg/L “as ammonia.” To facilitate comparson to the analytical results, we 

have converted and reported this HAL-US as 24.7 mg/L “as nitrogen.” 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. Other abbreviations: E, estimated or having a higher degree of uncertainty; LRL, laboratory reporting level; mg/L, milligram per liter; na, not available; V, analyte detected in sample and 

an associated blank, thus data are not included in groundwater quality assessment; ≤, less than or equal to; nc, not collected; —, not detected] 

GAMA well 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 + organicnitrogen) as nitrogen 

(mg/L) 

(62854) 

Phosphate, 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 level 24.7 10 1 na na na 

[LRL] [0.02] [0.04] [0.002] [0.06] [0.006] [0.4] 

Grid wells (19 wells sampled) 

MOJO-01 nc nc nc nc nc V0.2 

MOJO-05 nc nc nc nc nc V0.4 

MOJO-06 nc nc nc nc nc V0.3 

MOJO-09 nc nc nc nc nc 0.6 

MOJO-12 — 0.53 — 0.54 0.020 0.6 

MOJO-13 — 0.64 — 0.65 0.010 nc 

MOJO-14 E0.011 0.27 — 1 0.24 0.019 nc 

MOJO-15 — 0.49 — 1 0.50 0.018 nc 

MOJO-16 — 0.40 — 0.40 0.008 nc 

MOJO-17 — 4.09 — 4.27 0.038 0.6 

MOJO-18 — 0.57 — 1 0.55 0.036 V0.3 

MOJO-19 — 2.63 — 2.76 0.007 V0.3 

MOJO-25 — 8.94 E0.002 9.55 0.040 0.7 

MOJO-26 nc nc nc nc nc V0.3 

MOJO-27 — 2.31 E0.001 1 2.26 0.009 nc 

MOJO-29 — 1.07 — 1 1.04 0.011 nc 

MOJO-30 E0.012 1.51 E0.001 1 1.49 0.022 0.5 

MOJO-31 — 0.65 0.002 0.67 0.011 nc 

MOJO-34 nc nc nc nc nc V0.3 

MOJO-35 — 0.91 — 0.93 0.048 nc 

MOJO-36 — 0.06 0.009 E0.04 0.029 nc 

MOJO-39 — 1.56 — 1.64 0.012 nc 

MOJO-40 nc nc nc nc nc — 

MOJO-41 E0.011 0.12 — 1 0.11 0.011 V0.3 

MOJO-42 — 0.47 — 1 0.44 0.016 nc 

MOJO-49 2

— 2 4.19 2— 2 4.43 2 0.015 nc 

MOJO-51 nc nc nc nc nc V0.3 

Understanding wells (5 wells sampled) 

MOJOU-01 — 4.00 — 4.19 E0.005 nc 

MOJOU-02 0.021 — — — 0.034 nc 

MOJOU-03 0.028 5.84 0.016 6.07 0.079 nc 

MOJOU-04 — 0.18 — 0.18 0.016 nc 

MOJOU-05 0.055 ≤0.02 — 0.08 0.074 nc 

MOJOU-07 nc nc nc nc nc V0.4 

1 Total nitrogen in these samples is less than the sum of the filtered nitrogen analytes, but falls within the U.S. Geological Survey National Water Quality 

Laboratory acceptance criteria of a 10 percent relative percent difference. 2

Storage refrigerator exceeded maximum allowable temperature at NWQL before sample analysis. 
Table 9. Major and minor ions, silica, and total dissolved solids (TDS) detected in samples collected for the Mojave Groundwater Ambient Monitoring and Assessment 

(GAMA) study, California, February to April 2008.—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. Samples from the twenty-four slow wells were analyzed. Information about analytes given in table 3F. GAMA well identification No.: MOJO, Mojave study unit grid well; MOJOU, Mojave study unit understanding well. Threshold type and threshold level as of April 2, 2008. Bicarbonate and carbonate concentrations were calculated from the laboratory measured alkalinity and pH values using the advanced speciation method (http://or.water.usgs.gov/alk/methods.html) with pK1 = 6.35, pK2 = 10.33, and pKW = 14. See table 4 for the results of the preferred method (samples for which field alkalinities were performed). 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. The SMCL-CAfor chloride, sulfate, and total dissolved solids (TDS) have recommended and upper threshold values. The upper value is shown in parentheses. MCL-CA, California Department of Public Health maximum contaminant level; SMCL-CA, California Department of Public Health secondary maximum contaminant level. Other abbreviations: LRL, laboratory reporting level; mg/L, milligrams per liter; E, 

estimated or having a higher degree of uncertainty; na, not available; —, not detected; <, less than; *, value above threshold level; **, value above upper threshold level]

50 Table 9. Major and minor ions, silica, and total dissolved solids (TDS) detected in samples collected for the Mojave Groundwater Ambient Monitoring and Assessment (GAMA) study, California, February to April 2008. [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 the twenty-four slow wells were ana­ lyzed. Information about analytes given in table 3F. GAMA well identification No.: MOJO, Mojave study unit grid well; MOJOU, Mojave study unit understanding well. Threshold type and threshold level as of April 2, 2008. Bicarbonate and carbonate concentrations were calculated from the laboratory measured alkalinity and pH values using the advanced speciation method (http://or.water.usgs.gov/alk/methods. html) with pK1 = 6.35, pK2 = 10.33, and pKW = 14. See table 4 for the results of the preferred method (samples for which field alkalinities were performed). 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. The SMCL-CA for chloride, sulfate, and total dissolved solids (TDS) have recommended and upper threshold values. The upper value is shown in parentheses. MCL-CA, California Department of Public Health maximum contaminant level; SMCL­ CA, California Department of Public Health secondary maximum contaminant level. Other abbreviations: LRL, laboratory reporting level; mg/L, milligrams per liter; E, estimated or having a higher degree of uncertainty; na, not available; —, not detected; <, less than; *, value above threshold level; **, value above upper threshold level] Residue on Silica, GAMA well Calcium Magnesium Potassium Sodium Bromide Chloride Fluoride Iodide Sulfate evaporation Bicarbonate Carbonate as SiO2 identification (mg/L) (mg/L) (mg/L) (mg/L) (mg/L) (mg/L) (mg/L) (mg/L) (mg/L) (TDS) (mg/L) (mg/L) (mg/L) number (00915) (00925) (00935) (00930) (71870) (00940) (00950) (71865) (00945) (mg/L) (00955) (70300) SMCL- SMCL- Threshold type na na na na na na na MCL-CA na na SMCL-CA CA CA Threshold level na na na na na na na 250 (500) 2 na na 250 (500) 500 (1,000) [LRL] [0.04] [0.02] [0.02] [0.12] [1] [1] [0.02] [0.12] [0.12] [0.002] [0.018] [0.18] [10] Grid wells (19 wells sampled) MOJO-12 60.1 8.19 2.09 57.6 210 <1.0 0.09 39.8 0.32 0.004 26.0 75.2 383 MOJO-13 72.3 11.0 4.37 93.5 22 20.8 0.12 58.3 0.41 0.013 16.3 *295 *612 MOJO-14 3.93 0.299 0.62 48.8 102 10.5 0.02 3.88 0.49 0.006 17.5 9.24 146 MOJO-15 0.95 E0.018 0.34 47.2 85 15.1 E0.02 4.96 0.52 — 18.4 3.18 133 MOJO-16 10.9 0.574 1.24 28.6 96 1.3 0.03 6.17 0.16 — 20.2 2.69 117 MOJO-17 48.2 9.1 2.13 22.5 133 <1.0 0.09 34.6 0.35 — 25.9 25.7 263 MOJO-18 24.1 3.95 1.49 12.7 79 <1.0 0.05 15.6 0.27 — 25.7 13.6 144 MOJO-19 23.3 1.72 1.46 68.0 80 1.1 0.20 51.7 0.60 E0.001 16.8 56.9 277 MOJO-25 53.7 8.96 1.73 60.5 175 <1.0 0.11 59.7 0.62 0.013 28.3 52.7 414 MOJO-27 5.07 0.479 1.26 38.0 82 4.0 0.05 10.0 0.54 0.004 15.4 4.89 129 

MOJO-29 155 40.9 5.96 335 104 5.0 1.21 **639 0.41 0.006 33.2 *309 **1,660 MOJO-30 25.6 4.36 1.94 80.2 92 1.0 0.14 30.3 0.71 0.003 20.0 128 357 MOJO-31 27.9 5.33 2.81 60.4 107 1.0 E0.02 3.06 0.30 0.004 16.1 134 316 MOJO-35 46.7 8.09 2.67 66.7 180 <1.0 0.24 50.5 0.70 — 23.2 67.1 366 MOJO-36 19.2 3.21 2.4 89.5 184 1.0 0.09 36.8 1.94 0.035 40.8 49.9 341 MOJO-39 116 22.3 4.63 188 190 1.0 0.58 215 1.32 0.014 33.9 *306 **1,050 MOJO-41 58.8 6.44 1.14 84.2 232 1.0 0.19 84.2 0.26 — 27.5 48.7 435 MOJO-42 33.2 5.25 1.96 56.2 183 1.0 0.06 23.4 0.65 E0.001 29.2 39.1 279 

Groundwater Quality Data in the Mojave Study Unit, 2008: Results from the California GAMA Program 
 

Table 9. Major and minor ions, silica, and total dissolved solids (TDS) detected in samples collected for the Mojave Groundwater Ambient Monitoring and Assessment (GAMA) study, California, February to April 2008.—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. Samples from the twenty-four slow wells were analyzed. Information about analytes given in table 3F. GAMA well identification No.: MOJO, Mojave study unit grid well; MOJOU, Mojave study unit understanding well. Threshold type and threshold level as of April 2, 2008. Bicarbonate and carbonate concentrations were calculated from the laboratory measured alkalinity and pH values using the advanced speciation method (http://or.water.usgs.gov/alk/methods.html) with pK1 = 6.35, pK2 = 10.33, and pKW = 14. See table 4 for the results of the preferred method (samples for which field alkalinities were performed). 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. The SMCL-CAfor chloride, sulfate, and total dissolved solids (TDS) have recommended and upper threshold values. The upper value is shown in parentheses. MCL-CA, California Department of Public Health maximum contaminant level; SMCL-CA, California Department of Public Health secondary maximum contaminant level. Other abbreviations: LRL, laboratory reporting level; mg/L, milligrams per liter; E,

estimated or having a higher degree of uncertainty; na, not available; —, not detected; <, less than; *, value above threshold level; **, value above upper threshold level]

Residue on Silica, GAMA well Calcium Magnesium Potassium Sodium Bromide Chloride Fluoride Iodide Sulfate evaporation Bicarbonate Carbonate as SiO2 identification (mg/L) (mg/L) (mg/L) (mg/L) (mg/L) (mg/L) (mg/L) (mg/L) (mg/L) (TDS) (mg/L) (mg/L) (mg/L) number (00915) (00925) (00935) (00930) (71870) (00940) (00950) (71865) (00945) (mg/L) (00955) (70300) 

SMCL- SMCL- Threshold type na na na na na na na MCL-CA na na SMCL-CA CA CA 

Threshold level na na na na na na na 250 (500) 2 na na 250 (500) 500 (1,000) [LRL] [0.04] [0.02] [0.02] [0.12] [1] [1] [0.02] [0.12] [0.12] [0.002] [0.018] [0.18] [10] MOJO-49 122 51.0 14.4 463 148 <1.0 0.55 214 *2.61 0.012 48.6 **1,120 **2,240 

Understanding wells (5 wells sampled)

MOJOU-01 134 39.1 5.93 14.6 373 <1.0 0.04 23.7 0.37 — 14.1 173 *623 MOJOU-02 0.89 0.031 0.27 64.7 126 24.2 — 1.69 1.76 0.014 18.1 2.32 184 MOJOU-03 147 22.9 4.29 169 277 <1.0 0.49 185 0.44 0.099 22.6 *276 **1,050 MOJOU-04 13.0 0.664 2.68 177 170 1.8 0.12 77.2 *4.52 0.004 29.2 180 *581 MOJOU-05 1.26 E0.016 0.26 76.3 114 25.0 E0.02 1.98 *2.81 0.061 21.0 21.2 207 

Tables 51
 
, California, February to April 2008.—Continued 

[The five-digit U.S. Geological Survey (USGS) parameter code well ielow the constituent name is used to uniquely identify a specific constituent or property. Samples from the twenty-four slow wells were analyzed. table 3F. GAMA Identification number: MOJO, Mojave study grid well; MOJOU, Mojave study understanding well. Table 10. able 10. Trace elements collected for the Mojave Groundwater Ambient Monitoring and Assessment (GAMA) study, California, February to April 2008.[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 the twenty-four slow wellswere analyzed. All analytes are listed in All analytes are listed in table 3F. GAMA Identification No.: MOJO, Mojave study unit grid well; MOJOU, Mojave study unit understanding well. Threshold type and threshold

level as of level as of April 2, 2008. April 2, 2008. Threshold type: Maximum contaminant level thresholds are listed as MCL-US when the MCL-US and MCL-CA Maximum contaminant level thresholds are listed as MCL-US when the MCL-US and MCL-CA are identical, and as MCL-CA are identical, and as MCL-CA when the MCL-CA when the MCL-CA

is lower than the MCL-US or no MCL-US exists. is lower than the MCL-US or no MCL-US exists. AL-US, U.S. Environmental Protection AL-US, U.S. Environmental Protection Agency action level; HAL-US, U.S. Environmental Protection Agency action level; HAL-US, U.S. Environmental Protection Agency lifetime health advisory level;

MCL-CA, California Department of Public Health maximum contaminant level; MCL-US, U.S. Environmental Protection MCL-CA, California Department of Public Health maximum contaminant level; MCL-US, U.S. Environmental Protection Agency maximum contaminant level; NL-CA, California Departmentof Public Health notification level; SMCL-CA, California Department of Public Health secondary maximum contaminant level. of Public Health notification level; SMCL-CA, California Department of Public Health secondary maximum contaminant level. Other abbreviations: E, estimated or having a higher degree of E, estimated or having a higher degree of

uncertainty; LRL, laboratory reporting level; SRL, study reporting limit; μg/L, microgram per liter; na, not available; —, not detected; ≤, less than or equal to; *, value above threshold level]

Aluminum Antimony Arsenic Barium Beryllium Boron Cadmium Chromium Cobalt Copper Iron Lead GAMA well iden­ (μg/L) (μg/L) (μg/L) (μg/L) (μg/L) (μg/L) (μg/L) (μg/L) (μg/L) (μg/L) (μg/L) (μg/L) tification No. (01106) (01095) (01000) (01005) (01010) (01020) (01025) (01030) (01035) (01040) (01046) (01049) 

Threshold type MCL-CA MCL-US MCL-US MCL-CA MCL-US NL-CA MCL-US MCL-CA na AL-US SMCL-CA AL-US 

Threshold level 1,000 6 10 1,000 4 1,000 5 50 na 1,300 300 15 

[LRL/SRL] 1 [1.6] [0.14] [0.06] 1 [0.36] [0.008] [6] [0.04] 1 [0.42] [0.02] 1 [1.7] 1 [6] 1 [0.65] 

Grid wells (19 wells sampled)

MOJO-12 — — 1.3 61 — 94 — ≤0.07 0.18 ≤1.1 ≤6 ≤0.08

MOJO-13 — 0.15 1.6 45 — 15 — 6.0 E0.01 — — ≤0.11

MOJO-14 14.1 — *12.6 5.0 — 45 — 3.3 — — — ≤0.08

MOJO-15 35.4 0.15 *17.1 0.62 — 21 — 11.3 — ≤0.83 — ≤0.12

MOJO-16 4.1 — 0.85 10 — 8 — 7.6 — — — ≤0.08

MOJO-17 — — 0.25 47 — 18 — ≤0.23 — ≤1.2 — ≤0.50

MOJO-18 — — 0.18 25 — 11 — ≤0.37 — ≤1.1 — ≤0.58

MOJO-19 3.1 — 4.7 37 — 146 — 4.4 — ≤0.72 — ≤0.11

MOJO-25 ≤1.0 E0.09 4.3 89 E0.01 191 E0.03 ≤0.23 0.56 2.0 11 1.55

MOJO-27 12.7 — 2.9 6.0 — 11 — 14.6 — — — ≤0.04

MOJO-29 — — 1.1 29 — *1,280 — 4.0 0.10 — 18 0.70

MOJO-30 ≤1.0 E0.09 *14.6 50 — 85 — 2.3 E0.02 — 22 ≤0.35

MOJO-31 7.5 E0.09 2.9 23 E0.01 19 — 1.4 E0.02 — ≤6 ≤0.53

MOJO-35 9.0 — 1.6 75 — 383 — 1.3 0.03 — ≤6

—

MOJO-36 — E0.09 *50.5 40 — 639 — ≤0.08 — ≤0.88 — ≤0.34

MOJO-39 — — *19.7 45 — 771 E0.03 1.8 0.04 — 15 ≤0.36

MOJO-41 — — 1.5 152 — 154 — 2.0 0.02 ≤0.75 — 0.99

MOJO-42 ≤0.8 — 1.5 53 — 252 — 8.2 E0.01 ≤0.86 — ≤0.61

MOJO-49 E1.8 0.55 *27.4 12 — *5,690 0.10 4.6 0.06 ≤1.4 — 1.95

Understanding wells (5 wells sampled)

MOJOU-01 ≤1.0 — 0.12 32 E0.01 23 E0.02 ≤0.37 0.07 2.3 ≤6 3.10

MOJOU-02 28.7 E0.08 *39.8 0.82 — 148 — — — — — 

—

MOJOU-03 6.4 E0.09 2.6 38 — 748 0.06 0.54 6.0 ≤1.0 — ≤0.17

MOJOU-04 ≤1.2 0.31 *68.7 19 

— 857 0.04 1.2 — — 

—

—

MOJOU-05 36.5 E0.08 *62.2 2.0 — 145 0.05 — — — ≤6

—

52 Groundwater Quality Data in the Mojave Study Unit, 2008: Results from the California GAMA Program 
 

Table 10. Trace elements collected for the Mojave Groundwater Ambient Monitoring and Assessment (GAMA) study, California, February to April 2008. —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. Samples from the twenty-four slow wells were analyzed. All analytes are listed in table 3F. GAMA well identification No.: MOJO, Mojave study unit grid well; MOJOU, Mojave study unit understanding well. Threshold type and threshold level as of April 2, 2008. 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. AL-US, U.S. Environmental Protection Agency action level; HAL-US, U.S. Environmental Protection Agency lifetime health advisory level; 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. Other abbreviations: E, estimated or having a higher degree of uncertainty; LRL, laboratory reporting level; SRL, study reporting limit; μg/L, microgram per liter; na, not available; —, not detected; ≤, less than or equal to; *, value above threshold level]

Molyb- Lithium Manga- Nickel Sele- Silver Strontium Thal- Tungsten Uranium Vana- Zinc GAMA well identi- denum (μg/L) nese (μg/L) (μg/L) nium (μg/L) (μg/L) (μg/L) lium (μg/L) (μg/L) (μg/L) dium (μg/L) (μg/L) fication No. (μg/L) (01130) (01056) (01065) (01145) (01075) (01080) (01057) (01155) (22703) (01085) (01090) (01060) 

Threshold type na SMCL-CA HAL-US MCL-CA MCL-US SMCL-CA HAL-US MCL-US na MCL-US NL-CA SMCL-CA Threshold level na 50 40 100 50 100 4,000 2 na 30 50 5,000 [LRL/SRL] [1] 1 [0.2] [0.2] 1 [0.36] [0.04] [0.1] [0.8] [0.04] 1 [0.11] [0.02] 1 [0.11] 1 [4.8] 

Grid wells (19 wells sampled)

MOJO-12 4.1 0.8 2.2 0.39 — — 464 — 0.12 8.88 4.0 ≤2.9

MOJO-13 1.8 0.6 4.6 ≤0.15 1.6 — 1,210 — 0.19 1.20 15.3 ≤4.7

MOJO-14 2.8 — 4.5 — 0.11 — 96.7 — 0.62 1.21 43.6 — MOJO-15 1.7 — 1.6 — 0.13 — 18.2 — 0.69 0.80 *126 — MOJO-16 1.8 — — — 0.07 — 192 — E0.04 0.73 27.7 — MOJO-17 6.3 ≤0.1 0.9 ≤0.12 0.06 — 418 — — 7.24 1.9 ≤2.1

MOJO-18 5.2 — 0.8 — E0.03 — 206 — — 0.74 2.1 ≤1.6MOJO-19 6.9 ≤0.2 1.3 — 0.41 — 410 — 0.79 2.04 37.0 ≤2.0MOJO-25 11.6 0.6 5.7 2.3 0.06 — 1,310 — 0.37 1.73 12.5 17.6 MOJO-27 2.4 — 2.0 — 0.57 — 152 — 0.16 0.59 40.2 — MOJO-29 42.8 1.0 3.1 0.91 1.0 — 2,150 — 0.27 3.94 8.1 79.6 MOJO-30 12.3 3.0 5.3 ≤0.15 1.1 — 870 — 3.9 1.38 15.0 ≤2.5

MOJO-31 6.1 1.9 3.0 ≤0.11 1.9 — 429 — 0.22 1.06 24.6 6.9 

MOJO-35 9.6 0.4 4.4 ≤0.29 0.34 — 499 — 0.24 10.8 6.8 — MOJO-36 39.3 17.4 9.9 — 0.32 — 268 — 2.2 2.72 16.5 ≤2.8MOJO-39 89.9 1.3 11.6 0.42 1.9 — 2,480 — 4.3 12.6 14.4 ≤3.8MOJO-41 16.6 0.4 1.2 ≤0.18 0.13 — 684 — 0.06 7.27 11.5 32.1 MOJO-42 15.7 1.3 5.8 ≤0.12 0.13 — 331 — 0.13 8.68 7.7 ≤1.0

MOJO-49 429 0.6 *55.9 0.68 3.2 — *8,210 — 0.15 4.17 10.9 145 

Understanding wells (5 wells sampled)

MOJOU-01 4.2 ≤0.2 4.0 0.71 2.6 — 976 — — 3.08 0.86 ≤4.6MOJOU-02 2.1 0.4 4.0 — — — 17.6 — 3.5 3.14 *190 —MOJOU-03 31.1 *111 5.3 10.6 0.50 — 1,630 — 1.0 *36.2 3.7 ≤2.8MOJOU-04 21.2 0.4 37.6 — 0.18 — 172 — 15.2 2.39 27.6 —MOJOU-05 1.5 0.5 20.6 — — — 34.3 — 9.2 0.13 2.6 —

1 Study reporting limit (SRL) defined based on examination of GAMA quality-control samples collected from May 2004 through January 2008 (L.D. Olsen and M.S. Fram, U.S. Geological Survey, unpub. 

data, 2009). Values below SRL are reported as less than or equal to the value reported by the laboratory (≤). In the USGS NWIS database, the result is accompanied with the following comment: Result is < or = reported value, based on QC data (may include: field blanks, source-solution blanks, trip blanks, NWQL set blanks, NWQL blank water certificates, and USGS BQS Blind Blank Program data).

Tables 53
 
54 Groundwater Quality Data in the Mojave Study Unit, 2008: Results from the California GAMA Program 

Table 11. Species of inorganic arsenic, chromium, and iron detected in samples collected for the Mojave Groundwater Ambient 

Monitoring and Assessment (GAMA) study, California, February to April 2008. 

[Data in this table analyzed at U.S. Geological Survey (USGS) Trace Metals Laboratory using research methods and are not stored in the USGS NWIS database. 

Information about analytes given in table 3G. Samples from the twenty-four slow wells were analyzed; only wells with at least one detection are listed. GAMA 

well identification No.: MOJO, Mojave study unit grid well; MOJOU, Mojave study unit understanding well. Threshold type and threshold level as of April 2, 

2008. 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; MCL-CA, California Department of Public Health maximum contaminant level; SMCL-CA, California Department of Public Health secondary maximum contaminant level. 

Other abbreviations: MDL, method detection limit; na, not available; μg/L, microgram per liter; —, not detected; *, value above threshold level] 

GAMA 

well identification 

No. 

Iron 

(μg/L) 

Iron (II) 

(μg/L) 

Arsenic 

(μg/L) 

Arsenic (III) 

(μg/L) 

Chromium 

(μg/L) 

Chromium (VI) 

(μg/L) 

Threshold type SMCL-CA na MCL-US na MCL-CA na 

Threshold level 300 na 10 na 50 na 

[MDL] [2] [2] [0.5] [1] [1] [1] 

Grid wells (19 wells sampled) 

MOJO-12 7 4 0.83 — — — 

MOJO-13 3 — 0.73 — 7 4 

MOJO-14 — — 8.5 1 3 3 

MOJO-15 — — *13 — 12 10 

MOJO-16 — — — — 8 8 

MOJO-19 — — 3.1 — 5 4 

MOJO-25 7 3 2.7 — — — 

MOJO-27 — — 1.3 — 18 16 

MOJO-29 18 3 — — 5 4 

MOJO-30 17 5 7.3 — 3 2 

MOJO-31 4 — 1.6 — 1 1 

MOJO-35 8 — 0.71 — 1 1 

MOJO-36 — — *27 — — — 

MOJO-39 13 5 *13 — 2 2 

MOJO-41 3 — 0.65 — 2 2 

MOJO-42 — — 0.57 — 10 9 

MOJO-49 8 — 10 — 5 5 

Understanding wells (5 wells sampled) 

MOJOU-01 4 — — — — — 

MOJOU-02 — — *25 — — — 

MOJOU-03 — — 1.4 — — — 

MOJOU-04 — — *32 — 2 1 

MOJOU-05 — — *39 17 — — 
Table 12.able 12. Results for analyses of stable isotope ratios and tritium and carbon-14 activities detected in samples collected for the Results for analyses of stable isotope ratios and tritium and carbon-14 activities detected in samples collected for the 

Mojave Groundwater Ambient Monitoring and Assessment (GAMA) study Mojave Groundwater Ambient Monitoring and Assessment (GAMA) study, California, February to April 2008. , California, February to April 2008.—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. 

Information about analytes given in Information about analytes given in table 3Htable 3H. Samples from all fifty-nine wells were analyzed for stable isotopes of water and tritium; samples from twentythree of the slow wells were analyzed for carbon activities; samples from twenty-two of the slow wells were analyzed for isotopes of nitrate. Stable isotope three of the slow wells were analyzed for carbon activities; samples from twenty-two of the slow wells were analyzed for isotopes of nitrate. 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 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. reference material. GAMA well identification No.: well identification No.: MOJO, Mojave study unit grid well; MOJOU, Mojave study unit understanding well. MOJO, Mojave study unit grid well; MOJOU, Mojave study unit understanding well. Threshold type Threshold type 

and threshold level as of and threshold level as of April 2, 2008. Maximum contaminant level thresholds are listed as MCL-US when the MCL-US and MCL-CA April 2, 2008. Maximum contaminant level thresholds are listed as MCL-US when the MCL-US and MCL-CA are identical, and as are identical, and as 

MCL-CA when the MCL-CA when the MCL-CA is lower than the MCL-US or no MCL-US exists. is lower than the MCL-US or no MCL-US exists. Threshold type: eshold type: MCL-CA, California Department of Public Health maximum MCL-CA, California Department of Public Health maximum 

contaminant level. contaminant level. Other abbreviations:eviations: na, not available; nc, not collected; pCi/L, picocuries per liter; <, less than] na, not available; nc, not collected; pCi/L, picocuries per liter; <, less than] 

GAMA well 

identification 

No. 

δ2 H 

(per mil) 

(82082) 

δ18O 

(per mil) 

(82085) 

Tritium 

(pCi/L) 

(07000) 

δ15N 

of nitrate1 

(per mil) 

(82690) 

δ18O 

of nitrate1 

(per mil) 

(63041) 

δ13C2 

(per mil) 

(82081) 

Carbon-142 

(percent 

modern) 

(49933) 

Threshold type na na MCL-CA na na na na 

Threshold level na na 20,000 na na na na 

Grid wells (52 wells sampled) 

MOJO-01 

MOJO-02 

MOJO-03 

MOJO-04 

MOJO-05 

MOJO-06 

MOJO-07 

MOJO-08 

MOJO-09 

MOJO-10 

MOJO-11 

MOJO-12 

MOJO-13 

MOJO-14 

MOJO-15 

MOJO-16 

MOJO-17 

MOJO-18 

MOJO-19 

MOJO-20 

MOJO-21 

MOJO-22 

MOJO-23 

MOJO-24 

MOJO-25 

MOJO-26 

MOJO-27 

MOJO-28 

MOJO-29 

MOJO-30 

–63.00 

–88.70 

–88.20 

–58.90 

–62.30 

–62.80 

–72.60 

–82.40 

–71.00 

–90.00 

–82.50 

–62.20 

–82.30 

–67.50 

–63.70 

–57.70 

–60.90 

–63.20 

–65.60 

–83.70 

–83.20 

–89.30 

–78.20 

–86.20 

–66.30 

–62.90 

–72.00 

–79.50 

–85.90 

–80.30 

–9.38 

–11.90 

–11.77 

–8.81 

–8.87 

–9.28 

–10.40 

–11.66 

–9.71 

–12.53 

–11.75 

–8.81 

–11.76 

–9.88 

–9.54 

–8.74 

–8.50 

–9.31 

–9.68 

–11.73 

–11.67 

–12.35 

–10.18 

–11.97 

–9.40 

–8.90 

–10.31 

–11.42 

–11.48 

–11.09 

<1.0 

<1.0 

<1.0 

<1.0 

8.6 

5.1 

<1.0 

<1.0 

2.6 

<1.0 

<1.0 

1.6 

<1.0 

<1.0 

<1.0 

<1.0 

9.6 

9.3 

1 

<1.0 

<1.0 

<1.0 

<1.0 

<1.0 

2.2 

1.6 

<1.0 

10.9 

<1.0 

1.0 

nc 

nc 

nc 

nc 

nc 

nc 

nc 

nc 

nc 

nc 

nc 

11.96 

18.39 

4.53 

3.74 

2.76 

7.65 

3.11 

7.66 

nc 

nc 

nc 

nc 

nc 

16.40 

nc 

3.70 

nc 

8.78 

7.30 

nc 

nc 

nc 

nc 

nc 

nc 

nc 

nc 

nc 

nc 

nc 

6.10 

10.04 

-0.70 

-0.15 

-0.85 

1.26 

1.50 

1.34 

nc 

nc 

nc 

nc 

nc 

3.44 

nc 

0.98 

nc 

-0.21 

3.08 

nc 

nc 

nc 

nc 

nc 

nc 

nc 

nc 

nc 

nc 

nc 

–12.95 

–10.00 

–11.39 

–13.16 

–13.71 

–12.47 

–11.38 

–11.17 

nc 

nc 

nc 

nc 

nc 

–13.97 

nc 

–12.39 

nc 

–10.25 

–11.52 

nc 

nc 

nc 

nc 

nc 

nc 

nc 

nc 

nc 

nc 

nc 

96.57 

8.97 

48.32 

38.63 

63.64 

113.00 

104.60 

61.12 

nc 

nc 

nc 

nc 

nc 

81.24 

nc 

18.14 

nc 

26.54 

35.72 

Tables 55 
56 Groundwater Quality Data in the Mojave Study Unit, 2008: Results from the California GAMA Program 

Table 12. Results for analyses of stable isotope ratios and tritium and carbon-14 activities detected in samples collected for the 


Mojave Groundwater Ambient Monitoring and Assessment (GAMA) study, California, February to April 2008.—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. 

Information about analytes given in table 3H. Samples from all fifty-nine wells were analyzed for stable isotopes of water and tritium; samples from twentythree of the slow wells were analyzed for carbon activities; samples from twenty-two of the slow wells were analyzed for isotopes of nitrate. 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. GAMA well identification No.: MOJO, Mojave study unit grid well; MOJOU, Mojave study unit understanding well. Threshold type 

and threshold level as of April 2, 2008. 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. Threshold type: MCL-CA, California Department of Public Health maximum 

contaminant level. Other abbreviations: na, not available; nc, not collected; pCi/L, picocuries per liter; <, less than] 

GAMA well 

identification 

No. 

Threshold type 

Threshold level 

MOJO-31 

MOJO-32 

MOJO-33 

MOJO-34 

MOJO-35 

δ2 H 

(per mil) 

(82082) 

na 

na 

–83.70 

–66.00 

–90.60 

–58.10 

–61.10 

δ18O 

(per mil) 

(82085) 

na 

na 

–11.7 

–9.30 

–11.96 

–8.27 

–8.61 

Tritium 

(pCi/L) 

(07000) 

MCL-CA 

20,000 

<1.0 

<1.0 

<1.0 

8.3 

1.0 

δ15N 

of nitrate1 

(per mil) 

(82690) 

na 

na 

9.05 

nc 

nc 

nc 

7.62 

δ18O 

of nitrate1 

(per mil) 

(63041) 

na 

na 

6.48 

nc 

nc 

nc 

1.68 

δ13C2 

(per mil) 

(82081) 

na 

na 

–12.36 

nc 

nc 

nc 

–11.11 

Carbon-142 

(percent 

modern) 

(49933) 

na 

na 

27.81 

nc 

nc 

nc 

90.49 

MOJO-36 

MOJO-37 

MOJO-38 

MOJO-39 

MOJO-40 

–62.10 

–60.90 

–59.30 

–66.60 

–73.90 

–8.62 

–8.59 

–8.39 

–8.86 

–9.70 

<1.0 

<1.0 

<1.0 

<1.0 

<1.0 

16.65 

nc 

nc 

8.20 

nc 

6.36 

nc 

nc 

-0.46 

nc 

–8.64 

nc 

nc 

–7.63 

nc 

36.03 

nc 

nc 

71.89 

nc 

MOJO-41 

MOJO-42 

MOJO-43 

MOJO-44 

MOJO-45 

–51.70 

–61.00 

–87.40 

–60.50 

–61.00 

–6.52 

–8.64 

–11.58 

–8.45 

–8.67 

<1.0 

<1.0 

<1.0 

1.0 

2.9 

6.17 

5.25 

nc 

nc 

nc 

–1.70 

–1.14 

nc 

nc 

nc 

–13.16 

–11.94 

nc 

nc 

nc 

81.57 

87.91 

nc 

nc 

nc 

MOJO-46 

MOJO-47 

MOJO-48 

MOJO-49 

MOJO–50 

–63.00 

–87.70 

–93.10 

–88.00 

–63.50 

–9.27 

–12.10 

–12.91 

–10.78 

–8.98 

2.6 

<1.0 

<1.0 

<1.0 

6.7 

nc 

nc 

nc 

9.44 

nc 

nc 

nc 

nc 

3.43 

nc 

nc 

nc 

nc 

nc 

nc 

nc 

nc 

nc 

nc 

nc 

MOJO–51 

MOJO–52 

–54.10 

–59.00 

–7.16 

–8.45 

<1.0 nc 

<1.0 nc 

Understanding wells (5 wells sampled) 

nc 

nc 

nc 

nc 

nc 

nc 

MOJOU-01 –81.00 –11.42 8.3 7.76 –1.71 –12.13 91.28 

MOJOU-02 –86.00 –12.14 <1.0 nc nc –9.12 1.99 

MOJOU-03 –61.40 –8.03 6.7 17.46 9.03 –12.87 91.96 

MOJOU-04 –84.10 –11.51 <1.0 6.58 2.39 –10.02 19.00 

MOJOU-05 –95.90 –13.17 <1.0 nc nc –11.71 1.85 

MOJOU-06 –60.50 –8.45 1.0 nc nc nc nc 

MOJOU-07 –70.50 –9.37 2.2 nc nc nc nc 

1

Isotopes of nitrate were sampled at 22 slow wells. 

2

Carbon activities were sampled for at the 24 slow wells. 
Tables 57 

Table 13A. Radium isotope activity levels detected in samples collected for the Mojave Groundwater Ambient Monitoring and 

Assessment (GAMA) study, California, February to April 2008. 

[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 the twenty-four slow wells were analyzed. Table 3H contains additional information about the analytes. Values less than the sample-specific critical 

level (ssLC) are reported as non-detections (—). GAMA well identification No.: MOJO, Mojave study unit grid well; MOJOU, Mojave study unit understanding well. Threshold type and threshold level as of April 2, 2008. Threshold type: Maximum contaminant level thresholds are listed as MCL-US when the MCLUS 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. Other abbreviations: CSU, 1-sigma combined standard uncertainty; pCi/L, picocurie per liter; —, not detected; ≤, less 

than or equal to] 

GAMA 

well identification No. Radium-226 (pCi/L) (09511) Radium-228 (pCi/L) (81366) 

Threshold type MCL-US MCL-US 

Threshold level 1

5 15 

result ± CSU ssLC result ± CSU ssLC 

Grid wells (19 wells sampled) 

MOJO-12 0.113 ± 0.016 0.017 — 0.22 

MOJO-13 0.072 ± 0.037 0.017 — 0.23 

MOJO-14 0.056 ± 0.013 0.016 — 0.23 

MOJO-15 ≤0.038 ± 0.012 0.014 — 0.22 

MOJO-16 ≤0.034 ± 0.012 0.016 — 0.25 

MOJO-17 0.069 ± 0.016 0.018 0.30 ± 0.11 0.25 

MOJO-18 0.055 ± 0.014 0.014 — 0.26 

MOJO-19 0.077 ± 0.017 0.018 — 0.25 

MOJO-25 0.045 ± 0.012 0.014 0.25 ± 0.076 0.18 

MOJO-27 ≤0.020 ± 0.011 0.013 — 0.20 

MOJO-29 0.120 ± 0.021 0.013 0.68 ± 0.092 0.18 

MOJO-30 0.063 ± 0.014 0.013 0.26 ± 0.091 0.22 

MOJO-31 ≤0.040 ± 0.012 0.013 — 0.22 

MOJO-35 0.164 ± 0.024 0.016 0.23 ± 0.086 0.21 

MOJO-36 0.119 ± 0.019 0.014 — 0.22 

MOJO-39 0.065 ± 0.015 0.014 0.38 ± 0.100 0.22 

MOJO-41 0.133 ± 0.021 0.016 0.32 ± 0.082 0.19 

MOJO-42 ≤0.020 ± 0.012 0.016 — 0.17 

MOJO-49 ≤0.023 ± 0.011 0.015 — 0.20 

Understanding wells (5 wells sampled) 

MOJOU-01 0.082 ± 0.015 0.015 0.43 ± 0.100 0.23 

MOJOU-02 — 0.017 — 0.18 

MOJOU-03 0.059 ± 0.015 0.017 0.35 ± 0.097 0.19 

MOJOU-04 0.046 ± 0.015 0.017 0.20 ± 0.071 0.17 

MOJOU-05 — 0.016 — 0.19 

1

The MCL-US threshold for radium is the sum of radium-226 and radium-228. 
58 Groundwater Quality Data in the Mojave Study Unit, 2008: Results from the California GAMA Program 

Table 13B. Gross alpha and gross beta radioactivity detected in samples collected for the Mojave Groundwater Ambient Monitoring 

and Assessment (GAMA) study, California, February to April 2008. 

[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 the twenty-four slow wells were analyzed. Table 3H contains additional information about the analytes. The reference nuclide for measurement of 

gross alpha is thorium-230 and the reference nuclide for measurement of gross beta is cesium-137. Measured values less than the sample-specific critical level 

(ssLC) are reported as non-detections (—). GAMA Identification number: MOJO, Mojave study unit grid well; MOJOU, Mojave study unit understanding 

well. Threshold type and threshold level as of April 2, 2008. 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. Other abbreviations: CSU, 1-sigma combined standard uncertainty; pCi/L, picocurie per liter; —, not detected; *, value 

above threshold level] 

GAMA well 

identification 

number 

Gross alpha radioactivity, 

72-hour count 

(pCi/L) 

(62636) 

Gross alpha radioactivity, 

30-day count 

(pCi/L) 

(62639) 

Gross beta radioactivity, 

72-hour count 

(pCi/L) 

(62642) 

Gross beta radioactivity, 

30-day count 

(pCi/L) 

(62645) 

Threshold 

type MCL-US MCL-US MCL-CA MCL-CA 

Threshold 

level 15 15 50 50 

result ± CSU ssLC result ± CSU ssLC result ± CSU ssLC result ± CSU ssLC 

Grid wells (19 wells sampled) 

MOJO-12 11.1 ± 1.6 0.70 8.60 ± 1.4 0.44 2.60 ± 0.61 0.77 4.86 ± 0.77 0.85 

MOJO-13 — 1.7 1.04 ± 1.1 1.7 4.97 ± 0.78 1.0 6.90 ± 1.1 1.2 

MOJO-14 1.25 ± 0.51 0.50 0.73 ± 0.48 0.59 0.88 ± 0.40 0.60 — 1.0 

MOJO-15 0.71 ± 0.35 0.34 0.82 ± 0.47 0.82 — 0.59 — 0.71 

MOJO-16 1.20 ± 0.49 0.49 1.43 ± 0.48 0.37 1.47 ± 0.46 0.68 1.11 ± 0.39 0.59 

MOJO-17 9.40 ± 1.5 0.60 2.98 ± 0.81 0.53 2.77 ± 0.77 1.1 4.00 ± 0.54 0.66 

MOJO-18 2.43 ± 0.70 0.61 — 0.63 1.56 ± 0.61 1.0 — 0.99 

MOJO-19 5.00 ± 1.1 0.77 3.15 ± 0.86 0.67 1.61 ± 0.66 1.0 1.91 ± 0.46 0.66 

MOJO-25 1.86 ± 0.77 0.99 — 0.69 2.41 ± 0.51 0.80 2.67 ± 0.86 1.3 

MOJO-27 — 0.45 0.88 ± 0.35 0.36 1.62 ± 0.41 0.58 1.58 ± 0.41 0.58 

MOJO-29 11.0 ± 3.1 2.9 8.00 ± 2.7 2.8 3.55 ± 0.50 0.68 3.18 ± 0.67 1.1 

MOJO-30 2.96 ± 0.95 0.82 1.62 ± 0.82 0.97 2.18 ± 0.48 0.66 2.42 ± 0.49 0.67 

MOJO-31 2.11 ± 0.69 0.56 1.20 ± 0.61 0.65 2.50 ± 0.49 0.67 2.60 ± 0.49 0.66 

MOJO-35 11.4 ± 1.7 0.63 11.0 ± 1.8 1.2 3.10 ± 0.58 0.77 6.84 ± 0.84 1.1 

MOJO-36 4.38 ± 0.92 0.71 4.05 ± 0.86 0.54 1.82 ± 0.71 1.0 3.64 ± 0.50 0.64 

MOJO-39 *18.0 ± 3.2 2.5 *18.2 ± 3.2 2.2 6.17 ± 0.69 0.81 8.69 ± 0.81 0.86 

MOJO-41 11.5 ± 1.8 0.69 5.40 ± 0.86 1.1 2.41 ± 0.57 0.80 3.75 ± 0.59 0.81 

MOJO-42 10.6 ± 1.5 0.60 8.50 ± 1.3 0.53 2.37 ± 0.42 0.56 4.45 ± 0.65 0.85 

MOJO-49 7.10 ± 3.2 3.7 8.90 ± 3.4 4.0 15.5 ± 1.5 1.6 14.0 ± 1.3 1.3 

Understanding wells (5 wells sampled) 

MOJOU-01 — 2.1 2.44 ± 0.84 0.71 5.33 ± 0.76 0.99 6.70 ± 0.75 0.90
 

MOJOU-02 3.09 ± 0.82 0.63 4.58 ± 0.93 0.42 — 0.61 1.58 ± 0.43 0.62
 

MOJOU-03 *29.1 ± 4.3 2.3 *29.1 ± 4.3 2.0 4.48 ± 0.60 0.78 4.24 ± 0.88 1.3
 

MOJOU-04 —(1) 0.65 1.70 ± 1.0 1.0 —(1) 0.70 4.16 ± 0.98 1.4
 

MOJOU-05 — 0.67 — 0.58 — 0.70 — 0.64
 

1

72-hour holding time exceeded by 2 days. 
Tables 59 

Table 13C. Radon-222 detected in samples collected for the 

Mojave Groundwater Ambient Monitoring and Assessment 

(GAMA) study, California, February to April 2008. 

[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 the twenty-four slow wells were analyzed. Table 3I contains 

additional information about the analytes. Two MCLs have been proposed 

for Radon-222. The proposed alternative MCL is in parentheses.GAMA well 

identification No.: MOJO, Mojave study unit grid well; MOJOU, Mojave 

study unit understanding well. Threshold type and threshold level as of April 

2, 2008. 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. MCLUS, U.S. Environmental Protection Agency maximum contaminant level. 

Other abbreviations: 2SCU, 2-sigma combined uncertainty; pCi/L, picocurie 

per liter; *, value above threshold level] 

Radon-222 

GAMA well identification No. (pCi/L) 

(82303) 

Threshold type proposed MCL-US 

Threshold level 2 300 (4,000) 

result ± 2SCU 

Grid wells (19 wells sampled) 

MOJO-12 *500 ± 23 

MOJO-13 *600 ± 23 

MOJO-14 *520 ± 21 

MOJO-15 *460 ± 21 

MOJO-16 *430 ± 23 

MOJO-17 *780 ± 22 

MOJO-18 *740 ± 20 

MOJO-19 *600 ± 20 

MOJO-25 *380 ± 23 

MOJO-27 *450 ± 22 

MOJO-29 *380 ± 23 

MOJO-30 300 ± 21 

MOJO-31 *350 ± 23 

MOJO-35 *560 ± 28 

MOJO-36 300 ± 24 

MOJO-39 *650 ± 21 

MOJO-41 *380 ± 21 

MOJO-42 *540 ± 24 

MOJO-49 *550 ± 23 

Understanding wells (5 wells sampled) 

MOJOU-01 *340 ± 23 

MOJOU-02 230 ± 23 

MOJOU-03 *570 ± 24 

MOJOU-04 *310 ± 27 

MOJOU-05 190 ± 22 
60 Groundwater Quality Data in the Mojave Study Unit, 2008: Results from the California GAMA Program 

Appendix
 
 

 

Appendix 61 

Appendix 

This appendix includes discussions of the methods used 

to collect and analyze groundwater samples and report the 

resulting water-quality data. These methods were selected to 

obtain representative samples of the groundwater from each 

well and to minimize the potential for contamination of the 

samples or bias in the data. Procedures used to collect and 

assess quality-control data, and the results of the quality-control assessments also are discussed. 

Sample Collection and Analysis 

Groundwater samples were collected using standard and 

modified USGS protocols from the USGS NAWQA program 

(Koterba and others, 1995), the USGS National Field Manual 

(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. 

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 to the well-head 

as possible. The sampling point was also located upstream of 

well-head treatment systems (if any) for all sites except for 

MOJO-22, which had a down-hole chlorination system that 

could not be turned off prior to groundwater sampling. For the 

fast (and fast plus DOC) schedules, samples were collected at 

the well head using a foot-long length of Teflon tubing. For 

the slow (and slow plus DOC) schedules, the samples were 

collected inside an enclosed chamber located inside a mobile 

laboratory and connected to the well head by a 10–50-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, groundwater was pumped 

through a flow-through chamber fitted with a multi-probe 

meter that simultaneously measures the water-quality indicators (field parameters) —dissolved oxygen, temperature, pH, 

turbidity, 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; 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 then were collected. 

Field measurements and instrument calibrations were 

recorded by hand on field record sheets and electronically in 

PCFF, a software package designed by the USGS with support from the GAMA program. Analytical service requests 

also were managed by PCFF. Information from PCFF was 

uploaded directly into NWIS at the end of every week of 

sample collection. 

For analyses requiring filtered water, groundwater 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). Both 

perchlorate and chromium (abundance and speciation) samples 

required filtering using a small 0.45-μm pore sized disk filter 

attached to a syringe. Prior to sample collection, polyethylene 

sample bottles were pre-rinsed two times using deionized 

water, and then once with sample water 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 NWQL.

Temperature-sensitive samples were stored on ice prior 

to, and during daily shipping to the various laboratories. The 

non-temperature sensitive samples for tritium, noble gases, 

chromium speciation, and stable isotopes of hydrogen and 

oxygen in water were shipped monthly, while temperaturesensitive samples for volatile organic compounds, pesticides, 

perchlorate, NDMA, dissolved organic carbon (DOC), radium 

isotopes, gross alpha and gross beta radioactivity, and radon222 samples were shipped daily. The temperature-sensitive 

samples for stable isotopes of nitrogen and oxygen in nitrate 

and arsenic and iron speciation were stored on ice, archived in 

a laboratory freezer, and shipped after results for nitrate and 

the metal concentrations were received from the NWQL. 

Detailed sampling protocols for individual analyses and 

groups of analytes are described in Koterba and others (1995), 

the USGS National Field Manual (Wilde and others, 1999; 

2004), and in the references for analytical methods listed 

in table A1; only brief descriptions are given here. Volatile 

organic compounds (VOCs) samples were collected in 40-mL 

sample vials that were purged with three vial volumes of 

sample water before bottom filling to eliminate atmospheric 

contamination. Six normal (6-N) hydrochloric acid (HCl) was 

added as a preservative to the VOC samples. Each sample 

to be analyzed for perchlorate was collected in a 125-mL 

polystyrene bottle and then filtered in two or three 20-mL

aliquots through a syringe-tip filter into a sterilized 125-mL

bottle. Tritium samples were collected by bottom filling one 

1-L polyethylene bottle and one 1-L glass bottle with unfiltered groundwater, after first overfilling the bottles with three 

volumes of water. Samples for analysis of stable isotopes of 

hydrogen and oxygen in water were collected in a 60-mL clear 

glass bottle filled with unfiltered water, sealed with a conical 

cap, and secured with electrical tape to prevent leakage and 

evaporation. 

Pesticides and pesticide degradation products, pharmaceutical compounds, and NDMA samples were collected in 

1-L baked amber bottles. Pesticide and pharmaceutical samples were filtered through a 0.3-μm nominal pore-size glass 

fiber filter during collection, whereas the NDMA samples were 

filtered at Weck Laboratories, Inc. prior to analysis. Samples 

of NDMA were collected in containers treated with 0.05 g of 

sodium thiosulfate (Na2

S2O3). 
62 Groundwater Quality Data in the Mojave Study Unit, 2008: Results from the California GAMA Program

Groundwater samples for major and minor ions, trace 

elements, alkalinity, and total dissolved solids (TDS) analyses required filling one 250-mL polyethylene bottle with 

untreated groundwater, and one 500-mL and one 250-mL 

polyethylene bottle with filtered groundwater (Wilde and 

others, 2004). Filtration was done using a 0.45-μm pore-size 

Whatman capsule filter. The 250-mL filtered sample then was 

preserved with 7.5-N nitric acid. Arsenic and iron speciation 

samples were filtered into a 250-mL polyethylene bottle that 

was covered with tape to prevent light exposure and preserved 

with 6-N hydrochloric acid. The nutrient and stable isotopes 

of nitrogen and oxygen in nitrate samples each were filtered 

into 125-mL brown polyethylene bottles. Radium isotopes and 

gross alpha and gross beta radiation samples were filtered into 

1-L polyethylene bottles and acidified with nitric acid. Carbon 

isotope samples were filtered and bottom filled into 500-mL 

glass bottles that first were overfilled with three bottle volumes 

of groundwater. These samples had no headspace and were 

sealed with a conical cap to avoid atmospheric contamination. 

Samples for alkalinity titrations were collected by filtering 

groundwater into 500-mL polyethylene bottles.

DOC, chromium, radon-222, and noble gases were collected from the hose bib at the well head, regardless of the 

sampling schedule (fast plus DOC, slow, or slow plus DOC). 

DOC was collected using a 50-mL syringe and 0.45-μm disk 

filter. For each sample, 50-mL of blank water and 50-mL of 

groundwater were filtered through the apparatus before filtering 100-mL of groundwater into a 125-mL baked glass bottle 

(Wilde and others, 2004). Each sample then was preserved 

immediately by lowering the pH to 2 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 groundwater, 

4-mL of sample water was forced through the disk filter; the 

next 2-mL of the groundwater was 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-mL of sample water, an additional 

2-mL of sample water was collected in a second centrifuge 

vial. Both vials were preserved with 10-μL of 7.5-N nitric acid 

(Ball and McClesky, 2003a,b).

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 value assembly using a glass 

syringe affixed with a stainless-steel needle. The sample was 

then injected into a 25-mL vial partially filled with scintillation 

mixture (mineral oil) and shaken. The vial then was placed 

in an insulated cardboard tube to prevent the warming of the 

sample during shipping. 

Noble gases were collected in 3⁄8-inch copper tubes using 

reinforced nylon tubing connected to the hose bib at the wellhead. Groundwater 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 groundwater for analyses of noble gases 

(Weiss, 1968). 

Alkalinity was measured in the mobile laboratory at the 

well site on filtered samples by Gran’s titration method (Gran, 

1952). Titration data were entered directly into PCFF and the 

concentrations of bicarbonate (HCO3

-

) and carbonate (CO3

2–) 

automatically were calculated from the titration data using the 

advanced speciation method. Concentrations of HCO3

-

 and 

CO3

2– also were calculated from the laboratory alkalinity and 

pH measurements. Calculations were made in a spreadsheet 

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

gov/alk/methods.html) with pK1 = 6.35, pK2 = 10.33, and 

pKW = 14. 

Eight laboratories performed chemical analyses for this 

study (table A1), although most of the analyses were performed at the NWQL or by labs contracted by the NWQL. 

The NWQL maintains a rigorous quality-assurance program 

(Pirkey and Glodt, 1998; Maloney, 2005). Laboratory qualitycontrol samples, including method blanks, continuing calibration verification standards, standard reference samples, 

reagent spikes, external certified reference materials, and 

external blind proficiency samples, are analyzed regularly. 

Method detection limits are tested continuously and laboratory reporting levels updated accordingly. NWQL maintains 

National Environmental Laboratory Accreditation Program 

(NELAP) and other certifications (http://nwql.usgs.gov/Public/

Performance/publiclabcertcoverpage.html). 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 the National Field 

Quality Assurance program that includes annual testing of all 

USGS field personnel for proficiency in making field waterquality measurements (http://qadata.cr.usgs.gov/nfqa). Results 

for analyses made at the NWQL or by laboratories contracted 

by the NWQL are uploaded directly into NWIS by the NWQL. 

Results from the USGS Branch of Quality Systems quality assurance program indicate that iron and manganese had 

negative analytical biases (of 16 and 6 percent, respectively); 

uranium and zinc had positive analytical biases (of “slight” 

and 11 percent, respectively) during the time that MOJO 

samples were analyzed at the NWQL (U.S. Geological Survey 

Branch of Quality Systems, 2008). The results suggest that 

iron and manganese concentrations may be slightly underestimated and uranium and zinc concentrations may be slightly 

overestimated.

Data Reporting

The following section details the laboratory reporting 

conventions and the constituents that are determined by 

multiple methods or by multiple laboratories.
 63 

Reporting Limits 

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 actually is present in a sample) to less 

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

is set at two times the long-term method detection level (LTMDL). The LT-MDL is derived from the standard deviation of 

at least 24 MDL determinations made over an extended period 

of time. LT-MDLs continually are monitored and updated. The 

method detection limit (MDL) is the minimum concentration 

of a substance that can be measured and reported with 99-percent confidence that the concentration is greater than zero (at 

the MDL there is less than 1 percent chance of a false positive) 

(Childress and others, 1999; U.S. Environmental Protection 

Agency, 2002). The USGS NWQL updates LRL values regularly and the values listed in this report were in effect during 

the period analyses were made for groundwater samples from 

the MOJO study (February to April 2008). 

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 LT-MDL 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 and 

pesticides). Compounds are identified by presence of characteristic fragmentation patterns in their mass spectra in addition to being quantified by measurement of peak areas at their 

associated chromatographic retention times. E-coded values 

also may result from detections outside the range of calibration standards, for detections that did not meet all laboratory 

quality-control criteria, and for samples that were diluted prior 

to analysis (Childress and others, 1999). 

Some constituents 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 method uncertainty generally 

indicates the precision of a particular analytical measurement; 

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

Results for most constituents are presented using the 

LRL or MRL values provided by the analyzing laboratories. 

Results for some constituents are presented using raised study 

reporting limits (SRLs) derived from assessment of data from 

quality-control samples associated with groundwater samples 

collected as part of the GAMA project. The SRLs were 

determined by statistical assessment of results from the field 

blanks collected during the first 21 GAMA study units (May 

2004 through January 2008) (L.D. Olsen and M.S. Fram, U.S. 

Geological Survey, unpub. data, 2009). The statistical analysis 

used order statistical and binomial probabilities to construct an 

upper confidence limit for the amount of contamination potentially present in field blanks, and by inference, in groundwater 

Appendix 

samples (Hahn and Meeker, 1991). The upper confidence limit 

as the maximum concentration of a constituent for which there 

is a 90-percent confidence that no more than 10 percent of the 

groundwater samples might have a higher concentration of 

that constituent due solely to contamination of the groundwater sample during sample collection, handling, and analysis. 

This maximum concentration corresponds to the concentration 

in the field blank that is at the 95th percentile of the 86 field 

blanks used in the statistical assessment. For most constituents, this maximum concentration was below the LRL or MRL 

for the constituent. Data for such constituents are reported 

with the LRL or MRL. For some constituents, this maximum 

concentration was greater than the LRL or MRL. An SRL then 

was defined as equal to the concentration in the 95th percentile field blank. Detections of those constituents reported by 

the laboratory with concentrations greater than the LRL or 

MDL but less than the SRL are considered non-detections in 

this report, and are reported in the tables with a “less-than-orequal-to” (≤) sign preceding the reported value.

The methods used for analysis of radiochemical constituents (gross alpha radioactivity, gross beta radioactivity, and 

radium isotopes) measure activities by counting techniques 

(table A1). The reporting limits for radiochemical constituents 

are based on sample-specific critical levels (ssLC) (McCurdy 

and others, 2008). The critical level is analogous to the LTMDL used for reporting analytical results for organic and 

non-radioactive inorganic constituents. Here, the critical level 

is defined as the minimum measured activity that indicates 

a positive detection of the radionuclide in the sample with 

less than a 5 percent probability of a false positive detection. 

Sample-specific critical levels are used for radiochemical 

measurements because the critical level is sensitive to sample 

size and sample yield during analytical processing, as well as 

being dependent on instrument background, counting times 

for the sample and background, and the characteristics of the 

instrument being used and the nuclide being measured. An 

ssLC is calculated for each sample, and the measured activity in the sample is compared to the ssLC associated with that 

sample. Measured activities less than the ssLC are reported as 

non-detections. 

The analytical uncertainties associated with measurement 

of activities are also sensitive to sample-specific parameters, 

including sample size, sample yield during analytical processing, and time elapsed between sample collection and various 

steps in the analytical procedure, as well as parameters associated with the instrumentation. Therefore, measured activities 

of radioactive constituents are reported with sample-specific 

combined standard uncertainties (CSU) (tables 13A,B). 

Specifically, activities of radium isotopes and gross alpha 

and gross beta radiation are reported with sample-specific 

CSU. The CSU is reported at the 68 percent confidence level 

(1-sigma). Radon activities are measured by a different laboratory than the other radioactive constituents, and the laboratory 

reports results with 2-sigma (95-percent confidence level) 

standard combined uncertainties. (table 13C). 
 

 

 

 

64 Groundwater Quality Data in the Mojave Study Unit, 2008: Results from the California GAMA Program 

Notation Tritium also is measured at two laboratories: Lawrence

Livermore National Laboratory (LLNL) and U.S. GeologiStable isotopic compositions of oxygen, hydrogen, cal Survey Stable Isotope and Tritium Laboratory (SITL), but 

nitrogen, and carbon are reported as relative isotope ratios in only the data from SITL were available for reporting at the 

units of per mil using the standard delta notation (Coplen and time of this publication. 

others, 2002): For arsenic, chromium, and iron concentrations, the 

Rsample

1 

reference 

where 

i is o the atomic mass of the heavier isotope of 

element, 

E is the element (O for oxygen-18, C for carbon, 

N for nitrogen,or H for hydrogen), 

the ratio of the abundance of the heavier

18 13 2 isotope of the element ( O, C, or H) to 

the lighter isotope of the element, 

16 12 1 ( O, C, or H) in the sample and, 

the ratio of the abundance of the heavier where 

isotope of the element to the lighter isotope Fe(T

of the element in the reference material Fe(II

hydrogen. 

R is sample 

R is reference 

The reference material for oxygen and hydrogen is 

Vienna Standard Mean Ocean Water (VSMOW), which is 

assigned δ18O and δ2H values of zero per mil (note than δ2H 

is sometimes written as δD because the common name of the 

heavier isotope of hydrogen, hydrogen-2, is deuterium). The 

reference material for carbon is Vienna Pee Dee Belemnite 

(VPDB), which is assigned a δ13C value of zero per mil. The 

reference material for nitrogen is atmospheric nitrogen gas, 

⎤

⎥

⎦ 

which is assigned a δ15N value of zero 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 

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 on the basis of the procedure 

recommended by the NWQL. 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 is generally preferred. However, the 

method with higher LRLs may be selected as the preferred 

method to provide consistency with historical data analyzed 

by the same method. 

Some of the water-quality indicators (field parameters)—

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. 

⎡

⎢

⎣ 

 iE = − i1 000, per mil R

approved method, Schedule 1948, used by the NWQL is 

preferred over the research methods used by the USGS Trace 

Metal Laboratory. The concentrations measured by the Trace 

Metal Laboratory only are used to calculate ratios of redox 

As(V) Cr(VI) species for each element, for arsenic, for As(III) Cr(III) Fe(III) chromium, and for iron. For example: Fe(II)

Fe(III) Fe(T) - Fe(II) = Fe(II) Fe(II) 

) is the total iron concentration (measured),
 

) is the concentration of ferrous iron (measured), and
 

Fe(III) is the concentration of ferric iron (calculated).
 

Quality Assurance 

The purpose of quality assurance is to identify which 

data best represent environmental conditions and which may 

have been affected by contamination or bias during sample 

collection, processing, storage, transportation, or laboratory 

analysis. Four types of quality-control (QC) tests were used 

in this study: blank samples were collected to assess positive 

bias due to contamination during sample handling or analysis; 

replicate samples were collected to assess variability; matrix 

spike tests were done to assess positive or negative bias; and 

surrogate compounds were added to samples analyzed for 

organic constituents to assess bias of laboratory analytical 

methods. In this report, detections of organic constituents in 

groundwater samples that may have resulted from contamination were flagged with a “V” remark code, and were not 

considered detections for calculations of detection frequencies in water-quality assessments. Detections of inorganic 

constituents in groundwater samples that may have resulted 

from contamination during sample handling or analysis were 

flagged with a “≤” remark code to indicate that the amount of 

potential contamination may have been sufficient to change 

a non-detection into a detection relative to the stated reporting level. Because of the potential contamination, the actual 

concentration in the groundwater sample may be less than or 

equal to (≤) the measured concentration. The evaluation of 

QC data presented in this report was based on results for QC 

samples collected for the MOJO study unit and on results for 

QC samples for the 21 GAMA study units sampled from May 

2004 through January 2008. 
 

 

 

Appendix 65 

The quality-assurance protocols used for this study 

followed the protocols used by the USGS NAWQA program (Koterba and others, 1995) and described in the USGS 

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

dated). The quality assurance plan followed by the NWQL, the 

primary laboratory used to analyze samples for this study, is 

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

Blanks 

The primary purposes of collecting blanks are to evaluate the magnitude of potential contamination of samples with 

analytes of interest during sample handling or analysis, and to 

identify and mitigate these sources of sample contamination. 

Blank Collection and Analysis 

Two types of blanks were collected: source-solution and 

field blanks. Source-solution blanks were collected to assess 

potential contamination of samples during transport and 

analysis, and potential contamination of the certified blank 

water obtained from the USGS NWQL. Field blanks were 

collected to assess potential contamination of samples during 

collection, processing, transport, and analysis. Blanks were 

collected using blank water certified by the NWQL to contain 

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

study. Nitrogen-purged, organic-free blank water was used 

for field blanks of organic constituents, and inorganic-free 

blank water was used for field blanks of other constituents. For 

MOJO, field blanks and source-solution blanks were collected 

at 8 percent of the wells sampled. Field blanks were analyzed 

for VOCs; pesticides; pharmaceuticals; perchlorate; NDMA; 

nutrients; dissolved organic carbon; major and minor ions; 

silica; TDS; trace elements; arsenic, chromium, and iron speciation; and radioactive constituents. Certified blank water was 

not available for tritium or noble gases, thus, field blanks were 

not collected for these 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 groundwater samples. For field blanks, blank 

water either was pumped or poured through the sampling 

equipment (fittings and tubing) used to collect groundwater, 

then processed and transported using the same protocols used 

for the groundwater samples. Eight to 12 liters of blank water 

were pumped or poured through the sampling equipment 

before each field blank was collected.

Assessment of Blank Results 

Contamination in blanks may originate from several 

sources that require different strategies for assessment of 

potential contamination of groundwater samples during 

sample collection, handling, and analysis. Four primary modes 

of contamination are assessed in the event of detections in 

field-blanks or atypical results in groundwater samples: 

(1) impurities in the water used to collect the blanks, (2) 

contamination during sample collection and handling from a 

known source or condition present at the field site, (3) carryover of material on the sampling equipment from one sample 

to the next sample, (4) systematic and random contamination 

from field and laboratory equipment and processes. The fourth 

source of contamination (systematic and random) is being 

addressed using a larger set of field blank results from multiple 

studies, in addition to the results from field blanks collected 

during MOJO. The development of this approach and its 

methods are described by L.D. Olsen and M.S. Fram (U.S. 

Geological Survey, unpub. data, 2009). 

The first potential mode evaluated is the presence of 

impurities in the water used to collect the field blank. Because 

the blanks were collected using blank water certified by the 

NWQL to contain less than the LRL or MRL of the analytes 

investigated in the study, the blank water itself is very rarely 

the source of constituents detected in field blanks. However, 

blank water sometimes is used before the certification process 

has been completed, thus, the certificates of analysis always 

must be checked. 

The second potential mode evaluated is contamination 

from identifiable, known sources that are present at a specific 

field site. Contamination from specific sources may produce 

distinctive patterns of detections in field blanks and groundwater samples, particularly for the VOCs. Substances that 

may be encountered at the field site, such as cements used on 

PVC piping, the methanol used to clean sample lines, and the 

chlorinated tap-water used in the USGS standard cleaning 

procedure of submersible sampling pumps and sample lines, 

contain recognizable associations of VOC constituents. For 

example, cements used on PVC piping are primarily composed of tetrahydrofuran with lesser amounts of acetone and 

methyl ethyl ketone (2-butanone). Methanol, used to clean 

sample lines has the propensity to capture VOCs from the 

atmosphere. Chlorinated tap water used in large amounts during the cleaning of submersible pumps and Teflon sample lines 

at monitoring or observation well sites has known disinfection 

by-products in the water. These VOCs, called trihalomethanes 

(THMs), are composed of bromodichloromethane, bromoform 

(tribromomethane), chloroform (trichloromethane), and dibromochloromethane). However, detection of these recognizable 

associations of VOC constituents in groundwater samples does 

not necessarily indicate contamination during sample collection, because these VOC constituents also may occur together 

in groundwater. 
66 Groundwater Quality Data in the Mojave Study Unit, 2008: Results from the California GAMA Program 

If a recognizable association of VOC constituents was 

detected in a field blank or in a groundwater sample, then the 

field notes and photographs from the site at which the sample 

was collected were examined for presence of conditions that 

may have resulted in contamination of the field blank or 

groundwater sample during sample collection. If the constituents were present in the field blank and groundwater sample 

from the same site at similar concentrations and the field notes 

or photographs indicated that the probable contaminant source 

was present, then the detections of those constituents in the 

groundwater sample were V-coded, and all other groundwater 

samples collected at sites where the same condition may have 

occurred were considered for V-coding. If the constituents 

were present in a groundwater sample and not the associated 

field blank, or a groundwater sample from a site where no 

blanks were collected, and the field notes or photographs indicated that the presence of conditions that may have resulted 

in contamination of the groundwater sample during sample 

collection, the data were considered for V-coding. If no conditions that may have resulted in contamination of the groundwater sample during sample collection were identified in the 

field notes or photographs, then V-codes were not applied. 

The third potential mode of contamination that was evaluated was carry-over from the previous groundwater sample 

or field blank collected with the same equipment. Carry-over 

between samples is very rare because the procedures used to 

clean the equipment between samples have been developed 

and extensively tested to assure that carry-over is mitigated 

as much as possible. Potential carry-over was evaluated using 

time-series analysis to look for patterns suggestive of carryover of constituents from a sample with high concentrations 

to the next groundwater sample or field blank collected with 

the same equipment. If non-detections were reported in field 

blanks or groundwater samples collected after the collection 

of groundwater samples containing high concentrations of the 

constituent, then carry-over as a mode of contamination was 

ruled out. 

The fourth potential mode of contamination that was 

evaluated was random or systematic contamination from field 

or laboratory equipment or processes. All detections in field 

blanks that could not be accounted for by impurities in the 

source-solution water, specific known conditions at field 

sites, or carry-over between samples were evaluated for 

random contamination. Random contamination in field and 

laboratory processes has an equal chance of affecting each 

groundwater sample, thus, strategies for flagging detections of 

constituents that are subject to random contamination in field 

and laboratory processes must be applied to all groundwater 

samples. 

Different notation was used for flagging detections of 

organic and inorganic constituents that may have been subjected to contamination during sample collection, handling, 

and analysis. Inorganic constituents naturally are present in 

groundwater, and the concerns about inorganic constituents 

generally are related to concentration, rather than to detection 

(presence or absence). In contrast, concerns about organic 

constituents generally are related to both detection and concentration. Therefore, different schema are used for assessing 

and flagging data for organic and inorganic constituents.

For organic constituents, V-codes were applied. The 

purpose of V-coding was to flag detections that have a greater 

chance of being false-positive detections. A false-positive 

detection is a detection that is caused by contamination during 

sample collection, handling, and analysis of a groundwater 

sample that would otherwise have a non-detection for that 

constituent. Results with V-codes were not considered detections of the constituent for this study and were not included in 

calculations of detection frequencies for organic constituents. 

The V-coding level was defined as the highest concentration of the constituent detected in a field blank plus the 

LT-MDL (equal to 1⁄2 the LRL) for that constituent. Detections 

of the constituent in groundwater samples at concentrations 

less than this V-coding level were flagged with a “V” in front 

of the reported value in the data tables. The highest concentration measured in a blank was assumed to represent the highest 

potential amount of contamination, thus, the V-code flags 

results that could have changed from non-detection to a detection relative to the LT-MDL, due to contamination. Results 

with V-codes were not considered detections of the constituent 

for this study and were not included in calculations of 

detection frequencies for organic constituents. 

Inorganic constituents can be present naturally in groundwater, and the concerns about inorganic constituents generally 

are related to concentration, rather than to detection (presence 

or absence). In contrast, concerns about organic constituents 

generally are related to both detection and concentration. For 

inorganic constituents, a “≤” symbol was applied to lowconcentration detections of constituents that may have been 

affected by contamination. The ≤ symbol means that the 

concentration of the constituent in the groundwater sample is 

less than or equal to the measured concentration (including the 

possibility that it may be less than the LT-MDL and, therefore, 

a non-detection). For select trace elements (aluminum, chromium, copper, lead, manganese, nickel, tungsten, vanadium, 

and zinc), the concentration cutoff, hereafter referred to as 

the study reporting limit, SRL, for applying the ≤ symbol was 

determined from a statistical assessment of results for 86 field 

blanks collected between May 2004 and January 2008. The 

concentration threshold for applying the ≤ symbol was equal 

to the concentration of the field blank ranked at the 90 percent 

confidence level for the 90th percentile of the binomial distribution of the 86 field blanks (L.D. Olsen and M.S. Fram, U.S. 

Geological Survey, unpub.data, 2009). 

For all other inorganic constituents, the SRL for applying the ≤ symbol was determined from assessment of the 

field blanks collected at MOJO sites only, and was defined as 

equal to the highest concentration measured in the five field 

blanks collected at MOJO sites (field blanks were collected at 

8 percent of the wells sampled). In the data tables, a ≤ symbol 

was put in front of measured values that were less than the 

threshold concentration. Future reports in this series will use 
Appendix 67 

the approach of L.D. Olsen and M.S. Fram for all inorganic 

constituents. 

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 in determining 

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, 

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 were 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. High RSD values for a compound may indicate analytical uncertainty at low concentrations, particularly for concentrations within an order of magnitude of LT-MDL or MDL. 

Sequential replicate samples were collected at 7 percent of the 

wells sampled. 

Matrix Spikes 

Addition of a known concentration of a constituent 

(‘spike’) to a replicate environmental sample enables the analyzing laboratory to determine the effect of the matrix, in this 

case groundwater, on the analytical technique used to measure 

the constituent. The known compounds added in matrix spikes 

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

enables an analysis of matrix interferences on a compoundby-compound basis. Matrix spikes were added by the laboratory performing the analysis. Low matrix-spike recovery may 

indicate that the compound might not be detected in some 

samples if it were present at very low concentrations. Low and 

high matrix-spike recoveries may be a potential concern if the 

concentration of a compound in a groundwater sample is close 

to the MCL: a low recovery could result in a falsely measured 

concentration below the MCL, whereas, a high recovery could 

result in a falsely measured 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 Schedule 2020 (Connor 

and others, 1998), 60 to 120 percent for NWQL Schedule 

2003 (Sandstrom and others, 2001), and 60 to 130 percent 

for Schedule 2080 (Kolpin and others, 2002). Based on these 

ranges, 70 to 130 percent was defined as the acceptable range 

for matrix-spike recoveries for organic compounds in this 

study. 

Matrix spikes were performed for VOCs, pesticides, 

pharmaceuticals, perchlorate, and NDMA because the analytical methods for these constituents are chromatographic and 

may be susceptible to matrix interferences. Replicate samples 

for matrix-spike additions were collected at 7 percent of the 

wells sampled, although not all analyte classes were tested at 

every well (tables A5A–C). 

Surrogates 

Surrogate compounds are added to environmental 

samples in the laboratory prior to analysis to evaluate the 

recovery of similar constituents. Surrogate compounds were 

added to all groundwater and quality-control samples that 

were analyzed for VOCs and pesticides (table A6). Most of the 

surrogate compounds are deuterated analogs of compounds 

being analyzed. For example, the surrogate toluene-d8 that is 

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 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 (Connor and 

others, 1998; Sandstrom and others, 2001). 
 

 

 

68 Groundwater Quality Data in the Mojave Study Unit, 2008: Results from the California GAMA Program 

Quality-Control Results 

Detections in Field and Source-Solution Blanks 

Field blanks were collected at 8 percent of the sites 

sampled in MOJO. Table A3 presents a summary of detections 

in field blanks. The only field blanks for which VOC detections were observed was the one associated with the monitoring wells (MOJOU-02 through MOJOU-05); therefore these 

four wells were examined more carefully. No VOCs were 

detected in the associated source-solution blank; therefore, 

the source blank water was not considered the source of the 

contamination. Toluene was the only VOC detected in the field 

blank that also was detected in monitoring well groundwater 

samples. Due to the detection of toluene in the field blank, toluene detections were subject to a V-coding level of 0.049 μg/L 

(E0.04 μg/L plus 1⁄2 the LRL of 0.018 μg/L). Toluene was 

detected at a concentration of E0.04 μg/L and 1.06 μg/L in 

two monitoring well groundwater samples (MOJOU-03 and 

MOJOU-05); the former of these detections was V-coded 

as a non-detection. Detections of bromodichloromethane, 

chloroform (trichloromethane), and dibromochloromethane 

in the field blank may have been due to the large amounts of 

chlorinated tap-water used in the USGS cleaning procedure 

of the submersible sampling pump and Teflon sampling line 

before the VOC field blank was collected (Wilde, F.D., ed., 

2004). It is theorized that the increased use of chlorinated 

tap-water in this cleaning procedure is substantially different 

than the cleaning procedure used for the standard MOJO sampling; therefore, only monitoring wells MOJOU-02 through 

MOJOU-05 were examined more carefully. No groundwater 

samples had measured levels of bromodichloromethane, 

chloroform (trichloromethane), and dibromochloromethane 

therefore, no values were V-coded as a result. Bromodichloromethane and methyl ethyl ketone (2-butanone) were the only 

other VOCs detected in the field blank, and these detections 

were considered to be random contamination, which has an 

equal chance of affecting each groundwater sample. Therefore, 

strategies for flagging detections of constituents that are subject to random contamination must be applied to all groundwater samples. No groundwater samples had measured levels of 

these two VOCs; therefore, no values were V-coded as a result 

(table 5). 

Three field blanks were collected for analysis of nutrients 

in MOJO. Nitrite plus nitrate, as nitrogen (NO2

 + NO3), was 

the only nutrient detected in one field blank, a study reporting limit, (SRL) of E0.02 mg/L. This blank detection was 

considered to be random contamination, which has an equal 

chance of affecting each groundwater sample, thus, strategies for flagging detections of constituents that are subject 

to random contamination must be applied to all groundwater 

samples. None of the corresponding environmental samples 

had measured levels of NO2

 + NO3 at or below the SRL with 

the exception of a monitoring well (MOJOU-05). This sample 

had NO2

 + NO3 detected at a concentration of E0.02 mg/L; 

therefore, this value was flagged with a ≤ symbol as a result of 

the blank detection (table 8). 

One field blank was collected for analysis of dissolved 

organic carbon (DOC). DOC was detected at a concentration 

of E0.2 mg/L, and low concentrations of DOC were detected 

in field blanks collected in previous GAMA study units (Bennett and others, 2006; Kulongoski and Belitz, 2007). Thus, 

the data for all groundwater samples with concentrations at or 

below E0.4 mg/L (0.2 mg/L plus 1⁄2 the LRL of 0.4 mg/L) were 

V-coded as non-detections (table 8). 

Field blanks were collected at 3 of the 24 sites sampled 

for analysis of major and minor ions, silica, and TDS. Calcium 

was the only major or minor ion detected in the field blank, 

creating a study reporting limit (SRL) of 0.04 mg/L. This 

blank detection was considered to be random contamination, 

which has an equal chance of affecting each groundwater 

sample, thus, strategies for flagging detections of constituents 

that are subject to random contamination must be applied 

to all groundwater samples. No groundwater samples were 

below 0.04 mg/L, therefore, no values were marked with the ≤ 

symbol (table 9). 

Trace-element data were assessed for potential flagging 

of results using the GAMA study reporting limits (SRLs), 

which are based on results for 86 field blanks collected 

between May 2004 and January 2008, in conjunction with 

the three field blanks collected at MOJO sites. Aluminum, 

chromium, copper, lead, manganese, nickel, tungsten, vanadium, and zinc have SRLs. Measured values that are less than 

the SRL are flagged with a ≤ symbol in table 10. Zinc was the 

only one of these trace elements detected at a concentration of 

E1.1 μg/L in a field blank. All measured detections of zinc less 

than the SRL level of 4.8 μg/L were flagged with a ≤ symbol 

(table 10). Silver was the only other trace metal detected in the 

field blank, but there were no measurable detections of silver 

in any of the wells in MOJO, therefore, this detection was not 

of potential QC concern. 

One field blank was collected for analysis of radioactive 

constituents. Radium-226 was measured at an activity of 

0.033 ± 0.011 pCi/L in the field blank. Six detections of 

radium-226 had an activity less than 0.044 pCi/L, the upper 

confidence limit of the maximum activity measured in the 

blank; these data were flagged with a ≤ symbol (table 13A). 

No compounds were detected in any of the 10 sourcesolution blanks. Additionally, no constituents were detected in 

field blanks for the following analyte groups: pesticides and 

pesticide degradates (five field blanks), perchlorate (five field 

blanks), NDMA (three field blanks), arsenic, chromium, and 

iron species analysis at the USGS Trace Metal Laboratory 

(two field blanks). 
 

 

 

69 

Variability in Replicate Samples 

Table A4 summarizes the results of replicate analyses for 

constituents detected in groundwater samples collected in the 

MOJO study. Concentrations or activities in the environmental 

and replicate samples are reported for all replicate analyses 

with RSD values greater than 20 percent. The majority of 

replicate sample pairs collected during the MOJO study had 

RSDs of less than 20 percent. Of the more than 700 replicate pairs of constituents analyzed, only five pairs had RSDs 

greater than 20 percent. One VOC (1,2,4-trimethylbenzene) 

had two replicate pairs with RSDs greater than 20 percent, 

these pairs both included one detection and one non-detection. 

At these low concentrations, small deviations in measured 

values result in large RSDs. The only other constituents with 

replicate pairs with a RSDs above 20 percent were; arsenic 

(total [analyzed by the USGS Trace Metal Laboratory]), oxygen isotopes in nitrate, gross alpha radioactivity 30-day count, 

radium-226 (two replicate pairs), and tritium. No replicate 

pairs had RSDs greater than 20 percent in the following analyte groups or constituents; pesticide and pesticide degradates, 

perchlorate, NDMA, nutrients, DOC, major and minor ions, 

silica, TDS, and trace elements. No environmental data were 

flagged as a result of variability in replicate analyses.

Matrix-Spike Recoveries 

Tables A5A–C presents a summary of matrix-spike recoveries for the MOJO study. The addition of a spike or known 

concentration of a constituent to an environmental sample 

enables the analyzing laboratory to determine the effect of the 

matrix, in this case groundwater, on the analytical technique 

used to measure the constituent. Four environmental samples 

were spiked with VOCs to calculate matrix-spike recoveries 

(table A5A). All of the 85 VOC spike compounds had median 

matrix-spike recoveries within the acceptable range of 70 to 

130 percent. Two VOC spike compounds, bromomethane 

(methyl bromide) and vinyl bromide (bromoethene) had one 

matrix-spike recovery greater than 130 percent; however, 

they were not detected in groundwater samples. VOC spike 

compounds that had at least one matrix-spike recovery below 

70 percent were; acetone (one spike), dichlorodifluoromethane 

(two spikes), styrene (two spikes), and these compounds were 

not detected in groundwater samples (table 3A). [NOTE that 

low recoveries may indicate that the compound might not have 

been detected in some samples if it was present at very low 

concentrations]. 

Four groundwater samples were spiked with pesticide 

and pesticide degradate compounds to calculate matrixspike recoveries. Thirty-two of the 63 spike constituents had 

median matrix-spike recoveries within the acceptable range 

of 70 to 130 percent (table A5B). Seven of the 10 compounds 

detected in groundwater samples had median matrix-spike 

recoveries within the acceptable range. Median spike-matrix 

recoveries for three compounds detected in groundwater 

samples were below the acceptable range; deethylatrazine 

Appendix 

(2-Chloro-4-isopropylamino-6-amino-s-triazine) (54 percent); 

fipronil (66 percent), and fipronil sulfide (64 percent). Two 

spike compounds, (fenamiphos and phorate oxon) had at least 

one recovery greater than 130 percent; however, they were 

not detected in groundwater samples. Fifty-three pesticide and 

pesticide degradate spike compounds had at least one recovery 

below 70 percent. Of these compounds; 3,4-dichloroaniline, 

deethylatrazine (2-Chloro-4-isopropylamino-6-amino-striazine), fipronil, fipronil sulfide, metolachlor, prometon, and 

simazine were the only compounds also detected in groundwater samples (table 3B). None of the nine groundwater samples 

with environmental detections and unacceptable recoveries in 

matrix spikes were analyzed in the same batch, thus, none of 

the pesticide and pesticide degradate environmental detections 

were flagged (table 6). [NOTE that low recoveries may indicate that the compound might not have been detected in some 

samples if it was present at very low concentrations]. 

Four groundwater samples were spiked with perchlorate 

and two samples were spiked with NDMA at Weck Laboratories, Inc. For perchlorate, the median matrix-spike was used 

and for NDMA the median matrix-spike was calculated as the 

average of the recoveries for the two spike samples. All spike 

recoveries were within the acceptable range of 70 to 

130 percent (table A5C). 

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

publication. 

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 the surrogate, analytical 

schedule on which it was applied, the number of analyses for 

blank and environmental samples, the number of surrogate 

recoveries below 70 percent, and the number of surrogate 

recoveries above 130 percent for the blank and groundwater 

samples. Blank and environmental samples were considered 

separately to assess whether the matrices present in groundwater samples affect surrogate recoveries. No systematic differences between surrogate recoveries in blank and groundwater 

samples were observed. 

In MOJO most surrogate recoveries were within acceptable range of 70 to 130 percent recovery. In total, 96 percent 

of the surrogate recoveries for VOC and 81 percent of the 

surrogate recoveries for pesticide analyses were within the 

acceptable range. 
70 Groundwater Quality Data in the Mojave Study Unit, 2008: Results from the California GAMA Program 

Appendix Tables
 
Appendix Tables 71

Table A1. Analytical methods used for the determination of organic and inorganic constituents by the U.S. Geological Survey (USGS) National Water Quality Laboratory (NWQL) and 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. UV, ultraviolet; VOC, volatile organic compounds]

Analyte Analytical Method Laboratory and analytical schedule Citation(s)

Water-quality indicators

Field parameters Calibrated field meters and test kits USGS field measurement U.S. Geological Survey, variously dated

Organic constituents

VOC Purge and trap capillary gas NWQL, Schedule 2020 Connor and others, 1998

chromatography/mass spectrometry

Pesticides and degradates Solid-phase extraction and gas NWQL, Schedule 2003 Zaugg and others, 1995; Lindley and 

chromatography/mass spectrometry others, 1996; Madsen and others, 2003; 

Sandstrom and others, 2001

Pharmaceuticals Solid-phase extraction and HPLC/mass NWQL, Schedule 2080 Kolpin and others, 2002; Furlong and 

spectrometry others, 2008

Constituents of special interest

Perchlorate Liquid chromatography with mass Weck Laboratories, Inc., standard U.S. Environmental Protection Agency, 

spectrometry/mass spectrometry operating procedure ORG099.R01 2005(USEPA Method 331.0)

N-nitrosodimethylamine (NDMA) Isotopic dilution with gas chromatography Weck Laboratories, Inc., standard U.S. Environmental Protection Agency, 

and chemical-ionization mass spectrom- operating procedure ORG065.R10 1989; Plomley and others, 1994etry (USEPA Method 1625 modified)

Inorganic constituents

Nutrients Alkaline persulfate digestion, Kjedahl NWQL, Schedule 2755 Fishman, 1993; Patton and Kryskalla, 2003

digestion

Dissolved organic carbon (DOC) UV-promoted persulfate oxidation and NWQL, laboratory code 2612 Brenton and Arnett, 1993

infrared spectrometry

Major and minor ions, trace elements and Atomic absorption spectrometry, colo- NWQL, Schedule 1948 Fishman and Friedman, 1989; Fishman, 

nutrients rimetry, ion-exchange chromatography, 1993; Faires, 1993; McLain, 1993; 

inductively-coupled plasma atomic Garbarino, 1999; Garbarino and Damrau, emission spectrometry and mass 2001; American Public Health Associaspectrometry tion, 1998; Garbarino and others, 2006

Chromium, arsenic and iron speciation Various techniques of ultraviolet visible USGS Trace Metal Laboratory, Boulder, Stookey, 1970; To and others, 1998; Ball 

(UV-VIS) spectrophotometry and atomic Colorado (USGSTMCO) and McCleskey, 2003a and 2003b; absorbance spectroscopy McCleskey and others, 2003
72 Table A1. Analytical methods used for the determination of organic and inorganic constituents by the U.S. Geological Survey (USGS) National Water Quality Laboratory (NWQL) and 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. UV, ultraviolet; VOC, volatile organic compounds] Analyte Analytical Method Laboratory and analytical schedule Citation(s) Stable isotopes Stable isotopes of hydrogen and oxygen in Gaseous hydrogen and carbon dioxide- water water equilibration and stable-isotope mass spectrometry Nitrogen and oxygen isotopes of nitrate Denitrifier method and mass spectrometry Carbon isotopes Accelerator mass spectrometry USGS Stable Isotope Laboratory, Reston, Epstein and Mayeda, 1953; Coplen and Virginia (USGSSIVA), NWQL Schedule others, 1991; Coplen, 1994 1142 USGS Stable Isotope Laboratory, Reston, Révész and Casciotti, 2007 Virginia (USGSSIVA), NWQL Lab Code 2900 University of Waterloo, Environmental Donahue and others, 1990; Jull and others, Isotope Lab (CAN-UWIL); University of 2004 Arizona Accelerator Mass Spectrometry Lab (AZ-UAMSL), NWQL Schedule 2015 Radioactivity and gases Tritium Tritium and noble gases Radon-222 Radium isotopes Gross alpha and gross beta radioactivity Electrolytic enrichment-liquid scintillation Helium-3 in-growth and mass spectrometry Liquid scintillation counting Alpha activity counting Alpha and beta activity counting USGS Stable Isotope and Tritium Laborato­ ry, Menlo Park, California (USGSH3CA) Lawrence Livermore National Laboratory (CA-LLNL) NWQL, Schedule 1369 Eberline Analytical Services (CA-EB­ ERL), NWQL Schedule 1262 Eberline Analytical Services, NWQL Schedule 1792 Thatcher and others, 1977 Moran and others, 2002; Eaton and others, 2004 American Society for Testing and Materi­ als, 1998 Kreiger and Whittaker, 1980 (USEPA meth­ ods 903 and 904) Kreiger and Whittaker, 1980 (USEPA method 900.0) 

Groundwater Quality Data in the Mojave Study Unit, 2008: Results from the California GAMA Program 
Appendix Tables 73 

Table A2. Preferred analytical schedules for constituents appearing on multiple schedules for samples collected for the Mojave 

Groundwater Ambient Monitoring and Assessment (GAMA) study, California, February to April 2008. 

[Preferred analytical schedules are generally the methods of analysis with the greatest accuracy and precision out of the ones used for the compound in question 

except in cases where consistency with historic data analyzed using the same method is preferred. LLNL, Lawrence Livermore National Laboratory; SITL, U.S. 

Geological Survey Stable Isotope and Tritium Laboratory; TML, U.S. Geological Survey Trace Metal Laboratory, Boulder, Colorado; np, no preference] 

Constituent Primary constituent 

classification 

Analytical 

schedules 

Preferred analytical 

schedule 

Results from both methods reported 

Alkalinity Water-quality indicator Field, 1948 Field 

Arsenic, total Trace element 1948, TML 1948 

Chromium, total Trace element 1948, TML 1948 

Iron, total Trace element 1948, TML 1948 

pH Water-quality indicator Field, 1948 Field 

Specific conductance Water-quality indicator Field, 1948 Field 

Tritium Inorganic tracer LLNL, SITL np 
74 Groundwater Quality Data in the Mojave Study Unit, 2008: Results from the California GAMA Program 

Table A3. Constituents detected in field blanks collected for the Mojave Groundwater Ambient Monitoring and Assessment (GAMA) 

study, California, February to April 2008. 

[V-coded data are reported but not used in summary statistics; CSU, combined standard uncertainty; E, estimated or having a higher degree of uncertainty; 

pCi/L, picocuries per liter; mg/L, milligrams per liter; ssLC, sample-specific critical level; μg/L, micrograms per liter]

Constituent Number of field blank 

detections/analyses 

Concentrations detected 

in field blanks 

Number of groundwater 

samples V-coded 

Organic constituents (μg/L) 

Chloroform (Trichloromethane) 1/5 0.49 0 

Bromochloromethane 1/5 E0.06 0 

Bromodichloromethane 1/5 0.42 0 

Dibromochloromethane 1/5 0.20 0 

Methyl ethyl ketone (2-butanone, 1/5 2.29 0 

MEK) 

Toluene 1/5 E0.04 1 

Nutrients (mg/L) 

Dissolved organic carbon (DOC) 1/1 E0.2 10 

Nitrite plus nitrate, as nitrogen 1/3 E0.02 1 

Major and minor ions (mg/L) 

Calcium 1/3 0.04 0 

Inorganic constitutents (μg/L) 

Silver 1/3 0.19 0 

Zinc 1/3 E1.1 0 

Radioactive constituents (pCi/L) 

Radium-2261 1/1 0.033 ± 0.011 (0.015) 6 

1

Radon-226 concentration is reported as the result ± CSU (ssLC). 
Appendix Tables 75 

Table A4. Quality-control summary of replicate analyses collected for the Mojave Groundwater Ambient Monitoring and Assessment 

(GAMA) study, California, February to April 2008. 

[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] 

Number of relative standard Maximum relative Measured values for pairs deviations greater than Constitutent standard deviation with RSD greater than 20 20 percent/number of (percent) (environmental/replicate) replicate pairs 

 Volatile organic compounds (VOC) from Schedule 2020 

1,2,4-Trimethylbenzene 2/4 113 (E0.09; —)(— , E0.06) 

All additional VOCs from Schedule 2020 0/4 <20 nv

 Pesticides and pesticide degradates from Schedule 2003 

All pesticides and pesticide degradates from 0/4 <20 nv

Schedule 2003 

Constituents of special interest1 

Perchlorate 0/4 <20 nv
 

N-nitrosodimethylamine (NDMA) 0/2 <20 nv

 Major ions, minor ions, trace elements, nutrients, and arsenic, chromium, and iron speciation 

Arsenic (total) (μg/L)2 1/2 22 (0.65; 0.89) 

Iron (total), iron(III), chromium (total), 0/2 <20 nv 

chromium(VI), arsenic(III) (μg/L)2 

All major ions, minor ions, trace elements 0/2 <20 nv

from schedule 1948, nutrients from schedule 2755, and dissolved organic carbon 

(DOC) from lab code 2612 

Isotopes and radioactivity 

Oxygen isotopes in nitrate 1/2 29 (1.26; 1.92)
 

Gross alpha 30-day radioactivity 1/2 43 (3.00; 5.60)
 

Radium-226 2/2 55 (0.072; 0.163)(0.133; 0.090)
 

Tritium 1/4 52 (0.6; 1.3)
 

All additional isotopes and radioactive 0/2 <20 nv

constituents 

1

Analyses performed at Weck Laboratories, Inc., City of Industry, California.
 

2

Analyses performed at U.S. Geological Survey Trace Metal Laboratory, Boulder, Colorado.
 
Table A5A. Quality-control summary for matrix-spike recoveries of volatile organic compounds (VOCs) in samples collected for the 

Mojave Groundwater Ambient Monitoring and Assessment (GAMA) study, California, February to April 2008.—Continued 

[Acceptable recovery range is between 70 and 130 percent] 

76 Groundwater Quality Data in the Mojave Study Unit, 2008: Results from the California GAMA Program 

Table A5A. Quality-control summary for matrix-spike recoveries of volatile organic compounds (VOC) in samples collected for the 

Mojave Groundwater Ambient Monitoring and Assessment (GAMA) study, California, February to April 2008. 

[Acceptable recovery range is between 70 and 130 percent] 

Number of Minimum Maximum Median 

Constituent spike recovery recovery recovery 

samples (percent) (percent) (percent) 

Acetone 4 69 111 88 

Acrylonitrile 4 102 112 106 

tert-Amyl methyl ether (TAME) 4 100 113 107 

Benzene 4 99 111 103 

Bromobenzene 4 98 114 105 

Bromochloromethane 4 103 109 107 

Bromodichloromethane1 4 103 113 107 

Bromoform (Tribromomethane)1 4 90 105 104

 Bromomethane (Methyl bromide) 4 112 158 116 

n-Butylbenzene 4 82 96 91 

sec-Butylbenzene 4 92 108 102 

tert-Butylbenzene 4 102 114 106 

Carbon disulfide 4 76 92 84 

Carbon tetrachloride (Tetrachloromethane)1 4 101 123 107 

Chlorobenzene1 4 101 111 105 

Chloroethane 4 100 115 102 

Chloroform (Trichloromethane)1 4 103 120 113 

Chloromethane 4 94 111 108 

3-Chloropropene 4 110 121 116 

2-Chlorotoluene 4 97 112 104 

4-Chlorotoluene 4 96 104 100 

Dibromochloromethane1 4 96 103 100 

1,2-Dibromo-3-chloropropane (DBCP) 4 91 108 97 

1,2-Dibromoethane (EDB) 4 101 115 104 

Dibromomethane 4 98 114 110 

1,2-Dichlorobenzene 4 99 110 104 

1,3-Dichlorobenzene1 4 98 110 103 

1,4-Dichlorobenzene 4 95 106 102 

trans-1,4-Dichloro-2-butene 4 91 112 96 

Dichlorodifluoromethane (CFC-12) 4 63 97 75 

1,1-Dichloroethane (1,1-DCA)1 4 103 118 109 

1,2-Dichloroethane (1,2-DCA)1 4 98 111 108 

1,1-Dichloroethene (1,1-DCE)1 4 102 118 107 

cis-1,2-Dichloroethene (cis-1,2-DCE)1 4 101 116 108 

trans-1,2-Dichloroethene (trans-1,2-DCE)1 4 105 118 106 

1,2-Dichloropropane 4 102 112 107 

1,3-Dichloropropane 4 104 112 106 

2,2-Dichloropropane 4 87 96 94 

1,1-Dichloropropene 4 95 115 100 

cis-1,3-Dichloropropene 4 88 100 99 

trans-1,3-Dichloropropene 4 85 102 95 

Diethyl ether 4 107 116 111 

Diisopropyl ether (DIPE) 4 103 118 108 

Ethylbenzene 4 97 107 105 

Ethyl tert-butyl ether (ETBE) 4 100 115 108 

Ethyl methacrylate 4 98 106 99 

o-Ethyl toluene (1-Ethyl-2-methyl benzene) 4 90 104 100 
Appendix Tables 77 

Table A5A. Quality-control summary for matrix-spike recoveries of volatile organic compounds (VOCs) in samples collected for the 

Mojave Groundwater Ambient Monitoring and Assessment (GAMA) study, California, February to April 2008.—Continued 

[Acceptable recovery range is between 70 and 130 percent] 

Number of Minimum Maximum Median 

Constituent spike recovery recovery recovery 

samples (percent) (percent) (percent) 

Hexachlorobutadiene 4 79 91 84 

Hexachloroethane 4 90 112 100 

2-Hexanone (n-Butyl methyl ketone) 4 91 103 96 

Iodomethane (Methyl iodide) 4 81 123 113 

Isopropylbenzene 4 95 108 104 

4-Isopropyl-1-methyl benzene 4 90 102 101 

Methyl acrylate 4 102 109 105 

Methyl acrylonitrile 4 100 110 108 

Methyl tert-butyl ether (MTBE)1 4 102 111 106 

Methyl iso-butyl ketone (MIBK) 4 97 107 102 

Methylene chloride (dichloromethane)1 4 98 108 104 

Methyl ethyl ketone (2-butanone, MEK) 4 85 111 98 

Methyl methacrylate 4 95 108 100 

Naphthalene 4 97 113 105 

Perchloroethene (PCE, tetrachloroethene) 4 98 112 104 

n-Propylbenzene 4 88 104 98 

Styrene 4 15 98 80 

1,1,1,2-Tetrachloroethane 4 101 113 107 

1,1,2,2-Tetrachloroethane 4 100 111 105 

Tetrahydrofuran1 4 88 112 105 

1,2,3,4-Tetramethylbenzene 4 92 107 102 

1,2,3,5-Tetramethylbenzene 4 96 111 109 

Toluene1 4 98 108 103 

1,2,3-Trichlorobenzene 4 102 110 104 

1,2,4-Trichlorobenzene 4 93 102 97 

1,1,1-Trichloroethane (1,1,1-TCA) 4 99 120 109 

1,1,2-Trichloroethane (1,1,2-TCA) 4 99 113 104 

Trichloroethene (TCE)1 4 100 113 104 

Trichlorofluoromethane (CFC-11)1 4 98 126 108 

1,2,3-Trichloropropane (1,2,3-TCP) 4 98 108 103 

Trichlorotrifluoroethane (CFC-113) 4 84 111 100 

1,2,3-Trimethylbenzene 4 100 111 109 

1,2,4-Trimethylbenzene1 4 80 103 96 

1,3,5-Trimethylbenzene 4 90 103 101 

Vinyl bromide (Bromoethene) 4 112 158 116 

Vinyl chloride (Chloroethene) 4 102 124 108 

m- and p-Xylene 4 93 105 102 

o-Xylene 4 93 107 105 1

Constituents detected in groundwater samples. 
Table A5B. Quality-control summary for matrix-spike recoveries of pesticides and pesticide degradates in samples collected for the 

Mojave Groundwater Ambient Monitoring and Assessment (GAMA) study, California, February to April 2008.—Continued 

[Acceptable recovery range is between 70 and 130 percent] 

78 Groundwater Quality Data in the Mojave Study Unit, 2008: Results from the California GAMA Program 

Table A5B. Quality-control summary for matrix-spike recoveries of pesticides and pesticide degradates in samples collected for the 

Mojave Groundwater Ambient Monitoring and Assessment (GAMA) study, California, February to April 2008. 

[Acceptable recovery range is between 70 and 130 percent] 

Number of Minimum Maximum Median 

Constituent spike recovery recovery recovery 

samples (percent) (percent) (percent) 

Acetochlor 4 59 92 82 

Alachlor 4 64 94 86 

Atrazine1 4 75 94 86 

Azinphos-methyl 4 47 129 58 

Azinphos-methyl oxon 4 20 50 29 

Benfluralin 4 34 61 52 

Carbaryl 4 60 110 70 

2-Chloro-2,6-diethylacetanilide 4 58 96 83 

4-Chloro-2-methylphenol 4 47 86 64 

Chlorpyrifos 4 39 74 66 

Chlorpyrifos oxon 4 10 55 17 

Cyfluthrin 4 40 64 48 

Cypermethrin 4 40 71 47 

Dacthal (DCPA) 4 89 94 91 

Deethylatrazine (2-Chloro-4-isopropylamino-6­ 4 43 69 54 

amino-s-triazine)1 

Desulfinylfipronil 4 70 100 78 

Desulfinylfipronil amide 4 71 128 79 

Diazinon 4 62 95 81 

3,4-Dichloroaniline 4 64 90 76 

Dichlorvos 4 7 19 13 

Dicrotophos 4 15 37 28 

Dieldrin 4 74 121 100 

2,6-Diethylaniline 4 75 96 81 

Dimethoate 4 27 51 38 

Ethion 4 49 82 68 

Ethion monoxon 4 48 82 68 

2-Ethyl-6-methylaniline 4 78 104 82 

Fenamiphos 4 71 148 89 

Fenamiphos sulfone 4 56 112 74 

Fenamiphos sulfoxide 4 7 40 24 

Fipronil1 4 45 99 66 

Fipronil sulfide1 4 48 101 64 

Fipronil sulfone 4 45 71 59 

Fonofos 4 58 86 76 

Hexazinone 4 39 69 53 

Iprodione 4 41 67 46 

Isofenphos 4 48 102 74 

Malaoxon 4 29 74 51 

Malathion 4 43 92 71 

Metalaxyl 4 65 96 83 

Methidathion 4 63 90 83 

Metolachlor 4 64 95 83 

Metribuzin 4 50 87 73 

Myclobutanil 4 56 91 80 

1-Naphthol 4 17 30 21 
Appendix Tables 79 

Table A5B. Quality-control summary for matrix-spike recoveries of pesticides and pesticide degradates in samples collected for the 

Mojave Groundwater Ambient Monitoring and Assessment (GAMA) study, California, February to April 2008.—Continued 

[Acceptable recovery range is between 70 and 130 percent] 

Number of Minimum Maximum Median 

Constituent spike recovery recovery recovery 

samples (percent) (percent) (percent) 

Paraoxon-methyl 4 24 50 33 

Parathion-methyl 4 42 76 59 

Pendimethalin 4 60 123 70 

cis-Permethrin 4 34 64 50 

Phorate 4 31 81 61 

Phorate oxon 4 53 162 75 

Phosmet 4 8 25 13 

Phosmet oxon 4 0 51 14 

Prometon1 4 50 83 70 

Prometryn 4 61 91 82 

Pronamide (Propyzamide) 4 57 95 80 

Simazine1 4 63 92 79 

Tebuthiuron 4 65 113 88 

Terbufos 4 42 83 71 

Terbufos oxon sulfone 4 29 85 49 

Terbuthylazine 4 73 102 88 

Tribufos 4 35 66 53 

Trifluralin 4 40 67 60 1

Constituents detected in groundwater samples. 

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

N-nitrosodimethylamine (NDMA) in groundwater samples collected for the Mojave Groundwater 

Ambient Monitoring and Assessment (GAMA) study, California, February to April 2008. 

[Acceptable recovery range is between 70 and 130 percent] 

Constituent 

Number of 

spike 

samples 

Minimum 

recovery 

(percent) 

Maximum 

recovery 

(percent) 

Median 

recovery 

(percent) 

Perchlorate1 4 99 110 103 

N-nitrosodimethylamine (NDMA)1 2 95 127 2

111 

1

Constituents detected in groundwater samples.
 

2

 Median matrix-spike recovery was calculated as the average of the two recoveries for NDMA. 
80 Table A6. Quality-control summary for surrogate recoveries of volatile organic compounds (VOCs), pesticides and pesticide degradates in samples collected for the Mojave Groundwater Ambient Monitoring and Assessment (GAMA) study, California, February to April 2008. [VOC, volatile organic compound] Number of Number of Number of Number of Constitutent Median surrogate surrogate Median surrogate surrogate Number Number Analytical or constitu- recovery recoveries recoveries recovery recoveries recoveries Surrogate of blanks of sample schedule ent class in blanks below 70 above 130 in samples below 70 above 130 analyses analyses analyzed (percent) percent in percent in (percent) percent in percent in blanks blanks samples samples 1-Bromo-4-fluorobenzene 2020 VOC 6 97 0 0 59 91 0 0 1,2-Dichloroethaned4 2020 VOC 6 108 0 0 59 114 0 7 Toluened8 2020 VOC 6 99 0 0 59 98 0 0 Diazinond10 2003 Pesticide 5 73 2 0 59 78 21 0 α-HCHd6 2003 Pesticide 5 85 0 0 59 84 1 0 

Groundwater Quality Data in the Mojave Study Unit, 2008: Results from the California GAMA Program 
 

 

 

 

 

 

 

Manuscript approved for publication, March 19, 2009 

Prepared by the USGS Publishing Network, 

Publishing Service Center, Sacramento, California 

For more information concerning the research in this report, contact the 

California Water Science Center Director, 

U.S. Geological Survey, 6000 J Street
 

Sacramento, California 95819
 

http://ca.water.usgs.gov
 
Mathany and Belitz—Groundwater Quality Data in the Mojave Study Unit, 2008: Results from the California GAMA Program—Data Series 440 

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