U.S. Department of the Interior

U.S. Geological Survey

Data Series 747

Prepared in cooperation with the California State Water Resources Control Board

Groundwater-Quality Data in the Bear Valley and

Selected Hard Rock Areas Study Unit, 2010:

Results from the California GAMA Program

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

Santa Ana River

Mojave Rive r

Deep Creek

Bear Creek Big Bear Lake

Baldwin Lake Silverwood

Lake

Lake Arrowhead

10

215

California Aqueduct

Big Bear Lake

Highland

Big Bear City

Lake Arrowhead

Crestline

38

18

18

138
Cover photographs:

Top right: Well near Lake Arrowhead, California. (Photograph taken by Tracy Davis, 

U.S. Geological Survey).

Bottom right: View of mountains near Big Bear Lake, California. (Photograph taken by Jennifer Shelton, 

U.S. Geological Survey).
Groundwater-Quality Data in the Bear Valley and 

Selected Hard Rock Areas Study Unit, 2010: 

Results from the California GAMA Program

By Timothy M. Mathany and Kenneth Belitz

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

Prepared in cooperation with the California State Water Resources Control Board 

Data Series 747

U.S. Department of the Interior

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

SALLY JEWELL, Secretary

U.S. Geological Survey

Suzette M. Kimball, Acting Director

U.S. Geological Survey, Reston, Virginia: 2013

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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, 2013, Groundwater-quality data in the Bear Valley and Selected Hard Rock Areas 

study unit, 2010: Results from the California GAMA Program: U.S. Geological Survey Data Series 747, 86 p.
iii

Contents

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

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

Purpose and Scope ..............................................................................................................................3

Hydrogeologic Setting ..................................................................................................................................5

BEAR Study Unit—Bear Valley Study Area......................................................................................5

BEAR Study Unit—Selected Hard Rock Areas Study Area...........................................................8

Methods ........................................................................................................................................................10

Study Design........................................................................................................................................10

Sample Collection and Analysis.......................................................................................................11

Data Reporting.....................................................................................................................................11

Quality-Assurance Methods.............................................................................................................11

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

Comparison Benchmarks ..................................................................................................................12

Water-Quality Results ................................................................................................................................13

Water-Quality Indicators (Field and Laboratory) ..........................................................................13

Organic Constituents..........................................................................................................................13

Constituents of Special Interest.......................................................................................................14

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

Isotopic Tracers and Dissolved Noble Gases ................................................................................15

Uranium and Other Radioactive Constituents................................................................................15

Future Work ..................................................................................................................................................16

Summary .......................................................................................................................................................16

Acknowledgments.......................................................................................................................................17

References Cited..........................................................................................................................................17

Appendix .......................................................................................................................................................64
iv

Tables

1. Identification, sampling, and construction information for sites sampled for the 

Bear Valley and Selected Hard Rock Areas GAMA study unit, California, 

April to August 2010 ........................................................................... 23

2. Classes of chemical constituents and field water-quality indicators collected for 

the Bear Valley and Selected Hard Rock Areas GAMA study unit, California, 

April to August 2010 ........................................................................... 25

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

and reporting information for the USGS National Water Quality Laboratory 

Schedule 2020 ................................................................................. 26

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

benchmarks, and reporting information for the USGS National Water Quality 

Laboratory Schedule 2033 .................................................................. 29

3C. Pharmaceutical compounds, primary uses or sources, comparison benchmarks, 

and reporting information for the USGS National Water Quality Laboratory 

Schedule 2080 ................................................................................. 32

3D. Wastewater indicator compounds, primary uses or sources, comparison 

benchmarks, and reporting information for the USGS National Water Quality 

Laboratory Schedule 1433 .................................................................. 33

3E. Constituents of special interest, primary uses or sources, comparison 

benchmarks, and reporting information for Weck Laboratories, Inc., 

City of Industry, California, analyses ...................................................... 35

3F. Trace elements, comparison benchmarks, and reporting information for the 

USGS National Water Quality Laboratory Schedule 1948................................. 36

3G. Nutrients and dissolved organic carbon, comparison benchmarks, and reporting 

information for the USGS National Water Quality Laboratory Schedule 2755 and 

Laboratory Code 2613 ........................................................................ 37

3H. Major and minor ions, silica, total dissolved solids, and alkalinity, comparison 

benchmarks, and reporting information for the USGS National Water Quality 

Laboratory Schedule 1948 .................................................................. 38

Figures

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

the Bear Valley and Selected Hard Rock Areas (BEAR) GAMA study unit ............ 4

2. Map showing the geology of the Bear Valley and Selected Hard Rock 

Areas (BEAR) GAMA study unit ............................................................ 6

3. Map showing the boundaries of the Bear Valley study area, topographic features, 

major cities, major roads, and hydrologic features, the location of California 

Department of Public Health (CDPH) sites, and the distribution of the grid cells, 

and the location of sampled grid and understanding sites, Bear Valley and 

Selected Hard Rock Areas (BEAR) GAMA study unit .................................... 7

4. Map showing the boundaries of the Selected Hard Rock Areas study area, 

topographic features, major cities, major roads, hydrologic features, the location 

of California Department of Public Health (CDPH) sites, and the distribution of the 

grid cells, and the location of sampled grid and understanding sites, Bear Valley 

and Selected Hard Rock Areas (BEAR) GAMA study unit .............................. 9
v

3I. Arsenic and iron species, comparison benchmarks, and reporting information 

for the USGS National Research Laboratory Trace Metal Laboratory, 

Boulder, Colorado, analyses.................................................................. 38

3J. Dissolved noble gases, isotopic tracers, and uranium and other radioactive 

constituents, comparison benchmarks, and reporting information for 

laboratory analyses ........................................................................... 39

4. Water-quality indicators in samples collected for the Bear Valley and Selected 

Hard Rock Areas GAMA study unit, California, April to August 2010 .................. 40

5. Volatile organic compounds detected in samples collected for the Bear Valley 

and Selected Hard Rock Areas GAMA study unit, California, 

April to August 2010 ........................................................................... 43

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

Bear Valley and Selected Hard Rock Areas GAMA study unit, California, 

April to August 2010 ........................................................................... 49

7. Wastewater indicator compounds detected in samples collected for the 

Bear Valley and Selected Hard Rock Areas GAMA study unit, California, 

April to August 2010 ........................................................................... 50

8. Perchlorate detected in samples collected for the Bear Valley and Selected 

Hard Rock Areas GAMA study unit, California, April to August 2010 .................. 51

9. Trace elements detected in samples collected for the Bear Valley and Selected 

Hard Rock Areas GAMA study unit, California, April to August 2010 .................. 52

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

Bear Valley and Selected Hard Rock Areas GAMA study unit, California, 

April to August 2010 ........................................................................... 56

11. Major and minor ions, silica, and total dissolved solids detected in samples 

collected for the Bear Valley and Selected Hard Rock Areas GAMA study unit, 

California, April to August 2010 ............................................................ 58

12. Arsenic and iron species detected in samples collected for the Bear Valley and 

Selected Hard Rock Areas GAMA study unit, California, April to August 2010 ...... 60

13. Isotopic tracers detected in samples collected for the Bear Valley and 

Selected Hard Rock Areas GAMA study unit, California, April to August 2010 ...... 61

14. Uranium and other radioactive constituents detected in samples collected 

for the Bear Valley and Selected Hard Rock Areas GAMA study unit, California, 

April to August 2010 ........................................................................... 63

Tables—Continued
vi

Conversion Factors and Datums

Inch/Pound to SI

Multiply By To obtain

inch (in.) 2.54 centimeter (cm)

foot (ft) 0.3048 meter (m)

mile (mi) 1.609 kilometer (km)

square mile (mi2) 2.590 square kilometer (km2) 

quart (qt) 0.9464 liter (L)

pound, avoirdupois (lb) 0.4536 kilogram (kg)

SI to Inch/Pound

Multiply By To obtain

centimeter (cm) 0.3937 inch (in.)

meter (m) 3.2808 foot (ft)

kilometer (km) 0.6214 mile (mi)

square kilometer (km2) 0.3861 square mile (mi2)

liter (L) 1.0567 quart (qt)

gram (g) 0.03527 ounce, avoirdupois (oz)

kilogram (kg) 2.205 pound, avoirdupois (lb)

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

°F=(1.8×°C)+32.

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). 

Concentrations of radioactive constituents in water (except uranium) are given in picocuries per 

liter (pCi/L). 

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).

Land-surface altitude, as used in this report, refers to distance above the vertical datum and is 

reported as feet above mean sea level (ft above msl).
vii

Selected Terms and Symbols

α	 significance level

x activities of a radioactive constituent in a groundwater sample

y activities of a radioactive constituent in a replicate sample

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

and 1 atmosphere of pressure) per gram of water

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

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

as per mil

= equal to

> greater than 

≥ greater than or equal to

< less than

≤ less than or equal to

x multiplied by 

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

— not detected

p p-value (probability) 

pH a measure of the acidity or basicity of a solution

pK1,2 negative logarithms of the acid dissociation constants for carbonic acid

pKw negative logarithm of the acid dissociation constant of water

R ratio

σ	 sigma (standard deviation)

± plus or minus

* concentration greater than the benchmark level

** concentration greater than the upper benchmark level

Abbreviations and Acronyms

AL action level 

AL-US action level (USEPA)

APE Alternate Place Entry program designed for USGS sampling

BEAR Bear Valley and Selected Hard Rock Areas study unit

BEAR-G Selected Hard Rock Areas study area (grid site)

BEAR-S Bear Valley study area (grid site)

BEAR-U Bear Valley and Selected Hard Rock Areas study unit (understanding site)
CASRN Chemical Abstract Service (American Chemical Society) Registry Number®

CSU combined standard uncertainty

E estimated or having a higher degree of uncertainty

GAMA Groundwater Ambient Monitoring and Assessment Program

GPS global positioning system

HAL lifetime health advisory level

HAL-US lifetime health advisory level (USEPA)

IBSP Inorganic Blind Sample Program (USGS)

I-MDL interim method detection limit

HPLC high-performance liquid chromatography

LRL laboratory reporting level

LSD land-surface datum

LT-MDL long-term method detection level

MCL maximum contaminant level

MCL-CA maximum contaminant level (CDPH)

MCL-US maximum contaminant level (USEPA)

MDL method detection limit

MRL minimum reporting level

MU method uncertainty

na not available

NAD normalized absolute difference (between replicate analyses for a radioactive 

constituent)

nc not collected

NFM National Field Manual (USGS)

NFQA National Field Quality Assurance Program (USGS)

NL notification level

NL-CA notification level (CDPH)

np no preference

ns not spiked (groundwater sample)

nv no measured value or no value in category

NWIS National Water Information System (USGS)

PBP Priority Basin Project

PCFF Personal Computer Field Form program designed for USGS sampling

QA quality assurance

viii

Abbreviations and Acronyms—Continued
QC quality control

RL reporting level

RPD relative percent difference

RSD relative standard deviation

RSD5-US risk-specific dose at a risk factor of 10–5 (USEPA)

SD standard deviation

SMCL secondary maximum contaminant level

SMCL-CA secondary maximum contaminant level (CDPH)

SMCL-US secondary maximum contaminant level (USEPA)

SRL study reporting level (concentration cutoff for applying the ≤ symbol in reporting 

results)

ssLC sample-specific critical level

UV ultraviolet

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)

WIC wastewater indicator compound

Organizations

BQS Branch of Quality Systems (USGS)

CDPH California Department of Public Health

CDPR California Department of Pesticide Regulation

CDWR California Department of Water Resources

LLNL Lawrence Livermore National Laboratory, Livermore, California

NAWQA National Water-Quality Assessment Program (USGS)

NELAP National Environmental Laboratory Accreditation Program

NIST National Institute of Standards and Technology

NRP National Research Program (USGS)

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

SITL Stable Isotope and Tritium Laboratory, Menlo Park, California (USGS)

SWRCB California State Water Resources Control Board

TML Trace Metal Laboratory, Boulder, Colorado (USGS)

USEPA U.S. Environmental Protection Agency

ix

Abbreviations and Acronyms—Continued
x

USGS U.S. Geological Survey

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

Selected Chemical Names

CaCO3 calcium carbonate

CO3

2– carbonate ion

CFC-11 trichlorofluoromethane

1,1-DCA 1,1-dichloroethane

1,1-DCE 1,1-dichloroethene

DOC dissolved organic carbon

H2O water

HCl hydrochloric acid

HCO3

– bicarbonate ion

MTBE methyl tert-butyl ether

NDMA N-nitrosodimethylamine

PCE perchloroethene (tetrachloroethene)

SiO2 silicon dioxide

1,1,1-TCA 1,1,1-trichloroethane

TCE trichloroethene

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

TDS total dissolved solids

THM trihalomethane

VOC volatile organic compound

Organizations—Continued
Abstract 

Groundwater quality in the 112-square-mile Bear Valley 

and Selected Hard Rock Areas (BEAR) study unit was 

investigated by the U.S. Geological Survey (USGS) from 

April to August 2010, as part of the California State Water 

Resources Control Board (SWRCB) Groundwater Ambient 

Monitoring and Assessment (GAMA) Program’s Priority 

Basin Project (PBP). The GAMA-PBP was developed in 

response to the California Groundwater Quality Monitoring 

Act of 2001 and is being conducted in collaboration with 

the SWRCB and Lawrence Livermore National Laboratory 

(LLNL). The BEAR study unit was the thirty-first study unit 

to be sampled as part of the GAMA-PBP.

The GAMA Bear Valley and Selected Hard Rock Areas 

study was designed to provide a spatially unbiased assessment 

of untreated-groundwater quality in the primary aquifer 

system and to facilitate statistically consistent comparisons 

of untreated groundwater quality throughout California. The 

primary aquifer system is defined as the zones corresponding 

to the perforation intervals of wells listed in the California 

Department of Public Health (CDPH) database for the BEAR 

study unit. Groundwater quality in the primary aquifer system 

may differ from the quality in the shallow or deep waterbearing zones; shallow groundwater may be more vulnerable 

to surficial contamination.

In the BEAR study unit, groundwater samples were 

collected from two study areas (Bear Valley and Selected Hard 

Rock Areas) in San Bernardino County. Of the 38 sampling 

sites, 27 were selected by using a spatially distributed, 

randomized grid-based method to provide statistical 

representation of the primary aquifer system in the study unit 

(grid sites), and the remaining 11 sites were selected to aid in 

the understanding of the potential groundwater-quality issues 

associated with septic tank use and with ski areas in the study 

unit (understanding sites).

The groundwater samples were analyzed for organic 

constituents (volatile organic compounds [VOCs], pesticides 

and pesticide degradates, pharmaceutical compounds, and 

wastewater indicator compounds [WICs]), constituents 

of special interest (perchlorate, N-nitrosodimethylamine 

[NDMA], and 1,2,3-trichloropropane [1,2,3-TCP]), and 

inorganic constituents (trace elements, nutrients, dissolved 

organic carbon [DOC], major and minor ions, silica, total 

dissolved solids [TDS], alkalinity, and arsenic and iron 

species), and uranium and other radioactive constituents 

(radon-222 and activities of tritium and carbon-14). Isotopic 

tracers (of hydrogen and oxygen in water, of nitrogen and 

oxygen in dissolved nitrate, of dissolved boron, isotopic ratios 

of strontium in water, and of carbon in dissolved inorganic 

carbon) and dissolved noble gases (argon, helium-4, krypton, 

neon, and xenon) were measured to help identify the sources 

and ages of sampled groundwater. In total, groundwater 

samples were analyzed for 289 unique constituents and 

8 water-quality indicators in the BEAR study unit.

Quality-control samples (blanks, replicate pairs, or matrix 

spikes) were collected at 13 percent of the sites in the BEAR 

study unit, and the results for these samples were used to 

evaluate the quality of the data from the groundwater samples. 

Blank samples rarely contained detectable concentrations of 

any constituent, indicating that contamination from sample 

collection or analysis was not a significant source of bias in 

the data for the groundwater samples. Replicate pair samples 

all were within acceptable limits of variability. Matrix-spike 

sample recoveries were within the acceptable range (70 to 

130 percent) for approximately 84 percent of the compounds.

This study did not evaluate the quality of water delivered 

to consumers. After withdrawal, groundwater typically is 

treated, disinfected, and (or) blended with other waters to 

maintain water quality. Regulatory benchmarks apply to 

water that is delivered 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 benchmarks established by the 

U.S. Environmental Protection Agency (USEPA) and CDPH, 

and to non-health-based benchmarks established for aesthetic 

concerns by CDPH. Comparisons between data collected 

for this study and benchmarks for drinking water are for 

illustrative purposes only and are not indicative of compliance 

or non-compliance with those benchmarks.

Groundwater-Quality Data in the Bear Valley and 

Selected Hard Rock Areas Study Unit, 2010: 

Results from the California GAMA Program

By Timothy M. Mathany and Kenneth Belitz
2 Groundwater-Quality Data in the Bear Valley and Selected Hard Rock Areas Study Unit, 2010

All concentrations of organic and special-interest 

constituents from grid sites sampled in the BEAR study unit 

were less than health-based benchmarks. In total, VOCs were 

detected in 17 of the 27 grid sites sampled (approximately 

63 percent), pesticides and pesticide degradates were detected 

in 4 grid sites (approximately 15 percent), and perchlorate was 

detected in 21 grid sites (approximately 78 percent). 

Inorganic constituents (trace elements, major and minor 

ions, nutrients, and uranium and other radioactive constituents) 

were sampled for at 27 grid sites; most concentrations were 

less than health-based benchmarks. Exceptions include 

one detection of arsenic greater than the USEPA maximum 

contaminant level (MCL-US) of 10 micrograms per liter 

(μg/L), three detections of uranium greater than the MCL-US 

of 30 μg/L, nine detections of radon-222 greater than the 

proposed MCL-US of 4,000 picocuries per liter (pCi/L), and 

one detection of fluoride greater than the CDPH maximum 

contaminant level (MCL-CA) of 2 milligrams per liter. 

Concentrations of inorganic constituents with non-healthbased benchmarks (iron, manganese, chloride, and TDS) 

were less than the CDPH secondary maximum contaminant 

level (SMCL-CA) in most grid sites. Exceptions include two 

detections of iron greater than the SMCL-CA of 300 μg/L and 

one detection of manganese greater than the SMCL-CA of 

50 μg/L. 

Introduction 

About one-half of the water used for public and 

domestic drinking-water supply in California is groundwater 

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

groundwater in aquifers used for public drinking-water supply 

and to establish a baseline groundwater-quality monitoring 

program, the California State Water Resources Control Board 

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

(USGS) and Lawrence Livermore National Laboratory 

(LLNL), implemented the Groundwater Ambient Monitoring 

and Assessment (GAMA) Program in 2000 (California 

Environmental Protection Agency, 2011, website at http://

www.waterboards.ca.gov/water_issues/programs/gama/). 

The main goals of the GAMA Program are to improve 

groundwater monitoring and to increase the availability of 

groundwater-quality data to the public. The GAMA Program 

currently consists of four projects: (1) the GAMA Priority 

Basin Project (PBP) conducted by the USGS (U.S. Geological 

Survey, 2011a, California Water Science Center website at 

http://ca.water.usgs.gov/gama/); (2) the GAMA Domestic Well 

Project conducted by the SWRCB; (3) the GAMA Special 

Studies Project conducted by LLNL; and (4) GeoTracker 

GAMA, conducted by the SWRCB. The GAMA-PBP 

primarily focuses on the deep part of the groundwater 

resource, which is typically used for public drinking-water 

supply. The GAMA Domestic Well Project generally focuses 

on the shallow aquifer systems, which may be particularly at 

risk as a result of surficial contamination. The GAMA Special 

Studies Project focuses on using research methods to help 

explain the source, fate, transport, and occurrence of chemicals 

that can affect groundwater quality. GeoTracker GAMA is an 

online database providing all published and quality-assurance/

quality-control (QA/QC) approved analytical data from the 

GAMA Program (California State Water Resources Control 

Board, 2009, website at https://geotracker.waterboards.ca.gov/

gama/). GeoTracker GAMA also stores groundwater-quality 

data and related reports collected by other State agencies, 

such as the California Department of Public Health (CDPH), 

California Department of Water Resources (CDWR), and 

California Department of Pesticide Regulation (CDPR), and 

data collected by the SWRCB and Regional Boards from 

groundwater monitoring wells at contaminated or remediated 

sites.

The GAMA Program was initiated by the SWRCB 

in 2000 and later expanded by the Groundwater Quality 

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

Sections 10780–10782.3 of the California Water Code, 

Assembly Bill 599). The GAMA-PBP assesses groundwater 

quality in key groundwater basins that account for more 

than 90 percent of all groundwater used for public supply in 

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

with the SWRCB, developed the monitoring plan to assess 

groundwater basins through direct and other statistically 

reliable sample approaches (Belitz and others, 2003; 

California State Water Resources Control Board, 2003). 

Additional partners in the GAMA-PBP include LLNL, 

CDPH, CDWR, CDPR, local water agencies, and well owners 

(Kulongoski and Belitz, 2004). Participation in the GAMAPBP is entirely voluntary.

The GAMA-PBP is unique in California because it 

includes many chemical analyses that are not otherwise 

available in the statewide water-quality monitoring datasets. 

Groundwater samples collected for the GAMA-PBP are 

analyzed for approximately 300 chemical constituents by 

using methods with lower detection limits than required by 

the CDPH for regulatory monitoring of water from drinkingwater wells. These analyses will be especially useful for 

providing an early indication of changes in groundwater 

quality. In addition, the GAMA-PBP analyzes samples for 

a suite of constituents more extensive than that required by 

the CDPH and for a suite of chemical and isotopic tracers 

for understanding hydrologic and geochemical processes.

This understanding of groundwater composition is useful 

for identifying the natural and human factors affecting water 

quality. Understanding the occurrence and distribution of 

chemical constituents of significance to water quality is 

important for the long-term management and protection of 

groundwater resources.
Introduction 3

The ranges of hydrologic, geologic, and climatic 

conditions in California were considered in this statewide 

assessment of groundwater quality. Belitz and others (2003) 

partitioned the State into 10 hydrogeologic provinces, 

each with distinctive hydrologic, geologic, and climatic 

characteristics: Cascades and Modoc Plateau, Klamath 

Mountains, Northern Coast Ranges, Central Valley, Sierra 

Nevada, Basin and Range, Southern Coast Ranges, Transverse 

Ranges and selected Peninsular Ranges, Desert, and San 

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

include groundwater basins and subbasins designated by the 

CDWR (California Department of Water Resources, 2003). 

Groundwater basins and subbasins generally consist 

of relatively permeable, unconsolidated deposits of alluvial 

origin. Eighty percent of California’s approximately 16,000 

active and standby drinking-water wells listed in the statewide 

database maintained by the CDPH (hereinafter referred to as 

CDPH wells) are located in CDWR-designated groundwater 

basins and subbasins within the 10 hydrogeologic provinces. 

Groundwater basins and subbasins were prioritized for 

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

the basin, with secondary consideration given to municipal 

groundwater use, agricultural pumping, the number of 

formerly leaking underground fuel tanks, and the number of 

registered pesticide applications (Belitz and others, 2003). 

Of the 472 basins and subbasins designated by the CDWR, 

116 priority basins contain approximately 95 percent of 

the CDPH wells located in basins. In addition, some areas 

outside of the defined groundwater basins were included to 

represent the 20 percent of the CDPH wells not located in 

the groundwater basins. The priority basins, selected low-use 

basins, and selected areas outside of groundwater basins were 

grouped into 35 GAMA Priority Basin Project study units 

that together represent approximately 95 percent of all CDPH 

wells. 

The data collected in each study unit are used for three 

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

of the current quality of the groundwater resource; 

(2) Understanding—identification of the natural and human 

factors affecting groundwater quality; and (3) Trends—

detection of changes in groundwater quality over time 

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

to characterize the quality of groundwater in the primary 

aquifer system of the study units, not the treated drinking 

water delivered to consumers by water purveyors. The primary 

aquifer system is defined as parts of aquifers corresponding to 

the perforation intervals of wells listed in the CDPH databases 

for the study units. The CDPH database lists wells and 

springs used for public drinking-water supplies and includes 

wells and springs from systems classified as community 

(such as those in cities, towns, and mobile-home parks), 

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

workplaces, and restaurants), and transient, non-community 

(such as those in campgrounds and parks). Collectively, the 

CDPH refers to these as “public-supply” wells and springs 

(hereinafter referred to as CDPH sites). Groundwater quality 

in the primary aquifer system may differ from the quality in 

the shallow or deep parts of the aquifer system. As a result, 

samples from shallow wells (such as many private domestic 

wells and groundwater monitoring wells) and springs can have 

greater concentrations of constituents (such as volatile organic 

compounds [VOCs], nitrate, and microbial indicators) from 

anthropogenic sources than samples from wells screened in 

the underlying primary aquifer system (U.S. Environmental 

Protection Agency, 2008a; Landon and others, 2010).

The Bear Valley and Selected Hard Rock Areas study 

unit (hereinafter referred to as the BEAR study unit) lies 

within the Transverse Ranges and selected Peninsular Ranges 

hydrogeologic province described by Belitz and others 

(2003) (fig. 1). Groundwater is a major source of public 

drinking-water supply for many of the communities located 

in the BEAR study unit (Big Bear Area Regional Wastewater 

Agency, 2011; Lake Arrowhead Community Services District, 

2011a); therefore, the BEAR study unit was considered high 

priority for sampling to provide adequate representation 

of the Transverse Ranges and selected Peninsular Ranges 

hydrogeologic province. 

This USGS Data Series Report is one of a series of 

reports presenting the water-quality data collected by the 

USGS in the BEAR study unit for the GAMA-PBP. Data 

Series Reports for each of the GAMA-PBP study units 

are available from the U.S. Geological Survey (2011b) at 

http://ca.water.usgs.gov/projects/gama/includes/GAMA_

publications.html.

Purpose and Scope

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

hydrogeologic setting of the BEAR study unit, the study 

design, and the study methods; (2) the analytical results for 

groundwater samples collected in the BEAR study unit, and 

(3) the results of QC analyses. Groundwater samples were 

analyzed for water-quality indicators; organic, special-interest, 

and inorganic constituents; isotopic tracers; uranium and 

other radioactive constituents; and dissolved noble gases. 

The chemical data presented in this report were evaluated by 

comparison to State and Federal drinking-water standards. The 

health-based and non-health-based benchmarks considered for 

this report are those established by the U.S. Environmental 

Protection Agency (USEPA) and (or) the CDPH. Discussion 

of the factors that influence the distribution and occurrence of 

the constituents detected in groundwater samples will be the 

subject of subsequent publications.
4 Groundwater-Quality Data in the Bear Valley and Selected Hard Rock Areas Study Unit, 2010

Figure 1. Hydrogeologic provinces of California and the location of the Bear Valley and Selected Hard Rock Areas (BEAR) 

Groundwater Ambient Monitoring and Assessment (GAMA) study unit.

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

Bear Valley and

Selected Hard Rock

Areas study unit

(figures 3 and 4)

Bakersfield

San

Francisco

Sacramento

OREGON

NEVADA

MEXICO

ARIZONA

Redding

Los Angeles

San Diego

PA C I F I C O C E A N

0 100 200 MILES

0 100 200 KILOMETERS

Shaded relief derived from U.S. Geological Survey

National Elevation Dataset, 2006. 

Albers Equal Area Conic Projection

Provinces from Belitz and others, 2003

sac12-0450_Figure 01
Hydrogeologic Setting 5

Hydrogeologic Setting 

The BEAR study unit is located in the eastern part of 

the San Bernardino National Forest in southern California, 

and covers 112 square miles (mi2) in San Bernardino County, 

California (fig. 2). The BEAR study unit includes two study 

areas: the CDWR-defined groundwater basin of Bear Valley 

(California Department of Water Resources, 2003) and the 

USGS-defined Selected Hard Rock Areas. 

The climate in the BEAR study unit is typical of 

mountainous areas in southern California, with warm summers 

and cold winters (PRISM Climate Group, 2011). General 

precipitation distribution in the study unit reflects a slight rain 

shadow effect from west to east due to the mountain peaks that 

separate the two study areas. Average annual rainfall totals 

in the study unit range from about 34 inches per year (in/yr) 

on the eastern slopes of the Selected Hard Rock Areas study 

area, to approximately 18 in/yr along the southeastern part 

of the Bear Valley study area (PRISM Climate Group, 2011; 

Western Regional Climate Center, 2011; Flint and Martin, 

2012). Annual snow accumulation in the study unit averages 

approximately 54 in/yr at Big Bear Lake and 48 in/yr at Lake 

Arrowhead (U.S. Department of Commerce, National Oceanic 

and Atmospheric Administration, 2011; Western Regional 

Climate Center, 2011).

BEAR Study Unit—Bear Valley Study Area

The Bear Valley study area is 30.6 mi2 in area and 

occupies the extent of the Bear Valley groundwater basin as 

defined by CDWR. The Bear Valley groundwater basin is 

an east-west trending alluvial valley surrounding Big Bear 

and Baldwin Lakes and is located at the base of a northfacing slope of the San Bernardino Mountains (California 

Department of Water Resources, 2004). The boundaries 

of the study area are approximately defined by the limit of 

Quaternary alluvial sediments of the Bear Valley groundwater 

basin (fig. 2). 

The Bear Valley study area is surrounded by the San 

Bernardino Mountains, with land-surface altitudes ranging 

from approximately 6,700 feet above mean sea level (ft above 

msl) on the valley floor to over 10,200 ft above msl on the 

southern border. Two lakes—Big Bear and Baldwin—are the 

major water-body features in the study area. Big Bear Lake is 

a man-made lake that is used for public recreation as well as a 

water supply for the San Bernardino area (Big Bear Municipal 

Water District, 2011). The lake is fed by runoff from numerous 

creeks (Grout, Caribou, Rathbun, Metcalf, and Kidd) that 

drain the surrounding mountains and valley floor. Baldwin 

Lake (typically dry) receives occasional runoff from Caribou 

Creek and numerous intermittent streams originating from the 

surrounding mountains. The only significant surface-water 

outflow from any of the lakes is from Big Bear Lake to the 

west through the Bear Valley Dam and into Bear Creek, which 

flows into the Santa Ana River 8 miles (mi) to the south (Flint 

and Martin, 2012) (fig. 3A, B). 

The primary aquifer system in the study area occurs in 

the upper and middle aquifers of a three-tiered alluvium-filled 

aquifer system that is underlain by basement rocks (California 

Department of Water Resources, 2004; Flint and Martin, 2012) 

(fig. 2). Recent gravity model results indicate that the alluvial 

deposits range from less than 500 feet (ft) thick on the edges 

of the study area and on the eastern end of Big Bear Lake to 

more than 1,500 ft thick beneath the center of Big Bear Lake 

and to the west of Baldwin Lake (Flint and Martin, 2012). 

The underlying basement rocks are of pre-Tertiary age and 

are principally made up of large granitic bodies and to a lesser 

extent metamorphosed sedimentary rock and gneiss. Fractured 

basement rock is known to make a small contribution 

to groundwater resources in the study area (California 

Department of Water Resources, 2004). 

The upper aquifer is composed of gravel and sand 

deposits of Holocene age, which transmit groundwater readily. 

This aquifer is thin and unsaturated in the western part of the 

study area, but in the eastern part of the study area it reaches 

more than 200 ft thick (California Department of Water 

Resources, 2004; Flint and Martin, 2012). The middle aquifer 

consists of older fan deposits and older alluvium made up of 

various amounts of silt, gravel, sand, and clay. This aquifer 

is found throughout the study area and ranges from 150 ft 

to more than 800 ft thick. Groundwater found in the older 

alluvial sediments of the middle aquifer is generally confined 

under fine sediments, whereas groundwater found in older 

fan sediments are generally unconfined to semi-confined. The 

lower aquifer is made up of coarse sands, pebbles, gravels, 

and sandy clays and is likely restricted to the eastern part of 

the study area near Baldwin Lake (GEOSCIENCE Support 

Services, Inc., 2006). The deposits that make up the lower 

aquifer are up to 120 ft thick (California Department of Water 

Resources, 2004; Flint and Martin, 2012). 

The general groundwater-flow direction in the study area 

is from the sides of the study area, following the topography of 

the valley towards Big Bear or Baldwin Lakes. A groundwater 

divide is present between Big Bear Lake and Baldwin Lake 

near Big Bear City. Faults may act as hydrologic barriers 

to groundwater movement in the study area (California 

Department of Water Resources, 2004).

Groundwater recharge in the study area occurs from 

direct percolation of precipitation, infiltration of runoff from 

the surrounding mountains, and underflow from fractured 

basement rocks (California Department of Water Resources, 

2004; GEOSCIENCE Support Services, Inc., 2006; Flint 

and Martin, 2012). Where present, the permeable recent 

alluvium allows rapid infiltration of available rainfall and 

runoff (GEOSCIENCE Support Services, Inc., 2006; Flint and 

Martin, 2012).
6 Groundwater-Quality Data in the Bear Valley and Selected Hard Rock Areas Study Unit, 2010

Figure 2. Geology of the Bear Valley and Selected Hard Rock Areas (BEAR) Groundwater Ambient Monitoring and Assessment 

(GAMA) study unit.

sac12-0450_fig 02_regional geology

117°15’ 117° 116°45’

34°

30’

34°

15’

Plio-Pleistocene sediment

Quaternary alluvium

SEDIMENTARY ROCKS OTHER

Quaternary playa

Quaternary other sediment

Tertiary nonmarine sediment

Granitic rocks

Metamorphic other

Metasediment

Ultramafic/mafic

EXPLANATION

BEAR study unit

 boundary

Lake Stream

Aqueduct

0 5 10 MILES

0 5 10 KILOMETERS

Geology from Saucedo and others, 2000.

Faults—Dashed where uncertain;

 dotted where concealed 

San Andreas Fault Zone

Cleghorn

Fault

Zone Tunnel Ridge Fault 

Bear Valley

study area shown on

figures 3A and 3B

Selected Hard Rock Areas

study area shown on

figures 4A and 4B
Hydrogeologic Setting 7

Figure 3. Boundaries of the Bear Valley study area, topographic features, major cities, major roads, and hydrologic features, 

(A) the location of California Department of Public Health (CDPH) sites, and (B) the distribution of the grid cells, and the location of 

sampled grid and understanding sites, Bear Valley and Selected Hard Rock Areas (BEAR) Groundwater Ambient Monitoring and 

Assessment (GAMA) study unit.

sac12-0450_fig 03ab

38

38

18

18

38

38

18

18

BEAR-S14

BEAR-S13

BEAR-S12

BEAR-S11

BEAR-S10

BEAR-S09 BEAR-S08

BEAR-S07

BEAR-S06

BEAR-S05

BEAR-S04

BEAR-S03

BEAR-S02

BEAR-S01

BEAR-U09

BEAR-U08 BEAR-U07

BEAR-U06

BEAR-U04

BEAR-U03

BEAR-U02

116°55’ 116°50’ 116°45’

34° 19’

34° 15’

34° 12’

Big Bear Lake

Big Bear City

Big Bear Lake

Caribou Creek

Grout Creek

Bear

Creek

Kidd

Creek

Metcalf

Creek

Rathbun Creek

Baldwin

Lake

0 1 2 3 4 5 MILES

0 1 2 3 4 5 KILOMETERS

EXPLANATION

Bear Valley

 study area 

Lake 

Seasonal dry lake 

Faults—Dashed where

 uncertain; dotted where

 concealed Cities

California Department of

 Public Health (CDPH) site

San Bernardino Mts

Van Dusen Canyon

Poligue Canyon

Grays

Peak

Delamar Mtn

Bertha Peak

Gold Mtn

Gold Hill

Sugarloaf Mtn

Snow Summit

Nelson Ridge

Deadmans Ridge

Bear

Valley

Dam

34° 19’ 116°55’ 116°50’ 116°45’

34° 15’

34° 12’

Big Bear Lake

Big Bear City

Big Bear Lake

Caribou Creek

Grout Creek

Bear

Creek

Kidd

Creek

Metcalf

Creek

Rathbun Creek

Baldwin

Lake

0 1 2 3 4 5 MILES

0 1 2 3 4 5 KILOMETERS

San Bernardino Mts

Van Dusen Canyon

Poligue Canyon

Grays

Peak

Delamar Mtn

Bertha Peak

Gold Mtn

Gold Hill

Sugarloaf Mtn

Snow Summit

Nelson Ridge

Deadmans Ridge

Bear

Valley

Dam

BEAR grid site and identifier

BEAR understanding site

 and identifier

A

B
8 Groundwater-Quality Data in the Bear Valley and Selected Hard Rock Areas Study Unit, 2010

BEAR Study Unit—Selected Hard Rock Areas 

Study Area

The Selected Hard Rock Areas study area (hereinafter 

referred to as the Hard Rock study area) is 81.5 mi2 in area, 

is located approximately 3 mi west of the Bear Valley study 

area, and is defined by the USGS as the granitic bedrock area 

surrounding Lake Arrowhead (fig. 2). Two major mountain 

peaks (Butler and Crafts) separate the eastern parts of the Hard 

Rock study area from the Bear Valley study area. The study 

area was derived from five surface-water watersheds that are 

in granitic bedrock (Silverwood Lake-West Fork Mojave 

River, Grass Valley Creek-West Fork Mojave River, Willow 

Creek, Upper Deep Creek, and Holcomb Creek; Watershed 

Boundary Dataset, U.S. Department of Agriculture-Natural 

Resources Conservation Service and others, 2013) located on 

the north-facing slope of the San Bernardino Mountains. The 

study area was defined as those parts of the five surface-water 

watersheds that are within 1.86-mi (3-kilometer [km]) radius 

buffers (circles) around the CDPH wells located in those 

watersheds (fig. 4) (additional discussion in the section titled 

“Study Design”). 

Land-surface altitudes in the study area range from 

approximately 3,200 ft above msl near Silverwood Lake in 

the western part of the study area, to more than 7,800 ft above 

msl at Keller Peak, in the San Bernardino Mountains. The 

western reaches of the study area are drained by the West Fork 

of the Mojave River to Silverwood Lake, north to the Mojave 

River Forks Reservoir. The eastern parts of the study area are 

drained by Deep Creek and its numerous tributaries northward 

to the Mojave River Forks Reservoir. Small ephemeral 

streams drain the central parts of the study area towards Lake 

Arrowhead (fig. 4). Two man-made lakes—Arrowhead and 

Silverwood—are the largest surface-water features in the study 

area. Lake Arrowhead, which provides some water supply 

to the local community and the San Bernardino area, is also 

a private recreational facility (Arrowhead Lake Association, 

2011; Lake Arrowhead Community Services District, 2011b). 

Silverwood Lake was created as part of the California State 

Water Project and is a water source for the communities in the 

nearby mountain and desert areas (California Department of 

Water Resources, 2011a, b). 

The primary aquifer system in the study area consists 

of the fractured granite bedrock of the western part of the 

Bear Valley study area (fig. 2). The primary aquifer system 

is considered to be confined to semi-confined. In the Lake 

Arrowhead area, the hard rock aquifer is known to extend 

to a depth of 500 ft (GEOSCIENCE Support Services, Inc., 

2008). In addition to the production wells that are drilled into 

the granitic bedrock, numerous springs and horizontal wells 

are a major source of water in the study area (Lake Arrowhead 

Community Services District, 2011a). These springs and 

horizontal wells flow under artesian conditions for all or most 

of the year (GEOSCIENCE Support Services, Inc., 2008; 

California Department of Public Health, 2009). Additionally, 

throughout the study area, a layer of thin alluvial deposits 

derived from weathering and erosion of the surrounding 

mountains overlies the granitic bedrock (GEOSCIENCE 

Support Services, Inc., 2008). The effect that these alluvial 

deposits have on the hard rock aquifer system is unknown.

Groundwater flow in the study area is through numerous 

fracture systems related to local and regional faults (fig. 2). 

The largest of these is the Cleghorn fault zone, which is 

located in the western part of the study area (Bryant, 2003). 

The Tunnel Ridge Fault (also known as the Tunnel Ridge 

Lineament) is a significant northeast-trending fault that is 

known to transport groundwater in the northern and central 

parts of the study area (Bryant, 1987). There are also unnamed 

faults in the northeastern part of the study area (fig. 4), but the 

effect of these faults on groundwater movement is not known. 

Groundwater recharge in the study area occurs from the 

ambient recharge of runoff and snowmelt that penetrates the 

granitic bedrock through faults and fractures at high elevations 

in the surrounding mountains (Lake Arrowhead Community 

Services District, 2011c).
Hydrogeologic Setting 9

Figure 4. Boundaries of the Selected Hard Rock Areas study area, topographic features, major cities, major roads, hydrologic 

features, (A) the location of California Department of Public Health (CDPH) sites, and (B) the distribution of the grid cells, and 

the location of sampled grid and understanding sites, Bear Valley and Selected Hard Rock Areas (BEAR) Groundwater Ambient 

Monitoring and Assessment (GAMA) study unit.

sac12-0450_fig 04ab

215

18

330

18

138

215

18

330

18

138

BEAR-G13

BEAR-G12

BEAR-G11 BEAR-G10

BEAR-G09

BEAR-G08

BEAR-G07

BEAR-G06

BEAR-G05

BEAR-G04 BEAR-G03

BEAR-G02

BEAR-G01

BEAR-U11

BEAR-U10

BEAR-U05

BEAR-U01

117°20’ 117°15’ 117°10’ 117°5’ 34° 19’

34° 15’

34° 11’

0 1 2 3 4 5 MILES

0 1 2 3 4 5 KILOMETERS

Lake Arrowhead Green Valley Lake

Deep Creek

Crab Creek

Hooks Creek

Sheep Creek

Holcomb Creek

Little Bear Creek

California Aqueduct

West Fork Mojave River

Silverwood

Lake

Lake

Arrowhead

Lake

Gregory

San Bernardino Mts

The Pinnacles Shay Mts

Deer

Mtn

Keller Peak

Arrowhead

Peak

Jobs

Peak

Cleghorn

Fault Zone

Crestline

Strawberry

Peak

San Andreas Fault Zone

Crafts Peak

Butler Peak

117°20’ 117°15’ 117°10’ 117°5’ 34° 19’

34° 15’

34° 11’

0 1 2 3 4 5 MILES

0 1 2 3 4 5 KILOMETERS

Lake Arrowhead Green

Valley

Lake

California Aqueduct

Silverwood

Lake

Lake

Arrowhead

Lake

Gregory

San Bernardino Mts

The Pinnacles Shay Mts

Deer

Mtn

Keller Peak

Arrowhead

Peak

Jobs

Peak Crestline

Strawberry

Peak

San Andreas Fault Zone

Crafts Peak

Butler Peak

EXPLANATION

Selected Hard Rock

 Areas study area 

Lake 

Seasonal dry lake 

Faults—Dashed where

 uncertain; dotted where

 concealed 

Watersheds from U.S. 

 Department of Agriculture–

 Natural Resources

 Conservation Service

 and others, 2013 

Cities

California Department of

 Public Health (CDPH) site

BEAR grid site and identifier

BEAR understanding site

 and identifier

Upper

Deep Creek

Holcomb Creek

Willow Creek

Silverwood LakeWest Fork Mojave River

Grass Valley CreekWest Fork Mojave River

Upper

Deep Creek

Holcomb Creek Willow Creek

Silverwood LakeWest Fork Mojave

River

Grass Valley CreekWest Fork Mojave River

Cleghorn

Fault Zone

A

B
10 Groundwater-Quality Data in the Bear Valley and Selected Hard Rock Areas Study Unit, 2010

Methods 

Methods used for the GAMA-PBP were selected to 

achieve the following objectives: (1) collect groundwater 

samples that are statistically representative of the primary 

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

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

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

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

relevant documentation. The appendix contains detailed 

descriptions of the sample-collection protocols, analytical 

methods, and the QC data analysis.

Study Design

The wells and springs (hereinafter referred to as “sites”) 

selected for sampling in the BEAR study unit reflect the 

combination of two site-selection strategies. For the first 

strategy, 27 randomized sites were selected to provide a 

statistically unbiased, spatially distributed assessment of the 

quality of groundwater used for public drinking-water supply. 

Sites sampled as part of the spatially distributed, randomized 

grid-cell network, hereinafter, are referred to as “grid sites.” 

For the second strategy, 11 non-randomized sites (hereinafter 

referred to as “understanding sites”) were sampled in the Bear 

Valley and Hard Rock study areas to aid in the understanding 

of the groundwater-quality issues associated with septic tank 

use and also ski area land use.

The spatially distributed grid sites were selected by 

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

randomized grid-based method divides a study area into equalarea grid cells; however, geographic features may force a grid 

cell to be divided into multiple pieces to obtain the designated 

coverage area for each cell. For instance, a part of a grid cell 

may be located on either side of a mountain range, but the grid 

cell is still considered one grid cell. 

In the BEAR study unit, the approach was to sample one 

available CDPH site located within each grid cell. If a grid 

cell contained more than one CDPH site, each was randomly 

assigned a rank. The highest ranking CDPH site that met 

basic sampling criteria (for example, sampling point located 

prior to treatment or capability to pump for several hours) 

was sampled. If a grid cell contained no accessible CDPH 

sites, then other types of sites, such as domestic or irrigation 

wells, were considered for sampling. These non-CDPH sites 

were identified from USGS well databases or by door-to-door 

canvassing. When applicable, non-CDPH wells with depths 

and screened intervals similar to those in CDPH wells in the 

area were selected. 

The Bear Valley study area was divided into 15 equalarea grid cells, each approximately 1.6 mi2

 (approximately 

4.2 square kilometers [km2]) in area; grid sites in 14 of the 

15 cells were sampled (fig. 3B). The Hard Rock study area 

was divided into 15 equal-area grid cells, each approximately 

5.4 mi2 (approximately 14.1 km2) in area; grid sites in 13 of 

the 15 cells were sampled (fig. 4B). 

The design of the grid cells varied between the Bear 

Valley and Hard Rock study areas because of differences in 

the distributions of CDPH sites. In the Bear Valley study area, 

CDPH sites are fairly evenly distributed throughout the entire 

study area (fig. 3A). Consistent with GAMA-PBP design in 

other study units with regularly distributed CDPH sites, the 

15 grid cells cover the entire CDWR-defined Bear Valley 

groundwater basin (fig. 3B).

In contrast, CDPH sites in the surface-water watersheds 

in granitic rock on the north-facing slope of the San 

Bernardino Mountains are not evenly distributed over the area 

(fig. 4A). To minimize the number of cells without any sites, 

only parts of the watersheds near CDPH sites were included 

in the gridded area. A 1.86-mi (3-km) radius circle (buffer) 

was drawn around each CDPH site, and the collective area 

encompassed by the circles was divided into 15 grid cells 

(fig. 4B). This strategy has been used in other GAMA-PBP 

study units with few and (or) unevenly distributed CDPH sites 

(Fram and Belitz, 2007; Shelton and others, 2013). 

The 27 grid sites (20 wells and 7 springs; table 1) 

sampled in the BEAR study unit were numbered in the order 

in which samples were collected in each study area with the 

suffix varying by geologic formations: “S” for the sedimentary 

deposits of the Bear Valley study area and “G” for the granitic 

rocks of the Hard Rock study area (figs. 3B, 4B).

The 11 understanding sites (6 wells and 5 springs; 

table 1) sampled as part of the BEAR study unit were 

not included in the statistical characterization of water 

quality because inclusion of these sites would lead to the 

overrepresentation of some grid cells. Of the understanding 

sites, four were selected specifically to gain information about 

possible occurrence of nitrate in groundwater due to septic 

system use. Five of the understanding sites were selected to 

investigate potential water-quality issues associated with ski 

areas. These 11 additional sites were numbered in the order of 

sample collection with the prefix: “BEAR-U” (“U” indicates 

“understanding”) (figs. 3B, 4B). 

The GAMA alphanumeric identification number for 

each sample, along with the date sampled, land-surface 

altitude, site type, and available construction information is 

shown in table 1. Groundwater samples were collected from 

26 production wells (25 CDPH wells and 1 domestic well) and 

12 springs (10 CDPH springs and 2 springs used for industrial 

activity) during the time period from April to August 2010.

Site locations were verified by using a global positioning 

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

existing well information in USGS and CDPH databases, and 

information provided by well owners, drillers’ logs, and other 

sources of site information. Site and sample information was 

recorded in the field by hand on field sheets, and electronically 

on field laptop computers using the Alternate Place Entry 

(APE) program designed by the USGS. All information 

was verified and entered into the USGS National Water 

Information System (NWIS) database. Site owner, site use, 

and site location are not published.
Methods 11

Sample Collection and Analysis

Samples were collected in accordance with the USGS 

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

variously dated) and modified USGS National Water-Quality 

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

sampling protocols. These sampling protocols were followed 

so that samples representative of groundwater in the aquifer 

system were collected at each site and so that the samples were 

collected and handled in ways that minimized the potential 

for contamination. Use of the sampling protocols also allows 

comparison with data collected by GAMA-PBP throughout 

California and with other USGS projects in California and the 

Nation. 

All 38 sites in the BEAR study unit were sampled for a 

standard constituent group (table 2). Groundwater samples 

were analyzed for 85 VOCs (table 3A); 83 pesticides and 

pesticide degradates (table 3B); 14 pharmaceutical compounds 

(table 3C); 3 constituents of special interest (table 3E); 

25 trace elements (table 3F); 5 nutrients and dissolved organic 

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

dissolved solids (TDS), and laboratory alkalinity (table 3H); 

arsenic and iron species (table 3I); and 5 dissolved noble 

gases, 8 isotopic tracers, uranium, and 3 other radioactive 

constituents (table 3J). In addition, 9 of the BEAR-U sites 

were sampled for 60 wastewater indicator compounds (WICs) 

(table 3D), and 8 of the BEAR-U sites had field alkalinity 

measured (table 2). The methods used for sample collection 

and analysis are described in the appendix section titled 

“Sample Collection and Analysis.”

Data Reporting

Many of the constituents presented in this report have 

different laboratory reporting conventions; additionally, some 

of the constituents were analyzed by different analytical 

laboratories or methods. The appendix section titled “Data 

Reporting” gives details about the laboratory reporting 

conventions for all constituents and the method preferences 

for those constituents that were analyzed by multiple methods 

or by multiple laboratories in the BEAR study unit.

Quality-Assurance Methods

The QA/QC procedures used for this study followed the 

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

variously dated) and used by the NAWQA Program (Koterba 

and others, 1995). The QA plan followed by the National 

Water Quality Laboratory (NWQL), the primary laboratory 

used to analyze samples for this study, is described in 

Pirkey and Glodt (1998) and Maloney (2005). QC samples 

collected in the BEAR study unit are blank samples, 

replicate pair samples, and matrix- and surrogate-spike 

samples. 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. QA/QC 

procedures and results are described in the appendix section 

titled “Quality-Assurance and Quality-Control Methods and 

Results.”

Quality-Control Results

Results of QC analyses (blank samples, replicate pair 

samples, and matrix- and surrogate-spike samples) were 

used to evaluate the quality of the data for the groundwater 

samples. On the basis of detections in laboratory and field 

blank samples collected for this and for previous GAMAPBP study units, the laboratory reporting levels (LRLs) for 

19 constituents were raised in this report (Olsen and others, 

2010; Fram and Belitz, 2011; Fram and others, 2012). The 

GAMA Program refers to these raised reporting levels as 

“study reporting levels” (SRLs). Detections of two VOCs 

(toluene and 1,2,4-trimethylbenzene), five pharmaceutical 

compounds (acetaminophen, caffeine, carbamazepine, 

1,7-dimethylxanthine, and sulfamethoxazole) and one WIC 

[tris(2-butoxyethyl) phosphate] with concentrations less than 

their respective SRLs were reclassified as non-detections 

and not presented in this report to reduce the likelihood of 

reporting results that could be false positives. Detections of 

11 inorganic constituents (chromium, cobalt, copper, iron, 

lead, manganese, nickel, tungsten, zinc, fluoride, and DOC) 

with concentrations less than their respective SRLs are flagged 

with a less than or equal to symbol (≤) in this report because 

the concentrations of these constituents could be less than 

or equal to the reported value (see table A3 and additional 

discussion in the appendix section titled “Blank Samples”). 

Variability for all of the replicate pair samples for constituents 

detected in samples was within the acceptable limits. Results 

from the replicate pairs confirm that the procedures used to 

collect and analyze the samples did not introduce unacceptable 

levels of contamination or variability (see table A4A–C and 

additional discussion in the appendix section titled “Replicate 

Pairs”). Median matrix-spike sample recoveries for 37 of the 

232 organic and special-interest constituents analyzed were 

outside of the acceptable range of between 70 and 130 percent. 

Constituents with low recoveries might not have been detected 

in some samples if they were present at concentrations near 

the LRLs, and constituents with high recoveries may indicate 

that reported values could be greater than what is in the 

sample (see table A5B-C and additional discussion in the 

appendix section titled “Matrix Spikes”).
12 Groundwater-Quality Data in the Bear Valley and Selected Hard Rock Areas Study Unit, 2010

Comparison Benchmarks

Concentrations of constituents detected in groundwater 

samples were compared with USEPA and CDPH regulatory 

and non-regulatory drinking-water health-based benchmarks 

and benchmarks established for aesthetic purposes (California 

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

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

in this report are meant to characterize the quality of the 

untreated groundwater within the primary aquifer system 

of the BEAR study unit and are not intended to represent 

the treated drinking water delivered to consumers by water 

purveyors. The chemical composition of treated drinking 

water may differ from untreated groundwater because treated 

drinking water may be subjected to disinfection, filtration, 

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

prior to its delivery to consumers. Comparisons of untreated 

groundwater to benchmarks are for illustrative purposes only 

and are not indicative of compliance or non-compliance with 

drinking-water regulations. The following benchmarks 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. The CDPH has established MCLs for 

additional constituents not regulated by the USEPA, 

as well as lowered the benchmark concentrations for a 

number of constituents with MCLs established by the 

USEPA. In this report, a benchmark set by the USEPA 

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

and one set by the CDPH that is more stringent 

than the MCL-US is labeled “MCL-CA.” Well 

owners are notified when constituents are detected at 

concentrations greater than an MCL-US or MCL-CA 

benchmark in samples collected for the GAMA-PBP, 

but these detections do not constitute violations of the 

CDPH regulations.

• AL–Action Level. Legally enforceable standards that 

apply to public water systems and are designed to 

protect public health by limiting the levels of copper 

and lead in drinking water. Detections of copper or 

lead greater than the action-level benchmarks trigger 

requirements for mandatory water treatment to reduce 

the corrosiveness of water to water pipes. The action 

levels established by the USEPA and the CDPH are the 

same; thus, these benchmarks are labeled “AL-US” in 

this report.

• SMCL–Secondary Maximum Contaminant Level. 

Non-enforceable standards applied to constituents that 

affect the aesthetic qualities of drinking water, such 

as taste, odor, and color, or the technical qualities of 

drinking water, such as scaling and staining. Both 

the USEPA and the CDPH define SMCLs, but unlike 

MCLs, SMCLs established by the CDPH are not 

required to be at least as stringent as those established 

by the USEPA. SMCLs established by the CDPH are 

used in this report (SMCL-CA) for all constituents that 

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

because no SMCL-CA has been defined.

• NL–Notification Level. Health-based notification 

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

of the constituents in drinking water that lack MCLs. 

If a constituent is detected in drinking water at 

concentrations greater than its NL-CA, California State 

law requires timely notification of local governing 

bodies and recommends consumer notification.

• HAL–Lifetime Health Advisory Level. The 

maximum concentration of a constituent at which its 

presence in drinking water is not expected to cause any 

adverse carcinogenic effects for a lifetime of exposure. 

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

are calculated assuming consumption of 2 liters (L) 

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

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

a person’s exposure comes from drinking water.

• RSD5–Risk-Specific Dose. The concentration of 

a constituent in drinking water corresponding to 

an excess estimated lifetime cancer risk of 1 in 

100,000. RSD5 is an acronym for risk-specific 

dose at the 10–5 risk level (10–5 equals 1/100,000). 

RSD5s are calculated by dividing the 10–4 cancerrisk concentration established by the USEPA by 10 

(RSD5-US).

For constituents with regulatory benchmarks, detections 

in groundwater samples were compared with the MCL-US, 

MCL-CA, or AL-US. Constituents with SMCLs were 

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

conductance, and total dissolved solids, the CDPH defines 

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

these constituents in groundwater samples were compared 

with both levels. The SMCL-US levels for these constituents 

correspond to their recommended SMCL-CAs. Detected 

concentrations of constituents without a regulatory benchmark 

or an SMCL were compared with the NL-CA. For constituents 

without a regulatory benchmark, SMCL, or NL-CA, detected 

concentrations were compared with the HAL-US. For 

constituents without a regulatory benchmark, SMCL, NL-CA, 
Water-Quality Results 13

or HAL-US, detected concentrations were compared with 

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

comparison benchmark for a constituent with more than one 

type of established benchmark will not necessarily result in 

selection of the benchmark with the lowest concentration. For 

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

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

benchmark selected by this hierarchy is the SMCL-CA. 

The comparison benchmarks used in this report are listed 

in tables 3A–J for all constituents and in tables 4–14 for 

constituents detected in groundwater samples from the BEAR 

study unit. Not all constituents analyzed for this study have 

established benchmarks available. Detections of constituents 

at concentrations greater than the selected comparison 

benchmarks are marked with asterisks (*) in tables 4, 9, 11, 

12, and 14. 

Water-Quality Results 

Results from analyses of groundwater samples from the 

BEAR study unit are presented in tables 4–14. Groundwater 

samples collected in the BEAR study unit were analyzed for 

8 water-quality indicators and up to 289 unique constituents; 

217 of those constituents were not detected in any of the 

samples, and 72 constituents were detected (tables 3A–J, 4). 

Water-quality indicators measured in the field and at the 

NWQL are included in table 4. The results of groundwater 

analyses organized by compound classes are presented in 

tables 5–14: 

• Organic constituents

• Volatile organic compounds (table 5)

• Pesticides and pesticide degradates (table 6)

• Wastewater indicator compounds (table 7)

• Constituents of special interest (table 8)

• Inorganic constituents

• Trace elements (table 9)

• Nutrients and dissolved organic carbon (table 10)

• Major and minor ions, silica, and total dissolved 

solids (table 11)

• Arsenic and iron species (table 12)

• Isotopic tracers (table 13) 

• Uranium and other radioactive constituents (table 14) 

Water-Quality Indicators (Field and Laboratory) 

Measurements of turbidity, dissolved oxygen, pH, 

specific conductance, alkalinity, and associated parameters 

(water temperature and bicarbonate and carbonate 

concentrations) are presented in table 4. Turbidity and 

dissolved oxygen, alkalinity, bicarbonate, and carbonate 

concentrations are used as indicators of processes that affect 

water chemistry. 

The pH value indicates the acidity of the water. Low 

pH in water may contribute to corrosion of pipes, and high 

pH in water may contribute to scaling. Field and laboratory 

pH values for 5 of the 27 of the grid sites sampled (1 in the 

Bear Valley study area and 4 in the Hard Rock study area) 

were outside of the SMCL-US range for pH (< 6.5 or > 8.5) 

(table 4). Three BEAR-U site samples also had pH values 

outside of the SMCL-US range for pH. Laboratory pH 

values may be dissimilar to field pH values because the pH 

of groundwater may change upon removal from the ambient 

environment and exposure to the atmosphere; therefore, the 

field measurements are preferred over the laboratory results. 

Specific conductance is the measure of electrical 

conductivity of the water and is proportional to the amount 

of dissolved solids in the water. Field specific-conductance 

values for all 38 sites sampled in the BEAR study unit were 

at concentrations less than the recommended SMCL-CA of 

900 microsiemens per centimeter at 25 degrees Celsius (μS/cm 

at 25°C) (table 4). 

Organic Constituents

VOCs are present in paints, solvents, fuels, fuel additives, 

refrigerants, fumigants, and disinfected water, and are 

characterized by their tendency to evaporate. VOCs generally 

persist longer in groundwater than in surface water because 

groundwater is isolated from the atmosphere. 

Of the 85 VOCs analyzed in the BEAR study unit, 16 

were detected in groundwater samples; all concentrations 

were less than health-based benchmarks (table 5). One or 

more VOCs were detected in 17 of the 27 grid sites sampled 

(about 63 percent detection frequency). VOCs were detected 

in 11 of the 14 grid sites sampled in the Bear Valley study 

area (approximately 79 percent). VOCs were detected in 6 of 

the 13 grid sites sampled in the Hard Rock study area (about 

46 percent). One or more VOCs were detected in six BEAR-U 

site samples.

Chloroform (trichloromethane), methyl tert-butyl 

ether (MTBE), perchloroethene (PCE, tetrachloroethene), 

bromodichloromethane, 1,1,1-trichloroethane (1,1,1-TCA), 

and 1,2,4-trimethylbenzene were each detected in more than 

10 percent of the grid sites in both the BEAR study unit and 

the Bear Valley study area. Chloroform was detected in more 

than 10 percent of the grid sites in the Hard Rock study area. 

Chloroform is a byproduct of drinking-water disinfection and 
14 Groundwater-Quality Data in the Bear Valley and Selected Hard Rock Areas Study Unit, 2010

is among the most commonly detected VOCs in groundwater 

nationally (Zogorski and others, 2006). 

Pesticides are chemicals used to control weeds, insects, 

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

settings, and include herbicides, insecticides, and fungicides. 

Pesticide degradates are the product of the environmental 

transformations of the parent pesticide, and they can have 

similar properties to the parent pesticide (Andreu and Pico, 

2004).

Of the 83 pesticides and pesticide degradates analyzed in 

the BEAR study unit, 2 pesticides (simazine and prometon) 

were detected in groundwater samples; all concentrations were 

less than health-based benchmarks (table 6). Simazine was 

detected in 4 of the 27 grid sites sampled (about 15 percent 

detection frequency), and prometon was detected in 1 of the 

grid sites sampled in the BEAR study unit.

Specifically, simazine was detected in 3 of the 14 grid 

sites sampled (approximately 21 percent) and prometon was 

detected in 1 of the grid sites sampled in the Bear Valley 

study area. Simazine was detected in 1 of the 13 grid sites 

sampled in the Hard Rock study area. Additionally, simazine 

was detected in one BEAR-U site sample. Simazine is among 

the nation’s most commonly detected pesticide compounds in 

groundwater (Gilliom and others, 2006). 

Pharmaceutical compounds may enter the environment 

in many ways, including through leaking septic systems and 

sewer lines, discharge of treated wastewater, seepage from 

landfills, land application of manure fertilizers, and runoff 

from animal wastes (Fram and Belitz, 2011). Pharmaceutical 

compounds were not detected at concentrations greater than or 

equal to the SRLs defined by Fram and Belitz (2011) in any of 

the grid or understanding sites; therefore, a results table is not 

presented in this report. 

WICs are usually found in urban wastewater and include 

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

compounds. WICs were not detected in any of the 27 grid 

sites sampled in the BEAR study unit. Tris(2-butoxyethyl) 

phosphate and phenol were detected in two BEAR-U site 

samples (table 7).

Constituents of Special Interest

Perchlorate, N-nitrosodimethylamine (NDMA), and 

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

special interest in California because they may adversely 

affect water quality and recently have been detected in water 

supplies (California Department of Public Health, 2008b). 

NDMA and 1,2,3-TCP were not detected in any of the grid 

or understanding sites; as a result, these constituents are not 

included in table 8.

Perchlorate was detected in 21 of 27 grid sites sampled in 

the BEAR study unit (about 78 percent detection frequency). 

Perchlorate was not detected at concentrations greater than the 

MCL-CA of 6 μg/L in any of the grid or understanding sites 

sampled in the BEAR study unit.

Perchlorate was detected in 13 of the 14 grid sites 

sampled in the Bear Valley study area (approximately 

93 percent) and in 8 of the 13 grid sites sampled in the Hard 

Rock study area (about 62 percent). Additionally, perchlorate 

was detected in eight BEAR-U samples. 

Inorganic Constituents

Health-based or non-health-based benchmarks have 

been established for 22 of 25 trace elements analyzed in this 

study (tables 3F, H). Of the 16 trace elements with healthbased benchmarks, most detected concentrations in the sites 

sampled in the BEAR study unit were less than established 

benchmarks, with the exception of one detection of arsenic 

greater than the MCL-US of 10 μg/L (BEAR-S04; table 9) 

and one detection of fluoride greater than the MCL-CA of 

2 milligrams per liter (BEAR-S12; table 11).

The CDPH has established non-health-based secondary 

benchmarks (SMCL-CAs) that are based on aesthetic 

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

properties (such as scaling and staining) of water, rather than 

on human-health concerns for iron, manganese, silver, zinc, 

chloride, sulfate, and TDS. 

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 concentrations greater than the SMCL-CA 

of 300 μg/L were detected in two grid sites sampled in the 

Hard Rock study area, and a manganese concentration greater 

than the SMCL-CA of 50 μg/L was detected in one grid site 

sampled in the Hard Rock study area (table 9). Additionally, 

iron was measured at a concentration greater than the 

SMCL-CA in one BEAR-U site sample, and manganese was 

measured at concentrations greater than the SMCL-CA in two 

BEAR-U site samples. All silver, zinc, chloride, sulfate, and 

TDS concentrations detected in samples were less than the 

corresponding SMCL-CA benchmarks (tables 9, 11).

Nutrients (nitrogen and phosphorus) and 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. All concentrations of nutrients in samples 

from the BEAR study unit were less than health-based 

benchmarks (table 10).

Arsenic and iron occur as different species depending on 

the oxidation-reduction state of the groundwater. The oxidized 

and reduced species have different solubilities in groundwater, 

and the relative proportions of the oxidized and reduced 

species of each element can be used in the interpretation of the 

oxidation–reduction conditions of the aquifer. 

Concentrations of total arsenic and total iron reported 

by the NWQL in table 9 are considered to be more accurate 

than the concentrations reported by the USGS National 

Research Program (NRP) Trace Metal Laboratory (TML), 
Water-Quality Results 15

Boulder, Colorado, in table 12 (see the appendix section 

titled “Constituents Determined by Multiple Methods or 

Laboratories”). Iron concentrations (reported from the USGS 

NRP-TML) greater than the SMCL-CA of 300 μg/L were 

detected in samples from two grid sites and one understanding 

site (table 12).

Isotopic Tracers and Dissolved Noble Gases

The isotopic ratios, activities, and concentrations of many 

elements are used as tracers of hydrologic processes. Stableisotope ratios of hydrogen and oxygen in water (δ2

H and 

δ18O) aid in the interpretation of the sources of groundwater 

recharge. These stable-isotope 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 or directly from groundwater 

close to land surface once in the aquifer system (Clark and 

Fritz, 1997). In the BEAR study unit, the stable-isotope ratios 

of hydrogen ranged from –99.3 to –49.6 per mil, and the stable 

isotope ratios of oxygen ranged from –13.55 to –5.72 per mil 

(table 13).

Stable-isotope ratios of nitrogen and oxygen in dissolved 

nitrate (δ15N and δ18O) can be used to aid in interpretation of 

sources and processes affecting nitrate in the groundwater 

(Clark and Fritz, 1997). The isotopic ratios of nitrogen and 

oxygen in dissolved nitrate ranged from –0.39 to 18.67 

(table 13).

Stable-isotope ratios of boron in water (δ11B) may be 

useful in distinguishing the sources of boron in groundwater. 

Natural sources include igneous rocks, evaporate minerals, 

seawater, and geothermal waters (Coplen and others, 2002; 

U.S. Geological Survey, 2004).

Isotopic ratios of strontium in water (87Sr/86Sr) reflect 

the amounts of strontium (and other inorganic constituents) 

the aquifer materials are contributing to the groundwater 

system. In regions that have diverse geology, isotopic ratios 

of strontium may aid in identifying groundwater-flow paths 

(Clark and Fritz, 1997). The isotopic ratios of strontium 

ranged from 0.70994 to 0.77499 (table 13).

Tritium activities and helium isotope ratios 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 of atmospheric 

testing of nuclear weapons between 1952 and 1963. Thus, 

concentrations of tritium greater than background levels 

generally indicate the presence of water recharged since the 

early 1950s. Helium isotope ratios can be used in conjunction 

with tritium concentrations to estimate ages for young 

groundwater (Clark and Fritz, 1997). Of the isotopic tracer 

constituents analyzed for this study, tritium is the only one 

with a health-based benchmark. All measured tritium activities 

in samples from the sites in the BEAR study unit were 

more than three orders of magnitude less than the MCL-CA 

benchmark (table 14).

Carbon-14, a radioactive isotope of carbon, is an 

age-dating tracer. Low levels of carbon-14 are produced 

continuously by interaction of cosmic radiation with the 

Earth’s atmosphere and are incorporated into atmospheric 

carbon dioxide. Carbon dioxide dissolves in precipitation, 

surface water, and groundwater exposed to the atmosphere, 

thereby entering the hydrologic cycle. Because carbon-14 

decays with a half-life of approximately 5,700 years, low 

activities of carbon-14, relative to modern values, generally 

indicate a presence of groundwater that is several thousands of 

years old or more (Clark and Fritz, 1997). Carbon-14 activities 

ranged from 5.540 to 108.5 percent modern carbon, and the 

stable isotopes of carbon in dissolved inorganic carbon (δ13C) 

ranged from –19.66 to –8.08 per mil (table 13).

Gases dissolve in water that is in contact with the 

atmosphere, and the solubilities of the different gas species 

vary with temperature. Concentrations of dissolved noble 

gases are used to estimate the conditions of groundwater 

recharge, particularly the temperature of the water at the time 

of recharge (Clark and Fritz, 1997).

Uranium and Other Radioactive Constituents

Radioactivity is the release of energy or energetic 

particles during changes in the structure of the nucleus of an 

atom. Most 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 

an aquifer. Uranium and thorium decay in a series of steps 

eventually forming stable isotopes of lead (Soddy, 1913; 

Faure and Mensing, 2005). Radon-222 is a radioactive isotope 

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. 

Uranium concentrations greater than the MCL-US of 

30 μg/L were detected in samples from three grid sites in the 

Hard Rock study area (table 14). Additionally, uranium was 

measured at a concentration greater than the MCL-US in a 

sample from one BEAR-U site.

Radon-222 activities greater than the proposed MCL-US 

of 4,000 picocuries per liter (pCi/L) were detected in samples 

from nine grid sites in the Hard Rock study area (table 14). 

Additionally, radon-222 activity was measured greater than the 

proposed MCL-US in five BEAR-U samples (one in the Bear 

Valley study area and four in the Hard Rock study area). The 

proposed MCL-US will apply if the state or local water agency 
16 Groundwater-Quality Data in the Bear Valley and Selected Hard Rock Areas Study Unit, 2010

has an approved multimedia mitigation program to address 

radon levels in indoor air (U.S. Environmental Protection 

Agency, 1999). 

Future Work

Subsequent reports for the BEAR study unit will be 

focused on assessment of the data presented in this report by 

using statistical, qualitative, and quantitative approaches to 

evaluate the natural and human factors affecting groundwater 

quality in the BEAR study unit. Water-quality data contained 

in the CDPH databases will be used in combination with the 

data that are presented in this report. These subsequent reports 

will include results for the stable isotopes of boron in water 

and the LLNL results (dissolved noble gases, tritium activity, 

and helium isotope ratios) for the BEAR study unit.

Summary 

Groundwater quality in the 112-square-mile Bear Valley 

and Selected Hard Rock Areas (BEAR) study unit was 

investigated by the U.S. Geological Survey (USGS) from 

April to August 2010, as part of the Priority Basin Project 

(PBP) of the California State Water Resources Control 

Board (SWRCB) Groundwater Ambient Monitoring and 

Assessment (GAMA) Program. The GAMA Program was 

created to provide a comprehensive baseline of groundwater 

quality in the State of California. The GAMA-PBP was 

created as a result of the Groundwater Quality Monitoring 

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

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

of groundwater. The GAMA-PBP is being conducted by 

the USGS in cooperation with the SWRCB and Lawrence 

Livermore National Laboratory (LLNL).

The GAMA BEAR study was designed to provide a 

spatially unbiased assessment of untreated-groundwater 

quality in the primary aquifer system and to provide 

statistically consistent comparisons of groundwater quality 

throughout California. The primary aquifer system is defined 

as the zones corresponding to the perforation intervals of wells 

listed in the California Department of Public Health (CDPH) 

database for the BEAR study unit. The quality of groundwater 

in the primary aquifer system may differ from that in shallow 

or deep water-bearing zones; shallow groundwater may be 

more vulnerable to surficial contamination. 

This study did not evaluate the quality of water delivered 

to consumers; after withdrawal from the ground, water 

typically is treated, disinfected, and blended with other 

waters to maintain acceptable water quality. The benchmarks 

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

the consumer, not to untreated groundwater. However, to 

provide context for the results, concentrations of constituents 

measured in these groundwater samples were compared with 

benchmarks established by the U.S. Environmental Protection 

Agency (USEPA) and the CDPH.

The BEAR study unit is located within the Transverse 

Ranges and selected Peninsular Ranges hydrogeologic 

province and includes one groundwater basin (Bear Valley) 

defined by the California Department of Water Resources. The 

BEAR study included analyses of the groundwater quality 

from 38 wells and springs (hereinafter referred to as sites) in 

San Bernardino County, California. A total of 27 sites were 

selected by using a randomized grid approach to achieve a 

statistically unbiased representation of groundwater used for 

public drinking-water supplies (grid sites). In addition, 11 sites 

were selected to provide data to aid in the understanding of 

the effects of septic tank use and the potential groundwaterquality issues associated with ski areas in the study unit 

(understanding sites). 

Groundwater samples were analyzed for water-quality 

indicators, organic constituents, constituents of special 

interest, inorganic constituents, and uranium and other 

radioactive constituents. Isotopic tracers and dissolved noble 

gases also were measured to provide a dataset that will 

be used to interpret the sources and ages of groundwater 

in a subsequent report. In total, 289 unique constituents 

and 8 water-quality indicators were measured. This report 

describes the sampling, analytical, and quality-assurance 

methods used in the study and presents the results of the 

chemical analyses of the groundwater samples.

Quality-control samples (blanks, replicates, and matrix 

spikes) were collected at 13 percent of the wells in the BEAR 

study unit, and the results for these samples were used to 

evaluate the quality of the data for the groundwater samples. 

Blanks rarely contained detectable concentrations of any 

constituent. Replicate samples were within acceptable limits of 

variability, and matrix-spike recoveries were generally within 

the acceptable range.

Organic and inorganic constituents were sampled at all 

38 sites in the BEAR study unit, and most detections were 

measured at concentrations less than health-based benchmarks. 

In the Bear Valley study area grid sites, one detection of 

arsenic was greater than the USEPA maximum contaminant 

level (MCL-US) and one detection of fluoride was greater 

than the CDPH maximum contaminant level (MCL-CA). 

In the Selected Hard Rock Areas study area grid sites, three 

detections of uranium were greater than the MCL-US, nine 

detections of radon-222 were greater than the proposed 

MCL-US, two detections of iron were greater than the CDPH 

secondary maximum contaminant level (SMCL-CA), and one 

detection of manganese was greater than the SMCL-CA.

In the BEAR study unit understanding sites, one detection 

of uranium was greater than the MCL-US, five detections of 

radon-222 were greater than the proposed MCL-US, and two 

detections of manganese were greater than the SMCL-CA.
References Cited 17

Acknowledgments

The authors thank the following cooperators for their 

support: the California State Water Resources Control 

Board, California Department of Public Health, California 

Department of Water Resources, and Lawrence Livermore 

National Laboratory. We especially thank the site owners and 

water purveyors for allowing the U.S. Geological Survey to 

collect samples from their sites.

References Cited

American Public Health Association, 1998, Standard 

methods for the examination of water and wastewater 

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

Association, American Water Works Association, and Water 

Environment Federation, p. 3-37–3-43.

American Society for Testing and Materials, 1998, Water 

and environmental technology, in Annual book of ASTM 

standards: Philadelphia, Pa., American Society for Testing 

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

Anderson, R.L., 1987, Practical statistics for analytical 

chemists: New York, Van Nostrand Reinhold Company, 

Inc., 315 p.

Andreu, V., and Pico, Y., 2004, Determination of pesticides 

and their degradation products in soil—Critical review and 

comparison of methods. Trends in Analytical Chemistry, 

v. 23, no. 10–11, p. 772–789, accessed December 11, 2011, 

at http://www.uv.es/~pico/papers/35.pdf.

Arrowhead Lake Association, 2011, Home Page, accessed 

December 13, 2011, at http://www.ala-ca.org.

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.

Big Bear Area Regional Wastewater Agency, 2011, 

Water supplies, accessed December 12, 2011, at http://

bigbearwatersolutions.org/Water-Supplies.htm. 

Big Bear Municipal Water District, 2011, Lake stabilization—

In-Lieu Water Program, accessed December 12, 2011, at 

http://www.bbmwd.com/Lake_Stabilization.html.

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

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

Laboratory—Determination of dissolved organic carbon 

by UV-promoted persulfate oxidation and infrared 

spectrometry: U.S. Geological Survey Open-File 

Report 92-480, 12 p.

Bryant, W.A., 1987, Cleghorn and related faults, San 

Bernardino County: California Division of Mines and 

Geology Fault Evaluation Report FER-187, California 

Division of Mines and Geology Open-File Report 90-14, 

13 p., accessed December 13, 2011, at ftp://ftp.consrv.

ca.gov/pub/dmg/shezp/FER_187/042887.pdf.

Bryant, W.A., compiler, 2003, Fault number 108b, Cleghorn 

fault zone, Northern Cleghorn section, in Quaternary fault 

and fold database of the United States: U.S. Geological 

Survey, accessed December 15, 2011, at http://earthquakes.

usgs.gov/regional/qfaults.

Bullen, T.D., Krabbenhoft, D.P., and Kendall, Carol, 1996, 

Kinetic and mineralogic controls on the evolution of 

groundwater chemistry and 87Sr/86Sr in a sandy silicate 

aquifer, northern Wisconsin, USA: Geochimica et 

Cosmochimica Acta, v. 60, no. 10, p. 1807–1821.

California Department of Public Health, 2008a, California 

drinking water-related laws—Drinking water-related 

regulations, Title 22: California Department of Public 

Health, accessed October 6, 2011, at http://www.CDPH.

ca.gov/certlic/drinkingwater/Pages/Lawbook.aspx.

California Department of Public Health, 2008b, Drinking 

water notification levels—Notification levels: California 

Department of Public Health, accessed October 6, 2011, 

at http://www.CDPH.ca.gov/certlic/drinkingwater/Pages/

NotificationLevels.aspx.

California Department of Public Health, 2009, Drinking 

Water Source Assessment and Protection Program site 

locations [digital data]: California Department of Public 

Health, Division of Drinking Water and Environmental 

Management, produced by the Information Center for the 

Environment, Davis, California.

California Department of Water Resources, 2003, California’s 

groundwater update 2003: California Department of Water 

Resources Bulletin 118, 246 p., accessed October 25, 2011, 

at http://www.groundwater.water.ca.gov/bulletin118.

California Department of Water Resources, 2004, California’s 

groundwater—Individual basin descriptions, Bear Valley 

Groundwater Basin: California Department of Water 

Resources Bulletin 118, accessed November 25, 2011, at 

http://www.water.ca.gov/pubs/groundwater/bulletin_118/

basindescriptions/8-9.pdf.

California Department of Water Resources, 2011a, California 

State Water Project today, accessed December 5, 2011, at 

http://www.water.ca.gov/swp/swptoday.cfm.

California Department of Water Resources, 2011b, Locations: 

Silverwood Lake, accessed December 5, 2011, at http://

www.water.ca.gov/recreation/locations/silverwood/.
18 Groundwater-Quality Data in the Bear Valley and Selected Hard Rock Areas Study Unit, 2010

California Environmental Protection Agency, 2011, GAMA—

Groundwater Ambient Monitoring and Assessment 

Program: State Water Resources Control Board website, 

accessed October 14, 2011, at http://www.waterboards.

ca.gov/water_issues/programs/gama/.

California 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, 121 p. accessed 

October 11, 2011, at http://www.waterboards.ca.gov/gama/

docs/final_ab_599_rpt_to_legis_7_31_03.pdf.

California State Water Resources Control Board, 2009, 

Geotracker GAMA: State Water Resources Control Board 

database, accessed October 14, 2011, at https://geotracker.

waterboards.ca.gov/gama/.

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

Maloney, T.J., 1999, New reporting procedures based on 

long-term method-detection levels and some considerations 

for interpretations of water-quality data provided by the 

U.S. Geological Survey National Water Quality Laboratory: 

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

Clark, I.D., and Fritz, P., 1997, Environmental isotopes in 

hydrogeology: Boca Raton, Florida, CRC Press LLC, 328 p.

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

and Abney, S.R., 1998, Methods of analysis by the 

U.S. Geological Survey National Water Quality 

Laboratory—Determination of 86 volatile organic 

compounds in water by gas chromatography/mass 

spectrometry, including detections less than reporting limits: 

U.S. Geological Survey Open-File Report 97-829, 78 p.

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

oxygen isotopic abundances: Pure and Applied Chemistry, 

v. 66, p. 273–276.

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

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

Vocke, R.D., Jr., Révész, 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 Water-Resources Investigations Report 01-4222, 

98 p.

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

Improvements in the gaseous hydrogen-water equilibrium 

technique for hydrogen isotope analysis: Analytical 

Chemistry, v. 63, p. 910–912.

Donahue, D.J., Linick, T.W., and Jull, A.J.T., 1990, Isotoperatio and background corrections for accelerator mass 

spectrometry radiocarbon measurements: Radiocarbon, 

v. 32, book 2, p. 135–142.

Dwyer, G.S., and Vengosh A., 2008, Alternative filament 

loading solution for accurate analysis of boron isotopes 

by negative thermal ionization mass spectrometry: Eos 

Transactions AGU, v. 89, no. 53, Abstract H51C-0824. 

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

content of water from natural sources: Geochimica et 

Cosmochimica Acta, v. 4, p. 213–224.

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.

Farrar, J.W., and Long, H.K., 1997, Report on the 

U.S. Geological Survey’s evaluation program for standard 

reference samples distributed in September 1996—T-143 

(trace constituents), T-145 (trace constituents), M-140 

(major constituents), N-51 (nutrient constituents), P-27 

(low ionic strength constituents), and Hg-23 (mercury): 

U.S. Geological Survey Open-File Report 97-20, 145 p.

Faure, Gunter, and Mensing, T.M., 2005, Isotopes—Principles 

and Applications (3d ed.): Hoboken, New Jersey, John 

Wiley & Sons, Inc., 897 p.

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

U.S. Geological Survey National Water Quality 

Laboratory—Determination of inorganic and organic 

constituents in water and fluvial sediments: U.S. Geological 

Survey Open-File Report 93-125, 217 p.

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

determination of inorganic substances in water and fluvial 

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

Flint, L.E., and Martin, Peter, eds., with contributions by 

Brandt, Justin, Christensen, A.H., Flint, A.L., Flint, L.E., 

Hevesi, J.A., Jachens, Robert, Kulongoski, J.T., 

Martin, Peter, and Sneed, Michelle, 2012, Geohydrology of 

Big Bear Valley, California: Phase 1—Geologic framework, 

recharge, and preliminary assessment of the source and 

age of groundwater: U.S. Geological Survey Scientific 

Investigations Report 2012-5100, 112 p. (Also available at 

http://pubs.usgs.gov/sir/2012/5100/.)

Fram, M.S., and Belitz, Kenneth, 2007, Ground-water quality 

data in the Southern Sierra study unit, 2006—Results from 

the California GAMA Program: U.S. Geological Survey 

Data Series 301, 78 p. (Also available at http://pubs.usgs.

gov/ds/301.)
References Cited 19

Fram, M.S., and Belitz, Kenneth, 2011, Occurrence 

and concentrations of pharmaceutical compounds in 

groundwater used for public drinking-water supply in 

California: Science of the Total Environment, v. 409, no. 18, 

p. 3409–3417. (Also available at http://www.sciencedirect.

com/science/article/pii/S0048969711005778.)

Fram, M.S., Olsen, L.D., and Belitz, Kenneth, 2012, 

Evaluation of volatile organic compound (VOC) 

blank data and application of study reporting levels to 

groundwater data collected for the California GAMA 

Priority Basin Project, May 2004 through September 2010: 

U.S. Geological Survey Scientific Investigations 

Report 2012-5139, 94 p.

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

2008, Determination of human-health pharmaceuticals 

in filtered water by chemically modified styrenedivinylbenzene resin-based solid-phase extraction and highperformance liquid chromatography/mass spectrometry: 

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

sec. B, chap. B5, 56 p.

Gagnon, A.R., and Jones, G.A., 1993, AMS-graphite target 

production methods at the Woods Hole Oceanographic 

Institution during 1986–1991: Radiocarbon, v. 35, book 2, 

p. 301–310.

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

U.S. Geological Survey National Water Quality 

Laboratory—Determination of dissolved arsenic, boron, 

lithium, selenium, strontium, thallium, and vanadium 

using inductively coupled plasma-mass spectrometry: 

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

Garbarino, J.R., 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.

GEOSCIENCE Support Services, Inc., 2006, Geohydrologic 

evaluation of nitrate in ground water in the Lake William 

area, Baldwin Lake watershed, March 17, 2006: Official 

Report, 22 p.

GEOSCIENCE Support Services, Inc., 2008, Lake 

Arrowhead Community Services District results of drilling, 

construction, development and testing LACSD well no. 8, 

June 25, 2008: Official Well Report, 15 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, p. 661.

Hahn, G.J., and Meeker, W.Q., 1991, Statistical intervals—A 

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

392 p. 

Hem, J.D., 1985, Study and interpretation of the chemical 

characteristics of natural water: U.S. Geological Survey 

Water-Supply Paper 2254, 263 p., 3 pls.

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

Lovelace, J.K., and Maupin, M.A., 2009, Estimated use of 

water in the United States in 2005: U.S. Geological Survey 

Circular 1344, 52 p.

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.

Kulongoski, J.T., and Belitz, Kenneth, 2004, Groundwater ambient monitoring and assessment program: 

U.S. Geological Survey Fact Sheet 2004-3088, 2 p.

Lake Arrowhead Community Services District, 2011a, 

History—The history of the Lake Arrowhead water and 

wastewater system, accessed December 14, 2011, at http://

www.lakearrowheadcsd.com/Index.aspx?page=25.

Lake Arrowhead Community Services District, 2011b, Water 

services, accessed December 14, 2011, at http://www.

lakearrowheadcsd.com/Index.aspx?page=4.

Lake Arrowhead Community Services District, 2011c, Water 

services—Groundwater, accessed December 14, 2011, at 

http://www.lakearrowheadcsd.com/Index.aspx?page=46.

Landon, M.K., Belitz, Kenneth, Jurgens, B.C., 

Kulongoski, J.T., and Johnson, T.D., 2010, Status and 

understanding of groundwater quality in the Central–

Eastside San Joaquin Basin, 2006: California GAMA 

Priority Basin Project: U.S. Geological Survey Scientific 

Investigations Report 2009-5266, 97 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 October 18, 2011, at http://pubs.

water.usgs.gov/twri9A2/.
20 Groundwater-Quality Data in the Bear Valley and Selected Hard Rock Areas Study Unit, 2010

Lewis, M.E., 2006, Dissolved oxygen (ver. 2.1): 

U.S. Geological Survey Techniques of Water-Resources 

Investigations, book 9, chap. A6.2, accessed October 18, 

2011, at http://pubs.water.usgs.gov/twri9A6.2/.

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

Determination of low concentrations of acetochlor in 

water by automated solid-phase extraction and gas 

chromatography with mass selective detection: Journal of 

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

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

Methods of analysis by the U.S. Geological Survey 

National Water Quality Laboratory—A method supplement 

for the determination of fipronil and degradates in water by 

gas chromatography/mass spectrometry: U.S. Geological 

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

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

U.S. Geological Survey National Water Quality Laboratory: 

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

accessed November 8, 2011, at http://pubs.usgs.gov/

of/2005/1263/.

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.

McNichol, A.P., Gagnon, A.R., Jones, G.A., and 

Osborne, E.A., 1992, Illumination of a black box—Analysis 

of gas composition during graphite target preparation, 

in Long, A., and Kra, R.S., eds., Proceedings of the 14th 

International 14C Conference: Radiocarbon, v. 34, book 3, 

p. 321–329.

McNichol, A.P., Jones, G.A., Hutton, D.L., and Gagnon, A.R., 

1994, The rapid preparation of seawater ∑CO2 for 

radiocarbon analysis at the National Ocean Sciences AMS 

Facility: Radiocarbon, v. 36, book 2, p. 237–246.

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: 

Lawrence Livermore National Laboratory internal report 

UCRL-AR-148831, 25 p.

Mueller, D.K., and Titus, C.J., 2005, Quality of nutrient data 

from streams and ground water sampled during water 

years 1992–2001: U.S. Geological Survey Scientific 

Investigations Report 2005-5106, 27 p.

Okamoto, H.S., Steeber, W.R., Remoy, R., Hill, P., 

and Perera, S.K., eds., 2002, Determination of 

1,2,3-trichloropropane in drinking water by purge and trap 

gas chromatography/mass spectrometry (February 2002): 

California Department of Health Services, Division of 

Drinking Water and Environmental Management, Sanitation 

and Radiation Laboratories Branch, accessed November 4, 

2011, at http://www.cdph.ca.gov/certlic/drinkingwater/

Documents/Drinkingwaterlabs/TCPbyPT-GCMS.pdf.

Olsen, L.D., Fram, M.S., and Belitz, Kenneth, 2010, 

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 2009-5220, 47 p.

Parr, J.G., and Porterfield, D.R., 1997, Evaluation of 

radiochemical data usability: U.S. Department of Energy, 

Office of Environmental Management, es/er/ms-5, 30 p.

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., accessed 

February 3, 2011, at 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. 4437–4443.

PRISM Climate Group, Oregon State University, 2011, 

United States average annual precipitation, maximum and 

minimum temperature, 1971–2010, accessed November 14, 

2011, at http://prism.oregonstate.edu/.

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 October 17, 2011, at http://pubs.water.

usgs.gov/twri9A6.3/.
References Cited 21

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

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

Code 2900, chap. C17, in Révész, Kinga, and Coplen, T.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.

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

and Schroeder, M.P., 2001, Methods of analysis by 

the U.S. Geological Survey National Water Quality 

Laboratory—Determination of moderate-use pesticides 

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

extraction and gas chromatography/mass spectrometry: 

U.S. Geological Survey Water-Resources Investigations 

Report 01-4098, 70 p.

Saucedo, G.J., Bedford, D.R., Raines, G.L., Miller, R.J., and 

Wentworth, C.M., 2000, GIS data for the geologic map of 

California (version 2.0): Sacramento, California, California 

Department of Conservation, Division of Mines and 

Geology.

Schneider, R.J., Jones, G.A., McNichol, A.P., von Reden, K.F., 

Elder, K.A., Huang, K., and Kessel, E.D., 1994, 

Methods for data screening, flagging, and error analysis 

at the National Ocean Sciences AMS Facility: Nuclear 

Instruments and Methods in Physics Research, book 92, 

p. 172–175. 

Scott, J.C., 1990, Computerized stratified random siteselection approaches for design of a ground-water-quality 

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

Investigations Report 90-4101, 109 p.

Shelton, J.L., Fram, M.S., and Belitz, Kenneth, 2013, 

Groundwater-quality data in the Cascade Range and Modoc 

Plateau study unit, 2010—Results from the California 

GAMA Program: U.S. Geological Survey Data Series 688, 

124 p.

Soddy, F., 1913, Radioactivity: Annual Reports on the 

Progress of Chemistry, v. 10, p. 262–288.

State of California, 2001a, Assembly Bill No. 599, 

Chapter 522, accessed November 16, 2011, at http://www.

swrcb.ca.gov/gama/docs/ab_599_bill_20011005_chaptered.

pdf.

State of California, 2001b, Groundwater Monitoring Act of 

2001: California Water Code, part 2.76, Sections 10780–

10782.3, accessed November 16, 2011, at http://www.

leginfo.ca.gov/cgi-bin/displaycode?section=wat&gr

oup=10001-11000&file=10780-10782.3.

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

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

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

Report 95-352, 120 p.

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

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

determination of dissolved Fe(III) concentration in acid 

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

p. 807–813.

U.S. Department of Agriculture–Natural Resources 

Conservation Service, U.S. Geological Survey, and 

U.S. Environmental Protection Agency, 2013, Watershed 

Boundary Dataset: HUC12-180902080201, HUC12-

180902080202, HUC12-180902080103, HUC12-

180902080102, and HUC12-180902080101, accessed 

January 14, 2013, at http://datagateway.nrcs.usda.gov.

U.S. Department of Commerce, National Oceanic and 

Atmospheric Administration, National Climatic Data 

Center, 2011, Annual climatological summary—Big Bear 

Lake (2005–2010), accessed December 2, 2011, at http://

cdo.ncdc.noaa.gov/ancsum/ACS?coban=04074199999.

U.S. Environmental Protection Agency, 1989, Semivolatile 

organic compounds by isotope dilution GSMS (July 1989): 

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

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, and 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, U.S. Environmental Protection Agency 

Document # 815-R-05-007, 34 p., accessed October 11, 

2011, at http://www.epa.gov/safewater/methods/pdfs/

methods/met331_0.pdf.

U.S. Environmental Protection Agency, 2008a, Ground 

Water Rule—Source assessment guidance manual: 

U.S. Environmental Protection Agency Document # 815-

R-07-023, 34 p., accessed March 6, 2013, at http://

www.epa.gov/ogwdw/disinfection/gwr/pdfs/guide_gwr_

sourcewaterassessments.pdf.
22 Groundwater-Quality Data in the Bear Valley and Selected Hard Rock Areas Study Unit, 2010

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

contaminants, accessed November 11, 2011, at http://www.

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

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

water health advisories—2006 Drinking water standards 

and health advisory tables, accessed November 11, 2011, at 

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

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 

November 17, 2011, at http://water.usgs.gov/owq/

FieldManual/. 

U.S. Geological Survey, 2004, Resources on isotopes: Periodic 

table—Boron: U.S. Geological Survey Isotopic Tracers 

Project, accessed May 2, 2012, at http://wwwrcamnl.

wr.usgs.gov/isoig/period/b_iig.html.

U.S. Geological Survey, 2011a, What is the Priority Basin 

Project?: U.S. Geological Survey California Water Science 

Center website, accessed November 23, 2011, at http://

ca.water.usgs.gov/gama/.

U.S. Geological Survey, 2011b, Publications: U.S. Geological 

Survey California Water Science Center website, accessed 

November 23, 2011, at http://ca.water.usgs.gov/gama/

includes/GAMA_publications.html.

U.S. Geological Survey, 2011c, Inorganic blind sample 

project: U.S. Geological Survey Branch of Quality Systems, 

accessed December 14, 2011, at http://bqs.usgs.gov/ibsp/

qadata.shtml.

Vengosh, A., Chivas, A.R., and McCulloch, M.T., 1989, Direct 

determination of boron and chlorine isotopes in geological 

materials by negative thermal ionization mass spectrometry: 

Chemical Geology, v. 79, p. 333–343.

Vogel, J.S., Nelson, D.E., and Southon, J.R., 1987, 14C 

background levels in an accelerator mass spectrometry 

system: Radiocarbon, v. 29, book 3, p. 323–333.

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

studies on sealed water samples: Deep Sea Research, 

v. 15, p. 721–735.

Western Regional Climate Center, 2011, Western Regional 

Climate Center, summary climate data for Southern 

California, average monthly climate summary, accessed 

December 2, 2011, at http://www.wrcc.dri.edu/summary/

Climsmsca.html.

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 

December 8, 2011, at http://pubs.water.usgs.gov/twri9A3/.

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

Survey Techniques of Water-Resources Investigations, 

book 9, chap. A6.1, accessed December 8, 2011, at http://

pubs.water.usgs.gov/twri9A6.1/.

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 

December 8, 2011, 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 December 8, 2011, 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 December 8, 2011, 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 December 8, 2011, at http://pubs.water.

usgs.gov/twri9A5/.

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

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

Survey National Water Quality Laboratory—Determination 

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

capillary-column gas chromatography/mass spectrometry: 

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

Zaugg, S.D., Smith, S.G., Schroeder, M.P., Barber, L.B., 

and Burkhardt, M.R., 2002, Methods of analysis by 

the U.S. Geological Survey National Water Quality 

Laboratory—Determination of wastewater compounds 

by polystyrene-divinylbenzene solid-phase extraction and 

capillary-column gas chromatography/mass spectrometry: 

U.S. Geological Survey Water-Resources Investigations 

Report 01-4186, 37 p.

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

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

Toccalino, P.L., 2006, Volatile organic compounds in the 

Nation’s ground water and drinking-water supply wells: 

U.S. Geological Survey Circular 1292, 101 p.

Tables
Tables 23

Table 1. Identification, sampling, and construction information for sites sampled for the Bear Valley and Selected Hard Rock Areas 

(BEAR) Groundwater Ambient Monitoring and Assessment (GAMA) study unit, California, April to August 2010.

[Land-surface datum (LSD) is a datum plane that is approximately at land surface at each site. The altitude of the LSD is described in feet above the North 

American Vertical Datum of 1988 (NAVD 88). GAMA site identification number: BEAR-S, Bear Valley study area grid site; BEAR-G, Selected Hard Rock 

Areas study area grid site; BEAR-U, Bear Valley and Selected Hard Rock Areas study unit understanding site. Other abbreviations: ft, feet; na, not available]

GAMA site 

identification 

number

Sampling information

Site type

Construction information

Date sampled 

(m/dd/ yyyy)

Altitude of LSD 

(ft above NAVD 88)

Well depth 

(ft below LSD)

Depth to top 

perforation 

(ft below LSD)

Depth to bottom 

perforation 

(ft below LSD)

BEAR grid sites (27 sites sampled)

Bear Valley study area (14 grid sites sampled)

BEAR-S01 4/26/2010 6,795 Production 370 150 210

BEAR-S02 4/26/2010 6,904 Production 365 154 211

BEAR-S03 4/27/2010 6,757 Production 48 28 48

BEAR-S04 4/27/2010 6,770 Production 290 55 290

BEAR-S05 4/28/2010 6,917 Production 710 210 690

BEAR-S06 4/29/2010 7,223 Production 586 292 576

BEAR-S07 4/29/2010 7,057 Production 330 50 325

BEAR-S08 5/3/2010 7,024 Production 760 230 750

BEAR-S09 5/3/2010 6,794 Production 400 50 400

BEAR-S10 5/4/2010 7,274 Production 268 160 238

BEAR-S11 5/5/2010 6,749 Production 536 200 516

BEAR-S12 5/5/2010 6,719 Production 174 91 166

BEAR-S13 5/6/2010 6,764 Production 236 40 218

BEAR-S14 5/6/2010 7,264 Spring at LSD at LSD at LSD

Selected Hard Rock Areas study area (13 grid sites sampled)

BEAR-G01 4/19/2010 6,403 Production 230 na na

BEAR-G02 4/19/2010 5,403 Spring at LSD at LSD at LSD

BEAR-G03 4/20/2010 4,753 Production 300 na na

BEAR-G04 4/21/2010 5,343 Spring at LSD at LSD at LSD

BEAR-G05 4/21/2010 5,443 Spring at LSD at LSD at LSD

BEAR-G06 4/22/2010 3,843 Spring at LSD at LSD at LSD

BEAR-G07 5/10/2010 5,143 Production 500 120 500

BEAR-G08 5/10/2010 5,205 Production 703 223 703

BEAR-G09 8/19/2010 4,723 Production 500 na na

BEAR-G10 5/12/2010 6,944 Production 220 na na

BEAR-G11 5/13/2010 4,763 Spring at LSD at LSD at LSD

BEAR-G12 5/19/2010 6,113 Spring at LSD at LSD at LSD

BEAR-G13 6/30/2010 5,288 Production 375 na na

BEAR understanding sites (11 sites sampled)

BEAR-U01 1 4/20/2010 6,203 Production 380 200 380

BEAR-U02 4/28/2010 6,751 Production 300 na na

BEAR-U03 1 5/4/2010 7,254 Production 106 66 106

BEAR-U04 1 5/4/2010 7,344 Production 215 na na

BEAR-U05 5/12/2010 7,104 Spring at LSD at LSD at LSD
24 Groundwater-Quality Data in the Bear Valley and Selected Hard Rock Areas Study Unit, 2010

GAMA site 

identification 

number

Sampling information

Site type

Construction information

Date sampled 

(m/dd/ yyyy)

Altitude of LSD 

(ft above NAVD 88)

Well depth 

(ft below LSD)

Depth to top 

perforation 

(ft below LSD)

Depth to bottom 

perforation 

(ft below LSD)

BEAR understanding sites (11 sites sampled)—Continued

BEAR-U06 1 6/14/2010 7,654 Spring at LSD at LSD at LSD

BEAR-U07 1 6/14/2010 7,114 Spring at LSD at LSD at LSD

BEAR-U08 1 6/15/2010 7,144 Spring at LSD at LSD at LSD

BEAR-U09 1 6/15/2010 7,279 Production 168 54 162

BEAR-U10 1 6/16/2010 6,724 Spring at LSD at LSD at LSD

BEAR-U11 1 8/19/2010 4,723 Production 500 na na

1

 Wastewater indicator compounds were collected at this site in addition to the standard set of constituents.

Table 1. Identification, sampling, and construction information for sites sampled for the Bear Valley and Selected Hard Rock Areas 

(BEAR) Groundwater Ambient Monitoring and Assessment (GAMA) study unit, California, April to August 2010.—Continued

[Land-surface datum (LSD) is a datum plane that is approximately at land surface at each site. The altitude of the LSD is described in feet above the North 

American Vertical Datum of 1988 (NAVD 88). GAMA site identification number: BEAR-S, Bear Valley study area grid site; BEAR-G, Selected Hard Rock 

Areas study area grid site; BEAR-U, Bear Valley and Selected Hard Rock Areas study unit understanding site. Other abbreviations: ft, feet; na, not available]
Tables 25

Table 2. Classes of chemical constituents and field water-quality indicators collected for the Bear Valley and Selected Hard Rock 

Areas (BEAR) Groundwater Ambient Monitoring and Assessment (GAMA) study unit, California, April to August 2010.

Constituent classes Constituent 

class table

Results 

table

Field water-quality indicators 

Dissolved oxygen, temperature, pH, and specific conductance — 4

Turbidity — 4

Field alkalinity, bicarbonate, and carbonate 1 — 4

Organic constituents

Volatile organic compounds (VOCs) 3A 5

Pesticides and pesticide degradates 3B 6

Pharmaceutical compounds 3C none 2

Wastewater indicator compounds (WICs) 3 3D 7

Constituents of special interest

Perchlorate 3E 8

1,2,3-Trichloropropane (1,2,3-TCP) 3E none 4

N-Nitrosodimethylamine (NDMA) 3E none 4

Inorganic constituents

Trace elements 3F 9

Nutrients 3G 10

Dissolved organic carbon (DOC) 3G 10

Major and minor ions, silica, and total dissolved solids (TDS) 3H 11

Laboratory alkalinity, bicarbonate, and carbonate 3H 4

Arsenic and iron species 3I 12

Stable isotopes

Stable isotopes of hydrogen and oxygen in water 3J 13

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

Stable isotopes of boron in water 3J none 5

Isotopic ratios of strontium in water 3J 13

Stable isotopes of carbon in dissolved inorganic carbon and carbon-14 abundance 3J 13

Radioactivity and dissolved noble gases

Uranium 3F 14

Tritium 3J 14

Radon-222 3J 14

Dissolved noble gases, tritium, and helium isotope ratios 3J none 6

1

 Constituents were sampled for eight understanding sites.

2

 Constituent(s) not detected at concentration(s) greater than the study reporting level(s) in groundwater samples; therefore, a results table is not presented in 

this report.

3

 Constituent was sampled for nine understanding sites.

4

 Constituent was not detected in groundwater samples.

5

 Results for stable isotopes of boron in water analyzed by U.S. Geological Survey National Research Program, Metals Isotope Research Laboratory, Menlo 

Park, California, were not completed in time for inclusion in this report; results will be presented in a subsequent publication.

6

 Results for dissolved noble gases, tritium, and helium isotope ratios analyzed by Lawrence Livermore National Laboratory (LLNL), Livermore, California, 

were not completed in time for inclusion in this report; results will be presented in a subsequent publication.
26 Groundwater-Quality Data in the Bear Valley and Selected Hard Rock Areas Study Unit, 2010 Table 3A.

Volatile organic compounds (VOCs), primary uses or sources, comparison benchmarks, and reporting information for the U.S. Geological Survey (USGS) National 

Water Quality Laboratory (NWQL) Schedule 2020.

[The five-digit USGS parameter code is used to uniquely identify a specific constituent or property. LRL, benchmark type, and benchmark level as of April 1, 2010. Benchmark type: Maximum contaminant level benchmarks are listed as MCL-US if 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 (USEPA) lifetime health advisory level; MCL-CA, California Department of Public Health (CDPH) maximum contaminant level; MCL-US, USEPA maximum contaminant level; NL-CA, CDPH notification level; RSD5-US, USEPA risk-specific dose at a risk factor of 10–5. Other abbreviations: CASRN, Chemical Abstract Service Registry Number; LRL, laboratory reporting level; 

SRL; study 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 CASRN 1 LRL or SRL (μg/L) Benchmark type Benchmark level (μg/L) Detection

Acetone Solvent 81552 67-64-1 3.4 na na

—

Acrylonitrile Organic synthesis 34215 107-13-1 0.8 RSD5-US 0.6

—

tert-Amyl methyl ether (TAME) Gasoline oxygenate 50005 994-05-8 0.06 na na

—

Benzene Gasoline hydrocarbon 34030 71-43-2 0.026 MCL-CA 1 —Bromobenzene Solvent 81555 108-86-1 0.022 na na

—

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

D

Bromodichloromethane Disinfection byproduct (THM) 32101 75-27-4 0.034 MCL-US 3 80

D

Bromoform (Tribromomethane) Disinfection byproduct (THM) 32104 75-25-2 0.1 MCL-US 3 80

D

Bromomethane (Methyl bromide) Fumigant 34413 74-83-9 0.2 HAL-US 10

—

n-Butylbenzene Gasoline hydrocarbon 77342 104-51-8 0.08 NL-CA 260

—

sec-Butylbenzene Gasoline hydrocarbon 77350 135-98-8 0.034 NL-CA 260

—

tert-Butylbenzene Gasoline hydrocarbon 77353 98-06-6 0.06 NL-CA 260

—

Carbon disulfide Organic synthesis 77041 75-15-0 0.1 NL-CA 160

—

Carbon tetrachloride (Tetrachloromethane) Solvent 32102 56-23-5 0.052 MCL-CA 0.5

D

Chlorobenzene Solvent 34301 108-90-7 0.016 MCL-CA 70

—

Chloroethane Solvent 34311 75-00-3 0.06 na na

—

Chloroform (Trichloromethane) Disinfection byproduct (THM) 32106 67-66-3 0.03 MCL-US 3 80

D

Chloromethane Solvent 34418 74-87-3 0.14 HAL-US 30

—

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

—

2-Chlorotoluene Solvent 77275 95-49-8 0.028 NL-CA 140

—

4-Chlorotoluene Solvent 77277 106-43-4 0.042 NL-CA 140

—

Dibromochloromethane Disinfection byproduct (THM) 32105 124-48-1 0.12 MCL-US 3 80

D

1,2-Dibromo-3-chloropropane (DBCP) Fumigant 82625 96-12-8 0.34 MCL-US 0.2

—

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

—

Dibromomethane Solvent 30217 74-95-3 0.05 na na

—

1,2-Dichlorobenzene Solvent 34536 95-50-1 0.028 MCL-CA 600

—

1,3-Dichlorobenzene Solvent 34566 541-73-1 0.024 HAL-US 600

—

1,4-Dichlorobenzene Fumigant 34571 106-46-7 0.026 MCL-CA 5 —trans-1,4-Dichloro-2-butene Organic synthesis 73547 110-57-6 0.36 na na

—

Dichlorodifluoromethane (CFC-12) Refrigerant 34668 75-71-8 0.1 NL-CA 1,000

—
Tables 27

Constituent 

(synonym or abbreviation)

Primary use 

or source

USGS 

parameter code CASRN 1 LRL or SRL (μg/L) Benchmark type Benchmark level (μg/L) Detection

1,1-Dichloroethane (1,1-DCA) Solvent 34496 75-34-3 0.044 MCL-CA 5 D

1,2-Dichloroethane (1,2-DCA) Solvent 32103 107-06-2 0.08 MCL-CA 0.5 —1,1-Dichloroethene (1,1-DCE) Organic synthesis 34501 75-35-4 0.022 MCL-CA 6 D

cis-1,2-Dichloroethene (cis-1,2-DCE) Solvent 77093 156-59-2 0.022 MCL-CA 6 —

trans-1,2-Dichloroethene (trans-1,2-DCE) Solvent 34546 156-60-5 0.018 MCL-CA 10 —1,2-Dichloropropane Fumigant 34541 78-87-5 0.026 MCL-US 5 —

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

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

1,1-Dichloropropene Organic synthesis 77168 563-58-6 0.03 na na —

cis-1,3-Dichloropropene Fumigant 34704 10061-01-5 0.1 RSD5-US 4 4 —

trans-1,3-Dichloropropene Fumigant 34699 10061-02-6 0.14 RSD5-US 4 4 —Diethyl ether Solvent 81576 60-29-7 0.08 na na —

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

Ethylbenzene Gasoline hydrocarbon 34371 100-41-4 0.1 MCL-CA 300 —

Ethyl tert-butyl ether (ETBE) Gasoline oxygenate 50004 637-92-3 0.032 na na —

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

o-Ethyl toluene (1-Ethyl-2-methyl benzene) Gasoline hydrocarbon 77220 611-14-3 0.032 na na —Hexachlorobutadiene Organic synthesis 39702 87-68-3 0.06 RSD5-US 9 —

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

2-Hexanone (n-Butyl methyl ketone) Solvent 77103 591-78-6 0.46 na na —

Iodomethane (Methyl iodide) Organic synthesis 77424 74-88-4 0.26 na na —

Isopropylbenzene Gasoline hydrocarbon 77223 98-82-8 0.042 NL-CA 770 —

4-Isopropyl-1-methyl benzene Gasoline hydrocarbon 77356 99-87-6 0.06 na na —

Methyl acrylate Organic synthesis 49991 96-33-3 0.56 na na —

Methyl acrylonitrile Organic synthesis 81593 126-98-7 0.26 na na —

Methyl tert-butyl ether (MTBE) Gasoline oxygenate 78032 1634-04-4 0.1 MCL-CA 13 D

Methyl iso-butyl ketone (MIBK) Solvent 78133 108-10-1 0.32 NL-CA 120 —

Methylene chloride (Dichloromethane) Solvent 34423 75-09-2 0.038 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 0.22 na na —

Table 3A. Volatile organic compounds (VOCs), primary uses or sources, comparison benchmarks, and reporting information for the U.S. Geological Survey (USGS) National Water Quality Laboratory (NWQL) Schedule 2020.—Continued[The five-digit USGS parameter code is used to uniquely identify a specific constituent or property. LRL, benchmark type, and benchmark level as of April 1, 2010. Benchmark type: Maximum contaminant level benchmarks are listed as MCL-US if 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 (USEPA) lifetime health advisory level; MCL-CA, California Department of Public Health (CDPH) maximum contaminant level; MCL-US, USEPA maximum contaminant level; NL-CA, CDPH notification level; RSD5-US, USEPA risk-specific dose at a risk factor of 10–5. Other abbreviations: CASRN, Chemical Abstract Service Registry Number; LRL, laboratory reporting level; 

SRL; study reporting level; THM, trihalomethane; D, detected in groundwater samples (table 5); na, not available; μg/L, micrograms per liter; —, not detected]
28 Groundwater-Quality Data in the Bear Valley and Selected Hard Rock Areas Study Unit, 2010 Constituent (synonym or abbreviation) Primary use or source USGS parameter code CASRN 1 LRL or SRL (μg/L) Benchmark type Benchmark level (μg/L) Detection Naphthalene Gasoline hydrocarbon 34696 91-20-3 0.18 NL-CA 17

—

Perchloroethene (PCE, Tetrachloroethene) Solvent 34475 127-18-4 0.026 MCL-US 5 D

n-Propylbenzene Solvent 77224 103-65-1 0.036 NL-CA 260

—

Styrene Gasoline hydrocarbon 77128 100-42-5 0.03 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 0.14 MCL-CA 1 —Tetrahydrofuran Solvent 81607 109-99-9 1.4 na na

—

1,2,3,4-Tetramethylbenzene Gasoline hydrocarbon 49999 488-23-3 0.08 na na

—

1,2,3,5-Tetramethylbenzene Gasoline hydrocarbon 50000 527-53-7 0.08 na na

—

Toluene Gasoline hydrocarbon 34010 108-88-3 2 0.69 MCL-CA 150 D 2

1,2,3-Trichlorobenzene Organic synthesis 77613 87-61-6 0.06 na na

—

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 0.03 MCL-CA 200

D

1,1,2-Trichloroethane (1,1,2-TCA) Solvent 34511 79-00-5 0.046 MCL-CA 5 —

Trichloroethene (TCE) Solvent 39180 79-01-6 0.022 MCL-US 5 DTrichlorofluoromethane (CFC-11) Refrigerant 34488 75-69-4 0.08 MCL-CA 150

D

1,2,3-Trichloropropane (1,2,3-TCP) Solvent, organic synthesis 77443 96-18-4 0.12 HAL-US 40

—

Trichlorotrifluoroethane (CFC-113) Refrigerant 77652 76-13-1 0.034 MCL-CA 1,200

—

1,2,3-Trimethylbenzene Gasoline hydrocarbon 77221 526-73-8 0.06 na na

—

1,2,4-Trimethylbenzene Gasoline hydrocarbon 77222 95-63-6 2 0.56 NL-CA 330 D 2

1,3,5-Trimethylbenzene Organic synthesis 77226 108-67-8 0.032 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 0.06 MCL-CA 0.5

—

m- plus p-Xylene Gasoline hydrocarbon 85795 108-38-3 / 106-42-3 0.4 MCL-CA 5 1,750

—

o-Xylene Gasoline hydrocarbon 77135 95-47-6 0.1 MCL-CA 5 1,750

—

1 This report contains CAS Registry Numbers® (CASRNs), which is a Registered Trademark of the American Chemical Society. CAS recommends the verification of the CASRNs through CAS Client 

ServicesSM.

2 The SRL was defined by Fram and others (2012).3 The MCL-US benchmark for trihalomethanes is the sum of chloroform, bromoform, bromodichloromethane, and dibromochloromethane.4 The RSD5 benchmark for 1,3-dichloropropene is the sum of its isomers (cis and trans).5 The MCL-CA benchmarks for 

m- plus p-xylene and o-xylene is the sum all three xylene compounds.

Table 3A.

Volatile organic compounds (VOCs), primary uses or sources, comparison benchmarks, and reporting information for the U.S. Geological Survey (USGS) National 

Water Quality Laboratory (NWQL) Schedule 2020.—Continued[The five-digit USGS parameter code is used to uniquely identify a specific constituent or property. LRL, benchmark type, and benchmark level as of April 1, 2010. Benchmark type: Maximum contaminant level benchmarks are listed as MCL-US if 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 (USEPA) lifetime health advisory level; MCL-CA, California Department of Public Health (CDPH) maximum contaminant level; MCL-US, USEPA maximum contaminant level; NL-CA, CDPH notification level; RSD5-US, USEPA risk-specific dose at a risk factor of 10–5. Other abbreviations: CASRN, Chemical Abstract Service Registry Number; LRL, laboratory reporting level; 

SRL; study reporting level; THM, trihalomethane; D, detected in groundwater samples (table 5); na, not available; μg/L, micrograms per liter; —, not detected]
Tables 29

Table 3B. Pesticides and pesticide degradates, primary uses or sources, comparison benchmarks, and reporting information for the 

U.S. Geological Survey (USGS) National Water Quality Laboratory (NWQL) Schedule 2033.

[The five-digit USGS parameter code is used to uniquely identify a specific constituent or property. LRL, benchmark type, and benchmark level as of April 1, 

2010. Benchmark type: Maximum contaminant level benchmarks are listed as MCL-US if 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 (USEPA) lifetime health advisory level; MCL-CA, 

California Department of Public Health maximum contaminant level; MCL-US, USEPA maximum contaminant level; RSD5-US, USEPA risk-specific dose at 

a risk factor of 10–5. Other abbreviations: CASRN, Chemical Abstract Service Registry Number; LRL, laboratory reporting level; D, detected in groundwater 

samples (table 6); na, not available; μg/L, micrograms per liter; —, not detected]

Constituent 

(synonym or abbreviation)

Primary use 

or source

USGS 

parameter code CASRN LRL 

(μg/L)

Benchmark 

type

Benchmark level 

(μg/L) Detection

Acetochlor Herbicide 49260 34256-82-1 0.010 na na —

Alachlor Herbicide 46342 15972-60-8 0.008 MCL-US 2 —

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

Azinphos-methyl Insecticide 82686 86-50-0 0.12 na na —

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

Benfluralin Herbicide 82673 1861-40-1 0.014 na na — 1

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

Carbofuran Insecticide 82674 1563-66-2 0.060 MCL-CA 18 —

2-Chloro-2,6-diethylacetanilide Herbicide degradate 61618 6967-29-9 0.010 na na —

4-Chloro-2-methylphenol Herbicide degradate 61633 1570-64-5 0.0032 na na —

Chlorpyrifos Insecticide 38933 2921-88-2 0.010 HAL-US 2 —

Chlorpyrifos oxon Insecticide degradate 61636 5598-15-2 0.05 na na — 1

Cyanazine Herbicide 04041 21725-46-2 0.022 HAL-US 1 —

Cyfluthrin Insecticide 61585 68359-37-5 0.016 na na — 1

λ-Cyhalothrin Insecticide 61595 91465-08-6 0.010 na na — 1

Cypermethrin Insecticide 61586 52315-07-8 0.020 na na — 1

DCPA (Dacthal) Herbicide 82682 1861-32-1 0.0076 HAL-US 70 —

Deethylatrazine (2-Chloro-4-

isopropylamino-6-amino-s-triazine)

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

Desulfinylfipronil Insecticide degradate 62170 na 0.012 na na —

Desulfinylfipronil amide Insecticide degradate 62169 na 0.029 na na —

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

Diazinon oxon Insecticide degradate 61638 962-58-3 0.0060 na na —

3,4-Dichloroaniline Herbicide degradate 61625 95-76-1 0.0042 na na —

3,5-Dichloroaniline Herbicide degradate 61627 626-43-7 0.0030 na na —

Dichlorvos Insecticide 38775 62-73-7 0.02 na na — 1

Dicrotophos Insecticide 38454 141-66-2 0.08 na na — 1

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

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

Dimethoate Insecticide 82662 60-51-5 0.006 na na — 1

Disulfoton Insecticide 82677 298-04-4 0.04 HAL-US 0.7 —

Disulfoton sulfone Insecticide degradate 61640 2497-06-5 0.0136 na na —

α-Endosulfan Insecticide 34362 959-98-8 0.006 na na —

Endosulfan sulfate Insecticide degradate 61590 1031-07-8 0.014 na na —

Ethion Insecticide 82346 563-12-2 0.008 na na —

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

Ethoprophos Herbicide 82672 13194-48-4 0.016 na na —

S-Ethyl-dipropylthiocarbamate (EPTC) Herbicide 82668 759-94-4 0.0020 na na —

2-Ethyl-6-methylaniline Herbicide degradate 61620 24549-06-2 0.0098 na na —

Fenamiphos Insecticide 61591 22224-92-6 0.030 HAL-US 0.7 —
30 Groundwater-Quality Data in the Bear Valley and Selected Hard Rock Areas Study Unit, 2010

Constituent 

(synonym or abbreviation)

Primary use 

or source

USGS 

parameter code CASRN LRL 

(μg/L)

Benchmark 

type

Benchmark level 

(μg/L) Detection

Fenamiphos sulfone Insecticide degradate 61645 31972-44-8 0.053 na na —

Fenamiphos sulfoxide Insecticide degradate 61646 31972-43-7 0.08 na na — 1

Fipronil Insecticide 62166 120068-37-3 0.018 na na —

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

Fipronil sulfone Insecticide degradate 62168 120068-36-2 0.024 na na — 1

Fonofos Insecticide 04095 944-22-9 0.0044 HAL-US 10 —

Hexazinone Herbicide 04025 51235-04-2 0.008 HAL-US 400 — 1

Iprodione Fungicide 61593 36734-19-7 0.014 na na —

Isofenphos Insecticide 61594 25311-71-1 0.006 na na —

Malaoxon Insecticide degradate 61652 1634-78-2 0.08 na na —

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

Metalaxyl Fungicide 61596 57837-19-1 0.007 na na —

Methidathion Insecticide 61598 950-37-8 0.006 na na —

Metolachlor Herbicide 39415 51218-45-2 0.014 HAL-US 700 —

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

Molinate Herbicide 82671 2212-67-1 0.002 MCL-CA 20 —

Myclobutanil Fungicide 61599 88671-89-0 0.010 na na —

1-Naphthol Insecticide degradate 49295 90-15-3 0.036 na na — 1

Oxyfluorfen Herbicide 61600 42874-03-3 0.010 na na — 1

Paraoxon-methyl Insecticide degradate 61664 950-35-6 0.010 na na —

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

Pendimethalin Herbicide 82683 40487-42-1 0.012 na na —

cis-Permethrin Insecticide 82687 54774-45-7 0.014 na na — 1

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

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

Phosmet Insecticide 61601 732-11-6 0.034 na na — 1

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

Prometon Herbicide 04037 1610-18-0 0.012 HAL-US 100 D

Prometryn Herbicide 04036 7287-19-6 0.006 na na —

Pronamide Herbicide 82676 23950-58-5 0.0036 RSD5-US 20 —

Propanil Herbicide 82679 709-98-8 0.010 na na —

Propargite Insecticide 82685 2312-35-8 0.020 na na —

cis-Propiconazole Fungicide 79846 60207-90-1 0.006 na na — 2

trans-Propiconazole Fungicide 79847 60207-90-1 0.02 na na —

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

Tebuconazole Fungicide 62852 107534-96-3 0.020 na na — 1

Tebuthiuron Herbicide 82670 34014-18-1 0.028 HAL-US 500 — 2

Tefluthrin Insecticide 61606 79538-32-2 0.010 na na — 1

Terbufos Insecticide 82675 13071-79-9 0.018 HAL-US 0.4 —

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

Table 3B. Pesticides and pesticide degradates, primary uses or sources, comparison benchmarks, and reporting information for the 

U.S. Geological Survey (USGS) National Water Quality Laboratory (NWQL) Schedule 2033.—Continued

[The five-digit USGS parameter code is used to uniquely identify a specific constituent or property. LRL, benchmark type, and benchmark level as of April 1, 

2010. Benchmark type: Maximum contaminant level benchmarks are listed as MCL-US if 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 (USEPA) lifetime health advisory level; MCL-CA, 

California Department of Public Health maximum contaminant level; MCL-US, USEPA maximum contaminant level; RSD5-US, USEPA risk-specific dose at 

a risk factor of 10–5. Other abbreviations: CASRN, Chemical Abstract Service Registry Number; LRL, laboratory reporting level; D, detected in groundwater 

samples (table 6); na, not available; μg/L, micrograms per liter; —, not detected]
Tables 31

Constituent 

(synonym or abbreviation)

Primary use 

or source

USGS 

parameter code CASRN LRL 

(μg/L)

Benchmark 

type

Benchmark level 

(μg/L) Detection

Terbuthylazine Herbicide 04022 5915-41-3 0.006 na na —

Thiobencarb Herbicide 82681 28249-77-6 0.016 MCL-CA 70 —

Tribufos Defoliant 61610 78-48-8 0.018 na na — 1

Trifluralin Herbicide 82661 1582-09-8 0.018 HAL-US 10 —

1

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

if it was present at very low concentrations.

2

 The median matrix-spike recovery was greater than 130 percent. High recoveries may indicate that reported values could be greater than the true 

concentration in the sample.

Table 3B. Pesticides and pesticide degradates, primary uses or sources, comparison benchmarks, and reporting information for the 

U.S. Geological Survey (USGS) National Water Quality Laboratory (NWQL) Schedule 2033.—Continued

[The five-digit USGS parameter code is used to uniquely identify a specific constituent or property. LRL, benchmark type, and benchmark level as of April 1, 

2010. Benchmark type: Maximum contaminant level benchmarks are listed as MCL-US if 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 (USEPA) lifetime health advisory level; MCL-CA, 

California Department of Public Health maximum contaminant level; MCL-US, USEPA maximum contaminant level; RSD5-US, USEPA risk-specific dose at 

a risk factor of 10–5. Other abbreviations: CASRN, Chemical Abstract Service Registry Number; LRL, laboratory reporting level; D, detected in groundwater 

samples (table 6); na, not available; μg/L, micrograms per liter; —, not detected]
32 Groundwater-Quality Data in the Bear Valley and Selected Hard Rock Areas Study Unit, 2010

Table 3C. Pharmaceutical compounds, primary uses or sources, comparison benchmarks, and reporting information for the 

U.S. Geological Survey (USGS) National Water Quality Laboratory (NWQL) Schedule 2080.

[The five-digit USGS parameter code is used to uniquely identify a specific constituent or property. Abbreviations: CASRN, Chemical Abstract Service 

Registry Number; SRL, study reporting level; na, not available; μg/L, micrograms per liter; —, not detected]

Constituent Primary use 

or source

USGS 

parameter code CASRN SRL 1

(μg/L)

Benchmark 

type

Benchmark 

level Detection

Acetaminophen Analgesic 62000 103-90-2 0.06 na na —

Albuterol Bronchodilator 62020 18559-94-9 0.04 na na —

Caffeine Stimulant 50305 58-08-2 0.10 na na —

Carbamazapine Anticonvulsant, mood stabilizer 62793 298-46-4 0.03 na na —

Codeine Opiod narcotic 62003 76-57-3 0.023 na na —

Cotinine Nicotine metabolite 62005 486-56-6 0.019 na na —

Dehydronifedipine Antianginal metabolite 62004 67035-22-7 0.04 na na —

Diltiazem Antianginal, antihypertensive 62008 42399-41-7 0.04 na na —

1,7-Dimethylxanthine Caffeine metabolite 62030 611-59-6 0.06 na na —

Diphenydramine Antihistime 62796 147-25-0 0.02 na na —

Sulfamethoxazole Antibacterial 62021 723-46-6 0.08 na na —

Thiabendazole Anthelmintic 62801 148-79-8 0.03 na na —

Trimethoprim Antibacterial 62023 738-70-5 0.017 na na —

Warfarin Anticoagulant 62024 81-81-2 0.05 na na —

1

 The SRLs were defined by Fram and Belitz (2011).
Tables 33

Table 3D. Wastewater indicator compounds, primary uses or sources, comparison benchmarks, and reporting information for the U.S. Geological Survey (USGS) National 

Water Quality Laboratory (NWQL) Schedule 1433.

[The five-digit USGS parameter code is used to uniquely identify a specific constituent or property. LRL, benchmark type, and benchmark level as of April 1, 2010. Benchmark type: Maximum contaminant level benchmarks are listed as MCL-US if 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 (USEPA) lifetime health advisory level; MCL-CA, California Department of Public Health (CDPH) maximum contaminant level; MCL-US, USEPA maximum contaminant level; NL-CA, CDPH notification level; RSD5-US, USEPA risk specific dose at a risk factor of 10–5. Other abbreviations: CASRN, Chemical Abstract Service Registry Number; LRL, laboratory reporting level; 

SRL, study reporting level; D, detected in groundwater samples (table 7); na, not available; μg/L, micrograms per liter; —, not detected]

Constituent 

(synonym or abbreviation)

Primary use 

or source

USGS 

parameter code CASRN LRL or SRL (μg/L) Benchmark type Benchmark level (μg/L) Detection

Acetophenone Fragrance, flavor additive 62064 98-86-2 0.4 na na —

Acetyl hexamethyl tetrahydronaphthalene (AHTN) Musk fragrance 62065 21145-77-7 0.028 na na —

Anthracene Wood preservative, combustion product 34221 120-12-7 0.028 na na —

Anthraquinone Textile dye, seed treatment 62066 84-65-1 0.16 na na —

Benzo[a]pyrene Combustion product 34248 50-32-8 0.050 MCL-US 0.2 —

Benzophenone Fixative for perfumes and soaps 62067 119-61-9 0.08 na na —

Bromacil Herbicide 04029 314-40-9 0.36 HAL-US 70 —

Bromoform (tribromomethane) Disinfection byproduct (THM) 34288 75-25-2 0.10 MCL-US 80 — 1

3-tert-Butyl-4-hydroxy anisole (BHA) Antioxidant, general preservative 62059 25013-16-5 8 na na — 1Caffeine Beverages 50305 58-08-2 0.06 na na —

Camphor Flavor, odorant, ointments 62070 76-22-2 0.044 na na —

Carbaryl Insecticide 82680 63-25-2 0.38 RSD5-US 400 —

Carbazole Insecticide 62071 86-74-8 0.030 na na —

Chlorpyrifos Insecticide 38933 2921-88-2 0.16 HAL-US 2 —

Cholesterol Fecal indicator, plant sterol 62072 57-88-5 2 na na — 1

3-β-Coprostanol Carnivore fecal indicator 62057 360-68-9 1.8 na na —

Cotinine Primary nicotine metabolite 62005 486-56-6 0.6 na na —

p-Cresol Wood preservative 62084 106-44-5 0.08 na na —

4-Cumylphenol Nonionic detergent metabolite 62060 599-64-4 0.06 na na —

Diazinon Insecticide 39572 333-41-5 0.16 HAL-US 1 —

1,4-Dichlorobenzene Moth repellant, fumigant, deodorant 34572 106-46-7 0.040 MCL-CA 5 —

N,N-Diethyl-meta-toluamide (DEET) Insecticide 62082 134-62-3 0.06 na na —

2,6-Dimethylnaphthalene Diesel fuel, kerosene 62055 581-42-0 0.06 na na — 1

4-Nonylphenol diethoxylates Nonionic detergent metabolite 62083 na 5.0 na na — 14-Octylphenol diethoxylates Nonionic detergent metabolite 61705 na 1.0 na na — 14-Octylphenol monoethoxylates Nonionic detergent metabolite 61706 na 1.0 na na — 1Fluoranthene Component of coal tar and asphalt 34377 206-44-0 0.024 na na —

Hexahydrohexamethylcyclopentabenzopyran 

(HHCB) 

Musk fragrance 62075 1222-05-5 0.052 na na —
34 Groundwater-Quality Data in the Bear Valley and Selected Hard Rock Areas Study Unit, 2010 Constituent (synonym or abbreviation) Primary use or source USGS parameter code CASRN LRL or SRL (μg/L) Benchmark type Benchmark level (μg/L) Detection Indole Pesticide ingredient 62076 120-72-9 0.08 na na — 1 Isoborneol Fragrance in perfume 62077 124-76-5 0.18 na na

—

Isophorone Solvent 34409 78-59-1 0.08 HAL-US 100

—

Isopropylbenzene Fuels, paint thinner 62078 98-82-8 0.30 NL-CA 770 — 1

Isoquinoline Flavors, fragrances 62079 119-65-3 0.046 na na — 1d-Limonene Fungicide 62073 5989-27-5 0.08 na na — 1Menthol Cigarettes, cough drops, liniment 62080 89-78-1 0.32 na na

—

Metalaxyl Herbicide, fungicide 50359 57837-19-1 0.12 na na

—

3-Methyl-1(H)-indole (Skatole) Fragrance, stench in feces 62058 83-34-1 0.036 na na

—

5-Methyl-1H-benzotriazole Antioxidant in antifreeze and deicers 62063 136-85-6 1.2 na na — 1

1-Methylnaphthalene Gasoline, diesel fuel, crude oil 62054 90-12-0 0.022 na na

—

2-Methylnaphthalene Gasoline, diesel fuel, crude oil 62056 91-57-6 0.036 na na

—

Methyl salicylate Liniment, UV-absorbing lotion 62081 119-36-8 0.044 na na

—

Metolachlor Herbicide 39415 51218-45-2 0.08 HAL-US 700

—

Naphthalene Fumigant, moth repellent, gasoline 34443 91-20-3 0.040 NL-CA 17

—

para-Nonylphenol (total) Nonionic detergent metabolite 62085 84852-15-3 2 na na

—

4-n-Octylphenol Nonionic detergent metabolite 62061 1806-26-4 0.16 na na

—

4-tert-Octylphenol Nonionic detergent metabolite 62062 140-66-9 0.14 na na

—

Perchloroethene (PCE, Tetrachloroethene) Solvent 34476 127-18-4 0.12 MCL-US 5 — 1

Phenanthrene Manufactured explosives 34462 85-01-8 0.032 na na

—

Phenol Disinfectant, organic synthesis 34466 108-95-2 0.16 HAL-US 2,000

D

Prometon Herbicide 04037 1610-18-0 0.12 HAL-US 100

—

Pyrene Component of coal tar and asphalt 34470 129-00-0 0.042 na na

—

β-Sitosterol Plant sterol 62068 83-46-5 4 na na — 1

β-Stigmastanol Plant sterol 62086 19466-47-8 2.6 na na — 1Tributyl phosphate Antifoaming agent, flame retardant 62089 126-73-8 0.16 na na

—

Triclosan Disinfectant, antimicrobial 62090 3380-34-5 0.20 na na

—

Triethyl citrate (ethyl citrate) Cosmetics, pharmaceuticals 62091 77-93-0 0.38 na na

—

Triphenyl phosphate Plasticizer 62092 115-86-6 0.12 na na

—

Table 3D.

Wastewater indicator compounds, primary uses or sources, comparison benchmarks, and reporting information for the U.S. Geological Survey (USGS) National 

Water Quality Laboratory (NWQL) Schedule 1433.—Continued[The five-digit USGS parameter code is used to uniquely identify a specific constituent or property. LRL, benchmark type, and benchmark level as of April 1, 2010. Benchmark type: Maximum contaminant level benchmarks are listed as MCL-US if 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 (USEPA) lifetime health advisory level; MCL-CA, California Department of Public Health (CDPH) maximum contaminant level; MCL-US, USEPA maximum contaminant level; NL-CA, CDPH notification level; RSD5-US, USEPA risk specific dose at a risk factor of 10–5. Other abbreviations: CASRN, Chemical Abstract Service Registry Number; LRL, laboratory reporting level; 

SRL, study reporting level; D, detected in groundwater samples (table 7); na, not available; μg/L, micrograms per liter; —, not detected]
Tables 35

Constituent 

(synonym or abbreviation)

Primary use 

or source

USGS 

parameter code CASRN LRL or SRL (μg/L) Benchmark type Benchmark level (μg/L) Detection

Tris(2-butoxyethyl)phosphate Flame retardant 62093 78-51-3 2 0.30 na na D

Tris(2-chloroethyl)phosphate Plasticizer, flame retardant 62087 115-96-8 0.10 na na —

Tris(dichlorisopropyl)phosphate Flame retardant 62088 13674-87-8 0.16 na na —

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.2 The SRL was defined based on the highest concentration detected in the BEAR blank samples.

Table 3D. Wastewater indicator compounds, primary uses or sources, comparison benchmarks, and reporting information for the U.S. Geological Survey (USGS) National Water Quality Laboratory (NWQL) Schedule 1433.—Continued[The five-digit USGS parameter code is used to uniquely identify a specific constituent or property. LRL, benchmark type, and benchmark level as of April 1, 2010. Benchmark type: Maximum contaminant level benchmarks are listed as MCL-US if 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 (USEPA) lifetime health advisory level; MCL-CA, California Department of Public Health (CDPH) maximum contaminant level; MCL-US, USEPA maximum contaminant level; NL-CA, CDPH notification level; RSD5-US, USEPA risk specific dose at a risk factor of 10–5. Other abbreviations: CASRN, Chemical Abstract Service Registry Number; LRL, laboratory reporting level; 

SRL, study reporting level; D, detected in groundwater samples (table 7); na, not available; μg/L, micrograms per liter; —, not detected]

Table 3E. Constituents of special interest, primary uses or sources, comparison benchmarks, and reporting information for Weck Laboratories, Inc., City of Industry, California, analyses.[The five-digit USGS parameter code is used to uniquely identify a specific constituent or property. MRL, benchmark type, and benchmark level as of April 1, 2010. Benchmark type: Maximum contaminant level benchmarks are listed as MCL-US if the MCL-US and MCL-CA are identical, and as MCL-CA when the MCL-CA is lower than the MCL-US or no MCL-US exists. HAL-US, U.S. Environmental Protection Agency lifetime health advisory; MCL-CA, California Department of Public Health (CDPH) maximum contaminant level; NL-CA, CDPH notification level. Other abbreviations: USGS, U.S. Geological Survey; CASRN, Chemical Abstract Service Registry Number; MRL, minimum reporting level; D, detected in groundwater samples (table 8); μg/L, micrograms per liter; —, not detected]

Constituent 

(synonym or abbreviation)

Primary use 

or source

USGS 

parameter code CASRN MRL (μg/L) Benchmark type Benchmark level (μg/L) Detection

Perchlorate Rocket fuel, fireworks, flares 63790 14797-73-0 0.10 MCL-CA 6 D1,2,3-Trichloropropane (1,2,3-TCP) Fumigant, solvent 77443 96-18-4 0.005 HAL-US 40 —N-Nitrosodimethylamine (NDMA) Disinfection byproduct 34438 62-75-9 0.002 NL-CA 0.010 —
36 Groundwater-Quality Data in the Bear Valley and Selected Hard Rock Areas Study Unit, 2010

Table 3F. Trace elements, comparison benchmarks, and reporting information for the U.S. Geological Survey (USGS) National Water 

Quality Laboratory (NWQL) Schedule 1948.

[The five-digit USGS parameter code is used to uniquely identify a specific constituent or property. LRL, benchmark type, and benchmark level as of April 1, 

2010. Benchmark type: Maximum contaminant level benchmarks are listed as MCL-US if 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 (USEPA) action level; HAL-US, USEPA lifetime 

health advisory level; MCL-CA, California Department of Public Health (CDPH) maximum contaminant level; MCL-US, USEPA maximum contaminant 

level; NL-CA, CDPH notification level; SMCL-CA, CDPH secondary maximum contaminant level. Other abbreviations: CASRN, Chemical Abstract 

Service Registry Number; LRL, laboratory reporting level; SRL, study reporting level; D, detected in groundwater samples (table 9); na, not available; μg/L, 

micrograms per liter; —, not detected]

Constituent USGS 

parameter code CASRN LRL or SRL 

(μg/L)

Benchmark 

type

Benchmark level 

(μg/L) Detection

Aluminum 01106 7429-90-5 3.4 MCL-CA 1,000 D

Antimony 01095 7440-36-0 0.054 MCL-US 6 D

Arsenic 01000 7440-38-2 0.04 MCL-US 10 D

Barium 01005 7440-39-3 0.14 MCL-CA 1,000 D

Beryllium 01010 7440-41-7 0.012 MCL-US 4 D

Boron 01020 7440-42-8 2.8 NL-CA 1,000 D

Cadmium 01025 7440-43-9 0.02 MCL-US 5 D

Chromium 01030 7440-47-3 1

 0.42 MCL-CA 50 D

Cobalt 01035 7440-48-4 2

 0.42 na na —

Copper 01040 7440-50-8 1

 1.7 AL-US 1,300 D

Iron 01046 7439-89-6 1

 6 SMCL-CA 300 D

Lead 01049 7439-92-1 1

 0.65 AL-US 15 D

Lithium 01130 7439-93-2 0.44 na na D

Manganese 01056 7439-96-5 0.79 SMCL-CA 50 D

Molybdenum 01060 7439-98-7 0.014 HAL-US 40 D

Nickel 01065 7440-02-0 1

 0.36 MCL-CA 100 D

Selenium 01145 7782-49-2 0.040 MCL-US 50 D

Silver 01075 7440-22-4 0.010 SMCL-CA 100 D

Strontium 01080 7440-24-6 0.40 HAL-US 4,000 D

Thallium 01057 7440-28-0 0.020 MCL-US 2 D

Tungsten 01155 7440-33-7 1

 0.11 na na D

Vanadium 01085 7440-62-2 0.16 NL-CA 50 D

Zinc 01090 7440-66-6 1

 4.8 SMCL-CA 3 5,000 D

1

 The SRL was defined by Olsen and others (2010).

2

 The SRL was defined based on the highest concentration detected in the Bear Valley and Selected Hard Rock Areas (BEAR) blank samples.

3

 Zinc also has a HAL-US benchmark of 2,000 μg/L.
Tables 37

Table 3G. Nutrients and dissolved organic carbon (DOC), comparison benchmarks, and reporting information for the U.S. Geological 

Survey (USGS) National Water Quality Laboratory (NWQL) Schedule 2755 and Laboratory Code 2613.

[The five-digit USGS parameter code is used to uniquely identify a specific constituent or property. LRL, benchmark type, and benchmark level as of April 1, 

2010. Benchmark type: Maximum contaminant level benchmarks are listed as MCL-US if 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 (USEPA) lifetime health advisory level; 

MCL-US, USEPA maximum contaminant level. Other abbreviations: CASRN, Chemical Abstract Service Registry Number; LRL, laboratory reporting level; 

SRL, study reporting level; D, detected in groundwater samples (table 10); na, not available; mg/L, milligrams per liter; BEAR, Bear Valley and Selected Hard 

Rock Areas study unit]

Constituent USGS 

parameter code CASRN LRL or SRL 

(mg/L)

Benchmark 

type 

Benchmark level 

(mg/L) Detection

Ammonia (as nitrogen) 00608 7664-41-7 0.02 HAL-US 1

 24.7 D

Nitrate plus nitrite (as nitrogen) 00631 na 0.04 MCL-US 10 D

Nitrite (as nitrogen) 00613 14797-65-0 0.001 MCL-US 1 D

Total nitrogen (ammonia + nitrite + nitrate + organic nitrogen) 62854 17778-88-0 0.10 na na D

Phosphate, orthophosphate (as phosphorus) 00671 14265-44-2 0.008 na na D

Dissolved organic carbon (DOC) 00681 na 2

 0.8 na na D

1

 The HAL-US is 30 mg/L “as ammonia.” To facilitate comparison to the analytical results, we have converted and reported this HAL-US as 24.7 mg/L “as 

nitrogen.”

2

 The SRL was defined based on the highest concentration detected in the BEAR blank samples.
38 Groundwater-Quality Data in the Bear Valley and Selected Hard Rock Areas Study Unit, 2010

Table 3H. Major and minor ions, silica, total dissolved solids (TDS), and alkalinity, comparison benchmarks, and reporting information 

for the U.S. Geological Survey (USGS) National Water Quality Laboratory (NWQL) Schedule 1948.

[The five-digit USGS parameter code is used to uniquely identify a specific constituent or property. LRL, benchmark type, and benchmark level as of April 1, 

2010. Benchmark type: Maximum contaminant level benchmarks are listed as MCL-US if 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 (CDPH) maximum contaminant level; 

SMCL-CA, CDPH secondary maximum contaminant level. Other abbreviations: CASRN, Chemical Abstract Service Registry Number; LRL, laboratory 

reporting level; SRL, Study Reporting Level; D, detected in groundwater samples (table 11); na, not available; mg/L, milligrams per liter; SiO2, Silica; 

CaCO3, calcium carbonate; BEAR, Bear Valley and Selected Hard Rock Areas study unit]

Constituent 

(synonym or abbreviation)

USGS 

parameter code CASRN LRL or SRL 

(mg/L)

Benchmark 

type

Benchmark level 

(mg/L) Detection

Bromide 71870 24959-67-9 0.02 na na D

Calcium 00915 7440-70-2 0.044 na na D

Chloride 00940 16887-00-6 0.12 SMCL-CA 1

 250 (500) D

Fluoride 00950 16984-48-8 2

 0.055 MCL-CA 2 D

Iodide 71865 7553-56-2 0.002 na na D

Magnesium 00925 7439-95-4 0.016 na na D

Potassium 00935 7440-09-7 0.064 na na D

Sodium 00930 7440-23-5 0.10 na na D

Sulfate 00945 14808-79-8 0.18 SMCL-CA 1

 250 (500) D

Silica (as SiO2

) 00955 7631-86-9 0.058 na na D

Residue on evaporation (total dissolved solids, TDS) 70300 na 10 SMCL-CA 1

 500 (1,000) D

Laboratory alkalinity (as CaCO3

) 3 29801 na 1 na na D

1

 The SMCL-CAs for chloride, sulfate, and TDS have recommended and upper benchmark values. The upper benchmark value is shown in parentheses.

2

 The SRL was defined based on the highest concentration detected in the BEAR blank samples.

3

 Laboratory alkalinity results are presented in table 4.

Table 3I. Arsenic and iron species, comparison benchmarks, and reporting information for the U.S. Geological Survey (USGS) National 

Research Laboratory (NRP) Trace Metal Laboratory (TML), Boulder, Colorado, analyses.

[The five-digit USGS parameter code is used to uniquely identify a specific constituent or property. MDL, benchmark type, and benchmark level as of April 1, 

2010. Benchmark type: Maximum contaminant level benchmarks are listed as MCL-US if 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 (USEPA) maximum contaminant level; SMCL-US, USEPA secondary maximum contaminant level. Other 

abbreviations: MDL, method detection limit; CASRN, Chemical Abstract Service Registry Number; na, not available; μg/L, micrograms per liter; D, detected 

in groundwater samples (table 12)]

Constituent USGS 

parameter code CASRN MDL 

(μg/L)

Benchmark 

type

Benchmark level 

(μg/L) Detection

Arsenic (total) 99033 7440-38-2 0.5 MCL-US 10 D

Arsenic-III 99034 22569-72-8 1 na na D

Iron (total) 01046 7439-89-6 2 SMCL-CA 300 D

Iron-II 01047 7439-89-6 2 na na D
Tables 39

Table 3J. Dissolved noble gases, isotopic tracers, and uranium and other radioactive constituents, comparison benchmarks, and 

reporting information for laboratory analyses.

[The five-digit USGS parameter code is used to uniquely identify a specific constituent or property. Laboratory entity codes in the 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. Benchmark type and benchmark value as of April 1, 2010. Benchmark type: Maximum contaminant level benchmarks are listed as MCL-US if 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. Elements: H, hydrogen; 

O, oxygen; N, nitrogen; B, boron; Sr, strontium; C, carbon. Reporting units: μg/L, micrograms per liter; pmc, percent modern carbon; pCi/L, picocuries per 

liter; cm3 STP/g, cubic centimeters of gas at standard temperature and pressure per gram of water. Other abbreviations: USGS, U.S. Geological Survey; 

CASRN, Chemical Abstract Service Registry Number; %, percent; na, not available; D, detected in groundwater samples (tables 13 and 14); ssLC, samplespecific critical level; NRP, USGS National Research Program]

Constituent

USGS 

parameter 

code

CASRN Method 

uncertainty

Reporting 

units

Benchmark 

type

Benchmark 

level Detection

Dissolved noble gases 1

Argon 85563 7440-37-1 2% cm3 STP/g na na na

Helium-4 85561 7440-59-7 2% cm3

 STP/g na na na

Krypton 85565 7439-90-9 2% cm3

 STP/g na na na

Neon 61046 7440-01-09 2% cm3

 STP/g na na na

Xenon 85567 7440-63-3 2% cm3

 STP/g na na na

Isotopic tracers

Helium-3 / Helium-4 1 61040 na / 7440-59-7 0.8% atom ratio na na na

d2

H in water 2 82082 na 2 per mil na na D

d18O in water 2 82085 na 0.2 per mil na na D

d15N in dissolved nitrate 2 82690 na 0.5 per mil na na D

d18O in dissolved nitrate 2 63041 na 1.0 per mil na na D

d11B in water 3 62648 na na per mil na na na 4

Strontium isotope ratio in water (87Sr/86Sr) 3 75978 na 0.0 atom ratio na na D

d13C in dissolved inorganic carbon 5 82081 na 0.1 per mil na na D

Uranium and other radioactive constituents

Uranium 6 22703 7440-61-1 0.008 μg/L MCL-US 30 D

C-14 5 49933 14762-75-5 0.0 pmc na na D

Radon-222 6 82303 14859-67-7 ssLC pCi/L MCL-US (Proposed) 4,000 D

Tritium 1 07000 10028-17-8 1 pCi/L MCL-CA 20,000 na

Tritium 7 07000 10028-17-8 0.32–0.41 pCi/L MCL-CA 20,000 D

1

 Lawrence Livermore National Laboratory, Livermore, California (CA-LLNL). Results for dissolved noble gases, tritium, and helium isotope ratios were not 

completed in time for inclusion in this report; results will be presented in a subsequent publication.

2

 USGS Stable Isotope Laboratory, Reston, Virginia (USGSSIVA).

3

 USGS NRP Metals Isotope Research Laboratory, Menlo Park, California (USGSMICA).

4

 Results for stable isotopes of boron in water analyzed by USGS NRP Metals Isotope Research Laboratory were not completed in time for inclusion in this 

report; results will be presented in a subsequent publication.

5

 Woods Hole Oceanographic Institution, National Ocean Sciences Accelerator Mass Spectrometry Facility [NOMAS], Woods Hole, Massachusetts 

(MA-WHAMS).

6

 USGS NWQL, Denver, Colorado.

7

 USGS Stable Isotope and Tritium Laboratory [SITL], Menlo Park, California (USGSH3CA).
40 Groundwater-Quality Data in the Bear Valley and Selected Hard Rock Areas Study Unit, 2010 Table 4.

Water-quality indicators in samples collected for the Bear Valley and Selected Hard Rock Areas (BEAR) Groundwater Ambient Monitoring and Assessment (GAMA)

study unit, California, April to August 2010.

[The five-digit USGS parameter code below the constituent name is used to uniquely identify a specific constituent or property. GAMA site identification number: BEAR-S, Bear Valley study area grid site; BEAR-G, Selected Hard Rock Areas study area grid site; BEAR-U, Bear Valley and Selected Hard Rock Areas study unit understanding site. Benchmark type, benchmark level, and RL as of April 1, 2010. Benchmark 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, degrees Celsius; mg/L, milligrams per liter; nc, not collected; na, not available; NTRU, nephelometric turbidity unit; RL, reporting limit or range; μS/cm, microsiemens per centimeter; <, less than; >, greater than; CaCO3, calcium carbonate; *, concentration is greater than the benchmark level; —, not detected; E, estimated or having a higher degree of uncertainty]

GAMA site 

identification 

number

Turbidity, 

field 

(NTRU) 

(63676)

Dissolved 

oxygen, 

field 

(mg/L) 

(00300) 

Water 

temperature, 

field 

(°C) 

(00010)

pH, field 

(standard 

units) 

(00400)

pH, laboratory 

(standard 

units) 

(00403)

Specific 

conductance, 

field 

(μS/cm at 25°C) 

(00095)

Specific 

conductance, 

laboratory 

(μS/cm at 25°C) 

(90095)

Alkalinity, 

field 

(mg/L as 

CaCO3) 

(29802)

Alkalinity, 

laboratory 

(mg/L as 

CaCO3) 

(29801)

Bicarbonate, 

field 

(mg/L) 

(63786)

Bicarbonate, 

laboratory 2

(mg/L)

Carbonate, 

field 

(mg/L) 

(63788)

Carbonate, 

laboratory 2

(mg/L)

Benchmark 

type

na na na SMCL-US SMCL-US SMCL-CA SMCL-CA na na na na na na

Benchmark 

level

na na na <6.5 or >8.5 <6.5 or >8.5 1 900 (1,600) 1 900 (1,600) na na na na na na

[RL] [0.1] [0.2] [0.0–38.5] [0–14] [0–14] [5] [5] [1] [1] [1] [1] [1] [1]

BEAR grid sites (27 sites sampled)Bear Valley study area (14 grid sites sampled)BEAR-S01 0.1 1.7 12.5 7.5 7.5 559 565 nc 235 nc 286 nc 0.4

BEAR-S02 0.1 6.8 11.0 7.6 7.6 277 278 nc 136 nc 165 nc 0.3

BEAR-S03 0.1 4.4 11.0 6.5 6.8 332 328 nc 130 nc 159 nc

—

BEAR-S04 0.6 0.2 13.5 *9.1 *9.0 367 373 nc 176 nc 196 nc 9.0

BEAR-S05 0.2 1.8 14.0 8.2 8.2 250 256 nc 122 nc 147 nc 1.1

BEAR-S06 0.2 7.0 12.0 nc 7.5 437 452 nc 251 nc 305 nc 0.4

BEAR-S07 0.2 5.1 9.0 nc 7.4 666 688 nc 328 nc 399 nc 0.5

BEAR-S08 0.1 6.6 13.0 7.5 7.7 380 387 nc 204 nc 248 nc 0.6

BEAR-S09 0.1 6.8 12.0 6.8 7.5 333 341 nc 161 nc 196 nc 0.3

BEAR-S10 0.1 6.1 13.0 6.8 6.8 365 379 nc 126 nc 154 nc

—

BEAR-S11 0.2 4.1 13.0 7.5 7.5 438 446 nc 214 nc 260 nc 0.4

BEAR-S12 0.9 3.4 16.0 7.4 7.1 387 398 nc 175 nc 213 nc 0.1

BEAR-S13 0.3 6.2 13.0 7.2 7.4 397 400 nc 196 nc 239 nc 0.3

BEAR-S14 0.7 7.8 11.0 7.5 7.7 443 449 nc 223 nc 271 nc 0.6
Tables 41

GAMA site 

identification 

number

Turbidity, 

field 

(NTRU) 

(63676)

Dissolved 

oxygen, 

field 

(mg/L) 

(00300) 

Water 

temperature, 

field 

(°C) 

(00010)

pH, field 

(standard 

units) 

(00400)

pH, laboratory 

(standard 

units) 

(00403)

Specific 

conductance, 

field 

(μS/cm at 25°C) 

(00095)

Specific 

conductance, 

laboratory 

(μS/cm at 25°C) 

(90095)

Alkalinity, 

field 

(mg/L as 

CaCO3) 

(29802)

Alkalinity, 

laboratory 

(mg/L as 

CaCO3) 

(29801)

Bicarbonate, 

field 

(mg/L) 

(63786)

Bicarbonate, 

laboratory 2

(mg/L)

Carbonate, 

field 

(mg/L) 

(63788)

Carbonate, 

laboratory 2

(mg/L)

Benchmark 

type

na na na SMCL-US SMCL-US SMCL-CA SMCL-CA na na na na na na

Benchmark 

level

na na na <6.5 or >8.5 <6.5 or >8.5 1 900 (1,600) 1 900 (1,600) na na na na na na

[RL] [0.1] [0.2] [0.0–38.5] [0–14] [0–14] [5] [5] [1] [1] [1] [1] [1] [1]

BEAR grid sites (27 sites sampled)—ContinuedSelected Hard Rock Areas study area (13 grid sites sampled)BEAR-G01 0.8 3.3 12.0 7.2 7.1 230 234 nc 115 nc 140 nc 0.1

BEAR-G02 nc 6.8 10.0 *6.1 *6.3 194 197 nc 44.0 nc 53.7 nc —

BEAR-G03 nc 3.6 9.5 *6.1 6.9 124 122 nc 52.0 nc 63.4 nc —

BEAR-G04 nc 4.1 8.0 6.5 7.2 195 194 nc 97.0 nc 118 nc 0.1

BEAR-G05 nc 1.2 7.0 7.2 7.6 199 202 nc 99.0 nc 120 nc 0.2

BEAR-G06 nc 2.9 12.5 7.1 7.3 392 398 nc 194 nc 236 nc 0.2

BEAR-G07 nc 2.5 11.5 7.3 7.5 325 329 nc 158 nc 192 nc 0.3

BEAR-G08 1.4 2.6 12.5 7.7 8.0 278 286 nc 145 nc 175 nc 0.8

BEAR-G09 3.0 0.7 14.5 7.0 7.7 332 340 nc 167 nc 203 nc 0.5

BEAR-G10 nc 3.7 10.5 7.3 7.4 360 371 nc 185 nc 225 nc 0.3

BEAR-G11 nc 7.8 14.0 *6.4 7.2 207 211 nc 73.0 nc 88.9 nc 0.1

BEAR-G12 6.0 5.2 9.5 *6.3 6.8 191 190 nc 98.0 nc 119 nc —

BEAR-G13 nc 5.6 16.5 6.8 6.8 368 368 nc 175 nc 213 nc 0.1

Table 4. Water-quality indicators in samples collected for the Bear Valley and Selected Hard Rock Areas (BEAR) Groundwater Ambient Monitoring and Assessment (GAMA) study unit, California, April to August 2010.—Continued[The five-digit USGS parameter code below the constituent name is used to uniquely identify a specific constituent or property. GAMA site identification number: BEAR-S, Bear Valley study area grid site; BEAR-G, Selected Hard Rock Areas study area grid site; BEAR-U, Bear Valley and Selected Hard Rock Areas study unit understanding site. Benchmark type, benchmark level, and RL as of April 1, 2010. Benchmark 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, degrees Celsius; mg/L, milligrams per liter; nc, not collected; na, not available; NTRU, nephelometric turbidity unit; RL, reporting limit or range; μS/cm, microsiemens per centimeter; <, less than; >, greater than; CaCO3, calcium carbonate; *, concentration is greater than the benchmark level; —, not detected; E, estimated or having a higher degree of uncertainty]
42 Groundwater-Quality Data in the Bear Valley and Selected Hard Rock Areas Study Unit, 2010 GAMA site identification number Turbidity, field (NTRU) (63676) Dissolved oxygen, field (mg/L) (00300) Water temperature, field (°C) (00010) pH, field (standard units) (00400) pH, laboratory (standard units) (00403) Specific conductance, field (μS/cm at 25°C) (00095) Specific conductance, laboratory (μS/cm at 25°C) (90095) Alkalinity, field (mg/L as CaCO3) (29802) Alkalinity, laboratory (mg/L as CaCO3) (29801) Bicarbonate, field (mg/L) (63786) Bicarbonate, laboratory 2 (mg/L) Carbonate, field (mg/L) (63788) Carbonate, laboratory 2 (mg/L) Benchmark type na na na SMCL-US SMCL-US SMCL-CA SMCL-CA na na na na na na Benchmark level na na na <6.5 or >8.5 <6.5 or >8.5 1 900 (1,600) 1 900 (1,600) na na na na na na [RL] [0.1] [0.2] [0.0–38.5] [0–14] [0–14] [5] [5] [1] [1] [1] [1] [1] [1] BEAR understanding sites (11 sites sampled) BEAR-U01 nc 4.0 9.5 7.1 7.3 344 342 152 152 185 185 0.2 0.2 BEAR-U02 0.7 5.5 13.0 7.5 7.6 563 581 nc 253 nc 307 nc 0.6 BEAR-U03 0.1 6.2 14.0 6.8 7.4 405 410 128 131 156 159

— 0.2

BEAR-U04 1.9 4.4 13.0 7.3 7.9 358 331 119 123 145 149 0.1 0.5

BEAR-U05 nc 2.2 7.0 *6.2 6.5 82.0 88.0 nc 39.0 nc 47.6 nc

—

BEAR-U06 nc 4.8 8.0 *6.0 7.0 171 184 60.5 65.0 73.7 79.2

—

—

BEAR-U07 nc 5.0 9.0 6.5 6.7 346 357 126 139 154 170

—

—

BEAR-U08 nc 5.1 13.0 7.7 7.9 360 369 116 126 141 153

— 0.6

BEAR-U09 nc 2.2 11.5 7.1 7.5 608 628 289 304 352 370

— 0.5

BEAR-U10 0.8 6.3 7.0 *5.6 E7.2 89.0 E97.0 nc 45.0 nc 54.8 nc

—

BEAR-U11 1.0 1.2 16.5 6.8 7.5 301 303 143 154 174 187 0.3 0.3

1 The SMCL-CA for specific conductance has recommended and upper benchmark values. The upper value is shown in parentheses.2 Bicarbonate and carbonate concentrations were calculated from the laboratory alkalinity and pH values using the advanced speciation method (http://or.water.usgs.gov/alk/methods.html) with pK1 = 6.35, 

pK2 = 10.33, and pKW = 14.

Table 4.

Water-quality indicators in samples collected for the Bear Valley and Selected Hard Rock Areas (BEAR) Groundwater Ambient Monitoring and Assessment (GAMA) 

study unit, California, April to August 2010.—Continued[The five-digit USGS parameter code below the constituent name is used to uniquely identify a specific constituent or property. GAMA site identification number: BEAR-S, Bear Valley study area grid site; BEAR-G, Selected Hard Rock Areas study area grid site; BEAR-U, Bear Valley and Selected Hard Rock Areas study unit understanding site. Benchmark type, benchmark level, and RL as of April 1, 2010. Benchmark 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, degrees Celsius; mg/L, milligrams per liter; nc, not collected; na, not available; NTRU, nephelometric turbidity unit; RL, reporting limit or range; μS/cm, microsiemens per centimeter; <, less than; >, greater than; CaCO3, calcium carbonate; *, concentration is greater than the benchmark level; —, not detected; E, estimated or having a higher degree of uncertainty]
Tables 43

Table 5. Volatile organic compounds (VOCs) detected in samples collected for the Bear Valley and Selected Hard Rock Areas (BEAR) Groundwater Ambient Monitoring and 

Assessment (GAMA) study unit, California, April to August 2010.

[The five-digit USGS parameter code below the constituent name is used to uniquely identify a specific constituent or property. Samples from all 38 sites were analyzed, but only samples with detections are listed. Detected constituents are grouped by primary use or source and listed in order of decreasing detection frequency in the 27 grid sites. All constituents are listed in table 3A. GAMA site identification 

number: BEAR-S, Bear Valley study area grid site; BEAR-G, Selected Hard Rock Areas study area grid site; BEAR-U, Bear Valley and Selected Hard Rock Areas study unit understanding site. Benchmark type, benchmark level, and LRL as of April 1, 2010. Benchmark type: Maximum contaminant level benchmarks are listed as MCL-US if 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 (USEPA) maximum contaminant level; MCL-CA; California Department of Public Health maximum contaminant level; HAL-US, USEPA lifetime health advisory level. Other abbreviations: USGS, U.S. Geological Survey; E, estimated or having a higher degree of uncertainty; LRL, laboratory reporting level; μg/L, micrograms per liter; na, not available; —, not detected]

Primary use or source Trihalomethanes

GAMA site 

identification number

Chloroform 

(Trichloromethane) 

(μg/L) 

(32106)

Bromodichloromethane 

(μg/L) 

(32101) 

Dibromochloromethane

(μg/L) 

(32105)

Bromoform 

(Tribromomethane) 

(μg/L) 

(32104)

Benchmark type MCL-US MCL-US MCL-US MCL-US

Benchmark level 1 80 1 80 1 80 1 80

[LRL] [0.03] [0.034] [0.12] [0.1]

BEAR grid sites (27 sites sampled)Number of sites with detections 11 4 1 1

Detection frequency (percent) 40.7 14.8 3.7 3.7

Total detections (number)Bear Valley study area (14 grid sites sampled)BEAR-S01 0.05 — — —

BEAR-S02 — — — —

BEAR-S03 E0.01 — — —

BEAR-S04 — — — —

BEAR-S05 — — — —

BEAR-S07 0.12 0.17 0.30 0.32

BEAR-S09 0.15 E0.03 — —

BEAR-S10 E0.02 — — —

BEAR-S11 — — — —

BEAR-S12 — — — —

BEAR-S13 0.07 0.08 — —

Number of sites with detections 6 3 1 1

Detection frequency (percent) 42.9 21.4 7.1 7.1

Total detections (number)
44 Groundwater-Quality Data in the Bear Valley and Selected Hard Rock Areas Study Unit, 2010 Primary use or source Trihalomethanes GAMA site identification number Chloroform (Trichloromethane) (μg/L) (32106) Bromodichloromethane (μg/L) (32101) Dibromochloromethane (μg/L) (32105) Bromoform (Tribromomethane) (μg/L) (32104) Benchmark type MCL-US MCL-US MCL-US MCL-US Benchmark level 1 80 1 80 1 80 1 80 [LRL] [0.03] [0.034] [0.12] [0.1] BEAR grid sites (27 sites sampled)—Continued Selected Hard Rock Areas study area (13 grid sites sampled) BEAR-G03 E0.02

—

—

—

BEAR-G08 E0.01

—

—

—

BEAR-G09 0.06

—

—

—

BEAR-G10

—

—

—

—

BEAR-G11 0.16 0.10

—

—

BEAR-G13 E0.03

—

—

—

Number of sites with detections 5 1 0 0

Detection frequency (percent) 38.5 7.7 0 0

Total detections (number)BEAR understanding sites (11 sites sampled) 3

BEAR-U01 0.94 0.58 E0.1

—

BEAR-U03

—

—

—

—

BEAR-U04 E0.02

—

—

—

BEAR-U08

—

—

—

—

BEAR-U09

—

—

—

—

BEAR-U11 E0.02

—

—

—

Table 5.

Volatile organic compounds (VOCs) detected in samples collected for the Bear Valley and Selected Hard Rock Areas (BEAR) Groundwater Ambient Monitoring and 

Assessment (GAMA) study unit, California, April to August 2010.—Continued[The five-digit USGS parameter code below the constituent name is used to uniquely identify a specific constituent or property. Samples from all 38 sites were analyzed, but only samples with detections are listed. Detected constituents are grouped by primary use or source and listed in order of decreasing detection frequency in the 27 grid sites. All constituents are listed in table 3A. GAMA site identification 

number: BEAR-S, Bear Valley study area grid site; BEAR-G, Selected Hard Rock Areas study area grid site; BEAR-U, Bear Valley and Selected Hard Rock Areas study unit understanding site. Benchmark type, benchmark level, and LRL as of April 1, 2010. Benchmark type: Maximum contaminant level benchmarks are listed as MCL-US if 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 (USEPA) maximum contaminant level; MCL-CA; California Department of Public Health maximum contaminant level; HAL-US, USEPA lifetime health advisory level. Other abbreviations: USGS, U.S. Geological Survey; E, estimated or having a higher degree of uncertainty; LRL, laboratory reporting level; μg/L, micrograms per liter; na, not available; —, not detected]
Tables 45

Primary use or source Solvents

GAMA site 

identification number

Perchloroethene 

(PCE, Tetrachloroethene) 

(μg/L) 

(34475)

1,1,1-Trichloroethane 

(1,1,1-TCA) 

(μg/L) 

(34506)

Methylene chloride 

(Dichloromethane) 

(μg/L) 

(34423)

1,1-Dichloroethane 

(1,1-DCA) 

(μg/L) 

(34496)

Carbon tetrachloride 

(Tetrachloromethane) 

(μg/L) 

(32102)

Trichloroethene 

(TCE) 

(μg/L) 

(39180)

Benchmark type MCL-US MCL-US MCL-US MCL-CA MCL-CA MCL-US

Benchmark level 5 200 5 5 0.5 5

[LRL] [0.026] [0.03] [0.038] [0.044] [0.052] [0.022]

BEAR grid sites (27 sites sampled)Number of sites with detections 5 3 1 1 1 1Detection frequency (percent) 18.5 11.1 3.7 3.7 3.7 3.7Total detections (number)Bear Valley study area (14 grid sites sampled)BEAR-S01 E0.02 E0.02 — E0.02 — —

BEAR-S02 — — E0.021 — — —

BEAR-S03 0.04 — — — — —

BEAR-S04 — — — — — —

BEAR-S05 — — — — — —

BEAR-S07 — — — — — —

BEAR-S09 0.03 — — — — —

BEAR-S10 0.04 E0.02 — — — —

BEAR-S11 0.04 — — — — —

BEAR-S12 — E0.02 — — 0.18 0.28

BEAR-S13 — — — — — —

Number of sites with detections 5 3 1 1 1 1

Detection frequency (percent) 35.7 21.4 7.1 7.1 7.1 7.1

Total detections (number)

Table 5. Volatile organic compounds (VOCs) detected in samples collected for the Bear Valley and Selected Hard Rock Areas (BEAR) Groundwater Ambient Monitoring and Assessment (GAMA) study unit, California, April to August 2010.—Continued[The five-digit USGS parameter code below the constituent name is used to uniquely identify a specific constituent or property. Samples from all 38 sites were analyzed, but only samples with detections are listed. Detected constituents are grouped by primary use or source and listed in order of decreasing detection frequency in the 27 grid sites. All constituents are listed in table 3A. GAMA site identification 

number: BEAR-S, Bear Valley study area grid site; BEAR-G, Selected Hard Rock Areas study area grid site; BEAR-U, Bear Valley and Selected Hard Rock Areas study unit understanding site. Benchmark type, benchmark level, and LRL as of April 1, 2010. Benchmark type: Maximum contaminant level benchmarks are listed as MCL-US if 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 (USEPA) maximum contaminant level; MCL-CA; California Department of Public Health maximum contaminant level; HAL-US, USEPA lifetime health advisory level. Other abbreviations: USGS, U.S. Geological Survey; E, estimated or having a higher degree of uncertainty; LRL, laboratory reporting level; μg/L, micrograms per liter; na, not available; —, not detected]
46 Groundwater-Quality Data in the Bear Valley and Selected Hard Rock Areas Study Unit, 2010 Primary use or source Solvents GAMA site identification number Perchloroethene (PCE, Tetrachloroethene) (μg/L) (34475) 1,1,1-Trichloroethane (1,1,1-TCA) (μg/L) (34506) Methylene chloride (Dichloromethane) (μg/L) (34423) 1,1-Dichloroethane (1,1-DCA) (μg/L) (34496) Carbon tetrachloride (Tetrachloromethane) (μg/L) (32102) Trichloroethene (TCE) (μg/L) (39180) Benchmark type MCL-US MCL-US MCL-US MCL-CA MCL-CA MCL-US Benchmark level 5 200 5 5 0.5 5 [LRL] [0.026] [0.03] [0.038] [0.044] [0.052] [0.022] BEAR grid sites (27 sites sampled)—Continued Selected Hard Rock Areas study area (13 grid sites sampled) BEAR-G03

—

—

—

—

—

—

BEAR-G08

—

—

—

—

—

—

BEAR-G09

—

—

—

—

—

—

BEAR-G10

—

—

—

—

—

—

BEAR-G11

—

—

—

—

—

—

BEAR-G13

—

—

—

—

—

—

Number of sites with detections 0 0 0 0 0 0Detection frequency (percent) 0 0 0 0 0 0Total detections (number)BEAR understanding sites (11 sites sampled) 3

BEAR-U01

— E0.02 E0.029

—

—

—

BEAR-U03 E0.01

—

—

—

—

—

BEAR-U04

—

—

—

—

—

—

BEAR-U08

—

—

—

—

—

—

BEAR-U09

—

—

—

—

—

—

BEAR-U11

—

—

—

—

—

—

Table 5.

Volatile organic compounds (VOCs) detected in samples collected for the Bear Valley and Selected Hard Rock Areas (BEAR) Groundwater Ambient Monitoring and 

Assessment (GAMA) study unit, California, April to August 2010.—Continued[The five-digit USGS parameter code below the constituent name is used to uniquely identify a specific constituent or property. Samples from all 38 sites were analyzed, but only samples with detections are listed. Detected constituents are grouped by primary use or source and listed in order of decreasing detection frequency in the 27 grid sites. All constituents are listed in table 3A. GAMA site identification 

number: BEAR-S, Bear Valley study area grid site; BEAR-G, Selected Hard Rock Areas study area grid site; BEAR-U, Bear Valley and Selected Hard Rock Areas study unit understanding site. Benchmark type, benchmark level, and LRL as of April 1, 2010. Benchmark type: Maximum contaminant level benchmarks are listed as MCL-US if 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 (USEPA) maximum contaminant level; MCL-CA; California Department of Public Health maximum contaminant level; HAL-US, USEPA lifetime health advisory level. Other abbreviations: USGS, U.S. Geological Survey; E, estimated or having a higher degree of uncertainty; LRL, laboratory reporting level; μg/L, micrograms per liter; na, not available; —, not detected]
Tables 47

Primary use or source Hydrocarbons Gasoline oxygenate Organic synthesis Fire retardant Refrigerant

Detections 

per site

VOC 

detection 

summary

GAMA site 

identification number

1,2,4-Trimethylbenzene 

(μg/L) 

(77222)

Toluene 

(μg/L) 

(34010)

Methyl tert-butyl ether 

(MTBE) 

(μg/L) 

(78032)

1,1-Dichloroethene 

(1,1-DCE) 

(μg/L) 

(34501)

Bromochloromethane 

(μg/L) 

(77297)

Trichlorofluoromethane 

(CFC-11) 

(μg/L) 

(34488)

Benchmark type NL-CA MCL-CA MCL-CA MCL-CA HAL-US MCL-CA

Benchmark level 330 150 13 6 90 150

[LRL] 2 [0.56] 2 [0.69] [0.1] [0.022] [0.06] [0.08]

BEAR grid sites (27 sites sampled)Number of sites with detections 3 1 8 2 0 0 17

Detection frequency (percent) 11.1 3.7 29.6 7.4 0 0 63

Total detections (number) 43Bear Valley study area (14 grid sites sampled)BEAR-S01 0.77 — E0.08 — — — 6

BEAR-S02 — — E0.09 — — — 2

BEAR-S03 — — 0.10 — — — 3

BEAR-S04 — — 0.14 — — — 1

BEAR-S05 — — E0.06 — — — 1

BEAR-S07 — — E0.07 — — — 5

BEAR-S09 — — — — — — 3

BEAR-S10 — — E0.08 — — — 4

BEAR-S11 — — E0.03 — — — 2

BEAR-S12 0.71 — — E0.01 — — 5

BEAR-S13 — — — — — — 2

Number of sites with detections 2 8 1 0 0 11Detection frequency (percent) 14.3 57.1 7.1 0 0 79Total detections (number) 34

Table 5. Volatile organic compounds (VOCs) detected in samples collected for the Bear Valley and Selected Hard Rock Areas (BEAR) Groundwater Ambient Monitoring and Assessment (GAMA) study unit, California, April to August 2010.—Continued[The five-digit USGS parameter code below the constituent name is used to uniquely identify a specific constituent or property. Samples from all 38 sites were analyzed, but only samples with detections are listed. Detected constituents are grouped by primary use or source and listed in order of decreasing detection frequency in the 27 grid sites. All constituents are listed in table 3A. GAMA site identification 

number: BEAR-S, Bear Valley study area grid site; BEAR-G, Selected Hard Rock Areas study area grid site; BEAR-U, Bear Valley and Selected Hard Rock Areas study unit understanding site. Benchmark type, benchmark level, and LRL as of April 1, 2010. Benchmark type: Maximum contaminant level benchmarks are listed as MCL-US if 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 (USEPA) maximum contaminant level; MCL-CA; California Department of Public Health maximum contaminant level; HAL-US, USEPA lifetime health advisory level. Other abbreviations: USGS, U.S. Geological Survey; E, estimated or having a higher degree of uncertainty; LRL, laboratory reporting level; μg/L, micrograms per liter; na, not available; —, not detected]
48 Groundwater-Quality Data in the Bear Valley and Selected Hard Rock Areas Study Unit, 2010 Primary use or source Hydrocarbons Gasoline oxygenate Organic synthesis Fire retardant Refrigerant Detections per site VOC detection summary GAMA site identification number 1,2,4-Trimethylbenzene (μg/L) (77222) Toluene (μg/L) (34010) Methyl tert-butyl ether (MTBE) (μg/L) (78032) 1,1-Dichloroethene (1,1-DCE) (μg/L) (34501) Bromochloromethane (μg/L) (77297) Trichlorofluoromethane (CFC-11) (μg/L) (34488) Benchmark type NL-CA MCL-CA MCL-CA MCL-CA HAL-US MCL-CA Benchmark level 330 150 13 6 90 150 [LRL] 2 [0.56] 2 [0.69] [0.1] [0.022] [0.06] [0.08] BEAR grid sites (27 sites sampled)—Continued Selected Hard Rock Areas study area (13 grid sites sampled) BEAR-G03

—

—

—

—

—

— 1

BEAR-G08

—

—

—

—

—

— 1

BEAR-G09

— 1.39

—

—

—

— 2

BEAR-G10

—

—

— 1.39

—

— 1

BEAR-G11 0.67

—

—

—

—

— 3

BEAR-G13

—

—

—

—

—

— 1

Number of sites with detections 1 1 0 1 0 0 6

Detection frequency (percent) 7.7 7.7 0 7.7 0 0 46

Total detections (number) 9BEAR understanding sites (11 sites sampled) 3

BEAR-U01

—

— 0.24

— E0.03

— 7

BEAR-U03

—

—

—

—

—

— 1

BEAR-U04

—

—

—

—

—

— 1

BEAR-U08

—

— 0.64

—

—

— 1

BEAR-U09

—

—

—

—

— 0.11 1

BEAR-U11

—

—

—

—

—

— 1

1 The MCL-US benchmark for trihalomethanes is for the sum of chloroform, bromoform, bromodichloromethane, and dibromochloromethane.2 The SRLs for toluene (0.69 μg/L) and 1,2,4-trimethylbenzene (0.56 μg/L) were defined by Fram and others (2012). Detections of toluene (BEAR-U11: E0.05 μg/L) and 1,2,4-trimethylbenzene (BEAR-S06: 

E0.01 μg/L; BEAR-S14: 0.25 μg/L; BEAR-G03: E0.02 μg/L; BEAR-G07: 0.14 μg/L; BEAR-G09: 0.26 μg/L; BEAR-G12: E0.02 μg/L; BEAR-U04: 0.16 μg/L; BEAR-U06: E0.05 μg/L; BEAR-U07: E0.05 μg/L; BEAR-U08: E0.06 μg/L; BEAR-U09: E0.07 μg/L; BEAR-U10: 0.20 μg/L; and BEAR-U11: 0.20 μg/L) have been reclassified as non-detections and are not presented in this report.

3 Understanding sites were not included in statistical calculations.

Table 5.

Volatile organic compounds (VOCs) detected in samples collected for the Bear Valley and Selected Hard Rock Areas (BEAR) Groundwater Ambient Monitoring and 

Assessment (GAMA) study unit, California, April to August 2010.—Continued[The five-digit USGS parameter code below the constituent name is used to uniquely identify a specific constituent or property. Samples from all 38 sites were analyzed, but only samples with detections are listed. Detected constituents are grouped by primary use or source and listed in order of decreasing detection frequency in the 27 grid sites. All constituents are listed in table 3A. GAMA site identification 

number: BEAR-S, Bear Valley study area grid site; BEAR-G, Selected Hard Rock Areas study area grid site; BEAR-U, Bear Valley and Selected Hard Rock Areas study unit understanding site. Benchmark type, benchmark level, and LRL as of April 1, 2010. Benchmark type: Maximum contaminant level benchmarks are listed as MCL-US if 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 (USEPA) maximum contaminant level; MCL-CA; California Department of Public Health maximum contaminant level; HAL-US, USEPA lifetime health advisory level. Other abbreviations: USGS, U.S. Geological Survey; E, estimated or having a higher degree of uncertainty; LRL, laboratory reporting level; μg/L, micrograms per liter; na, not available; —, not detected]
Tables 49

Table 6. Pesticides and pesticide degradates detected in samples collected for the Bear Valley and Selected Hard Rock Areas (BEAR) 

Groundwater Ambient Monitoring and Assessment (GAMA) study unit, California, April to August 2010.

[The five-digit USGS parameter code below the constituent name is used to uniquely identify a specific constituent or property. Samples from all 38 sites were 

analyzed, but only samples with detections are listed. Constituents are listed in order of decreasing detection frequency in the 27 grid sites. All constituents 

are listed in table 3B. GAMA site identification number: BEAR-S, Bear Valley study area grid site; BEAR-G, Selected Hard Rock Areas study area grid 

site; BEAR-U, Bear Valley and Selected Hard Rock Areas study unit understanding site. Benchmark type, benchmark level, and LRL as of April 1, 2010. 

Benchmark type: Maximum contaminant level benchmarks are listed as MCL-US if 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 (USEPA) maximum contaminant level; HAL-US, 

USEPA lifetime health advisory level. Other abbreviations: USGS, U.S. Geological Survey; E, estimated or having a higher degree of uncertainty; LRL, 

laboratory reporting level; μg/L, micrograms per liter; —, not detected]

Primary use 

or source Herbicides

Pesticide 

detections 

per site

Pesticide 

detection 

summary

GAMA site 

identification number

Simazine 

(μg/L) 

(04035)

Prometon 

(μg/L) 

(04037)

Benchmark type MCL-US HAL-US

Benchmark level 4 400

[LRL] [0.006] [0.012]

BEAR grid sites (27 sites sampled)

Number of sites with detections 4 1 4

Detection frequency (percent) 14.8 3.7 15

Total detections (number) 5

Bear Valley study area (14 grid sites sampled)

BEAR-S01 E0.007 — 1

BEAR-S03 0.01 E0.01 2

BEAR-S10 0.01 — 1

Number of sites with detections 3 1 3

Detection frequency (percent) 21.4 7.1 21

Total detections (number) 4

Selected Hard Rock Areas study area (13 grid sites sampled)

BEAR-G01 0.01 — 1

Number of sites with detections 1 0 1

Detection frequency (percent) 7.7 0 8

Total detections (number) 1

BEAR understanding sites (11 sites sampled) 1

BEAR-U03 0.03 — 1

1

 Understanding sites were not included in statistical calculations.
50 Groundwater-Quality Data in the Bear Valley and Selected Hard Rock Areas Study Unit, 2010

Table 7. Wastewater indicator compounds (WICs) detected in samples collected for the Bear Valley and Selected Hard Rock Areas 

(BEAR) Groundwater Ambient Monitoring and Assessment (GAMA) study unit, California, April to August 2010.

[The five-digit USGS parameter code below the constituent name is used to uniquely identify a specific constituent or property. Samples from nine 

understanding sites were analyzed, but only samples with detections are listed. All constituents are listed in table 3D. GAMA site identification 

number: BEAR-U, Bear Valley and Selected Hard Rock Areas study unit understanding site. Benchmark type, benchmark level, and LRL as of April 1, 2010. 

Benchmark type: HAL-US, USEPA lifetime health advisory level. Other abbreviations: USGS, U.S. Geological Survey; USEPA, U.S. Environmental 

Protection Agency; WIC, wastewater indicator compound; E, estimated or having a higher degree of uncertainty; LRL, laboratory reporting level; SRL, study 

reporting level; μg/L, micrograms per liter; na, not available; ≤, less than or equal to; —, not detected]

Primary use 

or source Flame retardant Disinfectant

WIC 

detections 

per site

GAMA site 

identification number

Tris(2-butoxyethyl) phosphate 

(μg/L) 

(62093)

Phenol 

(μg/L) 

(34466)

Benchmark type na HAL-US

Benchmark level na 2,000

[LRL or SRL] [0.30] 1 [0.16]

BEAR understanding sites (9 sites sampled) 

BEAR-U06 ≤0.10 E0.10 1

BEAR-U08 0.95 — 1

1

 The SRL was defined based on the highest concentration detected in the BEAR blank samples.
Tables 51

Table 8. Perchlorate detected in samples collected for the Bear Valley and Selected Hard Rock Areas (BEAR) Groundwater Ambient 

Monitoring and Assessment (GAMA) study unit, California, April to August 2010.

[The five-digit USGS parameter code below the constituent name is used to uniquely identify a specific constituent or property. Information about 

the constituent given in table 3E. Samples from all 38 sites were analyzed, but only samples with detections are listed. GAMA site identification 

number: BEAR-S, Bear Valley study area grid site; BEAR-G, Selected Hard Rock Areas study area grid site; BEAR-U, Bear Valley and Selected Hard 

Rock Areas study unit understanding site. Benchmark type, benchmark level, and MRL as of April 1, 2010. Benchmark type: Maximum contaminant level 

benchmarks are listed as MCL-US if 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: USGS, U.S. Geological Survey; MRL, method 

reporting level; μg/L, micrograms per liter; —, not detected; na, not available]

GAMA site 

identification number

Perchlorate 

(μg/L) 

(63790)

GAMA site 

identification number

Perchlorate 

(μg/L) 

(63790)

Benchmark type MCL-CA Benchmark type MCL-CA

Benchmark level 6 Benchmark level 6

[MRL] [0.10] [MRL] [0.10]

BEAR grid sites (27 sites sampled) BEAR grid sites (27 sites sampled)—Continued

Number of sites with detections 21 Selected Hard Rock Areas study area (13 grid sites sampled)

Detection frequency (percent) 78 BEAR-G02 0.47

Bear Valley study area (14 grid sites sampled) BEAR-G03 0.28

BEAR-S01 0.23 BEAR-G04 0.20

BEAR-S02 0.11 BEAR-G05 0.14

BEAR-S03 0.27 BEAR-G06 0.15

BEAR-S05 0.17

BEAR-S06 0.22 BEAR-G11 0.15

BEAR-G12 0.10

BEAR-S07 0.20 BEAR-G13 0.13

BEAR-S08 0.14 Number of sites with detections 8

BEAR-S09 0.26 Detection frequency (percent) 62

BEAR-S10 0.96 BEAR understanding sites (11 sites sampled) 1

BEAR-S11 0.26 BEAR-U01 0.20

BEAR-U02 0.40

BEAR-S12 0.20 BEAR-U03 0.47

BEAR-S13 0.24 BEAR-U04 0.49

BEAR-S14 0.13 BEAR-U06 0.28

Number of sites with detections 13

Detection frequency (percent) 93 BEAR-U07 0.50

BEAR-U09 0.20

BEAR-U11 na 2

1

 Understanding sites were not included in statistical calculations.

2

 Sample was broken during shipment to the laboratory.
52 Groundwater-Quality Data in the Bear Valley and Selected Hard Rock Areas Study Unit, 2010 Table 9. Trace elements detected in samples collected for the Bear Valley and Selected Hard Rock Areas (BEAR) Groundwater Ambient Monitoring and Assessment (GAMA) study unit, California, April to August 2010. [The five-digit USGS parameter code below the constituent name is used to uniquely identify a specific constituent or property. Samples from all 38 sites were analyzed. Information about the constituents is given in table 3F. GAMA site identification number: BEAR-S, Bear Valley study area grid site; BEAR-G, Selected Hard Rock Areas study area grid site; BEAR-U, Bear Valley and Selected Hard Rock Areas study unit understanding site. Benchmark type, benchmark level, and LRL as of April 1, 2010. Benchmark type: Maximum contaminant level benchmarks are listed as MCL-US if 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 (USEPA) action level; HAL-US, USEPA lifetime health advisory level; MCL-CA, California Department of Public Health (CDPH) maximum contaminant level; MCL-US, USEPA maximum contaminant level; NL-CA, CDPH notification level; SMCL-CA, CDPH secondary maximum contaminant level. Other abbreviations: USGS, U.S. Geological Survey; E, estimated or having a higher degree of uncertainty; LRL, laboratory reporting level; SRL, study reporting level; μg/L, micrograms per liter; na, not available; —, not detected; ≤, less than or equal to; *, concentration is greater than the benchmark level] GAMA site identification number Aluminum (μg/L) (01106) Antimony (μg/L) (01095) Arsenic (μg/L) (01000) Barium (μg/L) (01005) Beryllium (μg/L) (01010) Boron (μg/L) (01020) Cadmium (μg/L) (01025) Chromium (μg/L) (01030) Cobalt (μg/L) (01035) Copper (μg/L) (01040) Iron (μg/L) (01046) Lead (μg/L) (01049) Benchmark type MCL-CA MCL-US MCL-US MCL-CA MCL-US NL-CA MCL-US MCL-CA na AL-US SMCL-CA AL-US Benchmark level 1,000 6 10 1,000 4 1,000 5 50 na 1,300 300 15 [LRL or SRL] [3.4] [0.054] [0.04] [0.14] [0.012] [2.8] [0.02] [0.42] 1 [0.42] 2 [1.7] 1 [6] 1 [0.65] 1 BEAR grid sites (27 sites sampled) Bear Valley study area (14 grid sites sampled) BEAR-S01

—

— 1.1 134

— 30

— 0.79 ≤0.05 ≤0.65

— ≤0.17

BEAR-S02

—

— 1.4 63.9

— 6 — 0.60 ≤0.03 ≤1.1

— ≤0.39

BEAR-S03

—

— 0.13 41.0

— 26

— ≤0.12 ≤0.05 5.4 ≤3 ≤0.29

BEAR-S04 E3.3 0.08 *35.2 13.2

— 150 0.04

— ≤0.02

— 7 ≤0.08

BEAR-S05

—

— 1.5 35.7

— 9 — 2.7 ≤0.03

—

— ≤0.22

BEAR-S06

—

— 0.36 73.2

— 8 — 0.43 ≤0.05 3.2

— ≤0.45

BEAR-S07

—

— 0.38 89.9

— 11

— ≤0.10 ≤0.05 5.0

— ≤0.40

BEAR-S08

—

— 0.20 30.1

— 8 — 0.64 ≤0.05

—

— ≤0.12

BEAR-S09

—

— 0.09 28.0

— 6 — 0.43 ≤0.05 1.9

— 1.1

BEAR-S10

—

— 0.05 22.0

— 16 E0.02 ≤0.24 ≤0.05 3.4 21 ≤0.50

BEAR-S11

—

— 0.43 37.6

— 14 E0.02 0.88 ≤0.10 ≤0.98

— ≤0.29

BEAR-S12

—

— 0.21 21.6

— 32 0.03 1.7 ≤0.05

—

— ≤0.26

BEAR-S13

—

— 0.16 29.4

— 5 — 2.0 ≤0.09 ≤1.1

— ≤0.20

BEAR-S14 E2.5

— 0.12 19.5

— 11 E0.02 ≤0.10 ≤0.08 2.0

— ≤0.37

Selected Hard Rock Areas study area (13 grid sites sampled)BEAR-G01 17.3

— 0.30 3.08 E0.01 5 E0.02

— ≤0.02 ≤0.97 12 ≤0.09

BEAR-G02 17.0 E0.03 E0.03 6.01 0.02 5 E0.02

— ≤0.28 3.2 10 ≤0.26

BEAR-G03 5.8

— E0.03 8.20

— 4 —

— ≤0.06 2.1 ≤5 4.1

BEAR-G04

—

— 0.14 20.7

— E2 0.06

— ≤0.11 ≤0.81 *356 2.8

BEAR-G05

— E0.03 0.06 5.13

— 5 0.10

— ≤0.31

— *435 ≤0.19
Tables 53

GAMA site 

identification 

number

Aluminum 

(μg/L) 

(01106) 

Antimony 

(μg/L) 

(01095) 

Arsenic 

(μg/L) 

(01000) 

Barium 

(μg/L) 

(01005) 

Beryllium 

(μg/L) 

(01010)

Boron 

(μg/L) 

(01020) 

Cadmium 

(μg/L) 

(01025) 

Chromium 

(μg/L) 

(01030) 

Cobalt 

(μg/L) 

(01035) 

Copper 

(μg/L) 

(01040) 

Iron 

(μg/L) 

(01046) 

Lead 

(μg/L) 

(01049) 

Benchmark type MCL-CA MCL-US MCL-US MCL-CA MCL-US NL-CA MCL-US MCL-CA na AL-US SMCL-CA AL-US

Benchmark level 1,000 6 10 1,000 4 1,000 5 50 na 1,300 300 15

[LRL or SRL] [3.4] [0.054] [0.04] [0.14] [0.012] [2.8] [0.02] [0.42] 1 [0.42] 2 [1.7] 1 [6] 1 [0.65] 1

BEAR grid sites (27 sites sampled)—ContinuedSelected Hard Rock Areas study area (13 grid sites sampled)—ContinuedBEAR-G06 — E0.03 0.05 12.8 — 31 — — ≤0.01 ≤1.1 — ≤0.14BEAR-G07 — — 0.09 6.64 — 6 0.05 — ≤0.09 5.6 — 3.5

BEAR-G08 — E0.04 0.44 1.77 — 4 0.03 ≤0.11 ≤0.10 2.8 ≤4 1.5

BEAR-G09 — — 0.06 8.75 — 5 — — ≤0.05 — 119 0.83

BEAR-G10 — — 0.77 5.08 E0.01 8 E0.02 — ≤0.10 ≤0.74 — ≤0.22

BEAR-G11 4.2 — 0.06 3.38 — 7 — ≤0.10 ≤0.04 3.2 — 0.73

BEAR-G12 3.7 — 0.25 1.36 0.03 3 0.07 — ≤0.13 ≤0.70 12 ≤0.24

BEAR-G13 — — 0.05 7.58 E0.01 4 — ≤0.08 ≤0.07 ≤0.59 — ≤0.47

BEAR understanding sites (11 sites sampled)BEAR-U01 — — 0.05 10.4 — 6 — — ≤0.08 ≤1.1 — 1.2

BEAR-U02 — E0.03 0.50 57.5 — 24 0.02 ≤0.14 ≤0.17 1.8 — ≤0.44

BEAR-U03 — — 0.14 26.3 — 34 0.02 ≤0.13 ≤0.06 3.5 7 ≤0.46

BEAR-U04 — — 0.16 7.40 0.01 8 E0.01 ≤0.13 ≤0.03 3.1 10 ≤0.09

BEAR-U05 94.6 — E0.03 2.99 0.05 4 — — ≤0.04 27.4 72 10.3

BEAR-U06 9.3 — 0.08 5.89 E0.01 10 — ≤0.08 ≤0.07 2.8 22 0.65

BEAR-U07 — — 0.32 54.8 — 9 — ≤0.09 ≤0.16 ≤1.3 — ≤0.21

BEAR-U08 — — 4.2 8.71 E0.01 39 E0.01 — ≤0.10 — 102 ≤0.09BEAR-U09 — — 0.44 72.4 — 15 0.02 ≤0.07 ≤0.17 ≤1.4 — ≤0.26

BEAR-U10 12.3 E0.04 0.08 3.97 0.05 E2 E0.02 — ≤0.19 5.0 40 ≤0.58

BEAR-U11 10.3 0.14 0.07 4.23 — 4 — — ≤0.11 — *487 1.7

Table 9. Trace elements detected in samples collected for the Bear Valley and Selected Hard Rock Areas (BEAR) Groundwater Ambient Monitoring and Assessment (GAMA) study unit, California, April to August 2010.—Continued[The five-digit USGS parameter code below the constituent name is used to uniquely identify a specific constituent or property. Samples from all 38 sites were analyzed. Information about the constituents is given in table 3F. GAMA site identification number: BEAR-S, Bear Valley study area grid site; BEAR-G, Selected Hard Rock Areas study area grid site; BEAR-U, Bear Valley and Selected Hard Rock Areas study unit understanding site. Benchmark type, benchmark level, and LRL as of April 1, 2010. Benchmark type: Maximum contaminant level benchmarks are listed as MCL-US if 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 (USEPA) action level; HAL-US, USEPA lifetime health advisory level; MCL-CA, California Department of Public Health (CDPH) maximum contaminant level; MCL-US, USEPA maximum contaminant level; NL-CA, CDPH notification level; SMCL-CA, CDPH secondary maximum contaminant level. Other abbreviations: USGS, U.S. Geological Survey; E, estimated or having a higher degree of uncertainty; LRL, laboratory reporting level; SRL, study reporting level; μg/L, micrograms per liter; na, not available; —, not detected; ≤, less than or equal to; *, concentration is greater than the benchmark level]
54 Groundwater-Quality Data in the Bear Valley and Selected Hard Rock Areas Study Unit, 2010 GAMA site identification number Lithium (μg/L) (01130) Manganese (μg/L) (01056) Molybdenum (μg/L) (01060) Nickel (μg/L) (01065) Selenium (μg/L) (01145) Silver (μg/L) (01075) Strontium (μg/L) (01080) Thallium (μg/L) (01057) Tungsten (μg/L) (01155) Vanadium (μg/L) (01085) Zinc (μg/L) (01090) Benchmark type na SMCL-CA HAL-US MCL-CA MCL-US SMCL-CA HAL-US MCL-US na NL-CA SMCL-CA Benchmark level na 50 40 100 50 100 4,000 2 na 50 5,000 [LRL or SRL] [0.44] [0.79] 2 [0.014] [0.36] 1 [0.040] [0.010] [0.40] [0.020] [0.11] 1 [0.16] [4.8] 1 BEAR grid sites (27 sites sampled) Bear Valley study area (14 grid sites sampled) BEAR-S01 5.0 ≤0.20 0.526 ≤0.27 0.45

— 536

— 0.31 7.8 ≤2.5

BEAR-S02 3.2 ≤0.25 0.235 ≤0.13 0.41

— 678

— 0.11 9.6 ≤2.1

BEAR-S03 2.9

— 0.157 ≤0.23 0.05

— 210

—

— 2.1 ≤3.5

BEAR-S04 3.6 ≤0.70 6.24

— 0.89

— 82.8

— 8.3 16.1

—

BEAR-S05 2.0 ≤0.40 0.591 ≤0.09 0.09

— 216

— 1.1 10.4 ≤2.6

BEAR-S06 1.3

— E0.014 ≤0.27 0.07

— 182

— ≤0.01 2.0

—

BEAR-S07 0.8 ≤0.16 0.669 0.36 0.06

— 302

— ≤0.01 1.7 6.8

BEAR-S08 1.5

— 0.273 ≤0.30 0.17

— 191

— ≤0.03 1.3

—

BEAR-S09

—

— 0.399 ≤0.24 0.27

— 167

— ≤0.03 1.1 ≤1.4

BEAR-S10 2.3 ≤0.28 2.36 0.56 0.85

— 164

— 0.21 1.2 ≤3.9

BEAR-S11 1.9 1.9 0.870 0.50 0.33

— 218

— 0.87 9.7

—

BEAR-S12 E0.30

— 2.88 ≤0.32 0.14

— 127

— 7.0 3.9 ≤4.1

BEAR-S13

— ≤0.40 0.262 0.55 0.12

— 201

— ≤0.06 2.1 7.1

BEAR-S14 1.3 ≤0.17 0.886 0.45 0.33

— 99.3

— 0.13 0.39 24.0

Selected Hard Rock Areas study area (13 grid sites sampled)BEAR-G01 108 ≤0.42 2.40 ≤0.11 0.04

— 457

— ≤0.02 0.78 18.7

BEAR-G02 11.0 1.0 E0.025 ≤0.17 0.17 0.02 289

—

— 0.83 22.9

BEAR-G03 6.1 ≤0.73 0.156 ≤0.13 0.08

— 117

— ≤0.01 1.4 12.1

BEAR-G04 14.3 10.4 0.047 ≤0.33 E0.03

— 153

—

— 2.1 63.4

BEAR-G05 12.1 22.3 0.260 ≤0.20 0.06

— 184

—

— 1.2 80.3

Table 9. Trace elements detected in samples collected for the Bear Valley and Selected Hard Rock Areas (BEAR) Groundwater Ambient Monitoring and Assessment (GAMA) study unit, California, April to August 2010.—Continued[The five-digit USGS parameter code below the constituent name is used to uniquely identify a specific constituent or property. Samples from all 38 sites were analyzed. Information about the constituents is given in table 3F. GAMA site identification number: BEAR-S, Bear Valley study area grid site; BEAR-G, Selected Hard Rock Areas study area grid site; BEAR-U, Bear Valley and Selected Hard Rock Areas study unit understanding site. Benchmark type, benchmark level, and LRL as of April 1, 2010. Benchmark type: Maximum contaminant level benchmarks are listed as MCL-US if 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 (USEPA) action level; HAL-US, USEPA lifetime health advisory level; MCL-CA, California Department of Public Health (CDPH) maximum contaminant level; MCL-US, USEPA maximum contaminant level; NL-CA, CDPH notification level; SMCL-CA, CDPH secondary maximum contaminant level. Other abbreviations: USGS, U.S. Geological Survey; E, estimated or having a higher degree of uncertainty; LRL, laboratory reporting level; SRL, study reporting level; μg/L, micrograms per liter; na, not available; —, not detected; ≤, less than or equal to; *, concentration is greater than the benchmark level]
Tables 55

GAMA site 

identification 

number

Lithium 

(μg/L) 

(01130) 

Manganese 

(μg/L) 

(01056) 

Molybdenum 

(μg/L) 

(01060) 

Nickel 

(μg/L) 

(01065) 

Selenium 

(μg/L) 

(01145) 

Silver 

(μg/L) 

(01075) 

Strontium 

(μg/L) 

(01080)

Thallium 

(μg/L) 

(01057) 

Tungsten 

(μg/L) 

(01155)

Vanadium 

(μg/L) 

(01085) 

Zinc 

(μg/L) 

(01090)

Benchmark type na SMCL-CA HAL-US MCL-CA MCL-US SMCL-CA HAL-US MCL-US na NL-CA SMCL-CA

Benchmark level na 50 40 100 50 100 4,000 2 na 50 5,000

[LRL or SRL] [0.44] [0.79] 2 [0.014] [0.36] 1 [0.040] [0.010] [0.40] [0.020] [0.11] 1 [0.16] [4.8] 1

BEAR grid sites (27 sites sampled)—ContinuedSelected Hard Rock Areas study area (13 grid sites sampled)—ContinuedBEAR-G06 23.1 ≤0.20 2.25 ≤0.28 0.19 — 292 — ≤0.01 2.5 ≤4.3

BEAR-G07 37.3 2.8 1.84 0.56 0.15 — 444 — ≤0.05 0.92 92.8

BEAR-G08 16.1 ≤0.15 2.22 0.53 0.71 — 138 E0.02 0.12 2.4 109

BEAR-G09 38.4 *50.1 2.00 ≤0.10 0.09 — 447 — ≤0.02 0.70 425

BEAR-G10 48.6 6.0 2.73 0.71 E0.03 — 642 — — 0.72 147

BEAR-G11 16.4 ≤0.74 0.651 ≤0.25 0.26 — 125 — ≤0.08 2.5 63.9

BEAR-G12 65.1 2.0 0.028 ≤0.32 E0.03 — 151 — — 0.54 33.0

BEAR-G13 33.3 ≤0.40 0.885 0.47 0.11 — 250 — — 4.8 —

BEAR understanding sites (11 sites sampled)BEAR-U01 32.3 — 0.08 ≤0.16 0.09 — 221 — — 2.1 —

BEAR-U02 5.7 ≤0.33 2.57 ≤0.26 0.30 — 118 — 1.8 2.0 ≤3.4

BEAR-U03 2.7 ≤0.18 5.07 0.51 1.3 — 192 — 0.13 1.5 ≤1.8

BEAR-U04 5.9 5.1 1.55 ≤0.26 0.56 — 92.3 — 0.64 1.5 5.2

BEAR-U05 22.9 1.5 E0.025 ≤0.23 E0.03 — 65.7 — — 0.33 ≤2.0

BEAR-U06 1.6 ≤0.50 E0.026 ≤0.30 — — 203 — ≤0.03 0.52 22.8

BEAR-U07 1.9 ≤0.30 0.286 0.51 E0.03 — 397 — ≤0.03 1.6 7.4

BEAR-U08 2.3 *108 2.75 0.72 E0.02 — 581 — 0.89 0.19 12.7

BEAR-U09 0.90 ≤0.22 1.48 1.0 0.46 — 306 — ≤0.03 1.3 ≤4.7

BEAR-U10 18.2 1.4 — ≤0.28 — — 136 — — 0.53 13.4BEAR-U11 44.9 *155 1.26 ≤0.12 — — 540 — ≤0.05 0.34 256

1 The SRL was defined by Olsen and others (2010).2 The SRL was defined based on the highest concentration detected in the BEAR blank samples.

Table 9. Trace elements detected in samples collected for the Bear Valley and Selected Hard Rock Areas (BEAR) Groundwater Ambient Monitoring and Assessment (GAMA) study unit, California, April to August 2010.—Continued[The five-digit USGS parameter code below the constituent name is used to uniquely identify a specific constituent or property. Samples from all 38 sites were analyzed. Information about the constituents is given in table 3F. GAMA site identification number: BEAR-S, Bear Valley study area grid site; BEAR-G, Selected Hard Rock Areas study area grid site; BEAR-U, Bear Valley and Selected Hard Rock Areas study unit understanding site. Benchmark type, benchmark level, and LRL as of April 1, 2010. Benchmark type: Maximum contaminant level benchmarks are listed as MCL-US if 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 (USEPA) action level; HAL-US, USEPA lifetime health advisory level; MCL-CA, California Department of Public Health (CDPH) maximum contaminant level; MCL-US, USEPA maximum contaminant level; NL-CA, CDPH notification level; SMCL-CA, CDPH secondary maximum contaminant level. Other abbreviations: USGS, U.S. Geological Survey; E, estimated or having a higher degree of uncertainty; LRL, laboratory reporting level; SRL, study reporting level; μg/L, micrograms per liter; na, not available; —, not detected; ≤, less than or equal to; *, concentration is greater than the benchmark level]
56 Groundwater-Quality Data in the Bear Valley and Selected Hard Rock Areas Study Unit, 2010

Table 10. Nutrients and dissolved organic carbon (DOC) detected in samples collected for the Bear Valley and Selected Hard Rock 

Areas (BEAR) Groundwater Ambient Monitoring and Assessment (GAMA) study unit, California, April to August 2010.

[The five-digit USGS parameter code below the constituent name is used to uniquely identify a specific constituent or property. Samples from all 38 sites were 

analyzed for nutrients and DOC. Information about the constituents given in table 3G. GAMA site identification number: BEAR-S, Bear Valley study area grid 

site; BEAR-G, Selected Hard Rock Areas study area grid site; BEAR-U, Bear Valley and Selected Hard Rock Areas study unit understanding site. Benchmark 

type, benchmark level, and LRL as of April 1, 2010. Benchmark type: Maximum contaminant level benchmarks are listed as MCL-US if 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 

(USEPA) lifetime health advisory level; MCL-US, USEPA maximum contaminant level. Other abbreviations: USGS, U.S. Geological Survey; LRL, laboratory 

reporting level; E, estimated or having a higher degree of uncertainty; SRL, study reporting level; mg/L, milligrams per liter; na, not available; —, not detected; 

≤, less than or equal to; NWQL, USGS National Water Quality Laboratory]

GAMA site 

identification 

number

Ammonia 

(as nitrogen) 

(mg/L) 

(00608)

 Nitrite 

(as nitrogen) 

(mg/L) 

(00613)

Nitrite plus nitrate 

(as nitrogen) 

(mg/L) 

(00631)

Total nitrogen 

(ammonia + nitrate 

+ nitrite + organic 

nitrogen) 

(mg/L) 

(62854)

Phosphate, 

orthophosphate 

(as phosphorus) 

(mg/L) 

(00671)

DOC 

(mg/L) 

(00681)

Benchmark type HAL-US MCL-US MCL-US na na na

Benchmark level 1

 24.7 1 10 na na na

[LRL or SRL] [0.02] [0.001] [0.04] [0.10] [0.006] [0.8] 2

BEAR grid sites (27 sites sampled)

Bear Valley study area (14 grid sites sampled)

BEAR-S01 — — 1.42 1.49 0.021 ≤0.6

BEAR-S02 — — 0.15 0.14 0.045 ≤0.5

BEAR-S03 — — 1.51 1.55 0.103 0.9

BEAR-S04 — — 0.50 0.52 0.025 —

BEAR-S05 — — 0.22 0.21 0.013 —

BEAR-S06 — — 0.47 0.50 0.022 —

BEAR-S07 — — 1.33 1.38 0.055 ≤0.8

BEAR-S08 — — 0.12 0.12 0.042 —

BEAR-S09 — — 0.49 0.51 0.074 —

BEAR-S10 — — 4.03 4.16 0.028 ≤0.4

BEAR-S11 — — 0.92 0.94 0.018 —

BEAR-S12 — — 0.31 0.32 0.060 —

BEAR-S13 — — 1.09 1.06 0.092 ≤0.4

BEAR-S14 — — 0.36 0.36 0.015 ≤0.6

Selected Hard Rock Areas study area (13 grid sites sampled)

BEAR-G01 — — 0.22 0.22 0.018 ≤0.5

BEAR-G02 — — 0.40 0.41 0.058 ≤0.5

BEAR-G03 — — 0.11 0.12 0.026 ≤0.7

BEAR-G04 — 0.004 0.99 1.00 0.021 —

BEAR-G05 E0.014 0.005 0.40 0.43 0.010 —

BEAR-G06 — — 0.22 0.25 0.019 ≤0.4

BEAR-G07 — — E0.04 E0.10 0.016 ≤0.7

BEAR-G08 — — 0.07 E0.07 0.032 —

BEAR-G09 — 0.007 0.17 0.19 0.012 ≤0.6

BEAR-G10 — — 0.10 0.12 0.009 ≤0.6
Tables 57

GAMA site 

identification 

number

Ammonia 

(as nitrogen) 

(mg/L) 

(00608)

 Nitrite 

(as nitrogen) 

(mg/L) 

(00613)

Nitrite plus nitrate 

(as nitrogen) 

(mg/L) 

(00631)

Total nitrogen 

(ammonia + nitrate 

+ nitrite + organic 

nitrogen) 

(mg/L) 

(62854)

Phosphate, 

orthophosphate 

(as phosphorus) 

(mg/L) 

(00671)

DOC 

(mg/L) 

(00681)

Benchmark type HAL-US MCL-US MCL-US na na na

Benchmark level 1

 24.7 1 10 na na na

[LRL or SRL] [0.02] [0.001] [0.04] [0.10] [0.006] [0.8] 2

BEAR grid sites (27 sites sampled)—Continued

Selected Hard Rock Areas study area (13 grid sites sampled)—Continued

BEAR-G11 — — 3.83 3.76 0.030 —

BEAR-G12 — — 0.25 0.25 0.072 ≤0.6

BEAR-G13 — — 0.33 0.30 0.049 ≤0.4

BEAR understanding sites (11 sites sampled)

BEAR-U01 — — 1.24 1.26 0.018 —

BEAR-U02 — — 0.97 1.00 0.019 ≤0.4

BEAR-U03 — — 6.81 7.19 0.069 ≤0.6

BEAR-U04 — — 0.52 0.54 0.120 ≤0.4

BEAR-U05 — — 0.65 0.72 0.028 1.7

BEAR-U06 — — 0.71 0.78 0.034 3.2

BEAR-U07 — — 1.85 1.95 0.029 1.1

BEAR-U08 — — E0.02 3

 — 0.009 ≤0.5

BEAR-U09 — — 1.74 1.85 0.028 2.8

BEAR-U10 — — 0.47 0.47 0.103 ≤0.4

BEAR-U11 — 0.006 0.07 E0.06 0.010 ≤0.4

1

 The HAL-US is 30 mg/L “as ammonia.” To facilitate comparison to the analytical results, we have converted and reported this HAL-US as 24.7 mg/L “as 

nitrogen.”

2

 The SRL was defined based on the highest concentration detected in the BEAR blank samples.

3

 Total nitrogen concentration in this sample is less than the sum of the filtered nitrogen analytes and falls outside the USGS NWQL acceptance criterion of a 

10 percent relative percent difference. However, the absolute difference is ≤0.02 mg/L, thus, the difference is unlikely to affect interpretation of the data.

Table 10. Nutrients and dissolved organic carbon (DOC) detected in samples collected for the Bear Valley and Selected Hard Rock 

Areas (BEAR) Groundwater Ambient Monitoring and Assessment (GAMA) study unit, California, April to August 2010.—Continued

[The five-digit USGS parameter code below the constituent name is used to uniquely identify a specific constituent or property. Samples from all 38 sites were 

analyzed for nutrients and DOC. Information about the constituents given in table 3G. GAMA site identification number: BEAR-S, Bear Valley study area grid 

site; BEAR-G, Selected Hard Rock Areas study area grid site; BEAR-U, Bear Valley and Selected Hard Rock Areas study unit understanding site. Benchmark 

type, benchmark level, and LRL as of April 1, 2010. Benchmark type: Maximum contaminant level benchmarks are listed as MCL-US if 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 

(USEPA) lifetime health advisory level; MCL-US, USEPA maximum contaminant level. Other abbreviations: USGS, U.S. Geological Survey; LRL, laboratory 

reporting level; E, estimated or having a higher degree of uncertainty; SRL, study reporting level; mg/L, milligrams per liter; na, not available; —, not detected; 

≤, less than or equal to; NWQL, USGS National Water Quality Laboratory]
58 Groundwater-Quality Data in the Bear Valley and Selected Hard Rock Areas Study Unit, 2010

Table 11. Major and minor ions, silica, and total dissolved solids (TDS) detected in samples collected for the Bear Valley and Selected 

Hard Rock Areas (BEAR) Groundwater Ambient Monitoring and Assessment (GAMA) study unit, California, April to August 2010.

[The five-digit USGS parameter code below the constituent name is used to uniquely identify a specific constituent or property. Samples from all 38 sites were 

analyzed. Information about the constituents given in table 3H. GAMA site identification number: BEAR-S, Bear Valley study area grid site; BEAR-G, 

Selected Hard Rock Areas study area grid site; BEAR-U, Bear Valley and Selected Hard Rock Areas study unit understanding site. Benchmark type, benchmark 

level, and LRL as of April 1, 2010. Benchmark type: Maximum contaminant level benchmarks are listed as MCL-US if 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 (CDPH) 

maximum contaminant level; SMCL-CA, CDPH secondary maximum contaminant level. Other abbreviations: LRL, laboratory reporting level; SRL, study 

reporting level; mg/L, milligrams per liter; SiO2, silicon dioxide; E, estimated or having a higher degree of uncertainty; na, not available; —, not detected; ≤, less 

than or equal to; *, concentration is greater than the benchmark level]

GAMA site 

identification 

number

Bromide 

(mg/L) 

(71870) 

Calcium 

(mg/L) 

(00915) 

Chloride 

(mg/L) 

(00940) 

Fluoride 

(mg/L) 

(00950) 

Iodide 

(mg/L) 

(71865)

Magnesium 

(mg/L) 

(00925) 

Potassium 

(mg/L) 

(00935) 

Sodium 

(mg/L) 

(00930) 

Sulfate 

(mg/L) 

(00945) 

Silica 

(as SiO2

) 

(mg/L) 

(00955) 

TDS 

(mg/L) 

(70300)

Benchmark type na na SMCL-CA MCL-CA na na na na SMCL-CA na SMCL-CA

Benchmark level na na 1

 250 (500) 2 na na na na 1 250 (500) na 1 500 (1,000)

[LRL or SRL] [0.02] [0.044] [0.12] [0.06] 2 [0.002] [0.016] [0.064] [0.10] [0.18] [0.058] [10]

BEAR grid sites (27 sites sampled) 

Bear Valley study area (14 grid sites sampled)

BEAR-S01 0.06 50.4 16.4 0.53 0.002 34.1 2.15 19.8 47.2 25.4 345

BEAR-S02 E0.02 32.8 4.5 0.14 — 10.1 1.56 12.7 9.9 23.7 172

BEAR-S03 0.04 39.8 21.3 ≤0.05 E0.001 6.9 2.18 13.1 6.8 23.5 209

BEAR-S04 0.03 2.0 4.3 1.0 0.019 1.4 1.13 81.3 14.4 9.7 220

BEAR-S05 0.03 18.3 5.0 0.37 — 8.0 1.44 21.0 6.0 13.8 149

BEAR-S06 E0.01 67.0 2.8 ≤0.04 — 15.3 1.06 6.3 1.9 21.1 248

BEAR-S07 0.05 82.6 14.1 0.22 E0.001 35.5 3.57 7.3 42.8 19.0 398

BEAR-S08 E0.02 45.5 2.9 0.10 — 18.8 1.88 10.7 8.5 28.5 220

BEAR-S09 0.03 37.2 5.6 0.12 — 17.3 1.58 8.7 15.8 26.8 197

BEAR-S10 0.14 36.8 20.4 2.0 E0.002 7.5 1.98 28.4 17.0 25.8 247

BEAR-S11 0.04 48.0 8.7 0.40 E0.001 18.4 1.58 20.0 12.8 20.6 253

BEAR-S12 0.03 29.7 5.6 *2.8 E0.001 10.9 1.12 41.7 20.6 22.2 239

BEAR-S13 0.05 46.8 8.8 ≤0.06 — 17.6 1.93 11.2 5.3 29.7 224

BEAR-S14 E0.01 37.8 1.54 0.17 — 34.9 2.94 2.8 22.8 15.0 246

Selected Hard Rock Areas study area (13 grid sites sampled)

BEAR-G01 — 32.6 5.3 E0.08 — 1.9 0.54 14.4 2.6 20.0 159

BEAR-G02 0.02 19.8 28.8 ≤0.05 — 2.9 1.21 11.9 4.3 32.8 153

BEAR-G03 E0.01 12.7 6.2 — 0.002 2.8 1.62 7.8 4.3 24.3 98.0

BEAR-G04 E0.01 19.9 3.6 0.10 — 5.6 2.04 10.8 0.85 31.1 150

BEAR-G05 — 23.8 2.8 ≤0.06 — 5.1 2.99 9.1 1.8 18.2 119

BEAR-G06 0.03 49.8 7.3 0.29 E0.001 12.3 2.63 17.9 15.5 30.6 258

BEAR-G07 0.05 42.1 12.3 0.20 0.013 3.3 1.74 24.2 3.0 20.8 209

BEAR-G08 — 46.5 3.9 0.24 — 4.8 1.36 8.1 4.6 32.7 202

BEAR-G09 0.03 38.0 8.1 0.15 0.004 8.4 2.72 19.4 2.1 19.0 187

BEAR-G10 E0.02 55.8 5.8 0.14 E0.001 3.3 0.28 16.5 7.9 16.2 225

BEAR-G11 0.04 19.0 6.5 0.09 — 4.9 2.11 12.2 7.5 32.0 153

BEAR-G12 E0.02 27.4 2.7 0.13 E0.001 2.1 0.91 9.7 2.6 42.7 151

BEAR-G13 0.04 40.2 11.9 0.10 E0.002 14.2 4.23 16.5 3.8 30.3 229
Tables 59

GAMA site 

identification 

number

Bromide 

(mg/L) 

(71870) 

Calcium 

(mg/L) 

(00915) 

Chloride 

(mg/L) 

(00940) 

Fluoride 

(mg/L) 

(00950) 

Iodide 

(mg/L) 

(71865)

Magnesium 

(mg/L) 

(00925) 

Potassium 

(mg/L) 

(00935) 

Sodium 

(mg/L) 

(00930) 

Sulfate 

(mg/L) 

(00945) 

Silica 

(as SiO2

) 

(mg/L) 

(00955) 

TDS 

(mg/L) 

(70300)

Benchmark type na na SMCL-CA MCL-CA na na na na SMCL-CA na SMCL-CA

Benchmark level na na 1

 250 (500) 2 na na na na 1 250 (500) na 1 500 (1,000)

[LRL or SRL] [0.02] [0.044] [0.12] [0.06] 2 [0.002] [0.016] [0.064] [0.10] [0.18] [0.058] [10]

BEAR understanding sites (11 sites sampled)

BEAR-U01 E0.02 40.4 14.5 0.04 — 12.3 3.25 13.2 3.3 18.3 215

BEAR-U02 0.04 50.5 14.3 0.81 E0.001 33.2 2.17 19.1 40.8 25.0 343

BEAR-U03 0.10 41.4 22.1 0.99 E0.002 12.2 2.02 20.8 15.8 27.7 262

BEAR-U04 0.16 30.1 20.4 0.20 E0.002 11.3 5.04 18.0 15.6 19.6 203

BEAR-U05 — 10.2 1.4 0.05 E0.001 0.78 0.36 5.4 1.34 25.2 73.0

BEAR-U06 0.03 15.6 9.4 0.14 0.003 5.3 1.87 11.0 5.7 25.3 123

BEAR-U07 0.06 39.8 15.8 0.13 0.004 12.5 3.46 13.5 12.9 34.3 241

BEAR-U08 0.03 34.3 5.4 1.3 0.008 9.0 2.48 32.0 52.9 14.3 230

BEAR-U09 0.05 71.0 9.8 0.24 0.003 38.7 4.35 8.5 23.9 23.5 374

BEAR-U10 — 8.4 1.7 E0.07 — 0.60 0.73 9.3 0.48 39.9 90.0

BEAR-U11 E0.02 31.6 7.0 0.14 0.004 7.0 2.53 19.9 1.5 16.7 172

1

 The SMCL-CA for chloride, sulfate, and TDS have recommended and upper benchmark values. The upper benchmark value is shown in parentheses.

2

 The SRL was defined based on the highest concentration detected in the BEAR blank samples.

Table 11. Major and minor ions, silica, and total dissolved solids (TDS) detected in samples collected for the Bear Valley and Selected 

Hard Rock Areas (BEAR) Groundwater Ambient Monitoring and Assessment (GAMA) study unit, California, April to August 2010.—

Continued

[The five-digit USGS parameter code below the constituent name is used to uniquely identify a specific constituent or property. Samples from all 38 sites were 

analyzed. Information about the constituents given in table 3H. GAMA site identification number: BEAR-S, Bear Valley study area grid site; BEAR-G, 

Selected Hard Rock Areas study area grid site; BEAR-U, Bear Valley and Selected Hard Rock Areas study unit understanding site. Benchmark type, benchmark 

level, and LRL as of April 1, 2010. Benchmark type: Maximum contaminant level benchmarks are listed as MCL-US if 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 (CDPH) 

maximum contaminant level; SMCL-CA, CDPH secondary maximum contaminant level. Other abbreviations: LRL, laboratory reporting level; SRL, study 

reporting level; mg/L, milligrams per liter; SiO2, silicon dioxide; E, estimated or having a higher degree of uncertainty; na, not available; —, not detected; ≤, less 

than or equal to; *, concentration is greater than the benchmark level]
60 Groundwater-Quality Data in the Bear Valley and Selected Hard Rock Areas Study Unit, 2010

Table 12. Arsenic and iron species detected in samples collected for the Bear Valley and Selected Hard Rock Areas (BEAR) 

Groundwater Ambient Monitoring and Assessment (GAMA) study unit, California, April to August 2010.

[The five-digit USGS parameter code below the constituent name is used to uniquely identify a specific constituent or property. Data in this table was generated 

at the USGS NRP-TML, Boulder, Colorado, using research methods. Information about the constituents given in table 3I. Samples were collected at all 38 sites, 

but only samples with detections are listed. GAMA site identification number: BEAR-S, Bear Valley study area grid site; BEAR-G, Selected Hard Rock Areas 

study area grid site; BEAR-U, Bear Valley and Selected Hard Rock Areas study unit understanding site. Method detection limit, benchmark type, and benchmark 

level as of April 1, 2010. Benchmark type: Maximum contaminant level benchmarks are listed as MCL-US if 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: USGS, U.S. Geological Survey; NRP, USGS National Research Program; TML, Trace Metal Laboratory; MDL, method detection limit; 

na, not available; μg/L, micrograms per liter; *, concentration is greater than the benchmark level; —, not detected]

GAMA site 

identification number

Arsenic 

(total) 

(99033) 

(μg/L)

Arsenic-III 

(99034) 

(μg/L) 

Iron 

(total) 

(01046) 

(μg/L) 

Iron-II 

(01047) 

(μg/L) 

Benchmark type MCL-US na SMCL-CA na

Benchmark level 10 na 300 na

[MDL] [0.5] [1] [2] [2]

BEAR grid sites (27 sites sampled)

Bear Valley study area (14 grid sites sampled)

BEAR-S01 0.9 — — —

BEAR-S02 1.0 — — —

BEAR-S03 — — 2.4 —

BEAR-S04 *29.5 — 5.6 2.0

BEAR-S05 1.3 — — —

BEAR-S07 — — 2.1 —

BEAR-S10 — — 4.7 2.9

Selected Hard Rock Areas study area (13 grid sites sampled)

BEAR-G01 — — 6.6 4.2

BEAR-G02 — — 11.8 8.3

BEAR-G03 — — 2.0 —

BEAR-G04 — — *384 330

BEAR-G05 — — *445 308

BEAR-G09 — — 2.5 —

BEAR-G10 — — 2.6 —

BEAR-G12 — — 11.4 8.3

BEAR understanding sites (11 sites sampled)

BEAR-U04 — — 7.8 4.4

BEAR-U05 — — 23.0 16.8

BEAR-U06 — — 21.3 12.9

BEAR-U08 4.4 3.7 105 87.3

BEAR-U10 — — 43.7 35.5

BEAR-U11 — — *516 203
Tables 61

Table 13. Isotopic tracers detected in samples collected for the Bear Valley and Selected Hard Rock Areas (BEAR) Groundwater 

Ambient Monitoring and Assessment (GAMA) study unit, California, April to August 2010.

[The five-digit USGS parameter code below the constituent name is used to uniquely identify a specific constituent or property. Information about the 

constituents given in table 3J. Samples from all 38 sites were analyzed, with the exception of the stable isotopes of carbon in dissolved inorganic carbon 

and carbon-14 abundance (30 sites). Stable isotope ratios of hydrogen, oxygen, nitrogen, and carbon 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. Isotopic ratios of strontium are reported 

as the abundance of atoms of the heavier isotope to the lighter isotope of the element. Results for stable isotopes of boron in water analyzed by USGS 

NRP Metals Isotope Research Laboratory, Menlo Park, California, were not completed in time for inclusion in this report; results will be presented in a 

subsequent publication. GAMA site identification number: BEAR-S, Bear Valley study area grid site; BEAR-G, Selected Hard Rock Areas study area grid 

site; BEAR-U, Bear Valley and Selected Hard Rock Areas study unit understanding site. Benchmark type and benchmark level as of April 1, 2010. Other 

abbreviations: USGS, U.S. Geological Survey; H, hydrogen; O, oxygen; N, nitrogen; Sr, strontium; C, carbon; na, not available; NRP, USGS National Research 

Program]

GAMA site 

identification 

number

d2H in water 

(per mil) 

(82082)

d18O in water 

(per mil) 

(82085)

d15N in nitrate 

(per mil) 

(82690)

d18O in nitrate 

(per mil) 

(63041)

Strontium isotope ratio 

(d87Sr/d86Sr) 

(atom ratio) 

(75978)

d13C 

(per mil) 

(82081)

Carbon-14 

(percent modern) 

(49933)

Benchmark type na na na na na na na

Benchmark level na na na na na na na

BEAR grid sites (27 sites sampled)

Bear Valley study area (14 grid sites sampled)

BEAR-S01 –80.9 –11.20 10.23 2.31 0.71761 –13.61 78.58

BEAR-S02 –80.8 –11.54 7.99 –3.03 0.71437 –14.14 76.35

BEAR-S03 –75.8 –10.83 8.00 1.48 0.71250 –15.90 102.2

BEAR-S04 –83.4 –11.52 13.49 0.80 0.71096 –8.08 5.540

BEAR-S05 –83.9 –11.84 11.4 –2.87 0.71992 –12.16 37.13

BEAR-S06 –84.5 –11.90 5.08 –2.87 0.71292 –11.56 74.96

BEAR-S07 –73.9 –10.27 7.57 0.19 0.71256 –13.31 94.87

BEAR-S08 –88.3 –12.32 4.23 –5.60 0.71979 –11.89 69.58

BEAR-S09 –89.5 –12.44 6.65 –2.38 0.72045 –12.67 82.24

BEAR-S10 –93.3 –12.54 7.11 –3.27 0.74468 na 1 na 1

BEAR-S11 –85.6 –11.95 8.54 0.08 0.72429 na 1 na 1

BEAR-S12 –87.6 –12.19 6.92 –4.90 0.72179 –12.33 68.37

BEAR-S13 –85.5 –12.05 8.72 0.07 0.72063 –12.83 73.97

BEAR-S14 –87.1 –12.37 1.43 1.83 0.71863 na 1 na 1

Selected Hard Rock Areas study area (13 grid sites sampled)

BEAR-G01 –68.6 –10.16 3.35 1.77 0.71085 –18.07 76.82

BEAR-G02 –58.7 –9.05 4.49 9.94 0.71088 –20.36 108.1

BEAR-G03 –57.3 –8.90 2.33 3.16 0.71101 –20.39 105.8

BEAR-G04 –68.1 –10.0 0.02 0.06 0.71083 –18.30 98.42

BEAR-G05 –64.7 –9.86 1.20 4.26 0.71096 –17.35 86.96

BEAR-G06 –62.6 –9.31 1.63 4.95 0.71046 –16.42 88.34

BEAR-G07 –59.0 –9.04 10.71 3.27 0.71040 –17.45 78.03

BEAR-G08 –60.9 –9.46 2.72 3.77 0.71067 na 1 na 1

BEAR-G09 –66.0 –9.97 5.25 6.43 0.71007 –17.35 71.66

BEAR-G10 –71.2 –10.7 6.91 2.29 0.71080 –15.91 80.07

BEAR-G11 –54.2 –8.73 –0.39 10.42 0.71416 –18.92 99.33

BEAR-G12 –71.5 –10.60 3.76 2.62 0.71093 na 1 na 1

BEAR-G13 –66.4 –9.97 7.01 4.42 0.71045 –18.18 95.12
62 Groundwater-Quality Data in the Bear Valley and Selected Hard Rock Areas Study Unit, 2010

GAMA site 

identification 

number

d2H in water 

(per mil) 

(82082)

d18O in water 

(per mil) 

(82085)

d15N in nitrate 

(per mil) 

(82690)

d18O in nitrate 

(per mil) 

(63041)

Strontium isotope ratio 

(d87Sr/d86Sr) 

(atom ratio) 

(75978)

d13C 

(per mil) 

(82081)

Carbon-14 

(percent modern) 

(49933)

Benchmark type na na na na na na na

Benchmark level na na na na na na na

BEAR understanding sites (11 sites sampled)

BEAR-U01 –65.4 –9.72 7.23 3.69 0.71124 na 1 na 1

BEAR-U02 –83.0 –11.22 6.36 0.72 0.71337 –10.64 82.87

BEAR-U03 –87.7 –11.49 7.60 –2.40 0.73860 –14.56 97.06

BEAR-U04 –99.3 –13.55 6.21 –1.58 0.77499 na 1 na 1

BEAR-U05 –68.5 –10.31 5.52 2.74 0.71069 na 1 na 1

BEAR-U06 –60.3 –8.07 4.47 2.22 0.72344 –17.31 106.8

BEAR-U07 –49.6 –5.72 1.56 1.84 0.71187 –16.13 102.5

BEAR-U08 –81.0 –11.57 18.67 19.66 0.71553 –11.11 51.92

BEAR-U09 –55.3 –6.72 4.78 3.63 0.71235 –12.44 89.50

BEAR-U10 –69.8 –10.58 4.68 6.65 0.71022 –19.66 108.5

BEAR-U11 –65.1 –10.02 11.71 7.14 0.70994 –17.77 67.48

1

 Sample was broken during shipment to the laboratory.

Table 13. Isotopic tracers detected in samples collected for the Bear Valley and Selected Hard Rock Areas (BEAR) Groundwater 

Ambient Monitoring and Assessment (GAMA) study unit, California, April to August 2010.—Continued

[The five-digit USGS parameter code below the constituent name is used to uniquely identify a specific constituent or property. Information about the 

constituents given in table 3J. Samples from all 38 sites were analyzed, with the exception of the stable isotopes of carbon in dissolved inorganic carbon 

and carbon-14 abundance (30 sites). Stable isotope ratios of hydrogen, oxygen, nitrogen, and carbon 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. Isotopic ratios of strontium are reported 

as the abundance of atoms of the heavier isotope to the lighter isotope of the element. Results for stable isotopes of boron in water analyzed by USGS 

NRP Metals Isotope Research Laboratory, Menlo Park, California, were not completed in time for inclusion in this report; results will be presented in a 

subsequent publication. GAMA site identification number: BEAR-S, Bear Valley study area grid site; BEAR-G, Selected Hard Rock Areas study area grid 

site; BEAR-U, Bear Valley and Selected Hard Rock Areas study unit understanding site. Benchmark type and benchmark level as of April 1, 2010. Other 

abbreviations: USGS, U.S. Geological Survey; H, hydrogen; O, oxygen; N, nitrogen; Sr, strontium; C, carbon; na, not available; NRP, USGS National Research 

Program]
Tables 63

Table 14. Uranium and other radioactive constituents detected in samples collected for the Bear Valley and Selected Hard Rock Areas 

(BEAR) Groundwater Ambient Monitoring and Assessment (GAMA) study unit, California, April to August 2010.

[The five-digit number in parentheses below the constituent name is the USGS parameter code used to uniquely identify a specific constituent or property. 

Samples from all 38 sites were analyzed. Information about the constituents given in table 3J. Tritium activities less than the sample-specific critical level (ssLC) 

are reported as non-detections (—). The reporting level (RL) for uranium is an LRL. GAMA site identification number: BEAR-S, Bear Valley study area grid 

site; BEAR-G, Selected Hard Rock Areas study area grid site; BEAR-U, Bear Valley and Selected Hard Rock Areas study unit understanding site. Benchmark 

type and benchmark level as of April 1, 2010. Benchmark type: Maximum contaminant level benchmarks are listed as MCL-US if 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. Other abbreviations: USGS, U.S. Geological Survey; 

RL, reporting level; CSU, combined standard uncertainty; pCi/L, picocurie per liter; μg/L, micrograms per liter; ±, plus or minus; *, concentration is greater than 

the benchmark level]

GAMA site 

identification 

number

Radon-222 

(pCi/L) 

(82303)

Tritium 

(pCi/L) 

(07000)

Uranium 

(μg/L) 

(22703)

GAMA site 

identification 

number

Radon-222 

(pCi/L) 

(82303)

Tritium 

(pCi/L) 

(07000)

Uranium 

(μg/L) 

(22703)

Benchmark 

type

 MCL-US 

(Proposed) MCL-CA MCL-US Benchmark 

type

 MCL-US 

(Proposed) MCL-CA MCL-US

Benchmark 

level 4,000 20,000 30 Benchmark level 4,000 20,000 30

[RL] Result ± CSU ssLC Result ± CSU ssLC [0.008] [RL] Result ± CSU ssLC Result ± CSU ssLC [0.008]

BEAR grid sites (27 sites sampled) BEAR grid sites (27 sites sampled)—Continued

Bear Valley study area (14 grid sites sampled) Selected Hard Rock Areas study area (13 grid sites sampled)—Continued

BEAR-S01 320 ± 22 14 5.5 ± 0.35 0.32 2.7 BEAR-G06 2,660 ± 150 12 3.1 ± 0.32 0.32 16.7

BEAR-S02 280 ± 21 14 2.1 ± 0.32 0.32 1.7 BEAR-G07 *19,300 ± 1,000 12 4.0 ± 0.32 0.32 *57.0

BEAR-S03 1,580 ± 89 16 8.9 ± 0.41 0.32 0.93 BEAR-G08 *16,300 ± 870 12 3.4 ± 0.32 0.32 *61.8

BEAR-S04 330 ± 24 16 1.1 ± 0.32 0.32 3.1 BEAR-G09 *4,300 ± 230 12 2.8 ± 0.34 0.32 17.5

BEAR-S05 300 ± 25 22 — 0.32 1.2 BEAR-G10 *7,100 ± 380 13 6.5 ± 0.54 0.48 25.4

BEAR-S06 232 ± 17 12 0.7 ± 0.32 0.32 0.24 BEAR-G11 3,040 ± 170 11 8.4 ± 0.48 0.38 5.5

BEAR-S07 151 ± 13 12 7.4 ± 0.38 0.32 0.80 BEAR-G12 *10,600 ± 570 11 8.0 ± 0.51 0.41 18.6

BEAR-S08 490 ± 33 18 — 0.32 0.86 BEAR-G13 2,510 ± 140 11 4.6 ± 0.48 0.41 18.2

BEAR-S09 2,080 ± 120 17 1.7 ± 0.32 0.32 0.86 BEAR understanding sites (11 sites sampled) 

BEAR-S10 3,900 ± 210 14 3.0 ± 0.32 0.32 7.7 BEAR-U01 *7,400 ± 400 16 6.2 ± 0.41 0.32 *43.7

BEAR-U02 290 ± 25 22 3.2 ± 0.32 0.32 2.7

BEAR-S11 400 ± 26 13 3.6 ± 0.32 0.32 3.8 BEAR-U03 2,460 ± 140 14 7.3 ± 0.38 0.32 7.0

BEAR-S12 1,600 ± 90 13 — 0.32 2.2 BEAR-U04 *4,600 ± 250 14 0.6 ± 0.32 0.32 11.0

BEAR-S13 2,250 ± 120 12 1.5 ± 0.32 0.32 1.8 BEAR-U05 *7,000 ± 380 13 11.6 ± 0.57 0.41 1.9

BEAR-S14 206 ± 16 11 9.0 ± 0.41 0.32 0.57

Selected Hard Rock Areas study area (13 grid sites sampled) BEAR-U06 2,920 ± 160 13 13.8 ± 0.64 0.41 0.20

BEAR-G01 *10,300 ± 550 15 5.5 ± 0.41 0.32 *87.2 BEAR-U07 570 ± 35 13 10.6 ± 0.57 0.41 0.58

BEAR-G02 *7,800 ± 420 15 9.8 ± 0.48 0.32 1.5 BEAR-U08 1,670 ± 92 11 — 0.38 0.14

BEAR-G03 3,260 ± 180 16 14.0 ± 0.57 0.32 0.47 BEAR-U09 950 ± 54 11 10.4 ± 0.57 0.41 1.8

BEAR-G04 *22,200 ± 1,200 14 6.1 ± 0.41 0.32 13.8 BEAR-U10 *8,000 ± 430 13 9.2 ± 0.54 0.41 1.4

BEAR-G05 *6,900 ± 370 14 6.2 ± 0.35 0.32 19.8 BEAR-U11 *4,600 ± 250 12 1.0 ± 0.32 0.32 26.7
64 Groundwater-Quality Data in the Bear Valley and Selected Hard Rock Areas Study Unit, 2010

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 

site and to minimize the potential for contamination of the 

samples or bias in the data. Procedures used to collect and 

assess QC data, and the results of the QC assessments also are 

discussed. 

In the BEAR study unit, groundwater samples were 

collected and QA/QC procedures were implemented by 

using standard and modified USGS protocols from the NFM 

(U.S. Geological Survey, variously dated; Wilde and others, 

1999, 2004) and the NAWQA Program (Koterba and others, 

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

laboratory used to analyze samples for this study, is described 

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

Sample Collection and Analysis

Samples were collected from two types of sites: 

production wells and springs (“springs” in this study unit 

include horizontal wells). Sites classified as production 

wells are vertically drilled into the ground and have pumps 

that bring the groundwater from the aquifer system to land 

surface and into a distribution system. Sites were classified 

as springs if groundwater discharged naturally at land surface 

from the aquifer without a drilled hole or if the well was 

drilled horizontally. A few springs had pumps to transport 

groundwater from the spring to a storage tank at a higher 

elevation. 

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 by using 

Teflon® tubing with brass and stainless-steel fittings attached 

to a sampling point (usually a hose-bib fitting) on the well 

discharge pipe as close to the wellhead as possible. The 

sampling point was located upstream from water-storage tanks 

or wellhead treatment systems (if present). If a chlorinating 

system was attached to the well, the chlorinator was shut 

off, when possible, before the well was purged and sampled, 

in order to clear all chlorine out of the system. The absence 

of free chlorine was verified by using a Hach® field test kit. 

Samples were collected inside an enclosed chamber located 

inside a mobile laboratory and connected to the wellhead 

by a 10–50 ft length of the Teflon® tubing (Lane and others, 

2003). All fittings and lengths of Teflon® tubing were cleaned 

between samples (Wilde, 2004). All of the springs had 

sampling points on discharge pipes similar to the sampling 

points found on wells. Field water-quality indicators were 

measured and samples were collected by using the same 

protocols as used for wells.

For the field measurements, groundwater was pumped 

through a flow-through chamber (attached to the sampling 

point) fitted with a multi-probe meter that simultaneously 

measures the field water-quality indicators—dissolved oxygen, 

temperature, pH, and specific conductance. Turbidity was 

measured in the field with a calibrated turbidity meter. Field 

measurements were made in accordance with protocols in the 

USGS NFM (Radtke and others, 2005; Wilde and Radtke, 

2005; Lewis, 2006; Wilde, 2006; Wilde and others, 2006). 

All sensors on the multi-probe meter were calibrated daily. 

Measured turbidity, dissolved oxygen, temperature, pH, 

and specific conductance values were recorded at 5-minute 

(min) intervals, and when these values remained stable for 

a minimum of 30 min, samples for laboratory analyses then 

were collected. 

Field measurements and instrument calibrations were 

recorded on field record sheets and electronically in the 

Personal Computer Field Form (PCFF) program on field 

laptop computers. Analytical service requests for the NWQL 

were generated by PCFF, whereas analytical service requests 

for non-NWQL analysis were entered into laboratory-specific 

spreadsheets. Information from PCFF was uploaded directly 

into the USGS NWIS database at the end of the week of 

sample collection. 

Prior to sample collection, polyethylene sample bottles 

were pre-rinsed three times with deionized water and then 

once with native sample water before sample collection. 

Samples requiring acidification were acidified to a pH of 

between 2 and 1 with the appropriate acids by using ampoules 

of certified, traceable concentrated acids obtained from the 

NWQL.

Samples for the analysis of VOCs were collected in three 

40-milliliter (mL) sample vials that were purged with three 

vial volumes of unfiltered groundwater before bottom-filling 

to eliminate atmospheric contamination. One to one (1:1) 

hydrochloric acid to water (HCl/H2

O) solution was added as 

a preservative to the VOC samples. Samples for analysis of 

1,2,3-TCP were collected by top-filling two 40-mL sample 

vials that were pre-treated with 0.5 mL 6-Normal (N) HCl 

acid (as a preservative), at Weck Laboratories, Inc. (Weck), 

City of Industry, California. 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 of unfiltered 

groundwater through a 0.20-micrometer (μm) pore-size 

Corning® syringe-tip disk filter into a sterilized 125-mL 

bottle. Samples for the analysis of tritium 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 unfiltered groundwater. Samples 

for analysis of stable isotopes of hydrogen and oxygen in 

water were collected in a 60-mL clear glass bottle filled with 

unfiltered groundwater, sealed with a conical cap, and secured 

with electrical tape to prevent leakage and evaporation.
Appendix 65

Samples were collected in 1-L baked amber glass bottles 

for the analyses of pesticides and pesticide degradates, 

pharmaceutical compounds, WICs, and NDMA. Samples 

for analyses of pesticides and pesticide degradates, 

pharmaceutical compounds, and WICs were filtered through a 

0.7-μm nominal pore-size glass fiber filter during collection, 

whereas the samples for NDMA analysis were filtered at 

Weck prior to analysis. NDMA sample bottles, treated 

with 0.05 grams (g) of sodium thiosulfate (Na2S2O3) (as a 

preservative), were provided by Weck.

Groundwater samples for trace element, major and 

minor ion, silica, and TDS analyses required filling one 

250-mL polyethylene bottle with unfiltered groundwater 

and one 500-mL and one 250-mL polyethylene bottle with 

filtered groundwater (Wilde and others, 2004). Filtration 

was done by using a 0.45-μm pore-size PALL® unvented 

capsule filter that was pre-rinsed with 2 L of deionized water 

and then rinsed with 1 L of groundwater prior to sampling. 

The 250-mL filtered sample then was preserved with 7.5-N 

nitric acid. Samples to be analyzed for nutrients and stable 

isotopes of nitrogen and oxygen in dissolved nitrate each were 

filtered into 125-mL brown polyethylene bottles. Samples 

for analyses of arsenic and iron species were filtered into a 

250-mL polyethylene bottle that was covered with tape to 

prevent light exposure and preserved with 6-N hydrochloric 

acid. Samples for analyses of stable isotopes of boron in water 

and isotopic ratios of strontium in water were filtered into one 

250-mL polyethylene bottle and secured with electrical tape 

to prevent leakage and evaporation. Samples for analyses of 

stable isotopes of carbon in dissolved inorganic carbon and 

carbon-14 abundance were bottom-filled into 500-mL glass 

bottles that first were overfilled with three bottle volumes 

of filtered groundwater. These samples had no headspace 

and were sealed with conical caps to avoid atmospheric 

contamination. Samples for field alkalinity titrations were 

collected by filtering groundwater into a 500-mL polyethylene 

bottle.

Samples for analysis of DOC were collected from the 

hose bib at the wellhead by using a Teflon® filtration apparatus 

attached to a foot-long length of Teflon® tubing. For each 

sample, 100 mL of groundwater and (or) certified inorganicfree blank water was first filtered to waste through the baked 

0.7-μm nominal pore-size glass-fiber filter, then 100 mL of 

groundwater was filtered into a 125-mL baked amber glass 

bottle (Wilde and others, 2004). Each sample then was 

preserved immediately by lowering the pH to between 2 and 1 

with 4.5-N sulfuric acid.

For the collection of groundwater for analysis of radon222, a stainless-steel and Teflon® valve assembly was attached 

to the sampling port at the wellhead (Wilde and others, 2004). 

The valve was closed partially to create back pressure, and 

a 10-mL groundwater sample was taken through a Teflon®

septum on the valve assembly by using a glass syringe 

affixed with a stainless-steel needle. The sample was then 

injected into a 25-mL vial partially filled with a scintillation 

mixture (mineral oil) and shaken. The vial then was placed 

in an insulated cardboard tube to protect the sample during 

shipping.

Dissolved noble gases were collected in 3⁄8-inch-diameter 

copper tubes by using reinforced nylon tubing connected 

to the hose bib at the wellhead. Groundwater was flushed 

through the tubing to dislodge any bubbles before the 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 dissolved noble gases (Weiss, 

1968). 

Field alkalinity was measured in the mobile laboratory at 

the field site. Alkalinity was measured on filtered groundwater 

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–) were automatically 

calculated from the titration data by using the advanced 

speciation method (http://or.water.usgs.gov/alk/methods.html) 

with pK1 = 6.35, pK2 = 10.33, and pKW = 14. Concentrations 

of HCO3

–

 and CO3

2– also were calculated from the laboratory 

alkalinity and laboratory pH measurements. 

Temperature-sensitive samples were stored on ice prior 

to and during daily shipping to the various laboratories. 

The non-temperature- or non-time-sensitive samples for 

tritium, stable isotopes of hydrogen and oxygen in water, 

stable isotopes of boron in water, isotopic ratios of strontium 

in water, and dissolved noble gases were shipped monthly. 

Temperature- or time-sensitive samples for VOCs, pesticides 

and pesticide degradates, pharmaceutical compounds, WICs, 

perchlorate, NDMA, 1,2,3-TCP, trace elements, nutrients, 

DOC, major and minor ions, silica, and TDS were shipped 

daily. The temperature-sensitive samples for arsenic and iron 

species were stored on ice and shipped weekly. Samples for 

stable isotopes of nitrogen and oxygen in dissolved nitrate 

and stable isotopes of carbon in dissolved inorganic carbon 

and carbon-14 abundance were stored on ice, archived in 

a laboratory refrigerator and (or) freezer, and shipped after 

results for nitrate and alkalinity were received from the 

NWQL.

Eight laboratories performed chemical analyses for 

this study (table A1), although most of the analyses were 

performed at the NWQL or by laboratories contracted by 

the NWQL. The NWQL maintains a rigorous QA program 

(Pirkey and Glodt, 1998; Maloney, 2005). Laboratory QC 

samples, including method blanks, continuing calibration 

verification standards, standard reference samples, reagent 

spikes, external certified reference materials, and external 

blind proficiency samples, are analyzed regularly. Method 

detection limits are tested continuously, and laboratory 

reporting levels are updated accordingly. NWQL maintains 

National Environmental Laboratory Accreditation Program 

(NELAP) and other certifications (http://nwql.usgs.gov/

Public/Performance/publiclabcertcoverpage.html). In addition, 

the USGS Branch of Quality Systems (BQS) maintains 

independent oversight of QA at the NWQL and laboratories 

contracted by the NWQL. The BQS also runs the National 

Field Quality Assurance Program (NFQA) that includes 
66 Groundwater-Quality Data in the Bear Valley and Selected Hard Rock Areas Study Unit, 2010

annual testing of all USGS field personnel for proficiency 

in making field water-quality measurements (http://qadata.

cr.usgs.gov/nfqa/). Results for analyses made at the NWQL 

or by laboratories contracted by the NWQL are uploaded 

directly into the USGS NWIS database. Results of analyses 

made at other laboratories are compiled in a project database 

and uploaded from there into the USGS NWIS database. Some 

laboratory QC data are stored in the USGS NWIS database 

also.

Data Reporting

Laboratory Reporting Conventions

The USGS NWQL uses different conventions for 

reporting results for organic, inorganic, and radioactive 

constituents. The USGS NWQL used the LRL and long-term 

method detection level (LT-MDL) for reporting analytical 

results for organic and inorganic constituents (note that the 

reporting convention for inorganic constituents was changed 

in October 2010, after samples from the BEAR study unit 

were analyzed, to a reporting convention that only uses 

the LT-MDL). 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 USGS NWQL updates LRL values 

regularly, and the values listed in this report were in effect 

during the period that groundwater samples from the BEAR 

study unit were analyzed (April to August 2010). The LRL 

usually is set at two times the LT-MDL. The LT-MDL is 

derived from the standard deviation of at least 24 method 

detection level (MDL) determinations made over an extended 

period of time. The MDL is the minimum concentration of a 

substance that can be measured and reported with 99-percent 

confidence that the concentration is greater than zero (at the 

MDL there is less than a 1-percent chance of a false positive). 

LT-MDLs continually are monitored and updated (Childress 

and others, 1999; U.S. Environmental Protection Agency, 

2002). 

Concentrations between the LRL and the LT-MDL are 

reported as having a higher degree of uncertainty (coded by 

the letter “E” preceding the values in the tables and text). For 

inorganic constituents, concentrations less than the LT-MDL 

are reported as non-detections with a dash (–) in the data 

tables. For organic constituents analyzed with information-rich 

methods, detections less than the LT-MDL have high certainty 

of presence, but the precise concentration is uncertain. These 

values are also E-coded. Information-rich methods are those 

that utilize gas chromatography or high-performance liquid 

chromatography (HPLC) with mass spectrometry detection, 

such as those methods used to analyze VOCs, pesticides and 

pesticide degradates, and WICs. Compounds are identified 

by presence of characteristic fragmentation patterns in their 

mass spectra in addition to being quantified by measurement 

of peak areas at their associated chromatographic retention 

times. E-coded values also may result from detections outside 

the range of calibration standards, from detections that did not 

meet all laboratory QC criteria, and from samples that were 

diluted prior to analysis (Childress and others, 1999).

Some constituents in this study are reported by using 

minimum reporting levels (MRLs) or method uncertainties 

(MU). The MRL is the smallest measurable concentration of 

a constituent that may be reliably reported by using a given 

analytical method (Timme, 1995). The MU generally indicates 

the precision of a particular analytical measurement; it gives a 

range of values wherein the true value will be found. 

Results for most constituents are given by using the LRL, 

MDL, or MRL values provided by the analyzing laboratories. 

Results for some organic and inorganic constituents are 

presented with raised SRLs derived from assessing results 

from QC samples associated with groundwater samples 

collected as part of the GAMA-PBP (see the appendix section 

titled “Detections in Blank Samples and Application of 

SRLs”). 

The methods used for analysis of the radioactive 

constituents (radon-222 and tritium) measure activities by 

counting techniques (table A1). Activity often is used instead 

of concentration for reporting the presence of radioactive 

constituents. Activity of these constituents in groundwater 

is measured in units of picocuries per liter, where 1 pCi/L 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 reporting limits for radon-222 and tritium are based 

on sample-specific critical levels (ssLC) (McCurdy and others, 

2008). The critical level is analogous to the LT-MDL used for 

reporting analytical results for organic and non-radioactive 

inorganic constituents. Here, the critical level is defined as 

the minimum measured activity that indicates a positive 

detection of the radionuclide in the sample with less than a 

5-percent probability of a false positive detection. Samplespecific critical levels are used for radioactive measurements 

because the critical level is sensitive to sample size and 

sample yield during analytical processing and is dependent on 

instrument background, on counting times for the sample and 

background, and on the characteristics of the instrument being 

used and the nuclide being measured. An ssLC is calculated 

for each sample, and the measured activity in the sample is 

compared to the ssLC associated with that sample. Measured 

activities less than the ssLC are reported as non-detections with 

a dash (–) in the data tables.

The analytical uncertainties associated with measurement 

of activities also are sensitive to sample-specific parameters, 

including sample size, sample yield during analytical 

processing, and time elapsed between sample collection and 

various steps in the analytical procedure, as well as parameters 

associated with the instrumentation. Therefore, measured 

activities of radioactive constituents are reported with samplespecific combined standard uncertainties (CSU). The CSU is 

reported at the 68-percent confidence level (1-sigma).
Appendix 67

Stable isotopic compositions of hydrogen, oxygen, 

nitrogen, boron, and carbon are reported as relative isotope 

ratios in units of per mil by using the standard delta notation 

(Coplen and others, 2002):

 x per mil i sample

reference

E

R

R = −

















1 1 000, , (A1)

where 

i is the atomic mass of the heavier isotope of 

the element;

E is the element (H for hydrogen, O for oxygen, 

N for nitrogen, B for boron, C for carbon);

Rsample is the ratio of the abundance of the heavier 

isotope of the element (2H, 18O, 15N, 11B, 13C) to the lighter isotope of the element 

(1H, 16O, 14N, 10B, 12C) in the sample; and

Rreference is the ratio of the abundance of the heavier 

isotope of the element to the lighter isotope 

of the element in the reference material.

The reference material for oxygen and hydrogen is 

Vienna Standard Mean Ocean Water (VSMOW), which is 

assigned δ18O and δ2H values of 0 per mil (note that δ2H is 

sometimes written as δD because the common name of the 

heavier isotope of hydrogen, hydrogen-2, is deuterium). The 

reference material for nitrogen is atmospheric nitrogen gas, 

which is assigned a d15N value of 0 per mil. The reference 

material for boron is the National Institute of Standards and 

Technology (NIST) reference material SRM 951 boric acid, 

which is assigned a δ11B value of 0 per mil (Coplen and others, 

2002). The reference material for carbon is Vienna Pee Dee 

Belemnite (VPDB), which is assigned a δ13C value of 0 per 

mil. 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. Isotopic ratios of strontium in water are presented 

as the abundance of atoms of the heavier isotope (87Sr) to the 

lighter isotope (86Sr) of the element.

Constituents Determined by Multiple Methods or 

Laboratories

Twenty-one constituents targeted in this study were 

measured by more than one analytical method 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 (http://wwwnwql.cr.usgs.gov/

dyn.shtml?Preferred_method_selection_procedure). 

The water-quality indicators—alkalinity, pH, and specific 

conductance—were measured in the field and at the NWQL. 

The field measurements are the preferred method for all 

three constituents; however, both measurements are reported 

(table 4). Field values are generally preferred because field 

conditions are considered more representative of groundwater 

conditions (Hem, 1985).

1,4-Dichlorobenzene, isopropylbenzene, naphthalene, 

PCE, and bromoform (tribromomethane) each appear on the 

following NWQL analytical schedules: VOCs (Schedule 

2020; table 3A) and WICs (Schedule 1433; table 3D). For 

constituents collected on Schedules 2020 and 1433, the 

preferred method was Schedule 2020. 

Carbaryl, chlorpyrifos, diazinon, metalaxyl, metolachlor, 

and prometon each appear on the following NWQL analytical 

schedules: pesticides and pesticide degradates (Schedule 2033; 

table 3B) and WICs (Schedule 1433; table 3D). For 

constituents collected on Schedules 2033 and 1433, the 

preferred method was Schedule 2033.

Caffeine and cotinine each appear on the following 

NWQL analytical schedules: pharmaceutical compounds 

(Schedule 2080; table 3C) and WICs (Schedule 1433; 

table 3D). For constituents collected on both Schedules 2080 

and 1433, the preferred method was Schedule 2080.

1,2,3-TCP was measured at the NWQL (reporting level 

was an LRL of 0.12 μg/L) and Weck (reporting level was 

an MRL of 0.005 μg/L) (tables 3A, E). 1,2,3-TCP was not 

detected in any samples analyzed by either method, so this 

compound is not listed in tables 5 and 8. 

For total arsenic and total iron concentrations, the 

approved method, Schedule 1948 (table 3F), used by the 

NWQL is preferred over the research methods used by 

the USGS NRP-TML (table 3I); however, results from 

both measurements are reported (tables 9 and 12). The 

concentrations of arsenic and iron measured by the USGS 

NRP-TML only are used to calculate ratios of redox species.

For example,

Fe III Fe T Fe II ( ) () ( ) = - , (A2)

where 

Fe(T) is the total iron concentration (measured),

Fe(II) is the concentration of ferrous iron 

(measured), and

Fe(III) is the concentration of ferric iron (calculated).

Tritium also was measured at two laboratories: LLNL and 

USGS Stable Isotope and Tritium Laboratory, Menlo Park, 

California (SITL) (table 3J). Only tritium data from the SITL 

were available for reporting at the time of this publication 

(table 14). 

Quality-Assurance and Quality-Control Methods 

and Results

The purpose of QA/QC is to identify which data best 

represent groundwater conditions and which may have been 

affected by contamination or bias during sample collection, 

processing, storage, transportation, and (or) laboratory 

analysis. Four types of QC measurements were evaluated in 

this study: (1) blank samples were collected to assess positive 
68 Groundwater-Quality Data in the Bear Valley and Selected Hard Rock Areas Study Unit, 2010

bias as a result of contamination during sample handling 

or analysis, (2) replicate samples were collected to assess 

variability, (3) matrix-spike tests were done to assess positive 

or negative bias for organic constituents, and (4) surrogate 

compounds were added to samples analyzed for organic 

constituents to assess potential bias from laboratory analytical 

methods. 

Blank Samples

The primary purposes of collecting blank samples are 

to evaluate the magnitude of potential contamination of 

samples with compounds of interest during sample handling 

or analysis, and to identify and mitigate the sources of sample 

contamination.

Methods of Blank Sample Collection and Analysis

Blank samples were collected by using blank water 

certified by the NWQL to contain less than the reporting levels 

for selected constituents investigated in the study (http://

wwwnwql.cr.usgs.gov/USGS/OBW/obw.html). Nitrogenpurged, organic-free blank water was used for blanks of 

organic constituents, and inorganic-free water was used for 

blanks of inorganic constituents. Three types of blanks were 

collected: field blank samples, source-solution blank samples, 

and equipment blank samples.

Field blank samples were collected to assess whether 

contamination of samples was introduced during collection, 

processing, transport, and analysis. To collect field blanks, 

blank water either was pumped or poured through the 

sampling equipment (fittings and tubing) used to collect 

groundwater samples, then processed and transported by 

using the same protocols used for the groundwater samples. 

Typically, 12 L of blank water were pumped through the 

sampling equipment before each field blank was collected. 

Field blanks were analyzed for VOCs, pesticides and pesticide 

degradates, pharmaceutical compounds, WICs, perchlorate, 

1,2,3-TCP, NDMA, trace elements, nutrients, DOC, major and 

minor ions, silica, TDS, and arsenic and iron species. 

A source-solution blank sample was collected at the 

beginning of a study or when using a new lot of blank water 

to assess potential contamination of samples during transport 

and analysis and potential contamination of the certified blank 

water obtained from the NWQL. Source-solution blanks 

were collected by pouring blank water directly into sample 

containers that were preserved, stored, shipped, and analyzed 

in the same manner as the groundwater samples. The sourcesolution blank sample was analyzed for VOCs, pharmaceutical 

compounds, WICs, perchlorate, NDMA, 1,2,3-TCP, trace 

elements, major and minor ions, silica, and TDS. 

An equipment blank sample was collected at the 

USGS San Diego Projects Office before the start of the 

sampling period to assess whether the sampling equipment 

was sufficiently clean (after a long period of storage) to be 

used for collection of groundwater samples in the BEAR 

study unit. The equipment blank sample was analyzed for 

VOCs, pesticides and pesticide degradates, pharmaceutical 

compounds, WICs, perchlorate, 1,2,3-TCP, NDMA, trace 

elements, nutrients, DOC, major and minor ions, silica, and 

TDS.

Blank samples were not collected for radon because 

the laboratory determines an ssLC value for each sample. 

The ssLC is the minimum measured value that indicates a 

non-zero amount of the radionuclide in the sample. Stated 

another way, it is the amount of the radionuclide that is 

statistically significantly greater than the amount in a blank. 

In addition, blank samples were not collected for tritium or 

dissolved noble gases. Tritium and dissolved noble gases 

are in the atmosphere and would dissolve into any solution 

used in collecting a blank, making it impractical to collect 

a blank for these constituents. Isotopic ratios of hydrogen, 

oxygen, nitrogen, boron, strontium, and carbon are an intrinsic 

property of any of these elements; therefore, the concept of a 

blank does not apply to these ratios.

Methods of Determining Study Reporting Levels (SRLs)

The SRLs for selected VOCs were defined by Fram 

and others (2012) on the basis of the assessment of results 

from field blank samples, source-solution blank samples, 

laboratory instrument blank samples, and groundwater 

samples from the first 32 GAMA-PBP study units (May 2004 

through September 2010). SRLs were established for those 

VOCs that had evidence of potential contamination due to 

field or laboratory processes. Detections of VOCs having 

concentrations less than or equal to the SRLs were reclassified 

as non-detections.

The SRLs for pharmaceutical compounds were defined 

by Fram and Belitz (2011) and correspond to the highest 

LT-MDL or interim method detection limit (I-MDL) used 

by the NWQL during the first 31 GAMA PBP study units 

(May 2004 through June 2010). Detections of pharmaceutical 

compounds having concentrations less than or equal to the 

SRLs were reclassified as non-detections. 

The SRLs for trace elements were defined by Olsen and 

others (2010) on the basis of statistical assessment of results 

from the field blanks from the first 20 GAMA PBP study 

units (May 2004 through January 2008). The assessment 

used order statistics and binomial probabilities to construct 

an upper confidence limit (Hahn and Meeker, 1991) for the 

maximum concentration of constituents possibly introduced 

while groundwater samples were collected, transported, and 

analyzed. Detections of trace elements having concentrations 

less than or equal to the SRLs were reported with a ≤ symbol 

preceding the value to indicate that the true value may be less 

than or equal to the reported value (including the possibility of 

being a non-detection). 

The SRLs for three other constituents collected for the 

BEAR study unit [tris(2-butoxyethyl) phosphate, fluoride, 

and DOC] were defined as equal to the highest concentration 

measured in the blank samples. Detections of constituents in 
Appendix 69

groundwater samples at concentrations less than or equal to 

the SRLs defined by the blank samples were reclassified as 

non-detections (for organic constituents) or reported with a 

≤ symbol preceding the value (for inorganic constituents) as 

described by Fram and others (2012), Fram and Belitz (2011), 

and Olsen and others (2010). 

In the USGS NWIS database, data affected by SRLs (if 

any) are accompanied with the following comment: “Result is 

< or = reported value, based on QC data.”

Detections in Blank Samples and Application of SRLs

Table A3 presents a summary of detections in the blank 

samples and the SRLs applied for the BEAR study unit. Blank 

samples were collected at 13 percent of the sites sampled in 

the BEAR study unit. 

VOCs were not detected in the five blank samples (three 

field blanks, one source-solution blank, and one equipment 

blank) collected for the BEAR study unit. Two VOCs (toluene 

and 1,2,4-trimethylbenzene) have SRLs defined by Fram and 

others (2012) and were detected in groundwater samples. 

Toluene has an SRL of 0.69 μg/L as defined by Fram and 

others (2012) and was detected in two groundwater samples 

at concentrations of E0.05 μg/L and 1.39 μg/L (table 5). The 

measured concentration of E0.05 μg/L was reclassified as a 

non-detection and not included in the calculation of detection 

frequency (table 5, footnote #2). 

1,2,4-Trimethylbenzene has an SRL of 0.56 μg/L as 

defined by Fram and others (2012) and was detected in 

16 groundwater samples at concentrations ranging from 

E0.01 μg/L to 0.77 μg/L (median 0.15 μg/L). Thirteen of the 

detections were at concentrations less than the SRL and were 

reclassified as non-detections and not presented in table 5

(footnote #2). The three remaining detections were considered 

to be representative of groundwater quality and are presented 

in table 5. 

Pharmaceutical compounds were not detected in the 

five blank samples collected for the BEAR study unit, but 

they have SRLs defined by Fram and Belitz (2011). Five 

pharmaceutical compounds (acetaminophen, caffeine, 

carbamazepine, 1,7-dimethylxanthine, and sulfamethoxazole) 

were detected in groundwater samples at concentrations 

less than the SRLs. These results were reclassified as nondetections and not presented in this report. 

Three blank samples (one field blank, one sourcesolution blank, and one equipment blank) were collected 

in the BEAR study unit for the analysis of WICs. Tris(2-

butoxyethyl) phosphate was detected in the equipment blank 

at a concentration of E0.30 μg/L. An SRL was defined on the 

basis of the blank detection and was applied to the result from 

one groundwater site. This detection of tris(2-butoxyethyl) 

phosphate (E0.10 μg/L) was reclassified as a non-detection in 

table 7.

Five blank samples were collected in the BEAR study 

unit for the analysis of trace elements. Seven trace elements 

(arsenic, cobalt, copper, lead, manganese, nickel, and zinc) 

were detected in one or more of the blanks collected. Three 

trace elements (chromium, iron, and tungsten) were detected 

in groundwater samples at concentrations less than or equal to 

the SRLs defined by Olsen and others (2010).

A summary of inorganic blank sample detections and (or) 

concentration ranges and SRL applications is listed here:

• Arsenic was detected in one field blank at a 

concentration of 0.05 μg/L. Arsenic does not have an 

SRL defined by Olsen and others (2010). It has been 

determined that one field blank detection out of five 

blank samples in the BEAR study unit is not enough 

evidence to indicate that there has been a change in 

patterns of arsenic detections in blanks from what 

was observed by Olsen and others (2010); therefore, 

application of an SRL was not necessary.

• Chromium has an SRL of 0.42 μg/L as defined by 

Olsen and others (2010). This SRL was applied to the 

results from 13 groundwater sites (table 9).

• Cobalt was detected in three field blanks and in the 

equipment blank at concentrations ranging from 

0.11 μg/L to 0.42 μg/L. An SRL of 0.42 μg/L was 

established on the basis of the field blank results and 

was applied to the results from all 38 groundwater sites 

(table 9). 

• Copper was detected in one field blank at a 

concentration of E0.99 μg/L. Copper has an SRL 

of 1.7 μg/L as defined by Olsen and others (2010). 

An SRL of 1.7 μg/L was applied to the results from 

13 groundwater sites (table 9). 

• Iron has an SRL of 6 μg/L as defined by Olsen and 

others (2010). This SRL was applied to the results from 

three groundwater sites (table 9).

• Lead was detected in two field blanks at concentrations 

of 0.13 μg/L and 0.60 μg/L. Lead has an SRL of 

0.65 μg/L as defined by Olsen and others (2010). 

An SRL of 0.65 μg/L was applied to the results from 

27 groundwater sites (table 9). 

• Manganese was detected in three field blanks and in 

the equipment blank at concentrations ranging from 

E0.16 μg/L to 0.79 μg/L. Manganese has an SRL of 

0.20 μg/L as defined by Olsen and others (2010). An 

SRL of 0.79 μg/L was established on the basis of the 

field blank results and was applied to the results from 

19 groundwater sites (table 9). 

• Nickel was detected in one field blank at a 

concentration of 0.14 μg/L. Nickel has an SRL of 

0.36 μg/L as defined by Olsen and others (2010). 

An SRL of 0.36 μg/L was applied to the results from 

24 groundwater sites (table 9). 
70 Groundwater-Quality Data in the Bear Valley and Selected Hard Rock Areas Study Unit, 2010

• Tungsten has an SRL of 0.11 μg/L as defined by Olsen 

and others (2010). This SRL was applied to the results 

from 15 groundwater sites (table 9).

• Zinc was detected in one field blank at a concentration 

of 3.0 μg/L. Zinc has an SRL of 4.8 μg/L as defined 

by Olsen and others (2010). An SRL of 4.8 μg/L 

was applied to the results from 12 groundwater sites 

(table 9). 

Five blanks were collected in the BEAR study unit 

for the analysis of nutrients and DOC. Nutrients were not 

detected in any of the blank samples, but DOC was detected 

in the equipment blank at a concentration of 0.8 milligram per 

liter (mg/L). An SRL was defined on the basis of the blank 

detection and was applied to the results from 21 groundwater 

sites (table 10). 

Five blanks were collected in the BEAR study unit for the 

analysis of the major and minor ions, silica, and TDS. Major 

and minor ions, silica, and TDS were not detected in any of 

the blank samples with the exception of fluoride, which was 

detected in one field blank at a concentration of 0.06 mg/L. An 

SRL was defined on the basis of the blank detection and was 

applied to the results from five groundwater sites (table 11). 

Three field blanks were collected in the BEAR study unit 

for the analysis of arsenic and iron species at the USGS NRPTML. Arsenic and iron species were not detected in any blank 

samples with the exception of iron (total), which was detected 

in one field blank at a concentration of 0.003 μg/L. Iron (total) 

was not detected at concentrations less than 0.003 μg/L; 

therefore, application of an SRL was not necessary.

Detections in blank samples did not occur in the BEAR 

study unit for these constituent groups: pesticides and 

pesticide degradates and the constituents of special interest.

Replicate Pairs

Sequential replicate pairs were collected to assess 

the precision of the water-quality data. Estimates of data 

precision are needed to assess whether differences between 

concentrations in samples are because of differences in 

groundwater quality or because of variability that may result 

from collecting, processing, and analyzing the samples. 

Methods of Assessment of Replicate Pairs

Three methods for measuring replicate pair variability 

were used to assess precision over the range of measured 

concentrations in groundwater samples. The variability 

between results in the replicate pairs was represented by the 

absolute standard deviation (SD) for low concentrations and 

by relative standard deviation (RSD) for high concentrations 

(Anderson, 1987; Mueller and Titus, 2005). The RSD is 

defined as the SD divided by the mean concentration for 

each replicate pair expressed as a percentage. The boundary 

between concentrations for each metric was defined as 5 times 

(x) the selected reporting level (RL) for each constituent. The 

RL may be an LRL, SRL, MDL, or MRL for each constituent; 

therefore the SD was used for pairs with mean concentrations 

< 5xRL, and the RSD was used for pairs with mean 

concentrations > 5 xRL. 

Replicate pairs for all constituents except for radioactive 

constituents were evaluated as follows. 

• If both values were reported as detections, the SD or 

RSD was calculated. Acceptable variability is defined 

as an SD of < 1⁄2 RL or an RSD of < 10 percent. For 

comparison, an RSD of 10 percent is equivalent to a 

relative percent difference (RPD) of 14 percent.

• If both values were reported as non-detections, the 

variability was set to zero by definition. 

• If one value was reported as a non-detection, and the 

other value was reported as a detection < RL, then a 

value of zero was substituted for the non-detection, 

and the SD was calculated. Substituting zero for the 

non-detection would yield the maximum estimate of 

variability for the replicate pair. 

• If one value was reported as a non-detection and the 

other value was flagged with a ≤ symbol, or if both 

values were flagged with a ≤ symbol, the SD was not 

calculated because the values may be analytically 

identical. The ≤ symbol indicates that the value is 

a maximum potential concentration and the true 

concentration could be < RL for the other sample in the 

pair.

• If one value was reported as a non-detection and the 

other value was reported as a detection > RL, the 

variability for the pair was considered unacceptable.

Replicate pairs for radioactive constituents were 

evaluated by using the following equation (Parr and 

Porterfield, 1997; McCurdy and others, 2008) to calculate the 

normalized absolute difference (NAD):

2 2

X Y

x y NAD

CSU CSU

- ≤

+

(A3)

where

x = activities of a radioactive constituent in the 

groundwater sample,

y = activities of the same radioactive constituent 

in the replicate sample,

CSUx = combined standard uncertainty of x at the 1σ 

confidence level, and

CSUy = combined standard uncertainty of y at the 1σ 

confidence level.

Values < 1.65 for the NAD correspond to a significance level 

(α) of 5 percent (α = 0.05), indicating differences that are 

acceptably small and not statistically significant.
Appendix 71

If results from replicate pairs indicate that variability is 

unacceptable for a constituent, then this greater variability 

must be considered when interpreting the data. If measured 

concentrations are slightly greater than a water-quality 

benchmark, then actual concentrations could be less than that 

benchmark. Similarly, if measured concentrations are less 

than a water-quality benchmark, then actual concentrations 

could be greater than a benchmark. If a constituent has 

high variability in replicate pairs, then a larger difference 

between concentrations measured in two samples is required 

to conclude that the two samples have significantly different 

concentrations. 

Variability in Replicate Pairs

Tables A4A–C summarize the results of the replicate pair 

analyses for constituents detected in groundwater samples 

collected in the BEAR study unit. Replicate pairs were 

collected for 11 percent of the samples collected. 

Three replicate pairs were analyzed for the VOCs. Nine 

of the 16 VOCs detected in groundwater samples had replicate 

pairs that were composed of two values reported as nondetections. The seven remaining VOCs yielded replicate pairs 

reported either as two non-detections, one value as a detection 

and one as a non-detection, or two detections. The replicate 

pair analyses of these VOCs resulted in SDs and RSDs within 

acceptable variability (table A4A). 

Four replicate pairs were analyzed for the pesticide and 

pesticide degradate compounds. Three of the four replicate 

pairs for both simazine and prometon were composed of two 

values reported as non-detections. The remaining replicate 

pair for simazine resulted in one value reported as a detection 

and one as a non-detection. The replicate pair for prometon 

yielded two values reported as detections. The replicate pair 

analyses for simazine and prometon resulted in SDs within 

acceptable variability (table A4A). 

One replicate pair was analyzed for the WICs. Both 

replicate pairs for tris(2-butoxyethyl) phosphate and phenol 

were composed of two values reported as non-detections. As a 

result, these constituents are not presented on table A4A. 

Four replicate pairs for perchlorate, 1,2,3-TCP, and 

NDMA were analyzed at Weck for variability. One of the 

replicate pairs for perchlorate and all of the replicate pairs 

for 1,2,3-TCP and NDMA were composed of two values 

reported as non-detections. The three remaining replicate pairs 

for perchlorate yielded two values reported as detections, 

and each replicate pair analysis resulted in an SD within 

acceptable variability (table A4A). 

Four replicate pairs were analyzed for DOC, and one of 

these pairs was composed of two values reported as nondetections. The three remaining replicate pairs yielded two 

values reported as detections, and all replicate pair analyses 

resulted in SDs within acceptable variability (table A4A).

Four replicate pairs were analyzed for trace elements, 

nutrients, major and minor ions, silica, TDS, and arsenic 

and iron species. All replicate pairs were either composed of 

two values reported as non-detections or two values reported 

as detections. The analyses for all replicate pairs reported 

as detections resulted in SDs and RSDs within acceptable 

variability (table A4B). 

Four replicate pairs were analyzed for tritium and 

radon-222. All replicate pairs yielded statistically similar 

results (α ≤ 0.05) and were, therefore, considered acceptable 

(table A4C).

Groundwater detections were not modified on the basis of 

the replicate pair analyses.

Matrix Spikes

Addition of a known concentration of a constituent 

(spike) to a replicate groundwater sample enables the 

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 analyzed in the groundwater samples. This 

enables an analysis of matrix interferences on a compoundby-compound basis. For this study, matrix spikes were added 

by the laboratories performing the analysis rather than in the 

field. 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 benchmark; a low recovery could result 

in a falsely measured concentration less than the benchmark, 

whereas a high recovery could result in a falsely measured 

concentration greater than the benchmark.

The GAMA-PBP defined the data-quality objective 

range for acceptable median matrix-spike recoveries as 70 

to 130 percent. Only constituents with median matrix-spike 

recoveries outside of this range were flagged as having 

unacceptable recoveries. Matrix-spike tests were performed 

for VOCs, pesticides and pesticide degradates, WICs, 1,2,3-

TCP, and NDMA because the analytical methods for these 

constituents may be susceptible to matrix interferences. 

Matrix-Spike Recoveries

Tables A5A–D presents a summary of matrix-spike 

recoveries for the BEAR study unit. Spiked samples were 

collected at 13 percent of the sites sampled. 

Five groundwater samples were spiked with VOCs 

to calculate matrix-spike recoveries. Median matrix-spike 

recoveries for all 85 spike compounds were between 70 and 

130 percent (table A5A). 

Four groundwater samples were spiked with pesticide 

and pesticide degradate compounds to calculate matrixspike recoveries. Median matrix-spike recoveries for 61 of 

the 83 spike compounds were between 70 and 130 percent. 

Twenty of the spike compounds had median matrix-spike 

recoveries < 70 percent, and two had median matrix-spike 

recoveries > 130 percent. Both of the spike compounds 

detected in groundwater samples (simazine and prometon) had 

median matrix-spike recoveries within the acceptable range 

(table A5B). 
72 Groundwater-Quality Data in the Bear Valley and Selected Hard Rock Areas Study Unit, 2010

One groundwater sample was spiked with WICs to 

calculate matrix-spike recoveries. Matrix-spike recoveries 

for 45 of the 60 spike compounds were between 70 and 

130 percent. Fifteen of the spike compounds had median 

matrix-spike recoveries < 70 percent. Both of the compounds 

detected in groundwater samples [phenol and tris(2-

butoxyethyl) phosphate] had median matrix-spike recoveries 

within the acceptable range (table A5C). 

Four groundwater samples were spiked with NDMA 

and 1,2,3-TCP to calculate matrix-spike recoveries at Weck. 

All median matrix-spike recoveries were between 70 and 

130 percent (table A5D). 

Groundwater detections were not modified on the basis of 

the matrix-spike recovery analyses.

Surrogate Compounds

Surrogate compounds are added to groundwater samples 

in the laboratory prior to analysis to evaluate the recovery 

of similar constituents. Surrogate compounds were added in 

the laboratory to all groundwater and QC samples that were 

analyzed by the NWQL for VOCs, pesticides and pesticide 

degradates, and WICs. Surrogates are used to identify general 

problems that may arise during laboratory sample analysis 

that could affect the analysis results for all compounds in 

that sample. Potential problems include matrix interferences 

(such as high levels of DOC) that produce a positive bias or 

incomplete laboratory recovery (possibly because of improper 

maintenance and calibration of analytical equipment) that 

produces a negative bias. A 70 to 130 percent recovery of 

surrogates, in general, is considered acceptable; values outside 

this range indicate possible problems with the processing and 

analysis of samples (Connor and others, 1998; Sandstrom and 

others, 2001).

Surrogate Compound Recoveries

Table A6 presents a summary of the surrogate compound 

recoveries for the BEAR study unit. The table lists the 

surrogate compound, the analytical schedule on which it was 

applied, the number of analyses for blank and groundwater 

samples, the number of surrogate recoveries < 70 percent, 

and the number of recoveries > 130 percent for the blank and 

groundwater samples. Blank and groundwater samples were 

considered separately to assess whether or not the matrixes 

present in groundwater samples affect surrogate compound 

recoveries. 

Most surrogate compound recoveries for the blank 

and groundwater samples were within the acceptable range 

of 70 to 130 percent. In total, 87 percent of the blank and 

88 percent of the groundwater sample surrogate recoveries for 

VOC analyses were within the acceptable range. In addition, 

100 percent of the blank and 97 percent of the groundwater 

sample surrogate recoveries for pesticide and pesticide 

degradate analyses were within the acceptable range. Finally, 

67 percent of the blank and groundwater sample surrogate 

recoveries for WICs analyses were within the acceptable range 

(table A6). There were no significant differences between 

VOC, pesticide and pesticide degradate, and WIC surrogate 

recoveries in blank and groundwater samples (Wilcoxon rank 

sum test, p < 0.05).

Groundwater detections were not modified on the basis of 

the surrogate compound recovery analyses.

Laboratory Bias in Trace Element Analyses

Laboratory bias as indicated from internal laboratory 

QC tests was investigated to determine whether or not the 

BEAR study unit data were affected by laboratory procedures. 

The BQS operates the Inorganic Blind Sample Project (IBSP) 

to monitor and evaluate the quality of results for analyses of 

trace elements, nutrients, major and minor ions, silica, and 

TDS by the NWQL. The IBSP submits standard reference 

samples consisting of natural matrix water samples spiked 

with reagent chemicals that contain known concentrations of 

the inorganic constituents (Farrar and Long, 1997). The IBSP 

data are readily available on the BQS website, and the BQS 

issues monthly summaries of the results, reporting the amount 

of bias (if any) observed in the results (U.S. Geological 

Survey, 2011c).

The BQS monthly summaries were examined for April 

through August 2010, the period of time during which samples 

were analyzed for the BEAR study unit. During this time 

period, the BQS reported that three inorganic constituents 

showed evidence of bias: a positive bias for barium and 

cadmium and a negative bias for magnesium. Examination of 

the results for the IBSP samples for these three constituents 

indicated that the analytical biases reported by the BQS were 

not significant for the data collected for the BEAR study unit. 

The IBSP samples for barium had concentrations 

ranging from 26.0 μg/L to 63.0 μg/L. The average difference 

between the measured and expected concentrations was 

1.0 μg/L (standard deviation = 2.0 μg/L), and the average 

RPD between the measured and expected concentrations was 

2 percent (standard deviation = 5 percent). The MCL-CA 

for barium is 1,000 μg/L, thus the estimate of bias from the 

ISBP samples would be relevant for assessment of whether 

groundwater samples have barium concentrations greater 

than or less than the MCL-CA concentration or greater than 

or less than 1⁄2 of the MCL-CA concentration. However, the 

maximum concentration of barium in samples from the BEAR 

study unit was 134 μg/L (table 9); thus, a potential positive 

bias of 1.0 μg/L, or 2 percent, would not result in a measured 

concentration greater than either threshold when the true 

concentration would have been below the threshold.

The IBSP samples for cadmium had concentrations 

ranging from 0.18 μg/L to 1.7 μg/L. The average difference 

between the measured and expected concentrations was 

0.12 μg/L (standard deviation = 0.09 μg/L), and the average 

RPD between the measured and expected concentrations was 
Appendix 73

19 percent (standard deviation = 30 percent). The MCL-US 

for cadmium is 5 μg/L; thus, the estimate of bias from the 

ISBP samples would be relevant for assessment of whether 

groundwater samples have cadmium concentrations greater 

than or less than the MCL-US concentration or greater than 

or less than 1⁄2 of the MCL-US concentration. However, the 

maximum concentration of cadmium in samples from the 

BEAR study unit was 0.10 μg/L (table 9); thus, a potential 

positive bias of 0.12 μg/L, or 19 percent, would not result in a 

measured concentration above either threshold when the true 

concentration would have been below the threshold.

The IBSP samples for magnesium had concentrations 

ranging from 0.05 mg/L to 7.3 mg/L. The average difference 

between the measured and expected concentrations was 

–0.18 mg/L (standard deviation = 0.21 mg/L), and the average 

RPD between the measured and expected concentrations 

was –5 percent (standard deviation = 3 percent). A negative 

bias of 0.18 mg/L, or 5 percent, can only potentially affect 

measured concentrations of less than 7.3 mg/L in BEAR study 

unit groundwater samples (table 11). Magnesium does not 

currently have an established regulatory or non-regulatory 

health-based benchmark or a non-regulatory benchmark 

established for aesthetic concerns; therefore, this negative bias 

will not affect the assessments of groundwater quality being 

made by the GAMA-PBP.
74 Groundwater-Quality Data in the Bear Valley and Selected Hard Rock Areas Study Unit, 2010 Table A1. Analytical methods used by the U.S. Geological Survey (USGS) National Water Quality Laboratory and contract laboratories. [Laboratory entity codes in the USGS National Water Information System (NWIS) for laboratories other than the USGS National Water Quality Laboratory (NWQL) are given in parentheses after the laboratory names. Abbreviations: UV, ultraviolet; USEPA, U.S. Environmental Protection Agency; VOC, volatile organic compound; WIC, wastewater indicator compound; TDS, total dissolved solids; DOC, dissolved organic carbon; NRP, USGS National Research Program] Constituent classes Analytical method Laboratory and analytical schedule Citation(s) Water-quality indicators Field parameters Calibrated field meters and test kits USGS field measurement U.S. Geological Survey, variously dated Organic constituents VOCs Purge and trap capillary gas chromatography/ mass spectrometry NWQL, Schedule 2020 Connor and others, 1998 Pesticides and pesticide degradates Solid-phase extraction and gas chromatography/ mass spectrometry NWQL, Schedule 2033 Zaugg and others, 1995; Lindley and others, 1996; Sandstrom and others, 2001; Madsen and others, 2003 Pharmaceutical compounds Solid-phase extraction and HPLC/mass spectrometry NWQL, Schedule 2080 Kolpin and others, 2002; Furlong and others, 2008 WICs Polystyrene-divinylbenzene solid-phase extraction and capillary-column gas chromatography/mass spectrometry NWQL, Schedule 1433 Zaugg and others, 2002 Constituents of special interest Perchlorate Liquid chromatography with mass spectrometry/ mass spectrometry (USEPA Method 331.0) Weck Laboratories, Inc. [Weck], City of Industry, California (CA-WECK), standard operating procedure ORG099.R01 U.S. Environmental Protection Agency, 2005 1,2,3-Trichloropropane (1,2,3-TCP) Isotopic dilution purge and trap/gas chromatography/mass spectrometry Weck Laboratories, Inc. [Weck], City of Industry, California (CA-WECK), standard operating procedure ORG083 Okamoto and others, 2002

N-Nitrosodimethylamine (NDMA) Isotopic dilution with gas chromatography 

and chemical-ionization mass spectrometry (USEPA Method 1625 modified)

Weck Laboratories, Inc. [Weck], City of Industry, 

California (CA-WECK), standard operating procedure ORG065.R10

U.S. Environmental Protection Agency, 1989; 

Plomley and others, 1994

Inorganic constituents and DOC

Trace elements, major and minor ions, and TDS Atomic absorption spectrometry, colorimetry, 

ion-exchange chromatography, inductivelycoupled plasma with atomic emission spectrometry, and mass spectrometry

NWQL, Schedule 1948 Fishman and Friedman, 1989; Fishman, 1993; 

Faires, 1993; McLain, 1993; Garbarino, 1999; American Public Health Association, 1998; Garbarino and others, 2006

Nutrients Alkaline persulfate digestion, Kjedahl digestion NWQL, Schedule 2755 Fishman, 1993; Patton and Kryskalla, 2003

DOC UV-promoted persulfate oxidation and infrared 

spectrometry

NWQL, Laboratory Code 2613 Brenton and Arnett, 1993

Arsenic and iron species Various techniques of ultraviolet visible 

(UV-VIS) spectrophotometry and atomic absorbance spectroscopy

USGS NRP Trace Metal Laboratory [TML], 

Boulder, Colorado (USGSTMCO)

Stookey, 1970; To and others, 1998; McCleskey 

and others, 2003
Appendix 75

Constituent 

classes

Analytical 

method

Laboratory and 

analytical schedule Citation(s)

Isotopic tracers

Stable isotopes of hydrogen and oxygen in water Gaseous hydrogen and carbon dioxide–water 

equilibration and stable-isotope mass spectrometry

USGS Stable Isotope Laboratory, Reston, 

Virginia (USGSSIVA), NWQL Schedule 1142

Epstein and Mayeda, 1953; Coplen and others, 

1991; Coplen, 1994

Stable isotopes of nitrogen and oxygen in 

dissolved nitrate

Denitrifier method and mass spectrometry USGS Stable Isotope Laboratory, Reston, 

Virginia (USGSSIVA), NWQL Laboratory Code 2900

Révész and Casciotti, 2007

Stable isotopes of boron in water Negative thermal-ionization mass spectrometry USGS NRP Metals Isotope Research Laboratory, 

Menlo Park, California (USGSMICA)

Vengosh and others, 1989; Dwyer and Vengosh, 

2008

Isotopic ratio of strontium in water Chemical separations and thermal-ionization 

mass spectrometry

USGS NRP Metals Isotope Research Laboratory, 

Menlo Park, California (USGSMICA)

Bullen and others, 1996

Stable isotopes of carbon in dissolved inorganic 

carbon and carbon-14 abundance

Accelerator mass spectrometry Woods Hole Oceanographic Institution, 

National Ocean Sciences Accelerator Mass Spectrometry Facility [NOSAMS], Woods Hole, Massachusetts (MA-WHAMS), NWQL Schedule 2255

Vogel and others, 1987; Donahue and others, 

1990; McNichol and others, 1992; Gagnon and Jones, 1993; McNichol and others, 1994; Schneider and others, 1994

Uranium and other radioactive constituents and dissolved noble gases

Tritium Electrolytic enrichment-liquid scintillation USGS Stable Isotope and Tritium Laboratory 

[SITL], Menlo Park, California (USGSH3CA), NWQL Schedule 1565

Thatcher and others, 1977

Radon-222 Liquid scintillation counting NWQL, Schedule 1369 American Society for Testing and Materials, 1998

Dissolved noble gases, tritium, and helium 

isotope ratios

Helium-3 in-growth and mass spectrometry Lawrence Livermore National Laboratory 

[LLNL], Livermore, California (CA-LLNL)

Moran and others, 2002; Eaton and others, 2004

Table A1. Analytical methods used by the U.S. Geological Survey (USGS) National Water Quality Laboratory (NWQL) and contract laboratories.[Laboratory entity codes in the USGS National Water Information System (NWIS) for laboratories other than the USGS National Water Quality Laboratory (NWQL) are given in parentheses after the laboratory names. Abbreviations: UV, ultraviolet; USEPA, U.S. Environmental Protection Agency; VOC, volatile organic compound; WIC, wastewater indicator compound; TDS, total dissolved solids; DOC, dissolved organic carbon; NRP, USGS National Research Program]
76 Groundwater-Quality Data in the Bear Valley and Selected Hard Rock Areas Study Unit, 2010

Table A2. Preferred analytical methods or laboratories for selected constituents collected for the Bear Valley and Selected Hard Rock 

Areas (BEAR) Groundwater Ambient Monitoring and Assessment (GAMA) study unit, California, April to August 2010.

[Preferred analytical methods or laboratories were selected on the basis of the procedure recommended by the NWQL (http://wwwnwql.cr.usgs.gov/dyn.

shtml?Preferred_method_selection_procedure). Abbreviations: USGS, U.S. Geological Survey; NWQL, USGS National Water Quality Laboratory, Denver, 

Colorado; NRP, USGS National Research Project; VOC, volatile organic compound; WIC, wastewater indicator compound; Weck, Weck Laboratories Inc., City 

of Industry, California; TML, USGS NRP Trace Metal Laboratory, Boulder, Colorado; LLNL, Lawrence Livermore National Laboratory, Livermore, California; 

SITL, USGS Stable Isotope and Tritium Laboratory, Menlo Park, California; np, no preference]

Constituent 

(synonym or abbreviation)

Primary constituent 

classification

Analytical methods 

or laboratory

Preferred analytical 

method or laboratory

Results from the preferred method reported

1,4-Dichlorobenzene VOC Schedule 2020 (NWQL), Schedule 1433 (NWQL) Schedule 2020

Isopropylbenzene VOC Schedule 2020 (NWQL), Schedule 1433 (NWQL) Schedule 2020

Naphthalene VOC Schedule 2020 (NWQL), Schedule 1433 (NWQL) Schedule 2020

Perchloroethene (PCE, Tetrachloroethene) VOC Schedule 2020 (NWQL), Schedule 1433 (NWQL) Schedule 2020

Bromoform (Tribromomethane) VOC Schedule 2020 (NWQL), Schedule 1433 (NWQL) Schedule 2020

Carbaryl Pesticide Schedule 2033 (NWQL), Schedule 1433 (NWQL) Schedule 2033

Chlorpyrifos Pesticide Schedule 2033 (NWQL), Schedule 1433 (NWQL) Schedule 2033

Diazinon Pesticide Schedule 2033 (NWQL), Schedule 1433 (NWQL) Schedule 2033

Dichlorvos Pesticide Schedule 2033 (NWQL), Schedule 1433 (NWQL) Schedule 2033

Metalaxyl Pesticide Schedule 2033 (NWQL), Schedule 1433 (NWQL) Schedule 2033

Metolachlor Pesticide Schedule 2033 (NWQL), Schedule 1433 (NWQL) Schedule 2033

Prometon Pesticide Schedule 2033 (NWQL), Schedule 1433 (NWQL) Schedule 2033

Caffeine WIC Schedule 2080 (NWQL), Schedule 1433 (NWQL) Schedule 2080

Cotinine WIC Schedule 2080 (NWQL), Schedule 1433 (NWQL) Schedule 2080

Results from both methods or laboratories reported

pH Water-quality indicator field, Schedule 1948 (NWQL) field

Specific conductance Water-quality indicator field, Schedule 1948 (NWQL) field

Alkalinity Water-quality indicator field, Schedule 1948 (NWQL) field

1,2,3-Trichloropropane (1,2,3-TCP) VOC Schedule 2020 (NWQL), Weck Weck

Arsenic (total) Trace element Schedule 1948 (NWQL), TML Schedule 1948

Iron (total) Trace element Schedule 1948 (NWQL), TML Schedule 1948

Tritium Isotopic tracer SITL, LLNL np
Appendix 77

Table A3. Constituents detected in blank samples and the study reporting level (SRL) analysis for the Bear Valley and Selected Hard Rock Areas (BEAR) Groundwater Ambient Monitoring and Assessment (GAMA) study unit, California, April to August 2010.[Abbreviations: RL, reporting level; ≤, less than or equal to; VOC, volatile organic compound; WIC, wastewater indicator compound; E, estimated or having a higher degree of uncertainty; μg/L, micrograms per liter; mg/L, milligrams per liter; —, not detected; nv, no value in category]

Constituent

Number of blank detections / 

total number of blank samples RL Concentration(s) detected in the blank sample(s) SRL 1 Number of groundwater samples ≤-coded / total number of detections Field blank Source-solution blank Equipment blank

VOCs (μg/L)

Toluene 0/3 0/1 0/1 0.018 — 0.69 B 1/2

1,2,4-Trimethylbenzene 0/3 0/1 0/1 0.032 — 0.56 B 13/16

Pharmaceutical compounds (μg/L)

Acetaminophen 0/3 0/1 0/1 0.01 — 0.06 C 1/1

Caffeine 0/3 0/1 0/1 0.007 — 0.10 C 1/1Carbamazepine 0/3 0/1 0/1 0.015 — 0.03 C 1/11,7-Dimethylxanthine 0/3 0/1 0/1 0.01 — 0.06 C 1/1Sulfamethoxazole 0/3 0/1 0/1 0.05 — 0.08 C 1/1

WICs (μg/L)

Tris(2-butoxyethyl) phosphate 0/1 0/1 1/1 0.8 E0.30 0.30 A 1/2

Trace elements (μg/L)

Arsenic 1/3 0/1 0/1 0.044 0.05 nv 2 0/38

Chromium 0/3 0/1 0/1 0.12 — 0.42 D 13/22

Cobalt 3/3 0/1 1/1 0.010 0.09, 0.11, 0.11, 0.42 0.42 A 38/38Copper 1/3 0/1 0/1 1.0 E0.99 1.7 D 13/30Iron 0/3 0/1 0/1 6 — 6 D 3/18

Lead 2/3 0/1 0/1 0.030 0.13, 0.60 0.65 D 27/38

Manganese 3/3 0/1 1/1 0.26 E0.16, E0.19, E0.21, 0.79 0.79 A 19/32Nickel 1/3 0/1 0/1 0.12 0.14 0.36 D 24/37Tungsten 0/3 0/1 0/1 0.02 — 0.11 D 15/28Zinc 1/3 0/1 0/1 2.8 3.0 4.8 D 12/32

Major and minor ions (mg/L)

Fluoride 1/3 0/1 0/1 0.08 E0.06 0.06 A 5/38

Dissolved organic carbon (DOC) (mg/L)

DOC 0/3 0/1 1/1 0.66 0.8 0.8 A 21/26

Arsenic and iron species (μg/L)

Iron (total) 1/3 nv nv 0.002 0.003 nv 3 0/18

1 SRLs were defined: A, by the highest concentration in blank samples collected for the BEAR study unit; B, by Fram and others (2012); C, by Fram and Belitz (2011); and D, by Olsen and others (2010).2 It has been determined that the field blank detection is not enough evidence to indicate that there has been a change in patterns of arsenic detections in blanks from what was observed by Olsen and others 

(2010); therefore, application of an SRL was not necessary.

3 Constituent was not detected in groundwater samples at concentrations less than the SRL; therefore, application of an SRL was not necessary.
78 Groundwater-Quality Data in the Bear Valley and Selected Hard Rock Areas Study Unit, 2010

Table A4A. Replicate pair analysis for organic constituents, constituents of special interest, and dissolved organic carbon (DOC) 

detected in samples collected for the Bear Valley and Selected Hard Rock Areas (BEAR) Groundwater Ambient Monitoring and 

Assessment (GAMA) study unit, California, April to August 2010.

[Constituents for which all replicate pairs were non-detections are not listed. Abbreviations: SD, standard deviation; RSD, relative standard deviation; 

>, greater than; <, less than; RL, reporting level; nv, no value in category]

Constituent 

(synonym or abbreviation)

Number of replicate pairs with 

non-detections in both samples / 

number of replicate pairs

Number of SDs > 1⁄2 RL / number of 

replicate pairs with concentrations 

< 5 times the RL 

Number of RSDs > 10 percent / 

number of replicate pairs with 

concentrations > 5 times the RL

Volatile organic compounds (VOC) 

Chloroform (Trichloromethane) 1/3 0/1 0/1

Methyl tert-butyl ether (MTBE) 2/3 0/1 nv

Perchloroethene (PCE, 

Tetrachloroethene)

1/3 0/2 nv

Bromodichloromethane 1/3 0/2 nv

1,2,4-Trimethylbenzene 2/3 nv 0/1

1,1-Dichloroethene (1,1-DCE) 2/3 0/1 nv

Bromochloromethane 2/3 0/1 nv

Pesticides and pesticide degradates

Simazine 3/4 0/1 nv

Prometon 3/4 0/1 nv

Constituent of special interest

Perchlorate 1/4 0/3 nv

Dissolved organic carbon (DOC)

DOC 1/4 0/3 nv
Appendix 79

Table A4B. Replicate pair analysis for inorganic constituents detected in samples collected for the Bear Valley and Selected Hard 

Rock Areas (BEAR) Groundwater Ambient Monitoring and Assessment (GAMA) study unit, California, April to August 2010.

[Constituents for which all replicate pairs were non-detections are not listed. Abbreviations: SD, standard deviation; RSD, relative standard deviation; 

RL, reporting level; >, greater than; <, less than; SiO2, silicon dioxide; ≤, less than or equal to; nv, no value in category]

Constituent

Number of replicate pairs with 

non-detections or ≤ symbols in both 

samples / number of replicate pairs 

Number of SDs > 1⁄2 RL / number of 

replicate pairs with concentrations 

< 5 times the RL

Number of RSDs > 10 percent / 

number of replicate pairs with 

concentrations > 5 times the RL

Trace Elements

Antimony 2/4 0/2 nv

Arsenic 0/4 0/3 0/1

Barium 0/4 nv 0/4

Boron 0/4 0/2 0/2

Cadmium 2/4 0/2 nv

Chromium 2/4 0/2 nv

Cobalt 0/4 0/3 0/1

Copper 0/4 0/3 0/1

Iron 2/4 0/2 nv

Lead 0/4 0/4 nv

Lithium 1/4 nv 0/3

Manganese 2/4 0/1 0/1

Molybdenum 0/4 nv 0/4

Nickel 0/4 0/3 0/1

Selenium 0/4 0/2 0/2

Strontium 0/4 nv 0/4

Tungsten 1/4 0/3 nv

Uranium 0/4 nv 0/4

Vanadium 0/4 nv 0/4

Zinc 0/4 0/3 0/1

Nutrients 

Nitrate plus nitrite (as nitrogen) 1/4 0/1 0/2

Nitrite (as nitrogen) 3/4 0/1 nv

Total nitrogen (ammonia + nitrite + 

nitrate + organic nitrogen)

1/4 0/1 0/2

Phosphate, orthophosphate 

(as phosphorus)

0/4 0/2 0/2

Major and minor ions, silica, and total dissolved solids (TDS) 

Bromide 0/4 0/4 nv

Calcium 0/4 nv 0/4

Chloride 0/4 nv 0/4

Fluoride 0/4 0/3 0/1

Iodide 1/4 0/3 nv

Magnesium 0/4 nv 0/4

Potassium 0/4 nv 0/4

Sodium 0/4 nv 0/4

Sulfate 0/4 nv 0/4

Silica (as SiO2

) 0/4 nv 0/4

TDS 0/4 nv 0/4

Arsenic and iron species

Iron (total) 2/4 0/2 nv

Iron-II 2/4 0/2 nv
80 Groundwater-Quality Data in the Bear Valley and Selected Hard Rock Areas Study Unit, 2010

Table A4C. Replicate pair analysis for radioactive constituents 

detected in samples collected for the Bear Valley and Selected 

Hard Rock Areas (BEAR) Groundwater Ambient Monitoring and 

Assessment (GAMA) study unit, California, April to August 2010.

[For activities of radioactive constituents, a replicate pair analysis is defined as 

acceptable if the p-value for the normalized absolute difference is less than the 

significance level, α = 0.05. Abbreviations: α, significance level; >, greater 

than]

Constituent Number of replicate pairs with 

p > 0.05 / number of replicate pairs 

Radon-222 0/4

Tritium 0/4
Appendix 81

Table A5A. Matrix-spike recoveries for volatile organic compounds (VOCs) in samples collected for the Bear Valley and Selected Hard 

Rock Areas (BEAR) Groundwater Ambient Monitoring and Assessment (GAMA) study unit, California, April to August 2010.

[Acceptable recovery range is between 70 and 130 percent]

Constituent 

(synonym or abbreviation)

Number of spiked 

samples collected

Minimum recovery 

(percent)

Maximum recovery 

(percent)

Median recovery 

(percent)

Acetone 5 95 131 113

Acrylonitrile 5 98 117 111

tert-Amyl methyl ether (TAME) 5 86 103 97

Benzene 5 99 141 103

Bromobenzene 5 90 100 99

Bromochloromethane 1 5 97 111 103

Bromodichloromethane 1 5 93 102 97

Bromoform (Tribromomethane) 1 5 83 105 88

Bromomethane (Methyl bromide) 5 104 110 109

n-Butylbenzene 5 75 99 89

sec-Butylbenzene 5 81 105 102

tert-Butylbenzene 5 85 114 106

Carbon disulfide 5 66 80 75

Carbon tetrachloride (Tetrachloromethane) 1 5 95 106 100

Chlorobenzene 5 93 98 97

Chloroethane 5 91 109 103

Chloroform (Trichloromethane) 1 5 99 127 110

Chloromethane 5 91 113 100

3-Chloropropene 5 110 118 113

2-Chlorotoluene 5 95 110 101

4-Chlorotoluene 5 87 109 95

Dibromochloromethane 1 5 88 106 94

1,2-Dibromo-3-chloropropane (DBCP) 5 81 108 88

1,2-Dibromoethane (EDB) 5 92 104 100

Dibromomethane 5 94 107 101

1,2-Dichlorobenzene 5 94 114 104

1,3-Dichlorobenzene 5 87 104 94

1,4-Dichlorobenzene 5 90 112 93

trans-1,4-Dichloro-2-butene 5 91 100 98

Dichlorodifluoromethane (CFC-12) 5 70 89 74

1,1-Dichloroethane (1,1-DCA) 1 5 104 110 108

1,2-Dichloroethane (1,2-DCA) 5 105 115 109

1,1-Dichloroethene (1,1-DCE) 1 5 90 101 96

cis-1,2-Dichloroethene (cis-1,2-DCE) 5 99 106 101

trans-1,2-Dichloroethene (trans-1,2-DCE) 5 93 107 101

1,2-Dichloropropane 5 95 104 97

1,3-Dichloropropane 5 99 106 103

2,2-Dichloropropane 5 77 91 89

1,1-Dichloropropene 5 90 100 93

cis-1,3-Dichloropropene 5 81 87 86

trans-1,3-Dichloropropene 5 72 90 78

Diethyl ether 5 107 119 109

Diisopropyl ether (DIPE) 5 96 109 102
82 Groundwater-Quality Data in the Bear Valley and Selected Hard Rock Areas Study Unit, 2010

Constituent 

(synonym or abbreviation)

Number of spiked 

samples collected

Minimum recovery 

(percent)

Maximum recovery 

(percent)

Median recovery 

(percent)

Ethylbenzene 5 87 229 94

Ethyl tert-butyl ether (ETBE) 5 91 99 93

Ethyl methacrylate 5 91 96 92

o-Ethyl toluene (1-Ethyl-2-methyl benzene) 5 78 102 98

Hexachlorobutadiene 5 71 90 78

Hexachloroethane 5 80 109 87

2-Hexanone (n-Butyl methyl ketone) 5 92 105 100

Iodomethane (Methyl iodide) 5 107 119 111

Isopropylbenzene 5 83 116 109

4-Isopropyl-1-methyl benzene 5 73 103 98

Methyl acrylate 5 105 117 111

Methyl acrylonitrile 5 103 124 114

Methyl tert-butyl ether (MTBE) 1 5 102 115 104

Methyl iso-butyl ketone (MIBK) 5 99 107 101

Methylene chloride (Dichloromethane) 1 5 92 107 100

Methyl ethyl ketone (2-butanone, MEK) 5 101 120 110

Methyl methacrylate 5 83 95 92

Naphthalene 5 77 106 99

Perchloroethene (PCE, Tetrachloroethene) 1 5 88 100 93

n-Propylbenzene 5 78 106 96

Styrene 4 79 165 94.2

1,1,1,2-Tetrachloroethane 5 88 102 99

1,1,2,2-Tetrachloroethane 5 95 110 105

Tetrahydrofuran 5 90 121 102

1,2,3,4-Tetramethylbenzene 5 72 104 97

1,2,3,5-Tetramethylbenzene 5 80 114 107

Toluene 1 5 96 300 103

1,2,3-Trichlorobenzene 5 85 105 94

1,2,4-Trichlorobenzene 5 71 96 83

1,1,1-Trichloroethane (1,1,1-TCA) 1 5 98 103 101

1,1,2-Trichloroethane (1,1,2-TCA) 5 96 105 100

Trichloroethene (TCE) 1 5 91 102 95

Trichlorofluoromethane (CFC-11) 1 5 91 113 106

1,2,3-Trichloropropane (1,2,3-TCP) 5 95 109 107

Trichlorotrifluoroethane (CFC-113) 5 70 102 92

1,2,3-Trimethylbenzene 5 80 114 107

1,2,4-Trimethylbenzene 1 5 87 318 106

1,3,5-Trimethylbenzene 5 84 109 104

Vinyl bromide (Bromoethene) 5 96 107 98

Vinyl chloride (Chloroethene) 5 96 119 107

m- and p-Xylene 5 86 119 104

o-Xylene 5 85 117 93

1

 Constituents detected in groundwater samples.

Table A5A. Matrix-spike recoveries for volatile organic compounds (VOC) in samples collected for the Bear Valley and Selected Hard 

Rock Areas (BEAR) Groundwater Ambient Monitoring and Assessment (GAMA) study unit, California, April to August 2010.—Continued

[Acceptable recovery range is between 70 and 130 percent]
Appendix 83

Table A5B. Matrix-spike recoveries for pesticides and pesticide degradates in samples collected for the Bear Valley and 

Selected Hard Rock Areas (BEAR) Groundwater Ambient Monitoring and Assessment (GAMA) study unit, California, April to 

August 2010.

[Acceptable recovery range is between 70 and 130 percent]

Constituent 

(synonym or abbreviation)

Number of spiked 

samples collected

Minimum recovery 

(percent)

Maximum recovery 

(percent)

Median recovery 

(percent)

Acetochlor 4 96 136 103.4

Alachlor 4 98 120 105.8

Atrazine 4 9 109 101.5

Azinphos-methyl 4 77 140 95.2

Azinphos-methyl oxon 4 51 136 68.6

Benfluralin 4 57 70 59.5

Carbaryl 4 100 169 125.0

Carbofuran 4 95 152 122.6

2-Chloro-2,6-diethylacetanilide 4 94 132 104.3

4-Chloro-2-methylphenol 4 69 85 76.1

Chlorpyrifos 4 67 86 82.9

Chlorpyrifos oxon 4 19 78 35.7

Cyanazine 4 62 114 109.6

Cyfluthrin 4 49 75 63.7

λ-Cyhalothrin 4 46 59 48.5

Cypermethrin 4 53 75 62.0

DCPA (Dacthal) 4 103 110 107.2

Deethylatrazine (2-Chloro-4-

isopropylamino-6-amino-s-triazine) 

4 24 99 79.3

Desulfinylfipronil 4 90 127 94.7

Desulfinylfipronil amide 4 56 115 87.0

Diazinon 4 88 108 92.8

Diazinon oxon 4 100 119 105.9

3,4-Dichloroaniline 4 84 95 87.5

3,5-Dichloroaniline 4 92 97 94.7

Dichlorvos 4 17 48 32.5

Dicrotophos 4 35 49 44.5

Dieldrin 4 76 94 83.2

2,6-Diethylaniline 4 92 103 96.1

Dimethoate 4 48 77 61.8

Disulfoton 4 63 128 71.6

Disulfoton sulfone 4 81 131 99.2

α-Endosulfan 4 76 89 78.4

Endosulfan sulfate 4 70 91 75.5

Ethion 4 71 89 76.3

Ethion monoxon 4 82 98 89.8

Ethoprophos 4 100 129 107.2

S-Ethyl-dipropylthiocarbamate (EPTC) 4 92 104 95.1

2-Ethyl-6-methylaniline 4 83 102 93.1

Fenamiphos 4 89 132 93.9

Fenamiphos sulfone 4 76 139 92.0

Fenamiphos sulfoxide 4 28 74 32.9

Fipronil 4 81 113 96.3
84 Groundwater-Quality Data in the Bear Valley and Selected Hard Rock Areas Study Unit, 2010

Constituent 

(synonym or abbreviation)

Number of spiked 

samples collected

Minimum recovery 

(percent)

Maximum recovery 

(percent)

Median recovery 

(percent)

Fipronil sulfide 4 76 128 81.0

Fipronil sulfone 4 58 71 63.0

Fonofos 4 90 95 92.4

Hexazinone 4 34 75 64.7

Iprodione 4 66 102 75.5

Isofenphos 4 94 134 96.4

Malaoxon 4 73 132 99.6

Malathion 4 96 140 103.5

Metalaxyl 4 100 120 111.2

Methidathion 4 80 103 97.7

Metolachlor 4 91 131 99.4

Metribuzin 4 89 126 98.1

Molinate 4 96 115 99.2

Myclobutanil 4 35 108 88.2

1-Naphthol 4 36 61 46.8

Oxyfluorfen 4 58 70 66.2

Paraoxon-methyl 4 49 95 71.5

Parathion-methyl 4 79 89 84.3

Pendimethalin 4 70 86 81.7

cis-Permethrin 4 59 82 65.8

Phorate 4 73 80 74.4

Phorate oxon 4 118 132 124.4

Phosmet 4 26 74 32.5

Phosmet oxon 4 23 93 28.6

Prometon 1 4 11 115 98.3

Prometryn 4 6 109 103.4

Pronamide 4 84 98 90.4

Propanil 4 87 203 100.5

Propargite 4 68 112 71.4

cis-Propiconazole 4 22 162 151.9

trans-Propiconazole 4 6 101 87.2

Simazine 1 4 10 99 88.6

Tebuconazole 4 19 84 65.3

Tebuthiuron 4 141 178 157.3

Tefluthrin 4 33 68 43.9

Terbufos 4 75 86 81.1

Terbufos oxon sulfone 4 59 139 93.4

Terbuthylazine 4 17 109 104.5

Thiobencarb 4 95 127 97.9

Tribufos 4 44 80 51.8

Trifluralin 4 69 97 75.4

1

 Constituents detected in groundwater samples.

Table A5B. Matrix-spike recoveries for pesticides and pesticide degradates in samples collected for the Bear Valley and 

Selected Hard Rock Areas (BEAR) Groundwater Ambient Monitoring and Assessment (GAMA) study unit, California, April to 

August 2010.—Continued

[Acceptable recovery range is between 70 and 130 percent]
Appendix 85

Table A5C. Matrix-spike recoveries for wastewater indicator compounds (WICs) in samples collected for the Bear Valley and Selected 

Hard Rock Areas (BEAR) Groundwater Ambient Monitoring and Assessment (GAMA) study unit, California, April to August 2010.

[Acceptable recovery range is between 70 and 130 percent.]

Constituent 

(synonym or abbreviation)

Number of 

spiked samples 

collected

Recovery 

(percent)

Constituent 

(synonym or abbreviation)

Number of 

spiked samples 

collected

Recovery 

(percent)

Acetophenone 1 101 Isophorone 1 91

Acetyl hexamethyl tetrahydronaphthalene 

(AHTN) 

1 88 Isopropylbenzene 1 64

Anthracene 1 83 Isoquinoline 1 64

Anthraquinone 1 96 d-Limonene 1 44

Benzo[a]pyrene 1 88 Menthol 1 95

Benzophenone 1 92 Metalaxyl 1 104

Bromacil 1 98 3-Methyl-1(H)-indole (Skatole) 1 79

Bromoform (tribromomethane) 1 61 5-Methyl-1H-benzotriazole 1 64

3-tert-Butyl-4-hydroxy anisole (BHA) 1 45 1-Methylnaphthalene 1 74

Caffeine 1 95 2-Methylnaphthalene 1 74

Camphor 1 96 Methyl salicylate 1 92

Carbaryl 1 72 Metolachlor 1 93

Carbazole 1 93 Naphthalene 1 83

Chlorpyrifos 1 80 para-Nonylphenol (total) 1 77

Cholesterol 1 61 4-n-Octylphenol 1 74

3-β-Coprostanol 1 71 4-tert-Octylphenol 1 79

Cotinine 1 74 Perchloroethene (PCE, Tetrachloroethene) 1 25

p-Cresol 1 85 Phenanthrene 1 93

4-Cumylphenol 1 83 Phenol 1 1 92

Diazinon 1 107 Prometon 1 98

1,4-Dichlorobenzene 1 71 Pyrene 1 93

N,N-Diethyl-meta-toluamide (DEET) 1 106 β-Sitosterol 1 64

2,6-Dimethylnaphthalene 1 64 β-Stigmastanol 1 69

4-Nonylphenol diethoxylates 1 63 Tributyl phosphate 1 88

4-Octylphenol diethoxylates 1 47 Triclosan 1 83

4-Octylphenol monoethoxylates 1 61 Triethyl citrate (ethyl citrate) 1 93

Fluoranthene 1 98 Triphenyl phosphate 1 92

Hexahydrohexamethylcyclopentabenzopyran 

(HHCB) 

1 86 Tris(2-butoxyethyl) phosphate 1 1 86

Indole 1 57 Tris(2-chloroethyl) phosphate 1 98

Isoborneol 1 86 Tris(dichlorisopropyl) phosphate 1 92

1

 Constituent detected in groundwater samples.

Table A5D. Matrix-spike recoveries for constituents of special interest in samples collected for the Bear Valley and Selected Hard 

Rock Areas (BEAR) Groundwater Ambient Monitoring and Assessment (GAMA) study unit, California, April to August 2010.

[Acceptable recovery range is between 70 and 130 percent]

Constituent 

(synonym or abbreviation)

Number of spiked 

samples collected

Minimum recovery 

(percent)

Maximum recovery 

(percent)

Median recovery 

(percent)

N-Nitrosodimethylamine (NDMA) 4 96 127 111.2

1,2,3-Trichloropropane (1,2,3-TCP) 4 92 119 111.1
86 Groundwater-Quality Data in the Bear Valley and Selected Hard Rock Areas Study Unit, 2010 Table A6. Surrogate compound recoveries for volatile organic compounds (VOCs), pesticides and pesticide degradates, and wastewater indicator compounds (WICs) in samples collected for the Bear Valley and Selected Hard Rock Areas (BEAR) Groundwater Ambient Monitoring and Assessment (GAMA) study unit, California, April to August 2010.

[Abbreviations: NWQL, U.S. Geological Survey National Water Quality Laboratory; <, less than; >, greater than]

Surrogate 

compound

NWQL 

analytical 

schedule

Constituent 

class analyzed

Number of 

blank samples 

analyzed

Median recovery 

in blank samples 

(percent)

Number of 

surrogate 

recoveries 

< 70 percent in 

blank samples

Number of 

surrogate 

recoveries 

> 130 percent in 

blank samples

Number of 

groundwater 

samples 

analyzed

Median recovery 

in groundwater 

samples 

(percent)

Number of 

surrogate 

recoveries 

< 70 percent in 

groundwater 

samples

Number of 

surrogate 

recoveries 

> 130 percent 

in groundwater 

samples

1-Bromo-4-fluorobenzene 2020 VOC 5 95 0 0 38 91 0 0

1,2-Dichloroethane-d4 2020 VOC 5 120 0 2 38 125 0 14Toluene-d8 2020 VOC 5 94 0 0 38 94 0 0

Diazinon-d10 2033 Pesticide 4 77 0 0 38 78 2 0

α-HCH-d6 2033 Pesticide 4 87 0 0 38 87 0 0

Caffeine-13C 1433 WIC 3 90 0 0 9 93 0 0

Decafluorobiphenyl 1433 WIC 3 36 3 0 9 47 9 0

Fluoranthene-d10 1433 WIC 3 89 0 0 9 94 0 0
Appendix 87

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Mathany and Belitz—Groundwater-Quality Data in the Bear Valley and Selected Hard Rock Areas Study Unit, 2010: Results from the California GAMA Program —

 Data Series 747