Prepared in cooperation with the California State Water Resources Control Board and the 

U.S. Geological Survey National Water-Quality Assessment Program 

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

Groundwater-Quality Data in the Northern Coast Ranges 

Study Unit, 2009: Results from the California GAMA Program

U.S. Department of the Interior

U.S. Geological Survey

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Data Series 609
Cover:

Top right: Public supply well, Mendocino, California. (Photograph taken by Stephen Schmitt, U.S. Geological Survey.)

Bottom left: Eel River from California Highway 162, near Covelo, California. (Photograph taken by Barbara Dawson, U.S. Geological Survey.)

Bottom right: Trinidad Head Memorial, Trinidad, California. (Photograph taken by George Bennett V, U.S. Geological Survey.)
Groundwater-Quality Data in the Northern 

Coast Ranges Study Unit, 2009: Results 

from the California GAMA Program

By Timothy M. Mathany, Barbara J. Dawson, Jennifer L. Shelton, and 

Kenneth Belitz

Prepared in cooperation with the California State Water Resources Control 

Board and the U.S. Geological Survey National Water-Quality Assessment 

Program

Data Series 609

U.S. Department of the Interior

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

KEN SALAZAR, Secretary

U.S. Geological Survey

Marcia K. McNutt, Director

U.S. Geological Survey, Reston, Virginia: 2011

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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., Dawson, B.J., Shelton, J.L., and Belitz, Kenneth, 2011, Groundwater-quality data in the northern Coast 

Ranges study unit, 2009: Results from the California GAMA Program: U.S. Geological Survey Data-Series 609, 92 p.
iii

Contents

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

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

Purpose and Scope ..............................................................................................................................5

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

Northern Coast Ranges–Interior Basins Study Area......................................................................5

Northern Coast Ranges–Coastal Basins Study Area .....................................................................9

Methods ........................................................................................................................................................13

Study Design........................................................................................................................................13

Sample Collection and Analysis.......................................................................................................14

Data Reporting.....................................................................................................................................14

Quality-Assurance Methods.............................................................................................................14

Water-Quality Results ................................................................................................................................14

Quality-Control Results ......................................................................................................................14

Comparison Benchmarks ..................................................................................................................14

Groundwater-Quality Data ................................................................................................................16

Field Water-Quality Indicators ................................................................................................16

Organic Constituents.................................................................................................................16

Constituent of Special Interest................................................................................................17

Inorganic Constituents..............................................................................................................17

Isotopic Tracers and Dissolved Noble Gases .......................................................................18

Radioactive Constituents..........................................................................................................18

Microbial Indicators..................................................................................................................19

Future Work ..................................................................................................................................................19

Summary .......................................................................................................................................................19

Acknowledgments.......................................................................................................................................20

References Cited..........................................................................................................................................20

Appendix........................................................................................................................................................69
iv

Figures

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

Northern Coast Ranges (NOCO) Groundwater Ambient Monitoring and

Assessment (GAMA) study unit and study areas ....................................... 4

Figure 2. Map showing the Northern Coast Ranges (NOCO) Groundwater Ambient

Monitoring and Assessment (GAMA) study unit showing the location of the

northern part, the central part, the southern part of the Interior Basins study

area (NOCO-IN), the boundaries of the California Department of Water

Resources (CDWR) defined groundwater basins, the distribution of the Interior

Basins study area grid cells, the location of California Department of Public

Health (CDPH) wells, and the location of sampled grid wells, major cities,

major roads, topographic features, and hydrologic features ........................ 6

Figure 3. Map showing the Northern Coast Ranges (NOCO) Groundwater Ambient

Monitoring and Assessment (GAMA) study unit showing the location of the

northern part, the central part, the southern part of the Coastal Basins study

area (NOCO-CO), the boundaries of the California Department of Water

Resources (CDWR) defined groundwater basins, the distribution of the Coastal

Basins study area grid cells, the location of California Department of Public

Health (CDPH) wells, and the location of sampled grid wells, major cities,

major roads, topographic features, and hydrologic features ........................ 10

Tables

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

the Northern Coast Ranges (NOCO) Groundwater Ambient Monitoring and

Assessment (GAMA) study, California, June to November 2009 ..................... 28

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

for the slow well-sampling schedule in the Northern Coast Ranges (NOCO)

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

June to November 2009..................................................................... 30

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

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

Water Quality Laboratory Schedule 2020 ................................................ 31

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

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

Water Quality Laboratory Schedule 2033 ................................................ 34

Table 3C. Perchlorate, primary uses or sources, comparative benchmarks, and reporting

information for Weck Laboratories, Inc. analyses....................................... 36

Table 3D. Trace elements, comparative benchmarks, and reporting information for the

U.S. Geological Survey National Water Quality Laboratory Schedules 2710......... 37

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

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

Laboratory Schedule 2755 and Laboratory Code 2613 ................................. 38

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

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

Survey National Water Quality Laboratory Schedule 2750 ........................... 38

Table 3G. Isotopic and radioactive constituents, comparative benchmarks, and reporting

information for laboratory analyses ...................................................... 39
v

Tables—Continued

Table 3H. Dissolved noble gases, comparative benchmarks, and reporting information

for the Lawrence Livermore National Laboratory analyses ........................... 40

Table 3I. Microbial indicators, comparative benchmarks, and reporting information for

the U.S. Geological Survey Ohio Microbiology Laboratory and field analyses ...... 40

Table 4. Field water-quality indicators in samples collected for the Northern Coast

Ranges (NOCO) Groundwater Ambient Monitoring and Assessment (GAMA)

study, California, June to November 2009 ................................................ 41

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

Northern Coast Ranges (NOCO) Groundwater Ambient Monitoring and

Assessment (GAMA) study, California, June to November 2009 ..................... 44

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

Northern Coast Ranges (NOCO) Groundwater Ambient Monitoring and

Assessment (GAMA) study, California, June to November 2009 ..................... 46

Table 7. Perchlorate detected in the samples collected for the Northern Coast Ranges

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

California, June to November 2009 ...................................................... 47

Table 8. Trace elements detected in the samples collected for the Northern Coast

Ranges (NOCO) Groundwater Ambient Monitoring and Assessment (GAMA)

study, California, June to November 2009 ................................................ 48

Table 9. Nutrients and dissolved organic carbon (DOC) detected in samples collected

for the Northern Coast Ranges (NOCO) Groundwater Ambient Monitoring and

Assessment (GAMA) study, California, June to November 2009 ..................... 54

Table 10. Major and minor ions, silica, and total dissolved solids (TDS) detected in

samples collected for the Northern Coast Ranges (NOCO) Groundwater

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

November 2009 .............................................................................. 56

Table 11. Results for analyses of stable isotope ratios, tritium activity, and carbon-14

abundance detected in samples collected for the Northern Coast Ranges

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

California, June to November 2009 ...................................................... 59

Table 12A. Radon-222 detected in samples collected for the Northern Coast Ranges

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

California, June to November 2009 ...................................................... 61

Table 12B. Radium isotopes detected in samples collected for the Northern Coast Ranges

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

California, June to November 2009 ...................................................... 62

Table 12C. Gross alpha and gross beta radioactivity detected in samples collected for the

Northern Coast Ranges (NOCO)Groundwater Ambient Monitoring and

Assessment (GAMA) study, California, June to November 2009 ..................... 64

Table 12D. Lead-210 and polonium-210 detected in samples collected for the Northern

Coast Ranges (NOCO) Groundwater Ambient Monitoring and Assessment

(GAMA) study, California, June to November 2009 .................................... 66

Table 13. Microbial indicators detected in samples collected for the Northern Coast

Ranges (NOCO) Groundwater Ambient Monitoring and Assessment (GAMA)

study, California, June to November 2009 ................................................ 68
vi

Conversion Factors, Datums, and Abbreviations and 

Acronyms

Conversion Factors

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)

pound, avoirduois (lb) 0.45359 kilogram (kg)

SI to Inch/Pound

Multiply By To obtain

centimeter (cm) 0.3937 inch (in.)

micrometer (μm) 3.3 × 10–6 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).

Turbidity is given in nephelometric turbidity units (NTRU). 

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 are given in picocuries per liter (pCi/L). 
vii

Conversion Factors, Datums, and Abbreviations and 

Acronyms—Continued

Datums

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).

Selected Terms and Symbols

α confidence level

cm3

 STP/g cubic centimeters of gas at standard temperature and 

pressure (0 degrees Celsius and 1 atmosphere of pressure) 

per gram of water

δ i

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

to the more common lighter isotope of that element, relative 

to a standard reference material, expressed as per mil

= equal to

> greater than

≥ greater than or equal to

< less than

≤ less than or equal to

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

— not detected

p significant level

pH measure of the acidity of water

pK1,2 acid dissociation constants of carbonic acid

pKw acid dissociation constant of water

R result

z test statistic

± plus or minus

* value is greater than benchmark level

** value is greater than upper benchmark level

Abbreviations and Acronyms

AL action level

AL-US action level (USEPA)

APE Alternate Place Entry Form program designed for USGS sampling

CAS Chemical Abstract Service (American Chemical Society)

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

CSU combined standard uncertainty

DWP Domestic Well Project (SWRCB)

E estimated or having a higher degree of uncertainty

GAMA Groundwater Ambient Monitoring and Assessment Program

GPS Global Positioning System
viii

HAL lifetime health advisor y level

HAL-US lifetime health advisory level (USEPA)

HPLC high-performance liquid chromatography

LRL laboratory reporting level

LSD land surface datum

LT-MDL long-term method detection level

M presence verified but not quantified

MCL maximum contaminant level

MCL-US maximum contaminant level (USEPA)

MCL-CA maximum contaminant level (CDPH)

MDL method detection limit

MRL minimum reporting level

MU method uncertainty

na not available

nc not collected

NELAP National Environmental Laboratory Accreditation Program

NFM National Field Manual (USGS)

NFQA National Field Quality Assurance Program (USGS)

NL notification level

NL-CA notification level (CDPH)

NOCO Northern Coast Ranges study unit

NOCO-CO Coastal Basins study area

NOCO-IN Interior Basins study area

nv no measured value or no value in category

np no preference

NWIS National Water Information System (USGS)

OBSP Organic Blind Sample Program (USGS)

PBP Priority Basin Project

PCFF Personal Computer Field Form program designed for USGS sampling

QA quality assurance

QC quality control

RL reporting level

RPD relative percent difference

RSD relative standard deviation

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

S most probable value

SD standard deviation

SMCL secondary maximum contaminant level

SMCL-CA secondary maximum contaminant level (CDPH)

SMCL-US secondary maximum contaminant level (USEPA)

Conversion Factors, Datums, and Abbreviations and 

Acronyms—Continued

Abbreviations and Acronyms—Continued
ix

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

ssLC sample-specific critical level

TT Treatment Technique

TT-US Treatment Technique (USEPA)

U.S. United States

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)

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

NAWQA National Water-Quality Assessment (USGS)

NWQL National Water Quality Laboratory (USGS)

SWRCB California State Water Resources Control Board

USEPA U.S. Environmental Protection Agency

USGS U.S. Geological Survey

Selected Chemical Names

CaCO3 calcium carbonate

CO3

–2 carbonate

CFC chlorofluorocarbon

DOC dissolved organic carbon

H2

O water

HCl hydrochloric acid

HCO3

– bicarbonate

MTBE methyl tert-butyl ether

PCE perchloroethene (tetrachloroethene)

SiO2 silicon dioxide

TCE trichloroethene

TDS total dissolved solids

THM trihalomethane

VOC volatile organic compound

Conversion Factors, Datums, and Abbreviations and 

Acronyms—Continued

Abbreviations and Acronyms—Continued
x

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Abstract 

Groundwater quality in the 633-square-mile Northern 

Coast Ranges (NOCO) study unit was investigated by the U.S. 

Geological Survey (USGS) from June to November 2009, as 

part of the California State Water Resources Control Board 

(SWRCB) Groundwater Ambient Monitoring and Assessment 

(GAMA) Program’s Priority Basin Project (PBP) and the 

U.S. Geological Survey National Water-Quality Assessment 

Program (NAWQA). 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 NOCO study unit was the thirtieth study unit to 

be sampled as part of the GAMA-PBP.

The GAMA Northern Coast Ranges study was designed 

to provide a spatially unbiased assessment of untreatedgroundwater quality in the primary aquifer systems, and to 

facilitate statistically consistent comparisons of untreated 

groundwater quality throughout California. The primary 

aquifer systems (hereinafter referred to as primary aquifers) 

are defined as that part of the aquifer corresponding to 

the perforation intervals of wells listed in the California 

Department of Public Health (CDPH) database for the 

NOCO study unit. The quality of groundwater in shallow 

or deep water-bearing zones may differ from the quality of 

groundwater in the primary aquifers; shallow groundwater 

may be more vulnerable to surficial contamination.

In the NOCO study unit, groundwater samples were 

collected from 58 wells in 2 study areas (Interior Basins and 

Coastal Basins) in Napa, Lake, Mendocino, Glenn, Humboldt, 

and Del Norte Counties. The 58 wells were selected by using a 

spatially distributed, randomized grid-based method to provide 

statistical representation of the study areas. GAMA-PBP wells 

sampled as part of the spatially-distributed, randomized gridcell network are referred to as “grid wells.” 

The groundwater samples were analyzed for organic 

and special-interest constituents (volatile organic compounds 

[VOC], pesticides and pesticide degradates, and perchlorate), 

naturally occurring inorganic constituents (trace elements, 

nutrients, dissolved organic carbon [DOC], major and minor 

ions, silica, total dissolved solids [TDS], and alkalinity), 

radioactive constituents (radon-222, radium isotopes, 

gross alpha and gross beta radioactivity, lead-210, and 

polonium-210), and microbial indicators (F-specific and 

somatic coliphage, Escherichia coli [E. coli] and total 

coliform). Naturally occurring isotopes (stable isotopes of 

hydrogen and oxygen in water, stable isotopes of carbon in 

dissolved inorganic carbon, activities of tritium, and carbon-14 

abundance), and dissolved noble gases also were measured 

to identify the sources and ages of the sampled groundwater. 

In total, 239 constituents and 12 field water-quality indicators 

were measured.

Three types of quality-control samples (blanks, 

replicates, and matrix-spikes) were collected at up to 

12 percent of the wells in the NOCO 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, suggesting that 

contamination from sample collection procedures was not 

a significant source of bias in the data for the groundwater 

samples. Replicate samples generally were within the limits of 

acceptable analytical reproducibility. Matrix-spike recoveries 

were within the acceptable range (70 to 130 percent) for 

approximately 89 percent of the compounds.

This study did not attempt to evaluate the quality of water 

delivered to consumers; after withdrawal from the ground, 

untreated groundwater typically is treated, disinfected, and 

(or) blended with other waters to maintain water quality. 

Regulatory benchmarks apply to water that is served to the 

consumer, not to untreated groundwater. However, to provide 

some context for the results, concentrations of constituents 

measured in the untreated groundwater were compared with 

regulatory and non-regulatory health-based benchmarks 

established by the U.S. Environmental Protection Agency 

(USEPA) and CDPH, and to non-regulatory 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 Northern Coast Ranges 

Study Unit, 2009: Results from the California GAMA 

Program

By Timothy M. Mathany, Barbara J. Dawson, Jennifer L. Shelton, and Kenneth Belitz
2 Groundwater-Quality Data in the Northern Coast Ranges Study Unit, 2009: Results from the California GAMA Program

Most inorganic constituents that were detected in 

groundwater samples from the 58 grid wells in the NOCO 

study unit were detected at concentrations less than drinkingwater benchmarks. In addition, all detections of organic and 

special-interest constituents from NOCO study-unit well 

samples were less than health-based benchmarks.

In total, VOCs were detected in 22 of the 58 wells 

sampled (approximately 38 percent), and pesticides and 

pesticide degradates were detected in 6 wells (approximately 

10 percent) in the NOCO study unit. In the Interior 

Basins (NOCO-IN) study area, VOCs were detected in 

13 of the 28 wells sampled (approximately 46 percent), 

and pesticides and pesticide degradates were detected in 

5 wells (approximately 18 percent). In the Coastal Basins 

(NOCO-CO) study area, VOCs were detected in 9 of the 

30 wells sampled (approximately 30 percent), and pesticide 

degradates were detected in 1 well. 

Trace elements were sampled at all 58 wells in the 

NOCO study unit, and most detections in groundwater 

samples were less than health-based benchmarks. Exceptions 

in the NOCO-IN study area include two detections of 

arsenic greater than the USEPA maximum contaminant level 

(MCL-US) of 10 micrograms per liter (μg/L), one detection 

of barium greater than California maximum contaminant level 

(MCL-CA) of 1,000 μg/L, and five detections of boron greater 

than the CDPH notification level (NL-CA) of 1,000 μg/L. 

All detections of trace elements from wells in the NOCO-CO 

study area were less than health-based benchmarks. In 

addition, all detections of nutrients, major and minor ions, and 

radioactive constituents from all of the NOCO study-unit wells 

were less than health-based benchmarks. 

Results for trace elements, major ions, and TDS with 

non-regulatory benchmarks set for aesthetic concerns from the 

28 NOCO-IN study-area wells showed that iron concentrations 

greater than the CDPH secondary maximum contaminant level 

(SMCL-CA) of 300 μg/L were detected in 7 wells. Manganese 

concentrations greater than the SMCL-CA of 50 μg/L were 

detected in 12 wells. TDS concentrations greater than the 

SMCL-CA recommended benchmark of 500 mg/L were 

measured in 4 of the 28 NOCO-IN study-area wells. 

In the 30 NOCO-CO study-area wells, iron 

concentrations greater than the SMCL-CA were detected 

in 8 wells, and manganese concentrations greater than the 

SMCL-CA were detected in 11 wells. 

Microbial indicators (viral and bacterial) were sampled 

for at 57 wells in the NOCO study unit. One or more microbial 

indicator was detected in 22 wells (11 of 28 NOCO-IN 

study-area wells and 11 of 29 NOCO-CO study-area wells).

Introduction 

About one-half of the water used for public and 

domestic drinking-water supply in California is groundwater 

(Hutson and others, 2004). 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 (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 

three Projects: the (1) 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 

(DWP) conducted by the SWRCB; and (3) GAMA Special 

Studies conducted by LLNL. The GAMA-PBP primarily 

focuses on the deep part of the groundwater resource, 

which is typically used for public drinking-water supply. 

The GAMA-DWP generally focuses on the shallow aquifer 

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

surficial contamination. 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. 

All published and quality-assurance/quality-control 

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

Program are stored in the web-based Geotracker Database 

(California State Water Resources Control Board, 2009, 

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

The Geotracker Database also stores groundwater-quality 

data and related reports collected by other State agencies, 

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

California Department of Water Resources (CDWR), 

California Department of Pesticide Regulation (CDPR), and 

data collected by the SWRCB and Regional Boards from 

environmental monitoring wells at contaminated and (or) 

remediated sites.
Introduction 3

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; 2001b, 

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 over 

90 percent of all groundwater in the state. For the GAMAPBP, 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 

GAMA-PBP is entirely voluntary.

The GAMA-PBP is unique in California because it 

includes many chemical analyses that are not otherwise 

available in statewide water-quality monitoring datasets. 

Groundwater samples collected for the GAMA-PBP 

are typically analyzed for approximately 300 chemical 

constituents using analytical methods with lower detection 

limits than required by the CDPH for regulatory monitoring 

of drinking-water 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 CDPH and for a suite of chemical and isotopic 

tracers for exploring 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.

The range of hydrologic, geologic, and climatic 

conditions in California must be considered in an assessment 

of groundwater quality. Belitz and others (2003) partitioned 

the State into 10 hydrogeologic provinces, each with 

distinctive hydrologic, geologic, and climatic characteristics: 

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 or 

volcanic 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 groundwater 

basins and subbasins within the 10 hydrogeologic provinces. 

Groundwater basins and subbasins were prioritized for 

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

basin, with secondary consideration given to municipal 

groundwater use, agricultural pumping, the number of 

formerly leaking underground fuel tanks, and registered 

pesticide applications (Belitz and others, 2003). Of the 

472 basins and subbasins designated by the CDWR, 116 

priority basins were selected and grouped into 35 study units, 

representing approximately 95 percent of the CDPH wells 

in California. In addition, some areas outside of the defined 

groundwater basins were included in the nearest respective 

study unit to achieve representation of the 20 percent of the 

CDPH wells not located in the groundwater basins. 

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 (Kulongoski and 

Belitz, 2004). The assessments are intended to characterize 

the quality of groundwater in the primary aquifer systems of 

the study units, not the treated drinking water delivered to 

consumers by water purveyors. The primary aquifer systems 

(hereinafter referred to as primary aquifers) are defined as that 

part of the aquifer corresponding to the perforation intervals 

of wells listed in the CDPH databases for the study units. The 

CDPH database lists wells used for municipal and community 

drinking-water supplies, and includes wells from systems 

classified as non-transient (such as those in cities, towns, and 

mobile-home parks) and transient (such as those in schools, 

campgrounds, and restaurants). Collectively, the CDPH refers 

to these wells as “public-supply” wells. Groundwater quality 

in shallow or deep parts of the aquifer systems may differ from 

that in the primary aquifers. In particular, shallow groundwater 

may be more vulnerable to surface contamination. As a result, 

samples from shallow wells (such as many private domestic 

wells and environmental monitoring wells) can have higher 

concentrations of constituents from anthropogenic sources 

(such as VOCs and nitrate) than samples from wells screened 

in the underlying primary aquifers (Landon and others, 2010).

This USGS Data Series Report is the first in a series 

of reports presenting the water-quality data collected in the 

Northern Coast Ranges study unit (hereinafter referred to as 

the NOCO study unit) and is similar to USGS Data Series 

Reports written for the GAMA-PBP study units sampled to 

date. Data Series Reports and additional reports addressing 

the status, understanding, and trends aspects of the waterquality assessments of each study unit are available from the 

U.S. Geological Survey (2011b) at http://ca.water.usgs.gov/

projects/gama/includes/GAMA_publications.html.
4 Groundwater-Quality Data in the Northern Coast Ranges Study Unit, 2009: Results from the California GAMA Program

Figure 1. Hydrogeologic provinces of California and the location of the Northern Coast Ranges (NOCO) 

Groundwater Ambient Monitoring and Assessment (GAMA) study unit and study areas.

Basin and Range

Central

Valley

Klamath

Mountains

Desert

Cascades and

Modoc Plateau

Transverse Ranges and

selected Peninsular Ranges

Southern Coast

Ranges

Sierra

Northern Nevada

Coast

Ranges

San Diego

Drainages

Bakersfield

San

Francisco

Sacramento

OREGON

NEVADA

MEXICO

ARIZONA

Redding

Los Angeles

San Diego

PA C I F I C O C E A N

0 200 MILES

0 200 KILOMETERS

Shaded relief derived from from National Elevation

Dataset (U.S. Geological Survey, 2006) 

Albers Equal-area Conic Projection

Provinces from Belitz and others, 2003.

Northern Coast RangesCoastal Basins 

study area

(figure 3)

Northern Coast RangesInterior Basins

study area

(figure 2)

IP018470_Figure 01
Hydrogeologic Setting 5

Purpose and Scope

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

design, including the hydrogeologic setting of the NOCO 

study unit and the study methods; (2) the analytical results 

for groundwater samples collected in the NOCO study unit, 

and (3) the results of QC analysis. Groundwater samples 

were analyzed for field water-quality indicators, organic, 

special-interest, and inorganic constituents, radioactive 

constituents, naturally-occurring isotopes, microbial 

indicators, and dissolved gases. The chemical data presented 

in this report were evaluated by comparison to State and 

Federal drinking-water regulatory and other non-regulatory 

standards that are applied to treated drinking water. Regulatory 

and non-regulatory 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.

The NOCO study unit lies in the central, western, and 

northern part of the Northern Coast Ranges hydrogeologic 

province as described by Belitz and others (2003). 

Groundwater is a major source of public drinking-water 

supply for many of the cities located in the NOCO study 

unit (Water Education Foundation, 2006). Therefore, the 

NOCO study unit was considered high priority for sampling 

to provide adequate representation of the Northern Coast 

Ranges hydrogeologic province. In addition, the NOCO study 

unit was considered a high priority for sampling to complete 

assessment of groundwater quality in the California Coastal 

Basins Principal Aquifer of the United States (U.S. Geological 

Survey, 2003) by the U.S. Geological Survey’s National 

Water-Quality Assessment (NAWQA) Program (Lapham and 

others, 2005). As a result, the NAWQA groundwater status 

and trends study collaborated with the GAMA-PBP to assess 

groundwater quality in the NOCO study unit. 

Hydrogeologic Setting 

The NOCO study unit is located in Northern California 

within the CDWR-defined Sacramento River and North Coast 

hydrogeologic regions and includes a total of 34 groundwater 

basins and subbasins (California Department of Water 

Resources, 2004a–gg). Combined, these basins and subbasins 

define the extent of the two study areas (Interior Basins and 

Coastal Basins) of the NOCO study unit, and cover an area 

of 633 square miles (mi2) in Napa, Sonoma, Colusa, Lake, 

Mendocino, Glenn, Humboldt, and Del Norte Counties, 

California (figs. 2A–C and 3A–C).

Northern Coast Ranges–Interior Basins 

Study Area

The Interior Basins study area (hereinafter referred to 

as the NOCO-IN study area) is 256 mi2 in area and contains 

23 CDWR-defined basins (California Department of Water 

Resources, 2004a–w). The NOCO-IN study area is located 

in a region of Northern California approximately 25 to 

60 mi inland of the Pacific Ocean and about 60 to 130 mi 

north of San Francisco. The study area consists primarily 

of noncontiguous inland valleys whose boundaries on the 

west, north, east, and south are the surrounding hills and (or) 

mountains. In the central part of the study area, some of the 

inland valleys share Clear Lake as a border (fig. 2A–C).

Land-surface altitudes in the study area range from about 

475 feet above mean sea level (ft above msl) near the town 

of Hopland, to over 4,200 ft above msl on Mount Konocti, 

located just east of the town of Kelseyville. The major surface 

drainage features of the study area are the Eel, Russian, and 

Navarro Rivers and their tributaries: all of which have their 

headwaters outside of the study area and terminate in the 

Pacific Ocean. There are also large creeks (Outlet, Stoney, 

Scotts, St. Helena, and Pope) and numerous small creeks that 

drain the valleys of the study area (fig. 2A–C). 

The climate in the study area is classified as 

Mediterranean, with warm to hot dry summers and cold, wet 

winters (National Oceanic and Atmospheric Administration, 

2010). Practically all precipitation in the study area occurs in 

the fall and winter months, with average annual precipitation 

ranging from a low of around 22 inches (in.) near the town of 

Stonyford, to more than 65 in. near the town of Laytonville 

(California Department of Water Resources, 2004i, r; U.S. 

Department of Commerce, 2010).

The primary aquifers in the study area occur in 

Quaternary-alluvium groundwater basins made up of sand, 

silt, gravel, and clay eroded from the surrounding hills. 

These deposits interfinger with and grade into alluvial fan 

and terrace deposits along the sides of the valleys, and older 

more consolidated alluvium at depth, and in some valleys, 

finer-grained lake deposits towards the center of the basins. 

Groundwater conditions are mostly unconfined, with some 

confined areas toward the center of valleys and at depth 

(California Department of Water Resources, 2004e–w). 

The major rock types surrounding the alluvial valleys are 

the Jurassic-Cretaceous Franciscan Formation (mudstone, 

graywacke sandstones, chert) and ophiolitic and metamorphic 

volcanic rocks (Muir and Webster, 1977; Farrar, 1986; 

California Department of Water Resources, 2004e–w). 
6 Groundwater-Quality Data in the Northern Coast Ranges Study Unit, 2009: Results from the California GAMA Program

Figure 2. The Northern Coast Ranges (NOCO) Groundwater Ambient Monitoring and Assessment (GAMA) study unit showing the 

location of (A) the northern part, (B) the central part, (C) the southern part of the Interior Basins study area (NOCO-IN), the boundaries 

of the California Department of Water Resources (CDWR) defined groundwater basins, the distribution of the Interior Basins study area 

grid cells, the location of California Department of Public Health (CDPH) wells, and the location of sampled grid wells, major cities, major 

roads, topographic features, and hydrologic features.

101

20

Covelo

Willits

Stonyford

Laytonville

Potter Valley

NOCO-IN28

NOCO-IN26

NOCO-IN23

NOCO-IN16

NOCO-IN15

NOCO-IN11

NOCO-IN06

NOCO-IN05

NOCO-IN03

NOCO-IN04

Bartlett Springs Fault Zone

0 5 10 Miles

0 5 10 Kilometers

MENDOCINO CO

LAKE CO

LAKE CO

GLENN CO

GLENN CO

TEHAMA CO

COLUSA CO

Lake

Pillsbury

Eel River

Eel River

STUDY AREA

Shaded relief derived from U.S. Geological Survey

National Elevation Dataset, 2006. 

Albers Equal Area Conic Projection

EXPLANATION

IP018470_Figure 02a

Mill Creek

Outlet Creek

Randomized

 sampling

 grid cell 

California Department

 of Public Health (CPDH)

 well Water bodies

Stream or river

NOCO grid well and identifier Northern Coast

Ranges—

Interior Basins

Shown on

 figure 2B

NOCO-IN15

Faults—Dashed where uncertain;

 Dotted where concealed 

Stoney Creek

A
Hydrogeologic Setting 7

Maacama Fault

Clover Valley Fault Zone

Russian River

Russian River

101

101

29

20

20

128

Mt.

Big Valley Konocti

Basin

Ukiah

Lakeport

Boonville

Kelseyville

Redwood Valley

Hopland

NOCO-IN27

NOCO-IN24

NOCO-IN21 NOCO-IN18

NOCO-IN20

NOCO-IN19

NOCO-IN17

NOCO-IN14

NOCO-IN13

NOCO-IN12

NOCO-IN10

NOCO-IN09

NOCO-IN08

NOCO-IN07

NOCO-IN02

NOCO-IN01

0 5 10 Miles

0 5 10 Kilometers

LAKE CO

MENDOCINO CO

COLUSA CO

SONOMA CO

GLENN

CO

Lake

Pillsbury

Lake

Mendocino

Clear Lake

Navarro River

Scotts Creek

Scotts Creek

Big Valley Fault

Wight Way Fault

STUDY AREA

Shaded relief derived from U.S. Geological Survey

National Elevation Dataset, 2006. 

Albers Equal Area Conic Projection

EXPLANATION

IP018470_Figure 02b

Randomized

 sampling

 grid cell 

California Department

 of Public Health (CPDH)

 well Water bodies

Stream or river

NOCO grid well and identifier Northern Coast

Ranges—

Interior Basins

Shown on

 figure 2A

NOCO-IN08

Faults—Dashed where uncertain;

 Dotted where concealed 

B

Figure 2.—Continued
8 Groundwater-Quality Data in the Northern Coast Ranges Study Unit, 2009: Results from the California GAMA Program

29

128

Middletown

Pope Valley

Aetna Springs

NOCO-IN25

NOCO-IN22

0 2.5 5 Miles

0 2.5 5 Kilometers

122°40' 122°30'

38°

40'

NAPA CO

LAKE CO

Pope Creek

St. Helena Creek

STUDY AREA

Shaded relief derived from U.S. Geological Survey

National Elevation Dataset, 2006. 

Albers Equal Area Conic Projection

EXPLANATION

IP018470_Figure 02c

SONOMA CO

Collayomi Fault Zone

Randomized

 sampling

 grid cell 

California Department

 of Public Health (CPDH)

 well Water bodies

Stream or river

NOCO grid well and identifier Northern Coast

Ranges—

Interior Basins

NOCO-IN22

Faults—Dashed where

 uncertain

C

Figure 2.—Continued
Hydrogeologic Setting 9

In groundwater basins near Clear Lake, the major rock type 

is Quaternary volcanic rock associated with the Clear Lake 

or Sonoma Volcanic fields (Soil Mechanics and Foundation 

Engineers Inc., 1967; Earth Sciences Associates, 1978; 

California Department of Water Resources, 2004a–d). In 

the Big Valley basin, groundwater also is supplied by thin 

volcanic ash layers/lenses interbedded with low permeability 

sediments (California Department of Water Resources, 2004b). 

The general groundwater-flow direction in the study area 

is from the sides toward the center of the valleys, following 

the topography and the direction of surface-water flow. The 

study area has several northwest-trending faults (Maacama, 

Big Valley, and Wight Way) and fault zones (Bartlett, Clover 

Valley, and Collayomi) that act as hydrologic barriers to 

groundwater movement (California Department of Water 

Resources, 2004a–w) (fig. 2A–C). 

Groundwater recharge in the study area occurs from 

a mixture of ambient recharge (direct percolation of 

precipitation and irrigation waters, infiltration of run-off 

from surrounding hills, and seepage from rivers and creeks) 

(California Department of Water Resources, 2004a–w).

Northern Coast Ranges–Coastal Basins 

Study Area

The Coastal Basins study area (hereinafter referred to as 

the NOCO-CO study area) is 377 mi2 in area and contains a 

total of 11 CDWR-defined basins and subbasins (California 

Department of Water Resources, 2004x–gg). The study area 

is located along the Northern California coast beginning just 

north of Point Arena and extending to the Oregon border. The 

study area has three distinct sections (northern, central, and 

southern), each bordered on the west by the Pacific Ocean 

and on the north, east, and south by the hills surrounding the 

coastal valleys (fig. 3A–C). 

Land-surface altitudes in the study area range from 

sea level where the study area boundary touches the Pacific 

Ocean, to approximately 500 ft above msl in the hills above 

the city of Fortuna. The major surface drainage features of the 

study area are the Smith, Klamath, Mad, Eel, Noyo, and Big 

Rivers and their tributaries: all of which have their headwaters 

outside of the study area and terminate in the Pacific Ocean. 

The climate in the study area is influenced by the Pacific 

Ocean and is classified as coastal (National Oceanic and 

Atmospheric Administration, 2010). It is characterized by 

cool to mild summers and cold wet winters. Coastal fog and 

low clouds are common throughout the year. Average annual 

precipitation in the study area ranges from a low of around 

38 in. near the town of Trinidad to a high of approximately 

79 in. near the town of Klamath (U.S. Department of 

Commerce, 2010). 

The primary aquifers in the northern part of the study 

area principally occur in the Smith River Plain, a marine 

terrace made up of Holocene alluvial fan and floodplain 

deposits; in the Pleistocene terrace deposits; and in the 

Pleistocene Battery Formation (California Department of 

Water Resources, 1987, 2004x). In the central part of the 

study area the primary aquifers occur in groundwater basins 

consisting of alluvial deposits associated with drowned river 

mouths of the Klamath, Mad, and Eel Rivers. The alluvial 

deposits consist of Holocene alluvium, dune sand, the 

Pleistocene Hookton Formation, and the deeper PliocenePleistocene Carlotta Formation (Johnson, 1978; California 

Department of Water Resources, 2004y–dd). Primary aquifers 

in the southern part of the study area are found in the Fort 

Bragg-area terrace deposits. These deposits are discontinuous, 

uplifted, and dissected Pleistocene marine terraces along 

the Pacific Ocean. The terrace deposits consist of semiconsolidated clay, silt, sand, and gravel derived from adjacent 

formations (largely the Franciscan Formation), that are up to 

150-ft thick (California Department of Water Resources, 1982, 

2004ff–gg). 

The groundwater basins in the northern and central parts 

of the study area are in hydraulic connection with the Pacific 

Ocean and sea water extends as a transition wedge underneath 

fresh groundwater in some of the basins. In the southern part 

of the study area the uplifted terrace deposits prevent hydraulic 

connection between groundwater basins and the Pacific Ocean 

(California Department of Water Resources, 2004x–gg).

The general groundwater-flow direction in the study area 

is from east to west towards the Pacific Ocean. In the northern 

part of the study area, dune sand accumulation has created 

Lake Earl (fig. 3A), which acts as a restrictive structure to 

groundwater movement. In the central and southern parts of 

the study area several northwest trending faults (Freshwater 

and Table Bluff) and fault zones (Little Salmon and San 

Andreas) act as hydrologic barriers (California Department of 

Water Resources, 2004x–gg) (fig. 3B, C). 

Groundwater recharge in the study area occurs from 

a mixture of ambient recharge (direct percolation of 

precipitation and irrigation waters, infiltration of run-off from 

surrounding areas, seepage from the Smith, Klamath, Mad, 

Eel, Noyo, and Big Rivers and their tributaries, and seepage 

from small creeks that flow into Humboldt and Arcata Bays) 

and subsurface inflow (from non-alluvial geologic units that 

bound the alluvial basins) (California Department of Water 

Resources, 2004x–gg).
10 Groundwater-Quality Data in the Northern Coast Ranges Study Unit, 2009: Results from the California GAMA Program

Figure 3. The Northern Coast Ranges (NOCO) Groundwater Ambient Monitoring and Assessment (GAMA) study unit showing 

the location of (A) the northern part, (B) the central part, (C) the southern part of the Coastal Basins study area (NOCO-CO), the 

boundaries of the California Department of Water Resources (CDWR) defined groundwater basins, the distribution of the Coastal 

Basins study area grid cells, the location of California Department of Public Health (CDPH) wells, and the location of sampled 

grid wells, major cities, major roads, topographic features, and hydrologic features.

199

101

NOCO-CO24

NOCO-CO23

NOCO-CO22

NOCO-CO16

NOCO-CO15

NOCO-CO14

0 5 10 Miles

0 5 10 Kilometers

Pacific Ocean

Fort Dick

Klamath

Crescent City

Randomized

 sampling

 grid cell 

California Department

 of Public Health (CPDH)

 well Water bodies

Stream or river

NOCO grid well and identifier

STUDY AREA

Northern Coast

Ranges—

Coastal Basins

Shaded relief derived from U.S. Geological Survey

National Elevation Dataset, 2006. 

Albers Equal Area Conic Projection

EXPLANATION

IP018470_Figure 03a

NOCO-CO15

Lake

Earl

Smith River

KlamathRiver

DEL NORTE CO

HUMBOLDT CO

A
Hydrogeologic Setting 11

299

96

101

Eureka

Arcata

Fortuna

Trinidad

HUMBOLDT CO

NOCO-CO29

NOCO-CO27

NOCO-CO26

NOCO-CO25

NOCO-CO20

NOCO-CO18

NOCO-CO13

NOCO-CO10

NOCO-CO09

NOCO-CO04

NOCO-CO30

NOCO-CO28

NOCO-CO21

NOCO-CO19

NOCO-CO17

NOCO-CO12

NOCO-CO11

NOCO-CO08

NOCO-CO07

NOCO-CO03

0 2.5 5 10 Miles

0 5 10 2.5 Kilometers

Pacific Ocean

Arcata

Bay

Humboldt

Bay

Big Lagoon

Eel River

Mad River

Table Bluff Fault

Freshwater Fault

Little Salmon Fault Zone

Shaded relief derived from U.S. Geological Survey

National Elevation Dataset, 2006. 

Albers Equal Area Conic Projection

EXPLANATION

IP018470_Figure 03b

Randomized

 sampling

 grid cell 

California Department

 of Public Health (CPDH)

 well Water bodies

Stream or river

NOCO grid well and identifier

STUDY AREA

Northern Coast

Ranges—

Coastal Basins

NOCO-CO11

Faults—Dashed where uncertain;

 Dotted where concealed

B

Figure 3.—Continued
12 Groundwater-Quality Data in the Northern Coast Ranges Study Unit, 2009: Results from the California GAMA Program

San Andreas Fault Zone

1

128

Mendocino

Manchester

Fort Bragg

NOCO-CO06

NOCO-CO05

NOCO-CO02

NOCO-CO01

Point Arena

0 5 10 Miles

0 5 10 Kilometers

Pacific Ocean

Big River

Noyo River

MENDOCINO CO

Shaded relief derived from U.S. Geological Survey

National Elevation Dataset, 2006. 

Albers Equal Area Conic Projection

EXPLANATION

IP018470_Figure 03c

Randomized

 sampling

 grid cell 

California Department

 of Public Health (CPDH)

 well Water bodies

Stream or river

NOCO grid well and identifier

STUDY AREA

Northern Coast

Ranges—

Coastal Basins

NOCO-CO05

Faults—Dashed where uncertain

C

Figure 3.—Continued
Methods 13

Methods 

Methods used for the GAMA-PBP were selected to 

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

for suitable statistical representation; (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 and analytical 

methods, the QA plan, and the results of analyses of QC 

samples.

Study Design

The 58 wells in this study are located within surficial 

alluvium and were selected for sampling to provide a 

statistically unbiased, spatially-distributed assessment 

of the quality of groundwater resources used for public 

drinking-water supply. Wells sampled as part of the 

spatially-distributed, randomized grid-cell network, 

hereinafter, are referred to as “grid wells”.

The spatially-distributed wells were selected using a 

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

grid-based method divides the study areas into equal-area 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 NOCO study unit, an attempt was made to sample 

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

cell contained more than one CDPH well, each well randomly 

was assigned a rank. The highest ranking well that met basic 

sampling criteria (for example, sampling point located prior 

to treatment, or capability to pump for several hours) was 

sampled. If a grid cell contained no accessible CDPH wells, 

then other types of wells, such as domestic, irrigation, and 

(or) industrial, were considered for sampling. An attempt was 

made to select these “alternative” wells by choosing ones 

with depths and screened intervals similar to CDPH wells in 

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

to provide a spatially distributed, randomized monitoring 

network. 

The NOCO-IN study area was divided into 30 equal-area 

grid cells, 8.5 mi2 (22 square kilometers [km2]) in area; a total 

of 28 wells were sampled inside this grid network (fig. 2A–C). 

The NOCO-CO study area was divided into 30 equal-area 

grid cells, 12.5 mi2 (approximately 32 km2) in area. In the grid 

network of the NOCO-CO study area, coverage was complete, 

with every grid cell represented by a well sampled (fig. 3A–C). 

The 58 grid wells sampled in the NOCO study unit were 

named for the study area where they were located by using 

the prefix “NOCO-IN” for the Interior Basins study area and 

“NOCO-CO” for the Coastal Basins study area, and by using a 

suffix numbered in the order of sample collection within each 

study area (figs. 2A-C and 3A-C). Unlike previous Data Series 

Reports written for the GAMA-PBP study units, all of the 

wells sampled in the NOCO study unit were classified as grid 

wells; therefore, none of the wells in the NOCO study unit 

were considered “understanding wells.”

The GAMA alphanumeric identification number 

for each well, along with the date sampled, sampling 

schedule, land-surface altitude, well type, and available 

well-construction information is shown in table 1. 

Groundwater samples were collected from 29 CDPH wells, 

16 domestic wells, 7 irrigation wells, 3 industrial wells, 

1 abandoned well, 1 stock-supply well, and 1 spring during the 

period from June to November 2009. 

Well locations were verified by using global positioning 

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

comparison with existing well information in USGS and 

CDPH databases, and information provided by well owners. 

Drillers’ logs or other sources of construction information 

were obtained when available. Well information and location 

were recorded by hand on field sheets, and electronically on 

field laptop computers using the Alternate Place Entry Form 

(APE) program designed by the USGS. All information was 

verified and then uploaded into the USGS National Water 

Information System (NWIS). Well owner, well category, and 

well location information is confidential.

The wells in the NOCO study unit were sampled for a 

standard set of constituents, including: field water-quality 

indicators, organic and special-interest constituents, naturally 

occurring inorganic constituents, radioactive constituents, 

microbial indicators, naturally occurring isotopes, and 

dissolved noble gases. 

Most of the constituents were specified for collection by 

the NAWQA Program for Major Aquifer Studies assessments. 

Selected constituents, including perchlorate, stable isotopes 

of hydrogen and oxygen in water, tritium, stable isotopes 

of carbon in dissolved inorganic carbon and carbon-14 

abundance, and dissolved noble gases, were specified for 

collection by the GAMA-PBP and similar data have been 

collected in other basins in California. 

The standard set of constituents was termed the “slow” 

schedule (table 2). In addition to the slow schedule, mercury 

was added for the NOCO-IN study area and iodide was added 

for the NOCO-CO study area. Slow refers to the time required 

to sample the well for all the analytes on the schedule. One 

slow well could be sampled in 1 day. In NOCO, all 58 of the 

wells were sampled on the slow schedule (table 1).
14 Groundwater-Quality Data in the Northern Coast Ranges Study Unit, 2009: Results from the California GAMA Program

Sample Collection and Analysis

Samples were collected in accordance with the protocols 

established by the NAWQA Program (Koterba and others, 

1995) and the USGS National Field Manual (NFM) (U.S. 

Geological Survey, variously dated). These sampling protocols 

are followed so that representative samples of groundwater are 

collected at each site, and so that the samples are collected and 

handled in ways that minimize the potential for contamination.

Table 3A–I list the compounds analyzed in each 

constituent class. Groundwater samples were analyzed for 

85 VOCs (table 3A); 83 pesticides and pesticide degradates 

(table 3B); perchlorate (table 3C); 24 trace elements 

(table 3D); 5 nutrients and DOC (table 3E); 9 major and minor 

ions, silica, TDS, and laboratory alkalinity (table 3F); stable 

isotopes of hydrogen and oxygen in water, stable isotopes 

of carbon in dissolved inorganic carbon, and 9 radioactive 

constituents, including tritium and carbon-14 abundance 

(table 3G); 5 dissolved noble gases and helium stable isotopic 

ratios (table 3H); and 4 microbial indicators (table 3I). The 

methods and laboratories used for sample collection and 

analysis are described in the appendix section titled “Sample 

Collection and Analysis.”

Data Reporting

The methods and conventions used for reporting the data 

are described in the appendix section titled “Data Reporting.” 

Two field water-quality indicators—pH and specific 

conductance—were measured in the field and at the USGS 

National Water Quality Laboratory (NWQL), and both results 

are reported (see appendix section titled “Field Water-quality 

Indicators Measured by Multiple Methods”). 

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 USGS NAWQA Program 

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

NWQL, the primary laboratory used to analyze samples 

for this study, is described in Pirkey and Glodt (1998) and 

Maloney (2005). QC samples collected in the NOCO study 

are: blanks, replicates, and matrix and surrogate spikes. QC 

samples were collected to evaluate potential contamination, as 

well as bias and variability of the data that may have resulted 

from sample collection, processing, storage, transportation, 

and laboratory analysis. QA/QC procedures and results are 

described in the appendix section titled “Quality-Assurance 

Methods.”

Water-Quality Results 

Quality-Control Results

Results of QC analyses (blanks, replicates, and matrix 

and surrogate spikes) were used to evaluate the quality of the 

data for the groundwater samples. On the basis of detections 

in NWQL blanks and blanks collected for this and previous 

GAMA-PBP study units, some of the detections reported 

by the laboratory for five VOCs, seven trace elements, and 

DOC were considered suspect and, therefore, were either 

removed from the set of groundwater-quality data presented 

in this report or flagged with a ≤ symbol (see table A2 and 

additional discussion in the appendix section titled “Detections 

in Blanks and SRL Analysis”). Results from the replicates 

confirm that the procedures used to collect and analyze the 

samples were consistent. Variability for nearly 100 percent 

of the replicate pairs for constituents detected in samples was 

within the acceptable limits (table A3A–C). Median matrixspike recoveries for 19 of the 169 organic and special-interest 

constituents analyzed were lower than the acceptable limit 

of 70 percent (tables 3B and A4B). Constituents for which 

low recoveries occurred might not have been detected in 

some samples if they were present at concentrations near 

the laboratory reporting levels (LRLs). These compounds 

are indicated with a footnote in the “Detection” column of 

table 3B. The QC results are described in the appendix section 

titled “Quality-Control Results.”

Comparison Benchmarks

Concentrations of constituents detected in groundwater 

samples were compared with CDPH and USEPA 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, 2008a–c). The chemical data presented 

in this report are meant to characterize the quality of the 

untreated groundwater within the primary aquifers of the 

NOCO 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 drinkingwater regulations. The following benchmarks were used for 

comparisons:
Water-Quality Results 15

• MCL—Maximum Contaminant Level. Legally 

enforceable standards that apply to public-water 

systems and are designed to protect public health by 

limiting the levels of contaminants in drinking water. 

MCLs established by the USEPA are the minimum 

standards with which States are required to comply, 

and individual States may choose to set more stringent 

standards. CDPH has established MCLs for additional 

constituents not regulated by the USEPA, as well as 

lowered the benchmark concentration for a number of 

constituents with MCLs established by the USEPA. 

In this report, a benchmark set by the USEPA and 

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

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

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

constituents are detected at concentrations greater than 

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

collected for the GAMA-PBP, but these detections do 

not constitute violations of CDPH regulations.

• AL—Action Level. Legally enforceable standards 

that apply to public-water systems and are designed to 

protect public health by limiting the levels of copper 

and lead in drinking water. Detections of copper or 

lead greater than the action-level benchmarks trigger 

requirements for mandatory water treatment to reduce 

the corrosiveness of water to water pipes. The action 

levels established by the USEPA and CDPH are the 

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

this report.

• TT—Treatment Technique. Legally enforceable 

standards that apply to public-water systems and 

are designed to protect public health by limiting the 

levels of microbial constituents in drinking water. 

TT requirements are applied when water delivered to 

consumers exceeds specified action levels. Detections 

of microbial constituents greater than benchmarks 

trigger requirements for mandatory additional 

disinfection during water treatment. The action levels 

established by the USEPA and CDPH are the same; 

thus, these benchmarks are labeled “TT-US” in this 

report.

• SMCL—Secondary Maximum Contaminant Level. 

Non-enforceable standards applied to constituents that 

affect the aesthetic qualities of drinking water, such 

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

drinking water, such as scaling and staining. Both the 

USEPA and CDPH define SMCLs, but unlike MCLs, 

SMCLs established by CDPH are not required to be 

at least as stringent as those established by USEPA. 

SMCLs established by CDPH are used in this report 

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

values. The SMCL-US is used for pH because no 

SMCL-CA has been defined.

• NL—Notification Level. Health-based notification 

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

the constituents in drinking water that lack MCLs. 

If a constituent is detected at concentrations greater 

than its NL-CA, California State law requires timely 

notification of local governing bodies and recommends 

consumer notification.

• HAL—Lifetime Health Advisory Level. The 

maximum concentration of a constituent at which its 

presence in drinking water is not expected to cause any 

adverse carcinogenic effects for a lifetime of exposure. 

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

are calculated assuming consumption of 2 liters (L) 

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

a 70-kilograms (kg) (154-lb) adult and that 20 percent 

of a person’s exposure comes from drinking water.

• RSD5—Risk-Specific Dose. The concentration of 

a constituent in drinking water corresponding to an 

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

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

RSD5s are calculated by dividing the 10–4 cancer 

risk concentration established by the USEPA by 10 

(RSD5-US).

For constituents with MCLs, detections in groundwater 

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

Constituents with SMCLs were compared with the SMCL-CA. 

For chloride, sulfate, specific conductance, and TDS, CDPH 

defines a “recommended” and an “upper” SMCL-CA; 

detections of these constituents in groundwater samples 

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

constituents corresponds to the recommended SMCL-CA. 

Detected concentrations of constituents without an MCL or 

SMCL were compared to the NL-CA. For constituents without 

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

compared with the HAL-US. For constituents without an 

MCL, SMCL, NL-CA, or HAL-US, detected concentrations 

were compared with the RSD5-US. For constituents without 

an MCL, SMCL, NL-CA, or HAL-US, or RSD5-US, detected 

concentrations were compared with the AL-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 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 table 3A–I for all constituents and in tables 4–13

for constituents detected in groundwater samples from the 

NOCO study unit. Established benchmarks are not available 

for all constituents analyzed for this study. Detections of 

constituents at concentrations greater than the selected 

comparison benchmark are marked with asterisks in tables 4, 

8, and 10. 
16 Groundwater-Quality Data in the Northern Coast Ranges Study Unit, 2009: Results from the California GAMA Program

Groundwater-Quality Data

Results from analyses of untreated groundwater samples 

from the NOCO study unit are presented in tables 4–13. These 

results are separated into the two study areas that make up the 

NOCO study unit (NOCO-IN and NOCO-CO). Groundwater 

samples collected in the NOCO study unit were analyzed for 

239 constituents; 157 of those constituents were not detected 

in any of the samples, and 76 constituents were detected 

(table 3A–I). The results from LLNL for five dissolved noble 

gases and for helium isotope ratios have not been received 

and are not presented in this report; they will be included in a 

subsequent publication. 

For organic and special-interest (perchlorate) constituent 

classes, the results tables include the following summary 

statistics: the number of wells from which each analyte was 

detected, the frequency at which it was detected (in relation 

to the number of wells in the study unit and each study area), 

and the total number of constituents detected at each well. For 

the inorganic, isotopic, and radioactive constituent classes, 

the tables include all of the wells, constituents, and samples 

analyzed. For the microbial indicators, the table includes only 

those wells where detections occurred. 

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 5–13: 

• Organic constituents

• Volatile organic compounds (VOC) (table 5)

• Pesticides and pesticide degradates (table 6)

• Perchlorate (table 7)

• Inorganic constituents

• Trace elements (table 8)

• Nutrients and dissolved organic carbon (DOC) 

(table 9)

• Major and minor ions, silica, and total dissolved 

solids (TDS) (table 10)

• Isotopic tracers (table 11)

• Radioactive constituents 

• Radon-222 (table 12A)

• Radium isotopes (table 12B)

• Gross alpha and gross beta radioactivity (table 12C)

• Lead-210 and polonium-210 (table 12D)

• Microbial indicators (table 13)

Field Water-Quality Indicators 

Field measurements of turbidity, dissolved oxygen, and 

water temperature, and field and laboratory measurements of 

pH, specific conductance, alkalinity, and associated parameters 

(bicarbonate and carbonate concentrations) are presented in 

table 4. Turbidity, dissolved oxygen, alkalinity, dissolved 

oxygen, and bicarbonate and carbonate concentrations are 

used as indicators of natural processes that affect water 

chemistry. The pH value indicates the acidity of the water. 

Specific conductance is the measure of electrical conductivity 

of the water and is proportional to amount of total dissolved 

solids in the water. 

Field pH values for 14 of the 58 grid wells sampled 

(9 NOCO-IN study-area wells and 5 NOCO-CO study-area 

wells) in the NOCO study unit were outside of the SMCL-US 

range for pH (<6.5 or >8.5) (table 4). 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.

Specific-conductance values (both field and laboratory) 

for three NOCO-IN study-area wells were greater than the 

recommended SMCL-CA of 900 microsiemens per centimeter 

(μS/cm). 

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, 8 were detected in NOCO 

study-unit groundwater samples; all detections in gridwell samples were at concentrations less than health-based 

benchmarks (table 5). One or more VOCs were detected in 

22 of the 58 NOCO study-unit grid wells sampled (about 

38 percent detection frequency). In the NOCO-IN study area, 

VOCs were detected in 13 of the 28 wells (approximately 46 

percent). VOCs that were detected in more than 10 percent 

of the NOCO-IN study-area wells were chloroform 

(trichloromethane), 1,1,1-trichloroethane (1,1,1-TCA), and 

methyl tert-butyl ether (MTBE). In the NOCO-CO study 

area, VOCs were detected in 9 of the 30 wells (approximately 

30 percent). Chloroform was the only VOC detected in more 

than 10 percent of the NOCO-CO study-area wells (table 5). 

Chloroform is among the most commonly detected VOCs in 

groundwater nationally (Zogorski and others, 2006).

Pesticides include herbicides, insecticides, and 

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

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

the 83 pesticides and pesticide degradates analyzed at all of 

the grid wells in the NOCO study unit, 2 pesticides (simazine 
Water-Quality Results 17

and atrazine) and 1 pesticide degradate (deethylatrazine) 

were detected in groundwater samples; all detections were at 

concentrations less than health-based benchmarks (table 6). 

One or more pesticide compounds were detected in 6 of the 

58 NOCO study-unit grid wells (about 10 percent detection 

frequency). In the NOCO-IN study area, pesticides and 

pesticide degradates were detected in 5 of the 28 wells 

(approximately 18 percent). The herbicide simazine was 

detected in more than 10 percent of the NOCO-IN well 

samples. Simazine was detected in 1 of the 30 wells sampled 

in the NOCO-CO study area (table 6). Simazine is among the 

nation’s most commonly detected pesticide compounds in 

groundwater (Gilliom and others, 2006).

Constituent of Special Interest

Perchlorate is a constituent of special interest in 

California because it may adversely affect water quality 

and recently has been found in water supplies (California 

Department of Public Health, 2008b). Perchlorate was 

analyzed for at all 58 grid wells in the NOCO study unit 

and was detected in 14 of the 58 wells (about 24 percent 

detection frequency). In the NOCO-IN study area, perchlorate 

was detected in 9 of 28 wells (approximately 32 percent). 

In the NOCO-CO study area, perchlorate was detected in 

5 of 30 wells (approximately 17 percent). Perchlorate was 

not measured at concentrations greater than the MCL-CA of 

6 micrograms per liter (μg/L) in any of the wells in the NOCO 

study unit (table 7). 

Inorganic Constituents

Unlike the organic constituents and the constituent 

of special interest, most of the inorganic constituents are 

naturally present in groundwater, although their concentrations 

may be influenced by human activities. 

Regulatory health-based or non-regulatory aesthetic 

benchmarks have been established for 22 of 24 trace elements 

analyzed in this study (table 3D). Of the 18 trace elements 

with health-based benchmarks, concentrations of most 

detections of the trace elements in the 58 NOCO study-unit 

grid wells were less than these benchmarks (table 8). The 

exceptions were a few detections of arsenic, barium, and 

boron greater than benchmarks in NOCO-IN study-area wells. 

Arsenic concentrations greater than the USEPA maximum 

contaminant level (MCL-US) of 10 μg/L were detected in 2 

of 28 NOCO-IN study-area wells. A barium concentration 

greater than the MCL-CA of 1,000 μg/L was detected in one 

NOCO-IN study-area well. Boron concentrations greater than 

the CDPH notification level (NL-CA) of 1,000 μg/L were 

detected in five NOCO-IN study-area wells. All detections 

of trace elements in NOCO-CO study-area wells were at 

concentrations less than regulatory health-based benchmarks 

(table 8).

Note that results from the USGS Branch of Quality 

Systems (BQS) QA program (within the USGS Office of 

Water Quality) during the time period that NOCO studyunit samples were analyzed at the NWQL indicate negative 

analytical biases for iron and magnesium (of 25 and 

7.8 percent, respectively) and positive analytical bias for 

uranium (of 13 percent) (U.S. Geological Survey, 2009). The 

results suggest that iron and magnesium concentrations may 

be slightly underestimated and uranium concentrations may be 

slightly overestimated. 

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. High concentrations of nitrate can adversely 

affect human health, particularly the health of infants. 

Nutrients and DOC were sampled for at all 28 grid wells 

in the NOCO-IN study area and at 29 of 30 grid wells in 

the NOCO-CO study area. Nutrients were not measured at 

concentrations greater than health-based benchmarks in any of 

the 57 wells in the NOCO study unit (table 9).

The levels of certain trace elements, major-ion 

composition, and total dissolved solids (TDS) content in 

groundwater affect the aesthetic properties of water, such as 

taste, color, and odor, and the technical properties of water, 

such as scaling and staining. Although there are no adverse 

health effects directly associated with these properties, they 

may reduce consumer satisfaction with the water or may 

have economic effects. The CDPH has established nonenforceable benchmarks (SMCL-CAs) that are based on 

aesthetic properties 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, 

manganese, silver, zinc, chloride, sulfate, and TDS were 

sampled for at all 58 wells in the NOCO study unit.

Iron concentrations greater than the SMCL-CA of 

300 μg/L was detected in seven NOCO-IN study-area wells 

and in eight NOCO-CO study-area wells (table 8). 

Manganese concentrations greater than the SMCL-CA of 

50 μg/L was detected in 12 NOCO-IN study-area wells and 

11 NOCO-CO study-area wells (table 8). 

TDS concentrations greater than the recommended 

SMCL-CA benchmark of 500 mg/L was detected in four 

NOCO-IN study-area wells (table 10). 

All silver, zinc, chloride, and sulfate concentrations 

detected in the 58 NOCO study-unit wells were less than the 

corresponding SMCL-CA (tables 8, 10).
18 Groundwater-Quality Data in the Northern Coast Ranges Study Unit, 2009: Results from the California GAMA Program

Isotopic Tracers and Dissolved Noble Gases

The isotopic ratios, activities, and abundances of many 

elements and the concentrations of dissolved gases (including 

noble gases) may be used as tracers of hydrologic processes 

(Clark and Fritz, 1997). 

The isotopic ratios of hydrogen and oxygen in 

water (table 11) aid in the interpretation of the sources of 

groundwater recharge. These stable isotopic ratios reflect the 

altitude, latitude, and temperature of precipitation and also 

the extent of evaporation of the water in surface-water bodies 

or soils prior to infiltration into the aquifer or directly from 

groundwater close to land surface once in the aquifer system. 

Tritium activities (table 11), helium isotope ratios, 

and carbon-14 abundance (table 11) provide information 

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

is a short-lived radioactive isotope of hydrogen that is 

incorporated into the water molecule. Low levels of tritium 

are produced continuously by interaction of cosmic radiation 

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

produced as a result atmospheric testing of nuclear weapons 

between 1952 and 1963. Thus, concentrations of tritium 

greater than background generally indicate the presence of 

water recharged since the early 1950s. Helium isotope ratios 

are used in conjunction with tritium concentrations to estimate 

ages for young groundwater. 

Carbon-14 (table 11) is a radioactive isotope of carbon. 

Low levels of carbon-14 are produced continuously by 

interaction of cosmic radiation with the Earth’s atmosphere, 

and incorporated into atmospheric carbon dioxide. Carbon 

dioxide dissolves in precipitation, surface water, and 

groundwater exposed to the atmosphere, thereby entering the 

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

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

relative to modern values, generally indicate a presence of 

groundwater that is several thousand years old. 

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 recharge water. 

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 NOCO 

study-unit grid wells were more than three orders of 

magnitude less than the MCL-CA benchmark (table 11).

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 

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

eventually forming stable isotopes of lead (Soddy, 1913; Faure 

and Mensing, 2005). Radium-226, radium-228, and radon-222 

are radioactive isotopes formed during the uranium or thorium 

decay series. In each step in the decay series, one radioactive 

element turns into a different radioactive element by emitting 

an alpha or a beta particle from its nucleus. For example, 

radium-226 emits an alpha particle and therefore turns into 

radon-222. Radium-228 decays to form actinium-228 by 

emission of a beta particle. Polonium-210 is a radioactive 

decay product in the natural uranium-238 decay series; along 

with lead-210 it is one of two relatively long-lived decay 

products of radon-222 (U.S. Department of Energy, 2005). 

The alpha and beta particles emitted during radioactive 

decay are hazardous to human health because these energetic 

particles may damage cells. Radiation damage to cell DNA 

may increase the risk of getting cancer.

Activity often is used instead of concentration for 

reporting the presence of radioactive constituents. Activity of 

radioactive constituents in groundwater is measured in units 

of picocuries per liter (pCi/L), and 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. 

Radon-222 was sampled for at 57 wells, radium isotopes 

(radium-226 and radium-228), lead-210, and polonium-210 

were sampled for at 54 wells, and gross alpha and gross beta 

radioactivity were sampled for at all 58 wells in the NOCO 

study unit. 

Radon-222 activities for all NOCO study-unit well 

samples were less than the proposed MCL-US of 4,000 pCi/L 

(table 12A). The proposed MCL-US will apply if the 

state or local water agency has an approved multimedia 

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

Environmental Protection Agency, 1999).

Radium isotopes (radium-226 and radium-228) activities 

for all NOCO study-unit well samples were less than the 

MCL-US of 5 pCi/L (table 12B). The MCL-US benchmark for 

radium is the sum of radium-226 and radium-228.

Gross alpha and gross beta radioactivity for all NOCO 

study-unit well samples was less than established health-based 

benchmarks (table 12C). One gross alpha radioactivity sample 

(72-hour count) and one gross beta radioactivity sample 

(72-hour count) were counted after the 72-hour time period 

at the laboratory. A delay in the counting by the laboratory 

may result in lower activities than may have been observed 

for these analytes if the count had been preformed within the 

72-hour time period; the results for these two analytes are 

footnoted in table 12C.

Lead-210 was detected in 2 of 24 NOCO-IN studyarea wells and in 3 of 30 NOCO-CO study-area wells. 

Polonium-210 was detected in 6 NOCO-IN study-area wells 

and in 11 NOCO-CO study-area wells (table 12D).
Summary 19

Microbial Indicators

Water is disinfected during drinking-water treatment to 

prevent diseases that may be spread by water-borne microbial 

constituents derived from human or animal wastes. The 

specific viruses and bacteria responsible for diseases generally 

are not measured because routine analytical methods are not 

available. Measurements are made of more easily analyzed 

microbial constituents that serve as indicators of the presence 

of human or animal waste in water. Drinking water purveyors 

respond to detections of microbial indicators by applying 

additional disinfection agents to the water.

Microbial indicators were sampled for at 57 grid wells in 

the NOCO study unit. F-specific coliphage (a viral indicator) 

was detected in 2 of 29 NOCO-CO study-area wells. Somatic 

coliphage (a viral indicator) was detected in 2 of 28 NOCO-IN 

study-area wells and in 1 NOCO-CO study-area well. 

Escherichia coli (E. coli) (a bacterial indicator) was detected 

in one NOCO-IN study-area well and in three NOCO-CO 

study-area wells. Total coliform (a bacterial indicator) was 

detected in 10 NOCO-IN study-area wells and in 9 NOCO-CO 

study-area wells (table 13). The health-based benchmarks 

for microbial indicators are based on recurring detections in 

treated drinking water, thus, the detections reported here do 

not constitute an exceedance of the benchmarks. 

Future Work

Subsequent reports will be focused on assessment of the 

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

qualitative, and quantitative approaches to evaluate the 

natural and human factors affecting groundwater quality in 

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

CDPH databases will be compiled, evaluated, and used in 

combination with the data that are presented in this report. 

Additionally, these subsequent reports will include the LLNL 

results (dissolved noble gases and helium isotope ratios) for 

the NOCO study unit.

Summary 

Groundwater quality in the 633-square-mile Northern 

Coast Ranges (NOCO) study unit was investigated by the U.S. 

Geological Survey (USGS) from June to November 2009, 

as part of the Priority Basin Project (PBP) of the California 

State Water Resources Control Board (SWRCB) Groundwater 

Ambient Monitoring and Assessment (GAMA) PBP. The 

GAMA Program was created to provide a comprehensive 

baseline of groundwater quality in the state. 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 NOCO study 

unit sampling was conducted with support from the U.S. 

Geological Survey’s National Water-Quality Assessment 

(NAWQA) Program to assess the California Coastal Basins 

principal aquifer.

The GAMA NOCO study was designed to provide 

a spatially unbiased assessment of untreated groundwater 

quality in the primary aquifer systems and to facilitate 

statistically consistent comparisons of untreated groundwater 

quality throughout California. The primary aquifer systems 

(hereinafter referred as primary aquifers) are defined as that 

part of the aquifer corresponding to the perforation intervals 

of wells listed in the California Department of Public Health 

(CDPH) database for the NOCO study unit. The quality of 

groundwater in shallow or deep water-bearing zones may 

differ from that in the primary aquifers; shallow groundwater 

may be more vulnerable to surficial contamination.

This study did not attempt to evaluate the quality of 

water delivered to consumers; after withdrawal from the 

ground, water typically is treated, disinfected, and blended 

with other waters to maintain acceptable water quality. 

Regulatory benchmarks apply to treated water that is served 

to the consumer, not to untreated groundwater. However, 

to provide some context for the results, concentrations of 

constituents measured in the untreated groundwater were 

compared with regulatory and non-regulatory health-based 

benchmarks established by the U.S. Environmental Protection 

Agency (USEPA) and CDPH, and non-regulatory benchmarks 

established for aesthetic concerns by CDPH.

The NOCO study unit is located in the central, western, 

and northern parts of the Northern Coast Ranges hydrologic 

province and includes a total of 34 groundwater basins and 

subbasins defined by the California Department of Water 

Resources. The NOCO study included assessment of the 

groundwater quality from 58 wells in Napa, Lake, Mendocino, 

Glenn, Humboldt, and Del Norte Counties, California. 

All 58 wells were selected using a spatially distributed, 

randomized grid-based method to provide statistical 

representation of the study areas. GAMA-PBP wells sampled 

as part of the spatially distributed, randomized grid-cell 

network are referred to as “grid wells.”

Groundwater samples were analyzed for field waterquality indicators, organic and special-interest constituents, 

naturally occurring inorganic constituents, radioactive 

constituents, and microbial indicators. Naturally-occurring 

isotopes and dissolved noble gases also were measured to 

provide a dataset to interpret the sources and ages of the 

sampled groundwater. In total, 239 constituents and 12 field 

water-quality indicators were measured. This report describes 

the sampling, analytical, and QA methods used in the study, 

and present the results of the chemical analyses made of the 

groundwater samples.
20 Groundwater-Quality Data in the Northern Coast Ranges Study Unit, 2009: Results from the California GAMA Program

All detected concentrations of organic constituents, 

nutrients, major and minor ions, and radioactive constituents 

in samples collected from the 58 grid wells in the NOCO 

study unit were less than health-based benchmarks. Of the 

28 wells in the Interior Basins (NOCO-IN) study area, two 

detections of arsenic were greater than the USEPA maximum 

contaminant level (MCL-US), one detection of barium was 

greater than CDPH maximum contaminant level (MCL-CA), 

and five detections of boron were greater than the CDPH 

notification level (NL-CA).

Concentrations of most of the samples from NOCO 

study-unit grid wells collected for trace elements, major ions, 

and TDS measured less than the non-enforceable benchmarks 

set for aesthetic concerns. Iron was detected at concentrations 

greater than the CDPH secondary maximum contaminant 

level (SMCL-CA) of 300 μg/L in 7 wells in the NOCO-IN 

study area and 8 wells in the NOCO-CO study area. 

Manganese was detected at concentrations greater than the 

SMCL-CA of 50 μg/L in 12 NOCO-IN study-area wells and 

in 11 NOCO-CO study-area wells. TDS concentrations greater 

than the SMCL-CA recommended benchmark of 500 mg/L 

were measured in four NOCO-IN study-area wells. 

Microbial indicators (viral and bacterial) were sampled 

for at 57 wells in the NOCO study unit. One or more microbial 

indicator was detected in 11 wells in both the NOCO-IN and 

NOCO-CO study areas.

Acknowledgments

The authors thank the following cooperators for their 

support: the California State Water Resources Control Board, 

U.S. Geological Survey National Water-Quality Assessment 

Program, California Department of Public Health, California 

Department of Water Resources, and Lawrence Livermore 

National Laboratory. We especially thank the well owners and 

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

collect samples from their wells.

References Cited

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.

Barnes, Ivan, 1964, Field measurement of alkalinity and pH: 

U.S. Geological Survey Water-Supply Paper 1535–H, 17 p.

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.

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

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

Laboratory—Determination of dissolved organic carbon 

by UV-promoted persulfate oxidation and infrared 

spectrometry: U.S. Geological Survey Open-File 

Report 92-480, 12 p.

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

Survey Techniques of Water-Resources Investigations, 

book 9, chap. A7.2, accessed March 23, 2010, at http://pubs.

water.usgs.gov/twri9A7.2/.

California Department of Public Health, 2008a, California 

drinking water-related laws—Drinking water-related 

regulations, Title 22: California Department of Public 

Health, accessed March 17, 2010, 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 March 17, 2010, 

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

NotificationLevels.aspx.

California Department of Water Resources, 1982, Northern 

District, June 1982, Mendocino County coastal ground 

water study, 86 p.

California Department of Water Resources, 1987, Smith 

River Plain Ground Water Study, Sacramento: California 

Department of Water Resources, Northern District, Report 

No. 7, 147 p.

California Department of Water Resources, 2003, California’s 

groundwater update 2003: California Department of Water 

Resources Bulletin 118, 246 p., accessed March 2, 2010, 

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

update2003.cfm.

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

groundwater—Individual basin descriptions, Upper Lake 

Valley: California Department of Water Resources Bulletin 

118, accessed March 2, 2010, at http://www.water.ca.gov/

pubs/groundwater/bulletin_118/basindescriptions/5-13.pdf.

California Department of Water Resources, 2004b, 

California’s groundwater—Individual basin descriptions, 

Big Valley: California Department of Water Resources 

Bulletin 118, accessed March 2, 2010, at http://

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

basindescriptions/5-15.pdf.
References Cited 21

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

groundwater—Individual basin descriptions, Long Valley: 

California Department of Water Resources Bulletin 118, 

accessed March 2, 2010, at http://www.water.ca.gov/pubs/

groundwater/bulletin_118/basindescriptions/5-31.pdf.

California Department of Water Resources, 2004d, 

California’s groundwater—Individual basin descriptions, 

Pope Valley: California Department of Water Resources 

Bulletin 118, accessed March 2, 2010, at http://

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

basindescriptions/5-68.pdf.

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

groundwater—Individual basin descriptions, Scotts Valley: 

California Department of Water Resources Bulletin 118, 

accessed March 2, 2010, at http://www.water.ca.gov/pubs/

groundwater/bulletin_118/basindescriptions/5-14.pdf.

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

groundwater—Individual basin descriptions, High Valley: 

California Department of Water Resources Bulletin 118, 

accessed March 2, 2010, at http://www.water.ca.gov/pubs/

groundwater/bulletin_118/basindescriptions/5-16.pdf.

California Department of Water Resources, 2004g, 

California’s groundwater—Individual basin descriptions, 

Coyote Valley: California Department of Water 

Resources Bulletin 118, accessed March 2, 2010, at 

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

basindescriptions/5-18.pdf.

California Department of Water Resources, 2004h, 

California’s groundwater—Individual basin descriptions, 

Collayomi Valley: California Department of Water 

Resources Bulletin 118, accessed March 2, 2010, at 

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

basindescriptions/5-19.pdf.

California Department of Water Resources, 2004i, 

California’s groundwater—Individual basin descriptions, 

Stonyford Town Area: California Department of Water 

Resources Bulletin 118, accessed March 2, 2010, at 

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

basindescriptions/5-63.pdf.

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

groundwater—Individual basin descriptions, North 

Fork Cache Creek: California Department of Water 

Resources Bulletin 118, accessed March 2, 2010, at 

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

basindescriptions/5-93.pdf.

California Department of Water Resources, 2004k, 

California’s groundwater—Individual basin descriptions, 

Middle Creek: California Department of Water Resources 

Bulletin 118, accessed March 2, 2010, at http://

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

basindescriptions/5-94.pdf.

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

groundwater—Individual basin descriptions, Covelo Round 

Valley: California Department of Water Resources Bulletin 

118, accessed March 2, 2010, at http://www.water.ca.gov/

pubs/groundwater/bulletin_118/basindescriptions/1-11.pdf.

California Department of Water Resources, 2004m, 

California’s groundwater—Individual basin descriptions, 

Laytonville Valley: California Department of Water 

Resources Bulletin 118, accessed March 2, 2010, at 

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

basindescriptions/1-12.pdf.

California Department of Water Resources, 2004n, 

California’s groundwater—Individual basin descriptions, 

Little Lake Valley: California Department of Water 

Resources Bulletin 118, accessed March 2, 2010, at 

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

basindescriptions/1-13.pdf.

California Department of Water Resources, 2004o, 

California’s groundwater—Individual basin descriptions, 

Anderson Valley: California Department of Water 

Resources Bulletin 118, accessed March 2, 2010, at 

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

basindescriptions/1-19.pdf.

California Department of Water Resources, 2004p, 

California’s groundwater—Individual basin descriptions, 

Garcia River Valley: California Department of Water 

Resources Bulletin 118, accessed March 2, 2010, at 

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

basindescriptions/1-20.pdf.

California Department of Water Resources, 2004q, 

California’s groundwater—Individual basin descriptions, 

Hettenshaw Valley: California Department of Water 

Resources Bulletin 118, accessed March 2, 2010, at 

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

basindescriptions/1-36.pdf.

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

groundwater—Individual basin descriptions, Lower 

Laytonville Valley: California Department of Water 

Resources Bulletin 118, accessed March 2, 2010, at 

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

basindescriptions/1-38.pdf.

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

groundwater—Individual basin descriptions, Williams 

Valley: California Department of Water Resources Bulletin 

118, accessed March 2, 2010, at http://www.water.ca.gov/

pubs/groundwater/bulletin_118/basindescriptions/1-43.pdf.

California Department of Water Resources, 2004t, California’s 

groundwater—Individual basin descriptions, Gravelley 

Valley: California Department of Water Resources Bulletin 

118, accessed March 2, 2010, at http://www.water.ca.gov/

pubs/groundwater/bulletin_118/basindescriptions/1-48.pdf.
22 Groundwater-Quality Data in the Northern Coast Ranges Study Unit, 2009: Results from the California GAMA Program

California Department of Water Resources, 2004u, 

California’s groundwater—Individual basin descriptions, 

Potter Valley: California Department of Water Resources 

Bulletin 118, accessed March 2, 2010, at http://

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

basindescriptions/1-51.pdf.

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

groundwater—Individual basin descriptions, Ukiah Valley: 

California Department of Water Resources Bulletin 118, 

accessed March 2, 2010, at http://www.water.ca.gov/pubs/

groundwater/bulletin_118/basindescriptions/1-52.pdf.

California Department of Water Resources, 2004w, 

California’s groundwater—Individual basin descriptions, 

Sanel Valley: California Department of Water Resources 

Bulletin 118, accessed March 2, 2010, at http://

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

basindescriptions/1-53.pdf.

California Department of Water Resources, 2004x, 

California’s groundwater—Individual basin descriptions, 

Smith River Plain: California Department of Water 

Resources Bulletin 118, accessed March 2, 2010, at 

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

basindescriptions/1-1.pdf.

California Department of Water Resources, 2004y, 

California’s groundwater—Individual basin descriptions, 

Mad River Lowland Subbasin: California Department of 

Water Resources Bulletin 118, accessed March 2, 2010, at 

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

basindescriptions/1-8.01.pdf.

California Department of Water Resources, 2004az, 

California’s groundwater—Individual basin descriptions, 

Dows Prairie School Area Subbasin: California Department 

of Water Resources Bulletin 118, accessed March 2, 2010, 

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

basindescriptions/1-8.02.pdf.

California Department of Water Resources, 2004aa, 

California’s groundwater—Individual basin descriptions, 

Eureka Plain: California Department of Water Resources 

Bulletin 118, accessed March 2, 2010, at http://

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

basindescriptions/1-9.pdf.

California Department of Water Resources, 2004bb, 

California’s groundwater—Individual basin descriptions, 

Eel River Valley: California Department of Water 

Resources Bulletin 118, accessed March 2, 2010, at 

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

basindescriptions/1-10.pdf.

California Department of Water Resources, 2004cc, 

California’s groundwater—Individual basin descriptions, 

Lower Klamath River Valley: California Department of 

Water Resources Bulletin 118, accessed March 2, 2010, at 

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

basindescriptions/1-14.pdf.

California Department of Water Resources, 2004dd, 

California’s groundwater—Individual basin descriptions, 

Big Lagoon Area: California Department of Water 

Resources Bulletin 118, accessed March 2, 2010, at 

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

basindescriptions/1-27.pdf.

California Department of Water Resources, 2004ee, 

California’s groundwater—Individual basin descriptions, 

Fort Bragg Terrace Area: California Department of Water 

Resources Bulletin 118, accessed March 2, 2010, at 

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

basindescriptions/1-21.pdf.

California Department of Water Resources, 2004ff, 

California’s groundwater—Individual basin descriptions, 

Ten Mile River Valley: California Department of Water 

Resources Bulletin 118, accessed March 2, 2010, at 

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

basindescriptions/1-40.pdf.

California Department of Water Resources, 2004gg, 

California’s groundwater—Individual basin descriptions, 

Big River Valley: California Department of Water 

Resources Bulletin 118, accessed March 2, 2010, at 

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

basindescriptions/1-45.pdf.

California Environmental Protection Agency, 2011, GAMA—

Groundwater Ambient Monitoring and Assessment 

Program: State Water Resources Control Board website, 

accessed February 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 January 11, 

2010, 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 February 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.
References Cited 23

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

P., 2002, Compilation of minimum and maximum 

isotope ratios of selected elements in naturally occurring 

terrestrial materials and reagents: U.S. Geological Survey 

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.

Earth Sciences Associates, 1978, Upper Lake Ground Water 

Investigations for Lake County Flood Control and Water 

Conservation District, January 1978, 25 p.

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.

Eichrom Technologies, LLC., 2009, Analytical Procedures 

Rev. 2.0: Lead-210 and Polonium-210 in Water, accessed on 

March 8, 2010, at http://www.eichrom.com/docs/methods/

pdf/otw01-20_pb-po-water.pdf.

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.

Farrar, C.D., 1986, Ground-water resources in Mendocino 

County, California: U.S. Geological Survey WaterResources Investigations Report 85-4258, 81 p.

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

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

Wiley & Sons, Inc., 897 p.

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

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

John Wiley & Sons, 3,168 p., accessed on March 16, 2010, 

at http://ie.lbl.gov/toipdf/toi20.pdf.

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 OpenFile 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 

Water-Resources Investigations, book 5, chap. A1, 545 p.

Fram, M.S., Olsen, L.D., and Belitz, Kenneth, 2011, Review 

of volatile organic compound blank data collected for 

the California Groundwater Ambient Monitoring and 

Assessment (GAMA) Program, May 2004–October 2009: 

U.S. Geological Survey Scientific Investigations Report, in 

press.

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, thalium, and vanadium using 

inductively coupled plasma-mass spectrometry: U.S. 

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

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

by the U.S. Geological Survey National Water Quality 

Laboratory—Determination of organic plus inorganic 

mercury in filtered and unfiltered natural water with cold 

vapor–atomic fluorescence spectrometry: U.S. Geological 

Survey Water-Resources Investigations Report 01–4132, 

16 p.

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

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

and soil samples using collision/reaction cell inductively 

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

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

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

P.A., Martin, J.D., Nakagaki, N., Nowell, L.H., Scott, 

J.C., Stackelberg, P.E., Thelin, G.P., and Wolock, D.M., 

2006, The quality of our nation’s waters—Pesticides in 

the nation’s streams and groundwater, 1992–2001: U.S. 

Geological Survey Circular 1291, 172 p.

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

potentiometric titration, Part II: Analyst, v. 77, p. 661.
24 Groundwater-Quality Data in the Northern Coast Ranges Study Unit, 2009: Results from the California GAMA Program

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

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

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

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

392 p. 

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.

Hoaglin, D.C., 1983, Letter values–A set of selected order 

statistics, in Hoaglin, D.C., Mosteller, F., and Tukey, J.W., 

eds., Understanding robust and exploratory data analysis: 

New York, John Wiley & Sons, p. 33–54.

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

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

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

1268, 46 p.

Johnson, M., 1978, Ground-water conditions in the Eureka 

area, Humboldt County, California, 1975: U.S. Geological 

Survey Water-Resources Investigations Report 78-127, 

45 p.

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

Groundwater data-collection protocols and procedures 

for the National Water-Quality Assessment Program—

Collection and documentation of water-quality samples 

and related data: U.S. Geological Survey Open-File 

Report 95-399, 113 p.

Kreiger, H.L., and Whittaker, E.L., 1980, Prescribed 

procedures for measurement of radioactivity in drinking 

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

80-032, 142 p. (Also available as PB80-224744 at http://

www.ntis.gov)

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

ambient monitoring and assessment program: U.S. 

Geological Survey Fact Sheet 2004–3088, 2 p.

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 September 17, 2009, at http://

pubs.water.usgs.gov/twri9A2/.

Lapham, W.W., Hamilton, P.A., and Myers, D.N., 2005, 

National Water-Quality Assessment Program—Cycle II—

Regional assessments of aquifers: U.S. Geological Survey 

Fact Sheet 2005-3013, 4 p., accessed April 22, 2010, at 

http://pubs.usgs.gov/fs/2005/3013/.

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

Geological Survey Techniques of Water-Resources 

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

2009, 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 

March 8, 2010, at http://pubs.usgs.gov/of/2005/1263/.

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 ∑C02 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.
References Cited 25

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

data from streams and groundwater sampled during water 

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

Investigations Report 2005–5106, 27 p.

Muir, K.S., and Webster, D.A., 1977, Geohydrology of part of 

the Round Valley Indian Reservation, Mendocino County, 

California: U.S. Geological Survey Water-Resources 

Investigations Report 77-22, 40 p.

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

U.S. Geological Survey Techniques of Water-Resources 

Investigations, book 9, chap. A7.1, accessed February 16, 

2009, at http://pubs.water.usgs.gov/twri9A7.1/.

National Oceanic and Atmospheric Administration, 2010, 

Climate of California, accessed April 26, 2010, at http://

www.wrcc.dri.edu/narratives/CALIFORNIA.htm.

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.

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 12, 2010, at http://pubs.er.usgs.gov/usgspubs/fs/

fs02698.

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

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

Techniques of Water-Resources Investigations, book 9, 

chap. A6.3, accessed March 17, 2010, at http://pubs.water.

usgs.gov/twri9A6.3/.

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.

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 site 

selection approaches for design of a groundwater quality 

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

Investigations Report 90-4101, 109 p.

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

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

volatile organic compounds in active public supply wells as 

groundwater tracers in the Los Angeles physiographic basin, 

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

Investigations Report 01-4188, 29 p.

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

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

Soil Mechanics and Foundation Engineers Inc., March 1967, 

Big Valley Ground-Water Recharge Investigation for Lake 

County Flood Control and Water Conservation District, 

62 p.

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

522, accessed February 14, 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 February 14, 2011, at http://www.leginfo.

ca.gov/cgi-bin/displaycode?section=wat&group=10001-

11000&file=10780-10782.3.

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.

U.S. Department of Commerce, National Climatic Data 

Center, 2010, accessed March 30, 2010, at http://www.ncdc.

noaa.gov/oa/ncdc.html.

U.S. Department of Energy, 2005, Argonne National 

Laboratory, EVS—Human Health Fact Sheet, August 2005, 

accessed January 14, 2010, at http://www.ead.anl.gov/pub/

doc/polonium.pdf.

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.
26 Groundwater-Quality Data in the Northern Coast Ranges Study Unit, 2009: Results from the California GAMA Program

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

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

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

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

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

total coliforms and Escherichia coli in water by membrane 

filtration using a simultaneous detection technique (MI 

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

R-02-024.

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

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

Code of Federal Regulations, Title 40, 136 p.

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

Determination of perchlorate in drinking water by liquid 

chromatography electrospray ionization mass spectrometry 

(Revision 1.0, January 2005): Office of Groundwater 

and Drinking Water, EPA Document # 815-R-05-007, 

34 p., accessed January 11, 2010, at http://www.epa.gov/

safewater/methods/pdfs/methods/met331_0.pdf.

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

contaminants, accessed January 11, 2010, at http://www.

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

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

health advisories–2006 Drinking water standards and health 

advisory tables, accessed January 11, 2010, at http://www.

epa.gov/waterscience/criteria/drinking/.

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

radon in drinking water rule, accessed January 11, 2010, at 

http://www.epa.gov/ogwdw/radon/proposal.html.

U.S. Geological Survey, 2003, Principal aquifers of the 48 

conterminous United States, Hawaii, Puerto Rico, and 

the U.S. Virgin Islands, available online at http://www.

nationalatlas.gov/mld/aquifrp.html. 

U.S. Geological Survey, 2006, National Elevation Dataset 

(NED): U.S. Geological Survey database, accessed 

February 14, 2011, at http://ned.usgs.gov/.

U.S. Geological Survey, 2009, Branch of Quality Systems, 

August 2009, Inorganic blind sample project, accessed 

January 15, 2010, at http://bqs.usgs.gov/ibsp/qadata.shtml.

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

Project: California Water Science Center website, accessed 

February 14, 2011, at http://ca.water.usgs.gov/gama/.

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

Water Science Center website, accessed February 14, 

2011, at http://ca.water.usgs.gov/gama/includes/GAMA_

publications.html.

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 January 16, 

2010, at http://water.usgs.gov/owq/FieldManual/. 

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.

Water Education Foundation, 2006, Where does my water 

come from?: Sacramento, Calif., Water Education 

Foundation,, accessed January 13, 2010, at http://www.

water-ed.org/watersources/default.asp.

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

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

p. 721–735.

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

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

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

March 8, 2010, 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 March 8, 2010, 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 

March 8, 2010 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 March 8, 2010, 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 March 8, 2010, 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 March 8, 2010, at http://pubs.water.usgs.

gov/twri9A5/.

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

California GAMA program—Groundwater quality in the 

San Diego drainages hydrologic province, California, 2004: 

U.S. Geological Survey Data-Series 129, 91 p.
References Cited 27

Yurewicz, M.C., 1981, Incremental field titration of 

bicarbonate: U.S. Geological Survey Water Resources 

Division Bulletin, October–December 1981, p. 8–13.

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

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

Survey National Water Quality Laboratory–Determination 

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

capillary-column gas chromatography/mass spectrometry: 

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

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

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

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

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

Geological Survey Circular 1292, 101 p.
28 Groundwater-Quality Data in the Northern Coast Ranges Study Unit, 2009: Results from the California GAMA Program

Table 1. Identification, sampling, and construction information for wells sampled for the Northern Coast Ranges (NOCO) Groundwater 

Ambient Monitoring and Assessment (GAMA) study, California, June to November 2009.

[GAMA well identification number: NOCO-IN, Interior Basins study area grid well; NOCO-CO, Coastal Basins study area grid well. Numbered suffix 

indicates the order of sample collection within each study area. Sampling schedule is described in table 2. Land-surface datum (LSD) is a datum plane that is 

approximately at land surface at each well. The altitude of the LSD is described in feet above the North American Vertical Datum 1988. Abbreviations: ft, feet; 

NAVD 88, North American Vertical Datum 1988; na, not available]

Sampling information Construction information

GAMA well

identification

number

Date sampled 

(mm/dd/ yyyy)

Sampling 

schedule

Altitude of LSD 

(ft above

NAVD88)

Well type

Well depth 

(ft below 

LSD)

Depth

to top

perforation 

(ft below LSD)

Depth to

bottom

perforation 

(ft below LSD)

NOCO grid wells

NOCO-IN01 06/01/2009 Slow 748 Production 165 79 157

NOCO-IN02 06/02/2009 Slow 363 Production 120 60 120

NOCO-IN03 06/03/2009 Slow 1,673 Production 58 33 58

NOCO-IN04 06/04/2009 Slow 1,385 Production 55 na na

NOCO-IN05 06/08/2009 Slow 1,633 Production 60 na na

NOCO-IN06 06/10/2009 Slow 1,342 Production 1 136 na na

NOCO-IN07 06/15/2009 Slow 523 Production 40 23 38

NOCO-IN08 06/16/2009 Slow 483 Production 40 25 40

NOCO-IN09 06/17/2009 Slow 713 Production 400 148 385

NOCO-IN10 06/18/2009 Slow 553 Production 101 35 94

NOCO-IN11 06/22/2009 Slow 958 Production 100 60 100

NOCO-IN12 06/23/2009 Slow 558 Production 215 40 215

NOCO-IN13 06/24/2009 Slow 599 Production 36 15 36

NOCO-IN14 06/25/2009 Slow 658 Production 135 75 135

NOCO-IN15 07/06/2009 Slow 1,856 Production 300 80 220

NOCO-IN16 07/07/2009 Slow 1,845 Production 152 39 152

NOCO-IN17 07/08/2009 Slow 1,368 Production 75 na na

NOCO-IN18 07/09/2009 Slow 1,360 Production 170 50 160

NOCO-IN19 07/13/2009 Slow 823 Production 80 21 80

NOCO-IN20 07/14/2009 Slow 1,470 Production 75 na na

NOCO-IN21 07/15/2009 Slow 361 Production 52 40 48

NOCO-IN22 07/16/2009 Slow 801 Production 180 na na

NOCO-IN23 07/20/2009 Slow 1,399 Production 142 40 142

NOCO-IN24 07/21/2009 Slow 1,380 Production 116 70 115

NOCO-IN25 07/22/2009 Slow 1,072 Production 283 56 217

NOCO-IN26 07/23/2009 Slow 1,154 Production 126 30 114

NOCO-IN27 07/27/2009 Slow 1,776 Production 155 40 115

NOCO-IN28 07/28/2009 Slow 1,345 Production 1 41 na na

NOCO-CO01 07/29/2009 Slow 71 Production 25 16 18

NOCO-CO02 07/30/2009 Slow 48 Production 55 35 55

NOCO-CO03 08/03/2009 Slow 38 Production 380 280 370

NOCO-CO04 08/04/2009 Slow 243 Production 325 na na

NOCO-CO05 08/05/2009 Slow 126 Production 2 15 10 10
Table 1 29

Sampling information Construction information

GAMA well

identification

number

Date sampled 

(mm/dd/ yyyy)

Sampling 

schedule

Altitude of LSD 

(ft above

NAVD88)

Well type

Well depth 

(ft below 

LSD)

Depth

to top

perforation 

(ft below LSD)

Depth to

bottom

perforation 

(ft below LSD)

NOCO grid wells—Continued

NOCO-CO06 08/06/2009 Slow 95 Production 37 20 37

NOCO-CO07 08/10/2009 Slow 124 Production 130 0 130

NOCO-CO08 08/11/2009 Slow 33 Production 215 150 210

NOCO-CO09 08/12/2009 Slow 5 Production 397 356 376

NOCO-CO10 08/13/2009 Slow 115 Production 225 210 220

NOCO-CO11 08/17/2009 Slow 50 Production 115 43 103

NOCO-CO12 08/18/2009 Slow 56 Production 62 na na

NOCO-CO13 08/19/2009 Slow 318 Production 100 34 100

NOCO-CO14 08/24/2009 Slow 42 Production 32 20 32

NOCO-CO15 08/25/2009 Slow 27 Production 85 30 85

NOCO-CO16 08/26/2009 Slow 56 Production 75 38 58

NOCO-CO17 08/27/2009 Slow 153 Production 50 23 50

NOCO-CO18 08/31/2009 Slow 39 Production 65 55 60

NOCO-CO19 09/01/2009 Slow 37 Production 50 na na

NOCO-CO20 09/02/2009 Slow 93 Spring na na na

NOCO-CO21 09/03/2009 Slow 24 Production 168 146 166

NOCO-CO22 09/14/2009 Slow 15 Production 35 na na

NOCO-CO23 09/15/2009 Slow 39 Production 45 35 45

NOCO-CO24 09/16/2009 Slow 24 Production 15 na na

NOCO-CO25 09/17/2009 Slow 13 Production 193 175 193

NOCO-CO26 10/05/2009 Slow 267 Production 15 15 15

NOCO-CO27 10/06/2009 Slow 8 Production 400 na na

NOCO-CO28 10/06/2009 Slow 18 Production 120 na na

NOCO-CO29 10/07/2009 Slow 10 Production 200 na na

NOCO-CO30 10/0/2009 Slow 390 Production 196 166 196

1

 Well depth estimated from hole depth.

2

 Well depth estimated from a variety of well records.

Table 1. Identification, sampling, and construction information for wells sampled for the Northern Coast Ranges (NOCO) Groundwater 

Ambient Monitoring and Assessment (GAMA) study, California, June to November 2009.—Continued

[GAMA well identification number: NOCO-IN, Interior Basins study area grid well; NOCO-CO, Coastal Basins study area grid well. Numbered suffix 

indicates the order of sample collection within each study area. Sampling schedule is described in table 2. Land-surface datum (LSD) is a datum plane that is 

approximately at land surface at each well. The altitude of the LSD is described in feet above the North American Vertical Datum 1988. Abbreviations: ft, feet; 

NAVD 88, North American Vertical Datum 1988; na, not available]
30 Groundwater-Quality Data in the Northern Coast Ranges Study Unit, 2009: Results from the California GAMA Program

Table 2. Classes of chemical constituents and field water-quality indicators collected for the slow well-sampling schedule in the 

Northern Coast Ranges (NOCO) Groundwater Ambient Monitoring and Assessment (GAMA) study, California, June to November 2009.

Analyte classes Slow

schedule

Analyte list

table

Results

table

Field water-quality indicators 

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

Turbidity X 4

Field alkalinity, bicarbonate, and carbonate X 4

Organic constituents

Volatile organic compounds (VOC) X 3A 5

Pesticides and pesticide degradates X 3B 6

Constituent of special interest

Perchlorate X 3C 7

Inorganic constituents

Trace elements X 3D 8

Nutrients X 3E 9

Dissolved organic carbon (DOC) X 3E 9

Major and minor ions, silica, and total dissolved solids (TDS) X 3F 10

Stable isotopes

Stable isotopes of hydrogen and oxygen in water X 3G 11

Stable isotopes of carbon in dissolved inorganic carbon and carbon-14 abundance X 3G 11

Radioactivity and dissolved noble gases

Tritium X 3G 11

Radon-222 X 3G 12A

Radium isotopes X 3G 12B

Gross alpha and gross beta radioactivity X 3G 12C

Lead-210 X 3G 12D

Polonium-210 X 3G 12D

Dissolved noble gases and helium isotope ratios X 3H none 1

Microbial constituents

F-specific coliphage X 3I 13

Somatic coliphage X 3I 13

Escherichia coli (E. coli) X 3I 13

Total coliform X 3I 13

1 Results for dissolved noble gases and helium isotope ratios analyzed by Lawrence Livermore National Laboratory (LLNL) were not completed in time for 

inclusion in this report; results will be presented in a subsequent publication.
Table 3A 31

Table 3A. Volatile organic compounds (VOC), primary uses or sources, comparative benchmarks, and reporting information for the U.S. Geological Survey National Water Quality Laboratory Schedule 2020.[USGS parameter code: The five-digit code is used to uniquely identify a specific constituent or property. CAS number: CAS Registry Numbers® (CASRNs) is a registered trademark of the American 

Chemical Society. CAS recommends the verification of the CASRNs through CAS Client ServicesSM. LRL, Benchmark type, and Benchmark level: Data as of October 8, 2009. Benchmark type: Maximum 

contaminant level benchmarks are listed as MCL-US when the MCL-US and MCL-CA are identical, and as MCL-CA when the MCL-CA is lower than the MCL-US or no MCL-US exists. Abbreviations: USGS, U.S. Geological Survey; CAS, Chemical Abstracts Service; LRL, laboratory reporting level; SRL, study reporting level; μg/L, micrograms per liter; HAL-US, USEPA lifetime health advisory level; MCL-CA, CDPH maximum contaminant level; na, not available; MCL-US, USEPA maximum contaminant level; –, not detected; D, detected in groundwater samples (table 5); GAMA, Groundwater Ambient Monitoring and Assessment Program; NOCO, Northern Coast Ranges study unit; NL-CA, CDPH notification level; THM, trihalomethane; RSD5-US, USEPA risk specific dose at a risk factor of 10-5; USEPA, 

U.S. Environmental Protection Agency; CDPH, California Department of Public Health]

Constituent Primary use or source

USGS

parameter

code

CAS number LRL/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 –

Bromodichloromethane Disinfection by-product (THM) 32101 75-27-4 0.034 MCL-US 1 80 D

Bromoform (Tribromomethane) Disinfection by-product (THM) 32104 75-25-2 0.1 MCL-US 1 80 –

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 2 0.06 NL-CA 160 D

Carbon tetrachloride (Tetrachloromethane) Solvent 32102 56-23-5 0.052 MCL-CA 0.5 –

Chlorobenzene Solvent 34301 108-90-7 0.016 MCL-CA 70 –Chloroethane Solvent 34311 75-00-3 0.06 na na –Chloroform (Trichloromethane) Disinfection by-product (THM) 32106 67-66-3 2 0.02 MCL-US 1 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 by-product (THM) 32105 124-48-1 0.12 MCL-US 1 80 –

1,2-Dibromo-3-chloropropane (DBCP) Fumigant 82625 96-12-8 0.34 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 –

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 –
32 Groundwater-Quality Data in the Northern Coast Ranges Study Unit, 2009: Results from the California GAMA Program Constituent Primary use or source USGS parameter code CAS number LRL/SRL (μg/L) Benchmark type Benchmark level (μg/L) Detection 1,1-Dichloroethene (1,1-DCE) Organic synthesis 34501 75-35-4 0.022 MCL-CA 6 – 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 3 4 – trans-1,3-Dichloropropene Fumigant 34699 10061-02-6 0.14 RSD5-US 3 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 0.036 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 –

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 –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 4 Gasoline hydrocarbon 77128 100-42-5 0.03 MCL-US 100 –

Table 3A. Volatile organic compounds (VOC), primary uses or sources, comparative benchmarks, and reporting information for the U.S. Geological Survey National Water 

Quality Laboratory Schedule 2020.—Continued

[USGS parameter code: The five-digit code is used to uniquely identify a specific constituent or property. CAS number: CAS Registry Numbers® (CASRNs) is a registered trademark of the American 

Chemical Society. CAS recommends the verification of the CASRNs through CAS Client ServicesSM. LRL, Benchmark type, and Benchmark level: Data as of October 8, 2009. Benchmark type: Maximum 

contaminant level benchmarks are listed as MCL-US when the MCL-US and MCL-CA are identical, and as MCL-CA when the MCL-CA is lower than the MCL-US or no MCL-US exists. Abbreviations: USGS, U.S. Geological Survey; CAS, Chemical Abstracts Service; LRL, laboratory reporting level; SRL, study reporting level; μg/L, micrograms per liter; HAL-US, USEPA lifetime health advisory level; MCL-CA, CDPH maximum contaminant level; na, not available; MCL-US, USEPA maximum contaminant level; –, not detected; D, detected in groundwater samples (table 5); GAMA, Groundwater Ambient Monitoring and Assessment Program; NOCO, Northern Coast Ranges study unit; NL-CA, CDPH notification level; THM, trihalomethane; RSD5-US, USEPA risk specific dose at a risk factor of 10-5; USEPA, 

U.S. Environmental Protection Agency; CDPH, California Department of Public Health]
Table 3A 33

Table 3A. Volatile organic compounds (VOC), primary uses or sources, comparative benchmarks, and reporting information for the U.S. Geological Survey National Water 

Quality Laboratory Schedule 2020.—Continued

[USGS parameter code: The five-digit code is used to uniquely identify a specific constituent or property. CAS number: CAS Registry Numbers® (CASRNs) is a registered trademark of the American 

Chemical Society. CAS recommends the verification of the CASRNs through CAS Client ServicesSM. LRL, Benchmark type, and Benchmark level: Data as of October 8, 2009. Benchmark type: Maximum 

contaminant level benchmarks are listed as MCL-US when the MCL-US and MCL-CA are identical, and as MCL-CA when the MCL-CA is lower than the MCL-US or no MCL-US exists. Abbreviations: USGS, U.S. Geological Survey; CAS, Chemical Abstracts Service; LRL, laboratory reporting level; SRL, study reporting level; μg/L, micrograms per liter; HAL-US, USEPA lifetime health advisory level; MCL-CA, CDPH maximum contaminant level; na, not available; MCL-US, USEPA maximum contaminant level; –, not detected; D, detected in groundwater samples (table 5); GAMA, Groundwater Ambient Monitoring and Assessment Program; NOCO, Northern Coast Ranges study unit; NL-CA, CDPH notification level; THM, trihalomethane; RSD5-US, USEPA risk specific dose at a risk factor of 10-5; USEPA, 

U.S. Environmental Protection Agency; CDPH, California Department of Public Health]

Constituent Primary use or source

USGS

parameter

code

CAS number LRL/SRL (μg/L) Benchmark type Benchmark level (μg/L) Detection

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 1 Gasoline hydrocarbon 34010 108-88-3 0.018 MCL-CA 150 –

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 –

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

1,2,3-Trichloropropane (1,2,3-TCP) Solvent/organic synthesis 77443 96-18-4 0.12 na 5 na –

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 4 Gasoline hydrocarbon 77222 95-63-6 0.032 NL-CA 330 –

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 D

m- and p-Xylene Gasoline hydrocarbon 85795 108-38-3 / 106-42-3 0.08 MCL-CA 6 1,750 –

o-Xylene Gasoline hydrocarbon 77135 95-47-6 0.032 MCL-CA 6 1,750 –

1 The MCL-US benchmarks for THM is the sum of chloroform, bromoform, bromodichloromethane, and dibromochloromethane.2 SRL defined based on the highest concentration detected in the NOCO study unit blanks. Values below the SRL are reported as ≤ the value reported by the laboratory. In the USGS NWIS database, the result 

is accompanied with the following comment: Result is < or = reported value, based on a detection in a blank.

3 The RSD5 benchmark for 1,3-dichloropropene is the sum of its isomers (cis and trans).4 Constituent excluded from dataset on the basis of the examination of quality-control samples collected for the first 27 GAMA study units (May 2004 through October 2009) and in laboratory instrument and 

preparation blanks analyzed during the same time period as the samples (Fram and others, 2011).

5 In earlier reports in this series, the NL-CA (0.005 μg/L) was used as the comparison benchmark for 1,2,3-TCP.6 The MCL-CA benchmarks for m - and p-Xylene and o-Xylene is the sum all three xylene compounds.
34 Groundwater-Quality Data in the Northern Coast Ranges Study Unit, 2009: Results from the California GAMA Program

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

U.S. Geological Survey National Water Quality Laboratory Schedule 2033.

[USGS parameter code: The five-digit code is used to uniquely identify a specific constituent or property. CAS number: CAS Registry Numbers® (CASRNs) 

is a registered trademark of the American Chemical Society. CAS recommends the verification of the CASRNs through CAS Client ServicesSM. LRL, 

Benchmark type, and Benchmark level: Data as of October 8, 2009. Benchmark type: Maximum contaminant level benchmarks are listed as MCL-US 

when the MCL-US and MCL-CA are identical, and as MCL-CA when the MCL-CA is lower than the MCL-US or no MCL-US exists. Abbreviations: USGS, 

U.S. Geological Survey; CAS, Chemical Abstracts Service; LRL, laboratory reporting level; μg/L, micrograms per liter; na, not available; MCL-US, USEPA 

maximum contaminant level; MCL-CA, CDPH maximum contaminant level; RSD5-US, USEPA risk specific dose at a risk factor of 10-5; HAL-US, USEPA 

lifetime health advisory level; –, not detected; D, detected in groundwater samples (table 6); USEPA, U.S. Environmental Protection Agency; CDPH, California 

Department of Public Health]

Constituent Primary use or 

source

USGS

parameter 

code

CAS

number

 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 D

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 –

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 0.003 na na – 1

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 –

λ-Cyhalothrin Insecticide 61595 91465-08-6 0.010 na na – 1

Cypermethrin Insecticide 61586 52315-07-8 0.020 na na –

DCPA (Dacthal) Herbicide 82682 1861-32-1 0.008 HAL-US 70 –

Deethylatrazine (2-Chloro-4-

isopropylamino-6-amino-striazine)

Herbicide degradate 04040 6190-65-4 0.014 na na D 1

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 0.006 na na –

3,4-Dichloroaniline Herbicide degradate 61625 95-76-1 0.004 na na –

3,5-Dichloroaniline Herbicide degradate 61627 626-43-7 0.003 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 0.014 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 0.002 na na –

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

Fenamiphos Insecticide 61591 22224-92-6 0.030 HAL-US 0.7 –

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 –
Table 3B 35

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

U.S. Geological Survey National Water Quality Laboratory Schedule 2033.—Continued

[USGS parameter code: The five-digit code is used to uniquely identify a specific constituent or property. CAS number: CAS Registry Numbers® (CASRNs) 

is a registered trademark of the American Chemical Society. CAS recommends the verification of the CASRNs through CAS Client ServicesSM. LRL, 

Benchmark type, and Benchmark level: Data as of October 8, 2009. Benchmark type: Maximum contaminant level benchmarks are listed as MCL-US 

when the MCL-US and MCL-CA are identical, and as MCL-CA when the MCL-CA is lower than the MCL-US or no MCL-US exists. Abbreviations: USGS, 

U.S. Geological Survey; CAS, Chemical Abstracts Service; LRL, laboratory reporting level; μg/L, micrograms per liter; na, not available; MCL-US, USEPA 

maximum contaminant level; MCL-CA, CDPH maximum contaminant level; RSD5-US, USEPA risk specific dose at a risk factor of 10-5; HAL-US, USEPA 

lifetime health advisory level; –, not detected; D, detected in groundwater samples (table 6); USEPA, U.S. Environmental Protection Agency; CDPH, California 

Department of Public Health]

Constituent Primary use or 

source

USGS

parameter 

code

CAS

number

 LRL

(μg/L)

Benchmark

type

Benchmark 

level

(μg/L)

Detection

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

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

Fonofos Insecticide 04095 944-22-9 0.004 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 – 1

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 – 1

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 –

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 0.051 na na – 1

Prometon Herbicide 04037 1610-18-0 0.012 HAL-US 100 –

Prometryn Herbicide 04036 7287-19-6 0.006 na na –

Pronamide Herbicide 82676 23950-58-5 0.004 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 –

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 –

Tebuthiuron Herbicide 82670 34014-18-1 0.028 HAL-US 500 –

Tefluthrin Insecticide 61606 79538-32-2 0.010 na na – 1

Terbufos Insecticide 82675 13071-79-9 0.018 HAL-US 0.4 – 1

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

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.
36 Groundwater-Quality Data in the Northern Coast Ranges Study Unit, 2009: Results from the California GAMA Program

Table 3C. Perchlorate, primary uses or sources, comparative benchmarks, and reporting information for Weck Laboratories, 

Inc. analyses.

[USGS parameter code: The five-digit code is used to uniquely identify a specific constituent or property. CAS number: CAS Registry Numbers®

(CASRNs) is a registered trademark of the American Chemical Society. CAS recommends the verification of the CASRNs through CAS Client 

ServicesSM. MRL, Benchmark type, and Benchmark level: Data as of October 8, 2009. Benchmark type: Maximum contaminant level benchmarks 

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

exists. Abbreviations: USGS, U.S. Geological Survey; CAS, Chemical Abstract Service; MRL, minimum reporting level; μg/L, micrograms per liter; 

MCL-CA, CDPH maximum contaminant level; D, detected in groundwater samples (table 7); MCL-US, USEPA maximum contaminant level; CDPH, 

California Department of Public Health; USEPA, U.S. Environmental Protection Agency]

Constituent Primary use or source

USGS

parameter

code

CAS

number

 MRL

(μg/L)

Benchmark

type

Benchmark

level

(μg/L)

Detection

Perchlorate Rocket fuel, fireworks, flares 63790 14797-73-0 0.10 MCL-CA 6 D
Table 3D 37

Table 3D. Trace elements, comparative benchmarks, and reporting information for the U.S. Geological Survey National 

Water Quality Laboratory Schedules 2710.

[USGS parameter code: The five-digit code is used to uniquely identify a specific constituent or property. CAS number: CAS Registry Numbers®

(CASRNs) is a registered trademark of the American Chemical Society. CAS recommends the verification of the CASRNs through CAS Client 

ServicesSM. LRL, Benchmark type, and Benchmark level: Data as of October 8, 2009. Benchmark type: Maximum contaminant level 

benchmarks are listed as MCL-US when the MCL-US and MCL-CA are identical, and as MCL-CA when the MCL-CA is lower than the MCL-US or 

no MCL-US exists. Abbreviations: USGS, U.S. Geological Survey; CAS, Chemical Abstracts Service; LRL, laboratory reporting level; SRL, study 

reporting level; μg/L, micrograms per liter; MCL-CA, CDPH maximum contaminant level; MCL-US, USEPA maximum contaminant level; NL-CA, 

CDPH notification level; na, not available; AL-US, USEPA action level; SMCL-CA, CDPH secondary maximum contaminant level; HAL-US, 

USEPA lifetime health advisory level; na, not available; D, detected in groundwater samples (table 8); GAMA, Groundwater Ambient Monitoring 

and Assessment Program; NWIS, National Water Information System; QC, quality control; NWQL, National Water Quality Laboratory; BQS, 

Branch of Quality Systems; NOCO, Northern Coast Ranges study unit; CDPH, California Department of Public Health; USEPA, U.S. Environmental 

Protection Agency]

Constituent

USGS

parameter

code

CAS number LRL/SRL

(μg/L)

Benchmark

type 

Benchmark

level 

(μg/L)

Detection

Aluminum 01106 7429-90-5 1 1.6 MCL-CA 1,000 D

Antimony 01095 7440-36-0 0.054 MCL-US 6 D

Arsenic 01000 7440-38-2 0.044 MCL-US 10 D

Barium 01005 7440-39-3 1 0.36 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 0.010 na na D

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 2 1.1 AL-US 15 D

Lithium 01130 7439-93-2 0.44 na na D

Manganese 01056 7439-96-5 1 0.2 SMCL-CA 50 D

Mercury 71890 7439-97-6 1 0.012 MCL-US 2 D

Molybdenum 01060 7439-98-7 0.028 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

Uranium 22703 7440-61-1 0.008 MCL-US 30 D

Vanadium 01085 7440-62-2 1 0.11 NL-CA 50 D

Zinc 01090 7440-66-6 1 4.8 SMCL-CA3 5,000 D

1

 SRL defined based on examination of GAMA quality-control samples collected from May 2004 through January 2008 (Olsen and others, 

2010). Values less than the SRL are reported as less than or equal to the value reported by the laboratory. In the USGS NWIS database, the result 

is accompanied with the following comment: Result is less than or equal to reported value, based on QC data (may include: field blanks, sourcesolution blanks, trip blanks, NWQL set blanks, NWQL blank water certificates, and USGS BQS Blind Blank Program data).

2

 SRL defined based on the highest concentration detected in the NOCO study unit blanks. Values less than the SRL are reported as less than or 

equal to the value reported by the laboratory. In the USGS NWIS database, the result is accompanied with the following comment: Result is less than 

or equal to reported value, based on a detection in a blank.

3

 The SMCL for zinc is listed as SMCL-CA because SMCLs established by the CDPH are used in this report for all constituents with SMCL-CA 

values.
38 Groundwater-Quality Data in the Northern Coast Ranges Study Unit, 2009: Results from the California GAMA Program

Table 3E. Nutrients and dissolved organic carbon (DOC), comparative benchmarks and reporting information for the U.S. Geological 

Survey National Water Quality Laboratory Schedule 2755 and Laboratory Code 2613.

[USGS parameter code: The five-digit code is used to uniquely identify a specific constituent or property. CAS number: CAS Registry Numbers® (CASRNs) 

is a registered trademark of the American Chemical Society. CAS recommends the verification of the CASRNs through CAS Client ServicesSM. LRL, 

Benchmark type, and Benchmark level: Data as of October 8, 2009. Benchmark type: Maximum contaminant level benchmarks are listed as MCL-US when 

the MCL-US and MCL-CA are identical, and as MCL-CA when the MCL-CA is lower than the MCL-US or no MCL-US exists. Abbreviations: USGS, U.S. 

Geological Survey; CAS, Chemical Abstracts Service; LRL, laboratory reporting level; SRL, study reporting level; μg/L, micrograms per liter; mg/L, milligrams 

per liter; na, not available; HAL-US, USEPA lifetime health advisory level; MCL-US, USEPA maximum contaminant level; D, detected in groundwater samples 

(table 9); NOCO, Northern Coast Ranges study unit; NWIS, National Water Information System; MCL-CA, CDPH maximum contaminant level; USEPA, U.S. 

Environmental Protection Agency; CDPH, California Department of Public Health; ]

Constituent

USGS

parameter

code

CAS number LRL/SRL 

(μg/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 0.002 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 0.006 na na D

Dissolved organic carbon (DOC) 00681 na 2 0.7 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

 SRL defined based on the highest concentration detected in the NOCO study unit blanks. Values less than the SRL are reported as less than or equal to the 

value reported by the laboratory. In the USGS NWIS database, the result is accompanied with the following comment: Result is less than or equal to reported 

value, based on a detection in a blank.

Table 3F. Major and minor ions, silica, total dissolved solids (TDS), and alkalinity, comparative benchmarks, and reporting information 

for the U.S. Geological Survey National Water Quality Laboratory Schedule 2750.

[USGS parameter code: The five-digit code is used to uniquely identify a specific constituent or property. CAS number: CAS Registry Numbers® (CASRNs) 

is a registered trademark of the American Chemical Society. CAS recommends the verification of the CASRNs through CAS Client ServicesSM. LRL, 

Benchmark type, and Benchmark level: Data as of October 8, 2009. Benchmark type: Maximum contaminant level benchmarks are listed as MCL-US 

when the MCL-US and MCL-CA are identical, and as MCL-CA when the MCL-CA is lower than the MCL-US or no MCL-US exists. Abbreviations: USGS, 

U.S. Geological Survey; CAS, Chemical Abstracts Service; LRL, laboratory reporting level; mg/L, milligrams per liter; SiO2, silicon dioxide; CaCO3, calcium 

carbonate; na, not available; SMCL-CA, CDPH secondary maximum contaminant level; MCL-CA, CDPH maximum contaminant level; D, detected in 

groundwater samples (table 10); MCL-US, USEPA maximum contaminant level; CDPH, California Department of Public Health; USEPA, U.S. Environmental 

Protection Agency]

Constituent

USGS

parameter

code

CAS number LRL

(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 2 250 (500) D

Fluoride 00950 16984-48-8 0.08 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 2 250 (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 2 500 (1,000) D

Laboratory alkalinity 1 (as CaCO3) 29801 na 1 na na D

1

 The recommended SMCL-CA benchmarks for chloride, sulfate, and TDS are listed with the upper SMCL-CA thresholds in parentheses.

2

 Laboratory alkalinity results for one sample are presented in table 4.
Table 3G 39

Table 3G. Isotopic and radioactive constituents, comparative benchmarks, and reporting information for laboratory analyses.

[USGS parameter code: The five-digit code is used to uniquely identify a specific constituent or property. CAS number: CAS Registry Numbers® (CASRNs) 

is a registered trademark of the American Chemical Society. CAS recommends the verification of the CASRNs through CAS Client ServicesSM. Reporting 

level, Benchmark type, and Benchmark level: Data as of October 8, 2009. Stable isotope ratios are reported in the standard delta notation (δ), the ratio of 

a heavier isotope to more common lighter isotope of that element, relative to a standard reference material. Benchmark type: Maximum contaminant level 

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

MCL-US exists. Abbreviations: USGS, U.S. Geological Survey; CAS, Chemical Abstracts Service; pCi/L, picocuries per liter; na, not available; MU, method 

uncertainty; ssLC, sample-specific critical level; CSU, combined standard uncertainty; MCL-US, USEPA maximum contaminant level; MCL-CA, CDPH 

maximum contaminant level; D, detected in groundwater samples (tables 11 and 12A through 12D); USEPA, U.S. Environmental Protection Agency; CDPH, 

California Department of Public Health]

Constituent

USGS

parameter

code

CAS number

Reporting

level

type

Reporting

level or 

uncertainty

Benchmark

type

Benchmark

level Detection

Stable isotope ratios (per mil)

δ2H in water 1 82082 na MU 2 na na D

δ18O in water 1 82085 na MU 0.20 na na D

δ13C in dissolved inorganic carbon 2 82081 na 1-sigma 0.05 na na D

Radioactive constituents (percent modern)

Carbon-14 2 49933 14762-75-5 1-sigma 0.002 na na D

Radioactive constituents (pCi/L)

Radon-222 3 82303 14859-67-7 ssLC CSU Proposed MCL-US 4,000 D

Tritium 4 07000 10028-17-8 ssLC CSU MCL-CA 20,000 D

Radium-226 5 09511 13982-63-3 ssLC CSU MCL-US 6 5 D

Radium-228 5 81366 15262-20-1 ssLC CSU MCL-US 6 5 D

Gross alpha radioactivity, 72-hour and 

30-day counts 5

62636, 62639 12587-46-1 ssLC CSU MCL-US 15 D

Gross beta radioactivity, 72-hour and 

30-day counts 5

62642, 62645 12587-47-2 ssLC CSU MCL-CA 50 D

Lead-210 5 17503 14255-04-0 ssLC CSU na na D

Polonium-210 5 19503 13981-52-7 ssLC CSU na na D

1

 USGS Stable Isotope Laboratory, Reston, Virginia (USGSSIVA).

2

 Woods Hole Oceanographic Institution, National Ocean Sciences Accelerator Mass Spectrometry Facility (contract laboratory, NOSAMS).

3

 USGS National Water Quality Laboratory (USGSNWQL).

4

 USGS Stable Isotope and Tritium Laboratory, Menlo Park, California (USGSH3CA).

5

 Eberline Analytical Services (contract laboratory, CA-EBERL).

6

 The MCL-US benchmark for radium is the sum of radium-226 and radium-228.
40 Groundwater-Quality Data in the Northern Coast Ranges Study Unit, 2009: Results from the California GAMA Program

Table 3H. Dissolved noble gases, comparative benchmarks, and reporting information for the Lawrence Livermore National 

Laboratory analyses.

[USGS parameter code: The five-digit code is used to uniquely identify a specific constituent or property. CAS number: CAS Registry Numbers®

(CASRNs) is a registered trademark of the American Chemical Society. CAS recommends the verification of the CASRNs through CAS Client ServicesSM. 

Abbreviations: USGS, U.S. Geological Survey; CAS, Chemical Abstracts Service; na, not available; cm3 STP/g, cubic centimeters of gas at standard 

temperature and pressure per gram of water]

Constituent

USGS

parameter 

code

CAS number

Method 

uncertainty 

(percent)

Reporting

units

Benchmark

type

Benchmark

value Detection

Dissolved noble gases 

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

Helium-3 / Helium-4 61040 na / 7440-59-7 0.75 atom ratio na na na

Table 3I. Microbial indicators, comparative benchmarks, and reporting information for the U.S. Geological Survey Ohio Microbiology 

Laboratory and field analyses.

[USGS parameter code: The five-digit code is used to uniquely identify a specific constituent or property. CAS number: CAS Registry Numbers® (CASRNs) 

is a registered trademark of the American Chemical Society. CAS recommends the verification of the CASRNs through CAS Client ServicesSM. MDL, 

Benchmark type, and Benchmark value: Data as of October 8, 2009. Benchmark type: Maximum contaminant level benchmarks are listed as MCL-US 

when the MCL-US and MCL-CA are identical, and as MCL-CA when the MCL-CA is lower than the MCL-US or no MCL-US exists. Abbreviations: USGS, 

U.S. Geological Survey; MDL, method detection limit; mL, milliliter; TT-US, USEPA treatment technique (a required process intended to reduce the level of 

contamination in drinking water); MCL-US, USEPA maximum contaminant level; D, detected in groundwater samples (table 13); MCL-CA, CDPH maximum 

contaminant level; USEPA, U.S. Environmental Protections Agency; CDPH, California Department of Public Health]

Constituent

USGS 

parameter 

code

Primary source MDL Benchmark type Benchmark value Detection

F-specific coliphage 99335 Sewage and animal

waste indicator

na TT-US 99.99 percent killed /

inactivated

D

Somatic coliphage 99332 Sewage and animal

waste indicator

na TT-US 99.99 percent killed /

inactivated

D

Escherichia coli (E. coli) 1 90901 Sewage and animal

waste indicator

1 colony /100 mL TT-US Zero D

Total coliform - (including fecal 

coliform and E. coli) 1

90900 Sewage and animal

waste indicator

1 colony / 100 mL MCL-US 5 percent of samples

positive per month

D

1

Analyzed in the field.
Table 4 41

Table 4. Field water-quality indicators in samples collected for the Northern Coast Ranges (NOCO) Groundwater Ambient Monitoring and Assessment (GAMA) study, California, June to November 2009. [The five-digit USGS parameter code in parentheses below the constituent name is used to uniquely identify a specific constituent or property. GAMA well identification number: NOCO-IN, Interior Basins study area grid well; NOCO-CO, Coastal Basins study area grid well. Numbered suffix indicates the order of sample collection within each study area. Benchmark type, Benchmark level, and RL: Data as of October 8, 2009. Abbreviations: NTRU, nephelometric turbidity unit; mg/L, milligrams per liter; °C, degree Celsius; μS/cm, microsiemens per centimeter; CaCO3, calcium carbonate; mg/L, milligrams per 

liter; SMCL-CA, CDPH secondary maximum contaminant level; na, not available; SMCL-US, USEPA secondary maximum contaminant level; <, less than; >, greater than; RL, reporting limit or range; *, value greater than benchmark level; E, estimated or having a higher degree of uncertainty; nc, not collected; –, not detected; USGS, U.S. Geological Survey; CDPH, California Department of Public Health; USEPA, U.S. Environmental Protection Agency]

GAMA well 

identification 

number

Turbidity, 

field

(NTRU) 

(63676)

Dissolved 

oxygen, 

field

(mg/L)

(00300) 

Water 

temperature, 

field 

(°C) 

(00010)

pH, lab 

(standard 

units) 

(00403)

pH, field 

(standard 

units) 

(00400)

Specific 

conductance, 

lab 

(μS/cm at 25 °C) 

(90095)

Specific

conductance, 

field 

(μS/cm at 25°C) 

(00095)

Alkalinity, 

lab 

(mg/L as 

CaCO3) 

(29801)

Alkalinity, 

field 

(mg/L as 

CaCO3) 

(39086)

Bicarbonate, 

field 

(mg/L) 

(00453)

Bicarbonate 3

(mg/L)

Carbonate, 

field 

(mg/L) 

(00452)

Carbonate 3

(mg/L)

Benchmark type SMCL-CA na na SMCL-US SMCL-US SMCL-CA SMCL-CA na na na na na na

Benchmark level 1 5 na na <6.5 or >8.5 <6.5 or >8.5 2 900 (1,600) 2 900 (1,600) na na na na na na

[RL] [0.1] [0.2] [0.0–38.5] [0–14] [0–14] [5] [5] [1] [1] [1] [1] [0.1] [0.1]

NOCO grid wells (58 wells sampled)NOCO-IN01 0.5 0.7 20.0 7.7 7.5 246 245 nc 121 147 nc – ncNOCO-IN02 0.6 7.0 17.5 7.3 7.2 280 276 nc 116 141 nc – ncNOCO-IN03 9.8 0.7 12.5 7.1 *6.1 162 160 nc 75.4 91.9 nc – ncNOCO-IN04 100 10.9 14.0 7.1 *6.3 285 273 nc 120 146 nc – ncNOCO-IN05 16.0 0.3 16.0 7.0 6.7 576 580 nc 150 183 nc – ncNOCO-IN06 0.4 0.4 15.0 7.2 7.2 385 373 nc 198 240 nc 0.3 ncNOCO-IN07 0.3 1.3 14.5 6.7 *6.0 255 247 nc 97.9 119 nc – ncNOCO-IN08 0.2 5.5 14.0 7.0 6.6 390 384 nc 154 188 nc – ncNOCO-IN09 0.2 <1 20.0 7.7 7.5 443 444 nc 222 271 nc – ncNOCO-IN10 0.4 5.0 16.0 7.0 *6.4 222 219 nc 87.9 107 nc – ncNOCO-IN11 1.1 0.3 18.0 7.1 6.8 343 341 nc 4 158 4 192 nc 4 0.1 ncNOCO-IN12 0.8 2.2 19.0 7.3 6.9 300 289 nc 4 126 4 153 nc 4 0.2 ncNOCO-IN13 0.1 3.8 16.0 6.7 *6.1 281 275 nc 4 108 4 131 nc 4 – ncNOCO-IN14 0.3 <0.2 18.5 7.5 7.3 326 322 nc 4 127 4 154 nc 4 0.4 ncNOCO-IN15 8.7 <0.2 15.5 8.0 7.1 303 294 nc 153 187 nc – ncNOCO-IN16 4.1 1.9 15.0 6.9 *6.4 163 158 nc 68.3 83.3 nc – ncNOCO-IN17 0.6 6.2 18.5 7.7 6.9 243 243 nc 95.2 116 nc – ncNOCO-IN18 0.1 1.3 19.0 6.9 6.7 587 582 nc 244 298 nc – ncNOCO-IN19 0.3 2.6 18.5 7.1 *6.0 269 267 nc 67.7 82.6 nc – ncNOCO-IN20 4.6 0.3 23.0 7.0 *6.3 *1,320 *1,310 nc 671 818 nc 0.4 ncNOCO-IN21 1.7 <0.2 18.5 6.9 6.8 *982 *964 nc 420 512 nc 0.4 ncNOCO-IN22 0.6 0.5 25.0 7.5 7.4 900 893 nc 422 513 nc 1.0 ncNOCO-IN23 0.3 1.9 15.0 7.6 7.2 266 254 nc 117 142 nc – ncNOCO-IN24 0.2 3.8 18.5 7.6 7.3 339 331 nc 171 208 nc – ncNOCO-IN25 0.4 0.7 19.0 7.7 7.5 413 409 nc 213 260 nc – nc
42 Groundwater-Quality Data in the Northern Coast Ranges Study Unit, 2009: Results from the California GAMA Program GAMA well identification number Turbidity, field (NTRU) (63676) Dissolved oxygen, field (mg/L) (00300) Water temperature, field 

(°C) 

(00010)

pH, lab 

(standard 

units) 

(00403)

pH, field 

(standard 

units) 

(00400)

Specific 

conductance, 

lab 

(μS/cm at 25 °C) 

(90095)

Specific

conductance, 

field 

(μS/cm at 25°C) 

(00095)

Alkalinity, 

lab 

(mg/L as 

CaCO3) 

(29801)

Alkalinity, 

field 

(mg/L as 

CaCO3) 

(39086)

Bicarbonate, 

field 

(mg/L) 

(00453)

Bicarbonate 3

(mg/L)

Carbonate, 

field 

(mg/L) 

(00452)

Carbonate 3

(mg/L)

Benchmark type SMCL-CA na na SMCL-US SMCL-US SMCL-CA SMCL-CA na na na na na na

Benchmark level 1 5 na na <6.5 or >8.5 <6.5 or >8.5 2 900 (1,600) 2 900 (1,600) na na na na na na

[RL] [0.1] [0.2] [0.0–38.5] [0–14] [0–14] [5] [5] [1] [1] [1] [1] [0.1] [0.1]

NOCO grid wells (58 wells sampled)—ContinuedNOCO-IN26 0.2 4.8 18.0 7.3 6.7 424 414 nc 171 208 nc – ncNOCO-IN27 0.2 <0.2 18.0 *6.2 *6.0 *1,040 *1,030 nc 578 705 nc – ncNOCO-IN28 0.2 <0.2 15.5 7.5 7.2 661 618 nc 344 418 nc 0.7 ncNOCO-CO01 1.2 <0.2 13.0 7.3 7.2 367 358 nc 100 122 nc 0.1 ncNOCO-CO02 0.2 11.8 13.5 6.7 6.5 247 250 nc 23.9 29.1 nc – nc

NOCO-CO03 0.2 1.3 11.0 7.9 7.7 166 160 nc 56.6 69.0 nc – ncNOCO-CO04 0.3 <0.2 12.5 7.6 7.5 701 687 nc 350 427 nc – ncNOCO-CO05 0.6 5.2 12.0 *5.7 *5.6 196 196 nc 11.3 13.8 nc – ncNOCO-CO06 2.4 4.1 12.0 6.6 6.5 453 397 nc 52.0 63.4 nc – ncNOCO-CO07 18.0 10.4 11.5 7.0 6.5 174 160 nc 55.6 67.8 nc – ncNOCO-CO08 0.1 <0.2 14.5 7.2 7.5 328 317 nc 134 164 nc 0.2 ncNOCO-CO09 0.2 <0.2 18.0 7.5 7.5 715 701 nc 243 295 nc 0.6 ncNOCO-CO10 0.2 3.3 13.0 7.9 7.8 287 274 nc 130 158 nc 0.4 ncNOCO-CO11 0.6 1.3 14.5 6.8 6.7 434 420 nc 178 218 nc – ncNOCO-CO12 0.5 1.1 15.5 7.2 6.8 319 312 nc 76.4 93.2 nc – ncNOCO-CO13 0.3 7.1 13.0 7.2 *6.3 206 203 nc 35.0 42.6 nc – ncNOCO-CO14 0.5 9.7 13.0 7.3 7.7 237 227 83.0 nc nc 101 – 0.1NOCO-CO15 0.2 6.9 10.5 7.4 *6.4 E67.0 63.0 nc 16.9 20.6 nc – ncNOCO-CO16 0.3 7.9 13.0 7.5 6.7 180 171 nc 81.1 98.8 nc – ncNOCO-CO17 0.2 3.1 15.0 6.8 6.5 339 331 nc 143 174 nc – ncNOCO-CO18 0.2 0.3 14.5 6.7 6.5 436 435 nc 183 223 nc 0.1 ncNOCO-CO19 0.2 0.2 13.5 7.0 6.6 474 466 nc 173 211 nc 0.1 ncNOCO-CO20 0.3 6.1 12.5 7.8 7.5 414 405 nc 165 200 nc 0.6 nc

Table 4. Field water-quality indicators in samples collected for the Northern Coast Ranges (NOCO) Groundwater Ambient Monitoring and Assessment (GAMA) study, California, June to November 2009.—Continued [The five-digit USGS parameter code in parentheses below the constituent name is used to uniquely identify a specific constituent or property. GAMA well identification number: NOCO-IN, Interior Basins study area grid well; NOCO-CO, Coastal Basins study area grid well. Numbered suffix indicates the order of sample collection within each study area. Benchmark type, Benchmark level, and RL: Data as of October 8, 2009. Abbreviations: NTRU, nephelometric turbidity unit; mg/L, milligrams per liter; °C, degree Celsius; μS/cm, microsiemens per centimeter; CaCO3, calcium carbonate; mg/L, milligrams per 

liter; SMCL-CA, CDPH secondary maximum contaminant level; na, not available; SMCL-US, USEPA secondary maximum contaminant level; <, less than; >, greater than; RL, reporting limit or range; *, value greater than benchmark level; E, estimated or having a higher degree of uncertainty; nc, not collected; –, not detected; USGS, U.S. Geological Survey; CDPH, California Department of Public Health; USEPA, U.S. Environmental Protection Agency]
Table 4 43

Table 4. Field water-quality indicators in samples collected for the Northern Coast Ranges (NOCO) Groundwater Ambient Monitoring and Assessment (GAMA) study, California, June to November 2009.—Continued [The five-digit USGS parameter code in parentheses below the constituent name is used to uniquely identify a specific constituent or property. GAMA well identification number: NOCO-IN, Interior Basins study area grid well; NOCO-CO, Coastal Basins study area grid well. Numbered suffix indicates the order of sample collection within each study area. Benchmark type, Benchmark level, and RL: Data as of October 8, 2009. Abbreviations: NTRU, nephelometric turbidity unit; mg/L, milligrams per liter; °C, degree Celsius; μS/cm, microsiemens per centimeter; CaCO3, calcium carbonate; mg/L, milligrams per 

liter; SMCL-CA, CDPH secondary maximum contaminant level; na, not available; SMCL-US, USEPA secondary maximum contaminant level; <, less than; >, greater than; RL, reporting limit or range; *, value greater than benchmark level; E, estimated or having a higher degree of uncertainty; nc, not collected; –, not detected; USGS, U.S. Geological Survey; CDPH, California Department of Public Health; USEPA, U.S. Environmental Protection Agency]

GAMA well 

identification 

number

Turbidity, 

field

(NTRU) 

(63676)

Dissolved 

oxygen, 

field

(mg/L)

(00300) 

Water 

temperature, 

field 

(°C) 

(00010)

pH, lab 

(standard 

units) 

(00403)

pH, field 

(standard 

units) 

(00400)

Specific 

conductance, 

lab 

(μS/cm at 25 °C) 

(90095)

Specific

conductance, 

field 

(μS/cm at 25°C) 

(00095)

Alkalinity, 

lab 

(mg/L as 

CaCO3) 

(29801)

Alkalinity, 

field 

(mg/L as 

CaCO3) 

(39086)

Bicarbonate, 

field 

(mg/L) 

(00453)

Bicarbonate 3

(mg/L)

Carbonate, 

field 

(mg/L) 

(00452)

Carbonate 3

(mg/L)

Benchmark type SMCL-CA na na SMCL-US SMCL-US SMCL-CA SMCL-CA na na na na na na

Benchmark level 1 5 na na <6.5 or >8.5 <6.5 or >8.5 2 900 (1,600) 2 900 (1,600) na na na na na na

[RL] [0.1] [0.2] [0.0–38.5] [0–14] [0–14] [5] [5] [1] [1] [1] [1] [0.1] [0.1]

NOCO grid wells (58 wells sampled)—ContinuedNOCO-CO21 4.6 0.4 14.5 7.2 7.0 705 715 nc 342 416 nc 0.4 ncNOCO-CO22 1.2 7.5 13.0 7.3 6.7 335 329 nc 108 132 nc 0.1 ncNOCO-CO23 0.3 6.3 14.5 7.4 *6.2 E96.0 92.0 nc 35.0 42.6 nc – nc

NOCO-CO24 2.0 0.8 12.5 7.0 6.8 252 244 nc 85.7 104 nc – ncNOCO-CO25 0.4 0.3 14.0 7.4 6.7 341 332 nc 121 147 nc 0.1 ncNOCO-CO26 2.2 4.2 12.0 7.3 *5.5 193 186 nc 28.3 34.5 nc – ncNOCO-CO27 E61.0 0.2 15.5 7.1 6.8 693 675 nc 259 316 nc – ncNOCO-CO28 5.2 0.4 14.0 7.2 7.2 693 672 nc 322 392 nc – ncNOCO-CO29 0.3 0.4 13.0 7.5 7.3 420 418 nc 210 256 nc – ncNOCO-CO30 0.2 4.6 15.5 7.7 7.1 227 222 nc 76.4 93.2 nc – nc

1 The SMCL-CA for turbidity pertains only to surface-water site samples.2 The SMCL-CA for specific conductance has recommended and upper threshold values. The upper value is shown in parentheses.3 Bicarbonate and carbonate concentrations were calculated from the laboratory alkalinity and pH values using the advanced speciation method (http://or.water.usgs.gov/alk/methods.html) with pK1 = 6.35, 

pK2 = 10.33, and pKW = 14.

4 Alkalinity, bicarbonate, and carbonate values generated by the Gran’s titration method (USGS parameter codes: 29802, 63786, and 63788; respectively).
44 Groundwater-Quality Data in the Northern Coast Ranges Study Unit, 2009: Results from the California GAMA Program Table 5. Volatile organic compounds (VOC) detected in samples collected for the Northern Coast Ranges (NOCO) Groundwater Ambient Monitoring and Assessment (GAMA) study, California, June to November 2009. [The five-digit USGS parameter code in parenthesis below the constituent name is used to uniquely identify a specific constituent or property. Samples from all 58 grid wells were analyzed, but only samples with detections are listed. Analytes are listed in order of decreasing detection frequency in the 58 grid wells. All analytes are listed in table 3A. GAMA well identification number: NOCO-IN, Interior Basins study area grid well; NOCO-CO, Coastal Basins study area grid well. Numbered suffix indicates the order of sample collection within each study area. Benchmark type, Benchmark level, and LRL: Data as of October 8, 2009. Benchmark type: Maximum contaminant level benchmarks are listed as MCL-US when the MCL-US and MCL-CA are identical, and as MCL-CA when the MCL-CA is lower than the MCL-US or no MCL-US exists. Abbreviations: μg/L, micrograms per liter; MCL-US, USEPA maximum contaminant level; MCL-CA; CDPH maximum contaminant level; NL-CA, CDPH notification level; LRL, laboratory reporting level; SRL, study reporting level; –, not detected; E, estimated or having a higher degree of uncertainty; USGS, U.S. Geological Survey; USEPA, U.S. Environmental Protection Agency; CDPH, California Department of Public Health] Primary use or source Trihalomethane Solvent Gasoline Organic synthesis Solvent Trihalomethane Solvent Organic synthesis Detections per well VOC detection summary 1 GAMA well identification number Chloroform (Trichloro- methane) (μg/L) (32106) 1,1,1- Trichloro- ethane (1,1,1-TCA) (μg/L) (34506) Methyl tert- butyl ether (MTBE) (μg/L) (78032) Carbon disulfide (μg/L) (77041) 1,1-Di- chloro- ethane (1,1-DCA) (μg/L) (34496) Bromo- dichloro- methane (μg/L) (32101) Perchloro- ethene (PCE, Tetrachloro- ethene) (μg/L) (34475) Vinyl chloride (Chloroethene) (μg/L) (39175) Benchmark type MCL-US MCL-US MCL-CA NL-CA MCL-CA MCL-US MCL-US MCL-CA Benchmark level 80 200 13 160 5 2 80 5 0.5 [LRL/SRL] 3 [0.02] [0.02] [0.1] 3 [0.06] [0.04] [0.04] [0.04] [0.08] NOCO grid wells (58 wells sampled) Number of wells with detections 14 4 4 2 2 2 2 1 22 Detection frequency (percent) 24.1 6.9 6.9 3.4 3.4 3.4 3.4 1.7 38 Total detections 31 Inland Basins study area (28 grid wells sampled) NOCO-IN02 0.11 – – – – – – – 1 NOCO-IN03 – 1.52 – – E0.08 – – – 2 NOCO-IN04 – E0.03 – – – – – – 1 NOCO-IN05 – – 0.1 – – – – – 1 NOCO-IN07 ≤0.01 – – – – – – – 0 NOCO-IN09 – – 0.4 – – – – – 1 NOCO-IN11 – E0.02 – – E0.03 – – – 2 NOCO-IN13 E0.09 0.14 – – – – E0.03 – 3 NOCO-IN16 E0.04 – – – – – – – 1 NOCO-IN17 0.25 – – – – – – – 1 NOCO-IN19 13.0 – – – – 0.43 – E0.1 3 NOCO-IN20 – – – 0.07 – – – – 1 NOCO-IN21 – – 0.2 – – – – – 1 NOCO-IN22 – – – ≤0.04 – – – – 0 NOCO-IN24 E0.02 – – – – – – – 1 Number of wells with detections 6 4 3 2 2 1 1 1 13 Detection frequency (percent) 21.4 14.3 10.7 3.6 7.1 3.6 3.6 3.6 46

Total detections 19
Table 5 45

Table 5. Volatile organic compounds (VOC) detected in samples collected for the Northern Coast Ranges (NOCO) Groundwater Ambient Monitoring and Assessment (GAMA) study, California, June to November 2009.—Continued [The five-digit USGS parameter code in parenthesis below the constituent name is used to uniquely identify a specific constituent or property. Samples from all 58 grid wells were analyzed, but only samples with detections are listed. Analytes are listed in order of decreasing detection frequency in the 58 grid wells. All analytes are listed in table 3A. GAMA well identification number: NOCO-IN, Interior Basins 

study area grid well; NOCO-CO, Coastal Basins study area grid well. Numbered suffix indicates the order of sample collection within each study area. Benchmark type, Benchmark level, and LRL: Data as 

of October 8, 2009. Benchmark type: Maximum contaminant level benchmarks are listed as MCL-US when the MCL-US and MCL-CA are identical, and as MCL-CA when the MCL-CA is lower than the MCL-US or no MCL-US exists. Abbreviations: μg/L, micrograms per liter; MCL-US, USEPA maximum contaminant level; MCL-CA; CDPH maximum contaminant level; NL-CA, CDPH notification level; LRL, laboratory reporting level; SRL, study reporting level; –, not detected; E, estimated or having a higher degree of uncertainty; USGS, U.S. Geological Survey; USEPA, U.S. Environmental Protection Agency; CDPH, California Department of Public Health]

Primary use or source Trihalomethane Solvent Gasoline Organic synthesis Solvent Trihalomethane Solvent Organic synthesis

Detections 

per well

VOC

detection 

summary 1

GAMA

well

 identification

number

Chloroform 

(Trichloromethane)

(μg/L)

(32106)

1,1,1-

Trichloroethane 

(1,1,1-TCA)

(μg/L)

(34506)

Methyl tertbutyl ether 

(MTBE)

(μg/L)

(78032)

Carbon

disulfide

(μg/L)

(77041)

1,1-Dichloroethane 

(1,1-DCA) 

(μg/L) 

(34496)

Bromodichloromethane

(μg/L)

(32101)

Perchloroethene (PCE, 

Tetrachloroethene) 

(μg/L) 

(34475)

Vinyl chloride 

(Chloroethene) 

(μg/L)

(39175)

Benchmark type MCL-US MCL-US MCL-CA NL-CA MCL-CA MCL-US MCL-US MCL-CA

Benchmark level 80 200 13 160 5 2 80 5 0.5

[LRL/SRL] 3 [0.02] [0.02] [0.1] 3 [0.06] [0.04] [0.04] [0.04] [0.08]

Coastal Basins study area (30 grid wells sampled)NOCO-CO05 E0.07 – – – – – – – 1

NOCO-CO06 0.14 – – – – – – – 1

NOCO-CO07 E0.06 – – – – – – – 1

NOCO-CO13 0.24 – – – – E0.07 E0.03 – 3

NOCO-CO14 0.71 – – – – – – – 1

NOCO-CO18 – – E0.1 – – – – – 1

NOCO-CO23 E0.03 – – – – – – – 1

NOCO-CO26 0.12 – – – – – – – 1

NOCO-CO29 E0.02 – – 0.12 – – – – 2

Number of wells with detections 8 0 1 1 0 1 1 0 9

Detection frequency (percent) 26.7 0 3.3 3.3 0 3.3 3.3 0 30

Total detections 12

1 SRLs for styrene, toluene, and 1,2,4-trimethylbenzene were defined on the basis of concentrations and detection frequencies in field blanks and source-solution blanks collected for the first 27 GAMA

Priority Basin Project (PBP) study units (May 2004 through October 2009) and in laboratory instrument and preparation blanks analyzed during the same time period as the samples. These constituents were detected more frequently in blanks than in groundwater samples and, therefore, all detections of these constituents were removed from the GAMA PBP groundwater-quality datasets. Concentrations detected in 

the NOCO study unit: styrene (NOCO-CO27: E0.03 μg/L), toluene (NOCO-CO24: E0.06 μg/L), and 1,2,4-trimethylbenzene (NOCO-IN03: E0.02 μg/L; NOCO-IN04: E0.05 μg/L; NOCO-IN05: E0.09 μg/L; NOCO-IN06: E0.07 μg/L; NOCO-IN15: E0.04 μg/L; NOCO-IN16: E0.11 μg/L; NOCO-IN18: E0.09 μg/L; NOCO-IN20: E0.05 μg/L; NOCO-IN23: E0.04 μg/L; NOCO-IN28: E0.07 μg/L; NOCO-CO02: E0.05 μg/L; NOCO-CO11: E0.04 μg/L; NOCO-CO12: E0.03 μg/L; NOCO-CO13: E0.03 μg/L; NOCO-CO14: E0.03 μg/L; NOCO-CO16: E0.08 μg/L; NOCO-CO17: E0.04 μg/L; NOCO-CO27: E0.02 μg/L; NOCO-CO28: E0.04 μg/L).

2 The MCL-US benchmarks for trihalomethanes is for the sum of chloroform, bromoform, bromodichloromethane, and dibromochloromethane.3 SRL defined based on the highest concentration detected in NOCO blanks. Values below the SRL are reported as ≤ the value reported by the laboratory. In the USGS NWIS database, the result is 

accompanied with the following comment: Result is < or = reported value, based on a detection in a blank.
46 Groundwater-Quality Data in the Northern Coast Ranges Study Unit, 2009: Results from the California GAMA Program

Table 6. Pesticides and pesticide degradates detected in samples collected for the Northern Coast Ranges (NOCO) 

Groundwater Ambient Monitoring and Assessment (GAMA) study, California, June to November 2009. 

[The five-digit USGS parameter code below the constituent name is used to uniquely identify a specific constituent or property. Samples from all 58 

grid wells were analyzed, but only samples with detections are listed. Analytes are listed in order of decreasing detection frequency in the 58 grid 

wells. All analytes are listed in table 3B. GAMA well identification number: NOCO-IN, Interior Basins study area grid well; NOCO-CO, Coastal 

Basins study area grid well. Laboratory reporting level, benchmark type, and benchmark level as of October 8, 2009. Benchmark type: Maximum 

contaminant level benchmarks are listed as MCL-US when the MCL-US and MCL-CA are identical, and as MCL-CA when the MCL-CA is lower 

than the MCL-US or no MCL-US exists. MCL-US, U.S. Environmental Protection Agency maximum contaminant level; MCL-CA; California 

Department of Public Health maximum contaminant level. Other abbreviations: E, estimated or having a higher degree of uncertainty; LRL, 

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

Primary use or source Herbicide Herbicide degradate Herbicide

Detections 

per well

Pesticide 

detection 

summary

GAMA well 

identification number

Simazine

(μg/L)

(04035)

Deethylatrazine 

(2-Chloro-4-

isopropylamino-6-

amino-s-triazine) 

(μg/L)

(04040)

Atrazine

(μg/L)

(39632)

Benchmark type MCL-US na MCL-CA

Benchmark level 4 na 1

[LRL] [0.01] [0.014] [0.007]

NOCO grid wells (58 wells sampled)

Number of wells with detections 6 2 2 6

Detection frequency (percent) 10.3 3.4 3.4 10

Total detections 10

Interior Basins study area (28 grid wells sampled)

NOCO-IN04 E0.009 E0.006 0.011 3

NOCO-IN07 E0.005 E0.006 E0.005 3

NOCO-IN08 E0.007 – – 1

NOCO-IN13 E0.005 – – 1

NOCO-IN24 E0.009 – – 1

Number of wells with detections 5 2 2 5

Detection frequency (percent) 17.9 7.1 7.1 18

Total detections 9

Coastal Basins study area (30 grid wells sampled) 

NOCO-CO26 0.030 – – 1

Number of wells with detections 1 0 0 1

Dectection frequency (percent) 3.3 0 0 3

Total detections 1
Table 7 47

Table 7. Perchlorate detected in the samples collected for 

the Northern Coast Ranges (NOCO) Groundwater Ambient 

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

November 2009. 

[The five-digit USGS parameter code in parenthesis below the constituent 

name is used to uniquely identify a specific constituent or property. 

Information about the analyte is given in table 3C. Samples from all 58 grid 

wells were analyzed for perchlorate, but only samples with detections are 

listed. GAMA well identification number: NOCO-IN, Interior Basins study 

area grid well; NOCO-CO, Coastal Basins study area grid well. Numbered 

suffix indicates the order of sample collection within each study area. 

Benchmark type, Benchmark level, and MRL: Data as of October 8, 2009. 

Benchmark type: Maximum contaminant level benchmarks are listed as 

MCL-US when the MCL-US and MCL-CA are identical, and as MCL-CA 

when the MCL-CA is lower than the MCL-US or no MCL-US exists. 

Abbreviations: μg/L, micrograms per liter; MCL-CA, CDPH maximum 

contaminant level; MRL, method reporting level; MCL-US, USEPA 

maximum contaminant level; USGS, U.S. Geological Survey; CDPH, 

California Department of Public Health; USEPA, U.S. Environmental 

Protection Agency]

GAMA well 

identification 

number

Perchlorate

(μg/L)

(63790)

Benchmark type MCL-CA

Benchmark level 6

[MRL] [0.10]

NOCO grid wells (58 wells sampled)

Number of wells with detections 14

Detection frequency (percent) 24

NOCO Inland Basins Study Area (28 grid wells sampled)

NOCO-IN02 0.11

NOCO-IN08 0.13

NOCO-IN11 0.14

NOCO-IN12 0.18

NOCO-IN13 0.17

NOCO-IN17 0.41

NOCO-IN19 0.27

NOCO-IN26 0.27

NOCO-IN28 0.26

Number of wells with detections 9

Detection frequency (percent) 32

NOCO Coastal Basins Study Area (30 grid wells sampled)

NOCO-CO05 0.26

NOCO-CO11 0.13

NOCO-CO13 0.12

NOCO-CO14 0.12

NOCO-CO17 0.73

Number of wells with detections 5

Detection frequency (percent) 17
48 Groundwater-Quality Data in the Northern Coast Ranges Study Unit, 2009: Results from the California GAMA Program Table 8. Trace elements detected in the samples collected for the Northern Coast Ranges (NOCO) Groundwater Ambient Monitoring and Assessment (GAMA) study, California, June to November 2009. [The five-digit USGS parameter code in parenthesis below the constituent name is used to uniquely identify a specific constituent or property. Samples from all 58 wells were analyzed, with the exception of mercury, which was sampled for at the 28 grid wells in NOCO-IN. Information about the analytes given in table 3D. GAMA well identification number: NOCO-IN, Inland Basins study area grid well; NOCO-CO, Coastal Basins study area grid well. Numbered suffix indicates the order of sample collection within each study area. Benchmark type, Benchmark level, and LRL: Data as of October 8, 2009. Benchmark type: Maximum contaminant level benchmarks are listed as MCL-US when the MCL-US and MCL-CA are identical, and as MCL-CA when the MCL-CA is lower than the MCL-US or no MCL-US exists. Abbreviations: μg/L, micrograms per liter; MCL-CA, CDPH maximum contaminant level; MCL-US, USEPA maximum contaminant level; NL-CA, CDPH notification level; na, not available; AL-US, USEPA action level; SMCL-CA, CDPH secondary maximum contaminant level; LRL, laboratory reporting level; SRL, study reporting level; –, not detected; E, estimated or having a higher degree of uncertainty; *, value greater than benchmark level; S, most probable value; ≤, less than or equal to; NWIS, National Water Information System; QC, quality control; NWQL, National Water Quality Laboratory; BQS, Branch of Quality Systems; USGS, U.S. Geological Survey; CDPH, California Department of Public Health; USEPA, U.S. Environmental Protection Agency] GAMA well 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/SRL] [1.6] 1 [0.054] [0.044] [0.36] 1 [0.012] [2.8] [0.02] [0.42] 1 [0.010] [1.7] 1 [6] 1 [1.1] 2 NOCO grid wells (58 wells sampled) NOCO-IN01 – E0.03 0.57 55 – 89.0 0.03 – – – – ≤0.43 NOCO-IN02 – – 0.54 47 – 108 – ≤0.14 – ≤1.5 – ≤0.20 NOCO-IN03 – – 0.06 37 – 10.0 – ≤0.17 0.08 ≤0.85 243 – NOCO-IN04 – – 0.08 62 – 68.0 – ≤0.13 0.10 2.7 128 – NOCO-IN05 – – *57.2 158 E0.02 *2,310 – ≤0.08 0.11 – *3,420 – NOCO-IN06 – – 2.7 256 – 85.0 E0.02 – 0.18 – *409 ≤0.11 NOCO-IN07 – E0.02 0.09 92 – 122 E0.01 ≤0.16 0.07 1.9 22 ≤0.28 NOCO-IN08 – E0.04 0.17 173 – 231 E0.01 ≤0.25 0.04 7.1 – ≤0.89 NOCO-IN09 – – 0.62 208 – 112 0.04 – 0.02 – 178 ≤0.15 NOCO-IN10 – – 0.07 45 – 174 – ≤0.13 0.02 2.9 30 ≤0.15 NOCO-IN11 – – 7.9 123 – *1,020 – – 0.14 – *745 – NOCO-IN12 – E0.02 0.19 84 – 29.0 – ≤0.10 E0.01 4.9 – 3.05 NOCO-IN13 – – 0.07 94 – 112 – ≤0.08 0.03 6.3 ≤4 ≤0.11 NOCO-IN14 15.2 E0.02 0.39 65 – 220 E0.01 – 0.05 – *305 ≤0.08 NOCO-IN15 S2.2 S0.09 S9.4 S10.4 – *S1,009 S0.05 ≤0.03 S0.02 ≤0.55 ≤5 ≤0.01 NOCO-IN16 – E0.02 0.11 62 – 63.0 – ≤0.14 0.02 ≤0.53 48 ≤0.07 NOCO-IN17 8.2 – 0.21 24 – 102 – 1.2 E0.01 ≤0.86 – 1.43 NOCO-IN18 – E0.03 0.23 104 – 258 – ≤0.26 0.05 ≤0.73 – ≤0.07 NOCO-IN19 – – 0.13 91 – 20.0 – ≤0.25 0.03 5.9 – ≤0.54 NOCO-IN20 – E0.03 3.5 *1,230 – 231 – ≤0.28 0.11 – *1,620 ≤0.14 NOCO-IN21 – – 0.07 270 – 296 – – 0.13 – *1,340 ≤0.04 NOCO-IN22 – 0.07 1.5 383 E0.02 *8,470 – – 0.43 – 126 – NOCO-IN23 – E0.03 0.16 160 – 54.0 – ≤0.16 0.03 ≤0.95 – ≤0.13

NOCO-IN24 – 0.06 1.1 95 – 131 – 0.67 0.02 ≤1.2 ≤4 ≤0.19

NOCO-IN25 – – 0.34 197 – 789 – ≤0.33 0.03 – 158 –
Table 8 49

Table 8. Trace elements detected in the samples collected for the Northern Coast Ranges (NOCO) Groundwater Ambient Monitoring and Assessment (GAMA) study, California, 

June to November 2009.—Continued 

[The five-digit USGS parameter code in parenthesis below the constituent name is used to uniquely identify a specific constituent or property. Samples from all 58 wells were analyzed, with the exception of mercury, which was sampled for at the 28 grid wells in NOCO-IN. Information about the analytes given in table 3D. GAMA well identification number: NOCO-IN, Inland Basins study area grid well; NOCO-CO, Coastal Basins study area grid well. Numbered suffix indicates the order of sample collection within each study area. Benchmark type, Benchmark level, and LRL: Data as of October 8, 2009. 

Benchmark type: Maximum contaminant level benchmarks are listed as MCL-US when the MCL-US and MCL-CA are identical, and as MCL-CA when the MCL-CA is lower than the MCL-US or no MCL-US exists. Abbreviations: μg/L, micrograms per liter; MCL-CA, CDPH maximum contaminant level; MCL-US, USEPA maximum contaminant level; NL-CA, CDPH notification level; na, not available; 

AL-US, USEPA action level; SMCL-CA, CDPH secondary maximum contaminant level; LRL, laboratory reporting level; SRL, study reporting level; –, not detected; E, estimated or having a higher degree of 

uncertainty; *, value greater than benchmark level; S, most probable value; ≤, less than or equal to; NWIS, National Water Information System; QC, quality control; NWQL, National Water Quality Laboratory; 

BQS, Branch of Quality Systems; USGS, U.S. Geological Survey; CDPH, California Department of Public Health; USEPA, U.S. Environmental Protection Agency]

GAMA well

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/SRL] [1.6] 1 [0.054] [0.044] [0.36] 1 [0.012] [2.8] [0.02] [0.42] 1 [0.010] [1.7] 1 [6] 1 [1.1] 2

NOCO grid wells (58 wells sampled)—ContinuedNOCO-IN26 – 0.05 0.55 100 – 532 – 0.76 0.04 ≤0.70 ≤2 ≤0.06

NOCO-IN27 – – *23.2 254 0.03 *2,380 – 0.52 1.6 – *20,200 –

NOCO-IN28 – E0.03 0.46 283 – 161 E0.02 – 0.15 – 38 ≤0.42

NOCO-CO01 4.7 – 1.4 40 E0.01 156 – ≤0.11 0.02 – *1,100 ≤0.05

NOCO-CO02 – – 0.22 12 – 18.0 – ≤0.21 E0.01 ≤1.2 9 ≤0.14

NOCO-CO03 4.4 E0.04 6.1 7.0 – 11.0 – 2.0 0.02 – 15 ≤0.06

NOCO-CO04 – – 2.8 454 – 156 – ≤0.07 0.10 – *554 –

NOCO-CO05 17.7 E0.02 0.06 72 0.06 39.0 0.02 ≤0.31 0.06 6.9 – ≤0.54

NOCO-CO06 6.8 0.05 0.18 18 0.04 57.0 0.05 ≤0.13 2.2 7.3 63 ≤0.24

NOCO-CO07 – – 0.08 3.0 – 11.0 – 7.7 0.12 4.1 ≤3 ≤0.41

NOCO-CO08 – E0.03 0.17 129 – 61.0 – – 0.06 – 34 –

NOCO-CO09 – – 3.6 48 – 982 – ≤0.07 0.05 – *526 –

NOCO-CO10 – 0.04 1.8 4.0 – 11.0 – 6.3 0.06 ≤0.95 ≤4 ≤0.07

NOCO-CO11 – E0.03 0.11 224 – 46.0 – ≤0.12 0.10 ≤1.5 ≤3 ≤0.16

NOCO-CO12 – – 0.21 6.0 – 16.0 – 0.80 0.03 ≤0.52 14 ≤0.14

NOCO-CO13 – 0.42 0.53 72 – 39.0 – 3.0 0.05 3.8 ≤2 ≤0.80

NOCO-CO14 – E0.03 1.6 2.0 – 11.0 – 21.0 E0.02 – 37 ≤0.09

NOCO-CO15 – – E0.05 9.0 – 16.0 – ≤0.15 – – – ≤0.09

NOCO-CO16 – – 0.07 10 – 10.0 – 5.1 0.03 2.1 ≤2 ≤0.71

NOCO-CO17 – E0.04 0.06 100 – 69.0 – ≤0.07 0.05 6.0 – ≤0.97

NOCO-CO18 – – 1.7 275 – 47.0 – ≤0.21 0.06 – *5,090 ≤0.03

NOCO-CO19 – E0.04 0.15 172 – 74.0 0.03 – 0.47 ≤1.0 – ≤1.01

NOCO-CO20 – 0.04 0.72 91 – 37.0 – 2.0 0.05 3.8 – ≤0.72
50 Groundwater-Quality Data in the Northern Coast Ranges Study Unit, 2009: Results from the California GAMA Program Table 8. Trace elements detected in the samples collected for the Northern Coast Ranges (NOCO) Groundwater Ambient Monitoring and Assessment (GAMA) study, California, June to November 2009.—Continued [The five-digit USGS parameter code in parenthesis below the constituent name is used to uniquely identify a specific constituent or property. Samples from all 58 wells were analyzed, with the exception of mercury, which was sampled for at the 28 grid wells in NOCO-IN. Information about the analytes given in table 3D. GAMA well identification number: NOCO-IN, Inland Basins study area grid well; NOCO-CO, Coastal Basins study area grid well. Numbered suffix indicates the order of sample collection within each study area. Benchmark type, Benchmark level, and LRL: Data as of October 8, 2009. Benchmark type: Maximum contaminant level benchmarks are listed as MCL-US when the MCL-US and MCL-CA are identical, and as MCL-CA when the MCL-CA is lower than the MCL-US or no MCL-US exists. Abbreviations: μg/L, micrograms per liter; MCL-CA, CDPH maximum contaminant level; MCL-US, USEPA maximum contaminant level; NL-CA, CDPH notification level; na, not available; AL-US, USEPA action level; SMCL-CA, CDPH secondary maximum contaminant level; LRL, laboratory reporting level; SRL, study reporting level; –, not detected; E, estimated or having a higher degree of uncertainty; *, value greater than benchmark level; S, most probable value; ≤, less than or equal to; NWIS, National Water Information System; QC, quality control; NWQL, National Water Quality Laboratory; BQS, Branch of Quality Systems; USGS, U.S. Geological Survey; CDPH, California Department of Public Health; USEPA, U.S. Environmental Protection Agency] GAMA well 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/SRL] [1.6] 1 [0.054] [0.044] [0.36] 1 [0.012] [2.8] [0.02] [0.42] 1 [0.010] [1.7] 1 [6] 1 [1.1] 2 NOCO grid wells (58 wells sampled)—Continued NOCO-CO21 E2.4 – 9.3 466 – 113 – ≤0.34 0.19 – *7,330 – NOCO-CO22 22.7 E0.02 0.33 12 – 11.0 – 0.52 0.42 – 10 ≤0.18 NOCO-CO23 14.7 E0.02 0.12 17 – 8.0 – 1.3 E0.01 ≤1.2 ≤2 ≤0.24 NOCO-CO24 11.4 0.06 4.1 4.0 – 10.0 – 2.5 0.70 ≤0.67 *4,290 ≤0.42 NOCO-CO25 – – 0.26 16 – 15.0 0.03 ≤0.09 0.50 – 6 ≤0.32 NOCO-CO26 44.8 – 0.12 62 E0.01 39.0 0.03 0.46 0.12 ≤1.6 25 ≤0.03 NOCO-CO27 – – 0.20 271 – 114 – ≤0.31 0.11 – *3,080 ≤0.06 NOCO-CO28 – – 0.06 252 – 261 – 0.93 0.14 – *716 ≤0.10 NOCO-CO29 E1.9 E0.03 0.88 168 – 61.0 – – 0.48 – 71 ≤0.02 NOCO-CO30 – – 0.22 40 – 12.0 – ≤0.18 0.02 ≤1.2 ≤3 ≤0.37
Table 8 51

Table 8. Trace elements collected for the Northern Coast Ranges (NOCO) Groundwater Ambient Monitoring and Assessment (GAMA) study, California, June to November 2009.—Continued [The five-digit USGS parameter code in parenthesis below the constituent name is used to uniquely identify a specific constituent or property. Samples from all 58 wells were analyzed, with the exception of mercury, which was sampled for at the 28 grid wells in NOCO-IN. Information about the analytes given in table 3D. GAMA well identification number: NOCO-IN, Inland Basins study area grid well; NOCO-CO, Coastal Basins study area grid well. Numbered suffix indicates the order of sample collection within each study area. Benchmark type, Benchmark level, and LRL: Data as of October 8, 2009. 

Benchmark type: Maximum contaminant level benchmarks are listed as MCL-US when the MCL-US and MCL-CA are identical, and as MCL-CA when the MCL-CA is lower than the MCL-US or no MCL-US exists. Abbreviations: μg/L, micrograms per liter; MCL-CA, CDPH maximum contaminant level; MCL-US, USEPA maximum contaminant level; NL-CA, CDPH notification level; na, not available; 

AL-US, USEPA action level; SMCL-CA, CDPH secondary maximum contaminant level; LRL, laboratory reporting level; SRL, study reporting level; –, not detected; E, estimated or having a higher degree of 

uncertainty; *, value greater than benchmark level; S, most probable value; ≤, less than or equal to; NWIS, National Water Information System; QC, quality control; NWQL, National Water Quality Laboratory; 

BQS, Branch of Quality Systems; USGS, U.S. Geological Survey; CDPH, California Department of Public Health; USEPA, U.S. Environmental Protection Agency]

GAMA well identification 

number

Lithium 

(μg/L) 

(01130) 

Manganese 

(μg/L) 

(01056) 

Mercury 

(μg/L) 

(71890) 

Molybdenum 

(μg/L)

(01060) 

Nickel

(μg/L) 

(01065) 

Selenium 

(μg/L) 

(01145) 

Silver

(μg/L) 

(01075) 

Strontium 

(μg/L) 

(01080)

Thallium 

(μg/L) 

(01057) 

Uranium 

(μg/L) 

(22703)

Vanadium 

(μg/L) 

(01085) 

Zinc

(μg/L) 

(01090)

Benchmark type na SMCL-CA MCL-US HAL-US MCL-CA MCL-US SMCL-CA HAL-US MCL-US MCL-US NL-CA SMCL-CA

Benchmark level na 50 2 40 100 50 100 4,000 2 30 50 5,000

[LRL/SRL] [0.44] [0.2] 1 [0.012] 1 [0.028] [0.36] 1 [0.040] [0.010] [0.40] [0.020] [0.008] [0.11] 1 [4.8] 1

NOCO grid wells (58 wells sampled)—Continued

NOCO-IN01 2.7 *84.4 – 9.4 ≤0.13 – – 140 – 0.20 1.4 ≤2.9

NOCO-IN02 2.2 – – 1.1 ≤0.24 0.07 – 216 – 0.07 2.1 ≤2.3

NOCO-IN03 E0.6 6.3 – E0.04 1.4 E0.04 – 92.6 – – 0.28 ≤1.0

NOCO-IN04 E0.8 *73.2 – 0.2 1.3 0.42 – 194 – 0.04 0.23 8.8

NOCO-IN05 E1.0 *1,590 – 1.5 0.74 – – 1,050 – E0.004 E0.14 –NOCO-IN06 5.1 *1,390 – 4.1 0.55 – – 270 – 0.06 0.46 –NOCO-IN07 1.5 0.3 – 0.1 4.2 0.11 – 146 – 0.01 0.25 ≤2.8

NOCO-IN08 2.5 0.2 – 0.3 0.88 0.13 – 434 – 0.13 0.52 ≤3.1

NOCO-IN09 6.1 *193 – 16.4 ≤0.09 – – 334 – 0.75 0.99 ≤1.8

NOCO-IN10 1.2 0.6 – 0.1 0.56 0.07 – 167 – 0.01 0.40 ≤3.2

NOCO-IN11 1.4 *263 – 1.0 0.83 – – 286 – 0.02 0.49 13.0NOCO-IN12 6.6 0.6 – 0.5 ≤0.24 0.07 – 143 – 0.09 1.5 21.8NOCO-IN13 1.9 – – 0.1 1.7 0.24 – 196 – 0.01 0.32 ≤2.0

NOCO-IN14 4.6 *308 – 2.4 ≤0.15 – 0.011 162 – 0.14 0.58 ≤3.0

NOCO-IN15 S1.7 S33.8 – S29.6 ≤0.31 S0.03 – S24.6 – S0.05 S0.49 ≤1.7

NOCO-IN16 1.5 2.4 – 0.5 0.60 0.12 – 162 – 0.09 0.41 ≤1.1

NOCO-IN17 4.2 0.4 – 0.4 ≤0.20 0.41 E0.007 54.9 – E0.004 4.9 5.6NOCO-IN18 3.3 0.6 – 0.2 2.5 0.22 – 386 – 0.16 1.5 –NOCO-IN19 3.6 1.3 – 0.1 2.0 0.12 – 122 – – 0.48 ≤3.5

NOCO-IN20 87.3 *199 – 0.1 1.1 E0.05 – 645 – – 0.16 ≤1.1

NOCO-IN21 5.3 *197 – E0.05 1.9 E0.04 – 407 – 0.01 E0.15 –NOCO-IN22 28.2 *92.7 – 0.4 10.5 – – 490 – 0.02 0.24 ≤4.5

NOCO-IN23 4.1 0.6 – 0.4 ≤0.34 0.47 – 333 – 0.13 0.42 ≤1.1

NOCO-IN24 3.9 0.4 – 0.3 1.4 0.09 – 163 – 0.07 2.5 ≤1.7
52 Groundwater-Quality Data in the Northern Coast Ranges Study Unit, 2009: Results from the California GAMA Program GAMA well identification number Lithium (μg/L) (01130) Manganese (μg/L) (01056) Mercury (μg/L) (71890) Molybdenum (μg/L) (01060) Nickel (μg/L) (01065) Selenium (μg/L) (01145) Silver (μg/L) (01075) Strontium (μg/L) (01080) Thallium (μg/L) (01057) Uranium (μg/L) (22703) Vanadium (μg/L) (01085) Zinc (μg/L) (01090) Benchmark type na SMCL-CA MCL-US HAL-US MCL-CA MCL-US SMCL-CA HAL-US MCL-US MCL-US NL-CA SMCL-CA Benchmark level na 50 2 40 100 50 100 4,000 2 30 50 5,000 [LRL/SRL] [0.44] [0.2] 1 [0.012] 1 [0.028] [0.36] 1 [0.040] [0.010] [0.40] [0.020] [0.008] [0.11] 1 [4.8] 1 NOCO grid wells (58 wells sampled)—Continued NOCO-IN25 19.0 38.0 – 1.5 0.59 – – 148 – – 0.18 – NOCO-IN26 9.0 ≤0.1 – 0.5 3.1 0.19 – 499 – 0.04 1.2 ≤1.5 NOCO-IN27 131 *1,010 – 0.4 2.5 E0.03 – 1,040 – – 0.65 ≤4.6 NOCO-IN28 8.1 *1,120 – 4.7 0.54 – – 408 – 0.84 0.78 ≤2.1 NOCO-CO01 6.4 *164 nc 0.3 ≤0.27 – – 107 – 0.01 0.91 22.5 NOCO-CO02 E0.9 0.9 nc 0.1 ≤0.14 0.10 – 191 – – 0.92 ≤3.2 NOCO-CO03 8.3 9.5 nc 0.2 ≤0.32 0.08 – 36.4 – 0.01 4.1 – NOCO-CO04 7.2 *629 nc 0.7 ≤0.31 – – 503 – – E0.16 13.3 NOCO-CO05 E0.8 8.2 nc E0.01 ≤0.30 E0.04 – 81.7 – – 0.25 8.8 NOCO-CO06 7.1 24.4 nc 0.1 11.0 0.41 – 243 – 0.01 0.65 14.1 NOCO-CO07 1.6 3.2 nc – 0.91 E0.06 – 54.2 – 0.01 1.4 ≤1.4 NOCO-CO08 E0.8 13.8 nc 0.7 ≤0.25 – – 439 – 0.27 0.98 7.7 NOCO-CO09 9.1 *123 nc 0.2 ≤0.12 – – 118 – – 0.43 ≤2.8 NOCO-CO10 7.1 0.3 nc 0.2 0.38 0.18 – 143 – 0.13 4.2 5.7 NOCO-CO11 3.2 32.3 nc 0.2 1.7 0.44 – 261 – 0.09 E0.14 6.0 NOCO-CO12 4.1 3.3 nc 0.3 2.5 0.09 – 73.0 – E0.01 0.89 ≤1.8 NOCO-CO13 1.5 5.3 nc 0.1 0.82 E0.04 – 147 – 0.01 0.23 ≤4.5 NOCO-CO14 2.4 1.8 nc E0.03 0.48 0.08 – 55.4 – 0.02 2.8 ≤2.5 NOCO-CO15 – ≤0.1 nc 0.1 ≤0.20 E0.05 – 49.7 – – 0.20 ≤1.8 NOCO-CO16 – – nc E0.04 76.4 0.18 E0.004 30.4 – – 0.25 ≤3.7 NOCO-CO17 2.5 ≤0.1 nc 0.1 0.51 0.31 – 282 – 0.04 E0.13 ≤4.3 NOCO-CO18 3.2 *1,280 nc 0.4 0.60 – – 334 – – 0.26 ≤4.0 NOCO-CO19 3.3 *532 nc 0.3 3.5 E0.04 – 514 – 0.08 0.35 ≤1.8 Table 8. Trace elements collected for the Northern Coast Ranges (NOCO) Groundwater Ambient Monitoring and Assessment (GAMA) study, California, June to November 2009.—Continued [The five-digit USGS parameter code in parenthesis below the constituent name is used to uniquely identify a specific constituent or property. Samples from all 58 wells were analyzed, with the exception of mercury, which was sampled for at the 28 grid wells in NOCO-IN. Information about the analytes given in table 3D. GAMA well identification number: NOCO-IN, Inland Basins study area grid well; NOCO-CO, Coastal Basins study area grid well. Numbered suffix indicates the order of sample collection within each study area. Benchmark type, Benchmark level, and LRL: Data as of October 8, 2009. Benchmark type: Maximum contaminant level benchmarks are listed as MCL-US when the MCL-US and MCL-CA are identical, and as MCL-CA when the MCL-CA is lower than the MCL-US or no MCL-US exists. Abbreviations: μg/L, micrograms per liter; MCL-CA, CDPH maximum contaminant level; MCL-US, USEPA maximum contaminant level; NL-CA, CDPH notification level; na, not available; AL-US, USEPA action level; SMCL-CA, CDPH secondary maximum contaminant level; LRL, laboratory reporting level; SRL, study reporting level; –, not detected; E, estimated or having a higher degree of uncertainty; *, value greater than benchmark level; S, most probable value; ≤, less than or equal to; NWIS, National Water Information System; QC, quality control; NWQL, National Water Quality Laboratory; BQS, Branch of Quality Systems; USGS, U.S. Geological Survey; CDPH, California Department of Public Health; USEPA, U.S. Environmental Protection Agency]
Table 8 53

Table 8. Trace elements collected for the Northern Coast Ranges (NOCO) Groundwater Ambient Monitoring and Assessment (GAMA) study, California, June to November 2009.—Continued [The five-digit USGS parameter code in parenthesis below the constituent name is used to uniquely identify a specific constituent or property. Samples from all 58 wells were analyzed, with the exception of mercury, which was sampled for at the 28 grid wells in NOCO-IN. Information about the analytes given in table 3D. GAMA well identification number: NOCO-IN, Inland Basins study area grid well; NOCO-CO, Coastal Basins study area grid well. Numbered suffix indicates the order of sample collection within each study area. Benchmark type, Benchmark level, and LRL: Data as of October 8, 2009. 

Benchmark type: Maximum contaminant level benchmarks are listed as MCL-US when the MCL-US and MCL-CA are identical, and as MCL-CA when the MCL-CA is lower than the MCL-US or no MCL-US exists. Abbreviations: μg/L, micrograms per liter; MCL-CA, CDPH maximum contaminant level; MCL-US, USEPA maximum contaminant level; NL-CA, CDPH notification level; na, not available; 

AL-US, USEPA action level; SMCL-CA, CDPH secondary maximum contaminant level; LRL, laboratory reporting level; SRL, study reporting level; –, not detected; E, estimated or having a higher degree of 

uncertainty; *, value greater than benchmark level; S, most probable value; ≤, less than or equal to; NWIS, National Water Information System; QC, quality control; NWQL, National Water Quality Laboratory; 

BQS, Branch of Quality Systems; USGS, U.S. Geological Survey; CDPH, California Department of Public Health; USEPA, U.S. Environmental Protection Agency]

GAMA well identification 

number

Lithium 

(μg/L) 

(01130) 

Manganese 

(μg/L) 

(01056) 

Mercury 

(μg/L) 

(71890) 

Molybdenum 

(μg/L)

(01060) 

Nickel

(μg/L) 

(01065) 

Selenium 

(μg/L) 

(01145) 

Silver

(μg/L) 

(01075) 

Strontium 

(μg/L) 

(01080)

Thallium 

(μg/L) 

(01057) 

Uranium 

(μg/L) 

(22703)

Vanadium 

(μg/L) 

(01085) 

Zinc

(μg/L) 

(01090)

Benchmark type na SMCL-CA MCL-US HAL-US MCL-CA MCL-US SMCL-CA HAL-US MCL-US MCL-US NL-CA SMCL-CA

Benchmark level na 50 2 40 100 50 100 4,000 2 30 50 5,000

[LRL/SRL] [0.44] [0.2] 1 [0.012] 1 [0.028] [0.36] 1 [0.040] [0.010] [0.40] [0.020] [0.008] [0.11] 1 [4.8] 1

NOCO grid wells (58 wells sampled)—Continued

NOCO-CO20 14.0 4.4 nc 0.8 0.67 0.38 – 129 – 0.27 1.3 ≤1.6

NOCO-CO21 3.7 *605 nc 0.3 0.74 E0.05 – 403 – – 0.32 15.2NOCO-CO22 – 33.3 nc 0.1 35.1 0.20 E0.005 33.2 – – 0.52 11.2

NOCO-CO23 – – nc E0.05 8.0 E0.03 E0.009 61.5 – – 0.27 ≤3.3

NOCO-CO24 1.2 *53.4 nc 0.1 22.1 E0.05 – 45.6 – 0.01 2.0 ≤2.9

NOCO-CO25 2.9 *148 nc E0.04 4.8 – – 144 – 0.03 3.8 ≤2.0

NOCO-CO26 – 47.0 nc E0.03 2.4 – – 88.1 – – 0.39 7.2NOCO-CO27 9.2 *156 nc 0.1 0.44 0.05 – 165 – – 0.26 ≤1.6

NOCO-CO28 5.2 *714 nc 0.1 0.87 0.06 – 408 – – 0.61 –NOCO-CO29 1.2 *667 nc 1.2 1.1 – – 518 – 1.17 0.38 6.8NOCO-CO30 4.6 10.0 nc 0.2 ≤0.33 0.57 – 45.9 – 0.02 0.95 8.0

1 SRL defined based on examination of GAMA quality-control samples collected from May 2004 through January 2008 (Olsen and others, 2010). Values below SRL are reported as less than or equal to the 

value reported by the laboratory. In the USGS NWIS database, the result is accompanied with the following comment: Result is less than or equal to reported value, based on QC data (may include: field blanks, source-solution blanks, trip blanks, NWQL set blanks, NWQL blank water certificates, and USGS BQS Blind Blank Program data)

2 SRL defined based on the highest concentration detected in the NOCO study unit blanks. Values below the SRL are reported as less than or equal to the value reported by the laboratory. In the USGS NWIS 

database, the result is accompanied with the following comment: Result is less than or equal to reported value, based on a detection in a blank.
54 Groundwater-Quality Data in the Northern Coast Ranges Study Unit, 2009: Results from the California GAMA Program

Table 9. Nutrients and dissolved organic carbon (DOC) detected in samples collected for the Northern Coast Ranges (NOCO) 

Groundwater Ambient Monitoring and Assessment (GAMA) study, California, June to November 2009.

[The five-digit USGS parameter code in parenthesis below the constituent name is used to uniquely identify a specific constituent or property. Samples from 

57 grid wells were analyzed. Information about the analytes given in table 3E. GAMA well identification number: NOCO-IN, Interior Basins study area grid 

well; NOCO-CO, Coastal Basins study area grid well. Numbered suffix indicates the order of sample collection within each study area. Benchmark type, 

Benchmark level, and LRL: Data as of October 8, 2009. Benchmark type: Maximum contaminant level benchmarks are listed as MCL-US when the MCL-US 

and MCL-CA are identical, and as MCL-CA when the MCL-CA is lower than the MCL-US or no MCL-US exists. Abbreviations: mg/L, milligrams per liter; 

DOC, dissolved organic carbon; HAL-US, USEPA lifetime health advisory level; MCL-US, USEPA maximum contaminant level; na, not available; LRL, 

laboratory reporting level; SRL, study reporting level; –, not detected; E, estimated or having a higher degree of uncertainty; ≤, less than or equal to; MCL-CA, 

CDPH maximum contaminant level; NWIS, National Water Information System; NWQL, National Water Quality Laboratory; USGS, U.S. Geological Survey; 

USEPA, U.S. Environmental Protection Agency; CDPH, California Department of Public Health]

GAMA well

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) 

as 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/SRL] [0.02] [0.002] [0.04] [0.10] [0.006] [0.7] 2

NOCO grid wells (57 wells sampled) 3

NOCO-IN01 0.06 E0.001 0.18 0.25 0.096 ≤0.3

NOCO-IN02 – – 1.49 1.52 0.142 ≤0.3

NOCO-IN03 – – 0.20 0.21 0.011 ≤0.6

NOCO-IN04 0.03 – 1.77 1.87 0.017 ≤0.6

NOCO-IN05 0.58 E0.001 – 0.63 1.33 1.2

NOCO-IN06 0.39 – – 0.41 0.241 ≤0.3

NOCO-IN07 – – 0.19 0.23 0.014 0.8

NOCO-IN08 – E0.001 0.44 4 0.44 0.021 ≤0.5

NOCO-IN09 0.13 – – 4 0.12 0.128 ≤0.3

NOCO-IN10 – – 0.36 0.40 0.012 ≤0.3

NOCO-IN11 E0.01 0.002 1.03 1.09 0.187 ≤0.3

NOCO-IN12 – – 1.67 1.71 0.036 –

NOCO-IN13 – – 1.02 1.05 0.017 ≤0.2

NOCO-IN14 0.03 – – 5 – 0.042 ≤0.2

NOCO-IN15 0.05 – – E0.07 2.41 0.8

NOCO-IN16 – – 0.23 4 0.22 0.016 ≤0.3

NOCO-IN17 – – 3.81 3.96 0.067 ≤0.2

NOCO-IN18 – – 0.61 0.63 0.047 ≤0.5

NOCO-IN19 E0.02 E0.002 3.52 4 3.50 0.034 1.0

NOCO-IN20 7.89 – – 8.62 2.34 4.3

NOCO-IN21 0.35 0.007 0.08 0.48 0.031 1.1

NOCO-IN22 0.34 – – 0.34 0.045 ≤0.5

NOCO-IN23 – – 0.36 5 0.29 0.011 ≤0.3

NOCO-IN24 – – 0.08 5 E0.05 0.033 ≤0.5

NOCO-IN25 0.16 – – 4 0.15 0.346 ≤0.3

NOCO-IN26 – – 0.16 0.16 0.043 ≤0.3

NOCO-IN27 2.14 0.004 – 2.27 0.304 2.9

NOCO-IN28 0.48 – – 4 0.44 0.057 ≤0.4

NOCO-CO01 0.03 – – E0.08 0.079 1.6

NOCO-CO02 – – 8.00 8.40 0.074 –

NOCO-CO03 – – 0.12 0.12 0.056 –

NOCO-CO04 4.31 – – 4.39 1.60 1.6

NOCO-CO05 E0.02 – 3.84 4 3.71 0.009 ≤0.3
Table 9 55

GAMA well

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) 

as 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/SRL] [0.02] [0.002] [0.04] [0.10] [0.006] [0.7] 2

NOCO grid wells (57 wells sampled) 3—Continued

NOCO-CO06 – – E0.03 5 – 0.011 ≤0.3

NOCO-CO07 – – 0.62 0.66 0.049 –

NOCO-CO08 – – – – 0.027 ≤0.2

NOCO-CO09 0.77 – – 0.83 0.579 1.1

NOCO-CO10 – – 0.20 0.20 0.192 0.8

NOCO-CO11 – – 2.86 2.91 0.013 ≤0.3

NOCO-CO12 – – 2.99 4 2.97 0.071 –

NOCO-CO13 – – 5.48 4 5.44 0.013 –

NOCO-CO15 – – 0.47 4 0.43 0.012 –

NOCO-CO16 – – 0.51 4 0.47 0.017 ≤0.4

NOCO-CO17 – – 0.66 4 0.63 E0.006 ≤0.4

NOCO-CO18 0.22 – – 0.24 E0.006 1.5

NOCO-CO19 E0.01 0.006 3.07 3.26 0.008 0.9

NOCO-CO20 – E0.001 0.60 5 0.60 0.037 ≤0.4

NOCO-CO21 1.78 0.002 – 2.04 0.870 4.6

NOCO-CO22 – 0.021 4.70 4 4.53 0.044 ≤0.6

NOCO-CO23 – – 0.15 0.15 0.013 ≤0.3

NOCO-CO24 0.37 0.005 0.30 0.86 0.281 4.5

NOCO-CO25 – – – – 0.092 –

NOCO-CO26 – – 0.22 0.26 E0.007 1.6

NOCO-CO27 1.49 – – 1.65 0.111 2.5

NOCO-CO28 4.15 – – 4.58 2.25 4.5

NOCO-CO29 0.18 – – 0.21 0.051 ≤0.5

NOCO-CO30 – – 0.58 4 0.56 0.016 –

1

 The HAL-US is 30 mg/L “as ammonia.” To facilitate comparson to the analytical results, we have converted and reported this HAL-US as 24.7 mg/L “as 

nitrogen.”

2

 SRL defined based on the highest concentration detected in the NOCO study unit blanks. Values less than the SRL are reported as less than or equal to the 

value reported by the laboratory. In the USGS NWIS database, the result is accompanied with the following comment: Result is less than or equal to reported 

value, based on a detection in a blank.

3

 Samples from NOCO-CO14 were not collected. 

4

 Total nitrogen concentrations in these samples are less than the sum of the filtered nitrogen analytes, but fall within the USGS NWQL acceptance criteria of 

a 10 percent or less relative percent difference.

5

 Total nitrogen concentrations in these samples are less than the sum of the filtered nitrogen analytes and fall outside the USGS NWQL acceptance criterion 

of a 10 percent relative percent difference. The absolute difference is ≤ 0.07 mg/L.

Table 9. Nutrients and dissolved organic carbon (DOC) detected in samples collected for the Northern Coast Ranges (NOCO) 

Groundwater Ambient Monitoring and Assessment (GAMA) study, California, June to November 2009.—Continued

[The five-digit USGS parameter code in parenthesis below the constituent name is used to uniquely identify a specific constituent or property. Samples from 

57 grid wells were analyzed. Information about the analytes given in table 3E. GAMA well identification number: NOCO-IN, Interior Basins study area grid 

well; NOCO-CO, Coastal Basins study area grid well. Numbered suffix indicates the order of sample collection within each study area. Benchmark type, 

Benchmark level, and LRL: Data as of October 8, 2009. Benchmark type: Maximum contaminant level benchmarks are listed as MCL-US when the MCL-US 

and MCL-CA are identical, and as MCL-CA when the MCL-CA is lower than the MCL-US or no MCL-US exists. Abbreviations: mg/L, milligrams per liter; 

DOC, dissolved organic carbon; HAL-US, USEPA lifetime health advisory level; MCL-US, USEPA maximum contaminant level; na, not available; LRL, 

laboratory reporting level; SRL, study reporting level; –, not detected; E, estimated or having a higher degree of uncertainty; ≤, less than or equal to; MCL-CA, 

CDPH maximum contaminant level; NWIS, National Water Information System; NWQL, National Water Quality Laboratory; USGS, U.S. Geological Survey; 

USEPA, U.S. Environmental Protection Agency; CDPH, California Department of Public Health]
56 Groundwater-Quality Data in the Northern Coast Ranges Study Unit, 2009: Results from the California GAMA Program Table 10. Major and minor ions, silica, and total dissolved solids (TDS) detected in samples collected for the Northern Coast Ranges (NOCO) Groundwater Ambient Monitoring and Assessment (GAMA) study, California, June to November 2009. [The five-digit USGS parameter code in parenthesis below the constituent name is used to uniquely identify a specific constituent or property. Samples from all 58 grid wells were analyzed, with the exception of iodide, which was sampled for at the 30 grid wells in NOCO-CO. Information about the analytes given in table 3F. GAMA well identification number: NOCO-IN, Interior Basins study area grid well; NOCO-CO, Coastal Basins study area grid well. Numbered suffix indicates the order of sample collection within each study area. Benchmark type, Benchmark level, and LRL: Data as of October 8, 2009. Benchmark type: Maximum contaminant level benchmarks are listed as MCL-US when the MCL-US and MCL-CA are identical, and as MCL-CA when the MCL-CA is lower than the MCL-US or no MCL-US exists. Abbrevations: mg/L, milligrams per liter; SiO2, silicon dioxide; na, not available; SMCL-CA, CDPH secondary maximum contaminant level; MCL-CA, CDPH maximum contaminant level; LRL, laboratory reporting level; E, estimated or having a higher degree of uncertainty; –, not detected; nc, not collected; *, value greater than benchmark level; MCL-US, USEPA maximum contaminant level; USGS, U.S. Geological Survey; CDPH, California Department of Public Health; USEPA, U.S. Environmental Protection Agency] GAMA well 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) Residue on evaporation (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] [0.02] [0.044] [0.12] [0.08] [0.002] [0.016] [0.064] [0.10] [0.18] [0.058] [10] NOCO grid wells (58 wells sampled) NOCO-IN01 0.03 14.3 3.95 0.42 nc 4.17 0.65 34.9 2.12 21.7 161 NOCO-IN02 0.04 25.8 9.71 0.17 nc 10.1 0.73 18.8 5.90 26.9 181 NOCO-IN03 E0.01 11.5 3.67 E0.08 nc 10.5 0.35 5.45 1.45 17.0 113 NOCO-IN04 E0.01 27.2 8.16 0.11 nc 12.7 0.89 11.3 7.65 17.2 176 NOCO-IN05 0.24 42.9 87.9 0.25 nc 22.0 0.69 35.9 1.72 30.1 343 NOCO-IN06 0.03 26.6 4.45 0.19 nc 22.3 0.53 21.3 1.26 25.0 215 NOCO-IN07 0.03 15.8 11.0 E0.09 nc 15.6 0.72 10.7 12.6 17.6 153 NOCO-IN08 0.08 36.1 10.8 0.10 nc 19.7 1.33 13.8 29.4 15.4 231 NOCO-IN09 0.04 25.5 9.21 0.22 nc 9.24 0.84 60.3 2.43 26.3 280 NOCO-IN10 E0.01 19.8 5.51 E0.08 nc 12.2 0.58 7.73 13.6 17.5 134 NOCO-IN11 0.06 28.1 5.33 E0.08 nc 21.7 0.56 12.0 11.5 22.5 203 NOCO-IN12 0.03 16.2 10.2 0.26 nc 16.1 0.81 24.2 4.01 28.6 184 NOCO-IN13 0.04 20.8 6.63 E0.09 nc 17.0 0.76 10.6 18.2 19.1 159 NOCO-IN14 0.05 31.4 13.7 0.34 nc 7.04 0.74 25.1 14.9 24.1 193 NOCO-IN15 E0.02 1.98 2.26 0.29 nc 1.45 0.23 65.5 2.89 18.8 194 NOCO-IN16 E0.02 12.4 7.68 E0.06 nc 5.46 0.52 13.2 3.71 14.1 99.0 NOCO-IN17 0.05 9.24 11.4 0.22 nc 17.6 0.32 13.9 4.62 37.2 171 NOCO-IN18 E0.02 50.1 6.86 – nc 43.6 0.84 11.3 61.7 25.9 354 NOCO-IN19 0.10 18.5 17.8 E0.08 nc 13.2 0.38 14.6 24.2 29.3 167 NOCO-IN20 0.08 67.0 50.4 0.13 nc 132 2.92 26.9 1.98 97.6 *766
Table 10 57

Table 10. Major and minor ions, silica, and total dissolved solids (TDS) detected in samples collected for the Northern Coast Ranges (NOCO) Groundwater Ambient Monitoring and Assessment (GAMA) study, California, June to November 2009.—Continued[The five-digit USGS parameter code in parenthesis below the constituent name is used to uniquely identify a specific constituent or property. Samples from all 58 grid wells were analyzed, with the exception of iodide, which was sampled for at the 30 grid wells in NOCO-CO. Information about the analytes given in table 3F. GAMA well identification number: NOCO-IN, Interior Basins study area grid well; 

NOCO-CO, Coastal Basins study area grid well. Numbered suffix indicates the order of sample collection within each study area. Benchmark type, Benchmark level, and LRL: Data as of October 8, 2009. 

Benchmark type: Maximum contaminant level benchmarks are listed as MCL-US when the MCL-US and MCL-CA are identical, and as MCL-CA when the MCL-CA is lower than the MCL-US or no MCL-US exists. Abbrevations: mg/L, milligrams per liter; SiO2, silicon dioxide; na, not available; SMCL-CA, CDPH secondary maximum contaminant level; MCL-CA, CDPH maximum contaminant level; 

LRL, laboratory reporting level; E, estimated or having a higher degree of uncertainty; –, not detected; nc, not collected; *, value greater than benchmark level; MCL-US, USEPA maximum contaminant level; 

USGS, U.S. Geological Survey; CDPH, California Department of Public Health; USEPA, U.S. Environmental Protection Agency]

GAMA well 

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) 

Residue on 

evaporation

(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] [0.02] [0.044] [0.12] [0.08] [0.002] [0.016] [0.064] [0.10] [0.18] [0.058] [10]

NOCO grid wells (58 wells sampled) NOCO-IN21 0.03 56.4 23.6 – nc 90.3 1.37 20.5 107 37.7 *598

NOCO-IN22 0.17 28.5 40.4 0.36 nc 61.9 1.70 78.1 12.8 73.7 *560

NOCO-IN23 – 34.5 3.42 E0.06 nc 9.37 0.84 6.68 14.2 14.1 155

NOCO-IN24 E0.01 17.9 5.01 – nc 29.8 1.49 8.09 4.76 31.1 199

NOCO-IN25 0.02 13.4 6.70 E0.07 nc 27.4 1.25 38.9 2.42 68.0 275

NOCO-IN26 0.05 41.5 23.5 – nc 13.4 0.83 22.2 4.24 16.3 245

NOCO-IN27 – 63.5 15.6 0.23 nc 70.8 4.66 56.4 E0.11 105 *684

NOCO-IN28 0.14 42.3 8.37 0.21 nc 35.8 0.86 53.0 3.88 21.1 393

NOCO-CO01 0.14 6.61 40.7 0.17 0.007 3.70 4.44 59.0 10.6 23.2 223

NOCO-CO02 0.16 7.33 34.9 – – 3.66 1.28 31.6 8.24 27.5 180

NOCO-CO03 0.05 5.67 13.9 E0.09 0.004 8.82 1.00 11.1 3.99 23.3 104

NOCO-CO04 0.11 51.9 18.8 E0.06 0.013 39.3 6.23 27.8 4.81 37.7 393

NOCO-CO05 0.10 4.48 29.5 – 0.002 4.00 2.02 22.3 11.3 16.0 114NOCO-CO06 0.26 20.1 92.7 0.34 0.009 10.7 1.57 47.1 20.3 27.0 268

NOCO-CO07 0.16 6.73 15.4 – E0.001 7.12 0.79 14.3 2.31 28.2 110

NOCO-CO08 0.03 46.8 7.71 E0.07 0.006 8.18 1.02 7.70 7.11 16.1 195

NOCO-CO09 0.37 15.5 78.1 E0.09 0.084 14.5 4.12 113 – 46.5 423

NOCO-CO10 0.02 29.4 6.96 E0.08 – 13.7 0.92 7.79 8.30 27.3 172

NOCO-CO11 0.04 39.2 11.6 0.12 – 24.8 1.29 11.2 17.8 18.3 250

NOCO-CO12 0.16 11.2 33.2 0.11 0.003 16.8 1.05 23.3 9.05 25.9 179

NOCO-CO13 0.07 12.6 18.1 – – 4.69 1.02 16.8 8.56 13.7 131

NOCO-CO14 0.08 8.34 15.5 – – 16.4 0.62 12.6 3.98 28.0 133

NOCO-CO15 0.02 4.49 5.38 – – 1.45 0.47 4.67 2.68 9.63 38.0
58 Groundwater-Quality Data in the Northern Coast Ranges Study Unit, 2009: Results from the California GAMA Program Table 10. Major and minor ions, silica, and total dissolved solids (TDS) detected in samples collected for the Northern Coast Ranges (NOCO) Groundwater Ambient Monitoring and Assessment (GAMA) study, California, June to November 2009.—Continued [The five-digit USGS parameter code in parenthesis below the constituent name is used to uniquely identify a specific constituent or property. Samples from all 58 grid wells were analyzed, with the exception of iodide, which was sampled for at the 30 grid wells in NOCO-CO. Information about the analytes given in table 3F. GAMA well identification number: NOCO-IN, Interior Basins study area grid well; NOCO-CO, Coastal Basins study area grid well. Numbered suffix indicates the order of sample collection within each study area. Benchmark type, Benchmark level, and LRL: Data as of October 8, 2009. Benchmark type: Maximum contaminant level benchmarks are listed as MCL-US when the MCL-US and MCL-CA are identical, and as MCL-CA when the MCL-CA is lower than the MCL-US or no MCL-US exists. Abbrevations: mg/L, milligrams per liter; SiO2, silicon dioxide; na, not available; SMCL-CA, CDPH secondary maximum contaminant level; MCL-CA, CDPH maximum contaminant level; LRL, laboratory reporting level; E, estimated or having a higher degree of uncertainty; –, not detected; nc, not collected; *, value greater than benchmark level; MCL-US, USEPA maximum contaminant level; USGS, U.S. Geological Survey; CDPH, California Department of Public Health; USEPA, U.S. Environmental Protection Agency] GAMA well 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) Residue on evaporation (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] [0.02] [0.044] [0.12] [0.08] [0.002] [0.016] [0.064] [0.10] [0.18] [0.058] [10] NOCO grid wells (58 wells sampled)—Continued NOCO-CO16 E0.01 3.25 4.31 – – 19.3 0.34 3.21 1.81 26.9 119 NOCO-CO17 0.04 41.1 8.69 E0.08 – 12.0 1.48 11.0 14.8 13.0 190 NOCO-CO18 0.16 41.0 22.3 0.14 0.020 19.2 1.38 15.8 10.3 22.2 242 NOCO-CO19 0.08 55.2 22.2 E0.07 0.009 19.5 1.60 13.8 22.7 17.4 274 NOCO-CO20 0.08 25.2 22.4 0.26 – 27.1 2.33 16.6 17.7 20.9 234 NOCO-CO21 0.33 59.4 45.6 0.34 0.101 36.6 3.52 28.0 – 35.2 415 NOCO-CO22 0.05 6.59 16.3 – 0.003 34.5 1.54 5.33 6.43 33.0 193 NOCO-CO23 E0.01 4.86 5.20 E0.06 0.002 5.41 0.56 4.10 2.98 11.4 61.0 NOCO-CO24 0.05 8.57 18.2 – 0.005 16.2 1.78 7.50 1.49 30.4 158 NOCO-CO25 0.15 17.8 31.1 0.12 0.022 13.8 1.37 26.8 0.40 38.8 212 NOCO-CO26 0.12 5.38 40.8 E0.04 0.003 4.62 0.60 22.2 4.59 9.77 106 NOCO-CO27 0.48 23.7 63.8 0.19 0.139 31.1 4.19 66.6 – 39.5 394 NOCO-CO28 0.27 37.3 30.6 0.39 0.033 25.0 11.8 62.6 – 50.2 405 NOCO-CO29 0.20 62.0 14.4 0.10 0.005 10.7 1.28 8.82 8.68 17.3 246 NOCO-CO30 0.06 7.84 13.6 0.15 – 13.7 0.70 14.9 17.0 19.6 133

1 The SMCL-CA for chloride, sulfate, and TDS have recommended and upper benchmark values. The upper value is shown in parentheses.
Table 11 59

Table 11. Results for analyses of stable isotope ratios, tritium activity, and carbon-14 abundance detected in samples 

collected for the Northern Coast Ranges (NOCO) Groundwater Ambient Monitoring and Assessment (GAMA) study, California, 

June to November 2009.

[The five-digit USGS parameter code in parenthesis below the constituent name is used to uniquely identify a specific constituent or property. 

Information about the analytes given in table 3G. Samples from all 58 grid wells were analyzed for stable isotopes of hydrogen and oxygen in 

water and tritium activities. Samples from 57 grid wells were analyzed for stable isotopes of carbon in dissolved inorganic carbon and carbon-14 

abundance. Stable isotope ratios are reported in the standard delta notation (δ), the ratio of a heavier isotope to more common lighter isotope of that 

element, relative to a standard reference material. Tritium values less than the sample-specific critical level (ssLC) are reported as non-detections 

(–). GAMA well identification number: NOCO-IN, Interior Basins study area grid well; NOCO-CO, Coastal Basins study area grid well. 

Numbered suffix indicates the order of sample collection within each study area. Benchmark type and Benchmark level: Data as of October 8, 

2009. Benchmark type: Maximum contaminant level benchmarks are listed as MCL-US when the MCL-US and MCL-CA are identical, and as 

MCL-CA when the MCL-CA is lower than the MCL-US or no MCL-US exists. Abbreviations: H, hydrogen; O, oxygen; pCi/L, picocuries per 

liter; C, carbon; CSU, 1-sigma combined standard uncertainty; na, not available; MCL-CA, CDPH maximum contaminant level; –, not detected; nc, 

not collected; ±, plus or minus; MCL-US, USEPA maximum contaminant level; USGS, U.S. Geological Survey; CDPH, California Department of 

Public Health; USEPA, U.S. Environmental Protection Agency]

GAMA well 

identification 

number

δ2H

(per mil) 

(82082)

δ18O

(per mil) 

(82085)

Tritium 

(pCi/L) 

(07000)

δ13C 

(per mil) 

(82081)

Carbon-14 

(percent 

modern) 

(49933)

Benchmark type na na MCL-CA

20,000

na na

Benchmark level na na na na

Result ± CSU ssLC

NOCO grid wells (58 wells sampled) 1

NOCO-IN01 -51.15 -7.86 0.30 ± 3.2 0.30 -20.30 39.85

NOCO-IN02 -42.08 -6.36 4.5 ± 0.41 0.35 -19.72 81.92

NOCO-IN03 -48.97 -7.52 4.2 ± 0.41 0.35 -21.93 105.0

NOCO-IN04 -50.42 -7.59 5.8 ± 0.41 0.32 -20.21 98.00

NOCO-IN05 -53.95 -8.01 4.7 ± 0.38 0.35 -20.55 57.55

NOCO-IN06 -63.01 -9.20 – 0.35 -20.47 32.19

NOCO-IN07 -50.97 -7.46 9.0 ± 0.51 0.38 -19.08 103.4

NOCO-IN08 -46.84 -7.05 6.9 ± 0.45 0.35 -14.05 86.51

NOCO-IN09 -52.17 -7.68 0.30 ± 0.35 0.35 -18.41 21.92

NOCO-IN10 -49.31 -7.19 6.9 ± 0.38 0.32 -16.18 100.8

NOCO-IN11 -54.81 -8.20 4.4 ± 0.32 0.32 -16.81 82.25

NOCO-IN12 -46.28 -6.55 3.4 ± 0.32 0.32 -19.01 85.25

NOCO-IN13 -48.04 -7.25 11.4 ± 0.48 0.32 -19.39 104.1

NOCO-IN14 -50.02 -7.40 2.6 ± 0.32 0.32 -19.65 55.91

NOCO-IN15 -67.87 -9.68 1.2 ± 0.32 0.32 -21.62 27.39

NOCO-IN16 -64.21 -9.46 5.7 ± 0.35 0.32 -19.06 77.94

NOCO-IN17 -55.46 -7.93 1.5 ± 0.32 0.32 -14.87 75.29

NOCO-IN18 -49.63 -7.16 4.2 ± 0.32 0.32 -15.25 76.82

NOCO-IN19 -47.12 -7.17 6.6 ± 0.35 0.32 -21.07 104.5

NOCO-IN20 -48.92 -6.45 4.5 ± 0.32 0.32 -9.57 27.95

NOCO-IN21 -49.62 -7.10 5.8 ± 0.35 0.32 -15.93 104.0

NOCO-IN22 -45.14 -6.62 3.2 ± 0.32 0.32 -11.84 23.98

NOCO-IN23 -60.75 -9.11 6.5 ± 0.35 0.32 -14.44 90.74

NOCO-IN24 -50.14 -7.34 6.3 ± 0.35 0.32 -11.93 86.43

NOCO-IN25 -49.46 -7.46 5.7 ± 0.38 0.32 -11.85 57.90

NOCO-IN26 -70.85 -10.3 8.1 ± 0.38 0.32 -14.54 97.49

NOCO-IN27 -60.09 -8.56 3.4 ± 0.32 0.32 -10.85 5.000

NOCO-IN28 -63.53 -9.16 0.67 ± 0.32 0.32 -21.61 10.52

NOCO-CO01 -37.68 -5.97 3.2 ± 0.32 0.32 -20.15 56.74

NOCO-CO02 -34.32 -5.56 4.8 ± 0.32 0.32 -22.49 106.1

NOCO-CO03 -47.13 -7.10 0.35 ± 0.32 0.32 -20.50 74.12

NOCO-CO04 -47.57 -7.45 – 0.32 -22.18 14.26

NOCO-CO05 -37.17 -6.03 6.2 ± 0.32 0.32 -22.74 107.4
60 Groundwater-Quality Data in the Northern Coast Ranges Study Unit, 2009: Results from the California GAMA Program

Table 11. Results for analyses of stable isotope ratios, tritium activity, and carbon-14 abundance detected in samples 

collected for the Northern Coast Ranges (NOCO) Groundwater Ambient Monitoring and Assessment (GAMA) study, 

California, June to November 2009.—Continued

[The five-digit USGS parameter code in parenthesis below the constituent name is used to uniquely identify a specific constituent or property. 

Information about the analytes given in table 3G. Samples from all 58 grid wells were analyzed for stable isotopes of hydrogen and oxygen in 

water and tritium activities. Samples from 57 grid wells were analyzed for stable isotopes of carbon in dissolved inorganic carbon and carbon-14 

abundance. Stable isotope ratios are reported in the standard delta notation (δ), the ratio of a heavier isotope to more common lighter isotope of that 

element, relative to a standard reference material. Tritium values less than the sample-specific critical level (ssLC) are reported as non-detections 

(–). GAMA well identification number: NOCO-IN, Interior Basins study area grid well; NOCO-CO, Coastal Basins study area grid well. 

Numbered suffix indicates the order of sample collection within each study area. Benchmark type and Benchmark level: Data as of October 8, 

2009. Benchmark type: Maximum contaminant level benchmarks are listed as MCL-US when the MCL-US and MCL-CA are identical, and as 

MCL-CA when the MCL-CA is lower than the MCL-US or no MCL-US exists. Abbreviations: H, hydrogen; O, oxygen; pCi/L, picocuries per 

liter; C, carbon; CSU, 1-sigma combined standard uncertainty; na, not available; MCL-CA, CDPH maximum contaminant level; –, not detected; nc, 

not collected; ±, plus or minus; MCL-US, USEPA maximum contaminant level; USGS, U.S. Geological Survey; CDPH, California Department of 

Public Health; USEPA, U.S. Environmental Protection Agency]

GAMA well 

identification 

number

δ2H

(per mil) 

(82082)

δ18O

(per mil) 

(82085)

Tritium 

(pCi/L) 

(07000)

δ13C 

(per mil) 

(82081)

Carbon-14 

(percent 

modern) 

(49933)

Benchmark type na na MCL-CA

20,000

na na

Benchmark level na na na na

Result ± CSU ssLC

NOCO grid wells (58 wells sampled) 1 —Continued

NOCO-CO06 -34.47 -5.80 7.2 ± 0.35 0.32 -22.48 92.00

NOCO-CO07 -45.30 -7.02 12.5 ± 0.57 0.38 -22.98 103.0

NOCO-CO08 -53.20 -7.91 2.2 ± 0.41 0.38 -15.62 69.12

NOCO-CO09 -49.50 -7.44 – 0.35 -10.42 8.980

NOCO-CO10 -49.30 -7.53 3.7 ± 0.41 0.38 -17.21 73.48

NOCO-CO11 -49.60 -7.36 5.4 ± 0.41 0.35 -20.57 94.01

NOCO-CO12 -45.60 -7.03 1.2 ± 0.48 0.45 -22.01 78.60

NOCO-CO13 -46.10 -7.04 5.5 ± 0.45 0.38 -19.76 89.48

NOCO-CO14 -45.60 -7.08 4.7 ± 0.38 0.38 nc nc

NOCO-CO15 -43.30 -7.07 6.0 ± 0.41 0.32 -16.30 99.13

NOCO-CO16 -47.20 -7.39 7.4 ± 0.45 0.32 -21.63 102.8

NOCO-CO17 -49.50 -7.48 7.6 ± 0.48 0.38 -19.29 92.23

NOCO-CO18 -46.10 -6.99 5.7 ± 0.41 0.32 -21.46 85.85

NOCO-CO19 -45.40 -6.80 5.2 ± 0.41 0.32 -20.13 103.3

NOCO-CO20 -45.50 -7.02 5.3 ± 0.35 0.32 -19.95 65.91

NOCO-CO21 -48.50 -7.29 2.4 ± 0.32 0.32 -13.08 56.89

NOCO-CO22 -43.50 -6.77 4.7 ± 0.32 0.32 -21.16 106.2

NOCO-CO23 -45.60 -7.18 6.0 ± 0.32 0.32 -17.37 100.0

NOCO-CO24 -41.70 -6.68 4.0 ± 0.32 0.32 -22.29 102.9

NOCO-CO25 -53.60 -7.82 – 0.32 -20.30 9.820

NOCO-CO26 -40.60 -6.44 6.2 ± 0.38 0.32 -23.00 106.4

NOCO-CO27 -49.60 -7.55 – 0.32 -16.12 5.200

NOCO-CO28 -48.20 -7.27 – 0.32 -1.43 50.74

NOCO-CO29 -48.00 -7.16 9.2 ± 0.41 0.32 -18.87 76.53

NOCO-CO30 -49.80 -7.47 10.3 ± 0.54 0.38 -21.81 59.22

1

 Stable isotopes of carbon in dissolved inorganic carbon and carbon-14 abundance sample from NOCO-CO14 were not collected. 
Table 12A 61

GAMA well 

identification 

number

Radon-222 

(pCi/L) 

(82303)

Result ± CSU ssLC

Benchmark type Proposed MCL-US

Benchmark level 4,000

NOCO grid wells (57 wells sampled) 1

NOCO-IN01 1,150 ± 65 11

NOCO-IN02 1,270 ± 71 12

NOCO-IN03 550 ± 33 12

NOCO-IN04 670 ± 40 11

NOCO-IN05 320 ± 22 12

NOCO-IN06 238 ± 17 12

NOCO-IN07 272 ± 19 11

NOCO-IN08 300 ± 20 12

NOCO-IN09 870 ± 50 12

NOCO-IN10 360 ± 23 11

NOCO-IN11 560 ± 34 12

NOCO-IN12 390 ± 26 13

NOCO-IN13 350 ± 23 11

NOCO-IN14 460 ± 29 12

NOCO-IN15 690 ± 41 11

NOCO-IN16 460 ± 29 11

NOCO-IN17 650 ± 38 11

NOCO-IN18 790 ± 46 11

NOCO-IN19 500 ± 31 11

NOCO-IN20 340 ± 23 13

NOCO-IN21 350 ± 23 11

NOCO-IN22 54 ± 9 11

NOCO-IN23 195 ± 15 12

NOCO-IN24 370 ± 24 12

NOCO-IN25 360 ± 24 12

NOCO-IN26 180 ± 14 11

NOCO-IN27 277 ± 19 12

NOCO-IN28 460 ± 29 13

Table 12A. Radon-222 detected in samples collected for the Northern Coast Ranges (NOCO) Groundwater Ambient Monitoring and 

Assessment (GAMA) study, California, June to November 2009. 

[The five-digit USGS parameter code in parathesis below the constituent name is used to uniquely identify a specific constituent or property. Samples from 

57 grid wells were analyzed. Information about the analyte given in table 3G. GAMA well identification number: NOCO-IN, Interior Basins study area grid 

well; NOCO-CO, Coastal Basins study area grid well. Numbered suffix indicates the order of sample collection within each study area. Benchmark type and 

Benchmark level: Data as of October 8, 2009. Benchmark type: Maximum contaminant level benchmarks are listed as MCL-US when the MCL-US and 

MCL-CA are identical, and as MCL-CA when the MCL-CA is lower than the MCL-US or no MCL-US exists. Other Abbreviations: CSU, 1-sigma combined 

standard uncertainty; pCi/L, picocuries per liter; ssLC, sample-specific critical level; MCL-US, USEPA maximum contaminant level; MCL-CA, CDPH 

maximum contaminant level; USGS, U.S. Geological Survey; USEPA, U.S. Environmental Protection Agency; CDPH, California Department of Public Health]

GAMA well 

identification 

number

Radon-222 

(pCi/L) 

(82303)

Result ± CSU ssLC

Benchmark type Proposed MCL-US

Benchmark level 4,000

NOCO grid wells (57 wells sampled) 1

—Continued

NOCO-CO01 242 ± 17 11

NOCO-CO02 1,690 ± 94 11

NOCO-CO03 139 ± 13 12

NOCO-CO04 57 ± 9 11

NOCO-CO05 256 ± 19 14

NOCO-CO06 530 ± 32 12

NOCO-CO07 1,250 ± 70 11

NOCO-CO08 930 ± 53 11

NOCO-CO09 69 ± 10 12

NOCO-CO10 290 ± 20 12

NOCO-CO11 265 ± 19 12

NOCO-CO12 330 ± 22 11

NOCO-CO13 530 ± 33 12

NOCO-CO15 520 ± 31 11

NOCO-CO16 117 ± 12 12

NOCO-CO17 440 ± 27 10

NOCO-CO18 77 ± 10 12

NOCO-CO19 176 ± 14 11

NOCO-CO20 256 ± 18 12

NOCO-CO21 78 ± 10 11

NOCO-CO22 98 ± 11 12

NOCO-CO23 228 ± 17 11

NOCO-CO24 46 ± 8 11

NOCO-CO25 490 ± 30 11

NOCO-CO26 155 ± 14 12

NOCO-CO27 280 ± 20 11

NOCO-CO28 75 ± 10 11

NOCO-CO29 560 ± 34 11

NOCO-CO30 300 ± 20 11

1

 Sample from NOCO-CO14 was not collected.
62 Groundwater-Quality Data in the Northern Coast Ranges Study Unit, 2009: Results from the California GAMA Program

Table 12B. Radium isotopes detected in samples collected for the Northern Coast Ranges (NOCO) 

Groundwater Ambient Monitoring and Assessment (GAMA) study, California, June to November 2009. 

[The five-digit USGS parameter code in parenthesis below the constituent name is used to uniquely identify a specific constituent or 

property. Samples from 54 grid wells were analyzed. Information about the analyte given in table 3G. Measured values less than the 

sample specific critical level (ssLc) are reported as non-detections. GAMA well identification number: NOCO-IN, Interior Basins 

study area grid well; NOCO-CO, Coastal Basins study area grid well. Numbered suffix indicates the order of sample collection 

within each study area. Benchmark type and Benchmark level: Data as of October 8, 2009. Benchmark type: Maximum 

contaminant level benchmarks are listed as MCL-US when the MCL-US and MCL-CA are identical, and as MCL-CA when the 

MCL-CA is lower than the MCL-US or no MCL-US exists. Abbreviations: pCi/L, picocuries per liter; CSU, combined stardard 

uncertainty; MCL-US, USEPA maximum contaminant level; –, not detected at an activity above the sample-specific critical level; 

MCL-CA, CDPH maximum contaminant level; USGS, U.S. Geological Survey; USEPA, U.S. Environmental Protection Agency; 

CDPH, California Department of Public Health]

GAMA well 

identification 

number

Radium-226

(pCi/L) 

(09511)

Radium-228

(pCi/L)

(81366)

Result ± CSU ssLC Result ± CSU ssLC

Benchmark type MCL-US MCL-US

Benchmark level 1

 5 1 5

NOCO grid wells (54 wells sampled) 2

NOCO-IN05 0.062 ± 0.013 0.016 – 0.22

NOCO-IN06 0.023 ± 0.011 0.018 – 0.24

NOCO-IN07 0.0261 ± 0.068 0.012 0.26 ± 0.16 0.23

NOCO-IN08 0.0607 ± 0.0098 0.012 – 0.20

NOCO-IN09 0.0607 ± 0.0094 0.012 – 0.21

NOCO-IN10 0.0146 ± 0.0076 0.014 – 0.19

NOCO-IN11 0.0375 ± 0.0086 0.012 – 0.24

NOCO-IN12 0.04 ± 0.01 0.017 – 0.19

NOCO-IN13 0.0395 ± 0.0086 0.014 – 0.23

NOCO-IN14 0.0247 ± 0.0078 0.012 – 0.22

NOCO-IN15 0.0154 ± 0.0061 0.013 – 0.24

NOCO-IN16 0.0239 ± 0.0058 0.0095 – 0.25

NOCO-IN17 – 0.015 – 0.17

NOCO-IN18 0.04 ± 0.01 0.015 – 0.20

NOCO-IN19 0.032 ± 0.012 0.016 – 0.21

NOCO-IN20 0.523 ± 0.052 0.018 0.7 ± 0.1 0.22

NOCO-IN21 0.139 ± 0.017 0.015 – 0.19

NOCO-IN22 0.075 ± 0.012 0.015 – 0.19

NOCO-IN23 – 0.019 – 0.22

NOCO-IN24 0.034 ± 0.009 0.015 – 0.27

NOCO-IN25 0.065 ± 0.011 0.017 – 0.16

NOCO-IN26 0.0196 ± 0.0077 0.015 – 0.16

NOCO-IN27 0.087 ± 0.011 0.011 – 0.22

NOCO-IN28 0.0341 ± 0.0075 0.012 – 0.19

NOCO-CO01 0.0411 ± 0.0091 0.015 – 0.20

NOCO-CO02 0.04 ± 0.01 0.015 – 0.22

NOCO-CO03 0.032 ± 0.0094 0.014 – 0.23

NOCO-CO04 0.20 ± 0.023 0.013 – 0.22

NOCO-CO05 0.061 ± 0.011 0.016 0.217 ± 0.071 0.17

NOCO-CO06 0.0440 ± 0.0097 0.016 0.172 ± 0.066 0.16

NOCO-CO07 – 0.015 – 0.21

NOCO-CO08 – 0.015 – 0.28

NOCO-CO09 0.0202 ± 0.0077 0.014 – 0.37

NOCO-CO10 0.0131 ± 0.0066 0.012 – 0.22
Table 12B 63

Table 12B. Radium isotopes detected in samples collected for the Northern Coast Ranges (NOCO) 

Groundwater Ambient Monitoring and Assessment (GAMA) study, California, June to November 2009. —

Continued

[The five-digit USGS parameter code in parenthesis below the constituent name is used to uniquely identify a specific constituent or 

property. Samples from 54 grid wells were analyzed. Information about the analyte given in table 3G. Measured values less than the 

sample specific critical level (ssLc) are reported as non-detections. GAMA well identification number: NOCO-IN, Interior Basins 

study area grid well; NOCO-CO, Coastal Basins study area grid well. Numbered suffix indicates the order of sample collection 

within each study area. Benchmark type and Benchmark level: Data as of October 8, 2009. Benchmark type: Maximum 

contaminant level benchmarks are listed as MCL-US when the MCL-US and MCL-CA are identical, and as MCL-CA when the 

MCL-CA is lower than the MCL-US or no MCL-US exists. Abbreviations: pCi/L, picocuries per liter; CSU, combined stardard 

uncertainty; MCL-US, USEPA maximum contaminant level; –, not detected at an activity above the sample-specific critical level; 

MCL-CA, CDPH maximum contaminant level; USGS, U.S. Geological Survey; USEPA, U.S Environmental Protection Agency; 

CDPH, California Department of Public Health]

GAMA well 

identification 

number

Radium-226

(pCi/L) 

(09511)

Radium-228

(pCi/L)

(81366)

Result ± CSU ssLC Result ± CSU ssLC

Benchmark type MCL-US MCL-US

Benchmark level 1

 5 1 5

NOCO grid wells (54 wells sampled) 2—Continued

NOCO-CO11 0.055 ± 0.014 0.016 – 0.21

NOCO-CO12 – 0.016 – 0.22

NOCO-CO13 0.053 ± 0.0095 0.012 – 0.23

NOCO-CO14 0.0169 ± 0.0066 0.013 – 0.25

NOCO-CO15 – 0.015 – 0.18

NOCO-CO16 – 0.015 – 0.16

NOCO-CO17 0.045 ± 0.013 0.014 – 0.18

NOCO-CO18 0.074 ± 0.012 0.016 – 0.18

NOCO-CO19 0.0326 ± 0.0094 0.017 – 0.18

NOCO-CO20 0.026 ± 0.011 0.014 – 0.20

NOCO-CO21 0.073 ± 0.014 0.014 0.284 ± 0.076 0.18

NOCO-CO22 0.0243 ± 0.0082 0.014 – 0.18

NOCO-CO23 0.0348 ± 0.0085 0.013 – 0.16

NOCO-CO24 – 0.017 – 0.22

NOCO-CO25 0.037 ± 0.012 0.016 – 0.18

NOCO-CO26 0.0363 ± 0.0095 0.016 – 0.18

NOCO-CO27 0.209 ± 0.022 0.012 – 0.20

NOCO-CO28 0.116 ± 0.015 0.015 – 0.19

NOCO-CO29 0.0161 ± 0.0096 0.015 – 0.18

NOCO-CO30 – 0.017 – 0.17

1

 The MCL-US benchmark for radium is the sum of radium-226 and radium-228.

2

 Samples from NOCO-IN01 through NOCO-IN04 were not collected.
64 Groundwater-Quality Data in the Northern Coast Ranges Study Unit, 2009: Results from the California GAMA Program

Table 12C. Gross alpha and gross beta radioactivity detected in samples collected for the Northern Coast Ranges (NOCO)

Groundwater Ambient Monitoring and Assessment (GAMA) study, California, June to November 2009. 

[The five-digit USGS parameter code in parenthesis below the constituent name is used to uniquely identify a specific constituent or property. Samples from 

all 58 grid wells were analyzed. Information about the analytes given in table 3G. The reference nuclide for measurement of gross alpha is thorium-230, and 

the reference nuclide for measurement of gross beta is cesium-137. Measured values less than the sample-specific critical level (ssLC) are reported as nondetections. GAMA well identification number: NOCO-IN, Interior Basins study area grid well; NOCO-CO, Coastal Basins study area grid well. Numbered 

suffix indicates the order of sample collection within each study area. Benchmark type and Benchmark level: Data as of October 8, 2009. Benchmark 

type: Maximum contaminant level benchmarks are listed as MCL-US when the MCL-US and MCL-CA are identical, and as MCL-CA when the MCL-CA is 

lower than the MCL-US or no MCL-US exists. Abbreviations: pCi/L, picocuries per liter; CSU, combined standard uncertainty; MCL-US, USEPA maximum 

contaminant level; MCL-CA, CDPH maximum contaminant level; –, not detected; USGS, U.S. Geological Survey; USEPA, U.S. Environmental Protection 

Agency; CDPH, California Department of Public Health]

GAMA well 

identification

number

Gross alpha

radioactivity, 

72-hour count 

(pCi/L) 

(62636)

Gross alpha 

radioactivity, 

30-day count 

(pCi/L)

(62639)

Gross beta 

radioactivity, 

72-hour count 

(pCi/L) 

(62642)

Gross beta 

radioactivity, 

30-day count 

(pCi/L) 

(62645)

Result ± CSU ssLC Result ± CSU ssLC Result ± CSU ssLC Result ± CSU ssLC

Benchmark type MCL-US MCL-US MCL-CA MCL-CA

Benchmark level 15 15 50 50

NOCO grid wells (58 wells sampled)

NOCO-IN01 – 0.59 – 0.44 – 0.45 – 0.49

NOCO-IN02 – 0.62 – 1.0 – 0.46 0.65 ± 0.31 0.48

NOCO-IN03 – 0.57 – 0.29 – 0.59 – 0.46

NOCO-IN04 – 0.81 – 0.53 0.7 ± 0.4 0.63 0.89 ± 0.43 0.71

NOCO-IN05 – 0.87 – 0.66 – 0.79 – 0.77

NOCO-IN06 – 0.59 – 0.44 0.9 ± 0.3 0.46 – 0.45

NOCO-IN07 – 0.44 – 0.48 0.72 ± 0.29 0.44 – 0.77

NOCO-IN08 7.0 ± 1.1 0.57 2.50 ± 0.61 0.57 1.35 ± 0.33 0.49 2.91 ± 0.43 0.59

NOCO-IN09 1.82 ± 0.53 0.60 0.97 ± 0.42 0.48 0.65 ± 0.31 0.50 0.88 ± 0.48 0.75

NOCO-IN10 – 0.43 0.77 ± 0.32 0.39 2.13 ± 0.33 0.44 2.06 ± 0.44 0.69

NOCO-IN11 – 0.42 0.52 ± 0.24 0.25 0.62 ± 0.29 0.44 0.54 ± 0.29 0.44

NOCO-IN12 – 0.38 – 0.41 1.1 ± 0.37 0.56 1.2 ± 0.37 0.56

NOCO-IN13 – 0.94 – 0.40 0.7 ± 0.3 0.46 – 0.45

NOCO-IN14 – 0.50 – 1.1 – 0.73 0.6 ± 0.3 0.47

NOCO-IN15 – 1.4 – 0.48 – 0.55 – 0.49

NOCO-IN16 – 0.33 – 0.26 – 0.69 – 0.53

NOCO-IN17 – 0.41 0.45 ± 0.24 0.29 – 0.44 – 0.42

NOCO-IN18 0.82 ± 0.43 0.52 – 0.80 – 0.71 – 0.60

NOCO-IN19 – 0.41 – 0.49 – 0.56 0.66 ± 0.29 0.46

NOCO-IN20 7.3 ± 1.7 1.5 – 1.4 4.48 ± 0.54 0.65 2.59 ± 0.48 0.67

NOCO-IN21 1.46 ± 0.81 1.0 – 1.1 0.87 ± 0.34 0.52 0.91 ± 0.34 0.52

NOCO-IN22 1.56 ± 0.82 1.0 – 1.1 0.99 ± 0.32 0.49 1.71 ± 0.36 0.52

NOCO-IN23 – 0.38 – 0.57 0.71 ± 0.29 0.44 – 0.62

NOCO-IN24 – 0.49 – 0.49 1.56 ± 0.33 0.48 1.2 ± 0.4 0.6

NOCO-IN25 – 0.55 – 0.61 0.88 ± 0.46 0.72 0.56 ± 0.34 0.53

NOCO-IN26 0.90 ± 0.39 0.39 0.72 ± 0.44 0.56 – 0.70 – 0.86

NOCO-IN27 – 1.2 – 1.1 4.58 ± 0.49 0.58 3.97 ± 0.44 0.51

NOCO-IN28 0.94 ± 0.56 0.65 1.23 ± 0.51 0.65 – 0.82 0.9 ± 0.5 0.80

NOCO-CO01 0.91 ± 0.49 0.51 0.69 ± 0.49 0.57 3.92 ± 0.53 0.63 2.97 ± 0.48 0.62

NOCO-CO02 0.43 ± 0.25 0.32 – 0.55 1.36 ± 0.46 0.7 1.56 ± 0.39 0.57

NOCO-CO03 – 0.29 – 0.38 1.04 ± 0.28 0.41 1.14 ± 0.39 0.58

NOCO-CO04 2.12 ± 0.78 0.86 – 0.71 5.16 ± 0.71 0.96 4.78 ± 0.66 0.88

NOCO-CO05 1.76 ± 0.38 0.26 0.65 ± 0.38 0.47 1.81 ± 0.31 0.41 1.65 ± 0.39 0.55
Table 12C 65

Table 12C. Gross alpha and gross beta radioactivity detected in samples collected for the Northern Coast Ranges Groundwater 

Ambient Monitoring and Assessment (GAMA) study, California, June to November 2009.—Continued 

[The five-digit USGS parameter code in parenthesis below the constituent name is used to uniquely identify a specific constituent or property. Samples from 

all 58 grid wells were analyzed. Information about the analytes given in table 3G. The reference nuclide for measurement of gross alpha is thorium-230 and 

the reference nuclide for measurement of gross beta is cesium-137. Measured values less than the sample-specific critical level (ssLC) are reported as nondetections. GAMA well identification number: NOCO-IN, Interior Basins study area grid well; NOCO-CO, Coastal Basins study area grid well. Numbered 

suffix indicates the order of sample collection within each study area. Benchmark type and Benchmark level: Data as of October 8, 2009. Benchmark 

type: Maximum contaminant level benchmarks are listed as MCL-US when the MCL-US and MCL-CA are identical, and as MCL-CA when the MCL-CA is 

lower than the MCL-US or no MCL-US exists. Abbreviations: pCi/L, picocuries per liter; CSU, combined standard uncertainty; MCL-US, USEPA maximum 

contaminant level; MCL-CA, CDPH maximum contaminant level; –, not detected; USGS, U.S. Geological Survey; USEPA, U.S. Environmental Protection 

Agency; CDPH, California Department of Public Health]

GAMA well 

identification

number

Gross alpha

radioactivity, 

72-hour count 

(pCi/L) 

(62636)

Gross alpha 

radioactivity, 

30-day count 

(pCi/L)

(62639)

Gross beta 

radioactivity, 

72-hour count 

(pCi/L) 

(62642)

Gross beta 

radioactivity, 

30-day count 

(pCi/L) 

(62645)

Result ± CSU ssLC Result ± CSU ssLC Result ± CSU ssLC Result ± CSU ssLC

Benchmark type MCL-US MCL-US MCL-CA MCL-CA

Benchmark level 15 15 50 50

NOCO grid wells (58 wells sampled)—Continued

NOCO-CO06 0.61 ± 0.37 0.47 – 0.63 1.51 ± 0.32 0.45 0.59 ± 0.33 0.52

NOCO-CO07 – 0.42 – 0.34 – 0.41 – 0.43

NOCO-CO08 – 1.2 – 0.48 – 0.55 1.25 ± 0.33 0.49

NOCO-CO09 – 1.2 – 0.81 4.17 ± 0.64 0.87 2.88 ± 0.82 1.3

NOCO-CO10 – 0.47 – 0.50 0.54 ± 0.32 0.50 0.69 ± 0.41 0.65

NOCO-CO11 1.18 ± 0.44 0.47 – 0.47 1.22 ± 0.37 0.56 0.71 ± 0.35 0.55

NOCO-CO12 – 0.57 – 0.38 – 1.0 0.68 ± 0.35 0.55

NOCO-CO13 – 0.34 1.03 ± 0.56 0.82 0.95 ± 0.28 0.42 0.65 ± 0.29 0.45

NOCO-CO14 – 1 0.47 – 0.31 – 1 0.63 – 0.46

NOCO-CO15 – 0.52 – 0.28 – 0.43 – 0.38

NOCO-CO16 1.35 ± 0.36 0.21 – 0.26 – 0.70 – 0.41

NOCO-CO17 1.32 ± 0.46 0.52 – 0.52 1.56 ± 0.32 0.46 0.95 ± 0.28 0.43

NOCO-CO18 2.05 ± 0.59 0.51 – 0.68 2.19 ± 0.45 0.64 1.07 ± 0.45 0.70

NOCO-CO19 1.3 ± 0.5 0.51 0.87 ± 0.45 0.58 1.19 ± 0.35 0.51 1.54 ± 0.34 0.49

NOCO-CO20 0.63 ± 0.46 0.59 – 0.53 1.64 ± 0.43 0.64 2.15 ± 0.49 0.72

NOCO-CO21 – 0.94 – 1.0 3.46 ± 0.47 0.64 2.85 ± 0.37 0.47

NOCO-CO22 – 0.30 – 0.32 1.73 ± 0.31 0.42 1.33 ± 0.29 0.42

NOCO-CO23 – 0.32 – 0.33 0.94 ± 0.35 0.55 – 0.56

NOCO-CO24 0.54 ± 0.24 0.31 0.34 ± 0.22 0.29 1.28 ± 0.35 0.53 1.5 ± 0.36 0.53

NOCO-CO25 1.35 ± 0.41 0.38 0.05 ± 0.33 0.44 1.6 ± 0.3 0.42 0.86 ± 0.29 0.44

NOCO-CO26 0.8 ± 0.33 0.39 – 0.46 1.59 ± 0.45 0.68 1.2 ± 0.4 0.59

NOCO-CO27 1.23 ± 0.66 0.82 – 0.83 3.54 ± 0.63 0.87 2.39 ± 0.61 0.87

NOCO-CO28 1.36 ± 0.71 0.87 – 0.87 9.75 ± 0.92 0.99 9.41 ± 0.91 0.97

NOCO-CO29 2.2 ± 0.5 0.38 – 0.49 0.88 ± 0.37 0.57 1.0 ± 0.3 0.44

NOCO-CO30 – 0.36 – 0.31 – 0.77 – 0.44

1

 Counted 4 days after collection.
66 Groundwater-Quality Data in the Northern Coast Ranges Study Unit, 2009: Results from the California GAMA Program

Table 12D. Lead-210 and polonium-210 detected in samples collected for the Northern Coast Ranges 

(NOCO) Groundwater Ambient Monitoring and Assessment (GAMA) study, California, June to November 2009. 

[The five-digit USGS parameter code in parenthesis below the constituent name is used to uniquely identify a specific constituent 

or property. Samples from 54 grid wells were analyzed. Information about the analytes given in table 3G. Measured values less 

than the sample-specific critical level (ssLC) are reported as non-detections. GAMA well identification number: NOCO-IN, 

Interior Basins study area grid well; NOCO-CO, Coastal Basins study area grid well. Numbered suffix indicates the order of 

sample collection within each study area. Abbreviations: pCi/L, picocuries per liter; CSU, combined standard uncertainty; na, 

not available; –, not detected; USGS, U.S. Geological Survey]

GAMA well 

identification 

number

Lead-210 

(pCi/L) 

(17503)

Polonium-210 

(pCi/L)

(19503)

Result ± CSU ssLC Result ± CSU ssLC

Benchmark type na na

Benchmark level na na

NOCO grid wells (54 wells sampled) 1

NOCO-IN05 – 0.21 – 0.020

NOCO-IN06 – 0.19 – 0.037

NOCO-IN07 – 0.20 – 0.045

NOCO-IN08 – 0.18 – 0.048

NOCO-IN09 – 0.16 0.038 ± 0.017 0.024

NOCO-IN10 – 0.16 – 0.026

NOCO-IN11 – 0.22 0.023 ± 0.014 0.019

NOCO-IN12 – 0.17 0.020 ± 0.014 0.024

NOCO-IN13 – 0.18 – 0.030

NOCO-IN14 – 0.18 0.024 ± 0.015 0.019

NOCO-IN15 0.2 ± 0.3 0.23 0.049 ± 0.018 0.018

NOCO-IN16 – 0.20 – 0.023

NOCO-IN17 – 0.21 – 0.020

NOCO-IN18 – 0.20 – 0.024

NOCO-IN19 – 0.20 – 0.019

NOCO-IN20 – 0.24 – 0.020

NOCO-IN21 – 0.20 – 0.021

NOCO-IN22 – 0.18 – 0.027

NOCO-IN23 – 0.24 – 0.017

NOCO-IN24 – 0.20 – 0.023

NOCO-IN25 0.2 ± 0.4 0.20 0.023 ± 0.014 0.015

NOCO-IN26 – 0.19 – 0.022

NOCO-IN27 – 0.21 – 0.024

NOCO-IN28 – 0.20 – 0.029

NOCO-CO01 – 0.21 0.050 ± 0.029 0.032

NOCO-CO02 – 0.25 – 0.032

NOCO-CO03 – 0.18 – 0.022

NOCO-CO04 – 0.18 – 0.018

NOCO-CO05 – 0.18 – 0.021

NOCO-CO06 – 0.23 0.030 ± 0.015 0.016

NOCO-CO07 0.3 ± 0.23 0.18 – 0.014

NOCO-CO08 – 0.19 – 0.017

NOCO-CO09 – 0.17 0.040 ± 0.022 0.025

NOCO-CO10 – 0.19 – 0.018
Table 12D 67

Table 12D. Lead-210 and polonium-210 detected in samples collected for the Northern Coast Ranges 

Groundwater Ambient Monitoring and Assessment (GAMA) study, California, June to November 2009.—Continued

[The five-digit USGS parameter code in parenthesis below the constituent name is used to uniquely identify a specific constituent

or property. Samples from 54 grid wells were analyzed. Information about the analytes given in table 3G. Measured values less

than the sample-specific critical level (ssLC) are reported as non-detections. GAMA well identification number: NOCO-IN, 

Interior Basins study area grid well; NOCO-CO, Coastal Basins study area grid well. Numbered suffix indicates the order of 

sample collection within each study area. Abbreviations: pCi/L, picocuries per liter; CSU, combined standard uncertainty; na, 

not available; –, not detected; USGS, U.S. Geological Survey]

GAMA well 

identification 

number

Lead-210 

(pCi/L) 

(17503)

Polonium-210 

(pCi/L)

(19503)

Result ± CSU ssLC Result ± CSU ssLC

Benchmark type na na

Benchmark level na na

NOCO grid wells (54 wells sampled) 1

—Continued

NOCO-CO11 – 0.20 0.025 ± 0.017 0.021

NOCO-CO12 – 0.18 – 0.035

NOCO-CO13 – 0.19 – 0.029

NOCO-CO14 – 0.21 – 0.026

NOCO-CO15 – 0.20 – 0.025

NOCO-CO16 – 0.19 0.52 ± 0.059 0.028

NOCO-CO17 – 0.39 – 0.020

NOCO-CO18 0.6 ± 0.7 0.26 – 0.023

NOCO-CO19 – 0.20 – 0.016

NOCO-CO20 – 0.27 – 0.023

NOCO-CO21 – 0.26 0.033 ± 0.017 0.017

NOCO-CO22 – 0.29 0.037 ± 0.017 0.023

NOCO-CO23 – 0.26 – 0.020

NOCO-CO24 – 0.24 – 0.043

NOCO-CO25 – 0.21 0.031 ± 0.016 0.019

NOCO-CO26 – 0.20 0.038 ± 0.015 0.018

NOCO-CO27 0.7 ± 1.1 0.28 0.040 ± 0.025 0.031

NOCO-CO28 – 0.27 – 0.020

NOCO-CO29 – 0.24 0.045 ± 0.019 0.022

NOCO-CO30 – 0.46 – 0.020

1

 Samples from NOCO-IN01 through NOCO-IN04 were not collected.
68 Groundwater-Quality Data in the Northern Coast Ranges Study Unit, 2009: Results from the California GAMA Program

Table 13. Microbial indicators detected in samples collected for the Northern Coast Ranges (NOCO) Groundwater Ambient 

Monitoring and Assessment (GAMA) study, California, June to November 2009. 

[The five-digit USGS parameter code in parentheses below the constituent name is used to uniquely identify a specific constituent or property. Samples 

from 57 grid wells were analyzed, but only samples with detections are listed. Information about the analytes is given in table 3I. GAMA well 

identification number: NOCO-IN, Interior Basins study area grid well; NOCO-CO, Coastal Basins study area grid well. Numbered suffix indicates the 

order of sample collection within each study area. Benchmark type and Benchmark level: Data as of October 8, 2009. Benchmark type: Maximum 

contaminant level benchmarks are listed as MCL-US when the MCL-US and MCL-CA are identical, and as MCL-CA when the MCL-CA is lower than 

the MCL-US or no MCL-US exists. Abbreviations: mL, milliliter; TT-US, USEPA treatment technique (a required process intended to reduce the level 

of contamination in drinking water); MCL-US, USEPA maximum contaminant level; –, not detected; M, presence verified but not quantified; E, estimated 

or having a higher degree of uncertainty; >, greater than; MCL-CA, CDPH maximum contaminant level; USGS, U.S. Geological Survey; USEPA, U.S. 

Environmental Protection Agency; CDPH, California Department of Public Health]

GAMA well 

identification

number

Coliphage 

F-specific

(99335)

Coliphage

somatic

(99332)

Escherichia coli

(E. coli) 

colonies/ 100 mL

(90901)

Total coliform 

colonies/ 100 mL 

(90900)

Benchmark type TT-US TT-US TT-US MCL-US

Benchmark level 99.9 percent

 Killed/inactive

99.9 percent

 Killed/inactive

No fecal coliforms

are allowed

5 percent of 

samples per month

NOCO Grid wells (57 wells sampled) 1

NOCO-IN03 – – E1 31

NOCO-IN04 – – – E3

NOCO-IN05 – – – 31

NOCO-IN07 – – – E1

NOCO-IN08 M – –

NOCO-IN12 – – – E9

NOCO-IN14 – – – 47

NOCO-IN17 – – – E6

NOCO-IN22 – – – >80

NOCO-IN26 – M – E2

NOCO-IN28 – – – E1

NOCO-CO05 – – E1 –

NOCO-CO12 – – – 32

NOCO-CO17 – – – E1

NOCO-CO19 – – – E14

NOCO-CO20 – – E5 E120

NOCO-CO22 – – – E2

NOCO-CO23 M – – E5

NOCO-CO24 – – – E120

NOCO-CO25 M – – –

NOCO-CO27 – – – E12

NOCO-CO29 – M 36 E150

1

 Samples from NOCO-CO14 were not collected. 
Appendix 69

Appendix

This appendix includes discussions of the methods used 

to collect and analyze groundwater samples and to report the 

resulting water-quality data. These methods were selected to 

obtain representative samples of the groundwater from each 

well and to minimize the potential for contamination of the 

samples or bias in the data. Procedures used to collect and 

assess QC data, and the results of the QC assessments also are 

discussed. 

In the NOCO study unit, groundwater samples were 

collected and QA/QC procedures were implemented by 

using standard and modified USGS protocols from the 

NAWQA Program (Koterba and others, 1995), the NFM (U.S. 

Geological Survey, variously dated), and protocols described 

by Shelton and others (2001), Bushon (2003), Myers (2004), 

and Wright and others (2005). The QA plan followed by the 

NWQL, the primary laboratory used to analyze samples for 

this study, is described in Maloney (2005) and Pirkey and 

Glodt (1998). 

Sample Collection and Analysis

Prior to sampling, each well was pumped continuously 

to purge at least three casing-volumes of water from the 

well (Wilde and others, 1999). Groundwater samples were 

collected through Teflon® tubing attached to a sampling 

point on the well (or spring) discharge pipe with brass and 

stainless-steel fittings. The sampling point was located as close 

as possible to the well-head or point where the spring issued 

from the ground, upstream from water-storage tanks, and 

from well-head treatment system (if a system existed). For the 

slow schedule, samples were either collected at the well head 

using a foot-long length of Teflon® tubing or collected inside 

an enclosed chamber located inside a mobile laboratory and 

connected to the well head by a 10–50 ft length of the Teflon®

tubing (Lane and others, 2003). All fittings and lengths of 

tubing were cleaned between samples (Wilde, 2004).

For the field measurements, groundwater was run through 

a flow-through chamber fitted with a multi-probe meter that 

simultaneously measures the field water-quality indicators—

dissolved oxygen, temperature, pH, and specific conductance. 

Field measurements were made in accordance with protocols 

in the NFM (Radtke and others, 2005; Wilde and Radtke, 

2005; Lewis, 2006; Wilde, 2006; Wilde and others, 2006). 

All sensors on the multi-probe meter were calibrated daily. 

Turbidity was measured in the field with a calibrated turbidity 

meter. Measured temperature, dissolved oxygen, pH, specific 

conductance, and turbidity values were recorded at 5-min 

intervals for at least 30 min, and when these values remained 

stable for 20 min, samples for laboratory analyses then were 

collected. 

Field measurements and instrument calibrations were 

recorded by hand on field record sheets and electronically 

in the Personal Computer Field Form (PCFF) program. 

Analytical service requests for the NWQL 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 NWIS at 

the end of every week of sample collection. 

Prior to sample collection, polyethylene sample bottles 

were pre-rinsed three times using deionized water, and then 

once with sample water before sample collection. Samples 

requiring acidification were acidified to a pH of between 2 

and 1 with the appropriate acids using ampoules of certified, 

traceable concentrated acids obtained from the NWQL.

Temperature-sensitive samples were stored on ice prior 

to and during daily shipping to the various laboratories. The 

non-temperature sensitive samples for tritium, dissolved noble 

gases, and stable isotopes of hydrogen and oxygen in water 

were shipped monthly. Temperature- or time-sensitive samples 

for VOCs, pesticides and pesticide degradates, perchlorate, 

trace elements, nutrients, DOC, major and minor ions, silica, 

TDS, radon-222, radium isotopes, gross alpha and gross 

beta radioactivity, lead-210, polonium-210, and F-specific 

and somatic coliphage were shipped daily. The temperaturesensitive samples for stable isotopes of carbon in dissolved 

inorganic carbon and carbon-14 abundance, were stored on 

ice, archived in a laboratory refrigerator, and shipped after all 

of the alkalinity measurements were collected.

Detailed sampling protocols for individual analyses 

and groups of analytes are described in Koterba and others 

(1995), the NFM (Wilde and others, 1999, 2004), and in the 

references for analytical methods listed in table A1; only brief 

descriptions are given here. VOC samples were collected in 

three 40-mL sample vials that were purged with three vial 

volumes of groundwater before bottom filling to eliminate 

atmospheric contamination. One to one (1:1) hydrochloric acid 

to water (HCl/H2O) solution was added as a preservative to 

the VOC samples. 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 groundwater through a 

0.20-μm pore-size Corning® syringe-tip disk filter into a 

sterilized 125-mL bottle. Tritium samples were collected by 

bottom filling a 1-L polyethylene bottle after first overfilling 

the bottle 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.

Pesticides and pesticide degradates samples were 

collected in a 1-L baked amber glass bottle after first filtering 

groundwater through a baked 0.7-μm nominal pore-size glass 

fiber filter.
70 Groundwater-Quality Data in the Northern Coast Ranges Study Unit, 2009: Results from the California GAMA Program

Groundwater samples for trace elements, major and 

minor ions, silica, TDS, and field alkalinity analyses required 

filling one 250-mL polyethylene bottle with unfiltered 

groundwater, and one 500-mL and one 250-mL polyethylene 

bottle with filtered groundwater (Wilde and others, 2004). 

Filtration was done using a 0.45-μm pore-size Whatman®

vented capsule filter that was pre-rinsed with 2-L of deionized 

water, then rinsed with 1-L of groundwater prior to sampling. 

Each 250-mL filtered sample then was preserved with 7.5-N 

nitric acid. Mercury samples were collected by filtering 

groundwater into a 250-mL glass bottle and preserving with 

6-N hydrochloric acid. Iodide samples were collected by 

filling a 250-mL polyethylene bottle with filtered groundwater. 

Radium isotope, gross alpha and gross beta radioactivity, 

Lead-210, and Polonium-210 samples were each filtered 

into individual 1-L polyethylene bottles and then preserved 

with 7.5-N nitric acid. Nutrient samples were collected by 

filtering groundwater into a 125-mL brown polyethylene 

bottle. Stable isotopes of carbon in dissolved inorganic carbon 

and carbon-14 abundance samples were filtered and bottom 

filled into 500-mL glass bottles that first were overfilled with 

three bottle volumes of 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.

DOC samples were collected from the hose bib at the 

well head using a Teflon® filtration-apparatus attached to a 

foot-long length of Teflon® tubing. For each sample, 100-mL 

of certified inorganic-free 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 radon-222 samples, a stainless-steel 

and Teflon® valve assembly was attached to the sampling 

port at each well head (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 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 using reinforced nylon tubing connected to the 

hose bib at the wellhead. Groundwater was flushed through the 

tubing to dislodge 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). 

Samples for analysis of the microbial indicators also 

were collected at the well head following protocols described 

in Bushon (2003) and Myers (2004). Prior to the collection 

of samples, the sampling port was sterilized using isopropyl 

alcohol, and then groundwater was run through the sampling 

port for at least three minutes to remove any traces of the 

sterilizing agent. Two sterilized 250-mL Teflon® bottles were 

then filled with groundwater for coliform analyses (E. coli and 

total coliform determinations) and one sterilized 3-L polypropylene carboy was filled for coliphage analyses (F-specific and 

somatic coliphage determinations).

Field alkalinity, E. coli, and total coliforms were 

measured in the mobile laboratory at the well site. Alkalinity 

was measured on filtered samples by the incremental titration 

method (Barnes, 1964; Yurewicz, 1981) or by Gran’s titration 

method (Gran, 1952). Titration data were entered directly 

into PCFF and the concentrations of bicarbonate (HCO3

-

) 

and carbonate (CO3

2-) automatically were calculated from the 

titration data using the advanced speciation method (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. 

E. coli and total coliform plates were prepared using 

sterilized equipment and reagents (Myers, 2004). Plates were 

counted under an ultraviolet light, following a 22-24 hour 

incubation time at 35 degrees Celsius (°C), and the results 

were entered directly into PCFF. 

Eight laboratories performed chemical and microbial 

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 evaluated continuously and 

laboratory reporting levels updated accordingly. NWQL 

maintains National Environmental Laboratory Accreditation 

Program (NELAP) and other certifications (http://www.nelacinstitute.org/accred-labs.php). In addition, the 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 

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 NWIS by the NWQL. Results of analyses made at other 

laboratories are compiled in a project database and uploaded 

from there into NWIS. Some laboratory QC data are stored in 

NWIS also.
Appendix 71

Data Reporting

The following section gives details for the laboratory 

reporting conventions and the constituents that are determined 

by multiple methods or by multiple laboratories.

Reporting Limits

The NWQL uses the LRL as a benchmark for reporting 

analytical results. The LRL is set to minimize the reporting 

of false negatives (not detecting a compound when it actually 

is present in a sample) to less than 1 percent (Childress and 

others, 1999). The NWQL updates LRL values regularly, and 

the values listed in this report were in effect during the period 

that analyses were made for groundwater samples from the 

NOCO study (June to November 2009).

The LRL usually is set at two times the long-term method 

detection level (LT-MDL). The LT-MDL is derived from 

the standard deviation of at least 24 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 1 percent chance of a false positive). LT-MDLs 

continually are monitored and updated (Childress and others, 

1999; U.S. Environmental Protection Agency, 2002b). 

Concentrations less than the LT-MDL are reported as nondetections and noted with a dash (–) in the data tables..

Detections between the LRL and the LT-MDL are 

reported as estimated concentrations (coded by the letter E 

preceding the values in the tables and text). For informationrich methods, detections less than the LT-MDL have high 

certainty of detection, but the precise concentration is 

uncertain. These values are also E-coded. Information-rich 

methods are those that utilize gas chromatography or highperformance liquid chromatography (HPLC) with mass 

spectrometry detection (VOCs and pesticides). Compounds 

are identified by presence of characteristic fragmentation 

patterns in their mass spectra in addition to being 

quantified by measurement of peak areas at their associated 

chromatographic retention times. E-coded values also 

may result from detections outside the range of calibration 

standards, 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 using 

minimum reporting levels (MRLs) or method uncertainties 

(MU). The MRL is the smallest measurable concentration 

of a constituent that may be reliably reported using a given 

analytical method (Timme, 1995). The MU generally indicates 

the precision of a particular analytical measurement; it gives a 

range of values wherein the true value will be found. 

Results for most constituents are presented using the 

LRL, MDL, MRL, or MU values provided by the analyzing 

laboratories. Results for some organic and inorganic 

constituents are presented using study reporting levels (SRL) 

derived from assessment of data from QC samples associated 

with groundwater samples collected as part of the GAMAPBP (see the appendix section titled “Assessment of Blank 

Results and SRLs”).

The methods used for analysis of radiochemical 

constituents (tritium, radon-222, radium isotopes, gross alpha 

and gross beta radioactivity, lead-210, and polonium-210) 

measure activities by counting techniques (table A1). The 

reporting limits for radiochemical constituents are based on 

sample-specific critical levels (ssLC) (McCurdy and others, 

2008). The critical level is analogous to the LT-MDL used for 

reporting analytical results for organic and non-radioactive 

inorganic constituents. Here, the critical level is defined as the 

minimum measured activity that indicates a positive detection 

of the radionuclide in the sample with less than a 5 percent 

probability of a false positive detection. Sample-specific 

critical levels are used for radiochemical measurements 

because the critical level is sensitive to sample size and 

sample yield during analytical processing and is dependent on 

instrument background, on counting times for the sample and 

background, and on the characteristics of the instrument being 

used and the nuclide being measured. An ssLC is calculated 

for each sample and the measured activity in the sample is 

compared to the ssLC associated with that sample. Measured 

activities less than the ssLC are reported as non-detections with 

a dash (–) in the data tables. 

The analytical uncertainties associated with measurement 

of activities also are sensitive to sample-specific parameters, 

including sample size, sample yield during analytical 

processing, and time elapsed between sample collection and 

various steps in the analytical procedure, as well as parameters 

associated with the instrumentation. Therefore, 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). 

Notation

Stable isotopic compositions of oxygen, carbon, and 

hydrogen are reported as relative isotope ratios in units of 

per mil using the standard delta notation (Coplen and others, 

2002):
72 Groundwater-Quality Data in the Northern Coast Ranges Study Unit, 2009: Results from the California GAMA Program

 

1 x 1,000 per mil,

where

is the atomic mass of the heavier isotope

of the element,

is the element (O for oxygen, C for 

carbon, H for hydrogen),

is the ratio of the abunda

i sample

reference

sample

R

E

R

i

E

R

 

δ= −      

18 13 2

16 12 1

nce of the 

heavier isotope of the element 

( O, C, H) to the lighter isotope of 

the element ( O, C, H) in the sample, 

and

is the ratio of the abundance of the 

heavier isotope of the element

Rreference

 to the 

lighter isotopeof the element in the 

reference material.

(1)

The reference material for oxygen and hydrogen is 

Vienna Standard Mean Ocean Water (VSMOW), which is 

assigned δ18O and δ2H values of 0 per mil (note than δ2H is 

sometimes written as δD because the common name of the 

heavier isotope of hydrogen, hydrogen-2, is deuterium). The 

reference material for carbon is Vienna Pee Dee Belemnite 

(VPDB), which is assigned a δ13C value of 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.

Field Water-Quality Indicators Measured by 

Multiple Methods

Some of the field water-quality indicators—pH and 

specific conductance—were measured in the field and at the 

NWQL. The field measurements are the preferred method for 

the two constituents because groundwater samples change 

once they are removed from the ambient environment; 

however, both measurements are reported. Field values are 

generally preferred because field conditions are considered 

more representative of groundwater conditions (Hem, 1985).

Quality-Assurance Methods

The purpose of QA is to identify which data best 

represent environmental conditions and which may have 

been affected by contamination or bias during sample 

collection, processing, storage, transportation, or laboratory 

analysis. Four types of QC tests were used in this study: 

(1) blank samples were collected to assess positive bias as a 

result of contamination during sample handling or analysis, 

(2) replicate samples were collected to assess variability, 

(3) matrix spike tests were done to assess positive or negative 

bias, and (4) surrogate compounds were added to samples 

analyzed for organic constituents to assess bias of laboratory 

analytical methods. Results that were found to have significant 

contamination bias, on the basis of the QC data collected 

from this study and previous studies, were flagged with an 

appropriate remark code (described in subsequent sections) 

and rejected from subsequent use, including calculations of 

detection frequency. 

Blanks

The primary purposes of collecting blanks are to 

evaluate the magnitude of potential contamination of samples 

with compounds of interest during sample handling or 

analysis and to identify and mitigate these sources of sample 

contamination. 

Blank Collection and Analysis

Blanks were collected using blank water certified by the 

NWQL to contain less than the LRL, MDL, or MRL of the 

analytes investigated in the study (http://wwwnwql.cr.usgs.

gov/USGS/OBW/obw.html). Nitrogen-purged, organic-free 

blank water was used for blanks for organic constituents 

and inorganic-free blank water was used for blanks for other 

constituents. 

Field blanks were collected to assess potential 

contamination of samples during collection, processing, 

transport, and analysis. Source-solution blanks were collected 

to assess potential contamination of samples during transport 

and analysis, and potential contamination of the certified blank 

water obtained from the NWQL. The equipment blank was 

collected at the USGS Sacramento Field Office three weeks 

prior to the start of the NOCO study unit sampling period to 

assess potential contamination of samples from equipment 

storage.

Field blanks were analyzed for VOCs, pesticides and 

pesticide degradates, perchlorate, trace elements, nutrients, 

DOC, major and minor ions, silica, TDS, radium isotopes, 

gross alpha and gross beta radioactivity, lead-210, and 

polonium-210. Source-solution blanks were analyzed for 

VOCs, perchlorate, trace elements, nutrients, radium isotopes, 

gross alpha and gross beta radioactivity, lead-210, and 

polonium-210. The equipment blank was analyzed for VOCs, 

perchlorate, trace elements, nutrients, DOC, and lead-210.

Blanks were not collected for tritium and 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 analytes. Stable-isotopic ratios of carbon, hydrogen, 

and oxygen are an intrinsic property of any of these elements; 

therefore, the concept of a blank does not apply to these ratios. 
Appendix 73

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 using the same protocols as were used for the 

groundwater samples. Source-solution blanks were collected 

at the sampling site by pouring blank water directly into 

sample containers that were preserved, stored, shipped, and 

analyzed in the same manner as the groundwater samples. 

For the equipment blank, blank water was pumped through 

the sampling equipment (fittings and tubing) used to collect 

groundwater, then processed and transported using the same 

protocols used for the groundwater samples. Twelve liters of 

blank water were pumped or poured through the sampling 

equipment before each field and (or) equipment blank was 

collected.

Assessment of Blank Results and SRLs

Contamination in blanks may originate from several 

different types of sources that require different strategies 

for assessment of potential contamination of groundwater 

samples during sample collection, handling, and analysis. 

Four primary modes of contamination are assessed in the 

event of detections in blanks or atypical results in groundwater 

samples: (1) impurities in the water used to collect the blanks, 

(2) contamination during sample collection and handling 

from a known source or condition present at the field site, 

(3) carry-over of material on the sampling equipment from 

one sample to the next sample, (4) systematic and random 

contamination from field or laboratory equipment and 

processes. The fourth source of contamination (systematic and 

random) is being addressed using a larger set of field blank 

results from multiple studies, in addition to the results from 

blanks collected from the NOCO study unit. The development 

of this approach and its methods are described by Olsen and 

others (2010) and Fram and others (2011).

The first potential mode evaluated is the presence of 

impurities in the water used to collect the blank. Because 

the blanks were collected using blank water certified by the 

NWQL to contain less than the LRL, MDL, or MRL of the 

analytes investigated in the study, the blank water is rarely the 

source of constituents detected in blanks. Blank water used 

in the NOCO study unit was certified by the NWQL prior to 

blank collection. 

The second potential mode evaluated is contamination 

from identifiable, known sources present at a specific field 

site. Contamination from specific sources may produce 

distinctive patterns of detections in blanks and groundwater 

samples, particularly for the VOCs. Substances that may be 

encountered at the field site contain recognizable associations 

of VOC constituents. For example, cements used on PVCpiping are primarily composed of tetrahydrofuran with lesser 

amounts of acetone and methyl ethyl ketone (2-butanone). 

However, detection of these recognizable associations of VOC 

constituents in groundwater samples does not necessarily 

indicate contamination during sample collection because these 

VOC constituents also may occur together in groundwater.

If a recognizable association of VOC constituents was 

detected in a field blank or in a groundwater sample, the 

field notes and photographs from the site at which the field 

blank or groundwater sample was collected were examined 

for conditions that may have caused the field blank or the 

groundwater sample to be contaminated. If such conditions 

were present, the detections of VOC constituents in the field 

blank or groundwater sample were considered suspect. 

The third potential mode of contamination evaluated 

was carry-over from the previous groundwater sample 

or blank collected with the same equipment. Carry-over 

between samples is rare because the procedures used to 

clean the equipment between samples have been developed 

and extensively tested to assure that carry-over is mitigated 

as much as possible. Potential carry-over was evaluated 

using time-series analysis to look for patterns suggestive 

of carry-over of constituents from a sample with high 

concentrations to the next groundwater sample or blank 

collected with the same equipment. If non-detections were 

reported in blanks or groundwater samples collected after 

the collection of groundwater samples containing high 

concentrations of the constituent, then carry-over as a mode of 

contamination was ruled out. 

The fourth potential mode of contamination evaluated 

was random or systematic contamination from field or 

laboratory equipment or processes. All detections in 

blanks that could not be accounted for by impurities in the 

source‐solution water, by specific known conditions at field 

sites, or by carry-over between samples were evaluated for 

random contamination. Random contamination in field and 

laboratory processes has an equal chance of affecting each 

groundwater sample; thus, strategies for flagging detections of 

constituents that are subject to random contamination in field 

and laboratory processes must be applied to all groundwater 

samples. Random or systematic contamination in field and 

laboratory processes generally is the most common of the four 

modes of contamination and is addressed by applying SRLs. 

SRLs for some organic constituents were defined on 

the basis of concentrations and detection frequencies in field 

blanks and source-solution blanks collected for the first 27 

GAMA-PBP study units (May 2004 through October 2009) 

and in laboratory instrument and preparation blanks analyzed 

during the same time period as the samples (Fram and 

others, 2011). Acetone, 2-butanone, ethylbenzene, styrene, 

tetrahydrofuran, toluene, 1,2,4-trimethylbenzene, m-xylene 

plus p-xylene, and o-xylene were detected more frequently 

in blanks than in groundwater samples and, therefore, all 

detections of these constituents were removed from the 

GAMA-PBP groundwater-quality datasets. 

For organic constituents detected less frequently in blanks 

than in groundwater samples, the concentration corresponding 

to the 95th percentile of the cumulative frequency distribution 

of the field blanks, source-solution blanks, or laboratory 

blanks, whichever was highest, was defined as the SRL. For 

most constituents, the 95th percentiles of the cumulative 

frequency distributions were non-detections (values below the 
74 Groundwater-Quality Data in the Northern Coast Ranges Study Unit, 2009: Results from the California GAMA Program

LRL), thus, no SRLs were required. Concentrations of those 

constituents reported by the laboratory that were less than 

the SRL are marked with a less than or equal to (≤) symbol 

preceding the reported value. Organic constituent results with 

a ≤ symbol were not considered detections in the GAMA-PBP 

study and were not included in the calculations of detection 

frequencies.

The SRLs for all trace elements except lead were 

determined by statistical assessment of results from the 

field blanks collected in the first 20 GAMA-PBP study units 

(May 2004 through January 2008) (Olsen and others, 2010). 

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, 

handled, transported, and analyzed. The resulting SRLs for 

trace elements were set at concentrations representing a 

confidence limit of 90 percent for the 90th percentile of the 

86 field blanks used in the assessment. Concentrations of those 

constituents reported by the laboratory that were less than the 

SRL are marked with a ≤ symbol preceding the reported value.

For all other inorganic constituents, the SRL for applying 

the ≤ symbol was determined from assessment of the blanks 

collected in the NOCO study unit and was defined as equal to 

the highest concentration measured in the blanks. 

Replicates

Sequential replicate samples were collected to assess 

the precision of the water-quality data. Estimates of data 

precision are needed to assess whether differences between 

concentrations in samples are because of differences in 

groundwater quality or because of variability that may result 

from collecting, processing and analyzing the samples. 

Two methods for measuring variability were needed to 

adequately assess precision over the broad range of measured 

concentrations of most constituents. The variability between 

measured concentrations in the pairs of sequential replicate 

samples was represented by the 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 of samples expressed as 

a percentage. The boundary between concentrations for which 

variability is assessed with SD and concentrations for which 

variability is assessed with RSD was defined as five times the 

LRL, SRL, MDL, MRL or MU for each constituent. 

 For this study, acceptable precision for replicate sample 

pairs is defined as follows:

• For concentrations less than (<) five times the LRL, 

SRL, MDL, MRL, or MU, an SD of <1⁄2 LRL, SRL, 

MDL, MRL, or MU is acceptable.

• For concentrations greater than or equal to (≥) five 

times the LRL, SRL, MDL, MRL, or MU, an RSD of 

<10 percent is acceptable. For comparison, an RSD of 

10 percent is equivalent to a relative percent difference 

(RPD) of 14 percent. 

• For activities of radiochemical constituents (except 

carbon-14), replicate pairs with values that are 

statistically indistinguishable at a confidence level (α) 

of α = 0.05 are defined as acceptable. 

If results from replicate sample pairs indicate that 

precision is unacceptable for a constituent and no specific 

reason can be identified, 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 slightly less 

than that benchmark. Similarly, if measured concentrations 

are slightly less than a water-quality benchmark, then actual 

concentrations could be slightly greater than a benchmark. 

Also, if a constituent has high variability in replicate sample 

pairs, then a larger difference between concentrations 

measured in two samples is required to conclude that the two 

samples have significantly different concentrations. 

Replicate pairs of analyses of all constituents except for 

radiochemical constituents were evaluated as follows: 

• If both values were reported as detections, the SD was 

calculated if the mean concentration was <5 times 

the LRL/SRL/MDL/MRL/MU for the constituent or 

the RSD was calculated if the mean concentration 

was ≥ 5 times the LRL/SRL/MDL/MRL/MU for the 

constituent. 

• 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 less than the 

LRL, MDL, MRL, or MU, then a value of zero was 

substituted for the non-detection and the SD calculated. 

Substituting zero for the non-detection yielded the 

maximum estimate of variability for the replicate pair. 

• If one value for a sample pair was reported as a nondetection and the other value was reported as a ≤-coded 

value (less than or equal to the SRL), or if both values 

were reported as ≤-coded values (less than or equal to 

the SRL), the SD was not calculated because the values 

may be analytically identical. The ≤-code indicates that 

the value is a maximum potential concentration and 

that concentration may be low enough to be reported as 

a non-detection. 

• If one value was reported as a non-detection and the 

other value was reported as a detection greater than the 

LRL, SRL, MDL, MRL, or MU, the variability for the 

pair was considered unacceptable.
Appendix 75

• Replicate pairs of analyses of radiochemical 

constituents were evaluated using the following 

equation (McCurdy and others, 2008):

( )

1 2

2 2

1 2

1 2

1 2

,

where

is the test statistic,

 and are the results for the two samples in

the rep

and are the combined standard 

standard

licat

 uncertanties associated 

with the

e pair and,

 re

R R

z

CSU CSU

z

R R

CSU CSU

− =

+

sults.

 (2)

Matrix Spikes

Addition of a known concentration of a constituent 

(spike) to a replicate environmental sample enables the 

analyzing laboratory to determine the effect of the matrix, 

in this case groundwater, on the analytical technique used 

to measure the constituent. The known compounds added 

in matrix spikes are the same as those being analyzed in the 

method. This enables an analysis of matrix interferences on a 

compound-by-compound basis. For this study, matrix spikes 

were added by the laboratory performing the analysis. Low 

matrix-spike recovery may indicate that the compound might 

not be detected in some samples if it were present at very low 

concentrations. Low and high matrix-spike recoveries may be 

a potential concern if the concentration of a compound in a 

groundwater sample is close to the health-based benchmark; a 

low recovery could result in a falsely measured concentration 

less than the health-based benchmark, whereas a high recovery 

could result in a falsely measured concentration greater than 

the heath-based 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 (with a footnote 

in table 3) as having unacceptable recoveries. For many 

constituents, an acceptable range of 70 to 130 percent for 

median matrix-spike recovery was more restrictive than the 

acceptable control limits for laboratory-set spike recoveries. 

Laboratory-set spikes are aliquots of laboratory blank water 

to which the same spike solution used for the matrix-spikes 

has been added. One set spike is analyzed with each set of 

samples. Acceptable control limits for set spikes are defined 

relative to the long-term variability in recovery. For example, 

for many NWQL schedules acceptable set spike recovery is 

within ± 3 F-pseudosigma of the median recovery for at least 

30 set spikes (Conner and others, 1998). The F-pseudosigma 

is calculated by dividing the fourth-spread (analogous to 

interquartile range) by 1.349; therefore, the smaller the 

F-pseudosigma the more precise the determinations (Hoaglin, 

1983). 

 Matrix spikes were performed for VOCs, pesticides and 

pesticide degradates, and perchlorate because the analytical 

methods for these constituents may be susceptible to matrix 

interferences. Positive-control matrix spikes were performed 

for the viral indicators (F-specific coliphage and somatic 

coliphage) at the USGS Ohio Water Microbiology Laboratory 

to determine if the groundwater matrix interferes with 

microbial growth. 

Surrogates

Surrogate compounds are added to environmental 

samples in the laboratory prior to analysis to evaluate the 

recovery of similar constituents. Surrogate compounds were 

added to all groundwater and QC samples that were analyzed 

for VOCs and pesticides and pesticides degradates. Most of 

the surrogate compounds are deuterated analogs of compounds 

being analyzed. For example, the surrogate toluene-d8 that is 

used for the VOC analytical method has the same chemical 

structure as toluene, except that the eight hydrogen-1 atoms on 

the molecule have been replaced by deuterium (hydrogen-2). 

Toluene-d8 and toluene behave very similarly in the analytical 

procedure, but the small mass difference between the two 

results in slightly different chromatographic retention times; 

thus, the use of a toluene-d8 surrogate does not interfere with 

the analysis of toluene (Grob, 1995). Only 0.015 percent of 

hydrogen atoms are deuterium (Firestone and others, 1996); 

thus, deuterated compounds like toluene-d8 do not occur 

naturally and are not detected in environmental samples. 

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).

Quality-Control Results

Detections in Blanks and SRL Analysis

Table A2 presents a summary of detections in the blanks 

(six field blanks, seven source-solution blanks, and the 

equipment blank) and the SRL analysis for the NOCO study 

unit. Field and source-solution blanks were collected at 5 to 

12 percent of the sites sampled in the NOCO study unit; not 

all analyte classes were tested at every well. 
76 Groundwater-Quality Data in the Northern Coast Ranges Study Unit, 2009: Results from the California GAMA Program

Of the 14 blanks analyzed for VOCs; chloroform 

and carbon disulfide each were detected in one blank. The 

chloroform blank detection was considered to be random 

contamination, likely from a field process, but whose exact 

source could not be identified. This blank detection had 

an equal chance of affecting each groundwater sample. 

Chloroform was detected in the blank at a concentration 

of E0.02 μg/L, creating a SRL of 0.02 μg/L. Chloroform 

was detected at a concentration less than the SRL in one 

groundwater sample and was flagged with a ≤ symbol. The 

result was considered a non-detection and was not included in 

the calculations of chloroform detection frequencies (tables 5

and A2). 

The carbon disulfide blank detection in the NOCO study 

unit also was considered to be random contamination and 

had an equal chance of affecting each groundwater sample. 

Carbon disulfide was detected in the blank at a concentration 

of E0.06 μg/L, creating a SRL of 0.06 μg/L. Carbon disulfide 

was detected at a concentration less than the SRL in one 

groundwater sample and was flagged with a ≤ symbol. The 

result was considered a non-detection and was not included 

in the calculations of carbon disulfide detection frequencies 

(tables 5 and A2). 

GAMA SRLs from Fram and others (2011) were used for 

acetone, 2-butanone, ethylbenzene, styrene, tetrahydrofuran, 

toluene, 1,2,4-trimethylbenzene, m-xylene plus p-xylene, 

and o-xylene. Three of these VOCs (styrene, toluene, 

and 1,2,4-trimethylbenzene) were detected in the NOCO 

study-unit groundwater samples. These detections were 

not considered to represent groundwater quality and were 

excluded from the dataset presented in this report (tables 3A, 

5, and A2). 1,2,4-trimethylbenzene was detected in 7 of 

14 blanks collected in the NOCO study unit (table A2). 

Eight blanks were collected for analysis of trace 

elements. Three trace elements were detected in at least one 

blank; copper, lead, and nickel (table A2). The detections 

of copper and nickel were at concentrations less than the 

SRL assigned by Olsen and others (2010). A SRL for lead 

(1.1 μg/L) was established on the basis of the highest detected 

concentration in the five blanks. Measured concentrations that 

were less than the SRL were flagged with a ≤ symbol (table 8). 

There were no other trace elements detected in any of the 

blanks in the NOCO study unit.

GAMA SRLs from Olsen and others (2010) were used 

for aluminum, barium, chromium, copper, iron, manganese, 

mercury, nickel, vanadium, and zinc. Measured concentrations 

that were less than the SRL were flagged with a ≤ symbol in 

table 8. 

Seven blanks were collected for analysis of DOC and it 

was detected in two of the blanks (table A2). A SRL for DOC 

(0.7 mg/L) was established on the basis of the highest detected 

concentration in the two blanks. Measured concentrations that 

were less than the SRL were flagged with a ≤ symbol (table 9). 

Four blanks were collected for analysis of radioactive 

constituents. Results from blanks were not used to define 

SRLs for radiochemical constituents because the low 

activities of these constituents occasionally reported in 

GAMA-PBP blanks are thought to be an artifact of the 

algorithms used to convert instrument response to activities 

for blank samples, rather than to reflect presence of these 

constituents in blank samples (Sylvia Stork, U.S. Geological 

Survey, written commun., 2010). Activities of radiochemical 

constituents reported in blanks were all lower than most of 

the activities reported in the NOCO study-unit groundwater 

samples, indicating that groundwater samples likely were 

not significantly contaminated by these constituents during 

collection, handling, or analysis. Radium-226 had measureable 

activities in the three blanks, gross alpha radioactivity 

(30-day count) in one blank, and polonium-210 in two blanks 

(table A2).

Constituents were not detected in the blanks for the 

following analyte groups: pesticides and pesticide degradates 

(3 blanks); perchlorate (14 blanks); mercury (4 blanks); 

nutrients (5 blanks); major and minor ions, silica, and TDS 

(4 blanks); iodide (3 blanks); radium-228, gross alpha 

radioactivity (72-hour), gross beta radioactivity (72-hour and 

30-day counts), and lead-210 (4 blanks). 

Variability in Replicate Samples

Table A3A–C summarizes the results of replicate analyses 

for constituents detected in groundwater samples collected 

in the NOCO study unit. Replicate analyses were made on 

approximately 3 to 10 percent of the samples collected.

Of the 930 replicate pairs of constituents analyzed, 65 

were for constituents detected in at least one groundwater 

sample. Of these 65 pairs, 1 pair (nickel) was outside the 

limits for acceptable precision. Results for replicate analyses 

for constituents that were not detected in groundwater samples 

are not reported in table A3A–C. 

Four replicate pairs of samples were analyzed for the 

85 VOCs and all pairs yielded two values reported as nondetections with the exception of two replicate pairs of MTBE 

and one replicate pair of chloroform. The replicate pairs for 

MTBE and chloroform each yielded two values reported as 

detections and all replicate pair analysis resulted in SDs within 

acceptable precision (table A3A). 

Four replicate pairs of samples were analyzed for the 

83 pesticide and pesticide degradate compounds and all 

pairs consisted of two values reported as non-detections 

(table A3A). 

Six replicate pairs for perchlorate were analyzed at Weck 

Laboratories, Inc. for variability. All of the replicate pairs for 

perchlorate yielded two values reported as non-detections 

(table A3A). 
Appendix 77

 Six replicate pairs of samples were analyzed for 

DOC. One replicate pair yielded two values reported as 

detections and resulted in a SD within acceptable precision. 

Four replicate pairs consisted of two values measured at 

concentrations less than the SRL of 0.7 mg/L; therefore, 

variability was not calculated (table A3A). 

Replicate pairs of samples were analyzed for trace 

elements (three to six pairs), nutrients (five pairs), major and 

minor ions (three to four pairs), silica and TDS (four pairs), 

and isotope tracers (two to five pairs). With the exception of 

one replicate pair of nickel, the SD values for all pairs with 

concentrations < 5 times the LRL/SRL <1⁄2 LRL/SRL and the 

RSD values for all pairs with concentrations ≥ 5 times the 

LRL/SRL were <10 percent (table A3B).

The SD for one replicate pair for nickel was 0.20 μg/L 

(1⁄2 SRL is 0.18 μg/L). However, the concentration of nickel 

in the sample was less than 1 μg/L (more than two orders 

of magnitude lower than the corresponding MCL-CA of 

100 μg/L) (tables 3D and 8). A slight decrease in precision at 

these low concentrations is unlikely to affect the assessments 

of groundwater quality being made by the GAMA-PBP 

because the assessment for nickel is focused on distribution 

of concentrations greater than 50 μg/L (1⁄2 the MCL-CA 

benchmark).

One replicate pair for radon-222 and four replicate pairs 

for radium isotopes, gross alpha and gross beta radioactivity, 

lead-210, and polonium-210 were analyzed for variability. 

All replicate pairs for the radioactive constituents yielded 

statistically similar results (p ≤0.05) and were, therefore, 

considered acceptable (table A3C). 

Environmental detections were not modified on the basis 

of the replicate analysis.

Matrix-Spike Recoveries

Table A4A–D presents a summary of matrix-spike 

recoveries for the NOCO study unit. Replicate samples for 

spike additions were collected at approximately 3 to 7 percent 

of the wells sampled, not all analyte classes were tested at 

every well.

Two groundwater samples were spiked with VOCs to 

calculate matrix-spike recoveries at the NWQL. Median 

matrix-spike recoveries for all 85 VOC spike compounds were 

within the acceptable range (table A4A). 

Four groundwater samples were spiked with pesticide 

and pesticide degradate compounds, to calculate matrix-spike 

recoveries at the NWQL. Median matrix-spike recoveries 

for 64 of the 83 spike compounds were within the acceptable 

range of 70 to 130 percent (table A4B). The median matrixspike recoveries for two of the three compounds detected in 

groundwater samples (atrazine and simazine) were within the 

acceptable range (tables 3B and 6). Note that low matrix-spike 

recoveries may indicate that the compound might be present at 

very low concentrations but not detected in some samples.

The median spike-matrix recovery for deethylatrazine 

was less than the acceptable range (58.8 percent). 

Deethylatrazine was detected at a concentration (E0.006 μg) 

less than the LRL of 0.014 μg in two grid wells in the NOCO 

study unit (table 6). Because deethylatrazine was detected at 

concentrations an order of magnitude less than the LRL, it was 

determined that the less than the acceptable median spikematrix recovery did not affect the analysis and results from the 

NWQL. 

At least one matrix-spike recovery for 36 pesticide 

and pesticide degradate spike compounds was less than 

70 percent. Of these pesticide and pesticide degradate spike 

compounds, deethylatrazine was the only one detected in 

groundwater samples, and the concentrations could be biased 

low (tables 3B, 6, and A4B). A similar pattern of unusually 

low matrix-spike recoveries that started in March 2008 was 

noted in an assessment of method performance by the Organic 

Blind Sample Program (OBSP) of the BQS (http://bqs.usgs.

gov/OBSP/).

Two groundwater samples were spiked with perchlorate 

to calculate matrix-spike recoveries at Weck Laboratories, 

Inc. All median matrix-spike recoveries were between 70 and 

130 percent (table A4C). 

Four groundwater samples were spiked with F-specific 

and somatic coliphage at the USGS Ohio Water Microbiology 

Laboratory to determine if the groundwater matrix interferes 

with growth. All four samples tested positive for F-specific 

and somatic coliphage, which indicates matrix interferences 

were not a problem (table A4D).

Environmental detections were not modified on the basis 

of the matrix-spike recovery analysis.
78 Groundwater-Quality Data in the Northern Coast Ranges Study Unit, 2009: Results from the California GAMA Program

Surrogate Compound Recoveries

Table A5 presents a summary of the surrogate recoveries 

for the NOCO study unit. Surrogate compounds were added 

to environmental samples in the laboratory and analyzed to 

evaluate the recoveries of similar constituents. 

Table A5 lists the surrogate, the analytical schedule on 

which it was applied, the number of analyses for blank and 

environmental samples, the number of surrogate recoveries 

less than 70 percent, and the number of surrogate recoveries 

greater than 130 percent for the blank and groundwater 

samples. Blank and environmental samples were considered 

separately to assess whether the matrixes present in 

groundwater samples affect surrogate recoveries. 

In the NOCO study unit, most surrogate recoveries 

for the blank and environmental samples were within the 

acceptable range of 70 to 130 percent. In total, 81 percent 

of the blank and 78 percent of the environmental sample 

surrogate recoveries for VOC analyses were within the 

acceptable range (table A5). Additionally, 100 percent 

of the blank and 94 percent of the environmental sample 

surrogate recoveries for pesticide and pesticide degradate 

analyses were within the acceptable range (table A5). There 

were no significant differences between VOC and pesticide 

and pesticide degradate surrogate recoveries in blank and 

environmental samples (Wilcoxon rank sum test, p < 0.05). 

Environmental detections were not modified on the basis 

of the surrogate recovery analysis.
Appendix 79

Table A1. Analytical methods used for the determination of organic and inorganic constituents by the U.S. Geological Survey (USGS) National Water Quality Laboratory (NWQL) and contract laboratories.[Laboratory entity codes in the USGS National Water Information System (NWIS) for laboratories other than the USGS National Water Quality Laboratory (NWQL) are given in parentheses after the laboratory names. Abbreviations: VOC, volatile organic compounds; DOC, dissolved organic carbon; USEPA, U.S. Environmental Protection Agency; UV, ultraviolet; SAL, single-agar layer; MI agar, supplemented nutrient agar in which coliforms (total and Escherichia coli) produce distinctly different fluorescence under ultraviolet lighting; 

USGS, U.S. Geological Survey; NWQL, National Water Quality Laboratory; LLNL, Lawrence Livermore National Laboratory]

Analyte Analytical method Laboratory and analytical schedule Citation(s)

Water-quality indicatorsField parameters Calibrated field meters and test kits USGS field measurement U.S. Geological Survey, variously dated

Organic constituentsVOCs 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

Constituent of special interestPerchlorate Liquid chromatography with mass 

spectrometry/mass spectrometry (USEPA Method 331.0)

Weck Laboratories, Inc., City of Industry, 

California (CA-WECK), standard operating procedure ORG099.R01

U.S. Environmental Protection Agency, 2005

Inorganic constituentsNutrients 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

Major and minor ions, trace elements 

and nutrients

Atomic absorption spectrometry, colorimetry, 

ion-exchange chromatography, inductivelycoupled plasma atomic emission spectrometry, and mass spectrometry

NWQL, Schedules 2710 and 2750 Fishman and Friedman, 1989; Fishman, 1993; 

McLain, 1993; Garbarino, 1999; Garbarino and Damrau, 2001; Garbarino and others, 2006

Stable isotopesStable 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 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 (MAWHAMS), 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
80 Groundwater-Quality Data in the Northern Coast Ranges Study Unit, 2009: Results from the California GAMA Program Table A1. Analytical methods used for the determination of organic and inorganic constituents by the U.S. Geological Survey (USGS) National Water Quality Laboratory (NWQL) and contract laboratories.—Continued [Laboratory entity codes in the USGS National Water Information System (NWIS) for laboratories other than the USGS National Water Quality Laboratory (NWQL) are given in parentheses after the laboratory names. Abbreviations: VOC, volatile organic compounds; DOC, dissolved organic carbon; USEPA, U.S. Environmental Protection Agency; UV, ultraviolet; SAL, single-agar layer; MI agar, supplemented nutrient agar in which coliforms (total and Escherichia coli) produce distinctly different fluorescence under ultraviolet lighting; USGS, U.S. Geological Survey; NWQL, National Water Quality Laboratory; LLNL, Lawrence Livermore National Laboratory] Analyte Analytical method Laboratory and analytical schedule Citation(s) Radioactivity and gases Tritium Electrolytic enrichment-liquid scintillation USGS Stable Isotope and Tritium Laboratory, Menlo Park, California (USGSH3CA), NWQL Schedule 1565 Thatcher and others, 1977 Dissolved noble gases 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 Radon-222 Liquid scintillation counting NWQL, Schedule 1369 American Society for Testing and Materials, 1998 Radium isotopes Alpha activity counting Eberline Analytical Services (CA-EBERL), NWQL Schedule 1262 Kreiger and Whittaker, 1980 (USEPA methods 903 and 904) Gross alpha and gross beta radioactivity Alpha and beta activity counting Eberline Analytical Services, (CA-EBERL), NWQL Schedule 1792 Kreiger and Whittaker, 1980 (USEPA method 900.0) Lead-210 Beta activity counting Eberline Analytical Services (CA-EBERL), NWQL Laboratory Code 2170 Eichrom Technologies, Inc., 2009 Polonium-210 Alpha activity counting Eberline Analytical Services (CA-EBERL), NWQL Laboratory Code 1550 Eichrom Technologies, Inc., 2009 Microbial constituents F-specific and somatic coliphage Single-agar layer (SAL) and two-step enrichment methods USGS Ohio Water Microbiology Laboratory (USGSOHML) U.S. Environmental Protection Agency, 2001 Escherichia coli (E. coli) and total coliform Membrane filter technique with “MI agar” USGS field measurement U.S. Environmental Protection Agency, 2002a; U.S. Geological Survey, variously dated
Appendix 81

Table A2. Constituents detected in blanks and the study reporting level (SRL) analysis for the Northern Coast Ranges (NOCO) Groundwater Ambient Monitoring and Assessment (GAMA) study, California, June to November 2009.[Sources of SRL: NOCO field blanks, the SRL was assigned a value equal to the highest concentration in field blanks collected for this study unit; report by Olsen and others (2010): the SRL was defined on the basis of the examination of quality-control samples collected for the first 20 GAMA study units; report by Fram and others (2011): constituent excluded from dataset on the basis of the examination of quality-control samples collected for the first 27 GAMA study units (May 2004 through October 2009) and in laboratory instrument and preparation blanks analyzed during the same time period as the samples. Abbreviations: LRL, laboratory reporting level; SRL, study reporting level; ≤, less than or equal to; VOC, volatile organic compounds; μg/L, micrograms per liter; DOC, dissolved organic carbon; E, estimated 

or having a higher degree of uncertainty; pCi/L, picocuries per liter; ±, plus or minus; ssLC, sample-specific critical level; –, not detected]

Constituent

Number 

of blank 

detections/ 

analyses

Concentrations

detected in blanks

SRL 

concentration Source of SRL

Number of 

groundwater

samples

≤-coded

Number of 

groundwater

detections

excluded from 

dataset

Volatile organic compounds (VOC) (μg/L)Carbon disulfide 1/14 E0.06 0.06 NOCO field blanks 1 1Chloroform (trichloromethane) 1/14 E0.02 0.02 NOCO field blanks 1 1Styrene 0/14 – LRL Fram and others, 2011 0 1

Toluene 0/14 – LRL Fram and others, 2011 0 1

1,2,4-trimethylbenzene 7/14 0.30, 0.09, E0.03, E0.05, E0.04, E0.02, E0.02 LRL Fram and others, 2011 0 19

Trace elements (μg/L)Aluminum 0/8 – 1.6 Olsen and others, 2010 0 0

Barium 0/8 – 0.36 Olsen and others, 2010 0 0

Chromium 0/8 – 0.42 Olsen and others, 2010 30 0

Copper 1/8 0.62 1.7 Olsen and others, 2010 18 0

Iron 0/8 – 6 Olsen and others, 2010 11 0

Lead 5/8 1.1, 0.12, 0.07, 0.11, E0.04 1.1 NOCO field blanks 45 0

Manganese 0/8 – 0.2 Olsen and others, 2010 3 0

Nickel 1/8 E0.10 0.36 Olsen and others, 2010 17 0Vanadium 0/8 – 0.1 Olsen and others, 2010 0 0

Zinc 0/8 – 4.8 Olsen and others, 2010 35 0

Dissolved organic carbon (DOC) (mg/L)DOC 2/7 E0.3, 0.7 0.7 NOCO field blanks 29 0

Radioactive constiuents (pCi/L)Radium-226 3/4 0.0286 ± 0.0083, ssLC = 0.014; 

0.0153 ± 0.0081, ssLC = 0.012; 

0.0239 ± 0.0082, ssLC = 0.015

– NOCO field blanks 0 0

Gross alpha radioactivity, 30-day count 1/4 0.114 ± 0.091, ssLC = 0.11 – NOCO field blanks 0 0

Polonium-210 2/4 0.032 ± 0.014, ssLC = 0.018; 

0.019 ± 0.012, ssLC = 0.014

– NOCO field blanks 0 0
82 Groundwater-Quality Data in the Northern Coast Ranges Study Unit, 2009: Results from the California GAMA Program Table A3A. Quality-control summary for replicate analyses of organic constituents, constituent of special interest, and dissolved organic carbon (DOC) detected in samples collected for the Northern Coast Ranges (NOCO) Groundwater Ambient Monitoring and Assessment (GAMA) study, California, June to November 2009. 

[Abbreviations: ≤, less than or equal to; SD, percent standard deviation; LRL, laboratory reporting level; SRL, study reporting level; RSD, percent relative standard deviation; VOC, volatile organic compound; DOC, dissolved organic carbon; nv, no value in category]

Constituent

Number of 

non-detects/ 

number of 

replicates

Number of 

≤-coded 

replicates

Number of SDs 

greater than 

1⁄2 / LRL/SRL number 

of replicates with 

concentration less 

than 5 times the LRL

Concentrations of 

replicates with SDs 

greater than 

1⁄2 / LRL/SRL 

(environmental, 

replicate) 

Number of RSDs 

greater than 

10 percent/ number 

of replicates with 

concentration greater 

than 5 times the LRL/SRL

Concentrations 

of replicates with 

RSDs greater 

than 10 percent 

(environmental, 

replicate) 

Volatile organic compounds (VOC) (Schedule 2020)Chloroform (Trichloromethane) 3/4 nv 0/1 nv nv nv

1,1,1-Trichloroethane (1,1,1-TCA) 4/4 nv nv nv nv nv

Methyl tert-butyl ether (MTBE) 2/4 nv 0/2 nv nv nv

Carbon disulfide 4/4 nv nv nv nv nv

1,1-Dichloroethane (1,1-DCA) 4/4 nv nv nv nv nv

Bromodichloromethane 4/4 nv nv nv nv nv

Perchloroethene (PCE, Tetrachloroethene) 4/4 nv nv nv nv nv

Vinyl chloride (Chloroethene) 4/4 nv nv nv nv nv

Pesticides and pesticide degradates (Schedule 2033)Deethylatrazine (2-Chloro-4-isopropylamino-6-aminos-triazine) 4/4 nv nv nv nv nv

Atrazine 4/4 nv nv nv nv nv

Simazine 4/4 nv nv nv nv nv

Constituent of special interestPerchlorate 6/6 nv nv nv nv nv

Dissolved organic carbon (DOC) DOC 1/6 4 0/1 nv nv nv
Appendix 83

Table A3B. Quality-control summary for replicate analyses of inorganic constituents, isotope tracers, and tritium detected in samples 

collected for the Northern Coast Ranges (NOCO) Groundwater Ambient Monitoring and Assessment (GAMA) study, California, June to 

November 2009. 

[Abbreviations: ≤, less than or equal to; SD, percent standard deviation; LRL, laboratory reporting level; SRL, study reporting limit; MDL, method detection 

limit; MRL, minimum reporting level; RSD, percent relative standard deviation; μg/L, micrograms per liter; TDS, total dissolved solids; SiO2, silicon dioxide; 

H, hydrogen; O, oxygen; C, carbon; nv, no value in category]

Constituent

Number of 

non-detect 

or ≤-coded 

replicates/

number of 

replicates 

Number of SDs 

greater than 

1⁄2 LRL/SRL/MDL/MRL 

number of replicates 

with concentration 

less than 5 times 

the LRL/SRL/MDL/

MRL/MU

Concentrations 

of replicates with 

SDs greater than 1⁄2 

LRL/SRL/MDL/MRL 

(environmental, 

replicate) 

Number of RSDs 

greater than 

10 percent/ number 

of replicates with 

concentration greater 

than 5 times the LRL/

SRL/MDL/MRL/MU

Concentrations 

of replicates with 

RSDs greater 

than 10 percent 

(environmental, 

replicate) 

Trace Elements (μg/L)

Aluminum 4/6 0/2 nv nv nv

Antimony 3/6 0/3 nv nv nv

Arsenic 0/6 0/2 nv 0/4 nv

Barium 0/6 nv nv 0/6 nv

Beryllium 6/6 nv nv nv nv

Boron 0/6 0/1 nv 0/5 nv

Cadmium 4/6 0/2 nv nv nv

Chromium 2/6 0/3 nv 0/1 nv

Cobalt 0/6 0/5 nv 0/1 nv

Copper 5/6 0/1 nv nv nv

Iron 0/4 0/1 nv 0/3 nv

Lead 1/6 0/5 nv nv nv

Lithium 0/6 0/3 nv 0/3 nv

Manganese 0/6 nv nv 0/6 nv

Molybdenum 0/6 nv nv 0/6 nv

Nickel 0/6 1/6 (0.60, 0.88) nv nv 

Selenium 4/6 0/2 nv nv nv

Silver 6/6 nv nv nv nv

Strontium 0/6 nv nv 0/6 nv

Uranium 0/6 0/4 nv 0/2 nv

Vanadium 0/6 0/3 nv 0/3 nv

Zinc 2/6 0/4 nv nv nv

Nutrients 

Ammonia (as nitrogen) 2/5 0/1 nv 0/2 nv

Nitrate plus nitrite (as nitrogen) 3/5 0/1 nv 0/1 nv

Nitrite (as nitrogen) 5/5 nv nv nv nv

Total nitrogen (ammonia + nitrite + 

nitrate + organic nitrogen)

0/5 0/5 nv nv nv

Phosphate, orthophosphate (as 

phosphorus)

0/5 0/2 nv 0/3 nv
84 Groundwater-Quality Data in the Northern Coast Ranges Study Unit, 2009: Results from the California GAMA Program

Table A3B. Quality-control summary for replicate analyses of inorganic constituents, isotope tracers, and tritium detected in samples 

collected for the Northern Coast Ranges (NOCO) Groundwater Ambient Monitoring and Assessment (GAMA) study, California, June to 

November 2009.—Continued 

[Abbreviations: ≤, less than or equal to; SD, percent standard deviation; LRL, laboratory reporting level; MDL, method detection limit; MRL, minimum 

reporting level; RSD, percent relative standard deviation; μg/L, micrograms per liter; TDS, total dissolved solids; SiO2, silicon dioxide; H, hydrogen; O, oxygen; 

C, carbon; nv, no value in category]

Constituent

Number of 

non-detect 

or ≤-coded 

replicates/

number of 

replicates 

Number of SDs 

greater than 

1⁄2 LRL/SRL/MDL/MRL 

number of replicates 

with concentration 

less than 5 times 

the LRL/SRL/MDL/

MRL/MU

Concentrations 

of replicates with 

SDs greater than 1⁄2 

LRL/SRL/MDL/MRL 

(environmental, 

replicate) 

Number of RSDs 

greater than 

10 percent/ number 

of replicates with 

concentration greater 

than 5 times the LRL/

SRL/MDL/MRL/MU

Concentrations 

of replicates with 

RSDs greater 

than 10 percent 

(environmental, 

replicate) 

Major and minor ions, silica, and total dissolved soilds (TDS) 

Bromide 0/4 0/3 nv 0/1 nv

Calcium 0/4 nv nv 0/4 nv

Chloride 0/4 nv nv 0/4 nv

Fluoride 0/4 0/4 nv nv nv

Iodide 0/3 0/2 nv 0/1 nv

Magnesium 0/4 nv nv 0/4 nv

Potassium 0/4 nv nv 0/4 nv

Sodium 0/4 nv nv 0/4 nv

Sulfate 0/4 nv nv 0/4 nv

Silica (as SiO2) 0/4 nv nv 0/4 nv

TDS 0/4 nv nv 0/4 nv

Isotope tracers and radioactivity 

δ2H in water 0/2 nv nv 0/2 nv

δ18O in water 0/2 nv nv 0/2 nv

δ13C in dissolved inorganic carbon 0/5 nv nv 0/5 nv

Carbon-14 0/5 nv nv 0/5 nv
Appendix 85

Table A3C. Quality-control summary for replicate analyses of radioactive constituents detected 

in samples collected for the Northern Coast Ranges (NOCO) Groundwater Ambient Monitoring and 

Assessment (GAMA) study, California, June to November 2009. 

[For activities of radiochemical constituents, a replicate pair of analyses is defined as acceptable if the p-value for the 

normalized absolute difference is less than (or equal to) the significance level, α = 0.05. Abbreviations: nv, no value in 

category; <, less than; >, greater than]

Constituent

Number of pairs 

with p > 0.05/

number of replicates 

Activites for replicate 

pairs with p > 0.05

(environmental, replicate)

Tritium 0/0 nv

Radon-222 0/1 nv

Radium-226 0/4 nv

Radium-228 0/4 nv

Gross alpha radioactivity, 72 hour count 0/4 nv

Gross alpha radioactivity, 30 day count 0/4 nv

Gross beta radioactivity, 72 hour count 0/4 nv

Gross beta radioactivity, 30 day count 0/4 nv

Lead-210 0/4 nv

Polonium-210 0/4 nv
86 Groundwater-Quality Data in the Northern Coast Ranges Study Unit, 2009: Results from the California GAMA Program

Table A4A. Quality-control summary for matrix-spike recoveries of volatile organic compounds (VOC) in samples collected for the 

Northern Coast Ranges (NOCO) Groundwater Ambient Monitoring and Assessment (GAMA) study, California, June to November 2009. 

[Acceptable recovery range is between 70 and 130 percent]

Constituent

Number of 

spike 

samples

Minimum 

recovery 

(percent)

Maximum 

recovery 

(percent)

Median 

recovery 

(percent)

Acetone 2 112 115 113.5

Acrylonitrile 2 109 114 111.5

tert-Amyl methyl ether (TAME) 2 99 108 103.5

Benzene 2 100 104 102.0

Bromobenzene 2 98 99 98.5

Bromochloromethane 2 111 112 111.5

Bromodichloromethane 1 2 101 111 106.0

Bromoform (Tribromomethane) 2 98 104 101.0

Bromomethane (Methyl bromide) 2 105 111 108.0

n-Butylbenzene 2 91 92 91.5

sec-Butylbenzene 2 93 96 94.5

tert-Butylbenzene 2 100 106 103.0

Carbon disulfide 1 2 79 86 82.0

Carbon tetrachloride (Tetrachloromethane) 2 102 103 102.0

Chlorobenzene 2 98 99 98.5

Chloroethane 2 96 109 102.5

Chloroform (Trichloromethane) 1 2 104 112 108.0

Chloromethane 2 102 109 105.5

3-Chloropropene 2 110 112 111.0

2-Chlorotoluene 2 100 104 102.0

4-Chlorotoluene 2 100 100 100.0

Dibromochloromethane 2 104 106 105.0

1,2-Dibromo-3-chloropropane (DBCP) 2 101 106 103.5

1,2-Dibromoethane (EDB) 2 105 116 110.5

Dibromomethane 2 107 111 109.0

1,2-Dichlorobenzene 2 101 106 103.5

1,3-Dichlorobenzene 2 97 99 98.0

1,4-Dichlorobenzene 2 91 101 96.0

trans-1,4-Dichloro-2-butene 2 98 99 98.5

Dichlorodifluoromethane (CFC-12) 2 78 84 81.0

1,1-Dichloroethane (1,1-DCA) 1 2 107 111 109.5

1,2-Dichloroethane (1,2-DCA) 2 100 112 106.0

1,1-Dichloroethene (1,1-DCE) 2 102 113 107.5

cis-1,2-Dichloroethene (cis-1,2-DCE) 2 103 109 106.0

trans-1,2-Dichloroethene (trans-1,2-DCE) 2 105 106 106.5

1,2-Dichloropropane 2 93 110 101.5

1,3-Dichloropropane 2 103 113 108.0

2,2-Dichloropropane 2 71 98 84.5

1,1-Dichloropropene 2 92 95 93.5

cis-1,3-Dichloropropene 2 91 104 97.5

trans-1,3-Dichloropropene 2 89 102 95.5

Diethyl ether 2 117 121 119.0

Diisopropyl ether (DIPE) 2 102 110 106.0

Ethylbenzene 2 93 94 93.5

Ethyl tert-butyl ether (ETBE) 2 98 104 101.0

Ethyl methacrylate 2 100 100 100.0

o-Ethyl toluene (1-Ethyl-2-methyl benzene) 2 87 95 91.0

Hexachlorobutadiene 2 78 85 81.5

Hexachloroethane 2 96 106 101.0

2-Hexanone (n-Butyl methyl ketone) 2 107 108 107.5

Iodomethane (Methyl iodide) 2 113 125 119.0
Appendix 87

Table A4A. Quality-control summary for matrix-spike recoveries of volatile organic compounds (VOC) in samples collected for the 

Northern Coast Ranges (NOCO) Groundwater Ambient Monitoring and Assessment (GAMA) study, California, June to November 2009.—

Continued 

[Acceptable recovery range is between 70 and 130 percent]

Constituent

Number of 

spike 

samples

Minimum 

recovery 

(percent)

Maximum 

recovery 

(percent)

Median 

recovery 

(percent)

Isopropylbenzene 2 93 97 95.0

4-Isopropyl-1-methyl benzene 2 95 97 96.0

Methyl acrylate 2 111 111 111.0

Methyl acrylonitrile 2 117 120 118.5

Methyl tert-butyl ether (MTBE) 1 2 105 116 110.5

Methyl iso-butyl ketone (MIBK) 2 104 105 104.5

Methylene chloride (Dichloromethane) 2 103 104 103.5

Methyl ethyl ketone (2-butanone, MEK) 2 110 116 113.0

Methyl methacrylate 2 98 104 101.0

Naphthalene 2 100 100 100.0

Perchloroethene (PCE, Tetrachloroethene) 1 2 105 105 105.0

n-Propylbenzene 2 92 95 93.5

Styrene 2 95 96 95.5

1,1,1,2-Tetrachloroethane 2 98 112 105.0

1,1,2,2-Tetrachloroethane 2 106 115 110.5

Tetrahydrofuran 2 110 120 115.0

1,2,3,4-Tetramethylbenzene 2 94 101 97.5

1,2,3,5-Tetramethylbenzene 2 104 113 108.5

Toluene 2 99 103 101.0

1,2,3-Trichlorobenzene 2 102 105 103.5

1,2,4-Trichlorobenzene 2 89 95 92.0

1,1,1-Trichloroethane (1,1,1-TCA) 1 2 101 107 104.0

1,1,2-Trichloroethane (1,1,2-TCA) 2 108 111 109.5

Trichloroethene (TCE) 2 93 101 97.0

Trichlorofluoromethane (CFC-11) 2 97 103 100.0

1,2,3-Trichloropropane (1,2,3-TCP) 2 103 103 103.0

Trichlorotrifluoroethane (CFC-113) 2 81 97 89.0

1,2,3-Trimethylbenzene 2 99 112 105.5

1,2,4-Trimethylbenzene 2 101 107 104.0

1,3,5-Trimethylbenzene 2 92 97 94.5

Vinyl bromide (Bromoethene) 2 102 108 105.0

Vinyl chloride (Chloroethene) 1 2 93 124 108.5

m- and p-Xylene 2 100 101 100.5

o-Xylene 2 91 93 92.0

1 Constituents detected in groundwater samples.
88 Groundwater-Quality Data in the Northern Coast Ranges Study Unit, 2009: Results from the California GAMA Program

Table A4B. Quality-control summary for matrix-spike recoveries of pesticides and pesticide degradates in samples collected for the 

Northern Coast Ranges (NOCO) Groundwater Ambient Monitoring and Assessment (GAMA) study, California, June to November 2009. 

[Acceptable recovery range is between 70 and 130 percent]

Constituent

Number of 

spike 

samples

Minimum 

recovery 

(percent)

Maximum 

recovery 

(percent)

Median 

recovery 

(percent)

Acetochlor 4 80 118 96.8

Alachlor 4 83 117 102.8

Atrazine 1 4 81 120 105.4

Azinphos-methyl 4 78 108 96.6

Azinphos-methyl oxon 4 41 100 57.4

Benfluralin 4 63 89 70.1

Carbaryl 4 80 124 95.3

Carbofuran 4 81 110 99.1

2-Chloro-2,6-diethylacetanilide 4 91 130 103.1

4-Chloro-2-methylphenol 4 49 69 61.7

Chlorpyrifos 4 80 88 82.5

Chlorpyrifos-oxon 2 16 21 18.7

Cyanazine 4 78 124 130.1

Cyfluthrin 4 75 83 81.7

λ-Cyhalothrin 4 42 51 47.0

Cypermethrin 4 71 79 75.5

DCPA (Dacthal) 4 101 122 109.3

Deethylatrazine (2-Chloro-4-isopropylamino-6-

amino-s-triazine) 1

4 49 75 58.8

Desulfinylfipronil 4 82 116 100.8

Desulfinylfipronil amide 4 72 110 97.3

Diazinon 4 88 100 92.2

Diazinon oxon 4 60 78 71.3

3,4-Dichloroaniline 4 64 84 73.3

3,5-Dichloroaniline 4 73 96 84.4

Dichlorvos 4 14 22 18.1

Dicrotophos 3 31 52 45

Dieldrin 4 95 115 99.3

2,6-Diethylaniline 4 78 98 88.6

Dimethoate 4 35 47 43.6

Disulfoton 4 67 86 79.8

Disulfoton sulfone 4 67 87 78.3

α-Endosulfan 4 81 108 86.8

Endosulfan sulfate 4 75 106 92.9

Ethion 4 52 84 69.9

Ethion monoxon 4 68 84 78.8

Ethoprophos 4 79 108 85.5

S-Ethyl-dipropylthiocarbamate (EPTC) 4 83 102 90.7

2-Ethyl-6-methylaniline 4 75 104 86.4

Fenamiphos 4 75 100 90.7

Fenamiphos sulfone 4 68 115 114.1

Fenamiphos sulfoxide 3 33 47 40

Fipronil 4 89 115 101.4

Fipronil sulfide 4 83 120 106.3

Fipronil sulfone 4 61 107 87.5

Fonofos 4 78 98 86.7

Hexazinone 4 50 77 65.1

Iprodione 4 38 48 46.9

Isofenphos 4 81 111 93.1

Malaoxon 4 68 95 74.7

Malathion 4 76 103 87.8
Appendix 89

Table A4B. Quality-control summary for matrix-spike recoveries of pesticides and pesticide degradates in samples collected for the 

Northern Coast Ranges (NOCO) Groundwater Ambient Monitoring and Assessment (GAMA) study, California, June to November 2009.—

Continued 

[Acceptable recovery range is between 70 and 130 percent]

Constituent

Number of 

spike 

samples

Minimum 

recovery 

(percent)

Maximum 

recovery 

(percent)

Median 

recovery 

(percent)

Metalaxyl 4 84 120 103.0

Methidathion 4 71 90 83.3

Metolachlor 4 80 120 103.3

Metribuzin 4 69 92 85.7

Molinate 4 83 105 91.2

Myclobutanil 4 75 100 81.5

1-Naphthol 4 22 86 50.0

Oxyfluorfen 4 54 82 68.2

Paraoxon-methyl 4 44 65 51.6

Parathion-methyl 4 69 91 77.1

Pendimethalin 4 75 118 95.2

cis-Permethrin 4 76 81 77.5

Phorate 4 62 84 76.6

Phorate oxon 4 73 100 82.8

Phosmet 3 6 9 8

Phosmet oxon 2 1 7 4.1

Prometon 4 40 111 87.5

Prometryn 4 84 118 95.5

Pronamide 4 79 106 91.9

Propanil 4 76 120 93.6

Propargite 4 69 91 74.1

cis-Propiconazole 4 83 135 103.5

trans-Propiconazole 4 79 97 86.4

Simazine 1 4 76 120 97.1

Tebuconazole 4 54 82 72.1

Tebuthiuron 4 96 186 124.7

Tefluthrin 4 49 73 62.0

Terbufos 4 60 83 69.3

Terbufos oxon sulfone 4 58 98 77.7

Terbuthylazine 4 89 119 104.6

Thiobencarb 4 88 121 103.1

Tribufos 4 48 71 58.9

Trifluralin 4 76 93 79.2

1 Constituents detected in groundwater samples.
90 Groundwater-Quality Data in the Northern Coast Ranges Study Unit, 2009: Results from the California GAMA Program

Table A4C. Quality-control summary for matrix-spike recoveries of perchlorate in samples collected for the Northern Coast Ranges 

(NOCO) Groundwater Ambient Monitoring and Assessment (GAMA) study, California, June to November 2009. 

[Acceptable recovery range is between 70 and 130 percent]

Constituent

Number of 

spike 

samples

Minimum 

recovery 

(percent)

Maximum 

recovery 

(percent)

Median 

recovery 

(percent)

Perchlorate 1 2 103 112 107.5

1 Constituent detected in groundwater samples.

Table A4D. Quality-control summary of microbial indicator positivespike results in samples collected for the Northern Coast Ranges 

(NOCO) Groundwater Ambient Monitoring and Assessment (GAMA) 

study, California, June to November 2009. 

Constituent

Number of 

spike 

samples

Positivespike

results

F-specific coliphage 1 4 Detected 2

Somatic coliphage 1 4 Detected 2

1 Constituents detected in groundwater samples.

2

 A detection indicates the groundwater matrix does not affect the detection of 

coliphage.
Appendix 91

Table A5. Quality-control summary for surrogate recoveries of volatile organic compounds (VOC) and pesticides and pesticide degradates in samples collected for the Northern Coast Ranges (NOCO) Groundwater Ambient Monitoring and Assessment (GAMA) study, California, June to November 2009.[Abbreviation: VOC, volatile organic compound]

Surrogate Analytical schedule Constitutent or constituent class analyzed Number of blanks analyses Median recovery in blanks (percent)

Number of 

surrogate 

recoveries 

less than 

70 percent 

in blanks

Number of 

surrogate 

recoveries 

greater than 

130 percent 

in blanks

Number 

of sample 

analyses

Median 

recovery 

in samples 

(percent)

Number of 

surrogate 

recoveries 

less than 

70 percent 

in samples

Number of 

surrogate 

recoveries 

greater than 

130 percent 

in samples

1-Bromo-4-fluorobenzene 2020 VOC 14 84 0 0 58 80 0 0

1,2-Dichloroethane-d4 2020 VOC 14 132 0 8 58 136 0 38

Toluene-d8 2020 VOC 14 94 0 0 58 93 0 0

Diazinon-d10 2033 Pesticide 3 101 0 0 58 100 6 0

α-HCH-d6 2033 Pesticide 3 106 0 0 58 99 0 1
92 Groundwater-Quality Data in the Northern Coast Ranges Study Unit, 2009: Results from the California GAMA Program

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Mathany and others—Groundwater-Quality Data in the Northern Coast Ranges Study Unit, 2009: Results from the California GAMA Program—Data Series 609

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