In cooperation with the California State Water Resources Control Board 

Ground-Water Quality Data in the Monterey Bay and 

Salinas Valley Basins, California, 2005—Results 

from the California GAMA Program 

Data Series 258 

Santa Cruz 

Monterey

Paso Robles 

Salinas 

Version 1.1 

U.S. Department of the Interior 

U.S. Geological Survey 
Photographs by Andrea Altmann, U.S. Geological Survey
 

 

 

 

 

 

 

 

Ground-Water Quality Data in the 

Monterey Bay and Salinas Valley Basins, 

California, 2005—Results from the 

California GAMA Program 

By Justin T. Kulongoski and Kenneth Belitz 

Prepared in cooperation with the California State Water Resources Control Board 

Data Series 258 

Version 1.1 

U.S. Department of the Interior 

U.S. Geological Survey 
 

 

 

U.S. Department of the Interior 

DIRK A. KEMPTHORNE, Secretary 

U.S. Geological Survey 

Mark D. Myers, Director 

U.S. Geological Survey, Reston, Virginia: 2007 

Revised: 2011 

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World Wide Web: http://www.usgs.gov 

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U.S. Government. 

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


reproduce any copyrighted materials contained within this report.
 

Suggested reference:
 

Kulongoski, Justin T., and Belitz, Kenneth, 2007, Ground-Water Quality Data in the Monterey Bay and Salinas Valley 


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

iii 

Contents 

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

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

Purpose and Scope ..............................................................................................................................2
 

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

Hydrogeologic Setting of the Monterey Bay and Salinas Valley GAMA Study Unit ..........................4
 

Santa Cruz Study Area.........................................................................................................................6
 

Monterey Bay Study Area...................................................................................................................6
 

Salinas Valley Study Area .................................................................................................................10
 

Paso Robles Study Area ....................................................................................................................10
 

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

Sampling Design .................................................................................................................................10
 

Sample Collection...............................................................................................................................14
 

Sample Analysis..................................................................................................................................15
 

Data Reporting Conventions .............................................................................................................16
 

Laboratory Reporting Levels and Detection Limits ..............................................................16
 

Constituents on Multiple Analytical Schedules....................................................................17
 

Quality Control.....................................................................................................................................17
 

Blank Samples............................................................................................................................17
 

Replicate Samples.....................................................................................................................18
 

Matrix Spikes..............................................................................................................................18
 

Surrogate Compounds ..............................................................................................................18
 

Results ...........................................................................................................................................................18
 

Quality-Control Samples....................................................................................................................18
 

Detections in Blanks .................................................................................................................18
 

Variability in Replicate Samples..............................................................................................19
 

Matrix Spike Recoveries ..........................................................................................................19
 

Surrogate Compound Recoveries...........................................................................................19
 

Ground-Water Quality ........................................................................................................................20
 

Volatile Organic Compounds and Gasoline Additives .........................................................20
 

Pesticides and Pesticide Degradates ....................................................................................20
 

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

Nutrients and Dissolved Organic Carbon ..............................................................................21
 

Major and Minor Ions and Total Dissolved Solids................................................................21
 

Trace Elements...........................................................................................................................21
 

Radioactivity, Isotopes, and Dissolved Gases ......................................................................22
 

Microbial Constituents..............................................................................................................22
 

Summary........................................................................................................................................................22
 

References....................................................................................................................................................23
 

TABLES ..........................................................................................................................................................27
 
 

iv 

Figures 

Figure 1.	 Map showing the 10 hydrogeologic provinces identified for the California GAMA 

study with the Monterey Bay and Salinas Valley GAMA study unit outlined......... 3 

Figure 2.	 Map showing the Monterey Bay and Salinas Valley GAMA study unit, locations 

of study areas, major cities, rivers, creeks, ground-water basins, and 

subbasins .................................................................................... 5 

Figure 3.	 Map showing the Santa Cruz study area, the locations of the randomized 

sampling grid cells, and the randomized public-supply wells sampled in the 

Monterey Bay and Salinas Valley GAMA study, California ........................... 7 

Figure 4.	 Map showing the Monterey Bay study area, the locations of the randomized 

sampling grid cells, the flow-path and monitoring wells sampled, and the 

randomized public-supply wells sampled in the Monterey Bay and Salinas 

Valley GAMA study, California ............................................................ 8 

Figure 5.	 Map showing the Salinas Valley study area, the locations of the randomized 

sampling grid cells, and the randomized public-supply wells sampled in the 

Monterey Bay and Salinas Valley GAMA study, California ........................... 11 

Figure 6.	 Map showing the Paso Robles study area, the locations of the randomized 

sampling grid cells, and the randomized public-supply wells sampled in the 

Monterey Bay and Salinas Valley GAMA study, California ........................... 12 

Figure 7.	 Map showing the Monterey Bay and Salinas Valley GAMA study unit, locations 

of study areas, target wells, and 10-square-mile randomized sampling 

grid cells .................................................................................... 13 

Tables 

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

the Monterey Bay and Salinas Valley Ground-Water Ambient Monitoring and 

Assessment (GAMA) study, California, July to October 2005 ........................ 28 

Table 2A.	 Volatile organic compounds and gasoline additives, primary use or source, 

U.S. Geological Survey (USGS) parameter code, Chemical Abstract Service 

(CAS) number, laboratory reporting level (LRL) for the USGS National Water 

Quality Laboratory analytical schedule 2020, type of comparison threshold for 

ground-water detections, and the corresponding threshold value .................. 31 

Table 2B.	 Gasoline additives, gasoline oxygenates, and gasoline degradates, primary use 

or source, U.S. Geological Survey (USGS) parameter code, Chemical Abstract 

Service (CAS) number, laboratory reporting level (LRL) for the USGS National 

Water Quality Laboratory analytical schedule 4024, type of comparison threshold 

for ground-water detections, and the corresponding threshold value ............... 33 

Table 2C.	 Pesticides and pesticide degradates, primary use or source, U.S. Geological 

Survey (USGS) parameter code, Chemical Abstract Service (CAS) number, 

laboratory reporting level (LRL) for the USGS National Water Quality Laboratory 

analytical schedule 2003, type of comparison threshold for ground-water 

detections, and the corresponding threshold value .................................... 34 

Table 2D.	 Pesticides and pesticide degradates, primary use or source, U.S. Geological 

Survey (USGS) parameter code, Chemical Abstract Service (CAS) number, 

laboratory reporting level (LRL) for the USGS National Water Quality Laboratory 

analytical schedule 2060, type of comparison threshold for ground-water 

detections, and the corresponding threshold value .................................... 36 

Table 2E.	 Constituents of special interest, primary use or source, Chemical Abstract 

Service (CAS) number, Montgomery Watson-Harza Laboratory minimum reporting 

level (MRL), type of comparison threshold for ground-water detections, and the 

corresponding threshold value ............................................................ 38 
v 

Table 2F.	 Nutrients and dissolved organic carbon, U.S. Geological Survey (USGS) 

parameter code, Chemical Abstract Service (CAS) number, laboratory reporting 

level (LRL) for the USGS National Water Quality Laboratory (NWQL) analytical 

schedule 2755 and laboratory code 2613, type of comparison threshold for 

ground-water detections, and the corresponding threshold value .................. 39 

Table 2G.	 Major and minor ions and trace elements, U.S. Geological Survey (USGS) 

parameter code, Chemical Abstract Service (CAS) number, laboratory reporting 

level (LRL) for the USGS National Water Quality Laboratory analytical schedule 

1948, type of comparison threshold for ground-water detections, and the 

corresponding threshold value ............................................................ 40 

Table 2H.	 Arsenic, chromium, and iron speciation, U.S. Geological Survey (USGS) 

parameter code, Chemical Abstract Service (CAS) number, method detection 

level (MD), for the USGS Trace Metal Laboratory, Boulder, Colorado, type of 

comparison threshold for ground-water detections, and the corresponding 

threshold value .............................................................................. 41 

Table 2I. Isotopic and radioactive constituents, U.S. Geological Survey (USGS) 

parameter code, Chemical Abstract Service (CAS) number, reporting level type, 

reporting level or uncertainty, type of comparison threshold for ground-water 

detections, and the corresponding threshold value .................................... 42 

Table 2J.	 Tritium and noble gases, Chemical Abstract Service (CAS) number, method 

uncertainty (MU) and reporting units for the Lawrence Livermore National 

Laboratory, type of comparison threshold for ground-water detections, and 

the corresponding threshold value ...................................................... 43 

Table 2K.	 Microbial constituents, U.S. Geological Survey (USGS) parameter code, 

primary use or source, and method detection limit (MDL) for the USGS Ohio 

Microbiology Laboratory .................................................................. 44 

Table 3. Classes of chemical and microbial constituents and water-quality indicators 

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

Monterey Bay and Salinas Valley Ground-Water Ambient Monitoring and 

Assessment (GAMA) study, California, July to October 2005 ........................ 45 

Table 4. 	 Analytical methods used for the determination of organic, inorganic, and 

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

Quality Laboratory (NWQL) and additional contract laboratories ..................... 46 

Table 5. Constituents analyzed in ground-water samples collected for the MontereySalinas Ground-Water Ambient Monitoring and Assessment (GAMA) study, 

California, July to October 2005, that appear on multiple analytical schedules, 

primary constituent classification, analytical schedules each constituent 

appears on, and preferred analytical schedule.......................................... 47

 Table 6. Quality-control summary for volatile organic compounds, gasoline additives, 

pesticides, pesticide degradates, major and minor ions, trace elements, 

nutrients, and dissolved organic carbon detected in source-solution blanks, 

field blanks, and the minimum concentrations in ground-water samples collected 

for the Monterey Bay and Salinas Valley Ground-Water Ambient Monitoring and 

Assessment (GAMA) study, California, July to October 2005 ........................ 48 

Table 7. Quality-control summary of replicate samples for constituents collected for 

the Monterey Bay and Salinas Valley Ground-Water Ambient Monitoring and 

Assessment (GAMA) study, California, July to October 2005 ........................ 49 
vi 

Table 8A. Quality-control summary of matrix spike recoveries of volatile organic compounds, 

gasoline additives, NDMA, perchlorate, and 1,2,3-trichloropropane in samples 

collected for the Monterey Bay and Salinas Valley Ground-Water Ambient 

Monitoring and Assessment (GAMA) study, California, July to October 2005 ...... 50 

Table 8B. Quality-control summary of matrix spike recoveries of pesticides and pesticide 

degradates in samples collected for the Monterey Bay and Salinas Valley 

Ground-Water Ambient Monitoring and Assessment (GAMA) study, California, 

July to October 2005 ........................................................................ 52 

Table 9. Quality-control summary of surrogate recoveries in environmental, blank, and 

replicate samples for volatile organic compounds, gasoline additives, pesticides, 

pesticide degradates, and constituents of special interest, collected for the 

Monterey Bay and Salinas Valley Ground-Water Ambient Monitoring and 

Assessment (GAMA) study, California, July to October 2005 ........................ 55 

Table 10. Water-quality indicators determined in the field for the Monterey Bay and 

Salinas Valley Ground-Water Ambient Monitoring and Assessment (GAMA) 

study, California, July to October 2005 ................................................... 56 

Table 11. Results of analyses for volatile organic compounds (VOCs) and gasoline 

additives in unfiltered ground-water samples collected for the Monterey Bay 

and Salinas Valley Ground-Water Ambient Monitoring and Assessment (GAMA) 

study, California, July to October 2005 ................................................... 59 

Table 12. Pesticides and pesticide degradates detected in filtered ground-water samples 

collected for the Monterey Bay and Salinas Valley Ground-Water Ambient 

Monitoring and Assessment (GAMA) study, California, July to October 2005 ...... 65 

Table 13. Results of analyses by Montgomery Watson-Harza Laboratory for the constituents 

of special interest: perchlorate, N-nitrosodimethylamine (NDMA), and 1,2,3­

trichloropropane (1,2,3-TCP) in the unfiltered ground-water samples collected 

for the Monterey Bay and Salinas Valley Ground-Water Ambient Monitoring and 

Assessment (GAMA) study, California, July to October 2005 ........................ 67 

Table 14. Nutrients and dissolved organic carbon in filtered ground-water samples 

collected for the Monterey Bay and Salinas Valley Ground-Water Ambient 

Monitoring and Assessment (GAMA) study, California, July to October 2005 ...... 68 

Table 15. Major and minor ions and dissolved solids in filtered ground-water samples 

collected for the Monterey Bay and Salinas Valley Ground-Water Ambient 

Monitoring and Assessment (GAMA) study, California, July to October 2005 ...... 69 

Table 16. Trace elements in filtered ground-water samples collected for the Monterey 

Bay and Salinas Valley Ground-Water Ambient Monitoring and Assessment 

(GAMA) study, California, July to October 2005 .......................................... 70 

Table 17. Inorganic arsenic and iron speciation results for filtered ground-water samples 

collected for the Monterey Bay and Salinas Valley Ground-Water Ambient 

Monitoring and Assessment (GAMA) study, California, July to October 2005 ...... 73 

Table 18. Chromium speciation results for filtered ground-water samples collected for 

the Monterey Bay and Salinas Valley Ground-Water Ambient Monitoring and 

Assessment (GAMA) study, California, July to October 2005 ........................ 74 

Table 19. Summary of radioactive constituents and carbon isotopes for filtered groundwater samples collected for the Monterey Bay and Salinas Valley Ground-Water 

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

October 2005 ................................................................................. 76 
vii 

Table 20.	 Hydrogen and oxygen isotopes in unfiltered ground-water samples collected 

for the Monterey Bay and Salinas Valley Ground-Water Ambient Monitoring and 

Assessment (GAMA) study, California, July to October 2005 ........................ 79 

Table 21.	 Tritium and noble gas results, analyzed at Lawrence Livermore National Laboratory, 

for unfiltered ground-water samples collected for the Monterey Bay and Salinas 

Valley Ground-Water Ambient Monitoring and Assessment (GAMA) study, California, 

July to October 2005 ........................................................................ 81 

Table 22.	 Summary of microbial indicators detected in ground-water samples collected 

for the Monterey Bay and Salinas Valley Ground-Water Ambient Monitoring and 

Assessment (GAMA) study, California, July to October 2005 ........................ 84 

Abbreviations and Acronyms 

AF atomic fluorescence 

AL California Department of Health Services Advisory Level 

CAS Chemical Abstract Service (American Chemical Society) 

CCV continuing calibration verification 

CSU combined standard uncertainty 

DLR detection level for the purpose of reporting 

DO dissolved oxygen 

DOC dissolved organic carbon 

E estimated value 

GAMA Ground-Water Ambient Monitoring and Assessment program 

GFAA Agraphite furnace atomic absorption 

HAL-US U.S. Environmental Protection Agency Lifetime Health Advisory 

HCl hydrochloric acid 

LRL laboratory reporting level 

LSD land-surface datum 

LT-MDL long-term method detection level 

MCL maximum contaminant level 

MCL-CA California Department of Health Services Maximum Contaminant Level 

MCL-US United States Environmental Protection Agency Maximum Contaminant Level 

MD method detection level 

MDL method detection limit 

MRL minimum reporting level 

MS Monterey Bay and Salinas Valley Study Unit 

MSMB Monterey Bay and Salinas Valley Study Unit: Monterey Bay study area 

MSMBFP Monterey Bay and Salinas Valley Study Unit: Monterey Bay study area flow-path well 

MSMBMW Monterey Bay and Salinas Valley Study Unit: Monterey Bay study area monitoring well 

MSPR Monterey Bay and Salinas Valley Study Unit: Paso Robles study area 
viii 

MSSC Monterey Bay and Salinas Valley Study Unit: Santa Cruz study area 

MSSV Monterey Bay and Salinas Valley Study Unit: Salinas Valley study area 

MTBE methyl tert-butyl ether 

MU method uncertainty 

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

na not available 

NAWQA National Water-Quality Assessment (USGS) 

nc sample not collected 

nd no data 

NDMA N-nitrosodimethylamine 

NL California notification level (CADHS) 

No. number 

PCE tetrachloroethene 

PMC percent modern carbon 

QC quality control 

RSD relative standard deviation 

SC specific conductance 

SMCL secondary maximum contaminant level 

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

SMCL-US United States Environmental Protection Agency secondary maximum contaminant level 

SMOW Standard Mean Ocean Water 

SSMDC sample specific minimum detectable concentration 

TCE trichloroethene 

TCP 1,2,3-trichloropropane 

TDS total dissolved solids 

TT treatment technique 

UCMR unregulated contaminant monitoring regulation 

V value censored due to blank contamination 

VE estimated value censored due to blank contamination 

VOC volatile organic compound 

Organizations 

CADHS California Department of Health Services 

CAEPA California Environmental Protection Agency 

DWR California Department of Water Resources 

LLNL Lawrence Livermore National Laboratory 

MWH Montgomery Watson-Harza Laboratory 

NCDC National Climate Data Center 

NRP National Research Program (USGS) 

NWIS National Water Information System (USGS) 

NWQL National Water Quality Laboratory 

USEPA U.S. Environmental Protection Agency 

USGS U.S. Geological Survey 
ix 

Units of Measure 

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

atmosphere of pressure) 

δ delta notation, expressed as per mil 

ft foot (feet) 

in. inch (inches) 

kg kilogram 

L liter 

lb pound 

mg milligram 

mg/L milligrams per liter 

mi mile 

mi2 square mile 

mL milliliter 

μg microgram 

μg/L micrograms per liter 

μL microliter 

μm micrometer 

pCi/L picocuries per liter 

per mil parts per thousand 

ppb parts per billion (μg/L) 

ppm parts per million (mg/L) 

ppt parts per trillion (μg/mL) 

TU tritium unit 
x
 

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Ground-Water Quality Data in the Monterey Bay and 

Salinas Valley Basins, California, 2005—Results from the 

California GAMA Program 

By Justin T. Kulongoski and Kenneth Belitz 

Abstract 

Ground-water quality in the approximately 1,000-squaremile Monterey Bay and Salinas Valley study unit was investigated from July through October 2005 as part of the California 

Ground-Water Ambient Monitoring and Assessment (GAMA) 

program. The study was designed to provide a spatially unbiased assessment of raw ground-water quality, as well as a statistically consistent basis for comparing water quality throughout California. Samples were collected from 94 public-supply 

wells and 3 monitoring wells in Monterey, Santa Cruz, and 

San Luis Obispo Counties. Ninety-one of the public-supply 

wells sampled were selected to provide a spatially distributed, 

randomized monitoring network for statistical representation 

of the study area. Six wells were sampled to evaluate changes 

in water chemistry: three wells along a ground-water flow path 

were sampled to evaluate lateral changes, and three wells at 

discrete depths from land surface were sampled to evaluate 

changes in water chemistry with depth from land surface. 

The ground-water samples were analyzed for volatile 

organic compounds (VOCs), pesticides, pesticide degradates, 

nutrients, major and minor ions, trace elements, radioactivity, 

microbial indicators, and dissolved noble gases (the last in 

collaboration with Lawrence Livermore National Laboratory). 

Naturally occurring isotopes (tritium, carbon-14, helium-4, 

and the isotopic composition of oxygen and hydrogen) also 

were measured to help identify the source and age of the 

sampled ground water. In total, 270 constituents and waterquality indicators were investigated for this study. 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 (or) blended with other waters to 

maintain water quality. In addition, regulatory thresholds apply 

to treated water that is served to the consumer, not to raw 

ground water. 

In this study, only six constituents, alpha radioactivity, 

N-nitrosodimethylamine, 1,2,3-trichloropropane, nitrate, 

radon-222, and coliform bacteria were detected at concentrations higher than health-based regulatory thresholds. Six 

constituents, including total dissolved solids, hexavalent 

chromium, iron, manganese, molybdenum, and sulfate were 

detected at concentrations above levels set for aesthetic 

concerns. 

One-third of the randomized wells sampled for the 

Monterey Bay and Salinas Valley GAMA study had at least a 

single detection of a VOC or gasoline additive. Twenty-eight 

of the 88 VOCs and gasoline additives investigated were found 

in ground-water samples; however, detected concentrations 

were one-third to one-sixty-thousandth of their respective 

regulatory thresholds. Compounds detected in 10 percent or 

more of the wells sampled include chloroform, a compound 

resulting from the chlorination of water, and tetrachloroethylene (PCE), a common solvent. 

Pesticides and pesticide degradates also were detected 

in one-third of the ground-water samples collected; however, 

detected concentrations were one-thirtieth to one-fourteenthousandth of their respective regulatory thresholds. Ten of 

the 122 pesticides and pesticide degradates investigated were 

found in ground-water samples. Compounds detected in 10 

percent or more of the wells sampled include the herbicide 

simazine, and the pesticide degradate deethylatrazine. 

Ground-water samples had a median total dissolved 

solids (TDS) concentration of 467 milligrams per liter (mg/L), 

and 16 of the 34 samples had TDS concentrations above 

the recommended secondary maximum contaminant level 

(SMCL—a threshold established for aesthetic qualities: taste, 

odor, and color) of 500 mg/L, while four samples had concentrations above the upper SMCL of 1,000 mg/L. Concentrations of nitrate plus nitrite ranged from 0.04 to 37.8 mg/L 

(as nitrogen), and two samples had concentrations above the 

health-based threshold for nitrate of 10 mg/L (as nitrogen). 

The median sulfate concentration in ground-water samples 

was 138 mg/L, and five samples had concentrations above the 

recommended SMCL of 250 mg/L, while only one sample 

had a concentration above the upper SMCL of 500 mg/L. Iron 

concentrations above the SMCL of 300 micrograms per liter 

(μg/L) were measured in three samples, and manganese concentrations were above the SMCL of 50 μg/L in eight samples. 

A molybdenum concentration above the Lifetime Health Advisory of 40 μg/L was measured in one sample, and hexavalent 

chromium (VI) concentrations above the detection level for 

the purpose of reporting (DLR) of 1 μg/L were measured in 86 

samples. 
 

2 Ground-Water Quality Data, Monterey Bay and Salinas Valley Basins 2005—Results, Calif. GAMA Program 

 Radon-222 was detected in all 31 ground-water samples 

collected, with activities ranging from 170 to 1,610 picocuries 

per liter (pCi/L). Twenty-three radon samples were above 300 

pCi/L, a proposed health-based threshold. Alpha radiation was 

detected above the health-based threshold of 15 pCi/L in one 

sample. 

Microbial constituents were analyzed in 30 groundwater samples. Coliform bacteria was detected in four 

samples. Counts ranged from an estimated 1 colony per 100 

milliliter (mL) to 110 colonies per 100 mL. Thresholds for 

microbial constituents are based on recurring detection, and 

these constituents will be monitored during future sampling. 

Introduction 

To assess the quality of ground water from public-supply 

wells and establish a program for monitoring trends in groundwater quality, the U.S. Geological Survey (USGS), in collaboration with the California State Water Resource Control 

Board and Lawrence Livermore National Laboratory (LLNL), 

implemented a statewide ground-water-quality monitoring 

and assessment program (http://ca.water.usgs.gov/gama/). 

The USGS developed a comprehensive approach for this 

effort (Belitz and others, 2003; http://water.usgs.gov/pubs/ 

wri/wri034166/). The Ground-Water Ambient Monitoring and 

Assessment (GAMA) program is a comprehensive assessment 

of Statewide ground-water quality designed to help better 

understand and identify risks to ground-water resources. The 

assessment will be based on ground-water samples collected 

at many locations across California in order to characterize its 

constituents and identify trends in water quality (for example, 

Wright and others, 2005; Kulongoski and others, 2006). The 

results of the sampling and analysis provide information for 

water agencies to address a variety of issues ranging in scale 

from local water supply to statewide resource management. 

The GAMA program was developed in response to the 

Ground-Water Quality Monitoring Act of 2001 (CAL. WATER 

§§ 10780-10782.3): a public mandate to assess and monitor 

the quality of ground water used as public supply for municipalities in California. The goal of the Ground-Water Quality 

Monitoring Act of 2001 is to improve statewide ground-water 

monitoring and facilitate the availability of information about 

ground-water quality to the public. 

The three main objectives of GAMA are (1) status, to 

assess the current quality of the ground-water resource; (2) 

trends, to detect changes in ground-water quality; and (3) 

understanding, to identify the natural and human factors 

affecting ground-water quality (Kulongoski and Belitz, 2004). 

This report will present an assessment of the quality of the 

ground-water resource (objective (1) – status) in the Monterey 

Bay and Salinas Valley GAMA study unit, while subsequent 

interpretive reports will address the trends and understanding 

listed in objectives (2) and (3). 

The GAMA program is unique because the data collected 

during the study include analyses for an extensive number of 

chemical constituents, analyses that are not normally available. This broader understanding of ground-water composition 

will be especially useful for providing an early indication of 

changes in water chemistry. Additionally, the GAMA program 

will analyze this broader suite of constituents at detection limits that are lower than those currently required by the California Department of Health Services (CADHS). An understanding of the occurrence and distribution of these constituents 

is important for the long term management and protection of 

ground-water resources.

 The range of hydrologic, geologic, and climatic conditions that exist in California must be considered in an assessment of ground-water quality (Belitz and others, 2003). To 

accomplish this, the State was partitioned into 10 hydrogeologic provinces, each with distinctive hydrologic, geologic, 

and climatic characteristics (fig. 1). The ground-water basins 

within these hydrologic provinces generally consist of relatively permeable, unconsolidated deposits of alluvial or volcanic origin (California Department of Water Resources, 2003). 

For the purpose of designing the GAMA program, groundwater basins were prioritized (for sampling) on the basis of the 

number of public-supply wells in the basin (Belitz and others, 

2003). Secondary consideration was given to the amount of 

municipal ground-water use, agricultural pumping, the number 

of leaking underground fuel tanks, and pesticide application 

within a basin. Similar adjacent ground-water basins were 

then combined and designated as GAMA study units. The 

Monterey Bay and Salinas Valley GAMA study unit, hereafter 

referred to as the MS study unit, lies in the Southern Coast 

Ranges Hydrogeologic province (fig. 1), and contains eight 

ground-water basins that are considered high priority based on 

the number of public-supply wells, basin location, agricultural 

use, and pesticide applications within each basin (Belitz and 

others, 2003). 

Purpose and Scope 

The purpose of this report is to present the results of analyses for organic and inorganic constituents, microbial constituents, and water-quality indicators from ground-water samples 

collected in the MS study unit. Discussions of the factors that 

influence the distribution and occurrence of the compounds 

and microbial constituents detected in ground-water samples 

will be the subject of subsequent publications. 
Introduction 3 

124
 122
 120
 118
 116
 114 42
 

40
 

38
 

36
 

34
 

Basin and Range 

Klamath 

Mountains 

Desert 

Cascades and 

Modoc Plateau 

Transverse Ranges and 

selected Peninsular Ranges 

Southern 

Coast

 Ranges 

Sierra 

Nevada 

Central 

Pacific Ocean 

Valley 

Northern 

Coast 

Ranges 

San Diego 

Drainages 

Sacramento 

Bakersfield 

San Francisco 

OREGON 

NEVADA 

MEXICO 

ARIZONA 

Redding 

Los Angeles 

San Diego 

0 200 MILES

0 200 KILOMETERS

Monterey Bay and 

Salinas Valley 

GAMA Study Unit 

Base from U.S. Geological Survey National Elevation 

Dataset, 2006, Albers Equal-Area Conic Projection 

Figure 1. The 10 hydrogeologic provinces identified for the California GAMA study with the Monterey Bay and Salinas Valley GAMA 

study unit outlined. 
 

 

4 Ground-Water Quality Data, Monterey Bay and Salinas Valley Basins 2005—Results, Calif. GAMA Program 

This study determined the chemical and biological constituents of untreated aquifer water. In order to provide context 

for these results, the analytical results reported in this study 

were compared to state and federal drinking water standards 

that apply to treated drinking water. Samples collected for this 

program do not represent the water delivered to consumers; 

after withdrawal from the ground, water typically is treated, 

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

water quality. Regulatory thresholds are established by the 

United States Environmental Protection Agency (USEPA), the 

California Environmental Protection Agency (CAEPA), and 

(or) the California Department of Health Services (CADHS). 

Health-based regulatory thresholds include maximum contaminant levels (MCLs); health-based advisory levels (ALs), 

notification levels (NLs); or the USEPA Lifetime Health 

Advisory (HALs). 

Non-enforceable thresholds established for aesthetic 

qualities (taste, odor, and color) include California secondary 

maximum contaminant levels (SMCLs-CA), and detection 

limits for the purposes of reporting (DLR) set by the CADHS 

for the purposes of tracking unregulated chemicals for which 

monitoring is required. The SMCLs-CA for chloride, sulfate, 

specific conductance, and total dissolved solids include recommended thresholds (same as the United States SMCLs), upper 

thresholds, and short term thresholds for each constituent. The 

data presented in this report are intended to characterize the 

quality of untreated ground-water resources within the study 

unit, not the treated drinking water delivered to consumers by 

water purveyors. 

Detection frequencies, or the percentage of ground-water 

samples in which a constituent is observed, were reported 

for the VOCs, pesticides, and pesticide degradates. Detection 

frequencies are useful for determining trends in ground-water 

quality. Also presented in this report are the results and analyses of quality-control samples collected during the Monterey 

Bay and Salinas Valley GAMA study. Samples for pharmaceutical compounds were also collected as part of this study; 

however, the presentation of these results and their associated 

quality assurance/quality control are beyond the scope of this 

report and will be presented in a future report. 

Acknowledgments 

The authors thank the following agencies for their support: California Water Boards, California Department of 

Health Services (CADHS), California Department of Water 

Resources (DWR), and Lawrence Livermore National 

Laboratory (LLNL). 

We also thank the cooperating well owners and water 

purveyors for their generosity in allowing the USGS to collect 

samples from their wells. 

Hydrogeologic Setting of the Monterey 

Bay and Salinas Valley GAMA Study 

Unit 

The Monterey Bay and Salinas Valley (MS) study unit 

covers approximately 1,000 mi2 in Monterey, Santa Cruz, and 

San Luis Obispo Counties across the central coast region of 

California (fig.2). It lies within the Southern Coast Ranges 

hydrogeologic province (Belitz and others, 2003), and includes 

eight ground-water basins and eight subbasins as defined by 

the California Department of Water Resources (California 

Department of Water Resources, 2003) (fig. 2). The wells 

sampled as part of this study generally are located around the 

Monterey Bay and along the Salinas River Valley. 

The Salinas Valley is the largest of the intermontane valleys of the Southern Coast Ranges, and extends southeastward 

120 mi from Monterey Bay to Paso Robles. The Salinas Valley 

formed, in part, as a result of normal faulting along the King 

City (Rinconda-Reliz) Fault that runs north along the western 

margin of the valley from King City in the south to Monterey 

Bay in the north (California Department of Water Resources, 

2003). Normal movement along the fault, valley-side down, 

allowed the deposition of a westward thickening alluvial 

wedge (Showalter and others, 1983). The Salinas Valley has 

been filled up to 10,000 ft on the east, and up to 15,000 ft on 

the west, with Tertiary and Quaternary marine and terrestrial 

sediments that include up to 2,000 ft of saturated alluvium 

(Showalter and others, 1983). Water-bearing units, which lie 

above mostly non-water-bearing and consolidated granitic 

basement, include the Miocene-age Monterey Formation and 

Pliocene- to Pleistocene-age Paso Robles Formation, and 

Pleistocene to Holocene alluvium. 

The climate in the Monterey Bay and Salinas Valley area 

is characterized by warm, dry summers and cool, moist winters. At the National Climate Data Center (NCDC) station in 

Monterey, on the basis of a 50-year record, the average annual 

temperature is 57oF, and the average annual precipitation is 

20 in., occurring as rain during the winter and early spring. 

However, the distribution of precipitation across the area is 

dependent on the topography and the prevailing winds, with an 

increase in precipitation concomitant to an increase in altitude. Precipitation also decreases with latitude from north to 

south in the study unit. Fifty-year climate records from NCDC 

stations from Santa Cruz to Paso Robles show that the mean 

annual precipitation decreases from 31 in. in Santa Cruz in the 

north, to 13 in. in Paso Robles in the south (fig. 2). 

The MS study unit ground-water basins are drained by 

several rivers and their principal tributaries, including the 

Salinas Valley drained by the Salinas River; the Pajaro Valley 

drained by the Pajaro River; the Santa Cruz area drained by 

the San Lorenzo River; and Carmel Valley drained by the 

Carmel River (fig. 2). 
Hydrogeologic Setting of the Monterey Bay and Salinas Valley GAMA Study Unit 5 

122 120 

San 

Lorenzo 

River 

Salinas River 

San Benito 

River 

Salinas 

River 

San Joaquin River

Fresno River 

Arroyo Seco 

Los Gatos Creek 

Carmel River 

Panoche Creek 

Cholame 

Creek

Nacimiento River 

Chowchilla River 

San Juan Creek 

Pajaro 

River 

San Antonio River 

San Lorenzo Creek 

Llagas Creek 

FRESNO CO

MERCED CO 

MADERA CO 

MONTEREY CO 

SAN LUIS OBISPO CO 

SAN BENITO CO 

SANTA 

CLARA CO 

KINGS CO 

KERN 

CO 

SANTA

 CRUZ

 CO 

SOQUEL VALLEY 

CARMEL VALLEY 

PAJARO VALLEY 

SCOTTS VALLEY 

FELTON AREA 

Paso Robles Area 

SALINAS VALLEY 

WEST SANTA 

CRUZ TERRACE 

Upper Valley Aquifer 

SALINAS VALLEY 

Forebay Aquifer 

SALINAS VALLEY 

Corral de Tierra Area 

SALINAS VALLEY 

Seaside Area 

SALINAS VALLEY 

180/400 Foot Aquifer 

SALINAS VALLEY 

Langley Area 

SALINAS VALLEY 

East Side Aquifer 

SALINAS VALLEY 

SANTA CRUZ PURISIMA 

FORMATION 

37 

36 

Salinas 

Monterey 

King City 

Santa Cruz Watsonville 

Paso Robles 

0 20 40 MILES 

Pacific Ocean 

Monterey 

Bay 

Base from U.S. Geological Survey National Elevation 

Dataset, 2006, Albers Equal-Area Conic Projection 

0 20 40 KILOMETERS EXPLANATION 

Ground-water basin SALINAS VALLEY
 

Upper Valley Aquifer
 Study Areas 

Ground-water subbasin 

Santa Cruz Salinas Valley Ground-water basin boundary 

Monterey Bay Paso Robles Ground-water subbasin boundary 

Figure 2. The Monterey Bay and Salinas Valley GAMA study unit, locations of study areas, major cities, rivers, creeks, ground-water 

basins, and subbasins. 
 

 

6 Ground-Water Quality Data, Monterey Bay and Salinas Valley Basins 2005—Results, Calif. GAMA Program 

Sources of ground-water recharge include percolation 

of precipitation, river and stream infiltration, and agricultural 

irrigation and return flow. Amongst the four study areas, 

the Santa Cruz study area has the least recharge from irrigation, whereas the Paso Robles study area has the least input 

from precipitation. The contribution of these inputs is also 

dependent on the hydrogeologic setting of each area, which is 

described below from north to south. 

Santa Cruz Study Area 

The Santa Cruz (MSSC) study area includes the following ground-water basins, the Felton Area; Scotts Valley; 

Santa Cruz Purisima Formation Highlands; West Santa Cruz 

Terrace; and Soquel Valley (fig. 2), all as defined by the DWR 

Bulletin 118 (2003). For the purposes of this study, these 

basins were grouped into the MSSC study area on the basis 

of having underlying Purisima Formation geology; however, 

two wells near the town of Felton were sampled to represent 

the Felton Ground-Water Basin, which is metamorphic terrain 

(fig. 2). The MSSC study area is bounded to the north, east, 

and west by the Santa Cruz Mountains, with altitudes as high 

as 2,900 ft, and to the south by Monterey Bay and the Pajaro 

Valley Ground-Water Basin. 

Mean annual precipitation at Santa Cruz is 31 in. and 

mean annual temperature is 57oF, based on a 50-year record 

from NCDC. The MSSC study area is drained by the San 

Lorenzo River and numerous creeks and their tributaries 

(fig. 3). Sources of ground-water recharge include percolation 

of rainfall, and river and stream infiltration. 

In the north of the MSSC study area, the Santa Cruz Purisima Formation Highlands Ground-Water Basin is defined by 

the geologic boundary of the Purisima Formation. The upper 

Pliocene Purisima Formation is the primary water-bearing unit 

and consists of poorly consolidated, silty to clean, very fine 

to medium-grained sandstone beds interbedded with siltstone. 

The formation ranges in thickness from 600 ft in the north to 

1,000 ft in the south near Soquel (Muir, 1980). 

The West Santa Cruz Terrace and Soquel Valley GroundWater Basins lie to the south of the Santa Cruz Purisima Formation Highlands Ground-Water Basin. In the Soquel Valley 

Ground-Water Basin, the water-bearing sediments consist of 

the Pliocene Purisima Formation, overlain by the Pleistocene 

Aromas Sands Formation and by Quaternary terrace deposits. The Purisima Formation and Quaternary terrace deposits 

have been incised locally by streams, and these channels 

have been filled with Quaternary alluvium (Muir, 1980). The 

Purisima Formation is a sequence of gray-to-blue, moderately 

consolidated, silty to clean, fine to medium sandstone containing siltstone and claystone interbeds (Greene, 1970). To the 

southeast, the Purisima Formation is overlain by hydraulically 

unconfined Aromas Sands. The Aromas Sands Formation 

is brown to red, poorly consolidated, fine to coarse-grained 

sandstone containing lenses of silt and clay (California Department of Water Resources, 2003). The West Santa Cruz Terrace 

Ground-Water Basin contains water-bearing sediments derived 

from the Purisima Formation, Quaternary terrace deposits, 

and alluvium along the San Lorenzo River and other streams 

(fig. 2). The Purisima Formation, the main water-bearing 

formation, is a thick sedimentary sequence with a fossiliferous marine rock base that grades to continental deposits in 

its upper portion. The thin terrace deposits and alluvium are 

poorly cemented, moderately permeable gravel, sands, silts 

and silty clays, and yield only minor quantities of ground 

water to wells (Greene, 1970). 

The Scotts Valley and Felton Area Ground-Water Basins 

are small alluviated valleys located in the Santa Cruz Mountains (fig. 2). The 2-mi2

 Felton Area Ground-Water Basin and 

the 1.2-mi2 Scotts Valley Ground-Water Basin contain the 

following formations, from oldest to youngest: granitic basement, Tertiary Lompico Sandstone, Monterey Shale, Santa 

Margarita Sandstone, and Quaternary alluvium. The principal 

water-bearing formation is the unconfined Santa Margarita 

Sandstone, which is up to 350 ft thick. The underlying Lompico Sandstone also yields water to a lesser extent, and is up to 

600 ft thick. 

Monterey Bay Study Area 

The Monterey Bay (MSMB) study area, as defined for the 

MS study unit, extends from east of Santa Cruz south along 

the Monterey Bay to the Forebay of the Salinas Valley. The 

MSMB study area covers approximately 450 mi2 and includes 

most of the Quaternary sediment filled basins in this area 

(figs. 2 and 4), which include the Pajaro Valley, Carmel Valley, 

and the following subbasins of the Salinas Valley: 180/400­

Foot Aquifer, Eastside Aquifer, Seaside Area, Langley Area, 

and Corral de Tierra Area, as defined by the DWR Bulletin 

118 (2003). For the purposes of this study, these basins and 

subbasins were grouped together in the MSMB study area 

because these basins contain similar Quaternary deposits. 

Mean annual precipitation at Monterey is 20 in, and mean 

annual temperature is 57oF, based on a 50-year record from 

NCDC. The MSMB study area is drained by the Salinas and 

Carmel Rivers and their tributaries (fig. 2). Sources of groundwater recharge include percolation of precipitation, agricultural return flow, and river and stream runoff infiltration in the 

unconfined areas, but surficial recharge does not occur in the 

confined areas. In the confined areas, recharge is from underflow originating in upper valley areas, and ground water flows 

north and west towards the discharge zones in the walls of the 

submarine canyon in Monterey Bay (Greene, 1970; Durbin 

and others, 1978). 
 

 

 

SANTA CRUZ CO 

SANTA CLARA CO 

River 

San Lorenzo 

Hester Creek 

Lompico Creek 

Laurel Creek 

Granite Creek 

Burns Creek 

Bean Creek 

Bull Creek 

Amaya Creek 

Fall Creek 

Valencia Creek 

Love Creek 

Bridge Creek 

Pajaro River 

Rider Creek 

Hughes Creek 

Aptos Creek 

Hendrys Creek 

Hinckley Creek 

Borregas Creek 

Zayante Creek 

Crystal Creek

Llagas Creek 

Carbonera Creek 

Wilder Creek 

Ruins Creek 

Bates Creek 

Uvas Creek 

Bear Creek 

Soquel Creek 

Los Gatos Creek 

Herbert Creek 

Zayante Creek 

Uvas Creek 

Soquel Creek 

Llagas Creek 

Aptos Creek 

Corralitos Creek 

Llagas Creek 

Soquel Creek 

Newell Creek 

Soquel Creek 

Carbonera Creek 

37 

37 

7 

122 121 50’ 

10’ 

oy

Hydrogeologic Setting of the Monterey Bay and Salinas Valley GAMA Study Unit C C r reek

Santa Cruz Mountains 

SC-09

SC-05

SC-01
 SC-04

SC-08
 SC-13

SC-12

SC-11

SC-07
 SC-03

Santa Cruz 

SC-10
 SC-02
 

SC-06

Monterey 

Bay 

MONTEREY 

CO 

Base from U.S. Geological Survey National Elevation 0 6 MILES 

Dataset, 2006, Albers Equal-Area Conic Projection 

EXPLANATION 0 6 KILOMETERS 

Santa Cruz study area 

SC-01 Randomized publicRandomized sampling supply well sampled 

grid cell 

Figure 3. The Santa Cruz study area, the locations of the randomized sampling grid cells, and the randomized 

public-supply wells sampled in the Monterey Bay and Salinas Valley GAMA study, California. 
 Ground-Water Quality Data, Monterey Bay and Salinas Valley Basins 2005—Results, Calif. GAMA Program 

122 121 50’ 121 40’ 121 30’ 121 20’ 

37 

36 

50’ 

36 

40’ 

36 

30’ 

0 5 10 KILOMETERS 

MONTEREY CO

SAN BENITO CO 

SANTA CLARA CO 

Salinas River 

San Benito River 

River 

Pajaro 

Carmel River 

Uvas Creek 

Llagas Cr 

San Lorenzo River 

P acif ic Ocean 

Monter e y 

Bay 

MB-48

MB-47

MB-46

MB-45

MB-44

MB-43

MB-42

MB-41

MB-40

MB-22

MB-39

MB-38

MB-30 MB-37

MB-36

MB-35

MB-34

MB-33

MB-32

MB-31

MB-29

MB-27 MB-28

MB-26

MB-25

MB-24

MB-23

MB-21

MB-20

MB-19

MB-18

MB-3

Santa Cruz 

MB-17

MB-16

MB-15

MB-14

MB-13

MB-11

MB-10

MB-9

MB-8

MB-7

MB-6

MSMB-5

MB-4

MB-2

MB-1

MB 

MW1-3

MB 

FP-1 FP-3

MB 

FP-2

MB 

MB-12

EXPLANATION 

Salinas 

0 5 10 MILES Base from U.S. Geological Survey National Elevation 

Dataset, 2006, Albers Equal-Area Conic Projection 

Sierra de Salinas 

Mountains

Gabilan 

Santa Cruz Mountains 

Monterey Bay study area 

Randomized sampling grid cell 

MB-15 Randomized public-supply well sampled 

MBFP-2 Flow-path well sampled 

MBMW1-3 Monitoring well sampled 

Figure 4. The Monterey Bay study area, the locations of the randomized sampling grid cells, the flow-path and monitoring wells 

sampled, and the randomized public-supply wells sampled in the Monterey Bay and Salinas Valley GAMA study, California. 
Hydrogeologic Setting of the Monterey Bay and Salinas Valley GAMA Study Unit  

The MSMB study area is bounded to the west by Monterey Bay and to the southwest by the Sierra de Salinas 

Mountains, which have altitudes as high as 4,470 ft. It is 

bounded to the east by the Santa Cruz Mountains in the north, 

and the Gabilan Range further south, which have altitudes as 

high as 3,450 ft. The study area is bounded to the north by the 

surface expression of the geologic contact between Quaternary 

alluvium of the Pajaro Valley and marine sedimentary deposits 

of the Pliocene Purisima Formation (California Department of 

Water Resources, 2003). 

The northern Pajaro Valley Basin of the MSMB study 

area contains water-bearing geologic units that include, from 

oldest to youngest, the Purisima Formation, the Aromas Sands, 

Terrace Deposits, Quaternary alluvium, and Dune Deposits 

(Johnson and others, 1988). The Purisima Formation mainly is 

marine in origin, and contains a thick sequence of highly variable sediments ranging from shale beds near its base to continental deposits in its upper portion (Johnson and others, 1988). 

The sediments primarily are poorly consolidated, moderately 

permeable gravel, sands, silts, and silty clays (Johnson and 

others, 1988). The Aromas Sands Formation is composed of 

friable, quartzose, well-sorted brown to red sands that generally are medium-grained and weakly cemented with iron oxide 

(Johnson and others, 1988). This unit ranges in thickness from 

100 ft above sea level in the foothills, to nearly 900 ft below 

sea level near the mouth of the Pajaro River (Allen, 1946). The 

Aromas Sands, considered the primary water-bearing unit of 

the basin, consists of upper eolian and lower fluvial sand units 

that are separated by confining layers of interbedded clays and 

silty clay (Johnson and others, 1988). The Terrace Deposits 

consist of unconsolidated gravel, sand, silt, and clay overlain 

by alluvium. The alluvium is composed of Pleistocene terrace 

materials, which is overlain by Holocene alluvium, consisting 

of sand, gravel, and clay deposited by the Pajaro River, and 

dune sands, with an average thickness of 50-300 ft (Johnson 

and others, 1988). A 400-ft deep, inland-projecting buried 

paleodrainage of the Salinas River acts as the southern subbasin boundary and restricts flow into the 180/400-Foot Aquifer 

Subbasin. 

South of the Pajaro Valley Basin lay the 180/400-Foot 

Aquifer and Langley Area Subbasins. The 24-mi2

 Langley 

Area Subbasin is a series of low hills composed of the following formations, from oldest to youngest: the Pliocene to 

Pleistocene Paso Robles Formation, the Pleistocene Aromas 

Sands, Quaternary terrace deposit, Holocene alluvium, and 

sand dunes (California Department of Water Resources, 1977). 

Outcrops of the Aromas Sands compose most of the subbasin, 

but exposures of Quaternary terrace deposits and Holocene 

alluvium along creeks form a small portion of the southeast 

subbasin. The lower portion of the Aromas Sands interfingers 

with the upper portion of the Paso Robles Formation to form 

the 400-Foot Aquifer to the west in the Salinas Valley 

180/400-Foot Aquifer Subbasin. 

The 180/400-Foot Aquifer Subbasin contains three 

water-bearing units, the 180-Foot, the 400-Foot, and the 900­

Foot Aquifers, named for the average depth at which they are 

found. The confined 180-Foot Aquifer occurs only in this subbasin, as its confining blue clay layer thins and disappears east 

of the subbasin. The 180-Foot Aquifer consists of interconnected sand, gravel, and clay lenses, and ranges in thickness 

from 50 ft near Salinas, to 150 ft near Monterey Bay (Durbin 

and others, 1978). The 180-Foot Aquifer is separated from the 

400-Foot Aquifer by a zone of lesser aquifers and aquitards 

that range in thickness from 10 to 70 ft. The 400-Foot Aquifer 

consists of sands, gravels, and clay lenses, with an average 

thickness of 200 ft (Durbin and others, 1978). The upper portion of the aquifer may be correlative with the Aromas Sands 

and the lower portion with the upper part of the Paso Robles 

Formation (Montgomery-Watson Consulting Engineers, 1994). 

The 900-Foot Aquifer is present in the lower Salinas Valley. It 

consists of alternating layers of sand, gravels and clays with a 

total thickness of up to 900 ft thick and is separated from the 

400-Foot Aquifer by a blue marine clay aquitard. 

To the east of the 180/400-Foot Aquifer is the Eastside 

Aquifer Subbasin. This 90-mi2

 subbasin contains the same 

water-bearing units as the 180/400-Foot Aquifer Subbasin. 

However, the blue clay layer that confines the 180-Foot 

Aquifer does not extend into the Eastside Aquifer Subbasin. 

To the south of the 180/400-Foot Aquifer Subbasin are 

the Seaside Area and Corral de Tierra Area Subbasins. These 

subbasins contain water-bearing units that include, from oldest 

to youngest: the Miocene and Pliocene Santa Margarita Formation, the Pliocene Paso Robles Formation, the Pleistocene 

Aromas Formation, and Pleistocene and Holocene age alluvial 

deposits (Muir, 1982). Although the aggregate maximum 

thickness of these units is more than 1,000 ft, surface outcrops 

are limited to alluvial sand and terrace deposits (Muir, 1982). 

The Santa Margarita Formation has a maximum thickness of 

225 ft, and is a poorly consolidated marine sandstone (Muir, 

1982). The Paso Robles Formation is the primary water-bearing unit in the area and consists of sand, gravel, and clay 

interbedded with some minor calcareous beds (Muir, 1982). 

The Aromas Formation is grouped with the dune sand deposits within this subbasin due to their similarities. These units 

consist of relatively clean red to yellowish-brown, well sorted 

sand and are estimated to range in thickness from 30 to 50 ft 

near the coast to up to 200 ft inland (Muir, 1982). 

The Carmel Valley Ground-Water Basin is a small 

intermontane basin that lies along the Carmel River south of 

the Seaside Subbasin. The basin contains younger alluvium 

and river deposits, and older alluvium and terrace deposits, 

underlain by Monterey Shale and Tertiary sandstone units. The 

younger alluvium comprises the main water-bearing units and 

consists of boulders, gravel, sand, silt, and clay, with a 

thickness between 30 to 180 ft (Kapple and others, 1984). 
 

 

 

10 Ground-Water Quality Data, Monterey Bay and Salinas Valley Basins 2005—Results, Calif. GAMA Program 

Salinas Valley Study Area 

The Salinas Valley (MSSV) study area (figs. 2 and 5) 

includes the following ground-water subbasins of the Salinas Valley basin: the Forebay Aquifer and the Upper Valley 

Aquifer, as defined by the DWR Bulletin 118 (2003). For the 

purposes of this study, these subbasins were combined into the 

MSSV study area on the basis of similar geology of the upper 

and central Salinas Valley. The MSSV study area’s northern boundary is shared with the 180/400-Foot Aquifer and 

Eastside Aquifer Subbasins. To the west, the MSSV study area 

is bounded by the Sierra de Salinas and Santa Lucia Ranges, 

with altitudes up to 4,850 ft, and to the east, it is bounded by 

the Gabilan Range. The southern boundary, at the constriction 

of the Salinas Valley where Sargent Creek joins the Salinas 

River, is shared with the Paso Robles Area Subbasin and 

separates the upper and lower Salinas River drainage basins. 

Mean annual precipitation at Salinas is 15 in. and mean 

annual temperature is 58oF, based on a 50-year record from 

NCDC. The MSSV study area is drained by the Salinas River 

and its tributaries. Sources of ground-water recharge include 

river and stream runoff infiltration and applied irrigation water. 

The MSSV study area covers approximately 300 mi2 of 

the central Salinas Valley. The main water-bearing units of this 

subbasin are unconsolidated to semi-consolidated and interbedded gravel, sand and silt, alluvial-fan, and river deposits 

(Durbin and others, 1978). These deposits form the 180-Foot 

and 400-Foot Aquifers that are mentioned previously in the 

MSMB study area description. The northern boundary of the 

MSSV study area marks the southern boundary of the confining conditions for the 180-Foot Aquifer, while just south 

of Arroyo Seco in the center of the MSSV study area (the 

southern boundary of the Forebay Aquifer subbasin), marks 

the southern boundary of the confining conditions above the 

400-Foot Aquifer. In the Forebay Aquifer Subbasin, ground 

water is found in the lenses of sand and gravel that are interbedded with massive units of finer grained material (Durbin 

and others, 1978). In the northern Forebay Aquifer subbasin, 

the unconfined 180-Foot Aquifer varies in thickness from 

50 to 150 ft, with an average of 100 ft, and is separated from 

the 400-Foot Aquifer by a zone of discontinuous sands and 

blue clays called the 180/400-Foot Aquiclude. The aquiclude 

ranges in thickness from 10 to 70 ft, above the 400-Foot 

Aquifer, which has an average thickness of 200 ft (Durbin 

and others, 1978). To the south, the Upper Aquifer Subbasin, 

a lateral equivalent to the 180/400-Foot Aquifers, includes 

unconsolidated to semi-consolidated and interbedded gravel, 

sand, and silt of the Paso Robles Formation alluvial fan and 

river deposits, but the 400-Foot Aquiclude is absent in this 

portion of the valley. 

An additional deeper aquifer consisting of alternating layers of sand-gravel mixtures and clays, the 900-Foot Aquifer, is 

present in the Forebay Aquifer Subbasin of the Salinas Valley, 

but does not extend into the Upper Valley Aquifer Subbasin 

owing to the southward shoaling of the basement complex 

(Durbin and others, 1978). 

Paso Robles Study Area 

The Paso Robles (MSPR) study area (figs. 2 and 6) lies 

within the Paso Robles Area Subbasin of the Salinas Valley 

Basin, as defined by the DWR Bulletin 118 (2003). For the 

purposes of this study, the Quaternary alluvium that fills the 

valleys in this subbasin is designated as the MSPR study area 

(fig. 6), which excludes the higher altitude Quaternary-Pleistocene deposits. The MSPR study area is bounded to the east by 

the Temblor Range, to the south by the La Panza Range, to the 

west by the Santa Lucia Range, and to the north by the Upper 

Salinas Valley Aquifer Subbasin (California Department of 

Water Resources, 2003). 

Mean annual precipitation at Paso Robles is 13 in. and 

mean annual temperature is 60oF, based on a 50-year record 

from NCDC. Sources of ground-water recharge include 

infiltration of precipitation, return flow from irrigation, and 

seepage from rivers and streams. 

The MSPR study area covers approximately 300 mi2

 of 

valley sediments in the low-lying areas along the San Antonio and Nacimiento Rivers in the west, the Salinas River and 

Huerhuero Creek in the south, the Estrella River in the center, 

and the San Juan Creek to the southeast (fig. 6). These rivers 

and their tributaries drain the MSPR study area. Water-bearing 

formations in this study area include the Quaternary alluvium, 

which consists of unconsolidated, fine- to coarse-grained sand 

with pebbles and boulders up to 130 ft thick near the Salinas 

River (California Department of Water Resources, 1999). 

Methods 

Methods used for the GAMA program were selected to 

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

suitable for statistical analysis, (2) ensure sample collection 

in a consistent manner, (3) analyze samples using proven 

and reliable laboratory methods, (4) assure the quality of the 

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

relevant documentation. 

Sampling Design 

This study utilized the ground-water basins identified by 

the DWR (2003) for the study area boundaries (fig. 2). Each of 

the study areas was subdivided into grid cells approximating 

10 mi2

 (fig. 7) to provide a spatially unbiased and consistent 

assessment of ground-water quality (Scott, 1990). For this 

assessment, the MSSC study area was divided into 21 grid 

cells, the MSMB study area into 48 grid cells, the MSSV 

study area into 31 grid cells, and the MSPR study area into 16 

grid cells. 
Methods 11 

121 30’ 121 20’ 121 10’ 121 120 50’

36 

30’ 

36 

20’ 

36 

10’ 

36 

0 5 10 15 MILES EXPLANATION 

Salinas River 

Salinas River 

San Antonio River

Nacimiento River 

San Lorenzo Creek 

SV-14 Gabilan Mountains 

San Benito River 

Arroyo Seco 

SV-19

SV-18 SV-17

SV-16 SV-15

SV-13 SV-12

SV-11

SV-10

SV-9 SV-8

SV-7

SV-6

SV-5

SV-4

SV-3

SV-2

SV-1

MONTEREY CO

SAN BENITO CO 

King City 

P acif ic 

Ocean 

Base from U.S. Geological Survey National Elevation 

Dataset, 2006, Albers Equal-Area Conic Projection 

Sierra de Salinas

Santa Lucia Mountains 

0 5 10 15 KILOMETERS Salinas Valley study area 

Randomized sampling grid cell
 

SV-1 Randomized public-supply well sampled
 

Figure 5. The Salinas Valley study area, the locations of the randomized sampling grid cells, and the randomized public-supply wells 

sampled in the Monterey Bay and Salinas Valley GAMA study, California. 
12 Ground-Water Quality Data, Monterey Bay and Salinas Valley Basins 2005—Results, Calif. GAMA Program 

120 50’ 120 40’ 120 30’ 120 20’ 

35 

50’ 

35 

40’ 

35 

30’ 

San Juan Creek 

Cholame Creek 

Estrella River

Huerhuero

Creek 

Salinas River 

Las Tablas Creek

PR-05

Robles 

PR-11

PR-10

PR-09

PR-08

PR-07

PR-06

PR-02

PR-01

SAN LUIS OBISPO CO 

MONTEREY CO 

KERN CO 

FRESNO CO 

KINGS CO 

0 5 10

River 

PR-04 PR-03

15 MILES 

EXPLANATION 

Paso 

Pacific Ocean 

Base from U.S. Geological Survey National Elevation 

Dataset, 2006, Albers Equal-Area Conic Projection 

La Panza Mountains 

Temblor Mountains

Santa Lucia Mountains 

San

Antonio

River

Nacimiento 

0 5 10 15 KILOMETERS Paso Robles study area 

Randomized sampling grid cell 

PR-01 Randomized public-supply well sampled 

Figure 6. The Paso Robles study area, the locations of the randomized sampling grid cells, and the randomized public-supply wells 

sampled in the Monterey Bay and Salinas Valley GAMA study, California. 
Salinas River 

San Benito River 

Salinas 

River 

San Joaquin River

Fresno River 

Arroyo Seco 

Los Gatos Creek 

Carmel River 

Panoche Creek 

Cholame 

Creek 

Nacimiento River 

Chowchilla River 

San Juan Creek 

Pajaro

River 

San Antonio River 

San Lorenzo Creek 

Llagas Creek 

FRESNO CO

MERCED CO 

MADERA CO 

MONTEREY CO 

SAN BENITO CO 

37 

36 

Methods 13 

122 120 

San SANTA 

Lorenzo CRUZ River CO 

SANTA CLARA CO 

Santa Cruz 

Monterey 

Bay 

Salinas 

Monterey 

King City 

KINGS CO 

Pacific Ocean 

SAN LUIS OBISPO CO 

KERN 

Shandon CO 

Paso Robles 

Base from U.S. Geological Survey National Elevation 

Dataset, 2006, Albers Equal-Area Conic Projection 

EXPLANATION 

0 

0 20 

20 

40 KILOMETERS 

40 MILES 

Study Areas 

Santa Cruz Salinas Valley Randomized sampling

 grid cell 

Monterey Bay Paso Robles Public-supply well 

Figure 7. The Monterey Bay and Salinas Valley GAMA study unit, locations of study areas, target wells, and 10-square-mile 

randomized sampling grid cells. 
14 Ground-Water Quality Data, Monterey Bay and Salinas Valley Basins 2005—Results, Calif. GAMA Program 

Initial target wells (public-supply wells, fig. 7) were 

obtained from statewide databases maintained by the USGS 

and the CADHS. If a grid cell contained more than one publicsupply well, each well in that grid cell was randomly assigned 

a rank. In each grid cell with multiple wells, the highest 

ranked well was given priority for sampling. An attempt was 

made to select one well per grid cell, but some grid cells did 

not contain accessible wells. Wells from adjacent cells were 

selected to substitute for grid cells that had no active wells. 

In this fashion, a public-supply well was selected for each 

cell to provide a spatially distributed, randomized monitoring 

network for each study area. Wells sampled as part of the 

grid-cell network are referred to, hereafter, as randomized 

wells. 

Additional wells were sampled for the better understanding of a specific topic, including the contribution of aquifers 

of different depths to water supply (depth-dependent sampling 

of the monitoring wells), and the source and movement of 

ground water along the Salinas River (flow-path wells). Wells 

sampled as part of these studies for better understanding were 

excluded from the overall statistical characterization of water 

quality in the MS study unit, as the inclusion of the monitoring 

and flow-path wells would have caused overrepresentation of 

certain cells. 

Randomized wells sampled as part of the MS study unit 

were numbered with the following prefixes based on study 

area: the Santa Cruz study area (MSSC), the Monterey Bay 

study area (MSMB), the Salinas Valley study area (MSSV), 

and the Paso Robles study area (MSPR). Additional (nonrandomized) wells were sampled in the Monterey Bay study area 

to ascertain ground-water quality along flow paths (designated 

MSMBFP), and at monitoring wells (designated MSMBMW). 

Table 1 (all tables are shown in back of report) provides 

the GAMA identification number for each well, along with 

time and date sampled, sampling schedule, and well-construction information. Ground-water samples were collected from 

94 public-supply wells and 3 monitoring wells from July 

through October 2005. Of the 94 public-supply wells sampled, 

51 were in the MSMB study area, 11 in the MSPR study area, 

13 in the MSSC study area, and 19 in the MSSV study area. 

Three monitoring wells located in the MSMB study area also 

were sampled for the studies for better understanding. 

For this study, raw (untreated) ground-water samples 

were analyzed for 88 VOCs; 122 pesticides and pesticide 

degradates; 3 constituents of special interest [N-nitrosodimethylamine (NDMA), 1,2,3-trichloropropane (TCP), and perchlorate]; 5 nutrients; dissolved organic carbon (DOC); 10 major 

and minor ions; 25 trace elements; 12 isotopic constituents; 

5 noble gases; alpha and beta radioactivity; and the microbial 

constituents coliform bacteria and coliphage (tables 2A–2K). 

General water-quality indicators that were determined in the 

field were pH, specific conductance (SC), dissolved oxygen 

(DO), temperature, alkalinity, and turbidity. 

Sample Collection 

Ground-water samples were collected and analyzed for 

the constituents listed on either the fast, slow, or monitoring-well sampling schedules (table 3). Sixty-three wells were 

sampled on the fast schedule, 31 wells were sampled on the 

slow schedule, and 3 wells were sampled on the monitoring-well schedule. All three schedules included the analytes 

listed on the fast schedule. However, at some wells, additional 

analytes were added to the fast schedule for special studies 

for better understanding. For the purposes of this study, this 

expanded analyte list was named the “slow schedule.” Similarly, at the monitoring wells, additional analytes were added 

and this schedule was named the “monitoring well schedule.” 

The fast schedule included analyses for 219 constituents and 

2 water-quality indicators, while the slow schedule included 

analyses of 264 constituents and 6 water-quality indicators. 

The monitoring well schedule included analyses of 254 constituents and 5 water-quality indicators. In the MS study unit, 

65 percent of the ground-water wells were sampled on the fast 

schedule, 32 percent on the slow schedule, and 3 percent on 

the monitoring well schedule. 

Samples were collected using the USGS National WaterQuality Assessment (NAWQA) program protocols (Koterba 

and others, 1995; U.S. Geological Survey, 2006). These sampling protocols ensure that a representative sample of ground 

water was collected at each site and that the samples were collected and handled in a way that minimized the potential for 

airborne contamination of samples and cross contamination 

between samples collected at wells. Additional details 

on sample collection may be found in the analytical method 

references discussed in the Sample Analysis section of this 

report. 

Prior to sampling, each well was pumped continuously 

to purge at least three casing-volumes of water from the 

well. Samples were collected from hose-bibs or access points 

located ahead of points of filtration or chemical treatment, 

such as chlorination. If a chlorinating system was attached to 

the well, the chlorinator was shut off at least 24 hours prior to 

purging and sampling the well to purge the system of extraneous chlorine. For the fast schedule, samples were collected 

at the well head using a foot-long length of Teflon tubing. 

For the slow schedule, the samples were collected inside an 

enclosed flow-through chamber located inside a mobile laboratory and connected to the well head by a 10-50 ft length of 

the Teflon tubing. 

For the field measurements (water-quality indicators), 

ground water was pumped through a flow-through chamber 

fitted with a multi-probe meter that simultaneously measures 

pH, DO, temperature, SC, and turbidity. Measured temperature, pH, DO, and SC values were recorded at 5-minute intervals, for at least 30 minutes, and when these values remained 

stable for 20 minutes, samples for laboratory analyses were 

then collected. For analyses requiring filtered water, ground 

water was diverted through a 0.45-micrometer (μm) vented 

capsule filter or disk filter. Prior to sample collection, 
Methods 15 

polyethylene sample bottles were pre-rinsed three times using 

native water. Samples for some constituents were acidified 

to a pH of 2 or less for preservation. Temperature-sensitive 

samples were stored on ice prior to daily shipping to the various laboratories. The non-temperature-sensitive samples for 

tritium, noble gases, chromium speciation, and the isotopic 

composition of oxygen and hydrogen were shipped monthly, 

whereas volatile organic compounds, pesticides, compounds 

of special interest, dissolved organic carbon, radium isotopes, 

gross alpha and beta radioactivity, and radon-222 samples 

were shipped daily.

 Samples for volatile organic compounds (VOCs), and 

gasoline additives (table 2A, 2B), and 1,2,3-trichloropropane 

(1,2,3-TCP) (table 2E) were collected in 40-mL sample vials 

that were purged with three vial volumes of sample water 

before bottom-filling to eliminate atmospheric contamination. Six normal (6N) hydrochloric acid (HCl) was added as 

a preservative to the VOC samples, but not to the gasoline 

additive samples, nor to the 1,2,3-TCP samples. Pesticides, 

pesticide degradation products (tables 2C, 2D), and NDMA 

(table 2E) samples were collected in 1-L baked amber bottles. 

Pesticide samples were filtered with a glass-fiber filter, 

whereas the NDMA samples were filtered at the Montgomery 

Watson-Harza laboratory prior to analysis. Perchlorate (table 

2E) samples were collected in 125-mL polyethylene bottles. 

Nutrient (table 2F) samples were filtered into 125-mL brown 

polyethylene bottles. DOC (table 2F) samples were collected 

at the well head after rinsing the sampling equipment with 

universal blank water. Each ground-water sample for DOC 

was collected using a 50-mL syringe and 0.45-μm disk filter 

to filter the water into 125-mL baked glass bottles and then 

preserved with 4.5 N sulfuric acid. 

Ground-water samples for major and minor ions, and 

trace elements, alkalinity, and total dissolved solids (table 2G) 

each required filling one 250-mL polyethylene bottle with raw 

ground water, and one 500-mL and one 250-mL polyethylene bottles with filtered ground water. Each 250-mL filtered 

sample then was preserved with 7.5 N nitric acid. Mercury 

(table 2G) samples were collected by filtering ground water 

into 250-mL glass bottles and preserving each with 6 N HCl. 

Arsenic and iron speciation (table 2H) samples were each filtered into 250-mL polyethylene bottles that were covered with 

tape to prevent light exposure, and preserved with 6 N HCl. 

Chromium, radon-222, tritium, and dissolved gases were 

collected from the hose bib at the well head, regardless of the 

sampling schedule (slow, fast, or monitoring well). Chromium 

speciation (table 2H) samples were collected using a 10-mL 

syringe with an attached 0.45-μm disk filter. After the syringe 

was thoroughly rinsed and filled with ground water, 4 mL 

were forced through the disk filter, and the next 2 mL of the 

ground water were filtered slowly into a small centrifuge vial 

for analysis of total chromium. Hexavalent chromium, Cr 

(VI), then was collected by attaching a small cation exchange 

column to the syringe filter, and after conditioning the column 

with 2 mL of sample water, 2 mL were collected in a second 

centrifuge vial. Both vials were preserved with 10 μL of 7.5 N 

nitric acid (Ball and McCleskey, 2003). 

Tritium (table 2I) samples were collected at the well 

head by bottom-filling 1-L polyethylene bottles with unfiltered ground water, after first overfilling the bottles with three 

volumes of water. Samples for the isotopic composition of 

oxygen and hydrogen (table 2I) were collected in 60-mL clear 

glass bottles filled with unfiltered water, sealed with conical caps, and secured with electrical tape to prevent leakage 

and evaporation. Radium isotopes and gross alpha and beta 

radiation (table 2I) samples were filtered into 1-L polyethylene 

bottles and then each acidified with nitric acid. Each carbon 

isotope (table 2I) sample was filtered before bottom-filling two 

500-mL glass bottles that were first overfilled with three bottle 

volumes of ground water. These samples had no headspace, 

and were sealed with a conical cap to avoid atmospheric contamination. Samples for alkalinity titrations were collected by 

filtering ground water into 500-mL polyethylene bottles. 

For the collection of radon-222 (table 2I), a stainless steel 

and Teflon valve assembly was attached to the hose bib at the 

well head. The valve was closed partially to create back pressure, and a 10-mL sample was taken through a Teflon septum 

on the value assembly using a glass syringe affixed with a 

stainless-steel needle. The sample then was injected into a 

25-mL vial partially filled with scintillation mixture (mineral 

oil) and shaken. The vial then was placed in a cardboard 

tube in order to shield it from light during shipping (U.S. 

Geological Survey, 2006). 

Noble gases (table 2J) were collected in 3/8-in. copper 

tubes using reinforced nylon tubing connected to the hose bib 

at the wellhead. Ground water was flushed through the tubing to dislodge any bubbles before flow was restricted with a 

back-pressure valve. Clamps on either side of the copper tube 

then were tightened, trapping a sample of ground water for 

analyses of noble gases (Weiss, 1968). 

Microbial constituents also were collected at the well 

head (table 2K). Prior to the collection of samples, the 

sampling port was sterilized using isopropyl alcohol, and 

ground water was run through the sampling port for at least 

3 minutes to remove any traces of the sterilizing agent. Two 

sterilized 250-mL bottles then were filled with ground water 

for coliform bacteria analyses (total and Escherichia coliform 

determinations), and one sterilized 3-L carboy was filled for 

coliphage analyses (F-specific and somatic-coliphage 

determinations). 

Sample Analysis 

Table 4 lists the analytes, the method(s) used for analysis, 

the laboratory that performed the analyses, and the citations 

that describe the methods in detail. Nine laboratories performed chemical and microbial analyses for the MS study (see 

table 4). 
 

 

 

 

 

16 Ground-Water Quality Data, Monterey Bay and Salinas Valley Basins 2005—Results, Calif. GAMA Program 

In addition to the analytes and their corresponding laboratory methods listed in table 4, selected analyses were done 

in the field. Alkalinity and the concentrations of bicarbonate (HCO3

-

) and carbonate (CO3

2-) were measured by USGS 

technicians on filtered samples using the Gran titration method 

(U.S. Geological Survey, 2006). Turbidity, pH, SC, and 

temperature were measured in the field with calibrated instruments. Dissolved solids were determined by weighing the 

sample residue on evaporation at 180°C (Fishman and Friedman, 1989). Total coliform bacteria and Escherichia coliform 

(E. coli) were counted, following a 22–24-hour incubation 

time, under an ultraviolet light. 

Data Reporting Conventions 

Data reporting for the GAMA program addresses two 

important issues beyond simply presenting the concentrations 

of the constituents detected. First, it is important to document each laboratory’s capability to either detect an analyte, 

or to report its absence with confidence. This documentation 

includes the laboratory reporting levels and detection limits for 

each analyte (tables 2A–2K), and is explained in the Laboratory Reporting Levels and Detection Limits section. Second, 

for analytes that were analyzed using more than one method, it 

is important to know which method is the preferred method; to 

accomplish this, we present reporting conventions for constituents on multiple analytical schedules in the Constituents on 

Multiple Analytical Schedules section. 

The isotopic composition of oxygen and hydrogen of a 

sample are expressed in standard delta (δ) notation, in units of 

permil (parts per thousand), as the differences relative to 

Standard Mean Ocean Water (SMOW) (Craig, 1961). For 

example, 

18 18 16 18 16 δ O = [( O/ Osample - O/ OSMOW )/ 

18 16 3 ( O/ OSMOW )] × 10 (permil), 

and 

2 2 1 2 1 δ H = [( H/ Hsample - H/ HSMOW )/ 

2 1 3 ( H/ HSMOW )] × 10 (permil). 

By convention the value of SMOW is 0 per mil. 

Carbon-13 abundance is expressed by means of the 

standard δ13C parameter, in units of per mil, which is the difference in the carbon-13/carbon-12 ratio relative to University 

of Chicago Peedee Formation Standard (PDB) (Friedman and 

O’Neil, 1977). For example, 

13 13 12 13 12 δ C = [( C/ Csample - C/ CPDB )/ 

13 12 3 ( C/ CPDB )] × 10 (permil). 

The concentration of tritium (hydrogen-3) is 

measured in picocuries per liter of water (pCi/L). A picocurie 

per liter represents 2.22 disintegrations of hydrogen-3 per 

minute per liter of water. 

Laboratory Reporting Levels and Detection Limits 

The USGS NWQL uses the laboratory reporting level 

(LRL) as a threshold for reporting analytical results. The LRL 

is set to minimize the reporting of false negatives (not detecting a compound when it actually is present in a sample) to less 

than 1 percent (Childress and others, 1999). The LRL is set 

at two times the long-term method detection level (LT-MDL), 

which is the average method detection limit calculated from 

multiple analytical measurements (>50) of low-level standard 

solutions. The method detection limit 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 method detection limit, there is a less than 

1 percent chance of a false positive) (U.S. Environmental 

Protection Agency, 2002a). 

Detections below the LRL are reported as estimated 

concentrations (designated with an “E” before the value in the 

tables and text). For information-rich methods (including the 

VOC method used in this study), detections below LT-MDL 

also are reported as E-coded values. E-coded values also result 

from detections outside the range of calibration for detections 

that did not pass laboratory quality-control criteria, and for 

samples that were diluted prior to analysis. 

Some concentrations in this study are reported using minimum reporting levels (MRLs) or method uncertainties. The 

MRL is the smallest measurable concentration of a constituent 

that may be reported reliably using a given analytical method 

(Timme, 1995). The method uncertainty generally indicates 

the precision of a particular analytical measurement; it gives a 

range of values wherein the true value will be found. 

The reporting levels for selected radioactive constituents 

(gross-alpha radioactivity, gross-beta radioactivity, radium226, and radium-228) are based on a sample-specific 

minimum detectable concentration (SSMDC), a critical value 

(also sample specific), and the combined standard uncertainty 

(CSU) (U.S. Environmental Protection Agency and others, 

2004). In this report, a result above the critical value represents 

a greater-than-95-percent certainty that the result is greater 

than zero (significantly different from the instruments background response to a blank sample), whereas a result above 

the SSMDC represents a greater-than-95-percent certainty 

that the result is greater than the critical value (U.S. Environmental Protection Agency and others, 2004). Using these 

reporting level elements, three unique cases were possible 

when screening the raw analytical data. First, if the analytical result is less than the critical value (case 1), the analyte is 

considered not detected, and a value is presented in the table 

as less than the SSMDC. If the analytical result is greater than 

the critical value, the ratio of the CSU to the analytical result 

(relative CSU) was calculated as a percent. For those samples 
 

Methods 17 

with results that have a relative CSU less than 20 percent, the 

analytical result is reported unqualified (case 2). For those 

samples with results that have a relative CSU greater than 

20 percent, the analytical results were qualified as estimated 

values and are preceded in the table with an “E” (case 3). For 

table clarity, only the screened results are reported here. 

Constituents on Multiple Analytical Schedules 

Fourteen constituents targeted in the MS study were 

measured on more than one analytical schedule, or at more 

than one laboratory (table 5). Results from certain analytical 

schedules are preferred over others because the methodology 

is more accurate or precise, and generally yields a greater 

sensitivity for a given compound. The preferred method for 

USGS laboratories was selected by the laboratory on the basis 

of detection levels (http://wwwnwql.cr.usgs.gov/USGS/Preferred_method_selection_procedure.html). If a VOC, gasoline 

additive, pesticide, or pesticide degradate appears on multiple 

USGS analytical schedules, then only the measurement determined by the preferred analytical schedule is reported. 

Five constituents also were analyzed by more than one 

laboratory, in which case both results are reported. The VOC 

1,2,3-trichloropropane was analyzed at both the NWQL and at 

the Montgomery Watson-Harza laboratory (MWH). Since the 

MWH laboratory had a lower reporting level (0.005 μg/L), it 

was the preferred method for this constituent. Ground-water 

samples for arsenic, chromium, and iron also were analyzed at 

two different laboratories; total concentrations were measured 

at the NWQL in Denver, Colorado, while elemental speciation 

was measured at the USGS National Research Program (NRP) 

laboratory in Boulder, Colorado. For arsenic, chromium, and 

iron, the standard analytical techniques were preferred to the 

research laboratory methods. 

Quality Control 

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

include source-solution blanks, field blanks, replicates, matrix 

spikes, and surrogates. QC samples were collected to evaluate 

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

resulted from sample collection, processing, storage, transportation, and laboratory analysis. The data handling protocols, 

and the quality control design and assessment that the USGS 

field members and laboratories utilized, follow the Quality 

Assurance plan of the National Water Quality Laboratory 

(Maloney, 2005). 

Blank Samples 

Blank samples (blanks) were collected using nitrogenpurged pesticide-grade “Universal” blank water that was 

certified to contain less than the LRL or MRL of the analytes 

investigated in the study. Two types of blanks were collected: 

source-solution blanks, and field blanks. Source-solution 

blanks were collected to verify that the blank water used for 

the field blanks was free of analytes. Source-solution blanks 

and field blanks were collected at 12 percent of the wells 

sampled, to determine if equipment or procedures used in the 

field or laboratory introduced contamination. 

Source-solution blanks were collected at the sampling 

site by pouring blank water directly into sample containers 

that were preserved, stored, shipped, and analyzed in the same 

manner as the ground-water samples. For field blanks, blank 

water was either pumped or poured through the sampling 

equipment (fittings and tubing) used to collect ground water, 

then processed and transported using the same protocols as 

for the ground-water samples. Field blanks were analyzed for 

VOCs, pesticides, nutrients, dissolved organic carbon, major 

and minor ions, trace elements, and the microbial constituents. 

If a constituent was detected in a field blank, the associated source-solution blank results were examined for similar 

constituent detections. If the field blank and the source-solution blank contained the constituent, then the source-solution 

water was interpreted as the origin of the contamination in the 

blanks, and the field-blank detections using the same blank 

water were disregarded. If a field-blank detection could not 

be attributed to the source solution, then the ground-water 

samples collected prior to and following the collection of the 

blank were evaluated. If the ground-water samples prior to 

or following the collection of the contaminated field blank 

had no detections, then carry-over contamination was ruled 

out. If an analyte was detected in a blank at a concentration 

greater than the concentration measured in a ground-water 

sample collected prior to or following the blank sample, then 

that ground-water value was censored (table 6). Censored 

values are indicated by a ‘V’ or ‘VE’ preceding the value in 

the tables, and were not considered in the summary statistics. 

If a compound was detected in multiple field blanks, and the 

detections could not be attributed to the source-solution water, 

then any ground-water sample that had a detection of that 

compound in question was evaluated for possible 

contamination and censored if necessary. 
 

1 Ground-Water Quality Data, Monterey Bay and Salinas Valley Basins 2005—Results, Calif. GAMA Program 

Replicate Samples 

Sequential replicate samples (replicates) were collected 

to assess variability that may result from the processing and 

analyses of inorganic and organic constituents. Relative 

standard deviation (RSD) of the measured values was used 

to determine the variability within replicate pairs for each 

constituent (table 7). The RSD is defined as the standard 

deviation of the replicate pair, divided by the mean concentration for each replicate pair of samples, multiplied by 100, with 

the result expressed as a percentage. If one value in a sample 

pair was reported as a nondetection, and the other value was 

reported as an estimated value below the LRL or MRL, the 

RSD was set to zero because the values are analytically identical. If one value in a sample pair was reported as a nondetection and the other value was greater than the LRL or MRL, 

then the nondetection value was set equal to one-quarter of the 

LRL (Childress and others, 1999) and the RSD was calculated. 

High RSD values for replicates with low concentrations may 

indicate higher analytical uncertainty, particularly for 

concentrations within an order of magnitude of LT-MDL or 

MDL. 

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 ground water, on the analytical technique used to measure 

the constituent. The constituents added (matrix spikes) are the 

same as those being analyzed in the method. This addition 

enables an analysis of matrix interferences on a compoundby-compound basis. The following matrix spikes were added 

to 10 percent of the samples in the MS study: VOCs, gasoline 

additives, pesticides, and pesticide degradates, at the laboratory performing the analysis. Compounds with low recoveries 

(<70 percent) are of potential concern if environmental concentrations are close to the MCLs; a concentration below an 

MCL could be falsely indicated (tables 8A–8B). Conversely, 

compounds with high recoveries (>130 percent) are of potential concern if the environmental concentrations exceed MCLs: 

a high recovery could falsely indicate a concentration above 

the MCL. Recoveries between 70 to 130 percent for matrix 

spikes were considered acceptable in this study (Fishman and 

Friedman, 1989). 

Surrogate Compounds 

Surrogate compounds (surrogates) are added to environmental samples in the laboratory prior to analyses in order to 

evaluate the recovery of similar constituents. Surrogate compounds were added to all ground-water and quality-control 

samples that were analyzed for VOCs, gasoline additives, pesticides, pesticide degradates, and constituents of special interest. The compounds selected for use as surrogates normally 

are not found in environmental samples and are used to identify potential problems associated with laboratory analyses. 

Potential problems include matrix interferences (such as high 

levels of dissolved organic carbon) that produce a positive 

bias, and (or) incomplete laboratory recovery (possibly due to 

improper maintenance and calibration of analytical equipment) 

that produces a negative bias. Surrogates are used to identify 

general problems that may arise during sample analysis that 

could affect the analytical results for all compounds, whereas 

matrix spikes are used to indicate problems with specific 

compound analysis. A 70-130 percent recovery of surrogates 

generally is considered acceptable; values outside this range 

indicate possible problems with the processing and analysis 

of samples (table 9) (Connor and others, 1998; Sandstrom and 

others, 2001). 

Results 

Quality-Control Samples 

Field blanks were taken for the VOCs, gasoline additives, 

pesticides, pesticide degradates, nutrients, dissolved organic 

carbon, major and minor ions, trace elements, microbial 

indicators, and iron, arsenic and chromium speciation samples. Universal blank water is not available for the following 

constituents: isotopic composition of oxygen and hydrogen, 

carbon-14, tritium, noble gases, or radioactivity; as a result, 

field blanks were not collected for these constituents. 

In the MS study unit, replicates were collected for all 

constituents in order to check to reproducibility (precision) 

of analytical results. Matrix spikes were only added to the 

VOCs, gasoline additives, pesticides, pesticide degradates, and 

constituents of special interest samples because these samples 

were analyzed by chromatographic techniques, which are 

more susceptible to matrix interferences. The microbial indicator samples were spiked to confirm that the collection and 

handling procedures adequately preserved these samples. 

Surrogate compounds also were only added to VOCs 

and gasoline additives, pesticides, pesticide degradates, and 

constituents of special interest samples in order to verify the 

analytical techniques. 

Detections in Blanks 

In the MS study unit, field blanks were collected at 

approximately 12 percent of the sites sampled. Table 6 presents a summary of compound detections in field blanks. The 

VOCs observed in field blanks, with their maximum detected 

concentration in parentheses, include 1,2,4-trimethylbenzene 

(0.56 μg/L), 2-butanone (ethyl methyl ketone) (30.8 μg/L), 

acetone (12 μg/L), carbon disulfide (E0.09 μg/L), chloroform 

(trichloromethane) (0.10 μg/L), ethylbenzene (E0.03 μg/L), 
 

 

 

 

m-xylene plus p-xylene (E0.12 μg/L), o-xylene (E0.05 μg/L), 

tetrachloroethene (PCE) (E0.03 μg/L), toluene (0.19 μg/L), 

and trichlorofluoromethane (0.11 μg/L). All of the environmental samples collected prior to and following these field 

blanks were free from these constituents (except toluene), 

hence no ground-water sample detections were censored 

(besides toluene) as a result of these blank detections. As a 

result of the high detection frequency for toluene in blanks, all 

four environmental toluene detections were censored, and will 

not be considered in the statistical results. Toluene concentrations observed in the environmental samples had a maximum 

concentration of 0.05 μg/L, which is 3,000 times less than the 

California regulatory MCL of 150 μg/L. 

No detections of pesticide compound were detected in the 

corresponding blank samples. 

Four common ions were detected in field blanks, with 

their maximum concentrations in parentheses: Ca (0.24 mg/L), 

Mg (E0.007 mg/L), Na (0.70 mg/L), and Si (3.9 mg/L). All 

of the environmental samples analyzed had detections of Ca, 

Mg, Na, or Si at concentrations 6 to 90 times greater than 

these values, hence no ground-water detections were censored. 

Fourteen trace elements were detected in field blanks, with 

maximum concentrations in parentheses: Al (45 μg/L), As 

(0.52 μg/L), Ba (0.20 μg/L), Cr (0.09 μg/L), Co (0.04 μg/L), 

Cu (3.1 μg/L), Fe (21 μg/L), Pb (0.14 μg/L), Mn (E0.20 μg/L), 

Ni (0.36 μg/L), Sr (0.58 μg/L), W (0.36 μg/L), V (0.42 μg/L), 

and Zn (3.70 μg/L) (table 6). As a result of the blank detections, 12 ground-water detections were censored: one aluminum, arsenic, chromium, manganese; three lead; and five copper. Dissolved organic carbon (DOC) was detected in five out 

of five blanks, with a maximum concentration of 40 mg/L. As 

a result, six ground-water detections for DOC were censored. 

Censored values were all below regulatory thresholds. 

Variability in Replicate Samples 

The majority of replicate sample pairs collected during the MS study had relative standard deviations (RSDs) of 

less than 20 percent (table 7). Thirteen replicate sample pairs 

representing 7 chemical constituents, 3 replicate sample pairs 

of radionuclides, and 2 replicate sample pairs for radioactivity 

had RSDs greater than 20 percent (table 7). However, many 

of the replicate sample pairs with high RSDs had measured 

concentrations near the LRL for these constituents, and at 

these low concentrations, small deviations in measured values 

may account for the large RSDs. Because the variability in 

measurements occurred at low concentrations, close to the 

method detection levels and well below regulatory thresholds, 

this variability was not of QC concern, and no detections were 

censored as a result of variability in replicate sample samples. 

Matrix Spike Recoveries 

Tables 8A and 8B present a summary of matrix spike 

recoveries for the MS study. Addition of a spike or known 

Results 1 

concentration of a constituent to an environmental sample 

enables the analyzing laboratory to determine the effect of the 

matrix, in this case ground water, on the analytical technique 

used to measure the constituent. Acceptable spike recovery 

values range between 70 and 130 percent (Friedman and 

Erdmann, eds., 1982). Nine environmental samples were 

spiked with VOCs, and 4 environmental samples were spiked 

with the 3 constituents of special interest—NDMA, perchlorate, and 1,2,3-TCP—in order to calculate matrix spike 

recoveries (table 8A). Seventy-two of the 88 VOC spike 

compounds, plus the 3 constituents of special interest, had 

recoveries within the acceptable range of 70 and 130 percent. 

Three VOC spike compounds had at least one matrix spike 

recovery greater than 130 percent; however, these compounds 

were not detected in ground-water samples. Dichlorodifluoromethane and styrene were the only VOC spike compounds that 

had a recovery below 70 percent; however, these compounds 

were not detected in ground-water samples. [NOTE—low 

recoveries may indicate that this compound might not have 

been detected in some samples if it was present at very low 

concentrations.] 

Nine environmental samples were spiked with pesticide 

or pesticide degradate compounds to calculate matrix-spike 

recoveries. Acceptable spike recovery values ranged between 

70 and 130 percent. Twenty-six of the 64 spike compounds 

had recoveries between the acceptable range of 70 and 130 

percent (table 8B). Zero spike compounds had recoveries 

greater than 130 percent. Thirty-eight spike compounds had 

recoveries below 70 percent. Of these 38 spike compounds, 

none were detected in ground-water samples. [NOTE—low 

recoveries may indicate that this compound might not have 

been detected in some samples if it was present at very low 

concentrations.] 

Three microbial indicator samples were spiked with Fspecific and somatic coliphage. All three samples tested 

positive for F-specific coliphage and somatic coliphage. 

Surrogate Compound Recoveries 

Surrogate compounds were added to environmental samples in the laboratory and analyzed to evaluate the recovery of 

similar constituents. Table 9 lists each surrogate; the analytical 

schedule on which it was applied; the number of analyses for 

ground-water samples, blank samples, and sample replicates; 

and the number of surrogate recoveries below 70 percent, 

between 70 and 130 percent, and above 130 percent for the 

ground-water samples, blanks, and replicates. Greater than 

95 percent of the ground-water samples, blanks, and replicate 

samples had recoveries of the surrogates between the acceptable limit of 70 and 130 percent (Fishman and Friedman, 

1989). No ground-water sample detections were censored as a 

result of surrogate recovery data. 
 

 

 

20 Ground-Water Quality Data, Monterey Bay and Salinas Valley Basins 2005—Results, Calif. GAMA Program 

Ground-Water Quality 

Results from analyses of raw (untreated) ground water 

for the MS study unit are presented in tables 10–22. Table 10 

includes water-quality indicators measured in the field, while 

tables 11–22 present the results of ground-water analyses 

organized by the compound types and classes: VOCs and 

gasoline additives; pesticides and pesticide degradates; 

constituents of special interest; nutrients; major and minor 

ions; trace elements; arsenic and iron; chromium; isotopes 

and radioactivity; and microbial constituents. The summary 

tables present only the constituents that were detected, and 

only samples that had at least one compound detected. In each 

table, the sites are grouped by study area, and the first column 

lists the GAMA identification number for each well. The 

remaining columns list the constituents detected, the USGS 

parameter code used to identify the compound and store the 

information in a computerized database [National Water 

Information System (NWIS)], and units of measurement, the 

laboratory reporting level (LRL) for which the compound may 

be detected, and the concentrations at which the constituents 

were detected. 

The tables include the measured concentration of each 

constituent, the number of wells at which it was detected, the 

frequency at which it was detected (in relation to the total 

number of randomized wells sampled), and the total number of 

constituents detected at each well. Results from the flow-path 

wells are presented in the tables, but these results were not 

included in statistical compilations because these wells were 

not part of the randomized well selection. Detections that have 

concentrations or activities above the established thresholds, 

MCL, SMCL, HAL, NL, or DLR, are indicated in the tables 

by an asterisk in the remarks column before the value. 

Volatile Organic Compounds and 

Gasoline Additives 

Analytical results of VOCs and gasoline additives from 

USGS NWQL schedules 2020 and 4024 are presented in 

table 11, which reports results from the preferred analytical 

method where more than one method was used. Ground-water 

samples for analysis of VOCs and gasoline additives were 

collected at the 94 public-supply wells and the 3 monitoring wells sampled in the MS study unit. Twenty-eight VOCs 

and gasoline additives were detected in 39 wells in the MS 

study unit. Forty percent of the 97 wells sampled had at least 

one detection of a VOC and gasoline additive, but detected 

concentrations were one-third to one-sixty-thousandth of their 

respective regulatory thresholds. Three of the 97 wells 

sampled were flow-path wells, and 3 were monitoring 

wells, and these 6 wells were not included in the following 

calculations of detection frequency. 

Twenty-seven of the 88 VOCs analyzed were detected 

in ground-water samples from randomized wells in the MS 

study unit. VOCs detected in 10 percent or more of the wells 

include trichloromethane (chloroform), which was detected in 

20 of the 91 randomized wells sampled, and tetrachlorethylene 

(PCE), which was detected in 9 of the 91 randomized wells 

sampled. In total, 34 wells (of the 91 randomized wells) had 

86 detections, for a VOC detection frequency of 37 percent. 

None of the VOCs and gasoline additive concentrations measured were greater than their respective thresholds established 

for regulatory purposes. 

Pesticides and Pesticide Degradates 

Ground-water samples for pesticides and pesticide 

degradates, using USGS analytical schedules 2003 and 2060, 

were collected at 97 wells in the MS study unit (table 12). Ten 

pesticides and pesticide degradates were detected in 28 wells 

in the total MS study unit; however, detected concentrations 

were one-thirtieth to one-fourteen-thousandth of their respective regulatory thresholds. Three of the 97 wells sampled 

were flow-path wells, and 3 were monitoring wells, and these 

6 wells were not included in the calculations of detection 

frequency. 

Ten of the 122 pesticides and pesticide degradates investigated were detected in ground-water samples from the 91 randomized wells in the MS study unit. Compounds detected in 

10 percent or more of the randomized wells include simazine, 

an herbicide, which was detected in 16 of the 91 ground-water 

samples, and deethylatrazine (2-chloro-4-isopropylamino-6­

amino-s-triazine), a pesticide degradate, which was detected 

in 10 of the 91 ground-water samples. In total, 43 detections 

in 27 randomized wells were observed in the MS study unit. 

None of the pesticide concentrations measured were greater 

than threshold concentrations established for regulatory 

purposes. 

Constituents of Special Interest 

Ground-water samples for the constituents of special 

interest—perchlorate, N-nitrosodimethylamine (NDMA), 

and 1,2,3-trichloropropane (1,2,3-TCP)—were collected 

at 34 wells, 31 public-supply wells and 3 monitoring wells 

(table 13). NDMA was detected in two wells at concentrations 

above the regulatory threshold of 0.01 μg/L. 1,2,3-TCP 

was detected in one well above the regulatory threshold of 

0.005 μg/L. Perchlorate was not detected in any ground-water 

samples. 
 

 

Results 21 

Nutrients and Dissolved Organic Carbon 

Samples for the analysis of nutrients and dissolved 

organic carbon (DOC) were collected at 34 wells, 31 publicsupply wells and 3 monitoring wells (table 14) sampled only 

under the slow schedule in the MS study unit. Ammonia was 

detected in 9 of the 34 samples, at concentrations ranging 

from 0.04 to 1.60 mg/L (as nitrogen). Nitrate plus nitrite was 

detected in 24 of the 34 ground-water samples, whereas nitrite 

was detected in only 3 of the 34 samples. Concentrations of 

nitrate plus nitrite ranged from (estimated value) E0.04 mg/L 

to 37.8 mg/L (as nitrogen), with two samples above the regulatory threshold of 10 mg/L (as nitrogen). Nitrite was detected 

in 3 wells at concentrations that ranged from E0.004 mg/L 

to 0.008 mg/L— much below the nitrite MCL of 1 mg/L (as 

nitrogen). Total dissolved nitrogen (nitrate plus nitrite plus 

ammonia plus organic-N) was measured in 34 wells at concentrations that ranged from 0.09 to 37.5 mg/L (as nitrogen). 

Dissolved phosphorus (as orthophosphate) was measured in all 

34 wells at concentrations that ranged from E0.005 to 0.106 

mg/L (as phosphorus). DOC was measured in 34 wells at 

concentrations that ranged from E0.2 to 4.4 mg/L. Six samples 

had DOC detections in the preceding blanks greater than the 

sample values, and hence were censored and these data were 

not used for summary statistical calculations. Censored values 

are preceded by a V or VE in table 14. 

Major and Minor Ions and Total Dissolved Solids 

Samples for the analysis of major and minor ions and 

dissolved solids (DS) were collected at 31 public-supply wells 

and 3 monitoring wells (table 15) in the MS study unit. The 

following results are for the public-supply wells only. Calcium 

concentrations ranged from 15.4 to 171 mg/L, with a median 

value of 56 mg/L. Magnesium concentrations ranged from 

0.64 to 73.1 mg/L, with a median value of 21 mg/L. Potassium 

concentrations ranged from 1.46 to 16.9 mg/L, with a median 

value of 3.05 mg/L. Sodium concentrations ranged from 20.3 

to 209 mg/L, with a median value of 65.2 mg/L. Bromide 

concentrations ranged from 0.04 mg/L to 0.92 mg/L, with a 

median value of 0.27 mg/L. Chloride concentrations ranged 

from 11.2 to 241 mg/L, with a median value of 72.5 mg/L. 

Fluoride concentrations ranged from 0.10 to 0.50 mg/L, with a 

median value of 0.30 mg/L. Iodide concentrations ranged from 

E0.001 mg/L to 0.205 mg/L, with a median value of 0.006 mg/ 

L. Silica concentrations ranged from 24.4 to 71.2 mg/L, with 

a median value of 39.7 mg/L. Sulfate concentrations ranged 

from 6.8 to 563 mg/L, with a median value of 138 mg/L. Five 

samples had sulfate concentrations above the recommended 

SMCL threshold of 250 mg/L, and one sample had sulfate 

concentrations greater than the upper SMCL of 500 mg/L. 

TDS concentrations, measured as residue on evaporation at 

180°C, ranged between 281 and 1,330 mg/L, with a median 

value of 467 mg/L. Sixteen samples had TDS concentrations 

above the recommended SMCL threshold of 500 mg/L, and 4 

samples had concentrations greater than the upper SMCL of 

1,000 mg/L. 

Trace Elements 

Samples for the analysis of trace elements were collected 

at 31 public-supply wells and 3 monitoring wells (table 16) 

in the MS study unit. Censored values were not considered 

as detections for this study. Aluminum was detected in 10 

ground-water samples with concentrations ranging from E0.8 

to 20 μg/L; one aluminum detection was censored due to 

the presence of aluminum in the preceding blank. Antimony 

was detected in 9 ground-water samples, with concentrations 

ranging from E0.11 to 0.39 μg/L. Arsenic was detected in 

29 ground-water samples, with concentrations ranging from 

0.2 to 7.3 μg/L; one arsenic detection was censored due to 

the presence of arsenic in the preceding blank. Barium was 

detected in 34 ground-water samples, with concentrations 

ranging from 4.0 to 191 μg/L. Beryllium was detected in 2 

ground-water samples, with concentrations ranging from 0.06 

to 1.28 μg/L. Boron was detected in 34 ground-water samples, 

with concentrations ranging from 30 to 753 μg/L. Cadmium 

was detected in 23 ground-water samples, with concentrations 

ranging from E0.02 to 0.37 μg/L. Chromium was detected in 

24 ground-water samples, with concentrations ranging from 

E0.04 to 14.2 μg/L; one chromium detection was censored due 

to the presence of chromium in the preceding blank. Cobalt 

was detected in 33 ground-water samples, with concentrations 

ranging from E0.03 to 1.2 μg/L. Copper was detected in 28 

ground-water samples, with concentrations ranging from E0.3 

to 5.4 μg/L; five copper detections were censored due to the 

presence of copper in the preceding blank. 

Iron was detected in 23 ground-water samples, with 

concentrations ranging from E4.0 to 2,830 μg/L; three samples 

had iron concentrations above the non-health-based SMCL 

threshold of 300 μg/L. Three iron detections were censored 

due to the presence of iron in the preceding blank. Lead was 

detected in 27 ground-water samples, with concentrations 

ranging from E0.06 to 6.62 μg/L. Lithium was detected in 

34 ground-water samples, with concentrations ranging from 

3.4 to 110 μg/L. Manganese was detected in 31 ground-water 

samples, with concentrations ranging from E0.1 to 2,410 μg/L; 

eight of the samples had concentrations of manganese above 

the non-health-based SMCL threshold of 50 μg/L. One manganese detection was censored owing to the presence of manganese in the preceding blank. Mercury was detected in 3 of the 

samples, ranging in concentration from E0.01 to 0.05 μg/L. 
 

22 Ground-Water Quality Data, Monterey Bay and Salinas Valley Basins 2005—Results, Calif. GAMA Program 

Molybdenum was detected in 34 ground-water samples, 

with concentrations ranging from 0.9 to 42.6 μg/L; one of 

the public-supply wells had concentrations of molybdenum 

above the HAL threshold of 40 μg/L. Nickel was detected in 

34 ground-water samples, with concentrations ranging from 

0.42 to 7.24 μg/L. Selenium was detected in 29 ground-water 

samples, with concentrations ranging from E0.06 to 

17.6 μg/L. Silver was not detected in any ground-water 

samples. Strontium was detected in 34 ground-water samples, 

with concentrations ranging from 226 to 1,790 μg/L. Thallium 

was detected in 3 ground-water samples, with concentrations 

ranging from E0.02 μg/L to 0.05 μg/L. Tungsten was detected 

in 4 ground-water samples, with concentrations ranging from 

0.15 to 0.90 μg/L. Uranium was detected in 31 ground-water 

samples, with concentrations ranging from E0.03 to 28.9 μg/L. 

Vanadium was detected in 31 ground-water samples, with concentrations ranging from E0.1 to 20.5 μg/L. Zinc was detected 

in 33 ground-water samples, with concentrations ranging from 

E0.38 to 1,470 μg/L. 

Table 17 presents the results from the USGS NRP Boulder lab for 38 samples collected for total dissolved inorganic 

arsenic and iron, as well as for the individual species arsenic 

(III) and iron (II). Total arsenic and iron results agree well 

with samples from the same wells identified in table 16, which 

were analyzed at the USGS NWQL in Denver. 

Table 18 presents chromium speciation analyses from 

the USGS NRP Boulder lab for total dissolved chromium and 

hexavalent chromium (VI) in all 97 ground-water samples. 

Values ranged from <1.0 to 36.0 μg/L. None of the total 

chromium concentrations were above the regulatory threshold 

of 50 μg/L; however, 86 ground-water samples had chromium 

(VI) values above 1 μg/L, the DLR threshold. Detection limits 

for the purposes of reporting (DLR) are set by CADHS for the 

purposes of tracking unregulated chemicals for which 

monitoring is required. 

Radioactivity, Isotopes, and Dissolved Gases 

Gross alpha and beta radioactivity and isotope activities 

were measured in selected ground-water samples collected 

for the MS study unit (table 19). Alpha radioactivity (72­

hour and 30-day count) and beta radioactivity (72-hour and 

30-day count) samples for analysis were collected at 34 wells; 

samples for radium-226, radium-228, and radon-222 were 

collected at 31 wells; and samples for carbon isotope samples 

were collected at 33 wells. Alpha radioactivity in the 34 

samples (table 19) ranged from below quantification limits to 

17.4 picocuries per liter (pCi/L) for 72-hour counts, and from 

below quantification limits to 16.3 pCi/L for 30-day counts. 

One alpha radioactivity sample exceeded the MCL threshold 

of 15 pCi/L for both the 72-hour and 30-day counts with values of 17.4 and 16.3, respectively. Beta radioactivity in the 34 

samples ranged from below quantification limits to 21.2 pCi/L 

for 72-hour counts, and from below quantification limits to 

21.4 pCi/L in 30-day counts. Radium-226 was detected in 

30 out of the 31 samples, with a maximum concentration of 

0.58 pCi/L. Radium-228 was detected in 15 out of 31 samples, 

with a maximum concentration of 0.96 pCi/L. Radon-222 was 

detected in all 31 samples collected, and had activities ranging 

from 170 to 1,610 pCi/L. Twenty-three samples for radon222 activities were above the proposed MCL of 300 pCi/L. 

Ground-water samples for carbon-14, as percent modern carbon (pmc), and delta carbon-13, as per mil, were collected at 

33 wells, and results ranged from 5.68 to 100.1 pmc, and from 

-20.4 to -10.5 per mil, respectively. The isotopic composition 

of carbon is reported, in delta notation, as per mil (parts per 

thousand). 

Ground-water samples for the isotopic composition of 

oxygen and hydrogen, analyzed at the USGS Stable Isotope 

Laboratory, were collected at all 97 wells (table 20). Tritium 

was detected in 61 out of 97 samples, with activities that 

ranged from less than 1 to 14 pCi/L. 

Tritium and noble gas samples, analyzed at the LLNL, 

were collected at 97 wells (table 21). Tritium activities, measured by the helium in-growth method, ranged from below 1 

to 17 pCi/L. Noble gas concentrations and the helium isotope 

ratios (helium-3/helium-4) measured in each sample are 

presented in table 21. 

Microbial Constituents 

Ground-water samples from 30 wells in the MS study 

unit were analyzed for microbial constituents (table 22). 

The following microbial constituents were determined: total 

coliform bacteria and Escherichia coliform, and the viruses 

F-specific coliphage and somatic coliphage. Coliform bacteria 

was detected in four wells. Counts ranged from an estimated 

1 colony/100 mL to 110 colonies/100 mL. MCLs for microbial 

constituents are based on recurring detection, and counts will 

be monitored during future sampling. 

Summary 

The Monterey Bay and Salinas Valley GAMA study 

assessed the quality of ground water from 94 public-supply wells and 3 monitoring wells across the approximately 

1,000 mi2 study unit. Ground-water samples were analyzed 

for volatile organic compounds (VOCs), pesticides, pesticide 

degradates, nutrients, major and minor ions, trace elements, 

microbial indicators, and noble gases. Naturally occurring isotopes (tritium, carbon-14, oxygen-18, deuterium, and helium4) also were measured in these samples to provide a data set 

that will be used to help interpret the source and age of the 

sampled ground water. In total, 270 constituents and waterquality indicators were investigated for this study. 

Results from 91 randomized wells, statistically representative of the study unit, show that only six constituents—alpha 

radioactivity, N-nitrosodimethylamine, 1,2,3-trichloropropane, 

nitrate, radon-222, and coliform bacteria—were detected at 

concentrations higher than those thresholds set for 
References 23 

health-based regulatory purposes. Six constituents—total 

dissolved solids, hexavalent chromium, iron, manganese, 

molybdenum, and sulfate—were detected at concentrations 

above levels set for aesthetic concerns. 

In this study, one-third of the randomized wells sampled 

had at least a single detection of a VOC or gasoline additive. 

Twenty-seven of the 88 VOCs and gasoline additives investigated were found in ground-water samples; however, detected 

concentrations were one-third to one-sixty-thousandth of 

their respective regulatory thresholds. Compounds detected in 

10 percent or more of the samples include chloroform, a 

compound resulting from the chlorination of water, and 

tetrachloroethene, a common solvent. 

Pesticides and pesticide degradates were detected in onethird of the ground-water samples collected; however, detected 

concentrations were one-thirtieth to one-fourteen-thousandth 

of their respective regulatory thresholds. Ten of the 122 

pesticides and pesticide degradates investigated were found in 

ground-water samples. Compounds detected in 10 percent or 

more of the samples included the herbicide simazine, and the 

pesticide degradate deethylatrazine. 

Total dissolved solids (TDS), major and minor ions, 

nutrients, and trace-element samples were collected at 31 

public-supply wells and 3 monitoring wells. The median TDS 

value was 467 mg/L; 16 samples had TDS concentrations 

above the recommended SMCL of 500 mg/L; and 4 samples 

had concentrations greater than the upper SMCL of 1,000 mg/ 

L. Concentrations of nitrate plus nitrite ranged from 0.04 to 

37.8 mg/L (as nitrogen), and 2 samples had concentrations 

above the regulatory threshold of 10 mg/L (as nitrogen). The 

median sulfate concentration in ground-water samples was 

138 mg/L, and 5 samples had concentrations above the recommended SMCL of 250 mg/L, while one sample’s concentration was greater than the upper SMCL of 500 mg/L. Iron 

concentrations above the SMCL of 300 μg/L were measured 

in 3 samples, and manganese concentrations were above the 

SMCL of 50 μg/L in 8 samples. A molybdenum concentration 

above the HAL of 40 μg/L was measured in one sample, and 

chromium (VI) concentrations above the DLR of 1 μg/L were 

measured at 86 samples.

 Radon-222 was detected in all 31 ground-water samples 

collected, with activities ranging from 170 to 1,610 pCi/L. 

Twenty-three radon samples were above the proposed threshold of 300 pCi/L. Alpha radiation was detected above the 

regulatory threshold of 15 pCi/L in one sample. 

Microbial constituents were analyzed in 30 ground-water 

samples. Coliform bacteria was detected in four samples. 

Counts ranged from an estimated 1 colony per 100 mL to 

110 colonies per 100 mL. 

Future work will combine the data presented in this 

report with various statistical and qualitative approaches to 

identify the natural and human factors affecting ground-water 

quality, and to detect changes in ground-water quality. 

References 

Allen, J.E., 1946, Geology of the San Juan Bautista quadrangle: California Division of Mines Bulletin 133, 112 p. 

American Society for Testing and Materials, 1998a, Annual 

book of ASTM standards—water and environmental 

technology: American Society for Testing and Materials 

v. 11.02 Water (II), 1048 p. 

American Society for Testing and Materials, 1998b, Annual 

book of ASTM standards—water and environmental 

technology: American Society for Testing and Materials, 

v. 11.01 Water (I), 890 p. 

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

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

Belitz, K., Dubrovsky, N.M., Burow, K., Jurgens, B., and 

Johnson, T., 2003, Framework for a ground-water 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 UVpromoted persulfate oxidation and infrared spectrometry: 

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

CAL. WATER §§ 10780-10782.3, State of California: 

accessed on September 18, 2006, at 

http://www.leginfo.ca.gov/cgi-bin/displaycode?section=wat 

&group=10001-11000&file=10780-10782.3 

California Department of Water Resources, 1977, North Monterey water resources investigation: California Department 

of Water Resources, Central district report to the Monterey 

County Flood Control and Water Conservation District, 20 

p. 

California Department of Water Resources, 1999, Evaluation 

of groundwater overdraft in the Southern Central Coast 

Region, Part 2: California Department of Water Resources, 

116 p. 

California Department of Water Resources, 2003, California’s 

groundwater: California Department of Water Resources 

Bulletin 118, 246 p. 

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

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

Geological Survey National Water Quality Laboratory: 

U.S. Geological Survey Open-File Report 99-193, 19 p. 
24 Ground-Water Quality Data, Monterey Bay and Salinas Valley Basins 2005—Results, Calif. GAMA Program 

Clarke, W.B., Jenkins, W.J., and Top, Z., 1976, Determination of tritium by mass spectrometric measurement of He-3: 

International Journal of Applied Radiation and Isotopes, 

v. 27, p. 515–522. 

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

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

chromatography/mass spectrometry, including detections 

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

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

oxygen isotopic abundances: Pure and Applied Chemistry, 

v. 66, p. 273–276. 

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. 

Craig, H., 1961, Standard for reporting concentrations of 

deuterium and oxygen-18 in natural waters: Science, v 133., 

p. 1833–1934. 

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

background corrections for accelerator mass spectrometry 

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

Durbin, T.J., Kapple, G.W., and Freckleton, J.R., 1978, Twodimensional and three-dimensional digital flow models of 

the Salinas Valley Ground-Water Basin, California: U.S. 

Geological Survey Water-Resources Investigations 

Report 78-113, 134 p. 

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

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

Report 93-125, 217 p. 

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

determination of inorganic substances in water and fluvial 

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

Friedman, I., and O’Neil, J.R., 1977, Compilation of stable 

isotope fractionation factors of geochemical interest—In 

M. Fleischer, ed., Data of Geochemistry, chapter KK: U.S. 

Geological Survey Professional Paper 440-KK, 12 p. and 49 

fig. 

Friedman, L.C., and Erdmann, D.E., 1982, Quality assurance practices for the chemical and biological analyses of 

water and sediments: U.S. Geological Survey Techniques of 

Water-Resource Investigations, Book 5, Chap. A6, 181 p. 

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

strontium, thallium, 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. 

Greene, H.G., 1970, Geology of southern Monterey Bay and 

its relationship to the ground-water basin and seawater 

intrusion: U.S. Geological Survey Open-File Report 1465 

[now 70-141], 50 p. 

Hautman, D.P., Munch, D.J., Eaton, A.D., and Haghani, 

A.W., 1999, Method 314.0 Determination of perchlorate in 

drinking water using ion chromatography, revision 1.0: U.S. 

Environmental Protection Agency, accessed on July 7, 2006, 

at http://www.epa.gov/safewater/methods/pdfs/met314.pdf 

Johnson, M.J., Londquist, C.J., Laudon, J., and Mitten, H.T., 

1988, Geohydrology and mathematical simulation of the 

Pajaro Valley Aquifer system, Santa Cruz and Monterey 

Counties, California: U.S. Geological Survey WaterResources Investigations Report 87-4281, 62 p. 

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

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

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

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

Planetary Change, v. 41, p. 309–323. 

Kapple, G.W., Mitten, H.T., and Durbin, T.J., 1984, Analysis 

of the Carmel Valley alluvial ground-water basin, Monterey 

County, California: Monterey Peninsula Water-Management 

District Report 83-4580, 45 p. 

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

Ground-water data-collection protocols and procedures for 

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

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

113 p. 

Kulongoski, J.T., and Belitz, K., 2004, Ground-water ambient monitoring and assessment program: U.S. Geological 

Survey Fact Sheet 2004–3088, 2 p. 
References 25 

Kulongoski, J.T., Belitz, K., and Dawson, B.J., 2006, Groundwater quality data in the North San Francisco Bay Hydrologic Provinces, California, 2004—Results from the California Ground-Water Ambient Monitoring and Assessment 

(GAMA) Program: U.S. Geological Survey Data Series 

167, 100 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, version 

1.3, 9 November 2005, chapters and appendixes variously 

paged, accessed on December 8, 2006, at: http://pubs.usgs. 

gov/of/2005/1263/pdf/OFR2005-1263.pdf). 

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

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

generation atomic absorption spectrometry: U.S. Geological 

Survey Water-Resources Investigations Report 03–4117, 

14 p. 

Montgomery-Watson Consulting Engineers, 1994, Salinas 

River Basin water resources management plan task 1.09 

Salinas Valley groundwater flow and quality model report: 

Prepared for Monterey County Water-Resources Agency, 

33 p. 

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

contamination vulnerability assessment for the LivermoreAmador and Niles Cone Groundwater Basins: UCRL-AR148831, 25 p. 

Muir, K.S., 1980, Seawater intrusion and potential yield of 

aquifers in the Soquel-Aptos area, Santa Cruz County, California: U.S. Geological Survey Water Resources Investigations Report 80-84, 29 p. 

Muir, K.S., 1982, Ground water in the Seaside area, Monterey County, California: U.S. Geological Survey WaterResources Investigations Report 82-10, 37 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 phosphorus in water: U.S. 

Geological Survey Water-Resources Investigations Report 

03–4174, 33 p. 

Rose, D.L., and Sandstrom, M.W., 2003, Methods of analysis by the U.S. Geological Survey National Water Quality Laboratory—Determination of gasoline oxygenates, 

selected degradates, and BTEX in water by heated purge 

and trap/gas chromatography/mass spectrometry: U.S. 

Geological Survey Water-Resources Investigations Report 

03–4079, 31 p. 

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

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

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

Investigations Report 90-4101, 109 p. 

Showalter, P., Akers, J.P., and Swain, L.A., 1983, Design of 

a ground-water quality monitoring network for the Salinas 

River Basin, California: U.S. Geological Survey WaterResources Investigation Report 83-4049, 74 p. 

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

U.S. Geological Survey Techniques of Water-Resources 

Investigations, chapter A5, 95 p. 

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

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

95-352, 120 p. 

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

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

determination of dissolved Fe(III) concentration in acid 

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

p. 807–812. 

U.S. Environmental Protection Agency, 1980, Prescribed procedures for measurement of radioactivity in drinking water: 

(EPA/600/4-80-032), 6 p. 

U.S. Environmental Protection Agency, 1995, Method 524.2, 

Measurement of purgeable organic compounds in water by 

capillary column gas chromatography/mass spectrometry: 

U.S. Environmental Protection Agency EPA/600/R-95-131. 

U.S. Environmental Protection Agency, 1996, Method 

8270C—semivolatile organic compounds by gas chromatography/mass spectrometry, revision 3: U.S. Environmental 

Protection Agency, 54 p. 

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

Male-specific (F+) and somatic coliphage in water by twostep enrichment procedure: EPA-821-R-01-030, 32 p. 

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

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

Code of Federal Regulations, Title 40, 136 p. 

U.S. Environmental Protection Agency, 2002b, Method 

1604—Total coliforms and Escherichia coli in water by 

membrane filtration using a simultaneous detection technique (MI medium): 14 p. 
26 Ground-Water Quality Data, Monterey Bay and Salinas Valley Basins 2005—Results, Calif. GAMA Program 

U.S. Environmental Protection Agency and others, 2004, 

National primary drinking water regulations, analytical 

method for uranium: U.S. Code of Federal Regulations, 

Title 40, part 141, revised as of June 2004, p. 31008– 

31013. 

U.S. Geological Survey, 2006, National field manual for the 

collection of water-quality data: U.S. Geological Survey 

Techniques of Water-Resources Investigations, book 9, 

chaps. A1–A9, accessed on July 7, 2006, at http://pubs. 

water.usgs.gov/twri9A. 

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

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

p. 721–735. 

Wright, M.T., Belitz, K., and Burton, C.A., 2005, California 

GAMA Program; Ground-water quality in the San Diego 

Drainages hydrogeologic province, California, 2004: U.S. 

Geological Survey Data Series 129, 91 p. 
Tables 27
 

TABLES
 
Table 1. 

W , California, July to October 2005—Continued. 

[Sampling schedule: Well schedules described in table 3. MSMB, Monterey Bay study area well; MSMBFP, Monterey Bay study area flow-path well; 

MSMBMW, Monterey Bay study area monitoring well; MSPR, Paso Robles study area well; MSSC, Santa Cruz study area well; MSSV, Salinas Valley 

study area well; ft, feet; LSD, land surface datum; MW, monitoring well schedule; mm/dd/yy, month/day/year; nd, no data] 

2 Ground-Water Quality Data, Monterey Bay and Salinas Valley Basins 2005—Results, Calif. GAMA Program 

Table 1. Identification, sampling, and construction information for wells sampled for the Monterey Identification, sampling, and construction information for wells sampled for the Monterey Bay and Salinas V Bay and Salinas V alley Ground- alley GroundW ater Ambient Monitoring and Assessment (GAMA) study ater Ambient Monitoring and Assessment (GAMA) study, California, July to October 2005. 

[Sampling schedule: Well schedules described in table 3. MSMB, Monterey Bay study area well; MSMBFP, Monterey Bay study area flow-path well; 

MSMBMW, Monterey Bay study area monitoring well; MSPR, Paso Robles study area well; MSSC, Santa Cruz study area well; MSSV, Salinas Valley study 

area well; ft, feet; LSD, land surface datum; MW, monitoring well schedule; mm/dd/yy, month/day/year; nd, no data] 

GAMA Sampling information Construction information 

identification 

No. 

Date 

(mm/dd/yy) 

Sampling 

schedule 

Well depth 

(ft below LSD) 

Top of highest 

perforation 

(ft below LSD) 

Bottom of lowest 

perforation 

(ft below LSD) 

Monterey Bay wells 

MSMB-01 08/04/05 Fast nd nd nd 

MSMB-02 08/10/05 Fast 288 188 218 

MSMB-03 08/31/05 Fast 1,364 1,301 1,361 

MSMB-04 08/17/05 Slow 800 200 800 

MSMB-05 08/08/05 Fast nd nd nd 

MSMB-06 08/08/05 Fast 600 240 585 

MSMB-07 08/08/05 Fast 680 470 580 

MSMB-08 08/16/05 Fast 550 440 520 

MSMB-09 08/15/05 Slow 466 198 446 

MSMB-10 08/30/05 Fast 600 500 600 

MSMB-11 08/18/05 Fast 590 300 nd 

MSMB-12 09/14/05 Slow nd nd nd 

MSMB-13 08/17/05 Fast 557 315 535 

MSMB-14 08/03/05 Fast nd nd nd 

MSMB-15 08/04/05 Fast nd nd nd 

MSMB-16 08/17/05 Fast 552 315 535 

MSMB-17 08/09/05 Fast 630 370 610 

MSMB-18 08/11/05 Slow nd nd nd 

MSMB-19 08/16/05 Fast 518 nd nd 

MSMB-20 08/16/05 Slow 177 103 147 

MSMB-21 09/20/05 Fast nd nd nd 

MSMB-22 09/19/05 Slow nd nd nd 

MSMB-23 08/30/05 Fast nd nd nd 

MSMB-24 08/09/05 Fast 600 300 600 

MSMB-25 09/15/05 Fast nd nd nd 

MSMB-26 08/11/05 Fast 650 451 624 

MSMB-27 08/03/05 Fast 610 nd nd 

MSMB-28 08/03/05 Fast nd nd nd 

MSMB-29 08/30/05 Slow 274 129 256 

MSMB-30 08/08/05 Slow 668 475 652 

MSMB-31 08/11/05 Fast 619 198 607 

MSMB-32 08/31/05 Fast 214 nd nd 

MSMB-33 09/13/05 Slow nd nd nd 

MSMB-34 08/16/05 Fast 510 220 490 

MSMB-35 09/20/05 Slow nd nd nd 

MSMB-36 08/10/05 Fast 640 392 620 

MSMB-37 09/01/05 Slow 810 310 810 

MSMB-38 08/11/05 Fast 630 360 610 

MSMB-39 09/19/05 Fast nd nd nd 

MSMB-40 08/29/05 Slow nd nd nd 

MSMB-41 09/20/05 Fast nd nd nd 

MSMB-42 08/10/05 Fast 105 55 95 

MSMB-43 09/23/05 Fast nd nd nd 

MSMB-441 09/19/05 Fast nd nd nd 

MSMB-441 09/22/05 Slow nd nd nd 
Tables 2 

Table 1. Identification, sampling, and construction information for wells sampled for the Monterey Bay and Salinas Valley GroundWater Ambient Monitoring and Assessment (GAMA) study, California, July to October 2005—Continued. 

[Sampling schedule: Well schedules described in table 3. MSMB, Monterey Bay study area well; MSMBFP, Monterey Bay study area flow-path well; 

MSMBMW, Monterey Bay study area monitoring well; MSPR, Paso Robles study area well; MSSC, Santa Cruz study area well; MSSV, Salinas Valley 

study area well; ft, feet; LSD, land surface datum; MW, monitoring well schedule; mm/dd/yy, month/day/year; nd, no data] 

GAMA Sampling information Construction information 

identification 

No. 

Date 

(mm/dd/yy) 

Sampling 

schedule 

Well depth 

(ft below LSD) 

Top of highest 

perforation 

(ft below LSD) 

Bottom of lowest 

perforation 

(ft below LSD) 

Monterey Bay wells—Continued 

MSMB-45 08/10/05 Slow 148 55 128 

MSMB-46 09/20/05 Fast nd nd nd 

MSMB-47 08/03/05 Slow nd nd nd 

MSMB-48 09/21/05 Fast nd nd nd 

MSMBFP-01 08/17/05 Fast 1,650 970 1,100 

MSMBFP-021 08/09/05 Fast 524 360 524 

MSMBFP-021 08/31/05 Slow 524 360 524 

MSMBFP-03 08/09/05 Slow 342 120 340 

MSMBMW-01 09/21/05 MW nd nd nd 

MSMBMW-02 09/22/05 MW nd nd nd 

MSMBMW-03 09/22/05 MW nd nd nd 

Paso Robles wells 

MSPR-01 07/19/05 Slow 500 150 500 

MSPR-02 07/27/05 Fast 290 120 290 

MSPR-03 07/28/05 Fast 680 260 660 

MSPR-04 07/28/05 Fast 775 275 775 

MSPR-05 07/27/05 Fast 840 nd nd 

MSPR-06 07/27/05 Fast 166 126 166 

MSPR-07 07/21/05 Fast nd nd nd 

MSPR-08 07/20/05 Slow 300 100 300 

MSPR-09 07/18/05 Fast 502 nd nd 

MSPR-10 07/18/05 Slow 238 nd nd 

MSPR-11 07/21/05 Fast nd nd nd 

Santa Cruz wells 

MSSC-01 08/29/05 Fast nd nd nd 

MSSC-02 09/12/05 Fast nd nd nd 

MSSC-03 08/29/05 Fast 117 30 100 

MSSC-04 08/25/05 Slow 360 155 355 

MSSC-05 08/30/05 Fast 1,700 700 1,670 

MSSC-06 08/24/05 Slow 230 110 200 

MSSC-07 08/23/05 Slow 656 232 644 

MSSC-08 09/15/05 Slow 238 204 238 

MSSC-09 08/31/05 Fast nd nd nd 

MSSC-10 08/29/05 Fast 540 380 520 

MSSC-11 09/13/05 Fast 320 255 320 

MSSC-12 09/12/05 Fast nd nd nd 

MSSC-13 09/13/05 Fast nd nd nd 

Salinas Valley wells 

MSSV-01 07/26/05 Slow nd nd nd 

MSSV-021 07/28/05 Fast 130 80 130 

MSSV-021 08/04/05 Slow 130 80 130 

MSSV-031 08/02/05 Fast 140 90 140 

MSSV-031 09/12/05 Slow 140 90 140 

MSSV-04 08/02/05 Fast 432 120 424 

MSSV-05 07/25/05 Fast 190 110 180 

MSSV-06 08/02/05 Fast 220 160 220 
30 Ground-Water Quality Data, Monterey Bay and Salinas Valley Basins 2005—Results, Calif. GAMA Program 

Table 1. Identification, sampling, and construction information for wells sampled for the Monterey Bay and Salinas Valley GroundWater Ambient Monitoring and Assessment (GAMA) study, California, July to October 2005—Continued. 

[Sampling schedule: Well schedules described in table 3. MSMB, Monterey Bay study area well; MSMBFP, Monterey Bay study area flow-path well; 


MSMBMW, Monterey Bay study area monitoring well; MSPR, Paso Robles study area well; MSSC, Santa Cruz study area well; MSSV, Salinas Valley 


study area well; ft, feet; LSD, land surface datum; MW, monitoring well schedule; mm/dd/yy, month/day/year; nd, no data]
 

GAMA Sampling information Construction information 

identification 

No. 

Date 

(mm/dd/yy) 

Sampling 

schedule 

Well depth 

(ft below LSD) 

Top of highest 

perforation 

(ft below LSD) 

Bottom of lowest 

perforation 

(ft below LSD) 

Salinas Valley wells—Continued 

MSSV-07 08/02/05 Slow 212 130 202 

MSSV-08 08/04/05 Fast nd nd nd 

MSSV-09 09/14/05 Fast nd nd nd 

MSSV-10 09/21/05 Fast nd nd nd 

MSSV-11 07/25/05 Slow 883 313 863 

MSSV-12 08/01/05 Fast nd nd nd 

MSSV-13 09/15/05 Fast 300 nd nd 

MSSV-14 08/01/05 Fast 235 106 232 

MSSV-15 08/01/05 Fast 200 60 180 

MSSV-16 09/14/05 Fast 800 200 790 

MSSV-17 09/14/05 Fast nd nd nd 

MSSV-18 08/01/05 Slow nd nd nd 

MSSV-19 07/27/05 Slow 830 500 816 

1

Wells sampled twice. 
Table 2A. Volatile organic compounds and gasoline additives, primary use or source, U.S. Geological Survey (USGS) parameter 

code, Chemical Abstract Service (CAS) number, laboratory reporting level (LRL) for the USGS National Water Quality Laboratory 

analytical schedule 2020, type of comparison threshold for ground-water detections, and the corresponding threshold value— 

Continued. 

[The five-digit USGS parameter code is used to uniquely identify a specific constituent or property; DLR, California Department of Health Services 

detection limit for the purposes of reporting; HAL-US, U.S. Environmental Protection Agency Lifetime Health Advisory; MCL-CA, California 

Department of Health Services maximum contaminant level; MCL-US, U.S. Environmental Protection Agency maximum contaminant level; NL-CA, California Department of Health Services notification level; RSD5-US, U.S. Environmental Protection Agency risk specific dose at a risk factor of 10E-5 μg/L; 

na, not available; μg/L, micrograms per liter] 

 

Tables 31 

Table 2A. Volatile organic compounds and gasoline additives, primary use or source, U.S. Geological Survey (USGS) parameter code, 

Chemical Abstract Service (CAS) number, laboratory reporting level (LRL) for the USGS National Water Quality Laboratory analytical 

schedule 2020, type of comparison threshold for ground-water detections, and the corresponding threshold value. 

[The five-digit USGS parameter code is used to uniquely identify a specific constituent or property; DLR, California Department of Health Services detection 

limit for the purposes of reporting; HAL-US, U.S. Environmental Protection Agency Lifetime Health Advisory; MCL-CA, California Department of Health 

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

Health Services notification level; RSD5-US, U.S. Environmental Protection Agency risk specific dose at a risk factor of 10E-5 μg/L; na, not available; 

μg/L, micrograms per liter] 

USGS Threshold Constituent Primary use CAS LRL Threshold parameter value (common name) or source number (μg/L) type code (μg/L) 

Acetone Solvent 81552 67-64-1 6 na na 

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

Benzene Gasoline hydrocarbon 34030 71-43-2 0.021 MCL-CA 1 

Bromobenzene Solvent 81555 108-86-1 0.028 na na 

Bromochloromethane Fire retardant 77297 74-97-5 0.12 HAL-US 90 

Bromodichloromethane (THM) Disinfection by-product 32101 75-27-4 0.028 MCL-US1 80 

Bromoform (Tribromomethane, THM) Disinfection by-product 32104 75-25-2 0.1 MCL-US1 80 

2-butanone (MEK, Methyl ethyl ketone) Solvent 81595 78-93-3 2 HAL-US 4,000 

n-Butylbenzene Gasoline hydrocarbon 77342 104-51-8 0.12 NL-CA 260 

sec-Butylbenzene Gasoline hydrocarbon 77350 135-98-8 0.06 NL-CA 260 

tert-Butylbenzene Gasoline hydrocarbon 77353 98-06-6 0.06 NL-CA 260 

Carbon disulfide Organic synthesis 77041 75-15-0 0.038 NL-CA 160 

Carbon tetrachloride (Tetrachloromethane) Solvent 32102 56-23-5 0.06 MCL-CA 0.5 

Chlorobenzene Solvent 34301 108-90-7 0.028 MCL-CA 70 

Chloroethane Solvent 34311 75-00-3 0.12 na na 

Chloroform (Trichloromethane, THM)) Disinfection by-product 32106 67-66-3 0.024 MCL-US1 80 

Chloromethane Refrigerant/organic synthesis 34418 74-87-3 0.17 HAL-US 30 

3-Chloro-1-propene Organic synthesis 78109 107-05-1 0.5 na na 

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

4-Chlorotoluene Solvent 77277 106-43-4 0.05 NL-CA 140 

Dibromochloromethane (THM) Disinfection by-product 32105 124-48-1 0.10 MCL-US1 80 

1,2-Dibromo-3-chloropropane (DBCP) Fumigant 82625 96-12-8 0.51 MCL-US 0.2 

1,2-Dibromoethane (EDB) Fumigant 77651 106-93-4 0.036 MCL-US 0.05 

Dibromomethane Solvent 30217 74-95-3 0.050 na na 

1,2-Dichlorobenzene Solvent 34536 95-50-1 0.048 MCL-CA 600 

1,3-Dichlorobenzene Solvent 34566 541-73-1 0.03 HAL-US 600 

1,4-Dichlorobenzene Fumigant 34571 106-46-7 0.034 MCL-CA 5 

trans-1,4-Dichloro-2-butene Organic synthesis 73547 110-57-6 0.70 na na 

Dichlorodifluoromethane (CFC-12) Refrigerant 34668 75-71-8 0.18 NL-CA 1,000 

1,1-Dichloroethane Solvent 34496 75-34-3 0.035 MCL-CA 5 

1,2-Dichloroethane Solvent 32103 107-06-2 0.13 MCL-CA 0.5 

1,1-Dichloroethene (DCE) Organic synthesis 34501 75-35-4 0.024 MCL-CA 6 

cis-1,2-Dichloroethene Solvent 77093 156-59-2 0.024 MCL-CA 6 

trans-1,2-Dichloroethene Solvent 34546 156-60-5 0.032 MCL-CA 10 

Dichloromethane (Methylene chloride) Solvent 34423 75-09-2 0.06 MCL-US 5 

1,2-Dichloropropane Fumigant 34541 78-87-5 0.029 MCL-US 5 

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

2,2-Dichloropropane Fumigant 77170 594-20-7 0.05 na na 

1,1-Dichloropropene Organic synthesis 77168 563-58-6 0.026 na na 

cis-1,3-Dichloropropene Fumigant 34704 10061-01-5 0.05 RSD5-US2 4 

trans-1,3-Dichloropropene Fumigant 34699 10061-02-6 0.09 RSD5-US2 4 

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

Diisopropyl ether (DIPE) Gasoline oxygenate 81577 108-20-3 0.10 na na 

Ethylbenzene Gasoline hydrocarbon 34371 100-41-4 0.030 MCL-CA 300 

Ethyl tert-butyl ether (ETBE) Gasoline oxygenate 50004 637-92-3 0.030 DLR 3 

Ethyl methacrylate Organic synthesis 73570 97-63-2 0.18 na na 
 

32 Ground-Water Quality Data, Monterey Bay and Salinas Valley Basins 2005—Results, Calif. GAMA Program 

Table 2A. Volatile organic compounds and gasoline additives, primary use or source, U.S. Geological Survey (USGS) parameter 

code, Chemical Abstract Service (CAS) number, laboratory reporting level (LRL) for the USGS National Water Quality Laboratory 

analytical schedule 2020, type of comparison threshold for ground-water detections, and the corresponding threshold value— 

Continued. 

[The five-digit USGS parameter code is used to uniquely identify a specific constituent or property; DLR, California Department of Health Services 

detection limit for the purposes of reporting; HAL-US, U.S. Environmental Protection Agency Lifetime Health Advisory; MCL-CA, California 

Department of Health Services maximum contaminant level; MCL-US, U.S. Environmental Protection Agency maximum contaminant level; NL-CA, California Department of Health Services notification level; RSD5-US, U.S. Environmental Protection Agency risk specific dose at a risk factor of 10E-5 μg/L; 

na, not available; μg/L, micrograms per liter] 

USGS Threshold Constituent Primary use CAS LRL Threshold parameter value (common name) or source number (μg/L) type code (μg/L) 

1-Ethyl-2-methylbenzene (o-Ethyl Gasoline hydrocarbon 77220 611-14-3 0.06 na na 

toluene) 

Hexachlorobutadiene Organic synthesis 39702 87-68-3 0.14 RSD5-US 9 

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

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

Isopropylbenzene (Cumene) Gasoline hydrocarbon 77223 98-82-8 0.038 NL-CA 770 

4-Isopropyl-1-methylbenzene Gasoline hydrocarbon 77356 99-87-6 0.08 na na 

Methyl acrylate Organic synthesis 49991 96-33-3 1.0 na na 

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

Methyl bromide (Bromomethane) Fumigant 34413 74-83-9 0.33 HAL-US 10 

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

Methyl iodide (Iodomethane) Organic synthesis 77424 74-88-4 0.50 na na 

Methyl isobutyl ketone (MIBK) Solvent 78133 108-10-1 0.37 NL-CA 120 

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

Methyl tert-pentyl ether (tert-Amyl Gasoline oxygenate 50005 994-05-8 0.04 DLR 3 

methyl ether, TAME) 

Naphthalene Gasoline hydrocarbon 34696 91-20-3 0.52 NL-CA 17 

n-Propylbenzene Solvent 77224 103-65-1 0.042 NL-CA 260 

Styrene Gasoline hydrocarbon 77128 100-42-5 0.042 MCL-US 100 

1,1,1,2-Tetrachloroethane Solvent 77562 630-20-6 0.03 na na 

1,1,2,2-Tetrachloroethane Solvent 34516 79-34-5 0.08 MCL-CA 1 

Tetrachloroethene (PCE) Solvent 34475 127-18-4 0.030 MCL-US 5 

Tetrahydrofuran Solvent 81607 109-99-9 1.2 na na 

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

1,2,3,5-Tetramethylbenzene Gasoline hydrocarbon 50000 527-53-7 0.18 na na 

Toluene Gasoline hydrocarbon 34010 108-88-3 0.02 MCL-CA 150 

1,2,3-Trichlorobenzene Organic synthesis 77613 87-61-6 0.18 na na 

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

1,1,1-Trichloroethane (TCA) Solvent 34506 71-55-6 0.032 MCL-CA 200 

1,1,2-Trichloroethane Solvent 34511 79-00-5 0.04 MCL-CA 5 

Trichloroethene (TCE) Solvent 39180 79-01-6 0.038 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 0.18 NL-CA 0.005 

1,1,2-Trichloro-1,2,2-trifluoroethane Refrigerant 77652 76-13-1 0.038 MCL-CA 1,200 

(CFC-113) 

1,2,3-Trimethylbenzene Gasoline hydrocarbon 77221 526-73-8 0.09 na na 

1,2,4-Trimethylbenzene Gasoline hydrocarbon 77222 95-63-6 0.056 NL-CA 330 

1,3,5-Trimethylbenzene Organic synthesis 77226 108-67-8 0.044 NL-CA 330 

Vinyl bromide (Bromoethene) Fire retardant 50002 593-60-2 0.10 na na 

Vinyl chloride (Chloroethene) Organic synthesis 39175 75-01-4 0.08 MCL-CA 0.5 

m- and p-Xylene Gasoline hydrocarbon 85795 108-38-3 / 0.06 MCL-CA 1,750 

106-42-3 

o-Xylene Gasoline hydrocarbon 77135 95-47-6 0.038 MCL-CA 1,750 

1

The MCL-US, and MCL-CA thresholds for trihalomethanes are the sum of chloroform, bromoform, bromodichloromethane, and dibromochloromethane. 

2

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

Tables 33 

Table 2B. Gasoline additives, gasoline oxygenates, and gasoline degradates, primary use or source, U.S. Geological Survey 

(USGS) parameter code, Chemical Abstract Service (CAS) number, laboratory reporting level (LRL) for the USGS National Water 

Quality Laboratory analytical schedule 4024, type of comparison threshold for ground-water detections, and the corresponding 

threshold value. 

[The five-digit USGS parameter code is used to uniquely identify a specific constituent or property; DLR, California Department of Health Services 

detection limit for the purposes of reporting; HAL-US, U.S. Environmental Protection Agency Lifetime Health Advisory; MCL-US, U.S. Environmental 

Protection Agency maximum contaminant level; NL-CA, California Department of Health Services notification level; na, not available; μg/L, micrograms 

per liter] 

USGS Threshold Constituent Primary use CAS LRL Threshold parameter value (common name) or source number (μg/L) type code (μg/L) 

Acetone Solvent 81552 67-64-1 1.2 na na 

tert-Amyl alcohol Gasoline oxygenate 77073 75-85-4 1.0 na na 

tert-Butyl alcohol (TBA) Oxygenate/degradate 77035 75-65-0 1 NL-CA 12 

Diisopropyl ether Gasoline oxygenate 81577 108-20-3 0.06 na na 

Ethyl tert-butyl ether (ETBE) Gasoline oxygenate 50004 637-92-3 0.06 DLR 3 

Methyl acetate Solvent 77032 79-20-9 0.43 na na 

Methyl tert-butyl ether (MTBE) Gasoline oxygenate 78032 1634-04-4 0.05 MCL-US 13 

Methyl tert-pentyl ether Gasoline oxygenate 50005 994-05-8 0.05 DLR 3 
T 

ponding threshold value—Continued. 

iv 

v y 

maximum contaminant lev ic dose at a risk f v 

 

34 Ground-Water Quality Data, Monterey Bay and Salinas Valley Basins 2005—Results, Calif. GAMA Program 

T able 2C. able 2C. Pesticides and pesticide degradates, primary use or source, U.S. G Pesticides and pesticide degradates, primary use or source, U.S. Geological Survey (USGS) parameter code, Chemical eological Survey (USGS) parameter code, Chemical

Abstract Service (CAS) number Abstract Service (CAS) number, laboratory reporting level (LRL) for the USGS National W , laboratory reporting level (LRL) for the USGS National Water Quality Laboratory analytical schedule ater Quality Laboratory analytical schedule

2003, type of comparison threshold for ground-water detections, and the corres 2003, type of comparison threshold for ground-water detections, and the corresponding threshold value. 

[The f - [The fiv e-digit USGS parameter code is used to uniquely identify a specif e-digit USGS parameter code is used to uniquely identify a specif ic constituent or property; HAL-US, U.S. En ic constituent or property; HAL-US, U.S. En vironmental Protection Agenc vironmental Protection Agenc y Life y Life­ time Health Advisory; MCL-CA, California Department of Health Services maximum contaminant le time Health Advisory; MCL-CA, California Department of Health Services maximum contaminant lev el; MCL-US, U.S. En el; MCL-US, U.S. En vironmental Protection Agenc vironmental Protection Agency 

maximum contaminant lev el; RSD5-US, U.S. En el; RSD5-US, U.S. En vironmental Protection Agenc vironmental Protection Agenc y risk specif y risk specific dose at a risk f actor of 10E-5 μg/L; na, not a actor of 10E-5 μg/L; na, not av ailable; μg/L, ailable; μg/L, 

micrograms per liter] micrograms per liter]

Constituent 

(common name) 

Primary use 

or source 

USGS 

parameter 

code 

CAS 

number

 LRL 

(μg/L) 

Threshold 

type 

Threshold 

value 

(μg/L) 

Acetochlor Herbicide 49260 34256-82-1 0.006 na na 

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

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

Azinphos-methyl Insecticide 82686 86-50-0 0.05 na na 

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

Benfluralin Herbicide 82673 1861-40-1 0.01 na na 

Carbaryl Insecticide 82680 63-25-2 0.041 RSD5-US 400 

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

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

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

Chlorpyrofos, oxygen analog Insecticide degradate 61636 5598-15-2 0.0562 na na 

Cyfluthrin Insecticide 61585 68359-37-5 0.053 na na 

Cypermethrin Insecticide 61586 52315-07-8 0.046 na na 

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

Deethylatrazine (2-Chloro-4-isopropylami- Herbicide degradate 4040 6190-65-4 0.014 na na 

no-6-amino-s-triazine) 

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 0.0045 na na 

Dichlorvos Insecticide 38775 62-73-7 0.013 na na 

Dicrotophos Insecticide 38454 141-66-2 0.0843 na na 

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

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

Dimethoate Insecticide 82662 60-51-5 0.0061 na na 

Ethion Insecticide 82346 563-12-2 0.016 na na 

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

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

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

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

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

Fipronil Insecticide 62166 120068-37-3 0.016 na na 

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

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

Fonofos Insecticide 4095 944-22-9 0.0053 HAL-US 10 

Hexazinone Herbicide 4025 51235-04-2 0.026 HAL-US 400 

Iprodione Fungicide 61593 36734-19-7 0.026 na na 

Isofenphos Insecticide 61594 25311-71-1 0.011 na na 

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

Malathion Insecticide 39532 121-75-5 0.027 HAL-US 100 

Metalaxyl Fungicide 61596 57837-19-1 0.0069 na na 

Methidathion Insecticide 61598 950-37-8 0.0087 na na 

Metolachlor Herbicide 39415 51218-45-2 0.006 HAL-US 700 

Metribuzin Herbicide 82630 21087-64-9 0.028 HAL-US 70 

Myclobutanil Fungicide 61599 88671-89-0 0.033 na na 

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

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

Parathion-methyl Insecticide 82667 298-00-0 0.015 HAL-US 1 

Pendimethalin Herbicide 82683 40487-42-1 0.022 na na 

cis-Permethrin Insecticide 82687 54774-45-7 0.006 na na 
 

Tables 35 

Table 2C. Pesticides and pesticide degradates, primary use or source, U.S. Geological Survey (USGS) parameter code, Chemical 

Abstract Service (CAS) number, laboratory reporting level (LRL) for the USGS National Water Quality Laboratory analytical schedule 

2003, type of comparison threshold for ground-water detections, and the corresponding threshold value—Continued. 

[The five-digit USGS parameter code is used to uniquely identify a specific constituent or property; HAL-US, U.S. Environmental Protection Agency Lifetime Health Advisory; MCL-CA, California Department of Health Services maximum contaminant level; MCL-US, U.S. Environmental Protection Agency 

maximum contaminant level; RSD5-US, U.S. Environmental Protection Agency risk specific dose at a risk factor of 10E-5 μg/L; na, not available; μg/L, 

micrograms per liter] 

Constituent 

(common name) 

Primary use 

or source 

USGS 

parameter 

code 

CAS 

number

 LRL 

(μg/L) 

Threshold 

type 

Threshold 

value 

(μg/L) 

Phorate Insecticide 82664 298-02-2 0.055 na na 

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

Phosmet Insecticide 61601 732-11-6 0.0079 na na 

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

Prometon Herbicide 4037 1610-18-0 0.01 HAL-US 100 

Prometryn Herbicide 4036 7287-19-6 0.0059 na na 

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

Simazine Herbicide 4035 122-34-9 0.005 MCL-US 4 

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

Terbufos Insecticide 82675 13071-79-9 0.017 HAL-US 0.4 

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

Terbuthylazine Herbicide 4022 5915-41-3 0.0083 na na 

Trifluralin Herbicide 82661 1582-09-8 0.009 HAL-US 10 
Table 2D. 

ponding threshold value—Continued. 

[The five-digit USGS parameter code is used to uniquely identify a specific constituent or property; HAL-US, U.S. Environmental Protection Agency Lifetime Health Advisory; MCL-CA, California Department of Health Services maximum contaminant level; MCL-US, U.S. Environmental Protection Agency 

maximum contaminant level; na, not available; RSD5, risk specific dose at 10E-5 μg/L; μg/L, micrograms per liter] 

 

36 Ground-Water Quality Data, Monterey Bay and Salinas Valley Basins 2005—Results, Calif. GAMA Program 

Table 2D. Pesticides and pesticide degradates, primary use or source, U.S. G Pesticides and pesticide degradates, primary use or source, U.S. G eological Survey (USGS) parameter code, Chemical eological Survey (USGS) parameter code, Chemical 

Abstract Service (CAS) number Abstract Service (CAS) number, laboratory reporting level (LRL) for the USGS National W , laboratory reporting level (LRL) for the USGS National Water Quality Laboratory analytical schedule ater Quality Laboratory analytical schedule 

2060, type of comparison threshold for ground-water detections, and the corres 2060, type of comparison threshold for ground-water detections, and the corresponding threshold value. 

[The five-digit USGS parameter code is used to uniquely identify a specific constituent or property; HAL-US, U.S. Environmental Protection Agency Lifetime 

Health Advisory; MCL-CA, California Department of Health Services maximum contaminant level; MCL-US, U.S. Environmental Protection Agency maximum contaminant level; na, not available; RSD5, risk specific dose at 10E-5 μg/L; μg/L, micrograms per liter] 

USGS Threshold Constituent Primary use CAS LRL Comparison parameter value (common name) or source number (μg/L) type code (μg/L) 

Acifluorfen Herbicide 49315 50594-66-6 0.028 na na 

Aldicarb1 Insecticide 49312 116-06-3 0.04 MCL-US 3 

Aldicarb sulfone Insecticide/ 49313 1646-88-4 0.018 MCL-US 3 

degradate 

Aldicarb sulfoxide Degradate 49314 1646-87-3 0.022 MCL-US 4 

Atrazine Herbicide 39632 1912-24-9 0.008 MCL-CA 1 

Bendiocarb Insecticide 50299 22781-23-3 0.020 na na 

Benomyl Fungicide 50300 17804-35-2 0.022 na na 

Bensulfuron-methyl Herbicide 61693 83055-99-6 0.018 na na 

Bentazon Herbicide 38711 25057-89-0 0.012 MCL-CA 18 

Bromacil Herbicide 04029 314-40-9 0.018 HAL-US 70 

Bromoxynil Herbicide 49311 1689-84-5 0.028 na na 

Caffeine Beverages 50305 58-08-2 0.018 na na 

Carbaryl Herbicide 49310 63-25-2 0.018 RSD5-US 400 

Carbofuran Herbicide 49309 1563-66-2 0.016 MCL-CA 18 

Chloramben, methyl ester Herbicide 61188 7286-84-2 0.024 na na 

Chlorimuron-ethyl Herbicide 50306 90982-32-4 0.032 na na 

3-(4-Chlorophenyl)-1-methyl urea Degradate 61692 5352-88-5 0.036 na na 

Chlorothalonil Herbicide 49306 1897-45-6 0.035 RSD5 15 

Clopyralid Herbicide 49305 1702-17-6 0.024 na na 

Cycloate Herbicide 04031 1134-23-2 0.014 na na 

2,4-D (2,4-Dichlorophenoxyacetic acid) Herbicide 39732 94-75-7 0.038 MCL-US 70 

2,4-D methyl ester (2,4-Dichlorophenoxyacetic acid Herbicide 50470 1928-38-7 0.016 na na 

methyl ester) 

2,4-DB (4-(2,4-Dichlorophenoxy)butyric acid) Herbicide 38746 94-82-6 0.020 na na 

DCPA (Dacthal) monoacid Degradate 49304 887-54-7 0.028 na na 

Deethylatrazine (2-Chloro-4-isopropylamino-6-amino- Degradate 04040 6190-65-4 0.028 na na 

s-triazine; CIAT) 

Deethyldeisopropyl atrazine (2-Chlor-4,6-diamino-s- Degradate 04039 3397-62-4 0.04 na na 

triazine) 

Deisopropyl atrazine (2-chloro-6-ethylamino-4-amino- Degradate 04038 1007-28-9 0.08 na na 

s-triazine; CEAT) 

Dicamba Herbicide 38442 1918-00-9 0.036 HAL-US 4,000 

Dichlorprop Herbicide 49302 120-36-5 0.028 na na 

Dinoseb Herbicide 49301 88-85-7 0.038 MCL-CA 7 

Diphenamid Herbicide 04033 957-51-7 0.010 HAL-US 200 

Diuron Herbicide 49300 330-54-1 0.015 HAL-US 10 

Fenuron Herbicide 49297 101-42-8 0.019 na na 

Flumetsulam Herbicide 61694 98967-40-9 0.040 na na 

Fluometuron Herbicide 38811 2164-17-2 0.016 HAL-US 90 

Hydroxyatrazine (2-Hydroxy-4-isopropylamino-6­ Degradate 50355 2163-68-0 0.032 na na 

ethylamino-s-triazine) 

3-Hydroxycarbofuran Degradate 49308 16655-82-6 0.008 na na 

Imazaquin Herbicide 50356 81335-37-7 0.036 na na 

Imazethapyr Herbicide 50407 81335-77-5 0.038 na na 

Imidacloprid Insecticide 61695 138261-41-3 0.020 na na 

Linuron Herbicide 38478 330-55-2 0.014 na na 

MCPA (2-Methyl-4-chlorophenoxyacetic acid) Herbicide 38482 94-74-6 0.030 HAL-US 30 

MCPB (4-(2-Methyl-4-chlorophenoxy) butyric acid) Herbicide 38487 94-81-5 0.010 na na 

Metalaxyl Fungicide 50359 57837-19-1 0.012 na na 
 

Tables 37 

Table 2D. Pesticides and pesticide degradates, primary use or source, U.S. Geological Survey (USGS) parameter code, Chemical 

Abstract Service (CAS) number, laboratory reporting level (LRL) for the USGS National Water Quality Laboratory analytical schedule 

2060, type of comparison threshold for ground-water detections, and the corresponding threshold value—Continued. 

[The five-digit USGS parameter code is used to uniquely identify a specific constituent or property; HAL-US, U.S. Environmental Protection Agency Lifetime Health Advisory; MCL-CA, California Department of Health Services maximum contaminant level; MCL-US, U.S. Environmental Protection Agency 

maximum contaminant level; na, not available; RSD5, risk specific dose at 10E-5 μg/L; μg/L, micrograms per liter] 

USGS Threshold Constituent Primary use CAS LRL Comparison parameter value (common name) or source number (μg/L) type code (μg/L) 

Methiocarb Insecticide 38501 2032-65-7 0.010 na na 

Methomyl Insecticide 49296 16752-77-5 0.020 HAL-US 200 

Metsulfuron methyl1 Herbicide 61697 74223-64-6 0.025 na na 

Neburon Herbicide 49294 555-37-3 0.012 na na 

Nicosulfuron Herbicide 50364 111991-09-4 0.04 na na 

Norflurazon Herbicide 49293 27314-13-2 0.020 na na 

Oryzalin Herbicide 49292 19044-88-3 0.012 na na 

Oxamyl Insecticide 38866 23135-22-0 0.030 MCL-CA 50 

Picloram Herbicide 49291 1918-02-01 0.032 MCL-US 500 

Propham Herbicide 49236 122-42-9 0.030 HAL-US 100 

Propiconazole Fungicide 50471 60207-90-1 0.010 na na 

Propoxur Insecticide 38538 114-26-1 0.008 na na 

Siduron Herbicide 38548 1982-49-6 0.020 na na 

Sulfometuron-methyl Herbicide 50337 74222-97-2 0.038 na na 

Tebuthiuron Herbicide 82670 34014-18-1 0.026 HAL-US 500 

Terbacil Herbicide 04032 5902-51-2 0.016 HAL-US 90 

2,4,5-Trichlorophenoxyacetic acid (2,4,5-T) Negative ion 99958 93-76-5 0.1 na na 

surrogate/ 

herbicide 

Triclopyr Herbicide 49235 55335-06-3 0.026 na na 

1

Although listed as an LRLs, these constitiuents are reported using method reporting levels (MRLs). 
 

3 Ground-Water Quality Data, Monterey Bay and Salinas Valley Basins 2005—Results, Calif. GAMA Program 

Table 2E. Constituents of special interest, primary use or source, Chemical Abstract Service (CAS) number, Montgomery WatsonHarza Laboratory minimum reporting level (MRL), type of comparison threshold for ground-water detections, and the corresponding 

threshold value. 

[The five-digit USGS parameter code is used to uniquely identify a specific constituent or property; NL-CA, California notification level; μg/L, micrograms 

per liter] 

Threshold Constituent Primary use CAS MRL Comparison value (common name) or source number (μg/L) type (μg/L) 

Perchlorate Rocket fuel, fireworks, flares 14797-73-0 0.5 NL-CA 6 

1,2,3-Trichloropropane (TCP) Industrial solvent, organic synthesis 96-18-4 0.005 NL-CA 0.005 

N-Nitrosodimethylamine Rocket fuel, plasticizer, disinfection byproduct 62-75-9 0.002 NL-CA 0.010 

(NDMA) 
 

Tables 3 

Table 2F. Nutrients and dissolved organic carbon, U.S. Geological Survey (USGS) parameter code, Chemical Abstract Service 

(CAS) number, laboratory reporting level (LRL) for the USGS National Water Quality Laboratory (NWQL) analytical schedule 2755 and 

laboratory code 2613, type of comparison threshold for ground-water detections, and the corresponding threshold value. 

[The five-digit USGS parameter code is used to uniquely identify a specific constituent or property; HAL-US, U.S. Environmental Protection Agency lifetime health advisory level; MCL-US, U.S. Environmental Protection Agency maximum contaminant level; na, not available; mg/L, milligrams per liter] 

Constituent (common name) 

USGS 

parameter 

code 

CAS 

number

 LRL 

(mg/L) 

Comparison 

type 

Threshold 

value 

(mg/L) 

Ammonia 00608 7664-41-7 0.010 HAL-US 30 

Nitrite (as nitrogen) 00613 14797-65-0 0.002 MCL-US 1 

Nitrate plus nitrite (as nitrogen) 00631 na 0.060 MCL-US 10 

Total nitrogen (ammonia, nitrite, nitrate, organic nitrogen) 62854 17778-88-0 0.06 na na 

Phosphorus, phosphate, orthophosphate (as phosphorus) 00671 14265-44-2 0.006 na na 

Dissolved organic carbon (DOC) 00681 na 0.33 na na 
 

40 Ground-Water Quality Data, Monterey Bay and Salinas Valley Basins 2005—Results, Calif. GAMA Program 

Table 2G. Major and minor ions and trace elements, U.S. Geological Survey (USGS) parameter code, Chemical Abstract Service 

(CAS) number, laboratory reporting level (LRL) for the USGS National Water Quality Laboratory analytical schedule 1948, type of 

comparison threshold for ground-water detections, and the corresponding threshold value. 

[The five-digit USGS parameter code is used to uniquely identify a specific constituent or property; AL-US, U.S. Environmental Protection Agency action 

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

level; SMCL-CA, California Department of Health Services secondary maximum contaminant level; na, not available; mg/L, milligrams per liter; μg/L, 

micrograms per liter] 

USGS CAS Comparison Threshold Constituent parameter LRL number type value code 

Major and minor ions (mg/L) (mg/L) 

Bromide 71870 24959-67-9 0.02 na na 

Calcium 00915 7440-70-2 0.02 na na 

Chloride 00940 16887-00-6 0.2 SMCL-CA 1 250 (500) 

Fluoride 00950 16984-48-8 0.10 MCL-CA 2 

Iodide 78165 7553-56-2 0.002 na na 

Magnesium 00925 7439-95-4 0.008 na na 

Potassium 00935 7440-09-7 0.16 na na 

Silica 00955 7631-86-9 0.04 na na 

Sodium 00930 7440-23-5 0.20 na na 

Sulfate 00945 14808-79-8 0.18 SMCL-CA 1 250 (500) 

Residue on evaporation (total dissolved solids, TDS) 70300 na 10 SMCL-US 1 500 (1,000) 

Trace elements (μg/L) (μg/L) 

Aluminum 01106 7429-90-5 1.6 MCL-CA 1,000 

Antimony 01095 7440-36-0 0.2 MCL-US 6 

Arsenic 01000 7440-38-2 0.12 MCL-US 10 

Barium 01005 7440-39-3 0.2 MCL-CA 1,000 

Beryllium 01010 7440-41-7 0.06 MCL-US 4 

Boron 01020 7440-42-8 8 NL-CA 1,000 

Cadmium 01025 7440-43-9 0.04 MCL-US 5 

Chromium 01030 7440-47-3 0.04 MCL-CA 50 

Cobalt 01035 7440-48-4 0.04 na na 

Copper 01040 7440-50-8 0.4 AL-US 1,300 

Iron 01046 7439-89-6 6 SMCL-CA 300 

Lead 01049 7439-92-1 0.08 AL-US 15 

Lithium 01130 7439-93-2 0.6 na na 

Manganese 01056 7439-96-5 0.2 SMCL-CA 50 

Mercury 71890 7439-97-6 0.010 MCL-US 2 

Molybdenum 01060 7439-98-7 0.4 HAL-US 40 

Nickel 01065 7440-02-0 0.06 MCL-CA 100 

Selenium 01145 7782-49-2 0.08 MCL-US 50 

Silver 01075 7440-22-4 0.20 SMCL-CA 100 

Strontium 01080 7440-24-6 0.4 HAL-US 4,000 

Thallium 01057 7440-28-0 0.04 MCL-US 2 

Tungsten 01155 7440-33-7 0.06 na na 

Uranium 22703 7440-61-1 0.04 MCL-US 30 

Vanadium 01085 7440-62-2 0.10 NL-CA 50 

Zinc 01090 7440-66-6 0.6 HAL-US 2,000 

1

The recommended SMCL-CA thresholds for chloride, sulfate, and TDS are listed with the upper SMCL-CA thresholds in parentheses. 
Tables 41 

Table 2H. Arsenic, chromium, and iron speciation, U.S. Geological Survey (USGS) parameter code, Chemical 

Abstract Service (CAS) number, method detection level (MD), for the USGS Trace Metal Laboratory, Boulder, 

Colorado, type of comparison threshold for ground-water detections, and the corresponding threshold value. 

[The five-digit USGS parameter code is used to uniquely identify a specific constituent or property. DLR, California Department of Health 

Services detection limit for the purposes of reporting; HAL-US, U.S. Environmental Protection Agency lifetime health advisory; MCLCA, California Department of Health Services maximum contaminant level; MCL-US, U.S. Environmental Protection Agency maximum 

contaminant level; na, not available; μg/L, micrograms per liter] 

USGS Constituent CAS MD Comparison Threshold parameter (valence state) number (μg/L) type (μg/L) code 

Arsenic (III) 99034 22569-72-8 1 na na 

Arsenic (total) 01000 7440-38-2 0.5 MCL-US 10 

Chromium (VI), hexavalent 01032 18540-29-9 1 DLR 1 

Chromium (total) 01030 7440-47-3 1 MCL-CA 50 

Iron (II) 01047 7439-89-6 2 na na 

Iron (total) 01046 7439-89-6 2 HAL-US 300 
42 Ground-Water Quality Data, Monterey Bay and Salinas Valley Basins 2005—Results, Calif. GAMA Program 

Table 2I. Isotopic and radioactive constituents, U.S. Geological Survey (USGS) parameter code, Chemical Abstract Service (CAS) 

number, reporting level type, reporting level or uncertainty, type of comparison threshold for ground-water detections, and the 

corresponding threshold value. 

[The five-digit USGS parameter code is used to uniquely identify a specific constituent or property; MCL-CA, California Department of Health Services 

maximum contaminant level; MCL-US, U.S. Environmental Protection Agency maximum contaminant level; d, notation, in per mil, of the differences in 

oxygen-18/oxygen-16 and hydrogen-2/hydrogen-1 ratios relative to Standard Mean Ocean Water (SMOW), and the difference in the carbon-13/carbon-12 

ratio relative to University of Chicago Peedee Formation Standard; MRL, minimum reporting level; MU, method uncertainty; na, not available; pCi/L, 

picocuries per liter; SSMDC, sample specific minimum detectable concentration] 

Constituent 

USGS 

parameter 

code 

CAS 

number 

Reporting 

level type 

Reporting 

level or 

uncertainty 

Comparison 

type 

Threshold 

value 

Reporting 

units 

Radon-222 82303 14859-67-7 SSMDC see Table 19 Proposed MCL-US 300 pCi/L 

Tritium1 07000 10028-17-8 MRL 1 MCL-CA 20,000 pCi/L 

d2

H of water2 82082 na MU 2 na na Per mil 

d18O of water2 82085 na MU 0.20 na na Per mil 

Gross-alpha radioactivity, 

72 hr count3 

62636 12587-46-1 SSMDC see Table 19 MCL-US 15 pCi/L 

Gross-alpha radioactivity, 

30 day count3 

62639 12587-46-1 SSMDC see Table 19 MCL-US 15 pCi/L 

Gross-beta radioactivity, 

72 hr count3 

62642 12587-47-2 SSMDC see Table 19 MCL-CA 50 pCi/L 

Gross-beta radioactivity, 

30 day count3 

62645 12587-47-2 SSMDC see Table 19 MCL-CA 50 pCi/L 

Radium-2263 09511 13982-63-3 SSMDC see Table 19 MCL-US6 5 pCi/L 

Radium-2283 81366 15262-20-1 SSMDC see Table 19 MCL-US6 5 pCi/L 

d13C of dissolved inorganic 

carbon4 

82081 na 1 sigma 0.05 na na Per mil 

Carbon-145 49933 14762-75-5 1 sigma 0.002 na na Percent 

modern 

carbon 

1

USGS Stable Isotope and Tritium Laboratory, Menlo Park, California.
 

2

USGS Stable Isotope Laboratory, Reston, Virginia.
 

3

Eberline Analytical Services, Richmond, California.
 

4

University of Waterloo, Ontario, Canada.
 

5

University of Arizona, Accelerator Mass Spectrometry Laboratory, Tucson, Arizona.
 

6

The MCL-US threshold for radium is the sum of radium-226 and radium-228.
 
Tables 43 

Table 2J. Tritium and noble gases, Chemical Abstract Service (CAS) number, method uncertainty (MU) and reporting 

units for the Lawrence Livermore National Laboratory, type of comparison threshold for ground-water detections, and the 

corresponding threshold value. 

[The five-digit USGS parameter code is used to uniquely identify a specific constituent or property. MCL-CA, California Department of Health 

Services maximum contaminant level; na, not available; cm3 STP/g, cubic centimeters of gas at standard temperature and pressure per gram of 

water; pCi/L, picocuries per liter] 

Constituent CAS 

number 

MU 

(percent) 

Reporting 

units 

Threshold 

type 

High 

threshold 

(pCi/L) 

Argon 7440-37-1 2 cm3

STP/g na na 

Helium-3 / Helium-4 ratio na / 7440-59-7 0.75 na na na 

Helium-4 7440-59-7 2 cm3

STP/g na na 

Krypton 7439-90-9 2 cm3

STP/g na na 

Neon 7440-01-09 2 cm3

STP/g na na 

Tritium 10028-17-8 1 pCi/L MCL-CA 20,000 

Xenon 7440-63-3 2 cm3

STP/g na na 
 

44 Ground-Water Quality Data, Monterey Bay and Salinas Valley Basins 2005—Results, Calif. GAMA Program 

Table 2K. Microbial constituents, U.S. Geological Survey (USGS) parameter code, primary use or source, and method detection limit 

(MDL) for the USGS Ohio Microbiology Laboratory. 

[The five-digit USGS parameter code is used to uniquely identify a specific constituent or property; MCL-US, U.S. Environmental Protection Agency 

maximum contaminant level; na, not available; mL, milliliters; TT, treatment technique - a required process intended to reduce the level of contamination in 

drinking water] 

USGS Microbial Primary use Comparison Threshold parameter MDL constituent or source type value code 

Escherichia coliform 

(E. coli) 

90901 Sewage and animal waste 

indicator / Intestinal tracts 

of humans and animals 

1 colony / 

100 mL 

TT No fecal coliforms are allowed. 

Total coliform (including 

fecal coliform and 

E. coli) 

90900 Water-quality indicator / Soil, 

water, and intestinal tracts 

of animals 

1 colony / 

100 mL 

MCL-US No more than 5 percent samples total 

coliform-positives in a month. 

Every sample that has total coloforms must be analyzed for fecal 

coliforms; no fecal coliforms are 

allowed. 

F-specific coliphage 99335 Viral indicator / Intestinal 

tracts of warm-blooded 

na TT 99.99 percent killed / inactivated 

animals 

Somatic coliphage 99332 Viral indicator / Fecal contaminated waters 

na TT 99.99 percent killed / inactivated 
Tables 45 

Table 3. Classes of chemical and microbial constituents and water-quality indicators collected for the fast, slow, and monitoring 

well sampling schedules in the Monterey Bay and Salinas Valley Ground-Water Ambient Monitoring and Assessment (GAMA) 

study, California, July to October 2005. 

[DO, dissolved oxygen; NDMA, N-nitrosodimethylamine; SC, specific conductance] 

Fast schedule analyte list 

Water-quality indicators (SC and temperature) 

Volatile organic compounds 

Gasoline additives 

Pesticides and pesticide degradates 

Chromium abundance and speciation 

Stable isotopes of hydrogen and oxygen 

Tritium1 

Tritium and noble gases2 

Slow schedule analyte list 

Water-quality indicators (pH, SC, DO, temperature, alkalinity, turbidity) 

Volatile organic compounds 

Gasoline additives 

Pesticides and pesticide degradates 

Constituents of special interest (perchlorate, NDMA, 1,2,3-trichloropropane) 

Nutrients and dissolved organic carbon 

Major and minor ions and trace elements 

Chromium abundance and speciation 

Arsenic and iron speciation 

Stable isotopes of hydrogen and oxygen 

Carbon isotopes 

Radium isotopes 

Radon-222 

Tritium1 

Tritium and noble gases2 

Gross alpha and beta radiation 

Microbial constituents 

Monitoring well schedule analyte list 

Water-quality indicators (pH, SC, DO, temperature, alkalinity) 

Volatile organic compounds 

Gasoline additives 

Pesticides and pesticide degradates 

Constituents of special interest (perchlorate, NDMA, 1,2,3-trichloropropane) 

Nutrients and dissolved organic carbon 

Major and minor ions and trace elements 

Chromium abundance and speciation 

Arsenic and iron speciation 

Stable isotopes of hydrogen and oxygen 

Tritium1 

Tritium and noble gases2 

Gross alpha and beta radiation 

1

 Analyzed at the U.S. Geological Survey Stable Isotope and Tritium laboratory, Menlo Park, California. 

2

 Analyzed at the Lawrence Livermore National Laboratory, Livermore, California. 
46 Ground-Water Quality Data, Monterey Bay and Salinas Valley Basins 2005—Results, Calif. GAMA Program Table 4. Analytical methods used for the determination of organic, inorganic, and microbial constituents by the U.S. Geological Survey (USGS) National Water Quality Laboratory (NWQL) and additional contract laboratories. [MI agar, supplemented nutrient agar in which coliforms (total and Escherichia) produce distinctly different fluorescence under ultraviolet lighting; UV, ultraviolet; VOCs, volatile organic compounds; δ, del notation expressed as per mil] Analyte Method Laboratory Citation(s) VOCs Purge and trap capillary gas chromatography- NWQL Connor and others, 1998 mass spectrometry Gasoline additives and (or) Heated purge and trap, gas chromatography- NWQL Rose and Sandstrom, 2003 oxygenates mass spectrometry Pesticides and pesticide degradates Solid-phase extraction and chromatography- NWQL Sandstrom and others, 2001 mass spectrometry Major and minor ions, trace Inductively coupled plasma mass spectrometry, NWQL Fishman and Friedman, 1989; Fishman, 1993; elements and nutrients graphite furnace atomic absorption, atomic Garbarino, 1999; Garbarino and Damrau, fluorescence, and colorimetry 2001; Patton and Kryskalla, 2003 Dissolved organic carbon UV-promoted persulfate oxidation and infrared NWQL Brenton and Arnett, 1993 spectrometry Radon-222 Liquid scintillation counting NWQL American Society for Testing and Materials, 1998a, b Stable isotopes of water: δD and Gaseous hydrogen and carbon dioxide-water USGS Stable Isotope Laboratory, Reston, Coplen and others, 1991; Coplen, 1994

δ18O equilibration 

Virginia 

Chromium, arsenic, and iron Ultraviolet visible (UV-VIS) spectrophotometry USGS Trace Metal Laboratory, Boulder, To and others, 1998; Ball and McCleskey, 2003; 

speciation and atomic absorbance spectroscopy Colorado McCleskey and others, 2003

F-specific and somatic coliphage Single-agar layer (SAL) and two-step enrich- USGS Ohio Water Microbiology Labora- U.S. Environmental Protection Agency, 2001

ment methods tory 

Tritium Electrolytic enrichment-liquid scintillation USGS Stable Isotope and Tritium Labora- Thatcher and others, 1977

tory, Menlo Park, California 

Perchlorate and 

N-nitrosodimethyl- Chromatography and mass spectrometry Montgomery Watson-Harza Laboratory U.S. Environmental Protection Agency, 1996; 

amine (NDMA) Hautman and others, 1999

1,2,3-Trichloropropane Gas chromatography/electron-capture detector Montgomery Watson-Harza Laboratory U.S. Environmental Protection Agency, 1995

Tritium and noble gases Helium-3 in-growth and mass spectrometry Lawrence Livermore National Laboratory Clarke and others, 1976; Moran and others, 2002

Radium-226, -228, gross alpha/ Alpha activity counting Eberline Analytical Services U.S. Environmental Protection Agency, 1980

beta radioactivity 

Carbon isotopes: δ13C Accelerator mass spectrometry University of Waterloo, Environmental Donahue and others, 1990; Jull and others, 2004

Isotope Laboratory; University of Arizona Accelerator Mass SpectrometryLaboratory 

Total and Escherichia coliform Membrane filter technique with “MI agar,” USGS field measurement U.S. Environmental Protection Agency, 2002b 

colony counting 
Tables 47 

Table 5. Constituents analyzed in ground-water samples collected for the Monterey-Salinas Ground-Water Ambient Monitoring 

and Assessment (GAMA) study, California, July to October 2005, that appear on multiple analytical schedules, primary constituent 

classification, analytical schedules each constituent appears on, and preferred analytical schedule. 

[The preferred analytical methods had better accuracy, precision, or a lower reporting level for the respective constituent. Abbreviations: MWH, Montgomery Watson-Harza Laboratory; NPR, USGS National Research Program; NWQL, USGS National Water Quality Laboratory; USGS, U.S. Geological Survey; 

VOC, volatile organic compound] 

USGS NWQL Primary Preferred analytical Constituent constituent analytical schedules/ classification schedule methods 

1,2,3-Trichloropropane (1,2,3-TCP) VOC 2020, MHW MWH 

Acetone VOC 2020, 4024 2020 

Atrazine Pesticide 2003, 2060 2003 

Carbaryl Pesticide 2003, 2060 2003 

Deethylatrazine (2-Chloro-4-isopropylamino-6-amino-s-triazine) Pesticide degradate 2003, 2060 2003 

Diisopropyl ether VOC 2020, 4024 2020 

Ethyl tert-Butyl ether (ETBE) VOC 2020, 4024 2020 

Metalaxyl Pesticide 2003, 2060 2060 

Methyl tert-butyl ether (MTBE) VOC 2020, 4024 2020 

Methyl tert-pentyl ether VOC 2020, 4024 2020 

Tebuthiuron Herbicide 2003, 2060 2003 

Total arsenic Trace element 1948, NRP speciation 1948 

Total chromium Trace element 1948, NRP speciation 1948 

Total iron Trace element 1948, NRP speciation 1948 

Tritium Isotope ingrowth, counting ingrowth 
4 Ground-Water Quality Data, Monterey Bay and Salinas Valley Basins 2005—Results, Calif. GAMA Program 

 Table 6. Quality-control summary for volatile organic compounds, gasoline additives, pesticides, pesticide degradates, major and 

minor ions, trace elements, nutrients, and dissolved organic carbon detected in source-solution blanks, field blanks, and the minimum 

concentrations in ground-water samples collected for the Monterey Bay and Salinas Valley Ground-Water Ambient Monitoring and 

Assessment (GAMA) study, California, July to October 2005. 

[Data censored due to associated blank contamination are reported but not used in summary statistics; E, estimated value; μg/L, micrograms per liter; —, not 

detected]. 

Minimum Number of Maximum Number of concentration field blank concentration environmental Constituent detected in detections/ detected in samples environmental analyses field blanks censored1 

samples 

Volatile organic compounds and gasoline additives and (or) oxygenates (μg/L) 

Acetone 1/20 12 — 0 

2-Butanone (methyl ethyl ketone) 2/20 30.8 E0.9 0 

Carbon disulfide 2

2/20 E0.09 E0.02 0 

Chloroform (trichloromethane) 2

1/20 0.10 E0.01 0 

Ethylbenzene 2/20 E0.03 E0.07 0 

Tetrachloroethylene (PCE) 1/20 E0.03 E0.01 0 

Toluene 2

13/20 0.19 E0.01 4 

Trichlorofluoromethane 2

2/20 0.11 — 0 

1,2,4-Trimethylbenzene 1/20 0.56 E0.02 0 

m-Xylene plus p-xylene 3/20 E0.12 E0.03 0 

o-Xylene 2/20 E0.05 — 0 

Pesticide and (or) pesticide degradates (μg/L) 

none 

Nutrients and dissolved organic carbon (mg/L) 

Dissolved organic carbon (DOC) 5/5 40 E0.20 6 

Phosphorus, phosphate, orthophosphate (as phosphorus) E0.005 E0.005 0 

Major and minor ions (mg/L) 

Calcium 3/5 0.24 15.4 0 

Magnesium E0.007 0.64 0 

Silica 5/5 3.90 24.4 0 

Sodium 3/5 0.70 20.3 0 

Trace elements (μg/L) 

Aluminum 4/5 45 E1.0 1 

Arsenic 1/5 0.52 0.20 1 

Barium 2/5 0.20 4.00 0 

Chromium 2/5 0.09 E0.03 1 

Cobalt 1/5 0.04 E0.03 0 

Copper 1/5 3.10 E0.20 5 

Iron 2/5 21 E3.00 3 

Lead 2/5 0.14 E0.06 0 

Manganese 1/5 E0.20 E0.10 1 

Nickel 1/5 0.36 0.42 0 

Strontium 1/5 0.58 226 0 

Tungsten 1/5 0.36 0.15 0 

Vanadium 1/5 0.42 E0.10 0 

Zinc 2/5 3.70 0.38 0 

1

Environmental samples were not censored as a result of detections in the corresponding blank samples if the environmental samples taken prior to, and following the blank sample detections were free from the constituent observed in the blank sample. 

2

Constituents also detected in associated source-solution blanks.
Tables 4 

Table 7. Quality-control summary of replicate samples for constituents collected for the Monterey Bay and Salinas Valley GroundWater Ambient Monitoring and Assessment (GAMA) study, California, July to October 2005. 

[E, estimated value; mg/L, milligram per liter; μg/L, microgram per liter; na, not available; pCi/L, picocurie per liter; TU, tritium unit; <, less than] 

Number of relative 

Constitutent 

standard 

deviations 

greater than 

20 percent/ 

number of 

Maximum 

relative 

standard 

deviation 

(percent) 

Environmental 

value; 

replicate 

value 

replicate pairs 

Volatile organic compounds, gasoline oxygenates and additives from schedules 2020 and 4204 

Carbon disulfide (μg/L) 1/8 121 < 0.04; 0.13 

All additional VOCs from schedule 2020 and 4024 0/8 < 20 na 

Pesticides and pesticide degradates from schedules 2003 and 2060 

Caffeine (μg/L) 1/3 66 E 0.004; E 0.011 

All additional pesticides and pesticide degradates from schedule 2003 0/8 < 20 na 

All additional pesticides and pesticide degradates from schedule 2060 0/3 < 20 na 

Constituents of special interest1 

Perchlorate, 1,2,3-Trichloropropane, and N-Nitrosodimethylamine 0/1 < 20 na 

Major ions, minor ions, trace elements, and nutrients 

Dissolved organic carbon (mg/L) 1/3 28 E 0.2; E 0.3 

Arsenic (μg/L) 1/3 28 0.2; 0.3 

Iron (μg/L) 1/3 70 18; E 6 

Manganese (μg/L) 1/3 28 0.6; 0.4 

Zinc (μg/L) 1/3 110 6.5; 0.8 

All additional major ions, minor ions, trace elements, and nutrients from schedules 0/3 < 20 na 

1948 and 2755 

Isotopes, radioactivity, and noble gases 

Radium-2262

 (pCi/L) 1/2 75 0.02; 0.064 

Radium-2282 (pCi/L) 1/2 25 0.158; 0.110 

Tritium3

 (TU) 1/6 32 1.5; 2.3 

Tritium4

 (TU) 1/8 44 1.0; 1.9 

Alpha radioactivity, 72-hour count2

 (pCi/L) 1/2 141 0.02; 0.00 

Beta radioactivity, 72-hour count2

 (pCi/L) 1/2 22 3.7; 5.0 

All additional isotopes, radioactivity, and (noble gases)3 0/2 (0/9) < 20 na 

Microbial indicators 

F-specific and somatic coliphage 0/2 < 20 na 

E. Coli, and total coliforms 0/30 < 20 na 

1

Analyses performed at Montgomery Watson-Harza Laboratories, Monrovia, California. 

2

Analyses performed at Eberline Analytical Services, Richmond, California. 

3

Analyses performed at Lawrence Livermore National Laboratory, Livermore, California. 

4

Analyses performed at U.S. Geological Survey, Menlo Park, California. 
Table A. Quality-control summary of matrix spike recoveries of volatile organic compounds, gasoline additives, NDMA, perchlorate, 

and 1,2,3-trichloropropane in samples collected for the Monterey Bay and Salinas Valley Ground-Water Ambient Monitoring and 

Assessment (GAMA) study, California, July to October 2005—Continued.

[Acceptable recovery range is between 70 and 130 percent]

50 Ground-Water Quality Data, Monterey Bay and Salinas Valley Basins 2005—Results, Calif. GAMA Program 

Table A. Quality-control summary of matrix spike recoveries of volatile organic compounds, gasoline additives, NDMA, perchlorate, 

and 1,2,3-trichloropropane in samples collected for the Monterey Bay and Salinas Valley Ground-Water Ambient Monitoring and 

Assessment (GAMA) study, California, July to October 2005. 

[Acceptable recovery range is between 70 and 130 percent] 

Number Minimum Maximum Median 

Constituent (common name) of spiked recovery recovery recovery 

samples (percent) (percent) (percent) 

1,1,1,2-Tetrachloroethane 9 88 98 96 

1,1,1-Trichloroethane (TCA)1 9 96 104 98 

1,1,2,2-Tetrachloroethane 9 89 107 98 

1,1,2-Trichloroethane 9 79 100 89 

1,1,2-Trichlorotrifluoroethane (CFC-113) 9 84 105 96 

1,1-Dichloroethane1 9 94 103 98 

1,1-Dichloroethylene (DCE) 9 88 102 94 

1,1-Dichloropropene 9 95 138 102 

1,2,3,4-Tetramethylbenzene 9 97 121 106 

1,2,3,5-Tetramethylbenzene (isodurene) 9 111 124 115 

1,2,3-Trichlorobenzene1 9 94 118 102 

1,2,3-Trichloropropane 9 87 107 97 

1,2,3-Trimethylbenzene1 9 97 106 97 

1,2,4-Trichlorobenzene 9 88 106 97 

1,2,4-Trimethylbenzene 9 102 121 111 

1,2-Dibromo-3-chloropropane (DBCP) 9 91 113 102 

1,2-Dibromoethane 9 88 102 92 

1,2-Dichlorobenzene 9 87 109 100 

1,2-Dichloroethane 9 98 107 107 

1,2-Dichloropropane 9 89 96 94 

1,3,5-Trimethylbenzene 9 98 109 104 

1,3-Dichlorobenzene 9 89 104 98 

1,3-Dichloropropane 9 98 107 98 

1,4-Dichlorobenzene 9 87 104 98 

1,2,3-Tricholorpropane (TCP)2 4 88 103 90 

2,2-Dichloropropane 9 83 91 87 

2-Chlorotoluene 9 91 106 100 

2-Hexanone 9 93 108 98 

3-Chloropropene 9 100 110 103 

4-Chlorotoluene 9 91 104 100 

4-Isopropyl-1-methylbenzene 9 94 107 99 

4-Methyl-2-pentanone 9 88 103 92 

Acetone1,3 9 97 128 107 

Acrylonitrile 9 97 106 106 

Benzene 9 100 113 104 

Bromobenzene 9 88 98 94 

Bromochloromethane1 9 94 111 103 

Bromodichloromethane 9 96 106 100 

Bromoethene 9 96 128 112 

Bromoform (tribromomethane)1 9 82 100 93 

Bromomethane 9 86 139 118 

Butylbenzene 9 83 94 88 

Carbon disulfide1 9 71 95 88 

Chlorobenzene 9 88 104 94 

Chloroethane 9 88 106 88 

Chloroform (trichloromethane)1 9 94 126 100 

Chloromethane 9 88 119 100 

cis-1,2-Dichloroethylene1 9 94 106 102 

cis-1,3-Dichloropropene 9 82 92 86 

Dibromochloromethane1 9 89 107 95 

Dibromomethane 9 91 111 100 

Dichlorodifluoromethane (CFC-12) 9 59 91 88 
Tables 51 

Table A. Quality-control summary of matrix spike recoveries of volatile organic compounds, gasoline additives, NDMA, perchlorate, 

and 1,2,3-trichloropropane in samples collected for the Monterey Bay and Salinas Valley Ground-Water Ambient Monitoring and 

Assessment (GAMA) study, California, July to October 2005—Continued. 

[Acceptable recovery range is between 70 and 130 percent] 

Number Minimum Maximum Median 

Constituent (common name) of spiked recovery recovery recovery 

samples (percent) (percent) (percent) 

Dichloromethane (methylene chloride) 9 95 107 101 

Diethyl ether 9 100 113 100 

Diisopropyl ether1 9 90 105 97 

Ethyl methacrylate 9 86 98 90 

2-Butanone (Ethyl methyl ketone) 9 98 119 104 

Ethylbenzene 9 91 113 102 

Hexachlorobutadiene 9 84 99 92 

Hexachloroethane 9 89 106 95 

Isopropylbenzene 9 96 115 104 

m- and p-Xylene1 9 95 118 107 

Methyl acetate 4 96 106 102 

Methyl acrylate 9 94 108 102 

Methyl acrylonitrile 9 97 115 106 

Methyl iodide 9 80 152 124 

Methyl methacrylate 9 78 90 84 

Methyl tert-butyl ether (MTBE)1,3 9 94 110 94 

Naphthalene 9 89 128 104 

Nitrosodimethylamine (NDMA)2 4 81 95 91 

n-Propylbenzene 9 91 109 98 

o-Ethyl toluene 9 93 107 102 

o-Xylene1 9 93 105 100 

Perchlorate2 4 40 84 78 

sec-Butylbenzene 9 94 109 96 

Styrene 9 64 109 100 

Methyl tert-pentyl ether1 9 91 109 97 

tert-Amyl alcohol 4 83 97 94 

tert-Butyl alcohol 4 84 95 92 

tert-Butyl ethyl ether (ETBE)1 9 87 115 102 

tert-Butylbenzene 9 104 117 110 

Tetrachloroethylene (PCE)1 9 88 121 96 

Tetrachloromethane (carbon tetrachloride)1 9 91 104 98 

Tetrahydrofuran1 9 107 128 112 

Toluene1 9 91 100 96 

trans-1,2-Dichloroethylene 9 96 106 104 

trans-1,3-Dichloropropene 9 84 99 92 

trans-1,4-Dichloro-2-butene 9 91 121 108 

Trichloroethylene (TCE)1 9 90 100 94 

Trichlorofluoromethane (CFC-11) 9 85 101 96 

Vinyl chloride 9 96 125 106 1Constituents detected in ground-water samples. 

2

Constituents analyzed by Montgomery Watson-Harza Laboratory, Monrovia, California, on the Constitutents of Special Interest Schedule. 

3

Constituents on schedules 2020 and 4024; only values from schedule 2020 are reported because it is the preferred analytical schedule. 
Table B. 

, California, July 

to October 2005—Continued. 

[Acceptable recovery range is between 70 and 130 percent] 

52 Ground-Water Quality Data, Monterey Bay and Salinas Valley Basins 2005—Results, Calif. GAMA Program 

Table B. Quality-control summary of matrix spike recoveries of pesticides a Quality-control summary of matrix spike recoveries of pesticides a nd pesticide degradates in samples collected nd pesticide degradates in samples collected 

for the Monterey Bay and Salinas V for the Monterey Bay and Salinas Valley Ground-W alley Ground-Water Ambient Monitoring and Assessment (GAMA) study ater Ambient Monitoring and Assessment (GAMA) study, California, July to 

October 2005. 

[Acceptable recovery range is between 70 and 130 percent] 

Number Minimum Maximum Median 

Constituent (common name) of spiked recovery recovery recovery 

samples (percent) (percent) (percent) 

1-Naphthol 9 9 51 19 

2,6-Diethylaniline 9 85 103 92 

2-Chloro-2′,6′-diethylacetanilide 9 82 109 101 

2-Ethyl-6-methylaniline 9 82 100 87 

3,4-Dichloroaniline 9 61 88 83 

4-Chloro-2-methylphenol 9 35 68 59 

Acetochlor 9 82 101 96 

Alachlor 9 86 106 102 

Atrazine1 9 87 119 99 

Azinphos-methyl 9 50 109 81 

Azinphos-methyl oxygen analog 9 30 98 69 

Benfluralin, water 9 45 67 57 

Carbaryl 9 79 162 121 

Chlorpyrifos 9 75 100 92 

Chlorpyrifos oxygen analog 9 10 92 49 

cis-Permethrin 9 43 81 55 

Cyfluthrin 9 34 59 53 

Cypermethrin 9 34 55 52 

Dacthal (DCPA)1 9 87 111 105 

Deethylatrazine (2-chloro-4-isopropylamino-6-amino-s-triazine)1 13 17 115 59 

Deisopropyl atrazine (2-chloro-6-ethylamino-4-amino-s-triazine)1 4 44 90 71 

Desulfinyl fipronil 9 86 102 95 

Desulfinylfipronil amide 9 18 97 79 

Diazinon 9 80 97 93 

Diazinon oxygen analog 9 50 100 92 

Dichlorvos 9 20 71 46 

Dicrotophos 9 10 49 29 

Dieldrin1 9 74 112 84 

Dimethoate 9 13 40 28 

Ethion 9 48 83 76 

Ethion monoxon 9 50 98 84 

Fenamiphos 9 70 120 80 

Fenamiphos sulfone 9 37 94 77 

Fenamiphos sulfoxide 9 20 69 40 

Fipronil 9 62 101 91 

Fipronil sulfide 9 80 100 91 

Fipronil sulfone 9 64 87 75 

Fonofos 9 77 96 91 

Fonofos oxygen analog 0 0 0 0 

Hexazinone 9 23 86 73 

Iprodione 0 0 0 0 

Isofenphos 9 87 119 101 

Malaoxon 9 54 116 96 

Malathion 9 82 128 114 

Metalaxyl 9 79 107 98 

Methidathion 9 74 110 91 

Methyl paraoxon 9 30 71 65 

Methyl parathion 9 53 83 74 

Metolachlor1 9 98 123 114 

Metribuzin 9 42 93 75 

Myclobutanil 9 67 90 82 

Pendimethalin 9 54 109 87 
Tables 53 

Table B. Quality-control summary of matrix spike recoveries of pesticides and pesticide degradates in samples collected 

for the Monterey Bay and Salinas Valley Ground-Water Ambient Monitoring and Assessment (GAMA) study, California, July 

to October 2005—Continued. 

[Acceptable recovery range is between 70 and 130 percent] 

Number Minimum Maximum Median 

Constituent (common name) of spiked recovery recovery recovery 

samples (percent) (percent) (percent) 

Phorate 9 34 89 74 

Phorate oxygen analog 9 59 121 91 

Phosmet 9 0 25 12 

Phosmet oxygen analog 9 0 29 10 

Prometon1 9 80 102 95 

Prometryn 9 90 108 103 

Pronamide 9 78 101 93 

Simazine1 9 71 110 95 

Tebuthiuron 9 60 139 105 

Terbufos 9 59 101 86 

Terbufos oxygen analog sulfone 9 40 131 102 

Terbuthylazine1 9 91 111 102 

Trifluralin 9 47 75 65 

2,4-D (2,4-dichlorophenoxyacetic acid) 4 104 130 120 

2,4-D methyl ester 4 88 107 99 

2,4-DB (4-(2,4-dichlorophenoxy)butanoic acid) 4 84 101 90 

2-Hydroxy-4-isopropylamino-6-ethylamino-s-triazine (hydroxyatrazine) 4 103 115 112 

3-Hydroxy carbofuran 4 74 106 101 

3-Ketocarbofuran1 4 37 90 74 

Acifluorfen 4 107 162 127 

Aldicarb 4 32 75 63 

Aldicarb sulfone 4 40 94 63 

Aldicarb sulfoxide 4 71 105 96 

Atrazine1 4 64 117 99 

Bendiocarb 4 84 98 87 

Benomyl 4 69 105 77 

Bensulfuron 4 88 122 106 

Bentazon 4 92 142 110 

Bromacil 4 64 110 91 

Bromoxynil 4 72 97 90 

Caffeine1 4 74 130 106 

Carbaryl 4 84 110 102 

Carbofuran 4 82 110 103 

Chloramben methyl ester 4 68 106 97 

Chlorimuron 4 55 81 74 

Chlorodiamino-s-triazine 4 68 146 109 

Chlorothalonil 4 16 69 42 

Clopyralid 4 61 85 75 

Cycloate 4 80 114 96 

Dacthal monoacid 4 108 138 126 

Dicamba 4 84 106 102 

Dichlorprop 4 84 118 106 

Dinoseb 4 100 142 121 

Diphenamid1 4 84 114 110 

Diuron 4 80 118 108 

Fenuron1 4 76 110 106 

Flumetsulam 4 92 191 121 

Fluometuron 4 84 118 110 

Imazaquin 4 85 170 115 

Imazethapyr1 4 112 158 122 

Imidacloprid 4 100 167 119 

Linuron 4 84 114 108 
54 Ground-Water Quality Data, Monterey Bay and Salinas Valley Basins 2005—Results, Calif. GAMA Program 

Table B. Quality-control summary of matrix spike recoveries of pesticides and pesticide degradates in samples collected 

for the Monterey Bay and Salinas Valley Ground-Water Ambient Monitoring and Assessment (GAMA) study, California, July 

to October 2005—Continued. 

[Acceptable recovery range is between 70 and 130 percent] 

Number Minimum Maximum Median 

Constituent (common name) of spiked recovery recovery recovery 

samples (percent) (percent) (percent) 

MCPA (2-Methyl-4-chlorophenoxyacetic acid) 4 88 105 100 

MCPB (4-(2-Methyl-4-chlorophenoxy) butyric acid) 4 84 105 94 

Metalaxyl 4 84 118 108 

Methiocarb 4 88 110 102 

Methomyl 4 38 115 94 

Metsulfuron1 4 44 93 60 

3-(4-Chlorophenyl)-1-methyl urea 4 64 114 85 

Neburon 4 84 118 110 

Nicosulfuron 4 65 183 117 

Norflurazon 4 84 129 114 

Oryzalin 4 80 110 97 

Oxamyl 4 80 110 93 

Picloram 4 94 105 97 

Propham 4 90 115 109 

Propiconazole 4 80 114 100 

Propoxur 4 75 108 102 

Siduron 4 88 122 114 

Sulfometuron-methyl 4 86 131 103 

Tebuthiuron 4 79 124 108 

Terbacil 4 71 117 106 

Triclopyr 4 100 126 110 

1

Constituents detected in ground-water samples. 
Tables 55 

Table . Quality-control summary of surrogate recoveries in environmental, blank, and replicate samples for volatile organic 

compounds, gasoline additives, pesticides, pesticide degradates, and constituents of special interest, collected for the Monterey Bay 

and Salinas Valley Ground-Water Ambient Monitoring and Assessment (GAMA) study, California, July to October 2005. 

Number of 

Surrogate Analytical 

schedule 

Constitutent 

class 

analyses 

(environmental, blank, 

replicate) 

Number of 

surrogate 

recoveries 

below 70 

percent (environmental, 

blank, 

replicate) 

Number of 


surrogate 


recoveries 


between 


70 and 130 


percent (environmental, 


blank, 


replicate)
 

Number of 

surrogate 

recoveries 

above 130 

percent (environmental, blank, 

replicate) 

1,2-Dichloroethane-d4 2020, 4024 Volatile organic com­ 100, 20, 16 0, 0, 0 82, 17, 14 18, 3, 2 

pound 

1-Bromo-4-fluorobenzene 2020, 4024 Volatile organic com­ 100, 20, 16 16, 3, 3 84, 17, 13 0, 0, 0 

pound 

Toluene-d8 2020, 4024 Volatile organic com­ 100, 20, 16 0, 0, 0 100, 20, 16 0, 0, 0 

pound 

Isobutyl alcohol-d6 4024 Gasoline additive 34, 6, 6 1, 0, 0 33, 6, 6 0, 0, 0 

alpha-HCH-d6 2003 Pesticide or degradate 97, 11, 16 3, 0, 0 94, 11, 16 0, 0, 0 

Diazinon-d10 2003 Pesticide or degradate 97, 11, 16 16, 2, 3 81, 5, 13 0, 0, 0 

2,4,5-T (2,4,5-trichlorophenoxyace­ 2060 Pesticide or degradate 34, 5, 6 2, 0, 2 26, 3, 4 6, 2, 0 

tic acid) 

Barban 2060 Pesticide or degradate 34, 5, 6 1, 0, 0 32, 5, 6 1, 0, 0 

Caffeine-13C 2060 Pesticide or degradate 34, 5, 6 0, 0, 0 25, 2, 3 9, 3, 3 

Toluene-d8 MWH1 Constituent of special 34, 7, 4 0, 0, 0 34, 7, 4 0, 0, 0 

interest 

NDMA-d6 MWH1 Constituent of special 33, 7, 4 3, 0, 0 30, 7, 4 0, 0, 0 

interest 

1

Constituent analyzed at Montgomery Watson-Harza Laboratory (MWH), Monrovia, California. 
 

 

 

 

 

 

 

56 Ground-Water Quality Data, Monterey Bay and Salinas Valley Basins 2005—Results, Calif. GAMA Program 

Table 10. Water-quality indicators determined in the field for the Monterey Bay and Salinas Valley Ground-Water Ambient Monitoring 

and Assessment (GAMA) study, California, July to October 2005. 

[The five-digit number below the constituent name is the U.S. Geological Survey parameter code used to uniquely identify a specific constituent or property; 

MSMB, Monterey Bay study area well; MSMBFP, Monterey Bay study area flow-path well; MSMBMW, Monterey Bay study area monitoring well; MSPR, 

Paso Robles study area well; MSSC, Santa Cruz study area well; MSSV, Salinas Valley study area well; SMCL-CA, California Department of Health Services 

secondary maximum contaminant level; SMCL-US, U.S. Environmental Protection Agency secondary maximum contaminant level; C, celsius; mg/L, milligrams per liter; mm, millimeter; na, not available; nc, sample not collected; NTU, nephelometric turbidity unit; μS/cm, microsiemens per centimeter; <, less 

than; >, greater than; *, value exceeds regulatory threshold] 

GAMA 

identification 

No. 

Turbidity 

(NTU) 

(63676) 

Barometric 

Pressure 

(mm of 

mercury) 

(00025) 

Dissolved 

oxygen 

(mg/L) 

(00300) 

pH, field 

(standard 

units) 

(00400) 

Specific 

conductance, 

field 

(μS/cm at 25 

degrees C) 

(0005) 

Water 

temperature 

(degrees 

C) 

(00010) 

Alkalinity 

(mg/L as 

CaCO3

) 

(202) 

Bicarbonate 

(mg/L as 

HCO3

) 

(6376) 

Carbonate 

(mg/L as 

CO3

) 

(637) 

Threshold type na na na SMCL-US SMCL-CA1 na na na na 

Threshold na na na <6.5 or >.5 00 na na na na 

MSMB-01 nc nc 8.6 nc *907 20.1 nc nc nc 

MSMB-02 nc nc 2.2 nc 885 21.7 nc nc nc 

MSMB-03 nc nc 1.9 nc 338 33.2 nc nc nc 

MSMB-04 0.1 761 0.1 8.1 *1,210 23.0 163 199 2 

MSMB-05 nc nc 7.8 nc 397 18.5 nc nc nc 

MSMB-06 nc nc 1.2 nc 615 19.5 nc nc nc 

MSMB-07 nc nc 4.3 nc 708 24.7 nc nc nc 

MSMB-08 nc nc 2.5 nc 469 14.5 nc nc nc 

MSMB-09 0.1 760 2.9 7.3 435 17.5 173 211 0 

MSMB-10 nc nc 4.3 nc *1,080 20.1 nc nc nc 

MSMB-11 nc nc 1.3 nc 591 22.0 nc nc nc 

MSMB-12 0.2 762 0.2 8.8 538 31.7 135 161 2 

MSMB-13 nc nc 3.9 nc 648 19.2 nc nc nc 

MSMB-14 nc nc 4.1 nc *1,180 21.9 nc nc nc 

MSMB-15 nc nc 0.6 nc *1,240 20.9 nc nc nc 

MSMB-16 nc nc 4.1 nc 651 19.7 nc nc nc 

MSMB-17 nc nc 1.8 nc *953 22.0 nc nc nc 

MSMB-18 0.1 763 3.5 7.3 499 20.6 138 168 0 

MSMB-19 nc nc 2.9 nc 622 20.4 nc nc nc 

MSMB-20 0.2 763 0.9 7.3 753 19.0 300 366 0.5 

MSMB-21 nc nc 0.2 nc 534 16.2 nc nc nc 

MSMB-22 0.1 761 0.1 7.4 *985 18.2 311 378 0.8 

MSMB-23 nc nc 2.7 nc 693 20.6 nc nc nc 

MSMB-24 nc nc 7.5 nc 555 18.7 nc nc nc 

MSMB-25 nc nc 4.5 nc 562 23.1 nc nc nc 

MSMB-26 nc nc 2.7 nc 777 22.0 nc nc nc 

MSMB-27 nc nc nc nc *1,050 21.9 nc nc nc 

MSMB-28 nc nc nc nc 719 20.2 nc nc nc 

MSMB-29 0.1 759 3.5 7.3 *1,580 16.4 374 454 0.9 

MSMB-30 0.2 757 4.0 6.7 894 22.3 180 219 0 

MSMB-31 nc nc 5.2 nc 594 16.4 nc nc nc 

MSMB-32 nc nc 8.4 nc 353 18.4 nc nc nc 

MSMB-33 0.3 753 1.4 7.2 567 19.0 148 180 0.2 

MSMB-34 nc nc 0.2 nc 711 23.4 nc nc nc 

MSMB-35 0.2 762 nc 7.3 *1,260 16.0 330 401 0.5 

MSMB-36 nc nc 0.4 nc 568 20.7 nc nc nc 

MSMB-37 0.1 757 5.4 7.0 711 23.1 152 184 0.2 

MSMB-38 nc nc 4.3 nc 756 21.2 nc nc nc 

MSMB-39 nc nc nc nc 801 20.0 nc nc nc 

MSMB-40 0.1 nc 4.3 7.2 694 21.7 157 191 0.3 

MSMB-41 nc nc 0.7 nc 572 18.3 nc nc nc 

MSMB-42 nc nc 9.4 nc 438 17.6 nc nc nc 

MSMB-43 nc nc 1.8 nc *1,440 16.3 nc nc nc 

MSMB-44 0.1 759 4.9 7.2 *1,820 18.0 306 372 0.7 
 

 

 

 

 

 

 

Tables 57 

Table 10. Water-quality indicators determined in the field for the Monterey Bay and Salinas Valley Ground-Water Ambient Monitoring 

and Assessment (GAMA) study, California, July to October 2005—Continued. 

[The five-digit number below the constituent name is the U.S. Geological Survey parameter code used to uniquely identify a specific constituent or property; 

MSMB, Monterey Bay study area well; MSMBFP, Monterey Bay study area flow-path well; MSMBMW, Monterey Bay study area monitoring well; MSPR, 

Paso Robles study area well; MSSC, Santa Cruz study area well; MSSV, Salinas Valley study area well; SMCL-CA, California Department of Health Services 

secondary maximum contaminant level; SMCL-US, U.S. Environmental Protection Agency secondary maximum contaminant level; C, celsius; mg/L, milligrams per liter; mm, millimeter; na, not available; nc, sample not collected; NTU, nephelometric turbidity unit; μS/cm, microsiemens per centimeter; <, less 

than; >, greater than; *, value exceeds regulatory threshold] 

Specific Water Barometric Bicar- Dissolved pH, field conductance, tempera- Alkalinity Carbonate GAMA Turbidity Pressure bonate 

oxygen (standard field ture (mg/L as (mg/L as identification (NTU) (mm of (mg/L as (mg/L) units) (μS/cm at 25 (degrees CaCO ) CO ) No. (63676) mercury) 3 HCO ) 3

(00300) (00400) degrees C) C) (202) 3 (637) (00025) (6376) (0005) (00010) 

Threshold type na na na SMCL-US SMCL-CA1 na na na na 

Threshold na na na <6.5 or >.5 00 na na na na 

MSMB-45 1.2 762 1.3 6.6 497 17.4 100 122 0 

MSMB-46 nc nc 0.7 nc 746 16.7 nc nc nc 

MSMB-47 0.1 759 2.8 7.7 541 25.7 136 165 0 

MSMB-48 nc nc 12.0 nc *912 17.7 nc nc nc 

MSMBFP-01 nc nc 0.3 nc 615 29.1 nc nc nc 

MSMBFP-02 0.1 758 1.4 7.3 *1,240 19.8 295 359 0.5 

MSMBFP-03 0.1 nc 1.3 6.9 *1,360 19.2 224 nc nc 

MSMBMW-01 2.9 nc 2.2 8.2 670 24.2 175 nc nc 

MSMBMW-02 3.8 nc 4.6 7.7 606 24.0 187 nc nc 

MSMBMW-03 1.7 nc 3.8 7.1 567 23.4 159 nc nc 

MSPR-01 0.1 737 4.0 7.1 847 18.0 260 316 0.3 

MSPR-02 nc nc 2.0 nc *1,140 21.2 nc nc nc 

MSPR-03 nc nc 1.7 nc 815 24.0 nc nc nc 

MSPR-04 nc nc 1.1 nc 871 28.2 nc nc nc 

MSPR-05 nc nc 0.2 nc *941 30.8 nc nc nc 

MSPR-06 nc nc 6.2 nc 871 22.4 nc nc nc 

MSPR-07 nc nc nc nc 719 24.5 nc nc nc 

MSPR-08 0.1 743 0.8 7.5 *1,140 21.0 219 267 0.4 

MSPR-09 nc nc nc nc *1,590 23.5 nc nc nc 

MSPR-10 0.2 744 0.1 7.2 *1,480 20.0 275 335 0.1 

MSPR-11 nc nc nc nc 605 24.0 nc nc nc 

MSSC-01 nc nc 8.4 nc 475 13.5 nc nc nc 

MSSC-02 nc nc 0.2 nc *978 18.3 nc nc nc 

MSSC-03 nc nc 2.8 nc 495 16.7 nc nc nc 

MSSC-04 1.5 746 0.4 7.6 783 19.7 135 164 0.4 

MSSC-05 nc nc 1.8 nc 823 26.6 nc nc nc 

MSSC-06 0.1 759 0.2 7.5 694 18.5 128 156 0.1 

MSSC-07 0.1 759 0.3 7.7 505 24.9 nc nc nc 

MSSC-08 0.2 758 0.2 7.6 403 19.6 165 200 0.1 

MSSC-09 nc nc 6.6 nc 446 17.2 nc nc nc 

MSSC-10 nc nc 5.5 nc 646 23.4 nc nc nc 

MSSC-11 nc nc 0.1 nc 414 17.7 nc nc nc 

MSSC-12 nc nc 0.2 nc 444 15.7 nc nc nc 

MSSC-13 nc nc 3.0 nc 326 16.8 nc nc nc 

MSSV-01 0.4 748 0.1 7.0 *1,650 28.4 305 372 0.1 

MSSV-02 0.1 752 0.1 7.2 509 19.2 154 187 0.4 

MSSV-03 0.1 756 0.6 7.3 *1,060 18.4 171 208 0.4 

MSSV-04 nc nc nc nc 615 21.7 nc nc nc 

MSSV-05 nc nc <0.1 nc 590 18.6 nc nc nc 

MSSV-06 nc nc nc nc 538 19.1 nc nc nc 

MSSV-07 nc 754 0.1 7.5 534 19.0 149 181 0.2 

MSSV-08 nc nc 3.5 nc *1,390 19.2 nc nc nc 

MSSV-09 nc nc 4.7 nc 815 18.0 nc nc nc 

MSSV-10 nc nc 2.2 nc 599 18.4 nc nc nc 
 

 

 

 

 

 

 

5 Ground-Water Quality Data, Monterey Bay and Salinas Valley Basins 2005—Results, Calif. GAMA Program 

Table 10. Water-quality indicators determined in the field for the Monterey Bay and Salinas Valley Ground-Water Ambient Monitoring 

and Assessment (GAMA) study, California, July to October 2005—Continued. 

[The five-digit number below the constituent name is the U.S. Geological Survey parameter code used to uniquely identify a specific constituent or property; 

MSMB, Monterey Bay study area well; MSMBFP, Monterey Bay study area flow-path well; MSMBMW, Monterey Bay study area monitoring well; MSPR, 

Paso Robles study area well; MSSC, Santa Cruz study area well; MSSV, Salinas Valley study area well; SMCL-CA, California Department of Health Services 

secondary maximum contaminant level; SMCL-US, U.S. Environmental Protection Agency secondary maximum contaminant level; C, celsius; mg/L, milligrams per liter; mm, millimeter; na, not available; nc, sample not collected; NTU, nephelometric turbidity unit; μS/cm, microsiemens per centimeter; <, less 

than; >, greater than; *, value exceeds regulatory threshold] 

Specific Water Barometric Bicar- Dissolved pH, field conductance, tempera- Alkalinity Carbonate GAMA Turbidity Pressure bonate 

oxygen (standard field ture (mg/L as (mg/L as identification (NTU) (mm of (mg/L as (mg/L) units) (μS/cm at 25 (degrees CaCO ) CO ) No. (63676) mercury) 3 HCO ) 3

(00300) (00400) degrees C) C) (202) 3 (637) (00025) (6376) (0005) (00010) 

Threshold type na na na SMCL-US SMCL-CA1 na na na na 

Threshold na na na <6.5 or >.5 00 na na na na 

MSSV-11 0.2 753 8.0 7.4 473 17.9 138 168 0.8 

MSSV-12 nc nc nc nc 387 14.3 nc nc nc 

MSSV-13 nc nc 10.4 nc 345 13.9 nc nc nc 

MSSV-14 nc nc nc nc* *1,830 18.2 nc nc nc 

MSSV-15 nc nc nc nc 606 18.2 nc nc nc 

MSSV-16 nc nc 7.7 nc nc 20.0 nc nc nc 

MSSV-17 nc nc 4.5 nc 341 14.5 nc nc nc 

MSSV-18 0.1 756 0.3 7.6 848 25.4 156 189 0.55 

MSSV-19 0.1 756 2.5 7.4 708 23.4 156 191 0.1 

1

SMCL-CA threshold for specific conductance has a recommended value of 900 mg/L, an upper value of 1,600 mg/L, and a short term value of 2,200 mg/L. 
Tables 59 

Table 11. Results of analyses for volatile organic compounds (VOCs) and gasoline additives in unfiltered ground-water 

samples collected for the Monterey Bay and Salinas Valley Ground-Water Ambient Monitoring and Assessment (GAMA) study, 

California, July to October 2005. 

[The five-digit number below the constituent name is the U.S. Geological Survey parameter code used to uniquely identify a specific constituent or 

property. Out of 97 samples, only those with detections are listed. MSMB, Monterey Bay study area well; MSMBFP, Monterey Bay study area flowpath well; MSMBMW, Monterey Bay study area monitoring well; MSPR, Paso Robles study area well; MSSC, Santa Cruz study area well; MSSV, 

Salinas Valley study area well; HAL-US, U.S. Environmental Protection Agency Lifetime Health Advisory; MCL-US, U.S. Environmental Protection 

Agency defined maximum contaminant level; MCL-CA; California Department of Health Services defined maximum contaminant level; NL, California notification level; E, estimated value; LRL, laboratory reporting level; na, not available; V or VE, value censored due to blank contamination and 

not included in ground-water quality analyses; μg/L, micrograms per liter; —, not detected; percentage values are detection frequencies] 

TetraGAMA 

identification 

No. 

Chloroform 

(Trichloro 

methane) 

(μg/L) 

(32106) 

Tetrachloro 

ethene 

(PCE) 

(μg/L) 

(34475) 

Carbon 

disulfide 

(μg/L) 

(77041) 

1,2,4-

Trimethyl 

benzene 

(μg/L) 

(77222) 

tert-Butyl 

methyl 

ether 

(MTBE) 

(μg/L) 

(78032) 

Trichloro 

ethene 

(TCE) 

(μg/L) 

(39180) 

Bromodichloro 

methane 

(μg/L) 

(32101) 

cis-1,2-

Dichloro 

ethylene 

(μg/L) 

(77093) 

chloro 

methane 

(carbon 

tetrachloride) 

(μg/L) 

Bromoform 

(tribromo 

methane) 

(μg/L) 

(32104) 

Dibromochloro 

methane 

(μg/L) 

(32105) 

(32102) 

Threshold MCL-US HAL-US NL NL MCL-CA MCL-CA MCL-US MCL-CA MCL-CA MCL-US MCL-US 

type 

Threshold 80 10 160 330 13 5 80 6 0.5 80 80 

(μg/L) 

LRL [0.02] [0.03] [0.04] [0.06] [0.1] [0.04] [0.03] [0.02] [0.06] [0.1] [0.1] 

MSMB-01 0.17 — — — E0.1 — — — — — — 

MSMB-02 0.17 0.48 — — E0.1 E0.06 E0.08 — — — E0.1 

MSMB-05 E0.09 E0.09 — — E0.1 — E0.04 — — 0.84 0.2 

MSMB-08 E0.02 — — E0.03 — — — — — — — 

MSMB-11 — E0.01 — — — — — — — — — 

MSMB-13 E0.08 0.43 — — — 0.80 — 0.38 E0.03 — — 

MSMB-15 — — — 0.22 — — — — — — — 

MSMB-16 E0.04 E0.04 — — — 0.41 — E0.04 E0.06 — — 

MSMB-18 E0.02 — — E0.05 — — — — — — — 

MSMB-20 E0.07 0.24 — — — 0.23 — 0.56 E0.02 — — 

MSMB-24 0.14 E0.08 — — — — — — — — — 

MSMB-29 — — — E0.02 — — — — — — — 

MSMB-30 E0.07 2.05 — E0.02 — — — — E0.07 — — 

MSMB-31 E0.02 — — — — — — — — — — 

MSMB-32 E0.03 — — — — — — — — — — 

MSMB-33 0.12 — E0.02 — — — — — — — — 

MSMB-36 — — — — — — E0.06 — — 0.59 0.2 

MSMB-40 — — — — — — — — — — — 

MSMB-42 — — — — 2.2 — — — — — — 

MSMB-45 — — — 0.11 — — — — — — — 

MSPR-02 — — — — — — — — — — — 

MSPR-04 E0.04 — — — — — — — — — — 

MSPR-06 E0.01 — — — — — — — — — — 

MSPR-08 E0.04 — — — — — — — — 0.11 — 

MSPR-10 — — E0.07 — — — — — — — — 
60 Ground-Water Quality Data, Monterey Bay and Salinas Valley Basins 2005—Results, Calif. GAMA Program 

Table 11. Results of analyses for volatile organic compounds (VOCs) and gasoline additives in unfiltered ground-water samples 

collected for the Monterey Bay and Salinas Valley Ground-Water Ambient Monitoring and Assessment (GAMA) study, California, July to 

October 2005—Continued. 

[The five-digit number below the constituent name is the U.S. Geological Survey parameter code used to uniquely identify a specific constituent or property. Out 

of 97 samples, only those with detections are listed. MSMB, Monterey Bay study area well; MSMBFP, Monterey Bay study area flow-path well; MSMBMW, 

Monterey Bay study area monitoring well; MSPR, Paso Robles study area well; MSSC, Santa Cruz study area well; MSSV, Salinas Valley study area well; 

HAL-US, U.S. Environmental Protection Agency Lifetime Health Advisory; MCL-US, U.S. Environmental Protection Agency defined maximum contaminant 

level; MCL-CA; California Department of Health Services defined maximum contaminant level; NL, California notification level; E, estimated value; LRL, 

laboratory reporting level; na, not available; V or VE, value censored due to blank contamination and not included in ground-water quality analyses; μg/L, 

micrograms per liter; —, not detected; percentage values are detection frequencies] 

TetraGAMA 

identification 

No. 

Chloroform 

(Trichloro 

methane) 

(μg/L) 

(32106) 

Tetrachloro 

ethene 

(PCE) 

(μg/L) 

(34475) 

Carbon 

disulfide 

(μg/L) 

(77041) 

1,2,4-

Trimethyl 

benzene 

(μg/L) 

(77222) 

tert-Butyl 

methyl 

ether 

(MTBE) 

(μg/L) 

(78032) 

Trichloro 

ethene 

(TCE) 

(μg/L) 

(39180) 

Bromodichloro 

methane 

(μg/L) 

(32101) 

cis-1,2-

Dichloro 

ethylene 

(μg/L) 

(77093) 

chloro 

methane 

(carbon 

tetrachloride) 

(μg/L) 

Bromoform 

(tribromo 

methane) 

(μg/L) 

(32104) 

Dibromochloro 

methane 

(μg/L) 

(32105) 

(32102) 

Threshold MCL-US HAL-US NL NL MCL-CA MCL-CA MCL-US MCL-CA MCL-CA MCL-US MCL-US 

type 

Threshold 80 10 160 330 13 5 80 6 0.5 80 80 

(μg/L) 

LRL [0.02] [0.03] [0.04] [0.06] [0.1] [0.04] [0.03] [0.02] [0.06] [0.1] [0.1] 

MSSC-01 — — E0.03 — — — — — — — — 

MSSC-02 E0.02 — — — — — — — — — — 

MSSC-03 E0.04 — — — — — — — — — — 

MSSC-04 — E0.08 — — 1.5 E0.10 — E0.07 — — — 

MSSC-06 — — 0.17 — — — — — — — — 

MSSV-01 — — E0.06 — — — — — — — — 

MSSV-03 0.46 — — — — — E0.06 — — — — 

MSSV-05 — — 0.16 — — — — — — — — 

MSSV-08 E0.02 — — — — — — — — — — 

Number of 

wells with 20 9 6 6 5 5 4 4 4 3 3 

detections 

Detection 

frequency 22 10 7 7 5 5 4 4 4 3 3

(percent) 

Flow-path wells1 

MSMBFP-02 — — — — — E0.06 — — — — — 

MSMBFP-03 1.94 — — — — — 0.71 — — 0.64 E0.7 

MSMBMW-01 — 3.95 — — — — — — — — — 

MSMBMW-02 — E0.06 — — — — — — — — — 

MSMBMW-03 — 0.19 — E0.04 — — — — — — — 1

Flow-path wells were not included in statistical calculations. 
Tables 61 

Table 11. Results of analyses for volatile organic compounds (VOCs) and gasoline additives in unfiltered ground-water samples 

collected for the Monterey Bay and Salinas Valley Ground-Water Ambient Monitoring and Assessment (GAMA) study, California, 

July to October 2005—Continued. 

[The five-digit number below the constituent name is the U.S. Geological Survey parameter code used to uniquely identify a specific constituent or property. Out of 97 samples, only those with detections are listed. MSMB, Monterey Bay study area well; MSMBFP, Monterey Bay study area flow-path well; 

MSMBMW, Monterey Bay study area monitoring well; MSPR, Paso Robles study area well; MSSC, Santa Cruz study area well; MSSV, Salinas Valley 

study area well; HAL-US, U.S. Environmental Protection Agency Lifetime Health Advisory; MCL-US, U.S. Environmental Protection Agency defined 

maximum contaminant level; MCL-CA; California Department of Health Services defined maximum contaminant level; NL, California notification level; 

E, estimated value; LRL, laboratory reporting level; na, not available; V or VE, value censored due to blank contamination and not included in groundwater quality analyses; μg/L, micrograms per liter; —, not detected; percentage values are detection frequencies] 

1,1,2- 2-BuGAMA 

identification 

No. 

Tetrahydro 

furan 

(μg/L) 

(81607) 

Trichlorotrifluoro 

ethane 

(CFC-113) 

(μg/L) 

1,1-Dichloro 

ethane 

(μg/L) 

(34496) 

1,1-Dichloro 

ethene 

(μg/L) 

(34501) 

1,2-Dichloro 

propane 

(μg/L) 

(34541) 

tanone 

(Ethyl 

methyl 

ketone) 

(μg/L) 

Benzene 

(μg/L) 

(34030) 

Dibromo 

methane 

(μg/L) 

(30217) 

Dichloro 

methane 

(μg/L) 

(34423) 

Diisopropyl 

ether 

(μg/L) 

(81577) 

Ethyl 

benzene 

(μg/L) 

(34371) 

(77652) (81595) 

LRL na [0.04] [0.04] [0.02] [0.03] [4 (2)] [0.02] [0.05] [0.1] [0.1] [0.03] 

Threshold na MCL-US MCL-CA MCL­ MCL­ na MCL-CA na MCL-US na MCL-CA 

type CA US 

Threshold [1] 1,200 5 6 0.5 na 1 na 5 na 300 

(μg/L) 

MSMB-01 — — — — — — — — — — — 

MSMB-02 — — — — — — — — — — — 

MSMB-05 — — E0.04 — — — — — — — E0.07 

MSMB-08 — — — — — — — — — — — 

MSMB-11 — — — — — — — — — — — 

MSMB-13 — — — — — — — — — — — 

MSMB-15 — — — — — — — — — — — 

MSMB-16 — — — — — — — — — — — 

MSMB-18 — — — — — — — — — — — 

MSMB-20 — — — — — — — — — — — 

MSMB-24 — — — E0.02 — — — — — — — 

MSMB-29 — — — — — — — — — — — 

MSMB-30 — — — — — — — — — — — 

MSMB-31 — — — — — — — — — — — 

MSMB-32 — — — — — — — — — — — 

MSMB-33 — — — — — — — — — — — 

MSMB-36 — — — — — — — E0.07 — — — 

MSMB-40 — E0.07 — — — — — — — — — 

MSMB-42 — — — — — — — — — — — 

MSMB-45 — — — — — — — — — — — 

MSPR-02 E0.8 — — — — — — — — — — 

MSPR-04 — — — — — — — — — — — 

MSPR-06 — — — — — — — — — — — 

MSPR-08 — — — — — — — — — — — 

MSPR-10 — — — — — — — — — — — 
62 Ground-Water Quality Data, Monterey Bay and Salinas Valley Basins 2005—Results, Calif. GAMA Program 

Table 11. Results of analyses for volatile organic compounds (VOCs) and gasoline additives in unfiltered ground-water samples 

collected for the Monterey Bay and Salinas Valley Ground-Water Ambient Monitoring and Assessment (GAMA) study, California, 

July to October 2005—Continued. 

[The five-digit number below the constituent name is the U.S. Geological Survey parameter code used to uniquely identify a specific constituent or property. Out of 97 samples, only those with detections are listed. MSMB, Monterey Bay study area well; MSMBFP, Monterey Bay study area flow-path well; 

MSMBMW, Monterey Bay study area monitoring well; MSPR, Paso Robles study area well; MSSC, Santa Cruz study area well; MSSV, Salinas Valley 

study area well; HAL-US, U.S. Environmental Protection Agency Lifetime Health Advisory; MCL-US, U.S. Environmental Protection Agency defined 

maximum contaminant level; MCL-CA; California Department of Health Services defined maximum contaminant level; NL, California notification level; 

E, estimated value; LRL, laboratory reporting level; na, not available; V or VE, value censored due to blank contamination and not included in groundwater quality analyses; μg/L, micrograms per liter; —, not detected; percentage values are detection frequencies] 

GAMA 

identification 

No. 

Tetrahydro 

furan 

(μg/L) 

(81607) 

1,1,2-

Trichlorotrifluoro 

ethane 

(CFC-113) 

(μg/L) 

(77652) 

1,1-Dichloro 

ethane 

(μg/L) 

(34496) 

1,1-Dichloro 

ethene 

(μg/L) 

(34501) 

1,2-Dichloro 

propane 

(μg/L) 

(34541) 

2-Butanone 

(Ethyl 

methyl 

ketone) 

(μg/L) 

(81595) 

Benzene 

(μg/L) 

(34030) 

Dibromo 

methane 

(μg/L) 

(30217) 

Dichloro 

methane 

(μg/L) 

(34423) 

Diisopropyl 

ether 

(μg/L) 

(81577) 

Ethyl 

benzene 

(μg/L) 

(34371) 

LRL na [0.04] [0.04] [0.02] [0.03] [4 (2)] [0.02] [0.05] [0.1] [0.1] [0.03] 

Threshold na MCL-US MCL-CA MCL­ MCL­ na MCL-CA na MCL-US na MCL-CA 

type CA US 

Threshold 

(μg/L) 

[1] 1,200 5 6 0.5 na 1 na 5 na 300 

MSSC-01 — — — — — — — — — — — 

MSSC-02 2.0 — — — — E0.9 — — — — — 

MSSC-03 — — — — — — — — — — — 

MSSC-04 — — — — — — E0.05 — — E0.06 — 

MSSC-06 — — — — — — — — — — — 

MSSV-01 — — — — — — — — — — — 

MSSV-03 — — — — E0.03 — — — E 0.04 — — 

MSSV-05 — — — — — — — — — — — 

MSSV-08 — — — — — — — — — — — 

Number of 

wells with 2 1 1 1 1 1 1 1 1 1 1 

detections 

Detection 

frequency 2 1 1 1 1 1 1 1 1 1 1 

(percent) 

Flow-path wells1 

MSMBFP-02 — — 0.12 0.34 — — — — — — — 

MSMBFP-03 — — — — — — — — — — — 

MSMBMW-01 — — — — — — — — — — — 

MSMBMW-02 — — — — — — — — — — — 

MSMBMW-03 — — — — — — — — — — — 

1

Flow-path wells were not included in statistical calculations. 
Tables 63 

Table 11. Results of analyses for volatile organic compounds (VOCs) and gasoline additives in unfiltered 

ground-water samples collected for the Monterey Bay and Salinas Valley Ground-Water Ambient Monitoring and 

Assessment (GAMA) study, California, July to October 2005—Continued. 

[The five-digit number below the constituent name is the U.S. Geological Survey parameter code used to uniquely identify a specific 

constituent or property. Out of 97 samples, only those with detections are listed. MSMB, Monterey Bay study area well; MSMBFP, 

Monterey Bay study area flow-path well; MSMBMW, Monterey Bay study area monitoring well; MSPR, Paso Robles study area well; 

MSSC, Santa Cruz study area well; MSSV, Salinas Valley study area well; HAL-US, U.S. Environmental Protection Agency Lifetime 

Health Advisory; MCL-US, U.S. Environmental Protection Agency defined maximum contaminant level; MCL-CA; California Department of Health Services defined maximum contaminant level; NL, California notification level; E, estimated value; LRL, laboratory 

reporting level; na, not available; V or VE, value censored due to blank contamination and not included in ground-water quality analyses; μg/L, micrograms per liter; —, not detected; percentage values are detection frequencies] 

GAMA 

identification 

No. 

Isopropyl 

benzene 

(μg/L) 

(77223) 

m-Xylene 

plus 

p-xylene 

(μg/L) 

(85795) 

tertAmyl 

alcohol 

(μg/L) 

(77073) 

tertButyl 

benzene 

(μg/L) 

(77353) 

trans1,2-Dichloro 

ethene 

(μg/L) 

(34546) 

1,1,1-

Trichloro 

ethane 

(TCA) 

(μg/L) 

(34506) 

Detections 

per 

well 

LRL [0.04] [0.06] [1] [0.06] [0.03] [0.03] 

Threshold na MCL-CA na na MCL-CA MCL-US 

type 

Threshold na 1,750 na na 10 200 

(μg/L) 

MSMB-01 — — — — — — 2 

MSMB-02 — — — E0.01 — — 7 

MSMB-05 — — — — — — 8 

MSMB-08 — E0.03 — — — — 3 

MSMB-11 — — — — — — 1 

MSMB-13 — — — — — — 5 

MSMB-15 — — — — — — 1 

MSMB-16 — — — — — — 5 

MSMB-18 — — — — — — 2 

MSMB-20 — — — — E0.02 — 6 

MSMB-24 — — — — — — 3 

MSMB-29 — — — — — — 1 

MSMB-30 — — — — — — 4 

MSMB-31 — — — — — — 1 

MSMB-32 — — — — — — 1 

MSMB-33 — — — — — — 2 

MSMB-36 — — — — — — 4 

MSMB-40 — — — — — — 1 

MSMB-42 — — — — — — 1 

MSMB-45 — — — — — — 1 

MSPR-02 — — — — — — 1 

MSPR-04 — — — — — — 1 

MSPR-06 E0.02 — — — — — 2 

MSPR-07 — — — — — — 1 

MSPR-08 — — — — — — 2 

MSPR-10 — — — — — — 1 

MSSC-01 — — — — — — 1 

MSSC-02 — — — — — — 3 
64 Ground-Water Quality Data, Monterey Bay and Salinas Valley Basins 2005—Results, Calif. GAMA Program 

Table 11. Results of analyses for volatile organic compounds (VOCs) and gasoline additives in unfiltered 

ground-water samples collected for the Monterey Bay and Salinas Valley Ground-Water Ambient Monitoring and 

Assessment (GAMA) study, California, July to October 2005—Continued. 

[The five-digit number below the constituent name is the U.S. Geological Survey parameter code used to uniquely identify a specific 

constituent or property. Out of 97 samples, only those with detections are listed. MSMB, Monterey Bay study area well; MSMBFP, 

Monterey Bay study area flow-path well; MSMBMW, Monterey Bay study area monitoring well; MSPR, Paso Robles study area well; 

MSSC, Santa Cruz study area well; MSSV, Salinas Valley study area well; HAL-US, U.S. Environmental Protection Agency Lifetime 

Health Advisory; MCL-US, U.S. Environmental Protection Agency defined maximum contaminant level; MCL-CA; California Department of Health Services defined maximum contaminant level; NL, California notification level; E, estimated value; LRL, laboratory 

reporting level; na, not available; V or VE, value censored due to blank contamination and not included in ground-water quality analyses; μg/L, micrograms per liter; —, not detected; percentage values are detection frequencies] 

GAMA 

identification 

No. 

Isopropyl 

benzene 

(μg/L) 

(77223) 

m-Xylene 

plus 

p-xylene 

(μg/L) 

(85795) 

tertAmyl 

alcohol 

(μg/L) 

(77073) 

tertButyl 

benzene 

(μg/L) 

(77353) 

trans1,2-Dichloro 

ethene 

(μg/L) 

(34546) 

1,1,1-

Trichloro 

ethane 

(TCA) 

(μg/L) 

(34506) 

Detections 

per 

well 

LRL [0.04] [0.06] [1] [0.06] [0.03] [0.03] 

Threshold 

type 

na MCL-CA na na MCL-CA MCL-US 

Threshold 

(μg/L) 

na 1,750 na na 10 200 

MSSC-03 — — — — — — 1 

MSSC-04 — — E0.7 — — — 7 

MSSC-06 — — — — — — 1 

MSSV-01 — — — — — — 1 

MSSV-03 — — — — — — 4 

MSSV-05 — — — — — — 1 

MSSV-08 — — — — — — 1 

Number of 

wells with 1 1 1 1 1 0 86 Total detections 

detections 

Detection 

frequency 1 1 1 1 1 0 34 Total wells 

(percent) 

Flow-path wells1 

MSMBFP-02 — — — — — E0.02 4 

MSMBFP-03 — — — — — — 4 

MSMBMW-01 — — — — — — 1 

MSMBMW-02 — — — — — — 1 

MSMBMW-03 — — — — — — 2 

1

Flow-path wells were not included in statistical calculations. 
Tables 65 

Table 12. Pesticides and pesticide degradates detected in filtered ground-water samples collected for the Monterey 

Bay and Salinas Valley Ground-Water Ambient Monitoring and Assessment (GAMA) study, California, July to October 

2005. 

[The five-digit number below the constituent name is the U.S. Geological Survey parameter code used to uniquely identify a specific constituent or property. Out of 97 samples, only those with detections are listed. MSMB, Monterey Bay study area well; MSMBFP, Monterey 

Bay study area flow-path well; MSMBMW, Monterey Bay study area monitoring well; MSPR, Paso Robles study area well; MSSC, Santa 

Cruz study area well; MSSV, Salinas Valley study area well; HAL-US, U.S. Environmental Protection Agency Lifetime Health Advisory; 

MCL-US, U.S. Environmental Protection Agency defined maximum contaminant level; MCL-CA, California Department of Health Services defined maximum contaminant level; E, estimated value; LRL, laboratory reporting level; na, not available; VE, estimated value censored due to blank contamination and not included in ground-water quality analyses; μg/L, microgram per liter; —, not detected; percentage 

values are detection frequencies] 

Deethyl Dacthal GAMA Simazine Atrazine Caffeine Metolachlor atrazine (DCPA) identification (μg/L) (μg/L) (μg/L) (μg/L) (μg/L) (μg/L) No. (04035) (3632) (50305) (3415) (04040) (262) 

Threshold type MCL-US na MCL-CA na MCL-CA HAL-US 

Threshold (μg/L) 4 na 1 na 4 100 

[LRL] [0.005] [0.006 (0.03)] [0.007] [0.01] [0.003] [0.006] 

MSMB-01 0.009 — — — — — 

MSMB-02 0.020 E0.007 0.035 — — — 

MSMB-05 — E0.004 — — — — 

MSMB-19 — E0.004 0.008 — — — 

MSMB-20 — — — — — E0.005 

MSMB-30 — E0.004 — — — — 

MSMB-35 — — — E0.008 — — 

MSMB-44 — E0.003 — — — — 

MSMB-46 — — — — E0.004 — 

MSPR-01 0.008 — — — — — 

MSPR-04 0.010 E0.010 0.011 — — — 

MSPR-08 0.008 E0.006 E0.005 — — — 

MSPR-09 — E0.005 E0.006 — — — 

MSPR-11 0.007 — — — — — 

MSSC-01 — — — — — E0.007 

MSSV-03 E0.005 — — — — — 

MSSV-04 — E0.005 — — — — 

MSSV-05 0.008 — — — — — 

MSSV-06 E0.005 — — — — — 

MSSV-07 0.008 — — — — — 

MSSV-08 E0.005 — — — E0.004 — 

MSSV-09 E0.008 — — — — — 

MSSV-11 0.010 — — E0.012 — — 

MSSV-12 E0.006 — — — — — 

MSSV-14 E0.006 E0.006 — — — — 

MSSV-15 E0.006 — — — E0.002 — 

MSSV-19 — — — E0.004 — — 

Number of wells 16 10 5 3 3 2 

with detections 

Detection frequency 18 11 5 3 3 2 

(percent) 

Flow-path wells1 

MSMBMW-03 — — — E0.012 — — 
66 Ground-Water Quality Data, Monterey Bay and Salinas Valley Basins 2005—Results, Calif. GAMA Program 

Table 12. Pesticides and pesticide degradates detected in filtered ground-water samples collected for 

the Monterey Bay and Salinas Valley Ground-Water Ambient Monitoring and Assessment (GAMA) study, 

California, July to October 2005—Continued. 

[The five-digit number below the constituent name is the U.S. Geological Survey parameter code used to uniquely identify a 

specific constituent or property. Out of 97 samples, only those with detections are listed. MSMB, Monterey Bay study area 

well; MSMBFP, Monterey Bay study area flow-path well; MSMBMW, Monterey Bay study area monitoring well; MSPR, 

Paso Robles study area well; MSSC, Santa Cruz study area well; MSSV, Salinas Valley study area well; HAL-US, U.S. 

Environmental Protection Agency Lifetime Health Advisory; MCL-US, U.S. Environmental Protection Agency defined 

maximum contaminant level; MCL-CA, California Department of Health Services defined maximum contaminant level; E, 

estimated value; LRL, laboratory reporting level; na, not available; VE, estimated value censored due to blank contamination 

and not included in ground-water quality analyses; μg/L, microgram per liter; —, not detected; percentage values are detection 

frequencies] 

Deisopropyl Terbuthyl GAMA Dieldrin Prometon atrazine azine Detections identification (μg/L) (μg/L) (μg/L) (μg/L) per well No. (39381) (04037) (04038) (04022) 

LRL [0.08] [0.009] [0.01] [0.01] 

Threshold type na na HAL-US na 

Threshold (μg/L) na na 100 na 

MSMB-01 — — E0.01 — 2 

MSMB-02 — E0.006 — — 4 

MSMB-05 — — — — 1 

MSMB-19 — — — — 2 

MSMB-20 — — — — 1 

MSMB-30 — — — — 1 

MSMB-35 — — — — 1 

MSMB-44 — — — — 1 

MSMB-46 — — — — 1 

MSPR-01 — — — — 1 

MSPR-04 — — — — 3 

MSPR-08 — — — — 3 

MSPR-09 — — — — 2 

MSPR-11 — — — — 1 

MSSC-01 — — — — 1 

MSSV-03 — — — — 1 

MSSV-04 — — — — 1 

MSSV-05 — — — — 1 

MSSV-06 — — — — 1 

MSSV-07 — — — E0.01 2 

MSSV-08 — — — — 2 

MSSV-09 — — — — 1 

MSSV-11 E0.004 — — — 3 

MSSV-12 — — — — 1 

MSSV-14 — — — — 2 

MSSV-15 — — — — 2 

MSSV-19 — — — — 1 

Number of wells 1 1 1 1 43 Total detections 

with detections 

Detection frequency 1 1 1 1 27 Total wells 

(percent) 

Flow-path wells1 

MSMBMW-03 — — — — — 

1

Flow-path wells were not included in statistical calculations. 
 

 

Tables 6

Table 13. Results of analyses by Montgomerey Watson-Harza Laboratory for the 

constituents of special interest: perchlorate, N-nitrosodimethylamine (NDMA), and 

trichloropropane (1,2,3-TCP) in the ground-water samples collected in the Monterey Bay 

and Salinas Valley Ground-Water Ambient Monitoring and Assessment (GAMA) study, 

California, July to October 2005. 

[The five-digit number below the constituent name is the U.S. Geological Survey parameter code used to 

uniquely identify a specific constituent or property; MSMB, Monterey Bay study area well; MSSC, Santa 

Cruz study area well; MRL, method reporting level; NL, California notification level; μg/L, microgram per 

liter; —, analyzed but not detected] 

GAMA Perchlorate N-nitrosodi- 1,2,3-trichloroidentification (μg/L) methylamine propane 

No.1 (μg/L) (μg/L) 

Threshold type NL NL NL 

Threshold (μg/L) 6 0.01 0.005 

[MRL] [0.5] [0.002] [0.005] 

MSMB-44 — 0.0030 0.034 

MSSC-08 — 0.0022 — 

1

Out of 97 samples, only those with detections are listed. 
 

6 Ground-Water Quality Data, Monterey Bay and Salinas Valley Basins 2005—Results, Calif. GAMA Program 

Table 14. Nutrients and dissolved organic carbon in filtered ground-water samples collected for the Monterey Bay and Salinas 

Valley Ground-Water Ambient Monitoring and Assessment (GAMA) study, California, July to October 2005. 

[The five-digit number below the constituent name is the U.S. Geological Survey parameter code used to uniquely identify a specific constituent or property; 

MSMB, Monterey Bay study area well; MSMBFP, Monterey Bay study area flow-path well; MSMBMW, Monterey Bay study area monitoring well; MSPR, 

Paso Robles study area well; MSSC, Santa Cruz study area well; MSSV, Salinas Valley study area well; HAL-US, U.S. Environmental Protection Agency 

Lifetime Health Advisory; MCL-US, U.S. Environmental Protection Agency maximum contaminant level; E, estimated value; LRL, laboratory reporting level; 

mg/L, milligrams per liter; na, not available; V or VE, value censored due to blank contamination and not included in ground-water quality analyses; *, value 

exceeds regulatory threshold; —, not detected] 

Total nitrogen 

GAMA 

identification 

No. 

Ammonia as 

nitrogen 

(mg/L) 

(0060) 

Dissolved 

organic 

carbon 

(mg/L) 

(0061)

 Nitrite as 

nitrogen 

(mg/L) 

(00613) 

Nitrite plus 

nitrate 

as nitrogen 

(mg/L) 

(00631) 

(nitrate + nitrite + 

ammonia + 

organicnitrogen) 

as nitrogen 

(mg/L) 

Phosphorous 

as 

orthophos ­

phate 

(mg/L) 

(00671) 

(6254) 

Threshold type HAL-US na MCL-US MCL-US na na 

Threshold (mg/L) 30 na 1 10 na na 

[LRL] [0.04] [0.3] [0.00] [0.06] [0.03] [0.006] 

MSMB-04 — — — — — 0.011 

MSMB-09 — E0.2 — 0.09 0.13 0.079 

MSMB-12 0.50 0.4 — — 0.55 0.013 

MSMB-18 — E0.3 — 0.67 0.70 0.057 

MSMB-20 — 0.4 — 1.60 1.75 0.068 

MSMB-22 — 1.8 — — — 0.014 

MSMB-291 — 4.4 — 4.67 4.56 0.066 

MSMB-30 — E0.3 — 3.87 4.00 0.060 

MSMB-33 — 0.4 E0.005 1.52 1.55 0.039 

MSMB-35 0.07 1.8 — — 0.17 0.048 

MSMB-37 — VE0.2 — 1.64 1.68 0.054 

MSMB-40 — E0.3 — 1.18 1.18 0.034 

MSMB-441 — V1.0 — *37.8 37.5 0.025 

MSMB-45 0.11 1.3 0.008 — 0.17 0.075 

MSMB-47 — VE0.2 — 0.56 0.59 — 

MSMBFP-021 — 0.7 — *11.6 11.4 0.016 

MSMBFP-03 — 0.5 — 9.34 9.55 0.060 

MSMBMW-01 — VE0.3 — 0.80 0.82 0.006 

MSMBMW-02 — VE0.3 — 0.95 1.02 0.009 

MSMBMW-03 — V0.4 — 1.38 1.40 0.066 

MSPR-01 — 1.0 — 2.19 2.25 0.010 

MSPR-081 — — 3.57 3.74 E0.005 

MSPR-10 — 0.4 E0.004 0.38 0.40 E0.005 

MSSC-04 0.70 0.8 — — 0.75 0.007 

MSSC-06 0.07 0.4 — — 0.09 0.103 

MSSC-07 0.68 0.4 — — 0.70 0.018 

MSSC-08 0.35 0.7 — — 0.39 0.075 

MSSV-01 1.60 0.9 — — 1.64 E0.005 

MSSV-02 — 0.6 — 0.31 0.40 0.051 

MSSV-03 — 1.3 — E0.04 0.10 0.106 

MSSV-07 — 0.7 — 1.03 1.17 0.040 

MSSV-11 — 0.4 — 1.85 1.96 0.013 

MSSV-18 0.04 0.3 — 0.24 0.30 0.007 

MSSV-19 — 0.4 — 1.02 1.06 0.011 

1

Total nitrogen in these samples is less than the sum of the filtered nitrogen analytes, but falls within the U.S. Geological Survey National Water Quality Laboratory acceptance criterion of a 10 percent relative percent difference. 
 

 

 

 

 

 

 

 

 

 

 

 

 

Tables 6 

Table 15. Major and minor ions and dissolved solids in filtered ground-water samples collected for the Monterey Bay and Salinas 

Valley Ground-Water Ambient Monitoring and Assessment (GAMA) study, California, July to October 2005. 

[The five-digit number below the constituent name is the U.S. Geological Survey parameter code used to uniquely identify a specific constituent or property; 

MSMB, Monterey Bay study area well; MSMBFP, Monterey Bay study area flow-path well; MSMBMW, Monterey Bay study area monitoring well; MSPR, 

Paso Robles study area well; MSSC, Santa Cruz study area well; MSSV, Salinas Valley study area well; MCL-US, U.S. Environmental Protection Agency 

maximum contaminant level; SMCL-CA, California Department of Health Services secondary maximum contaminant level; SMCL-US, U.S. Environmental 

Protection Agency secondary maximum contaminant level; LRL, laboratory reporting level; mg/L, milligrams per liter; E, estimated value; na, not available; 

nd, no data; *, value exceeds regulatory threshold; —, not detected] 

Total 

dissolved 

GAMA 

identification 

No. 

Calcium 

(mg/L) 

(0015) 

Magnesium 

(mg/L) 

(0025) 

Potassium 

(mg/L) 

 (0035) 

Sodium 

(mg/L) 

(0030) 

Bromide 

(mg/L) 

(7170) 

Chloride 

(mg/L) 

 (0040) 

Fluoride 

(mg/L) 

 (0050) 

Iodide 

(mg/L) 

(7165) 

Silica 

(mg/L) 

(0055) 

Sulfate 

(mg/L) 

(0045) 

solids 

(residue 

on evaporation) 

(mg/L) 

(70300) 

Threshold 

type na na na na na 

SMCLCA MCL-US na na SMCLCA1 SMCL-CA2 

Threshold 

(mg/L) na na na na na 250 2 na na 250 500 

[LRL] [0.02] [0.00] [0.16] [0.2] [0.02] [0.2] [0.1] [0.002] [0.04] [0.1] [10] 

MSMB-04 40.2 52.4 16.9 112 1.01 241 E0.1 E0.015 31.2 61.9 *658 

MSMB-09 49.5 20.8 1.85 20.3 — 17.0 0.3 0.004 34.0 31.6 281 

MSMB-12 15.4 0.64 3.78 130 0.42 123 0.1 0.049 39.0 46.4 446 

MSMB-18 34.8 14.6 1.97 45.7 E0.01 61.2 0.2 — 51.1 14.4 302 

MSMB-20 78.9 32.7 2.53 39.0 0.28 31.3 0.2 0.008 37.5 54.3 464 

MSMB-22 69.2 53.2 2.56 69.1 0.27 73.9 0.2 0.041 30.9 125 *619 

MSMB-29 163 62.0 5.46 149 0.66 68.3 0.2 0.012 37.3 *445 *1,230 

MSMB-30 84.0 30.9 2.21 58.4 0.38 112 0.3 E0.002 45.5 88.1 *547 

MSMB-33 27.7 11.0 1.93 69.7 0.22 71.2 0.4 0.029 31.4 6.80 312 

MSMB-35 100 57.9 2.36 89.5 0.92 98.2 0.3 0.030 31.5 216 *828 

MSMB-37 47.0 16.2 1.81 75.8 0.36 113 0.5 0.003 45.5 15.2 425 

MSMB-40 58.4 22.3 3.46 57.9 0.29 48.0 0.4 0.003 41.2 133 *517 

MSMB-44 171 73.1 4.07 118 0.52 112 0.3 E0.004 36.6 *387 *1,300 

MSMB-45 50.6 14.9 3.17 27.2 0.08 29.1 0.3 E0.002 24.4 102 326 

MSMB-47 47.7 15.8 2.50 40.9 0.12 28.2 0.2 — 46.8 92.6 366 

MSMBFP-02 120 46.0 4.55 83.6 0.34 76.0 0.3 — 43.1 223 *853 

MSMBFP-03 114 49.6 4.24 84.8 0.58 178 0.3 0.004 41.0 161 *826 

MSMBMW-01 39.0 14.4 3.28 74.0 0.22 69.6 0.2 0.003 47.3 32.7 386 

MSMBMW-02 32.3 11.1 5.31 71.3 0.19 58.8 0.5 0.003 43.8 30.9 378 

MSMBMW-03 43.6 14.9 3.46 49.3 0.22 69.4 0.3 E0.001 44.7 26.3 360 

MSPR-01 100 38.1 1.54 34.5 0.25 58.8 0.2 0.002 37.7 126 *593 

MSPR-08 59.2 55.3 3.00 102 0.32 111 0.4 0.035 51.0 173 *725 

MSPR-10 124 58.9 4.17 209 0.29 86.5 0.4 0.009 39.9 *563 *1,330 

MSSC-04 72.8 8.93 2.68 76.2 0.28 44.1 0.1 0.022 39.4 180 *518 

MSSC-06 70.4 16.8 6.95 43.0 0.36 70.0 0.1 0.004 67.8 102 455 

MSSC-07 40.3 14.9 5.49 44.0 0.28 22.7 0.4 0.007 63.4 38.9 348 

MSSC-08 43.4 13.2 5.07 21.4 0.04 11.2 0.3 0.003 71.2 26.6 287 

MSSV-01 134 62.9 14.1 138 0.43 99.2 0.1 0.075 55.1 *449 *1,190 

MSSV-02 52.6 22.1 1.46 25.7 0.06 18.9 0.2 0.007 32.6 78.4 332 

MSSV-03 106 41.0 1.77 51.1 0.27 70.7 0.3 0.020 32.5 *272 *723 

MSSV-07 50.2 20.6 1.47 28.3 0.08 24.0 0.2 0.005 35.6 79.2 347 

MSSV-11 55.5 14.3 2.54 21.3 0.04 11.2 0.3 — 29.6 80.8 322 

MSSV-18 55.5 18.8 2.77 95.4 0.45 115 0.2 0.205 37.1 111 *555 

MSSV-19 57.2 21.4 3.09 61.2 0.16 41.8 0.3 0.003 44.1 136 470 

1

SMCL-CA threshold for sulfate has a recommended value of 250 mg/L, an upper value of 500 mg/L, and a short-term value of 600 mg/L.
 

2

SMCL-CA threshold for total dissolved solids has a recommended value of 500 mg/L, an upper value of 1,000 mg/L, and a short-term value of 1,500 mg/L.
 
 

 

70 Ground-Water Quality Data, Monterey Bay and Salinas Valley Basins 2005—Results, Calif. GAMA Program 

Table 16. Trace elements in filtered ground-water samples collected for the Monterey Bay and Salinas Valley Ground-Water 

Ambient Monitoring and Assessment (GAMA) study, California, July to October 2005. 

[The five-digit number below the constituent name is the U.S. Geological Survey parameter code used to uniquely identify a specific constituent or property; 

MSMB, Monterey Bay study area well; MSMBFP, Monterey Bay study area flow-path well; MSMBMW, Monterey Bay study area monitoring well; MSPR, 

Paso Robles study area well; MSSC, Santa Cruz study area well; MSSV, Salinas Valley study area well; HAL-US, U.S. Environmental Protection Agency 

Lifetime Health Advisory; MCL-CA, California Department of Health Services maximum contaminant level; MCL-US, U.S. Environmental Protection 

Agency maximum contaminant level; NL, California notification level; SMCL-US, U.S. Environmental Protection Agency secondary maximum contaminant 

level; TT-US, U.S. Environmental Protection Agency treatment technique; E, estimated value; LRL, laboratory reporting level; na, not available; V or VE, 

value censored due to blank contamination and not included in ground-water quality analyses; μg/L, micrograms per liter; —, not detected; *, value exceeds 

regulatory threshold] 

GAMA Aluminum Antimony Arsenic Barium Beryllium Boron Cadmium Chromium Cobalt 

identification (μg/L) (μg/L) (μg/L) (μg/L) (μg/L) (μg/L) (μg/L) (μg/L) (μg/L) 

no. (01106) (0105) (01000) (01005) (01010) (01020) (01025) (01030) (01035) 

Threshold type MCL-US MCL-US MCL-US MCL-CA MCL-US NL MCL-US MCL-CA na 

Threshold 1,000 6 10 1,000 4 1,000 5 50 na (μg/L) 

[LRL] [2] [0.2] [0.2] [0.2] [0.06] [] [0.04] [0.] [0.014] 

MSMB-04 E1 — — 4 — 88 — — 0.073 

MSMB-09 E0.9 — 0.6 26 — 64 — 14.2 0.059 

MSMB-12 7 — 2.3 23 — 131 — E0.04 — 

MSMB-18 — — 1.4 51 — 32 E0.03 13.1 0.059 

MSMB-20 — — 0.7 59 — 162 — 7.4 0.126 

MSMB-22 E1 — 0.56 96 — 463 E0.02 0.07 0.161 

MSMB-29 E1 — 2.6 46 — 656 0.37 E0.6 0.299 

MSMB-30 E0.9 E0.11 3.3 89 — 46 0.04 3.5 0.183 

MSMB-33 — 0.39 7.3 87 — 168 0.07 0.2 0.127 

MSMB-35 E1 E0.14 V0.5 191 1.28 427 — VE0.03 1.2 

MSMB-37 VE1 E0.13 5.5 37 — 144 E0.02 0.13 0.094 

MSMB-40 — — 1.0 72 — 146 — 3.5 0.101 

MSMB-44 — — 1.2 48 — 325 0.14 6.6 E0.030 

MSMB-45 — — 0.8 62 — 30 0.07 — 0.267 

MSMB-47 — — 1.9 55 — 84 E0.03 6.3 0.061 

MSMBFP-02 — — 1.6 46 — 252 0.12 2.8 0.282 

MSMBFP-03 — — 1.4 128 — 87 0.18 5.4 0.125 

MSMBMW-01 10 E0.17 3.2 78 0.06 129 E0.03 6.5 0.180 

MSMBMW-02 20 E0.17 2.1 86 — 118 E0.03 7.3 0.050 

MSMBMW-03 3 E0.17 2.7 71 — 49 0.04 4.2 0.180 

MSPR-01 — — 1.3 55 — 76 0.32 — 0.221 

MSPR-08 — E0.12 3.6 73 — 488 0.06 1.1 0.128 

MSPR-10 — — 1.3 16 — 753 0.07 — 0.390 

MSSC-04 — — — 24 — 151 — — 0.144 

MSSC-06 — — 0.2 22 — 47 — — 0.179 

MSSC-07 — — — 10 — 288 — — 0.094 

MSSC-08 E1 — — 9.0 — 83 — — 0.065 

MSSV-01 — — 4.8 13 — 285 — — 0.192 

MSSV-02 — E0.11 1.3 41 — 80 0.11 E0.4 0.077 

MSSV-03 — — 2.6 55 — 240 0.04 E0.03 0.219 

MSSV-07 E0.8 — 1.4 36 — 153 0.06 E0.7 0.112 

MSSV-11 E0.9 — 0.8 54 — 34 0.13 1.2 0.082 

MSSV-18 E1 — 1.6 108 — 330 E0.03 3.7 0.106 

MSSV-19 E0.8 — 1.8 40 — 208 0.05 4.7 0.108 
 

Tables 71 

Table 16. Trace elements in filtered ground-water samples collected for the Monterey Bay and Salinas Valley Ground-Water 

Ambient Monitoring and Assessment (GAMA) study, California, July to October 2005—Continued. 

[The five-digit number below the constituent name is the U.S. Geological Survey parameter code used to uniquely identify a specific constituent or property; 

MSMB, Monterey Bay study area well; MSMBFP, Monterey Bay study area flow-path well; MSMBMW, Monterey Bay study area monitoring well; MSPR, 

Paso Robles study area well; MSSC, Santa Cruz study area well; MSSV, Salinas Valley study area well; HAL-US, U.S. Environmental Protection Agency 

Lifetime Health Advisory; MCL-CA, California Department of Health Services maximum contaminant level; MCL-US, U.S. Environmental Protection 

Agency maximum contaminant level; NL, California notification level; SMCL-US, U.S. Environmental Protection Agency secondary maximum contaminant 

level; TT-US, U.S. Environmental Protection Agency treatment technique; E, estimated value; LRL, laboratory reporting level; na, not available; V or VE, 

value censored due to blank contamination and not included in ground-water quality analyses; μg/L, micrograms per liter; —, not detected; *, value exceeds 

regulatory threshold] 

Molyb- GAMA Copper Iron Lead Lithium Manganese Mercury Nickel Selenium denum identification (μg/L) (μg/L) (μg/L) (μg/L) (μg/L) (μg/L) (μg/L) (μg/L) (μg/L) no. (01040) (01046) (0104) (01130) (01056) (710) (01065) (01145) (01060) 

Threshold type TT-US SMCL-US NL na SMCL-US MCL-US HAL-US MCL-CA MCL-US 

Threshold 1,300 300 15 na 50 2 40 100 50 (μg/L) 

[LRL] [0.4] [6] [0.0] [0.6] [0.2] [0.01] [0.4] [0.06] [0.4] 

MSMB-04 4.4 48 0.55 10.9 13.3 — 2.1 1.22 — 

MSMB-09 E0.4 18 0.25 13.2 0.6 — 5.0 1.80 0.9 

MSMB-12 VE0.3 11 — 45 5.5 — 4.5 0.42 E0.1 

MSMB-18 0.7 — 0.14 16.1 — — 0.9 1.35 0.9 

MSMB-20 0.8 — 0.85 18.2 1.6 — 2.3 2.68 2.0 

MSMB-22 — 90 — 12.8 *60.8 — 4.2 1.41 — 

MSMB-29 3.9 VE4.0 3.60 19.4 3.2 — 36.7 4.74 9.8 

MSMB-30 4.0 9.0 0.94 29 1.3 E.010 2.7 4.26 4.8 

MSMB-33 VE0.2 87 0.46 5.8 *208 — *42.6 0.87 0.2 

MSMB-35 2.0 35 E0.15 19.3 *2,410 — 3.7 7.24 0.1 

MSMB-37 V1.9 VE6.0 0.38 56.1 VE0.1 — 6.3 1.67 — 

MSMB-40 1.5 — 0.82 15.6 E0.1 — 3.6 1.47 0.6 

MSMB-44 0.68 E4.0 0.59 35 0.6 — 8.2 0.76 6.2 

MSMB-45 0.6 *2,830 0.14 3.4 *170 — 3.7 2.74 0.5 

MSMB-47 0.6 10 1.99 16.6 0.8 — 6.8 1.49 1.4 

MSMBFP-02 2.2 VE3.0 0.65 30.8 — — 4.6 5.49 2.4 

MSMBFP-03 2.3 23 0.43 17.2 0.3 .050 1.8 2.99 6.2 

MSMBMW-01 0.6 — — 25.8 0.4 — 10.4 1.42 0.8 

MSMBMW-02 0.42 — — 43.3 0.8 — 11.5 2.10 1.0 

MSMBMW-03 0.45 — — 28.4 1 — 4.9 4.20 1.9 

MSPR-01 2.0 E4.0 3.52 7.9 0.2 — 6.2 4.67 7.3 

MSPR-08 1.9 10 0.09 86.1 1 .030 17.8 2.44 2.7 

MSPR-10 5.4 185 — 110 *78.4 — 18.2 5.20 17.6 

MSSC-04 0.7 37 — 71 13.8 — 2.1 4.04 0.4 

MSSC-06 0.7 *657 0.09 19.1 *197 — 2.8 3.44 0.7 

MSSC-07 E0.3 92 E0.06 45.7 38.8 — 2.9 1.84 — 

MSSC-08 VE0.2 218 0.38 35.2 *63 — 2.3 0.80 — 

MSSV-01 1.1 *508 6.62 95.6 34.5 — 18.2 4.17 0.4 

MSSV-02 0.4 — 0.33 8.8 5.1 — 4.8 1.73 0.4 

MSSV-03 V1.5 33 0.17 25.5 *536 — 6.3 3.52 0.4 

MSSV-07 1.2 6.0 4.03 16.5 E0.2 — 4.0 0.48 1.2 

MSSV-11 0.6 — 0.17 9.4 E0.2 — 6.2 2.20 0.9 

MSSV-18 0.8 24 0.29 33.7 19.3 — 11.5 1.03 1.6 

MSSV-19 1.0 7.0 0.15 23.5 2.7 — 9.5 1.93 2.0 
72 Ground-Water Quality Data, Monterey Bay and Salinas Valley Basins 2005—Results, Calif. GAMA Program 

Table 16. Trace elements in filtered ground-water samples collected for the Monterey Bay and Salinas Valley 

Ground-Water Ambient Monitoring and Assessment (GAMA) study, California, July to October 2005—Continued. 

[The five-digit number below the constituent name is the U.S. Geological Survey parameter code used to uniquely identify a specific 

constituent or property; MSMB, Monterey Bay study area well; MSMBFP, Monterey Bay study area flow-path well; MSMBMW, 

Monterey Bay study area monitoring well; MSPR, Paso Robles study area well; MSSC, Santa Cruz study area well; MSSV, Salinas 

Valley study area well; HAL-US, U.S. Environmental Protection Agency Lifetime Health Advisory; MCL-CA, California Department 

of Health Services maximum contaminant level; MCL-US, U.S. Environmental Protection Agency maximum contaminant level; NL, 

California notification level; SMCL-US, U.S. Environmental Protection Agency secondary maximum contaminant level; TT-US, U.S. 

Environmental Protection Agency treatment technique; E, estimated value; LRL, laboratory reporting level; na, not available; V or 

VE, value censored due to blank contamination and not included in ground-water quality analyses; μg/L, micrograms per liter; —, not 

detected; *, value exceeds regulatory threshold] 

GAMA Silver Strontium Thallium Tungsten Uranium Vanadium Zinc 

identification (μg/L) (μg/L) (μg/L) (μg/L) (μg/L) (μg/L) (μg/L) 

no. (01075) (0100) (01057) (01155) (22703) (0105) (0100) 

Threshold type na HAL-US MCL-US na MCL-US NL SMCL-US 

Threshold (μg/L) na 4,000 2 na 30 50 5,000 

[LRL] [0.2] [0.4] [0.04] [0.5] [0.04] [0.1] [0.04] 

MSMB-04 — 276 — — 0.74 0.3 3.0 

MSMB-09 — 248 — — 0.50 3.7 6.5 

MSMB-12 — 284 — — E0.03 — E0.38 

MSMB-18 — 239 — — 0.91 12.6 0.8 

MSMB-20 — 504 — — 1.72 4.4 1.4 

MSMB-22 — 698 — — 2.38 4.8 E0.59 

MSMB-29 — 785 — — 17.20 7.3 8.0 

MSMB-30 — 494 E0.02 — 5.94 7.1 4.5 

MSMB-33 — 245 — — 0.21 1.0 4.0 

MSMB-35 — 699 — — 1.35 3.0 6.6 

MSMB-37 — 374 — — 1.79 11.1 3.2 

MSMB-40 — 326 — — 4.80 16.7 8.2 

MSMB-44 — 996 — — 18.50 4.9 3.9 

MSMB-45 — 255 — — 0.20 0.8 1.8 

MSMB-47 — 395 — — 3.00 12.8 2.5 

MSMBFP-02 — 696 — — 13.10 9.7 4.3 

MSMBFP-03 — 671 — — 9.12 6.2 2.9 

MSMBMW-01 — 401 — 0.9 3.50 18.9 E0.4 

MSMBMW-02 — 332 — 0.4 2.21 12.4 — 

MSMBMW-03 — 260 — 0.5 2.21 3.9 0.97 

MSPR-01 — 455 0.04 — 2.58 2.4 3.1 

MSPR-08 — 1,330 — — 18.30 20.5 9.4 

MSPR-10 — 1,790 — — 28.90 6.8 3.3 

MSSC-04 — 900 — — — 0.3 2.6 

MSSC-06 — 226 — — E0.03 — 10.0 

MSSC-07 — 467 — — — 0.4 1.7 

MSSC-08 — 281 — 0.2 — — 3.0 

MSSV-01 — 1,530 0.05 — 0.37 E0.1 1,470 

MSSV-02 — 326 — — 1.42 3.4 1.0 

MSSV-03 — 688 — — 3.00 0.8 4.6 

MSSV-07 — 344 — — 1.09 3.7 1.7 

MSSV-11 — 293 — — 4.08 3.7 E0.5 

MSSV-18 — 572 — — 2.83 9.4 1.4 

MSSV-19 — 436 — — 4.13 9.6 3.7 
Tables 73 

Table 17. Inorganic arsenic and iron speciation results for 

filtered ground-water samples collected for the Monterey Bay 

and Salinas Valley Ground-Water Ambient Monitoring and 

Assessment (GAMA) study, California, July to October 2005. 

[The five-digit number below the constituent name is the U.S. Geological 

Survey parameter code used to uniquely identify a specific constituent or 

property; MSMB, Monterey Bay study area well; MSMBFP, Monterey Bay 

study area flow-path well; MSMBMW, Monterey Bay study area monitoring well; MSPR, Paso Robles study area well; MSSC, Santa Cruz study area 

well; MSSV, Salinas Valley study area well; HAL-US, U.S. Environmental 

Protection Agency Lifetime Health Advisory; MCL-US, U.S. Environmental Protection Agency maximum contaminant level; MDL, method detection 

limit; na, not available; μg/L, micrograms per liter; —, not detected] 

Arsenic Arsenic, Iron, Iron (II), GAMA (III), dissolved dissolved dissolved identification dissolved (μg/L) (μg/L) (μg/L) No. (μg/L) (033) (01046) (01047) (034) 

Threshold type MCL-US na HAL-US na 

Threshold 

(μg/L) 10 na 300 na 

[MDL] [0.5] [1] [1] [1] 

MSMB-04 <0.5 <1 45 9.0 

MSMB-09 <0.5 <1 <2 <2 

MSMB-12 1.5 <1 13 12 

MSMB-18 0.7 <1 <2 <2 

MSMB-20 <0.5 <1 <2 <2 

MSMB-22 <0.5 <1 72 64 

MSMB-29 2.1 <1 <2 <2 

MSMB-30 1.8 <1 24 3.0 

MSMB-33 4.3 2.1 77 54 

MSMB-35 <0.5 <1 16 14 

MSMB-37 4.1 <1 3.0 <2 

MSMB-40 0.6 <1 16 3.0 

MSMB-44 1.2 <1 3.0 <2 

MSMB-45 0.6 <1 2,560 2,550 

MSMB-47 1.1 <1 13 4.0 

MSMBFP-02 1.5 <1 <2 <2 

MSMBFP-03 1.4 <1 23 7.0 

MSMBMW-01 2.5 <1 2.0 <2 

MSMBMW-02 1.3 <1 3.0 <2 

MSMBMW-03 2.5 <1 3.0 <2 

MSPR-01 1.1 <1 3.0 2.0 

MSPR-08 2.2 <1 10 7.0 

MSPR-10 0.9 <1 173 146 

MSSC-04 <0.5 <1 31 30 

MSSC-06 <0.5 <1 607 588 

MSSC-07 <0.5 <1 86 60 

MSSC-08 0.6 <1 203 186 

MSSV-01 4.2 3.3 478 468 

MSSV-02 1.7 <1 5.0 4.0 

MSSV-03 1.9 <1 39 24 

MSSV-07 0.8 <1 <2 <2 

MSSV-11 <0.5 <1 2.0 <2 

MSSV-18 0.9 <1 25 11 
74 Ground-Water Quality Data, Monterey Bay and Salinas Valley Basins 2005—Results, Calif. GAMA Program 

Table 1. Chromium speciation results for filtered ground-water samples collected for the Monterey Bay and Salinas Valley GroundWater Ambient Monitoring and Assessment (GAMA) study, California, July to October 2005. 

[The five-digit number below the constituent name is the U.S. Geological Survey parameter code used to uniquely identify a specific constituent or property; 

MSMB, Monterey Bay study area well; MSMBFP, Monterey Bay study area flow-path well; MSMBMW, Monterey Bay study area monitoring well; MSPR, 

Paso Robles study area well; MSSC, Santa Cruz study area well; MSSV, Salinas Valley study area well; MCL-CA, California Department of Health Services 

maximum contaminant level; DLR, detection level for the purposes of reporting; MDL, method detection limit; μg/L, micrograms per liter; —, not detected; 

*, value exceeds regulatory threshold] 

Chromium (VI), Chromium (VI), Chromium, Chromium, GAMA (hexavalent) GAMA (hexavalent) dissolved dissolved identification dissolved identification dissolved (μg/L) (μg/L) no. (μg/L) no. (μg/L) (01030) (01030) (01032) (01032) 

Threshold type MCL-CA DLR Threshold type MCL-CA DLR 

Threshold (μg/L) 50 1 Threshold (μg/L) 50 1 

[MDL] [0.1] [0.1] [MDL] [0.1] [0.1] 

MSMB-01 8 *9 MSMB-45 3 *2 

MSMB-02 <1 <1 MSMB-46 33 *33 

MSMB-03 17 *16 MSMB-47 1 *1 

MSMB-04 <1 <1 MSMB-48 36 *34 

MSMB-05 25 *22 MSMBFP-01 <1 <1 

MSMB-06 <1 <1 MSMBFP-02 3 *3 

MSMB-07 7 *8 MSMBFP-03 8 *7 

MSMB-08 1 *1 MSMBMW-01 8 *7 

MSMB-09 17 *13 MSMBMW-02 13 *13 

MSMB-10 23 *23 MSMBMW-03 12 *11 

MSMB-11 7 *7 MSPR-01 <1 <1 

MSMB-12 2 *2 MSPR-02 6 *5 

MSMB-13 6 *6 MSPR-03 6 *4 

MSMB-14 8 *7 MSPR-04 6 *5 

MSMB-15 6 *6 MSPR-05 4 *5 

MSMB-16 5 *4 MSPR-06 7 *7 

MSMB-17 14 *12 MSPR-07 4 *4 

MSMB-18 13 *13 MSPR-08 1 *1 

MSMB-19 12 *12 MSPR-09 2 *2 

MSMB-20 8 *7 MSPR-10 <1 <1 

MSMB-21 28 *27 MSPR-11 1 *1 

MSMB-22 3 *3 MSSC-01 10 *10 

MSMB-23 19 *16 MSSC-02 18 *15 

MSMB-24 10 *10 MSSC-03 1 *2 

MSMB-25 18 *18 MSSC-04 3 *2 

MSMB-26 5 *5 MSSC-05 11 *7 

MSMB-27 7 *6 MSSC-06 2 *2 

MSMB-28 8 *8 MSSC-07 2 *2 

MSMB-29 2 *2 MSSC-08 2 *3 

MSMB-30 8 *6 MSSC-09 13 *16 

MSMB-31 <1 <1 MSSC-10 9 *9 

MSMB-32 19 *19 MSSC-11 18 *18 

MSMB-33 3 *2 MSSC-12 16 *14 

MSMB-34 <1 <1 MSSC-13 12 *17 

MSMB-35 3 *5 MSSV-01 3 *3 

MSMB-36 <1 <1 MSSV-02 2 *2 

MSMB-37 20 *20 MSSV-03 8 *7 

MSMB-38 4 *4 MSSV-04 8 *8 

MSMB-39 nc nc MSSV-05 5 *4 

MSMB-40 4 *4 MSSV-06 7 *8 

MSMB-41 33 *33 MSSV-07 2 *2 

MSMB-42 <1 <1 MSSV-08 17 *22 

MSMB-43 5 *6 MSSV-09 31 *26 

MSMB-44 24 *22 MSSV-10 32 *42 
Tables 75 

Table 1. Chromium speciation results for filtered ground-water 

samples collected for the Monterey Bay and Salinas Valley 

Ground-Water Ambient Monitoring and Assessment (GAMA) 

study, California, July to October 2005—Continued. 

[The five-digit number below the constituent name is the U.S. Geological 

Survey parameter code used to uniquely identify a specific constituent or 

property; MSMB, Monterey Bay study area well; MSMBFP, Monterey Bay 

study area flow-path well; MSMBMW, Monterey Bay study area monitoring 

well; MSPR, Paso Robles study area well; MSSC, Santa Cruz study area well; 

MSSV, Salinas Valley study area well; MCL-CA, California Department of 

Health Services maximum contaminant level; DLR, detection level for the 

purposes of reporting; MDL, method detection limit; μg/L, micrograms per 

liter; —, not detected; *, value exceeds regulatory threshold] 

Chromium (VI), 

GAMA 

identification 

no. 

Chromium, 

dissolved 

(μg/L) 

(01030) 

(hexavalent) 

dissolved 

(μg/L) 

(01032) 

Threshold type MCL-CA DLR 

Threshold (μg/L) 50 1 

[MDL] [0.1] [0.1] 

MSSV-11 4 *3 

MSSV-12 7 *5 

MSSV-13 8 *12 

MSSV-14 12 *10 

MSSV-15 6 *6 

MSSV-16 22 *22 

MSSV-17 2 *2 

MSSV-18 4 *3 

MSSV-19 7 *7 
 

76 Ground-Water Quality Data, Monterey Bay and Salinas Valley Basins 2005—Results, Calif. GAMA Program 

Table 1. Summary of radioactive constituents and carbon isotopes for filtered ground-water samples collected for the Monterey 

Bay and Salinas Valley Ground-Water Ambient Monitoring and Assessment (GAMA) study, California, July to October 2005. 

[The five-digit number below the constituent name is the U.S. Geological Survey parameter code used to uniquely identify a specific constituent or property; 

MSMB, Monterey Bay study area well; MSMBFP, Monterey Bay study area flow-path well; MSMBMW, Monterey Bay study area monitoring well; MSPR, 

Paso Robles study area well; MSSC, Santa Cruz study area well; MSSV, Salinas Valley study area well; MCL-CA, California Department of Health Services 

maximum contaminant level; MCL-US, U.S. environmental Protection Agency maximum contaminant level; Delta, notation, in per mil, of the differences in 

the carbon-13/carbon-12 ratio relative to University of Chicago Peedee Formation Standard; E, estimated value; na, not available; nc, sample not collected; 

pCi/L, picocuries per liter; SSMDC, sample specific minimum detectable concentration; *, value exceeds regulatory threshold; <, less than] 

GAMA 

identification 

no. 

Result 

Alpha radioactivity, 

72-hour count 

pCi/L) 

(62636) 

Critical 

value 

1-sigma 

combined 

uncertainty 

SSMDC Result 

Alpha radioactivity, 

30-day count 

(pCi/L) 

(6263) 

Critical 

value 

1­

sigma 

combined 

uncertainty 

SSMDC Result 

Beta radioactivity, 

72-hour count 

(pCi/L) 

(62642) 

Critical 

value 

1-sigma 

combined 

uncertainty 

SSMDC 

Threshold 

type 

MCLUS1 na na na MCL-US1 na na na MCL-CA na na na 

Threshold 15 na na na 15 na na na 50 na na na 

MSMB-04 <2.9 1.3 0.75 2.9 <2.1 0.82 0.55 2.1 18.6 1.1 2.1 2.3 

MSMB-09 E0.5 0.4 0.32 1.0 <1.3 0.52 0.37 1.3 E1.8 0.77 0.53 1.6 

MSMB-12 <1.7 0.7 0.55 1.7 E1.1 0.81 0.61 1.9 4.9 1.1 0.94 2.4 

MSMB-18 <2.5 1.0 0.55 2.5 <1.5 0.65 0.40 1.5 E3.1 1.8 1.20 3.7 

MSMB-20 E1.5 0.7 0.57 1.5 E2.5 0.43 0.60 1.1 E2.4 1.1 0.74 2.2 

MSMB-22 E2.3 0.8 0.74 1.9 E2.4 0.74 0.79 1.7 E3.8 1.1 0.80 2.2 

MSMB-29 E13.4 2.5 3.00 5.6 E8.2 1.40 1.80 3.4 9.3 1.2 1.30 2.5 

MSMB-30 E4.5 1.2 1.10 2.6 E2.0 1.10 0.87 2.5 E4.8 1.4 1.10 3.0 

MSMB-33 E1.4 0.7 0.57 1.7 <2.0 0.89 0.70 2.0 E1.8 1.1 0.72 2.2 

MSMB-35 <3.7 1.6 1.10 3.7 <4.0 1.80 1.10 4.0 <4.9 2.4 1.5 4.9 

MSMB-37 E2.8 0.8 0.80 1.8 E2.5 0.87 0.88 2.0 E2.3 1.3 0.88 2.6 

MSMB-40 E4.5 0.7 0.92 1.7 E3.2 0.70 0.77 1.6 E3.7 0.9 0.75 1.9 

MSMB-44 11.2 1.6 2.20 3.8 14.1 2.00 2.80 4.6 6.0 1.3 1.0 2.6 

MSMB-45 E2.5 0.5 0.89 1.7 E0.8 0.45 0.35 1.1 E4.7 1.2 1.00 2.6 

MSMB-47 E5.8 1.2 1.60 3.1 E1.5 0.90 0.72 2.1 E4.1 1.9 1.40 3.9 

MSMBFP-02 9.1 1.5 1.80 3.5 E5.9 1.60 1.50 3.6 4.7 1.0 0.80 2.0 

MSMBFP-03 E6.1 1.8 1.60 4.2 E3.3 1.50 1.20 3.4 7.1 1.0 1.00 2.1 

MSMBMW-01 E4.4 0.8 0.91 1.7 5.2 0.59 0.95 1.4 6.6 1.2 1.10 2.5 

MSMBMW-02 4.4 0.6 0.82 1.4 E3.1 0.53 0.68 1.3 4.4 0.9 0.78 1.9 

MSMBMW-03 E2.5 0.5 0.60 1.2 E1.8 0.52 0.52 1.2 E2.3 1 0.69 2.0 

MSPR-01 E4.1 0.8 1.00 1.8 E3.4 0.92 0.91 2.1 <3.3 1.6 0.95 3.3 

MSPR-08 12.7 1.1 2.00 2.7 11.3 0.91 1.70 2.1 1.7 1.8 1.20 3.7 

MSPR-10 *17.4 1.4 2.80 3.5 *16.3 1.80 2.80 4.1 6.6 1.5 1.20 3.2 

MSSC-04 E1.7 1.1 0.97 2.5 <1.9 0.82 0.55 1.9 E2.7 1.2 0.80 2.4 

MSSC-06 <1.5 0.6 0.40 1.5 <1.8 0.77 0.41 1.8 8.5 1.1 1.20 2.2 

MSSC-07 E1.1 0.7 0.51 1.6 <2.9 1.10 0.70 2.9 6.3 0.9 0.90 1.9 

MSSC-08 E3.2 1.3 1.20 3.2 <1.0 0.45 0.26 1.0 7.6 1.2 1.30 2.6 

MSSV-01 E5.4 1.2 1.60 3.0 E3.2 0.93 1.00 2.4 21.2 1.4 2.40 2.8 

MSSV-02 E1.1 0.4 0.44 1.0 <1.7 0.77 0.47 1.7 E1.7 0.9 0.58 1.8 

MSSV-03 5.1 0.7 1.00 1.6 E3.2 0.73 0.86 1.8 E2.0 1.4 0.92 2.9 

MSSV-07 E0.5 0.5 0.35 1.1 E0.7 0.53 0.40 1.2 E1.9 0.8 0.58 1.7 

MSSV-11 E3.1 0.7 1.00 2.0 E2.3 0.47 0.51 1.1 E3.6 1.3 0.97 2.8 

MSSV-18 E4.7 0.7 1.10 1.7 E3.3 0.65 0.77 1.6 E2.8 1 0.75 2.1 

MSSV-19 4.2 0.6 0.81 1.4 E2.5 1.10 1.00 2.5 3.7 1.1 0.83 2.3 1

Combined Radium-226 plus Radium-228. 

2

Proposed MCL-US. 
 

Tables 77 

Table 1. Summary of radioactive constituents and carbon isotopes for filtered ground-water samples collected for the Monterey 

Bay and Salinas Valley Ground-Water Ambient Monitoring and Assessment (GAMA) study, California, July to October 2005— 

Continued. 

[The five-digit number below the constituent name is the U.S. Geological Survey parameter code used to uniquely identify a specific constituent or property; 

MSMB, Monterey Bay study area well; MSMBFP, Monterey Bay study area flow-path well; MSMBMW, Monterey Bay study area monitoring well; MSPR, 

Paso Robles study area well; MSSC, Santa Cruz study area well; MSSV, Salinas Valley study area well; MCL-CA, California Department of Health Services 

maximum contaminant level; MCL-US, U.S. environmental Protection Agency maximum contaminant level; Delta, notation, in per mil, of the differences in 

the carbon-13/carbon-12 ratio relative to University of Chicago Peedee Formation Standard; E, estimated value; na, not available; nc, sample not collected; 

pCi/L, picocuries per liter; SSMDC, sample specific minimum detectable concentration; *, value exceeds regulatory threshold; <, less than] 

Beta radioactivity, Radium-226 30-day count (pCi/L) GAMA (pCi/L) (0511) identification (62645) 

no. 1-sigma 1-sigma Critical Result combined SSMDC Result Critical value combined SSMDC value uncertainty uncertainty 

Threshold MCL-CA na na na MCL-US1 na na na type 

Threshold 50 na na na 1

5 na na na 

MSMB-04 20.8 0.83 2.20 1.7 E0.075 0.014 0.016 0.034 

MSMB-09 E1.8 0.91 0.62 1.9 E0.059 0.017 0.013 0.036 

MSMB-12 E4.8 1.3 0.98 2.6 0.255 0.013 0.024 0.031 

MSMB-18 E1.8 0.65 0.45 1.3 E0.047 0.015 0.012 0.033 

MSMB-20 E3.0 1.1 0.81 2.4 <0.034 0.015 0.010 0.034 

MSMB-22 4.1 0.99 0.77 2.0 0.058 0.01 0.011 0.024 

MSMB-29 15.9 1.3 1.90 2.6 E0.040 0.015 0.013 0.035 

MSMB-30 5.5 0.75 0.78 1.5 0.326 0.017 0.022 0.036 

MSMB-33 E2.8 1.2 0.80 2.4 E0.075 0.019 0.017 0.044 

MSMB-35 <5.0 2.5 1.60 5.0 0.111 0.016 0.017 0.037 

MSMB-37 E2.5 1.4 0.89 2.8 0.075 0.013 0.013 0.029 

MSMB-40 5.8 0.91 0.87 1.9 0.092 0.011 0.014 0.027 

MSMB-44 16.4 1.2 1.90 2.5 0.071 0.014 0.012 0.03 

MSMB-45 3.4 0.62 0.54 1.3 0.072 0.013 0.013 0.03 

MSMB-47 E3.6 1.2 0.88 2.6 0.103 0.009 0.015 0.024 

MSMBFP-02 12.5 0.97 1.50 2.0 E0.066 0.017 0.014 0.037 

MSMBFP-03 5.5 1.2 0.97 2.5 0.212 0.017 0.018 0.036 

MSMBMW-01 6.7 1.1 1.00 2.2 nc 

MSMBMW-02 5.2 0.91 0.83 1.9 nc 

MSMBMW-03 E3.2 0.98 0.72 2.0 nc 

MSPR-01 <3.2 1.6 1.00 3.2 0.284 0.010 0.017 0.021 

MSPR-08 9.7 1.3 1.40 2.6 0.230 0.012 0.021 0.029 

MSPR-10 14.8 2.7 2.40 5.4 0.155 0.011 0.013 0.023 

MSSC-04 E3.6 1.2 0.88 2.5 0.097 0.014 0.014 0.031 

MSSC-06 8.1 1.2 1.20 2.5 E0.020 0.013 0.009 0.029 

MSSC-07 7.0 1.6 1.30 3.3 0.169 0.014 0.014 0.029 

MSSC-08 4.9 0.81 0.74 1.7 E0.028 0.019 0.013 0.042 

MSSV-01 21.4 1.1 2.40 2.3 0.372 0.012 0.025 0.028 

MSSV-02 E1.8 0.84 0.58 1.7 0.061 0.012 0.011 0.027 

MSSV-03 E3.9 1.3 0.94 2.6 0.576 0.016 0.036 0.037 

MSSV-07 E2.0 0.73 0.52 1.5 0.083 0.011 0.012 0.025 

MSSV-11 3.8 0.65 0.60 1.3 0.141 0.017 0.016 0.036 

MSSV-18 5.0 1.2 0.95 2.4 0.169 0.013 0.015 0.028 

MSSV-19 3.9 1.1 0.80 2.2 0.127 0.011 0.014 0.025 

1

Combined Radium-226 plus Radium-228. 

2

Proposed MCL-US. 
 

 

 

 

7 Ground-Water Quality Data, Monterey Bay and Salinas Valley Basins 2005—Results, Calif. GAMA Program 

Table 1. Summary of radioactive constituents and carbon isotopes for filtered ground-water samples collected for the Monterey 

Bay and Salinas Valley Ground-Water Ambient Monitoring and Assessment (GAMA) study, California, July to October 2005— 

Continued. 

[The five-digit number below the constituent name is the U.S. Geological Survey parameter code used to uniquely identify a specific constituent or property; 

MSMB, Monterey Bay study area well; MSMBFP, Monterey Bay study area flow-path well; MSMBMW, Monterey Bay study area monitoring well; MSPR, 

Paso Robles study area well; MSSC, Santa Cruz study area well; MSSV, Salinas Valley study area well; MCL-CA, California Department of Health Services 

maximum contaminant level; MCL-US, U.S. environmental Protection Agency maximum contaminant level; Delta, notation, in per mil, of the differences in 

the carbon-13/carbon-12 ratio relative to University of Chicago Peedee Formation Standard; E, estimated value; na, not available; nc, sample not collected; 

pCi/L, picocuries per liter; SSMDC, sample specific minimum detectable concentration; *, value exceeds regulatory threshold; <, less than] 

Radon-222 Carbon-14 

GAMA 

identification 

Radium-22 

(pCi/L) 

(1366) 

Radon-222 

(pCi/L) 

(2303) 

2-sigma 

combined 

uncertainty 

(pCi/L) 

Delta 

carbon-13 

(per mil) 

Carbon-14 

(percent 

modern) 

(433) 

counting 

error, water, 

filtered, percent modern 

No. (76002) (434) 

Result Critical 

value 

1-sigma 

combined 

uncertainty 

SSMDC Result Result Result Result Result 

Threshold type MCL-US1 na na na MCL-US2 na na na na 

Threshold 1

5 na na na 300 na na na na 

MSMB-04 E0.37 0.25 0.12 0.53 *300 21 –15.50 5.7 0.1 

MSMB-09 E0.41 0.21 0.09 0.45 210 19 –14.60 73.0 0.4 

MSMB-12 <0.61 0.28 0.12 0.61 *1,450 36 –14.13 6.3 0.2 

MSMB-18 <0.70 0.33 0.14 0.70 *360 20 –15.10 55.9 0.3 

MSMB-20 <0.67 0.31 0.12 0.67 *480 23 –16.80 76.8 0.4 

MSMB-22 <0.48 0.22 0.14 0.48 250 19 –13.67 80.1 0.4 

MSMB-29 E0.49 0.22 0.10 0.48 *340 20 –16.15 96.0 0.4 

MSMB-30 E0.31 0.22 0.10 0.47 *560 24 –14.40 78.9 0.4 

MSMB-33 <0.58 0.27 0.11 0.58 *1,610 36 –17.32 53.8 0.4 

MSMB-35 E0.29 0.21 0.09 0.45 170 16 –14.56 96.8 0.5 

MSMB-37 <0.51 0.24 0.10 0.51 *750 26 –14.35 57.2 0.4 

MSMB-40 E0.46 0.26 0.14 0.56 *460 23 –11.77 72.6 0.4 

MSMB-44 E0.24 0.22 0.13 0.47 *410 22 nc nc nc 

MSMB-45 E0.53 0.23 0.12 0.49 260 19 –13.40 91.7 0.4 

MSMB-47 <0.39 0.18 0.08 0.39 *610 25 –10.60 32.4 0.2 

MSMBFP-02 <0.54 0.25 0.10 0.54 *450 22 –14.53 92.9 0.5 

MSMBFP-03 E0.56 0.21 0.22 0.45 *560 23 –15.70 89.9 0.4 

MSMBMW-01 nc nc nc –12.64 19.7 0.2 

MSMBMW-02 nc nc nc –13.38 43.3 0.3 

MSMBMW-03 nc nc nc –14.07 72.4 0.4 

MSPR-01 E0.36 0.21 0.12 0.46 *650 24 –14.30 90.5 0.4 

MSPR-08 <0.58 0.27 0.14 0.58 *470 23 –12.90 47.4 0.3 

MSPR-10 E0.42 0.21 0.12 0.45 *450 22 –13.00 67.1 0.3 

MSSC-04 E0.66 0.27 0.16 na 280 19 –19.50 65.6 0.3 

MSSC-06 <0.45 0.21 0.10 0.45 190 18 –20.40 71.2 0.3 

MSSC-07 E0.56 0.21 0.13 0.45 280 20 –14.30 31.3 0.2 

MSSC-08 <0.59 0.27 0.10 0.59 200 17 –15.97 57.2 0.4 

MSSV-01 0.96 0.22 0.13 0.46 *390 20 –15.10 8.8 0.1 

MSSV-02 <0.53 0.25 0.11 0.53 *650 25 –12.50 100.1 0.4 

MSSV-03 E0.25 0.25 0.11 0.53 *930 29 –13.09 99.0 0.5 

MSSV-07 <0.47 0.22 0.09 0.47 *590 23 –12.60 99.8 0.4 

MSSV-11 <0.46 0.21 0.09 0.46 *820 28 –10.50 89.4 0.4 

MSSV-18 <0.44 0.21 0.10 0.44 *680 26 –10.80 16.2 0.2 

MSSV-19 <0.54 0.25 0.12 0.54 600 26 –10.80 33.6 0.2 

1

Combined Radium-226 plus Radium-228. 

2

Proposed MCL-US. 
 

  

Tables 7 

Table 20. Hydrogen and oxygen isotopes in unfiltered ground-water samples collected for the Monterey Bay and Salinas Valley 

Ground-Water Ambient Monitoring and Assessment (GAMA) study, California, July to October 2005. 

[The five-digit number below the constituent name is the U.S. Geological Survey parameter code used to uniquely identify a specific constituent or property; 

MSMB, Monterey Bay study area well; MSMBFP, Monterey Bay study area flow-path well; MSMBMW, Monterey Bay study area monitoring well; MSPR, 

Paso Robles study area well; MSSC, Santa Cruz study area well; MSSV, Salinas Valley study area well; MCL-CA, California Department of Health Services 

maximum contaminant level; δ, notation, in per mil, of the differences in oxygen-18/oxygen-16 and hydrogen-2/hydrogen-1 ratios relative to Standard Mean 

Ocean Water (SMOW); na, not available; pCi/L, picocuries per liter; —, not detected] 

Tritium 2- Tritium 2­

sigma sigma GAMA δ2

H δ1O GAMA δ2H δ1O Tritium combined Tritium combined identification (per mil) (per mil) identification (per mil) (per mil) (pCi/L) uncertainty (pCi/L) uncertainty No. (202) (205) No. (202) (205) (pCi/L) (pCi/L) 

(755) (755) 

Threshold type na na MCL-CA na Threshold type na na MCL-CA na 

Threshold na na 20000 na Threshold na na 20000 na 

MSMB-01 –43.9 –6.26 1.0 1.0 MSMB-44 –37.9 –5.64 7.4 1.0 

MSMB-02 –41.9 –6.34 4.5 1.0 MSMB-45 –42.3 –6.60 7.0 1.0 

MSMB-03 –50.7 –7.38 — 0.6 MSMB-46 –38.9 –5.70 7.0 1.0 

MSMB-04 –45.9 –7.32 2.2 1.0 MSMB-47 –45.6 –6.92 — 1.0 

MSMB-05 –37.2 –6.00 3.8 1.0 MSMB-48 –42.9 –6.30 4.5 0.6 

MSMB-06 –34.0 –5.81 1.6 0.6 MSMBFP-01 –54.8 –7.94 0.6 1.0 

MSMB-07 –35.9 –6.05 0.6 0.6 MSMBFP-02 –38.8 –5.68 9.3 1.0 

MSMB-08 –36.9 –6.01 3.8 1.0 MSMBFP-03 –41.9 –6.14 3.8 0.6 

MSMB-09 –36.5 –6.14 1.6 1.0 MSMBMW-01 –46.6 –6.78 — 0.6 

MSMB-10 –38.5 –5.80 0.6 0.6 MSMBMW-02 –45.3 –6.67 — 0.6 

MSMB-11 –42.3 –6.35 1.0 1.0 MSMBMW-03 –41.8 –6.46 — 0.6 

MSMB-12 –46.2 –6.80 — 0.6 MSPR-01 –38.3 –5.65 7.0 0.6 

MSMB-13 –44.5 –6.59 0.6 0.0 MSPR-02 –40.0 –6.14 4.5 0.6 

MSMB-14 –44.8 –6.43 0.6 1.0 MSPR-03 –58.4 –8.30 0.3 0.6 

MSMB-15 –43.6 –6.32 2.2 0.6 MSPR-04 –53.0 –7.47 1.6 0.6 

MSMB-16 –45.6 –6.72 1.0 0.6 MSPR-05 –56.8 –8.09 0.6 0.6 

MSMB-17 –43.2 –6.40 — 1.0 MSPR-06 –43.8 –6.27 1.6 0.6 

MSMB-18 –38.6 –6.24 — 0.6 MSPR-07 –45.0 –5.83 — 0.6 

MSMB-19 –39.4 –5.94 0.3 1.0 MSPR-08 –44.3 –6.25 0.6 0.6 

MSMB-20 –35.4 –5.53 2.6 1.0 MSPR-09 –55.2 –7.93 — 0.6 

MSMB-21 –38.0 –6.11 — 0.6 MSPR-10 –49.3 –7.08 — 0.6 

MSMB-22 –38.8 –5.81 1.0 0.6 MSPR-11 –50.9 –7.46 — 0.6 

MSMB-23 –39.4 –6.04 — 0.6 MSSC-01 –33.8 –5.90 8.0 1.0 

MSMB-24 –40.1 –6.14 1.0 0.6 MSSC-02 –28.8 –5.06 7.4 0.6 

MSMB-25 –43.0 –6.29 0.3 0.6 MSSC-03 –32.9 –5.66 6.7 1.0 

MSMB-26 –43.9 –6.68 1.3 1.0 MSSC-04 –35.4 –5.70 5.4 1.0 

MSMB-27 –48.0 –6.81 0.6 0.6 MSSC-05 –38.1 –6.25 — 0.6 

MSMB-28 –46.5 –6.66 1.6 0.6 MSSC-06 –32.9 –5.45 4.5 1.0 

MSMB-29 –37.8 –5.60 9.0 1.0 MSSC-07 –34.0 –5.80 1.3 1.0 

MSMB-30 –43.4 –6.49 0.3 0.6 MSSC-08 –35.6 –5.86 — 0.6 

MSMB-31 –41.7 –6.30 6.7 1.0 MSSC-09 –34.2 –6.12 4.5 0.6 

MSMB-32 –41.6 –6.13 1.3 0.6 MSSC-10 –39.2 –6.32 — 0.6 

MSMB-33 –41.0 –6.28 1.6 0.6 MSSC-11 –38.1 –6.28 — 0.6 

MSMB-34 –40.0 –6.08 1.0 1.0 MSSC-12 –36.9 –6.18 — 0.6 

MSMB-35 –37.6 –5.37 8.0 1.0 MSSC-13 –34.7 –6.11 13.8 1.0 

MSMB-36 –42.3 –6.34 1.6 0.6 MSSV-01 –54.2 –7.41 — 0.6 

MSMB-37 –42.4 –6.39 — 1.0 MSSV-02 –34.0 –4.85 6.7 0.6 

MSMB-38 –43.7 –6.54 1.9 0.6 MSSV-03 –34.0 –4.59 6.7 0.6 

MSMB-39 –45.1 –6.72 1.0 0.6 MSSV-04 –43.7 –6.05 2.2 1.0 

MSMB-40 –44.3 –6.74 1.6 0.6 MSSV-05 –36.6 –5.29 6.4 0.6 

MSMB-41 –36.2 –5.43 11.8 1.0 MSSV-06 –34.9 –4.87 6.7 1.0 

MSMB-42 –44.5 –6.69 6.4 0.6 MSSV-07 –34.2 –4.88 6.0 1.0 

MSMB-43 –37.0 –5.32 10.2 0.6 MSSV-08 –33.8 –4.94 7.4 1.0 
 

 

0 Ground-Water Quality Data, Monterey Bay and Salinas Valley Basins 2005—Results, Calif. GAMA Program 

Table 20. Hydrogen and oxygen isotopes in unfiltered groundwater samples collected for the Monterey Bay and Salinas Valley 

Ground-Water Ambient Monitoring and Assessment (GAMA) 

study, California, July to October 2005—Continued. 

[The five-digit number below the constituent name is the U.S. Geological 

Survey parameter code used to uniquely identify a specific constituent or 

property; MSMB, Monterey Bay study area well; MSMBFP, Monterey Bay 

study area flow-path well; MSMBMW, Monterey Bay study area monitoring well; MSPR, Paso Robles study area well; MSSC, Santa Cruz study area 

well; MSSV, Salinas Valley study area well; MCL-CA, California Department 

of Health Services maximum contaminant level; δ, notation, in per mil, of 

the differences in oxygen-18/oxygen-16 and hydrogen-2/hydrogen-1 ratios 

relative to Standard Mean Ocean Water (SMOW); na, not available; pCi/L, 

picocuries per liter; —, not detected] 

Tritium 2­

GAMA 

identification 

No. 

δ2

H 

(per mil) 

(202) 

δ1O 

(per mil) 

(205) 

Tritium 

(pCi/L) 

sigma 

combined 

uncertainty 

(pCi/L) 

(755) 

Threshold type na na MCL-CA na 

Threshold na na 20000 na 

MSSV-09 –33.1 –4.69 6.4 0.6 

MSSV-10 –29.1 –3.83 8.0 1.0 

MSSV-11 –45.7 –7.00 8.6 0.6 

MSSV-12 –44.8 –7.14 8.0 1.0 

MSSV-13 –45.4 –7.15 5.1 0.6 

MSSV-14 –43.1 –6.13 5.8 0.6 

MSSV-15 –27.0 –3.58 7.0 1.0 

MSSV-16 –46.2 –7.16 — 1.0 

MSSV-17 –48.2 –7.46 3.5 1.0 

MSSV-18 –48.0 –7.04 — 0.6 

MSSV-19 –45.2 –6.74 — 0.6 
 

 

Tables 1 

Table 21. Tritium and noble gas results, analyzed at Lawrence Livermore National Laboratory, for unfiltered ground-water samples 

collected for the Monterey Bay and Salinas Valley Ground-Water Ambient Monitoring and Assessment (GAMA) study, California, July 

to October 2005. 

[The five-digit number below the constituent name is the U.S. Geological Survey parameter code used to uniquely identify a specific constituent or property; 

MSMB, Monterey Bay study area well; MSMBFP, Monterey Bay study area flow-path well; MSMBMW, Monterey Bay study area monitoring well; MSPR, 

Paso Robles study area well; MSSC, Santa Cruz study area well; MSSV, Salinas Valley study area well; MCL-CA, California Department of Health Services 

maximum contaminant level; cm3 STP g–1 H20, cubic centimeters at standard temperature and pressure per gram of water; na, not available; nc, sample not 

collected; pCi/L, picocuries per liter] 

Helium–3/ Helium–4 Neon Argon Krypton Xenon Tritium Dissolved 

Helium–4 (5561) (61046) (5563) (5565) (5567) GAMA Collection Tritium measurement gas (atom ratio) identification date (pCi/L) 	 uncertainty (+/–) analysis (cm3

 STP g–1 H O) No. (mm/dd/yy) (07000)	 (61040)	 2 (pCi/L) date 


(07001) (mm/dd/yy)
 x 10–6 x 10–7 x 10–7 x 10–4 x 10– x 10– 

Threshold type na MCL-CA na na na na na na na na 

Threshold na 20,000 na na na na na na na na 

MSMB-01 08/04/05 2.65 0.3 08/30/05 0.97 0.73 2.22 3.53 7.72 1.08 

MSMB-02 08/10/05 5.85 0.3 09/01/05 0.54 2.76 3.94 4.48 8.95 1.16 

MSMB-03 08/31/05 <1.0 0.2 11/14/05 0.22 4.97 2.28 4.73 9.06 1.29 

MSMB-04 08/17/05 <1.0 0.2 09/07/05 0.49 2.86 3.25 5.03 11.4 1.57 

MSMB-05 08/08/05 3.71 0.3 08/31/05 1.44 0.48 2.15 3.46 7.93 1.12 

MSMB-06 08/08/05 2.00 0.2 08/31/05 1.26 0.58 2.49 4.12 9.41 1.29 

MSMB-07 08/08/05 1.73 0.2 08/31/05 0.83 1.09 2.91 4.56 10.1 1.46 

MSMB-08 08/16/05 3.51 0.3 09/07/05 1.64 0.57 2.28 4.01 9.03 0.00 

MSMB-09 08/15/05 <1.0 0.1 09/09/05 1.37 0.76 3.35 4.63 10.0 1.27 

MSMB-10 08/30/05 <1.0 0.2 11/14/05 1.33 0.67 2.65 4.88 8.85 1.16 

MSMB-11 08/18/05 <1.0 0.2 09/07/05 0.18 11.18 3.35 4.48 9.74 1.28 

MSMB-12 09/14/05 <1.0 0.2 10/28/05 0.29 2.71 2.48 4.07 9.08 1.24 

MSMB-13 08/17/05 1.07 0.2 09/07/05 1.10 0.85 2.74 3.95 8.79 1.13 

MSMB-14 08/03/05 <1.0 0.3 08/30/05 1.09 0.89 3.10 4.32 9.48 1.23 

MSMB-15 08/04/05 2.43 0.3 08/30/05 1.37 0.89 3.60 4.65 9.71 1.25 

MSMB-16 08/17/05 <1.0 0.2 09/08/05 1.09 0.84 2.67 3.89 8.74 1.17 

MSMB-17 08/09/05 <1.0 0.2 08/31/05 0.14 17.8 3.30 4.43 9.62 1.28 

MSMB-18 08/11/05 <1.0 0.2 09/01/05 0.94 1.07 3.00 4.43 9.30 1.20 

MSMB-19 08/16/05 <1.0 0.2 09/07/05 1.32 0.58 2.46 3.87 8.56 1.14 

MSMB-20 08/16/05 2.70 0.2 09/07/05 1.31 0.71 2.85 4.21 9.35 1.20 

MSMB-21 09/20/05 <1.0 0.2 11/29/05 1.31 0.66 2.77 4.33 9.28 1.31 

MSMB-22 09/19/05 1.48 0.3 11/29/05 1.51 0.61 2.51 3.80 8.23 1.15 

MSMB-23 08/30/05 <1.0 0.2 11/14/05 1.23 0.59 2.26 4.47 8.24 1.12 

MSMB-24 08/09/05 1.73 0.2 09/01/05 1.31 0.53 2.15 3.46 7.76 1.06 

MSMB-25 09/19/05 <1.0 0.2 11/14/05 0.20 7.33 3.21 5.34 9.60 1.20 

MSMB-26 08/11/05 1.89 0.2 09/01/05 0.88 1.40 3.11 4.08 9.40 1.22 

MSMB-27 08/03/05 1.49 0.2 08/31/05 0.40 2.58 3.17 4.40 9.45 1.29 

MSMB-28 08/03/05 2.18 0.2 08/31/05 1.31 0.70 2.62 3.92 8.86 1.21 

MSMB-29 08/30/05 7.86 0.6 10/28/05 1.64 0.56 2.31 3.39 7.99 1.07 

MSMB-30 08/08/05 <1.0 0.2 08/31/05 0.76 1.45 3.18 4.39 9.57 1.29 

MSMB-31 08/11/05 7.33 0.4 09/01/05 1.60 0.84 3.49 4.65 10.5 1.33 

MSMB-32 08/31/05 1.71 0.2 11/14/05 1.36 0.47 1.96 4.03 7.51 1.02 

MSMB-33 09/13/05 2.50 0.3 11/14/05 0.67 2.64 2.50 5.06 8.24 1.11 

MSMB-34 08/16/05 <1.0 0.2 09/07/05 0.97 0.86 2.52 3.95 9.09 1.21 

MSMB-35 09/20/05 9.02 0.5 11/29/05 1.41 0.72 3.04 4.06 8.54 1.12 

MSMB-36 08/10/05 2.76 0.2 09/01/05 0.27 5.54 3.18 4.43 9.07 1.29 

MSMB-37 09/01/05 <1.0 0.2 10/28/05 0.12 24.4 3.35 4.42 9.45 1.19 

MSMB-38 08/11/05 3.18 0.2 09/01/05 0.77 1.52 3.05 4.12 9.47 1.24 
 

 

2 Ground-Water Quality Data, Monterey Bay and Salinas Valley Basins 2005—Results, Calif. GAMA Program 

Table 21. Tritium and noble gas results, analyzed at Lawrence Livermore National Laboratory, for for unfiltered ground-water samples 

collected for the Monterey Bay and Salinas Valley Ground-Water Ambient Monitoring and Assessment (GAMA) study, California, July to 

October 2005—Continued. 

[The five-digit number below the constituent name is the U.S. Geological Survey parameter code used to uniquely identify a specific constituent or property; 

MSMB, Monterey Bay study area well; MSMBFP, Monterey Bay study area flow-path well; MSMBMW, Monterey Bay study area monitoring well; MSPR, 

Paso Robles study area well; MSSC, Santa Cruz study area well; MSSV, Salinas Valley study area well; MCL-CA, California Department of Health Services 

maximum contaminant level; cm3 STP g–1 H20, cubic centimeters at standard temperature and pressure per gram of water; na, not available; nc, sample not 

collected; pCi/L, picocuries per liter] 

Helium–3/ Helium–4 Neon Argon Krypton Xenon Tritium Dissolved 

Helium–4 (5561) (61046) (5563) (5565) (5567) GAMA Collection Tritium measurement gas (atom ratio) identification date (pCi/L) 	 uncertainty (+/–) analysis (cm3

 STP g–1 H O) No. (mm/dd/yy) (07000)	 (61040)	 2 (pCi/L) date 


(07001) (mm/dd/yy)
 x 10–6 x 10–7 x 10–7 x 10–4 x 10– x 10– 

Threshold type na MCL-CA na na na na na na na na 

Threshold na 20,000 na na na na na na na na 

MSMB-39 09/19/05 2.33 0.2 10/28/05 1.14 0.92 2.98 4.12 8.87 1.23 

MSMB-40 08/29/05 1.57 0.2 10/28/05 1.23 1.15 3.63 5.06 11.0 1.42 

MSMB-41 09/20/05 13.97 0.7 10/28/05 2.59 0.64 2.68 3.87 8.57 1.11 

MSMB-42 08/10/05 7.70 0.4 09/07/05 1.33 7.31 31.9 9.06 34.4 0.00 

MSMB-43 09/23/05 12.69 0.6 10/28/05 2.36 0.50 2.13 3.51 7.86 1.10 

MSMB-44 09/19/05 13.36 0.6 10/27/05 1.81 0.55 2.38 3.72 8.35 1.08 

MSMB-45 08/10/05 6.47 0.3 01/10/06 1.29 0.94 3.44 4.26 8.81 1.15 

MSMB-46 09/20/05 7.80 0.4 10/28/05 1.78 0.66 2.72 3.90 8.60 1.10 

MSMB-47 08/03/05 <1.0 0.2 08/31/05 0.67 2.15 3.75 4.61 9.82 1.27 

MSMB-48 09/21/05 5.07 0.3 01/11/06 1.31 1.12 4.11 4.81 9.56 1.22 

MSMBFP-01 08/17/05 <1.0 0.2 09/08/05 0.13 14.0 2.71 4.16 9.52 1.31 

MSMBFP-02 08/09/05 10.01 0.5 09/01/05 1.66 0.73 2.77 3.92 8.41 1.19 

MSMBFP-03 08/09/05 4.83 0.3 08/31/05 1.59 0.64 2.57 3.95 9.04 1.18 

MSMBMW-01 09/21/05 <1.0 0.2 10/29/05 0.15 11.8 3.07 4.25 9.33 1.25 

MSMBMW-02 09/22/05 <1.0 0.2 11/15/05 0.22 6.14 3.19 3.84 9.43 1.21 

MSMBMW-03 09/22/05 <1.0 0.2 11/23/05 0.65 1.90 3.50 4.61 9.30 1.21 

MSPR-01 07/19/05 7.27 0.4 08/26/05 1.27 1.39 4.91 5.15 10.1 1.26 

MSPR-02 07/27/05 5.23 0.3 08/24/05 0.32 4.06 2.25 3.65 8.11 1.10 

MSPR-03 07/28/05 <1.0 0.2 08/24/05 0.30 5.32 2.47 3.86 8.83 1.18 

MSPR-04 07/28/05 1.88 0.2 08/25/05 0.28 5.63 2.30 3.66 8.01 1.13 

MSPR-05 07/27/05 1.26 0.2 08/24/05 0.26 7.34 2.74 4.08 9.21 1.21 

MSPR-06 07/27/05 2.07 0.2 08/24/05 1.24 0.66 2.37 3.45 7.48 0.95 

MSPR-07 07/21/05 <1.0 0.2 08/26/05 0.98 0.82 2.42 3.43 7.33 0.99 

MSPR-08 07/20/05 1.55 0.6 08/25/05 0.90 0.94 2.37 3.67 8.10 1.13 

MSPR-09 07/18/05 <1.0 0.2 01/10/06 0.26 14.4 2.66 3.79 8.43 1.13 

MSPR-10 07/18/05 <1.0 0.1 08/25/05 0.47 3.10 3.09 4.05 8.61 1.15 

MSPR-11 07/21/05 2.15 0.2 08/26/05 1.17 0.84 2.85 4.20 8.88 1.19 

MSSC-01 08/29/05 11.9 0.6 nc nc nc nc nc nc nc 

MSSC-02 09/12/05 9.00 0.4 nc nc nc nc nc nc nc 

MSSC-03 08/29/05 10.24 0.5 11/28/05 1.32 0.53 2.17 3.59 7.78 1.10 

MSSC-04 08/25/05 5.62 0.3 11/29/05 1.02 1.52 2.55 4.81 8.38 1.16 

MSSC-05 08/30/05 <1.0 0.2 nc nc nc nc nc nc nc 

MSSC-06 08/24/05 4.57 0.3 11/28/05 1.53 0.54 2.25 3.64 8.04 1.13 

MSSC-07 08/23/05 <1.0 0.3 11/28/05 0.64 1.42 2.29 3.73 8.20 1.15 

MSSC-08 09/15/05 4.39 0.3 11/29/05 1.32 0.52 2.20 3.43 7.57 1.06 
 

 

Tables 3 

Table 21. Tritium and noble gas results, analyzed at Lawrence Livermore National Laboratory, for unfiltered ground-water samples 

collected for the Monterey Bay and Salinas Valley Ground-Water Ambient Monitoring and Assessment (GAMA) study, California, July to 

October 2005—Continued. 

[The five-digit number below the constituent name is the U.S. Geological Survey parameter code used to uniquely identify a specific constituent or property; 

MSMB, Monterey Bay study area well; MSMBFP, Monterey Bay study area flow-path well; MSMBMW, Monterey Bay study area monitoring well; MSPR, 

Paso Robles study area well; MSSC, Santa Cruz study area well; MSSV, Salinas Valley study area well; MCL-CA, California Department of Health Services 

maximum contaminant level; cm3 STP g–1 H20, cubic centimeters at standard temperature and pressure per gram of water; na, not available; nc, sample not 

collected; pCi/L, picocuries per liter] 

Helium–3/ Helium–4 Neon Argon Krypton Xenon Tritium Dissolved 

Helium–4 (5561) (61046) (5563) (5565) (5567) GAMA Collection Tritium measurement gas (atom ratio) identification date (pCi/L) 	 uncertainty (+/–) analysis (cm3

 STP g–1 H O) No. (mm/dd/yy) (07000)	 (61040)	 2 (pCi/L) date 


(07001) (mm/dd/yy)
 x 10–6 x 10–7 x 10–7 x 10–4 x 10– x 10– 

Threshold type na MCL-CA na na na na na na na na 

Threshold na 20,000 na na na na na na na na 

MSSC-09 08/31/05 8.68 0.5 11/29/05 1.46 0.59 2.54 3.79 8.28 1.11 

MSSC-10 08/29/05 4.17 0.2 11/28/05 0.93 0.85 2.70 4.47 10.0 1.40 

MSSC-11 09/13/05 4.09 0.3 11/29/05 1.33 0.95 11.3 4.98 9.91 1.26 

MSSC-12 09/13/05 4.34 0.8 11/29/05 1.34 0.75 3.44 4.80 10.1 1.31 

MSSC-13 09/13/05 16.88 0.7 11/29/05 1.50 0.45 2.18 4.02 9.29 1.25 

MSSV-01 07/26/05 <1.0 0.3 08/24/05 0.42 12.1 2.39 3.76 8.20 1.14 

MSSV-02 07/28/05 7.26 0.4 08/25/05 1.54 0.49 2.09 3.49 7.95 1.06 

MSSV-03 08/02/05 8.34 0.5 08/30/05 0.58 3.87 1.97 3.32 7.58 1.03 

MSSV-04 08/02/05 2.19 0.2 08/27/05 1.28 0.92 3.30 3.82 8.26 1.09 

MSSV-05 07/25/05 7.54 0.4 08/25/05 1.22 10.0 2.08 3.45 7.67 1.07 

MSSV-06 08/02/05 7.72 0.6 08/30/05 1.43 0.54 2.25 3.41 7.67 1.04 

MSSV-07 08/02/05 7.29 0.4 08/27/05 1.41 0.56 2.32 3.48 7.74 1.04 

MSSV-08 08/04/05 9.09 0.5 01/10/06 1.14 0.79 2.36 3.52 7.76 1.06 

MSSV-09 09/14/05 7.79 0.4 01/10/06 1.42 1.07 4.15 4.69 9.17 1.14 

MSSV-10 09/21/05 7.43 0.4 10/27/05 1.39 0.51 2.13 3.45 7.73 1.04 

MSSV-11 07/25/05 9.30 0.4 08/25/05 1.58 1.62 5.80 5.84 11.1 1.38 

MSSV-12 08/01/05 7.13 0.4 08/26/05 1.41 1.22 4.89 5.37 10.7 1.33 

MSSV-13 09/15/05 6.42 0.4 01/10/06 1.37 1.09 4.45 4.98 10.0 1.28 

MSSV-14 08/01/05 5.86 0.3 08/26/05 1.29 0.93 2.87 4.06 9.04 1.19 

MSSV-15 08/01/05 7.49 0.6 01/10/06 1.34 1.23 4.86 5.74 10.9 1.31 

MSSV-16 09/14/05 <1.0 0.2 10/27/05 1.40 0.78 3.25 4.33 9.19 1.22 

MSSV-17 09/14/05 6.30 0.6 10/27/05 1.44 0.74 3.02 4.28 9.46 1.26 

MSSV-18 08/01/05 <1.0 0.2 nc nc nc nc nc nc nc 

MSSV-19 07/27/05 <1.0 0.1 08/24/05 0.78 2.28 3.41 4.45 9.41 1.20 
 

4 Ground-Water Quality Data, Monterey Bay and Salinas Valley Basins 2005—Results, Calif. GAMA Program 

Table 22. Summary of microbial indicators detected in ground-water samples collected for 


the Monterey Bay and Salinas Valley Ground-Water Ambient Monitoring and Assessment 


(GAMA) study, California, July to October 2005.
 

[The five-digit number below the constituent name is the U.S. Geological Survey parameter code used to 


uniquely identify a specific constituent or property; MSMB, Monterey Bay study area well; MSMBFP, Monterey Bay study area flow-path well; MSPR, Paso Robles study area well; MSSC, Santa Cruz study area well; 


MSSV, Salinas Valley study area well; MCL-US, U.S. Environmental Protection Agency maximum contaminant level; E, estimated value; mL, milliliter, —, not detected; TT, treatment technique; *, value exceeds 


regulatory threshold]
 

GAMA Coliphage Coliphage E. coli colonies/ Total coliforms 

Identification F-specific somatic 100 mL colonies/ 100 mL 

no. (335) (332) (001) (000) 

Threshold type TT TT TT MCL-US 

No fecal . percent . percent Threshold coliforms are 5 percent Killed/Inactive Killed/Inactive allowed 

MSMB-04 — — — — 

MSMB-09 — — — — 

MSMB-12 — — — — 

MSMB-18 — — — — 

MSMB-20 — — — — 

MSMB-22 — — — *

2 

MSMB-29 — — — — 

MSMB-30 — — — — 

MSMB-33 — — — — 

MSMB-35 — — — — 

MSMB-37 — — — — 

MSMB-40 — — — — 

MSMB-44 — — — *

110 

MSMB-45 — — — — 

MSMB-47 — — — — 

MSMBFP-02 — — — — 

MSMBFP-03 — — — — 

MSPR-01 — — — — 

MSPR-10 — — — — 

MSSC-04 — — — — 

MSSC-06 — — — — 

MSSC-07 — — — — 

MSSC-08 — — — *

5 

MSSV-01 — — — — 

MSSV-02 — — — — 

MSSV-03 — — — — 

MSSV-07 — — — — 

MSSV-11 — — — *

E1 

MSSV-18 — — — — 

MSSV-19 — — — — 

 

Kulongoski and Belitz—Ground-Water Quality Data in the Monterey Bay and Salinas Valley Basins, California, 2005— 

Results from the California GAMA Program—Data Series 258 Verson 1.1 

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