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GAMA: Groundwater Ambient Monitoring & Assessment Program

GAMA – Groundwater Ambient Monitoring & Assessment Program

“CAS” California Aquifer Susceptibility Assessment

Prior to 2003, GAMA conducted the California Aquifer Susceptibility (CAS) Assessment. The CAS Assessment addressed the relative susceptibility to contamination of public wells. This effort was the foundation for the GAMA Priority Basin Project.

GAMA has evaluated the susceptibility of groundwater to contamination in several areas of the state. The California Aquifer Susceptibility (CAS) assessment was performed from 2000 to 2003 in collaboration with the U.S. Geological Survey (USGS) and Lawrence Livermore National Laboratory (LLNL).

CAS was a study of the water quality and relative susceptibility of groundwater that serves as a source for public drinking water. Two types of groundwater tests were performed in the assessment: age-dating and low-level VOC analyses. Age-dating (tritium-helium analysis) is used to provide information on the presence of young groundwater and low level VOC analysis is used as an "early warning" for potential contamination.

Widespread use of regulated chemicals has occurred following World War II. As a result, groundwater that has recharged during the past 50 years is considered to be more susceptible to contamination from various land-use activities. Low-level VOC analytical results (for example: methyl tert-butyl ether or MTBE) will allow water managers to identify trends in groundwater quality in their region and respond before concentrations reach action levels.

CAS was enhanced as a result of the Groundwater Quality Monitoring Act of 2001 (AB 599 – Liu).

Over 1,000 Public Drinking Water Wells Which Have Been Sampled During CAS

Year Sampled Geographic Area Number of Wells Sampled Inter-Agency Cooperation Available Reports
2000
Los Angeles County
Orange County
(LA/Santa Ana)
178
USGS, LLNL
Reports Available
2001
Alameda County
47
LLNL
Reports Available
2001
Santa Barbara County
(Carpinteria)
4
LLNL
To be included in GAMA report
2001
Riverside County
(San Jacinto)
34
USGS, LLNL
Report Available
Appendix 1-3
Appendix 4-6
Appendix 7-9
Appendix 10-12
2001/2002
Fresno County
Stanislaus County (Modesto)
50
40
USGS, LLNL
Report Available
2001/2002
Santa Clara County
San Mateo County
184
29
LLNL
Report Available
2001/2002
Sacramento County
123
LLNL
Report Available
2001/2002
San Joaquin County
107
LLNL
To be Posted Soon
2003
Butte County (Chico)
Glenn County
Modoc County
Siskiyou County
Plumas County
Shasta County
160
LLNL
Report Available
2002/2003
San Bernardino County
(Victorville)
33
USGS, LLNL
Report Available
2002/2003
Los Angeles County
(Antelope Valley / Palmdale)
32
USGS, LLNL
Report Available
2002/2003
Kern County (Bakersfield)
43
USGS, LLNL
Report Available
  • Map of CAS focus areas.

  • Digital photographs of a CAS sampling event
    • Photo #1 - A photograph of a municipal well field containing several public supply wells
    • Photo #2 - Shows how water samples are typically collected from large supply wells
    • Photo #3 - A close-up of a water sample being collected
    • Photo #4 - Transferring samples to the various sampling containers
    • Photo #5 - One of the sampling devices and containers used for the isotopic sample