“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
