HR: 1340h
AN: H33E-1688    [Abstracts]
TI: Distribution of Perchlorate in Aquifers Used for Public Water Supply in California, USA
AU: * Fram, M S
EM: mfram@usgs.gov
AF: USGS, 6000 J St., Placer Hall, Sacramento, CA 95819-6129, United States
AU: Belitz, K
AF: USGS, 4165 Spruance Rd., Ste. 200, San Diego, CA 92101-0812, United States
AU: Burton, C
AF: USGS, 4165 Spruance Rd., Ste. 200, San Diego, CA 92101-0812, United States
AU: Densmore, J N
AF: USGS, 6000 J St., Placer Hall, Sacramento, CA 95819-6129, United States
AU: Kent, R H
AF: USGS, 4165 Spruance Rd., Ste. 200, San Diego, CA 92101-0812, United States
AU: Kulongoski, J T
AF: USGS, 4165 Spruance Rd., Ste. 200, San Diego, CA 92101-0812, United States
AU: Land, M T
AF: USGS, 4165 Spruance Rd., Ste. 200, San Diego, CA 92101-0812, United States
AU: Landon, M K
AF: USGS, 4165 Spruance Rd., Ste. 200, San Diego, CA 92101-0812, United States
AU: Montrella, J
AF: USGS, 4165 Spruance Rd., Ste. 200, San Diego, CA 92101-0812, United States
AU: Shelton, J L
AF: USGS, 6000 J St., Placer Hall, Sacramento, CA 95819-6129, United States
AU: Wright, M T
AF: USGS, 4165 Spruance Rd., Ste. 200, San Diego, CA 92101-0812, United States
AB: Perchlorate has been detected in public-supply wells that tap aquifers in many parts of California. Two data sets are available, one collected by the California Department of Public Health (CDPH) for compliance of drinking water with health-based standards, and one by the California State Water Resources Control Board Groundwater Ambient Monitoring and Assessment Program (GAMA) for statewide assessment of the quality of untreated groundwater. The GAMA Priority Basin project is conducted by the USGS. GAMA uses a reporting limit (RL) of 0.5 μg/L, and samples primarily public-supply wells. The wells are selected on a spatially distributed, randomized network designed to permit statistically robust characterization of aquifer water quality in study areas and comparisons on regional and statewide scales. CDPH uses an RL of 4 μg/L and includes all public- supply wells for which data are available. The two datasets yield different distributions of perchlorate detections. GAMA data for 14 study areas (766 wells), representing 60 of the 116 priority groundwater basins in California, have a 22% detection frequency for perchlorate at RL= 0.5 μg/L, 3% at RL= 4 μg/L, and < 2% greater than the California Notification Level (NL) of 6 μg/L. In contrast, CDPH data for the same areas (2930 wells) have a 10% frequency at RL= 4 μg/L and 7% greater than the NL. The higher detection frequency in the CDPH database may be due to the high density of wells in a region with many known industrial, aerospace, and military perchlorate users. Among the 14 GAMA study areas, 2 had no detections of perchlorate. Detection frequency was > 40% in 3 areas with high densities of known perchlorate users. Ten areas had detection frequencies between 6 and 37%. Perchlorate has several sources in California: natural, legacy fertilizers, use of Colorado River water on the landscape, and industrial, aerospace, and military users. The distribution of perchlorate detections, combined with other water-quality and tracer data collected by GAMA are expected to aid in the determination of the relative importance of these various sources of perchlorate to groundwater in different regions of California.
DE: 1803 Anthropogenic effects (4802, 4902)
DE: 1831 Groundwater quality
DE: 1848 Monitoring networks
SC: Hydrology [H]
MN: 2007 Fall Meeting