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2007 Ground Water Summit |
Wednesday, May 2, 2007 : 8:00 a.m.
Water Quality Impacts from On-Site Waste Disposal Systems in the Cherry Valley Community of Interest
In the City of Beaumont and surrounding unincorporated areas, the only source of drinking water is groundwater, supplied by Beaumont-Cherry Valley Water District, from the Beaumont Management Zone. Rising nitrate levels have been observed in wells underlying the Cherry Valley Community of Interest (CVCOI) and, recently, nitrate-nitrogen (NO3-N) concentrations in a couple of groundwater production wells have approached the maximum contaminant level of 10 mg/L. On-Site Waste Disposal Systems (OSWDS) have been identified as a possible source of nitrate in the groundwater underlying the CVCOI because of the density of households that rely on such systems. The Santa Ana Regional Water Quality Control Board requires a minimum lot size of one half acre per OSWDS. In the CVCOI, about 800 of the approximate 1,900 developed lots with OSWDS are on less than half acre size parcels. At build-out, the total number of lots with OSWDS could reach about 8,800.
Field studies were conducted to determine the source of nitrate to groundwater. Nine production wells were sampled and groundwater samples were analyzed for δ15N and pharmaceuticals and personal care products (PPCPs). All groundwater samples were within the range of δ15N values of nitrate from septic tank effluent. Six of the nine wells had detectable levels of PPCPs, which included acetaminophen, ibuprofen, sulfamethoxazole, estradiol, progesterone, and testosterone.
The potential nitrate load to groundwater was estimated using literature values of nitrate concentrations in septic tank effluent and the average annual discharge volume for OSWDS in the CVCOI. At build out, the future discharge from OSWDS is projected to be about 13 to 21 percent of the total recharge in the Beaumont Management Zone. This equates to about 185,000 to 500,000 pounds of nitrogen entering the groundwater from OSWDS per year.
Field studies were conducted to determine the source of nitrate to groundwater. Nine production wells were sampled and groundwater samples were analyzed for δ15N and pharmaceuticals and personal care products (PPCPs). All groundwater samples were within the range of δ15N values of nitrate from septic tank effluent. Six of the nine wells had detectable levels of PPCPs, which included acetaminophen, ibuprofen, sulfamethoxazole, estradiol, progesterone, and testosterone.
The potential nitrate load to groundwater was estimated using literature values of nitrate concentrations in septic tank effluent and the average annual discharge volume for OSWDS in the CVCOI. At build out, the future discharge from OSWDS is projected to be about 13 to 21 percent of the total recharge in the Beaumont Management Zone. This equates to about 185,000 to 500,000 pounds of nitrogen entering the groundwater from OSWDS per year.
Kristal Davis Fadtke, Wildermuth Environmental Kristal Davis is a Senior Scientist with Wildermuth Environmental, Inc. Ms. Davis graduated Magna Cum Laude from the University of California, Riverside with a B.S. in Environmental Science in 2000. In 2002, she completed her M.S. in Soil and Water Science at the University of California, Riverside. Her thesis research on indicator microorganisms in drinking water reservoirs was published in Water Research.