COMPLIANCE INFO_1997-2008 - Laserfiche WebLink

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KLEINFELDER File No. 20-3978-01.W10 July 26, 1997 7. Nitrate concentrations as NO3 ranged from ND to 130 mg/L in the water samples obtained. The highest concentration was in the upgradient well (MW-5). The high concentration of 100 mg/L in the domestic well at the farmhouse may be present due to the relatively close septic tanks and leachfields (2 each within approximately 100 feet). Because the sandy soils present in the Manteca area are so permeable, the October 1992 U.S. Department of Agriculture Soil Conservation Service "Soil Survey of San Joaquin County, California" flags both the Delhi and Tinnin Series of soils which are native to the project site area as having the potential for onsite sewage disposal systems to contaminate groundwater supplies. 8. In general, the groundwater samples obtained can best be characterized as a calcium- magnesium bicarbonate water with a high mineral content, particularly near the lime ponds. All of the water samples would make for a poor quality drinking water. Additionally, high concentrations (over the Maximum Contaminant Level) of arsenic and barium exist in many of the samples. Barium has even been detected in the off- site upgradient well at concentrations in excess of the MCL. The source of the arsenic and barium are unknown. Despite the closure of the factory over one year ago, the barium and arsenic concentrations appear to be consistent with, or slightly higher than past monitoring events. Additionally, elevated nitrate levels exist both on and off-site likely as a result of the permeable soils in areas where fertilizers are used or septic systems exist. 9. Other than the continued monitoring of groundwater as required by the Waste Discharge Requirements for the ponds on site, Kleinfelder would recommend no further actions as it relates to the results of this sampling. 10. Should discolored soil, odors, or other evidence of contamination be encountered during site grading, development, etc., our office should be notified immediately. 11. All wells should be properly abandoned in accordance with State and local laws and regulation. Please consult our office prior to well abandonment to make sure the wells are not required for any ongoing monitoring. 12. A copy of this report should be submitted to the San Joaquin County Public Health Services Department Environmental Health Division and the Central Valley Office of the State of California Regional Water Quality Control Board by the Atherton- Kirk for their review and consideration. 20-3978-01.W10/2017L155 Page 19 of 50 Copyright 1997,Kleinfelder,Inc.