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December 22 , 1988 Page 5 Project 156-117 . 1 Pesticides DDE and DDT were detected in soil sample DH-3 under Total Threshold Limit Concentration (TTLC ) conditions and are well below the California Department of Health Services (DHS ) established TTLC limits . The detected amounts are also below the Soluble Threshold Limit Concentration ( STLC) limits ( see Table 2 ) . The pesticides were not detected in any of the ground water samples . Antimony, arsenic , barium, chromium, cobalt , copper, lead, mercury, nickel , thallium, vanadium, and zinc were detected below the DHS TTLC limits in soil sample DH-2 ( 2 . 5 feet ) analyzed under TTLC conditions . The amounts detected are also below the STLC limits with the exception of arsenic , barium, nickel , thallium and vanadium. However , since these levels do not exceed ten times the STLC limits , a waste extraction test (WET) is not warranted ( see Table 2 ) . Arsenic , barium, chromium, cobalt , copper, lead, mercury, nickel , thallium, vanadium, and zinc were detected in the , ground water sample from MW-2 . The amounts of copper , mercury, and zinc detected are below Federal EPA standards for drinking water. The amounts of arsenic , barium, chromium, and lead detected exceed the EPA standards for drinking water , however, the amounts detected are well below the EPA EP Toxicity levels for hazardous waste ( see Table 3 ) . Presently there are no established EPA drinking water standards for cobalt , nickel , thallium, or vanadium. All laboratory analyses are presented in Appendix B. Conclusions/Recommendations Results of the chemical analyses indicate the presence of arsenic , barium, chromium and lead exceeding EPA drinking water standards in the shallow ground water extracted from MW-2 . The elevated concentrations of these constituents does not appear to be attributable to an on-site source , and may reflect background water quality in the shallow aquifer beneath the site , particularly due to the subject site ' s proximity to the San Joaquin Delta. Laboratory analysis has revealed that the subsurface soils and shallow ground water do not contain compounds for which analyses were performed in concentrations considered to be hazardous , therefore ; the drill hole cuttings and ground water contained during the field investigation can be disposed of on-site . In accordance with your request and as required by the SJLHD monitoring well permit process , a copy of this report has been forwarded to Diane Hinson of the SJLHD. GBetac_Associates . Inc. oe�)