REMOVAL 2002 CLOSURE IN PLACE - Laserfiche WebLink

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' • eQ 21 August 2002 Dennis H. Catanyag San Joaquin County ' Environmental Health Department Page 2 1 confirmed these findings. The results of integrity testing (Attachment A) indicated that the primary tank was "tight," but the outer shell allowed water to enter the interstitial space. In response, POSDEF emptied the primary tank and affixed a lock to the fill 1 spout,which has ensured the tank has not been used since 19 April 1998. Used oil is now placed in an aboveground storage tank that is equipped with an integral secondary containment system. This new aboveground tank is located within a berm designed to contain spills or releases in the unlikely event that both the primary and secondary walls of the aboveground tank should fail(Figure 2). In September 1998, POSDEF retained Wright Environmental Services, hie. ("Wright") to characterize environmental conditions in the proximity of the underground storage tank. Wright completed two borings at or near each end of the tank (Figure 4). From each of ' the borings, one sample of pea gravel beneath the tank was obtained at a depth of 5 feet below ground surface ("bgs"). Wright analyzed the two collected samples for total petroleum hydrocarbons as gasoline; TPH as diesel; benzene, toluene, ethylbenzene, ' xylenes (`STEX"); chlorinated volatile organic compounds ("VOCs"); polychorinated biphenyls ("PCBs"); and metals listed in the State Water Resources Control Board Leaking Underground Fuel Tank manual consisting of cadmium, trivalent chromium, ' lead, nickel, and zinc. A copy of Wright's report, dated 29 October 1998, transmitting the analytical results to the San Joaquin County Environmental Health Department ("EHD"), is included as Attachment B. ' No BTEX, chlorinated VOCs, or PCBs were detected in the fill samples. No lead or cadmium was measured above analytical method reporting limits of 5 and 0.5 mg/kg for these metals, respectively. Trivalent chromium, nickel, and zinc were detected at concentrations indicative of natural occurring levels. In the two soil samples, chromium concentrations were 11 and 15 mg/kg, nickel concentrations were 14 and 20 mg/kg, and zinc concentrations were 25 and 30 mg/kg. Typical chromium, nickel, and zinc concentrations in California soil are on the order of 70, 30, and 100 mg/kg, respectively. TPH reported as motor oil was detected in one sample at 43 mg/kg. The analytical results of samples obtained by Wright corroborate the integrity testing finding that no significant releases from the used oil tank occurred. ' NECESSITY FOR IN-PLACE CLOSURE OF TANK ' Excavation of the underground storage tank would be extremely difficult while the POSDEF facility is operational. The tank is located next to a concrete column that ' supports the platform upon which the electrical power generation turbine sits (Figures 1