REMOVAL 2002 CLOSURE IN PLACE - Laserfiche WebLink

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eKI 11 September 2002 Dennis H. Catanyag San Joaquin County LEnvironmental Health Department Page 2 L polyurethane and is equipped with a sacrificial anode cathodic protection system to resist the effects of soil corrosion. L When the used oil tank was in operation, it was continuously monitored for leaks by an L electronic leak detector installed within the interstitial space of the tank. On 20 March 1998, the electronic leak detector activated an alarm in the POSDEF control room. POSDEF personnel inspected the tank and determined that the outer shell that served as the secondary containment system was compromised. Water had entered the outer shell and triggered the alarm. Tank integrity testing performed on 19 April 1998 confirmed these findings. The results of tank integrity testing (Attachment A) indicated that the primary tank was "right,"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 spout,which has ensured the tank has not been used since 19 April 1998. Used oil is now L 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 Lof the aboveground tank fail. In September 1998,POSDEF retained Wright Environmental Services,Inc. ("Wright")to Lcharacterize environmental conditions in the proximity of the underground storage tank. Wright completed borings SB-1 and SB-2 at or near each end of the tank. From each of the borings, one sample of pea gravel beneath the tank was obtained at a depth of 5 feet Lbelow ground surface ("bgs"). Wright analyzed the two collected samples for total petroleum hydrocarbons as gasoline ("TPH-U'); TPH as diesel ("TPH-D"); benzene, L toluene, ethylbenzene, xylenes (`BTE) "); 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 PHS/EHD, is included as Attachment B. LNo 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 L 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 l 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 L