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KEI-P92-0205.QR1 . April 2 , 1993 Page 3 DISCUSSION AND RECOMMENDATIONS Based on the analytical results for the ground water samples collected and evaluated to date, and no evidence of free product or sheen in any of the wells, KEI recommends the continuation of the current ground water monitoring and sampling program, per KEI 's proposal (KEI-P92-0205 .P3) dated October 6 , 1992 . KEI recently discovered that the Christy boxes for wells MW2 , MW6, and MW7 were in need of repair. KEI will repair or replace the Christy boxes and then resurvey all of the wells to Mean Sea Level (MSL) during the next quarter. A file review was conducted by KEI on April 27 , 1992 , at the San Joaquin County Public Health Services Agency. Files were reviewed for the sites adjacent to the former Unocal bulk plant, including the Time Oil, Tesoro Petroleum, S&T Services, and Southern Pacific Pipeline (SPPL) sites. It is also KEI ' s understanding that a large petroleum release occurred at the nearby Arco Terminal during a fire at the terminal in the early 1980 ' s . The locations of all of these sites relative to the Unocal site are shown on the attached Figure 5. Based on monitoring data compiled in a comprehensive report dated November 1989 by Emcon Associates, in June of 1989 the ground water flow direction was complex, but generally towards the southeast. This was reportedly consistent with piezometer readings from 1987 which also indicated a southeasterly ground water flow direction. Based on a southeasterly regional flow direction, the Unocal site is downgradient from the Time Oil, Tesoro Petroleum, SPPL, S&T Services, and Arco sites. The following is a brief summary of analytical data contained in the November of 1989 Emcon report: Ground water monitoring and sampling was conducted at the sites in June of 1989 . At the Time Oil site, sheen was detected in one well and free product was detected in five of the wells at thicknesses ranging from 0 . 01 foot to 0 .42 foot. Sheen was detected in three of the wells at the Tesoro site. TPH as gasoline was detected in ground water samples at the Tesoro and SPPL sites at concentrations ranging from 1, 000 ppb to 100, 000 ppb, and from 1, 000 ppb to 2 ,000 ppb, respectively. Benzene was detected at levels of up to 10 , 000 ppb at the Time Oil and SPPL sites, and up to 5, 000 ppb at the Tesoro Petroleum site.