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w UnacM Cc ration R=6.93 2000 Crow Place.x ,400 P.Q Box 51 San Califomla 94583 Telephone( f 0)867-0760 0)277-2 Facsimile( t 309 UNOCAL76 April 13 1993 them Region Ms. Elizabeth Thayer porate Enwonmental nedkation and Technology Y Regional Water Quality Control Board Central Iralley Region 3443 Ro tier Road Sacramento, Ca 95827-3098 n rvi tion. O1 601. E. ettleman Lane Lodi, ' ornia i Dear Ms. i nayct. This letter is written to formally request that a meetin be scheduled regarding the subject Unocal site. The meeting should include the Regional W ter Quality Control Board (RWQCB), Central Valley Region, Mr. Harlin Knoll from the San J aquin County Public Health Services (SJCPHS) Department, Unocal Corporation, and Kap 'an Engineering, Inc. (KEI). Subsequent to removal of underground fuel storage tanks waste oil tank and product piping at the subject site in February and March of 1991, Unocal Corporation has complied with all of the requirements set forth in the Tri-Regional Guidelines of the RWQCB. Soil samples collected from beneath the underground fuel storage tank pit foil wing overexcavation indicated non- detectable concentrations of TPH as gasoline except for A ppm detected in one sample. KEI has conducted a quarterly groundwater monitoring and sa mpling program since the installation of the first wells in August of 1991, which have consis ndy-indicated:non-detectable to:low n concentrations of dissolved hydrocarbons. Two exploratory borings and nine monitoring wells have n installed at the site. A cumulative total of 143 soil samples were collected and analzsed during site characterization. Of these samples, 139 indicated non-detectable concentrations of T PH as gasoline and 137 indicated non- detectable concentrations of benzene. The four samples at indicated detectable levels of TPH. as gasoline had levels ranging from 1.9 ppm to 5.7 ppm, while the sic samples that showed detectable levels of benzene had levels ranging from 0.0094 to 1.9 ppm. Based on the aforementioned discussion, there does not appear to be any significant soil contamination remaining at the subject site. ' As recommended in the LUFr Manual, KEI generated a mputer model utilizing the SESOIL software package which indicated that the low levels of contamination detected do not appear to pose any significant threat for the degradation of the current groundwater quality. Unocal, therefore, requests a meeting be held to discuss partial site closure (for contamination issues).