SITE INFORMATION AND CORRESPONDENCE

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MEMORANDUM CALIFORNIA REGIONAL WATER QUALITY CONTROL BOARD • CENTRAL VALLEY REGION 3443 Routier Road, Suite A Phone: (916) 255-3000 Sacramento, CA 95827-3098 CALNET: 8494-3000 TO: Wendy L. Cohen FROM: Joel Weiss Senior Engineer Engineering Geologist DATE: 4 January 1994 SIGNATURE: zb SUBJECT: SANTA FE PACIFIC PIPELINE LEAK, HOLT, SAN JOAQUIN COUNTY INITIAL LEAK On 9 January 1986, free product was discovered in wells at the Arcady Oil Company waste mud disposal site in Holt. A leak was subsequently found in a fuel pipeline operated by Southern Pacific Pipe Line, Inc. (SPPL). (Santa Fe Pacific Pipeline Partners, L.P. (SFPP) subsequently took over responsibility). The pipeline crosses the Arcady site as well as the adjacent Trapper Slough. At the time, the Arcady site had 12 monitoring wells around its perimeter (M1-M10, 01 and 02). No well construction data are available for five of these original wells (M8-M10, 01 and 02). Flooding in February of 1986 dispersed fuel into the surrounding surface waters. A cleanup of the surface waters was carried out by IT Corporation. To help facilitate cleanup, a.bypass pipe system was constructed. Arcady Oil Company and SPPL jointly hired the Mark Group, Inc. (MGI) to provide technical services for future site assessment and remediation requirements. A 31 March 1986 report by MGI presents descriptions of the original leak and the emergency cleanup activities which occurred. I was not able to find this report in our files. 1987 SITE ASSESSMENTS In October 1987, MGI submitted a report entitled Site Characterization and Remedial Action Report, Pipeline Leak Assessment. As part of this initial site assessment, MGI drilled 14 borings and installed three monitoring wells. The new wells were labeled N6, N7 and N8. Two of the new wells and three existing wells contained free product. Logging of all boring activity provided a general description of the subsurface geology. From the surface to a depth of approximately 20 feet, the lithology is silty clays, clayey sands, sands, peat, and clay on the bottom. Ground water is encountered between five and 15 feet below the ground surface (bgs). The various wells are screened through different combinations of opposing lithologies. The ground water gradient is in a southeast direction. The consultant's remedial recommendation was to construct a collection trench and sump immediately downgradient of the advancing contaminant plume. The trench was proposed to be approximately 500 feet long and to extend three feet below the ground water table. The extracted hydrocarbons and ground water would undergo onsite treatment with subsequent discharge to the adjacent Trapper Slough.