SITE INFORMATION AND CORRESPONDENCE

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MEMORANDUM CALIFORNIA REGIONAL WATER QUALITY CONTROL BOARD - CENTRAL VALLEY REGION 3443 Routier Road Phone: (916) 361-5600 Sacramento, CA 95827-3098 ATSS : 8-495-5600 TO: Antonia Vorster �( FROM: Robert Niblack Senior Engineer Engineering Geologist DATE: 14 July 1987 SIGNATURE:_ �r.� SUBJECT: MOBIL TERMINAL UNDERGROUND TANK REPORT, SAN JOAQUIN COUNTY I have reviewed a "Subsurface Investigation Report" completed by Kaprealian Engineering, Inc. on behalf of Mobil Oil Corporation. This report claims to summarize the tank inspection and soil and water sampling conducted during the removal of two underground tanks at the Mobil Terminal on Navy Drive in Stockton. Several items still need to be addressed in order for this report to be considered complete under the underground tank report guidelines set by Gordon Boggs' memo of 24 March 1987 . Kaprealian Engineering should address those details listed under the heading of "Preliminary Report" in this memo, as well as those details which can be addressed, given the work completed to date, under the heading "Problem Assessment" . In addition, the following comments should be considered. Comments 6 through 10 concern a workplan which should be required to determine the lateral and vertical extent of contamination at this site: 1. Correctly identify tank "A" and tank "B" in the report. The site plan labels do not match the narrative description. Sample labels are misleading. According to Doug Wilson, San Joaquin Local Health District , water was riot encountered in pit "A" , "A" as labeled on the site plan. However, the report states that water sample "AW" was taken from the pit of tank "A" . In the fo?.lowi nn_ comments I will refer to the excavations as labeled on the site plan, 2. Identify the type and extent of floating product uncovered in the excavation for tank "B" . Doug Wilson said he observed floating product on the water in the excavation. He was accompanied by Mardo Kaprealian, consultant to Mobil , as the excavation was uncovered . Ton Vorster and I also observed floating product in the excavation several days later. In a telephone conversation with Mr. Kaprealian I was told he would not describe the film on the water surface as floating product. He also said that the film aid not cover the entire water surface. He described the covering on the water as a sheen. I asked him to describe his observations in detail in the future.