SITE INFORMATION AND CORRESPONDENCE_CASE 1

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Soil impacted by chemicals of concern, including total petroleum hydrocarbons as gasoline (TPH-g) and gasoline components benzene,toluene,ethylbenzene and xylenes (BTEX), was found in the tank excavation located northeast of the forklift shop. Hydrocarbon impacts were not found in the tank excavation locattd northwest of the shop. We understand excavated soils were aerated, resampled, and used to backfill the excavations. Six monitoring wells have been installed onsite. The most significant petroleum hydrocarbon impacts were found at monitoring well MW-4, which appears to have been located adjacent to the larger underground storage tank excavation. Groundwater extracted from MW-4 has contained concentrations of TPH-g as high as 9,100 parts per billion(ppb). Site groundwater is encountered at a depth of approximately 6 feet below ground surface (bgs); reportedly the first significant zone of saturation(aquifer material)occurs at 15 feet bgs. The onsite groundwater hydraulic gradient is reported by previous investigators to vary from the westerly to northeasterly direction. A groundwater remediation system utilizing carbon filtration was installed onsite and began operation in May 1991. Well MW-4 provided the influent flow to the system. Reportedly,the flow rate ranged from approximately 0.5 gallons per minute (gpm) to 3 gpm. The system appears to be inactive at this time. In a letter dated May 2, 1995, San Joaquin County PHS/EHD requested that a "Corrective Action Plan" (CAP) be submitted by July 24, 1995. The Scope of Work described below is intended to address the issues raised in their letter, and to assist TVG in obtaining regulatory closure of the site in a cost-effective manner. PROPOSED SCOPE OF SERVICES In response to your request, we have developed our approach into several detailed Tasks. The following is a description of these Tasks: Task 1.0 Update Field Investigation Plans We recognize that TVG has invested considerable resources to conduct site activities performed to date. Consequently, we will utilize to the maximum extent possible, Health and Safety PIans (HASP), and soil and groundwater Sampling and Analysis Plans (SAP) prepared by previous investigators. Both plans will be prepared in accordance with Tri Regional guidelines and under the supervision of a California Registered Geologist. The plans will be submitted in draft form for TVG's review and comment prior to submitting them to PHS/EHD. The budget assumes that review comments will not be substantial or require significant revision. Tn Valley Gro.vm SECOR' N 1130p.rpt June 1,1995