SITE INFORMATION AND CORRESPONDENCE_FILE 1

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Proposed Corrective Action Langston Is Market 15615 Seventh Street, Lathrop, California Executive Summary Langston's Market is a small,privately owned convenience store that previously sold gasoline. The market is located at 15615 Seventh Street in Lathrop and is surrounded by residential and other commercial properties. A tank failure occurred in June 1990 following a helium pressure test of one of the three 4,000 gallon underground gasoline tanks (UST). Approximately 1,200 gallons of leaded gasoline was lost from the tank. All three USTs were removed shortly thereafter. A preliminary environmental investigation of the property was conducted at the request of Mr. Langston in April 1992. This investigation included the drilling of several exploratory soil borings in the vicinity of a failed 4,000 gallon underground gasoline tank. The borings demonstrated that soil contamination in the vicinity of the former UST extended down to the water table,with little lateral spreading. In 1993 four monitoring wells were installed. Laboratory sampling has disclosed varying concentrations of gasoline and gasoline constituents in all four wells.. The wells are part of the active sampling program to monitor the quality and migration of the groundwater beneath the site. Sampling is conducted according to regulatory protocol and guidelines. A corrective action clean-up has been proposed that will involve the removal of soils containing gasoline with the use of a backhoe type excavator. Due to the existing building location directly over the contaminated zone, sandy soil conditions, and high probability of soil caving, the building must be removed from the site prior to excavation activities. Approximately 3,000 tons (2,000 cubic yards) of soil will be excavated from the contaminated zone. Approximately 1400 tons may be free of contamination and potentially used for backfill material. All soil excavated and stockpiled will be sampled and analyzed by a state certified laboratory to determine appropriate disposition. The analytical results will be reviewed and submitted to an approved disposal facility. Using proper procedures the soil will be transported to the disposal facility by a licensed transporter. The soil will be covered with plastic to prevent run-off or aeration if the material is to be stored for more than one day. During the excavation process the contaminated groundwater and free product will be pumped from the excavation to temporary storage tanks as necessary to minimize saturation of the excavated soil. Laboratory sampling will include the floor and sidewalls of the excavation, soil stockpiles, and water in the storage tanks. Bacld'illing of the excavated area will commence after confirmation sample analyses demonstrate t contaminated soils have been removed to project acceptance levels. Backfill will be compacted and verified by testing. The monitoring wells will remain on site and will continue to be actively monitored according to regulatory guidelines. Issues related to groundwater clean-up will be evaluated after the soil clean-up has been completed. WHF, Inc. , Environmental and Engineering Group PO Bax 576729,Modesto, California 95357-6729 (209)579-8138