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Ih lY l 4J.. 1 9 *M/ Mr. Carl Navarra Report of Tank Removal January 16, 1999 Page Three of the dispensers at the pump island were sampled. These were sampled by an independent sampling firm and the samples were taken at the location directed by the San Joaquin County Public Health representative. During the course of the sampling the pipe trench was over excavated and four additional underground storage tanks were exposed. These tanks were badly deteriorated and date from the earliest service station activity at this site estimated to be in the 1930's. These tanks were of 1000 gallon capacity. Due to the extreme age of these tanks and the extensive deterioration it was not possible to inert these tanks. The tanks were removed in the presence of the San Joaquin County Public Health representative on December 28, 1998. Due to the poor condition it was determined that it would be appropriate to crush them prior to disposal off site. The tanks were manifested as non hazardous solid waste and placed in a dumpster for off site disposal. The area beneath the tanks was sampled by an independent sampling firm in the presence of the San Joaquin County Public Health representative. These tanks were located above the water table and, therefore, only soil samples were taken. Piping associated with these tanks was also manifested and placed in the dumpster for off site disposal. %1W Following the discovery of four unknown tanks a locator firm was contacted and requested to assist in location of any other tanks and piping on the site. Areas for buried piping removal and possible underground tanks sites were identified. These were investigated using a Komatsu PC200LC-5 excavator. No additional tanks were discovered but significant additional piping was identified and removed. This piping was also manifested, loaded in dumpsters and shipped off site for disposal. On January 5, 1999 the last pipe trench were sampled by an independent sampling firm in the presence of the San Joaquin County representative. A large area of the site has now been characterized due to the wide distribution of pipe trenches,.liispenser islands and tank pits. This enabled the distribution of hydrocarbon affectedAtb be identified on the site. The sample locations are shown on Figures 1 through 8. Sample data is presented in Table 1. All product piping was manifested and shipped off site for disposal. Following exploration of possible tank sites and removal of piping identified by the locator the tank pits were backfilled using 6 inch surge rock to stabilize the soil below the water table (located at approximately 9 feet). 230 tons of 6 inch surge rock was brought to the site. Also 24 loads(approximately 400 yards) of clean granular material was imported as backfill for the tank pits. Once this surge rock had bridged the soft soil and a firm base was established, backfill using granular material compacted with a 66 inch pad foot vibratory compactor was