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Chevron/.South El Dorado 5 September 1990 During the- excavation activity, two additional tanks were discover:.ed and removed. The:soil beneath these two tanks was sampled .and analyzed. The analytical results for these samples reported.. them to be below the laboratory Method Detection Limit (MDL) of: 1 ppm for TPH-as-gasoline. A second excavation was performed in the vicinity of the, former waste oil tank. Upon reaching the limit of the excavation equipment, samples were collected for analysis. The results of these analyses showed concentrations of. Total Oil-and-Grease (TOG) ranging from below MDL to 21 ppm. soil Aeration and Excavation Backfilling. From January to August 1990, the excavated' soil was passively aerated on site in accordance with guidelines presented by the San Joaquin County Local Health District (SJCLHD.) ..and the Air Pollution Control District. At -the request of the SJCLHD, a . schedule of soil turning and sampling was maintained to document the progress of soil aeration. Upon completion of the aeration of gasoline hydrocarbons and final - approval from the SJCLHD, .the aerated soil was used; to backfill. the excavation. The backfill material- was properly;';compacted under the supervision of Bay Area Geotechnical Group (BAGG) , ' a licenced geotechnical engineering subcontractor. Mon toring Well Installation. On August 15 and 16, 1990, three monitoring ,wells were installed on site by Groundwater Technology (Figure 2 - Site Plan). During drilling, .soil samples from selected intervals were collected for analysis. The intervals, analyzed included the sample taken from approximately 3-feet above the first appearance of water in each well and samples from 18. 5-feet and 34. 0-feet below grade in MW-3 - Laboratory results from soil samples collected from the soil _ . GROUNDWATER TECHNOLOGY, INC.