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r 2. PREVIOUS INVESTIGATIONS The following summary of the work completed at the site is organized by task, not necessarily by chronology. Because of the large number of site visits by both GTI and EA, this format pro- vides the most succinct summary. 2- 1 UNDERGROUND TANK REMOVAL AND SOIL SAMPLING Three 8,000-gallon fuel tanks and one 500-gallon waste oil tank were removed on 4 February 1986 by American Environmental Management Corporation of Rancho Cordova, California. GTI per -- sonnel monitored the tank removal and screened the soils in the i — tank excavations with an HNU photoionization detector. Single soil. samples were collected from six locations (5-1 through S-6,, _ Figure 3 ) atthe time of the tank excavation. The samples were . taken from areas where petroleum odors and soil discoloration were..detected and from the areas below the product tanks and the waste oil: tank. These samples were collected by removing soil with. the backhoe and then placing the soil in brass tabes. The ( " anai.yticai ;results from the testing of these samples are shown in Table 2. The extent of the soil contamination in the tank pit . was described in the GTI report. as "localized. Prior to back- j filling "of. the tank pit, "representatives from Groundwater Technology. and the San Joaquin Local Health District determined - 1 that excavation" of the minor amount of contaminated soil was unnecessary". (GTI 1986a): 2.2 . DRILLING AND SAMPLING OF SOIL BORINGS On 9 and .10 January '.1986, GTI personnel supervised the drilling of four soil borings (Figure 3) located: "along the path of the fuel lines" (SBI--SB3 ) and near .the .waste oil tank excavation (SB4.) to sample the soil for the presence of hydrocarbons (GTI i986a) . Two soil samples were collected at .5 feet and 10 feet e25/71050%8-89/txt 5 F N1111 ON090MEEM11 5101WIN all m1@111