SITE INFORMATION AND CORRESPONDENCE

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Mr. John Welty April 10, 1990 Page 7 In August 1989, three off-site soil borings were drilled and three 2-inch-diameter monitoring wells were installed to varying depths as proposed in Southland's June 1989 work plan. Construction details of the wells are given in Table 1. Table 1. Construction Details of Cluster Wells 15 Well I.D. Total depth, feet Screened interval MW-15A 75 70-75 MW-15B 69 64-69 MW-15C 62 34-62 As shown in Table 1, Wells 15A and 15B have a 1-foot separation between their screened zones and Well I5C has a 2-foot separation between Well 15B and a 28-foot screened interval. A well was sampled in the November 1989 and February 1990 reports, but GTI did not specify which zone was sampled. Both sample events indicated nondetectable levels of gasoline compounds. Without sampling each zone (Wells A, B, and C), the wells do not provide information on the vertical extent of contamination. Analytical Results Tables 2 and 3 summarize the total petroleum hydrocarbon (TPH) concentrations detected in the wells located around the site. Wells 8 and 12 are located on the TGA property. Wells 10 and PW-2 are located southeast (downgradient) of the TGA property. Well 12 was analyzed from October 3, 1986 to May 12, 1987, and indicated TPH concentrations greater than 100 parts per billion (ppb) in each of the five sampling events. On April 14, 1987, the concentration of TPH exceeded 7,000 ppb. Sampling of Well 12 was discontinued after this time and plans for abandonment and replacement were proposed in GTI's May 1989 Project Update Report. Sampling of domestic well TMG has identified TPH levels exceeding 100 ppb in 4 of 66 sampling events. TPH levels were found at less than 100 ppb in 6 bf 66 sampling events. The remaining sample results indicated non detectable levels. As of June 20, 1989, the most recent detectable concentrations of TPH was on November 30, 1988 (15 ppb). Benzene concentrations were greater than the State Maximum Contaminant Levels for drinking water of 1 ppb in the October 16, 1987 (48 ppb) and the February 11, 1988 (62 ppb). Brown and Caldwell r.