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vim _Y - s ♦ "•- � t cam' - 4 i 7 'W.-' .t �.' •,Mn 3 j 1 File No. 2070-2 19 September 1988 5. Environmental Sciences and Engineering (ESE} was contracted to investigate the =tamination found above. ESE's field investigation was conducted in two phases. In the first phase, conducted during the week. of . 6 July 1537, one monitoring well (Mot-1, 95 feet deep) was constructed. In the second phase, conducted September 1987, two additional monitoring wells were installed (MW-2 and MW-3, refer to site plan) During the construction of each well, the soil piofilz war, recorded, and soil samples werr, taken at 5 foot vartical internals. The groundwater was also sampled. (;groundwater depths of approximately 35 feet care: recorded.) 6. The soil and gro-a:3water sanples taku:n by ESE were chemically analyzed by Anlab La.)oratory in Sacramento. The soil sample taken from MW-1 at 55 feet below ground .surface was determined to contain elevated levels GTE TPH. Soil samples taken at 30 and 35 feet in MW-2 were dei:ermined to contain elevated levels of TPH and lead. Benzene, t•--Luene, xylene, and TPH were detected in the groundwater sample tah3n from MU-1. However, laboratory analysis k of groundwatersainplss taken from MW-2 and MW-3 showed no detectable concentrat-ions of these constituents. 7. The three monitoring wells installed by ESE were situated in nearly a straight line (resuluing in a questionable determination of the groundwater gradient) . In add=tion, the zero line of contamination had nut yet been determined (both up and �. downgradient) . Anderson Geutechnical Consultants (AGC) took over the investigation in order to resolve these issues. F I 8. In January 1988, :nierson Geotechnical Consultants installed two additional monitosinc, wells (MW-4 and MW-5, bo'ch 55 feet deep, see Figure I.I . From the AGC groundwater elevation measurements, it was determined that the groundwater gradient f+ tended to the east, Lather than to the northwest, as ESE had i determined. Groundwz.•_�er samples taken from MW-4 and MW-5 were ' analyzed by'' Caliroriv'a Analytical Labs, in West Sacramento. ( • Benzene, toluene, ane. xylene were detected in the sample taken from MW--4. Low leve:.s of toluene were detected in the sample taken from MW-5 (see F`;.'gure 1) . J,II. PP.i?POSED WORK?LAN i i. 9. On 16 June 1988. representatives of AGC met with Mr. Gordon Lee Boggs of the Reg:, -)nal water Quality, Control Board to review i the status of the invvR tigation. tor. aogg's concerns were: 1) the questionable gr..dient determination by ESE, 2) the contamination found it, MW-4, which is u,)gradient of the removed { -2- r r a I 'f • :i 1 r k