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• <br /> rRasMA <br /> September 15, 1993 Working To Restore Nature <br /> A. Teichert & Son, Tracy, California <br /> the initial sampling event immediately following well completion The hydrocarbons <br /> detected during that sampling event may have been due to contaminated equipment <br /> In November 1987, the tank cavity was over-excavated to 28 feet below grade in an effort <br /> to remove soil affected by hydrocarbons Analytical results of soil samples collected from <br /> the base of the excavation indicated that relatively low concentrations of gasoline <br /> hydrocarbons (200 parts per billion [ppb] ethylbenzene, 20 ppb toluene, 3,250 ppb xylene) <br /> were detected in only one sample, which was collected nearest to well BH-1 <br /> • <br /> ASSESSMENT OF SOIL AND GROUNDWATER <br /> The drilling operations, soil sampling, well construction and development, and water <br /> sampling are summarized below Our field methods are described in an attachment to this <br /> • report. Copies of the Chain of Custody Records and laboratory reports for soil and water <br /> samples are attached Work was conducted according to field methods outlined in our <br /> Work PIan No 123009-1W, dated June 11, 1993 <br /> Drilling, oil Sampling, and Well Construction <br /> • • On July 6, 7, and 8, 1993, a geologist from RESNA observed Westex Drilling (Westex) of <br /> West Sacramento, California, drill three 8-inch-diameter soil borings (B-1 through B-3) and <br /> install three groundwater monitoring wells (MW-2 through MW-4) at the site <br /> Soil samples were collected during drilling at approximately 5-foot intervals for possible <br /> laboratory analyses and to evaluate the geology beneath the site Samples were identified <br /> using visual and manual methods and classified according to the Unified Soil Classification <br /> System (Plate 3) During drilling, groundwater was encountered at approximately 87 to 88 <br /> feet below surface grade Descriptions of the materials encountered are presented in the <br /> Logs of Borings (Plates 4 through 15) Soil beneath the site consists primarily of <br /> • interbedded layers of silt to clayey silt and sand to gravelly sand <br /> Westex installed groundwater monitoring wells MW-2 through MW-4 in borings B-1 through <br /> B-3,respectively Well construction details are illustrated on the Logs of Borings Four soil <br /> samples were collected from the drill cuttings and composite into one sample in the <br /> laboratory for analyses Analytical results of the composite soil sample were used to <br /> evaluate disposal options of the drill cuttings. Results of analyses are presented in the <br /> attached Laboratory Reports <br /> • <br /> 0803gtak <br /> 123009-1 2 <br /> • <br />