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filr .. <br /> Geofvgicaf Technics <br /> 7601'River 7,pad `Fnvimnr wtcaf Cmwtda VSpuia au <br /> nfo&sta,C-R 95351 <br /> (zo9,!5je.raos <br /> PHASE II <br /> j Ground Water Assessment <br /> B C&D Property <br /> GT-8 <br /> 1.0 PURPOSE AND SCOPE <br /> The purpose of Phase H ground water assessment is to finish defining the lateral and vertical <br /> extent of the ground water contamination plume at BC os b Property in Tracy,California <br /> as (Figure 1). <br /> „. We propose to install four ground water monitoring wells during this phase of investigation. <br /> Three monitoring wells will be installed into the first aquifer surrounding the ground water <br /> contamination plume which was tentatively defined during phase I of investigation. One € <br /> monitoring well will be installed into the second aquifer and will be placed to the north of the <br /> fo=er tank location. The proposed location of theses wells are shown in the Site Map(in <br /> pocket). Each monitoring well will be developed,sampled,and the samples will be analyzed <br /> for the following petroleum hydrocarbons: gasoline,benzene,toluene,and xylene(BTX). <br /> 3 <br /> 'r <br /> SITE HISTORY <br /> i <br /> J <br /> A property assessment was conducted in 1987. In the course of that study,both soil and ground <br /> E , <br /> water contamination was discovered. The information gathered during that project is <br /> sums-narized below. <br /> The;hallow subsurface sediments studied during this project are characterized by a bimodal <br /> distribution(above 9 feet sand dominates,below 9 feet cloy dominates). Much of the shallow <br /> J sediments(upper 3 to 4 feet)are composed of fill material brought in to level the property. <br /> Incorporated in this material is a variety of debris including wood,metal,bricks and gravel. <br /> The first ground water was encountered at about 12.5 feet. The water bearing strata composed of <br /> clayey sand,sandy clay or clayey silt,is about 2 feet thick,extending from about 13 to 15 feet <br /> (Figure 2). The regional ground water gradient is to the north,however due to leakage of the <br /> irrigation pipe near the north side of the property,the flow of this shallow ground water at <br /> the time it was measured was to the south. <br /> -- - - T Soil-cont'aniimfion f5 m;tricted to a narrow horizon above the ground water(from about-12:5 up- -- -to 9 feet). The contamination is located in a circle around the previous fuel tank location, <br />