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mg : -1 1- X Mgggqgo gat tF Ir aL Geokgicaf Technics_- "01 qu-rxMd Maaw,CA .95351 PHASE 1I Ground Water Assessment William Stewart's Properl.y GT-18 1.0 PURPOSE AND -SCOPE a]and vertical The purpose of Phase II ground water asessment is to finish defining the later of the ground water contami ti�'Plume at Stewart's Beacon Property in Tracy, extents na on california.(Figure I). monitoring wells during this phase of investigation. We ptopose to instal!three ground water Two monitoring wells will be installed into the first aquifer down gradient of?�hc leakiiig es ond'�quifcr and will be underground fuel tank. one monitoring well will be installed into th ec placed to the north of the former tank location. The proposed locations of these wells are shown in the Property Boundary Map(Figure 3). Each monitorirg well will be developed, sampled,and the samples will be analyzed for the following petroleum hydrocarbons: gasorine,benzene,toluene,and xylene(BTX). 2.0 SITE HISTORY A preliminary investigation report was submitted on July 1,1988,discussing the results of the soil and ground water assessment. That information is summarized below. al the o I s The upper 21 fe-et of strata was investigated during this project. In this intery , sii ns inter ded characterize by fine grained sediments which are dominated by clay rich horizo bed water bearing with thinner silt or sand horizons. Below 20 feet is a silty clay,above 20 fe.et,. rs between 20 to 17 feet. A soft wet sandy clay occurs zone composed of$'I ty and clayey sand occu und m 14 up to about 11 or 10 feet is a clayey sand that also contains gro from 17 up to 14 feet. Fro north. Above 11 or 10 feet is a sandy water barring. This sand grades laterally into a silt to the clay unit that has a few feet of organic rich top soil near the surface. The ground water gradient is to the north,which is reflocted in the migration path of mi as not moved contamination. Analytical data shows that soil or ground water conta nation h south of the tank,but has moved at least 50 feet to the noith(location of MW#1). soil ut directly from the contamination has two modes of dispersal. 1)that which has migrated o by ground water movement. The cross section given in tankand 2)that which is dispersed% 3 shows the generalized interpretation of contamination distribution. Figure MIN vvv�