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water sample analyses is presented in Table 1. The official <br /> laboratory reports and chain of custody documents are <br /> included in Appendix G. <br /> 6.0 SITE GEOLOGY AND HYDRMIEOLOGY <br /> A brief description of site geology and hydrogeology based on <br /> the results of the drilling activities is presented below. <br /> - 6.1 a t e Geoloc[y- <br /> From review of the soil boring logs, it is apparent that <br /> the predominant subsurface soil types at the site are clays <br /> and silty clays, with lenses of sand, gravel, and silt-sand <br /> mixtures, as shown in Figures 4 and 5. The lenses appear to <br /> be discontinuous and limited in lateral extent. Figure 4 <br /> shows the north-south hydrogeologic cross section, A-A' , <br /> while the east-west hydrogeologic cross section, B-B' , is <br /> shown in Figure 5. <br /> As described in Section 2.3, Regional Geology and <br /> Hydrogeology, and as noted in the soil boring logs, the <br /> surficial deposits are Quaternary alluvial deposits of <br /> irregularly stratified, poorly sorted, unconsolidated <br /> -� and gravel deposited in stream <br /> deposits of mud, silt, sand, <br /> and river beds and on adjoining flood plains. Although none <br /> of the borings were drilled deeper than 30 feet below grade, <br /> it is unlikely that the thickness of the near surface deposit <br /> exceeds 40 feet. <br /> - 6.2 ;te ydrog�QlQgX <br /> The ground water elevation data for all existing monitoring <br /> wells, as measured on August 27, 1990, was used to develop <br /> the ground water elevation map, shown in Figure 3. The ground <br /> water flow direction was calculated to be to the north/ <br /> northwest, with an average gradient of approximately <br /> 0.005 foot per foot. The average depth to ground water in <br /> the wells was approximately 5.8 feet below grade. The water <br /> level measured in mi-5 was about 0.07 foot higher than Mod-3, <br /> which is only about 8 feet west of .Mtl-5. A slow recharge/ <br /> recovery rate was also observed in W-3 during the initial <br /> pump test compared to MW-2 and MW-5. For these reasons, the <br /> water level data for MW-3 was not cons:.dered in the <br /> development of the ground water elevatiktin contour map. <br /> Review of past ground water monitoring data revealed recent <br /> changes in ground water flow direction. Ground water <br /> monitoring conducted on July 12, 1990 indicated a northwest <br /> ground-water_ flow,-direction-.which-was--probablyr-_due-to-the------- <br /> 13 <br /> ue-ta-the-- --13 <br />