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..1 <br /> Harlen Knoll <br /> February 2, 1990 <br /> Page 4 <br /> Water Level Measurements <br /> Water level measurements will be taken from all three monitoring wells. A Solonist Model <br /> 101 electric water level sounder will be used to measure water depths. Groundwater <br /> elevations and gradients will be calculated based on these depth measurements. <br /> SOIL CONTAMINATION ASSESSMENT <br /> Two soil borings, one shallow and one deep, will be drilled to assess whether a significant <br /> amount of oily waste remains in the soil following the January 17, excavation activities. <br /> Locations of the proposed borings are shown on Figure L One of the sites is located <br /> immediately south of the former tank, adjacent to the facility's service garage. This boring <br /> will be drilled to a depth of 15 feet and will be continuously logged. Samples will be <br /> collected at 5-foot intervals and at the groundwater interface. Additional samples will be <br /> collected from core samples which visibly indicate contamination. Samples will be collected <br /> by cutting the 2-inch diameter core into 4-inch long segments and placing the samples into <br /> clean glass jars with teflon-lined lids. The samples will be labeled, placed in a chilled ice <br /> chest and transported within 24 hours to California Water Labs in Modesto, California. <br /> Each soil sample will be evaluated only for oil and grease (EPA Method 9070). <br /> A second, deeper boring will be drilled north west of the tank excavation and will be used <br /> to evaluate the subsurface geology and hydrogeology. Specifically it will be designed to <br /> provide information on the thickness of the water table aquifer and ascertain the presence <br /> of confining layer of sufficiently low permeability beneath the aquifer to prevent the <br /> vertical migration of chlorinated hydrocarbon compounds. Although the boring will be <br /> logged lithologically, no soil samples will be collected for analysis. <br /> ENVIRONMENTAL ASSESSMENT REPORT <br /> An Environmental Assessment Report summarizing the results of this investigation will be <br /> forwarded to the San Joaquin Health Department upon completion of the study. At a <br /> minimum, the report will include site plans showing the surveyed locations of borings, and <br /> wells, logs of all borings, summaries and details of laboratory chemical analysis, results of <br /> field screening for organic chemicals, chain of custody record for the handling of all <br /> samples and recommendations for further groundwater monitoring or alternative remedial <br /> activities. <br />