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LMLEEDSHILL•HERKENHOFF, INC <br /> September 1990 <br /> A reference point (RP) elevation was established by licensed surveyors to within 0 01 foot <br /> for the newly installed monitoring well and the five existing wells at this site for vertical <br /> ' gradient control <br /> ' GROUNDWATER SAMPLING <br /> Representative groundwater samples were collected from MW6 on August 15, 1990 using <br /> ' established protocol as specified in the USGS "National Handbook of Recommended <br /> Methods for Water Data Acquisition," which provides guidelines for the collection of <br /> representative groundwater samples. The 4-inch diameter monitoring well was sampled <br /> with a 3-inch diameter Teflon bailer. Several well volumes of water were removed prior <br /> ' to sampling, while field measurements of conductivity (SC), pH, temperature, and visual <br /> observations were made to ensure the collection of a stable, representative groundwater <br /> sample. The groundwater sampling field data sheets are presented in Appendix B. <br /> On August 29, 1990, additional groundwater samples were collected for confirmation of <br /> ' previous results from MW4 and MW6 using the protocol described above <br /> The water samples were collected in sterile 40 ml glass VOA sampling bottles, <br /> appropriately labelled and preserved according to standard EPA methods The sample <br /> was cooled to 4 degrees Celsius at the site and maintained at that temperature until <br /> received at the laboratory. Samples were received at the laboratory within 24 hours of <br /> collection under appropriate chain-of-custody procedures, and extracted prior to <br /> expiration of approved holding times. Chain-of-custody forms are presented in <br /> Appendix B. <br /> GEOLOGIC CROSS-SECTIONS <br /> Geologic cross-sections were prepared based on lithologic information obtained from the <br /> drilling of SB21(MW6), S1322, and S1323, and previous information from the drilling of <br /> MW5. The Unified Soil Classification System was used to classify the sods Discrete sod <br /> ' samples were taken every 5 feet using the modified split-spoon sampler. The drill cuttings <br /> were continuously observed to verify the discrete sample classifications made at five-foot <br /> intervals. A continuous sampling technique, described previously, was used for SS21 <br /> Sods in this areaen r ll consist g e a y co s st of low plasticity silts, clays, and fine sands with some <br /> ' clayey silts and silty clays. <br /> 6 <br /> 1 <br />