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Pilot Testing Report and Conceptual Corrective Action Plan July 15, 1994 Manna Pro, 4004 South EI Dorado, Stockton, CA 5 2 2 1 Extraction Well Installation On September 21, 1993, Groundwater Technology supervised the installation of one 4-inch-diameter ' extraction well (EW-1) using hollow-stem auger drilling techniques The well location is provided on Figure 2 Before the well was installed, a 7-inch-diameter pilot borehole was drilled, logged, and ' sampled using a split-spoon sampler Samples were collected in brass tubes and selected for laboratory analysis based on lithology and field readings with a photoionization detector (PID) Selected soil samples were analyzed for BTEX, TPH-G, and TPH-D Soil samples were submitted for ' analysis from depths of 33 5 feet, 43 5 feet, 48 5 feet, 56 feet, and fit feet The results are provided in Appendix A, and summarized in Table 1 Following soil sampling, the borehole was redrilled with 12-inch-diameter hollow stem augers for well construction The extraction well was installed to a depth of 55 feet below grade The well was constructed using 4-inch-diameter polyvinyl chloride (PVC) continuous wrapped well screen (0 020-inch slot size) and 4-inch-diameter PVC casing The borehole annulus was filled with sand from the well bottom to approximately 2 feet above the top of the well screen A bentonite seal, approximately 2 feet thick, was placed above the sand pack, and subsequently hydrated with clean water The remaining annular space was filled with a cement grout mixture A flush-mount watertight manhole with locking well cap was installed at the surface for wellhead protection Soil ' boring and well construction logs are presented in Appendix B After well installation, the extraction well was developed using a surge and bad technique to remove suspended sediments from the well casing and sand filter pack, and to improve hydraulic ' communication with the aquifer Well development water was placed in 55-gallon drums and was appropriately disposed of offsite Wellhead elevations were surveyed by Groundwater Technology field staff relative to existing monitoring wells 2 2 2 Observation Well Installation On September 22 and 23, 1993, Groundwater Technology supervised the installation of three nested observation wells using hollow-stem auger techniques Before observation well installation, 7-inch- diameter pilot boreholes were drilled and logged, and sod samples were collected The boreholes were rednlled using 10 25-inch-diameter augers for observation well construction The observation well locations are provided on Figure 2 Soil samples were collected from each borehole in brass tubes using a split-spoon sampler, and analyzed for BTEX, TPH-G, and TPH-D The samples were ' 2879R034 070 GROUNDWATER E' TECHNOLOGY, INC