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of ![RNIB Mr. Bill Vizza . 30 November 1993 Page 2 diesel tank has not occurred In order to further demonstrate that petroleum hydrocarbons compounds in groundwater are not above concentrations detectable by laboratory analytical methods, we are recommending that one additional set of groundwater samples be collected during February 1994. Since chemicals were not detected in soil and groundwater samples collected during October 1993, we also recommend that soil and groundwater currently stored within 55- gallon capacity drums be considered for disposal at the City's facilities. Drummed soil and groundwater should be considered for disposal at the City's solid waste disposal facility and wastewater treatment facility, respectively. SOIL AND GROUNDWATER INVESTIGATION On 7 October 1993, three monitoring wells were installed at the locations shown on Figure I The location of MW-1 and MW-2 were changed from the locations shown in the original work plan to better accommodate suspected groundwater flow direction and facility layout. MW-1 was relocated south of the original position in order to provide better down gradient monitoring and to avoid drilling through the concrete driveway. MW-2 was moved to the . west of the original location to avoid the underground water conveyance piping and to provide better down gradient monitoring Soil samples were collected at five-foot intervals, beginning at ground surface. Since the groundwater surface was penetrated at depth of approximately 6 feet, the five-foot soil sample from each soil boring was selected for laboratory analysis as it was collected immediately above groundwater Soil Sawling Procedures Drilling and sampling were performed in accordance with ASTM Standard Method D1452-80, "Soil Investigation and Sampling by Auger Borings." Drilling operations were performed with a wheel-mounted, hollow stem auger flight drill rig equipped with 8-inch outside diameter augers. Soil samples were collected from each of the boreholes at the specified depths for Iogging and analytical purposes. Samples were collected by advancing the auger to a point immediately above the desired sampling depth interval and then driving a modified California split-spoon sampler, lined with three brass liners, into the undisturbed soil. The sampler was driven using an manually operated slide hammer with a per-blow force equivalent to a 140-pound hammer with a 30-inch free-fall drop, in accordance with ASTM • Standard Method D1586-84, "Penetration Test Split Barrel Sampling of Sail." Blow counts were recorded in six-inch intervals during every sampling event.