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Page 5 January 30, 1992 Job No 400511-SA of 99 feet with 30 feet of screen The construction details of the new wells are summarized in Table A. ' The locations of all wells are shown on the Site Plan Showing Lines of Cross Sections, Figure 2 ' 4.1 Borehole Advancement and Soil Sampling The groundwater monitoring and vapor extraction wells were drilled on September 23 through October 16, 1991 by Pierson Drilling of Modesto, California under the supervision of a DERS field geologist The boreholes were drilled using 8-inch O D hollow-stem augers All bits, drill rods, and augers were steam-cleaned prior to use Soil samples were collected from the borings using a 15-foot x 2 5-inch I D split-barrel sampler The split-barrel was advanced into the undisturbed soil beyond the ' tip of the auger to collect soil samples The sampling of the boreholes was conducted at 5-foot intervals starting with a sample collected at 5 to 6 5-feet below the ground surface Prior to each sampling, the samplers were thoroughly washed and rinsed to avoid cross-contaminating the samples The soil samples collected from the boreholes were selected for analysis based on headspace Organic Vapor Meter (OVM) readings as described in Appendix A OVM values are presented on the well logs The boreholes were logged and all soil samples were visually classified (ASTM D-2487-85) The well logs are attached m Appendix B Soil cuttings from the borings were placed on visqueen, covered with t r visqueen, and stored on-site inside a fenced enclosure for security Soil samples from each borehole were submitted to the State of California-licensed laboratory, Trace Analysis Laboratory, Inc (Hayward), for total petroleum hydrocarbons as gasoline (TPHg) analysis by the DHS method, and ' benzene, toluene, xylenes, and ethylbenzene (BTXE) by EPA Method 8020 Routine chain-of-custody procedures were employed 4.2 Monitoring Well Installation ' The four monitoring wells, MW-27, MW-28, MW-29, and MW-30 were constructed with threaded aded flush ' joint 2-inch diameter, schedule 40 PVC screen and riser pipe(see Well Logs,Appendix B) A summary of the well construction details for all the new wells at the site is presented in Table A The wells were finished with traffic boxes set in a 2-foot diameter circular concrete pad The traffic boxes were ' typically set about an inch above the existing ground surface to help divert surface water away from the well Each well is equipped with a locking, watertight, expanding cap The new monitoring wells were developed by hand bailing and surging until the groundwater contained minor particulate turbidity The water extracted during well development was contained in drums and stored on-site inside the fence for later recycling Based on laboratory results, noncontamirnated water will be disposed on-site or by discharge permit and contaminated water will be recycled at a licensed facility 4005111 Rev 1 c3' Du Pont Environmental Remediation Services Pnnted on Re tied Pa Per