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' All drilling activities were completed inaccordance with California Department of Water Resources (DWR) Well Standards (Bulletin 74-90) and in accordance with ESE Standard ' Operating Procedure No 1 for Soil Borings and Soil Sampling with Hollow-Stem Augers in Unconsolidated Formations (Appendix D - FSE Standard Operating Procedures) 3.2 Monitoring Well Installation Development, and Ground Water Sampling During the first phase of drilling, FSE installed three ground water monitoring wells in three 1 of the borings Three four-inch ground water monitoring wells were installed at the site in October 1990 The wells were completed to a depth of approximately 47 feet below ground surface (bgs) Screened intervals were from approximately 35 to 45 feet bgs and a sanitary seal comprised of approximately two feet of bentonite pellets and the remaining 33 feet was filled with a bentomte/neat cement grout Sanitary seal emplacement was witnessed by a representative from the County During the second phase of drilling, ESE installed one ground water monitoring well west and downgradient of the former tank excavation This well was completed as a four-mch ground ' water monitoring well to a total depth of approximately 45 feet bgs Screened interval for this well was from approximately 26 to 45 feet bgs A sanitary seal consisting of approximately three feet of bentonite pellets and 23 feet of bentomte/neat cement grout was emplaced under the supervision of the County Subsequent to their installation, and prior to the sanitary seal emplacement, all wells were ' developed by surging and pumping techniques Wells were surged with a "surge block" which was repeatedly pushed through the water to the well bottom and then pulled back out of the water Thus surging technique allows the sand pack to settle and draws any fine sediment ' trapped in the sand pack into the well The well is then purged of a minimum of 10 well casing volumes of water using a clean submersible pump or clean bailer The physical parameters of ' temperature, conductivity, and pH are monitored as well as the visual clarity of the water bemg removed When the purged water is relatively sediment free and the physical parameters have stabilized, pumping is stopped and development is completed After development, the sanitary seal is installed All development activities were completed in accordance with ESE SOP No 2 (Appendix D) ' Ground water samples were collected from the three wells (MW-1, MW-2, and MW-3) on a quarterly basis from October 1990 until May 1993 at which time samples were collected quarterly from four wells (MW-1 through MW4) Ground water samples were collected by ' first measuring the depth to static ground water, calculating the minimum purge volume, and purging the well of at least three well casing volumes of water During the purging process, pH, temperature, and electrical conductivity were monitored on a regular basis to ensure a ' representative sample of the surrounding formational water would be acquired After purging the wells, a sample was collected by lowering a clean bailer into the well and extracting ground water with the bailer The water was decanted from the bailer into the proper laboratory ' supplied bottles, immediately placed in a cooler on ice, and transported under chain of custody • ' F 169351861CLOSURE RPT 7 Environmental Science&Engtneermg Inc 1