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r 4 Additional Site Assessment Report and Corrective Action Work Plan 3 The Southland Corporation,Store#20632 4827 DaVinci Drive Stocidon CA Janua 8 1997 bottom to approximately one foot above the top of the well screen A surge-block was used to assist packing/settling the sand around the well screen prior to setting the bentonite seal The well annulus was sealed with approximately two feet of bentonite pellets saturated in place on top of the sand pack,and neat-cement grout to approximately 10 inches BGS The wellheads are protected at the surface by locking, water-tight well caps and traffic-rated street boxes(with watertight bolted lids)set in concrete W811 construction details are shown on the drill logs in Appendoc A On September 21 and 22, 1997,the wells were developed using a PVC bailer to remove fine-grained sediment from the well and sand pack Prior to development activities,depth to water was measured relative to top-of-well-casing to determine the static water level in the wells Approximately four casing volumes of water was extracted from each well and stored in a DOT-approved 55-gallon drum pending transportation and disposal The top of casing and nm of each well box was surveyed in November, 1997,by Morrow Surveying for horizontal position and elevation relative to mean sea level datum using City of Stockton Benchmark#232 as a reference The resultant map is included in Appendix B Field notes from the well installation are included in Appendix C 3.5 Groundwater Monitoring and Sampling . On October 17, 1997, depth to water in each well was measured to the nearest 0 01 foot from the top of the well casing using an ORS Environmental Equipment INTERFACE PROBES'"Well Monitoring System Field data sheets are provided in Appendix C Subsequent to monitoring,at least four well volumes of water was bailed from each monitoring well to ensure stabilization of pH,electrical conductivity,and temperature. The purge water was stored In a DOT- approved 55-gallon drum. The groundwater samples were collected using disposable bailers,then transferred to 40-millilrter glass vials filled to zero headspace and acidified to a pH of 2 The samples were sealed using Teflon septum caps,labeled,placed on ice in an Insulated container,and transported under chain-of-custody to state-certiified WEST Laboratories in Davis.California The groundwater samples were analyzed for BTEX,TPH-G and MTBE using EPA methods 8020/modified 8015 If MTBE was detected by EPA method 8020,its presence was confirmed using EPA method 8260 4.0 RESULTS 4.1 Geology The relatively level site is located at an elevation of approximately 2 feet above mean sea level. According to the California Division of Mines and Geology(Jennings, 1977)the site is underlain by Quaternary alluvial . deposits FLUOR DANIEL Gil rpt