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60 2905 W Benjamin Holt Drive, Stockton, California August 12, 1994 0 Chevron USA Products Company Page 4 All rinse water generated from steam cleaning was temporarily stored in Department of Transportation (DOT)-approved 55-gallon drums on site Sod from the borings was placed on and covered with plastic sheeting on site pending characterization and disposal Approximately one cubic yard of sod was removed from the site on July 7, 1994 by Integrated Waste Management, Inc and transported to BFI landfill in Livermore, California for disposal 3.3 Groundwater Monitoring Well Installation/Development One monitoring well (MW-9) was installed within the deep (30 feet BGS) boring drilled In the planter located on the corner of West Benjamin Holt Drive and Plymouth road (Figure 2) The monitoring well was constructed of 2-inch-diameter, schedule 40 PVC casing with flush threads, and 0 020-inch-slot well screen The well screen was installed from the bottom of the boring (30 feet BGS) up to 10 feet BGS Sand was placed In the well annulus from the bottom of the well to approximately 2 feet above the top of the well screen Bentonite was placed on top of the sand from 9 to 7 feet BGS The well annulus was sealed to approximately 1 foot BGS with a bentonite and neat-cement grout The wellhead is protected at the surface by a locking cap and a traffic-rated street box (with a watertight bolted lid) set in concrete Well construction details are shown in the drill log attached in Appendix B Upon completion, the new monitoring well was developed to remove fine-grained sediments from the well filter pack On June 27, 1994, Groundwater Technology personnel surged and bailed approximately four well volumes of water from MW-9 using a clean PVC bailer Temperature, pH, and conductivity measurements, recorded while purging stabilized after four volumes of groundwater had been removed (Appendix C) Water generated during the development process was pumped to a DOT-approved purge water trader and transported to the Chevron refinery in Richmond, California for recycling Following installation, the new wellhead was professionally surveyed for elevation relative to mean sea level (Appendix D) 34 Groundwater Monitoring and Sampling On June 27, 1994, depth to water in groundwater monitoring wells MWA through MW-9 was gauged from tap-of-casing to determine the static water level and to check for the presence of separate-phase hydrocarbons (SP) The water level was measured using an ORS Environmental Equipment INTERFACE PROBE TV Well Monitoring System, consisting of a dual optical sensor and electrical conductivity probe, that distinguishes between water and petroleum products GROUNDWATER 0017aear rpt �' TECHNOLOGY