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Monitoring Well and Sparge Points installation Report—Former Unocal Station#2859,Stockton,CA August 19,2002 Soil cuttings generated during drilling activities were stockpiled on-site, and were placed on and covered with plastic Composite disposal confirmation sample SP-I-A,B,C,D was collected from the stockpiled soil cuttings (Table 2) Stockpile sampling procedures are presented in Appendix A Well Installation Groundwater monitoring wells MW-20 and MW-21 were constructed using 2-inch diameter Schedule 40 polyvinyl chloride (PVC) casing and 0 020-inch machine slotted screen material Well MW-20 is screened from 85 to 90 feet bgs, and well MW-21 is screened from 50 to 60 feet bgs The annular space around the screened interval in each well is packed with Monterey #3 graded sand The sandpack is followed by a sea] of bentonite chips, then neat cement to approximately ]-foot bgs The top of the well is protected by a vault box, locking well cap, and lock The vault box is installed flush with the ground surface, and is set in concrete The C-SpargeT"' wells are constructed using 314-inch diameter Schedule 40 PVC casing and 2-inch diameter PVC microsparge screen material C-SpargeTM wells SP-1A, SP-2A and SP-3A are screened from 27 5 to 30 feet bgs, wells SP-113, SP-2B and SP-313 are screened from 57 5 to 60 feet bgs, and wells SP-1C and SP-2C are screened from 87 5 to 90 feet bgs The annular space around the spargepoint screens in each well is packed with Lonestar #2/12 sand Above the sandpack, the sparge wells are constructed similar to the monitoring wells Well construction details are included with the boring logs in Appendix C Well Monitoring, Development and Sampling The newly installed groundwater monitoring wells were developed on March 11, 2002, by Woodward Drilling, Inc (C57 #710079) On April 11, 2002, wells MW-20 and MW-21 were monitored and sampled by GR Wells were checked for the presence of separate phase hydrocarbons (SPHs) No SPHs were observed in the wells Purge water generated during development and sampling procedures have been removed from the site and transported to Tosco's Rodeo refinery for disposal Copies of the monitoring well observation summary and sampling field data sheets are included in Appendix D Wellhead Survey Following installation of the wells, the top of casing and vault box elevations of all newly installed wells were surveyed by Morrow Surveying (license#5161) The horizontal locations, including GPS longitude and latitude of all newly installed wells were measured A copy of the surveyor's report is included in Appendix E RESULTS OF THE SUBSURFACE INVESTIGATION Soil encountered during this investigation consisted of interbedded clay and sand to the total depth explored Soil color varied from dark brown to dark grayish brown and dark yellowish brown in all well borings Soil encountered during this investigation is similar to previous investigations at and in the vicinity of the site Groundwater in wells MW-20 and MW-21 stabilized at a depth of approximately 24 to 25 feet below top of casing Detailed descriptions of the soil encountered during drilling are presented is on the boring logs in Appendix C 24007206-1 4