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Monitoring Well Installation Report-Tosco(Former BP)SS#11195,Lathrop California ,,-....,. July 24,2002 3.1 Drilling Activities On May 28 and 29, 2002, a GR geologist observed Woodward Drilling Inc., of Rio Vista, California (C57 #710079), install five off-site groundwater monitoring wells (MW-13 through MW-17) at the locations shown on Figure 2. The well borings were drilled to depths ranging from 20 to 21 feet bgs using 8-inch diameter hollow-stem augers driven by a truck mounted drilling rig. Soil samples were collected at approximate 5400t intervals beginning at 5 feet bgs. The GR geologist prepared logs of the borings and screened the soil samples in the field for the presence of volatile organic compounds (VOC). Screening data are presented on the boring logs (Appendix B): Copies of the Drilling Permits are included in Appendix B. Groundwater monitoring wells were constructed in the borings using two-inch diameter Schedule 40 PVC well casing and 0.020-inch machine-slotted well screen. Lonestar #3 graded sand was placed in the annular space of the wells across the entire screened interval and extending 1- foot above the top of the screen. The wells were then sealed with 2 feet of hydrated bentonite followed by neat cement grout. The top of each well is protected by a vault box, locking well cap, and lock. Well construction details are presented on the boring logs in Appendix B. Mr. Michael J, Infurna. of the SJCPHS-EHD was on site to observe the grouting procedures. Soil cuttings generated during drilling activities were placed on and covered with plastic. A -= composite disposal confirmation sample Comp-1 (A,B,C,D) was collected from the stockpiled soil cuttings. Stockpile sampling procedures are presented in Appendix.A. 3.2 Well Monitoring Development and Sampling On June 18, 2002, static groundwater levels were.measured in the new and preexisting wells. All wells were checked for the presence of separate-phase hydrocarbons. Separate-phase hydrocarbons were not present in any of the wells. Static water level data and groundwater elevations are summarized in Table 1. - i After the static water levels were measured, the new monitoring wells (MW-13 through MW-17) were developed by GR personnel using a 2-inch diameter stainless steel bailer and submersible pump. Copies of the GR Well Development and Groundwater Sampling Field Data Sheets are included in Appendix C. A Potentiometric Map is included with this report as Figure 2. I After development, groundwater samples were collected from the monitoring wells as specified by I GR's Field Methods and Procedures (Appendix A). Water purged during well development and sampling was transported to the Tosco Refinery in Rodeo, California, for disposal. 3.3 Wellhead Survey Following installation, the well casing elevations and horizontal coordinates of the new wells were 140193.12-2 k 5 t