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.� S E C 0 R • Mr Harlan Knoll January 14, 2004 Page 3 of the water usage Another well is located at a residence (Well DW-4) at 8732 Davis Road, approximately 180 feet north of the site SECOR field staff located what appeared to be a domestic water supply well (Well DW-1) on the property located at 8855 Thornton Road, approximately 281 feet northwest of the site The resident was not available to confirm the existence of the well, and a well survey form was not completed by the property owner, however, the possible domestic well was housed in a similar enclosure as the previously identified wells in the field SECOR identified other sensitive receptors within 2,000 feet of the site The closest school is "A Better Road", located approximately 900 feet to the north of the site Two surface water bodies were also identified Mosher Slough (approximately 260 feet south of the site), and South Bear Creek (approximately 1,300 feet northwest of the site) Groundwater monitoring and sampling of the existing monitoring well network has been performed on a quarterly basis since February 1999 Depth to water through the third quarter 2003 at the site has ranged from 26 29 feet to 37 84 feet bgs Groundwater flow direction during the third quarter 2003 was reported to the northeast, with a hydraulic gradient of 0 002 feet/foot (ft/ft) SCOPE OF WORK Between November 19 and 24, 2003, SECOR oversaw the installation of two on-site and one off-site deep groundwater monitoring wells (MW-8 through MW-10) at locations shown on Figure 2 Drilling ) activities were performed by Cascade Drilling of Rancho Cordova, California As required by the Occupational Health and Safety Administration (OSHA) Standard "Hazardous Waste Operations and Emergency Response" guidelines (29 CFR 1910 120), and by California Occupational Health and Safety Administration (Cal-OSHA) "Hazardous Waste Operations and Emergency Response" guidelines (CCR Title 8, Section 5192), SECOR prepared a site-specific Health and Safety Plan (HASP) Prior to the commencement of fieldwork, the HASP was updated with appropriate field personal and subcontractor information The field staff and contractors a reviewed the HASP before beginning field operations at the site The completed scope of work is discussed below • Monitoring Well Installation The exploratory borings for groundwater monitoring wells MW-8, MW-9, and MW-10 were drilled to depths of 111 feet, 110 5 feet, and 111 5 feet bgs, respectively l-ithology of soils was analyzed based on soil cuttings to a depth of 50 feet bgs in the boring for well MW-10, and to a depth of 70 feet bgs in the boring for well MW-8 L.ithology of soils encountered during the advancement of the boring for well MW-9, beyond 50 feet bgs in the boring for well MW-10, and beyond 70 feet bgs in the boring for well MW-8 was analyzed at 10-foot intervals to the total depth explored The wells were installed using air rotary drilling equipment with a casing hammer to prevent cross-contamination of shallow impacts into deeper zone soil and groundwater The monitoring wells were completed at depths of 108 feet (MW-9) and 109 feet bgs (MW-8 and MW-10), and were constructed with 2-Inch diameter schedule 40 PVC casings with approximately 10 feet of 0 020-inch slotted screen material All work was conducted in accordance with stipulations of permits obtained from the SJCEHD and the CSPWD SJEHD and CSPWD permits are included in Attachment 2 Field and laboratory procedures are presented in I\ConocoPhillips\Tosco Marketmg18671IReports\Assessment Rpt doc SECOR International Incorporated