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S E C ® R Mr Harlan Knoll April 14, 2003 Page 2 California Department of Water Resources (DWR) files for locating water supply wells in the area, contacting the local water purveyor (San Joaquin County), and a conducting a door-to-door field survey In search of any wells or other sensitive receptors within 1,000 feet of the site Four wells were Identified within the surveyed area, one municipal well and three domestic wells The domestic well was identified as Colonial Heights municipal water supply well 43 (Well DW-3) The location of Well DW-3 was verified in the field and surveyed, and is situated 260 feet south of the site, on the south bank of Mosher Slough, which borders the intersection of Thornton Road and Davis Road Three additional water supply wells in the area were identified One well was Identified at Bear Creek Veterinarian Hospital (Well DW-2), located at 8728 Thornton Road Well DW-2 is located 444 feet north of the site Another well is located at a residence (Well DW-4), located at 8732 Davis Road (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 and is 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 The site is currently monitored and sampled on a quarterly basis During the last quarterly groundwater monitoring event conducted on February 3, 2003, maximum concentrations of TPHg and MtBE were reported at 69 ppb and 1,900 ppb, respectively BTEX were not detected in any of the wells sampled during the first quarter 2003 Depth to groundwater at the site ranged from approximately 29 feet below ground surface (bgs) to approximately 37 bgs during 2002 Groundwater flow direction was to the northeast at a gradient of 0 001 feet per foot ft/ft during the first quarter 2003 PROPOSED SCOPE OF WORK The scope of work for this site assessment will include the drilling and installation of one sentry well (SW-1) between the site and the San Joaquin County Colonial Heights Municipal Well #3 which is located 260 feet south of the site and the drilling and installation of one well onsite (MW-8) in order to delineate the vertical extent of MtBE in the groundwater (Figure 2) Y The specific scope of work is discussed below Site Specific Health and Safety Pian 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 f (Cal-OSHA) "Hazardous Waste Operations and Emergency Response" guidelines (CCR Title 8, Section 5192), SECOR will prepare a Site-Specific Health and Safety Plan prior to the commencement of fieldwork The Site-Specific Health and Safety Plan will be reviewed by the field staff and contractors before beginning field operations at the site Permitting Groundwater monitoring well installation permits and soil boring permits will be obtained from San Joaquin County Environmental Health Department (SJCEHD) and encroachment permits will be obtained from the City of Stockton Public Works Department v� Deep Well Installation The on site deep well (MW-8) will be drilled to a total depth of approximately 110 feet bgs at the location shown on Figure 2 Depth to groundwater at the site has ranged from approximately 25 feet bgs to approximately 38 feet bgs The soil boring will be drilled using either an 8-inch and 12-Inch diameter hollow-stem auger or air rotary drill rig with hammer WPLAN sentry well install SECOR International Incorporated Ia - A