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Ms. Lori Duncan October 3, 2003 Page 3 of 7 Sensitive Receptor Survey Ground Zero previously conducted a survey of production and/or domestic wells within 2000 feet of site, which was included in the Well Installation Workplan dated August 10, 2000. As part of the survey, Ground Zero contacted the California Department of Water Resources (DWR), the City of Manteca, and EHD, and conducted a drive-by survey of the area. A table and accompanying figure identified fifteen wells located near the site, including six wells within 2,000 feet of the site. The figure also identified nine residences within that distance for which no documentation of any well was available from either DWR or EHD. Ground Zero stated in the report that, although no well logs were available, each of these residences was likely to have their own domestic well. Pursuant to EHD's request for additional information, Mr. Marty Harris of Tuff Boy conducted additional survey to confirm that the residences identified by Ground Zero each have a domestic well for drinking water. Information obtained by Mr. Harris is included in Attachment A. It should be noted that the facility well is used for process water and in the restrooms only. Drinking water is delivered to the site by Alhambra. PROPOSED WORK PLAN To further evaluate the vertical and lateral extent of groundwater contamination at the site the following scope of work is proposed: Investigation of the Lateral Extent of Groundwater Contamination Ground Zero proposes to install three additional shallow monitoring wells to further investigate the lateral extent of groundwater contamination. To address EHD's concern that well MW 1 is not located close enough to the source area, Ground Zero proposes to install a groundwater monitoring well adjacent to the former UST using a limited access drilling rig. To address EHD's concern that lateral definition is incomplete until non-detect points are established in all quadrants, Ground Zero proposes to install one additional groundwater monitoring well north/northwest of well MW2 and one additional groundwater monitoring well west of well MW3. It is not possible to drill an upgradient monitoring well due to the configuration of the site and the adjacent residential property. The locations of proposed groundwater monitoring wells are presented on Figure 6. The proposed additional wells will be installed to a depth of approximately 19 feet bgs. The pilot borings will be advanced by a drilling contractor with a California C-57 license using a rig equipped with 8-inch diameter hollow stern augers. The borings will be completed as groundwater monitoring wells and will be constructed of 2-inch diameter, Schedule 40 PVC blank and slotted casing. The screened interval will consist of 0.010" machine-slotted casing. Since groundwater beneath the site is very shallow (approximately 5-7.5 feet bgs) The wells will be screened from approximately 4 feet bgs to approximately 19 feet bgs. The filter pack will consist of No. 2112 woolsey.cht/reports/wo rkp la".mws