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Ms.Mart Lagorio • November 10,2000 Page 2 Site Preparation and Health and Safety Permits will be obtained from San Joaquin County Environmental Health Division (County) for the wells. Once permits are approved, monitor well locations will be clearly marked by staking each proposed location. Prior to conducting intrusive activities at the Site, Underground Service Alen (USA) will be notified of the proposed drilling activities and a dig alert number will be obtained. The actual well location may be adjusted or omitted in the field to account for subsurface obstructions and utilities. A site-specific Health and Safety Plan will be on-site during the field work activities (Exhibit A). Monitor Well Installation To accomplish these objectives, Brown and Caldwell proposes a minimum of 5 groundwater monitoring wells: one well placed within the fill area (existing pad); two wells in the apparent upgradient direction, and two wells in the apparent downgradient direction. As noted previously, the actual locations will depend on access restrictions posed at the site and the location of underground utilities. Based on preliminary information in the area of the Site, the depth to first groundwater may vary between 5 and 15 feet below ground surface (bgs). The actual depth to first groundwater will be determined at the time the wells are installed and the construction depths will be modified to account for the water table depth. Assuming groundwater is at a depth of 10 feet bgs, monitor wells will extend to a maximum depth of approximately 20 feet bgs. The wells will be constructed of 2" diameter PVC casing and screen. Based on initial observations of Site soils (fine grained to clayey), the screen will consist of a 0.01 slot size. The slot size of the well screen may be modified based on observations of subsurface soil encountered during installation. The well screen will extend from above the water table to approximately 20 feet bgs. The filter pack will extend from the base of the borehole to at least two feet above the top of the screen. A minimum two-foot thick bentonite transition seal will be placed on top of the filter pack. The remainder of the borehole to within one foot of the surface will be filled with cement-bentonite grout. Depending on the actual depth to first groundwater the well depth, sand pack height, and bentonite thickness may vary. The boreholes will not be advanced more than 5 feet into clay unless continuous samples are collected. The maximum penetration into a clay will be 10 feet. If the subsurface is comprised of clay,the wells will be constructed with only ten feet of screen beneath the water table. A locking protective steel casing will be set in concrete to form the surface completion of the wells placed around the fill material. A flush mounted well box will be used in the area of the existing pad(fill area). The well located within the fill (existing pad) will be advanced through a permanent conductor casing installed though the fill. A nominal 12-inch diameter borehole will be drilled to approximately 1 foot below the base of the fill, and an 9-inch diameter conductor casing grouted/cemented in place. This will provide protection against cross contamination of the native soil and groundwater by the fill material during the well installation process. The borehole will then be advanced through the conductor casing with 6-inch aueers and the well constructed through the hollow stem. \9-o During borehole advancement, soil samples will be collected at approximately 5-foot intervals using a California modified split-spoon sampler lined with stainless steel sleeves. The samples will be examined for lithologic characterization and described using the Unified Soils P:\20000\20587\WKPLNwe lsLdoc