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MONITORING WELL INSTALLATION WORK PLAN 1.0 INTRODUCTION In 2001, five groundwater monitoring wells were installed at the Pilkington North America, Inc. (Pilkington) facility located at 500 East Louise Avenue (Site), Lathrop, San Joaquin County, California (Figures 1 and 2, Appendix A). The wells were installed under Waste Discharge Requirements (WDR) Order No. 5-01-114 issued by the Central Valley Regional Water Quality Control Board (Regional Board) dated May 24, 2001. Subsequent to installation, the wells have been sampled according to Monitoring and Reporting Program(MRP)No. 5-01-114. The work plan for the initial monitoring well installation was approved by the Regional Board in a letter dated August 14, 2001. In that letter, the Regional Board indicated that a measured gradient different than the assumed gradient to the north may require the installation of additional well(s). Subsequent monitoring has indicated a general gradient to the south. Consequently, in a letter dated January 18, 2005, the Regional Board directed the installation of additional groundwater monitoring wells. This work plan was prepared by Condor Earth Technologies, Inc. (Condor) at the request of Pilkington to propose the location of two additional monitoring wells constructed identically to the existing wells. 2.0 SITE BACKGROUND INFORMATION Pilkington operates a float glass furnace facility at the Site. The facility stockpiles raw material, manufactures glass products, and warehouses products prior to shipment. Wastewater is generated from groundwater infiltration, float glass manufacturing, cooling tower and boiler blowdown,reverse osmosis reject water, and domestic wastewater. Domestic wastewater is disinfected prior to commingling with the process water. The area within the Site boundaries consists of approximately 176 acres. Approximately 75.4 acres are available for land application of wastewater. Wastewater has been applied to the lawn areas (11.4 acres), Site A (42 acres), and Site C (8.5 acres). Approval for the use of Site B has been requested of the Regional Board. The Site layout is shown on the map (Figure 2). The potential impact I of water storage and discharge to land is regulated by the WDR cited above. 3.0 MONITORING WELL LOCATIONS AND RATIONALE Two additional monitoring wells are proposed for the Site. The locations and rationale for each "- monitoring well are described in this section. The proposed monitoring wells are shown on Figure 2. The first proposed additional monitoring well will be located at the west end of the facility, and at the southern end of the lawn area. This location is expected to provide the most southerly location of the irrigated lawn areas. The second proposed monitoring well will be located near the southern end of Area B. This location is intended to provide down-gradient monitoring for both Areas B and C. As has been previously noted, the below-grade facilities in the area of the furnace are below existing groundwater, and sump pumps discharge infiltrating water out of these basements. Consequently, there is a localized gradient in the immediate area of the eastern half of the facility. The two additional monitoring wells are at a sufficient distance from these basement sumps that they are expected to indicate the area gradient and not the localized gradient produced by the dewatering sumps. IL 1) CONDOR