SITE INFORMATION AND CORRESPONDENCE

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URS Ms. Karen Niiya Page 2 Regional Water Quality Control Board-Central Valley Region October 28,2005 THIRD QUARTER 2005 GROUNDWATER MONITORING ACTIVITIES On September 1, 2005, URS conducted groundwater monitoring at the site,which included the following tasks: • Measure groundwater levels in the six on-site monitoring wells (MW-12 and MW-19 through MW-23)and calculated the hydraulic gradient at the site; • Purge and collect groundwater samples from the six monitoring wells • Prepare this report summarizing the analytical results. The depth-to-groundwater and total depth of each well were measured to an accuracy of 0.01 feet below ' ground surface (bgs) to a known surveyed point at each well location with an electronic water level indicator prior to purging. These measurements were used to calculate the purging volume and groundwater elevation for each well. Approximately three well volumes were purged from each well prior to sampling. Purging was performed by using dedicated, single-use, high-density polyethylene bailers. As each well was purged, temperature, pH, specific conductivity, and total dissolved solids were monitored periodically to verify the groundwater entering the well was indicative of aquifer conditions. Dissolved oxygen and ferrous iron were measured prior to collecting the groundwater sample. After the purge volume was reached and when the above parameters indicated that the water in each well was representative of the aquifer, a water sample was collected from the well. Each sample was collected by lowering a new pre-cleaned, dedicated bailer slowly to the water line and allowing it to fill while causing minimal agitation to the water column. Groundwater samples were carefully transferred to pre-cleaned, laboratory-provided sample containers. Once collected, the sample containers were labeled with the time and date of collection, project and sample identification codes, sampler's initials, type of analysis to be performed, and preservative method. rThe samples were then sealed in plastic bags and stored in an ice-filled chest at approximately 4 degrees Celsius until delivery to the laboratory. Each groundwater sample was delivered to the laboratory within the designated holding time and was accompanied by appropriate chain-of-custody documentation. The groundwater samples were submitted to Curtis&Tompkins Laboratories in Berkeley,California. THIRD QUARTER 2005 GROUNDWATER MONITORING RESULTS Groundwater elevations at the site wells have increased relative to the previous groundwater monitoring event conducted in June 2005. The direction of groundwater flow beneath the site for this sampling event was to the southwest with an average hydraulic gradient of 0.0018 feet per foot.The flow direction and gradient were consistent with historical data for the site. Figure 4 and Table 1 provide groundwater flow direction and gradient data.Field sampling data sheets are provided as Appendix A.The laboratory analytical data reports and chain-of custody documentation are provided in Appendix B. K:\Wp =ss122200 uel Vo Wmd Insii,wion\S P WAQMRS QTR 05QVI.SIPP-3QMR05 Re n.tl