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CLEARWATER G R O U P Environmental Services temperature, conductivity, and pH were made and recorded on Monitoring Well Data Sheets for each well Well stabilization data are included in Appendix A Following purging, each well was allowed to recharge to at least 80% of its static water level prior to sampling Groundwater samples were obtained from each well using disposable polyethylene bailers and decanted into clean laboratory supplied bottles Samples were labeled, documented on a chain-of-custody form, and placed on ice in a cooler for transport to the project laboratory Groundwater samples were analyzed by Kiff Analytical Labs, located in Davis California, a California State-certified laboratory, for concentrations of TPHg, BTEX and MTBE by EPA Method 8260B Groundwater samples collected for MNA data were delivered to CytoCulture Environmental Biotechnology Laboratories (CytoCulture) in Richmond, California All field work was conducted in accordance with Clearwater's Groundwater Monitoring and Sampling Field Procedures and Natural Attenuation Processes and Recommended Monitoring Guidelines included in this report as Appendix B GROUNDWATER MONITORING AND SAMPLING RESULTS Groundwater sampling results for gasoline range hydrocarbons are summarized as follows Depth to groundwater range 8 88 (MW-2) to 1104 (MW-8) feet below • to -of-casin TQC Flow direction and gradient Southeast at approximately 0 004 feet/foot Benzene concentration range From not detectable (MW-2, MW-3, MW- 4) to 2,400 micrograms per liter (Rg/L) in MW-5B Toluene concentration range From<0 50 Rg/L (MW-2, -3, -4, -7, & MW- 8)to 630 tig/L MW-5B Ethylbenzene concentration range From <0 50 Rg/L (MW-2, -3, -4, -7, &MW- 8)to 550 -5B Xylenes concentration range From <0 50 Rg/L (MW-2, -3, -4, & MW-8) to 1,300 MW-5B TPH-g concentration range From <50 Rg/L (MW-2, -3, and MW-4) to 16,000 -5B MTBE concentration range Not detected in concentrations exceeding indicated laboratory method reporting limits (<0 50 R to<10 g/L The groundwater flow direction and gradient as determined by this sampling event is substantially the same as was determined by previous monitoring events Groundwater elevation and analytical data are included in Table 1 A groundwater elevation map based on the groundwater elevation data from all monitoring wells was prepared and is presented as Figure 3 A revised dissolved-phase hydrocarbon distnbution map including iso-concentration contours of benzene in groundwater is presented as Figure 4 Analytical reports for this groundwater monitoring event are included as Appendix C ZB178C/2Q03 Monitoring Rpt 4 September 15,2003