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l� 44 <br /> CLEARWATER <br /> G R O U P <br /> Environmental Services <br /> Following purging, each well was allowed to recharge to at least 80% of its static water level <br /> prior to sampling Groundwater samples were obtained from each well using disposable <br /> polyethylene bailers Samples were labeled, documented on a Cham-of-custody form, and placed <br /> on ice in a cooler for transport to the project laboratory All groundwater samples were analyzed <br /> by KIFF Analytical Labs, a DHS certified laboratory, for concentrations of TPHg, BTEX and <br /> MTBE by EPA Method 8260B All field work was conducted in accordance with Clearwater's <br /> Groundwater Monitoring and Sampling Field Procedures included in this report as Appendix A <br /> GROUNDWATER MONITORING AND SAMPLING RESULTS <br /> Groundwater sampling results are summarized as follows <br /> Depth to groundwater range 10 42 (MW-2) to 12 04 (MW-8) feet below <br /> to -of-casing (TOC) <br /> Flow direction and gradient Southeast at approximately 0 0040 ft/ft <br /> Benzene concentration range From not detectable (MW-2, MW-3, MW- <br /> 4) to 1,700 µg/L (MW-5B) <br /> Toluene concentration range From <0 50 µg/L (MW-2, -3, -4, -7, & MW- <br /> 8) to 1,200 µg/L (MW-5B) <br /> Ethylbenzene concentration range From <0 50 gg/L (MW-2, -3, -4, -7, &MW- <br /> 8) to 710 g/L (MW-5B) <br /> Xylenes concentration range From <0 50 µg/L. (MW-2, -3, -4, & MW-8) <br /> to 2,500 g/L MW-5B) <br /> TPH-g concentration range From <50 pg/L (MW-2, MW-4) to 21,000 <br /> µg/L (MW-5B) <br /> MTBE concentration range Not detected in concentrations exceeding <br /> indicated laboratory method reporting limits <br /> (<0 50 pg/L to<5 0 µg/L) <br /> The groundwater flow direction and gradient as determined by this sampling event is <br /> substantially the same as was determined by previous monitoring events Groundwater elevation <br /> and analytical data are included in Table 1 A groundwater elevation map based on the <br /> groundwater elevation data from all monitoring wells was prepared and is enclosed as Figure 3 <br /> A revised iso-concentration map of benzene in groundwater is enclosed as Figure 4 Analytical <br /> reports for this groundwater sampling event are included as Appendix C <br /> SUMMARY AND CONCLUSIONS <br /> Results from this quarterly monitoring event appear to confirm results reported from previous <br /> groundwater monitoring activities, namely that the contaminant plume is currently delineated <br /> Contaminant concentrations appear to be highest in the MW-5B well <br /> ZB178C/4Q Monitoring Rpt 4 January 8,2003 <br />