ARCHIVED REPORTS_XR0008538 - Laserfiche WebLink

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CLEARWATER • R O P En in veranrnlal Snwces accordance with the procedures detailed in the approved workplan Wells MW-9 through MW-12 were constructed using two-mch diameter schedule 40 PVC well casing materials The wells were completed at 65 feet bgs and screened from the completed depth to 40 feet bgs to allow for water table fluctuation The well construction logs are presented with the boring logs in Appendix B Soil boring, well installation, and well development protocols are presented in Appendix A Well Development, Surveying and Groundwater Sampling The top of PVC well casing for each new well was tied into the existing well survey datum on June 7 and June 8, 2001 The wells were developed until parameters had stabilized and the wells recharged to 85% Well development data sheets are presented in Appendix C Groundwater samples were collected from the new well and each existing monitoring well on June 7 and June 8, 2001 Groundwater sampling was conducted in accordance with the attached protocols (Appendix A) The samples were analyzed for concentrations of TPH-G by EPA Method 8015 and for BTEX and MTBE using EPA Method 8020 The water samples were analyzed by Entech Analytical, a DOHS certified ELAP laboratory located in Sunnyvale, CA The new wells were surveyed into the existing wells on June 8, 2001 to incorporate them into the groundwater monitoring program and to establish accurate and current groundwater elevation and flow direction data Results of the Site Investigation The results of the investigative tasks described in the preceding section of this letter report are discussed as follows Soil Sampling - Chemical Testing Results As mentioned above, soil samples were selected for laboratory analysis based on field screening and significant changes in lithology and analyzed for TPH-G, BTEX and MTBE by EPA Method 8260 The samples selected for laboratory analysis are indicated on Table 1 The samples collected from all of the borings indicated soils free of detectable levels of hydrocarbons or only very low levels The maximum concentration of TPH-G detected in any soil sample was measured at 1,100 mg/kg in MW-10 at 40 feet bgs Concentrations of TPH-G did not exceed 20 mg/kg in samples collected from MW-9 or MW-11 Benzene was measured at a maximum concentration of 15 mg/kg in MW-12 at 60 feet bgs Concentrations Page 5