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Geological Technics lac. Page 4 . <br /> I Groundwater Monitoring Report <br /> Project No.750.2 <br /> April 12,2004 <br /> Thegroundwater samples were analyzed for: <br /> • Benzene, Toluene, Ethyl Benzene, and Xylene (BTEX)by EPA method 8020/8015 <br /> 4 <br /> L • Total Petroleum Hydrocarbons as Gasoline (TPH-G) by EPA method 8020/8015(M) <br /> • Fuel oxygenated compounds (MTBE, DIPS,.ETBE, TAME & TBA) by EPA method <br /> 8260 <br /> I <br /> The detection limits for the above analyses are listed in Table.3 of Appendix A and the lab <br /> r data are presented in Appendix B. <br /> L <br /> As required under AB2886, the laboratory data was submitted electronically to GeoTracker <br /> rr on January 23, 2004. The confirmation number is 4258009016. <br /> L <br /> 3 <br /> 2.0 INTERIM SITE WORK <br /> I ' <br /> On September 5, 2003, GTI and Gregg Drillinginstalled 2 soil borings at the Former Arco <br /> Csite. The soil cuttings were placed into six 55-gallon DOT approved containers, properly <br /> labeled and temporarily stored on-site. <br /> On October 28, 2003,GTI and Clean Harbors Environmental Services Inc personnel arrived <br /> on site and removed the soil drums. The soil was taken to Clean Harbors Aragonite LLC, <br />{ 11800 North Aptus Road, Aragonite, Utah for disposal. The work was under State Manifest <br /> i L Document Number 22745352 and a copy of the manifest is attached as Appendix D. <br /> L3.0 FINDINGS & RECOMMENDATIONS <br /> is <br /> Findings <br /> The results of the groundwater sample analyses show the following: <br /> • Five of the six monitoring wells were non-detect for all analyzed compounds. <br /> f • MW-2 showed the presence of 0.3 µg/L of total xylenes and was non-detect for all other <br /> analyzed constituents <br /> • MW-1 was completely non-detect for the fourth consecutive monitoring event.: Chart I <br /> illustrates the gradual decrease in groundwater elevation over time and the exponential <br /> decrease in TPH-G concentrations in MW-i:: <br /> • Vertical groundwater gradient was calculated for the event of December 9, 2003, and <br /> was found to be insignificant. The magnitude of the vertical gradient has been getting <br /> progressively smaller during the last several monitoring events. <br /> • Oxidation-Reduction Potential measurements (Table 4) are positive for all the wells. <br /> This suggests that the volume of contaminants leaching into groundwater has been <br /> � gg g <br /> stopped and that biodegradation of the contaminants is at a rate sufficient_to mitigate the <br />