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16 October 2013 AGE Project No. 99-0682 Page 4 of 5 • The highest concentration of dissolved hydrocarbons continues to occur in the area of the former USTs. TPH-g, TPH-d, BTEX compounds and 1,2-DCA were reported at significant concentrations in the water sample collected from monitoring wells MW-1A (screened from 20-40 feet bsg) and MW-8 (screened from 59-69 feet bsg). Additionally, significant concentrations of dissolved hydrocarbons have been reported at well MW-11, northeast of the former UST area, indicating a historical groundwater flow direction. • Historically, contaminants have generally increased in well MW-8, located in the source area, and contaminants have decreased in well MW-7 since the initial monitoring of the wells in April 2007. During the September 2013 monitoring event, concentrations of contaminants in well MW-1A remained stable compared to the March 2013 event but have decreased significantly compared to the April 2012 sampling event; concentrations began to decrease in well MW-1A during the chemical oxidation pilot test performed in June and July 2012 and have not rebounded since the pilot test. Contaminant concentrations in MW-8 decreased following the start of the pilot test in June 2012 but had rebounded to historical concentrations in July 2012 and remained at historical concentrations during the previous event in March 2013 and the current September 2013 event. Concentrations of contaminants remained generally stable in wells MW-6 and MW-7 compared to concentrations detected in April, June and July 2012 and the most recent sampling event in September 2013. Concentrations of contaminants in well MW-9 remained non-detect during the September 2013 event compared to the March 2013 event. Overall, natural attenuation does not appear to be producing a declining trend; however, performance of the pilot test in June and July 2012 appears to have produced a declining trend in well MW-1A and in well MW-11. Graphs depicting trends in contaminant concentrations in wells MW-1A, MW-6, MW-7 and MW-8 are included in Appendix D! • Currently, the lateral extent of petroleum hydrocarbon-impacted groundwater in the upper water bearing units (HU1) appears to be defined to the southeast (MW-4) of the former UST area, north (MW-3 and MW-5), west (MW-2), east of well MW-6 and south of the site by soil boring samples (Appendix A). • The lateral extent of hydrocarbon-impacted groundwater within the 60 to 75 feet bsg QQ�- water bearing zone (HU2-3) is defined to the west-northwest by well MW-9, to the �rcv a� south by boring CPT-5, to the east or southeast with samples from boring B-5, and to the northwest by boring CPT-6. The lateralextent__of hydrocarbon-impar.___ o�,• tgroundwater is undefined to the north and northeast of the site, as illustrated in ,�.�'e W 1�,t Figure 6. V0 W Cr Historical) concentrations of contaminants have generally declined vertical) in the Y, g Y Y source area (MW-1A and MW-8). However, following the performance of the Advanced GeoEnvironmental,Inc.