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Ms. Amaru January 15, 2014 Table 1 shows historical ground water analytical data for each of these wells. Piezometers were installed by the Navy for water level measurements only,and have never been sampled for chemical analysis. Ground water elevation contour maps showing ground water flow directions for the CA,WA,and WB zones are attached to this workplan as Appendix A(Figures 10 through 15). Surveyed coordinates for each of the wells and piezometers,and original boring and construction logs are attached as Appendix B. Discussion Of the wells shown in the table above,Wells W-39,W-56,W-150,W-240,W-241,and W-249 are associated with Site 7,Site 8,or IAS-10. Site 8 was closed with no further action in 2004;a Closure Report for Site 7 and a Preliminary Endangerment Assessment for IAS-10,both requesting closure,were submitted in June 2004 and April 2005,respectively. As shown in Table 1, these wells have never had any detected VOCs, PCBs,OCPs,or SVOCs since installation,with three exceptions: • A single Methyl tort-butyl ether(MTBE)concentration reported in Well W-240(0.55 pg/L, far below the Environmental Screening Level of 5 pg/L for a drinking water source). No gasoline compounds have ever been reported in ground water from Site 7. • A single concentration of 1,2-Dichloroethene(12 pg/L)was reported in Well W-56 in 1996. 1,2- DCE has not been reported in analytical results from this well before or after this reported occurrence,nor at any other ground water well at IAS-10. • A single TPH(mo)concentration was reported in Well W-56 in 1998. This reported concentration is likely the result of natural peat,prior to TPI-I analysis using silica gel cleanup techniques to isolate naturally occurring non-petroleum hydrocarbons. No TPH compounds were reported in resampling of W-56 in 1999. The remaining wells(W-30,W-152,W-153,W-155,W-177,and W-184)are associated with Northern and Central Landfill sites IAS-11,IAS-13,IAS-15,and Site 38,where trace VOC concentrations(mainly vinyl chloride)were historically reported (Table 1). VOC plumes associated with the landfills to the west of these locations have decreased markedly in areal extent in the years since 2000,and these wells are now either outside the historical plume area or the plumes are now fully attenuated to below reporting limits. Recent sampling(December 2013)indicates no detectable VOCs in any of these wells. Figures 23 through 25(attached)show isoconcentration contours for vinyl chloride in ground water in the Central Landfills area in 2008. Vinyl chloride historically detected in wells W-152,W-153,and W-155(CA zone;Figure 23)has not been reported above detection limits in these wells since 2011,1998,and 2008, respectively. Well W-30(WA zone;Figure 24)has not had detectable vinyl chloride since 2010. Figures 38 through 40(attached)show isoconcentration contours for vinyl chloride in the Northern Landfills in 1999 and 2008,and highlight shrinking of the residual vinyl chloride plume away from wells W-177(CA zone)and W-184(WA zone). Well W-177 has not had detectable vinyl chloride since 1999,W- 184 has not had any chlorinated VOC detection above water quality goals with the exception of a single 1,2-Dichloroethane detection(0.7Jµg/L)reported in 1999(Table 1). Recent monitoring of the attenuating vinyl chloride plumes in the landfills is now focused on wells in the in the core of the historical source areas to the west(Figures 23 through 25,and 38 through 40). The Page 3 of 31