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I05 May 1997 AGE-NC Protect No 95-0173 ' Page 10 of 29 ' during performance of IAS can cause the dissolved hydrocarbon plume to migrate beyond its original horizontal extent Depth to ground water measurements are summarized in Table 6 4 2 5 Laboratory Results of Ground Water Samples p ka-V ' A laboratory analysis of a ground water sample collected from AW-1 reported dissolved iron and manganese at concentrations of 0 33 parts per million (ppm, reported as milligrams per liter) and 4 4 ppm,respectively Analytical results of the ground water sample are summarized in Table No 5 The ' laboratory report (AAL Batch Number 97-1111-010) and chain-of-custody form is presented in Appendix C Based on the guide How to Evaluate Alternative Cleanup Technologies For UST Sites (October 1994) published by the United States Environmental Protection Agency (EPA) Office of USTs, the presence of dissolved iron (Fe") in ground water can reduce the permeability of the saturated zone soils during air sparging operations The guide further states in Exhibit VII-12 Dissolved Iron And Aar Sparging Effectiveness that concentrations of dissolved Fe" less than 10 mg/1 are acceptable concentrations for air sparging, concentrations between 10 mg/l. and 20 mg/1 would require periodic testing or periodic replacement, if concentrations were greater than 20 mg/l, then air sparging was not recommended Results of the laboratory analysis indicated that dissolved iron and manganese conditions at the site are favorable for air sparging activity 5.0. ASSESSMENT OF HYDROCARBON-IMPACTED SOIL AND GROUND WATER Between July 1996 and January 1998, eight soil borings (B1 through B8), nine ground water monitoring wells(MW-1 through MW-9),two SVE wells(VW-1 and VW-2),two IAS NAells (AW-1 and AW-2) were installed and six ground water monitoring/sampling events performed at the site to investigate the extent of hydrocarbon-impacted soil and ground water in the vicinity of the former USTs The greatest concentrations of petroleum hydrocarbon-impacted soil has been encountered at SVE well VW-2, IAS well AW-1 and soil boring B2 The greatest concentrations of dissolved petroleum hydrocarbon impacted ground water has been encountered from wells VW-1 and MW-3 Analytical results of soil and ground water samples are summarized in Tables No 1, 2 and 3 T+trnt—v S onrl F. rio ,rT nan Aral htinnlnmr Wnrl gelet-ted cnil ca�mnlP lnratiom beneath the Site in cro4S 1 .5LA a ✓ l Al V LJL✓p}VL b4}144 Ka a.KaL.i}L.rb' J+ '--- `. sectional view Figures 7 and 8 depict the estimated extent of contoured TPH-g concentrations beneath the site in cross sectional view Figure 9 depicts the estimated extent of contoured TPH-g ' concentrations in plan view When the data collected at the site is plotted in both plan view and cross cpptii i%"-al-L7is-;lr tbp nnnarFnt xinhimp of mi-trnh-iim ,mnartPrl snil beneath the site is anDroximately ' 14,748 cubic yard (Appendix G) .` A mass-volume calculation using the data collected during investigation of the former UST area, Advanced CcoEmiron mental,Inc