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2.9 Bi-Weekly— Eree-Floating Hydrocarbon Measurement and Removal <br /> Since the discovery of the free-floating hydrocarbons in monitoring well <br /> MW-5, ASE has measured the thickness of the free-floating hydrocarbons <br /> in monitoring wells MW-5 and MW-6 and then removed all accumulated <br /> free-floating hydrocarbons in the well with a bailer every two weeks prior <br /> to January 2000 and monthly after January 2000 <br /> 2. 1 0 >7 c mher 1999 ,Area Nell Survey <br /> In December 1999, ASE conducted a more detailed area well survey f or <br /> the site than the one previously conducted This survey identified 5 7 <br /> wells within a 2,000-foot radius of the site Of these 57 wells, 39 are <br /> domestic, 3 are irrigation only, and 15 are of unknown usage <br /> 2. 11 March 2000 Monitoring Well Installation <br /> In March 2000, ASE installed groundwater monitoring wells MW-11 <br /> through MW-15 and piezometers P-1 through P-5 (Figure 3) Monitoring <br /> wells MW-13 through MW-15 and piezometers P-1 through P-5 are <br /> screened between 9-feet bgs and 19-feet bgs Monitoring wells MW-11 <br /> and MW-12 are screened between 55-feet bgs and 70-feet bgs <br /> Free-floating hydrocarbons were present in monitoring well MW-5, no <br /> free-floating hydrocarbons were present in any of the surrounding <br /> monitoring wells or piezometers High hydrocarbon concentrations were <br /> detected in groundwater samples collected from monitoring well MW-6, <br /> with toluene, ethyl benzene and total xylene concentrations in this well <br /> exceeding DHS MCLS Groundwater samples collected from monitoring <br /> well MW-4 contained 3 8 ppb benzene and 43 ppb MTBE Groundwater <br /> samples collected from monitoring well MW-3 contained 12 ppb MTBE <br /> and 44 ppb tert-butanol (TBA) Groundwater samples collected from <br /> downgradtent monitoring wells MW-13 and MW-14 contained 490 p p b <br /> and 38 ppb MTBE, respectively The groundwater sample collected from <br /> monitoring well MW-13 also contained 100 ppb TBA Groundwater <br /> samples collected from shallow monitoring wells MW-1, MW-2 and MW-15 <br /> did not contain concentrations of any compound above DHS MCLs for <br /> drinking water <br /> None of the wells screened below 19-feet bgs contained any compound at <br /> concentrations exceeding DHS MCLs However, various compounds were <br /> detected in groundwater samples collected from all of these wells at <br /> concentrations below DHS MCLs including MTBE, TBA, PCE and 1,2-DCP In <br /> Frank's One Stop Remedial Action Plan — August 2001 <br /> -5- <br />