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F t� <br /> Mr Harlan Knoll <br /> April 24, 2000 <br /> Page 2 <br /> In August 1990, WaterWork Corp drilled four soil borings (SB-1, SB-2, SB-3 and SB-4) and <br /> installed one groundwater monitoring well (MW-1) The locations of these four borings and <br /> one well are shown on the attached Figure 1 Results of the soil and groundwater sampling <br /> indicated that groundwater had been impacted by gasoline hydrocarbons but that the majority <br /> of the hydrocarbon mass was concentrated in soil between 10 and 20 feet below ground <br /> surface (bgs) The soil sample results are summarized in the attached Table 1 <br /> Between May 1992 and May 1994, Resna installed four additional groundwater monitoring <br /> wells (MW-2, MW-3, MW-4, and MW-5) These well locations are also shown on the <br /> attached Figure 1 <br /> On June 29, 1995, Groundwater Technology, Inc (GTI) published their Environmental <br /> Assessment Report documenting the installation of two vapor extraction well nests (VW-I <br /> and VW-2) and two single vapor extraction wells (VW-3 and VW-4), and the pilot testing <br /> and modeling of soil vapor extraction Based on their findings, GTI recommended that the <br /> site be remediated by soil vapor extraction plus air sparging from MW-1 <br /> By January 1996, the groundwater table had risen above the top of the screen interval in all <br /> • five groundwater monitoring wells, and had entered the screen interval of the two deeper soil <br /> vapor extraction wells (VW-1D and VW-2D) Coincidentally, from July 1995 to April 1996, <br /> groundwater samples collected on four quarterly occasions from the five monitoring wells <br /> did not contain detectable concentrations of TPH-as-gasoline <br /> In August 1996, sampling of the five original monitoring wells was discontinued and the <br /> sampling of the two deeper vapor extraction wells (VW-1D and VW-2D) was initiated <br /> Groundwater samples collected from VW-ID and VW-21) contained detectable <br /> concentrations of TPH-as-gasoline, benzene, and methyl tertiary butyl ether(MTBE) <br /> On April 28, 1998, Ramage Environmental installed two additional groundwater monitoring <br /> wells (MW-6 and MW-7) to re-establish d groundwater table monitoring and sampling <br /> capability at the site Since the installation of these new wells, groundwater has been <br /> monitored and sampled on a quarterly basis from MW-6, MW-7, VW-1D and VW-21) <br /> On June 2, 1999, ENSR Consultants started up a soil vapor extraction system at the site <br /> Initially, ENSR extracted from VW-ID, VW-1S, VW-2S, VW-3, and VW-4 After several <br /> months of operation, air sparging was initiated in MW-1 According to ENSR, over 7,000 <br /> pounds of gasoline hydrocarbons have been removed from the subsurface, to date Currently, <br /> the system remains operational, however, mass removal rates have declined significantly <br /> i <br />