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Working To Restore Nature <br /> f=� <br /> 3.2 Assessment of Groundwater Contamination <br /> Neither TPHd nor BTEX have been detected to date in groundwater samples from wells MW-1, <br /> MW-2, and MW-5. TPHd has been periodically detected in well MW-3 and in well MW-6 on <br /> r one occasion during the fourth quarter of 1993. Groundwater in well MW-4 has not been <br /> sampled because of the presence of free product. <br /> Based upon groundwater monitoring data and analytical results collected to date, it is estimated <br /> 3 that 60 to 70 gallons of free product and 1.5 gallons of dissolved petroleum hydrocarbons exist <br /> .=� in the saturated zone. These estimates are based upon the following assumptions: an aquifer <br /> thickness of 17 feet, an effective soil porosity of 20%, and an average free product thickness <br /> F <br /> of 0.5 feet. The estimated areal extent of contamination in the groundwater is illustrated on <br /> Figure 4. <br /> 4.0 REMEDIATION ALTERNATIVES <br /> An initial screening of various soil and groundwater remediation alternatives was presented in <br /> the Phase II Problem Assessment Report (RESNA, November 1993). Alternatives were either <br /> retained or eliminated based on their applicability to the site. The following sections detail the <br /> relative merit and feasibility of selected remedial alternatives for both soil and groundwater. <br /> Based upon the size of the site, the extent and type of hydrocarbon contamination in soil, <br /> hydrocarbon concentrations, and the type of soil present at the site, the following general <br /> response alternatives for remediation of soil at the site have been considered: <br /> Tr< <br /> N o Alternative 1 - Excavation and Groundwater Extraction <br /> r1 <br /> o Alternative 2 - In-situ Enhanced Bioremediation <br /> 4.1 Description of Alternatives <br /> �1 <br /> 4.1.1 Alternative 1 - Excavation and Groundwater Extraction <br /> This remedial alternative involves the physical removal of contaminated soil (both above and <br /> below the saturated zone) along with extraction of groundwater from the open excavation <br /> F:> and/or groundwater extraction wells. An estimated total volume of 1500-2400 cubic yards <br /> of soil would require removal. Approximately 650-700 cubic yards have been impacted. <br /> C:- W0365%REPORTSICAP0294 TFNL 4 <br />