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the site. Additionally, potential impacts from previous service <br /> station operation at the northeast and northwest corners of Wilson <br /> Way and Market Street are unknown. <br /> The source of several chlorinated hydrocarbon compounds detected in <br /> wells MW-4 , MW-6, MW-7 and possibly present in MW-8 is unknown. <br /> These compounds are associated with recent (less than 20 years) <br /> gasoline formulations, degreasing and dry cleaning operations, and <br /> insecticide applications. It appears likely that the source of <br /> these compounds is unrelated to the service station operation at <br /> the subject property. <br /> 9.0 RECONNENDATIONS <br /> Based upon this and previous environmental investigations MCA <br /> recommends the following; <br /> Drilling of one additional confirmatory soil borings southwest of / <br /> the former UST excavation located near the central portion of the V <br /> site to verify that soil impacted by gasoline hydrocarbons has been <br /> adequately removed from the former UST excavation (Figure 3) . <br /> 6 <br /> ` Implementing a quarterly groundwater monitoring program at the site <br /> to verify concentrations of hydrocarbons previously detected in <br /> groundwater at the site and downgradient to the northeast. <br /> Analyses should include TPHg using EPA Method 8015, and BTEX and <br /> chlorinated hydrocarbons by EPA method 8240. <br /> Reviewing data from environmental investigations that have been <br /> conducted for the service station upgradient of the site to the <br /> west to evaluate if a release from that site or others is, or <br /> potentially could, migrate towards the subject site. <br /> Installing additional off-site groundwater monitoring wells <br /> northeast of offsite well MW-8 and due east of onsite well MW-3 in <br /> order to delineate the lateral extent of gasoline hydrocarbons in <br /> groundwater downgradient of the site (Figure 3) . <br /> Installing one additional offsite groundwater monitoring well due <br />' north of onsite well MW-1, across Market street, in order to <br /> delineate the lateral extent of gasoline hydrocarbons in <br /> groundwater crossgradient of the site (Figure 3) . <br /> t i <br /> Preparing disposal plan for soil and groundwater generated during <br /> the environmental investigations conducted at the site after <br /> t characterization of the site has been completed. <br /> E <br /> f Conducting an interim remediation feasibility study to evaluate <br /> remedial options and associated costs for the interim remediation <br /> . of soil and groundwater impacted by gasoline hydrocarbons. <br /> 8 <br /> I <br />