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• <br /> 0 Mr. Ambross DeGross <br /> Page 2 <br /> October 2, 1989 <br /> CONCLUSIONS: <br /> 1. More information must be provided regarding the source or sources of <br /> release. Because the regular gasoline supply line failed tightness <br /> tests on four occasions before finally testing tight and because free <br /> product levels increased substantially between July 1 and August 2, 1988. <br /> This is not indicative of a 26 yearerelease. <br /> warrantAlso, <br /> further <br /> discrepancies in the regular supply linetests <br /> investigation of the supply lines. <br /> 2. The area of influence of the proposed free product recovery system <br /> appears to be adequate for the amount of free product indicated in the <br /> report. However, there has been no data reported to support the <br /> conclusion that free product is limited to 250 square feet. <br /> 3. The proposed soil venting system appears to be adequate for the <br /> remediation of soil contamination at the site. However, several <br /> additional design characteristics that are outlined in the <br /> Recommendation Section must be incorporated. <br /> 4. A determination for the need <br /> faftermore complete groundwater dissolved <br /> petroleum <br /> hydqualityrocarbon <br /> recovery system should be made <br /> • data is available. The proposed MW-4 will be needed to generate this data. <br /> 5. The proposed location for MW-4 is not in an optimal position to be used <br /> as a downgradient well. <br /> The MPCA staff hereby approves the Corrective Action Design with the following <br /> modifications: <br /> 1. More information must be provided regarding the source or sources of <br /> release. Because the regular gasoline supply linebecause <br /> tests on four occasions before finally testing tight and frce <br /> product levels increased substantially between July 1 and A>>gust 2, 1988, <br /> it is unclear whether there has been ur continues to be a release other <br /> than the 3,000 gallon release in 1963. <br /> 2. The proposed soil vent system shall include the following modifications <br /> and qualificati---. <br /> A. Air flow measurements should be taken at each individual Soil Vapor <br /> Vent (SVV). <br /> B. Each SVV should have an individual valve to control air flow. <br /> C. SW emissions should be analyzed for BETX as well as total <br /> hydrocarbons. <br /> • D. A water vapor trap should be installed in front of the blower to <br /> alleviate condensation problems during winter operation. <br />