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! <br /> ! � <br /> Mr. Don Morrison <br /> Page Z <br /> June 29, 1993 <br /> 3. Five soil borings were conducted at the Site to determine the extent and <br /> magnitude of soil contamination. Soil samples were monitored for the <br /> presence of organic vapors with a photoionization detector. With the <br /> exception of samples collected between the depth of 1 to 3 feet below land <br /> surface, no organic vapor were detected which exceeded the background <br /> organic vapor concentrations. Three soil samples were collected for <br /> chemical analysis. Only low levels of petroleum constituents were <br /> detected. Water samples were collected from three of the borings as well, <br /> but the petroleum parameters analyzed for were not detected. <br /> 4. At the conclusion of the soil borings, additional soil excavation was <br /> conducted to remove some of the remaining contaminated soil. This <br /> additional excavation activity occurred on July 16, 1992. An additional 30 <br /> cubic yards of contaminated soil was removed and was later thermally <br /> treated along with the original 10 cubic yards of soil removed during March <br /> 1992. The highest soil sample exhibited a soil vapor jar-headspace <br /> concentration of 15 ppm. Soil samples collected for chemical analysis from <br /> the excavation were non-detect for the analyzed petroleum parameters. <br /> Water entered the excavation and two samples were collected for chemical <br /> analysis. Benzene, total benzene, ethyl benzene, xylene, toluene, and <br /> total petroleum hydrocarbons as gasoline were detected at concentrations of <br /> 160 ug/L, 404 ug/L, and 8.8 mg/L, respectively. Some contaminated soil <br /> remains beneath the concrete apron of the nearby garage. <br /> 5. A vapor risk assessment was conducted in the basement of the nearby utility <br /> room. No organic vapors were detected. Two water wells are located 25 and <br /> 125 feet from the former underground storage tank (UST). There are no logs <br /> for these wells, but the wells are reported to have been conducted to the <br /> depths of 250 and 300 feet below �land surface. The closer well was <br /> installed in 1969. A water sample was collected from the closer well, but <br /> none of the analyzed petroleum parameters were detected. <br /> 6. Based upon the observations and the results of the investigation, <br /> contaminated soil and ground water are limited to within 15 feet of the <br /> former UST. The majority of contaminated soil has been removed from the <br /> Site. The dissolved benzene concentrations detected in excavation water is <br /> below the ground water cleanup goal established for many sites (100 times <br /> the Recommended Allowable Limit). <br /> Based on the data provided by you in the report referenced above, we believe <br /> that these actions have adequately addressed the petroleum tank release. <br /> Therefore, MPCA staff does not intend to require any more investigation or <br /> cleanup work in response to this release. However, the MPCA reserves the right <br /> to reopen this file and require additional work if in the future more work is <br /> determined to be necessary. If you, or other parties, come upon any evidence <br /> of contamination other than what was previously reported, you are required by <br /> Minnesota law to notify the MPCA immediately. <br />