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Ms. Kasey Foley Oroject E11-01.03 <br /> April 18, 1991 <br /> Page 2 <br /> EMCON has made the following observations and conclusions regarding <br /> the piping and sump. <br /> First, although 4 of the 18 soil samples analyzed contained detectable <br /> no. 6 fuel oil concentrations (calculated as diesel; detected concentrations <br /> ranged from 15 to 730 milligrams per kilogram [mg/kg]), none of the sam- <br /> ples contained detectable concentrations of aromatic volatile organic com- <br /> pounds (benzene, toluene, ethylbenzene, or xylenes). <br /> Second, the threat of impacting ground water due to vertical migration of <br /> the remaining no. 6 fuel oil appears minimal. This conclusion is drawn <br /> based on the following three reasons: <br /> 1 . The area with the highest no. 6 fuel oil concentrations <br /> (courtyard sump area) would be resurfaced after in-place <br /> closure to further reduce rainwater infiltration and vertical <br /> migration. <br /> 2. No. 6 fuel oil migrates relatively slowly compared to other <br /> petroleum hydrocarbons. This is partially due to its rela- <br /> tively low solubility in water. Maximum oil solubilities in <br /> water are in the range of hundreds of milligrams per kilo- <br /> gram in comparison to benzene which has a solubility of <br /> 1,780 mg/kg at 25 degrees Celsius (Patterson, James <br /> William, 1985. 65uustriai vtia5iewaterreau7ieni Technol- <br /> ogy. 2nd edition. Stoneham: Butterworth Publishers). <br /> 3. A portion of the indigenous microorganisms have likely <br /> acclimated to no. 6 fuel oil as a carbon source and are <br /> degrading the material. Although a specific scholastic or <br /> governmental research reference is not provided to sup- <br /> port this statement, the growing use of indigenous mi- <br /> croorganisms for bioremediation should cause one to ac- <br /> cept this acclimation as a likely event. <br /> In summation, it appears reasonable to conclude that the combined infil- <br /> tration reduction, attenuation, and biological degradation will protect the <br /> underlying ground water from impact due to remaining no. 6 fuel oil in the <br /> soil. <br /> Lastly, EMCON observed the severe access restrictions which disallow <br /> the use of conventional excavation equipment to access the courtyard <br /> sumps (unless they are lifted over the buildings using a crane or freight <br /> helicopter). As an alternative, the sumps could feasibly be removed using <br /> hand-operated equipment such as jackhammers, shovels, etc. The com- <br /> plication arises out of the need to install shoring for the excavation. This <br /> adm\ad154 <br />