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October 25, 1993 <br /> 6.0 DISCUSSION <br /> Field and analytical laboratory test results indicate that diesel soil contamination does <br /> not extend to the points sampled for analysis beneath the western sidewalk near the former <br /> diesel tank area Previous investigations indicated a low concentration at 30 6 ppm TPHd in <br /> the western wall at a depth of 6 ft No soil contamination was detected at 2 ft or at 16 ft The <br /> previous excavation pit was approximately 10 ft long Based on this, contamination from the <br /> diesel tank or pump islands is confined to a maximum of 10-ft long segment of soil along the <br /> western property boundary The contamination does not extend beneath the sidewalk off-site <br /> nor does it extend vertically beyond 16 ft <br /> Previous investigations encountered TPH diesel contamination in groundwater <br /> downgradient from the former waste oil tank One sample(February 1990) contained 350m <br /> TPHd and a second sample (April 1990) contained 59 ppm At the time of our initial site visit <br /> (August 1993), it was noted that the well did not have a watertight utility box to prevent <br /> surface infiltration The interior of the well utility box was coated with an oily substance <br /> presumed to be from surface run- <br /> off This materials may have entered the well in the past The <br /> well utility box and plastic well cap were replaced with a watertight utility box and brass and <br /> aluminum locking well cap The well was redeveloped and sampled Analytical test results <br /> indicate that the groundwater did not contain any detectable petroleum constituents at the time <br /> of sampling <br /> At this time, groundwater does not appear impacted by the former waste oil tank, the <br /> former diesel tanks, nor the former pump islands <br /> 7.0 CONCLUSIONS <br /> Based on the field and analytical data generated during this investigation and the data <br /> collected in previous studies we conclude the following <br /> + f) Possible diesel soil contamination along the western boundary appears to be limned to <br /> the upper 6-ft of soil in a section of the wall that is less than 10-ft long The <br /> contamination does not appear to spread laterally beneath the sidewalk nor vertically to <br /> depth likely to impact groundwater <br /> 2) Groundwater does not appear to be impacted by waste oil or diesel contamination <br /> P1 <br /> ROGER <br /> 323-8011tpr - - MDT <br /> ASSOCIATES <br />