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2373 Mariposa Road August 16, 1999 <br /> Pro ect 9688 Page 8 <br /> feet and ND at 31 feet TPH-G and TEPH showed a similar distribution with <br /> maximum levels at 11 feet (26 ppm of TPH-G and 210 of TEPH) <br /> BTEX levels corresponded to the TPH-G and TPH-D levels except for the <br /> sample from 66 feet Although there was no detectable TPH-G, TPH-D or <br /> TEPH, there was detectable BTEX in the 66 foot sample, at low levels <br /> ' The maximum contaminant levels roughly correspond to the elevations of <br /> the bottom of the removed USTs <br /> There is at least 35 feet of uncontaminated soil above the groundwater which <br /> was first encountered in the boring at 68 feet <br /> The TPH-D levels detected in the boring generally correspond to those found <br /> in boring F5 by William j Hunter in 1994 <br /> Groundwater Conditions <br /> The first groundwater sample was taken from the site There was no <br /> detectable TPH-G, TEPH, Toluene, MTBE or Lead in the sample TPH-D was <br /> detected at 0 5 ppm Benzene, Ethylbenzene and Xylenes were detected at 1, 1 <br /> and 2 ppb respectively <br /> Possible Sources <br /> The tanks which were removed from the site in 1987 were stated to have <br /> contained gasoline, but there has been anecdotal evidence that there may <br /> have been diesel stored in them at one time The tanks have been removed <br /> and the backfill soil around the tank area appears to only have minor <br /> contamination There is significant soil contamination at the 11 foot level but <br /> it decreases to non-detect between 25 and 31 feet It is likely that the <br /> contamination encountered may be due to the tanks which were removed <br /> However, the proximity of USTs, fuel pumps and surface spills on the <br /> adjacent property may be contributory to some of the soil contamination <br /> Because of the presence of about 30 feet of uncontaminated soil above the <br /> groundwater, the source of the minor groundwater contamination could be <br /> related to an off-site source, although there is no definitive proof of such <br /> RECOMMENDATIONS <br /> Because of the limited vertical extent of the soil contamination, and the <br /> minor amount of groundwater contamination detected, it is our opinion that <br /> 1 the site be closed with no further remediation or monitoring work <br /> WILLIAM DUBOVSKY ENVIRONMENTAL <br />