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' 4�l rh 5 EXECUTIVE SUMMARY The project objectives were to further define the extent of impacted soil and groundwater, and establish a groundwater monitoring capability at the site To achieve these objectives, three on- site groundwater monitoring wells (MW-1, MW-2 and MW-3) were installed Soils to 65 feet mostly consisted of massive clay and silt soils, and relatively thin and discontinuous sand intervals less than five feet thick During drilling, saturated soil was first observed at approximately 56 to 57 feet below ground surface (bgs), and the static depth to the groundwater table, ranged from 46 28 to 46 72 feet bgs As such, groundwater appears to be present under semi-confined conditions The groundwater surface appears as a regular plane ' dipping to the north at a gradient of approximately 0 00157 foot/foot The analytical results suggest that the impacts to soil and groundwater beneath the site appear to be concentrated beneath the west side of the former fuel farm, and attenuate to the north and south The petroleum hydrocarbons in soil and groundwater appear to consist mostly of gasoline and BTEX compounds Concentrations of jet fuel hydrocarbons are generally lower, and concentrations of oxygenate compounds are absent in soil and relatively low in 1 groundwater MTBE was not detected in soil or groundwater In soil, only 3 of the 15 samples analyzed contained detectable concentrations of petroleum hydrocarbons The highest concentrations of petroleum hydrocarbons were observed between 45 and 55 feet within the capillary fringe and zone of groundwater fluctuation Laterally, the extent of impacted soil appears to be limited to beneath the former fuel farm Vertically, the extent of impacted soil appears to be defined The groundwater samples collected from all three monitoring wells contained detectable concentrations of petroleum hydrocarbons The highest concentrations were detected at MW-1 ' 840 micrograms per Inter (µgll) of Total Petroleum Hydrocarbons (TPH)-as-jet fuel, 7,700 µg/1 of TPH-as-gasoline, 1,300 pg/I of benzene, 460 µg/I of toluene, 490 µg11 of ethylbenzene, and 670 µg/1 of xylenes The lateral extent of impacted groundwater is not defined Based on these conclusions, Ramage Environmental recommends that the three monitoring wells be monitored and sampled on a quarterly basis to confirm petroleum hydrocarbon concentrations and groundwater flow and gradient characteristics The first quarterly groundwater monitoring event is scheduled for February 2003 ., 4