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EXECUTIVE SUMMARY The objectives of the project were to further define the extent of impacted soil and groundwater beneath the site and adjacent areas To achieve these objectives, soil and groundwater samples were collected for laboratory analysis from seven direct-push soil borings (G-6 through ' G-12) Soil boring G-6 was advanced to the second groundwater-bearing interval beneath the former underground storage tanks (UST) The other six borings were drilled to the first groundwater (i e , groundwater table) In addition, groundwater in the three existing on-site monitoring wells was monitored, sampled and laboratory-analyzed Soils observed during drilling consisted of interbedded sequences of clay, silt and fine sand During a previous investigation, a well-graded sandy gravel soil was observed at a depth of approximately 43 feet On December 19, 2002, the static depth to the groundwater table, as measured in the three monitoring wells, ranged from 20 90 feet bgs in MW-2 to 21 12 feet bgs in MW-3 The resulting groundwater surface appears as a regular plane dipping to the northwest ' at a gradient of approximately 0 0033 foot/foot In soil, only two of the 12 samples analyzed during the investigation contained detectable concentrations of only Total Petroleum Hydrocarbons (TPH)-as-diesel, at a maximum concentration of 2 4 milligrams per kilogram (mg/kg) As such, the extent of impacted soil appears to be mostly defined ' In the second groundwater-bearing interval, the groundwater-grab sample collected at approximately 44 feet below ground surface (bgs) from G-6 contained 260 micrograms per liter (4g11) of TPH-as-diesel, 0 7 µg/I of benzene, 0 6 µg11 of toluene, 1 1 µg/I of ethylbenzene, and 1 9 µg/l of xylenes As such, the vertical extent of impacted groundwater remains undefined At the groundwater table, four of the six groundwater-grab samples contained detectable concentrations of TPH-as-diesel and/or TPH-as-gasoline Benzene, the five oxygenates and 1,2-dichloroethane (1,2-DCA) were not detected in any of these six groundwater-grab samples The lateral extent of impacted groundwater at the groundwater table appears to be mostly defined for TPH-as-diesel, undefined for TPH-as-gasoline, and fully defined for benzene The groundwater samples collected from all three of the groundwater monitoring wells contained detectable concentrations of petroleum hydrocarbons The highest concentrations were detected in the groundwater sample collected from MW-1 5,100 µg/I of TPH-as-diesel, 6,500 µg11 of TPH-as-gasoline, 28 µg/I of benzene, 1,100 µg/1 of ethylbenzene, and 51 µg/1 of xylenes The five oxygenate compounds and 1,2-DCA were not detected in any of the monitoring well groundwater samples Based on these conclusions, Ramage Environmental recommends that a work plan be prepared to expand the groundwater table monitoring network at the site Additional groundwater table monitoring wells and one deeper monitoring well near the former USTs should be included The three existing monitoring wells will continue to be monitored and sampled on a quarterly basis The next monitoring event is scheduled for March 2003 ' 4 1