ARCHIVED REPORTS_XR0003239 - Laserfiche WebLink

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1 r 4 0 CONCLUSIONS AND RECOMMENDATIONS 1 The results of this investigation indicate that gasoline compounds have impacted soil and ' groundwater beneath the former USTs The nature of the gasoline in soil and groundwater appears to be relatively free of oxygenate compounds, except for 8 4 micrograms per liter (µg11) of DIPS in groundwater at MW-3 In soil, gasoline compounds were detected from 15 feet to the total drilling depth of 35 feet to the ' two borings (MW-1 and MW-2) adjacent to the former USTs Vertically, the extent of impacted soil is undefined Based on soil sample analytical results from Geoprobe borings G-1 and G-2, ' the lateral extent of impacted soil above 25 feet bgs appears to be limited to the vicinity of the former UST system The extent of impacted soil below 25 feet bgs appears to be more extensive and undefined, probably due to migration in groundwater In groundwater, significant concentrations of TPH-as-gasoline, BTEX compounds and 1,2-DCA were detected in the three monitoring wells in closest proximity to the former UST system The rplume impacted groundwater appears to be defined at MW-4 to the north-northeast of the former USTs Since the groundwater flow direction was calculated to be toward the east-southeast instead of north-northeast as expected, the downgradient extent of impacted groundwater is undefined Based on these conclusions, Ramage Environmental recommends that the tvee monitoring wells be monitored and sampled on a quarterly basis to confirm gasoline concentrations and ' groundwater flow and gradient characteristics The first quarterly groundwater monitoring event is scheduled for October 2002 If the flow direction remains toward the east-southeast, it may be necessary to install additional monitoring well(s) to define the downgradient extent of impacted groundwater r r r � 1 13 r i