ARCHIVED REPORTS XR0000090 - Laserfiche WebLink

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28 5 CONCLUSIONS Conclusions reached on the basis of this and previous investigations includes the ' following 1 Shallow groundwater at the facility, which is under confined or semi-confined conditions, flows northeasterly at approximately 0 23 ft/d The groundwater surface gradient is 2 5 x 10-3 ft/ft In March 1994, this shallow groundwater was ' approximately 55 feet BGS, but has been observed closer to the surface prior to the recent drought conditions 2 Shallow groundwater at this facility is impacted with gasoline-type petroleum hydrocarbons The highest TVH-G and BTEX concentrations were measured in groundwater samples collected from Monitoring Well MW-1 The cross-gradient ' limits of gasoline impact, as shown on figures 9 and 10, are situated near wells MW-4 and MW-10 to the northwest, and wells MW-5 and MW-12 to the southeast The upgradient and downgradient extent of impact is defined by wells MW-9 and ' MW-3, respectively 3 Chemical analysis of soil samples collected during this investigation inaicates that the extent of any remaining residual gasoline-impacted soil is limited Hydrocarbons may be expected in soils located near the vadose zone/groundwater table contact, within the area of gasoline-impacted groundwater The benzene concentration ' measured in the 60-foot-depth soil sample from Borehole MW-13, collected lust below the groundwater table, is a result of contamination from gasoline-impacted groundwater at that location ' 4 The five new wells installed as part of this project are suitably situated at locations to serve as components of a groundwater remediation system The new wells are ' screened sufficiently deep enough, below the groundwater table, to accommodate drawdown should pumping be used as a cleanup method These wells could also ' serve as conduits to introduce enhancing nutrients for the naturally occurring microorganisms, which have been shown to grow on the hydrocarbon constituents, should biological treatment be utilized I Future work at the Rainbo/Earth Grains facility will include continued monitoring, ' and a review of suitable corrective action alternatives to remediate the gasoline-impacted groundwater Following that review, Burlington will prepare a corrective action plan, describing a proposed cleanup method, for submittal to the PHS/EHD 04/94/121382/125997/STOCKREP REP/1 I