ARCHIVED REPORTS XR0006812 - Laserfiche WebLink

Home Browse Search

F Perimeter and downgradient of the former gasoline/diesel tank pit (TP1) Soil contamination in these areas extends vertically to the shallow water table. Vertical migration of contaminants ' appears to have been fairly rapid with little lateral spreading (Figure 5). 6.2 Groundwater Impact The lateral extent of groundwater contamination has been defined in most sectors of the site. Analysis of groundwater samples collected from the monitoring wells, and soil samples collected from the capillary fringe in the borings and wells, has provided constraints on the limits of ' contamination in the following areas: the product lune area; the waste oil pit area; and the western, southern and eastern sides of the gasoline/diesel tank pit (TPl) These appear to ' comprise three discrete areas of groundwater contamination (Figure 5) The downgradient limit of affected groundwater emanating from the tank pit has not been defined. The validity of utilizing soil samples collected from the capillary fringe as indicators of underlying groundwater contamination is supported by the analytical results of samples collected from the monitoring wells Soil samples collected from monitoring wells MWl and MW2 were found to be significantly impacted, as was groundwater. The soil sample collected from MW3 contained no detectable contaminants and the groundwater in this well was clean. The lateral ' distance of the wells from the source of the leaks (especially MW 1) confirm that the soil contamination detected therein is truly due to capillary phenomena and not simply a result of ' previous vertical transport. The reasonable inference from the data is that, at this site, capillary fringe soils serve as reliable indicators of groundwater impact The lack of appreciable downgradient migration of contaminated groundwater may be due to the ' recent vintage of the leak combined with the low velocity silt/clay aquifer. R-012792 LF 7