The Highway 101 Landfill - what have we learned?
Harding, Jennifer L.
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The Highway 101 Landfill between Upper Sackville and Mount Uniacke, Nova Scotia has been in operation since 1977. Hydrochemical tests were routinely collected on 63 monitoring wells located at various depths in and around the landfill site. This project investigated significant chemical changes in the groundwater since the initiation of the landfill. Ammonia, total dissolved solids, and arsenic were selected as primary indicators of contamination with iron, potassium, and sulphate as secondary indicators. Eleven well sites located strategically down-gradient from the landfill were considered. Comparison occurred between the measurements taken from this subset of wells and the previously determined background levels from in and around the landfill site. Impacted wells were defined as those in which measured parameter concentrations were consistently above the threshold of mean background plus two standard deviations. Four of these well sites showed initial impact in the late 1980's to early 1990's. Impact occurred at all depths measured (surfical, shallow bedrock, and deep bedrock), but in general, the first wells impacted are the surficial wells. In most cases the timing of impact for deep bedrock wells was impossible to determine because of late installation dates. The parameters showing first impacts were ammonia and total dissolved solids. Using the initial impact dates and the distance along groundwater flow lines (a few hundred meters) estimates of minimum contaminant flow velocities of 12.8 m/yr to 21.3 m/yr were calculated. These velocities are important as they can give an estimated on when the leachate plume will reach the Sackville River if no remediation methods are installed. The most suitable methods appear to be hydrodynamic control and inceptor wells or a combination of the two. Keywords: leachate, contaminant plume, monitoring wells, landfill, indicator parameters, hydrogeochemistry, background threshold, impacted wells, remediation Pages: 95 Supervisor: Gunter Muecke