An evaluation of the performance of prototype instrumented soil covers at the Regina municipal landfill

The City of Regina Fleet Street landfill, north-east of Regina, Saskatchewan, is approaching its maximum capacity after a 47-year operating life and plans are now being made for its closure. As part of closure planning work, four test plots encompassing two different cover designs (a capillary break cover and a store-and-release cover) were constructed on the landfill in the summer of 2004. One cover of each design was constructed on both the north facing and the south facing slopes. The overall objective of this thesis is to evaluate the preliminary performance of the four test plots on the City of Regina landfill with regards to net percolation, gas flux, water balance and vegetation. To meet this overall objective three specific objectives were developed as follows: •Evaluate the performance and integrity of the monitoring scheme. •Characterize the properties of the soil covers on the four test plots. •Develop a preliminary water balance using the monitoring field data. A field instrumentation program was carried out which included detailed monitoring of gas composition, volumetric water content, matric suction and temperature within the cover profile as well as measurements of interflow, runoff and site-specific meteorology. Generally, the instrumentation performed well with the exception of the tipping bucket which did not accurately measure precipitation. Evaluation of the covers revealed that the slope aspect exerts greater influence over the water balance than that exerted by cover design itself. The south test plots were drier than the north, experienced more net radiation, and generally had more abundant vegetation. A water balance was conducted for each test plot at the upper, mid and lower slope. It is clear that a capillary break was not maintained on the north slope for the entire monitoring period and the percolation from the store-and-release cover was less than that of the capillary break cover. The south test plots were very dry and net percolation was nearly the same for both test plots. Therefore, it is believed that the store-and-release covers are performing better than the capillary break covers