Evaluation of soil top-cover systems to minimize infiltration into a sanitary landfill: A case study

The design of a top-cover system is a very important aspect of the closure of sanitary landfills. Soil material properties, sequencing, and vegetation are critical to top-cover design. To date, very few field investigations have been undertaken to determine the effectiveness of these designs. Results from a field investigation of top-covers proposed for an active landfill site in south Florida are reported here. Measurements were made of each component of the water balance equation: S = P +I] – ET +R +Q] whereS, P, I, ET, R, andQ represent water storage, rainfall, irrigation, evapotranspiration, surface runoff, and deep seepage, respectively. Deep seepage, determined using soil water tensiometers, is the amount of water infiltrating the landfill top-cover and is therefore the upper limit of potential leachate generation.Results indicate that the locally available rock tailings (carbonate silt) is an effective topliner component of the top-cover system. The results of the field investigation also showed that the EPA water balance model used to estimate infiltration during landfill design was greater than the actual field measurements.