Unsaturated seepage analysis for an ordinary solid waste sanitary landfill in Costa Rica

Sanitary Landfills in tropical areas are subjected to specific conditions such as high temperatures, intense precipitation, and highly organic solid waste with high biodegradation rates. Unsaturated seepage inside the cells of an Ordinary Solid Waste (OSW) Sanitary Landfill in Costa Rica, Central America was studied. It is essential to better understand the seepage behavior for this type of disposal infrastructure due to its physical and hydraulic properties high variation and degradation of the deposited materials, which are complex and exhibit high uncertainty. It is imperative that leachate movement inside the cells of the landfill is accurately estimated to design more efficient systems and optimize the sanitary landfill operation. Field exploration was performed to extract samples from the field representing different OSW ages. Then, a series of laboratory testing was performed to obtain the physical, hydraulic properties, and biodegradation behavior of the OSW and cover soil such as specific gravity of the solids, grain size distribution, Soil-water characteristic curve, K-curve, and Atterberg limits. Additionally, climatic conditions affecting the degree of saturation were assessed by performing a water balance. This information was utilized to estimate flow rates for different scenarios using a HELP model, an empirical model, and two different models using the SlideTM software from RocscienceTM and later on compare them to actual field data available. The model that better predicted the actual flow rate was the HELP model.