Trihydro has been the prime consultant assisting the Eden Valley Solid Waste Disposal District (EVSWDD) with various solid waste management projects since 2006. Changes to their solid waste management system have been driven by Wyoming Department of Environmental Quality (WDEQ) concerns with existing groundwater monitoring data and limited remaining permitted disposal capacity at their unlined landfill. Additionally, the results of the integrated solid waste management (ISWM) plan prepared by Trihydro demonstrated that the continued operation of the landfill is not economically feasible.
Initial project activities included a groundwater investigation and expansion of the groundwater monitoring network for the unlined landfill. Once a final decision was made to close the landfill, Trihydro designed, permitted, and constructed a new transfer station, and is assisting the EVSWDD with the operations contract. Most recently, Trihydro designed and permitted a water balance cover system for the 20 acre unlined landfill footprint. The water balance cover project included identification and characterization of a suitable borrow source, a vegetation survey, and extensive unsaturated flow modeling of various climatic conditions to demonstrate cover system performance. In conjunction with the closure permit application process, Trihydro facilitated negotiations with the WDEQ for a deferred closure schedule that will accommodate a large amount of debris from an upcoming school construction and demolition project.