LEACHATE AND LANDFILL GAS EXTRACTION FROM AN UNLINED LANDFILL

摘要

In order to deal with high leachate levels within the Sioux Falls Regional Sanitary Landfill, R. W. Beck worked with the City of Sioux Falls to design a dual-phase leachate and landfill gas extraction system in the unlined 100-acre portion of the City of Sioux Falls Landfill, located approximately 6 miles west of Sioux Falls, South Dakota. This $1.1 million dollar system consists of 19 (of approximately 100 eventual) vertical leachate and landfill gas extraction wells, connecting laterals and headers, leachate drains, and lift stations to dewater the Landfill. Historically, high leachate levels (up to 60 feet above the base of the landfill) needed to be drawn down in order to satisfy regulatory closure requirements and allow landfill gas collection and recovery. R. W. Beck designed a unique extraction system utilizing a single well casing and drain system combining both gas and liquids recovery. Pneumatic leachate pumps were installed in each well, discharging leachate to the perimeter landfill gas header pipe, where the leachate and condensate are separated out at six different lift stations. When designing this system, R. W. Beck evaluated several options for removing the leachate from the landfill. These options included: 1. Horizontal wells vs. vertical wells 2. Well design for collection of both leachate and landfill gas 3. Electric pumps vs. pneumatic pumps 4. Optimum spacing and location of vertical wells 5. Collection and perimeter manifold piping orientation The system has been operational since October, 2005. The lessons learned during the design, construction and operation of the system will be beneficial to a large number of landfill professionals and managers who have leachate management issues. This project has also spurred a landfill gas utilization project due to the amount of landfill gas collected by the newly constructed system.