HORIZONTAL DIRECTIONALLY DRILLED WELLS FOR LANDFILL LEACHATE AND GAS CONTROL: A PILOT STUDY

The Sioux Falls Regional Sanitary Landfill is located approximately 7 miles west of Sioux Falls. The facility began receiving municipal waste in the late 1970s, and portions of the facility are nearing completion. The oldest portions of the facility were constructed prior to the onset of RCRA Subtitle D regulations and are not equipped with leachate collection systems.

The soils underlying the facility are composed of clay-rich glacial till. The till has a very low hydraulic conductivity, effectively preventing exfiltration of leachate from the facility. This has resulted in the build-up of leachate within those portions of the facility that are not equipped with leachate collections systems.

In a pro-active effort, the City of Sioux Falls sought methods by which to control and reduce the leachate accumulations and deal with subsequent landfill gas accumulations. One of those methods was the installation of a leachate drain via a horizontal directionally drilled well. To evaluate this technology, a pilot study was performed on an emergency cell at the facility. The well was installed in late 2001. The long-term test pumping portion of the pilot study began in August 2002 and ended in January 2004.

This presentation provides the details of the well installation including the selection of the pilot site, the contractor selection, the well installation procedures and the results of the pumping test.