Evaluation of geotextile filter in a collection system at fresh kills landfill

The New York City Department of Sanitation has retained consultants to design a leachate collection system for the Fresh Kills Landfill in New York City. Fresh Kills Landfill is regarded as the world's largest landfill. Because of an Order on Consent the landfill is required to have a leachate collection system by 1996. Design of the collection system includes a trench backfilled with granular material wrapped in a geotextile filter. The geotextile filter will be a critical component of the collection system and will be designed to meet soil retention and permeability requirements for the system. An existing leachate collection trench with a non-woven geotextile filter was constructed at the landfill in 1988. This collection trench and geotextile filter were exhumed, sampled and analyzed in 1993 to determine the effectiveness of the geotextile filter. Information gained from this study was utilized for the design of future leachate collection systems. Results of this study will be the subject of this paper. This study was unique in the sense that a geotextile filter was used for the first time in the collection trench at the Fresh Kills Landfill. In addition an evaluation of its performance had not been investigated before. The geotextile filter was analyzed to determine the impacts of burial and filtration of leachate in a landfill environment on the hydraulic and mechanical properties of the material. Also, the potential for biological growth on the geotextile filter was investigated. Results of this study identified minor clogging of the geotextile filter due to soil particle retention within the pores of the non-woven material. A slight reduction in permittivity was observed due to particulate clogging.