You are here:
LEACHATE CLOGGING ASSESSMENT OF GEOTEXTILE AND SOIL LANDFILL FILTERS
Citation:
Koerner, R. M. AND G. R. Koerner. LEACHATE CLOGGING ASSESSMENT OF GEOTEXTILE AND SOIL LANDFILL FILTERS. U.S. Environmental Protection Agency, Washington, D.C., EPA/600/R-95/141 (NTIS PB95-265542), 1995.
Impact/Purpose:
publish information
Description:
The liquids management strategy for any municipal or hazardous waste landfill requires a knowledgeable design strategy for the leachate collection system located at the base of the waste mass. Such leachate collection systems generally consist of sumps, perforated pipes, drainage materials (gravel soils or geonets) and filter materials (sand soils or geotextiles). The solid waste mass lies above the filter, although sometimes a protective soil acts as a intermediate layer. As leachate migrates through the waste mass it must be intercepted, collected and transported by the leachate collection system. Since leachate is often high in suspended solids and microorganism content, concerns over excessive clogging of the leachate collection system are often expressed. More specifically, the filter is the target material due to its small opening spaces with respect to the other materials that are involved. Thus, this project is completely oriented toward the filter material of the leachate collection system. Both sand soil and geotextile filters are investigated, although more emphasis is on geotextiles due to their greater current usage in this application. A multifaceted approach leading to a design methodology was the focus of this study. The project consisted of exhuming four sites-of-opportunity which essentially established ground truth. Three of the sites had excessively clogged geotextiles and the fourth was marginally adequate. Parallel to the field work was the laboratory evaluation of 12 commonly used filters; (10 geotextiles and 2 soils) using four different permeating liquids (water and 3 different leachates) under three different accelerated leachate flow rates. This required 144 ASTM D1987 flow columns to be constructed. Each were used for time periods of up to one year in order to establish equilibrium permeability values. From this data, master curves of the twelve filters were generated. Parallel to the field and laboratory efforts just noted was a computer modeling effort (using the HELP model) to investigate flow rate sensitivity to different leachate collection materials and to obtain the required, i.e., site specific, flow rates for the four exhumed sites. These three activities (field exhuming, laboratory testing and computer analysis) were brought together in a design model which can be used to calculate the factor-of-safety for a leachate collection system filter in any site specific and material specific design. A Project Summary is also available (EPA/600/SR-95/141).