FAQs
I’ve heard that all landfill liners and leachate collection systems ultimately fail. Is that true?
Conestoga Landfill’s liner and leachate collection system exceed all state requirements.
Since opening in 1994, Conestoga Landfill has constructed a primary and secondary composite liner system within the landfill waste disposal area. A composite liner consists of a flexible HDPE geomembrane placed over an underlying layer of compacted, low permeability soil. These composite liner systems serve as a barrier preventing the infiltration of landfill leachate from entering the surrounding soil and rock stratum.
The primary composite liner system is designed to contain rainfall that has infiltrated through the waste mass and other liquids that have come in contact with the waste. These liquids are referred to as “leachate” and are collected within sumps, designed as part of the leachate collection system that lies immediately above the primary composite liner, and are removed from the landfill through a series of pipes for treatment. The secondary composite liner system, which includes a leachate detection zone, is placed beneath the primary composite liner to provide redundant protection.
A committee studying HDPE (high-density polyethylene) liners for the U.S. Environmental Protection Agency estimated the anticipated life of these landfill liners to be in “terms of hundreds of years.” This time frame is well beyond the period needed to protect a site from transmitting leachate.
The leachate collection system constructed within Conestoga Landfill’s waste disposal area is comprised of an 18-inch thick layer of aggregate combined with a network of HDPE pipes placed across the floor of the landfill. The floor of the leachate collection system is sloped to one of two sumps that are designed to collect leachate. The leachate is subsequently removed from the landfill by a pump system. After installation of the final cover cap across the surface of the waste disposal area, stormwater percolation through the waste mass will decline to a point where the in-place waste mass will generate negligible amounts of leachate.