Will Posi-Shell Damage my Leachate Collection System?

NO - Posi-Shell has been used at conventional and bioreactor landfills for 20 years with no documentation of damage to leachate collection systems. The cement ingredients in Posi-Shell harden on the surface of the waste at the time of application. This one-time hydraulic cement reaction occurs only when the cover is first applied. If the hardened material later breaks up and is transported by liquids to the leachate system, it behaves the same as any other dirt, dust or other solid particles in the leachate. Soil covers contribute far more available solids than thin Posi-Shell coatings, and C&D landfills with a large amount of old cement materials do not report any greater incidence of leachate line clogging than MSW landfills.

It is true that leachate collection piping often exhibits a scaly hard build-up known in the landfill industry as “Bio-Rock,” however, this occurs in landfills not using Posi-Shell as frequently as in those which do. Bio-Rock is generally formed by complex biochemical oxidation-reduction reactions with leachate solids slowly flowing through the intermittent semi-aerobic conditions in the leachate collection pipes. This explains pipe camera observations that there are no “stalagtites” forming downward from the perforation holes; instead the Bio-Rock builds in thin, hard layers from the bottom up, beginning at the leachate flow-line in the pipe.

You can use Posi-Shell with complete confidence, based upon decades of experience, that no damage will be done to your leachate collection system. The important key to a well functioning leachate collection system is regular, normal cleaning of collection lines to remove “Bio-Rock” before it clogs the line; this maintenance is equally important for landfills using Posi-Shell or for landfills using any other type of cover.