Posi-Shell®: Frequently Asked Questions
Posi-Shell is a spray-applied mineral mortar coating, similar to stucco, used as landfill daily cover, intermediate cover, erosion and odor control.
Q) What is the composition of Posi-Shell?
Posi-Shell Advanced Formulation is a mixture of water or leachate, PSM-200 Setting Agent, and Posi-Pak® P-100 fibers. Portland Cement is often added and color can be adjusted with dyes or the use of waste latex paint.
PSM-200™ Setting Agent is a powdered combination of finely ground volcanic clay, natural and synthetic adhesives. It is non-toxic and delivered in convenient 50-lb (23 kg) bags.
Q) What are Posi-Pak P-100 fibers?
The Posi-Pak P-100 fibers are very fine polyester reinforcing fibers specially coated to disperse in liquid slurries without clumping.
Q) What do P-100 fibers do in the Posi-Shell mixture?
They eliminate cracking and increase durability.
Q) Why should I use Posi-Shell?
Posi-Shell is a multi-purpose product which saves airspace, provides a durable cover and is easy to apply.
Q) How much does Posi-Shell cost?
The typical daily cover cost, including equipment and materials, is usually 3-5 cents per square foot.
Q) How is Posi-Shell different than other spray applied products?
Posi-Shell uses mineral mortar where others use paper and water or foam.
Q) Can Posi-Shell be used for long-term cover?
Yes. In addition to daily and intermediate cover, Posi-Shell is used for long-term cover and erosion control. With the addition of Portland cement, durability of up to several years is possible.
Q) Will Posi-Shell Damage my Leachate Collection Systemr?
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(when used) 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. North America's leading leachate maintenance contractor reports that the occurance of Bio-Rock is independent of the use, or non-use of Posi-Shell.
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.
Contact Landfill Service Corporation to schedule your free Posi-Shell Demonstration.