High-Tech Landfill Caps

by Joseph C. Barbagallo, Engr.; Malcolm Pirnie, Inc., White Plains, NY,
Salvatore J. Triano, (M.ASCE), Project Engr.; Malcolm Pirnie, Inc., White Plains, NY,

Serial Information: Civil Engineering—ASCE, 1993, Vol. 63, Issue 5, Pg. 66-68

Document Type: Feature article


Just as federal and state regulations detail every aspect of landfill location, construction and operation, they now detail every aspect of its design closure. A typical municipal solid waste landfill cap, from the bottom up, consists of a gas venting layer, a low permeability barrier layer (soil, a geosynthetic clay liner and/or a geomembrane), a barrier protection layer, and a vegetative soil layer. Many landfill caps, however, are non-typical, requiring additional layers for erosion protection, soil separation, drainage or veneer reinforcement. Some, like those on Long Island in New York State, are subject to extra regulations for protection of the aquifer water supply. Some existing landfills have slopes that exceed the regulatory 35% limit. To avoid extensive cut and fill regrading for compliance, caps on these very steep slopes may include a flexible armor system—a concrete revetment similar to those used to stabilize shorelines. The armor, or revetment mat, consists of rectangular blocks cast-in-place in a staggered pattern created by encasing nylon reinforcing cables between two layers of fabric that act as the mat forms. A sand/cement concrete grout is pumped into the fabric envelope after placement on the slope and insertion of the nylon reinforcing cables. The cables allow the mat to adapt to changing subgrade conditions that may occur as the landfill settles after closure.

Subject Headings: Cables | Soil gas | Permeability (soil) | Soil stabilization | Landfills | Municipal wastes | Layered soils | Clays | New York | United States

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