AREA A/B ENGINEERING REPORT - Waste Management

Geosyntec Consultants
design), capillary-break ET cover systems, phytoremediation ET cover systems, and exposed
geomembrane cover systems. These alternatives were all considered favorably in a nationwide
USEPA-sponsored study. 13 These designs are often implemented as part of sustainable landfill
designs, and include all-soil final covers constructed to be naturally analogous and compatible
with the local ecosystem. Such “natural analog” cover designs provide protection of the
environment equivalent to the Subtitle D prescriptive cover, but with the added benefits of
enhanced methane oxidation, reduced GHG emissions, and ability to allow controlled infiltration
for enhanced waste degradation.
3.4.2 Key Environmentally Protective Features of Final Cover Systems
Final cover systems are an important complement to liner systems as a component of waste
containment at landfills, and Subtitle D regulations require that the final cover system be placed
over the landfill within one year after the waste reaches its final permitted height. Beyond
providing containment, the final cover system also fulfills other important functions:
• Promoting surface water runoff (which protects surface water from impacts
due to contact with waste), and controlling infiltration of precipitation into the
waste (which in turn controls leachate and landfill gas generation);
• Minimizing erosion, and controlling the occurrence of litter, disease vectors,
and other nuisances;
• Protecting air quality by controlling landfill gas emissions and odors; and
• Meeting aesthetic and other end use goals.
The final cover system provides ongoing environmental protection in conjunction with the short-
and long-term goals for reuse of the landfill property (e.g., improved gas-to-energy operations,
recreational land use options, and/or increased area for natural habitat).
3.4.3 Long-Term Performance of Final Cover Systems
Long-term cover system performance is related to the ability of the barrier,
drainage, and vegetative support layers to continue functioning as designed. The
effectiveness of the drainage and vegetative support layers is easily observed by
the absence of significant erosion damage and bare areas during cover inspections.
For landfills whose final cover system is designed to limit percolation, the
effectiveness of the barrier layer can be directly measured by overall reduction in leachate flow
rates over time from the LCRS, and indirectly measured by the level of gas emissions from the
13 The Alternative Cover Assessment Program (ACAP), sponsored by the USEPA, has established field demonstrations
at 12 sites nationwide to evaluate the performance of various alternative cover systems, as described by Benson et
al. (2005) and Dwyer (2003).
MD10186.doc 47 29 March 2009