AREA A/B ENGINEERING REPORT - Waste Management

Geosyntec Consultants
• Regulatory oversight of landfill siting and design, including thorough site
characterization, identification of potential migration pathways, and identification of
a groundwater monitoring system capable of detecting a potential upset of the
landfill system;
• An engineered or natural liner system that is appropriately designed for known and
projected climatic, hydrogeologic, and other site-specific conditions to provide
containment and prevent leakage of leachate to the subsurface;
• Operation of the leachate management system to maintain minimal head-on-liner
and preserve liner integrity, with standard operating procedures undertaken by a
trained workforce;
• Operation of the gas management system with a workforce trained in preventative
and response maintenance to prevent vertical or lateral migration of landfill gas,
thus minimizing the potential for impact to the vadose zone and groundwater;
• An engineered or natural analog cover system that is appropriately designed for
known and projected climatic, hydrogeologic, and other site-specific conditions,
functioning to provide containment and control infiltration and leachate generation;
and
• Active groundwater monitoring with independent professional sampling and
laboratory analysis of water samples to promptly evaluate potential upset of the
liner, leachate, or gas management systems.
As the above list illustrates, no single system is relied upon to protect groundwater. Similarly, it is
the combination of multiple systems and active management (including monitoring) that is
designed to provide protection of other environmental media regardless of the limitations of any
given system design or site characteristic.
6.1.2 Predictability in Landfill Performance Trends
A sizable body of scientific knowledge exists to demonstrate the long-term
performance of landfills under different design, operating, and closure conditions,
focused on the overall predictability of LFG generation and composition and
leachate quality over time based upon the stage and degree of waste
decomposition (see discussion in Appendix A). In summary, the literature shows that:
• MSW landfill leachate is a non-hazardous liquid whose constituent concentrations follow
downward trends that are predictable with time after capping;
• Up to half of the organic carbon within MSW is sequestered in landfills (see Section 7.2)
and will not emerge in leachate;
• Mobilization of inorganic compounds in leachate over the long term is controlled by
MD10186.doc 77 29 March 2009