AREA A/B ENGINEERING REPORT - Waste Management

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landfill system components that are strictly operated and monitored through post closure;
and
• As waste material in a landfill degrades, the bottom-most layers become well
decomposed and act as a biofilter, attenuating both degradable organics and nondegradable
inorganics in leachate (see Section 1.4.3).
Furthermore, as discussed in Section 1.4.1, it is well documented that LFG generation from MSW
landfills decreases with waste age. This behavior is also observed for long-term settlement,
because such settlement is more significantly linked to waste biodegradation rather than to
physical effects.
6.2 Providing Long-Term Landfill Integrity
6.2.1 Responding to Minor Upsets of Landfill Operational Systems
The operational performance of a landfill is actively monitored under the terms of RCRA Subtitle
D regulations and each facility’s operating permit. This monitoring is a key element in the
regulatory program because:
• The processes that could result in potential impacts to human health and the environment if
uncontrolled (i.e., biodegradation occurring in the waste mass, producing leachate and
LFG) are well known and largely predictable, and the monitoring system alerts the
operator to deviations from containment standards;
• Monitoring systems and processes are stipulated in facility permits and overseen by state
regulators; and
• After landfill closure, monitoring discloses whether the systems are functioning as designed.
Deviations from performance goals trigger investigation and response actions.
Monitoring systems thus function as “early warning” systems, designed to
detect unexpected landfill behavior or system upsets, and triggering
appropriate response before environmental media can be significantly
compromised. It is important to note, moreover, that system upsets are rare at
managed landfills because of the overlap that exists between integrated
systems and monitoring components.
6.2.2 The Potential for Extensive Landfill Failure
A performance-based design approach includes accommodation for the potential for catastrophic
failure. Seismic design standards require that landfills are constructed to be resistant to damage
from earthquakes; similarly, landfill closure designs must include final cover systems that are
capable of withstanding large storm events.
MD10186.doc 78 29 March 2009