AREA A/B ENGINEERING REPORT - Waste Management

Geosyntec Consultants
behind the limited number of landfill failures that have occurred due to human error have been
well researched and documented. Lessons have been learned and are appropriately considered
in the design and operation of modern landfills. Extensive failures and manmade emergencies at
modern MSW landfills are ultimately avoidable through proper landfill design, construction,
operation, and routine maintenance practiced in accordance with regulations.
An important finding from the above review of landfill failures is that none was found to have
occurred at a closed landfill at which a final cover system had been installed. Ultimately, the
factors influencing landfill structural stability improve over time – particularly at closed landfills
that have a demonstrated trend of reduced landfill gas and leachate generation (as previously
summarized in Section 6.1.2). Specifically, long-term stability of the final cover system is
maintained through proper maintenance, monitoring, and gas management until all performancebased
objectives are achieved. Appendix C to
this document provides a more in-depth
discussion of this important issue.
In consideration of the history of
landfill structural stability postclosure,
it is not reasonable to
expect that replacement of the
final cover system will be
necessary. Relevant factors are
evaluated for potential causes of
instability before post-closure care is
permitted to end.
Extensive Landfill Failures are
Rare and Preventable
Major failures at regulated solid waste landfills are very
rare. Of the handful of documented catastrophic
failures, none was the result of a natural disaster and all
could have been prevented with changes in design,
operation, and/or maintenance practices. Natural
disasters have been reported to cause only minor, easily
repairable damage to vegetation and surface features.
6.2.3 Performance-Based Maintenance and Ending Care at Closed Landfills
Once a landfill is closed and a PCC program is established, monitoring data provide direct
evidence that the landfill is performing as expected. Multiple studies of actual landfill data
indicate that, with proper maintenance of the final cover system, landfills show decreasing
leachate volumes and improvement in its quality after capping. Similarly, the landfill will begin a
decreasing landfill gas generation trend within a year or so after capping (assuming active
treatment of waste does not continue at time of closure, in which case the time the commencement
date of the decreasing trend may be extended). With a decrease in leachate and landfill gas
generation over time, the need for continuous active system management also decreases. In this
way, managed care routinely performed during operations reduces the effort needed during a
landfill’s post-closure care period.
As designed under RCRA Subtitle D and as confirmed by the studies summarized in Section 6.1.2
(and in more detail in Appendix C), monitoring can determine the point at which active landfill
management is no longer needed and regulators can be confident of protection of human health
and the environment in the absence of this care. In this regard, performance-based
methodologies for evaluating post-closure care, including those outlined by EREF (2006) and ITRC
MD10186.doc 80 29 March 2009