AREA A/B ENGINEERING REPORT - Waste Management

Geosyntec Consultants
It should be understood from the outset of any discussion on PCC that the Subtitle D solid waste
regulations do not stipulate a fixed period for providing care; rather, the regulations require that
monitoring and care activities continue until a demonstration can be made that it is technically
appropriate to end PCC. Subtitle D regulations allow the state Director to reduce or terminate
PCC at MSW landfills once it is demonstrated that the landfill does not present a threat to HHE at
the point of exposure or, conversely, to extend PCC if needed (USEPA, 1993). In addition to the
Subtitle D solid waste regulations, other state and local regulations (e.g. security, general liability
management, property, custodial and property ownership ordinances, and/or deed restrictions)
often preclude an owner/operator from changing or ending site care provisions unless it is
demonstrably appropriate to do so. The main issue faced by the regulatory and regulated
community therefore is how to make a technically defensible demonstration that PCC may be
extended, reduced, or terminated.
Some States have begun implementing regulatory approaches to evaluate ending PCC in terms of
waste stabilization (e.g., Florida Administrative Code, Chapter 62-701.620.1, Rule Workshop
Draft August 2007; Wisconsin Administrative Code, Chapter NR 514.07(9), WDNR March 2007).
These approaches have focused on development of landfill operations and management
techniques to promote long-term threat reduction through enhanced waste degradation (i.e.,
enhanced organic stability) rather than reduced infiltration and leachate generation (i.e.,
containment and isolation). A number of such proactive landfill operations approaches (e.g.,
leachate recirculation, alternative covers) are available to optimize the moisture content necessary
for enhanced waste degradation while effectively managing leachate and LFG generation until
the landfill no longer represents a threat at the point of exposure (ITRC, 2003 and 2006a).
Building on the above but going a step further to include all landfill operational conditions, a
performance-based approach focuses PCC obligations on actual landfill conditions and defines
when the end of regulatory PCC is appropriate for site-specific conditions, potential threats to
HHE, and future use of the property. Performance-based approaches to evaluating PCC focus on
identifying and quantifying the potential for a landfill to pose a threat to HHE at the point of
exposure and evaluating the duration for which care is necessary. This type of evaluation
generally involves examining statistical trends in leachate, LFG generation, and/or groundwater
quality, as well as other relevant biological, chemical, and/or physical data, to predict future
performance based on current or past trends. A number of key reference tools for making
statistically valid, site-specific, performance-based assessments of PCC at MSW landfills have
recently been developed through multi-year studies of PCC, including Gibbons & Bull (2006),
ITRC (2006b), and EREF (2006). The fundamental approach, termed the Evaluation of Post-
Closure Care (EPCC) Methodology, involves a series of evaluations that help an owner/operator
assess the potential for impacts after PCC is modified or terminated. If an evaluation shows that
no impacts are expected, then monitoring is recommended to confirm the conclusion. If, on the
other hand, impacts are expected, then the owner/operator continues PCC until such time that
impacts are not expected after PCC is ended. In this way, rather than relying on a determination
that PCC is either complete or must be continued at the same level of intensity, the methodology
evaluates each potential exposure mechanism and allows for the possibility that certain aspects of
PCC could be discontinued while others are maintained. For example, it may be appropriate to
MD10186.doc 145 29 March 2009