AREA A/B ENGINEERING REPORT - Waste Management

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B1. OVERVIEW B1.1 Containment System Design and Performance Appendix B Geosyntec Consultants LANDFILL CONTAINMENT SYSTEM PERFORMANCE AND LONGEVITY Subtitle D landfill liner systems and their overlying leachate collection systems are a reliable component of the engineered systems that provide protection of human health and the environment (HHE) for as long as that protection is needed. The expected longevity of Subtitle D liner system and final cover system components, coupled with the demonstrated ability of such systems to reduce leachate generation and improve leachate quality over time (see Appendix A), means that closed landfills relying on Subtitle D compliant liner systems and final cover systems can expect to be protective of HHE over the very long-term. Modern engineered landfills are designed and constructed to minimize or eliminate the release of constituents into the environment. As part of this effort, MSW landfills are required by Federal, state, and/or local regulations to apply final cover over the waste materials. Final covers for Subtitle D landfills are engineered systems that isolate the waste and provide protection of HHE. The demonstrated ability of Subtitle D final cover systems to contain waste and to control, or progressively reduce, leachate generation over time means that closed landfills can rely on Subtitle-D compliant final cover systems to perform as designed for a very long time, perhaps for a period of hundreds of years or more. Historically, low-permeability barrier components have been prescribed for final cover systems in regulations without consideration of site-specific conditions. These prescriptive covers typically include a compacted clay liner or a geomembrane. However, the Subtitle D regulations include a provision for using alternative covers that meet certain performance requirements, and as many as 20 states have approved alternative covers for landfills. B1.2 Organization of this Appendix Many unsubstantiated and often erroneous opinions have been expressed questioning the performance and longevity of MSW landfill containment systems (i.e., liner, leachate collection, and final cover systems). This has led to the perception in some public quarters that geomembrane liners will fail, that leachate collection systems will clog, fail, and require major maintenance before the end of post-closure care (PCC), and that cover systems will not be maintained to meet their performance specifications over the long term. To address these concerns directly, the discussion is this appendix is focused on the following three main subject areas: • Long-terms performance of liner systems; MD10186.doc 123 29 March 2009
• Long-term performance of leachate collection systems; and • Final cover system performance and longevity. Geosyntec Consultants These three subjects are addressed in the following subsections of this appendix. In each subsection, a convenient green box “at a glance” synopsis of salient technical responses is provided, representing the state-of-the-practice along with references for seminal supporting material from peer-reviewed research, journal articles, and operational practice. Thereafter, a brief summary of the body of knowledge in support of the synopsis is provided. B2. LONG-TERM PERFORMANCE OF LINER SYSTEMS B2.1 Technical Synopsis • Recent studies reinforce the finding that trends in MSW leachate and LFG generation and composition are predictable and, in general, decrease over time following landfill closure; • At landfills where low-permeability cover systems having a geomembrane barrier are installed, the time period for significant leachate and LFG production is generally anticipated to be on the order of tens of years after closure; • While the geomembrane component of a composite liner may have a service life on the order of 1,000 years, the service life of the low-permeability soil component of a composite liner is on the order of several thousands of years and are relied upon at critical waste containment facilities that require a service life for exceptionally long time periods (e.g., tens of thousands of years); and • The expected service life of the components of a composite liner system in an appropriately designed and constructed MSW landfill is therefore far in excess of the time period for significant leachate and LFG production. Seminal Supporting References: Koerner, et al., 1990; Bonaparte, 1995; Rowe, 1998; Bonaparte, et al., 2002a; Koerner & Hsuan, 2002; Rowe, 2005. B2.2 Summary of Supporting Body of Knowledge Reports of landfill leachate quality and quantity over time show predictable patterns of improvement that support the conclusion that well-designed and operated modern landfills will not be expected to impact HHE over the long term. Leachate generation rates at a landfill are highest early in the active life of the facility, with the rates decreasing with time as the landfill is MD10186.doc 124 29 March 2009
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ENVIRONMENTAL PROTECTION AT THE MAN
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TABLE OF CONTENTS Geosyntec Consult
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TABLE OF CONTENTS (continued) Geosy
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TABLE OF CONTENTS (continued) Geosy
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DEFINITIONS AND LIST OF ACRONYMS AC
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EXECUTIVE SUMMARY Geosyntec Consult
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Geosyntec Consultants time, the lan
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Long-Term Liner System Performance
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Geosyntec Consultants generation is
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Geosyntec Consultants cover systems
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Beyond Waste Containment - Landfill
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Geosyntec Consultants • Section 3
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Geosyntec Consultants Required by r
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• Landfill gas system monitoring
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Geosyntec Consultants An extensive
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1.4.2 Permanent Storage of Biogenic
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2. REGULATORY OVERSIGHT OF MANAGED
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2.2.1 Siting Considerations Geosynt
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Geosyntec Consultants The LCRS is i
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• Control moisture and percolatio
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3. DESIGN COMPONENT SYSTEMS OF A MA
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Prescriptive Final Cover System 1.
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3.2.2 Key Environmentally Protectiv
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Geosyntec Consultants selected and
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Geosyntec Consultants • Leachate
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Geosyntec Consultants secondary, an
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Geosyntec Consultants along with re
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Geosyntec Consultants cover surface
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3.5 Gas Management System Geosyntec
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Geosyntec Consultants • Passive c
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Geosyntec Consultants out certain p
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Geosyntec Consultants on the curren
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4. OPERATION AND MAINTENANCE OF A M
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Geosyntec Consultants permit condit
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Geosyntec Consultants • Standard
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Geosyntec Consultants Design of the
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Geosyntec Consultants waste constit
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5. ENVIRONMENTAL MONITORING AT MANA
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Geosyntec Consultants safeguards fo
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Page 93 and 94: Waste Treatment Attribute Siting an
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AREA A/B ENGINEERING REPORT - Waste Management

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