so the landfill is closed, now what? - swana nj · leachate no longer poses a threat to human ......
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So the Landfill is Closed, Now What?Understanding Current Approaches to Post-Closure Care
Dr. Bryan Staley, PE, President and CEO
Protection of human health and the environment (HHE) by reducing potential threats to acceptable levels at the relevant point of exposure (POE)
Typically the closest property boundary location where human or ecological receptor could be exposed and receive a dose via potential migration pathway as defined under RCRA (US EPA, 1993)
Authority rests with state agencies to determine sufficient PCC time period, but no guidelines exist that allow agency to determine this
The general assumption is a prescriptive 30-year term for PCC, but the regulation is actually performance based (40 CFR§258.61 –RCRA Subtitle D)
For example: “…stop managing leachate if
the owner or operator demonstrates that
leachate no longer poses a threat to human
health and the environment [HHE]…”
Why End Post Closure Care (PCC)?
• Resource optimization
• Beneficial land reuse • Recreational• Ecological Habitat• Commercial• Agricultural
• Cost certainty
• Liability management
• Community goodwill
• Avoid an ever increasing workload
• Ever-increasing number of sites being closed
• Focus regulation and attention where most needed
Current Decision Model for PCC under Subtitle D
Post-
Clo
sure
Care
Period
Yes
Site Closure
Implement Post-Closure Care Program
End Post-Closure Care
Has duration of Post-Closure Care been 30 years, or a
shorter/longer period allowed/required by
the Director?
No
How can the
Director
determine
this?
How does
the Director
define this?
Why Now?
RCRA – No Guidance for Termination of PCC
30 Years PCC Period Are Ending
No Common Defined ApproachesoDon’t Need 50 Different Solutions
Support Performance Based ApproachoData, Data, Data
YearOperating landfills
1990 6300
2010 1572
2013 1540
2018 ~1500SOURCE: Laner et al. (2012); EREF (2016)
Far more landfills today are closed than are open.
Approaches for Performance Based PCC
Organic Stabilization
demonstration of a relatively inert waste mass
Functional Stability
considers long-term emissions in context of threat potential WITHOUT active controls
measured at a point between landfill and POE
• Goal in either case is going from active post-closure care to a point of custodial or ‘de minimus’ care where HHE is protected
Active Post-Closure Care
Source: Morris & Barlaz, 2017
MW1
MW2
SUMP-1
Surface
Water
Discharge
GP-1
SUMP-3
SUMP-2
LANDFILL
Leachate
Storage Tank
Gas
Flare
Station
GP-2 Homes
GP-3
Custodial or ‘de minimus’ Care
Source: Morris & Barlaz, 2017
SUMP-1
Surface
Water
Discharge
SUMP-3
SUMP-2
LANDFILL
Passive
Gas
Biofilter
Property
Boundary
Homes
Organic Stabilization
Requires near-complete degradation of waste mass (i.e. inert solids in the waste mass)
May offer maximum protection of HHE but also may be ‘overkill’
Approaches suggested typically do not allow for a ‘step down’ in PCC activities over time
Can imply very long-term (30+ years) or near perpetual care under a regulated program (Scharff et al., 2011)
Little consideration of cost; likely most expensive option
Demonstrating Organic Stability
53800
6550
825
0
10000
20000
30000
40000
50000
60000
0 10 20 30 40 50 60
CO
D C
on
cen
trati
on
(m
g/L
)
L/S
Chemical Oxygen Demand
Bioreactor Leaching
Typically two characteristics of concern for waste mass: Extent of biodegradation
Remaining LFG production
Remaining settlement
Leaching potential Assessment of future leachate quality
Interpretation of how to demonstrate/implement varies
Implies characterization of buried solids that is representative of the entire waste mass No guidance on what testing is appropriate and target levels; wide
range of tests could be used (Wagland et al., 2009)
Trends in LFG, settlement, leachate generation may provide suitable surrogates
Case Study on Solids Analysis
• normalizing to VS is critical (pure
cellulose 414.8; pure HC 424.2)
• Solid analysis shows high variability
despite significant downtrend in CH4
generation
BMP of Excavated Samples
Post-Closure Methane Collection Data
pure cellulose 414.8; pure hemicellulose 424.2
Source: Morris and Barlaz, 2017
Functional Stability
Relies on conservative impact assessments to define PCC monitoring and management (Morris and Barlaz, 2011)
Central elements include: Leachate and LFG management
Groundwater monitoring
Cover maintenance
Eliminates active controls, replacing them with passive measures, once minimal impact target levels have been achieved for each element
Allows for remaining elements of concern to receive focused attention, with the receiving environment and property end-use being important inputs to the evaluation
Optimizes management strategies; minimizes costs
Demonstrating Functional Stability
Analysis of LFG Collection Using Functional Stability Approach
• Plot measured data
• Run LANDGEM model for LFG generation
• Run LANDGEM model for collected LFG
• Align with data so model results match observations, which
provides a projection of future LFG collected
• Determine when stability target for LFG is achieved
LFG production is stable or decreasing < 10% of peak LFG generation
Settlement is essentially complete <5% annually relative to cumul. total post-closure volume reduction
Leachate quality is stable or improving satisfy criteria for ‘gateway indicators’ (e.g. BOD/COD < 0.1) then
meet WQS (preferably at source or, failing that, at POC)
Emissions of leachate/LFG will not unacceptably impact HHE via potential pathways to air, groundwater, surface water or vadosezone
Critical aspect of the approach is a confirmation monitoring program, which is designed to track when active controls can be stopped and a full transition from PCC to custodial care can occur
Current US Landfill Post Closure Care Termination Requirements
Per Subtitle D
Subtitle D with
Modifications
Functional Stability
Organic Stability
Source: Jeff Murray (2019)
Current Activities & Next Steps
Work with State Programs and Encourage Regional Approaches
Instill More Confidence in Mitigation of Risks
Smoother Transition to Long-Term Management and Re-use
SWANA Policy on PCC termination
Supports use of performance based evaluations
Makes recommendations for state programs
Simplify the messaging for functional stability approaches
Peer reviewed research documents performance based methodologies relatively well, but the findings need to be communicated more effectively to a non-academic audience
Current documentation is lengthy and highly detailed
• ITRC guidance document on performance-based PCC (2006)
• EREF guidance document on performance-based PCC (2006, 2011)
Need to make initial introduction to concepts easier to understand and follow for agencies, planners, consultants
Key Guidance Documents
Environmental Research & Education Foundation
1. “Performance Based System for Post Closure Care at MSW Landfills”,
September 2006
2. “Determining Critical Data Requirements for Implementation of the EPCC
Methodology Prerequisites Module”, March 2011
3. “Transitioning from Active to Passive Care at Municipal Landfills: Full-Scale
Site Evaluations using the EPCC Methodology”, April 2016
https://erefdn.org/research-grants-projects/eref-project-publications/
Interstate Technology & Regulatory Council
1. “Evaluating, Optimizing, or Ending Post-Closure Care at Municipal Solid
Waste Landfills Based on Site-Specific Data Evaluations”, September 2006
https://itrcweb.org/Guidance/GetDocument?documentID=4&documentID=4
