are you prepared to close your ash ponds?
Post on 25-May-2015
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Are You Prepared to Close Your Ash Ponds?
R. Kent Nilsson, P.E.Senior Consulting Engineer
TRC Environmental Corporation
Drawbacks of Learning by Trial and Error…
Drivers for Pond Closure
Regulatory requirements Plant retirements Changes to facility operations Environmental liability management Political/social pressures
Regulatory Requirements
EPA has agreed to take final action on Coal Combustion Residuals (CCR) by December 19, 2014
Revised RCRA Subtitle “D” standards are the most likely outcome
Likely to be implemented at state level Closure also affected by Effluent Limitation Guidelines (ELGs)
Recent developments may influence outcome Final rule likely to be litigated
Regulatory Requirements – Ash Ponds
Anticipated RCRA Subtitle “D” requirements: Rule effective 6 months after promulgation Ponds not meeting liner requirements must stop accepting waste within 5 years of finalization of rules Groundwater monitoring required within 1 year after effective date Ponds must be closed within 2 years of last receiving waste
Strategy
Mapping out a strategic plan must consider the questions: Close now or later? Future end use of property? Close in‐place or remove the residuals? What are the costs?
Strategy
A Generic Decision Matrix
Strategy – Close Now or Later?
Dictated by: Regulatory framework and its timing Short and long‐term risk profile Retiring plant or continuing to operate Changes to facility operating requirements (e.g. wet ash v. dry ash handling) Costs and funding
Strategy – Close Now or Later?
Closure schedule affected by: Regulatory requirements/deadlines Future site use Pond size Ash pond assessment and preparation of design and bid package Regulatory approvals
Strategy – Future End Use of Property?
Retiring plants need to clearly define Prime redevelopment locations may require stricter clean‐up Site specific conditions (e.g., wetlands) Ash geotechnical properties
Strategy – Close In‐place or Remove the Residuals?
Viable market for pond material? Long‐term obligations? Long‐term environmental liabilities? Future land use? Sufficient on‐site borrow material? Construct on‐site landfill? Staffing demands/outside resources? Political/social pressures? Cost?
Need a Plan and Schedule
Risk Considerations
Planning for potential risks and liabilities: Geotechnical evaluation Environmental assessment (including risk assessment) Social/political analysis Landfill/pond closure design Permitting Construction engineering
Groundwater Investigation/Remedial Options
Groundwater Investigation– Likely required to ascertain environmental impact of existing unlined
ponds– Investigation plan should take into account
Point of compliance Constituents of concern Well placement Well construction Sampling protocol Quality assurance/quality control Background conditions
Remedial Options– Evaluate as warranted– Incorporate into closure plan
Closure Considerations
Pond size Dewatering requirements/methods Final use considerations Remediation integration Constructability concerns Health and safety Site configuration constraints Long‐term maintenance
Pond Closure – Health and Safety
Dust control and monitoring
In‐place Closure
Pros: Generally less expensive than relocation to a lined landfill Approach keeps haul vehicles off of public roads and highways Proximate to existing facilities If space‐constrained, can be used as landfill base
In‐place Closure
Cons: Perceived “unknowns” in the final storage conditions
Increased social/political opposition to in‐place closure, especially in environmentally sensitive areas
In‐place Closure
May not be feasible in an environmentally sensitive or recreational area
In‐place Closure Solutions
In‐place Closure Solutions
In‐place Closure Solutions
Pond Closure – Final Use Considerations
Solar farm
Closure by Removal Considerations
Beneficial reuse Disposal in off‐site Subtitle “D” landfill Disposal in on‐site Subtitle “D” landfill Consolidation with ash in existing lined pond
Closure by Removal
Beneficial reuse opportunities: Engineered fill*
Stabilized road base Concrete admixture Other
* Pending EPA ruling
Removal of Residuals
Beneficial reuse as a road construction material
Closure by Removal
Closure by Removal
Closure by Removal
Closure by Removal– Final Use Considerations
Closure by Removal
Ash dewatering using geotubes
Pond Closure ‐ Constructability
Slope stability
Pond Closure ‐ Constructability
Ash liquefaction
Construction costs
Ash volumes–actual conditions v. designed Moisture content – don’t pay to haul water Haul distances – keep them short Double handling of material Synthetic construction materials Long‐term monitoring On‐site landfill v. off‐site commercial landfill Leachate management
Questions/Comments?
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