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Tennessee Valley Authority — Technical Presentation (May 2010)
24 slides from Tennessee Valley Authority's technical presentation, May 2010
Slide 1: TVA Kingston Fossil Fuel Plant Release Site: Selected Remedy for Embayment and Dredge Cell EE/CA
TVA Kingston Fossil Fuel Plant Release Site Selected Remedy for Embayment and Dredge Cell EE/CA May 2010
Slide 2: Engineering Evaluation/Cost Analysis (EE/CA)
Engineering Evaluation/ Cost Analysis (EE/CA) Time Critical 3.3 Million CYS • 3 alternatives developed and released for 75‐day public comment period (January 19 – April 5, 2010) • Seamless transition of work at the completion of Time‐Critical dredging Non-Time Critical 2.4 Million CYS
Slide 3: EE/CA: Removal Action Objectives
Engineering Evaluation/ Cost Analysis (EE/CA) Removal Action Objectives (RAOs): (All alternatives met) • Minimize contact • Minimize migration • Minimize exposure • Restore embayment • Close former dredge cell • Safely dispose of all waste streams
Slide 4: EE/CA Alternatives
EE/CA Alternatives • Common Elements – Restoration of embayments to pre‐spill conditions – Closure of failed dredge cell and adjacent Ash Pond – Enhanced perimeter dikes (designed to withstand liquefaction of foundation ash at earthquake loads) • Significant Differences – Disposal off‐site vs. on‐si
Slide 5: EE/CA Alternatives: Cost, Elevation, Duration
EE/CA Alternatives Closure Project Alt. Offsite disposal Cost Elevation Duration $440 1 2.8 million cys 790’ MSL 3.5 years million $720 2 6.8 million cys 765’ – 780’ MSL 5 years million $270 3 0 790’ – 805’ MSL 4.1 years million
Slide 6: Input from Community on EE/CA Alternatives
Input from Community on EE/CA Alternatives • Individual Citizens/Civic Groups – Based on written and verbal comments, majority support on‐site disposal options (Alternative 3) • Roane County Community Advisory Group – Supported none of the EE/CA alternatives • Environmental Groups: Environmental Int
Slide 7: Alternative Evaluation Criteria
Alternative Evaluation Criteria • Effectiveness – Achieve Removal Action Objectives (RAOs) – Compliance with other laws/regulations (ARARs) – Short and Long‐term protection of human health & environment • Implementability – Time to achieve RAOs – Construction and technology performance for excavatio
Slide 8: Selected Alternative (3B) On-Site Disposal
Selected Alternative (3B) On‐Site Disposal Closure Project Alt. Offsite disposal Cost Elevation Duration $268 3B 0 790’ MSL 4.1 years million Shipping and Largest, most Closes Lowest Disposal risks robust permitted cost eliminated perimeter dike landfill alternative
Slide 9: Major Components Alternative (3b): Infrastructure and Excavation
Major Components Alternative (3b) • Infrastructure – Ash consolidation in North Embayment to isolate fresh water springs – Swan Pond Circle Road underpass/bridge – North Embayment construction traffic connects to East/West haul road • Excavation of Swan Pond Embayment – Conducted primarily with exca
Slide 10: Major Components Alternative (3b): Working Platform and Dry Ash Stacking
Major Components Alternative (3b) • Construct Working Platform/Dry Ash Stacking – Working platform constructed of geo‐grid, sand, and stone for capillary break and stable working surface – Place thin layers of dry ash at optimum moisture content per test embankment program criteria
Slide 11: Major Components Alternative (3b): Perimeter Dike Stabilization
Major Components Alternative (3b) • Install Perimeter Dike Stabilization – > 16,000 linear feet of perimeter dike foundation to prevent release of ash after liquefaction of foundation ash under earthquake loads – > 12,000 soil‐cement borings installed to bedrock (60 – 70 feet deep) requiring 260,000
Slide 12: Major Components Alternative (3b): Water Management
Major Components Alternative (3b) • Water Management – Relocate existing clean water ditch to access adjacent ash – Continue best management practices for storm water runoff • Dike 2 and Settling Basins – Remove 1,400 ft Dike 2 that served as containment barrier and haul road for Time‐Critical activ
Slide 13: Major Components Alternative (3b): Restore Embayment Ecosystem
Major Components Alternative (3b) • Restore Embayment Ecosystem – Excavate to native material – Restore complex mosaic of forested, scrub‐shrub, aquatic, and emergent wetland plant communities – Species composition and density based on historical embayment habitat and surrounding reference stations
Slide 14: Major Components Alternative (3b): Grade and Cover Dredge Cell
Major Components Alternative (3b) • Grade and Cover Dredge Cell and Ash Pond – Re‐grade dredge cell and ash pond to 790 feet msl – Place 2 feet of clay and 1 foot of topsoil on top of graded ash – Vegetate cover to control dust generation, promote water runoff, and provide erosion control • Monitori
Slide 15: Rationale for Selecting Alternative (3b)
Rationale for Selecting Alternative (3b) • Eliminates Off‐Site Disposal Impacts and Risks – Transportation risks – Disposal capacity issues – Acceptability of offsite disposal • Safe Containment of Ash – Perimeter diking system addresses identified failure factors (fill geometry, fill rate, foundati
Slide 16: No Liner or Leachate Collection: Groundwater Flow
No Liner or Leachate Collection • Groundwater Flow to Site ‐ Silty clay layer beneath site acts as barrier to metal migration ‐ Groundwater does not migrate to drinking water wells, moves downgradient to river ‐ New perimeter dike will reduce lateral groundwater movement ‐ Clay and soil cover will r
Slide 17: No Liner or Leachate Collection: No Metals Leaching
No Liner or Leachate Collection • No Metals Leaching – After over 50 years of groundwater in contact with ash, water quality does not currently exceed drinking water standards – EPA Science Panel and USACE/ERDC studies after spill conclude metals not readily leaching off ash under site‐specific cond
Slide 18: No Liner or Leachate Collection: No Groundwater Plume
No Liner or Leachate Collection • No Groundwater Plume – Semiannual monitoring over past 10 years – 2 of 40 samples since release in ballfield exceeded arsenic levels – No arsenic exceedances in past 7 months Downgradient Wells
Slide 19: Proposed Coal Ash Regulation
Proposed Coal Ash Regulation • In its proposed regulation, EPA is proposing to allow any state or federally required cleanup that begins prior to the effective date of the final coal ash rule to be completed. The cleanup would of course need to be performed in accordance with the respective order th
Slide 20: Dike Construction Before Failure
Dike Construction Before Failure
Slide 21: New Perimeter Dike
New Perimeter Dike LANDFILLED ASH EARTHEN BERM FOUNDATION IMPROVEMENTS WORKING PLATFORM SANDY SILT TO SILTY SAND HYDRAULICALLY PLACED ASH LOPE PROTECTION
Slide 22: Aerial View of Impoundment
Aerial View of Impoundment CHURCH SLOUGH BERKSHIRE SLOUGH (WEST EMBAYMENT) (NORTH EMBAYMENT) SWAN POND ROAD PLANT INTAKE CHANNEL CLOSED DREDGE CELL SWAN POND CIRCLE ROAD CLOSED ASH POND DIKE C EMORY RIVER STILLING POND
Slide 23: Schedule for Implementation
Schedule for Implementation
Slide 24: Next Steps
Next Steps • River System Sampling and Analysis Plan – Characterize ash – Assess impacts to human health – Assess impacts to ecosystems – Continued monitoring after clean‐up – Will be posted to website end of May • Additional Comment Period of at least 30 days – Action Memorandum (May 19 – June 18)
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