TVA CCR Pond Closures Shane Harris, PMP and Nick McClung, PE - - PowerPoint PPT Presentation

TVA CCR Pond Closures

Shane Harris, PMP and Nick McClung, PE 3/20/18

Highlights

Strategic Approach National Environmental Policy Act Post Closure Care

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CCR Program Closure Cases

John Sevier Bottom Ash Pond – Closure by Consolidation Colbert Ash Pond 4 – Closure in Place

CCR Strategic Approach

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Closure of Wet CCP Facilities

• Types of Ponds:
• Ash Ponds
• Chemical Ponds
• Dredge Cells
• Gypsum Ponds
• Good Alignment with CCR

Rule Compliance

Dry Storage Closure of Wet CCP Facilities Water Treatment & Management Wet-to-Dry CCP Process Conversion CCP Facility Stabilization / Remediation

In order to meet the commitment to convert all wet CCR operations to dry operations, GC established the following 5-step strategy, first prioritizing stability of facilities and then progressing to dry CCR processes.

National Environmental Policy Act (NEPA)

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All federal agencies are to prepare detailed statements assessing the environmental impact of and alternatives to major federal actions significantly affecting the environment.

• Three documents to comply – Environmental

Impact Statement (EIS), Environmental Assessment (EA), and Categorical Exclusion (CE).

• NEPA requires public comment.
• EIS process is about 3 years to complete.

Programmatic NEPA - EIS

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Site Specific NEPA - EA

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• Performed 10 EAs for ponds across TN, KY and

AL.

• Closure-in-place was the selected option.
• Held 10 public meetings for each closure.
• Total time for EIS and EA ~1.5 years.
• TVA is currently performing supplemental EAs for

some of these initial documents.

CCR Rule-Closure Performance Standards

“both methods of closure (i.e., clean closure and closure with waste in place) can be

equally protective”- CCR Rule p.21412

• CCR unit must be closed in a manner that will

control post-closure infiltration

• CCR unit must be closed in a manner that will

preclude the probability of impounding water

• CCR unit must be closed in a manner that will

provide for slope stability

• CCR unit must be closed in a manner that will

minimize the need for further maintenance

• CCR unit must be closed in shortest amount of

time consistent with generally accepted engineering practices

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John Sevier Fossil (JSF) Bottom Ash Pond (BAP)– Closure by Consolidation

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JSF BAP – Stilling Pond

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JSF BAP – Water Decanting

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• Water quality for NPDES permit was met

for duration of the project.

• All water was pumped through the

spillways to Outfall 006.

• Discharge was limited to 10 Million

Gallons per Day.

• Closely monitored for total suspended

solids during decanting of pond water. Also monitored TSS of Holston River (discharge waterway).

• Flow rate was monitored with a flow

gauge.

• Other parameters in the NPDES permit

were monitored weekly when the BAP was discharging.

JSF BAP – Stilling Pond

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Removal of Fly Ash from Stilling Pond

JSF BAP – New Dike

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Clay being placed for division of closed in place portion from the removed portion.

JSF BAP – Before Closure

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JSF BAP – Preparation for Liner

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JSF BAP – Liner Placement

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JSF BAP – Closure Complete

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COF Ash Pond 4 – Closure in Place

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Placed in service in the 1970’s. Initially received both fly and bottom ash but once the baghouse was added only bottom ash was sluiced to the pond. Upstream construction done in the early 1980’s. Approximately 25,000 tons per year of bottom ash was sluiced to the pond. Estimated 3.2 MM tons of ash in the pond.

History and operation

COF Ash Pond 4 –Closure in Place

• Bottom ash relatively free draining
• Good soil source close by
• Only half of pond (52 acres) held water

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Highlights Hard Spots

• Seismic improvements needed
• Sump flows from plant continue
• Creek adjacent to pond
• “Phantom” oil and grease
• Creating appropriate grades over long

distances

COF AP4 Closure – Seismic Remediation

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4100 Manitowoc Crane 4 gang auger DMM Wall

COF Ash Pond 4 – Sump Flow Re-route

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CYROP New discharge line Previous discharge point Previous Sump discharge point into pond New sump discharge point into CYROP

To Plant To Plant

COF Ash Pond 4 – Cane Creek

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Creek less than 50’ from toe in some areas Widening of working platform and revetment Close proximity to Cane creek was not only a physical constraint but diligence to prevent any fuel or oil releases was a constant threat.

COF Ash Pond 4 – Water handling

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• Still had to meet NPDES permit requirements

during de-canting operations.

• PH, TSS, oil & grease without the benefit of

large volume of water.

• Utilized a lake tank. 600,000 gallon capacity
• Batched water. Once parameters were met,

pumped to CYROP.

• First third took minimal effort. As we got

lower, increased additives were needed.

• Operation went on for most of the duration of

project.

Water quality

COF Ash Pond 4 – Closure Grades

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COF Ash Pond 4 – Pore water readings

430.00 435.00 440.00 445.00 450.00 455.00 460.00 COF_P4_PZ1 COF_P4_PZ11 COF_P4_PZ14 COF_P4_PZ15 COF_P4_PZ4 COF_P4_PZ7 COF_P4_PZ9 COF_PZ4_16S Initial 3’ draw down Closure Construction

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Post-Closure Care

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• Maintenance and

Liner Care Groundwater Monitoring Geotechnical Instrumentation