TVA CCR Pond Closures Shane Harris, PMP and Nick McClung, PE 3/20/18
Highlights CCR Program Strategic Approach National Environmental Policy Act Post Closure Care Closure Cases John Sevier Bottom Ash Pond – Closure by Consolidation Colbert Ash Pond 4 – Closure in Place TVA CCR Pond Closures | 2
CCR Strategic Approach 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 . Closure of Wet CCP Facilities Dry • Types of Ponds: Storage o Ash Ponds Closure of Wet CCP Facilities o Chemical Ponds Water Treatment & o Dredge Cells Management o Gypsum Ponds Wet-to-Dry CCP Process Conversion • Good Alignment with CCR Rule Compliance CCP Facility Stabilization / Remediation TVA CCR Pond Closures | 3
National Environmental Policy Act (NEPA) 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. TVA CCR Pond Closures | 4
Programmatic NEPA - EIS TVA CCR Pond Closures | 5
Site Specific NEPA - EA • 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. TVA CCR Pond Closures | 6
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 TVA CCR Pond Closures | 7
John Sevier Fossil (JSF) Bottom Ash Pond (BAP)– Closure by Consolidation TVA CCR Pond Closures | 8
JSF BAP – Stilling Pond TVA CCR Pond Closures | 9
JSF BAP – Water Decanting • 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 . TVA CCR Pond Closures | 10
JSF BAP – Stilling Pond Removal of Fly Ash from Stilling Pond TVA CCR Pond Closures | 11
JSF BAP – New Dike Clay being placed for division of closed in place portion from the removed portion. TVA CCR Pond Closures | 12
JSF BAP – Before Closure TVA CCR Pond Closures | 13
JSF BAP – Preparation for Liner TVA CCR Pond Closures | 14
JSF BAP – Liner Placement TVA CCR Pond Closures | 15
JSF BAP – Closure Complete TVA CCR Pond Closures | 16
COF Ash Pond 4 – Closure in Place History and operation 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. TVA CCR Pond Closures | 17
COF Ash Pond 4 –Closure in Place Highlights • Bottom ash relatively free draining • Good soil source close by • Only half of pond (52 acres) held water Hard Spots • Seismic improvements needed • Sump flows from plant continue • Creek adjacent to pond • “Phantom” oil and grease • Creating appropriate grades over long distances TVA CCR Pond Closures | 18
COF AP4 Closure – Seismic Remediation 4100 Manitowoc Crane 4 gang auger DMM Wall TVA CCR Pond Closures | 19
COF Ash Pond 4 – Sump Flow Re-route New sump CYROP discharge point into CYROP New discharge line To Plant Previous discharge point Previous Sump discharge point into pond To Plant TVA CCR Pond Closures | 20
COF Ash Pond 4 – Cane Creek Close proximity to Cane creek was not only a physical constraint but diligence to prevent any fuel or oil releases was a constant threat. Creek less than 50’ from toe in Widening of working platform some areas and revetment TVA CCR Pond Closures | 21
COF Ash Pond 4 – Water handling Water quality • 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. TVA CCR Pond Closures | 22
COF Ash Pond 4 – Closure Grades TVA CCR Pond Closures | 23
COF Ash Pond 4 – Pore water readings Initial 3’ draw down 460.00 COF_P4_PZ1 455.00 COF_P4_PZ11 450.00 COF_P4_PZ14 445.00 COF_P4_PZ15 440.00 COF_P4_PZ4 435.00 Closure Construction COF_P4_PZ7 430.00 COF_P4_PZ9 COF_PZ4_16S TVA CCR Pond Closures | 24
Post-Closure Care Geotechnical • Maintenance and Groundwater Monitoring Instrumentation Liner Care TVA CCR Pond Closures | 25
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