1812_DukeMarshall_BiweeklyUpdate_FID1624574_20211014

Duke Energy Carolinas LLC, Marshall Steam Station
October 14, 2021
NCDEQ Division of Waste Management (DWM) Solid Waste Section Marshall Steam Station Bi-Weekly Update
September 30 through October 14, 2021
Below is the bi-weekly summary for Marshall Steam Station Solid Waste facility and project activities, regulatory
submittals and approvals, and upcoming items.
Facility and Project Activities:
1) General:
• Site -wide water level sweep conducted on 9/30 to support groundwater level evaluation for the Q3
Industrial Landfill No.1 Groundwater Conditions Quarterly Report.
2) Dry Ash Landfill (1804-INDUS-1983):
• No general facility updates.
Phase I:
• Continued excavation, with approximately 134,944 cubic yards (CY) of coal combustion residuals
(CCR) excavated to date. The estimated total CCR to be excavated from this facility is 522,000 CY.
• Some of the original soil cap continues to be reserved for interim cover as part of construction of ILF
Phase 2.
Phase II:
• A new stability feature design was provided to NCDEQ for the south finger of the landfill; the new
design would affect the current closure plan design under review by DWM.
3) FGD Landfill (1809-INDUS-2006):
• Completed semi-annual Q3 groundwater, surface water, and leachate sampling on 9/28/2021.
• No other general facility updates.
4) Industrial Landfill No.1 (1812-INDUS-2008
• Normal operations for Phase 1.
• Water levels in 26 piezometers and groundwater monitoring in the ILF area continue to be monitored.
o AECOM collected manual water level measurements and downloaded transducer data from
the 26 piezometer and well locations on 10/1/21 and 10/14/21.
o Transducer data and manual water level data indicate groundwater levels have started to
decrease.
ILF Phase 2, Cell 5:
• Blanket Underdrain Construction commenced on 9/20/21 and is expected to be complete 10/15/21.
o Continued excavation and dewatering for the construction of the blanket underdrain:
■ Excavated approximately 36,825 CY of material for the installation of the blanket
underdrain.
• Dewatering is ongoing with an average flowrate of approximately 6 gallons per
minute.
o Continued construction of the underdrain:
■ All underdrain underlying pipe has been installed as of 10/8/21.
■ Approximately 565 tons of 78 stone for the blanket drain has been placed.
■ Approximately 31.5 tons of 57 stone around underdrain piping has been placed.
■ Construction of the underdrain is expected to be completed by 10/15/21.
o Construction progress photos from 10/8/21 and 10/12/21 are available for DWM to
download on Duke Energy's FTP site.
• Abandonment of piezometer CLF21-16 and installation of piezometers CLF21-18, CLF21-19, CLF21-
20 occurred 10/9/21 and 10/10/21. Transducers were installed in the three new piezometers on
10/11/21.
• Subgrade installation (top of under drain 78 stone to bottom of clay liner) is expected to start on
10/15/21 and be completed by 10/29/21.
• Temporary pumps are proposed to be used during initial operations of the underdrain. Notification
will be provided to DWM for the use and timeframe of temporary pumps, prior to initial operations.
ILF Phase 2, Cell 6:
• Continued installation of the subgrade based on the approved design modifications.
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Duke Energy Carolinas LLC, Marshall Steam Station October 14, 2021
• Dewatering in the former ash basin finger within the footprint of Cell 6 is being maintained, with an
average flowrate of approximately 7 gallons per minute.
ILF Future Phases Area:
• Excavation of CCR has been suspended while construction of the underdrain in Phase 2, Cell 5
continues.
o To date, with the approximately 235,168 CY of CCR have been excavated. The estimated
total CCR to be excavated from this area is 1.5M CY.
• Dewatering of existing excavation rim ditches is being maintained.
5) Structural Fill (CCB0031):
• A new onsite soil borrow area to support the capping of the Structural Fill is planned to be developed for
Approximately 15 acres, southeast of the Structural Fill.
• A new stability feature design was provided to NCDEQ for the north ash basin finger below the Structural
Fill; the new design would affect the current closure plan design under review by DWM.
6) Leachate Basin
• The installation of the geosynthetic clay liner followed by the geo-membrane liner are anticipated to
begin installation on 10/20/21.
• Temporary pumps are proposed to be used during initial operations of the leachate basin in early 2022.
Notification will be provided to DWM for the use and timeframe of temporary pumps, prior to initial
operations.
7) MAR-152 Stormwater Redirect Project:
• Stormwater basin construction is complete.
• Wrapping up punchlist items and completing structural work around wet well structure and valve vault.
• Project completion expected by the end of October 2021.
8) Other Ash Basin Closure Protects:
• Continued ash basin dewatering, with current elevation of the pond at 776.0 NAVD 88.
• No other general closure project updates.
Regulatory:
• Duke Energy Received approval from DWM for piezometer abandonment and installations in footprint of ILF
Phase 2, Cell 5 on 10/5/2021.
• Duke Energy submitted the Dam Buffer Excavation Plan to Dam Safety on 10/8/21.
• DWM Site visit to observe construction of Cell 5 and the leachate basin is scheduled for 10/19/21.
• The Structural Fill Application for Permit Modification - Amended Closure Plan Response to Comments was
submitted to DWM on 8/19/21. To date, no comments or response has been received from DWM.
• The Dry Ash Landfill Phase II Application for Permit Modification - Amended Closure Plan was submitted to
DWM on 8/30/21. To date, no comments or response has been received from DWM.
Upcoming:
• A response to Condition #1 of the September 17, 2021 DWM letter will be submitted by October 15, 2021.
• A response to Condition #2 of the September 17, 2021 DWM letter will be submitted by early November
2021.
• The MAR-152 HCIC Soil Sampling Report is anticipated to be submitted to DWM early November 2021.
• The first Groundwater Conditions Quarterly Report for the Industrial Landfill No.1 will be submitted on or
before December 1, 2021.
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