DukeAsheville_DWR1964 BasinRequestApprovalLetter_FID1681498_20220527

ROY COOPER
Governor
ELIZABETH S. BISER
Secretary
Jessica Bednarcik
Senior Vice President
Environmental, Health & Safety
Duke Energy
526 South Church Street
Mail Code EC3XP
Charlotte, North Carolina 28202
NORTH CAROLINA
Environmental Quality
May 27, 2022
Subject: Asheville Steam Electric Plant
1964 Basin — Request to Leave Ash in Place
Dear Ms. Bednarcik:
On April 29, 2022, the North Carolina Department of Environmental Quality (DEQ) received a
request from Duke Energy to leave ash within the footprint of the 1964 Ash Basin due to the
impracticality of further removal and safety concerns (Email from Ashley Healy to Eric Smith
dated April 29, 2022 with attachments). It should be noted that neither DEQ nor Duke Energy has
quantified the exact amount of ash to remain and the term, de minimis, used in Duke Energy's
request, is subjective based on Duke Energy's estimates.
According to Duke Energy, the area in which the ash is located is an irregular, vertical to partially
sloped weathered fractured bedrock wall along the waste boundary of the eastern side of the 1964
ash basin, near the divider dike. Duke Energy stated that the following efforts have been made to
date to remove ash from the exposed bedrock area:
• Mechanical excavation has been performed, with an abundance of weathered rock and
large boulders removed. More rock than ash has been excavated to remove visible ash from
the wall surface and from within the crevasses of the weathered rock. Excavated rock has
and will remain within the waste boundary of the basin.
• Ongoing washing of the exposed bedrock area with pressurized water has occurred over
the period of April 17 through April 27, 2022. The latest washing occurred on April 27,
2022.
• Efforts towards clean closure continue, focusing on the lower, safely accessible areas of
the exposed fractured bedrock area and have been effective at removing nearly all of the
visible ash.
DQbiA North Carolina Department of Environmental Quality
E�� 217 West Jones Street 1 1601 Mail Service Center I Raleigh, North Carolina 27699-1601
NORTH CAHOI INA i
919,707,8600

Duke Energy also states that the following post -closure conditions will be met:
• The area will be backfilled with excavated in situ rock and soil with the post -closure grades
of this area being generally consistent with the surrounding elevations and graded towards
the west. The 1964 ash basin overall post -closure grades and conditions will allow for
construction of future infrastructure within the former ash basin footprint.
• Based on updated groundwater modeling for the upcoming 2022 Corrective Action Plan
Update submittal, the water table is predicted to be near the elevation of the floor of the
basin in this area (approximately 2000 ft. NAVD 88). Limited groundwater recharge has
been observed during dewatering in the area. The ash left in place would effectively be
above the water table.
Based on the information provided, DEQ concurs that further removal of the ash appears to be
technically impractical and potentially unsafe. DEQ recommends that groundwater levels in this
area continue to be monitored to ensure that the water table remains below any remaining ash.
If any of the post -closure conditions change such as an unexpected rise in water levels, Duke
Energy shall inform DEQ of the changes and DEQ shall have the right to determine if any further
actions are required based on the nature of those changes.
If you have any other questions, please contact Ted Campbell (Asheville Regional Office) at (828)
296-4500 or Eric Smith (Central Office) at [phone].
Sincerely,
Sushma Masemore, P.E.
Assistant Secretary for Environment
cc: Ted Campbell — WQROS Asheville Regional Office (electronic)
Ed Sullivan — Duke Energy (electronic)
John Toepfer — Duke Energy (electronic)
Scott Davies — Duke Energy (electronic)
Edward Mussler — DWM — Solid Waste Section (electronic)
D E Q North Carolina Department of Environmental Quality
217 West Jones Street 1 1601 Mail Service Center I Raleigh, North Carolina 27699-1601
NORTH CAHOI.INA �
nema wofEeNmn tsiQ­i 919,707,8600