3620_DukeAllen_SSLF_DWM_DewateringCommentsandResponses_FID_20230605

Moutos, Sarah
From: Murphy, Courtney <[e-mail]>
Sent: Monday, June 5, 2023 4:10 PM
To: Moutos, Sarah
Cc: Osborn, Claire J; Russ, Jordan A; Healy, Ashley Lisbeth; Hardin, Tyler; Witt, Kimberlee;
Stanley, Sherri; Mussler, Ed; Costner, Brandy F
Subject: RE: [External] Duke Energy-Allen_3620-INDUS SSLF_Well Installation REQUEST FOR
APPROVAL
Attachments: WS0300028_20230602_PERM_MOD.docx.pdf
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Sarah —
See attached recovery well permit modification received from DWR last Friday (modified from original permit issued in
December 2022 for the pilot section of the SSLF dewatering system). For clarity, note that although the attached permit
mod mentions 53 dewatering wells, we only anticipate 41 additional dewatering wells (12 observations water level PZs
are also planned and DWR added them together when they issued this permit mod).
I have provided responses to your questions below in red. If the Section would still like to further discuss any of those or
additional questions, just let me know the Section's availability this week, and I'll set something up. Drill crews and
equipment are standing by pending necessary approvals for this scope.
Thank you,
Courtney Uk Murphy, PG
Lead Environmental Specialist
EHS Waste & Groundwater Programs
Courtnev.Murohv(@duke-energv.com
Office: 704.382.7171
Mobile: [phone]
From: Moutos, Sarah <[e-mail]>
Sent: Thursday, June 1, 2023 10:07 AM
To: Murphy, Courtney <[e-mail]>
Cc: Osborn, Claire J <[e-mail]>; Russ, Jordan A <[e-mail]>; Healy, Ashley Lisbeth
<[e-mail]>; Hardin, Tyler <Tyler.Hardin @duke-energy.com>; Witt, Kimberlee
<[e-mail]>; Stanley, Sherri <[e-mail]>; Mussler, Ed
<[e-mail]>; Costner, Brandy F <[e-mail]>
Subject: RE: [External] Duke Energy-Allen_3620-INDUS SSLF_Well Installation REQUEST FOR APPROVAL

Good morning Courtney,
Thank you for your email and the attached figure showing the proposed locations for the existing dewatering system
expansion to support ash basin closure and SSLF construction activities. I had a few questions after reviewing the figure.
It appears the majority of the proposed extraction wells, monitoring wells, and piezometers are going to be installed in
the footprint of the SSLF. How long will this dewatering system expansion be in place? Currently being modeled (will be
shown in forthcoming tech memo companion document to SSLF PTC Mod request), but anticipate at least 9 months.
Will the system expansion still be there when the SSLF is ready for liner installation? No, the current plan is to
decommission the dewatering system once the SSLF construction drain becomes operational and before liner
construction.
Is this assisting with achieving groundwater separation for construction or is this supporting corrective action for site
groundwater? This dewatering system is not designed specifically to support groundwater corrective action, although
the extracted water will be captured and treated before discharge via a permitted NPDES WW outfall, similar to current
groundwater corrective action at the Allen site. This SSLF dewatering system will have a dual-purpose to facilitate ash
excavation within and just upgradient of the SSLF footprint and to further expedite groundwater level decline in the
vicinity of the SSLF (expedited quicker than what the proposed SSLF construction drain is expected to do alone). This
dewatering system is a key component to staying on -track with the overall Allen ash basin closure schedule and
respective regulatory deadlines. Is the footprint of the SSLF changing because of the proposed location of the system
expansion? No, the SSLF footprint is not changing.
I would imagine the Section would like to discuss these and additional questions with you once everyone gets to review
the permit mod and this request. We will reach out to schedule a time with you to discuss and get further clarification.
Regards,
Sarah
Sarah M Moutos
Environmental Program Consultant
Division of Waste Management — Solid Waste Section
North Carolina Department of Environmental Quality
919-707-8287 (phone and fax)
Sarah. Moutos(&dea. nc.00v
Physical Address and Fed Ex: 217 West Jones Street, Raleigh, NC 27603
Mailing Address and Postal Mail: 1646 Mail Service Center, Raleigh, NC 27699-1646
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6eparhnen141 Enrlrwin�enl�E QuaiiiY\
NCDEO: Solid Waste Section
NCDEQ; Solid Waste Section Financial Assurance (Effective July 1, 2020. REVISED RULES)
Pleas note my email address has changed to Sarah.MoutosOdeq.nc. ov , Please udate my point of contact information.
Email correspondence to and from this address is subject to the North Carolina Public Records Law and may be disclosed to third parties.
From: Murphy, Courtney <[e-mail]>
Sent: Wednesday, May 31, 2023 7:50 AM
To: Moutos, Sarah <[e-mail]>

Cc: Osborn, Claire J <[e-mail]>; Russ, Jordan A <[e-mail]>; Healy, Ashley Lisbeth
<[e-mail]>; Hardin, Tyler <[e-mail]>; Witt, Kimberlee
<[e-mail]>
Subject: [External] Duke Energy-Allen_3620-INDUS SSLF—Well Installation REQUEST FOR APPROVAL
Importance: High
CAUTION: External email. Do not click links or open attachments unless verified. Report suspicious emails with the Report Message
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Ms. Moutos —
As mentioned most recently on the monthly call yesterday, see attached well schematic and site figure that provide well
construction details and show proposed locations of 61 extraction wells and 12 water level observation piezometers that
Duke Energy is planning to install as part of an existing dewatering system expansion to support ash basin closure and
SSLF construction activities at the Allen Steam Station. As shown on the attached Site Figure, the proposed east and
west expansions of the dewatering system would be primarily located within the future SSLF footprint, although there
are some eductor (extraction) wells on both the east and west sides and one observation piezometer on the east side
that appear outside the SSLF footprint.
Please note that we have submitted similar information to NCDEQ DWR as required and requested a modification to the
existing GW22W water withdrawal permit for the pilot section. The dewatering contractor is available to begin well
installations asap pending receipt of the DWR permit and your approval of the well installations with respect to the SSLF.
Thank you in advance for your consideration of this request, and don't hesitate to reach out to me via email or mobile
number noted below if you have questions or need additional information.
Respectfully,
Courtney W- Murphy, PG
Lead Environmental Specialist
EHS Waste & Groundwater Programs
[e-mail]
Office: 704.382.7171
Mobile: [phone]
Email correspondence to and from this address may be subject to the North Carolina Public Records Law and may be disclosed to third parties by an authorized
state official.