NCS000546_Contingency Outfall Plans for Spillway Projects_20151112

From: Chernikov, Sergei
To: Hartfield, Ross Evan; Randall, Mike
Cc: Khan, Zahid; Poupart, Jeff
Subject: RE: Contingency Outfall Plans for Spillway Projects at Allen
Date: Thursday, November 12, 2015 10:19:38 AM
Attachments: imaae001.ioa
Ross,
The DWR has no objections against the proposed project provided that the following
conditions are met:
1) During the pumping, the facility shall conduct weekly monitoring for the
following parameters: total arsenic, total selenium, total mercury (method
1631 E), total chromium, total lead, total cadmium, total copper, total zinc, and
total dissolved solids (TDS).
2) All other terms and conditions of the existing permit shall be met.
3) The water quality standards in the receiving stream shall not be contravened.
4) The facility shall continuously monitor TSS concentration and the dewatering
pump shall be shutoff automatically when the limits are exceeded. The
pumping is allowed to continue if interruption might result in a dam failure or
damage.
Best regards,
Sergei
Sergei Chernikov, Ph.D.
Environmental Engineer II
Complex NPDES Permitting Unit
Tel. [phone]
Fax: [phone]
1617 Mail Service Center, Raleigh, NC 27699-1617
Express Mail: 512 N. Salisbury St., Raleigh, NC 27604
From: Hartfield, Ross Evan [maiIto: Ross. Hartfield @duke-energy.com]
Sent: Tuesday, October 27, 2015 3:46 PM
To: Chernikov, Sergei <[e-mail]>; Randall, Mike <[e-mail]>
Cc: Khan, Zahid <[e-mail]>
Subject: Contingency Outfall Plans for Spillway Projects at Allen
Sergei and Mike,
Attached are drawings for two planned projects at Allen that are designed to address deficient riser
structures in the retired and active ash basins and to repair signs of aging in the outfall pipes of the

retired and active ash basins. Both riser structures will be abandoned, and alternative spillways will
be installed. In the course of installed the alternate spillways in both of these ash basins, water level
management will play a key role. To start, it is planned that the water levels (at least in the active ash
basin) will be sufficiently lowered to provide safe and practical access to the work area and to
provide sufficient freeboard during critical work activities. Because of unpredictable plant operations
and precipitation, it is difficult to say if the estimates of freeboard will be sufficient for periods of
critical work activities, so I am proposing some contingencies for your consideration and approval.
Retired Ash Basin:
This project will require water management before and during construction. To allow abandonment
of the existing outfall structure, we are requesting to be allowed to pump the inflow of water, which
would normally flow into the riser structure and out stormwater outfall SW015, into cell 3 of the
active ash basin. It is estimated that the pumping would be sustained for 2-3 weeks. Running a pipe
(for pumping purposes) to overland to place adjacent to SWO15 would be impractical due to the
railroad lines that run in between the riser structure and the outfall.
Active Ash Basin:
Because we plan to lower the water level of the active ash basin before construction, "pumping
around" the construction area is a planned contingency should a large precipitation event occur or
plant operations provide more input to the active ash basin that exceeds our estimate of sufficient
freeboard. To allow for such a contingency while work is being conducted on the riser structure, new
spillway, or NPDES outfall 002, we ask to be able to pump any excess water from the active ash basin
to the retired ash basin, which will then discharge from stormwater outfall SW015. If we need to
employ this contingency plan, we estimate that the pumping would be needed for 1-2 weeks.
Running a pipe (for pumping purposes) overland to place adjacent to NPDES outfall 002 would be
impractical because it would have to cross the road and therefore block access to the work area.
If you have any questions, concerns, or comments regarding this project, please feel free to contact
me. I look forward to hearing from you.
MI
Ross E. Hartfield
Environmental Specialist 2 1 EHS CCP Compliance and Permitting
526 South Church Street I EC13K I Charlotte, NC 28202
Office: 980 373 6583
Cell: 225 2813971
Fax: [phone]
Ross. HartfieldCcDduke-energy.com