20220398 Ver 3_Comment Response letter_20230301

C-AD0� C
Civil
Design
Concepts, PA
February 28, 2023
Ms. Chonticha McDaniel
NCDEQ - Division of Water Resources
401 and Buffer Branch
1617 Mail Service Center
Raleigh, NC 27699-1612
Re: Mitchell County Middle School
Project ID: DWR 223-0398
CDC Project No.: 12208
Dear Ms. McDaniel,
On behalf of the Mitchell County Middle School, we are pleased to submit the requested
additional information for NCDEQ review and approval. The comments from your email dated
January 27, 2023, are summarized below along with the project's associated responses (in blue).
1. Please add planting plan for the vegetative shelf on plan sheet C942. CDC — Information has
been added to C942.
2. We received the signed O&M agreement but no O&M Plan is provided. Please provide a
complete O&M plan for the wet pond. CDC — An O&M Manual has been completed and is
provided.
3. Please note that the Division's preferred method for dewatering the wet pond for
maintenance is pump. However, if a gate valve and drainpipe at the bottom of the outlet
structure are being proposed, we need to add extra measures to ensure proper water quality
protection for downstream surface waters while also allowing operational functions of the
stormwater treatment wet pond. Therefore, please either revise the dewatering method or
provide an O&M plan that also includes the following:
a) Please provide a locking system to restrict access to the handwheel located on the riser
platform. This will ensure only authorized personnel can open/close the gate valve and
such activities are recorded on the inspection/maintenance log. CDC — The valve has
been removed from the detail.
Mailing Address: P.O. Box 5432, Asheville, NC 28813
168 Patton Avenue Asheville, NC 28801 52 Walnut Street — Suite 9, Waynesville, NC 28786
Phone [phone] Fax [phone] Phone: [phone] Fax: [phone]

Mitchell County Middle School
February 28, 2023
Page 2
b) Please provide additional details on operation and maintenance of the gate valve such
as maximum time or duration needed to perform valve testing or maintenance, how often
valve testing/maintenance is required, how downstream outfalls will be monitored during
the test to ensure no excessive amount of pond -bottom water and/or sediment being
discharged to the downstream surface waters. CDC — The valve has been removed from
the detail. A note has been added that any dewatering must be made by a pump with a
floating inlet to minimize discharge of collected sediment.
c) Please also include inspection activities, date of inspection, and name of personnel
who perform the inspection to the record keeping section of the O&M plan. CDC — The
inspection details have been outlined in the O&M Manual.
Thank you for your assistance with this project. If you should have any questions or comments
regarding this submittal, please do not hesitate to contact our office.
Sincerely,
Michael Cain, P E.
Civil Design Concepts, P.A.
[e-mail]