NC0050342_Authorization to Construct_20030325

NPDES DOCUHENT SCANNING COVER SHEET
NPDES Permit:
NC0050342
Muddy Creek WWTP
Document Type:
Permit Issuance
Wasteload Allocation
Authorization to Construct (AtC)
-., Y
Permit Modification
Complete File - Historical
Engineering Alternatives (EAA)
Correspondence
Owner Name Change
Instream Assessment (67b)
Speculative Limits
Environmental Assessment (EA)
Document Date:
March 25, 2003
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1tAR-25-2003 TUE 11:37 AM HAZEN SAWYER
FAX NO 7043573152 P. 01
QF 4Michael !. rasley, l,ovemor
19 William G. Russ Jr., Secretary
Q. �— n ;1 - North Carolina Department of Environment and Natural Resources
U /� !/If Gregory J Thorpe, Ph.D.
/ Acting Director
1 rC Division Of Water Quality
Ar'(
Mr. Michael Parker
Hazen and Sawyer
4944 Parkway Plaza Blvd., Suite 375
Charlotte, North Carolina 28217
January 17, 2002
Subject: Winston-Salem Muddy Creek WWTP
Dechlorination I:acility Mixing Improvements
Dear Mr. Parker,
Thank you for consulting with the Division prior to starting construction on the dechlorination facilities
at the Winston-Salem Muddy Creek WWTP. The Division hereby grants your request. An Authorizations
to Construct is not required for the project proposed in your December 18, 2001 letter. If the projects
expands beyond the scope outlined in this letter an Authorization to Construct may be required.
The Division request that after construction is complete that the attached Engineering Certification be
returned to the Division at the address listed on the certification. The Division will then update the
Muddy Creek WWTP's permit during the next scheduled permit renewal.
If you have any questions, please do not hesitate to call me at 919-733-5083 x508
JAN ?CZ
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5incerely,
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Michael J. Myers
Post -it" Fax Note 7671
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Customer Service
1 800 623.77.18

HAZEN AND SAWYER
Environmental Engineers & Scientists
December 18, 2001
Mr. Michael Myers
NC DENR — Division of Water Quality
1617 Mail Service Center
Raleigh, NC 27699-1617
Re: Winston-Salem Muddy Creek WWTP
Dechlorination Facility Mixing Improvements
Dear Michael:
Hazen and Sawyer, P.C.
4944 Parkway Plaza Blvd.
Suite 375
Charlotte, NC 28217
704 357-3150
c Fax: [phone]
c
.141:7:)5 z" ,9
I am writing with regard to the Dechlorination Facility Mixing Improvements
project proposed for the Winston-Salem Muddy Creek WWTP. The project will
provide an oxidation-reduction potential (ORP) analyzer and a mixing chamber to
optimize sodium bisulfite feed associated with the dechlorination process
currently utilized for the plant effluent flow.
A remote dechlorination facility located on Frye Bridge Road currently feeds
sodium bisulfite directly into the existing Muddy Creek WWTP 66" outfall line to
dechlorinate the treated effluent. The plant consistently meets its chlorine limit of
28 µg/L, but the current control strategy does not allow adjustment of the sodium
bisulfite dose setpoint, and overfeeding can occur during low flow conditions. The
current control strategy is configured to flow pace sodium bisulfite in accordance
with plant effluent flow rate via a remote 4-20 mA signal.
The proposed improvements include installation of an ORP analyzer that will
provide an output signal to the existing programmable logic controller (PLC) to
adjust the sodium bisulfite dose periodically. The sodium bisulfite feed rate will
continue to be flow -paced continuously during these intervals. The automatic
adjustment of dose will refine the sodium bisulfite demand as effluent flow
characteristics change, providing chemical cost savings to the plant while still
complying with its chlorine limit. Additionally, a mixing vault will be constructed
upstream of the proposed ORP analyzer to enhance mixing of sodium bisulfite
into the plant effluent.
Hazen and Sawyer, on behalf of the City of Winston-Salem, requests that no
modification be required to the existing operating permit for the Muddy Creek
WWTP due to the proposed improvements described above and that an
authorization -to -construct (ATC) not be required. This request is made
considering that flow pacing will continue to be the primary control mechanism
New York, NY • Armonk, NY • Upper Saddle River, NJ • Raleigh, NC • Charlotte, NC • Vienna, VA • Hollywood, FL • Boca Raton, FL • Fort Pierce, FL • Jupiter, FL • Miami, FL • Bogota, D.E. Colombia

utilized to feed sodium bisulfite, but that the ORP analyzer will periodically adjust
the dose setpoint to optimize chemical usage.
Please provide Hazen and Sawyer with written confirmation that permit
modification and subsequent ATC is not required. Should you need additional
information to facilitate your review, please contact me at [phone]. Thank
you for your consideration of this request.
Sincerely,
H ZEN AND SAWYER P.C.
Michael D. Parker, P.E.
Principal Engineer
Cc: NC DENR — Winston-Salem Branch
Stan Webb — City of Winston-Salem
Chris Shamel — City of Winston-Salem
Jim Struve — Hazen and Sawyer
File