NC0021717_Flow Meter Calibration Efforts_20220118

wI`K�S490 TOWN OF WILKESBORO
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• '•'. • P.O.Box 1056. 203 West Main Street
‘ se Wilkesboro,North Carolina 28697
www.wilkesboronc.org RECEIVED
°ppORATE- Phone [phone] • Fax [phone]
.I A N 1 9 2022
NCDEQ/DVR/NPDES
January 18, 2022
NC DEQ Winston-Salem Regional Office
450 West Hanes Mill Road, Suite 300
Winston-Salem, NC 27105
NC DEQ-DWR - Municipal NPDES Permitting
217 West Jones Street
Raleigh, NC 27603
Dear Mr. Lon Snider Environmental Regional Supervisor, Ms. Jenny Graznak Assistant
Environmental Regional Supervisor, and Mr. Michael Montebello, Supervisor- Municipal
Permitting,
We are writing to provide an update on the Cub Creek Wastewater Treatment Plant(WWTP) (Permit
Number NC0021717) flow monitoring calibration efforts, 2021 plant flow data, and the WWTP upgrade
process.
Flow Meter Calibration Efforts
In a virtual meeting on September 15, 2021, we discussed the plant's influent and effluent flow meter
discrepancies and highlighted our concerns that the effluent Parshall flume may not be accurately
measuring plant effluent flow. At that time, we presented findings that field measurements of the
existing Parshall flume at the WWTP suggested that there is an 8 percent difference between standard
dimensions and the measured dimensions of the Parshall flume. The dimensional difference is more
prominent in the upper portion of the fiberglass flume and closer to standard at the base of the flume.
Therefore, lower flows through the flume would be more accurately measured, while the margin of error
would increase at higher flows through the flume. Following this meeting, a plan was developed to
install temporary effluent flow monitoring as a way to validate our assumptions and to determine a
proper calibration curve for the Parshall flume
Temporary effluent flow measuring facilities were then installed and placed into service by Gavel &
Dorn Engineering, PLLC (Gavel & Dorn) on November 23, 2021. A Hach® submerged area velocity
flow meter was installed in a new manhole downstream of the existing effluent flow measuring structure
(i.e , effluent pipeline to the Yadkin River). The goal of this temporary metering is to develop a flow
correlation between the Parshall flume and temporary flow meter. Temporary flow monitoring has been
in place since November 23, 2021 and will continue through January 2022.
MIKE INSCORE KENNETH D.NOLAND JAMES K.BYRD NELLIE ARCHIBALD RUSSELL F.FERREE
Mayor Town Manager Town Clerk JIMMY HAYES Mayor Pro Tern
townmanager©wilkesboronc.org ANDREW"ANDY"SOOTS
Council Members

Due to below average precipitation and reduced flows from Tyson Foods in November and December
2021, effluent wastewater flows have been below normal during the period of temporary effluent flow
monitoring. At these lower flows, temporary metering has confirmed that the flume is providing reliable
measurements as originally believed. The Town initiated a brief instantaneous effluent flow on one
occasion, and we have found that at 11.8 MGD, the Parshall flume is over stating flow by 6 percent. At
this time, due to the lack of qualifying rain fall events, no conclusions can be made with respect to the
flume accuracy at higher flows due to the lower-than-normal flow conditions.
2021 Annual Average Effluent Flow
The Town of Wilkesboro's effluent self-monitoring for the calendar year January 2021-December 2021
indicate that the WWTP operated at 85.8 percent of the permitted capacity. The average flow was
calculated to be 4.206 MGD.
Proposed Upgrades to the WWTP
In May 2021, HDR Engineering Inc. of the Carolinas (HDR) completed a Preliminary Engineering
Report(PER), which evaluated options for upgrading and expanding the WWTP. This PER was
presented to the Town Council in June 2021. From this PER, the Town of Wilkesboro selected the
AquaNereda®aerobic granular sludge (AGS) process. The AGS process can achieve simultaneous
nitrification, denitrification, and phosphorus removal through a batch reactor process.
HDR is now proceedingwith the design of the proposed WWTP upgrade and expansion. In addition to
9 P P P9 P
expanding the WWTP, the Town of Wilkesboro is also actively seeking to reduce rainfall related inflow
and infiltration into the collection system as well as within the confines of Tyson's industrial facilities.
Provided that the 2021 annual average effluent flow was 4.206 MGD (85.8 percent of permitted
capacity), the PER has been completed, and that HDR is now proceeding with the development of
design documents, we are requesting that NC DEQ-DWR reevaluate and retract the sewer extension
moratorium. We have an immediate need for a sewer line extension, and your assistance is greatly
appreciated.
We would welcome the opportunity to discuss these items with you and can schedule a meeting at your
earliest convenience.
Sincerely,
V�
Kenneth Noland
Town Manager