NC0023906_Wasteload Allocation_20220128

• RECEIVED
WILSON JAN 28 2022
NORTH C A R O L I N A NCDEQ/DWPJNPDES
January 25, 2022
Mr. Jeff Poupart
Supervisor, Wastewater Branch Unit
North Carolina Division of Water Resources
1617 Mail Service Center
Raleigh, NC 27699-1617
Re: Water Quality Modeling Approach to Support Increased Wasteload Allocation
Hominy Creek Water Reclamation Facility (NC0023906)
City of Wilson
Dear Mr. Poupart:
In August 2021, the City's consultant informally reached out to the Division of Water Resources (DWR) to
request speculative limits for an expansion of the City's Hominy Creek Water Reclamation Facility (WRF)
from 14 to 20.7 million gallons per day (mgd). Our Hominy Creek WRF discharges to Contentnea Creek,
a Class C Sw-NSW water in the Neuse River basin. A meeting (via Teams call)was held with City staff,
Hazen and Sawyer, Water Environment Consultants, and DWR staff on December 3, 2021 to discuss our
request for an expanded discharge.
The supplemental classification of swamp waters recognizes receiving streams that are characterized by
low velocity, are naturally more acidic, and have periodic excursions of naturally low dissolved oxygen
(DO). Contentnea Creek is 303d listed as a category 5 for benthos from the Wiggins Mill Reservoir to the
confluence with Nahunta Swamp based on a"Fair" rating from a benthic sample collected in 1996. The
stream is also listed as category 3a for DO, or not sufficient data for a designated use support
determination.
Per discussions with DWR staff, DWR does not have a methodology to assess compliance for receiving
streams classified as swamp waters. Unlike neighboring states, North Carolina does not have a
de minimis threshold for DO. However, based on our recent discussions with DWR staff, it is our
understanding that DWR will consider an expanded discharge to Contentnea Creek contingent upon a
modeling approach that considers the naturally low DO condition of the receiving stream. DWR staff
requested that we memorialize our modeling approach prior to proceeding with a modeling study for our
proposed expansion.

Our consultant team has conducted a preliminary review of our existing and proposed expanded
hydraulic discharge into Contentnea Creek. A defining tenet of our approach is that our existing Hominy
Creek WRF discharge is not causing a decline in receiving stream water quality. A preliminary model
demonstrated that our existing discharge of 14 mgd resulted in an unmeasurable reduction in DO
compared to a baseline condition. The baseline condition excluded our WRF discharge. The preliminary
model at 14 mgd also demonstrated an increase in stream velocity and reaeration downstream.
Preliminary model runs using our proposed discharge of 21 mgd (using 5 mg/L BOD and 1 mg/L
ammonia effluent limits) also demonstrated improved downstream velocity and reaeration concurrent with
an unmeasurable change in DO compared to the baseline condition.
We respectfully request that DWR staff consider permitting our expansion to Contentnea Creek if a
calibrated and verified model demonstrates similar findings to our preliminary model results (e.g., the
proposed expansion will not cause a measurable reduction in DO during critical conditions). We request a
meeting with DWR to discuss our approach, as we would like to commission our consultants to proceed
with the modeling effort. Our annual average WRF flow is approaching 80 percent of our maximum month
design capacity. Our consultant team will develop a study plan in coordination with the Modeling and
Assessment Branch. We are anticipating stream data collection this summer of 2022 to assess the warm-
weather condition.
Sincerely,
////444,4y i°44,314
Barry Parks
Director of Water Resources
City of Wilson
cc: Julie Grzyb, Division of Water Resources
Karen Higgins, Division of Water Resources
Mike Montebello, Division of Water Resources
David Hill, Division of Water Resources
Jeff DeBessonet, PE Water Environment Consultants
Matt Goodrich, PE, Water Environment Consultants
David Wankmuller, PE, Hazen and Sawyer
Mary Sadler, PE, Hazen and Sawyer
Tony Sears, Deputy City Manager, City of Wilson
Jimmy Pridgen, Water Reclamation Manager, City of Wilson