NC0026611_Report_20240401

DocuSign Envelope ID: 266BB3B0-8687-4CD6-8883-5CECD5D2805A
ROY COOPER
Governor
ELIZABETH S. BISER
Secretary
RICHARD E. ROGERS, JR.
Director
Daniel Williams, Public Services Director
Town of Morehead City
1100 Bridges Street
Morehead City, NC 28557
Dear Mr. Williams:
NORTH CAROLINA
Environmental Quality
April 1, 2024
Subject: Review of CORMIX Model Results
Morehead City WWTP
NPDES Permit No. NCO026611
Carteret County
This letter provides a dilution factor and a revised reasonable potential analysis (RPA) for the Morehead City
WWTP (NC0026611). The Division received the "Modeling Report for Mixing Zone Analysis of Calico
Creek at the Morehead City, NC Wastewater Treatment Plant Outfall (NC0026611): Dilution Evaluation with
CORMIX Model" on December 22, 2023, from Tetra Tech on behalf of the Town of Morehead City.
The Division evaluated the dilution as predicted by the CORMIX model and established a chronic mixing
zone based on a dilution of 4.75:1 for chronic toxicants. This dilution was derived by averaging the "partially
submerged" results at nine (9) meters downstream. A revised RPA was performed based on effluent data from
February 2019 - February 2024 for nickel, copper, and zinc. As a result of the RPA, limits for nickel and zinc
were eliminated. The predicted concentrations for nickel and zinc are less than 50% of the allowable
concentration therefore no monitoring is required.
For copper, the revised RPA demonstrated reasonable potential to exceed the facility's allowable
concentrations based on state surface water standards, therefore monthly average and daily maximum limits
will remain in the permit. The whole effluent toxicity test requirement will be modified to a chronic test at
21 % effluent concentration in the permit modification/renewal.
The current NPDES permit expires on July 31, 2024, therefore these permit modifications will be included in
the permit reissuance and will require a public notice.
Should you have any questions about this review or NPDES permitting requirements, please feel free to contact
Kristin Litzenberger at [phone] / kistin.litzenberger(kdeq.nc.gov or Michael Montebello at
Michael.Montebellogdeq.nc. gov.
Respectfully,
Do'c'fu,Si-gne'Id by, A A
C464531431644FE...
Michael Montebello
NPDES Program Branch Chief
North Carolina Department of Environmental Quality I Division of Water Resources
512 North Salisbury Street 1 1617 Mail Service Center I Raleigh, North Carolina 27699-1617
NORTH CARCLINA
919.707.9000

DocuSign Envelope ID: 266BB3B0-8687-4CD6-8883-5CECD5D2805A
ec: NPDES Files [Laserfiche]
Town of Morehead City / Chuck Falls [[e-mail]]; Brandi Thomas [[e-mail]]
Tetra Tech / Hillary Yonce [[e-mail]]; Katie Elliott [[e-mail]]; Ellie Kremer
[ellie.kremer@tetratech. com]
Shealy Consulting / Laura Davis [[e-mail]]
McDavid Associates / David Gurley III [[e-mail]]; Tyndall Lewis [[e-mail]]
DWR / Derek Denard [[e-mail]]; Kristin Litzenberger [[e-mail]]; Nick Coco
[[e-mail]. gov]
WIRO / Tom Tharrington [[e-mail]]
REQ5 North Carolina Department ofEnvironmental Quality I Division ofWater Resources
512 North Salisbury Street 1 1611 Mail Service Center I Raleigh, North Carolina 27699-1611
NORTH CAROLINA 919.707.9000
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