NC0085359_Comments_20201230

Public Works
4600 Goldmine Rd
Monroe NC 28110
Union County
1T7042891434. RECEIVED
• • ment
www.unioncountync.gov DEC 3 0 2020
EST. 1842
NCDEQIDWR/NPDES
December 21, 2020
Mr.Mike Montebello
Water Quality Permitting Section—NPDES
Division of Water Resources
North Carolina Department of Environmental Quality
1617 Mail Service Center
Raleigh,NC,27699-1617
RE: Union County Public Works
Twelve Mile Creek Water Reclamation Facility
NPDES Permit Renewal,Permit No.NC0085359
Dear Mr.Montebello,
Union County Public Works Department(UCPW)received the Draft National Pollutant Discharge
Elimination System(NPDES)permit for our Twelve Mile Creek Water Reclamation Facility(WRF)on
December 7,2020. We have reviewed our draft permit and wish to provide the following comments to the
Division of Water Resources(DWR).
1. On the supplement to the cover sheet,the description of the facility infrastructure is inaccurate.The
following list of components is an accurate description of the WRF infrastructure:
• Mechanical Bar Screens
• Influent Pump Station with Standby Generator
• Vortex Grit Tanks
• Carbon Odor Control Facility
• Biological Nutrient Removal(BNR)Distribution Box
• Four(4)BNR Basins with anaerobic, anoxic and aerobic zones
• Blower Building with Standby Generator
• MLSS Distribution Box
• Sodium Aluminate Storage and Feed Facilities for Chemical Phosphorus Trim
• Four(4)Final Clarifiers
• Three(3)Disc Filters
• One(1)UV Disinfection Facility
• Cascade Post Aeration
• Thickening/Dewatering Facility(two(2)gravity belt thickeners and two(2)belt filter
presses)
• Four(4)Aerobic Digesters with Jet Aeration
• 2-Stage Wet Scrubber Odor Control Facility
• Main Plant Standby Generator
Additionally,please update the treatment unit description in the Fact Sheet table of Basic Facility
Information.
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2. Please update the permitted flow in the Fact Sheet table of Basic Facility Information to remove the
6 mgd plant capacity.
3. Revision to Title Header: The title header of A.(3.)should be modified to reflect a design flow of
12 mgd and not 10 mgd. The header should be revised as follows:
EFFLUENT LIMITATIONS AND MONTIORING REQUIREMENTS [12.0 MGD]
4. WER Confirmation Provision Section A.(8): The County conducted a Water Effect Ratio(WER)
study for copper and zinc in 2005/2006. Section A.(8)needs to be updated to change"silver"to zinc."
The Fact Sheet documents that a WER study for copper and zinc was conducted.
5. Effluent Limitations and Monitoring Requirements(A.(1),A.(2),and A.(3))—Frequency of
monitoring for total nitrogen and phosphorus: The draft permit indicates a change in the frequency of
monitoring for total nitrogen and phosphorus from"monthly"to"weekly"on all three effluent limits
pages. Our current permit requires monthly monitoring for total nitrogen and phosphorus. We believe
that this change is in error,as page 11 of the Fact Sheet does not provide a basis for the increased
monitoring frequency for these two parameters. Please revise the monitoring requirements for
nitrogen and phosphorus from a weekly requirement to a monthly requirement per our current permit.
If you have any questions regarding any of the NPDES permit renewal application materials,please
contact me at(704)296-4215 or [e-mail].
Sincerely,
(Log— 4t(14
Andrew Neff,PE
Water and Wastewater Division Director
cc:
Bart Farmer, Union County Public Works, Water Reclamation Facilities Superintendent
Jonathan Jordan,Union County Public Works, Supervisor Twelve Mile Creek WRF
Mary Sadler,PE,Hazen and Sawyer
Jim Struve, PE, Hazen and Sawyer
et Co&
yo9 1 Q Page 2
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