NC0026441_Correspondence_20240703

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Governor
ELIZABETH S.BISER '+wi a nw ar
Secretary
RICHARI)E.ROGERS,JR. NORTH CAROLINA
Director Environmental Quality
July 3, 2024
Mr. Jack Meadows, Interim Town Manager
Town of Siler City
PO Box 769
Siler City,North Carolina 27344
Subject: Request for Additional Information
SOC Update and Path Forward
Town of Siler City
NPDES Permit NCO026411
Dear Mr. Meadows:
The Division of Water Resources (Division) received a presentation titled, "Town of Siler City Special
Order of Consent Update and Path Forward" (Update) from Hazen and Sawyer on behalf of the Town of
Siler City (Town) on May 14, 2024. The Update indicates that the Town is not expected to meet the
deadlines outlined in the active Special Order By Consent WQ S22-033 (SOC) and proposes new interim
measures by the Town to install treatment to mitigate the impacts of the Town's non-compliance in the near
term while the Town continues to progress toward installation of equipment outlined in their 6.0 MGD
expansion plan per Authorization to Construct Permit 026441A01.
Given the absence of supporting data and technical information in the Update, the Division is not in a
position to properly evaluate the Town's proposal. Division personnel therefore request the following
additional information:
• It appears based on the language in the Update that the proposed 4-stage BNR improvement is the
result of a conversion of an existing structure. Please identify which structure is to be converted
and provide a description of how the conversion of that structure's function will impact the
treatment at the facility.
• Please provide a narrative description of the scope of work associated with the interim process
improvement identified in the Update.
• Please provide design calculations for the 4-stage BNR system,including all influent design
criteria and any corresponding blower and pump sizing calculations.
• The Update appears to indicate that the 4-stage BNR system is designed based on 2023 flows.
Please provide justification for this design decision, as the current facility is permitted for 4.0
MGD and the Town has noted plans to upgrade its facility to 6.0 MGD by 2027.
• Please provide explanation as to how this design will sufficiently treat total nitrogen to meet
permit limits in each interim year preceding completion of expansion construction. The Update
notes that the requirements would be met in 2025,but does not speak to 2026 or 2027.
• The proposed interim measure would include the construction of one(1)4-stage BNR system.
Should this system require maintenance,how would the Town ensure adequate treatment to
accomplish compliance with the loading limits identified in the current NPDES permit, active
SOC and in the Update itself?
The Update includes a very aggressive schedule, specifically noting the submittal of an Authorization to
Construct permit application by the end of July 2024. The Division questions whether the proposed
schedule is feasible based on the information provided to date. To facilitate the Division's expedited
E Q�� North Carolina Department of Environmental Quality I Division of Water Resources
4512 North Salisbury Street 1 1611 Mail Service Center I Raleigh,North Carolina 27699-1611
NO CARO�INA _
DeperVneM of EnWronmenGl puall 919'707'900(]

consideration of this proposal,please provide a response within fourteen(14)days of the date noted on this
letter.
If you have any questions concerning this permit,please contact Nick Coco at(919)707-3609 or via email
at [e-mail].
Sincerely,
DocuSigned by:
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Nick Coco, PE
ARPA Environmental Program Supervisor II
Division of Water Resources,NCDEQ
Hardcopy: NPDES Files
Central Files
Ecopy: US EPA Region 4
DWR/Raleigh Regional Office/Water Quality
DWR/Municipal Unit—Pretreatment
DWR/Compliance and Expedited Unit
City of Sanford/Victor Czar
Town of Siler City/Chris McCorquodale
Hazen and Sawyer/Associate Vice President/J. Brenan Buckley, PE
E Q�� North Carolina Department of Environmental Quality I Division of Water Resources
4512 North Salisbury Street 1 1611 Mail Service Center I Raleigh,North Carolina 27699-1611
NO CARO�INA _
DeperVneM of EnWronmenGl puall� 919.707.9000