NC0021873_PT HWA approval_20210903

DocuSign Envelope ID: CB9C0971-DC56-42C4-B020-CA6D6922FE48
ROY COOPER
Governor
ELIZABETH S. BISER
Secretary
S. DANIEL SMITH
Director
NORTH CAROLINA
Environmental Quality
September 3, 2021
Via email: [e-mail]
Town of Mayodan
Attn: Melessa Hopper, Town Manager
P.O. Box 1279
Mayodan, NC 27012
Subj ect: Pretreatment Review of Headworks Analysis
Program: Town of Mayodan
NPDES Permit No: NC0021873- Mayodan WWTP
Rockingham County
Dear Ms. Hopper:
The Municipal Unit of the Division of Water Resources has reviewed the Headworks Analysis
(HWA) for the Town of Mayodan for its wastewater treatment plant (WWTP) working under the
NPDES Permit No NC0021873. The HWA was initially received by the Division on August 24,
2020, followed by more information and revisions received on May 10, 2021, and July 30, 2021.
We regret the delay in providing this review.
The Division concurs with the HWA calculations for all pollutants of concern, with the updates,
corrections, and observations discussed below. These approved Maximum Allowable
Headworks Loadings (MAHLs), Maximum Allowable Industrial Loadings (MAILs), and the basis
for these values are found on the last page of the enclosed HWA and Allocation Table (AT)
spreadsheet, which has the updates and corrections marked.
Please feel free to contact the Municipal Unit if you have any questions or concerns about the
changes outlined below. All corrected spreadsheets were emailed to you for your files, with the
changes highlighted. Please ensure to replace or update POTW's HWA AT spreadsheets and
supporting documents with these approved ones.
1. HWA Updates and Corrections
a. Arsenic and Molybdenum Water Quality Stream Standards: The HWA was updated
to use the site -specific water quality standards (WQS) for Arsenic, 150 ug/1. The
WQS for Molybdenum was updated to 2 mg/1, corresponding to the WQS for human
health (See Attached 2018 RPA).
b. Sludge Calculations: When the HWA was first submitted did not apply the 40 CFR
503 Standards for the Use or Disposal of Sewage Sludge as the POTW's sludge
program was transitioning to use a third party to land apply the POTW's sludge. By
August 2021, the POTW's agreement with Synagro has been finalized; therefore,
the HWA was updated to calculate allowable loads based on the sludge ceiling
standards from Synagro's sludge permit and Mayodan's data from Synagro's
Annual Sludge. When POTWs generate sludge disposed of by land application or
compost by a third party, the generating POTW is still responsible for compliance
with 40 CFR 403 Pretreatment and 40 CFR 503 Standards for the use or disposal
of sewage sludge. The POTWs must develop Sludge Allowable Headworks
£ D_E
NORTH CAROLINA
Department of Environmental Quality
North Carolina Department of Environmental Quality I Division of Water Resources
512 North Salisbury Street 11617 Mail Service Center I Raleigh, North Carolina 27699-1617
919.707.9000

DocuSign Envelope ID: CB9C0971-DC56-42C4-B020-CA6D6922FE48
Loadings (AHLs) using 40 CFR 503 standards in their Headworks Analysis (HWA)
and include 40 CFR 503 parameters in their Long/Short Term Monitoring Plans
(L/STMPs)
c. AT Calculations: The flow permit limit for Strum, Ruger & Company, pipe number
0001 was corrected from 0.36 MGD to 0.0360 MGD, as outlined in the approved
March 10, 2021, industrial user permit (IUP).
d. Mercury: The removal rate was changed to 0.01%. Additional sampling for influent
and effluent mercury began in May. Submit the updated spreadsheets upon
recalculating the HWA AT with the 2021 mercury results by July 26, 2022.
2. Next HWA Due date: The HWA approved today is based on DMR/LTMP data for the
period of March 2016 through June 2020. Unless conditions at the POTW change
significantly and thus warrant an earlier submittal (see Comprehensive Guide, Section B),
the POTW must submit an updated site -specific HWA by October 1, 2025.
Regardless of this approval action today, within 180 days of the effective date of any
reissued/modified NPDES permit, the Permittee would be required to submit to the Division a
written technical evaluation of the need to revise local limits (i.e., an updated HWA or
documentation of why one is not needed) NNPDES Permit Section D, 4.1. This action may include
revising, updating, or adding to the list of Significant Industrial Users (SIUs) and/or modifying
SIU Industrial User Pretreatment Permit (IUP) limits. In addition, any executed Special Order
of Consent (SOC) conditions or requirements related to pretreatment or pretreatment program
updates must be complied with separately from this approval action.
Federal and State pretreatment regulations require the local delegated pretreatment program to
effectively control and document the discharge of wastewater from Significant/Categorical
Industrial Users to the POTW. It is the POTW's responsibility to ensure that these objectives are
consistently met.
Thank you for your continued support of the Pretreatment Program. If you have any questions or
comments, please contact my staff Diana [[e-mail]], the Pretreatment
Coordinator Keyes [[e-mail]], or the Unit Supervisor, Michael at
[[e-mail]].
Sincerely,
,-DocuSigned by:
�C464531431644FE...
for S. Daniel Smith, Director
Division of Water Resources
dy/Mayodan hwa_august_202 1
Attachments:
2021 Approved HWA-AT
2020 Dissolved Metals Calculator Sheet
2018 RPA Input Sheet from NPDES Permit Renewal Fact Sheet
cc with attachments:
Nadine Blackwell, Pretreatment Coordinator
Jim Gonsiewski, Winston-Salem Regional Office
Municipal Unit File and Central Files (Laserfiche)