NC0020621_HWA Approval_20220321

ROY COOPER
Governor
ELIZABETH S. BISER
Secretary
RICHARD E. ROGERS, JR.
Director
NORTH CAROLINA
Environmental Quality
Town of Boone
Mr. Rick Miller, Public Works Director
PO Drawer 192
Boone, North Carolina 28607
Transmitted via email to [e-mail]
Subject: HWA Review
Program: Town of Boone
Permit NC0020621, 4,82 MGD
Jimmy Smith WWTP
Watauga County, WSRO
Dear Permittee:
The Municipal Unit of the Division of Water Resources has reviewed the Headworks Analysis (HWA) for
the Town of Boone for its wastewater treatment plant (WWTP) working under the NPDES Permit No
NC0020621 (effective on October 1, 2021). The HWA was initially received by the Division on September
28, 2020, followed by more information and revisions received on September 22, 2021. We regret the delay
in providing this review.
The Division concurs with the HWA calculations for all pollutants of concern, with the 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. All corrected spreadsheets are emailed 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 Corrections
a. Uncontrollable Flow was corrected from 2.48 to 2.54 MGD according to the Mass Balance Sheet
calculation.
b. Water Quality Stream Standards: The HWA was updated to use the site -specific water quality
standards (WQS) used in the current NPDES permit for arsenic, cadmium, chromium, copper,
cyanide, lead, mercury, molybdenum, nickel, selenium, silver, and zinc. (See attached the 2021
reasonable potential analysis (RPA)). All WQS used the 0.5 safety factor to protect outstanding
waters (C+ waters) per 15A NCAC 02B .0224(c)(2)(G).
c. NPDES Limits: The HWA was updated from 5 to 20.0 mg/1 to use the current NPDES permit
limit for total suspended solids (TSS).
d. Allocation Table (AT) Calculations: In the HWA review process, the Permittee dropped an SIU,
Hospitality Mints, LLC; the AT has been updated to reflect those changes.
2. HWA Observations
a. Design Values: It was noted that you calculated the ammonia design value based on the TKN
design value using the 40:25 ratio from Metcalf & Eddie. This literature value is acceptable at
this time.
b. Removal Rates and minimum pass -through loading: Ensure to include in the next HWA
reviewing cycle removal rates for total phosphorous (TP), total nitrogen (TN), and acrylonitrile.
3. Required Updates
a. IUP renewal: In the HWA review process, it was noted that the Industrial User Permit (IUP) for
Charleston Forge expired on 12/31/2021. Please submit the IUP renewal as soon as possible.

b. LTMP updates
Submit the updated Long -Term Monitoring Plan (LTMP) by May 4, 2022, addressing:
i. The Division recommends including the following pollutants of concern (POC) in the
LTMP: Acrylonitrile, TN, and TP. These are POCs per the current NPDES permit
monitoring requirements.
ii. The target Practical Quantification Level (PQL) for the following parameter shall be
updated in the LTMP: silver (from 5.0 to 1.0 µg/1).
iii. The Division recommends updating the PQL for the following parameters: arsenic
(from 10.0 to 2.0 µg/1), cadmium (from 2.0 to 0.5 µg/1), lead (from 10.0 to 2.0 µg/1),
and molybdenum (from 100.0 to 10.0 µg/1).
iv. Mercury sampling for all LTMP locations shall use Method 1631E.
4. Next HWA Due date: The HWA approved today is based on DMR/LTMP data for December 2016
through July 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 July 1, 2026.
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 IWS/L-STMP/HWA or documentation of why one is not
needed) INPDES 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,
for Richard E. Rogers, Director
Division of Water Resources
dy/ _hwa_2022
Attachments:
2022 Approved HWA-AT
2021 RPA Input Sheet from NPDES Permit Renewal Fact Sheet
cc with attachments:
Karen Reece, Town of Boone — Pretreatment Coordinator
Alexander Lowe, Winston-Salem Regional Office
Municipal Unit File and Central Files (Laserfiche)