NC0066516_Pretreatment_HWA_Letter_20220623

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ROY COOPER
Governor
ELIZABETH S. BISER
Secretary
RICHARD E. ROGERS, JR.
Director
NORTH CAROLINA
Environmental Quality
6/23/2022
Town of Fuquay-Varina
Attn: Chris Grimes, Utility Operations Manager
401 Old Honeycutt Rd.
Fuquay-Varina, NC 27526
Email: [e-mail]
Subject: HWA Approval
Program: Town of Fuquay-Varina
NPDES Permit No NC0066516, 3.0 MGD
Permit Class A Residuals No WQ0020016
Terrible Creek WWTP
Wake County, RRO
Dear Permittee:
The Municipal Unit of the Division of Water Resources has reviewed the Headworks Analysis
(HWA) for the Town of Fuquay-Varina for its wastewater treatment plant (WWTP) working under
the NPDES Permit No NC0066516 (effective on July 1, 2021). The HWA was initially received
by the Division on August 31, 2020, followed by more information and revisions received on
December 31, 2021, January 19, 2022, and February 15, 2022. 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. The approved Maximum Allowable Headworks
Loadings (MAHLs), Maximum Allowable Industrial Loadings (MAILs), and the basis for these
values are found in the enclosed HWA and Allocation Table (AT) spreadsheet, which has the
updates and corrections highlighted. Please ensure to replace or update the POTW's HWA AT
spreadsheets with this approved one.
1. HWA Corrections
a. POTW Average Flow: This was updated to 1.226 based on using all average
monthly data from the DMRs for the time period.
b. NPDES Limits: Copper was added as a pollutant of concern in the 2021 NPDES
renewal, therefore the limit was added to the HWA.
c. Water Quality Stream Standards: The HWA was updated to use the site -specific
water quality standards (WQS) for silver, molybdenum, and zinc, and reductions for
cadmium. (See the RPA Input Tab in the HWA-AT Spreadsheet).
d. Removal Rates and Uncontrollable: Removal rates were updated to include all
average monthly data from the DMRs for the time period. This update affected the
removal rates for BOD, TSS, and copper. The HWA was corrected to reflect these
new values. The updated flow and removal rates information was also updated in
the uncontrollable mass balance spreadsheet. This necessitated an update of the
uncontrollable flow in the HWA spreadsheet to 1.219 MGD (cell C9 in HWA)
according to the Mass Balance sheet calculation.

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e. Sludge: The sludge to disposal flow and % solids to disposal values were added
based on the 2020 Residuals Summary from the McGill Annual Report (permit#
WQ0006816).
f. HASL: Cadmium, copper, and zinc were overallocated based on sludge AHL so the
Division completed the HASL worksheet. Values were entered using the 2020
Residuals Summary from the McGill Annual Report (permit# WQ0006816). By
using the HASL calculations, the overallocation for cadmium, copper, and zinc were
resolved in the allocation table.
g. Mercury: The HWA showed a calculated over allocation based on uncontrollable.
The mercury effluent data shows non-compliance with the PQL listed in the current
LTMP. The POTW shall require the 1631 method at the influent and effluent with a
PQL of 1 ng/L.
h. Silver: The HWA showed a calculated over allocation based on the dissolved
metals stream standard. Recently DWR has decided to allow POTWs the option of
using zero for data reported as below PQL (Practical Quantitation Limit) data
when the PQL is sufficiently low (best available PQL). All recent WWTP influent
and effluent silver data was below 1 ug/L PQL. Based on this data, the HWA was
revised to use zero for the uncontrollable. If any future data shows a reported value
above 1 ug/L PQL, contact the Pretreatment staff of the Municipal Unit within 30
days to discuss the need for future action. This change still resulted in a negative
allocation for silver. The POTW must revise their IUPs silver limit to resolve this
overallocation. Please submit this IUP modification to the Division by August 31,
2022.
i. Design: Updated the design values to match the Design Annual Averages from the
Authorization to Construct Application: Design Calculations.
j. Allocation Table: The AT was updated to reflect the new SIU effective and
expiration dates.
2. Required Updates
a. LTMP updates
Submit the updated Long -Term Monitoring Plan (LTMP) by August 31, 2022,
addressing:
i. The target PQL for the following parameter shall be updated in the LTMP:
silver from (0.005 to 0.000001 mg/L).
ii. The Division recommends updating the PQL for the following parameters:
cadmium (from 0.002 to 0.0005 mg/L) and lead (from 0.01 to 0.002 mg/L).
iii. The HWA includes uncontrollable sampling data. Please include this location
in your revised plan.
iv. Arsenic, mercury, molybdenum, and selenium are 40 CFR 503 required
pollutants for sludge. Please add these POCs to the Sampling Plan and
Detection Level tables. PQLs should be: Arsenic = 0.002 mg/L, Mercury =
0.000001 mg/L (EPA Method 1631E), Molybdenum = 0.01 mg/L, Selenium =
0.005 mg/L.
3. Next HWA Due date: The HWA approved today is based on DMR/LTMP data for the
period of July 2018 through June 2020. Unless conditions at the POTW change
significantly and thus warrant an earlier submittal (see Comprehensive Guide, Chapter 5,
Section B), the POTW must submit an updated site -specific HWA by August 31, 2026
(after the reissue of the next NPDES permit renewal).

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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.]. 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 cooperation of the Pretreatment Program. If you have any questions
or comments, please contact the Pretreatment Coordinator Keyes McGee
[keyes.mcgee (a�ncdenr. gov] .
Sincerely,
DocuSigned by:
IUatati, , V WiAlt.k .1.0
C464531431644FE...
for Richard E. Rogers Jr., Director
Division of Water Resources
kl/Fuquay.HWA.2022.Approval
Attachments:
Fuquay.Approved HWA-AT (66516).2022
cc with attachments:
Adam Stephenson, Town of Fuquay-Varina (astephenson@,fuquay-varina.org)
DWR Raleigh Regional Office — Pretreatment/ Cheng Zhang
Municipal Unit File
cc without attachments:
Central Files (Laserfiche)