NC0023906_Pretreatment_HWA_LTMP_Letter_20240223

DocuSign Envelope ID:7600046E-9F78-43FF-95CF-84DC5E9E02A8
ROY COOPER cd _
Governor d C
ELIZABETH S.BISER ;e
Secretary •E .
RICHARD E.ROGERS,JR. NORTH CAROLINA
Director Environmental Quality
Via Electronic Mail(Ipruitt(a-)wilsonnc.com) 2/23/2024
Laura Pruitt
Water Reclamation Compliance Coordinator
City of Wilson
P.O. Box 10
Wilson,NC 27893
Subject: Pretreatment Review of Long Term Monitoring Plan and Head Works Analysis
Program: City of Wilson
Wastewater Treatment Plant: Hominy Creek Water Reclamation Facility
NPDES#: NC0023906,Wilson County
Dear Laura Pruitt:
The Municipal Unit of the Division of Water Resources has reviewed the updated Long Term Monitoring Plan
(LTMP), the Headworks Analysis (HWA), and the Allocation Table (AT) for the City of Wilson (NC0023906).
The submission was received by the Division on 3/17/2023 (HWA and AT) and 5/27/2023 (LTMP).
The Division finds the LTMP sufficient for implementation, but it requires further revision, as discussed below.
The Division concurs with the HWA calculations except for the following corrections and observations discussed
below. Proper implementation of an LTMP is also required by your NPDES permit. Please refer to the
Comprehensive Guidance for North Carolina Pretreatment Programs (Comprehensive Guide) for additional
information and examples.Modifications to the LTMP must be approved by the Division. 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 AT spreadsheet, which has the observations and requests
highlighted. Please ensure to replace or update the POTW's previous HWA AT spreadsheets with this approved
one.
• Long Term Monitoring Plan Corrections and Observations
o Please specify which method is used to test for Mercury influent and effluent concentrations, and
the Practical Quantitation Limit (PQL). This is the data used to calculate the removable rate for
mercury found in the document"Influent and Effluent RR spreadsheet HWA 2023".As a reminder,
the required method for testing Mercury in effluent is EPA Method 1631 with a Practical
Quantitation Limit of 1 ng/l.
o The Long Term Monitoring Plan does not indicate sampling for an uncontrolled sample location.
The Division requests that the POTW research a location where uncontrolled sampling could be
performed and provide a map with the identified location. This sampling location should be free
from Significant Industrial User effluent contributions.
o Please update the Practical Quantitation Limits(PQLs)to match the Comp Guide linked above.
• HWA and AT Corrections and Observations
o There is a projected overallocation for Silver in the HWA—AT spreadsheet that requires further
information. The Industry Loading is 0.0937 lbs/day, the MAHL is 0.0214 lbs/day, and the
Uncontrolled Loading is 0.0759 lbs/day [which should be verified as accurate.]. This leads to a
projected overallocation of 0.1423 lbs/day [ subject to additional verification].
North Carolina Department of Environmental Quality I Division of Water Resources
D E Q�� 512 North Salisbury Street 11611 Mail Service Center I Raleigh,North Carolina 27699-1611
NORTH cnaoVF 919.707.9000
DepYaanl of EmYaanental Oual�

DocuSign Envelope ID:7600046E-9F78-43FF-95CF-84DC5E9E02A8
o The PQLs used for Silver were inconsistent throughout the sampling period.Please utilize the PQL
guidance in the Comp Guide, linked above. Exceptions can be made due to extenuating
circumstances which should be reported to the Division.
o Our review indicated a possible overallocation of Silver,has the City of Wilson provided a roadmap
or any specific plans to conduct further sampling of uncontrolled loading or other means?
The Division requests that the City of Wilson propose a timeline to respond to and meet the corrections and
observations outlined above.The City of Wilson may request a reply with additional information within 30 days of
the date in this letter to discuss the findings presented by the Division.
Regardless of approval action today, within 180 days of the effective date of any reissued or 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, or documentation of why one is not needed). This action may include revising,
updating,or adding to the list of Significant Industrial Users(SIUs).Pursuant to 15A NCAC 2H.0907(b)either the
Division or the permittee may initiate pretreatment program revisions.
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 with the Pretreatment Program. If you have any questions or comments,
please contact Natalie Gorensek[email:natalie.gorensekAdeq_nc.gov] at(919)707-3660 or Keyes McGee at(919)
707-3626 [email: ke, e�geekdeq.nc.gov].
Sincerely,
nhg/wil_hominy_ltmphwa_2024
Ec: Municipal Unit File DocuSigned by:
Cheng Zhang,RRO Nl i�,(A au,(,
Central Files(Laserfiche) C464531431644FE...
Michael J. Montebello,NPDES Branch Chief
Division of Water Resources
D E Q�� North Carolina Department of Environmental Quality I Division of Water Resources
512 North Salisbury Street 1 1611 Mail Service Center I Raleigh,North Carolina 27699-1611
NORTH CAROUNA _
eep,�„F r��,�wla,\ /./ 919.707.9000