NC0074268_Pretreatment_HWA_letter_20200415

ROY COOPER
Governor
MICHAEL S. REGAN
Secretary
S. DANIEL SMITH
Director
NORTH CAROLINA
Environmental Quality
April 15, 2020
Via Electronic Mail ([e-mail])
Mike Alexander
Pretreatment Supervisor
Two Rivers Utilities
P.O. Box 1748
Gastonia, NC 28053
Subject: Pretreatment Review of Headworks Analysis (HWA)
Two Rivers Utilities; Gaston County
WWTP: Crowders Creek, NPDES#: NCO074268
Dear Mr. Alexander:
The Pretreatment, Emergency Response, and Collection Systems Unit (PERCS) of the Division of
Water Resources has reviewed the updated Headworks Analysis (HWA) for Two Rivers Utilities
Crowders Creek WWTP (NC0074268). This HWA was received by the Division on October 31,
2019. We apologize for the late response.
The Division concurs with the HWA calculations for all parameters of concern with the following
minor corrections. These approved Maximum Allowable Headworks Loadings (MAHL), Maximum
Allowable Industrial Loadings (MAIL), and the basis for these values are found on the last page of
the attached HWA spreadsheet. The results of the HWA are also listed in the bottom section of
the attached Allocation Table.
1. TN and TP loadings: TN NPDES mass limit has been converted to concentration limit by
dividing 64,251 Ibs/summer by 214 days/summer by the converter 8.34 by POTW average
flow 3.291 MGD. Concentration limits for TP was derived by dividing 18,245 Ibs/year by 365
days/year by the converter 8.34 by POTW average flow 3.291 MGD. The NPDES loadings
formula were updated but the values did not change. Normally we would use the design flow
in the formula to be more conservative as the POTW average flow increases every year.
However, using the average flow is allowed as long as the POTW updates the average flow
(Cell C8) every year. Please update the average flow before November 1, 2021.
2. Mercury primary removal rate: was removed as mercury was not sampled at primary clarifier.
The update did not change the MAHL for mercury as mercury is limited by stream standards.
Next HWA Due Date: Unless conditions at the POTW change significantly and thus warrant an
earlier submittal (see Comprehensive Guide), the POTW must submit an updated HWA on or
D E Q�� North Carolina Department of Environmental Quality I Division of Water Resources
512 North Salisbury Street 1 1650 Mail Service Center I Raleigh, North Carolina 27699-1650
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before November 1, 2024.
Thank you for your continued cooperation with the Pretreatment Program. If you have any
questions or comments, please contact me at 919-707-3627 [email: [e-mail]].
Sincerely,
DocuSigned by:
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Vivien Zhong, Engineer
vz/Two Rive rs_crowders_hwa_015
ec: PERCS Unit File
Wes Bell, Mooresville Regional Office (via email)
Central Files (LF)