NC0020451_Pretreatment_HWA_Letter_20190304

ROY COOPER
Governor
MICHAEL S. REGAN
Secretary
LINDA CULPEPPER
Director
Brandon Patrick
Pretreatment Coordinator
Town of West Jefferson
Po Box 490
West Jefferson, NC 28694
NORTH CAROLINA
Environmental Quality
March 4, 2019
Subject: Pretreatment Review of Headworks Analysis
Program: Town of West Jefferson, NPDES #: NCO020451
Ashe County
Dear Mr. Patrick:
The Pretreatment, Emergency Response, and Collection Systems (PERCS) Unit of the Division of Water
Resources has reviewed the Headworks Analysis (HWA) for the Town of West Jefferson. This HWA was
received by the Division on February 6, 2019 via email.
The Division concurs with the HWA calculations for all pollutants of concern, with corrections discussed
below. The 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 enclosed HWA
spreadsheet, which has the corrections marked. The results of the HWA are also listed in the bottom
section of the enclosed Allocation Table.
HWA Corrections: Please feel free to contact me if you have any questions about the changes outlined
below or if the POTW does not agree with the modifications. The corrections did lead to the mercury
and silver over allocation, reasons caused the over allocation and recommendations to resolve the
issue would be discussed below. All corrected spreadsheets were emailed to you for your files, with
the changes highlighted. Please ensure the POTW's HWA, AT, and other supporting documents
contain these corrected documents, especially the Allocation Table. As needed, please mark any
original documents as "replaced" or "voided."
A. POTW flows: POTW average flow was adjusted to 0.3025 MGD from 0.296 MGD to match the
removal rates sheet, uncontrollable flow was changed to 0.2961 MGD from 0.006425 MGD as
uncontrollable flow is total POTW influent flow minus total significant industrial user flow, as
shown in uncontrollable mass balance sheet Cell D23.
B. Pass Through Loading Calculations:
i) Removal rate for Hg was changed to 60% literature removal rate as the influent and effluent
have different detection levels (DL). Most of the influent values are less than 100 ng/L, while
the effluent using the DL of 0.5 ng/L, and the removal rate of 99.57% was highly likely to be
overestimated. The change caused mercury over allocation, but no action is required as long
North Carolina Department of Environmental Quality I Division of Water Resources
512 North Salisbury Street 1 1617 Mail Service Center I Raleigh, North Carolina 27699-1617
Noana GwauNn �
919.707.9000

as the POTW effluent meet the stream standard of 12 ng/L, and do not received Mercury from
any industries. However, if you would like to resolve the over allocation on paper, please use
one of the following method:
(a) Use the lower detection level (0.5 ng/L) at the influent so that the removal rate could
be calculated using real data;
(b) Caclulate the removal rate from the sludge data. Removal rate equals sludge pounds
divided by the influent pounds and the influent pounds equals effluent pounds plus
sludge pounds. Please contact me if you require assistance with the calculation.
ii) The dissolved metal water quality standards: The dissolved metal stream standards were
calculated (see attached calculator). The more stringent of column 5 & 6 were selected and
entered into the column F of the pass -through loading calculations. Copper, silver and zinc
are no longer action level pollutants and the changes caused silver over allocation. Since the
POTE effluent is below 1 ug/L (current lowest detection level), it is recommended to use the
lowest silver detection level available at all sampling locations and add silver monitoring
requirements for the SIU.
C. Sludge Calculations: The Sludge Site Acres was corrected to match sludge permit attachment B
total acreage, assuming all fields were used for the POTW land application. If this is not the case,
please contact me and we will adjust the acrage accordingly.
D. HASL: for arsenic were used (Cell D138 were checked) to avoid over allocation caused by sludge
ceiling standards.
2. STMP: Please update the detection levels in Section G as necessary and remove the uncontrollable
sampling frequency in section E if the POTW chooses not to do uncontrollable sampling. Please submit
the updated STMP before April 1, 2019.
3. HWA Due Dates: The HWA approved today is based on STMP and DMR data from January through
December 2018. Unless conditions at the POTW change significantly and thus warrant an earlier
submittal (see Comprehensive Guide, Section e). The next due date for HWA is April 1, 2024 and the
STMP quarterly sampling should be performed in calendar year 2023.
Thank you for your continued cooperation with the Pretreatment Program. If you have any questions or
comments, please contact me at [phone] [email: [e-mail]] or Deborah Gore,
Unit Supervisor at [phone] [email: Debora [e-mail]].
Sincerely,
DocuSignened by:
E42E88CDBD404A7_.
Vivien Zhong, PERCS Unit
vz/Westjefferson.H WA. 2019
Enclosures: Updated HWA—AT, Calculator and mass balance spreadsheets
Ec: PERCS Unit
Jim Gonsiewski, WSRO
Central Files