NC0027103_Pretreatment_HWA_letter_20200413

ROY COOPER
Governor
MICHAEL S. REGAN
Secretary
S. DANIEL SMITH
Director
NORTH CAROLINA
Environmental Quality
April 9, 2020
Via Electronic Mail ([e-mail])
Tyler Thomas, Town Manager
Town of Pembroke
PO Box 866
Pembroke, NC 28372
Subject: Pretreatment Review of Headworks Analysis (HWA)
Program: Town of Pembroke; Robeson County
NPDES Number: NCO027103
Dear Mr. Thomas:
The Pretreatment, Emergency Response, and Collection Systems Unit (PERCS) of the Division of Water
Resources has reviewed the Headworks Analysis (HWA) for the Town of Pembroke. The HWA was
submitted by Lisa Osthues, the pretreatment consultant, on behalf of the Town and was received by the
Division on October 1, 2019. We apologize for the late response.
The Division concurs with the HWA calculations for all pollutants of concern, with corrections discussed
below. A copy of the corrected HWA with highlighted changes has been sent by email. The changes did
not cause over allocation.
The following corrections were made during the review of the HWA:
1) Design: Per 2007 letter, the 1.5 multiplier cannot be applied to TSS because there were a couple TSS
violations in January 2019 and November 2018 respectively. In the design document, the 30 mg/L is
for TKN, which includes both ammonia and organic nitrogen. In the HWA the design value of ammonia
was required. 30 mg/L was used for ammonia at the time. A more accurate value could be calculated
with the influent ratio of ammonia and TKN provided.
2) Stream standards: All the stream standards were halved because the receiving stream is classified as
High Quality Waters (HQW).
3) Sludge: Sludge information was removed as the sludge was disposed by a contact hauler and the
POTW does not hold a sludge permit.
4) Detection Levels: for chromium, copper and mercury did not meet what were specified in the Short
Term Monitoring Plan (STMP). Please use the detection levels listed in your approved STMP for all
future STMP monitoring.
5) STMP:
a) STMP should be monitored once every quarter instead of in four executive months.
Oaparhnenl o<Envlmmm�nla49ualiH
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
919.707.9000

b) STMP requires the POTW to sample the SIU for all Pollutants of Concern (POCs) once every five
years. The data submitted indicated that the POTW failed to sample the POCs other than BOD and
TSS. Please remember to sample all POCs at the SIU for future STMP sampling. If this is not the
case, please submit the data and updated uncontrollable mass balance before May 15, 2020.
c) Arsenic, cyanide, mercury, molybdenum, silver, selenium, % solids and sludge to disposal flow
could be removed from the STMP as the POTW does not hold a sludge permit.
d) Please start your next STMP no later than August 1, 2023 per your approved STMP to allow you
enough time to complete the HWA.
6) Next HWA Due Date: This HWA submission was based on LTMP data from January 2016 through
August 2019. The next updated HWA will be due October 1, 2024, unless conditions change that
would require the City to perform a HWA at an earlier date.
Thank you for your continued support of the Pretreatment Program. If you have any questions or
comments, please contact Vivien Zhong at [phone] [email: [e-mail]].
Sincerely,
by:
EDocuSigned
AtA' -
xjE42E88CDBD404A7...
ivien Zhong, ngineer
vz/Pembroke_HWA_001
ec: Central Files (LF)
PERCS Unit file
Cheng Zhang, RRO
Lisa Osthues, pretreatment consultant