NC0041696_Other_20230504

DocuSign Envelope ID: D4B6515A-EA4E-4F81-B481-2A2E3CF62471
of1Nc STATE�A'
ROY COOPER
Governor 2r
ELIZABETH S.BISER
Secretary
RICHARD E.ROGERS,JR. NORTH CAROLINA
Director Environmental Quality
May 2, 2023
Mr. Greg Padgett, Water Resources Director
Town of Valdese
PO Box 339
Valdese,North Carolina 28690
Subject: Letter of Understanding
Full-Scale Peracetic Acid Pilot Study
Lake Rhodhiss WWTP
Burke County
NCO041696
Dear Mr. Padgett:
A request for an Understanding to conduct a full-scale pilot study for one month utilizing Peracetic
Acid (PAA) as a disinfectant was received March 29, 2023, by the Division of Water Resources
(Division). By definition, Pilot Studies are for a short duration, typically a few weeks to a year
unless it is determined by the NCDEQ Permit Writer that a longer duration is necessary for a
complete analysis and assessment. Studies are conducted in limited scope and duration to assess
the viability of the change to full-scale implementation, thus the study must be of a size that can
adequately demonstrate full-scale implementation. The Town of Valdese's Lake Rhodhiss WWTP
(NC0041696) intends to utilize VigorOx's WWT II Peracetic Acid 15.9% for the study in hopes
to replace the existing primary disinfectant, chlorine gas and sodium dioxide gas.
Given the short duration of the project (From May 22, 2023 to June 23, 2023) and the minimal
likelihood of discernible water quality impacts, the Division is providing Town of Valdese the
following Understanding to Conduct:
A full-scale pilot study which feeds PAA 15.9% from a tote into the contact chambers via a pump
skid that will sit next to the chlorine contact chamber. A dose of 2.0 mg/L (as PAA) will be used
during the first week of trial. Weekly adjustment of the PAA dose will be made as needed, based
on the observed microbial indicator counts from the previous week. During the trial period, the
Site personnel and Sterling Water Technologies/Coyne Chemical staff will review testing data
weekly and make necessary adjustment for dosing.
This Letter of Understanding is subject to the following conditions:
1. The project shall not cause or contribute to any violation of water quality standards in Lake
Rhodhiss (Catawba River),which is classified WS-IV,B, CA waters in the Catawba River
Basin. The NPDES permit terms and conditions shall be complied with during the pilot
study at the facility.
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
� Nor
919.707.9000

DocuSign Envelope ID: D4B6515A-EA4E-4F81-B481-2A2E3CF62471
2. The facility shall keep chlorine gas and sodium dioxide gas onsite during the duration of
the full-scale pilot study as a backup and notify the Division if returns to gaseous chlorine
for disinfection for any reason.
3. Monitoring and Reporting.
a. No later than 2 days prior to initiating the pilot study and 2 days following the completion
of the pilot study, the Town of Valdese shall notify the Asheville Regional Office and the
NPDES Municipal Permitting Unit.
b. Collect daily effluent water samples at the current effluent sampling point and
monitor parameters including Total Fecal Coliform,PAA residual,BOD, TSS,pH,
temperature and DO.
c. Collect weekly effluent water samples at the current effluent sampling point and
monitor chloride (sample prior to and after addition of PAA) and CBOD.
d. Report the monitoring results mentioned in Condition 3.b weekly to the Division
by email to michael.montebellogncdenr.gov. Final summary reports for the PAA
pilot study shall be made in writing and sent to:
NCDEQ/DWR NPDES
Municipal Permitting Unit
Attn: Michael Montebello
1617 Mail Service Center
Raleigh,NC 27699-1617
and by email to: michael.montebello(ancdenr.gov
e. The Town shall report to the Asheville Regional Office any noncompliance that
potentially threatens public health or the environment. Any information shall be
provided orally within 24 hours from the time the Town becomes aware of the
circumstances. A written report shall also be provided within five days of the time
the Town becomes aware of the circumstances. Occurrences outside normal
business hours may also be reported to the Division's Emergency Response
personnel at(800) 858-0368 or(919) 733-3300.
4. The Town shall make available upon the Division's request any monitoring results or other
information necessary to ensure compliance with this letter of approval.
The Division may modify this Letter of Understanding upon the written request of the Town. The
Division also reserves the right to modify or withdraw this Letter of Understanding if the project
does not conform to the above conditions or results in unacceptable impacts to water quality. In
such case,the Division shall notify the Town in writing of its findings and identify actions required
of the Town.
Pl 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
919.707.9000

DocuSign Envelope ID: D4B6515A-EA4E-4F81-B481-2A2E3CF62471
This Letter of Understanding applies only to conducting the full-scale PAA pilot study from May
22, 2023 to June 23, 2023. If the Town elects to permanently utilize PAA to replace the existing
gaseous chlorine for disinfection,the Division will consider the results of this study and the scope
of work in order to determine whether the system will require other permits.
If you have any questions concerning this letter,please contact Michael Montebello at(919) 707-
3624 or at michael.montebellokncdenr.gov.
Sincerely,
EDocuSigned by:
C464531431644FE...
Michael Montebello, Branch Chief
NPDES Municipal Permitting Unit
Hardcopy: NPDES Files
Ecopy: DWR/Asheville Regional Office
Pl 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
919.707.9000