NC0024970_Other_20230911

North Carolina Department of Environmental Quality Division of Water Resources
512 North Salisbury Street 1611 Mail Service Center Raleigh, North Carolina 27699-1611
919.707.9000

September 11, 2023
Mr. Joseph Lockler, Operations Chief
Charlotte Water
5100 Brookshire Boulevard
Charlotte, North Carolina 28216
Subject: Letter of Understanding
North Plant Interim Fermenter Pilot Study
McAlpine Creek WWMF
Mecklenburg County
NC0024970
Dear Mr. Lockler:

A request for the continuation of an ongoing pilot study utilizing an Interim Fermenter at the North
Plant of the McAlpine Creek WWMF (NC0024970) was received on May 17, 2023, by the
Division of Water Resources (Division). An initial demonstration study for the Interim Fermenter
was conducted from July 28, 2019 to February 27, 2020. At that time, Charlotte Water pursued a
longer-term operating experience, keeping the Interim Fermenter in operation since September
2020. As the study has thus far demonstrated promising results, Charlotte Water has requested
continuation of the pilot study until a time in which a permanent installation can be commissioned
and built.

Permanent installation of the Interim Fermenter is anticipated in 2026. Given the results of the
study thus far and the minimal likelihood of discernible water quality impacts, the Division is
providing Charlotte Water the following Understanding to Conduct for:

Charlotte Water’s ongoing pilot study at the McAlpine Creek WWMF utilizes the Interim
Fermenter as a sidestream process to create anaerobic conditions necessary for enhanced biological
phosphorous removal.

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
McAlpine Creek, which is classified C waters in the Catawba River Basin. The NPDES
permit terms and conditions shall be complied with during the pilot study at the facility.

2. The facility shall keep ferric chloride onsite during the duration of the pilot study as a
backup means of phosphorous removal and notify the Division if ferric chloride is fed
along with the reasoning behind its addition in the monthly report following incident.

3. Monitoring and Reporting.
a. Collect weekly effluent water samples at the current effluent sampling point and
monitor parameters including Total Phosphorous, CBOD5, ammonia, pH,
temperature and DO.
b. Report the monitoring results mentioned in Condition 3.a monthly to the Division
via the electronic Discharge Monitoring Report (eDMR) system.
DocuSign Envelope ID: 7787C0D2-CD8E-44F4-B4CE-72E599B7A116

North Carolina Department of Environmental Quality Division of Water Resources
512 North Salisbury Street 1611 Mail Service Center Raleigh, North Carolina 27699-1611
919.707.9000

c. Charlotte Water shall report to the Mooresville Regional Office any noncompliance
that potentially threatens public health or the environment. Any information shall
be provided orally within 24 hours from the time Charlotte Water becomes aware
of the circumstances. A written report shall also be provided within five days of the
time Charlotte Water becomes aware of the circumstances. Occurrences outside
normal business hours may also be reported to the Division’s Emergency Response
personnel at [phone] or [phone].

4. Charlotte Water shall make available upon the Division’s request any monitoring results
or other information necessary to ensure compliance with this letter of approval.

5. Annual report on the performance of the Interim Fermenter and a final summary report for
the Interim Fermenter pilot study shall be made in writing prior to permanent installation
and sent to:

NCDEQ/ DWR NPDES
Municipal Permitting Unit
Attn: Michael Montebello
1617 Mail Service Center
Raleigh, NC 27699-1617
and by email to: [e-mail]

6. Charlotte Water shall notify the Mooresville Regional Office by telephone and in writing
at least seven days prior to completion of permanent installation of the Interim Fermenter.

The Division may modify this Letter of Understanding upon the written request of Charlotte Water.

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 Charlotte Water in writing of its findings and
identify actions required of Charlotte Water.

This Letter of Understanding applies only to conducting the Interim Fermenter pilot study from
September 11, 2023 until a time in which a permanent installation can be commissioned and built.
If Charlotte Water elects to permanently install the Interim Fermenter, 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 [e-mail].

Sincerely,

for Michael Montebello, Branch Chief
NPDES Municipal Permitting Unit
Hardcopy: NPDES Files
Ecopy: DWR/Mooresville Regional Office
DocuSign Envelope ID: 7787C0D2-CD8E-44F4-B4CE-72E599B7A116