WQCS00009_NOV-2022-DV-0142 Response_20220606

ISO 140011015 . NC Star Pubic Sector • ISO IS401,2018
June 6, 2022
W. Corey Basinger, Regional Supervisor
Water Quality Regional Operations Section
Division of Water Resources, NCDEQ, MRO
610 East Center Avenue, Suite 301
Mooresville, NC 28115
Re: NOV-2022-DV-0142, Collection System Permit No. WQCS0009
Water and Sewer Authority of Cabarrus County (WSACC) Collection System
Cabarrus County
Dear Mr. Basinger:
WATER & SEWER AUTHORITY
OF CABARRUS COUNTY
232 Davidson Hwy.
Concord, NC 28027
704.786.1783 • 704.795.1564 Fax
www.wsacc.org
RECEIVED/NCDEQ/DWR
JUN �. j O
6 IOORESVILWQROS
LE REGIONAL OFFICE
WSACC is in receipt of the NOV for a Sanitary Sewer Overflow near 6775 Retreat Road, Concord, NC. Below
is a summary of background information and steps taken as a result of the overflow:
6775 Retreat Road Isolation Valve Failure and Spill
The wastewater spill was caused by a contractor (Laughlin -Sutton Construction Company) replacing the
air relief valve as part of the Lower Rocky River Pump Station Expansion project. To complete the air
relief valve replacement in the vault, an isolation valve had to be shut, and the piping downstream of the
isolation valve had to be removed and replaced. Although the isolation valve appeared to be shut and
sealed at first, the isolation valve did not seal off correctly, and the pressure in the force main eventually
caused the isolation valve to leak.
The referenced pump station and force main was installed in 2002, and upgrades for additional capacity
and continued reliability are currently in progress as part of the Lower Rocky River Pump Station
Expansion project.
The spill was discovered by a WSACC employee at approximately 2:20 pm on 4/20/2022. WSACC
deployed a crew to the scene and adjusted the isolation valve so that it sealed off correctly. A WSACC
employee was able to shut the valve and stop the spill at approximately 3:00 pm. WSACC personnel
picked up debris from the spill and treated the area with lime. WSACC evaluated the downstream
portions of the Rocky River to check for any adverse effects to wildlife and found no evidence of fish
kills or other adverse conditions which had affected wildlife in the Rocky River.
The Lower Rocky River Pump Station Expansion project includes replacement of several air relief
valves. Following this spill, WSACC worked with the contractor and consulting engineer for this
project to update the plan for future air relief valve replacements to minimize the risk of future spills.
The updated plan includes provisions such as further exercising the isolation valves prior to the work at
each air relief valve vault and flushing out any accumulated grease or other debris from the isolation
valves into an adjacent gravity sewer line. Additionally, WSACC will have a bypass pump on hand for
each remaining air relief valve replacement to pump from the air relief vault to the adjacent gravity
sewer line if needed.
- WSACC monitors this line on a regular basis and will continue to be proactive in watching for any leaks
or needed repairs.

WSACC will continue to work with the contractor and our consulting engineer to monitor this area as work
continues to progress, along with monitoring other areas throughout our system. WSACC will also continue to
be proactive to protect our facilities and to take all steps possible to prevent future spills. Please let me know if
you have any questions.
Sincerely,
Thomas Hahn, PE
Assistant Engineering Director
cc: Mr. Chad VonCannon, Engineering Director
Mr. Wayne Lyles, Interceptor Supervisor