WQCS00031_NOV-2019-DV-0311 Response_20190827

Orange Water and Sewer Authority
IOWASAI OWASA is Carrboro-Chapel Hill's not -far -profit public service agency
delivering high quality water, wastewater, and reclaimed rfl%re6P6YR*ironmental Quality
August 27, 2019 G 2 9 200
Raleigh Regional Office
Mr. Rick Bolich, L.G. Assistant Supervisor
Water Quality Regional Operations Section
Raleigh Regional Office
Division of Water Resources, North Carolina Division of Environmental Quality
3800 Barrett Drive
Raleigh, NC 27609
SUBJECT: Response to Notice of Violation (NOV-2019-DV-031 l )
April 13, 2019 Self -Reported Sanitary Sewer Overflows
Dear Mr. Bolich,
As requested in your letter of August 13, 2019 (received on August 19, 2019) we are writing to
provide information about the Sanitary Sewer Overflows (SSOs) experienced on April 13, 2019
at or near our Rogerson Drive pump station and force main in Chapel Hill.
Initial Response
On April 12, 2019, OWASA's water treatment plant operator received a call around 9 FM stating;
there was a SSO near the intersection of Rogerson Drive and Highway 54 in Chapel Hill. Our
on -call person was dispatched to the area and arrived on the scene about 15 minutes later. The
SSO was determined to be the result of a break in our 30" force main that conveys roughly half
of the wastewater in our service area to our wastewater treatment plant. Due to the break being
located in the crown of the pipe and being located in a section of the force main that typically
flows by gravity, the majority of the flow remained in the force main and continued to be
pumped to our plant. Unfortunately, our options to address the SSO were limited due to the
persistent storm conditions (nearly 3 inches of rain), the size of the force main, flow rates in the
force main and limited options for temporary bypass pumping operations. Our only strategy to
mitigate the SSO at the site of the break was to restrict the pumping capabilities at the station
discharging to the force main, which resulted in other SSOs around the station. Extensive efforts
were made to contain the SSOs, collect the spilled wastewater and properly dispose of it
including positioning staff at key locations to monitoring the SSOs, placing straw bales around
spills. cleaning up areas with our vacuum equipment and transporting it to unaffected areas of the
collection system. Once the storm event passed and flows to the station returned to normal. the
SSOs around the station ceased (this all occurred in less than 24 hours). The heavy rainfall
diluted the wastewater that reached surface waters and no fish kills were observed. We
400 Jones Ferry Road, Carrboro, NC 27510 0 919-968-4421 0 [e-mail] Q @0WA5A1 ® www.owasa.org

Mr. Rick Bolich
August 27, 2019
Page 2
conducted water quality monitoring of the impacted surface waters as well. Areas impacted by
the SSOs were neutralized with lime.
Temporary Bvpass
In order to repair the force main break, a temporary bypass would need to be installed. Due to
the size of the force main, the need to install line stops and the need to fuse large diameter bypass
piping (tasks which OWASA has no in-house capabilities to perform), we elected to procure
emergency contracting services. Our contractor was on the scene within hours of notification,
however, line stop insertion is a highly specialized service and crews needed to mobilize from
Florida and Texas to assist in this effort. Despite these and other challenges, the temporary
bypass was in service by April 16, 2019. With the bypass in service, we had our first
opportunity to excavate the area of the break and investigate the cause.
Root Cause of the Break
These SSOs were a direct result of a premature structural failure of the 30" ductile iron pipe
force main (this pipe was only 27 years old and its condition was indicated it to be acceptable in
our most recent condition assessment from 6 years ago). Once the force main break was
exposed, the extensive corrosion in the crown of the pipe was evident. We used our camera
equipment to evaluate the condition of the pipe upstream and downstream of the break between
the line stops. This entire span of pipe (--500 feet), with the exception of a short portion near the
uppermost line stop which was originally installed in a different phase, was observed to be in a
similar condition. The corrosion appeared to be the result of a failure of the lining.
Permanent Repairs
The section of pipe between the initial line stops was replaced with --500 feet of 30" PVC.
However, the section downstream of the initial repair ( 700 feet crossing under Highway 54)
was installed in the same phase and was suspected to be in the same condition. Therefore, we
elected to install a full -capacity temporary bypass underneath Highway 54 to facilitate the
replacement of the section of pipe downstream of the initial repair with PVC as well (-700 feet)
and would avoid any SSOs during peak flow events. While this bypass was being established,
diesel pumps and lay flat hoses were placed at critical locations to address any potential SSOs
that may have occurred in the interim. Currently, the full -capacity temporary bypass remains in
service and the pipe replacement is underway. To date, OWASA has spent $3.2 million
responding to this SSO. We estimate the full cost of the repairs will be between $4 and $5
million and that they will be completed in October with road surface restoration soon after. We
believe this is a prudent investment in improving the reliability and resiliency of a critical
component of our wastewater collection system infrastructure.
Onnoina Efforts to Improve the Wastewater Collection Svstem
OWASA is committed to improving the condition and reliability of our wastewater collection
system with a stated goal of experiencing zero overflows within a twelve-month period. This
force main has previously been identified as a critical piece of infrastructure. Prior to this event

Mr. Rick Bolich
August 27, 2019
Page 3
we had spent about $300,000 on condition assessments (which indicated the condition of the
pipe to be acceptable) and risk response planning. We had also begun to study alignments for a
redundant force main. More generally, over the course of the next five fiscal years we have
nearly $1 5 million budgeted to perform sanitary sewer condition assessments and rehabilitation
of our wastewater collection system. We expect this level of effort will reduce the occurrence of
future SSOs throughout the collection system.
While we fully understand that any SSO is unacceptable and a violation of our collection system
permit, we believe we responded to these SSOs in a timely and environmentally responsible
manner. In responding to this event, we addressed the immediate need to halt the SSO and
remedy impacts to the area. We have also reduced the potential risks of future SSOs in this
critical piece of infrastructure.
We hope that the information provided herein is helpful to you and please feel free to contact us
should you have any further questions.
Sincerely,
Q- 9 &444
Ed Kerwin
Executive Director
cc: Todd Taylor, General Manager of Operations
Mary Darr, Director of Engineering and Planning
Jesse Duclau, Distribution and Collection Systems Manager
Monica Dodson, Wastewater Treatment and Biosolids Recycling Manager
File