WQ0038008_More Information (Received)_20220121

hazenandsawyer.com

Hazen and Sawyer
4011 WestChase Blvd, Suite 300
Raleigh, NC 27607 • 919.833.7152
January 21, 2022
Jason T. Robinson, P.E.
North Carolina Department of Environment and Natural Resources
Division of Water Quality
Water Quality Regional Operations Section
512 N. Salisbury St., Suite 925
Raleigh, North Carolina 27604

Re: Snow Hill Road Pump Station – Partial Certification
Dear Mr. Robinson:
Hazen and Sawyer and the City of Durham plan to submit partial certification for Sewer
Permit WQ0038008 for replacement of the Snow Hill Road Pump Station (SHRPS) and
the associated gravity sewer. The force main associated with the permit has not been
constructed at this time but design plans have been completed and the easement
acquisition process has been started. A small portion of the 20-inch force main has been
installed and is connected to the existing 12-inch force main on a temporary basis. The
functional testing has been completed and the pump station is ready for operation.

To complete the gravity sewer associated with the permit, we will need to receive
wastewater into the new SHRPS via bypass pumping. The partial certification will be to
receive bypassed wastewater into the new pump station and discharge it using a portion
of the 20-inch force main and the existing 12-inch force main. The flow from the new pump
station during the temporary period when the 12-inch force main is in service will be limited
to an acceptable flowrate based upon hydraulic and transient evaluations until the 20-inch
force main is constructed, certified, and put into operation.

To ensure that the flows are acceptable for the 12-inch force main, we have discharged
clean water at the maximum flowrate and pressure that the 12-inch will receive and
experienced no issues. In addition, the transient evaluation included a power loss scenario
at the peak flow condition and the existing air/vacuum valves were adequate to limit the
pressure to an acceptable range during the analysis. Finally, the City of Durham has tested
the thickness of the force main in multiple locations and found that there was no significant
material loss in the pipe.

Included in the partial certification will be design calculations for the interim pump
operating conditions, including the firm capacity of the pump station and transient analysis
of the interim conditions.

Following the installation of the permitted gravity sewers, we will submit a second partial
certification that will include record drawings of the pump station, gravity sewers and the
portion of the 20-inch force main that was installed. Funding is now available for the
completion of the 20-inch force main, of which 45% will require easement acquisition. Due
to the unknown time related to easement acquisition, the installation of the entire 20-inch
force main is expected to be completed in approximately two (2) years but we are
evaluating installing the 55% of the force main that does not require new easements as
– 2 – January 21, 2022

soon as possible to benefit the pumping conditions of the pump station. Partial
certifications would be provided for any of the force main that could be placed in service
prior to the completion of the entire main.

If you have any questions regarding the details of the proposed partial certification,
please don’t hesitate to contact me at 919-863-1011 or [e-mail].

Best Regards,

Brian Porter, P.E.
Senior Associate
Hazen and Sawyer
Cc: Bryant Green (City of Durham), Vince Chirichella (Durham County), Brandon Campbell (Wharton Smith),
Matt Cartwright (Freese & Nichols), Scott Vinson (NCDENR), Tom Tant (Hazen), Jerry Morrone (City of
Durham)