Underground Construction - November 2020 - 30

Emergency Bypass Aids Critical Los Angeles Sewer Repairs
sewage pumps - two primary and two on
standby. Due to the space limitations,
the Xylem team staged the pumps in an
alternating pattern, making the first and
third pumps the primary pumps and the
second and fourth pumps the standby
pumps. Warren said the unconventional
solution worked well to ensure proper
flow is maintained.
Four 2,500-foot lines of 24-inch HDPE
pipe run from each pump to an alternate

sewer trunk line called the Northeast
Interceptor Sewer. Burying the pipe
under the street ensures traffic flow
along Avenue 19 is not impeded.
In order to meet fluctuating flow
conditions and address ragging concerns,
the Xylem team opted to mount the
Flygt 3531 pumps on a slide rail system
typically used in permanent pump system
designs. In a standard bypass scenario,
a special crane must be used to pull the

piping and the pump at the same time.
" Using a slide rail system was safer
and easier, " said Warren.
Each pump was fitted with a Godwin
variable frequency drive (VFD) to optimize
energy consumption and allow the pumps
to automatically start and stop, maintaining
a consistent sewer level. The VFDs are
networked together so they could be
controlled by a Godwin Advanced Remote
Monitoring control panel. In addition to
remote monitoring, this wireless technology
enabled control of the pump from any
smartphone, tablet or desktop computer.
The control panel also provided clog
detection. When a pump started to clog,
the pump's motor amps rise and the flow
drops. The system then alerted pump
watch personnel, who addressed the
clog by following a step-by-step plan of
backflushing the pump. The process took
less than five minutes, during which
the standby pumps automatically started
and took over pumping.
" From wherever I was, I could monitor
the pump performance and communicate
to our pump watch team when we need
to backflush pumps to prevent ragging, "
Warren explained.
Two diesel generators were set up onsite
- one to power the two submersible pumps
and a second as a standby. If the primary
generator failed, the standby generator automatically started and took over supplying
primary power to the bypass system.

Peace of mind
After nearly seven months of planning
and setup, sewer repair and rehabilitation
activities began in June 2019. The
temporary bypass system operated
continuously over a nine-month period.
The combination of reliable primary
pumps supported by backup pumps,
a redundancy system, and remote
monitoring and control of the operation
provided city managers with confidence
and peace of mind.
" We were able to optimize the bypass
system and allow the city and the
contractor to monitor flow rates and
responses from anywhere in real time, "
said Warren. *
FOR MORE INFORMATION?
Xylem, (914) 323-5700, xylem.com

30

NOVEMBER 2020 | UCONonline.com
http://www.xylem.com http://www.UCONonline.com
Underground Construction - November 2020

Table of Contents for the Digital Edition of Underground Construction - November 2020
