Underground Construction - January 2018 - 34

Contingency Planning Invaluable During
Historic Rainfall In Memphis

In March 2016, 16 inches of rain
fell on the city of Memphis, TN,
half of which fell during a two-day
deluge. This unprecedented rainfall
eroded the soil supporting a 96inch sanitary sewer main that carried wastewater to one of the city's
central treatment plants.
The damaged sewer main
crossed South Cypress Creek and
carried wastewater to the T.E.
Maxson Wastewater Treatment
Plant in Memphis. With nearly 40
million gallons per day (MGD) of
raw sewage escaping into Cypress
Creek, an emergency bypass was
needed to facilitate the repair work
on the existing sewer main.
City officials immediately activated their Emergency Response
Plan, gathering the management
team from the Public Works Division and bringing in global water technology authority Xylem
to help assess the damage and
map out an action plan. Xylem
mobilized an expert team and
cutting-edge pumps and accessories, delivering a comprehensive
turnkey solution that was up and
running in record time.
The emergency bypass system
needed to handle 160 MGD at
peak flow. Before pumping could
begin, several "critical path" construction projects were required
to support the bypass, including
a 2,400-foot-long, 40-foot-wide

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road through swamp land, so
the site could be accessed. Over
6,500 yards of recycled material was hauled in to act as a base
for the right-of-way. In addition,
two 86-inch culverts, side-by-side,
each 100 feet long, were installed
to contain the bypass piping as it
crossed Cypress Creek.
A suction pit, measuring 150
feet wide on each side and 40
feet deep, was created to hold the
pumps; the base of the pit was
built using 40,000 cubic yards of
imported material.
Typically, this magnitude of a
bypass pumping solution would
take between two and three weeks
to be designed and constructed.
However, the team of nearly 200
people completed the emergency
task in just six days.

Dewatering solution
Fourteen Godwin Dri-Prime
CD400M diesel pumps were installed to handle the 160 MGD
peak flow. Each pump would push
approximately 11.5 MGD through
24-inch HDPE suction tubes and
18-inch discharge tubes and into
an 8-foot square, concrete manhole structure.
To accommodate the 2,400-foot
distance from the suction point to
the discharge location, the bypass
utilized 30,000 feet of piping that
Xylem shipped in from its rental

locations up and down the East
coast. A dozen factory-trained and
-certified fusion technicians, some
from as far away as California,
operated fusion machines in four
different staging areas. Working
non-stop for a week, the teams
fused together 50-foot pieces of
pipe into 500-foot sections that
were then moved into place along
the right-of-way.
As the piping was set, the other
nine pumps were installed. An
additional CD400M pump was
also available onsite as a backup
option, offering peace of mind to
the Memphis officials and allowing
them to focus on replacing the
damaged sewer main.
In addition to the primary bypass, Xylem installed a separate
36-inch bypass line to handle 11
MGD of flow and ensure minimal impact on the structure.
This bypass utilized two Godwin
hydraulically driven CD300M
pumps and one backup pump - all
run by diesel power packs located
100 feet away, behind a berm, for
flood protection and to prevent
environmental contamination. The
discharge piping consisted of two
18-inch HDPE pipes that ran for
2,400 feet to the same discharge
structure as the primary bypass.

lem switched over to 24/7 bypass
operating mode. Two teams of
onsite mechanics worked around
the clock, alternating shifts to operate, monitor, service and repair
the pumps, and turn them on and
off as flow fluctuated. The bypass
system worked exactly as planned,
pumping approximately 60 to 160
MGD of raw sewage.
"Xylem was able to marshal the
equipment, the pumps and whatever else was needed and get the
job done - plus they had people
who knew how to utilize those
resources," said Paul Patterson,
environmental engineering administrator, City of Memphis. "One of
the benefits of the turnkey solution is that it allowed the city to
focus our resources and our efforts
entirely on design and construction, and getting the pipe replaced.
And that was key."
The fact that Memphis had an
emergency preparedness contingency plan in place enabled city
officials to respond without delay
when severe weather hit, minimizing environmental impact and ensuring regulatory compliance from
the damaged sewer line.

Crisis averted

Godwin Pumps,
856-467-3636, www.godwinpumps.com

Once the pumps were online, Xy-

FOR MORE INFORMATION:
Xylem
914-323-5700, xylem.com

Underground Construction January 2018

http://www.xylem.com http://www.godwinpumps.com http://www.ucononline.com

Underground Construction - January 2018

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