Underground Construction - November 2020 - 29

" If the void got worse, the transmission
tower was in danger of collapsing, causing
power lines to fall onto the 110 freeway, "
said Nate Warren, sales engineer with
Xylem.
Following the completion of the
contingency plan, Xylem worked with
Artukovich on developing a temporary
sewer bypass system to route sewage
around the repair site. Due to space
constraints and large volumes of traffic
in the area, a traditional aboveground
centrifugal bypass pumping solution
was ruled out.

Complex challenges

Initially, the city scheduled repairs on
a nearly half-mile stretch of the 48-inchwide pipe in 2020, but the risk of a
sinkhole under the train tracks resulted in
fast tracking the $20-million-plus project.
In November 2018, the city of Los
Angeles developed a contingency plan
to provide emergency response services
in the event of a sewage spill or further
underground structural failures. Xylem
Rental Solutions worked with the city
and its contractor, Vido Artukovich &
Sons, to implement the plan.

When project planning got underway in
January 2019, it was discovered that the
sewer pipeline was buried 50-feet deep,
roughly 20-feet deeper than initially
thought. This proved challenging to
designing a temporary bypass system,
as crews could not dig down to the
deteriorating pipeline without threatening
nearby infrastructure.
Designing and installing the suction
pit for the bypass pumping operation was
equally challenging because of the depth
With help from the contractor's Project
Manager Anthony Artukovich, Xylem
created a process to allow construction
crew members to safely enter and exit
the pit to make sewer repairs.
The significant depth of the pit also
meant installing steel support braces for
reinforcement, narrowing the diameter

of the pit. However, design specifications
required adequate spacing between
pumps to maintain proper flow.
" If the pumps were too close, they
would fight each other for flow, "
Warren explained.
With the bypass pipeline pushing out
into Avenue 19, a popular alternate route
for those commuting to suburbs just
north of Los Angeles, such as Burbank and
Glendale, special considerations also had
to be made to avoid disrupting traffic.

Maintaining water flow
Despite multiple challenges, Xylem
designed and, along with Artukovich's
help, built a successful temporary
bypass system. Running from Riverside
Drive and San Fernando Road to Avenue
19 near Humboldt Street, the system
moves a peak flow of 40 million gallons
per day (MGD).
As the main 40-MGD bypass system
was being constructed, a 20-foot suction
pit was excavated over the 35-foot deep
sewer on Avenue 19 to stage multiple
Flygt 3531, 24-inch, 335-horsepower
electric submersible sewage pumps.
The priming system is powered by a
diesel air compressor, and Godwin
GHPU90 power packs drive the
submersible pumps. This solution
allowed Xylem to install a 24-MGD
pumping system in a small working area.
The 40-MGD bypass system consisted
of four Flygt 3531 electric submersible
UCONonline.com | NOVEMBER 2020

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Underground Construction - November 2020

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