Underground Construction - January 2022 - 45

LEFT: Addressing the limited space and project requirement to
evenly divide the flow from eight pumps into four aeration basins,
stakeholders implemented a common manifold that hydraulically
balanced the system flow.
ABOVE: The bypass required holding the water level in the aeration
basin vertically within eight inches - similar bypass projects typically
allow three to five feet of variance to control the water level.
Connecting high-resolution, submersible level transducers to
variable frequency drives (VFD) controlled the pump operation
according to flow, ensuring water levels remained within the allowable
eight-inch depth. The four primary electric pumps operated to
each manage two inches of water vertically. The four diesel pumps
were each offset by one inch. This arrangement kept the amount of
water coming in consistent with the amount being pumped out -
staying within the eight-inch variance.
Backup
control the water level. If the water lowered too far, the aeration
paddles would no longer touch the water, preventing them from
introducing air into the waste stream. Conversely, if the water rose
too high, it would trip the breaker.
Solutions
Addressing these challenges required placing eight, 18-inch DR17
HDPE suction tubes into the aeration basin and mating them to
eight 12-inch pumps. Each pump discharged utilizing 12-inch
DR26 HDPE pipes connected to a discharge manifold that, in
turn, tied into four parallel runs of 24-inch DR26 HDPE pipe. In
addition, four 24-inch pipes connected between the clarifiers.
Because of the limited space to run these pipes between the
aeration basin and the four clarifiers, they had to be placed much
closer together than usual during a bypass. Sunbelt Rentals
also had to figure out how to position the pumps. The solution
consisted of four electric 150 HP, 12-inch pumps operating
on the temporary site utility power that was available. These
pumps handled the peak flow and the average daily flow during
the bypass. Four diesel 150 HP, 12-inch pumps backed up the
electric pumps for a power-out condition. Because of the limited
space, project managers needed to alter the pump configuration,
staggering the electric and diesel pumps.
While the diesel pumps served as backup to the main electric pumps,
the PumpSentri telemetry system from Sunbelt Rentals provided
further protection. PumpSentri - integrated on both the electric
driven and diesel driven pumps - offered remote monitoring and
data logging throughout the bypass. This eliminated the need to
employ a 24-hour, onsite pump watch, as well as the associated cost.
PumpSentri also allowed fault alarms to be selected according to
stakeholders' preference - text, email or voice call. Emergency project
contacts receive alerts when standby pumps turn on or water levels are
too high. It is added assurance to safeguard against critical conditions
that could damage equipment or jeopardize a bypass project.
In the case of the Lower Berkeley WWTP project, PumpSentri alerted
personnel of one potential event.
The system also allowed project managers to monitor pump activity
around the clock, along with providing information on pump vacuum
pressure, discharge pressure and vibration. Check-engine status and
runtime were also accessible.
With innovative solutions to address both space limitations and
tight water-level variance, improvements to the aeration system at
the Lower Berkeley WWTP were a success. As with any bypass project,
clear communication and a solid partnership between stakeholders also
contributed to getting the job done well and on time. The project took
two months to complete. *
DWIGHT EVANS is the manager - technical support, Pump Solutions
for Sunbelt Rentals
UCONonline.com | JANUARY 2022 45
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Underground Construction - January 2022

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