Underground Infrastructure - July 2023 - 25

REHABTECHNOLOGY
Caverns of Calloway -
Dirt Pipes are Expensive
Tom Davies, P.E. and Gary Oradat, P.E. of Trinity River Authority of Texas, and Nicole Conner, P.E. of Kennedy Jenks
After a heavy rainfall in June 2022, the
Trinity River Authority (TRA) was
notified of a sanitary sewer overflow
(SSO) on a sewer line within the Walker
Calloway System, a 4.7-mile wastewater
collection system built, owned and operated
by TRA. The line delivers wastewater
from North Richland Hills and Hurst
to a discharge point in the Fort Worth
wastewater system for further transportation
and treatment.
The TRA is a state-level agency tasked
by the state of Texas with managing the
quality of water in the Trinity River watershed
throughout the state, from its most
upstream reaches near the Oklahoma border
to where the river discharges into the
Gulf of Mexico near Baytown, Texas. The
TRA Northern Region collects and treats
235 MGD of wastewater for 1.5 million
people in the DFW region in north Texas.
The Walker Calloway System is
unique in the TRA system in that the
interceptor is maintained but flows are
not treated. TRA agreed to take over the
operation and maintenance of the interceptor
as a service approximately 20 years
ago to minimize service disruptions and
maximize maintenance efforts. Hurst and
North Richland Hills approve and give
funding for capital upgrades, but TRA
implements and oversees them.
TRA commenced a capacity and condition
assessment in 2011, and a program
to rehabilitate or replace the interceptor's
seven primary segments (FIGURE 1),
beginning at the downstream end of the
interceptor, was initiated in 2016. Each
phase of the program is comprised of sevFIGURE
1: Walker Calloway system map and phase status
eral thousand feet of wastewater pipeline:
Phase 1 construction was completed in
February 2020, construction of Phases 2
and 3 is imminent, and Phase 4's final design
is underway (preliminary design was
completed in May 2022). Despite the advancement
of the rehabilitation work, the
deterioration of the original pipeline continued,
eventually contributing to a large
SSO in the interceptor's Calloway Branch.
Storm damage
This segment of the original WalkerCalloway
System was constructed of
27-inch unlined reinforced concrete pipe
(RCP) in 1970. Late afternoon on Friday,
June 4, 2022, the Calloway Branch of the
Walker-Calloway drainage channel system
was overwhelmed by a significant rain
storm that produced nearly four inches of
rain in less than two hours. Flows accumulated
swiftly in the Calloway Branch drainage
channel,
overpowering
numerous
bridges that span over it, and also found
their way into the Walker-Calloway interceptor
system as infiltration and inflow.
Almost immediately following
the
heavy rain event, a resident noticed an
overflow at a sewer manhole and contacted
the city of Hurst. The city noted upon
arrival that the overflow was on the TRA
managed portion of the system.
UndergroundInfrastructure.com | JULY 2023 25
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Underground Infrastructure - July 2023

Table of Contents for the Digital Edition of Underground Infrastructure - July 2023

Underground Infrastructure - July 2023 - 1
Underground Infrastructure - July 2023 - 2
Underground Infrastructure - July 2023 - 3
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