Underground Construction - February 2021 - 29

some areas of very hard rock, some areas
of poor alluvial soils. We used sheet piling
for some areas and a slide rail system. The
rock was very hard - we tried trenching,
chemical expansion grouting, hoe ram/
hammering and finally blasting. "
Trenches were dug with a Caterpillar
335 excavator, a large, zero tail swing
machine that was needed due to tight work
area. Trench width and depth varied. Pipe
bedding was stone, and the trench was
filled with flowable back fill.

Pipe installation
Prior to installation, the pipe was stored in or
near the frequently flooding creek bed. Pipe
was handled and positioned with a Mi-Jack
gentry crane and pushed into place with an
excavator. The crane had to have the capacity
to lift the pipe, plus the width to straddle the

ditch/excavation, but was limited in height
to clear under multiple bridges.
" The majority of the project was in Bear
Grass Creek, which is an improved concrete
channel, " said Seal. " During construction,
flow was diverted to one side of the channel
using a gravity system constructed from a
slip-formed barrier wall. "
According to Kevin Baas, P.E., senior
technical manager at Thompson Pipe,
" Rigid PCCP was the clear choice for this
project. PCCP won't float away and is
strong enough to withstand harsh installation environments. Flexible pipe requires
at least four to six feet of cover and cannot
be stored in areas where flooding occurs.
And unlike flexible pipe, PCCP does not
require special bedding or backfill.
" A post construction hydrostatic test was
not a feasible option in this situation, " Baas
added, " so contractor personnel air tested
individual joints to confirm leak-free joints. "
The project also included extensive
removal and replacement of the improved
concrete channel in the South Fork of

Beargrass Creek, erosion and sediment
control, a vehicle access ramp and various
surface restorations, such as both asphalt
paving and concrete flatwork.
From start to completion, construction
required two years.
With more than 3,200 miles of sanitary
sewer lines in service, MSD collects wastewater from more than 270,000 homes,
businesses and industries in the Louisville
metropolitan area.
Based in North Kansas City, Mo., Garney
Construction is one of the nation's leading
contractors for water and wastewater systems and has a regional office in Louisville.
Thompson Pipe Group offers a wide range
of precast, pressure and trenchless pipes,
and engineering and logistic services. *
FOR MORE INFORMATION:
Garney Construction, (816) 741-4600, garney.
com
Thompson Pipe Group, (972) 262-3600,
thompsonpipegroup.com
Hazen and Sawyer (502) 290-6187,
hazenandsawyer.com
Caterpillar, (309) 675-1000, cat.com
UCONonline.com | FEBRUARY 2021

29

https://www.garney.com/ https://www.garney.com/ http://www.thompsonpipegroup.com http://www.hazenandsawyer.com http://www.cat.com http://www.UCONonline.com

Underground Construction - February 2021

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