Underground Infrastructure - January 2023 - 19

Measuring 275 feet (or the length of 17 cars), the TBM used
on the project is one of only a handful of similar pieces of equipment
in the world. In addition to keeping the work below ground,
the TBM was also expected to help shorten the project timeline.
However, Dig Greenville encountered an unforeseen obstacle
in this respect: the geology of the tunnel zone.
" Th e tunnel boring machine can only work through one type
of material,'' Jones noted. " Right when we were gett ing started,
we saw that the granite was not where we thought it was. "
As a result of this complication, construction began with a
starter tunnel. Ultimately, 41 separate blasts would be required
over a nine-month period, in addition to the hard labor of hand
digging at the very outset.
" What we found was about 240 feet of clay and rock that we
had to dig out,'' Jones said.
" It cost us about 10 months of project time. Th e tunnel
boring machine can dig out about 40-50 feet per day. We were
only digging out about two feet per day. It was very time- and
labor-intensive just to get started. "
Workers also had to fabricate and install a customized steel
shield to keep the 14-foot-round starter tunnel secure.
Once the TBM could be put into operation, the project
advanced more quickly. Aſt er nine months of boring through
intact Gneiss bedrock, " Carrie " emerged from the ground on
Westfi eld Street near Greenville's Kroc Center, having traveled
twice under the Reedy River.
By then, the amount of crushed rock removed by the machine
would fi ll 11 Olympic-size swimming pools. And as Joel
Jones noted, even with the unexpected delay, Dig Greenville
came in within the original project budget.
Out of sight, but key to growth
Despite the scale of the undertaking, the Reedy River Basin
Sewer Tunnel is largely invisible to Greenville residents, except
for discreet access doors at each end.
Th e BILCO Company manufactured 13 fl oor doors of
various sizes for the project. Th e doors allow access to vertical
shaſt s - one is 35 feet deep, the other is 105 feet deep - in which
workers will descend, or lower equipment, into the tunnel.
BILCO fl oor doors are designed with engineered liſt assistance
to ensure safe, easy, door operation.
" We used those types of doors fairly oſt en on our projects,
especially at pump stations,'' Jones said. " We fi nd they have
good durability and reliability. "
Greenville's prudent investment in this critical infrastructure
sets the stage for future growth. Th e work itself may be far
below the ground, hidden from view. But in an age when wild
weather is no longer the exception, the ongoing prosperity of
this charming Southern city will be clear to see. UI
ABOUT THE AUTHORS: Katherine Bonamo and Thomas Renner write
on trade industry topics for publications throughout the United States.
FOR MORE INFORMATION:
BILCO Company, (800) 366-6530, bilco.com
Lovsuns Canada, (905) 364-1055, lovsuns.com/
Black & Veatch, (913) 458-2000, bv.com
© 2022 McElroy Manufacturing, Inc. MMI block is a registered trademark
of McElroy Manufacturing, Inc. All rights reserved.
UndergroundInfrastructure.com | JANUARY 2023 19
Productive equipment helps
you be more efficient on the job. McElroy's line
of fusion machines and accessories has been
trusted on the jobsite for over fifty years for that
very reason. Finish your job in less time, with
the confidence and data that it's done correctly.
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Underground Infrastructure - January 2023

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