Underground Infrastructure - January 2023 - 18

Digging Deep for Resilience
tended sources. Long sewers may also need the depth to allow
for a sufficient gradient over their length.
In the case of Dig Greenville, the plan called for installing
the new line 100 feet below ground.
" While it is pricier to build, a deep sewer tunnel powered by
gravity will be far less costly over its lifecycle for ReWa, while
providing the reliable additional capacity Greenville needed as
it continues to grow,' said ReWa CEO Joel Jones, who took
over as executive director from Rich earlier this year.
Black & Veatch led the design and provided construction
management services. The tunnel is expected to serve the
Greenville community for the next century. A major challenge
was putting the structure in place - right beneath the heart of
a busy downtown.
" We wanted to gain the trust of the community from the
very beginning, " said Jones. " We had a series of meetings where
we showed the community that we were serious about the concerns
and taking them into consideration. "
Steve O'Donnell, Black & Veatch construction manager,
held a regular series of open conversations over coffee ( " Sippin'
with Steve " ), which continued, virtually, when the pandemic
intervened. Project planners also strove to limit the degree of
disruption for Greenville residents from the outset.
Teams built wooden fencing around the construction to
minimize the aesthetic impact. At the Greenville Zoo, located
near one end of the new tunnel, ReWa created a new parking lot
to offset the temporary loss of other parking spaces, ultimately
increasing the zoo's total parking capacity.
Road closures were largely limited to a two-month winter
period, when one roadway was closed off to facilitate quicker
construction for a sewer crossing across Richland Creek and to
accommodate the city's streambank restoration program.
But the use of a tunnel boring machine (TBM) for the
dig was key to keeping the impact of the project out of sight.
If ReWa had chosen to rebuild the existing sewer line, which
closely followed the path of the Reedy River basin through
Greenville, this would have been a far more disruptive option
for city residents, requiring significant trench work.
With a TBM, " The tunnel is bored from one end, resulting
in surface impact only at either end of the tunnel, rather than
all along the sewer route if conventional construction methods
were used, " said Jones.
Seven feet in diameter and approximately 6,000 feet long,
the completed sewer is virtually invisible to the public. Entry
shafts at each end are the only hint of the massive line under
the surface. The pipes are encased in granite, lined with fiberglass
and grouted. The gravity-fed system means no mechanical
equipment is needed to convey the flow of wastewater.
Bump in the road
The initial plan in Greenville was for subcontractor Super
Excavators of Wisconsin to bore the entire tunnel with a double-shielded
rock gripper TBM made by Lovsuns Canada, once
an access shaft had been created.
A 130-ton tunnel boring machine, known in the Greenville community
as " Carrie, " helped expedite drilling of the 1.3-mile tunnel. (Photo courtesy
of Black & Veatch)
Project at a Glance
What: Dig Greenville, also known as the Reedy River Basin Sewer
Tunnel, is a 1.3-mile gravity-fed sewer line in South Carolina.
Project details: The $46-million project started in 2018 and
concluded in 2022. It is the largest infrastructure project in
Greenville's history. The project is expected to support Greenville's
wastewater conveyance needs for the next century.
Why it's important: The existing sewer line face pressure from
increasing population. Without more capacity, the community
would be at risk for overflow.
Digging deep: The tunnel is located as far as 100 feet beneath the
surface. Few people will even know it's there. The only evidence
visible are access points at each end. Thirteen floor-access doors
manufactured by BILCO enable workers to install, remove and repair
equipment.
A $46 million project in Greenville, S.C., established a 1.3-mile underground
tunnel for wastewater conveyance. (Photo by Eric Glenn Photography)
18 JANUARY 2023 | UndergroundInfrastructure.com
Did you know? Greenville is sixth in population and growth rate
in South Carolina. UI
http://www.UndergroundInfrastructure.com
Underground Infrastructure - January 2023

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