Underground Infrastructure - January 2023 - 17

Digging Deep for Resilience
City on the Upswing Builds for the Future
Katherine Bonamo and Thomas Renner
In recent years, resilience has been much in the news.
Individuals are encouraged to prize adaptability. Parents strive
to raise children who will trust themselves in adversity. And
cities, whose vibrancy has been threatened by the global pandemic,
are now seeking ways to bounce back.
Resilience is an essential concept for water infrastructure as
well, defined by the American Society of Civil Engineers as " a
system's ability to withstand and adapt to the impacts of natural
and/or manmade disasters. " As climate instability increases
the likelihood of heavy downpours, sewer systems without ample
capacity are increasingly vulnerable to overflow.
In September 2022, for example, rainfall of nearly 5 inches
within 24 hours led to overflow conditions in Milwaukee,
Wis. Approximately 765 million gallons of wastewater were
discharged into Lake Michigan, the Milwaukee River and other
local waterways.
In Greenville, S.C., officials have made the smart choice to
take the long view. The population of Greenville County, now
exceeding half a million residents, has more than doubled since
1970. Rather than wait for a maxed-out sewer system to be
overwhelmed by some future storm, regional authorities chose
to get out ahead of the growing city's needs. The Dig Greenville
project, also called the Reedy River Basin Sewer Tunnel, cost
$46 million and is the largest infrastructure project in the city's
191-year history.
" Dig Greenville is one of the most important infrastructure
investments needed to ensure economic growth in the area,''
said Graham Rich, chief executive officer of ReWa, the regional
water management organization.
Due to this project, " ... sewer lines and the area along the
Reedy River will be at lower risk for sewer overflows, especially
when rainfall is high, " he said. It also ensures " Greenville's
future, economic development since, without it, no additional
wastewater flows could be added to the existing lines. "
Deep dive
When seeking the best long-term alternative for the Greenville
area, ReWa considered no fewer than 18 different options before
settling on a final approach: construction of a new 1.3-mile
gravity sewer tunnel.
As the name suggests, gravity sewers rely on careful design
to transport waste without the added energy costs of pumping.
However, such sewers typically need to be situated far enough
below the ground that they can receive gravity flow from all inOPENING
PHOTO: Work on the Dig Greenville project began in 2018 and concluded earlier this year. (Photo courtesy of Black & Veatch)
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Underground Infrastructure - January 2023

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