Even Before National Legislation South Carolina Community Invested Heavily In Wastewater Pipeline
By Thomas Renner
Last November, with the Infrastructure Investment and Jobs Act, Congress appropriated $55 billion for the U.S. Environmental Protection Agency to improve wastewater and drinking water infrastructure. Undoubtedly, such investment is needed.
A 2021 report card from the American Society of Civil Engineers awarded the United States a D+ for its wastewater infrastructure. The report found 15 percent of wastewater treatment plants are exceeding capacity. Of the 16,000 wastewater treatment plants in the U.S., 81 percent have reached their design limits. “As many treatment plants and collection networks approach the end of their lifespans, the financial responsibilities for operation and maintenance will become more costly” the ACSE report noted. The same analysis found that in 2019, the investment gap in the wastewater industry was a staggering $81 billion.
Unlike many other communities, the city of Greenville, S.C., found itself ahead of the curve when it comes to improving its wastewater management system. Nearly 15 years ago, community leaders recognized the population growth and understood that the city’s wastewater conveyance infrastructure needed a major upgrade. Earlier this year, a 1.3-mile gravity-fed sewer line opened in Greenville. 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.
“It definitely puts not just the downtown, but rather the whole city in a better position for the future,’’ Mayor Knox White said when the project was introduced in 2016.
Renewable Water Resources (ReWa), a 97-year-old organization that protects the region’s waterways and wastewater infrastructure, spearheaded the effort. Black & Veatch led the design and provided construction management services. The tunnel is expected to serve the Greenville community for the next century.
“Dig Greenville is one of the most important infrastructure investments needed to ensure economic growth in the area,’’ said Graham W. Rich, Chief Executive Officer of ReWa, when the project started. “With this investment and hard work, sewer lines and the area along the Reedy River will be at lower risk for sewer overflows, especially when rainfall is high. This investment and work were also required to ensure Greenville’s future economic development since, without it, no additional wastewater flows could be added to the existing lines.”
Mayor White knows Greenville better than anyone. A city native, he joined the City Council in 1983 and became Mayor in 1995. When he took office, the city’s population stood at around 240,000.
Now, the city’s population stands at more than 550,000. White and city leaders have transformed the municipality. His tenure as mayor has been defined by neighborhood revitalization, economic development, and critical projects for downtown. “I’ve always wanted Greenville to be the most beautiful, livable, welcoming city in America,’’ White wrote on the city’s website.
White’s vision has helped him earn national recognition. In 2018, Time magazine selected White as one of “31 People Changing the South.” He has spearheaded economic development in the city, located in the state’s “Upstate Region” and about halfway between Charlotte and Atlanta. With shopping, restaurants, cultural events, craft breweries and events nearly 300 days a year, residents and visitors certainly dig Greenville.
In many growing communities in the U.S. population growth strains existing infrastructure, and that problem also faced Greenville. Without more capacity, the community would be at risk from increased overflows. This risk posed a direct threat to water quality, the environment and economic development.
“If nothing is done, ReWa’s sewer lines and the area along the Reedy River would be at a higher risk for the environmental impact of sewer overflows,’’ Rich said. “Furthermore, economic development would be threatened because no additional wastewater flows can be added to the sewer lines. While the project is a long-term fix, Dig Greenville will also meet immediate needs by providing an increased buffer against sewer surcharges due to inflow and infiltration during rain events.”
ReWa considered 18 alternatives before deciding on the gravity sewer tunnel. Rebuilding the sewer line was prohibitive, and too disruptive to the city and water basin. Planners chose to install the new line underground, approximately 100 feet below the heart of the city.
“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 Chief Executive Officer Joel Jones, who took over as Executive Director from Rich earlier this year.
The tunnel is 7 feet in diameter and virtually invisible to the public. Entry shafts at each end are the only hint of the massive pipe 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.
“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,’’ Jones said.
The initial plan was to drill from the downstream access shaft through the hard rock below with a tunnel boring machine. Before the TBM could be launched, however, a geotechnical investigation found the tunnel zone was composed of soil and different types of rock in varying conditions.
“The tunnel boring machine can only work through one type of material,’’ Jones said. “Right when we were getting started, we saw that the granite was not where we thought it was.”
The complication resulted in hand-digging a starter tunnel. Starter tunnel construction also included drill and blast methods that required 41 blasts over a 9-month period. Each blastwas modified to fit the zone’s complex geology. Workers also fabricated and installed a customized steel shield to secure ground support for the 14-foot-round horseshoe-shaped starter tunnel.
“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. The 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-intensive and labor-intensive just to get started.”
The tunnel boring machine helped workers pick up the pace after completing the starter tunnel. The 130-ton TBM, made by The Robbins Company in Canada, measures 249 feet and is one of only a handful of similar pieces of equipment in the world. Super Excavators of Wisconsin started tunnel digging in March 2018 and completed their work in September 2020.
The TBM was critical to the completion of the project in that it offered a far more efficient drilling method. TBMs are used as an alternative to drilling, blasting and hand-mining to excavate tunnels with a circular cross-section through layers of soil and rock.
The machines significantly minimize disturbance to the surrounding ground and area. They are frequently used in urban areas and reduce project completion times.
Out of Sight
For a project of this magnitude and duration, workers were surprisingly able to stay out of the public glare. Almost all the construction took place underground, out of sight of city residents.
Teams constructed wooden fencing around the construction to minimize the aesthetic impact of the project. During a two-month winter period, one roadway was closed off to facilitate quicker construction for a sewer crossing across Richland Creek and to accommodate the city’s streambank restoration project.
While largely hidden from the public, the beginning and end points of the construction are identifiable by access doors.
The BILCO Company manufactured 13 floor access doors of various sizes for the project. The doors allow access to vertical shafts – one is 35 feet deep, the other is 105 feet deep – in which workers will descend into the tunnel or lower equipment into the tunnel. BILCO floor doors are designed with engineered lift assistance to ensure safe, easy, door operation.
“We used those types of doors fairly often on our projects, especially at pump stations,’’ Jones said. “We find they have good durability and reliability.”
Keeping Residents Connected
While most of the work was hidden, ReWa made sure to maintain a dialogue with city residents. The construction sites were near city residences and a local zoo. Residents were understandably concerned about how the project would impact their quality of life.
“We put in a good bit of effort to educate the public, get their feedback and learn what they had concerns about,’’ Jones said. “We wanted to gain the trust of the community from the very beginning. We had a series of meetings where we showed the community that we were serious about their concerns and taking them into consideration.”
While largely unseen, the community impact was substantial. Road closures, noise, vibration, safety and site restoration were all of community concern. Two important community cornerstones, Cleveland Park and the Greenville Zoo, were directly within the conveyance line.
ReWa established different communication vehicles, including a website dedicated to the project, a Facebook page, a 24-hour hotline, quarterly meetings and e-blasts. Greenville citizens had a wealth of resources to keep tabs on the project and voice their concerns.
“Some of the most concerned community members were our biggest advocates at the end,’’ Rich said. “They appreciated the transparency we provided. We told them they were going to hear noise and we’d do what we can to mitigate disruption. If they heard something of concern, they could reach out to us. Relationships with the community were our biggest challenges, but also one of our biggest accomplishments.”
A Model to Follow
When it comes to wastewater, America’s commitment to improvement has been sorely lacking.
In 1988, the ASCE awarded the U.S. a “C” grade for its wastewater infrastructure. That is the high-water mark for the last 30-plus years. Every grade since has been a D+ or worse. Overall, the U.S. earned a “C-“ from the ASCE in 2021. While no categories earned a failing grade, 11 of the 17 categories earned marks of “D+” or worse. Rail (“B”) and Ports (”B-“) earned the highest marks. In most U.S. homes, such a report card would result in extra chores, confiscation of the smartphone and angry phone calls to educators.
The federal legislation passed last year is a promising start. In addition, the Dig Greenville project sets up a template other communities can follow. Planning, research, communication and commitment – financial and mentally – are solid starting points.
While large-scale infrastructure projects frequently experience significant overruns in budget and time, the Dig Greenville project proved that does not always have to be the case. The project experienced a setback in drilling the starter tunnel, but that was the only hiccup in a multi-year project that also included fallout from an international pandemic.
“We had to add about 10 months due to the schedule, but we were able to keep it within the original project budget,’’ Jones said. “We were able to find some cost savings in some other areas and we had some good bids when we started.”
On its own, Dig Greenville will do little to improve the nation’s poor infrastructure grade. Its completion is evidence, however, that communities that demonstrate vision, intelligence and commitment can provide solutions to address infrastructure issues.
“It’s been a challenging project, but a fun one to be involved with,’’ Jones said. “It’s a good feeling to know that we are contributing to the long-term viability of the community. It took a lot of work to make it a success, and it came about through the efforts of a large group of people.”
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. 13 floor access doors manufactured by BILCO provide workers access to install, remove and repair equipment.
Did you know? Greenville is sixth in population and growth rate in South Carolina.
Thomas Renner writes about construction, engineering, architecture, and other trade industry topics for publications throughout the United States.