Building Back Stronger: McGill’s Role in Erwin Utilities’ Recovery After Helene
Tropical Storm Helene Hits Erwin
The flooding caused by Tropical Storm Helene was unlike anything the community of Erwin, Tennessee, had ever experienced. What began as scattered power outages from high winds on the morning of Friday, September 27, 2024, escalated into a catastrophic event. With 24 inches of rainfall in Western North Carolina, the Nolichucky River swelled to 16 times its normal flow and reached widths of one mile wide in the Town of Erwin, pushing floodwater far outside its normal banks. The upstream rainfall and unconstrained floodwater resulted in the worst flood in the region’s history. The industrial park, wastewater treatment plant (WWTP), and much of the surrounding area were devastated by the surging Nolichucky River, which left a trail of destruction in its wake. Chestoa Bridge was washed away and Ballad’s Regional Hospital, the entire industrial park, portions of Interstate 26 (I-26), and a bridge on I-26 over the Nolichucky River were all destroyed, functionally separating Unicoi County into two unconnected portions on either side of the Nolichucky River. Tragically, the flood also resulted in loss of life, displaced residents, and severe economic impact, including unemployment and business closures.
In the face of this unprecedented disaster, Erwin Utilities needed immediate and comprehensive support to restore its operations and plan for the weeks ahead. The storm had severely damaged power, fiber, water, and wastewater systems. While water production facilities remained intact, water and sewer lines were severed across the community. The WWTP was submerged under 12 feet of floodwater, leaving behind a thick layer of debris, mud, and silt. Every concrete basin had three to five feet of mud and silt, electrical systems were short circuited, and most treatment components were rendered inoperable. The situation demanded urgent action.
McGill Steps in During a Crisis
Recognizing the gravity of the situation, McGill swiftly mobilized to support Erwin Utilities. While the Utility’s dedicated staff worked tirelessly to remove mud, stabilize and repair broken water and sewer lines, and assess the damage, McGill’s team stepped in to design and implement temporary wastewater treatment solutions, prioritize repairs at the WWTP, and map both immediate and intermediate recovery options to plan the first 120 days of the emergency response. These measures were critical to restoring basic services and ensuring the community’s health and safety while long-term recovery plans were being developed.
Bypassing the Industrial Park
One of the most pressing challenges was the destruction of the gravity sewer main over the Nolichucky River and the length of the industrial park. A temporary bypass pumping system to collect and transport wastewater to the WWTP, which would serve 538 residents disconnected by the flood, was a key recovery focus for the Tennessee Department of Environment and Conservation (TDEC), Environmental Protection Agency (EPA), and Tennessee Department of Transportation (TDOT). McGill worked closely with Erwin Utilities to identify the optimal routing for the bypass, leveraging existing infrastructure and aligning temporary measures with future planned improvements. This forward-thinking approach not only addressed the immediate crisis but also laid the groundwork for long-term resilience. The bypass solution included:
- Designing and implementing a lift station and temporary sewer lines to convey flows from the south end of the County back to the WWTP
- Coordinating with Erwin Utilities staff to inspect manholes and identify the most efficient route
- Ensuring the temporary system could handle the community’s needs while minimizing disruption
Innovative Temporary Repairs to the WWTP
McGill proposed an innovative and cost-effective strategy for restoring temporary operations at the WWTP using a phased emergency and intermediate approach. Initial recovery plans involved repurposing the existing anaerobic digesters into aerobic activated sludge units to allow for repair of the damaged rotating biological contactors (RBCs), which were the primary biological treatment process. This approach not only expedited the restoration of services but also minimized costs and provided an alternative to mobile treatment units.
Key components of the temporary repairs included:
- Coordinating with TDEC, EPA, and contractors for the placement of a new, gravel road and laydown soil for seeding to provide access to buildings and process equipment for cleaning equipment and vacuum trucks
- Removing silt and debris from critical areas, including the influent lift station, grit channel, primary and secondary clarifiers, and chlorine contact basins
- Repairing and inspecting mechanical equipment and pumps to ensure functionality
- Coordinating with electrical contractors for replacement of controls, drives, and other critical equipment necessary to restore treatment operations
- Planning for and cost analysis of removal and disposal of damaged RBC media, drives, and covers
- Planning, design, and bidding for cleaning out anaerobic digesters
- Repairing clarifier mechanisms at the primary and secondary clarifiers
- Inspecting and troubleshooting electrical components, then repairing or replacing them, as needed
- Repairing and replacing a 24-inch sewer interceptor damaged by the flood and recovery activities by CSX
- Preparing asset replacement costs needed for permanent repair and replacement
- Designing in place modifications to the WWTP outfall, as needed, to restore hydraulic function and protect the outfall until a new outfall can be designed, permitted and constructed
- Designing in place pump and piping alterations necessary to install and set up a new centrifuge and restore solids processing
These solutions allowed Erwin Utilities to resume wastewater treatment operations quickly, providing a lifeline to the community during a critical time.
Repairing Water and Sewer Connections Across the Nolichucky River
Some of the most striking images from the disaster showed the floodwaters reaching staggering heights near the Jackson-Love Bridge. Recognizing the need for durable, long-term solutions, McGill supported Erwin Utilities in planning and designing permanent water and sewer installations at this critical location. The bidding and construction for this project is set to start in March 2025. The project includes:
- Surveying and designing 415 linear feet (LF) of 8-inch restrained joint ductile iron pipe (DIP) water line and 415 LF of 6-inch restrained joint DIP force main sewer installed by pipe hanger system under the existing Jackson-Love Bridge over the Nolichucky River (these pipes are insulated and heat-traced to avoid freezing)
- Surveying and designing 400 LF of 8-inch restrained joint DIP water line and 400 LF of 6-inch restrained joint DIP force main sewer installed by open-cut along Jackson-Love Highway
- Designing modifications to the bridge, including 2 bridge abutments, 5 diaphragms, and 15-inch steel encasements and appurtenances at each concrete apron
- Securing necessary permits and managing the bidding and award process
- Providing construction administration to ensure the project was held to the highest standards
A Partnership Built on Trust and Expertise: Designing a Permanent Solution
Throughout the ongoing recovery process, McGill’s collaboration with Erwin Utilities is marked by trust, innovation, and a shared commitment to the community. By combining McGill’s technical knowledge with Erwin Utilities’ local knowledge and dedication, the team is overcoming immense challenges and delivering solutions that are restoring services, while also supporting grant funding, design, and planning needed to build back stronger and be more resilient and prepared for the future.
Erwin Utilities and McGill are currently working with the Federal Emergency Management Agency (FEMA) to tackle the following tasks to replace temporary repairs with permanent solutions. We are working on:
- Replacing influent pump stations
- Replacing the media, bearings, and gearboxes of the RBCs
- Restoring the anaerobic digester
- Rebuilding the drying beds
- Replacing the rented centrifuge with a permanent replacement
- Installing a fully integrated chemical feed system
- Addressing all plant instrumentation, which was comprised in the flood
McGill continues to work closely with Erwin Utilities to develop these permanent solutions at the current site and build toward a long-term project to design an effective WWTP at a new site. This long-term project involves comprehensive planning, innovative design, and strategic implementation to ensure the community has a reliable, state-of-the-art system capable of withstanding future challenges. We will work with the community to seek funding to meet both short-term and long-term goals. Together, McGill and Erwin Utilities are not just rebuilding, but reimagining the future of infrastructure in Erwin.
