As they drive along the mile-and-a-half-long stretch that is Pickwick Dam, TVA employees and contractors alike are proud that the five-year project to strengthen the dam against seismic events is nearly complete — ahead of schedule, millions of dollars under budget and without any work-related safety or environmental incidents. The project has also earned several awards.
Constructed in 1938, Pickwick Dam impounds more than 43,000 acres of lake water, houses two active locks and remains heavily trafficked with barges that transport directly to the Gulf of Mexico as part of the Tennessee-Tombigbee Waterway. But when the dam’s south embankment failed to pass TVA’s seismic stability guidelines in 2014, Bernie Auld, senior program manager of River System Dam Safety knew it was time for an upgrade.
“This was a complicated process because it’s a hydraulic-filled dam,” says Auld. “Pickwick was built using dredged materials from the river and since these materials weren’t compacted, an earthquake could have liquefied the dam, causing deformations and possible loss of the reservoir.”
The main concerns were protecting the downstream communities, maintaining navigability and sustaining the area’s high recreation level. To do all of that safely and efficiently, Dam Safety knew it would be a long and complicated project.
With the help of multiple TVA groups including Project Services & Facilities Management, Surveying, ITMA, ESS, and Environmental Support Generation and Valley Projects, Dam Safety developed the massive project plan and then collaborated with TVA’s Civil Project Management team to complete the updates.
Partnering with local contractors, TVA Generation Construction and Barnard Construction Company, Inc. constructed upstream and downstream berms and extended fills to help prevent deformation should a large seismic event occur. A new flexible toe drain system and an immense sand and gravel filter system on the downstream side were also added. More than 900,000 tons of rock and nearly 1,000,000 tons of soil were used to ensure that TVA’s Dam Safety design criteria was met.
“This has been a long road from start to finish,” says Lawanda Hayes, senior project manager, Civil Project Management. “Pickwick Dam is unique in the fact that dams of its kind are no longer being built, though it was state-of-the-art for its time. It’s also located near the New Madrid Seismic Zone, so all of these characteristics were a major factor in how the job had to be done.”
Due to the installation of a state-of-the-art warning system, Pickwick Landing reservoir was able to operate under its current guide curve. Since the lake was not lowered during the construction phase, Dam Safety training was essential throughout the project. The project team, including Dam Safety Civil Engineer Ellen Money, performed a construction potential failure mode analysis to determine the possible ways the dam could fail during construction.
“Based on our findings, we determined the areas of construction that could have the most impact on the dam and developed a site-specific training. Everyone on site was required to take this training and pass a test at the end,” Money says. “Dewatering, excavation and several other construction tasks were part of the training. The training helped the teams be more aware, keeping the dam and everyone around it safe.”
“Everything has risks, but the key is to understand and mitigate them before going in,” says Auld. “The daily trainings based on this analysis and the teams’ constant mindfulness of safety is what we believe helped to prevent any environmental and safety events from occurring throughout the project’s entirety.”
In addition to safety precautions, the operating lake level created several challenges on the upstream side for the work teams. Not only did they use marine-based equipment, but they also had supplies shipped in on barges; installed an automated instrumentation system to ensure the dam didn’t move while performing the updates; and displaced a soft, 14-foot layer of sediment that had accumulated since the dam’s initial construction as part of the upstream berm construction.
According to Hayes, the weather added further challenges, dumping large amounts of rain in 2019 that plagued the teams with historic flooding conditions.
“Experts say it was 300 percent of the average rainfall for that time of the year,” she says. “It caused a three-week delay in the beginning, and we continued to experience flooding throughout the course of the project. Expecting the best but preparing for the worst really turned out to be beneficial for us overall. We had rock and soil stockpiles there on site ahead of time and — despite the flooding — were able to just about complete the project several months ahead of schedule and $26 million under budget.”
Only a small amount of work is left to do. It’s expected to be finished in the fall of 2022.
With most team members counting the Pickwick update as one of their biggest successes, they believe that inclusion and intentional teamwork were crucial to its overall outcome. Project recognitions have included the annual USSD Excellence in Construction Projects Award, the Construction Users Roundtable Project Excellence Award and the American General Contractors Build America Award.
“It’s incredibly important that everyone feels comfortable to bring what they offer to the table,” Money says. “People want to be involved beyond their daily tasks, and a sense of ownership gives them a reason to speak up when they see a problem. Being included, and including others, gave us all a sense of ownership and deeper awareness for why we were doing the project.”
Hayes agreed, noting that to include everyone they often had to shift their own perspective to that of the other teams.
“There were many teams involved that brought unique outlooks and different levels of experience to the table,” she says. “These types of projects require the inclusion of a diverse group of subject-matter experts, and the key with ours was one-on-one relationships and learning not to be so transactional with other groups. We had to learn different management and communication standards to do so, but we worked better together once we did.”
Though the project is nearly complete and the teams have parted ways, many say that they’re walking away with a better sense of what it’s like to be a part of TVA and what it means to ensure that historic sites like Pickwick are stable for future generations.
“The pride and satisfaction that we all have for the completion of this project stems from the fact that we know we’re leaving our families — who live and work in the area — with a quality result,” Hayes says. “And we do it knowing that we’ve helped to make the Valley a better, safer place for others to live and work.”