In 2019, city officials in Chattanooga, Tennessee announced that they were taking action to prevent the overflow of wastewater into the Tennessee River from their combined sanitary sewer system.  The initiative would require the construction of three large storage tanks at the Hamm Road Equalization Station with a combined capacity of 30 million gallons.  Part of the construction project would require a large retaining wall to provide a necessary maintenance access road adjacent to the location of the new tanks.

Ryan Viva of U.S. Retaining Walls, the retaining wall installation contractor, considered several types of retaining wall systems, but concluded that Redi-Rock would offer the most cost-effective solution given the limited site access and required construction schedule. Viva and his team then reached out to Redi-Rock producer, Bradley Tank and Pipe of Cleveland, Tennessee for assistance in preparing an accurate bid proposal for the project. 

Bradley Tank and Pipe retained the services of JC Hines and Associates for the preliminary wall design and detailed material quantities.  Following acceptance of the U.S. Retaining Walls proposal by the City, the team at JC Hines went to work to prepare the final retaining wall construction drawings. 

JC Hines and Associates completed the retaining wall design based upon the site plans prepared by Civil Engineers, Hazen and Sawyer. The final design required a retaining wall with a maximum height of 22.5 feet, although the wall height averaged almost 20 feet over its 518 foot length. “Once we bid with this design, the City was on board,” said Ryan Viva. “We won this job by being able to build such a big wall as gravity.” JC Hines and Associates designed the wall on a concrete footing for increased stability. Viva reported that this footing, the size of the Redi-Rock XL blocks and the lack of geogrid reinforcement allowed his team to progress much more efficiently securing the significant cost and time savings planned in the initial proposal. U.S. Retaining Walls completed the installation of this 10,173 square-foot wall in just 33 working days.  

Bradley Tank and Pipe produced and supplied all 1,074 Redi-Rock blocks for this project. “Redi-Rock was an excellent choice for this wall,” said Andrew Butler of Bradley Tank and Pipe. “By utilizing the new XL Redi-Rock blocks, JC Hines avoided geogrid reinforcement and associated costs for the City. This design saved money, time, and space.” During construction, the engineers, producers, and installers were all synchronized perfectly, as the adjacent wastewater tanks were already in place. “Trucks had about six inches to miss the tanks or the new wall,” said Ricky Butler of Bradley Tank and Pipe. “It was a hugely collaborative project.” The retaining wall runs directly beside two of the three tanks for its entirety.  

“The City of Chattanooga is very pleased with the look, cost, and function of this wall,” said Ryan Viva. Operation of the Storage Station began in the summer of 2022. According to the City of Chattanooga, an estimated 18 million gallons of wastewater and rainwater have already been diverted to the overflow tanks and later released into the city’s treatment plant for purification.