Water treatment facility in need of preventative repairs
Apr. 19—During its April 2 meeting the Lenoir City Council awarded a contract to Freyssinet Incorporated to conduct preventive repairs at the George L. Bernhardt Sr. Rhodhiss Lake Water Treatment Plant. The contract is for $844,051.50 with an additional $84,405 set aside as a construction contingency, as recommended by the engineer of record, McGill Associates. The damages to the basin do not affect the quality of the water, according to Lenoir Public Utilities director Jeff Church.
Clean water is a resource often taken for granted, and the treatment process is not well known to many members of the public despite the ubiquity of the product. Lenoir's water treatment superintendent Kevin Matheson explains that, at the Lake Rhodhiss plant, water is pumped out of the lake from well below the photosynthetic layer (where algae forms) and into the flash mix basin. A flash mixer incorporates alum into the water rapidly to ensure the chemical is well-distributed throughout the lake water. Allum serves as a coagulant in the treatment process, helping to flocculate unwanted particles into heavy clumps.
The water passes into slow-mix flocculation basins, where the clumping process is assisted with slow-moving paddles, before passing into sedimentation basins. Here the particles' combined weight lets them sink into a sludge at the bottom of the basin. By this process the lake water undergoes a 10-20 fold reduction in turbidity before finally leaving the plant a 0.9 NTU, on average, according to Matheson. The sludge is set aside to be trucked to a wastewater treatment plant, while the clear water is filtered and stored in a tank where final chemicals are added before the water is pumped out to consumers. The entire process takes around 2.5 hours, filtration only accounting for a few minutes.
Matheson revealed that the Lenoir plant treats an average of 6 million gallons a day, though if necessary it could process up to 12 million. The water is pumped to residents of Lenoir and other Caldwell County communities. Other repairs will need to be made to the sedimentation and flocculation basins in the future, but for now it is the flash mix basin that needs them the most. Without the flash mixers, some other rapid mix mechanism would need to be used to ensure the plant is able to meet the needs of the community.
The plant has been operational since 1956, and the flash mix basin has been in use since 1976. Over the past half-century, the 19-foot-tall concrete basin has weathered and deteriorated. The concrete has begun to crack and chip away in a process called spalling and water seeps out through the cracks from the interior. Freyssinet, as a part of repairs, will both replace spalling concrete and inject epoxy into the cracks. The Virginia-based company will also apply an epoxy coating to the basin interior, which will extend its lifespan.
The contract specifies that repairs will be concluded by August 23, 2024.
