Northport Intake Repairs
Mainstream Commercial Divers, Inc. (Mainstream) was contracted by Mark Johnson Construction to provide a dive crew and equipment for the repair of an intake structure on Lake Tuscaloosa in Northport, Alabama.
An underwater inspection had previously been conducted by Mainstream for the city’s engineering consultant. The consultant then designed repairs to the structure and its components consisting of removal and replacement of the existing screens, valves, valve stems and stem guides; demolition and replacement of structural tie-rods; demolition of existing concrete splash guards; and the application of high-performance coating and corrosion protection systems.
The new valve stems, guides, and tie rods were installed using bolted clamps fabricated from stainless steel. Denso Series 70 products were used as a coating repair on the pipe piles, w-beam supports, and the intake caisson pipes. The diver used a 5k pressure washer to clean the steel down to the lake bottom in 48’ of water and covered the pitted areas using an underwater paste. The pipes and w-beams were then covered with the Denso wrap materials installed to the manufacturer’s specifications.
This project was completed safely and on-time. Careful coordination with the plant operators and site investigations were made to ensure that running pumps were either locked out/tagged out and the valves were closed or properly screened off and that no differential pressure hazard would pose a threat to the safety of the diver. Since the plant had to maintain intake operation to supply the local water district, the diver’s work was performed at a safe distance from the operating pumps.