Built in 1967, a 28-million-gallon potable water tank that serves the residents of the Alderwood Water District had never been taken down for maintenance, nor had a companion 20-million-gallon tank that had been erected in 1976. But last September, the larger of the tanks was emptied in order to begin a two-year maintenance project that would address coatings, corrosion issues, structural repairs and updating safety and security features on both units.
At present, 500,000 square feet of the interior and exterior has been blasted and coated. The existing coal tar interior system is being removed, and the steel blasted to SP10 before application begins. Application teams are scheduled to begin the exterior of the larger tank in June, and begin the project’s final major phase, the smaller tank’s interior, in September.
Contractor: Dunkin & Bush, Redmond, Wash.
Owner: Alderwood Water and Wastewater District
Engineer: Gerald Duppong (CH2M Hill)
Interior: Three coats of Sherwin-Williams MacroPoxy 646 NSF
Exterior: One coat of MacroPoxy 646 NSF, one coat of Sherwin-Williams High Solids Polyurethane