The tank surface had bumps, cracks and ridges. Rebar was exposed and rusting in some places |
Martin Reservoir, one of the city's storage facilities, required a new coating and lining system after 47 years of nearly non-stop service. A 20-million-gallon concrete underground water facility built in 1964, the reservoir stores potable water for Tucson and surrounding areas, with an average flow of 6 million gallons per day. The reservoir was the largest and most critical storage tank to the system when it was first built, and now is a component of the city's sustainable water policy that stores a combination of ground water and water pumped from the Colorado River into the Tucson Basin. Reservoir inspections reported signs of a deteriorated lining, bringing urgency to the rehabilitation project.
After a competitive bidding process, Tucson Water awarded a contract to Ashton Contractors and Engineers of Tucson, who subcontracted with Murphy Industrial Coatings, Signal Hill, CA, to find a flexible lining with fast cure time, low solvents and high durability paired with on-site training for rehabilitation staff. Martin Reservoir would be out of service for three months while rehabilitation teams drained the tank, stripped its deteriorating butyl rubber liner, and prepared and recoated the concrete surface.
With counsel from RFI Consultants, Phoenix, AZ, Tucson Water selected Sherwin-Williams' SherFlex™ Elastomeric Polyurethane, a 100 percent solids, spray applied, aromatic polyurethane coating and lining that can be applied at thicknesses of 30-250 mils in multiple passes during a single application. SherFlex is designed for use in immersion service as part of a tough, flexible, impact resistant coating and lining system in potable water tanks of more than 3,000 gallons. Its fast cure time, durability and no VOCs, along with the company's on-site training capabilities, made it a fit for the project.
"Choosing a coating isn't like going down to your local Sherwin-Williams store and picking up a gallon of paint," said Eric Brackman, owner, RFI Consultants LLC. "These coatings are demanding. You have to know what you're doing, especially when the surface is in poor condition. Once we pulled the existing liner, it looked like the dark side of the moon."
Because the liner in the reservoir had not been replaced since its construction in 1964, Tucson Water had informed contractors that it was likely the surface would not be ideal for applying a new liner. After stripping the tank, the project team found the surface was in need of repair before coating. It had bumps, cracks and ridges throughout the 22-degree slopes from floor to ceiling. Rebar was exposed and rusting.