Water and Wastewater Tanks

WATER AND WASTEWATER TANKS
- Application of 100% Solids Polyurethane Coatings

Using common duct tape and a 100% solids polyurethane coating, the City of Vienna was able to rehabilitate a water treatment tank that was in danger of being scrapped. In doing so, they saved close to $60,000.

Vienna is a small city of 10,000 located in West Virginia. The tank in question is a small steel ground storage reservoir (20'X16') that is used for potable water treatment. Back in 1990, the Vienna Public Works officials were faced with the real possibility of having to replace this tank, due to extensive corrosion and leakage.

Inside the treatment tank are several steel baffles that run the full height of the tank to provide thorough mixing of the water and treatment chemicals. These inner baffles were severely pitted as well as having up to 2 inch diameter holes in them. On the outside of the tank, several of the weld seams were corroded and leaking. At the time it was felt that the only solution was to replace the tank.

In February of 1990, Lewis Estep of Estep Painting out of Charleston, West Virginia, came up with a unique and effective solution to this problem.

Estep started by repairing the worst of the holes with welded steel plate. All of the steel was then blasted and duct tape was placed on the back side of the remaining 30 to 40 holes. A NSF 61 listed 100% solids polyurethane, was then spray applied to a thickness of 250 mils (1/4"). This mil build was achieved in approximately 20 passes with about 30 to 60 seconds of waiting between passes. The balance of the baffle surfaces and tank interior were sprayed with 60 to 70 mils of the polyurethane coating in order to fill in the deep pitting and completely seal the tank.

The tank rehabilitation was completed and the tank back in service after just one week. The job cost approximately $20,000 (plus one roll of duct tape), considerably less than the estimated $80,000 for a new tank.

A year later, in March of 1991, the tank was emptied and inspected. The Director of Public Works of the City of Vienna, reported that "the tank and coating were in perfect shape". He expects the tank to last at least another 20 years before any repair work is necessary. He was quoted as saying "In my 30 years of painting water tanks I have tried every new thing that has ever come onto the market and this polyurethane is the best stuff I have ever seen".

A Winnipeg based company, recently adopted the 100% solids polyurethane coating technology in order to enhance the marketability and longevity of the pre-fabricated sewage treatment facilities that they manufacture. Because their technology is a leading edge treatment process exhibiting long term viability, it is imperative that the physical plant process hardware and tankage have a compatible long term life expectancy.

The most critical component affecting the life expectancy of the treatment plant is the tankage life cycle which is directly determined by the integrity of the coating system being used.

Since the formation of the company, the Winnipeg company has been on a constant quest to identify the best available coating system. Through an exhaustive selection process, a 100% solids polyurethane coating system was identified as the best available coating system for the protection of the steel treatment plants.

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