The Sherwin-Williams Co.
Industrial & Marine Coatings
101 Prospect Ave. NW * Cleveland, OH 44115
Phone 800/524-5979 * www.sherwin-williams.com
The town of Ocean City, Md., has 3,500 year-round residents, but when tourist season arrives, the population swells to 400,000. While tourism is a boon to Ocean City, it puts stress on the town's municipal water system. The situation has been exacerbated by steadily deteriorating conditions at one of the town's three water treatment plants. Despite the city's diligent efforts, the result of repairs made to stop water seepage cracks from occurring in two potable water reinforced concrete tanks were short-lived.
Ocean City officials decided to try Sherwin-Williams EnviroLastic Polyurea coating as a long-term solution for its concrete cracking problem. Because of its flexibility, polyurea is not affected by temperature extremes and is an excellent choice for lining potable concrete tanks compared to traditional epoxy coatings, which can crack as the substrate expands and contracts.
Problems mounted
Ocean City water treatment plants produced 1.9 billion gallons of water in 2002. The Gorman Avenue Water Treatment Plant, composed of two operating facilities, includes a structurally sound North Tank completed in 1988 and a deteriorating South Tank, built in 1972.
"The worst cracks occurred at the South Tank's clarifier and pump basin and measured six to eight feet long by about 1/16-in. wide," said Dave Johnstone, resident engineer, Whitman, Requardt & Associates. "Maintenance crews repaired the cracks regularly by injecting them with epoxy or caulking material, but they kept reappearing."
Because the polyurea technology was new to both Ocean City officials and to the engineering firm, Sherwin-Williams representatives invited them to attend a regional seminar and polyurea demonstration the manufacturer was hosting. Three coating crew employees from B&H Coatings, a Maryland industrial painting contractor specializing in polyurea projects, demonstrated the proper techniques for applying the EnviroLastic Polyurea.
The demonstration offered the opportunity to learn more about the product, its recommended uses and performance in the field.
Johnstone observed that reinforced concrete is "notorious for movement." During extreme temperature changes, it can expand or contract, which can cause the concrete to fracture.
"After seeing the demo, we were sold on polyurea as a solution to our concrete cracking problem," said Johnstone. "Because of its elastomeric properties--400% elasticity--the polyurea coating can stretch without ripping and can bridge gaps up to 1/8-in., making it ideal for protecting concrete substrates."
B&H Coatings was awarded the South Tank polyurea coating project. City officials requested the repairs take place during the winter, so there would be no interference with the water treatment operation during the peak summer months.
The coating was applied on the South Tank clarifier and pump basin. It dried to the touch in about three minutes and cured in 24 hours.
From the contractor's perspective, the ability to coat the water tanks at freezing temperatures together with the fast cure time resulted in speeding the job to completion.
After completing the South Tank repairs, Ocean City officials commissioned B&H to coat the clarifier and pump basin at the North Tower with EnviroLastic. The newer structures were in better condition and did not require as much preparation work. As a result, the polyurea installation was quickly completed within two weeks.
