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Project

The 6-million-gallon Pohakapu Reservoir PotableWater Tank in Kailua,Hawaii had been leaking due to a design flaw and was losing up to several hundred gallons of water daily.The original design for the concrete tank had been successfully employed for smaller tanks,but according to field personnel, the higher pressure caused by the greater volume of water ultimately forced a separation between the walls and floor of the tank,thus causing the leak.

Participants

Owner:Board ofWater Supply, City and County of Honolulu
Engineer:Kai Hawaii, Honolulu
Contractor:Abhe-Svoboda, Inc.,Kapolei, Hawaii

Solution

A coating system was specified that would provide internal flexibility, minimize the existing structural concerns and ensure a longer service life for the tank.Application teams applied five passes of Sherwin-Williams P105 Sealer to the floors to mitigate moisture vapor, then a single coat of Corobond Conductive Primer to the entire interior. Then, a coat of Sherwin-Williams Envirolastic AR520PW, at an average of 75 mils,was applied to the floor and walls of the tank.Specifiers determined that the polyurea coating would allow for future expansion of the concrete tank and act as an internal bladder should concrete delamination occur in the future.

The approximately $300,000 application was successfully completed and the tank was returned to service in March 2008.

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