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World's Largest Water Purification System Gets a New Roof

Flex Membrane International

Chicago’s James W. Jardine Water Filtration Plant, processes and dispenses almost one billion gallons of water each day, more than any other purification system in the world. The concrete vaulted edifice went online in 1964 on a 60-acre peninsula off the banks of Lake Michigan. After a half-century of constant 80-degree relative humidity and chlorine processing inside the facility corroded roof channels, it was time for a total makeover.

After two years of demolishing a 50-year-old graveled coal tar pitch roof, disposing of 6,100 tons of debris, installing 712,000 board feet of cellular glass insulation, and replacing 30,000 precast concrete roof channels, workers capped off the plant with 10.3 acres of Flex FB Elvaloy KEE thermoplastic membrane. The last of 1,086 rolls of the Flex fleece-backed membrane was installed in late September 2014.

The project began with the erection of a 112,000-sqare-foot plywood scaffolding platform blanketed by a 60 mil membrane that established a leak-free zone over concrete filter beds below and allowed the plant to operate without interruptions. Next came removal of the coal tar roof and cellular glass insulation.

Sixty-six different types and sizes of precast concrete channels weighing between 225 to 500 pounds were hoisted up by a specially modified crane, and all 30,000 had to be individually inspected and approved before installation. Seven miles of backer rod filled in seams between these slabs.

The Flex FB Elvaloy KEE 90 mil membrane was installed in hot asphalt onto a built-up roofing assembly. Dupont Elvaloy KEE is a high molecular weight solid plasticizer that does not migrate out of the membrane while maintaining flexibility and toughness throughout its service life. The result is 448,000 square feet of hot-air welded membrane, an integrated whole impervious to Chicago wind and weather extremes, chemicals, UV light, and hundreds of birds congregating on the roof and leaving acidic deposits behind.

posted:  1/5/2015