James W. Jardine Water Filtration Plant, Chicago
Roofing contractor: Trinity Roofing Service, Chicago
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 water-filtration plant with 10.3 acres of Flex FB Elvaloy KEE thermoplastic membrane.
The 90-mil membrane was installed in hot asphalt onto a built-up roofing assembly, topping off a total roof system backed by a 30-year warranty. 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.
Roof membrane manufacturer: Flex Membrane International Corp.
Built on rubble from the Great Chicago Fire of 1871, the concrete-vaulted plant went online in 1964 on a 60-acre peninsula off the banks of Lake Michigan next to Navy Pier. Almost 1 billion gallons of water funnel into the plant each day, where it is processed and dispensed to 5 million consumers throughout Chicago and surrounding communities.
“The Jardine plant is an engineering marvel, but a half-century of constant 80-degree relative humidity and chlorine processing inside the facility corroded roof channels,” says John Cronin, president of Trinity Roofing Service. “It was time for a total makeover.”
The project began with erection of a 112,000-square-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-car roof and cellular glass insulation. Weight restrictions stipulated that dumping take place in a single staging area, requiring crew members to travel up to 10 miles per day back and forth over the roof to discharge loads during latter stages of the project.
Sixty-six different types and sizes of precast concrete channels, weighing between 225 to 500 pounds, were hoisted up by a specially modified crane; all 30,000 channels had to be individually inspected and approved before installation. Seven miles of backer rod filled in seams between these slabs.
Topping off the structure is 448,000 square feet of hot-air welded roof membrane, which is impervious to Chicago wind and weather extremes, chemicals, UV light, and hundreds of birds congregating on the roof and leaving acidic deposits behind. The plant’s new roof system is expected to perform reliably for many decades.