Reservoir gets unique cover

The Columbian Park Water Reservoir in Lafayette, Ind., supplies drinking water to the surrounding community and protects the water supply from a variety of elements. But until recently, the reservoir was protected from direct sunlight, vandalism and park animals by a floating polyethylene fabric that had to be replaced approximately every 15 years at considerable expense. Additionally, the cover had the cleaned on a regular basis, which meant costly maintenance.

The bid process began with a list of requirements: the new cover had to be clear-span, because it was impossible to build supports into the reservoir; it had to be corrosion-resistant; and it had to be as maintenance-free as possible.

Temcor, Carson, Calif, proposed an aluminum truss-vault roof system to cover the 42,423-sq.-ft. reservoir. The clear-span roof is resistant to moisture and corrosion and requires minimal maintenance. The company also engineered a unique erection system for covering the reservoir, which reaches depths of 27 feet, without taking it out of service.

However, the biggest challenge was figuring out a way to assemble the massive truss-vault sections for the roof and get them into place without interfering with the active reservoir.

Instead of using conventional construction methods, the company employed a special u-channel track constructed along the sides of the reservoir, bolted to the sides of the grade beam foundation and extending past the end of the reservoir, ending at a construction staging area.

The first of 11 trusses was built in place over the track in the staging area. The truss, built with wheels fitted into the u-channel, was then pushed back 20 feet away from the staging area and over the reservoir.

Once supported in its upright position with a slide assembly, the second truss was completed, rolled along the tracks, attached to the first truss, and the two trusses were pushed back another 20 feet.

When all of the truss sections were completed, the roof frame was jacked up so the wheels could be removed. The roof frame was then lowered back down and bolted to the walls of the reservoir, and the aluminum panels were installed into the closure system. The roof system was completed in 10 weeks.