U.S. Water News Online
WASHINGTON -- Once a barren, dusty expanse, Tempe's Town Lake has become a center of recreational activities and development that is boosting the local economy and spirit. The lake is a finalist in the American Consulting Engineers Council's 34th annual Engineering Excellence Award competition for its design by CH2M Hill.
The Salt River was once an uncontrolled river flowing through the City of Tempe, Arizona. Beginning in the early 1900s, dams were constructed in the nearby mountains to capture the water for irrigation and electricity, turning the river into a dry wasteland for most of the year. In 1996, Arizona State University architecture students conceived the idea of creating a waterway that would provide the community with recreational and commercial opportunities while addressing flood control and wildlife habitat issues.
CH2M Hill, which conducted the project's feasibility and designed the lake, addressed a number of problems including retaining the lake's costly water supply. The east and west boundaries required dams designed not only to keep water at a level necessary to maintain quality, but also to control flooding of up to 215,000 cubic feet per second. Working closely with the city, the project team proposed air-filled rubber dams for their flexibility, strength, and appearance. The dams can be inflated or deflated in less than an hour. The lake is the first project in Arizona to use rubber dams. Under normal conditions, water cascades over the dams, creating an attractive waterfall effect, which also protects them from the Arizona sun. The overflowing water is captured downstream and pumped back into the lake.
Because Tempe Town Lake has no natural source of feedwater, the city must purchase any water lost to maintain the desired level. CH2M Hill's subsurface investigation uncovered a complex geology that could result in a significant amount of seepage. To prevent losses from beneath the lake, the project team designed a unique seepage control system consisting of slurry walls and recovery wells. This system is designed to capture 40 million gallons of water per day and return it to the lake. The Tempe Town Lake is one of 162 finalists that were judged on March 17-18 by a panel of judges with backgrounds in engineering, architecture, government, media, academia, and the military. The winners will be announced at ACEC's annual convention in May in Buffalo.
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