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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