New lake dam to be made of steel
The Tempe City Council decided early this year the best replacement for the rubber dam in Tempe Town Lake is a steel-hinged crest gate.
The temporary rubber bladder, on loan from Bridgestone since the original burst more than five months ago, must be replaced by Dec. 28, 2015 to avoid costs.
The decision will be formally agreed on during a Jan. 19 council meeting.
Tempe replaced the burst bladder and constructed a pedestrian bridge intended to shade the dam from the intense Arizona sun, but city council is aiming to build a dam to last long-term.
Tempe Mayor Hugh Hallman said the rubber bladders were not intended to last forever, but the Council is now looking to longevity.
“We will make decisions for the long-term, thinking of the cyclical cost the same way we all think about making purchases for ourselves,” Hallman said.
City officials analyzed more than 20 different dam options and narrowed them down to three viable designs.
After considering designs such as a Sumitomo Rubber Dam, the same one used previously, and an Obermeyer Gate, which also uses rubber bladders, the council unanimously agreed the most reliable and cost efficient design would be a hydraulic-hinged crested gate made of steel.
The steel-gated dam met all of the city’s requirements for safety, reliability, durability, cost-effectiveness and investment value, said Jeff Kulaga, assistant city manager.
“When we did the engineering analysis, this steel-gated dam came out on top,” Kulaga said.
Both the Sumitomo Rubber Dam and the Obermeyer Gate were estimated to need replacement every 10 years.
The City estimated the cost of the Sumitomo Rubber Dam to be about $179.2 million and the Obermeyer gate to be about $74.4 million over the next 50 years, including replacement costs.
The hydraulic-hinged, crested gate would only need to have parts replaced periodically and is estimated to cost $68.1 million over the next 50 years, the least expensive of the three viable options.
Only Bridgestone can repair its rubber dams, but the new steel design offers more alternatives for the City when something breaks, Vice Mayor Joel Navarro said.
In addition to its practical benefits, the steel-gated dam will extend the lake by 100 feet and improve the aesthetic quality of the area near the Tempe Center for the Arts, Hallman said.
“The best technology for longevity and reduction for risk of rupture is the hinge-crest gates,” he said. “It’s nice that the math turns out in a way that it is the best choice for our community as well.”
A public meeting to discuss the decision with Tempe residents will be held at the Tempe Center for the Arts Wednesday at 5:30 p.m.
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