River Shifters 

Where the rubber meets the wave for Boise's new river recreation park.

Kayakers keen to enjoy the features of Boise's forthcoming river recreation park should thank some unfamiliar technology, specifically air-filled rubber bladders. The technology behind the forthcoming Ray Neef MD River Recreation Park incorporates multiple adjustable rubber tubes, similar to a bike's innertube, in which air pressure can be fine-tuned to control the river. The park broke ground the first week of October.

"The wave shapers have, on the upstream side, a rubber air bladder that lifts up a concrete filled gate--a steel gate. It's attached with a hinge to the wave-shaper deck," said Michael Smith engineer with Obermeyer Hydro Inc., the Fort Collins, Colo., manufacturer of the grate dam.

The plan includes the replacement of the Thurman Mill diversion dam currently installed near Quinn's pond with the Obermeyer dam, as well as two wave shapers designed by McLaughlin Whitewater Design Group of Denver. The wave shaper will create two separate waves, 25 feet and 30 feet respectively. The plan also includes waterside seating and areas for swimming and beaches.

The park's planned cost is $6.7 million, with the first phase accounting for $3.8 million. The city, the J.A. and Kathryn Albertson Foundation, and a fund-raising campaign have netted most of the funds for phase one.

Air filled rubber dams aren't new, said Smith, but their design has moved away from the traditional models, like those used Tempe, Ariz., that recently failed.

On the evening of July 19, Tempe's inflatable rubber Town Lake Dam burst, sending three-fourths of the mammoth lake cascading in 6-to-8-foot waves through the dry Salt River beds from which the lake was created. The rubber dams that had corralled almost 1 billion gallons of water were installed by the now derelict industrial works arm of the Japanese company Bridgestone.

The rubber used in Tempe's dams was directly exposed to the harsh Arizona summer sun and temperature, weakening them until they eventually burst. A sprinkler system was installed to keep the rubber cool and wet to avoid another failure, but the errors, be they Bridgestone's or Tempe's, cost the project millions (Tempe has since decided to stick with them).

"We used to use those," said Principal Engineer Rick McLaughlin. "One of the first projects we built was with a tube-type dam. The one we did here in Denver was cut up by a vandal."

The Obermeyer system is different. For one, the tubes aren't exposed, and Boise's weather conditions are much different from Tempe's. McLaughlin said they selected this system because it's safer and because it does more than just block water. It creates waves as well as continues to divert water for the canal system; it's cutting-edge technology, according to the City of Boise.

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