Spillway Renovation Prepares It for Century to Come

2013-01-22T01:00:00Z Spillway Renovation Prepares It for Century to ComeBY LAURIE WELCH lwelch@magicvalley.com Twin Falls Times-News
January 22, 2013 1:00 am  • 

RUPERT • The team that built the Minidoka Dam a century ago wouldn’t recognize it today.

A $21.3 million renovation of the dam’s spillway is forging ahead, transforming the structure that gave first life to Minidoka County’s farm fields.

The construction work on the new spillway and head works began more than a year ago and is continuing through the winter. On schedule, the project is expected to be complete in March 2015.

"It's going very well," said John Tiedeman, activity manager for the U.S. Bureau of Reclamation. "The project is about half complete."

Money for the $21.3 million project comes from the Burley and Minidoka irrigation districts, which passed respective $7.9 million and $14.75 million bond issue elections in February 2010 to pay for their portions of the spillway project.

The spillway replacement project at the dam, which lies about 18 miles northeast of Rupert, includes demolishing the existing 2,237-foot-long pier and stop log structure and replacing it with a roller-compacted concrete gated spillway. The structure will include control gates for the irrigation districts.

It’s not the first time the dam or associated facilities have been upgraded. Its power plant needed to be replaced by the 1990s — that project was finished in 1997. And in 1994, structures at the associated Walcott Lake Park were refurbished, including new boat ramps, shelters, restrooms, and a new overnight camping area and sewage treatment facility, according to BOR historian Eric A. Stene.

The newest renovations — arguably the most significant overhaul of the dam itself — requires 26,000 cubic yards of concrete for the new spillway and head works. Each section of the spillway has 12 gates and requires nearly 2 million pounds of concrete.

Tiedeman said the radial gates are in and the deck on the spillway is in place. Crews are now working on the head works for the irrigation districts, which must be operational by April 1 for the start of the irrigation season.

"Work kind of slows down in the winter but we have the concrete company make as many placements as possible," Tiedeman said. "Work will continue to go full bore on the Burley and Minidoka head works to make sure they are ready for the irrigation season."

This spring, the crews will also put in the new top section of the spillway — replacing 3,500 stop logs that had to be manually adjusted to control the water level.

"It will eliminate the need for that," Tiedeman said.

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