Reclamation Commissioner Keys Announces Contract Award For Excavation Of The Outlet Works Tunnel For Ridges Basin Dam

Media Contact: Ken Beck, 970-385-6558
Doug Hendrix, 801-524-3837

For Release: September 23, 2004

Bureau of Reclamation Commissioner John Keys announced today that Reclamation has awarded a contract in the amount of $5.9 million to Weeminuche Construction Authority (WCA) for excavation of the outlet works tunnel at Ridges Basin Dam. Upon completion of the Animas-La Plata Project, located in southwestern Colorado, the outlet works tunnel will be used to release water from the Ridges Basin Dam back to the Animas River.

"With construction of this tunnel beginning soon, we're clearly making significant progress on the structural components of the Animas-La Plata Project," said Reclamation Commissioner John W. Keys. "As of the third quarter of this year, we will have seen major progress on construction of the entire Animas-La Plata Project - including work in support of the Durango Pumping Plant and inlet conduit, the Ridges Basin Dam and Reservoir, the Navajo Nation Municipal Pipeline, and the Cultural and Environmental Mitigation activities."

Construction of the outlet works for the dam will require WCA project workers to excavate a 1,400-foot long tunnel through the solid rock of Carbon Mountain. Additionally, construction of the outlet works will require WCA workers to erect an initial ground support system, construct a concrete protective slab in the tunnel invert, and install a baffled apron discharge structure for passage of water during heavy runoff conditions. Excavation of the tunnel through Carbon Mountain will also provide storm water control and diversion of Basin Creek during construction of Ridges Basin Dam.

To construct the outlet works, WCA will excavate the tunnel corridor using two distinct methods. The upstream portion of the tunnel will be dug through a Lewis shale rock formation using a roadheader excavation machine. The roadheader machine uses dual rotating cutter heads equipped with carbide cutting teeth for shaving the rock. The downstream section of the tunnel will be excavated simultaneously (through the Pictured Cliffs sandstone formation) from the opposite direction, using conventional drilling and blasting techniques. WCA anticipates an 8 to 9-month construction schedule beginning this fall for excavation of the tunnel, working two 10-hour shifts a day from both directions.

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Relevant Link:

Animas-La Plata Project web site