Workers shore up Lake Lowell dam deficiency
Mike Vogt/IPT
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Mike Vogt/IPT
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Mike Vogt/IPT
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Thursday, January 17th, 2008
CANYON COUNTY — Work crews continue to work to fix a deficiency detected by U.S. Bureau of Reclamation officials at Lake Lowell’s Upper Deer Flat Dam.
Crews will be working throughout the year with a projected completion date of February 2009 on the Caldwell Canal outlet. A March 2008 completion date is predicted for work on the Nampa Canal outlet.
Officials raised both safety and structural concerns after instrumentation ratings indicated water could have been flowing through the dam at the Caldwell outlet. An emergency was declared on May 13, 2005, and an emergency berm was placed around the Caldwell Canal outlet works intake tower as a temporary measure.
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- Upper_Dam_Work_1C.jpg
A construction worker guides a steel beam into place Wednesday during construction of a new conduit for water on the upper dam at Lake Lowell.
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A construction crew works on the Nampa Canal outlet on the Upper Dam at Lake Lowell.
Mike Vogt/IPT - upper-dam.jpg
A construction worker guides a steel beam into place in construction of a new Caldwell Canal outlet works conduit for the water on the Upper Dam Wednesday afternoon.
Mike Vogt/IPT
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The reservoir was also restricted to 5 feet in elevation.
Daily monitoring continues until the modifications are completed. Much of the construction centers on the removal and the replacement of the Caldwell Canal outlet works conduit.
The modifications also include removing and replacing a 20-foot downstream section of the Nampa Canal outlet works.
“It’s unusual in that we declared an emergency,” said Larry Wolf, safety dams programs manager. “We found some things that were alarming. We found voids under the Caldwell Canal. Material had been washed out. It had been losing support underneath the outlet works conduit. We found soft foundation materials underneath the conduit near the outlet works tower.”
The findings prompted a series of actions to alleviate the possibility of a structural failure in the dam.
“It was alarming that those indications were there,” Wolf said. “It was more than normal wear and tear. New cracks were appearing in the conduit. We had to do something right away, but it does take awhile, a long time to get to get investigations, designs, approval lined up.”
The Deer Flat dams consist of four earthen structures — the Upper, Middle and Lower dams and East Dike. Together, the four embankments form Lake Lowell. The dams were constructed about 100 years ago, an age considered to be the end of the dam’s lifespan.
The lake holds about 173,100 acre-feet of water when full, providing irrigation water to local farmers and residents in addition to recreation and wildlife benefits.
A significant dam break could endanger lives and property. However, maps displaying potential flooding because of dam failures are off-limits to the general public because of restrictions placed on highly sensitive information since the Sept. 11, 2001, terrorist attacks.
“Even though there’s a deficiency, keep in mind that Reclamation has a top-notch safety dams program in place where we periodically investigate our structures,” Wolf said. “And we have emergency plans in place. In case something were to happen, we are able to act on that very quickly.”
“We are able to identify deficiencies before they become a failure. Just like this case here (with Deer Flat). We identified the deficiencies, it was alarming because of what we found. We exercised our emergency action plan.”
