Juneau utility completes 2nd avalanche diverter

Alaska Electric Light and Power has erected a second barrier to the destructive power of avalanches.

Two large avalanches in the spring of 2008 and winter 2009 crippled several towers along a 43-mile power line route from the Snettisham Lake hydroelectric facility. AEL&P was forced to burn expensive diesel in its backup generators for weeks.

AEL&P received a $2 million grant from the State of Alaska’s Renewable Energy Fund to build a series of wedge-shaped metal avalanche diversion structure uphill of their vulnerable transmission towers.

“If an avalanche comes toward the tower, these structures are designed to split the avalanche and divert it around the tower,” Eric Eriksen, vice-president of transmission and distribution at AEL&P said in a press release.

The first avalanche diversion was installed in 2009 and withstood an avalanche in March that reached halfway up its 40-foot height, a 3.5 out of 5 on an avalanche scale.

The utility announced Thursday that it has finished construction of its second diversion at a tower 4/5 in the mile three and mile four section of the Snettisham power line, which took the brunt of the 2008, 2009 slides. This season AEL&P also began construction on a third $2.2 million diversion nearby.

Avalanche diversion isn’t the only mitigation measure AEL&P takes to prevent avalanche damage to assets. To knock down avalanche dangers before they grow the utility employs a concussion release mechanism called the Daisy Bell. The bell is flown in by helicopter and a gas charge is remotely detonated within the bell, triggering an avalanche.

With this grant AEL&P was able to build avalanche protection under its normal budget process. Customer rates already reflect the cost of construction.

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