New leak at Mirror Pond dam prompts more repairs

A PacifiCorp worker on Thursday spotted a leak in a gate section of the century-old hydroelectric dam that forms Bend’s Mirror Pond, an official said. While smaller than a leak that occurred three years ago, it’s still enough of a concern to prompt lowering the pond by about four feet for two weeks of repairs, he added.

The hydro operator noticed the leak in an area at one end of the dam “that is essentially a gate that allows us to allow ice or debris buildup to pass through,” said utility spokesman Bob Gravely.

“It is a wooden structure made out of logs stacked on top of one another,” Gravely said. “One of the bottom logs failed, so it is allowing more water to pass through than is desired.”

The spokesman said they already had begun lowering the level of the pond. “We expect it to be lowered for about two weeks, to allow us to replace that piece of the gate,” he said.

The utility issued a news release Friday regarding the leak from the chute section of the dam and said the river level had been lowered by about four feet.

“Mirror Pond in downtown Bend will be lower than normal for the next few weeks,” said Mark Sturtevant, who oversees hydro operations for PacifiCorp. “This will be noticeable, but this is a maintenance issue that does not impact the integrity of the dam or create a public safety issue.”

Unlike the major repairs that cost $250,000 in 2013, this time “it is a maintenance issue, not a structural issue,” Gravely added. “This does not impact long-term plans or the structure of the dam at all.”

The leak three years ago prompted Pacific Power to announce it wanted to divest itself of the under-3-megawatt dam to the community, amid years of wrangling over its fate. The debate was sparked by discussions about how to remove decades of silt buildup in the iconic pond.

Eearlier this year, the utility did a quiet about-face and said it plans to keep producing power there. While city and Bend Park and Rec District leaders adopted a “community vision” last year, a utility official said this summer that none of the proposals it had been presented with appeared viable, in terms of “being affordable, doable for the community, while leaving Pacific Power customers whole.”

Coincidentally, the Park and Recreation Board is being asked by staff Tuesday night to approve a contract for about $200,000 with GreenWorks PC for design and engineering plans for bank realignment and restoration along the edges of the pond. They will look at methods, identify permit requirements and come up with detailed cost estimates.

The park district has allocated more than $1.1 million for the work in the 2017-18 fiscal year.