Dam leak turns Bend’s Mirror Pond into mudflat

Repairs to begin in early November

Stephen Hamway | The Bulletin @Shamway1 View stories and bio

Bend residents visiting Mirror Pond recently saw exposed berms and portions of the bank normally covered by water, after a small leak in the wooden paneling on Newport Avenue Dam caused water levels at Mirror Pond to drop by 2 feet over the last several days.

Bob Gravely, spokesman for Pacific Power, which manages the dam, said workers discovered the leak Wednesday and are planning to repair it, but may not be able to get heavy equipment in place and start work until early November.

“We think it will take a few weeks to get everything in order,” Gravely said.

The dam, which was built more than a century ago to bring hydroelectric power to Central Oregon, has been increasingly prone to leaks in recent years. Gravely said Pacific Power placed wooden paneling over a defunct outlet in the dam about 25 years ago, but the structure has degraded over time. He noted that this was the fourth leak in the dam since 2008, though this one is less severe than previous leaks.

In prior instances, the utility has had success driving sheet pile — pieces of interlocking steel sheets — into the river bed on the upstream side of the wooden panels, which Gravely said keeps the water from reaching the leaking sheet. After this round of construction, Gravely said the entire face of the dam will be reinforced by the metal sheets, which the utility hopes will prevent future leaks.

“This will allow us to maintain the pond for the foreseeable future,” he said.

The leak was compounded by lower-than-normal water levels throughout the Upper Deschutes due to the end of irrigation season. Kate Fitzpatrick, program director for the Deschutes River Conservancy, said the amount of water in the river normally drops during the start of October, when irrigation districts begin ramping down the water they divert for farmers.

Since the end of September, the amount of water released from Wickiup Reservoir has dropped from 820 cubic feet per second to 105 on Monday, an 87 percent decline, according to the U.S. Bureau of Reclamation.

Gravely said the utility can normally regulate how much water stays in Mirror Pond, but having a hole in the dam affects its ability to do so.

Gravely said he doesn’t expect the leak to get worse, but noted that water levels could be as far as 4 feet below normal before the utility is able to repair the dam.

However, Gravely emphasized that the dropping water levels don’t pose a danger to the public, and added that the decline should be gradual enough to keep the fish in the pond from being stranded.

Mirror Pond collects sediment that flows in from the Deschutes River, which has prompted questions about how best to pay for the dredging of the pond. After a fundraising effort by Mirror Pond Solutions, a company formed in 2013 by local businessmen Bill Smith and Todd Taylor, fell short of its target, representatives from the company, the city of Bend and the Bend Park & Recreation District have met several times to discuss funding options.

Gravely said the dam construction will take about a month once it begins, and shouldn’t affect the timeline of the proposed dredging effort.

https://www.bendbulletin.com/localstate/6600505-151/dam-leak-causes-water-at-mirror-pond-to