Mirror Pond dropping again Monday

The water behind the Newport Avenue Dam should start dropping Monday, allowing crews from PacifiCorp to inspect the leak that’s turned much of Mirror Pond into a mudflat.

The company that owns and operates the downtown Bend dam discovered the leak Oct. 2. Water levels in Mirror Pond dropped by roughly 2 feet in the days that followed as water drained through the leak. The pond then rebounded briefly as water managers upstream adjusted flows in the Deschutes River to prepare for the end of irrigation season. The water level has since receded a second time, stabilizing at around 2 feet below its typical winter level. PacifiCorp spokesman Bob Gravely said the company now plans to draw down the water even further in order to get a better look at the damaged area starting Monday.

Gravely said it’s unclear how far the water will have to come down to allow crews to inspect the leak.

“We don’t know exactly. What’s going to happen is, our folks will be at the dam monitoring it, and there will come a time when they say, ‘We can do this now,'” he said.

Under state law, if a water release from a dam is likely to create excessive turbidity — suspended silt — downstream, the dam operator must seek permission from the Oregon Department of Environmental Quality.

Eric Nigg, water quality manager for the DEQ Bend office, said his office granted PacifiCorp permission to lower water levels under a provision that allows violations of the state’s turbidity standards under narrowly defined standards.

In consultation with the Oregon Department of Fish & Wildlife, the DEQ settled on allowing PacifiCorp to drain the pond at a rate of 2 inches per hour, and refill it at a rate of 4 inches per hour. Nigg said the “ramp rate,” as it’s called, should minimize downstream turbidity and the risk that fish could be stranded by rapidly falling water. The utility had originally requested a ramp rate of 6 inches per hour both for lowering and raising the water level, Nigg said.

Under the conditions set by DEQ, PacifiCorp will be monitoring turbidity levels and any fish stranding during its operations.

Gravely said PacifiCorp suspects the risk to fish and other wildlife is minimal.

“We don’t think it’s very likely here at all,” he said. “The pond, it’s already down, and this will be done so gradually we don’t think it’s very likely.”

Gravely said the draw down of water is likely to take two to three days, while actual inspection is expected to last about eight hours. Any repairs to the dam are likely to occur at a later date, which would necessitate another draw down of water levels.

Source: The Bulletin ©2013

Dam Removal Training Videos from American Rivers

American Rivers is one of the leading experts in managing and implementing stream barrier removal projects.

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Inspection of Newport dam at least a week away

The corporation that owns Newport Avenue Dam does not expect to begin its inspection of a recently discovered leak for at least another week, a PacifiCorp spokesman said Thursday.

Spokesman Bob Gravely said the company is still working its way through regulatory matters and developing a plan for safely lowering water levels to allow inspectors access to the dam. Mirror Pond, the body of water at the heart of Bend, should remain at or near its current level — about two feet below normal, until the hole is fixed.

“I think this leak is such that with the flows as they are — and as is kind of typical for this time of year — we don’t think we can raise the water level without doing something about the leak,” Gravely said. “It is a bit like the drain in the bathtub effect; if the drain is open, you can only get so much water in the bathtub.”

PacifiCorp, a multi-state utility that operates in Oregon as Pacific Power, has patched smaller holes in the dam three times in the last five years. Past repairs were made by bolting a large piece of metal over the hole; a technique called sheet pile, Gravely said. Sheet pile is effective, he said, and a sheet pile fix would allow PacifiCorp to resume hydroelectric generation. But with the dam now more than 100 years old, continued age-related deterioration is likely, he said.

“It sounds easy enough to go fix this, but we could be right back here in eight months or a year and a half from now,” he said. “It’s the roof analogy: How long do you keep patching leaks in the roof before you take a look at (replacing) the roof.”

Gravely declined to estimate the cost of repairing the latest hole, how long it would take PacifiCorp to make the decision or complete the repairs.

Along with extensive mudflats along the river channel, the lower water has exposed the poor condition of the rock walls marking the typical high water line. Jim Figurski with the Bend Park & Recreation District said the crumbling walls present a potential safety hazard.

“We’re evaluating the conditions there and looking at it. And if there’s a decision it’s really unsafe, it’ll probably get taped off,” he said. “But, we haven’t made that determination yet. “

Figurski, who has been heading up the park district portion of the larger community conversation about silt accumulation in Mirror Pond, said nearly every proposal under consideration calls for removing most of the rock wall along the edge of Drake Park in order to create a more natural riverbank. The walls are not well built, he said. And in some locations have allowed water to seep in beneath nearby footpaths. Earlier this year, the park district tore up paver bricks along a long section of the path that had become buckled due to water seepage, Figurski said.

Although PacifiCorp’s long-term plans for the dam are still unknown, the park district has been exploring the possibility of a water rights transfer that could allow the dam to remain, even if the utility abandons power generation at the site. Figurski said although PacifiCorp’s water rights require the dam be used to produce electricity, the park district has asked state agencies about a modification that would allow the dam to remain solely for the purpose of maintaining Mirror Pond.

Source: The Bulletin ©2013

Dredge the pond

When the dam broke and drained Mirror Pond, we all looked at the dry riverbed. The pond drained and the solution appeared. Dry dredge Mirror Pond. Drain it, dredge it dry and then fix the dam. Dry dredge is cheap, easy and fast. We were thinking we could only wet dredge, which is expensive and takes lots of time. I say this winter, we drain Mirror Pond, do the dry dredge and then fill it back up in the summer.

Charles Baer
Bend

PacifiCorp: Inspection tied to leak, not debate

By Hillary Borrud / The Bulletin

PacificCorp’s decision to inspect the Mirror Pond dam is independent of the discussion about the future of the pond, a spokesman said Monday.

At the same time, PacifiCorp spokesman Bob Gravely said a thorough inspection of the dam could produce some of the information necessary to make a decision about the future of the pond. Silt buildup could eventually create mud flats in Mirror Pond, and officials are discussing how to manage this section of the Deschutes River in the future.

PacifiCorp, a Northwest utility that operates as Pacific Power in Oregon, discovered a leak in the dam, which is more than 100 years old, on Wednesday. It was the third leak in the last five years. The utility installed sheet piling to control the previous leaks.

PacifiCorp repaired at least one of the previous leaks without lowering the water level in Mirror Pond, Gravely said.

This time, the water level already dropped significantly due to the leak, and PacifiCorp plans to further lower the water in order to conduct the inspection. The utility has not set a date for the inspection, so it is unclear when the water level will increase in the pond.

“It leaked once, it leaked twice and now this is a third one, so we think this is more of a pattern,” Gravely said. “It’s hard to see it as isolated events when it happened three times in five years … With this third one, we just wanted to take a look at the broader situation, and we also think the community is interested at this point to get a better sense of the future as well,” Gravely said. At the same time, Gravely said, the utility is not conducting the inspection because of discussions about the future of Mirror Pond. “I think we would be doing this anyway,” he said.

Gravely said the decision to inspect the dam is also tied to economics. “Primarily, the cost of power is much lower, so that effects the overall calculations of repairs and continuing to go forward,” Gravely said.

Two local public officials were supposed to meet behind closed doors with PacifiCorp in early September and then report back to the full Mirror Pond ad hoc committee, which was formed to research options for the future of the pond and potentially select a plan. However, one of those officials, City Councilor Mark Capell, said Monday that he and park district Executive Director Don Horton have not met with PacifiCorp.

The six-member Mirror Pond ad hoc committee planned to hold its meetings behind closed doors, in part so that it could meet privately with PacifiCorp representatives. But the ad hoc committee stopped the practice after just one meeting when at least one lawyer said it violated Oregon public meetings law.

Instead, it formed a subcommittee that consists of Capell, Horton and park district lawyer Neil Bryant to meet privately with the utility.

Capell said he did not know about the leak in the dam and the drop in water levels until he read about them in Saturday’s edition of The Bulletin. Capell said he hopes to meet with PacifiCorp representatives by the end of this month.

“I have no way of knowing what they’re thinking because we haven’t met,” Capell said.

Gravely said the meeting was delayed because Horton is traveling.

The Oregon Water Resources Department manages rivers and other bodies of water. Kyle Gorman, south central region manager with the Oregon Water Resources Department, said the utility does not require permission from his agency to lower the water level.

“What they want to do as far as lowering the water to go in and inspect would be routine, and I don’t see why our department would object,” Gorman said.

PacifiCorp was not even required to notify the state of the leak and subsequent drop in the water level of Mirror Pond, but the utility did so as a courtesy, Gorman said.

Source: The Bulletin ©2013