The water level behind the Newport Avenue Dam appears to have stabilized, a representative of PacifiCorp said Tuesday, but will drop further when crews begin inspecting a recently discovered leak.
PacifiCorp spokesman Bob Gravely said the utility has not been able to get an inspection crew lined up since the discovery of the leak last Wednesday. Once a crew is ready, the sluice gates at the base of the dam will be opened to create a roughly 24-hour window to examine the leak's source and any other potential problems along the face of the dam.
Gravely said the water level in Mirror Pond will drop sharply during the inspection, but will quickly return to its current level - roughly two feet below normal - after the inspection is complete. He said in its current state, the dam and the pond are functioning like a bathtub with an overflow drain - unless water flowing into the pond is substantially increased, the water level will remain the same.
Gravely said although the leak appears to be repairable at this point, PacifiCorp won't know what its next move is until the inspection is completed. The future of the 100-year-old hydropower dam has been central to the question of what should be done about silt buildup in Mirror Pond, and PacifiCorp has said the time will come when the dam is no longer economical to operate — in 2008 and 2009, the company repaired three separate breaches in the dam, all of which were determined to be age-related.
PacifiCorp will share the findings of its inspection and its possible options with the committee studying the siltation question, Gravely said. Since the process began earlier in the year, the public discussion has focused largely around two options, leaving the dam in place and dredging the pond, or removing the dam to create more natural river conditions.
“It's not going to be a strictly internal thing,” Gravely said. “We will let folks know what we're finding, we'll be in contact with the leaders there in the city that are managing the process.”
Jim Figurski, a consultant working on the siltation issue for the Bend Park & Recreation District, said the current state of Mirror Pond is similar to what might be expected if the dam were removed. The mudflats that have emerged around Mirror Pond would not have to be a permanent fixture if the dam were removed, he said — most likely, portions of the now-muddy areas would be planted with aquatic plants, while other portions would be shaped to create a combination of dry land and more natural riverbank. The channel could be moved to a limited extent, Figurski said, but would eventually find its own course.
“If this is where the project ends up, in a dam-removal scenario, a complete dam-removal scenario, there's a chance within that scenario to sculpt the edges a bit and also sculpt the plant communities a bit, at least initially,” he said.
Figurski said he's located photos from 1995, the last record of Mirror Pond being as low as it is now. He said he took a trip around the pond Tuesday morning to compare the 1995 photos with the current view and found them quite similar, suggesting the last dredging in 1984 was followed by a period of rapid silt accumulation that has since slowed.
The committee is taking advantage of the low waters to approach the family that claims to own the bottom of the pond about testing the mud for contaminants. The McKay family of Portland acquired the land before construction of the dam, and recently reasserted their claim. Figurski said the family has been hesitant to allow the mud to be tested, as they could be held liable for cleaning up any hazardous materials discovered during testing.
The McKay claim is one of several issues that prevent the pond from being dredged now, Figurski said. Even if the family approved of such a plan, permits would need to be issued and the state Division of State Lands would want to review dredging plans, he said.
Jeremy Giffin, watermaster for the Deschutes River basin, said water levels in Mirror Pond should remain relatively stable through the winter even if the dam is not repaired. By adjusting the amount of water let out of Wickiup Reservoir and the amount sent to irrigation districts that pull water from the river upstream, around 550 cubic feet per second are flowing into Mirror Pond today, Giffin said. Flows will be reduced to around 500 cubic feet per second next week, he said.
“What we're seeing in Mirror Pond right now is more a result of the dam leak than it is from the river flow,” Giffin said. “This is a typical wintertime flow we're seeing.”
Later this month, park district Executive Director Don Horton and Bend City Councilor Mark Capell are scheduled to meet with PacifiCorp to learn more about the company's longer-term plans for the Newport Avenue Dam. The meeting had been scheduled prior to the discovery of the new leak.
Capell said he doesn't think the committee can make a decision on Mirror Pond until it gets greater clarity from PacifiCorp.
“Our goal is to find out what they want to do and how do we move forward together,” Capell said. “And, they've been really good about saying they want to do what's best for the community, and so do we, so let's get it done.”