Replace Mirror Pond dam, officials say

Committee calls for replacement structure

By Hillary Borrud / The Bulletin / @hborrud

Published May 22, 2014 at 12:01AM

The Bend Park & Recreation District should replace Mirror Pond dam, not attempt to rehabilitate it, according to a majority of officials at a meeting about the dam on Wednesday.

Mirror Pond ad hoc committee members said they will investigate the total cost to replace the dam. A majority of the committee members at the meeting also said they will plan to include fish passage in any new dam on the Deschutes River. The committee decided in December that it wants to maintain Mirror Pond, the body of water created by a century-old dam on the Deschutes River in downtown Bend.

The meeting Wednesday was the first time the committee had met since consultants hired by the park district completed a report on their inspection of the dam. The consultants, Phoenix, Ariz.-based contractor Gannett Fleming Inc., said officials who want to keep Mirror Pond should consider replacing the dam or completely overhauling the structure.

Engineers for Gannett Fleming determined the dam will eventually fail and estimated the potential cost to replace it. At the low end, the total cost to replace or rehabilitate the dam and dredge sediment might be at least $3.9 million, if the state does not require the owner to install fish passage and the owner can dredge the sediment behind the structure for the lowest estimated price. The high end of the cost could reach $22.8 million, based on estimates included in the report. Neither the low nor the high estimate includes permitting costs, engineering design or any river habitat restoration.

Local officials are discussing whether the park district should acquire the dam from PacifiCorp, which wants to transfer ownership of the dam to another entity because the utility has said it no longer makes financial sense to maintain it.

Erik Huffman, an engineer who worked on the inspection report, provided a brief overview Wednesday of the findings. Park district Executive Director Don Horton asked Huffman if sheet piling, which PacifiCorp has installed along portions of the dam that leaked, has contributed to deterioration of the old timber crib dam. Continuous contact with water helps to preserve wood dams, and Horton suggested the piling reduced the contact with water along parts of the dam.

Huffman said that although the inspection report didn’t address this issue, “It would be then an environment that would be conducive to rot, yes.”

Six of the nine Mirror Pond ad hoc committee members were at the meeting Wednesday, and most of them said the park district should replace the dam.

“I think we understand there is a finite time left in the life of this spillway,” said Scott Wallace, chairman of the park district board of directors and a committee member.

City Councilor and committee member Victor Chudowsky said the report made it clear the dam should be replaced. Chudowsky said the committee should commission more research into the options to replace the dam, including an alternative concept aimed at maintaining the pond while allowing boaters passage at the dam. The park district has been meeting with members of the Bend Paddle Trail Alliance, who pitched the concept several months ago.

City Councilor and committee member Mark Capell said he wants to explore replacing the dam, but has not ruled out removing the dam and allowing this section of the Deschutes River to freely flow.

Bend Community Development Director Mel Oberst, a member of the committee, proposed including fish passage in any future structure built to preserve Mirror Pond.

The only committee member who opposed replacing the dam was citizen Ned Dempsey.

“I don’t see it’s really feasible to put a new dam in the Deschutes River,” Dempsey said. “We’re taking dams out everywhere.”

Dempsey continued to disagree with the rest of the committee later in the meeting. “For the record, I don’t agree that the dam is in trouble,” Dempsey said. “Crane Prairie is a wood dam.” Crane Prairie Reservoir is in south Deschutes County.

— Reporter: 541-617-7829, hborrud@bendbulletin.com