A close look at Bend’s Mirror Pond dam
三月 06, 2014
Bend BulletinBy Scott Hammers
The committee looking into what should be done with Mirror Pond got an up-close look at the leaking dam there Wednesday, joining representatives of PacifiCorp on a tour of the more than 100-year-old facility.
The ad hoc committee, formed last fall, includes representatives from the city of Bend, the Bend Park & Recreation District and the general public. It will weigh in on the relative merits of dredging the pond, keeping the dam, which is owned by PacifiCorp, removing the dam and other alternatives.
The group’s tour came one day before a team of consultants hired by the park district is due to arrive in Bend to inspect the dam. PacifiCorp has been lowering the level of Mirror Pond in recent days to allow for a safe inspection, but water levels should be headed back up this weekend.
Jim Figurski, the head of the park district’s efforts on Mirror Pond-related matters, said the inspection should provide a better idea of what kind of maintenance costs the city or park district would have to bear if they were to acquire the dam from PacifiCorp. PacifiCorp has committed to repairing a hole that opened up in the dam last fall, dropping water levels to nearly 7 feet below seasonal normals, but is looking to divest itself of the dam as a generation facility.
“Part of the analysis is what would we need to do for a 50-year or more fix, not just a 10-year fix or a near-term fix,” Figurski said.
He expects the consultants will have a complete report for the committee by the end of the month.
On the back deck of the powerhouse, members of the tour group learned Wednesday how the gates at the base of the dam can be manipulated to control how much water flows out, allowing the dam operator to maintain Mirror Pond at a consistent elevation.
They peeked into buckets of bottles, cans and old tennis balls that are scattered across the dam property, all of them retrieved from the pond above the dam with the help of a long-handled net.
Descending a ladder to a wide lawn hemmed in by the dam on the upstream side and barbed wire on the downstream side, the group examined a now rarely used gate at the north edge of the spillway, where boards can be removed to discharge ice and debris into a crudely constructed rock and concrete sluice gate.
Water seeps through several points along the concrete dam face, nourishing thick cushions of moss sprouting from the stained walls, and as suggested by the footprints dotting the mud below, a handful of raccoons and other small animals that find their way through the fences.
Mark Tallman, vice president of renewable resources for PacifiCorp, said the seepage is a cosmetic problem more than a safety issue.
“The dam is just like a drafty house, it’s just old,” he said.
Visitors donned fireproof suits before venturing inside the powerhouse, where three large generating wheels sat idle Wednesday on account of the lowered water levels. When turning, the three generators can produce enough electricity to power 300 to 400 homes.
Tallman told tour members the powerhouse is still potentially dangerous even when the generators aren’t spinning due to a live power line running across the ceiling that — under the right circumstances — can throw off high-voltage arcs. The controls for the adjacent substation are also inside the powerhouse, Tallman said, cautioning the visitors to avoid touching any of the equipment.
“It is possible, if you accidentally touch or move the wrong handle, you could put Bend in the dark,” he said.
Scott Wallace, a member of the park district board and a member of the ad hoc committee, said he expects the behind-the-scenes tour will prove useful once the engineering report is complete. Until Wednesday, Wallace said he only had a hazy idea of what went on at the Mirror Pond dam.
“I grew up in Bend, and this is the closest I’ve ever come to the powerhouse,” he said.
City Councilor and committee member Victor Chudowsky said he was impressed by the architecture of the powerhouse. If the city or the park district acquires the dam someday, it would be ideal if the powerhouse could be preserved, he said, possibly as some kind of small museum where visitors could learn about how electricity is generated and about a notable piece of Bend history.
Chudowsky said the tour confirmed much of what he already knew — that the dam is old, and in places, starting to fail. Though its days as a power generation facility may be numbered, the dam may still be the easiest and least expensive way to preserve Mirror Pond into the future, he said.
“Really, what we need to be deciding is, is this an asset or a liability, then go from there,” Chudowsky said.
— Reporter: 541-383-0387, firstname.lastname@example.org
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