Mirror Pond’s sediment buildup may be dredged

Looking north at Mirror Pond, with Newport Avenue Bridge at upper left, mud flats are visible. A committee has said that Mirror Pond, which stretches from the Galveston Avenue Bridge to the Newport bridge, would likely need to be dredged to remove sediment buildup, but that the city of Bend should seek public input and explore all options. Photo: Rob Kerr / The Bulletin

If Bend residents want Mirror Pond to remain the wide-open pool that has become an icon of the city, some dredging would likely be needed, a committee of technical water experts concluded.

But once the sediment is removed, the city should take steps to ensure it won’t have to dredge as much in the future, committee members said.

“That was a big issue. We don’t want to be dredging this thing and then dredge it again and again and again. We want a proactive solution that will last a century or two,” said Brad Kerr, a member of the committee who also designs fishing habitats.

Before any of the dredging begins, the committee suggests the city hire consultants to further study the problems facing Mirror Pond and ask the community what it would like to see happen to one of Bend’s gems located near downtown.

In the last seven months, a group of hydrologists, biologists, water managers and other experts in the water field have been meeting to discuss Mirror Pond, which is increasingly filling up with silt. The committee members came from public agencies, nonprofit organizations and private consulting businesses.

During the five meetings, the group created a report, which is still in draft form and could be released to councilors sometime this month.

Early in the discussions, the group determined that sediment buildup at Mirror Pond had not reached a crisis point, so there was plenty of time to put a plan in place for dredging.

While there are some emerging bare spots, Wendy Edde, a water resource specialist for the city, said the group didn’t see broad, major mudflats developing for the next five to 10 years.

“Not having to do something immediately is a good thing. It will allow us time to prepare, to get the information we need and put in a really good project,” Edde said.

Their conclusion came a few months after city staff had drafted a report that stated if nothing was done, the growing sediment may turn Mirror Pond into wetlands. That would have put Mirror Pond under more stringent federal regulations, making dredging of the pond even more difficult.

The report also noted that without action, the pond would “increasingly present odor and aesthetic problems.”

Today, water levels are so shallow during the year that geese can walk across the pond and plants poke through the surface of the water. Islands with trees and shrubs also have sprouted.

Mirror Pond is not a natural feature. Part of the Deschutes River that spans from the Galveston Avenue Bridge to the Newport Avenue Bridge, Mirror Pond was formed in 1910 when a power company installed a hydroelectric dam on the Deschutes River just north the Newport Bridge.

Sedimentation was not an issue until the mid-1970s, when the lumber mills downstream stopped using the river to float logs. Because the pond is unnaturally wide, the river slows down and deposits the sediment it has picked up along the way.

City Councilor Jim Clinton, who headed the technical committee, said the group agreed that it would be likely that some dredging or sediment removal would happen in the next few years at Mirror Pond, but it didn’t determine if the entire pond should be dredged. It’s also too soon to say how much it could cost.

“Everyone agreed if you wanted to keep it looking like a pond, you are going to have to remove sediment,” Clinton said. “Everyone wanted to do something after the sediment was removed to avoid doing it as frequently as every 20 years.”

The question of how much dredging should be done is tied to what the community would like Mirror Pond to be in the future.

“There is at least a majority on council that do not want to do away with Mirror Pond, but what does that mean?” asked Ryan Houston, a committee member who is also the executive director of the Upper Deschutes Watershed Council. He noted for some residents, Mirror Pond could mean picturesque still-water views or stagnant water with weeds and a stench. Part of people’s connection to Mirror Pond could be tied to the concrete walkway around Drake Park or the calm water where people can paddle canoes.

“What are we trying to retain and what is up for negotiation? As a committee, we can’t answer that question. There needs to be a good public process to answer that,” Houston said. “If you interview 50 people, you would probably get 50 different answers on what attributes are worth saving.”

The long-term options of what to do to Mirror Pond depend on those answers.

The two extremes would be for the pond to return to its natural course in the river or for the city to keep the pond as it is now and dredge every couple of decades.

A more likely option is for the city to do some continual dredging in smaller sections of the pond, but to put in features that would reduce — or redirect — the amount of sediment that is dropped in the area.

Among the alternatives is to restore parts of the bank of the pond that have hard surfaces, such as the concrete wall that lines Drake Park, with more natural vegetation. Doing so would prevent erosion.

The city also could put in some man-made features underneath the water along the riverbed that would create a narrow channel in the center of the river. The man-made features, which could be a simple as mounds of dirt and rock placements, would act as ridge allowing water to move faster through the channel, carrying the sediment along with it.

“It would still look by and large like it does today,” Kerr said. “It would be deeper and keep moving sediments.”

Another option is for the city to keep Mirror Pond as it is from certain view points, such as maintaining the picture postcard setting from the city’s Riverfront Plaza. The lower part of the river could be returned to its more narrow natural course.

Also, islands that currently exist could be left in place or expanded, which would also narrow the channel and increase the speed of water flowing through the area.

“That would be less expensive to do and just as good for the river,” Kerr said. “But it doesn’t allow or doesn’t lend to more areas of open water.”

Another idea is to use some of the sediment that is dredged up to extend the land off the parks that border Mirror Pond.

What options work best should be what consultants and the public input dictate, committee members recommend.

“The potential is incredible,” Kerr said. “We have a beautiful place now. We could make something that really pops people’s eyes out. You drive to the Metolius to see really beautiful (scenery). If we have a chance to do something like that in the middle of town, I think we should take it.”

Before dredging Mirror Pond, the city of Bend needs permits from federal and state agencies. Clinton said that with the set of approvals required, dredging probably wouldn’t occur until late 2007 at the very earliest.

Source: The Bulletin ©2006

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