Next phase of Silver Lake Dam work on tap for decision

Jun. 15—ROCHESTER — The next steps in planning to dredge Silver Lake and replace the existing dam will be proposed Monday.

With plans nearly a third complete, the Rochester City Council will be asked to approve a contract for nearly $800,000 with WHKS and Co. to complete final designs and manage the project through 2025.

Council members will also be asked during their regular meeting at 6 p.m. Monday in council chambers of the city-county Government Center to allow staff to seek construction bids for the project, once the design is complete.

"Ultimately, the council would need to accept the bids, but we'd like permission to go out for bids once we have the final design in place to see where the final project costs will be," Rochester Deputy Public Works Director Aaron Luckstein said during a recent council study session.

During the discussion earlier this week, council members expressed various levels of support and opposition to the proposed dam changes.

Council member Shaun Palmer raised questions about the cost and need for the modifications, while council member Patrick Keane said he's ready to support the project after years of discussion.

The dredging portion of the project has been in the works under a 2016 WHKS contract, with the potential for changing the dam site added in 2019. From there, a concept was developed to take advantage of plans to lower the lake level for dredging.

While the lake will need to be lowered to allow dredging next year, Rochester Project Development Manager Matt Crawford said the water level change won't be permanent, even if the dam replacement is approved.

"There will be no change to the evaluations," he said of the long-term impact of the proposed dam change. "It will match the current conditions."

The concept calls for creating a new dam structure approximately 700 feet east of the existing dam, with the remaining lake being held at the level seen today.

"We are attempting to preserve 85%, or at least 85%, of the lake," Luckstein said, acknowledging some community concerns about the lake's future .

The new dam structure will allow upstream fish passage throughout the year, with the potential for recreational pools for kayaking when enough water is flowing through the system.

"As water goes up, it starts going through the wave pools," Rochester Project Development Manager Matt Crawford told the council. "As we have more water, the wave pools are more active."

With added design work remaining, Luckstein said the city must be able to show the Minnesota Department of Natural Resources and U.S. Army Corps of Engineers that the new dam structure won't send more water downstream than already flows in that direction.

While the dam isn't considered part of the water retention portion of the city's flood-control system, it works with the dredged channel through Silver Lake to help move potential flood water through the city.

Crawford said water is retained in reservoirs around the city, and the river and lake guide the water to stem city and downstream flooding, but the dam's only function is to create a recreational lake.

He said the proposed work is intended to enhance the recreational function, while also offering the potential for additional dredging to expand benefits.

The initial proposal, with a $5.5 million estimate for the dam replacement and at least $4 million for required dredging, will also include preparation for a potential trail extension on the north side of Silver Lake, which would provide passage under the North Broadway Avenue bridge.

Luckstein said currently available funds won't be enough to finish the trail, or a proposed pedestrian bridge and south trail, but additional funding sources are being studied.

Completion of the northern trails is estimated to cost an additional $500,000, with $1 million needed for a south trail under the Broadway bridge and a nearly $2.2 million cost for the proposed pedestrian bridge.

If the council approves efforts to move forward, city staff is also seeking permission to negotiate details related to accepting a nearly $2.4 million state grant for the dam project, which would require future council approval for acceptance.

Another $2 million is expected to be sought through Rochester Public Utilities, which would see a similar cost savings by avoiding a nearly nearly $1.2 million overhaul of the gates at the top of the current dam, as well as future maintenance costs.

"If council takes no action, I think that's the direction to RPU to spend the $1.2 million to overhaul the leaf gates, which essentially means that the dam will remain in place," Luckstein said.

If the replacement is approved, approximately $1.1 million in additional city funds will be needed, and Luckstein said Public Works staff will present proposed options on Monday.

"We are evaluating funding options," he said.

While the city cannot use funds from the recent sales tax extension for the dam project, it has flood-control reserves from the 1989 sales tax approval and stormwater funds that could be used with council approval.

Luckstein said many details will remain in the works as design efforts continue, with plans for working with lake neighbors and holding additional public input sessions as plans are nearly the-thirds complete.