Long-awaited Port flooding fix to take shape this summer

After years of planning, residents of Port Washington’s west side will see the first step in a flooding mitigation plan take shape this summer.

The Common Council on Tuesday approved a final engineering proposal from Stantec, its engineering firm, for improvements to the Spinnaker West detention pond.

“I’m very excited for this project,” Ald. Jonathan Pleitner said. 

Acknowledging that it took a significant amount of time to get to this point, he lauded the fact the city studied the problem to ensure it is doing the right thing and was able to obtain a “huge” $400,000 grant to help pay for the work.

“I’m glad we did this the right way,” Pleitner said.

Ald. Dan Benning concurred, adding, “Knowing this has a high, high probability of working gives me a great deal of confidence that this will work.”

The proposal was recommended last week by the Board of Public Works, which also reviewed a preliminary engineering memorandum for the project.

“This is step one toward our overall project,” Public Works Director Rob Vanden Noven said. “This is a step in the right direction.”

During intense storms, he said, the increased pond size will primarily help homeowners east of Spring Street, not those west of Spring Street, where some of the city’s most intense flooding has been registered.

That’s because larger culverts are needed at Garfield and Spring streets before residents on the west side will see a benefit during larger storms, he said.

“In the 100-year storm, they would not see a significant benefit with just this work. They’ll still see potential flooding,” Vanden Noven said. “But this has to come first.”

The tentative plan is for the city to do the culvert work in 2022, he said, although funds for this phase have not been budgeted.

The pond work would be done this summer.

Torrential rains have caused significant flooding in the Larabee Street basin in recent years, destroying yards and damaging homes, and homeowners have called on the city to eliminate the problem.

The current project, which has its roots in a 2015 flooding mitigation study, calls for digging out the overbanks of the creek channel leading into the existing pond and creating a weir wall to hold back more water than the pond currently holds, engineer Rich Klein of Stantec said.

“That storage is what allows the peak flow downstream to decrease,” he said.

“The same amount of water will move through the system, it’ll just move through the system slower.”

As water builds up behind the weir wall, it will overflow through a notch and flow into a chamber intended to dissipate some of its energy, then onto a spillway and onto the street, Klein said.

Board member Phil Bruno asked if the city could increase the storage capacity by digging deeper ponds. 

It’s possible, Klein said, but the increased capacity would be minimal. The pond would then have to be a wet pond, which requires more maintenance.

The board approved a $189,000 final engineering proposal from Stantec that would take the project from the final design engineering through construction, inspection and site restoration and also includes grant compliance work.

Construction of the pond is expected to cost $350,000, Vanden Noven said.

Stantec and the city have procured a $400,000 Sustain the Great Lakes grant for the project, and the city has to provide a $200,000 match, Vanden Noven said.

The city is hoping to receive additional grant money that it could use as part of its matching funds, he said.

At least a portion of the match will likely come in the restoration work done by city crews, Vanden Noven said.