Flooding prevention remains top of mind for DeForest Village Board trustees.
An analysis presented at the village board’s committee of the whole meeting Tuesday, Oct. 15, included four potential projects aimed at alleviating flooding in the municipality.
Some trustees were skeptical about the impact they would have on flooding.
“You’re not giving me a whole lot of confidence that they are going to be a difference maker,” said Trustee Jeff Miller.
The analysis was put together by the engineering and landscaping firm Vierbicher. Company representatives were on hand Oct. 15 to offer explanations and answer questions.
One of the proposals involves $1.5 million worth of modifications to the Yankee Basin between U.S. Hwy. 51 and County Hwy. V and east and northeast of Dahl Park, including regrading it to add 2 feet of capacity. That would increase its volume by 22 percent for a drainage area of 665 acres and provide a 36 percent reduction in case of a 100-year storm event.
It would also help improve water quality, reducing sediment by 86 percent and phosphorus by 80 percent.
Additionally, the project includes changes to Yankee Basin’s outlet structure for better control of the water.
However, Vierbicher representatives admitted that while the Yankee Basin project would help, they couldn’t guarantee that it would stop future flooding.
The cost is also a concern, although Vierbicher representatives said they hoped their estimate was on the high side. Village Public Works Director Kelli Bialkowski also said that Dane County is very interested in the project and could provide urban water quality grant funding to help with costs.
However, when asked by Miller if the modification would eliminate the kind of flooding the village experienced last spring, Vierbicher’s Craig Mathews said it’s not going to prevent it.
Vierbicher’s Neil Pfaff said trying to model what happened last spring was problematic, because there was a fast melt and it was raining at the same time.
Village President Judd Blau said it was “a perfect storm” of factors that caused the flooding, including a quick jump in temperature.
“We may not see that again, but it could happen,” said Blau.
Trustee Abigail Lowry asked if Dahl Park was the most vulnerable part of the village with regard to flooding.
Mathews responded, “I’m tempted to say yes,” especially when it comes to large rain events. “It’s the most significant area where we see issues.”
The Yankee Basin project would help in alleviating flooding with a combination of lowering and raising its depth. Going higher creates more storage.
Three other options were proposed by Vierbicher. Constructing a Karow Property wet basin for $1.1 million, plus the cost of property acquisition, is one alternative. The project area covers 7 acres. The drainage area is 821 acres. There is no basin there now. In total, it would reduce water from a 100-year event by 3 to 4 percent, compared its existing conditions.
It would result in 67 percent reduction in sediment and reduce phosphorus by 60 percent. While Vierbicher notes the project would have water quality benefits, it would offer relatively low flood control, along with high construction costs and property acquisition.
There are also concerns about the neighborhood’s perception of the project. Also, officials said it is viewed less favorably by Dane County. That means it has less of a chance of receiving Dane County Water Quality Grant funding.
Two other possible projects involved upsizing rear yard storm sewer pipe in the DeForest Street area for $54,000 and $150,000 in modifications for area at Holum Street and Cleveland Avenue. The latter would add inlets and new piping, while providing a bypass to the south and berms around properties. The work would expand inlet capacity to get water off the street, according to Vierbicher. Aqua Dams could be included. They have rubber membranes that fill with water. Bialkowski said the village would explore what Aqua Dams could provide.
Both are considered non-grant projects, according to Vierbicher’s flood analysis.
The DeForest street project would increase pipe size from 8 inches to 18 inches to increase the capacity and ability to drain that area.
Grant opportunities include water quality grant funding that would provide a 50 percent match up to $500,000. There is also the possibility of a Yahara WINS Grant, which funds projects that aid in achieving clean water goals. Lastly, there is Urban Nonpoint Source Construction Grant funding available. Application would be made in April 2020 for possible construction in 2021 and could provide a 50 percent match up to $150,000.
Miller said none of these measures do anything to break up large chunks of ice that flow into pipes and lead to blockages, like those that exacerbated flooding last spring.
Village Administrator Steve Fahlgren addressed DeForest’s stormwater finances, saying that the village may need to raise rates higher than what was presented a year ago. The possibility of purchasing a new leaf-vac truck would have an impact as well.
Miller wondered if money from other cash-rich utilities could be used for such projects. Fahlgren explained that that was frowned upon.