Engineering

The City of Madison Engineering Division is focusing on a number of projects to show what the City and Engineering has done ‘Since 2018’ when a flood devastated our community on Aug. 20, 2018. In this blog post, we spoke with City of Madison Engineering Division Stormwater Engineer Grant Pokos about the Sprecher Road Greenway improvements.

What was the issue with flooding for Sprecher Road (Greenway)?

“I think the main problem with the Sprecher Greenway was erosion from the existing greenway. With each rainfall, the regional water passing through here continued removing soil from this area and passing it downstream. A greenway in this condition will not fix itself, it will only continue to get worse. The continuing erosion changes the layout of the original channel and possibly affects bank stability in the greenway leading to further problems. This sediment sent downstream can plug up downstream culverts and fill existing ponds, channels and other waterways. This can change the existing sections of downstream waterways, slowing their ability to pass stormwater and possibly raising water elevations after storms.”

What did we do to fix it?

“We analyzed this area to create a model to understand how much stormwater was flowing to this area. Once we had that information, we were able to create a sustainable channel section for construction that would safely pass the water through. We were also able to use the information from the modeling to select riprap and matting areas along the channel to help avoid future erosion. Riprap is stone used to reinforce an area so that the soil won’t be washed away. Matting is an engineered blanket that holds the soil and seed in place so grass and other vegetation can grow rather than being washed away. The backslopes leading to the channel were also softened from existing slopes to help avoid future bank erosion. As part of the construction, the overgrown vegetation was removed to allow for construction of the new channel. This gave us an opportunity to revegetate, or plant new currently with grass, and in the future, trees and shrubs in the area. The new vegetation added should allow for a more usable and sustainable greenway in the future. A maintenance access was also added as part of this project. This access will allow us to recognize potential problem areas before they become worse and maintain the greenway in the future.”

Why was there a problem/why did we fix it?

“There are different possible reasons that the erosion is happening in this area. The shear forces caused by storm events could be too high for the existing channel to stay in place. Over time, the greenway also became over grown, not allowing the vegetation that holds the soil in place to remain. Once these problems began, they won’t reverse on their own. We improved this greenway to stop the problem from continuing, improve vegetation and to protect the downstream stormwater system from additional future sediment loads.”

How much was the project?

“It’s not finalized yet, but approximately $325,000.00. This is a joint project with the City of Madison and our partners in the Town of Blooming Grove. The cost was split proportionately with the Citys’ share coming from the Stormwater Utility fees.”

How long did it take us to fix it?

"Discussions on this project started in early 2020 and the major portion of the design occurred in 2021. Construction began March 25, 2022, and the majority of the project is finished. There is still some vegetation maintenance and planting that will happen with this project.”

How much of an impact does this project have from a bigger picture perspective? Why is this important?

“This is important because erosion from this waterway affects every waterway downstream of it. As the flow characteristics of this channel changed, it changes the flow characteristics of the channels upstream and downstream from it. The longer that it went un-repaired the larger and more expensive the problem could have become.”

Anything else you want to mention about this project?

“Not only hydraulically was this area improved, but also we made this a better part of our stormwater system. The overgrown vegetation was removed and the area will be replanted to create a beautiful and sustainable area for years to come.”