Traffic jams are not new to Fitchburg, but consultants have found there’s one bottleneck – in the Goose Lake watershed – that is responsible for flooding and road closures on Fitchrona Road.
During a public information meeting held on Thursday, July 2, consultants Ann-Marie Kirsch and Amber Lefers from AE2S, who were hired this spring to examine water flow in Goose Lake, explained that flow out of Goose Lake is limited by roadblocks downstream such as culverts that are too small or uneven topography levels.
“Water really kind of acts like a traffic jam,” Kirsch explained. “Going down the Beltline, everything’s fine, everything’s fine, and then you see the orange lights up ahead … once the cars get past that restriction, the crash or the person pulled over, the cars can accelerate downstream, so to speak.
“Once there’s an impediment like an undersized culvert or jam in the system, the water truly backs up,” she added.
Goose Lake, Fitchrona Road and the area surrounding it near the 18-151 overpass have experienced flooding from the lake for the last two decades. Most recently, the city closed the road due to high water the same week the city reopened the Nesbitt-Fitchrona Road intersection with a new roundabout in October 2019. In 2018, record rainfalls caused the road to be closed twice in August.
Goose Lake is a glacial kettle, so while it’s still a part of a watershed, it has no natural outlets for water to flow out. Evaporation or infiltration into the ground are the only two ways for water to leave the lake, outside of the two culverts on the lake’s western side.
Water flows into Goose Lake from developed land in the northeast that sits at a higher elevation than the lake, Kirsch said, but as it attempts to flow out, the elevation of the land increases three different times. The initial path of exit for water out of Goose Lake is at a high elevation, and the two culverts help drain it into the wetland area.
But the small size of those culverts are considered roadblocks because the amount of water being through them is not enough to drain excess water out of the lake, which is a similar case for the other two culverts in water stream along Hwy. 18-151.
One is a 30-inch culvert under the highway from the 1990s through which the water flows in a ditch alongside the retention pond between the highway and Nesbitt Road. But it doesn’t fully join the Badger Mill Creek until it reaches a box culvert a few hundred feet down.
It’s also a challenge for the water to get out of the ditch into the box culvert, Kirsch said, as the elevation of the ditch dips a few feet before it reaches the culvert, which is much higher than the ditch.
Possible solutions could mean making the culvert under Hwy. 18-151 larger to allow for more water to flow, or adding a new culvert closer to the Badger Mill Creek so that the water doesn’t have to take such a long route to get into the rest of the watershed, Kirsch said. In any solution, the culverts on the western edge of Goose Lake will also need to be replaced with larger ones.
Any changes to the floodplain will require approval from FEMA, and if any land is disturbed in terms of an acre or more, the state Department of Natural Resources will need to sign off on it, Kirsch said. Additionally, any work done in the right-of-way along Hwy. 18-151 will require a permit from the Department of Transportation.
Any solutions will also need to be coordinated with Dane County Parks, which has land that sits downstream.
The city is limited in what it can do to solve flooding with Fitchrona Road itself– federal regulations prevent it from being raised under the 18-151 overpass, and the state Department of Transportation isn’t planning to do maintenance on the bridge for another 25 years, according to the request for proposals.