Oak Leaf Trail Sinkhole Needs Repair

An important piece of the Oak Leaf Trail is being threatened by a growing sinkhole.

The Zip Line, as it’s called, is a key part of the larger trail network, according to Milwaukee County Parks, as it provides a connection between downtown Milwaukee and the county line and then on to the Ozaukee Interurban Trail which runs all the way to Oostburg.

But a simple stone culvert is threatening The Zip Line. The culvert, more than 100 years old, provides a waterway for Crestwood Creek, a tributary of the Milwaukee River. The culvert is falling apart, and that has helped create sinkholes around the culvert. The trail has been closed because the possibility it could collapse is an obvious threat to safety.

All this comes from information in a grant application the parks department filed with the state Department of Transportation (WisDOT), for a Transportation Alternatives Program (TAP) grant, earlier this year. WisDOT recently announced it awarded $530,000 to the county to repair this section of the trail.

The Zip Line is a six-mile trail that branches off from the Milwaukee River Line and runs from Estabrook Park to Brown Deer Park. It is named for Harold “Zip” Morgan, an early bicycling advocate in Milwaukee.

It was built in 2015 as an extension of the Oak Leaf to connect to the Ozaukee Interurban Trail. An integral part of this project was converting just over 3 miles of railway corridor, abandoned by Union-Pacific in 2008, into a multi-use trail. The stone culvert that’s badly in need of repair was originally part of that rail corridor.

The parks department said the line is one of the most popular sections of the Oak Leaf, with more than 350,000 multi-use trips a year, on average. The line, by connecting the Oak Leaf to the Ozaukee Interurban, creates 48-miles of continuous off-road trail from Milwaukee to the north end of Ozaukee County.

Its use is steady throughout the week, which suggests it is used by commuters, the grant application noted.

The trail runs along the Johnson Controls corporate campus in Glendale. Grady L. Crosby, a vice president with Johnson Controls, is quoted in the application saying the trail adds to the overall value of their corporate campus.

The sinkhole is actually directly adjacent to the Johnson Controls campus. It started forming in 2018. It began as cracks in the pavement, according to the application, but has continued to grow until it became a circle of asphalt at least 15 feet in diameter that has sunk six to 10 inches into the ground.

The Zip Line serves a diverse array of neighborhoods, offers a key connection to a wider trail network outside of the county and is used by bicyclists commuting to work — cutting down on carbon emissions. Because of this, and the obvious safety concerns, the parks department will be asking WisDOT to make the project a priority so the trail can be reopened as soon as possible.

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