Parks Wants ‘Emergency’ Designation For Oak Leaf Sinkhole

The sinkhole on a portion of the Oak Leaf Trail located in Glendale needs emergency action, Milwaukee County Parks says.

The sinkhole is on a much traveled section of the trail called The Zip Line, and it’s being caused by the deterioration of a stone culvert beneath it. The Zip Line was built in 2015 using three miles of railway corridor abandoned by Union-Pacific in 2008. The stone culvert was constructed more than 100 years ago as part of the railway.

In 2020, the parks department was awarded a Transportation Alternatives Program (TAP) grant for $530,000 to fix the sinkhole along with a supplementary Recreational Trails Program Grant. Work was supposed to begin this fall. But the county has not received a feasible bid for the project and the culvert continues to deteriorate, putting it at greater risk of collapse.

Of the three bids received for the project, two came in higher than the available budget and the third did not meet the county’s Disadvantaged Business Enterprise Goals, which are intended to deal with past and present discrimination in government contracting.

So the parks department is asking the county board to designate the sinkhole an emergency, thereby authorizing the department to do anything necessary “to preserve property or protect life, health or welfare of person,” as a resolution that will go before the board spells out.

“We are very much concerned that the culvert will not survive another freeze-thaw cycle,” Jeremy Lucas, director of administration and planning for parks told Urban Milwaukee.

The culvert is a waterway for a tributary of the Milwaukee River called Crestwood Stream. If the culvert collapses this could block stream’s passage, leading to significant flooding of the surrounding properties. One neighbor to the east is the Johnson Controls corporate campus.

With the grant money, and more than $18,000 fundraised by the non-profit Friends of Milwaukee County Trails, construction to fix the culvert and repair the trail was supposed to begin this fall.

“Delaying the project for rebid is concerning,” Lucas said, given that the risk of collapse increases the longer the project is on hold.

If the emergency authorization is granted, the department will be able to act immediately on the project without rebidding it. Under the best case scenario, Lucas said, this would mean working with the state Department of Transportation, which awarded the TAP grant, to completely fix the culvert and trail and prevent a collapse over the winter. 

Worst case scenario, he said, would likely mean hiring a contractor for emergency demolition of the culvert and the section of trail that lies over it to prevent a collapse and subsequent flooding from a dammed-up Crestwood stream, Lucas said.

Currently the area is blocked off for safety purposes: if parks moved forward with emergency demolition it would create a “chasm” in the trail for the time being, Lucas said.

The full board will consider the emergency authorization for the project Thursday.