From the City of Minneapolis:

Due to bridge rehabilitation work, the Midtown Greenway will have intermittent and partial closures through June.  The work is taking place to improve safety for bicyclists and extend the useful life of bridges.  Between Cedar Avenue and Hennepin Avenue, a mobile operation is blasting off loose concrete (which has been falling onto the trail) and making repairs on the undersides of approximately 30 bridges.

In order to protect the safety of trail users, the Midtown Greenway will be closed and detoured for short stretches at times.  Detour routes following 28^th Street and 29^th Street will be posted in these instances.  Work will take place on weekdays beginning at 7:00am and last until 4:30pm (although it will typically be completed by 3:00pm).  At times when it is safe for bicyclists to go through the work site, crews will direct trail users to the side.  Please respect your safety and the safety of city crews by following posted signs and closures.  The trail will remain open at all other times (including evenings, nights, and weekends).

Further west on the Midtown Greenway, bridges over Lake Calhoun Parkway, the Lake Calhoun-Isles Channel, and Dean Parkway are also undergoing bridge rehabilitation work.  This work is taking place to widen the trail and extend the useful life of the bridges, and will last through mid-summer.  The trail at these bridges will not be closed, but will be narrowed at times.