10/1/17 update - the Trail is open again
OC Public Works will begin repairs on the Bay View Bridge at Upper Newport Bay located within the City of Newport Beach. Portions of the Brown/Bay View trail will be temporarily closed from July 31 to Sept. 15, 2017 for construction activities.
This is the trail that crosses the back bay between Jamboree and Irvine Ave. You can detour along Mesa Dr. just to the north. Here is a map of the detour.