The State of Michigan (MDOT) has jurisdiction over State Trunklines (Interstate Highways, U.S. Numbered Highways and State Highways) within the County. A screenshot from the MDOT Traffic Volume Map below shows these roads which mainly consist of I-94, US-23 and other State Highways like M-17, M-52, US-12 etc…
Although there can be unique situations, having jurisdiction over these roads means owning their right-of-way and also any related structures such as bridges, retaining walls, tunnels etc…
Within this context, MDOT publishes on-line the results of their bridge inspections of bridges with greater than a 20 foot span on their owned routes within the county. This link here is the homepage for these inspections and provides an explanation of the rating system and specific terms used. A link to the most recent inspection report (March 2015) is also provided. If you open that document, Washtenaw County begins on Page 75.
Below is a screen shot of Page 75 –
If the bridge rating gets low enough, the Bridge is considered “Structurally Deficient” which according to MDOT:
“A highway bridge is classified as structurally deficient if the deck, superstructure, substructure, or culvert is rated in “poor” condition (0 to 4 in the NBI rating scale). A bridge can also be classified as structurally deficient if its load carrying capacity is significantly below current design standards, or if a waterway below frequently overtops the bridge during floods.”
It’s interesting to look at this list and think about the bridges we drive over regularly that the state considers “structurally deficient”. Some of them have been repaired or replaced since this report was published (some spectacularly so) but others are still out there. At the time of the report, the bridge with the lowest rating in the county was the North Territorial Road Bridge over US-23.