That's too bad Alan. The Cedar Valley Nature Trail has been on my radar as a possible stop for my next trip out to Missouri to ride the Katy Trail. With any luck, a short term detour can be arranged until the bridge is repaired.
What section of the trail do you normally ride? Do you take single day trips or do you stay over somewhere? According to the Traillink.com map, it looks like the closure is around 20 miles north of the Cedar Rapids end of the trail. If that's your usual start point, you could still get in a 40 mile ride for the day.
I suppose you could always start at the Center Point trailhead and ride up toward Evansdale if it isn't too much out of the way to drive there.