Our US 61 bridge is supposed to be replaced Real Soon Now. After the I-35W bridge collapsed in Minneapolis, someone somewhere in MNDOT was told to take bridge safety seriously. So they reviewed every bridge in Minnesota. We’re told that our very own US 61 bridge was among the worst, and may have been the worst that was not abruptly closed.

Last week they hosted a meeting at City Hall about potential bridge designs. It was definitely worth the trip. While the bridge concepts themselves were worth discussing, even better were backdoor discussions of other improvements, notably a Spiral Bridge-like pigtail connecting the bridge’s walkway with downtown. There’s also discussion of using the bridge project as an excuse to get rid of the power substation eyesore on the river bank.

MNDOT has started a Hastings Bridge Project web site, and it includes a December ’08 report on bridge plans. They call it a ‘scoping study.’ It’s an interesting report – 44 pages. It provided some good perspective for going to the meeting.

There are three ‘frontrunners’ for the bridge design. Officially there are a few other options, but they typically cost more and/or have additional side-effects that make them unlikely for selection.

In all three cases, the existing bridge stays in place while the new one is built. Since the box girder is a twin bridge, they’ll probably build one side, demolish the old bridge, and then build the other.

Here is my interpretation of the 3 designs:

• The box girder bridge is a generic-looking highway bridge. This particular design is similar to the new Wacota Bridge on I494 near Newport. I think it’s also the design of the I35W rapid replacement bridge. The downside of this design (aside from being boring in appearance) is that it takes the longest to construct: ~3.6 years.
• The arch bridge is this is the closest in appearance to what we have now. In fact, the arch in the current plans looks a lot like the old Spiral Bridge arch. The odd thing about this bridge is tha they have to build the arch on the river bank upriver (like in the new riverfront park) and float it downriver. Construction time ~3.0 years.
• The cable bridge is a particularly innovative design. This would be the first cable bridge in Minnesota. There’s one downriver in Iowa; that’s the closest to here. The planners acknowledge the “important role” the bridge plays in Hastings’ city image, so I assume this design is intended to jazz that up. There is higher ‘risk’ in budget and schedule since no one around here has built one before. Construction time is ~3.1 years.

They apparently tried to get all these to cost about the same: $250 million give or take 20%. Of course, the cost uncertainty rises as the schedule stretches out. Officially the box girder is cheapest. Since it takes the longest to build, the cost estimate may be the least reliable.

The cable bridge could be dramatic. A basic design looks a bit too modern for Hastings, but that apparently can be fixed. One suggestion is to put a pattern on the concrete towers to suggest stonework like the Brooklyn Bridge. The result would be interesting. The raw estimates give this bridge the highest cost.

I suspect we’ll end up with the arch bridge. It’s the sort of thing people have come to expect on the bridge here. I’d be satisfied with it myself, though the cable bridge is very intriguing. Cost and schedule are reasonable, which should further lean things towards this design.

In any case, I hope we end up with the pedestrian pigtail. I wouldn’t mind getting rid of the power substation, too. The cost estimates for both of these additions seem about the same: $2.5 million. Some folks wonder if the power company is trying to nail us for more than the cost of moving the substation, but we’ll probably be stuck paying their price.