Know of any cheap, non-invasive bridges?

May 17, 2006 6:04 AM

Cheap and innovative bridge solution that doesn't interfere with the river, or the banks at all?

The span is roughly 125 feet at the best point to cross. Going down the traditional route and setting supports into the river itself costs an absolute fortune in permits and construction costs (I've heard of people paying $100,000 in similar situations), and isn't an affordable solution.

Has anyone seen, or heard of a solution for a problem like this that is, at least, capable of supporting the weight of a golf cart, or similar?

posted by jcruden to science & nature (14 comments total)

Why are you building a bridge? Will it only be used once, or will it remain for some time, or will it be permanent? I really think we need more information.
posted by Faint of Butt at 6:12 AM on May 17, 2006

Some sort of weird esoteric Chinese bridge?

I know nothing about bridges and this is all I can find about it. I apologise for my lack of Google-fu :(
posted by public at 6:30 AM on May 17, 2006

Actually I lie, there is more!
posted by public at 6:31 AM on May 17, 2006

The bridge would be used daily, on a permanent basis. It doesn't have to be fancy, but it would need to be pretty sturdy.
posted by jcruden at 6:32 AM on May 17, 2006

That is very interesting, public. Thanks!
posted by jcruden at 6:34 AM on May 17, 2006

125' is a pretty long bridge length. The cheapest route is to use something like an old railcar but their lengths go up to only 90'. Look for a narrower place in the stream/river. Sometimes you might be able to find an old truss bridge for a reasonable price for sale. The best bet is to check with your local engineering college and see if the college would be willing to design and build a bridge for a senior CE project.
posted by JJ86 at 6:59 AM on May 17, 2006

If your location is in West Virginia, and you are spanning a creek or river with a private bridge, you may still have some regulatory issues [PDF file linked] to deal with. It would be very much in your interest to get some advice about this before proceeding with any construction, since if you put something up that violates state laws or guidelines for such things, you could be liable for fines and remediation fees that could mount up to far greater costs than getting the right permits beforehand.

But an acceptable alternative may be to construct a crossing using appropriate sizes of culvert and rock fill to create the span structure, if the chasm you are spanning is not too deep. The state generally has an interest in seeing that property is developed and made accessible, since development increases the tax base, and promotes growth. If there are any other private bridges within a few miles of your crossing point up or downstream, it would be a good idea to talk with those landowners about their experiences, and maybe cite their structures to any regulating authorities you might deal with.
posted by paulsc at 7:15 AM on May 17, 2006

This site appears to sell used bridges, a million links and a discussion forum. It might be a good start.
posted by Lame_username at 7:21 AM on May 17, 2006

Cable car?
posted by weapons-grade pandemonium at 8:09 AM on May 17, 2006

I've seen pictures of a land rover crossing rope bridges in Pakistan. An engineered wire rope bridge may suit your purposes and only require concrete work on the shore at either end.
posted by Mitheral at 8:31 AM on May 17, 2006

How much traffic do you expect it to carry?
Vehicles, or only foot?
What is the maximum expected load?
  (You expecting to drive trucks across it?)
How long do you need for it to last?
How high are the banks over the water?
What is the soil made of?
Does the river flood? How much does it go up or down?
How much do the banks erode over a period of 20 years?

Engineering is all about details. You haven't told us enough to even begin making reasonable suggestions.
posted by Steven C. Den Beste at 9:16 AM on May 17, 2006

Agree. More details would be useful. In the meantime one possibility that is cheaper, innovative, and non-invasive but considerably less bridge-like is a hand operated ferry.
posted by catdog at 2:41 PM on May 17, 2006

Steven

from the original post
"capable of supporting the weight of a golf cart, or similar?"
posted by Megafly at 3:00 PM on May 17, 2006

The span is roughly 125 feet at the best point to cross. Going down the traditional route and setting supports into the river itself costs an absolute fortune in permits and construction costs (I've heard of people paying $100,000 in similar situations), and isn't an affordable solution.

If you think can put up a 125 foot bridge for under 100K then I've got one for sale. And some oceanfront property in Arizona.

There are basically no non-highway sized clearspan 125' bridges, especially ones that you can afford and even if you could magically find a bridge you'd have to put in abutments at probably another $30-50K for such a huge structure. Putting in a culvert and fill is a) potentially environmentally a real disaster and b) 125' of fill at say 6' height and 40' thick + pipe will also cost more than $100K to obtain and place.

If you give me more details I can give you more info but I price these projects out quite a bit and right now I'd say there's no way you're putting in a safe and durable road crossing in bridge form for that price.
posted by fshgrl at 9:32 PM on May 17, 2006