Bridge

[Anonymous Poster]

I have 70 acres in Missouri (north of Springfield) with a creek running through the middle of it. My gravel driveway is 1/2 mile in to the house then 1/2 mile out the other side. It crosses the creek just below my house. It has a culvert now and when it really rains the culvert is too small to allow all the water through and eventually it runs over the driveway taking all my gravel with it. This happens about twice a year. I think the sulution is to remove the culvert and replace it with a small bridge.
I can't find anything anywhere about small rural driveway bridges. Does anybody know if there are kit bridges or any other low to medium cost solutions. All I can find are golf course bridges made out of gold or platinum. Great forum, thanks.

 

[DVerbarg]

There have been some threads in the past about this. As I recall some have used old truck frames for the span (covering it with appropriate sized lumber) and there was also a mention of using an old semi flat bed as a bridge. Of course there were probably some other creative types who fabricated their own from scratch.

Could you put in a few larger culverts instead of one "smaller" one? Do you know how deep the water is on the driveway, when at its worst? If you take this measurement and the length of driveway the water is at this depth you can then calculate the size culvert(s) you would need to handle the flow. If the creek is small enough this might be the easiest and cheapest way for you to go.

 

[hwp]

How big a creek are you dealing with? Do you know the maximum flow rate of the creek? If not, is there a goverment agency that can tell you the maximum flow rate? How wide does the creek get? How well defined are the banks? Can you rest the ends of the bridge on the banks or would you have to build piers? Bridges are usually expensive to build even when crafted out of surplus supplies. A properly sized culvert will probably be cheaper than a bridge. Once you know the maximum flow rate of the creek, any culvert supllier can tell you what size culvert you need.

 

[kevinro]

There are several definite downsides to building a bridge vs installing a bigger culvert.

Unless you get it engineered, the bridge may end up being a disaster waiting to happen. There are many types of bridge design, but the main theme for all is that you are transferring the load of the bridge (and traffic) to two point loads. This requires that the banks of the creek be able to handle a fairly large point load. The fact that there is a creek there means that the banks of the creek are likely to be soft. The abutment, which are where the point loads meet the ground, need to be anchored to some solid materials, or they need to be physically quite large to spread the point load. They also need to be able to handle any lateral stresses that the flowing water may present. In addition, the materials that you used to create the bridge deck need to be able to direct the point load to the abutments. You also need to protect the abutments from being undermined by water flow.

The other downside is that the bridge needs to be built from materials. Most of the appropriate materials degrade over time (ie rust, rot, or stress). The bridge will both cost you more to install and more to maintain over time.

Another that you should consider is liability. If someone drives across your un-engineered bridge and it collapses, you could get nailed with an ugly liability suit. Chances of a culvert collapsing are far less, and would be less shocking to the jury.

A culvert, properly buried, spreads your point load over a much wider area. While the culvert may eventually decay, the decking for your 'bridge' is dirt or crusher run, which is likely to require less maintainence in the long run. You should be able to find known field engineering designs and materials for installing culverts.

Bridges are much more complex. Having said that, I am working on a bridge design to cross a creek on my property. I plan for it to be a pedestrian bridge, but I am also considering making it large enough to handle my JD-4500+backhoe+loader+bucket contents+myself (approx total is 6000lbs). Its that large weight that concerns me.

Kevin

 

[Thomas]

Maybe twin culverts w/a headed might be your answer,and double the size of the culvert intake.

Bridge does mean extra work in taking care of thru out the years,plus you have to consider heavy load limits $$$$,were a culvert if you place deep enough and the right stones,gravel etc..pack around it your all set for about any piece of equipment.

 

[Kent]

Culvert/Bridge Products

I had a deep/wide swale/ditch I wanted to cross. Local building supply houses don't even carry culvert around here, so I took a drive out to a Contech plant and they bent a 36" culvert into an arch shape about 24" tall. Perfect fit. They also sell end pieces to hold back the bank (I didn't get these as the swale is seasonal and sort of stable).

I was happily surprised they sell direct to the public (usually these type of places only sell to stores/contractors).

A 10' piece is the shortest you will want to go with. A 6' wide tractor seems like a tight rope walk when you subtract a foot on either side for "bare pipe" and a foot of border rocks to keep you on track. Next time I would go with the end pieces! (I think they were $50 each)

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