# Bridging a creek bed



## SkizzlePig (May 14, 2006)

I'd like to build (or install) a bridge over a creek. I've heard that you can use salvage flatbed rail cars and make a cheap bridge. Unfortunately, the salvage guys have identified this secondary market and the prices have jump 10 fold in the last year. Additionally, bringing a rail car to our property would be a logistical jigsaw puzzle. That got me thinking ...

What if I used two parallel tractor trailer flatbeds. They're still cheap (especially the salvage ones) and are rated to 80,000lbs. Two of them laying next to each other would give me a 16'+/- wide road deck.

Please tell me what y'all think ... tell why this wouldn't work ...


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## mark3885 (Dec 15, 2013)

What is the depth , amount of water flow,width of the creek?
I put in 2 plastic culverts to get me across my small creek. Initial cost was a little high but very little maintenance .


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## farmrbrown (Jun 25, 2012)

Unlikely Farmer said:


> I'd like to build (or install) a bridge over a creek. I've heard that you can use salvage flatbed rail cars and make a cheap bridge. Unfortunately, the salvage guys have identified this secondary market and the prices have jump 10 fold in the last year. Additionally, bringing a rail car to our property would be a logistical jigsaw puzzle. That got me thinking ...
> 
> What if I used two parallel tractor trailer flatbeds. They're still cheap (especially the salvage ones) and are rated to 80,000lbs. Two of them laying next to each other would give me a 16'+/- wide road deck.
> 
> Please tell me what y'all think ... tell why this wouldn't work ...


Yep.
Seen it done, not far from here. I was thinking of alternate ways a few years back when the bridge at my mom's place washed away.
Another idea was the frame from a burned out mobile home......???

The most important part isn't the span and the weight rating (as long as it's a decent minimum) it's the pilings and support at the banks. You've got to overbuild there for the once a decade flood, and keep the constant erosion at bay somehow. Having a little extra length is better than not enough.


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## Sawmill Jim (Dec 5, 2008)

Burned out house trailer frame is not a good idea :nono:


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## TnAndy (Sep 15, 2005)

farmrbrown said:


> You've got to overbuild there for the once a decade flood....


THAT is what is not done on a regular basis around here.....planning on that 'little creek' turning into a raging torrent once or twice in the owner's lifetime.

Look real close at how much watershed is upstream, and how much it could drain down your creek before you build.

Guy down from me moved here from Nevada. Built a bridge way too narrow, and low. I told him it would wash out eventually....well, it took 15 years, and he was dead already, but that's what happened. Bunch of limbs/trees/etc washed down against his obstruction, formed a great dam, then backed up and cut across the road where the creek hadn't run in a thousand years. 

Where the bridge used to be: (Normally, you could walk across that creek and not get your shins wet)














Lifted this guy's house, on the other side of the road, and washed it out in the road.











Another guy, other side of the mountain, put two LARGE ( like 6' diameter ) culverts in parallel across the creek on that side of the mountain. Told him the same thing...."you're building a dam". At the time, there was maybe 6" of water running thru them. He looked at me like I was nuts.

Sure enough, same storm sent 5" of rain in about 2 hours down 4,000ac of National Forest watershed, washed a bunch of trash up against his culverts, cut one of them out and pushed it down stream to the next dam.

His solution was to haul it back up there, install it again, and this time pour a 4" concrete driveway to hold them in. That won't work either. Just that next time, he will have to remove a broken concrete slab out of the creek in addition. I told him to use option 3 (below), but he didn't do it.

The key to building one that stands a better chance of not washing out IF you have a lot of watershed up stream is: (and this would seem like common sense, but apparently isn't  )

1. Build it high and wide enough that stuff will wash under it. (expensive)

2. Build it right down at creek level...put a series of small culverts in the creek, and pour a thick concrete roadway over the top. When the creek gets up, blocking the culverts with trash ( it will ), it then simply washes over the top, leaving you unable to cross until it goes back down, and you have to clean out your culverts after the flood. (less expensive) 

3. Build a small bridge. THEN cut a swale, or dip, in the property on one side or the other, so when the bridge does block up, the water has a nice, wide, gentle path to divert around the dam without cutting it out. (mid range on expense) You might have to repair some drive after the water runs across it, and clean out the floated trash up against the bridge, but it's cheaper than a new bridge.


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## Harry Chickpea (Dec 19, 2008)

Along the lines of #2, there are places around here where the owners (and county in one instance) have simply waited for low water and concreted over a natural ford to make it more stable. Other than a relatively tiny pipe used during construction, there is water flowing over it much of the year.


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## texican (Oct 4, 2003)

Why 16 feet wide? I'd not want it looking like a 'county road' and having people driving over it. Can't think of any kind of farm machinery that can't travel down an 8' wide road...


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## Evons hubby (Oct 3, 2005)

texican said:


> Why 16 feet wide? I'd not want it looking like a 'county road' and having people driving over it. Can't think of any kind of farm machinery that can't travel down an 8' wide road...


I put in 16' wide gates so I could get my hay equipment through them. No way I could take my haybine or even the rake across an 8' bridge. Collapsed down the haybine is a good 10 ft wide, probably closer to 13 or 14 total width when attached to the tractor.


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## AmericanStand (Jul 29, 2014)

texican said:


> Why 16 feet wide? I'd not want it looking like a 'county road' and having people driving over it. Can't think of any kind of farm machinery that can't travel down an 8' wide road...


LOL just the opposite here, they don't use much farm equipment that CAN get down a 8 foot road, even 16 is iffy!


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## JLMissouri (Dec 12, 2012)

Sawmill Jim said:


> Burned out house trailer frame is not a good idea :nono:


Why? I would think it would work fine for a light duty bridge, I have seen hundreds of car trailers built out of them that hold the weight a bridge would. As long as the metal wasn't heat damaged I don't see a reason it wouldn't work for a light bridge.

Just curious as I am planning on doing this with a trailer frame on a wet weather creek/ditch on my place for my small tractors and truck, nothing over 10,000lb.

I guy I know used a flatbed semi trailer as a bridge and it worked great. Even old flatbeds seem to hold their value although. They make quick bridges, and if used in the proper location will work for a long time.


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## SteveD(TX) (May 14, 2002)

JLMissouri said:


> Why? I would think it would work fine for a light duty bridge, I have seen hundreds of car trailers built out of them that hold the weight a bridge would. As long as the metal wasn't heat damaged I don't see a reason it wouldn't work for a light bridge.
> 
> Just curious as I am planning on doing this with a trailer frame on a wet weather creek/ditch on my place for my small tractors and truck, nothing over 10,000lb.
> 
> I guy I know used a flatbed semi trailer as a bridge and it worked great. Even old flatbeds seem to hold their value although. They make quick bridges, and if used in the proper location will work for a long time.


It will definitely work. Several years ago, a very wise rancher/engineer advised me on how to build a good bridge:
1) find a good sturdy 40-50 ft. flatbed trailer
2) cut off everything that doesn't look like a bridge

Of course, it's also good if you hoist it into place after welding plates onto it that match up with heavy steel bolts that have been set deep into reinforced concrete piers that have been properly anchored. Depending on the stability of the creekbanks, this may not be necessary.


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## JLMissouri (Dec 12, 2012)

SteveD, that is pretty much what I have planned. I have a 65' trailer frame that will be cut shorter and set on top of a concrete base on each side. I figured I would allow some limited wiggle for expansion and contraction. Weld on some side rails and plank it with some oak.

I need to cross a small wet weather stream that has high banks. I have one way across currently and that is the dam for my big pond which moderates the flow pretty well.


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## Missourifarmboy (Aug 24, 2014)

Depending on the depth why bother with a bridge. Around here you can always find large slabs of concrete or asphalt that you can piece in like a boat ramp. cheaper with little to no problems.


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## AmericanStand (Jul 29, 2014)

JLMissouri said:


> Why? I would think it would work fine for a light duty bridge, I have seen hundreds of car trailers built out of them that hold the weight a bridge would. As long as the metal wasn't heat damaged I don't see a reason it wouldn't work for a light bridge.
> 
> Just curious as I am planning on doing this with a trailer frame on a wet weather creek/ditch on my place for my small tractors and truck, nothing over 10,000lb.


 Those car trailers are made from the part of the trailer over the Axles , that's the beefiest part of the trailer.
Even then the frames are usually boxed in with additional metal.
They are also VERY  short compared to the original trailer.!
Way different when you start going over 20 feet long and suspending it from the ends.


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## JLMissouri (Dec 12, 2012)

AmericanStand said:


> Those car trailers are made from the part of the trailer over the Axles , that's the beefiest part of the trailer.
> Even then the frames are usually boxed in with additional metal.
> They are also VERY short compared to the original trailer.!
> Way different when you start going over 20 feet long and suspending it from the ends.


I agree on not using the entire length, it might bend in the middle from the weight. I am only going to use 20-30' of the frame, less than half.


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## simi-steading (Sep 27, 2012)

Missourifarmboy said:


> Depending on the depth why bother with a bridge. Around here you can always find large slabs of concrete or asphalt that you can piece in like a boat ramp. cheaper with little to no problems.


Around here, they just cut down the banks so you can drive through the creek.. I have a county road that takes you right through the creek on my property... always water in it... at the road crossing the water is about 10 feet wide and a foot deep all the time...


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## AmericanStand (Jul 29, 2014)

JLMissouri said:


> I agree on not using the entire length, it might bend in the middle from the weight. I am only going to use 20-30' of the frame, less than half.


If you can cut the piece out of the middle then weld the end pieces under it that will help a LOT
But its still pretty thin stuff.
Why not just buy a couple of 20 foot beams or better yet find a used bridge?


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## Molly Mckee (Jul 8, 2006)

Here permits involved in bridge building are both numerous and expensive. not getting them, fines are worse. It makes it hard to believe in other areas you can just bridge a creek.


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## JLMissouri (Dec 12, 2012)

AmericanStand said:


> If you can cut the piece out of the middle then weld the end pieces under it that will help a LOT
> But its still pretty thin stuff.
> Why not just buy a couple of 20 foot beams or better yet find a used bridge?


Because the trailer frame is already here and doesn't cost anything. It will support more weight than anything I have, and if I ever get something to big I will drive across the pond dam instead. I am sure there is probably some thin stuff, but most trailer frames I have seen will easily support the weight I will be driving across it. I frequently haul stuff weighing the same on a trailer built with a lighter frame.


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## simi-steading (Sep 27, 2012)

Molly Mckee said:


> Here permits involved in bridge building are both numerous and expensive. not getting them, fines are worse. It makes it hard to believe in other areas you can just bridge a creek.



Same here in WV. if you want to bridge or culvert any water way, you have to pull permits, or hope you don't get caught.. It goes through the DNR here.


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## JLMissouri (Dec 12, 2012)

Molly Mckee said:


> Here permits involved in bridge building are both numerous and expensive. not getting them, fines are worse. It makes it hard to believe in other areas you can just bridge a creek.


Sounds horrible, glad I live in a mostly free state. I bet they require a bribe if you want to build a house with your own money on land that is suppose to be yours as well.


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## simi-steading (Sep 27, 2012)

We can build a house here with no permits. The reason here in WV you have to have permits to bridge, culvert, or make any changes to creeks is because if they didn't people would be causing floods all over the place.. This area has a creek in almost every holler.. It's also to help control erosion.. Lots of that in this area too with all the hills. .


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## Cygnet (Sep 13, 2004)

We have a lot of what we term "low water crossings" here, some on fairly highly trafficked roads. Just a reinforced concrete ford, basically. Many of them have been in place since the 1930's when they were built by the CCC. 

Reason they're called low water crossings is you can't cross 'em during high water.


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## AmericanStand (Jul 29, 2014)

Im very concerned about that bridge being made out of trailer frame.
PLEASE do this. The way the state sets bridge weight limits is to measure the weight it takes to deflect the span 3/4 inch .Set the weight and measure the deflection in the middle of the bridge.
Then mark and live by the weight limit!


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## TacticalTrout (Jan 7, 2010)

simi-steading said:


> We can build a house here with no permits. The reason here in WV you have to have permits to bridge, culvert, or make any changes to creeks is because if they didn't people would be causing floods all over the place.. This area has a creek in almost every holler.. It's also to help control erosion.. Lots of that in this area too with all the hills. .


Thank you for explaining the reasoning in short, simple terms. So many folks don't understand how much of an impact they can have on flooding and erosion. Simple changes on a small creek can have major impacts farther downstream on that creek as well as any waterway that it feeds in to.


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## Gray Wolf (Jan 25, 2013)

Here's my take on this.... 

A bridge is designed to be suported on the ends a sag downward in the middle -- just like a railroad car or a semi trailer. Using the load rating on it makes sense.

A house trailer / car trailer / travel trailer is designed to be supported in the middle and sag on the ends. Making a bridge out of it puts loads in the wrong place and in the wrong direction. While it may work just fine, depending on the trailer's load rating seems a bit chancy to me.


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## SkizzlePig (May 14, 2006)

Thank for the feedback, guys ... I've been looking to source a couple flatbeds and place them side-by-side to create a 16' wide surface. I'll bolt in horizontal 2x10s to finish the deck. Theeennnn ... we'll place a pole building on top, creating a covered bridge look.

... buuuut ... I have a nagging question in my mind: How much of a concrete footing would I have to pour at each end of the bridge to set the flatbed ends on? I'm not looking to create a super heavy weight bridge, but it will need to bear 12 tons.

Any thoughts on the depth of concrete I'll need for the footings?


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## SkizzlePig (May 14, 2006)

To finish this thread out:

I spoke with a structural engineer that's a friend of a friend. He told me that I would need each footing to be 3' x 18' x 2' deep. 3000lb mix with grade 60 #5 rebar 12" on center (top AND bottom) 3" clear from all sides.

Now, engineering stamps or permit required since it's a private bridge without public or commercial traffic.


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## Gray Wolf (Jan 25, 2013)

If this is going to be your driveway to house/barn etc, remember that the public, meter readers, UPS, mailman, propane trucks, county tax man, stock trucks, farm equipment moving vans etc may be using it sooner or later. Be careful you aren't building a lawsuit.

There are many county, state and federal agencies that care about people building private bridges over streams/wetlands and they DO require permits. You should check and recheck on your lack of permits, flow restrictions you may create above the design storm, and lack of engineering design before you disturb the stream.

Good luck!


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## Gray Wolf (Jan 25, 2013)

Footing design is dependant on soils. Did your engineer know the bearing strength of your soil at the base depth?


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## SkizzlePig (May 14, 2006)

Thanks, Wolf! Reeeeeally good points. He didn't know *these* soils specifically, but he is familiar with the soils in general.

We will also be maintaining a separate "heavy entrance" onto the property. We'll direct all non-passenger traffic through that entrance. The heavy entrance will not include any creek crossing, but will have a locked gate.


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## Gray Wolf (Jan 25, 2013)

You might consider posting a big "max weight limit ____" sign just before your bridge. Delivery people and others will cheerfully drive past your locked gate and use the bridge anyway and the sign might shorten your lawsuit if something happens.

You also might put up a "max height" sign if you put a roof over it. Otherwise a USPS, FedEx, UPS box van that is under your weight limit might get shorter.


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