UPDATE on DIY bridge (long post)

[scootr]

Low water crossing ! Now you got me thinking...
I have a seasonal creek I cross to mow a section. The bottom of this creek is mostly sand on clay. A good place to get a tractor stuck. And being clay it stays wet and soft long after the rains have passed the field needs cutting.
I plan on digging down a bit and build back up with stones and concrete creating a low water crossway.
Construct in the dry season, let next yrs water flow over it

 

[dodge man]

A little off topic but there are some things you can do to improve the efficiency of culverts. Head walls are not there just to hold the culvert in place but to help the water to enter better. Just a chamfer, a slight taper, on a concrete box culvert helps. In almost all cases culverts don’t flow full, the water can’t enter fast enough.

 

[airbiscuit]

Here is a pretty good site about Low Water Crossings


Watershed, Soil and Air Technology and Development Program, Home Page

 

[scootr]

Here is a pretty good site about Low Water Crossings


Watershed, Soil and Air Technology and Development Program, Home Page

Thanks for that!
My project will be at grade I have a crossing I've used in dry times for years. The improvement will be a combination rock and concrete. Rock being available and concrete being expensive. I'l probably cut the grade down a foot or so and fill back up with solid material and rebar in the concrete for strength and to keep it in place if/when it cracks
I don't need no stinking culverts!

 

[Streetcar]

The skidder bridges which BCP linked to above are similar to what we use for bridge tops. They cost around $400 for a 4x16 foot panel; so $1200 for a 12 foot wide bridge. The waste blocks are about $50 each; they also would have to be delivered somehow. As I mentioned in his previous thread, we can do a 2 foot high span, 10-12 feet wide for around $3000 including excavator time. The only variable is how much fill he needs. I looked but no longer have any pictures.

These aren't cheap. I had one built about 4 years ago with a 10 foot span and it was well over $20K. Like everything else, concrete has gone up since then.

The problem with trying to move a stream bed is that during high flow, water is very good at going where it wants to go.

A skidder bridge will be washed downstream at first heavy rain event. At this location it would be temporary

 

[airbiscuit]

Here are his high water and low water pics

 

[C79]

I don't think anything is ever built to last forever. You only hope it lasts for your lifetime. The problem in my area is that all the cropfields are getting drain tile installed. Now you have hundreds of acres rapidly drawing to a ditch or stream that never dealt with that much water in a short time. The amounts of rain at once have been ramping up too. Good luck and hope it all works out for you.

 

[john_leslie]

First of all I want to thank everyone who made comments on my thread. Lots of opinions and ideas.
I think I might have made a mistake by calling it a bridge that I am wanting to build, rather than a low water crossing. Some suggested that I should build a bridge, and they’re probably right but I don’t think I can afford one. If I knew how much weight a concrete pad could support spanning 6,8 or 10 feet, I might give it a lot more thought.
Many comments were about the 36” culverts not being large enough & would get blown out. I certainly wouldn’t be able to handle that. My thoughts are if the crossing has an 18-24” deep concrete footing (ring foundation) around it, concrete completely surrounding both culverts (packed on the lower sides so there are no voids), a ‘dip’ in the middle, and a 6” pad, the water could flow over the crossing (after heavy rains) without compromising the integrity of the crossing. The culverts would help with the water passing as the creek goes down and we would be able to cross it sooner. Emergency Services, Home Health Providers and the pizza delivery guy could get to us sooner. ( I’m joking about the pizza delivery guy. The nearest pizza place, that delivers, is 40 miles from us.)
Many folks noticed that our driveway is not perpendicular to the running water. With the way the creek runs now, much of the water is directed down the driveway, before it hits a bank and turns downstream.We plan to hire a dozer to take out a coupe ‘twist & turns’ to correct that and to clean out a lot a materials that have filled in the crossing. From the high spot on each bank of the crossing the creek bed only drops about two feet and I think that’s one of the reasons the the water spreads out so much.I think I need to have it deeper on each side of the crossing, say 4 or 5 feet upstream and downstream.
The dozer can push the gravel & rock to shore up the creek banks. Rip rap could be added later as long as we make a crossing that can handle the weight and get the trucks across.
My big question now is, will my crossing & culverts get washed away, when it’s surrounded by 40 tons of packed 3/4” minus gravel and 20 yds of concrete.
My last question is, who wants to grab a shovel and join the fun if the project is a go?
TIA
Gary

Hi Gary. I dont post on here a lot, but your topic caught my attention. I have some Bar Joists that I drug home from a commercial job site. They can carry a pretty large load. I was going to put a bridge accross my creek with them, just never got to it. Here is what I am talking about: https://qph.fs.quoracdn.net/main-qimg-a525cf5443d250d9e449e6f275576fdf
I got mine free and they were built the wrong size so they were going to toss them. You could check with a local fabricator that makes these to see if they have any rejects or just to see what they would charge to fabricate them for you.

 

[Rockbadchild]

To me as long as the road before and after the culvert is not too elevated and since there is practically no banks you will be fin, by putting a ''restriction'' in the middle the water will rise and flow around it.

 

[ovrszd]

I don't think anything is ever built to last forever. You only hope it lasts for your lifetime. The problem in my area is that all the cropfields are getting drain tile installed. Now you have hundreds of acres rapidly drawing to a ditch or stream that never dealt with that much water in a short time. The amounts of rain at once have been ramping up too. Good luck and hope it all works out for you.

Being in hill ground farm land, we have a lot of fields that are terraced and tiled. They actually slow down the water runoff. Which is their intent. Structures here are built with very high freeboard on the dam and a small overflow tube to get the same result.

 

[Trackerjoe]

Please send me information on the bridge. Sounds great !

Can you please direct me to that post?

 

[garymartin63965]

Hi Gary. I dont post on here a lot, but your topic caught my attention. I have some Bar Joists that I drug home from a commercial job site. They can carry a pretty large load. I was going to put a bridge accross my creek with them, just never got to it. Here is what I am talking about: https://qph.fs.quoracdn.net/main-qimg-a525cf5443d250d9e449e6f275576fdf
I got mine free and they were built the wrong size so they were going to toss them. You could check with a local fabricator that makes these to see if they have any rejects or just to see what they would charge to fabricate them for you.

Yes Sir, I have my eye open for some but so far no luck. Any idea how tall they would need to be to carry the weight of, say a log truck and how close they would need to be? Like 2’OC?

 

[garymartin63965]

Can you please direct me to that post?

I’m not finding that post now. I’m thinking it was posted by Jstpssn but I’m not sure. Sorry

 

[garymartin63965]

I’m not finding that post now. I’m thinking it was posted by Jstpssn but I’m not sure. Sorry

Might also be under my first post ‘DIY Bridge’ but I can’t find it anywhere.

 

[Deanes]

I would look for a company that builds or installs precast concrete buildings. They will have some flawed pieces 20-40' long. Probably best to get them to deliver one. You should ask them about stress, but I have found they are fine for cars and pickups.
Also, I remember my dad built farm bridges with old railroad rails with rough sawed 2x10s bolted across them. Kind of springy, I never saw one fail.

 

[Eagle1]

I have walkover bridge like that not sure I would trust my truck on it. The 40' rails are springy just walking across.

 

[bcp]

Railroad rails are probably designed to span a gap of not more than about 2 feet.



Bruce

 

[rScotty]

To me as long as the road before and after the culvert is not too elevated and since there is practically no banks you will be fin, by putting a ''restriction'' in the middle the water will rise and flow around it.

Yes, that's exactly what happened to us. We watched from a hillside as a whole town's bridges and culverts washed away for different reasons - but the most common cause seemed to be that as the creek became a river, it would cut channels around obstructions in moments, undermine them, and then removed them.

It was awesome to watch, but what I'll remember is the incredible noise - like a prolonged train wreck that went on all day.

I now believe that there will always be a large enough flood to wash away whatever kind of bridge we build - unless it spans a ravine and is enough taller that the ravine to freely pass trees, trucks, and houses underneath.

That's why I said my new rule of thumb is If you have to drive downhill to get to the bridge, it probably isn't going to last.

Yet, even if flooding is becoming more common, most of the time there isn't a flood. It's water as usual. So I think the trick is to build something that will still be there when the water goes down. I like that reinforced concrete low water crossing with the sloped upstream and downstream sides.

rScotty