UPDATE on DIY bridge (long post)

[garymartin63965]

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

 

[Eagle1]

If you were close I'd join in some seat time. I just pulled out 40 or 50 tons of gravel from my creek to raise my roadbed while the water was down due to drought. Also managed to dig out and enlarge my cattle pond on top of the ridge. Our creek brings in tons and tons of gravel and I still have to remove a large island in the upper end of the pond next time the water level drops. It's like 1/4 acre gravel above full pond that was not there a couple of years ago.
As for things washing away, time and mother nature will work on it all the time. I found if you let things start to erode it never gets better by itself. I have no idea how many yards of material I have carried back up into the emergency outflow of my pond over the last 15 years or how many yards of gravel I moved out of the creek to use around the place. Living in the hills with live water comes with a price, at least we don't have standing water for long.

 

[Jstpssng]

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

Looking at the picture of the water running through, yes your culverts will wash out; along with anything else in it's path.
You might want to check before changing the path of the stream; although it's only intermittent, there still may be laws about it.
The bridge which I described will span 10-12 feet, and we routinely send 100,000 lb log trucks across them. As I said before they should only cost about $3-4000.

 

[Rustyiron]

You might investigate a box culvert. It's a big rectangular pipe. You'll need to find a concrete pre cast outfit. Between 2 pipes and a LOT of concrete it might be an option. They may also have other options being in the pre cast business.
Excuse me if this is irrelevant, I didn't completely read your last post.

 

[garymartin63965]

Looking at the picture of the water running through, yes your culverts will wash out; along with anything else in it's path.
You might want to check before changing the path of the stream; although it's only intermittent, there still may be laws about it.
The bridge which I described will span 10-12 feet, and we routinely send 100,000 lb log trucks across them. As I said before they should only cost about $3-4000.

Please send me information on the bridge. Sounds great !

 

[bcp]

Skidder bridges:

https://fpr.vermont.gov/sites/fpr/files/Forest_and_Forestry/Forest_Management/Library/FPR%20Skidder%20Bridge%20Guidebook%20feb2016.pdf

https://mywoodlot.com/blog/building-skidder-bridges-for-the-wac-bridge-loan-program

skidder bridge

skidder bridge

forestryforum.com

Tank car culverts:

tank car culverts at DuckDuckGo

DuckDuckGo. Privacy, Simplified.

duckduckgo.com

Bruce

 

[rScotty]

We designed several low water crossings of roughly the same size you are doing. The smallest one started with two 4' culverts and ended up using three 5 foot diameter culverts each 20 feet long. The idea behind a low water crossing is that water and debris will be deflected over the top during floods. So it's typical to use tapered aprons and heavy steel trash deflectors on the upsteam side ...on the inlets to the culverts. I'll add a picture.

When they work as they are supposed to, it doesn't really matter how much flow goes through the pipes, because it will not be sufficient to carry all the water. You are not going to be able to cross it when the water is up anyway. What you want to do is flow enough through the culverts to reduce the size of the lake which is forming upstream, while allowing the bulk of the flow to run unimpeded over the top of the low water crossing. When the water goes down, with luck your crossing has survived and will reappear.

The culverts themselves can be set in concrete or more commonly in stone with heavy riprap around the entrances. Concrete covering several layers of chain link fencing is one way to smooth the approach. Alternately, we use as many 3'x3' boulders on the upstream side as we can find - and larger ones for the outer banks. Anything much smaller is a waste of time. It's handy to have an excavator with a thumb for placing the rip rap. Also think about connecting the culverts to each other with heavy chain wrapped around them.

Yes, sometimes they do wash away. So do the best highway bridges, underpasses, and even that old standby: the multiple box culvert.
rScotty

 

[4570Man]

We designed several low water crossings of roughly the same size you are doing. The smallest one started with two 4' culverts and ended up using three 5 foot diameter culverts each 20 feet long. The idea behind a low water crossing is that water and debris will be deflected over the top during floods. So it's typical to use tapered aprons and heavy steel trash deflectors on the upsteam side ...on the inlets to the culverts. I'll add a picture.

When they work as they are supposed to, it doesn't really matter how much flow goes through the pipes, because it will not be sufficient to carry all the water. You are not going to be able to cross it when the water is up anyway. What you want to do is flow enough through the culverts to reduce the size of the lake which is forming upstream, while allowing the bulk of the flow to run unimpeded over the top of the low water crossing. When the water goes down, with luck your crossing has survived and will reappear.

The culverts themselves can be set in concrete or more commonly in stone with heavy riprap around the entrances. Concrete covering several layers of chain link fencing is one way to smooth the approach. Alternately, we use as many 3'x3' boulders on the upstream side as we can find - and larger ones for the outer banks. Anything much smaller is a waste of time. It's handy to have an excavator with a thumb for placing the rip rap. Also think about connecting the culverts to each other with heavy chain wrapped around them.

Yes, sometimes they do wash away. So do the best highway bridges, underpasses, and even that old standby: the multiple box culvert.
rScotty


View attachment 778103

Large diameter culverts are expensive. Moving and setting 3ft boulders isn’t cheap either. It seems to me like setting a railroad car bridge would be cheaper.

 

[hslogger]

Flatcar Bridges | Rick Franklin Corporation This guy has been working with the railroads since the seventies, rebuilding track when they have derailments. He salvages all kinds of material including flat cars and box cars. These decks make real good bridges. Put one down and be done with it.

 

[airbiscuit]

If this dry creek that gets pretty wet lies between your house and civilization, I would want to make a sufficient investment to make something rugged. I think you could find a junked out semi trailer from a construction company or heavy towing service.

The Box Culvert(s) idea isn't a bad one. Good for water flow, better for debris to flow through, and a dandy platform for your low water crossing.

 

[Streetcar]

The bridge or box culvert are good options but are very expensive.both will require significant fill on the approach. Rscotty shows there is no cheap fix for this problem with his experience in low crossings

 

[Jstpssng]

The bridge or box culvert are good options but are very expensive.both will require significant fill on the approach. Rscotty shows there is no cheap fix for this problem with his experience in low crossings

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.

If this dry creek that gets pretty wet lies between your house and civilization, I would want to make a sufficient investment to make something rugged. I think you could find a junked out semi trailer from a construction company or heavy towing service.

The Box Culvert(s) idea isn't a bad one. Good for water flow, better for debris to flow through, and a dandy platform for your low water crossing.

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.

 

[rScotty]

Large diameter culverts are expensive. Moving and setting 3ft boulders isn’t cheap either. It seems to me like setting a railroad car bridge would be cheaper.

Neither one is cheap, my experience is that cheap crossings don't last long.

Large diameter culverts and boulders are within reach of a person with a pickup truck and tractor with loader and hoe.. A trailer helps. A railroad car is a whole different level.

A low water crossing is a low tech way to carry heavy loads. It won't withstand a flood. Neither will many small bridges. At least not the ones built with pieces that are small enough to be moved with a crane. It's easy to design a bridge that costs as much as a house.

In many areas a bridge needs a level of professional design and inspection that a low water crossing does not require.

We've seen more flooding around here in the last decade than in the previous 50 years.

 

[ArlyA]

I've installed and repaired on many bridges and nearly all washed away in one event. The one seen below, was over 6ft above the creek, the civil and state engineers said it was high enough and good to go. It was anchored to concrete abutments that were pegged into bedrock. The structure weighted about 15,000lbs. We're told that rain and weather fluctuations are now a common event.

 

[Jstpssng]

I've installed and repaired on many bridges and nearly all washed away in one event. The one seen below, was over 6ft above the creek, the civil and state engineers said it was high enough and good to go. It was anchored to concrete abutments that were pegged into bedrock. The structure weighted about 15,000lbs. We're told that rain and weather fluctuations are now a common event. View attachment 778136View attachment 778137

Are you saying that this one washed? I would have thought it was plenty high enough.

 

[dodge man]

I think a low water crossing will work like you describe as long as too much water doesn’t go over the top or around it. I’m not sure 20 yards of concrete is enough though.

 

[ArlyA]

Are you saying that this one washed? I would have thought it was plenty high enough.

Yes, I have pics of it 1/4 a mile downstream but can not locate them. All the bridges in this canyon washed away. As you might guess, we are now advocates of higher, longer bridges.

 

[rScotty]

Are you saying that this one washed? I would have thought it was plenty high enough.

The "plenty high enough" is a real difficult thing to measure.

A good rule of thumb to start with is that a road should slope up to get to a bridge crossing. When the road slopes down, both the road and the bridge are already within the channel made by a previous flood.

rScotty

 

[bdhsfz6]

I'm not sure if this will be of any help, but our POA maintains a 60" pipe culvert which was placed back in 1913. Over the years, the pipe has corroded and is in danger of washing out. To take the strain off the culvert during high water events, we lowered the grade on the east side of the crossing which created a spillway to handle overflow. We placed used concrete highway dividers along the bank on the downstream side to minimize erosion.

The plan has worked well for many years with just minor gravel re-grading after high water events.

 

[Jstpssng]

The "plenty high enough" is a real difficult thing to measure.

A good rule of thumb to start with is that a road should slope up to get to a bridge crossing. When the road slopes down, both the road and the bridge are already within the channel made by a previous flood.

rScotty

It's above the stream banks, which is what I was looking at. We don't normally get the massive deluges seen in other parts of the country.

That does seem to be changing, though.