UPDATE on DIY bridge (long post)

   / UPDATE on DIY bridge (long post) #11  
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
 
   / UPDATE on DIY bridge (long post) #12  
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.
 
   / UPDATE on DIY bridge (long post) #13  
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.
 
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   / UPDATE on DIY bridge (long post) #14  
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.
middlebridge4 (DL).jpg
middlebridge3.jpg
 
   / UPDATE on DIY bridge (long post) #15  
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.
 
   / UPDATE on DIY bridge (long post) #16  
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.
 
   / UPDATE on DIY bridge (long post) #17  
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.
 
   / UPDATE on DIY bridge (long post) #18  
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
 
   / UPDATE on DIY bridge (long post) #19  
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.

Screenshot (23)b.jpg
 
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   / UPDATE on DIY bridge (long post) #20  
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.
 
 
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