Washed out bridge

[Rafterman]

This bridge is on our property on an abandoned town road. It is the access to the other side of the woodlot where we were hoping to cut this summer. In the past we were able to drive the tractor with a loaded log trailer across it no problem. Now it's washed out on both sides and looks like the logs shifted off the rocks. We are able to get machines down here to work on it but we are wondering what the best approach would be. We can get 4-6" (or 2") river stone for $31 a yard, thinking about just filling it back in with that then using a machine to push the bridge back into position. Also wondering about adding a culvert to one side of the bridge to accommodate the big water surges. Open to any suggestions.




This hole is about 6' deep. The picture is a little deceiving.

[PoginyHill]

How did the washout occur? Did it come down from the road that approaches the bridge? Or did the river level get up to the bridge?
If you alter anything, you'll want to consider seeing what the DEP will allow you to do for changes and/or what hurdles you might need to jump through if you want to be legal/proper, etc... Repairing what is there is probably fine without getting into any trouble.

Form the pics, it looks like it may be a road washout (both sides), not a river flood. If that's the case, you'll need to divert the water on the road before it reaches the bridge.

[Rafterman]

The water level did get up to the bridge. It usually happens once a year but maybe it was more water than normal with the amount of rain we got. Some must've been going across the top of the bridge with the amount of brush that's stuck to the decking. Pics from my dad a few days ago.

[rusticretreater]

Given that it appears you have large rock outcroppings to deal with, digging or shaping drainage looks to be pretty difficult.  The large washout should allow you to do some mitigation.

My suggestion is to change the current flow paths but also do some prevention.  The water washes down in large volumes on occasion which is the real problem.  The road channels it right to the bridge.

I can't tell how bad the erosion is to the side of the big washout. Push the bridge back into position, take that big rock the water didn't move and put it right in the path.  Fill that hole with big rocks and push rip-rap in between.  Then you want to get some kind of material that is malleable but when it dries and sets is harder than the soil.  Stone dust comes to mind.  

You use it and dirt to build long ramps to the bridge.  As far back as is necessary to keep the water from using the road as a channel.  The water will hit the ramp, won't want to go up the hill and peel off to the side.  A little shaping might help.  You will have to maintain the ramp ends to restore their effectiveness.  A hardware cloth or piece of chain link fence should be placed across the log ends at the bridge to keep the ramp from washing out under the bridge edge.  A 6x6 ledger log would be good here as well.

Addendum: You added pictures while I was typing.  I didn't imagine the creek actually got that high.  Now I would suggest inserting logs between the bridge log beams to span the hole created by the water and maybe place a culvert underneath. You then build more decking on top of the new logs and then build the ramp previously discussed.  You may want to do that on both sides of the bridge.

The bridge pier rocks appear to be large and stable enough that the water won't be able to do much more damage to the area.  Maybe raise the bridge just a tad?

[Resonator]

Fix comes down to how much you want to spend. Cheapest being just bringing in rock and gravel, possibly adding more culverts at the approaches. Most costly being to build a whole new bridge, depends how much traffic you plan to use it for.
One option I've seen is to use an old flatbed semi trailer for a bridge. Some also have used an old railroad flatcar, though they are much bigger and heavier to move and set.

One thing I can say for sure, if it flooded once, it can/will flood again. Whether from deep snow melting on a hot spring day, or from an intense thunderstorm that brings 4" of rain in a short time. (Been there, done that). 

[Ron Scott]

Check and work with the State and Federal permitting agencies having jurisdiction to determine what their minimum requirements will be to restore the bridge and roadbed on the river.

Some special funding may be available to help with the fix, especially if you have an approved forest stewardship plan and the bridge is necessary for implementing your timber management objectives.

[thecfarm]

We just had 4-5 inches of rain in the night. that did not help out much. 
That is rare, but could happen again.
Just like last December we had a big rain.  : 

[BargeMonkey]

 We have done 3 bridges in the last couple years for people with similar situations, all 3 where alot more crossing than you've got, I've got 1 to do this fall that's not quite as bad. Taking 40-45' flat bed trailers out of NJ cheap, cut the axles off and set them. Mafia blocks, best money you can spend to set a bridge on. Fix the base you've got, if you can set 4-6 blocks in each end, we built one we had 4 blocks high on the tall end. A piece of heavy conveyor belting is about the slickest thing I've seen to prevent water from running down a road like you've got, cut it in fairly deep, leave it up 8" of so, run over it, doesn't bother and will shed water off a road. 

[KEC]

Since the work might require some sort of permit, anything I've ever heard is that it is best to talk to the appropriate state agency people prior to doing anything. Gets you off on the right foot with them. In New York it is taboo to disturb a stream of that size without permits from our DEC (Dept. of Environmental Conservation).