How Would You Fix This Bridge?

[bdhsfz6]

The bridge was built in 1913 by dumping fill over a 6' diameter steel pipe, which is rotting away. The span over the pipe is around 20' to get to solid ground on either side. There is 36" of fill on top of the pipe, topped with 6" of modified gravel. Water is running beside the pipe and undermining what's left of it. As a result, the downstream side (left in pics 2 & 3), is subsiding. The aerial photo is north up orientation and the stream flow is top to bottom.

It's a private road, used by only a few property owners with limited resources. Contractor estimates to replace it with a 6' poly pipe are upward of $50K, which we can't afford. The price is elevated by DEP regulations which require the stream to be diverted during construction. The only way to do this is with large pumps. Stream flow and environmental impact studies prepared by a certified engineer are also required. Construction is made more difficult by overhead transmission lines.

The "cheap" fixes we've been looking at include using flatbed rail cars to span the pipe, or perhaps a 20' reinforced concrete slab. To avoid DEP regulations, anything we do can't disturb the stream.

Any ideas or suggestions would be greatly appreciated.

 

[Topzide]

Dig in abutments ti then span with rail cars or a reinforced concrete slab for a bridge. That way, you're not disturbing the stream flow. You'll need the abutments to keep the stream from eroding the banks of whatever bridge style you decide on. Now the DEP knows there is an issue, they'll keep a watch on you. Good luck.

 

[JJT]

Can you sleeve it with a 5' culvert pipe and grout the gap between the new culvert pipe and the old steel pipe?

 

[dodge man]

I assume this is a private drive? If you build a slab you need some kind of abutment to support it, maybe not with a rail car. I worked in the engineering world for nearly 40 years and stupid regulations can get ridiculous.

 

[airbiscuit]

Can you add pics looking through the culvert?

 

[LouNY]

The rail flat car would be nice, just set it on a couple of concrete slabs.
Or a pair of tractor trailer flat beds set side by side for a 16 ft wide bridge.

 

[Rustyiron]

How close to town and the "eyes" of the dirt police?

 

[Rustyiron]

That power line, do they occasionally access that line on your side of the creek. It crosses it but for how long? I'm guessing that your to the left in the overhead view.
(They might participate in this venture)

 

[RayIN]

Build a new box-type culvert beside the old one. When completed divert the creek to the new culvert. Box culverts have concrete wings and a concrete box(no bottom) for water flow. There is a box culvert in front of my house in the county road that's been there since the 1940's. I've watched fully-loaded tri-axle dump trucks drive over that culvert several times a day each spring and it's not been damaged yet.

A box culvert looks like a bridge and is often mistaken as such. This company builds pre-cast box culverts, but looking at them is a good visual aid to help understand how the look. Their design with a separate top is what I tried to describe, but turned upside down..

https://precast.org/theprecastshow/wp-content/uploads/sites/5/CP1-Box-Culvert-Design-Detailing_FINAL.pdf

 

[jigs_n_fixtures]

Build a new box-type culvert beside the old one. When completed divert the creek to the new culvert. Box culverts have concrete wings and a concrete box(no bottom) for water flow. There is a box culvert in front of my house in the county road that's been there since the 1940's. I've watched fully-loaded tri-axle dump trucks drive over that culvert several times a day each spring and it's not been damaged yet.

A box culvert looks like a bridge and is often mistaken as such. This company builds pre-cast box culverts, but looking at them is a good visual aid to help understand how the look. Their design with a separate top is what I tried to describe, but turned upside down..

https://precast.org/theprecastshow/wp-content/uploads/sites/5/CP1-Box-Culvert-Design-Detailing_FINAL.pdf

If you want to build a box culvert in place, check to see if your state highway department has the design available as a standard plan. Haven't checked in a while but Nevada, Idaho, and California used to have tem as standard plans available for free download. The Nevada ones have table which tell you how much concrete, and reinforcing steel is required.

 

[rScotty]

OK, you asked for suggestions. Here goes:
That's a nice project. BTW, & congratulations on getting 100+ years on the original.
Concrete box culverts are very nice, but spendy. But do that if you can afford it. Steel culvert is way less expensive, & 100 years is reasonable. Steel culvert quality varies a lot. Some of the better is heavier gauge and coated.

Just guessing based on our area, these 4 items listed below on a rural job, on a private road to private land could cost as little as $5K each or as much as twice that. Allow the same $5K for overruns and so you are at $25K. min. here. Not bad compared to $50K, and frankly the $50K you were originally estimated too far isn't out of line if this road sees tonnage or has to be rated in any special way - for fire trucks for example.

1. I would call around and see if I could get an older professional civil engineer on my side. His stamp will be needed, and he can design alternatives for some regulations. He has probably dozens of this type repair & has stream data and local knowledge.

2. Ask around to see if anyone sleeves old culverts. A 5 foot sleeving for existing 6 foot pipe can be considered a temporary internal diversion since it prevents the construction muck from being carried downstreanm - which from your photos is what is happening with the undermining going on right now. The civil engineer will need to draw up plans for the DEP so that the sleeving is an acceptable temporary bypass.

3. Expect to put in a pair of new six foot culverts - one on each side of the central sleeved pipe...or whatever fits. It's good practice to ALWAYS put in two or more same size culverts side by side - each one sized for full flow. Climate change means local flooding, so an even better idea is to have one or more offset above the others in case of flood debris plugging the lowers. This is the time to do this job because most local codes haven't changed as much as the climate will....yet.

4. Plan for a large excavator. Looks like a one day job but allow for two. The excavator should already have knowledge/permits for working around power lines.
Tell him he may need to do some compaction around and between culverts. He will know that anyway..
You could make back some of your cost if the culverts displace enough decent dirt to avoid having to bring in fill. But you won't know that until you dig.

5. Put the guard rails back to code.

Good luck,
rScotty