Steel smooth walled culvert fixing grade.

[brnt]

A contractor bored and installed a 150 foot steel smooth walled culvert under a secondary higheway. The grade on the culvert is flowing the wrong way.The contractor is proposing the fix the problem by digging and exposing the high end of the culvert to the road and with a welding/cutting torch removing small bands of steel. I don't know exactly how this works--I think by removing some of the steel from underneath the pipe the pipe will weaken and drop down. Anyone ever heard of this?

 

[bimr]

You have not given enough information to understand the issue, but it does not sound feasible. If the culvert drops, won't it leave a void under the highway?

What is the grade?

How deep and what size is the culvert?

If the Contractor made the mistake, have the Contractor install a new culvert.

 

[gbam]

Not knowing the particulars as bimr pointed out, is invert paving out of the question? It will reduce your inlet area but if the pipe is not extreamly adverse you may be alright. Need to verify the hydraulics. I am not sure of the total impact of what is being proposed. Maybe Jack & Bore a second pipe next to the original alogn with invert paving or some other option.

 

[brnt]

The cul;vert is quite deep--the highway goes thru a draw at this point and its probably 12 feet from the invert of the culvert to the top of the asphalt on the road. Its a 30 inch diameter culvert. The slope is supposed to be 1%. Right now the supposed low end of the culvert is 5 inches higher than the theoretical high end. There wouldn't be a void under the road because they are going to expose the pipe and remove fill from underneath it from the outlet to the edge of asphalt. I think the idea is you heat the underside of the pipe and it weakens the metal and it drops. The more I think about it the more it sounds like a shortcut/bandaid solution

 

[BenJohnson]

The contractor installed the pipe wrong. There is no other solution except to re-do the entire project. Water is not going to flow up hill and I am certain the culvert pipe was designed to withstand certain design loads. If you weaken the culvert, you only compound the problem - and I can't imagine how his proposed fix will put the pipe into the proper position.

At this point the problem becomes more of an insurance/ legal issue - and the contract specs should state how these problems are to be resolved. It may be arbitration, or some other form of dispute resolution. The bonding and insurance companies should be notified immediately. Don't try to be a nice guy and let the contractor get by without fixing his mistakes properly. If that culvert collapses in the future, you will be to blame.

The most logical solution seems to be to drill an new culvert parallel to the existing pipe - and this time it should be installed properly. You will have to modify the inflow and outflow structures to accommodate the change in culvert location (I hope that is possible).

 

[TerryScan]

Was there was any extra capacity in the original pipe design. If so, I would be curious how the calculations of the "as-built" culvert perform. Head will still create flow. There area models that will handle an adverse slope and account for the inlet being partially embedded (assuming it will fill to the outlet elevation).

 

[BenJohnson]

Was there was any extra capacity in the original pipe design. If so, I would be curious how the calculations of the "as-built" culvert perform. Head will still create flow. There area models that will handle an adverse slope and account for the inlet being partially embedded (assuming it will fill to the outlet elevation).[/indent]

That is a duct tape and bailing wire fix. You use tricks like that when you need a quick fix. This is new construction and the job should be performed according to plans and specs. Besides, there is a good likelihood that sediment will build up in the pipe which would at best be a maintenance problem - and at worse, upstream flooding or washout of the culvert.​

 

[dicksewerrat]

The Contractor could pipe rama 48 inch steel pipe around the existing 30 inch line. Putting the proper slope on the pipe. Then the pipe woould be oversized. I don't think he can pull the existing out and reinstall. He can also put a new 30 inch 2 feet away. And then fill the bad pipe with concrete. Make sure you check his calculations and setup before he starts to install any pipe.

Richard A. Cornelius, P.E.

http://WWW.amlinereast.com

 

[broseke]

I agree with the above comment, if it's a new installation and it's not to spec, the contractor should redo it at their expense. That being said, I see the options as:
1) Analyze the as-built pipe to see if it takes the design flow
2) Line the pipe (i.e. install a new culvert inside the old one, or install culvert liner plate), which would obviously create a higher and smaller opening