Culvert repair/extension: Concrete to HDPE

[Sarge338]

Good Morning Folks,

I have a culvert that was installed (I assume) when the home was built, in 1991. In attempting to prep for extending the culvert to widen the driveway a bit, I found the existing culvert was… suboptimal. For starters, it had been completely covered with dirt, leaves, etc. Once I uncovered the end, I found the old, concrete pipe was broken and FULL of mud. When I tried to uncover it to see if I could just cut off the broken bit, and extend it, I found that someone had broken a 5-foot section off of the main culvert pipe, put a “bend” in the line, and “joined” the two sections by putting a piece of sheet metal over it.

Well, I removed the 5-foot section and the “joint” metal. Now I have a jagged, concrete pipe end sticking out about 12” from under the concrete driveway. After cleaning the existing pipe, how would you recommend that I attach a HDPE culvert to this concrete pipe to repair and extend the culvert?

Thanks

 

[crashz]

Making a joint there could be done with hydraulic cement, but nothing will last. The running water and freeze/thaw will break it apart.

What is the diameter of the culver pipe? I would strongly consider lining it fully with a smaller HDPE pipe. Flow calculations usually prove that the difference in friction coefficients allow better flow through HDPE than concrete, so you won't loose much if anything. And joining the pipe will be much easier (if needed at all). Once lined, you want to protect the ends of pipe with stone or even use a HDPE headwall on each side.

 

[erikjohn67]

Making a joint there could be done with hydraulic cement, but nothing will last. The running water and freeze/thaw will break it apart.

What is the diameter of the culver pipe? I would strongly consider lining it fully with a smaller HDPE pipe. Flow calculations usually prove that the difference in friction coefficients allow better flow through HDPE than concrete, so you won't loose much if anything. And joining the pipe will be much easier (if needed at all). Once lined, you want to protect the ends of pipe with stone or even use a HDPE headwall on each side.

Manning's roughness coefficient is better for HDPE than concrete but the gains are made the longer the run of pipe gets. On a short run such as what is being considered it would negligible and the cross sectional area of the pipe being attached will control the amount of flow. That being said going smaller is probably not a good idea unless the pipe is already oversized for the drainage area it is servicing.

I would cut the RCP end so it is a clean end cut and so you can butt the other pipe directly up to it without and voids between the joint. Get how ever many bags of Qucikcrete with fiber and pour a collar all the way around. I would pour it as thick and wide as you can get away with in the area you are working in and you can back it up with some plywood cut pieces or if you have thin masonite that works really well and you can just back it up with wood stakes or dirt backfill. Make sure you dig under the joint and get concrete in there also. I would shoot for at least 3-4 inches thick and 12' across the joint (6" on each side). Again if you can get more that will just make it stronger. If you want to go overkill for a driveway connection you can throw some rebar or wire mesh in there for good measure.

It won't meet whatever building code the it would fall under but I have been doing DOT's work for over 20 years most departments have a similar type of connection detail for dis-similar pipes and they typically they require 6" to 8" thick with reinforcing and 1xPIPE ID overlap of the collar on each pipe. So if it was an 18" pipe the collar would be 3' long.

 

[JJT]

I'd simply replace the 30 year old culvert with plastic, 1 size bigger than the existing culvert.

 

[LouNY]

In my mind one major consideration would be are you extending the up stream or the down stream end.
How often has the culvert had heavy flow through it.
A replacement often is cheaper then trying to patch it.

 

[Sarge338]

To answer some of the questions asked…

We are talking about a 15” culvert… packed FULL of mud.

I m looking to extend the culvert on the downstream side of the driveway.

The culvert rarely has heavy flow. It is just for run off drainage… not any kind of steady stream.

The existing culvert is under a concrete driveway, so I don’t think that replacing the culvert would be cheaper.

 

[Sarge338]

 

[dirttoys]

Push the biggest plastic that will go through it, bury it, and readdress if it causes drainage issues more than once a year. But, only if it meets your local requirements, and looks ok to you and yours.

Best,

ed

 

[LouNY]

It doesn't seem like a high flow situation,
I'd get a double wall plastic culvert the same size, butt them together wrap the joint
good with some heavy plastic such as an old pool liner or some of this vinyl bill board material
that they sell for tarps. Compact the bottom of the ditch real good if it's loosened up.
Cover it up and forget about it.

 

[CADplans]

IMO,, you need a "headwall" more than a piece of culvert,,,


I have done four of these on my driveway, I got one more to do,,
My neighbor asked why I was doing them,,
I told him,,, "Boredom!!"