Culvert questions...

[JimS]

I need to put a small culvert (8 - 12 inches) under a single lane, private, gravel road. I have seen 12" minimum burial depth to top of culvert recommended a number of places for good protection from crushing. That would put the bottom of the inlet at 24" below the road. Due to several factors, including the contours of the land I want to keep the inlet a bit higher than the bottom of the culvert - about a foot below the road. I have looked at inlet boxes but they are expensive, seem like overkill and raise the inlet more than I need so would have to be cut down or modified somehow-side inlets might work. Also considered a slightly bigger vertical pipe section at the inlet as an inlet box. It occurred to me that I might just use a 45 degree fitting on the inlet, angled up. One foot over the 45 inlet will be one foot up which would work pretty well. Didn't plan to have a grate as it will just plug up with leaves, etc and most will flush though without the grate.

Want to do concrete as I think it will stand up better to bumps from mowers, etc but it is a lot more expensive (both material and install - others will do the install) so I think I may be back to HDPE (double wall, smooth bore plastic). Also not sure about 45 fittings in concrete. Someone suggested plastic with concrete ends but I am not sure how that would be joined - would like to avoid any on site concrete work. Flare at outlet would be good to limit erosion but have limited space on that side (length). And a plastic flare is likely to get beat up over time.

Would like to get some feedback on this or ideas on alternate solutions....

 

[Ed of all trades]

I h.ave a metal pipe under my road that was put in around 1980 and it is about 4" from the top of the road. No problems with dump trucks hauling 16 ton of stone and it used to have a tandem feed truck cross it twice a day often loaded. Are you talking plastic, it might be cheeper in the long run to go with metal. Ed

 

[BeezFun]

Ditto on using metal pipe instead of plastic, especially if you're someplace that freezes. Murphy's law says that if anyone drives off the road, it will be on the end of your plastic pipe.

 

[vtsnowedin]

You can make a drop inlet any depth you want out of solid concrete blocks. For the top you can use blocks up the two or three fill sides and a cover of either a steel plate or a concrete cover you can buy or cast yourself. The bottom can be crushed rock or precast concrete or more blocks laid out in a square. Or if you can get one cheap a four foot section of 24" culvert can be set in vertically with cutouts for the drive pipe and the throat of your ditch inlet.
The foot of cover really reduces the load on the pipe and if your in a frost active area keeps it from pumping up to the surface where the plows rip off the top.

 

[dave1949]

Is there some reason you can't ditch out/move the drop area 10'-12' back away from the culvert end? Seems like you are complicating the project by wanting to combine the drop and culvert end close together.

 

[DJ54]

You don't say where you are located, but if you can find some 12" tubular piling. I bought some surplus piling off a small bridge contractor for $7.00 per foot 3 years ago. Walls are approx. 3/16" thick.

 

[powerpace]

To give you a heads up. Over time the metal culvert will be more problems than the plastic. Load levels will be near the same and plastic will be easier to repair than metal. Where I live the County road department replaced all the steel culverts less than 30 inchs in diameter with plastic. Over a period of time certain types of soil will eat even a galvanized pipe. In the local area about 15 years. The culvert near my driveway was full of holes on the bottom side.

 

[lutt]

We quit using metal culverts years ago, most of the farm coops dont even stock them anymore, we use corragated plastic. Run over them with full size ag tractors, trailer trucks coming out of the field with loads of 80,000# gross of grain in the fall. No problems.You can get any size you want. We have had metal rust out in short time. Plastic is more cost effective in the long run.LUTT

 

[Stimw]

I put in a 12" plastic, ribbed, smooth interior on my culvert 14 years ago. They told me that with 1' of fill it was good for 75,000lbs. I have had fully loaded concrete trucks accross it with no problems. (34 yard pour)
Took out a galv that was 22 years old and rotted and crushed!

 

[s219]

I used ADS/Hancor N-12 dual wall HDPE pipe, 12" ID, 15" OD, and it's done great. A 20' section costs about $160 around here. I have 12" gravel (crusher run, layered and compacted) over the top, and we've had numerous cement trucks in and out with no problems.