Before you backfill and compact your culvert consider this! Have you ever noticed asphalt driveways with a bump directly over the ditch area of the driveway? Or a low spot in the same area? Two things you need to know before you go any further.
A lot of people never compact the material they place around the culvert. As sure as I am alive if you don't compact the material it will settle in after. When it settles, so does your asphalt and or paving stones. Do you have any idea how hard it is to fix something like this? Very difficult! If you have laid asphalt you can't fix it so it looks original. You need to cut the asphalt out and patch it.Who wants a patch on their new asphalt driveway?
Do you want to know what causes your culvert to rise? Of course this only happens in places that freezes. The frost goes down under the culvert and pushes it up. Stop the frost before it gets to the culvert by placing a sheet of 2 inch blue styrofoam directly over the pipe. Use 4X8 sheets and center them over the pipe. Cut 1 foot wide strips off a sheet and place it over the joints.
The material under the styrofoam must be compacted so it doesn't settle and crack the styrofoam. Make sure the styrofoam is secured and use a fine screened gravel for backfilling. If this procedure is done properly the frost will never get to the culvert.
!8 I have bought plastic pipes as long as 36 feet. The concrete culverts are 8 feet long; most driveways require three pipes 8 feet long. Most driveway culverts are 18” in diameter. If there is a heavier flow of water in the ditch you will be asked to install a larger one.
Anyone building a new home needs to contact the local government for their approval of the pipe. The pipe has to be big enough to handle the water, otherwise it will over flow and wash your driveway out. In the winter time it could freeze up and get plugged off, and then the water will run down the side of the road and cause problems with ice build up.
In rural areas it is the responsibility of the new home owner to organize and pay for the installation of their own driveway culvert. You must install the culvert you have been asked to install, if you don’t and it over flows you will be responsible for digging it up and replacing it with the proper size. Or the Department of Highways will fix the problem themselves and send you the bill.
If your driveway is going to be installed at the top of a hill chances are you won’t need a pipe because water will run both ways. Talk to the Highways people about this to see if they agree with you. They may say you can get away without a one. If you don’t need one, all you have to do is dig the topsoil out of the ditch and fill it in with gravel.
Important! The department of highways will also make sure you don’t install a culvert where it will cause traffic problems. You should have at least 300 feet of vision both ways so you don’t have to worry about pulling out in front of another vehicle. It is important that you choose a good spot to put your driveway; we don’t want anyone getting hurt or killed.
Plastic culverts need to be placed on a smooth, compacted surface. This will keep the inside of the culvert nice and flat on the bottom so water runs freely. Your culvert is now ready to be installed and backfilled with fine granular material. Bring the gravel up no more than half way on the pipe and level it off.
Make sure you crowd the material down in around the pipe with your shovel and then run a plate compactor over the material. Bring the material to the top of the pipe and compact it again. Make sure you don’t leave any valleys in the gravel because it won’t compact as good. Now you can completely back fill the pipe and smooth it off for one last compaction.
Important! Keep an eye open for big sharp rocks, don't let any sit directly over the pipe. The weight of the traffic can push the sharp rock through a plastic pipe.
Heavy machines can crush a plastic pipe if both sides of the pipe are not compacted properly. The water would still run through the pipe but not as fast. I have found that it is cheaper to do thing’s right the first time. If I can, I usually try to get a minimum of 12 inches of gravel over the pipe. This will depend on how deep the ditch is and how steep your driveway is.
A deep ditch will allow you to put plenty of material over the pipe. But a steep driveway won’t allow it! You tend to dig down to try to make a level spot at the foot of your driveway. This causes you to uncover the culvert. On some steep driveways I have used a 12 inch pipe because it will allow you to leave another 6 inches of material over the pipe. I did this knowing for a fact that the 12 inch culvert would handle the water in the ditch. Most importantly check with the local government to see if they approve of your idea.
The smaller 12 inch concrete pipes are sometimes used around new homes. You may have a small trickle of water you want to get from one spot to another. Or you may have a foot path on your building lot that has a wet spot. Simply dig a small ditch and lay the pipe in.