Culverts/pipes - lots of questions

   / Culverts/pipes - lots of questions #1  


Platinum Member
Feb 27, 2005
Chester County, SE PA
Kubota L5030 HST
I am in the process of reclaiming some of my property for horse pastures. There is a creek that runs through it and the previous owner had a 4 foot diameter (?) galvanized corrugated pipe put in the creek bed to create a crossing. Problem is he didn't do it right and the creek washed out the dirt around the pipe. I plan to rebuild it this summer and use it for a tractor crossing. However, I'm not so sure that the pipe is long enough for a safe crossing.

- How long should the pipe be for a safe tractor crossing?
- Is it easy to join 2 sections of pipe together?
- Would it be easier to just buy a longer section of pipe?
- Any idea how much corrugated metal pipe costs?
- Where can I get culvert pipe?
- How much weight can a pipe like that hold if it is surrounded by dirt?

Other areas of the property have a high water table (I don't want to use the term "wetlands"). I was going to try to use field tiles and smaller culverts to make it more usable for me, horses and the tractor. In some areas I may use 18" plastic corrugated pipe.

- Any idea how much weight 18" plastic pipe could hold?

FYI - my tractor weighs 4,000 pounds and I have a backhoe, FEL and ballasted tires. I guessing the whole thing could weigh over 6,000 pounds.
   / Culverts/pipes - lots of questions #2  
The corragated culvert will come in different guages. There are clamps available for joining sections together. Length of the culvert may depend on how you wish to finish the ends and how deep the cover is.

The plastic pipe loading will be dependant on it's gauge and buried depth. /forums/images/graemlins/grin.gif

   / Culverts/pipes - lots of questions #3  
I do a lot of "low cost," meaning whatever we can scrounge up, culvert work for the hunt club where I have a backhoe membership. All seat-of-the-pants, no formal training stuff, so any answers I might offer are strictly caveat emptor, and worth what you paid for them.
"Any idea how much weight 18" plastic pipe could hold?"
None. Same for metal. They're only to keep the dirt out of the hole. Deep enough and they'll carry any load, if they don't have dirt on top they won't stand one crossing. Depending on the fill you're using 12 to 18 inches from the road surface to the top of the pipe will carry anything short of a loaded dump truck.
Four-foot diameter pipe? Needs to be deeper. I'm sure there are engineers who would have a table that shows how much deeper for how much greater diameter. Or a formula that says something like,"One inch of depth for each two inches of diameter." The idea is that the dirt spreads the load around the pipe rather than having the weight press down onto it.
"How long should the pipe be for a safe tractor crossing?"
Well, what really matters is how wide the road bed is. If you can approach straight on, three feet wider than the wheels of your widest trailer would be a decent rule of thumb. If the pipe is to be eighteen inches below the surface it should be at least three feet longer than the road is wide. Here again, that depends. What you want is to be able to have the slope from the road to the top of the pipe gentle enough that the dirt doesn't fall away. If it's sand you need longer pipe, if you're going to build a concrete wall on each end six inches overhang would be plenty. /forums/images/graemlins/wink.gif
"Is it easy to join 2 sections of pipe together?"
No. At least, used metal pipe would be hard to do. If you're going to have much or even frequent flowing water you want a good seal. Any openings the water will find and eat away the dirt. First thing you know you've got sink holes between the sections.
"Would it be easier to just buy a longer section of pipe?"
Yes, but...
"Any idea how much corrugated metal pipe costs?"
Like I said, we mostly scrounge. Have old stuff donated. Best we can do with what we have to work with.
"Where can I get culvert pipe?"
I know the 8 to 24 inch plastic pipe is available from Lowes, etc. Not too pricey.
Like most home projects, there is the prime trade-off. The better you do it, the longer before you have to re-do it.
Good luck, Wm
   / Culverts/pipes - lots of questions #4  
You didn't say how long your 4 ft diamater pipe is. Depending on how far below grade it is and how much height you want to build up on the pipe, will dictate how wide your road across it will be.

To stop it from eroding again, you will need to put something on the upriver side to stop erosion. Rocks work if you have them, concrete sacks stacked on top of each other with rebar through them also work really good.

Once a culvert is packed down on all sides, it will be able to easily handle anything you own. My backhoe weighs 14,000 pounds and crosses my culverts all the time with no problems. I've run a 40,000 pound RV's over them also and just the other day a neighbor crossed a few moving a moble home off his land through mine. I dont' know what that weighs, but it wasn't a problem either.

Joining the culvets requires a sleeve that bolts over the two ends. Sleeves for that large a culvert would be fairly pricey, but I have no idea of how much.

A 12 inch plastic culvert 20 feet long goes for a little over $100 in East Texas. Lowes has them along with most farm supply stores.

Each size you go up just about doubles the amount of water you can handle. I use 12 inch for just about everything. 18 inch would be a waste of money for me, but you may need it. I'd ask around to see what others are using in your area before buying something so big.
   / Culverts/pipes - lots of questions #5  
If your creek tends to turn into a raging river, even once every other year or so, you might find out that a culvert isn't enough. A bridge might be a better option (there's lots of posts here about those). A consultation with a civil engineer or someone with the county, etc., might be a good investment.

   / Culverts/pipes - lots of questions #6  
According to the U.S. Army Combat Engineer manual, a culvert pipe should have from 12 inches to 50% of the diameter. 4ft pipe = 2ft of fill over it. I believe the 12 inches is the minimum for smaller diameter pipes. You wouldn't want to have only 12" over a 4ft pipe.
   / Culverts/pipes - lots of questions
  • Thread Starter
I should have said that I plan on putting dirt on top of the pipes. Sounds like if I have at last 24 inches on top I should be fine.

I think the existing pipe is about 5 or 6 feet wide at the top. The downstream side is cut at an angle so that the bottom of the pipe lying in the creek bed is twice as long. So, if my tractor is about 5-1/2 feet wide it sounds like I should have a pipe that is about 12 feet wide on top.

I have heard of using bags of unopened concrete (I think here at TBN) with rebar driven through them. That sounds like an excellent idea. I was also going to use some pieces of chain link fence sandwiched in between rocks or riprap to reinforce the upstream side of the pipe.

I would love to have a bridge over the creek but I am afraid that would be too much money and time.
   / Culverts/pipes - lots of questions #8  
A creek?
I'm from the other corner of the state, but when I had a project going a few years back, the excavator had to file paperwork ( I think it cost me $150) with some environmental engineer co. to tell us how to build a small crossing over a tributary that runs through my property.
They said what size pipe, how long, how to backfill, how to seed and use haybales to prevent bank erosion.... I actually got a set of plans back.

At least around here, there's a bunch of gov't people that get pretty fussy when it comes to doing anything to creeks and such and mine dries up every summer.
   / Culverts/pipes - lots of questions #9  
Can't give specific #s on what a 18 inch plastic pipe will hold, but from personnel experience it's alot. I replaced a 2 ft galvanized pipe in front of my house that was smashed during construction of it from the heavy trucks/equipment. The pipe was to big for the ditch as alot of it was exposed so the ground couldn't help support it. I replaced it with a 18 inch plastic pipe with a smooth inner lining to help with water flow, also think it helps with the pipe strength. Only has about 6 inches of dirt/gravel on top of it and a tri axle dump with full load of rock went over it with no problems. Also the road in front of the house as two 18 inch plastic pipes and they are also shallow at only 6-8 inches of earth and tar/gravel road above them and they handle the semi's, Large tractors, and everything else that uses the road with no problem. The pipe comes in twenty foot lengths which is plenty wide for a crossing and I think I paid around $75 dollars for it. Lowes has them. Got mine from a local hardware farm and country store. Don't even look at the old steel pipes. Even the DOT has switched to plastic.
   / Culverts/pipes - lots of questions #10  
Usually when a stream or river blows the fill material out, there's a couple of potential problems. The first and least likely is a bad installation, the second being an undersized culvert and third the culvert plugged. If you want a relatively maintenance free culvert crossing, it should be sized based on bankfull width of the channel. Any smaller and the channel becomes constricted and it creates all kinds of maintenance problems.

When a culvert constricts the channel, it increases the velocity and typically hoses out the downstream channel. In time the downstream banks will fail and begin eroding into the channel. It will also cause bed material to aggrade upstream of the culvert and possibly cause the channel to want to meander. This is less likely if the channel is incised or is trapped between bedrock or other hard material. The other problem is passage of debris. If the culvert is smaller than bankfull width, it increases the likelyhood of catching debris in the inlet and eventually plugging.

For installation help, here's a couple of references I use.
ADS and Contec

For tractor use, I'd calculate your culvert length based on the width of your tractor, 3' shoulders and 2:1 side slopes. This should give you plenty of room and enough shoulder for safety.