Questions You Should Know about Corrugated Steel Culvert Pipe

Corrugated metal pipes (CMPs) are some of the most commonly used materials for underground stormwater infrastructure. They go largely unnoticed, but are necessary to support the daily functions of our lives by properly moving water to avoid issues like water ponding, standing water on roadways, and localized flooding.

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CMPs are used for various underground infrastructure projects such as culverts, stormwater detention/retention systems, storm sewers, small bridge replacements, aeration pipes, material conduits, and more. 

CMPs can require frequent maintenance and repairs if they aren’t given adequate protection through the use of things like structural polymeric linings. Keep reading to learn about CMPs, 3 common issues they face, and how to fix them!

What is a Corrugated Metal Pipe?

A corrugated metal pipe (CMP) is a pipe—used for culverts and other underground infrastructure—that has a distinct set of parallel grooves and ridges. 

As mentioned, they’re most commonly used for drainage culverts, storm sewers, material conduits, and other underground stormwater conveyance infrastructure pieces. 

CMPs are commonly manufactured out of aluminum and steel, with different metallic coatings and alloys designed for different applications. 

Corrugated Metal Pipe Materials: 

Aluminum Alloy 

Aluminum alloy CMPs are designed to resist the effects of corrosion and abrasion underground. The surface of the core is coated with a higher-grade aluminum alloy.

Aluminized Steel 

Aluminized steel CMPs are manufactured by hot-dipping steel CMPs in commercially pure aluminum. These pipes can be effective at combating corrosion, in particular for culverts and drainage systems that involve acidic water. 

Galvanized Steel 

Galvanized steel pipes are manufactured using a process called—you guessed it—galvanizing. Galvanizing involves applying a zinc coating to the pipe, thus protecting the base layer of steel from corrosion. Typically less effective than aluminized steel, the zinc helps protect from corrosion by acting as a barrier between water and the steel, reducing the effects of rusting and deterioration for the short term. 

Asphalt-Coated Galvanized Steel

Asphalt-coated galvanized steel pipes are similar to galvanized steel pipes, but they’re coated on the interior and exterior with asphalt to delay corrosion and deterioration for a longer period. The asphalt, in combination with the zinc coating, provides additional abrasion resistance and helps to prevent water, debris, and abrasive run-off from reaching the base layer of steel.

Polymer-Coated Steel

Polymeric coatings and structural linings are emerging as great options in the industry to help CMPs stay sealed and strong. Polymeric coatings protect against abrasion from acids, salts, alkalis, and other materials that threaten CMPS in culverts and sewers. 

Common Corrugated Metal Pipe Problems: 

#1. Open Joints 

Corrugated metal pipe joints are the areas/pieces that connect different adjacent sections of pipe. These areas can be a source of problems if they are opened due to misalignment. In these scenarios, backfill material can erode into the pipe, causing structural deterioration and eventually failure if left untreated.

To fix open joints, a process called joint sealing is carried out. It’s as simple as it sounds—the joint is sealed off to prevent unwanted material from entering. Polymeric linings are great for joint sealing, providing structural rigidity against soil intrusion and hydrostatic pressure

#2. Voids 

Voids are unwanted gaps/spaces between the CMP and the soil. They’re addressed by using polyurethane grouting to fill the void and using polymeric linings to seal/strengthen the CMP.  

#3. Deteriorated Inverts

The invert of a corrugated metal pipe is the lowest point within the pipe that water flows across.

Since this is where the water makes the most contact with the pipe, it’s especially susceptible to abrasion during peak stormwater events and corrosion over time if left unprotected. Deteriorated CMP inverts are likely the most common and frustrating corrugated metal pipe problems that underground infrastructure professionals face. If the pipe doesn’t have a long-lasting, abrasion-resistant corrosive protective agent like a polymeric lining, it can rust through. 

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Once the invert rusts through, other serious problems can occur like voids or even total structural failure.

How Are These Problems Fixed? 

While there may be numerous approaches available in the market, many professionals are starting to see the advantages of trenchless pipe repair. 

Trenchless pipe repair means fixing underground pipes from the inside. These projects can be carried out to completion within a few working days, far shorter than digging from the surface and ripping up roadways to get to the pipes.

Polymeric linings—as mentioned in the Corrugated Metal Pipe problems section before—are a great trenchless solution for CMP repair and rehabilitation.

One of the best products any trenchless pipe repair professional can use is SprayWall®, a polymeric lining that not only seals CMPs but strengthens them as well. 

In fact, SprayWall® is scientifically proven to increase the load-carrying capacity of corrugated metal pipes by up to 800%.  

Last year, SprayWall® was chosen by the University of Texas at Arlington for a study aimed at creating testing and application standards for spray applied pipe rehabilitation liners in multiple Department of Transportation markets.

A key finding from the report was the fact that SprayWall® was strong enough to be considered structurally capable to perform as a new pipe inside of the host pipe. 

SprayWall® lasts over 50 years and cures completely within 72 hours of application. It begins to gel within 8 seconds and is tack-free after two minutes.

This means trenchless repair crews who use SprayWall® will have completed an entire project in the time a crew would need to dig up and bury what they’re working on. 

Overall, SprayWall® helps make CMP repair faster and more effective, with results that last for decades.

Conclusion

Underground infrastructure—supported by things like CMPs—is vital to our society, so it’s important that we keep it protected. 

Trenchless repair methods for corrugated metal pipes are proving to be the superior solutions when applicable, as they save communities time and money through long-lasting solutions and minimal disruptions. Whether the issue is corrosion leading to maintenance issues, or deteriorating inverts posing a threat for structural failure, trenchless solutions like SprayWall® can solve the problem. 

SprayWall® is minimally invasive and saves engineers, contractors, and communities their time and money. 

Have questions about SprayWall® or want to learn more about applying to become a Sprayroq™ Certified Partner? 

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. 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
http://www.wimmark.com/culvert_maintenance.htm 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. 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. 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.