Culvert - National Corrugated Steel Pipe Association

Corrugated steel pipe & plate has dominated the culvert application market since its emergence in the construction industry more than 100 years ago. Corrugated steel culverts, storm drains and sub drains are vital to the protection of streets, highways and railroads.

YiTong contains other products and information you need, so please check it out.

As the need for cost-effective, durable infrastructure has grown over the years, the corrugated pipe industry has responded.

Technological advancements provide more hydraulically efficient profiles and highly durable coatings, such as spiral rib pipe, polymer coatings, aluminized Type 2 steel and 2-ounce galvanized.

Corrugated steel pipe & plate culverts provide reliable, economical solutions to handle the flow, including debris, with minimum damage to the slope or culvert barrel. [hr]

Are you interested in learning more about Corrugated Metal Culvert Pipe? Contact us today to secure an expert consultation!

Strength of Steel

Corrugated steel culverts maintain the advantage of the strength of steel with a variety of coatings providing long service life. With allowable fill heights over 100 feet and minimum covers as low as 12 feet, corrugated steel pipes & plates can be matched to the strength required. Established long-term materials properties ensure product performance throughout the design life.

AISI-1Height of Cover Limits for Steel Pipe
H20 or H25 Live Load • 2-2/3 x 1/2 CorrugationDiameter or Span, in.Min.* Cover, in.Maximum cover (ft) for Specified Thickness (in.)0.....
15
18
21
24
30
36
42
48
54
60
66
72
78
84
90

12
12
12
12
12
12
12
12
12
12
12
12
12
12
12

198
165
141
124
99
83
71
62
(53)310
148
206
177
155
124
103
88
77
67
(57)248
217
173
145
124
108
94
80
68
(57)
(48)
(40)
(32)186
159
139
122
104
88
75
63
52
43

171
150
128
109
93
79
66
54
45Notes:
1. Fill heights in parentheses require standard trench installations; all others my be embankment or trench.2. In 12 in. through 36 in. diameter, heavier gages may be available – check with the manufacturer.* Minimum covers are measured from top of pipe to bottom of flexible pavement or top of pipe to top of rigid pavement. Minimum covers must be maintained in unpaved traffic areas.

“Real” Manning N-Values

Spiral Rib CSP.012Double Wall.012Concrete-Lined CSP.012Fully Paved cSP.-2⁄3 x 1/2 Helical12″.″.″.″.″.″.″.″.″ and larger.021

Superior Hydraulics

Corrugated steel pipe & plate provides “smooth” alternatives and fabricated fittings for superior hydraulics. Spiral rib pipe and fully lined CSP have the lowest Manning n-values of any storm sewer material. Small diameter helical CSP also has very low roughness coefficients as proven through independent testing. Fabricated fittings provide superior hydraulics by minimizing energy losses at junctions.

Durability of Coatings

These factors, along with a variety of coating systems, mean CSP can meet any service life requirement. Galvanized, aluminized and polymer-coated CSP are just a few of the coating options. Expected service life can be determined using the NCSPA Service Life Guidelines.

Cost and Installation Advantages

Corrugated steel pipe & plate provides the lowest installed cost compared to other materials. This is due to the low up-front material costs plus the added advantages of reduced installation costs, especially in large diameters. CSP is one-tenth the weight of reinforced concrete pipe (RCP) and comes in lengths of 20 feet or longer. Add this to fewer joints and easy, positive connections and it equals an installation cost advantage.

If you want to learn more, please visit our website Corrugated Metal Pipe.

I need to put in a 20' culvert to extend a road to an RV pad I am building. I need to be able to drive both a 14,000 # motorhome and my # tractor over the culvert, not at the same time.

I have seen both metal and plastic used, the costs are close in my area.

Which is the preferred type & why?

Second question:

How do I tell what size to use? The county says 12" minimum everywhere, but for the difference in cost I would rather do it right (maybe some overkill) the first time than replace it next year if it is too small.

From the topo map, it looks like the water from 10-20 acres of 15%+ slope drains through this spot. The culvert will have about a 10% slope.

I am sort of leaning to 24" diameter, which only costs twice as much as 12".

The culvert is going into a natural gully and not a ditch. I looks to me like there will be over 3' of fill over the culvert at one end, and over 5' at the other.

Third Question:

Do I need to fill around the culvert with gravel or can I just use the dirt I excavated for the RV pad?

Forth Question:

Should I have some kind of grate to prevent debris from entering the culvert? CurlyDave,

I like plastic since it won't rust.

You need at least 12" of material over the culvert to get the maximum strength. Mine is covered maybe 6"-8" but it handled 55-60,000 pound dump trucks just fine.

I used ABC to cover the culvert since that is what I was using to build the driveway. Most people would use whatever soil they had available.

I think mine is 18" in diameter. I got mine for free so I used it. I don't get much water in mine since the culvert is only about 50 feet from the top of a hill. I would want 18" or larger culvert since I think it would be harder to stop up in the first place and if it did get clogged it should be easier to clean out.

10-20 acres can generate alot of water. Since it sounds like you have a deep ditch a bigger culvert would be better. Bigger than you need is better than not enough culvert. You might want to contact you county extension office and see if they can give you some guidence to size the culvert. 1 inch of rain on 10 acres is alot of water....

Later,
Dan I'm a long way from being an expert here but with the weight on the MH (possible 8-9k# on the rear axle) and not knowing anything about the "dirt" I'd be a little concerned whether the plastic culvert could handle the stress. Does the galvinized steel have spiral flutes? This adds to the strength considerably. The trade off is that somewhere down the road the galv/steel may rust out as zinc is water soluable.

As for the grate, on a 24" culvert one might not be needed depending upon what gets washed down the gully. With a grate you could find yourself having to clean at least once a yr. I'd do some asking around from others in the area that have done it both ways and see what their feeling are.

Up the road a piece at MP #272. Plastic is better than metal for several reasons. First, it will never rust out on you. EVER. Second, get the type with the smooth inner wall. It stays cleaner and doesn't hold silt and debri. As for strenght, both rely on preasure from the fill material being equal on all sides. You need a certain amount of fill on top based on the size of the pipe you install to reach maximum strength. For an RV, you will need this. For a car or light tractor, the amount on top isn't as important.

Since you want to create a crossing over a ravine, go as big as you can. That ravine was created by allot of water. The size of it shoud tell you the amount of flow you have to deal with. 24 inches is a huge pipe and should be able to handle most situations, but there is a reason they make bigger pipes and/or install two side by side.

Putting grates in front will cause more problems than it would solve. Small leaves will wash right through it, but with a grate in front, they will create a dam. It's very rare to see one along highways or anyplace that they are put in profesionally, so I'm thinking you don't need one. I don't have any on mine and so far haven't had any issues.

Backfill is usually with clean soil, but sometimes sand is used instead. Rock isn't any good because of the voids and dificulty in getting it all compacted. At the entrance to the pipe you will need to put something down to stop erosion. I've used sacks of cement for this with good results. Of course, it's not as attractove as rock. If you use rock, be sure it's big enough not to wash away or let the water through it. Small rock is useless during a heavy storm.

And always plan for the very worse that can happen.

Eddie I am with Eddie. Go as big as you can. 10-20 acres draining thru a 6' or 7' deep ravine can be a lot of water. And you want it to go thru the culvert, not over the top.
And as Eddie said, don't use loose rock or gravel for fill. You don't want the water seeping around the sides of the culvert.
I have a 24" culvert in the ditch coming in off the road. I had to have some fill dirt hauled in but it was similar to what I have on my land. Once it is filled and packed, the circular nature of the pipe is very strong. Weight on top tends to push the dirt down around the sides of the pipe. That applies extra pressure to the sides adding support to the top. Due to the depth of my ditch, I have only about 1' fill on top of mine. But when I built my metal building, they brought in all materials on a flat bed semi. No problem at all driving it over the culvert. Oh. mine is metal.