Culvert Advice -- Plastic vs. Galvanized ?

[PineRidge]

Here's a bit of information that may be helpful to your application Building forest access roads

 

[CurlyDave]

Listen to the advice your've recieved and get the plastic culverts.

OK, I just called around & found plastic 24" culvert. I got the last two 20' sections they had & a coupler. About 20 miles away.

I paid for it over the phone & they will hold it until I can pick it up on 3-10-06.

They will even cut it in 5' increments and credit me back for any part I don't need. I have to wait until 3-9-06 to get out to make a measurement.

This board is a great resource. Thanks for steering me in the right direction.

Pix next week.

To get a decently wide roadbed you can actually drive down into the ravine meaning the road has a dip. This is beneficial in a few ways. One, you provide an overflow within the same ravine should the culverts plug. Yes it will ruin your road but the water is still in the channel. Two, the roadbed can be wider. And three, you won't have to haul in 40 yards of fill.


I recognize all of the advantages here. I have to keep the roadbed level enough to get the motorhome (a 30 foot Class C) across the ravine.

This limits the dip, but I will work out the geometry and then allow enough dip going into the ravine to keep the motorhome about 6" from dragging its tail.

Again, Thanks to all.

Dave

 

[3RRL]

Dave,
Cutting the road down in the ravine is what my road guy did to avoid all that fill. This particular culvert is 36" diameter in here. You can't see it from this picture but it does show a generous road width easily accessable with an RV and construction trucks have had no problem.

 

[SWinTexas05]

If the road is going to have a dip in it, make sure that the lowest part of the road is not directly on top of the pipe. This will prevent any water running down the surface of the road from washing the pipe out from above.

 

[SnoFalls]

</font><font color="blue" class="small">( Here's a bit of information that may be helpful to your application Building forest access roads )</font>
very nice link ....

 

[Highbeam]

"If the road is going to have a dip in it, make sure that the lowest part of the road is not directly on top of the pipe."

That won't matter with an appropriate crown. The crown will force any collected water to drain in the four corners.

Rob, love that pic with the toothmarks on the cutslope. Hope it doesn't slide.

 

[LBrown59]

I put in 120 feet of 15 inch double wall smooth bore plastic culvert last summer.

 

[3RRL]

Joe,
That's all granite (DG) and hard! Only about the top 5' to 6' is dirt. It also slopes back at a greater angle the the picture shows. It blew my mind when they cut through that ravine on my property. Actually, that ravine blew my mind! Man I wish he would have put in those smooth inside culverts. I didn't know any better at the time, but if I ever have to install another one, it'll be plastic and smooth inside.

 

[flusher]

My driveway is 20 feet wide, road base gravel 6" thick.
My contractor used a 12" diameter corrugated plastic culvert about 30' long at the end of the driveway.

Had more than a dozen concrete trucks roll over the culvert during house and garage construction with no problem.

The septic tank guy rolled over the culvert with my 1250 gallon concrete tank on his truck. No problem with the culvert.

A plastic culvert is more than enough for your tiny loads.

The only problem I had with the culvert came from the Public Works department. The inspector bitched about the length of the culvert. He said that he "didn't like to see" 12" diameter pipe that long. He was worried about blockage and said 18" would have been better. But we talked about it for a while and he finally signed off on the 12" pipe.

 

[CurlyDave]

Cutting the road down in the ravine is what my road guy did to avoid all that fill.

When I look at your picture, your ravine is closer to the Grand Canyon than it is to my puny little gully. /forums/images/graemlins/grin.gif

 

[Egon]

Cover over the culvert depends on the gauge of the culvert material and diameter. Suppliers should have charts for this. After a certain depth of cover the soil will bridge and support the loads.

Both the inlet and outlet ends should have some riprap on the side slopes and bottom to prevent washing. This is important on the outlet to prevent undercut.

Ideally the culvert should be placed on a compacted base and covered with light compacted lifts. A well graded crushed granular material can be used if available. Keep rocks away from the culvert.

The drainage area sounds considerable for the culvert size but that is affected by soil type and rainfall amounts. You will have seen how much water runs down the gully.

Egon /forums/images/graemlins/grin.gif

 

[kossetx]

Guys, Since you all know so much about culverts, I have a question. I have some 12" schedule 40 pvc pipe. Would 2 runs of this equal, lets say, an 18" single pipe. I know I can calculate area, I'm just asking would it in reality work as well. One thing nice about it is it is smooth inside. I hate to just throw it away.

 

[EddieWalker]

Sizeing pipe and the amount of flow it can handle is a pretty involved formula to get it right. For most people, the general rule of thumb it that for every half inch of diameter, you increas volume by 2 1/2 times.

The 18 inch will handle more water than the two twelve inch ones. Do you need that much capacity?? Will the two 12 do the job?? Hard to say without knowing how much flow you have or the size of your drainage.

The other problem with pipe is that outsides are smooth. It's impossible to stop water from travleing down the sides of the pipe with dirt alone. No matter how tight you compact it, water will still work it's way down the side.

Lake builders use special sleeves to stop this in dams. Concrete also works.

Again, it depends on how much water we're talking about here. Since you considered an 18 inch culvert, I'm assuming there's allot of water your dealing with.

Since the pipes are free, you could always pour concrete at the ends and be money ahead.

If it was me, I'd try the 12 inch pipe and see how it works. But I'm cheap that way and free sure beets out allot of the other negatives.

Eddie

 

[CurlyDave]

The link in PineRidge's post has a table which shows what size is needed.

In my case, I think the table indicates I need something in the 24-30" range.

I am going to go with 24" since I think I overestimated the acreage drained. Also, the only place this goes is to a motor home pad, where I will have septic, water, and power. If it fails, not moving the motor home until I repair it is not a big issue. Plus, the culvert is going to have a significant downslope 10% or so, which should increase its capacity.

If the culvert was on my main driveway, I would get a bigger size.

 

[LBrown59]

<font color="blue">
24 inches might not be enough.

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Maybe the ravine or ditch is to big rather than the culvert to small.
~~~~~~~~~ </font>
Case in point the road ditch along the front of my property is any where from 24'' to 60'' wide and 24'' to 60'' deep.
Last fall I installed 120 feet of 15'' DW Smother Bore plastic culvert in it. In 40 years of living here that ditch has never carried enough water to make the 12'' 40' long culvert under my driveway in that ditch flow at any where near its 12'' capacity even in the heaviest torrential prolonged downpours.

After this installation I've concluded: Base the size of culvert on the volume of water needing carried not the dimensions of the ditch.

 

[LBrown59]

</font><font color="blue" class="small">( I'd be a little concerned whether the plastic culvert could handle the stress.
)</font>

It's not the strength of the culvert that prevents collapse it's the equalized pressure of the earth around it.

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[Buckcreek]

i have a branch that runs through my property It dries up in the summer and runs pretty good through wet weather. i put some 24'' galvanized drain pipes in to get some room to turn around and park , I wonder how long these are expected to last. I need to install some more but where these will be i need them to last forever LOL and i need to be able to drive over them . What would ever one here use , maybe concrete culvert pipe.

 

[LBrown59]

<font color="blue"> He said that he "didn't like to see" 12" diameter pipe that long. He was worried about blockage and said 18" would have been better. </font>

********
Wonder what he'd say about my 160 feet of 15''?

 

[Highbeam]

Supposedly, the galvanized CMP pipes will last 30-50 years but we have all seen rusty ones. The coatings vary and have a large effect on life. The corrosivity and wetness of the ground makes a big difference too. Check out some of the websites from the manufacturers and they should give some guidance on expected life.

 

[KentT]

I thought these pictures might add some value to this topic. I just had guys put in an 18" plastic culvert for the driveway on my lot last week. Since there's no permanent running water, and just runoff from a relatively small area, I think 18" is actually larger than needed but I wanted that size as a minimum for easy cleanout, if needed.

Here's a series of pics that show it being installed:

Clearing the trees

Preparing a bed for the culvert

More bed preparation

Getting dirt off the stumps as he piles the brush

32 Feet of culvert lying in the bed, waiting on the fill dirt

Spreading the fill and packing it in

Smoothing the edge of the fill

He packed the edges (the banks) with the bucket, patting it down

Closeup of packing the banks using the bucket

One of the 12 tandem loads of moist, sticky clay that we covered it with

He built up the fill in layers about 6" deep, packing each layer by running over it

Final grade, after 2 tandem loads of topsoil added, and backbladed sith the dozer to sow grass seed in

Grass seed sown on banks, mulched with old hay, and waiting on first loads of base stone

Other end of circular driveway in same state -- waiting for base of 1/5-2" stone

We were lucky enough to find a guy in the neighborhood who was cutting the grade off behind his house -- giving away this nice red, sticky clay that we used to fill around the culvert. It packed so well just by repeately running the excavator over it that the loaded dump truck would barely make tracks in it... We spread the very thin layer of topsoil to cover the ugly clay, with most of it spilling down the banks on each side, just so there would we a good seedbed for sowing fescue to prevent erosion. Now, if my resident flock of wild turkeys don't eat all the grass seed, I should be in pretty good shape! /forums/images/graemlins/shocked.gif