Page 1 of 2 12 LastLast
Results 1 to 10 of 12
  1. #1
    Platinum Member
    Join Date
    Jul 2001
    Posts
    508
    Tractor
    L3410

    Default Drainage pipe depth

    I've been filling in a low area on my property near a waterway (US intracoastal waterway), and need to run a drain pipe for a distance of about 25 feet so run-off from a small, natural ditch (which only fills after a hard rain) on adjacent land (US Forest Service) can pass through a short peninsula of my land into the waterway. I have a (about) 3000 pound tractor, and don't want to crush the pipe as I box blade the area smooth prior to planting grass. I hope to use 4 or 6 inch PVC, the kind for connecting septic tanks to the house drain (fairly thick, not the usual thin corregated drainage pipe stuff), with a grate on the uphill end and a perforated sewer pipe extension on the other. How deep would I need to place a 4" pipe, or a 6" pipe?


  2. #2
    Epic Contributor Bird's Avatar
    Join Date
    Mar 2000
    Posts
    39,493
    Location
    Texas

    Default Re: Drainage pipe depth

    Cisco, once it's covered and the dirt packed around it, you'll be surprised at how much it would take to crush the pipe. My brother put two drainage pipes (4" schedule 40 PVC for one and now I've forgotten the name for the other black one of about the same thickness) under his driveway; no more than 3" deep and regularly drove an 18,000 pound truck over them with no problems.


  3. #3

    Join Date
    Aug 2000
    Posts
    3,371
    Location
    California - S.F. East Bay & Sierra foothills
    Tractor
    Kubota L2500DT Standard Transmission

    Default Re: Drainage pipe depth

    The rule of thumb for culvert pipe is 12" from top of pipe to road surface.

    Despite what you might think, culvert pipe is not particularly crush resistant by itself. It depends heavily on proper backfilling to achieve its strength. If the soil around the pipe can be compressed, the pipe will get compressed right along with it. [img]/w3tcompact/icons/frown.gif[/img]

    If you're only talking about 25 feet, I would backfill it the way you would a culvert. Make your ditch wide enough to allow proper tamping on either side of the pipe, and use a good crusher run, something with lots of fines, which will compact solidly. Add the backfill evenly on both sides an inch or two at a time, and tamp each layer as solidly as you can.

    Having said all that, one of my culverts wound up with only 8 inches of cover, but I backfilled it as described above. Going on its second year of service now, the pipe has been holding up just fine under repeated crossings of my 4,000 pound tractor (including FEL and box blade). [img]/w3tcompact/icons/smile.gif[/img]


  4. #4
    Epic Contributor Bird's Avatar
    Join Date
    Mar 2000
    Posts
    39,493
    Location
    Texas

    Default Re: Drainage pipe depth

    Harv, I certainly wouldn't argue that what you describe isn't "best", but it just ain't "necessary". I have three concrete culverts in the borrow ditch from the road into my place. They were there when I bought the place. One of them is about a twelve incher and it's covered with about 6" of dirt. It's been crossed by everything from cars and pickups to tractor trailer rigs moving mobile homes; never any damage. The main driveway has about an 8" culvert covered with 3" to 4" of clay and gravel, and the third one into the shop building is probably a 20" concrete culvert that was exposed when I bought the place and you couldn't have driven a compact car over it without hanging high center. I covered it with 2" to 3" of clay and Central Freight Lines backed a tractor/trailer across it to make a delivery, my brother's backed his tool truck across it, etc. I've never had a problem yet. I think the rule of thumb you mentioned is great (if you have the proper place to do it) and that'll handle any 18-wheeler on the road, but for most applications you'd be surprised at how little you can get away with and never have a problem.


  5. #5
    Veteran Member
    Join Date
    Oct 2001
    Posts
    1,163
    Location
    Upstate NY, USA
    Tractor
    Kubota L3710 HST and a Kubota ZD21 60Pro

    Default Re: Drainage pipe depth

    I've had several pieces of sched 40 under my drive for 8 - 10 years with 2 - 3" of fill over the top and no problems. I've had many concrete trucks, 10 wheel dumps and 18 wheelers in and out.

    I also have 8 pieces of 12" plastic culvert pipe on my tractor road with boards over the top - no crushing and my tractor weighs over 6000#. I also routinely cross this "bridge" with a loaded 1 ton dump, (12000#).


  6. #6

    Join Date
    Aug 2000
    Posts
    3,371
    Location
    California - S.F. East Bay & Sierra foothills
    Tractor
    Kubota L2500DT Standard Transmission

    Default Re: Drainage pipe depth

    <font color=blue>I have three concrete culverts</font color=blue>

    When I said culvert pipes have little crush resistance of their own, I was referring to metal and plastic pipes. Concrete pipes are different. They have a lot of crush resistance.

    I'll go along with the "just ain't necessary", though, if certain other conditions are right. I think the soil is the most critical factor. If it's largely organic and compresses when you drive over it, the pipe will wind up taking the full load. Your clay and gravel sounds like pretty sturdy stuff once it's compacted.

    The 12" rule of thumb shows up in virtually all of the culvert documentation I ever found (again, referring to plastic and metal pipes). The more specific rule is a percentage of the diameter of the pipe itself, but of course I can't remember what that number is. Come to think of it, for the smaller pipe that Cisco is talking about, that would probably work out to less than the 12" rule of thumb. [img]/w3tcompact/icons/crazy.gif[/img]

    The anecdotal "proof" that backfill matters could be evidenced by the septic lines that a contractor ran under one of the roads on my tractor property. It was the plastic stuff, buried about a foot, but just casually backfilled with the same stuff that came out of the ditch. Within 2 years we determined that the pipe was partially crushed from the little traffic that passed over it.

    What really ticks me off is that the plastic septic tank they installed was backfilled the same way, and it is now partially crushed, too. [img]/w3tcompact/icons/mad.gif[/img]

    Our soil is a mixture of organic and rocks. [img]/w3tcompact/icons/wink.gif[/img]


  7. #7
    Super Star Member Egon's Avatar
    Join Date
    Aug 2001
    Posts
    19,400
    Location
    Nova Scotia, Canada

    Default Re: Drainage pipe depth

    Harv.
    I was wondering, did the contractor fill the plastic septic tank with water before backfilling?
    Egon


  8. #8

    Join Date
    Aug 2000
    Posts
    3,371
    Location
    California - S.F. East Bay & Sierra foothills
    Tractor
    Kubota L2500DT Standard Transmission

    Default Re: Drainage pipe depth

    <font color=blue>did the contractor fill the plastic septic tank with water before backfilling?</font color=blue>

    Claims he did, but nobody believes him. [img]/w3tcompact/icons/tongue.gif[/img]

    I was a hundred miles away at the time. [img]/w3tcompact/icons/frown.gif[/img]


  9. #9
    Epic Contributor Bird's Avatar
    Join Date
    Mar 2000
    Posts
    39,493
    Location
    Texas

    Default Re: Drainage pipe depth

    Yeah, Harv, I'll agree that the type of material you're putting the culvert, pipe, or septic tank in makes a major difference. We have NO rocks at all and this clay is usually very solid, so there's no doubt that does make a difference.


  10. #10
    Platinum Member
    Join Date
    Nov 2000
    Posts
    578
    Location
    NC
    Tractor
    NH TC35D4

    Default Re: Drainage pipe depth

    A few years ago I sent and received some material from one of the local black poly pipes manufacturer. I got back a large stack of documentation and reference material. Basically, it was documentation from test done to convince NC to allow DOT to use the poly pipe for road work, instead of the concrete or galv steel.
    From the reading I got out of the tests they did, the "crush-proof-ness" of a poly pipe depends almost 98% on how the pipe was backfilled.
    If you cut a 1' trench and lay a 6" pipe and all you do is push the soil back into the trench without proper backfilling/compacting then the pipe is very susceptible to crushing.
    They had very specific requirements on the backfilling procedure. The first several inches of backfill was the most important. Packing the sides of the trench to certain levels prior to fully covering the pipe. Then laying 6"-1' of soil at a time and tamping to certain levels again until totally backfilled.
    Now remember, again, this was for DOT specs and trying to "plead" their case.
    But they really have the advantage in the longevity of their product, Steel--35yrs Concrete--75-100yrs Black Poly--500+yrs. Isn't affected by water,sun,soil,heat(under 250deg).

    Now if you cut a 6" trench and put a 6" pipe(snug fit) then the sides are already compacted and all you'd need is to insure the back fill is solid.
    Now if all you have is sand, this isn't going to make for good compaction in any case, so the deeper the better with sand.
    It's all about distributing the load and insuring the Poly pipe has nowhere to crush outward.

    gary







Page 1 of 2 12 LastLast

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  
© 2016 TractorByNet.com. TractorByNet is a registered trademark of IMC Digital Universe, Inc. Other trademarks on this page are the property of their respective owners.