Culverts (again but for a paved drive).

[sanmigmike]

I've looked at some of the threads on culverts and have some idea of what to do but...?

My "bad" neighbor (long story but it has changed for the better due to his ill wife) is getting his part of a shared road paved. But there is less that 200 feet of road that he doesn't use that he doesn't need paved. However, much to my delight and pleasure, he offered to go ahead and pave it and split the cost of that portion three ways, one third for him and then a third each for us and our other neighbor. (I think his wife being ill and urging him to mend his ways was a big part of it and me rescuing his tractor helped change him from being a "bad" neighbor.)

This portion goes through a nice wooded area that has a few low spots and a slope. During the wet season part of the road gets wet and at times flooded. Two areas are the worst and one is about 18 inches lower than the road on the high side, the area that the water flows from. He and I think it would be a good idea to put a culvert or some other way of draining that before it is paved. Not sure how much space we need under 2 inches of asphalt. Most of the threads I have found deal with putting it in a gravel drive so? Ideas? Suggestions?

 

[Defective]

I'd do a culvert under asphalt as if it were under gravel. Asphalt has no real strength. It only really acts as a binder to keep things from shifting.

 

[atgreene]

Whatever size culvert you put in, place that same ammount of gravel over it for cover. 8" culvert should have at a MINIMUM 8" of gravel, 12" culvert 12" etc...

Make sure you bed it in crushed gravel and compact it in lifts as you go. Nothing worse than paving a road over a poorly bedded culvert and having the pavement give out early.

Good luck.

 

[JDeerekid]

Same what "atgreene" said make sure you compact it really good as you go I would dig down a couple feet at least then start putting crushed gravel in at 2" incruments and compact then insert culvert where you want it and continue with the crushed gravel the same way. It is definately worth renting a vibrating compactor for this. If it is not done the correct way it will settle and you will be mad everytime you drive over it. My town highway department did one down the road from me. They dug up the road and put new culverts in and waited about a month before they actually paved it, but never compacted it properly and it settled about 4 inches over a couple months. After a couple months they came and patched it and now the road looks like crap becuase of the patch jobs.

Good luck whatever you do. It is definately nicer to have a paved road when winter comes around.

 

[Hillfarmer]

OK, it depends on the type of culvert used. I agree with the previous posts about 2 inches of asphalt having negligible strength characteristics. However the burial depth of the pipe depends on more than the size of the pipe. ADS the manufacturer of the corrugated black plastic pipe with a smooth interior wall requires a minimum of 12" of cover. This pipe is as durable as the metal if bedded properly but will crush if you look at it wrong if bedded improperly. The smooth interior wall makes it a lot easier to maintain especially for small diameter pipes. The metal pipe may require less bedding depending on the pipe wall thickness. One other thing when using any plastic pipe that will have asphalt placed over it you need the twelve inches of bedding cover to reduce the heat. Good luck with your project.

 

[atgreene]

Hillfarmer is right about the smooth bore, forgot to mention that in my post. A smooth bore will flow 25-35% more water than a likesized metal corugated.

As for heat, I doubt that will be an issue, but the deeper the better. Compaction in good gravel with a slight pitch is the key. As well as good catch basins on each end to prevent silt from entering the pipe.

Good luck.

 

[EddieWalker]

Two types of culverts. Metal, which rusts, and plastic, which has a smooth bore and ridges on the exterior for strenght. With my own money, I will only buy plastic.

First you need to decide how big of a pipe that you need. 12 inches would be the minimum. You can buy smaller, but they just plug up and cause allot of headaches. If it's just a few acres that you are draining, or then 12 inch is fine. 15 inch will handle well over twice as much water. If you can afford the extra $40, buy the 15 inch as it will handle most situations. 18inch and 24 inch are just huge and are more for highways and massive runoffs that will require rip rap and cement to protect the road too.

Rule of thump is to have half as much material on top of the pipe as it's diameter. A 12 inch culvert needs 6 inches of material above it. I wouldn't count blacktop pavement in this equation, but either good quality clay or road base type gravel. Don't use one size or rock, it must be a road base type of materail with a large variety of sizes to the stones. They sould have jagged edges and should include allot of fines in the mix.

Before paving, it's very, very ,very important to get propper compaction. Your car, truck or tractor will never achieve this. You need a roller if you will be paving anytime soon. A vibratory roller is even better. This needs to be done along the full length of the road that will be paved, and any low areas that you create need to be filled and built up, then compacted again before spenind the money of blacktop.

If blacktop moves or settles after it's installed, it will fail. Once it starts failing, it just gets worse. If you have good compaction, a residential driveway will easily last a decade witout any major issues.

Two inches is fine for auto traffic. If you are driving anything heavy on it, then you need four inches. Heavy would be a vehicle over 10,000 pounds. Most RV's are way over this amount, as are commercial vehicles and delivery trucks.

Nice to hear you worked things out with your neighbor.

Eddie

 

[Soundguy]

Two types of culverts. Metal, which rusts, and plastic, which has a smooth bore and ridges on the exterior for strenght. With my own money, I will only buy plastic.

rusts? not much.. as it's galvanized!.. maybee onthe cut edges or miter joints. but those can be dressed.. OR.. for extra protection. get asphalt coated metal pipes..

The GC I work for has put in alot of culvert pipes in the 24ys we have been in business.. never had to go repalce one due to rust. We've also ripepd out alot and repalced when doing new roads and driveways. I've yet to have pulled a culvert out that was younger than 20 years that had anything more than nuisance rust on it...

Plastic ont he other hand... well.. i expect that stuff to degrade onthe edges where exposed to uv light, and eventually recede.. causing dirt to fall intot he swale and choke the flow down.. over time of course..e tc. I'm also not a fan of hardi pipe for anything other than deep comercial projects where taxpayer money is an issue.

concrete drainage pipe, and where available, terra cotta drain pipes are also long term, durable possibilities.

On second thought..if I used the black plastic.. I think I would find it acceptable if i also used a concrete spillway and concreted inthe mitered end section so that no poly was exposed to the sun.. etc..

soundguy

 

[gemini5362]

OK my driveway has everything mentioned not to do here done to it and I dont want to even talk about how much gravel is over it. Thank god my culvert pipe cannot read this thread it would fail on me immediately if it knew how badly it is installed

 

[Hillfarmer]

Soundguy, I think you are talking about polyvinyl chloride (PVC) plastic and not high density polyethylene (HDPE). The HDPE does not have the same UV degredation potential as the PVC. Plus if you paint PVC it helps with the degredation problem. Mowers are a bigger concern for the end of plastic pipes, but better the pipe than the mower.

 

[EddieWalker]

rusts? not much.. as it's galvanized!..

I always wonder why people buy metal pipes, but until now, never really thougt about it other then it's just what they are used to and comfortable with. Here, in the land of red clay, they rust out fairly quickly. You can still buy them, but from what I'm told at the three places that I've bought them, the plastic culverts outsell the metal ones by a significant difference. The main reason that I'm told people buy metal is it's specified by the county, or it's what was already in there.

I never heard of any issues of the plastic pipe degrading. Is this something that you have seen personally? I have over a dozen of them in at my place and will buy another dozen in the next year or so. If they will degrade, then I need to address this and put concrete on the ends like you suggest.

Of the metal culverts that I've seen removed, rust is part of it, but so is blockage. They tend to hold material inside of them and over time, it just becomes easier to replace them then to try and clean them out. The plastic culverts are smooth on the inside and material doesn't seem to bind with the plastic like it does with the metal. Again, this is clay that I deal with and small amounts of gravel that we call iron ore.

Eddie

 

[rtimgray]

OK my driveway has everything mentioned not to do here done to it and I dont want to even talk about how much gravel is over it. Thank god my culvert pipe cannot read this thread it would fail on me immediately if it knew how badly it is installed

I'm gulity of a lot of that from what I read on this site. I know that what most folks say to do is a good practice, but in reality you can get by doing a lot less. We've even poured concrete on bare earth - didn't even put down a vapor barrier. Just scrape the grass and let it go.

Of course, it's only been there about 20 years, and had a couple of normal cracks. (this is for a barn floor). If anyone ever told it that it needs crushed, compacted stone and the grade should have been further excavated and that it needs rebar or welded wire and a vapor barrier, then we could be in big trouble. But I'm not gonna tell it.

And thank goodness nobody ever told my horses which side I'm supposed to approach from. I can't remember if you're never supposed to approach/mount 'em from the right or left - but evidently, none of the four of them can remember either, so we're mutually ignorant (i.e. blissful!).

Take care.

 

[Soundguy]

Soundguy, I think you are talking about polyvinyl chloride (PVC) plastic and not high density polyethylene (HDPE). The HDPE does not have the same UV degredation potential as the PVC. Plus if you paint PVC it helps with the degredation problem. Mowers are a bigger concern for the end of plastic pipes, but better the pipe than the mower.

I'm QUITE familiar with HDPE.. we install it all the time.. just about any plastic degrades to some extent with uv light.. some more than others.. sure hdpe holds up better than pvc.. but in the sun.. and after years.. plastic takes a hit vs coated metal..

soundguy

 

[Soundguy]

I am ov course, only speaking about florida, and my area.. can't speak for other areas. Keep in mind that homeowner / private road work is not the stuff we do.. we usually work for municipalities.. and as of yep.. I have really only seen metal or coated metal pipes with or without concrete miters and splash pads as culverts.. very rarely do we use plastic.. and on occasion.. we use hardi-pipe ( cemet-paper more or less.. ) and sometimes concrete pipe... both round and 'squash'.. etc.

soundguy

I always wonder why people buy metal pipes, but until now, never really thougt about it other then it's just what they are used to and comfortable with. Here, in the land of red clay, they rust out fairly quickly. You can still buy them, but from what I'm told at the three places that I've bought them, the plastic culverts outsell the metal ones by a significant difference. The main reason that I'm told people buy metal is it's specified by the county, or it's what was already in there.

I never heard of any issues of the plastic pipe degrading. Is this something that you have seen personally? I have over a dozen of them in at my place and will buy another dozen in the next year or so. If they will degrade, then I need to address this and put concrete on the ends like you suggest.

Of the metal culverts that I've seen removed, rust is part of it, but so is blockage. They tend to hold material inside of them and over time, it just becomes easier to replace them then to try and clean them out. The plastic culverts are smooth on the inside and material doesn't seem to bind with the plastic like it does with the metal. Again, this is clay that I deal with and small amounts of gravel that we call iron ore.

Eddie

 

[Aguanga]

Like soundguy, I also work for a general engineering contractor where we specialize in storm drain, sewer, water, and electric/communication conduit install. I'm not a fan of cmp for the same reasons eddie mentioned, but it does have some obvious functionality. Check with your local suppliers on pricing for cmp, hdpe, pvc (sdr35 sewer pipe), and rcp; then start making calls to local engineering contractors that install the stuff. You may be surprised to see how how cheap of a deal you can work out. Lots of good advice already given on install so I'll just add a couple of items to it... make sure you have good moisture on backfill. The most difficult area to compact is from bottom of pipe to springline (lower half of pipe) so if you're inexperienced or short on the right equipment, etc; I'd recommend a 1-2 sack concrete slurry for this region. A 12" pipe in 24" wide trench 30' long is just over a yard to accomplish this - cheap insurance. You'll get some better guidance with more info and or pictures - how deep are flowline of ditches relative to road height, how long, how much pitch or slope can you get in the line, how large of an area (watershed) will drain into and flow through the pipe, etc. I know Oregon can get a lot of rain at one time so it's better to go bigger within your budget. Remember that you have a highly compacted road, but if it's under standing water with the right soil conditions will pump and displace.

 

[atgreene]

A couple things to add here and clear-up. My expertise is in erosion management, road building and general excavation. It is also based in Maine where we get 4-5 feet of frost, so some of my info may not apply to your situation in warmer climates.

It sounds like you are simply draining a wet area on one side of the road to the lower side of the road. Not a stream bed or a common overtop situation?

A 12" smooth bore culvert is huge for most driveway applications. I'm all for overkill, but with proper plunge pools on both ends an 8" plastic smooth bore will handle vitually the same amount of water as a conventional 12" galvanized steel culvert.

You may be able to lay less material over the culvert than the diameter of the culvert, but it's not recomended for here. Maybe different elsewhere.

A vibratory plate compactor will do all the compaction you need for a driveway culvert if bedded in good quality 3/4" crushed gravel.

Galvanized culverts do rust out, but we have an excess of road salt to deal with here, so that may exacerbate the issue for us. I replace and install a lot of culverts, unless Maine DOT has anything to do with it, plastic goes in. Otherwise Maine DOT requires 15" aluminized steel minimum. What a waste.

Don't make this overly complicated, culverts are a pretty simple thing.

Good luck.

 

[gemini5362]

Like soundguy, I also work for a general engineering contractor where we specialize in storm drain, sewer, water, and electric/communication conduit install. I'm not a fan of cmp for the same reasons eddie mentioned, but it does have some obvious functionality. Check with your local suppliers on pricing for cmp, hdpe, pvc (sdr35 sewer pipe), and rcp; then start making calls to local engineering contractors that install the stuff. You may be surprised to see how how cheap of a deal you can work out. Lots of good advice already given on install so I'll just add a couple of items to it... make sure you have good moisture on backfill. The most difficult area to compact is from bottom of pipe to springline (lower half of pipe) so if you're inexperienced or short on the right equipment, etc; I'd recommend a 1-2 sack concrete slurry for this region. A 12" pipe in 24" wide trench 30' long is just over a yard to accomplish this - cheap insurance. You'll get some better guidance with more info and or pictures - how deep are flowline of ditches relative to road height, how long, how much pitch or slope can you get in the line, how large of an area (watershed) will drain into and flow through the pipe, etc. I know Oregon can get a lot of rain at one time so it's better to go bigger within your budget. Remember that you have a highly compacted road, but if it's under standing water with the right soil conditions will pump and displace.

Thank you very much for your post I now know that at least I did one thing right when I put in my culvert. You said to make sure you had good moisture on backfill. When I installed the new plastic ? culvert i rented a trackhoe and dug up the old one. I get the new one in place and it had started sprinkling. I decided that since all I was doing was covering it back up I could do that with my tractor and have two advantages. My tractor did not have a time meter measuring how much money I was going to owe when I got done and the tractor has a cab. I pulled the trackhoe up next to my tractor and got in the cab to start over to the culvert. it was about 2 or 3 minutes to the driveway where the culvert is. By the time I got there the rain had turned into a major heavens opening up gusher. It rained so much that I could not see out of my tractor windows with the wipers on high speed. I finally got the culvert covered so that it would not wash away. I am very very certain that I got enough moisture in the backfill of that culvert.