Culvert Project

[glennmac]

Harv-

Thanks for the info. I knew you would have done a lot of research. My culvert situation is different from yours, and certainly falls into the category of an experiment.

First, I have creek that flows all year. It meanders through my soft, flat wetland area. There is a defined channel about 40-45" deep with relatively steep bank walls.
There is about 3" of water in the one straight area where I am dropping the two 24" pipes.

This is an exercise in compromises. There is no way I can install a pipe that won't overflow during flood, simply because in flood the creek will overflow the banks and spread over the flat surrounding land. The only structure that could avoid overflow would be an arched bridge, but I have rejected that for cost reasons.

That leaves me with trying to use as much pipe diameter I can to contain high flows, consistent with the overfill requirements. The literature on the ADS plastic pipe says that with 12" of cover the pipe can handle "H-20 loads" and with 24" of cover it can handle "E-80" loads. Problem is, I can't track down what those things mean. But 12" seems to be an often repeated number, so that's the minimum I want. If I put a really high volume pipe, like 48" diameter, it will stick up higher than the banks. Even a 36" inside diameter pipe will mound up higher than the banks, and still won't contain flood flows. So, I opted for 2 24" pipes side-by-side. That gives me almost as much flow diameter as a 36" pipe, but allows me to put at least 15" of fill on top before I reach the bank height.

I will be able to get some gravel on the sides of the pipes, but they will basically be butting into each other in the middle and into the soft banks on the sides. I dont know how I am going to get gravel under the center point where the 2 pipes touch or under the "haunches" at the sides. I may try to lay sand bags in these places and try to rod gravel down into them. But the water will be trying to wash things away.

Geez, bursting upward through the surface! These 10' long pipes are definitely floating on the 3" of water now. There certainly will be a lot of upward buoyancy when the creek is full. My only hope is that the several tons of fill on top will be more than enough to counteract that. I know that one ton would sink a ten foot canoe, which should have more flotation the pipe.

Well, as I say, we'll see. The only thing going over this is the tractor, and I can easily tear it all out if it doesnt work.

Glenn

 

[Harv]

Glenn -

Hope I didn't come on like a know-it-all. /w3tcompact/icons/blush.gif

Truth be told, I think we're both in the same boat (bad analogy?). I've accumulated a lot of information, but I haven't adhered to hardly any of the rules myself. I'm in experimental mode, too.

My channels are quite shallow and they overflow their banks during heavy runoff. Deep down I think at least some of what I'm trying to do is futile, but since my goal is to have tractor access to as much of the property as I can for as much of the year as possible, I had to give it a try.

We should be making some interesting posts to this thread in a couple of months, no? /w3tcompact/icons/crazy.gif

 

[Harv]

Scruffy, Bird -

I almost forgot about your comments about the ready-mix concrete sacks. I have a way of over-thinking things like this, so this is how my "logic" went --

Since "proper" culvert backfill is supposed to slope upward from the bottom ends of the pipe at about a 45 degree angle, and I decided I couldn't afford to give up that much road width, I decided to shore up both ends as sort of retaining walls which would allow me to build up steeper.

My brilliant idea of using ready-mix was motivated by wanting to make these retaining walls as sturdy as I could without actually building forms and running rebar. As I looked at some of the recent retaining walls in my own suburban neighborhood I saw that they were all built with concrete blocks made just for that purpose. A lot of different colors and shapes, but the one common feature they shared was a "lip" on the bottom backside of each block which prevented it from being pushed forward relative to the block below it.

I actually did consider laying the paper sacks as they came from the store right on top of each other. But I didn't see anything about that structure that would offer much resistance to one-sided pressure, other than their sheer weight. By transferring the material to sand bags and not filling them too tightly, I wound up with building blocks that were easily conformed to the contours of the ground and the pipe and to each other. I tried to arrange them on top of each other in such a way that once they became rigid, their shape would prevent them from being pushed off of the bag below.

Overkill? Probably. In fact, I hope so. /w3tcompact/icons/smile.gif

 

[Rowski]

Harv, Glenn,

One thing to keep in mind it during heavy run off you need to make sure the culvert(s) don't get restricted or plug up!

Derek

 

[glennmac]

Harv-

Your culvert project pictures came at a very propitious time, as I have spent the last 4 days running around getting info and preparing to begin my culvert project. In fact, you raised an issue that I had never thought of and which is now terrifying me: whether I can use all 10' of my culvert or whether I will have to slope up the ends. I did the same arithmetic you did: 5' tractor, so 10' foot section of culvert should be enough. I am now kicking myself, since it now seems obvious that I can't get the fill right to the edge.

Right after your pictures I went to the hardware store to ask about the concrete trick of letting it harden in the bag under water. No one knew if it would work. They were nice enough to call the sacrete manufacturer, who said a bag would harden under water. Another guy cautioned me that inside the paper bag might be a plastic bag, and if that is so, the water won't penetrate the bag unless I re-bag it all in paper. Problems, problems, problems. I'm now going to experiment with your concept of laying sand bags along the top edge of the culverts.

If I hadn't already cut the 20' section of pipe in half, I probably would have spent more money to have a 20' crossing, but that of course would have required hand digging out a 20'+ section of the meandering creek.

I am taking pictures with my APS camera but will be unable to post in real time like you digital photo owners.

Glenn

 

[Harv]

Glenn -

I'm not sure you need to be terrified about the 10-foot pipe issue. Since I started my own project I've been looking more closely at other culverts as I come across them. Despite the "rule" about sloping up from the ends, it seems to be fairly common practice to do exactly what we're doing. In fact, on my last trip up to the property I drove by a culvert that had the vertical stack of sacks (couldn't tell what was in them) at either end. It appears to have been there for a number of years and it still looks great. Now, it did have a full 12" of coverage topped with asphalt, so that may be a factor, but judging from that and how solid my first culvert feels already, I'm somewhat encouraged.

Thanks for confirming that the concrete will harden under water. I thought I had heard that before, but I never really checked into it. /w3tcompact/icons/blush.gif

As for the bags themselves, I can tell you the "Quikrete" brand comes in all-paper bags. If you decide to go with sandbags anyway, both the burlap and the plastic kind are quite permeable to water. I'm using the plastic (35 cents each @ Orchard Supply) mostly 'cuz that's the best price I could find.

You've clearly got a good head on your shoulders, so I have a hunch you'll get the job done well. I'm looking forward to seeing your pictures.

I'm out the door again to re-visit my own project, so I'll post another update probably on Friday.

 

[scruffy]

Harv, and all, the concrete bags with the plastic liners are easily 'cured' of their propensity to keep water out. Take a piece of 1x4 and drive a few nails through one end, and as you put it in place, perforate the bag several times with a few blows (don't break the bag though!). This will allow the water to soak into the bag. I've used this method several times over the years, but with my preferred method of pushing the nail board in with my foot, rather than wacking (I broke a bag or two).

 

[Anonymous Poster]

Harv,

I've been following this with great interest, as I too have been considering installing a culvert over a stream in my woods. I think you're doing great. But your overflow sketch looks like the *bad* example from the Landowner's Guide to Building Forest Access Roads.

 

[glennmac]

Scruffy, thanks for the stabbing tip. Maybe I'll just use one of our el cheapo 25 year old steak knives that were never sharp to begin with. Nothing, not even concrete, could make them duller.

Three days of golldang rain again. My creek is rising and those two pipes are floating around. I have ropes through them but I can't lift them over the bank with my aging body. I maybe could FEL lift them out, but of course Kubota expressly forbids that practice.

Worse, the creek area is going back to terminal muddiness, and the gravel delivery guy will I am sure refuse to come down the hill to my creek area in these conditions. This means I will have to let him dump in an inconvenient remote area for me, or wait for drier weather and lose at least another weekend.

I am positive that weather used to be normal when I was a kid.

Glenn

 

[glennmac]

Dave-

I am confused by that drawing. I can't tell what it is trying to illustrate and what is the "bad" from the "good" in it.

My approach the the flooding issue is simplistic: c'est la vie; che sera sera; what will be will be (for you Doris Day fans). My creek is in a very flat area and is not flowing fast. Overflow will result in a gradual spread in all directions sort of evenly, not a torrent in any particular direction. So, I am not going to try to constuct an overflow channel. I think that might make things worse. Of course, if the creek were an intermittent one, tumbling with great force down a steep hill, I might have a different view.

Glenn