Culvert Question: Need to angle a piece

[beowulf]

A very small- but useful- pond here has an earthen dam. The overflow culvert is a 20' long, 12" dia. corrugated plastic culvert (like abs sort of). The pond-side end of the culvert is about 2 - 3 feet down from the top of the earthen dam and the culvert slopes down to a creek on the other side of the dam at a rather steep angle - guessing about 20 degrees or so. Also, it is not perpendicular to the dam but angles off at about 30 degrees. I have no idea why it was put in that way.

This means that the overflow does not directly go into the creek but flows off to one side of the creek and that causes a roadway there to be very narrow. If the culvert went straight across the dam it would be much better for the reasons I outline here. The second problem is that I want to widen the dam (dump more dirt/rock on the creek side) but cannot do so as it would cover the down-side culvert opening - so I want to extend the total run of the culvert.

So what I propose to do is to use a 10' 15" dia. section of the same kind of culvert (which I already have here) and cut one end at about a 20-25 degree angle and slip it over the down-side end of the 12" dia culvert (I know/hope it will just barely begin to slip over the 12" culvert which is likely near 15" for the outside dia.) and to use a plastic wrap around the "joint" and then to build a form which will allow me to pour concrete all around that joint. I also thought about slipping the 15" dia culvert over the 12" end and then about 3 feet down line from there to cut out a pie shaped section and turning it there, wrapping it and putting the concrete there as well. If this works out the end of the extended culvert will be right into the creek and will be sufficiently farther down so allow me to widen the dam on the creek-side.

I wanted to simply get another section of 12" dia. culvert and attach it with an "angled" coupling but I cannot find an angled coupling - don't think they make them.

I think I can make this work, but also think that someone out there may have a better idea, or have suggestions as to how best do it the way I am planning. I will also be adding another overflow culvert at the other end of the dam as the water flowing into this pond can be substantial in heavy rains and when the pond is already full I have had issues with the existing culvert handling the flow.

Digging out and realigning the old culvert is not an option.

 

[mddorange]

An option for the overflow would be to make a concrete spillway either in the center or at the other end that empties into the creek. You would lower the entrance of the spillway to the maximum height that you ever want the pond to be, thus taking care of the overflow.

 

[pmsmechanic]

I would be really reluctant to install a culvert with an angle bend in it. If you ever get some debris flowing down there and it get's stuck...how are you going to get at it to remove it? Now with both ends open you at least have the ability to get to the debris and remove it. Also you say the the 12" culvert is at it's limit to handle the present flow. If you install more culvert with a bend in it you are going to further decrease the flow.

If digging out and realigning the old culvert is not an option then what I would do is either install a new culvert or a concrete spillway as previously mentioned. Once the new spillway is operational then take proper steps to remove the old spillway.

 

[bindian]

This should work..... http://www.ads-pipe.com/sites/default/files/Fittings_HDPE_Dual_Wall_Fabricated_Bends.pdf from Advanced Drainage Systmes. But they are not cheap. I did the same thing, but I used a 15" concrete pipe. This is the culvert I am picking up in my avatar. Where I wanted the elbow, I just shoved the 12 inch culvert into it and wrapped heavy plastic around it and them surrounded with concrete. That was 9 years ago and no problems. As long as you shove into bigger pipe downstream, there will be no debris hangups. Smaller into bigger downstream can cause debris to hang up.
hugs, Brandi

 

[ultrarunner]

Just would want to make sure it can't separate...

In the 50's the county did one on Mom's property... water has undermined the joint and now it is eroding badly and will undermine the fire trail... county says it has not failed yet...

 

[bindian]

US Air Force Retired (1966-1988) ... mike

Mike,
Thanks for your service to our country!:thumbsup:
hugs, Brandi

 

[beowulf]

Thanks to all for responding. I really want to take it out and move as I like things done right and neatly, it but that could mean a bit of a wash out - water would start coming. I thought about digging down (most by hand) until I could get a chain under the low end to pull it up with the tractor but then I could not move it over to align it using the tractor as too far away from the trench I would have just dug. The pond lip of the culvert is packed in with dirt, rocks and gravel but once it is moved I see a wash out and the loose dirt created when I pull the culvert up would head down creek. Doable, but a degree of risk and much would need to be by hand as cannot get tractor to the bottom area.

Regarding the capacity / overflow of the existing culvert - it has been an issue three times over 30 years - the last time was last year when we had over 40 inches of rain when a normal year is 14-16 inches. I plan on installing a second culvert anyway to handle any overflow. I need to travel over the dam to get to part of our property with the tractor so not sure a spillway would work - and a lot of concrete. I think I can manage the next overflow with a second culvert.

I agree that a bend - even a slight one could be a problem - even going from smaller to larger culvert. And that could be an issue as when it rains hard the two ravines that feed into the pond bring debris into the pond. I have a "cage" of sorts - a wire frame about 3 foot square at the entrance to the culvert to catch large pieces of debris and that seems to work - small stuff goes on through and larger stuff gets caught and I keep it cleaned up.

You have all given me a lot to think about and I will figure something out. I do like things done right which would mean taking it out and realigning it but just not practical given where it is, that is, how deep down it is a the creek side of the dam. I guess it is 4 -5 feet down and I can only use a tractor for part of it. Dangerous to try to do any more with a tractor given the slope, stability and depth.

It the meantime I found a source locally for more culvert so I can get a section of that and install the second overflow while I figure this out. Looks like a light to average rain year. Thanks again for all of your input.

 

[mapper]

A bend in a culvert is asking for problems. A better solution is to place a larger section of pipe 24-30" vertically at the end of the original pipe, cut holes for the inlet and outlet pipes, angle the outlet to where you want to go.The vertical pipe should be tall enough to reach the surface, place a lid on it. In civil engineering terms this is a manhole. Drainage systems are never built with bends in the pipe, whenever ther is a turn, or large change in elevation it is accomplished with a manhole structure.

 

[bcp]

I plan on installing a second culvert anyway to handle any overflow.

Do it the other way around. Install a new, properly sized culvert as the main one. Use the existing culvert for the overflow.

Bruce

 

[beowulf]

Do it the other way around. Install a new, properly sized culvert as the main one. Use the existing culvert for the overflow.

Bruce

Thanks. Like it. I was going to install a second culvert anyway, but was not particularly thinking about the new one as a main one. I would still have to put in an angle in the existing one though as need to get the outlet at creek-side of dam to middle of creek instead of off to the side - want to do this as otherwise existing outlet on creek-side makes side access for my tractor road a bit too narrow and still need to extend the run to widen the dam. Question: relative heights at dam-side for existing and new overflow? Same, one lower - if so, by how much? I think I can use the same size (12" dia.) as that handles the drainage very well except for those few rare times when we have huge rainfalls. I am guessing the new overflow culvert would need to be a bit lower than the existing one.