glennmac
Veteran Member
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
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