pond repair

[muddigger]

I have a question or issue with my pond which is approximately 2 acres. The levy is dry and solid and about 10' across top from edge to edge. Levy is only about 5' tall on dry side with gradual slope toward open field area. Pond levy is also sloped on water side out to deeper water which is lower than ground level on backside of levy. Problem I have is there is a 12" safety overflow pipe going through levy about 8" above normal water level. There is also two 8" pipes which keep water at safe level until heavy rains and then when the 12" starts flowing which happens maybe twice a year it has created a muddy mucky water hole on backside of levy which is on level ground with the grassy field area. I can dig a ditch or install a drain pipe to a pond which is about 80 yards across the field. My question is the hole created by this overflow is about the size of a long wheelbase truck and about 12" of water standing in it and probably could sink a truck that size like quicksand. I'm afraid it's going to compromise the levy being so close to the backside and would like to fill in the hole
I can fill with large rocks or clay dirt and then rock levy on backside where pipe overflows then create drain to other pond across field. My main concern is when I start to fill hole could it blow under levy because the mud is so deep. The water hole is lower than water level in pond so I don't think it has leaked through levy core yet.

 

[muddigger]

Also does anyone know of someone familiar with levy repair in southwest TN. area?

 

[muddigger]

I have solved my previous pond drain problems. Now I would like to replace a 10" corrugated pipe which runs through levee with a 12" double wall pipe. The old pipe is only about 3" below grade and about 10" above water level. I would like to install new pipe lower so when my two 8" pipes can't maintain water level the 12" will flow sooner and keep water father below levee. I have thought about cutting off the two 8" pipes to lower water level but would rather keep water level as is if I can maintain it in severe rainy periods with the 12" overflow pipe. What I am concerned about is digging out old pipe not knowing how close I can go to water level without starting hydraulic piping. The water is currently about 10" below the pipe I am wanting to replace but I'm sure the earth below the pipe would be damp and I do not want to start a river through the levee. Any advice will help, I always do much research before putting the horse in front of the cart. I am also considering an automatic siphon drain but not very familiar with their performance and dependability. Does anyone know what would be a good one way valve for a siphon drain I think I will install a 4" and see how long it takes to lower water. I would feel safer to get water lower before replacing pipe across levee. What would be best material for compacting new pipe if I do it. I have access to a orange white clay mixture, would that work. The old pipe was installed about 15 years ago and was packed with fine limestone.

 

[dirtdobber1]

Hi muddigger,

I"m no engineer, but here are my thoughts on your situation. First, I assume (dangerous!) the soil in your levee has a good clay composition since it's holding water and not leaking. With that being the case, I would not be afraid to install the 12" pipe to within three inches of the water's surface. From what you have described, you have a fairly shallow cut to get what you want. The important thing is do not get at or below the water level such that water starts to escape. Some moisture in the soil is ok, but you don't want it to be wet. You can't compact mud.

Next, as far as compacting the new pipe....I'm suprised an aggregrate was used on the old pipe (perhaps I don't know what fine limestone is). I would compact clay soil around the pipe. Clay soil has very tiny disc shaped particles which compact tightly and stop the passage of water. Sand and other larger aggregate materials allow the water to pass through - pouring water on the beach - it just disappears.

What is really important is that you get the underside of the pipe properly compacted, as it is out of sight and out of reach once the pipe is in. You don't want this space to become a conduit for water passage. I believe guys in the dirt business actually make an arch shaped trench to recieve the pipe.

Another option for information would be from a university research facility. I don't know what TN has, but here in MS we have the MSU extension service that publishes lots of helpful information. You may want to check out their website.
Good luck

 

[Delmer]

Have you considered leaving the 10" and adding the new 12" along side of it? just to save the work of removing the old one and have one more overflow?

I wouldn't be concerned about approaching within an inch of the water level with your trench, you have a wide enough dam and it sounds like there's not a lot that would wash out even if you ripped it open and let it drain.

Are you thinking about a siphon for a permanent water level control, or just to lower the level for construction purposes? If you're just doing it temporarily for construction, you can put your pipes together for the siphon and put the bottom end in a barrel full of water, and pump the air out of the pipe to get it started. If it's permanent, set the pipe low enough through the dam that it will start at whatever water level you want to use it at, there's no reason to start a siphon if you don't have to. (this is assuming you have equipment to do this job. and not knowing your goals with the "siphon")

 

[muddigger]

I would leave the old pipe also but where it comes through the levee I need to run it another 65 feet to a drainage ditch so I can have access to get across with tractors and mowers. I got a good deal on some 12" pipe so that's why I'm replacing the 10" with the 12" all the way through. If I didn't need access that wide I'd bring the ditch closer to my pond. I want to see how much a 4" siphon will draw down the pond which is a little less than 2 acres. If it'll lower the water quick enough I may install it permanently but I would like to only start it manually when needed. The pond is in a valley surrounded by roughly 40acres of watershed. I might try a larger permanently installed siphon later if the 4" isn't quick enough. The two permanently installed 8" drains maintain level pretty good but have seen it not rain for many weeks and still be at least 2" stream coming out one of them and then when the worst rains come the other 10" goes full stream also and I will say I have still been worried at times but hasn't ran over levee in about 34 years. Hope that one last year was the 100 year one. But I'm gonna be getting more drains ready.lol

 

[muddigger]

As close as 3" would even scare me. I am gonna try to lower level a little more soon as I get a siphon drain set up.

 

[Delmer]

You could actually calculate what kind of flow you'd get with a particular siphon, based on head and resistance to flow, just like ohms law in electricity A=V/Ohms. Probably not that useful, just try to give the siphon more head, and the less resistance (use long radius fittings and the least horizontal distance you can to get the most height difference).