I joined this forum today because I need some serious advice on my pond problem. The ~44yo metal standpipe in my pond is at the end of its life. I've suspected a leak in the vertical section for a few months. Today I had a sewer guy run his camera down and he discovered 1" hole that's about 6ft below the surface. The current water level is about 4ft below top of pipe - partly from leak and also from our drought.

I've read plenty about temporary fixes such as patches and pipe liners, but the reality is this pipe shouldn't be my longterm plan. It seems to me it either needs to be decommissioned or dug out. And of course I need a new drainage system.

Digging out this pipe, of course, requires draining the pond (the pipe base is at the deepest part of this pond). Aside from the anguish of draining a pond that has tremendous fish habitat already, I think there are significant reasons why it might be better to decommission it rater than draining pond and digging it out. Even though the pond is down quite a bit, the vertical pipe is 22ft high and water depth around it is probably ~15ft still. That's a lot of draining to do.... But the even bigger issue is the total height of this dam (the exit of horizontal is lower still) is at least 30ft and the dam itself is my driveway. So digging out that pipe would take some serious excavation. And that doesn't even address the issue of putting the dam/driveway back together with necessary integrity. My excavator said - I can do it and would enjoy using my machines, but it really shouldn't be done.

Therein lies my question: How To Decommission A Pipe like mine.

I am far less worried about establishing the new drainage system than managing this current "end-of-life" standpipe. The horizontal section is definitely longer than the vertical, although I'm not entirely certain just how long.

Could folks tell me their experiences with decommissioning pipes like this and how it is best done? Obviously the pressures that deep are something to be reckoned with. And there are probably a lot of factors I haven't thought about. I am not a pond expert or engineer.

I greatly appreciate any advice.

Vic

You could hire a concrete pump and have a truck come out and pump it full of concrete. Then you could install an above ground siphon system, or improve and use the emergency spillway as the primary spillway. Most ponds around here only have one spillway...the over land one.

Thanks John.

Have you done that before or seen where it's been done and worked longterm? My "concern/question" has been whether that has inherent risk for breaking down over time, eg high pressures, air pockets, water tricking in, and eventually failing....

Also, is concrete the material to use or are there newer products that are better suited for a lasting solution? Someone mentioned bentonite, but perhaps that's no good and perhaps there are other materials...

I believe I'd look into a Tremie concrete pour used in underwater pours. Only the bottom of the stand pipe needs to filled with concrete to seal the exit. I don't think you need the whole pipe filled to the top. Then install a surface pipe or siphon system replacement.


http://www.concreteconstruction.net/article/tremie-concrete_o

I have an old metal standpipe in my pond. We moved here with the pond already existing. I am not certain about when the pond was built, but I assume in the 60's - 70's. My husband went out to unclog the standpipe and it broke off. We aren't sure how far down but since treating the algae bloom, we are losing water rapidly. It sounds like a bathtub filling up and water is gushing out the other side of the overflow pipe. Is there any way to decommission this standpipe without draining the entire pond? We tried to put a seal over the pipe, and worked but then we began finding seepage and leaking around the pipe. In fear of losing the entire dam, we removed the seal and the pond is now draining as mentioned above. It is well stocked with large bass and brim and grass carp and maybe others. We don't want to lose all the fish. Any suggestions? Also, once the standpipe is decommissioned, what type of overflow would be recommended? We do have an emergency spillway (just a sloped area to the side of the dam - no pipe or plastic) in addition to the standpipe.

Sounds like with active flow through the pipe, there is not much you can do as to permanent repair. You may need to drain, dig out part of the pipe on the inside of the dam, and plug with compacted clay. Then, you could install an external siphon system, or improve, possibly lower, and use the emergency spillway as the primary spillway. Depending on the rainfall run-off to pond size ratio, you may not need any other spillway than the overland one.