Pond Boss Forums POND CONSTRUCTION Building a dam sdr-35 question

I built a 1 1/2 acre pond(14ft at the dam) three years ago and my dam leaked. The contractor came back and worked on the dam and it leaked worst than before. Finally realized he had not cored the dam properly and every pond he built had problems. He will not be back and out of business.

My pond has a few small springs but rain runoff is my main source of water. It takes about 6 months to fill. I have 8" sdr-35 pipe with a 90 degree overflow that I use to drain the pond. It works but is really tough to push over to start draining. My new contractor who is well respected has suggested I put a valve on the back side of my dam on the end of the sdr-35 pipe and do away with the 90 degree overflow. He also recommended an overflow pipe through the dam at the top to drain before it hits the spillway. He is going to put in a new core at the base of the first dam and widen the dam to the appropriate width and slope. He is also adding two more anti-seep collars to the drain pipe.

Excuse my rambling but I want to give as much info as possible. Will the sdr-35 pipe work in this application with a valve on the end of the drainpipe or will it leak over time. Any suggestions? Thanks

Welcome to PB! While I don't have any experience working with that type of pipe, I'm sure someone will be chiming in within the next day that has pipe experience.

CB1, That's too bad you had a poor experience, but it sounds like your new contractor knows what he's talking about. As long as he can establish a solid core trench behind the initial dam, that should not leak. Have him put the 2 antiseep collars at the front edge and then middle of the core. Since you're going to drain the dam anyway, you might have him try to excavate out alongside the 8 inch pipe and put another antiseep collar towards the front side of the old dam. Then fill in that trench with solid clay as well. Make sure you're out there with a gas powered tamper to get good compaction along the pipe and antiseep collars.

In 5 of my dams we have a valve installed towards the backside of the dam. They are actually placed about 20 feet upstream from the downstream toe of the dam. Hence they have anywhere from 8-12 feet of the dam fill above them (so they won't freeze in our South Dakota winters). The valves are brass and have a 2x2 inch square handle on the top. We built a square out of plate steel that fits over this handle, and then welded a 15 ft piece of 1 inch square tubing to it. We use this "wrench" to open and close the valve. To access the valve we installed a 6 inch plastic tube above the valve to the surface (just like water systems use). You can buy a cap to install on the end of the pipe to keep the elements out.

Now one precaution. In NRCS documents they talk about the risk of putting a valve on the downstream side of a dam. The theory is that the water pressure in the pipe could cause it to blow right out through the backside of the dam. Think about having a straw in your mouth and blowing through it. If you keep up the pressure, but the end gets pinched off, the straw would blow out of your mouth, unless you held on tightly with you lips.

To prevent this from happening what we did was to construct a concrete footing of 4x4 feet and 6 inches thick (with rebar) on the front side of the dam where our tube comes out. Basically the end of the tube is in the middle of this footing. Make sure you compact the soil well where you put this footing, as you don't want it to settle.

Then we put a 90 elbow on the tube (facing up), and installed a vertical 6 foot section of pipe, with a trash guard at the top. We also drilled numerous 1 inch holes in the vertical pipe to help keep it from getting plugged up. Then on top of the footing we constructed a form around the elbow and pipe (approx 2x2 ft and 1 ft high). We left some rebar sticking up out of the footing to link into the new concrete that we would pour into this form.

This is probably overkill, but the few hours of work and 30 or so bags of concrete and some rebar were worth the peace of mind.

Definitely have your contractor put in a principal spillway tube with antiseep collars. Schedule 35 or 40 should work. Have him place metal culverts over the ends to keep the sunlight off the plastic. Or you can just keep paining it to keep the UV damage from occurring.

Since your dam is going to be much wider than necessary, you might consider making it taller as well, assuming the topography works.

you might have to get a schudule 35 to 40 adaptor and add a foot or so of sch 40 to it this way you can get a better quality valve to fit the sch. 40. then if you ever replace the 35 with 40 you still got your valve. the adaptor should be 30 bucks or so. i dont like the sch 35 but you allready got it in place. it might be fine i just dont prefer it. and bill is right if you put one there you will need to secure it i prefer using mege lug flange kits they have teeth so to speak that secure the valve to the pipe. if installing new pipe using joint restraints at each joint will keep the pipe from parting also. i use this set up when installing water lines through road bores it hasnt failed yet. i'm gonna edit myself again because i forgot something as usual. i would highly recommend you schudule 40 users to look into what they call true blue pipe. its a little higher but much lighter and stronger so they say. i have used it on 2 subdivisions and even ran over a piece with my backhoe and it didnt break it flexed. poly pipe is also very good the 8'' would come in 40' joints then you heat it and weld the plastic together even the valves its a good set up renting the machine to weld it is the only downfall. you could even weld 90's, 45's etc. on it. i dont think this poly is as sensitive to sunlight as sch 40 either its black and about 1/2 inch thick. i have welded up to 1/2 mile together then pulled it in place so its ok in my opinion.

Tim,

Good point. All we've used is Sch 40 as well.

Since you're rebuilding the whole works, have you considered a siphon type overflow?

I second the siphon system since you are redoing it.

Thanks for the info and I will be going with the siphon system.

? is a siphon system

siphon system

I bought my aerator from these folks. Very good transaction. Appears they have everything you need for pond mechanics and a good explanation of the siphon system.

http://www.ponddampiping.com/

buzz

ha......guess I should have checked out your link, esshup.