Pond Boss Forums POND CONSTRUCTION Building a dam Filter Diaphragm in lieu of Anti-Seep Collars

I'm building two ponds in South Carolina and the county natural resources department designed the dams with filter diaphragms in leiu of anti-seep collars. According to them, they are a better alternative. The dams will be approximately 22' high each, and both ponds average 2.5 surface acres fed by a 43 acre watershed and one small natural spring. Does anyone have any experience with this method? Thanks for any input.

g-8,

I have had experience with a sand diaphram (anti-seep device) on one of my ponds. They work GREAT! The project includes C-33 masonary sand compacted around the pipe in a specific location about 2 ft. thick. The balance of the pipe is then usually enveloped with 47-B gravel (concrete gravel) as a drain. The idea is any water that makes it to the sand envelope passes through at a very slow rate and then exits the fill through the envelope of gravel.. Its difficult to explain but works well! Be prepared for many additional costs however.

Good luck,
Ed

Sand filter diaphragms have been in use for 15 years and taking the place to the anti-seep collars. Water will pass threw all dams so the idea is to control the seepage.
It will take the hard work out of packing a pipe by bedding it with sand which is easy to pack as opposed to heavy clays.

Otto

Thank you very much for the input! I feel much better now about this design since I was unfamiliar with it until your replies.

Please tell us more about filter diaphragms. What are they like? How do you make them? Pros and cons of each? Are they mutually exclusive or can they be combined for increased assurance of effectiveness?

Those are great questions and hopefully more answers will follow from the "experts". I was told this a better design by a local South Carolina Natural Resources and Conservation District officer. He designed the two dam structures for me, and said they have had more failures with the traditional anti-seep collars. My contractor said over the past few years he has been installing more of the sand filter diaphragms as opposed to the anti-seep collars. This was the first I have ever heard of this design, and Pond Boss is absolutely the best place in the world to get answers!! Now, if I could only figure out how to stop the rain long enough to construct the dams I'd be batting 1,000.

Sand filters are designed to gather water and channel it threw the dam in a controlled fashion, anti-seep collars are trying to stop the water so you will not use them on the same pipe.

Generally a ditch 1 foot deep and the width of the pipe is dug under where the pipe will be placed, from the center of the dam to the to the end of the pipe. A second trench will be dug perpendicular to the first ditch at center line of the dam both will be filled with sand . The pipe is placed on the sand and sand is compacted half way up the side of the pipe.

From here on out the onsite material will be used to finish the packing of the pipe.

After the pipe is backfilled the perpendicular trench will be dug out an refilled with sand above the top of the pipe

The last 3 feet pipe will not have sand put will have gravel.

I may be able to explain this better on the phone.
940-736-5333-
800-882-3478

OTTO

I'm enthused and confused. Why doesn't the water pressure just wash out the sand?

Attachec is a base drawing of a typical sand diaphram from Nebraska.
It may take awhile to load.
I hope this helps to explain the procedure.
Ed

http://efotg.nrcs.usda.gov/references/public/NE/NE300-10-002.pdf

Thanks Mike and Ed!

Ed: You mentioned additional costs. Is it generally much more expensive than anti-seep collars?

Ed & Mike: Which option would you recommend? (my situation is a mostly clay soil type in the midwest with a pond of 2 - 3 acres and small enough watershed that I doubt pond would ever overflow)

Thanks!

Jeff

Jeff,

For your situation I would lean towards the anti-seep collars (at least two). Make sure they are water tight around the pipe. You may have to use some very thick mastic (tar) as a sealer. Good compaction of soil around the pipe and collars is the key! The butt end of your shovel works great as a compaction tool directly under the pipe. Do not tamp so tight as to lift or "bridge" the pipe!! Once you are about 1/3 way up the pipe have a mechanical tamper ready to finish the job.

Good luck,

Ed