Pond Boss Forums POND CONSTRUCTION Building a dam Are anti-seep collars obsolete?

Does anyone with experience in dam construction have familiarity with sand/gravel filters?

In my research I came across numerous papers including the FEMA Technical Manual: Conduits Through Embankment Dams and Filter Diaphragn Design Considerations that indicate anti-seep collars are old technology and continue to be used because �that�s the way it�s always been done�. The current �Best Practice� for controlling seepage is sand/gravel filters. These sound very similar to what Bob Lusk refered to in another thread as a �toe drain�.

P.S. Chapter 6 of the FEMA manual has the info on sand filters if you just want to download that part but the whole manual is interesting reading if you�re the construction type and have time to download 33 megs.

jsec
All dams seep and trying to stop it with an anti-seep may be old but it worked for years. The sand filter has been around for years and is good also.

A trench is dug under the pipe about 1 foot deep and filled with sand, the pipe is placed on top of the sand, and backed filled half way up the side of the pipe. The last six feet of pipe will have gravel under it instead of sand to let the water seep out.
This filter will not start at the front of the pipe but about half way down. At that point the sand is not just under the pipe but 3 feet above it, this will catch any water that is seeping threw the dam.

Anti-Seep collars are acceptable and the min. requirement in most municipalities, however sand/gravel filters are being becoming more prevalent.