Pond Boss Forums POND CONSTRUCTION Building a dam Filter Drain Diaphrams

Since the 80s, regulatory agencies in the US and around the world have slowly been realizing that anti-seep collars are at best marginally effective and at worst can contribute to dam failure. NRCS guidelines require a filter drain diaphram rather than anti-seep collars on all but "low hazard ponds" (defined in NRCS code 378).

To over simplify it, a filter drain diaphram is a 2' wide section of the drain pipe that is surounded by sand.

Has anyone here had a dam built using filter drain diaphrams on dam penetrations rather than anti-seep collars?

Thanks

All of the federal water shed projects here, NC MO, are using the filtered drain diaphram. It must work, but it sounds like an accident waiting to happen. All of the non federal farm ponds around here use seep collars.

Tractors with scrapers are the preffered method of compaction, dozers do an acceptable job with the clay in my area. A lot of the ponds around here were built with a dozer with nothing else used to compact the soil.

I just looked up a current copy of CPS 378. There is an Aug 2013 release of it. It was expanded from 6 to 16 pages. Anti-seep collars are no longer discussed as an alternative to the filter diaphragm. The copy Esshup cited a month or so ago was the short May 2011 version and it said "when anti-seep collars are used in lieu of drainage diaphragms, they shall..." It goes on to give brief details on spacing and adding 15% to path length for seepage. That entire section is not in the Aug 2013 version. Are they trying to never do anti-seep collars now?
Latest CPS 378

All I can say is I've never had a problem using an antiseep collar, but when my excavator neglected to use one on one of my ponds I had seepage along the pipe.

I've installed several of them.

Below is a quote from NEH Ch 45. The NEH I find online is version Jan 2007, so it is not nearly as current. They indicate here that anti-seep collars are acceptable for "low hazard dams" which likely is almost all of us. CPS 378 is the guideline that points us to, it's more current, and it does not allow anti-seep collars. Furthermore, the very next page in the NEH states that several properly constructed collars failed upon first filling. Just a guess, but they seem to have recently concluded that the risk of failure is just too high, even for a low hazard dam. Likely it's a function of hydralic pressure, soil type and compaction. As you point out, there are successful collars that have years in service.
If nobody here has a filter diaphragm (sand bed), then one wonders if the dam builders have sufficient background (or motivation) to change to a technology that is new, better, and likely more costly. They state collars were not allowed on "big dams" in 1985. They seem to be saying the same for little dams in 2013.


For many years, anti-seep collars were the standard
design approach used to block the flow of water at the
interface of the conduit and the backfill surrounding
the conduit for all embankments designed by most
design agencies. Based on knowledge gained during
the period of intensive embankment construction by
NRCS and other agencies in the 1960s through 1980s,
the use of anti-seep collars was reconsidered. Beginning
in the mid-1980s, anti-seep collars were eliminated
in designs of major embankment projects because
they were judged to be ineffective in preventing many
types of failures observed. All of the major embankment
design agencies, such as the U.S. Army Corps
of Engineers (USACE), Bureau of Reclamation, and
NRCS, as well as private consultants, now specify filter
diaphragms rather than anti-seep collars. Filter diaphragms
have been recognized as superior to anti-seep
collars as a seepage control measure. The NRCS still
allows the use of anti-seep collars for seepage control
along conduits for low hazard dams that are built according
to criteria in Conservation Practice Standard
(CPS) 378. Filter diaphragms are required design elements
in embankments that are outside of CPS 378.