Alternatives to Anti-seep collars

[drewnje]

I have a general question in regard to anti-seep collars. We typically spec in our sediment basins; however, recently I have heard people say that they are not very effective and are prone to failure, especially as it is hard to compact the soil between the collars during berm/impoundment construction. Are anti-seep collars still standard practice for outlet structures or are there better ways of dealing with seepage along the pipe?

Thanks,

Drew

 

[fattdad]

in graduate school, c. 1985, we were told not to use anti-seep collars. This is not new!

I'd use open-graded aggregate to surround the pipe for the lower third of its run. That way any water flowing along the pipe-to-backfill interface would have hydrostatic relief under burden and the risk of piping failure reduced.

This is a critical aspect to outlet pipe design! I've worked on several failures directy related to the topic of drainage along the pipe run!

f-d

¡papá gordo ain’t no madre flaca!

 

[beej67]

I've worked on several failures that didn't have anti-seep collars, and the inclusion of anti-seep collars is pretty standard in municipal and state details in this region of the country.

I'm very interested to hear more on this topic from engineers who don't recommend them, and what they do instead. I can't say I'm a huge fan of the method fatdad enumerated, though, because it would seem to me to encourage seepage instead of preventing it.

Definitely going into this thread with an open mind, though.

Hydrology, Drainage Analysis, Flood Studies, and Complex Stormwater Litigation for Atlanta and the South East -

http://www.campbellcivil.com

 

[fattdad]

Ah, but you'd have a concrete cradle to the spring line and regular backfill for the upper 2/3rds of the pipe run.

I could convene a few dozen geotechnical engineers who know the perils of anti-seep collars and have had such warnings delivered in graduate school. Few civil engineers get similar warnings.

Just for further discussion, I'd use gravel to backfill the lower 1/3rd of concrete in a principal spillway also (or any sort of concrete wier).

f-d

¡papá gordo ain’t no madre flaca!

 

[cvg]

seepage collars are not used for dams or levees any more and has been quite a long time since they were popular. just too many failures attributed to this detail. a drainage layer or filter diaphragm is a far better idea.

 

[drewnje]

The reason for my original question is that my state's sediment and erosion control manual specifies the use of anti-seep collars in sediment basin construction, so they are quite common here. I have always been aware of the difficulty in compacting the soil around the collars, but only recently have learned that they are not common practice in other parts.

 

[Drew08]

I think the confusion is the difference between a temporary sediment basin and a dam. A temporary sediment basin is intended to be small, cheap, quickly built, and removed after construction, and generally has no personal injury or property damage consequences in the event of failure beyond the scope of the construction project. A dam is large, permanent and can have high potential consequences in the event of a failure.

drewnje, if you are referencing an erosion and sediment control manual, I'm sure you are looking at the former, not a dam. Many state E&SC manuals do recommend anti-seep collars for temporary sediment basins, but you won’t see it in your state’s safe dam program’s design requirements.

 

[cvg]

it may be unlikely for a sed basin with a very low dam and only frequently filled with water that you have sufficient head for long enough time to cause piping failure. even if it does, the risk is small. so the anti seep collars are neither effective or high risk in this situation. doesn't matter if you include them or not

 

[beej67]

Watching this thread prompted me to do some more research. I ran into this:

http://www.mde.state.md.us/assets/document/damsafety/NRCS/2007_NRCS_Filter_Diaphragm.pdf

Learn something new every day. Thanks guys.

Hydrology, Drainage Analysis, Flood Studies, and Complex Stormwater Litigation for Atlanta and the South East -

http://www.campbellcivil.com

 

[cvg]

good discussion of the problem, of course written by one of the experts, RIP

 

[Twinkie]

Interesting discussion. I never knew that there was even an alternative. Thanks