spec for "clay dam" or other groundwater stop in trench

[chipomatic]

I'm designing sewer and drain pipe trenching and know there are wetlands and/or seawater nearby and the trenches will be in groundwater. I'm aware that "clay dams" have been used to prevent transportation of groundwater in trenches. I've also heard I won't be able to obtain clay. I'm looking for specifications and/or drawing details of a way to stop the flow of groundwater in a trench that will contain crushed stone up to 1 foot above the pipe. The soils in this area are also sandy and readily allow groundwater flow. Thanks.

 

[daddymem]

Is a Ripley's Dam applicable for your design?

http://www.epa.gov/region1/assistance/ceit_iti/tech_cos/mcr.html

I ain't never seen a hearse with a luggage rack.-GS

 

[cvg]

you might try a 1/2 sack or 1 sack flowable fill

 

[SlideRuleEra]

Where I work, coastal SC, sandy soil & high water tables are the norm. Instead of trying to stop the flow, the most cost-effective solution may be the use of diaphragm pumps (mud hogs) continuously during excavation/installation. For really deep, or wet, conditions, a wellpoint dewatering system may be needed.

Wellpoints are often though to be limited to use when they can surround the excavation. However they work quite nicely when installed on one side of, and parallel to a "linear" excavation, such as a pipe trench - they don't even have to be too close; placement 10' or more from the trench is typical.

http://www.SlideRuleEra.net

 

[chipomatic]

We were considering flowable fill but I like the looks of the Ripley's Dam. Unless something better comes along, I'm thinking we'll go with that. Thanks for your help!

 

[bltseattle]

Be careful when compacting around a rigid dam such as the Ripley's. Flowable fill would seal the trench edges whereas a rigid dam that is improperly backfilled and compacted may not be as effective as desired due to seepage around the edges.

 

[cvg]

cost of flowable fill may also be comparable, since there is relatively little labor involved to place it.