Vinyl Sheeting in Dam

[erich]

I'm working on a small dam rehab. It is a small (<10 ft high) earthen gravity dam that was originally built in the mid 1800s. It had a wooden cutoff wall to bedrock that has long since rotted out and been replaced numerous times. The owner wants to keep construction methods historical but I'm not liking the use of the wooden wall.
Anybody have any experience or resources with vinyl or rigid plastic sheeting that could be installed by hand or with conventional excavation machinery.
Thanks
-Erich

 

[PEinc]

If your dam is around 10' high, you would probably need sheeting that is about 20' long, give or take a few feet, unless rock is near the bottom of the dam. You could not drive these sheet by hand. Also, any obstructions from cobbles, boulders, or old sheeting could prevent the new sheets from being driven as needed. It would be a good idea to locate the new sheets away from the location of the old wooden cutoff wall.

http://www.PeirceEngineering.com

 

[erich]

Thanks for the quick response.
Yes bedrock is right at the bottom of the dam, the owner was planning on replacing the wood in kind by lowering the water in the dam and excavating out the old cutoff wall. My current plan is to attemp to trench into the bedrock and place sheeting in that trench maybe with some cement/bentonite grout at the toe.
But I'm looking for some references for the plastic sheeting. All the info my google-fu can find is for manufacturers in the UK or Europe. Here in New England I can't find anything.

 

[letrab]

Hi Erich The Bentonite soil cement in the trench seems like as good idea, why don't you continue it to the top and replace the timber with the plastic concrete barrier.
It will be easier to place.

If you want a plastic membrane, joining the adjacent sheets will be difficult. backfilling either side would also require selected material to ensure you do not rupture the membrane. I prefer HDPE to PVC, mainly because of puncture resistance.

 

[PEinc]

For vinyl sheeting information, try

http://www.northstarvinyl.com

http://www.PeirceEngineering.com

 

[PEinc]

Did you consider excavating a bentonite slurry trench, or jet grouting, or some other type of drilled and grouted cutoff wall? One of these may be a lot less damaging to the dam.

http://www.PeirceEngineering.com

 

[dgillette]

I definitely would not go near the wood option, regardless of historic significance. Some sort of cement-bentonite-maybe-sand slurry (don't ask me about mix design) could be put in with a medium-sized track hoe, trenched into rock if it's soft/weathered/fractured enough. The slurry pressure can keep the trench open.

Jet grouting does not seem like a good candidate for this site for several reasons, beginning with the cost of mobilizing equipment for such small dam.

If the wood is to be removed and a new cutoff to be installed in open cut, see

http://www.eng-tips.com/viewthread.cfm?qid=265437.

The cut slopes would need to be laid back pretty flat if workers would ever be in the trench. That could take out most of the dam.

Regards,
DRG

 

[GabionGuy]

Work was done in the late 90's in Ontario where a rotted timber crib and earth core dam was replaced with gabion baskets and geomembrane. The structure was 3-4m high and sitting on bedrock. It proved to be a very inexpensive option to the owner and was worked very well. The structure is a combination dam and overflow weir. I think there were some papers published about it.