I'm done with the excavation and am now lining my impoundment pond with what I think is a good quality clay, as described by various posts here on your wonderful website. I've got 2 feet of compacted clay on the dam, at about a 2:1 slope. Today we excavated a trench about 1/2 of the way into the dam, (about 25 feet) and placed a dry hydrant so we can draw water for fire protection here in Colorado : 6" PVC pipe that starts about 4 foot above the bottom and exits by the road on top of the dam, with 2 45 degree angles so that it does not go all the way thru the dam. However, it does go into the rotten granite and sandy soil that makes up that part of the dam. I am about to fill in the trench and after spending lots of my money on bringing in clay to line this previously leaking pond, I'm worried that I'll have water leaking around the pipe.
Do I need an antiseep collar or will just careful packing of the clay around the pipe be good enough since the pipe does not go thru the dam? If I use a collar, how far back along the pipe does it go? IF I pack the clay, how do you pack it under the pipe?
I've posted some other questions lately as I've been working on this project and have appreciated all the responses. So far so good! Barbara

Barbara:

Since it's in the dam AND since you have had to haul in clay due to the porous native soil, I would recommend taking the precautions of using an anti-seep collar and also carefully repacking the trench. Your dam is the place you least want a leak.

Our dry hydrant has no collar, but it's located on the side of the pond with the steepest slope, going into nothing but clay. We put two anti-seep collars on each of the lines (8" drain pipe and 1" water line for livestock) which go downhill from the pond.

Thanks for the advice. How far into the dam should the collar be located or does it matter? Could I make my own out of a piece of pond liner packed on both sides with clay and of course completely sealed around onto the pipe?

My best guess is to place it where it can be sealed the best. This might depend on variations in the dam material, or a location in the trench where it will be easier to work, or ???

It would certainly be possible to make a collar yourself. We purchased 4 anti-seep collar kits from a nearby drainage supply house; these consisted of a 4'x4' sheet of heavy, flexible rubber and 1"x2" fir strips to make a square framework. You cut a hole of appropriate size through the middle of the rubber and slide it onto the line in the dam either before or after stapling it to the square frame. The wood will of course rot in a couple of years, but it's job is to hold the rubber sheet in place while you pack clay as hard as possible on both sides of the sheet all around the pipe.

I messed up cutting the hole in one sheet, got a slice extending farther than the pipe diameter, and got creative in an attempt to fix it (and help fasten the torn sheet to the pipe) with rubber inner tubes, silicon seal, and cable ties. This held together fine while we backfilled and tamped; I don't know what it looks like now but the dam holds water.

I cannot guess as to the suitability of pond liner for this purpose (no experience with it), but 19 years of fixing (and all too frequently re-fixing) washed-out holes at cracks in field drainage tile has showed me that rigid, plastic-like materials (such as visquilene) are easily torn under ground by moving water. The thicker and the more pliable a material is, the better it should work for this purpose (old inner tubes are my favorite material for sealing tile repairs; I have not had to replace a fix made using them yet).

Barbara,
One way to compact around and under the pipe is with the round end of the shovel handle. Just use it like a tamper. The small surface of the shovel handle will pack dirt pretty tight. And it's not so heavy to use. Takes some patience....

Thanks for the suggestions. The track hoe was here over the last 2 days, and so I had to fill the trench with the dry hydrant and did not have time to put in a collar. All this pond work has been going on in the middle of my elk hunting season!Anyway, I did pack under and on the sides of the pipe with the shovel handle and then the contractor put guys to work with a jumping jack to compact the clay on top. I'm thinking of adding the pond liner collar on the surface and then hand compacting it with more clay.
Of course if I get an elk in the next day or two, then I'll probably blow off the collar project and put bentonite around it if it leaks next spring!
But the exciting news is that my excavate/build sedimenation galleries upstream/and line my leaky pond with clay and put in the dry hydrant project is finished! Now I'm filling it with water from the solar pump on the well which will take awhile, giving me time now to place the pea gravel, build more structure and start the recovery work from the surrounding track hoe damage. I'm going to have a fun winter working at the pond.
Thanks to everyone on this website-your advice has been very helpful. When I get a chance I'll post pictures. Barbara