Pond Boss Forums POND CONSTRUCTION Building a dam Option for plugging leak, seepage?

I've got a screwy problem with my dam, in that we have a natural gas seep directly under the outer skirt of it that is keeping the dam from sealing. Water is seeping about 1/2 way up the side of the dam, and running down. The dam at this point is very thick, probably 20' or so, so here is my theory:

The young man who started building our pond started it out larger, making the core/keyway out too far downhill. Then he started excavating out the basin from the other side uphill. In the process he found a lot of old farm tile (stone-lined), and ripped it out of the main basin. However I don't think he got the farm tile out between basin and the core which was too far downhill. So I think there is farm tile still between the basin and the core...

So his father (owner) comes along and they decide to build the pond smaller (not entirely sure why), so in the process knocked off the top of the core and pushed everything in 30 feet or so. Now there is a path for water down through the pond side, across through the farm tile segment up to the core, and then the natural gas seep is driving the water up the back dam side and old core front. The soil right there is like angel cake, fluffy and bubbles like crazy when you walk on it for about 50' of length. All natural gas and burns well. Along with this is a slowly increasing flow of water from something that should not leak.

The primary problem I think is a core and dam which do not line up, but secondary is this high-pressure gas keeping the soil from settling. Perhaps some of this gas is bursting up the bottom of the pond keeping it from sealing. Weird eh?

So the thought is to have the excavator back to re-make the core/keyway where it was started originally, and build it up to the height of the full basin, packing it really tight. The area between the old dam and this new one would be left to fart gas, or lift water, or whatever it wishes, perhaps lowering the old dam a bit to angle towards the water. Maybe even wind up capturing some of the potential spring there. I thought filling with porous material between the two would help let the gasses come out.

As far as I can tell, where the original core was has no problems withe the gas leak, or water leak as no water bubbles up at it or below it so it looks sound.

Does this plan make sense? What would he need to do to connect this new core to the old where there are no leaks? Would there be too much water to work it or is there risk of busting the old dam even though it is very thick?

Looking for suggestions, should I be critical of this guy and ask for help in covering expenses?

One more thing: I tested the water from the pond and from the seep to look for a match, and the seep has a LOT more harness than the pond, so could I go from:
Pond:
Alk: 120ppm
Hard: 50
Seep:
Alk: 240ppm
Hard: 250

A lot of crushed limestone much like Ag lime in our soil. Seems consistent with my theory. I think the leak is picking up speed since the lime is getting dissolved out.

Thanks.

I can draw up a crude diagram if this helps.

I like pushing it back to meet with the orig core (if it's good and tight), building up on the orig. core.

Can you put in a perforated pipe going to solid to direct the gas out and away from percolating? Can it be collected and used for anything? (are returns greater than the investment?)

I am hoping not to have to drain the pond, not to mention move my dock I put so much effort into which moving the current dam back would make me have to do, though I certainly would not mind a larger pond. That is why I think building a second dam behind the first would do the trick as I would not need to do either of these things.

Also I am afraid of exposing the gas leak into the pond basin as who knows what that would do to the DO and water quality in the pond. Perhaps a cheap way to get an aerator, but it is the wrong gas. Also worried if the water didn't leak back down wherever this gas is coming from.

I am hoping that we can extract clay materials from nearby on our land, or bring in good plugging fill as around here they are always looking for someplace to dump materials. I can have patience on getting this done right, and hopefully relatively cheap.

I like the idea of maybe excavating a shallow ditch between the two, and laying down gravel mix and perf pipe and fabric to ventilate the gas to a solid pipe. Then lay sealing materials over the top. At minimum there probably is enough gas to light some gas lamps on the dock, at max, who knows? I would love to run a line up to the house and heat with it, tired of lugging wood in all winter. By ventilating down deep, it would prevent pressure from building up and bursting any seals.

The stinky part of this is the tallest, most difficult part of the dam is tight as a drum. Not a leak to be seen. The part that is leaking isn't even that tall. I went down this morning and walked over the wettest section and it was like standing on a pillow. It is a good thing I don't smoke for all of the bubbles!

It is too nice of a pond not to invest a little more in. Some people think we put chemicals in it to get the awesome color, but it just so happens our pond water is of better quality than our well water. We have started getting those infamous "pool" friends that show up in hot weather.