Pond Boss Forums POND CONSTRUCTION Renovating a Pond or Lake? Ground water

Last spring when I was digging the hole for my pond using a rented mini-excavator we dug a hole about 5feet deep and 20 x 20. This was to be the size of my pond, but not the depth. It got deep because we had trouble figuring out the machine.....LOL
Then my wife looked at it thought it was too big, so I caved and it is now about 10' X 4' X 18 inches deep.

So after I bought a couple of dozen goldfish and she took to feeding them and then at the end of the summer she came to me and said...honey you were right, it's too small.
In October my neighbour was fixing his septic and had rented a mini backhoe and I asked him to come by and dig a hole for the expansion to save me renting a machine in the spring.

After he dug the hole in the same area as I had in the spring, it started to fill up with ground water and stayed full all winter until last week. It is now dry as a bone and brings me to my question.

If I put in the liner and some very large boulders at the bottom and on some shelves with lots of gravel and other rocks, will the ground water coming back in the fall be enough pressure to create what I have heard called whalebacks?

I would think it's going to be a matter of if your filled pond has enough water weight to hold any water pushing up under the liner.

I have a 6 by 6 by 3 foot deep pit I drop well water into before routing it to any of three ponds, depending on which gate valves are open and closed. I notice in early spring there is water under the liner pushing up after several months of noy pumping well water. However once I crank up the well and increase the water depth it doesn't seem to be an issue anymore.

1000 Islands welcome to the pond boss forum, I have a 1400 gallon backyard pond with a liner, no problems but I don't have a high water table, does your local water table fluctuate with the level of the ST. Lawrence river?
I would think that if you filled your pond liner when the water table was low that it would stay in position, but that's just a guess, hang on and maybe someone with expertise in high water tables will reply.

1000 island welcome to the show, we hope you enjoy it
You can get a valve in the liner that will allow water and gas to come in but not go out. It is a kind of flap, looks like the trunk of an elephant. Where it is needed it works great does not cost very much and is a live saver.
Check with the people that sold you the liner they should be able to help you out.

Thanks for the welcomes.

My big fear is that I will go forward and expand the pond and them when the water table rises, which seems to be at the end of the summer, the pressure will force the liner up and I'll have a floating pond.

The valve idea seems to be something I will look into, thanks otto. Do you have any suggestions where to look?

Look in the magazine. Get the number for Colorado Lining. Talk to Chris,

Not where I can get the number for you.