Pond Boss Forums POND CONSTRUCTION Soil questions Please explain this to me....

Can some of the soil guys explain what is happing to my pond site?
As in my previous posts; I laid down a bentonite blanket of material and tilled it in to blue/gray really good river clay.
Try to compact the leak area with a jumping jack compactor and found the ground acted like spounge cake. Brought in my tractor and more clay and compacted over and over and still had the spongy sub-surface. The crust kept raising up and wouldn't compact to a soild surface. I have about 3 feet of good clay over this area. Started filling the pond last night and it seemed to hold water. This mornig there is water, but I see bubbles all over the wet area. I know its because I couldn't get a soild compaction.

What is your best guess on what is going on and why can't I compact this area? Is there still a fix I or will it heal in time?

Is it holding the water ? The bubbles could mean several different things and not necessarily a leak.

scruffy, it sounds to me like a shallow water table problem. the way i see it you have two options:

1) continue to fill on suspect area (and lose depth) until you can get a firm compaction

2) get a backhoe in there, strip out the good clay you've brought in and save it, dig a test a hole in the suspect area to determine the geology (is it a groundwater containing sand, rock or silt, is it a local perched zone or part of a more extensive water table??)

you may find you can dig deeper, get to a hard soil horizon, and then seal it off with imported and compacted clay. if this is the case you will have removed the slushy soil, and then can and likely have to pump water out to keep it dry enough to work on.

on the other hand, you may find it continues as a saturated slushy soil horizon, and you have to seal yer pond well above this layer. it is hard to give advice on how to seal a pond when you dont know the deeper geology.

FWIW, welcome to the world of leaky ponds (i have one) and GOOD LUCK.......

edited post.....i should have mentioned as eric pointed out (posting at same time ) the obvious near future option is to see if what you have done is sufficient....if it leaks out, then you are faced with the two options i could think of posted above. as i understand it, the bubbles are usually organic gasses trapped in the soil and being released as the soil "wets" or becomes saturated by the new pond water.

Thanks Dave and Eric,

Yes, it is holding water only lt went down a little(1") over night. Still seeing bubbles over an area of of about 8 feet. Going to fill the pond and hope it will self seal with all the clay and bentonite I brought in.

"(is it a groundwater containing sand, rock or silt, is it a local perched zone or part of a more extensive water table?"

Dave;
I know the geology all to well, water table/rock ledge uncovered during the first dig. Perched area back filled last year. (Covered with 4 feet of clay/sand soil.) Trying to cover the area with clay can't compact it to a soild surface. Even if I dig out the area I don't think it will fill better than I have all ready done. Marked a stream while dowsing, that runs thought the leak area, must be quite a flow under ground.

You are most certainly right I'll have to live with a leaky pond. And I thought this ponding stuff was a slamp dunk in my area, the Lakes Region of NH. Boy was I wrong on this one.

Still looking for some creative suggestions that won't break the bank.
Thanks,

oh yeah, i remember the rock ledge part. well if yer pond ends up not holding the way you want it to, the obvious other "creative" solution would be a liner, in a pond yer size it might work real good.

if that appeals to you, i would research liners and cost out a few companies to get a feel for it........also search old threads on the forum.

you might also contact a couple local geotech firms, they could point you in the right direction. those guys work with landfills and use "geotextile fabrics" all the time. they may even have spare rolls or lying around.

any others here who have used a liner....maybe help scruffy out?