Pond Boss Forums POND CONSTRUCTION Soil questions clay plus liner??

So, I have a general question going out to all pondmeisters who like myself have struggled with leaky ponds. I was reading the recent bentonite thread and it occurred to me…….

has anyone ever used a synthetic liner in conjunction with clay?

In other words, I see a lot of folks talking about bringing in just bentonite, or just using a liner and comparing the pros and cons of each individually……it seems to me that on any size pond with marginal soils or marginal dam construction (sp. no keyway), there might be a cost efficiency to using both a liner with either native or imported clay.

The way I see it working would be to place the liner along the deepest portions of pond basin (where hydraulic pressure is greatest) and laying it from there up along dam face (to cover the dam material/native substrate contact), then compacting a thick clay layer berm (or strip) around edges of liner a sufficient distance on either side of the liner edge to effectively seal it off. This would be the tricky part, but I imagine a coverage of 5 to 10 feet on either side of the liner edge would hold. The clay could be feathered out from the liner in all directions to cover even more ground. Seems to me this method could potentially reduce the total amount of clay needed, and reduce the size of a synthetic liner needed to seal off the portions of a pond most prone to seepage……..

in my neck of the woods, if you have to import clay or clay soils, the trucking costs kill small budgets real fast.

DIED, I am considering doing that very thing, if, and when the pond level gets low enough in the fall. I'm sure it will be the usual long, hot, dry summer. I fall, I plan on renting a dozer, cleaning and deepen the shallow end. Then, dig a small pond in the shallow end to transfer the best fish. Rework the deep and dam area; line around the dam and seal the liner with clay. It has to improve on what I have now. Even with some seepage, there is a good watershed. I will post photos/results.

looking forward to yer progress burger. do you have a handle on where the pond is leaking?

i wasnt suggesting this as a smoking gun for leaky ponds, nor did i think it was a really "original" idea....i just havent seen anybody go this way, and kind of wondered, would the combination be effective or are there some really bad pitfalls to the idea? the biggest pitfall i see is not getting a good seal around the edge of the pond liner cause you cant blend in clay to the liner like you can soil on soil, and water will find its way. but if one were to pack enough of a clay berm or strip around edges it should hold a long time.

I figured many of us live with marginal soils and marginal dams and many of us have visible and measurable leaks and are looking for ways to slow them down because we dont have the budget to really do it right and go all the way. i opted for part imported clay to mix with some native clay soils i had on site, but thinking back i may have tried this idea...who knows, my pond could redevelop bad seepage and i may get to try it out, but i hope not.

DIED: I am wrestling with this very issue right now. We are planning for a pond about 120' x 100'. Wish it was bigger, but we are limited by a couple of geographic features that we cannot work around. The soil is generally sandy loam, although we believe that there may be a quality clay seam at a depth. (I am going to do some test holes this summer) A contractor has already given us a price of $22,000. This included the import of enough clay to make a five foot wide keyway around the pond.

I have since asked him how much cheaper it would be to dig the hole in the ground without a keyway and without the import of clay. If he could dig it and shape it and I could use a $6,000 liner, how much cheaper would it be? He didn't seem comfortable with the idea and indicated he has never done anything like that before. Bruce said that he hates seams, so it kind of scares me to use a liner at all.

I thought that if you go with a liner you have to go all of the way up and over or you will have significant leakage. Your idea may be a good one, though.

My thoughts are that if I am going to spend a lot of money, I am going to either line the entire thing with synthetic or line the entire thing with clay. But I am very new at this stuff.

DIED, I know the pond leaks near the dam/bottom interface. Possibly/probably some seepage thruout. At late last summer after severe drought, it was only the size of a good sized house. Normally 1/2 acre. I feel that if a liner edge is in 6 ft. of water, and clay weighs 2 times the water, it is the same as putting 3ft. clay over the edges of the liner, but with obviously even distribution of the weight. Doesn't really seem to be a concern. I figure if I stop even 1/2 the seepage and get the well cranked back up, I will be fine. Only need 2-3 ga. per minute for a few hrs. per day to deliver 200,000 ga. per year. Pond is about 450,000 ga. when full.

victor, because yer starting from scratch, you have the opportunity to "do it right" for yer situation. i would tend to agree with you to choose one method or the other. what are the pond objectives? if i had a choice, i would probably go with a "natural" clay substrate if fishing is the primary goal. if yer contractor is the only show in town, i wouldnt try to make him do something he has no experience with, but i might also be shopping around for others with more "pond" experience. good luck and keep us posted.

in my case, i bought the property with pond already built, already leaking, and in dire need of repair...so i had to pick my size band aid and attempt to correct some original construction flaws.

burger, dam/bottom interface was where mine was leaking in addition to the deepest areas in bedrock. my band aid covered these deepest areas and stretched up and across inside dam face not quite to high water level. back portions of my pond i believe are now the culprit for what i see seeping (in the summer) down in the creek bed daylighting 50 to 100 feet below toe of dam. it used to leak right at toe of dam. the current seep is about equivalent to a slow running garden hose, where before the whole creek ran pretty steady through about July/August or until the pond drained almost all the way down.

before clay installation you can see the groundwater surface in pond bottom, there was reverse flow at full pool probably causing most of the seepage.



i had about 200 tons of pure kaolinite trucked in and thank heaven had about the same amount of good red clay soils on-site to mix and add to the imported stuff. this kind of shows the band aid in the back ground covering the deep portions and extending up along dam face:



you can also see water coming down the original creek bed on the right, it immediately started to ride over the band aid, and began filling the pond up.

after we finished what we set out to do, this is what it looked like after about a week....we'd had no rain, this was just shallow groundwater making its way from above the pond, collecting in dug out creek channel, the lower portion of which we covered in clay, and riding up over top of band aid.



anyway, hope that gives some ideas of what or what not to do. good luck.

Died, I've been thinking I wish someone would invent the following.

I wish someone would make an extremely thin plastic, similar to celophone and shred it. THen you could take handfulls or truckloads of this fine plastic and spread over the pond area. It would be really really fine and light and moldable/mendable. In time pieces would gravitate towards the water movement, and get sucked in and clog it, similar to a toilet getting stopped up. Just a thought. I've used no more than a Wal Mart trash bag as a plug for my boats, at times. It doesn't take a lot to stop many leaks. Hope someone makes a million of my idea.

Eewww Died. Fresh bulldozer tracks in California. You're in trouble!!!!!!!!!! :p :p

DIED, good pics and info. Thanks.
Robinson, PI, as usual. :p I'm coming to Franklin again in April and May. Do you have any water? What about GG? Shud I bring my ultralite?

bm, we received 3 inches y'day. Pond is over 2 acres maybe 2.5. Water is still coming in, so I don't know if it's leaking. I put 1' of clay over most all of the bottom in November and compacted it in. Still have not stocked it as I don't want to jinks myself. Keep me posted when you come. Maybe this time it will be worth looking at. The water table really is low here. We received about 2 inches in Dec, 2 in Jan and 2 in February. We are very dry compared to usual. That 3 inch rain will help, but we need a whole lot more.

In April I'm headed back to Alabam' and hope to have a small siltation pond, 20'x30' with a depth of 3' at the levee, dug. The main 0.25acre pond, scheduled 2-3 ysr. later, may be a lined pond from 2' to 8' depths. So, I plan to pack some 12" soil on top of the bedrock, then I'd dig a trough centered in the levee(a sort of core), next lay the liner, and finish with the 2'+ of soil atop the liner. This ought to indicate if water will travel along the liner and beyond the trough to cause significant leakage. There's issues that possibly a liner could solve. Without the liner; 1) A traditional core trench would have to be cut in rock, expensive if possible. 2) 1,200 cu. yds. of clay needs to be hauled in, expensive. If the little pond seeps minimally, lining the deep section of the main pond and up the dam to 3' could become a viable alternative. Your thoughts and comments are welcomed.

I've always thought of using a liner like creating an aquarium. If the water comes over the top, it is breached.

However, I guess you could try it if you have enough clay over it to cut down on the amount of clay needed. Sounds touchy to me.

Mike Otto had a recent PB mag article about liners and might be worth contacting.

arent they beautiful? so symmetrical. they really hold a hydroseed job too. this spring (second one after hydroseed job) it looks like i successfully estblished the rye, native wildflower coverage. i was worried it would only look good for one year......thanks to dozer tracks

little strips of plastic.....hmmmm

so sauty, i dont think my dam was constructed with a keyway also because of bedrock. sounds like yer case is similar to what i was thinking about, and i agree w/ DD1, talk to some experienced folks like Otto.

re-thinking my long first post, my main question i guess is has anybody tried to use a liner as a leak band aid and seal liner edges with a clay border (that will all be underwater)?

D.I.E.D.
My thoughts are that it would work at the start if a person went to a lot of trouble sealing the edges.
On plastic pipe in dams we put anti-seep collars to keep crawdads from digging in the moisture on the outside of the pipe and creating a hole along the side the pipe.
Wonder if crawdads would try to dig along the liner and around the edges?
Do crawdads dig holes in clay liners?

What am I missing with all the worry about the water going UNDER the liner? If in 5 ft. of water, the liner is being pressed against the bottom at 2 lb. per sq. inch by the water column, or 288# per sq. ft.
Just as when lapping it over the side. Dig a trench, lay the liner. Fill the trench with dirt.


Editing another ill advised post. The bouyancy of the plastic trumps the weight of the water. Think I'll just shut up and lurk now.

D.I.E.D., I think you're on the right track with using clay as long as the slopes are a gentle 3:1. I've read that crawdads dig rather vigorously in shallow water, in clay, yet fizzle out down around 5ft. I doubt they would penetrate a 45mil liner. Yet, if the liner doesn't cover at least to the high water mark, they could be trouble(excepting a rather wide 20'+ dam crest). I'm hesitant about sealing the edges with clay for my use as some edges would be on 2:1 slopes. I'm considering dropping a load of 3/4" rock along the edges and seams. Another long shot I hope to experiment with is trying cement screws in the sandstone bedrock to help keep the liner in place and help with the seal. Really appreciate you guys as a resource. Putting in a pond atop Sand Mountain ain't gonna be easy.

Burgermeister

The pressure pushing the water behind, or under, the liner would be the same as the water pressure on the liner. So basically, if water can get to both sides the liner is just laying there.
Thats why there can't be any water penetration around the edges or through the liner.

Good explanation, Kent. So a puncture anywhere in the liner will breach the seal and equalize the pressure above and below.

When water gets under a liner you get what's affectionately known as a "whaleback".