Pond Boss Forums INTRO Questions & Observations Help with Leaky New Pond

I have just had a 2 acre pond built in the Texas Hill Country. We dammed a wet weather creek and made the dam out of clay we found close by. We thought the bottom of the creek was solid rock. The pond builder got it to where he could not move any more rock with a huge dozer. Upon a 2 inch rain, the pond filled about 5 feet deep. It sayed constant level for about 10 days and then began going down pretty fast -- maybe 4 iches a day. The pond guy is standing by his work and will fix it - he thinks there is a leak in the rock bottom. He thinks a liner is the best option to ensure it will hold. Any thoughts about other options, whether a liner is the way to go and if so, which liner? or any other suggestions? He suggested a product called pond gard. I very much appreciate any help.

Cheap alternative is to pack the bottom up to 18 inches of clay, rather than just a few inches worth, if clay resources is available for such task. The clay that you're using may contain higher content of sand, or loamy-sand. Thicker compact layer will slow down the leeching even more, but will not fully stop the saturation and leeching process for your particular clay content. I can't tell, since I don't don't have it in front of me. Maybe a geological location of your site could provide a better oversight, since I can use the USGS Soil Survey data to pull up your soil content. During hot days, the evaporation will be at a much higher rate than the percolation/leeching.

If you have the budget to go with a liner, even better. The cost will climb real fast for the liner to be covered on a 2 acres site.

If you go the liner route, it's got to end above the high water line, it won't work if it's just on the bottom. If it accidentally gets a hole, then it might not hold water. I'd go with clay, like Leo said, 18", but I'd opt for 24" packed with a sheepsfoot roller, in 6" lifts, not packed with tracks on a dozer.

Thanks for the responses - If the Dam is all clayed and won't leak, help me understand why the liner needs to be above the high water line. I think the issue is fissures in the "solid" rock bottom, not the dam. We were thining we could cut a two foot trench around the lower part of the dam and insert the liner there and then back fill it. Is the PB screen thinking this will not work?

How will you ensure that no water leaks past the edge of the liner? (not just at the dam side of the liner?) i.e. how will you seal the liner to the bottom of the pond?

When we put in our 1.5 acre pond about 5 years ago, after a promising initial start (I posted on here that it was "holding like a jug"), it kept developing sink holes in a deep, rocky area in the bottom of our pond. In my case it was a self inflicted wound & lesson learned the hard way - don't ever blast rock for additional depth and think you can later seal it. Hard to believe, but it seemed like a good idea at the time!

It's a long story, but after about 3 years trying a number of approaches to plug the various holes and cracks in the rock, including clay and bentonite, and having the material always give way underneath due to the water pressure, creating new sinkholes, we were literally out of options. Lining the entire pond was not feasible from a budget perspective, especially because the entire bank of the pond was lined in probably 1000+ yards of rock rip-rap (I'll bet you can guess where that came from - yep, the hole we blasted).

As a last resort we tried a synthetic liner on the bottom of the pond in the area with the sink holes.

I'm not recommending this approach at all, but what we did was have our contractor dig a trench all around the area on the bottom of the pond with the leaks, installed the synthetic liner and cut the edges of the liner so that they were at the bottom of the trench and then back filled the trench with clay, essentially creating a pond in the bottom of our pond. The risk was and is that the water will work its way under the partial liner and cause it to float out and let the water out the bottom of our pond again.

So far the patch has worked (knock on wood). The pond has now held for two years with no signs of any further sinkholes or problems with water infiltrating behind the liner, just some seepage in another area that we're working on next.

Again, I am not advocating a partial, underwater liner as a good way to go. We just had no other choice for our particular situation. I don't know if it would work in other circumstances (and we certainly weren't able to get a warranty from the contractor or the manufacturer that it would definitely work for us). It was just an unorthodox solution that seems to have worked for us.

If it were me, I would do what the other posters suggested and try packed clay. Also, if the fissures are visible, before putting the clay down you might want to try and work some crushed gravel or landscape fabric into them to clog them up and provide support for the clay liner.

From first hand experience, a leaking pond can almost drive you crazy. Good luck!

jnapier, did you bury the liner as well to hold it in-place to prevent floating? I could see putting a combination of smooth river-stone and pea gravel over the top to provide structure for life and weight to the liner.

jnapier:

You said you put clay in the bottom of the pond to stop the leak and it didn't work. How thick was the clay, and was it compacted after placement?

Thanks All for the tips and stories. We are going to drain the pond with pumps (if the leak doesn't do it for us). Requisition magnifying glasses and or microscopes to search for the cracks and fissures -- ie, study the rock bottom real hard. And then come up with a plan. It may be we go with packed and rolled clay on the bottom as a first attempt - we do have some close by that is good material. Or we may decide to go with the liner approach. It will be a tough call. If we go with the liner, I am thinking Reimforced polyethylene - the Pond Gard is just too dang expensive. If we go RPE, we will study burying it. I sure hope we can get it to work because I think it will be beautiful if we do. Pic attached

I hope you get it fixed. I really like the rock ledge!

Wow, me too...that's awesome. I never thought of doing something like that, now I want to go do it right now at my pond!

Liquidsquid, We did not add any rock on the bottom of the liner. I'm a little foggy on the details, but I think we concluded that if the bottom floated up a little bit from seepage that would be less likely to pull the liner out of the trench than if we had put material on the bottom to weight it down.

Esshup, I think we ended up with about 18" blanket of clay/bentonite. It was difficult to compact due to some of the area having relatively steep sides. The slope was made up of rubble, which was like a honeycomb and made it difficult to pinpoint the source of the leaks. The actual path of the water could follow the rocks 15' or more feet from where the sinkhole would appear.

Initially we had aboue 30 sink-holes. On recommendation of a geotech we'd patch the holes with a mixture of reject gravel and a type of unrefined bentonite/clay from a local bentonite mine (50/50), then fill it back up. The idea of the including the gravel was to provide some structure and to help fill in the fissures. Each time the number of sink holes would decrease and I'd think we were making progress until there was only one "problem" area. Unfortunately, we could never get that area to stop taking material, and the hole would move around on us each time we thought we had it.

There were some pretty depressing times, but we stuck with it, used the liner and now have a beautiful pond. In the end it was worth it.

jnapier - what liner did you choose? and why did you pick that one?

THanks

We used a liner from Bend Tarp & Liner for three reasons (1) it is a local company and we didn't have to pay shipping(I believe they ship around the world though); (2) with their heavier duty liner we didn't have to have a perfect underlayment for them to warrant against puncture (as opposed to water getting around the edge of the liner - that was my risk), which was important because of all of the rocks (we did try to remove some of the sharpest looking ones); and (3) They warranted the uncovered liner against U/V damage so long as it was under at least 6 inches of water (we weren't able to cover the liner because of slopes). I don't know if the last two features are unique to their product - we didn't shop too hard for other options given BT&L was local.

I believe the price was around $.42/ft for the liner. Install was additional.

I liked them and their product seems very tough and durable. Come to think of it, I should get my hands on an extra copy of PB magazine, give it to them and suggest they think about advertising.

When I spoke to the folks there, they had seen the partial lining attemtped before, and they told me they had seen some successes, but also some failures.

We are going to line the bottom with clay which we have near by. Our plan is to put it in in 6 inch lifts and then roll it with a sheepsfoot roller. Mike Otto recommended this - he was very gracious in offering his advice. Will let the forum know how it goes.

Take pictures if you can!

Will do.

Update: We have not yet begun to lay clay on the bottom of the pond, but will start this week. A bit of good news though, the water continued to drain from the pond until the water reached a level where there was no rock and just clay on the bottom. The water is holding at this level, which leads us to believe (fingers crossed) that once we have compacted clay over the rock, it will hold

I'll bet that if you follow Mike's advice to the "T" it'll stop leaking.

We were close to starting the clay lining process when we got a bunch of rain. Attached is a picture of the pond about 6 feet from being full. Bad news is we will lose this water and then have to put down the clay lining. Never thought I would be sorry to catch so much rain!

I feel your pain! Its a shame to lose the water, but from the sound of it, you'd lose it anyway to the leak.