Help- suburban dam needs sealing and keep frogs happy

[julia b]

I have an old 8x5 metre dam in a suburban block. Frogs are established which I think is wonderful. However, well into summer, the water level drops to a layer of smelly sludge. I'd like to make the area even more interesting with a pump and water feature. To do this I need a constant minimum water level. Topping it up in summer is just a waste of good water. Some sort of lining is the go. (I have cut down the two tired old willows hoping this will slow the water disappearance. Has helped a bit perhaps.) My options appear to be plastic lining or bentonite at this stage. Plastic is fairly OK to get my head around I suppose. Bentonite, I question. Particularly once it is in place with its layer. Does it have to remain untouched to be effective ? ie no one stepping on to it while sorting out the irises or dealing to the pump or the like. (I read somewhere the bentonite ends up the consistency on soft butter) I've heard it is quite expensive, which if it is fussy then it may not be suitable. Any views MOST WELCOME. This is my first forum exercise, be patient with me !

[bazman]

Hi Julia

Could you post a pic of the area and maybe where you think the water is leaveing the dam?

Making the dam deeper and using subsoil clays might help. how deep is your dam? could you get a backhoe or something larger in to do the work?

[Richard on Maui]

For a pond of that size bentonite shouldn't be too expensive. The idea is to mix it thoroughly with the top few inches of clay lining your pond, either raking it in to loose soil or tilling it in, then add the water. You have to have the right kind of soil though, as bentonite reacts improperly with the wrong types, and if your soil doesn't have enough clay then it won't work either.
There again, for a pond of that size a liner wouldn't be too costly either. I installed a big liner last year, and I hated it. We had to first pick all the rocks from the pond floor bigger than 3/8's of an inch then we had to line the whole surface area of the pond with used carpet (I killed my biodesel vw pickup in hauling it all out to the farm but that is more to do with my mechanical ineptitude than anything to do with ponds) to protect the liner against rocks that might work their way up through the soil, then stretch the liner into place, and then lay carpet around the top edge to protect any exposed liner against the ever intensifying UV. You have to dig an anchor trench all the way around the pond to hold the plastic up, and somehow not kick rocks in between the carpet and the liner as you backfill. If you do use a liner, my advice would be to get everything in place, then fill the pond, then backfill your anchor trench, to allow for stretch when the pond is full.
If bentonite would have worked with these soils, and I could have found some locally I would have tried it instead of plastic any day.

[julia b]

Hello there Bazman and Richard on Maui
This is very exciting for me to think that there are others out there interested in my dam ! I love having it and want to do the best for the whole environment and ecosystem already happening.
Looking at the photo, my feeling is that the seepage is happening on the left of picture, which is on the down side of the slope. Right is intake I'd say. Two days ago it was down to no water, just sludge. However, then we had an enormous volume of rain - hense the puddle in the bottom! Depth would get to one metre when full. I have yet to get a soil test, though will do so as it seems important for the potential use of bentonite.
As far as mechanical digging help, I'm not too hopeful as it is small and the sides are reasonably steep. I will get someone to have a serious look at it. I know a few strong youths that I was considering luring for the job ! It does seem necessary to clear off the sludgy layer to get to the clay.
AND next time it pours with rain I will go and wait and watch to see just how the water flows into the dam. Lucky that it is so close to the house!
I somewhere prefer not to use the plastic liner and Richard on Maui confirmed my thoughts.
Now, I dont know how to post the picture. Dammmm
I'm on a Mac. Perhaps I'll send this off at least, with a pic to come soon.
Cheers Julia B
Hi Julia

Could you post a pic of the area and maybe where you think the water is leaveing the dam?

Making the dam deeper and using subsoil clays might help. how deep is your dam? could you get a backhoe or something larger in to do the work?

[SueinWA]

Does anyone have any experience with using gley? I've only read about it. Most instructions seem to say to grow something in place, then mash and cover it until it gets gooey. Julia says she lives in the suburbs.... if people toss their lawn clippings, would a thick layer of that work?

Sue