Using Fly Ash to Decrease Seepage Rate In Pond 1

[MEM1]

Hello,

I want to use fly ash to decrease the seepage rate in runoff control structures at a feed yard. Fly ash is readly available at a local coal fired electric generating plant. I need to know how to calculate how much fly ash I will need. Can anyone help?

Thanks

 

[pigdog]

MEM 1
I suppose this is an established use for fly ash, but you might consider running a chemical analysis of it. Somewhere I read that mercury can wind up in fly ash, though I don't know how it would survive the heat. Anyway there are other heavy metals that could also be concentrated into the ash, so you might ask the question just in case.
I think the process is that somehow the mercury winds up as HgS which anaerobic bacteria breakdown for energy, converting the Hg into a mobile form and off into the water. Most likely the high organic content of the runoff is in a low oxygen state. At regulatory levels for mercury in the ppb range, it doesn't take much.
pigdog

 

[dicksewerrat]

I'd use bentonite instead of fly ash. Does the pond freeze? you can put it down on the ice and wait for spring.

 

[Grouser]

MEM1 please provide some additional info in order to clarify problem. Is leakage through porous granular soil? Fractured rock? Leaky concrete? Do you think leakage is relatively uniform over the pond bottom or locallized to some 'drains'. Fly ash is a pozzolan that can replace cenent in a concrete but it needs lime (cement) to work. Can pond be drained to allow repair / application of sealant? Is clay available near site? It is probably cheap and could be disbursed into pond water to seal small, slow drainage. Otherwise, cement, bentonite and maybe some flyash is the way to go.

 

[philhelf]

We had leaks in a settling pond for a coal wash plant. We put a dye into it so we could find the leaks, then later, we used bentonite which sealed the leaks fine.

 

[BigH]

My take on this (other than the good advice regarding the toxicity) is that you wish to reduce the seepage. I would surmise that since flyash (not bottom ash or near spigot flyash) is many silt sized, it may be less permeable than the stratum beneath. Also, fly ash, being "granular" in cohesion (not cohesive) will settle nicely. Given this, you will want to estimate the permeability of the fly ash in a "settled state" - presuming you are dumping through water. Once you know this, you can determine the thickness of the needed flyash to yield your required maximum seepage rate through the flyash into the underlying stratum. Sure, bentonite would work well and many use it. I remember reading some papers on how to "spread it". The ice idea is a good one (given you have ice - but if in Thailand or Indonesia, well . . .) - used this on a stabilizing berm for a causeway across very soft varved clays in northern Quebec once. Placed the berm on the ice, the ice melted and the berm "fell into place" so to speak. Hope you find something that will tweak you. Best regards.

 

[GeoPaveTraffic]

I agree with dicksewerrat, use bentonite. The environmental problems with using fly ash are likely to be very high.