New pond lining

[Benny74]

Hello all... I'm in the Florida Keys, and putting in a new pond about 8x5. it will have some tropical fish, water plants, waterfall, etc.... In looking into a liner vs concrete, I came on another idea. When I dig, I hit solid coral about a foot down. I have excavated the dirt and as much of the softer stone I could chip out. The coral really has wonderful natural contouring that I was able to accentuate with my grinder. concrete wouldn't look as good and a liner would be hard to fit to the holes and crevices.
My question is, to preserve the natural coral look and shape, would it be possible to directly seal it with some kind of epoxy, without either a liner or concrete? Could anyone recommend a product and/or method I could do myself?
Thanks for any help and input.

 

[j.w]

Benny
Really interesting idea but I haven't a clue on if a sealer would work. I'm sure others on here will have some good advice on what you might be able to use hopefully.

 

[Waterbug]

I assume by "coral" you mean caliche.

All things are possible. Epoxy, given a thick enough application, would certainly seal it. Epoxy can seal anything. Fiberglass would also work. But you wouldn't be able to see the caliche in either case.

Is your goal to see the caliche or just the contours you make?

In either case mortar or concrete would be a very temporary waterproofing at best. For concrete to hold water long term you need a minimum thickness of 4" and rebar. Otherwise water is loss thru cracks which all concrete develops.

There are things you can do to make it leak less, like adding bentonite clay, but that would cover the caliche as well and I don't see how contours would be maintained. I'd still expect a lot of water loss.

If the goal is to see the caliche I suggest digging the hole deeper, laying a EPDM liner and then mortaring chunks of caliche on top of the liner and up the sides. That's what I do with various kinds of rocks.

 

[gardengimp]

In this case, he means coral. A previously live organism. Now dead coral. The florida keys are an ancient coral reef. I don,t think it is possible to dig past it. The borrow pit on no name key is many many feet deep and still full of coral.

So far as I know, coral is far too porous to hold any kind of sealer. Coral can also be very sharp.

Waterbug knows a lot about this stuff, so we will let him fill us in, but I suspect you are going to need underlayment and a liner. An EPDM liner will contour nicely to the form of the pit you have dug.

 

[capewind]

ohhhh I am confused ... I thought coral was calcuim carbonate???

 

[capewind]

never mind ... did a search on caliche ...

 

[Waterbug]

To me coral is the form when in the sea, alive or dead. More of a surface formation. When compressed into "rock" I would call it coquina. When dissolved and redeposited I'd call it caliche or limestone depending on how it was formed. For the most part this is all calcium carbonate, we just use different terms to describe different forms just to make communication clearer. I for example would say most of the Keys are on limestone that was formed from coral. But that might just be me.

Getting back to Benny74...the reason I assume caliche is because it was found 1' down and that it could be worked with a grinder. To me that sounds more like caliche. My next guess would be limestone. To me coquina would be more of a crumbly material, more like Rice Crispy Treats, and a grinder wouldn't be the tool of choice. Perhaps Benny74 could provide more info?

If this really is coral then I'd have no idea how to handle that because I've never worked with it.

If it is coquina then the epoxy or fiberglass would work as long as the coquina has fairly good binder (isn't crumbly). If it's crumbly you have to be careful about shifting and settling because both epoxy and fiberglass needs to be supported unless very thick ($$$).

Caliche should provide a good enough base for epoxy and fiberglass, but that does depend on the thickness of the caliche layer. I'd say if it was about 12" thick or better it would be stable enough. If only a few inches thick I'd start to be concerned mainly because epoxy and fiberglass is so expensive you just have more at risk. As costs increase I like to reduce risk.

If this is limestone I'd say epoxy or fiberglass would be no problem at least for the base. You'd still need to provide structure for the 12" of soil but that's easy enough with poured concrete or concrete block.

Going back to the original question I would not consider coquina, caliche or limestone as something that could hold water very well. But it's relative what different people would consider "water tight". To me it means a loss of less than say 1 gal per year. I've met people losing 100 gals per week who considered their pond "water tight". I think a person's view depends somewhat on how much they have to pay for water.

 

[Benny74]

Thanks for the responses. My understanding is the upper Keys are a coral reef outcropping known as Key Largo Limestone. It is not crumbly or composed of calcrete or sediment, but preserves the features of the fossilized reef.
YEs my idea is to preserve these visual features, so I was hoping to clear coat rather than cover with EPDM. The grinder cuts it with the diamond wheel, but to remove large usable chunks to mortar down would be very difficult.
I suppose "water tight" depends on the size of your pond, but with 50 square feet I'd like to keep it closer to a gallon per year.

 

[Waterbug]

If you go with fiberglass resin only and no cloth it's transparent, kind of. It sure isn't clear though. And without the cloth the resin would have to be even thicker so even less clear. I doubt you'd be happy.

I assume you could buy the limestone locally rather than have to cut it yourself. However, even when placed on top of liner it can be difficult to see rock surface because it gets covered with muck and or algae. It can be kept pretty clean, but if you get rock with a lot of fossils the voids would get filled unless you did really good job cleaning.

Another choice is to do the same process as filled honed travertine (similar to your limestone). Voids are filled will a grout and then honed (ground, polished). The result is very easy to keep very clean. The grout is almost impossible to tell from the stone. Fossils can still be seen but you do lose texture detail. They use a slightly contrasting color grout, but you could use a higher contrast color to make fossils pop. While travertine is normally honed to a flat surface you could create any contours you'd like. Not too hard to do either.

You could also buy filled honed travertine tile for much of the pond and add a few select pieces of the local limestone. The travertine is pretty cheap at least here.

 

[Benny74]

I like the filling/ honing idea. Serveon Sealants makes a product called Rock Steel Ultraporous (link below), a silicon polymer that binds with the substrate to seal it. The company recommended ClearBlue (link below), which they said was similar but with larger chain molecules to cover better and absorb less. I'm hoping this will prevent algae growing on the coral and seal it well. If you have any thoughts please add.


http://serveonspecialtychemicals.com/ClearBlue.html
http://serveonspecialtychemicals.com/RS_Ultra_Porous_Data_Sht.html

 

[Waterbug]

In general I'm not a fan of any of the polymers in a submerged water application. Submerged and wet perform differently. My concern is the 2 materials aging differently and not looking right. When a cement type product is used with stone/mineral the two materials are basically the same and age well together. With a polymer you can get delamination, color changes, texture changes. That can mean the polymer holds up better than the natural material, but you still get a difference in appearance.

Not saying this would happen. Depends more on the natural material than the polymer in most cases imo and your tastes. Just something I've had problems with in the past.

 

[Benny74]

Ok, so forgive me for picking your brain, but if I were to fill wih grout and hone as you mentioned, what product would you recommend?

 

[HTH]

The bottom will grow algae which will hide the coral.

 

[Benny74]

So in that sense the polymer is the better choice.

 

[Waterbug]

Ok, so forgive me for picking your brain, but if I were to fill wih grout and hone as you mentioned, what product would you recommend?

Any cement type product. That can range from a pre-mixed mortar, to tile grout to mixing your own recipe. For example you can mix white portland cement, marble dust, lime, maybe some mortar clay, to get a very fine paste that polishes nicely. The white mortar they sell for setting glass block have a larger sand than I like for honing unless a rougher result is OK or desired.

Unsanded tile grout is the easiest to buy and get the color you want, but a little more expensive, but not a lot more if you buy large bags from mason supply stores. Most tile grouts are modified (some added polymers) but I've never had a huge problem with these I assume because they don't have a lot. They don't age as good imo but I'm starting to split hairs.