Rehab of old cracked concrete pond

[Lexx]

Our old 1960's pond has flaking plaster or concrete, whatever the stuff is. There's barely a shell underneath of it. I got a bid of $5500 to replaster it. Not gonna spend that kind of dough. I'm hoping I can use some sort of pond liner and just cover over all the old stuff. However, where the old waterfall was, there's a mix of granite rocks, volcanic rocks and then you can see the horizontal area where it transitions to the concrete/plaster. If I use a pond liner, is there a way to seal this area off and affix it to the stone so that water doesn't get under the liner?

If the liner can be fixed, my plan is to install a solar powered pond pump with a battery backup.

You can see the transition between the rock and the concrete/plaster:

Some of the flaking concrete/plaster:

 

[j.w]

@Lexx
Looks like a big job and I'll leave this for someone who has experience w/this sort of issue.

 

[GBBUDD]

You have a nice design from the over all pic it dos look nice. It appears there is a bog filter in the left corner. Now i have been a contractor and have build this that and the other think . the plaster coating looks as it is alagatoring requiring any loose areas be removed. that can be time consuming as well as tricky. Did the 5500 give a guarantee ? That actualy doesn't sound like a horrible number if there is. But once concrete gets to that point it is tricky and usualy no guarantee it will hold as what is holding on today where neighboring areas already failed it could be just a matter of time.
If the plaster is going to be scraped patched and then a complete coat of plaster 1/8" is then installed it should last a good decade if not more.
As to a liner yes it can be an option but the loose areas should still be removed to keep sharps from puncturing the liner. a non woven geotextile can also help with this. and then install and epdm rubber. there other options but that will provide the move flexable of your choices. The one thing it appears that it will not do so well with is the waterfall and the stream area . The bog will need to be cleaned out and have the water fall and stream remade. By the time you deal with all the wrinkles and overlaps of the liner it clearly will not have the look as the concrete did.

Third option is to chip out the loose plaster and or concrete patch them up and then apply a fiberglass coating or you can step down to a rubber spray coating or even a waterproof paint.

In short the 5500 is not a bad number if the company knows what is involved and does a nice job.