Moving pond - what to do with concrete? liner of old pond

Hi. I’m moving a pond by creating a smaller one next to it. First remove old pond water and liner (half of it anyway) then new pond earth can go straight in it.

But once I removed the plastic liner from the old pond I found it’s actually like a concrete or mortar like substance a couple of inches thick under. It seems to retain water.

I wondered what the easiest thing to do is to ensure when I do fill it in it’s not going to hold water and give me a bog where I grass over it. Needs to drain.

I thought either:
1) should remove ALL concrete. Hard work take ages
2) drill through various places to make lots of holes. I did drill through the base but doesn’t seem to be draining
3) remove chunks of it from the bottom, so leaving big gaps in places, no need to remove walled section. Thinking it would drain better this way.

Any other option? Hoping point 3 would suit might be the easiest and leave plenty of gaps for drainage.

Still might need to drill holes on the very bottom as it’s got water in I don’t know if I can remove the concrete or whatever it is under there.

P.S. the boulders on the right are a temporary makeshift retaining wall to keep the other half of the pond water in!

Thanks

Is it actually concrete ? Or could it be a mix of cement and sand intended to cushion and support the liner that's hardened?
Whacking a pick into it might break it up easier than you think? Or use an sds drill to make Swiss cheese

No I don’t think it’s concrete, but not sure what. But your description sounds more like it. It’s not as hard as concrete but it’s not smashing up when I whack it with a sledge helper, it dents. It’s softer that concrete.

I tried my hammer sds drill but that just makes a hole through and not cracks it up. So it’s a bit of a pain to get up as it’s not smashing into bits.

I’ll try my mattock pickaxe end.

but I guess I don’t have to pull it all up though? Just have enough gaps for drainage?

I think this sand/cement mix must have been the original liner before someone put the black membrane on because there’s a drain in this cement mix liner with a plug, to empty it I guess, but that’s utter pointless when the black membrane was put over it. The cement mix has a plastic liner beneath it, maybe that’s keeping the water in.

it seems a really over engineered pond!