I have to chuckle a bit at your optimism... "leaking isn't even possible"
Lots of folks here with lots of good clay but still due to improper compaction, improper construction of the dam, the base keyway, etc have a leaks.
You could consider a sand layer on top of the clay and then adding a polymer that grabs the granules of sand and binds them together into a hard surface (research soilfloc on the forum)
Of you could do as you suggested and add some type of setting cement.
Lol, yeah, I shouldn't have said that, as now it will....,.
With that said, it was nearly full all summer and there was no bleed out below the damn.
My woman and I talked about lining it all with sand, but fear that the sand will not hold on the slops, as there is nothing to bind it, as it doesn't pack like clay does. We had also talked of using a pre-mixed sand/portland mix and putting it over the clay and mixing it in.
I'll look up soilfloc.
Thanks
