Charlie, good ad in The Times. Here is an idea for a permanent and much cheaper solution to the liner problem. They line toxic waste dumps by mixing western bentonite (a clay from Montana?) into the soil which forms a liquid-tight bottom. When bentonite gets wet it swells up and flows into gaps and leaks and plugs them up.
Short of an earthquake opening a big crack it should last forever. If it were my lake I would broadcast it on the water like grass seed and not even bother to drain the lake. Who needs that mess, smell, and flies? I have used bentonite on the earthen dam on a very small pond and it really works. It is just like hand seeding rice. Throw it on, watch it sink and give it time to work.
I got the idea from the Minnesota or Wisconsin DNR that used broadcast seeders, like the ones used to over seed the park, but mounted on flat-bottom boats to fix a sand bottom lake that wouldn’t hold water.