1. Drain the reservoir, then repair any cracks and put waterproofing (they make a trowel-on concrete like spackling) on the inside surface.
2. Install a flexible sheet plastic liner or bladder (may or may not require draining the reservoir.
3. Don't drain the reservoir but have a not-so-deep sea diver go down and patch any cracks with hydraulic cement.
States can help recovery from hurricanes and tornadoes by not requiring due digence or prompt and timely correction of substandard conditions, and by providing continued liability insurance where companies drop homeowners.