That's a huge amount of effort (and carbon-fuel-powered energy) involved in capping the well. Based on the numbers they provide, I guess it's still worth it even if you consider the lifecycle of all the trucks and equipment and concrete. But that is quite an expensive procedure. Is it really so important to completely plug the hole with impermeable concrete? You can't plug it 1/3 of the way and then put a metal cap on with a 10-year maintenance schedule?