I have an idea for plugging the leak, but as I am not a scientist, I have no idea whether it's sound or not.
I drive around Detroit every day for work. I see vacant lots with lots of used tires dumped on them, and I assume this is the case in other big, fading, rust-belt cities. This is due to small tire companies disposing of their used tires in such a way to avoid paying the money to the disposal/recycling companies as required by law (the big stores, like Goodyear, Belle Tire, Discount Tire all have surcharges for disposal of used tires).
But regardless, the tires are still made of a material that can be recycled. Gather the old tires, melt them down and shoot that material at the leak in their "junk shot" plan. Maybe there's even a way to use to metal radial parts, too. Then surround the rubber with something more solid like concrete. I doubt that's a permanent solution, but it could work temporarily until they come up with a better plan.