Mr. Barbero said for the plug to have worked in New York, he would have had to have taken measurements and then built a custom-made balloon to those dimensions.
"To close a tunnel near the surface for surface runoff like what happened now is relatively easy," he said. "If we had been contacted some time ago, we could have easily designed one for that situation. If you want to seal a tunnel, I have a team that is ready to do this. We have the expertise."