The first rule of starting any project is to understand the current status of your site.
They obviously neglected to do a thorough exploration of mine and had no idea that the water level in mine was that far above grade. If they had they would have been more careful disturbing ground near an active seep.
The other thing that in retrospect should been done is making a study of the mine architecture relative to the ground surface to determine the likely source of the seeps.
Had they done that study they may have known that a shaft was close to the surface at that point and avoided disturbing the ground.
Of course depending on the age of the mine drawing may or may not be available.
Regardless of that the first thing that needed to be determined was the water level in the mine. The hydraulic pressure on the seep would be dependent on the height of the water in the mine.
Had they determined the height of water in the mine they might have had some idea of the problems they faced.
I wonder if they had any mining people or just environmental engineers. Most likely they wouldn’t tarnish their organization with people who once worked in a capitalist enterprise. One of the very few competent federal agencies I’ve dealt with was MSHA during the time period when they hired experienced miners.