The issue can often be detection as well. Our blowdown line (the line that pumps non-radioactive water from our cooling lake which we use as a dilution source for our liquid releases) releases ~25,000 gpm through a 4 foot wide concrete pipe. We release at most 20 gpm of heavily diluted waste water into this 25k gpm which then further dilutes in the river we make up/letdown to which has flows between 450,000 to 9,000,000 gpm.

The problem is detecting a 1-2 gpm leak through the pipe into the ground when you're pumping tens of thousands of gallons per minute.