Tonight, on News 12, our ongoing 'Failing Foundation' series this week puts a little-known, but fast-growing, threat under the microscope.

A startling monthslong Team 12 investigation finds that tens of thousands of people are living downstream from high-hazard dams that could lead to injuries, and even death, if repairs are not made.

COMPLETE COVERAGE - Failing Foundations: Check the condition of dams in your community  

There are more than 10,000 dams in New York, New Jersey and Connecticut.

Surprisingly, about a third of the ones that could cause the most damage are at risk of failing. “Unfortunately, dams will fail and if there are people living downstream of them, businesses, schools, other things, unfortunately, people could die. Or, even when in a failure, where you have an emergency action plan and people are evacuated in time, the devastation downstream is immense,” says Mark Ogden, of the Association of State Dam Safety Officials.

So, who's responsible and which of our local dams are most at risk? Our Senior Investigative Reporter Tara Rosenblum dives into the data.