“Back then, the river was embarrassing. It was a conveyor belt of trash,” said Miller as he handed me a photograph showing a tributary choked with broken appliances, tires, plastic kiddie pools and even a rusted blue car.

Chief among the junk: tires. Each year, the United States discards nearly 300m tires. While most are reused or recycled, millions slip through the cracks.

When Miller paddled past a tree where a tire had speared itself “like an olive on a toothpick”, he realized that tire would be there forever, unless someone did something.

So, he did. That fall, Miller gathered hundreds of tires then recruited friends to corral them downstream. Lacking boats, he devised a way to fill old tires with empty milk jugs to make them buoyant.