When environmentalist Brent Walls saw a milky-white substance in a stream flowing through a rural stretch of central Pennsylvania, he suspected the nearby rock mine was violating the law.
Recent rains had filled the ponds at the mine that allow sediment to settle out of the water, but Walls couldn’t easily take a look because they were surrounded by private property. To quickly investigate and avoid trespassing, Walls captured images of the area with his drone.
