At Hinckley Elementary School, students file into bathrooms during a break to use the toilets and sinks. As they make their way back to class, wastewater from the bathrooms travels to the Hinckley wastewater treatment plant, moves through the plant, goes to the Grindstone River, down the Kettle River, and into the St. Croix River. After a 92-mile journey, the wastewater ends up into Lake St. Croix.