Read the full story from NPR.
The floodwaters from Hurricane Harvey had to go somewhere.
The storm dumped 50 inches of rain on parts of the Houston area in late August. Much of the water made its way through streets and bayous and eventually drained into the Houston Ship Channel, the busy commercial waterway that allows ships to travel between the Gulf of Mexico and industrial facilities around Houston.
In the weeks since, the water has drained away, but scientists believe many of the contaminants it carried have not.