“OK, I’m going to take the sample right away,” said Patrick Fletcher, as he took a sample from the Potomac River. On Wednesday, Fletcher took bacterial samples from the Potomac River. “As a scientist, data is kind of my livelihood. The more data we have about this, the better,” he said of learning more about the river’s water quality. He’s a scientist, but in this role, he’s one of about 25 volunteers for the Potomac Riverkeeper Network.