Ed Merrifield has spent nearly a decade patrolling creeks, suing polluters and challenging regulators — all in the name of restoring the Potomac River to a fishable, swimmable waterway.

But now, Merrifield, 65, says it's time to retire from the organization he helped build. He will be stepping down as Potomac Riverkeeper at the end of December. Matthew Logan, former president of the C & O Canal Trust and the Potomac Conservancy, will be taking his place.

Merrifield, a chiropractor by training who is rarely seen without his signature fisherman's cap or a Potomac Riverkeeper baseball hat, has always loved the Potomac. He helped form the Riverkeeper organization in 2000. In 2003, he stepped up to become Riverkeeper. At that time, the movement was just getting a toehold in the Chesapeake Bay region; now Riverkeepers patrol 18 of its rivers.

Merrifield preceded them all, inspired many of them, and even hired a few of them. He grew the Potomac Riverkeeper organization from a one-man band to a staff of nine, including Riverkeepers for the Shenandoah and the Upper Potomac. Volunteers swelled from a handful to a dedicated crew of 300.

Merrifield and his staff stopped illegal discharges from several sewage treatment plants in Virginia and West Virginia, forced Maryland to clean up massive lead deposits in Seneca Creek and took an active role in drafting more stringent permits for stormwater and poultry farms in all three states. He was also a major force in the eventually successful fight to make Maryland poultry farmers' nutrient management plans public.

To commemorate his retirement, U.S. Rep. Jim Moran of Virginia entered a tribute into the Congressional Record, and a flag flew over the Capitol in Merrifield's honor.

"Ed is a titan," said Chris Trumbauer, who patrols the West and Rhode rivers. "My favorite Ed line is, 'we're just trying to get to 1985' — a reference to the original time line in the Clean Water Act. Unfortunately, we're not there yet, but we're a little closer because of Ed."