By David A. Fahrenthold
Washington Post Staff Writer
Tuesday, September 7, 2010; 11:28 PM
The Potomac River is cleaner now than it has been in decades, thanks largely to upgrades at Washington's sewage plant - and the proof is on the river bottom, where thickets of underwater grass are replacing mud and murk, according to a new scientific study.
The study, released Tuesday, paints an evocative picture of the Potomac's rebound from the 1960s, when its bottom was bare mud, its algae-choked water was AstroTurf green, and President Lyndon B. Johnson called the river a national disgrace.
Today, the river is clearer and heavily carpeted with grass. Scientists found that the Potomac's critical grass beds had doubled in size since 1990.
"These conditions are actually better than they were in the 1950s. The portion of the Potomac that we're talking about was completely devoid of vegetation in the 1950s," said Nancy Rybicki, a scientist with the U.S. Geological Survey and a co-author of the study.
But despite that good news, the Potomac is still full of other pollutants that have led District authorities to warn about swimming in it and eating its fish. Its ecosystems have been scrambled by invasive species, including snakehead fish. And an unknown chemical in the water is making male bass grow eggs.
So, if the Potomac is an environmental success story, that shows how low the bar for success has been set - both for the long-troubled river and for the nation's other polluted rivers and bays.
"When this all started . . . the problems with the water were visible and palpable, for the most part. We had this green goop" on the water, said Ed Merrifield, an environmental activist whose title is Potomac riverkeeper. "What we're left [with] are the invisible problems, which can still be very harmful to us."
The study covered the period from 1990 to 2007 and 50 miles of river, from Chain Bridge downstream to Maryland Point in Charles County. It was an unusually wide-angle look at the Potomac's rebound, which has mirrored gains in Boston Harbor and Cleveland's once-flammable Cuyahoga River.
The Potomac, which begins in Appalachian valleys to the west, once teemed with oysters, sturgeon and shad, but it was poisoned by sewage from the growing capital. By 1969, authorities had pronounced the river "a severe threat to the health of anyone coming into contact with it."
Its comeback has been closely tied to the Blue Plains treatment plant, which handles waste from the District and parts of Montgomery, Prince George's, Fairfax, Loudoun and Arlington counties. Its outflow is a river in itself: about 300 million gallons a day of treated sewage, enough to fill RFK Stadium.
In the past decade, responding to mandates from federal regulators, the plant has added $1 billion in new efforts that allow bacteria to consume the algae-feeding pollutant nitrogen in sewage. The new study determined that between 1990 and 2007, the average level of nitrogen in the river fell by nearly half.
The result, scientists said, was less murk. With less algae in the water, more light gets through to the river bottom. Given the chance, the river's plants came back, the study found: first some nonnative species, then an expanding number of grasses that had always lived in the Potomac. They now cover 8,441 acres of river bottom - and help their own cause by filtering dirt and pollutants out of the current as it passes.
It's not just scientists who have noticed the difference. Steve Chaconas, a bass guide who has worked the Potomac for more than 20 years, said fish can hide and hunt in the cool waters under the leaves. So that's where he fishes, dangling lures at the edge of grass beds in tributaries like Broad Creek and Piscataway Creek.
"If you find grass, you'll find bass," Chaconas said Tuesday. Chaconas said that recent construction on the Woodrow Wilson Bridge seemed to destroy some nearby grass beds but that overall the river is "absolutely a much better place to fish."
But even as the Potomac demonstrates the success of clean-water laws, it also reveals their limits.
The river is tainted by other pollutants that don't flow out of a sewage-plant pipe. Mercury, belched out of power-plant smokestacks, settles on the water and taints fish. The chemicals that cause the river's "intersex" fish could be pesticides or industrial chemicals, or both.
"We're doing other marvelous things with chemistry . . . that also can get into the environment and in very low concentrations can have these effects," said Donald F. Boesch, president of the University of Maryland Center for Environmental Science. Blue Plains is planning about $900 million in further improvements, but it seems unlikely to solve what's altering the fish. "They're caused by different aspects of how we live," Boesch said.
Also, the improvement in the Potomac means that cleaner water will flow into the Chesapeake Bay. But it does not reveal a cure for fixing the bay's long-standing problems.
According to Environmental Protection Agency estimates, just 19 percent of the Chesapeake's nitrogen comes from wastewater-treatment plants like Blue Plains. But 39 percent comes from manure and fertilizer washing off farms, and 12 percent comes from animal waste and fertilizer that flow into urban storm sewers. Fixing those systems will require much more money and perhaps unpopular crackdowns.
In recent days, state governments around the Chesapeake watershed have submitted detailed plans describing how they would solve these problems. The EPA says it will take two weeks to declare if they are sufficient.
"Where we've had control and we've had funding, we're starting to see the results of doing the right thing. The difficult thing ahead is the non-point sources" where pollution doesn't flow through a pipe, said Beth McGee, of the nonprofit Chesapeake Bay Foundation.
"We've solved maybe 20 percent of it," she said.