FOUR miles east of the White House, and in easy view of the Capitol dome, a dredge floats slowly back and forth between the banks of the Anacostia River, droning. Drawing water and sediment from the river bottom, it pumps it to the top of a nearby levee and spits it down the backside, forming a mud hill. This town, the busiest port for oceangoing vessels during colonial times other than Yorktown, Va., is now but a freckle on the long arm of the Chesapeake Bay. This river, cutting through the little-known back half of the nation's capital, is all but forgotten by most Washingtonians.
Four docks, built here in the late 1950s, are unused, rickety and rotting. Paper cups, hamburger wrappers, a diaper, and old tires hug the pilings - at least those that are not buried in silt.
``If you ever wondered what happens to the salt and sand they put on the roads all winter,'' says Doug Green, who sells boats from a parking lot next to the abandoned marina, ``it ends up right here.''
It all ends up here: sand and salt and motor oil and antifreeze and fertilizer and animal waste and countless other substances. The residue washed by rains and melting snow from city streets, lawns, parking lots, and construction sites finds its way to the Anacostia through perhaps a dozen streams in the suburban counties north of Washington.
The Anacostia, long in the shadow of its majestic neighbor the Potomac - which it joins just south of the Jefferson Memorial in the middle of the District of Columbia - suffers the plight of many urban rivers. Massive development along its banks has ruined its recreational value, and inadequate public access has bred ignorance of its trouble, say government officials and environmentalists.
``It would be a great source of recreation if it were only cleaned up,'' says Mr. Green, who grew up near here.
City, county, and state officials in the Anacostia watershed agree.
An accord signed by authorities in Maryland and the District in 1987 pledged regional cooperation in cleaning up the waterway. Under the agreement, the activities of state, county, and local officials are coordinated by the Metropolitan Washington Council of Governments (MWCOG). Another interagency group, the Interstate Commission on the Potomac River Basin (ICPRB), has been charged with fostering public interest in the Anacostia's plight.
That has not always been easy, says Beverly Bandler of ICPRB. And encouraging local newspapers and television stations to cover a recent cleanup effort by the Maryland National Guard proved fruitless. ``You drop the name Potomac and they show up there. You say Anacostia and they don't,'' Ms. Bandler says. (The Potomac River cleanup began in earnest only after record pollution in the summer of 1966 drew the attention of President Lyndon Johnson, some Anacostia-watchers say.)
Whereas the Potomac flows past Washington's prestigious Georgetown section and alongside major tourist areas, at points the Anacostia passes by tenements with the windows boarded up. Officials acknowledge that the low visibility and socioeconomic stress of the Anacostia community have, in some measure, put the river cleanup on a slow track.
Robert Boone, a stream coordinator with ICPRB, says there's a great task in simply changing the attitudes of residents and developers toward the river. For a long time, Mr. Boone says, ``the mentality was that all streams are gutters.'' But slowly, he says, that is changing.
One sign of change: A developer has offered seed money to start a private organization to preserve the Anacostia. In January, Boone says, he will leave his government job to create Save the Anacostia River - the first conservation organization to be devoted exclusively to the Anacostia River Basin.
Cleaning up the 100-mile tidal portion of the Potomac took more than a decade and over $1 billion. Restoring the 12-mile Anacostia is expected to take longer and cost more. The reason: a diffuse source of pollution.
``In the Potomac, pollution sources were easily identifiable point sources,'' says Wendy Chittenden, an environmental planner with MWCOG. ``All that was needed was to go into sewage-treatment plants and upgrade them.
``In the Anacostia, there is no single identified source,'' she says. ``The pollution comes from general urbanization.''
An explosion of development - gobbling up the countryside between Washington and Baltimore - has created thousands of acres of concrete surfaces. Such impermeable surfaces not only harbor the sediments that end up in the Anacostia, but also speed the flow of storm waters. And often, the fast-moving water will further erode unpaved lands and stream banks - compounding the sediment problem. In addition, experts say, toxic contaminants and dangerous nutrients tend to bond to silt particles - further concentrating pollution in the river. Such contamination may deplete the oxygen in the water, reduce or eliminate plant growth, and so destroy the habitat for aquatic life.
Furthermore, experts say, the pressure of tidal waters pushing up from the Chesapeake Bay into the Anacostia serves to trap much of the river's pollution at its mouth.
Increasingly, developers are required to mitigate the effects of development - by minimizing the impact of storm-water runoff at developed sites and by monitoring soil erosion on construction sites. But unfortunately, officials say, attention to such environmental details has not kept pace with development.
``Maryland has some fairly good laws dealing with sediment control,'' says Shannon Varner of the Maryland Public Interest Research Group. ``The problem is, they don't have enough people to go out and monitor them all the time.''
In response, Mr. Varner's group has organized and trained volunteers to walk the streams, spot pollution problems, and report them to local authorities for enforcement action.
Citizen involvement is modest, compared with the size of the problem facing the Anacostia. But changing the attitudes of residents and developers toward the Anacostia also helps a larger, even more complicated problem: preserving the nation's largest estuary.
``Just about anything that hits the water in Maryland is going to end up in the Chesapeake Bay,'' Varner says.