Polluted Potomac cleans up its act
River’s health best in years, study says
WASHINGTON — The Potomac River, once so polluted it was labeled a “national disgrace,’’ is now the cleanest it has been in decades — its comeback signaled by the re-growth of large areas of underwater grasses, according to a new scientific study.
The study, announced this week, details the Potomac’s slow transformation into an environmental success story.
The authors found that improvements at Washington’s Blue Plains sewage plant had cut down on choking, unnatural algae blooms, and that — once the water became cleaner and clearer — native plants rebounded, helping to clean the river further.
Scientists examined the stretch of river in the 50 miles downstream from Washington’s Chain Bridge.
Since 1990, they found, the amount of one key pollutant in this area had dropped by half.
Over the same period, the amount of grasses doubled, transforming the river bottom from a mud flat into a kind of underwater forest, more suitable for fish and blue crabs.
“These conditions are actually better than they were in the 1950s,’’ said Nancy Rybicki, a scientist with the US Geological Survey and an author of the study. “The portion of the Potomac that we’re talking about was completely devoid of vegetation in the 1950s.’’
She said the study signaled that millions spent to clean up the sewage plant had produced real results. “We are seeing change in habitat,’’ Rybicki said. “It’s paying off.’’
This good news underlines a striking trend in recent environmental history.
Some terribly polluted urban waterways have rebounded — one of the best examples is Boston Harbor — and the cause has usually been cleanups at sewage plants or factories.
It has proved much harder for authorities to reduce pollution that does not come from a pipe, such as the manure and fertilizer that washes off of farm fields.
Pollution from farms and city storm sewers — diffuse problems, and expensive to fix — have continued to trouble such water bodies as the Chesapeake Bay.
But the river’s health has improved with changes at Blue Plains, the massive plant in far Southwest Washington that treats waste from the District and surrounding counties.
The plant has spent about $1 billion to upgrade its treatment in the past decade, said George Hawkins, the general manager of D.C. Water, which runs the plant. In the next five years, Hawkins said, the plant will spend $900 million more for improvements.