Reservoirs at the Conowingo have captured sediment for more than
60 years, amassing 160 million tons, along with household
garbage, street junk, an occasional carcass and rotting wood. As
they fill, the reservoirs designed to protect the bay are
“becoming a source of pollution,” said Robert Hirsch, a
hydrologist for the U.S. Geological Survey and lead author of a
recent study that found more sediment than ever splashing from
behind the dam into the Chesapeake. “The way to look at it is
that in the past these reservoirs were a very helpful trap for
so much of this material coming out of the Susquehanna basin.
They are now no longer a very effective trap,” Hirsch said. The
mass of sediment awaits another weather event such as Tropical
Storm Lee , which sent a record 4 million tons of sediment
surging into the Chesapeake, turning it brown with pollution.
Along with the sediment already collected at the dam, an
additional 3 million tons a year arrives via the Susquehanna,
starting in New York state. Last year, Ma