A year ago, Gov. Larry Hogan put out a call for private industry to suggest how Maryland should address the pollution that was quickly piling up behind the Conowingo Dam — a staggeringly expensive problem that many policymakers thought could wait.
For nearly a century, the dam had stopped silt and polluting muck in the Susquehanna River from spilling into the Chesapeake Bay. There was wide agreement the reservoir behind the dam would eventually reach its capacity, and stop holding back the pollution.
But scientists now agree the dam is not stopping anything at all.
"I wouldn't so much say it's worse than we thought," said Robert M. Hirsch, a research...