Scenes of an Effort Impeded Unfold Across Chesapeake Watershed

Bentley, who designs satellite-guidance systems for NASA in Greenbelt, lives near the waterfront in Stevensville, Md., just across the Chesapeake Bay Bridge. His 30-year-old septic tank was working as it was meant to, which meant it was slowly leaking nitrogen into the dirt, where groundwater carried it to the bay.

Of all the Chesapeake's problems, this is the kind the cleanup has done the least to fix. Nitrogen from urban and suburban sources -- greasy city streets, fertilized lawns and a growing number of septic tanks -- has gone up 14 percent since 1985, and phosphorus has gone up 16 percent.

The problem: Cleaning up these sources requires digging up storm water pipes. Building "rain gardens" near mall parking lots. And tearing up Bentley's lawn.

In 2000, the state proposed requiring cleaner septic systems in areas near the shore; that idea was shot down after builders and real estate agents said it might chill the market for new homes. And, until 2006, Maryland homeowners who fixed the systems on their own got no reimbursement from the state.

"We knew, collectively, that septic systems were a source. But there wasn't a program in place," said Shari T. Wilson, the state's secretary of the environment.

There is now, funded by Maryland's "flush tax." Bentley got his tank replaced this year, which cost more than $10,000. The state paid all but $350.

That leaves at least 50,660 septic systems to fix in Maryland, officials say.

The state can afford about 650 a year.