Indeed, some of the rivers in the poorest health - the Patuxent, Severn, South and West - are those where many homes are on septic systems, said William C. Dennison of the University of Maryland Center for Environmental Science.
While a conventional septic system is designed to capture solids in a tank and neutralize disease-causing bacteria, the nitrogen seeps out unchecked through the drain field into groundwater and nearby streams.
In contrast, nitrogen-removing systems use motorized fans or pumps to inject air into the waste, stimulating bacteria that remove nitrogen from the wastewater, converting it to a gas, which is then expelled into the air. Such systems can reduce nitrogen levels in effluent by half or more, said Thomas H. Miller of the Maryland Cooperative Extension.
The state has been encouraging homeowners to voluntarily upgrade their septic systems, offering to cover the roughly $12,000 added cost of nitrogen-removing technology over a conventional system with funds raised from a $30 annual fee assessed on all current septic owners. To date, the Maryland Department of the Environment has underwritten 638 upgrades or replacements of old, failing septic systems.
At least three counties - Anne Arundel, Queen Anne's and Worcester - already require nitrogen-removing septic systems for new homes along the waterfront.
When signed into law by the governor, the state legislation will require the special systems for any new or replacement septic system within 1,000 feet of the Chesapeake and its tributaries, as well as along the coastal bays near Ocean City. Officials estimate there are 51,000 septics in those environmentally sensitive zones.
The measure requires the Department of the Environment to help homeowners pay for the added cost of a nitrogen-removing system, but only "if sufficient funds are available."
Realtors and homebuilders complained that the state should be required to pay for the systems if it was going to mandate them. Rural legislators also bridled at the requirement, which they said could hit the pocketbooks of struggling farmers and watermen.
"It's another increase in the cost of housing," said Michael Harrison of the Home Builders Association of Maryland.
But advocates said that while there is ample money to pay to replace existing septic systems near the waterfront, they did not believe the state should have to pay for pollution reductions that ought to be a condition of building a new home by the bay.
