As a nurse, Sharon Zimmer helped dialysis patients cleanse toxins from their blood. Now, the Port Tobacco resident is checking the temperature and health of Charles County's waterways.

Twice a month for the past three years, Zimmer and volunteers from the Port Tobacco Conservancy have traipsed through the woods and traveled by pontoon to test for harmful bacteria in two dozen spots along the river.

But members of the group have been underwhelmed by the Charles County Health Department's response to its findings.

"When we get the results back and the counts are high, we want someone to notify the public and put signs up," Zimmer said Tuesday of her testing for the disease-causing bacteria enterococci.

"We want somebody to take notice, and that is where we are having the problem."

In response this week to those concerns, also shared by residents of Swan Point, the Charles County Board of Commissioners directed health officials to expand their testing and take the lead in alerting the public to potential health hazards, especially near popular swimming and boating spots from Memorial Day to Labor Day.

"We need the structure and formality that the Health Department can bring to this," Commissioner Candice Quinn Kelly (R-La Plata) told health officials during the board's regular meeting Tuesday. "That will go a long way toward relieving the anxiety of citizens."

Commissioner Robert J. Fuller (D-St. Charles) agreed with that goal but cautioned that the county should not take over the job of state or federal environmental regulators.

"I'm not in support of Charles County taking responsibility for water that is not ours," he said.

Gary Davis, the department's environmental health director, said the new testing program would probably strain the county's resources. The department, he said, would continue to rely on volunteers such as the conservancy to help build a database of bacteria levels. The county could then determine whether certain areas require permanent signs.

The Port Tobacco Conservancy was assembled by a group of residents in 2001 because of concerns about a series of sewage spills from the La Plata Wastewater Treatment Plant. Jeffrey Ward, executive director, said those concerns have abated somewhat because of improvements to the plant.

But the group said the need for more prominent, permanent signs was highlighted this month after a power outage at the La Plata plant resulted in a spill of thousands of gallons of untreated sewage.

Signs posted on Valley and Rose Hill roads were typed on 81/2-by-11-inch pieces of paper, and the print was not visible from the road, Ward and Zimmer said.

In other business Tuesday, the commissioners signed off on new restrictions for developers and others seeking permits for outdoor burning. Burning is banned in Charles County during the summer because of air-quality concerns but will resume under the new conditions Sept. 1.

* Burning must be at least 1,500 feet from any occupied house or building unless it is contained and air is forced into the fire through mechanical means.

* Burning is prohibited within 600 feet of occupied buildings and on state holidays or weekends, from 5 p.m. Friday to 6 a.m. Monday.

* County fire communications officials must be notified 24 hours before burning begins.

For more information, call Mark Williams at the Health Department at 301-609-6751.