Last summer, after a week of heavy rain, some officials voiced concerns about the dam at St. Mary's Lake north of Callaway.

But that St. Mary's County dam held up through several days of tropical downpours that hit the Washington region during the last week of June.

State Sen. Roy P. Dyson (D-St. Mary's) summoned inspectors to the dam, fearing that Great Mills residents living downstream from the lake could face a scenario similar to that of those living in Montgomery County's Aspen Hill community, which was evacuated because the Lake Needwood dam there was weakened by the record-breaking rainfall.

Andrew Hanas, chief engineer for the state Department of Natural Resources, has updated Dyson on the emergency action plan that would kick in if the dam weakened or failed. The plan details how water would be directed to an emergency spillway and how the Great Mills area would be evacuated.

The 250-acre lake at St. Mary's River State Park was created in 1975 when the dam was built for flood control.

Water levels are monitored once a week -- or daily during a weather event -- via cylindrical observation wells drilled into the dam.

Officials gave the dam a clean bill of health after last summer's checkup.