Anne Arundel County officials were still trying yesterday to assess the damage caused by a "catastrophic" weekend spill that sent about 3 million gallons of sewage into a tributary of the Magothy River.
Crews closed the break Sunday - 24 hours after a corroding 36-inch line made of reinforced concrete collapsed at the Mill Creek Pumping Station in Arnold - but voluntary conservation efforts remain in place for about 11,000 households and businesses in Millersville, Severna Park, Arnold and Pasadena until a permanent repair can be made.
County officials are trying to measure the extent of the corrosion of the compromised line, which was installed when the pumping facility was built in 1973. Also, state officials are helping to determine the environmental impact to nearby wetlands and Mill Creek.
County officials said they hope to reach answers on both fronts this week.
The spill is believed to be the county's worst in at least 15 years, said Pam Jordan, spokeswoman for the county's land-use office.
"Most spills don't involve a collapse," Jordan said. "This was a worst-case scenario."
Jordan stressed that the break has not compromised the safety of drinking water, only the ability of the sewer system to handle wastewater in affected communities along the Broadneck Peninsula.
Mill Creek will remain closed to recreational use, and county health officials have recommended against fishing and crabbing there. Anyone coming into contact with the water should immediately wash with soap and warm water, they said.
"The sewage will pass along. ... Nature will ultimately take care of itself," Jordan said.
Crews were hopeful they could contain the break Saturday, but the collapse formed a sinkhole 100 feet in diameter and clogged the pumping station with mud and sewage. The break has been contained with a smaller bypass.
The sewage break marked the fourth to spill at least 10,000 gallons - the threshold level at which the state requires notification - in the county this year. The largest occurred March 7, when a county contractor drilled through a line, causing 120,000 gallons of sewage to flow into Cypress Creek, another Magothy River tributary.