Heavy rains caused a wastewater treatment plant at the Edgewood Area of Aberdeen Proving Ground to release some 250,000 gallons of partially treated sewage into the Bush River on Tuesday, base officials said.
Nearly 4 inches of rainfall within 24 hours sent the sewage from secondary clarifier tanks into a chlorine contact chamber and on to the river in Harford County, base spokesman Kelly Luster said.
The Bush River, which separates the Edgewood Area from the rest of the Army base, flows into the Chesapeake Bay. It was the largest spill into the river this year, according to the Maryland Department of the Environment database.
There aren't many spills reported in the Bush River, but they tend to be big and storm-related. Harford County reported a 1.8-million-gallon overflow from its Sod Run treatment plant in the aftermath of superstorm Sandy last October. In 2011, the county reported a 264,000-gallon overflow from Sod Run after Hurricane Irene hit in late August.
The last time Aberdeen Proving Ground had such a large spill was in July 2010, when officials reported a 2.5-million gallon overflow from the Edgewood Area treatment plant into King's Creek and the Bush River.
Luster said the county health department and the Maryland Department of the Environment were notified of the Tuesday overflow and signs prohibiting swimming, fishing, crabbing and shellfishing have been posted.
He said analysts from the Edgewood Area would continue to monitor the affected area to determine whether further treatment is needed.