Concrete that once blocked fish from swimming up the Patapsco River to spawn has a new life as home for aquatic creatures at the bottom of the Chesapeake Bay.
Water cannons blasted chunks of the demolished Simkins Dam off a barge Wednesday, completing the structure's transition from a river barrier to an oyster reef the size of two football fields. On Thursday and Monday, the Chesapeake Bay Foundation will seed the site at the mouth of the Chester River with 4 million baby oysters.
"This is definitely unique in dam removal projects," said Serena McClain, restoration director of the nonprofit group American Rivers.
The concrete chunks, most the size of soccer balls, rolled and rocketed off the barge deck before disappearing into 20 feet of water. When the twin cannons finished one pile, a massive yellow excavator moved another into range.
"People hear about dam demolition and they think waste. This is recycling at its best," said Stephanie Westby, oyster restoration manager for the National Oceanic and Atmospheric Administration. "It's a win for the fish in the upper Patapsco and a win for the fish in the bay."
NOAA paid $2.5 million for the dam removal last winter and $300,000 for the reef project.
Eliminating Simkins was part of a long-range plan by state officials and American Rivers to clear four dams and open 42 miles of the Patapsco main stem and 374 miles of tributaries to improve water quality and habitat for fish and other species. Eventually, officials hope shad and herring will return to their native spawning grounds and eels will carry water-filtering freshwater mussels upstream.
Union Dam, upstream of Simkins, came down early last year. Bloede Dam downstream is next, perhaps in 2013.
But removing Simkins wasn't the end of the process. The rubble that might have gone to a landfill — 2,800 cubic yards worth — was viewed by state officials, NOAA and the Chesapeake Bay Foundation as suitable material for an oyster reef.
"There's not enough oyster shell to build new reefs, so we have to look at other things," said Westby. "Historically, oysters were found at this location, so we hope that gives them a good chance to take hold again."
The concrete was separated from other construction materials, and iron reinforcing bars were removed. Boulder-size chunks were broken into smaller pieces to create nooks and crannies for fish. All of the material was tested for contaminants before being cleared for use, Westby said.
A number of sites in the bay were considered, including one near the mouth of the Patapsco River. Representatives from the Chesapeake Bay Foundation, the U.S. Fish and Wildlife Service and the Maryland Department of Natural Resources met with conservation groups, watermen and recreational anglers to get their blessing. Ultimately, cost and the state's oyster restoration plans focused attention on an area south of Rock Hall in Kent County.
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Designers worked with the Army Corps of Engineers and the Coast Guard to build a reef that would not impede vessels. The entire process took two years.
The Simkins project fits into an ambitious program that has placed or expanded more than 20 artificial reefs in the bay since 2002, using clean rubble from Memorial Stadium, the demolition of the old Woodrow Wilson Bridge that spanned the Potomac River and decking from the Bay Bridge.
Federal and state biologists are looking for other materials. Next year, the Maryland Artificial Reef Initiative will be testing limestone and granite as possible oyster and mussel habitat at a two-acre site at Hail Cove on the Chester River.
But until a new material can be found, there's concrete. Only one obstacle remains between Ellicott City and the mouth of the Patapsco: Bloede Dam in Patapsco Valley State Park near Elkridge. Money is tight, but preliminary planning and public outreach is under way, said Jim Thompson of the Department of Natural Resources.
Westby is already sizing up that 220-foot-long concrete structure.
"If we have the money, we'll find a site," she said.