About 100 tons of concrete from the old Severn River Bridge is being dumped onto the river bottom this morning just north of the new bridge to form what conservationists hope will become a reef for oysters to help cleanse the water.
Wednesday, about 1,350 tons of oyster shells is to be blasted off a barge by high-pressure hose into the waters of Round Bay to form two more reefs.
The moves are part of the first large-scale effort to restore the Severn River, which has been heavily silted by development. The silt has smothered oysters, which filter pollutants from the water, and choked off underwater grasses.
Because the oysters they feed on have disappeared, many birds also have left the river.
Conservationists hope the new reefs will give oysters a place to grow again.
Oysters, which have been devastated in the Chesapeake Bay by disease and silt, need a hard surface to attach themselves to and grow. The concrete from the old bridge and the shells should provide those surfaces.
The two projects became intertwined this month when crews from Langenfelder & Son Inc., the company bringing the shells, noticed that their 50-foot-wide barge could not get upstream until a large part of the old bridge came down, said William Moore, office manager of the company in Stevensville.
The first two sections on the Annapolis side were gone at the end of last week, giving the barge access to the river.
William Moulden, a Sherwood Forest resident and conservationist, devised the project as a way to create oyster beds that would help naturally purify the water and attract fish, and would serve as a pilot program for children in his community's summer camp to study artificial reefs and aquaculture.
The children would start the oysters in a classroom tank and eventually move them onto the reef.
Mr. Moulden has pursued plans for the 3-acre artificial reef and two shell reefs through the state bureaucracy.
The first small load of concrete was dropped into the river last week, and the metal from the span was taken to be reused by the State Highway Administration, said Chuck Brown, SHA spokesman. The second load of chunks from the bridge deck is due to be placed by a crane on the river bottom today.
The Department of Natural Resources is supervising the work by Cianbro Construction Corp. of Baltimore.
Mr. Moulden, a member of the Severn River Commission and a vice president of the Severn River Association, has been praised by many who are working on the projects.