Presentation on theme: "Dredging the Chesapeake Bay The 1999 Debate Heather Beall Intro to Coastal Management November 4, 2004."— Presentation transcript:
Dredging the Chesapeake Bay The 1999 Debate Heather Beall Intro to Coastal Management November 4, 2004
Where and Why to Dredge? In the Chesapeake Bay, around the harbors and tributaries. Sallow estuaries make it difficult for large shipping vessels to navigation into the harbor. Dredge in order to deepen water in order for ships to get to port and the dredging need to be continuous dredging to ensure depth.
The Debate Whether to dump dredged material (silt and clay matter) in to Site 104, which is a 4 mile deep trench or not. Site 104 was a dredged sediment dumping ground until 1975, when NOAA declared it a “discontinued dumping ground”.
Opposing Sides Environmental Marylanders Fear that the sediments will release stored up nutrients and contaminants in to an already sediment overloaded bay. Also feel that it is unfair for them to pay heavy fines when The Army Core of Engineers will be able to place 18 million cubic yards of sediment in the trench. Farmer have used no till and buffer strips as a method of farming, construction sites use sediment fences and hay bales. People have worked hard to protect the bay and don’t want their hard work reversed. Business Marylanders Believe it is necessary. The Baltimore Harbor area provides more than 127,000 jobs and nearly $18 million worth of economic benefit. Estimated Yearly Sediment Input into the Chesapeake SourceAmount of Sediment Rivers4.3 million cubic yards Shoreline Erosion 4.7 million cubic yards
The Science Report Was created by Don Boesch, the president of The University of Maryland Center for Environmental Science and 16 other scientists. Information was gathered from the scientists who work on issues relevant to the dredging issue. It was created to give to the Army Core of Engineers. To help in their decision of whether to dump dredged material in Site 104. The report focused on four different issues of concern. 1. Effects on Nutrient Loading 2. Transport and Fate of Dredged Sediments 3. Effects of Sediment Contaminants 4. Effects on Fish Habitats
Effects of Nutrient Loading Concern Placing dredged material in Site 104 would cause release of built of nutrients in to an already nutrient overloaded bay. Science Report Results Would only add a small fraction of phosphates and nitrates to the water. The input of nitrogen would equal less than 1% of what is put in from the land and the atmosphere in the next five years. Would only cause algal blooms locally and only for a few weeks. Would not affect algal biomass nor it would it cause a reduction of oxygen in the bay.
Transport and Fate of Dredged Materials Concerns If the sediment will drift off Site 104. If the characteristics of the bottom the trench will be affected. Science Report Results The physical characteristics of the bottom of the silt and clay trench will not change dramatically. Only about 6-12 percent of dredged material will escape from the trench causing a small plume of sediment that will settle out within hours. The sediments that are eroded by the tidal currents would mostly be replaced along the deeper channels of the bay.
Effects of Sediment Contamination Concerns The new dredged material placed in the trench will cause built contaminant to be released into the bay. Science Report Results Toxic compounds are generally bound to the silt and clay particles so the threat of toxic effects is quite small. The toxics on the surface of the dredged material once placed is very similar to the toxic that are on the surface already. Contaminants could also be taken up by organisms for a short period after the placement.
Effects on Fish Habitats Concerns By placing dredged material in the trench it will cover and harm and force out fish that live in the trench. Science Report Results Because the trench is located in the narrowest reaches of the bay and the water is deep it tends to be warmer than other surrounding bottom areas during winter. This makes it an important place for migrating fish moving to complete their life cycles. It also acts as a thermal refuge during the cold winter.
The Results It is still undecided if Site 104 will be used as a dumping ground for dredged material. On December 19, 2001 it was signed in under the Water Resources Development Act of 1999, as a five year dredging project. In February of 2002 it was decided that the first dredging project would be at the head of the Fort McHenry Channel. All the 4.39 million cubic yards of sediment will be placed on Hart-Miller Island. This first project started in March of 2002 and was completed in August of 2003. The first dredging project cost 30.5 million dollars. 67% was paid by the federal government while the other was 33% was paid for through the state.