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Dredging and Dredged Material Management « return to State of the Bay

The Tampa Bay region has developed a long-term plan specifically to address the issues associated with dredging and dredged material. This plan, a joint effort of the Tampa Bay Estuary Program and the Army Corps of Engineers, fosters coordination of dredging and dredged material management to maximize shared placement and beneficial use opportunities while minimizing the environmental impacts and costs associated with these activities. The plan is updated annually and is the driving force behind several recent pilot projects to explore innovative uses of dredge spoil.

Currently, dredging to maintain the bay's nautical channels generates about a million cubic yards of material each year, enough to fill Raymond James Stadium 10 times. Much of the sediment dredged during maintenance activities is deposited on two manmade spoil islands in Hillsborough Bay. Options for increasing the capacity of these islands are being studied; however, they eventually will reach capacity and alternatives will be necessary to accommodate the nearly 30 million cubic yards which will be created through the year 2030. Additional new spoil will be generated as a result of the Corps' Tampa and St. Petersburg Harbor Re-evaluation project, which is evaluating the need for additional passing and turning lanes, anchorage areas, creation of a loop channel, and several other navigational safety improvements to accommodate increased maritime commerce in the bay.

Finding environmentally useful ways to use the material dredged from the bay bottom will continue to be a key goal of the CCMP. Among the alternatives to traditional disposal of dredge spoil are: renourishing beaches and stabilizing shorelines; re-filling abandoned pits to restore tidal wetlands, re-creating longshore bars to aid in seagrass recovery, and filling of suitable manmade dredged holes in the bay.

A pilot project coordinated by TBEP and funded by a grant from the U.S. Environmental Protection Agency assessed the feasibility of filling dredge holes in the bay to improve fisheries habitat and encourage seagrass regrowth. Beginning in 2003, an advisory group convened for the project identified 11 priority dredge holes that could support seagrasses if filled to surrounding depth. The habitat value of the holes was then evaluated by a team of scientists to assess the existing fisheries utilization, benthic diversity and water quality.

Results from the research project indicated that most of the holes already were providing important habitat for a variety of commercially or recreationally important species. Water quality in most of the holes also was better than expected. As a result, the advisory committee recommended leaving 8 of the 11 holes as they are, and partially filling or enhancing three. A clear conclusion of the project is that each hole must be assessed independently to determine an appropriate management strategy.

Another possible use of dredged material is in the creation of shallow nearshore sandbars to help reduce wave erosion and facilitate seagrass recolonization in the quiet waters landward of the bars. In 2005, TBEP and a variety of partnering organizations initiated a multi-year pilot project to design and restore a degraded nearshore bar and monitor its impacts on surrounding areas. If successful, this project may pave the way for restoration of additional bars using dredge material of appropriate quality.

Upland disposal options for beneficial uses of dredge spoil also are being employed, including use of dredged material in habitat restoration projects at Cockroach Bay and in the Harbor Isles neighborhood of St. Petersburg. Additionally, Port Manatee plans to use the former state fish hatchery site to dispose of dredged material associated with port expansion.


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