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For those who are interested in technical data and environmental analysis, you will find the latest studies and reports available for review and download. "Waterway Infrastructure Report" In September 2008, Tetra Tech completed two surveys of infrastructure conditions on the tributaries of the Pocket. The purpose of the surveys was to assist in the development of the final dredging plan for the tributaries as well as to document pre-construction conditions. The material filling up the bottom of the Pocket has been tested by Tetra Tech, with encouraging results. We have summarized and simplified the report findings below. For the full report, click here. Seagrasses, a type of marine seed plant, are abundant at the mouth of Manatee Pocket. They grow best in shallow waters, where they can absorb warm sunlight. The edges of the Pocket provide a perfect environment for the beds, creating both a food source to marine animals and a shelter for their young. Yet while the Pocket provides an ideal location, the existing muck is preventing seagrass life in the majority of the Manatee Pocket. One of the dredging project’s main goals was specifically designed to remedy this, by carefully preserving existing seagrass beds and creating new growth areas. The project will remove muck along the shoreline and expose the sandy substrates below, so that seagrasses can once again take root and flourish. With all of this in mind, the objectives of the study were to identify how the muck is distributed in the channel, and then to locate, characterize, and map any seagrass beds that are present. The results: Muck Distribution: Substrates are primarily comprised of organic muck or some combination of sand and muck elsewhere. Clean sand exists near the mouth of the Pocket and at varying depths below the muck layer. Character of Seagrass Beds: Three species of seagrass were identified within the Manatee Pocket: Johnson's seagrass, paddle grass, and shoal grass. Seagrasses are mainly present in shallow areas close to shore and will not be affected by the proposed dredge footprint. Location of Sea Grass Beds: The beds are very patchy and mixed in their distribution; however some general observations were evident. Shoal grass is usually dominant closest to the shoreline, and is typically replaced by Johnson’s and paddle grass species further from shore. Although paddle grass is generally found in the deepest areas, it is restricted to depths of less than about five feet. Mapping of Sea Grass: The beds are somewhat ill-defined because of the patchy distribution and sparse coverage of the seagrass. "Within each bed, sparse to dense bottom coverage of grasses is interspersed with areas of barren substrate". Small grass beds mixed with Johnson's and paddle grasses occasionally reach collective bottom coverages of up to 75 percent; however "total bottom coverage within each bed as a whole was less than five percent". Although 82 grab samples were collected within the southern portion of the Manatee Pocket, no seagrasses were collected in the grabs. In fact, substrates were found to consist almost entirely of organic muck and were absent of any obvious macroinvertebrate fauna, with the exception of a single crab. Seagrasses are likely found less in this portion of the Pocket due to the combination of low light transmission and unsuitable substrates. Note to readers: Based on the results of the Seagrass study, the permitted dredging plans have been specifically tailored to preserve all of the seagrass beds. As a result, there will no permanent effects to seagrass beds. Any temporary effects will be negligible. For an Aerial Illustration, click here. "Waterway Infrastructure Report" Map of the Manatee Pocket Dredging Project This is a detailed map of the project, including the locations of seagrass beds and the proposed channel layout. Permit for the Manatee Pocket Dredging Project. Feasibility Report Seagrass Report Report on the Sediment and Water Testing program Geophysical Survey Private Dredging Private Dredging-Useful Information For a full graph of the Manatee Pocket Project, click here. |
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