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Does dredging help local wildlife in the long run?

Clay, sand, and silt left behind from dredging have been repurposed as marshes and wildlife habitats. Benefits to local wildlife include the removal of contaminated sediments and their relocation to safe, contained areas, and the possible improvement of water quality made by the restoration of water depth and flow.

There can be significant beneficial improvements from the use of clean maintenance dredgings to enhance mudflat and saltmarsh habitats and to mitigate losses of intertidal land through sea level rise and capital dredging operations.

A few ways dredging helps local wildlife are:

  • Removal of subtidal benthic species and communities.
  • Short-term increases in the level of suspended sediment can give rise to changes in water quality which can favorably affect marine life.
  • After the suspended sediments settle, the result is the smothering or blanketing of subtidal communities and or adjacent intertidal communities, which is used beneficially to raise the level of selected areas to offset sea level rise and erosion.
  • In soft sediment environments, recovery of animal communities occurs relatively quickly, and a more rapid recovery of communities has been observed in areas exposed to periodic disturbances, such as maintained channels.
  • In general, recovery times increase in stable gravel and sand habitats dominated by long-lived components with complex biological interactions controlling community structure.

These findings are supported by studies of the Georgia Estuary system, USA, which suggest that maintenance dredging has only a short term effect on the animal communities of the silt and clay sediments. Although almost complete removal of organisms occurs during dredging, recovery begins within one month, and within two months the communities were reported to be similar to pre-dredge conditions.

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Featured Project

Hurricane Damage Restoration

Florida Keys

Highlights:

  • Remote Island Location 3 miles from mainland in FL Keys
  • Hydraulic Dredging to Geotextile tubes
  • Automated Polymer Injection System for Material Dewatering and Clean Effluent Requirements
  • Dewatering site constructed on sectional barge at island location
  • Dredging, Dewatering, Hauling and Disposal all simultaneously
  • Geotextile tubes transported by barge back to mainland daily for offloading into trucks
  • Sensitive Marine Benthic Resource avoidance and protection integral part of project requirements

Background:

C&M Dredging performed an environmental restoration dredging project to reverse impacts caused by hurricane damage to an island resort in the Florida Keys. A canal system and basin system that was in place for barges and vessels that serviced the island resort daily had been filled in by hurricane-force winds and tidal surge.

The difficulty was that the project site was 3 miles from the mainland, on an island.

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