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Shoaling Prevention Systems

Shoaling Prevention Systems. An innovative alternative to maintenance dredging. Natural Equilibrium. Dock Owners’ Concerns With Dredging. High & rising cost Limited number of disposal area options Time Investment Environmental Concerns Scheduling conflicts. Mechanical Dredging

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Shoaling Prevention Systems

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  1. Shoaling Prevention Systems An innovative alternative to maintenance dredging

  2. Natural Equilibrium

  3. Dock Owners’ Concerns With Dredging High & rising cost Limited number of disposal area options Time Investment Environmental Concerns Scheduling conflicts

  4. Mechanical Dredging • Clam Shell/Bucket Dredge • Consolidated Materials • Higher Impact on Water Quality Standard Dredging Techniques • Hydraulic Dredging • Cutterhead/Hopper Dredge • Unconsolidated Materials

  5. Shoaling Prevention Approach Suspended Sediment Turbo Unit Ambient Current Jet Discharge Mud Bottom

  6. Flood Tidal Current Ebb Tidal Current System Operation Dock Turbo Units (4 Total) Control House Shoreline Operation is synchronized with the tides

  7. Environmental Concerns Adjacent shoaling impacts Near-Field Far-Field Water quality impacts Turbidity Dissolved Oxygen Marine organism impacts Fish Entrainment Benthic Impacts

  8. Near-Field Shoaling Monitoring Wilmington, NC installation

  9. Far-Field Shoaling Monitoring 11 1 2 8 7 6 9 5 10 4 3 Grays Harbor, WA Installation

  10. NTU Turbidity

  11. Dissolved Oxygen Savannah, GA installation

  12. Dissolved Oxygen Dredging decreases D.O. levels up to 83% Slower currents result in less vertical mixing Water is more oxygen rich closer to the surface Oxygen injection option

  13. Hydraulic Dredging • Adverse Impact on Water Quality • Entrainment Rate of up to 0.594 Fish per Cubic yard (<36” only) • Mortality Rate 100% Marine Organism Impacts - Fish • Shoaling Prevention System • No Detectable Adverse Impacts on Water Quality • Entrainment Rate of up to 0.01 Fish per Cubic Yard (<4 inches only) • Mortality Rate <1% Savannah, GA installation

  14. Prall’s Island • Conventional Dredging • Complete Destruction of Benthic Environment • Resuspended Sediments Suffocate Benthos • Release of Toxins Marine Organism Impacts - Benthos • Shoaling Prevention • Preserves Benthic Community • Sediment Load Remains Unchanged • No Detected Release of Toxins

  15. Conclusions Mechanical Dredges have been demonstrated to be more environmentally impacting than Hydraulic Dredges. Hydraulic Dredges have been demonstrated to be more environmentally impacting than Shoaling Prevention Systems. Shoaling Prevention Systems are less impacting due to the high volume, low velocity design and continuous operation affecting only unconsolidated sediment. Shoaling Prevention Systems have been in operation for more than fifteen years and have an excellent track record.

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