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PIANC report #100 Dredging Management Practices for the Environment 1 Axel Netzband (Chairman of WG 13) Working Group PIANC Envicom 13 Best Management.

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Presentation on theme: "PIANC report #100 Dredging Management Practices for the Environment 1 Axel Netzband (Chairman of WG 13) Working Group PIANC Envicom 13 Best Management."— Presentation transcript:

1 PIANC report #100 Dredging Management Practices for the Environment 1 Axel Netzband (Chairman of WG 13) Working Group PIANC Envicom 13 Best Management Practices Applied to Dredging and Dredged Material Disposal Projects for the Protection of the Environment PIANC Report 100 Dredging Management Practices for the Environment – A structured selection approach Navigating the Environment – Managing Risks and Sustaining Benefits New Orleans, October 28, 2009

2 PIANC report #100 Dredging Management Practices for the Environment 2 Starting point A wide variety of environmental management practices exists with the intention of reducing or eliminating perceived environmental risks. Restrictions and constraints may have significant logistical, execution schedule and cost implications. Balance the benefits of constructing and maintaining navigation infrastructure in a cost efficient manner and the recognised need to care for the environment. Make knowledgeable choices among existing BMPs, and identify promising alternatives to routinely applied practices.

3 PIANC report #100 Dredging Management Practices for the Environment 3 Definition of Management Practice A Management Practice is a practice intended to improve the environmental performance of a dredging project, inclusive of excavation, transport, and placement of dredged material. PIANC Envicom 13

4 PIANC report #100 Dredging Management Practices for the Environment 4 Description of Management Practices

5 PIANC report #100 Dredging Management Practices for the Environment 5 Environmental Windows (U.S.) A temporal constraint placed upon a dredging or dredged material disposal operation to protect biological resources or habitat. The window is the period during which dredging may occur. A seasonal restriction represents the period during which the operation is prohibited. … are a temporary moratorium on dredging, which equates to zero tolerance of risk … are institutionalized by default … have no predetermined performance standards

6 PIANC report #100 Dredging Management Practices for the Environment 6 The Precautionary Principle Where there are threats of serious or irreversible damage, lack of full scientific certainty shall not be used as a reason for postponing cost-effective measures to prevent environmental degradation. Principle 15 of the UN Rio Declaration on Environment and Development (1992)

7 PIANC report #100 Dredging Management Practices for the Environment 7 Is dredging clean sediment a risky business? With the exception of responses to exposure to contaminated sediments, many other forms of impact remain hypothetical and exceedingly few have been shown to be biologically meaningful at the population level Proving the negative (no impact) is essentially impossible

8 PIANC report #100 Dredging Management Practices for the Environment 8 Turbidity, Nature, and Human Activities

9 PIANC report #100 Dredging Management Practices for the Environment 9 Dredging impacts

10 PIANC report #100 Dredging Management Practices for the Environment 10 EU Communications Where there is scientific uncertainty, implement evaluation procedures and take appropriate preventive action in order to avoid damage to human health or to the environment. Renewed Sustainable Development Strategy, European Council (2006) The precautionary principle should be considered within a structured approach to the analysis of risk which comprises three elements: risk assessment, risk management, risk communication. The precautionary principle is particularly relevant to the management of risk. EU Communication on the precautionary principle (2000)

11 PIANC report #100 Dredging Management Practices for the Environment 11 Identification of Environmental Effects Physical Change Potential Environmental Effect Release of particulate matter Reduced light penetration Release of nutrients Release of toxic chemicals Release of organic matter User conflicts Dredging equipment presence Removal of sediment Placement of sediment Altered topography/ bathymetry Sedimentation induced by dredging Sedimentation induced by disposal Re-suspension of sediment matrix into water column Rock blasting Re-suspension of sediment matrix into water column Examples of impact Behavioural / physiological responses to increased suspended solids

12 PIANC report #100 Dredging Management Practices for the Environment 12 From Effects to Management Practices Physical Change Release of particulate matter Re-suspension of sediment matrix into water column NumberManagement Practice M1Select appropriate contracting approach and contract format M2Select the contractor based on best value or use pre-qualification to limit the bidders to qualified bidders. M3Use performance specifications (instead of method specifications) to allow operator flexibility M4Prepare project and site specific environmental and construction monitoring program. M5Use Adaptive Management approach during construction P1Reduce Dredging Requirements (i.e., horizontal and vertical extents) P2Optimise / increase dredging design for environmental benefit. P3Make changes to physical system to reduce sedimentation into project area P4Reduce or eliminate the need to dredge through using natural recovery and capping/cover options P5Sustainable placement of dredged material within the same sediment system P6Use of dredged material P7Optimise the design, location and configuration of the aquatic placement site P8Select appropriate placement option. P9Use clean dredged material for caps /covers over unsuitable sediment P10Habitat and species protection measures: impact minimisation P11Habitat enhancement options: enhance habitat development E1Use appropriate type and size of dredging equipment for the project. E2Select most appropriate type and size of mechanical dredger E3Select most appropriate type and size of bucket- ladder dredger. E4Select most appropriate type and size of hydraulic dredger E5Select most appropriate type and capacity of dredged material transportation method E6Select most appropriate type and size of haul / transport barge E7Select most appropriate type and size of barge offloading equipment E8Select most appropriate type of hydraulic pipeline E9Use special environmental equipment E10Use hydrodynamic dredging E13Modify existing equipment, if necessary, to make it (more) fit for purpose. E14Apply degassing systems to hydraulic dredging system E18Apply Green valve or Environmental Valve E19Filter overflow effluent from transport barges to improve the water quality into receiving waters. E20Inspect and maintain equipment in good working condition I1Tidal operations: flood/ebb and spring/ neap I2River Discharge dependent operations I3Time based operations: days / weeks/ day-night / weekdays-weekends. I4Seasonal restricted operations (Environmental Windows). I5Wind direction related operations. I6No access / No activity areas I7No bed contact zones I8No effect zones / Impact avoidance zones. I9Buffer zones Dr1Modify rate of operations Dr2Modify rate of excavation of mechanical dredgers. Dr3Modify mode of excavation for mechanical dredgers. Dr4Modify rate of excavation for hydraulic dredgers. Dr5Modify mode of excavation for hydraulic dredgers. Dr6Modify mode and speed of mechanical transportation (e.g., barges) Dr7Bed-levelling or ploughing to reduce over-dredging, in combination with other dredgers Dr8Reduce or eliminate overflow during hydraulic loading at hoppers or transport barges Dr9Reduce or eliminate use of lean mixture overboard pumping. Dr10No barge overfilling, when loading by mechanical dredgers Dr11Re-circulate process water from hopper or barge during loading. Dr12Rinse grab / bucket of mechanical excavator before lowering in water Dr13Use spill plate/apron during offloading Pl1Apply optimal sediment deposition method Pl2Hopper/ barge bottom door placement Pl3Rainbowing / sidecasting / spraying Pl4Direct hydraulic pipeline placement Pl5Use of baffle plates in pipeline outflow Pl6Use of tremie pipe Pl7Use of diffuser Pl8Use of Spreader Pl9Optimise rate/ concentration of mixture. Pl10Re-circulate hydraulic transport water from placement site back to hydraulic dredger Pl11Return placement site effluent to dredging site Pl12Optimize layout of storage basin. Pl13Optimise dimensions and location of overflow weir (i.e. waterbox) Pl14Optimise location of inflow point (i.e. hydraulic discharge end) Pl15Add a separate siltation pond to the disposal site Pl16Use additives / flocculants C4Use silt curtains to reduce loss of sediment from dredging operations. C5Use sheet pile walls to contain suspended sediments within enclosed area C6Use bubble curtain to limit spread of re-suspended sediments C7Dredger within enclosed compartment (e.g., caissons) to limit spread of re-suspended sediments. C14Use fish or marine mammal guiding systems.

13 PIANC report #100 Dredging Management Practices for the Environment 13 BMP selection process Project Description and Conceptual Design Environmental Characterisation Final Project Design Project Construction Monitoring Risk Communicatio Assessment of Impact and Risk Risk acceptable? MP Selection

14 PIANC report #100 Dredging Management Practices for the Environment 14 BMP Evaluation Matrix

15 PIANC report #100 Dredging Management Practices for the Environment 15 Definition of Best Management Practice A practice, or combination of practices, that is determined after problem assessment, examination of alternative practices, and appropriate stakeholder participation to be an effective, practicable (including technological, economic, social and institutional considerations) means of preventing, or reducing the potential environmental impacts associated with dredging related operations. PIANC Envicom 13

16 PIANC report #100 Dredging Management Practices for the Environment 16 Recommendations Each dredging project has to be assessed on its own. A comprehensive description of the project and an exhaustive examination of the environment may be necessary. Consider all management practices on an equal basis. Do not institutionalize management practices, but invest in the development of new and better alternatives. Be open. Communication at all stages is essential. It is no guarantee for success, but its prerequsite.

17 PIANC report #100 Dredging Management Practices for the Environment 17 Active Working Group members Consultants: Christine Adnitt - UK Haskoning Ltd Stefan Bolam – UKCEFAS Caroline Fletcher – UKHR Wallingford LTD Philip Spadaro – USABlasland, Bouck & Lee, Inc. Thomas S. Wang – USAAnchor Environmental, LLC Research: Raul Castro – SpainAZTI Fisheries & Food Technological Institute Peter Whitehead – UKABP Marine Environmental Research Ltd Contractors: Wouter Dirks – NetherlandsVan Oord Dredging Gerard van Raalte – NetherlandsHydronamics = Boskalis Dredging Makoto Fujino – JapanTOA Corporation Frederik Mink - BelgiumEuDA Authorities: Koenraad Mergaert – BelgiumMinistry of the Flemish Community Douglas Clarke – USAU.S. Army Engineer Research and Development Center André van Hassent – NetherlandsPort of Rotterdam Axel Netzband - GermanyHamburg Port Authority


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