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Axel Netzband (Chairman of WG 13)

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1 Axel Netzband (Chairman of WG 13)
Navigating the Environment – Managing Risks and Sustaining Benefits New Orleans, October 28, 2009 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 Axel Netzband (Chairman of WG 13)

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 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 Description of Management Practices

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 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 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 Turbidity, Nature, and Human Activities

9 Dredging impacts

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 Identification of Environmental Effects
Physical Change 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 Potential Environmental Effect Release of particulate matter Reduced light penetration Release of nutrients Release of toxic chemicals Release of organic matter User conflicts Examples of impact Behavioural / physiological responses to increased suspended solids

12 From Effects to Management Practices
Physical Change Re-suspension of sediment matrix into water column Release of particulate matter Number Management Practice M1 Select appropriate contracting approach and contract format M2 Select the contractor based on best value or use pre-qualification to limit the bidders to qualified bidders. M3 Use performance specifications (instead of method specifications) to allow operator flexibility M4 Prepare project and site specific environmental and construction monitoring program. M5 Use Adaptive Management approach during construction P1 Reduce Dredging Requirements (i.e., horizontal and vertical extents) P2 Optimise / increase dredging design for environmental benefit. P3 Make changes to physical system to reduce sedimentation into project area P4 Reduce or eliminate the need to dredge through using natural recovery and capping/cover options P5 Sustainable placement of dredged material within the same sediment system P6 Use of dredged material P7 Optimise the design, location and configuration of the aquatic placement site P8 Select appropriate placement option. P9 Use clean dredged material for caps /covers over unsuitable sediment P10 Habitat and species protection measures: impact minimisation P11 Habitat enhancement options: enhance habitat development E1 Use appropriate type and size of dredging equipment for the project. E2 Select most appropriate type and size of mechanical dredger E3 Select most appropriate type and size of bucket- ladder dredger. E4 Select most appropriate type and size of hydraulic dredger E5 Select most appropriate type and capacity of dredged material transportation method E6 Select most appropriate type and size of haul / transport barge E7 Select most appropriate type and size of barge offloading equipment E8 Select most appropriate type of hydraulic pipeline E9 Use special environmental equipment E10 Use hydrodynamic dredging E13 Modify existing equipment, if necessary, to make it (more) fit for purpose. E14 Apply degassing systems to hydraulic dredging system E18 Apply Green valve or Environmental Valve E19 Filter overflow effluent from transport barges to improve the water quality into receiving waters. E20 Inspect and maintain equipment in good working condition I1 Tidal operations: flood/ebb and spring/ neap I2 River Discharge dependent operations I3 Time based operations: days / weeks/ day-night / weekdays-weekends. I4 Seasonal restricted operations (Environmental Windows). I5 Wind direction related operations. I6 No access / No activity areas I7 No bed contact zones I8 No effect zones / Impact avoidance zones. I9 Buffer zones Dr1 Modify rate of operations Dr2 Modify rate of excavation of mechanical dredgers. Dr3 Modify mode of excavation for mechanical dredgers. Dr4 Modify rate of excavation for hydraulic dredgers. Dr5 Modify mode of excavation for hydraulic dredgers. Dr6 Modify mode and speed of ‘mechanical’ transportation (e.g., barges) Dr7 Bed-levelling or ploughing to reduce over-dredging, in combination with other dredgers Dr8 Reduce or eliminate overflow during hydraulic loading at hoppers or transport barges Dr9 Reduce or eliminate use of ‘lean mixture overboard’ pumping. Dr10 No barge overfilling, when loading by mechanical dredgers Dr11 Re-circulate process water from hopper or barge during loading. Dr12 Rinse grab / bucket of mechanical excavator before lowering in water Dr13 Use spill plate/apron during offloading Pl1 Apply optimal sediment deposition method Pl2 Hopper/ barge bottom door placement Pl3 Rainbowing / sidecasting / spraying Pl4 Direct hydraulic pipeline placement Pl5 Use of baffle plates in pipeline outflow Pl6 Use of tremie pipe Pl7 Use of diffuser Pl8 Use of Spreader Pl9 Optimise rate/ concentration of mixture. Pl10 Re-circulate hydraulic transport water from placement site back to hydraulic dredger Pl11 Return placement site effluent to dredging site Pl12 Optimize layout of storage basin. Pl13 Optimise dimensions and location of overflow weir (i.e. waterbox) Pl14 Optimise location of inflow point (i.e. hydraulic discharge end) Pl15 Add a separate siltation pond to the disposal site Pl16 Use additives / flocculants C4 Use silt curtains to reduce loss of sediment from dredging operations. C5 Use sheet pile walls to contain suspended sediments within enclosed area C6 Use bubble curtain to limit spread of re-suspended sediments C7 Dredger within enclosed compartment (e.g., caissons) to limit spread of re-suspended sediments. C14 Use fish or marine mammal guiding systems.

13 Project Description and Assessment of Impact and Risk
BMP selection process Project Description and Conceptual Design Environmental Characterisation Assessment of Impact and Risk Risk acceptable? MP Selection Risk Communicatio Final Project Design Project Construction Monitoring

14 BMP Evaluation Matrix

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 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 it’s prerequsite.

17 Active Working Group members
Consultants: Christine Adnitt - UK Haskoning Ltd Stefan Bolam – UK CEFAS Caroline Fletcher – UK HR Wallingford LTD Philip Spadaro – USA Blasland, Bouck & Lee, Inc. Thomas S. Wang – USA Anchor Environmental, LLC Research: Raul Castro – Spain AZTI Fisheries & Food Technological Institute Peter Whitehead – UK ABP Marine Environmental Research Ltd Contractors: Wouter Dirks – Netherlands Van Oord Dredging Gerard van Raalte – Netherlands Hydronamics = Boskalis Dredging Makoto Fujino – Japan TOA Corporation Frederik Mink - Belgium EuDA Authorities: Koenraad Mergaert – Belgium Ministry of the Flemish Community Douglas Clarke – USA U.S. Army Engineer Research and Development Center André van Hassent – Netherlands Port of Rotterdam Axel Netzband - Germany Hamburg Port Authority


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