Presentation on theme: "Axel Netzband (Chairman of WG 13)"— Presentation transcript:
1Axel Netzband (Chairman of WG 13) Navigating the Environment –Managing Risks and Sustaining BenefitsNew Orleans, October 28, 2009Working Group PIANC Envicom 13Best Management Practices Applied to Dredging and Dredged Material Disposal Projects for the Protection of the EnvironmentPIANC Report 100Dredging Management Practices for the Environment – A structured selection approachAxel Netzband (Chairman of WG 13)
2Starting pointA 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.
3Definition 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
5Environmental 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
6The 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)
7Is 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 levelProving the negative (no impact) is essentially impossible
10EU 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)
11Identification of Environmental Effects Physical ChangeDredging equipment presenceRemoval of sedimentPlacement of sedimentAltered topography/ bathymetrySedimentation induced by dredgingSedimentation induced by disposalRe-suspension of sediment matrix into water columnRock blastingRe-suspension of sediment matrix into water columnPotential Environmental EffectRelease of particulate matterReduced light penetrationRelease of nutrientsRelease of toxic chemicalsRelease of organic matterUser conflictsExamples of impactBehavioural / physiological responses to increased suspended solids
12From Effects to Management Practices Physical ChangeRe-suspension of sediment matrix into water columnRelease of particulate matterNumberManagement PracticeM1Select appropriate contracting approach and contract formatM2Select 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 flexibilityM4Prepare project and site specific environmental and construction monitoring program.M5Use Adaptive Management approach during constructionP1Reduce 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 areaP4Reduce or eliminate the need to dredge through using natural recovery and capping/cover optionsP5Sustainable placement of dredged material within the same sediment systemP6Use of dredged materialP7Optimise the design, location and configuration of the aquatic placement siteP8Select appropriate placement option.P9Use clean dredged material for caps /covers over unsuitable sedimentP10Habitat and species protection measures: impact minimisationP11Habitat enhancement options: enhance habitat developmentE1Use appropriate type and size of dredging equipment for the project.E2Select most appropriate type and size of mechanical dredgerE3Select most appropriate type and size of bucket- ladder dredger.E4Select most appropriate type and size of hydraulic dredgerE5Select most appropriate type and capacity of dredged material transportation methodE6Select most appropriate type and size of haul / transport bargeE7Select most appropriate type and size of barge offloading equipmentE8Select most appropriate type of hydraulic pipelineE9Use special environmental equipmentE10Use hydrodynamic dredgingE13Modify existing equipment, if necessary, to make it (more) fit for purpose.E14Apply degassing systems to hydraulic dredging systemE18Apply Green valve or Environmental ValveE19Filter overflow effluent from transport barges to improve the water quality into receiving waters.E20Inspect and maintain equipment in good working conditionI1Tidal operations: flood/ebb and spring/ neapI2River Discharge dependent operationsI3Time based operations: days / weeks/ day-night / weekdays-weekends.I4Seasonal restricted operations (Environmental Windows).I5Wind direction related operations.I6No access / No activity areasI7No bed contact zonesI8No effect zones / Impact avoidance zones.I9Buffer zonesDr1Modify rate of operationsDr2Modify 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 dredgersDr8Reduce or eliminate overflow during hydraulic loading at hoppers or transport bargesDr9Reduce or eliminate use of ‘lean mixture overboard’ pumping.Dr10No barge overfilling, when loading by mechanical dredgersDr11Re-circulate process water from hopper or barge during loading.Dr12Rinse grab / bucket of mechanical excavator before lowering in waterDr13Use spill plate/apron during offloadingPl1Apply optimal sediment deposition methodPl2Hopper/ barge bottom door placementPl3Rainbowing / sidecasting / sprayingPl4Direct hydraulic pipeline placementPl5Use of baffle plates in pipeline outflowPl6Use of tremie pipePl7Use of diffuserPl8Use of SpreaderPl9Optimise rate/ concentration of mixture.Pl10Re-circulate hydraulic transport water from placement site back to hydraulic dredgerPl11Return placement site effluent to dredging sitePl12Optimize 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 sitePl16Use additives / flocculantsC4Use silt curtains to reduce loss of sediment from dredging operations.C5Use sheet pile walls to contain suspended sediments within enclosed areaC6Use bubble curtain to limit spread of re-suspended sedimentsC7Dredger within enclosed compartment (e.g., caissons) to limit spread of re-suspended sediments.C14Use fish or marine mammal guiding systems.
13Project Description and Assessment of Impact and Risk BMP selection processProject Description andConceptual DesignEnvironmentalCharacterisationAssessment of Impact and RiskRisk acceptable?MP SelectionRisk CommunicatioFinal Project DesignProject ConstructionMonitoring
15Definition 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
16Recommendations 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.
17Active Working Group members Consultants:Christine Adnitt - UK Haskoning LtdStefan Bolam – UK CEFASCaroline Fletcher – UK HR Wallingford LTDPhilip Spadaro – USA Blasland, Bouck & Lee, Inc.Thomas S. Wang – USA Anchor Environmental, LLCResearch:Raul Castro – Spain AZTI Fisheries & Food Technological InstitutePeter Whitehead – UK ABP Marine Environmental Research LtdContractors:Wouter Dirks – Netherlands Van Oord DredgingGerard van Raalte – Netherlands Hydronamics = Boskalis DredgingMakoto Fujino – Japan TOA CorporationFrederik Mink - Belgium EuDAAuthorities:Koenraad Mergaert – Belgium Ministry of the Flemish CommunityDouglas Clarke – USA U.S. Army Engineer Research and Development CenterAndré van Hassent – Netherlands Port of RotterdamAxel Netzband - Germany Hamburg Port Authority