dredging: the factsIn particular, dredging is vital to the constructio - PDF document

dredging: the factsIn particular, dredging is vital to the construction anddepend. So, when, and why do we dredge? ¥ facilitate the emplacement of pipelines or immersed tunnel ¥ construct ßood control structures such as dams, dikes or levees; ¥ ensure ßood defences (by improving or maintaining the discharge capacity of watercourses);In addition, though perhaps less commonly, dredging may be Capital dredging in Hong Kong wasundertaken for both the new airport materials and commodities have been transported by water.cost effectiveness have resulted in larger, more efÞcient ships.Waterborne transport is vital to domestic and international ¥ Construction materials: an increasing quantity of marine Trailing suction hopper dredgers comeexpensive. Maintenance dredging is often a regular, perhapsannual ongoing, long-term activity. In either case, what are the¥ Excavation: this process involves the dislodgement and removalbody. A special machine - the dredger Ð is used to excavate thematerial either mechanically, hydraulically or by combinedaction. The main types of dredgers are described below.¥ Transport of excavated material: transporting materials fromOther, rarely used transport methods are truck and conveyor¥ Utilisation or disposal of dredged material: in construction varies widely, coming in many sizes and types, and includingmainly water-based and sometimes land-based machines.on the basis of propulsion, i.e. self-propelled versus stationary.¥ the nature, quantity and level of contamination of the materialTransport methods associated Close-up of a cutterhead. The encapsulated bucket dredgerequipment. an environmentally acceptable manner, in particular ensuringdredgers; auger dredger, disc cutter, scoop dredger and sweepDMAF accordingly. There are also regional conventions such a waterway, may not need to be the subject of detailed should, however, have studies carried out in order to ensure dealt with in an appropriate manner. Such investigations¥ TreatmentTheirrole in river, estuarine and costal zoneInenvironmental assessment therefore as a Þrst option the reloca- DREDGED MATERIAL MANAGEMENTALTERNATIVES are being taken in winter.Lake Ketelmeer, The Netherlands, comes ¥ coastal protection, e.g. beach nourishment, onshore/offshore ¥ habitat development or enhancement, e.g. aquatic habitats, ¥ land reclamation, e.g. for industrial development, housing, ¥ production of construction material, e.g. bricks, clay, aggregates;Operational feasibility, that is, the availability of suitable material inGenerally, clean or mildly contaminated sediments are disposed of in open-water, although the disposal of highly contaminated materialVariants of open-water disposal include:¥ unrestricted placement on waterbeds in the form of mounds;¥ placement with lateral containment in natural or man-madeCDFs), at near-shore sites or on land. whilst releasing the carrier water. For facilities receiving To achieve this, depending on the degree of intended isolation, Welded sheets of PEHD plastic in Hamburg, Germany.dredged material, thus reducing its quantity. groundwater quality, in the vicinity TreatmentTreatment is deÞned as the processing of contaminated dredgedTreatment methods range from separation techniques, in which ENVIRONMENTAL ISSUES and regions in the world. Yet any infrastructure or development¥ water quality, e.g. increase of suspended solids concentration¥ habitats and natural areas, e.g. habitat enhancement or ¥ local communities, e.g. the effects of noise; increased labour¥ changes to bathymetry or topography;¥ physical processes, e.g. waves, currents, or drainage, ¥ economic activities, e.g. commercial Þshing; From Sewer To Fishery Rhine bordering countries and the EC Commission supported it unanimously.species, such as salmon into the river. Emissions of some substances signiÞcance is necessary. The Òenvironmental impact assessmentÓoften be reduced to an acceptable level, or avoided altogether.¥ identify whether, when or where remedial actions are required.with them and reaching a consensus forms an important componentthe continuing input of contaminants to a water body, by a factory 7 recreational vessel.11th Floor, Blvd. du Roi Albert II, www.pianc-aipcn.org World Organization of Dredgingand Western Dredging Association¥To promote the development and exchange of professionalregulatory and managerial Ð inall Þelds concerned with dredgingdredged material;¥ To participate in the developmentpolicies, regulations, and guidelines on dredging and related matters;¥ To balance the environmental,related to dredging and dredgedprojects and to encourage open¥ To enhance contacts between professional entities concernedwith dredging and associated matters and between the dredgingwww.dredging.org Authority, Mail Bag Service 202,E-mail: david@pka.gov.mywww.woda.orgP.O. Box 5797, Vancouver, WA 98668-5797 USA. www.wesda.westerndredging.orgINFORMATION ON practices are in everybodyÕs interest.Mission: To inform the world aboutthe fundamental need for dredgingand environmental effects of dredging.To promote fair practice conditionsdredging industry and to improve the private dredging industry.www.iadc-dredging.comMission: One of IAPHÕs missions is to promote the development of theinternational port industry, by interregulations, standards and guidelinescovering the environment, includingdredging.7th Floor, South Tower, New PierTakeshiba, 1-16-1 Kaigan, Minato-ku,Tokyo 105-0022, Japan. www.iaphworldports.orgforemost professional organisation forthe promotion, management infrastructure and coastal zones, of all types of commercial and PERTINENT LITERATUREBray, RN, AD Bates and JM Land (1997).London, Sydney, Auckland.Development 5th edition, RN Bray,Editor.Rotterdam Public Works Dept. (2001)Stone Dumping Works.Report of PEC Working Group 19.Treatment of Contaminated DredgedWaterways, Report of PEC WorkingEnviCom Working Group 1.Environmental Terms and Terminology,EnviCom Working Group 3.EnviCom Working Group 5.Engineering Guidelines for Wetlandsstructures, EnviCom Working Group 7.Disposal, EnviCom Working Group 8.Facilities, EnviCom Working Group 11UNEP-GPA (2004) Key Principles forture, www.dredgeline.netwww.imiparalianature.orgwww.sednet.orgActivities, www.gpa.unep.orgOperations Technical Support,http://el.erdc.usace.army.mil/dotsMarsha Cohen, editor and coordinator.Sondra Adams, graphic designer.Typeset and printed by Opmeer Drukkerij bv, The Netherlandsdisc cutter.