Environmentally-friendly dredging

According to the new paper called Integrating Adaptive Environmental Management into Dredging Projects, AM can be an efficient and cost-effective management process where the objectives are clear, but the potential for local environmental effects are uncertain.

Chairman of the working group, Gerard van Raalte, said: “We encourage all stakeholders in this field to carefully look at the opportunities presented by adaptive management, as an alternative to applying the precautionary principle which may lead to inefficient use of resources without delivering environmental gain.”

One successful case study detailed in the paper is the Chevron-operated Wheatstone LNG Project in Western Australia, which involved dredging of a large volume of material over two years (2011 – 2013) to provide navigable waters for LNG shipments and trenching for trunkline installation.

The Wheatstone Project dredging conditions of approval included defined environmental protection outcomes for corals, seagrass, macro-algae and filter feeder communities.

A ‘trigger level’ approach to water quality monitoring was used help create robust thresholds with the Regulatory Authority to manage any potential environmental impacts so that dredging activity could be adapted at different stages throughout the project to always achieve compliance.

This also meant that warnings were available in sufficient time to avoid reaching the threshold of unacceptable impact that would have stopped the dredging activity.

The position paper is the product of an experienced group of CEDA/WEDA members including representatives from Boskalis, Royal Haskoning DHV, Witteveen+Bos, HR Wallingford, Jan De Nul and Hamburg Port Authority. It can be downloaded for free from CEDA