WORKING WITH NATURE: APPLYING THE PHILOSOPHY TO MAINTENANCE DREDGING

摘要

The 'Working with Nature' philosophy (PIANC, 2011) was developed to apply to the planning of new navigation infrastructure projects. This case study illustrates how elements of the philosophy can be applied to ongoing activities such as maintenance dredging. For many years, most of the material dredged by the Mersey Docks and Harbour Company (MDHC) from the docks, river entrances and approach channel to the Port of Liverpool has been taken to an offshore licensed disposal site. Much of the remainder has been deposited closer to the Port, within the estuary. MDHC's maintenance dredging and disposal regime has been assessed and shown to be compliant with both the EU Habitats Directive and the EU Water Framework Directive. No adverse environmental effects have been identified. Notwithstanding this compliance, several factors including potential cost and carbon savings led to MDHC organising a stakeholder meeting at the end of 2011 to discuss whether opportunities might exist to use the maintenance dredged materials beneficially - whether for environmental or engineering purposes. This initiative represented a significant departure from 'the norm' for MDHC who, in common with most other UK harbour authorities, have powers under their Local Act to carry out maintenance dredging, and regard such activities as 'internal' matters. It also represented a challenge for the stakeholder organisations as this was not a capital development project requiring compensation - a situation in which such organisations often 'call the shots' - but rather a voluntary initiative, the success of which would depend on collaboration, cooperation and compromise. This paper elaborates on the background to, and presents progress to date with, the Mersey sediment management study as it moves from option identification and assessment to implementation - based on the principles of Working with Nature and adaptive management.