Posted on May 17, 2016
By Larz Bourne, GreenPort
Most of the world’s ports require dredging works, be they capital dredging to enlarge and deepen access channels, turning basins and depth alongside or maintenance works to maintain these hard won margins for navigational safety.
Dredging also provides sand and gravel for the creation of land for new port developments, such as the recently completed Maasvlakte 2 project in the Netherlands.
Great efforts have been made over recent decades to optimise the environmental aspects of dredging whilst minimising or eliminating negative impacts of a powerful and potentially disruptive process.
In recent years there has been a growing call for innovative and cost effective solutions that seek to enhance or create natural ecosystems, adding biodiversity in and around the port while meeting economic objectives.
Leading this quest is the Netherlands-based Central Dredging Association (CEDA), whose role is to promote best practice across the industry and, among other concerns, seek to balance environmental, social and economic concerns related to dredging, as well as the handling and use of dredged materials. CEDA is the Europe, Africa and Middle East (EMEA) regional body of the World Organisation of Dredging Associations (WODA), along with the Western Dredging Association (WEDA) for the Americas and the Eastern Dredging Association (EADA) for the Asia Pacific region.
CEDA organises a Dredging Days conference to run concurrently with every Europort exhibition in Rotterdam. The most recent gathering of this biennial symposium provided an excellent opportunity to catch up on the latest dredging innovation in ports and look at how the industry is always moving forward with regards to enhancing its environmental credentials.
The event kicked off with a keynote speech by Tiedo Vellinga, professor of ports and waterways at Delft University of Technology and also the director of environmental monitoring for the Port of Rotterdam’s Maasvlakte 2 project. His paper about the implementation of sustainable design solutions in port development set the tone for much that followed at Dredging Days.
Addressing the idea of Ports of the Future, Mr Vellinga’s paper examined how port developers, facing global trade growth and ever larger ships, had to deal with a scarcity of suitable locations and the uncertain consequences of potential climate change also considering potential environmental impacts upon river and coastal ecosystems. These circumstances suggest a need for innovative solutions to port development challenges which are in harmony with the host ecosystem and are robust or adaptable under change.
The concept of ‘green growth’ combines environmental and social awareness to deliver sustainable port development. It is built on an improved long term cost-benefit strategy which sees successful ports and healthy ecosystems as compatible.
Rather than choose more traditional river/sea interface locations where port construction may disrupt natural processes – such as the distribution of sand along the coast and impact valuable ecosystems – the Port of the Future concept’s site location is based on the characteristics and processes of the ecosystem to ensure a sustainable future for new or expanding ports.
Ports of the Future uses a holistic or integrated approach to optimise the economic, environmental and social costs and benefits of ports. This includes connecting waterways, hinterland connections, the involvement of surrounding cities and the strengthening of adjacent coastlines.
As every port is unique, the Ports of the Future concept requires a tailor made solution for every specific situation. Thus every port development plan must be created in close collaboration with all stakeholders. The assessment of environmental impacts and locations in combination with current and future harbour technologies will make a big difference for their success.
Constructing ports following this new approach may be more costly at first but after time this investment will be paid back because optimised navigability and coastal flood protection will have been incorporated at the design stage. Dredging costs specifically should be lower as design considerations ensure sedimentation is kept to a minimum, therefore reducing the requirement for maintenance dredging.
Gerard van Raalte of Boskalis/Hydronamic bv followed with the presentation of a position paper produced by the CEDA Environment Commission, which he chaired, outlining concepts of integrating Adaptive Management (AM) for the enhancement of the environment via dredging activities, including placement, disposal and reclamation.
For dredging projects where the outcome is uncertain, or accompanied by a low confidence in the prediction of effects, a sequence of more intense and targeted monitoring, impact assessment and management actions might be implemented on a continuous or regular basis for the duration of (and after) the project, in order to keep project expectations and implementation requirements more manageable. This sequence of activities is jointly understood as AM, although interpretation and ways of implementation may vary considerably between projects, and even between different stakeholders on any project.
AM can be an efficient and cost-effective management process in dredging projects where the objectives are clear, yet the potential for local environmental effects are uncertain, and management actions can be implemented in a stepwise procedure to address those uncertainties as the project progresses.
It helps to achieve desired goals by addressing uncertainty, incorporating flexibility and robustness into project design, and using new information to inform decision making as the project develops. Goals include an efficient project design and streamlining implementation protocols to minimise wasted resources which, when holistically viewed, could be decreasing the project’s overall environmental footprint.
Alongside this AM in dredging projects represents a ‘modern’ approach and has the potential to become good practice in the future. It underlines the commitment to find suitable options with strength in process optimisation from various aspects. It is not likely that AM will become good practice for all kinds of dredging projects in the future, but the advantages are seen especially for the larger scale projects and multi-year projects, including maintenance works.
The need for integrating AM into dredging projects is already recognised, but will probably increase in future if not in response to the uncertainties resulting from climate change (CEDA, 2012), then in reaction to an ever growing awareness of the need for protection of the environment, as well as in connection to the ecosystem services approaches (CEDA, 2013).
An example of applied AM is the ongoing Poplar Island Environmental Restoration Project (PIERP) in the USA, which uses clean dredged material from the Chesapeake Bay approach channels.
AM at Poplar Island comprises developing initial project goals, periodically assessing progress towards them, and implementing corrective actions, if need be, in the future. Since habitat restoration was the aspect of the project where AM was applied, it focused on the following sub-goals: create a diversity of habitats including small island nesting habitat, tidal marsh habitat, upland habitats, quiescent conditions for submerged aquatic vegetation recovery and minimise/offset the loss of benthic habitat.
The AM sub-goals referenced above were broken into specific Adaptive Management elements in relation to habitat feature, desired attributes and estimated timeline. Specific targets were defined for each of these attributes, for example >80% of species composition to be achieved. Subsequently acceptable bounds were defined for each of the targets (+/- 20%).
Tools such as vegetative surveys, survey of cell elevations, material quality determinations, bird, fish and invertebrate surveys, benthic tissue sampling, marsh inundation studies, circulation studies, erosion analysis along dikes and shorelines/beaches and reef monitoring were used over time at varying frequencies to assess progress towards goals.
Depending on dredging cycles and material characteristics, different locations/cells along the wetland portions of the disposal facility were filled and subsequently planted. This allowed flexibility in operations, as well as response action planning in future years, should a different result from the AM plan be observed or trending. Applying the principles to this project helped to facilitate the creation of an environmentally beneficial project as part of a beneficial use maintenance dredging project.
“It’s amazing how quickly the concept of Adaptive Management is finding its way into the profession” said Gerard van Raalte. “What is needed now is guidance on how to apply it.”
CEDA recently presented a webinar and started a LinkedIn discussion group on the subject – to which all interested parties are invited. This group can be found by searching for: Central Dredging Association – CEDA Discussion Group on Adaptive Management.
Among the many other papers presented at CEDA Dredging Days updating and enhancing environmental best practice was EcoPlume: operational proactive environmental management of dredging projects by Arjan Mol, Tom De Wachter and Marc Huygens of the DEME Group.
EcoPlume is a system concept with the purpose of merging operational with environmental interests. It aims at optimising dredging operations while complying with environmental constraints. Doing so, the EcoPlume system becomes a crucial working tool to implement and deploy a successful adaptive project management in the day-to-day dredging operations.
In practice, an EcoPlume system forecasts the relevant water quality parameters given the scheduled and/or targeted dredging works planning. Based on this dredging operations can be adjusted in a day-to-day operational planning scheme to ensure that the water quality criteria are fulfilled at all times.
For further information about Ports of the Future, Green Growth, and Environmental Aspects of Dredging visit CEDA at www.dredging.org.
Source: GreenPort
