Guide for a Risk-Based Approach to Environmental Windows for Dredging and Navigation Infrastructure

Abstract: The World Association for Waterborne Transport Infrastructure (PIANC) EnviCom Working Group (WG) 227 is developing a practical guide to decision-making associated with the application of environmental windows for dredging and marine navigation infrastructure construction. The methodology builds on previous PIANC work, including WG 108 and WG 175. This presentation will introduce the new guidance document expected to be published in late 2024.

Dredging and construction of navigation infrastructure works are often restricted during certain periods to reduce potential impacts on environmental receptors. Times when the potential environmental impacts of the project are thought or perceived to be unacceptable—and, consequently, works are not allowed—are commonly defined as seasonal restrictions. Conversely, environmental windows are the periods when works are allowed. Limiting projects to fixed environmental windows often complicates contracting schedules by constricting them, adds challenges with respect to availability of construction equipment, and extends project timelines (which could result in additional environmental impacts). These limitations can also impact the safety of works and inflate their cost.

The precautionary principle is often used to establish environmental windows where caution is exercised based on uncertainty about the potential impacts of an action. Where there is uncertainty about the potential for adverse impact, the precautionary principle advises project planners to err on the side of caution. It follows, therefore, that if the uncertainty is reduced, then the level of caution can also be reduced. This guidance seeks to promote a risk-based management approach that can be used to reduce the level of uncertainty around potential environmental impacts of projects in order to develop and implement (adaptive) environmental windows that may allow the work to proceed and be managed responsibly, rather than impose a fixed environmental window.

The objective of this guide is to provide a risk-based decision-making process that can be applied in cases where restrictions on dredging and navigation infrastructure works may be considered. The guide aims to be accessible (easy to understand and apply), transparent, defendable, and robust. The guide describes the processes of developing environmental windows to allow dredging or construction activity to proceed while simultaneously mitigating risks to the environment. It is recognized that uncertainty and risk are key factors in the decision-making process relating to restrictions, which are discussed further in subsequent chapters of this guide. Case studies are used throughout this guide to demonstrate how successful outcomes can be achieved.

This guidance is intended for any individual or organization involved in dredging and navigation infrastructure works. The audience generally fits into one of these three main groups:
• People planning projects: proponents, consultants, and contractors that desire to minimize environmental impacts and maintain optimal dredging and construction operations
• People approving projects: government bodies and regulatory authorities that are usually responsible for setting seasonal restrictions and/or approving dredging with environmental windows
• People conducting projects: dredging companies and contractors that are engaged to perform a particular dredging or navigation infrastructure project

How does this project / topic contribute to the advancement of the industry and profession?: The guidance describes and recommends an effective approach for applying environmental windows to navigation infrastructure projects.

Does the project / topic implement new and innovative techniques, materials, technologies, and delivery methods?: Yes, it seeks to promote adaptive management approaches that manage risk rather than avoid it.

What was the most challenging aspect of your project / topic and how did you handle it to ensure success?: The approach may not be accepted in all international jurisdictions. The guidance provides case study examples to help gain acceptance of the recommended approach to applying environmental windows.

Who is the target audience for this paper?: The target audience is port environmental managers, consultants, and regulatory agencies.