Two-dimensional gravity modelling across the Faeroe-Shetland Basin was carried out on the basis of a published regional seismic section (Stoker et al.

Monitoring required by regulators as part of environmental approvals in Australia has become increasingly complex and is sometimes viewed simply as the cost of developing projects, particularly in recent years. Monitoring programs, however, provide an important opportunity to learn about complex ecological systems and how they fare during large-scale disturbances, potentially with both project-specific and industry-wide benefits. During the Chevron-operated Gorgon Project’s major-capital dredging program, an unprecedented amount of information was collected about water quality and coral. Water quality was monitored continuously at 36 sites and the condition of nearly 1,600 individually labelled corals measured fortnightly during 18 months. While daily and fortnightly reports were provided for compliance purposes, a significant investment was also made by Chevron to a Predictive Links investigation, to re-analyse data to gain a better understanding between water quality and sedimentation with changes in coral condition. This additional investment resulted in a number of important research findings including revised water-quality thresholds for maintaining coral health that are based uniquely on field measurements during an actual dredging program. Subsequently, when environmental approvals were being sought for the nearby Wheatstone project, Chevron had a much better understanding of dredging and its potential effects on coral reefs in the region. The Wheatstone program now incorporates these data and ideas, and has allowed Chevron to have greater confidence in the dredging program being proposed, the likely impacts on coral assemblages, and how these should be managed and monitored.

Dredging for the Chevron-operated Wheatstone LNG Project, near Onslow, Western Australia, involved movement of approximately 30 Mm3 of material over 23 months to provide safe navigation for LNG export as well as trunkline installation and stabilisation. Dredging was carried out in a sub-tropical, inshore environment near to biological benthic communities including corals, seagrasses, macroalgae and filter feeders, deemed sensitive to elevations in turbidity and/or sedimentation associated with dredging. Science and innovative technology was used to proactively and adaptively management dredging in order to afford a high level of environmental protection. Water quality data was transmitted via satellite to Perth where it was compared, daily, against management triggers derived from scientific analysis of an extensive dataset collected during a previous, nearby, dredging program. Accurate hindcast modelling, combined with MODIS satellite imagery, provided oversight of the extent and cause of observed turbid plumes, while forecast modelling provided predictions of the potential impacts of upcoming dredging activities, allowing for proactive changes to dredging activities to minimise potential impacts. Monitoring of benthic communities was undertaken using remotely operated underwater vehicles (ROVs) and water quality monitoring in the latter part of the program was undertaken using remotely operated Wave Gliders (Liquid Robotics), both of which resulted in significant safety improvements and cost savings and over traditional monitoring methods. Post-dredging surveys of benthic communities indicated that, despite their proximity to dredging activities and the enormity of dredged volumes, no detectable impacts had occurred as a result of dredging.