Frequently Asked Questions

The trial began on 3 October 2024 and ended on 30 November 2024, with various dredging methods and sites included in the Dredge Management Plan (DMP) to allow for a broad-scale trial that enabled the assessment of different dredging methods and sand sources and quality.

The DMP included dredging at four sand borrow areas and depositing in three sand placement areas.

Sand borrow areas:

1. North Haven Marina sand trap
2. West Beach sand bar
3. West Beach Harbour sand trap
4. West Beach rehandling area.

Sand placement areas:

1. Nearshore at West Beach
2. Onshore at West Beach
3. West Beach rehandling area.

Seagrasses are flowering plants that rely on sunlight to photosynthesise and grow. When there is abundant light, especially in summer, seagrass photosynthesis is high and the plant stores energy in reserve. When there is not enough light, seagrass plants draw energy from this reserve to stay healthy.

Fine particles and suspended sediment in the water scatters sunlight and makes the water look murky or cloudy – this is known as turbidity. Higher turbidity can increase light stress on seagrasses. The more that light is scattered and interrupted from reaching the seagrass, the less photosynthesis can occur. When sediment settles directly on seagrass leaves, light is prevented from reaching the plant which also reduces photosynthesis.

Turbidity was continuously monitored at six sites to ensure that it remained similar to background levels recorded before the trial. The DMP for the trial included strict turbidity thresholds called alarm and hold triggers. The alarm and hold triggers were in place to help mitigate any long-term impacts of elevated turbidity caused by the dredge trial. Alarm triggers were to indicate that operations should be immediately evaluated, the impacts assessed, and operations modified if required. Hold triggers were to result in a stop work order until turbidity returned to background levels. The turbidity thresholds were not reached during the trial.

The EPA also stipulated more stringent turbidity triggers from 1 November when light availability is most crucial to seagrass plants building their energy reserves.

The DMP for the trial required the preparation of a noise management plan. Baseline noise monitoring was undertaken to determine the existing environment in noise-sensitive locations that were most likely to be affected by noise from the trial.

The noise management plan included that routine attended noise monitoring would be undertaken at multiple stages throughout the trial, at noise-sensitive locations closest to work areas at West Beach and North Haven. The EPA also conducted independent monitoring of noise levels and assessed the noise generated against relevant legislation and guidelines.

The noise management plan included provision of a complaints phone number to be monitored 24 hours a day while works occurred. Site supervisors would investigate noise complaints to identify the cause and determine whether different work methods could be implemented to remove or minimise the noise. Guidelines used in the noise management plan aim to minimise nuisance for sensitive receivers during the day and avoid sleep disturbance at night.

Enquiries and complaints regarding noise generated by the dredge trial should be directed to the Department for Environment and Water in the first instance:

Email – DEW.ABMRImplementation@sa.gov.au
Phone (monitored 24/7) – 0461 535 823
Website – environment.sa.gov.au/topics/coasts

Environmental or pollution incidents can also be reported to the EPA through our online portal Your EPA.

The Adelaide Dolphin Sanctuary advised that literature suggests dolphins are likely to avoid dredging activities, however the EPA required the following actions as a precaution:

• Visual monitoring by a trained marine mammal observer within 300 metres of the dredge site
• Procedures to pause dredging when marine mammals are observed within 10 metres, by cutting power to the head of the cutter suction dredge
• Recording and reporting sightings of marine mammals.