Frequently Asked Questions

The trial will begin in late September/early October, with various dredging methods and sites included in the Dredge Management Plan (DMP) to allow for a broad-scale trial that enables the assessment of different dredging methods and sand sources and quality.

The DMP includes 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 will be continuously monitored at six sites to ensure that turbidity remains similar to background levels recorded before the trial. The DMP for the trial includes strict turbidity thresholds called alarm and hold triggers. The alarm and hold triggers will help to mitigate any long-term impacts of elevated turbidity caused by the dredge trial. The alarm trigger indicates that operations should be immediately evaluated, the impacts assessed, and operations modified if required. The hold trigger will result in a stop work order until turbidity returns to background levels.

The EPA is stipulating 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 requires the preparation of a noise management plan. Baseline noise monitoring was undertaken to determine the existing environment in noise-sensitive locations that are most likely to be affected by noise from the trial.

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

The noise management plan includes provision of a complaints phone number that will be monitored 24 hours a day while works occur. Site supervisors will investigate noise complaints to identify the cause and determine whether different work methods can 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 advises that literature suggests dolphins are likely to avoid dredging activities, however the EPA requires 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.