Frequently Asked Questions

The Phase II dredge trial includes collection of nearshore sand from one sand borrow area located at North Haven (used in the 2024 trial) and placing it at sand placement areas located at Henley Beach South and West Beach (used in the 2024 trial).

Timing for the commencement of the trial is to be confirmed and depends on EPA approval of the finalised management and monitoring plans. Dredging activities are expected to be completed by 30 September 2026. If the volume of sand able to be placed by 30 September is limited by operational constraints, the Department for Environment and Water (DEW) may make an application to the EPA to extend the dredging period. Any potential extension would be subject to appropriate regulatory and environmental management requirements.

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 reduce light available to 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.

As per the DMP for the trial, DEW’s contractor will continuously monitor turbidity at eight sites near to seagrass, sand borrow and placement areas, and background reference locations to ensure that turbidity remains similar to background levels recorded before and during the trial. Strict turbidity thresholds called alarm and hold triggers will be applied to help mitigate any long-term impacts of elevated turbidity caused by the dredge trial. An alarm trigger is an early warning signal indicating that operations should be immediately evaluated, the impacts assessed, and operations modified if required. A hold trigger results in a stop work order until turbidity returns below the trigger levels.

The DMP for the trial requires the preparation of a noise monitoring plan. Baseline noise monitoring has been conducted to determine the existing environment in noise-sensitive locations that are most likely to be affected by noise from the trial. Baseline noise monitoring was undertaken at North Haven and West Beach for the 2024 dredge trial with additional baseline monitoring conducted in relation to the new sand placement area at Henley Beach South.

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

Guidelines used in the noise management plan aim to minimise nuisance for sensitive receivers during the day and avoid sleep disturbance at night. The noise monitoring 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.

Enquiries and complaints regarding noise generated by the dredge trial should be directed to DEW in the first instance:

Email – DEWcoasts@sa.gov.au
Phone – (08) 8124 4928
Website – environment.sa.gov.au/topics/coasts/replenishment-program

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

The Adelaide Dolphin Sanctuary is adjacent to the dredging location and dolphins are likely to be attracted to the dredging operation. To minimise potential impacts to marine mammals, the EPA has required that:

• Trained marine mammal observers are stationed on all dredge vessels and that they monitor an observation zone for the presence of marine mammals.
• Procedures are in place to manage dredging when marine mammals are observed within the observation zone. When they come within 50 metres of the dredge equipment, dredging must cease immediately and not recommence until the marine mammal has relocated to a safe distance.
• All observations of marine mammals and management actions are recorded and reported.

The evaluation and approval of the dredge trial has been informed by the latest information on the condition of the nearshore marine environment after the harmful algal bloom. Within Adelaide’s nearshore marine environment, seagrass is generally the most sensitive organism in the receiving environment due to both its proximity to and sensitivity to reduced light caused by dredge turbidity. Turbidity triggers have been conservatively set to ensure that seagrass is protected from long-term reduction in light. Further, before and after-trial seagrass monitoring is required to ensure that environmental harm is minimised.

There is no evidence to suggest that Karenia cristata (the microalgae primarily responsible for the 2025–26 harmful algal bloom) can be re-ignited by dredging. Notwithstanding this, and noting public concerns related to the risk, the EPA will require that DEW undertakes water monitoring for potentially harmful microalgae twice a week during dredge activities to ensure any risk of a bloom is managed. In the unlikely event that potentially harmful microalgae are detected above a management trigger, the EPA may require modification or cessation of dredging.

The rehandling of dredged sand will be subject to strict turbidity triggers at all times. The monitoring sites and triggers are designed to ensure turbidity impacts to seagrass habitats are minimised. There is also an option to move sand closer to the shoreline using a cutter suction dredge (CSD) and pipeline diffuser where direct placement by barge is restricted by water depth. This rehandling method will only be undertaken if weather conditions permit. If the CSD is found to be triggering turbidity thresholds, the operation of the CSD must cease in accordance with the Water Quality Monitoring Plan.