Bay dredging work continues

Additional dredging works will see the Port MacDonnell boat ramp closed until Thursday.

Grant District Council received a request by the Department for Infrastructure and Transport (DIT) to close the boat ramp, which was closed yesterday due to additional dredging starting which is expected to have an impact on the harbour.

As a result the facility is expected to remain closed until later this week.

Council reported efforts have been made to align the closure against storm weather forecasts.

However, all other boat ramps will be operational.

Meanwhile, the department has warned residents of a short-term odour due to the removal of seagrass.

The department said a sediment plume may also occur in the water where dredging is taking place and the Environment Protection Authority (EPA) has been consulted.

According to the department, sediments dredged near the breakwater in the mooring grounds will comprise of sandy materials and are not likely to generate any persistent odour.

Since the project began in March around 37,000 cubic metres of sand and 1000 cubic metres of seaweed has been removed.

The project is expected to be completed in late July.

Some fluctuation due to weather and fishing fleets end of season has been taken into consideration.

The project has been contracted to Maritime Constructions and were subject to conditions of an EPA licence.

Before the start of the project the department had undertaken extensive consultation with the council over two and half years to ensure the dredging of the area would meet the needs of the community and relevant stakeholders.

Dredging of the area may create a moderate dredge plume in the immediate vicinity of the dredge and around the discharge and return water point.

Dredge plume formation at and near the disposal site will be monitored to ensure the plume does not encroach on any sensitive ecosystems or affect the amenity and safety of beach swimming areas.

Organic materials dredged from the channel are being screened, drained and progressively transported to the adjacent western beach or if causing too great a disturbance, off-site to the local transfer station.

Due to the presence of fine organic sludge in the seabed, fresh seaweed wrack is being removed first using a seaweed wrack screen where wrack will be progressively collected and removed.  

Following this, sludge will be pumped into geobags which filter sediment and allow silt free water to be released to drain. 

Both methods will require temporary space on the park directly east of the boat ramp to enable a good working area with drainage.  

This temporary works area will be required for approximately two months.  

The area will be landscaped and grass re-established at the end of the project.

Meanwhile, the department said noise levels will be reduced between 10pm and 7am to limit the impact on nearby residents.

The department has thanked the Port MacDonnell community for its patience while these works are undertaken.

The site requires a major dredging campaign to remove significant accumulation of sandy materials at the harbor entrance and mooring grounds as well as seaweed (wrack) from the channel.

Two locations have been chosen to deposit the dredged sand and seaweed wrack.

Sand from the harbor entrance is being used to replenish sandy beaches located to the east of the harbor area, while seaweed wrack from the channel is being removed via a separation system at the boat ramp and transported by truck off-site.

The department said the on-shore disposal of all sand and seagrass wrack was selected as the preferred method to minimise impacts to the nearshore reefs and seagrass beds in the vicinity of the harbor.

This is to help ensure the longer-term protection of the marine environment.

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