Lower Vasse River Management - Improving Water Quality

Removal of Sediment

This project is part of a multi-staged approach to reducing nutrients and improving health of the Lower Vasse River. The City aims to improve water quality of the River by progressing with the removal of sediment.

Nutrient-rich sediments have built up on the bed of the Lower Vasse River over many decades and are an important factor in fuelling the cycle of summertime algal blooms. 

While sediment removal alone is not expected to prevent algal blooms occurring in the River, it is an important step if we are to achieve the aim of significantly reducing the extent, severity and duration of blooms in the future.

Stage 1 Complete

Stage 1 of sediment removal was completed in May 2022 with 630 tonnes of sediment (dry solids) removed over the course of seven weeks.

The area dredged spanned from the Causeway Road Bridge to upstream from the pedestrian bridge on Peel Terrace.

The slurry of sediments was pumped into porous geotextile bags, which retained the fine sediments while water was expelled and returned to the River.

The sediments continued to dewater for an additional 6 months. The dewatered sediment are being treated for acid sulfate soil and transported off site for reuse.

Water quality in the River was closely monitored for the duration of the works to ensure no detrimental impacts from the dredging operation and the dewatering of the sediments.

Future Stages

Planning for additional sediment removal is progressing, with Stage 2 works planned for autumn 2023. The area proposed to be dredged is located upstream from the Causeway Road Bridge. The same laydown area in Rotary Park will be used for dewatering the sediments.

The City has been successful in securing a total of $407,964 in funding from the State Natural Resource Management's Community Stewardship Grant Program. Funds will assist with further sediment removal works in the Lower Vasse River in a section upstream of the Strelly Street Bridge (Stage 3).

As opportunities arise, more funding applications will be made to support continued sediment removal further up the River.

Image: Laydown area for geotextile bags – Rotary park

Project Timeline

February 2021 – Lower Vasse River Management Advisory Group selects sediment removal as the highest priority recommendation for implementation

April 2021 – City applied for funding under the Healthy Estuaries WA program for Stage 1 and WA Community Stewardship Program for Stage 2 of sediment removal

August 2021 – Council endorses $290,000 in 2021/22 budget towards sediment removal

September 2021 – City was awarded $350,000 under the Healthy Estuaries WA program

September 2021 – Tender for the first stage of sediment removal called

November 2021 - WA Community Stewardship Program funding application unsuccessful

December 2021 – Dredging contractor appointed

February 2022 – Environmental and Heritage approvals granted

March 2022 – Rotary park closed to set up dewatering bags laydown area

April to early June 2022 – Dredging works

April to June 2022 – Water quality monitoring

May 2022 - City applied for funding under the WA Community Stewardship Program for Stage 3 of sediment removal

June 2022 – Sediment slurry dewatering commence

November 2022 – City was awarded $407,000 under the State NRM Community Stewardship Program for Stage 3 of sediment removal

November 2022 – Dewatered sediments treated for Acid Sulfate Soils

December 2022 – Dewatered sediments transported offsite for reuse

March 2023 – Stage 2 of sediment removal (upstream of the Causeway Road Bridge) to commence

Autumn 2024 – Stage 3 of sediment removal (upstream of the Strelly Street Bridge) to commence

 

Mayor's Message - Lower Vasse River Sediment Removal Project

FAQs

Lower Vasse River Sediment Removal FAQs

Related Information

Sediment Disposal and Reuse Options Assessment

Environmental Management Plan for Carter's Freshwater Mussel Westralunio Carteri

Lower Vasse River - Dredge and Disposal Management Plan

Lower Vasse River - Acid Sulfate Soil and Dewatering Management Plan

 

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