One of the strategies of Revitalising Geographe Waterways is ‘Innovation and Remediation’, aiming to fast track water quality improvements in key Geographe waterways through innovative technology and remediation and by implementing key actions from water management plans. The Vasse Taskforce has prioritised investment in these projects because they address an immediate need and can deliver water quality outcomes in the short-term.
The Vasse Wonnerup Wetlands Partnership undertook an experimental project that removed approximately 787m3 (around 48 dry tonnes) of sediment in the Vasse Estuary alongside Estuary View Drive in Wonnerup. The project removed sediment along a 220m stretch that is exposed over summer months when water levels are low. Build-up and exposure of black ooze sediment in this area is thought to contribute to offensive odours over summer months, impacting livability for neighbours.
A layer of nutrient-rich, fine organic sediments has accumulated throughout the Lower Vasse River with an average depth of 450mm. This sediment provides an internal source of nutrients that contributes to algal growth in summer months.
The City of Busselton is leading this project to remove sediments from the lower sections of the river. The first two stages used a micro-dredge to plane sediment from the riverbed, which pumped the sediment as a slurry into porous geotextile bags. An inline flocculant polymer was used to help separate the water from sediment, and dewater was then expelled back to the river via a return chute. Both stages trialed phosphorus-binding clay products to treat the dewater, and the porous bags were left onsite to dewater for approximately 6 months before being opened and the sediment transported offsite.
Stage 3 is in the planning phase and has been funded through the City of Busselton and the State NRM program. Stage 3 is planned for the section upstream of the Strelly Street bridge.
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