Mt St Joseph Wetland Rectification

Altona, Vic

Project Duration

February to July 2024

Client

Melbourne Water

Project Value

$ 1.4m

The Mt St Joseph’s Wetland in Altona sits immediately upstream of Truganina Swamp in Altona. It was underperforming as a stormwater treatment wetland due to non-compliant bathymetry, sedimentation, invasion of typha weeds, and lack of necessary maintainable structures such as sediment ponds and appropriate civil structures. Within the next 2 years, industrial development is proposed upstream, which will increase runoff to this wetland, therefore it was important these issues were addressed to avoid future drainage issues.

The scope of works included:

Removal and disposal of 2500T of Cat D contaminated soil
Excavation of 5x new wetland ponds totalling 3,000m3
Construction of 3x new wetland berms totalling 600m3
Construction of a new weir wall structure and associated rockwork chute
Placement of 3,000m2 of topsoil and jute matting

key challenges

Management and disposal of contaminated materials on site
Ground conditions on site were extremely poor with the majority natural coastal deposits
Groundwater caused major instability in ground conditions
The site was separated into two halves with a rail corridor in between

key innovations

Due to the extreme ground instability caused by the groundwater, the entire project was completed on top of steel plates. The plates were used to distribute the weight of the plant over the soft ground.
The groundwater was so excessive that regular topsoiling methods would not have been possible. Instead, our methodology adapted a combination of coir matting, topsoil & jute matting to prevent slumping before the planting of the wetland.
Ground conditions did not enable construction of the weir wall as designed. Instead the wall was re-designed to distribute the weight over a larger area

Value for money

Re-designs & changes to methodologies were suggested/provided by Jaydo on a weekly basis
The client and consultant relied on Jaydo’s guidance for many of the design and constructability issues on site