Bunbury Ocean Outfall Foredune Re-creation and Restoration

 

 

 

 

 

 

Water Corporation

Current 360 Environmental staff provided overall project environmental management on behalf of the Water Corporation of Western Australia (Water Corporation) for the construction of an ocean outfall to dispose of treated wastewater from the Bunbury Wastewater Treatment Plant (WWTP) in 2002/2003.  The outfall is seven kilometres south of Bunbury and discharges 1.7 km offshore in waters 11m deep.  The Water Corporation prepared a Public Environmental Review (PER) for the proposal, and the Environmental Protection Authority (EPA) subsequently recommended environmental approval (Bulletin 1021, EPA 2001).  The outfall installation required the excavation of the beach from the primary foredune to beyond the surf zone. The pipeline excavation work also required temporary works to be built on the beach.

Rehabilitation

The beach historically had been accessed via a dune blow-out area.  Sand excavated was stockpiled and the beach contours reinstated at the completion of the project to reflect natural contours and match existing landforms.  All temporary construction facilities were removed from site and the foredune reinstated to restrict unauthorised vehicle access to the blow-out area.

Machinery was cleaned prior to transport to site to avoid the introduction of new weed species or soil borne pathogens.  Vegetation clearing was limited to activities essential for construction and clearing limits were surveyed and pegged in the field prior to the commencement of earthworks.  Cleared vegetation was mulched and windrowed for rehabilitation use.  This material was supplemented by sourcing local brush and using cleared remnant vegetation from a land development clearing project.  This stabilised the area and blocked access tracks.  Seed was then spread and seedlings planted.

Outcomes

 The community was encouraged to be involved throughout the ocean outfall project.  This was particularly evident during the rehabilitation program for the sand bowl and sand tracks.  A contract was established with NEEDAC (an Aboriginal Nursery originally established with help from the Water Corporation as part of the Harvey Stirling project) to assist with the rehabilitation of approximately three hectares of the primary dune and dune bowl area. 

After local seed collection, over 30 local species of plants were grown and planted (a total of approximately 28,000 seedlings) to revegetate the area. Rehabilitation signs were placed in four prominent locations to inform the public of the works and to keep people and vehicles out of the area.  In less than 12 months the rehabilitated area could be seen to be establishing well, despite the harsh coastal environment.

The Bunbury Ocean Outfall restoration program demonstrated a vision for community involvement where local indigenous representatives provided key resources.  The restoration resulted in a net environmental benefit where the dune blow out (which was otherwise subject to ongoing degradation) was stabilised.  The rehabilitation component assisted the project in winning the Institution of Engineers Awards 2003– Environment Category.

Contact

Email: admin@360environmental.com.au

Telephone: +61 8 9388 8360