Management Plans
Southern Gateway Alliance recognises the environmental challenges and constraints facing construction of the NPBH. As a commitment to protecting and enhancing the environment, SGA is implementing a number of environmental strategies and initiatives.
A series of Environmental Management Plans have been developed in collaboration with key stakeholders to identify potential impacts and detail management measures for the implementation of the project.
This includes Environmental Management Plans for the following areas:
- vegetation
- rehabilitation and landscape
- dieback and weed management
- topsoil
- surface and foreshore water
- fauna fencing and underpass
- European heritage
- Aboriginal heritage
- construction
Some of the environmental initiatives implemented by the Alliance are outlined below:
Cockatoo Nesting Boxes
Under the Fauna Management Plan, it was identified that construction of the Kwinana Freeway extension and Forrest Highway could potentially impact the breeding habitat of the White-tailed Black Cockatoo. Endemic to Western Australia and located in the South West, White-tailed Black Cockatoos require suitable tree hollows to nest and breed.
As a result of these findings, the environment team at SGA invested in purchasing and installing a collection of artificial nesting hollows. Known as Cockatubes, these robust, innovative and functional nesting hollows provide safe and secure habitation for the birds and were discreetly positioned high in tree canopies.
Developed in conjunction with the Department of Environment and Conservation, the Cockatubes were manufactured by the Serpentine-Jarrahdale Land Conservation District Committee.
Relocation of Native Grass Trees
Translocation of grass trees was a significant environmental achievement due to the volume of the relocations and the age of the trees involved. The average age of the grass trees ranged between 100 and 150 years.
The relocation process was often labour intensive and generally involved
a four step process including trimming, transportation, sourcing suitable
alternative environments and planting.
The majority of the transplantations took place on the Forrest Highway.
Protecting Local Fauna
The new route travels through various areas which are known to support both small and large native species including reptiles, small mammals and kangaroos.
To provide safe and secure passage for fauna, as well as protect road users, both the Kwinana Freeway extension and the Forrest Highway possess fauna fencing and underpasses at various locations.
The locations were chosen following a detailed investigation into the frequency, distribution and direction of local fauna movement and migration, as well as consultation with various local stakeholders.
On the Kwinana Freeway extension, more than 30km of fauna fencing and six underpasses have been installed throughout Baldivis and the Paganoni Reserve.
Approximately 16km of fauna fencing and six underpasses were installed on the Forrest Highway, primarily from Harvey River, through the Lake Clifton pine plantation on route to the tie in with Old Coast Road.
The fencing prevents fauna from crossing the road therefore minimising potential conflict with traffic, as well as guiding the animals to the underpasses. In addition to the underpasses, fauna will also have the opportunity to cross at bridge sites.
The fence is comprised of an extremely durable double layer, chain wire galvanised mesh and is, on average, 1.8 metres above ground. The fence also extends approximately 0.4 metres below ground to discourage fauna from burrowing underneath.
The underpasses vary in height and width – the larger models are 1.8m x 1.8m and the smaller models are 1.2m x 0.6m. Each underpass has an opening in the centre to let sunlight into what is effectively a tunnel and the floors have been lined with sand, mulch and small branches to encourage the local fauna to utilise them.
During construction the underpasses were in place for nearly one year prior to the project opening. During this time, the local fauna, specifically kangaroos and even emus were commonly seen using the passageways. It is hoped and expected that this will continue to occur into the future.
Harvey River Restoration Project
Whilst constructing the bridges across the Harvey River as part of the Forrest Highway, Southern Gateway Alliance realised the opportunity to further enhance the popular location for future generations.
The Alliance combined with the Harvey River Restoration Taskforce, the Peel-Harvey Catchment Council, Water Corporation and the Department of Water to re-establish connections between the lower Harvey River as well as a number of conservation category wetlands.
The restoration specifically included the installation of a riffle to trap sediment, rock protected wetland inlets and large woody debris to provide habitat for aquatic species. The project also aimed to control river bank erosion and included strategic revegetation and weed management.
History: The Harvey River Restoration Project commenced in November 2008 and concluded with the New Perth Bunbury Highway opening in 2009. The project area extended 1.3 kilometres upstream and 300 metres downstream from the Forrest Highway crossing, which is approximately 10 hectares in area. The Harvey River is one of the three major river systems flowing into the Peel-Harvey Estuary.
Location: The project area is located approximately 17km to the north-west of the Waroona town-site, abutting the Forrest Highway, and is bounded by Doman Road, Old Bunbury Road, and Dorsett Road.
Access and Facilities: The Forrest Highway crossing at the Harvey River features a walking track and bridle trail, which is an existing 10th Light Horse Brigade path which has been upgraded as part of the restoration project. Those wanting to access the location are advised to park at the rest area, north of the Dorsett Road interchange, which is approximately 100m away from the crossing. Toilet facilities are also provided at the rest area.
Drakaea elastica
One of the most significant environmental challenges faced by the project was construction of the road through the area of Paganoni Reserve in Karnup.
SGA’s project team spent over 12 months investigating alternative alignments for the 5 kilometre section of the Kwinana Freeway extension in order to minimise the impact on the population and habitat of rare orchid – Drakaea elastica, which were discovered in October 2006.
In recognition of the environmental significance of the Paganoni reserve, a number of measures were implemented to reduce the impact of the road.
Not only was the median reduced substantially to reduce the road footprint, SGA worked closely with a number of environmental stakeholders to develop a Construction Environment Management Plan specific to this location.
Some of the protection measures during construction included:
- Clearing for the alignment, Principal Shared Path and fence line was minimised as far as practicable for the safe construction and operation of the road
- Aboriginal Heritage sites namely the Serpentine River and the Ochre site clearly demarcated and any activity undertaken in and around the sites in accordance with a strict approval process
- Fauna fencing and underpasses installed to allow fauna to freely and safely cross under the Kwinana Freeway extension to either side of the reserve
- Areas of dieback free soil protected and areas of dieback appropriately managed and contained
- Dieback free topsoil stripped and stockpiled for future landscaping requirements, which aided in the regeneration of native seedlings and greatly increased the diversity and success of the revegetation
- Fencing and firebreaks installed to protect the reserve during and on completion of construction; and
- All construction personnel working in the area appropriately inducted to ensure all the above measures were put into practice
Prior to clearing commencing, the three Drakaea elastica plants located within the main alignment were translocated by SGA in cooperation with the Botanic Parks and Gardens Authority at Kings Park. The final road alignment avoided some 1300 plants.
The Drakaea elastica plants removed from the project site were successfully translocated to Kings Park.
The plants thrived in their new environment, with many boasting large healthy leaves and flower spikes, and were the focus of a major research program undertaken by the Botanic Gardens and Parks Authority.
The research team received a major joint grant with leading pollination experts in Germany and Canberra to investigate the co-evolution in the mycorrhizal and pollination specificity in the model genus Drakaea.
More specifically, the team will attempt to unearth the unique chemical signals in the plant pheromone that are critical to attract the male wasp to the orchid and achieve pollination.
The reality that many of the plants flowered was an unexpected bonus for the research team and meant greater opportunities to test for the presence of the specialised pollinating wasp.
DNA fingerprinting was also undertaken and involved the salvaged plants and the unique fungi associated with the species being characterised using advanced molecular techniques.
