Design & Construction


 

Landscaping

The Rehabilitation and Landscaping Plan for the Kwinana Freeway extension and Forrest Highway aimed to minimise the impact on vegetation, fauna and flora as well as provide good visual amenity.

The landscaping program used locally occurring native species to match the existing habitats and improve the diversity of plant species and communities within and adjacent to the highway. The plan considered the existing landscape character and was developed with input from key stakeholders.

The plan provides a safe driving experience for road users with clear sight lines and appropriate setbacks. The plan also aimed to enhance the appearance and function of the site for the benefit of motorists, pedestrians, cyclists and the community.

Rehabilitation and revegetation of areas within the road reserve was an integral part of the project and is expected to sustain and enhance vegetation values.

The landscape design philosophy was developed with consideration of the safety, social, resources management and ecological requirements of the project. The primary philosophies of the works included:

The Alliance’s landscaping team worked hard during the final months of construction to ensure the majority of seeding and revegetation of the project area was complete before the onset of the warmer months.

The revegetation for the Kwinana Freeway extension and Forrest Highway comprised seeding and planting of more than 240 hectares of the project site with more than 1200kg of seed and approximately 300,000 seedlings. More than 300,000 cubic metres of top soil and mulch was also mixed and spread as part of the program.

All sites adjacent to the route were planted and seeded, while the team is currently completing the planting of drainage basins, wetlands and sumps with wetland species as water levels recede.

Now the road is open to traffic, SGA will be responsible for the maintenance of landscape works for the next two years. Following that, Main Roads WA undertakes maintenance through their Term Network Contracts.

The landscaping team will undertake in-fill planting during 2010 and 2011, which will involve replacing seedlings that have died and re-seeding areas where germination densities are low.

The flora species, Everlastings, were used as a welcome statement to the new route and will as assist with soil stabilisation until the native vegetation has matured.

Eco Cell

As part of the revegetation and rehabilitation program the landscaping team used a product known as Eco Cell to control erosion in drainage areas.

The Eco Cell was placed underneath the top soil in erosion prone areas to prevent the earth from wearing away before the vegetation placed on top was mature enough to stabilise the soil.

Before the Eco Cell was placed the design formation was graded and a geotextile mat was laid as a base. Then the Eco Cell was then positioned and pinned into place, before the chambers were filled with topsoil and covered with mulch.

Finally, direct seeding of native shrubs and ground covers took place to completely stabilise the area.

The main location for the Eco Cell is in the area through the Forrest Highway’s most southern end and this product was chosen as an alternative to rock pitching, representing a significant cost saving for the Alliance.

Landscaping legacy for the Murray Lakes community

The largest bridge on the project, the Murray River bridge, was constructed via an incremental launch method to overcome the environmental challenges that its locality possesses.

Once the bridge was completed, the area was revegetated and any environmental impact from the highway’s construction was offset.

Immediately south of the Murray River bridge site is the Murray Lakes community, who benefited from the area’s landscaping program.

The community, who are located directly adjacent to the road and south of the bridge, now enjoy a specially designed landscaped environment and walk trail as part of the area’s rehabilitation.

Additional fill was imported to flatten the area, mature trees were pruned, a variety of mature seedlings were supplied and mulch and compost finished the area.

The newly planted flora, which includes medium shrubs, feature shrubs, ground cover and annuals, will be watered and fertilised for a year from the initial planting.

A three metre wide limestone walk trail was also constructed through the area. It is hoped the community will utilise the newly landscaped region for many years to come.

Local Amenities

A Principal Shared Path (PSP) was constructed alongside the highway to provide access for pedestrians and cyclists. The path was built on the western side of the highway from Safety Bay Road to South Yunderup, a distance of 32 kilometres. South of South Yunderup Road, cyclists will be permitted to ride on the sealed shoulder of the highway. The PSP connects to a number of local roads and underpasses have been provided at the interchanges to remove the need to cross opposing traffic.

Please click on below link to view PSP map.

Access to the shared path from local roads will be available from:

Rest areas and parking bays will be constructed to provide a place of refuge for drivers using the highway. It is intended that these amenities will be constructed in the southern section of the project, between South Yunderup and Lake Clifton, however, their locations are still to be finalised with stakeholders.

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