Reid Hwy Alexander Dve and Mirrabooka Ave Interchanges ▶

Aerial September 2011

The Brief

Revegetate the road verges, median strips, basins and associated areas totalling 18 ha impacted by construction activities, using direct seeding and seedling planting. Maintain the sites for three years until the completion criteria for native plant and weed cover and species diversity and other factors were achieved.

Aerial June 2017

Constraints & Issues

Working in long narrow strips along roads still open to traffic, with vehicles facilitating the ingress of weed seeds. Revegetation of high fill batters of bridge abutments relying on rainfall is typically challenging.

Our Management Approach

Intensive detailed planning was required because of the long narrow strips and various species mixes. Safety was of paramount importance in the high traffic environments. Large teams were used to minimise the need for traffic management and disruption to the public.

Revegetation commenced in winter 2012 using a combination of two strategies, direct seeding and tubestock planting. Over 66,000 seedlings were planted and 80 kg of native seed broadcast across the two project areas.

Few weeds were evident prior to the commencement of revegetation, and only minimal control by herbicide spraying was necessary during the course of the project.

The Outcome

A strict completion criteria for handover of the project was set including:

• Vegetation cover of 50% with no bare areas of more than 2 m²;
• At least 40% species richness and no less than ten species of shrubs or groundcovers or both occur within any 100 m² area;
• Where tree species are used representatives of all species must also be present;
• 75% survival of the total number of seedlings planted, and at least 10 plants per quadrant of 2.5m x 2.5m (excluding any weeds) for any 2 representative quadrants over any treated area of 100 m² for direct seeding;
• The vegetation condition must meet the criteria of being or showing healthy growth, showing no signs of disease and no signs of insect pest; and
• Declared plants and other high control priority species should be eradicated from the Site. And the presence of other nuisance species and their effect on new plant growth must be demonstrably manageable with minimum future maintenance requirements.

Alexander Dve interchange – handed over on time and 26% under budget.

Mirrabooka Ave interchange – handed over one year early (at MRWA request) and 30% under budget.

Camboon-Mirrabooka PSP – completed on time and on budget.