A STREETSCAPE WITH A SUSTAINABLE ETHOS

Rather than just tearing it down, this iconic streetscape in Newcastle has been saved thanks to some innovative thinking.

Located on the traditional lands of the Awabakal people stands the city of Newcastle, Australia’s second oldest colonial settlement. In the early 1930s, the city began planting trees in an effort to improve the environmental impacts of its mining and steel-making industries. During this time, large ficus microcarpa var hillii, commonly known as Hills Weeping Figs, were planted throughout Newcastle, including in the suburb of Cooks Hills along Laman Street. Over time, the trees created an iconic streetscape, their lush interlocking canopy creating what was often described as the town’s “green cathedral”.

A common feature of most fig species, including the Hills Weeping Fig, is the development of root buttresses, which are large protruding roots that grow out from the tree trunk. When grown in streetscapes, this causes many problems such as the uplifting and inevitable displacement of kerbs and pavement, as well as the fracturing of pipes and other underground utilities.

In light of this issue, a lot of the original Hills Weeping Figs planted in Newcastle had been removed, to mitigate unmanageable conflicts with property, utilities, roads and infrastructure. Due to years of root severance and ongoing injury to the structural integrity of the trees, the city also decided to adopt a precautionary approach and remove the trees located in Laman Street. At a massive size of 25 metres in height by 25 metres in width, these fig trees lacked proper supporting roots and were considered unstable.

In June 2012, after an involved public relations exercise, Newcastle Council underwent operations to remove the trees in Laman Street. Police protection was required for the operations team during the removal, as members of the public had become emotionally attached to these iconic city landmarks. However, in an endeavour to renew the Laman Street civic and cultural precinct, the city called in sustainable landscape experts Citygreen Systems to create a new streetscape, but with a more appropriate tree-pit design.

The renewal process posed many challenges. It was decided that ten Ficus microcarpa and two Jacaranda trees would be planted in place of the Hills Weeping Figs, along with two large cultivars with aggressive root systems. These trees needed to be successfully integrated into the new urban setting planned for the area, which necessitated successful growth beneath paved areas. The location of the new streetscape was the Newcastle Art Gallery, adjacent to the city’s venerable Centennial Park, thus ensuring the trees survival and adding value to the prestigious site.

To ensure the project’s success, the Citygreen Stratacell™ soil vault system was installed beneath the paving. The innovative Stratacell™ system allowed for permeable and load-bearing pavements to be placed over the top of buried cell modules filled with soil, which had strategic openings for the new trees to be planted inside. Supporting sustainability and a circular economy, 57 tonnes of recycled plastic was used to create the vaults, allowing the roots to establish themselves in uncompacted soil beneath the pavement.

The Stratacell™ system is the strongest soil management system available on the market. Its robust open matrix design ensures that any downward force is equally shared, without compromising soil space, for strong root growth. The strength of the system was crucial in the success of the Laman Street project, as it was able to accommodate heavy traffic loads while still allowing healthy tree root growth underground.

Due to the ease of installation of the Stratacell™ system, provisions were made to accommodate the buttressing nature of the ten fig tree species. The pervious paving on top of the vault allowed stormwater runoff to recharge the local groundwater, without adding any load to the traditional stormwater infrastructure. To date, there has been no runoff at all into the public stormwater system.

Several years later, the new trees have dramatically outperformed initial expectations. The 10-year canopy prediction for the project was reached in only four-and-a-half years, with the new figs beginning to interlock their canopies to recreate the arched look of the “green cathedral” that previously graced the site.

Proving a resounding success, the Citygreen Stratacell™ soil vault system has allowed the iconic Laman Street streetscape to live on, remaining an iconic landmark for future generations.

PROJECT PARTICULARS

Client City of Newcastle

Location Newcastle, New South Wales

Streetscape Citygreen Systems

COMPANY

Citygreen Systems

P             1300 066 949

E             info@citygreen.com

W            citygreen.com