Australia’s first Infrastructure Sustainability (IS) rating

Tenix has been awarded Australia’s first ever Infrastructure Sustainability (IS) Design rating, achieving an ‘Excellent’ rating level for the design of two sewage treatment plants (STPs) at Cannonvale and Proserpine in North Queensland.

Australia spent more than $60 billion creating infrastructure in 2011/12. This included investment in roads, ports, railways, bridges, telecommunications, water and wastewater, electricity generation, electricity transmission and distribution, and gas pipelines. The IS rating scheme, developed and administered by the Infrastructure Sustainability Council of Australia (ISCA), is a comprehensive scheme for evaluating the sustainability of the design, construction and operation of infrastructure in Australia, setting a beyond best-practice benchmark for sustainability in infrastructure.

The IS rating was achieved by Tenix for the design of Proserpine and Cannonvale STPs, which the company is also constructing and will operate and maintain on behalf of the Whitsunday Regional Council.

In using the IS rating tool for the project, Tenix was able to confirm that its treatment plant designs are beyond best practice. The designs achieved the highest possible score in the IS rating tool’s Materials and Innovation categories.

Equally, the IS rating process for the STPs allowed and encouraged Tenix to step up and identify and implement best-practice and innovative sustainability solutions in other areas to deliver long-term environmental, social and economic benefits for the Whitsunday region.

Tenix used a compact membrane bioreactor (MBR) design for the Cannonvale plant, and a sequence-batch reactor (SBR) at Proserpine, instead of the larger, more complex designs proposed by the client. This resulted in systems that require less building materials and have a smaller site footprint compared to the original designs. Both Tenix-designed plants will produce high-quality effluent using as little energy as possible, setting an industry benchmark in the process.

Cannonvale Sewage Treatment Plant under construction in the Whitsunday region.

As a result, the Tenix designs will achieve estimated annual electricity consumption savings and reduced carbon emissions of 305 MWh and 272 tonnes respectively compared to typical plant designs. This equates to annual savings of $75,000 in ongoing operational costs.

The design also uses fewer construction materials and incorporates re-use. For example, a cut:fill balance in the earthworks design minimises the import and export of material from each site, saving money and reducing waste charges and the associated emissions generated by transport. The design also avoided using asphalt for roads, instead using ‘green’ concrete supplied from a batch plant next to the Cannonvale STP. The green concrete used for the project substitutes up to 30% of cement component with fly ash from a nearby power station.

The materials specified in the initial design provided to Tenix and the council would have accounted for the equivalent of 5094 tonnes of CO₂ emissions. In contrast, Tenix’s design will only generate 3264 tonnes of CO_2e for materials (including the re-use of materials) - a 36% reduction (1830 tonnes) in emissions. As a result of expected operational energy consumption reductions and lower materials use, the ‘Excellent’ IS design rating will see a total of 15,400 tonnes of CO_2e saved across the construction and operation of the plants.

As a regional first, the council and Tenix developed a plan to identify and assess the risks posed by climate change to the design and operation of the upgraded Cannonvale and Proserpine plants. The analysis was based on climate projections sourced from CSIRO, the Bureau of Meteorology and external consultant modelling. Climate change-related hazards were identified, assessed and risk-mapped for various components of the plants and associated sewage collection and discharge networks over three time periods (present day, 2030 and 2070).

A number of very high risks were identified in relation to five components of the plants, including flood impacts (2030 and 2070 years), access to site, heatwave impacts on materials and cyclonic impacts on electrical controls. The risks and adaptation measures - excluding low risks - have been added to the project risk register and will be taken into account when preparing and implementing the site operations and maintenance plans for each of the plants.

Proserpine Sewage Treatment Plant under construction in the Whitsunday region.

A Local Participation Plan was also developed to ensure that at least 70% of the project’s procurement budget is spent within Queensland, and as much as possible of this in the local Whitsunday Region. To date, the plan has already been exceeded, with 50% of the project procurement expenditure spent in the Whitsunday region and a further 30% spent in south-east Queensland. Spend outside of Queensland has generally been for specialised equipment not available locally.

A number of other sustainability initiatives were also developed, including a Green IT plan (resulting in annual savings of 10.7 MWh and avoiding emission of 9.5 tonnes of CO_2e) and fuel-efficient vehicles to save fuel and reduce carbon emissions.

Site-based initiatives have included using recycled water for hydrostatic testing of the tanks (resulting in the saving of 2 ML of potable water - nearly the volume of an Olympic-sized swimming pool) and the installation and use of rainwater tanks for amenities and landscape irrigation.

There has also been a significant focus on ‘zero harm’ safety drivers across all project phases. To date, there have been no lost-time injuries recorded on site. In addition, a culture of reporting near-misses has been engendered as a basis for developing safety strategies to avoid possible injuries.

Tenix and Whitsunday Regional Council have shown leadership in demonstrating how sustainability of critical infrastructure can reap benefits to the local community and the environment - including, in this instance, the Great Barrier Reef Marine Park and the 74 Whitsunday Islands that fringe the coastline.

The IS rating scheme is focused on changing industry behaviour and making sustainability a priority in the planning, delivery and operation of infrastructure. Designing and delivering more sustainable infrastructure provides benefits to asset owners, users and society over the long life of infrastructure, including lower environmental impact, enhanced social outcomes, better asset performance and commercial advantages.