Costin Roe Consulting designed the integrated stormwater and remediation of a degraded section of the upper Cooks River, an asset of Sydney Water, resolving differing stakeholder requirements through collaboration to improve flood impacts and facilitate an environmentally-efficient industrial infill development.

The principles of Water-Sensitive Urban Design (WSUD) guided engineering by Costin Roe Consulting to design the remediation and upgrading of a section of the upper Cooks River, an asset of Sydney Water, which flows through a flood-affected industrial development at 15-19 Muir Road, Chullora NSW.

For consideration within this project, the 900m overall section of the upper Cooks River was divided into three subsections. The “upper third”, a 220m length of natural channel with vegetated banks, was overgrown, weed-infested, hazardous to access, and filled with rubbish and debris which impeded flow conveyance. The 320m “middle third” comprised a concrete-lined and brick-walled channel with failing walls and crossings, and steep banks overgrown with vegetation. The “lower third” consisted of covered culverts for 360m, followed by an open channel of concrete and brick for a further 320m.

An infill development proposed for the site would replace a disused, dilapidated, and contaminated former waste transfer centre with a state-of-the-art, 5 Star Green Star rated facility where more than 200 people would be employed. To facilitate this development, Frasers Property Australia, the developers, appointed Costin Roe Consulting to design the remediation and upgrading of the upper Cooks River section to the satisfaction of key stakeholders with differing requirements.

Stakeholder collaboration is key to successful water management design

Key stakeholders are Sydney Water, the NSW Office of Water, the City of Canterbury Bankstown Council, and Frasers Property Australia. The NSW Office of Water advocated for a naturalised system but was not responsible for maintenance. Sydney Water sought a hard-engineered system for maintenance minimisation. Council required WSUD principles in asset management, and Council and Sydney Water required the overland flow and flooding considerations associated with the site to be managed so that development would not increase identified flood impacts.

Through collaboration with stakeholders, Costin Roe Consulting devised an integrated solution which achieved stakeholder consensus by balancing differing stakeholder requirements with environmental imperatives, sustainable practicalities, and engineering best practice to deliver favourable outcomes.

According to the design by Costin Roe Consulting, the upper third subsection of the upper Cooks River was preserved as natural channel and cleared of weeds, rubbish, and debris. Banks were stabilised and revegetated with native plants. Maintenance access was provided. Flow conveyance was improved.

The middle third, formerly consisting of outdated and deteriorated open hard channel through the site, was upgraded by a combination of new hard channel and naturalised vegetated overbank overflow zones. This approach satisfied both the NSW Office of Water requirement for naturalisation and the Sydney Water requirement for maintenance minimisation.

The covered culverts of the lower third were extended, and flood storage zones increased. A formalised overland flow path was effectively established from the open channel through the project to Muir Road. Flood impacts were improved in areas previously identified as high hazard in 1% AEP events. The 100m extension of the closed culverts from the lower third subsection also allowed for the carpark of the new PFD facility to extend across the closed culverts, maximising land usage for the infill development.

WSUD translates into benefits for the community and environment

Flood modelling by Costin Roe Consulting, using methodologies approved by Council, successfully demonstrated that flood impacts in the area affected by the development would be maintained or improved by the project. The completed development provides a range of significant benefits to the community and environment. The potential for further development in the area was improved through integrated stormwater design, and the Sydney Water asset was remediated and upgraded without cost to the community or governing authorities.

The environmental improvements delivered by this project provided significant benefits to the community. The removal of rubbish and debris from the section of the river, the improvement in flow conveyance, increased flood storage zones, and formalisation of the overland flow pathway all translate into improvements in the environment, amenity, and water quality resulting from project completion. The success of this project delivered to the community and government a more durable, flood-responsive, environmentally sensitive, and sustainable section of urban waterway.

Sustainable industrial infill development benefits industry, the community, government, and economy. With a scarcity of greenfield development land available within the Sydney metropolitan area, industrial infill development allows businesses to locate facilities near to major transport routes, distribution centres, ports and airports; and helps to create jobs near outer urban residential areas where needed, leveraging existing infrastructure as Sydney continues to grow in population and increase in density.

The $70m 22,208 sqm facility completed by Frasers Property Australia for PFD Food Services has won the Industrial Development accolade at the Urban Taskforce Development Excellence Awards 2019 and the Industrial Development category honour at the UDIA NSW Crown Group Awards for Excellence 2019.

NSW Stormwater project

A section of the upper Cooks River project with the new open hard channel and vegetated overflow banks from the integrated stormwater design by Costin Roe Consulting (image: Mark Wilson, Costin Roe Consulting).

Infrastructure upgrade for PFD facility development 1Infrastructure upgrade for PFD facility development 2Infrastructure upgrade for PFD facility development 3

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