Metagarup Bridge and Gardens – Optus Stadium

April 2019

In 2018, the WA Government contracted Think Water Perth to complete the water systems work on the Metagarup Bridge as the result of the tender process. The main scope of the project was installing a mains water supply line and solenoid control cable through a service access area within the Metagarup Bridge. It involved installing eight inverted taps and QCV’s (quick coupling valves) along the 700 metres as Wash Down Access Points for the bridge and finally, install an automated irrigation system to the two large planter boxes at either end of the bridge.

Metagarup Bridge – Optus Stadium, Perth


There were several challenges in completing this project, firstly, the water supply came from the Optus Stadium side and specified as DN50 Schedule 40 galvanised pipe with victaulic couplings to connect every six metres under the bridge. However, due to the size of the service access point and due to practicality, we could only install in 3m lengths. The second challenge was other existing pipelines and the bridge’s steel construction, meaning we had to install over 70 pipe loops over a distance of 360m using DN50 Schedule 40 galvanised pipe with a number of penetrations through the bridge for the irrigation and QCV. The installation of this part was undertaken by a licensed plumber who was subcontracted (as per the requirements from the specifications) and took over three weeks to install the water supply line.

The other challenge was that the controller cable for the solenoid valves was specified to be installed in a 25mm HD conduit along existing cable tray under the bridge with other existing services. Think Water Perth had to install a two-wire cable for the irrigation solenoid valves within the bridge for the planter boxes from an existing irrigation controller (installed by us in Stage 1) on the opposite side of the bridge to the water mains. This represented further challenges similar to those faced installing the water line – the limited space and existing services within bridge service access areas. The team had to set up the two-wire cable on a roller system above bridge service area, feeding the cable through the service access point while pulling the cable through the 25mm HD conduit (4m lengths) and expansion loops (25mm flexi conduit). The complete installation of the 400 metres of two-wire cable took two people over three days.

Metagarup Bridge - Optus Stadium, Perth
Metagarup Bridge – Optus Stadium, Perth

The large planter enclosures were approximately 17m long x 8m wide and 1.4 metres deep. These were specified to be PVC pipe however, installing the PVC pipework before the installation of the soil and trees was not ideal. Our main concern with using PVC pipe were potential breakages occurring during landscaping, so we ended up installing SDR13.6 PE100 metric poly pipe with tapping saddles and two, of Ezy tube for each sprinkler. Hunter 4” Pro bodies were installed using spray heads and bubblers to emit the water directly to the plant base.

Whilst this wasn’t a large project, it threw up plenty of challenges in designing a solution really made the Think Water Perth team think outside the box. With the knowledge and experience that the Perth team have within their business, they were able to not only provide what is considered the best design at a competitive price but a solution that provides flexibility and long term benefits. Think Water Perth now also do the regular servicing and maintenance on this site.