Ertech Pty Ltd was awarded the contract to install a new bridge, fishway and automated weir gates for Perth’s Kent St Weir.
The project was facilitated by the Department of Water and Environmental Regulation and the Department of Biodiversity, Conservation and Attractions, together with the City of Canning.
The weir marks the point of transition from tidal-influenced saline water downstream, to a freshwater pool upstream.
Automated LayFlat gates control the height of the weir structure, preventing ingress of salt water during high tides when salt-water incursion is most likely to occur.
The weir maintains a retained upstream level during the extended summer period (normally low fluvial flow conditions), to benefit the freshwater environment. Additionally, automated management of the weir allows water to flow downstream during periods in which the river experiences higher flows (usually during the winter and spring rain events).
The LayFlat gates are connected to a compact hydraulic drive system, operated by a control panel over 40m away. The gates and associated operating systems are designed to withstand fully immersed conditions during flood events.
The weir upgrade provided the opportunity to incorporate a fish ladder into the structure. A sidewinder gate, segmented stopboards with stainless steel frames and marine grade aluminium stopboard segments provide manual control of the fishway entry and exit points. Due to the highly corrosive saline environment, the LayFlat weir gates, Fishway SideWinder, embedded frames and in-stream cabling were all fabricated from super duplex stainless steel.
Originally constructed in 1926, the latest refurbishments to the 52m long Kent Street Weir ensures it remains safe for operators and the general public, as well as maintaining water quality for freshwater ecosystems upstream.