SCA’s Pheasants Nest Flow Management and Fish Passage Works

AWMA partnered Christie Civil and the SCA on this environmental project incorporating flow management and fish passage works south west of Sydney. AWMA designed and supplied a range of hydraulically actuated stainless steel gates including a sidewinder, V-notch penstock, overshots, undershots and a DLF (downwards opening penstock) 5.2m wide.

AWMA were required to custom design and manufacture five unique stainless steel penstocks to:

• Allow the accurate measurement and release of variable flows, through both Pheasants Nest and Broughtons Pass weirs. The works will provide for remote, responsive and safe operation of the new releases and will allow the SCA to meet new environmental release requirements.
• Improve the river systems upstream fish passage by constructing a vertical-slot fishway at Pheasants Nest weir. The fishway will help to reclaim fish habitat that has been lost due to the presence of the weir.

The stainless steel water control infrastructure included:

• Nepean Tunnel Entrance: An off-seating downward opening penstock with twin hydraulic cylinders on a gate measuring 5.2m wide will control a 3.2m supply level. Up to 30% of Sydney’s water supply could be directed through this gate;
• Broughtons Pass Weir Environmental Release Gate: An off-seating downward opening penstock with a single hydraulic cylinder actuator mounted on a concrete wall at a 64º inclination;
• Pheasants Nest Weir Environmental Release Gate: An off-seating V-Notch penstock with a single hydraulic cylinder actuator mounted on a concrete wall at a 60º inclination;
• Pheasants Nest Fish Way: An on-seating overshot penstock mounted sideways with a single hydraulic cylinder actuator;
• Pheasants Nest Weir Scour Valve Replacement: A manually operated, on-seating SLF penstock fitted with an IP68 rated actuation system. It is also fitted with a removable extension handle to ensure there is no protrusion above the concrete, into the walkway area.

The work under this contract will provide variable flow releases and allow SCA to set the supply and environmental releases locally or remotely. There is also the provision for remote monitoring as the penstocks with hydraulic cylinders have been fitted with transducers to remotely monitor gate positions.