Alongside Rangitata Diversion Race Management Ltd (RDRML) and key stakeholders, Riley has been involved in developing a new fish screening facility for the Rangitata Diversion Race. The project is on track to be commissioned in May 2022.
The main design requirement was to enable RDRML to take the required flows into the scheme while ensuring that any fish entering from the Rangitata River intake were provided with safe passage back to the river. This prevents the fish being swept into the 67km-long canal scheme.
Since starting work on the project in 2015, we have undertaken geotechnical investigations and detailed hydraulic and civil design, as well as construction monitoring, for the new screening facility.
Once complete, the fish screen will be the largest and most complex ever built in New Zealand, and among the largest in the world.
The final scheme comprises new rock and gravel lined supply canals, feeding into a 105m-long reinforced concrete screening facility – complete with a full-length walkway.
The main fish screening structure incorporates more than 430m2 of screen area (circular and flat screens). This is designed to laterally capture more than 30m3/s of flow while safely returning fish to the Rangitata River via a 190m fish bypass channel.