During the gold rush era the Little and Big Peninsula Tunnels were created on the Yarra River to enable alluvial gold miners to readily access the bed in the cut-off sections of river channel.  With over 1 km of effective river reach effectively abandoned, MWC have been exploring the feasibility of reengaging the section of channel cutoff by the Big Peninsula Tunnel. On face value the project appeared to offer an easy gain towards meeting significant river health improvement outcomes.  However, the project from investigation through to construction has confronted many challenges, including:

• Investigations - Defining clear objectives given:
  • Retaining flows in the tunnels- Flows had to be retained for historical significance, and site amenity acknowledging its status as a the tourist attraction;
  • Ecological improvements – The observed environmental values that had adapted within the abandoned channel, and demonstrating ecological benefits of reengaging in terms connectivity and habitat for fish, frogs and macroinvertebrate
  • Hydraulic dis-connectivity – the various barriers to overcome to establish an effective through flow
• Design - Overcoming physical constraints including engineering solutions for:
  • The MWC Water Main and pipe tracks crossings
  • Access road  and culvert crossing
  • Channel bed re-profiling whilst minimising disturbance
• Implementation  – Undertaking works the sensitive environment, in terms of:
  • meeting stringent local planning requirements and approvals
  • managing access to site and construction footprint
  • Limitations on construction methods

Following implementation the project presents an opportunity to verify ecological outcomes through ongoing monitoring and research.