Wyangala Dam Stage 1b Safety Upgrade - Spillway Downstream Chute Wall Raising

State Water continually undertakes investigations to ensure that all its dams meet the requirements of the NSW Dams Safety Committee. Recent risk assessment found that all its dams are safe for day-to-day operations, however, at some dams, the spillways are not big enough to safely handle a large to extreme flood that would occur in a rare event. Wyangala Dam is one of seven State Water dams that requires safety upgrades for extreme floods. The proposed stage 1 of the development of the dam safety upgrade is maximising flow though the existing spillway gates by raising the gates by 1.4 metres higher than the current position, raising the spillway downstream chute walls as well as raising parapet wall crest by 1.8 metres. Stage 2 involves constructing an auxiliary spillway to achieve full compliance with the Probable Maximum Flood (PMF). It is proposed that raising the gates and the spillway downstream chute walls to be undertaken as an initial task. Safety upgrade works for raising the spillway downstream chute walls includes construction of new buttresses and support walls, raising reinforced concrete spillway chute walls and new structural steel access platform and ladders to exhaust fan on LHS chute wall. Other works that are required in this project include the effective disposal of waste; Excavation, removal and replacement of portion of the existing backfill on the RHS chute wall to allow construction of the RHS buttress; Relocation/re-establishment of any site services disturbed by the works.

Challenges

Working in a remote rural area and no electronic communications and working at heights adjacent to dam gates

Clients Specific Needs

Accelerating program to mitigate disruption to SWC Operations Team

Any specific OH & S or environmental issues

A site specific environmental plan has been developed as a management tool to prevent pollution to the Lachlan River.