Menai Reservoir Roof Renewal & Relining

The Menai Reservoir (WS0268) was built in 1978 and is part of the Woronora water delivery system. Its capacity is 25ML and serves approximately 16,500 people. The circular reservoir has a diameter of 51.5m and a depth of 12.7m.

The reservoir was constructed with a concrete floor slab, welded steel plate walls and an aluminium sheet roof supported by 14 radial steel rafters with intermediate steel purlins. Two annular rings of intermediate columns, in conjunction with the central column, support the rafters. Due to the high level of corrosion/damage to the roof structure and walls, Freyssinet Australia was engaged to perform roof renewal and relining works.

The scope of works included:

• Installation of modular galvanised steel handrails.
• Installation of stainless steel roof ventilators.
• Installation of new stainless steel internal ladder and platform.
• Demolition of existing roof structure and removal of bituminous lining.
• Design management of fabrication drawings for all new roof structures.
• Installation of new roof structure – including galvanized rafters, cross beams, cross bracing, and aluminium purlins.
• Significant compensation plate welding to 85% of the reservoir diameter using flux-core arc welding.
• Abrasive blasting and relining of reservoir with high build epoxy coating.
• Hazardous coating management including removal and disposal of lead-containing paint.
• Installation of electrical systems for security, mixer motor and telemetry.
• Installation of cathodic protection system.