PROJECT SCOPE

The project involved remediation works to two of Seqwater’s weirs, namely Mt Crosby and Wilson Weir. Works at Wilson Weir near Gatton involved the following:

• Construction of gabion and reno mattress structures
• ±5,000m3 of select backfill material to the above structures
• ±11,000m3 of impervious fill
• Construction of concrete capping slabs to the weir abutments
• Miscellaneous fencing, signage, landscaping etc.

A particularly challenging aspect of the contract was the construction of the bottom row of gabions below the water level and on the irregular river bed of the Lockyer Creek.

In order to facilitate this a coffer dam structure was constructed which allowed a binding layer of concrete to be poured to ensure a level surface for the commencement of gabion works. The construction of the gabion structures and reno mattresses to tie in with existing structures and at varying levels also required special attention to detail.

Works at the Mt Crosby Weir involved:

• ±25,000m3 of cut to spoil
• ±3,000m3 of filter material
• ±6,000m3 of transition rockfill
• ap (±900Ømm)

Each of the engineered layers mentioned above required compliance with stringent material quality specifications and in particular, a very narrow grading envelope.

KEY STAFF

• Ben Dyson – Const. Manager
• Anton Rheeder – Project Mgr.
• Bryce Wilson – Project Mgr.
• Brian Moore – Site Supervisor
• Rob Forrest – Site Supervisor

Challenges

• High water levels on Lockyer Creek during the construction period necessitated the construction of coffer dams for gabion installation on both banks
• Steep existing slopes required the use of innovative construction techniques to ensure the safety of construction personnel