Following the September and February Canterbury Earthquakes, the 137m high radio mast foundations settled significantly and rotated. This was a consequence of lateral ground spreading and liquefaction.  The remedial work required stabilisation of the 48 tonne mast and re-tensioning of the guy rope system.

The Mast was then lowered with helicopter by riggers in preparation for remediation of the existing foundation system.

The scope required the following work:

• De-watering of the site with existing water table above ground over the majority of site due to settlement of the whole site
• Supply and Installation of 22No. 17m long 323mm diameter double helix screw piles
• Extension of the 6 existing anchor blocks and construction of new central mast foundation
• Modifications to existing earthing radial system, inclusive of fully welded insitu concrete reinforcing cages
• Formation of new yard area and refurbishment of the ACU Hut
• Raising the existing 170 tonne Transmitter hut approximately 450mm on a further 6No. 17m 323mm diameter screw piles, following settlement
• All excavation, backfilling and completion of fencing compounds

This project had an extremely tight programme, following delays in resolving insurance claim details. Hunter Civil delivered the project ahead of the contract due date by undertaking double pumping of the ground water to accelerate the excavation and anchor construction.

Confidence in Hunter Civil’s ability to expedite works, additional works to raise the 170t transmitter hut were then negotiated with TRN. These works were also of a high technical nature and required an innovative approach to combine the temporary solution with the permanent works design.