|
Customer: Christchurch City Council Contract Type: Design and Construct Location: Christchurch, New Zealand   |
Fast Facts
|
We upgraded Christchurch's main sewer, dealing with a major earthquake mid-project. The award of the project followed our successful completion of the record breaking Christchurch Ocean Outfall project for Christchurch City Council.
Our work involved 4 km of tunnelling for a 1,350 mm diameter gravity sewer, and trenched excavation of 2 km for a pumped sewer line between 450 mm and 1,050 mm diameter. We also did some pipe-jacking under rail, low covers and from road surfaces to pipe crown.
Our work was high risk work, including tunnel installation adjacent to live traffic, under streams, in and around Hagley Park. The trenchless installation was done across 10 drives up to 650 m in length, launched from 11 shafts. We used a slurry shield micro tunnel boring machine.
Most of the pipe-jack installations were carried out in a 24/7 operation due to the highly variable ground conditions and low covers likely to cause high friction loads on the pipes.
We implemented a proactive approach to health and safety with specific emphasis on worker participation in the identification of hazards, behavioural training, and the preparation of safety documentation. All our work activities were isolated from the public and traffic by barriers and fences.
An earthquake in Christchurch during construction had a major impact on our progress.
Members of our team assisted with the City's emergency response, including rescuing several members of the public trapped in buildings adjacent to our works, and emergency repair works following the quake.
Nearly 25,000 man hours were spent on the repairs of 32 pump stations, sewers and rising mains before the emergency works were handed over to the rebuild team, and tunnelling could recommence.
Tunnelling continued through the aftershocks, however the remaining drives were shortened from 600 m to 400 m for risk mitigation.
