The main issues faced by Wellington Water were:
- Finding a camera that could film such a small pipe over such a long distance to identify the problem;
- How to clear 3.6km of debris from the lines which had washed in from the interceptor above;
- How to make repairs 250m down the tunnel without entering it;
- Repairing the pipelines to PN35 operating pressure in one continuous 1.8km length;
- Undertake all of this work from either end of the tunnel with the majority of Wellington’s sewer flowing in the tunnel above the pipes throughout the works.
- Both ends of the tunnel had very little operating footprint and were in highly built-up residential areas of the city. This project also had major national media coverage and political oversight.
- There was a nationwide lockdown and an escalating global crisis due to COVID-19.
There were no pipe cameras in the world that could reach the distances required in such a small diameter pipe. Therefore, H&B and our camera specialist designed and constructed a camera that was able to give a full live stream of the pipeline, 3D scan and measure the damage to 0.01mm accuracy. This was the first of its kind in the world. After obtaining the footage of both pipelines and determining that the Amex pressure liner could be used, the pipelines had to be flushed, pigged and cleaned to enable us to install the mechanical couplers over the sections of pipe that were broken. This was a very technical procedure since the installation of the couplers were approximately 250 meters into the pipeline and they had to be installed with great precision to ensure adequate coverage of the breakage was achieved. With the successful installation of the couplers then the final cleaning could be undertaken followed by the lining works which occurred over two days. Destructive tests of the liner and couplers achieved a PN75 burst rating this excluded the steel host pipe.
It was the first time the Amex pressure liner had been used in the Southern Hemisphere and it was a world record installation length. To make the contract works even more challenging, we had to procure and complete the work in the middle of the global pandemic of COVID-19 and our national Level 4 lockdown. Due to the critical and urgent nature of the works, this was signed off by the Prime Minister of New Zealand as an essential job that had to commence even though the entire country was locked down. We were the first company in NZ to be allowed to fly essential workers into the country under the state of emergency and also had to find a way, with the help of the NZ and German governments, of flying a liner this large into NZ with all international travel grounded or severely reduced.
This contract is very similar in nature to the works at the subject of this tender. They both have similar installation lengths with the only real variable being the size of pipe diameter. All installation methodologies and plant requirements will be exactly the same as this contract.
