- Demolition of existing manhole structure
- Construction of new major junction chamber (6m x 2.5m) at the intersection of Christchurch’s two main trunk sewer lines
- Installation of a temporary by-pass
- Commissioning of the new structure
This project was significant for the sheer size and volume of the structures involved, given location of the work site at the intersection of Christchurch’s two major relief lines. The junction chamber constructed was huge – measuring 6m x 2.5m and the two main trunk sewer lines experienced flows of up to 900l/sec at peak times. This required expert deployment of eight pumps to achieve successful bypass.
All works requiring temporary by-pass were high risk and demanded expert planning and industry-leading best practice to achieve completion within the tight timeframes associated with periods of low flow. Because of this, our crews were often deployed between midnight and early morning, when usage was low, so disruption to residents and risk could be minimised.
The project benefited from our expertise in value engineering which enabled the structure to be constructed to a high quality, cost effectively We used an innovative methodology to precast the new concrete walls and lid, onsite, and then lower into position. We also fastracked the curing process for the precast panels, so these could be lifted after just 24 hours (rather than seven days). This resulted in significant cost savings and enabled us to adhere to programme. However, early lifting was only possible due to our robust QA processes and testing regimes.
Our team included the specific knowledge and skillsets of four CCC Registered Drainlayers. The complexity of the existing infrastructure and services also demanded expertise in Permit to Work protocols to ensure all activities could be completed safely. Our success on this project was achieved through deployment of a proven team with the ability to innovate and value engineer to achieve quality, while saving time and cost.
Many of the lessons learned and expertise gained, including the same construction methods, have already been replicated on subsequent projects to achieve similar efficiencies.
Client: McConnell Dowell for SCIRT
Start Date: April 2016
Completion Date: October 2016