WSP co-developed a framework with Capital Water and Wellington Water to prioritise pipes in the worst condition in areas with minimal constructability challenges. The renewals could be programmed and undertaken with consideration of asset condition and constructability. Assets with high priority but greater construction difficulty were programmed later, to give time for more investigation and stakeholder consultation. Most work involved investigations, including reivew of CCTV footage and physical inspections where possible. WSP initiated meetings with the contractor early in the process, plus walk-throughs with the contractor, consultant and Wellington Water operations personnel.
WSP used a standardised delivery model, process and design for the programme work, which enabled increased use of trenchless technology. Adopting trenchless technology reduces carbon emissions, and the requirement for engineered backfill which has high carbon cost through manufacturing, transport and compaction. Typical pipe sizes ranged from 150mm to 225mm in diameter, and over 4km of pipe length was installed. The pipe installation methodology was predominantly trenchless (80%) with a smaller portion open trenched (20%).