Interflow (NZ) Ltd and client Alliance partners Hasting District Council and MWH Global were presented the INGENIUM Excellence award for the rehabilitation of the Hastings No. 3 Trunk Sewer, located in the Hawkes Bay region of New Zealand. The award for a ‘Physical works project with a total cost less than two million dollars’ was announced at the Association of Local Government Engineering New Zealand’s annual conference dinner in Hamilton on 6 June.

A total of 628 m of the No.3 Trunk sewer was continuously lined by Interflow using their Rotaloc System. The pipe, which varied in diameter from 1,575 mm to 1,800 mm, was the largest sewer pipe attempted to be rehabilitated in New Zealand.

Constructed in the 1970s, the No.3 Trunk Sewer was a reinforced concrete pipeline that was significantly deteriorated from hydrogen sulphide attack. The pipe is located under residential properties, adjacent to footpaths and busy roads, and below commercial orchards and shelterbelts. Because of the pipeline diameter, the only option previously available to the client for rehabilitation was open trench and relay, which would have caused considerable disruption to the orchard growers, residents, local traffic and the environment. Recognising the potential benefits of a trenchless solution, MWH Engineer Jaco Wagenaar researched rehabilitation options on the ASTT website before negotiating a contract with Interflow to provide a solution to rehabilitate the trunk sewer.

Interflow Business Development Manager Glenn Edwards said “Co-operation between Hastings District Council and Interflow was a key element to the success of this project. The client was willing to invest in the ‘concept’ supplying the project requirements and working with Interflow to develop the project solution.”

The solution in this case meant bringing the Rotaloc system into the country. Although Interflow’s smaller diameter (less than 1 m) Expanda Lining system is now well established in New Zealand, this was the first time Rotaloc had been used here.

“Rotaloc is a spirally wound-in-place PVC liner that is able to be used to renew sewer or stormwater pipes between 800 mm to 1,800 mm, and provided the best available solution for this problem” said Mr Edwards.

Interflow and the client were successfully able to provide a solution that not only met all of the requirements of the project, but also provided the client with the highest value solution and best value for money.

ASTT Councillor for New Zealand Steve Apeldoorn who attended the awards dinner, said “This project demonstrated how co-operation and constructive relationships between client and contractor benefited both parties; no one lost on this project, everyone was a winner; the project came in under budget and under time. This award is recognition of how Trenchless Technology is able to provide real solutions in terms of environmental, economic, social and cultural issues.”