Orewa West Wastewater Project an innovative Solution

Watercare installed a 3.2 km 450 and 630 OD wastewater trunk gravity pipe line to service a 235 ha greenfields development (9,400 people) in Orewa north of Auckland. The pipeline is up to 30 metres deep and crosses the Orewa River and a geological fault line.

The original concept solution was a conventional wastewater trunk collection system and consisted of several pump stations with the associated gravity and rising mains.

This paper deals with the development of an innovative and cost-effective solution and its successful implementation. The final solution was a gravity pipeline and one lifting pump station, eliminating all the inline pump stations and corresponding rising mains. In addition, in-line operational storage was provided at minimal additional cost.

The route of the pipeline runs through hilly terrain which resulted in very deep manholes.

Durability and operational efficiencies were major considerations in the development of the final implemented solution and took into account Watercare’s operational requirements. Learnings with regards to optimisation of concept designs can be of benefit to other future projects.

This paper demonstrates how a complex and challenging project can be solved by an innovative, cost-effective solution and successfully implemented.