Project Ductus Wastewater Outfall Pipeline

Over $400M in capital works have been completed at the ODL site in Glenavy, South Canterbury. This includes securing critical resource consents, such as those needed for Stage 3’s ocean outfall, which allows treated wastewater disposal.

Each stage of development involved integrating advanced technologies and suppliers from Europe, the UK, and China, with unique challenges like ensuring compliance with New Zealand’s building codes. Stage 2A notably involved the complex task of integrating a ‘flat packed’ building from China. Babbage's team also fully designed and detailed a new laboratory for ODL, ensuring it met both New Zealand’s IANZ standards and YiLi’s specific requirements, which align with their facilities in China.

This project entailed designing a wastewater ocean outfall from ODL's plant in Glenavy, South Canterbury to the Pacific Ocean. The pipeline design comprised of a 7km long inland pipeline and a 500m submarine outfall with three diffusers at the end of the outfall. The pipeline was designed to be a DN415 rising main housed in a 1.0m casing pipe. It included sections to be constructed via trenching as well as direct pipe tunnelling for the outfall. Currently, Babbage is leading the construction of the $40M ocean outfall project, known as Project Ductus, which is scheduled for completion in early 2025.

Challenges

Challenging sea conditions to undertaking field investigations. Diverse terrain with fluctuating ground levels necessitated careful pipe alignment to minimise earthworks. Vertical alignment posed a risk of negative pressure, requiring measures to ensure structural integrity.