Client: Tasman District Council

Duration: March 2021 to October 2022

Background

The existing Pōhara water treatment plant needed a significant upgrade to bring it up to the required industry and regulatory standards. The plant serves a small community in Golden Bay, Tasman District. This community has a variable population, with the largest user being a popular campground. The source is surface water from a small, “flashy” catchment which is exposed to high turbidity events. The key purpose of this project was to bring the Pōhara Water Treatment Plant up to meet the New Zealand Drinking Water Standards (DWSNZ), as it previously provided inadequate treatment and protection to the public.

Delivery Solution

The upgrade includes an ultra-filtration membrane unit which will make sure the plant complies with the New Zealand Drinking Water Standards as it provides a barrier to protozoa. The scope included the design and installation of membrane filtration providing 4-log credit treatment, a new building to house the membrane treatment unit, associated process pipework, compressed air, chemical clean process, discharge to waste system, site access and stormwater improvements, power and automation upgrades, potable water storage upgrade, SiD and HAZOP facilitation, and the development of construction and as-built drawings and operations and maintenance manuals.

Outcome

During the project, Downer collaborated with the client on risk using change registers to plan and be aware of potential scope changes and their time and cost implications. This collaborative way of managing risk and scope has been successful in this project for the Tasman District Council. One of the main challenges of the project was the confined site layout as there was very little spare room, and access to site was also limited. 

As part of the upgrade, Downer has been able to improve the site layout even with the addition of a new building. In addition, the close proximity of this site to neighbouring properties has been a critical factor during construction, and, as such, crews have paid special attention to minimising disturbance while completing the works. There were no complaints or issues raised from the surrounding stakeholders. The overall water quality out of the new plant has increased significantly, with the turbidity of treated water decreasing by a factor of 50 during fair weather, and even higher during poor weather.