What is so exciting about the delivery of a 60mld floating pump station? During a drought & pandemic? Within 12 months?

Greg Cameron (MTL NZ Ltd), Holger Zipfel (MTL NZ Ltd) and Sven Harlos (Watercare Services Ltd)

Why did we design, build and commission a 60MLD floating pump station in the Waikato River?

Watercare have commissioned a Water Treatment Plant (WTP) as part of the Waikato River to Redoubt (R2R) programme to deliver an additional 50 million litres of treated water per day (MLD) from the Waikato River to Auckland as urgent drought mitigation. This plant needed to be designed, constructed, and commissioned within a 12 months’ timeframe – to enable water delivery to Auckland by Winter 2021. A conventional pump station with fixed intake screens, tunnel and wet well with raw water pumps could not have been completed within the drought response timeframe – an acceptable alternative solution was required.

What are the challenges associated with a floating pump station in the Waikato River?

The items below are some of the major challenges we faced during the design and execution of this project – a combination of stakeholder management, engineering and operational continuity:

• The downstream intake of the existing 175 MLD water treatment plant (20m) always had to be kept operational and protected during investigation and construction

• Finding an acceptable and least intrusive solution with Waikato Tainui and the Te Taniwha O Waikato

• Varying river levels from 0.5m (minimum river level) to 5.65m (flood condition)

• River flows of up to 2m/s

• Pump station debris loading with frequent “floating islands”

• Wave & seismic actions

• Unwanted visitors, operator / maintenance safety

How can you meet all these requirements and deliver this project on time?

In a nutshell – it took an integrated approach between floating pump station design, operational and maintenance requirements, partnering with equipment suppliers & procurement fast tracking, continuous contractor and fabricator design input and focused interface management with the downstream water treatment plant process components.

Procurement focused design

From the early stages the team had to focus on program, starting with the selection of robust equipment. Our design focus was the early procurement definition of these long-lead time items:

- The pump station design relied heavily on a well-established marine pontoon structure – LinkfloteTM pontoons made by Volker Brooks (UK)

- Intake screens were sourced from a supplier with a proven operational track record in New Zealand – AWMA (Australia)

- Submersible pumps were sourced out of Germany by KSB

- Hoses to achieve the required pump station river level variation were sourced by HCD out of Australia

- Access gangways were designed and fabricated locally by Manson Engineering in Henderson

- The pump hoist was supplied by Monocrane

What ties this all together?

A well set up local fabricator (JP Marshall - Hamilton) with in-house fabrication support provided design input before construction drawings were issued mid-November 2021. 

In-depth and agile collaboration between the supplier, designer, and constructor (Brian Perry Civil), regular factory and site inspections, were key to this successfully implemented project.