Branch River Infiltration Gallery

Project Info

Client: Manawa Energy

Collaborators: Fulton Hogan Civil
(Taylors partnered with Fulton Hogan Civil as the Concrete construction subcontractor)

Project Description

Taylors were contracted to construct the Branch River Intake enhancement at the Branch River Hydro Electric Power Scheme. The work involved the construction of an intake gallery system under the river bed upstream
from the existing weir and intake.

Key Project Challenges
The installation of large 2.5m HDPE pipes and a new transition to the existing canal.

Installation of the infiltration gallery and concrete structure below the river bed.

Hydro Scheme shutdown required to complete the works.

Key Achievements 
The infiltration gallery consisted of a precast concrete box structure with stainless steel mesh screens perpendicular to the concrete. The works involved a shutdown of the power scheme to allow the in-river works to be completed.

Works also included control gates and commissioning, significant earthworks for the HDPE pipe, riprap, flood management, river diversion works, pumping, crushing and screening of all aggregates on site, and temporary works design.

The new intake increases the intake’s capacity, enabling the scheme to use its full consented take. It also means that it is able to operate when the river is in flood, which was not possible for the previous intake.

This project commenced in October 2021 at Branch River in the Wairau Valley area near Blenheim.

The new intake increases the intake’s capacity, enabling the scheme to use its full consented take. Importantly, it is able to operate when the river is in flood, which was not possible for the previous intake. The new intake is expected to bring in 10GWh/yr of additional generation and provide redundancy and flexibility to the intake system minimising outage times in future, which is great news for the community it serves.

The key focus area of this contract was ‘in river’ work installing the infiltration gallery 1.5m below the river bed.

A specially-made bucket attachment was engineered by the Taylors workshop team for the pipe installation for this project. This meant that the team did not have to manually compact the gravel bedding as the pipe was lowered into place.

This work required by this project was especially challenging as the river had to be diverted and a bund created for this purpose in order to keep water out of the work area. This required constant dewatering using pumps.

It was crucial that care was taken while working in the river with the crew conducting bird nesting surveys prior to river work.

The completion of this project was affected by a limited window to do the work because of the weather. An unseasonal flood in January meant the river levels did not drop in the time expected, which meant the timeframe for ‘in river’ work was put under additional pressure.

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