Red Hills Creek Diversion

Hydro Tasmania has taken up the challenge to identify and develop opportunities from the current system, which could be captured to restore lost water inflows rather than just accepting a reduced system capacity. On this basis a target to identify 1000 GWh of additional energy from system enhancements of the Hydro Tasmania’s assets was set. The Red Hills Creek Diversion Project is part of targeted catchment diversion and diversion upgrades.

An objective of the project was to increase existing storages, such as Lake Plimsol, to capture grater inflow to be release during drier periods. Lake Plimsol was reduced in size in the mid 1990s due to the need to cut costs. This project is part of Hydro Tasmania’s plan to upgrade or redevelop existing power stations, some of which are up to 70 years old.

Positioning two structures on the Red Hills Creek and Number 1Creek to capture the natural overland run-off and that of several creek tributaries, the project sees a V drain which catches the overland flow and channels it through a series of pipes which ultimately diverts the flow under a roadway and to a tunnel portal into a natural watercourse.

The catchment goes into an eight-kilometre tunnel from the Anthony Dam and then into the underground Tribute Power station. Development of the Red Hills Creek diversion tunnel utilised hand held machine and drill and blast techniques. This provided the following advantages:

• A minimum of soil to be removed
• Tunnel slope to allow natural drainage, eliminating the need for a pump during the excavation cycle
• Hand held development to provide greater control over the finished contours of the tunnel design

Charging and blasting was carried out with the aim of minimising damage to the walls and backs of the tunnel. This required careful selection of explosives and charging to conform to the rock type and geotechnical conditions.

One of the major challenges facing the project was the weather. In one week more than 250mm of rain fell on the site making conditions extremely difficult for heavy machinery. Also, as a design and construct project a number of design changes were required as the project developed. Unexpected variations in rock structure required the need for alternative structures to be developed.

The Red Hills diversion project will contribute an additional five percent output on the existing power station while contributing to Hydro Tasmania’s objective to source an additional 1000 GWh of additional energy from its existing generation assets.