The wind farm will be connected to the Tasmanian grid via a new 12.5km transmission line that will join up to a connection point at the existing Reece Dam.
Zinfra were engaged by TasNetworks to design and construct the 11km Single Circuit 220kV Steel Pole Transmission Line, a 220kV Switching Station, and a 1.5km Dual Circuit 220kV Lattice Steel Tower Transmission Line across the Reece Dam wall connecting into the Hydro Tasmania Reece Power Station. Scope of works include:
Clearing, stock piling and site development: Vegetation management;
Construction of temporary and permanent access tracks;
Benching and levelling of proposed construction area;
Stockpiling of construction aggregate.
Switching Station design and construction: 6 x 220kV disconnectors
3 x 220kV circuit breakers;
Associated post insulators & solid bus;
12 x Capacitive Voltage Transformers (CVTs);
New conduit systems to new equipment;
New Pre-fabricated control building;
New fence arrangement;
New access track & associate internal pathways;
Associated secondary cabling and equipment;
Associated primary conductor and compression fittings.
Transmission line design and construction: 11km single and 1.5km dual circuit 220kV transmission line to the new Dual OPGW Circuit Pieman Switching Station;
Two new circuits with hard tee at the Farrell – Reece No.1 and No.2 translines adjacent to the Reece Power Station;
Pole and tower foundation designs allowing for foundation type selection based on confirmed ground conditions;
Pole and tower erection;
All associated stringing activities.
Challenging Weather Conditions
Occurring on the Tasmanian west coast, the project area receives a high monthly rainfall average exceeding 200mm. The construction of all-weather access tracks and hardstands allowed for the tower foundations to progress despite these high rainfalls, including the wettest month on record for fifty years.
Environmentally Sensitive Area
The approved alignment for the line was designed to follow existing roadways and easements to best manage the impacts on sensitive environments. As such, the construction methodology focused on utilising helicopter stringing techniques to further minimise any impact to vegetation, which required great skill and precision by Zinfra’s pilot. Where practicable the height of vegetation for the clearance zone was increased towards the structures where wires were higher and in low areas such as gullies and creeks where there was increased ground clearance (as the line spans between elevated terrain points).
An avifauna management plan was also developed specifically to protect any native species that would be present on site. All on-site personnel were trained to identify all threatened bird and animal species likely to be encountered.
Constrained Tower Sites
The project team were required to contend with constrained tower sites, with one particular site (89A) located on a steep hillside with an existing tower in place. A 3D modelling of the new tower 89A’s location was undertaken to provide optimum benching requirements to accommodate the tower and maintain access to the existing tower 90, suitable to its location.
Poor Ground Conditions
Poor ground conditions were encountered along the transmission line which required special designs including the addition of large piers to achieve bearing capacity. The design and construction of micropile pole foundations also offered significant savings to the client over alternative latent condition foundations. Throwing up differing challenges, our team encountered a mix of rock, sand, silt, clay and gravels and high water tables that had to be addressed. A high ground water table was also encountered at numerous structure foundations which required the optimisation of tower foundation types and micropiling. This provided further cost savings to the client.
Approximately 55,000 hours were worked to the point of commissioning with no LTIs or environmental incidents, with Zinfra achieving full EPA compliance during the project’s monthly audits.
The project was completed on schedule to budget, and the client’s satisfaction. Zinfra’s work was publicly commended by TasNetworks CEO Lance Balcombe and Project Director, Mr Lyndon Frearson who said,
“We’re really pleased this important project has been completed by local contractors, TasNetworks, Zinfra and Gradco to a high standard.”
The first wind turbine has since been fully installed, with concrete foundations for the remainder well underway. First electricity will soon be generated and transported to the grid for use via the newly installed lines and substation extension completed by Zinfra.