Tower assembly and biosecurity on agenda for QLD transmission network

Tower assembly and biosecurity on agenda for QLD transmission network
Powerlink project managers Alvin Kumar and David Vroom inspect Yuleba North to Blythdale construction works

Enhancing safety and environmental outcomes is a key focus for Powerlink Queensland as it extends the high voltage electricity transmission network into Queensland’s North West Surat Basin.

Powerlink executive manager infrastructure delivery and technical services Greg Rice said the state-owned corporation had long-term experience in delivering large-scale complex transmission solutions, with competitive advantages in easement acquisition, construction and ongoing maintenance.

“This includes completing more than 30 transmission connection services for loads and generators in the last 15 years, while delivering on environmental, social and safety requirements,” Mr Rice said.

Mr Rice said Powerlink had collaborated with its construction contractor John Holland to trial a number of initiatives as part of delivering the project’s latest transmission line, Yuleba North to Blythdale.

“The 57km double circuit 275kV transmission line between Yuleba North and Blythdale substations is the final transmission line component of our construction activities in the region,” Mr Rice said.

“Together with John Holland we are trialling a number of innovative work practices in relation to tower assembly and biosecurity.”

The ‘Pin and Pot’ method was used for tower assembly to improve safety. A technique called ‘geofencing’ was also used to deliver better biosecurity outcomes.

Assembling 30 tonne steel transmission towers up to 60m in height can be a complex task as it involves working in constrained locations and at heights, combined with sections of a tower being lifted into place. Nonetheless, Powerlink manager projects Colin Langton said while there are stringent procedures in place for tower assembly, John Holland has enhanced the process with the application of the Pin and Pot method.

“This modified technique eliminates any potential or inadvertent risk to the riggers who are working at heights near suspended loads,” Mr Langton said.

“The Pin and Pot method further builds on the hierarchy of controls already in place to safeguard the common approach of tower assembly which includes strict safety procedures like exclusion zones and spotters.”

The common tower assembly method used across the industry requires riggers to climb the base section of the tower to guide the other sections into place.

“Under the method, Pot guides are installed at the top of each section of the tower and Pin guides are installed at the bottom of the higher sections,” Mr Langton said.

“The sections are then lifted to an upright position using a large mobile crane and the crane driver is able to use the installed Pin guides to align with the Pot guides positioned on the section below.

“The positioning is aided by riggers on the ground using guide ropes from a safe distance.”

An innovative approach to minimising the spread of declared weeds was another contemporary work method trialled during construction of the Yuleba North to Blythdale transmission line.

A pre-construction weed survey undertaken in consultation with landholders and other key stakeholders identified the potential to group properties affected by construction activities into six colour-coded zones.

“The zones are based on weed species within areas bounded by roads and creeks,” Mr Langton said.

“These biosecurity zones help minimise the risk of weed spread over the footprint of the transmission line.”

This technique allows construction vehicles and machinery to operate across an area of similar environmental risk on one weed certification, which is valid for a fixed time period, restricting movements to a single zone and ensuring activities comply with zone specific protocols.

“Each vehicle is also required to undergo a weekly wash down to further minimise the potential risk of spreading weeds,” Mr Langton said.

“Colour-coded magnets are displayed on construction vehicles to easily identify which of the six geographical zones they are operating in and to improve visibility for landholders.”

John Holland project manager Warren Monks said a number of supportive processes had also been introduced to further improve the biosecurity method.

“We are using buses to transport crews to work sites to reduce vehicle movements and employing third party weed inspection officers who are embedded within the team to ensure full compliance of all wash downs,” Mr Monks said.

“Geofencing software is also being used which works in conjunction with the In Vehicle Monitoring System (IVMS) to track each vehicle to ensure it is within the correct zone and maintaining the weekly wash downs and other requirements.”

Once construction on the Yuleba North to Blythdale transmission line is complete expected by early 2016, Powerlink will undertake further surveys with the assistance of an independent expert to assess the effectiveness of the biosecurity management measures.