A 304 km underground pipeline is used to transport concentrate, in a slurry form, from Minerals and Metals Group (MMG) Century’s mine operations at Lawn Hill in northwest Queensland to its port facility at Karumba on the Gulf of Carpentaria.

Following a failure on the pipeline in October 2009, the decision was made to install a 1.2 km bypass pipeline around the damaged section, at the 115 km point of the existing pipeline. The bypass pipeline is 300 mm in diameter and made of API 5L X70 steel.

MMG spokesperson Sally Cox said “The pipeline is integral to the mine’s ability to transport its product to customers, so the bypass installation project needed to be undertaken efficiently and effectively and with accordance in regulatory requirements.”

The works to install the bypass were undertaken from October to December 2009.

The project was managed by MMG employees with the support of a number of contractors. Approximately 100 people worked on the project, including high pressure pipeline welders, earthworks operators, cultural monitors, community relations representatives, supervisors and engineers.

Ensuring safe slurry

MMG Century’s main area of safety focus was around heat and fatigue management. During the summer months in remote northwest Queensland, average temperatures are between 30 and 38 degrees Celsius, with significant humidity. Ms Cox said “Working in these conditions is difficult so we focused on ensuring that all personnel were sufficiently hydrated and rested.”

All works at the site were conducted under MMG’s safety management standards and safe work procedures, with the pipeline considered part of the MMG Century site. Job safety assessments were undertaken prior to all tasks being commenced.

Challenge of the Century

“Given the importance of the pipeline as an integral piece of infrastructure to the mine, the project was to be undertaken as quickly as possible, while ensuring an ongoing focus on safety, the environment and community concerns,” said Ms Cox.

Due to strict time constraints, a major challenge included the efficient procurement and transportation of the pipe and related roads and services. The looming wet season due to hit northern Queensland in December had the potential to make engineering works more difficult, so timely completion of the project was important. A particular resourcing challenge was the availability of specialised welders.

From an environmental perspective, the company needed to ensure that the zinc concentrate slurry in the line did not leak out during the bypass installation. This was managed by freezing the line prior to cutting it to insert the bypass.

From an engineering perspective, this posed the biggest challenge. MMG had to achieve a freeze on the existing line before the line was cut and the bypass inserted in very hot conditions. Liquid nitrogen was used to achieve the freeze. A wonderful example of innovation at work occurred as the team working on the line freeze changed the methodology as changing circumstance required.

The remote location not only held challenges in terms of working conditions but also in the transportation of people and equipment. This was managed with a combination of helicopter and vehicle transportation dedicated to work on the project.

Stakeholder liaison

Ms Cox said that stakeholder communication was a major part of the project.

MMG worked closely with the pastoralists on whose property the pipeline failed to ensure they were satisfied with the clean up process. Other key stakeholders were the appropriate government departments and regulators, including the Queensland Department of Environment and Resource Management (DERM).

Regular liaison was undertaken to ensure that the works were undertaken within MMG Century environmental licence conditions and to the satisfaction of the regulator. DERM representatives visited the site on a number of occasions.

MMG also focused on communication with local stakeholders including Indigenous groups to ensure that no sites of heritage significance were impacted by the works, and local pastoralists to ensure they were kept updated on all heavy transportation through the area and any access to or works on their properties. All liaison and stakeholder relations were conducted by MMG’s Stakeholder Relations team.

MMG engaged cultural monitors from local Indigenous groups to be on site at the project during major works.

The bypass was successfully completed and, following work to bleed air out of the line and ensure consistent flow, the pipeline was recommissioned on 23 December 2009. By the end of March 2010, MMG had transported 243,308 tonnes of zinc concentrate through the pipeline.