Major utility providers are making the switch to composite materials for their projects because they’re finding them to be safer, more durable, and easier to operate.

While traditional metals still have their place in civil works, composite material products made of fibre reinforced plastic (FRP) are growing in popularity and demand.

In fact, Jemena, a leading national energy infrastructure utility, along with its delivery and maintenance service partner, Zinfra, made the switch to composite materials for its cable pit lids and cable trench covers entirely in 2020, and now exclusively uses FRP.

Following this, the North East Link Project contracted Jemena to construct a Zone Substation (ZSS) and this project has followed a similar path, exclusively using FRP cable pit lids and cable trench covers.

So what motivated major energy infrastructure organisations like Jemena and Zinfra to make the switch and why are other businesses doing the same?

Metal covers and lids are no longer safe and easy to use

Trench covers and pit lids play an important role in civil works projects to cover up and provide access to trenches and pits where cables, valves, and other electrical equipment are stored.

Unfortunately, utility and service providers are finding that traditional metal access covers and pit lids are no longer a viable option due to problems with their: 


Heavy-duty metal covers and lids are incredibly heavy and can be difficult to move. When workers need to lift them, this becomes an occupational hazard if the lid falls, slips, or becomes too heavy for the worker to safely manoeuvre.  


Many covers and lids are in open spaces and often have heavy machinery driving over them daily, or have heavy foot traffic going over the top. Metal can quickly corrode under these conditions. 

The reduced durability and longevity of metal covers mean that they become safety hazards and need to be replaced more often. 

Production and installation  

The production of metal covers can vary, and installation can take more time than anticipated due to their weight, which puts projects at risk of costly delays. 

With all these challenges, providers are looking for new materials that can guarantee a safer environment and longer-lasting materials. And they’ve found the perfect solution in FRP covers. 

Jemena updates its standard drawings to a Terra Firma composite specification

Being on the cutting edge of technology, Jemena is one of the first utility providers to make the switch to composite lids and covers.

Jemena started transitioning to composite trench lids and pit covers in 2020, with trial retrofit installations at two existing zone substations using Terra Firma’s D240 cable pit lids and trench covers. Following the success of these, Terra Firma began working with Jemena on standardising a comprehensive range of cable trench covers, cable pit lids, and control room floor panels that met the load-bearing requirements of AS3996.  

Working closely with Jemena’s plant engineering team, Terra Firma developed a labelling standard for each cover with Safe Work Loads (SWLs) so that maintenance operatives could easily identify which covers were trafficable and which were not. 

As a result Jemena then updated its standard drawings to a Terra Firma composite specification. From there on, Jemena has been specifying and installing Terra Firma lids on all its Victorian projects, including four zone substation upgrades. 

Engineering initiatives to deliver safer workplaces

Composites see success on the North East Link Project

The North East Link Project (NELP) is one of the biggest civil works projects in Melbourne, changing the way people move around in the north-east. These tunnels will bridge the gaps in the city’s freeway network and take 15,000 trucks off local roads and save drivers up to 35 minutes of travel time. 

Jemena, who owns and operate over $11 billion worth of electricity and gas assets, was contracted to design and construct a zone substation to supply power for this project.  

With a $1 million daily delay fee and close proximity to the road, the covers and lids Jemena used needed to be: 

  1. Installed on time; 
  2. Cohesive with the visual appearance of the substation; 
  3. Easily accessible; 
  4. Safe to handle and install; and 
  5. Appropriately labelled with SWLs. 

Terra Firma provided Jemena with two different class-rated covers that suited different purposes and locations: 

  1. C150   are designed with a Safe Working Load of 5000KG’s, so that mobile plant, scissor lifts and other maintenance vehicles can traverse across them. 
  2. D240 – the heavy duty D240 covers are designed with a Safe Working Load of 8000KG’s and are typically installed on road crossings within the sub station. During installation and post-installation, the NELP found a multitude of benefits to using Terra Firma’s FRP covers. 

The lighter weight of FRP covers saved hours of time during installation and post-installation. Installing the covers was quick and easy, and once workers started using them, they found that it only took minutes, rather than hours, to lift each cover, inspect or move the cables in the trench, and close the trench back up. 

Safer sites 

Terra Firma’s FRP trench covers are safer to operate and reduce occupational health and safety risks on-site. This means that workers feel safe, can do their jobs without disruption, and are at a reduced risk of accidents that could lead to heavy fines for the company. 


In addition to preventing massive penalties for delays and safety incidents, the Terra Firma Pit Lids are on average 31% cheaper in capital cost and 61% in maintenance costs, not to mention they are projected to last fifty years. This provides considerable savings to Jemena instantly and over time.

Environmentally friendly 

While not a major focus on this project, another benefit for Jemena is that Terra Firma’s FRP trench covers significantly reduced the environmental impact of the project. This is because the production of FRP requires less energy to manufacture and transport than steel or aluminium. 

Terra Firma’s FRP products reduce occupational health and safety risks on-site

Consider using composites at your next civil works project

Higher safety and longevity standards for civil works projects mean that traditional materials like steel, iron, and concrete are no longer cutting it. With composites growing in popularity and demand, there’s no better time to make the switch than now. 

Terra Firma is Australia’s leading manufacturer and supplier of fibreglass composite pit lids, access covers and FRP grating. Proudly Australian-owned and made, our products make the best use of cutting-edge technologies and leading R&D. 

If you’d like to know how composite materials could benefit your next project, you can contact us here to discuss it. Alternatively, watch our Civil Infrastructure Safety video here.

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