Ventia was engaged by Transport for NSW to remediate a 6.2-hectare site at Camellia to the south of the Parramatta River in Sydney's West as part of the Parramatta Light Rail Stage 1 project.

As part of the Parramatta Light Rail Stage 1 project, the site for the future light rail Stabling and Maintenance Facility (SaMF) at 6 Grand Avenue, Camellia, was required to be remediated to address chemical contamination resulting from the land's historical industrial use. 

Ventia's General Manager Environmental Services, Adam Fletcher said: "We are incredibly proud of our team of environmental specialists and their pursuit of innovative solutions to deliver successful remediation and rehabilitation outcomes."

Our team worked with our client and other important stakeholders to deliver an innovative solution to a complex environmental challenge, successfully completing two phases of work to remediate the site.

Asbestos manufacturing on the old Camellia site

The site was historically used for chemical manufacturing, such as asbestos production.

 

The Camellia site has a legacy of chromium production, amongst other co-contaminants including asbestos and chlorofluorocarbons. Ventia's remediation approach included the construction of hydraulic barrier around the perimeter and an engineered capping system and a containment cell. Ground improvement was required through the contaminated materials to facilitate the SaMF construction. Management of surface water and treatment of groundwater was also required during construction.

"The first portion of the remediation work involved installing an underground barrier wall around the site to prevent contaminated groundwater from migrating beyond the site."

"The second portion of the remediation work involved improving the ground geotechnically, constructing an onsite waste containment cell, and installing an integrated capping system across the surface of the site," he said.
 

Our Solution

Hydraulic Barrier Wall (HBW) 

The design of the HBW comprises a subsurface barrier wall forming a closed polygon around the site perimeter. The total perimeter length of the wall is approximately 1.0 km. The wall extends from the existing surface down to bedrock with a maximum wall depth between 15m and 20m below the existing ground surface level on the site.

The functionality of the Hydraulic Barrier Wall design was to ensure key objectives of the Remediation Action Plan (RAP) were met. These included the elimination of contamination exposure pathways via:

  • groundwater;
  • vapour in the upper vadose zone; and
  • chromium dust through wicking.

 

The Hydraulic Barrier Wall was constructed with a modified long reach excavator that could dig to depths of up to 10-12 metres. A clamshell bucket, supported by a crane was used to reach and achieve bedrock key in depths beyond 12m from the site surface.

Trench stability was maintained by replacing the excavated soil with a bentonite slurry, which was pumped from temporary bentonite ponds located within the site boundary. Following excavation, excavated clay soil was mixed with the bentonite slurry to form a soil-bentonite mix and placed into the wall, displacing the bentonite slurry, and forming a curtain of bentonite-soil around the perimeter of the site forming the Hydraulic Barrier Wall.

Ground Improvement

The remediation design required a site wide capping system which could not be penetrated, which meant the traditional pilling methods could not be considered as foundations for future infrastructure on the site. To ensure the site was geotechnically suitable for the future site infrastructure, a grid-based ground improvement solution was developed across large areas, with the goal to stiffen the sub-surface strata to meet strict bearing and settlement criteria.

Over 4,000 Contiguous Flight Auger (CFA) piles were constructed across various locations on the site. Two CFA rigs were used to install the ground improvement piles at various levels and to various depths. The design constraints led to piles requiring installation at various levels across the site, which required a complex pilling platform design and staging considerations.

Containment Cell

Due to design constraints, the excavation levels and design resulted in a net cut surplus of 65,000m3 of contaminated material. To reduce the cost associated with sending contaminated material to landfill, Ventia developed an onsite containment cell solution. The containment cell was able to be integrated with the hydraulic barrier wall and capping system and was designed to hold approximately 14,000m3 of contaminated material.

The containment cell was constructed using various geosynthetic and geocomposite lining systems to encapsulate the contaminated material. On completion, over 14,500m3 of material was successfully encapsulated within the containment cell. 

Integrated Capping System

To address primary RAP objectives, Ventia designed and constructed a capping system that was integrated with the HBW. The capping system incorporated layered components to ensure the following functionality was achieved:

  • Mitigation of soil vapour (both indoor and outdoor as dictated by the permanent facility design) from Volatile Chlorinated Hydrocarbons (VCHs);
  • Create a physical barrier to prevent site users from accessing contaminated materials; and 
  • Prevent Chromium (VI) wicking into future site structures/ infrastructure and paved surfaces.

Stockpiling of contaminated materials prior to placement in containment cell

Remediation of the site included stockpiling of contaminated materials prior to placement in containment cells.

 

The capping system construction involved:

  • Excavation of over 65,000m3 of contaminated material, requiring stockpiling, waste classification and offsite disposal to a licensed landfill or placed in the on-site containment cell, considering a waste hierarchy system;
  • Over 218,000m2 of liner materials placed to form the capping system, comprising of geocomposite and geosynthetic clay lining products;
  • Approximately 35,000 tonnes of aggregate imported and placed to form the capillary break layer which eliminates chromium wicking to the site surface;
  • Approximately 28,000 tonnes of bearing soil imported to form an impermeable layer over the capillary break and to provide a smooth surface for the placement of an impermeable clay liner;
  • Over 250,000 tonnes of Sydney sandstone imported, placed, and compacted on the site to finish levels. Sandstone was sourced from other Sydney based infrastructure projects due to its suitability for re-use on the site as an engineered product. This saved the sandstone from being trucked offsite for disposal at licensed landfill facilities. 

 

Project outcomes and benefits

  • Project maintained a zero Lost Time Injury rate.
  • Construction of over 1.0km of low permeability soil bentonite cut-off wall 
  • Flexibility in re-design of the ground improvement and integrated capping systems to meet the needs of the client and key project stakeholders to ensure suitable future use as a stabling and maintenance facility.
  • Inclusion of an on-site containment cell which holds over 14,500m3 of re-directed site won contaminated spoil originally destined for offsite disposal to a landfill.
  • Over 250,000 tonnes of sandstone imported, placed, and compacted to form the final finish surface. The sandstone was a by-product of various Sydney infrastructure (tunnelling) projects in progress at the time and was able to be diverted from landfill for re-use on the site, greatly assisting with achieving a positive sustainability rating for the project.

 

Recognition of the success of the project 

In 2022, the Camellia Remediation Project has been decorated with two awards:

  • Highly Commended: Environment Award - 2022 Civil Contractors Federation NSW Earth Awards. The awards recognises companies who have recently been involved in a project which has excelled in environmental performance and outcomes. 
  • Winner: UNE Sydney Excellence in Education, Training & Careers Award - 2022 Western Sydney Awards for Business Excellence (WSABE) for the implementation of industry leading education and training programs on the project. 

 

Ventia ream pictured at the awards night

The project won the UNE Sydney Excellence in Education, Training & Careers Award category at the 2022 Western Sydney Awards for Business Excellence.
 

Workforce Sustainability Outcomes

Working collaboratively to change the industry

When Ventia was looking for a sub-contractor to deliver the civil works for the Camellia Remediation Project, we wanted an organisation invested in diversity and inclusion outcomes. Ventia engaged an Emu Plains business, Sage Civil and one of the reasons, was managing director Asha Russell and her advocacy for increasing the participation of women and Indigenous workers in the civil industry in NSW. While Sage Civil use their pink and purple machinery as a clear visual to highlight the lack of gender diversity on project sites, being engaged by Ventia helped both organisations to develop initiatives that will continue across future projects.

Upskilling safely for success

A hurdle often cited as a reason for lack of diversification is how to train and upskill operators without compromising safety or causing delays to the project schedule. Contractors often require operators to have practical experience to work on site so they can manage project productivity and safety.

But unless projects are willing to provide experience, how can operators gain the necessary on-the-job skills to increase their productivity and on-site safety awareness and prevention?

To address this issue, Ventia and Sage Civil collaborated on several training and mentoring opportunities for the project.

Upskilling operators on the job

With the support of Ventia's project management team and the client, the first program provided the opportunity for Sage Civil employees to upskill their tickets while working on site. With the assistance of Fusion Training, an Indigenous training organisation, operators were able to attain Verification of Competency (VOC) tickets and Statements of Attainments (SOA) while working on the project. This is a significant change in project delivery as operators are usually required to have their Statement of Attainment before entry on to site. 

Traineeships for the future 

The ability to recognise and retain talent is important to most organisations, especially when there is a national skills shortage. A workplace that encourages on-going learning and professional development at all levels of employment, provides opportunities for people who may not otherwise be able to undertake it without continued guidance. 

On the Camellia Remediation Project, three Certificate III in Civil Construction Plant Operations traineeships were made available. When COVID-19 protocols were implemented so the site could continue remediation works during the construction lockdown, an additional traineeship in Certificate IV in Work Health and Safety was provided to support the HSE Coordinator.

By the project's end, female participation had increased to 28% - a significant improvement from the industry average of 1% for blue collar or trades.

 

Recognising gender diversity

During delivery of the Camellia Remediation Program, Ventia and Sage Civil committed to improving diversity on the project site. One of the ways to do this was to use Sage Civil's pink machinery which is becoming synonymous with engaging women in civil. The Ventia project team agreed the machinery provided the perfect opportunity to raise the profile of gender diversity in construction. By project's end, 28% of the Sage Civil direct hire workforce were women, a sharp improvement from the industry average of 1% for blue collar or trades. 

Upskilling for a flexible workforce

The training initiative to allow the workforce to upskill while working on site produced impressive results. In total, 44% of the workforce took the opportunity to gain additional qualifications which resulted in a total of 50 Verification of Competency certifications and 38 Statements of Attainment.
As the operators are now qualified for multiple machines, this provided added benefits for the workers and the project.

In the first instance, the operators were able to stay on site longer and take on new responsibilities, once their original roles were complete. As a result of their training, they could now be reassigned to different areas of the project using different machinery. For the project, having site-inducted, multi-skilled operators meant greater flexibility in delivery, especially during COVID-19 lockdowns when it was difficult to onboard new staff due to strict safety protocols.