Down Defence – VacSkip – Enhancing Environmental Outcomes and Asset Management Capabilities at Defence Estates across Australia

ELEMENT A – Project Summary

Australian Defence sites have become increasingly reliant on hydro-vacuum excavation
methods during completion of construction and maintenance activities. This process produces a
slurry mixture of the water and solid material removed from the excavation site.
At present, sites which contain contaminated soil (e.g PFAS) pose a problem to the continued
use of this method. While contaminated water can be filtered and contaminated dirt can be
disposed of in special facilities, contaminated slurry must undergo a separation process to allow
for disposal.
Downer Defence has recently pioneered the implementation of a simple, safe and cost-effective
solution to the management of contaminated spoils, known as a ‘VacSkip’.

ELEMENT B – Project description

In recent years there has been a significant increase in the use and reliance on hydro-vacuum
excavation over more traditional mechanical means (e.g excavators) which can risk damaging
buried services. The by-product of this process is a slurry mixture of the water and the solid
material (known as spoil) removed from the excavation site. This material is retained in the ‘vac
truck’ and typically disposed of off-site by contractors.
At present, sites which contain contaminated soil pose a problem to the continued use of this
method. Contaminated water can be filtered, contaminated dirt can be disposed of in special
facilities. Contaminated slurry however cannot be readily processed and instead must undergo
a separation process (water and solids) to allow for disposal.
At present Australian Defence sites, such as those managed by Downer Defence, have:

  1. The need to use hydro-vacuum excavation during construction and maintenance
    projects to lower the risk of damaging or interrupting services.
  2. Issues with contaminated soils.
    To date, the common solution to this issue is for contractors to construct a ‘turkey’s nest’ which
    is formed by heaping soil/ hay bails into a closed shape and lining the inner surface with thin
    plastic to create a small pond or dam. The vac truck spoils are then poured into the Turkey’s
    nest and allowed to dry by solar evaporation or mixing with additional dry material.
    This process has the following limitations:
  3. It is at the mercy of the weather. Covering the ponds is difficult to achieve using
    temporary structures while permanent covering structures would limit evaporation
    rates. As a result, during rain events ‘turkey’s nests’ may become rehydrated and
    risk being over-filled.
  4. Difficult to determine if leaks through the plastic lining are occurring.
  5. Further site excavation and approvals are required to construct a turkey’s nest.
  6. They are typically unsightly (Figure 1 below).
    Asset Management Excellence Awards – Asset Management Innovation Award 3
    March 2023

immediately after dumping of vac truck spoils and prior to final preparation plastic covering.
Inspired by a desire to challenge the status-quo, since 2019 Downer Defence have actively
engaged with, and supported a regional Queensland-based start-up company called VacSkip
Australia to implement their product into the Defence markets in both Queensland, NSW and
the ACT.

The ‘VacSkip’ is a patented solution designed to store and dry slurry captured during hydrovacuum excavation of soil. The equipment is comprised primarily of a fabricated steel base and retractable water-proof tarp system. The steel base forms a shallow, open top vessel and a skid for transport and on-site placement. The retractable tarp protects the contents of the vessel from fresh water ingress during rain events.

The unit features an automated 12V control system which signals the tarp system to close when
rain drops are identified. Following completion of the rain event the tarp system automatically
retracts (opens) to facilitate solar evaporation of the contents. The 12V system is powered by a
solar panel and on-board battery.

VacSkip implementation offers the following benefits:

  1. Offers users improved environmental outcomes and asset management capabilities.
  2. Portable solar powered, standalone units can be rapidly deployed to locations as
  3. Large surface area to depth ratio facilitates rapid solar evaporation of excess water.
  4. Automated retractable tarp system ensures the stored material is protected from
    further water ingress during rain events, without the need for operator intervention.
  5. Eliminates the potential for contaminated slurry to leach into the ground.
  6. Improve capacity to manage contamination issues on-site.
  7. Reduce costs for offsite removal and testing of vacuum excavation spoils.
    Figure 2 – ‘VacSkip’ in the open/drying configuration.
    Figure 3 – ‘VacSkip’ in the closed configuration (during rain events).
    Prior to Downer Defence’s wider implementation of the VacSkip units across the Defence
    Estate, in 2019 a formal trial of the unit commenced at Swartz Barracks in Queensland. Based
    on the success of this trial, coupled with the release of a new solar-heated model, in 2021 a
    Asset Management Excellence Awards – Asset Management Innovation Award 5
    March 2023
    second formal trial commenced at RMC Duntroon in the ACT to test the efficacy of the units in
    vastly diverse environmental conditions.
    In March 2022, at the completion of the trial period, a Post Implementation Review (PIR) was
    conducted in the ACT with all relevant stakeholders present. From this review the following
    benefits were identified with the use of the VacSkip units:
  • Improved environmental outcomes through reliable onsite containment and automated
    drying of potentially contaminated materials.
  • Improved alignment with Defence’s asset management objectives by reducing the
    amount of waste that is sent offsite.
  • Improved ability to manage emergency excavation works effectively and timely on site
    without the need to build unsightly ‘turkey’s nests’.
  • Improved public image through utilisation of cutting-edge environmental management
  • The client (Defence) has been satisfied with the use of the VacSkip and, together with
    their environmental teams, are actively encouraging further implementation across the
    Based on these findings, in March 2022 Downer Defence committed to expand their
    implementation of the units across a range of Defence sites, including:
  • RMC Duntroon, ACT
  • HMAS Harman, ACT
  • Swartz Barracks, Oakey QLD
  • Borneo Barracks, Cabarlah QLD
  • Lavarack Barracks, Townsville QLD
  • RAAF Townsville, QLD

    As of March 2023, the pioneering implementation of the VacSkip units across Defence estates in Australia is continuing with additional units currently under manufacture by VacSkip Australia to meet both committed and forecasted demand.

    ELEMENT C – Opinion as to the specific contribution
    made by the nominated individual /team

    The Downer Defence team has demonstrated a high level of technical expertise, innovation,
    and project management capabilities in pioneering the implementing the Vacskip waste
    management solution into the Defence sector.
    The team’s ability to collaborate with stakeholders, design and implement a bespoke solution,
    and manage the project effectively has resulted in a significant reduction in waste disposal costs
    and landfill, as well as an improvement in environmental/sustainability outcomes.
    The team’s success is a testament to their technical excellence, creativity, and commitment to
    delivering value to the Department of Defence and Defence Estate stakeholders.

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