Impact assessments

The Department is committed to delivering sustainable transport, infrastructure and programs in a manner that balances economic, environmental and social needs.

In doing this, it is important to minimise the impacts from construction and operational activities and where possible further enhance environmental and social outcomes to deliver lasting benefits to the community.

This is achieved by:

  • assessing environment, heritage and social risks together with identifying and then ensuring implementation of risk mitigation measures
  • integrating environment and heritage considerations into decision making
  • ensuring that contractors undertaking work are aware of and abide by the environmental and heritage obligations
  • continually improving and updating the standards and guidelines for environment and heritage management.

The Department sets out guidelines and standards to assess and manage the environmental and heritage aspects of infrastructure projects in an Environment and Heritage Technical Manual (EHTM).

  • Summary

    Download a summary of the PAR in PDF format

Environment and heritage impact assessments

Assessments have been undertaken for the T2D Project including its alternatives and objectives and its impacts on environment, heritage and social aspects within and adjacent to the project corridor. As part of this process a range of measures to offset any potential negative impacts have been identified.

The objectives are to:

  • adequately assess the potential environment, heritage and social impacts of the project
  • ensure that environment, heritage and social considerations are integrated into decision making processes and all project phases
  • identify opportunities to avoid, minimise, mitigate and where appropriate, offset impacts
  • identify necessary departmental or legislative environment and heritage approvals, permits and authorisations to progress the project to the delivery and for operation
  • ensure that constraints, mitigation measures and offset opportunities identified in the development of the project are carried through to the procurement, delivery, and realisation of the project
  • contribute to ecologically sustainable development and demonstrate general environmental duty and due diligence in relation to environmental, heritage and social outcomes.

Given the project’s size and scale and the wide community interest, the outcomes of the assessments are being shared publicly in the form of a Project Assessment Report (PAR).

Describing the T2D Project corridor

To support the assessment process, the project corridor has been considered in three sections:

The assessment methodology

The following steps have been undertaken to provide a consistent evaluation of the diverse range of potential environment, heritage and social impacts.

Process chart outlining the impact assessment methodology. The chart shows the following steps: 1: Identify activities and aspects from the project description. 2: Identify impacts. 3: Assess residual risk considering the application of recommended mitigation measures. 4: Assign a consequence rating for each impact. 5: Assign a likelihood for each impact. 6: Assign a risk for each impact. 7: Recommend mitigation and opportunity enhancement measures. 8: Prepare a summary of impacts pre and post mitigation.
Diagram: Assessment methodology.

Identify the activities and aspects

“Activities” are either construction or operational actions while "aspects” refer to subjects such as noise, vegetation, air quality, water quality and Aboriginal cultural heritage.

For example, traffic movements of trucks carrying excavated spoil is a construction activity. The hauling of spoil in trucks can affect a range of aspects, including air quality.

Identify the impacts

An impact is the positive or negative effect of a construction or operational activity on an identified aspect.

For instance, non-hazardous waste or litter created as part of construction (activity) has the potential to have an adverse impact on surface water quality and general amenity (impact).

Assign a consequence rating

Consequences are the outcome of the impact. Each consequence may be rated as insignificant, minor, medium, major or critical based on:

  • duration of the impact
  • area extent – for instance, within the site boundary, within suburb or council precinct
  • sensitivity of receiving environment and/or community
  • reversibility.

Using the above example, the consequence of construction litter impacting surface water is considered minor because it is non-hazardous and temporary and the project is surrounded by an urban environment. Furthermore, the consequence is reversable.

Assign a likelihood rating

Assigning the likelihood of an impact occurring is based on technical specialist investigations and/or detail and experience from similar projects. The likelihood ratings extend from rare to almost certain.

In this case, the likelihood that litter from construction would enter surface water bodies is considered likely, without mitigation.

Assign a risk rating

After rating the consequence and likelihood of an impact, the risk level of the impact is determined. Risk can be characterised and described as the consequence of what could happen; and the likelihood of those consequences occurring. The risk ratings are defined as being low to extreme.

Again, using the same example, the risk of litter from construction impacting surface water bodies is considered moderate, if not mitigated.

The objective of this assessment is to identify the main risks to the environment, to heritage and the community that could result from the project during construction and operation. Impacts assigned a risk level of extreme, high or moderate will require mitigation to minimise the risk level. Impacts that are assessed as low typically will not require specific mitigation to be applied beyond general construction techniques.

Recommend mitigation and opportunities for design development

Recommending mitigation measures and identifying opportunities for design development are an integral part of the assessment process. Mitigation is the term used to describe the action that lessens or eases the harshness or intensity of an impact or possible impact.

The following mitigation hierarchy has been applied to each of the aspects:

  • propose an alternative option that avoids or reduces impact through design
  • mitigate impacts at source or at receiving environment and/or community
  • restore or fix the temporary effect
  • offset the impact.

Mitigation measures for all extreme, high and medium risk impacts have been proposed. While the majority of the impacts identified can be mitigated by implementing relevant measures in the Department’s Master Specification and utilising common industry practice, additional project specific mitigation and design measures have also been identified.

Again, using the same example: To mitigate impact of dust generated by the truck movements of excavated spoil, speed limits within work areas can be applied, loads can be covered, wheel washes installed, haul routes can be defined, and water carts can be used for dust suppression.

Assess residual impacts

Residual impacts are those that remain after the mitigation and opportunities for design development have been applied. While these measures reduce the temporary and permanent impacts a residual impact may still be evident for some aspects. The next stage of design develop will take the residual impacts identified in the assessments as inputs to further refine impact reduction.

What's not included in this PAR

The PAR considered both the construction and operation of the T2D Project within the project corridor. It does not extend to the following associated works and infrastructure:

  • spoil facilities
  • pre-cast facilities
  • haulage routes
  • upgrades to road networks, facilities and amenity, such as those detailed in Broader network upgrades.

These works and infrastructure are subject to separate planning, design and assessment processes in accordance with the Department’s EHTM requirements.

Cumulative impact

The PAR does not assess cumulative impact. Cumulative impact considers the combination of multiple impacts that may result when the project is considered alongside other proposed non-Department projects in the same area.

The responsibility and management of cumulative impacts of non-Department projects are outside of direct Department control. Consideration of how cumulative impacts can be influenced by the Department indirectly includes engagement with the responsible parties to identify opportunities for aligning mitigation measures, realising benefits and engaging with the community and stakeholders on broader cumulative impacts where they occur.