Environmental impact assessment 

Environmental impact assessment (EIA) is the process by which a decision-maker identifies and evaluates the likely environmental effects of a proposed activity before deciding whether, and on what conditions, it should be allowed to proceed. It is not itself an approval — it is an information-gathering and evaluative process that feeds into a separate approval decision made under planning, environmental or resource legislation.

Purpose

EIA exists to make sure that the environmental consequences of a proposal are properly understood, exposed to scrutiny, and weighed by the decision-maker before an irreversible decision is made, rather than discovered afterwards. It typically requires the proponent (the person or entity proposing the activity) to gather and disclose information about likely impacts, allows government agencies and the public an opportunity to comment, and requires the decision-maker to take the resulting information into account. Because it is a process obligation, a failure to carry out an assessment properly, or a failure to consider its results, can itself be a ground for legal challenge, independently of whether the outcome ultimately reached was substantively reasonable.

A sliding scale of assessment intensity

Not every proposal is assessed the same way. Australian environmental and planning statutes generally set up a tiered system, under which the intensity of assessment increases with the scale and sensitivity of the likely impact:

• At the lightest end, a proposal may simply require a referral or screening decision — a threshold determination by the relevant authority or minister as to whether the likely impact is significant enough to require any further assessment at all. Many proposals are screened out at this stage because their likely impacts are assessed as not significant.
• Where impacts are more than minor but not likely to be highly significant, a proposal may require a preliminary or documented assessment — a more structured but still relatively contained report addressing identified issues.
• At the most intensive end, a proposal with potentially significant or contested impacts may require a full environmental impact statement (EIS) or public environmental review, involving detailed technical studies across multiple disciplines, a period of public exhibition and submission, and often independent expert review before a final decision is made.

The purpose of this graduated structure is to direct the most detailed scrutiny toward proposals where it is actually needed, without requiring every minor proposal to undergo the same lengthy process as a major project.

Assessment can arise at more than one level

Because environmental approval in Australia is split between state/territory and Commonwealth regimes, the same project can trigger separate assessment obligations at each level. A state or territory planning or environment statute may require assessment of a project's impacts within that jurisdiction. Independently, if the project is likely to have a significant impact on a matter of national environmental significance, the Commonwealth Environment Protection and Biodiversity Conservation Act 1999 (Cth) requires a proponent who thinks the project may be a controlled action to refer it to the Commonwealth environment minister, who decides whether Commonwealth assessment and approval is required and, if so, at what level of intensity. That referral step is not open at a time when an "alternate pathway" applies to the action: as at 3 October 2026, s 71A, in force since 24 August 2026, provides that a person must not then refer a proposal for a controlled-action decision.² The pathways include a declaration, or a declaration in a bilateral agreement, that a class of actions needs no approval under Part 9, an approval under s 146B following a strategic assessment, and the bioregional plan arrangements for restricted and priority actions, but each is conditional. An action specified in an exclusion determination is outside the declaration pathways, so is a larger action of which only a component is covered by a declaration, and a s 146B approval counts only where s 146D(2) applies. The bioregional-plan limbs depend on plan provisions that are not in the Act as compiled at 24 August 2026. Section 71A was inserted by item 160 of Schedule 1 to the Environment Protection Reform Act 2025 (Cth), which Proclamation (No. 2) 2026 commenced on 24 August 2026; the bioregional-plan provisions are in Part 12A, inserted by item 323, which that Proclamation did not commence.³⁴ A referral made while no pathway applies continues even if a pathway later starts to apply, unless it is withdrawn. An action specified in an exclusion determination under s 36B, or in a determination made in accordance with a bilateral agreement as mentioned in s 65B, is instead taken to have been referred under s 68(1) when the determination is made, a rule that has applied since 24 August 2026.⁵ Where both levels are engaged, mechanisms exist for accreditation of a single assessment process to avoid unnecessary duplication, but the underlying legal obligations, and the decision-makers responsible for them, remain distinct. A student should never assume that satisfying a state assessment process automatically satisfies any Commonwealth obligation, or vice versa.

What a decision-maker does with an assessment

Having received an assessment, the decision-maker does not automatically have to refuse an approval merely because impacts are identified. The assessment informs the decision but does not dictate it: the decision-maker typically retains a broad discretion to approve a proposal subject to conditions designed to avoid, mitigate or offset identified impacts, to refuse approval altogether, or in rare cases to approve without conditions. The adequacy of the assessment, and whether the decision-maker genuinely engaged with it, are common grounds on which an approval decision is later challenged.

Applying this in a problem question

1. Identify which statute — state, territory or Commonwealth — is said to require assessment of the proposal, and confirm assessment obligations for each level separately.
2. Determine where the proposal likely sits on the tiered scale: a screening/referral decision, a documented assessment, or a full environmental impact statement or public environmental review.
3. Check whether the proposal may be a controlled action, for example because a matter of national environmental significance is potentially affected, which would require a separate Commonwealth referral under the EPBC Act, unless an alternate pathway applies to the action.¹
4. Distinguish the assessment process itself from the final approval decision — an inadequate assessment is a different legal problem from an unreasonable approval decision.
5. Identify what the decision-maker did with the assessment: genuine consideration, imposition of conditions, or an apparent failure to engage with what the assessment found.