Mining water approvals
Surface water engineering across WA mining approvals
Overview
Fiord Group is a hydrology and environmental engineering practice working on the surface water side of Western Australian mining approvals. That spans two separate statutory processes: the EPA’s Part IV environmental impact assessment, where the Inland Waters factor sets what has to be demonstrated, and DWER’s Part V works approvals, where the water infrastructure has to be designed, sized and dimensioned before it can be built. The practice supplies the hydrological evidence for the first and the water engineering for the second, working from one model rather than two.
Why the gap opens where it does
The two approvals are often described as stages of one process. They are not. Part IV is an impact assessment: it decides whether a proposal may be implemented and on what conditions, and it is assessed against environmental factors and their objectives. Part V is a construction and operating regime: section 52 of the Environmental Protection Act 1986 makes carrying out work that causes premises to become prescribed premises an offence unless it is done in accordance with a works approval, and section 54 requires that application to be supported by plans and specifications. One asks whether the impact is acceptable. The other asks whether the described structure does what the applicant says it does.
The gap opens between them because the water evidence changes form. A storage that exists at referral stage as a volume in a water balance has to exist at works approval stage as a plan area, with a depth, a freeboard, a spillway set at a level and an access width. Those are decided after the referral figure has been drawn — and where a Part IV condition has fixed the cleared area in between, the design has to close inside a number nobody was holding while both halves were still moving.
The second reason the seam is expensive is that a works approval package spans two engineering disciplines. Fill and compaction specification, liner selection and batter stability geometry are geotechnical and civil. Storage sizing, design storm inflow, evaporation, freeboard, spillway hydraulics, diversion capacity, flood routing and sediment basin sizing are water. This practice is the water half, and says so, for the same reason it distinguishes hydrology from hydrogeology on the Inland Waters factor: naming the half that is not ours is what makes the half that is ours worth relying on.
The pathway
Three stages, in the order the evidence has to exist
- Resolve the water numbers before the referral figure is drawnBefore referralStorage capacity carried through to a plan area at top water level, with a stated freeboard, a spillway invert and discharge path, and an access width — so the area that gets cleared and the area that can be built inside it are the same number.
- Answer the Inland Waters questions off the same modelThrough the assessmentHydrological regime characterisation, predicted change and residual impact against the EPA’s Inland Waters objective, supplied to the environmental consultant running the assessment rather than as a competing approvals practice.
- Carry it into the works approval as engineered designInto Part VPond and storage sizing, spillway and overflow design, diversion channels, site drainage and the site water balance — the water half of a Part V works approval package, drawn from the model that already answered Part IV.
Reading
The questions that come before the decision
- Does a mine need a works approval in Western Australia?Works approvalsIt depends on whether any part of the operation is a prescribed premises, and that is a question about categories and thresholds rather than about scale or intent. Schedule 1 of the Environmental Protection Regulations 1987 lists the categories, each with a production or design capacity at which the premises becomes prescribed.
- Why does an EPA approval not let you start building?Approvals sequenceBecause the two approvals answer different questions, and only one of them is about the thing being built. An assessment under Part IV of the Environmental Protection Act 1986 decides whether a proposal may be implemented and subject to what conditions.
- Why does a water storage sized at referral stage not fit the approved footprint?Mine water designBecause a volume is not a footprint. A storage sized at referral stage is usually sized volumetrically — operating volume plus an allowance for the design storm — and that number is what the clearing figure gets drawn around.
Common questions
- Does an EPA Part IV approval let a mine start construction?
- No. A Ministerial Statement decides whether a proposal may be implemented and on what conditions. Construction of a prescribed premises is authorised separately under Part V of the Environmental Protection Act 1986 by a works approval, and section 52 makes carrying out that work an offence unless it is done in accordance with one. They are different approvals, from different decision-makers, against different tests.
- When does a mine need a DWER works approval?
- Where any part of the operation falls within a category in Schedule 1 of the Environmental Protection Regulations 1987 and meets its threshold. Category 5, processing or beneficiation of metallic or non-metallic ore, and Category 6, mine dewatering, are both set at 50 000 tonnes or more per year. An operation triggers every category it meets rather than choosing one.
- Can a works approval be processed while the EPA assessment is still running?
- It is not barred. Since the 2024 amendments, section 41 holds up only restricted decisions — a prescribed class set out in Part 2B of the Environmental Protection Regulations 1987, covering decisions under planning legislation and petroleum hydraulic fracturing decisions. A Part V works approval is in neither class. Whether it is prudent to seek one before Part IV conditions are settled is a separate, project-specific judgement.
- Why do mine water storages end up too large for the approved footprint?
- Because a volume is not a footprint. A storage sized volumetrically at referral stage has no area until a depth is fixed, and freeboard, the spillway and its discharge path, crest access and batters then add further plan area on top of the wetted footprint. All of those are settled after the clearing figure is drawn, and Part IV conditions commonly fix a spatial extent rather than a capacity.
- Does the practice run the approvals process?
- No. Environmental consultants run the Part IV process — the impact assessment, the offset strategy and the Ministerial Statement negotiation — and the practice supplies the surface water evidence underneath it. On the Part V side the work is the water engineering the application is built on: sizing, hydraulics, water balance, spillways and drainage. Designing water infrastructure is not the same act as running an approvals process.
- Does the practice provide geotechnical design or certification for containment infrastructure?
- No. Fill and compaction specification, liner selection and batter stability geometry are geotechnical and civil scope and stay with the engineers who hold it. Where a works approval requires a Critical Containment Infrastructure Report or an Environmental Compliance Report to carry a declaration, that is detailed in the conditions of the works approval and is a matter for a professional with the qualifications or experience the department requires.
Sources
- WA Legislation — Environmental Protection Act 1986 (Parts IV and V)
- WA Legislation — Environmental Protection Regulations 1987 (Schedule 1; Part 2B)
- EPA — Environmental Factor Guideline: Inland Waters (29 June 2018)
- DWER — Industry Regulation Guide to Licensing (June 2019)
- WA Government — Licences and works approvals for prescribed premises (Part V)