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Parliamentary Questions

Question Without Notice No. 1312 asked in the Legislative Council on 31 October 2019 by Hon Dr Steve Thomas

Minister responding: Hon D.J. Kelly
Parliament: 40 Session: 1

Answered on

FORRESTFIELD–AIRPORT LINK — DEWATERING

1312. Hon Dr STEVE THOMAS to the minister representing the Minister for Water:

My question without notice, of which considerable notice has been given, is to the minister representing the Minister for Water. Sorry, Minister for Environment, you miss out today.

I refer to the Forrestfield–Airport Link project and my question without notice 1157, asked on 16 October, which identified that 656 million litres of water has been dewatered from the FAL project and reinjected into the extraction sites.

(1) Can water reinjected into soil or aquifers on the route of the FAL project connect or mix with water in the area's underground aquifers, watertables or surface waterways?

(2) What prevents the reinjected water from mixing with the area's underground aquifers, watertables or surface waterways?

(3) Is there any way the reinjected water could carry PFAS chemicals into the area's underground aquifers, watertables or surface waterways?

(4) Could any of this reinjected water find its way into the Swan River system?

(5) What monitoring has been conducted to assess whether PFAS from the FAL project dewatering has reached the area's underground aquifers, watertables or surface waterways, and please provide the results?

Hon ALANNAH MacTIERNAN replied:

I thank the member for the question. The following information has been provided by the Minister for Water.

(1)–(3) The Department of Water and Environmental Regulation does not regulate the reinjection of dewatered water. However, the project managers have advised the department that as part of the Forrestfield–Airport Link construction, dewatering is required to allow for the construction of underground structures such as stations and tunnel portals. Dewatering involves removing groundwater to temporarily lower the watertable within the work area to allow soil to be evacuated. The watertable is the top surface of the superficial aquifer. The department advises that the dewatered water from the FAL project is reinjected back into the superficial aquifer from which it was removed. Therefore, dewatered water and the superficial aquifer water are from the same source and, when mixed, would have a similar base chemistry. The natural pathways of the superficial aquifer in the area would continue.

(4) Groundwater in the superficial aquifers in the area flows to the Swan River.