Remaining North West Transmission Developments Contaminated Land Assessment
From 2022 to 2025, pitt&sherry’s contaminated land team were responsible for assessment of the potential for the Remaining NWTD route to disturb areas of contaminated land, acid sulfate soils (ASS) and naturally occurring asbestos (NOA) for Tetra Tech Coffey Pty Ltd on behalf of TasNetworks.
Background
As Tasmania’s energy demands increase, TasNetworks needs to strengthen the state’s transmission network. The North West Transmission Developments (NWTD) will include new and upgraded overhead transmission lines (OHTLs), substations and switching stations. NWTD will support new renewable energy developments and generate significant benefits and opportunities for Tasmanian communities and businesses.
The project is proposed to be delivered across two stages. The first stage will link Cressy, Sheffield and Burnie, and the second stage will connect Staverton, Hampshire Hills and Burnie. Two spurs will be constructed between the Stowport area and Heybridge. A permit is required for the section of new OHTL between Staverton to Hampshire Hills, and a separate permit is required for the remaining sections of the project (Remaining NWTD). The Remaining NWTD includes constructing new double-circuit OHTLs, dismantling of the existing single circuit 220 kV OHTLs from Palmerston to Sheffield and Sheffield to Burnie, constructing a new switching station at Hampshire Hills, modifying the Palmerston, Sheffield and Burnie substations, modifying two short sections of the existing 110 kV Sheffield to Burnie OHTL, and modifying the 22 kV distribution network where the new OHTL crosses distribution lines.
Project aim
The objectives of this assessment were to obtain and compile available information on the current and historical uses of land along the Remaining NWTD route and immediate surrounds, and assess the following in response to the planning criteria:
- The potential for contamination, ASS or NOA to be present within the Study Area, including targeted sampling
- The potential for possible contamination, ASS or NOA to impact on human health and/or environmental values within the Study Area from a contamination perspective
- The risks posed by any potential, or identified contamination, ASS or NOA to human health and/or the environment during use (i.e. construction and operation) and during excavation works for the project; and
- Whether any specific remediation and/or protection measures (e.g. management) are required to be implemented before or during project excavation works.
What we did
Works included:
- Detailed site history review (SHR) to identify potentially contaminating activities (PCAs) and associated contaminants of potential concern (CoPC) and likelihood of encountering ASS and NOA
- Conceptual site model and assessment of source-pathway-receptor linkages
- Sampling plan for intrusive investigations
- Soil investigations to assess suitability of the Remaining NWTD route for the project
- Indicative classification of soils for offsite disposal
- Identification of any ongoing management and/or remediation works (where relevant); and
- Reporting.
Outcomes
The contaminated land assessment report is a key input of the Environmental Impact Statement for approval of the project.
The intention is that the assessment works will provide TasNetworks confidence that the risks posed by any potential, or identified, contamination to human health and/or the environment during use (i.e. construction and operation) and during excavation works for the project are either low and acceptable or where required management measures have been provided.
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