Gnarabup wastewater planning

The proposed pipeline will transfer all wastewater from Gnarabup to Margaret River for treatment.Most of the pipeline will be located underneath road verges, mainly along Wallcliffe Road.

This route was chosen to help reduce environmental impacts and to minimise disruption to traffic during construction.

We’ll continue to refine the design and share updates as more details become available.

Currently we are completing investigations, design work and ensuring the pipeline is a viable upgrade option for the Gnarabup wastewater system, should an upgrade be required.

Our preference for a potential future upgrade to the Gnarabup wastewater system – should it be required for significant additional future wastewater flow – is to transfer all wastewater from Gnarabup to Margaret River for treatment. This project is currently focussed on determining if the construction of a proposed pipeline is a viable upgrade option.

Should an upgrade be required and the proposed pipeline is constructed we would then address the future of the Gnarabup Wastewater Treatment Plant.

We plan wastewater treatment capacity upgrades based on the latest population forecast data* and operational lifespan.  Based on existing population forecasts, this plant can safely treat wastewater for the next decade. After that, we will need a higher capacity scheme.

A decision to make changes to the operations of the wastewater scheme will be considered if the wastewater volume is expected to rise a lot, in a short period of time.

A project will only be activated once development is certain and funding requirements have been determined - at which time a delivery timeframe will be established.

*Historical Australian Bureau of Statistics data and location specific projection data is considered in establishing a forecast for a town. Potential tourist/visitor developments are also considered. Based on this information, residential growth in the area is expected to continue.

We do not plan to truck wastewater as a permanent solution for Gnarabup.

We will truck wastewater only if the plant can't handle it, such as during maintenance. We may also do this as a temporary measure during peak summer season, while building the long-term solution.

Currently, Prevelly does not have reticulated sewerage. Water Corporation is not planning any infill sewerage for this project.

Gnarabup WWTP meets strict conditions under its environmental licence with Department of Water and Environmental Regulation (DWER).

We undertake thorough environmental monitoring to comply with all the conditions of our operating licence. This includes monitoring bores to review groundwater quality upstream and downstream of the plant and this data is reported to DWER annually. DWER has reviewed the site and approved its operation until 2023.

The treated wastewater is disposed of via infiltration beds. These are large ponds where treated wastewater is stored and either evaporated or infiltrated into the ground, similar to stormwater ponds.

We have carried out several environmental surveys to better understand the plants and animals in the area where construction is proposed.

In spring 2022 and 2024, we conducted detailed assessments of flora, vegetation and local wildlife. These surveys helped us confirm the types of plants growing there, their condition and the kinds of animals that may live in or use the area.

A targeted survey was also completed in spring 2024, to investigate for any rare plant species within the project area. From these studies, we found that the area includes suitable habitat for Black Cockatoos and Western Ringtail Possums.  No Threatened or Priority flora species were found in the proposed project area during the surveys.

This information will help to guide our planning and decision-making.

Yes, some clearing will be needed to construct the proposed pipeline. We’re working closely with environmental consultants and construction contractors to avoid and reduce impacts on significant trees and wildlife habitats wherever possible.

We’ve made changes to the proposed pipeline’s location and construction methods to help reduce the amount of clearing required. We have located the proposed pipeline in already cleared verge areas, where possible, to minimise impacts to significant environmental values.

In uncleared areas we will install the proposed pipeline using underground horizontal drilling, which allows us to install the pipeline with less disturbance to the surface. We have also considered the location of machinery for the horizontal drilling to minimise impacts to significant trees.

We’re still finalising the clearing figures for the construction of the proposed pipeline.

Our team has been working hard to reduce the amount of clearing required by carefully choosing the pipeline’s location and using construction methods that reduce the environmental impact. To protect important habitat, we’re using horizontal drilling in areas where mature or significant trees have been identified. This method helps us reduce the impact to trees that provide valuable shelter for wildlife.

The final impact figures will be included in our referral to the Environmental Protection Authority (EPA). The public will have an opportunity to review and provide feedback as part of that process.

As the proposed pipeline work would occur in road verges, we’ll work with the Shire of Augusta-Margaret River to develop a revegetation plan.

This plan will address the revegetation of areas that aren’t needed for ongoing pipeline maintenance.

Environmental surveys of the pipeline alignment have identified potential environmental risks to Matters of National Environmental Significance (MNES) as outlined in the Environment Protection and Biodiversity Conservation Act 1999, including impacts on habitat trees for the Black Cockatoo and Western Ringtail Possum.

Due to the identified environmental impacts associated with construction of the pipeline, the proposal will be referred to both the EPA and the Department of Climate Change, Energy, the Environment and Water (DCCEEW) in accordance with the Environment Protection and Biodiversity Conservation Act 1999.

We will keep you updated on the timings of these referrals. 

We understand that construction can be disruptive, and we’re committed to working closely with the community to reduce any impacts as much as possible.

If this potential project goes ahead, we will continue to engage with the community to better understand concerns around construction impacts and explore ways to minimise them – especially during peak tourist season and major events.

People living near the construction area may notice some noise, vibration, or dust. These impacts will vary depending on where you live, and the type of work being done. Water Corporation and its contractor will take steps to manage these impacts

The proposed pipeline is a pressure main that carries wastewater from homes and businesses to a treatment plant or recovery facility. The wastewater is pushed through the pipe using pumps, which helps move it uphill or over long distances where gravity alone wouldn’t work.

There are no household or businesses sewer connections on the wastewater pressure main. Your existing connection to our wastewater system will not be impacted.

If the proposed pipeline goes ahead:

• A detailed traffic plan will be developed by the contractors and approved by the Shire of Augusta Margaret River.
• The plan will maintain public access and make sure people can still get around safely.
• We’ll share this plan with the community, so you know what to expect.
• We’ll make sure you can still access your property during construction.