Seaham Weir Refurbishment and Modification Project

The Weir is more than 50 years old and in its current form, while suitable for water supply purposes, cannot meet the required actions from the 2014 Lower Hunter Water Plan (LHWP) because the existing gates do not enable suitable flow control and restrict fish passage.

The Weir consists of a rock weir, concrete spillway, flow control gates and a fishway. The Weir also protects the water in the Weir pool from salty tidal water. The project will provide upgrades to improve safety and water flow controls down the River and maintain appropriate water levels. The installation of new low flow weir gates will enable the Weir to operate more effectively and allow releases of smaller amounts of water more regularly when required, reducing large or sudden changes in Weir pool water levels. The new integrated fishway is designed to improve the ability of fish to move both up and down the River.

This project is a vital part of Hunter Water’s program to replace and upgrade water and wastewater-related assets across the Region. Hunter Water looks forward to continually improving the infrastructure that delivers quality outcomes for the community and the environment in which we live.

• safety and compliance refurbishment of the existing weir gates
• installation of four new low flow weir gates on the eastern side of the Weir to allow smaller releases of water when needed
• installation of a new fishway on the eastern side of the Weir for improved fish passage both up and down the River.

The Seaham Weir on the Williams River is a crucial part of Hunter Water’s drinking water supply infrastructure, as it creates a freshwater pool that provides around 40% of the water in Grahamstown Dam, providing drinking water to the communities of Newcastle and the Lower Hunter.

Currently water is released, or flows past Seaham Weir, depending on the flow rate of the river. Water can be released through flow under two large gates, over the Weir wall (during floods) and through the fishway. The Weir pool must be maintained at a specific level to reduce erosion of the river bank and prevent flooding of surrounding properties. The gates are opened when the water rises in order to prevent flood events, to allow flushing and environmental flows, and for maintenance purposes.

Operation of the Weir and flow levels are highly regulated by the NSW Government to balance the competing demands of the water (including environmental flows, water shortage risks and fish passage).

The rules that govern the opening and closing of the gates are contained in the Water Supply Work and Water Use Approval for the Seaham Weir Management Zone of the Williams River Water Source (20CA212238) which, in turn, reflects the requirements of the Water Sharing Plan for the Hunter Unregulated and Alluvial Water Sources 2009. There are also rules established around the environmental needs and benefits of the River. These are set out in the 2014 Lower Hunter Water Plan (LHWP) and are informed by a range of government departments and working groups. It is these rules that require the improvement of the fish passage at the Weir. There are environmental actions that Hunter Water must undertake in relation to the management and operation of Seaham Weir. A number of these relate to the type and amount of water released from the Weir and depend on the amount of water in the River.

The Review of Environmental Factors (REF) for this project was placed on public exhibition in 2017. At that time a communication program was undertaken to make all potential stakeholders aware of the opportunity to provide comment on the proposal and its potential impacts. This included signage, advertisements in the local newspapers and letters to key stakeholders. The project was also promoted on the Hunter Water website.

Project construction will be undertaken by Abergeldie, from late August 2021 and is expected to be completed in November 2023.

Nearby residents may experience some construction impacts such as an increase in traffic, noise and dust. We will seek to reduce these impacts as much as possible.

Most activity will be carried out from 7am until 6pm Monday to Friday and 8am to 1pm Saturday, weather permitting. If we need to work outside these times, notifications will be issued.

Hunter Water will ensure at least one of the existing weir gates remains operational during the construction period and that the new low flow gates and fishway will have no impact on water levels, upstream or downstream in accordance with existing requirements.