Customer: NSW & Queensland Governments
Contract: Design, Construct, Operate & Maintain
Location: Tweed Heads, NSW
The NSW and Queensland State Governments awarded McConnell Dowell the contract to design, construct and operate the Tweed River Entrance Sand Bypassing. The main objectives of the project are to establish and maintain a safe and navigable entrance to the Tweed River; and to restore and maintain the ecology and amenity of beaches on the southern Gold Coast.
The main feature of the facility is the sand collection jetty which is approximately 450 m long and extends approx 300 m from the shoreline.
An unobtrusive control building housing the pumps, electrical equipment and control system sits at the shore end of the jetty. A 5 km long slurry pipeline transports the sand from the facility under the Tweed River, through the townships of Tweed and Coolangatta to the discharge outlets located at Point Danger, Snapper Rocks and Kirra Point.
A low-profile pump station on the Tweed River entrance supplies water from the river to the control building. The sand collection system is the key to success of the project. A sand trap or depression is formed under the jetty by the operation of 11 submerged jet pumps approximately 10 m below the seabed. Natural wave action feeds sand into this trap. Up to five jet pumps are then used to create a sand-water flume which flows under gravity to the control area. The water and sand mixture is then pumped under the Tweed River and to one of the sand outlets.
The design and construction phase involved a wide and multi-disciplined range of activities – from jetty piling, concrete foundations and building work through to design and installation of pipelines (trenched and trenchless), piping, equipment and electrical wiring.
The project was completed on time, within budget, without lost-time injury and without any environmental incidents.
McConnell Dowell continues its role in the project as the operator and maintainer of the system for 25 years. A purpose built computerised control system is used to manage the facility which was designed for unattended night-time operations. McConnell Dowell collects detailed records for its government clients including pump activity statistics and sand quantities pumped to each outlet.
Tweed Sand Bypassing has a wide range of stakeholders who each have a certain priority for the management of the coastline depending on their specific interests. Examples of these stakeholders include recreational fishermen, tourism operators, swimmers and surfers. Managing the interests of such a wide range of stakeholders is a very difficult process, but an important part of McConnell Dowell's operational focus.