Logan River catchment early works - Cedar Grove Weir
Client: Queensland Water Infrastructure
Location: Queensland, Australia
Date: March 2007 – January 2008
Planning, designing, and constructing a concrete weir and pump station to increase reliable water supply for a rapidly growing region
Background
Cedar Grove Weir (CGW) is part of a region-wide, long-term water supply scheme developed in response to drought which severely affected water supplies in Brisbane and surrounds. This development is near an area of rapid urban and industrial growth and connects areas with an oversupply of water to areas lacking water via a network of storages and potable bulk water pipelines..
The CGW is a pumping pool for captured releases from Wyaralong Dam located upstream and also catches water from the Logan River during higher flow periods, and connects to the regional South East Queensland Water Grid.
Solution
Queensland Water Infrastructure engaged Entura as part of the Water Infrastructure Solutions Alliance to design, procure and construct the Logan River catchment early works.
The CGW is a 102 m long stepped concrete weir constructed within the naturally formed river channel of the Logan River at Cedar Grove. The weir is a combination of steel sheet piling driven down through the alluvial layers of the river with concrete benches and riprap, rock mattresses and ecocell to provide resistance against erosion on the horizontal surfaces and stream banks. Provision was made for installation of crest gates within the Stage 1 weir structure to increase the storage capacity at a later date.
To enable downstream environmental flows to be maintained when flow over the weir structure ceases, an outlet pipe has been provided through the weir. A fish lock system was provided to enable the passage of fish both upstream and downstream.
Outcome
The design of CGW was fast-tracked and was commissioned on schedule ready to successfully service the critical water needs of south-east Queensland. Due to the rapid growth of the region, Entura designed the project for long-term durability and to be able to accommodate potential future developments, while still preserving environmental values.
Cedar Grove Weir together with the Wyaralong Dam and Bromelton off-stream storage will yield 26 000 ML per year to the SEQ Water Grid.
