“The full reconstruction of Six Mile Creek Dam at Lake Macdonald will increase the dam's resilience to extreme events and bring the dam in line with modern engineering design standards,’’ he said.
Seqwater has been undertaking studies to minimise any environmental impacts associated with the construction of the new concrete spillway and new embankments either side.
Boats fitted with special sonar equipment have been traversing Lake Macdonald to identify and count fish species in the water.
As a result of the studies, Seqwater has updated its initial design of the dam spillway and rephased the lowering of the lake to 2021 to meet environmental conditions.
The project will start next year with a range of construction works including replacing the road bridge to the Noosa Water Treatment Plant and the relocation of existing utilities and services.
The re-phasing will also allow Seqwater to complete a range of projects to improve the operational capability of the Water Grid ahead of the lake lowering. These projects will bolster water supply security on the Sunshine Coast.
Mr Neil Brennan said the new design of the spillway, would better assist the passage of aquatic life moving over the spillway when the storage was at capacity.
“The revised design features what’s known as an ‘ogee-style’ spillway which allows fish and turtles in the storage to slide safely into the pooled water below,’’ he said.
“The new timeline for the lake lowering will provide us with more time to finalise our aquatic management plan to allow the safe lowering of the dam and the relocation of aquatic life.
“It also enables us to meet one of the strict conditions of approval for this project: to only lower the lake in a narrow window between March and August, outside the wet season.
“The lake will now remain open to recreation activities during 2020.”
The lake lowering and project timing remains subject to further water supply security assessments which will be undertaken during 2020 and early 2021.
The Lake Macdonald project is part of Seqwater’s Dam Improvement Program - a rolling program of dam upgrades across South East Queensland to ensure Seqwater's dams meet national and state safety standards into the future.
For more information about the Lake Macdonald Dam project visit www.seqwater.com.au/project/lake-macdonald-dam-upgrade