A $500 million dam upgrade is about to intensify as workers race the clock to complete a key stage of the project.
A Lake Macdonald Dam Improvement Project construction notice has been issued, stating that the spillway and embankments are about to be demolished to make way for new infrastructure.
A spokesperson for the state’s water supply authority stressed the importance of the works.
“Seqwater is nearing completion of the temporary dam (cofferdam),” they said.
“With the cofferdam in place, and acting as a temporary dam, works will move into phase two: demolition of the existing spillway and embankments, which is a critical part of the overall dam upgrade.”
For more local news videos SUBSCRIBE to our YouTube channel. Just click here.
Demolition is expected to start on mid to late-April and will involve 24-hour continuous operations for about 15 days, weather permitting.
The construction notice stated that this phase “is both critical and time-sensitive”.
“Removing the old structure as quickly as possible helps protect the dam foundations and reduces the chance of water flowing through the site and materials dislodging and moving downstream,” it said.
“Safety improves significantly once the old structure is removed, and a stable working platform is in place.
“Continuous work is an important part of keeping the site safe throughout the demolition process.”
The Seqwater spokesperson said the accelerated construction approach was designed to protect the site, maintain safe lake levels and downstream flows during the demolition period.
“We have well-established plans in place to pause and secure the site should weather conditions shift unexpectedly throughout the demolition phase,” they said.
Related story: Rare cod among hundreds of fish relocated for dam works
The demolition phase was delayed from March 9, and again from March 16.
“The demolition program is highly weather dependent, and recent and ongoing rainfall since March 6, of approximately 190mm in the Lake MacDonald Dam catchment has resulted in inflows to the dam, causing the dam level to rise and spill excess water downstream.”
“As a result, additional time is required to prepare the site. This includes lowering the lake to 39 per cent and dewatering the area between the cofferdam and the existing dam wall.
“The safety of the community, our workforce and the surrounding environment remains our highest priority, and the decision to reschedule has been made to ensure the works can proceed safely. “
Seqwater and construction partner John Holland will have specialist crews monitoring operations and environmental controls around the clock, and will continue to work closely with nearby residents.
Lake Macdonald Dam is an ungated earth and rockfill embankment built in 1965 and upgraded in 1980. The existing 90m spillway is made up of roughly 90 concrete slabs over compacted earth.
The dam has operated safely but the methodologies and data used to estimate extreme rainfall events have progressed since the dam was originally constructed.
Once the demolition is completed, construction of the new dam will begin.
The new design includes a split-level concrete spillway, a lower ogee crest at the original lake level, and an upper labyrinth spillway to safely manage higher flows.
The total approved cost for the dam safety and water security project is $427.7 million, funded through Seqwater’s capital works program.
The spokesperson said the upgrade would significantly benefit the region.
“Seqwater is investing in Lake Macdonald Dam to ensure it meets modern engineering and design standards and continues to operate safely and provide local water security for generations to come,” they said.
The project will support more than 150 jobs.
Work started in late 2024 and is expected to finish in about late 2029, subject to weather and site conditions.
