Works to repair scour damage downstream of the Fred Haigh Dam spillway near Gin Gin in Queensland, Australia, have recently been completed, SunWater has announced.
The works repaired the damage caused by the energy impact of floodwater on the spillway channel, sustained during weather events in 2011, 2013 and 2017.
The works commenced in September 2020 and involved excavating 500m3 of rock, constructing a 400m drainage system and installing 100 anchors downstream of the spillway, followed by a fibre-reinforced concrete slab over the top.
The slab contains more than 1500m3 of concrete and 13 tonnes of mesh to reinforce the spillway channel and ensure the dam continues to function as designed.
The work builds upon the initial stage of repairs, completed in 2019, to improve the spillway chute’s ability to withstand extreme floods. This included earthworks to clear debris in the spillway channel and filling and grading scour holes to reduce the possibility of further scouring and better match the natural slope of the channel.
The Comprehensive Risk Assessment process for Fred Haigh Dam continues this year to thoroughly assess the risks associated with the dam and provide recommendations for any longer-term risk reduction.
The mass concrete slab below the main spillway