SUMA Park Dam may be experiencing too much of a good thing, with the contractor under pressure to finish work before water levels rise.
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The dam has risen from 55 per cent in June to 59 per cent by July 20, with water reaching 5.5 metres below the spillway.
While NSW Water has welcomed the additional water security, the news is not so welcome for Suma Park contractor Geotech Pty Ltd, which has relied on low water levels to raise and strengthen the dam wall.
According to a report from Orange City Council technical services director Chris Devitt, rains have saturated the ground and caused the Gosling Creek and Spring Creek dams to overflow into Suma Park.
“Significant future rain events may result in quick jumps to the supply level in Suma with a potential overtopping of the spillway within a one-month period,” he said.
“The contractor is endeavouring to complete all concrete works below the spillway as early as possible to avoid the works being inundated.”
The concrete works involve the stilling basin at the foot of the dam wall where 446 anchors are being drilled as deep as 27 metres into the bedrock.
The council’s infrastructure policy committee chair and councillor Reg Kidd said inundation would not damage the work, but it could stall it.
“We need to be ready and to plan for possible outcomes,” he said.
“If work has to stop on that part of the site, work can continue on the auxiliary dam construction.
“While it might delay construction, the prospect of going into summer with a full Suma Park Dam is a prospect Orange residents would welcome.”
The dam has filled quickly before - in early August 2010 it was at 32 per cent, but water was flowing over the spillway by August 26.
According to Weatherzone, falls of two to 10 millimetres are expected early next week and on August 18, with a further rain event at the end of the month.
danielle.cetinski@fairfaxmedia.com.au