Canberra's $155 million Murrumbidgee to Googong pipeline project is almost on time and within budget, with completion expected in July.
Some disruption was caused by the recent flood in the river, but it was less significant than at the Cotter Dam, where the 40-metre-high wall was submerged. Construction of the wall to its final 80-metre height is due to resume next month.
Actew project manager for the Murrumbidgee to Googong water transfer Simon Webber said all of the pipeline was in the ground and pressure testing was about 70 per cent complete.
Flooding in the Murrumbidgee River had delayed work by about a month. Water had to be pumped from the low-level pump station but unlike the dam, equipment had not been inundated.
''There may have been some marginal delay costs but all up we will deliver under budget,'' Mr Webber said.
The pipeline would be operational by about July but rehabilitation of land would continue for some time.
Water will be removed from the river at a low-lift pump station. Three submersible pumps will lift the water about 50 metres to a high-lift pump station on Angle Crossing Road. From there the water will be lifted about another 200 metres to Gibraltar Pass, about seven kilometres from the river.
Water from Gibraltar Pass will flow about five kilometres, falling some 100 metres to a mini hydro plant which will produce about 20 per cent of the energy required to pump water from the river.
As part of the project, Actew has bought carbon offsets including forests in Western Australia. Water will be discharged from the pipeline into Burra Creek from where it will flow 13 kilometres into Googong Dam.
Under the operational guidelines, subject to a minimum river flow, up to 100 megalitres a day can be transferred from the river to the dam until it is about 80 per cent full. Googong Dam has a capacity of about 120 gigalitres and at present is effectively full.
Mr Webber said this was a long-term water security project.
''It is important to know this is going to be an asset for the community for a long time,'' Mr Webber said.
The detailed ACT and Commonwealth approval had set strict environmental flow requirements before water may be removed from the river. Mr Webber said the mini hydro turbine had been installed and the generator would be installed in May. Two large pumps for the high-lift pump station were due to arrive soon.
The pipeline crosses 17 private land holdings, land owned by Actew and ACT Parks and Conservation land. It also passes through a road reserve in the Palerang Council's jurisdiction.
Care had been taken to ensure the flow did not damage Burra Creek. Recent floods had given reasonable confidence flows from the pipeline would not damage the creek. The daily 100 megalitres would be tiny compared to the water which had flowed in the creek during the floods.
However, areas identified in the environmental study would be monitored and if necessary would be stabilised.
The 11.8 kilometre, one-metre diameter pipe includes 600 metres of mild steel to cope with the high pressure at the pumping stage. The rest is a traditional water supply pipe made of ductile iron.