Contact Energy is required to manage works in the bed of the Manuherikia River to mitigate effects of flooding that may arise because of the dams it operates on the Clutha River, a condition of one of its resource consents to operate the dams.
Contact Energy has also applied to the Central Otago District Council (CODC) for a resource consent to excavate sediment at the Lowburn Inlet between May and November this year.
However, CODC planning manager Louise van der Voort said there were still some outstanding consent requirements for the excavating work about to begin in the Manuherikia River.
As part of the conditions to operate its dams on the Clutha River, Contact Energy was granted consent in 2007 from the Otago Regional Council (ORC) for authorised works in two sections of the Manuherikia River.
‘‘However, the proposed works breach a rule in the [Central Otago] district plan to do with the excavation 10 metres within a water body.
"Because that rule's breached, they need to apply for resource consent with the CODC,'' Ms van der Voort said.
‘‘They [Contact Energy] submitted something prior to Christmas and I've gone back and said they needed written approvals from the affected parties, some of them being neighbours.
‘‘We're expecting them to lodge a consent [application] with written approvals in the near future.''
Once the application was lodged, the council would be making a decision whether to notify the public, she said.
‘‘Provided all the written approvals have been obtained, I don't foresee that it will need public notification.''
Contact Energy communications manager Jonathan Hill said the company did require one consent for excavation work in the Galloway area, but the works in the lower part of the Manuherikia River near the Linger and Die area were fully permitted.
‘‘We have prepared an application to give to council and we are currently consulting with a number of parties before formally lodging the finalised consent application,'' Mr Hill said.
The first section of the work (the lower reach) is from the confluence with the Clutha River, at Alexandra, and 1.37km upstream to Shaky Bridge where 50,000m3 of gravel will be excavated.
This will involve excavation of sediment up to 2m in depth from the terraces and beaches beside the current river channel.
The location of the existing river channel will remain, but will be made deeper by up to 1m.
The gravel will be deposited at the Linger and Die site and an area on the opposite bank.
‘‘Between the Linger and Die stopbanks, there is a proposal to turn that area into a park, re-sow it and plant trees as a recreational asset for the local community,'' Mr Hill said.
A deep water hole for swimming was also being created under the Shaky Bridge, he said.
The second section (the upper reach) either side of the Galloway Bridge, includes excavation of 50,000m3 of gravel less than 1m in depth, but up to 1.5m in places, over 2.54km.
The location of the existing river channel will remain except at the Galloway Bridge where it will follow the 1979 channel.
There are three sites on land near the bridge where gravel will be deposited.
The works are scheduled to take place from February to July to be undertaken from 7am to 7pm six days per week, excluding Sunday.
‘‘We appreciate there will be some inconveniences, but the community will be better off in terms of flood mitigation and in terms of developing a recreational facility,'' Mr Hill said.
Maintenance of the river beds will be an ongoing exercise and excavation may need to be carried out every three to five years.
Alexandra District Flood Action Society president Stan Randle, of Earnscleugh, who represented the group at the Clutha River resource consent Environment Court hearings that were held at various times between 2002 and 2006, said the excavation work was what Contact Energy said it would do, but he had reservations about its effectiveness.
‘‘The sediment going into the lake will be minimised as well as helping the flooding in the Manuherikia Basin,'' Mr Randle said.
However, he was still concerned about the risk of flooding in Alexandra.
‘‘The thing that I think is important is that the problem of the sediment in the lake itself [Lake Roxburgh] is still there.
‘‘They're trying to stop it getting any worse and use the scouring [of the river] to flush it further down the lake.'' By using the 1979 levels, the material going into the lake from the Manuherikia River would be minimised, he said.
‘‘It depends on the weather and it depends on nature in a way.''
If there was a ‘‘hundred-year flood'', as there was in 1878 when 4400 cumecs of water came through, ‘‘we would be in big trouble''.
