Dredge and replace option investigated
15 September 2004
Dredge and replace option for Orakei Creek to be investigated Auckland City is to investigate a dredge and replace option for addressing the build-up of sediment in the arms of the creek leading to the Orakei Basin.
Auckland City’s Works Committee resolved today to look into removing up to 300mm of contaminated sediment and replacing it with clean material.
Dredging the creek arms had been put forward as a possible solution but at the May meeting of the Works Committee, this option was deferred because of the potential to cause land instability to properties in the area.
Councillor Bill Christian, chairperson of the Works Committee, says council officers and the Orakei Basin Protection Group looked into eleven options.
They found that ten of them had significant consent or engineering risks and as such, did not warrant further investigation.
“Removing 300mm of contaminated soil and replacing it with the same depth of clean material appears to be viable option and officers will now investigate this further,” says Mr Christian.
Further investigation will focus on: identifying acceptable clean material the optimised scope of the physical work construction methodology the cost of the project and use of the Infrastructure Auckland subsidy of $2.3 million consent issues the impacts of the pending foreshore and seabed legislation.
Mr Christian says that if it went ahead, removing the contaminated 300mm of sediment would work in conjunction with other major projects to improve the water quality in the basin.
“The restoration of the Waiatarua wetlands and the separation of stormwater and sewage in the Meadowbank catchment have been the main projects we have undertaken to improve the water quality.
“The work that we are now investigating would contribute to this work by providing the greatest opportunity to remove the accumulated polluted sediment.”