About 20,000 tonnes of sediment have been removed from the lower Ōpawāho/Heathcote River to help reduce the risk of flooding in the area.
Further dredging will be done later in the year, after the īnanga (whitebait) spawning season.
Thousands of fish have also been relocated from the work site.
In the three months to 24 January, 3623 fish were moved upstream, including 531 shortfin eels, 76 longfin eels, 153 īnanga, 2717 common and giant bullies and three black flounders.
The dredging work is being carried out between Opawa Road and the Woolston Cut (an engineered channel) under the Christchurch City Council’s Land Drainage Recovery Programme.
Stage one of the “in-river” work – from Radley Street to the Woolston Barrage – has been completed, with the barge due to be removed this month.
Work is also well advanced on stage two, from Opawa Road to Radley Street. Contractors will dredge a section of stage two upstream of Radley Street from Clarendon Terrace this month using a long-reach excavator operating from the bank.
Council Land Drainage Manager Keith Davison says the work is already having a positive impact on the local environment.
“It has effectively boosted the post-earthquake capacity of the river, lessening the flooding risk to nearby streets and homes,” Mr Davison says.
“The next phase of work on stage one to regrade the banks and improve the local landscape and ecological habitat will further complement the river work.
“However, we will soon hit the ‘pause button’ on the stage two dredging work to allow for the īnanga spawning season. Dredging will restart on 1 June.”
Dredging from June will be from both sides of the river – between Clarendon Terrace and Richardson Terrace – and work is expected to continue until later this year.
The river will be closed to recreational use in work areas because of safety issues and sediment controls.
Single-lane traffic controls will also be introduced to manage truck access.
In the meantime, contractors will focus on the stage one work to regrade the banks, build a footpath through Laura Kent Reserve and carry out landscape planting. Local schools will also help out with the planting in Connal Reserve.
“Walkways on both sides of the river will be closed during periods of the stage one work, with safety fencing and signage in place,” Mr Davison says.
A final bank tidy-up and landscaping will be completed along Richardson Terrace and Clarendon Terrace following the completion of the stage two work, with planting in May-June 2020.
Planning and design for the third and final stage of dredging from Beckford Road to Opawa Road is well under way, with on-site work expected to start in late 2019.