Collaborative approach to riverbank solution

Hamilton City Council will work closely with stakeholder organisations to develop a plan for addressing instability issues on the Waikato River’s western bank in the city centre.

The riverbank walkway between London Street and the Claudelands Bridge has been closed since July due to two landslips. Council commissioned engineering firm Tonkin & Taylor to produce a geo-technical report into the two slips, the stability of the 600-metre stretch of riverbank, and what remedial options are available. The findings of Tonkin & Taylor’s report were presented to Council today (24 May).

Tonkin & Taylor’s report has emphasised the landslips are the result of a natural process in a moving environment. The Tonkin & Taylor report has been provided to stakeholder organisations Waikato-Tainui, Vector and Kiwirail, who own assets in the area.

“The report has also identified the possibility of further instability on the slope, potentially creating a risk to the assets owned by Council and those organisations,” says Chris Allen, Council’s General Manager City Infrastructure.  “We’ve begun discussions with the other asset owners on how best to collectively manage these riverbank instability issues.”

Tonkin and Taylor has recommended it is important to undertake some further testing which will involve drilling to find out the true strength of some lower soil layers before a preferred remedial option can be identified.

Mr Allen says Council has accepted this recommendation as well as a further advice to undertake stability and risk assessment of the road bridge abutment which sits on piles deep into the ground.  Local firm Bloxam Burnett and Olliver, who have significant and recent experience in this type of bridge assessment work, has been engaged to work closely with Tonkin and Taylor and Kiwirail.

“We have undertaken a visual site assessment pending this further investigation and there is nothing to indicate that there is any immediate risk to the road bridge. We will be doing some more drainage control and  carefully and regularly inspecting the riverbanks for any signs of further movement, and over the next few weeks will put in a more comprehensive monitoring system to alert us to any increased risk,” says Mr Allen.

The riverbank walkway between London Street and Alma Street will remain closed while further discussions with stakeholders take place, and options for a solution are explored.