18 February 2020
Interim fix for exposed old landfill
The Gore District Council is planning on having an interim fix in place by early next week for the old Gore landfill exposed during recent flooding.
The Council has moved quickly to prevent any harmful effects from the old landfill, exposed when floodwaters scoured the banks of the Waikaka Stream, near Hamilton Park.
Work has already started on the immediate actions outlined in a report by one of New Zealand’s leading engineering and design consultancies Harrison Grierson.
Transport Manager Peter Standring said layers of geotextile and geogrid will be placed over the exposed areas to prevent landfill material entering the river and help reduce further bank erosion.
“Geotextile and geogrid is an inexpensive interim option that we can quickly put in place.”
Fencing was being put up at Gore to keep people and animals away from the potential unstable sections of the riverbank, and weekly site inspections would be carried out.
“We will also look to remove any visible debris from the stream as soon and as safely as possible.”
Next week a LiDAR survey will be undertaken using a plane flying the affected section of the stream. The survey will provide a complete picture about the extent of the damage and the accuracy of contour data along the stream.
“The survey will give us a basis for future monitoring and a profile of the exposed areas for any engineering design solutions.”
Harrison Grierson representatives visited the landfill sites at Gore and Mataura last week to make an assessment and identify possible remedial options.
They found the Gore landfill was vulnerable to further erosion and scouring, and requiring immediate interim work. The Mataura site, which is on the banks of the Waimumu Stream near State Highway 1, was comparatively stable and suited to a single, long term solution.
The recommended long term solution for the Gore site was for gabion baskets to be placed along an extended section of the stream to avoid further erosion in another section of the landfill.
A combination of gabion baskets and filter sock or edge savers was recommended for Mataura.
The report says both sites may pose an environmental risk to the river and local community. However, there should be further investigations to fully assess those risks and identify actions to mitigate them.
Mr Standring said the Council was committed to minimising the impact on the environment and community.
The Waikaka walkway, at Hamilton Park, has been effected by the scouring and remains closed to the public.