Old landfill sites at Gore and Mataura pose environmental risk

Tuesday, 18 February 2020

Gore District Council transport manager Peter Standring, right, and Landpro surveyor Hamish Weir, left, at the old Gore landfill site, which was exposed by floodwaters during Southland floods.

An engineers' report into old landfill sites at Gore and Mataura says both sites may pose an environmental risk to the river and community.

The disused landfill at Gore was exposed when floodwaters scoured the banks of the Waikaka Stream, during widespread flooding in Southland last week.

Flooding exposed rubbish form an old landfill in Gore, which has now been assessed by engineers. This photo was taken as floodwaters subsided.

Work has already started on the immediate actions outlined in a report engineering and design consultants Harrison Grierson, who visited the landfill sites last week to make an assessment and identify possible remedial options.

Council transport manager Peter Standring said layers of geotextile and geogrid would be placed over the exposed areas to prevent landfill material entering the river and help reduce further bank erosion.

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'Geotextile and geogrid is an inexpensive interim option that we can quickly put in place. We will also look to remove any visible debris from the stream as soon and as safely as possible.'

The engineers found the Gore landfill, which closed in 2005, was vulnerable to further erosion and scouring, and required immediate interim work.

The Mataura site, which was 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 is 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.

Last week council general manager infrastructure Ramesh Sharma said if anyone saw debris that needed to be removed, they should contact the council.

Next week a LiDAR survey would be undertaken using a plane flying the affected section of the stream.

It would 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,' Standring said.

The council was committed to minimising the impact on the environment and the community, he said.