Seventeen former landfill sites within the Southland District (SDC) have been identified as presenting a possible risk, according to a report from environmental science consultancy e3 Scientific.

Leachate impacting surface water or groundwater quality, or potential exposure to erosion/flooding were identified as the possible risks.

The controversial Colac Bay landfill, as well as sites at Otautau, Bayswater, Wreys Bush, Thornbury and Riverton Rocks were all flagged for further investigation.

The consultants, commissioned by the SDC, investigated 56 sites within the district before identifying the 17 possible risk sites.

Their recommendations included preparing a detailed site management plan for each site, sampling of surface water/groundwater for leachate contaminants and the assessment of at-risk sites by a coastal engineer for stability and protection options.

Strategic manager water and waste Mike Bourke said the Colac Bay site has been assessed three times in the past and while beach erosion was still occuring, it was a long way off yet.

"It is considered that the site may be vulnerable in the long term, but current risk is low,”  Bourke said.

However further water sampling would now be conducted as well as continued monitoring of the coastline for erosion.

$12 million of protection or removal work at Otautau, Bayswater, Wreys Bush, Thornbury and Riverton Rocks had also now been added to the 2024-5 long term plan, with completion dates within the next 15- 20 years.

The Bluecliffs Beach Road dump site, near Tuatapere, wasn't included in the e3 Scientific inreport because the SDC hadn't been aware of its existence.

Historically, waste disposal in Southland was decentralised with most townships having one or more local tip sites, often located in empty gravel pits.

However since the Resource Management Act 1991 came into effect,many were closed rather than granted a consent.

SDC, as the successor of the local authority who operated or allowed the landfill, remains responsible for any future works.