Otago Regional Council regulatory and communications general manager Richard Saunders said it was possible there were landfills in the Otago region that were not listed on the council’s database.
And while only four landfills were listed among the region’s contaminated sites, another 75 landfills had not been investigated, he said.
The ‘‘not investigated’’ status meant contamination could have happened at the site, but the landowner had not investigated, or supplied information to the council to confirm the site’s status, Mr Saunders said.
The Otago Daily Times asked whether the remaining landfills would be investigated, when they would be investigated, and by whom.
The ODT also asked if it was concerning so many landfills had yet to be investigated.
Mr Saunders said the national environmental standard for assessing and managing contaminants in soil to protect human health (NESCS) provided rules regarding the disturbance, subdivision, and land-use change of potentially contaminated land.
It was the responsibility of landowners to undertake investigations, he said.
Preliminary site investigations and detailed site investigations were required when landowners wanted to do something on a landfill site that required consent.
Work was often prioritised when the land was expected to be developed, he said.
Sites were often broken up into smaller sections.
Where an investigation had demonstrated an area of 30sqm had once been used as a farm landfill, for example, that 30sqm land was given an individual site number, he said.
Yet, far more than 173 landfills met the Government’s hazardous activities and industries list (Hail) criteria for landfills, Mr Saunders said.
The council’s Hail register counted 288 landfill sites, Mr Saunders said.
But the category included, for example, residential, agricultural and commercial building waste disposal that would not normally be associated with landfill operations.
There could also be duplicates, or miscategorisations, on the council’s list, he said.
Council staff were now working through the list to make sure it was accurate, he said.
Across Otago, 71 landfill sites had management in place, which included active remediation, monitoring, and management with consents, Mr Saunders said.
The four landfill sites known to be contaminated were the Old Coach Rd Landfill, in Kaitangata, a private part of a closed landfill in North Taieri, and two closed landfill plots side by side in Wingatui, he said.
