Waste soil from the cleanup of a Kapuni well site was so contaminated it had to be taken out of the region for dumping.
The soil - about 50 cubic metres or two to three truckloads - had too much hydrocarbon contamination to meet Taranaki Regional Council limits, and was taken to Wellington for disposal.
Cleanup of the long-standing contamination at Kapuni well sites started with soil containing hydrocarbons and metals from fluids produced from the KA2 well site.
The TRC has a limit on the concentration of hydrocarbons it will accept for disposal on land.
If the soil has too much oil in it, it has to go to a landfill, director environment quality Gary Bedford said.
The most contaminated soil from KA2 was taken to a certified treatment facility in Wellington. A further 200 cu m was moved to a landfarm in Taranaki.
The cleanup of KA2 has now finished and three more well sites are still to be cleaned up. It is understood a second well site could be cleaned up by Christmas.
There are about seven land remediation sites in the region consented by the regional council.
"The consents control the amount of material that can be deposited, the depth they can be deposited and what it can contain," Mr Bedford said.
"We require full records before anything can go on to the site and we have good monitoring results to show the biodegradation, using natural organisms in the soil, is very effective at reducing hydrocarbons - basically oxidising them and removing them from the soil."
Shell Todd Oil Services general manager Rob Jager said cleaning up these sites was a top priority for STOS.
"We are installing monitoring bores at the sites to determine whether . . . there are any impacts. If there are, we will work with regulators on the best way forward. At present we don't know how long this will take but we are committed to doing a thorough job."
In the past, fluids from well operations were intermittently released into pits within the Kapuni field.
These pits were used, infrequently, for temporary containment, and were unlined, which was common industry practice at the time, Mr Jager said.
"We no longer use unlined pits in our operations."
In the past, some pits were used to take fluids from fracked wells.
However fracking returns are highly unlikely to be the source of the affected soil, Mr Jager said.
Steel tanks will be used to fully contain all fluids during the drilling operations later this year.
- Taranaki Daily News
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