Mobil spokesman Alan Bailey said Mobil no longer had any use for the site, which was leased from the port, so its facilities were demolished and the tanks removed last November.
The assessment included testing of the soil and any groundwater for contamination.
If required, remedial work would be undertaken, which could involve excavating and removing soil and replacing it with clean fill, he said.
"Any site where bulk fuel has been stored for a number of years is likely to require something."
The closure of the site was part of the rationalisation of bulk storage facilities by fuel companies around the country aimed at improving efficiency.
Mobil's nearest bulk storage to Dunedin was now in Bluff or Christchurch.
Otago Regional Council resource management director Selva Selvarajah said staff had visited the site after the tanks were removed.
No visible signs of contamination were found.
They would review the completed environmental report against guidelines for industrial sites.
If the site did not meet those guidelines, Mobil would be required to clean up the site, he said.
