The old diesel tanks, beneath the Valley Project workspace in Allen St, North East Valley, were discovered at the end of last year.
The community organisation was later notified on July 9 that the tanks had leaked. Later that day regional council staff visited the site.
Council compliance manager Martin King said staff had since been back to check the site and would continue to do so.
"There are no health risks from the leak."
Council staff identified several cups worth of diesel had leaked from behind a concrete retaining wall.
They set up a boom to capture the diesel spill.
With help from the council, the Valley Project has hastened plans to get WorkSafe to backfill the tank with concrete and permanently block any leakage.