The chemicals were illegally stockpiled by companies, including property owner Sustainable Solvents Group, who intended to distil and recycle solvents used in engineering, dry cleaning, printing and painting.
About 1 million litres were never distilled and have remained in rusting, leaking drums for several years while officials tried to get the companies to deal with the mess.
Last year Whangārei District Council obtained an interim enforcement order which allowed it to clean up the site and bill the owners.
The costs were being covered by the Ministry for the Environment, WorkSafe, Northland Regional Council and Whangārei District Council.
The bill is three times more than the last big chemical clean-up undertaken by government agencies, after an electroplating company in Timaru stockpiled 90,000 litres of toxic chemicals.