The question of liability over the 2005 Buncefield oil depot blast is to be decided at the High Court.
Mr Justice David Steel's ruling will clarify who should pay the property damage bills of individual and business claimants outside the site's perimeter.
The explosion - widely thought to be the largest ever in peacetime Europe - was the result of an overspillage at the Hertfordshire depot.
It is believed 300 tonnes of petrol spilled over from the top of one of the storage tanks.
It formed a huge vapour cloud which ignited, causing widespread damage and injuring 43 people.
The site is operated by Hertfordshire Oil Storage Ltd (HOSL) - a joint venture between Total with 60% and Chevron with 40%.
Total has claimed that Chevron should share responsibility for the incident while Chevron, which denies liability, says Total was in day-to-day control at the site.
At the trial of the action, in the autumn, Jonathan Gaisman QC, representing the claimants outside the fence, said that his clients' unsatisfied insurance claims totalled £370 million.
