LPG Storage Facilities and the Seveso III Directive: Application of the Index Method and Verification of Territorial Compatibility

Liquefied petroleum gas (LPG) storage facilities represent a significant share of major accident hazard establishments in Italy and fall under the Seveso III framework (Directive 2012/18/EU, implemented through Legislative Decree 105/2015). Despite the availability of the Italian index method established by the Ministerial Decree of 15 May 1996, no structured pathway has been articulated that connects index-based risk screening directly to territorial compatibility verification in a single, auditable workflow. This paper addresses that gap by demonstrating how the index method applies to upper-tier LPG facilities and by proposing a six-step operator-to-authority workflow for territorial compatibility checks. The method decomposes the plant into logical units, computes intrinsic risk indicators (fire, confined explosion, explosion in air, and general risk), and derives compensated indices that credit prevention and mitigation measures. A representative upper-tier case study-a 1,400-tonne facility with two underground tanks, pumping and compression equipment, and a truck loading bay-illustrates the full application and shows how credited safety measures shift all logical units into Category A. Credible accidental scenarios and conservative effect-distance modelling then feed the proposed workflow, yielding defensible planning inputs for land-use compatibility decisions. The results confirm that the index method, when applied with explicit auditability requirements and integrated with consequence modelling, provides a coherent and repeatable screening route from Safety Report obligations to territorial planning.

Keywords: LPG storage, Seveso III, major accident hazards, index method, Safety Report, land-use planning, territorial compatibility.