When Enough Is Enough: A New Way to Prove Environmental Risk Is ALARP

Offshore petroleum activities must demonstrate that environmental impacts and risks are both of an acceptable level and reduced to a level that is As Low As Reasonably Practicable (ALARP) under the Offshore Petroleum and Greenhouse Gas Storage (Environment) Regulations 2023. In practice, many Environment Plans rely on qualitative matrices and “good industry practice” statements that offer limited transparency around trade-offs, uncertainty, and the point of gross disproportion. This paper presents a practical, regulator-ready evolution of environmental ALARP specifically designed for Australian offshore submissions. The framework separates the distinct tests of acceptability and ALARP, then applies a disciplined semi-quantitative process to each impact/risk pathway: regulated baselines are established, discretionary control measures are evaluated using conservative intrinsic-effectiveness estimates (structured around six explicit attributes), marginal reductions are calculated against normalised cumulative sacrifice, and the threshold of gross disproportion is identified through second-order polynomial trendlines and marginal-benefit charts. A mandatory cross-pathway validation step ranks reduction per unit sacrifice across all pathways, providing objective, system-level evidence that effort has been allocated proportionately to consequence and uncertainty. Applied to a recent marine seismic survey in the Otway, the method transparently directed the greatest discretionary effort toward high-consequence, high-uncertainty pathways (underwater sound, marine fauna interactions) while correctly limiting intervention in pathways already controlled by legislation. By exposing rather than concealing judgement, the framework delivers the most traceable, replicable, and defensible environmental ALARP demonstration currently available and one that finally answers “when is enough, enough?” with evidence rather than assertion.