Risk-Based Zoning for Toxic-Gas Pipelines

Implicit in the operation of a toxic-gas pipeline is the possibility of an accidental release, which could have serious consequences if upwind of a nearby populated area. Concern for public safety leads to the establishment of isolation corridors or buffer zones to reduce and control the hazard to human settlements. Although "worst case" or "average case" are often used in the determination of safe distances, a probabilistic approach (risk analysis) is superior because it identifies important factors, it makes maximum use of available data, it allows comparison of alternatives, and it quantifies intuitive risk considerations. To illustrate the method, a risk model developed for sour gas pipelines in the Province of Alberta, Canada is outlined and an actual risk-distance curve is presented. The current zoning regulations in Alberta are summarized.