Frequent Questions

Methods to identify affected populations

As part of the risk management program, a facility owner or operator must prepare an off-site consequence analysis (OCA) and estimate in the risk management plan (RMP) the residential population within the geographical area that could be affected by the hypothetical worst-case or alternative releases that the facility has analyzed (40 CFR §68.30(a)).  What data and methods can a facility use to identify the population affected?

A facility owner or operator may use the most recent Census data, or other updated information, to estimate the population potentially affected (§68.30(c)). EPA does not require the facility to update Census data or conduct any surveys to develop its estimates.

Some examples of methods that may be used to estimate the population include using Geographic Information System (GIS) software and obtaining the latest Census data (such as through In addition, the mapping application Mapping Applications for Response, Planning, and Local Operational Tasks (MARPLOT), from the Computer-Aided Management of Emergency Operations (CAMEO) software suite (, and the Circular Area Profiles application ( from the Missouri Census Data Center tools utilize current data from the 2010 Census.

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