Brown Field Municipal Airport Land Use Compatibility Plan

Appendix DMethods for Determining Concentrations of PeopleINTRODUCTIONThe underlying safety compatibility criterion used by the San Diego County Airport Land UseCommission (ALUC) in this Airport Land Use Compatibility Plan (the Compatibility Plan) is “usageintensity”—the maximum number of people per acre that can be in a given area at any one time. If aproposed use exceeds the maximum intensity, it is considered incompatible and thus inconsistent withcompatibility planning policies. The usage intensity concept is identified in the California Airport LandUse Planning Handbook (the Handbook) as the measure best suited for assessing land use safetycompatibility with airports. The Handbook is published by the California Department of Transportation,Division of Aeronautics, and is required under State law to be used as a guide in preparing airport landuse compatibility plans.It is recognized, though, that “people per acre” is not a common measure in other facets of land useplanning. This Compatibility Plan, therefore, also uses the more common Floor Area Ratio (FAR) as ameasure of usage intensity on the local level. The local implementing agency is responsible fordetermining which method of identifying usage intensity is best suited to their jurisdiction. This appendixprovides guidance on ways to determine usage intensity and defines the relationships between thismeasure, FAR, and other measures used in land use planning. For a discussion of the rationale for use ofpeople per acre as a measure of risk exposure, see Appendix C.COUNTING PEOPLEThe most difficult task in calculating usage intensity is estimating the number of people expected to use aparticular facility under normal circumstances. All people—not just employees, but also customers andvisitors—who may be on the property at a single point in time, whether inside or outside, must becounted. The only exceptions are rare special events, such as an air show at an airport, for which afacility is not designed and not typically used, and for which extra safety precautions can be taken, asappropriate.Ideally, the actual number of people for which the facility is designed would be known. For example, thenumber of seats in a proposed movie theater can be determined with accuracy once the theater size isdecided. Other buildings, though, may be built as a shell and the eventual number of occupants notknown until a specific tenant is secured. Furthermore, even then, the number of occupants can change inthe future as tenants change. Even greater uncertainty is involved with relatively open uses that do nothave fixed seating—retail stores or sports parks, for example.D–1Brown Field Municipal Airport Land Use Compatibility PlanJanuary 25, 2010