OFM produces annual population estimates for ‘special areas’ required by statue. Special areas include highway urban areas, public transportation benefit areas, and the thermal electric generating facility area. The special area estimates are based on data produced by the Small Area Estimate Program using GIS-based spatial interpolation procedures.
Highway urban area population estimates
OFM produces annual population estimates for Highway Urban Areas (HUAs) as defined by the Federal Highway Administration (FHWA). HUAs include all areas defined as urbanized by the Census bureau but can and usually do include areas beyond the Census Bureau defined boundaries. For urban areas of 5,000 through 49,999 people, FHWA uses city limits or Census Designated Place boundaries, with some adjustments, as the minimum area.
Public transportation benefit area population estimates
OFM produces annual population estimates for Public Transportation Benefit Areas (PTBA) as well as Unincorporated Public Transportation Benefit Areas as defined by Washington State Department of Revenue. PTBAs are Washington State transit areas established by public vote. Population estimates are produced in accordance with RCW 36.57A.010.
Thermal electric generating facility area population estimates
OFM produces annual population estimates for incorporated places, unincorporated areas, fire protection districts, and library districts within the Thermal Electric Generating Facility Area (TEGFA). This boundary is defined as the area lying within thirty-five miles of the most commonly used entrance of the Columbia Generating Station (formerly known as the Hanford Nuclear Reservation) and is south of the southern boundary of township fifteen north. Population estimates are used for the annual distribution of tax proceeds in accordance with RCW 54.28.055. These taxes are dispersed as part of the Public Utility District Privilege Tax.