Document Type

Technical Report

Publication Date



Demographic surveys -- Oregon, Oregon -- Population -- Statistics, Sewer districts -- Oregon -- Portland Metropolitan Area


The Tri-City Service District (TCSD) and Clackamas County Service District #1 (CCSD #1), both of Clackamas County, requested that the Population Research Center (PRC) at Portland State University produce long-term population forecasts for each of the two sewer service districts. In addition, CCSD#1 requested that forecasts also be developed to include the entire city of Damascus to account for possible future annexation into its district; and the city of Milwaukie, as CCSD#1 leases services to Milwaukie. The forecast horizon extends 30 years from 2010 to 2040, and projections are produced in 5-year intervals. For the 2010-2015 interval, forecast numbers for single years are included. Forecasts for three growth scenarios – high, medium, and low scenarios – are developed to account for different probabilities of demographic events. We consider the medium growth forecast to be the most-likely scenario. We also include in this report an analysis of recent demographic trends that have bearing on our assumptions for future growth in study areas.

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