A risky bet on population.

Byline: The Register-Guard

Portland State University's Population Research Center estimates that the city of Coburg's population will double to 2,000 by 2030. A consulting firm working under contract to the city estimated that the population will triple. On Wednesday, the Lane County Board of Commissioners voted to allow Coburg to hitch its fate to the larger figure, while accepting PSU's numbers for other cities. Much is riding on whether the board made the right choice - and Coburg residents have reason to be nervous.

Accurate population projections matter, because if cities fail to prepare for growth they can find themselves stuck with inadequate streets, schools and other costly chunks of infrastructure. If they prepare for growth that doesn't materialize, cities might make larger-than-needed investments and find fewer people to pay for them.

That's the dilemma in Coburg. The city is building a $25 million waste treatment system. Sewers are a key to Coburg's growth; without them, not much development can occur. But the cost of the system is fixed, while the number of people who will pay for it is uncertain.

If PSU's projection is correct, the cost must be spread among fewer people, resulting in higher rates and assessments. If the consultant is right, a larger number of new arrivals will pick up much of the tab, resulting in lower costs for current residents.

There's reason to believe Coburg will grow. It's close to the emerging employment center in the northern part of the Eugene-Springfield area, including the new River Bend hospital. In recent years, Coburg has been an employment center in its own right, with more jobs than residents because of the recreational vehicle industry. Coburg is a nicely self- contained community with small-town atmosphere, yet it's convenient to the urban area - making it a likely candidate for residential growth.

Even PSU, however, projected faster growth in Coburg than has been seen in the past. In the 28 years between 1980 and 2008, according to PSU figures, Coburg's population grew by 54 percent. PSU projected 100 percent growth in the next 22 years. The county accepted the consultant's projection of 200 percent.

Construction of a sewer system will remove an impediment to Coburg's growth, which may allow pent-up demand to cause a growth spurt. But if growth continues at the pace of recent decades, or even if it only accelerates to the rate projected by PSU, the city will have pushed sewer costs onto future residents who won't be there to pay them. That would leave Coburg residents on the hook for sewer costs.

As Yogi Berra said, predictions are risky, especially when they're about the future. People in Coburg have a lot riding on this one - so much that the city should be looking for a way to make the sewer project pencil out under a more conservative growth projection.