(Troutdale, OR) -- A proposal for a penny-a-gallon gasoline tax in Troutdale is leading in initial returns. The tax, which would be phased in over three years, is ahead by a 53-47-percent margin. So far, about two-thirds of those voting in the Riverdale School District are favoring a five-year local-option levy to fund operations. It would mean a dollar-37 for each one-thousand dollars in assessed value.