(Troutdale, OR)  --  Voters in Troutdale have until eight o'clock tonight to return their ballots for the proposed three-cents-a-gallon gas tax to pay for street maintenance.  The tax would be phased in over three years.  The Riverdale School District is asking its voters to approve a five-year local-option levy to fund operations.  The proposed levy is a-dollar-37 for each one-thousand-dollars of assessed property value.