Polk County supervisors plan to use one-third of the revenue that would be generated by an extra 1-cent sales tax for mental health services, with another one-third devoted to property tax relief in unincorporated areas and the final third used for capital projects, also in unincorporated areas, according to a resolution that will be up for a vote Tuesday. The tax, called a local option sales and service tax, has been approved by every community in Polk County — except Polk City and Sheldahl, which already have the tax. Under state law, supervisors are required to call for the election after receiving notice from cities representing more than 50 percent of the county’s population that they support the measure. That threshold was reached earlier this month after the Des Moines and West Des Moines city councils voted to support a local option sales tax. In November, voters in Dallas County, including cities such as West Des Moines and Urbandale that straddle Polk and Dallas counties, gave overwhelming approval to the tax. That vote prompted action among Polk County communities. The Iowa Department of Revenue has estimated that the county’s take from the additional tax will be about $11.6 million in unincorporated areas. Supervisors will set the vote for March 6, with the tax taking effect July 1, the same date the Dallas County tax is effective. The total revenue generated in all of Polk County is estimated at $80.7 million, with $38 million generated in Des Moines. Des Moines lawyer and economic development leader Steve Zumbach, a participant in a previous failed effort to approve the tax, weighs in on why he thinks this vote could have a different outcome in this Business Record Insider article.