About 10 percent of Clark County voters who received ballots for the Aug. 17 primary election have returned them to the county elections office, despite a misdated instruction sheet included with some ballots. The county mailed 218,166 ballots last week and had received 22,620 returns as of Aug. 5, the latest tally available. County auditor Greg Kimsey has predicted a ballot return of 38 percent to 40 percent. Ballots must be postmarked by Aug. 17 or delivered to the elections office or drop-off boxes by 8 p.m. on Election Day. The deadline for voter registration by mail has passed, but people can register in person at the elections department, 1408 Franklin St., through Monday.The primary election will winnow the candidate field to the top two vote-getters in races for U.S. Senate, the 3rd Congressional District, two open legislative seats and several local offices. The winners will face off in the November general election. In races with just two candidates, both will advance to the general election.Clark County voters will pick the top two candidates for county assessor, county prosecuting attorney, state Supreme Court justice, Clark Public Utilities commissioner, and Vancouver city council.Voters also will decide whether to renew emergency medical services tax levies in Fire District 6 and the city of Washougal and whether to allow the Fort Vancouver Regional Library to restore its regular property tax levy.