SWAMPSCOTT-Selectmen voted this week to fill a vacancy in the Police Department as soon as possible.Selectmen have called for a civil service list to fill a patrolman position vacated when Thomas Wrenn resigned in April after being arrested by the Drug Enforcement Agency for possession with intent to distribute oxycodone.As long as Wrenn’s position remains unfilled, Chief Ronald Madigan said he expects an increase in overtime costs. Madigan pointed out the town laid off Officer Richard Alex on June 30, 2007 and, with Wrenn’s resignation, the department is down four officers so it is important to fill the vacant position.Town Administrator Andrew Maylor said contractual agreements require minimum staffing levels.?Filling the position is the right thing to do,” he said. “It was the right decision.”Calls to Board of Selectman Chairman Anthony Scibelli were not immediately returned on Thursday. Selectman Jill Sullivan said the decision to fill the position was unanimous and everyone is anxious to fill it as soon as possible.Maylor said it would take weeks to go through the civil service process and it could take up to several months to hire an additional officer.