IOWA CITY — Police said they discovered 30 pounds of marijuana after a traffic stop Tuesday evening.According to Iowa City police, one of the department’s K-9 officers made a traffic stop at Dubuque Street and Interstate 80 around 8:25 p.m. Tuesday. The officer reported detecting “a lot of cover smell” coming from the vehicle and dispatched his canine partner.Police said the dog alerted on the vehicle, indicating that drugs were present.