The city is preparing to offer outdoor seating permits to local restaurants, saying it will allow eateries to expand their service and add to the city’s vitality. Applications will be available soon, and the new program is expected to begin in June, officials said. Applications must be reviewed and approved by various city departments and receive final approval from the Department of Public Works. Brian Connors, deputy planner for economic development, said interest in outdoor dining has been growing in recent years, and he would expect it to continue to grow as tourism expands in the city. Union Station reopened last year after being vacant for decades, and the MGM Springfield casino opens on Aug. 24.