The Coastal Cooperative Alliance for Seacoast Transportation is beefing up its bus service later this month as the result of a Department of Transportation grant to mitigate traffic disruption during reconstruction of the Little Bay bridges between Dover and Newington. COAST Route 2, which connects Rochester, Somersworth, Dover, Newington, and Portsmouth, will be improved so there is a bus every half-hour heading south to Portsmouth between 5:30 and 9 a.m. and every half hour from 3 to 6 p.m. heading north from the Port City. The two routes of the Portsmouth-Pease Trolley system will undergo a similar schedule enhancement. The grant will fund the increased service for five years. The new schedule will begin June 25.