Work to replace a natural-gas main along Main Street began last week, and will likely result in some traffic slowness and service interruption through the summer, according to National Grid . Construction began Monday at Main and Grant streets, and will eventually extend to Main at Moody streets. The work will take place between 9 a.m. and 4 p.m. Mondays through Fridays, and possibly on some nights and weekends. Crews will replace approximately 1,500 feet of 4-inch cast-iron mains with a single stronger and longer-lasting 8-inch plastic main. The project will increase gas capacity for local customers and enable National Grid to continue providing safe and reliable service to homes and businesses, according to a statement from the company. During the project, Main Street will remain open to traffic and police will help control traffic flow when lanes are closed. After the work is completed, National Grid will require customers to switch to the new gas main, resulting in a temporary service interruption. The company said it would notify customers before turning off service, and contact customers to schedule dates convenient for them to switch to the new main. Community members with questions or concerns should contact Victor Santana at 781-907-2205.