The town’s highest elected official on Monday night said he’s poised to sign an agreement that will bring natural gas to New Canaan public buildings, businesses and some homes, signaling the introduction in earnest of a widely anticipated energy source following years of stop-and-go efforts. First Selectman Rob Mallozzi and representatives from Eversource unveiled a plan to bring a 4.7 mile “trunk line” up Route 106 from Stamford to serve New Canaan High School, South School, Saxe Middle School, the YMCA and Waveny Care Center, as well as East School, in 2018. After that, Eversource’s program manager for gas expansions, Chris Luca, told members of the Utilities Commission at their regular meeting, the company in 2019 will lay an additional five miles of lines to bring natural gas to residences along the South Avenue corridor, from Farm Road toward the downtown. Additionally, Eversource will offer natural gas to residences where it makes sense along the route to East School—the proposed route calls for a line to run down Harrison and then up Main and along Lakeview to the school. And then in 2020, the natural gas line build-out will come to the business district, Luca said.