A plan to provide Norton with a new town hall and a new senior center faces its first key hurdle when voters decide this month whether to fund design and oversight of the project. The $1.5 million spending request is coming before voters at the Fall Town Meeting Oct. 23. The funding would come from a one-time building fee the town received from Alnylam, a Cambridge-based pharmaceutical company that plans to construct a manufacturing facility in Norton, Town Manager Michael D. Yunits said by e-mail. Built in 1907, the existing town hall on East Main Street was originally the gymnasium of a private girls school. It was converted to town hall in 1978. “The space is dysfunctional with no conference rooms and offices open to each other,” said Yunits, adding that the building also does not meet codes governing space per employee. The existing senior center began life as a one-room schoolhouse on Bay Road in the 1880s. It was moved to its current spot on West Main Street in the 1940s and was used as a firehouse before it was converted to the senior center in the late 1970s. Yunits said the building is too small to meet the needs of the town’s fast-growing senior population and lacks adequate parking. The town is evaluating several potential sites for its replacement. The new town hall would be built behind the existing one. Once the design is complete, voters will be asked to approve funding for construction of the overall project, currently estimated at $12 million.John Laidler can be reached at email@example.com.