The annual town election season is officially underway. Town Clerk Marsha L. Silvia recently advised residents that nomination papers for the April 26 election are now available in her office. Voters this year will be filling one seat apiece on the Board of Selectmen, the Board of Assessors, the Sewer Commission, the Park and Recreation Commission, and the Cemetery Commission. With Bridgewater voters, they will also be electing a Raynham member and a Bridgewater member of the Bridgewater-Raynham Regional District School Committee. School Committee candidates file nomination papers in their own town but appear on the ballot in both towns, Silvia said in an interview. The deadline to obtain nomination papers is March 6, and to return them, March 10.