After four contentious years, the nuts and bolts of the contract dispute between the city and its firefighters’ union should be decided during a two-day arbitration hearing in the fall. The city and the Watertown Professional Fire Fighters Association Local 191 will meet on Oct. 18 in an “interest arbitration” proceeding regarding the overall firefighters contract. The 68-member union has been without a contract since July 2014. The main sticking point remains the “minimum manning” stipulation that requires 15 firefighters are on duty at all times. How much firefighters are paid and how much they pay for health benefits will be determined during the arbitration hearing, City Attorney Robert J. Slye said.