The threatened strike of Rialto theater service workers union SEIU Local 32BJ has been averted following an agreement reached late Thursday with the Broadway League for a tentative three-year contract. The pact provides improved health-care coverage, raises and pensions for the roughly 240 union workers in 30 Broadway theaters, including cleaners and porters.Workers were able to secure a dollar an hour boost over the life of the three-year contract, equaling a 6.2% raise. The existing contract is set to expire Dec. 31. While the settlement remains tentative until it has been ratified, terms are expected to be confirmed. Local 32BJ is the largest property service union in the country, with many workers employed on Broadway for as long as 25 years.