Employees with the Graton Resort & Casino have voted to unionize, a move that adds the Rohnert Park tribal gaming destination to the widening trend of union representation of casino workers nationwide.

The vote by Graton casino employees sets in motion collective bargaining for a new contract with the casino, which opened in November. Union officials said they will look to protect benefits currently offered to casino employees, including 100 percent employer paid health care to all employees who work more than 20 hours a week.

“There is no preset list of demands,” said Sarah Norr, a researcher with Unite Here Local 2850, which will represent 600 casino janitors, cooks, waiters and gaming workers. “Definitely solidifying existing benefits is important to our workers.”

More than 70 percent of affected employees decided to join the union in an election that began last month. The other 30 percent did not participate in the process. Union organizers announced the results of the election Tuesday.

The move comes as union membership is declining nationwide but growing among casino workers. Unite Here represents 100,000 workers at gambling sites in the United States and Canada. About half of casino workers are unionized in California and nationally, according to Unite Here.

Under an agreement between Unite Here and the Federated Indians of the Graton Rancheria, which owns the casino, workers were allowed to choose whether to become union members without interference from the employer. Tribal Chairman Greg Sarris, who pressed for the deal to allow unionization, said he was pleased workers at the casino, one of Sonoma County’s largest service employers, would have their benefits contractually ensured.

“I’m so happy that people will have good jobs with us for as long as we’re around,” he said. “The selling point is not that people get better benefits, but that they get to keep them.”

Union leaders said the first step in the contract negotiations will be to survey the workers and find out what they want in a contract.

Norr, the Unite Here official, said job security is important, as well as establishing a process for firing workers with cause. Some workers have voiced concern after seeing coworkers fired, supposedly for taking too many sick days. Sarris said adjusting the number of workers is typical in the first few months of a business’s opening.

Organizers planned a separate drive later this year to unionize the 400 employees in the casino’s restaurants and food court. Those employees work for the restaurateurs, not the casino, and are not covered under the agreement that guarantees the right to unionize. Additional classes of employees, including managers, card dealers and security are not part of current union deal.

Overall, about 1,200 people work at the Rohnert Park gambling complex, managed by Las Vegas-based Station Casinos.

Labor officials said the successful organizing effort is the product of a positive relationship with the Graton tribe.

“This victory is the result of years of work by Sonoma County union members and community leaders, and of the leadership of the Graton Federated Tribes, who have been committed from day one to operating a casino where workers have the freedom to decide about union representation without interference,” Wei-Ling Huber, president of Oakland-based Unite Here Local 2850, noted.