The future shape of gambling in Sonoma County gained greater detail Monday as Station Casinos released the first official drawings of the enormous Indian casino under construction outside Rohnert Park.

Five months after its tribal backers won final federal approval to move ahead, the largest casino resort in the Bay Area is starting to take shape on the northwest edge of Rohnert Park.

Nine years after the Federated Indians of Graton Rancheria announced plans to open a casino in Sonoma County, inciting opposition and controversy, the tribe has cleared its last governmental hurdle. In a quiet milestone, the federal government Friday let an agreement between the state and the tribe, known as a compact, take effect by acting neither to reject or approve it. The compact allows the tribe to operate a Las Vegas-style casino with slot machines and banking card games.

Relations between Sonoma County officials and the Indian tribe that has started work on a 3,000-slot machine casino next to Rohnert Park appear to have soured as the two sides approach negotiations about how the tribe will alleviate the project’s impacts. The chairman of the Federated Indians of Graton Rancheria on Wednesday said county supervisors are ‘putting out inaccurate and misleading information about our project.’

Work began Monday at the site of the planned Indian casino on Rohnert Park’s northwest outskirts.

County officials hold most of the cards when negotiating conditions for new developments. But they now have a weak hand in confronting a project they roundly oppose, the Federated Indians of Graton Rancheria’s plan to open a casino outside Rohnert Park.

The plan to build one of California’s largest casinos just outside Rohnert Park moved to the verge of fruition Thursday when the state Assembly approved a gambling agreement to allow work to start on the project. The Assembly ratified the agreement between the governor and the Federated Indians of Graton Rancheria, called a compact, on a 64-3 vote with no discussion. That sends it on the federal government for final approval, which most experts believe is virtually assured.

The state Senate is set to vote Monday on the governor’s agreement with the Federated Indians of Graton Rancheria that the tribe needs to start work on a $700 million casino next to Rohnert Park. It would be the latest in a series of developments in the past month that have moved the tribe’s controversial casino plans — in the works for nine years — to the verge of fruition. Political and Indian gambling experts suggested on Friday that the road is virtually clear for the tribe.

The Sonoma County Indian tribe that wants to open a casino adjacent to Rohnert Park secured some significant — if not exactly enthusiastic — support Wednesday from a Southern California tribe that runs one of the state’s largest casinos. Speaking at an Assembly committee hearing, a lobbyist for the Pechanga Band of Luiseno Indians in Riverside County said the tribe did not oppose an agreement that would allow the Federated Indians of Graton Rancheria to open a 3,000-slot machine casino just west of Highway 101 behind the Scandia Family Fun Center.

The head of the Indian tribe that plans to build a Las Vegas-style casino outside Rohnert Park said Tuesday its agreement with the state allowing the project to start will be good in a ‘new and novel way’ for all involved, including the larger North Bay community. ‘We created something that will indeed benefit Indian and non-Indian alike,’ said Greg Sarris, chairman of the Federated Indians of Graton Rancheria, during a three-hour state Senate committee meeting.