The Graton Resort & Casino, which is set to open outside Rohnert Park on Nov. 5, could mean an increase of 40,800 vehicle trips a day on Highway 101, a report prepared for the county says, but some officials said the figure could be much lower.

"If that is the case, it would be a backup from Rohnert Park Expressway to Petaluma," CHP Officer Jon Sloat said, referring to the upper-end projections.

The Board of Supervisors is to review today the report by consultant Robert Marcucci, a former San Rafael Fire Chief, part of a presentation that focuses on preparations for the casino's opening weeks.

In 2012, according to Caltrans data, the combined number of north- and southbound vehicle trips on Highway 101 south of Wilfred Avenue — which will be the primary freeway exit for the casino— averaged 97,000 a day.

Officials who have been planning for the opening for two months say they are prepared for the worst eventualities. But they generally downplayed that possibility, while also acknowledging that bad traffic backups are a worry.

"It's a high number," Rohnert Park Public Safety Director Brian Masterson said of Marcucci's projections. Based on conversations with casino management, numbers more along the lines of 8,000 to 10,000 visitors a day are expected, Masterson said.

Also, traffic to the casino will be spread over the 24 hours a day it is open, ameliorating its impact.

"It trickles in, versus one huge rush," Masterson said. "That is an advantage."

The casino's environmental report anticipated 14,274 additional vehicle trips a day because of the project. Casino opponents have consistently said the number would be 40,000.

"We have plans going from if we don't see much of any impact to what do we do if there's complete gridlock," Darrin Jenkins, Rohnert Park's assistant city manager, said of the city's preparations for the casino's opening weeks.

The city is now widening Golf Course Drive West (formerly Wilfred Avenue) to provide access to the casino. The Federated Indians of Graton Rancheria, the casino's owner, paid for the road project.

The tribe also made a one-time $1.5 million payment to the county to pay for additional services and measures to address the influx of casino patrons and an expected jump in emergency calls, which the report estimates could hit 30 a day in the first weeks.

From the point of view of emergency services — fire, police and ambulance calls — Masterson said, "Our biggest concern is traffic volume and traffic congestion. Can we provide an acceptable level of service to get to where we need to be in an acceptable amount of time?"

Among the services being paid for by funds from the tribe are two fire engines, one stationed at the casino, and the other rotating between Rohnert Park, Rincon Valley and Rancho Adobe fire stations. An ambulance also will be stationed at the casino, and Rohnert Park is contracting with the CHP for extra motorcycle officers for traffic control on city streets.

County Director of Fire and Emergency Services Roberta MacIntyre noted that local agencies routinely collaborate on managing large public events such as the recent Gran Fondo or Nascar races at Infineon Raceway, which generally attract about 100,000 over two days.

"For us to gear up for these large-scale events is not alien to us. We may have some bumps in the road, but overall I'm confident that we're going to be just fine," MacIntyre said.

"I'm not terribly worried about people getting hurt or injured and not being able to get medical treatement; I think we've got that covered," she said. "But day-to-day traffic, I imagine that's going to be a frustration for people for several weeks."

Marcucci, the consultant who prepared the report, said his numbers are based on an independent 2005 analysis of the Lytton Pomo tribe's San Pablo Casino, which assumed that each of the facility's slot machines generates 13.6 vehicle trips each weekday.

"I use those numbers from San Pablo because I think they will correspond, but I don't think anyone really knows what the traffic generation's going to be in Rohnert Park," Marcucci said.

The $800 million Graton Resort & Casino has 3,000 slot machines and 144 table games, as well as four full-service restaurants and a nine-restaurant food marketplace.

It is the largest casino in the Bay Area and the closest to its main population centers. Those factors, together with its location on Highway 101, suggest the vehicle trips number could be more than he projected, Marcucci said.

"I think it will be equal to (San Pablo) if not more," he said.

Longterm planning for how increased traffic and more demand for services form the casino will affect emergency response service will take some time, said Central Fire Authority Chief Doug Williams.

The authority includes the Rincon Valley fire department, which will serve the casino, along with the Rohnert Park and Rancho Adobe departments.

"When we have some real data to work with, we'll see how that affects our ability to serve the facility and the community," Williams said.

You can reach Staff Writer Jeremy Hay at 521-5212 or jeremy.hay@pressdemocrat.com.