Parking, traffic to be manageable at arena, report says

Rendering released on Dec. 10, 2014 showing the southeast entrance of the Golden State Warriors' proposed new arena in San Francisco's Mission Bay area. The arena would seat 18,000 people, have a view deck, and include a 24,000 square foot public plaza on the southeast side and a 35,000 square foot public plaza on the Third Street side. Completion is slated for the start of the 2018-19 NBA season. ProEXR File Description =Attributes= cameraAperture (float): 36.000000 cameraFarClip (float): 1000.000000 cameraFarRange (float): 1000.000000 cameraFov (float): 69.363388 cameraNearClip (float): 0.000000 cameraNearRange (float): 0.000000 cameraProjection (int): 0 cameraTargetDistance (float): 200.000000 cameraTransform (m44f) channels (chlist) compression (compression): Zip16 dataWindow (box2i): [0, 0, 4999, 3237] displayWindow (box2i): [0, 0, 4999, 3237] gamma (float): 1.000000 lineOrder (lineOrder): Increasing Y pixelAspectRatio (float): 1.000000 screenWindowCenter (v2f): [0.000000, 0.000000] screenWindowWidth (float): 1.000000 tiles (tiledesc): [64, 64] =Channels= A (half) B (half) G (half) R (half) less Rendering released on Dec. 10, 2014 showing the southeast entrance of the Golden State Warriors' proposed new arena in San Francisco's Mission Bay area. The arena would seat 18,000 people, have a view deck, and ... more Photo: Images Rendered By Steelblue., Courtesy Of MANICA Architecture. Photo: Images Rendered By Steelblue., Courtesy Of MANICA Architecture. Image 1 of / 24 Caption Close Parking, traffic to be manageable at arena, report says 1 / 24 Back to Gallery

The Golden State Warriors’ battle to build a $1 billion arena in San Francisco’s Mission Bay is shaping up to be as fierce as the team’s showdown against LeBron James and his Cleveland Cavaliers.

On Friday, the day after the Warriors won their first NBA Finals game in four decades, city officials released an 800-page environmental impact report on the proposed 18,000-seat arena, a document that over the next few months will be as obsessively dissected as the championship series itself. But there’s already a plan to deal with one issue: traffic.

Backed by Mayor Ed Lee and San Francisco’s political establishment, the Warriors plan is facing unanticipated opposition by the Mission Bay Alliance, a newly formed group of wealthy UCSF donors and bioscience executives. They contend that the arena would snarl traffic around the new $1.6 billion UCSF Benioff Children’s Hospital San Francisco, creating dangerous delays for the patients and physicians trying to get to the medical center.

UCSF administrators are not affiliated with the alliance, instead offering tentative support of the arena as long as traffic and parking issues can be ironed out.

Assurances from city

On Friday, officials from the Mayor’s Office of Economic and Workforce Development touted the report at a news conference, calling it a comprehensive study of the project and every conceivable implication it could have. Ken Rich, the agency’s development director, said the report “deliberately looks at the worst case of any impacts” the project might have.

“Will there be traffic? There will. Will we be able to handle it? We will,” Rich said.

Opponents said they would review the environmental impact report “with a fine-tooth comb” and left open the possibility of both legal challenges and a possible ballot initiative. The alliance will spend millions to defeat the arena and has retained four law firms to fight it, according to Sam Singer, its spokesman.

“Essentially what the city and Warriors are trying to do is jam an elephant into a VW. It’s neither comfortable for the elephant nor advantageous for the VW,” Singer said. “There is no way to place an 18,000-seat arena that is going to have an event every other day dead across the street from a major hospital and not have it significantly impact the ability of patients to reach that hospital as well as physicians and nurses to get to work.”

Most of the debate over traffic impact centers on the “shoulder period” from 6:30 to 7:30 p.m. on weekdays, a time when downtown rush hour traffic is still heavy, when Mission Bay residents are trying to get home, and when fans would be trying to get to the arena to catch a game or concert.

That potential traffic jam nightmare scenario would be attacked through a combination of beefed-up public transit and a “traffic separation” plan aimed at funneling arena-bound cars onto certain streets while hospital and neighborhood vehicles are routed onto others, according to Adam Van de Water, the city’s point person on the arena project.

“We can confidently state there will be no significant impact to emergency vehicles or to standard elements studied in the EIR,” Van de Water said.

‘Hospital only’ lane

The details are still being worked out, but it’s likely that cars going to the arena would be directed onto 16th Street, Third Street and Illinois Street, while hospital and other traffic would be funneled to Owens Street, Minnesota Street, Fourth Street and Seventh Street.

The vehicle segregation would be coordinated by signs and 21 traffic control officers deployed to make sure the drivers don’t deviate from the prescribed routes. There would also be a designated “hospital only” lane coming off of the Mariposa exit from Interstate 280.

The number of traffic control officers is roughly the same as are deployed for Giants home games, despite the fact that the Warriors arena would hold less than half the number of fans as AT&T Park.

“We are throwing a lot of personnel at it,” Rich said.

On the transit side, the city is looking to invest $40 million on public transit improvements, including four new T-Third streetcars, an expanded platform and installation of a crossover track to allow trains to pass each other on the Third Street right of way. The improvements would cost the city about $6.6 million a year to operate.

“That is a legacy improvement that goes beyond the Warriors project,” and Peter Albert, manager of urban planning at the San Francisco Municipal Transportation Agency. “Those improvements are going to help the whole city.”

New parking plans

Beyond the traffic issue, project opponents say the 11 acres the Warriors are planning to build on should be set aside for biotech or medical research. Singer accused the Warriors of “trying to create another Fisherman’s Wharf in Mission Bay” and “trading future biosciences for a sports arena.”

Also Friday, the city revealed new parking plans for the arena, which would have 1,082 spaces. The city is in talks with the port to create two additional lots, one on a port-owned property at 19th and Illinois streets and a second on a triangular dirt lot just north of Pier 80. Taken together, the two lots could accommodate an additional 1,200 cars.

Mission Bay already has 9,100 parking spots within a half mile of the proposed arena. The existing parking is 36 percent occupied on weeknights and fills up to 77 percent occupancy during Giants games, according to the city.

By comparison, Oracle Arena in Oakland, where the Warriors now play, has 10,000 parking spots, 4,000 of which are used for Warriors games

Those wishing to comment on the environmental impact report, which covers everything from impacts on noise to dust to shadows, have 45 days to do so. Such reports are rarely overturned in San Francisco. “We have a pretty good record,” Rich said.

UCSF’s Mission Bay hospital opened in February. In the first year, the hospital expects to deliver 2,600 infants and perform more than 9,500 surgeries. UCSF Chancellor Sam Hawgood said he is supportive of the proposed arena, “as long as the traffic can be managed to ensure the safety of patients, visitors, and health care workers in the Mission Bay hospitals.”

“Patient safety is UCSF’s top priority,” he said.

J.K. Dineen is a San Francisco Chronicle staff writer. E-mail: jdineen@sfchronicle.com Twitter: @sfjkdineen