The cost of building a bigger Muni Metro platform to handle fans at the Mission Bay arena is growing faster than the Warriors’ injury list.

The plan is to tear out the 130-foot-long Metro platform, just down Third Street from the under-construction Chase Center, and build a 320-foot replacement right in front of the arena.

Cost: $33 million.

Building the new platform, however, is just part of the job. To handle more trains quickly, Muni has to realign the tracks that serve the stop, and that will require modifying nearby streets. All of which will add $18 million to the bill.

That’s $51 million, or about $160,000 per foot of platform.

But wait — that’s not all. Muni will spend an additional $11 million for new Metro cars, bringing the total cost of setting up light-rail service to the arena to $62 million.

“This is a massive undertaking, and my chief concern is how much money the arena will really generate for the city to pay this back,” said Art Torres, a member of the Municipal Transportation Agency board.

Torres’ concern is prompted in part by news that Muni already is coming up short on the project and will need borrow $10 million from the city to complete the job.

“And we still don’t know what might happen once they actually start the work” this month, Torres said.

The MTA sees the expanded service as essential to keep the already-congested Mission Bay neighborhood from turning into gridlock on nights when games, concerts or other events are happening at the arena.

The initial estimate for the new platform in 2015 was about $27 million. Costs started going up quickly, in part because of a yearlong delay brought on by a lawsuit filed by the Mission Bay Alliance, which opposed the 18,500-seat arena.

Another issue was a lack of interest by contractors to even bid on the project.

“In this market, many contractors do not need to find work in a firm fixed price bidding environment,” Muni staff wrote in a report to the MTA board.

In other words, with the Bay Area building boom, there was plenty of work available in the private sector “where profit margins may be higher and risks lower,” the staff report said.

Under their deal with the city, the Warriors are kicking in $19 million. The rest will come from transportation bonds and the Mission Bay Transportation Improvement Fund, which will be made up of money brought in by the arena and nearby businesses.

“But there is no money in the fund now,” Torres said. That means the MTA has to cover the construction costs up front.

However, Muni spokesman Paul Rose said there will be “more than enough dollars in the (fund) to make up our costs.”

“There will be no impact on other transit projects,” he said.

At least that’s the plan.

Central casting: The recent vote by the the Democratic County Central Committee to endorse former state Sen. Mark Leno and Supervisor Jane Kim, in that order, for San Francisco mayor came as no surprise — but it was not without drama.

For weeks, the progressive-dominated committee had been wrangling over which candidate should get the top endorsement and who should be No. 2. Leno’s first-place finish was “a real boost” for him and “a vote for change at City Hall,” said former Supervisor David Campos, the committee’s chair.

To the surprise of many, Supervisor London Breed took herself out of the running for the third-slot endorsement — even though some thought she had the votes.

“You think so, really?” Breed said with a laugh after the vote, adding that the Leno-Kim endorsement was all part of a precut deal.

Former Supervisor Angela Alioto came up way short on the endorsement vote as well, even though she’s a member of the central committee.

“I guess I’m too moderate for the group,” Alioto said. “They really got in my face for supporting giving the police Tasers.”

There was one bright spot for her. “Jane Kim called me after to say she was sorry for how things turned out,” Alioto said.

“I respect and appreciated that,” she said. “It was nice. Very nice.”

Tipping the hat: The Giants will stage a “living memorial” to the late Mayor Ed Lee at their home opener Tuesday.

The on-field tribute will include all the city’s living ex-mayors — Sen. Dianne Feinstein, Art Agnos, Frank Jordan, Willie Brown, Lt. Gov. Gavin Newsom and Supervisor London Breed — along with current Mayor Mark Farrell and Lee’s widow, Anita Lee.

Lee, who died of a heart attack Dec. 12, was known to occasionally wear an incredibly loud orange blazer in support of the Giants. He worked with the team for decades as head of the Department of Public Works and as city administrator, and was mayor during the 2012 and 2014 championship seasons.

“He was such a huge Giants fan and a fan of the Giants family,” said team Vice President Staci Slaughter.