Alameda County’s top bureaucrat must be a hard worker because, it seems, she never takes a vacation. In return, when she retires, she’s going to be pulling down a pension that tops half a million dollars a year.

It’s not that County Administrator Susan Muranishi isn’t entitled to a day off now and then — she gets five weeks of vacation a year. But the 39-year veteran of county service has been piling it up, big time — at last check, she had nine months of unused vacation on the books.

So she sells some of it back to the county — boosting both her salary and her pension. In 2014, Muranishi received $29,914 as compensation for unused time off, and last year she unloaded $30,512 worth of vacation days she hadn’t taken.

That money helped bring Muranishi’s pay in 2015 to $501,500 — the most of any county administrator in the Bay Area.

When the 66-year-old Muranishi retires, she’ll be entitled to an annual pension equaling her highest pay level. That means if she walks away tomorrow, she will get $501,500 a year — for life.

“It’s a racket,” said former state Assemblyman Joe Nation, a Democrat from the North Bay who now teaches public policy at Stanford University.

Nation, a vocal advocate for pension reform, said “the idea that anyone would get a half-million-dollar-a-year pension for life is obscene for anyone, but doubly obscene for someone trusted to watch over the taxpayers’ money.”

Whatever you want to call it, the sell-backs are completely legal and above board under the county pension plan.

Muranishi’s pension will be based on her $339,838 basic salary, plus a host of bonuses and enhancements that the Board of Supervisors has approved over the years. They include a “longevity” bonus for having stayed with the county for more than 30 years, a $24,000-a-year performance bonus, and an “equity pay” bonus that guarantees that Muranishi makes at least 10 percent more than any other county employee.

Even Muranishi’s $8,611-a-year car allowance goes into her yearly pension total. As does her vacation sell-back.

“They know the system, and they make the most of it,” Nation said of the pension push.

Muranishi did not respond to calls or emails for comment. But from the looks of things, she rarely — if ever — takes a day off.

“We get emails from her at 3 in the morning,” said an admiring Scott Haggerty, president of the Board of Supervisors. “She is a very hard worker. In fact, she has been acknowledged by her peers to be one of the best county administrators in the state.”

Haggerty said there’s not much the county can do about Muranishi’s pension deal — the courts have ruled that the sell-backs and other pay pension enhancements are untouchable for longtime workers, though the rules have been changed for newer employers.

But then, there’s not much Haggerty wants to do about Muranishi’s deal.

“Quite frankly, Susan Muranishi is an asset to this county and is operating in a legal and consistent manner,” he said.

“Just like any other county employee, she has the legal right to sell back her vacation,” Haggerty said. “Furthermore, we are lucky that she has stayed here in this county for so long when she could have made more money elsewhere in the private sector.”

The administrator oversees the county’s budget and finances, plus programs such as economic development, diversity and risk management. Her office also acts as clerk for the Board of Supervisors and is in charge of implementing its decisions.

“Our county has one of the highest reserves in the state of California, and during the last recession this county was able to weather the storm with not one single layoff,” Haggerty said. “That is the story you should be printing.”

Haggerty was the only supervisor who took the time to talk to us about Muranishi’s pay and pension. Supervisor Nate Miley told us via text that he was “extremely busy these days with my normal workload and also preparing for re-election.” Supervisors Keith Carson, Wilma Chan and Richard Valle did not respond to requests for comment.

Nation said it’s common for administrators to earn enviable amounts of money. In most cases, top-ranking bureaucrats — whether working for a city, county or transit agency such as BART — benefit from the very pay and pension packages that they negotiate with the unions that represent their workers.

When a low-paid janitor gets a pay hike, so does the manager at the top of the food chain. Of course, when your pay is $300,000-plus, a raise of 1 or 2 percent works out to a lot more green than it does for the janitor.

“So they don’t push that hard” when negotiating workers’ contracts, Nation said. “Until the self-interest is taken out of the equation, we are going to continue to have stories like this.”

San Francisco Chronicle columnists Phillip Matier and Andrew Ross appear Sundays, Mondays and Wednesdays. Matier can be seen on the KPIX TV morning and evening news. He can also be heard on KCBS radio Monday through Friday at 7:50 a.m. and 5:50 p.m. Got a tip? Call (415) 777-8815, or email matierandross@sfchronicle.com. Twitter: @matierandross