How many firefighters does Houston need, and how many can it afford?

Those are the questions that ought to be top of mind as on-again, off-again negotiations between Mayor Sylvester Turner and the Houston Firefighter Association continue over how quickly to implement firefighter pay raises averaging 29 percent that were approved by voters in November.

The mayor keeps warning, as he did before the Prop. B vote, that Houston has hundreds more firefighters than it can afford. As a result, he had urged firefighters to accept a phased-in plan for Prop. B salaries over five years if they wanted to avoid 400 pink slips.

Union officials, unsurprisingly, are screaming bloody murder. They say the pay raises — which they urged as a way to create pay parity between firefighters and police — are overdue since voters spoke in November. And they say they’ve already offered their own compromise, which in return for no layoffs would allow the city to phase in pay raises between now and the end of fiscal year 2021, or nearly three years from now.

With no deal, Turner finally announced Monday that the city will send out firefighters’ first Prop. B-adjusted paychecks in May — making layoffs likely. Firefighters will also receive lump sum back pay accumulating since January, a $31 million cost that the city must dip into reserves to pay.

Layoffs, which could affect as many as 400 firefighters and 100 municipal employees, would have to be approved by the City Council. But resistance may be futile. Council must pass a balanced budget and, in Houston, the mayor controls the agenda.

What a mess. The Chronicle editorial board didn’t endorse Prop. B, largely because a cash-strapped city with a structural deficit caused by a voter-imposed revenue cap can’t afford raises costing $100 million in the first year. But now that it has passed, we can’t understand why the mayor and firefighters can’t reach a compromise on how to implement the raises. Isn’t there some middle ground between a phase-in over five years versus three years?

Regardless, the hothouse rhetoric on the part of the firefighters’ union is self-defeating. Union president Patrick “Marty” Lancton and others have accused the mayor of putting citizens’ lives at risk in order to score political points.

Nonsense. Turner is acting responsibly on behalf of the entire city — at great political risk, we might add. He could have coasted to re-election if he’d just given his old friends the firefighters, an influential voting bloc, all they wanted. In negotiations over both pension reform and raises, Turner passed up the popular route for the fiscally responsible one.

No one disputes the Prop. B pay raises are large enough to put Houston’s budget under significant strain. Turner was always going to have to make difficult decisions about where to cut. This year, tough decisions include whether the city has more firefighters than it can afford.

Answering that requires knowing how many firefighters Houston needs to stay safe. The mayor’s office cites a 2017 study presented to City Council that found the city could get by with hundreds fewer firefighters, especially if HFD’s role in providing ambulances and emergency medical service could be lightened.

The findings, part of a 10-year city financial plan by consultants at PFM Group, found that among major U.S. cities, Houston has one of the lowest-staffed police departments, but its fire department ranks second only to New York in full-time employees per capita. The report recommended numerous efficiencies, considering: 64 percent of HFD responses were for emergency medical calls in 2015, structural fires accounted for only about 29 percent of fire incidents, and 1 in 8 calls for service was a false alarm.

Lancton says another city study recommended more, not fewer, firefighters.

Even if that’s the case, adding firefighters isn’t an option after Prop. B. Nor is adding all the police officers that most agree our city desperately needs.

The union knew the consequences of jacking up firefighter salaries — the consequences on public safety and on their colleagues’ jobs. They campaigned for it anyway.

We do agree with what Lancton told the editorial board last week: The union says, “The promises made by the voters to Houston firefighters have to mean something.”

The voters have spoken. Now what’s fair for all of Houston is for the mayor and City Council to consider closely just how many firefighters we need, then reconcile that with what we can afford.

In that light, and while that debate continues, Turner’s efforts to slow-walk the pay increases appears prudent, not political.