More than half of the district’s roughly 150 full-time workers — among them battalion chiefs, captains and firefighter paramedics — earned more than $300,000 in total compensation in 2015, according to data collected by Transparent California, a nonprofit watchdog.

The county’s median household income is roughly $80,000.

One reason for the high compensation: It can be cheaper for jurisdictions to pay big overtime — at 1.5 times or double regular pay — than it would be to add staff because of the pension liabilities attached to each new hire.

For San Ramon firefighters, every dollar of salary means roughly one more dollar in pension contributions, said Paige Meyer, the fire chief. “When I’m paying over $2 for a full-time employee and I can pay a dollar and a half for overtime,” he said, “I’ve got a substantial savings.”

As a result, a firefighter paramedic with a salary of $87,700 who puts in long overtime hours can end the year with total compensation well above a quarter-million dollars.

Pensions guaranteed to California police and fire personnel allow them to retire in their 50s and draw 70 percent or more of their peak pay as long as they live. Most private sector employees have no pensions.