Construction is under way on a new, earthquake-safe San Francisco General Hospital.

City officials gathered Thursday to break ground on the $887 million project to replace the city’s only trauma center. The nine-story hospital will have 284 acute-care beds and be built among San Francisco General’s historic buildings on Potrero Avenue.

Construction begins less than a year after voters overwhelmingly approved the bond measure to fund the project.

It’s expected to open by 2015, the year the state has set for hospitals to meet seismic upgrade requirements.

Members of the Service Employees International Union who work at the hospital were also on hand for Thursday’s groundbreaking, protesting recent layoffs and pay cuts.