 finds that more than 250 workers have died in trench cave-ins over the last decade. Those deaths were preventable, experts say. And the federal regulatory and enforcement agency in charge of workplace safety, OSHA, has done little to hold companies accountable. NPR's Robert Benincasa reports. Ken Bruno hasn't been back here on this street in Boston's South End since 2016, but he remembers what took place that October day as though it were yesterday.