Winch Pins, Kills Bridge Worker : Safety: The fatal accident at the scene of a trolley bridge under construction raises questions.

A 52-year-old construction worker was killed Friday afternoon when he was pinned by a winch used in the construction of a new San Diego Trolley bridge crossing West Main Street in El Cajon.

The man was identified by the San Diego County Medical Examiner’s office as Leonard Joseph Wallace of El Cajon.

The cause of the accident is being investigated by the state’s Occupational Safety and Health Administration. National Projects Inc., the company building the bridge, said it has sent its own safety manager to the scene as well.

El Cajon Police Lt. Bill McClurg said the winch was being put into position by a large crane when it inexplicably struck and pinned Wallace. He was declared dead at the scene by a Lifeflight medical team about a half-hour after the 1:37 p.m. incident.

One witness said the crane seemed to tip forward because of the weight of the winch--estimated by one worker at 7,000 pounds--and that the construction worker was struck as the winch unexpectedly fell on him.

The crane’s cable fell slack for a moment before it again tightened, the witness said.

It was at least clear that the winch did not altogether fall from the crane because the cable was still intact afterward, McClurg said.

“Among the questions we’re looking into is whether the victim was in the wrong place, or whether the crane was being properly operated,” McClurg said.

The winch was one of six being used to help lower to the ground the support timbers and steel I-beams used in the construction of the bridge, situated alongside the eastbound off-ramp of Interstate 8 at West Main Street. When completed, the bridge will allow the San Diego Trolley to cross over West Main Street rather than cross it at street level as it now does.

No one else was injured in the incident, and afterward co-workers were interviewed by Cal-OSHA and police investigators.

The bridge is being constructed by National Projects, a subsidiary of the Boise, Ida.-based Morrison Knudsen Corp. Company spokeswoman Dede Ryan said the company’s safety manager left for San Diego Friday afternoon to help with the investigation.

Times correspondent Richard Core contributed to this article.