The latest incident at an LRT construction site in Ottawa is raising fresh concerns about workplace safety as crews bear down to finish the $2.1-billion project on time.

On Wednesday a crane operator jumped from the machine's cab as it crashed to the ground at the eastern portal of the train tunnel near the University of Ottawa.

A cement mixer dropped on the tunnel floor when a crane collapsed at the LRT tunnel's eastern portal sits near a staircase used by workers. No one was injured in the April 26, 2017 incident. (Ashley Burke/CBC) No one was injured, but workers told CBC News they were shaken, calling the incident another "near-miss."

A cement mixer being hoisted by the crane fell down a shaft to the tunnel floor, and the crane's boom landed near scaffolding that workers used to access the tunnel.

The president of the Ottawa and District Labour Council, Sean McKenny, worried someone could have been killed.

"I think we're lucky this time," said McKenny. "We may not be so lucky next time."

There have been a number similar incidents since work on the project began. Some have made headlines, others have not. Here's a summary of incidents uncovered by CBC.

Truck piston smashes through cab

On March 12, 2017, a dump truck was unloading inside the LRT tunnel when the hydraulic lift mechanism failed, sending a piston "through the operator cabin, causing the hydraulic fluid to spill," according to the Ministry of Labour's report on the incident.

It sounded like a gun went off. As soon as it broke, it blew fluid everywhere. - Witness to March 12 incident

A worker who witnessed the incident told CBC the piston drove itself into the middle of the cab, centimetres from where the driver was sitting.

"It sounded like a gun went off," the worker said. "As soon as it broke, it blew fluid everywhere."

CBC has agreed to protect the identities of that worker and others because they signed a confidentiality agreement and fear they could lose their jobs.

Bridge collapse

On Feb. 19, 2016, a portion of a bridge collapsed on top of heavy equipment at the Bayview LRT construction site. Crews were demolishing the overpass when "it collapsed onto an excavator," according to the Ministry of Labour.

A worker who was there at the time said it was lucky the operator wasn't crushed.

"It almost killed him. If he had've swung right he would have been dead, no doubt about it," the worker said.

The Ministry of Labour said no one was injured, but equipment was damaged.

The Bayview bridge partially collapsed on a contractor's machinery during the bridge's demolition on March 7, 2016. (Submitted )

Sinkholes

Moments before a portion of Rideau Street fell into a large sinkhole on June 8, 2016, an OC Transpo bus full of passengers passed over the area. The collapse also swallowed an unoccupied van and three lanes of roadway.

A report released earlier in April found ongoing work on the LRT tunnel below, combined with the volatile nature of the ground in the area, was the likely cause of the collapse.

A large sinkhole swallowed three lanes of Rideau Street on June 8, 2016. (CBC)

The site on Waller Street where the crane collapsed Wednesday is the same spot that saw an earlier sinkhole on Feb. 21, 2014. That chasm was eight metres wide and 12 metres deep, and sparked some of the earliest concerns about safety on the project.

"I think we are very fortunate there were no injuries associated with the incident," said then deputy city manager Nancy Schepers at the time.

An earlier sinkhole opened up at the intersection of Laurier Avenue E. and Waller Street near the University of Ottawa on Feb. 21, 2014. ((Blair Gable/Reuters))

Concrete mishap

On Nov. 10, 2016, rescue crews raced to the same location to help three workers involved in an incident inside the tunnel.

Officials said at least one of the workers was in a basket spraying concrete on the tunnel wall when the material failed to stick and fell.

The metal mesh on the tunnel wall buckled and got tangled in the basket. One worker suffered a hand injury, paramedics said.

Emergency crews rescued three workers who became trapped inside the tunnel in November 2016. (Professional Paramedic Association of Ottawa)

Electrical issues

July 14, 2016. A union representing electrical workers claims this photo is evidence of a botched wiring job on the LRT project in Ottawa. (IBEW) A man working at the Albert Street LRT construction site suffered an electric shock when his ankle came into contact with a live wire on

The Ministry of Labour investigated another "electrical equipment failure/explosion" on Nov. 7, 2016.

"A short circuit occurred within a traction power substation. A flash was created and exited the venting at the bottom of the panel," according to the Ministry's description.

Fire inside tunnel

A fire broke out inside the downtown tunnel on June 4, 2016 at Parliament Station at O'Connor and Queen streets. The Ministry of Labour told CBC it was notified about the fire two days later.

Nobody was hurt in the incident but some workers and former workers have contacted CBC to say they're concerned about health and safety on the project.

"There was a fire and there were no hoses to put it out," said one former worker, who asked not to be named.

Information provided by workers has been verified by CBC.

Officials preach safety

Following Wednesday's crane mishap, transit boss John Manconi told reporters he's leaving nothing to chance.

"I don't want to mix luck with safety because safety is a culture, safety is a system," said Manconi. "There are laws protecting those employees working on this site, and any site in Ottawa."

Ottawa's general manager of transportation John Manconi defended the LRT project's workplace safety record. (CBC News)

The technical director of the Rideau Transit Group (RTG), the consortium building the light rail system, also insisted safety is a priority.

"As far as industry standard is concerned we are bettering industry standard," said RTG technical director Peter Lauch. "It's a construction site, it's a tough place to work at times. But still, having said that, we stand by our safety record."

The Ministry of Labour said it issued 150 work orders to RTG between the end of September 2016 and mid-March 2017, which it said is an average number for a project that size.

The vast majority of the orders issued concerned the tunnel rather than above-ground work.

RTG said 11 people have had to take time off work due to injuries sustained on the job, a record the consortium said rates better than the industry standard.

No workers have been killed on the project, which is due for completion in 2018.