Scott Ritchie, who on Tuesday told an inquest into the tragedy he did not know the Thunder River Rapid Ride’s south water pump had tripped twice hours before the incident, said ride operators had a clear procedure to follow when a pump failed.

The inquest is investigating the cause of the malfunction on the ride that killed Sydney mother Cindy Low and Canberra mother Kate Goodchild, her brother Luke Dorsett and his partner Roozi Araghi on Tuesday, October 25, 2016.

On Tuesday Mr Ritchie stated he did not believe the south water pump was the cause of the fatal tragedy, because procedures were in place for ride operators to respond to a pump failure.

Mr Ritchie continued giving evidence on Wednesday, questioned by barrister Steven Whybrow, who represented the father of Luke and Kate, and Kate’s partner.

Mr Ritchie insisted that ride operators correctly following procedures would prevent accidents.

He admitted he had not read the procedures for ride operators and only had a “vague idea” of what operators were trained to do.

He agreed operators under stress could forget their training.

In February 2016, the Thunder River Rapids Ride was left running and unattended, with rafts flowing through the ride and a maintenance trolley also being taken down the ride.

Mr Ritchie wrote an email to Dreamworld’s engineering staff telling them he had reminded all staff of correct procedure at the time.

Questioned over the two emergency stop buttons at the ride - a nine-second conveyor stop at the ride operator’s main panel and a two-second fast stop at the unload area - Mr Ritchie backtracked on initial evidence stating that he did not know what the nine-second button did.

In a video of a walkthrough with police inspectors he conducted shortly after the tragedy, Mr Ritchie was seen describing what the nine-second stop button did.

“In reflection, I knew what that did - I was under a lot of stress, sir,” Mr Ritchie told Mr Whybrow on Wednesday.

Mr Whybrow asked Mr Ritchie if he thought it appropriate for there to be no fast-stop button for the senior ride operator to press in event of an emergency.

“Because there were two operators I don’t think that was necessary,” Mr Ritchie said.

On the day of the tragedy, the two-second fast stop was not pressed when the raft carrying the four victims came over the top of the conveyor and collided with an empty raft close to the unload area, flipping over and killing all four.

Junior ride operator Courtney Williams gave evidence to the inquest in June that she did not press the button and was not aware of what it did.

Senior ride operator Peter Nemeth told the inquest in June he had pressed the nine-second button at his operator panel and was horrified to see the conveyor continue to move.

A 2013 audit of the ride recommended simplifying the Thunder River Rapids Ride’s emergency shutdown procedure to automate it with a single shutdown button.

Mr Ritchie told the inquest he stood by a diagnosis he made on the south water pump on the Saturday before the tragedy, and was confident the pump’s repeated breakdowns were not a risk to guest or staff safety.

He had arranged for an external servicing technician, Michael Takac, to visit Dreamworld and inspect on Thursday, but the fatal accident happened before Mr Takac had attended.

He also said that if Wayne Cox, the engineering supervisor on duty with him that Tuesday, had escalated the second pump breakdown to him, he "would have taken action" to shut down the ride for the day.

Dreamworld's own policies required a ride to be shut down until a supervisor had inspected and cleared it if the same fault happened twice within 24 hours, meaning the Thunder River Rapids Ride should not have been operating when the tragedy occurred.

An email from Mr Ritchie to external contractors PFI showed that safety upgrades to the ride were delayed by three months to February 2016, because Mr Ritchie could not secure $2400 in overtime payments.

The overtime was needed to ensure the safety upgrades did not cut into the theme park's opening hours and risk the extremely popular Thunder River Rapids Ride being closed to guests.

Concluding his evidence on Wednesday morning, Mr Ritchie stood and asked for permission to address the families of the four victims.

After an often combative two-day session of giving evidence in which he spoke clearly and decisively, Mr Ritchie's voice wavered for the first time.

"I deeply apologise for not being able to make eye contact with you during this time," he told the families.

"I wanted to give my evidence without emotion.

"Please accept my sympathies for everything you are going through."

The inquest continues.