A year after the accident that claimed four lives, the amusement park's owners, Ardent Leisure, are refusing to admit liability for the suffering of families of two of the victims, Canberra mother Kate Goodchild, 32, and her brother Luke Dorsett, 35.

Queensland authorities are considering whether to impose penalties over the deaths, having recently finished investigating the Gold Coast theme park.

Ms Goodchild, Mr Dorsett, his partner Roozi Araghi, 38 and Sydney mother Cindy Low, 42, were killed on October 25 last year when the iconic Thunder River Rapids ride malfunctioned.

Miraculously, Ms Goodchild's 12-year-old daughter Ebony survived when she was thrown clear.

Ms Goodchild's partner, David Turner – who had been watching the ride from nearby with the couple's eight-month-old daughter, Evie – leapt into the water to reach his family.

Kim Dorsett, mother of Ms Goodchild and Mr Dorsett, has detailed the anguish still felt by the family, saying getting out of bed is a major achievement one year on from the tragedy.

Lawyers for a number of family members, Canberra law-firm, Aulich Civil Law, last year gave Ardent Leisure Limited notice of their intention to make claims for damages for personal injury, wrongful death, and loss of dependency arising from the accident.

Ardent has also received a notice of claim with respect to the estates of Ms Goodchild and Mr Dorsett.

More than 10 months later, Ardent Leisure continues to deny liability for the majority of the claims.

However, lawyers for Ardent Leisure, Moray & Agnew, have admitted liability for Mr Turner's personal injury claim.

It also admitted the fatal accident had been caused because of the theme parks failure to switch off the ride before the rafts collided.

Dreamworld's denial could mean the still grieving family would be forced fight the matter in court to prove liability and obtain compensation.

Ardent Leisure declined to discuss the legal proceedings.

"As you appreciate, this is a week of great sensitivity, and out of respect for the victims and families, it is not appropriate to engage in the discussions regarding the issues," a statement said

However, Ardent Leisure said Dreamworld planned to "respectfully and thoughtfully acknowledge the one-year anniversary of last year's tragedy".

Ardent Leisure said it would hold a private staff service – presided over by a local pastor – and an Aboriginal Smoking Ceremony to mark the anniversary.

Ardent Leisure chairman, Gary Weiss, members of the board, and Dreamworld management and staff are expected to attend the service.

"First and foremost our hearts and thoughts remain with the families and all those affected by the tragedy during this very difficult period," the statement said

"Out of respect for the privacy of the families and their own private arrangements during this period, this will be a private service for staff. We ask that this is respected."

The Queensland safety watchdog and police have both completed investigations into the fatal accident.

A Workplace Health and Safety Queensland spokesperson said Queensland Industrial Relations Minister Grace Grace had been briefed on the findings of the investigation.

Ms Grace said it was now a matter for Workplace Health and Safety Queensland to determine the legal consequences, which could include penalties of six years jail and fines of almost $4 million.

The safety watchdog said it would not publicly release the findings while it considered "what the legal consequences of the investigation are, including whether any charges should be laid.

That process is expected to take several months.

"Given the possibility of pending legal action, the investigation report cannot be released nor further discussed at this time," a QHSQ spokesperson said.

Queensland Police confirmed it had also completed its investigation and forwarded the report to the coroner.

Police reportedly recommended no criminal charges be laid over the tragedy; however the coroner has the final say over whether any staff will be charged.

Earlier this month, the Queensland government passed tough new industrial manslaughter laws, increasing maximum penalties of 20 years imprisonment for an individual or maximum fine of $10 million for a corporate offender.

The laws are not retrospective so will not apply to the Dreamworld disaster.

The inquest is expected to be held next year.