(Updates with comments from TransCanada, details about allegations and background)
By Mike De Souza
CALGARY, Oct 30 (Reuters) - Canada's energy regulator in a report released on Friday found that six of 16 pipeline safety allegations against TransCanada Corp were "partially substantiated."
The National Energy Board (NEB) said it found no reason to issue any enforcement action in response to the complaints that were raised by a whistleblower.
The regulator also said it concluded that none of the allegations posed an immediate threat to the safety of workers, the public or the environment.
TransCanada, the country's second largest pipeline operator, said in a statement on Friday that it cooperated fully with the investigation and that only four allegations involved an infraction of internal company procedures.
The NEB rejected the most serious allegations of dangerous welds and the alleged failure to report some incidents to the regulator. It said these allegations were not substantiated based on its review of the evidence.
The regulator partially confirmed allegations related to some minor pipeline damage, inadequate welding work and inspections, as well as allegations of poor worker safety practices.
In one case, the company said a welding inspector made an "honest mistake" by mixing up machines needed to complete a test.
"It is important to note that none of these allegations posed either an immediate or long term threat to the public, our employees or our assets," said TransCanada spokesman Davis Sheremata.
The report comes at a time when the Canadian pipeline operator awaits the final U.S. administration verdict on its long-debated Keystone XL oil pipeline.
The whistleblower was the second company employee to raise safety allegations about TransCanada to the NEB since 2011.
In 2014, the board released an audit that included a review of complaints raised by a previous whistleblower, Evan Vokes, about safety oversight that were valid. But at that time, the NEB said it was satisfied with the company's response and found no immediate threat to public safety.
TransCanada's network of more than 68,000 km of natural gas pipelines tap into virtually all major gas supply basins in North America. It has had some significant ruptures on these lines in recent years, including an October 2013 rupture in Northern Alberta and another in southern Manitoba in January 2014. In the Manitoba incident, Canada's transportation safety board concluded the rupture started in a decades-old crack that the company had failed to detect. One of the company's brand new lines in Wyoming also ruptured in 2011. (Reporting by Mike De Souza; editing by G Crosse and Andrew Hay)