Enbridge's plan to remediate 117 pump stations to comply with National Energy Board regulations was made public this week and it shows it will take the country's largest pipeline company at least three years to bring its systems up to code.

The company said the three-year timeline was needed to carefully consider "the impacts of installing this equipment on the system, while at the same time ensuring that the proper designs, protocols and procedures are developed."

CBC News reported in May that Enbridge was ordered by the NEB to install auxiliary power units in 117 of its 125 Canadian pump stations. These facilities are responsible for keeping oil and gas moving through the company's vast pipeline network.

Along with the missing backup power systems, the NEB found that Enbridge didn't have emergency shutdown buttons at 83 of it pump stations. The company remedied that problem by the end of April. The systems will return a pump station to a fail-safe position — essentially, shutting it down — at the push of a button.

While Enbridge was quick to recognize and fix the emergency shutdown issue, the company made sure to distinguish that from installing 117 auxiliary power units.

"There is a significant difference between replacing a switch and upgrading, enhancing or replacing an entire power source," Enbridge spokesman Graham White wrote in an email to CBC News.

Enbridge questioned why backup power was needed given that the situations where it would be used are so rare.

"It is only in the event of a power outage and an emergency situation occurring simultaneously that the alternate power source would be called upon to isolate the station. In that regard, Enbridge still has questions with respect to the need, from a practical perspective, for installing power generation of this nature.

"Nevertheless, Enbridge's [corrective action plan] addresses the requirement to install alternate sources of power," wrote Enbridge vice-president David Bryson in the cover letter to the plan.

Carole Léger-Kubeczek, a spokeswoman for the NEB, said the board is satisfied with Enbridge's schedule and mitigation measures.

"The board realizes that designing, troubleshooting and implementing the backup power requirements at over 100 stations takes time to be done properly," Léger-Kubeczek wrote in an email to CBC News.

She added that Enbridge is required to report to the board at prescribed intervals and that the NEB will verify compliance through inspections and meetings if necessary as the plan is implemented.

Enbridge has noted that it does have backup power systems at the stations, but they use what is known as an uninterrupted power supply, which can keep the lights on but are not powerful enough to shut the valves that would stop the oil flowing in the event of a spill or other accident.

An auxiliary power unit — such as a diesel generator — would be strong enough to return a pump station to a fail-safe condition. In the event of an external power failure, it would allow Enbridge to shut down a facility remotely from its operations centre in Edmonton. In the event that the operations centre couldn't remotely shut down a pump station, a person should still be able to go out to a station, hit the emergency shutdown button and the auxiliary power unit would provide the power to turn off the facility.

The backup power rule has been on the NEB's books since 1999. The emergency shutdown button has been a must since at least 1994.

In May, the NEB said Enbridge's confusion may have stemmed from the fact that the energy regulator has only just switched the focus of its inspections to make these particular safety regulations a higher priority.

Enbridge presented the corrective action plan to the regulator April 15 and the NEB approved it May 2. A redacted version was posted on the NEB website on Wednesday.

An NEB spokeswoman said before posting the plan the board had to ensure there was no information in it "that had the potential to compromise the safety and security of facilities and operations."