A lack of detailed inspection procedures contributed to the March crude oil leak from a storage tank at the Enbridge Pipelines Inc. Edmonton Terminal in Sherwood Park, Alta., according to a Transportation Safety Board of Canada (TSB) report issued this week.
During a routine verification on 20 March 2017, Enbridge employees discovered traces of crude oil on the water surface in a creek that runs through the company’s Edmonton Terminal. The source of the leak was a three-inch ball valve from an on-site storage tank. An estimated 10 cubic metres of product was released into the tank’s secondary containment berm. Three cubic metres of the product were then released from the berm through its storm water drainage system into the creek.
Emergency response resources, which were available on site, were deployed within a few minutes to identify the origin of the leak and mitigate the impacts of the release. As a result, all released product was recovered from the containment berm and from the creek before the product reached the nearby North Saskatchewan River.
There were no injuries and no evacuation was required.
The investigation determined that the leak occurred when a gasket between the two halves of the ball valve was displaced out of its original position, likely due to volume expansion of frozen water within the valve. The product that was released into the creek flowed from a sluice gate valve at the end of the berm’s storm water drain pipe. The sluice gate valve could not achieve a liquid-tight seal due to corrosion.
Although Enbridge conducts inspections at regular intervals, detailed procedures had not been implemented to assist inspectors with evaluating the condition of tank or berm components and with determining whether the components were suitable for continued service.
Following the occurrence, Enbridge initiated actions to ensure that all tank and containment berm components are thoroughly inspected. The company also reviewed its maintenance procedures as well as its hazard assessment and emergency response plans. The National Energy Board, which is responsible for regulating pipelines under federal jurisdiction, monitored the clean-up process and initiated a review of the occurrence to verify Enbridge’s compliance with regulatory requirements, ensuring that the company took adequate corrective, preventive and safety actions.
Source: newswire.ca; TSB investigation report (P17H0019)
