A DN 600 hydrocarbon pipeline is damaged while a DN 500 pipeline was being laid using a horizontal directional drilling (HDD) technique in an area already containing 17 other pipelines.

Environmental consequences

A total of 1000 m3 of crude condensate gushed out, but most was collected. The emergency response plan was implemented.  Flame retardant foam was sprayed all over the scene of the incident, preventing the spilt oil from igniting.

The air, soil, and groundwater were continuously monitored. Monitoring of the air was discontinued on 17 April 2017 as the test results did not indicate any contaminants. Most of the spill was collected using pumps and a Hydrovac system. Operations to remove and replace the contaminated soil ended on 20 July 2017. Cleanup operations, including monitoring of the soil and groundwater, are expected to continue until at least 2020.

Causes

The investigation conducted by the Canadian authorities found that HDD had been carried out without first confirming, via on-site measurements, the pipeline’s exact location and depth of cover at the pipe crossing. Instead, the contractor that carried out the work had relied on measurements taken on an adjacent pipeline. This was not the procedure usually followed. In addition, a checklist incorrectly indicated that the depths of all the pipelines to be crossed had been visually checked. The work was the result of a collective memorandum of understanding amongst the various stakeholders (companies operating the pipeline, public works company).

Measures taken

Following the event, the procedures governing work in the vicinity of the other pipelines were improved by carriers as well as the contractors in charge of carrying out the work. They will issue more specific guidelines to their employees in the future.