De Beers fined $350,000 for diesel spill at former N.W.T. mine site

De Beers Canada has been ordered to pay a $350,000 fine for an oil spill at its former Snap Lake diamond mine site five years ago. 

On Dec. 7, 2017, an employee forgot to close a storage tank valve while refilling the tank.

That caused the tank to overfill and about 1,100 litres of diesel was released into the environment.

The diamond mining company pleaded guilty and was sentenced in territorial court Monday to charges under the Canadian Environmental Protection Act. 

The employee who forgot to close the valve had worked until 2:30 a.m. the previous morning repairing a generator after a power outage at the mine, according to the agreed statement of facts submitted in the case. The incident also occurred immediately before a shift change. 

A member of the new crew discovered the mistake later that day and De Beers reported the spill on Dec. 8, 2017. Its initial report estimated that only about 500 litres had overflowed from the tank. That was revised to 5,903 litres in a follow-up report to the Maceknzien Valley Land and Water Board (MVLWB) on Dec. 20, and then again revised "following further investigation."

De Beers now estimates the spill to have been less than 1,125 litres.   

Following the spill, De Beers employees shoveled four drums of contaminated snow out of the affected area. It also attempted to excavate frozen ground, but was unable to do so because of the tank's proximity to buildings and equipment.

In Jan. 2018, the company, along with the territorial government, began environmental inspections. An initial assessment indicated "no environmental harm." In May, however, the inspection report noted a diesel smell and in July it noted "some staining on the ground where the spill had occurred."

In Aug. 2018, De Beers excavated test pits to determine the extent and depth of the oil spill. Results in three of those sites established the diesel "had likely infiltrated into the underlying ground and dispersed away from the spill site."

Further testing in 2019 and 2020, conducted by De Beers and approved by the MVLWB, found no traces of hydrocarbons in the surface water and said the spill "is not expected to cause adverse effects" to aquatic life, does not pose a human health risk and has not adversely affected the drinkability of the water. 

In the aftermath of the spill, De Beers has updated its operating procedures to require that the worker refueling the tank, call a second employee when the refueling process begins and then again when it ends to eliminate relying on a single worker. 

The company has also committed to reviewing training documents with its staff. 

Monday's sentencing, which the judge accepted, came as a joint submission between Crown prosecutor Morgan Fane and Melanie Gaston, who was representing De Beers.