A Spill Risk Assessment of the Enbridge Northern Gateway Project

The Bercha Group (2012a) concludes that risks to individuals from operations at the
marine terminal are within tolerable limits. Based on Individual Specific Risks
thresholds, the authors determine that risks to the public in the area surrounding the
terminal are insignificant at less than one in one million, while risks to workers are
higher although tolerable at a range of between one in 10,000 and one in 100,000. The
authors recommend mitigation measures to ensure safe operational and work
procedures at the marine terminal.
3.3. Spills from Pipeline Operations
The ENGP regulatory application contains several pipeline spill estimates. In its
regulatory application submitted in 2010, Enbridge prepared a section in Volume 7B
estimating return periods for spills that occur along the pipeline route. In 2012,
WorleyParsons and the Bercha Group submitted additional risk analyses estimating
pipeline spill likelihood for the project.
Volume 7B of the Enbridge application identifies return periods for a hydrocarbon 4
release that occurs along the pipeline route. Enbridge calculates spill return periods
with liquid pipeline failure frequency data from 1991 to 2009 from the National Energy
Board (NEB). Enbridge notes that NEB data include pipelines up to 50 years old that
use older technology and building material standards associated with an increased
frequency of failures compared to modern pipelines (Enbridge 2010b Vol. 7B, p. 3-­‐1).
Accordingly, Enbridge factored improved design features and mitigation planning
characteristic of modern pipelines into its failure frequency calculations and expects
improvement factors to decrease the probability of a pipeline failure relative to NEB
failure frequency data (Enbridge 2010b Vol. 7B, p. 3-­‐1).
Enbridge estimates return periods for various spill size categories of hydrocarbon
releases for six regions along the pipeline route. Enbridge bases spill size categories on
NEB classifications whereby a small spill is less than 30 m 3 , a medium spill ranges
between 30 and 1,000 m 3 , and a large spill exceeds 1,000 m 3 (Enbridge 2010b Vol. 7B).
Enbridge identifies the six physiographic regions along the pipeline route as the Eastern
Alberta Plains, the Southern Alberta Uplands, Alberta Plateau, Rocky Mountains,
Interior Plateau, and the Coast Mountains. Table 12 presents spill return periods
calculated by Enbridge for medium and large spills in the six regions. Although
Enbridge presents spill return periods separately for each region, we combine return
periods for medium and large spills for the entire length of the pipeline that results in a
return period of 28 years.
4 Enbridge (2010b Vol. 7B p. 3-­‐1) refers to pipeline spills as hydrocarbon spills. We interpret hydrocarbon
spills to include both oil and condensate and thus assume spill return periods represent oil or condensate
spills.
12