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Trans Mountain Pipeline (ULC)
Trans Mountain Expansion Project
Volume 7
Volume 7 - Risk Assessment and Management of Pipeline and Facility Spills
Page 7–138
Scenario 4: Fraser River and Delta near Port Mann Bridge, British Columbia,
RK 1,167.5
The hypothetical full bore rupture spill scenario on the bank of the Fraser River near the Port
Mann Bridge (RK 1,167.5) was established as 1,250 m
of CLWB for the purpose of detailed
spill modeling and the pipeline ERA. Subsequent spill outflow modelling volume estimates show
slightly different predicted release volumes. The ERA has not been modified to reflect this
refinement as the ecological consequences described below are still valid.
The hypothetical spill location is adjacent to railway yards on the south side of the Fraser River,
a short distance downstream from the Port Mann Bridge. At this location, the pipeline is within a
few hundred metres of the river, and it is likely that culverts and other drainage systems would
rapidly transport most of the spilled oil from the spill location to the river. For this reason, there
was assumed to be no hold-up of spilled oil on land, although it is possible that by blocking such
culverts or ditches as an early emergency response action, a considerable amount of oil could
be prevented from reaching the water. The Fraser River at this location is about 450 m wide,
with a gentle meander and a sand bed. Shorelines are highly developed with wharves, pilings,
log booms and rip-rap. Flows are strongly seasonal, ranging from approximately 7,000 to
12,000 m
/s in June (during freshet), to 2,000 m
/s or lower during winter.
Owing to the complex nature of interactions between spilled oil and water, suspended sediment,
and hydrology as the Fraser River enters the delta, this spill example is supported by stochastic
oil spill fate and transport modeling (Modeling the Fate and Behaviour of Marine Oil Spills for the
Trans Mountain Expansion Project [Volume 8C, TR 8C-12, S9]). In addition, the evaluation is
supported by reference to two case studies described in the Qualitative Ecological Risk
Assessment of Pipeline Spills Technical Report (TR 7-1): the Kalamazoo River oil spill, since
that oil spill involved a similar form of diluted bitumen; and the DM 932 spill in the lower
Mississippi River, since that involved a heavy oil, and a large river/estuary system with high
suspended sediment load. Consideration was also given to information that was developed
during the Gainford experimental study (see Gainford Study in Volume 8C, TR 8C-12, S7) and
as part of the proposed Vancouver Airport Fuel Delivery Project (Vancouver Airport Fuel
Facilities Corporation [VAFFC] 2012a).
Three environmental conditions were considered for this spill example:
A winter condition between December and March. Air temperatures are
assumed to be around the freezing mark, but snow cover is not guaranteed,
and the river is ice-free. The river flow is in a low range (around 2,000 m
A summer condition between June and August, with air temperatures 15 to
25°C. The river is in freshet, with flow greater than 6,000 m
/s, and potentially
approaching 12,000 m
A spring or fall condition between April and June, or September and November.
The river flow is in a moderate range, at around 5,000 m
/s, and the air
temperatures are cool, between 0 and 15°C.
The ERA scenario evaluation did not consider the probability of occurrence of the spill nor the
various design, engineering, maintenance, inspection and other preventative programs that
Trans Mountain will have in place to reduce the likelihood of spills occurring, the details of which
can be found in Section 2.0. Rather, this evaluation assessment was performed based on the
premise that the spill had occurred despite these preventative programs. In addition, the