Trans Mountain Pipeline (ULC)
Trans Mountain Expansion Project
Volume 8A – Marine Transportation
10 Per Cent Under Keel Clearance Requirement
Since channel width varies with tidal height so then does the extent to which tankers can be
loaded. Occasionally, under the largest high tides, Aframax tankers can load up to about
90,000 tonnes (approximately 80 per cent DWT capacity) of cargo and based on the average
density of heavy crude oil loaded at Westridge Marine Terminal this is equivalent to about
(615,000 bbls). However, over the tidal cycle the average cargo loaded would be
about 550,000 bbls (equivalent to about 70 per cent DWT capacity). The effect of the draft
restrictions on cargo capacity were taken into consideration by Trans Mountain when estimating
the extent of tanker traffic that might result from the Project. This estimate was used in the
quantitative risk assessment (TERMPOL 3-15, Volume 8C-12) of an oil spill occurring from one
of these tankers.
Project-Related Changes to Marine Transportation and Traffic Volumes
Vessel Type and Marine Traffic Volume
As a result of the Project, marine traffic volume calling at the Westridge Marine Terminal will
increase. The types of vessels calling at the Westridge Marine Terminal (
, barges, Panamax
and Aframax size tankers) will not change as a result of the Project. As well, the vessels calling
at the Westridge Marine Terminal after the Project is in operation will continue to use the
existing marine transportation routes depicted in Figure 1.3.1.
Obermeyer pers. comm.
This cross section represents the narrowest portion of the Second
Narrows MRA passage.
10 PER CENT UNDER KEEL