The Alberta Oil Sands Pipeline System (AOSPL) is a 435 km long, 559 mm
diameter pipeline that transports the entire production of synthetic crude oil
from the Syncrude Canada Inc. plant to the Edmonton Area where it is distributed
to local refineries and to other pipeline systems leaving Alberta. The
AOSPL system has been operated by its agent, AEC Pipelines, a division of
Alberta Energy Company Ltd. since April 1, 1987.
The pipeline was constructed in 1976 and 1977 with the northern 290 km
portion constructed in winter and the southern 145 km constructed in summer.
As part of its on-going operating and maintenance program, AEC Pipelines
regularly reviews the pipeline route for possible leaks as well as any
evidence of surface erosion or instability. Company policy is to correct any
potential problems to ensure the integrity of the pipeline system. Two sites
were judged to require preventative erosion control measures in 1989 - the
north-facing slope at the Athabasca River crossing and the north-facing slope
at the House River crossing.
The remedial work was successful in correcting the drainage and erosion
problems at both sites . . Based on the observations at these sites, the
following recommendations are suggested for use in designing surface drainages
on pipeline rights-of-way:
1. Surface drainages, particularly erosion control berms, should be
reviewed by the designers during construction. Typical drawings
are often not site-specific and do not fit the topography after
construction. Many times, important design decisions are left to
the pipeline inspector or the contractor.
2. Erosion control berms must be set at a steep enough angle that
sediment does not accumulate. A minimum downslope angle of 5°
(9%, 11:1) is recommended to maintain water flow through a
well-vegetated erosion channel. Steeper angles may be necessary
on excessively steep slopes. Potential erosion in the channels by
the use of rip-rap, matting, or sand bags.
3. Erosion berms should not change angle but have a consistent
downslope gradient. Berms should not become ·more shallow at the
downslope end if sedimentation is to be avoided. Gradients should
be confirmed with the aid of device to measure angles
(clinometer).
4. Erosion control berms should channel water completely off the
right-of-way and discharge into dense vegetation where there is a
minimum risk of erosion damage.
5. Erosion control berms that cross the pipeline trench should be
designed in such a manner that subsidence of the trench backfill
will not render the drainage inoperable. Such designs could
include sandbag fill, a short, steep gradient protected by rip-rap,
or compact backfill.