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Updated August 2023

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Failure type (general)
Each incident reported to the AER is assigned a category that identifies the main reason an incident occurred. Incidents are initially assigned a general failure type, such as internal corrosion or construction deficiency. The general failure types listed below are divided into specific causes of failure (cause type). For example, an incident may be due to internal corrosion, but CO2 corrosion specifically caused the failure.

  • Construction deficiency: A failure caused by using improper construction or design practices or both.
  • Damage by others; contact damage: A failure caused by physical damage (hit, leak, or rupture) to the pipe coating or the pipe during ground disturbance activities. See the definition of "contact damage" in the Pipeline Rules.
  • Earth movement: The movement of the ground surrounding a pipeline can exert a force on the pipe, causing it to fail. Ground movement may be a natural event or the result of human activity. Natural events include frost heaves, slope movement, flood, landslide, subsidence, and washouts. Excavation activity can also induce earth movement. 
  • External corrosion: A failure caused by corrosion of the outside of the pipe, valve, fitting, flange, or inline coupler. Also includes fretting damage. Corrosion may occur on coated pipes if the coating is damaged.
  • Internal corrosion: A failure caused by corrosion of the inside of the pipe, valve, fitting, flange, or inline coupler.
  • Installation leak: If the incident type is installation leak , then the failure type will also be called "installation leak."
  • Mechanical joint failure: Either a failure on metallic pipelines of mechanical interference joints (e.g., Thru-Kote Welded, Crimp Kote, Sure Lok, Pronto Lock, Zap-Lok, Twin Lok) or a failure on a nonmetallic pipelines at mechanical couplings, including crimped metallic connections on spoolable composite pipe. Corrosion at metallic connections on a nonmetallic pipeline is reported under the failure type "Corrosion external" or "Corrosion internal."
  • Mechanical pipe damage: Damage by human-induced mechanical activities to pipelines, risers, or piping not related to a ground disturbance that results in unintentional damage and a release (e.g., truck running into a riser, cultivator hitting pipeline while cultivating to a depth of 45 centimetres or shallower).
  • Miscellaneous: A failure not covered under the other failure causes. May include pipeline erosion from external jetting action from nearby pipeline failures, lightning strikes, vandalism, damage caused by wildlife or livestock, and plastic liner failures that result in a release to the environment through the vent.
  • Miscellaneous joint failure: Joint failure of different pipe materials, including failure at a butt fusion, electrofusion, or other fusion joint on plastic pipe, failure at a bonded or solvent-welded joint on PVC pipe, failure at a high-energy joint on an aluminum pipe, or at a threaded or bonded joint on a fibreglass pipe.
  • Operator error: A failure caused by the operator, including improperly closing or opening a valve, operating the pipeline with missing components, bypassing safety controls, or not following operating procedures for temperature changes or operating pressure. This category does not include failures from ground disturbance, mechanical pipe damage, or pressure test failures. Operator error does not include incidents where normal operating pressure was increased to maximum operating pressure or slightly less to resolve a problem, such as a stuck pig, because operator error would not be the primary cause of the failure. Such incidents would fall under other failure categories (e.g., external corrosion that reduced the wall thickness, failing when the pressure was increased).
  • Overpressure failure: A failure where the pipeline pressure exceeds the design limit. Overpressure may result from frozen lines, lack of pressure control or lack of an overpressure protection device, or temperature increase in a shut-in line. Failures from reduced wall thickness due to corrosion are reported under the failure type "Corrosion internal" or "Corrosion external." Leaks from frozen aboveground valves are reported under the failure type "Valve or fitting failure." Overpressure due to the operator’s actions is reported under the failure type "Operator error."
  • Pipe body failure: A failure that occurs in the pipe body due to material flaws, defects, or sensitivity to the operating environment. Examples include stress-corrosion cracking, sulphide stress cracking, hydrogen-induced cracking, brittle cracks, running cracks, fatigue cracking, cyclic stress damage, laminations, or separations. Also includes degradation of nonmetallic materials. 
  • Seam failure: A failure due to a leak or fracture at a long-seam weld or spiral weld. Seam leaks or fractures are rarely due to corrosion but are mechanical failures of a defective manufactured weld.
  • Unknown: A failure where the cause cannot be determined because the pipeline cannot be exposed, recovered, or examined. Only used when the cause is truly unknown and not when the cause is temporarily unknown.
  • Valve or fitting failure: A release associated with packing, gaskets, flanges, fittings, or pigging facility components or failures in the valve body.
  • Weld failure: A failure due to a defect at a weld or in the heat-affected zone of a weld. Includes branch, fillet, and circumferential (girth) welds.


Incident consequence rating
A consequence rating is assigned to each incident to indicate the magnitude of its effects. The AER uses three incident consequence ratings: low, medium, and high. 

  • High: incidents with a significant impact or adverse effect on a sensitive water body or the environment, wildlife, livestock, workers, or the public
  • Medium: incidents with a moderate impact or adverse effect on a sensitive water body or the environment, wildlife, livestock, workers, or the public
  • Low: incidents with little to no impact or adverse effect on a sensitive water body or the environment, wildlife, livestock, workers, or the public

Clause of CSA Z662: Oil and gas pipeline systems provides the following considerations for determining a sensitive water body:

  1. disruption to commercial navigational activities
  2. use as a major drinking water or food source
  3. presence and type of fish species
  4. reliance of endangered or protected species on the use of the water body

AER inspectors review each incident and assign a consequence rating based on the information available and the actual effects of the specific incident.

Incident date
The day that the incident happened as reported by the licensee.

Incident location
The legal land description of where the incident happened (e.g., Legal Subdivision 1, Section 77, Township 66, Range 3, West of the 4th Meridian).

Incident ratio
The number of incidents per 1000 kilometres (km) of pipeline length. Usually expressed as a function of time (e.g., 2.5 incidents per 1000 km per year).

Incident type
All pipeline incidents are grouped into one of the following categories when they are reported:

  • GSPT: Low-consequence release caused by a leak at a gasket, seal, packing gland, or threaded fitting (GSPT) that can be stopped by mechanical adjustments (e.g., tightening of bolts or replacing seals) and that does not indicate a pipeline or valve integrity issue.
  • Hit: Contact damage to a pipeline or its coating during ground disturbance that does not result in the release of a substance. See the definition of "ground disturbance" in the Pipeline Act. Note that the following are not considered a hit and do not need to be reported as an incident:
    • minor damage to a pipeline's coating sustained during hand excavation and external cleaning
    • pre-existing damage to the coating that is revealed during the unearthing of the pipeline
  • Installation leak: Releases from equipment at an auxiliary site, such as a compressor, pumping station, tank farm, or meter station, which are listed as an installation on the pipeline licence. These incidents are reportable under the Pipeline Act. However, because they do not actually involve a pipeline, the option of viewing incidents according to pipeline specifications, such as pipe material, pipe type, or pipeline length, is not available. 
  • Leak: A release of a substance from a pipeline that does not immediately impair its operation.
  • Rupture: A break or burst in the pipeline that renders it inoperable.

Integrity management programs
Integrity management programs represent specific plans a company uses within an operating area or for specific pipelines. These programs address known threats and potential risks identified in the company’s risk assessments. Programs may include specific operational and maintenance procedures for an individual pipeline or a pipeline system, depending on the risk.

Internal protection
The type of internal protection used to prevent corrosion. The most common types include expanded liners, free-standing liners, and thin-film coating.


Joint type
The method used to join the pipe segments. The most common types are welded, flanged, threaded, mechanical coupling, butt fusion, and bonded.


The holder of a pipeline licence. A licensee bears responsibility for the construction and safe operation of the pipeline. The licensee is also responsible for decommissioning, abandoning, and reclaiming the pipeline.

Liquid release volume
The total volume in cubic metres (m3) of liquid released during a pipeline incident. The released substance can be

  • fresh water (e.g., potable water or surface water),
  • hydrocarbon liquids (e.g., crude oil, condensate, liquid petroleum products, and natural gas liquids),
  • non-fresh water (e.g., produced water), or
  • refined liquids (e.g., lubricants, solvent, diesel fuel, gasoline, heating oil, kerosene).


Maximum operating pressure
The maximum pressure at which a pipeline is licensed to operate.


Nominal pipe size
The outside diameter of a pipeline as a nominal size expressed in inches (see table below). Different pipe materials have dimensions that vary from the nominal, thus the AER groups pipeline diameter using ranges extending from below to above the nominal size.

Nominal pipe size

Outside diameter


 0 to ≤81


>81 to ≤108


>108 to ≤134.2


>134.2 to ≤193.7


>193.7 to ≤246.1


>246.1 to ≤298.5


>298.5 to ≤339.8


>339.8 to ≤431.7


>431.7 to ≤533.5


>533.5 to ≤736.5


>736.5 to ≤838.5


>838.5 to ≤939.5




Oil-well effluent
A mixture of unrefined oil, gas, and produced water.

Operation and maintenance procedures
Step-by-step actions for performing specific tasks related to the operation of pipeline assets. For example, how to pig a pipeline would include all activities from checking pig sizing and conditions before pigging to assessing the condition of pig senders and receivers and addressing potential upset conditions during pigging. Operational procedures standardize activities that effectively and reliably control hazards associated with the operation of the pipeline and reduce operating risk.


Pipe grade
The grade assigned to the pipe varies depending on the pipe material. Steel and aluminum pipe are graded based on the pipe material strength, composite pipe is graded based on its pressure rating, and plastic piping is graded based on its dimensional ratio.

Pipe material
Common materials used to make pipe include steel, composite, fibreglass, polyethylene, and aluminum.

Pipe substance
The substance a pipeline is licensed to transport. If a pipeline is licensed to carry more than one substance, the substance of record is the substance with the highest priority (see table below).





Sour natural gas

Natural gas with >10 moles per kilomole of hydrogen sulphide content


High vapour pressure products

Butane, ethylene, propane, pentanes, liquid ethane


Low vapour pressure products

Condensate, diesel fuel, gasoline, heating oil, hydrocarbons, diluents, kerosene, solvents


Crude oil

Blended crude bitumen, crude oil, synthetic crude oil


Oil -well effluent

A mixture of unrefined oil, gas, and produced water


Natural gas

Methane, natural gas with ≤10 moles per kilomole of hydrogen sulphide


Fuel gas

Fuel gas


Salt water

Produced water


Miscellaneous liquids

Ammonia, caustic, glycol, methanol, polymer, sulphur, carbon dioxide


Miscellaneous gases

Air, ammonia, carbon dioxide, ethane, helium, hydrogen, nitrogen, steam


Fresh water

Potable water, surface water

Pipe type
A pipe's manufacturing standard or product identifier.

Produced water
Water from a wellbore that is produced as a by-product of oil and gas production.


Risk management
Risk management involves identifying, evaluating, and prioritizing potential hazards and threats to a company’s pipeline system. Companies must use this information to effectively allocate and plan resources to monitor, reduce, and control the probability or impact of a potential incident.


Strike area
An administrative geographical boundary used in relation to potential resource accumulations (e.g., Pembina, Provost, Suffield). For a map of Alberta's strike areas, see Map-94, available on the AER website, > Providing Information > Data and Reports > Maps, Map Viewers, and Shapefiles.