Pipeline Profiles: Enbridge Mainline

Pipeline system and key points

Section updated May 2021

The Enbridge Canadian Mainline system (Mainline) is Canada’s largest transporter of crude oil, moving western Canadian crude oil production to markets in eastern Canada and the U.S. Midwest. The Mainline also transports refined petroleum products to Saskatchewan and Manitoba and natural gas liquids to the U.S. Midwest and into Sarnia, Ontario. The original pipeline from Edmonton, Alberta to Superior, Wisconsin was built in 1950. In 1953 it was extended to Sarnia, Ontario. The Mainline has been expanded and upgraded during the last thirty years to its current configuration and capacity. CER-regulated assets include approximately 6 600 km of operating pipeline and various auxiliary infrastructure.

The Mainline originates in Edmonton, Alberta and extends east across the Prairies. The pipeline crosses the Canada-U.S. border near Gretna, Manitoba, where it joins with the Enbridge Lakehead System (U.S. Section of the Mainline). At Superior, Wisconsin the Lakehead System branches into two segments. The northern segment, Line 5, passes through northern Wisconsin and Michigan, including under the Straits of Mackinac, before crossing into Ontario at Sarnia. The southern segment (Lines 6, 14 and 61) contours south of Lake Michigan, passing through the Chicago area en-route to Flanagan, Illinois where there are interconnects with downstream pipelines and storage facilities. The southern segment also includes Line 78, which originates near Griffiths/Hartsdale in Indiana and extends northeast towards Ontario, terminating near Sarnia, Ontario. From Sarnia, Lines 7 and 11 continue to Westover and Nanticoke in Ontario. Also from Sarnia, the Mainline connects with Line 9.

The Mainline directly connects to 14 refineries and connects to a number of pipelines including CER-regulated lines (Keystone Pipeline, Express Pipeline, Wascana Pipeline) as well as U.S. regulated lines (Spearhead, Flanagan South, Mustang, Toledo, and Southern Access Extension). The directly connected Canadian refineries include Cooperative Refinery Complex in Regina as well as four refineries in Ontario (two in Sarnia, and one in each of Nanticoke and Corunna).

Official CER documents related to the construction, operation and maintenance of the Enbridge Mainline pipeline can be found here: Enbridge Mainline regulatory documents [Folder 92263].

You can see the Enbridge Mainline and all CER-regulated pipelines on the CER’s Interactive Pipeline Map. The map shows more detailed location information, the products carried by each pipeline, the operating status and more. There is also a map on Enbridge’s website.

Pipeline map

Enbridge Mainline pipeline system map

Source: CER

Text version of this map

This map provides an overview of the Enbridge Mainline Pipeline System.

Throughput and capacity

Section updated quarterly (early March, mid-May, mid-August and mid-November)

Note: The physical capacity of a pipeline is based on many factors such as the products being carried, direction of flow, pipeline pumping capacity, and maintenance work or other pressure restrictions. The actual physical capacity of the pipeline may, at times, be higher than the assumed operational capacity stated here.

Open data can be freely used and shared by anyone for any purpose. The data for these graphs are available.


Section updated April 2021

Enbridge has filed several facility applications over the last number of years to expand capacity and optimize configuration. The Enbridge Canadian Mainline transports about 58% of all Canadian crude oil exports. Available capacity on the Enbridge Canadian Mainline has increased from around 2.1 million barrels per day (MMb/d) (333.9 10³ m³/d) in 2010 to almost 3 MMb/d (477 10³ m³/d) in 2020.

In 2014 and 2015, Enbridge completed the Canadian portions of the Alberta Clipper (Line 67) Expansion Project ([Folder 873410] and [Folder 1019340]), increasing capacity by a total of 0.35 MMb/d (55.6 10³ m³/d) to the full design capacity of 0.8 MMb/d (127 10³ m³/d). This, together with flexibility enhancements, has resulted in higher throughputs on the Enbridge Mainline.

In 2014, Enbridge filed an application with the NEB for the Line 3 Replacement Program [Folder 2545522], which would restore capacity of the pipeline to 0.76 MMb/d (121 10³ m³/d). With the recommendation of the NEB, the Governor in Council approved the project in November 2016.

The $5.3-billion Canadian portion of the Line 3 Replacement Program went into service in December 2019. With the new replacement line operational, the existing Line 3 pipeline in Canada will be decommissioned in accordance with regulatory requirements. In December 2020, Enbridge received the final permit from Minnesota state regulators for the US$2.9 billion U.S. portion of Line 3 yet to be replaced. Construction has begun on that final segment of Line 3.

In 2018, Enbridge and Westover Express filed a joint application with the NEB [Folder 3562780] for the sale of Line 10 to Westover Express Pipeline Limited, a subsidiary of United Refining Company. United Refining Company owns a refinery in Warren, Pennsylvania that receives crude oil from Line 10 and the Kiantone Pipeline. In May 2019 the CER granted leave to sell Line 10.

On 13 November 2020, the State of Michigan notified Enbridge Inc. that the 1953 easement allowing it to operate Line 5 in the Straits of Mackinac is being revoked and terminated. The notice, which Enbridge is disputing, requires Enbridge to cease operations of the dual pipelines in the Straits by May 2021. On 12 January 2021, Enbridge issued a letter stating that its review showed the State lacked the authority to terminate or revoke the 1953 easement.

Nomination and Verification Procedures

Section updated June 2020

Pipeline tariffs specify the procedures by which shippers are to submit nominations for transportation service, including the form and timing of nominations. The tariffs also set out the rights and authorities of pipeline companies to verify nominations. The CER regulates and determines compliance with tariffs for pipelines under its jurisdiction, which include the major export pipelines from western Canada. Pipeline companies and shippers are required to follow the rules and regulations of transportation service as set out in the tariffs.

Enbridge uses three types of verification on the Enbridge Mainline. First, supply is verified by requiring each shipper to submit a certificate, executed by an officer of the shipper company, confirming that the shipper has the capability and intent to tender each crude type and volume, and that the nomination has not been inflated to factor in apportionment. Second, volumes must be verified by the connecting upstream facility. Third, each downstream destination facility must submit monthly verification affidavits, attesting that it is capable of receiving, and intends to receive, the crude oil volumes nominated to it.


Section updated June 2020

A shipper must submit nominations each month to it wishes to move its oil on a pipeline. Shippers must submit nominations for both committed (or contracted) transportation service, if available, as well as uncommitted transportation service. If the total volume of nominations for uncommitted capacity is more than what is available, the pipeline company must “apportion” the nominations.

Apportionment is the percentage by which each shipper’s nominated volume is reduced in order to match the pipeline’s uncommitted capacity. Generally, apportionment is applied equally across all shippers seeking to use that capacity: for example, if shipper A nominates 100 barrels and shipper B nominates 1 000 barrels, then, under 10% apportionment, shipper A will be able to ship 90 barrels, and shipper B will ship 900 barrels.

The interactive graph below shows data for nominations and apportionment on the Enbridge Mainline.

Open data can be freely used and shared by anyone for any purpose. The data for these graphs are available.


Section updated June 2020

A toll is the price charged by a pipeline company for transportation and other services. Tolls allow pipeline companies to safely operate and maintain pipelines. Tolls also provide funds for companies to recover capital (the money used to build the pipeline), pay debts, and provide a return to investors. The interactive graph below shows the tolls for key paths on the pipeline since 2006.

Open data can be freely used and shared by anyone for any purpose. The data for these graphs are available.

Mainline tolls are set according to a negotiated settlement, the Competitive Toll Settlement (CTS), which is in effect from 2011 until 2021. The tolls are fixed, meaning they don’t change a lot from year to year. However, tolls are adjusted annually with the gross domestic product index and other factors. Because tolls are fixed, if throughput decreases Enbridge faces additional financial risks compared to the previous cost of service tolling method. Shippers pay international joint tolls for crude oil shipped from Canada to the U.S., or Canadian tolls for crude oil shipped solely within Canada. These tolls are based on volumes, the various pipeline routes (combinations of receipt and delivery points) and the qualities of the crude oil to be shipped.

The Enbridge Mainline currently provides entirely uncommitted capacity to its shippers. In December 2019, Enbridge filed an application with the CER for approval of a new service and tolling framework, seeking to have it in place when the current CTS expires. Enbridge proposes to offer long-term contracts on the Mainline for up to 90% of the capacity, with at least 10% of capacity remaining available for uncommitted service. [Folder 3895249]

Official CER documents related to the traffic, tolls and tariffs for the Enbridge Mainline can be found here: Enbridge Mainline toll documents [Folder 155829].

Abandonment funding

Section updated June 2020

The CER requires pipeline companies to set aside funds to safely cease operations of a pipeline at the end of its useful life. In 2016, Enbridge Pipelines Inc. estimated it would cost $1 743 million to do this for the Enbridge Mainline. These funds will be collected over 40 years and are being set aside in a trust.

Table 1: Enbridge Mainline’s abandonment trust fund balance
  2015 2016 2017 2018 2019
Trust fund balance ($) 33 800 000 80 181 000 120 700 000 182 600 000 226 100 000

Official CER documents related to abandonment funding can be found here, sorted by year and by company: abandonment funding documents [Folder 3300366].

Financial information

Section updated June 2020

Financial resource requirements

Section updated June 2020

The Canada Energy Regulator Act requires major oil pipeline companies to set aside $1 billion to pay for the costs of any incident that occurs, such as a spill. See sections 136 to 142 of the Act for more information. Enbridge Pipelines Inc. demonstrated that its has financial resources in excess of $1 billion dollars. Official CER documents related to Enbridge’s financial resources can be found here: Enbridge financial resources requirements documents [Folder 2955535].

Enbridge Mainline financial information

Section updated June 2020

Pipeline companies report important financial information to the CER quarterly or annually. A strong financial position enables pipeline companies to maintain their pipeline systems, attract capital to build new infrastructure, and meet the market’s evolving needs. The data in this table comes from Annual Filing of CTS (Competitive Toll Settlement) Reports [Folder 805818] with the CER.

The Enbridge Mainline operates under a negotiated settlement.

Table 2: Enbridge Mainline financial data (excludes Lines 8 and 9)
  2012 2013 2014 2015 2016 2017 2018 2019
Net plant (million $) 5 193 5 683 6 387 8 785 8 824 8 952 8 857 13 608
Revenues (million $) 2 805 1 692 3 423
Corporate financial information

Section updated June 2020

The Enbridge Mainline is owned by Enbridge Pipelines Inc., a subsidiary of Enbridge Inc. In addition to the Canadian portion of the Enbridge Mainline, Enbridge Pipelines Inc. also owns the Canadian portion of the Southern Lights Pipeline, as well as renewable power generation assets. Credit ratings continue to be investment grade.

Credit ratings provide an idea of the financial strength of a company, including its ability to attract capital to build new infrastructure and meet financial obligations. The credit ratings below are expert opinions of how likely the debt issuer is to live up to its obligations.

Table 3: Enbridge Pipelines Inc. credit ratings
  2012 2013 2014 2015 2016 2017 2018 2019
Revenues (million $) 1 242 1 222 697 2 757 3 431 2 327 4 074
DBRS credit rating A A A A A A A A
S&P credit rating A- A- A- BBB+ BBB+ BBB+ BBB+ BBB+
Financial regulatory audits

Section updated June 2020

The CER audits pipeline companies to confirm compliance with the Canadian Energy Act, regulations, CER orders and CER decisions. Financial regulatory audits focus on toll and tariff matters such as detecting cross-subsidies. Enbridge Mainline’s last audit was completed in December 2009. Official CER documents related to Enbridge Mainline’s financial regulatory audits can be found here: [Folder 587320]

Safety and Environment

Conditions Compliance

Section updated June 2021

Every pipeline company in Canada must meet federal, provincial or territorial, and local requirements. This includes Acts, Regulations, rules, bylaws, and zoning restrictions. Pipelines are also bound by technical, safety, and environmental standards along with company rules, protocols and management systems. In addition to these requirements, the Commission may add conditions to regulatory instruments that each company must meet. Conditions are project-specific and are designed to protect public and the environment by reducing possible risks identified during the application process.

Condition compliance is part of the CER's oversight and enforcement action is taken when required.

Conditions can be related to a specific region, or apply to the pipeline project as a whole. The map below displays the number of in progress and closed conditions mapped to economic regions as defined by Statistics Canada.

Conditions can typically be either in-progress or closed. The CER follows up on in-progress conditions.


This status refers to conditions that continue to be monitored by the CER. This happens when:

  • condition filings have not yet been received by the CER; or,
  • filings have been received but are under review or do not yet meet requirements; or,
  • a project is not completed and it has conditions, which have not been met; or,
  • a project has a post-construction condition, but a requirement has not yet been completed; or,
  • some conditions may be active indefinitely or refer to the continued operation of a pipeline.

This status refers to:

  • condition requirements that have been satisfied, and no further submissions from the company are required; or
  • conditions whose filings or actions apply to a specific phase that have been fulfilled as the phase is completed (i.e. a specific filing during construction phase). Note: comments on the required actions can still be received.

Source and description

Data Source: Open Government

Description: The above map displays the number of CER conditions associated with projects approved by the Commission. The map is split into two tabs which show in-progress and closed conditions separately, mapped to an economic region. If a company has no in-progress conditions specific to an economic region, the dashboard will default to show the closed conditions by region. An additional view is available which contains the number of in-progress and closed conditions that don't have a corresponding economic region in the dataset. The map regions are shaded based on the number of conditions, with lighter colored regions containing fewer conditions compared to darker colors. Conditions that apply to more than one region are double counted in the map, and these conditions will appear in the map region total and map region breakdown for each applicable region. The condition counts contained in the map navigation buttons represent total conditions without region double counting.

Open data can be freely used and shared by anyone for any purpose. The data for these graphs are available [CSV].

Have you checked out the CER's interactive conditions data visualization? This tool offers a deep dive into the CER's conditions compliance data and process, exploring conditions across all CER regulated companies by keyword, project, and location.

Pipeline Incidents

Section updated June 2021

The information presented here is based on CER data (2008 to current) for incidents reported under the Onshore Pipeline Regulations and the Processing Plant Regulations. New data is added quarterly. Learn more on how incident data collection has evolved since the NEB (now the CER) was established in 1959.

Companies must report events, such as incidents, to the CER in accordance with the CER Event Reporting Guidelines. Knowing what happened, and why, helps us find ways to prevent them from happening again.

What is an incident? (Onshore Pipeline Regulations (OPR))

As defined in the OPR, “incident” means an occurrence that results in:

  1. the death or serious injury to a person;
  2. a significant adverse effect on the environment;
  3. an unintended fire or explosion;
  4. an unintended or uncontained release of low vapour pressure (LVP) hydrocarbons in excess of 1.5 m³
  5. an unintended or uncontrolled release of gas or high vapour pressure (HVP) hydrocarbons;
  6. the operation of a pipeline beyond its design limits as determined under CSA Z662 or CSA Z276 or any operating limits imposed by the CER.
What is an incident? (Processing Plant Regulations (PPR))

As defined in the PPR, “incident” is defined as an occurrence that results or could result in a significant adverse effect on property, the environment, or the safety of persons. For the purposes of incident reporting in the PPR, events that fall under this definition include, but are not limited to:

  1. the death or serious injury to a person;
  2. a significant adverse effect on the environment;
  3. an unintended fire or explosion that results in or has the potential to result in damage to company, public/crown or personal property;
  4. an unintended or uncontained release of low vapour pressure (LVP) hydrocarbons in excess of 1.5 m³
  5. an unintended or uncontrolled release of gas, HVP hydrocarbons, hydrogen sulfide or other poisonous gas; or
  6. the operation of a plant beyond its design limits or any limits imposed by the CER.
Incidents and the CER

Companies self-report incidents and are expected to take a precautionary approach in doing so. This means that even when there is doubt as to whether an incident should be reported, the company must report it. The approach is, “When in doubt, report.” This is consistent with CER-regulated companies’ responsibility for anticipating, preventing, mitigating and managing incidents of any size or duration.

The CER reviews all reported incidents to assess whether companies have taken the appropriate corrective actions and to identify potential trends in incidents. Each incident is given a status indicating the current stage of the CER's incident review.

CER Status
  • Initially Submitted: The company has notified the CER that an incident has occurred and provided preliminary information. A review has been initiated.
  • Submitted: The company has submitted all of the required information and the CER is reviewing the incident.
  • Closed: The CER’s incident review has been completed and the file is closed.
Incident type definitions: one incident can have multiple types
  • Release of Substance (featured in the dashboard) - Any time a product is unintentionally released. (Releases of non-gas low pressure products in volumes of less than 1.5 m³ are exempt from reporting.)
  • Adverse Environmental Effects - When any chemical substance is released at a concentration or volume that has the potential to change the ambient environment in a manner that would cause harm to human life, wildlife or vegetation (e.g., glycol, potassium carbonate, methanol, methanol mix from hydrostatic testing, etc.).
  • Explosion - An unintended explosion
  • Fatality - Any death involving employees, contractors or members of the public related to the construction, operation, maintenance or abandonment of pipelines
  • Fire - An unintended fire
  • Operation Beyond Design Limits Includes situations, such as:

    • over-pressures - i.e., pressures that are higher than the maximum the equipment was designed to safely handle;
    • vibration beyond design limits;
    • slope movements causing movement in the pipeline beyond design limits;
    • pipe exposures in rivers or streams; and
    • introduction of an inappropriate product (e.g., sour gas in excess of CSA limits)

    Operation beyond design limit is typically linked to an over-pressure of the product in the pipe; however, if a pipe was exposed to excessive vibration and was not designed for this, this could be considered operation beyond design limits. Operation beyond design limits does not include equipment contacting the pipe, or corrosion pits, etc.

  • Serious Injury (CER or Transportation Safety Board) - Any serious injury involving employees, contractors or members of the public related to the construction, operation or maintenance of pipelines.
Are there any incidents near me?
Select range (100km):
Source and description

Data Source: Open Government

Description: The above map displays the location of product release incidents that have occured on the pipeline system since 2008. The map defaults to show incidents as bubbles which are colored based on the substance released. Incidents on the map can be re-categorized based on the most recently available status of the CER's incident review, the year in which the incident was reported, and the province/territory where the incident occured. The incident map bubble can be switched to show the estimated volume of product released, with larger map bubbles showing larger release volumes relative to other product releases on the system. The incident data can also be toggled to display a stacked bar chart of incidents over time by clicking on the incident trends button above the map. The stacked bars dispaly the number of product release incidents by year, with bar color segments corresponding to the various products released. Similiar to the map, incidents can be re-categorized by clicking on the side buttons to view a breakdown of incidents by status, what happened, why it happened, and province/territory.

Open data can be freely used and shared by anyone for any purpose. The data for these graphs are available.

Have you checked out the CER's interactive incident data visualization? This tool offers a deep dive into the CER's incident data trends, exploring incidents across all CER regulated companies.

Emergency management

Section updated June 2020

The CER checks to make sure companies are keeping pipelines safe by doing inspections, in-depth safety audits, and other activities. Yet, even with these precautions, an emergency could still happen. Sound emergency management practices improve public safety and environmental protection outcomes, and provide for more effective emergency response.

The CER holds its regulated companies responsible for anticipating, preventing, mitigating, and managing incidents of any size or duration. Each company must have an emergency management program that includes detailed emergency procedures manuals to guide its response in an emergency situation. We oversee the emergency management program of a regulated company’s projects as long as they operate.

The CER requires companies to publish information on their emergency management program and their emergency procedures manuals on their websites so Canadians can access emergency management information. To view Enbridge Mainline’s regional Integrated Contingency Plan, go to Enbridge’s Field Emergency Response Plans website, where the company’s plans are organized by area of operation.

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