How Would Oil Spills Affect the Great Lakes?

Oil production in the north-central United States and western Canada has increased rapidly since 2010. Its transport near or through the Great Lakes region via pipelines and rail has expanded as well. What does this mean for the lakes in terms of environmental threats posed by crude oil transport, and what do we know about potential impacts from a spill in freshwater ecosystems like the Great Lakes?

The International Joint Commission’s Great Lakes Science Advisory Board sought to determine observed and potential impacts of crude oil spills on Great Lakes water quality and ecosystem health, as well as areas of particular vulnerability to oil spills and potential responses to spills. Other reports have analyzed the risk of the likelihood of oil spills in the region, such as for the Line 5 pipeline in the Straits of Mackinac (including the work of the Michigan Pipeline Safety Advisory Board), thus the board’s focus in this report.

Findings and recommendations for additional research and monitoring needs also are included in this report from the board’s Science Priority Committee “Potential Ecological Impacts of Crude Oil Transport in the Great Lakes Basin.”

Pipelines are the dominant mode of transporting crude oil through or near the Great Lakes basin, followed by rail transport. Crude oil is not transported by ship in the lakes, although barge transport occurs on the St. Lawrence River downstream of Montreal. Potential impacts from oil spills are affected by its density and viscosity, which affect how it behaves in the environment after being released. For example, will the oil spread, evaporate, disperse, dissolve or settle to the sediment?

Where it spills is another important parameter in terms of the potential for it to move into larger lakes from connecting rivers, spread if released in an area with complex currents that can change over a short period of time, and seasonal obstacles such as winter ice that may make a spill difficult to detect and clean up.

Most data on ecological impacts from oil spills reflects large releases into oceans, such as the Exxon Valdez spill in Alaska in 1989 and the Deepwater Horizon drilling rig accident in the Gulf of Mexico in 2010. Oil behaves differently in freshwater environments and may have more consequences because the salt in salt water helps accelerate the degradation of the chemicals in the oil. 

Two releases that provide data on the impacts of spills in freshwater environments are a pipeline rupture that released about 24,000 barrels of crude oil into a tributary of the Kalamazoo River in southwestern Michigan in July 2010 and a rail accident and spill in July 2013 in Lac-Mégantic, Quebec.

Considering the available scientific data, the committee found that all levels of the aquatic food chain would be impacted, from plankton to fish, fish-eating birds and mammals. That the lakes provide the largest source of fresh surface water for almost 40 million people and drinking water for many of these residents adds significant impacts to spills, particularly in areas where spreading is a primary result. The risk of a spill affecting drinking water is significant, particularly when currents transport crude oil to the vicinity of drinking water intakes.

Based on the location of existing crude oil transport infrastructure near or in the Great Lakes and information on biodiversity and high-value habitats in the lakes and nearshore areas, the committee identified 15 areas that are particularly vulnerable to crude oil spills. The level of vulnerability depends on the amount of exposure to oil, the sensitivity of the area or habitat, how resilient the area may be to spills, and the type and amount of oil released. Most areas are near oil pipelines or rail corridors, and five areas are near refineries.

 Description of 15 areas of ecological vulnerability to oil spills in the Great Lakes basin. Credit: Science Priority Committee report

Adequate response to an oil spill to minimize damage is critical. The report highlights key government agencies responsible for spill response, as well as the types of actions undertaken to contain and remove spilled oil. Despite the capabilities that exist for spill response, challenges remain for spill response in ice-covered waters, for spills of heavier crudes that sink immediately following a spill or after weathering, and at sensitive habitats where response actions may negatively impact those habitats.

The report identifies science gaps and recommends additional research on the impacts of various crude oil types on freshwater ecosystems that are transported in the region and how to improve siting and design of future oil transport infrastructure in the region. These findings will help to improve spill response measures throughout the region, as well as potentially aid in decisions on oil transport infrastructure siting, to protect drinking water sources as well as ecosystem health.