The Kalamazoo River Oil Spill
How a Pipeline Rupture Created One of the Largest Inland Oil Spills in U.S. History
This article documents the 2010 Enbridge oil spill that devastated the Kalamazoo River in Michigan, one of the largest inland oil spills in American history. The disaster sparked ongoing debates about pipeline safety in the Great Lakes region.
On July 25, 2010, an Enbridge pipeline ruptured near Marshall, Michigan, spilling more than one million gallons of crude oil into Talmadge Creek and the Kalamazoo River. The disaster went undetected for 17 hours as company operators repeatedly pumped more oil into the failing line. The cleanup took five years and cost over $1 billion, making it one of the most expensive pipeline accidents in history.
What Happened
On Sunday, July 25, 2010, at approximately 5:58 p.m., a 40-foot segment of Enbridge Energy’s Line 6B ruptured about 0.6 miles downstream of the Marshall, Michigan pump station. The 30-inch pipeline carried diluted bitumen (dilbit) — heavy crude oil from Canada’s Athabasca oil sands — to refineries in the United States.
The rupture created a 6-foot break in the pipeline, sending crude oil gushing into Talmadge Creek, a tributary of the Kalamazoo River.
The 17-Hour Delay
The rupture went undetected for nearly 17 hours. During this time, Enbridge operators:
- Misinterpreted low-pressure alarms as a routine “column separation”
- Repeatedly increased pressure on the line to clear the supposed bubble
- Restarted the pipeline twice, pumping additional oil into the environment
- Only learned of the rupture when a local utility worker reported it
The delay allowed the spill to grow catastrophically larger than it would have been with proper detection and response.
The Oil: Diluted Bitumen
The type of oil spilled made cleanup exceptionally difficult. Diluted bitumen (dilbit) is heavy crude oil from tar sands that is mixed with lighter hydrocarbons to allow it to flow through pipelines.
Why Dilbit Is Different
Unlike conventional crude oil, when dilbit spills into water, the volatile diluents evaporate, leaving the heavier bitumen to sink. Traditional oil spill cleanup methods — designed for floating oil — were largely ineffective. Much of the oil settled to the river bottom, requiring dredging rather than skimming.
The Cleanup: Five Years and $1.2 Billion
Cleanup Timeline
What Went Wrong
Federal investigators found multiple failures that contributed to the disaster:
Key Findings
- Pipeline defects: Enbridge had long known the 41-year-old pipeline was riddled with cracks and corrosion
- Regulatory failure: Federal regulators at PHMSA allowed defects to persist and approved Enbridge’s inadequate emergency response plan
- Detection failures: Control room operators lacked proper training to identify rupture warnings
- Response delay: Company procedures led operators to pump more oil rather than shut down
- Communication gaps: No system to quickly verify external reports of leaks
Environmental Impact
The spill caused extensive environmental damage:
- 35 miles of the Kalamazoo River closed for nearly two years
- Thousands of animals killed, including birds, fish, and mammals
- Wetlands contaminated with heavy oil
- Sediment dredging required to remove sunken bitumen
- Long-term effects on aquatic ecosystems
One positive outcome: the removal of Ceresco Dam as part of cleanup efforts restored fish passage between Marshall and Battle Creek for the first time in over a century.
The Settlement
In July 2016, Enbridge agreed to pay $177 million in a settlement with the U.S. Justice Department and Environmental Protection Agency. The total cost to Enbridge, including cleanup, settlements, and restoration, exceeded $1.2 billion.
The Lasting Legacy: Line 5 Debate
The Kalamazoo River disaster sparked ongoing debates about Enbridge’s Line 5 pipeline, which runs through the Straits of Mackinac — the narrow waterway connecting Lake Michigan and Lake Huron.
Line 5 carries up to 540,000 barrels of oil per day through a 4.5-mile underwater segment in the Straits. Concerns about a potential spill in the Great Lakes — which contain 20% of the world’s fresh surface water — have made Line 5 one of Michigan’s most contentious environmental issues.
Ongoing Debates
- Michigan Governor Gretchen Whitmer ordered Line 5 shut down in 2020 (order challenged in court)
- Enbridge proposes a tunnel to encase a new pipeline segment beneath the Straits
- Environmental groups continue to call for complete shutdown
- Federal government involved in negotiations between Michigan and Canada
Lessons Learned
The Kalamazoo River spill led to improved pipeline safety regulations and increased scrutiny of tar sands oil transportation:
- Enhanced training requirements for pipeline control room operators
- Improved leak detection systems
- Greater awareness of dilbit’s unique cleanup challenges
- Increased public attention to pipeline safety in the Great Lakes region
Protecting Michigan’s Waters
The Kalamazoo River disaster remains a powerful reminder of the risks pipeline infrastructure poses to Michigan’s waterways and the importance of stringent safety standards and emergency response capabilities.