TRAVERSE CITY (AP) – Environmental groups are raising concerns about transporting tar sands oil in underground pipelines on the second anniversary of a spill that polluted the Kalamazoo River.

A pipeline operated by Enbridge Inc. ruptured near Marshall on July 25, 2010, dumping more than 800,000 gallons into the river. It was the most expensive onshore spill in U.S. history, with cleanup costs exceeding $800 million.

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The line runs from Griffith, Ind., to Sarnia, Ontario.

Some of the oil was extracted from sands in western Canada. Environmentalists say tar sands oil is more corrosive to pipes than conventional oil, which Enbridge disputes.

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Rallies were held Wednesday in Michigan and at least eight other states to protest planned pipeline expansions.

Edmonton, Alberta-based Enbridge says it has made many pipeline safety improvements since the 2010 spill.

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