Twin oil pipelines beneath the Straits of Mackinac have had repeated problems with inadequate supports, a shortcoming that Michigan officials have described as violating a legal condition for placing the lines in the waterway, a newspaper reported Thursday.
The Petoskey News-Review said inspections by Enbridge Energy Partners had uncovered more than 200 instances in which excessive sections of its pipelines had no support from the lake bottom or man-made anchors. An easement granted by the state when the lines were laid in 1953 requires that no section longer than 75 feet be without such supports.
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Enbridge's Line 5 carries about 23 million gallons of crude oil and liquid natural gas daily between Superior, Wisconsin, and Sarnia, Ontario. A nearly 5-mile-long section, divided into two lines, runs along the bottom of the straits area where Lakes Huron and Michigan converge.
The company disclosed last summer that an inspection with a remote underwater vehicle turned up four locations where unsupported sections exceeded the limit. That followed the discovery of other spacing issues during a 2014 examination. State Attorney General Bill Schuette said they amounted to a violation of the easement's terms.
In response, Enbridge has installed more than 40 steel anchors held in place by screws drilled into the lakebed.
The News-Review reported that an Enbridge document posted on a state website listed more than 200 occurrences of unsupported spaces exceeding 75 feet. They were noted during inspections between 2005 and 2012. The longest reported gap totaled 54 feet beyond the limit, the newspaper reported. It said some of the excessively lengthy gaps were spotted in multiple inspections.
The findings show that Enbridge has violated the easement requirement "for a number of years," said Jennifer McKay of the Tip of the Mitt Watershed Council and a member of the Michigan Pipeline Safety Advisory Board. They also raise questions about the pipeline's integrity, she said.
Environmental groups have called for shutting down the pipeline, which Enbridge insists is in good shape.
Enbridge spokesman Ryan Duffy said the company inspects Line 5 for gaps every two years and places more supports as needed. Enbridge has requested state permission to add 22 more anchors this year, he said.
"The lakebed is a dynamic environment, there's a lot of currents that are shifting, there's erosion," Duffy said.