See how we monitor, support and stabilize Line 5 as it passes under Michigan's Straits of Mackinac
Line 5 span management program
Since constructing the Straits crossing, Enbridge has employed a span management program to monitor the length of unsupported spans and make necessary repairs to prevent the movement of the pipes along the lakebed.
Since 2002, we’ve used a screw anchor support system to secure the twin pipelines running along the bottom of the Straits. These 10-foot-long steel screws are augered into the lake bed on either side of the parallel lines, and hold a steel saddle that permanently supports the lines.
The Line 5 Straits crossing now has 128 support anchors, including four that were installed in October and November 2016.
Our 1953 easement agreement with the State of Michigan requires supports to be placed at a distance of no more than 75 feet. Since currents may cause the lake bed to shift naturally, we keep a close eye on these spans with underwater vehicles that visually inspect the exterior of Line 5 along the bottom of the Straits every two years.
Through one of these inspections, in June 2016, we identified four spans that slightly exceeded 75 feet. As a result, we secured the necessary permits and installed the four most recent anchors.
In 2014, we had installed 40 other screw anchor supports. And as a proactive measure, resulting from our June 2016 inspection, we’ve asked the Michigan Department of Environmental Quality and the Army Corps of Engineers for approval to install another 18 supports under washouts that span less than 75 feet.
Enbridge’s Line 5 support anchors have historically performed well, with no observed environmental impact. At no time has the safety or integrity of the Straits Crossing been compromised.
GPS data collected from in-line testing shows no measureable movement of the pipes under the Straits since the first GPS measurements were taken 10 years ago.
Looking for more information about our span management program? Learn more in our Line 5 Operational Reliability Report.