Enbridge, the Canadian pipeline company, is interested in building a 6.4-km long tunnel beneath the Straits of Mackinac, the Michigan waterway that connects Lake Huron and Lake Michigan -- an ecologically sensitive area and popular tourist destination -- constituting two of the Great Lakes. The company had applied last Wednesday for state and federal authorization to construct the short oil pipeline.

Enbridge submitted a joint application to the Michigan Department of Environment, Great Lakes and Energy and the U.S. Army Corps of Engineers. Approval from both is needed for the project to go forward.

Amber Pastoor, the Enbridge Project Manager, said “the Great Lakes Tunnel Project unequivocally is the most practical, long-term solution to delivering a secure energy supply to the region while enhancing environmental safeguards in the Straits.”  Line 5 each day carries 23 million gallons (87 million liters) of crude oil and natural gas liquids used for propane. It divides into two pipes beneath the straits.

Environmentalists have long sounded the alarm about an oil tunnel beneath the Michigan waterway. They maintain that Line 5 is vulnerable to leaks after lying on the bottom of the straights for 67 years.  Enbridge says it is in good condition and is monitored closely but agreed to spend $500 million on a replacement that would be housed in a tunnel drilled through bedrock underneath the straits.

Democratic Gov. Gretchen Whitmer also has spoken against the pipeline and tried unsuccessfully to negotiate an accelerated timeline for building the tunnel, which Enbridge plans to start next year and finish in 2024.

Michigan's environment department will take 30 days to determine whether the application is complete, spokesman Scott Dean said Wednesday.

In view of stay-at-home policies resulting from the coronavirus pandemic, “we are adapting our processes to handle these and other permit requests in a way that protects public health, complies with the law, and allows meaningful public participation and input,” Dean said.

Plans call for beginning work on the Lower Peninsula side of the straits and heading north, the company said, adding that the 25-acre (10-hectare) work site would maintain a 115-foot (35-meter) buffer from the Lake Michigan shoreline.

The north end of the tunnel boring will be on a 16-acre (6.5-hectare) parcel that Enbridge owns. The buffer space on that side of the straits will be at least 50 feet (15.2 meters), the company said.