Part 303 (Wetland)
Enbridge has requested a wetland permit under Part 303 which impacts less than 1/5 of an acre. They have filed a mitigation plan. There is some work around rare plant species in the area that would be impacted and mitigation steps that will be taken by Enbridge.
Part 327 (Water withdrawal registration)
The application notes that Enbridge may request water withdrawals from the Straits of Mackinac (the Straits) on both the north and south for purposes of tunnel construction.
Part 325 (Submerged lands)
The Great Lakes Submerged Lands Act is used primarily in the regulation of marinas and structures built on the bottomlands of the lake. In this situation, it will assess whether construction and operation of the tunnel and the pipeline within lake bottomlands will impair public uses of the Great Lakes such as fishing and navigation. Enbridge submitted a letter expressing their opinion that Part 325 did not apply, but Enbridge did submit a permit application.
Part 91 (Soil Erosion)
Enbridge would need to get Part 91 (Soil Erosion) permit from Emmet and Mackinac County first and then the state would review those permits.
Part 31 (NPDES) Water Discharge
The application identifies potential sources of water for use during the construction process to be up to 1.99 million gallons a day on the north side from the Straits, and up to 1.99 million gallons per day on the south side from the Straits. Under the proposed tunnel construction plan, Enbridge or their contractors would excavate materials out of the tunnel in the form of a slurry. Some of the material would be processed, a portion reused, and the remainder sent to a settling pond. Water from this pond would be treated to meet water quality standards and then discharged into the Straits.
Both stormwater and groundwater that infiltrates into the shaft and tunnel will be captured and handled in a manner that treats contaminants before being discharged into the Straits. It is anticipated that approximately 1,500 gallons per day could be generated on the north side, and approximately 15,000 gallons per day on the south side. The permit application proposes systems that could handle flows up to five times higher than those amounts.
If constructed, the finished pipeline is first filled with water and pressured to ensure it has been properly constructed and does not leak. This is called a hydrostatic test. The hydrostatic test of the pipeline is a general permit under Part 31 – meaning Enbridge would submit a certification that the hydrostatic test would be performed in compliance with the general permit. In this case, a hydrostatic test would take approximately one million gallons of water. This would be a one-time use of water. The application mentions municipal water or a potential water withdrawal as the source of this water. After the test was performed, the water would be pumped into the settling pond, any contaminants removed, and discharged back into the Straits.
For Part 17 (Michigan Environmental Protection Act)
Whenever a permit issued by EGLE may result in pollution and impairment of the environment, the Michigan Environmental Protection Act requires the department to explore whether there are feasible and prudent alternatives to the activity covered by the permit. An example of this type of analysis is included in Enbridge’s application and was prepared by Enbridge in 2018 as part of its earlier agreements with the Snyder administration [link].