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Another Enbridge Pipe Dream ----

High Voltage Power Lines Inside Enbridge Line 5 Tunnel  

Gary L. Street, M.S., P.E.

May 17, 2021

Enbridge continues to claim a Line 5 tunnel at the Straits may include high voltage power lines for transmission of electricity to the Upper Peninsula.  Let’s examine that proposal.

Unlike the lamp cords in your home, it is extremely dangerous – often fatal - for workers who get too close to high voltage the power lines when they are activated.   In this case, “high voltage” means 138,000 volts and “too close” means no closer than 11 feet.  See Appendix 1, item 3.

The current power lines that run under the Straits are owned by American Transmission Company (ATC), and operate at 138,000 volts - i.e., “high voltage”.

A recent sketch of the proposed Line 5 Tunnel is shown in Figure 1.  Figure 1 and Appendix 1 explain why the proposed tunnel is far too small to accommodate 138,000-volt power lines.

Figure 1

Considering the height of the Concrete Invert (about 5 feet), as shown in Figure 1,there is roughly 15 feet from the top of it, to the top of the tunnel.  Of course, the power lines will be below the top of the tunnel – perhaps 2 feet below (maybe more, maybe a little less) leaving about 13 feet from the Concrete Invert to the power lines.

Let’s assume a person assigned to work in the tunnel is 6 foot tall.  6 feet height + 11 feet minimum distance = 17 feet.  Oops!  We are now 4 feet too close to the 138,000-volt power lines.  And that also assumes the 6-foot worker never raises his/her hands above their head.

There is no way a 6-foot person can work in this space and maintain 11 feet of separation from the power lines.  It’s not possible.

What does American Transmission (ATC) Think?

“ATC does not believe that installing high voltage electric lines in close proximity to high pressure oil or gas lines is a good idea,” Vice President of External Affairs Tom Finco said in a ….. letter to the Chippewa Ottawa Resource Authority, an inter-tribal management body.

Summary

• 138,000-volt power lines must not  be installed in the proposed Enbridge tunnel.  The tunnel is far too small.  It would create an extremely hazardous - and OSHA illegal - work place.
• American Transmission makes it clear:  They will not put their high voltage power lines inside a tunnel that transports highly flammable materials.
• Enbridge must discontinue promoting the false claim that the tunnel can accommodate high voltage power lines.
• Enlarging the tunnel diameter from 20 feet to 25 feet (which allows little “safety factor”) would increase the cross-sectional area from 400 ft2 to 625 ft2.  An increase of 56%, leading to an enormous construction cost increase.  If the inside diameter were increased to 30 feet, the cross-sectional area would be 125% greater, and further escalation of costs.

Appendix 1

What Is a Safe Working Distance from Power Lines?

by Sarah Lambert - Updated September 30, 2017

Workers look to the Occupational Safety and Health Administration (OSHA) to understand how close they should be to power lines. As a general rule, 10 feet is the minimum safe working distance from power lines. To follow exact regulations, you should know the voltage of the power lines that you will be working near.

• OSHA Regulations

OSHA regulations dictate that all personnel and tools be a certain distance from overhead power lines whenever work needs to be done near them.

• Voltage Requirements

The distance you must be from power lines depends upon the voltage of those lines. The higher the voltage, or electric potential of the lines, the farther you should be from them when working.

• Eleven to Eighteen Feet

If the power line is 51,000 to 138,000 volts, you should work at least 11 feet away. If it is more than 230,000 volts, work at least 13 feet away. Finally, if it is 500,000 or more volts, work at least 18 feet away.

• Additional Requirements

In addition to distance requirements, OSHA law also requires that when work is done near power lines, the lines should be grounded or de-energized. This means that the lines must be on the ground or turned off to prevent accident or injury