Aviation: Minnesota Department of Transportation

Tall Towers

Minnesota Structure Height Regulations

Click here to download the Minnesota Airspace Obstructions brochure.

A permit from MnDOT may be required for the following wind turbines and other tall, non-transmitting structures located outside the zoned territory of any public use airports with airport zoning in place:

That are more than 500’ AGL anyplace in the state, or

when the structure is more than 200’ AGL within three nautical miles of an airport and increasing by 100’ for each additional mile out to six miles and 500’, or·
that would increase an instrument approach minimum flight altitude or increase its flight visibility minimums, or
that would increase the minimum obstruction clearance altitude of a federal airway, or
that penetrate any of the following imaginary surfaces: primary, horizontal, conical, approach, or transitional surfaces.
Note: MnDOT is not authorized to issue a permit for a tower greater than 1000’ with a few exceptions.

A permit from MnDOT is not required for wind turbines and other tall structures.....

that transmit, and therefore require a permit from the FCC, or
that are within the zoned territory of any public-use airport that has airport zoning.

To apply for this permit, the proponent should send their request by letter or email to MnDOT-Office of Aeronautics, 222 E. Plato Blvd., Saint Paul, MN 55107-1618. Our contact person for these permits is Darlene Dahlseide. She may be reached at darlene.dahlseide@state.mn.us. The request should contain the proponents information, a point of contact, the exact location of the structures, a diagram of its location relative to the nearest airport runway, the elevation of the structure above ground level, the ground elevation at the base of the structure, and the plans for marking and lighting the structure. If the proposed structure is a wind turbine the elevation should include the maximum height at the top of the rotating blades, and the marking and lighting should contain the plans for illuminating or marking the blades in addition to the tower. The request should also contain a copy of the Federal Aviation Administration’s (FAA) airspace determination.

Obtaining an Airspace Determination from the FAA

The proponent for a wind turbine or other tall tower will usually have to file a notice with the FAA so that they can do an airspace study. This is done by completing an FAA Form 7460 that is available electronically on the internet at: https://oeaaa.faa.gov/oeaaa/external/portal.jsp. This site has a Notice Criteria Tool to assist proponents in determining if they need to file for an airspace determination with the FAA. The filing requirements are set forth in the Code of Federal Regulations, Title 14, Part 77. The basic requirements are:

(1) Any construction or alteration of more than 200 feet in height above the ground level at its site.
(2) Any construction or alteration of greater height than an imaginary surface extending outward and upward at one of the following slopes:
- (i) 100 to 1 for a horizontal distance of 20,000 feet from the nearest point of the nearest runway of each airport specified in paragraph (a)(5) of this section with at least one runway more than 3,200 feet in actual length, excluding heliports
- (ii) 50 to 1 for a horizontal distance of 10,000 feet from the nearest point of the nearest runway of each airport specified in paragraph (a)(5) of this section with its longest runway no more than 3,200 feet in actual length, excluding heliports.
- (iii) 25 to 1 for a horizontal distance of 5,000 feet from the nearest point of the nearest landing and takeoff area of each heliport.
(3) Any highway, railroad, or other traverse way for mobile objects, of a height which, if adjusted upward the following amounts exceeds the standard of (1) or (2) above:
- 17 feet for an Interstate Highway that is part of the National System of Military and Interstate Highways where over-crossings are designed for a minimum of 17 feet vertical distance,
- 5 feet for any other public roadway,
- 0 feet or the height of the highest mobile object that would normally traverse the road, whichever is greater, for a private road,
- 3 feet for a railroad,
- and for a waterway or any other traverse way not previously mentioned, an amount equal to the height of the highest mobile object that would normally traverse it.
(4) When requested by the FAA, any construction or alteration that would be in an instrument approach area (defined in the FAA standards governing instrument approach procedures) and available information indicates it might exceed a standard of subpart C of the Code of Federal Regulations, Title 14, Part 77.

Note: A letter of "non-objection" from the FAA as a result of their airspace study does not constitute an "erection permit" nor does an "objection letter" to the tower proponent by the FAA constitute denial of an "erection permit."

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Tall Towers