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The outer surface, shown on Sarnia Airport Zoning plan No. 38-028-84-133, Sheets 1 to 9 inclusive and 11 and 12, dated March 17, 1986 is an imaginary surface located at a common plane established at a constant elevation of 45 m above the elevation of the airport reference point, except that, where that common plane is less than 9 m above the surface of the ground, the outer surface is an imaginary surface located at 9 m above the surface of the ground.
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