WAC 468-240-180. Obstruction lighting standards—Trees

A line of trees, with the individual trees located less than 150 feet apart, or a tree covered area should be lighted as an extensive obstruction in the manner set forth in the "E" specifications for prominent buildings and similar extensive obstructions, with the obstruction lights mounted on poles or towers, of a height slightly greater than the height of the outstanding trees. Individual trees and widely spaced trees should be lighted in accordance with the following specifications: (1) Specification "B-1." Poles of a height slightly greater than the height of the outstanding tree(s) should be installed adjacent to the tree(s) and lighted in accordance with the specifications hereinbefore prescribed for individual towers, poles and similar obstructions of a corresponding over-all height above ground, or water if so situated.