General Order 64
Section VII
Detail Construction Requirements – Tower Lines
73 Flexible Towers.
When
steel supports or towers are used which are not capable of withstanding
practically as great a stress longitudinally as transversely, anchor towers
shall be placed at interval not greater than 10 spans, which towers shall be
able to withstand the combined longitudinal tension (under the loading of
Section V) of all conductors up to 10,000 pounds plus one-half the excess above
10,000 pounds.