Whenever it is necessary to break through existing pavement for the purpose of constructing gas service facilities, the pavement and the base shall be removed to at least six inches (6") beyond the outer limits of the subgrade that is to be disturbed in order to prevent settlement, and a six inch (6") shoulder of undisturbed material shall be provided on each side of the excavated trench. The face of the remaining pavement shall be approximately vertical and straight. (1959 Code § 4-7-11)