In the construction of any new line of railway, grades shall be first given by the director of public works, the cost of which shall be paid by the company, and the work staked off to the required height of the tracks to be built, but this shall not be considered as the established grade proper, and shall be only for the purpose of making the grades uniform, it being considered impracticable to conform to every undulation of the streets as they now are in all portions of the city.
(1964 Code, § 31-18)