The said Department of Public Works shall grade, pave, or repave the said alleys or driveways, and construct or repair any retaining walls appurtenant thereto, in accordance with lines and grades established by the surveyor and regulator of the district in which said alleys or driveways and/or retaining walls appurtenant thereto are situate, and the said surveyor and regulator is hereby empowered to establish such lines and grades.
53 P.S. § 13872