For any real property with respect to which development has proceeded on the basis of a letter report or a geologic report which has been acknowledged by the City Engineer, no final inspection shall be completed or certificate of occupancy issued or performance bond released until the engineer or geologist who signed and approved that letter report or geologic report shall further certify that the completed improvements and structures conform to the descriptions and requirements contained in said letter or report. Provided, however, that improvements and structures may, with the consent of the City Engineer, deviate from the descriptions and requirements contained in the letter report or geologic report because of conditions which are discovered after acknowledgment by the City Engineer of the letter report or geologic report.