No person shall, without written permission of the Director, install any substructure, except manholes, vaults, valve casings, culverts, and catch basins at a vertical distance less than is necessary to place such substructure below the frost line if the Director concludes the substructure must be below the frost line. Nothing in this section shall impose a duty upon the permittee to maintain said specifications as required herein upon subsequent changes of grade in the surface unless the grade in said substructure interferes with the maintenance of, or travel on, a public street. (Ord. 2019-09, 5-9-2019)