Any permit issued pursuant to SMC 12.48.020(B) shall contain a provision that in the event that any future improvement of the street to accommodate public travel necessitates the relocation or removal of an encroachment placed pursuant thereto, the permittee will relocate or remove the same at his sole expense. In such case the City shall serve on the permittee a written demand specifying the place of relocation or that the encroachment must be removed from the City street, and specifying a reasonable time within which the work of relocation or removal must be commenced. The permittee must commence such relocation or removal within the time specified in such demand and thereafter diligently prosecute the same to completion.