In order to prevent or lessen the unnecessary hardship or practical difficulties in exceptional cases where it is difficult or impossible to comply with the strict letter of this chapter, the permittee or his designated agent shall have the option to apply for an exemption from any provisions of this chapter, to the city manager or designee. The city manager or designee shall exercise those powers on these matters in such a way that the public welfare is secured, and substantial justice done most nearly in accord with the intent and purpose of this chapter. (Prior code § 4506)