An area is qualified to become a specially benefited zone which:
1. Is a contiguous area, but the area of a zone may exclude wholly surrounded territory within its boundaries;
2. Is a depressed area;
3. Satisfies any additional criteria established by regulation of the Administrator consistent with the purposes of this chapter; and
4. Is entirely within a city or entirely within the unincorporated areas of a county, except where reasonable need is established for the zone to cover portions of more than one city or county.