Lots Held in Single and Separate Ownership. Any lot held in single and separate ownership at the effective date of this chapter which does not meet the minimum area and bulk requirements of the zoning district in which it is located may be used for any use permitted in that district, provided that all yard, height, impervious coverage, and common open space requirements are met. If the plans for the proposed use shall be approved by the Zoning Hearing Board, after review of such plans to assure reasonable compliance with the spirit of the zoning regulations for the district, and the water supply and sewage disposal facilities are certified as adequate by the Borough Engineer, a variance from the yard and impervious coverage requirements may be granted.