Expiration. Every permit and variance provided for in this chapter, unless otherwise conditioned as part of the permit or variance, expires and is null and void without further action by the City if the use, building or structure for which the permit was issued has not substantially commenced operation, or in the case of new construction, the construction has not been substantially commenced, within two years of the date of approval or, in the case of appeals, the date the approval was affirmed or a denial was reversed. In the case the permit or variance is accompanied by a rezoning, the approval date is not until the effective date of the rezoning. For purposes of this section, "construction that has substantially commenced" means the installation of a building foundation(s).