The "permit granting authority" shall mean the Board of Zoning Appeals.

Unless otherwise specifically designated under this bylaw, the special permit granting authority shall be the Board of Zoning Appeals.

Unless a lesser time is provided in this bylaw or specified in the decision of the special permit granting authority, a special permit shall lapse not later than 24 months, inclusive of such time required to pursue or await determination of an appeal under MGL c. 40A, § 10, from the grant of such permit if a substantial use thereof has not sooner commenced except for good cause or, in the case of a permit for construction, if construction has not begun by such date except for good cause.