The council shall make its own determination as to whether the proposed variance meets the standards outlined in Section 23.93.040(1), (2) and (3) and may approve, modify, or disapprove the decision of the planning commission. Any significant modification of the variance not previously considered by the planning commission during its hearing, may be, but is not required to be, referred to the planning commission for report and recommendation. The planning commission shall not hold a public hearing on the proposed modification. Failure to report upon the proposed modification within forty (40) days, or such longer period that the council may designate, shall be deemed an approval of the proposed modification.