Unless all bids referred to in Section 911.02 shall be rejected, the contract for the improvement of the street or alley involved shall be let to the bidder whom Council may deem capable of doing the work best for the public interest, considering responsibility, equipment and organization. After Council shall have entered into contract with such bidder, the Mayor shall at once return to all unsuccessful bidders their checks or deposits. The successful bidder, within fifteen days after the award of the contract to him, shall furnish bond with sureties to be approved by Council in such penalty as Council shall fix not exceeding the aggregate bid. After such bond shall have been given and approved, the deposit made by the contractor shall be returned to him; otherwise the same shall be forfeited for failure either to enter into contract or to furnish bond as aforesaid.