Withdrawal and/or modification of bids may be allowed upon written notice by the bidder concerned to the PBAC prior to the time and date set for the opening of the First Envelope as specified in Section 5.2. No bids shall be modified or withdrawn after this time. Bid modifications received after said period shall be considered late and will be returned unopened. Bids withdrawn after the bid opening date shall cause the forfeiture of the Project Proponent's Bid Security.