2.1.19 When entering into a PPP-DBFO deal, the public agency and the private provider should recognise that there will be a need for changes to the service delivered over the 15-30 year life of the contract. Where necessary, some aspects of the service requirements or service delivery methods can be changed, subject to agreement by the public agency and the private provider on cost. To ensure that agreement is reached quickly, the public sector can require a competitive tender for any works involving changes over a certain threshold. If a dispute arises regarding the scope of the changes, there is a binding dispute resolution procedure in the concession agreement.