If archaeologists determine the site contains highly significant cultural remains, the adverse development effects on the site must be mitigated through a structured programme that is often long and expensive. Mitigation can include preservation by record i.e. the site is destroyed by archaeological excavation rather than by the development and meticulous recording transfers the physical traces in the earth to information in archives. Mitigation also includes construction techniques which ensure that archaeological remains are protected in undisturbed parts of the site or even underneath the development. An example of this type of mitigation is the Viking remains at York.