 Active monitoring and deliberate protection may mitigate further rapid destruction making "in situ" preservation an option, but long-term survival can never be guaranteed.For very many sites, the costs are too great for either active measures to ensure "in situ" preservation or to provide for satisfactory conservation on recovery.Even the cost of proper and complete archaeological investigation may be too great to enable this to occur within a timescale that ensures that an archaeological record is made before data is inevitably lost.