Full Description ADOPTED_FROM:EN ISO 18557:2020 ISO 18557 presents guidelines for sampling strategies and characterization processes to assess the contamination of soils, buildings and infrastructures, prior to remediation and/or to check that the remediation objectives have been met (final release surveys). The principles presented need to be appropriately graded as regards the specific situations concerned (size, level of contamination?). It can be used in conjunction with each country\'s key documentation. ISO 18557 deals with characterization in relation to site remediation. It applies to sites contaminated after normal operation of older nuclear facilities. It could also apply to site remediation after a major accident, and in this case the input data will be linked to the accident involved. ISO 18557 complements existing standards, notably concerning sampling, sample preservation and their transport, treatment and laboratory measurements, but also those related to in situ chemical and radiological measurements. References in the Bibliography contain links to appropriate documentation and techniques as required by individual member countries. ISO 18557 does not apply to the following issues: execution of clean-up works, sampling and characterization of waste (conditioned or unconditioned) or to waste packages. It does not apply to groundwater characterization (saturated zone). Given the case-by-case nature of site remediation and decommissioning, the principles and guidance communicated in ISO 18557 are intended as general guidance only, not prescriptive requirements.