Remediation of contaminated sites and buildings

With regard to remediation of contaminated sites from past practices and/ or accidents, a set of international safety requirements has been agreed [42]. When dealing with post-accident situations, it is assumed that all immediate protective actions have already been undertaken.

The objective of remediation is to achieve optimised arrangements for protection of the public, the workers and the environment that maximises the net benefit to society. The goal of remediation activities is the timely and progressive reduction of hazard and eventually, if possible, the unre­stricted release of sites. However, there are situations where this goal cannot be achieved in a practical manner and then it must be demonstrated that at least any unacceptable risks to human health and the environment has been removed. Overall remediation activities must be aimed at reducing existing exposures and averting the potential for prolonged exposures to occur in the future.

The risks associated with non-radiological hazards should also be assessed in combination with radiological risks to develop an optimised remediation strategy. In the choice of the optimised remediation option, a wide variety of factors must be considered, such as the impacts on health, safety and the environment; and technical, social and financial factors.

Following the general requirements for radiation protection the remedial measures and protective actions that are to be implemented must be justified and optimised. A generic reference level for aiding decisions on remediation is an existing annual effective dose to the most exposed group of 10 mSv from all sources, including natural background radiation. Nevertheless, remedial measures would often be justified below the generic reference level and national authorities may define a lower reference level for identifying areas that might warrant remediation in the prevailing circumstances.

For all situations in which the dose thresholds for deterministic effects may be exceeded, the implementation of remedial measures or restrictions on access is required. An existing annual equivalent dose of 100 mSv (inclu­sive of all existing contributions, including doses due to natural background radiation) to any organ justifies intervention under almost any circum­stances, although national authorities could specifically determine that such measures are not justified in exceptional circumstances.

With respect to radiation protection of workers, during the implementa­tion of remedial measures, the exposure of workers must be controlled under the system of radiation protection for practices and the relevant limits must apply [38].

A national remediation strategy is needed to specify, prioritise and to ensure remediation situations are managed in a manner commensurate with the risks associated with the contaminated areas and taking into account possible effects on neighbouring countries. An appropriate waste management strategy and an associated legal framework must be estab­lished that are capable of dealing with the waste that arises from the reme­diation of contaminated areas.

National laws and regulations covering such matters as occupational and public radiation protection, environmental protection, transport of radioac­tive material, mining of ores and food standards, which may be administered by different government bodies, must be applied in a coherent regulatory process. The legal framework must ensure that adequate funding mecha­nisms are available and that responsibilities are assigned for the financing of remedial measures and protective actions to be taken after remediation that are proportionate, manageable and economically sustainable.

In formulating the national remediation strategy, it may be necessary to involve a number of government and private organisations, and other stake­holders. Also stakeholders’ involvement must be considered in the defini­tion, implementation and verification of remediation programmes, and mechanisms for regular public information exchange on the implementa­tion of these programmes must be in place.

The identified responsible parties for the remediation of an area are responsible for all aspects of safety until completion of the remediation activities. To ensure an adequate level of safety, the responsible parties must perform safety assessments and environmental impact assessments; prepare and implement appropriate safety procedures; apply good engineering practices; ensure that the staff are trained, qualified and competent; estab­lish and implement a quality assurance programme; and keep records as required by the regulatory body.

The responsible parties must also: (i) prepare and maintain remediation plans; (ii) establish and maintain arrangements for emergency planning commensurate with the hazards associated with the remediation activities; (iii) report incidents significant to safety to the regulatory body in a timely manner; (iv) identify an acceptable waste disposal or storage site, as appro­priate, for the generated waste; and (v) ensure that all waste is transported safely and in accordance with the requirements for its transport.

In general, remediation of a contaminated area involves preparation and approval of a remediation plan; remediation operations; and management of radioactive waste resulting from the remediation activities. It needs to be based on collection and assessment of all available information of current and past activities at the site. Therefore an appropriate assessment of both the radiological and non-radiological impacts of the situation must be per­formed and the benefits and detriments associated with possible remedial measures, including the associated restrictions and institutional arrange­ments following remediation must be identified based on established refer­ence levels as part of the decision-making process.

The management of radioactive waste arising from the implementation of remedial measures is one component of the entire decision-making process taking into account the amounts, characteristics, properties and types of radioactive waste. The management of radioactive waste must comply with the international and national requirements for waste manage­ment facilities [39-41].

The remediation plan has to be subject to the approval of the regulatory body prior to its implementation and must state, as a minimum: the goal for the remediation; reference levels for remediation; the nature, scale and duration of the remedial measures to be implemented; the waste disposal or storage site, as appropriate; any post-remediation restrictions; and the monitoring and surveillance programmes and arrangements for institu­tional control for the remediation area.

The formal termination of the remediation and the release from further responsibilities of the organisation responsible for implementing the reme­dial measures, is based on evaluation and verification of compliance with remediation criteria. It is important to note that the termination of remedia­tion must be subject to the formal approval of the regulatory body.

In the event that the approved remediation goals have not been met, further assessment must be performed by the responsible remediation organisation and decisions taken on whether further remedial measures or additional restrictions are required. Any modification to already approved remedial measures are subject to the approval of the regulatory body.

During the implementation of remedial measures, consideration must be given to (i) radiation safety, transport safety and waste safety, general health and safety issues and environmental issues so as to minimise hazardous impacts, and (ii) the potential for prolonged exposure after the termination of remediation activities.

The area has to be monitored and surveyed regularly during remediation so as to verify the levels of contamination; to ensure compliance with the requirements for site release and for waste management, and to detect any unexpected levels of radiation. Where necessary, revisions to the remedia­tion plan have to be justified and subject to the approval of the regulatory body.

Before an area can be released for unrestricted use, a survey must be performed to demonstrate that the end-point criteria and conditions, as established by the regulatory body, have been met. The organisation respon­sible for the surveillance and verification of activities must be clearly identi­fied. An appropriate programme, including any necessary provisions for monitoring and surveillance, has to be established to verify the long-term effectiveness of the completed remedial measures.

If surveillance and maintenance are required after remediation is com­pleted, a surveillance and maintenance plan must be prepared and periodi­cally reviewed by the responsible organisation. The plan is subject to approval by the regulatory body.

A final remediation report, including any necessary final confirmation survey, must be prepared and retained by the responsible party with other records, as appropriate, and a copy submitted to the regulatory body for information.

As part of the overall management system, arrangements for archiving, retrieval and amendment of all important records concerning the initial characterisation of the area, the choice of options for remediation and the implementation of remedial measures, including all restrictions and the results of all monitoring and surveillance programmes, must be established and maintained in all cases.

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