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2.4.1 Introduction

The historical site assessment is an investigation to collect existing information describing a site’s complete history from the start of site activities to the present time. The necessity for detailed information and amount of effort to conduct a historical site assessment depend on the type of site, associated historical events, regulatory framework, and availability of documented information. For example, some facilities – such as licensees following under nuclear regulations that routinely maintain records throughout their operations – already have historical site assessment information in place.

Other facilities may initiate a comprehensive search to gather historical site assessment information. In the former case, the historical site assessment is essentially complete and a review of the following sections ensures that all information sources are incorporated into the overall investigation. In still other cases, where sealed sources or small amounts of radio-nuclides are described by the historical site assessment, the site may qualify for a simplified decommissioning procedure.

The objectives of a historical site assessment could be:

  • To identify possible sources of radiological and non-radiological contamination and other hazards;
  • To identify the characteristics of the contaminants;
  • To identify related past activities or accidents that occurred on the site;
  • To determine the impact of the site on human health or the environment;
  • To provide input into the design of the characterization survey;
  • To provide an assessment of the likelihood of migration of contaminants;
  • To determine possible responsible parties.

The historical site assessment may provide information needed to calculate derived concentration guideline levels (DCGLs as described in Section 3.3.6) and furthermore provide information that reveals the magnitude of a site’s derived concentration guideline levels. This information is used for comparing historical data to potential derived concentration guideline levels and determining the suitability of the existing data as part of the assessment of the site. The historical site assessment also supports emergency response, removal activities, fulfils public information needs, and furnishes appropriate information about the site early in the site investigation process. For a large number of sites (e.g. currently licensed facilities), site identification and reconnaissance may not be needed. For certain response activities, such as reports concerning the possible presence of radioactivity, preliminary investigations may consist more of a reconnaissance and a scoping survey in conjunction with efforts to gather historical information.

The historical site assessment is typically described in three sections:

  • Identification of a candidate site;
  • Preliminary investigation of the facility or site;
  • Site reconnaissance.

The reconnaissance, however, is not a scoping survey. The historical site assessment is followed by an evaluation of the site based on information collected during the historical site assessment.