APPLICATION OF ENVIRONMENTAL RADON MONITORING TO REMEDIAL ACTION PROJECTS - A CANADIAN CASE-STUDY

Historic low-level radioactive wastes date back to 1933 in Canada, whe n a radium refinery began operation in Port Hope, Ontario. Residual wa stes and contaminated soils resulting from the waste management practi ces carried out in the early years of radium and uranium production we re discovered in the mid-1970s. The lack of a permanent disposal site for low-level radioactive wastes limited a large-scale cleanup to incl ude developed properties only. As a result, substantial quantities of contaminated soils remained in a number of large undeveloped areas, pe nding the availability of a permanent site. Radon emanation from radiu m contaminated soils located at, or near, the ground surface is a pote ntial route for radiation exposure to neighbouring residents. Atmosphe ric radon concentrations have been monitored in Port Hope since 1985, and radon concentrations above the range of local background concentra tions have been measured adjacent to the historic waste site described in this paper. Interim remedial work completed at this site in 1990 r esulted in an 85 to 100% reduction in incremental radon concentrations at the boundaries of neighbouring properties. A follow-up program to identify any remaining source(s) of elevated outdoor radon was initiat ed. Integrated radon measurements, as well as gamma radiation measurem ents, radon flux and radon grab sample measurements at this site, iden tified a localized area adjacent to the original remedial work area as the source. Further remedial work was carried out in late 1994 to eli minate the source of elevated radon which remained at this site. Recen t data indicate that atmospheric radon concentrations are now within t he background range. This remedial work project illustrates both the r ole of environmental radon monitoring in assessing the need for interi m work, and its usefulness in providing quantifiable measures of effec tiveness. Technical issues associated with the measurements and the an alyses of the data are also discussed. (C) 1996 Elsevier Science Ltd.