Site Characterisation Methods and Data Interpretation — The Drigg Site Characterisation

Abstract

Further site characterisation work is being undertaken to underpin the impact assessment of BNFL’s Drigg low level radioactive waste (LLW) disposal site. This site has been in operation for about forty years and is located approximately seven kilometres south of the Sellafield reprocessing plant in West Cumbria. The site accepts the majority of LLW produced in the U.K. which may be generated by hospitals and general industry as well as the nuclear industry itself. Historically, waste was tumble tipped into trenches which were then covered with an interim cap incorporating a plastic membrane. Waste is now placed in a concrete vault within steel Isofreight containers. This practice will continue through to the end of operations which is anticipated to be in the middle of the next century. Subsequently, a final closure cap will be emplaced over the disposal area.

The five year Drigg Site Characterisation programme was, therefore, set up in order to improve and build upon our current understanding of the geology and hydrogeology of the site. The first one and a half years are devoted entirely to data acquisition with the greatest activity surrounding the drilling and geophysical aspects of the programme Four years will be devoted to collecting a high quality time series data set of water levels, stream flows and meteorological variables and to produce a comprehensive interpretation of the hydrogeology of the site.

The programme to date has been very successful and the acquired information has enabled us to start refining our geological model of the site which will then be used to underpin our eventual conceptual hydrogeological model.