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• Introduction
• Site Setting
• Geology and Hydrogeology
• Investigations to date
• Current Understanding
  of the Site
• Strategy and Planning
• Regulatory Requirements
• Management Activities
  • Safety case
  • Best Practicable Means (BPM) Assessment
  • Groundwater Monitoring
  • Leak Detection
  • Site Procedures to Excavate and to Dispose of Soil
  • Phase 2 of the Sellafield Contaminated Land Management Programme
  • Data Information Management
  • External Stakeholders
• Supporting Information

Prior to the characterisation work carried out as part of the Sellafield Contaminated Land Study (SCLS), the understanding built up of the site was that:

• Explosives, explosive residues, asbestos, heavy metals and a range of organic compounds are potential contaminants of concern (PCOC) because of the historical use of the site as a Royal Ordnance Factory from 1941 to 1945.
• Sources of contamination as a result of nuclear operations are predominantly in the Separation Area.  The most significant leaks in the Separation Area are from six facilities, although minor spills from other buildings as well as pipelines and drains are likely to have contributed to the radioactivity in the ground.
• Migration of contaminants occurs in the groundwater. In addition to the natural characteristics of groundwater flow, the possible impact of features such as drains and building foundations as preferential pathways or barriers to flow is likely to be significant. The regional groundwater flow direction is from the high ground inland towards the coast in the south-west but local variations appear to exist, in particular an apparent westerly groundwater flow along the axis of the buried channel under Separation Area. Deeper migration pathways will probably enter the sandstone, where regions of enhanced fracture porosity associated with faults  could influence groundwater flow directions and complicate the simplified picture of contaminant migration parallel to the regional groundwater flow gradient towards the coast.
• The dominant radioactive contaminants in groundwater are strontium-90 (⁹⁰Sr), caesium-137 (¹³⁷Cs), tritium (³H) and technicium-99 (⁹⁹Tc).  The most mobile of these is ³H, which moves at the same velocity as groundwater, followed by ⁹⁹Tc and then to a much lesser extent ⁹⁰Sr. The least mobile of these in groundwater is ¹³⁷Cs. These contaminants are likely to be accompanied by other components of spent fuel reprocessing, such as nitrates. In addition, contaminants derived from typical industrial activity such as heavy metals, solvents, fuels and oils, may be present.

The work outside of the Separation Area carried out in the SCLS has shown that above the water table, levels of radioactivity are generally consistent with natural background levels. The majority of radioactive contamination occurs in the groundwater emanating from the south-east and south-west corners of the Separation Area and to a lesser extent from its western side. Separate small zones of groundwater with elevated radioactivity have been detected close to the River Calder. Within the wells it is rarely possible to distinguish specific contamination ‘fingerprints’ from individual buildings and it is likely that contamination from multiple sources disperses and merges together as it slowly migrates. The radioisotopes observed outside of Separation Area are either very mobile in groundwater, e.g. ³H and ⁹⁹Tc, or are less mobile but have slow decay rates, e.g. ⁹⁰Sr. As the individual radioisotopes migrate at different rates, the composition of contamination in the groundwater changes with distance from the source.

The SCLS work found only isolated occurrences of non-radioactive contamination of soil and groundwater outside of Separation Area and these were of relatively low concentration and limited in extent. Most of the soil samples containing non-radioactive contamination (primarily petroleum hydrocarbons and traces of solvents) were recovered from one location. Extensive field testing for contamination by explosives (TNT) and volatile organic compounds (solvents) during drilling operations produced no detectable results and there was no evidence of widespread contamination of groundwater by organic chemicals, either as a floating layer or in a dissolved phase. Some contamination of groundwater by inorganic chemicals (e.g. nitrate and ammonia) derived from spent fuel reprocessing operations was observed in the same area as the radioactive contamination emanating from the south west corner of the Separation Area.

An estimate of the total volume of soil contaminated with radioactivity above natural background levels has been made of the order of 13 million cubic metres. This figure is the best estimate available with the current data but has considerable uncertainty associated with it due to characterisation gaps in Separation Area which are being addressed by the project work under way. Of this estimated volume of contaminated soil, over 90% has been described at Sellafield as Very Low Level Waste (VLLW), the radioactivity being below 37 Bq/g and acceptable for disposal at one of the on site landfills. Of the remainder, approximately 1 million cubic metres is in the Low Level Waste (LLW) category (less than 4,000 Bq/g of alpha or 12,000 Bq/g of beta/gamma activity) which is acceptable for disposal at the Low Level Waste Repository in West Cumbria. There is no direct evidence of the volume of Intermediate Level Waste (ILW) in the ground (waste which is too radioactive to be disposed at the Low Level Waste Repository in West Cumbria) but an estimate of 1,600 m³ has been made from the known information of radioactive leaks in Separation Area.