Wartime legacy unearthed in Harwell clean up
A massive clean up operation is under way at the Southern Storage Area at the UKAEA's Harwell site. This case study reports on how the final phase of one of the country's most challenging land remediation programmes is being carried out on a site which was a wartime RAF baseOriginally an RAF airfield, the Harwell site in Oxfordshire, which is the headquarters of the United Kingdom Atomic Energy Authority (UKAEA), was taken over by the Ministry of Supply in 1945 to carry out research for the UK's nuclear energy programme.
UKAEA's focus for the past six years has been on dismantling its redundant nuclear facilities and environmentally restoring the site. Significant progress has been made with decommissioning its research reactors and removing major radioactive facilities.
The site restoration programme at Harwell aims to progressively remove the site from the constraints of nuclear regulation to increase its potential as an international business centre. Harwell is already host to a number of new and established companies and operates an innovation centre for fledgling businesses.
Southern Storage Area
Clean up of the SSA is one of UKAEA's largest decommissioning tasks at Harwell and is one of the most challenging land remediation programmes in the UK.
The Southern Storage Area is a seven-hectare site on the southern border of UKAEA Harwell. It is known locally as the "bomb dump" because it was the RAF munitions store during the Second World War. The Southern Storage Area is now derelict, the former RAF buildings have been removed and in the interim it was used by UKAEA to dispose of various materials.
UKAEA then used the site from 1952 to the mid 1960s for a variety of waste handling operations and for the burial of mixed chemical and beryllium-contaminated wastes. Beryllium is a light and strong material sometimes used in the aerospace and nuclear industries and can be hazardous if inhaled as dust. The wastes contain very low levels of radioactivity.
Work to restore the SSA has been ongoing since the 1980s and the final phase of work will involve returning the land to a safe and clean condition suitable, for example, as a recreational area. This is the last stage of a phased clean-up programme that has been ongoing since the 1980s. In addition, the restoration is a requirement before housing development can begin on the neighbouring Chilton Field site. The options for restoration of the SSA have been carefully considered using a public Environmental Assessment process. The Vale of White Horse District Council led this process as planning authority and Oxfordshire County Council, the Environment Agency and the Health and Safety Executive were involved.
Clean up programme
The site was initially cleaned up in the 1980s, when the buildings and surface wastes were removed. In the 1990s extensive surveys were completed to plan final restoration of the site. The site is currently secure and safe but it requires further clean up to remove remaining wastes and as a final check on its suitability for public access.
The remediation programme has involved the systematic excavation of the contaminated areas to one metre below meadow level. The excavated waste has been scrupulously examined, classified and disposed of accordingly.
Public safety has been a key priority throughout the project and has dominated the way that the work has been approached. As well as the risks inherent with any kind of remediation programme, the project team has also had to contend with the discovery of bomb casings, practice bombs and munitions. This has on occasion set the site's full-scale emergency plans into action. This has involved calling out the RAF bomb disposal unit, evacuating the school and nearby houses meaning that extreme caution is necessary in all aspects of the site work. Each cubic centimetre of the site has been painstakingly inspected to identify any potential explosives of either a chemical or military nature.
UKAEA has a small project management team at the SSA responsible for up to 40 contractors working on specific activities at any one time.
There are several remaining issues to deal with on the site. There are six small pits (total 370m?) containing laboratory wastes, including low levels of radioactivity, which has resulted in low level chemical groundwater pollution. This pollution has been dealt with by using a groundwater treatment plant on the site which has nearly completed its task. In addition, there are five larger pits (total 4,600 m?), which contain industrial wastes including beryllium contaminated materials. The remaining Southern Storage Area land has some minor areas of pollution removed and considerable quantities of RAF munitions removed or detonated in site by the Emergency Ordnance Department (EOD) that require clean up and may have some remaining RAF munitions. The area will undergo thorough checking before it can be declared clean.
UKAEA's specialist decommissioning teams follow a thorough and proven process for removing the waste is. All known wastes are removed from the pits and the rest of the site is thoroughly dug over searching for other wastes. Each stage of the process is carefully monitored.
Dealing with potential hazards
The principal hazard to members of the public from the works is the accidental release of hazardous dusts from the site. Given the amounts and types of material on the site there is not a serious hazard to the public, but nonetheless UKAEA will implement a precautionary approach to all works and excavation has taken place within tented enclosures.
Excavation of the pit wastes will be undertaken using methods that prevent dust generation, as far as practicable. All work will be subject to careful checking, monitoring and independent regulation.
Extensive monitoring of air quality both at the workplace and on all the site
boundaries will be undertaken to ensure the protective measures are effective.