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 base


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Originally 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.

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