U.K. Sends National Archives Underground

Information Management Journal, May/Jun 2004 by Swartz, Nikki

The United Kingdom's National Archives at Kew has begun the process of moving its records 150 meters (about 492 feet) below ground - from its current location at Hayes, Middlesex, to a salt mine in Winsford, Chesire.

The National Archives currently stores about 25 km (82,000 feet) of records at the Ministry of Defence site at Hayes. Kew has a total capacity of 161 km (528,215 feet) and about 145 km (475,722 feet) of that is full already. The office takes in about 2 km (6,562 feet) of records annually, so off-site storage is the only way forward, says David Thomas, director of government and archival services. He says storage is needed for about 25 km of records, which meets the environmental standards for the Storage of Archival Documents (BS 5454).

The first shaft of the salt mine was sunk in 1844 and is the oldest working pit in the United Kingdom. It now has more than 100 miles of underground roadways and produces rock salt, which is commonly used for deicing streets and sidewalks during the winter months.

According to Thomas, in World War II the mine was considered by the Public Records Office (PRO) as a place to re-house records during the V1 raids. It was rejected only because the British government, which was using it to store emergency food supplies, had installed a sprinkler system to protect valuable supplies against fire. The system used salt water, which was considered unacceptable for records. Later, after the sprinkler system and food were long gone, the mine was selected as a place for storing public records from Cheshire Record Office in 1998.

The mine offers a storage facility boasting low energy requirements, natural conditions that are a constant 14 degrees Celsius (57 degrees Fahrenheit) and 62 percent relative humidity. A small amount of dehumidification will adjust the relative humidity to BS 5454 standards. The records are stored in a series of rooms separated by blockwork walls with four-hour fire resistance. The salt walls have been de-scaled and cleaned with compressed air to remove all loose particles. Any remaining dust in the air will be filtered out. The documents will be stored in total darkness. A fire detection system is in place, although the risk of fire is considered extremely low. The mine is secure and because there are no sources of food, it is pest-free.

The major disadvantage of the mine, according to Thomas, is its distance from Kew. Because of this, after reviewing its storage strategy, the National Archives decided that it would only send its little-used records to the mine. These are mainly files that arc currently seen on microfilm at Kew. If people do need to see them, they can be retrieved from the mine within three business days - the same time it takes to get files from Hayes. To facilitate this, the National Archives has installed a terminal from DORIS, its document-ordering system, in the mine so that documents can be ordered and their production controlled in the same way as they are at Kew. DORIS was specified and built several years ago, but it was adapted for use in its new subterranean role.

Underground storage is more common in the United States. For example, Underground Vaults and Storage has operated a facility in a salt mine in Hutchinson, Kansas, for many years, while others who need records storage use abandoned gypsum or limestone mines.