The History of Preesall Salt Caverns

Preesall has a rich history of salt mining. Exploration began here in the 1870s and continued for over a hundred years into the early 1990s.

In the 1880s the Fleetwood Salt Company was formed. It extracted salt by allowing water into a shaft in the salt deposit and then pumping the brine solution to the surface.

When the Salt Union, which was formed in 1888, put up prices, the Fleetwood Salt Company (not a member of the Salt Union) expanded production and in 1890 the Fleetwood Salt Works commenced production. In 1891 approximately 500 tons of salt were being produced and by 1897 this had increased to 53,000 tons.

The Ammonia Soda Works which began operation in 1924 was linked by pipeline across the River Wyre to the wells supplying the brine.

In the 1890s rock salt mining began in the salt beds which were approximately 140 meters (470 feet) below the surface. A second level at 275 meters (900 feet) was opened later. The salt when excavated was pushed in carts to the shaft and lifted out of the mine. The mining operation by United Alkali was capable of producing 140,000 tonnes of rock salt per annum at its peak.

In the 1960s ICI developed at Preesall one of the first modern salt solution caverns in the world using gas padding to preserve the salt roof, an effect first observed in the 1890s. This is done by injecting sufficient gas into the cavern to maintain a gas ceiling during the washing so the roof salt does not dissolve. This ensures cavern integrity and stability and prevents surface subsidence. Thereafter ICI washed many subsequent caverns at Preesall using this technique.

Canatxx has made sonar surveys of fourteen of these relatively modern caverns and they are in stable condition today, over forty years after their creation.

Salt mining activities at Preesall that occurred prior to the 1950s did create a number of sink holes. The activities that created the sink holes are well understood, well documented and have no effect on the new gas storage caverns.