Here at Geo-Integrity Ltd. we recently undertook a Phase I Desk Study at Anderton, located north-west of Northwich in the county of Cheshire.
The Northwich area is well known for its extraction of salt since the Roman times. The salt in question belongs to the Northwich Halite Member which was deposited 220 million years ago during the Triassic Period. Similar to chalk, evaporates (natural salt deposits) are prone to both natural and artificial dissolution producing karstic landforms and subsidence which commonly include salt springs, indicative of continuing salt dissolution and the active nature of the karst processes.
Salt deposits, and dissolution, are also known to occur in Staffordshire, Worcestershire and across the Northeast, around Teeside and Middlesborough.
A paper titled Halite karst geohazards (natural and man-made) in the United Kingdom, Anthony H. Cooper, 2001 was used to obtain information on the history of salt extraction in the Northwich area. This paper records the Northwich area several times and describes the methods used to extract salt. Various techniques included wells to extract natural brine springs in the Roman times, boreholes with pumps commonly known as ‘wild brining’ which resulted in widespread subsidence during the 18th century, and conventional mining. Many of the mines were also flooded and pumped for brine this technique was termed ‘bastard brining’. This caused catastrophic mine collapse inducing surface subsidence on a very large and unprecedented scale around the Northwich area which created large lakes called meres and flashes.
The information compiled within this desk study has aided with identifying significant geotechnical hazards associated with salt dissolution in the site area. This then allows us to design an intrusive Phase II Site Investigation to aid with development design.
Here at Geo-Integrity we have undertaken many Phase I Desk Studies compiling relevant and useful data to aid with future site investigations. If you require a Phase I Desk Study please contact us on firstname.lastname@example.org or 01280 816409.