The last mine to be worked in Northwich was the Adelaide Mine in Marston but in 1928 even this had to be hastily evacuated due to flooding and with it saw the end of rocksalt mining in Northwich.
In the 1990s Vale Royal Borough Council (VRBC) announced that Northwich was sinking and that urgent work was required to infill four former mines – Barons Quay Mine, Witton Hall Mine, Penny’s Lane Mine and Newman’s Mine. Barons Quay was the largest and was also known as Leicester Street Mine. The situation had resulted in no new development being permitted in the town centre and property values and economic activity were depressed.
VRBC applied to English Partnerships, as part of the government’s Land Stabilisation Programme, for grant funding to carry out the work necessary and received funding and the project to infill the four salt mines to ensure the future stability of the town centre began. It was the largest project of its kind in the world, with 780,500 cubic metres of void filled at depths of 90m below ground.
The grout mix utilised Pulverised Fuel Ash, a waste product from power stations, making the process sustainable and cost effective. As the filling was taking place in rock salt areas the water used in the grout was actually brine to prevent the rock surround from dissolving. It was calculated that more than 97% of the material put in the mine was or would have become waste. The huge volume of grout was produced at a plant outside of the town centre and conveyed to the centre of the town via a drill bore made beneath a navigable river and adjacent to a Site of Biological Interest (SBI), reducing the impact to the town centre and SBI, but also considerably reducing the cost and time taken for the project and the health and safety risk.
The project was unique and completed on time and within budget thus allowing the planning moratorium to be lifted from the centre of Northwich, at the same time as releasing 32 hectares of land for regeneration.
The Northwich Salt Mines Stabilisation project won the following awards:
- Ground Engineering Sustainability 2008
- ICE North West Merit 2008
- Regional Monitor Excellence 2007
- Most Innovative Remediation Method, Innovation in Remediation 2006.