The stabilisation of abandoned chalk mines in Chantry Lane, Hatfield

Abandoned chalk mines are a significant risk to people, property and infrastructure. Due to the age of these features and historically poor record keeping, land above chalk mines has often been developed unknowingly, whilst the inadequate treatment of known workings is a major risk. In recent years there has been an increased public awareness in the subject following a number of high profile collapses in southern England. Ground remediation, either before or after a mine collapse can be costly, time consuming and inconvenient to repair. The allocation of responsibilities and liabilities surrounding these issues remains unclear.

This paper outlines the Chantry Lane chalk mine remediation project which further developed the holistic investigation, stabilisation and successful validation of chalk mine workings under and around live residential properties in Hatfield, Hertfordshire. Details are provided of the integrated approach used to effectively assess and treat the ground, including; investigation, drilling methods, infilling materials, the development of a specialist grout mix, injection methodology and validation. Using advanced and developed techniques ensured efficient safe project delivery whilst minimising environmental impact. Safety was of paramount importance for the workforce, public and residents that were present throughout the scheme.