Presence of Coal Seams at Sovereign Fold

Commencement date – August 2021

Completion Date – December 2021

The development site had several challenges due to the presence of coal seams and historical mining activities. E3P investigation revealed the risk of potential instability at the surface due to workings beneath the site. To mitigate this risk, E3P was commissioned to prepare a specification for the treatment of abandoned mine workings and validate the stabilisation works, as well as consult with the Coal Authority regarding the potential impacts of off-site shafts within influencing distance of the site boundary.

The challenges faced during the development were:

Uncertainty about the full depth and extent of workings beneath the site due to the number of seams mapped under the site.
Historical coverage of trees/woodland made mine stabilisation works challenging, which required site-wide drill and grout treatment before finalising the foundation schedule.
Treatment of mineshafts outside the application boundary was not possible, necessitating an alternative stabilisation solution for plots within influencing distance.

E3P coordinated and supervised the drill and grout treatment works, identifying 43 locations requiring grout injection due to local extraction and collapsed workings. The extent of shallow workings was determined through careful data collation and cross-sectional analysis, allowing for the use of raft foundations in limited areas, while mass trench and piled foundations were used elsewhere.

E3P also reviewed available data with regards to the Presence of Coal Seams and negotiated with the Coal Authority to propose a watching brief during ground stripping/excavation in garden areas within the zones of influence of off-site mine shafts. The proposal included the installation of stabilising geo-grids in gardens within the shaft zones of influence, for which E3P designed a specification that was accepted by the Coal Authority, negating the need for further investigations. Overall, E3P provided effective solutions to mitigate the risks posed by the historical mining activities, allowing for the successful completion of the development.