Van Elle were selected by Volker Fitzpatrick to deliver treatment of potential abandoned shallow mine workings and mine shafts to enable the construction of two new distribution warehouses at the G-Park industrial complex, Skelmersdale.
Project Background
The scope of our works included designing and implementing a drilling and grouting regime to investigate and treat potential shallow mine workings of the Arley Seam at varying depths, along with the probing for and treatment of 3No. mine shafts.
Challenges
Initially, the team verified the areas to be treated on site through investigation drilling. This involved identifying where the coal seam was outcropping in the north of the site, and determining the point to the south of the site where the level of rock cover was sufficient to meet the specified 10:1 thickness ratio (as outlined in Ciria C758D). After completing the investigation works, the area between the two identified points was treated accordingly.
Several treatment positions were located underneath overhead power lines, meaning angled drilling had to be implemented to treat these areas.
During the mine working treatment works, 2No. unrecorded mine shafts were located. These required cordoning off, with a safety platform installed and probing to confirm the extent. This, along with changing availability of site areas, required good communication and flexibility to rearrange the sequence of works at several points throughout the project.
Van Elle Solutions
The treatment targeted shallow coal seams ranging from 4.2 meters to 30.7 meters below ground level across the site.
Boreholes were strategically drilled based on the level of grout taken during the initial treatment. All boreholes were drilled to a depth of 1.0m below the seam to ensure full coverage and thorough treatment of the seam.
Using four Casagrande C6 drilling rigs and a 14-person team, a total of 2217No. boreholes were drilled (including validation holes), covering approximately 50,000m of drilling, with around 540 tons of grout injected.
The works also included probing for and treatment of 3No. mine shafts (only one of which was recorded prior). The exact locations were confirmed by probe drilling, before the shafts were treated by staged pressure grouting.
Despite the challenges faced and increased scope of works, the works were completed four weeks prior to the end of the 14-week programme.
Client Feedback – “It was an absolute pleasure to work with the entire Van Elle team on this project”. Mehmet Colak, Site Manager