RECENT COMPLETION of a £2M abandoned mine infilling programme in the West Midlands has prepared a 16ha brown- field site for a £25M regen- eration project.
South York- shire-based drilling and grouting con- tractor Amco Ground Engin- eering put on a 50-strong team to carry out the work of locat- ing the aban- doned mine shafts and coal seams and then injecting the PFA and cement based grout.
Work was undertaken as a subcontract to Birse Construction which is constructing design and build industrial units at the former wasteland site for Richardson Developments.
The project - which involved working to greater than usual depths for this type of remediation - involved treating old workings of the 6m-7m thick Staffordshire Thick coal seam. Resulting voids down to a depth of 60m were considered to have the potential to affect the ground surface, and therefore needed treating.
The infilling operation was also complicated by the age of the workings, for which few - if any - reliable records existed. Locating mine shafts was carried out by drilling a grid of 12,000 closely spaced shallow boreholes totalling around 150km of drilling across the whole of the site.
For the infilling operation Amco drilled a further 2,800 primary and secondary boreholes down to 60m, totalling 168km, and through these injected 14,650t of grout into the abandoned mine workings, completing the work within the tight 20 week schedule.