Time for another site investigation, the team are equipped and ready to get stuck in with a ground investigation commencing next week. The site in question; a large open space used by the public for dog walking and with bridleways going through it. Not so exciting on the surface, but what’s underneath the site is sure to be! Geology on site is indicated to comprise primarily of Pennine Middle Coal Measures, however, one of DCE’s main focuses will be to locate at what depth the coal outcrop that crosses site is at.
That’s not all, to spice things up, a high pressure gas pipeline goes through site from the southern-western corner through to the north-western corner as shown in the plan above. DCE have been in touch with Cadent to arrange that the proper precautions are taken; all exploratory holes have been moved 15m away from the pipeline as well as the use of Emtek panels when needing to cross the pipeline with our vehicles. The scope of works for this particular project goes as follows; 10 No. Rotary Holes drilled to varying depths between 20m-30m bgl, 7 No. Rotary Open Holes drilled to varying depths between 20m-30m bgl, 14 No. Trial Pits to a depth of 3m bgl and 8 No. Cable Percussion holes drilled to a depth of 7.5m bgl.
The aim of this ground investigation is to delineate any potential contaminants sources in addition to allow identification of any potential geotechnical constraints. Let’s see what the team unearths, the site is on a coalfield after all.
After almost three weeks worth of work, it has been hard going for the team in Wigan. Ground conditions have been reduced to a quagmire, the rigs and vehicles used to cross the site have been getting into difficulty. However, our team loves a challenge, slowly but surely, the scope of works is proceeding as expected, below are some photos of the most recent ground conditions. More news to follow!
Thankfully ground conditions had dramatically improved compared to the last time DCE were in the neighbourhood. Rotary Drilling in Wigan was the last scope of works on the list, the depth of the holes varied between 20m and 30m below ground level, this varying depth was in order to identify any shallows workings and seams near the coal outcrop across the site. 10 No. rotary cored holes and 7 No. rotary open holes were undertaken.
The final reports have been sent and DCE have finished the primary ground investigation work, monthly monitoring visits will be carried out over the course of six months. Discovery’s main findings are summarised below:
-Made Ground extends to 5.3m depth and has variable composition and strength.
-The Worsley 4 Foot coal seam subcrops on the site and has been positively identified in RC107 at an elevation of 28.40 m AOD. The seam dip has been calculated to be about 7 degrees and in a southerly direction. Loss of flush, poor recovery and evidence from drilling on the site to the east has confirmed provisionally the dip angle and direction.
-There has been no soil contaminant exceedances in soil.
-Made Ground and localised areas of natural ground will need moisture conditioning with lime or cement, the treatment is required in order to support the development loads without risk of unacceptable settlements taking place.
-Traditional pad foundations are expected to be suitable for the site once Made Ground has been treated and any higher moisture content natural materials have been conditioned.