Ground investigation in Greater Manchester.
From Bolton town centre to Trafford Park, Greater Manchester's ground ranges from stiff glacial clay and deep buried channels to peat mosses, coal workings and metres of made ground. We plan every investigation around it.
- Bedrock
- Coal Measures, Millstone Grit, sandstone
- Superficial
- Thick till, buried channels
- Coal legacy
- Bolton, Swinton, east Manchester
- Also watch for
- Made ground, peat, ground gas
The ground
What we usually find.
Manchester and Salford
- Varied bedrock. Pennine Coal Measures crop out widely in the north and east of the Manchester district, with Millstone Grit on the eastern edge and Sherwood Sandstone forming rockhead in the south.
- Thick glacial cover. Till forms an almost continuous cover on the lower ground in the south and west, and buried channels cut into the bedrock hold more than 80m of glacial deposits in places, including between Urmston and Eccles and under Chat Moss.
- Coal mining subsidence. Shallow workings around Swinton and near the City of Manchester Stadium have caused subsidence in the past, and there are many disused shafts and adits.
- Made ground and peat. Colliery spoil, quarry waste and refuse cover large areas, and Trafford Park sits on fill typically 2 to 3m thick, locally more than 8m. Chat Moss and Ashton Moss peat is locally over 3m thick.
Bolton
- In the coalfield. Coal Measures outcrop under most of the borough, which sits at the centre of the Lancashire coalfield, with Millstone Grit as well.
- Glacial lake deposits under the town centre, with around 20m of sand and gravel over sand and laminated clay and silt, and stiff clay till elsewhere.
- Peat and industry. Peat near Horwich, Red Moss and Smithills Moor, and a legacy of bleach and dye works, chemical and gas works, foundries and railway works.
What it means for your project
How we plan for it.
Deep or variable ground usually means cable percussion boreholes to get through the made ground and glacial soils, with careful logging and sampling where sands and clays alternate.
Coal Measures, peat and landfill can all produce ground gas, so gas and groundwater monitoring is often part of the scope near them.
Where a site lies within the Development High Risk Area, a coal mining desk check comes first, then rotary drilling for shallow workings where needed.
Brownfield sites need contamination testing alongside the geotechnical work.
Sources
British Geological Survey, Geology of the Manchester district, Sheet 85. Bolton Council, Contaminated Land Strategy (2015). Mining Remediation Authority, coal mining information.