Ground investigation in Merseyside and Cheshire.
South and west of Wigan, sandstone takes over from coal, and the story becomes made ground, buried valleys, sensitive groundwater and a long chemical industry legacy along the Mersey.
- Bedrock
- Mostly Sherwood Sandstone
- Superficial
- Till, deep valley deposits
- Groundwater
- Principal aquifer, rising in Liverpool
- Also watch for
- Industrial fill and contamination
The ground
What we usually find.
St Helens
- Coal Measures, Permian rocks and Sherwood Sandstone, under glacial till, sands and gravels and wind-blown Shirdley Hill Sand. Coal has been worked here since at least the mid-16th century.
- Glass, copper and alkali industry legacy, which means contamination testing is part of most brownfield investigations.
Warrington
- Sherwood Sandstone under most of the borough, a Principal aquifer with drinking water abstraction in the north. Glacial deposits are typically up to 10m thick but reach about 70m in deep channels along the Mersey and Sankey Brook.
- Some coal legacy towards the north, peat mosses to the north-east, and former landfills and works across the borough.
Liverpool, Widnes and Runcorn
- Sherwood Sandstone under the city, mantled by till up to 20m thick on lower ground, with buried valleys under the Mersey. The sandstone can weather to dense sand to considerable depth.
- Made ground on the waterfront and docks, and groundwater that is rising as abstraction has fallen.
- A heavy chemical legacy in Widnes and Runcorn, including caustic soda and soap industry waste tipped on former marshland by the Mersey.
What it means for your project
How we plan for it.
On waterfront, valley and fill sites, deeper boreholes take us through made ground and soft deposits, often with groundwater monitoring.
Over the sandstone aquifer, boreholes are designed so they don't open a path for contamination to reach the groundwater.
On former industrial land, contamination and ground gas are usually the focus, alongside the geotechnical work.
Towards the coal measures in the east, a coal mining check comes first, with rotary drilling where needed.
Sources
British Geological Survey, Geology of the Liverpool district, Sheet 96. St Helens Council, Contaminated Land Inspection Strategy 2025 to 2030. Warrington Borough Council, Contaminated Land Inspection Strategy (2023). Halton Borough Council, Contaminated Land Strategy 2008 to 2013.