The COAL AUTHORITY Management of Risks to Groundwater from Past Coal Mining Keith Parker Head of Estates and Environment The Coal Authority

Issues facing the Coal Authority CA is responsible for liabilities of Coal Mining pre 1994 privatisation CA is responsible for liabilities of Coal Mining pre 1994 privatisation Typically collieries closed s Typically collieries closed s Modern deep collieries Modern deep collieries Often final closures in the coalfield Often final closures in the coalfield Often under Permo-Triassic cover Often under Permo-Triassic cover Mine Water levels still rising Mine Water levels still rising Decades needed for full recovery Decades needed for full recovery Potential for aquifer contamination Potential for aquifer contamination Via shafts, direct connections, faults, etc Via shafts, direct connections, faults, etc Minewater will contaminate aquifers with Minewater will contaminate aquifers with Salinity, Sulphates, Chlorides, Iron, Manganese, etc Salinity, Sulphates, Chlorides, Iron, Manganese, etc

Risk arises through- Risk arises through- development of Driving Head from surface inflows through worked coal measures results in migration into overlying aquifer strata via man made connections or mining induced fractures development of Driving Head from surface inflows through worked coal measures results in migration into overlying aquifer strata via man made connections or mining induced fractures Major Aquifers at risk

Key risk areas Aquifers at risk Aquifers at risk Triassic Sandstone Aquifers in Triassic Sandstone Aquifers in Yorkshire, Nottinghamshire, Derbyshire, Lancashire, Staffordshire Yorkshire, Nottinghamshire, Derbyshire, Lancashire, Staffordshire Magnesian Limestone Aquifer in Magnesian Limestone Aquifer in County Durham (East of River Wear) County Durham (East of River Wear) Aquifers historically impacted Aquifers historically impacted Magnesian Limestone Aquifer in Magnesian Limestone Aquifer in South Durham – Hartlepool South Durham – Hartlepool A new threat to Groundwater Resource A new threat to Groundwater Resource Requires strategy covering decades Requires strategy covering decades

East of Wear Case Study Dawdon Horden Area of East of Wear mining block Source Protection Zones in Magnesian Limestone aquifer, courtesy of Environment Agency

Groundwater Risk Source Source Initially hypersaline water – up to 40,000 mg/l chlorides! Initially hypersaline water – up to 40,000 mg/l chlorides! offshore Permian evaporites offshore Permian evaporites Driving head developing from inland collieries Driving head developing from inland collieries Pathway Pathway Direct links (adits) from coastal shafts into Limestone Direct links (adits) from coastal shafts into Limestone Potential links through mining induced fractures over workings Potential links through mining induced fractures over workings Receptor Receptor Magnesian Limestone Aquifer Magnesian Limestone Aquifer Public supply wells (c 35 million litres/day) Public supply wells (c 35 million litres/day) Some very close to mine adits Some very close to mine adits Cones of depression induce minewater pollution Cones of depression induce minewater pollution

The COAL AUTHORITY Time-scales dictated by rising minewater

The pollution threat in E Durham Water well Old colliery “water drift” Old colliery sea drift Capped colliery shaft Further inland along the River Wear uncontrolled discharges will also occur.

The COAL AUTHORITY

East of Wear Summary Horden offers only temporary protection Horden offers only temporary protection Insufficient capacity to control whole area Insufficient capacity to control whole area Risk due to limited connections to other workings Risk due to limited connections to other workings A second plant at Dawdon is required imminently A second plant at Dawdon is required imminently Two pump stations will achieve long term control Two pump stations will achieve long term control It will take several years of balancing water levels and abstraction rates It will take several years of balancing water levels and abstraction rates East of Wear aquifer on the path to full protection East of Wear aquifer on the path to full protection Many other areas where aquifers will need protection from rising minewater Many other areas where aquifers will need protection from rising minewater

Groundwater Policy - Approach? Working together Working together CA/EA Memorandum of Understanding CA/EA Memorandum of Understanding Common goals Common goals Different skills and duties Different skills and duties View the big picture View the big picture Groundwater is part of the environmental mix Groundwater is part of the environmental mix Solutions inevitably have other impacts (waste, global warming etc) Solutions inevitably have other impacts (waste, global warming etc) Consider the environmental ‘balance sheet’ when assessing problems and identifying solutions Consider the environmental ‘balance sheet’ when assessing problems and identifying solutions Don’t compartmentalise the issue Don’t compartmentalise the issue Prioritisation is key Prioritisation is key

The COAL AUTHORITY Thank You