In the nineteenth and early twentieth centuries, Halkyn Mountain in north-east Wales was one of the most important lead mining areas in Britain. Mining had a dramatic effect on the landscape and created distinct communities. As lead miners probed deeper to reach new veins, water levels rose in shafts and passages. Empowered by Acts of Parliament, mine owners and syndicates embarked on drainage schemes and extensive tunneling, which enabled the flow of water away from the mines and access to the ore. Above ground, there were local anxieties over the spread of mine shafts and the impact of drainage tunnels on local water supplies. Tunnel expansion was subject to Parliamentary hearings and geologists appeared as expert witnesses to discuss the nature of carboniferous limestone and underground water flow.