A tunnel constructed for disposing of mine water. Long tunnels have been driven in some mining districts for the purpose of passing under the lower workings of several mines and tapping the water for the entire group. Where topographic features permit, a drain tunnel--more properly called an adit--may also be driven to serve a single mine. The chief advantages of a drain tunnel lie in saving the cost of pumping and eliminating the danger of the mine being flooded through failure of the pumps.