To extract the gas, a steel-encased hole is drilled into the coal seam below ground. As the pressure within the coal seam declines due to natural production or the pumping of water from the coalbed, both gas and "produced water" come to the surface through tubing. Then the gas is sent to a compressor station and into natural gas pipelines. The produced water is either reinjected into isolated formations, released into streams, used for irrigation, or sent to evaporation ponds. The water typically contains dissolved solids such as sodium bicarbonate and chloride but varies depending on the formation geology.