Starting in June 2003, NETL sponsored flyovers to survey approximately 70 sq. miles in the Wyoming portion of the Powder River Basin. Seven surveys were flown in 2003 over proposed and active CBNG areas. In July 2004, portions of two areas were reflown to determine changes in groundwater hydrology that had occurred in response to a year of CBNG activity. Two new areas with in-stream impoundments were flown also. In deployment of the airborne survey, a helicopter flies a prepared grid pattern about 200 feet above the ground. Dangling about 100 feet below the helicopter are two types of sensors, one that can detect wells by the magnetic properties of their steel casing and another that can detect in-ground conductors such as aquifers by the small currents that flow within them. Information from the survey is used to determine well location and the location, depth, and water quality of near- surface aquifers. In conjunction with the airborne survey, ground conductivity surveys are conducted on small subareas of the airborne survey to validate airborne results. Changes in ground conductivity provide a measure of produced water movement in near-surface aquifers.