DEVELOPMENT OF A COALBED NATURAL GAS REGIONAL SURFACE WATER MONITORING NETWORK IN THE POWDER RIVER BASIN

Coalbed Natural Gas (CBNG) represents a significant new domestic energy source; however, there are environmental challenges associated with its development. CBNG in the Powder River Basin (PRB), which is a geologic structural basin, is produced by reducing the hydrostatic pressure within the coal seam by removing coalbed water. This decrease in pressure causes the gas (primarily methane) to desorb from the coal surface and flow to the pumping well. Environmentally sound management of produced water is a major environmental issue associated with the development of CBNG.

Common methods of CBNG water management include direct discharge to surface waters, treatment and discharge to surface waters, and storage in impoundments. All of these management methods have the potential to impact surface water quality and quantity.

In order for agencies to make informed decisions regarding CBNG permitting, disseminate data to the public, and evaluate impacts to water quality, a plan for a Regional Surface Water Monitoring Network was developed for the Rosebud, Tongue, Powder, Belle Fourche, and Cheyenne watersheds, which cover most of the PRB. This network was developed by the PRB Interagency Working Group's Hydrology Task Group, which includes technical specialists from a wide range of Federal, State, local, and Tribal agencies.

The monitoring network has allowed for the collection of consistent, comparable data by many agencies, and the coordination of network operations has avoided duplication of effort. Available funding has been less than needed for full network operations, but is focused to ensure that the highest priority sites are monitored appropriately. Data reports are prepared annually, and interpretive reports are prepared every four years to coincide with the preparation of every other Integrated Water Quality Report (303(d)/305(b)) prepared by the Montana and Wyoming Departments of Environmental Quality under the Clean Water Act.