INTERAGENCY REGIONAL SURFACE WATER AND GROUNDWATER MONITORING IN RELATION TO CBNG DEVELOPMENT IN THE POWDER RIVER BASIN

Coal bed natural gas (CBNG) production requires the removal of groundwater from coal seam aquifers. This reduces the hydrostatic pressure within the coal seam which allows the methane to desorb from the coal and flow to the production wells. The management of this water, and the drawdown related impacts from its removal are major challenges associated with CBNG development in the Powder River Basin (PRB) of Wyoming and Montana.

Water management practices may include discharge to surface waters. Since CBNG water quality is substantially different that of surface waters changes in surface water quality may result. Drawdown of water levels within coal seam aquifers will cause wells and springs which are located within the drawndown area and derive their water from the developed coal seams to have decreased yields.

In order to address these regional issues the BLM developed the PRB Interagency Working Group for CBNG (IWG). This group serves as a forum to identify, discuss, and find solutions to issues of common concern to government agencies involved in permitting and monitoring CBNG development. The Hydrology task group has developed surface water and groundwater monitoring plans to provide for integrated data gathering and analysis across the PRB. This integrated approach allows for actual impacts to be better understood, and depicted in their appropriate context.

To date, observable changes in surface water quality have not been observed, and drawdown of 20' or more from CBNG development extends out approximately 1 mile from the edge of development. This lack of impacts to surface waters is partly due to changes in surface water standards.