Effect of Coalbed Methane Produced Water Discharge on Native and Reclaimed Stream Channels and Aquifers at Coal Mines in the Powder River Basin. Campbell County, Wyoming

Abstract

Production of coalbed methane has released large amounts of ground water to native stream channels in the eastern Powder River Basin in the vicinity of the largest coal mines in the United States. Water is pumped from coalbed methane wells to relieve pressure in the coal seam and release methane gas from the seam into the well. Rapid drawdown of water levels in the coal due to coalbed methane production has been observed in mine monitoring wells. Optimally for methane production, water levels in the coal are kept near the top of the coal seam. Following a number of years of water production from coalbed methane wells, water levels in the coal aquifer decline to below optimal levels and pumping ceases. Discharge of coalbed methane produced water has rendered normally ephemeral and intermittent streams temporarily perennial and produced short and long term effects to surface and alluvial water quality. Through diversion or pumping, coalbed methane produced water has also flowed through reclaimed stream channels and temporarily changed the character of the channels. Within the mine sites, coalbed methane produced water has aided dust suppression efforts and reduced the need for pumping from deep water supply wells. Salts have been dissolved from native stream channels and often deposited on mine haul roads through road watering. Produced water flowing in reclaimed stream channels has aided wetlands establishment efforts, raised backfill water levels, and helped to enable pronounced changes in ground water quality.