What is the recharge rate of a coal seam aquifer?
Aquifer recharge is the process whereby precipitation or surface water infiltrates below land surface and begins to flow in an aquifer system. Ground water flowing through coal seams in the Powder River Basin has infiltrated along clinker or scoria ridges, in stream valleys, and in some cases in sandy soils during years of heavy precipitation. In the case of CBNG produced water, recharge occurs many miles away from development sites. According to the Montana Bureau of Mines and Geology, monitoring and groundwater modeling indicates somewhere between a few years and 20 years for recharge to occur. The question of recharge time is a challenging one. In coal mining areas, recharge occurs within a few years (typically 3 to 4). However, open pit or strip coal mines normally cover an area of only a few square miles, and because the area of impact is relatively small, recharge can occur rapidly. With CBNG extraction, the area of impact may be as large as many adjacent townships (1 township=36
