GROUNDWATER BANKING: ONE MANAGEMENT OPTION TO MEET MARCELLUS WATER NEEDS

The Marcellus gas play underlies vast tracks of the Appalachian Basin where available ground and surface-water is highly variable and legal instruments often restrict withdrawals. From 1.0 to 10.0 mg are used per frack. Recovery and treatment of frack waters will not eliminate the need for makeup water to stimulate an estimated 10,000 to 20,000 gas wells that may be drilled within the basin. Aquifers are non-existent or supply minimal quantities of water for some prospects. Low flow characteristics of tributary streams, bypass flow requirements and aquatic ecosystem considerations restrict, even preclude seasonal surface withdrawals requiring costly trucking, piping and construction of on site storage facilities, disruptive of existing land uses.

Excess storm waters, seasonally available in many tributaries throughout the prospect, could be banked under appropriate hydrogeologic conditions for later withdrawal or stream-flow augmentation. Presence of permeable but unsaturated overburden or bedrock strata, confined aquifers that can be pressurized, available storage space in quarries, mines and existing pumping cones of depression are examples. Surface impoundments, infiltration galleries and wells that induce streambed infiltration can intercept sediment free stormwater. Where conditions favor, water can be piped and injected by gravity into permeable unsaturated overburden deposits or high capacity fracture zone-related bedrock well sites for later withdrawal. Chemical compatibility of mixed waters, maintenance of injection and recovery-well efficiencies together with management of potential pollutants contained in recharge waters are considerations. Four hydrogeologic settings illustrate the stormwater-banking concept that justifies research and demonstration efforts: Ridge and Valley, Allegheny Plateau and Laurel Highlands.