Topographic and Soil Constraints to Shale-Gas Development in the Northcentral Appalachians.

Worldwide, shale-gas development is becoming a feasible extraction practice; the northern Allegheny Plateau, USA is a region experiencing such development.  We used a GIS to investigate topographic and soil characteristics across existing and permitted gas pads in Pennsylvania, which could affect infrastructure development and reclamation success.  Results from this analysis, while regionally specific, can contribute knowledge for successful management of all shale-gas extraction.  Our results show that ~60% of existing and permitted pads occur on slopes at risk to some excess surface water movement and local erosion; pads occur most often on backslope landscape positions.  Pad development is occurring on soils with water tables within 50 cm of the surface, and soils with subsoil horizons (fragipans) that are known to result in surface drainage problems.  Most pads (73%) are developed on soils without drainage problems, but 21% are on potentially wet soils.  While shale-gas development disturbs a larger area than shallow gas development, this area is far smaller than typical coal-bed strip mining.  Aerial photography analysis from 2010 indicates a small proportion of pads have undergone restoration; restored pads were recontoured and planted with grass.  Restored agricultural lands returned to some crop production.  Grass, herbaceous, hardwood and conifer establishment appears suitable across the range of existing and permitted pads; however revegetation success may be limited be poor soil reclamation.  Invasive species establishment on the Plateau could be exacerbated by fertility and pH amendments during reclamation, especially if desired ground cover is out-competed by invasive species.