Natural gas drilling in the Marcellus Shale region: well pad densities and aquatic communities

Few studies have examined the relationship between natural gas development and surface water quality using well pad density (the number of well pads/km(2)) as an indicator of potential impacts to aquatic life, specifically fish, salamander, and crayfish assemblages. We tested the hypothesis that animal assemblages, assessed by densities of ecologically important species, will differ among groups of watersheds with different well pad densities. In 2011, sites were sampled in Pennsylvania between July 13 and September 14 (N = 28; 10 = no well pads, 8 = low density, 10 = moderate density). We did not detect evidence of impact on fish, salamander, and crayfish assemblages. It should be noted that this study primarily assessed infrastructure-related impacts. Watersheds under investigations in this study area included no stream withdrawals for drilling and relatively low well pad density (<= 0.541 well pads/km(2)), which reduces the amount of roads and pipeline as well as sediment runoff reaching the stream from this and other infrastructure during development. In addition, setback and landscape limitations also kept well pads relatively far from surface waters, and these watersheds remained highly forested after development because most were in state forests. Therefore, these findings represent the least intrusive scenario for impacts to aquatic communities while extracting natural gas.