IMPACTS OF SEDIMENT RUNOFF FROM OIL AND GAS PRODUCTION ACTIVITY ON THE WATER QUALITY OF STREAMS IN ADJACENT WATERSHEDS, ALLEGHENY NATIONAL FOREST, PENNSYLVANIA

Marcellus gas production activities result in the construction and use of unpaved access roads. This study examined the current impacts of unpaved roads built to service the oil industry in the Allegheny National Forest on sedimentation and stream ecology. Two adjacent watersheds, similar in size and topography but having low and very high road density, were identified for study. The Grunder Run study area has a contributing drainage of 12.4 square km, with a road density of 6.9 km per square km of drainage, and represented a watershed developed for oil and gas extraction. The Hedgehog Run study area served as a forested control site with a contributing drainage of 11.1 square km and road density of 1.2 km per square km. Both streams were instrumented with stream flow and water quality monitors with data transmitted via satellite telemetry. A rainfall simulation device was used to create repeatable rainfall events (1.5 cm per 30 min) and to collect sediment load data from selected 30.5 m sections of road. Of 14 sites measured, average sediment runoff equaled 11.2 kg per study, or 370 kg per kilometer for each 30 min simulated rainfall event. As a practical tool for the preliminary evaluation of sediment runoff potential, an index was developed using a GIS model based on high resolution elevation data derived from LIDAR to evaluate topographic parameters that significantly affect rainfall/runoff relationships for road segments. The model is being used to prioritize unpaved road-segments prior to the implementation of restoration and sedimentation management plans. Macroinvertebrates were collected during the early summer, late summer and fall from two sites each in study area. Surprisingly, macroinvertebrate fauna in both watersheds were similar in terms of overall taxa richness, EPT (mayfly/stonefly/caddisfly) richness values, and diversity indices. Preliminary analyses indicate that the presence/absence of selected macroinvertebrate indicator species may provide more specific indication of road-generated sediment impact than do total population indices.