Human activities have led to declines in stream functioning and stream restoration seeks to reverse this trend. Longwall coal mining, an underground full-extraction method, can cause surface subsidence, affecting streams by creating a series of deep pools that trap sediment, reduce habitat diversity, and impair macroinvertebrate and fish communities. Mining effects on streams must be mitigated to maintain the functions, values, and foreseeable uses of streams. Gate cutting is a procedure that alleviates pooling by reestablishing the stream grade, accompanied by procedures that stabilize the channel, restore substrates, and enhance in-stream and riparian habitats. We evaluated effectiveness of gate cuts at restoring streams affected by subsidence pooling at 18 independent restoration sites over two mines in southwestern Pennsylvania, U.S.A. At each site, sampling stations were established to monitor effects of mining subsidence and its restoration on macroinvertebrates, fish communities, and habitats. We tested for effects of sequential interventions (subsidence and restoration) on biological and habitat variables in a replicated before-after design, controlling for potentially confounding temporal effects (sample month and antecedent effective precipitation). All biological indices and substrate-related habitat indices declined following subsidence but improved following restoration. Macroinvertebrate indicex and taxa richness, substrates, and riparian vegetation continued to improve with time following restoration. Whereas other studies have concluded that biological communities may take many years to respond to restoration, these results indicate that where macroinvertebrate and fish communities are altered by subsidence pooling, they can be effectively restored using gate cuts to pre-mining levels within relatively short time periods.

The objectives of this research were to develop methods to discern between naturally occurring reductions in spring discharge from mining-induced reductions to spring discharge, evaluate available hydrologic, geologic, topographic, and mine-specific variables to determine which variables are related to mining-induced spring discharge impairment, and evaluate the variables to determine the seasonality differences or similarities among the variable effects. The study area is at one mine site in the northern Appalachian coal basin. Overburden thickness of the researched ground water sources above the mined coal bed level range from 135 feet to 550 feet. The overburden geology consists of cyclothemic deposits of sandstones, siltstones, shales, limestones, clays, and coal that comprise the Conemaugh and Monongahela Groups of Pennsylvanian age, and the lower part of the Dunkard Group, Washington and Greene Formations, undifferentiated, of Pennsylvanian and Permian age. The terrain of the research area is typical of the Appalachian Plateau physiographic province, having broad ridges, deeply incised valleys, and highly defined dendritic drainage. Land use is dominantly for farming. Average annual precipitation in the research area is 43 inches. Mining-induced subsidence resulted in a partial environmental effect to springs. Spring discharge responses for 77 springs were evaluated across subsidence events. The methodological procedure developed through numerous, iterative investigations differentiated quantitative values separating natural changes in spring discharge from mining-induced changes to spring discharge. The influences of precipitation and evapotranspiration conditions were accounted for during the natural variation analysis used to determine if changes to spring discharge were mining-induced. In addition, topographic, geologic, hydrologic, and mine-specific variables were statistically examined for significance of influence on spring discharge impairment during low and high evapotranspiration seasons. iii ACKNOWLEDGEMENTS The author wishes to thank his fiancée, co-workers, colleagues, family, and friends for the motivation and support expressed throughout the research. The author was not alone with the sacrifices that had to be made in order to acquire completion. The author wishes to thank the coal company for providing the opportunity, and data, intrinsic to this research project. The author is very grateful for this opportunity and if possible, will pass similar prospects onto other eager graduate students.

Mine subsidence can induce streambed ruptures that pirate surface water from a stream. Current understanding of the effects of longwall mining on streams lacks rigorous analytical approaches to detect hydrologic effects and does not consider the efficacy of streambed restoration techniques to address flow disruption. CONSOL Pennsylvania Coal Company, LLC (CPCC) collected and analyzed pre-mining, post-mining, and post-restoration stream discharge and flow duration data from 51.9 km of streams overlying its Bailey Mine to define pre-mining flow variability, detect post-mining changes, and evaluate post-intervention flow recovery. The primary intervention method for restoring stream flow was bedrock permeation grouting. Pre-mine and post-mine baseflow data were compared using both parametric and non-parametric hypothesis testing, which yielded similar results. An environmental flow assessment method for headwater streams using probabilistic risk assessment and correlation analysis of change threshold criteria was developed to differentiate hydrologic change as induced by mine subsidence or explained by natural variability. The method is objective, pragmatic, and statistically delimited.

The floodable volume of longwall gob can be of great importance in developing accurate coal mine operation plans, particularly for mine water management and environmental control strategies. Given the inaccessibility and difficulty in direct measurement of gob characteristics following gob recompression, hydrologic, geomechanical, and spatial data and principles were used to solve for the porosity and height of the residual gob using a mathematical model framework and bulking-based techniques. Based on this approach, gob porosity of Appalachian longwalls appears to be tighter than previously reported, ranging between 4.99 and 14.31%. Residual gob height, as normalized with respect to mine extraction height, ranges between 1.90 and 2.45. A novel, bedding-based bulking approach is ampliative with respect to existing roof caving and bulking fundamentals, as it has greater explanatory value compared with the traditional, lithologic-based bulking application. The efficacy of using the residual gob characteristics determined by the mathematical model and bedding-based bulking is examined using a causal comparative method, whereby time series prediction of historical groundwater rebound is compared with observed mine pool elevation data. Prediction accuracy is significantly improved using a prototype model to calculate void volume of longwall gob, specifically, the dependence of porosity of the gob material upon the longwall width to overburden depth ratio for movement basins of subcritical and critical panel widths. The potential implication of these findings toward hydrologic, geomechanical, and ventilation studies of longwall gob could be significant.