EVALUATING OPTIONS FOR LARGE-SCALE WATERSHED REMEDIATION 1

southeastern Ohio, and since the middle of the 19th century, extensive portions of the watershed have been subjected to underground and surface coal mining. A recent survey of the watershed has identified over 4,300 point sources of acid mine drainage which have rendered a number of stream reaches within the watershed sterile and unable to support diverse, aquatic life. In 2003, Dr. Stiles developed a model of those aspects of water quality related to Acid Mine Drainage (AMD) for the watershed using the TAMDL computer program developed at West Virginia University. The computer program TAMDL was designed to model stream water quality in watersheds affected by AMD and its treatment by simulating the evolution of stream pH, net acidity, and the concentrations of aluminum, iron, and manganese. The Monday Creek TAMDL model was then employed by the authors to develop a cost effective strategy for the treatment of AMD in the watershed. Since the close of this project, several passive and active treatment systems have been installed in the Monday Creek watershed. The objective of this new project was to recalibrate the TAMDL model created in 2003 for the new conditions in the watershed and use this recalibrated model to design a revised cost effective treatment strategy to bring the water quality conditions from their current level up to the remediation target conditions. The remediation target conditions for the Monday Creek watershed were those minimum and maximum pH levels and maximum aluminum and iron concentrations that would allow aquatic life to be reestablished in the main stem.