A system and method for in situ dewatering and stabilizing waste material deposits previously created from sluicing into a waste impoundment. The method includes access for installation of wells and grading for surface drainage and storm water control. If free water is present, primary dewatering siphons or decants the free water in the pond. The system includes vertical dewatering well installation that requires drilling, well completion materials for filtering leachate, and well pump installation for removing leachate from the well. Collection piping collects leachate from the wells and transfers the leachate to a discharge solution. The dewatering operation collects and removes leachate from the pond ash deposit and impoundment, reuses or treats the leachate at a discharge solution, remediates contaminants and/or hydraulic head in the impoundment, and consolidates and stabilizes the dewatered solids. Impoundment closure includes horizontal drains, final grading, final cover or overfill landfill development, and post closure.
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