Dealing with these situations can be a costly and controversial, making dam removal an increasingly viable option. Not all dams are candidates for removal, since they may continue to provide important benefits or removal could have adverse impacts. Nonetheless, when appropriate, dam removal can provide significant benefits.
The environmental benefits of dam removal include restoring natural river flows, removing blockages for fish migration, re-establishing the river habitat for fish and wildlife, and improving water quality. Restoring a river’s natural flow through dam removal also aids in increasing biodiversity through the restoration of vegetation and habitats. Dam removal enables fish to migrate freely upstream and downstream, improving their chances for successful reproduction. Dam removal can revitalize wetlands, which serve as nurseries for aquatic species, and can enhance plant growth along riverbanks that provide shelter and food for wildlife. Dam removal can also help the local community by offering increased opportunities for recreation and tourism related to the restored river.
While removal of some dams is straightforward and relatively inexpensive, for many dams, removal can be complicated. Dam removal involves assessment of the dam’s uses, sedimentation, structural quality, and steps for restoring the river. Dam removal usually also requires multiple regulatory permits, environmental review, and numerous safety precautions. The process of physical removal can vary because of the unique aspects of many dams and rivers. Usually it involves drawing down the reservoir through notching or other methods, excavating sediment or letting it flow downstream, removing the dam structure, and reshaping and reestablishing the riverbanks.
Despite the challenges involved, dam removal is on the rise, as evidenced by several recent high-profile projects. In October 2011, removal of the dam on Washington’s Elwha River began. This project, which is the largest dam removal project in United States history, was originally anticipated to take two or three years. Removal proceeded quickly, however, and the Elwha Dam was completely gone by spring 2012. Also in Washington, removal of the Condit Dam on the White Salmon River is expected to be completed by this fall. Removal of the Great Works Dam on the Penobscot River in Maine began June 2012. The same month, the California Public Utilities Commission approved a project to remove a nearly 100-year-old dam on the Carmel River. Although a safety notice for the dam was issued in the early 1990s, it took several decades to develop a solution that was feasible from an engineering, financial, and environmental standpoint. This dam removal project, which is a joint effort between a privately-owned water utility and federal and state agencies, demonstrates the challenges – and benefits – of dam removal.
