Dam Decommissioning and Removal: Challenges and Opportunities for Aging Infrastructure
Troy Naperala
AECOM
Travers City, MI
Authors: Troy Naperala, Seth Gentzler & Brandon Alderman
Decommissioning and removal of large dams is a significant undertaking. There are five (5) key considerations that tend to reoccur on projects. These are: social, ecological, care of water/dam safety, sediment management, and managing risks and expectations. Each of these is critical to success for a project and must be considered.
Social considerations include the impacts and uncertainty around property ownership, recreation, historic and cultural assets, and misconceptions about the purpose and benefit of the dam. These concerns can derail a project before it begins if not adequately addressed.
Ecological considerations such as waterway characteristics, vegetation, habitat features (upland and aquatic), as well as aquatic and terrestrial wildlife can impact success towards achieving long-term project goals.
Care of water/dam safety is a near-term concern for removing a dam. How to manage active flows and impoundment drawdown through a construction site while maintaining dam safety metrics has life safety aspects that must be considered commensurate to the risk they pose.
When sediment accumulation is significant managing it can be challenging. The difference between being able to flush accumulated sediment into the downstream river system versus dredging or mechanical removal can very large. The chemical quality of the sediments will have cost implications related to disposal, the physical characteristics of the sediment will determine if it can be reused, and the amount of sediment that is allowed to transport downstream is linked to ecological considerations (smothering, etc.) by regulators.
Managing expectations of the project partners, public, resource agencies, and regulators can minimize surprises and misconceptions. Inevitabilities such as turbidity, conditions of the reclaimed impoundment, effects of the reintroduced sediment load, and the condition of the newly exposed riverbanks can catch even the most informed project partner by surprise. Sharing time-lapse photos from previous projects help shape and manage expectations.
This presentation will use case studies to provide examples for each of these key considerations. Project examples will include the Boardman River Project (Michigan), College Lake Dam (Virginia) the Carmel River Reroute and San Clemente Dam Removal Project (California), and the Matilija Dam Removal (California) and Ecosystem Restoration project.
About Troy Naperala
Troy is the Midwest Market Sector Leader for Water Resources work. In this role he has been engaged in over 70 dam removal projects as the project engineer, project manager, or principal in charge. This work has given him insight into what makes a dam removal project successful from a variety of perspectives (engineer, biologist, ecologist, public official, and property neighbor). In this presentation he will share his views on the issues that have the most impact on how success is evaluated.