A fish barrier using elevated aqueous carbon dioxide (CO2) concentrations is proposed for Brandon Road Lock and Dam to prevent the spread of Asian carp into the Great Lakes. However, a CO2 barrier has never been assessed for potential environmental impacts, human health and safety risks, or for mechanical or structural deterioration of the lock and dam. Environmental impacts of the barrier will be modest and are restricted to the barrier vicinity. Nonetheless, significant asphyxia threats (CO2 is denser than air) exist in closed spaces (e.g., barges, ship hulls, and the lock chamber when the miter gates are closed). Potential exists for drowning or vessel sinking because CO2 bubbles reduce water density and the buoyant forces needed to float a human body or vessel. The increased risk caused by the reduction in buoyancy cannot be estimated without first knowing the design and operation of the CO2 delivery system. Lastly, elevated aqueous CO2 concentrations will increase the concrete deterioration rate. However, little information exists that can be used to estimate the potential for structural or mechanical damage. Constructing an elevated CO2 barrier is feasible at the Brandon Roads Lock and Dam; however, this comes with potentially substantial risks to human health and safety, and project integrity. More detailed studies should be conducted after the design and operation of an elevated CO2 barrier is known.
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