Key to removal of aged infrastructure: Historic dams
Civil engineers, we build it and build it to last. What if the original purpose for the facility is no longer applicable? Do we spend money to remove it when other necessary, critical infrastructure is in need of maintenance and repair? What if the facility is stable with no significant public safety risk? The cost-benefit analysis would typically not justify the removal.
This is often the case for our historic dams.
Dams are constructed for a variety of important reasons and many are no longer necessary for another variety of reasons. We acknowledge there are environmental impacts of these facilities yet are still challenged to finance removals. Considering the environmental opportunities of these removals has solved the funding dichotomy – offsetting and enhancing a necessary environmental impact. By identifying opportunities to provide compensatory mitigation for other project impacts within the watershed, those that have a justifiable purpose, we are seeing more of these aged facilities removed.
This concept although simple, is not so simple to execute. There are rigorous assessments that are required to evaluate the impacts of the dam removals. One significant consideration is the sediment management associated with the dam removal. The sediment characteristics, which have accumulated behind the dam, need to be carefully studied to evaluate their impacts if released downstream. Sediment load is a part of a healthy waterway, but sediment quantity and quality may have adverse impacts if released to the downstream system and requires careful consideration prior to removal.
Evaluations need to also consider other physical and ecological impacts to the stream such as stream hydrology, morphology, aquatic habitat and upland vegetation. We cannot disregard the social impacts, both beneficial and adverse, which can have a much wider reach than the physical and economic impacts.
Just as civil engineers apply rigorous study and consideration to building new infrastructure, we need to apply these same practices to the seemingly simple concept of removing infrastructure.
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