Dam removal continues to emerge as a viable mechanism for ecological restoration. There is uniqueness to each dam removal because of the physical characteristics that define the structure and its purpose, as well as varying conditions in the watersheds that the structures impound. In developing an approach, no two dam removals are exactly alike.
Over the last 15 years, KCI has participated in many dam removal projects throughout the Northeast, Mid-Atlantic and Southeast, and most recently in the Midwest. The implementation of innovative techniques in design and construction has resulted in demonstrated success over the course of long-term monitoring. Much like the entire environmental restoration field, dam removal is a quickly evolving science. Along with the successes, KCI has experienced challenges and setbacks in completing these projects. The ability to learn from these experiences and share these lessons within our teams and within the industry help us to be better practitioners and ultimately will lead to more successful dam removals. Four of our lessons learned topic areas include the following:
Ownership – Dam ownership can be a cloudy issue and determining correct or complete ownership can be difficult to ascertain through normal property discovery techniques. Identification of legal ownership for a structure is an essential first step. Deed language is important (above and beyond information recorded on parcel mapping). Research may be necessary to catalog ownership of the land prior to dam construction and determine whether the deed language has been modified. An example of a potential ownership issue is when property lines follow the centerline of the stream feature creating a situation where approval from multiple owners is needed to remove a structure. Further, the ability to access the dam location to conduct the removal and dispose of remnants may bring more landowners into play that may or may not have direct ties to the dam structure ownership. Undoubtedly, this coordination and negotiation can be challenging, but in many cases this process educates dam owners about their legal obligation for maintaining these structures and can build support for removing degraded or obsolete structures.
Dam Placement and the “Lay of the Land” – Design elements and considerations that increase the efficiency in removing structures and the likelihood for long term success can be developed through research early in project planning. The evaluation of historic aerial photographs and mapping, original construction plans and specifications, and information from the users of the dam and the surrounding areas can paint a thorough picture of the transition of the stream or river into an impounded water body. Restoring a stream back through a former impoundment can be complicated. Understanding a larger context of the waterway over its history helps us to incorporate natural features and site constraints into our restoration plans. Regardless of the level of design, a restoration based on an anthropogenic or imposed alignment has a decent probability of being featured in a future lessons-learned blog. The river and valley characteristics will drive much of the ultimate channel form following a dam removal and can be influenced heavily by the first large runoff events post-removal. Spending time in the field at the site and understanding the boundary conditions that do/will persist is another important step in achieving a successful restoration outcome.
Existing Infrastructure – Evaluating upstream and downstream reaches of the river can identify crucial design components. Channel morphology, bed materials, and presence of grade controls (e.g. bedrock) can help to provide connectivity through the impounded reach. Identification of submerged, but relict features (for instance floodplains that connect to features outside of the dam influence) can be important for conceptualizing what the stream or river will look like immediately following the removal. Some of the biggest challenges revolve around the infrastructure installed prior to or subsequent to the dam’s installation. Presence of infrastructure can complicate an otherwise modest project and can add a substantial financial burden to a dam removal effort. Several infrastructure issues that we have encountered on our dam removal projects include:
- building structures adjacent to an impoundment or the dam,
- utilities that may become exposed in the stream/river bed,
- hydraulic structures spanning the river (bridges and/or culverts),
- water intakes/diversions for agriculture, secondary supply, and/or recreation, and
- outfall infrastructure.
There may be a need to maintain a water source that the dam originally provided following a removal, which may require development of an alternative water source or a variation to the extent of the removal (e.g. partial removal for organism passage). The “discovery” of infrastructure can quickly halt restoration efforts if solutions cannot be agreed upon by the stakeholders. Unintended damage to infrastructure caused by post-construction changes in the river alignment could be an even worse and more costly consequence.
Contractor Coordination – Once the planning and design are complete, a committed contractor that is open to working with the designer and is aligned with the intent of the project will improve the outcome of the restoration project. The plan is the plan, but good contractors that approach the removal and restoration as a team member along with the designer and owner can minimize the effects of unforeseen conditions and constraints that may complicate construction. After already discussing the uniqueness of each project and considering that the best laid plans can’t always address everything, flexibility and finesse on the part of the contractor can keep projects on track. Plan changes should be discussed immediately with all project partners, including the regulatory agencies. Solutions need to be carefully thought through, because small changes can have a cascading effect on achieving the goals and the success of the restoration.
Some of the most critical components of dam removal and ecological restoration projects begin during project development rather than in the design phase or even after. An understanding of some of these lessons learned can minimize some of the greatest potential project hurdles. It is the environmental professional’s responsibility to convey to stakeholders and owners the scale and magnitude of what is being undertaken and the associated risks. Small considerations can have a big influence on projects where you can’t see everything in front of you before you start. Understanding aspects related to ownership, the context of the dam structure, infrastructure, and contractor-stakeholder coordination can greatly increase the likelihood of success on dam removal and ecological restoration projects.