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Removing Mill Pond Dam: How Seattle City Light Restored Sullivan Creek

In July 2020, the U.S. Forest Service reopened the Mill Pond Historic Site to park visitors. The story below details Seattle City Light's involvement with the Mill Pond Campground and habitat restoration efforts at Sullivan Creek.

In July 2020, the U.S. Forest Service reopened the Mill Pond Historic Site to park visitors. The story below details Seattle City Light’s involvement with the Mill Pond Campground and habitat restoration efforts at Sullivan Creek.

This story was published originally in the March 2020 issue of Northwest Public Power Association Bulletin Magazine. Please note: positions and titles of contributors may have changed since the time of original publication.

Crews removing Mill Pond Dam

Dam removals are multi-faceted projects that require a clear vision of the final goal and foresight to imagine the challenges that may arise. In 2017, Seattle City Light (City Light) took on this formidable task with the removal of Mill Pond Dam, a decommissioned dam built on Sullivan Creek, the largest tributary to the Boundary Hydroelectric Project reservoir in northeastern Washington. By November 2019, City Light had completed the habitat restoration of the pond site to resemble its original pre-dam habitat condition. Project success required a clear vision, adaptability and a strong focus and a passion for the community it serves.

Mill Pond Dam was formed originally when a log crib dam was installed in 1909 by the Inland Portland Cement Company. A gated, concrete dam measuring 134 feet long and 55 feet high was constructed immediately downstream of the log crib dam in 1921. Mill Pond Dam had not provided hydropower or flood protection for almost 50 years while contributing to ecosystem degradation in the Sullivan watershed. 

Boundary Hydroelectric Project from its Vista House
Boundary Hydroelectric Project from its Vista House

Boundary’s licensed capacity of 1,117 MW can supply more than 33% of the utility’s service area power needs. During FERC relicensing negotiations, City Light and stakeholders agreed that the Boundary Reservoir offered limited opportunities for native fish restoration. At the same time during relicensing, Pend Oreille PUD, the local PUD, was surrendering their license for the Sullivan Creek Hydroelectric facility, which included Mill Pond Dam. Stakeholders in both processes identified the removal of Mill Pond as a critical mitigation measure in revitalizing native salmonid habitat in the Sullivan Creek watershed.  

Mill Pond Dam and the Boundary Hydroelectric Project are literally across Washington state from City Light’s operations in Seattle. Communicating the reasoning, the impacts and ultimately the benefits of this project required a sound strategy from City Light’s project team and partner agencies.  

In 2015, the project team in collaboration with Hernann Ambion, City Light’s senior public relations specialist and Scott Thomsen, City Light’s senior strategic advisor, held a community meeting at the Cutter Theatre in Metaline Falls. The goal was to educate the community about the project, correct misinformation, seek input on recreation amenities that could be included in the project and ease the concerns of a community.

“Dam removals are fascinating and frankly are hard to accomplish on multiple levels. This isn’t the typical capital project that a utility works on day-to-day,” Ambion described. “This community had fished and enjoyed Mill Pond for most of their lives, and we wanted to honor that. There was great dialogue between the community, the contractors and the utility during that initial meeting. It allowed us to get everyone on the same page about the project while dispelling any misconceptions about why City Light was even involved with this project.”

To keep the community and utility employees informed of the project, City Light’s Communication team also created a short video with interviews from project leads and agencies explaining the project and its benefits.  

Mill Pond Dam before its removal

Initially, the FERC License order outlined a detailed approach to removing the dam and a highly engineered stream restoration, which required that the approximately 1 million cubic yards of accumulated sediment be retained on site. This approach would have likely resulted in costly long-term maintenance by City Light. Early on, the utility, in consultation with its stakeholders and an expert panel, agreed that a plan for a more natural and resilient restored site was needed. For Lloyd Dixon, senior capital project coordinator with City Light, this paradigm shift gave the utility the latitude to create a plan that ensured that the area would thrive for years to come.

“We wanted to look at this holistically, to re-create a stream and wetland complex that would be able to adapt to changing conditions and provide excellent habitat value to fish and wildlife. We reimagined the design of the project, so the methods were not overly prescriptive allowing the contractor to design and implement a project that placed the site on a trajectory of recovery while allowing the habitat to adapt to environmental changes accordingly,” Dixon explained. “We realized that the century’s worth of accumulated sand and gravel needed to flow downstream into the sediment-starved areas that the Mill Pond Dam had created. Stakeholder buyoff on this concept was an important paradigm shift for this project. Early in the project design process, we had a panel involved with experts in geomorphology and dam removal that agreed that flushing the sediment naturally downstream to the Pend Oreille River would benefit the entire ecosystem both from ecological and morphological standpoints.”

City Light built a system of engineered log jams, made from trees and logs, that will remain resilient and functional during flood events, mitigate the effects of climate change over time and provide significant habitat value for fish and wildlife. Dubbed the “unbreakable stream” by Dixon and his team, the system includes log structures in the active channel and side channels that will regulate sediment transport, trap large woody debris and support a healthy riparian ecosystem.  

The restored area where Mill Pond Dam once stood (After)

When the project was officially completed in November 2019, the removal and restoration project reconnected 46 stream miles of habitat above the former barrier. Because of the innovative approach to dam removal, the ecosystem can now evolve and thrive for the first time in 111 years. While the public will benefit from the newly installed amenities such as a complete-loop trail including two new bridges,  a picnic shelter, and improved campground facilities, according to John Armstrong, City Light’s manager of the Boundary Licensing Unit, the primary goal is for native fish to flourish in the watershed once again.

“City Light is proud to be a steward of this environment we operate in. We rely on science and being informed about the fish populations that we are responsible for,” Armstrong said. We acknowledge that Boundary Reservoir itself isn’t the best habitat for these populations, and research identified the best opportunities for success are within tributaries to the reservoir. We wanted to do it right. If you’re going to operate a big dam, there’s an environmental element and we take that responsibility seriously.”     

Removing Mill Pond Dam and restoring Sullivan Creek required focus, fostering strong local relationships and establishing a transparent dialogue with the community that it impacts. From the regulatory agencies who worked closely with City Light to the region who welcomed the contractors and City Light employees from Seattle into their community, this project required the expertise and vision of many people to make it a success. It’s because of those people that Sullivan Creek and its tributaries will flourish for decades to come.