Upper Falls Aesthetic Spill Project
Summary
Avista successfully restored two channels downstream of their Upper Falls Development on the Spokane River to look much the way it did long ago, before the channels were altered to divert water to numerous flour and lumber mills, as well as for hydropower generation. The channel restoration, using weirs shaped and colored to look like the bedrock throughout the river, spread water more evenly throughout the two channels and has now functioned successfully through an entire spill season. Combined, they produce an aesthetically pleasing flow over the falls that viewers can enjoy throughout the year.
Background
For hundreds of years, the Spokane River and falls served as the gathering place for Native American tribes. Today the falls are at the center of the 100-acre Riverfront Park in the heart of downtown Spokane, Washington. Avista owns five hydroelectric developments on the Spokane River, collectively known as the Spokane River Project. The Project received a new 50-year Federal operating license in 2009.
The Upper Falls Hydroelectric Development is located within Riverfront Park and has a licensed capacity of 10 megawatts. The development includes two dams on either side of Havermale Island in the Spokane River. The north channel dam and control works structure creates the by-pass reach that includes the Upper Falls, while the south channel contains a dam and headgate structure that leads to the powerhouse. The north cannel bypass reach splits into the North and South channels that flow around Canada Island. Although the development is operated as run-of-river, the two dams control the release of water to downstream areas of the Spokane River that are frequently viewed by the public.
The river channel at the Spokane Falls has been heavily impacted by human activity since the late 1800’s. Until recently, water flow slowed to a trickle (less than 30 cfs) in both channels during the summer months, with all of the water flowing through the south channel. The lack of water exposed barren river banks and rocks within the river. Aesthetic qualities including flow, mist, and sound, were severely diminished when water ceased to flow through the dams and downstream channels.
During the relicensing process for the project in early 2000s, stakeholders requested an aesthetics study for the Upper Falls development. The study focused on identifying the desirable viewing times and river flow attributes that appealed to the public. At the same time, Avista staff offered an innovative and creative idea: modifying river channels to change the appearance of the flowing water and balance the amount of water in each channel. The more than 40 stakeholder groups were open to the concept but were unsure that it would prove successful. Some stakeholders were persistent in requesting that Avista simply increase the amount and duration of aesthetic flows year-round rather than modifying the channel. Following extensive negotiations, stakeholders agreed with the proposal to evaluate channel modifications to determine if Avista could produce acceptable aesthetic spills with 300 cfs released from the dam, and if not it would release minimum aesthetic spills of at least 500 cfs on a year-round basis. Avista would also release 100 cfs during nighttime hours to accommodate downstream fish passage and to prevent stranding.
Subsequently, the Federal license for the Spokane River Project was issued by the Federal Energy Regulatory Commission and included the Washington Department of Ecology’s 401 Water Quality Certification. The Certification included a specific requirement for a year-round aesthetic spill at the Upper Falls HED that was based on stakeholder recommendations. The Washington State Department of Ecology later modified the Certification in accordance with a Settlement Agreement between Avista, the Sierra Club and the Center for Environmental Law and Policy. The Certification also required development of a long-term aesthetics spill plan, a pilot study to determine the effectiveness of possible channel modifications, analysis of the modifications with regard to any ecological impacts of modification such as fish entrainment, stranding or trapping. Ultimately, stakeholders were required to mutually agree on the success of the project.
Challenge
As license implementation began, and as Avista staff theorized, not only would channel modifications even out flows, but with proper planning less water (300 cfs) could provide the same or better visual and audible effects than more water (500 cfs) could. The additional water could be run through the powerhouse rather than spilled and would increase generation at Upper Falls, an appealing concept for the utility. Yet, to the knowledge of Avista’s staff or to the consultant teams that were working on the project, no project like this had been attempted in North America. The overall scale of the project was intimidating, and gaining stakeholder support and ultimately buy-in would prove challenging. Rather than hypothesize or model what impact channel modifications might have on flows, Avista initiated a real-life pilot-test in the river channel. Stakeholders were enlisted to evaluate the location, size and impact of the various weir structures on the aesthetic appeal of the river as 300 cfs was released into the bypass reach.
Prior to the pilot-test, some stakeholders expressed concern that balancing the water between the two channels could negatively detract from the south channel, which received the most flow during near-dry periods. As a result, the test focused on evaluating the way that flows influenced each channel.
The pilot-test process was designed to assess the effectiveness of potential channel modifications on the visual and audible effects of flows in the river. The goal was for the visual and audible effects to be similar to or better than those achieved by a spill of 500 cfs through the bypass reach without channel modifications. Over a period of months, Avista continued to work to identify possible locations for various weirs, basically engineered “rocks” used to modify the channel and redirect the water flow. Aerial photos and reconnaissance visits were critical in determining the proposed location and size of the prospective weirs. Test weirs were constructed of a mix of materials, including 1-cubic-yeard bags of pea gravel placed next to each other, smaller bags filled with sand, and ecology blocks (large concrete blocks). Many of the weirs had sheets of plastic attached to better deflect water. The test plan was approved by FERC in June 2010.
The pilot-test consisted of several components including establishing temporary river channel modifications, conducting a viewer preference survey, assessing results and obtaining data for use in construction of the permanent structures. Stakeholders were invited to join the Evaluation Team. The team included a diverse range of parties and organizations that had a keen interest and background in the aesthetic condition of the Upper Falls. The participating organizations included the Sierra Club, Spokane City Parks and Recreation, Ecology, Friends of the Falls, the Center for Environmental Law and Policy, and the Spokane Canoe and Kayak Club. In addition to these groups, representatives from Avista worked on the pilot-test and participated as Evaluation Team members, as did consultants agreed upon by Avista, the Center for Environmental Law and Policy, and the Sierra Club. Subject-matter experts served as Evaluation Team members and were present during the pilot-test to answer technical questions.
After each Evaluation Team review, suggestions were made regarding changes in the distribution of water between two channels and “fine tuning” changes within each channel to improve aesthetic flow characteristics. Suggestions that were agreed upon resulted in manipulating weirs or adding new ones. The process that was required to make these changes involved Avista shutting off flows from the Upper Falls Dam into the river channels, waiting several hours for the flows in the channel to be low enough to safely work in it, Land Expressions making the requested changes, Avista releasing 300 cfs back into the river, and then waiting several hours for the 300 cfs flows to stabilize in the river channels before the Evaluation Team could again make observations. After the conclusion of the pilot-test, all of the materials were removed from the river channels.
Avista also had numerous meetings with Washington Department of Fish and Wildlife (WDFW) and Washington Department of Ecology, in which downstream connectivity and entrainment were the focus of discussions. Prior to and throughout the pilot-test, biologists assessed the potential impacts of various flows in the study area, including the potential for fish entrainment. Any fish stranded, as the channels were emptied for the pilot-test, were hand captured and relocated downstream. All parties concluded that the structures used during the pilot-test maintained and appeared to enhance connectivity. This led the team to work with Washington Department of Fish and Wildlife during the design phase to ensure downstream passage and connectivity were incorporated into the weirs as appropriate. As a result, three of the weirs were modified during construction to allow fish to move downstream and to reduce the probability of stranding fish at night when the flows are reduced from 300 cfs to 100 cfs.
Innovation
The project is an exception in that it was truly a win-win for everyone involved. With a goal of not only evening and enhancing the flows in the two channels but also modifying the channels in a way that blended with the existing environment, Avista hired two specialty firms to develop detailed designs for the weirs to modify the channels. The two firms normally work on landscape architecture and creation of artificial rock structures for water features and exhibits. Reshaping the Spokane River was a water structure of a different scale altogether. The riverbed at the location of the falls includes various basalt rock formations, textures, and colors. Avista and its consultants worked closely with representatives from Washington Department of Fish and Wildlife and Washington State Department of Ecology as they designed the weirs. It was extremely important that the shapes and colors were consistent throughout each weir structure to ensure that the natural look was maintained even if the weir structures were damaged over time.
“Avista and our contractors took a new and creative approach to restoring the falls to a more natural state,” said Spokane River License Manager Speed Fitzhugh. “We matched the color, shape and texture of the weirs to that of the bedrock to produce seamless, natural looking river flows. As far as we’ve been able to determine, it’s the first project of its kind in North America.”
Results
Avista observed the weir structures through an entire spill season, declaring the project complete in fall 2012. Photo evidence shows that post construction, with 300cfs flowing through the channels, the Spokane Falls actually appear similar to the way they previously appeared with a 1,500 to 1,600 cfs flow. Informal surveys showed visitors lingering on bridges over the falls throughout the summer months, which virtually never happened when the two channels were dry. And, with 300 cfs flowing through the two channels, Riverfront Park visitors cannot locate the weir structures within the natural bedrock channels, indicating true success.
The total cost of the multi-year project was approximately $1,400,000. Although the additional generation benefits can be calculated, the overall value of the project to the more than 2 ½ million annual visitors to Riverfront Park is impossible to quantify.
Stakeholder Quotes
“For more than 120 years, Avista has been an integral part of the Spokane community. Providing services throughout the area, they have implemented projects that not only enhance their own functionality but that also improve the quality of life for residents in the cities they serve.
Avista’s completion of the Upper Falls Aesthetic Spill Project has enabled us to enjoy the Spokane Falls through every season. It has enhanced the beauty of our community without sacrificing the quality or efficiency of Avista’s services to citizens throughout the region. The innovative nature of the project, as well as the strong collaboration between Avista and multiple stakeholder groups, is a prime example of the quality of work Avista continues to produce in our community. Additionally, the project’s 12-year drive to completion is a testament to Avista’s thorough work and dedication to a successful project for our community.”
– City of Spokane
“This challenging project was achieved through the collaborative, thoughtful and hard work of Avista staff and multiple stakeholders from throughout the region.
Avista has again achieved excellence as an organization by continuing to work innovatively and collaboratively with our community ensuring challenging projects are completed to the satisfaction of all.”
– Spokane County
