Since 2005, McMillen has served as the design lead and dam safety consultant at Box Canyon Dam and associated project sites. We have provided regulatory support, dam safety services, design engineering, procurement and construction support, as well as assessments for upgrades to existing hydroelectric projects. Example projects include:
- Upstream and downstream fish passage
- Turbine/generator upgrades from 72 MW to 90 MW
- Trout Habitat Restoration Program and stream gauge monitoring
- Habitat restoration design and implementation
- Total Dissolved Gas (TDG) abatement plan with 110-ton spillway gate hoist designs
- Sullivan cold water intake pipe
- Calispell Creek slope/dike stability and risk analysis
Upstream fish passage and trap and haul facilities:
The 62-foot-high Box Canyon Dam was built in 1956 and prevented federally listed endangered/threatened aquatic species from migrating between breeding and feeding areas. To receive a renewed FERC license in 2005, upstream fish passage was required. This project provides safe and timely passage of juvenile, sub-adult, and adult species. It also enables the biological analyses of fish populations.
McMillen led the design for the upstream trap and haul facility, provided alternative analyses, participated in value engineering to lower construction costs, coordinated with FERC and numerous stakeholders, collaborated with the general contractor and vendors to consider constructability and operability, and provided engineering support during construction. As the design lead, we provided all civil, structural, mechanical, electrical, instrumentation and control, and geotechnical engineering and hydraulics analyses which included CDF modeling. We also assisted in the site selection and established the design criteria with FERC and stakeholders.
The fish enter through one of the two entrance pools where they are directed with energy dissipation valves that create Attraction Water Supply (AWS) flows. The upstream migrants travel up the 27-pool, weir and orifice fishway and enter the pre-sort holding pool through a vee-trap. Here, they are moved into a fish lock, transferred over a weir, and directed to the sorting table where biological studies can be completed if needed. Target fish are identified, measured, and tagged before being released. Those species that need to be transferred upstream are placed into a pipe leading to the transport pods where water and oxygen are provided, and the temperature is maintained. The pods are then loaded on a truck and driven to a release site at least one mile upstream of the spillway.
Is it working? The new upstream trap and haul fish facility began operating in April 2022 and is experiencing excellent results. In the first observation report, they witnessed the safe passage of 12 distinct species and confirmed that flows can attract larger fish while not posing as a deterrent to smaller or weaker fish. Nearly all tagged fish that entered the facility were recorded making it to the pre-sort pool vee-trap for a 92.8% rate of completing the upstream journey.
Dam safety services
McMillen conducted FERC Part 12D dam safety reviews for the last two cycles for the Box Canyon and Sullivan Creek Hydroelectric projects. This included preparation of the Part 12D reports, review and update of the Supporting Technical Information Document (STID), facilitating the Potential Failure Mode Analysis (PFMA) review session, and completion of the PFMA reports. We also assessed the earthen dike at Calispell Creek including a quantitative risk analysis and investigation program, developed a design to address unacceptable risks, and facilitated the PFMA session for the proposed design. In addition, since 2020, we have been providing Chief Dam Safety Engineer (CDSE) Services for both the Box Canyon and the Sullivan Creek Hydroelectric projects.
