Box Canyon Hydroelectric & Fish Passage

LOCATION:  Pend Oreille County, Washington   |   OWNER:  PUD, Pend Oreille County
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Our Hydroelectric Role

The Box Canyon Hydroelectric Project is owned by the Pend Oreille County Public Utility District (PUD) and was completed in 1956. The Box Canyon Dam is located on the Pend Oreille River, ninety miles north of Spokane, Washington and is a run-of-the-river project that was built near the exit of a narrow channel commonly referred as Box Canyon. It is bordered by steep rock cliffs and situated in a narrow portion of the state’s second largest river. The dam itself is 160 feet wide at the base and 62.4 feet high at the top of the gates. It is capable of supplying a maximum head of water of 46 feet.

Pend Oreille Public Utility District negotiated a settlement agreement as part of their 90MW Box Canyon Hydroelectric Project relicensing. The settlement agreement outlines the specific measures prescribed for the design, construction, operation, and maintenance of new projects for the Box Canyon Dam which shall be fully complete by July 2018.

Since 2005, McMillen Jacobs has been working in partnership with the PUD to provide overall project management along with design, engineering, licensing and relicensing support, construction oversight, abatement, and habitat restoration and much more.

As of 2015, McMillen Jacobs has provided the following various services on 14 separate projects which shall be fully complete by July 2018:

  • Total Dissolved Gas (TDG) Abatement Plan and Preliminary Design
  • Upstream Fish Passage
  • Downstream fish Passage
  • Sullivan Cold Water Intake Pipe
  • Sullivan Lake Dock
  • Calispell Creek Downstream Passage and Pumps
  • Calispell Creek Upstream Passage
  • THRP Stream Restoration Support
  • Turbine Generator Upgrade
  • Habitat Restoration Design and Implementation
  • Middle Fork Bridge Design
  • Wildlife Habitat Monitoring Plan
  • Services Provided
  • Civil: Structural, H&H, Geotechnical and General Civil for Hydropower, Dam & Water Conveyance and Associated Project Works
  • Electrical: Hydropower Facilities including Generation, Controls, SCADA, Substations and Balance of Plant Electrical
  • Mechanical: Hydromechanical, Valves, Gates
  • Preparation of Design Drawings using MicroStation
  • Alternatives Analyses
  • Value Engineering
  • Engineering Support During Construction
  • Project Management
  • Construction Specifications
  • Quality Control Field Inspection
  • Coordination with Federal, State and/or Local Agencies (FERC, EPA, TMDL)

Our Fish Passage Role

The Upstream Fish Passage Facility at Box Canyon Dam shall be operational by July 2018 and will provide effective, safe and timely passage of juvenile, sub-adult, and adult bull trout, westslope cutthroat trout and mountain whitefish, greater or equal to 4 inches (≈ 100 mm) in total length.

The Upstream Fish Passage Facility will include an entrance pool with a floor diffuser and four entrances which can be operated individually or in a combination of entrances depending on river flow, as well as a combination of flow between the powerhouse and the spillway. A 28-pool, weir and orifice, fish ladder will convey upstream migrants from the entrance pool to a holding pool where the fish will be trapped, collected, trucked and then released at least one mile from the spillway. An auxiliary water supply (AWS) pump station would pump water from the tailrace to the system with flow ranging from 100 to 250 cfs. Special provisions are being made to accommodate future AWS by gravity once the downstream fish passage facility, which is also part of the settlement agreement, is online. Our McMillen Jacobs modeling staff completed a CFD model of the tailrace to provide more detailed velocity information to assist with the design of the upstream fish passage structures.

As part of the project construction, a combination cellular and sheetpile/treme cofferdam will be constructed to isolate and dewater the construction site. The cellular cofferdam will be external from the existing non-overflow dam section to an existing rock port adjacent to the powerhouse. A sheetpile wall will be erected from the cellular cofferdam back to the powerhouse and used as a form to construct a treme concrete wall tied to the existing rock outcrop and powerhouse. The cofferdam has a height ranging from 30 feet to 60 feet following the channel bottom and is designed to withstand a river flow of 80,000 cfs.

McMillen Jacobs is currently preparing plans and specifications for the trap and haul upstream passage facility which includes the tailrace water supply pump station, entrance pool fish ladder, holding and sorting, and coordination and consultation efforts with the state and federal agencies and tribes. Our team is also working with the University of Iowa Hydraulic Research Institute to determine uplift and down pull forces on the spillway gates to provide design information for a new spillway gate operation that will reduce TDG levels. Our field technician staff is collecting additional data to document fish movement at the project, and they also just completed a load rejection field program.

With such a large and diverse stakeholder group, it was difficult to reach consensus on the design criteria for the fish passage facility. Stakeholders included USFS, USFWS, USACE, Kalispell Indian Tribe, Bureau of Indian Affairs, WDFW, WDOE, Seattle City Light, environmental groups, and local stakeholders. To assist, McMillen Jacobs designed a criteria memorandum and a logical work plan and coordinated closely with the stakeholder group at the project initiation and each month throughout the project. The memorandum included river hydrology, dam operations, fish size and swimming requirements for each specie, fish facility design criteria, and required monitoring. The work plan provided a logical work flow to set expectations. Prior to advancing the preliminary and final design, the design criteria memo was fully vetted, then served as the foundation of the design development.