The following projects represent a sampling of our work with PSE to enhance hydroelectric operations and improve the Baker River’s hatchery operations and fishery systems.
Lower Baker Dam Crest Improvements.
McMillen redesigned the entire crest of Lower Baker Dam to current hydraulic, structural, mechanical, and electrical standards. To prevent overtopping and abutment erosion, the floodwalls were raised approximately 15 feet. The top of the dam will be demolished, post-tension anchors were installed, and the top of the dam was raised 6 feet. The existing 22-spillway gate system will be replaced with 12 new vertical roller gates with 15-ton wire rope hoists.
Our team developed and executed a site investigation program including a geologic survey of the abutments, drilling through the dam crest, roped-access abutment mapping, scour analysis, abutment stability analysis, FERC coordination, and foundation and stability analysis of the new floodwall. To further validate the design and optimize the spillway, we led hydraulic testing on a 1:30 scale physical model of the entire dam to optimize the crest shape and evaluate scour on the canyon sidewalls and plunge pool.
Our scope of work includes plans, specifications, and other supporting construction documents, FERC-required quality and safety submittals, a project management plan, a proposed construction schedule and sequence, a design documentation report with calculations, a risk register, a quality control inspection plan, engineering considerations, and instructions report, and a draft operations and maintenance manual. We also developed a new dam stability monitoring system and performed dam finite element analysis (FEA) stability using linear and nonlinear models for the existing and new crest designs. Finally, a hydraulic physical model was created in addition to CFD models to ensure the hydraulic physical performance of the crest, the gates, and the PFMA flows.
Lower Baker Dam Debris Boom Design-Build.
McMillen was selected as the design-build contractor to design and construct a new 2,800-foot debris boom system to replace the existing one. The new debris boom was designed to meet PSE's dam safety and fish passage criteria. Additionally, McMillen provided design-only services to modify the existing Floating Surface Collector (FSC) Exclusion Net System.
The scope of work included designing and installing structural anchorage, which utilized a 3-point anchor layout with shore anchors and a lake anchor. The shore anchors consisted of a shackle plate connected to a reinforced concrete anchor block with grouted ground anchors. The lake anchor was a high-capacity Stevshark® drag-embedment type anchor. McMillen designed and installed all the anchors for the project. We also designed and installed a barge mooring system, which included a prismatic concrete block anchor with steel reinforcing bars and a lift point. The lakebed bathymetry was analyzed to determine the optimal placement of the anchor. A buoy was selected based on its buoyancy force to match the weight of the steel chain connecting the barge to the anchor.
Dam safety was a key project consideration, with a complete analysis of each debris boom element and a calculation of associated safety factors. Environmental sustainability and mitigation of impacts were also prioritized to prevent small woody debris from clogging the FSC and reducing fish mortality. The construction schedule was adjusted to accommodate the bird's nesting season, and efforts were made to reuse equipment and materials to minimize environmental impact.
Baker River FSC, Hydraulic and Fisheries Design.
McMillen was integral to the hydraulic and fisheries design team responsible for developing the fish screen configuration, hydraulic design, and operation. As part of the overall design assistance, our firm also provided design review and technical oversight of the mechanical systems, including primary and secondary pumps, fish screen cleaning systems, and fish collection, holding, and transport; PIT tag detection and counting systems; and overall FSC operation.
Key FSC features include:
- Shore-to-shore, surface-to-lakebed guide nets covering five acres of surface area
- A specially designed “net transition structure” linking the guide nets with the 130-foot by 60-foot, barge-like FSC, weighing 1,000 tons
- An elaborate fish-sampling station
- Enhanced fish-loading facilities for downstream “fish taxi” transport past the dams
In its first year of operation (2008), this FSC posted Baker Lake’s second-highest fish outmigration total on record. In 2009 and 2010, the FSC set new records by a wide margin—more than 520,000 juvenile salmon were collected in 2010, compared to a 24-year average of 176,000. This alternative was one of many that McMillen proposed earlier under a different contract. Our engineers led the development of downstream and upstream fish passage alternatives, including conventional screens, modular inclined screens, FSCs, fish ladders, and volitional trap and haul facilities.
Baker River Fish Hatchery Renovations.
McMillen was a subcontractor to the design-build lead and provided design and construction support to enhance the fish hatchery and refurbish the sockeye spawning beach near the Upper Baker Dam. McMillen completed the hydraulic analysis, site layout, and facility design for all the hatchery components, including modifications to the intake structure, new raw water pipeline, flow metering, head tank, and a sand separator utilizing a LAKOS separator system, hatchery building, outdoor rearing raceways, adult holding and spawning, storage building, clarifier, and chlorine/de-chlorination treatment facility.
The performance of the renovated facility increased sockeye fry production twofold from levels prior to 2008. Each year since completion, more than 5 million sockeye fry have been produced and released into the Baker Basin reservoirs. By comparison, PSE’s previous Baker River fish-culture facility, which slowly expanded from its start in the early 1970s, could produce about 1.7 million fry per year.
Baker River Hatchery Expansion Phase 2. McMillen was the general contractor for the phase 2 expansion which addressed multiple objectives to improve fish rearing, worker safety, and operations reliability. Work included the addition of four new concrete raceways, yard piping, crowders/screens, waste tank replacement, predator netting system, replacement of sand separators and modification of the support system in the existing head tank building, modifications to the existing domestic spring water piping, and replacement of three valve motor actuators.
