USACE Walla Walla Engineering IDIQ

Inspection/condition assessment, Alternatives analysis/feasibility study, Conceptual design, Engineering services, Final design, Environmental/permitting, Self-performed construction, Engineering during construction, Testing & commissioning
Professional services, On-call (MSA, IDIQ, MATOC)
Various locations in WA, OR, and ID
USACE Walla Walla District
why it matters

Walla Walla District (District) is the second largest hydropower producer for the US Army Corps of Engineers (USACE) with a total generating capacity of 4,413 megawatts. Their six hydro facilities are responsible for supplying energy to millions of people across Washington, Oregon, and Idaho. Since 2007, McMillen has been providing engineering design services to support the District’s mission while enhancing the efficiency of these facilities, ensuring a reliable power supply for the northwest region.

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McMillen’s strong and successful working relationship with the District stems from having completed many hydropower and civil works projects. Our expertise ranges from feasibility studies to major multimillion-dollar endeavors, and our comprehensive suite of services includes design, construction, technical reviews, and value engineering. With a deep understanding of USACE standards and practices, as well as experience with IDIQ contracts, our team is well-equipped to handle these projects. We provide the District with a highly qualified team of civil, structural, hydraulic, electrical, and mechanical engineers and fire protection experts. This allows us to efficiently manage multiple task orders and provide multi-disciplinary engineering services. Recognizing our capabilities, the District has awarded McMillen four Architect and Engineering Services IDIQ contracts. Our task orders have encompassed a wide range of projects, including gate and hoist upgrades, hydraulic modeling, potable water systems, turbine upgrades, and life safety alarm system upgrades. Through our ongoing collaboration, we are committed to delivering high-quality solutions that meet the District’s needs and contribute to the success of their operations. Examples of task orders for the District’s IDIQ contract include:

Dworshak Dam Regulating Outlet (RO) Valves, ID

McMillen performed feasibility through the final design for the RO upgrades. The project involved studying existing conditions and information, preparing a feasibility study, and developing a Design Documentation Report (DDR). Due to a lack of funding, the project was put on hold after the initial design was completed. However, in 2019, funding was approved, and McMillen was contracted again to update the design, develop 100% plans and specifications, and support construction.

The scope of the contract included refurbishing the mechanical systems of the radial gates/RO valves and replacing the existing hydraulic system. McMillen developed a new design for hydraulic operators, hydraulic power units, and new local and PLC controls. The team redesigned the eccentric cylinder to lock the gate position without the use of power, ensuring that the cylinder rods could not move from a loss of hydraulic system pressure.

To enhance safety, lockable isolation valves were provided within the control room to prevent valve movement when maintenance personnel were present in the gate chamber. The upgrade provided secondary containment on oil lines to actuate the RO cylinders. McMillen also developed plans and specifications for the concrete rehabilitation of the existing RO conduits that ran through the dam. The design included repair methods for concrete spalling, epoxy coating for the RO floors and walls, and painting. Special attention was given to the placement and location of instrumentation, wiring, and ancillary equipment to minimize water ingress and physical damage from water spray.

Life Safety Fire Alarm System Upgrades at Multiple Facilities, WA.

Our fire protection engineers have developed thorough evaluations and concept-level design for McNary, Dworshak, Ice Harbor, Lower Monumental, Little Goose, Lower Granite dams. In addition, McMillen is leading the full detailed design of the systems and associated components at McNary Dam, including a 3D scan and model of the powerhouse and credible fire scenario analysis. The modernization of the powerhouse included life safety, fire detection and notification, egress, smoke control systems, and complex computational fluid dynamics smoke modeling for various credible fire scenarios. We also provided additional Value Engineering Studies for selected facilities.

McNary Lock & Dam Potable Water System Upgrade, OR.

McMillen provided feasibility-level design, final plans, and specifications for the potable water system upgrade at the powerhouse, two machine shop and warehouse buildings, a yard fire suppression system, and two outdoor park restrooms. Potable water is supplied from two existing, deep groundwater wells to a finished water reservoir (FWR) tank for the facilities. The current FWR was not of sufficient volume to provide the required 3-hour water supply for fire protection to yard facilities and the required 600 gallons per minute maximum day flow to the powerhouse turbine units. The new FWR has been specially designed with two independent cells to allow either cell to operate independently while the other cell can be cleaned or maintained. In addition, McMillen designed the tank to be half buried, with part of the tank receiving an architectural berm and landscaping to provide minimal visual impact on the surrounding neighborhood. The McMillen team performed all hydraulic, structural, mechanical, electrical, geotechnical, and civil engineering.

Columbia River Treaty HEC-RAS Steady Flow Hydraulic Modeling (six reaches on the Columbia, Snake, and Clearwater Rivers), WA and ID.

As part of the 2014/2024 review of the Columbia River Treaty, McMillen developed, calibrated, and validated steady HEC-RAS models of the Columbia, Snake, and Clearwater Rivers. These models constituted over 300 stream miles and were worked off detailed LiDAR data. McMillen managed to closely calibrate results to measured values to simulate more critical events with greater confidence and provide USACE with accurate inundation maps of the area.


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