McMillen performed a full suite of services to design and build the Allison Creek Hydroelectric project, a new 6.7 MW hydroelectric facility near Valdez, Alaska. As the prime and design-build lead, we delivered everything from site analysis, permitting, and comprehensive design and engineering to self-performed construction and commissioning. The final project included development of a new powerhouse, substation, diversion structure, penstock, and supporting infrastructure.
Initial site investigations kicked off a host of investigative and design services. We performed geologic mapping, snow avalanche hazards analysis, geophysical surveys, and subsurface investigations with helicopter-assisted drill rigs. Our team also conducted comprehensive hydrologic and hydraulic analyses to confirm operating design flows for the powerhouse, penstock hydraulics, available flow at the diversion structure, and flood flows on Allison Creek. These investigations helped us identify geologic hazards, foundation design, and other constructability issues.
Following site investigations, our team developed all civil, structural, mechanical, electrical, and hydraulic engineering plans and served as engineer-of-record. The modeling team worked alongside our in-house construction team to develop effective construction sequencing for critical events like concrete pours. The final design underwent three formal client reviews and two Federal Energy Regulatory Commission (FERC) reviews. Despite multiple review periods, the design was completed in only five months, from initial concept to final stamped drawings.
Once the design was approved, our construction team got to work excavating the powerhouse, pouring concrete for the powerhouse, tailrace, and diversion structure, and installing 7,000 feet of penstock. We developed site access roads, drilled and blasted an access tunnel, erected and built out the powerhouse, and oversaw installation of the turbine/generator equipment and overhead transmission line. Construction windows were restricted to the summer months due to weather, resulting in an accelerated schedule. An effective approach and sound sequencing plans were critical to completing the work within the available construction period.
After construction, McMillen managed all startup and commissioning. This included testing and energizing a new 4-mile-long 25 kV transmission line and main power transformer; putting powerhouse systems into service; placing a 35-ton overhead crane into service and performing subsequent load testing; balance of plant; operational testing of the new turbine and generator; initial online testing; load rejection testing; and testing of safety systems. Our team assembled operations and maintenance manuals and provided final as-built drawings for the completed project.
Throughout the project, we managed the FERC licensing process. We assembled the Pre-Application Document, navigated the Alternative Licensing Process, developed study plans, conducted natural resource studies, filed the license application and Environmental Assessment documents, and submitted associated federal, state, and local permitting applications. Following receipt of the license, our team led environmental management plans, pre-construction filings, and environmental monitoring and reporting during construction. After construction and commissioning, our team continued to perform environmental monitoring and license implementation.
We paid particular attention to environmental and fish protection measures for the entirety of the project. We developed, administered, and adhered to more than 20 environmental and wildlife protection plans. These included work plans and submittals related to the care and diversion of waters on the project site, affecting fish passage and discharges directly into populated waters. We were particularly cognizant of procedures surrounding the use of heavy equipment within 100 inches of flowing waters, conversion of equipment to bio-friendly fluids, fueling and maintenance procedures, equipment storage and drip prevention, and spill containment and notification processes.
McMillen’s team worked in close partnership with our client, Copper Valley Electric Association (CVEA), throughout the design and build process. Regular collaboration and continuous communication allowed us to develop a subcontracting plan, an equipment procurement process, and a risk management methodology to effectively and efficiently address project risks. This fully integrated partnership allowed us to deliver the Allison Creek Hydroelectric facility $10M under the initial project budget.
