Tetra Tech INCA performed detailed designs and prepared construction drawings and specifications for Tieton Hydropower, LLC for this two-unit, 18 MW hydroelectric power plant located on the outlet works of the existing US Bureau of Reclamation (USBR) Tieton Dam. INCA reviewed all contractors’ manufacturer drawings and provided equipment inspections at sites within the US and China. INCA provided construction monitoring and commissioning and testing assistance.

The project includes the installation of ultrasonic flow meters on the existing penstocks and the relocation of two existing 6-foot diameter jet flow valves and integration of the jet flow valve controls with the turbine governors so that the Jet flow valves can be operated to regulate the flow releases when one or both units are down for maintenance or when the required releases are outside the range of flows that can be passed through the units. INCA’s work included structural analysis and several generation studies for selection, sizing and optimization of energy production.

Tetra Tech INCA worked directly with the Pittsburgh District and their contractor to optimize the design of a new floating guard wall for a new lock at Charleroi. Improvements in design are anticipated to provide a lower cost and a better performing structure. Some of these improvements included changes to rebar details to reduce installation time, changes in the concrete mix design to improve placement, revised ladder design, elimination of an intermediate joint to improve flotation and reduce cost, and simplification of wall armor embedments.

Tetra Tech INCA completed this concept study in 2005 for the Rock Island District, which followed work previously performed in 2000 to design 118-foot long post-tensioned concrete box beams for new lower guide walls on the Upper Mississippi River. Both design efforts required close coordination with Rock Island and St. Louis Districts.

INCA prepared design criteria, developed lock concepts, evaluated the new lock alternatives, prepared preliminary construction schedules (including considerations of required closures of the existing lock), and completed quantity take-off and planning level cost estimates. INCA recommended a lift-in precast concrete alternative for the new lock wall designs, and this general concept was selected as the basis for future design phases. In performance evaluations for this task order, INCA received an overall rating of Excellent and our design services were rated at Outstanding in all categories.

Bluestone Dam is a flood control dam located in southwest West Virginia that has a continuing problem of drift and debris loading in the upstream reservoir. To identify options for alleviating this problem, the Huntington District performed a study that recommended construction of a multi-level gated intake tower and tunnel through the dam, to pass the drift and debris.

Tetra Tech INCA was selected to:

• Evaluate the finite element analysis performed by WES
• Prepare a Seismic Response Spectrum finite element analysis of the Intake Tower
• Prepare a Seismic Time History finite element analysis of the Intake Tower and dam monolith
• Optimize the Intake Tower structural form and prepare construction documents
• Provide engineering support during construction

The tower is 116-feet tall and the operating deck was designed for 37 feet of submergence. The tower walls were designed for a total head differential of 106 feet.

INCA was the design engineer and construction manager for the expansion of an existing 2-bay transit center to a 4-bay transit center with a signalized intersection for the University of Washington Bothell/Cascadia Community College joint campus. Work for this project included field survey and basemapping, and the development of plans, specifications, and estimates for the improvements including curb, drainage and channelization improvements and traffic signal design. INCA provided a complete boundary survey and topographic mapping of the site, including surrounding roads and properties.