Tetra Tech INCA designed trunnion bearings, hydraulic machinery and associated control system for this innovative counterweightless trunnion-type bascule bridge. Because of the space restriction, the 81 foot long span was designed without the counterweight. It is lifted directly by the hydraulic machinery. The muscles of the machinery system are two 20-inch ID hydraulic cylinders. This bridge has two car traffic lanes, two bicycle paths, and a railroad track.
 

Concerns about declining salmon runs on the Columbia and Snake Rivers in the Pacific Northwest have generated environmental and political pressure at the regional and national level to improve fish survival around the dams. The Portland and Walla Walla Districts of the USACE are using a variety of physical and operational methods to improve salmon transit and survivability at their Columbia and Snake River dams. One of the most promising methods involves installing data sensing equipment within fish ladders to gather quality data on fish passage and survival through the system. Research and development of this technology led to the fabrication of the Passive Integrated Transponder (PIT) tag. Fish injected with PIT tags are automatically recognized by detecting/recording devices strategically located within collection facilities at hydroelectric dams. Their tags are detected and decoded in situ - eliminating the need to sacrifice, anesthetize, handle, or restrain the fish during data retrieval. When a tagged fish passes through an antenna containing electronic interrogation coils, its unique PIT tag code, along with the date, time, and location of its passage, is sent to a central database.
   
Approximately one million out-migrating juvenile salmon are injected with PIT tags each year, out of a typical total of 90 million. When the tagged adult returns to the Columbia River system to spawn, it is again automatically detected at the interrogation sites within the fish ladders as it travels up-river. These data detections are added to the previous information contained in the database about that individual fish to provide additional data of its history and its migration.

Tetra Tech INCA provided design services, on a fast-track basis, for fish ladder modifications for antennas and support facilities at three separate fish ladders for the Ice Harbor and Lower Granite Dams. INCA began work on this project with site visits to meet with fisheries agencies to clearly define the requirements for the work prior to beginning design. INCA then provided plans and specifications for installation of PIT Tag monitoring of adult fish passage through the fish ladders. Tasks included modification of existing weir orifices in the fish ladders to accommodate installation of government-furnished PIT Tag antennas; installation of transceiver cabinets to house antenna electronics; design of electronic rooms to house PIT Tag system electronics; installation of power and fiber optic cables between the electronics rooms and the transceiver cabinets; and installation of power and fiber optic communications between the existing project services and the new electronics rooms.

Due to the cyclic operation of watering and unwatering of the upstream gate at Ice Harbor Dam and Lower Monumental Dam, the gates experienced metal fatigue in the form of cracks developing in areas (across the upper and/or lower flanges). These gates needed fixes in place the spring of 2002 that were reliable for five years to allow time for a reliability analysis to be performed and, if needed, plans and specifications to be compiled for construction.

Tetra Tech INCA prepared a concept design report examining, from an engineering and cost perspective, various alternatives for refurbishing the upstream gate repairs at Ice Harbor Dan and Lower Monumental Dam. INCA compared the alternatives to the option of doing no refurbishing. The concept design report identified and examined, to a feasibility level, each option.

Tetra Tech INCA was a significant contributor as a designer of the Puget Sound’s premier transportation program of the 1980s, the improvements to the I-90 corridor across Mercer Island. This $23,000,000 construction effort was a major undertaking of WSDOT, resulting in several new approaches for integrating of landscape, transit, and community access. INCA provided preliminary design of the eight-lane depressed freeway, including landscaped cut and cover overpasses, aerial ramps, and transit access. INCA provided value engineering services and final design for numerous retaining walls with several construction techniques.

Jointly developed by Sound Transit and the Washington State Department of Transportation (WSDOT) as part of Sound Move, the region’s ten-year transit plan, this $22 million project constructed HOV ramps to connect I-90 to the Eastgate Park-and-Ride lot. These ramps increase speed and reliability of buses and carpools to and from the I-90 HOV lanes.