Tetra Tech INCA provided the Washington State Department of Transportation (WSDOT) with full scoping design and documentation for three proposed safety projects in the Northwest Region. The scoping design level was the first 10% to 15% design of these projects. These projects were proposed for funding to complete the design and construction in the 2007-2009 Biennium.

Key elements of this project included:

• Project Notebooks: These include full project definitions, assumptions, estimates, and schedules that assist the design team initiate the project design once it is funded.
• Preliminary Design: 10% to 15% design level plans and estimates provided in the WSDOT’s prescribed electronic format. This will enable the designer to start with tangible design data.
• Risk Assessment: A detailed risk identification for formal risk assessment, as well as support during the formal assessments for each project.
• Project Critical Path Method (CPM): A work breakdown structure and deliverables critical path schedule for each project, which will enable future designers to quickly start the design process.
   

The City of Everett, in a partnership with Boeing, WSDOT, and FHWA, undertook this project to accommodate the increase in traffic with the opening of Boeing’s 777 Plant. Tetra Tech INCA provided scoping, conceptual design, alternatives analyses, preliminary and final plans, specifications, cost estimates, and construction services for major interchange modifications. This section of SR 526 is a fully-directional, four-level interchange, over a mile in length. Proximity to the Everett Mall required year-around traffic flow during construction. The bridge is a five span, 1,055-foot long steel plate girder bridge, which is curved at a 700-foot radius and is designed in accordance with AASHTO’s Guide Specifications for Horizontally Curved Highway Bridges.

The bridge is a 5-span, 1,055-foot long steel plate girder bridge curved on a 700-foot radius. Supports for the structure consist of compound-radiused concrete columns atop 10-foot diameter drilled concrete shafts. The bridge deck and traffic barrier are composed of 5,000 psi concrete with a width of 25 feet between barriers.
 

Tetra Tech INCA provided support to the Washington Department of Transportation (WSDOT) design team in order to help keep the project design on track to meet the planned construction start date in late 2006. The services requested were the development of a construction staging strategy, construction staging plans, Clean Water Act Section 404(b)1 analysis reevaluation and all water related permit exhibits to the WSDOT project design team for a major 5-mile long highway widening project in Skagit County, Washington.

Key project elements included:

• Construction staging strategy technical memorandum, draft and final versions;
• Construction staging plans for inclusion in the final plan set;
• Section 404 (b)1 analysis reevaluation; and
• Joint Aquatic Resource Permit Application (JARPA) permit exhibits, draft and final versions.

The Upriver Hydroelectric project located on the Spokane River has spillway discharge capability provided by a concrete gravity dam. It is a high hazard dam founded on a gravel foundation. There are eight tainter gates that control the spillway.

Tetra Tech INCA provided static and seismic gravity dam stability analysis. Normal Operation, Flood, ICE Loading, and Earthquake load cases were considered. Work included review of FERC safety program reports, technical reports, static stability analyses and sensitivity analyses, seismic analyses, draft and final report.

INCA performed a stability analysis of the Upriver Dam spillway dam per the FERC guidelines and a sensitivity analysis of the dam stability based on different hydrostatic uplift pressures and foundation soil strength parameters.

Tetra Tech INCA was the structural designer for the South 160th Loop ramp. The project consisted of a new roadway that includes a 264-foot long, two span, cast-in-place concrete box girder bridge near the South 160th Street area.

Existing ramps north of the Sea-Tac International Airport parking garage will be at least partially demolished and removed. The bridge has a complex geometry with tight curves and skewed abutments and pier. The bridge is supported by spread footings.

The project included design, environmental review, site and hazardous material surveys, and relocations to support the development of a multi-lane return-to-terminal ramp on the Northern Airport Expressway in the vicinity of the South 160th Street overcrossing.