Sellwood Bridge Project - Alternative Screening

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Alternative Screening

The information below describes the alternatives screening process - how the Sellwood Bridge alternatives were developed, refined, and evaluated. The funnel diagram illustrates the process followed to narrow a group of preliminary concepts to a single preferred alternative. Each step included both technical analysis and public input. Five alternatives for detailed evaluation in the Draft Environmental Impact Statement (Draft EIS) were selected in October 2007. Identify Concepts In winter 2006, a long list of preliminary project concepts was compiled through a public workshop, an on-line survey, and a series of Community Task Force (CTF) meetings. Screen Concepts The project team screened these concepts to determine if they met the minimum "baseline" requirements of the project, called threshold criteria. These criteria were developed as part of the Evaluation Framework earlier in 2007 to ensure that all alternatives are feasible and solve the problems identified in the project Purpose and Need. Develop Alternatives The CTF reviewed concepts that met the threshold criteria during spring 2007. Some of the concepts were viewed as clearly inferior to others, and the CTF recommended elimination of them. In June 2007 the Policy Advisory Group (PAG) considered CTF recommendations and adopted a Range of Alternatives to be advanced for further analysis. The various combinations of alignment, cross-section, and interchange elements totaled 124 different alternatives. Concepts dropped from the range of alternatives will not be considered further. Evaluate Alternatives The second step of the evaluation process, conducted in June and July 2007, compared the remaining project alternatives against a broad set of evaluation criteria. The pie chart shows the evaluation categories and the CTF’s weightings that reflect their relative importance in achieving goals for the project.

A team of technical experts rated the performance of the 124 project alternatives against each of the 37 evaluation criterion selected by the CTF — producing 4,588 performance ratings! Following performance rating, a total score for each alternative was calculated by multiplying the sum of all the performance ratings times the weightings established by the CTF. The highest score represents the highest project value. A complete rating spreadsheet is available. The evaluation results (PDF, 1.13MB) will be used by the CTF along with public input to develop its recommendation for alternatives to be evaluated further in the Draft EIS. Select Preferred Alternative The alternatives screening was completed and the remaining five alternatives were re-evaluated against the evaluation framework. Results were used to support the recommendation of a preferred alternative that best met the purpose and need statement, technical considerations, local agency guidelines, and community desires (Alternative D). This alternative was recommended by the CTF and approved by the PAG. Local agency approval for the preferred alternative was received in summer 2009. Approval by FHWA is expected in summer/fall 2010.

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The screening process narrowed a group of preliminary concepts down to a few alternatives that were studied in the Draft Environmental Impact Statement (Draft EIS), and then narrowed further to a single preferred alternative.