(1) Air quality analysis for transportation plans, programs, and projects shall be modeled for criteria pollutants using EPA and the federal Department of Transportation approved methods.

(2) Air quality analysis procedures and methodology used in determining conformity for transportation plans and improvement programs shall be determined through consultation with the MPO, the United States Department of Transportation and the Environmental Protection Agency, the state departments of ecology and transportation, the local air authority, and other interested representatives of the public. The consultation procedure for SIP and maintenance plan development in the applicable SIP shall be used for the consultation process required by this section. The consultation process shall also be used for determining research and data collection efforts, and regional transportation model development, events that will trigger new conformity determinations, the status of TCMs, significant changes in project design and scope, and projects which require PM10 analysis. The specific analysis procedures and methodology selected shall comply with this chapter, the federal transportation conformity regulation (40 C.F.R. Part 51 Subpart T), and the applicable SIP. Agreement on the methods and assumptions including modeling parameters, model accuracy, and the base year against which alternatives are compared, shall be reached on all programs and plans prior to the conformity determination. Procedures, methodologies, and input parameters shall be reviewed and updated at least once every two years under the direction of the departments of ecology and transportation. Such review shall occur prior to conformity determination of transportation plan or TIP revisions.

(3) Procedures, methodologies, and assumptions for project analysis shall be consistent with those procedures, methodologies, and assumptions developed for analysis of transportation plans and improvement programs in subsection (2) of this section.

(4) Each MPO shall conduct conformity analyses of the transportation plan and improvement program developed in its region.

(5) The lead agency shall be responsible for project conformity analysis.

(6) The impact of preferred alternative transportation plans, improvement programs, and projects shall be quantified and compared for compliance to the SIP requirements, and the requirements of WAC 173-420-060, and 173-420-065. If modeling does not indicate that the requirements of this section are met, mitigating measures shall be required and the plan, improvement program, or project remodeled. All else being equal, the alternative with the lowest concentration shall be chosen over all other alternatives.