Juneau International Airport Environmental Impact Statement and Slough Studies
Federal Aviation Administration and SWCA, Inc.

VAI assisted SWCA Environmental Consultants and the Federal Aviation Administration in preparing an Environmental Impact Statement (EIS) for proposed runway safety improvements and airport facilities improvements at Juneau International Airport (JNU). The airport is bounded to the west by the Mendenhall River, to the north by uplands and to the south and east by tidal wetlands. The tidal wetlands beyond the airport boundary are part of the 4,000-ac Mendenhall Wetlands State Game Refuge complex that connects the Gastineau Channel and Fritz Cove.

VAI led the water resources tasks for the EIS including and river and tidal geomorphology and water quality. VAI prepared a Water Resources Technical Working Paper documenting conditions of surrounding rivers and creeks, ponds, palustrine and estuarine wetlands, and groundwater. VAI completed a literature review of geology, hydrology, hydraulics, and water quality and performed fluvial and tidal geomorphology field studies and conducted water quality measurements at JNU and the refuge. One alternative required the relocation of an outfall discharging in to the Mendenhall River. VAI developed a hydraulic model to analyze flow conditions under both high- and low-tide conditions to evaluate the resulting mixing zone.

VAI prepared three channel evolution scenarios for East Runway Slough evaluating impacts of various alternatives for runway safety and navigational improvements on water resources and hydraulics for the Draft, and Final EIS. VAI prepared technical memoranda on potential tidal channel impacts on East Runway Slough and lower floodplain impacts on the Mendenhall River. VAI met with resource agency staff to review methodologies, findings, and conclusions on impacts and to confirm appropriate mitigation for completing the Final EIS.