SITKA AIRPORT MODELING FOR
ENVIRONMENTAL IMPACT STUDY
Sitka, Alaska

The Federal Aviation Administration (FAA) is requiring that the runway safety area at the Sitka airport be expanded. The runway is built on fill material used to connect islands in Sitka Sound. Expansion at this location has the potential to affect tidal circulation, water quality, and wave climate of nearby locations including Sitka Harbor. Coast & Harbor Engineering (CHE) provided coastal analysis to support the Environmental Impact Statement (EIS) process. CHE documented with data analysis and numerical modeling the base condition of wave propagation, tidal current patterns and velocities, wave runup and overtopping of runway sideslopes, and flushing and relative concentration of water quality parameters. In the first phase of the study CHE developed and verified the tools for determining relative effects of alternative runway safety area expansion plans.

CHE performed the following project tasks:

		Developed detailed plan of study, modeling tasks, various engineering analysis and underwater environmental assets.
		Collected existing and new data for calibration and verification of numerical models.
		Performed wave propagation modeling with a 2-D model SWAN to transform deep water waves to the project area.
		Performed tidal circulation modeling using 2-D model ADCIRC, and analyzed the results that would indicate changes in tidal circulation and transport patterns caused by fill placement.
		Analyzed sediment transport and deposition and bottom sediment scouring using model SEDTRANS.
		Developed coastal engineering design criteria, including wave and current forces on structures, wave height for sizing of revetment armor and toe protection, and depth of scouring of bottom sediments by waves and currents in front of structures.