Potential effects to the environment were studied and presented in the DEIR. The DEIR identifies and evaluates measures to avoid, minimize and mitigate adverse impacts and describe the potential environmental effects of the proposed project and the steps that will be taken to alleviate them. Environmental review for the proposed project addresses the following resource areas: aesthetics, agricultural resources, air quality, biological resources, cultural resources, geology and soils, hazards and hazardous materials, hydrology and water quality, land use and planning, noise, safety and transportation and traffic.
The proposed project would result in changes to three types of noise: construction-related noise, aircraft-related noise, and traffic-related noise.
The Airport is currently used by the full spectrum of general aviation (i.e., private or corporate) aircraft. The majority of operations are by single-engine piston aircraft. This will continue to be the case whether or not the proposed project is implemented. The types of general aviation aircraft currently using the airport include: single- and twin-engine piston aircraft; single-and twin-engine turboprops; and the full range of jets from the smallest corporate jet to the Boeing 737 business jet. Airline service is currently provided using twin-engine turboprops. The mix of aircraft types will be identical whether or not the project is implemented, except that regional airline jets would be unlikely to use the Airport without the proposed improvements.
Due to the runway extension, aircraft landing from the northwest will be about 40 feet lower than today, while those departing to the south will be about 40 feet higher. The difference in height above the ground will mean that individual aircraft operations associated with the main runway (Runway 14/32) will be slightly louder to the northwest and slightly quieter to the southwest. Except in areas close to the airport the difference in sound levels may not be noticeable to residents. The loudest sound levels will continue to be generated by the larger corporate jets. Although the various models of regional airline jets vary in their sound levels, as a group they are similar to the turboprop airline aircraft currently in use.
The proposed project would result in changes to three types of noise: construction-related noise, aircraft-related noise, and traffic-related noise. The methods used for describing existing noise conditions and forecasting the future noise environment rely extensively on computer noise modeling. The noise environment is commonly depicted in terms of lines of equal noise levels, or noise contours.
The FAA's Integrated Noise Model (INM) Version 7.0b was used to model aviation operations for the Airport for purposes of identifying the extent of aircraft noise exposure. The INM is a large computer program developed to plot noise contours for airports. The program is provided with standard aircraft noise and performance data for over 100 civilian aircraft types that can be tailored to the characteristics of an airport, as well as a database of military aircraft types. Version 7.0b includes an updated database that includes some newer aircraft, the ability to include run-ups in the computations, the ability to include topography in the computations, and the increased differentiation between different types of aircraft (civil, military, and helicopter). Noise contour files from the INM were loaded into the ArcView Geographic Information System (GIS) software for plotting and land use analysis.
The INM program requires the input of the physical and operational characteristics of an airport. Physical characteristics include runway coordinates, airport altitude, and temperature and, optionally, topographical data. Operational characteristics include various types of aircraft data. This includes not only the aircraft types and flight tracks, but also departure procedures, arrival procedures, and stage lengths (flight distance) that are specific to the operations at an airport. Aircraft data needed to generate noise contours include:
• number of aircraft operations by type;
• types of aircraft;
• day/night time distribution by type;
• flight tracks;
• flight track and runway utilization by type;
• flight profiles;
• typical operational procedures; and
• average meteorological conditions.
The noise models address the impacts that construction-related noise, aircraft-related noise, and traffic-related noise would have on areas in the vicinity of the Airport that could be affected. Thus, the noise analysis is not limited to Airport property. As part of the aircraft noise model, both arrivals and departures are included into the parameters used in the model.
Three parcels totaling about 22 acres would be acquired before 2015 to implement the project. These parcels are needed to develop the parallel taxiway and provide for a standard Runway Safety Area for Runway 14/32, and realign a portion of Airport Creek. The County hopes to continue its policy of acquiring property through voluntary sale by the owner. The sales price for the property is based upon formal appraisals to ensure that property owners receive full market value. Relocation assistance is also provided, if the property owner wishes. Some properties must be acquired for the project to be constructed. If a property owner does not wish to sell, the County will be forced to condemn the property. Even if the property is condemned, the property owner will still receive full market value and be offered relocation assistance.
The Draft EIR identified four impacts that are considered to be significant and unavoidable. These impacts are: (1) operational increases in Greenhouse Gas emissions in 2030; (2) loss of Airport Creek wildlife movement corridor for large mammals; (3) short-term construction noise impacts; and (4) U.S. 101 freeway operation for 2030. All other impacts identified in the Draft EIR can be mitigated to a less-than-significant level.
Permits and approvals that would be required for the implementation of the proposed project include the following: (1) General Construction Stormwater Permit from the Regional Water Quality Control Board; (2) General Industrial Stormwater Permit from the Regional Water Quality Control Board; (3) Section 404 Permit from the U.S. Army Corps of Engineers; (4) Section 401 Permit from the Regional Water Quality Control Board; (5) 1602 Permit from the California Department of Fish and Game; (6) Amended Airport Permit from the State of California Division of Aeronautics; (7) Approval of Airport Master Plan from County of Sonoma Board of Supervisors; and (8) Approval of Amendments to the Air Transportation Element from County of Sonoma Board of Supervisors.