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72 to 95 decibels (dBA)2 at a distance of 50 feet.3 Materials handling equipment (concrete mixers) could generate noise levels ranging from 75 to 88 dBA at 50 feet. In general, noise levels generated from construction of the proposed project could range from 72 to 95 dBA at 50 feet, although the worst case noise is expected to be less than the higher range because there is no demolition of existing structures. Due to the relatively small scale of the project and the temporary nature of construction noise, this increase in noise level would not be substantial and would not be considered a significant impact of the project. However, the project could expose people using the trail and bridge to noise from aircraft operations at Oakland International Airport. The San Leandro General Plan (City of San Leandro, 2002) notes: Airport noise has been a persistent issue in San Leandro for over 50 years and has become a greater concern as traffic in and out of Oakland International Airport has increased. Residential areas in the City are located just over a mile from the end of the airport runways. There are plans to substantially increase passenger and cargo service at the airport, creating the potential for even more significant impacts to San Leandro homes and businesses. Oakland International Airport is subdivided into North and South airfields. The North Field contains three runways (9L127R, 9R/27L, and 15/33), as well as general aviation, maintenance, and some cargo facilities. The South Field includes the commercial passenger runways (11/29) and most cargo facilities. The flight path impacting San Leandro most directly is associated with landing aircraft on Runway 27R at the North Field. Most descending aircraft pass over Marina Square, the Timothy DrivelDavis West area, and the Adams Street industrial area before touching down. Helicopters also use this corridor. The City is also impacted by commercial flights using Runway 11/29. Although planes taking off and landing on this runway do not pass directly over San Leandro, the area between the runway and the San Leandro shoreline is open water, providing few opportunities for sound to be absorbed. Consequently, the San Leandro Marina and adjacent waterfront neighborhoods may experience high noise levels. Residential areas also may be impacted by high levels of airport noise when flight patterns are shifted due to inclement weather. Flight patterns that use Runway 27L most directly affect the project site, since arriving and departing planes fly directly over the proposed location of the Oyster Bay Slough bridge. Winds in the Bay Area predominantly blow from the west to the east and. historical data collected by the airport 2 Sound is measured in decibels (dB), often referred to a A-weighted decibels (dBA). The sound indices most commonly used to describe environmental noise are the Day-Night Average Sound Level (DNL) and the Community Noise Equivalent Level (CNEL). When calculating the 24-hour average of sound in an area, these two indices respond to the community's preference for a quieter environment in the evening and nighttime hours by assigning penalties to noises that occur during those specified hours prior to calculating the average. Both indices place a 10 dB penalty on all noises occurring from 10:00 p.m. to 7:00 a.m. The CNEL calculation varies in that it also places a 5 dB penalty on noise events during evening hours (7:00 p.m. to 10:00 p.m.). The two systems yield generally similar results and are used interchangeably. 3 In the absence of acoustical barriers, noise levels are reduced by 6 dBA for every doubling of distance from noise sources (due to atmospheric and ground absorption). Y 42041S.00693.doc - 4/5/07 -33-