13.0 Land Use and Population of 3 feet (1 meter) below grade (if required by the landowner); removal of Project roads; and restoration of disturbed lands. This impact is considered to be potentially significant, and mitigation is required. Mitigation Measure LU-4: Guarantee Bond or Corporate Surety To ensure that future land uses in the Project area are not inhibited after the Project is decommissioned, the Applicant shall: a. Set aside decommissioning funds in the form of a surety bond or other bond acceptable to the County as a specific Project budget item; b. Execute the surety bond or other County-accepted bond on behalf of the Project in favor of the County, with an independent administrator of such funds, to cover all decommissioning costs in an amount approved by the County; and c. Maintain the bond for the life of the Project and through any transfer of ownership. With implementation of this mitigation measure, this impact would be less than significant. 13.5 REFERENCES California Department of Conservation (CDC). 2008. California Farmland Conversion Report 2004-2006. Available: http://www.conservation.ca.gov/dlrp/fmmp/products/Pages/ReportsStatistics.aspx Accessed: March 1, 2010. California Department of Conservation (CDC). 2004. California Farmland Conversion Report 2000-2002. California Department of Finance. 2009. E-5 Population and Housing Estimates for Cities, Counties and the State, 2001-2009, with 2000 Benchmark. Available: http://www.dof.ca.gov/research/demographic/reports/estimates/e-5/2009/. Accessed: March 1, 2010. California Department of Water Resources (DWR). 2009. Suisun Marsh Facts. Available online at www.water.ca.gov/suisun/. Accessed on April 11, 2010. Updated December 22. JDA Aviation Technology Solutions. 2010. Assessment of Shiloh III Wind Project with Rio Vista Airport Master Plan. Prepared by Benjamin Doyle JDA Aviation Technology Solutions, Bethesda , Maryland. April 23, 2010. June 2010 13-25 Shiloh III Wind Energy Project Draft EIR 13.0 Land Use and Population KPFF Consulting Engineers (KPFF). 2010. Analysis and Commentary: Hazard Zones Resulting From Certain Defined Failures of REpower MM92 Wind Turbines at the Shiloh III Wind Energy Project, Solano County, California. January 8. Rio Vista. 2007. Rio Vista Municipal Airport Master Plan Update, Prepared for City of Rio Vista by Aries Consultants LTD, Morgan Hill, California. June. Solano County. 2008. Solano County General Plan. Prepared by: EDAW, Inc. and Englebright and Associates, Solano County, CA. December. Solano County. County Facts and Figures. Available: http://www.co.solano.ca.us/about_solano/county_facts_n_figures.asp. Accessed: March 1, 2010. Solano County Airport Land Use Commission. 1988. Airport/Land Use Compatibility Plan – Rio Vista Municipal Airport, New Rio Vista Airport. Solano County Airport Land Use Commission. 2002. Travis Air Force Base Land Use Compatibility Plan. Solano County, CA. Prepared by Shutt Moen Associates in association with Harris Miller Miller & Hanson, Inc. Solano County Department of Agriculture. 2008. 2008 Solano County Crop and Livestock Report. Fairfield, CA. Solano County Planning Division. 2008. Zoning Regulations, Compiled from Chapter 28 of the Code of Solano County, California. Solano County, California. U.S. Census Bureau, U.S. Department of Commerce. American Fact Finder. Information for Solano County, Zip Code 94512. Available: http://factfinder.census.gov. Accessed: March 1, 2010. U.S. Census Bureau, U.S. Department of Commerce. 2002. “American Communities Survey.” Available online at http://www.census.gov/acs/www/Products/ index.htm. Accessed March 22, 2006. U.S. Census Bureau, U.S. Department of Commerce. 2002. “Fact Sheet for Communities Profiles.” Available online at http://factfinder.census.gov. Accessed on March 22, 2006. June 2010 13-26 Shiloh III Wind Energy Project Draft EIR 14.0 Noise This page intentionally left blank 14.0 Noise 14.0 NOISE This chapter describes existing noise conditions in the Shiloh III Wind Energy Project Area proposed in the Montezuma Hills area of Solano County, California (see Figure 14.1-1) and noise that would be generated by construction equipment and operation of the wind turbines, which have the potential to result in increased noise levels near residences. It includes basic information on noise measurement and assessment, applicable noise regulations and guidelines, an evaluation of the existing noise environment, an assessment of expected noise levels, and a discussion of noise mitigation options. The information in this chapter is based on the March 22, 2010, Shiloh III Wind Project Noise Technical Report prepared by Illingworth & Rodkin, Inc., which includes assessment of the use of REpower MM92 2.0 MW model wind turbines for the Project. The technical report is included in Appendix E. 14.1 NOISE FUNDAMENTALS Noise may be defined as unwanted sound. Noise is usually objectionable because it is disturbing or annoying. The objectionable nature of noise could be caused by its pitch or its loudness. Pitch is the height or depth of a tone or sound, depending on the relative rapidity (frequency) of the vibrations by which it is produced. Higher-pitched signals sound louder to humans than sounds with a lower pitch. Loudness is intensity of sound waves combined with the reception characteristics of the ear. Intensity may be compared with the height of an ocean wave in that it is a measure of the amplitude of the sound wave. In addition to the concepts of pitch and loudness, there are several noise measurement scales that are used to describe noise in a particular location. A decibel (dB) is a unit of measurement that indicates the relative amplitude of a sound. Zero on the dB scale is based on the lowest sound level that the healthy, unimpaired human ear can detect. Sound levels in decibels are calculated on a logarithmic basis. An increase of 10 dBs represents a ten-fold increase in acoustic energy, while 20 dBs is 100 times more intense, 30 dBs is 1,000 times more intense, etc. There is a relationship between the subjective noisiness or loudness of a sound and its intensity. Each 10 dB increase in sound level is perceived as approximately a doubling of loudness over a fairly wide range of intensities. Technical terms are defined in Table 14.1-1. There are several methods of characterizing sound. The most commonly used method in California is the A-weighted sound level, or dBA. This scale gives greater weight to the frequencies of sound to which the human ear is most sensitive for typical environmentally occurring sounds. In special situations, the C-weighted sound level, or dBC, scale is sometimes used. This scale gives more weight to lower frequency noise. When it is used, the intent is to differentiate between noises that have varying amounts of low-frequency noise that would produce only small differences in the A-weighted sound level. June 2010 14-1 Shiloh III Wind Energy Project Draft EIR 14.0 Noise Table 14.1-1 Definition of Acoustical Terms Term Definitions Decibel (dB) A unit describing the amplitude of sound, equal to 20 times the logarithm to the base 10 of the ratio of the pressure of the sound measured to the reference pressure, which is 20 micropascals (20 micronewtons per square meter). Frequency, Hertz (Hz) The number of complete pressure fluctuations per second above and below atmospheric pressure. A-Weighted Sound Level The sound pressure level in decibels as measured on a sound-level (dBA) meter using the A-weighting filter network. The A-weighting filter de- emphasizes the very low and very high frequency components of the sound in a manner similar to the frequency response of the human ear and correlates well with subjective reactions to noise. All sound levels in this report are A-weighted, unless reported otherwise. C-Weighted Sound Level The sound pressure level in decibels as measured using the C- (dBC) weighting filter network. The C-weighting is very close to an unweighted or “flat” response. C-weighting is only used in special cases when low-frequency noise is of particular importance. L01, L10, L50, L90 The A-weighted noise levels that are exceeded 1%, 10%, 50%, and 90% of the time during the measurement period. Equivalent Noise Level (Leq) The average A-weighted noise level during the measurement period. Community Noise Equivalent The average A-weighted noise level during a 24-hour day, obtained Level (CNEL) after adding 5 dB in the evening from 7:00 p.m. to 10:00 p.m. and after adding 10 dB to sound levels measured in the night between 10:00 p.m. and 7:00 a.m. Day/Night Noise Level(Ldn) The average A-weighted noise level during a 24-hour day, obtained after adding 10 dBs to levels measured at night between 10:00 p.m. and 7:00 a.m. Lmax, Lmin The maximum and minimum A-weighted noise level during the measurement period. Ambient Noise Level The composite of noise from all sources near and far. The normal or existing level of environmental noise at a given location. Intrusive Noise that intrudes over and above the existing ambient noise at a given location. The relative intrusiveness of a sound depends on its amplitude, duration, frequency, and time of occurrence and tonal or informational content as well as the prevailing ambient noise level. Source: Illingworth & Rodkin, Inc./Acoustical Engineers 2010 Because sound levels can vary markedly over a short period of time, a method for describing either the average character of the sound or the statistical behavior of the variations must be utilized. Most commonly, environmental sounds are described in terms of an average level that has the same acoustical energy as the summation of all the time-varying events. This energy-equivalent sound/noise descriptor is called Leq. The most common averaging period is hourly, but Leq can describe any series of noise events of arbitrary duration.