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III. ENVIRONMENTAL SETTING,IMPACTS AND MITIGATION MEASURES D. NOISE TABLE III.D-5 COMPARISON OF EXTERIOR NOISE STANDARDS AND PROJECT NOISE LEVELS AT RESIDENTIAL PROPERTIES ON TEMPLE STREET Noise Level in dBA Project+ Project+6-foot 10-foot wall+ Level Not wall+hourly hourly limits on to be Project limits on green green waste Noise Descriptor Exceeded Existinga (no mitigation)b waste operationsc operationsd Daytime Hourly Leq 55 51 to 66 59 54 50 Nighttime Hourly Leq 45 52 to 63 59 50 46 a Range of hourly Leq values measured over four-day period(see Table IIID-2). Shown here for comparative purposes only. b Calculations of unmitigated noise from project operations are included in Table A-6 in Appendix A. c A 6-foot masonry wall is proposed as part of Mitigation Measure D.I c. The wall would attenuate(i.e.,reduce) noise from site operations on the east parcel before reaching the receiver(residences on Temple Street). Generally speaking,a noise barrier's effectiveness is determined by its ability to block the line of sight of the source from the receiver. The effectiveness of the 6-foot wall was evaluated by calculating the Fresnel number of the wall assuming a condition where the noise source was located 350 feet from the noise barrier and the noise receptor was located 50 feet beyond the noise barrier. These distances correspond to the shortest distance from the source (transfer station operations on the east parcel)and the closest residence on Temple Street. The frequency of the noise source was assumed to be between 550 Hertz(Hz)and 1,250 Hz. The calculations assume that the noise source is at a height of 8 feet and a noise receptor height of 5 feet. At low frequencies(e.g.,550 Hz),the 6-foot wall was estimated to afford a 5 dBA reduction,whereas at higher frequencies the wall could reduce noise by an estimated 8 dBA. Because the frequency of noise from trucks operating at slow speeds is typically low,the 5 dBA reduction in noise levels was assumed. These calculations also assume that greenwaste processing activities would be limited to after 7:00 a.m. d Using the same methods described above,a 10-foot wall was estimated to reduce noise from project operations by 9 dBA at low frequencies and I 1 dBA at higher frequencies. BOLD values are in excess of applicable standard. 80 DNL at adjacent industrial uses would be considered less than significant. Industrial land uses east and south of the site would be the most affected by noise from project operations. The most pervasive noise would come from the proposed greenwaste processing activities at the southeastern area of the site. A tub grinder and bucket loader operating simultaneously are assumed to produce noise levels of up to 93 Leq at a distance of 75 feet.l Figure II-2 in the Project Description shows that greenwaste processing could occur within 50 feet of adjacent industrial uses. Assuming an attenuation rate of 6 dBA per doubling of distance, noise from the tub grinder and bucket loader would be as high as 96 Leq at the closest industrial property. Noise at these levels would be substantially higher than under current conditions and would cause the DNL at adjacent industrial properties to rise above the level considered acceptable by the City. This would be a significant impact of the project if not mitigated. 1 Associates measured noise associated with greenwaste processing activities at Acme Fill Environmental Science A Landfill in Martinez,California,on October 7, 1999. Operating equipment included a bucket loader and tub grinder. Stockton Sravenger Transfer Station Expansion III.D.16 ESA/990190