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BENDER READY -MIX CONCRETE MANUFACTURING PROJECT Initial Study /Mitigated Negative Declaration individual responses vary considerably. Standards usually address the needs of the majority of the general population. SHORT -TERM NOISE IMPACTS Construction of the proposed project would occur over approximately three months. Construction activities would include minor demolition, grading, trenching, paving, and building construction. Ground -bome noise and other types of construction- related noise impacts would typically occur during the initial site preparation. This phase of construction has the potential to create the highest levels of noise; however, it is generally the shortest of all construction phases. Typical noise levels generated by construction equipment are shown in Table 4.124, Maximum Noise Levels Generated by Construction Equipment. Operating cycles for these types of construction equipment may involve one or two minutes of full power operation followed by three to four minutes at lower power settings. Other primary sources of acoustical disturbance would be due to random incidents, which would last less than one minute (such as dropping large pieces of equipment or the hydraulic movement of machinery lifts). Table 4.12 -4 Maximum Noise Levels Generated by Construction Equipment Concrete Saw 20 90 Concrete Mixer Truck 40 79 Backhoe 40 78 Dozer 40 82 Excavator 40 81 Forklift 40 78 Paver 50 77 Roller 20 80 Tractor 40 84 Water Truck 40 80 Grader 40 85 General Industrial Equipment 50 85 Note: 1 — Acoustical Use Factor (percent): Estimates the fraction of time each piece of construction equipment is operatinq at full power i.e., its loudest condition during a construction operation, Source: Federal Highway Administration, Roadway Construction Noise Model (FHWA- HEP -05- 054 ), January 2006. Chapter 10.28.040 of the City's Municipal Code states that construction activities are permitted during the hours of 7:00 AM and 8:00 PM on weekdays and Saturdays, and are not permitted on Sundays or Federal holidays. The City does not have noise limits during the allowed construction hours. As such, the Speech Interference Criteria is used to evaluate construction noise levels. For construction noise, a "substantial" noise increase can be defined as interference with activities during the day and night. One indicator that construction noise could interfere with daytime activities would be speech interference. As the City does not have quantitative guidelines for construction noise, the following criteria is utilized in the analysis to define relative construction - related noise impacts: Speech Interference Criteria. Speech Interference Level was designed as a simplified substitute for the Articulation Index.' It was originally defined as the average of the now I Articulation index takes into account that some frequencies are more effective in masking speech than others. The frequency range from 250 to 7000 Hz is divided into 20 bands. The difference between file average speech peak level in each of these bands is calculated and the resulting numbers combined to give a single index. JULY 2011 4.12 -4 lki L_i 11' Ll NOISE I