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3CC Tri-Valley Preschool Outdoor Play Area Noise 30 January 2017 Page 4 The noise at the residential property lines with children playing is expected to be well below the City land-use compatibility standard of DNL 60 dB. In addition,the noise from children playing(for up to 3 hours per day)is only expected to increase the ambient noise levels by 1 dB or less,which is not considered to be a noticeable change in community noise levels. As a"worst-case"scenario,we also calculated the duration of children playing that would only increase the DNL by 3 dB.A 3 dB increase in DNL is considered"just noticeable."A change between 3 dB to 5 dB is often used as a threshold of significance for noise impact analyses. We determine)that children could play outside for 8 hours per day and still only increase the ambient noise level by 3 dB (see data location ST4 in Table 2). Average Noise During Playtime(City Noise Ordinance) As stated above,we expect the average noise from children playing to be between 53 dB and 56 dB along the residential property lines. In Table 3 below,these levels are compared to the City Noise Ordinance standard and the measured typical ambient noise level during daytime hours. Table 2. Playtime Noise(Leg, dB) Residential City Noise Typical Average Noise Property Near Each Ordinance Measured Level from Measurement Standard Ambient Children Playing Location ST2 60(nighttime)ST3 51 55 53 53 70(daytime)ST4 51 56 Again,the noise at the residential property lines with children playing is expected to be below the City standards of 60 dB and 70 dB.At the nearest residential property line,we estimate that noise from children playing could be up to 5 dB above the existing ambient noise level,which could lie noticeable. COMMENTS No additional mitigation is needed to reduce noise from children playing to be commensurate with the City noise standards at neighboring residential properties. Acoustics Audiovisual However,while children are playing,the noise increase could be noticeable at the nearest residential Telecommunications property line. If this is a concern and additional noise reduction is desired,a noise barrier fence could security be considered.This would be located between the play yard and the property line. It may be placed around the play yard or along the residential property line.To achieve 5 dB of noise reduction,the fence would need to break line-of-sight between the play yard and the receivers and be constructed of 30 Suitor Street solid materials with a minimum surface weight of 3 psf.Leave no cracks,gaps, or leaks between the Floor 5 materials or between the fence and the ground.This could be achieved with a board-on-board wood Srys franc sco CA fence approximately 6 feet tall.Other options indude precast concrete panel or CMU block wall 94 104 construction. T 415 397.0442 F 4 15.397 0454 «,•,crosnxor corn tea :. Salter c s(