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02/05/98 THU 16:05 ~tX 6124825232 ~ R6JlSEY CO PUBLIC WORKS III 003 -~ Wagner Street, Roseville, (B) 512 Glenwood Avenue, Roseville, (C) the Ramsey County Women's Detention Center, and (D) a new house being conSU\lcted at the southwest corner of Mackubin and Larpenteur in Saint Paul. The MPCA daytime noise standard for residential receptors is L50 = 60 dB(A). The sound levels from the proposed concrete recycling operation projected for the residential receptors are lower than the measured weekday background sO\.lnd levels. with the exception of the Women's Detention Center. Projections were made assuming flat land wil:h no obstrUCtions. The actual sound levels experienced at the residential receptor sites should be Jower due to the sOWld barrier effect of gravel stockpiles, berms. and vegetation. Each crushing installation is unique and no one can accurately predict the sound level of a specific crushing installation.. We would not know the actual sound levels from our proposed concrete recycling plant until it was in operation. Also included on the table are results from SOW1d me~urcmcnts made on January 17, 1998 during a demonstration of a NSP tub grinder; weekday backgrQI,lDd sound level measurements recorded on 1anuary 30 and Feb('\lary 4, 1998; and the MPCA residential s.ound level standard. TABLE 2 Sound Source or Standard Sound Levels in dB(A) Site A Site B Site C Site D Tub Grinder (measured) 60.1 72_4 Concrete Recvclin2 (nrolected) 58.9-59.7 57.6-58.7 60.2~61.3 63.7-64.6 Weekday Background Sound Level 57.5-60.1 57.5-60.1 54.7 62.7-68.4 (measured) MPCA Davtime Residential Standard 60 60 60 60 MPCA noise standards are a L50 of 6OdB(A) during daytime for a residential area. During the NSP Tub Grinder demonstration the L-EQ sound level recorded at the closest residence, which was 340 feet nortb of the tub grinder, was 60.1 dB(A). This site was at a lower el=vation than the wb grinder, which wO\.lld increase the diffraction angle and therefore increase the effectiveness of sound attenuation by the benn constructed at the south edge of the tub grinder site. The L-EQ noise level recorded at the second residence, which was 520 feet north of the tub grinder and 30 feet higher than the closest residence) was 72.3 dB(A). This site is at a distance of 180 feet further a.way than site "N' but is at a higher elevation, at about 30 feet higher than site "At!, thus reducing the diffraction ang1e of the sound path over the berm compared to site "A".