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02/05/98 THU 16:05 P.\! 6124825232 ~ RAMSEY CO PUBLIC WORKS 141 003 '.. Wagner Street, Roseville, (B) 512 Glenwood Avenue. Roseville I (C) the Ramsey County Women's Detention Center. and (D) a new house being constrUcted at the southwest comer of Mackubin and Larpenteur in Saint Paul. The MPCA daytime noise standard for residential receptoI5 is LSO = 60 dB(A). The sound levels from the proposed concrete recycling operation projected for the residential receptors are lower than the measured weekday background sound levelsl with the exception ofthc: Women's Detention Center. Projections were made assuming flat land wilh no obsnuctions. The aCDJal sound levels experienced at the residential receptor sites should be lower due [0 the sound barrier effect of gravel stockpiles, berms, and vegetation. Each crushing instaUation is unique and no one can accurately predict the :iou.nd lcvel of a specifil; crushing installation.. We would not know the actual sound levels from OUr proposed concrete recycling plant unlil it was in operation. Also included on the table are results from sound mc~urcmcnts made on January 17, 1998 during a demonstration of a NSP tub grinder; weekday background sound level measurements recorded on January 30 and Feb(1,1ary 4, 1998; and the MPCA residential ~ouod 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 Recvclim~: (proiected) 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 LSO of 60dB(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 elevation than the tub grinder, which would 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 recOt'ded at the second residence, which was 520 feet north of the tub grinder and 30 feet higher than the closes[ residence) was 72.3 dB(A). This site is at a distance of 180 feet further away than site "A" but is at a higher elevation, at about 30 feet higher than site "A", thus reducing the diffraction angle of the sound path oyer the berm compared to site "An.