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02/05/98 TBlT 16:05 FAX 6124825232 ~ R~SEY CO PlmLIC WORKS ~003 '. Wagner Street, Roseville, (B) 512 Glenwood Avenue, Roseville, (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 Pau1. The MPCA daytime noise standard for residential receptors 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 levels, with the exception of the Women's Detention Center. Projections were made assuming flat land with no obstrUctions. The actual sound levels experienced at the residential receptor sites should be lower 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 OUT proposed COncrete recycling plant until it was in operation. Also included on the table are rcsults from sOW1d mCa.5urcmcnts made on January 17. 1998 during a demonstration of a NSP tub grinder; weekdAy backgrQund :sound level measurements recorded on January 30 and February 4, 1998; and the MPCA residential sound 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 Recycline (projected) 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 nortD 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 constrocted 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 away than site "Au but is at a higher elevation. at about 30 feet higher than site "A". thus reducing the diffraction ang1e of the sound path over the berm compared to site "A".