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02; 05/98 THU 16: 05 F.� 6124625232 R�IISEF CO PLBLIC R'ORKS Wagner Street, Roseville, (B) 512 Glenwood Avenue, Roseville ,(C) the Ramsey County Women's Detention Center, ax�d (I�) a new house being constructed at the southwest corner of Mackubin and Larpent�ur in Saint Paul. The MPCA daytime noise standard for residential receptors is T,50 = 60 cIB(Aj_ The sound levels from the proposed concrete recycling operation proj ected for the residential receptors are lower cha�� t6�e measured weekday background sound Ievels, with thc 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 �o the sound barrier e;tecr of gravel stockpiles, berms, and vegetation. Each crushing installation is unique and no one can accurately predict the sound 1cve1 of a specific crushing installation.. We would not know the actual sound Icvcls frOm our proposcd concrete recycling plant undl it was in OperatlOn. Also included on the table are results from sound mcasurcmcnts made ou January 17, 1998 during a demonstration of a NSP tub grinder; wcckday background sound level measurements recorded on January 30 and February 4, 1998; and t,hc MPCA residcntial sound level standard. TABL,E 2 or Standard Wcekday Background Sound Level Sound ?�vels m �oas Site A Site 8 Site C Site D 60.1 72.4 58.9-59.7 �7.6-58.7 6p.2-61.3 5 7. 5-60.1 57 _ 5-60.1 54. 7 60 60 6Q 63.7-64.6 62.7-68.4 MPCA noise standards are a L50 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 north 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 berm 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 away than site "A" but is at a higher elevation, at about 30 feet higher than site "A", thus reducing the diffraction anglo of the sound path over the berm compared to site "A". 60