1004 59TH PL SW 2016-01-01 MF Import

Noise Assessment: Broadway Apartments Project Michael R. Yantis Associates Inc., P.S. Page 6 interior Noise levels (Ldn) Recommended Land Use (windows closed) Less than 45 dBA Acceptable for residential use More than 45 dBA Unacceptable for residential use i Exterior noise levels expected at lots which are typically 5 feet below the roadway are within the range of 55-60 dBA (Ldn), identified as generally acceptable for residential land use. Within the next 5 years, increases in traffic levels will raise expected exterior noise levels by 5 dB, which will remain within the acceptable range at lot grade level, but will be expected to exceed 65 dBA (Ldn) at the second floor. Noise barriers or special construction techniques will thus be required to reduce interior levels to 45 dBA or lower (windows closed). MITIGATION Expected traffic noise levels for 1998 are expected to exceed the 65 c.dA (Ldn) maximum noise level at second floor windows of dwellings constricted adjacent to Merrill Creek- Park-way. reekParkway. Noise levels may be reduced by either improving the sound reduction of the wall and window construction of the dwellings or by constructing a barrier fence along the property line. Either method is required to reduce noise levels by at least 4 dB, resulting in interior second floor noise levels of less than 45 dBA (Ldn), Mitigation Option 1: Use NLR 25 dwelling constnrction. Typical building construction can be expected to provide approximately 20 dB noise level reduction (NLR) with windows closed. Typical Northwest building construction which meets current energy codes can be expected to provide approximately 25 dB noise level reduction (NLR) with windows closed. With such typical 25 dB NLR construction, expected interior 1998 noise levels in second floor bedrooms facing the roadway (south) will be 40-42 dBA (Ldn), with windows closed. Refer to Appendix II for a complete description of construction details which will meet the 25 dB NLR requirement.