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P. (206) 839-0819 F. (206) 839-0824 222 Etruria St, Suite Seattle, WA 98109 Memo To: Troy Stahlecker, University of Washington, Project Manager From: Justin Puggioni, SSA Acoustics, Technician Date: July 8, 2013 Re: UW Lander Hall Construction Noise Monitoring: Week -41 SSA Acoustics, LLP Dear Troy, This memo addresses the noise impact from the UW Lander Hall project construction activity to the UW Children s Center. This memo summarizes our current observations and data collected for the two week period between June 17, 2013 and June 30, 2013. The results include two long term measurements: one taken at the edge of the play area under the cover of the overhanging roof in the middle of the play area, and the other on the inside of the Children s Center in the commons area near the exterior window to the east. The results are limited to data recorded during the Children s Center hours of operation, which are 7:00 a.m. to 6:00 p.m. The Lander Hall and Children s Center sites both fall under Major Institution (MI) zoning. This type of zoning differs to sub zonings for noise compliance purposes. Both sites are considered commercial. The noise limits below are summarized from section 25.08. 410 25.08.425. Please refer to the exact noise ordinance for more complete information. Seattle Noise Ordinance: Chapter III Environmental Sound Levels 25.08.410- Exterior Sound Level Limits The limit for a commercial noise source to a commercial receiver is dba (Leq) at the property line. During a measurement interval, the Lmax may exceed the Leq by no more than 15 dba. 25.08.425 Sound Created by Construction and Maintenance Equipment The exterior sound level limits established in Section 25.08.410, as measured from the property line of the real property of another person or at a distance of feet from the construction noise source, whichever is greater, may be exceeded during the following times by the following: Within Commercial zones, between 7 a.m. and 7 p.m. on weekdays, limits may be exceeded by 25 dba for equipment on construction sites. Therefore, the ordinance requires that construction noise not exceed Leq dba at the Children s Center property lines, since the property line is approximately feet from the Lander Hall site, and noise level is limited at the property line or any person on the property at feet, whichever is greater. The code does not specify a different Lmax limit for construction activity. However, we assume that the Lmax limit increases with the Leq for construction activity.
Page 2 of 3 Since our outdoor monitor is placed adjacent to the playground and not at the north property line, we will establish an equivalent noise limit that factors in the increased noise reduction from the increased distance. We calculate that construction noise will only be 6 dba louder at the north property line of the Children s Center given the increase in proximity. Therefore, construction noise will not exceed the dba noise limit at the property line if it does not exceed 79 dba at the play area monitor location. These limits are shown as dotted lines on our data charts. Given that the Children s Center is simply classified as a commercial property, the noise ordinance does not factor in any additional level of sensitivity for a day care. Therefore, we recommend setting a goal of dba for construction noise at the outdoor play area in order to achieve an acceptable noise environment for children. This was also established as our goal for the previous year of noise monitoring for the UW ECC project. Site Observation: We visited the site at 10:00 a.m. on June 30, 2013. At this time, there was little to no noise from construction activity inside the center. A noise level of 59 dba was measured with a handheld sound level inside the commons area for a short duration. The main source of noise was from children and staff members. We also documented the exterior noise level of the Children s Center play area, which was 64 dba for a short duration. At this time there was audible construction activity.
Page 3 of 3 Data Summary: After reviewing the outdoor noise data, the Lmax noise limit was exceeded four times on June 17 between 11am-12pm, June 20 at 9am, June 20 between 11am-12pm and June 27 between 11am and 12pm at the play area during the two week period. The recorded Lmax noise levels during this time is most likely from noise sources generated in the play area. The Leq limit was not exceeded at any time within the monitoring period. Interior noise levels seem to be driven by interior noise sources and activity within the Children s Center. Though some construction noise will be audible at times; it is having very little effect on the measured interior noise levels. This concludes our findings based on the data collected for weeks -41. The measured results are attached in the charts with this memo. Please contact us if you have any questions or require additional information. Sincerely, SSA Acoustics, LLP Justin Puggioni Technician