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September 6, 2016 Lynn Goto Architect S + L Architects, LLC 2731 183rd Ave SE Snohomish, Wa 98290 Re: Environmental Noise Report Site: Willows Prep School, Redmond, Washington Dear Lynn, This report presents the results of the noise survey performed in the immediate vicinity of the proposed Willows Preparatory School project located at 12280 Redmond-Woodinville Road in Redmond, Washington. The purpose of this report is to document the extent and impact of environmental noise due to traffic and other sources in the immediate vicinity of the school. This report contains data on the existing and predicted noise environments, impact criteria, and evaluation of the data as they relate to the criteria and recommendations for improvement where appropriate. The site is bordered to the west by Redmond-Woodinville Road and by NE 124th Street to the north. The existing noise environment at the proposed site is primarily noise from traffic on the arterials and occasional aircraft. Weather conditions during the period of measurement was overcast with light winds and some precipitation. Hourly noise measurements were conducted with a Svantek 971 Environmental Noise Monitor on September 1st and 2nd between 7:00 AM and 5:00 PM. Equipment conforms to American National Standards Institute (ANSI) requirements for Type 1 instruments and is under current calibration. Our review was completed in accordance with WAC 246-366-030 Site Approval for Educational Facilities and WAC 246-366-110 Sound Control as required by the Health and Safety Guide for K-12 Schools in Washington and Redmond Municipal Code. PRIMARY AND SECONDARY SCHOOL REGULATIONS WAC-246-366-030: Noise from any source at a proposed site for a new school, an addition to an existing school, or a portable classroom shall not exceed an hourly average of 55 dBA and shall not exceed an hourly maximum of 75 dBA during the time of day the school is in session; except sites exceeding these levels are acceptable if a plan for sound reduction is included in the new construction proposal and the plan for sound reduction is approved by the health offices. WAC-246-366-110: Interior background noise levels at any student location within the classroom shall not exceed 45 dBA for 30 seconds. ATTACHMENT 20 ---PAGE BREAK--- Redmond Municipal Code According to Redmond Municipal Code section 6.36.060 Restrictions on residential development adjacent to arterials: This section applies to all residential short plats, subdivisions, and multi-family projects (five or more units) proposed after December 24, 1998. For all residential short plats, subdivisions, and multi-family projects proposed within 100 feet of an arterial or state highway that has an existing or projected traffic volume of 20,000 or more average daily trips, the applicant shall include sound attenuation measures in the site design and/or the design and construction plans of the structure(s). The applicant shall demonstrate that proposed measures provide sound attenuation and that the methods go beyond standard building construction practices. Measures that reduce noise at the site, such as building location, design, berms, noise attenuating fences, and barriers, to help mitigate outside noise exposure shall be used whenever practical in preference to measures which only protect interior spaces. Noise walls over eight feet in height shall be avoided unless all other mitigation measures are determined infeasible and impractical. Blank walls shall be prohibited. The Technical Committee shall approve appropriate methods for reducing noise levels. (Ord. 2590 § 2 (part), 2011). The planned use for the site is currently a school, with a proposal for student residences in the future. Therefore, this section along with the WAC requirements for schools were taken into consideration for the site noise evaluation. ATTACHMENT 20 ---PAGE BREAK--- NOISE MEASUREMENTS Noise measurements were conducted at the project site to quantify the existing noise environment. Measurements ran between 7 AM and 5 PM on September 1 and 2, 2016. The noise monitor was placed at a location representative of the proposed building expansion. The monitor was placed at location 1, which is representative of the proposed classroom building. Additional short-term measurements were conducted at locations 1 – 6 indicated in the following figure: Figure 1: Measurement Location 1 2 5 3 4 ATTACHMENT 20 ---PAGE BREAK--- MEASUREMENT RESULTS The hourly Leq and Lmax measurements are presented in the following chart: Chart 1: Hourly Noise Levels 30 40 50 60 70 80 90 7:00:00 AM 8:00:00 AM 9:00:00 AM 10:00:00 AM 11:00:00 AM 12:00:00 PM 1:00:00 PM 2:00:00 PM 3:00:00 PM 4:00:00 PM Sound Level, dBA re 20 Pa Time Hourly Noise Levels 9/1/16 Leq Lmax 30 40 50 60 70 80 90 7:00:00 AM 8:00:00 AM 9:00:00 AM 10:00:00 AM 11:00:00 AM 12:00:00 PM 1:00:00 PM 2:00:00 PM 3:00:00 PM 4:00:00 PM Sound Pressure Level, dBA re 20 µPa Time Hourly Noise Levels 9/2/16 Leq Lmax ATTACHMENT 20 ---PAGE BREAK--- The following are the Leq and Lmax ranges and average noise levels measured at the site: Long-Term Measurements: Day Leq Range Avg Leq Lmax Range Avg. Lmax Meets W.A.C. 9/1 63-67 64 74-82 77 NO 9/2 59-66 63 69-81 74 NO Short-Term Measurements Location Leq Lmax Meets W.A.C. 1 62 68 NO 2 69 78 NO 3 60 80 NO 4 62 69 NO 5 68 75 NO According to the measurement results, the hourly Leq noise levels exceed the W.A.C. requirements by 4 – 12 dBA, and the hourly Lmax levels by 2 – 7 dBA. Since the hourly noise levels exceed the W.A.C. site noise limits, a noise control plan will need to be included in the new construction design proposal, and include considerations for the exterior wall and window assemblies. Traffic Noise Impacts According to the traffic engineer, the private school (k-8) is anticipated to result in 619 new daily trips and 84 new PM peak-hour trips. According to the WSDOT Annual Traffic Report in the site vicinity, SR-202 milepost 4.27 has a projected growth rate of 6.4% per year. The school project is adding around 3% or half the projected annual amount. The amount of additional traffic due to the school relative to the current traffic volume is minimal and as such traffic noise is not expected to significantly increase above the current levels. The noise control plan for the site will address the current traffic noise impacts to the residential buildings as required under Redmond Municipal Code and the school buildings as required under WAC. Recommendations Classroom Building Since the hourly noise levels exceed the W.A.C. site noise limits, a noise control plan will need to be included in the new construction design proposal for the school. The noise control plan will need to include considerations for the exterior wall and window assemblies to reduce noise levels to the classrooms to meet interior noise level requirements. Student Residence Building The student residence building will need to have sound attenuation in the design that will reduce exterior noise levels to acceptable levels for residential use. The design will include selection of exterior windows, wall assemblies, and other elements to provide effective noise reduction. These elements will be addressed in the project as the design moves forward. ATTACHMENT 20 ---PAGE BREAK--- Please contact us if you have questions or need further information. Sincerely, SSA Acoustics, LLP Alan Burt, P.E. PARTNER ACOUSTICAL CONSULTANT This report has been prepared for the titled project or named part thereof and should not be used in whole or part and relied upon for any other project without the written authorization of SSA Acoustics, LLP. SSA Acoustics, LLP accepts no responsibility or liability for the consequences of this document if it is used for a purpose other than that for which it was commissioned. Persons wishing to use or rely upon this report for other purposes must seek written authority to do so from the owner of this report and/or SSA Acoustics, LLP and agree to indemnify SSA Acoustics, LLP for any and all resulting loss or damage. SSA Acoustics, LLP accepts no responsibility or liability for this document to any other party other than the person by whom it was commissioned. The findings and opinions expressed are relevant to the dates of the works and should not be relied upon to represent conditions at substantially later dates. Opinions included therein are based on information gathered during the study and from our experience. If additional information becomes available which may affect our comments, conclusions or recommendations SSA Acoustics, LLP reserves the right to review the information, reassess any new potential concerns and modify our opinions accordingly. ATTACHMENT 20