Church of the Redeemer. Los Altos Hills, California

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1 Los Altos Hills, California 8 February 2016 Prepared for: Church of the Redeemer, Los Altos Reyad Katwan In care of: The Republic Family of Companies 84 West Santa Clara Street, Suite 600 San Jose, CA Phone: rkatwan@republic-urban.com Prepared by: Charles M. Salter Associates, Inc. Greg R. Enenstein & Philip N. Sanders, LEED AP 100 W. San Fernando, Suite 430 San Jose, CA Phone: greg.enenstein@cmsalter.com philip.sanders@cmsalter.com CSA Project Number:

2 8 February 2016 Page 2 INTRODUCTION This report summarizes our environmental noise assessment for the Church of the Redeemer New Fellowship Hall and Classroom Building project in Los Altos, California. The project consists of a 2-story building with 9 classrooms and a 5429 square foot Fellowship Hall. The existing lawn will be utilized as an outdoor activity space associated with the classroom building. The site is located on Magdalena Avenue and is adjacent to an off-ramp for I-280. Following is a summary of our findings: 1. Estimated future noise levels at the setback of future buildings are CNEL 65 db and below a) Levels fall within the City s CNEL 70 db acceptable limit for schools and churches. b) Levels fall within the County s General Plan cautionary land use category 2. Standard building construction is expected to provide interior noise levels of CNEL 45 db or below, due to exterior sources. 3. Standard construction grade windows are expected to meet the County s General Plan maximum interior noise level goal for intermittent exterior sources. 4. Estimated noise from children playing in the central lawn is expected to meet the City and County s Municipal Code limits and not provide an impact to the CNEL at neighboring properties. 5. Noise from mechanical equipment should be designed to meet the limits provided in the City and County s Municipal Code. ACOUSTICAL CRITERIA Los Altos General Plan The Noise Element, Chapter 7 of the Los Altos General Plan, includes environmental noise compatibility guidelines for various land uses in the community and interior noise goals. The policies are summarized as follows: Policy 7.2: A maximum acceptable outdoor noise exposure level CNEL 1 70 db for churches and schools Policy 7.3: An interior noise goal of CNEL 45 db if outdoor noise levels cannot be mitigated to CNEL 70 db Los Altos Municipal Code Section of the Los Altos Municipal Code limits exterior noise levels at a property line and are summarized in Table 1, below. Table 1: Los Altos Municipal Code exterior noise limits Daytime (7 am - 10pm) Nighttime (10 pm -7 am) Noise occurring over 30 minutes per hour 55 db 45 db Instantaneous noise 75 db 65 db Furthermore, the Municipal Code states that if the character of the sound contains a steady audible tone, such as a whine, screech, or hum, or contains music or speech conveying informational content the limits in Table 1 shall be reduced by 5 db. 1 CNEL (Community Noise Equivalent Level) A descriptor for a 24-hour A-weighted average noise level. CNEL accounts for the increased acoustical sensitivity of people to noise during the evening and nighttime hours. CNEL penalizes sound levels by 5 db during the hours from 7 PM to 10 PM and by 10 db during the hours from 10 PM to 7 AM.

3 8 February 2016 Page 3 Santa Clara County General Plan The most recent County Noise Element is from the Santa Clara County General Plan, which includes land-use compatibility standards and recommended maximum interior noise levels for intermittent noise. Note that the County Noise Element is considerably more stringent than the Los Altos Noise Element and may be in the process of updates. Table 2, below displays noise compatibility standards for churches and schools: Table 2: Santa Clara County General Plan Noise Compatibility Standards for Churches and Schools Noise Level (DNL) 2 Noise Compatibility Evaluation Satisfactory - noise levels pose no serious threat to the proposed land use. The ambient noise level at the site is compatible with the land use category of the proposed project and 60 db or lower will not create annoyance and/or activity interference. Standard construction techniques will be adequate. Cautionary noise levels are those which could potentially pose a threat to the proposed Between 60 db and 65 db land use. The ambient noise level is great enough to require study on the compatibility of the proposed project. Normal building methods may not be adequate to protect the use. Critical noise levels are those which probably pose a threat to the proposed land use. The ambient noise level is severe. The situation requires rigorous analysis of the compatibility of the proposed project with the ambient noise level at the site. This analysis Above 65 db should include both exterior and interior impacts. Simple solutions to noise attenuation may not be adequate and uses should be allowed only if they have been designed for noise reduction by a professional who is competent in sound reduction. In addition the General Plan recommends maximum interior noise levels for intermittent noise of 45 db for churches, 50 db for school classrooms, and 55 db for other public buildings. Santa Clara County Noise Ordinance Section B of the Santa Clara County Noise Ordinance describes exterior noise level limits at a property line, and are consistent with those described above in the Los Altos Municipal Code. California Code of Regulations The 2013 California Green Building Standards Code (CALGreen) 3 contains acoustic requirements for nonresidential developments where CNEL, or hourly average (L eq (h) 4 ), sound levels exceed 65 db. These are summarized as follows: Prescriptive method: Wall and roof-ceiling assemblies exposed to the noise source shall have a composite STC rating of at least 50, with exterior windows having a minimum STC rating of 40 Performance method: Wall and roof-ceiling assemblies shall reduce average hourly noise levels to L eq (h) 50 db, or lower, in occupied areas during any hour of operation 2 DNL (Day-Night Average Sound Level) A descriptor for a 24-hour A-weighted average noise level. DNL accounts for the increased acoustical sensitivity of people to noise during the nighttime hours. DNL penalizes sound levels by 10 db during the hours from 10 PM to 7 AM. For practical purposes, the DNL and CNEL are usually interchangeable. DNL is sometimes written as L dn. 3 California Code of Regulations, Part 11: 2013 California Green Building Standards Code, Nonresidential Mandatory Measures, Section L eq(h) The equivalent steady-state A-weighted sound level that, in an hour, would contain the same acoustic energy as the timevarying sound level during the same hour.

4 8 February 2016 Page 4 NOISE ENVIRONMENT The noise environment at the site is most impacted by traffic on I-280 and Magdalena Avenue. The western edge of the site is approximately 220 feet from the centerline of I-280. To quantify the existing noise environment, two 24-hour monitors continuously measured noise levels at the site between 18 and 19 August In addition, two short-term spot measurements were conducted at additional locations and compared with corresponding time periods of the multi-day monitors to determine how noise levels vary across the site and at different elevations. Table 3 summarizes existing noise levels at the site. Figure 1, attached, shows the approximate measurement locations. Table 3: Existing Noise Environment Site Location Date / Time CNEL L1 Magdalena Avenue Monitor Approximately 45 southeast of Magdalena Avenue centerline, 500 east 69 db of I-280 centerline, 12 above grade South Site Monitor August 2015 L2 Approximately 330 east of I-280 centerline, 15 north of south property line, 10 above grade 62 db S1 Future Classroom Building Facade Spot 10:25-10:40 Approximately 245 east of I-280 centerline, 155 south of Magdalena 18 August 2015 Avenue centerline, 5 / 16 above grade 62/ 63 db S2 East Site Spot Approximately 485 east of I-280 centerline, 5 north of south property line, 5 above grade 10:35-10:50 19 August 2015 Typical maximum noise levels 5 at the site were 77 db at Monitor L1 and 71 db at Monitor L2. These maximums were generally from vehicles on I-280 and Magdalena Avenue. Based on the CNEL contour tables NEH-2 and NEH-3 in the Los Altos Noise Element, the City projects less than a 2 db increase in traffic noise from I-280 by Expected project-generated noise consists of mechanical equipment and children playing in the central lawn. We understand that up to approximately 40 children will be playing at a time, and the lawn is a distance of approximately 140 feet from the south property line. The existing church and new fellowship hall will provide shielding to the south property line. We have assumed that outdoor play activity will last for 2 hours per day and only occur during the daytime. 53 db 5 Lmax30 (Typical Maximum Sound Level) There is no standardized metric to quantify typical maximum sound levels in an environment (instead of the absolute maximum sound level for a measurement period). The metric L max30 comes from a paper by Rob Greene ( Max Level Intrusive Noise Limit: 1982 National Conference on Environmental and Occupational Noise ). It is based on the logarithmic average of the noisiest 30 percent of single events (e.g., train passbys, aircraft flyovers).

5 8 February 2016 Page 5 ANALYSIS AND RECOMMENDATIONS Land Use Compatibility Estimated future noise levels at the setback of future buildings are CNEL 65 db and below and L eq (h) 65 db and below. This meets the City s CNEL 70 db limit for acceptable noise levels for schools and churches and falls into the County s cautionary land-use compatibility category. Interior Noise Levels Based on estimated future noise levels, standard building construction is expected to provide interior levels of CNEL 45 db and below. Standard building construction is projected to meet the Santa Clara County General Plan typical maximum interior noise level goal of 45 db at the Hall, 50 db at classrooms, and 55 db at offices. While standard construction grade windows at classrooms with direct exposure to I-280 (i.e., Classrooms 4 & 5) provide the necessary sound insulation ratings to meet the Santa Clara County General Plan interior noise goal of 50 db for typical maximums, windows must be closed to maintain the noise goal. The building design should include an alternate means of ventilating Classrooms 4 & 5. CALGreen Since estimated future noise levels do not exceed L eq (h) 65 db, the CALGreen exterior noise intrusion criteria does not apply. Project Generated Noise The nearest sensitive receivers to children playing on the central lawn are at residential backyards and are approximately 160 feet from the lawn. Receiver locations are shown as R1, R2, and R3 in Figure 2, attached. Measurements at a prior site indicated that hourly average noise levels from 24 children playing were 69 db at a distance of 30 feet. Based on these measurements and adjusting for an increase in children, an increase in distance to the receivers, and shielding provided by the project buildings, we estimate hourly average noise levels at the nearest sensitive receivers to be approximately 45 to 50 db, which is projected to meet the Los Altos Municipal Code and Santa Clara County Noise Ordinance limits. Based on our estimates, project generated noise from children playing is not expected to impact the CNEL at the nearest sensitive receivers. However, receivers can expect the noise from children playing to still be audible at times. Mechanical equipment and locations have not currently been selected, but they should be designed to meet the property line noise limit of 55 db, or 45 db if they will operate at night. Equipment selection, and mitigation, such as noise barriers, should be incorporated into the design to meet these limits. * * *

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