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HomeMy WebLinkAbout8.1, Attch 3 Env Noise Assessment R©SEN GOLDBERG DER & LEWITZ, INC. arA Audlcvia ual cow'a .lta,;t' ENVIRONMENTAL NOISE IMPACT REPORT FOR: Montessori Plus 11900 Silvergate Drive Dublin, CA RGDL Project* 11-041 PREPARED FOR: City of Dublin 100 Civic Plaza Dublin, CA 94568 PREPARED BY: Harold S. Goldberg, P.E. Principal Consultant DATE: 15 July 2011 1100 Larkspur Landing Circle #375 . Larkspur CA 94939 • Tel 415 464 0150 o Fax 415 464 0155 a RGDLacoustics.com ATTACHMENT 3 Montessori Plus, Dublin, CA Environmental Noise Impact Report Page 1 15 July 2011 1. Introduction The proposed project is a new child care center at 11900 Silvergate Drive in Dublin California. The site is currently occupied by a commercial building and parking lot. The project includes an outdoor play area on the east and south sides of the building. This study estimates the noise levels that would be generated by the use of the outdoor play area and evaluates the potential for noise impact at the existing single-family homes near the site. The analysis includes ambient noise measurements at the site, noise measurements of a similar childcare facility and comparison of the noise levels with the City of Dublin's noise and land use compatibility standards. 2. Environmental Noise Fundamentals Noise can be defined as unwanted sound. It is commonly measured with an instrument called a sound level meter. The sound level meter captures the sound with a microphone and converts it into a number called a sound level. Sound levels are expressed in units of decibels. To correlate the microphone signal to a level that corresponds to the way humans perceive noise, the A-weighting filter is used. A-weighting de-emphasizes low-frequency and very high-frequency sound in a manner similar to human hearing. The use of A-weighting is required by most local General Plans as well as federal and state noise regulations (e.g. Caltrans, EPA, OSHA and HUD). The abbreviation dBA is sometimes used when the A-weighted sound level is reported. Because of the time-varying nature of environmental sound, there are many descriptors that are used to quantify the sound level. Although one individual descriptor alone does not fully describe a particular noise environment, taken together, they can more accurately represent the noise environment. The maximum instantaneous noise level (Lmax) is often used to identify the loudness of a single event such as a car passby or airplane flyover. To express the average noise level the Leq (equivalent noise level) is used. The LeQ can be measured over any length of time but is typically reported for periods of 15 minutes to 1 hour. The background noise level (or residual noise level) is the sound level during the quietest moments. It is usually generated by steady sources such as distant freeway traffic. It can be quantified with a descriptor called the Lgo which is the sound level exceeded 90 percent of the time. To quantify the noise level over a 24-hour period, the Day/Night Average Sound Level (DNL or Ldn) or Community Noise Equivalent Level (CNEL) is used. These descriptors are averages like the LeQ except they include a 10 dB penalty during nighttime hours (and a 5 dB penalty during evening hours in the CNEL) to account for peoples increased sensitivity during these hours. In environmental noise, a change in noise level of 3 dB is considered a just noticeable difference. A 5 dB change is clearly noticeable, but not dramatic. A 10 dB change is perceived as a halving or doubling in loudness. ROSEN GOLDBERG DER & LEwITZ, INC. 1100 Larkspur Landing Circle »375 ? Larkspur CA 94939 * Tel 415 464 0150 s Fax 415 464 0155 • RGDLacoustics.com Montessori Plus, Dublin, CA Environmental Noise Impact Report Page 2 15 July 2011 3. Acoustical Criteria 3.1. City of Dublin General Plan The Noise Element of the City's General Plan has policies regarding noise and land use compatibility. Table 1 provides guidelines for the compatibility of land uses with various noise exposures. The City uses the Community Noise Equivalent Level (CNEL) descriptor. A CNEL of 60 dBA or less is considered normally acceptable for residential land use. It should be noted that the City's compatibility standards are normally intended to be used for traffic and transit noise. Table 1: Land Use Compatibility for Community Noise Environments COMMUNITY NOISE EXPOSURE (dB) Land Use CatooorY Normally Conditionally Normally Clearly Acceptable Acceptable Unacceptable Unacceptable (Noise Insulation) Features Required Residential 60 or Im 60.70 70.75 over 75 Motels, hotels 60 or less 60.70 70.80 Over 80 Schools, churches, nursing 60 or less 60.70 70.80 over 80 homes Neighborhood parks 60 or less 60.65 65 - 70 Over 70 Offices: retail commercial 70 or less 70 - 75 75 - 80 Over 80 Industrial 70 or less 70 - 75 over 75 Conditionally acceptable expos ure requires noise insulation features in building design. Conventional construction, but with closed windows and fresh air supply systems or air conditioning vrill normally suffice. 3.2. City of Dublin Noise Ordinance Chapter 5.28 of the City of Dublin's Municipal Code prohibits "...loud, or disturbing, or unnecessary, or unusual or habitual noise or any noise which annoys or disturbs or injures or endangers the health, repose, peace or safety of any reasonable person of normal sensitivity present in the area". The noise ordinance states that it is appropriate to consider the level and character of the noise as well as the level and character of the background noise. Since the City's Noise Ordinance does not contain quantifiable noise level limits, it is not possible to apply the noise ordinance as a threshold for assessing project generated noise in the context of this noise study. 3.3. Increase in Noise The California Environmental Quality Act Guidelines require the determination of whether a project will generate a substantial increase in noise levels in the R05EN GOLDBERG DER & LEWITZ, luc. 1100 Larkspur Landing Circle #375 ? Larkspur CA 94939 ? Tel 415 464 0150 • Fax 415 464 0155 • RGDLacoustics.com Montessori Plus, Dublin, CA Environmental Noise Impact Report Page 3 15 July 2011 project vicinity above levels existing without the project. CEQA does not specify a method for determining when a project would cause a significant increase in noise. Likewise, the City of Dublin does not have criteria for determining when a noise increase is significant. A recent FAA Draft Policy discusses screening and impact thresholds for increases in aircraft noise. These thresholds are used to assess the significance of noise increases due to the project as follows - an increase in CNEL is significant if it is; • 5 dBA or greater and the future CNEL is less than 60 dBA or • 3 dBA or greater and the future CNEL is 60 dBA or greater and less than 65 dBA or 1.5 dBA or greater and the future CNEL is 65 dBA or greater. 4. Existing Noise Environment To quantify the existing ambient noise levels at the site a series of noise measurements were made at locations around the project site near the adjacent homes. The major source of noise during the ambient measurements was distant traffic on 1-680 and San Ramon Valley Boulevard as well as local traffic on Dublin Green Drive and Silvergate Drive. Table 3 shows the results of the short-term noise measurements. A 24-hour noise measurement was conducted at Location A. The measured CNEL was 55 dBA. The CNEL values in Table 3 are based on a correlation with the long-term noise measurement data. Table 3: Ambient Noise Measurement Results A-Weighted Noise Level, dBA Location Daterrime Laq L10 L50 Lgo CNEL Notes (Lmax) 1 26 April 2011 51 53 46 44 53 Cars on Silvergate, 58 11:36 -11:51 AM Truck on Dublin Green 61 26 April 2011 Cars on Dublin Green 60-64 2 11:53 AM -12:08 53 55 50 48 58 Truck on Silvergate 65 PM 3 26 April 2011 60 61 50 43 60 Aircraft 71 12:12 -12:30 PM Truck on Silvergate 83 ROSEN GOLDBERG DER & LEwITZ, INC. 1100 Larkspur Landing Circle 5375 ? Larkspur CA 94939 a Tel 415 464 0150 a Fax 415 464 0155 + RGDLacoustics.com Montessori Plus, Dublin, CA Environmental Noise Impact Report Page 4 15 July 2011 5. Analysis 5.1. Play Yard Noise at a Similar Facility To quantify the noise levels that would be generated by the use of the outdoor play yards, noise measurements were conducted at a similar facility, KinderCare Learning Center at 11925 Amador Valley Court on the morning of Friday, 17 April 2009. The noise measurements were conducted in the parking lot approximately 27 feet from the metal picket fence. There were ROSEN GOLDBERG DER & LEWITZ, bic. 1100 Larkspur Landing Circle »375. Larkspur CA 94939 s Tel 415 464 01 50 ? Fax 415 464 0155 • RGDLacoustics.com Figure 1: Site Plan and Ambient Noise Measurement Locations Montessori Plus, Dublin, CA Environmental Noise Impact Report Page 5 15 July 2011 three play yards in view of the measurement location and the children tended to congregate around the play structures. The pre-school yard had the most children (up to about 20) and the play structure was 90 feet from the noise measurement location. The toddler and infant yards had about nine children each and were to 115 and 210 feet away, respectively. The noise levels were dominated by the children's voices. Noise data was recorded for a total duration of 70 minutes and the average noise level (LeQ) was 59 dBA and the median noise level (L5D) was 55 dBA. Typical maximum noise levels from children yelling near the closest play structure were 65 to 70 dBA. The loudest yells generated an Lmax of 78 dBA and were from kids along the fence about 45 feet from the noise measurement location, yelling playfully at a truck driver in the parking lot. The children were soon instructed by the childcare staff to discontinue this activity. 5.2. Predicted Play Yard Noise Levels from the Project The proposed play yard at the Montessori Plus facility is shown in Figure 1. According to the project applicant the children would use the outdoor play area twice a day, for one hour in the morning and a half hour in the afternoon. During these times there would be up to 30 children in the outdoor play area. The remainder of the time the children would be indoors. Noise levels from the children playing were calculated based on the noise measurements at the KinderCare facility. Adjustments were made for the number of children and the distance between the play areas and the property lines. The results are shown in Table 4. The existing seven-foot-tall wooden property line fence between the project site and the home to the north will not significantly affect the play yard noise levels because the backyard elevation is about 3 feet higher than the bottom of the fence. The people standing in the backyard tend to look over the fence. Also, the upper part of the fence is lattice work which is not solid enough to act as a noise barrier. Therefore the predicted noise levels in Table 4 do not include any effect from the fence. Table 4: Project Generated Noise Levels Location q (dBLmax A) CNEL (dBA) North Property Line 61 79 49 West Property Line 46 60 34 Residence across Dublin 58 73 46 Green Drive Residences across Silvergate 56 70 44 Drive ROSEN GOLDBERG DER & LEWITZ, INC. 1100 Larkspur Landing Circle #375 + Larkspur CA 94939 + Tel 415 464 01 SO + Fax 415 464 0155 + RGDLacoustics.com Montessori Plus, Dublin, CA Environmental Noise Impact Report Page 6 15 July 2011 5.3. Comparison with Acoustical Criteria 5.3.1. City of Dublin General Plan The CNEL at the nearest residential property line from play yard noise will be 49 dBA which is well below the City's "normally acceptable" compatibility standard of CNEL 60 dBA. In fact, the use of the outdoor activity area could be increased beyond that expected, and still not exceed the standard. For example, if the number of children doubled (from 30 to 60) and the duration of use doubled (from 1.5 hours to 3 hours) then the CNEL would increase from 49 dBA to 55 dBA. Also, it should be noted that the calculated CNEL does not depend on the time of day that the play area is used as long as it is not before 7 AM or after 7 PM. 5.3.2. Increase in Noise The ambient CNEL is 53 to 60 dBA at the nearest residences. The addition of the play yard noise will increase the ambient CNEL by less than 1 dBA. This increase is less than the threshold of 3 dBA increase that would be considered significant. 6. Conclusions The noise from children using the proposed project's play yards is expected to be within "normally acceptable" levels of the City's General Plan Noise Element guidelines for single-family residential development. With the ambient traffic noise at the site, the play yard noise is not expected to significantly increase the long- term average noise levels at the nearby residences. ROSEN GOLDBERG DER & LEwITZ, Inc. 1100 Larkspur Landing Circle #375 # Larkspur CA 94939 # Tel 415 464 0150 # Fax 415 464 0155 * RGDLacoustics.com