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Home My WebLink About8.1 Attmt 5 Environmental Noise Impact Rept 04-24-2009ROSEN GOLDBERG DER & LEWITZ, INC. ENVIRONMENTAL. NOISE IMPACT REPORT FOR: Bright Horizons Children's Center Dublin, CA RGDL Project* 09-029 PREPARED FOR: City of Dublin 100 Civic Plaza Dublin, CA 94568 PREPARED BY: Harold S. Goldberg, P.E. Principal Consultant DATE: 24 April 2009 1100 Larkspur Landing Circle #375 ,,, Larkspur CA 94939 -Tel 415 464 0150 Fax 415 464 0155 ? RGDLacoustics.com Attachment 5 Bright Horizons Children's Center, Dublin, CA Environmental Noise Impact Report 1. Introduction Page 1 24 April 2009 The proposed project is a new child care center at 70311") Dublin Boulevard in Dublin California. The site is currently occupied by a commercial building and parking lot. The project includes outdoor play areas on the west side of the site. This study estimates the noise levels that would be generated by the use of the outdoor play areas and evaluates the potential for noise impact at the existing single-family homes to the north. 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 commo -ily 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 noire, 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-wE.,ighting 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 noire 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 ca led the L90 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 Ld„) 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 & I_EWITZ, Nc. 1100 Larkspur Landing Circle #375 Larkspur CA 94939 ? Tel 415 464 01 50 ?r Fax 41 S 464 0155 - RGDLacoustics.com Bright Horizons Children's Center, Dublin, CA Page 2 Environmental Noise Impact Report 24 April 2009 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 guideline, for the compatibility of land uses with various noise exposures. The City Lases 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 Category Normally Conditionally Normally Clearly Acceptable Acceptable Unacceptable Unacceptable (Noise Insulation) Features Required Residential 60 or less 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 exposure requires noise insulation features in building design. Conventional construction, but with closed windows and fresh air supply systems or air conditioning will 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. State of California's Model Noise Ordinance Since the City of Dublin does not have a quantitative noise ordinance for regulating noise generating projects, this report considers the noise level ROSEN GOLDBERG DER & LEWITZ, INC. 1 100 Larkspur Landing Circle #375 Larkspur CA 94939 _-• Tel 415 464 0150 , Fax 415 464 0155 - RGDLacoustics.com Bright Horizons Children's Center, Dublin, CA Environmental Noise Impact Report Page 3 24 April 2009 standards of the California's Model Noise Ordinance. The Model Noise Ordinance was created by the State Department of Health to provide guidance for communities in California to develop their own noise ordinances. The exterior noise level limits are shown in Table 2. These limits are not to be exceeded at the receiving land use for more than 30 minutes in an hour. This corresponds to the median noise level (1-50). The limits are to be adjusted based on the duration of the source, the level of the ambient noise, the character of the sound, and the location of the measurement. Table 2: California Model Noise Ordinance Exterior Noise Limits Noise Level (dBA) Receiving Land Use Cate or Time Period Noise Zone Classification g y Rural Suburban Suburban Urban 10pm-7am 40 45 50 One & Two Family Residential 7 am - 10 pm 50 55 60 Multiple Dwelling Residential 10 pm - 7 am 45 50 55 Public Space 7 am - 10 pm 50 55 60 Limited Commercial 10 pm - 7 am 55 Some Multiple Dwellings 7 am - 10 pm 60 10 pm-7am 60 Commercial 7am-10 pm 65 Light Industrial Anytime 70 Heavy Industrial Anytime 75 It should be noted that the Model Noise Ordinance has not been adopted by the City of Dublin nor is it enforced by the State of California. It is considered a reasonably protective limit and is discussed in this report to provide guidance to the City in reviewing the potential noise impacts of the project. 3.4. 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 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 ROSEN GOLDBERG DER & LEWITZ, IN-c. 1100 Larkspur Landing Circle #375 ?, Larkspur CA 94939 Tel 415 464 01 50 ? Fax 415 464 01 55 <- RGDLacoustics.com Bright Horizons Children's Center, Dublin, CA Environmental Noise Impact Report Page 4 24 April 2009 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 a location near the northwest corner of the site. This location is adjacent to the backyards of the existing homes which front along Maple Drive (see Figure 1). All but one of the nearby homes are one-story. The major source of noise during the ambient measurements was distant traffic on 1-580, 1-680 and Dublin Boulevard. Table 3 shows the results of the noise measurements from three visits, two on Wednesday 15 April 2009 and one on Friday 17 April 2009. Noise from the Dublin Services District was not a major noise source at the site. There were occasional car or pickup truck movements in the nearby parking lot, but no heavy machinery. A miner source of noise is the automatic gate that separates the Dublin San Ramon Services District from the site's parking lot. Occasionally cars or pickup trucks exit through this gate. The sound of the gate opening and closing generated a maximum noise level of 75 dBA at a distance of 27 feet. Because the cars travelled very close to the sound level meter, these events were excluded from the noise measurement results in Table 3. The CNEL from freeway noise is generally 2 to 3 dBA greater than the Leq during the peak hour therefore; the CNEL at the proz)erty line is approximately 60 dBA. Table 3: Ambient Noise Measurement Results A-Weighted Noise Level, dBA Date/Time Leq Lmax L2 LB Les L50 L90 15-Apr-09 9:18 - 10:18 AM 59 71 61 60 59 58 57 15-Apr-09 12:36 - 1:36 PM 57 68 62 60 58 56 54 17-Apr-09 12:15 - 1:00 PM 54 66 59 57 54 53 5 ROSEN GOLDBERG DER & LEWITZ, INC. 1100 Larkspur Landing Circle #375 ? Larkspur CA 94939 o Tel 415 464 01 50 ; Fax 415 464 0155 <>= RGDLacoustics.com Bright Horizons Children's Center, Dublin, CA Environmental Noise Impact Report Page 5 24 April 2009 Figure 1: Site Plan and Ambient Noise Measurement Location T=Story Residnece DSRSD Admin and Corp Yard Toddler Play Area Two's Play Area Pre-School Play Area Automatic 1 l j Gate LLJ J.J Yl 1 ?..L U s _? mt tent J t f 4 e) ouwxm I„r !:::ne.._ rift Q Noise Measurement Loci lion 06 01 ? CNLWIW.E - r%5?ING tit - L-7 - C?*VA ?? ?N2W? - -? - - - CLARK AVENUE 5. Analysis 5.1. Play Yard Noise at a Similar Facility Eft.ldn,.y. One-Story Residnece s One-Story Residnece I .- W W tl' N W J a N100- 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 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 (L50) 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. ROSEN GOLDBERG DER & I_EWITZ, Ir.c. 1100 Larkspur Landing Circlo #375 Larkspur CA 94939 , Tel 415 464 0150 - Fax 41 5 464 0155 RGDLacoustics.com Bright Horizons Children's Center, Dublin, CA Environmental Noise Impact Report 5.2. Predicted Play Yard Noise Levels from the Project Page 6 24 April 2009 The layout of the proposed play yards at the Bright Horizons facility is shown in Figure 1. According to Bright Horizons the children would use the outdoor play areas in the mornings form 8:30 AM to noon and in the afternoons from 2:30 to 6:00 PM, Monday through Friday. There would typically be 41 children at play at one time but the maximum permitted would be 114 children. Noise levels from the children playing were calcula-:ed 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. Table 4: Predicted Play Yard Noise Levels Noise Levels (dBA) at Residential Property Line Number of Children in Play Yards at One Time Leq L50 Lmax CNEL Typical 59 55 72 54 41 Children Maximum 64 60 72 58 114 Children There is an existing 5-foot high block wall separating the parking lot and the backyards of the adjacent homes. Since the children heights are generally less than 4 feet, this wall will break the line-of-sight between a person standing in the backyard and the children in the play areas. A solid barrier that breaks the line of the sight between a noise source and receiver provides a noise reduction of at least 5 dBA. In theory, the attenuation of voices would be less when the children are on the 2 to 4 foot high play structure platforms, however observations indicate that relatively few children are on the platforms and the majority of the noise is generated by the children at ground level. Therefore, the noise levels in Table 4 can be reduced by 5 dBA. to represent the noise exposure of residences in the backyards. 5.3. Comparison with Acoustical Criteria 5.3.1. City of Dublin General Plan The CNEL at the residential property line from play yard noise will be less than the City's "normally acceptable" compatibility standard of CNEL 60 dBA for both the typical and maximum number of children scenarios. 5.3.2. Increase in Noise The ambient CNEL is approximately 60 dBA at the property line. The addition of the play yard noise will increase the CNEL to 61 or 62 dBA at ROSEN GOLDBERG DER & LEWITZ, INC. 1100 Larkspur Landing Circl(> #375 ?, Larkspur CA 94939 u Tel 415 464 01 50 , Fax 415 464 0155 =A RGDLacoustics.com Bright Horizons Children's Center, Dublin, CA Environmental Noise Impact Report Page 7 24 April 2009 the property line depending on the number of children in the play yards. The increase in noise level of 1 to 2 dBA is less than the threshold of 3 dBA that would be considered significant. With the sound attenuation provided by the existing block wall, the total C:NEL in the backyard would be less than 60 dBA. 5.3.3. State of California's Model Noise Ordinance According to Table 2, the daytime noise level limit for suburban single- family areas is a median noise level (L50) of 55 dBA. This limit is to be adjusted based on the duration of the source, the level of the ambient noise, the character of the sound, and the location of the measurement. At times the ambient noise level exceeds this limit, and at other times the ambient is less. Therefore, in order to be cor servative this noise analysis does not apply an adjustment to the limit based on the ambient noise level. A 5 dBA reduction in the limit is appropriate because the noise source consists of voices which have a very identifiable character. A 5 dBA increase in the limit is appropriate bMause the measurement location is on the boundary of residential and commercial land uses. The applicable adjustments cancel each other out and the resulting noise level limit remains an L50 of 55 dBA. The play yard generated noise level in the backyards, including the 5 dBA of attenuation from the existing block wall would be an L50 of 55 dBA with the maximum permitted number of 114 children in the play area. This just meets the Model Noise Ordinance limit identified above. The play yard generated noise level in the backyards, with the typical number of 41 children in the play area would be 5 dBA less than the Model Noise Ordinance limit. 6. Conclusions The noise from children using the proposed project's platy 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. The play yard noise as received in the backyards of the adjacent homes would comply with the standards of the State of California's Model Noise Ordinance. ROSEN GOLDBERG DER & LEWITZ, lt.c. 1 100 Larkspur Landing Circle #375 ? Larkspur CA 94939 ? Tel 415 464 01 50 •? Fax 415 464 0155 - RGDLacoustics.com