HomeMy WebLinkAbout8.1 Attch 2 Noise Impact Report • •
ROSEN
GOLDBERG
DER &
LEWITZ, INC.
.-'s c,t.;tic?i 4tidic l&ual Crn,t111.Intc
ENVIRONMENTAL NOISE IMPACT REPORT FOR:
Dublin Preschool
7250 Amador Valley Boulevard
Dublin, CA
RGDL Project#: 12-032
PREPARED FOR:
City of Dublin
100 Civic Plaza
Dublin, CA 94568
PREPARED BY:
Harold S. Goldberg, P.E.
Principal Consultant
DATE:
24 May 2012
1100 Larkspur Landing Circle#375 Larkspur CA 94939 n^Tel 415 464 0150 *Fax 415 464 0155 RGDLacoustics.com
ATTACHMENT 2
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Dublin Preschool, Dublin, CA Page 1
Environmental Noise Impact Report 24 May 2012
1. Introduction
The proposed project is a new preschool facility at 7250 Amador Valley Boulevard
in Dublin California. The site is currently vacant. The project includes a one story
structure and an outdoor play area on the south and west 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
residences east of 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 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 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 _ Fax 415 464 0155 RGDLacoustics.com
• •
Dublin Preschool, Dublin, CA Page 2
Environmental Noise Impact Report 24 May 2012
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 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.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
ROSEN
GOLDBERG
DER&
LEWITZ,INC. 1100 Larkspur Landing Circle#375- Larkspur CA 94939 Tel 415 464 0150 4 Fax 415 464 0155 +RGDLacoustics.com
. .
Dublin Preschool, Dublin, CA Page 3
Environmental Noise Impact Report 24 May 2012
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 noise measurements were
made at locations around the project site and near the adjacent homes.
The major source of noise during the ambient measurements was distant traffic on
1-680 and Amador Valley Boulevard. Activity in the parking areas for the retail
center was also audible at times. Table 3 shows the results of the short-term noise
measurements at Location 1. Location 1 was chosen because it is closest point
along the residential property line to the proposed play yard. While Location 1 was
the most relevant location in the analysis, it was not practical to leave a monitor at
Location 1 because there was no pole to secure it. Therefore, the measurements
at Location 1 were short-term. Since the CNEL is a 24-hour descriptor a long-term
monitor at another location was used to calculate the CNEL. The average noise
level for each 15-minute interval during the 45-hour measurement is shown in
Figure 2. Location A was chosen for the long-term monitor because of the
presence of a light pole and the noise exposure was similar. The sound level
difference between Location A and Location 1 was determined by correlating the
simultaneous measurements at both locations. This sound level difference was
then applied to the CNEL measured at Location A to determine the CNEL at
Location 1 which is shown in Table 3.
ROSEN
GOLDBERG
DER&
LEWITZ,INC. 1100 Larkspur Landing Circle#375 Larkspur CA 94939 0 Tel 415 464 0150 o Fax 415 464 0155 RGDLacoustics.com
• •
Page 4
Dublin Preschool, Dublin, CA
Environmental Noise Impact Report 24 May 2012
Figure 1: Site Plan and Ambient Noise Measurement Locations
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Table 3: Ambient Noise Measurement Results
A-Weighted Noise Level, dBA
Location Date/Time
Leq Lmax L10 L50 Lgo CNEL
8 May 2012 60 69 62 60 56
11:45-2:25 P.M.
1 64
10 May 2012 55 69 57 54 52
10:10- 10:40 A.M.
ROSEN
GOLDBERG
DER&
LEWITZ,INC. 1100 Larkspur Landing Circle#375 Larkspur CA 94939 +Tel 415 464 0150 t.Fax 415 464 0155 4 RGDLacoustics.com
• S
Dublin Preschool, Dublin, CA Page 5
Environmental Noise Impact Report 24 May 2012
Figure 2: Long-Term Noise Measurement Results
Location A
90
80 f^,:
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10
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50
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0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 o
9. 9. 0. 0. 5. 9. 9. 5' S o O o 0 0 0 0 0 0
N 40 0 O N O N V' 0 Oo O N V t0 to 0 N 0 N V t0 O ON
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Tuesday,8 May 2012 Wednesday,9 May 2012 Thursday,10 May 2012
Time of Day
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
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 (Leg) 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&
LEWITZ,INC. 1100 Larkspur Landing Circle#375•.Larkspur CA 94939 •Tel 415 464 0150 a Fax 415 464 0155 a RGDLacoustics.com
• •
Dublin Preschool, Dublin, CA Page 6
Environmental Noise Impact Report 24 May 2012
5.2.Predicted Play Yard Noise Levels from the Project
The proposed play yard at the Dublin Preschool facility is shown in Figure 1.
According to the project applicant the children would use the outdoor play area
during 30 minute periods, four times per day. 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. A play structure would be located in the largest in
the portion of the play yard that is south of the new building. The middle of this
area is about 55 feet from the residential property line to the east. The project
building would shield the west most portion of the play area from the
residences.
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.
There is an existing wall/fence at the property line between the project site and
the homes to the east that is a composite of a masonry and wood. The lower
portion is a 6 foot tall masonry block wall. There is a 3-foot tall wood fence on
top of the masonry wall. The lower 2 feet of the wood fence is constructed of
overlapping boards and the upper 1 foot is wood lattice. Since the wall/fence
is located in a drainage swale, the top of the masonry wall is only about 4-feet
higher than the elevation of the proposed play area. Due to the relatively low
height of the wall and the fact that the wood portion has cracks and gaps that
let sound through, the fence will provide, limited noise reduction for people in
the backyards or first floors of the homes. However, the fence will not provide
noise reduction for the second floor rooms of the home at 7126 Portage Road.
Therefore, to be conservative, this noise analysis assumes that the fence does
not provide any noise reduction and the predicted noise levels in Table 4 do
not include any effect from the fence.
Table 4: Project Generated Noise Levels
Location (dBA) (dBA) CNEL(dBA)
East Property Line closest to 65 81 56
play yard
ROSEN
GOLDBERG
DER&
LEWITZ,INC. 1100 Larkspur Landing Circle#375+Larkspur CA 94939 *Tel 415 464 0150 Fax 415 464 0155 RGDLacoustics.com
• •
Dublin Preschool, Dublin, CA Page 7
Environmental Noise Impact Report 24 May 2012
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 56 dBA which is 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 duration of use doubled (from
2 hours to 4 hours) or the number of children are doubled, then the
CNEL would increase from 56 dBA to 59 dBA. Since the CNEL is a 24-
hour average it doesn't matter if the extra use occurs at a different time
(doubling the duration) or at the same time (doubling the kids). A useful
analogy is running a shower twice as long or at double the flow, it is still
the same effect on the daily water usage. 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 64 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. If the play time doubled, the CNEL would
increase by 1.2 dBA to from 64 to 65.2 dBA. Since this is greater than
65 dBA, the relevant increase threshold would be 1.5 dBA. Therefore,
the 1.2 dBA CNEL increase would be less than the threshold of 1.5 dBA.
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