HomeMy WebLinkAbout8.2 Attch 5 Env Noise AssessRosEN
~GLDBERG
D~IZ &
LEUUITZ, Inlc.
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 ®Fax 41 5 464 0155 $ RGDLacoustics.com
ATTACHMENT 5
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 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 Ldp) 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 &
~EWITZ, INC. 1700 Larkspur Landing Circle #375 ~ Larkspur CA 94939 r Tel 41 5 464 0150 * 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 Gateaon+ Normally Conditionally Normally Gleariy
Acce able. Acceptable Unaccer~abie Unacceptable
(Noise Insulation)
Features Required
Residential 80 ar less 80 - 70 7p • 75 Over 75
Motels, hotels 60 or iess 80 - 70 70.80 Over 80
Schools, churches, nursing fiO or less 60.70 70.80 Over 80
homes
Neighborhood parks 60 or less 80.85 85.70 Over 70
Offices: retail commercial 70 ar less 70 - 75 75 - 80 Over 80
Industrial 70 or less 70 - 75 Over 75
Conditionally acceptable exposure requires noise insulation #eatures in building deskjn. Gonveniio nal construction,
bu# with dosed 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 ~i375 ~ Larkspur CA 94939 ~ Tel 41 5 464 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
I-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
L
i /Ti
D
t
ocat
on me
a
e
Laq L,o L5o Lyo 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 #375 e Larkspur CA 94939 a Tel 415 464 01 SO + Fax 415 464 0155 s RGDLacoustics.com
Montessori Plus, Dublin, CA
Environmental Noise Impact Report
Page 4
15 July 2011
Figure 1: Site Plan and Ambient Noise Measurement Locations
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, INC. 1100 Larkspur Landing Circle #375 a Larkspur CA 94939 t Tel 41 5 464 01 50 * Fax 415 464 01 55' RGDLacoustics.com
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 (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.
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. and .
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 (dBA) (dgq) 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 He
LEWITZ, Irac. 1100 Larkspur Landing Circle #375 ~ Larkspur CA 94939 w Tel 41 S 464 0150 + Fax 415 464 01 55 ~ RGDLacoustics.com
Montessori Plus, Dublin, CA Page 6
Environmental Noise Impact Report 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, Irac. 1100 Larkspur Landing Circle #375 ~ Larkspur CA 94939 ~ Tel 41 5 464 01 50 a Fax 415 464 01 55 ®RGDLacoustics.com