HomeMy WebLinkAboutBates 17523-17571 Appendix I - Acoustics Assessment APPENDIX I
Acoustics Assessment for the Froom Ranch Project
I. 1 — Acoustic Assessment for the Froom Ranch Project 2017
I.2 — Acoustic Assessment for the Froom Ranch Project 2020
Froom Ranch Specific Plan Project
Final EIR
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APPENDIX I. 1
Acoustics Assessment for the Froom Ranch Project 2017
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4 5 d 8 P.o. BoX i4o6
San Luis Obispo
ACOUSt►Cs California 93406
David Lord, PhD dl(a�45dB.com tel. 805.704.8046
Sarah Taubitz, MSME st(a�45dB.com www.45dB.com
June 7,2017
Project 1721-1
RE: Client:
Acoustics Assessment John Madonna
Froom Ranch Project P.O. Box 5310
San Luis Obispo, CA 93401 San Luis Obispo, CA 93403
1 Summary
This is a report on the existing and future noise impacts on the proposed Froom Ranch Project
located on the southwest side of Los Osos Valley Road (LOVR), between Froom Ranch Road
and Calle Joaquin. All noise sources are considered, including occasional air traffic from San
Luis Obispo County Regional Airport, and vehicular traffic noise from adjacent Los Osos Valley
Road and Calle Joaquin, as well as U.S. Highway 101 to the southeast of the project. The intent
of this assessment is to determine noise levels that may potentially impact the proposed
residential units at the eastern edge and elsewhere throughout the site.
Several sound level measurement data sets were collected at different locations on site. Existing
sound levels were correlated for each of the measurement locations, for use in"calibrating" noise
modeling software. The objective is to generate existing sound level contours, which may be
compared with generalized sound level contours published by the City of San Luis Obispo in the
1996 Noise Element(Figures 5 and 6).
This report shows the results of an initial sound level survey to establish existing and future
sound level contours resulting from transportation noise.
Two sound level `portraits' for the overall site are shown in addition:
1. Existing sound levels with no development on the site, i.e., no project.
2. Potential future sound levels once the proposed project is built.
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Contents
1 Summary..........................................................................................................................1
2 Location...........................................................................................................................3
2.1 Sound Level Measurements.................................................................................5
2.2 Sound Level Contours..........................................................................................5
2.3 Contour Disparities..............................................................................................8
2.4 Graphic Results....................................................................................................9
2.5 Future Sound Leve1..............................................................................................10
3 Regulatory Setting ...........................................................................................................12
3.1 State Regulation...................................................................................................13
3.2 Local Regulation..................................................................................................13
4 Traffic Characteristics......................................................................................................14
4.1 Traffic Growth.....................................................................................................14
4.2 Traffic Flow and Sound Level.............................................................................15
5 Meteorological Conditions...............................................................................................16
6 Sound Level Data.............................................................................................................17
7 Conclusion.......................................................................................................................19
8 Glossary of Acoustical Terms..........................................................................................20
9 Sound Level Modeling and Measurement.......................................................................22
9.1 Sound level modeling ..........................................................................................22
9.2 Sound Level Measurement ..................................................................................22
10 References........................................................................................................................22
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2 Location
The project is located west of the intersection of Los Osos Valley Road and Calle Joaquin, near
the U.S. Highway 101 interchange. The project site is shown in Figure 1. Vicinity of Site,
currently open land separated from Los Osos Valley Road by shrubbery and trees and a barbed
wire fence.
The measurement stations on the site were chosen to be near potential future residential building
elevations exposed to Los Osos Valley Road, Calle Joaquin, and U.S. Highway 101 in the
distance.
During the sound level survey, occasional overflight of small aircraft was observed, departing
from San Luis Obispo County Regional Airport and over 1,000 feet above the project area.
Figure 1.Vicinity of Site,
southwest of Los Osos Valley Road and west of Calle Joaquin.
U.S.Highway 101 is further in the distance toward the southeast of the site.
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page 3 of 23 member: ASHRAE ASA INCE tel: 805.704.8046
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Figure 2.Sources of traffic noise: Los Osos Valley Road,
Calle Joaquin and U.S.Highway 101,two lanes.
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Location of the three transportation noise sources is shown in Figure 2.
Toward the southeast of the site, U.S. Highway 101 is a significant transportation noise source
with an Average Annual Daily Traffic Flow between 62,000 to 69,000.
Figure 3.2015 Traffic Volumes,U.S.Highway 101,from Caltrans data
Post Back Back gack Ahead Ahead qhead
�ist Rte CO Mile �escription Peak Peak �pT Peak Peak �pT
Hour Month Hour Month
D5 101 5L0 25.9t1 5AN LU15 0815P0,L05 OSOS ROA� 6900 76DOQ 6930D 59D0 67000 61900
05 101 5LQ 27.5d1 5AN LU15 D815P�,MADQNNA ROA� 5800 6600a 63700 630a 70400 65000
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Figure 4.Los Osos Valley Road,Calle Joaquin Average Daily Traftic
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2.1 Sound Level Measurements
Six sound level measurement sites are shown in Figure 6. Plan showing measurement stations
and sound levels, Leq= dBA, at each station. Two measurement sites are stationary; four sites
are spot check locations. In addition to the six sites, synchronized duplicate measurements were
made at the two stationary sites for a total of eight data sets. The sound level data was compared
with nearby data. The fixed measurement stations were then used to calibrate the noise modeling
software, in order to generate sound level contours based on precision measurements of existing
sound. Future sound level is projected using future growth assumptions for average daily traffic
flow.
2.2 Sound Level Contours
A Sound Level Contour is a line on a map that represents equal levels of noise exposure.
SoundPlan is an acoustics modeling software program used to calculate noise contours,based on
topographic relationships of noise sources and noise receivers. The standard calculation software
for modeling traffic noise is the Federal Highway Administration program, Transportation Noise
Model, TNM. SoundPlan, used for this report, implements TNM in its calculation.
On-site measured sound level values are used to calibrate and to validate the SoundPlan -
generated sound level contours. The graphic sound level contours depict sound level on the site
from a composite of three transportation noise sources: Los Osos Valley Road, Calle Joaquin
and U.S. Highway 101.
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Figure 5.Site Plan,proposed project
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Figure 6.Plan showing measurement stations and sound levels,Leq=dBA,at each station.
There were two stationary measurement stations,one next to LOVR and the other next to Calle Joaquin.
There were four `spot-check' stations near future potential building elevations.
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Figure 7. City of San Luis Obispo Sound Level Contours,based on a study by Brown Buntin,1991.
Results appear in City of San Luis Obispo Noise Element,last revised 1996.
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2.3 Contour Disparities
The difference between the sound level contours shown by the City in its 1996 Noise Element
exhibit and the measured and modeled contemporaneous sound level contours presented in this
report can be attributed to the difference in technology utilized in the 1990s and that used today.
In 1990, when the City's commissioned noise study was completed by Brown-Buntin Associates,
the method for drawing sound level contours was based on a mathematical calculation of sound
level at fixed and specific distances from the centerline of the roadway. The calculations ignored
the effects of topography, shielding by buildings, ground surface variations, absorption and
reflection. In 1990, sound level contours were drawn at a constant distance along major roads in
the city and ended at the city limits. The calculations accommodated three vehicle types, autos,
heavy trucks and medium trucks at constant speeds. Described at the time, "the noise contour
information prepared by the consultants and staff generally reflects conservative (worst case)
assumptions, so significant noise exposure concerns are not likely to be omitted or understated."
(See Reference 9.)
Today, using contemparary sound level mapping, there are noticeable effects and multiple
variations due to terrain, ground absorption, reflection and blocking of sound by the built
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45dB Acoustics, LLC Froom Ranch Project
environment. Noise contours change as urban density and traffic patterns change. Today's
sound level contours are a more realistic representation of actual conditions.
2.4 Graphic Results
Figure 8.This is the measured,existing 60 dBA Sound Level Contour,
based on measured values from the six stations shown previously.
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2.5 Future Sound Level
The calculated future Ldn/CNEL (year 2037) along the east and south side of the site will depend
on growth of traffic, generally accepted to be about one percent per year growth rate.
Figure 9.Future,calculated,60 dBA Sound Level Contour at Buildout or year 2037
� '`� 5 , +i -i si}.i ,
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Figure 10. No Project,Sound Level Contours Across the Site
.�`, p . ` > > . � . '�`"� .
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Figure 1L Future Sound Level Contours with Proposed Project(year 2037)
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3 Regulatory Setting
Noise is regulated at the federal, state and local levels through regulations,policies and/or
local ordinances. Local policies are generally adaptations of federal and state guidelines, adjusted
to prevailing local condition.
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3.1 State Regulation
The State of California's Guidelines for the PNeparation and Content of Noise Element
of the General Plan (1987) make reference to land use compatibility standards for community
noise environments as developed by the California Department of Health Services,
Office of Noise Control. Sound levels up to 65 Ldn or CNEL are determined to be normally
acceptable for multi-family residential land uses. Sound levels up to 70 CNEL are normally
acceptable for buildings containing professional offices or defined as business commercial.
All new Multi-Family housing must comply with California Code of Regulations (CCR)
Title 24. This is included in the California Building Code (CBC), Section 1207, "Sound
Transmission"—which specifies the maximum level of interior noise due to exterior sources
allowable for new residential developments.
3.2 Local Regulation
CCR Title 24 also defers to local requirements if applicable. The Noise Element of the City of
San Luis Obispo General Plan specifies a maximum allowable interior noise level of 45 dBA
Ldn for multi-family projects which is consistent with the above policies for interior noise and
also extends this requirement to new single-family dwellings. The City of San Luis Obispo Noise
Element also states that 60 dBA Ldn or less is the exterior noise goal for outdoor common areas,
defined as areas intended for the use and enjoyment of residents.
Guidelines for transportation noise exposure are contained in City of San Luis Obispo, General
Plan Noise Element and Noise Guidebook(1996). The maximum noise exposure standards for
noise-sensitive land uses are shown in Figure 12. The maximum noise exposure standards for
noise-sensitive land uses due to traffic are shown in Figure 13.
Figure 12.Community Noise Exposure Ldn/CNEL
Community Noise Exposure
J-` I,-- ' j ,J Ldn or CN�L,Db
55 60 65 70 75 80
Residences,Theatres, i i i i i i i i i:i i I i i f E j i
Auditoriums, Music Halls �� `� ��� , ,
F` �
Schools,Libraries, I I I I I[]1 I[I I I[[ []I
Museums,Hosp"�tals,
Nursing Hames, Meeling "��'�� �
Halls,Churches, _, .. � .. ,_
Mortuaries
Neighborhaod Parks �IIII[]11[III[[ []Illlllf[I]
�I I I 1 I I[1 I rlccept�hle,I�evelopinent msn�be�erinitted without speci$c noise stuclics or min��,*,ati��n.
K _. Gonditipnall�-r��ceptable,Decelopment ma��l�e�permieted if desi�ned tq meet noise
� expnsum standards;a specific noise studti�t is usua�l��reyuired.
Y -�- �1- `�• CTnacec�rabic,De��cl�,�,ment wirh accc�,riblc:cu�ise cs���surc �;enera113�is n��r p<�ssiblr.
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Figure 13.Maximum Exposure for Noise Sensitive Uses due to Traffic
.
!�„or CNEL,
Land Use Ld„or CNEL,in d8 in d8 L,g in db2 L,,,,.in db3
Residenees,hatels,matels,hospitals,nursing
60 45 - 60
homes
Neighborhood parks b5 - - -
�
lf[he locatran of auYdaor acYrvi[y areas is notshawn,Yhe ou[dnor naise stQndord shQll apply at Yhe property line of Yhe receiving Iand
use.
2 As determined for a typical worst-ccrse haur during periods of use.
jlma,rndoor standQrd opplies anfy[o rorlrood noise QY locQtions sauth of Orcutt Road.
4 Traffic Characteristics
This section examines the effects of traffic growth over time on the sound level contours of the
site, and the relationship of traffic flow to sound levels on site.
4.1 Traffic Growth
Federally funded projects and environmental reviews typically require the projection of traffic
volumes 10-30 years in the future, typically assuming a 1-2% annual growth in vehicle volume.
In this report, we have assumed a 20-year period of growth to year 2037, at an annual growth
rate of 1 percent(0.01). The calculation in Figure 14 shows the result for Los Osos Valley Road.
Figure 14.Growth of Noise from Average Daily Traffic
Grawfh a#Noise fram Average Daily Tra�c
45d8Acaustics Consuliing,ttC P.�.Box 1406 San Luis Obispo;CA 93406-1406
Fronm Ranch
Scenario 2
Calculation of added noise sources
{(10"-16]"10"(D9110}}
Present Noise Le�el (LDN} 60 dBA intensity= 1 E-10 Vlffcm2
present traffic flow 33258 ADT (average daily traffic�
future traffic flow 40581 ADT 0.864275 dBA additional
Future hioise Level (LDh!] 60.9 dBA 90hLDG10{D131D92�
scenario 2
332�8 present traffic ADT
D.Q1 Growth Rate 1 Year
20 number of years
�0581 future traffic ADT
Fu#ure = present x(1+i7"n
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4.2 Traffic Flow and Sound Level
Consulting the Highway Traffic Manual (reference 15) helps to understand the issues in
measuring sound level resulting from traf�c flow. There are several descriptors of traffic flow
from Average Daily Traffic (ADT) to Design Hourly Volume (DHV) of traffic on a road or
highway. DHV is sometimes used as a benchmark for sound level measurements. However, the
DHV is defined as the 30th highest hourly volume in the "design"year, whereas the Peak Hour
Volume (PHV) is defined as the highest hourly volume during an average day.
Depending on the type of roadway, the PHV may be from 5 to 45 percent lower than the DHV.
The definition infers that if a highway or street is to adequately serve throughout its life, its
physical capacity will only be exceeded for about 30 hours out of the total 8,760 hours in the
"design" year. The choice of the 30th highest hourly volume is a long-held concept which stems
from research published in A Policy on Geometric Design of Rural Highways (Reference 1.)
Figure 15.Relationship Between Peak-Hour and Average Daily Traffic Volumes.
35
37
p❑ w Th verpqp uC ua Dn
°" in ir ffi FI w
� 28 ----— -
m
U
ti
C ��
u SD H1� ExCB6d6d OT I�'J PBfC9Y11
�. af Locatfons
d
a n 20
m
o E
N�
OHV for traffit flow °}
i6
flucluaNans,15°/of � �
A07 v�
� # V2
TW
L .
7�-
❑O 8
x a
Exceeded a* 85 Percent
d af LoCations _
6 20 40 6p 80 1a0 f20 140 160
NuAIGor of Haurs ln One TeoY wlTh }Iflurly Yolum9
Grearer t�an That Snorn
Visually comparing the traffic flow trend lines above indicates that significant traffic flow
changes occur at the inflection point of the 30th highest volume hour of the year. The difference
in volume of traffic between the 1 st highest hourly volume and the 30th increases rapidly. For the
remainder of the hours between the 30th and the 170th, there is very little change in the slope of
the curves. This indicates that designing for that 30th hour would cover the expected traffic
volume at almost any given hour in a given day of a given week in a given month of a given
year.
Noise impacts are measured during the one-hour period when the worst-case noise levels are
expected to occur. This may or may not be the peak hour of traffic. That is, higher traffic
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volumes can lead to higher congestion and lower operating speeds. Since higher speeds lead to
higher noise emissions from motor vehicles, the worst-case noise levels may occur in hours with
lower volumes and higher speeds. In addition, vehicle mix may also change hourly. On many
highways, the percentage of heavy trucks is reduced during peak hour. Since heavy trucks have
greater sound emissions than passenger cars, vehicle mix is an important component in
determining the peak hour of noise impact.
During the sound level measurement for this project, Level of Service (LOS) was observable and
gives us confidence that we are measuring during a busy-but-not-congested time period.
The LOS during the measurements was generally Level B to Level C and at one time became
Level of Service D.
Figure 16.Level of Service vs General Operating Conditions
Le�el of Ser�ice General O eratin Conditions
A Free flow
B Reasonably free flow
C Stable flaw
D Approaching unstable flow
E Unstable flow
F Forced or breakdown flaw
5 Meteorological Conditions
During the measurement period from 10 am to 12 noon on Saturday, Apri122, 2017, the sky was
essentially clear and the wind speed was less than 10 mph from the west and north. Wind speed
and direction data was taken from San Luis Obispo County Regional Airport weather station.
Wind speed above 12 mph has an increasing adverse effect on the accuracy of sound level
measurements (reference: Federal Highway Administration, Noise Measurement).
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Figure 17.Weather conditions at SBP San Luis Obispo Airport,3.2 km SE of the project site.
F Tei�ipera[ure GeU�Fu�rd Average HighlL[ow �
EO ___ _ 27
10 j�— — -- ---� 21
60 ��� �'-- 15
50 =T� -����r ��—�.__ ��-- = 10
40 4
30 �
midnight1 2 3 4 5 6 I 8 9 70 11 hoon 1 2 3 4 5 6 7 S S 10 A1
kn Hg E;df01i16�IC Pf@S5Uf@ hPa
'0 0 14i6
29.9 1413
midnigMl 2 3 4 5 6 7 8 9 70 'r1 noan 1 2 3 4 5 6 7 8 3 �0 71
mpn �ii�fr�d SK�ee� �krtd Gust xmm
350:�g �qSp
�90.0 92
1�S r._ f��_` -�_ `_—��. � �8
9.0 - 0
midnightl 2 3 4 5 6 7 8 9 70 11 noon 1 2 3 4 S 6 7 8 9 1U 91
36�.0 �°�ind Uir(�1eyi . . .
. . , , • • • . , . . r .
zro-o �:�..
�en.v :_
sa.n � . .
o.v .
midnight1 2 3 4 5 6 I 8 9 70 11 noan 1 2 3 4 S 6 I 8 9 10 A,�,�„�„
6 Sound Level Data
Figure 18.Location Name,Coordinates and Sound Level,LAeq
Lacation Name Coordinates LAeq �
5C1 35.2451�7, -12�.684473 54.9
5C2 35.244282, -12Q.686455 54.9
5C3 35.24799Q, -12�.684612 58
5C4 35,247Q65, -12�,684385 53.8
5C5 35.248028, -12�.684247 61.6
5C6 35.245840, -120.685Q85 49.9
LT1 35.2451�7, -12�.684473 54.4
LT2 35.248028, -12�.684247 61.1
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Figure 19.Spectral quality of sound,Third Octave Bands at LTl,near Calle Joaquin.
�cW ul:iwl.:�•
1�
115 ".. .... ............ ..... ...... ............ ..... ..... .... .... .... .... .... .................
�
im , � --- -- -- ---- - -- - -- ---- - ---- — -- - ---- --
, , ,
ir� • , , , , ------------------------------ ------------------------------ ----------------------- -
, , , , , , , , , ,
, , , , , , , , , ,
, , , , ,
i�o -�... ---�-------'-------�-------'-------�-------'-------�------'-------�-------'------�-------�-------�-------'------�-------�------ �...
4 - ----- ------- ------- -------------- ------- -------------- ------- ------- ------ ------- ------- ------- ------ ------- ------ ---
� � � �
47 ----- ------ ------ ----- ----- ----- ------------ ----- ----- ----- ------- ------- ----- ----- ------- ------- ----- ..
. � � � � � � � � � � � � � � � � .
. . � � � � � � � � � � � � � � �
.3-. .....-----�------�------- . .
� � �
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� �
_n , , ' ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- �-
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'� - - --- -- - --- --- -- ------- -------------- ------- ------- - --
;� _... ---
;� .....:.......:...... :..
,�
.-�� , . '^� -:� :Cz 2� iOCz 13�� Lxlz lC`Jz 2C� Ilz i5kz =5iz 1[� .:.7 ';i: .^�� A �_
_::r =. �a�•e c+
.E:.
Figure 20. Spectral Quality of Sound,Third Octave Bands at LT2 near Los Osos Valley Road
��
� -�,.+�ra�e:L�c�.Pr��file.�h1 i;51:
5�
�F _ ________ _ _ • .
�� _______ _______ _______ ______ _______ _______ _______ ______ ______ _______ _______ _______ _ _
iF _______ _______ _______ ______ _______ _______ _______ ______ ______ _______ _______ _______ _
i� '__________,_________ _________ ____________________ _________ _________ ____________________ _________ _________ ________ _ _
'_ � � � � � � � � � �
'. _________________�__________'__________`_________._________�__________'__________`_________._________'________
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7 Conclusion
The measured and predicted sound levels impacting the proposed Villaggio project are a mix of
transportation noise along Los Osos Valley Road, the Calle Joaquin interchange with Highway
101, and to a lesser extent, Calle Joaquin west of Los Osos Valley Road. Future noise level from
transportation sources at buildout are predicted to result in an increase in sound level of about
one decibel in 20 years' time.
Perceived sound level studies reveal the subjective interpretation of sound differences. A one
dBA increase in sound level is barely noticeable to the most sensitive subjects. Sound level must
increase by five (5) dBA before most listeners report a noticeable or significant change in sound
level.
�9�-� �C�
for 45dB Acoustics, LLC
David Lord
page 19 of 23 member: ASHRAE ASA INCE tel: 805.704.8046
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45dB Acoustics, LLC Froom Ranch Proj ect
8 Glossary of Acoustical Terms
A-Weighted Sound Level (dBA)
The sound pressure level in decibels as measured on a sound level meter using the internationally
standardized A-weighting filter or as computed from sound spectral data to which A-weighting
adjustments have been made. A-weighting de-emphasizes the low and very high frequency
components of the sound in a manner similar to the response of the average human ear. A-
weighted sound levels correlate well with subjective reactions of people to noise and are
universally used for community noise evaluations.
Air-borne Sound
Sound that travels through the air, differentiated from structure-borne sound.
Ambient Sound Level
The prevailing general sound level existing at a location or in a space, which usually consists of a
composite of sounds from many sources near and far. The ambient level is typically defined by
the Leq level.
Background Sound Level
The underlying, ever-present lower level noise that remains in the absence of intrusive or
intermittent sounds. Distant sources, such as Traffic, typically make up the background. The
background level is generally defined by the L90 percentile noise level.
Community Noise Equivalent Level (CNEL)
The Leq of the A-weighted noise level over a 24-hour period with a 5 dB penalty applied to
noise levels between 7 p.m. and 10 p.m. and a 10 dB penalty applied to noise levels between 10
p.m. and 7 a.m. CNEL is similar to Ldn.
Day-Night Sound Level (Ldn)
The Leq of the A-weighted noise level over a 24-hour period with a 10 dB penalty applied to
noise levels between 10 p.m. and 7 a.m. Ldn is similar to CNEL.
Decibel (dB)
The decibel is a measure on a logarithmic scale of the magnitude of a particular quantity (such as
sound pressure, sound power, sound intensity) with respect to a reference quantity.
DBA or dB(A)
A-weighted sound level. The ear does not respond equally to all frequencies, but is less sensitive
at low and high frequencies than it is at medium or speech range frequencies. Thus, to obtain a
single number representing the sound level of a noise containing a wide range of frequencies in a
manner representative of the ear's response, it is necessary to reduce the effects of the low and
high frequencies with respect to the medium frequencies. The resultant sound level is said to be
A-weighted, and the units are dBA. The A-weighted sound level is also called the noise level.
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Energy Equivalent Level (Leq)
Because sound levels can vary markedly in intensity over a short period of time, some method
for describing either the average character of the sound or the statistical behavior of the
variations must be utilized. Most commonly, one describes ambient sounds in terms of an
average level that has the same acoustical energy as the summation of all the time-varying
events. This energy-equivalent soundlnoise descriptor is called Leq. In this report, an hourly
period is used.
Field Sound TNansmission Class (FSTC)
A single number rating similar to STC, except that the transmission loss values used to derive the
FSTC are measured in the field. All sound transmitted from the source room to the receiving
room is assumed to be through the separating wall or floor-ceiling assembly.
Outdoo�-Indoor Transmission Class (OITC)
A single number classification, specified by the American Society for Testing and Materials
(ASTM E 1332 issued 1994), that establishes the A-weighted sound level reduction provided by
building facade components (walls, doors, windows, and combinations thereo�,based upon a
reference sound spectra that is an average of typical air, road, and rail transportation sources. The
OITC is the preferred rating when exterior fa�ade components are exposed to a noise
environment dominated by transportation sources.
Single Event Noise Exposure Level (SENEL)
The time-integrated A-weighted sound pressure level of a single aircraft flyover (which exceeds
a threshold noise level) which is expressed by the level of an equivalent one-second duration
reference signal.
Sound Transmission Class (STC)
STC is a single number rating, specified by the American Society for Testing and Materials,
which can be used to measure the sound insulation properties for comparing the sound
transmission capability, in decibels, of interior building partitions for noise sources such as
speech,radio, and television. It is used extensively for rating sound insulation characteristics of
building materials and products.
Structure-Borne Sound
Sound propagating through building structure. Rapidly fluctuating elastic waves in gypsum
board,joists, studs, etc.
Subjective Loudness Level
In addition to precision measurement of sound level changes, there is a subjective characteristic
which describes how most people respond to sound:
• A change in sound level of 3 dBA is barely perceptible by most listeners.
• A change in level of 6 dBA is clearly perceptible.
• A change of 10 dBA is perceived as being twice (or ha� as loud.
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9 Sound Level Modeling and Measurement
9.1 Sound level modeling
Sound level contours compared to the measured sound level values were generated for
assessment using SoundPlan noise simulation software. The software calculates sound
attenuation of environmental noise around buildings. For this project, the land between the
sources (road and airport operations) and receiver project boundary, is generally flat and partially
paved. The modeling software calculates the sound field in accordance with ISO 9613-2
"Acoustics - Attenuation of sound during propagation outdoors, Part 2: General Method of
Calculation." This standard states that"this part of ISO 9613 specifies an engineering method for
calculating the attenuation of sound during propagation outdoors in order to predict the levels of
environmental noise at a distance from a variety of sources. The method predicts the equivalent
continuous A-weighted sound pressure level under meteorological conditions favorable to
propagation from sources of known sound emissions."
9.2 Sound Level Measurement
The protocol used for the sound level measurements is prescribed in detail by the American
Society for Testing and Materials (ASTM) in their E 1014 publication. The procedures and
standards in that document were met or exceeded for sound level measurements shown in this
report. The standards of ASTM E 1014 are exceeded by using Type 1 (Class 1) sound level
meters for all measurements in this report instead of less accurate Type 2 meters. Therefore, the
precision of the measurements in this report is likely to be better than+/- 1 dB. The sound level
meters used for measurements shown in this report are Norsonic Nor140 Sound Analyzers, with
synchronized time settings. These sound level meters meet all requirements of ANSI s1.4, IEC
651 for Class 1 accuracy. The sound level meters were calibrated before and after each sound
level measurement. The measurement results from both sound level meters running
simultaneously were compared and found to be in close agreement.
10 References
1. American Association of State Highway and Transportation Officials. 2011. A Policy on
Geometric Design of Highways and Streets.
2. American National Standards Institute, Inc. 2004.ANSI 1994 American National
Standard Acoustical Terminology. ANSI 5.1.-1994, (R2004),New York, NY.
3. American Society for Testing and Materials. 2004. ASTM E 1014 - 84 (Reapproved
2000) Standard Guide for Measurement of Outdoor A-Weighted Sound Levels.
4. Bolt, Beranek and Newman. 1973. Fundamentals and Abatement of Highway Traffic
Noise, Report No. PB-222-703. Prepared for Federal Highway Administration.
5. State of California Department of Transportation. 2011. California Airport Land Use
Planning Handbook.
6. California Department of Transportation (Caltrans). 1982. Caltrans Transportation
Laboratory Manual.
7. . 1998. Caltrans Traffic Noise Analysis Protocol for New Highway Construction
and Highway Reconstruction Projects
8. California Resources Agency. 2007. Title 14. California Code of Regulations Chapter 3:
page 22 of 23 member: ASHRAE ASA INCE tel: 805.704.8046
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45dB Acoustics, LLC Froom Ranch Project
Guidelines for Implementation of the California Environmental Quality Act Article 5.
Preliminary Review of Projects and Conduct of Initial Study Sections, 15060 to 15065.
9. City of San Luis Obispo, California. 1996. Noise Guidebook Measurement and
Mitigation Techniques.
10. City of San Luis Obispo, California, General Plan Noise Element.
11. City of San Luis Obispo, California, Public Works, Traffic Data. https:// o�o.,�UaRJIRq
12. Federal Highway Administration. 2006. FHWA Roadway Constr�uction Noise Model
User's Guide Final Report. FHWA-HEP-OS-054 DOT-VNTSC-FHWA-OS-01
13. Federal Highway Administration. 2011. Measurement of Highway-Related Noise.
https://goo.ql/dKlwZk
14. Harris, Cyril M., editor. 1979 Handbook of Noise Control.
15. Transportation Research Board. 2016. Highway Traffic Manual, a guide for multimodal
mobility analysis.
16. Interactive Sound Level Calculator, MAS Environmental https://goo.gl/23zTnQ
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APPENDIX I.2
Acoustics Assessment for the Froom Ranch Project 2020
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\ D a v i d L o r d, P h D dl@45dB.com
Sarah Taubitz, MSME st@45dB.com
45d B /`�CDUC�.s. �_� . California� Colorado
CONSULTANTS IN SOUND AND VIBRATION www.45dB.com
Apri19, 2020
Project 20031
Acoustics Assessment: Requestor/Client: Owner:
Froom Ranch Specific Plan RRM Design Group John Madonna
Attn.: Victor Montgomery Construction
City of San Luis Obispo, CA 3765 S. Higuera St., Suite 102 PO Box 5310
San Luis Obispo, CA 93401 San Luis Obispo, CA 93403
1 Executive Summary
The proposed Froom Ranch Specific Plan has been analyzed for potential noise impact from
stationary and transportation noise associated with commercial activity to the north of Froom
Ranch. Predictive noise modeling was used to evaluate existing and future land use for
compliance with the City of San Luis Obispo General Plan Noise Element.
Traffic counts from the City's published Average Daily Traffic levels were used to predict traffic
noise levels from Los Osos Valley Road(LOVR) to the east of the Specific Plan area, which
agreed with previous measurements. Utilizing industry-standard calculation methods within
SoundPLAN� software and reference noise emission data, the noise levels from activities such
as trucks maneuvering in and out of loading docks, trucks passing through the alley, forklifts,
HVAC noise and passenger vehicle parking lot activities were calculated for the potential noise-
sensitive receiver locations on the northern portion of the Froom Ranch Specific Plan.
Under the above conditions and assumptions, the land uses adjacent to Irish Hills Plaza
commercial zone along the north boundary are anticipated to comply with the Noise Element
requirements of the City of San Luis Obispo.
for 45dB Acoustics, LLC
�� ��
Sarah Taubitz, MSME David Lord, Ph.D.
This report(including any enclosures and attachments)has been prepared for the exclusive use and benefit of the addressee(s)
and solely.for the purpose for which it is provided.No part of this report shall be reproduced,distributed or communicated to
any third party without written permission. We do not accept any liability if this report is used for an alternative purpose from
which it is intended, nor to any third party.
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45dB Acoustics, LLC Froom Ranch Specific Plan
Contents
1 Executive Summary...........................................................................................................................................1
2 Intro d u ctio n........................................................................................................................................................3
3 Project Location.................................................................................................................................................3
4 City Noise Element.............................................................................................................................................6
5 Sound Level Modeling.......................................................................................................................................7
5.1 Noise Sources..................................................................................................................................................7
5.1.1 Traffic Noise..........................................................................................................................................7
5.1.2 Rooftop and other Mechanical Equipment............................................................................................7
5.1.3 Parking Lot Noise..................................................................................................................................7
5.1.4 Parking Lot Sweeping Noise(Less than Significant)............................................................................8
5.1.5 Intermittent Delivery Truck and Loading Dock Noise..........................................................................8
5.2 CNEL Sound Level Contours for Commercial and Tra�c Sources..............................................................10
6 Compatibility and Recommendations............................................................................................................11
7 Appendix...........................................................................................................................................................14
7.1 Terminology/Glossary...................................................................................................................................14
7.2 Calculating CNEL.........................................................................................................................................16
7.3 Traffic Noise Model(TNM)...........................................................................................................................17
7.4 SoundPLANOO Acoustics Software.................................................................................................................17
7.1 Coinputer Modeling of Transmission Class(STC)........................................................................................18
7.2 Characteristics of Sound...............................................................................................................................18
7.3 Evidence of Compliance................................................................................................................................19
8 References.........................................................................................................................................................20
List of Figures
Figure1: Project location................................................................................................................ 4
Figure 2: Identified noise sources of businesses to the north......................................................... 4
Figure 3: Froom Ranch site plan concept (RRM Design Group)................................................... 5
Figure 4: Noise Element's Maximum Noise Exposure for Transportation Sources ...................... 6
Figure 5: City of San Luis Obispo traffic volume for Los Osos Valley Road................................ 7
Figure 6: Vertical cross-section of line-source truck noise .......................................................... 10
Figure 7: CNEL Sound Level Contours from all sources with 60 dB contour in red................... 13
Figure 8: Comparison of INSUL and Laboratory Testing:........................................................... 18
List of Tables
Table 1: City Municipal Code Exterior Noise Limits..................................................................... 9
Table 2: Estimated Maximum Noises from Nearby Commercial Activities (Wood) .................. 10
Table 3: Sound Level Change Relative Loudness/Acoustic Energy Loss.................................... 19
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45dB Acoustics, LLC Froom Ranch Specific Plan
2 Introduction
This predictive noise modeling study of the Froom Ranch Specific Plan is intended to determine
the potential impact of noise associated with commercial operations in Irish Hills Plaza to the
north of the proposed Specific Plan. The following topics are presented:
• The topographical relationship of transportation noise sources in relation to the
existing and proposed built environment
• Identification of project-related noise sources and their characteristics, including
commercial noise from existing businesses to the north of Froom Ranch
• Determination of existing ambient sound levels as well as predicted sound level
contours predicted noise levels for proposed zoning of the Froom Ranch Specific Plan
• Basis for the sound level prediction, the noise attenuation measures to be applied, and
an analysis of results in comparison to applicable project requirements
Information on fundamentals of noise and vibration to aid in interpreting the report
3 Proj ect Location
The proposed Froom Ranch Specific Plan is located west of Los Osos Valley Road. A
commercial zone of businesses including Home Depot, Whole Foods Market, and TJ Maxx lie
directly to the north in the Irish Hills Plaza(Figure 1). Calle Joaquin creates the southern border
for the project, with Highway 101 further to the south.
Our previous reports included road traffic noise for the entire Froom Ranch area. This report
adds commercial noise related to business operations to the immediate north of Froom Ranch.
Figure 2 identifies the areas of commercial activity areas of the businesses to the north of the
project. This report focuses on the northern portion of Froom Ranch, as the southern portion of
the project is not affected by noise from these businesses.
page 3 of 20 noise management : room acoustics : environmental impact www.45dB.com
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45dB Acoustics, LLC Froom Ranch Specific Plan
Figure 1: Project location
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45dB Acoustics, LLC Froom Ranch Specific Plan
Figure 3: Froom Ranch site plan concept (RRM Design Group)
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page 5 of 20 noise management : room acoustics : environmental impact www.45dB.com
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45dB Acoustics, LLC Froom Ranch Specific Plan
4 City Noise Element
City of San Luis Obispo's General Plan, Noise Element provides regulation and guidelines
regarding noise. The Noise Element provides the conclusions, recommendations, and strategies
necessary to ensure an appropriately quiet and pleasurable interior environment for all. The
regulation of transportation noise sources such as roadway and train traffic primarily falls under
either State or Federal jurisdiction. Local jurisdiction may use land use and planning decisions
to limit locations or volumes of transportation noise sources to avoid development within
potential noise impact zones, or to shield impacted receivers or sensitive receptors.
This project is evaluated against the City's N�oise Element Table 1, Maximum noise Exposure for
Noise-Sensitive Uses Due to Transportation Noise Sources,reprinted in Figure 4. This table is
also reprinted in the Froom Ranch Specific Plan EIR as Table 3.10-5. CNEL and Lan are
typically within 1 dB of each other and can be considered to be equivalent here.
Figure 4: Noise Element's Maximum Noise Exposure for Transportation Sources
Tab�e 1, Maxim�ni hloise Exposure far Noise-Sensitiue Uses Que to Trai3s�kartation N�ise Saurces
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martuar�es
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Our analysis will provide modeled noise levels based upon existing traffic counts as well as
commercial delivery activities,parking lot sweeping, forklifts and stationary rooftop HVAC
noise for commercial businesses in Irish Hills Plaza to the north of Froom Ranch. Existing and
proposed noise levels based on these assumptions using the SoundPLANOO software along with
our underlying assumptions and model inputs are reported here. Observations on compatibility of
the proposed project with reference to these previously cited regulations is provided.
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45dB Acoustics, LLC Froom Ranch Specific Plan
5 Sound Level Modeling
5.1 Noise Sources
5.1.1 Traffic Noise
The SoundPLANOO noise model utilizes ADT traffic volume and the FHWA's Traffic Noise
Model (TNM) to calculate/predict day ("Ld"), evening ("Le"), and nighttime ("Ln"), and
composite day-evening-night levels "Lden" as desired. Lden and Community Noise Equivalent
("CNEL") noise levels are equivalents. The City of San Luis Obispo has published traffic counts
for Los Osos Valley Road from 20ll through 2015 (Figure 5). These figures are adjusted upward
to present year levels assuming a 1%per year growth rate. A linear noise source is used to
accurately represent traffic noise at the southern boundary of Irish Hills Plaza in our acoustic
model.
Figure 5: City of San Luis Obispo traffic volume for Los Osos Valley Road.
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5.1.2 Rooftop and other Mechanical Equipment
The heating, ventilating and air conditioning (HVAC) systems for maintaining comfortable
shopping temperatures within the Home Depot, TJ MaXx and Whole Foods stores consist of
packaged rooftop air conditioning systems. We included noise from all the rooftop units (RTU)
identified from Google Maps in our analysis. The contribution of RTUs are not significant when
compared to truck delivery and alley traffic noise.
5.1.3 Parking Lot Noise
The north boundary of Froom Ranch Specific Plan area faces adjacent on-grade parking near
Home Depot and TJ Maxx retail sales stores. Various noise events, including noise related to
automobile movement near driveways, infrequent alarms, car horns, door slams, and tire squeals,
may occur infrequently within the proposed parking areas and may be individually/
instantaneously audible from the Froom Ranch project areas. However, the averaged (CNEL or
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hourly) noise levels over time are relatively low when compared to the sources previously
described. The incremental increase in average noise level would be less than the 3-dBA
perceptibility threshold(see "Subjective Loudness Level" in Section 7.1) and therefore from the
standpoint of the Noise Element these noise sources are less-than-significant.
5.1.4 Parking Lot Sweeping Noise (Less than Significant)
The parking lot area requires a sweeping truck for routine cleaning during night and early
morning hours. As a means of determining the noise levels associated with sweeper truck
activities, field measurements have been conducted by Bollard Associates of a typical sweeper
vehicle during normal operation at a Home Depot store on Howe Avenue in Sacramento,
California. Sweeper truck noise levels were measured to be up to 75 dB Lmax at a reference
distance of 50 feet. However, due to the infrequency of this noise source, and comparing to the
sound levels already produced from the other sources as described, this also does not
significantly add to the existing noise levels produced by the alley and trucks themselves as
modeled.
5.15 Intermittent Delivery Truck and Loading Dock Noise
Local carrier vehicles, vendor vehicles, and Home Depot, TJ MaXx and Whole Foods
distribution center trucks accessing the project site have the potential to increase ambient noise
levels on the project site and in its vicinity. This is a noncontinuous sound level that does not
define an associated instantaneous maximum level that may occur from backup beeping,
honking, slamming doors, etc.
This condition is helpful only in attempting to address the Municipal Code requirements adapted
by the Froom Ranch EIR within Table 3.10-5 of that document,reprinted in Table 1. The
Municipal Code requirement states that the Maximum Acceptable Noise Level is not to be
exceeded more than 30 minutes in an hour(L50 or Lso in acoustic terminology). To use an
extreme example, a very loud, impulsive noise source such as a firing range would still be
compliant with this L50 requirement, as long as firearm shots are only present less than half the
time in a given hour.
Because environmental noise such as this—with random backup beeping, truck brakes, and other
instantaneous or"maximum" noises—is inherently stochastic in nature, there are theoretically an
infinite number of noise scenarios with varying instantaneous noise peaks all having the same
equivalent hourly Leq or daily CNEL. For this reason, it is impossible to guarantee without
exception that an instantaneous or short-duration sound level limit will not be exceeded in the
future, at any location. Given the maximum noise levels estimated within the EIR(reprinted in
Table 2), and on the condition that these noises would not occur more than 6 minutes per hour
even in the nighttime hours between l Opm and 7pm for the R-3-SP residences where these
noises will be loudest (per Table 2), then the resulting L50 with an otherwise quiet background
noise level will not exceed even the City's nighttime Exterior Noise Limit of SOdBA.
However, in this scenario the additional 1-minute-per-hour (L08 or Los) limit of 75 dBA shown
in Table 2 may be exceeded at the R3-SP location if more than 1 total minute of intermittent
noise occurs. This L08 level would require at least 60 or more intermittent noises—beeps, honks,
banging, or other such noises—and we anticipate that will not be the case. We conclude that the
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EIR limits as derived from the Municipal Code are not anticipated to be exceeded under any
foreseeable conditions or for any locations within the Froom Ranch site plan.
Having said that, we do recommend that prospective residents be forewarned of the possibility of
audible noise from the commercial zone which will inevitably occur from time to time, as the
Froom Ranch EIR has previously stated. Additionally, it may be prudent to design exterior
window-wall assemblies facing the commercial zone to the north to a higher degree of noise
isolation (Outdoor-Indoor Transmission Class, or"OITC") to further mitigate against these
short-duration sounds for interior habitable spaces for resident comfort, although it is not
required.
Table 1: City Municipal Code Exterior Noise Limits
T�ble 3.10-�7. �:it�of 5�n Luis Obis�o E�teriur �aise Limits
��� � � � �
�:
Lo��.�_�c�ie�iiuu-Densit�-Resi4ential(R-1 aud R- 1�:00 P�i—':�U��i �0
'�:��ons�en-�tiaml0pen�p;�ca(��OS) ,:00_��i-10:��F�i ��
���dnuni-au�Hi�-D�nsit�-Residential�R-3 aud R- 1�=00 P�i—?:�U�h'I ��
�� ?:00.���—10:{}4 P��i 55
O�'ice aud Public Facilit���D aud FF) 14:00 P�i—?:{}4���i 55
?:00.���—10:��P�i �0
�ei�ba�hood,R.etaiL C�iuu:.t:�it�-.D���,�roru a�c 14:0�P�i—?:{}[}�'I fi0
�oiui�t�onunercial��-�_C-�C-C,C�-D. C-T} ?:00.���—10:�4 P�i ��
S�-ice�ou�aercial(C�-S� �u��Time 7�
��auufacnuin�(�i} �u��T� ?�
'Ilig claaa:fic 3r o�of dif�'g:evt areaa of t�g cammm.Luit4-iu t�ma 6f Pll'�mnmaLtdl LlOS's��9��'s�fI be�eteruiined b�•
the��i�e�'c*trol Office�r}��a�d ti��ffuimtinuM•n,o-i�e Sur•�-cata.r�cdi3amal a�tia dassificanans shatiLd be use�as
d�S0�7Cld'$Cfl Iff:eCt�6C�1 Iar�'S 3IlS L1ElLE:e*aatns�u.iosent le�•ela than thasg sho�a F�usu�aC n,o-ise t�u.its arg
�tgn�ed grlu.�il}-£o�u�e at th��-a�indary��f in�.is�a:�e5 rather tban fa�noaae 7e�uctiom 3�zt�On th,e z�,e�Or� 1�3�
4� p.�'t] 1�83)
=d$.��4-�+�e��hted dseibel seale)e�npba5�ea tb,e range af yrnind freqngnri�s that are most au�iblg ta the h��man ear
(bet�-•een 1.�[1��S.U[14 Hem}.
'-Le-�eCS not ta bg�ceeded nia�e thaoi 30 mmutes io a�•ho-ur_
Saurce=C��t�'4�Sdg LV1S C�15�}4�OO�J. l
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Table 2: Estimated Maximum Noises from Nearby Commercial Activities (Wood)
Tabl� �.1Q-18. �Laaiu�um ��is� L��-�1 EstiIIxa�es �nd ��r�shalds �esultin� fra�x
�earh�• C_�maxercial�c ti�-iti�s
. � + L I Y � k F
} � ■ 11 �
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. . �
��maum�oise Le��l S5 77 ?6 72 6S 7�#
(�} i
.Cit�•Exterior��is� ... .
Liunt—�0 nu�rute�or I 6{} �� 6� �� I �� bQ
ma�e'{dB.��
. . . }._
Cilt}•E�tenar�oise 7� �SO 75 ?0 74 ?5
Liinat-1 nu�ut�(dB.��
'�aa�5�aucard for La.nc L�Se,�.zthin Sec�aus 9.1'.06U af the ��_t�-�i�.:uic:p.�l Coce.L=-�=1a not ta be exc�ecac�-g.—.
than 3�iuirutes ux auti-Ltrnu.
'-iraasg St�dard f�r Lauc C�Se,�.zthin Seetiam�_1i.�60 a�'the{'Et�-�'I�.micrpal Cacg.Lgrgls not t�be eac�eect�a fo-r mo-re
than a�e m�•.�tg in�3�ha•�r_
��R-�aamna Fr�am R anrh
5.2 CNEL Sound Level Contours for Commercial and Traffic Sources
The previous section discussed short duration/instantaneous/maximum noise levels as compared
to the Municipal Code. In this section, a 24-hour equivalent (CNEL) sound level map is
presented for the area, to compare with the primary applicable guidance document, the Noise
Element of the General Plan.
A linear noise source in the alleyway was modeled for deliveries to the back side of the existing
commercial businesses. The starting assumption from the Froom Ranch Specific Plan Draft EIR
is 82 truck trips per week. If a worst-case/maximum of 15 trips per day exists, then assuming the
noise exists during all 15 hours per day along the entire line source is conservative and can be
considered a"worst case" situation,providing a desirable safety factor for exterior noise level on
the design development for the project's buildings. Figure 6 shows a vertical cross section of
sound level contours passing through an RTU on top of Home Depot and the alley line source.
Figure 6: Vertical cross-section of line-source truck noise
� N¢iY_�!vtl
6�J �l7 71 ^J9riA}
69 �-'�
Home Depot �3� 1 69 67 65 6 :
�7�����1 � � ��'63 �J �..'.
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67 �
Additionally, Home Depot Garden Center and parking lot area noise source were added to the
model to include the lower-level noise. However, these noise sources are a less-than-significant
contribution.
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The resulting CNEL sound level contours in Figure 7 depict a realistic 24-hour scenario with a
maximum amount of activity and noise from these businesses. A conceptual future zoning map
has been underlaid in the image to assist in evaluation of compatibility. The 60-dBA contour line
is highlighted in red here, to aid in the compatibility assessment in the next section.
The future CNEL sound pressure levels (year 2040) across the site are expected remain within 1
dB of current predictions, assuming a 1%per year growth rate of combustion engine cars and
trucks.
6 Compatibility and Recommendations
The PF-SP (Public Spaces), C/OS-SP (Conservation–Open Space), and R3-SP (Medium-
Density Residential) zones of the specific plan do exceed 60 dBA in some locations toward the
commercial areas to the north of Froom Ranch. Per the City's Noise Element, neighborhood
parks and playgrounds would be compliant with these levels, but (private) residential outdoor
activity areas would not be compliant in the areas that exceed 60 dBA CNEL. So, the C/OS-SP
area is compliant. The PF-SP and R3-SP zones should be designed to locate residential outdoor
activity areas—i.e.,patios,balconies, etc.—on elevations that do not face the commercial areas
to the north, using the residential buildings themselves as an effective mitigating noise barriers.
Commercial zones labeled"CR-SP" are in compliance with these predicted noise levels.
The Noise Element requires that indoor spaces not exceed 45 dBA CNEL. Given a maximum
exterior level of 66 dBA for the northernmost corner of the R-3-SP zone facing the commercial
businesses to the north, industry-standard exterior wall-window assemblies can readily be
designed to render the interior sound levels to less than 45 dBA CNEL.
The calculation to verify outdoor-to-indoor transmission class (OITC) is complex,requiring
known receiving room volume, exact wall design detail, and respective areas of glazing and
walls comprising the composite assembly. However, we can state that dual glazing will be
sufficient. A thick or complex wall design is not anticipated to be required in order to
successfully mitigate against an eXterior noise level of up to 66 dBA CNEL per the Noise
Element.
Commercial and public space zones of the Froom Ranch Specific Plan are compatible with
predicted sound levels. Other outdoor activity areas for the individual residential housing
buildings in the R-3-SP and R-4-SP areas are recommended to be shielded from the commercial
area to the north by locating them to the south and out of line-of-sight of the commercial area.
Alternatively, although not required, an earth berm or noise barrier wall could be constructed that
not only slightly reduces these propagated levels onto Froom Ranch, but also blunts
instantaneous sound levels arising from individual truck and car pass-byes, vehicle horns, or any
other such sounds which, however compliant they may be, could be considered annoying to
future Froom Ranch residents. The psychoacoustic effect of not having direct line-of-sight to
noise sources is well-documented and not to be ignored—if a listener cannot see the noise
source, the probability of annoyance and audibility is decreased somewhat. A berm or wall may
also be desired for aesthetic reasons. However, it must be noted noise barriers are most effective
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either very near the source or the receiver—the CNEL levels are not anticipated to be reduced by
more than approximately 3dB since the parking lot, the RTUs, and the shipping docks will be
located away from the barrier, essentially allowing the noise to "jump" the barrier.
The exterior noise levels for this project are considered to be reasonable for a residential land
use, and exterior window-wall building assemblies can be designed such that interior spaces will
meet the State Building Code.
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Figure 7: CNEL Sound Level Contours from all sources with 60 dB contour in red
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7 Appendix
7.1 Terminology/Glossary
A-Weighted Sound Level(dBA)
The sound pressure level in decibels as measured on a sound level meter using the internationally
standardized A-weighting filter or as computed from sound spectral data to which A-weighting
adjustments have been made. A-weighting de-emphasizes the low and very high frequency
components of the sound in a manner similar to the response of the average human ear. A-
weighted sound levels correlate well with subjective reactions of people to noise and are
universally used for community noise evaluations.
Air-borne Sound
Sound that travels through the air, differentiated from structure-borne sound.
Ambient Sound Level
The prevailing general sound level existing at a location or in a space, which usually consists of a
composite of sounds from many sources near and far. The ambient level is typically defined by
the Leq level.
Background Sound Level
The underlying, ever-present lower level noise that remains in the absence of intrusive or
intermittent sounds. Distant sources, such as Traffic, typically make up the background. The
background level is generally defined by the L90 percentile noise level.
Community Noise Equivalent Level (CNEL)
The Leq of the A-weighted noise level over a 24-hour period with a 5 dB penalty applied to
noise levels between 7 p.m. and 10 p.m. and a 10 dB penalty applied to noise levels between 10
p.m. and 7 a.m. CNEL is similar to Ldn.
Day-Night Sound Level (Ldn)
The Leq of the A-weighted noise level over a 24-hour period with a 10 dB penalty applied to
noise levels between 10 p.m. and 7 a.m. Ldn is similar to CNEL.
Decibel(dB)
The decibel is a measure on a logarithmic scale of the magnitude of a particular quantity (such as
sound pressure, sound power, sound intensity) with respect to a reference quantity.
DBA or dB(A)
A-weighted sound leveL The ear does not respond equally to all frequencies, but is less sensitive
at low and high frequencies than it is at medium or speech range frequencies. Thus, to obtain a
single number representing the sound level of a noise containing a wide range of frequencies in a
manner representative of the ear's response, it is necessary to reduce the effects of the low and
high frequencies with respect to the medium frequencies. The resultant sound level is said to be
A-weighted, and the units are dBA. The A-weighted sound level is also called the noise level.
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Energy Equivalent Level (Leq)
Because sound levels can vary markedly in intensity over a short period of time, some method
for describing either the average character of the sound or the statistical behavior of the
variations must be utilized. Most commonly, one describes ambient sounds in terms of an
average level that has the same acoustical energy as the summation of all the time-varying
events. This energy-equivalent sound/noise descriptor is called Leq. In this report, an hourly
period is used.
Field Sound Transmission Class (FSTC)
A single number rating similar to STC, eXcept that the transmission loss values used to derive the
FSTC are measured in the field. All sound transmitted from the source room to the receiving
room is assumed to be through the separating wall or floor-ceiling assembly.
Outdoor-Indoor Transmission Class (OITC)
A single number classification, specified by the American Society for Testing and Materials
(ASTM E 1332 issued 1994), that establishes the A-weighted sound level reduction provided by
building facade components (walls, doors, windows, and combinations thereo fl,based upon a
reference sound spectra that is an average of typical air, road, and rail transportation sources. The
OITC is the preferred rating when exterior fa�ade components are exposed to a noise
environment dominated by transportation sources.
Percentile Sound Level, Ln
The noise level exceeded during n percent of the measurement period, where n is a number
between 0 and 100 (e.g., L10 or L90)
Sound Transmission Class (STC)
STC is a single number rating, specified by the American Society for Testing and Materials,
which can be used to measure the sound insulation properties for comparing the sound
transmission capability, in decibels, of interior building partitions for noise sources such as
speech, radio, and television. It is used extensively for rating sound insulation characteristics of
building materials and products.
Structure-Borne Sound
Sound propagating through building structure. Rapidly fluctuating elastic waves in gypsum
board,joists, studs, etc.
Sound Exposure Level (SEL)
SEL is the sound exposure level, defined as a single number rating indicating the total energy of
a discrete noise-generating event(e.g., an aircraft flyover) compressed into a 1-second time
duration. This level is handy as a consistent rating method that may be combined with other SEL
and Leq readings to provide a complete noise scenario for measurements and predictions.
However, care must be taken in the use of these values since they may be misleading because
their numeric value is higher than any sound level which existed during the measurement period.
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Subjective Loudness Level
In addition to precision measurement of sound level changes, there is a subjective characteristic
which describes how most people respond to sound:
• A change in sound level of 3 dBA is barely pe�ceptible by most listeners.
• A change in level of 6 dBA is clearly perceptible.
• A change of 10 dBA is subjectively perceived as being twice (or ha� as loud.
7.2 Calculating CNEL
Housing and Urban Development (HUD) Code of Federal Regulations (CFR), Part 51
Environmental Criteria and Standards, along with Federal Highway Administration (FHWA)
guidelines are used for estimating CNEL values based on"design hour" traffic flow
measurement.
Highway projects receiving Federal aid are subject to noise analyses under the procedures of the
FHWA. Where such analyses are available, they may be used to assess sites subject to the
requirements of this standard. The Federal Highway Administration employs two alternate sound
level descriptors (23 CFR 772.12):
(i) The A-weighted sound level not exceeded more than 10 percent of the time for the
highway design hour traffic flow, symbolized as L10; or
(ii) The equivalent sound level for the design hour, symbolized as Leq. The day-night
average sound level may be estimated from the design hour L10 or Leq values by the
following relationships,provided heavy trucks do not exceed 10 percent of the total
traffic flow in vehicles per 24 hours and the traffic flow between 10 p.m. and 7 a.m. does
not exceed 15 percent of the average daily traffic flow in vehicles per 24 hours:
(a) CNEL � L 10 (design hour) - 3 decibels
(b) CNEL� Leq(design hour) decibels
Existing highway traffic noise measurements are made to represent an hourly equivalent sound
level, Leq. Statistical accuracy requires a minimum measurement of approximately eight
minutes. Most highway agencies have automated measurement equipment and typically measure
15-minute time periods to represent the Leq. This is acceptable if unusual events do not occur
during the noisiest hour.
Measurements along low-volume highways may require longer measurement periods (e.g., 30-60
minutes) to attain desirable statistical accuracy. If information is not available to identify the
noisiest hour of the day or if there is public controversy at a specific location, 24-hour
measurements may be necessary.
The FHWA stipulates the use of noise meters with sufficient accuracy to yield valid data for the
particular project (ANSI 51.4-1983, TYPE II or better). The measurement procedure shall ensure
measurements have consistent and supportable validity. Traffic conditions, climatic conditions,
and land uses at the time of ineasurement shall be noted.
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7.3 Traffic Noise Model (TNM)
The Federal Highway Administration Traffic Noise Model (TNM) used for the sound level
analysis in this study, contains the following components:
1. Modeling of five standard vehicle types, including automobiles, medium trucks, heavy
trucks, buses, and motorcycles, as well as user-defined vehicles.
2. Modeling both constant- and interrupted-flow traffic using a field-measured data base.
3. Modeling effects of different pavement types, as well as the effects of graded
roadways.
4. Sound level computations based on a one-third octave-band data base and algorithms.
5. Graphically-interactive noise barrier design and optimization.
6. Attenuation over/through rows of buildings and dense vegetation.
7. Multiple diffraction analysis.
8. Parallel barrier analysis.
9. Contour analysis, including sound level contours,barrier insertion loss contours, and
sound-level difference contours.
These components are supported by a scientifically founded and experimentally calibrated
acoustic computation methodology.
7.4 SoundPLANOO Acoustics Software
SoundPLAN, the software used for this acoustic analysis, is an acoustic ray-tracing program
dedicated to the prediction of noise in the environment. Noise emitted by various sources
propagates and disperses over a given terrain in accordance with the laws of physics. Worldwide,
governments and engineering associations have created algorithms to calculate acoustical
phenomena to standardize the assessment of physical scenarios. Accuracy has been validated in
wide-ranging schenairos to be +/- 2.7 dBA with an 85% confidence level. At close-in distances
and simpler geometries, the accuracy may be as high as +/- 1 dB. SoundPLAN is compliant with
TNM standards described above.
The software calculates sound attenuation of environmental noise, even over complex terrain,
uneven ground conditions, and with complex obstacles. The modeling software calculates the
sound field in accordance with ISO 9613-2 "Acoustics -Attenuation of sound du�ing
propagation outdoo�s, Part 2: General Method of Calculation." This standard states that "this
part of ISO 9613 specifies an engineering method for calculating the attenuation of sound during
propagation outdoors, in order to predict the levels of environmental noise at a distance from a
variety of sources. The method predicts the equivalent continuous A-weighted sound pressure
level under meteorological conditions favorable to propagation from sources of known sound
emissions. These conditions are for downwind propagation under a well-developed moderate
ground-based temperature inversion, such as commonly occurs at night."
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7.1 Computer Modeling of Transmission Class (STC)
The use of computer modeling to estimate sound transmission class (STC) and outdoor-to-indoor
transmission class (OITC) ratings has become increasingly common. There are several factors to
consider when using software to estimate the sound insulation of architectural elements and
assemblies. One of the most important factors is the question of real-world accuracy. Others
include the use of analytical vs. empirical models, the complexity of assemblies that can be
modeled and the level of user experience and knowledge necessary to yield valid or useful
results.
Computational results using INSUL software yield octave or third-octave-band transmission loss
values as well as providing an estimated single-number STC rating. Modeled results are
compared to published laboratory test data for several representative assemblies in Figure 8.
Figure 8: Comparison of INSUL and Laboratory Testing:
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7.2 Characteristics of Sound
When an object vibrates, it radiates part of its energy as acoustical pressure in the form of a
sound wave. Sound can be described in terms of amplitude (loudness), frequency (pitch), or
duration (time). The human hearing system is not equally sensitive to sound at all frequencies.
Therefore, to approximate this human, frequency-dependent response, the A-weighted filter
system is used to adjust measured sound levels. The normal range of human hearing extends
from approximately 0 to 140 dBA. Unlike linear units such as inches or pounds, decibels are
measured on a logarithmic scale, representing points on a sharply rising curve. Because of the
physical characteristics of noise transmission and of noise perception, the relative loudness of
sound does not closely match the actual amounts of sound energy. Table 3 below presents the
subjective effect of changes in sound pressure levels.
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Table 3: Sound Level Change Relative Loudness/Acoustic Energy Loss
0 dBA Reference 0%
-3 dBA Barel Perce tible Chan e 50%
-5 dBA Readil Perce tible Chan e 67%
-10 dBA Half as Loud 90%
-20 dBA 1/4 as Loud 99%
-30 dBA 1/8 as Loud 99.9%
Source:Highway Tra�c Noise Analysis and Abatement Policy and Guidance,
U.S. Department of Transportation, Federal Highway Administration, Office of
Environinent and Plannin ,Noise and Air uali Branch, June 1995.
Sound levels are generated from a source and their decibellevel decreases as the distance from
that source increases. Sound dissipates exponentially with distance from the noise source. This
phenomenon is known as spreading loss. Generally, sound levels from a point source will
decrease by 6 dBA for each doubling of distance. Sound levels for a highway line source vary
differently with distance because sound pressure waves propagate along the line and overlap at
the point of ineasurement. A closely spaced, continuous line of vehicles along a roadway
becomes a line source and produces a 3 dBA decrease in sound level for each doubling of
distance. However, experimental evidence has shown that where sound from a highway
propagates close to "soft" ground(e.g.,plowed farmland, grass, crops, etc.), a more suitable
drop-off rate to use is not 3.0 dBA but rather 4.5 dBA per distance doubling (FHWA 2010).
When sound is measured for distinct time intervals, the statistical distribution of the overall
sound level during that period can be obtained. The Leq is the most common parameter
associated with such measurements. The Leq metric is a single-number noise descriptor that
represents the average sound level over a given period of time. For example, the L50 noise level
is the level that is exceeded 50 percent of the time. This level is also the level that is exceeded 30
minutes in an hour. Similarly, the L02, L08 and L25 values are the noise levels that are exceeded
2, 8, and 25 percent of the time or 1, 5, and 15 minutes per hour. Other values typically noted
during a noise survey are the Lmin and Lmax. These values represent the minimum and
maximum root-mean-square noise levels obtained over the measurement period.
Because community receptors are more sensitive to unwanted noise intrusion during the evening
and at night, State law requires that, for planning purposes, an artificial dB increment be added to
quiet-time noise levels in a 24-hour noise descriptor called the CNEL or Ldn. This increment is
incorporated in the calculation of CNEL or Ldn, described earlier.
7.3 Evidence of Compliance
Evidence of compliance shall consist of submittal of an acoustical analysis report,prepared
under the supervision of a person experienced in the field of acoustical engineering, with the
application for building permit. The report shall show topographical relationship of noise
sources and dwelling site, identification of noise sources and their characteristics,predicted noise
spectra at the exterior of the proposed dwelling structure considering present and future land
usage, basis for the prediction (measured or obtained from published data), noise attenuation
measures to be applied, and an analysis of the noise insulation effectiveness of the proposed
construction showing that the prescribed interior noise level requirements are met. If interior
allowable noise levels are met by requiring that windows be unopenable or closed, the design for
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the structure must also specify the means that will be employed to provide ventilation and
cooling, if necessary, to provide a habitable interior environment.
8 References
1. City of San Luis Obispo, California. General Plan Noise Element.
2. RRM Design Group. Froom Ranch Specific Plan Draft. July 2017.
3. Wood Environment&Infi^astructure Solutions, Inc. Draft Environmental Impact RepoNt
for Froom Ranch Specific Plan. SCH No. 2017071033. November 2019.
4. American National Standards Institute, Inc. 2004.ANSI 1994 American National
Standard Acoustical Terminology. ANSI 5.1.-1994, (R2004),New York,NY.
5. American Society for Testing and Materials. 2004. ASTM E 1014 - 84 (Reapproved
2000) Standard Guide for Measurement of Outdoor A-Weighted Sound Levels.
6. Bolt, Beranek and Newman. 1973. Fundamentals and Abatement of Highway Ti^affic
Noise, Report No. PB-222-703. Prepared for Federal Highway Administration.
7. California Department of Transportation (Caltrans). 1982. Caltrans Transportation
Laboratory Manual.
8. . 1998. Caltrans Traffic Noise Analysis Protocol for New Highway Construction
and Highway Reconstruction Proj ects
9. California Resources Agency. 2007. Title 14. California Code of Regulations Chapter 3:
Guidelines for Implementation of the California Environmental Quality Act Article 5.
Preliminary Review of Projects and Conduct of Initial Study Sections, 15060 to 15065.
10. FHWA Roadway Construction Noise Model User's Guide Final Report. FHWA-HEP-OS-
054 DOT-VNTSGFHWA-OS-01
11. Harris, Cyril M., editor. 1979 Handbook of Noise Control.
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