HomeMy WebLinkAboutEx 22_Noise Assessment.pdf
Prepared for:
Brent Planning Solutions
On behalf of:
Renton School District, King County, WA
Prepared by:
Ramboll US Corporation
Lynnwood, Washington
Date
November 22, 2020
RENTON SCHOOL DISTRICT –
ELEMENTARY SCHOOL NO. 16
NOISE ASSESSMENT
Renton School District –Elementary School No. 16
Noise Assessment
November 22, 2020 i Ramboll
CONTENTS
1. Introduction ......................................................................................... 1
2. Noise Level Terminology and Human Hearing ...................................... 1
3. Affected Environment ........................................................................... 2
3.1 Applicable Noise Regulations ......................................................................... 2
3.2 Land Uses and Zoning .................................................................................. 3
3.3 Existing Sound Levels .................................................................................. 3
4. Operational Noise Impact .................................................................... 6
4.1 Noise Sources ............................................................................................. 6
4.1.1 On-Site Traffic .................................................................................. 6
4.1.2 Emergency Generator ........................................................................ 6
4.1.3 Chiller .............................................................................................. 7
4.2 Analysis Methods ........................................................................................ 7
4.3 Noise Assessment Results ............................................................................ 7
4.3.1 Compliance of On-Site Sources with Noise Limits .................................. 7
4.3.2 Increases Over Existing Noise Levels From All Project Sources ................ 8
5. Conclusions .......................................................................................... 9
TABLES
Table 1: State Maximum Permissible Sound Levels (dBA) ............................................... 2
Table 2: Measured Existing Sound Levels (dBA) ............................................................ 4
Table 3: Calculated Sound Levels of On-site Sources (dBA) ............................................ 8
Table 4: Calculated Sound Level Increases during Morning Arrival (dBA) .......................... 9
FIGURES
Figure 1. Sound Level Measurement and Receptor Locations ........................................... 5
APPENDICIES
Appendix A: Sound Level Measurement Data
Renton School District –Elementary School No. 16
Noise Assessment
November 22, 2020 1 Ramboll
1. INTRODUCTION
This report documents the noise impact assessment performed by Ramboll US Corporation
(Ramboll) as part of the environmental review of Renton School District’s proposed
Elementary School No. 16. The school is proposed to be located off Duvall Road, between
NE 10th and NE 12th Streets in Renton, Washington. The nearest neighboring residential
properties are adjacent to the northern and southern property boundaries.
The analysis considered potential noise impacts at residences near the proposed project site
from vehicles traveling on on-site roadways, an emergency generator, and an air-cooled
chiller. The following report reviews noise terminology, regulatory and impact criteria
applicable to the project, and the methods and findings of the analysis.
2. NOISE LEVEL TERMINOLOGY AND HUMAN HEARING
The human ear responds to a very wide range of sound intensities. The decibel scale (dB)
used to describe sound is a logarithmic rating system which accounts for the large
differences in audible sound intensities. This scale accounts for the human perception of a
doubling of loudness as an increase of 10 dB. Therefore, a 70-dB sound level will sound
about twice as loud as a 60-dB sound level. People generally cannot detect differences of 1
dB; in ideal laboratory situations, differences of 2 or 3 dB can be detected by people, but
such a change probably would not be detectable in an average outdoor environment. A 5-dB
change would probably be perceived under normal listening conditions.
When addressing the effects of noise on people, it is useful to consider the frequency
response of the human ear. Sound-measuring instruments are therefore often programmed
to weight measured sounds based on the way people hear. The frequency-weighting most
often used is A-weighting because it approximates the frequency response of human
hearing and is highly correlated to the effects of noise on people. Measurements from
instruments using this system are reported in "A-weighted decibels" or dBA. All sound levels
in this evaluation are reported in A-weighted decibels.
Distance from the source, the frequency of the sound, the absorbency of the intervening
ground, obstructions, and duration of the noise-producing event all affect the transmission
and perception of noise. The degree of this effect also depends on who is listening and on
existing sound levels.
Renton School District –Elementary School No. 16
Noise Assessment
Ramboll 2 November 18, 2020
3. AFFECTED ENVIRONMENT
3.1 Applicable Noise Regulations
The proposed school property is located in the City of Renton and is subject to the noise
regulations established by the Renton Municipal Code (RMC). Section 8-7-2 of the RMC
identifies noise performance standards for commercial and industrial activities to be those
identified in Chapter 173-60 of the Washington Administrative Code (WAC). Although the
project is a public use, not commercial or industrial, no other quantitative limits are
identified in RMC, and the levels identified in WAC 173-60 are applied here.
WAC 173-60 establishes limits on sounds crossing property boundaries based on the
Environmental Designation for Noise Abatement (EDNA) of the sound source and the
receiving properties. The WAC EDNA classifications are based on the following land uses:
• Class A – Lands where human beings reside and sleep (e.g., residences hospitals,
camps, etc.)
• Class B – Commercial areas and community services not used for human habitation
(e.g., retail services, offices, schools, churches, etc.)
• Class C – Industrial and agricultural areas
The applicable noise limits for each EDNA Class source and receiver combination are listed
in Table 1.
Table 1. State Maximum Permissible Sound Levels (dBA)
EDNA of
Sound Source
EDNA of Receiving Property
Class A
Day/Night Class B Class C
Class A 55 / 45 57 60
Class B 57 / 47 60 65
Class C 60 / 50 65 70
The limitations for noise received in Class A EDNAs are reduced by 10 dBA during nighttime hours,
defined as between 10 PM and 7 AM.
Source: WAC 173-60-40
The "maximum permissible" environmental noise levels in Table 1 may be exceeded for
short periods by a total of not more than 15 minutes in any one-hour period. The allowed
short-term increases are as follows: 5 dBA for no more than 15 minutes in any hour, or 10
dBA for no more than 5 minutes of any hour, or 15 dBA for no more than 1.5 minutes of
any hour.
Renton School District –Elementary School No. 16
Noise Assessment
November 22, 2020 3 Ramboll
3.2 Land Uses and Zoning
The proposed school site and the surrounding properties are zoned Residential (R8) and
Residential Multi-Family (RMF). The use of the site for a school would classify the school as
a Class B noise source according to WAC 173-60-030. The adjacent residential properties
are classified as Class A receivers.
The noise limits for a Class B noise source affecting a Class A receiver are 57 dBA during
daytime hours (7 AM to 10 PM) and 47 dBA at night (10 PM to 7 AM). Allowable short-term
increases to the above levels are as described previously.
3.3 Existing Sound Levels
On October 6 to 7, 2020, Ramboll measured day-long sound levels in the vicinity of the new
school. Measurements were taken at three locations to determine the existing noise levels
near adjacent residential property boundaries. Measurements were taken near the
northwestern (SLM1), eastern (SLM2), and southeastern boundaries (SLM3) using Larson
Davis Type I sound level meters (Model LxT). The meters had been factory certified within
the previous 12 months and were field calibrated immediately prior to the measurement.
The microphones of the meters were fitted with wind screens and set approximately 5 feet
above the ground (at a typical listening height).
The measured sound levels are summarized in Table 2, and the sound level measurement
locations are depicted in Figure 1. Details of hourly sound level measurements are found in
Appendix A.
Renton School District –Elementary School No. 16
Noise Assessment
Ramboll 4 November 18, 2020
Table 2. Measured Existing Sound Levels (dBA)
Location Time of
Day (a)
Range of Sound Levels (dBA) (b)
Leq Lmax L2.5 L8.3 L25 L90
SLM1
Day 50 - 60 62 - 80 54 - 60 51 - 57 50 - 55 45 - 50
Night 48 - 55 54 - 68 45 - 53 42 - 50 40 - 48 38 - 44
School Day 53 - 60 62 - 80 54 - 59 53 - 56 51 - 54 45 - 50
SLM2
Day 60 - 67 76 - 96 68 - 71 65 - 70 61 - 68 45 - 56
Night 50 - 63 70 - 81 60 - 69 50 - 67 39 - 65 33 - 48
School Day 64 - 67 76 - 95 70 - 71 68 - 69 65 - 67 49 - 54
SLM3
Day 47 - 62 61 - 100 52 - 69 50 - 62 48 - 56 39 - 47
Night 36 - 46 54 - 67 43 - 51 38 - 49 35 - 47 33 - 40
School Day 47 - 56 61 - 80 52 - 62 50 - 60 48 - 52 40 - 45
(a) "Day" refers to the hours between 7 AM and 10 PM. "Night" refers to the hours between 10 PM
and 7 AM. “School Day” refers to the potential operating hours of the school, expected to fall
between 8 AM and 4 PM.
(b) The Leq is the "energy-averaged" sound level. The Lmax is the-highest measured sound level. The
L90 is the sound level exceeded 90% of the time and is often considered representative of the
background sound level. The L2.5, L8.3, and L25 County noise limit levels that are defined
previously in this report in the discussion of the regulatory noise limits.
These measurements were taken from October 6 to 7, 2020.
Renton School District –Elementary School No. 16
Noise Assessment
November 22, 2020 5 Ramboll
Figure 1. Sound Level Measurement and Receptor Locations
Renton School District –Elementary School No. 16
Noise Assessment
Ramboll 6 November 18, 2020
4. OPERATIONAL NOISE IMPACT
4.1 Noise Sources
Potential sources of noise associated with Elementary School No. 16 include buses and
vehicles traveling on on-site roadways, operation of an emergency generator during power
outages and monthly generator maintenance, and an air-cooled chiller. These noise sources
are described more completely below.
4.1.1 On-Site Traffic
On-site traffic would include school buses and parents and staff vehicles entering,
traversing, and departing on the site. Traffic volumes were provided by Heffron
Transpiration Inc. for the higher of the estimated AM and PM peak values of morning
arrival/drop-off and afternoon departure/pickup. Because traffic volumes during the
morning arrival hour are estimated to be greater than during afternoon departure, the focus
of the noise assessment is on the morning arrival hour. For purposes of this assessment,
peak morning arrival hour is assumed to occur between 8 and 9 AM, and the on-site traffic
speed is assumed to be 10 mph.
In the bus loop east of the school building, 8 school buses would enter the northern
driveway, drop off children, and depart south from the site during the peak morning arrival
hour.
In the parking area and parent drop-off loop south of the school building, 234 vehicles
would enter the site via the eastern driveway during peak morning arrival and exit from the
west driveway onto Chelan Ave NE. In addition, 53 vehicles would enter the eastern
driveway and remain on site and park in the southern lot.
4.1.2 Emergency Generator
An emergency generator is proposed to be located in a service yard on the west side of the
building. The service yard is assumed to be enclosed by an 8-foot high wall, except for an
access/opening. The emergency generator would not generally operate except in
emergencies during power outages, and emergency operation of the generators is exempt
from the noise limits. However, maintenance of the generator requires it be operated
occasionally, typically for one hour or so once a month. Maintenance would occur during
daytime hours only. At the time of this report, the exact make and model of the emergency
generator was unknown, but it is expected to have a capacity of 100 kilowatts and use
natural gas. The estimated sound level of the generator used in this analysis is 70 dBA at 23
feet.
Renton School District –Elementary School No. 16
Noise Assessment
November 22, 2020 7 Ramboll
4.1.3 Chiller
A Daikin air-cooled screw chiller (chiller) is proposed to be located in the service yard on the
east side of the building, near the generator. The chiller could operate anytime during the
day and also potentially during early morning hour between 6 and 7 AM, and noise from the
unit would be required to comply with both the daytime and stricter nighttime noise limits at
the nearest residences to the school. The chiller was conservatively assumed to be running
at 100% load, with a sound level of 70 dBA at 30 feet. Noise from chiller operations was
included in the assessment of early morning hours before 7 AM, during peak morning
arrival, and during daytime maintenance of the generator.
4.2 Analysis Methods
Ramboll assessed sound levels associated with expected on-site sources of noise for the
following three operating scenarios:
• Chiller Operation Only – operation of the chiller between 6 and 7 AM
• Peak Morning Arrival – operation of the chiller and on-site traffic between 8 and 9 AM
• Generator Maintenance – operation of the chiller and maintenance/operation of the
emergency generator during daytime hours
Noise modeling of on-site sources was completed using the CadnaA noise model. CadnaA is
a computer tool that calculates sound levels after considering the noise reductions or
enhancements caused by distance, topography, varying ground surfaces, atmospheric
absorption, and meteorological conditions. For point sources of noise, such as emergency
generators, the model uses algorithms that comply with the international standards in
ISO-9613-2:1996. For traffic noise emissions, the CadnaA model used for this analysis is
equipped with the US Federal Highway Administration (FHWA) Traffic Noise Model (TNM)
standard.
The modeling process includes the following steps: (1) characterizing the noise sources, (2)
creating 3-dimensional maps of the site and vicinity to enable the model to evaluate effects
of distance and topography on noise attenuation, and (3) assigning equipment and activity
sound levels to appropriate locations on the site. CadnaA then constructs topographic cross
sections to calculate sound levels in the vicinity of a project site.
4.3 Noise Assessment Results
4.3.1 Compliance of On-Site Sources with Noise Limits
Model-calculated results of the early morning chiller operation, morning arrival, and daytime
generator maintenance operations are presented in Table 3. As shown in Table 3,
expected activities on the site do not exceed the applicable daytime or nighttime noise
limits.
Renton School District –Elementary School No. 16
Noise Assessment
Ramboll 8 November 18, 2020
Table 3. Calculated Sound Levels of On-site Sources (dBA)
Receptor Chiller Only (a) Morning Arrival (b) Generator
Maintenance (c)
Noise
Limit(d)
R1 38 40 40 57 / 47
R2 40 46 43 57 / 47
R3 41 45 40 57 / 47
R4 44 48 47 57 / 47
R5 43 48 45 57 / 47
R6 39 46 41 57 / 47
R7 30 48 32 57 / 47
R8 27 48 29 57 / 47
R9 25 48 27 57 / 47
R10 25 48 24 57 / 47
R11 23 28 23 57 / 47
Notes:
(a) Early morning operation of the chiller (i.e., prior to 7 AM) would be subject to the stricter
nighttime noise limit.
(b) Morning arrival includes traffic traveling on-site between 8 and 9 AM and operation of the
chiller.
(c) Generator maintenance includes operation of the generator and chiller during daytime
hours.
(d) The noise limits are presented as daytime/nighttime limits. Daytime hours are between 7
AM and 10 PM. Nighttime hours are between 10 PM and 7 AM.
Source: Ramboll, 2020
4.3.2 Increases Over Existing Noise Levels From All Project Sources
In addition to considering compliance with the applicable noise limits, Ramboll considered
the potential for noise impacts due to project-related increases in sound levels compared to
background levels. The assessment was conducted for peak morning arrival only, since this
was the worst-case scenario considered. Project-related increases during both early morning
chiller operation and midday generator maintenance are expected to be lower. Furthermore,
potential increases during generator maintenance would be infrequent and short-term.
Table 4 displays the calculated sound level increases expected during morning arrival. As
shown, the highest calculated increase of 2 dBA could be expected at residences near the
south parking lot. No increases are expected near residences primarily affected by traffic
along Duvall Avenue Northeast. Increases of 0 to 2 dBA would not typically be discernable in
an active, outdoor environment.
Renton School District –Elementary School No. 16
Noise Assessment
November 22, 2020 9 Ramboll
Table 4. Calculated Sound Level Increases during Morning Arrival (dBA)
Receptor Measured
Existing Level(a)
Modeled Morning
Arrival (b)
Cumulative
Level(c)
Increase
Over Existing
R1 52 40 53 0
R2 52 46 53 1
R3 67 45 67 0
R4 67 48 67 0
R5 67 48 67 0
R6 67 46 67 0
R7 67 48 67 0
R8 50 48 52 2
R9 50 48 52 2
R10 50 48 52 2
R11 50 28 50 0
Notes:
The above values are rounded to the whole number, and apparent calculation errors are due to the
rounding.
(a) Existing sound levels are based on the hourly level between 8 and 9 AM (i.e., representing the
AM peak traffic hour)
(b) Model-calculated sound levels of all on-site traffic and chiller operation.
(c) Overall levels include the existing measured levels plus all project-related noise.
Source: Ramboll, 2020
5. CONCLUSIONS
The proposed new Elementary School No. 16 would introduce traffic, an emergency
generator, and cooling equipment to the project site. Model-calculated sound levels of chiller
operation indicate compliance with both the daytime and nighttime noise limits. Model-
calculated sound levels of on-site traffic and chiller operations during peak morning arrival
indicate compliance with the applicable noise limits during daytime hours. Similarly, model-
calculated sound levels of chiller operations simultaneously with generator maintenance
indicates this activity would comply with the daytime noise limits at all receptor locations.
Consideration of potential increases in noise due to morning arrival traffic and chiller
operation results in estimated increases of 0 to 2 dBA at all residences near the site. Such
increases in an active, outdoor environment would be difficult to discern, and the project is
not expected to result in substantial noise impacts.
Renton School District –Elementary School No. 16
Noise Assessment
A-1 Ramboll
APPENDIX A: SOUND LEVEL MEASUREMENT DATA
Ramboll A-2
SLM1 - Near Northern Property Boundary
Date/Time Leq Lmax L2.5 L8.3 L25 L90
10/6/20 14:00 53.2 76.2 57.1 55.2 53.4 49.7
10/6/20 15:00 53.5 74.5 57.0 55.8 54.1 49.5
10/6/20 16:00 53.3 67.6 57.4 55.8 54.2 49.6
10/6/20 17:00 56.1 79.8 60.3 56.6 54.8 50.0
10/6/20 18:00 52.9 71.7 56.7 55.2 53.4 48.8
10/6/20 19:00 52.4 77.3 56.8 54.6 52.4 47.7
10/6/20 20:00 49.9 63.3 54.5 52.5 50.6 45.9
10/6/20 21:00 49.5 73.8 54.5 52.3 49.7 45.4
10/6/20 22:00 46.0 64.7 51.3 48.4 46.2 42.9
10/6/20 23:00 44.5 59.2 50.1 47.2 44.6 41.0
10/7/20 0:00 42.4 59.6 47.8 44.9 42.3 39.3
10/7/20 1:00 41.7 59.5 46.4 44.2 41.9 38.6
10/7/20 2:00 40.3 56.2 44.7 42.3 39.9 38.4
10/7/20 3:00 42.3 60.7 48.9 44.5 41.0 38.2
10/7/20 4:00 41.8 54.0 46.3 44.2 42.2 39.0
10/7/20 5:00 46.2 65.8 51.5 48.7 46.5 41.4
10/7/20 6:00 48.3 67.8 53.4 50.2 48.1 44.1
10/7/20 7:00 49.0 65.7 53.7 51.3 49.5 45.5
10/7/20 8:00 52.4 75.9 55.8 53.6 51.5 46.0
10/7/20 9:00 52.5 79.6 55.7 53.9 51.9 45.8
10/7/20 10:00 49.8 61.8 54.2 52.6 50.8 45.3
10/7/20 11:00 52.8 74.1 58.6 56.4 53.2 46.7
10/7/20 12:00 53.7 78.6 57.4 56.0 53.3 47.5
10/7/20 13:00 51.3 68.0 56.1 54.1 51.9 46.7
Renton School District –Elementary School No. 16
Noise Assessment
A-3 Ramboll
SLM2 - Near Eastern Property Boundary
Date/Time Leq Lmax L2.5 L8.3 L25 L90
10/6/20 14:00 64.1 81.3 69.9 68.2 65.5 53.1
10/6/20 15:00 65.2 77.9 70.7 69.1 66.8 53.3
10/6/20 16:00 65.8 78.9 71.1 69.7 67.4 55.0
10/6/20 17:00 66.0 77.4 71.3 69.9 67.7 56.0
10/6/20 18:00 65.4 86.7 71.1 69.5 66.8 54.8
10/6/20 19:00 65.3 95.7 69.9 67.8 65.0 50.9
10/6/20 20:00 62.1 82.5 69.0 66.9 63.3 47.0
10/6/20 21:00 60.2 77.1 67.7 65.2 61.0 45.0
10/6/20 22:00 58.1 76.9 66.7 63.6 57.2 41.0
10/6/20 23:00 56.2 76.2 65.9 61.5 51.6 37.7
10/7/20 0:00 53.7 74.6 63.8 57.2 46.1 34.1
10/7/20 1:00 50.9 72.0 61.6 50.4 39.5 32.7
10/7/20 2:00 49.8 73.6 60.2 49.5 39.4 32.6
10/7/20 3:00 52.1 70.0 63.1 55.0 42.7 33.5
10/7/20 4:00 53.9 72.9 63.9 59.4 47.9 36.5
10/7/20 5:00 59.3 74.9 67.5 64.8 59.7 41.7
10/7/20 6:00 63.1 81.1 69.1 67.4 64.8 48.4
10/7/20 7:00 64.6 79.2 70.3 68.5 66.1 52.8
10/7/20 8:00 66.6 95.1 70.8 69.1 66.7 51.3
10/7/20 9:00 64.1 75.8 70.0 68.4 65.9 48.9
10/7/20 10:00 63.6 77.6 69.8 67.7 65.0 49.1
10/7/20 11:00 64.0 77.0 69.7 68.0 65.5 51.5
10/7/20 12:00 64.6 76.9 70.1 68.3 66.0 53.9
10/7/20 13:00 64.3 82.3 70.1 68.1 65.6 51.7
Ramboll A-4
SLM3 - Near Southern Property Boundary
Date/Time Leq Lmax L2.5 L8.3 L25 L90
10/6/20 14:00 55.8 80.5 61.6 60.4 52.3 45.4
10/6/20 15:00 49.8 60.8 54.4 52.8 50.9 44.8
10/6/20 16:00 53.0 74.8 60.6 54.0 51.6 45.5
10/6/20 17:00 62.4 100.5 68.5 62.4 55.8 47.1
10/6/20 18:00 50.2 72.9 54.8 52.9 50.8 44.9
10/6/20 19:00 50.3 74.0 55.4 53.0 50.4 43.5
10/6/20 20:00 46.8 64.5 52.4 50.4 47.7 39.6
10/6/20 21:00 46.8 61.7 53.3 50.6 47.5 39.2
10/6/20 22:00 43.8 59.3 50.3 48.0 44.4 37.0
10/6/20 23:00 41.5 58.4 49.0 45.6 40.9 34.8
10/7/20 0:00 39.2 60.5 46.3 42.8 37.2 33.4
10/7/20 1:00 36.3 58.9 43.7 38.9 35.0 32.6
10/7/20 2:00 36.0 58.1 43.0 38.4 34.7 32.7
10/7/20 3:00 40.3 60.2 47.5 41.8 36.3 33.2
10/7/20 4:00 39.3 53.6 45.4 43.1 39.2 34.7
10/7/20 5:00 44.0 64.0 50.1 47.3 44.5 38.2
10/7/20 6:00 46.2 66.7 51.0 49.3 47.2 39.8
10/7/20 7:00 48.1 73.6 53.1 50.7 48.5 41.5
10/7/20 8:00 49.9 78.7 53.3 51.1 48.9 41.3
10/7/20 9:00 46.9 70.7 51.8 50.2 48.1 39.5
10/7/20 10:00 46.7 63.0 51.8 49.9 47.8 40.4
10/7/20 11:00 47.1 65.9 52.4 50.1 47.8 41.5
10/7/20 12:00 47.8 72.0 52.6 50.4 48.2 42.1
10/7/20 13:00 48.4 68.3 53.8 50.9 48.2 41.5