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Noise Study Report
Boeing Renton Apron E – Phase I
Submitted to:
Debbie Jung
Emily George
KPFF
Response to City Comment #3 of 04/22/20
KPFF, 2020-05-13
Boeing Renton Apron E - Phase I Page 2
Document Information
FILE: Noise Study Report - Boeing Renton Apron E - Phase I
PROJECT #: 19-7174
PREPARED BY: Alan Burt, P.E.
SIGNED:
DATE: May 11, 2020
This report has been prepared for the titled project or named part thereof and should not be used in whole or part and relied upon for
any other project without the written authorization of SSA Acoustics, LLP. SSA Acoustics, LLP accepts no responsibility or liability for
the consequences of this document if it is used for a purpose other than that for which it was commissioned. Persons wishing to use
or rely upon this report for other purposes must seek written authority to do so from the owner of this report and/or SSA Acoustics,
LLP and agree to indemnify SSA Acoustics, LLP for any and all resulting loss or damage. SSA Acoustics, LLP accepts no
responsibility or liability for this document to any other party other than the person by whom it was commissi oned. The findings and
opinions expressed are relevant to the dates of the works and should not be relied upon to represent conditions at substantia lly later
dates. Opinions included therein are based on information gathered during the study and from our experience. If additional information
becomes available which may affect our comments, conclusions or recommendations SSA Acoustics, LLP reserves the right to review
the information, reassess any new potential concerns and modify our opinions accordingly.
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I. Introduction
The following report documents the results of the evaluation of noise levels from the proposed
aircraft stalls to the residential properties east of the proposed site and Renton Memorial Stadium
to the south as well as noise levels at the Cedar River trail. The evaluation and analysis are
based on noise data, proposed site design, and noise level criteria appropriate for the project.
II. DESIGN CRITERIA
ZONING & CODE REQUIREMENTS
According to the City of Renton, the project site and nearest surrounding properties are currently
zoned as follows:
Property Zoning
Project Site UC
East (Residential Properties) R-8
South (Renton Stadium) UC
According to Renton Municipal Code, UC properties are within “Commercial” zoning districts, and
R-8 properties are within “Residential” zoning districts. City of Renton adopts WAC Sections 173-
60-020, 173-60-040, 173-60-050, and 173-60-090 for maximum environmental noise levels. WAC
173-60 defines commercial use properties as Class B EDNA and residential use properties as
Class A EDNA. WAC 173-60 limits noise from a Class B EDNA (Commercial) property as follows:
Class B EDNA (Commercial) Receiver: Noise is limited to 60 dBA during daytime hours.
Class A EDNA (Residential) Receiver: Noise is limited to 57 dBA during daytime hours. During
nighttime, defined as the hours between 10 p.m. and 7 a.m., exterior sound level limits are
reduced by 10 dBA where the receiving property lies within a residential district of the City.
At any hour of the day or night the applicable noise limitations above may be exceeded for any
receiving property by no more than:
(i) 5 dBA for a total of 15 minutes in any one-hour period; or
(ii) 10 dBA for a total of 5 minutes in any one-hour period; or
(iii) 15 dBA for a total of 1.5 minutes in any one-hour period.
Under WAC 173-60-050, sounds created by aircraft engine testing and maintenance not related
to flight operations are exempt between 7:00 AM and 10:00 PM.
The current run-up test schedule consists of high-power runs allowed between 8 AM and 5 PM
and medium-power runs until 6 PM. Typical run-up tests last for about 35 – 40 minutes. During
the tests, the engines are at idle approximately 2/3 of the time (about 25 minutes) with engines at
full power for 1/3 of the time (two different runs for 5 minutes or less). One engine is tested at a
time.
Engine run-up testing conducted at the proposed stalls is therefore exempt from the code limits
as the run-up testing will occur only during daytime hours. The following provides an evaluation
of the run-up noise levels compared to code limits and existing sound levels and mitigation
measures intended to reduce the impact of noise levels to the surrounding properties.
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Run-up testing will vary in duration and extent throughout the day, however as noted the engines
run at full power for 5 minutes or less during a test. The engine noise is loudest at full power . In
the interest of minimizing impact during testing, it is recommended that noise levels from the run-
up testing not exceed ambient levels by more than 10 dBA, which is consistent with the 10 dB
short-duration increase allowed for up to 5 minutes above the code limits.
The following figure shows a zoning map of the project site and surrounding properties:
Figure 1: Proposed Site and Surround Properties (City of Renton GIS)
AMBIENT CONDITIONS
Existing ambient noise levels were measured at locations representative of the residential
properties to the east of the proposed project between 3/13 – 3/16, 2019. Measurements were
conducted with Svantek 971 noise monitors. The weather during the measurements was clear
and the roads were dry. Hourly average LEQ noise levels during daytime hours (between 7 AM –
10 PM) were between 57 – 63 dBA (average of 60 dBA).
Ambient noise levels at the Cedar River Trail park were measured on 5/6/2020. Noise levels
were between 50 – 55 dBA.
Please see the appendix for more information regarding the measurements.
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IV. PROJECT SITE
The following figure presents the project site plan with the proposed stalls.
Figure 2: Project Site
NOISE BARRIER
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IV. PREDICTED NOISE LEVELS
737 Engine Run-Up Testing Noise Levels:
The following are noise levels from measurements of 737 engine run-up, provided in a previous
study. Noise levels were measured at 50 feet from the engines.
Table 1: 737 Engine Noise Levels – Measured 50 feet from engine1
Octave Band Center Frequency (Hz)
Engine Power RPM dBA 63 125 250 500 1000 2000 4000 8000
100% 4300 105 112 112 107 102 98 95 92 93
86% 3700 100 102 103 101 97 94 91 90 91
50% 2200 88 81 81 80 81 79 78 84 82
1. Source data obtained from Renton Apron C ground runup stall noise study. Noise data is for 737 Max engines.
Predicted Noise Levels
Noise levels were calculated based on noise reduction over distance and noise reduction from
the barrier or intervening buildings or structures. It is important to note that engine run-up testing
is exempt from noise code limits and WAC as the testing is conducted only during daytime hours.
East Receiving Properties
The proposed aircraft location in the easternmost stall is approximately 400 feet to the nearest
residential zoned property to the east. A solid steel sound wall is proposed along the east and
north sides of the stalls to block noise to the properties to the east as shown in figure 1. The
proposed noise wall will be 25 feet tall.
The following are the predicted noise level at the east receiving property:
Table 2 - Predicted Noise Levels – East Receiving Properties (Residential)
737 Engine Sound Level Receiver
Distance
(feet)
Distance
Reduction1
Barrier
Reduction2
Lp,r
100% Power 105 dBA @ 50’ 400 -20 -15 70 dBA
86% Power 100 dBA @ 50’ 400 -20 -15 65 dBA
50% Power 86 dBA @ 50’ 400 -20 -15 51 dBA
Table Notes:
1. Distance Factor = 20*log(Dr/Ds) – 10*log(Q)
2. Barrier reduction from proposed noise barrier
According to the predicted noise levels, run-up engine noise levels will be between 51 – 70 dBA
at the residential receiving properties to the east. Noise levels will be within or slightly above
existing noise levels up to 86% power, and about 10 dBA above existing levels at 100% power.
This meets the recommended level increase above ambient levels to reduce the noise impact.
Note that without the sound wall, noise levels from the testing would be 66 – 85 dBA, which would
be significantly above existing levels.
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South Receiving Property (Renton Memorial Stadium)
The proposed aircraft locations in the stalls are each approximately 650 feet to the south property.
The paint hanger and will act as a noise barrier to the south property.
Table 3 - Predicted Noise Levels – South Receiving Property (Commercial)
737 Engine Sound Level Distance
(feet)
Distance
Reduction1
Barrier
Reduction2
Lp,r
100% Power 105 dBA @ 50’ 650 -25 -20 60 dBA
86% Power 100 dBA @ 50’ 650 -25 -20 55 dBA
50% Power 86 dBA @ 50’ 650 -25 -20 41 dBA
Table Notes:
1. Distance Factor = 20*log(Dr/Ds) – 10*log(Q)
2. Barrier reduction from intervening building
According to the predicted noise levels, run-up engine noise will be 41 – 60 dBA, which is within
the current background levels.
Cedar River Trail
The westernmost aircraft stall location is approximately 645 feet to the Cedar River trail to the
west. The existing stall walls and intervening buildings will act as a noise barrier to the trail.
Table 4 - Predicted Noise Levels – Cedar River Trail
737 Engine Sound Level Distance
(feet)
Distance
Reduction1
Barrier
Reduction2
Lp,r
100% Power 105 dBA @ 50’ 645 -25 -20 60 dBA
86% Power 100 dBA @ 50’ 645 -25 -20 55 dBA
50% Power 86 dBA @ 50’ 645 -25 -20 41 dBA
Table Notes:
1. Distance Factor = 20*log(Dr/Ds) – 10*log(Q)
2. Barrier reduction from intervening buildings and stalls
According to the predicted noise levels, run-up engine noise will be between 41 – 60 dBA which
is within the recommended range of noise levels at the trail.
Note that the distances between the engines and the sound wall and the receiving properties are
such that reflected sound energy from the sound wall will not increase noise levels from the
engines.
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V. ADDITIONAL MITIGATION CONSIDERATIONS
The currently proposed mitigation measures are designed to reduce noise levels from run-up
testing such that they are within the recommended increase above ambient at the residential
receiving properties to the east. Noise levels at the other locations will be within the
recommended noise level range due to the combination of distance and other intervening
elements. Additional mitigation measures may be considered, however, if in practice noise levels
are found to be higher than as predicted.
Note that extending the proposed noise wall further west or south will not be significantly effective
in further reducing noise levels to the residential properties to the east. Due to the geometry of
the stalls relative to the barriers and receiving properties, any flanking noise would either be
blocked by the barrier, or reduced to equivalent mitigated noise levels due to the distance between
the aircraft, barrier edge and receiver location.
The following are conceptual options to reduce noise levels, specific design of these or other
mitigation measures may be considered should these need to be implemented:
• Intermediate noise barriers between stalls
• Localized noise enclosures installed around the engines
VI. SUMMARY
This concludes the noise evaluation for the proposed 737 run-up stalls at the Boeing Renton
Apron E project.
Please contact us if you have questions or need further information.
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APPENDIX I: DESCRIPTORS
A. Descriptors and Terminology
A-Weighted Decibel (dBA) Human exposure to noise is typically measured as an A-weighted
sound level in units of decibels, symbolized as dBA. The A-weighting is a frequency-specific
weighting that corresponds approximately to the sensitivity of human hearing at the various
frequencies.
Sound levels vary significantly, depending on location and activities. Locations near highways or
urban arterials may be 70 dBA, whereas quiet rural areas may be 40 dBA. People normally
experience sound levels between about 30 and 90 dBA, depending on their activity. For example,
a nearby noisy vehicle, radio or power tool may produce 90 dBA; normal conversation is about
55 to 65 dBA; and a bedroom or quiet office is about 30 to 40 dBA.
Loudness is judged by an average listener to double for each 10 dBA increase in sound level.
For example, 60 dBA is judged to be twice as loud as 50 dBA and four times as loud as 40 dBA.
Leq: When measuring noise that is fluctuating over time it is common practice to use a descriptor
called equivalent A-weighted sound level, Leq. The Leq is the constant sound level in dBA,
which contains the same amount of sound energy over a given time period as the measured
fluctuating noise. Descriptors that are commonly used to describe noise from the environmental
noise are the Leq(h), the 24-hour Leq and the Ldn. The Leq(h) is the average sound in dBA over
a one hour period during the day or night. The 24-hour Leq is the average sound in dBA over a
24 hour period calculated using the hourly Leqs.
Lmax The Lmax is the highest RMS instantaneous sound level for a given sound event or time
period.
LDN/DNL: The day-night noise level (DNL or Ldn) is a 24-hour average with a 10 decibel penalty
added to the hourly leqs between 10 pm and 7 am. These are the most common references in
HUD guidelines, and Federal and State regulations.
STC/TL: Considering the acoustic performance of a building element such as a wall or floor,
the ability of the system to block the transmission of sound waves is important. The sound
transmission loss (TL) of a material or building partition is a measure of sound isolation ability.
Since TL is very frequency dependent, it is generally reported in the third octave frequency bands
between, as a minimum, 125 Hz and 4,000 Hz. As a convenience, a single number rating method
has been developed which allows a single value to be given to a transmission loss spectrum.
This rating is referred to as the sound transmission class (STC) rating which has been defined
in the American Society for Testing and Materials (ASTM) Standard E413. This standard defines
a procedure for determining the STC rating for a TL spectrum by fitting a contour to the one-third
octave band TL data.
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APPENDIX II: SITE NOISE MEASUREMENTS
Long and short-term ambient noise measurements were conducted March 13- 16, 2019 and May
6, 2020. Noise levels were measured by Svantek 971 integrating sound level meters. The
following figure presents the locations of each of the measurements.
Figure 3: Noise Measurement Locations
Measurement Results Summary:
Location Daytime Hourly Leq (dBA)
M1 57 – 63
M2 57 – 63
M3 50 – 55
M2
M1
M3