HomeMy WebLinkAboutFile Documents.1322 Snowbunny Ln.0291.2018 (23).ARBKBehrens and Associates, Inc.
Environmental Noise Control
Introduction 0
1320 Snowbunny Lane
Soil Stabilization Noise Modeling
Report
Prepared for:
Crawford Design Build
1101 Village Road, Unit LL2B
Carbondale, CO 81623
Prepared by:
Behrens and Associates, Inc.
13806 Inglewood Avenue
Hawthorne, California 90250
Shaun Norris
Staff Acoustical Engineer
Jason Peetz
Engineering Manager
April 24, 2019
Corporate Office: Hawthorne, California
Carson, California ~ Aledo, Texas ~ Napa California ~ Longmont, Colorado ~ McDonald, Pennsylvania
Phone 800-679-8633 ~ Fax 310-331-1538
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Introduction 1
1. Introduction
The purpose of this study is to provide a noise modeling assessment of the proposed soil stabilization activities
associated with the Crawford Design Build construction project located at 1320 Snowbunny Lane in Aspen, Colorado.
The assessment was performed to ensure the noise levels generated during the soil stabilization activities are in
compliance with the noise standards described in the City of Aspen Construction Management Plan Requirements
(April 2016).
This report provides the results of the predicted unmitigated and mitigated soil stabilization noise levels relative to
the relevant noise standards as well as mitigation recommendations needed to comply with the allowable noise levels.
Figure 1-1 shows the project site within the City of Aspen.
.
Figure 1-1 Project Site Location
1320 Snowbunny Lane
Project Site
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Noise Fundamentals 2
2. Noise Fundamentals
Sound is most commonly experienced by people as pressure waves passing through air. These rapid fluctuations in
air pressure are processed by the human auditory system to produce the sensation of sound. The rate at which sound
pressure changes occur is called the frequency. Frequency is usually measured as the number of oscillations per
second or Hertz (Hz). Frequencies that can be heard by a healthy human ear range from approximately 20 Hz to
20,000 Hz. Toward the lower end of this range are low-pitched sounds, including those that might be described as a
“rumble” or “boom”. At the higher end of the range are high-pitched sounds that might be described as a “screech”
or “hiss”.
Environmental noise generally derives, in part, from a combination of distant noise sources. Such sources may include
common experiences such as distant traffic, wind in trees, and distant industrial or farming activities. These distant
sources create a low-level "background noise" in which no particular individual source is identifiable. Background
noise is often relatively constant from moment to moment, but varies slowly from hour to hour as natural forces
change or as human activity follows its daily cycle.
Superimposed on this low-level, slowly varying background noise is a succession of identifiable noisy events of
relatively brief duration. These events may include the passing of single -vehicles, aircraft flyovers, screeching of
brakes, and other short-term events. The presence of these short-term events causes the noise level to fluctuate.
Typical indoor and outdoor A-weighted sound levels are shown in Figure 2-1. Detailed acoustical definitions have
been provided in Appendix A - Glossary of Acoustical Terms.
Figure 2-1 Typical Indoor and Outdoor A-Weighted Sound Levels
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Noise Standards 3
3. Noise Standards
The applicable noise guidelines for the project are contained within the City of Aspen Construction Management
Plan Requirements Manual (April 2016). Chapter 11.3: Noise Limits and Suppression Requirements provides the
following noise limits:
• Projects are limited to 70 decibels (dB) at the property line during the summer on season.
• In addition to the decibel limit listed above, projects located on the Mall will be limited to
70 decibels (dB) at the property line during the winter on season.
• All other times projects will be limited to 80 decibels (80dB) at the property line.
On Season Summer Time Frame: June 1st thru Labor Day
On Season Winter Time Frame: November 15th thru March 31st.
This property is not located on the mall, therefore, the analysis was conducted to ensure compliance with the On
Season Time Frame noise limit of 70 dBA. The A-weighting scale has been interpreted as applicable to the noise
limit to better represent the response to sound of human hearing.
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Soil Stabilization Noise Modeling 4
4. Soil Stabilization Noise Modeling
The noise modeling was completed with use of three-dimensional computer noise modeling software. All models in
this report were developed with SoundPLAN 8.0 software using the ISO 9613-2 standard. Noise levels are predicted
based on the locations, noise levels and frequency spectra of the noise sources, and the geometry and reflective
properties of the local terrain, buildings and barriers. To ensure a conservative assessment and compliance with ISO
9613-2 standards, light to moderate winds are assumed to be blowing from the source to receptor. The modeling
results predicted are dependent on equipment and mitigation orientation as indicated. Actual field sound level
measurements may vary from the modeled noise levels due to other noise sources such as traffic, other facilities,
other human activity, or environmental factors.
4.1 Modeled Soil Stabilization Activities
The proposed soil stabilization activities consist of micropiling. Noise models representing the micropiling activities
were created to predict the noise levels at the site and adjacent surroundings. The micropiling activities were modeled
at two locations along the proposed micropiling route for the site as shown in Figure 4-1. The sound power levels for
the micropiling equipment included in the modeling are listed in Table 4-1.
Sound level data utilized in the micropiling models was based on file data of the Furukawa HCR 900 and associated
components. Equipment placement and orientation was coordinated to minimize noise impact when possible. The
predicted modeling results are dependent on equipment and mitigation orientation as indicated.
Table 4-1 Modeled Construction Equipment Sound Power Levels
Modeled Equipment Activity Quantity Individual Component
Sound Power Level (dBA)
Furukawa HCR 900 Micropiling 1 113.8
Top Drive Engine Micropiling 1 111.5
Air Compressor Micropiling 1 105.3
The receiver locations where the noise level was evaluated have been chosen to be consistent with the requirements
of The City of Aspen Construction Management Plan. The requirements indicate that noise levels shall comply with
the applicable noise limits as measured at the project property line. The modeled equipment locations represent the
closest point from the equipment to the property line, or the loudest point along the property line. The project property
line and modeled equipment locations are shown in Figure 4-1.
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Soil Stabilization Noise Modeling 5
Figure 4-1 Modeled Equipment Locations and Property Line Receivers
4.2 Unmitigated Noise Modeling Results and Assessment
The results of the unmitigated noise modeling are presented in Table 4-2. The noise assessment locations in the table
correspond to the locations shown in Figure 4-1. The predicted noise levels represent only the contribution of the
proposed soil stabilization activities and do not include ambient noise or noise from other facilities. The results of the
unmitigated noise modeling are also shown as noise contour maps. Figure 4-3 shows the Location 1 Unmitigated
Micropiling Noise Contour Map in dBA, Figure 4-4 shows the Location 2 Unmitigated Micropiling Noise Contour
Map in dBA. The noise contours are provided in 5 dB increments with the color scale indicating the sound level of
each contour.
Table 4-2 Unmitigated Soil Stabilization Noise Levels (dBA)
Location Micropiling
Location 1
Micropiling
Location 2
West Property Line 77.2 75.8
East Property Line 91.7 93.5
North Property Line 87.8 78.5
South Property Line 76.1 79.6
Allowable Limit at Property Line 70.0
Property Line
Micropiling
Equipment
Location 1
Micropiling
Equipment
Location 2
Micropiling
Route
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Soil Stabilization Noise Modeling 6
The results of the unmitigated noise modeling predict that the micropiling noise levels will exceed the allowable City
of Aspen Construction Noise Limit at all receiver locations along the property line by as much as 23.5 dBA. As a
result, noise mitigation is recommended to reduce the noise levels to below the stated limits.
Figure 4-2 Noise Assessment Locations
South Property Line
Micropiling
Location 1
1320 Snowbunny
Lane Site
West Property Line
North Property Line
East Property Line
Micropiling
Location 2
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Soil Stabilization Noise Modeling 7
Figure 4-3 Location 1 Unmitigated Micropiling Noise Contour Map (dBA)
South Property Line
76.1 dBA
North Property Line
87.8 dBA
East Property Line
91.7 dBA
West Property Line
77.2 dBA
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Soil Stabilization Noise Modeling 8
Figure 4-4 Location 2 Unmitigated Micropiling Noise Contour Map (dBA)
South Property Line
79.6 dBA
North Property Line
78.5 dBA
East Property Line
93.5 dBA
West Property Line
75.8 dBA
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Soil Stabilization Noise Modeling 9
Noise Mitigation Recommendations
Mitigated noise models were created to include mitigation along the perimeter of the project site. Noise levels were
assessed at the project site property line in accordance with City of Aspen noise regulations. The recommended
mitigation to comply with the 70 dBA noise limit at the construction site is described below. Figure 4-5 and Figure
4-6 shows the Modeled Mitigation Layout for Location 1 and Location 2 respectively.
• Approximately 480 total linear feet of 14-foot high acoustical wall with a Sound Transmission Class (STC)
rating of at least 25 installed along the perimeter of the project site.
• Approximately 128 total linear feet of 12-foot high acoustical panels with a Sound Transmission Class (STC)
rating of at least 25 installed around the micro piling equipment.
Additional mitigation recommendations for construction sites are listed below:
1. All equipment should be switched off when not in use.
2. All equipment should be kept in good repair with all worn, loose and unbalanced machine parts to be replaced.
3. Equipment should be placed to maximize the distance between the noisy equipment and the neighboring
houses.
4. Construction operations are limited to the hours of 7:30 am to 5:30 pm Monday through Friday and 9:00 am
to 5:00 pm on Saturday. Construction on Sunday is prohibited.
5. “Residential” grade mufflers should be fitted to the exhaust outlets of all combustion engines.
6. Where possible, broadband white noise reversing alarms should be used in place of tonal reversing alarms
on trucks within the construction site.
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Soil Stabilization Noise Modeling 10
Figure 4-5 Modeled Mitigation Layout for Location 1
Micropiling Equipment
Location 1
32 ft
32 ft
128 Total Linear Feet of
12-foot-high STC-25
Acoustical Sound Panels
120 ft
480 Total Linear Feet of
14-foot-high STC-25
Acoustical Sound Panels
120 ft
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Soil Stabilization Noise Modeling 11
Figure 4-6 Modeled Mitigation Layout for Location 2
32 ft
32 ft
128 Total Linear Feet of
12-foot-high STC-25
Acoustical Sound Panels
120 ft
480 Total Linear Feet of
14-foot-high STC-25
Acoustical Sound Panels
120 ft
Micropiling Equipment
Location 1
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Soil Stabilization Noise Modeling 12
4.3 Mitigated Noise Modeling Results and Assessment
The results of the noise modeling with the inclusion of the noise mitigation recommendations are presented in Table
4-3. The noise assessment locations in the table correspond to the locations shown in Figure 4-1. The calculated noise
levels represent only the contribution of the proposed soil stabilization activities and do not include ambient noise or
noise from other facilities. The results of the mitigated noise modeling are also shown as noise contour maps. Figure
4-7 shows the Location 1 Mitigated Micropiling Noise Contour Map in dBA, Figure 4-8 shows the Location 2
Mitigated Micropiling Noise Contour Map in dBA. The noise contours are provided in 5 dB increments with the
color scale indicating the sound level of each contour.
Table 4-3 Mitigated Soil Stabilization Noise Levels (dBA)
Location Micropiling
Location 1
Micropiling
Location 2
West Property Line 66.1 66.2
East Property Line 75.4 77.0
North Property Line 73.6 67.0
South Property Line 64.5 67.8
Allowable Limit at Property Line 70.0
The mitigated noise modeling results indicate that with inclusion of the recommended mitigation measures, the
micropiling noise levels are predicted to exceed the 70 dBA noise limit established in the City of Aspen Construction
Management Plan Requirements by up to 7.0 dBA. However, with the inclusion of the recommended mitigation a
reduction up to 16.3 dBA and 16.5 dBA may be achieved at Location 1 and Location 2 respectively.
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Soil Stabilization Noise Modeling 13
Figure 4-7 Location 1 Mitigated Micropiling Noise Contour Map (dBA)
South Property Line
64.5 dBA
North Property Line
73.6 dBA
East Property Line
75.4 dBA West Property Line
66.1 dBA
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Soil Stabilization Noise Modeling 14
Figure 4-8 Location 2 Mitigated Micropiling Noise Contour Map (dBA)
South Property Line
67.8 dBA
North Property Line
67.0 dBA
East Property Line
77.0 dBA
West Property Line
66.2 dBA
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Conclusion 15
5. Conclusion
Noise models representing the proposed soil stabilization activities at the 1320 Snowbunny Lane project site were
created to assess the noise impact against the 70 dBA noise limit established in the City of Aspen Construction
Management Plan Requirements Manual (April 2016). The unmitigated modeling results indicate that the micropiling
activity would generate noise levels in excess of 70 dBA at all receiver locations and would, therefore, require sound
mitigation.
The resulting mitigated models demonstrated that with the inclusion of the recommended mitigation measures, the
proposed soil stabilization activities are predicted to exceed the noise limit of 70 dBA by up to 7.0 dBA. However,
with the inclusion of the recommended mitigation a reduction up to 16.3 dBA and 16.5 dBA may be achieved at
Location 1 and Location 2 respectively.
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Glossary of Acoustical Terms 16
Appendix A - Glossary of Acoustical Terms
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Glossary of Acoustical Terms 17
Ambient Noise
The all-encompassing noise associated with a given environment at a specified time, usually a composite of sound
from many sources both near and far.
Average Sound Level
See Equivalent-Continuous Sound Level
A-Weighted Sound Level, dB(A)
The sound level obtained by use of A-weighting. Weighting systems were developed to measure sound ina way that
more closely mimics the ear’s natural sensitivity relative to frequency so that the instrument is less sensitive to noise
at frequencies where the human ear is less sensitive and more sensitive at frequencies where the human ear is more
sensitive.
C-Weighted Sound Level, dBC
The sound level obtained by use of C-weighting. Follows the frequency sensitivity of the human ear at very high
noise levels. The C-weighting scale is quite flat and therefore includes much more of the low-frequency range of
sounds than the A and B scales. In some jurisdictions, C-weighted sound limits are used to limit the low-frequency
content of noise sources.
Community Noise Equivalent Level (CNEL)
A 24-hour A-weighted average sound level which takes into account the fact that a given level of noise may be more
or less tolerable depending on when it occurs. The CNEL measure of noise exposure weights average hourly noise
levels by 5 dB for the evening hours (between 7:00 pm and 10:00 pm), and 10 dB between 10:00 pm and 7:00 am,
then combines the results with the daytime levels to produce the final CNEL value. It is measured in decibels, dB.
Day-Night Average Sound Level (Ldn)
A measure of noise exposure level that is similar to CNEL except that there is no weighting applied to the evening
hours of 7:00 pm to 10:00 pm. It is measured in decibels, dB.
Daytime Average Sound Level
The time-averaged A-weighted sound level measured between the hours of 7:00 am to 7:00 pm. It is measured in
decibels, dB.
Decibel (dB)
The basic unit of measurement for sound level.
Direct Sound
Sound that reaches a given location in a direct line from the source without any reflections.
Divergence
The spreading of sound waves from a source in a free field, resulting in a reducti on in sound pressure level with
increasing distance from the source.
Energy Basis
This refers to the procedure of summing or averaging sound pressure levels on the basis of their squared pressures.
This method involves the conversion of decibels to pressures, then performing the necessary arithmetic calculations,
and finally changing the pressure back to decibels.
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Glossary of Acoustical Terms 18
Equivalent-Continuous Sound Level (Leq)
The average sound level measured over a specified time period. It is a single-number measure of time-varying noise
over a specified time period. It is the level of a steady sound that, in a stated time period and at a stated location, has
the same A-Weighted sound energy as the time-varying sound. For example, a person who experiences an Leq of 60
dB(A) for a period of 10 minutes standing next to a busy street is exposed to the same amou nt of sound energy as if
he had experienced a constant noise level of 60 dB(A) for 10 minutes rather than the time-varying traffic noise level.
Fast Response
A setting on the sound level meter that determines how sound levels are averaged over time. A fas t sound level is
always more strongly influenced by recent sounds, and less influenced by sounds occurring in the distant past, than
the corresponding slow sound level. For the same non-steady sound, the maximum fast sound level is generally
greater than the corresponding maximum slow sound level. Fast response is typically used to measure impact sound
levels.
Field Impact Insulation Class (FIIC)
A single number rating similar to the impact insulation class except that the impact sound pressure levels are measured
in the field.
Field Sound Transmission Class (FSTC)
A single number rating similar to sound transmission class except that the transmission loss values used to derive this
class are measured in the field.
Flanking Sound Transmission
The transmission of sound from a room in which a source is located to an adjacent receiving room by paths other
than through the common partition. Also, the diffraction of noise around the ends of a barrier.
Frequency
The number of oscillations per second of a sound wave
Hourly Average Sound Level (HNL)
The equivalent-continuous sound level, Leq, over a 1-hour time period.
Impact Insulation Class (IIC)
A single number rating used to compare the effectiveness of floor/ceiling assemblies in providing reduction of impact-
generated sound such as the sound of a person’s walking across the upstairs floor.
Impact Noise
The noise that results when two objects collide.
Impulse Noise
Noise of a transient nature due to the sudden impulse of pressure like that created by a gunshot or balloon bursting.
Insertion Loss
The decrease in sound power level measured at the location of the receiver when an element (e.g., a noise barrier) is
inserted in the transmission path between the sound source and the receiver.
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Glossary of Acoustical Terms 19
Inverse Square Law
A rule by which the sound intensity varies inversely with the square of the distance from the source. This results in a
6dB decrease in sound pressure level for each doubling of distance from the source.
Ln Sound Level
Time-varying noise environments may be expressed in terms of the noise level that is exceeded for a certain
percentage of the total measurement time. These statistical noise levels are denoted Ln, where n is the percent of time.
For example, the L50 is the noise level exceeded for 50% of the time. For a 1-hour measurement period, the L50 would
be the noise level exceeded for a cumulative period of 30 minutes in that hour.
Masking
The process by which the threshold of hearing for one sound is raised by the presence of another sound.
Maximum Sound Level (Lmax)
The greatest sound level measured on a sound level meter during a designated time interval or event.
NC Curves (Noise Criterion Curves)
A system for rating the noisiness of an occupied indoor space. An actual octave-band spectrum is compared with a
set of standard NC curves to determine the NC level of the space.
Noise Reduction
The difference in sound pressure level between any two points.
Noise Reduction Coefficient (NRC)
A single number rating of the sound absorption properties of a material. It is the average of the sound absorption
coefficients at 250, 500, 1000, and 2000 Hz, rounded to the nearest multiple of 0.05.
Octave
The frequency interval between two sounds whose frequency ratio is 2. For example, the frequency interval between
500 Hz and 1,000 Hz is one octave.
Octave-Band Sound Level
For an octave frequency band, the sound pressure level of the sound contained within that band.
One-Third Octave
The frequency interval between two sounds whose frequency ratio is 2^(1/3). For example, the frequency interval
between 200 Hz and 250 Hz is one-third octave.
One-Third-Octave-Band Sound Level
For a one-third-octave frequency band, the sound pressure level of the sound contained within that band.
Outdoor-Indoor Transmission Class (OITC)
A single number rating used to compare the sound insulation properties of building façade elements. This rating is
designed to correlate with subjective impressions of the ability of façade elements to reduce the overall loudness of
ground and air transportation noise.
Peak Sound Level (Lpk)
The maximum instantaneous sound level during a stated time period or event.
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Glossary of Acoustical Terms 20
Pink Noise
Noise that has approximately equal intensities at each octave or one-third-octave band.
Point Source
A source that radiates sound as if from a single point.
RC Curves (Room Criterion Curves)
A system for rating the noisiness of an occupied indoor space. An actual octave-band spectrum is compared with a
set of standard RC curves to determine the RC level of the space.
Real-Time Analyzer (RTA)
An instrument for the determination of a sound spectrum.
Receiver
A person (or persons) or equipment which is affected by noise.
Reflected Sound
Sound that persists in an enclosed space as a result of repeated reflections or scattering. It does not include sound that
travels directly from the source without reflections.
Reverberation
The persistence of a sound in an enclosed or partially enclosed space after the source of the sound has stopped, due
to the repeated reflection of the sound waves.
Room Absorption
The total absorption within a room due to all objects, surfaces and air absorption within the room. It is measured in
Sabins or metric Sabins.
Slow Response
A setting on the sound level meter that determines how measured sound levels are averaged over time. A slow sound
level is more influenced by sounds occurring in the distant past that the corresponding fast sound level.
Sound
A physical disturbance in a medium (e.g., air) that is capable of being detected by the human ear.
Sound Absorption Coefficient
A measure of the sound-absorptive property of a material.
Sound Insulation
The capacity of a structure or element to prevent sound from reaching a receiver room either by absorption or
reflection.
Sound Level Meter (SLM)
An instrument used for the measurement of sound level, with a standard frequency-weighting and standard
exponentially weighted time averaging.
Sound Power Level
A physical measure of the amount of power a sound source radiates into the surrounding air. It is measured in decibels.
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Glossary of Acoustical Terms 21
Sound Pressure Level
A physical measure of the magnitude of a sound. It is related to the sound’s energy. The terms sound pressure level
and sound level are often used interchangeably.
Sound Transmission Class (STC)
A single number rating used to compare the sound insulation properties of walls, floors, ceilings, windows, or doors.
This rating is designed to correlate with subjective impressions of the ability of building elements to reduce the overall
loudness of speech, radio, television, and similar noise sources in offices and buildings.
Source Room
A room that contains a noise source or sources
Spectrum
The spectrum of a sound wave is a description of its resolution into components, each of different frequency and
usually different amplitude.
Tapping Machine
A device used in rating different floor constructions against impacts. It produces a series of impacts on the floor under
test, 10 times per second.
Tone
A sound with a distinct pitch
Transmission Loss (TL)
A property of a material or structure describing its ability to reduce the transmission of sound at a particular frequency
from one space to another. The higher the TL value the more effective the material or structure is in reducing sound
between two spaces. It is measured in decibels.
White Noise
Noise that has approximately equal intensities at all frequencies.
Windscreen
A porous covering for a microphone, designed to reduce the noise generated by the passage of wind over the
microphone.
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